JP2004353007A

JP2004353007A - Method for recovering and reusing phosphate chemical processing liquid

Info

Publication number: JP2004353007A
Application number: JP2003148962A
Authority: JP
Inventors: Noriaki Kobayashi; 典昭小林; Tomohiro Osako; 友弘大迫
Original assignee: Nihon Parkerizing Co Ltd
Current assignee: Nihon Parkerizing Co Ltd
Priority date: 2003-05-27
Filing date: 2003-05-27
Publication date: 2004-12-16
Anticipated expiration: 2023-05-27
Also published as: JP4098669B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering and reusing phosphate chemical processing liquid, in which the accumulation of unnecessary components in a chemical processing vessel is prevented and a concentrating process is smoothly performed. <P>SOLUTION: The method for recovering and reusing the phosphate chemical processing liquid comprises a phosphate chemical processing process, successively, a water-washing process for water-washing the chemical processed material, a concentrating process for concentrating the drainage water for water washing with a reverse osmosis film and a process for returning back the obtained concentrated liquid into the chemical processing vessel, wherein in the concentrating process, the concentrating processing is performed after adding zinc compound water solution into the drainage water. Further, in the above concentrating process, the chemical processing liquid in amount equivalent to carry-out amount reducing according to the reduction of the treated material amount supplied into the chemical processing vessel, is forcedly taken out from the chemical processing vessel and mixed into the drainage water, and further, the water in amount equivalent to the drainage amount reduced according to the reduction of the treated material amount is mixed, and this mixed solution is concentrated by using the reverse osmosis film. At this time, further, the zinc water solution can be mixed. The above zinc compound water solution is desirable to contain at least one kind between zinc chloride and zinc sulfate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、塗装下地及び塑性加工に工業的に広く用いられているりん酸塩化成処理工程に関するもので、詳しくはりん酸塩化成処理後の水洗排水中の有効成分を系外に排出せず、りん酸塩化成処理液として回収再利用する方法に関する。
【０００２】
【従来の技術】
電気製品、自動車ボディー、自動車パーツなどは塗装下地の前処理としてりん酸塩化成処理が行われている。この処理は、化成処理槽中でりん酸塩化成処理液を自動車ボディー、自動車パーツなどの被処理物に接液させて化成処理するりん酸塩化成処理工程と、りん酸塩化成処理された被処理物を多段の水洗槽に移行して水洗する水洗工程とで行なっている。
【０００３】
りん酸亜鉛を用いて鋼部品を処理した場合のりん酸塩化成処理反応式を（１）式、（２）式に示す。この（１）式の反応を進行させるためには（２）式のように鋼部品をりん酸にてエッチングさせる。ここでエッチングした鉄分を除去するために（３）式に示すように酸化促進剤として、一般的な表面処理ラインでは常時亜硝酸ナトリウム水溶液が添加される。亜硝酸ナトリウムは、空気酸化して硝酸イオン（（４）式）となったり、Ｆｅと反応して一部アンモニウムとなる（（５）式）。更に、亜硝酸ナトリウムからはナトリウムが生じ、化成処理液中に蓄積してくる。
３Ｚｎ（Ｈ_２ＰＯ_４）_２ → ４Ｈ_３ＰＯ_４＋Ｚｎ_３（ＰＯ_４）_２（１）
Ｆｅ＋２Ｈ_３ＰＯ_４ → Ｆｅ（Ｈ_２ＰＯ_４）_２＋Ｈ_２（２）
酸性下でＮａＮＯ_２を添加するとＨＮＯ_２とナトリウムイオンとなる。
Ｆｅ（Ｈ_２ＰＯ_４）_２＋ＨＮＯ_２ → ＦｅＰＯ_４＋ＮＯ＋Ｈ_３ＰＯ_４＋Ｈ_２Ｏ（３）
ＨＮＯ_２＋Ｏ → ＨＮＯ_３（４）
３Ｆｅ＋ＨＮＯ_２＋７Ｈ_３ＰＯ_４ → ３Ｆｅ（Ｈ_２ＰＯ_４）_２＋ＮＨ_４Ｈ_２ＰＯ_４（５）
これら不要成分（硝酸、アンモニウム、ナトリウム）が化成処理液中に蓄積すると化成処理後に、黄錆、スケが発生するなどの悪影響を及ぼす。
【０００４】
また、化成処理槽中でりん酸塩化成処理した被処理物を水洗槽に移行させて水洗するとき、被処理物には化成処理槽中の化成処理液が付着している。そのため、水洗槽から排出される水洗排水中には、有効なりん酸塩化成処理成分と上記不要成分が混在する。そこで、省資源、公害防止の観点から、水洗槽から排出される水洗排水を廃棄することなく、逆浸透膜を使用して濃縮し、濃縮液は化成処理槽に戻し、透過水は水洗槽に戻して再利用するに方法が知られている。水洗排水中に含まれる亜鉛成分などの有効成分を充分に回収し再利用するには成分阻止率の高い逆浸透膜を使用する必要がある。最近市販されている成分阻止率の高い逆浸透膜は、ＮａＣｌ阻止率が９９％以上と高い値を示しており、このような逆浸透膜を使用した場合、有効成分の回収には有利であるが、反面不要成分も濃縮されて化成処理槽へ戻るため、化成処理槽中に上記の不要成分が蓄積していき悪影響を及ぼす問題点がある。そのため、不要成分透過性の高い逆浸透膜を使用する方法が提案されている（特許文献１、特許文献２）が、これには最近市販されている逆浸透膜が使用できない不便がある。また、逆浸透膜の耐用ｐＨ及び処理液の沈殿性を考慮して、水洗槽から排出される水洗排水に酸を添加しｐＨ制御して逆浸透膜に供給する手法があるが（特許文献３）、不要成分の阻止性には変化がない。
【０００５】
また、化成処理槽中では常に促進剤の分解によって不要成分が発生している。しかも、化成処理槽へは皮膜として析出した成分やスラッジとして沈殿した成分及び被処理物に付着して持ち出された成分を化成処理槽補給剤として化成処理槽へ供給し、化成処理槽の濃度を一定に保持しているが、この補給剤には液安定性を保持するために硝酸が添加され、このような成分も不要成分として化成浴中に蓄積していく。このようにして発生した不要成分は、被処理物に付着して次工程の水洗工程に持ち出されている。そのため、化成処理槽から水洗槽に持ち出される不要成分の量は、ラインの被処理物の処理量（生産量）に左右される。したがって、化成処理槽中の不要成分濃度はラインの被処理物の処理量（生産量）に左右される。設計時より生産量が低くなったラインでは化成処理槽中の不要成分の濃度が高くなる不都合があり、市販の逆浸透膜を使用して化成処理液を回収再利用する場合、通常のライン以上に不要成分が蓄積し、化成処理に悪影響を及ぼす。
【０００６】
【特許文献１】
特開昭５２−１２７４４４号公報
【特許文献２】
特公昭５９−１０４３０号公報
【特許文献３】
特開２００１−１６４３８９号公報
【０００７】
【発明が解決しようとする課題】
本発明は、上記の事情に鑑みなされたもので、化成処理槽中で被処理物を化成処理するりん酸塩化成処理工程と、りん酸塩化成処理された被処理物を水洗する水洗工程と、水洗槽から排出する水洗排水を逆浸透膜を使用して濃縮する濃縮工程と、濃縮工程で得られた濃縮液を化成処理槽に戻す工程とからなるりん酸塩化成処理液の回収再利用方法において、化成処理槽中の不要成分の蓄積を防ぎ、且つ濃縮工程を円滑に行う方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
すなわち、本発明は、化成処理槽中でりん酸塩化成処理液を被処理物に接液させて化成処理するりん酸塩化成処理工程と、りん酸塩化成処理された被処理物を多段の水洗槽を通して水洗する水洗工程と、水洗槽から排出する水洗排水を逆浸透膜を使用して濃縮する濃縮工程と、濃縮工程で得られた濃縮液を化成処理槽に戻す工程とからなるりん酸塩化成処理液の回収再利用方法おける上記の濃縮工程において、水洗槽から排出した水洗排水に亜鉛化合物水溶液を添加してから逆浸透膜で濃縮することを特徴とするりん酸塩化成処理液の回収再利用方法である。上記の亜鉛化合物水溶液は、硝酸亜鉛、塩化亜鉛及び硫酸亜鉛のうち少なくとも１種を含有するものが好ましい。
【０００９】
また、本発明は、化成処理槽中でりん酸塩化成処理液を被処理物に接液させて化成処理するりん酸塩化成処理工程と、りん酸塩化成処理された被処理物を多段の水洗槽を通して水洗する水洗工程と、水洗槽から排出する水洗排水を逆浸透膜を使用して濃縮する濃縮工程と、濃縮工程で得られた濃縮液を化成処理槽に戻す工程とからなるりん酸塩化成処理液の回収再利用方法における上記の濃縮工程において、前記水洗槽から排出する水洗排水に、（１）化成処理槽中に供給する被処理物の処理量の減少に応じて減少する持ち出し量（持ち出し量とは、被処理物に付着して水洗槽に移行するりん酸塩化成処理液の量をいう）のりん酸塩化成処理液を化成処理槽から強制的に抜き出して混合し、更に（２）被処理物の処理量の減少に応じて減少させた水洗水量分の水を混合し、この混合液を逆浸透膜を使用して濃縮することを特徴とするりん酸塩化成処理液の回収再利用方法である。このとき水洗排水に、更に（３）亜鉛水溶液を混合してもよい。
【００１０】
【発明の実施の形態】
本発明は、冷延鋼板、亜鉛メッキ鋼板等の鉄系材料或はアルミニウム系材料などを素材とした電気製品、自動車ボデー、自動車パーツ、建材などのりん酸塩化成処理に適用できる。また、使用するりん酸塩化成処理液としては、リン酸亜鉛系の他、りん酸亜鉛カルシウム系の化成処理液など従来既知の処理剤が挙げられる。中でも、りん酸亜鉛系化成処理液は、耐食性や塗装密着性が良好な皮膜を形成することから、自動車ボディーライン、建材ライン、電機部品ライン等において好ましく使用される。このりん酸亜鉛系化成処理液は、りん酸及び亜鉛を主成分とし、副成分としてニッケル、マンガンなどの重金属やフッ素、硝酸等を含んでもよい。更に亜硝酸等の促進剤となる酸化剤を含有してもよい。
【００１１】
図１は、本発明（請求項１発明）のりん酸塩化成処理液の回収再利用方法の一例を示した工程図である。１は化成処理槽である。２は第１水洗槽、３は第２水洗槽、４は第３水洗槽、５は脱イオン水洗槽である。６は脱イオン水給水管、７は水洗排水管である。電気製品、自動車ボデー、自動車パーツなどの被処理物は脱脂、表面調整後、化成処理槽１でりん酸塩化成処理される。化成処理された被処理物は化成処理液を付着した状態で水洗槽に移行され、水洗槽で被処理物に付着した化成処理液が除去される。水洗はディップ又はスプレーによる接液で行われる。この化成処理液を除去するための水洗工程は、第１水洗槽２、第２水洗槽３、第３水洗槽４で順次水洗され、最後に脱イオン水洗槽５で水洗する。水洗水は給水管６及び透過水配管１２より脱イオン水洗槽５に給水され、その水は順次各水洗槽をオーバーフローし、最終的に第１水洗槽２から水洗排水として水洗排水管７を通して排出される。この排出された水洗排水は、化成処理液の１／５〜１／５０の濃度である。
【００１２】
本発明では、最終的に水洗排水管７より排出される水洗排水をそのまま逆浸透膜を備えた濃縮装置に供給することなく、この水洗排水に亜鉛化合物水溶液を添加配合した後に濃縮装置に供給する。図１において、８は亜鉛化合物水溶液供給管、９は混合槽、１０は逆浸透膜を備えた濃縮装置である。第１水洗槽２より排水された水洗排水は水洗排水管７から混合槽９に送られ、ここで亜鉛化合物水溶液供給管８から供給する亜鉛化合物水溶液と混合され、次いで濃縮装置１０に送られる。濃縮装置１０の逆浸透膜で濃縮された濃縮液は適宜調整して濃縮液配管１１を通して化成処理槽１に戻し化成処理に再利用する。また逆浸透膜を透過した透過水は、透過水配管１２を通して脱イオン水洗槽５に戻して再利用する。この透過水は、電気伝導度の低い清浄な水であるので、そのまま水洗水として、あるいは更に高度処理を施して脱イオン水洗工程の脱イオン水として利用することができる。ここで高度処理とは、逆浸透膜による分離処理やイオン交換樹脂による吸着処理などを言う。
【００１３】
上記の亜鉛化合物水溶液としては、硝酸亜鉛、塩化亜鉛及び硫酸亜鉛のうちの少なくとも１種を含有する水溶液を用いるのが好ましい。特に好ましくは硝酸亜鉛である。これらの亜鉛化合物水溶液は液の安定性を高めるため酸性水溶液の状態で用いるのが好ましい。亜鉛化合物水溶液の使用可能なｐＨ範囲は、ｐＨ０〜７、好ましくはｐＨ１〜３である。例えば、硝酸亜鉛水溶液には液の安定性を高めるため少量の硝酸を添加するのが好ましい。また、酸化亜鉛なども酸性水溶液に溶解して用いることができる。亜鉛化合物水溶液を酸性にすることによって、後述する効果も生じる。
【００１４】
本発明では、水洗排水を濃縮するとき、水洗排水に亜鉛化合物水溶液を添加する。この亜鉛化合物水溶液を添加することによって、水洗排水中の不要成分の一つであるナトリウムイオンの逆浸透膜での阻止率を低下させる、すなわちナトリウムイオンを透過させ易くすることができる。例えば硝酸亜鉛を添加することによって、硝酸亜鉛が水洗排水中の成分と、２ＮａＨ_２ＰＯ_４＋Ｚｎ（ＮＯ_３）_２ → Ｚｎ（Ｈ_２ＰＯ_４）_２＋２ＮａＮＯ_３の反応を生じ、ここで生成したＮａＮＯ_３は逆浸透膜を透過しやすい。そして、このＮａＮＯ_３を透過させることによって、濃縮液中の不要成分であるナトリウム及び硝酸等の不要な酸を減少できるので、化成処理槽中の不要成分の蓄積を防ぐことができる。透過水中のナトリウムや硝酸等の不要成分は、前記した逆浸透膜による分離処理やイオン交換樹脂による吸着処理などで除去され系外に排出される。この透過水は水洗水として再利用できる。添加する亜鉛化合物水溶液の濃度は任意でよいが、亜鉛化合物の水洗排水への添加量は水洗排水に対してＺｎ濃度として１〜５００ｍｇ／Ｌ好ましくは５〜１００ｍｇ／Ｌである。
【００１５】
また、従来、化成処理槽には、化成処理で消費された成分、すなわち被処理物に付着して水洗槽に持ち出された化成処理液成分、被処理物の表面に皮膜として析出した成分及びスラッジとして沈殿した成分を、化成処理槽液給剤として供給して補っている。本発明の回収再利用方法を適用した場合、被処理物に付着して水洗槽に持ち出された化成処理液成分は濃縮して化成処理槽へ回収されるが、皮膜析出成分及びスラッジ成分は補給する必要がある。ここで、皮膜析出成分及びスラッジ成分はりん酸及び亜鉛が主成分であり、これらの成分を含む化成処理槽補給剤では、その液安定性を高めるため硝酸等の過剰の酸を添加する必要がある。本発明においては、水洗排水を濃縮するとき、水洗排水に亜鉛化合物水溶液を添加することによって、再利用する濃縮液中に亜鉛が存在するので、化成処理槽補給剤中の亜鉛を減少させることができ、これに伴って該補給剤中の硝酸を大幅に減少させることができる。その結果として、不要成分の一つである硝酸イオンの化成処理槽中ひいては系中での蓄積を抑制することができる。
【００１６】
更に、酸を添加して安定化した亜鉛化合物水溶液を用いるときは、該水溶液はｐＨが低くなっている。そのため、この亜鉛化合物水溶液を、水洗排水を濃縮するとき水洗排水に添加することによって、逆浸透膜の手前での水洗排水のｐＨ上昇を抑制することができる。このｐＨ上昇を抑制することによって、逆浸透膜の手前での沈殿を防いで、運転性に悪影響が及ぶのを防ぐことができる。亜鉛化合物水溶液を添加して、水洗排水のｐＨを１〜４、特に２〜３．５に調整するのが好ましい。
【００１７】
次に、本発明の請求項３に係る発明について説明する。特に、水洗排水を回収再利用するりん酸塩化成処理ラインにおいては、化成処理槽中のりん酸塩化成処理成分及び不要成分の量、また水洗槽に供給する水量、更には水洗排水の濃縮条件が事前に設計されており、その設計とおりに実施できるように管理されている。例えば、化成処理槽中のりん酸塩化成処理成分は消耗に応じて補充されている。ところで、被処理物例えば自動車ボディーのラインへの供給量が設計時より減少することがしばしば生じる。この被処理物の供給量が減少すると、被処理物に付着して化成処理槽から水洗槽に持ち出される化成処理液の量（持ち出し量）が減少する。化成処理液には不要成分も含まれており、その持出し量が減少することによって、化成処理槽中には不要成分が徐々に蓄積される不都合が生じる。
【００１８】
そこで、本発明の請求項３に係る発明は、化成処理槽から強制的に化成処理液を抜き出すことによってこの不都合をなくしたものである。更に、被処理物の供給量が減少すると、時間あたりに供給する水洗水の水量（給水量）も減少していき、不要成分が系外に出される排出される量（不要成分が逆浸透膜を透過する量）も減少する。本発明の請求項３に係る発明は、設計時と比較して不足した水洗水量分の水を、濃縮工程前に水洗排水に加えることによって、不要成分が透過側に抜ける量を設計とおりにし、化成処理槽中の不要成分の量を設計とおりにするものである。更に、本発明の請求項３に係る発明では、強制的に抜き出した化成処理液中の有効成分も水洗排水中の有効成分と一緒に濃縮され、濃縮液として化成処理槽に戻すことができる。
【００１９】
図２は、請求項３に係る発明のりん酸塩化成処理液の回収再利用方法の一例を示した工程図である。図２において、２１は化成処理槽である。２２は第１水洗槽、２３は第２水洗槽、２４は第３水洗槽、２５は脱イオン水洗槽である。６は脱イオン水給水管、７は水洗排水管である。電気製品、自動車ボデー、自動車パーツなどの被処理物は脱脂、表面調整後、化成処理槽２１でりん酸塩化成処理される。化成処理された被処理物は化成処理液を付着した状態で水洗槽に移行され、水洗槽で化成処理液が除去される。この化成処理液を除去するための水洗工程は、第１水洗槽２２、第２水洗槽２３、第３水洗槽２４で順次水洗され、最後に脱イオン水洗槽２５で水洗する。水洗水は給水管２６及び透過水配管３４より脱イオン水洗槽２５に脱イオン水が給水され、その水は順次各水洗槽をオーバーフローし、最終的に第１水洗槽２２から水洗排水として水洗排水管２７を通して排出される。一般的に、脱イオン水洗工程では被処理物を検知し、一定量スプレーするシステムとなっている。したがって、水洗水量は被処理物の流れる量すなわち生産量によって随時変化する。
【００２０】
排水管２７から排出した水洗排水は混合槽３１に送られる。一方、りん酸塩化成処理ラインの被処理物の処理量（生産量）が設計時より減少したとき、その処理量の減少に応じて減少する持ち出し量（被処理物に付着して水洗槽に移行するりん酸塩化成処理液の量）２８を、化成処理槽２１からポンプ又は自動弁等を利用して、強制的に抜き出す（すなわち、処理量（生産量）が減少したときに処理物に付着して持ち出される液量と強制的に抜き出す液量の和を、設計時の処理物に付着して持ち出される液量と等しくする）。この抜き出した化成処理液を混合槽３１に送る。また、りん酸塩化成処理ラインの被処理物の処理量（生産量）が設計時より減少したときには、それに応じて水洗水の水量も減少するが、その減少させた水洗水量を給水管２９より混合槽３１に入れ混合する。なお、減少させた水洗水量の給水（給水管２９の位置）は、濃縮装置３３へ供給する前であればいつでもよい。
【００２１】
次いで、この混合液を必要に応じて通常の濾過器３２で濾過して塵埃を除去した後、逆浸透膜を備えた濃縮装置３３に供給する。濾過器３２を設けることによって逆浸透膜の負担を軽減できる。濃縮装置３３の逆浸透膜で濃縮された濃縮液は適宜調整して濃縮液配管３４を通して化成処理槽２１に戻し化成処理に再利用する。また逆浸透膜を透過した透過水はそのまま或は適宜処理後に透過水配管３５を通して水洗槽２５に戻して水洗水として再利用する。更に、上記の三者混合のとき、混合槽３１に亜鉛化合物水溶液３０を添加して、上記した不要成分の蓄積を防いでもよい。
【００２２】
本発明では、給水量を一定とした場合、生産量が低下して水洗水の希釈倍率が上昇し、化成液相当まで濃縮するには濃縮水と透過水の液量比を変えなければいけないところを、強制的に化成処理槽中の化成処理液を抜き出し、実際の持ち出し液量と上記抜き出し量の和が設計時の持ち出し液量となるようにし、混合槽３１の希釈倍率を一定にする。送液する化成処理液量は生産量によって随時変化するので、混合槽中に電気伝導度計を設置し排出ポンプや自動弁を制御するか、定期的に遊離酸度及び全酸度を測定又は成分濃度を測定して排出ポンプの流量や自動弁を調整する方法等がある。なお、処理液の遊離酸度は処理液を１０ｍＬ採取し、ブロムフェノールブルーを指示薬として、０．１Ｎ苛性ソーダで滴定することにより求める。処理液の全酸度は処理液を１０ｍＬ採取し、フェノールフタレインを指示薬として、０．１Ｎ苛性ソーダで滴定することにより求める。この場合は、生産量によらず濃縮装置３３に送液される液量及び濃度はほぼ一定となるので、常に安定した透過性能、分離性能が得られる。
【００２３】
りん酸塩化成処理工程の一つである自動車ボディーラインを例に挙げて、更にこの容量収支について具体的に説明する。例えば、自動車ラインにおける持ち出し液量は生産量により変化し、設計時（高生産量時）の持ち出し量が３００Ｌ／ｈｒ程度で、生産量が半分に低下した場合（低生産量時）の持ち出し量は１５０Ｌ／ｈｒと仮定する。本発明では、低生産量時は高生産量時の持ち出し量と等しくなるよう排出ポンプ等で強制的に１５０Ｌ／ｈｒを抜き出す。また、通常のラインでは生産量が半分に低下した場合は、水洗水の給水量も減少し２８５０Ｌ／ｈｒとなるが、本発明では減少分の２８５０Ｌ／ｈｒ給水し、合計５７００Ｌ／ｈｒ給水する。本発明では上記のようなシステムを適用することによって、生産量の変動によらず常に６０００Ｌ／ｈｒ、化成処理液の２０倍希釈相当の液を分離処理することとなる。かつ、化成処理槽での不要成分濃度は設計通りの状態での運転が可能である。
【００２４】
この方法によると、化成処理槽から、化成処理槽中に供給する被処理物の処理量の減少に応じて減少する持ち出し量（被処理物に付着して水洗槽に移行するりん酸塩化成処理液の量）を強制的に抜き出すとき、化成処理槽中の不要成分も一緒に抜き出されるから、化成処理槽中に不要成分が蓄積するのを防ぐことができる。また、水洗槽から排出する水洗排水に、（１）化成処理槽から強制的に抜き出した化成処理液と、（２）被処理物の処理量の減少に応じて減少させた水洗水量分の水とを混合した混合液は、設計時の水洗排水とほぼ同じ組成及び液量になるから、濃縮条件を設計時と変えることなく濃縮処理を行うことができ、設計時と同じ組成及び量の濃縮液及び透過水を得ることができる。したがって、本発明方法によれば、たとえ生産量が減少した場合でも、不要成分の蓄積を設計時の値と同じにすることができる。
【００２５】
【実施例】
以下に、参考例、実施例、比較例を挙げて本発明を具体的に説明するが、本発明はこれら実施例に限定されるものではない。
【００２６】
参考例
りん酸亜鉛化成処理液中の硝酸の濃度が、りん酸塩皮膜の特性に及ぼす影響を調べるために、次の実験をした。
表面調整剤としてプレパレンＺＮ（登録商標：日本パーカライジング（株）製表面調整剤）を１ｇ／Ｌ濃度に水道水で希釈したものを使用し、また、リン酸亜鉛処理液としてパルボンドＷＬ３５（登録商標：日本パーカライジング（株）製りん酸亜鉛化成処理液）を４．８％に水道水で希釈し、Ｚｎ：１．８ｇ／Ｌ、Ｎｉ：１ｇ／Ｌ、Ｍｎ：０．５ｇ／Ｌ、ＰＯ４：１４ｇ／Ｌ、Ｆ：１ｇ／Ｌ、Ｓｉ：０．３ｇ／Ｌに調製しものを使用して、下記の処理工程でＳＰＣ鋼板（冷延鋼板）及びアルミ材（Ａ１１００材）を化成処理した。そして、化成処理液中の硝酸イオン濃度を変化させて化成処理し、得られた各濃度におけるりん酸塩皮膜について下記の評価を行なった。その結果を、表１、表２に示す。表１はＳＰＣ鋼板（冷延鋼板）、表２はアルミ材（Ａ１１００材）についての評価結果である。
【００２７】
〔処理工程〕
（１）アルカリ脱脂：４２℃、１２０秒スプレー
（２）水洗：室温、３０秒スプレー
（３）表面調整：室温、２０秒浸漬
（４）リン酸亜鉛処理：３５℃、１２０秒スプレー
（５）水洗：室温、３０秒スプレー
（６）脱イオン水洗：室温、３０秒スプレー
【００２８】
〔りん酸塩皮膜の評価方法〕
（１）外観
目視観察により、リン酸亜鉛皮膜のスケ、ムラの有無を確認した。評価は以下の通りとした。
○ 均一良好な外観
△ ムラ、スケあり
× スケ多し
【００２９】
（２）皮膜重量
化成処理後の処理板の重量を測定し、次いで化成処理板に下記に示す剥離液、剥離条件にて皮膜剥離処理を施し、その重量を測定し、剥離前後の重量差から単位面積当たりの皮膜重量を算出した。
剥離液：５％クロム酸水溶液
剥離条件：７５℃、１５分、浸漬剥離
【００３０】
【表１】

