JPH0726013A - Process for recovering lactam - Google Patents

Abstract

PURPOSE:To recover a high-purity lactam at a high yield by a simple process. CONSTITUTION:A lactam is recovered from a distillation residue which is obtd. by distilling, in the presence of an alkali, a crude lactam obtd. from extraction water produced as a by-product at a 6-nylon polymn. plant and/or a crude lactam obtd. from a product of depolymerization of a polymer scrap. The recovery is carried out by neutralizing or removing an alkaline compd. in the distillation residue, heating the residue and at least a half as much polycaprolactam to 260 deg.C or higher in the presence of phosphoric acid or its deriv. to cause the ring-opening polymn. of a lactam and oligomers in the residue, depolymerizing the resulting polycaprolactam, and recovering the resulting lactam monomer.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は６ナイロン重合プラント
から副生する抽出水および／または重合体屑の解重合物
から得られる粗ラクタムにアルカリ化合物を添加して蒸
留した後の、オリゴマーを含有する蒸留残渣からラクタ
ムモノマー（以下単にラクタムと呼ぶ）を回収する方法
に関する。FIELD OF THE INVENTION The present invention contains oligomers obtained by adding an alkali compound to a crude lactam obtained from a depolymerized product of extracted water and / or polymer scrap produced as a by-product from a nylon 6 polymerization plant and distilling it. The present invention relates to a method for recovering lactam monomer (hereinafter simply referred to as lactam) from a distillation residue.

【０００２】[0002]

【従来の技術】通常、オリゴマーはナイロンチップの抽
出水や重合体屑の解重合物から得られる粗ラクタム中な
どに多く含まれ、このオリゴマーをラクタム原料に戻し
て回収することは経済的に重要である。抽出水中のオリ
ゴマーでは抽出水を濃縮冷却しオリゴマーを晶析させ濾
過分離した後処理する方法が、また重合体屑の解重合物
から得られる粗ラクタム中のオリゴマーや抽出水のオリ
ゴマーを分離せずに蒸留した場合では蒸留残渣として残
ったオリゴマーを処理する方法が行われ、古くからいろ
いろな方法が提案されてきた。しかし、オリゴマーの中
の主成分である環状二量体は熱的、化学的にも安定であ
るため、ラクタムに戻して回収する際にはさまざまな問
題を抱えている。たとえばオリゴマーを燐酸やアルカリ
化合物触媒下で減圧または水蒸気蒸留させる方法（特公
昭４６−２４３８８号公報、特公昭４６−３１５３７号
公報など）ではオリゴマーの昇華が激しいためライン詰
まりが生じ易くまた収率も低い。オリゴマーを燐酸存在
下で加熱し、重合後に解重合させる方法（特開昭５９−
７０６６２号公報）ではオリゴマーが溶解・重合平衡に
達するまでの時間が長く、平衡に達する前に解重合させ
るとオリゴマーの昇華量が多くなる問題がある。またこ
の方法でアルカリ蒸留残渣のオリゴマーを用いる場合、
燐酸の活性が残渣中のアルカリで阻害されるため使用燐
酸量が多くなる問題もある。さらにオリゴマーをアルカ
リ触媒下で加熱し、重合後に解重合させる方法（特公昭
５９−６８４９号公報）では、触媒としてアルカリを使
用するため得られた粗ラクタムの品質が低く、満足な品
質を得るまでの精製が複雑になりラクタムの損失が多く
なる。2. Description of the Related Art Usually, a large amount of oligomers is contained in water extracted from nylon chips and crude lactam obtained from depolymerized polymer scraps. It is economically important to recover the oligomer by returning it to a lactam raw material. Is. In the case of oligomers in the extracted water, the method of concentrating and cooling the extracted water to crystallize the oligomers and separating them by filtration and then treating them is also possible. In the case of distilling into a mixture, a method of treating an oligomer remaining as a distillation residue is carried out, and various methods have been proposed for a long time. However, the cyclic dimer, which is the main component in the oligomer, is thermally and chemically stable, and therefore has various problems when it is returned to the lactam and recovered. For example, in a method of decompressing or steam distilling an oligomer in the presence of a phosphoric acid or an alkali compound catalyst (Japanese Patent Publication No. 46-24388, Japanese Patent Publication No. 46-31537), the sublimation of the oligomer is so severe that line clogging is likely to occur and the yield is also high. Low. A method of heating an oligomer in the presence of phosphoric acid to depolymerize it after polymerization (JP-A-59-59).
No. 70662), it takes a long time for the oligomer to reach the dissolution / polymerization equilibrium, and there is a problem that the amount of sublimation of the oligomer increases if the oligomer is depolymerized before the equilibrium is reached. When using an oligomer of the alkaline distillation residue in this method,
There is also a problem that the amount of phosphoric acid used increases because the activity of phosphoric acid is inhibited by the alkali in the residue. Further, in the method of heating an oligomer in the presence of an alkali catalyst and depolymerizing it after the polymerization (Japanese Patent Publication No. 59-6849), the quality of the crude lactam obtained is low because an alkali is used as a catalyst until a satisfactory quality is obtained. The purification is complicated and the loss of lactam increases.

