WO2009082009A1 - Method of decomposing thermoset resin and recovering product of decomposition - Google Patents

Abstract

A method by which reusable compounds can be efficiently recovered from products of the decomposition of a thermoset resin and which can facilitate the reuse of the aqueous solution resulting from the recovery of the compounds. In the method, a thermoset resin comprising a polyester moiety and a crosslink moiety where the polyester moiety is crosslinked is decomposed, and reusable products of the decomposition are recovered. This method comprises: (A) a step in which the thermoset resin is decomposed with subcritical water containing a hydroxylated inorganic compound having a valence of 2 or higher; (B) a step in which the decomposition products obtained are subjected to solid-liquid separation to recover a solid matter comprising a carboxylate of a compound comprising a residual acid group derived from the polyester and a residual group derived from the crosslink moiety; and (C) a step in which an acid is added to the solid matter recovered and the resultant mixture is subjected to solid-liquid separation to recover a solid matter containing that compound.

Description

Decomposition of thermosetting resin and recovery method of decomposition product

This patent application claims priority from Japanese Patent Application No. 2007-335218 (filing date: December 26, 2007), which is hereby incorporated by reference in its entirety. Shall be incorporated.
The present invention relates to a method for recovering recyclable decomposition products (for example, monomers, styrene-fumaric acid copolymer, etc.) by decomposing thermosetting resins with subcritical water.

Conventionally, most plastic waste has been landfilled or incinerated, and has not been effectively used as a resource. In addition, landfill disposal has problems such as difficulty in securing a landfill site and destabilization of the ground after landfilling, while incineration disposal causes furnace damage, generation of organic gases and odors, CO _2. There was a problem such as the occurrence of.

Therefore, in Japan, the Containers and Packaging Disposal Law was enacted in 1995, and plastic collection and reuse became mandatory. Furthermore, with the enforcement of various recycling laws, the flow of collection and recycling of products containing plastics tends to accelerate.

In recent years, it has been attempted to recycle plastic waste in accordance with these situations, and one of them is decomposition that can be reused by decomposing plastic using supercritical water or subcritical water as a reaction medium. A method for recovering the product has been proposed (see Patent Documents 1 to 5).

However, in these methods, since plastics are randomly decomposed, it is difficult to obtain a decomposition product having a constant quality.

As a technique for solving this problem, a thermosetting resin obtained by crosslinking a polyester composed of a polyhydric alcohol and a polybasic acid with a crosslinking agent is decomposed using subcritical water below the thermal decomposition temperature of the thermosetting resin. A technique for obtaining a styrene-fumaric acid copolymer together with a monomer that can be reused as a raw material for a thermosetting resin has been proposed (see Patent Document 6).
JP-T 56-501205 Japanese Patent Laid-Open No. 57-4225 Japanese Patent Laid-Open No. 5-31000 JP-A-6-279762 Japanese Patent Laid-Open No. 10-67991 International Publication WO2005 / 092962 Pamphlet

However, in the method of Patent Document 6, although a styrene-fumaric acid copolymer can be obtained, a thermosetting resin is added with subcritical water containing a water-soluble alkali such as potassium hydroxide or sodium hydroxide. Since it is decomposed, the styrene-fumaric acid copolymer produced by the decomposition reaction exists as a salt dissolved in an aqueous solution. Therefore, when plastics containing inorganic fillers such as calcium carbonate and aluminum hydroxide and inorganic substances such as glass fibers are decomposed with subcritical water, the resulting aqueous solution containing styrene-fumaric acid copolymer and inorganic substances are separated into solid and liquid. Thus, a step for recovering the separation liquid is required. However, the styrene-fumaric acid copolymer contained in the separation liquid is lost during the separation step, and further, an acid is added to the separation liquid to add a styrene-fumaric acid copolymer. A step of depositing a polymer and separating it into solid and liquid to recover the solid content is required, but there is a problem that the styrene-fumaric acid copolymer is lost in the separation step, The recovery rate of the produced styrene-fumaric acid copolymer was not sufficient. In addition, since the aqueous solution after recovering the styrene-fumaric acid copolymer contains resin-soluble components and salts other than the styrene-fumaric acid copolymer, treatment for wastewater treatment and reuse of the aqueous solution can be performed. There was a problem that it became necessary.

The present invention has been made in view of the circumstances as described above, and is a compound comprising a reusable polyester-derived acid residue and a cross-linked portion-derived residue from a decomposition product of a thermosetting resin. It is an object of the present invention to provide a method capable of efficiently recovering (for example, styrene-fumaric acid copolymer) and facilitating reuse of an aqueous solution after recovering the compound.

