JP2018177970A - Method and composition for depolymerization of epoxy resin cured article using transition metal salt or transition metal oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a depolymerization method of an epoxy resin capable of depolymerizing an epoxy resin cured article extremely simply at high speed under a condition of 200°C or lower, preferably 100°C or lower, and capable of reducing process cost and required energy, and a composition using the same.SOLUTION: There is provided a depolymerization method of an epoxy cured article, in which a depolymerization of an epoxy resin can be conducted extremely easily at high speed under a condition of 200°C or lower, preferably 100°C or lower by using a composition containing transition metal salt containing transition metal element (metal element belonging to 3 to 12 group in the periodic table) or transition metal oxide and a reaction solvent, and depolymerizing and decomposing an epoxy resin cured article as an oxidation reaction via the transition metal element is generated by the reaction solvent, and process cost and required energy can be reduced. There is provided a composition for depolymerization of the epoxy resin cured article, in which dielectric constant of the reaction solvent is 65 or more, preferably 70 or more, more preferably 75 or more, especially preferably 80 or more, and the reaction solvent is based on HO, preferably water.SELECTED DRAWING: None

Description

  The present specification relates to a depolymerization method of epoxy resin cured product using transition metal salt or transition metal oxide, and composition therefor, specifically, transition metal salt or transition metal oxide containing transition metal The present invention relates to a method for depolymerizing a cured epoxy resin product, a composition used therefor, a method for separating a filler from the cured epoxy resin product, and a filler obtained thereby.

  The epoxy resin is a thermosetting resin comprising a network polymer formed by the ring opening of an epoxy group which is generated when an epoxy monomer having two or more epoxy groups in the molecule is mixed with a curing agent. Epoxy resin is highly resistant to chemical components, has excellent durability, and has a low volumetric shrinkage rate during curing, so it is used as an essential high-performance material in all industrial fields such as adhesives, paints, electronics, electricity, civil engineering and construction It is done.

  In recent years, epoxy resin has been used in various fields such as aerospace field, information communication technology field, new energy field, etc. in combination with various filler materials in composite material field which has become an important matter. The demand is increasing worldwide. In particular, carbon fiber reinforced plastic (CFRP) mixed with carbon fiber is widely used as a core material in the automotive field and the aerospace field because it is lightweight and exhibits excellent physical properties and durability. . Epoxy resins are also widely used to make higher performance materials by mixing with other polymeric resin materials.

  Epoxy resins form a three-dimensional network cross-linked structure after curing, which has very strong properties in chemicals. While this has the advantage of imparting excellent durability and corrosion resistance to the material, it also has the disadvantage that it is very difficult to process and recycle the used material.

  As a result, most of the epoxy resin cured products are now treated in a backfill system, which is economically costly and may cause serious environmental pollution.

  In recent years, as the use amount of composite material of epoxy resin and filler gradually increases, in order to effectively separate and take out the filler material relatively expensive than the epoxy resin, it relates to a technology for selectively degrading the epoxy resin Research is actively progressing.

  Currently, the most commonly used method in the decomposition of epoxy resins and the separation of filler materials is pyrolysis. For example, in the case of a carbon fiber reinforced plastic (CFRP) using carbon fiber as a filler material, the annual annual sales under the initiative of Japanese companies such as Toray, Teijin, Mitsubishi, etc. Tons are treated and recycled by pyrolysis. However, in order to separate carbon fibers by a thermal decomposition step, a pretreatment step of mechanically crushing CFRP in advance is required, but carbon fibers are also crushed in the process of crushing CFRP to a size of several mm. Possibly, as a result, the problem that the short length of the recycled carbon fiber adversely affects the properties of the carbon fiber has arisen. Moreover, the thermal decomposition process requires a high temperature of 500 ° C. or more above all, and such high temperature causes a problem that human harmful substances such as dioxins are generated by the combustion of organic compounds.

Therefore, various chemical degradation methods have been investigated to effectively degrade epoxy resins at lower temperatures.
For example, when the epoxy resin is decomposed under supercritical or quasi-critical fluid, the epoxy resin cured product can be effectively treated at a temperature lower than the thermal decomposition process temperature of about 250 to 400 ° C. Using such a method has the advantage that the property degradation of the filler material to be recovered is relatively less than the property degradation due to the thermal decomposition method.

  However, according to the research results of the present inventors, the method still requires high temperature and high pressure of 10 atmospheres or more, which requires special process equipment that can withstand such conditions. Is not high.

  On the other hand, research has also been advanced to be able to decompose the epoxy resin under more general and mild process conditions, for example, multifunctional epoxy resin or acid anhydride type curing agent, or aromatic diamine type curing agent However, it is not possible to dissolve various epoxy resin cured products, such as epoxy resin cured products, which are relatively difficult to decompose, and the reaction time is long and much reaction energy is required. In addition, problems such as using many organic solvents which are harmful to human body as main solvents of reaction system are still included.

  In particular, a large number of prior art techniques are known in which organic solvents are used as the main solvent for the decomposition of epoxy resins.

  For example, it has been disclosed that an electrolyte containing an alkali group metal is added, and an organic solvent is added to depolymerize a waste printed circuit board (Patent Document 2).

  Moreover, after crushing and acid treatment of an epoxy resin, the technique of processing with an organic solvent and an oxidizing agent in the sealed reaction container is also disclosed (patent document 3).

  Furthermore, decomposition of epoxy resin with hydrogen peroxide and acetone is disclosed (Non-patent Document 2).

  Further, a technology for treating an epoxy resin composite material with a treatment liquid containing an alkali metal compound from which water has been removed and an organic solvent is disclosed (Patent Document 4).

  Further, it is disclosed that an epoxy resin prepolymer is brought into contact with an aprotic organic solvent having a dipole moment of 3.0 or more to dissolve the epoxy resin prepolymer in the solvent (Patent Document 5).

  In addition, it is disclosed that an organic solvent containing furan-2-carbaldehyde is used as an extraction solvent or cracking solvent for separating carbon fibers from CFRP (Patent Document 6).

  These techniques describe that the epoxy can be decomposed with organic solvents under mild conditions at relatively low temperatures.

  However, according to the research results of the present inventors, these techniques are organic solvent reaction systems that use the organic solvent itself as the main means for dissolving the epoxy resin, and the organic solvent itself acts as a new pollution source. From that, it has an essential limit that the problem of contamination with organic solvents has to be solved. In addition, there is the problem of applicability that is unsuitable for application to epoxy resins that are difficult to be decomposed, and a lot of energy is required for the reaction, and the reaction efficiency and the like are still not satisfactory.

Korean Patent Application Publication No. 2002-66046 Korean Patent Application Publication No. 2011-0113428 Chinese Patent No. 102391543 Japanese Patent Application Publication No. 2005-255899 Japanese Patent Application Publication No. 2013-107973 U.S. Patent Application Publication No. 2014-0023581

Mater. Res. Bull. 2004, 39, 1549 Green Chem. , 2012, 14, 3260

  In an exemplary embodiment of the present invention, in one aspect, the epoxy resin cured product can be depolymerized very easily and at high speed under conditions of, for example, 200 ° C. or less, preferably 100 ° C. or less, and the process cost and It is an object of the present invention to provide a method for depolymerizing an epoxy resin capable of reducing energy consumption and a composition used therefor.

