JP2005336323A - Method for recovering inorganic substance from plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering inorganic substances from plastics which permits isolation and recovery of a glass fiber from a plastic molded article containing the glass fiber, aluminum hydroxide and calcium carbonate. <P>SOLUTION: The glass fiber is isolated and recovered by steps comprising a step for treating the plastic molded article containing the glass fiber and aluminum hydroxide as the inorganic substances with a subcritical fluid to decompose the plastics into monomers and oligomers and to cause the inorganic substances to leave from the plastics, a step for separating inorganic substances from monomers and oligomers from the plastics, a step for causing aluminum hydroxide to dissolve in water by supplying an acid to water containing the separated inorganic substances, and a step for separating the glass fiber by filtering water where aluminum hydroxide is dissolved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for recovering an inorganic substance from a plastic molded article containing glass fiber, aluminum hydroxide, and calcium carbonate as an inorganic substance such as FRP.

  Reinforced plastics typified by FRP (glass fiber reinforced plastic) contain glass fiber and aluminum hydroxide as inorganic substances, and calcium carbonate in addition to glass fiber and aluminum hydroxide. Conventionally, it has been studied to recover glass fiber, sodium hydroxide, and calcium carbonate from plastic molding waste, and to recycle and reuse the recovered glass fiber, aluminum hydroxide, and calcium carbonate.

For example, a technique for separating and recovering glass fibers by contacting and reacting fiber-reinforced plastic with supercritical or subcritical water has been proposed (see, for example, Patent Document 1). That is, by decomposing plastics into monomers and oligomers using supercritical or subcritical water as a reaction solution, the glass fibers are separated from the plastics, and the mixture of the decomposed plastic monomers and oligomers and glass fibers is filtered. The glass fiber can be separated and recovered as a filtration residue.
Japanese Patent Laid-Open No. 10-87872

  However, in general, FRP contains aluminum hydroxide and calcium carbonate as described above in addition to glass fiber as an inorganic substance, and in a state where aluminum hydroxide and calcium carbonate are mixed with glass fiber in the above filtration residue. It exists and is mixed in various proportions depending on the type of FRP. Therefore, when material recycling of glass fiber is performed, strength reduction due to mixing of aluminum hydroxide or calcium carbonate and variation in the ratio occurs, and the physical properties of FRP recycled from glass fiber are likely to vary. It had a problem that it was difficult to use.

  The present invention has been made in view of the above points, and is made of an inorganic substance from plastic that can separate and recover glass fiber from a plastic molded article containing glass fiber, aluminum hydroxide, and calcium carbonate. An object of the present invention is to provide a recovery method, and further to provide a method of recovering an inorganic substance from plastic that can separate and recover aluminum hydroxide and calcium carbonate alone. .

  In the method for recovering an inorganic substance from plastic according to claim 1 of the present invention, a plastic molded article containing glass fiber and aluminum hydroxide as an inorganic substance is treated with a subcritical fluid to decompose the plastic into a monomer or an oligomer and to produce an inorganic substance. Detaching from the plastic, separating the inorganic from the plastic monomers and oligomers, supplying the acid to the water containing the separated inorganic and dissolving the aluminum hydroxide in water, and the aluminum hydroxide dissolved And a step of separating the glass fiber by filtering water.

The invention of claim 2 is the method according to claim 1, wherein the step of separating the inorganic substance from the plastic monomer or oligomer and the step of supplying the acid to the water containing the inorganic substance to dissolve the aluminum hydroxide in the water, It has the process of adjusting the pH of the water containing an inorganic substance to 8-10. Moreover, invention of Claim 3 is the water which aluminum hydroxide after isolate | separating glass fiber in Claim 1 or 2 melt | dissolved It is characterized by having a step of supplying aluminum to precipitate aluminum hydroxide.

  According to a fourth aspect of the present invention, in the third aspect, the alkali is supplied so that the pH of the water after supplying the alkali is 6-8.

  The invention of claim 5 is a process according to any one of claims 1 to 4, wherein a plastic molded article containing glass fiber, aluminum hydroxide and calcium carbonate is used as the inorganic substance, and the inorganic substance is separated from the plastic monomer or oligomer. , Supplying carbon dioxide gas to water containing glass fiber, aluminum hydroxide and calcium carbonate as an inorganic substance between the step of supplying acid to water containing inorganic substance and dissolving aluminum hydroxide in water. It comprises a step of dissolving in water and a step of filtering the water in which calcium carbonate is dissolved to separate glass fibers and aluminum hydroxide.

