JPH10231269A - Purification of lactic acid - Google Patents
Purification of lactic acidInfo
- Publication number
- JPH10231269A JPH10231269A JP9339593A JP33959397A JPH10231269A JP H10231269 A JPH10231269 A JP H10231269A JP 9339593 A JP9339593 A JP 9339593A JP 33959397 A JP33959397 A JP 33959397A JP H10231269 A JPH10231269 A JP H10231269A
- Authority
- JP
- Japan
- Prior art keywords
- lactic acid
- acid
- metal
- catalyst
- reduction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、乳酸の精製方法に
関する。乳酸は食品工業において、清涼飲料、酸性食
品、貯蔵食品、清酒等の製造に、或いは医薬品工業にお
いて、注射液等の医薬品の製造に広く利用されている。
また、最近では、生分解性樹脂の原料として化学工業に
おいても、広く利用されている。[0001] The present invention relates to a method for purifying lactic acid. Lactic acid is widely used in the food industry for producing soft drinks, acidic foods, stored foods, sake, and the like, or in the pharmaceutical industry for producing pharmaceuticals such as injections.
Recently, it has been widely used in the chemical industry as a raw material for biodegradable resins.
【０００２】[0002]
【従来の技術】乳酸は、工業的には発酵法、ラクトニト
リルの加水分解法、あるいは２−クロロプロピオン酸の
加水分解法等によって製造される。また、この他に、プ
ロピレンの窒素酸化物を用いた酸化や、プロピレングリ
コールやプロピレンオキシドの酸化、アセトアルデヒド
と一酸化炭素との反応等による合成も知られている。こ
れらの製造方法によって得られた乳酸の分離精製法とし
ては、乳酸を乳酸カルシウムとして晶析し、溶解性不純
物を分離した後、硫酸と反応させて乳酸に転換し、カル
シウム分を硫酸カルシウム結晶として分離する方法が広
く行われている。さらに乳酸の純度を高めるために活性
炭処理、反復晶析、イオン交換樹脂や有機溶媒による抽
出、電気透析等が併用されている。また、乳酸をメタノ
ールやエタノール等のアルコールでエステル化し、蒸留
することによって不純物を分離する方法など、さまざま
な精製手段を経ることによって純度の高い乳酸が得られ
ている。2. Description of the Related Art Lactic acid is industrially produced by fermentation, hydrolysis of lactonitrile, hydrolysis of 2-chloropropionic acid, and the like. In addition, oxidation using propylene nitrogen oxide, oxidation of propylene glycol or propylene oxide, synthesis of acetaldehyde with carbon monoxide, and the like are also known. As a method for separating and purifying lactic acid obtained by these production methods, lactic acid is crystallized as calcium lactate, soluble impurities are separated, and then reacted with sulfuric acid to be converted into lactic acid, and the calcium component is converted into calcium sulfate crystals. Separation methods are widely practiced. Activated carbon treatment, repeated crystallization, extraction with an ion-exchange resin or an organic solvent, electrodialysis and the like are also used to further increase the purity of lactic acid. Further, lactic acid having a high purity has been obtained through various purification means such as a method in which lactic acid is esterified with an alcohol such as methanol or ethanol and the impurities are separated by distillation.
【０００３】しかしながら、これらの方法で得られる乳
酸には、なお製造時の副生あるいは温度、光等の作用に
よる経時変化により、ピルビン酸、還元糖類をはじめと
する各種不純物が含まれている。その結果、臭いや乳酸
の熱安定性の点でさらに高品質を必要とする分野での使
用が制限されるという問題点があった。[0003] However, the lactic acid obtained by these methods still contains various impurities such as pyruvic acid and reducing saccharides due to by-products during production or aging with the action of temperature, light and the like. As a result, there is a problem that use in fields requiring higher quality in terms of odor and thermal stability of lactic acid is restricted.
【０００４】また、米国特許第５，３１０，８６５号
（特開平６−６５３６０号）には、乳酸等のヒドロキシ
カルボン酸類を、直接的に脱水縮合することにより、高
分子量のポリヒドロキシカルボン酸類を製造する技術及
び該ポリヒドロキシカルボン酸類を含む優れた強度を有
するフィルム、糸及び成形加工品を製造する技術が開示
されている。しかしながら、上記公知技術に従って、ポ
リ乳酸を製造する場合、実用的な強度を有する高分子量
のポリマーが得るために、比較的高品質の乳酸を使用し
ても、使用する乳酸の種類やロットの違いにより、得ら
れるポリ乳酸が着色することがあり、安定した品質のポ
リマーが得られないという問題があった。Further, US Pat. No. 5,310,865 (JP-A-6-65360) discloses that high-molecular-weight polyhydroxycarboxylic acids are obtained by directly dehydrating and condensing hydroxycarboxylic acids such as lactic acid. A technique for producing and a technique for producing a film, a yarn and a molded product having excellent strength containing the polyhydroxycarboxylic acid are disclosed. However, in the case of producing polylactic acid according to the above-described known technology, even if relatively high-quality lactic acid is used, a difference in the type of lactic acid to be used or the lot is required in order to obtain a high molecular weight polymer having practical strength. As a result, the resulting polylactic acid may be colored, and a polymer of stable quality cannot be obtained.
【０００５】ところで、乳酸中に微量に含まれる不純物
の精製法に関しては、特開昭５６−６５８４１号には、
乳酸水溶液に水を添加した後、蒸留することによる乳酸
の精製方法が開示されており、乳酸中に存在する数１０
ｐｐｍ相当のアルデヒド分を除去し、微量に混在する不
純物、例えば、メタノール、酢酸等も同時に留去される
結果、臭いも改善されることが記載されている。しかし
ながら、この方法は、精製のために、多量の水を添加す
る必要があり、濃縮蒸留に費用がかかる。また留出した
水の廃水処理の問題、さらには、この方法では効率良く
除去することが困難な不純物が依然として存在する。例
えば、ピルビン酸などの除去が困難であり、必ずしも満
足のいく精製方法とは言えなかった。[0005] Japanese Patent Application Laid-Open No. 56-65841 discloses a method for purifying a trace amount of impurities contained in lactic acid.
A method for purifying lactic acid by adding water to an aqueous lactic acid solution and then distilling the water is disclosed.
It is described that an aldehyde component equivalent to ppm is removed and impurities mixed in a trace amount, such as methanol and acetic acid, are simultaneously distilled off, so that the odor is also improved. However, this method requires a large amount of water to be added for purification, and the concentrated distillation is expensive. In addition, there is still a problem of wastewater treatment of distilled water, and there are still impurities that are difficult to remove efficiently by this method. For example, it was difficult to remove pyruvic acid and the like, and it was not always a satisfactory purification method.