【０００３】[0003]

【発明が解決しようとする課題】本発明は前記従来の方
法による問題を解決し、つまりオリゴマーの昇華をおさ
え、かつ回収するラクタムの品質を向上させることを課
題とするものである。SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the above-mentioned conventional methods, that is, to suppress the sublimation of oligomers and to improve the quality of lactam to be recovered.

【０００４】[0004]

【課題を解決するための手段】本発明者らは前記課題を
解決するために、オリゴマーを含有する蒸留残渣からラ
クタムを回収する方法について鋭意、研究検討を行った
結果、遂に本発明を完成するに到った。すなわち本発明
は、６ナイロン重合プラントから副生する抽出水および
／または重合体屑の解重合物から得られる粗ラクタムに
アルカリを添加して蒸留した後の蒸留残渣よりラクタム
を回収するに方法において、前記蒸留残渣中のアルカリ
化合物を中和または除去した後、燐酸またはその誘導体
の存在下で蒸留残渣の０．５倍量以上のポリカプロラク
タムと共に２６０℃以上に加熱し、蒸留残渣中のラクタ
ムおよびオリゴマーを開環重合させ、得られた該ポリカ
プロラクタムを解重合させてラクタムモノマーを回収す
ることを特徴とするラクタムの回収方法である。[Means for Solving the Problems] In order to solve the above problems, the present inventors have earnestly studied and studied a method for recovering lactam from a distillation residue containing an oligomer, and as a result, finally completed the present invention. Came to. That is, the present invention relates to a method for recovering a lactam from a distillation residue obtained by adding an alkali to a crude lactam obtained from a depolymerized product of extracted water and / or a polymer waste produced as a by-product from a 6-nylon polymerization plant and distilling it. After neutralizing or removing the alkaline compound in the distillation residue, the lactam and the lactam in the distillation residue are heated to 260 ° C. or more in the presence of phosphoric acid or a derivative thereof together with 0.5 times or more of the amount of the polycaprolactam of the distillation residue. A method for recovering a lactam, which comprises ring-opening polymerizing an oligomer and depolymerizing the obtained polycaprolactam to recover a lactam monomer.

【０００５】一般に、ナイロン重合プラントから副生す
る抽出水から得られるラクタムや、重合体屑の解重合物
から得られる粗ラクタムを、イオン交換樹脂処理や活性
炭処理、酸化処理などの精製処理をしたあとのラクタム
は、水酸化ナトリウムや水酸化カリウム等のアルカリ化
合物を添加するなどしてアルカリ条件下で蒸留精製さ
れ、ラクタム中に含まれるオリゴマーは蒸留残渣として
得られる。本発明はここで生じたアルカリ化合物を添加
して蒸留した後の残渣中のオリゴマーおよびモノマーか
ら、アルカリを中和または除去した後にラクタムをモノ
マーとして回収する方法である。Generally, a lactam obtained from extraction water by-produced from a nylon polymerization plant and a crude lactam obtained from a depolymerization product of polymer scraps are subjected to purification treatments such as ion exchange resin treatment, activated carbon treatment and oxidation treatment. The remaining lactam is distilled and purified under alkaline conditions by adding an alkaline compound such as sodium hydroxide or potassium hydroxide, and the oligomer contained in the lactam is obtained as a distillation residue. The present invention is a method of recovering a lactam as a monomer after neutralizing or removing an alkali from an oligomer and a monomer in a residue obtained by adding and distilling the generated alkali compound.

