JP3571210B2 - Toning method of powder coating - Google Patents

Description

【００３１】
〔式中、Ｒ^１ およびＲ^２ は同一または異なる低級アルキレン基を示す。ｘおよびｙは同一または異なって０または１以上の整数を表し、かつｘ＋ｙは１〜７である。〕
で表されるジオール成分と、
（ｉｉ） ジカルボン酸、その酸無水物または低級アルキルエステルと、
（ｉｉｉ） ３価以上の多価カルボン酸、その酸無水物もしくは低級アルキルエステル、または３価以上の多価アルコール
とを共重縮合してなり、かつその酸価（ＡＶ）に対する水酸基価（ＯＨＶ）の割合ＯＨＶ／ＡＶの値が１．２以上であるポリエステル樹脂が、好適な結着樹脂としてあげられる。
【００３２】
なお上記のポリエステル樹脂において、一般式（１） 中のＲ^１ およびＲ^２ に相当する低級アルキレン基としては、たとえばメチレン、エチレン、トリメチレン、プロピレン、テトラメチレン、エチルエチレン、ペンタメチレン、ヘキサメチレンなどの炭素数１〜６のアルキレン基があげられる。
一般式（１） 中のｘ＋ｙは、前記のように１〜７であり、好ましくは３〜５である。ｘ＋ｙが７を超えた場合には、ジオール成分の分子量が大きくなりすぎて、塗膜の透光性が低下するといった問題を生じる。
【００３３】
一般式（１） で表されるジオール成分としては、たとえばポリオキシプロピレン（２．２）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシプロピレン（３．３）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシエチレン（２．０）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシプロピレン（２）−ポリオキシエチレン（２）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシプロピレン（６．０）−２，２−ビス（４−ヒドロキシフェニル）プロパンなどがあげられる。
【００３４】
ジカルボン酸としては、たとえばシュウ酸、マロン酸、コハク酸、イタコン酸、グルタコン酸、アジピン酸、マレイン酸、フマル酸、シトラコン酸、メサコン酸、アゼライン酸、セバシン酸、シクロヘキサンジカルボン酸、フタル酸、イソフタル酸、テレフタル酸などがあげられる。これらのジカルボン酸は、酸無水物や低級アルキルとのエステルであってもよい。低級アルキルとしては、たとえばメチル、エチル、ｎ−プロピル、イソプロピル、ｎ−ブチル、イソ−ブチル、ｓ−ブチル、ｔ−ブチル、ｎ−ペンチル、ｎ−ヘキシルなどの炭素数１〜６のアルキル基があげられる。
【００３５】
３価以上の多価カルボン酸、その酸無水物もしくは低級アルキルエステル、および３価以上の多価アルコールは、ポリエステル樹脂の酸価および水酸基価を調整することと、ポリエステル樹脂を分岐状にすることを目的として配合される。３価以上の多価カルボン酸、その酸無水物もしくは低級アルキルエステルとしては、たとえばトリメリト酸、２，５，７−ナフタレントリカルボン酸、１，２，４−ナフタレントリカルボン酸、１，２，４−ブタントリカルボン酸、１，３−ジカルボキシル−２−メチル−２−メトキシカルボニルプロパン、テトラ（メトキシカルボニル）メタン、１，２，７，８−オクタンテトラカルボン酸などがあげられる。
【００３６】
３価以上の多価アルコールとしては、たとえばグリセリン、２−メチル−１，２，３−プロパントリオール、１，２，４−ブタントリオール、２−メチル−１，２，４−ブタントリオール、１，２，５−ペンタトリオール、ペンタエリトリトール、ジペンタエリトリトール、トリペンタエリトリトール、ヘキシトール、ソルビトール、１，４−ソルビタン、１，２，４−ベンゼントリオールなどがあげられる。
【００３７】
ポリエステル樹脂は、上記の各成分を、たとえば不活性ガス雰囲気下、１８０〜２５０℃の温度で共重縮合して合成される。
ポリエステル樹脂の酸価（ＡＶ）に対する水酸基価（ＯＨＶ）の割合ＯＨＶ／ＡＶの値は１．２以上であり、好ましくは１．２〜５０、より好ましくは２〜４０である。ＯＨＶ／ＡＶの値が１．２未満では、樹脂の透光性が低下したり、樹脂の最低溶融温度が高くなって、加熱溶融により連続した塗膜を形成するのが容易でなくなったり、あるいは粉体塗料の流動性が低下したりするといった問題を生じる。
【００３８】
なお酸価（ＡＶ）は、たとえばポリエステル樹脂をベンゼン−エタノール混合溶媒に溶かし、水酸化カリウムで滴定してその中和量から算出される。また水酸基価（ＯＨＶ）は、たとえばピリジン−無水酢酸混合溶媒（３．１：１）を用いてポリエステル樹脂中の遊離酸をアセチル化した後、樹脂に結合した酢酸を水酸化カリウムで滴定して滴定してその中和量から算出される。
【００３９】
上記のポリエステル樹脂は単独で使用できる他、前述した従来公知の種々の樹脂をブレンドしてもよい。他の樹脂をブレンドする場合、その配合量は、上記ポリエステル樹脂に対して１〜３０重量％程度が好ましい。
（着色剤）
シアン（Ｃ）系の着色剤としては、とくにフタロシアニン系顔料が好適に使用される。かかるフタロシアニン系顔料の具体例としては、たとえば一般式（２） ：
【００４０】
【化２】

【００４１】
〔式中、Ｘ^１ 、Ｘ^２ 、Ｘ^３ およびＸ^４ は同一または異なって水素原子、基（２ａ）または基（２ｂ）：
【００４２】
【化３】

【００４３】
を示す。Ｒ^３ およびＲ^４ は炭素数１〜５のアルキレン基である。〕
で表される銅フタロシアニン系顔料、たとえばカラーインデックスによる分類のうちＣ．Ｉ．ピグメントブルー１５（１５：１〜１５：４、Ｘ^１ 、Ｘ^２ 、Ｘ^３ およびＸ^４ がいずれも水素原子である化合物）やその誘導体、あるいは式（３） ：
【００４４】
【化４】

【００４５】
で表される無金属フタロシアニン系顔料（Ｃ．Ｉ．ピグメントブルー１６）などがあげられる。また、上記Ｃ．Ｉ．ピグメントブルー１５の誘導体としては、その部分塩素化物や、あるいは銅フタロシアニンのスルホン酸のバリウム塩（Ｃ．Ｉ．ピグメントブルー１７）などがあげられる。
また、上記以外の他のシアン系の着色剤としては、たとえば紺青（プルシアンブルー）、コバルトブルーなどの無機顔料、Ｃ．Ｉ．ピグメントブルー１８、Ｃ．Ｉ．ピグメントブルー１６などの有機顔料、Ｃ．Ｉ．バットブルー６、Ｃ．Ｉ．ソルベントブルー７０などの染料などがあげられる。
【００４６】
シアン系の着色剤の配合量は、シアン（Ｃ）の粉体塗料の場合、鮮明な色味がられ、しかも粉体塗料の透光性が低下しないことを考慮すると、結着樹脂１００重量部に対して１〜２０重量部程度、とくに２〜８重量部程度であるのが好ましい。またライトシアン（ＬＣ）の粉体塗料の場合、前述した色の階調の向上や粒状感をなくすることなどを考慮すると、組み合わせるシアンの粉体塗料の色濃度などにもよるが、結着樹脂１００重量部に対して０．１〜２．５重量部程度、とくに０．５〜２．０重量部程度であるのが好ましい。
【００４７】
マゼンタ（Ｍ）系の着色剤としては、たとえばキナクリドン系顔料が使用される。かかるキナクリドン系顔料の具体例としては、たとえば一般式（４） ：
【００４８】
【化５】

