JP2007051202A - Method for regenerating lactic acid-based biodegradable plastic - Google Patents

Method for regenerating lactic acid-based biodegradable plastic Download PDF

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JP2007051202A
JP2007051202A JP2005236656A JP2005236656A JP2007051202A JP 2007051202 A JP2007051202 A JP 2007051202A JP 2005236656 A JP2005236656 A JP 2005236656A JP 2005236656 A JP2005236656 A JP 2005236656A JP 2007051202 A JP2007051202 A JP 2007051202A
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lactic acid
carbon dioxide
supercritical
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Koichi Nakamura
晃一 中村
Seiji Akatsu
誠次 赤津
Masamitsu Nagahama
正光 長浜
Masahiko Yokosuka
正彦 横須賀
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/14—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with steam or water
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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Abstract

<P>PROBLEM TO BE SOLVED: To regenerate highly-purified lactic acid from a lactic acid-based biodegradable plastic waste without loosing quality due to the incorporation of impurities. <P>SOLUTION: The regeneration method comprises hydrolysis treatment and supercritical extraction treatment. The hydrolysis treatment is a treatment for reacting an object to be treated containing a biodegradable plastic derived from lactic acid with water under saturated steam pressure of about 140°C to hydrolyze the biodegradable plastic to form an aqueous lactic acid solution. The supercritical extraction treatment is a treatment for maintaining the aqueous lactic acid solution obtained by the hydrolysis treatment under a supercritical environment of carbon dioxide, that is, at a temperature of about 60°C and pressure of about 8 MP, removing a supercritical fluid of carbon dioxide in which the aqueous lactic acid solution is melted, and bringing the supercritical fluid back to ordinary temperature to form a purified lactic acid separated from carbon dioxide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、乳酸系生分解性プラスチックの再生方法、特に乳酸系生分解性プラスチックの廃棄物を生分解性プラスチックの原料に再生させる方法に関する。   The present invention relates to a method for regenerating lactic acid-based biodegradable plastics, and more particularly to a method for regenerating lactic acid-based biodegradable plastic wastes as raw materials for biodegradable plastics.

生分解性プラスチックとは、使用中は通常のプラスチックと同じ特性を持ちながら、使用後、微生物の働きによって水と二酸化炭素に分解されるプラスチックである。生分解性プラスチックはこれを大別すると、天然物系、微生物系、化学合成系、（石油由来）、化学合成系（天然物由来）などに分けられ、これまではＰＢＳ（ポリブチレンサクシネート）等の化学合成系（石油系）が主流であったが、最近では自然環境中で生分解するよりも植物等バイオマス由来点が強調されるようになり、とりわけ、トウモロコシを始め植物から製造されるＰＬＡ（ポリ乳酸）等の化学合成系（バイオマス由来）が注目されている。特に乳酸系生分解性プラスチックは、商品の包装容器、食器類、日用品、医療品、工業製品など多様な分野で使用されるようになった。   A biodegradable plastic is a plastic that has the same characteristics as ordinary plastic during use, but is decomposed into water and carbon dioxide by the action of microorganisms after use. Biodegradable plastics can be broadly divided into natural products, microbial systems, chemical synthesis systems (derived from petroleum), and chemical synthesis systems (derived from natural products). Until now, PBS (polybutylene succinate) Chemical synthesis system (petroleum system) such as the mainstream, but recently the point of origin of biomass such as plants has been emphasized rather than biodegradation in the natural environment, especially produced from plants such as corn Chemical synthesis systems (derived from biomass) such as PLA (polylactic acid) have attracted attention. In particular, lactic acid biodegradable plastics have been used in various fields such as product packaging containers, tableware, daily necessities, medical products, and industrial products.

生分解機能が求められる用途は、自然環境中に放置されるもの、コンポスト化が可能な材料、環境負荷が低い材料などが好適と考えられている。分解性では、ＰＢＳが優れるといわれているものの、また、生分解性プラスチックが自然界で細菌によって分解されるとしても、分解されるまでには長い時間が必要であり、しかも生分解性プラスチックの多くは、光や空気が無い状態においては、自然界でも分解が進まない。   Applications that require a biodegradation function are considered to be suitable for those that are left in the natural environment, materials that can be composted, materials that have a low environmental impact, and the like. Although it is said that PBS is superior in terms of degradability, even if biodegradable plastics are degraded by bacteria in nature, it takes a long time to be degraded, and many biodegradable plastics In the absence of light and air, decomposition does not proceed even in nature.

したがって、大量に廃棄されるプラスチックについては、生分解性といえども、自然環境中に放置することができず、埋め立てたとしても土中での生分解反応はきわめて緩慢のため、土に戻るまでの処分場を確保しなければならないという重大な問題に直面することになる。   Therefore, plastics that are disposed of in large quantities cannot be left in the natural environment even though they are biodegradable. Even if they are landfilled, the biodegradation reaction in the soil is extremely slow, You will face a serious problem of having to secure a disposal site.