In order to solve the above-mentioned problems, the present invention includes the following inventions [1] to [4]:
[1] A method for decomposing a thermosetting resin containing a polyester part and a crosslinked part thereof and recovering a reusable decomposition product,
(A) decomposing the thermosetting resin with subcritical water containing a divalent or higher hydroxyl group-containing inorganic compound;
(B) a step of solid-liquid separation of the obtained decomposition product and recovering a solid content containing a carboxylate salt of a compound comprising an acid residue derived from a polyester and a residue derived from a cross-linked part;
(C) After adding an acid to the recovered solid content, this is subjected to solid-liquid separation to recover the solid content containing the compound;
Including a method.
[2] (D) The method according to [1], further comprising the step of bringing the recovered solid content into contact with a solvent capable of dissolving the compound, and dissolving and recovering the compound in the solvent. .
[3] The method according to [1] or [2] above, wherein the separated filtrate after subcritical water decomposition is repeatedly reused as a feed liquid for subcritical water decomposition.
[4] The method according to any one of [1] to [3], wherein the divalent or higher hydroxyl group-containing inorganic compound comprises calcium hydroxide.

According to the present invention, hydrolysis is promoted by decomposition with subcritical water containing a divalent or higher hydroxyl group-containing inorganic compound, and as a solid content of the decomposition product, that is, as a water-insoluble salt, it is derived from polyester. A compound (for example, a styrene-fumaric acid copolymer) comprising an acid residue and a residue derived from a cross-linking moiety can be effectively obtained. Since the compound does not dissolve in the aqueous solution by decomposition with subcritical water, loss of the compound can be suppressed during separation from the aqueous solution. Further, the separation liquid at this time can be used again as subcritical water.

Then, after adding an acid to the solid content containing the recovered carboxylate of the compound, this is solid-liquid separated to recover the solid content containing the compound, and further contacted with a solvent capable of dissolving the compound Then, the compound can be efficiently recovered by dissolving the compound. The separated liquid after solid-liquid separation by adding an acid to the solid content containing the carboxylate of the compound can be reused as the acid added to the solid content containing the carboxylate of the compound.

In the above method, by using calcium hydroxide as a divalent or higher hydroxyl group-containing inorganic compound, hydrolysis of the polyester part can be promoted, and further, the compound can be efficiently recovered as a water-insoluble salt. Can do.

It is the flowchart which showed operation of Embodiment [1] of the method of this invention (only resin and using hydrochloric acid as an acid) in process order. It is the flowchart which showed operation of Embodiment [2] of the method of this invention (only resin uses sulfuric acid as an acid) in order of a process. It is the flowchart which showed operation of Embodiment [3] (resin and inorganic substance, using hydrochloric acid as an acid) of the method of this invention in order of a process. It is the flowchart which showed operation of Embodiment [4] (resin and inorganic substance, using sulfuric acid as an acid) of the method of this invention in order of a process. FIG. 2 is a diagram showing a styrene-fumaric acid carboxylate and a state after an acid is added thereto.

Hereinafter, embodiments [1] to [4] of the method of the present invention will be described in detail.

In the present invention, the thermosetting resin to be decomposed is obtained by cross-linking polyester, and includes a polyester part and its cross-linked part.

The polyester part is derived from a polyester in which a polyhydric alcohol residue and a polybasic acid residue are connected to each other through an ester bond by polycondensation of a polyhydric alcohol and a polybasic acid. The polyester part may contain a double bond derived from an unsaturated polybasic acid.

The cross-linked part is a part that cross-links the polyester part. Although a bridge | crosslinking part is a part originating in a crosslinking agent, for example, it is not specifically limited. The cross-linked part may be a part derived from one cross-linking agent, or may be a part derived from an oligomer or polymer obtained by polymerizing a plurality of cross-linking agents. Further, the bonding position and bonding mode between the crosslinked part and the polyester part are not particularly limited.

Therefore, the “thermosetting resin including a polyester part and a cross-linked part thereof” means a reticulated thermosetting resin (a reticulated polyester resin) in which a polyester obtained from a polyhydric alcohol and a polybasic acid is cross-linked via a cross-linked part. It is. Such a thermosetting resin may be any form of resin as long as the above-described effects can be obtained when the present invention is applied. That is, there are no restrictions on the type and structure of the resin, the type, amount, and degree of crosslinking of the crosslinking part (crosslinking agent).