【００４９】
〔式中、Ｑ^１ およびＱ^２ は同一または異なって水素原子、アルキル基またはアルコキシ基を示す。ただしＱ^１ 、Ｑ^２ は同時に水素原子でない。〕
で表されるキナクリドン系顔料、たとえばＣ．Ｉ．ピグメントレッド１２２〔Ｑ^１ およびＱ^２ がともにメチル基である化合物〕などがあげられる。
また、上記以外の他のマゼンタ系の着色剤としては、たとえばベンガラ、カドミウムレッド、鉛丹、硫化水銀カドミウム、マンガン紫、赤口黄鉛、モリブデンオレンジなどの無機顔料、Ｃ．Ｉ．ピグメントレッド３、Ｃ．Ｉ．ピグメントレッド３８、Ｃ．Ｉ．ピグメントレッド４８：２、Ｃ．Ｉ．ピグメントレッド４９：１、Ｃ．Ｉ．ピグメントレッド４９：２、Ｃ．Ｉ．ピグメントレッド５０、Ｃ．Ｉ．ピグメントレッド５７、Ｃ．Ｉ．ピグメントレッド６０、Ｃ．Ｉ．ピグメントレッド８１、Ｃ．Ｉ．ピグメントレッド９０、パーマネントレッドＦＮＧ、Ｃ．Ｉ．ピグメンバイオレット３、Ｃ．Ｉ．ピグメンバイオレット２５、Ｃ．Ｉ．ピグメントオレンジ５、Ｃ．Ｉ．ピグメントオレンジ１３、Ｃ．Ｉ．ピグメントオレンジ１６などの有機顔料、スピロンレッド、インダンスレンブリリアントオレンジＲＫ、インダンスレンブリリアントオレンジＧＫなどの染料などがあげられる。
【００５０】
マゼンタ系の着色剤の配合量は、マゼンタ（Ｍ）の粉体塗料の場合、鮮明な色味が得られ、しかも粉体塗料の透光性が低下しないことを考慮すると、結着樹脂１００重量部に対して１〜２０重量部程度、とくに２〜８重量部程度であるのが好ましい。またライトマゼンタ（ＬＭ）の粉体塗料の場合、前述した色の階調の向上や粒状感をなくすることなどを考慮すると、組み合わせるマゼンタの粉体塗料の色濃度などにもよるが、結着樹脂１００重量部に対して０．１〜２．５重量部程度、とくに０．５〜２．０重量部程度であるのが好ましい。
【００５１】
イエロー（Ｙ）系の着色剤としては、たとえば縮合アゾ系顔料、イソインドリン系顔料、あるいはベンズイミダゾロン系顔料などがあげられる。
このうち縮合アゾ系顔料としては、一般式（５） ：
【００５２】
【化６】

【００５３】
〔式中、Ｒ^５ およびＲ^６ は同一または異なってアルキル基またはハロゲン原子を示し、Ｒ^７ およびＲ^８ は同一または異なって基（５ａ）または（５ｂ）：
【００５４】
【化７】

【００５５】
を示す。〕
で表される化合物、たとえばＣ．Ｉ．ピグメントイエロー９３〔Ｒ^５ がメチル基、Ｒ^６ が塩素原子、Ｒ^７ およびＲ^８ がともに基（５ａ）である化合物〕、Ｃ．Ｉ．ピグメントイエロー９４〔Ｒ^５ およびＲ^６ がともに塩素原子、Ｒ^７ およびＲ^８ がともに基（５ｂ）である化合物〕、およびＣ．Ｉ．ピグメントイエロー９５〔Ｒ^５ およびＲ^６ がともにメチル基、Ｒ^７ およびＲ^８ がともに基（５ｂ）である化合物〕などがあげられる。
【００５６】
またイソインドリン系顔料としては、たとえば一般式（６） ：
【００５７】
【化８】

【００５８】
〔式中、Ａｒは基（６ａ）または（６ｂ）：
【００５９】
【化９】

【００６０】
を示す。〕
で表される化合物、たとえばＣ．Ｉ．ピグメントイエロー１０９〔Ａｒが基（６ａ）である化合物〕、Ｃ．Ｉ．ピグメントイエロー１１０〔Ａｒが基（６ｂ）である化合物〕などがあげられる。
さらにベンズイミダゾロン系顔料としては、式（７） ：
【００６１】
【化１０】

【００６２】
で表される化合物（Ｃ．Ｉ．ピグメントイエロー１５４）などがあげられる。
また、上記以外の他のイエロー系の着色剤としては、たとえば黄色酸化鉄、黄土、黄鉛、亜鉛黄、カドミウムイエロー、アンチモンイエローなどの無機顔料、Ｃ．Ｉ．ピグメントイエロー１、Ｃ．Ｉ．ピグメントイエロー３、Ｃ．Ｉ．ピグメントイエロー１２、Ｃ．Ｉ．ピグメントイエロー１３、Ｃ．Ｉ．ピグメントイエロー１６、Ｃ．Ｉ．ピグメントイエロー１７、Ｃ．Ｉ．ピグメントイエロー５５、Ｃ．Ｉ．ピグメントイエロー６５、Ｃ．Ｉ．ピグメントイエロー７３、Ｃ．Ｉ．ピグメントイエロー７４、Ｃ．Ｉ．ピグメントイエロー８３、Ｃ．Ｉ．ピグメントイエロー９７、Ｃ．Ｉ．ピグメントイエロー９８、Ｃ．Ｉ．ピグメントイエロー１１５、Ｃ．Ｉ．ピグメントイエロー１３０、Ｃ．Ｉ．ピグメントイエロー１３３、Ｃ．Ｉ．ピグメントイエロー１３８、Ｃ．Ｉ．ピグメントイエロー１６９などの有機顔料、Ｃ．Ｉ．ソルベントイエロー１６、Ｃ．Ｉ．ソルベントイエロー３３、Ｃ．Ｉ．ソルベントイエロー５６、Ｃ．Ｉ．ソルベントイエロー６０、Ｃ．Ｉ．ソルベントイエロー６１、Ｃ．Ｉ．ソルベントイエロー１６２、Ｃ．Ｉ．アシッドイエロー１、Ｃ．Ｉ．アシッドイエロー２３などの染料などがあげられる。
【００６３】
イエロー系の着色剤の配合量は、やはり鮮明な色味が得られ、しかも粉体塗料の透光性が低下しないことを考慮すると、結着樹脂１００重量部に対して１〜２０重量部程度、とくに１．５〜８重量部程度であるのが好ましい。
レッド（Ｒ）系の着色剤としては、たとえばナフトトール系顔料が使用される。かかるナフトトール系顔料の具体例としては、たとえば一般式（８） ：
【００６４】
【化１１】

【００６５】
で表される化合物（Ｃ．Ｉ．ピグメントレッド１７０）などがあげられる。
また、上記以外の他のレッド系の着色剤としては、たとえばＣ．Ｉ．ピグメントレッド５、Ｃ．Ｉ．ピグメントレッド１４６、Ｃ．Ｉ．ピグメントレッド１７７、Ｃ．Ｉ．ピグメントレッド１７８、Ｃ．Ｉ．ピグメントレッド２０２、Ｃ．Ｉ．ピグメントレッド２３８、Ｃ．Ｉ．ピグメントレッド２５１、Ｃ．Ｉ．ピグメントレッド２５４、Ｃ．Ｉ．ピグメントレッド２５５、Ｃ．Ｉ．ピグメントレッド２６４などの有機顔料などがあげられる。
【００６６】
レッド系の着色剤の配合量は、レッド（Ｒ）の粉体塗料の場合、鮮明な色味が得られ、しかも粉体塗料の透光性が低下しないことを考慮すると、結着樹脂１００重量部に対して１〜２０重量部程度、とくに２〜８重量部程度であるのが好ましい。またライトレッド（ＬＲ）の粉体塗料の場合、前述した色の階調の向上や粒状感をなくすることなどを考慮すると、組み合わせるレッドの粉体塗料の色濃度などにもよるが、結着樹脂１００重量部に対して０．１〜２．５重量部程度、とくに０．５〜２．０重量部程度であるのが好ましい。
【００６７】
クリア（Ｔ）系の粉体塗料は、上記の着色剤を添加せずに製造される。
（他の添加剤）
着色剤以外の他の添加剤としては、前述した電荷制御剤の他、硬化剤、平滑剤（流展剤）などの、従来公知の種々の添加剤があげられる。
このうち電荷制御剤は、粉体塗料を、たとえば前述した静電付着による塗布法、たとえばスプレーガンを用いた静電塗着法や、静電流動浸漬法などに使用する際に、その帯電量を向上し、かつ温度や湿度などの環境条件の変化に関係なく安定させるとともに、前記のように各色の粉体塗料ごとに帯電特性を揃えるためのもので、粉体塗料の帯電極性にあわせて正電荷制御剤と負電荷制御剤のうちのいずれか一方が使用される。
【００６８】
上記のうち正電荷制御剤としては、たとえばニグロシン系の電子供与性染料、ナフテン酸または高級脂肪酸の金属塩、アルコキシル化アミン、第４級アンモニウム塩、アルキルアミド、キレート、顔料、ふっ素処理活性剤などがあげられる。
また負電荷制御用の電荷制御剤としては、たとえば電子受容性の有機錯体、塩素化パラフィン、塩素化ポリエステル、酸基過剰のポリエステル、銅フタロシアニンのスルホニルアミン、芳香族オキシカルボン酸、芳香族ダイカルボン酸などがあげられる。
【００６９】
ただし透光性の粉体塗料においては、その色味にできるだけ影響を及ぼさないために、
（ａ） それ自体が無色または淡色で、かつ
（ｂ） 粉体塗料を白濁させないように結着樹脂との相溶性にすぐれるか、あるいは結着樹脂と相溶はしないが分散性にすぐれた
電荷制御剤が好適に使用される。
【００７０】
かかる条件を満たす正電荷制御剤としては、上記のうち第４級アンモニウム塩があげられ、負電荷制御剤としては、芳香族オキシカルボン酸、芳香族ダイカルボン酸などがあげられる。
上記のうち正電荷制御剤である第４級アンモニウム塩としては種々の化合物があげられるが、とくに一般式（９） ：
【００７１】
【化１２】