  In an exemplary embodiment of the present invention, in another aspect, an organic solvent reaction system, which is a reaction system using an organic solvent as a main solvent, can be replaced, whereby the organic solvent acts as a new contamination source. It is an object of the present invention to provide a method for depolymerizing an epoxy resin capable of minimizing environmental pollution and pollution by solving the problem of pollution by

  In an exemplary embodiment of the present invention, in another aspect, the depolymerization reaction efficiency of a cured epoxy resin product can be enhanced without using an organic solvent reaction system that is a reaction system using an organic solvent as a main solvent. An object of the present invention is to provide a method for depolymerizing an epoxy resin and a composition used therefor.

  In an exemplary embodiment of the present invention, there is provided, in another aspect, an epoxy resin depolymerization method and a composition used therefor, in which relatively hard to be decomposed epoxy resin cured products can be easily decomposed. To that purpose.

  In an exemplary embodiment of the present invention, and in another aspect, from an epoxy resin composite from which a recycled filler having excellent properties can be obtained by suppressing deterioration in the properties of the filler recovered after decomposition of the cured epoxy resin. It is an object of the present invention to provide a method of recovering a filler, and a filler thus obtained.

  In an exemplary embodiment of the present invention, a composition for depolymerizing epoxy resin, comprising: a transition metal salt or transition metal oxide containing a transition metal element; and a reaction solvent; Provide the goods. The reaction solvent may be a transition metal-mediated oxidation reaction of the chemical bond of the cured epoxy resin, such as a carbon-carbon bond oxidation reaction. Also, the transition metal salt may be capable of being dissociated by a reaction solvent.

  An exemplary embodiment of the present invention is a method for depolymerizing a cured epoxy resin, which comprises depolymerizing a cured epoxy resin using the composition for depolymerizing the cured epoxy resin. Provided is a method for depolymerizing a cured product.

  In an exemplary embodiment of the present invention, there is provided a method of separating a filler from a cured epoxy resin, which comprises depolymerizing a cured epoxy resin using the composition for depolymerizing the cured epoxy; Obtaining a filler from the product; and a method of separating the filler from the epoxy resin cured product, and a filler separated thereby.

  According to an exemplary embodiment of the present invention, depolymerization of an epoxy resin can be very easily and rapidly processed under conditions of, for example, 200 ° C. or less, preferably 100 ° C. or less, and the process cost and required energy Can be reduced. In addition, it is possible to replace a reaction system using an organic solvent as a main solvent, thereby minimizing environmental pollution and pollution by solving the contamination problem caused by the organic solvent acting as a new pollution source. In addition, the depolymerization reaction efficiency can be enhanced without using a reaction system containing an organic solvent as a main solvent. Furthermore, epoxy resin cured products that are relatively difficult to decompose can be easily decomposed. In addition, it is possible to obtain a recycled filler having excellent properties by suppressing the decrease in the properties of the filler recovered after the decomposition of the epoxy resin composite.

It is an exemplary reaction formula 1 showing oxidation of a chemical bond such as a carbon-carbon bond, for example, of an epoxy resin cured product. It is the photograph which image | photographed CFRP before depolymerization in Example 1 of this invention. It is the photograph which image | photographed the carbon fiber collect | recovered after depolymerization in Example 1 of this invention. It is the result of having measured the pH of the potassium permanganate aqueous solution of the reaction system in Example 1 of this invention, and the nitric acid aqueous solution of the reaction system in the comparative example 3, respectively. It is the photography image | photographed after filtration and isolation | separation of the manganese dioxide produced | generated by depolymerization reaction in Example 1 of this invention. Tensile strength for carbon fibers used for CFRP (designated as raw material carbon fibers, denoted as V-CF) in Example 1 of the present invention and recovered carbon fibers (designated as R-CF) as a result of Example 1 It is a graph which compares the result obtained from measurement. The results of FT-IR analysis of CFRP before depolymerization in Example 1 of the present invention, and the mixture of solids obtained by extracting and drying the product in the form of an aqueous solution remaining after filtering carbon fibers and manganese dioxide It is a FT-IR analysis result. It is the result which showed the result of Tables 4-6 in this experiment 2 by the decomposition rate of the epoxy resin by the dielectric constant of a reaction system. It is a graph which shows the X-ray-photoelectron-spectroscopy (XPS) result of the carbon fiber (displayed as CF) used for CFRP in this experiment 3. FIG. In this experiment 3 is a graph showing the X-ray photoelectron spectroscopy (XPS) result of a carbon fiber recovered after the depolymerization (R-CF and display) using KMnO _4. In this experiment 3 the results of XPS elemental content of carbon fiber recovered after the depolymerization using carbon fiber (CF display) and KMnO ₄ used for the CFRP.

Definition of Terms In the present specification, an epoxy resin cured product means any composite material including a cured epoxy resin or a cured epoxy resin. In addition, the epoxy resin cured product is defined not only to be completely cured but also to include a partially cured intermediate substance (so-called epoxy resin prepolymer) which is generated during the curing reaction.

  The composite material may contain various fillers and / or various polymer resins. The cured epoxy resin is produced by the curing reaction of an epoxy compound having two or more epoxy groups in the molecule and a curing agent. The types of epoxy resin and curing agent are not particularly limited. The epoxy resin may, for example, comprise a multifunctional epoxy resin. In addition, the curing agent includes, for example, those having an aromatic group or an aliphatic group. For example, it may have one or more groups selected from an amine group, an acid anhydride group, an imidazole group, and a mercaptan group in the molecule.

  In the present specification, a transition metal-mediated oxidation reaction is a chemical bond of an organic compound, for example, a cured epoxy resin, for example, a part of electrons constituting a carbon-carbon bond due to a change in the oxidation number of the transition metal. It means an oxidation reaction which transfers to a transition metal to cause oxidation.

  In the present specification, the filler means a filling material which constitutes an epoxy composite together with a cured epoxy resin.

  In the present specification, the polymer resin means a polymer resin constituting an epoxy resin complex in addition to the epoxy resin.

  In the present specification, the reaction solvent is not limited to a specific phase. Therefore, it may be mainly in the liquid phase but may contain the gas phase. It may also contain a supercritical phase.

In the present specification, H ₂ O is mainly liquid phase water, but is not limited to liquid phase and may include gas phase. It may also contain a supercritical phase.

  In the present specification, the aqueous solution is in the liquid phase unless it is particularly indicated that it is in the gaseous or supercritical state. Also, unless it is indicated that other solvents have been mixed, it is the solvent of water alone.

  In the present specification, the organic solvent reaction system means a reaction system using an organic solvent as a main solvent for the decomposition reaction of the cured epoxy resin.

In the present specification, the H ₂ O reaction system means a reaction system using H ₂ O as a main solvent for the decomposition reaction of the epoxy resin cured product. This is in contrast to organic solvent reaction systems, where H ₂ O-based reaction solvents are used during the depolymerization reaction. Although this H ₂ O-based reaction solvent may contain other solvents in addition to H ₂ O (that is, it can be applied as a mixed solvent), the dielectric constant can be obtained using this mixed solvent as well. Should be 65 or more, or preferably 70 or more, or 75 or more, or 80 or more. A particularly preferred example is one in which the H ₂ O-based reaction solvent consists of H ₂ O alone (the dielectric constant of water is about 80.2).