The thermosetting resin to which the present invention is applied is a resin that is cured (crosslinked) mainly by heating or the like. However, if the above-described effects can be obtained when the present invention is applied, by heating or the like. It may be an uncured resin that progresses in curing (crosslinking) or a partially cured resin.

Examples of the thermosetting resin to which the present invention is suitably applied include a reticulated polyester resin in which an unsaturated polyester composed of a polyhydric alcohol and an unsaturated polybasic acid is crosslinked with a crosslinking agent.

Specific examples of the polyhydric alcohol that is a raw material for the polyester part include glycols such as ethylene glycol, propylene glycol, neopentyl glycol, diethylene glycol, and dipropylene glycol. These can be used alone or in combination of two or more.

Specific examples of the polybasic acid that is a raw material for the polyester part include aliphatic unsaturated dibasic acids such as maleic anhydride, maleic acid, and fumaric acid. These can be used alone or in combination of two or more. A saturated polybasic acid such as phthalic anhydride may be used in combination with the unsaturated polybasic acid.

Cross-linking agents that crosslink polyester, which is a copolymer of polyhydric alcohol and polybasic acid, include styrene, but other cross-linking agents such as polymerizable vinyl monomers such as methyl methacrylate are also used in combination. Also good.

Further, in the thermosetting resin to be decomposed in the present invention, as in the embodiments [3] and [4], inorganic fillers such as calcium carbonate and aluminum hydroxide, chopped strands obtained by cutting rovings, etc. Inorganic substances such as glass fibers and other components may be contained.

In the present invention, the polyester is a decomposition product that can be reused by decomposing the thermosetting resin by the steps (A) to (D) of the following embodiments [1] to [4]. A compound (hereinafter referred to as “compound (I)”) comprising an acid residue derived from the residue and a residue derived from the cross-linking moiety is recovered. For example, when the thermosetting resin is obtained using fumaric acid or maleic acid as a polybasic acid and using styrene as a crosslinking agent, a styrene-fumaric acid copolymer is used as the compound (I). Is recovered.

Hereinafter, the method of the present invention will be described in the order of steps with reference to the flowcharts of FIGS. The following embodiments [1] to [4] are merely examples of the present invention, and the present invention is not limited to these embodiments.

In the embodiment [1] shown in FIG. 1, only the thermosetting resin is decomposed and the carboxylic acid salt of the styrene-fumaric acid copolymer is ring-opened using hydrochloric acid, whereby the styrene-fumaric acid copolymer is obtained. It is a method to collect.
The embodiment [2] shown in FIG. 2 is a styrene-fumaric acid copolymer obtained by ring-opening a carboxylate of a styrene-fumaric acid copolymer using sulfuric acid instead of the hydrochloric acid of the embodiment [1]. It is a method to collect.
In the embodiment [3] shown in FIG. 3, a thermosetting resin containing calcium carbonate and glass fiber is decomposed, and a styrene-fumaric acid copolymer carboxylate is ring-opened with hydrochloric acid to produce styrene- This is a method for recovering a fumaric acid copolymer.
The embodiment [4] shown in FIG. 4 is a styrene-fumaric acid copolymer obtained by ring-opening a carboxylate of a styrene-fumaric acid copolymer using sulfuric acid instead of the hydrochloric acid of the embodiment [3]. It is a method to collect.

First, the embodiment [1] will be described. First, the thermosetting resin is decomposed in subcritical water (step (A)). At this time, subcritical water containing a hydroxyl group-containing inorganic compound is used. Here, the “hydroxyl group-containing inorganic compound” is a catalyst that acts as a catalyst for the decomposition reaction, so that the compound (I) obtained by the decomposition does not dissolve in water as a carboxylate and is generated as a solid. That is, a hydroxyl group-containing inorganic compound is a compound that does not take into account its own solubility in water, but reacts with the carboxylic acid of compound (I) to form a water-insoluble substance. Such a hydroxyl group-containing inorganic compound is required to be a hydroxyl group-containing inorganic compound having a bivalent, trivalent or higher valence. In the case of monoatomic ions, a tetravalent (Sn) inorganic compound can be considered as the maximum valence. Specifically, calcium hydroxide, aluminum hydroxide, etc. can be illustrated as a suitable thing. For example, when calcium hydroxide is used, two carboxylic acids of the compound (I) are closed via a Ca atom, or, as shown in FIG. 5 described later, a carboxylic acid and a Ca atom of another compound (I). Since a ring is formed by bonding through the compound, the compound (I) is hardly dissolved in water.