生分解性廃棄物の処理方法に関しては、従来よりＥＭ菌の分解作用を利用する方法や加熱蒸気で減容化する方法などが試みられているが（特許文献１参照）、これらの方法は、主として生ごみを肥料化する方法である。さらに特許文献２には、生分解性廃棄物のリサイクル方法として生分解性廃棄物に加水分解処理と、乾燥処理とを行い、その処理物を資源として再生する方法が紹介され、さらにその応用展開技術として特許文献３には、処理物からは生分解性プラスチックの原料である乳酸を再生できることが記載されている。   Regarding the method for treating biodegradable waste, methods that utilize the decomposition action of EM bacteria and methods for reducing the volume with heated steam have been attempted (see Patent Document 1). This is mainly a method of turning garbage into fertilizer. Further, Patent Document 2 introduces a method for recycling biodegradable waste by hydrolyzing and drying the biodegradable waste, and recycling the treated product as a resource. As a technique, Patent Document 3 describes that lactic acid, which is a raw material for biodegradable plastics, can be regenerated from a processed product.

特許文献３に記載された方法は、容器または袋に生分解性プラスチックを用いれば容器又は袋と食品残渣とを分別することなく一括処理でき、廃棄物が生分解性プラスチックのみで構成されたのみであるときには、その原料である低分子化合物を再生できることが示唆されたものである。したがって乳酸系の生分解性プラスチックの廃棄物から生分解性プラスチックの原料である乳酸を回収するには、処理に先立って生分解性プラスチックと、他の廃棄物とを予め分別しておかなければならない。
特許公開２００２−１３６９４９号公報 特許公開２０００−１７６４１９号公報 特許公開２００５−１３１４８０号公報 If the biodegradable plastic is used for the container or the bag, the method described in Patent Document 3 can be collectively processed without separating the container or the bag and the food residue, and the waste is only composed of the biodegradable plastic. In this case, it is suggested that the low-molecular compound as the raw material can be regenerated. Therefore, in order to recover lactic acid, which is a raw material of biodegradable plastic, from lactic acid-based biodegradable plastic waste, it is necessary to separate the biodegradable plastic from other waste prior to treatment. .
Japanese Patent Publication No. 2002-136949 Japanese Patent Publication No. 2000-176419 Japanese Patent Publication No. 2005-131480

解決しようとする問題点は、乳酸系生分解性プラスチックの廃棄物から生分解性プラスチックの原料である乳酸を回収するには、処理に先立って生分解性プラスチックと、他の廃棄物とを予め分別しておかなければならなかった点である。   The problem to be solved is that in order to recover lactic acid, which is a raw material for biodegradable plastic, from lactic acid-based biodegradable plastic waste, the biodegradable plastic and other waste must be pre-treated prior to treatment. It was a point that had to be separated.

本発明は、生分解性プラスチックスと他の廃棄物とを予め分別することなく処理して生分解性プラスチックの原料である精製乳酸に容易に再生させる点を最も主要な特徴とする。   The most important feature of the present invention is that the biodegradable plastics and other waste are processed without being separated in advance and are easily regenerated into purified lactic acid which is a raw material of the biodegradable plastics.

本発明の乳酸再生方法によれば、乳酸系生分解性プラスチックの廃棄物から高度に精製された乳酸を生成することができ、生成された乳酸を再び重合することで生分解性プラスチック製品として再生することができる。しかも、再生プラスチック製品の廃棄物に加水分解処理、超臨界抽出処理を繰り返しても生成された乳酸の品質が劣化することはなく、繰り返し再生利用することができる。   According to the lactic acid regeneration method of the present invention, highly purified lactic acid can be produced from lactic acid-based biodegradable plastic waste, and the produced lactic acid is polymerized again to be regenerated as a biodegradable plastic product. can do. Moreover, the quality of the produced lactic acid does not deteriorate even if the waste of the recycled plastic product is repeatedly subjected to hydrolysis and supercritical extraction, and can be reused repeatedly.

乳酸系生分解性プラスチック廃棄物から高度に精製された乳酸を再生させるという目的を、加水分解処理と、これに続く超臨界抽出処理を行うことによって、被処理物中の異物の影響を受けずに実現した。   The purpose of regenerating highly purified lactic acid from lactic acid-based biodegradable plastic waste is not affected by foreign matter in the treated material by performing hydrolysis treatment and subsequent supercritical extraction treatment. Realized.