  In the present specification, the depolymerization time means the depolymerization reaction time required to completely decompose the epoxy resin cured product subjected to the depolymerization reaction. Here, completely decomposed means that substantially no cured product (solid product) of the epoxy resin is present (the epoxy resin residual ratio is 5% or less).

The decomposition rate (%) of the epoxy resin in the cured epoxy resin can be determined as follows. That is,
Decomposition rate (%) = [(Epoxy resin content in epoxy resin cured product-epoxy resin residual amount after decomposition) / (Epoxy resin content in epoxy resin composite material)] × 100
In addition, the epoxy resin residual rate is 100% -degraded rate (%).

  In the present specification, an epoxy resin cured product that is relatively difficult to decompose means an epoxy resin cured product that uses an epoxy resin monomer and / or a curing agent that is relatively difficult to decompose. For example, the polycyclic novolak resin is an epoxy resin monomer that is relatively difficult to be decomposed as compared to BPA. Also, for example, aromatic curing agents and acid anhydride curing agents are curing agents that are relatively difficult to decompose as compared to aliphatic curing agents.

  In the present specification, the dielectric constant may be measured using a liquid dielectric constant meter.

Description of a illustrative embodiment will be described in detail for the exemplary embodiment of the present invention.
In an exemplary embodiment of the present invention, a composition for depolymerizing epoxy resin, which is a transition metal salt or transition metal oxide containing a transition metal element (a metal element belonging to Groups 3 to 12 in the periodic table) And a reaction solvent containing composition for depolymerizing a cured epoxy resin, and a method for depolymerizing the cured epoxy resin with the composition.

Surprisingly, the epoxy resin cured product is extremely fast at a composition in which the specific compound and a predetermined reaction solvent (in particular, H ₂ O-based reaction solvent) are combined without using an organic solvent-based reaction system. And, it has become clear by the present inventors that the depolymerization can be easily carried out.

  In order to depolymerize the epoxy resin cured product with less energy under mild conditions of low temperature and to increase the reaction efficiency, it is considered important to select the reaction solvent and the specific compound to be used with the reaction solvent. Moreover, although mentioned later, in order to raise the depolymerization efficiency of the epoxy resin hardened | cured material of the said compound, it is thought that it is important to adjust the dielectric constant of a reaction solvent to more than predetermined value.

  During depolymerization according to an exemplary embodiment of the present invention, it is believed that an oxidation reaction mediated by a transition metal element occurs in the reaction solvent, and such an oxidation reaction constitutes an epoxy resin cured product, for example, It is believed that chemical bonds such as carbon-carbon bonds are broken to depolymerize the cured epoxy resin. Moreover, in order to perform such oxidation reaction with low energy, the dielectric constant of the reaction solvent needs to be adjusted to a predetermined value or more.

  Thus, in an exemplary embodiment of the present invention, the dielectric constant of the reaction solvent should be at least 65, or at least 70, or at least 75, or at least 80 in order to enhance the reaction efficiency.

In exemplary embodiments, such reaction solvent is preferably a H ₂ O-based reaction solvent. In depolymerizing a cured epoxy resin using a transition metal salt containing transition metal or a composition containing transition metal oxide, the dielectric constant of the H ₂ O-based reaction solvent used together is the depolymerization reaction of the cured epoxy resin. Affect the efficiency.

The reason is that, unlike organic solvents in organic solvent reaction systems, H ₂ O-based reaction solvents promote dissolution and / or ion dissociation of the transition metal salt or transition metal oxide, and an epoxy resin mediated by a transition metal element It is believed that it is involved in the oxidation reaction of a chemical bond such as a carbon-carbon bond in the cured product, and as a result, participates in the epoxy resin depolymerization reaction efficiency.

In an exemplary embodiment, the dielectric constant of the H ₂ O-based reaction solvent should be at least 65 or more, or 70 or more, or 75 or more, or 80 or more. A particularly preferred example is one in which the H ₂ O-based reaction solvent consists of H ₂ O alone (the dielectric constant of water is about 80.2) and the H ₂ O-based reaction solvent consists of H ₂ O alone The decomposition efficiency of the cured epoxy resin is dramatically increased (see Experimental Example 2 described later).

  Unlike this, in the above-mentioned prior art organic solvent-based reaction system according to the prior art, the cured epoxy resin is directly dissolved using an organic solvent as a main solvent.

  However, the organic solvent can not contribute to the depolymerization of the epoxy resin cured product because the solubility and the degree of ion dissociation are extremely low even when the transition metal salt or transition metal oxide is added. For example, in the case of NMP, the transition metal salt or the transition metal oxide is difficult to dissolve at a dielectric constant of 32.

  In this regard, the present inventors examined the decomposition efficiency of the epoxy resin cured product by the dielectric constant. As a result, for example, the transition metal salt having an ionic bond shows a difference in ion dissociation and reactivity between water and an organic solvent, resulting in a difference in the decomposition efficiency of the cured epoxy resin.

  The reason may be the difference in the solubility of the transition metal salt or transition metal oxide and / or the difference in the oxidation reaction between water and the organic solvent.

  First, in the case of the difference in solubility, the difference in polarity of the water and the organic solvent (that is, the dielectric constant) causes, for example, a difference in the solubility of the transition metal salt which is an ion binding substance. This is because the ion can not be dissociated unless the binding strength between the dipole and the ion of the solvent is larger than the ion-ion lattice energy of the ion binding substance.

  On the other hand, the transition metal salt or the transition metal oxide is an organic compound, that is, in the embodiment of the present invention, the epoxy resin cured product is oxidized while taking electrons from a chemical bond such as carbon-carbon bond at the same time as transition. The metal itself causes a reduction reaction to occur. In detail, different from alkali metal of oxidation number + 1, alkaline earth metal of oxidation number + 2, transition metal can have two or more oxidation forms (oxidation number), and such two or more kinds of An oxidation reaction occurs as the oxidation form changes during the reaction (ie, the reduction of the oxidation number). For example, in the case of manganese in the transition metal salt potassium permanganate (see the reaction formula 1 in FIG. 1), the oxidation number of +7 (potassium permanganate), the oxidation number of +6 (potassium manganate), oxidation of +4 Epoxy resin curing is an organic compound because it has three oxidation forms of number (manganese dioxide), and the relatively unstable +7 oxidation form changes to a stable +4 oxidation form during the reaction For example, an oxidation reaction in the form of taking electrons from a chemical bond such as a carbon-carbon bond will occur.

  This is different from, for example, the mechanism by which the anion in the peroxide form causes an oxidation reaction, such as NaOCl. In addition, since the method using potassium phosphate or the like is a transesterification reaction using a base, not an oxidation reaction, there is a difference from the mechanism of the embodiment of the present invention.

  In an exemplary embodiment of the present invention, the transition metal salt composition in the form of a transition metal oxide or salt is easily dissolved, so that dissociation of the metal is likely to occur and the oxidation reaction can be smoothly performed. And a solvent having a high dielectric constant equal to or higher than a predetermined value as described later.

Based on the above points, a solvent having a high dielectric constant, preferably a H ₂ O-based solvent, is used so that the transition metal salt or transition metal oxide can be effectively dissolved and oxidation reaction can be promoted. Is necessary for depolymerization. When an organic solvent is used, contamination with the organic solvent and a problem of recycling of the organic solvent occur, so from the environmental point of view, it is preferable to use a H ₂ O-based solvent, and in particular, it consists of H ₂ O alone. It is most preferred to use a solvent (100% by weight or 100% by volume of H ₂ O).