【００３１】
【表２】

【００３２】
表１、表２からわかるように、ＳＰＣ鋼板については硝酸濃度が２０ｇ／Ｌ以下の時は良好なりん酸塩皮膜が得られるが、３０ｇ／Ｌを越えると一部ムラ・スケが発生し、良好なりん酸塩皮膜が得られなくなっている。また、アルミ材についても２０ｇ／Ｌ以下の時は良好なりん酸塩皮膜が得られるが、３０ｇ／Ｌを越えるとスケが多く、良好なりん酸塩皮膜が得られなくなっている。したがって、各種材料で良好なりん酸塩皮膜を形成させるには硝酸イオン濃度を２０ｇ／Ｌ以下に保つことが好ましい。
【００３３】
実施例１
参考例に示す処理条件において、更に皮膜やスラッジとして消費される成分を補給しながらＳＰＣ鋼板（７０×１５０ｍｍ）の化成処理を行った。実験条件は以下のとおりである。
化成処理槽容量：５Ｌ
１台当り化成処理液持ち出し量：２ｍＬ／枚
処理タクト：５枚／ｈｒ
時間当たり持ち出し液量：１０ｍＬ／ｈｒ
促進剤：４．５ポイントとなるように常時補給
更に、化成処理液濃度及び液量が一定となるように各種成分を補給した。
なお、促進剤濃度は、キューネ管に類似の器具（通称：サッカロメーター）に５０ｍＬのサンプルを入れた後に、Ｇ２０５（登録商標、日本パーカライジング（株）製）を５ｇ添加し、発生したガス量を測定し、発生ガス量１ｍＬにつき１ポイントとした。
【００３４】
ＳＰＣ鋼板を化成処理槽中で上記の条件のもとで２５００枚化成処理した。このとき、化成処理液の化成処理槽中から持ち出れる液量の合計は５Ｌ（２５００枚×２ｍＬ）である。この持ち出し液５Ｌを水道水９５Ｌで希釈して、模擬水洗排水とした。この模擬水洗排水（化成処理液の２０倍希釈相当）に対して硝酸亜鉛水溶液を亜鉛濃度で５ｍｇ／Ｌ添加した。次いでこの硝酸亜鉛水溶液を添加した模擬水洗排水を化成処理液相当まで濃縮運転実験を行った。濃縮実験には、逆浸透膜であるＳＵＬＧ１０膜（東レ株式会社製、ＮａＣｌ阻止率：９９．５％）を濃縮分離膜として利用し、処理温度２５℃、圧力１．５ＭＰａ、濃縮液循環流量を１２〜１４Ｌ／分、ｐＨ２〜３．５で行った。得られた濃縮液（５Ｌ）及び透過液（９５Ｌ）のイオン濃度を表３に示す。
【００３５】
更に、この濃縮液５Ｌは化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。このような工程を繰り返すことにより不要成分であるナトリウム及び硝酸イオン濃度は蓄積していく。４ターンオーバー後の化成処理槽の化成処理液中の不要成分濃度を表３に示した。表３から、実施例１では、化成処理槽の硝酸イオン濃度は２２．７ｇ／Ｌとなるので、参考例の結果よりみて、材料によっては良好なりん酸塩皮膜が得られないことがわかる。
【００３６】
【表３】

【００３７】
実施例２
実施例１と同様な処理を行った。但し、模擬水洗水に対して硝酸亜鉛水溶液を亜鉛濃度で５０ｍｇ／Ｌ添加して、実施例１と同様な濃縮実験を行った。得られた濃縮液（５Ｌ）及び透過液（９５Ｌ）のイオン濃度を表４に示す。更に、この回収液５Ｌは化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の化成処理液中の不要成分濃度を表４に示した。この表４から、実施例２では、不要成分である硝酸イオンの蓄積濃度は１９．４ｇ／Ｌまで減少し、参考例の結果よりみて、材料によらず、良好なりん酸塩皮膜が得られる。
【００３８】
【表４】

【００３９】
比較例１
実施例１と同様な処理を行った。但し、模擬水洗排水に対して硝酸亜鉛水溶液を添加することなく、実施例１と同様な濃縮実験を行った。得られた濃縮液（５Ｌ）及び透過液（９５Ｌ）のイオン濃度を表５に示す。更に、この回収液５Ｌは化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の化成処理液中の不要成分濃度を表５に示した。表５から、この比較例１では、化成処理槽の硝酸イオン濃度は３０ｇ／Ｌまで蓄積するので、参考例の結果よりみて、良好なりん酸塩皮膜が得られないことがわかる。
【００４０】
【表５】