図１において、本発明は、乳酸系生分解性プラスチックを含む廃棄物を被処理物（Ｍ１）として、加水分解処理（Ｍ２）と、超臨界抽出処理（Ｍ３）とを順に行うものである。処理の結果、精製乳酸（Ｍ４）が生成され、得られた精製乳酸を原料として生分解性プラスチック製品（M５）に再生され、その製品が使用済みとなって廃棄されると、その廃棄物を被処理物（Ｍ１）として再び生分解性プラスチック製品の原料に再生される。本発明は上記Ｍ１〜Ｍ５のサイクルを繰り返すシステムを構築するものである。   In FIG. 1, the present invention performs a hydrolysis process (M2) and a supercritical extraction process (M3) in this order using a waste containing a lactic acid-based biodegradable plastic as an object to be processed (M1). As a result of the treatment, purified lactic acid (M4) is generated, and the resulting purified lactic acid is used as a raw material to be recycled into a biodegradable plastic product (M5). The material to be treated (M1) is regenerated again as a raw material for biodegradable plastic products. The present invention constructs a system that repeats the cycle of M1 to M5.

加水分解処理（Ｍ２）は、乳酸系生分解性プラスチックを含む被処理物を加水分解する処理である。処理に際しては、被処理物に総重量の約２０％の水分を加えて高温高圧の条件の下で、乳酸を原料とする生分解性プラスチックを含む被処理物と水（水蒸気）とを反応させると、生分解性プラスチックが加水分解されて乳酸水溶液になる。加水分解処理Ｍ２は、温度１４０℃の飽和水蒸気圧の条件の下で乳酸系生分解性プラスチックの加水分解反応を進行させることが必要である。   The hydrolysis treatment (M2) is a treatment for hydrolyzing an object to be treated containing a lactic acid biodegradable plastic. In the treatment, water of about 20% of the total weight is added to the object to be treated, and the object to be treated containing biodegradable plastic made from lactic acid is reacted with water (steam) under conditions of high temperature and high pressure. Then, the biodegradable plastic is hydrolyzed into a lactic acid aqueous solution. In the hydrolysis treatment M2, it is necessary to advance the hydrolysis reaction of the lactic acid-based biodegradable plastic under the condition of a saturated water vapor pressure at a temperature of 140 ° C.

超臨界抽出処理（Ｍ３）は、超臨界二酸化炭素を用いて加水分解処理によって生成した乳酸水溶液から乳酸を抽出する処理である。加水分解処理によって得られた乳酸水溶液を二酸化炭素の超臨界環境下（６０℃、８ＭＰ）に保つと、乳酸水溶液は二酸化炭素の超臨界流体に溶融する。次に乳酸水溶液を溶融した二酸化炭素の超臨界流体を取り出して常温にもどすと、二酸化炭素は気体となって蒸散し、二酸化炭素から分離された精製乳酸が得られる。   The supercritical extraction process (M3) is a process for extracting lactic acid from an aqueous lactic acid solution generated by hydrolysis using supercritical carbon dioxide. When the lactic acid aqueous solution obtained by the hydrolysis treatment is kept in a supercritical environment of carbon dioxide (60 ° C., 8 MP), the lactic acid aqueous solution melts into a supercritical fluid of carbon dioxide. Next, when the supercritical fluid of carbon dioxide in which the lactic acid aqueous solution is melted is taken out and returned to room temperature, the carbon dioxide is vaporized and evaporated to obtain purified lactic acid separated from the carbon dioxide.

以下に本発明による乳酸の再生方法の実施例を図によって説明する。図１において、本発明は、加水分解処理Ｍ２と、超臨界抽出処理Ｍ３とを組合せたものである。図２に加水分解処理を行うための装置を示す。図２において、加水分解処理を行う装置は、処理チャンバー１と、抽出管２と、冷却塔３と、循環ポンプ４との組み合わせからなっている。処理チャンバー１は、内部に投入された被処理物を加熱して加水分解処理を行う釜であり、その外壁には加熱ヒータ５が装備され、処理チャンバー１と、冷却塔３間は、前記抽出管２で接続されている。   Examples of the method for regenerating lactic acid according to the present invention will be described below with reference to the drawings. In FIG. 1, the present invention is a combination of a hydrolysis treatment M2 and a supercritical extraction treatment M3. FIG. 2 shows an apparatus for performing the hydrolysis treatment. In FIG. 2, the apparatus for performing the hydrolysis treatment is composed of a combination of a processing chamber 1, an extraction pipe 2, a cooling tower 3, and a circulation pump 4. The processing chamber 1 is a kettle that heats a workpiece to be processed and hydrolyzes it. The outer wall of the processing chamber 1 is equipped with a heater 5. The space between the processing chamber 1 and the cooling tower 3 is extracted. Connected by pipe 2.