  As described above, the depolymerization product (such as carbon fiber) produced by the oxidation reaction has an OH group. As a result, in an exemplary embodiment of the present invention, a depolymerization product of an epoxy resin cured product containing an OH group is provided as a depolymerization product of an epoxy resin cured product. As a reference, in Experiment 1 to be described later, FT-IR analysis results of the depolymerization product in which such an OH group is formed are shown, and from the analysis results, OH is obtained by depolymerization according to an exemplary embodiment of the present invention. It can be seen that many groups were generated.

  When depolymerizing a cured epoxy resin using the composition for depolymerizing a cured epoxy resin as described above, the cured epoxy resin which has reached the end of its life is different from the conventional one, for example, 200 ° C. or less, preferably 100 It can be processed very easily and at high speed with less energy under mild conditions of less than ° C. This indicates that the reaction temperature has been greatly reduced as compared to the conventional thermal decomposition method (about 200 to 400 ° C.).

Furthermore, when the reaction solvent and the compound are combined, for example, when the dielectric constant is low by using an organic solvent as in Comparative Example 1 (not dissolved) in which potassium permanganate aqueous solution and acetone are mixed, nitric acid aqueous solution It can be seen that the reaction efficiency is remarkably high as compared with Comparative Example 2 (reaction time 12 hours) using. Furthermore, unlike the conventional organic solvent-based reaction system technology, the use of an H ₂ O-based reaction system eliminates the use of an organic solvent harmful to the human body, which is environmentally advantageous.

  On the other hand, in an exemplary embodiment of the present invention, the filler material contained in the cured epoxy resin can be easily separated and recycled by performing the above-mentioned treatment. The filler thus obtained can suppress the deterioration of the properties of the filler despite the decomposition process, which is very advantageous for recycling.

In an exemplary embodiment, the transition metal salt or transition metal oxide containing the transition metal element is, for example, KMnO ₄ , MnO ₂ , K ₂ MnO ₄ , MnSO ₄ , CrO ₃ , Na ₂ Cr ₂ O ₇ , K ₂ Cr ₂ O ₇ , ZnCr ₂ O ₇ , H ₂ CrO ₄ , Pyridinium Chlorochromate (pyridinium chlorochromate), Pyridinium Dichromate (pyridinium dichromate), V ₂ O ₅ , RuCl ₃ , RuO ₂ , Tetrapropylammonium Perruthenate ruthenium tetrapropyl _{ammonium), MoO 3, K 3 [} Fe (CN) 6], FeCl 3, Fe (NO 3) 3 nonahydrate ( _{nonahydrate),} MeReO 3, CuCl, Cu _{ClO 4) 2, Cu (HCO} 2) 2 Ni (HCO 2) 2, Cu (OAc) 2, OsO 4, or and the like _{(NH 4) 2 Ce (NO} 3) 6. As described above, it is preferable to use a highly oxidative transition metal salt or transition metal oxide to carry out depolymerization by taking electrons from a chemical bond such as a carbon-carbon bond of a cured epoxy resin, for example. preferable. From such a side, for example, potassium permanganate which is a strong oxidizing agent is preferable. Moreover, potassium permanganate is preferable because of its excellent applicability and low cost.

  On the other hand, in the embodiment of the present invention, when depolymerizing using a transition metal salt or transition metal oxide containing a transition metal as described above, an oxidation reaction for depolymerization occurs through the transition metal, so The transition metal remains in the resulting filler, which is a reaction product.

  For example, in the case of depolymerizing a cured epoxy resin using potassium permanganate, manganese remains in the filler obtained after depolymerization. It is detected.

In an exemplary embodiment, the H ₂ O-based solvent is preferably an aqueous solution (H ₂ O alone) as described above.

In an exemplary embodiment, the pH conditions of the H ₂ O-based reaction solvent are adjusted to be weakly acidic, neutral, or basic at pH 1 or higher. By adjusting the pH conditions in this manner, it is believed that the oxidation reaction is likely to occur in the H ₂ O-based reaction system.

In a non-limiting example, the pH of the H ₂ O-based reaction system is 1 to 14, and in terms of reactivity, more preferably, the pH is preferably 3 to 12.

  In exemplary embodiments, the depolymerization reaction temperature is, for example, less than 250 ° C. (eg, 20-250 ° C.), or 200 ° C. or less (eg, 20-200 ° C.), or 100 ° C. or less (eg, 20-100) ° C, or 20-70 ° C.).

In an exemplary embodiment, the H ₂ O-based reaction solvent may be in the liquid phase, in the gas phase, or in the supercritical state. Using the one in the liquid phase simplifies the process and requires less reaction energy. In the embodiment of the present invention, even in the case of liquid phase, depolymerization can be carried out at low temperature and at high speed, but it goes without saying that those in the gas phase or supercritical state may be used intentionally. . In such a supercritical state, the reaction time can be further shortened, but there is a disadvantage that the reactor becomes complicated.

  In an exemplary embodiment, the step of surface treatment may be performed to increase the reaction surface area of the epoxy resin cured product before the epoxy resin cured product is subjected to a depolymerization reaction. As mentioned above, according to an exemplary embodiment of the present invention, the reaction time can be significantly reduced at low temperatures without additional pretreatment, but this surface treatment increases the reaction surface area. The reaction time that has been reduced can be further reduced. That is, the area of the cured epoxy resin is increased by the above-described surface treatment so that the subsequent depolymerization reaction can occur more smoothly.

  In an exemplary embodiment, as the surface treatment, either or both of physical surface treatment and chemical surface treatment may be performed in parallel.

  In a non-limiting example, the physical surface treatment may, for example, be grinding. The grinding method may be one or both selected from a dry grinding method and a wet grinding method, and a hammer mill, a cutter mill, a flake crusher, a feather mill, a pin mill, an impact mill, a mill It may be ground using one or more selected from the group consisting of jet mill, micron mill, ball mill, planetary mill, hydro mill, and aqualyzer. In an exemplary embodiment, the milled epoxy resin cure may have a size of 1 μm to 10 cm.

  In a non-limiting example, the chemical surface treatment may be to impregnate an acidic composition having a pH of less than 7 with the epoxy resin cured product.

  In a non-limiting example, the acidic composition used in the impregnation method may have a pH of 5.0 or less, a temperature of 20 to 250 ° C., and the acidic composition is impregnated with the epoxy resin cured product. The time to separate the epoxy resin cured product may be 0.1 to 24 hours. Then, the separated epoxy resin cured product is washed.

  In an exemplary embodiment, the cured epoxy resin to be decomposed may contain various fillers and / or polymer resins.

  In an exemplary embodiment, the filler is carbon fiber and others, graphite, graphene, graphene oxide, reduced graphene, carbon nanotube, glass fiber, inorganic salt, metal particle, ceramic material, monomolecular organic compound, monomolecular silicon compound, It may be one or more selected from silicon resin and the like.

  In an exemplary embodiment, the polymer resin is acrylic resin, olefin resin, phenol resin, natural rubber, synthetic rubber, aramid resin, polycarbonate, polyethylene terephthalate, polyurethane, polyamide, polyvinyl chloride, polyester, polystyrene, polyacetal, acrylonitrile It may be any one or more selected from butadiene styrene and styrene acrylonitrile.