The concentration in water of such a divalent or higher hydroxyl-containing inorganic compound is not particularly limited, but is preferably a saturated concentration or higher. Here, in the case of calcium hydroxide, the solubility is 0.17 g (water 100 g (25 ° C.)). Below the saturation concentration, the effect as a catalyst for the decomposition reaction is small, and the amount of the carboxylate of compound (I) produced is small.
The amount of the divalent or higher hydroxyl group-containing inorganic compound is not particularly limited, but is preferably 2 to 50 parts by mass with respect to 100 parts by mass of the thermosetting resin.

On the other hand, when an inorganic compound containing a monovalent hydroxide such as sodium hydroxide or potassium hydroxide is used, it becomes a water-soluble potassium salt or sodium salt, which cannot be separated and recovered.

In this step, water containing a divalent or higher hydroxyl group-containing inorganic compound is added to the thermosetting resin, and the temperature and pressure are increased to bring the water into a subcritical state and decompose the thermosetting resin. The amount of water added to the thermosetting resin is preferably in the range of 200 to 500 parts by mass with respect to 100 parts by mass of the thermosetting resin.

The decomposition treatment of plastic with subcritical water generally occurs by a thermal decomposition reaction and a hydrolysis reaction, and the same applies to thermosetting plastics produced from raw materials containing polyhydric alcohols and polybasic acids. However, the hydrolysis reaction becomes dominant. By setting the temperature and pressure of subcritical water to appropriate conditions, a hydrolysis reaction occurs selectively, and the polyhydric alcohol and polybasic acid monomers or oligomers in which a plurality of these are combined are decomposed.

Therefore, also in the present invention, the above thermosetting resin can be decomposed into polyhydric alcohol, polybasic acid and compound (I) by treatment with subcritical water. Monomers and oligomers obtained by decomposition can be recovered and reused as raw materials for producing plastics.

In the present invention, “subcritical water” means that the temperature of water is not more than the temperature of water (critical temperature 374.4 ° C.) and the temperature is 140 ° C. or more, and the pressure at that time is 0.36 MPa (140 Water in the range of (saturated vapor pressure at ° C) or higher. In this case, the ion product is about 100 to 1000 times that of water at normal temperature and pressure. In addition, since the dielectric constant of subcritical water decreases to the same level as an organic solvent, the wettability of the subcritical water to the thermosetting resin surface is improved. Hydrolysis is promoted by these effects, and the thermosetting resin can be monomerized and / or oligomerized.

In the present invention, the temperature of the subcritical water at the time of the decomposition reaction is lower than the thermal decomposition temperature of the thermosetting resin to be decomposed and recovered, and is preferably in the range of 180 to 300 ° C. If the temperature during the decomposition reaction is less than 180 ° C., the decomposition process takes a lot of time, so that the processing cost may increase, and the yield of compound (I) tends to decrease. When the temperature during the decomposition reaction exceeds 300 ° C., the thermal decomposition of the compound (I) becomes remarkable, and the compound (I) is reduced in molecular weight to produce a wide variety of derivatives, which can be recovered as the compound (I). Tend to be difficult.

The treatment time with subcritical water varies depending on the reaction temperature and other conditions, but is usually 1 to 4 hours. The pressure during the decomposition reaction varies depending on the reaction temperature and other conditions, but is preferably in the range of 2 to 15 MPa.

As described above, by decomposing the thermosetting resin with subcritical water containing a divalent or higher hydroxyl-containing inorganic compound, the carboxylate of the compound (I) produced by the decomposition reaction is precipitated as a water-insoluble component. And it collect | recovers as solid content with the inorganic compound containing a bivalent or more hydroxyl group. On the other hand, the polyester-derived monomers (polyhydric alcohol and polybasic acid) produced by the decomposition reaction are separated from solids such as the carboxylate of compound (I) as a water-soluble component. A partially dissolved divalent or higher hydroxyl-containing inorganic compound is also included in the water-soluble component.

Next, as shown in FIG. 1, the obtained decomposition product is subjected to solid-liquid separation to recover a solid content containing the carboxylate of compound (I) (step (B)).

Specifically, after the reaction vessel containing subcritical water and decomposition products is cooled, the contents of the vessel are separated into solid and liquid by a method such as filtration. Thereby, the carboxylate of compound (I) and the inorganic compound containing a divalent or higher hydroxyl group are separated as solids.