抽出管２は、処理チャンバー１の下部の蒸気戻り口６と、上部の蒸気送出口７間をつなぐ循環管路であり、冷却塔３は、その管路内に接続され、循環ポンプ４は、冷却塔３の上流側の管路内に接続されたものである。また、処理チャンバー１は、被処理物の投入口８と排出口９とを有し、その内部には、垂直軸を中心に回転しながら処理チャンバー１内に投入された被処理物を攪拌する攪拌羽根１０を装備している。   The extraction pipe 2 is a circulation pipe that connects between the lower steam return port 6 of the processing chamber 1 and the upper steam outlet 7, and the cooling tower 3 is connected in the pipe, and the circulation pump 4 is It is connected in the pipe line on the upstream side of the cooling tower 3. Further, the processing chamber 1 has an input port 8 and a discharge port 9 for the object to be processed, in which the object to be processed input into the processing chamber 1 is agitated while rotating about the vertical axis. A stirring blade 10 is provided.

冷却塔３は、抽出管２内の空気（蒸気）を冷却する熱交換器であり、循環ポンプ４は、被処理物の加水分解処理後、処理チャンバー１内の水蒸気を冷却塔３に強制送風するものである。冷却塔３には、ドレイン１１を備え、冷却塔３内に水蒸気中の加水分解成分である乳酸水溶液がためられ、冷却塔３内にためられた乳酸水溶液は、容器Ｖ１内に回収される。   The cooling tower 3 is a heat exchanger that cools the air (steam) in the extraction pipe 2, and the circulation pump 4 forcibly blows water vapor in the processing chamber 1 to the cooling tower 3 after hydrolysis of the object to be processed. To do. The cooling tower 3 is provided with a drain 11, an aqueous lactic acid solution that is a hydrolysis component in water vapor is stored in the cooling tower 3, and the aqueous lactic acid solution stored in the cooling tower 3 is collected in the container V <b> 1.

図３に超臨界抽出を行う装置の概要を示す。図３において、超臨界抽出を行う装置は、ピストン１２で圧縮室（以下セルという）１３と加圧室１４との２室に区画されたシリンダ１５のセル１３側に乳酸水溶液送入管１７と、純水送入管１８と、二酸化炭素の供給管１９と、超臨界流体送出管２０とを有するものである。ピストン１２は空気圧によって駆動され、ピストン１２で区画されたセル１３と加圧室１４の内圧は圧力計１６、２１で計測される。セル１３側のシリンダ１５の正面には覗き窓２２が設けられている。なお、ボンベ２３内の二酸化炭素はスクリューポンプ２４で二酸化炭素供給管１９に送り出されてシリンダ１５のセル１３内に供給される。   FIG. 3 shows an outline of an apparatus for performing supercritical extraction. In FIG. 3, the supercritical extraction apparatus includes a lactic acid aqueous solution feed pipe 17 on the cell 13 side of a cylinder 15 partitioned by a piston 12 into a compression chamber (hereinafter referred to as a cell) 13 and a pressurization chamber 14. And a pure water inlet pipe 18, a carbon dioxide supply pipe 19, and a supercritical fluid delivery pipe 20. The piston 12 is driven by air pressure, and the internal pressures of the cell 13 and the pressurizing chamber 14 defined by the piston 12 are measured by pressure gauges 16 and 21. A viewing window 22 is provided in front of the cylinder 15 on the cell 13 side. The carbon dioxide in the cylinder 23 is sent to the carbon dioxide supply pipe 19 by the screw pump 24 and supplied into the cell 13 of the cylinder 15.

本発明は、上記装置を用い、生分解性プラスチックを含む廃棄物を被処理物として加水分解処理と、超臨界抽出処理とを順に行うものである。上記装置を用いて乳酸系生分解性プラスチックを含む廃棄物を被処理物として乳酸系生分解性プラスチックの原料を再生させる要領を図４のフローチャートを用いて説明する。   In the present invention, the above-described apparatus is used to sequentially perform a hydrolysis process and a supercritical extraction process using a waste containing a biodegradable plastic as an object to be processed. A procedure for regenerating the raw material of the lactic acid biodegradable plastic using the above apparatus as a waste to be treated containing the lactic acid biodegradable plastic will be described with reference to the flowchart of FIG.

（１）加水分解処理
図４において、まず、乳酸系生分解性プラスチックを含む廃棄物を被処理物として投入量の総重量の２０％の水とともに処理チャンバー１内に投入し、処理チャンバー１を密閉する（ステップＳ１）。 (1) Hydrolysis treatment In FIG. 4, first, waste containing lactic acid-based biodegradable plastic is introduced into the treatment chamber 1 as a treatment object together with 20% of the total weight of the input amount. Seal (step S1).