【０００６】本発明において、アルカリ化合物を添加し
て蒸留した残渣のアルカリ化合物を中和または除去する
方法としては、たとえば蒸留残渣を溶融させ、これに硫
酸、塩酸などの無機塩を添加し単にアルカリを中和させ
る方法、蒸留残渣を溶融させこれに硫酸、塩酸などの無
機塩を添加しアルカリを中和後濾過除去する方法、硫酸
ナトリウム、燐酸ナトリウムなどの塩類の水溶液でアル
カリ成分を抽出除去する方法、蒸留残渣を水に溶解させ
これから有機溶媒でオリゴマーおよびモノマーのみを抽
出する方法、などが例として挙げられ、いずれを採用し
てもよい。In the present invention, as a method for neutralizing or removing the alkaline compound in the residue obtained by adding the alkaline compound and distilling, for example, the distillation residue is melted, and an inorganic salt such as sulfuric acid or hydrochloric acid is added thereto to simply remove the alkaline compound. Method, a method in which the distillation residue is melted, an inorganic salt such as sulfuric acid or hydrochloric acid is added to the solution, the alkali is neutralized and then filtered out, and an alkaline component is extracted and removed with an aqueous solution of salts such as sodium sulfate or sodium phosphate. Examples of the method include a method of dissolving the distillation residue in water and extracting only the oligomer and the monomer with an organic solvent, and any method may be adopted.

【０００７】このようにしてアルカリ化合物を中和また
は除去した蒸留残渣は、触媒として燐酸またはその誘導
体の存在下で蒸留残渣の０．５倍量以上のポリカプロラ
クタムと共に２６０℃以上に加熱し、蒸留残渣中のラク
タムおよびオリゴマーを開環重合後解重合させる。本発
明において前記触媒としての燐酸またはその誘導体の好
適な具体例としては、オルト燐酸、ピロ燐酸、メタ燐
酸、ポリ燐酸、三燐酸、亜燐酸、次亜燐酸、および燐酸
のアンモニウム塩、カリウム塩、ナトリウム塩、有機ホ
スホネート、有機ホスファイトあるいは燐の酸化物、硫
化物など燐酸の誘導体が挙げられる。添加量はポリカプ
ロラクタムと混合する蒸留残渣量によって適宜決定され
るが、蒸留残渣量とポリカプロラクタム量の合計量の
０．０１−５．０％が好ましく、５．０％を越えると重
合平衡時のオリゴマー量が増加し好ましくない。The distillation residue obtained by neutralizing or removing the alkali compound in this manner is heated to 260 ° C. or more in the presence of phosphoric acid or its derivative as a catalyst together with 0.5 times or more of the amount of the distillation residue, and polycaprolactam. The lactam and oligomer in the residue are depolymerized after ring-opening polymerization. In the present invention, preferable specific examples of phosphoric acid or its derivative as the catalyst include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, triphosphoric acid, phosphorous acid, hypophosphorous acid, and ammonium salts, potassium salts of phosphoric acid, Examples thereof include derivatives of phosphoric acid such as sodium salts, organic phosphonates, organic phosphites or phosphorus oxides and sulfides. The amount of addition is appropriately determined depending on the amount of distillation residue mixed with polycaprolactam, but 0.01 to 5.0% of the total amount of the amount of distillation residue and polycaprolactam is preferable. The amount of oligomers of is increased, which is not preferable.

