JPH08253619A - Method for treating plastic molded form - Google Patents

Abstract

PURPOSE: To sufficiently quickly conduct the subject decomposition treatment at room temperature or so, intended to reuse the decomposition product as a raw material, by bringing a specific molded form into contact with a solution containing an alkali (alkaline earth) metal compound of alkaline property and an alcohol. CONSTITUTION: This decomposition treatment is accomplished by bringing (A) a molded form consisting mainly of an ester linkage-contg. decomposable resin (e.g. polycaprolactone) into contact with a solution containing (B) at least an alkali (alkaline earth) metal compound of alkaline property (e.g. sodium hydroxide) and (C) an alcohol (methyl alcohol). It is preferable that the component A be treated by immersing it in a solution containing both the components B and C and added with (D) inorganic compound particles (e.g. alumina particles with a size of 10μm to several mm) followed by agitation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plastic molding,
More specifically, the present invention relates to a method for treating a molded body containing a biodegradable resin having an ester bond as a main component.

[0002]

2. Description of the Related Art Conventionally, as a method for treating a plastic containing a biodegradable resin as a main component, a method of incineration and a method of landfilling in soil are generally used like other plastics. Plastics whose main component is biodegradable resin,
It has the characteristic that it can be treated with relatively less energy than other plastics when incinerated, and that it is decomposed by microorganisms in the soil when it is landfilled. Further, as a method for treating a biodegradable resin having an ester bond,
For example, a method of hydrolyzing with lipase, which is an enzyme, has been reported (edited by Yoshiharu Dohi, published by the Industrial Research Board, “Biodegradable Polymer Material” P267 (199).
0)). Further, as a method of hydrolyzing the ester bond and treating, a method of immersing in water and heating and pressurizing (JP-A-5-178976), a method of treating with an alkaline aqueous solution (JP-A-6-49266) and the like are available. Proposed.

[0003]

Although the biodegradable resin can be treated with a relatively small amount of energy when incinerated as compared with other resins, it still consumes heat energy, and the amount of waste plastic is reduced. There are also problems such as a shortage of incineration facilities accompanying the increase. In addition, when landfilling is carried out, it is decomposed by microorganisms, but it takes a long time for the decomposition, so a large landfill area is required. There is also a problem that there is a large difference in degradability depending on the combination of the microorganism and the biodegradable resin. In addition, when a used plastic molded body is transported to an incinerator or a landfill, the molded body occupies a large space volume, so that the transportation efficiency is poor.
There is also a method of mechanically crushing and reducing the volume to carry it, but the current situation is that there are not many simple crushing devices. Further, in incineration or landfill treatment, plastic cannot be reused as a raw material or a monomer which is a constituent unit thereof.

Therefore, various methods of recycling plastics have been studied, but for example, the thermal decomposition treatment method requires a large amount of energy and a large-scale apparatus.
Further, the hydrolysis treatment with an enzyme such as lipase decomposes only a part of the polymer and requires a long time for decomposition, which is not practical. Further, the method of hydrolyzing the ester bond and applying heat or pressure requires a large-scale processing apparatus and consumes energy. Also, in the case of treating with an alkaline aqueous solution, it is common to perform treatment by heating to increase the decomposition rate, and at least a heating device is required. In view of the above, it is an object of the present invention to provide a method for treating a molded body containing a biodegradable resin having an ester bond as a main component, which can easily decompose the biodegradable resin portion into monomers. .

[0005]

According to the treatment method of the present invention, a molded article containing a biodegradable resin having an ester bond as a main component is treated with at least an alkaline alkali metal compound or an alkaline alkaline earth metal compound and alcohols. It is to be brought into contact with the solution containing. Further, the present invention, a molded body containing a biodegradable resin having an ester bond as a main component, containing at least an alkaline alkali metal compound or an alkaline alkaline earth metal compound and alcohols, and added inorganic compound particles The solution is immersed in the solution and stirred.

[0006]

According to the constitution of the present invention, since the treatment solution contains alcohols, the solvent effect on the resin allows the liquid to have high penetrability into the resin, and the radical attack to the ester bond portion is efficient. Is done in a regular manner. Therefore, the solvolysis of the ester bond is promoted, and the decomposition treatment can be carried out sufficiently quickly without heating or pressurizing. As a result, the biodegradable resin is decomposed into the monomer that is its constituent unit, so that it can be applied to chemical recycling. Further, by adding the inorganic compound particles to the solution and stirring, for example, when insoluble matter is generated on the surface of the molded body in the decomposition process, the insoluble matter is stripped off or the surface of the molded body itself is roughened. As a result, the decomposition efficiency can be further increased by adding a physical force such as increasing the contact efficiency with the liquid.

