WO2024209710A1 - Method for producing epoxy resin, method for producing epoxy resin composition, method for producing cured product, method for producing fiber-containing epoxy resin composition, method for producing diphenyl carbonate, and method for producing polycarbonate resin - Google Patents

Abstract

The present invention addresses the problem of providing novel chemical recycling by which an industrially useful epoxy resin can be provided. The problem is solved by a method for producing an epoxy resin, the method including a decomposition reaction for decomposing a polycarbonate resin in epihalohydrin, and a reaction step for obtaining an epoxy resin.

Description

Method for producing epoxy resin, method for producing epoxy resin composition, method for producing cured product, method for producing fiber-containing epoxy resin composition, method for producing diphenyl carbonate, and method for producing polycarbonate resin

The present invention relates to a method for producing an epoxy resin, a method for producing an epoxy resin composition containing the obtained epoxy resin, a method for producing a fiber-containing epoxy resin composition containing recycled fibers obtained together with an epoxy resin, a method for producing diphenyl carbonate from a dialkyl carbonate obtained together with an epoxy resin, and a method for producing a polycarbonate resin from the obtained diphenyl carbonate.

Technical Background

Polycarbonate resin has excellent mechanical properties, electrical properties, heat resistance, cold resistance, transparency, etc., and is a material used for a variety of applications. Demand for it is increasing, and the amount of discarded polycarbonate resin is also increasing accordingly. Therefore, it is becoming important to reuse discarded polycarbonate resin.

Under these circumstances, a method has been disclosed in which aromatic polycarbonate resin is decomposed with an aqueous metal hydroxide solution to obtain an aqueous solution of an alkali metal salt of an aromatic dihydroxy compound, and the aromatic dihydroxy compound is recovered from the aqueous solution (see Patent Document 1).

In addition to recovering aromatic dihydroxy compounds, methods have also been proposed for recovering dialkyl carbonates (see Patent Documents 2 and 3).

International Publication No. WO 2006/114893 Japanese Patent Application Publication No. 10-259151 JP 2002-212335 A

As described in the above Patent Documents 1 to 3, in conventional chemical recycling techniques for discarded polycarbonate resins, only dihydroxy compounds such as bisphenol A, or dihydroxy compounds such as bisphenol A and dialkyl carbonates are recovered, and in order to obtain industrially useful chemical products, further steps such as polycondensation and functionalization are required.
Furthermore, in chemical recycling technology for polycarbonate resins that contain reinforcing materials such as fibers to strengthen plastics, the reinforcing materials such as fibers are insoluble in the decomposition and purification processes, making the process complicated and making recycling difficult.
The present invention provides a new production method that can provide industrially useful epoxy resins and dialkyl carbonates.

As a result of intensive research into providing the above-mentioned new production method, the present inventors have found that epoxy resins can be obtained by subjecting polycarbonate resins to a decomposition reaction in epihalohydrin, and have completed a new chemical recycling technology for polycarbonate resins.
That is, the present invention includes the following inventions.

[1] A method for producing an epoxy resin, comprising a reaction step of obtaining an epoxy resin, the reaction step including a decomposition reaction of decomposing a polycarbonate resin in epihalohydrin.
[2] The method for producing an epoxy resin according to [1], wherein the decomposition reaction is carried out in the presence of a metal hydroxide.
[3] The method for producing an epoxy resin according to [1] or [2], wherein the decomposition reaction is carried out in the presence of an alcohol-based compound and co-produces a dialkyl carbonate together with the epoxy resin.
[4] The method for producing an epoxy resin according to any one of [1] to [3], wherein in the decomposition reaction, the water content is 5 mass% or less based on the total amount of raw materials.
[5] The method for producing an epoxy resin according to [1], wherein the decomposition reaction is carried out in the presence of a metal alkoxide to co-produce a dialkyl carbonate together with the epoxy resin.
[6] The method for producing an epoxy resin according to [1], wherein the polycarbonate resin is a fiber-containing polycarbonate resin, and recycled fibers are obtained together with the epoxy resin.
[7] The method for producing an epoxy resin according to [6], wherein the reaction step includes a separation step of performing solid-liquid separation into fibers and a solution.
[8] The method for producing an epoxy resin according to any one of [1] to [7], wherein the polycarbonate is an aromatic polycarbonate.
[9] The method for producing an epoxy resin according to any one of [1] to [8], wherein 1.0 to 20.0 moles of the epihalohydrin are used per mole of carbonate bond in the polycarbonate.
[10] A method for producing an epoxy resin composition, comprising blending a curing agent with the epoxy resin obtained by the method according to any one of [1] to [9].
[11] A method for producing a cured product, comprising curing the epoxy resin composition obtained by the method according to [10].
[12] A method for producing a fiber-containing epoxy resin composition, comprising a step of mixing the epoxy resin obtained by the method according to [6] or [7] with recycled fibers.
[13] A method for producing a fiber-containing epoxy resin cured product, comprising a step of curing the fiber-containing epoxy resin composition obtained by the method according to [12].
[14] A method for producing diphenyl carbonate, comprising a step of reacting the dialkyl carbonate obtained by the method according to any one of [3] to [5] with phenol.
[15] A method for producing a polycarbonate resin, comprising: a step of polymerizing the diphenyl carbonate obtained by the production method according to [14] through an ester exchange reaction.

The present invention provides a new chemical recycling technology for polycarbonate resin. Specifically, it provides a new production method that can provide industrially useful epoxy resins and dialkyl carbonates, and a new production method that can provide epoxy resins and recycled fibers. It also provides a method for producing an epoxy resin composition containing the obtained epoxy resin, a method for producing a fiber-containing epoxy resin composition from the obtained epoxy resin and recycled fibers, a method for producing diphenyl carbonate from the obtained dialkyl carbonate, and a method for producing polycarbonate resin from the obtained diphenyl carbonate.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following description, and can be modified as desired without departing from the spirit of the present invention. In this specification, when "~" is used to express a numerical value or physical property value before and after it, it is used to include the values before and after it.

A first embodiment of the present invention is a method for producing an epoxy resin, which includes a reaction step of obtaining an epoxy resin, which includes a decomposition reaction of decomposing a polycarbonate resin in epihalohydrin, and the decomposition reaction is preferably carried out in the presence of a metal hydroxide.
In the second embodiment, the process includes a decomposition reaction of decomposing a polycarbonate resin in epihalohydrin, the decomposition reaction being carried out in the presence of a metal hydroxide and an alcohol-based compound, and co-producing a dialkyl carbonate together with an epoxy resin.
In addition, the third embodiment is a production method which includes a decomposition reaction of decomposing a polycarbonate resin in epihalohydrin, the decomposition reaction being carried out in the presence of a metal alkoxide, and which co-produces a dialkyl carbonate together with an epoxy resin.
In addition, the fourth embodiment is a production method that includes a decomposition reaction in which a polycarbonate resin is decomposed in epihalohydrin, the polycarbonate resin being a fiber-containing polycarbonate resin, and producing regenerated fibers together with an epoxy resin.

In this specification, the "method of co-producing dialkyl carbonate together with epoxy resin" means recovering industrially useful epoxy resin and dialkyl carbonate together by chemically recycling polycarbonate resin. This method has a different objective from the method of obtaining dihydroxy compounds such as bisphenol A and dialkyl carbonate recovered in the conventional chemical recycling of polycarbonate resin.
In addition, in this specification, the term "recycled fiber" refers to a fiber that was once contained in a resin, extracted from the resin, and recycled so that it can be reused. For example, it is a fiber extracted from a composite material of polycarbonate resin and fiber, such as fiber-reinforced plastic (FRP).