  The invention of claim 6 is a process of filtering the water in which aluminum hydroxide is dissolved, using a plastic molded article containing glass fiber, aluminum hydroxide and calcium carbonate as an inorganic substance in any one of claims 1 to 4. Later, it has a step of supplying carbon dioxide gas to water containing glass fiber and calcium carbonate as an inorganic substance to dissolve calcium carbonate in water, and a step of separating glass fiber by filtering water in which calcium carbonate is dissolved. It is a feature.

  In addition, the invention of claim 7 is characterized in that in claim 5 or 6, after the step of filtering the water in which calcium carbonate is dissolved, the step of heating the filtered water to precipitate calcium carbonate. .

  The invention of claim 8 is characterized in that, in any one of claims 1 to 7, hydrochloric acid is used as the acid supplied in the step of dissolving aluminum hydroxide in water.

  The invention of claim 9 is characterized in that, in any of claims 3 to 8, sodium hydroxide is used as the alkali supplied in the step of depositing aluminum hydroxide.

  According to the present invention, after the glass fiber and aluminum hydroxide-containing plastics are decomposed as inorganic substances and the glass fibers and aluminum hydroxide are separated from the plastic, the glass fibers are separated from the aluminum hydroxide and recovered. The glass fiber can be separated and recovered independently.

  Further, according to the invention of claim 2, when the acid is supplied by adjusting the pH of water, the acid can be reacted with aluminum hydroxide without waste and without generating unnecessary precipitates. Aluminum oxide can be efficiently dissolved in water.

  According to the invention of claim 3, aluminum hydroxide dissolved in water can be deposited and recovered, and in addition to glass fiber, aluminum hydroxide can also be separated and recovered alone. .

  According to the invention of claim 4, it is possible to prevent aluminum hydroxide from being redissolved in water due to excessive supply of alkali, and to improve the recovery rate of aluminum hydroxide.

  According to the invention of claim 5, after the glass fiber, aluminum hydroxide, and calcium carbonate as an inorganic material are decomposed and the glass fiber, aluminum hydroxide, and calcium carbonate are separated from the plastic, the glass fiber is The glass fiber can be separated and recovered from aluminum hydroxide or calcium carbonate, and the glass fiber can be separated and recovered independently.

  According to the invention of claim 6, after the plastic containing glass fiber, aluminum hydroxide and calcium carbonate is decomposed as an inorganic substance, the glass fiber, aluminum hydroxide and calcium carbonate are separated from the plastic, The glass fiber can be separated and recovered from aluminum hydroxide or calcium carbonate, and the glass fiber can be separated and recovered independently.

  According to the invention of claim 7, calcium carbonate dissolved in water can be deposited and recovered, and in addition to glass fiber and aluminum hydroxide, calcium carbonate can also be separated and recovered independently. It is.

  Further, according to the inventions of claims 8 and 9, since the product by-produced by dissolution / precipitation of aluminum hydroxide is harmless sodium chloride, the waste liquid treatment is not particularly necessary, and the waste liquid treatment is labor-saving. Is something that can be done.

  Hereinafter, the best mode for carrying out the present invention will be described.

  In the present invention, the plastic to be decomposed / recovered may be any one of thermosetting and thermoplastic resins. Specifically, examples of the thermosetting resin include unsaturated polyester resin, acrylic resin, epoxy resin, polyurethane resin, amino resin, and phenol resin. Examples of the thermoplastic resin include polyvinyl chloride resin and polyethylene resin. Examples thereof include resins, polystyrene resins, polypropylene resins, polybutadiene resins, alkyd resins, polycarbonate resins, and polyamide resins.

  The plastics to be decomposed and recovered in the present invention are those containing glass fibers and aluminum hydroxide as inorganic substances, or those containing glass fibers, aluminum hydroxide and calcium carbonate as inorganic substances. Although it is possible to use plastics containing other components as inorganic components, in principle, it is preferable that the inorganic material does not substantially contain other components, and glass fibers are not contaminated with impurities. It becomes easy to recover aluminum hydroxide and calcium carbonate.

  First, an embodiment in which a plastic containing glass fiber and aluminum hydroxide is used as an inorganic substance will be described.

  As a first step, a plastic molded article containing glass fibers and aluminum hydroxide is treated with a subcritical fluid, and the plastics are decomposed into monomers and oligomers to release inorganic glass fibers and aluminum hydroxide from the plastics.