【００７２】
〔式中、Ｒ^ａ 、Ｒ^ｂ 、Ｒ^ｃ およびＲ^ｄ は、同一または異なって低級アルキル基、長鎖アルキル基、長鎖アルケニル基またはベンジル基を示し、Ａ⁻ はアニオンを示す。ただしＲ^ａ 〜Ｒ^ｄ は、少なくとも１個が長鎖アルキル基または長鎖アルケニル基であり、２個が低級アルキル基またはベンジル基である。〕
で表される化合物が好適に使用される。
【００７３】
上記一般式（９） においてＲ^ａ 〜Ｒ^ｄ に相当する長鎖アルキル基としては、たとえば、オクチル基、デシル基、ドデシル基、テトラデシル基、ヘキサデシル基、オクタデシル基、エイコシル基、ドコシル基、オレイル基、リノリル基、ヘキサデセシル基などがあげられる。また、長鎖アルケニル基としては、たとえば、上記長鎖アルキル基の分子中に１または２以上の二重結合を導入した基があげられる。
【００７４】
Ａ⁻ で表されるアニオンとしては、たとえば、モリブデン酸、リンモリブデン酸、ケイモリブデン酸、クロム・モリブデン酸、ブロム・モリブデン酸、タングステン酸、リンタングステン酸、ケイタングステン酸、クロム・タングステン酸、ブロム・タングステン酸、リンタングステン・モリブデン酸、ケイタングステン・モリブデン酸などのモリブデン原子やタングステン原子を含有する無機酸から誘導されるアニオン、塩素イオン、臭素イオン、ヨウ素イオン、硝酸イオン、硫酸イオン、過塩素酸イオン、安息香酸イオン、テトラフェニルホウ素イオン、ヘキサフルオロリンイオン、ナフトールスルホン酸イオンなどがあげられる。
【００７５】
上記一般式（９） で表される第４級アンモニウム塩の具体例としては、たとえば（Ｃ_１６Ｈ_３３）_２ Ｎ^＋ （ＣＨ_３ ）_２ ・１／４ Ｍｏ_８ Ｏ_２６ ^４− 、（Ｃ_１６Ｈ_３３）_２ Ｎ^＋ （ＣＨ_３ ）_２ ・１／６ Ｍｏ_７ Ｏ_２４ ^６− 、（Ｃ_１６Ｈ_３３）_２ Ｎ^＋ （ＣＨ_３ ）_２ ・１／２ ＷＯ_４ ^２− などがあげられ、これらを１種または２種以上混合して使用することができる。
【００７６】
電荷制御剤の配合量は、結着樹脂１００重量部に対して１〜１０重量部であるのが好ましく、１〜５重量部であるのがさらに好ましい。電荷制御剤の配合量が上記の範囲未満では、その添加効果が不十分になるおそれがあり、逆に上記の範囲を超えた場合には、透光性が低下したり色味が変化したりするおそれがある。硬化剤は、粉体塗料を加熱溶融させて塗膜を形成した際に、当該塗膜中で結着樹脂を架橋することによって塗膜を硬化させるためのものであって、かかる硬化剤としては、たとえばブロックイソシアネート、エポキシ樹脂、アミノ樹脂、アジリジン化合物、多価カルボン酸などがあげられる。
【００７７】
硬化剤は、硬化反応に寄与する官能基の当量に応じて、好適な配合量の範囲が設定される。硬化剤の配合量が好適な範囲より少ない場合は、その添加効果が不十分になるおそれがあり、逆に好適な範囲を超えた場合には、透光性が低下したり色味が変化したりするおそれがある。
平滑剤は、粉体塗料を加熱溶融させた際の流動性を向上して、塗膜をより平滑にするためのもので、かかる平滑剤としては、たとえばＢＡＳＦ社製の商品名「アクロナール４Ｆ」、東芝シリコーン社製の商品名「ＹＦ−３９１９」、モンサント社製の商品名「モダフロー２０００」などがあげられる。
【００７８】
平滑剤の配合量は、結着樹脂１００重量部に対して０．１〜２重量部であるのが好ましく、０．５〜１重量部であるのがさらに好ましい。平滑剤の配合量が上記の範囲未満では、その添加効果が不十分になるおそれがあり、逆に上記の範囲を超えた場合には、透光性が低下したり色味が変化したりするおそれがある。
上記以外にも粉体塗料には、たとえば硬化剤による硬化反応を補助するための硬化促進剤や、消泡剤、あるいは塗膜の耐蝕性を高めるためのエポキシ樹脂などの、さらに他の添加剤を配合してもよい。
【００７９】
（粉体塗料の製造方法）
粉体塗料は、前述したように粉砕法、すなわち上記の各成分を乾式ブレンダー、ヘンシェルミキサー、ボールミルなどを用いて予備混合した混合物を、ジェットミル、バンバリーミキサー、ロール、１軸または２軸の押出混練機などを用いて溶融混練したのち、えられた混練物を冷却して粉砕し、さらに必要に応じて分級することにより製造される他、重合法、マイクロカプセル重合法、スプレードライ法などを用いて製造することもできる。
【００８０】
粉体塗料の粒径は従来と同程度でよいが、２色以上を混合した際の色味の均一性を考慮すると、粒径が小さいほど好ましく、とくにその平均粒径が３０μｍ以下であるのが好ましい。
また、帯電性や塗膜の形成しやすさ、凝集のしにくさなどを考慮すると、粉体塗料の平均粒径は、上記範囲内でもとくに１μｍ以上であるのが好ましい。
【００８１】
さらに上記各特性のバランスを考慮すると、粉体塗料の平均粒径は、上記範囲内でもとくに５〜２０μｍであるのがとくに好ましい。
粉体塗料には、その流動性や帯電特性などを向上するとともに、前述したように、各色の粉体塗料ごとに帯電特性を揃えるために、各種の外添剤を添加してもよい。
【００８２】
上記外添剤としては、酸化アルミニウム、酸化けい素、酸化チタニウム、酸化亜鉛などの金属酸化物の微粉末や、あるいはふっ素樹脂微粒子などの、たとえば粒径１．０μｍ以下程度の、従来公知の種々の外添剤を使用でき、とくに疎水性または親水性のシリカ微粒子を含むシリカ系表面処理剤、たとえば超微粒子状無水シリカやコロイダルシリカなどが好適に使用される。
【００８３】
外添剤の添加量はとくに限定されず、従来と同程度でよい。具体的には、各色の、ドライブレンド前の粉体塗料１００重量部に対して、外添剤を、総量で０．１〜３．０重量部程度、添加するのが好ましいが、場合によっては、外添剤の添加量は、この範囲を外れてもよい。
（塗膜の形成）
上記本発明の調色方法にて調色された粉体塗料のうち透光性を有するものや淡色のものは、被塗物の色目にもよるが通常は、調色された粉体塗料の正確な色目を再現するために、隠蔽性の、とくに白色の下地塗膜を介装した上に、かかる透光性粉体塗料の層（上塗り塗膜）を形成するのが好ましい。
【００８４】
またその場合には、上記の下地塗膜を、安全性や環境に及ぼす影響などを考慮して、上塗り塗膜と同様に、粉体塗料にて形成するのが妥当である。
上記のように、ともに粉体塗料にて形成される下地塗膜と上塗り塗膜とを、被塗物上に積層する方法としては種々、考えられるが、製造工程の簡略化や生産ラインの省力化などを考慮すると、下地塗膜のもとになる粉体塗料と、上塗り塗膜のもとになる粉体塗料とをこの順に、被塗物上に静電付着させたのち、被塗物ごと加熱して一度に両塗膜を形成する方法（２コート１ベーク法）を採用するのが理想的である。
【００８５】
ただし、かかる２コート１ベーク法を実施するためには、接地された被塗物上に、下地塗膜のもとになる粉体塗料を、所定の極性に帯電させた状態で静電付着させた後、その上に、上塗り塗膜のもとになる粉体塗料を、上記と逆の極性に帯電させた状態で静電付着させる必要がある。両塗膜のもとになる粉体塗料を、ともに同極性に帯電させた場合には、膜厚が均一でむらのない上塗り塗膜を形成できないからである。
【００８６】
たとえば粉体スプレーガンを用いる場合は、後述する実施例に記載されているように、下地塗膜のもとになる粉体塗料を、摩擦帯電ガンを用いて正に帯電させた状態で、被塗物上に静電付着させ、ついでその上に、上塗り塗膜のもとになる、調色された粉体塗料を、コロナ帯電ガンを用いて負に帯電させた状態で、被塗物上に静電付着させるのがよい。
【００８７】
なお、上記下地塗膜のもとになる粉体塗料は、たとえば酸化チタンなどの無機顔料を含有しているのが好ましい。無機顔料を含有した粉体塗料を使用すると、積層された塗装塗膜全体の耐衝撃性や耐薬品性、とくに耐アルカリ性が向上するという利点がある。
【００８８】
【実施例】
《粉体塗料の調製》
〈シアン（Ｃ）系透光性粉体塗料〉
以下の各成分をヘンシェルミキサーで混合し、二軸混練機で溶融、混練したのち、ジェットミルを用いて粉砕し、気流分級機で分級して、体積中心粒径１３μｍの、シアン系透光性粉体塗料を製造した。