<Reaction process>
The reaction process includes a decomposition reaction in which polycarbonate resin is decomposed in epihalohydrin to obtain epoxy resin. This process relates to a new chemical recycling technology for polycarbonate resin, in which polycarbonate resin is decomposed in epihalohydrin to obtain epoxy resin.

(Polycarbonate resin)
The polycarbonate resin includes a polymer containing a carbonate bond (-O-C(=O)-O-). Although there are no limitations on the polycarbonate resin, it is preferable to use an aromatic polycarbonate resin in terms of availability of raw materials and usefulness of the epoxy resin to be produced.

The aromatic polycarbonate resin may be a polycarbonate resin containing a structural unit derived from an aromatic dihydroxy compound. Examples of the aromatic dihydroxy compound include bisphenols such as bisphenol A, bisphenol C, bisphenol F, bisphenol E, bisphenol Z, bisphenol S, bisphenol AD, bisphenol acetophenone, bisphenol trimethylcyclohexane, bisphenol fluorene, tetramethyl bisphenol A, tetramethyl bisphenol F, tetra-t-butyl bisphenol A, and tetramethyl bisphenol S; biphenol, tetramethyl biphenol, dimethyl biphenol, and tetra-t-butyl bisphenol; Examples of the phenol-based compounds include biphenols such as tylbiphenol; benzenediols such as hydroquinone, methylhydroquinone, dibutylhydroquinone, resorcin, and methylresorcin (here, "benzenediols" are compounds having one benzene ring, and two hydroxyl groups are directly bonded to the benzene ring); dihydroanthrahydroquinones such as dihydroanthrahydroquinone; dihydroxydiphenyl ethers such as dihydroxydiphenyl ether; thiodiphenols such as thiodiphenol; dihydroxynaphthalenes such as dihydroxynaphthalene; and dihydroxystilbenes such as dihydroxystilbene.
The aromatic polycarbonate resin may be a homopolymer using one of these aromatic dihydroxy compounds alone, or a copolymer using two or more of them.

Among the above-mentioned aromatic dihydroxy compounds, those having bisphenol A or bisphenol C as a main structural unit are particularly preferred from the viewpoints of reactivity, ease of availability of raw materials, and versatility of the resulting epoxy resin.
These aromatic polycarbonates may be used alone or in combination of two or more.

The polycarbonate resin is not limited to polycarbonate resin alone, but may be a composition containing one or more resins other than polycarbonate, such as polyester resins, polyarylate resins, etc. When using a composition containing a resin other than polycarbonate resin, it is preferable that the polycarbonate resin composition contains 50% by mass or more of polycarbonate resin, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

From the viewpoint of chemical recycling, the raw polycarbonate resin preferably contains used polycarbonate resin (hereinafter, sometimes abbreviated as "waste polycarbonate") that is treated as waste plastic. When using waste polycarbonate as the raw polycarbonate resin, it is preferable to wash, crush, pulverize, or the like in advance.
In addition, when using waste plastics containing polycarbonate resin, it is preferable to remove substances other than polycarbonate resin contained in the waste plastics as necessary. Examples of a method for removing substances other than polycarbonate resin include a method of dissolving waste plastics in epihalohydrin and, if necessary, an organic solvent, and filtering the solution to remove substances other than polycarbonate resin.

(fiber)
In the fourth embodiment, the fiber contained in the fiber-containing polycarbonate resin is not particularly limited as long as it is a fiber that can be contained in the polycarbonate resin, and examples thereof include glass fiber and carbon fiber. The shape, fiber diameter, aspect ratio, etc. of the fiber are not particularly limited, and it is sufficient that it can be contained in the polycarbonate. It is preferable that the fiber is capable of improving the mechanical strength of the cured product of the epoxy resin obtained from the decomposition reaction of polycarbonate and the recycled fiber, and is preferably carbon fiber.

(epihalohydrin)
Examples of epihalohydrins include epichlorohydrin, β-methylepichlorohydrin, epibromohydrin, etc. Among these, epichlorohydrin is particularly preferred from the viewpoints of reactivity, ease of availability of raw materials, and versatility of the resulting epoxy resin. These epihalohydrins may be used alone or in combination of two or more.

The amount of epihalohydrin used in the reaction step is not particularly limited, but is preferably 1 to 20 moles, more preferably 3 to 16 moles, and particularly preferably 6 to 14 moles per mole of carbonate bond in the raw polycarbonate resin. If the amount of epihalohydrin used is equal to or greater than the above lower limit, it is preferable in that undesirable side reactions such as crosslinking reactions can be suppressed. Also, if the amount of epihalohydrin used is equal to or less than the above upper limit, it is preferable in that industrial production efficiency is improved.

(Metal hydroxides and alcohol compounds)
In the first and fourth embodiments, the reaction step is preferably carried out in the presence of a metal hydroxide. In the second embodiment, the reaction step is carried out in the presence of a metal hydroxide and an alcohol-based compound. Examples of the metal hydroxide include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide; and alkaline earth metal hydroxides such as magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide.
From the viewpoint of raw material availability, alkali metal hydroxides are preferred, and sodium hydroxide is more preferred.

The metal hydroxide may be subjected to the reaction together with an alcohol-based compound as an alcohol solution of the metal hydroxide. The alcohol-based compound is not particularly limited as long as it is used as a solvent or dispersant for the metal hydroxide, and may be a monoalcohol or a polyol such as a diol-based compound or a glycol-based compound, but is preferably a monoalcohol, and more preferably a lower alcohol. Specifically, it is preferable to use methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, or the like.
The metal hydroxide concentration in the alcohol solution of the metal hydroxide used in the reaction step is not particularly limited, but is usually 5% by mass or more and 50% by mass or less.

In the reaction step, the metal hydroxide is continuously supplied within the reaction time, preferably 1 to 10 moles, more preferably 2.4 to 8 moles, and particularly preferably 3 to 6 moles per mole of carbonate groups contained in the polycarbonate resin. When the amount of metal hydroxide used is equal to or greater than the above lower limit, the reaction rates of the decomposition reaction and the epoxy group formation reaction can be sufficiently ensured, which is preferable from the standpoint of the quality and production efficiency of the obtained epoxy resin. In addition, when the amount is equal to or less than the above upper limit, it is preferable from the standpoint of suppressing over-reaction and side reactions such as crosslinking reactions.

(Metal alkoxide)
In the third and fourth embodiments, the reaction step is preferably carried out in the presence of a metal alkoxide. Examples of the metal in the metal alkoxide include alkali metals such as lithium, sodium, potassium, rubidium, and cesium; and alkaline earth metals such as magnesium, calcium, strontium, and barium. Examples of the alkoxide include methoxide, ethoxide, and propoxide. Examples of the alkoxide include methoxide, ethoxide, propoxide, and glycoxide.
The alcohol of the metal alkoxide is not particularly limited, and may be a monoalcohol or a polyol such as a glycol-based compound, but is preferably a monoalcohol. Examples of the monoalcohol include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, and t-butanol. Examples of the polyol include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, and glycerin. The glycol compound is a compound in which one hydroxyl group is bonded to each of two carbon atoms of an alkyl group having two or more carbon atoms, and examples of the glycol compound include ethylene glycol and propylene glycol.
The metal alkoxide may be used alone or in combination of two or more kinds. Among them, sodium methoxide is preferred from the viewpoint of industrial availability.