処理チャンバー１内に被処理物を投入したのち、投入口８を閉じ、タイマーをセットしてヒータ５に通電し、処理チャンバー１内を約１４０℃に加熱する（ステップＳ２）。処理チャンバー１内の圧力を、約１４０℃の加熱温度での飽和水蒸気圧に保つ。また、一定間隔（例えば２秒）ごとに1回程度攪拌羽根１０を回転駆動して処理チャンバー１内の原料を攪拌する。   After the workpiece is put into the processing chamber 1, the inlet 8 is closed, a timer is set, the heater 5 is energized, and the inside of the processing chamber 1 is heated to about 140 ° C. (step S2). The pressure in the processing chamber 1 is maintained at a saturated water vapor pressure at a heating temperature of about 140 ° C. Further, the stirring blade 10 is rotationally driven about once every fixed interval (for example, 2 seconds) to stir the raw material in the processing chamber 1.

この状態で一定時間をかけて加熱しながら処理チャンバー１内に発生する飽和水蒸気の雰囲気中に被処理物を曝して加水分解反応を進行させる。加水分解処理によって、乳酸系生分解性プラスチックの加水分解反応が進行して、乳酸水溶液の蒸気が生成し、その蒸気が処理チャンバー１を充満する。予め定められた時間経過後、ヒータ５の電源を遮断して加水分解処理を完了する（ステップＳ３）。   In this state, the object to be processed is exposed to an atmosphere of saturated water vapor generated in the processing chamber 1 while heating for a certain time, and the hydrolysis reaction proceeds. By the hydrolysis treatment, the hydrolysis reaction of the lactic acid-based biodegradable plastic proceeds to generate a vapor of the lactic acid aqueous solution, and the vapor fills the processing chamber 1. After elapse of a predetermined time, the power supply of the heater 5 is shut off to complete the hydrolysis process (step S3).

被処理物の加水分解処理に要する時間は、処理チャンバー１の容量にもよるが、通常は５〜８時間である。つまり密閉された処理チャンバー１内で、約１４０℃で加熱したときには、１４０℃での飽和水蒸気圧のもとで数時間のうちに被処理物中の生分解性プラスチックを加水分解することができる。加熱終了後、送出側、戻り側の抽出管２のバルブを開き、循環ポンプ４を起動して処理チャンバー１内の水蒸気を抽出管２内に吸引し、冷却塔３を経由させて一部を凝結させ、乾燥冷却後の水蒸気は再び処理チャンバー１内に戻し、処理チャンバー１内の水蒸気を冷却塔３と処理チャンバー１間で循環させる。冷却塔３内に送り込まれた水蒸気の一部は、冷却され、凝結して乳酸水溶液として冷却塔３内に貯められる（ステップＳ４）。   Although the time required for the hydrolysis treatment of the object to be treated depends on the capacity of the treatment chamber 1, it is usually 5 to 8 hours. That is, when heated in a sealed processing chamber 1 at about 140 ° C., the biodegradable plastic in the object to be processed can be hydrolyzed within a few hours under a saturated water vapor pressure at 140 ° C. . After completion of heating, the valves of the extraction pipe 2 on the delivery side and the return side are opened, the circulation pump 4 is started, the water vapor in the processing chamber 1 is sucked into the extraction pipe 2, and a part is passed through the cooling tower 3. The water vapor that has been condensed and dried and cooled is returned to the processing chamber 1 again, and the water vapor in the processing chamber 1 is circulated between the cooling tower 3 and the processing chamber 1. A part of the water vapor sent into the cooling tower 3 is cooled, condensed, and stored in the cooling tower 3 as an aqueous lactic acid solution (step S4).

処理チャンバー１内の水蒸気は、冷却処理が繰り返されることによって次第に温度・圧力が下がり、処理チャンバー１内が常温、常圧になったことを確認して冷却塔３のドレイン１１を開き、冷却塔３内で抽出された乳酸水溶液を容器Ｖ１内に回収すると共に処理チャンバー１内の固形生成物を排出口９から排出する。
（ステップＳ５）。 The water vapor in the processing chamber 1 gradually decreases in temperature and pressure as the cooling process is repeated, and after confirming that the processing chamber 1 is at room temperature and normal pressure, the drain 11 of the cooling tower 3 is opened. The aqueous lactic acid solution extracted in 3 is collected in the container V 1 and the solid product in the processing chamber 1 is discharged from the discharge port 9.
(Step S5).