製造したシアン系透光性粉体塗料はつぎに、当該粉体塗料１００重量部に対して０．４重量部の、負帯電用の表面処理剤としての微粉末シリカ〔日本アエロジル（株）製の商品名Ｒ９７２〕を、回転翼式のミキサー〔ＷＡＲＩＮＧ（ワリング）社製の商品名ＣＯＭＭＥＲＣＩＡＬ ＢＬＥＮＤＥＲ ＨＧＢ−ＳＳ〕を用いてかく拌混合して、調色に供した。
〈マゼンタ（Ｍ）系透光性粉体塗料〉
顔料として、Ｃ．Ｉ．ピグメントブルー１５：３に代えて、同量（３．０重量部）のＣ．Ｉ．ピグメントレッド１２２〔大日本インキ（株）製の商品名ＫｅｔＲｅｄ３０９〕を使用したこと以外はシアン系透光性粉体塗料と同様にして、体積中心粒径１３μｍの、マゼンタ系透光性粉体塗料を製造し、当該粉体塗料１００重量部に対して０．４重量部の微粉末シリカ〔前出のＲ９７２〕を、これも前出の回転翼式のミキサーを用いてかく拌混合して、調色に供した。
〈イエロー（Ｙ）系透光性粉体塗料〉
顔料として、Ｃ．Ｉ．ピグメントブルー１５：３に代えて、同量（３．０重量部）のＣ．Ｉ．ピグメントイエロー１５４〔チバガイギー社製の商品名Ｓｙｍｕｌｅｒ Ｆａｓｔ Ｙｅｌｌｏｗ４１９２〕を使用したこと以外はシアン系透光性粉体塗料と同様にして、体積中心粒径１３μｍの、イエロー系透光性粉体塗料を製造し、当該粉体塗料１００重量部に対して０．４重量部の微粉末シリカ〔前出のＲ９７２〕を、これも前出の回転翼式のミキサーを用いてかく拌混合して、調色に供した。
〈レッド（Ｒ）系透光性粉体塗料〉
顔料として、Ｃ．Ｉ．ピグメントブルー１５：３に代えて、同量（３．０重量部）のＣ．Ｉ．ピグメントレッド１７０〔山陽色素（株）製の商品名Ｂｒｉｌｌｉａｎｔ Ｃａｒｍｉｎｅ７００９〕を使用したこと以外はシアン系透光性粉体塗料と同様にして、体積中心粒径１３μｍの、レッド系透光性粉体塗料を製造し、当該粉体塗料１００重量部に対して０．４重量部の微粉末シリカ〔前出のＲ９７２〕を、これも前出の回転翼式のミキサーを用いてかく拌混合して、調色に供した。
〈クリア（Ｔ）系透光性粉体塗料〉
顔料を配合しなかったこと以外はシアン系透光性粉体塗料と同様にして、体積中心粒径１３μｍの、クリア系透光性粉体塗料を製造し、当該粉体塗料１００重量部に対して０．４重量部の微粉末シリカ〔前出のＲ９７２〕を、これも前出の回転翼式のミキサーを用いてかく拌混合して、調色に供した。
【００８９】
《調色例１》
上記粉体塗料の調製において製造した各色の粉体塗料のうちＣ、Ｍ、ＹおよびＴの４色の粉体塗料の帯電量（かく拌後３０秒の値、μＣ／ｇ）を、ブローオフ帯電量測定機を用いて測定したところ、下記表１に示す値となった。
【００９０】
【表１】

【００９１】
上記の測定結果より、帯電量の最大値Ｑ_ｍａｘ はシアンの粉体塗料の２３．８μＣ／ｇ、最小値Ｑ_ｍｉｎ はマゼンタの粉体塗料の１９．２μＣ／ｇ、両者の差ΔＱは４．６μＣ／ｇであり、このΔＱの値は、上記最大値Ｑ_ｍａｘ の２０％、つまり４．７６μＣ／ｇ未満であって、前記式を満たしていることが確認された。
そこで上記各粉体塗料を、下記表２に示す配合比（重量％）で配合し、混合装置としての回転翼式のミキサー〔前出のＷＡＲＩＮＧ社製のもの〕に供給して２５秒間、ドライブレンドした。
【００９２】
【表２】

【００９３】
なお上記の配合比は、目標色として、東洋インキ株式会社製のカラーカードのうちＣＦ０４６１（紫色）を用いて、先に説明した自動調色システムによって導き出し、ついでその結果に基づいて自動的に計量された値である。
《調色例２》
比較のために、マゼンタの粉体塗料として、微粉末シリカの添加量を調整して、帯電量を１８．１μＣ／ｇとしたものを他の粉体塗料と組み合わせて、上記と同じ配合比で、同条件でドライブレンドしたものを調色例２とした。
【００９４】
かかる調色例２は、帯電量の最大値Ｑ_ｍａｘ がシアンの粉体塗料の２３．８μＣ／ｇ、最小値Ｑ_ｍｉｎ がマゼンタの粉体塗料の１８．１μＣ／ｇ、両者の差ΔＱが５．７μＣ／ｇであって、このΔＱの値が、上記最大値Ｑ_ｍａｘ の２０％、つまり４．７６μＣ／ｇ以上である、前記式を満たしていない従来の配合に相当するものである。
【００９５】
《調色例３》
これも比較のために、シアンの粉体塗料として、微粉末シリカの添加量を調整して、帯電量を２５．３μＣ／ｇとしたものを他の粉体塗料と組み合わせて、上記と同じ配合比で、同条件でドライブレンドしたものを調色例３とした。
かかる調色例３は、帯電量の最大値Ｑ_ｍａｘ がシアンの粉体塗料の２５．３μＣ／ｇ、最小値Ｑ_ｍｉｎ がマゼンタの粉体塗料の１９．２μＣ／ｇ、両者の差ΔＱが６．１μＣ／ｇであって、このΔＱの値が、上記最大値Ｑ_ｍａｘ の２０％、つまり５．０６μＣ／ｇ以上である、やはり前記式を満たしていない従来の配合に相当するものである。
【００９６】
《塗膜の形成》
つぎに、上記で調色された３種の粉体塗料をそれぞれ、被塗物としてのＳＰＣＣ鋼板（縦１５０ｍｍ、横７０ｍｍ、厚み４０．８ｍｍ）の片面に先に、下記Ｉの条件で白色の粉体塗料を静電付着させた上に、下記ＩＩの条件で静電付着させ、ついで１８０℃で２０分間、焼き付けて、厚み３０〜３５μｍの白色下地層と、各粉体塗料からなる、厚み３０〜３５μｍの着色上塗層の２層構造を有する、トータルの厚み６５μｍの塗膜を作製した。
〈条件Ｉ（白色下地層の塗装）〉
・粉体供給：定量供給機〔三田工業（株）製の試作機〕、回転数＝３８０ｒ．ｐ．ｍ．、スクレーパー角度＝目盛り１
・被塗物搬送速度：５０ｍｍ／秒
・塗装機：バーカライジング社製、ＩＮＦ圧力＝３ｋｇ／ｃｍ^２ Ｇ、旋回圧力＝３ｋｇ／ｃｍ^２ Ｇ、搬送圧力＝３ｋｇ／ｃｍ^２ Ｇ
・ガン：摩擦帯電ガン、ノズル＝扇形
・ブース吸引風速：０．５９ｍ／秒
・塗装距離：３００ｍｍ
・ＳＰＣＣ鋼板への付着量：０．７ｇ
〈条件ＩＩ（着色上塗層の塗装）〉
・粉体供給：同上
・被塗物搬送速度：同上
・塗装機：同上
・ガン：コロナ帯電ガン、印加電圧＝−６０ｋＶ
・ブース吸引風速：同上
・塗装距離：同上
・ＳＰＣＣ鋼板への付着量：０．５ｇ
なお、白色下地層用の白色の粉体塗料としては、下記のものを使用した。
〈白色粉体塗料〉
顔料として、Ｃ．Ｉ．ピグメントブルー１５：３に代えて、３０重量部の酸化チタン〔石原テクノ（株）製の商品名ＣＲ−９０〕を使用し、かつ粉砕後に分級しなかったこと以外はシアン系透光性粉体塗料（Ｉ） と同様にして、体積中心粒径１７μｍの、白色粉体塗料を製造した。なお白色粉体塗料は、表面処理を施さずに、下地用に供した。
【００９７】
《調色の評価》
つぎに各塗膜を、前記分光光度計〔クラボウ（倉敷紡績株式会社）製のＸ−Ｒｉｔｅ ＳＰ６８〕を用いて測色して、その測色データの、目標色としての前記カラーカードの測色データとの色差ΔΕ^＊ を算出し、当該色差ΔΕ^＊ がしきい値０．８以下であったものを色目のずれなし（○）、０．８を超えたものを色目のずれあり（×）として評価した。
【００９８】
また、各塗膜を目視にて観察して、色の偏析、まだら感、濃淡などの不良の有無を観察した。判定方法としては、塗膜を２０ｃｍの位置から観察しても色の偏析、まだら感、濃淡などが見えないものを良好（○）、塗膜を４０ｃｍの位置から観察して上記の不良がはっきり見て取れるものを不良（×）、両者の中間、すなわち上記の不良が、塗膜を４０ｃｍの位置から観察したのでは見えないが、２０ｃｍの位置から観察すると見えるものはやや不良（△）とした。
【００９９】
結果を表３に示す。
【０１００】
【表３】