【０００６】[0006]
【発明が解決しようとする課題】従って本発明は、簡単
な操作によって乳酸に含まれるピルビン酸およびその他
の微量不純物を除去することによって、ピルビン酸を含
まず、臭いや熱安定性が改善された高品質の乳酸を得る
新規な乳酸の精製方法を提供することを課題とする。Accordingly, the present invention eliminates pyruvic acid and other trace impurities contained in lactic acid by a simple operation, thereby eliminating pyruvic acid and improving odor and heat stability. An object of the present invention is to provide a novel lactic acid purification method for obtaining high-quality lactic acid.
【０００７】[0007]
【課題を解決するための手段】本発明者らは、上記の点
に鑑み鋭意検討を行った結果、乳酸を、水素又は水素含
有ガスで接触還元する方法及び金属によって還元する方
法等の簡単な還元処理によって、ピルビン酸を含まず、
しかも臭いと熱安定性が大幅に改善された高品質の乳酸
が得られることを見出し、本発明を完成した。本発明の
これらの還元処理を行った乳酸をポリマー原料として使
用することにより、着色が少ない品質の安定したポリ乳
酸が得られる。Means for Solving the Problems The present inventors have made intensive studies in view of the above points, and as a result, have found simple methods such as a method of catalytically reducing lactic acid with hydrogen or a hydrogen-containing gas and a method of reducing lactic acid with a metal. By the reduction treatment, it does not contain pyruvic acid,
In addition, they have found that high-quality lactic acid with significantly improved odor and thermal stability can be obtained, and completed the present invention. By using the lactic acid subjected to these reduction treatments of the present invention as a polymer raw material, stable polylactic acid with little coloring and high quality can be obtained.
【０００８】本発明は、以下の〔１〕〜The present invention provides the following [1] to
〔９〕に記載し
た事項により特定される。 〔１〕 乳酸水溶液を、還元処理することを特徴とする
乳酸の精製方法。 〔２〕 精製された乳酸が、１８０℃、２時間加熱後の
ＡＰＨＡが５０未満である、請求項１記載の乳酸の精製
方法。 〔３〕 還元処理が、接触還元処理であることを特徴と
する、請求項１記載の乳酸の精製方法。It is specified by the items described in [9]. [1] A method for purifying lactic acid, comprising reducing an aqueous lactic acid solution. [2] The method for purifying lactic acid according to claim 1, wherein the purified lactic acid has an APHA of less than 50 after heating at 180 ° C for 2 hours. [3] The method for purifying lactic acid according to claim 1, wherein the reduction treatment is a catalytic reduction treatment.
【０００９】〔４〕 接触還元処理が、還元触媒とし
て、パラジウム、白金、及びそれらの化合物からなる群
から選択された少なくとも一種を使用するものである、
請求項３記載の乳酸の精製方法。 〔５〕 還元処理が、還元剤として金属を使用するもの
である、請求項１記載の乳酸の精製方法。 〔６〕 還元剤として使用する金属が、金属鉄、金属
錫、金属亜鉛からなる群から選択された少なくとも一種
である、請求項５記載の乳酸の精製方法。[4] The catalytic reduction treatment uses at least one selected from the group consisting of palladium, platinum and compounds thereof as a reduction catalyst.
The method for purifying lactic acid according to claim 3. [5] The method for purifying lactic acid according to claim 1, wherein the reduction treatment uses a metal as a reducing agent. [6] The method for purifying lactic acid according to claim 5, wherein the metal used as the reducing agent is at least one selected from the group consisting of metallic iron, metallic tin, and metallic zinc.
【００１０】〔７〕 請求項１によって精製された乳
酸。 〔８〕 ピルビン酸を５ｐｐｍ以下含有するポリ乳酸重
合用乳酸。[7] Lactic acid purified according to claim 1. [8] Lactic acid for polymerization of polylactic acid containing 5 ppm or less of pyruvic acid.
〔９〕 請求項８の乳酸を原料に使用して得られる、黄
色度（ＹＩ値）３．０以下のポリ乳酸。[9] A polylactic acid having a yellowness (YI value) of 3.0 or less, obtained using the lactic acid of claim 8 as a raw material.
【００１１】[0011]
【発明の実施の形態】以下、本発明について詳細に説明
する。本発明に用いられる乳酸は、どのような製法によ
って製造された乳酸にも適用でき、特に、発酵法によっ
た乳酸に好適に適用できる。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The lactic acid used in the present invention can be applied to lactic acid produced by any production method, and can be particularly suitably applied to lactic acid produced by a fermentation method.
【００１２】本発明において乳酸は、単量体としての乳
酸のみならず、オリゴマーとしてのオリゴ乳酸（数平均
分子量３００以下の乳酸縮合体）をも包含し、これらの
混合物をも包含する。オリゴ乳酸のうち、数平均分子量
が３００を越えるものは、一般的には、溶液粘度が高く
なる結果、還元操作が困難となったり、還元処理後に、
還元に使用した接触還元触媒や、還元剤として使用した
未反応の金属を除くことが困難となるため好ましくない
場合がある。In the present invention, lactic acid includes not only lactic acid as a monomer but also oligolactic acid (a lactic acid condensate having a number average molecular weight of 300 or less) as an oligomer, and also a mixture thereof. Among the oligolactic acids, those having a number average molecular weight of more than 300 generally have a high solution viscosity, so that the reduction operation becomes difficult or after the reduction treatment,
In some cases, it is difficult to remove the catalytic reduction catalyst used for the reduction and the unreacted metal used as the reducing agent, which is not preferable.
【００１３】本発明に係る精製方法に供される乳酸は、
通常、水溶液の状態である。乳酸水溶液中の乳酸濃度は
特に制限されず、任意の濃度の乳酸水溶液を使用するこ
とができるが、一般的には、濃度２０重量％以上のもの
が好ましい。本発明に係る精製方法に供される乳酸は、
通常、本発明に係る精製方法により精製された乳酸の使
用目的に適合するように、予め、水を添加したり、濃縮
したりして、乳酸水溶液の濃度を調整することが好まし
い。The lactic acid provided for the purification method according to the present invention comprises:
Usually, it is in the state of an aqueous solution. The concentration of lactic acid in the aqueous lactic acid solution is not particularly limited, and an aqueous lactic acid solution of any concentration can be used. Generally, a lactic acid solution having a concentration of 20% by weight or more is preferable. Lactic acid provided for the purification method according to the present invention,
Usually, it is preferable to adjust the concentration of the aqueous lactic acid solution by adding water or concentrating the lactic acid in advance so as to conform to the intended use of the lactic acid purified by the purification method according to the present invention.