【０００８】本発明で蒸留残渣に添加するポリカプロラ
クタムは紡糸や成形等の加工工程から発生する重合体の
屑を用いてもよいが、本発明により蒸留残渣中のラクタ
ムおよびオリゴマーをポリカプロラクタムと共に開環重
合させたポリカプロラクタムの一部をそのまま用いるこ
とも可能である。添加量としては蒸留残渣の０．５倍量
以上が好ましく、０．５倍量以下の場合は本発明の工程
中に蒸留残渣中のオリゴマーの昇華量が増加したり、加
熱溶解するまで長時間を有するなどの問題が生じる。反
応温度としては２６０℃以上、好ましくは２８０℃以上
である。また、３５０℃以上では生成したラクタム中に
熱分解物が多くなり品質を低下させるので好ましくな
い。The polycaprolactam to be added to the distillation residue in the present invention may be polymer scraps generated from processing steps such as spinning and molding, but according to the present invention, the lactam and oligomer in the distillation residue are opened together with the polycaprolactam. It is also possible to use a part of the ring-polymerized polycaprolactam as it is. The addition amount is preferably 0.5 times the amount of the distillation residue or more, and when it is 0.5 times the amount or less, the sublimation amount of the oligomer in the distillation residue increases during the process of the present invention, or it takes a long time to dissolve by heating. There is a problem such as having. The reaction temperature is 260 ° C or higher, preferably 280 ° C or higher. Further, if the temperature is 350 ° C. or higher, the thermal decomposition products are increased in the produced lactam and the quality is degraded, which is not preferable.

【０００９】このようにして開環重合させて得られたポ
リカプロラクタムは、引き続き過熱水蒸気を吹き込んだ
り、加熱減圧で蒸留することにより解重合させる。この
解重合反応は開環重合を行った反応容器にそのまま過熱
水蒸気を吹き込むバッチ式で行っても良いし、開環重合
させたポリカプロラクタムを別に準備した解重合反応容
器に移送後に解重合を行うことも可能である。さらには
開環重合させたポリカプロラクタムを、ポリカプロラク
タムの紡糸や成形等の加工工程から発生する重合体の屑
を解重合させる反応容器に導入してこれらの重合体の屑
と混合して解重合させても良い。The polycaprolactam thus obtained by ring-opening polymerization is depolymerized by subsequently blowing in superheated steam or distilling it under reduced pressure with heating. This depolymerization reaction may be carried out in a batch system in which superheated steam is directly blown into the reaction vessel in which ring-opening polymerization has been carried out, or the depolymerization is carried out after transferring the ring-opening polymerized polycaprolactam to a separately prepared depolymerization reaction vessel. It is also possible. Furthermore, the ring-opening polymerized polycaprolactam is introduced into a reaction vessel for depolymerizing polymer scraps generated from processing steps such as spinning and molding of polycaprolactam, and mixed with these polymer scraps to depolymerize. You may let me.

【００１０】なお、この開環重合させたポリカプロラク
タムを解重合反応容器に移送させる際、全量を移送せず
に一部を開環重合反応容器中に残し、これを本発明にお
けるアルカリ成分を除去した蒸留残渣に添加するポリカ
プロラクタムとして利用し、この中に次のアルカリ成分
を除去した蒸留残渣および触媒を加え本発明の開環重合
を繰り返しても良い。When the ring-opening polymerized polycaprolactam is transferred to the depolymerization reaction container, the whole amount is not transferred and a part is left in the ring-opening polymerization reaction container to remove the alkali component in the present invention. The ring-opening polymerization of the present invention may be repeated by using as a polycaprolactam to be added to the above-mentioned distillation residue and adding the following distillation residue from which the alkaline component has been removed and a catalyst.

【００１１】[0011]