【００４１】
実施例３
実施例２の設計条件で実施するとき、その生産量を設計時の５０％に低下させた。すなわち、被処理物の処理タクトを５枚／ｈｒの５０％の２．５枚／ｈｒにした。この生産量低下で被処理物に付着して持ち出される化成処理液量も１０ｍＬ／ｈｒ５０％、すなわち５ｍＬ／ｈｒになった。
【００４２】
本実施例では、化成処理槽から化成処理液を５ｍＬ／ｈｒの流量で強制的に抜き出して混合槽に流入させた。この混合槽に模擬水洗排水を流入させ、更に混合液の化成処理液濃度がその２０倍希釈相当の濃度になる量の水を流入させた。すなわち、混合槽中の混合液が設計時の水洗排水の組成及び液量と同等になるようにした。更に、混合槽に硝酸亜鉛水溶液を亜鉛濃度で５０ｍｇ／Ｌ添加した。このようにして調製した混合液を、実施例１と同様な濃縮実験を行った。得られた濃縮液は化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽中の不要成分濃度は、硝酸イオン濃度が１９．４ｇ／Ｌ、ナトリウム濃度が８．２ｇ／Ｌであった。この実施例では、化成処理槽の硝酸イオン濃度は１９．４ｇ／Ｌまで減少するので、参考例の結果よりみて、材料によらず良好なりん酸塩皮膜が得られることがわかる。
【００４３】
この方法によれば、生産量の低下によって被処理物に付着して化成処理槽中から持ち出される不要成分の量が減少しても、その分が化成処理槽中から強制的に抜き出するため、不要成分である硝酸イオン、ナトリウムの化成処理槽中の蓄積量が少なく、また生産量を設計時の５０％に低下させても、濃縮工程を設計時と同じ条件でそのまま遂行できる。
【００４４】
比較例２
実施例２の設計条件で実施するとき、その生産量を設計時の５０％に低下させた。すなわち、被処理物の処理タクトを５枚／ｈｒの５０％の２．５枚／ｈｒにした。この生産量低下で被処理物に付着して持ち出される化成処理液量も１０ｍＬ／ｈｒ５０％、すなわち５ｍＬ／ｈｒになった。この条件のもとで実施例２と同様な濃縮実験を行った。得られた濃縮液は化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽中の不要成分濃度は、硝酸イオン濃度が４５．４ｇ／Ｌ、ナトリウム濃度が１７．８ｇ／Ｌであった。この方法では、生産量の低下によって被処理物に付着して化成処理槽中から持ち出される不要成分の量が減少するため、不要成分である硝酸イオン、ナトリウムの蓄積量が多くなっている。実施例３と比較すると、不要成分である硝酸イオンが４５ｇ／Ｌまで蓄積し、参考例の結果よりみて、良好なりん酸塩皮膜が得られないことがわかる。
【００４５】
比較例３
（１）実施例１の被処理物の処理タクトを６枚／ｈｒに増加する（時間当りの持出し量も１２ｍＬ／ｈｒに増加する）以外は、実施例１の条件にしたがって、ＳＰＣ鋼板を化成処理槽中で３０００枚化成処理した。この時に化成処理槽から持ち出される化成処理液の合計量は６Ｌ（３０００枚×２ｍＬ）である。その持ち出し液６Ｌを水道水１１４Ｌで希釈して模擬水洗排水（化成処理液の２０倍希釈相当）とした。この模擬水洗排水に対して硝酸亜鉛を添加することなく、実施例１と同様に化成液相当までの濃縮実験を行った。実験の結果濃縮液（６Ｌ）及び透過水（１１４Ｌ）得られ、得られた濃縮液は化成処理槽に戻し、全酸度、有利酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の化成処理液中の不要成分濃度は、硝酸イオン濃度が１９．２ｇ／Ｌ、ナトリウム濃度が８．１ｇ／Ｌであった。この例では化成処理槽の硝酸イオン濃度が１９．２ｇ／Ｌとなるので、参考例の結果よりみて、材料によらず良好なリン酸塩皮膜が得られることがわかる。
【００４６】
（２）ところが、上記（１）例において、被処理物の数量が減少すると、不要成分化成処理液中の濃度が高くなり、良好なリン酸塩皮膜が得られなくなる。その例を以下に示す。
すなわち、上記（１）例の設計条件で実施するとき、その生産量（処理タクト）を５０％に低下させ、処理タクト３枚／ｈｒにし時間当りの持出し量を６ｍＬ／ｈｒにした。この生産量を低下させた条件のもとで、実施例１の条件にしたがって、ＳＰＣ鋼板を化成処理槽中で１５００枚化成処理した。この時に化成処理槽から持ち出される化成処理液の合計量は３Ｌ（１５００枚×２ｍＬ）である。その持ち出し液３Ｌを水道水５７Ｌで希釈して模擬水洗排水（化成処理液の２０倍希釈相当）とした。この模擬水洗排水に対して、上記（１）例と同様の濃縮実験を行い、化成処理液相当まで濃縮した。得られた濃縮液３Ｌは化成処理槽に戻し、全酸度、遊離酸度および各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の化成処理液中の不要成分濃度は、硝酸イオン濃度が４１．３ｇ／Ｌ、ナトリウム濃度が１６．３ｇ／Ｌであった。
【００４７】
この方法では、生産量の低下によって被処理物に付着して化成処理槽から持ち出される不要成分の量が減少し、更に、水洗水量が減少した分透過する不要成分の量も少なくなるため、不要成分でなる硝酸イオン、ナトリウムイオンの蓄積量が多くなっている。この硝酸イオン濃度では、参考例の結果よりみて、良好なりん酸塩皮膜が得られないことがわかる。
【００４８】
実施例３
比較例３の（２）例の条件で実施した。但し、持ち出し液３Ｌを水道水５７Ｌで希釈した模擬水洗排水６０Ｌ（化成処理液の２０倍希釈相当）をそのまま濃縮実験に掛けることなく、この模擬水洗排水６０Ｌを混合槽に入れ、▲１▼ 化成処理槽から強制的に抜き出した化成処理液３Ｌ（比較例３の（１）例について、その（２）例にように５０％生産量低下した時に減少する持出し量＝６Ｌ−３Ｌ＝３Ｌ）、及び ▲２▼ 混合槽中の化成処理液の濃度を２０倍稀釈濃度にする量の水量（すなわち、生産量の減少に伴って減少する水洗水量）５７Ｌを混合槽に入れて混合してから、比較例３の（２）例と同様の濃縮実験を行い、化成処理液相当まで濃縮した。得られた濃縮液６Ｌは化成処理槽に戻し、全酸度、遊離酸度及び各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の不要成分濃度は、硝酸イオン濃度が１９．１ｇ／Ｌ、ナトリウム濃度が８．０ｇ／Ｌであった。参考例の結果よりみて、良好なリン酸塩皮膜が得られることがわかる。
【００４９】
この方法によれば、生産量の低下によって被処理物に付着して化成処理槽中から持ち出される不要成分の量が減少しても、その減少分を化成処理槽から強制的に抜き出すため、化成処理槽から排出される不要成分の量は比較例３の（１）例と同じ値となる。さらに、化成処理液の持ち出し分と抜き出し分を２０倍希釈となるように給水をすることによって、不要成分が透過側に抜ける量も比較例３の（１）例と同じ量になる。その結果、生産量が設計時の５０％に低下させても、濃縮工程を設計時と同じ条件でそのまま遂行できる。
【００５０】
比較例４
比較例３の（２）例の条件で実施した。但し、持ち出し液３Ｌを水道水５７Ｌで希釈した模擬水洗排水６０Ｌ（化成処理液の２０倍希釈相当）をそのまま濃縮実験に掛けることなく、この模擬水洗排水６０Ｌを混合槽に入れ、更に混合槽に化成処理槽から強制的に抜き出した化成処理液３Ｌ〔比較例３の（１）例において、その（２）例にように５０％生産量低下した時に減少する持出し量＝６Ｌ−３Ｌ＝３Ｌ〕を入れて混合してから、この混合液を比較例３の（２）例と同様の濃縮実験を行い、化成処理液相当まで濃縮した。得られた濃縮液６Ｌは化成処理槽に戻し、全酸度、遊離酸度および各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の不要成分濃度は、硝酸イオン濃度が３１．３ｇ／Ｌ、ナトリウム濃度が１２．６ｇ／Ｌであった。
【００５１】
この方法では、生産量の低下に伴って被処理物に付着して化成処理槽から持ち出される不要成分の量が減少するが、その減少分を化成処理槽から強制的に抜き出すので、化成処理槽から排出される不要成分の量は変わらない。しかし、生産量の減少に伴って減少する水洗水量の減少分は混合槽に補充されない。そのため、濃縮工程にかける液の量が少なくなって濃縮効率が悪くなり、逆浸透膜を透過する不要成分の量が少なくなり、従って不要成分である硝酸イオン、ナトリウムイオンの蓄積量が多くなっている。不要成分である硝酸イオンが３１．３ｇ／Ｌまで蓄積し、参考例の結果よりみて、良好なりん酸塩皮膜が得られないことがわかる。
【００５２】
比較例５
比較例３の（２）例の条件で実施した。但し、比較例３の（２）例では持ち出し液３Ｌを水道水５７Ｌで希釈して模擬水洗排水６０Ｌ（化成処理液の２０倍希釈相当）を調製しているが、本比較例では持ち出し液３Ｌを水道水１１４Ｌで希釈して模擬水洗排水１１７Ｌ（化成処理液の４０倍希釈相当）を調製した。この模擬水洗排水に対して比較例３の（２）例と同様の濃縮実験を行い、化成処理液相当まで濃縮した。得られた濃縮液３Ｌは化成処理槽に戻し、全酸度、遊離酸度および各成分濃度を調整した。この工程を１ターンオーバーとして、計４ターンオーバー実施した。４ターンオーバー後の化成処理槽の不要成分濃度は、硝酸イオン濃度が２８．９ｇ／Ｌ、ナトリウム濃度が１１．７ｇ／Ｌであった。
【００５３】
この方法では、比較例３の（２）例と同じく、生産量の低下に伴い被処理物に付着して化成処理槽から持ち出される不要成分の量が減少するので、化成処理液中の不要成分の蓄積を防ぐことができない。化成処理槽からの持出し液を、比較例３の（２）例の倍に希釈してから濃縮しても、不要成分である硝酸イオン、ナトリウムイオンの蓄積を防ぐことはできなく、その結果、不要成分である硝酸イオンが２８．９ｇ／Ｌまで蓄積し、参考例の結果よりみて、良好なりん酸塩皮膜が得られないことがわかる。
【００５４】
【発明の効果】
従来、りん酸塩化成処理工程で排出される水洗排水を再利用することが知られているが、化成処理液中に不要成分が蓄積するためその実施は困難であった。本発明によれば、化成処理剤中の不要成分の蓄積を少なくすることができ、効率良く再利用できる。そのため、化成処理液成分を回収し再利用することで、りん酸塩化成処理工程の廃棄物の最少化を可能とすることができる。また、りん酸塩化成処理工程ラインで、その処理量（生産量）が変動しても、常に同条件でりん酸塩化成処理液の成分回収再利用が可能である。
【図面の簡単な説明】
【図１】本発明の処理工程の一例を示した工程図
【図２】本発明の処理工程の一例を示した工程図
【符号の説明】
１，２１化成処理槽、２，２２第１水洗槽、３，２３第２水洗槽、
４，２４第３水洗槽、５，２５脱イオン水洗槽、６，２６給水管、
７，２７水洗排水管、８，３０亜鉛化合物水溶液供給管、
９，３１混合槽、１０，３３濃縮装置、１１，３４濃縮水配管
１２，３５透過水配管２８化成処理液抜き出し管、２９給水管、
３２濾過器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a phosphate chemical conversion treatment step which is widely used industrially for coating undercoating and plastic working.More specifically, the present invention relates to a method in which active components in washing wastewater after phosphate chemical treatment are not discharged out of the system. And a method of recovering and reusing as a phosphate chemical conversion treatment liquid.
[0002]
[Prior art]
BACKGROUND ART Phosphate conversion treatment is performed on electrical products, automobile bodies, automobile parts, and the like as a pretreatment of a paint base. This treatment includes a phosphate chemical conversion treatment step in which a phosphate chemical conversion treatment liquid is brought into contact with an object to be treated such as an automobile body and an automobile part in a chemical conversion treatment tank to form a chemical conversion treatment. The process is carried out in a washing step in which the processed material is transferred to a multi-stage washing tank and washed.
[0003]
Formulas (1) and (2) show the phosphate conversion treatment reaction formula when steel parts are treated with zinc phosphate. In order to make the reaction of the equation (1) proceed, the steel part is etched with phosphoric acid as in the equation (2). Here, in order to remove the etched iron content, an aqueous sodium nitrite solution is constantly added as an oxidation accelerator in a general surface treatment line as shown in the formula (3). Sodium nitrite is oxidized by air to form nitrate ions (formula (4)), or reacts with Fe to partially form ammonium (formula (5)). Further, sodium is generated from sodium nitrite and accumulates in the chemical conversion solution.
3Zn (H ₂ PO ₄ ) ₂ → 4H ₃ PO ₄ + Zn ₃ (PO ₄ ) ₂ (1)
Fe + 2H ₃ PO ₄ → Fe (H ₂ PO ₄ ) ₂ + H ₂ (2)
NaNO under acid ₂ HNO ₂ And sodium ions.
Fe (H ₂ PO ₄ ) ₂ + HNO ₂ → FePO ₄ + NO + H ₃ PO ₄ + H ₂ O (3)
HNO ₂ + O → HNO ₃ (4)
3Fe + HNO ₂ + 7H ₃ PO ₄ → 3Fe (H ₂ PO ₄ ) ₂ + NH ₄ H ₂ PO ₄ (5)
When these unnecessary components (nitric acid, ammonium, sodium) accumulate in the chemical conversion treatment solution, they have adverse effects such as yellow rust and scum after the chemical conversion treatment.
[0004]
Further, when the object subjected to the phosphate conversion treatment in the chemical conversion treatment tank is transferred to a water washing tank and washed with water, the chemical treatment liquid in the chemical conversion treatment tank adheres to the object to be treated. Therefore, in the washing wastewater discharged from the washing tank, the effective phosphate chemical conversion treatment component and the above-mentioned unnecessary component are mixed. Therefore, from the viewpoint of saving resources and preventing pollution, the wastewater discharged from the washing tank is concentrated without using the reverse osmosis membrane, and the concentrated liquid is returned to the chemical treatment tank, and the permeated water is sent to the washing tank. Methods for returning and reusing are known. It is necessary to use a reverse osmosis membrane having a high component rejection rate in order to sufficiently recover and reuse an effective component such as a zinc component contained in washing water. A recently marketed reverse osmosis membrane with a high component rejection has a high value of NaCl rejection of 99% or more. Use of such a reverse osmosis membrane is advantageous for recovering an active ingredient. However, since the unnecessary components are also concentrated and returned to the chemical conversion treatment tank, there is a problem that the unnecessary components accumulate in the chemical conversion treatment tank and exert an adverse effect. For this reason, a method using a reverse osmosis membrane having high unnecessary component permeability has been proposed (Patent Literatures 1 and 2), but this method has a disadvantage that a commercially available reverse osmosis membrane cannot be used recently. In addition, there is a method in which an acid is added to the washing wastewater discharged from a washing tank to control the pH and supply the acid to the reverse osmosis membrane in consideration of the durable pH of the reverse osmosis membrane and the sedimentability of the treatment solution (Patent Document 3 ), There is no change in the rejection of unnecessary components.
[0005]
Further, in the chemical conversion treatment tank, unnecessary components are always generated due to decomposition of the accelerator. In addition, the components deposited as a film, the components precipitated as sludge, and the components adhered to the object to be treated and taken out to the chemical conversion treatment tank are supplied to the chemical conversion treatment tank as a replenisher for the chemical conversion treatment tank, and the concentration of the chemical conversion treatment tank is reduced. Although kept constant, nitric acid is added to this replenisher in order to maintain liquid stability, and such components also accumulate in the formation bath as unnecessary components. The unnecessary components thus generated adhere to the object to be processed and are carried out to the next washing step. Therefore, the amount of the unnecessary component taken out of the chemical conversion treatment tank to the washing tank depends on the treatment amount (production amount) of the object to be treated in the line. Therefore, the concentration of the unnecessary component in the chemical conversion treatment tank depends on the processing amount (production amount) of the object to be processed in the line. There is a disadvantage that the concentration of undesired components in the chemical conversion tank increases when the production volume is lower than at the time of design.When recovering and reusing the chemical conversion solution using a commercially available reverse osmosis membrane, Unnecessary components accumulate in the steel and adversely affect the chemical conversion treatment.
[0006]
[Patent Document 1]
JP-A-52-127444
[Patent Document 2]
JP-B-59-10430
[Patent Document 3]
JP 2001-164389 A
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and a phosphate conversion treatment step of performing a chemical conversion treatment of an object to be treated in a chemical conversion treatment tank, and a water washing step of rinsing the phosphate conversion-treated object with water. Recovery and reuse of phosphate chemical conversion solution consisting of a concentration step of concentrating the washing wastewater discharged from the washing tank using a reverse osmosis membrane and a step of returning the concentrated solution obtained in the concentration step to the chemical treatment tank It is an object of the present invention to provide a method for preventing accumulation of unnecessary components in a chemical conversion treatment tank and smoothly performing a concentration step.
[0008]
[Means for Solving the Problems]
In other words, the present invention provides a phosphate conversion treatment step in which a phosphate conversion treatment liquid is brought into contact with an object to be treated in a chemical conversion treatment tank, and a phosphate conversion treatment step in which a phosphate conversion treatment is performed in multiple stages. Phosphoric acid comprising a water washing step of washing through a water washing tank, a concentration step of concentrating the washing wastewater discharged from the water washing tank using a reverse osmosis membrane, and a step of returning the concentrated liquid obtained in the concentration step to a chemical conversion treatment tank. In the above-mentioned concentration step in the method for recovering and recycling a chemical conversion treatment solution, the phosphate conversion treatment solution is characterized in that a zinc compound aqueous solution is added to the washing wastewater discharged from the washing tank and then concentrated with a reverse osmosis membrane. It is a collection and reuse method. The aqueous zinc compound solution preferably contains at least one of zinc nitrate, zinc chloride and zinc sulfate.
[0009]