【０１０１】
表より、調色に使用する各色の粉体塗料の帯電量を、前記特定の範囲内に揃えることによって、色の偏析、まだら感、濃淡などの不良のない、ほぼ均一な色目を有する塗膜を形成できることが判った。
【０１０２】
【発明の効果】
以上、詳述したように本発明によれば、複数色の粉体塗料をドライブレンドしているにもかかわらず、色の偏析、まだら感、濃淡などの不良のない、ほぼ均一な色目を有する塗膜を形成することのできる、新規な粉体塗料の調色方法を提供できるという特有の作用効果を奏する。
【図面の簡単な説明】
【図１】本発明の調色方法の一例の、各工程を示す流れ図である。
【図２】上記調色方法のうち、あらかじめ、使用する複数色の粉体塗料の個々について測色した複数の基礎データから、計算反射率および３刺激値を算出する工程を示す流れ図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a toning method for toning by blending powder paints of a plurality of colors.
[0002]
[Prior art]
2. Description of the Related Art In recent years, powder coatings that use air as a medium without using a solvent, have high safety, and have little effect on the environment, are becoming widespread in the field of home appliances and the like. In general, a powder coating is produced by blending a colorant and other additives in a binder resin that forms a powder, melt-kneading, pulverizing, and classifying.
[0003]
Then, the powder coating charged to a certain polarity by, for example, friction or corona discharge, was electrostatically adhered to the surface of the grounded article and then heated and melted, or floated and flowed in an air stream. By inserting the preheated object to be coated into the powder coating, and melting and flowing the powder coating on the surface of the object using the preheating, the surface of the object is coated. To form a continuous coating film.
[0004]
[Problems to be solved by the invention]
However, powder coatings are becoming widespread in so-called large-lot coatings that consume large quantities of coatings of the same color, such as the home appliances mentioned above, but small-sized coatings that require small amounts of multicolored coatings are needed. In the field of painting lots or in the field of painting where fine adjustment of color is required after toning, the diffusion rate is low and the current situation is that it does not reach the level of conventional solvent-based paints.
[0005]
One of the causes is that the conventional method for producing a powder coating is not suitable for the production of a small lot, and the color tone cannot be easily adjusted unlike the conventional solvent-based coating.
That is, a conventional powder coating is prepared by adding a coloring agent toned to a target color to a binder resin which is a base of the powder, so that the color is adjusted to a predetermined color in advance. Manufactured in.
[0006]
For this reason, conventional powder coatings are suitable for painting large lots that require a large amount of paint of the same color, but only a small amount of paint of a given color is required. In other words, it is not suitable because it cannot be turned around, and the color cannot be easily adjusted.
Therefore, in order to solve such a problem and to easily cope with painting of a small lot and fine adjustment of color, so-called three primary colors of cyan (C), magenta (M), and yellow (Y), for example. A multi-color powder coating, especially a translucent powder coating that is colored in each color, is blended according to the target color, and a mixing device such as a rotary blade mixer is used. Dry blending, and toning a powder paint having a predetermined color tone by mixing colors.
[0007]
However, when the above-mentioned toning method is actually carried out, there is a problem that defects such as color segregation, mottle, and shading easily occur in a coating film formed using the powder coating after toning. Was.
An object of the present invention is to form a coating film having a substantially uniform tint without defects such as color segregation, mottle, and shading despite dry blending a plurality of color powder coatings. It is an object of the present invention to provide a new method of toning a powder coating material.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the inventors first studied the causes of the above-described various defects in the coating film.
As a result, conventionally, when dry-blending powder paints of a plurality of colors, there is a large variation in the charge amount of each powder paint. When the body paint is flowed to be supplied to the coating machine, for example, agglomeration of the powder paint of each color with different charge amount occurs, and this agglomerate causes the granularity of the formed coating film to be noticeable. They were found to be large enough to be visible, and to cause defects such as color segregation, mottle, and shading.
[0009]
Therefore, in order to solve such a problem, as a result of examining that the amount of charge of the powder coating of each color is adjusted within a certain range before toning by dry blending, as a result, each color before the toning was examined. Maximum value Q of charge amount of powder coating_maxAnd the minimum value Q_minΔQ (= Q_max−Q_min) Is the following formula:
[0010]
(Equation 2)
ΔQ <| Q_max| × 0.20
If the charge amount of each color powder paint is adjusted in advance so as to satisfy, the aggregation of each color powder paint described above and the accompanying color segregation in the coating film, mottle, shading, etc. It has been found that the occurrence of defects can be reliably prevented, and the present invention has been completed.
[0011]
Therefore, the method for toning a powder coating of the present invention is as follows.ColoredMulti-color, TranslucentPowder paintAnd a colorless and transparent powder paint containing no colorantAre blended at a predetermined ratio, and when a dry blend is performed using a mixing device to perform toning, the maximum value Q of the charge amount of the powder coating of each color before toning is adjusted._maxAnd the minimum value Q_minΔQ (= Q_max−Q_min) Is characterized in that the charge amount of each color powder coating material is adjusted in advance so as to satisfy the above expression.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described.
The powder coating used in the toning method of the present invention includes, for example, magenta (C), magenta (M), and yellow (Y) described above, and in particular, magenta ( Three colors of cyan (C), red (R) and yellow (Y) to which red (R) is added instead of M)ToAnd colorless and transparent (clear, T) plus C, M, Y, T or C, R, Y, T, or these four colors to reproduce the color gradation even more finely C, LC, and M to which two colors of light cyan (LC) and light magenta (LM), or two colors of light cyan (LC) and light red (LR) are added, in order to eliminate granularity in the coating film. , LM, Y, T or C, LC, R, LR, Y, T, etc., in a plurality of colors, and a plurality of translucent powder paints in advance.
[0013]
Among the above-mentioned colored translucent powder coatings, for example, a transparent binder resin, a coloring agent such as a pigment, and other additives as necessary, using a dry blender, a Henschel mixer, a ball mill, etc. The mixture thus preliminarily mixed is melt-kneaded using, for example, a jet mill, a Banbury mixer, a roll, a single-screw or twin-screw extrusion kneader, and the obtained kneaded material is cooled and pulverized. It is manufactured by classification.
[0014]
The clear (T) powder coating is produced in the same manner as described above except that no coloring agent is added.
Each of the above powder coatings is compatible with each other in consideration of the ease of dry blending, or the fact that when baking to form a coating film, it is necessary to consider melting and integrating uniformly to form a continuous and uniform coating film. It is preferably formed of an excellent binder resin, and more preferably formed of the same binder resin.
[0015]
In the present invention, the charge amount of the powder paint of each color including clear is set to the maximum value Q as described above._max(Electric charge value of powder paint of each color having the largest charge amount) and minimum value Q_minΔQ (= Q) from (the charge amount value of the smallest charge amount among the powder paints of each color)_max−Q_min) Has the formula:
[0016]
(Equation 3)
ΔQ <| Q_max| × 0.20
That is, the maximum value Q of the charge amount_maxBefore the dry blending and toning, it is necessary to make them equal to less than 20% of the absolute value of.
When the difference ΔQ is out of the above range, the charge amounts of the powder paints of the respective colors vary greatly, and the powder paints of the different colors have different charge amounts as described above in the powder paint after toning. Coagulation occurs, and accordingly, defects such as color segregation, mottle, and shading occur in the coating film.
[0017]
In addition, as described above, in order to make the charge amount of the powder coating of each color before toning uniform, for example, among the other additives blended in the powder coating described above, the type of the charge control agent described later and The blending amount may be adjusted, or a particulate external additive having a charge amount adjusting function may be added to each of the powder coatings of each color before the toning by dry blending.
[0018]
Among these, for example, as an external additive used in a powder coating for negative charging using a corona charging gun, which is one type of the electrostatic adhesion method, fine particles which also function as a fluidizing agent for the powder coating are used. A silica-based surface treatment agent in the form of a gel is preferably used.
As described above, the method for toning a powder coating according to the present invention using the powder coatings of the respective colors having the same charge amount as described above is performed manually by relying on the knowledge, experience, and intuition of the operator. For example, as shown in FIG. 1, an automatic toning system for powder coating is used which automatically performs from the color measurement of the target color of the toning to the preparation and toning of the powder coating of each color. It is preferable to carry out.
[0019]
According to such an automatic toning system, internal factors such as a worker's skill level, a health state, a psychological state, and the like, or a type of a toned color (for example, a very light color) ), There is an advantage that there is no possibility that the toning result will vary due to external factors such as environmental conditions (season, weather, time, light state, etc.) at the time of work.
[0020]
In this automatic toning system, first, a color sample of a target color is measured using a colorimetric device such as a spectrophotometer [Step S1].
Next, a wavelength-reflectance curve is created from the result of the color measurement [Step S2]. Then, based on the Kubelka-Munk's law, the light of the light at the wavelength at regular intervals (for example, every 20 nm) is obtained. A K / S value, which is a ratio between the absorption coefficient K and the scattering coefficient S, is calculated [Step S3].
[0021]
Next, as shown in FIG. 2, the K / S value is adjusted in advance with respect to each of the powder coatings of a plurality of colors to be used by adjusting the mixing ratio of the powder coatings to the clear powder coating. K / S value [(K / S) of a plurality of basic data 1 to n measured by changing the color density of₁~ (K / S)_nIs calculated using the calculated reflectance, and the spectral reflectance curves are matched [Step S4]. Then, the result of the isometric match and the tristimulus value calculated from the calculated reflectance are calculated. Then, the mixing ratio of the powder paint of each color is calculated by performing a metameric match using the above to match the three stimulus values [Step S5].
[0022]
Next, based on the calculation results, the powder coating materials of each color are measured using a measuring device [Step S6], and supplied to a mixing device to dry blend [Step S7].
Then, the dry-blended powder coating material was subjected to test coating under the same conditions as the actual coating (step S8), and then colorimetrically measured using the colorimeter, and the colorimetric data was measured first. The presence or absence of a color shift is determined by comparing with the colorimetric data of the target color [Step S9].
[0023]
If there is a color shift in this determination, the blending ratio of the powder paint of each color is corrected and calculated based on the two colorimetric data [Step S10], and based on the result, Step S6 is performed again. To S9 are repeated.
Then, in the determination of step S9, when the color shift between the coating film and the target color is eliminated, the toning of the powder paint is completed.
[0024]
As a criterion for determining the presence or absence of a color shift in step S9, for example, the color difference ΔΕ between the colorimetric data of the target color and the colorimetric data of the coating film is used.^*Is adopted. Specifically, for example, the color difference ΔΕ between the colorimetric data of the target color and the colorimetric data of the coating film^*However, it may be determined that there is no color shift when the threshold value is equal to or less than a preset threshold value, and that the color difference is higher when the threshold value is exceeded. The threshold value is not limited to this, but may be ΔΕ^*= 0.8 is preferable.
[0025]
In addition, if the dry blending is insufficient in the dry blending step of step S7 in the above-described toning method, the aggregates of the powder paint for each color are not sufficiently disintegrated. In addition, when the dry blend is excessive, since the agglomeration of the powder coating occurs on the contrary, the granularity of the coating film becomes remarkably large in each case, and the present invention is carried out. Despite this, defects such as color segregation, mottle and shading may occur.
[0026]
Therefore, it is necessary to set the optimal time of the dry blending, and the color difference ΔΕ^*Is preferably adopted.
That is,
(I) A powder paint sample to be used for toning is dry-blended using a mixing device in advance of the toning, and the hue in the powder state of the sample in the middle is measured by a colorimeter. The color difference between the latest colorimetric value and the previous colorimetric value^*Of the dry blending required for the value to become equal to or less than the threshold value (preferably 0.8 or less), and based on the data, set the actual dry blending time of the powder coating. Or
(Ii) The actual color paint in the middle of dry blending is sampled at regular intervals using a mixing device, and the hue in the powder state is measured using a color measurement device to obtain the latest color measurement. Color difference Δ 値 between the value and its previous colorimetric value^*Dry blending ends when the value falls below the threshold (preferably 0.8 or less)
As a result, it is possible to produce a dry-blended powder coating material which is free from defects such as color segregation, mottle and shading.
[0027]
Examples of each component constituting the powder coating of a plurality of colors including clear used in the toning method of the present invention include, but are not limited to, the following materials.
(Binder resin)
As the binder resin, among various conventionally known resins used in powder coatings, in order to impart light transmission to the powder coating, it is excellent in light transmission, and when applied to an object to be coated or Any of various resins that can be melted by heating after coating to form a continuous coating film can be used.
[0028]
Examples of such a binder resin include, but are not limited to,
Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer ), Methyl methacrylate copolymer styrene -α- chloromethyl acrylate, styrene - acrylonitrile - homopolymers or copolymers containing styrene resin (styrene or styrene substitution products, such as acrylic acid ester copolymer),
Acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenyl methacrylate, α-methyl methyl acrylate Acrylic resin (homopolymer or copolymer mainly composed of (meth) acrylic acid and its ester),
Polyvinyl chloride, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-ethyl acrylate copolymer, polyvinyl butyral, ethylene-vinyl acetate copolymer, polyester resin, epoxy resin, silicone resin, and the like, these alone, Alternatively, two or more kinds are used in combination.
[0029]
Among the above, particularly preferred binder resins include styrene-based resins, acrylic resins, and polyester resins.
(I) General formula (1):
[0030]
Embedded image