In the reaction step, the metal alkoxide is continuously supplied within the reaction time, preferably 1 to 10 moles, more preferably 2.4 to 8 moles, and particularly preferably 3 to 6 moles per mole of carbonate groups contained in the polycarbonate resin. When the amount of metal alkoxide used is equal to or greater than the above lower limit, the reaction rates of the decomposition reaction and the epoxy group formation reaction can be sufficiently ensured, which is preferable from the standpoint of the quality and production efficiency of the obtained epoxy resin. In addition, when the amount is equal to or less than the above upper limit, it is preferable from the standpoint of suppressing over-reaction and side reactions such as crosslinking reactions.

The reaction temperature in the reaction process is preferably 30 to 100°C, in order to ensure a sufficient reaction rate. The reaction time is preferably 10 to 360 minutes, more preferably 20 to 300 minutes, and particularly preferably 30 to 240 minutes, in order to allow the reaction to proceed sufficiently.

After the reaction is complete, a post-treatment step can be carried out if necessary. In the post-treatment step, insoluble by-product salts are removed by filtration or washing with water, and unreacted epihalohydrin is then removed by distillation under reduced pressure to obtain the desired epoxy resin and dialkyl carbonate.

In addition, in the reaction process, catalysts such as quaternary ammonium salts such as tetramethylammonium chloride and tetraethylammonium bromide; tertiary amines such as benzyldimethylamine and 2,4,6-tris(dimethylaminomethyl)phenol; imidazoles such as 2-ethyl-4-methylimidazole and 2-phenylimidazole; phosphonium salts such as ethyltriphenylphosphonium iodide; and phosphines such as triphenylphosphine may be used.

In addition, in the reaction process, inert organic solvents such as alcohols such as ethanol and isopropanol; glycols such as ethylene glycol, diethylene glycol, propylene glycol and polyethylene glycol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane and ethylene glycol dimethyl ether; glycol ethers such as propylene glycol monomethyl ether; aprotic polar solvents such as dimethyl sulfoxide and dimethylformamide; and aromatic hydrocarbon solvents such as toluene and xylene may be used.

Furthermore, when the epoxy resin obtained as described above has too much saponifiable halogen, it is possible to obtain a purified epoxy resin with a sufficiently reduced amount of saponifiable halogen by reprocessing. That is, the crude epoxy resin obtained by the reaction is redissolved in an inert organic solvent such as isopropyl alcohol, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, dioxane, methoxypropanol, or dimethyl sulfoxide, and an alkali metal hydroxide or metal alkoxide is added as a solid or aqueous solution to carry out a ring-closing reaction at a temperature of about 30 to 120°C, more preferably 40 to 110°C, and even more preferably 50 to 100°C for 0.1 to 8 hours, more preferably 0.3 to 7 hours, and even more preferably 0.5 to 6 hours, and then the excess metal hydroxide or secondary salt is removed by a method such as water washing, and the organic solvent is distilled off under reduced pressure and/or steam distillation is carried out to obtain an epoxy resin with a reduced amount of hydrolyzable halogen.
If the reaction temperature is too low or the reaction time is too short, the ring-closing reaction may not proceed, whereas if the reaction temperature is too high or the reaction time is too long, the reaction may proceed, but may result in problems such as high molecular weight, high epoxy equivalent, and high viscosity.

In the first and fourth forms, the decomposition reaction of polycarbonate in the reaction step is carried out by azeotroping the reaction liquid while maintaining a predetermined temperature as necessary, to obtain volatile vapor. The resulting vapor is then cooled to obtain a condensate, which is then subjected to oil/water separation, and the dehydrated oil is returned to the reaction system, whereby the water produced by glycidylation and the water derived from the aqueous metal hydroxide solution are dehydrated. This can reduce the amount of water in the system, and promote the formation of epoxy groups by the metal hydroxide.

The method for separating epihalohydrin from the azeotropic condensate is not particularly limited, but for example, the azeotropic condensate can be separated by settling in a settling separator and only the epihalohydrin in the lower layer is continuously returned to the system, thereby circulating the epihalohydrin. In order to maintain the molar ratio of epihalohydrin in the system, the amount of epihalohydrin remaining in the settling separator is preferably 5 mass% or less relative to the total amount of charged epihalohydrin.

In the reaction step of the fourth embodiment, the content of water relative to the total amount of the raw materials is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, and it is particularly preferable that no water is present in the reaction system. By keeping the amount of water relative to the total amount of the raw materials below the upper limit, hydrolysis of the carbonate ester can be suppressed, and a dialkyl carbonate can be efficiently obtained.
The content of water relative to the total amount of raw materials indicates the mass ratio of water contained in all raw materials used relative to the total amount of all raw materials used in the reaction, and does not include water produced by the reaction.

(Separation process)
The reaction step of the fourth embodiment preferably includes a separation step of performing solid-liquid separation of the fiber and the solution. The separation step separates the epoxy resin solution and the regenerated fiber, and each can be obtained. In the separation step, an organic solvent such as toluene and water are added to the reaction solution, and the regenerated fiber can be separated by filtering.

(Obtained epoxy resin)
The epoxy equivalent of the epoxy resin obtained through the reaction step is preferably 50 to 10,000 g/eq, more preferably 100 to 5,000 g/eq, and particularly preferably 150 to 3,000 g/eq, as measured according to JIS K 7236. When the epoxy equivalent of the obtained epoxy resin is within the above range, the crosslink density increases when cured with various curing agents, and a cured product having excellent chemical resistance and the like can be obtained.

(Obtained dialkyl carbonate)
The dialkyl carbonate obtained through the reaction process can be used as a raw material for producing polycarbonate by the melting method. It is preferable that the dialkyl carbonate is recovered by distillation. Therefore, the alkyl of the dialkyl carbonate is preferably an alkyl having 10 or less carbon atoms, more preferably an alkyl having 6 or less carbon atoms, and particularly preferably an alkyl having 4 or less carbon atoms. Specifically, dimethyl carbonate, diethyl carbonate, and dibutyl carbonate are particularly preferable.
The dialkyl carbonate thus obtained is preferably converted to diphenyl carbonate by transesterification with phenol and used as a raw material for the production of polycarbonate by a melt process. The diphenyl carbonate can be produced by a known method for producing diphenyl carbonate from dialkyl carbonate (for example, JP-A-3-291257).
For example, diphenyl carbonate can be produced by a method in which dialkyl carbonate and phenol are used as raw materials, an ester exchange reaction is carried out to obtain an alkylphenyl carbonate, and the alkylphenyl carbonate is then subjected to a disproportionation reaction to obtain diphenyl carbonate. As a catalyst for this ester exchange reaction, a known catalyst used for producing diphenyl carbonate can be used. For example, an organic titanium catalyst such as tetraphenoxytitanium can be used.

<Epoxy resin composition>
The epoxy resin obtained above can be mixed with a curing agent to produce an epoxy resin composition. In addition, other epoxy compounds, curing accelerators, other components, etc. can be appropriately mixed into the epoxy resin composition as necessary.