Further, the present invention provides a phosphate conversion treatment step in which a phosphate conversion treatment liquid is brought into contact with an object to be treated in a chemical conversion treatment tank, and a phosphate conversion treatment step is performed in a multi-stage process. Phosphoric acid comprising a water washing step of washing through a water washing tank, a concentration step of concentrating the washing wastewater discharged from the water washing tank using a reverse osmosis membrane, and a step of returning the concentrated liquid obtained in the concentration step to a chemical conversion treatment tank. In the above-mentioned concentration step in the method for recovering and recycling a chemical conversion treatment liquid, the washing wastewater discharged from the washing tank is taken out by the method according to (1) a reduction in the treatment amount of the object to be supplied into the chemical conversion treatment tank. The amount of phosphatization solution (the amount taken out is the amount of phosphatization solution attached to the object to be treated and transferred to the washing tank) is forcibly withdrawn from the chemical conversion tank and mixed. Further, (2) it is reduced in accordance with a decrease in the throughput of the object to be processed. Mixing the amount of washing water content of the water, a recovery method for recycling phosphate chemical conversion treatment liquid, characterized in that concentrated using a reverse osmosis membrane of this mixture. At this time, (3) a zinc aqueous solution may be further added to the washing wastewater.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
INDUSTRIAL APPLICABILITY The present invention can be applied to phosphate conversion treatment of electric products, automobile bodies, automobile parts, building materials and the like using iron-based materials or aluminum-based materials such as cold-rolled steel sheets and galvanized steel sheets. Examples of the phosphate chemical conversion treatment solution include conventionally known treatment agents such as zinc phosphate-based chemical conversion treatment solutions in addition to zinc phosphate-based chemical conversion treatment solutions. Above all, a zinc phosphate-based chemical conversion treatment liquid is preferably used in an automobile body line, a building material line, an electric parts line, and the like because it forms a film having good corrosion resistance and coating adhesion. The zinc phosphate-based chemical conversion treatment liquid may contain phosphoric acid and zinc as main components, and may include heavy metals such as nickel and manganese, fluorine, and nitric acid as subcomponents. Further, an oxidizing agent serving as an accelerator such as nitrous acid may be contained.
[0011]
FIG. 1 is a process diagram showing an example of a method for recovering and recycling a phosphate chemical conversion treatment solution according to the present invention (claim 1). 1 is a chemical conversion treatment tank. 2 is a first washing tank, 3 is a second washing tank, 4 is a third washing tank, and 5 is a deionized washing tank. 6 is a deionized water supply pipe, and 7 is a flush drain pipe. The objects to be treated, such as electric appliances, automobile bodies, and automobile parts, are subjected to phosphate conversion treatment in the chemical conversion treatment tank 1 after degreasing and surface conditioning. The chemical conversion treatment target object is transferred to a washing tank with the chemical conversion treatment liquid attached thereto, and the chemical conversion treatment liquid attached to the treatment target object is removed in the water washing tank. Rinsing is performed by dipping or spraying. In the rinsing step for removing the chemical conversion treatment liquid, the first rinsing tank 2, the second rinsing tank 3, and the third rinsing tank 4 are sequentially rinsed, and finally, the deionized rinsing tank 5 is rinsed. The washing water is supplied to the deionized washing tank 5 from the water supply pipe 6 and the permeated water pipe 12, and the water sequentially overflows each washing tank, and is finally discharged from the first washing tank 2 as the washing drain through the washing drain pipe 7. Is done. The discharged washing water has a concentration of 1/5 to 1/50 of the chemical conversion treatment liquid.
[0012]
In the present invention, the rinsing wastewater finally discharged from the rinsing drainage pipe 7 is not supplied to the concentrating device provided with the reverse osmosis membrane as it is, but the zinc compound aqueous solution is added to the rinsing wastewater and then supplied to the concentrating device. . In FIG. 1, reference numeral 8 denotes a zinc compound aqueous solution supply pipe, 9 denotes a mixing tank, and 10 denotes a concentration device provided with a reverse osmosis membrane. The washing drainage drained from the first washing tank 2 is sent from a washing drain pipe 7 to a mixing tank 9, where it is mixed with a zinc compound aqueous solution supplied from a zinc compound aqueous solution supply pipe 8, and then sent to a concentration device 10. The concentrated liquid concentrated by the reverse osmosis membrane of the concentrating device 10 is appropriately adjusted, returned to the chemical conversion treatment tank 1 through the concentrated liquid pipe 11, and reused in the chemical conversion treatment. Further, the permeated water that has passed through the reverse osmosis membrane is returned to the deionized water washing tank 5 through the permeated water pipe 12 for reuse. Since the permeated water is clean water having low electric conductivity, it can be used as washing water as it is or as deionized water in a deionized water washing step after further advanced treatment. Here, the advanced treatment refers to a separation treatment using a reverse osmosis membrane or an adsorption treatment using an ion exchange resin.
[0013]
As the aqueous zinc compound solution, an aqueous solution containing at least one of zinc nitrate, zinc chloride and zinc sulfate is preferably used. Particularly preferred is zinc nitrate. These aqueous zinc compound solutions are preferably used in the form of an acidic aqueous solution in order to enhance the stability of the solution. The usable pH range of the aqueous zinc compound solution is pH 0 to 7, preferably pH 1 to 3. For example, it is preferable to add a small amount of nitric acid to the aqueous zinc nitrate solution in order to enhance the stability of the solution. Further, zinc oxide or the like can be used by dissolving it in an acidic aqueous solution. By making the aqueous solution of the zinc compound acidic, the effects described later also occur.
[0014]
In the present invention, when the washing wastewater is concentrated, an aqueous solution of a zinc compound is added to the washing wastewater. By adding the aqueous solution of the zinc compound, the rejection of sodium ions, one of the unnecessary components in the washing wastewater, at the reverse osmosis membrane can be reduced, that is, sodium ions can be easily permeated. For example, by adding zinc nitrate, zinc nitrate can be added to the components in the washing wastewater and 2NaH ₂ PO ₄ + Zn (NO ₃ ) ₂ → Zn (H ₂ PO ₄ ) ₂ + 2NaNO ₃ The reaction of NaNO ₃ Easily permeates reverse osmosis membranes. And this NaNO ₃ By permeating the solution, unnecessary acids such as sodium and nitric acid, which are unnecessary components in the concentrated solution, can be reduced, so that accumulation of the unnecessary components in the chemical conversion treatment tank can be prevented. Unwanted components such as sodium and nitric acid in the permeated water are removed by the above-described separation treatment using a reverse osmosis membrane or adsorption treatment using an ion exchange resin, and are discharged out of the system. This permeated water can be reused as washing water. The concentration of the aqueous zinc compound solution to be added may be arbitrary, but the amount of the zinc compound added to the washing wastewater is 1 to 500 mg / L, preferably 5 to 100 mg / L as the Zn concentration with respect to the washing wastewater.
[0015]
Conventionally, in the chemical conversion treatment tank, components consumed in the chemical conversion treatment, that is, chemical conversion treatment liquid components adhered to the object to be treated and taken out to the washing tank, components deposited as a film on the surface of the object to be treated, and sludge The component precipitated as is supplied as a liquid feed in the chemical conversion treatment tank to supplement it. When the recovery and reuse method of the present invention is applied, the chemical conversion liquid component attached to the object to be treated and taken out to the washing tank is concentrated and collected in the chemical conversion tank, but the film deposition component and the sludge component are supplied. There is a need to. Here, the film deposition component and the sludge component are mainly composed of phosphoric acid and zinc, and in a chemical conversion tank replenisher containing these components, it is necessary to add an excess acid such as nitric acid in order to enhance the liquid stability. is there. In the present invention, when the washing wastewater is concentrated, by adding a zinc compound aqueous solution to the washing wastewater, since zinc is present in the concentrated solution to be reused, it is possible to reduce zinc in the chemical conversion tank replenisher. The nitric acid in the replenisher can be greatly reduced accordingly. As a result, accumulation of nitrate ion, which is one of the unnecessary components, in the chemical conversion treatment tank and further in the system can be suppressed.
[0016]
Further, when an aqueous zinc compound solution stabilized by adding an acid is used, the aqueous solution has a low pH. Therefore, by adding this aqueous solution of the zinc compound to the washing wastewater when the washing wastewater is concentrated, it is possible to suppress an increase in the pH of the washing wastewater before the reverse osmosis membrane. By suppressing the increase in pH, sedimentation before the reverse osmosis membrane can be prevented, and adverse effects on operability can be prevented. It is preferable to add a zinc compound aqueous solution to adjust the pH of the washing water to 1 to 4, particularly 2 to 3.5.
[0017]
Next, the invention according to claim 3 of the present invention will be described. In particular, in the phosphate conversion line that collects and reuses washing wastewater, the amount of phosphate chemical conversion components and unnecessary components in the chemical conversion treatment tank, the amount of water supplied to the washing tank, and the concentration conditions of the washing wastewater Are designed in advance and managed so that they can be implemented as designed. For example, the phosphate chemical conversion treatment components in the chemical conversion treatment tank are replenished as they are consumed. By the way, the supply amount to the object to be processed, for example, the line of the automobile body, often decreases from the design time. When the supply amount of the treatment object decreases, the amount of the chemical conversion treatment liquid that adheres to the treatment object and is taken out of the chemical conversion treatment tank to the washing tank (takeout amount) decreases. Unnecessary components are also contained in the chemical conversion treatment liquid, and a reduction in the amount of the unnecessary components causes a problem that the unnecessary components are gradually accumulated in the chemical conversion treatment tank.
[0018]
Therefore, the invention according to claim 3 of the present invention eliminates this inconvenience by forcibly extracting the chemical conversion treatment liquid from the chemical conversion treatment tank. Further, when the supply amount of the object to be treated decreases, the amount of washing water supplied per hour (water supply amount) also decreases, and an unnecessary component is discharged out of the system (the unnecessary component is discharged through a reverse osmosis membrane). ). The invention according to claim 3 of the present invention is to add an amount of water that is insufficient compared with the time of design to the washing wastewater before the concentration step, so that the amount of unnecessary components that escape to the permeation side is as designed, The amount of the unnecessary component in the chemical conversion treatment tank is set as designed. Further, in the invention according to claim 3 of the present invention, the active ingredient in the chemical conversion treatment liquid that is forcibly extracted is also concentrated together with the active ingredient in the washing wastewater, and can be returned to the chemical conversion treatment tank as a concentrated liquid.
[0019]
FIG. 2 is a process chart showing an example of the method for recovering and recycling a phosphate chemical conversion treatment solution according to the third aspect of the present invention. In FIG. 2, reference numeral 21 denotes a chemical conversion treatment tank. 22 is a first washing tank, 23 is a second washing tank, 24 is a third washing tank, and 25 is a deionized washing tank. 6 is a deionized water supply pipe, and 7 is a flush drain pipe. Objects to be treated, such as electric appliances, automobile bodies, and automobile parts, are degreased and surface-adjusted, and then subjected to a phosphate conversion treatment in a chemical conversion tank 21. The chemical conversion treatment target object is transferred to a washing tank with the chemical conversion treatment liquid attached thereto, and the chemical conversion treatment liquid is removed in the washing tank. In the rinsing step for removing the chemical conversion treatment liquid, the first rinsing tank 22, the second rinsing tank 23, and the third rinsing tank 24 are sequentially rinsed, and finally, the deionized rinsing tank 25 is rinsed. The deionized water is supplied to the deionized water rinsing tank 25 from the water supply pipe 26 and the permeated water pipe 34, and the water sequentially overflows each of the water rinsing tanks. Discharged through tube 27. Generally, in the deionized water washing process, a system is used in which an object to be processed is detected and a predetermined amount is sprayed. Therefore, the amount of washing water changes as needed depending on the flow amount of the object to be treated, that is, the production amount.