【００１４】一般に、還元処理の方法は、新実験化学講
座１５巻、酸化と還元〔II〕（丸善、東京、１９９７
年）に記載されているように、金属及び金属塩による還
元、金属水素化物による還元、金属水素錯化合物による
還元、接触還元、電界還元、リン化合物による還元等が
あるが、本発明において、還元処理の方法は、乳酸及び
／又は水に対して実質的に影響を与えることなく、ま
た、乳酸及び／又は水により実質的に阻害されることな
く、乳酸水溶液中に混在する酸化物を還元する操作であ
れば、特に制限されない。従って、金属ナトリウム、リ
チウムアルミニウムハイドライド、ボラン等の水との反
応性が高い化合物を使用する還元処理は好ましくない
し、ナトリウムボロンハイドライド、ヒドラジン、ジイ
ミド等の乳酸との反応性が高い化合物を使用する還元処
理は利用できない。In general, the method of reduction treatment is described in New Experimental Chemistry, Vol. 15, Oxidation and Reduction [II] (Maruzen, Tokyo, 1997).
), Reduction with a metal and a metal salt, reduction with a metal hydride, reduction with a metal hydride complex, catalytic reduction, electric field reduction, reduction with a phosphorus compound, and the like. The treatment method reduces oxides mixed in the lactic acid aqueous solution without substantially affecting lactic acid and / or water and without being substantially inhibited by lactic acid and / or water. The operation is not particularly limited. Therefore, reduction treatment using a compound having high reactivity with water such as sodium metal, lithium aluminum hydride, and borane is not preferable, and reduction using a compound having high reactivity with lactic acid such as sodium boron hydride, hydrazine, and diimide is not preferable. Processing not available.
【００１５】本発明において、還元処理の方法は、上述
の如く、乳酸及び／又は水に対して実質的に影響を与え
ることなく、また、乳酸及び／又は水により実質的に阻
害されなければ、いかなる方法も用いることができる
が、還元操作及び後処理の利便性、試薬の入手の利便性
等を考慮すると、接触還元による還元処理、金属鉄、金
属錫、金属亜鉛等の金属を還元剤として使用する還元処
理が好ましい。In the present invention, as described above, the method of the reduction treatment does not substantially affect lactic acid and / or water, and if it is not substantially inhibited by lactic acid and / or water, Any method can be used, but in consideration of the convenience of reduction operation and post-treatment, the convenience of obtaining reagents, etc., reduction treatment by catalytic reduction, metal such as iron, metal tin, and metal zinc are used as reducing agents. The reduction treatment used is preferred.
【００１６】本発明の方法において、還元処理の方法が
接触還元の方法である場合、接触還元とは、還元方法の
一種であって、適当な触媒の存在下に水素を用いて、乳
酸中に存在する乳酸以外の被還元性不純物、例えば、ピ
ルビン酸、還元糖等の不純物を還元する方法を言う。本
発明において、接触還元には、新実験化学講座１５巻、
酸化と還元〔II〕、３３３頁−４４８（丸善、東京、１
９９７年）に記載されている方法を包含する。In the method of the present invention, when the reduction treatment is a catalytic reduction method, the catalytic reduction is a kind of reduction method, and is carried out by using hydrogen in the presence of a suitable catalyst to convert lactic acid into lactic acid. It refers to a method of reducing existing reducible impurities other than lactic acid, for example, impurities such as pyruvic acid and reducing sugar. In the present invention, the catalytic reduction includes a new experimental chemistry course, Vol. 15,
Oxidation and reduction [II], pp. 333-448 (Maruzen, Tokyo, 1
997).
【００１７】本発明において、通常、接触還元は、乳酸
水溶液に、触媒を加え、水素又は水素と窒素やアルゴン
等の不活性なガスとからなる水素含有ガスにより還元処
理する。反応の終点は水素ガスの吸収を測定し、水素ガ
スの吸収が停止するところである。In the present invention, the catalytic reduction is usually carried out by adding a catalyst to an aqueous solution of lactic acid and performing a reduction treatment with hydrogen or a hydrogen-containing gas comprising hydrogen and an inert gas such as nitrogen or argon. The end point of the reaction is where the absorption of hydrogen gas is measured and the absorption of hydrogen gas stops.
【００１８】本発明の接触還元に用いられる触媒は、乳
酸と反応して変化しないものであれば、特に制限されな
い。本発明の接触還元に用いられる触媒の具体例として
は、例えば、パラジウム、白金、ロジウム、ルテニウ
ム、銅等を挙げることができる。これらの触媒は、一種
類でも二種類以上の組み合わせでも使用することができ
る。これらの触媒は金属の状態でも使用できるが、通常
はカーボン、硫酸バリウム、シリカゲル、アルミナ等の
担体表面に担持させて用いられる。工業的にはパラジウ
ム、白金触媒をそれぞれ活性炭やアルミナに担持させた
ものが好適に用いられる。これらの触媒の使用量は、原
料の乳酸水溶液に対して、金属として０．０１−３０重
量％の範囲であり、通常、担体に担持させて用いる場合
では０．０１−５重量％の範囲である。The catalyst used in the catalytic reduction of the present invention is not particularly limited as long as it does not change by reacting with lactic acid. Specific examples of the catalyst used for the catalytic reduction of the present invention include, for example, palladium, platinum, rhodium, ruthenium, copper and the like. These catalysts can be used alone or in combination of two or more. Although these catalysts can be used in a metal state, they are usually used by being supported on a carrier surface such as carbon, barium sulfate, silica gel, and alumina. Industrially, those in which palladium and platinum catalysts are respectively supported on activated carbon and alumina are preferably used. The amount of these catalysts used is in the range of 0.01 to 30% by weight as a metal based on the aqueous lactic acid solution as a raw material, and usually in the range of 0.01 to 5% by weight when used on a carrier. is there.
【００１９】本発明の接触還元の反応温度は、一般的に
は０−１５０℃の範囲、好ましくは１０−１００℃の範
囲である。The reaction temperature of the catalytic reduction of the present invention is generally in the range of 0-150 ° C, preferably in the range of 10-100 ° C.
【００２０】本発明の接触還元方法において、反応圧力
は通常、５０ｋｇ／ｃｍ2 以下の任意の圧力が用いら
れ、反応を常圧で行ってもよい。In the catalytic reduction method of the present invention, the reaction pressure is usually any pressure of 50 kg / cm 2 or less, and the reaction may be carried out at normal pressure.
【００２１】還元処理が終了した後、反応系内を窒素等
の不活性ガスに置換し、触媒と乳酸を分離する。乳酸水
溶液と触媒の分離方法は、特に制限されない。乳酸水溶
液と触媒は、例えば、触媒を濾過により、又は、触媒を
含む乳酸水溶液を静置、若しくは、遠心沈降させて乳酸
水溶液をデカントする等の簡単な操作によって、分離す
ることができる。分離した触媒は回収して再使用するこ
とができる。After the completion of the reduction treatment, the inside of the reaction system is replaced with an inert gas such as nitrogen to separate lactic acid from the catalyst. The method for separating the aqueous lactic acid solution and the catalyst is not particularly limited. The aqueous lactic acid solution and the catalyst can be separated, for example, by filtration of the catalyst or by a simple operation such as allowing the aqueous lactic acid solution containing the catalyst to stand or by centrifugal sedimentation to decant the aqueous lactic acid solution. The separated catalyst can be recovered and reused.