【実施例】以下、実施例を用いて本発明を具体的に説明
するが、本発明はこれらの実施例により限定されるもの
ではない。なお実施例中単に部とあるのは重量部を示
す。 実施例１ ６ナイロン重合プラントから副生する抽出水から得られ
た粗ε−カプロラクタムに２０％水酸化ナトリウム水溶
液を１重量％添加した後蒸留した残渣（オリゴマー６７
％、モノマー３１％水酸化ナトリウム２部含有）４００
部および重合体屑の解重合物から得られる粗ε−カプロ
ラクタムを過マンガン酸カリウム酸化処理した後の蒸留
残渣（オリゴマー６１％、モノマー３７％水酸化カリウ
ム２部含有）１００部を１２０℃に加熱溶融させこれに
５０％硫酸水溶液２０部を加え中和し、硫酸ナトリウム
を濾過除去した。これの１００部に紡糸工程より発生し
たポリε−カプロラクタムの屑糸１００部およびオルト
燐酸１．０部を加え窒素で置換した後３００℃に加熱し
た。５時間後蒸留残渣はポリε−カプロラクタムに完全
に溶解し、平衡に達した。ただちにこの中に３２０℃の
過熱水蒸気を吹き込み解重合を行い、生成したモノマー
を流出させた。粗ε−カプロラクタムの収率は９１．８
％（投入した残渣と添加した屑糸の合計量を基準）であ
った。The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by weight". Example 1 1% by weight of 20% aqueous sodium hydroxide solution was added to crude ε-caprolactam obtained from extraction water by-produced from a 6 nylon polymerization plant, and the residue was distilled (oligomer 67
%, Monomer 31%, containing 2 parts of sodium hydroxide) 400
Of 100 parts of a distillation residue (containing 61% of oligomers, 37% of monomers and 2 parts of potassium hydroxide) obtained by subjecting crude .epsilon.-caprolactam obtained from the depolymerization of 1 part and polymer scraps to potassium permanganate oxidation is heated to 120.degree. After melting, 20 parts of 50% sulfuric acid aqueous solution was added thereto for neutralization, and sodium sulfate was removed by filtration. To 100 parts of this was added 100 parts of poly ε-caprolactam waste fiber generated in the spinning step and 1.0 part of orthophosphoric acid, and the mixture was replaced with nitrogen and heated to 300 ° C. After 5 hours, the distillation residue was completely dissolved in poly ε-caprolactam and reached equilibrium. Immediately thereafter, superheated steam at 320 ° C. was blown into the mixture to carry out depolymerization, and the produced monomer was allowed to flow out. The yield of crude ε-caprolactam is 91.8.
% (Based on the total amount of the added residue and the added waste thread).

【００１２】実施例２ 実施例１と同様にして蒸留残渣を中和後、ポリε−カプ
ロラクタムに溶解、開環重合させた。重合体の１２０部
を溶融状態のまま、紡糸や成形等の加工工程から発生す
る重合体の屑を解重合させる解重合反応釜に投入し、紡
糸や成形等の加工工程から発生する重合体の屑（合計５
００部、オルト燐酸２．０部）と共に水蒸気吹き込みを
行い解重合させた。粗ε−カプロラクタムの収率は９
２．０％であった。Example 2 In the same manner as in Example 1, the distillation residue was neutralized, dissolved in polyε-caprolactam, and subjected to ring-opening polymerization. With 120 parts of the polymer in a molten state, the polymer is discharged into a depolymerization reaction kettle for depolymerizing polymer waste generated from processing steps such as spinning and molding, and the polymer generated from processing steps such as spinning and molding is charged. Scraps (total 5
(00 part, 2.0 parts of orthophosphoric acid) was blown with steam to depolymerize. The yield of crude ε-caprolactam is 9
It was 2.0%.

【００１３】実施例３ 実施例２で行った重合体の残りの８０部に、実施例１で
用いたアルカリ成分を除去した蒸留残渣１２０部とオル
ト燐酸０．６部を加え窒素で置換した後３００℃に加熱
した。５時間後蒸留残渣はポリε−カプロラクタムに完
全に溶解し、平衡に達した。この重合体の１２０部を溶
融状態のまま、実施例２と同様に紡糸や成形等の加工工
程から発生する重合体の屑を解重合させる解重合反応釜
に投入し、紡糸や成形等の加工工程から発生する重合体
の屑（合計５００部、オルト燐酸２．０部）と共に水蒸
気吹き込みを行い解重合させた。残りの重合体８０部に
上記と同様の操作を合計５回繰り返した。５回の粗ε−
カプロラクタムの平均収率は９２．２％であった。Example 3 To the remaining 80 parts of the polymer obtained in Example 2, 120 parts of the distillation residue used in Example 1 from which the alkali component had been removed and 0.6 part of orthophosphoric acid were added and replaced with nitrogen. Heated to 300 ° C. After 5 hours, the distillation residue was completely dissolved in poly ε-caprolactam and reached equilibrium. While 120 parts of this polymer was kept in a molten state, it was put into a depolymerization reaction kettle for depolymerizing polymer waste generated from processing steps such as spinning and molding in the same manner as in Example 2, and processing such as spinning and molding. Depolymerization was carried out by blowing steam with polymer scraps (total 500 parts, orthophosphoric acid 2.0 parts) generated from the process. The same operation as above was repeated 5 times in total for the remaining 80 parts of the polymer. 5 times of coarse ε-
The average yield of caprolactam was 92.2%.