On the other hand, an aqueous solution in which a polyhydric alcohol as a monomer component and a polybasic acid (organic acid) are dissolved is separated as a separation filtrate. This separated filtrate can be reused for decomposition of other thermosetting resins as subcritical water while containing polyhydric alcohol and polybasic acid. Moreover, it is possible to recover the polyhydric alcohol and polybasic acid at a high concentration by sequentially reusing them and dissolving the polyhydric alcohol and polybasic acid generated in each decomposition reaction sequentially in the aqueous solution. .

Next, as shown also in FIG. 1, after adding hydrochloric acid to the solid content collect | recovered at the process (B) and changing the carboxylate of compound (I) into compound (I), compound (I) is included. The solid content is recovered (step (C)). At this time, calcium hydroxide, which is a divalent or higher hydroxyl group-containing inorganic compound, is dissolved in water as a water-soluble calcium salt by adding hydrochloric acid.

Specifically, the carboxylate of compound (I) present in the solid content after decomposition is present in the state shown in FIG. The salt of the compound (I) includes a skeleton of an acid residue derived from a polyester and a skeleton of a residue derived from a cross-linked part (when the compound (I) is a styrene-fumaric acid copolymer, a styrene skeleton and a fumaric acid skeleton). It is a carboxylate in a state (—COO—M—OOC—) in which a metal M derived from a divalent or higher hydroxyl group-containing inorganic compound is bonded to a carboxyl group and exhibits water insolubility. In this state, since it is difficult to dissolve in a water-soluble alkali or an organic solvent, which will be described later, hydrochloric acid is added to open the carboxylic acid group of the compound (I) that is ring-closed via the divalent or higher metal M. Compound (I) that can be dissolved in a water-soluble alkali or an organic solvent. And this can be separated into solid and liquid to recover the compound (I).

In addition, the solid content after decomposition contains calcium hydroxide which is a divalent or higher hydroxyl group-containing inorganic compound, and by adding hydrochloric acid, it becomes a water-soluble calcium salt and dissolves in water. Thus, compound (I) can be recovered.

As the acid used in the step (C), the carboxylate of the compound (I) can be converted into a water-soluble alkali described later and a compound (I) that can be dissolved in an organic solvent. Examples include those in which calcium hydroxide, which is an inorganic compound having a hydroxyl value or higher, is dissolved to form a water-soluble calcium salt and dissolved in water, such as hydrochloric acid and nitric acid.

The concentration and supply amount of the acid in the step (C) are not particularly limited, but all the carboxylic acid groups in the compound (I) can be ring-opened, and further hydroxylated, which is a divalent or higher hydroxyl group-containing inorganic compound. What is necessary is just to supply more than the quantity which can dissolve calcium. In the case of hydrochloric acid, for example, when concentrated hydrochloric acid (about 35% solution) is used, 60 to 150 parts by mass of concentrated hydrochloric acid and 100 parts by mass of calcium hydroxide with respect to 100 parts by mass of compound (I) ~ 450 parts by mass are preferred. That is, when both compound (I) and calcium hydroxide are 100 parts by mass, the total amount of concentrated hydrochloric acid is 360 to 600 parts by mass. From the viewpoint of workability, it is preferable to dilute the acid with water to a concentration at which the solid content is immersed. However, excessive dilution is not preferable because the amount of waste water increases.

Further, the acid supply in the step (C) may be performed by adding a predetermined amount of acid to the solid content recovered in the step (B), or the solid content is immersed in a predetermined amount of acid. You may go by doing.

The filtrate (aqueous solution) separated in step (C) is added again to the solid content recovered in step (B) as hydrochloric acid and / or water for diluting hydrochloric acid used in step (C). It can be reused to convert the carboxylate to compound (I). When the concentration of dissolved salt increases by repeated reuse, the salt is recovered by evaporating water. The evaporated water can be reused.

Next, the embodiment [2] will be described. The thermosetting resin is decomposed in subcritical water (step (A)), and as shown in FIG. 2, the obtained decomposition product is solid-liquid separated and contained with the carboxylate of compound (I). The solid content is recovered (until step (B) is the same as in the embodiment [1]).

Also, the separated filtrate can be reused as a subcritical water for the decomposition of other thermosetting resins while containing the polyhydric alcohol and the polybasic acid, as in the embodiment [1]. Moreover, it is possible to recover the polyhydric alcohol and polybasic acid at a high concentration by sequentially reusing them and dissolving the polyhydric alcohol and polybasic acid generated in each decomposition reaction sequentially in the aqueous solution. .