【００２２】本発明において、還元処理の方法が金属を
還元剤として使用する方法である場合、乳酸水溶液中、
酸性条件下で金属を還元剤として使用し、乳酸中に存在
する乳酸以外の被還元性不純物、例えば、ピルビン酸、
還元糖等の不純物を還元する。この時、塩酸、硫酸、硝
酸等の鉱酸を同時に添加し、酸の強度を上げることによ
って、還元反応の速度を速めることも可能であるが、通
常、乳酸自身の酸としての作用で充分に還元反応を行う
ことができる。In the present invention, when the method of the reduction treatment is a method using a metal as a reducing agent, the method comprises the steps of:
Using a metal as a reducing agent under acidic conditions, reducible impurities other than lactic acid present in lactic acid, for example, pyruvic acid,
Reduces impurities such as reducing sugars. At this time, mineral acid such as hydrochloric acid, sulfuric acid, nitric acid and the like can be added at the same time to increase the strength of the acid, thereby increasing the speed of the reduction reaction. However, the action of lactic acid itself as an acid is usually sufficient. A reduction reaction can be performed.
【００２３】本発明の方法で用いられる還元剤としての
金属は、金属鉄、金属錫、金属亜鉛が好ましい。本発明
の方法で用いられる還元剤としての金属の使用量は、乳
酸中に混在する乳酸以外の不純物に対して、充分な、あ
るいは大過剰の量を通常使用する。The metal used as the reducing agent in the method of the present invention is preferably metallic iron, metallic tin, or metallic zinc. The amount of metal used as a reducing agent used in the method of the present invention is usually a sufficient amount or a large excess with respect to impurities other than lactic acid mixed in lactic acid.
【００２４】反応温度は、一般的には０−１５０℃の範
囲、好ましくは１０−１００℃の範囲である。The reaction temperature is generally in the range from 0 to 150 ° C, preferably in the range from 10 to 100 ° C.
【００２５】本発明の方法で、金属を還元剤として使用
する方法の実施の形態としては、乳酸水溶液中に粉末状
の金属を添加し、所定温度で攪拌し、還元を行った後、
未反応の金属を濾過したり、未反応の金属を含む乳酸水
溶液を静置、若しくは、遠心沈降させてデカントする等
の簡単な操作によって分離する操作を包含する。他の実
施の形態として、粒状の還元剤をカラム等の充填塔に装
入し、その中を乳酸水溶液を流通させながら還元を行う
方法等をも包含する。In an embodiment of the method of the present invention in which a metal is used as a reducing agent, a metal in the form of powder is added to an aqueous lactic acid solution, and the mixture is stirred at a predetermined temperature and reduced.
It includes an operation of separating unreacted metal by a simple operation such as filtering, or an aqueous solution of lactic acid containing an unreacted metal is allowed to stand or centrifugally settled and decanted. Another embodiment includes a method in which a granular reducing agent is charged into a packed tower such as a column, and reduction is performed while flowing an aqueous lactic acid solution through the packed tower.
【００２６】反応の終点は、ＨＰＬＣ等により適宜乳酸
中のピルビン酸等の不純物の分析を行い、不純物が還元
されて、検出されなくなったところで還元操作を終了す
る。過剰に使用して残った未反応の金属は繰り返し再使
用することができ、操作は回分式、半回分式、連続式の
いずれの方法でも実施可能である。At the end point of the reaction, impurities such as pyruvic acid in lactic acid are appropriately analyzed by HPLC or the like. When the impurities are reduced and no longer detected, the reduction operation is terminated. The unreacted metal remaining in excess can be reused repeatedly, and the operation can be carried out by any of batch, semi-batch and continuous methods.
【００２７】本発明の方法で、金属を還元剤として使用
して還元操作を行った乳酸水溶液中には、反応した金属
成分、鉱酸を添加した場合には添加した鉱酸成分が溶解
している。これら乳酸中の不純物を還元処理するために
使用した成分を分離除去する方法は特に限定されない。
例えば、金属成分を、Ｈ−型強酸性イオン交換樹脂によ
って除去する方法、鉱酸成分をＯＨ型または乳酸型強塩
基性アニオン交換樹脂によって処理する方法等のイオン
交換樹脂によって処理する方法が実施可能である。ある
いは、本発明の金属による還元処理方法は、金属による
還元処理を行った後、他の公知の精製方法、例えば、乳
酸をアルコールと反応させ、乳酸エステルとして蒸留、
分離した後、乳酸エステルを加水分解して乳酸を精製す
る方法と組み合わせて用いることができる。In the method of the present invention, the reacted metal component and, when a mineral acid is added, the dissolved mineral acid component is dissolved in the aqueous lactic acid solution subjected to the reducing operation using the metal as a reducing agent. I have. The method of separating and removing the components used for reducing the impurities in the lactic acid is not particularly limited.
For example, a method of treating a metal component with an H-type strongly acidic ion exchange resin, a method of treating a mineral acid component with an OH type or lactic acid type strongly basic anion exchange resin, or a method of treating with an ion exchange resin can be performed. It is. Alternatively, the metal reduction treatment method of the present invention is a method in which, after performing a reduction treatment with a metal, other known purification methods, for example, reacting lactic acid with an alcohol and distilling as lactic acid ester,
After separation, the lactic acid ester can be used in combination with a method of hydrolyzing the lactic acid ester to purify lactic acid.
【００２８】このようにして、本発明の方法によって還
元処理された乳酸は、処理前と比較して、乳酸中に含ま
れるピルビン酸を還元処理すると同時にアルデヒド化合
物等の不純物が還元処理される結果、ピルビン酸を実質
的に含まず、熱安定性に優れ、しかも臭い（臭気性）の
低減に関して、大幅に改善された高品質の乳酸が得られ
る。具体的には、市販の乳酸中には、数十ｐｐｍ−数百
ｐｐｍ、乳酸の種類によっては１０００ｐｐｍを超える
量のピルビン酸が含まれているが、本発明の方法により
還元処理を行うと、ＨＰＬＣによる分析で（検出限界：
５ｐｐｍ）ピルビン酸は検出されなくなる。The lactic acid thus reduced by the method of the present invention is obtained by reducing pyruvic acid contained in lactic acid and simultaneously reducing impurities such as aldehyde compounds as compared with before the treatment. In addition, high-quality lactic acid is obtained which is substantially free of pyruvic acid, has excellent thermal stability, and is significantly improved in reducing odor (odor). Specifically, commercially available lactic acid contains several tens ppm to several hundred ppm, depending on the type of lactic acid, pyruvic acid in an amount exceeding 1000 ppm, but when the reduction treatment is performed by the method of the present invention, Analysis by HPLC (detection limit:
5 ppm) pyruvate is no longer detectable.