[0031]
[Wherein, R¹And R²Represents the same or different lower alkylene groups. x and y are the same or different and each represents 0 or an integer of 1 or more, and x + y is 1 to 7. ]
A diol component represented by
(Ii) a dicarboxylic acid, its anhydride or lower alkyl ester,
(Iii) Trivalent or higher polyhydric carboxylic acid, its anhydride or lower alkyl ester, or trivalent or higher polyhydric alcohol
And a polyester resin having a ratio of a hydroxyl value (OHV) to an acid value (AV) of OHV / AV of 1.2 or more is a preferred binder resin.
[0032]
In the above polyester resin, R in the general formula (1)¹And R²Examples of the lower alkylene group corresponding to are alkylene groups having 1 to 6 carbon atoms such as methylene, ethylene, trimethylene, propylene, tetramethylene, ethylethylene, pentamethylene, and hexamethylene.
X + y in the general formula (1) is 1 to 7, as described above, and preferably 3 to 5. When x + y exceeds 7, there is a problem that the molecular weight of the diol component becomes too large and the light transmittance of the coating film is reduced.
[0033]
Examples of the diol component represented by the general formula (1) include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (3.3) -2,2- Bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2) -polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (6.0) -2,2-bis (4-hydroxyphenyl) propane.
[0034]
Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, itaconic acid, glutaconic acid, adipic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, phthalic acid, and isophthalic acid. Acid, terephthalic acid and the like. These dicarboxylic acids may be esters with acid anhydrides or lower alkyls. Examples of the lower alkyl include an alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, s-butyl, t-butyl, n-pentyl and n-hexyl. can give.
[0035]
Trivalent or higher polycarboxylic acids, their anhydrides or lower alkyl esters, and trivalent or higher polyhydric alcohols adjust the acid value and hydroxyl value of the polyester resin and make the polyester resin branched. It is blended for the purpose. Examples of the trivalent or higher polycarboxylic acid, its anhydride or lower alkyl ester include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4- Butanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methoxycarbonylpropane, tetra (methoxycarbonyl) methane, 1,2,7,8-octanetetracarboxylic acid and the like.
[0036]
Examples of the trihydric or higher polyhydric alcohol include glycerin, 2-methyl-1,2,3-propanetriol, 1,2,4-butanetriol, 2-methyl-1,2,4-butanetriol, Examples thereof include 2,5-pentatriol, pentaerythritol, dipentaerythritol, tripentaerythritol, hexitol, sorbitol, 1,4-sorbitan, and 1,2,4-benzenetriol.
[0037]
The polyester resin is synthesized by copolycondensation of the above-mentioned components at a temperature of 180 to 250 ° C. in an inert gas atmosphere, for example.
The ratio of the hydroxyl value (OHV) to the acid value (AV) of the polyester resin, OHV / AV, is 1.2 or more, preferably 1.2 to 50, and more preferably 2 to 40. When the value of OHV / AV is less than 1.2, the light transmittance of the resin is lowered, the minimum melting temperature of the resin is increased, and it is not easy to form a continuous coating film by heating and melting, or There is a problem that the fluidity of the powder coating material is reduced.
[0038]
The acid value (AV) is calculated, for example, by dissolving a polyester resin in a benzene-ethanol mixed solvent, titrating with potassium hydroxide, and calculating the neutralization amount. The hydroxyl value (OHV) is determined by, for example, acetylating a free acid in a polyester resin using a mixed solvent of pyridine and acetic anhydride (3.1: 1), and then titrating acetic acid bound to the resin with potassium hydroxide. It is calculated from the neutralization amount by titration.
[0039]
The above-mentioned polyester resin can be used alone, or may be blended with various previously known resins. When blending another resin, the blending amount is preferably about 1 to 30% by weight based on the polyester resin.
(Colorant)
As the cyan (C) colorant, a phthalocyanine pigment is particularly preferably used. Specific examples of such a phthalocyanine pigment include, for example, a compound represented by the following general formula (2):
[0040]
Embedded image

