JP4806757B2 - Decomposition and recovery method of thermosetting resin - Google Patents

Description

  The present invention relates to a method for decomposing and recovering a thermosetting resin by decomposing a thermosetting resin with subcritical water and recovering a modified product of 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. Without being able to deposit the styrene-fumaric acid copolymer directly as a solid content of the decomposition product, and the thermosetting that can efficiently recover the styrene-fumaric acid copolymer in a form that is easy to reuse An object is to provide a method for decomposing and recovering resin.

  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 solid-liquid separation of the obtained decomposition product, recovering the solid content containing the styrene-fumaric acid copolymer (B), contacting the recovered solid content with alcohol, And a step (C) of esterifying the styrene-fumaric acid copolymer and recovering an alcohol-modified product of the styrene-fumaric acid copolymer.

  Second, in the first thermosetting resin decomposition / recovery method, the alcohol is octanol.

  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.

  Furthermore, since the solid content of the decomposition product is treated with an alcohol having a solubility of the styrene-fumaric acid copolymer that is higher than that of water and low in solubility in water, the decomposition product contains inorganic and undecomposed substances. Even if it contains a thermosetting resin, the styrene-fumaric acid copolymer can be efficiently recovered from the solid content as an alcohol-modified product. Moreover, this esterified alcohol-modified product is suitable for reuse as a low shrinkage material for thermosetting resins.

  According to the second invention, since octanol is used as the alcohol, in addition to the effects of the first invention, the styrene-fumaric acid copolymer is sufficiently esterified without requiring harsh conditions. In addition, a modified product particularly suitable for reuse as a low shrinkage material of a thermosetting resin can be obtained.

  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, even when the thermothermosetting resin composition to be decomposed contains calcium carbonate, the alcohol-modified product of the styrene-fumaric acid copolymer can be efficiently recovered.

  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 portion and a cross-linked portion 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 portion. 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 particular restrictions on the type and structure of the resin, the type and amount of the cross-linking part (cross-linking agent), and the degree of cross-linking.

  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 above-described thermosetting resin is decomposed and the alcohol-modified product of 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 an alcohol such as octanol to esterify the styrene-fumaric acid copolymer of the solid content, so that the styrene-fumaric acid copolymer is obtained. The alcohol-modified product is recovered (step (C)).

  Specifically, an alcohol having a higher solubility of styrene-fumaric acid copolymer 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. And the styrene-fumaric acid copolymer is esterified to obtain an alcohol-modified product.

  For example, when octanol is used as the alcohol, the solid content is immersed in octanol, heated while being stirred, and then solid-liquid separated. The styrene-fumaric acid copolymer dissolved in octanol is esterified and can be recovered as an octanol modified product of the styrene-fumaric acid copolymer.

  The alcohol used in the present invention is not particularly limited as long as the solubility of the styrene-fumaric acid copolymer is higher than that of water, the solubility in water is low, and the styrene-fumaric acid copolymer can be esterified. Recycled alcohol-modified products as solubility of styrene-fumaric acid copolymer, solubility in water, reactivity with styrene-fumaric acid copolymer, low shrinkage material, etc. In consideration of the usability and the like, a monovalent alcohol is preferable, and a linear saturated alcohol having 6 or more carbon atoms, particularly a linear saturated alcohol having 6 to 18 carbon atoms is particularly preferable. These saturated alcohols may have a substituent such as an alkyl group, a cycloalkyl group, a phenyl group, or a benzyl group. Of these saturated alcohols, primary or secondary alcohols are preferred. In particular, styrene-fumaric acid copolymer can be sufficiently esterified without requiring harsh conditions, and compatibility with other components when reusing thermosetting resin as a low shrinkage material, etc. In view of the above, octanol is preferred because a particularly suitable modified product can be obtained.

  The condensation (esterification) rate of the carboxylic acid group in the alcohol-modified product of the styrene-fumaric acid copolymer obtained by esterification of the styrene-fumaric acid copolymer depends on the amount of alcohol used and the reaction conditions. When the modified product is used for a low shrinkage material of a thermosetting resin, the condensation rate is 50 to 100 mol%, preferably 80 to 100 mol%, and is suitable for the use. can do.

  The alcohol-modified product of the styrene-fumaric acid copolymer thus obtained can be reused in a form separated from the inorganic substance in the solid content, but low shrinkage of plastics etc. in a state containing the inorganic substance. You may make it reuse as a material or a dispersing agent.

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

  Thereafter, by adding an alcohol such as octanol in step (C), the styrene-fumaric acid copolymer is dissolved in the alcohol, and an alcohol-modified product of the styrene-fumaric acid copolymer is generated by an esterification reaction. Can be recovered.

  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, Compared with the method shown in FIG. 1, the octanol-modified product of the styrene-fumaric acid copolymer can be recovered with 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 260 ° C., and the pure water in the reaction tube 1 was left in a subcritical state for 4 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 13.7 g of octanol, stirred in an oil bath at 195 ° C. for 8 hours, and then filtered to separate the octanol dissolved product and the octanol undissolved product. The weight of the dissolved octanol was measured, and the recovery rate of the octanol modified product of the styrene-fumaric acid copolymer was calculated by the following formula.
Recovery rate (%) = (Amount of dissolved octanol) / (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 octanol modified product, and the like.

From the results shown in Table 1, a styrene-fumaric acid copolymer is obtained as a water-insoluble component by decomposing a thermosetting resin with subcritical water containing no alkali. Further, an octanol modified product of the styrene-fumaric acid copolymer is obtained. It was shown that it can be recovered.
<Example 2>
In Example 1, before the solid content recovered after decomposition with subcritical water was immersed in octanol, 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 to obtain an octanol modified product of a styrene-fumaric acid copolymer. Table 1 shows the test conditions, the decomposition rate of the thermosetting resin, the recovery rate of the styrene-fumaric acid copolymer octanol modified product, and the like.

  From the results shown in Table 1, a styrene-fumaric acid copolymer is obtained as a water-insoluble component by decomposing a thermosetting resin with subcritical water containing no alkali. Further, an octanol modified product of the styrene-fumaric acid copolymer is obtained. As a high yield.

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, A step (B) of recovering a solid content containing an acid copolymer, and contacting the recovered solid content with an alcohol to esterify the styrene-fumaric acid copolymer of the solid content. And a step (C) of recovering the alcohol-modified product.   The method for decomposing and recovering a thermosetting resin according to claim 1, wherein the alcohol is octanol.   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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