JPH05178977A - Method for treating molded polymer article - Google Patents

Abstract

PURPOSE:To simply and easily carry out the recovery and reuse of a molded article mainly comprising a lactic acid polymer by bringing the article into contact with a high-temp. high-pressure steam. CONSTITUTION:A molded article mainly comprising a lactic acid polymer or a polylactide comprising, a copolymer obtd. by copolymerizing a lactic acid polymer with a polyglycolic acid, is thermally treated at 100 deg.C or higher under 1 atm or higher in the presence of water to effect hydrolysis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a polymer molded article which is a waste. More specifically, the present invention relates to a method for treating a polymer molded article, which reduces the molecular weight of the polymer molded article and at the same time disintegrates the morphology, thereby facilitating disposal or reuse of the polymer molded article.

[0002]

2. Description of the Related Art Heretofore, no simple treatment method has been proposed for a molded article mainly made of lactic acid polymer, which facilitates disposal or reuse of the molded article. As a method for treating a polyester compound, a hydrolysis method using lipase has been proposed, but an enzymatic agent such as lipase is expensive, has a long reaction time, and there are many polyesters which are not decomposed. Was not satisfactory as a disposal method for waste disposal or reuse.

Although many treatment methods for thermally decomposing polymer molded articles under strong heat have been proposed, all of them require a large-scale apparatus and are insufficient as a method for treating polymer molded articles.

[0004]

Since a polymer molded article is usually molded into a shape having a space inside a container or the like, it occupies a large volume and is inefficient in storage and transportation even after use. In order to solve this, a method of crushing the polymer molded product by mechanical force and reducing it to a small space has also been proposed, but in reality there is no device for crushing the polymer molded product, so it is actually inefficient. I had no choice but to carry out storage and transportation.

It is known that plastics mainly composed of lactic acid polymer are biodegradable. Therefore, when these polymers are used for landfill, they may be decomposed by microorganisms and disappear. However, in many cases, it does not decompose as it is, and even if it decomposes, it takes a long time to decompose and disappear, so a huge landfill is required.

The above-mentioned polymer molded product locally requires a large amount of oxygen when the waste product after use is to be incinerated and disposed of as a solid molded product. For this reason, when a solid molded product is burned in an ordinary incinerator, incomplete combustion often occurs, and soot and solid residue often remain.

A molded product mainly composed of a lactic acid polymer is partially oxidized and decomposed when heated and melted, so that it is difficult to recover and use it as a raw material for a new molded product as it is. However, by reducing the molecular weight while preventing oxidation and making it into powder or liquid, it can be newly used as a synthetic raw material and can be recovered and used again as a resource.
That is, an object of the present invention is to provide a method for recovering and using the above-mentioned polymer molded product by a simple method.

[0008]

According to the present invention, a molded article mainly composed of a lactic acid polymer is heated and pressurized to 100 ° C or higher and 1 atm or higher, preferably 120 ° C or higher and 2 atm or higher in the presence of water. Provided is a method for treating a polymer molded article, which comprises hydrolyzing the molded article.

That is, according to the present invention, when the above-mentioned polymer molded product is brought into contact with steam at high temperature and high pressure, preferably in a closed container capable of preventing oxidation by air contact, the polymer is hydrolyzed to have a low molecular weight and paste. It was completed by discovering that it will be in the form of powder or powder.

In the present invention, the term "molded product mainly composed of a lactic acid polymer" means a molded product having a polylactide which is a lactic acid polymer alone or a copolymer of a lactic acid polymer and polyglycolic acid as a main polymer component.

The present invention will be described in more detail based on the following examples. Examples 1 and 2, Comparative Example 1 Sample 1 (Example 1): Polylactic acid having an L / D ratio of 95/5 and a weight average molecular weight of about 230,000, which was molded into pellets having a diameter of 4 mm and a length of 3 mm, Sample 2 ( Example 2): Polylactic acid having an L / D ratio of 85/15 and a weight average molecular weight of about 200,000 formed into a pellet having a diameter of 3 mm and a length of 4 mm. Sample 3 (Comparative Example 1): 1 mm thick sheet-shaped polypropylene ,

Each of Samples 1 to 3 was placed in a test tube and brought into contact with steam at 120 ° C. and 2 atm for 1 hour in a sterilizing autoclave. As a result, the polylactic acid of Sample 1 and Sample 2 had their shapes considerably disintegrated, and easily powdered by pinching them with fingers. No morphological change was observed in the polypropylene of Sample 3.

Example 3 Polylactic acid having a L / D ratio of 85/15 and a weight average molecular weight of about 200,000, which was formed into a pellet having a diameter of 3 mm and a length of 4 mm, was used as a sample. I checked.

Samples were placed in four test tubes, four of which were placed in a reaction autoclave, and each was placed at 120 ° C., 2 atm, 140 ° C., 3 atm, 160 ° C., 6 atm and 180 atm.
It was contacted with water vapor at 11 ° C. for 1 hour. After the treatment, the shape of each sample is observed, and tetrahydrofuran (TH
It melt | dissolved in F) and the average molecular weight was investigated by the gel permeation chromatography (GPC).

The shape of all the steam-treated samples had collapsed. The samples treated at 160 ° C. and 180 ° C. easily became powders when pressed with a finger. The samples treated at 120 ° C. and 140 ° C. became powdery when pressed with a finger, although they had a slightly stronger force than those treated at 160 ° C. and 180 ° C. FIG. 1 shows the measurement results of the weight average molecular weight of polylactic acid. The higher the temperature, the lower the weight average molecular weight.

Example 4 Polylactic acid having a L / D ratio of 85/15 and a weight average molecular weight of about 200,000, which was formed into a pellet having a diameter of 3 mm and a length of 4 mm, was used as a sample, and was subjected to steam hydrolysis due to a difference in treatment time. I checked the degree. Put each sample into 8 test tubes,
Four of them were contacted with steam in an autoclave at 120 ° C. and 2 atm of steam, and the other four were contacted with steam at 140 ° C. and 3 atm of steam for 15 minutes, 30 minutes, 60 minutes, and 90 minutes, respectively. After treatment, dissolve each sample in THF,
The average molecular weight was measured by GPC. The measurement results are shown in FIG. The longer the contact time, the lower the average molecular weight.

[0017]

EFFECTS OF THE INVENTION According to the method of the present invention, a molded product mainly made of lactic acid polymer is powdered, and its volume is greatly reduced as compared with the molded product, so that efficient storage and transportation can be achieved. Furthermore, according to the method of the present invention, the powder can be made into powder with a small amount of labor and energy, and therefore, it can be burned with a constant thermal power when incinerated. Also, when used for landfill, the landfill is stabilized in a short time. According to the method of the present invention, a way to reuse the powdered polymer as a synthetic raw material is opened. Furthermore, since medical wastes to which blood or the like containing pathogenic microorganisms, viruses and the like may adhere can be treated without separately performing sterilization treatment, treatment at the waste generation source becomes easy.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the treatment temperature of lactic acid polymer and the decrease in molecular weight.

FIG. 2 is a graph showing the relationship between the treatment time of lactic acid polymer and the decrease in molecular weight.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Atsushi Okabayashi 2-33 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A method for treating a polymer molded article, which comprises subjecting a molded article mainly composed of a lactic acid polymer to heating and pressurization at 100 ° C. or higher and 1 atm or higher in the presence of water to hydrolyze the molded article.