（２）超臨界抽出処理
次に乳酸水溶液の超臨界抽出処理を行うが、その処理に先立って、装置の圧縮室（セル）１３内に、超臨界二酸化炭素を導入し、セル１３内をピストン１２で圧縮して温度約６０℃、圧力約８ＭＰの超臨界環境をセル１３内に形成する（ステップＳ６）。この状態で容器Ｖ１内の乳酸水溶液をポンプでくみ上げて超臨界環境のセル１３内に導入し、乳酸水溶液を超臨界状態にある二酸化炭素流体に溶け込ませる（ステップＳ７）。必要であれば、ポンプを駆動して純水送入管１８を通して所定量の純水をセル１３内に圧入し、純水と二酸化炭素との超臨界エマルジョンを形成させる（ステップＳ８）。 (2) Supercritical extraction treatment Next, supercritical extraction treatment of an aqueous lactic acid solution is performed. Prior to the treatment, supercritical carbon dioxide is introduced into the compression chamber (cell) 13 of the apparatus, and the inside of the cell 13 is moved to the piston. 12 is compressed to form a supercritical environment in the cell 13 at a temperature of about 60 ° C. and a pressure of about 8 MP (step S6). In this state, the lactic acid aqueous solution in the container V1 is pumped up and introduced into the cell 13 in the supercritical environment, and the lactic acid aqueous solution is dissolved in the carbon dioxide fluid in the supercritical state (step S7). If necessary, the pump is driven to press-fit a predetermined amount of pure water into the cell 13 through the pure water inlet pipe 18 to form a supercritical emulsion of pure water and carbon dioxide (step S8).

一定時間後、バルブを開いてセル１３内の二酸化炭素の超臨界流体又はエマルジョンを超臨界流体送出管２０が外部に排出して容器Ｖ２内に回収する（ステップＳ９）。セル１３から取り出された超臨界エマルジョンは、常温、常圧に戻され、二酸化炭素は、ガス化して放散され、二酸化炭素の超臨界流体に含まれていた乳酸が容器内に回収される（ステップＳ１０）。   After a certain time, the valve is opened, and the supercritical fluid or emulsion of carbon dioxide in the cell 13 is discharged to the outside by the supercritical fluid delivery pipe 20 and collected in the container V2 (step S9). The supercritical emulsion taken out from the cell 13 is returned to room temperature and normal pressure, carbon dioxide is gasified and released, and lactic acid contained in the supercritical fluid of carbon dioxide is recovered in the container (step). S10).

本発明において、加水分解処理と、超臨界抽出処理とは、必ずしも連続的に一連に行う必要はなく、加水分解処理によって生成した乳酸水溶液を適宜取り出して超臨界抽出処理を行えばよい。超臨界抽出処理によって生成した乳酸液は精製乳酸であり、回収された乳酸を重合させて生分解性プラスチックに加工できる。なお、被処理物中に、乳酸系生分解性プラスチック以外の不純物が含まれていても加水分解処理によって分解されるのは、生分解性物質だけであり、ポリエチレンなどのプラスチックはそのまま釜の中に残されて生分解性プラスチックから分離される。   In the present invention, the hydrolysis treatment and the supercritical extraction treatment do not necessarily need to be performed continuously in series, and the supercritical extraction treatment may be performed by appropriately taking out the aqueous lactic acid solution produced by the hydrolysis treatment. The lactic acid solution produced by the supercritical extraction process is purified lactic acid, and the recovered lactic acid can be polymerized and processed into a biodegradable plastic. Even if impurities other than lactic acid-based biodegradable plastics are contained in the object to be treated, only biodegradable substances are decomposed by the hydrolysis treatment, and plastics such as polyethylene remain in the kettle. To be separated from the biodegradable plastic.

なお、生分解性物質の分解処理の方法として、例えば３８０℃、２２Ｍｐａのような高温、高圧の超臨界水の雰囲気のもとで生分解性物質を熱分解する方法が知られている。本発明は１４０℃での飽和水蒸気圧のもとで加水分解処理するため、超臨界水による熱分解処理に比べて処理時間に長時間を要することになるが、生分解性物質は、１３０℃を越えると急激に分解が進むといわれている。本発明は、加水分解処理温度を約１４０℃に抑え、処理時間をかけて良質の精製乳酸を生成させるものである。   As a method for decomposing a biodegradable substance, a method is known in which a biodegradable substance is thermally decomposed in a high-temperature, high-pressure supercritical water atmosphere such as 380 ° C. and 22 Mpa. Since the present invention hydrolyzes under a saturated water vapor pressure at 140 ° C., it takes a longer time than the thermal decomposition treatment with supercritical water. It is said that the decomposition proceeds rapidly when exceeding. In the present invention, the hydrolysis treatment temperature is suppressed to about 140 ° C., and a high-quality purified lactic acid is produced over the treatment time.