【００２９】更に、本発明の方法で精製した乳酸を原料
として使用して、直接脱水縮合することにより乳酸系ポ
リマーを製造する場合、着色の少ないポリマーを安定し
て得ることができる。乳酸を原料として使用してポリマ
ーを得る方法は、既に知られている。例えば、米国特許
第５，３１０，８６５号及び特開平６−６５３６０号に
は、ヒドロキシカルボン酸類の加熱脱水縮合反応を触媒
の存在下、有機溶媒中で行い、生成した水を該有機溶媒
と共に反応系外に留出させるとともに、留出した有機溶
媒に溶解する水分量以下の水分量を有する有機溶媒を追
加溶媒として反応系に装入しながら反応することを特徴
とする、ポリヒドロキシカルボン酸の製造方法が開示さ
れている。Furthermore, when a lactic acid-based polymer is produced by direct dehydration condensation using lactic acid purified by the method of the present invention as a raw material, a polymer with little coloring can be obtained stably. A method for obtaining a polymer using lactic acid as a raw material is already known. For example, U.S. Pat. No. 5,310,865 and JP-A-6-65360 disclose that a thermal dehydration condensation reaction of hydroxycarboxylic acids is carried out in an organic solvent in the presence of a catalyst, and the produced water is reacted with the organic solvent. Distilled out of the system, characterized by reacting while charging the organic solvent having a water content of less than the amount of water dissolved in the distilled organic solvent into the reaction system as an additional solvent, polyhydroxycarboxylic acid A manufacturing method is disclosed.
【００３０】この方法にしたがって、原料に乳酸を使用
してポリ乳酸を製造する場合、実用的な強度を持った高
分子量（重量平均分子量５０，０００以上）のポリ乳酸
を得るためには、比較的品質の高い乳酸が用いられる
が、乳酸の種類によっては、高分子量のポリ乳酸が得ら
れるものであっても、乳酸中に少量のピルビン酸が混入
するため、得られたポリ乳酸に着色が見られたり、ある
いは同じグレードの乳酸を使用しても、乳酸のロットの
違いによって、得られるポリ乳酸の着色の度合いがばら
つき、安定した品質のポリマーを継続的に得ることが困
難であった。しかしながら、本発明の還元処理して精製
したピルビン酸を実質的に含まない乳酸を使用すること
によって、米国特許第５，３１０，８６５号開示の方法
に従って脱水縮合反応を行うことにより、イエローイン
デックスが３．０以下の着色の少ない高分子量のポリマ
ーを安定して得ることができる。According to this method, when lactic acid is used as a raw material to produce polylactic acid, in order to obtain a high molecular weight (weight average molecular weight of 50,000 or more) polylactic acid with practical strength, Although high-quality lactic acid is used, depending on the type of lactic acid, even if a high-molecular-weight polylactic acid can be obtained, a small amount of pyruvic acid is mixed in the lactic acid, and the resulting polylactic acid is colored. Even if lactic acid of the same grade is used or the same grade of lactic acid is used, the degree of coloring of the obtained polylactic acid varies depending on the lot of lactic acid, and it has been difficult to continuously obtain a polymer of stable quality. However, by using the lactic acid substantially free of pyruvic acid purified by the reduction treatment of the present invention, the yellow index can be reduced by performing the dehydration condensation reaction according to the method disclosed in US Pat. No. 5,310,865. It is possible to stably obtain a high-molecular-weight polymer with less coloring of 3.0 or less.
【００３１】[0031]
【実施例】以下に実施例をあげて本発明を詳述する。な
お、本発明における実施例の記載は、本発明の内容の理
解を支援するための説明であって、その記載は本発明の
技術的範囲を狭く解釈する根拠となる性格のものではな
い。The present invention will be described in detail below with reference to examples. It should be noted that the description of the embodiments in the present invention is a description for assisting the understanding of the contents of the present invention, and the description is not a character that is a basis for interpreting the technical scope of the present invention narrowly.
【００３２】この実施例で用いた分析、評価方法は、以
下のとおりである。乳酸不純物の分析は、ピルビン酸を
代表例として挙げたが、本発明の方法で還元処理される
不純物はピルビン酸のみに限定されるものではない。実
施例においては、特に説明がない限りは、重量基準で記
載した。The analysis and evaluation methods used in this example are as follows. In the analysis of lactic acid impurities, pyruvic acid was given as a representative example, but impurities to be reduced by the method of the present invention are not limited to pyruvic acid alone. In the examples, the description is based on weight unless otherwise specified.
【００３３】（１）乳酸中の不純物の分析（ピルビン
酸） ピルビン酸の分析は以下に示すＨＰＬＣ条件で行った。
ピルビン酸の検出限界は５ｐｐｍであった。 ＜ＨＰＬＣ分析条件＞ カラム：ＹＭＣ Ａ−３１２ ＯＤＳ（６ｍｍ×１５０
ｍｍ） 移動相：アセトニトリル／水＝５／９５（ｐＨ＝２．０
／リン酸） 流速 ：１．０ｍｌ／ｍｉｎ 検出 ：λ＝２２５ｎｍ(1) Analysis of impurities in lactic acid (pyruvic acid) The analysis of pyruvic acid was performed under the following HPLC conditions.
The detection limit of pyruvic acid was 5 ppm. <HPLC analysis conditions> Column: YMC A-312 ODS (6 mm × 150
mm) Mobile phase: acetonitrile / water = 5/95 (pH = 2.0
/ Phosphoric acid) Flow rate: 1.0 ml / min Detection: λ = 225 nm
【００３４】（２）乳酸の熱安定性試験 乳酸の熱安定性を計る方法として、乳酸を１８０℃、２
時間加熱した後の着色の程度をＡＰＨＡ法で測定した。
ＡＰＨＡ法の色数標準液は、塩化白金カリウム（K2PtCl
6 ）１．２４６ｇ（白金として５００ｍｇ）、塩化コバ
ルト（CoCl2 ・6H2O）１．０ｇを塩酸１００ｍｌに溶か
し、水で１リットルに薄める。これを色数５００とす
る。試薬はいずれも特級、水は蒸留水を用いる。色数１
００、５０、２０、１０等は、色数５００の液をそれぞ
れ蒸留水で５、１０、２５、５０倍に薄めて作る。規定
の大きさの試験管（径約３ｃｍ、長さ約２０ｃｍ）に入
れて、試験管上面から肉眼で試料色と比較し、同じ感じ
の標準色数液番号で表示する。標準色数液の長期の保存
は困難なので、適当な時期に作りかえる。(2) Thermal Stability Test of Lactic Acid As a method for measuring the thermal stability of lactic acid,
The degree of coloring after heating for an hour was measured by the APHA method.
