JP4754246B2 - Plastic disassembly method - Google Patents

Description

  The present invention particularly relates to a method for decomposing a plastic suitable for a plastic containing an unsaturated polyester resin typified by FRP (fiber reinforced plastic).

  Plastics are lightweight, high-strength, strong against rust and corrosion, free to color, excellent in electrical insulation, easy to mold, and capable of mass production. It is used in large quantities as materials for household goods. For this reason, the amount of waste plastic continues to increase.

Conventionally, most of the waste plastic has been disposed of by landfill or incineration. However, when waste plastic is landfilled, the ground after landfill becomes unstable, and it is difficult to secure land for landfill. In addition, when waste plastic is incinerated, harmful gases (for example, CO ₂ ) and bad odors are generated, which not only causes concern about environmental pollution, but also causes a problem that the incinerator is damaged.

  Therefore, the Containers and Packaging Waste Law (Recycling Law) was enacted in 1995, and waste plastics were collected and required to be reused. With the enforcement of this law, the development of technologies for recycling waste plastics is rapidly progressing.

  For example, a method for recovering an oily substance obtained by thermally decomposing waste plastic using supercritical water as a reaction medium is disclosed (see Patent Document 1).

In addition, after crushing the cured unsaturated polyester resin, which is waste plastic, the decomposition product obtained by decomposing with dicarboxylic acid or diamine at a temperature of about 100 ° C. to 300 ° C. is reused as a resin raw material. A method of re-synthesizing is also disclosed (see Patent Document 2).
Japanese Patent Laid-Open No. 10-67991 Japanese Patent Laid-Open No. 9-221565

  However, when the waste plastic is pyrolyzed using the supercritical method described in Patent Document 1 described above, the treatment temperature is too high, so that the main chain and the side chain in the waste plastic are cleaved randomly and the resulting oily oil is obtained. The substance contained many kinds of low molecular weight components. The oily substance obtained by pyrolyzing waste plastic is mainly reused as a liquid fuel. However, in order to ensure the quality of the oily substance after pyrolysis, the oily substance is treated with a catalyst (for example, Zeolite) must be modified and post-treatment is required, which has been a factor in increasing the treatment cost. Further, even when the reforming process is performed, it is difficult to reuse the reformed product oil as a petroleum product (for example, kerosene or light oil) itself.

  Further, in the method described in Patent Document 2, the obtained decomposition product can be reused as an unsaturated polyester resin raw material. However, when the cured unsaturated plastic is decomposed at a high temperature exceeding 250 ° C., the thermal decomposition proceeds. Therefore, there has been a problem that the strength of the thermosetting resin is lowered when re-cured. Furthermore, even when the temperature at the time of decomposition was a low temperature of about 100 ° C. to 250 ° C., the recovery rate of the resin raw material that can be recovered after the thermal decomposition was low. For these reasons, the proportion of the recovered raw material resin used as a product after recuring has been low.

The present invention has been made to solve the above-described problems. That is, the plastic decomposition method of the present invention is at least one selected from polyhydric alcohols and maleic anhydride, maleic acid, and fumaric acid. and acids, the plastic containing the cross-linked polyester resin comprising a cross-linking agent, the same or similar with acids constituting the cross-linked polyester resin, maleic acid anhydride, of at least one selected from among maleic acid and fumaric acid Treatment with 180-270 ° C. subcritical water with acid added to hydrolyze the crosslinked polyester resin into a polyhydric alcohol and an acid , containing a copolymer of an acid and a crosslinking agent constituting the crosslinked polyester resin A decomposition product is obtained .

  According to the method for decomposing a plastic of the present invention, it is possible to accelerate the hydrolysis of the plastic containing the polyester resin to increase the decomposition rate, and to recover the resin raw material in a form that can be easily reused. As a result, waste plastic can be recycled and effectively used.