【００１４】比較例１ 実施例１で用いた６ナイロン重合プラントから副生する
抽出水から得られた粗ラクタムを蒸留した残渣８０部お
よび重合体屑の解重合物から得られる粗ε−カプロラク
タムをイオン交換処理した後の蒸留残渣２０部にオルト
燐酸０．５部を添加し窒素で置換した後３００℃に加熱
した。７時間後でも反応系中に１８％のオリゴマーが残
存しており、平衡には達していなかった。これに実施例
１と同様にして過熱水蒸気を吹き込み解重合を行い、生
成モノマーを流出させた。粗ε−カプロラクタムの収率
は７１％であり、平衡に達しきれなかったオリゴマーお
よび一部のモノマーは解重合残渣として反応釜中に残っ
た。Comparative Example 1 80 parts of a residue obtained by distilling a crude lactam obtained from the extraction water by-produced from the 6-nylon polymerization plant used in Example 1 and crude ε-caprolactam obtained from a depolymerized product of polymer scraps 0.5 part of orthophosphoric acid was added to 20 parts of the distillation residue after the ion exchange treatment, the atmosphere was replaced with nitrogen, and the mixture was heated to 300 ° C. Even after 7 hours, 18% of the oligomer remained in the reaction system and the equilibrium was not reached. In the same manner as in Example 1, superheated steam was blown in to carry out depolymerization, and the produced monomer was caused to flow out. The yield of crude ε-caprolactam was 71%, and the oligomer and some monomers which could not reach the equilibrium remained in the reaction vessel as depolymerization residues.

【００１５】[0015]

【発明の効果】以上かかる構成よりなる本発明方法を採
用することにより、ラクタムを高い収率で回収でき、工
程中の残渣も少ない。また抽出水からのオリゴマーを晶
析分離する必要がないため、工程が簡略化できるなど経
済的に優位である。さらに本発明で得られたラクタムモ
ノマーは不純物が少なく以後の精製も容易であので、産
業界に寄与すること大である。By adopting the method of the present invention having the above constitution, lactam can be recovered in a high yield, and the amount of residue in the process is small. Further, since it is not necessary to crystallize and separate the oligomer from the extracted water, the process can be simplified, which is economically advantageous. Further, the lactam monomer obtained in the present invention has few impurities and is easy to be purified thereafter, which greatly contributes to the industrial field.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 ６ナイロン重合プラントから副生する抽
出水および／または重合体屑の解重合物から得られる粗
ラクタムにアルカリを添加して蒸留した後の蒸留残渣よ
りラクタムを回収するに方法において、前記蒸留残渣中
のアルカリ化合物を中和または除去した後、燐酸または
その誘導体の存在下で蒸留残渣の０．５倍量以上のポリ
カプロラクタムと共に２６０℃以上に加熱し、蒸留残渣
中のラクタムおよびオリゴマーを開環重合させ、得られ
た該ポリカプロラクタムを解重合させてラクタムモノマ
ーを回収することを特徴とするラクタムの回収方法。1. A method for recovering lactam from a distillation residue obtained by adding an alkali to a crude lactam obtained from a depolymerized product of extracted water and / or polymer scrap produced as a by-product from a nylon 6 polymerization plant, and recovering the lactam from the distillation residue. After neutralizing or removing the alkaline compound in the distillation residue, the lactam and the lactam in the distillation residue are heated to 260 ° C. or more in the presence of phosphoric acid or a derivative thereof together with 0.5 times or more of the amount of the polycaprolactam of the distillation residue. A method for recovering a lactam, which comprises subjecting an oligomer to ring-opening polymerization and depolymerizing the obtained polycaprolactam to recover a lactam monomer.