In an exemplary embodiment, the transition metal salt or transition metal oxide is 0.001 to 99% by weight based on the weight of the entire composition (H ₂ O-based reaction solvent + transition metal salt). You may In a non-limiting example, when the H ₂ O reaction solvent is, for example, an aqueous solution, the transition metal salt or transition metal oxide is 0.001 based on the entire transition metal salt or the aqueous solution containing the transition metal oxide. It may be contained in the range of -99% by weight.

In an exemplary embodiment, the epoxy resin cured product is 1 to 90 parts by weight based on 100 parts by weight of the depolymerization composition (H ₂ O reaction solvent + transition metal salt or transition metal oxide). It may be. In a non-limiting example, when the H ₂ O reaction solvent is an aqueous solution, the epoxy resin cured product may be 1 to 90 parts by weight with respect to 100 parts by weight of a transition metal salt or an aqueous solution containing a transition metal oxide.

In an exemplary embodiment, when the transition metal salt is, for example, MnO ₂ , oxygen gas is bubbled into water to prepare a KMnO ₄ aqueous solution, and a cured epoxy resin composition is added to this to prepare a composition for depolymerization. May be provided to the epoxy resin cured product.

  Meanwhile, in an exemplary embodiment of the present invention, as described above, depolymerizing an epoxy resin composition with a depolymerization composition containing a transition metal salt or transition metal oxide containing a transition metal and a reaction solvent; There is provided a method of separating a filler from an epoxy resin cured product, which comprises the steps of: obtaining a filler from a product after depolymerization, for example, by filtration or extraction; and a filler obtained thereby.

  The filler separated and recovered from the epoxy resin cured product can suppress the property deterioration as compared to that before being used for the epoxy resin cured product, whereby a recycled filler excellent in the properties can be obtained.

  For example, as can be confirmed from the examples to be described later, when the filler is a carbon fiber, the reduction in properties such as tensile strength and elongation relative to the raw material filler carbon fiber contained in the epoxy resin cured product is, for example, 13% or less Or it is understood that it is extremely low at 10% or less. Incidentally, in the case of carbon fibers recovered from CFRP using a thermal decomposition method, a decrease in tensile strength of 15% or more relative to the raw material carbon fibers is exhibited (Non-patent Document 1). On the other hand, when depolymerized according to the embodiment of the present invention, carbon fibers with significantly reduced tensile strength properties can be recovered.

In an exemplary embodiment, the method may repeat the decomposition process by adding a new epoxy resin cured product to the remaining H ₂ O reaction solvent after depolymerizing the epoxy resin cured product.

  The filler can be separated from the product obtained by depolymerizing the cured epoxy resin product by the above method, for example, by filtration, extraction and washing.

  Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various embodiments can be embodied within the scope of the claims, and the embodiments below merely disclose the present invention. It will be appreciated that it is merely for the purpose of facilitating the practice of the invention by those skilled in the art.

[Experiment 1]
Water alone was used in the following examples. An aqueous solution (liquid phase) was used in the other examples except that the aqueous solution in the supercritical state was used in Example 2. The dielectric constant of water is 80.2.

  On the other hand, in Comparative Example 1, the dielectric constant was about 44 using a mixed solvent of water and acetone. In Comparative Example 2, a nitric acid aqueous solution was used.

  On the other hand, in Example 3, the amount of waste CFRP is increased by 15 times in comparison with Example 1, and in Example 4, the amount of waste CFRP is made the same as in Example 3, and potassium permanganate is used. The amount of aqueous solution is also increased.

  Moreover, Example 5 implemented depolymerization after grinding of waste CFRP, Example 6 implemented depolymerization after impregnating waste CFRP with acetic acid, and Example 7 included waste CFRP. Depolymerized after grinding and impregnation.

Example 8 uses chromium oxide (VI) (CrO ₃ ) as a transition metal oxide, and Example 9 uses vanadium pentoxide (V ₂ O ₅ ) as a transition metal oxide. In Example 10, ruthenium chloride (RuCl ₃ ) is used as a transition metal salt, and in Example 11, molybdenum oxide (MoO ₃ ) is used as a transition metal oxide. Example 12 uses rhenium methyl trioxide (MTO) as a transition metal oxide, and Example 13 uses osmium tetraoxide (OsO ₄ ) as a transition metal oxide.

[Example 1: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber)]
The epoxy resin cured product used in Example 1 is waste CFRP. The waste CFRP comprises an epoxy resin cured product produced by using an epoxy compound in the form of a diglycidyl ether of bisphenol A containing a halogen element and an aromatic curing agent containing an aromatic amine group, and a carbon fiber. Since this CFRP uses an aromatic curing agent, it is generally known to be considerably difficult to decompose.

  After charging 0.1 g of the waste CFRP into 70 mL of a 2 mol / L aqueous solution of potassium permanganate contained in an open glass container, the mixture was stirred at 70 ° C. A pressurized reactor (Autoclave) was not used.

  FIG. 2A is a photograph of CFRP before depolymerization in Example 1 of the invention, and FIG. 2B is a photograph of carbon fiber recovered after depolymerization in Example 1 of the invention.

  FIG. 3 shows the results of measurement of the pH of the aqueous solution of potassium permanganate in the reaction system of Example 1 of the present invention and the pH of the aqueous solution of nitric acid in the reaction system of Comparative Example 3, and FIG. It is a photograph taken after filtration and separation of manganese dioxide generated by the reaction.

  In addition, Table 1 shows the time when the depolymerization of the epoxy resin was completed, and Table 2 shows the results of measuring the pH of the aqueous potassium permanganate solution obtained after the depolymerization of the epoxy resin. Table 3 and FIG. 5 show the change of.

  After confirming that the epoxy resin had been substantially completely depolymerized (residuality 5% or less) after 3 hours, carbon fiber and manganese dioxide in an aqueous solution were filtered using cellulose filter paper of Advantec. After that, the carbon fiber was separated, washed and dried. From the measurement results of the dried carbon fiber thermogravimetric analyzer (TGA), it was confirmed that there was no epoxy residue.

  In addition, in order to confirm that a large amount of C-OH bond is formed in the depolymerization product of Inventive Example 1, FT-IR analysis of CFRP and the depolymerization product before depolymerization is performed, 6 shows.

  The depolymerization product is a solid mixture obtained by filtering the carbon fiber and manganese dioxide in Example 1, and then extracting the product in the form of an aqueous solution remaining using dichloromethane and drying. In the case of FT-IR analysis, using a Thermo Scientific Nicolet iS 10 instrument, pellets were prepared using a solid mixture and potassium bromide, and then a 500 cm-1 to 4000 cm-1 wave number interval was measured. From the FT-IR results, it could be confirmed that a large number of OH groups were generated.

[Example 2: Depolymerization of epoxy resin cured product in CFRP using supercritical potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber)]
After charging 0.1 g of the same CFRP used in Example 1 to 70 mL of a 2 mol / L aqueous solution of potassium permanganate contained in a batch reactor equipped with a pressure gauge, the reactor is closed and then the electric heating jacket is used. And heated at 374 ° C. At this time, the pressure displayed on the pressure gauge was 221 bar.

  After one hour, the reactor was allowed to cool to room temperature, and then it was confirmed whether the epoxy resin inside the reactor had been depolymerized.

  The reaction time was increased in units of 1 hour, and the time when the decomposition of the epoxy resin was completed is shown in Table 1.