  Hereinafter, a plastic disassembling method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  The plastic that is decomposed using the plastic decomposing method according to the embodiment of the present invention is a plastic that includes a polyester resin composed of a polyhydric alcohol and an acid. For example, a copolycarbonate of a polyhydric alcohol and an unsaturated polybasic acid is used. An unsaturated polyester resin obtained by crosslinking the coalescence with a crosslinking agent. The plastic is not limited to these, and may be a composite material such as FRP (fiber reinforced plastic) containing a polyester resin. Examples of the polyhydric alcohol include, but are not limited to, glycols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. Examples of unsaturated polybasic acids include, but are not limited to, aliphatic unsaturated dibasic acids such as maleic anhydride, maleic acid, and fumaric acid. Examples of the crosslinking agent include, but are not limited to, polymerizable vinyl monomers such as styrene and methyl methacrylate.

  FIG. 1 shows a plastic disassembling method according to an embodiment of the present invention. As shown in FIG. 1, first, a thermosetting resin containing a polyester resin is mixed with water containing a polyvalent carboxylic acid (step A).

  The polyvalent carboxylic acid to be contained in water is preferably at least one selected from maleic anhydride, maleic acid and fumaric acid.

  Here, the mixing ratio of the thermosetting resin and water is not particularly limited, but it is preferable to add 100 to 500 parts by mass of water with respect to 100 parts by mass of the thermosetting resin. Moreover, the ratio of the polyvalent carboxylic acid to be contained in water is not particularly limited, but it is preferable to contain 10 to 50 parts by mass of the polyvalent carboxylic acid in water with respect to 100 parts by mass of the thermosetting resin.

  Next, the polyester resin is decomposed by bringing water to a subcritical state below the critical point (critical temperature 374.4 ° C., 22.1 MPa) (step B).

  In general, the treatment for decomposing plastic occurs by a pyrolysis reaction and a hydrolysis reaction, and the same applies to a thermosetting resin produced from a raw material containing a polyhydric alcohol and an acid. When it is processed by bringing it into contact with a thermosetting resin, the hydrolysis reaction becomes more dominant than the thermal decomposition. For this reason, hydrolysis reaction occurs selectively and can be decomposed into polyhydric alcohol and acid monomers or oligomer units in which a plurality of these are combined.

  For this reason, the temperature at the time of decomposition in Step B is a temperature at which the thermosetting resin is hydrolyzed, less than the temperature at which the thermosetting resin is thermally decomposed, and less than the temperature at which the copolymer of the acid and the crosslinked portion is thermally decomposed. It is preferable that Specifically, it is 180-270 degreeC. This is because, when the temperature is lower than 180 ° C., a treatment time of several tens of hours is required and the reaction takes a long time. On the other hand, if the thermosetting resin is decomposed under high temperature (about 360 ° C) and high pressure (about 20MPa) using critical water (critical temperature 374.4 ° C, critical pressure 22.1MPa) exceeding 270 ° C, This is because thermal decomposition rather than decomposition proceeds, the acid and cross-linked copolymer are decomposed, and the acid and cross-linked copolymer cannot be recovered. Because. The pressure at the time of decomposition is preferably 7 MPa or less. In addition, the decomposition time varies depending on the decomposition temperature, but is preferably about 1 to 4 hours when the temperature is not higher than the temperature at which the thermal decomposition reaction does not proceed.

  Here, the polyvalent carboxylic acid contained in water has the effect of promoting the hydrolysis reaction of the plastic, so it decomposes compared to the case where the plastic tic is hydrolyzed without containing the polyvalent carboxylic acid in water. The rate increases. Furthermore, the polyvalent carboxylic acid having the effect of promoting the hydrolysis reaction is the same or similar to the acid constituting the polyester resin, and can be reused as a resin raw material. The process of separating and collecting becomes unnecessary.

  When the polyester resin is treated with subcritical water (step B), an aqueous solution is obtained, and in this aqueous solution, a decomposed polyhydric alcohol, an unsaturated polybasic acid, and a copolymer of an acid and a cross-linked part are contained. included. As a result, the polyhydric alcohol and unsaturated polybasic acid, which are monomers obtained by decomposing the polyester resin, the acid, which is an oligomer, and a copolymer of the cross-linked portion are recovered, and the monomer and oligomer are recycled as plastic raw materials. Can be used.