更に超臨界抽出処理において、乳酸水溶液中に、生ごみなどの生分解性物質、塩その他の不純物が含まれていても、温度約６０℃、圧力約８ＭＰの条件で二酸化炭素の超臨界流体に溶解するのは乳酸だけであるから、被処理物中に乳酸系生分解性プラスチック以外の例えば塩分などの不純物が含まれていれることが処理の妨げにはならず、最終的に二酸化炭素の超臨界流体をガスに戻せば、ガスは放散されて容器Ｖ２に精製乳酸が抽出されるのである。もっとも、被処理物中の乳酸系生分解性プラスチックの純度が高ければ高いほど処理効率は高く、不純物の混入量は少ないほど望ましいのは云うまでもない。   Furthermore, in the supercritical extraction process, even if biodegradable substances such as garbage, salts and other impurities are contained in the lactic acid aqueous solution, it is converted to a supercritical fluid of carbon dioxide at a temperature of about 60 ° C. and a pressure of about 8 MP. Since only lactic acid dissolves, the inclusion of impurities other than lactic acid-based biodegradable plastics, such as salt, in the object to be treated does not hinder the treatment, and ultimately the excess of carbon dioxide. If the critical fluid is returned to the gas, the gas is dissipated and the purified lactic acid is extracted into the container V2. Needless to say, the higher the purity of the lactic acid-based biodegradable plastic in the object to be treated, the higher the treatment efficiency, and the smaller the amount of impurities, the better.

もし、ステップＳ１０で回収された精製乳酸に水分が含まれていたとしても、容器内に回収された乳酸水溶液を、そのまま２２０℃〜２４０℃に加熱し、飽和水蒸気圧（３０〜３３気圧）のもとで気化させ、その気体を冷却すると、凝縮温度の違いから乳酸と水とを分離して回収することができる。   Even if the purified lactic acid recovered in step S10 contains moisture, the aqueous lactic acid solution recovered in the container is heated as it is to 220 ° C. to 240 ° C., and the saturated water vapor pressure (30 to 33 atm) is reached. When the gas is originally vaporized and the gas is cooled, lactic acid and water can be separated and recovered from the difference in condensation temperature.

本発明によれば、乳酸系生分解性プラスチックの廃棄物を比較的短時間で処理できるだけでなく、精製乳酸として回収でき、回収された精製乳酸をポリ乳酸に重合して再び生分解性プラスチック原料に再生することができ、このサイクルを何度繰り返しても再生乳酸に原料としての劣化がなく、したがって本発明によれば、廃棄物処理の問題、資源の有効活用の問題を解決してまことに好ましい資源のクローズドサイクルシステムを実現できる。   According to the present invention, it is possible not only to treat lactic acid biodegradable plastic waste in a relatively short time, but also to recover it as purified lactic acid. The recovered purified lactic acid is polymerized into polylactic acid and again biodegradable plastic raw material No matter how many times this cycle is repeated, the regenerated lactic acid does not deteriorate as a raw material. Therefore, according to the present invention, the problem of waste treatment and the problem of effective utilization of resources are solved. A resource closed cycle system can be realized.

本発明方法の概念を示す図である。It is a figure which shows the concept of this invention method. 加水分解部の構成図である。It is a block diagram of a hydrolysis part. 臨界抽出部の構成図である。It is a block diagram of a critical extraction part. 本発明方法のフローを示す図である。It is a figure which shows the flow of this invention method.

符号の説明Explanation of symbols

１ 処理チャンバー
２ 抽出管
３ 冷却塔
４ 循環ポンプ
５ 加熱ヒータ
６ 蒸気戻り口
７ 蒸気送出口
８ 投入口
９ 排出口
１０ 攪拌羽根
１１ ドレイン
１２ ピストン
１３ セル
１４ 加圧室
１５ シリンダ
１６，２１ 圧力計
１７ 乳酸水溶液送入管
１８ 純水送入管
１９ 二酸化炭素供給管
２０ 超臨界流体送出管
２２ 覗き窓
２３ ボンベ
２４ スクリューポンプ DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Extraction pipe 3 Cooling tower 4 Circulating pump 5 Heater 6 Steam return port 7 Steam delivery port 8 Input port 9 Outlet port 10 Stirring blade 11 Drain 12 Piston 13 Cell 14 Pressurization chamber 15 Cylinders 16 and 21 Pressure gauge 17 Lactic acid aqueous solution feed pipe 18 Pure water feed pipe 19 Carbon dioxide supply pipe 20 Supercritical fluid delivery pipe 22 Viewing window 23 Cylinder 24 Screw pump

Claims (5)