After confirming that the epoxy resin was substantially completely depolymerized after 2 hours, carbon fibers and manganese dioxide in the reactor were filtered, and the carbon fibers were separated, washed and dried.
The time when the depolymerization of the epoxy resin was completed is shown in Table 1.

[Example 3: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber): CFRP amount increase]
On the other hand, this time, the condition (that is, 2 mol / L potassium permanganate aqueous solution) was the same as Example 1 except that the amount of waste CFRP was increased to 15 times (that is, 1.5 g). After charging to 70 mL, the results of stirring at 70 ° C. were examined.

After confirming that the epoxy resin was substantially completely depolymerized after 10 hours, the carbon fiber and manganese dioxide in the aqueous solution were filtered, and the carbon fiber was separated, washed and dried.
The time when the depolymerization of the epoxy resin was completed is shown in Table 1.

[Example 4: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber): Change in depolymerization conditions]
This time, after charging 1.5 g of waste CFRP used in Example 1 (identical to Example 3) into 100 mL of a 4 mol / L potassium permanganate aqueous solution placed in an open glass container, it was stirred at 90 ° C. . A pressurized reactor (Autoclave) was not used.

  After confirming that the epoxy resin was substantially completely depolymerized after 7 hours, the carbon fiber and manganese dioxide in the aqueous solution were filtered, and the carbon fiber was separated, washed and dried.

  The time when the depolymerization of the epoxy resin was completed is shown in Table 1. In addition, the measurement results of the tensile strength of the carbon fiber recovered as a result of Example 4 are shown in Table 3.

[Example 5: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber): Depolymerization after CFRP grinding]
The conditions were the same as in Example 4 except that 1.0 kg of waste CFRP was ground into fragments having an average diameter of 2.0 mm using a Barley Grinder Crusher manual grinder manufactured by Wellbom Co., Ltd. in China.

  After charging 1.5 g of the crushed cured product of epoxy resin into 100 mL of a 4 mol / L aqueous solution of potassium permanganate contained in an open glass container, it was stirred at 90.degree. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 4 hours, the carbon fiber and manganese dioxide in the aqueous solution were filtered, and the carbon fiber was separated, washed and dried.
The time when the depolymerization of the epoxy resin was completed is shown in Table 1.

[Example 6: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber): Depolymerization after CFRP impregnation]
The conditions were the same as in Example 4 except that 1.5 g of waste CFRP was added to 100 mL of 99% acetic acid and heated at 120 ° C. for 30 minutes. After heating, the cured epoxy resin was separated, washed with 20 mL of acetic acid and then dried.

  After charging the dried cured epoxy resin product into 100 mL of a 4 mol / L aqueous potassium permanganate aqueous solution placed in an open glass container, it was stirred at 90 ° C. A pressurized reactor (Autoclave) was not used.

  After confirming that the epoxy resin was substantially completely depolymerized after 5 hours, the carbon fiber and manganese dioxide in the aqueous solution were filtered, and the carbon fiber was separated, washed and dried.

  The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1. In addition, the measurement results of the tensile strength of the carbon fiber used in Example 6 of the present invention are shown in Table 3.

[Example 7: Depolymerization of epoxy resin cured product in CFRP using potassium permanganate (KMnO ₄ ) aqueous solution and separation of filler (carbon fiber): CFRP crushing and depolymerization after impregnation]
The conditions were the same as in Example 6 except that 1.0 kg of waste CFRP was crushed into fragments having an average diameter of 2.0 mm using a Micro Hammer Cutter Mill automatic grinder made by Glen Creston, UK.

  After 1.5 g of the crushed cured epoxy resin was added to 100 mL of 99% acetic acid and heated at 120 ° C. for 30 minutes, the cured epoxy resin was separated, washed with 20 mL of acetone and then dried.

  After charging the dried cured epoxy resin product into 100 mL of a 4 mol / L potassium permanganate aqueous solution placed in an open glass container, it was stirred at 90.degree. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 3 hours, the carbon fiber and manganese dioxide in the aqueous solution were filtered, and the carbon fiber was separated, washed and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

Example 8 Depolymerization of Epoxy Resin Cured Product Containing Filler (Graphene) Using Chromium (VI) Aqueous Solution and Separation of Filler (Graphene)
The cured product used in Example 8 is composed of an epoxy resin and graphene which are produced using an epoxy compound in the form of glycidyl ether of cresol novolac and a curing agent containing an aromatic amine group. The CFRP is generally known to be considerably difficult to be decomposed because it uses a novolak epoxy compound and an aromatic curing agent.

  After charging 0.1 g of the cured epoxy resin into 70 mL of a 2 mol / L chromium oxide aqueous solution placed in an open glass container, the mixture was stirred at 70 ° C. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 6.5 hours, the graphene and the chromium (III) oxide in the aqueous solution were filtered, and then the graphene was separated, washed and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

[Example 9: Depolymerization of epoxy resin cured product containing filler (graphene oxide) using vanadium pentoxide (V ₂ O ₅ ) aqueous solution and separation of filler (graphene oxide)]
The cured product used in the present Example 9 is composed of an epoxy resin cured product and graphene oxide produced using a curing agent containing an epoxy compound in the form of glycidyl amine and an acid anhydride group.

  After charging 0.1 g of a cured product containing an epoxy resin into 70 mL of a 2 mol / L aqueous solution of vanadium pentoxide contained in an open glass container, it was stirred at 70.degree. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 6 hours, graphene oxide in an aqueous solution was separated by filtration and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

Example 10 Depolymerization of Epoxy Resin Cured Product Containing Filler (Carbon Nanotube) Using Ruthenium Chloride (RuCl ₃ ) Aqueous Solution and Separation of Filler (Carbon Nanotube)
The cured product used in this Example 10 is the same as Example 8 from a cured epoxy resin product and a carbon nanotube which were produced using an epoxy compound in the form of glycidyl ether of cresol novolac and a curing agent containing an aromatic amine group. Become.

  After charging 0.1 g of a cured product containing an epoxy resin into 70 mL of a 2 mol / L ruthenium chloride aqueous solution placed in an open glass container, it was stirred at 70 ° C. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 5.5 hours, the carbon nanotubes in the aqueous solution were separated by filtration and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

Example 11 Depolymerization of Epoxy Resin Cured Product Containing Filler (Glass Fiber) Using Molybdenum Oxide (MoO ₃ ) Aqueous Solution and Separation of Filler (Glass Fiber)
The cured product used in this Example 11 is the same as Example 8 from an epoxy resin cured product and a glass fiber produced using an epoxy compound in the form of glycidyl ether of cresol novolac and a curing agent containing an aromatic amine group. Become.

  After charging 0.1 g of a cured product containing an epoxy resin into 70 mL of a 2 mol / L aqueous solution of molybdenum oxide contained in an open glass container, it was stirred at 70 ° C. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 6.5 hours, after filtering the glass fiber and molybdenum in the aqueous solution, the glass fiber was separated, washed and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

[Example 12: Depolymerization of epoxy resin cured product containing filler (alumina) using methyl rhenium trioxide (MTO) aqueous solution and separation of filler (alumina)]
The cured product used in the present Example 12 is composed of an epoxy resin cured product and alumina produced using an epoxy compound in the form of diglycidyl ether of bisphenol A and a curing agent containing an aliphatic amine group.

