JP2003128835A - Method for decomposing polyolefin resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for decomposing a polyolefin resin in a short period of time without generating problems of environmental pollution. SOLUTION: The polyolefin resin is subjected to at least one treatment selected from pulverization, treatment for imparting porous structure and treatment for imparting hydrophilic property to obtain a treated material. The treated material is buried in the soil in a dumping ground before a mixed solution of laccase and mediator is sprayed, or the treated material is charged into the mixed solution of laccase and mediator to decompose the polyolefin resin by the action of the mixed solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing a polyolefin resin, and more particularly to treating the polyolefin resin in the presence of an enzyme and a mediator at room temperature without causing environmental pollution problems. Regarding the method of decomposing in a short period of time.

[0002]

2. Description of the Related Art Currently, in Japan, about 15 million tons of plastics are produced annually, and about 40% of these are polyolefin resins mainly composed of polyethylene and polypropylene. Polyolefin resins are resistant to water, oil, chemicals, and have excellent moldability. There are various grades from soft to hard. When thinning, the contents become transparent and the contents are visible, and when thickening, rigidity is required. It can be applied to an extremely wide range of product fields, such as products, and can be used not only for films and daily necessities, but also for electric wire coverings, pipes, cable coverings, industrial parts such as automobiles, foaming cushioning materials and heat insulating materials. It is also used for.

However, as the problems of plastic wastes on the environment have become more serious in recent years, the treatment of waste polyolefin resin has become a problem. Currently, incineration, landfill in the disposal site, and recycling are implemented as treatment methods. However, it has been pointed out that incineration of an olefin resin causes a higher combustion energy than paper and the like, which damages the incinerator and causes an environmental pollution problem.

In addition, it is difficult to secure a new landfill for landfilling in the landfill. It has been confirmed that polyolefin resins are hard to decompose and do not decompose even after decades of landfill. For this reason, if landfilling is insufficient, waste may be scattered and cause a problem of environmental pollution. Recycling has not yet reached the point where various polyolefin resins are separated, collected, and processed.

For this reason, studies have been made to decompose polyolefin resins by utilizing the biodegradability of microorganisms. For example, Japanese Patent Application Laid-Open No. 6-70783 discloses a technique relating to a method of decomposing a polyolefin polymer compound with a wood-destroying basidiomycete. However, this method is not a technique that can be applied to a general purpose because it requires the use of special microorganisms, the culture conditions are limited, and it takes time to decompose.

Further, Japanese Patent Laid-Open No. 11-158318 discloses a technique relating to a method for decomposing low density polyethylene by a specific microorganism belonging to the genus Bacillus. However, this method requires long-term treatment (several months) under specific culture conditions in order to proceed with decomposition.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for decomposing a polyolefin resin at room temperature in a short period of time without causing a problem of environmental pollution.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, by treating a polyolefin resin in the presence of a laccase and a mediator, an environmental pollution problem is not caused. They have found that they can decompose at room temperature in a short period of time, and have completed the present invention.

That is, the present invention comprises the following aspects. (1) A method for decomposing a polyolefin resin, which comprises treating the polyolefin resin in the presence of a laccase and a mediator and decomposing it. (2) Decomposition of the polyolefin resin according to (1), wherein the polyolefin resin has been subjected to at least one treatment selected from a hydrophilic treatment, a powdering treatment and a porosifying treatment. Method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The polyolefin resin to which the decomposition method of the present invention is applied is a polymer obtained by homopolymerizing olefins such as ethylene, propylene, butene, and methylpentene, and is obtained by copolymerizing two or more kinds of olefins. A polymer obtained by copolymerizing a carboxylic acid, a carboxylic acid salt, a carboxylic acid alkyl ester or the like with one or more olefins.

Examples of such resins include low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, polybutene-1, polymethylpentene-1, ethylene-propylene copolymer, ethylene-
Ethylene-α-olefin copolymers such as butene copolymers,
Examples thereof include ethylene-vinyl acetate copolymers and ethylene-methyl methacrylate copolymers.

The method for polymerizing these polyolefin resins is not limited, and it is possible to use a polyolefin resin by a high pressure radical polymerization method, a low pressure polymerization method using a Ziegler catalyst, a low pressure or high pressure polymerization method using a metallocene catalyst, and the like. I can.

The form of the polyolefin resin may be any of powder, pellet, film, fiber, porous, plate, etc., but powder, pellet, fiber, porous Is preferable because it can have a large contact area with laccase or a mediator, and more preferably powdered, porous or hydrophilized.
As a method of pulverizing, there is a method of pulverizing with a crusher such as a crusher, a hammer mill or a jet mill.