加水分解処理と、超臨界抽出処理とを有する乳酸系生分解性プラスチックの再生方法であって、
加水分解処理は、水分を加えて生分解性プラスチックを含む被処理物を加水分解する処理であり、
超臨界抽出処理は、超臨界二酸化炭素を用いて加水分解処理によって生成した乳酸水溶液から乳酸を抽出する処理であることを特徴とする乳酸系生分解性プラスチックの再生方法。 A method for regenerating a lactic acid-based biodegradable plastic having a hydrolysis treatment and a supercritical extraction treatment,
The hydrolysis treatment is a treatment for adding water to hydrolyze the object to be treated including biodegradable plastic,
A method for regenerating a lactic acid-based biodegradable plastic, wherein the supercritical extraction treatment is a treatment for extracting lactic acid from a lactic acid aqueous solution produced by hydrolysis using supercritical carbon dioxide. 加水分解処理は、被処理物の総量の約２０％の水分を加え、約１４０℃の飽和水蒸気圧の下で、乳酸を原料とする生分解性プラスチックを含む被処理物と水とを反応させ、生分解性プラスチックを加水分解して乳酸水溶液を生成させる処理であり、
超臨界抽出処理は、加水分解処理によって得られた乳酸水溶液を温度約６０℃、圧力約８ＭＰの二酸化炭素の超臨界環境に保ち、乳酸水溶液を溶融した二酸化炭素の超臨界流体を取り出し、常温にもどして二酸化炭素から分離された精製乳酸を生成させる処理であることを特徴とする請求項１に記載の乳酸系生分解性プラスチックの再生方法。 In the hydrolysis treatment, about 20% of the total amount of water to be treated is added, and the material to be treated containing biodegradable plastic made from lactic acid is reacted with water under a saturated water vapor pressure of about 140 ° C. , A process that hydrolyzes biodegradable plastic to produce an aqueous lactic acid solution,
In the supercritical extraction treatment, the aqueous lactic acid solution obtained by the hydrolysis treatment is kept in a supercritical environment of carbon dioxide at a temperature of about 60 ° C. and a pressure of about 8 MP, and a supercritical fluid of carbon dioxide in which the aqueous lactic acid solution is melted is taken out to room temperature. The method for regenerating a lactic acid-based biodegradable plastic according to claim 1, wherein the method is a process of returning to produce purified lactic acid separated from carbon dioxide. 乳酸系生分解性プラスチックを含む廃棄物を被処理物として投入量の総重量の２０％の水とともに処理チャンバー内に投入して密閉するステップと、処理チャンバー内を１４０℃に加熱するステップと、処理チャンバー内の圧力を、１４０℃の加熱温度での飽和水蒸気圧に保ち、被処理物の加水分解反応を進行させるステップと、被処理物の加熱終了後、処理チャンバー内の水蒸気を乳酸水溶液に凝結させるステップと、抽出された乳酸水溶液を回収するステップと、温度約６０℃、圧力約８ＭＰの二酸化炭素の超臨界環境を形成するステップと、超臨界環境内に乳酸水溶液を導入して二酸化炭素の超臨界流体に溶け込ませるステップと、二酸化炭素の超臨界流体を回収するステップと、回収した二酸化炭素の超臨界流体を、常温、常圧に戻し、二酸化炭素をガス化して放散し、精製乳酸を回収するステップとを有することを特徴とする請求項１に記載の乳酸系生分解性プラスチックの再生方法。   Throwing waste containing lactic acid-based biodegradable plastic into the processing chamber together with 20% of the total weight of the input as a processing object, sealing the processing chamber, heating the processing chamber to 140 ° C., Maintaining the pressure in the processing chamber at a saturated water vapor pressure at a heating temperature of 140 ° C., and advancing the hydrolysis reaction of the object to be processed; and after the heating of the object to be processed, the water vapor in the processing chamber is changed to a lactic acid aqueous solution. A step of condensing, a step of recovering the extracted aqueous lactic acid solution, a step of forming a supercritical environment of carbon dioxide at a temperature of about 60 ° C. and a pressure of about 8 MP, and introducing a lactic acid aqueous solution into the supercritical environment to introduce carbon dioxide The step of dissolving in the supercritical fluid, the step of recovering the supercritical fluid of carbon dioxide, and returning the recovered supercritical fluid of carbon dioxide to normal temperature and normal pressure , Carbon dioxide and dissipated gasified, the method of reproducing lactic acid-based biodegradable plastic according to claim 1, characterized in that a step of recovering purified lactic acid. 純水と二酸化炭素との超臨界エマルジョンを形成させるステップをさらに有し、二酸化炭素の超臨界流体を回収するステップに代えて超臨界エマルジョンを回収することを特徴とする請求項３に記載の記載の乳酸系生分解性プラスチックの再生方法。   4. The method according to claim 3, further comprising the step of forming a supercritical emulsion of pure water and carbon dioxide, wherein the supercritical emulsion is recovered instead of the step of recovering the supercritical fluid of carbon dioxide. To recycle lactic acid-based biodegradable plastics. 超臨界抽出処理は、加水分解処理によって生成した乳酸水溶液を適宜取り出して行われるものであることを特徴とする請求項１又は３に記載の乳酸系生分解性プラスチックの再生方法。   The method for regenerating a lactic acid-based biodegradable plastic according to claim 1 or 3, wherein the supercritical extraction treatment is performed by appropriately taking out a lactic acid aqueous solution produced by the hydrolysis treatment.
JP2005236656A 2005-08-17 2005-08-17 Method for regenerating lactic acid-based biodegradable plastic Pending JP2007051202A (en)

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