  After charging 0.1 g of a cured product containing an epoxy resin into 70 mL of a 2 mol / L MTO aqueous solution placed in an open glass container, it was stirred at 70.degree. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 7 hours, alumina in an aqueous solution was separated by filtration and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

Example 13 Depolymerization of Epoxy Resin Cured Product Containing Filler (Silicon Carbide) Using Osmium Tetraoxide (OsO ₄ ) Aqueous Solution and Separation of Filler (Silicon Carbide)
The cured product used in the present Example 13 is composed of an epoxy resin cured product and silicon carbide which are produced using an epoxy compound in the form of diglycidyl ether of bisphenol A and a curing agent containing an aliphatic amine group.

  After charging 0.1 g of a cured product containing an epoxy resin into 70 mL of a 2 mol / L osmium tetraoxide aqueous solution placed in an open glass container, the mixture was stirred at 70 ° C. A pressurized reactor (Autoclave) was not used.

After confirming that the epoxy resin was substantially completely depolymerized after 4.5 hours, silicon carbide in an aqueous solution was separated by filtration and dried.
The time when the depolymerization of the cured epoxy resin was completed is shown in Table 1.

[Comparative example 1: Depolymerization of epoxy resin cured product in CFRP using mixed solution of potassium permanganate aqueous solution and acetone (KMnO ₄ + H ₂ O + acetone) and separation of carbon fiber]
0.1 mL of a mixture of 0.1 g of CFRP identical to that used in Example 1 placed in an open glass container, 11 mL of a mixed solution of 2 mol / L hydrogen peroxide solution and 33% (volume ratio in all solvents) acetone That is, after charging acetone to 33% by volume and the water volume ratio to 67% in all the solvents, the mixture was stirred at 70 ° C.

  The presence or absence of depolymerization of the epoxy resin is shown in Table 1. In Comparative Example 1, the epoxy resin did not depolymerize (decomposition ratio 4.5%, 28%, or 34%), and it was not possible to separate the carbon fiber.

  In this comparative example, it is considered that depolymerization hardly occurs because the dielectric constant of the reaction system is low, dissolution and ion dissociation of potassium permanganate are difficult to occur, and formation of OH group by oxidation reaction is small. . Despite using the same CFRP as in the example (the curing agent for the epoxy resin cured product is considerably difficult to be decomposed by the aromatic diamine system), unlike the example, no depolymerization occurs. It is noted that.

[Comparative Example 2: Decomposition of epoxy resin using nitric acid aqueous solution and separation of carbon fiber]
After charging 0.1 g of CFRP identical to that used in Example 1 into a 2 mol / L nitric acid aqueous solution placed in an open glass container, it was stirred at 70 ° C.

  FIG. 2 shows the result of measuring the pH of the aqueous nitric acid solution containing CFRP. In addition, Table 1 shows the time when decomposition of the epoxy resin was completed, and Table 2 shows the result of measuring the pH of the aqueous nitric acid solution obtained after filtering the carbon fiber.

  After confirming that the epoxy resin was completely depolymerized after 12 hours, carbon fibers in an aqueous solution were separated by filtration and dried.

[Epoxy decomposition experimental results of Examples and Comparative Examples and characterization of recovered filler]
The time taken for the decomposition of the epoxy resin in Examples and Comparative Examples is shown in Table 1. Moreover, the result of having measured pH of the potassium permanganate aqueous solution and nitric acid aqueous solution obtained after filtering carbon fiber in Example 1 and Comparative Example 2 was represented in Table 2.

  As can be seen from the examples of Table 1 and the comparative examples, in the case of the examples, the reaction time was relatively fast although the reaction temperature was low. On the other hand, it was confirmed that decomposition of the cured epoxy resin did not occur particularly when acetone was contained in the reaction solvent at about 33% by volume (dielectric constant: about 44) in Comparative Example 1.

  On the other hand, in the case of Comparative Example 2 in which a nitric acid aqueous solution was used, the reaction time was 4 times as slow as in Example 1 in which a potassium permanganate aqueous solution was used. Also, as can be confirmed from Table 2, the composition used in Example 1 exhibited a higher pH value than the aqueous nitric acid solution, and it was confirmed that the working conditions were more mild.

  FIG. 5 shows carbon fibers (designated as raw material carbon fibers, denoted as V-CF) used for CFRP of Example 1 of the present invention and carbon fibers collected as a result of Example 1 (designated as R-CF). It is a graph which compares the result obtained from measurement of tensile strength.

  From the measurement results of tensile strength of carbon fiber recovered from Example 1, carbon fiber with less decrease in tensile strength (within 10%) recovered from CFRP by decomposing CFRP using the method of the embodiment of the present invention It confirmed that it was possible. This is because the carbon fiber recovered from CFRP using the thermal decomposition method shows a reduction in tensile strength of 15% or more relative to the raw material (non-patent document 1), the depolymerization method according to the embodiment of the present invention Indicates that carbon fibers with high characteristics can be recovered.

  On the other hand, in Examples 4 to 7 of Table 1, although the same epoxy resin cured product and depolymerization composition are used, Examples 5 to 7 are carried out including the surface treatment step, and Example 4 Was carried out without including the surface treatment step. Even in the case of Example 4, the depolymerization was carried out at high speed, but it was confirmed that the cured epoxy resin was depolymerized at a higher speed by including the surface treatment step, and Example 7 including both the grinding and impregnation steps. It was confirmed that the depolymerization of the cured epoxy resin was completed at the earliest stage.

  Such shortening of the depolymerization completion time is considered to be due to further activation of depolymerization due to the increase in the reaction surface area of the cured epoxy resin product by the surface pretreatment. Such activation of depolymerization is caused not only by the increase of physical surface area using the grinding method but also by the increase of chemical surface area using the impregnation method.

  Also, as can be confirmed from Table 3, the tensile strength of the carbon fiber recovered as a result of Example 6 including the impregnation step is higher than the tensile strength of the carbon fiber recovered as a result of Example 4 not including the impregnation step. It confirmed that it was excellent. This indicates that the decrease in the time taken for the depolymerization of the cured epoxy resin product by the surface treatment step further reduces the deterioration in the properties of the carbon fiber that can occur in the depolymerization step.

  From such measurement results of tensile strength, it was confirmed that carbon fibers excellent in physical properties can be recovered from CFRP by depolymerizing the cured epoxy resin product using the method of the embodiment of the present invention.

[Experiment 2]
In this experiment 2, using a mixed solvent of water and various organic solvents (acetone, isopropyl alcohol, ethanol) as the reaction solvent, the dielectric constant is changed by changing the mixing ratio, and the degree of epoxy depolymerization by it is It was measured. As a compound, potassium permanganate (KMnO ₄ ) was used. Experimental conditions and results are shown in Tables 4 to 6.

^{* In the} said table, content of the epoxy resin before the depolymerization reaction of CFPR was 19.4 weight% (weight% of the epoxy resin in total CFRP). The amount of residual epoxy indicates the amount after 24 hours or 5 hours based on this. For example, 19.1% by weight after 24 hours means that the weight% of epoxy resin in total CFRP after 24 hours of depolymerization reaction is 19.1% by weight. On the other hand, 0% by weight after 5 hours means that the residual amount of epoxy resin is already 0% by weight in the total CFRP after 5 hours. This shows a remarkable difference as compared with the result that a considerable amount of epoxy resin of 10% by weight or more remains after 24 hours.