As the form of the polyolefin resin before pulverization, various forms such as pellet form, sheet form and plate form can be used. The porosity can be obtained by kneading an additive or the like having poor compatibility with the polyolefin resin by a twin-screw extruder or the like to finely disperse the additive, and then washing and extracting the additive with a suitable solvent.

Laccase and mediator are hydrophilic, and by making the polyolefin resin hydrophilic,
The affinity with laccase or mediator is increased and the decomposition is promoted. As a method of hydrophilizing, a means such as addition of a substance having a polar group such as silica, introduction of a polar group into the resin by corona treatment or flame treatment can be used.

In order to accelerate the decomposition of the polyolefin resin, it is preferable to carry out at least one of the powdering, porosifying and hydrophilizing treatments. The powdering, porosifying and hydrophilizing treatments are carried out. It is more preferable to do everything.

The laccase used in the present invention is a kind of phenol oxidase, and is a copper protein enzyme having a molecular weight of about 61,000 and having copper at the active center. This enzyme performs 4-electron oxidation of a compound having a phenolic hydroxyl group as a substrate while reducing molecular oxygen to 2 molecules of water.

Laccase is a rhus family Rhus vernicifera
It is an enzyme that is first discovered in DC emulsion and has a blue color and is derived from plants (such as sumac, vegetables and fruits) and mold. In recent years, laccase derived from wood-destroying basidiomycetes
It has attracted attention as one of the enzymes involved in the decomposition of lignin, which is a natural polymer.

The laccase used in the present invention may be one that has been separated and purified from a culture of a microorganism such as wood-destroying basidiomycete in advance, or the culture may be used. or,
In addition to this, a treated product of the culture can also be used. Here, the culture refers to a mixture of bacterial cells and a culture solution obtained by culturing a microorganism, but in the present invention, bacterial cells such as wet cake separated from the bacterial cell culture, its residue and solid matter. It is also possible to use a culture solution that has been completely removed. In addition, the processed product refers to all of the concentrated, dried, or diluted culture solution.

The mediator used in the present invention refers to a compound having a property of itself becoming a radical by the action of the above-mentioned laccase. Here, a radical refers to a molecule having one or more unpaired electrons.

Examples of such mediators are:
1-hydroxybenzotriazole (HBT), N-hydroxy-N-phenylacetamide, N-acetyl-
N-phenylhydroxylamine, violuric acid, N-hydroxyacetanilide, 2,2′-azinobis (3-
Ethylbenzothiazoline-6-sulfonate), benzotriazole, remazole brilliant blue, chlorpromazine, promazine, 1-nitroso-2-naphthol-3,6-disulfonic acid, 2-nitroso-1-naphthol-4-sulfonic acid, 3 Examples include compounds such as -hydroxyanthranilic acid and derivatives thereof. Among these, those containing an N-hydroxy, oxime, or N-oxide structure in the molecule are preferable, and 1-vitroxybenzotriazole (HBT) or its derivative is more preferable.

In order to efficiently decompose the polyolefin resin by the decomposition method of the present invention, it is necessary to treat the laccase and the mediator at the same time. This is because it is presumed that the action of laccase oxidizes the mediator to generate a radical, and this radical oxidatively attacks the polyolefin resin to cleave the main chain and the decomposition proceeds in a chain. .

In the decomposition method of the present invention, the amount of laccase added to the polyolefin to be decomposed is 0.13 nkat to 1 mg of the polyolefin.
A range of 25 nkat is preferred (kat: katal
International unit of enzyme activity, 1kat is the amount of activity that can decompose or synthesize 1 mol of substrate per second). In the present invention, the amount of the mediator added together with laccase is 4 × 10 ⁻⁵ mM to 4 laccase / nkat.
The range of × 10 ^-3 mM is preferable.

The decomposition treatment by the decomposition method of the present invention is carried out by bringing laccase and a mediator into contact with each other. Specifically, a method of landfilling a polyolefin resin in soil at a disposal site, etc., and spraying a mixed solution of laccase and mediator, containing a polyolefin resin as a substrate in the mixed solution of laccase and mediator and decomposing it There are ways. The decomposition efficiency can be further increased by mixing, stirring and shaking the mixture of the mixed liquid and the polyamide resin. In this case, the mixed solution can be prepared by adding a laccase and a mediator to a buffer solution such as phosphoric acid, citric acid or malonic acid. By using a buffer solution, the pH value can be kept within a certain range and the enzyme activity of laccase can be kept within an appropriate range. When a laccase-producing microorganism is used as a laccase source, a nitrogen source, inorganic salts, etc. necessary for culturing the microorganism are appropriately used.