<Fiber-containing epoxy resin composition>
A fiber-containing epoxy resin composition can be produced by mixing the obtained epoxy resin with recycled fibers. Also, a fiber-containing epoxy resin composition can be produced by mixing the obtained epoxy resin with recycled fibers and a curing agent.
If necessary, other epoxy compounds, curing accelerators, other components, etc. may be appropriately blended into the fiber-containing epoxy resin composition.

(Hardening agent)
A curing agent is a substance that contributes to the crosslinking reaction and/or chain extension reaction between epoxy groups of an epoxy compound. In this specification, even substances that are usually called "curing accelerators" are considered to be curing agents as long as they contribute to the crosslinking reaction and/or chain extension reaction between epoxy groups of an epoxy compound.

The amount of hardener to be added is preferably 0.1 to 1000 parts by mass, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 60 parts by mass or less, per 100 parts by mass of epoxy resin.

When the epoxy resin composition contains an epoxy compound other than the above epoxy resins, the amount of the curing agent is preferably 0.1 to 1000 parts by mass, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 60 parts by mass or less, per 100 parts by mass of the total epoxy resin components as solids. The more preferred amounts of the curing agent are as follows, depending on the type of curing agent:

In this specification, "solids" refers to the components excluding the solvent, and includes not only solid epoxy compounds, but also semi-solid and viscous liquid substances. Also, "total epoxy resin components" refers to the sum of the above epoxy resins and other epoxy resins described below.

In the method for producing an epoxy resin composition, it is preferable to use as the curing agent at least one selected from the group consisting of polyfunctional phenols, polyisocyanate compounds, amine compounds, acid anhydride compounds, imidazole compounds, amide compounds, cationic polymerization initiators, and organic phosphines.

Examples of polyfunctional phenols include bisphenols such as bisphenol A, bisphenol F, bisphenol S, bisphenol B, bisphenol AD, bisphenol Z, and tetrabromobisphenol A; biphenols such as 4,4'-biphenol and 3,3',5,5'-tetramethyl-4,4'-biphenol; catechol, resorcin, hydroquinone, and dihydroxynaphthalenes; and compounds in which the hydrogen atoms bonded to the aromatic rings of these compounds are substituted with non-interfering substituents such as halogen groups, alkyl groups, aryl groups, ether groups, ester groups, and organic substituents containing hetero elements such as sulfur, phosphorus, and silicon.
Further examples include novolaks and resols which are polycondensates of these phenols, or monofunctional phenols such as phenol, cresol, and alkylphenol with aldehydes.

Examples of polyisocyanate compounds include polyisocyanate compounds such as tolylene diisocyanate, methylcyclohexane diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, trimethylhexamethylene diisocyanate, and lysine triisocyanate. Further examples include polyisocyanate compounds obtained by reacting these polyisocyanate compounds with compounds having at least two active hydrogen atoms such as amino groups, hydroxyl groups, carboxyl groups, and water, or trimers to pentamers of the above polyisocyanate compounds.

Examples of amine compounds include aliphatic primary, secondary, and tertiary amines, aromatic primary, secondary, and tertiary amines, cyclic amines, guanidines, and urea derivatives, and specific examples include triethylenetetramine, diaminodiphenylmethane, diaminodiphenyl ether, metaxylenediamine, dicyandiamide, 1,8-diazabicyclo(5,4,0)-7-undecene, 1,5-diazabicyclo(4,3,0)-5-nonene, dimethylurea, and guanylurea.

Examples of acid anhydride compounds include phthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and condensates of maleic anhydride and unsaturated compounds.

Examples of imidazole compounds include 1-isobutyl-2-methylimidazole, 2-methylimidazole, 1-benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and benzimidazole. Note that imidazole compounds also function as curing accelerators, which will be described later, but in the present invention they are classified as curing agents.

Examples of amide compounds include dicyandiamide and its derivatives, polyamide resins, etc.

The cationic polymerization initiator generates cations by heat or irradiation with active energy rays, and examples of the cationic polymerization initiator include aromatic onium salts. Specific examples include compounds consisting of an anion component such as SbF ₆ ^- , BF ₄ ^- , AsF ₆ ^- , PF ₆ ^- , CF ₃ SO ₃ ^2- , or B(C ₆ F ₅ ) ₄ ^- and an aromatic cation component containing an atom such as iodine, sulfur, nitrogen, or phosphorus. Diaryliodonium salts and triarylsulfonium salts are particularly preferred.

Examples of organic phosphines include tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine. Examples of phosphonium salts include tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, and tetrabutylphosphonium tetrabutylborate. Examples of tetraphenylboron salts include 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate.

The above curing agents may be used alone or in combination of two or more of the same or different types.

When using polyfunctional phenols, amine compounds, or acid anhydride compounds as the curing agent, it is preferable to use them so that the equivalent ratio of the functional groups in the curing agent (hydroxyl groups of polyfunctional phenols, amino groups of amine compounds, or acid anhydride groups of acid anhydride compounds) to the total epoxy groups in the epoxy resin composition is in the range of 0.8 to 1.5. When using polyisocyanate compounds, it is preferable to use them in an equivalent ratio of 1:0.01 to 1:1.5, in terms of the number of isocyanate groups in the polyisocyanate compound to the number of hydroxyl groups in the epoxy resin composition. When using imidazole compounds, it is preferable to use them in a range of 0.5 to 10 parts by mass per 100 parts by mass of all epoxy resin components as solids in the epoxy resin composition. When using amide compounds, it is preferable to use them in a range of 0.1 to 20% by mass with respect to the total amount of all epoxy resin components and amide compounds as solids in the epoxy resin composition. When a cationic polymerization initiator is used, it is preferably used in the range of 0.01 to 15 parts by mass relative to 100 parts by mass of all epoxy resin components as solid contents in the epoxy resin composition. When organic phosphines are used, it is preferably used in the range of 0.1 to 20% by mass relative to the total amount of all epoxy resin components as solid contents in the epoxy resin composition and organic phosphines.

In addition to the curing agents listed above, for example, mercaptan compounds, organic acid dihydrazides, boron halide amine complexes, etc. can also be used as curing agents in the epoxy resin composition. These curing agents may be used alone or in combination of two or more.

(Other epoxy resins)
In the method for producing an epoxy resin composition and the method for producing a fiber-containing epoxy resin composition, epoxy resins other than the above-mentioned epoxy resins (sometimes referred to as "other epoxy resins" in this specification) can be used. Examples of the other epoxy resins include glycidyl ether type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, biphenyl type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, tetrabromobisphenol A type epoxy resins, and other polyfunctional phenol type epoxy resins, epoxy resins obtained by hydrogenating the aromatic rings of the above-mentioned aromatic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. The above-mentioned other epoxy resins may be used alone or in combination of two or more.

When the epoxy resin composition and the fiber-containing epoxy resin composition contain the above-mentioned epoxy resin and other epoxy resins, the proportion of the other epoxy resin in the total epoxy resin components as solids in the epoxy resin composition and the fiber-containing epoxy resin composition is preferably 1 mass% or more, more preferably 5 mass% or more, and on the other hand, is preferably 99 mass% or less, more preferably 95 mass% or less. By having the proportion of the other epoxy resin be equal to or more than the above lower limit, the physical property improvement effect by blending the other epoxy resin can be sufficiently obtained. On the other hand, by having the proportion of the other epoxy resin be equal to or less than the above upper limit, the effect of chemical recyclability by the above-mentioned epoxy resin can be sufficiently obtained.