[0007]

Examples The biodegradable resin having an ester bond used in the present invention is a polymer obtained by polycondensing a carboxyl group and a hydroxyl group, a polymer obtained by ring-opening polymerization of a cyclic ester compound, and examples thereof include polycaprolactone. Polypropiolactone, polycaprolactone diol, polyhydroxybutyric acid, ε-caprolactone / adipic acid / hexamethylene diol copolymer, polyethylene malonate, polyethylene succinate, polyethylene glutarate,
Polyethylene adipate, polyethylene pimelate, polyethylene suberate, polyethylene azelate, polyethylene sebacate, polyethylene decamethylate, polytetramethylene succinate, polypentamethylene succinate, polyhexamethylene succinate, polytrimethylene adipate, polytetra Methylene adipate, polyhexamethylene adipate, polytrimethylene sebacate, polytetramethylene sebacate, polyhexamethylene sebacate, polyethylethylene succinate, poly-1,2-dimethylethylene succinate, polymethylethylene adipate, polymethyl Ethylene sebacate, poly-1-methyltrimethylene succinate,
Poly-2,2-dimethyltrimethylene succinate, poly-1-methyltrimethylene adipate, poly-2,2
-Dimethyltrimethylene adipate, poly-1-methyltrimethylene sebacate, poly-2,2-dimethyl trimethylene sebacate, polyhexamethylene maleate, polycis-2-butene adipate, polytrans-2
-Butene adipate, polycis-2-butene sebacate, poly-trans-2-butene sebacate, poly-2
-Butene sebacate, polytetramethylcyclobutane succinate, polytetramethylcyclobutane adipate, polycyclohexylene dimethyl succinate, polycyclohexylene dimethyl adipate, polybutylene adipate, polybutylene succinate, polylactic acid, polyhydroxyvaleric acid, polyhydroxybutyric acid- Examples thereof include hydroxyvaleric acid copolymer.

The molded article containing the biodegradable resin as a main component used in the present invention includes other thermoplastic resins, fillers, reinforcing materials, colorants, thickeners, release agents, plasticizers, and antioxidants. You can mix agents and antistatic agents. These additives can be mixed to the extent that they are compatible or sufficiently dispersed with the biodegradable resin and do not affect the decomposition treatment. Among these, coloring agents, thickeners, mold release agents, plasticizers, antioxidants, and antistatic agents exhibit the effect as additives even if added in a small amount, so addition within a few percent is preferable. The mixing amount of other additive materials will be described below. Examples of the thermoplastic resin to be mixed include polyethylene, polypropylene, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, vinylidene chloride resin, polyethylene terephthalate, vinyl chloride resin, vinyl chloride resin, polyvinyl alcohol, polyvinyl butyral, polystyrene, ABS resin. , Methacrylic resin, polyurethane, polyphenylene oxide and the like. Among these thermoplastic resins, in the case of a resin having a bond such as an ester bond, an amide bond, a urethane bond, which easily causes solvolysis, mixing with a biodegradable resin also causes solvolysis of those bonds. Since it is promoted, sufficient degradability can be obtained even when about 3000 parts by weight is added to 100 parts by weight of the biodegradable resin. Therefore, in the case of a thermoplastic resin having at least one kind of bond among an ester bond, an amide bond, and a urethane bond, within about 3000 parts by weight with respect to 100 parts by weight of the biodegradable resin, and in the case of other thermoplastic resins Is preferably within about 100 parts by weight.

Examples of the filler include calcium carbonate, calcium silicate, magnesium carbonate, barium sulfate, calcium sulfate, kaolin, aluminum hydroxide,
Examples thereof include talc, mica, diatomaceous earth, glass balls, silica gel and the like. The amount of the filler mixed is preferably within about 300 parts by weight with respect to 100 parts by weight of the biodegradable resin. As the reinforcing material, glass fiber is mainly used,
Other than that, organic fibers such as polyacrylonitrile-based, rayon-based or pitch-based carbon fibers, vinylon, polypropylene, polyester and aramid fibers can also be used. The amount of the reinforcing material mixed is 100 biodegradable resin.
It is preferably within about 100 parts by weight with respect to parts by weight. As the colorant, a general dye or pigment can be used,
For example, iron oxide, titanium oxide, cadmium yellow, cadmium red, chrome yellow, chrome vermilion, inorganic pigments such as ultramarine and azo compounds, cyanine blue,
Examples thereof include organic pigments such as chlorinated cyanine blue and cyanine green, dyes such as indigo red and oil red, and carbon black. However, considering the recycling of the decomposition products of the biodegradable resin after the decomposition treatment, iron oxide or titanium oxide, due to the ease of separation from the decomposition treatment solution,
Particulate colorants that are insoluble in the processing solution, such as carbon black, are preferred.