[0020]
Wash water discharged from the drain pipe 27 is sent to the mixing tank 31. On the other hand, when the processing amount (production amount) of the object to be treated in the phosphate chemical conversion treatment line is reduced from the design time, the carry-out amount (according to the decrease in the amount to be treated and attached to the object to be washed into the washing tank) is reduced. The amount of the transferred phosphate chemical conversion solution) 28 is forcibly extracted from the chemical conversion treatment tank 21 by using a pump or an automatic valve (that is, when the processing amount (production amount) decreases, The sum of the amount of the liquid that is attached and taken out and the amount of the liquid that is forcibly extracted is made equal to the amount of the liquid that is attached to and taken out of the processing target at the time of design). The extracted chemical conversion treatment liquid is sent to the mixing tank 31. Further, when the processing amount (production amount) of the object to be treated in the phosphate conversion treatment line is reduced from the design time, the amount of washing water is also reduced accordingly. Mix in mixing tank 31. The supply of the reduced amount of washing water (the position of the water supply pipe 29) may be performed at any time before the supply to the concentration device 33.
[0021]
Next, this mixed liquid is filtered by a usual filter 32 as necessary to remove dust, and then supplied to a concentrating device 33 provided with a reverse osmosis membrane. By providing the filter 32, the load on the reverse osmosis membrane can be reduced. The concentrated liquid concentrated by the reverse osmosis membrane of the concentrating device 33 is appropriately adjusted, returned to the chemical conversion treatment tank 21 through the concentrated liquid piping 34, and reused in the chemical conversion treatment. The permeated water that has passed through the reverse osmosis membrane is returned to the washing tank 25 through the permeated water pipe 35 as it is or after appropriate treatment, and is reused as washing water. Furthermore, in the case of the above-mentioned three-way mixing, the zinc compound aqueous solution 30 may be added to the mixing tank 31 to prevent the above-mentioned accumulation of unnecessary components.
[0022]
In the present invention, when the water supply amount is constant, the production amount decreases, the dilution ratio of the washing water increases, and the concentration ratio of the concentrated water and the permeated water must be changed in order to concentrate to the equivalent of a chemical solution. Forcibly, the chemical conversion treatment liquid in the chemical conversion treatment tank is withdrawn so that the sum of the actual amount of the liquid to be taken out and the above-mentioned withdrawal amount is the amount of the liquid to be taken out at the time of design, and the dilution ratio of the mixing tank 31 is kept constant. Since the amount of the chemical conversion solution to be sent changes at any time depending on the production amount, install an electric conductivity meter in the mixing tank and control the discharge pump or automatic valve, or measure the free acidity and total acidity regularly or measure the component concentration. To adjust the flow rate of the discharge pump and the automatic valve. The free acidity of the treatment liquid is determined by collecting 10 ml of the treatment liquid and titrating with 0.1 N sodium hydroxide using bromophenol blue as an indicator. The total acidity of the treatment liquid is determined by sampling 10 mL of the treatment liquid and titrating with 0.1 N caustic soda using phenolphthalein as an indicator. In this case, since the amount and concentration of the liquid sent to the concentrator 33 are substantially constant regardless of the production amount, stable permeation performance and separation performance are always obtained.
[0023]
The capacity balance will be specifically described by taking an automobile body line, which is one of the phosphate conversion treatment steps, as an example. For example, the amount of liquid taken out in an automobile line varies depending on the amount of production, and the amount taken out at the time of design (high production amount) is about 300 L / hr, and the amount taken out when the production amount is reduced by half (low production amount). Is assumed to be 150 L / hr. In the present invention, 150 L / hr is forcibly extracted by a discharge pump or the like so as to be equal to the carry-out amount during the high production amount when the production amount is low. Further, when the production amount is reduced by half in the normal line, the supply amount of the washing water is also reduced to 2850 L / hr, but in the present invention, the reduced amount of 2850 L / hr is supplied, and the total supply is 5700 L / hr. In the present invention, by applying the system as described above, a liquid equivalent to 6000 L / hr, which is equivalent to a 20-fold dilution of the chemical conversion treatment liquid, is always separated regardless of the fluctuation of the production amount. In addition, it is possible to operate the unnecessary component concentration in the chemical conversion treatment tank as designed.
[0024]
According to this method, the carry-out amount that decreases from the chemical conversion treatment tank according to the decrease in the treatment amount of the object to be supplied to the chemical treatment tank (the phosphate conversion treatment that adheres to the object and moves to the washing tank) When the liquid amount) is forcibly extracted, unnecessary components in the chemical conversion treatment tank are also extracted together, so that accumulation of unnecessary components in the chemical conversion treatment tank can be prevented. In addition, the washing wastewater discharged from the washing tank contains (1) a chemical conversion treatment liquid that is forcibly extracted from the chemical conversion treatment tank, and (2) a water equivalent to the washing water amount reduced according to the decrease in the treatment amount of the object to be treated. Since the mixed solution obtained by mixing with the above has almost the same composition and liquid volume as the rinsing wastewater at the time of design, the concentration treatment can be performed without changing the concentration conditions from that at the time of the design, and the same composition and amount as at the time of the design are concentrated. Liquid and permeate can be obtained. Therefore, according to the method of the present invention, the accumulation of the unnecessary components can be made equal to the value at the time of design even if the production amount is reduced.
[0025]
【Example】
Hereinafter, the present invention will be described specifically with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples.
[0026]
Reference example
The following experiment was conducted to examine the effect of the concentration of nitric acid in the zinc phosphate conversion treatment solution on the properties of the phosphate film.
As a surface conditioner, a solution prepared by diluting Preparen ZN (registered trademark: a surface conditioner manufactured by Nippon Parkerizing Co., Ltd.) with tap water to a concentration of 1 g / L, and Palbond WL35 (registered trademark: Zinc phosphate chemical conversion solution manufactured by Nippon Parkerizing Co., Ltd.) was diluted to 4.8% with tap water, Zn: 1.8 g / L, Ni: 1 g / L, Mn: 0.5 g / L, PO: 14 g. / L, F: 1 g / L, Si: 0.3 g / L, and SPC steel plate (cold rolled steel plate) and aluminum material (A1100 material) were subjected to chemical conversion treatment in the following processing steps. Then, the chemical conversion treatment was performed by changing the nitrate ion concentration in the chemical conversion treatment solution, and the following evaluations were performed on the obtained phosphate films at each concentration. The results are shown in Tables 1 and 2. Table 1 shows the evaluation results for the SPC steel plate (cold rolled steel plate), and Table 2 shows the evaluation results for the aluminum material (A1100 material).
[0027]
[Treatment process]
(1) Alkaline degreasing: spray at 42 ° C for 120 seconds
(2) Rinse: Spray for 30 seconds at room temperature
(3) Surface adjustment: room temperature, immersion for 20 seconds
(4) Zinc phosphate treatment: spray at 35 ° C for 120 seconds
(5) Rinse: Spray for 30 seconds at room temperature
(6) Deionized water washing: spray at room temperature for 30 seconds
[0028]
[Evaluation method of phosphate film]
(1) Appearance
By visual observation, the presence or absence of invisibility and unevenness of the zinc phosphate film was confirmed. The evaluation was as follows.
○ Uniform good appearance
△ There is unevenness and invisibility
× Many invisibility
[0029]
(2) Film weight
Measure the weight of the treated plate after the chemical conversion treatment, then subject the chemical conversion treated plate to the following peeling solution and peeling treatment under peeling conditions, measure the weight, and determine the film weight per unit area from the weight difference before and after peeling. The weight was calculated.
Stripping solution: 5% chromic acid aqueous solution
Peeling conditions: 75 ° C, 15 minutes, immersion peeling
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
As can be seen from Tables 1 and 2, for the SPC steel sheet, when the nitric acid concentration is 20 g / L or less, a good phosphate film can be obtained, but when the nitric acid concentration exceeds 30 g / L, some unevenness / scaling occurs, A good phosphate film cannot be obtained. Also, when the aluminum material is 20 g / L or less, a good phosphate film can be obtained, but when it exceeds 30 g / L, there are many scars and a good phosphate film cannot be obtained. Therefore, in order to form a good phosphate film with various materials, it is preferable to keep the nitrate ion concentration at 20 g / L or less.
[0033]
Example 1
Under the processing conditions shown in Reference Example, a chemical conversion treatment was performed on an SPC steel sheet (70 × 150 mm) while replenishing components consumed as a film or sludge. The experimental conditions are as follows.
Chemical conversion tank capacity: 5L
Chemical removal liquid per unit: 2mL / sheet
Processing tact: 5 sheets / hr
Amount of liquid taken out per hour: 10 mL / hr
Accelerator: always replenish to 4.5 points
Further, various components were replenished so that the concentration and the amount of the chemical conversion treatment solution became constant.
The accelerator concentration was determined by adding 5 g of G205 (registered trademark, manufactured by Nippon Parkerizing Co., Ltd.) after placing a 50 mL sample in a device similar to a Kuhne tube (commonly called a saccharometer), and adding the amount of gas generated. Was measured, and was set to 1 point per 1 mL of generated gas.
[0034]
2,500 sheets of SPC steel sheets were subjected to a chemical conversion treatment in a chemical conversion treatment tank under the above conditions. At this time, the total amount of the chemical conversion treatment liquid taken out of the chemical conversion treatment tank is 5 L (2500 sheets × 2 mL). 5 L of the taken-out liquid was diluted with 95 L of tap water to obtain a simulated washing drainage. An aqueous zinc nitrate solution at a zinc concentration of 5 mg / L was added to the simulated washing wastewater (corresponding to a 20-fold dilution of the chemical conversion solution). Next, a concentration operation experiment was performed on the simulated washing wastewater to which the aqueous zinc nitrate solution was added to a chemical conversion treatment solution. For the concentration experiment, a SULG10 membrane (manufactured by Toray Industries, Inc., NaCl rejection: 99.5%), which is a reverse osmosis membrane, was used as the concentration separation membrane, and the treatment temperature was 25 ° C., the pressure was 1.5 MPa, and the concentration of the concentrated solution was circulated. The reaction was performed at a pH of 12 to 14 L / min and a pH of 2 to 3.5. Table 3 shows the ion concentrations of the obtained concentrated liquid (5 L) and permeated liquid (95 L).
[0035]
Further, 5 L of the concentrated solution was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. By repeating such a process, the concentrations of the unnecessary components sodium and nitrate ions accumulate. Table 3 shows the concentration of the unnecessary components in the chemical conversion solution in the chemical conversion tank after 4 turns. From Table 3, it can be seen that in Example 1, the nitrate ion concentration in the chemical conversion treatment tank was 22.7 g / L, so that a good phosphate film could not be obtained depending on the material, depending on the results of Reference Example.
[0036]
[Table 3]