  In this decomposition process using a subcritical fluid, a plastic and fluid that has been cut or coarsely pulverized according to the size of the container and sealed in a container having heat resistance and pressure resistance, and the fluid is in a subcritical state. By heating and pressurizing, the plastic resin component can be decomposed into monomers or oligomers using the subcritical fluid as a reaction solvent, and the inorganic glass fiber and aluminum hydroxide embedded in the plastic resin component Can be released by decomposition of the resin component.

  Examples of the fluid used in the subcritical state used in the present invention include, but are not limited to, water, monohydric alcohols, polyhydric alcohols, and the like, and mixtures thereof. Moreover, when using water as a fluid, it is preferable to use what was desalted beforehand. Further, in order to further promote the decomposition of the plastic, an aqueous solution of an alkali metal hydroxide can be used as a fluid. As the alkali metal, potassium hydroxide, sodium hydroxide, or the like can be used.

  The blending amount of the fluid with respect to the plastic is preferably in the range of 100 to 500 parts by mass with respect to 100 parts by mass of the plastic. If the blending amount of the fluid is less than 100 parts by mass, it is difficult to stably decompose the plastic. Conversely, if the amount exceeds 500 parts by mass, the cost of the fluid treatment after decomposition is increased, which is preferable. Absent.

  About decomposition temperature, the range of 180-270 degreeC is preferable. If the decomposition temperature is less than 180 ° C., it takes a long time to decompose, and conversely if it exceeds 270 ° C., the effect of thermal decomposition increases, and the resin may not be recovered as a monomer or oligomer. Absent. The decomposition time and decomposition pressure are not particularly limited, but in the above decomposition temperature range, a range of 1 to 4 hours and 2 to 15 MPa is preferable. Moreover, when using the aqueous solution of an alkali metal hydroxide as a fluid, it is preferable to add the alkali metal hydroxide in a range of 20 to 100 parts by mass with respect to 100 parts by mass of the plastic.

  In the presence of the subcritical fluid as described above, the resin monomer or oligomer is dissolved in the fluid by decomposing the plastic into the resin monomer or oligomer, the inorganic glass fiber, and aluminum hydroxide, and the inorganic glass is dissolved. A liquid in which fibers and aluminum hydroxide are dispersed is obtained. Then, by filtering this liquid in the next step, the resin monomer or oligomer can be separated from the inorganic glass fiber and aluminum hydroxide. The filtrate after filtration is a fluid in which resin monomers or oligomers are dissolved, and the residue is a mixture of inorganic glass fibers and aluminum hydroxide.

  After separating the inorganic glass fiber and aluminum hydroxide as a residue in the separation step, a mixture of the glass fiber and aluminum hydroxide is dispersed in water, and an acid is supplied to the dispersed water. In the step of supplying the acid, the aluminum hydroxide in the mixture becomes an aluminum salt soluble in water and is dissolved in water, and only the glass fibers are dispersed in water. As the acid, any inorganic acid can be used without particular limitation. For example, hydrochloric acid can be used as described below. The supply amount of the acid is not particularly limited, but is preferably set to an amount sufficient to dissolve the total amount of aluminum hydroxide dispersed in water as an aluminum salt in water.

  Here, before the step of supplying acid, the glass fiber can be recovered as milled fiber by pulverizing the mixture of separated inorganic glass fiber and aluminum hydroxide using a pulverizer. . In this pulverization step, either a dry pulverization method in which a mixture of inorganic glass fibers and aluminum hydroxide is pulverized in a dry state or a wet pulverization method in which the mixture is dispersed in water and then pulverized may be used. As the pulverizing means, various pulverizing means such as a ball mill, a roller mill, a jet mill, a vibration mill, a planetary mill, and a stirring frame mill can be used.

  In addition, by washing the mixture of the above-described glass fiber and aluminum hydroxide separated and recovered with water before the step of supplying acid, the mixture of glass fiber and aluminum hydroxide is dispersed in water, It is preferable to adjust the pH of water in which glass fibers and aluminum hydroxide are dispersed to about 8 to 10. By adjusting the pH of water in which glass fibers and aluminum hydroxide are dispersed by adjusting the pH by washing in this way, the acid is not wasted and unnecessary precipitates are removed. It can be made to react with aluminum hydroxide without generating it, and the efficiency of dissolving aluminum hydroxide as an aluminum salt can be increased by supplying an acid. In particular, when an aqueous solution of an alkali metal hydroxide is used as the subcritical fluid, the alkali metal hydroxide adheres to the mixture of glass fiber and aluminum hydroxide separated and recovered after the decomposition treatment with the subcritical fluid. Therefore, if an acid is supplied as it is dispersed in water as it is, the alkali metal hydroxide reacts with the acid, and unnecessary substances may be deposited. Is a particularly useful process.