The color number standard solution of the APHA method is potassium platinum chloride (K 2 PtCl
6 ) Dissolve 1.246 g (500 mg as platinum) and 1.0 g of cobalt chloride (CoCl 2 .6H 2 O) in 100 ml of hydrochloric acid and dilute to 1 liter with water. This is assumed to be 500 colors. All reagents are of special grade, and distilled water is used for water. Number of colors 1
00, 50, 20, 10 and the like are prepared by diluting a liquid having a color number of 500 by 5, 10, 25, and 50 times with distilled water. A test tube (diameter: about 3 cm, length: about 20 cm) is placed in a test tube of a specified size, compared with the sample color with the naked eye from the top of the test tube, and indicated by a standard color number liquid number having the same feeling. Since it is difficult to store the standard color liquids for a long period of time, rebuild them at an appropriate time.
【００３５】（３）重量平均分子量 得られたポリ乳酸の重量平均分子量（Ｍｗ）は、ゲルパ
ーミエーションクロマトグラフィー（カラム温度４０
℃、クロロホルム溶媒）により、ポリスチレン標準サン
プルとの比較で求めた。(3) Weight average molecular weight The weight average molecular weight (Mw) of the obtained polylactic acid was determined by gel permeation chromatography (column temperature 40
C, chloroform solvent) in comparison with a polystyrene standard sample.
【００３６】（４）黄色度（ＹＩ値） 得られたポリ乳酸から、２ｍｍ厚のプレートサンプルを
作成し、これについて黄色度をＪＩＳ Ｋ−７１０３に
従って、ＳＭカラーコンピューター（型式：ＳＭ−６−
ＩＳ−２Ｂ、スガ試験機（株））にて測定した。(4) Yellowness (YI value) A plate sample having a thickness of 2 mm was prepared from the obtained polylactic acid, and the yellowness of the sample was measured according to JIS K-7103 using an SM color computer (model: SM-6-).
IS-2B, Suga Test Instruments Co., Ltd.).
【００３７】実施例１ 攪拌装置、温度計を備えた密閉型還元反応器に市販のＬ
−乳酸（濃度８８％）１８５ｇに５％パラジウム−アル
ミナ触媒（ＮＥケムキャット社製）３．０８ｇを加え系
内を窒素置換した。系内を水素で置換した後２５℃で激
しく攪拌しながら、常圧で接触還元処理を行った。攪拌
４０分で４５ｍｌの水素を吸収し、これ以上の吸収が認
められなくなったので、攪拌１時間後に反応を終了し
た。系内を窒素で置換した後、触媒を濾過により分離し
て、還元処理した乳酸を得た。この乳酸中のピルビン酸
を分析したところ、処理前は４８０ｐｐｍ含まれていた
ものが、処理後には検出されなかった。また、処理前は
乳酸とは異なる異臭が感じられたが、処理後の乳酸には
異臭は感じられなかった。接触還元処理後の乳酸を１８
０℃、２時間加熱した後のＡＰＨＡを測定したところ、
処理前の乳酸を１８０℃、２時間加熱した時のＡＰＨＡ
が８０であったのに対し、３０で着色の程度も改善され
ていた。Example 1 A commercially available L was placed in a closed reduction reactor equipped with a stirrer and a thermometer.
-3.08 g of 5% palladium-alumina catalyst (manufactured by NE Chemcat) was added to 185 g of lactic acid (concentration: 88%), and the system was purged with nitrogen. After the inside of the system was replaced with hydrogen, a catalytic reduction treatment was performed at normal pressure while vigorously stirring at 25 ° C. 45 ml of hydrogen was absorbed in 40 minutes of stirring, and no further absorption was observed, so the reaction was terminated after 1 hour of stirring. After purging the system with nitrogen, the catalyst was separated by filtration to obtain reduced lactic acid. Analysis of pyruvate in this lactic acid showed that it contained 480 ppm before treatment, but was not detected after treatment. Before the treatment, an off-flavor different from that of lactic acid was felt, but after the treatment, no off-flavor was felt. 18 Lactic acid after catalytic reduction
When the APHA after heating at 0 ° C. for 2 hours was measured,
APHA when lactic acid before treatment is heated at 180 ° C for 2 hours
Was 80, whereas at 30, the degree of coloring was also improved.
【００３８】実施例２ 使用する触媒を５０％含水５％パラジウム−カーボン触
媒（ＮＥケムキャット社製）１．１６ｇに変更し、６０
℃で接触還元処理する他は実施例１と同様に処理を行っ
た。攪拌３０分で４５ｍｌの水素を吸収し、これ以上の
吸収が認められなくなったので、攪拌１時間後に反応を
終了した。系内を窒素で置換した後、触媒を濾過により
分離して、還元処理した乳酸を得た。この乳酸中のピル
ビン酸を分析したところ、処理前は４８０ｐｐｍ含まれ
ていたものが、処理後には検出されなかった。また、処
理前は乳酸とは異なる異臭が感じられたが、処理後の乳
酸には異臭は感じられなかった。接触還元処理後の乳酸
を１８０℃、２時間加熱した後のＡＰＨＡを測定したと
ころ２０であった。Example 2 The catalyst used was changed to 1.16 g of a 50% water-containing 5% palladium-carbon catalyst (manufactured by NE Chemcat Co., Ltd.).
The treatment was performed in the same manner as in Example 1 except that the catalytic reduction treatment was performed at ℃. After 30 minutes of stirring, 45 ml of hydrogen was absorbed, and no further absorption was observed, so the reaction was terminated after 1 hour of stirring. After purging the system with nitrogen, the catalyst was separated by filtration to obtain reduced lactic acid. Analysis of pyruvate in this lactic acid showed that it contained 480 ppm before treatment, but was not detected after treatment. Before the treatment, an off-flavor different from that of lactic acid was felt, but after the treatment, no off-flavor was felt. APHA after heating the lactic acid after the catalytic reduction treatment at 180 ° C. for 2 hours was 20.
【００３９】実施例３ 実施例１で使用した市販のＬ−乳酸（濃度８８％）２０
０ｇに５ｇの鉄粉を添加し、７０℃で攪拌した。ＨＰＬ
Ｃによりピルビン酸が検出されなくなるまで攪拌を続け
た後、濾過により未反応の鉄粉を乳酸水溶液から分離し
た。次に、この乳酸水溶液を室温まで冷却した後、Ｈ−
型に調整したイオン交換樹脂カラム（ＤＩＡＩＯＮ Ｓ
Ｋ１Ｂ）に通液し、溶解している鉄分を除去した。得ら
れた乳酸を１８０℃、２時間加熱した後のＡＰＨＡを測
定したところ２０であった。また、処理前は乳酸とは異
なる異臭が感じられたが、処理後の乳酸には異臭は感じ
られなかった。Example 3 Commercially available L-lactic acid (concentration: 88%) used in Example 1 20
5 g of iron powder was added to 0 g, and the mixture was stirred at 70 ° C. HPL
After stirring was continued until pyruvic acid was no longer detected by C, unreacted iron powder was separated from the aqueous lactic acid solution by filtration. Next, after cooling this aqueous lactic acid solution to room temperature, H-
Ion-exchange resin column (DIAION S)
K1B) to remove dissolved iron. APHA was measured after heating the obtained lactic acid at 180 ° C. for 2 hours and found to be 20. Before the treatment, an off-flavor different from that of lactic acid was felt, but after the treatment, no off-flavor was felt.