^{** The} decomposition rate was determined as follows as described above.
Decomposition rate = [(Epoxy resin content before depolymerization reaction of CFRP-epoxy resin content after depolymerization reaction of CFRP) / epoxy resin content before depolymerization reaction of CFRP] × 100

  FIG. 7 shows the results of Tables 4 to 6 in the present Experiment 2 as the decomposition rate of the epoxy resin according to the dielectric constant of the reaction system.

  As can be seen from the figure, when the dielectric constant is 65 or more, it can be seen that the gradient of the depolymerization efficiency sharply increases. On the other hand, in the case of water alone, a decomposition rate of 100 was achieved in 5 hours instead of 24 hours, and it was shown that the decomposition rate was dramatically increased when using water alone as compared with the case of mixing with an organic solvent. The

[Experiment 3]
In this experiment, X-ray photoelectron spectroscopy (XPS) analysis of carbon fiber recovered by depolymerization using carbon fiber used for CFRP and KMnO ₄ in Example 1 was performed.

  FIG. 8A is a graph showing the results of X-ray photoelectron spectroscopy (XPS) of a carbon fiber (denoted as CF) used for CFRP in this Experiment 3.

FIG. 8B is a graph showing the X-ray photoelectron spectroscopy (XPS) results of the carbon fiber recovered by depolymerization using KMnO ₄ in Experiment 3.

FIG. 8C is a graph showing XPS elemental content results of carbon fibers (indicated as CF) used for CFRP in the present Experiment 3 and carbon fibers (indicated as R-CF) recovered by depolymerization using KMnO ₄ . It is.

  As can be seen from FIGS. 8A to 8C, in R-CF recovered using potassium permanganate, it is confirmed that the Mn element, which is the residue of the transition metal salt, is detected at 2.1% or less. Can.

  As can be seen from the above, it is understood that water alone is particularly preferable as the reaction solvent used together with the transition metal salt or transition metal oxide containing a transition metal in the composition for depolymerization according to the embodiment of the present invention. In the case of mixing other solvents including water, it shows that the dielectric constant of the mixed solvent shows a sharp increase in decomposition rate at least 65 or more, and when the dielectric constant becomes high and water is used alone, the reaction is While the time itself decreased significantly, it showed a dramatic increase in reaction efficiency.

Claims (21)

It is a composition for depolymerization of a cured epoxy resin product,
A transition metal salt or transition metal oxide containing a transition metal element and a reaction solvent,
The composition for depolymerizing epoxy resin cured product characterized in that the reaction solvent is a reaction solvent capable of causing an oxidation reaction of a chemical bond of the epoxy resin cured product mediated by transition metal.   The composition for depolymerization of a cured epoxy resin according to claim 1, wherein the chemical bond is a carbon-carbon bond.   The said reaction solvent is a reaction solvent in which a transition metal salt can be dissociated, The composition for depolymerization of the epoxy resin hardened | cured material of Claim 1 or 2 characterized by the above-mentioned.   The said reaction solvent has a dielectric constant of 65 or more, 70 or more, 75 or more, or 80 or more, for depolymerization of the epoxy resin cured product according to any one of claims 1 to 3. Composition. The reaction solvent includes _{H 2} O, any one of the preceding claims, characterized in that the dielectric constant is 65 or more, or 70 or more, or 75 or more, or 80 or more _{H 2} O based reaction solvent The composition for depolymerization of the epoxy resin hardened | cured material as described in 1 item. The composition according to claim 5, wherein the H ₂ O is in a liquid phase, a gas phase, or a supercritical state.   The composition for depolymerizing a cured epoxy resin product according to claim 5, wherein the reaction solvent is water alone.   The composition according to claim 7, wherein the composition exhibits a pH of 1 to 14 or 3 to 12.   The transition metal includes Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W It is 1 or more types chosen from the group which consists of, Re, Os, Ir, Pt, Au, Hg, The composition for depolymerization of the epoxy resin hardened | cured material as described in any one of Claims 1-8 characterized by the above-mentioned. . The transition metal salt or transition metal oxide may be KMnO ₄ , MnO ₂ , K ₂ MnO ₄ , MnSO ₄ , MnSO ₄ , CrO ₃ , Na ₂ Cr ₂ O ₇ , K ₂ Cr ₂ O ₇ , ZnCr ₂ O ₇ , H ₂ CrO ₄ , Pyridinium Chlorochromate (pyridinium chlorochromate), Pyridinium Dichromate (pyridinium dichromate), V ₂ O ₅ , RuCl ₃ , RuO ₂ , Tetrapropylammonium Perruthenate (tetrapropylammonium perruthenate), MoO ₃ , K ₃ [Fe (Fe _{CN) 6], FeCl 3,} Fe (NO 3) 3 nonahydrate ( _{nonahydrate), MeReO 3, CuCl, Cu} (ClO 4) 2, Cu (HCO 2) 2 Ni (HCO 2 10. One or more members selected from the group consisting of ₂ ), Cu (OAc) ₂ , OsO ₄ and (NH ₄ ) ₂ Ce (NO ₃ ) _{6, according} to any one of claims 1 to 9. Composition for depolymerization of epoxy resin cured product.   The epoxy resin according to any one of claims 1 to 10, wherein the transition metal salt or transition metal oxide is contained in a range of 0.001 to 99% by weight with respect to the whole composition. Composition for depolymerization of cured product. A method for depolymerizing a cured epoxy resin product, comprising
A method for depolymerizing a cured epoxy resin product comprising depolymerizing the cured epoxy resin product using the composition for depolymerizing the cured epoxy resin product according to any one of claims 1 to 11.   The method according to claim 12, wherein the reaction temperature is 20 to 200 ° C or 20 to 100 ° C.   The epoxy resin cured product is used in a range of 1 to 90 parts by weight based on 100 parts by weight of the composition for depolymerization, The method for depolymerizing the epoxy resin cured product according to claim 12 or 13.   The method according to any one of claims 12 to 14, wherein a new epoxy resin cured product is added to the reaction solvent remaining after depolymerizing the epoxy resin cured product, and the depolymerization process is repeated. Depolymerization method of epoxy resin cured product.   The method according to any one of claims 12 to 15, wherein the surface treatment is carried out to increase the reaction surface area of the cured epoxy resin before the cured epoxy resin is subjected to a depolymerization reaction. Depolymerization method of epoxy resin cured product.   The method for depolymerizing a cured epoxy resin product according to claim 16, wherein as the surface treatment, physical surface treatment and / or chemical surface treatment are both carried out in parallel.   The method of depolymerizing the cured epoxy resin product according to claim 17, wherein the physical surface treatment is one or more selected from a dry grinding method and a wet grinding method.   The method for depolymerizing a cured epoxy resin according to claim 17, wherein the chemical surface treatment comprises impregnating the acidic composition having a pH of less than 7 with the cured epoxy resin.   The transition metal remains in the filler obtained after depolymerization, The depolymerization method of the epoxy resin hardened material as described in any one of Claims 12-19 characterized by the above-mentioned. A method of separating a filler from an epoxy resin cured product, comprising
A step of depolymerizing a cured epoxy resin using the composition for depolymerizing a cured epoxy resin according to any one of claims 1 to 11; and obtaining a filler from a product of the depolymerization;
A method of separating a filler from an epoxy resin cured product, comprising: