JP4806758B2 - Decomposition and recovery method of thermosetting resin - Google Patents

Description

  The present invention relates to a method for decomposing and recovering a thermosetting resin in which a thermosetting resin is decomposed with subcritical water to recover a styrene-fumaric acid copolymer.

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.

  For this reason, the Containers and Packaging Disposal Law was enacted in 1995, and plastics must be collected and reused. Furthermore, with the enforcement of various recycling laws, the flow of collection and recycling of products containing plastics tends to accelerate.

  In recent years, attempts have been made to recycle plastic waste in accordance with these circumstances, and as one of them, a method for decomposing and recovering plastic using supercritical water or subcritical water as a reaction medium 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 copolymer of a crosslinking agent and a polybasic acid (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 JP-A-5-31000 JP-A-6-279762 Japanese Patent Laid-Open No. 10-67991 International Publication WO2005 / 092962 Pamphlet

  However, in this method, although a styrene-fumaric acid copolymer can be obtained, since the thermosetting resin is decomposed with subcritical water containing a catalytic amount of alkali, the styrene-fumaric acid produced by the decomposition reaction. The copolymer exists as a salt dissolved in an aqueous solution. Therefore, in order to recover the styrene-fumaric acid copolymer, a step of adding a strong acid to the aqueous solution to form an acidic aqueous solution and precipitating the styrene-fumaric acid copolymer is further required.

  The aqueous solution after recovering the styrene-fumaric acid copolymer contains a polyhydric alcohol and a polybasic acid, which are monomer components that can be reused as a resin raw material, and the like. Since the catalyst further contains alkali, there is a problem that treatment for dealing with the strong acid and the alkali of the catalyst is necessary when recycling polyhydric alcohol and polybasic acid or treating wastewater. It was.

  The present invention has been made in view of the circumstances as described above, and requires a step of adding a strong acid to the liquid of the decomposition product of the thermosetting resin with subcritical water to precipitate a styrene-fumaric acid copolymer. The method of decomposing and recovering a thermosetting resin that can directly precipitate a styrene-fumaric acid copolymer as a solid content of a decomposition product without causing the styrene-fumaric acid copolymer to be recovered efficiently It is an issue to provide.

  The present invention is characterized by the following in order to solve the above problems.

1stly, the decomposition | disassembly and collection | recovery method of the thermosetting resin of this invention is a process (A) which decomposes | disassembles the thermosetting resin containing a polyester part and its bridge | crosslinking part with the subcritical water which does not contain the alkali as an additive. And (B) recovering the solid content containing the styrene-fumaric acid copolymer by solid-liquid separation of the obtained decomposition product, and the recovered solid content of the styrene-fumaric acid copolymer. And a step (C) of bringing the styrene-fumaric acid copolymer into contact with a solvent having a higher solubility than water and recovering the styrene-fumaric acid copolymer in the solvent.

  Second, in the first method for decomposing and recovering a thermosetting resin, the solvent in which the solubility of the styrene-fumaric acid copolymer is higher than that of water is acetone.

  Thirdly, in the decomposition or recovery method of the first or second thermosetting resin, in step (A), the thermosetting resin composition containing the thermosetting resin and calcium carbonate is subcritical water. In step (B), the resulting decomposition product is subjected to solid-liquid separation to recover a solid content containing a styrene-fumaric acid copolymer and calcium carbonate, and the solid content is converted to calcium carbonate. It is characterized by mixing with an acid that reacts with water to form a water-soluble calcium salt and water to dissolve calcium carbonate in water, and then solid-liquid separation to recover the solid content.

  According to the first aspect of the invention, since the thermosetting resin is decomposed with subcritical water substantially containing no alkali, styrene-fumaric acid copolymer is used as a solid content of the decomposition product, that is, as a water-insoluble component. Coalescence precipitates. Therefore, the styrene-fumaric acid copolymer is easily separated as a solid content without requiring an additional step of adding a strong acid to precipitate the styrene-fumaric acid copolymer as in the case of performing decomposition in the presence of an alkali. be able to.

  Moreover, since the aqueous solution containing polyhydric alcohol and polybasic acid, which is a recovered liquid component, does not contain the strong acid or the alkali of the catalyst, it is easy to reuse these monomer components and to treat waste water.

  Further, since the styrene-fumaric acid copolymer is dissolved and recovered from the solid content of the decomposition product using a solvent in which the solubility of the styrene-fumaric acid copolymer is higher than that of water, an inorganic substance is included in the decomposition product. Even if it contains undecomposed thermosetting resin, the styrene-fumaric acid copolymer can be efficiently recovered.

  According to the second invention, since acetone is used as a solvent for dissolving the styrene-fumaric acid copolymer from the solid content of the decomposition product, in addition to the effects of the first invention, the styrene-fumaric acid copolymer is used. Can be recovered particularly efficiently.

  According to the third invention, since the calcium carbonate is dissolved in water from the solid content obtained by solid-liquid separation of the decomposition product of subcritical water, the first and second In addition to the effects of the invention, the styrene-fumaric acid copolymer can be efficiently recovered even if the thermothermosetting resin composition to be decomposed contains calcium carbonate.

  The present invention is described in detail below.

  In the present invention, the thermosetting resin to be decomposed / recovered is obtained by crosslinking polyester, and includes a polyester part and its crosslinked 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.

  A crosslinked part is a part which bridge | crosslinks a 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, “a 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 through 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.

  In the present invention, the term “thermosetting resin composition” refers to the thermosetting resin described above and other components such as inorganic fillers such as calcium carbonate and glass fibers such as chopped strands obtained by cutting rovings. Means contained.

  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, 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.

  The cross-linking agent that crosslinks the polyester, which is a copolymer of polyhydric alcohol and polybasic acid, contains styrene as an essential component, but also uses other cross-linking agents such as polymerizable vinyl monomers such as methyl methacrylate. May be.

  In the present invention, the thermosetting resin is decomposed and the styrene-fumaric acid copolymer is recovered by the following steps (A) to (C). Hereinafter, the method of the present invention will be described in the order of steps with reference to the flowchart of FIG.

  First, a thermosetting resin is decomposed | disassembled in the subcritical water which does not contain an alkali substantially (process (A)). Here, “substantially free of alkali” means that an alkali such as an alkali metal hydroxide that acts as a catalyst for the decomposition reaction is not contained in an amount exceeding at least an effective amount as a catalyst. It means a condition in which the obtained styrene-fumaric acid copolymer does not dissolve in water as a salt and almost all of it exists as a styrene-fumaric acid copolymer. Therefore, the presence of a very small amount of alkali that can be eluted from the thermosetting resin is allowed.

  In this step, neutral water substantially containing no alkali is added to the thermosetting resin, and the temperature and pressure are increased to bring the water to a subcritical state, thereby decomposing 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 this invention, it can decompose | disassemble into a polyhydric alcohol, a polybasic acid, and a styrene-fumaric acid copolymer by making said thermosetting resin contact subcritical water, and processing.

  In the present invention, “subcritical water” means that the temperature of water is not higher than the critical point of water (critical temperature 374.4 ° C., critical pressure 22.1 MPa) and the temperature is 140 ° C. or higher (in this case, ion Since the product is about 100 times the normal temperature and the dielectric constant of water is about 50% lower than the normal temperature, hydrolysis is accelerated and the thermosetting resin can be monomerized), and the pressure at that time is 0.36 MPa (Saturated vapor pressure of 140 ° C.) Water in a range above.

  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 requires a lot of time, and thus the processing cost may increase, and the yield of the styrene-fumaric acid copolymer tends to decrease. When the temperature during the decomposition reaction exceeds 300 ° C., the thermal decomposition of the styrene-fumaric acid copolymer becomes remarkable, and the styrene-fumaric acid copolymer is reduced in molecular weight to produce a wide variety of styrene derivatives. It tends to be difficult to recover as a fumaric acid copolymer.

  The treatment time with subcritical water varies depending on conditions such as reaction temperature, but is usually 1 to 4 hours. Although the pressure at the time of a decomposition reaction changes with conditions, such as reaction temperature, Preferably it is the range of 2-15 Mpa.

  As described above, by decomposing the thermosetting resin in a state containing substantially no alkali, the styrene-fumaric acid copolymer produced by the decomposition reaction is precipitated as a water-insoluble component, and the thermosetting resin composition It is recovered as a solid content together with other inorganic substances contained in the product and undecomposed thermosetting resin. On the other hand, the polyester-derived monomers (polyhydric alcohol and polybasic acid) produced by the decomposition reaction are separated from solids such as a styrene-fumaric acid copolymer as a water-soluble component.

  Next, as shown also in FIG. 1, the obtained decomposition product is subjected to solid-liquid separation to recover a solid content containing a styrene-fumaric acid copolymer (step (B)).

  Specifically, after cooling the reaction vessel containing subcritical water and decomposition products, the contents of the vessel are subjected to solid-liquid separation by a method such as filtration. Thereby, the styrene-fumaric acid copolymer is separated as a solid content together with other inorganic substances contained in the thermosetting resin composition, such as calcium carbonate, glass fiber, and undecomposed thermosetting resin. .

  On the other hand, an aqueous solution in which a polyhydric alcohol and a polybasic acid as monomer components 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 in FIG. 1, the solid content recovered in the step (B) is brought into contact with a solvent such as acetone to dissolve the solid content styrene-fumaric acid copolymer, and the styrene-fumaric acid copolymer is dissolved. Is recovered (step (C)).

  Specifically, a solvent in which the solubility of the styrene-fumaric acid copolymer is higher than that of water is supplied to the solid content, whereby the styrene-fumaric acid copolymer is converted into other inorganic substances in the solid content or undecomposed. Separate from thermosetting resin.

  For example, when acetone is used as a solvent, the solid content is immersed in acetone, heated while being stirred, and then solid-liquid separated. The styrene-fumaric acid copolymer dissolved and recovered in acetone can be reused as a low shrinkage material of a thermosetting resin after the modification treatment.

  As the solvent used for dissolving the styrene-fumaric acid copolymer from the solid content of the decomposition product, an organic solvent having high solubility with respect to the styrene-fumaric acid copolymer in the solid content of the decomposition product is used. It is done. A specific example of such a solvent is acetone.

  Furthermore, in this invention, when the object of decomposition | disassembly and collection | recovery is a thermosetting resin composition containing calcium carbonate, after decomposing | disassembling a thermosetting resin composition in subcritical water in a process (A), a process ( In B), the obtained decomposition product is subjected to solid-liquid separation to recover a solid content containing a styrene-fumaric acid copolymer and calcium carbonate, and the solid content is further reacted with calcium carbonate to form a water solution. After mixing with the acid which forms a calcium salt, and water, calcium carbonate is dissolved in water, solid-liquid separation may be performed to recover the solid content. A flowchart of the present invention including this step is shown in FIG.

  Specifically, as shown in FIG. 2, hydrochloric acid or the like is added to the solid content obtained by solid-liquid separation of the decomposition product of subcritical water, and calcium carbonate in the solid content is converted into water as a water-soluble calcium salt. Dissolve in. The acid to be used may be other than hydrochloric acid as long as it generates a water-soluble calcium salt.

  Thereafter, as step (C), the recovered solid content is immersed in a solvent such as acetone as described above, and the styrene-fumaric acid copolymer is dissolved in the solvent, thereby recovering the styrene-fumaric acid copolymer. Can do.

  Thus, even if calcium carbonate is contained in the thermosetting resin composition to be decomposed by removing calcium carbonate using an acid from a solid containing styrene-fumaric acid copolymer and calcium carbonate, As compared with the method shown in FIG. 1, the styrene-fumaric acid copolymer can be recovered at a higher yield.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, 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 and 16 g of pure water were charged into the reaction tube 1 shown in FIG. 3, and the inside was replaced with argon gas and hermetically sealed. The reaction tube 1 was immersed in a constant temperature bath 2 at 230 ° C., and the pure water in the reaction tube 1 was left in a subcritical state for 8 hours so as to decompose the thermosetting resin.

  Then, the reaction tube 1 was taken out from the thermostat 2 and immersed in the cooling bath 3, and the reaction tube 1 was rapidly cooled to room temperature. The content of the reaction tube 1 after the decomposition treatment is a water-soluble component, an insoluble resin residue, calcium carbonate, and glass fiber. The content of the reaction tube 1 is separated and recovered by filtering the content of the reaction tube 1. .

And the decomposition rate of the thermosetting resin was computed by the following formula.
Decomposition rate (%) = (Amount of thermosetting resin before decomposition−Amount of thermosetting resin remaining after decomposition) / (Amount of thermosetting resin before decomposition) × 100
Next, the collected solid content was immersed in 20 ml of acetone and stirred for 2 hours, followed by filtration to separate the dissolved acetone and the undissolved acetone. The weight of the acetone dissolved product was measured, and the recovery rate of the styrene-fumaric acid copolymer was calculated according to the following formula.
Recovery rate (%) = (Amount of dissolved acetone) / (Amount of styrene-fumaric acid copolymer contained in thermosetting resin) × 100
Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer, and the like.
<Example 2>
In Example 1, before the solid content recovered after decomposition with subcritical water was immersed in acetone, this solid content was immersed in hydrochloric acid to dissolve calcium carbonate in the solid content. Otherwise, the test was conducted under the same conditions as in Example 1, and the styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer, and the like.
<Example 3>
A test was conducted under the same conditions as in Example 1 except that the decomposition temperature of the thermosetting resin was changed to 280 ° C. and the decomposition time was changed to 4 hours, and a styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer, and the like.
<Example 4>
In Example 1, the decomposition temperature of the thermosetting resin was changed to 280 ° C., the decomposition time was changed to 4 hours, and before the solid content recovered after decomposition with subcritical water was immersed in acetone, the solid content was converted to hydrochloric acid. So as to dissolve calcium carbonate in the solid content. Otherwise, the test was conducted under the same conditions as in Example 1, and the styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer, and the like.
<Example 5>
The solid content recovered after the decomposition with subcritical water was immersed in 20 ml of methanol instead of acetone and stirred for 2 hours, followed by filtration to separate a methanol dissolved product and a methanol undissolved product. Otherwise, the test was conducted under the same conditions as in Example 1, and the styrene-fumaric acid copolymer was recovered. Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer, and the like.

  From the result of Table 1, in Examples 1-5, a styrene-fumaric acid copolymer is obtained as a water-insoluble component by decomposing | disassembling a thermosetting resin with the subcritical water which does not contain an alkali, and uses a collection | recovery solvent. It was shown that the styrene-fumaric acid copolymer can be recovered. In particular, in the case of Examples 1 to 4 using acetone as the recovery solvent, the styrene-fumaric acid copolymer can be recovered with a high yield, and in Examples 2 and 4, before the solid content is immersed in acetone. In addition, the styrene-fumaric acid copolymer could be recovered in a higher yield by immersing this solid in hydrochloric acid to dissolve calcium carbonate in the solid.

It is the flowchart which showed operation of the decomposition | disassembly and collection | recovery method of the thermosetting resin in one Embodiment of this invention in process order. It is the flowchart which showed operation of the decomposition | disassembly and collection | recovery method of the thermosetting resin in another embodiment of this invention in process order. It is the figure which showed roughly the apparatus structure of the reaction system and cooling system which were used in the Example.

Claims (3)

A step (A) of decomposing a thermosetting resin containing a polyester part and its cross-linked part with subcritical water not containing an alkali as an additive, and separating the resulting decomposition product into a solid-liquid solution, The step (B) of recovering the solid content containing the acid copolymer, and the recovered solid content are brought into contact with a solvent having a solubility of the styrene-fumaric acid copolymer higher than that of water. And a step (C) of recovering the coalescence by dissolving it in the solvent.   The method for decomposing and recovering a thermosetting resin according to claim 1, wherein the solvent having a higher solubility of the styrene-fumaric acid copolymer than water is acetone.   In step (A), a thermosetting resin composition containing a thermosetting resin and calcium carbonate is decomposed with subcritical water, and in step (B), the obtained decomposition product is solid-liquid separated, A solid content containing a styrene-fumaric acid copolymer and calcium carbonate is recovered, and the solid content is mixed with an acid that reacts with calcium carbonate to form a water-soluble calcium salt and water to thereby remove calcium carbonate. 3. The method for decomposing and recovering a thermosetting resin according to claim 1 or 2, wherein the solid content is recovered by solid-liquid separation after being dissolved in the thermosetting resin.

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