  And the glass fiber can be collect | recovered as a residue of filtration by the process which the aluminum hydroxide obtained by said process melt | dissolves as aluminum salt, and filters the water in which the glass fiber is disperse | distributing. Since aluminum hydroxide is dissolved in the filtrate and is not contained in the filtration residue, glass fibers that do not contain aluminum hydroxide as an impurity can be recovered alone. Here, when the crushing step is provided as described above, the glass fibers can be recovered as milled fibers.

  On the other hand, aluminum hydroxide is dissolved in the filtrate as an aluminum salt. By supplying alkali to the filtrate, the aluminum salt dissolved in the filtrate returns to aluminum hydroxide insoluble in water. Precipitate and precipitate. Therefore, by filtering this water, aluminum hydroxide can be recovered as a residue.

  Here, if the supply of alkali in this alkali supply step becomes excessive, the precipitated aluminum hydroxide will be dissolved again in water, so that the pH of the water after the alkali supply will be 6-8. It is preferable to adjust the supply amount.

  The alkali to be used is not particularly limited as long as it is an inorganic base. However, when hydrochloric acid is used as an acid for solubilizing aluminum hydroxide as described above, sodium hydroxide is used as the alkali. Is preferably used.

That is, when hydrochloric acid is reacted with aluminum hydroxide, Al (OH) ₃ + 3HCl → AlCl ₃ (dissolved in water) + 3H ₂ O
And when this is reacted with sodium hydroxide, AlCl ₃ + 3NaOH → Al (OH) ₃ (deposited and precipitated) + 3NaCl
Thus, since the by-product is sodium chloride, the waste liquid treatment is not particularly necessary, and the waste liquid treatment can be saved.

  Next, an embodiment in which a plastic containing glass fiber, aluminum hydroxide, and calcium carbonate is used as the inorganic substance will be described.

  In this way, when the plastic containing glass fiber, aluminum hydroxide and calcium carbonate as an inorganic substance is decomposed in the decomposition process using the subcritical fluid, the inorganic substance embedded in the resin component of the plastic Glass fiber, aluminum hydroxide and calcium carbonate can be separated from the resin component. Accordingly, in this decomposition treatment step, a liquid in which resin monomers or oligomers are dissolved in the fluid and inorganic glass fibers, aluminum hydroxide and calcium carbonate are dispersed is obtained. In the next separation step, the resin monomer or oligomer, inorganic glass fiber, aluminum hydroxide, and calcium carbonate can be separated by filtering the liquid. The filtrate after the filtration is a fluid in which the monomer or oligomer of the resin is dissolved, and the residue is a mixture of inorganic glass fibers, aluminum hydroxide and calcium carbonate.

  After separating glass fiber, aluminum hydroxide, and calcium carbonate as a residue in the above process, a mixture of these inorganic substances is dispersed in water, and carbon dioxide gas is supplied to the dispersed water. In this process of supplying carbon dioxide gas, the calcium carbonate in the mixture undergoes the following chemical reaction to become water-soluble calcium bicarbonate and dissolves in water, and only glass fiber and aluminum hydroxide are dispersed in water. It will be in the state. The supply amount of carbon dioxide gas is not particularly limited, but is preferably set to a supply amount sufficient to dissolve the total amount of calcium carbonate dispersed in water as calcium bicarbonate.

CaCO ₃ + CO ₂ + H ₂ O → Ca (HCO ₃ ) ₂ (dissolved in water)
Here, before the step of supplying carbon dioxide gas, after the separated and recovered mixture of glass fiber, aluminum hydroxide and calcium carbonate is washed with water, the mixture of glass fiber, aluminum hydroxide and calcium carbonate is washed with water. It is preferable to adjust the pH of the water in which these inorganic substances are dispersed to about 8 to 10 by dispersing them in the water. By adjusting the pH of water in which each inorganic substance is dispersed to about 8 to 10 by washing and adjusting the pH in this way, the supplied carbon dioxide gas can be dissolved in water without waste. It is possible to increase the efficiency of dissolving calcium carbonate as calcium hydrogen carbonate by supplying carbon dioxide. When the pH of water is less than 8 or when the pH exceeds 10, the solubility of carbon dioxide gas in water is low, and the effect of increasing the efficiency of dissolution of calcium carbonate in water cannot be expected. In particular, when an alkali metal hydroxide aqueous solution is used as the subcritical fluid, the alkali metal hydroxide adheres to the inorganic mixture separated and recovered by the subcritical fluid decomposition treatment. If the carbon dioxide gas is supplied after being dispersed in water in this state, the alkali metal hydroxide and the carbon dioxide gas react with each other, and unnecessary substances may be deposited. Is a particularly useful process.