[0041]
[Where X¹, X², X³And X⁴Are the same or different and represent a hydrogen atom, a group (2a) or a group (2b):
[0042]
Embedded image

[0043]
Is shown. R³And R⁴Is an alkylene group having 1 to 5 carbon atoms. ]
Copper phthalocyanine pigments represented by, for example, C.I. I. Pigment Blue 15 (15: 1 to 15: 4, X¹, X², X³And X⁴Are all hydrogen atoms) and derivatives thereof, or formula (3):
[0044]
Embedded image

[0045]
And a metal-free phthalocyanine-based pigment (CI Pigment Blue 16). The above C.I. I. Examples of the derivatives of Pigment Blue 15 include partially chlorinated products thereof, and barium salts of sulfonic acids of copper phthalocyanine (CI Pigment Blue 17).
Examples of other cyan-based coloring agents other than the above include inorganic pigments such as navy blue (Prussian blue) and cobalt blue; I. Pigment Blue 18, C.I. I. Organic pigments such as CI Pigment Blue 16; I. Bat Blue 6, C.I. I. Dyes such as Solvent Blue 70;
[0046]
The amount of the cyan-based coloring agent is 100 parts by weight of the binder resin in the case of the cyan (C) powder coating, considering that a vivid color tone is obtained and that the light transmittance of the powder coating does not decrease. It is preferably about 1 to 20 parts by weight, especially about 2 to 8 parts by weight. In the case of a light cyan (LC) powder coating, the binder resin may vary depending on the color density of the cyan powder coating to be combined in consideration of the above-described improvement in color gradation and elimination of granularity. It is preferably about 0.1 to 2.5 parts by weight, particularly about 0.5 to 2.0 parts by weight, per 100 parts by weight.
[0047]
As the magenta (M) colorant, for example, a quinacridone pigment is used. Specific examples of such a quinacridone pigment include, for example, a compound represented by the following general formula (4):
[0048]
Embedded image

[0049]
[Where Q¹And Q²Represents the same or different and represents a hydrogen atom, an alkyl group or an alkoxy group. But Q¹, Q²Are not simultaneously hydrogen atoms. ]
Quinacridone pigments such as C.I. I. Pigment Red 122 [Q¹And Q²Are both methyl groups].
Other magenta-based coloring agents other than those described above include inorganic pigments such as redwood, cadmium red, leadtan, cadmium mercury sulfide, manganese purple, red-mouthed graphite, and molybdenum orange. I. Pigment Red 3, C.I. I. Pigment Red 38, C.I. I. Pigment Red 48: 2, C.I. I. Pigment Red 49: 1, C.I. I. Pigment Red 49: 2, C.I. I. Pigment Red 50, C.I. I. Pigment Red 57, C.I. I. Pigment Red 60, C.I. I. Pigment Red 81, C.I. I. Pigment Red 90, Permanent Red FNG, C.I. I. Pigment Violet 3, C.I. I. Pigment Violet 25, C.I. I. Pigment Orange 5, C.I. I. Pigment Orange 13, C.I. I. Organic pigments such as CI Pigment Orange 16, dyes such as Spiron Red, Indanthrene Brilliant Orange RK, and Indanthrene Brilliant Orange GK.
[0050]
The amount of the magenta-based coloring agent is set to 100% by weight of the binder resin in the case of the magenta (M) powder coating, considering that a clear color is obtained and the light transmittance of the powder coating does not decrease. The amount is preferably about 1 to 20 parts by weight, particularly about 2 to 8 parts by weight based on parts. In the case of a light magenta (LM) powder coating, the binding depends on the color density of the magenta powder coating to be combined in consideration of the above-described improvement of the color gradation and elimination of the granularity. It is preferably about 0.1 to 2.5 parts by weight, particularly about 0.5 to 2.0 parts by weight, based on 100 parts by weight of the resin.
[0051]
Examples of yellow (Y) colorants include condensed azo pigments, isoindoline pigments, and benzimidazolone pigments.
Among them, the condensed azo pigment is represented by the general formula (5):
[0052]
Embedded image

[0053]
[Wherein, R⁵And R⁶Represents the same or different alkyl groups or halogen atoms;⁷And R⁸Are the same or different groups (5a) or (5b):
[0054]
Embedded image

[0055]
Is shown. ]
A compound represented by, for example, C.I. I. Pigment Yellow 93 [R⁵Is a methyl group, R⁶Is a chlorine atom, R⁷And R⁸Are both groups (5a)], C.I. I. Pigment Yellow 94 [R⁵And R⁶Are both chlorine atoms, R⁷And R⁸Is a group (5b), and C.I. I. Pigment Yellow 95 [R⁵And R⁶Are both methyl groups, R⁷And R⁸Wherein both are groups (5b).
[0056]
As the isoindoline pigment, for example, a compound represented by the following general formula (6)
[0057]
Embedded image

[0058]
Wherein Ar is a group (6a) or (6b):
[0059]
Embedded image

[0060]
Is shown. ]
A compound represented by, for example, C.I. I. Pigment Yellow 109 [compound wherein Ar is group (6a)], C.I. I. Pigment Yellow 110 (compound in which Ar is group (6b)).
Further, as a benzimidazolone pigment, a compound represented by the formula (7):
[0061]
Embedded image

[0062]
(CI Pigment Yellow 154) and the like.
Other yellow-based colorants other than those described above include, for example, inorganic pigments such as yellow iron oxide, loess, graphite, zinc yellow, cadmium yellow, and antimony yellow; I. Pigment Yellow 1, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 17, C.I. I. Pigment yellow 55, C.I. I. Pigment Yellow 65, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 83, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 98, C.I. I. Pigment yellow 115, C.I. I. Pigment Yellow 130, C.I. I. Pigment yellow 133, C.I. I. Pigment yellow 138, C.I. I. Organic pigments such as C.I. Pigment Yellow 169; I. Solvent Yellow 16, C.I. I. Solvent Yellow 33, C.I. I. Solvent Yellow 56, C.I. I. Solvent Yellow 60, C.I. I. Solvent Yellow 61, C.I. I. Solvent Yellow 162, C.I. I. Acid Yellow 1, C.I. I. Dyes such as Acid Yellow 23;
[0063]
The mixing amount of the yellow colorant is about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin, considering that a clear color is obtained and the light transmittance of the powder coating is not reduced. It is particularly preferred that the amount is about 1.5 to 8 parts by weight.
As the red (R) -based coloring agent, for example, a naphthol-based pigment is used. As a specific example of such a naphthol-based pigment, for example, a general formula (8):
[0064]
Embedded image

[0065]
(CI Pigment Red 170) and the like.
Other red-based coloring agents other than the above include, for example, C.I. I. Pigment Red 5, C.I. I. Pigment Red 146, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 202, C.I. I. Pigment Red 238, C.I. I. Pigment Red 251, C.I. I. Pigment red 254, C.I. I. Pigment Red 255, C.I. I. And organic pigments such as CI Pigment Red 264.
[0066]
The mixing amount of the red-based colorant is 100% by weight of the binder resin in the case of a red (R) powder coating, considering that a clear color is obtained and the light transmittance of the powder coating is not reduced. The amount is preferably about 1 to 20 parts by weight, particularly about 2 to 8 parts by weight based on parts. In the case of the light red (LR) powder coating, the binding depends on the color density of the red powder coating to be combined in consideration of the above-mentioned improvement of the color gradation and elimination of the granularity. It is preferably about 0.1 to 2.5 parts by weight, particularly about 0.5 to 2.0 parts by weight, based on 100 parts by weight of the resin.
[0067]
The clear (T) powder coating is produced without adding the above-mentioned coloring agent.
(Other additives)
Examples of the additives other than the colorant include various kinds of conventionally known additives such as a curing agent and a leveling agent (flowing agent) in addition to the charge control agent described above.
Of these, the charge control agent is used when the powder coating is used in, for example, the above-described coating method by electrostatic adhesion, for example, the electrostatic coating method using a spray gun, or the electrostatic flow immersion method. And to stabilize regardless of changes in environmental conditions such as temperature and humidity, and to make the charging characteristics uniform for each color powder coating as described above, according to the charging polarity of the powder coating. One of a positive charge control agent and a negative charge control agent is used.
[0068]
Examples of the positive charge control agent include a nigrosine-based electron donating dye, a metal salt of naphthenic acid or a higher fatty acid, an alkoxylated amine, a quaternary ammonium salt, an alkylamide, a chelate, a pigment, a fluorinated activator, and the like. Is raised.
Examples of the charge control agent for controlling negative charges include electron-accepting organic complexes, chlorinated paraffins, chlorinated polyesters, polyesters having an excess of acid groups, sulfonylamine of copper phthalocyanine, aromatic oxycarboxylic acids, and aromatic dicarboxylic acids. Acids and the like.
[0069]
However, in the case of translucent powder coatings, in order not to affect the color as much as possible,
(A) itself is colorless or pale, and
(B) Excellent compatibility with the binder resin so that the powder coating does not become cloudy, or excellent compatibility with the binder resin but excellent dispersibility
Charge control agents are preferably used.
[0070]
Among the above, quaternary ammonium salts can be mentioned as the positive charge control agent satisfying the above conditions, and aromatic oxycarboxylic acids and aromatic dicarboxylic acids can be mentioned as the negative charge control agents.
Among the above, the quaternary ammonium salt which is a positive charge control agent includes various compounds, and in particular, the compound represented by the general formula (9):
[0071]
Embedded image