In the step (C), by adding sulfuric acid instead of hydrochloric acid, the carboxylic acid group of the compound (I) that is ring-closed via the metal M having a valence of 2 or more can be opened, but it is insoluble in water. Calcium sulfate, a calcium salt, is produced. Calcium sulfate, which is a dihydric or higher hydroxyl group-containing inorganic compound, is also produced by adding sulfuric acid.

Similarly to sulfuric acid, an acid capable of ring-opening the carboxylic acid group of compound (I) that is ring-closed via a divalent or higher-valent metal M and forming a salt insoluble in water is also a process. (C) can be used. Examples of such acids include sulfuric acid and phosphoric acid.
Here, the concentration and supply amount of the acid in the step (C) are, in the case of sulfuric acid, for example, when concentrated sulfuric acid (about 98% solution) is used, concentrated sulfuric acid is 30 to 50 per 100 parts by mass of the compound (I). Concentrated sulfuric acid is preferably 130 to 170 parts by mass with respect to 100 parts by mass of calcium hydroxide. That is, when both compound (I) and calcium hydroxide are 100 parts by mass, the total amount of concentrated sulfuric acid is 160 to 220 parts by mass. From the viewpoint of workability, it is preferable to dilute the acid with water to a concentration at which the solid content is immersed. However, excessive dilution is not preferable because the amount of waste water increases.

The filtrate (aqueous solution) separated in step (C) is added again to the solid content recovered in step (B) as sulfuric acid and / or water for diluting sulfuric acid used in step (C). It can be reused to convert the carboxylate to compound (I). Since this aqueous solution contains no salt, it can be reused over and over again.

Next, as shown in FIG. 2, the solid content (mixture of compound (I) and calcium sulfate) recovered in step (C) is brought into contact with a solvent such as acetone to dissolve the solid content compound (I). Then, the compound (I) is recovered (step (D)).

Specifically, a solvent capable of dissolving the compound (I) is supplied to the solid content, and this is stirred at room temperature to dissolve the compound (I) in the solvent, and then other inorganic substances in the solid content. Separate from (calcium sulfate). Next, the solvent is evaporated to recover the compound (I).

Such a solvent capable of dissolving the compound (I) is used for dissolving only the compound (I) from the solid content of the decomposition product. Examples of the solvent include water, water-soluble alkaline aqueous solutions, and organic solvents such as acetone, tetrahydrofuran (THF), methanol, octanol, and chloroform.
In addition, these solvents can be used individually by 1 type or in combination of 2 or more types.
The amount of the solvent used is, for example, 200 to 3000 parts by mass of acetone with respect to 100 parts by mass of compound (I) in the case of acetone with respect to compound (I).

Next, the embodiment [3] will be described. The decomposition target is a thermosetting resin containing inorganic substances (calcium carbonate and glass fiber). In the same manner as in the embodiment [1], the product is decomposed in subcritical water (step (A)), and as shown in FIG. A solid content in which a divalent or higher hydroxyl group-containing inorganic compound and an inorganic substance (calcium carbonate, glass fiber) are mixed is recovered (step (B)).

Also, the separated filtrate can be reused as a subcritical water for the decomposition of other thermosetting resins while containing the polyhydric alcohol and the polybasic acid, as in the embodiment [1]. Moreover, it is possible to recover the polyhydric alcohol and polybasic acid at a high concentration by sequentially reusing them and dissolving the polyhydric alcohol and polybasic acid generated in each decomposition reaction sequentially in the aqueous solution. .

In the step (C), by adding hydrochloric acid as in the embodiment [1], the carboxylic acid group of the compound (I) that is ring-closed via the divalent or higher metal M can be opened, Calcium hydroxide, which is a divalent or higher hydroxyl group-containing inorganic compound, and calcium carbonate in the inorganic substance are dissolved in water as water-soluble calcium salts.
Then, the glass fiber in compound (I) and an inorganic substance is collect | recovered as solid content by carrying out solid-liquid separation.
Here, the acid in Step (C) and the concentration and supply amount thereof are, in the case of hydrochloric acid, for example, when concentrated hydrochloric acid (about 35% solution) is used, from 60 parts by mass of concentrated hydrochloric acid to 100 parts by mass of Compound (I). Concentrated hydrochloric acid is preferably 300 to 450 parts by mass with respect to 150 parts by mass and calcium hydroxide of 100 parts by mass, and concentrated hydrochloric acid is preferably 210 to 300 parts by mass with respect to 100 parts by mass of calcium carbonate. That is, when the compound (I), calcium hydroxide, and calcium carbonate are each 100 parts by mass, the total amount of concentrated hydrochloric acid is 570 to 900 parts by mass. From the viewpoint of workability, it is preferable to dilute the acid with water to a concentration at which the solid content is immersed. However, excessive dilution is not preferable because the amount of waste water increases.