  Moreover, it is preferable to cool the water in which the mixture of glass fiber, aluminum hydroxide and calcium carbonate is dispersed to 0 to 20 ° C. before the step of supplying carbon dioxide gas. Gases such as carbon dioxide gas are known to have a water solubility inversely proportional to temperature. If the water temperature is low in the process of supplying carbon dioxide gas, carbon dioxide gas can be dissolved in water without waste. It is possible to increase the efficiency of dissolving calcium carbonate as calcium hydrogen carbonate by supplying carbon dioxide by providing a step of cooling the water and adjusting the water temperature in the range of 0 to 20 ° C. It is. When the temperature of water exceeds 20 ° C., the solubility of carbon dioxide gas in water is low, and the effect of increasing the efficiency of dissolution of calcium carbonate in water cannot be expected.

  And the glass fiber obtained in the above process is dissolved as calcium bicarbonate, and the glass fiber and aluminum hydroxide are separated as a residue of filtration by filtering the water in which the glass fiber and aluminum hydroxide are dispersed. Is something that can be done.

  On the other hand, in the filtrate obtained in the filtration and separation step, calcium carbonate is dissolved as calcium hydrogen carbonate. By heating this filtrate, carbon dioxide gas is vaporized and carbon dioxide gas is removed from the filtrate. By doing so, calcium hydrogen carbonate returns to calcium carbonate in the next chemical reaction, and calcium carbonate insoluble in water precipitates. Therefore, by filtering this water, calcium carbonate can be recovered as a residue. Although heating temperature is not specifically limited, About 80-100 degreeC is preferable.

Ca (HCO ₃ ) ₂ → CaCO ₃ (precipitation) + H ₂ O + CO ₂ (vaporization)
Conventionally, calcium carbonate used for industrial materials such as plastics is generally heavy calcium carbonate obtained by pulverizing calcium carbonate pulverized in a mine as it is in consideration of the cost. Light calcium carbonate that is highly purified by removing impurities is rarely used. However, in the present invention, when calcium carbonate is dissolved in water as calcium hydrogen carbonate as described above, impurities contained in heavy calcium carbonate are removed as insoluble matter and recovered as described above. Calcium carbonate can be obtained as so-called light calcium carbonate containing no impurities.

  Further, after separating the glass fiber and aluminum hydroxide as a residue in the filtration separation step, the mixture of the glass fiber and aluminum hydroxide is dispersed in water in the same manner as in the acid supply step described above. To supply acid. In this acid supply step, the aluminum hydroxide in the mixture becomes an aluminum salt soluble in water and dissolves in water, and only glass fibers are dispersed in water.

  Next, the glass fiber can be recovered as a residue of filtration by filtering the water obtained by this step in which the aluminum hydroxide is dissolved as an aluminum salt and the glass fiber is dispersed. Since calcium carbonate has already been separated, aluminum hydroxide is dissolved in the filtrate and is not included in the filtration residue, so glass fiber that does not contain calcium carbonate or aluminum hydroxide as an impurity is collected alone. Is something that can be done. Here, when the crushing step is provided before the step of supplying acid or the step of supplying carbon dioxide gas as described above, the glass fiber can be recovered as milled fiber.

  On the other hand, aluminum hydroxide is dissolved in the filtrate as an aluminum salt. By supplying alkali to the filtrate in the same manner as the alkali supply step, the aluminum salt dissolved in the filtrate is dissolved. It returns to aluminum hydroxide which is insoluble in water, and precipitates. Therefore, by filtering this water, aluminum hydroxide can be recovered as a residue.

  Here, the order of the steps is not limited to the above. For example, in the dispersion water in which glass fiber, aluminum hydroxide, and calcium carbonate are dispersed, the step of dissolving calcium hydroxide as described above, the step of precipitating and collecting calcium carbonate, and the step of dissolving aluminum hydroxide In addition to the step of depositing and recovering aluminum hydroxide, the step of dissolving aluminum hydroxide, the step of dissolving aluminum hydroxide, the step of precipitating and recovering aluminum hydroxide, the step of dissolving calcium carbonate, The step of depositing and collecting calcium carbonate may be performed later. Also, as described above, in the dispersion water in which glass fiber, aluminum hydroxide and calcium carbonate are dispersed, aluminum hydroxide and calcium carbonate are dissolved in water, respectively, and filtered in this state to recover glass fiber. Is also possible.