【００４０】実施例４ 実施例１で使用した市販のＬ−乳酸（濃度８８％）２０
０ｇに５ｇの錫粉を添加し、７０℃で攪拌した。ＨＰＬ
Ｃによりピルビン酸が検出されなくなるまで攪拌を続け
た後、濾過により未反応の錫粉を乳酸水溶液から分離し
た。次に、この乳酸水溶液を室温まで冷却した後、Ｈ−
型に調整したイオン交換樹脂カラム（ＤＩＡＩＯＮ Ｓ
Ｋ１Ｂ）に通液し、溶解している錫分を除去した。得ら
れた乳酸を１８０℃、２時間加熱した後のＡＰＨＡを測
定したところ２０であった。また、処理前は乳酸とは異
なる異臭が感じられたが、処理後の乳酸には異臭は感じ
られなかった。Example 4 Commercially available L-lactic acid (concentration: 88%) 20 used in Example 1
5 g of tin powder was added to 0 g and stirred at 70 ° C. HPL
After stirring was continued until pyruvic acid was no longer detected by C, unreacted tin powder was separated from the aqueous lactic acid solution by filtration. Next, after cooling this aqueous lactic acid solution to room temperature, H-
Ion-exchange resin column (DIAION S)
K1B) to remove dissolved tin. APHA was measured after heating the obtained lactic acid at 180 ° C. for 2 hours and found to be 20. Before the treatment, an off-flavor different from that of lactic acid was felt, but after the treatment, no off-flavor was felt.
【００４１】実施例５ 実施例２で得られた還元処理を行った８８％Ｌ−乳酸１
０３．２ｇ、重合触媒として酸化第一錫０．４３ｇを５
００ｍｌの丸底フラスコに装入し、１４０℃／１００ｍ
ｍＨｇで３時間、系外に水を留去しながら加熱攪拌し
た。その後、ｏ−ジクロロベンゼン７２ｇが入ったＤｅ
ａｎ Ｓｔａｒｋｔｒａｐを装着し、さらに反応マスに
ｏ−ジクロロベンゼン７２ｇを加えて１４０℃／２７０
ｍｍＨｇで４時間共沸脱水した。Ｄｅａｎ Ｓｔａｒｋ
ｔｒａｐを取り外し、モレキュラーシーブ３Ａが３０ｇ
充填され、ｏ−ジクロロベンゼンで満たされた管を取り
つけ、還流により留出する溶媒がモレキュラーシーブを
通って再び系内に戻るようにして、１４０℃／２７０ｍ
ｍＨｇで２４時間、系内に水を混入させないようにしな
がら加熱攪拌し、反応させた。Example 5 88% L-lactic acid 1 subjected to the reduction treatment obtained in Example 2
33.2 g, 0.43 g of stannous oxide as a polymerization catalyst
Charge into a 00 ml round bottom flask, 140 ° C / 100m
The mixture was heated and stirred at mHg for 3 hours while distilling water out of the system. Then, De containing 72 g of o-dichlorobenzene was added.
An Starktrap was attached, and 72 g of o-dichlorobenzene was added to the reaction mass.
It was azeotropically dehydrated for 4 hours at mmHg. Dean Stark
Remove the trap and 30g of molecular sieve 3A
A tube filled and filled with o-dichlorobenzene was attached, and the solvent distilled at reflux was returned to the system through the molecular sieve at 140 ° C./270 m
The mixture was heated and stirred at mHg for 24 hours while preventing water from being mixed into the system, and reacted.
【００４２】この反応液を３０℃まで冷却し、０．７％
塩酸／イソプロピルアルコール溶液８００ｍｌを加え、
１時間攪拌した後、吸引濾過し、触媒を除去した。続い
て、濾塊をイソプロピルアルコール６００ｍｌで攪拌し
た後、吸引濾過する操作を濾液が中性になるまで行い、
その後、６０℃熱風乾燥し、５９．６ｇ（収率８２％）
のポリ乳酸を得た。得られたポリ乳酸の重量平均分子量
は１４３，０００であり、その黄色度（ＹＩ値）は１．
５であった。The reaction solution was cooled to 30 ° C.
Add 800 ml of hydrochloric acid / isopropyl alcohol solution,
After stirring for 1 hour, suction filtration was performed to remove the catalyst. Subsequently, the filtrate was stirred with 600 ml of isopropyl alcohol, and the operation of suction filtration was performed until the filtrate became neutral.
After that, it was dried with hot air at 60 ° C., and 59.6 g (82% yield).
Of polylactic acid was obtained. The weight average molecular weight of the obtained polylactic acid was 143,000, and its yellowness (YI value) was 1.
It was 5.
【００４３】実施例６ 実施例３で得られた還元処理乳酸を行った８８％Ｌ−乳
酸を使用する以外は実施例５に示した重合操作と同様の
操作を行いポリ乳酸６０．０ｇ（収率８３％）を得た。
得られたポリ乳酸の重量平均分子量は１４５，０００で
あり、その黄色度（ＹＩ値）は１．３であった。Example 6 The same operation as the polymerization operation shown in Example 5 was carried out except that 88% L-lactic acid obtained by reducing the lactic acid obtained in Example 3 was used. 83%).
The weight average molecular weight of the obtained polylactic acid was 145,000, and its yellowness (YI value) was 1.3.
【００４４】比較例１ 実施例１で使用した市販のＬ−乳酸（濃度８８％）２０
０ｇに、蒸留水２００ｇを加え、温度５０〜５５℃、９
０〜５０ｍｍＨｇの減圧下で全液が２００ｇになるまで
濃縮した。処理後の乳酸は、異臭は感じられなかった
が、ピルビン酸含有量を測定したところ、４２０ｐｐｍ
と、処理前と比較してわずかに減少しただけであった。
処理後の乳酸を１８０℃、２時間加熱した後のＡＰＨＡ
を測定したところ５０であった。このようにして得られ
た８８％Ｌ−乳酸を使用し、実施例５に示した重合操作
と同様の操作を行いポリ乳酸５９．５ｇ（収率８２％）
を得た。得られたポリ乳酸の重量平均分子量は１４５，
０００であり、その黄色度（ＹＩ値）は４．３であっ
た。Comparative Example 1 The commercially available L-lactic acid (concentration 88%) 20 used in Example 1
0 g, 200 g of distilled water was added, and the temperature was
The solution was concentrated under reduced pressure of 0 to 50 mmHg until the total amount of the solution became 200 g. Lactic acid after the treatment did not have an off-flavor, but when the pyruvic acid content was measured, it was 420 ppm.