At this time, in the same manner as in the embodiment [1], the filtrate was again added to the solids recovered in the step (B) as hydrochloric acid and / or water for diluting hydrochloric acid used in the step (C). It can be reused to convert the carboxylate to compound (I). When the concentration of dissolved salt increases by repeated reuse, the salt is recovered by evaporating water. The evaporated water can be reused.

Next, as shown in FIG. 3, the solid content (mixture of compound (I) and glass fiber) recovered in step (C) is brought into contact with a solvent such as acetone to dissolve the solid content compound (I). Then, it is separated from the glass fiber by solid-liquid separation, and acetone or the like is vaporized to recover the compound (I) (step (D)).
Here, the solvent used in the step (D) and the amount used thereof are the same as those in the embodiment [2].

Next, the embodiment [4] will be described. The decomposition target is a thermosetting resin containing inorganic substances (calcium carbonate and glass fiber). In the same manner as in the embodiment [1], the product is decomposed in subcritical water (step (A)), and the resulting decomposition product is separated into solid and liquid as shown in FIG. A solid content in which a divalent or higher hydroxyl group-containing inorganic compound and an inorganic substance (calcium carbonate, glass fiber) are mixed is recovered (step (B)).

Also, the separated filtrate can be reused as a subcritical water for the decomposition of other thermosetting resins while containing the polyhydric alcohol and the polybasic acid, as in the embodiment [1]. Moreover, it is possible to recover the polyhydric alcohol and polybasic acid at a high concentration by sequentially reusing them and dissolving the polyhydric alcohol and polybasic acid generated in each decomposition reaction sequentially in the aqueous solution. .

In the step (C), by adding sulfuric acid as in the embodiment [2], the carboxylic acid group of the compound (I) that is ring-closed via the divalent or higher metal M can be opened, Calcium sulfate, a calcium salt that is insoluble in water, is produced. Calcium sulfate, which is a dihydric or higher hydroxyl group-containing inorganic compound, is also produced by adding sulfuric acid. Furthermore, calcium sulfate is produced by adding sulfuric acid to calcium carbonate in the inorganic substance.
Then, it collects as solid content which compound (I), calcium sulfate, and glass fiber mixed by carrying out solid-liquid separation.
Here, in the case of sulfuric acid, for example, when concentrated acid (about 98% solution) is used, the acid and the concentration and supply amount in step (C) are 30 to 30% concentrated sulfuric acid with respect to 100 parts by mass of compound (I). Concentrated sulfuric acid is preferably 130 to 170 parts by mass with respect to 50 parts by mass and 100 parts by mass of calcium hydroxide. Further, 100 to 150 parts by mass of concentrated sulfuric acid is preferable with respect to 100 parts by mass of calcium carbonate. That is, when the compound (I), calcium hydroxide, and calcium carbonate are each 100 parts by mass, the total amount of concentrated sulfuric acid is 260 to 370 parts by mass. From the viewpoint of workability, it is preferable to dilute the acid with water to a concentration at which the solid content is immersed. However, excessive dilution is not preferable because the amount of waste water increases.

The filtrate (aqueous solution) separated in step (C) is added again to the solid content recovered in step (B) as sulfuric acid and / or water for diluting sulfuric acid used in step (C). It can be reused to convert the carboxylate to compound (I). Since this aqueous solution contains no salt, it can be reused over and over again.

Next, as shown in FIG. 4, the solid content (compound (I), calcium sulfate, glass fiber mixture) recovered in the step (C) is brought into contact with a solvent such as acetone to obtain the solid content compound (I). Is dissolved into solid and liquid, separated from calcium sulfate and glass fiber, and acetone is vaporized to recover the compound (I) (step (D)).
Here, the solvent used in the step (D) and the amount used thereof are the same as those in the embodiment [2].

The compound (I) recovered by the method of the present invention as shown in the embodiments [1] to [4] of FIGS. 1 to 4 is modified to impart compatibility with the raw material of the thermosetting resin. Thus, it can be reused as a low shrinkage agent that suppresses the curing shrinkage of the thermosetting resin, and in the alkaline salt state, it can be reused in a dispersant such as cement or pigment, a detergent builder, or the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example 1>
Unsaturated polyester was synthesized by polycondensation of glycols composed of propylene glycol, neopentyl glycol and dipropylene glycol with maleic anhydride in equimolar amounts. 165 parts by mass of calcium carbonate and 90 parts by mass of glass fiber are blended in 100 parts by mass of a liquid resin in which an equimolar amount of styrene as a crosslinking agent is blended in this unsaturated polyester varnish (no solvent added), and this is cured and cured. A saturated polyester resin molded product (hereinafter referred to as “thermosetting resin”) was obtained.