  From the series of steps as described above, the inorganic substance obtained as a residue by filtering after subcritical decomposition of the plastic is separated separately for each material of glass fiber, aluminum hydroxide, and calcium carbonate, and collected independently. Is something that can be done. Further, by grinding the glass fiber, it can be recovered as a milled fiber having a high added value, and the calcium carbonate can also be recovered as a light calcium carbonate having a high added value. And, by using the glass fiber, aluminum hydroxide, and calcium carbonate collected in this way as an inorganic material for filling plastics, it is possible to perform material recycling that makes it difficult for the properties of recycled plastics to vary. It is.

  Next, the present invention will be specifically described with reference to examples.

(Example 1)
Contains glass fiber and aluminum hydroxide obtained by mixing and pressing 30% by weight of unsaturated polyester resin, 45% by weight of aluminum hydroxide, and 25% by weight of glass fiber as plastic for subcritical water decomposition treatment. A flat plate FRP was used.

  Then, 600 g of coarsely pulverized FRP and 2400 g of an aqueous potassium hydroxide solution having a concentration of 1 mol / L were put in a pressure vessel and sealed, and the pressure vessel was put in a heating tank and heated. The heating tank is designed to heat the water in the tank to a temperature of 230 ° C. with a heater, and the water in the pressure vessel is in a subcritical state (a state below a critical point (critical temperature 374 ° C., critical pressure 22.1 MPa)). I made it. It hold | maintained in this state for 2 hours, After decomposing | disassembling FRP, it cooled to room temperature, took out the content from the pressure vessel, and filtered the content. The residue was obtained by separating the filtrate by filtration in this way. This residue is a mixture of glass fiber and aluminum hydroxide.

  Next, 300 g of residue, 200 g of water, and 400 g of 5 mm balls were placed in a 120 φmm pot mill, pulverized for 4 hours, and filtered to obtain a pulverized product as the residue.

  Next, after 1 g of this pulverized product was dispersed in 10 mL of water, 30 mL of hydrochloric acid having a concentration of 1 mol / L was mixed, whereby aluminum hydroxide in the dispersed water was dissolved in water as an aluminum salt, and only glass fibers were in water. Dispersed water in a dispersed state was obtained.

  Finally, 0.4 g of glass fiber was separated and recovered as a residue by filtering this dispersed water.

(Example 2)
In the same manner as in Example 1, the subcritical decomposition treatment, the filtration separation, and the filtration residue were pulverized, and the pulverized product was dispersed in water and stirred, washed, and filtered several times. After confirming that the pH of the wash water was 10 or less, the solution was filtered again to obtain 300 g of residue.

  Thereafter, 1 g of this residue was dispersed in 10 mL of water, and 10 mL of hydrochloric acid having a concentration of 1 mol / L was mixed, whereby aluminum hydroxide in the dispersed water was dissolved in water as an aluminum salt, and only glass fibers were dispersed in water. Dispersed water in a state was obtained.

  Finally, 0.4 g of glass fiber was separated and recovered as a residue by filtering this dispersed water.

(Example 3)
In the same manner as in Example 2, after subcritical decomposition treatment, filtration separation, filtration residue filtration, pH adjustment by washing the pulverized product, water dispersion of the pulverized product, acid supply, glass fiber recovery by filtration, The pH was adjusted to 7.3 by supplying 9.6 mL of a 1 mol / L sodium hydroxide aqueous solution to the filtrate in which aluminum hydroxide was dissolved, thereby obtaining a precipitate of aluminum hydroxide. After that, 0.4 g of aluminum hydroxide was recovered by filtering and drying the residue.

Example 4
In Example 3, 0.3 g of aluminum hydroxide was recovered in the same manner as in Example 3 except that an aqueous ammonia solution having a concentration of 1 mol / L was used instead of the aqueous sodium hydroxide solution having a concentration of 1 mol / L.

(Example 5)
In Example 3, the same procedure as in Example 3 was performed, except that the supply amount of the sodium hydroxide aqueous solution having a concentration of 1 mol / L was changed to 30 mL and the pH was adjusted to 13.4. In this case, aluminum hydroxide could not be recovered by redissolving.