The epoxy resin composition may be diluted by blending a solvent in order to adjust the viscosity of the epoxy resin composition appropriately when handling it, such as when forming a coating film. The solvent is used to ensure ease of handling and workability when molding the epoxy resin composition, and there is no particular limit to the amount used. As mentioned above, in this invention, the terms "solvent" and "solvent" are used to distinguish between the forms of use, but the same or different substances may be used independently.

As the solvent, one or more of the organic solvents exemplified as reaction solvents used in the production of epoxy resins can be used.

The epoxy resin composition and fiber-containing epoxy resin composition may contain other components in addition to the components listed above. Examples of other components include curing accelerators (excluding those that fall under the category of curing agents), coupling agents, flame retardants, antioxidants, light stabilizers, plasticizers, reactive diluents, pigments, inorganic fillers, organic fillers, etc. The other components listed above can be used in appropriate combinations depending on the desired physical properties of the epoxy resin composition and fiber-containing epoxy resin composition.

[Cured Product]
The epoxy resin composition and the fiber-containing epoxy resin composition can be cured to obtain a cured product. The term "curing" used here means intentionally curing an epoxy compound by heat and/or light, and the degree of curing can be controlled depending on the desired physical properties and applications.

The method of curing the epoxy resin composition and fiber-containing epoxy resin composition to produce a cured product varies depending on the ingredients and amounts of the epoxy resin composition and fiber-containing epoxy resin composition, and the shape of the compound, but typically involves heating at 50-200°C for 5 seconds to 180 minutes. This heating is preferably performed in two stages, with a primary heating at 50-160°C for 5 seconds to 30 minutes, and a secondary heating at 90-200°C, which is 40-120°C higher than the primary heating temperature, for 1 minute to 150 minutes, in order to reduce poor curing.

When producing a cured product as a semi-cured product, the curing reaction of the epoxy resin composition and the fiber-containing epoxy resin composition may be allowed to proceed to an extent that the shape can be maintained by heating or the like. If the epoxy resin composition and the fiber-containing epoxy resin composition contain a solvent, most of the solvent is removed by heating, reducing pressure, air drying, or other methods, but up to 5% by mass of the solvent may remain in the semi-cured product.

The dialkyl carbonate obtained together with the epoxy resin by the above method can be reacted with phenol to give diphenyl carbonate, which can be polymerized by transesterification to give polycarbonate resin.
The production of the above diphenyl carbonate and the production of the polycarbonate resin can be carried out according to a conventional method.

The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples. Note that the values of various manufacturing conditions and evaluation results in the following examples are meant as preferred upper or lower limit values in the embodiments of the present invention, and the preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values and the values in the following examples or values between the examples.
The epoxy equivalent of the epoxy resin obtained in the following examples was measured in accordance with JIS K 7236.

[analysis]
The production of the epoxy resin was confirmed by high performance liquid chromatography according to the following procedure and conditions.
Equipment: JASCO RHPLC, JASCO 03150-3M Unifinepak C18 3 μm 150 mm × 3.0 mm ID
Method: Gradient method Analysis temperature: 40°C
Eluent composition:
Liquid A: acetonitrile Liquid B: distilled water At analysis time 0 minutes, the ratio of liquid A: liquid B was 30:70 (volume ratio, the same applies below), and from analysis time 0 to 25 minutes, the ratio gradually became 100:0.
Flow rate: 0.40 mL/min Detection wavelength: 280 nm

The production and quantification of dialkyl carbonate were carried out by gas chromatography according to the following procedure and conditions.
Apparatus: AGILENT TECHNOLOGIES 7820GC SYSTEM
AGILENT HP-1 30m x 0.25mm 0.25μm
Detection method: FID
Vaporization chamber temperature: 230°C
Detector temperature: 300°C
From 0 to 5 minutes of analysis time, the column temperature was kept at 50°C, from 5 to 30 minutes of analysis time, the column temperature was gradually increased to 280°C, and from 30 to 40 minutes of analysis time, the column temperature was maintained at 280°C.

Example A: First Form
(Example A1)
A separable flask reactor having a thermometer, a dropping funnel, a stirrer, a nitrogen inlet tube, and a cooling tube was charged with 150 parts by mass of Iupilon S-3000R (Mitsubishi Engineering Plastics bisphenol A type polycarbonate resin), 653 parts by mass of epichlorohydrin (12.0 moles per mole of carbonate bonds in polycarbonate), and heated to 100 ° C. to dissolve the polycarbonate. After cooling, 255 parts by mass of isopropanol and 90 parts by mass of water were added, and the temperature was raised to about 40 ° C. under a nitrogen gas atmosphere. Then, 216 parts by mass of 48% by mass aqueous sodium hydroxide solution (sodium hydroxide was supplied so that the amount of carbonate bonds in the polycarbonate was 4.4 moles) was continuously added dropwise while the temperature was raised to 65 ° C., and the reaction was carried out for 120 minutes. Thereafter, 466 parts by mass of water was added, and the water layer was separated from the oil, thereby removing salts produced by the reaction, residual sodium hydroxide, etc. from the resin solution and terminating the reaction.

The reaction solution obtained was gradually heated and the pressure in the system was reduced, and the system was held at 150°C and 5 mmHg for 30 minutes, after which isopropanol and excess epichlorohydrin were completely removed from the system. After that, the system was returned to normal pressure while nitrogen was sealed in, and 300 parts by mass of methyl isobutyl ketone was added to obtain a methyl isobutyl ketone solution of crude resin. 100 parts by mass of water was added to this solution to separate the water layer, and then the water layer removed with 100 parts by mass of water was repeatedly washed with water several times until it became neutral, obtaining a methyl isobutyl ketone solution of epoxy resin. The solution was heated and reduced pressure to distill off methyl isobutyl ketone, and the system was held at 150°C and 5 mmHg for 30 minutes to completely remove methyl isobutyl ketone, obtaining a liquid epoxy resin. The obtained epoxy resin had an epoxy equivalent of 222 g/eq.

(Example A2)
In the same apparatus as in Example A1, 75 parts by mass of Iupilon S-3000R (Mitsubishi Engineering Plastics bisphenol A type polycarbonate resin), 327 parts by mass of epichlorohydrin (12.0 moles per mole of carbonate bonds in polycarbonate) were charged, and the polycarbonate resin was dissolved by heating to 100 ° C. After cooling, 191 parts by mass of propylene glycol monomethyl ether and 52 parts by mass of water were added, and the temperature was raised to about 65 ° C. under a nitrogen gas atmosphere. Then, 123 parts by mass of 48% by mass aqueous sodium hydroxide solution (sodium hydroxide was supplied so that the amount was 5.0 moles per mole of carbonate bonds in polycarbonate) was continuously dropped while raising the temperature to 85 ° C., and the reaction was carried out for 120 minutes. Then, 214 parts by mass of water was added, and the oil-water separated water layer was separated to remove salts generated by the reaction from the resin solution, residual sodium hydroxide, etc., and the reaction was stopped.