And only a slight decrease as compared to before the treatment.
APHA after heating the treated lactic acid at 180 ° C for 2 hours
Was 50. Using the thus obtained 88% L-lactic acid, the same operation as the polymerization operation shown in Example 5 was performed to obtain 59.5 g of polylactic acid (82% yield).
I got The weight average molecular weight of the obtained polylactic acid is 145,
000 and its yellowness (YI value) was 4.3.
【００４５】比較例２ 実施例１で使用した還元処理前の８８％Ｌ−乳酸をその
まま重合に使用し、実施例５に示した重合操作と同様の
操作を行いポリ乳酸５８．５ｇ（収率８１％）を得た。
得られたポリ乳酸の重量平均分子量は１４３，０００で
あり、その黄色度（ＹＩ値）は４．８であった。実施例
５、６及び比較例１、２の重合により得られたポリ乳酸
の重量平均分子量、黄色度（ＹＩ値）と、原料として使
用した乳酸中のピルビン酸含有量、１８０℃、２時間加
熱後の着色の程度（ＡＰＨＡ）の関係を表−１（表１）
に示した。Comparative Example 2 Using the 88% L-lactic acid before reduction treatment used in Example 1 as it was for polymerization, the same operation as the polymerization operation shown in Example 5 was performed to obtain 58.5 g of polylactic acid (yield). 81%).
The weight average molecular weight of the obtained polylactic acid was 143,000, and its yellowness (YI value) was 4.8. Weight average molecular weight and yellowness (YI value) of polylactic acid obtained by polymerization of Examples 5 and 6 and Comparative Examples 1 and 2, pyruvic acid content in lactic acid used as a raw material, heating at 180 ° C for 2 hours Table 1 (Table 1) shows the relationship between the degree of subsequent coloring (APHA).
It was shown to.
【００４６】[0046]
【表１】 [Table 1]
【００４７】[0047]
【発明の効果】このようにして、本発明の方法によって
還元処理された乳酸は、処理前と比較して、乳酸中に含
まれるピルビン酸を還元処理すると同時にアルデヒド化
合物等の不純物が還元処理される結果、ピルビン酸を実
質的に含まず、熱安定性に優れ、しかも臭い（臭気性）
の低減に関して、大幅に改善された高品質の乳酸が得ら
れる。更に、本発明の方法で精製した乳酸を原料として
使用して、直接脱水縮合することにより乳酸系ポリマー
を製造する場合、着色の少ないポリマーを安定して得る
ことができる。As described above, the lactic acid reduced by the method of the present invention is obtained by reducing pyruvate contained in lactic acid and simultaneously reducing impurities such as aldehyde compounds as compared with before the treatment. As a result, it does not substantially contain pyruvic acid, has excellent thermal stability, and has an odor (odor)
With respect to the reduction of lactic acid, a significantly improved high-quality lactic acid is obtained. Furthermore, when a lactic acid-based polymer is produced by directly dehydrating and condensing lactic acid purified by the method of the present invention as a raw material, a polymer with little coloring can be obtained stably.
Claims (9)
とする乳酸の精製方法。1. A method for purifying lactic acid, comprising reducing an aqueous lactic acid solution.
熱後のＡＰＨＡが５０未満である、請求項１記載の乳酸
の精製方法。2. The method for purifying lactic acid according to claim 1, wherein the purified lactic acid has an APHA of less than 50 after heating at 180 ° C. for 2 hours.
特徴とする、請求項１記載の乳酸の精製方法。3. The method for purifying lactic acid according to claim 1, wherein the reduction treatment is a catalytic reduction treatment.
ジウム、白金、及びそれらの化合物からなる群から選択
された少なくとも一種を使用するものである、請求項３
記載の乳酸の精製方法。4. The catalytic reduction treatment according to claim 3, wherein at least one selected from the group consisting of palladium, platinum and their compounds is used as the reduction catalyst.
The method for purifying lactic acid according to the above.
るものである、請求項１記載の乳酸の精製方法。5. The method for purifying lactic acid according to claim 1, wherein the reduction treatment uses a metal as a reducing agent.
金属錫、金属亜鉛からなる群から選択された少なくとも
一種である、請求項５記載の乳酸の精製方法。6. The metal used as a reducing agent is metallic iron,
The method for purifying lactic acid according to claim 5, wherein the method is at least one selected from the group consisting of metallic tin and metallic zinc.
乳酸重合用乳酸。8. A lactic acid for polymerization of polylactic acid, containing 5 ppm or less of pyruvic acid.
る、黄色度（ＹＩ値）３．０以下のポリ乳酸。9. A polylactic acid having a yellowness (YI value) of 3.0 or less, obtained using the lactic acid of claim 8 as a raw material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33959397A JP3880175B2 (en) | 1996-12-20 | 1997-12-10 | Purification method of lactic acid |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8-341908 | 1996-12-20 | ||
| JP34190896 | 1996-12-20 | ||
| JP33959397A JP3880175B2 (en) | 1996-12-20 | 1997-12-10 | Purification method of lactic acid |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10231269A true JPH10231269A (en) | 1998-09-02 |
| JP3880175B2 JP3880175B2 (en) | 2007-02-14 |
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ID=26576464
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP33959397A Expired - Fee Related JP3880175B2 (en) | 1996-12-20 | 1997-12-10 | Purification method of lactic acid |
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| Country | Link |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014193895A (en) * | 1999-03-22 | 2014-10-09 | Purac Biochem Bv | Purification method of lactic acid on an industrial scale |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2842581A1 (en) | 2011-07-22 | 2013-01-31 | Toray Industries, Inc. | Method for producing organic acid |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5035058B1 (en) * | 1969-05-23 | 1975-11-13 | ||
| JPH0665360A (en) * | 1991-12-19 | 1994-03-08 | Mitsui Toatsu Chem Inc | Polyhydroxycarboxylic acid and its production |
| US5488156A (en) * | 1994-12-23 | 1996-01-30 | Uop | Preparation of a heat-stable lactic acid |
| JPH10120776A (en) * | 1996-09-02 | 1998-05-12 | Mitsui Chem Inc | Production of aliphatic polyester |
-
1997
- 1997-12-10 JP JP33959397A patent/JP3880175B2/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5035058B1 (en) * | 1969-05-23 | 1975-11-13 | ||
| JPH0665360A (en) * | 1991-12-19 | 1994-03-08 | Mitsui Toatsu Chem Inc | Polyhydroxycarboxylic acid and its production |
| US5488156A (en) * | 1994-12-23 | 1996-01-30 | Uop | Preparation of a heat-stable lactic acid |
| JPH10120776A (en) * | 1996-09-02 | 1998-05-12 | Mitsui Chem Inc | Production of aliphatic polyester |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014193895A (en) * | 1999-03-22 | 2014-10-09 | Purac Biochem Bv | Purification method of lactic acid on an industrial scale |
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