(Example 6)
FRP (“FRP bathtub” manufactured by Matsushita Electric Works Co., Ltd .: made of unsaturated polyester resin, 43.5% by mass of calcium carbonate, 25% by mass of aluminum hydroxide, 23% by mass of glass fiber) is used as a plastic for subcritical water decomposition treatment. It was. Then, 600 g of coarsely pulverized FRP and 2400 g of an aqueous potassium hydroxide solution having a concentration of 1 mol / L were put in a pressure vessel and sealed, and the pressure vessel was put in a heating tank and heated. The heating tank is designed to heat the water in the tank to a temperature of 230 ° C. with a heater, and the water in the pressure vessel is in a subcritical state (a state below a critical point (critical temperature 374 ° C., critical pressure 22.1 MPa)). I made it. It hold | maintained in this state for 2 hours, After decomposing | disassembling FRP, it cooled to room temperature, taken out the content from the pressure vessel, and filtered the content. The residue was obtained by separating the filtrate by filtration in this way. This residue is a mixture of glass fiber, aluminum hydroxide and calcium carbonate.

  Next, 200 g of residue, 200 g of water, and 400 g of 5 mm balls were placed in a 120 φmm pot mill, pulverized for 4 hours, and filtered to obtain a pulverized residue. Furthermore, this pulverized product was dispersed in water, and stirring, washing, and filtration were repeated several times. After confirming that the pH of the washing water as the filtrate was 10 or less, the residue was filtered again. 200 g was obtained.

  Next, 1 g of this residue was dispersed in 1 L of water, and then 10 L of carbon dioxide gas (standard gas for experiment) was blown at room temperature to dissolve calcium carbonate in the dispersed water. The glass fiber and aluminum hydroxide were dissolved in water. Dispersed water in a dispersed state was obtained.

  Next, this dispersed water is filtered, and the filtrate in which calcium carbonate is dissolved is heated to 80 to 100 ° C. to vaporize and remove carbon dioxide gas, thereby precipitating calcium carbonate, and filtering this precipitate. By collecting, 0.4 g of calcium carbonate was obtained.

  Further, after the residue obtained by filtering the dispersed water is dispersed in 10 mL of water, 10 mL of hydrochloric acid having a concentration of 1 mol / L is mixed, so that the aluminum hydroxide in the dispersed water dissolves in the water as an aluminum salt, and the glass fiber. Only dispersed water was obtained in the state of being dispersed in water.

  And by filtering this dispersed water, 0.4 g of glass fiber was separated and recovered as a residue.

  Finally, the pH was adjusted to 7.2 by supplying 9.2 mL of a 1 mol / L sodium hydroxide aqueous solution to the filtrate in which aluminum hydroxide was dissolved to obtain a precipitate of aluminum hydroxide. And 0.3g of aluminum hydroxide was collect | recovered by filtering and drying a residue.

(Example 7)
In the same manner as in Example 6, the pH was adjusted by subcritical decomposition treatment, filtration separation, pulverization of the filtration residue, and washing of the pulverized product, filtration, and a mixture of glass fiber, aluminum hydroxide, and calcium carbonate as the filtration residue. Obtained.

  Next, this filtration residue is dispersed in 10 mL of water, and then mixed with 10 mL of hydrochloric acid having a concentration of 1 mol / L, the aluminum hydroxide in the dispersed water is dissolved in the water as an aluminum salt, and the glass fiber and calcium carbonate are dissolved in the water. Dispersed water in a dispersed state was obtained.

  Next, this dispersed water was filtered, and the pH was adjusted to 7.3 by supplying 9.5 mL of a 1 mol / L sodium hydroxide aqueous solution to the filtrate in which aluminum hydroxide was dissolved. A precipitate was obtained. And 0.3g of aluminum hydroxide was collect | recovered by filtering and drying a residue.

  Further, after the residue obtained by filtering the dispersion water is dispersed in 1 L of water, 10 L of carbon dioxide gas (experimental standard gas) is blown at room temperature to dissolve the calcium carbonate in the dispersion water, and only the glass fiber Dispersed water in a state of being dispersed in water was obtained.

  Next, by filtering this dispersed water, 0.4 g of glass fiber was separated and recovered as a residue.

  Finally, the filtrate obtained by filtering the dispersed water is heated in the same manner as in Example 6 to vaporize and remove carbon dioxide gas, thereby precipitating calcium carbonate, and collecting the precipitate by filtration to recover carbonic acid. 0.4 g of calcium was obtained.

(Comparative example)
FRP used in Example 1 was coarsely pulverized, 600 g of this FRP and 2400 g of a potassium hydroxide aqueous solution having a concentration of 1 mol / L were each put in a pressure vessel and sealed, and this pressure vessel was put in a heating tank and heated. . The heating tank is designed to heat the water in the tank to a temperature of 230 ° C. with a heater, and the water in the pressure vessel is in a subcritical state (a state below a critical point (critical temperature 374 ° C., critical pressure 22.1 MPa)). I made it. It hold | maintained in this state for 2 hours, After decomposing | disassembling FRP, it cooled to room temperature, taken out the content from the pressure vessel, and filtered the content. The residue was obtained by filtering in this manner to obtain 400 g of residue.