Examples of the thickener include magnesium oxide, magnesium hydroxide, calcium hydroxide, polyvalent isocyanate compounds and the like. Examples of the release agent include fluorine-based surfactants and zinc stearate. Examples of the plasticizer include phthalic acid esters, phosphoric acid esters, epoxidized soybean oil, fatty acid esters, and the like. As the antioxidant, for example,
Examples thereof include butylhydroxytoluene, butylhydroxyanisole, diphenylamine, and phenylenediamine derivatives. As the antistatic agent, various anionic, cationic and nonionic surfactants are used.

The treatment solution used in the present invention contains at least an alcohol and an alkaline alkali metal compound or an alkaline alkaline earth metal compound. Examples of the alkaline alkali metal compound or the alkaline alkaline earth metal compound include water. Sodium oxide,
Examples thereof include potassium hydroxide, barium hydroxide, sodium methoxide, sodium ethoxide, potassium butoxide and the like. Examples of alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, t-butyl alcohol, and the like. However, due to the size of the ester bond portion which is solvolytic, methyl alcohol, ethyl alcohol. , Propyl alcohol is preferred. Incidentally, these alcohols and alkaline alkali metal compounds or alkaline alkaline earth metal compounds are not only single components,
Multiple may be included.

In order to improve the resin permeability of the treatment solution, for example, acetone, tetrahydrofuran, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol, diethylene glycol diethyl ether, diethylene glycol dimethyl ether. , Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dimethylformamide, dimethylamine and the like may be added. In addition, the treatment temperature may be higher, of course, since a higher decomposition rate can be obtained, but the treatment temperature is preferably not higher than the boiling point of the contained alcohols. The inorganic compound particles added to the treatment solution used in the present invention may be any stable compound that does not react with the treatment solution or decomposition products.
The particle size is also appropriately selected depending on the size and shape of the molded product to be treated, but it is preferably several mm to 10 μm in consideration of separation by a filter. Examples of the material of the inorganic compound include alumina, chromium oxide, cerium oxide, iron oxide, silicic acid, calcium carbonate and the like. As a dispersant for improving the dispersion stability of these particles, for example, sodium hexametaphosphate, condensed sodium naphthalenesulfonate, an ionic surfactant, a nonionic surfactant, polyethylene glycol, etc. are added. Good.

The present invention will be described in more detail with reference to specific examples. [Example 1] In this example, polyethylene adipate was used as the biodegradable resin having an ester bond.
A plate-shaped molded body of mm × 20 mm × 1 mm was prepared. As a treatment solution, 1.1 g of sodium hydroxide and 21.
A solution obtained by mixing 0 g and 6.0 g of water was used. The molded body was immersed in this solution at room temperature (20 ° C.), and its weight was measured at regular intervals to determine the decomposition rate. as a result,
The decomposition rate was 100 mg / H. Furthermore, the decomposed liquid after complete disintegration was analyzed by liquid chromatography (HPLC-7000).
As a result of analysis with a series (Hitachi, Ltd.), it was confirmed that it was almost completely decomposed into ethylene glycol and adipic acid.

As a comparative example, the same experiment was carried out by changing the treatment solution to water only, a mixed solution of 21.0 g of ethanol and 7.0 g of water, and a mixed solution of 1.1 g of sodium hydroxide and 27.0 g of water. When it was carried out, it was not decomposed in the case of only water and ethanol water, and in the case of the aqueous solution of sodium hydroxide, it was decomposed at a very slow rate of 0.9 mg / H. Furthermore, the treatment solution is 1.1 g of sodium hydroxide.
In the case of a mixed liquid of 27.0 g of water and water, when the liquid was heated to 40 ° C. and the same experiment was performed, the decomposition rate was 2.0 mg / H.
Met. The above results are summarized in Table 1.

[0015]

[Table 1]

From these results, using the treatment solution of the present invention, in comparison with conventional alkaline water at room temperature, about 10% was obtained.
It was found that a decomposition rate of 50 times was obtained even when compared with alkaline water heated to 0 times and 40 ° C.