[0037]
Example 2
The same processing as in Example 1 was performed. However, a concentration experiment similar to that of Example 1 was performed by adding a zinc nitrate aqueous solution at a zinc concentration of 50 mg / L to the simulated washing water. Table 4 shows the ion concentrations of the obtained concentrated liquid (5 L) and permeated liquid (95 L). Further, 5 L of the recovered liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. Table 4 shows the concentration of the unnecessary components in the chemical conversion solution in the chemical conversion tank after 4 turns. From Table 4, in Example 2, the accumulated concentration of the unnecessary component nitrate ion was reduced to 19.4 g / L, and a good phosphate film was obtained irrespective of the material from the results of Reference Example. .
[0038]
[Table 4]

[0039]
Comparative Example 1
The same processing as in Example 1 was performed. However, the same concentration experiment as in Example 1 was performed without adding a zinc nitrate aqueous solution to the simulated washing wastewater. Table 5 shows the ion concentrations of the obtained concentrated liquid (5 L) and permeated liquid (95 L). Further, 5 L of the recovered liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. Table 5 shows the concentration of the unnecessary components in the chemical conversion solution in the chemical conversion tank after 4 turns. From Table 5, it can be seen that in Comparative Example 1, since the nitrate ion concentration in the chemical conversion treatment tank was accumulated up to 30 g / L, a good phosphate film could not be obtained from the results of Reference Example.
[0040]
[Table 5]