The reaction solution obtained was gradually heated and the pressure in the system was reduced, and the system was held at 150°C and 5 mmHg for 30 minutes, after which propylene glycol monomethyl ether and excess epichlorohydrin were completely removed from the system. After that, the system was returned to normal pressure while nitrogen was sealed in the system, and 150 parts by mass of methyl isobutyl ketone was added to obtain a methyl isobutyl ketone solution of crude resin. 17 parts by mass of 48% by mass sodium hydroxide aqueous solution was added to this solution, and the reaction was carried out at 65°C for 60 minutes, after which 100 parts by mass of water was added to separate the water layer, and the water layer removed with 100 parts by mass of water was washed several times until it became neutral, obtaining a methyl isobutyl ketone solution of epoxy resin. The solution was heated and placed under reduced pressure to distill off methyl isobutyl ketone, and the solution was held at 150°C and 5 mmHg for 30 minutes to completely remove methyl isobutyl ketone, obtaining a liquid epoxy resin. The obtained epoxy resin had an epoxy equivalent of 189 g/eq.

(Example A3)
A separable flask reactor equipped with a thermometer, a dropping funnel, a stirrer, a nitrogen inlet tube, and an oil-water separator having a cooling tube was charged with 300 parts by mass of Iupilon S-3000R (bisphenol A type polycarbonate resin manufactured by Mitsubishi Engineering Plastics Corporation) and 833 parts by mass of epichlorohydrin (7.6 mol per mol of carbonate bonds in polycarbonate), and the mixture was heated to 100° C. to dissolve the polycarbonate resin. After cooling to 80°C, the system was decompressed to 550-570 mmHg, and then 390 parts by mass of 48% by mass aqueous sodium hydroxide solution (sodium hydroxide was supplied so that the amount was 4.0 moles per mole of carbonate bonds in the polycarbonate) was continuously added dropwise while maintaining the pressure in the system, while the temperature was raised to 88-92°C, water and epichlorohydrin were azeotroped, the upper layer of water was removed from the azeotropic condensate via an oil-water separator, and the lower layer of epichlorohydrin was circulated in the reaction system for 120 minutes. Thereafter, the circulation of epichlorohydrin refluxed to the oil-water separator was stopped, and the temperature in the system was gradually increased while epichlorohydrin was discharged outside the system, and the pressure in the system was reduced, and the system was held for 30 minutes from the time when 140°C and 5 mmHg were reached, and excess epichlorohydrin was completely removed outside the system.

Then, nitrogen was sealed in the system and the pressure in the system was returned to normal, 500 parts by mass of toluene and 1000 parts by mass of water were added, and the water layer was separated from the oil-water separation, and the salt generated by the reaction and the remaining sodium hydroxide were removed from the resin solution, and a toluene solution of crude resin was obtained. 8 parts by mass of 48% by mass sodium hydroxide aqueous solution was added to this solution, and after reacting at 80°C for 1 hour, 700 parts by mass of water was added to separate the water layer, and then the water layer removed with 700 parts by mass of water was washed several times until it became neutral, and a toluene solution of epoxy resin was obtained. The toluene was distilled off from this solution under heating and reduced pressure, and the toluene was completely removed by holding it at 150°C and 5 mmHg for 30 minutes, and a liquid epoxy resin was obtained. The obtained epoxy resin had an epoxy equivalent of 189 g/eq.

The raw materials used in Examples A1 to A3 and the epoxy equivalents of the resulting epoxy resins are summarized in Table 1.

[Evaluation Results]
As can be seen from the results of Example A above, by carrying out a decomposition reaction using polycarbonate and epihalohydrin as raw materials in the presence of a metal hydroxide, it is possible to directly produce epoxy resins using polycarbonate as a raw material in a continuous manner. In addition, it is expected that waste polycarbonate can be used as a raw material for producing epoxy resins, and furthermore, the production process can be simplified, so that the epoxy resin production method of this embodiment is expected to be an industrially useful method for producing epoxy resins in a short process.

<Example B: Second Form>
[Method of producing tetraphenoxytitanium]
(Reference Example B1)
A 500 mL three-neck flask equipped with a receiver and a distillation tube was charged with 200 parts by mass of phenol and 100 parts by mass of toluene, and the flask was circulated and replaced with nitrogen. The flask was immersed in a 100 ° C. oil bath to obtain a uniform solution. 57 parts by mass of tetraisopropoxytitanium was added thereto. When the internal temperature of the bottom of the flask was maintained at 100 ° C., distillation of the generated isopropyl alcohol began. Then, the internal temperature was gradually raised to 116 ° C., and 80 parts by mass of a distillate, which is a mixture of isopropyl alcohol and toluene, was distilled. 50 parts by mass of hexane was added to the obtained residue, and the mixture was cooled to room temperature and crystallized. The precipitated red crystals were obtained by filtration, and dried in a rotary evaporator equipped with an oil bath at an oil bath temperature of 140 ° C. and a pressure of 50 Torr to obtain 60 parts by mass of tetraphenoxytitanium.

(Example B1)
A separable flask reactor having a thermometer, a dropping funnel, a stirrer, a nitrogen inlet tube, and a cooling tube was charged with 75 parts by mass of 7027J (Mitsubishi Chemical's bisphenol A type polycarbonate resin), 327 parts by mass of epichlorohydrin (12 moles per mole of carbonate bonds in polycarbonate), and heated to 100 ° C. to dissolve the polycarbonate resin, and then cooled to about 40 ° C. under a nitrogen gas atmosphere. Thereafter, a 10% by mass ethanolic potassium hydroxide solution was continuously added dropwise to 65 ° C., which was prepared by dissolving 47 parts by mass of potassium hydroxide (FUJIFILM Wako Pure Chemical Industries, Ltd., special grade, purity 85.0 +%, water content 14%) in 349 parts by mass of ethanol (Nacalai Tesque, special grade, purity 85.0 +%, water content 14%) (2.4 moles per mole of carbonate bonds in polycarbonate), and the reaction was carried out for 120 minutes. The content of water relative to the total amount of the raw materials used was 0.8%. Then, 230 parts by mass of water was added, and the insoluble matter was removed by filtering with filter paper. The water layer obtained by the oil-water separation was separated to remove salts generated by the reaction, residual potassium hydroxide, etc. from the resin solution, and the reaction was terminated.

The reaction liquid obtained was gradually heated and the pressure in the system was reduced, and the temperature was kept at 150°C and 5 mmHg for 30 minutes, and ethanol, excess epichlorohydrin, and diethyl carbonate were completely distilled out of the system. The distillate was 757 parts by mass. A part of the distillate obtained was extracted and analyzed by gas chromatography, which showed that diethyl carbonate was 3% by mass and the recovery rate was 65%. After that, the system was returned to normal pressure while nitrogen was sealed in the system, and 150 parts by mass of methyl isobutyl ketone was added to obtain a methyl isobutyl ketone solution of crude resin. 14 parts by mass of 48% aqueous sodium hydroxide solution was added to this solution, and the reaction was carried out at 65°C for 1 hour, after which 100 parts by mass of water was added to separate the aqueous layer, and then the aqueous layer removed with 100 parts by mass of water was washed several times until it became neutral, and a methyl isobutyl ketone solution of epoxy resin was obtained. The solution was heated and reduced pressure to remove methyl isobutyl ketone, and the temperature was maintained at 150°C and 5 mmHg for 30 minutes to completely remove the methyl isobutyl ketone, yielding a liquid epoxy resin. The resulting epoxy resin had an epoxy equivalent of 184 g/eq.