[Example 2] The polymer of Example 1 was changed to polylactic acid, and the same solution as in Example 1 was used as the treatment solution. An experiment similar to that of Example 1 was conducted. The decomposition rate was 80 m.
It was g / H, and almost completely decomposed to lactic acid. As a comparative example, the treatment solution was only water, a mixed solution of 21.0 g of ethanol and 7.0 g of water, 1.1 g of sodium hydroxide and 2 parts of water.
When the same experiment was carried out by changing three kinds of the mixed solution of 7.0 g, it was not decomposed at all in the case of only water and ethanol water, and the decomposition rate was 5 mg in the case of the aqueous solution of sodium hydroxide.
It decomposed at a slow rate of / H. Further, when the treatment solution was a mixed solution of 1.1 g of sodium hydroxide and 27.0 g of water, when the same experiment was performed by heating the solution to 40 ° C. and 60 ° C., the decomposition rate was 31 mg at 40 ° C. /
It was 84 mg / H in H and 60 degreeC. The above results are summarized in Table 2. However, the case of only water that was not decomposed at all and the case of ethanol water were omitted.

[0018]

[Table 2]

From these results, when the treatment solution of the present invention is used, in comparison with conventional alkaline water at room temperature, it is almost 16
The decomposition rate was 2.5 times that of alkaline water heated to 40 ° C. It was found that the conventional alkaline water was heated to 60 ° C. and finally the decomposition rate was almost the same as that of the solution of the present invention (20 ° C.).

Example 3 The polymer of Example 1 was changed to polycaprolactone, and the same solution as in Example 1 was used as the treatment solution. An experiment similar to that in Example 1 was conducted. The decomposition rate was 13 mg / H. And almost completely decomposed to hydroxycaproic acid. As a comparative example, the same experiment was carried out by changing the treatment solution to water only, a mixed solution of ethanol 21.0 g and water 7.0 g, and a mixed solution of sodium hydroxide 1.1 g and water 27.0 g. , Water alone and ethanol water did not decompose at all, and sodium hydroxide aqueous solution decomposed at a very slow rate of 0.006 mg / H. Furthermore, when the treatment solution was a mixed solution of 1.1 g of sodium hydroxide and 27.0 g of water, when the solution was heated to 40 ° C. and 60 ° C. and a similar experiment was conducted, the decomposition rate was 0.4 at 40 ° C. 009 mg / H, 60
The temperature was 0.01 mg / H at 0 ° C., and heating up to 60 ° C. showed almost no effect of promoting the decomposition rate by heating. Since the melting point of polycaprolactone was 60 ° C., the plate-like sample was deformed into an ellipse in the experiment at 60 ° C. Table 3 summarizes the above results. However, the case of only water that was not decomposed at all and the case of ethanol water were omitted.

[0021]

[Table 3]

From these results, it was found that when the treatment solution of the present invention is used, a decomposition rate of three digits or more can be obtained as compared with the treatment with alkaline water up to 60 ° C.

Example 4 Polylactic acid was used as the biodegradable resin having an ester bond, the treatment solution was adjusted to have a sodium hydroxide concentration of 3.9 wt%, and the ratio of ethanol and water was changed. The same decomposition treatment experiment was performed. Table 4 shows the relationship between the weight fraction of ethanol with respect to water and the decomposition rate. The decomposition rate with a weight fraction of 0 is the result when a mixed solution of 1.1 g of sodium hydroxide and 27.0 g of water of the comparative example of Example 2 was used (20 ° C.).

[0024]

[Table 4]

From these results, as the proportion of ethanol increases, the decomposition rate also increases, and the weight fraction of ethanol and the decomposition rate are in a substantially proportional relationship. Ethanol is added to an aqueous sodium hydroxide solution to give 30% ethanol. It was found that when the solution was used, the decomposition rate was about 5 times, and when the solution was 100% ethanol of sodium hydroxide, the decomposition rate was 20 times that of the aqueous solution.

Example 5 Polyethylene adipate was used as a biodegradable resin having an ester bond, and a treatment solution was 0.5 g of barium hydroxide and 15.0 of methanol.
An experiment was conducted in the same manner as in Example 1 using a solution obtained by mixing 1 g of water and 15.0 g of water. As a result, the decomposition rate was 27 mg / H. As a comparative example, the same experiment was performed by changing the treatment solution to water alone, a mixed solution of 15.0 g of methanol and 15.0 g of water, and a mixed solution of 0.5 g of barium hydroxide and 30.0 g of water. , Water alone and methanol water did not decompose at all, and barium hydroxide aqueous solution decomposed at a very slow rate of 0.04 mg / H. Furthermore, when the treatment solution is a mixed solution of 0.5 g of barium hydroxide and 30.0 g of water, the solution is
When the same experiment was performed by heating to 0 ° C., the decomposition rate was 0.1 mg / H. The above results are summarized in Table 5. However, the case of only water that was not decomposed at all and the case of methanol water were omitted.