4 g of this thermosetting resin, 16 g of pure water, and 0.24 g of calcium hydroxide are charged in a reaction tube, immersed in a constant temperature bath at 260 ° C., and the pure water in the reaction tube is immersed in a subcritical state for 4 hours. The thermosetting resin was decomposed by leaving it to stand.

Thereafter, the reaction tube was taken out of the thermostatic bath and immersed in a cooling bath, and the reaction tube was rapidly cooled to room temperature. The contents of the reaction tube after the decomposition treatment were a water-soluble component, an undissolved resin residue, calcium carbonate, and glass fiber, and the solid content was separated and recovered by filtering the content.

Next, about 3.7 g of this solid content (all residues after decomposition) is immersed in 40 mL of 1N hydrochloric acid to dissolve calcium carbonate in the solid content, and the carboxylic acid of the styrene-fumaric acid copolymer in the undissolved resin residue. The acid group was opened by reacting with the closed calcium, and the solid content was separated and recovered.

Then, the solid content was immersed in 20 mL of acetone and filtered to separate into an acetone dissolved product and an acetone undissolved product. The weight of the acetone dissolved product was measured, and the recovery rate of the styrene-fumaric acid copolymer was calculated by the following formula.
Recovery rate (%) = (Amount of dissolved acetone) / (Amount of styrene-fumaric acid copolymer contained in thermosetting resin) × 100
Here, the “amount of acetone-dissolved material” is the weight of the solid material remaining after evaporation of the acetone solution obtained by dissolving the styrene-fumaric acid copolymer when acetone is added to the solid material. is there.
The “amount of styrene-fumaric acid copolymer contained in the thermosetting resin” is the number of molecules derived from acid residues and cross-linked parts calculated by analyzing the compound obtained by decomposition by NMR. It is the estimated content of the compound (I) obtained from the ratio and the amount of the crosslinked part molding material used.
Table 1 shows the test conditions and the results of the recovery of the styrene-fumaric acid copolymer.

<Example 2>
In Example 1, a test was performed under the same conditions as in Example 1 except that the amount of calcium hydroxide was changed to 0.95 g, and a styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions and the results of the recovery of the styrene-fumaric acid copolymer.

<Example 3>
In Example 1, a test was conducted under the same conditions as in Example 1 except that the amount of calcium hydroxide was changed to 1.18 g, and a styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions and the results of the recovery of the styrene-fumaric acid copolymer.

<Comparative example>
In Example 1, a test was conducted under the same conditions as in Example 1 except that calcium hydroxide was not used, and a styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions and the results of the recovery of the styrene-fumaric acid copolymer.

From the results in Table 1, by decomposing the thermosetting resin with subcritical water containing a divalent or higher hydroxyl group-containing inorganic compound (Examples 1 to 3), no divalent or higher hydroxyl group-containing inorganic compound is contained. Compared with the comparative example decomposed with subcritical water, it was confirmed that the recovery rate of the styrene-fumaric acid copolymer was drastically improved.

Claims (4)

A method of recovering a reusable decomposition product by decomposing a thermosetting resin containing a polyester part and its cross-linked part,
(A) decomposing the thermosetting resin with subcritical water containing a divalent or higher hydroxyl group-containing inorganic compound;
(B) a step of solid-liquid separation of the obtained decomposition product and recovering a solid content containing a carboxylate salt of a compound comprising an acid residue derived from a polyester and a residue derived from a cross-linked part;
(C) After adding an acid to the recovered solid content, this is subjected to solid-liquid separation to recover the solid content containing the compound;
Including a method. (D) The method of Claim 1 which further includes the process which makes the collect | recovered solid content contact the solvent which can dissolve the said compound, and melt | dissolves and collect | recovers the said compound in the said solvent. The method according to claim 1 or 2, wherein the separated filtrate after subcritical water decomposition is repeatedly reused as a feed liquid for subcritical water decomposition. The method according to any one of claims 1 to 3, wherein the divalent or higher hydroxyl group-containing inorganic compound comprises calcium hydroxide.

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