(Example B2)
A portion of the distillate obtained in Example B1 was extracted and analyzed by gas chromatography. It was found to consist of 44% by mass of ethanol, 3% by mass of diethyl carbonate, and 35% by mass of epichlorohydrin (the remaining component was presumed to be water).
The obtained fraction (750 parts by mass) was placed in a distillation column equipped with a Sulzer Lab Packing (structured packing) rectification column, a distillation tube, a reflux timer, a pressure regulator, a thermometer, a stirrer and an oil bath. First, the internal temperature was raised to 110°C under normal pressure, and ethanol and water were distilled off under total distillation conditions. Next, total reflux operation was performed under normal pressure and 110°C, and the pressure was set to 66 kPa, and the reflux ratio was gradually reduced from 2 while observing the column top temperature and the results of gas chromatography of the fraction, to obtain a fraction mainly composed of epichlorohydrin, and then 15 parts by mass of diethyl carbonate with a purity of 99% by mass or more was obtained as the main fraction.

15 parts by mass of the obtained diethyl carbonate, 100 parts by mass of phenol, and 1 part by mass of tetraphenoxytitanium obtained in Reference Example B1 were placed in a distillation column equipped with a distillation tube that could be kept warm by a ribbon heater, a pressure regulator, a thermometer, a stirrer, and an oil bath. The internal temperature was then raised to 100°C, and the ethanol was distilled off. Next, the internal temperature was raised from 100°C to 200°C, and the pressure was gradually lowered from normal pressure to 30 kPa, thereby distilling off the diethyl carbonate and phenol to obtain a bottom residue. After the pressure was restored, a 10% by mass aqueous solution of sodium hydroxide was added to the bottom residue, and the pressure was gradually lowered from normal pressure to 1 kPa to distill off the water and ethylphenyl carbonate, and 3 parts by mass of diphenyl carbonate was distilled off as the main fraction.

(Example B3)
In a 45 mL glass reaction vessel equipped with a stirrer and a distillation tube, 10 parts by mass of bisphenol A (manufactured by Mitsubishi Chemical Group), 10 parts by mass of the diphenyl carbonate obtained in Example B2, and 18×10 ⁻⁶ parts by mass of a 400 ppm by mass aqueous cesium carbonate solution were placed. The glass reaction vessel was depressurized to about 100 Pa, and then the operation of returning the pressure to atmospheric pressure with nitrogen was repeated three times to replace the inside of the reaction vessel with nitrogen. Thereafter, the reaction vessel was immersed in an oil bath at 220° C. to dissolve the contents.
The stirrer was rotated at 100 revolutions per minute, and the pressure in the reaction vessel was reduced from 101.3 kPa to 13.3 kPa absolute pressure over a period of 40 minutes while distilling off phenol produced as a by-product in the oligomerization reaction of bisphenol A and diphenyl carbonate in the reaction vessel.

The pressure inside the reaction vessel was then maintained at 13.3 kPa, and the ester exchange reaction was carried out for 80 minutes while further distilling off phenol.
Thereafter, the temperature outside the reaction vessel was raised to 290° C., and the pressure inside the reaction vessel was reduced from 13.3 kPa to 399 Pa absolute over a period of 40 minutes, and the distilled phenol was removed outside the system.
Thereafter, the absolute pressure of the reaction vessel was reduced to 30 Pa, and the polycondensation reaction was carried out. When the agitator of the reaction vessel reached a predetermined stirring power, the polycondensation reaction was terminated. The time from raising the temperature to 290° C. to completing the polymerization was 120 minutes.
Next, the reaction vessel was restored to an absolute pressure of 101.3 kPa with nitrogen, and then the pressure was increased to a gauge pressure of 0.2 MPa, and the polycarbonate resin was extracted from the reaction vessel to obtain a polycarbonate resin.

The raw materials used in Example B1, the epoxy equivalent of the resulting epoxy resin, and the dialkyl carbonate recovery rate are summarized in Table 2.

<Example C: Third Form>
In the same manner as in Reference Example B1 of Example B, 60 parts by mass of tetraphenoxytitanium was obtained.

(Example C1)
A separable flask reactor having a thermometer, a dropping funnel, a stirrer, a nitrogen inlet tube, and a cooling tube was charged with 75 parts by mass of 7027J (Mitsubishi Chemical's bisphenol A type polycarbonate resin), 327 parts by mass of epichlorohydrin (12 moles per mole of carbonate bonds in polycarbonate), and heated to 100 ° C. to dissolve the polycarbonate resin, and then cooled to about 40 ° C. under a nitrogen gas atmosphere. Then, 136 parts by mass of 28% sodium methoxide methanol solution (sodium methoxide was supplied so that the amount of sodium methoxide was 2.4 moles per mole of carbonate bonds in polycarbonate) was continuously added dropwise while raising the temperature to 65 ° C., and the reaction was carried out for 120 minutes. Then, 230 parts by mass of water was added, and the water layer separated from the oil and water was separated to remove salts generated by the reaction from the resin solution, residual sodium methoxide, etc., and the reaction was stopped.

The reaction liquid obtained was gradually heated and the pressure in the system was reduced, and the system was held at 150°C and 5 mmHg for 30 minutes, and methanol, excess epichlorohydrin, and dimethyl carbonate were completely distilled out of the system. The distillate was 287 parts by mass. A part of the distillate obtained was extracted and measured by gas chromatography, and the dimethyl carbonate was 5% by mass and the recovery rate was 54%. After that, the system was returned to normal pressure while nitrogen was sealed in the system, and 150 parts by mass of methyl isobutyl ketone was added to obtain a methyl isobutyl ketone solution of crude resin. 100 parts by mass of water was added to this solution to separate the water layer, and then the water layer removed with 100 parts by mass of water was washed several times until it became neutral, and a methyl isobutyl ketone solution of epoxy resin was obtained. The solution was heated and reduced pressure to distill off methyl isobutyl ketone, and the solution was held at 150°C and 5 mmHg for 30 minutes to completely remove methyl isobutyl ketone, and a liquid epoxy resin was obtained. The epoxy resin obtained had an epoxy equivalent of 198 g/eq.

(Example C2)
A part of the distillate obtained in Example C1 was extracted and analyzed by gas chromatography, which revealed that it was 10% by mass of methanol, 5% by mass of dimethyl carbonate, and 69% by mass of epichlorohydrin (the remaining components were estimated to be water). In order to remove water from the distillate, 287 parts by mass of the distillate and 100 parts by mass of molecular sieves 3A (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were fed into an eggplant-shaped flask and allowed to stand overnight. Then, 205 parts by mass of the supernatant were decanted and placed in a distillation apparatus equipped with a thermometer, a distillation tube, a stirrer, an oil bath, and a pressure regulator. The pressure was gradually reduced from normal pressure to 20 kPa to distill off a mixture of dimethyl carbonate and methanol, and 30 parts by mass of fraction A was obtained.

30 parts by mass of the obtained fraction A and 100 parts by mass of anisole were placed in a distillation apparatus equipped with a thermometer, a distillation tube, a stirrer, an oil bath, and a pressure regulator. The internal temperature was set to 80° C., and 20 parts by mass of fraction B, mainly composed of methanol, was distilled off to obtain 110 parts by mass of bottom residue. The bottom residue was extracted and analyzed by gas chromatography, revealing that it contained 8% by mass (110 parts by mass × 8% by mass = 9 parts by mass) of dimethyl carbonate.
To 110 parts by mass of the resulting bottoms, 100 parts by mass of phenol and 1 part by mass of tetraphenoxytitanium obtained in Reference Example B1 were added. Thereafter, the internal temperature was increased to 100° C., and methanol was distilled off. Next, the internal temperature was increased from 100° C. to 200° C., and the pressure was gradually decreased from normal pressure to 10 kPa, whereby phenol and dimethyl carbonate were distilled off, and then 0.5 parts by mass of diphenyl carbonate was distilled off.