[0041]
Example 3
When implemented under the design conditions of Example 2, the production volume was reduced to 50% of the design level. That is, the processing tact of the object to be processed was set to 2.5 sheets / hr, which is 50% of 5 sheets / hr. Due to this decrease in the production amount, the amount of the chemical conversion treatment liquid adhered to the object and taken out also became 10 mL / hr 50%, that is, 5 mL / hr.
[0042]
In this example, the chemical conversion treatment liquid was forcibly extracted from the chemical conversion treatment tank at a flow rate of 5 mL / hr and flowed into the mixing tank. Simulated washing wastewater was flowed into this mixing tank, and further, water was flowed in such an amount that the concentration of the chemical conversion treatment liquid in the mixed liquid became a concentration equivalent to a 20-fold dilution. That is, the mixed liquid in the mixing tank was made equal to the composition and liquid amount of the washing water at the time of design. Further, a zinc nitrate aqueous solution was added to the mixing tank at a zinc concentration of 50 mg / L. The mixture thus prepared was subjected to the same concentration experiment as in Example 1. The obtained concentrated liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. As for the concentration of the unnecessary components in the chemical conversion treatment tank after four turns over, the nitrate ion concentration was 19.4 g / L and the sodium concentration was 8.2 g / L. In this example, since the nitrate ion concentration in the chemical conversion treatment tank was reduced to 19.4 g / L, it can be seen from the results of the reference examples that a good phosphate film could be obtained regardless of the material.
[0043]
According to this method, even if the amount of unnecessary components attached to the object to be treated and taken out of the chemical conversion treatment tank due to a decrease in the production amount is reduced, the amount is forcibly extracted from the chemical conversion treatment tank, Even if the amount of unnecessary components such as nitrate ions and sodium accumulated in the chemical conversion treatment tank is small, and the production amount is reduced to 50% of the designed value, the enrichment step can be performed under the same conditions as at the designed time.
[0044]
Comparative Example 2
When implemented under the design conditions of Example 2, the production volume was reduced to 50% of the design level. That is, the processing tact of the object to be processed was set to 2.5 sheets / hr, which is 50% of 5 sheets / hr. Due to this decrease in the production amount, the amount of the chemical conversion treatment liquid adhered to the object and taken out also became 10 mL / hr 50%, that is, 5 mL / hr. A concentration experiment similar to that in Example 2 was performed under these conditions. The obtained concentrated liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. The concentration of the unnecessary components in the chemical conversion treatment tank after 4 turns was such that the nitrate ion concentration was 45.4 g / L and the sodium concentration was 17.8 g / L. In this method, since the amount of the unnecessary component that adheres to the object to be treated and is taken out of the chemical conversion treatment tank decreases due to the decrease in the production amount, the accumulated amount of the unnecessary components such as nitrate ion and sodium increases. Compared with Example 3, nitrate ions, which are unnecessary components, accumulated up to 45 g / L, and it can be seen from the results of Reference Example that a good phosphate film could not be obtained.
[0045]
Comparative Example 3
(1) Except for increasing the processing tact of the object to be treated in Example 1 to 6 sheets / hr (the take-out amount per hour also increases to 12 mL / hr), the SPC steel sheet was formed in accordance with the conditions of Example 1. 3,000 sheets were subjected to a chemical conversion treatment in a treatment tank. At this time, the total amount of the chemical conversion treatment liquid taken out of the chemical conversion treatment tank is 6 L (3000 sheets × 2 mL). 6 L of the taken-out liquid was diluted with 114 L of tap water to obtain a simulated washing wastewater (corresponding to a 20-fold dilution of the chemical conversion treatment liquid). A concentration experiment up to a chemical conversion solution was conducted in the same manner as in Example 1 without adding zinc nitrate to the simulated washing wastewater. As a result of the experiment, a concentrated solution (6 L) and a permeated water (114 L) were obtained. The obtained concentrated solution was returned to the chemical conversion treatment tank, and the total acidity, the advantageous acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. The concentration of the unnecessary components in the chemical conversion solution in the chemical conversion tank after 4 turns was such that the nitrate ion concentration was 19.2 g / L and the sodium concentration was 8.1 g / L. In this example, since the nitrate ion concentration in the chemical conversion treatment tank was 19.2 g / L, it can be seen from the results of the reference examples that a good phosphate film could be obtained regardless of the material.
[0046]
(2) However, in the above example (1), when the number of objects to be treated decreases, the concentration in the unnecessary component chemical conversion treatment liquid increases, and a favorable phosphate film cannot be obtained. An example is shown below.
That is, when carrying out under the design conditions of the above (1) example, the production amount (processing tact) was reduced to 50%, the processing tact was 3 pieces / hr, and the carry-out amount per hour was 6 mL / hr. Under the conditions in which the production was reduced, 1500 sheets of SPC steel sheets were subjected to the chemical conversion treatment in the chemical conversion treatment tank in accordance with the conditions of Example 1. At this time, the total amount of the chemical conversion treatment liquid taken out of the chemical conversion treatment tank is 3 L (1500 sheets × 2 mL). 3 L of the taken-out liquid was diluted with 57 L of tap water to obtain a simulated washing wastewater (corresponding to a 20-fold dilution of the chemical conversion treatment liquid). The simulated washing wastewater was subjected to the same concentration experiment as in the above (1) example, and concentrated to a chemical conversion treatment solution. 3 L of the obtained concentrated liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. Regarding the concentration of the unnecessary components in the chemical conversion treatment solution in the chemical conversion treatment tank after 4 turns over, the nitrate ion concentration was 41.3 g / L and the sodium concentration was 16.3 g / L.
[0047]
In this method, the amount of unnecessary components attached to the object to be treated and taken out of the chemical conversion treatment tank is reduced due to the decrease in the production amount, and the amount of unnecessary components that permeates is reduced by the reduced amount of washing water. The accumulated amounts of nitrate ion and sodium ion, which are components, are increasing. At this nitrate ion concentration, it can be seen from the results of the reference examples that a good phosphate film could not be obtained.
[0048]
Example 3
It carried out on the conditions of the (2) example of the comparative example 3. However, 60 L of the simulated washing wastewater (3 L of the taken-out liquid) diluted with 57 L of tap water (equivalent to a 20-fold dilution of the chemical conversion treatment liquid) was directly put into the mixing tank without directly conducting the concentration experiment. 3 L of the chemical conversion treatment liquid forcibly extracted from the treatment tank (for the (1) example of Comparative Example 3, as in the (2) example, the carry-out amount reduced when the production amount is reduced by 50% = 6 L−3 L = 3 L), And {circle around (2)} the amount of water (ie, the amount of washing water that decreases as the production volume decreases) in an amount that dilutes the concentration of the chemical conversion treatment solution in the mixing tank by 20 times (that is, the amount of washing water that decreases as the production volume decreases) is mixed in the mixing tank; The same concentration experiment as in Example (2) of Comparative Example 3 was performed, and the mixture was concentrated to a chemical conversion treatment solution. 6 L of the obtained concentrated solution was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. The concentration of the unnecessary components in the chemical conversion treatment tank after 4 turns was such that the nitrate ion concentration was 19.1 g / L and the sodium concentration was 8.0 g / L. It can be seen from the results of the reference examples that a good phosphate film was obtained.
[0049]
According to this method, even if the amount of undesired components attached to the object to be treated and taken out of the chemical conversion treatment tank due to a decrease in the production amount decreases, the reduced amount is forcibly extracted from the chemical conversion treatment tank. The amount of the unnecessary component discharged from the processing tank has the same value as that of the comparative example 3 (1). Further, by supplying water so that the carry-out portion and the withdrawal portion of the chemical conversion treatment liquid are diluted 20-fold, the amount of the unnecessary component that escapes to the permeation side becomes the same as that of the comparative example 3 (1). As a result, even if the production amount is reduced to 50% of the design time, the enrichment step can be performed as it is under the same conditions as at the time of design.
[0050]
Comparative Example 4
It carried out on the conditions of the (2) example of the comparative example 3. However, 60 L of the simulated washing wastewater obtained by diluting 3 L of the taken-out liquid with 57 L of tap water (corresponding to a 20-fold dilution of the chemical conversion treatment liquid) was directly put into the mixing tank without directly conducting the concentration experiment. 3 L of chemical conversion treatment liquid forcibly extracted from the chemical conversion tank [in the (1) example of Comparative Example 3, the carry-out amount that decreases when the production amount decreases by 50% as in the (2) example = 6 L−3 L = 3 L] Was added and mixed, and then the mixed solution was subjected to the same concentration experiment as in Example (2) of Comparative Example 3, and concentrated to a chemical conversion treatment solution. 6 L of the obtained concentrated liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. After four turns over, the concentration of the unnecessary components in the chemical conversion treatment tank was such that the nitrate ion concentration was 31.3 g / L and the sodium concentration was 12.6 g / L.
[0051]
According to this method, the amount of the unnecessary component that adheres to the object to be treated and is taken out of the chemical conversion treatment tank with a decrease in the production amount is reduced, but the reduced amount is forcibly extracted from the chemical conversion treatment tank. The amount of undesired components discharged from the plant does not change. However, the decrease in the amount of washing water that decreases with the decrease in the production amount is not replenished to the mixing tank. For this reason, the amount of the liquid to be subjected to the concentration step is reduced, and the concentration efficiency is deteriorated, and the amount of the unnecessary component permeating the reverse osmosis membrane is reduced. Therefore, the accumulated amount of the unnecessary components such as nitrate ion and sodium ion is increased. I have. Nitrate ions, which are unnecessary components, accumulated up to 31.3 g / L, and it can be seen from the results of the reference examples that a good phosphate film could not be obtained.
[0052]
Comparative Example 5
It carried out on the conditions of the (2) example of the comparative example 3. However, in Comparative Example 3 (2), 3 L of the taken-out liquid was diluted with 57 L of tap water to prepare 60 L of simulated washing wastewater (corresponding to a 20-fold dilution of the chemical conversion liquid). Was diluted with 114 L of tap water to prepare 117 L of simulated washing wastewater (corresponding to a 40-fold dilution of the chemical conversion treatment liquid). A concentration experiment similar to that of Example (2) of Comparative Example 3 was performed on the simulated washing wastewater, and concentrated to a chemical conversion treatment solution. 3 L of the obtained concentrated liquid was returned to the chemical conversion treatment tank, and the total acidity, the free acidity, and the concentration of each component were adjusted. This process was defined as one turnover, and a total of four turns were performed. After four turns over, the concentration of the unnecessary components in the chemical conversion treatment tank was such that the nitrate ion concentration was 28.9 g / L and the sodium concentration was 11.7 g / L.
[0053]
In this method, as in the case of the example (2) of Comparative Example 3, the amount of the unnecessary components attached to the object to be treated and taken out of the chemical conversion treatment tank decreases with a decrease in the production amount. Can not prevent the accumulation of Even if the liquid taken out from the chemical conversion treatment tank was diluted twice as much as the (2) example of Comparative Example 3 and then concentrated, the accumulation of unnecessary components such as nitrate ion and sodium ion could not be prevented. Nitrate ions, which are unnecessary components, accumulated up to 28.9 g / L, and it can be seen from the results of the reference examples that a good phosphate film could not be obtained.
[0054]
【The invention's effect】
Conventionally, it is known to reuse washing water discharged in a phosphate chemical conversion treatment step, but it has been difficult to carry out such treatment because unnecessary components are accumulated in a chemical conversion treatment liquid. ADVANTAGE OF THE INVENTION According to this invention, accumulation | storage of the unnecessary component in a chemical conversion treatment agent can be reduced and it can be reused efficiently. Therefore, by collecting and reusing the components of the chemical conversion treatment liquid, it is possible to minimize the amount of waste in the phosphate chemical conversion treatment step. Further, even if the processing amount (production amount) varies in the phosphate conversion treatment process line, it is possible to always recover and reuse the components of the phosphate conversion treatment solution under the same conditions.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an example of a process of the present invention.
FIG. 2 is a process chart showing an example of a process of the present invention.
[Explanation of symbols]
1,21 chemical conversion treatment tank, 2,22 first washing tank, 3,23 second washing tank,
4,24 3rd washing tank, 5,25 deionized washing tank, 6,26 water supply pipe,
7,27 flush drainage pipe, 8,30 zinc compound aqueous solution supply pipe,
9,31 Mixing tank, 10,33 Concentrator, 11,34 Concentrated water piping
12,35 Permeated water pipe 28 Chemical conversion liquid extraction pipe, 29 Water supply pipe,
32 filter