The decomposition treatment condition in the present invention is that the temperature is 15
It is preferable that the treatment is carried out at ˜45 ° C. and pH 4.0 to 7.0 because the enzyme activity of laccase or the growth rate of microorganisms can be decomposed at room temperature in a short period of time. Further temperature 25-45 ℃, pH
The condition of 4.5 to 5.0 is more preferable. Under these conditions, the polyolefin resin can be decomposed in a short period of about 5 to 10 days without causing environmental pollution problems. Next, the evaluation method used in the present invention will be described.

<Biodegradability Evaluation 1> Regarding the biodegradability of the polyolefin resin, the elongation and strength were measured by a tensile test method for a sheet-shaped sample according to JIS K 7127,
The value of each untreated sample was defined as 100 and expressed as a percentage.
The size of the sample is 60 mm in length and 10 mm in width. Tensile test conditions are a tensile speed of 10 mm / min and a chuck-to-chuck distance of 30.
mm.

<Biodegradability Evaluation 2> The biodegradability of the polyolefin resin was evaluated by the change in the weight average molecular weight and the number average molecular weight of the resin measured by GPC. The measurement conditions when the polyolefin resin is polyethylene are as follows.
Measuring device is Waters ALC / GPC150C
As for the mold and column, Showa Denko AT-807S (1 piece) and Tosoh GMH-HT6 (2 pieces) were connected in series. The mobile phase is trichlorobenzene (TCB) and the column temperature is 1
40 ° C, flow rate 1.0 ml / min, sample concentration 20-30 mg
(PE) / 20 ml (TCB). A differential refractometer was used as a detector.

The present invention will be described below with reference to examples.

Example 1 100 including malonic acid buffer solution (concentration of 50 mmol aqueous solution) 50 ml and laccase 500 nkat
A polyethylene membrane (Hypore PE-1100A manufactured by Asahi Kasei Corporation, which was made hydrophilic by adding silica to polyethylene and then made porous to have a porosity of about 50%, a length of 60 mm, and a width of 10 mm) was placed in a ml Erlenmeyer flask. Add 10 sheets (weight of about 40mg per sheet) and add 1 as a mediator.
-Hydroxybenzotriazole (HBT) 0.2m
A mole was added, and the mixture was shaken at 30 ° C. for 5 days (150 times / min) for decomposition treatment.

The number of processing days is 0 (unprocessed), 1 day, 2 days,
According to the method of biodegradability evaluation 1 for each sample for 3 days and 5 days, a tensile test was performed to evaluate changes in elongation and strength. The results are shown in Table 1. In addition, according to the method of biodegradability evaluation 2, the change in average molecular weight was evaluated for each sample having 0 days of treatment (untreated), 1 day, 3 days, and 5 days. The results are shown in Table 2.

[0030]

Comparative Example 1 The same treatment as in Example 1 was carried out except that 1-hydroxybenzotriazole was not added. Each sample was treated for 0 days (untreated), 1 day, 2 days, 3 days, and 5 days, and evaluated according to the method of biodegradability evaluation 1. The results are shown in Table 1.

[0031]

[Table 1]

[0032]

[Table 2]

As is clear from Table 1, when the polyethylene membrane was treated in the presence of laccase and mediator (HBT), the elongation was reduced to almost 0 after 2 days of treatment, and the strength was about 60% of that of the untreated case. Falls to. It can be seen that the polyethylene film disintegrates after 3 days of treatment and becomes powdery after 5 days, and the decomposition proceeds at room temperature for a short period of time. On the other hand, it is clear that even after 5 days of treatment, the elongation without addition of the mediator is 80% of the untreated, the strength is almost the same as that of the untreated, and the decomposition is not progressed. Further, as is clear from Table 2, the weight average molecular weight of 2 according to the treatment method of the present invention.
It can be seen that 58,000 polyethylene was decomposed in a short time with a weight average molecular weight of 19,600 after 5 days of treatment.

[0034]

EFFECTS OF THE INVENTION According to the decomposition method of the present invention, it is possible to decompose a polyolefin resin, which has been difficult to decompose in the past, at room temperature in a short period of 5 to 10 days without causing an environmental pollution problem. It is useful for solving the problem of plastic waste treatment.

Continued front page    F-term (reference) 4F301 AA12 AA13 AA14 CA04 CA09                       CA10 CA11 CA12 CA23 CA33                       CA72

Claims (2)

[Claims] 1. A method for decomposing a polyolefin resin, which comprises treating a polyolefin resin in the presence of a laccase and a mediator to decompose the resin. 2. The polyolefin resin has been subjected to at least one treatment selected from hydrophilization treatment, powderization treatment and porosification treatment.
The method for decomposing a polyolefin resin as described in 1.