  Next, 200 g of residue, 200 g of water, and 400 g of 5 mm balls were placed in a 120 φmm pot mill, pulverized for 4 hours, and filtered to obtain a residue of pulverized material.

  About the inorganic substance collect | recovered by Examples 1-7 and a comparative example as mentioned above, the average particle diameter of glass fiber, aluminum hydroxide, and a calcium carbonate is measured using "SALD-2000" by Shimadzu Corporation, and also collection | recovery operation | work The main component of the waste liquid after completion was measured. Confirmation of the separated and recovered material was performed by elemental analysis (IPC emission spectroscopic analysis). These results are shown in Table 1.

  As seen in Table 1, in the comparative example, the glass fiber cannot be separated and recovered alone from the FRP containing glass fiber and aluminum hydroxide. It could be separated and recovered alone.

  In Example 2, the amount of hydrochloric acid used to dissolve aluminum hydroxide can be less than that in Example 1 by adjusting the pH.

  In Example 3, aluminum hydroxide could also be separated and recovered, and only safe sodium chloride was mixed in the waste liquid after recovering aluminum hydroxide. On the other hand, in Example 4 in which the kind of alkali is different from Example 3, waste liquid treatment is necessary because aluminum chloride is mixed in the waste liquid. The aluminum hydroxide was dissolved as an aluminate.

  Further, in Examples 6 and 7, glass fiber, aluminum hydroxide and calcium carbonate can be separated and recovered independently from FRP containing glass fiber, aluminum hydroxide and calcium carbonate as inorganic substances. It was a thing.

Claims (9)

  A plastic molded product containing glass fiber and aluminum hydroxide as an inorganic substance is treated with a subcritical fluid to decompose the plastic into monomers and oligomers and to release the inorganic substances from the plastic, and to separate the inorganic substances from the plastic monomers and oligomers. A step of supplying an acid to the water containing the separated inorganic substance to dissolve the aluminum hydroxide in the water, and a step of separating the glass fiber by filtering the water in which the aluminum hydroxide is dissolved. A method for recovering inorganic substances from plastics.   The pH of the water containing the inorganic substance is adjusted to 8 to 10 between the step of separating the inorganic substance from the plastic monomer or oligomer and the step of supplying the acid to the water containing the inorganic substance to dissolve the aluminum hydroxide in the water. The method for recovering an inorganic substance from plastic according to claim 1, further comprising a step.   The method for recovering an inorganic substance from plastic according to claim 1 or 2, further comprising a step of supplying an alkali to water in which the aluminum hydroxide is dissolved after separating the glass fibers to precipitate the aluminum hydroxide. .   The method for recovering an inorganic substance from plastic according to claim 3, wherein the alkali is supplied so that the pH of the water after supplying the alkali is 6-8.   Using a plastic molded product containing glass fiber, aluminum hydroxide and calcium carbonate as the inorganic substance, separating the inorganic substance from the plastic monomer and oligomer, and supplying the acid to the water containing the inorganic substance to dissolve the aluminum hydroxide in the water And a step of supplying carbon dioxide gas to water containing glass fiber, aluminum hydroxide and calcium carbonate as an inorganic substance to dissolve the calcium carbonate in water, and filtering the water in which the calcium carbonate is dissolved to glass The method for recovering an inorganic substance from plastic according to any one of claims 1 to 4, further comprising a step of separating fibers and aluminum hydroxide.   Supplying carbon dioxide gas to water containing glass fiber and calcium carbonate as an inorganic substance after a step of filtering water in which aluminum hydroxide is dissolved using a plastic molded article containing glass fiber, aluminum hydroxide and calcium carbonate as an inorganic substance And a step of dissolving the calcium carbonate in water, and a step of filtering the water in which the calcium carbonate is dissolved to separate the glass fibers. Recovery method.   The method for recovering an inorganic substance from plastic according to claim 5 or 6, further comprising the step of heating the filtered water to precipitate calcium carbonate after the step of filtering water in which calcium carbonate is dissolved.   The method for recovering an inorganic substance from plastic according to any one of claims 1 to 7, wherein hydrochloric acid is used as an acid supplied in the step of dissolving aluminum hydroxide in water.   The method for recovering an inorganic substance from plastic according to any one of claims 3 to 8, wherein sodium hydroxide is used as the alkali supplied in the step of depositing aluminum hydroxide.