Claims

A phosphate conversion treatment step in which a phosphate conversion treatment liquid is brought into contact with an object to be treated in a chemical conversion tank, and a water washing in which the phosphate conversion-treated object is rinsed through a multi-stage washing tank. A phosphate conversion treatment solution comprising a process, a concentration step of concentrating the washing wastewater discharged from the washing tank using a reverse osmosis membrane, and a step of returning the concentrated solution obtained in the concentration step to the chemical conversion treatment tank. A method for recovering and recycling a phosphate chemical conversion treatment solution, comprising adding a zinc compound aqueous solution to washing water discharged from a washing tank and concentrating the solution with a reverse osmosis membrane in the above concentration step in the recycling method.

2. The method according to claim 1, wherein the aqueous zinc compound solution contains at least one of zinc nitrate, zinc chloride and zinc sulfate.

A phosphate conversion treatment step in which a phosphate conversion treatment liquid is brought into contact with an object to be treated in a chemical conversion tank, and a water washing in which the phosphate conversion-treated object is rinsed through a multi-stage washing tank. A phosphate conversion treatment solution comprising a process, a concentration step of concentrating the washing wastewater discharged from the washing tank using a reverse osmosis membrane, and a step of returning the concentrated solution obtained in the concentration step to the chemical conversion treatment tank. In the above-described concentration step in the recycling method, the washing wastewater discharged from the washing tank is added to (1) the carry-out amount (the carry-out amount) which decreases in accordance with the decrease in the treatment amount of the treatment object supplied into the chemical conversion treatment tank. The amount of the phosphatization solution attached to the object to be treated and transferred to the washing tank is forcedly withdrawn from the chemistry treatment tank and mixed. For the reduced amount of washing water Mixed, recovered and reused method phosphate chemical conversion treatment liquid, characterized in that concentrated using a reverse osmosis membrane of this mixture.

2. In the concentration step in the method for recovering and recycling a phosphate chemical conversion treatment liquid according to claim 1, the washing wastewater discharged from the water washing tank is further supplied with (1) a chemical conversion treatment tank in addition to a zinc compound aqueous solution. The amount of the phosphate conversion treatment liquid that is reduced in accordance with the decrease in the treatment amount of the object (the amount of removal is the amount of the phosphate conversion treatment liquid attached to the object to be treated and transferred to the washing tank). Forcibly withdrawn from the chemical conversion tank, mixed, and (2) mixed with water for the amount of washing water reduced in accordance with the decrease in the treatment amount of the object to be treated. A method for recovering and reusing a phosphate chemical conversion treatment solution, comprising concentrating the solution.

5. The method of claim 4, wherein the aqueous zinc compound solution contains at least one of zinc nitrate, zinc chloride and zinc sulfate.

The method for recovering and reusing a phosphate chemical conversion treatment solution according to any one of claims 1 to 5, wherein the phosphate chemical conversion treatment solution is a zinc phosphate type or a zinc calcium phosphate type.

The method for recovering and reusing a phosphate chemical conversion treatment solution according to any one of claims 1 to 6, wherein the permeated water that has passed through the reverse osmosis membrane in the concentration step is used for washing water.