[0027]

[Table 5]

As described above, even if the kinds of the alcohols and the alkaline alkali metal compound or the alkaline alkaline earth metal compound in the treatment solution are changed from those in Example 1,
A sufficient effect of promoting the decomposition rate of the treatment solution of the present invention with respect to the alkaline aqueous solution was obtained.

[Embodiment 6] FIG. 1 shows the outline of a method of adding inorganic compound particles to a solution and stirring the mixture. Polyethylene adipate was used as the biodegradable resin having an ester bond to obtain a plate-shaped molded body 1 of 10 mm × 20 mm × 1 mm. As a processing solution 2, sodium hydroxide 1.1
g, ethanol 21.0 g, and water 6.0 g were used as a solution, and calcium carbonate particles (particle size 350 to 500 μm) 5 g were added as the inorganic compound particles 3 to the solution. The molded body was immersed in this solution at room temperature (20 ° C.), the stirring blade 4 was rotated at a rotation speed of 100 rpm and stirred, and the weight was measured at regular intervals to determine the decomposition rate.
As a result, the decomposition rate was 260 mg / H. When a similar experiment was conducted using a treatment solution containing no calcium carbonate particles, the decomposition rate was 180 mg / H.
It was confirmed that not only the stirring but also the addition of the inorganic compound particles and stirring promoted the decomposition rate.

Example 7 Polylactic acid was used as a biodegradable resin having an ester bond, and 100 parts by weight of this resin was added with 200 parts by weight of calcium carbonate and 1 part of glass fiber.
0 part by weight was added to prepare 10 g of a dish-shaped molded body.
As the treatment solution, a solution prepared by mixing 25 g of sodium hydroxide, 210 g of ethanol and 60 g of water was used, and calcium carbonate particles (particle size 350 to 500 μm) were added to the solution.
50 g was added. The molded body was added to this solution at room temperature (20
C.) and the stirring blade was rotated at a rotation speed of 100 rpm to stir, and a decomposition treatment experiment was performed. As a result, the molded body gradually began to lose its surface and edges from about 2 hours after the start of decomposition, and became almost in a separated state within about 10 hours.
From this result, it was found that even a molded product obtained by mixing the biodegradable resin with the additive can be decomposed and disintegrated into pieces like the molded product containing only the biodegradable resin.

In the above examples, sodium hydroxide and barium hydroxide were used as the alkaline alkali metal compound or alkaline alkaline earth metal compound, but the invention is not limited to these, and they may be dissolved in water. Any metal compound showing alkalinity may be used. Although ethanol and methanol were used as alcohols, the alcohols are not limited to these. Further, even in the case of a molded body containing as a main component a mixture of a plurality of biodegradable resins, it can be treated with this treatment solution in the same manner. Furthermore, it is of course possible to treat the molded body with the present treatment solution after crushing it into small pieces. Further, although the stirring blade is used as a method for stirring the treatment solution in the examples, the method is not limited to this method, and the solution may be flowed, so that the solution may be circulated by a pump, bubbling or the like may be performed. . Furthermore, not only the flow of the solution but also ultrasonic waves may be applied to accelerate the collapse of the molded body due to physical force and the solvolysis.

[0032]

As described above, according to the present invention, since the treatment solution contains alcohols, the permeability of the solution into the resin is high, and the ester bond is efficiently attacked. The solvolysis of the ester bond is promoted, and the biodegradable resin having the ester bond can be decomposed sufficiently quickly at about room temperature without heating or pressurizing. Therefore, it is also effective for energy saving, and the monomer of the decomposition product can be reused as a resin raw material. Furthermore, the decomposition efficiency can be further increased by adding the inorganic compound particles to the solution and stirring.

[Brief description of drawings]

FIG. 1 is a schematic view showing a method for treating a plastic molded body according to an embodiment of the present invention.

[Explanation of symbols]

 1 molded body 2 treatment solution 3 inorganic compound particles 4 stirring blade

Claims (2)

[Claims] 1. A plastic which is characterized in that a molded body containing a biodegradable resin having an ester bond as a main component is brought into contact with a solution containing at least an alkaline alkali metal compound or an alkaline alkaline earth metal compound and an alcohol. Method of treating molded body. 2. A solution containing a molded body containing a biodegradable resin having an ester bond as a main component, containing at least an alkaline alkali metal compound or an alkaline alkaline earth metal compound and an alcohol, and inorganic compound particles added thereto. A method for treating a plastic molded body, which comprises immersing in a plastic and stirring.