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

Example In this example, the following cured polyester resin was used as the plastic. The cured product of the polyester resin is a varnish in which a polyhydric alcohol glycol propylene glycol 65 wt%, neopentyl glycol 10 wt%, dipropylene glycol 25 wt% and an unsaturated organic acid maleic anhydride are mixed with glycols in an equivalent amount In addition, 165 parts by mass of calcium carbonate and 90 parts by mass of glass fiber are mixed with 100 parts by mass of a polyester resin in which styrene is blended in an equivalent amount to the varnish as a crosslinking agent and cured.

  Next, 4 g of the cured polyester resin is mixed with 16 g of water containing 0.24 g of maleic anhydride, and after the mixed solution 1 is charged into the reaction tube 2 shown in FIG. 2 (a), the reaction tube 2 is filled with argon. It was replaced with gas. Maleic anhydride contained in water was equivalent to maleic anhydride contained in the cured polyester resin.

  Thereafter, the reaction tube 2 was immersed in a constant temperature bath 3 at 230 ° C., and the aqueous solution in the reaction tube 1 was left in a subcritical state for 12 hours, and the cured polyester resin was decomposed for 12 hours. In addition, a stirring blade 4 is attached to the thermostatic chamber 3 so that the temperature in the reaction tube 2 can be maintained uniformly.

  Thereafter, the reaction tube 2 taken out from the thermostatic bath 2 was immersed in the cooling bath 5 shown in FIG. 2 (c), and the reaction tube 1 was rapidly cooled to room temperature.

  The content 6 in the reaction tube 2 after cooling contains water-soluble components, unreacted resin residue, calcium carbonate, and glass fiber. The content 6 is filtered to separate solids and react. Recovered from tube 2.

  The water-soluble component and the unreacted resin residue were analyzed, the glycol monomer component was quantified from the water-soluble component by gas chromatography analysis (GC analysis), and the glycol recovery rate was calculated from Equation 1.

Glycol recovery rate (%) = (Amount of glycol monomer component / Estimated content of glycol monomer component of cured product) × 100 [Equation 1]
Further, the organic monomer component was quantified by ion exchange chromatography analysis (IC analysis), and the organic acid recovery rate was calculated from Equation 2.

Recovery rate of organic acid (%) = (amount of organic acid monomer component / estimated content of organic acid monomer component of cured product) × 100 [Equation 2]
Further, the decomposition rate (%) was calculated from the unreacted resin residual amount according to Equation 3.

Decomposition rate = ((amount of resin in cured product−amount of unreacted resin residue) / amount of resin in cured product) × 100
... [Formula 3]
Comparative Example In this comparative example, the cured product of the polyester resin was decomposed in the same manner as in Example 1 except that 16 g of pure water was used instead of water containing 0.24 g of maleic anhydride. Thereafter, using the same method as in Example 1, the recovery rate and decomposition rate of glycol and organic acid were calculated.

The results calculated from the examples and comparative examples are shown in Table 1.

  As shown in Table 1, in the example in which maleic anhydride was added to water and the cured product of the polyester resin was treated with subcritical water, compared to the comparative example in which maleic anhydride was not added to water, The decomposition rate was high. For this reason, it was demonstrated that maleic anhydride, which is a polyvalent carboxylic acid contained in water, has an effect of promoting hydrolysis of the cured product of the polyester resin.

It is a figure explaining the decomposition | disassembly method of the plastic which concerns on embodiment of this invention. It is a figure explaining the process of the decomposition | disassembly method of the plastic in the Example which concerns on embodiment of this invention.

Explanation of symbols

1 ... mixture,
2 ... reaction tube,
3 ... constant temperature bath,
4 ... stirring blade,
5 ... Cooling tank,
6 ... Contents (water-soluble component, unreacted resin residue, calcium carbonate and glass fiber),

Claims (1)

A plastic containing a cross-linked polyester resin comprising a polyhydric alcohol , at least one acid selected from maleic anhydride, maleic acid and fumaric acid, and a cross-linking agent is the same as the acid constituting the cross-linked polyester resin. Or similar treatment with 180-270 ° C. subcritical water to which at least one acid selected from maleic anhydride, maleic acid and fumaric acid is added, and the crosslinked polyester resin is treated with a polyhydric alcohol and an acid. method for decomposing plastics hydrolyzed, and wherein the obtaining a decomposition product containing a copolymer of an acid and a crosslinking agent constituting the crosslinked polyester resin.

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