(Example C3)
In a 45 mL glass reaction vessel equipped with a stirrer and a distillation tube, 10 parts by mass of bisphenol A (manufactured by Mitsubishi Chemical Group), 10 parts by mass of the diphenyl carbonate obtained in Example C2, and 18×10 ⁻⁶ parts by mass of a 400 ppm by mass aqueous cesium carbonate solution were placed. The glass reaction vessel was depressurized to about 100 Pa, and then the operation of returning the pressure to atmospheric pressure with nitrogen was repeated three times to replace the inside of the reaction vessel with nitrogen. Thereafter, the reaction vessel was immersed in an oil bath at 220° C. to dissolve the contents.
The stirrer was rotated at 100 revolutions per minute, and the pressure in the reaction vessel was reduced from 101.3 kPa to 13.3 kPa absolute pressure over a period of 40 minutes while distilling off phenol produced as a by-product in the oligomerization reaction of bisphenol A and diphenyl carbonate in the reaction vessel.

The pressure inside the reaction vessel was then maintained at 13.3 kPa, and the ester exchange reaction was carried out for 80 minutes while further distilling off phenol.
Thereafter, the temperature outside the reaction vessel was raised to 290° C., and the pressure inside the reaction vessel was reduced from 13.3 kPa to 399 Pa in absolute pressure over 40 minutes, and the distilled phenol was removed from the system. Thereafter, the absolute pressure inside the reaction vessel was reduced to 30 Pa, and the polycondensation reaction was carried out. When the agitator in the reaction vessel reached a predetermined stirring power, the polycondensation reaction was terminated. The time from raising the temperature to 290° C. to completing the polymerization was 120 minutes.
Next, the reaction vessel was restored to an absolute pressure of 101.3 kPa with nitrogen, and then the pressure was increased to a gauge pressure of 0.2 MPa, and the polycarbonate resin was extracted from the reaction vessel to obtain a polycarbonate resin.

The raw materials used in Example C1, the epoxy equivalent of the resulting epoxy resin, and the dialkyl carbonate recovery rate are summarized in Table 3.

<Example D: Fourth Form>
(Example D1)
A thermometer, a dropping funnel, a stirrer, a nitrogen inlet tube, and a separable flask reactor having a cooling tube were charged with 93 parts by mass of Pyrofil pellets PC-C-20 (Mitsubishi Chemical carbon fiber-containing BPA type polycarbonate fiber content 20 wt%) and 327 parts by mass of epichlorohydrin (epichlorohydrin was supplied so that the amount of epichlorohydrin was 12 moles per mole of carbonate bonds in the polycarbonate), and the mixture was heated to 100 ° C. to dissolve the polycarbonate resin, and then cooled to about 40 ° C. under a nitrogen gas atmosphere. Then, 136 parts by mass of 28% sodium methoxide methanol solution (sodium methoxide was supplied so that the amount of sodium methoxide was 2.4 moles per mole of carbonate bonds in the polycarbonate) was continuously added dropwise while the temperature was raised to 65 ° C., and the reaction was carried out for 120 minutes. Thereafter, 230 parts by mass of water was added, and the water layer was separated from the oil, thereby removing salts produced by the reaction, residual sodium methoxide, etc. from the resin solution and terminating the reaction.

The reaction solution obtained was gradually heated and the pressure in the system was reduced, and the system was held at 150°C and 5 mmHg for 30 minutes, during which methanol, excess epichlorohydrin, and dimethyl carbonate were completely removed from the system. After that, nitrogen was sealed in the system and the system was returned to normal pressure, and 233 parts by mass of toluene and 500 parts by mass of water were added, and the carbon fiber was separated by filtration. The oil layer obtained by separating and removing the aqueous layer of the filtrate was then added with 100 parts by mass of water, and the separated and removed aqueous layer was repeatedly washed with water several times until it became neutral, to obtain a toluene solution of epoxy resin. The toluene was removed from this solution by heating and reducing the pressure, and the system was held at 150°C and 5 mmHg for 30 minutes to completely remove the toluene, to obtain a liquid epoxy resin. The epoxy resin obtained had an epoxy equivalent of 261 g/eq. The carbon fiber separated by filtration was washed with water and acetone to remove any attached resin or inorganic salts, and then dried at 120°C for 2 hours to obtain 17.5 parts by mass of recycled carbon fiber. The recycled fiber recovery rate was 94%.

(Example D2)
8 parts by mass of the epoxy resin produced in Example D1, 2 parts by mass of the recycled carbon fiber produced in Example D1, and 3 parts by mass of jER Cure ST14 (amine curing agent manufactured by Mitsubishi Chemical) were mixed to obtain a resin composition. The obtained composition was poured into a mold and heated at 100°C for 2 hours and then at 170°C for 1 hour to obtain a recycled carbon fiber reinforced plastic.

The raw materials used in Example D1, the epoxy equivalent of the resulting epoxy resin, and the recycled fiber recovery rate are summarized in Table 4.

Claims (15)

A method for producing an epoxy resin, comprising a reaction step in which a polycarbonate resin is decomposed in epihalohydrin to obtain an epoxy resin. The method for producing an epoxy resin according to claim 1, wherein the decomposition reaction is carried out in the presence of a metal hydroxide. The method for producing an epoxy resin according to claim 2, wherein the decomposition reaction is carried out in the presence of an alcohol-based compound and co-produces a dialkyl carbonate along with the epoxy resin. The method for producing an epoxy resin according to claim 3, wherein the water content in the decomposition reaction is 5 mass% or less relative to the total amount of raw materials. The method for producing an epoxy resin according to claim 1, wherein the decomposition reaction is carried out in the presence of a metal alkoxide, and a dialkyl carbonate is co-produced along with the epoxy resin. The method for producing an epoxy resin according to claim 1, wherein the polycarbonate resin is a fiber-containing polycarbonate resin, and recycled fibers are obtained together with the epoxy resin. The method for producing an epoxy resin according to claim 6, wherein the reaction process includes a separation process for separating the fibers and the solution into solid and liquid. The method for producing an epoxy resin according to claim 1, wherein the polycarbonate is an aromatic polycarbonate. The method for producing an epoxy resin according to claim 1, wherein 1.0 to 20.0 moles of the epihalohydrin are used per mole of carbonate bond in the polycarbonate. A method for producing an epoxy resin composition, comprising blending a curing agent with the epoxy resin obtained by the method according to claim 1. A method for producing a cured product, comprising curing an epoxy resin composition obtained by the method according to claim 10. A method for producing a fiber-containing epoxy resin composition, comprising the step of mixing the epoxy resin obtained by the method according to claim 6 with recycled fibers. A method for producing a fiber-containing epoxy resin cured product, comprising a step of curing the fiber-containing epoxy resin composition obtained by the method according to claim 12. A method for producing diphenyl carbonate, comprising the step of reacting the dialkyl carbonate obtained by the method described in claim 3 or 5 with phenol. A method for producing a polycarbonate resin, comprising: a step of polymerizing the diphenyl carbonate obtained by the production method according to claim 14 through an ester exchange reaction.