[0072]
[Wherein, R^a, R^b, R^cAnd R^dRepresents the same or different and is a lower alkyl group, a long-chain alkyl group, a long-chain alkenyl group or a benzyl group;⁻Represents an anion. Where R^a~ R^dIs at least one long-chain alkyl group or long-chain alkenyl group, and two are lower alkyl groups or benzyl groups. ]
The compound represented by is preferably used.
[0073]
In the above general formula (9), R^a~ R^dExamples of the long-chain alkyl group corresponding to are octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, eicosyl group, docosyl group, oleyl group, linolyl group, and hexadecesyl group. Examples of the long-chain alkenyl group include groups in which one or more double bonds have been introduced into the molecule of the long-chain alkyl group.
[0074]
A⁻Examples of the anion represented by are molybdic acid, phosphomolybdic acid, silicomolybdic acid, chromium molybdic acid, bromomolybdic acid, tungstic acid, phosphotungstic acid, silicotungstic acid, chromium tungstate, bromotungsten Acids, anions derived from molybdenum atoms such as phosphotungsten / molybdic acid, silicotungsten / molybdic acid and inorganic acids containing tungsten atoms, chloride ions, bromine ions, iodine ions, nitrate ions, sulfate ions, perchlorate ions Benzoate ion, tetraphenyl boron ion, hexafluorophosphate ion, naphthol sulfonate ion and the like.
[0075]
Specific examples of the quaternary ammonium salt represented by the general formula (9) include, for example, (C₁₆H₃₃)₂N⁺(CH₃)₂・ 1/4 Mo₈O₂₆ ^4-, (C₁₆H₃₃)₂N⁺(CH₃)₂・ 1/6 Mo₇O₂₄ ^6-, (C₁₆H₃₃)₂N⁺(CH₃)₂・ 1/2 WO₄ ^2-And the like, and these can be used alone or in combination of two or more.
[0076]
The compounding amount of the charge control agent is preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the binder resin. If the amount of the charge control agent is less than the above range, the effect of adding the charge control agent may be insufficient.If the amount exceeds the above range, the light transmittance may decrease or the color may change. There is a possibility that. The curing agent is for curing the coating film by crosslinking the binder resin in the coating film when the powder coating is heated and melted to form a coating film. Examples thereof include blocked isocyanates, epoxy resins, amino resins, aziridine compounds, polycarboxylic acids and the like.
[0077]
A suitable range of the amount of the curing agent is set according to the equivalent of the functional group that contributes to the curing reaction. If the amount of the curing agent is less than the preferred range, the effect of the addition may be insufficient.If the amount exceeds the preferred range, on the other hand, the light transmittance is reduced or the color is changed. Or
The leveling agent is used to improve the fluidity of the powder coating when heated and melted, and to make the coating film smoother. Examples of the leveling agent include “Acronal 4F” (trade name, manufactured by BASF). "YF-3919" manufactured by Toshiba Silicone Co., Ltd. and "Modaflow 2000" manufactured by Monsanto.
[0078]
The blending amount of the leveling agent is preferably 0.1 to 2 parts by weight, more preferably 0.5 to 1 part by weight, based on 100 parts by weight of the binder resin. If the blending amount of the leveling agent is less than the above range, the effect of the addition may be insufficient.On the contrary, if it exceeds the above range, the light transmittance is reduced or the color is changed. There is a risk.
In addition to the above, other additives such as a curing accelerator for assisting a curing reaction by a curing agent, an antifoaming agent, or an epoxy resin for enhancing corrosion resistance of a coating film are also included in the powder coating. May be blended.
[0079]
(Production method of powder coating)
As described above, the powder coating is a pulverization method, that is, a mixture obtained by premixing the above components using a dry blender, a Henschel mixer, a ball mill, or the like, and then jet-milling, Banbury-mixer, roll, single-screw or twin-screw extrusion. After being melt-kneaded using a kneader or the like, the obtained kneaded material is cooled and pulverized, and is further manufactured by classifying as necessary, a polymerization method, a microcapsule polymerization method, a spray drying method, and the like. It can also be manufactured using.
[0080]
The particle size of the powder coating may be the same as the conventional one, but considering the uniformity of the color when two or more colors are mixed, the smaller the particle size is, the more preferable it is, especially the average particle size is 30 μm or less. Is preferred.
In consideration of the chargeability, the ease of forming a coating film, the difficulty of aggregation, and the like, the average particle size of the powder coating material is preferably 1 μm or more within the above range.
[0081]
Further, in consideration of the balance between the above properties, the average particle size of the powder coating is particularly preferably 5 to 20 μm within the above range.
Various external additives may be added to the powder coating in order to improve its fluidity and charging characteristics, and to make the charging characteristics uniform for each powder coating as described above.
[0082]
Examples of the external additives include fine particles of metal oxides such as aluminum oxide, silicon oxide, titanium oxide, and zinc oxide, and fine particles of fluorine resin, such as fine particles of fluorine resin, for example, having a particle diameter of about 1.0 μm or less. In particular, silica-based surface treating agents containing hydrophobic or hydrophilic silica fine particles, such as ultrafine anhydrous silica and colloidal silica, are preferably used.
[0083]
The amount of the external additive to be added is not particularly limited, and may be the same as in the related art. Specifically, it is preferable to add an external additive in a total amount of about 0.1 to 3.0 parts by weight to 100 parts by weight of the powder coating before dry blending for each color. The amount of the external additive may be out of this range.
(Formation of coating film)
Of the powder coatings toned by the toning method of the present invention, those having a light-transmitting property and light-colored ones usually depend on the color of the object to be coated. In order to reproduce an accurate color tone, it is preferable to form a layer of such a translucent powder coating (overcoating film) after interposing a hiding, particularly white undercoating film.
[0084]
In such a case, it is appropriate to form the undercoat film with a powder coating, like the overcoat film, in consideration of the influence on safety and the environment.
As described above, various methods are conceivable for laminating an undercoating film and an overcoating film, both formed of a powder coating, on an object to be coated. Taking into account, the powder paint that forms the base coat and the powder paint that forms the top coat are electrostatically deposited on the work in this order, and then the work is performed. Ideally, a method in which both coatings are formed at a time by heating together (two coats and one bake method) is ideal.
[0085]
However, in order to carry out the two-coat one-bake method, a powder coating, which is a base of a base coating film, is electrostatically adhered to a grounded object to be coated in a predetermined polarity. After that, it is necessary to electrostatically adhere a powder coating on which a top coat is to be formed in a state where the powder coating is charged in the opposite polarity to the above. This is because if both powder coatings are charged to have the same polarity, it is impossible to form an even coating film having a uniform thickness.
[0086]
For example, when a powder spray gun is used, as described in an example described later, the powder coating that forms the base coating film is charged positively using a triboelectric charging gun, and then coated. The toned powder coating, which is the basis of the overcoat film, is negatively charged using a corona charging gun, and then electrostatically adhered on the coating object. It is good to make it electrostatically adhere to.
[0087]
It is preferable that the powder coating used as the base coating film contains an inorganic pigment such as titanium oxide. The use of a powder coating containing an inorganic pigment has the advantage of improving the impact resistance and chemical resistance, particularly alkali resistance, of the entire laminated coating film.
[0088]
【Example】
<< Preparation of powder coating >>
<Cyan (C) -based translucent powder coating>
The following components were mixed with a Henschel mixer, melted and kneaded with a twin-screw kneader, pulverized using a jet mill, and classified with an airflow classifier to obtain a cyan translucent material having a volume center particle size of 13 μm. A powder coating was produced.

Next, 0.4 parts by weight of the produced cyan-based light-transmitting powder coating was used as fine powder silica as a surface treatment agent for negative charging with respect to 100 parts by weight of the powder coating (manufactured by Nippon Aerosil Co., Ltd.). R972] was stirred and mixed using a rotary blade type mixer [COMMERCIAL BLENDER HGB-SS manufactured by WARING (Walling) Co.], and subjected to toning.
<Magenta (M) translucent powder coating>
As a pigment, C.I. I. Pigment Blue 15: 3 and the same amount (3.0 parts by weight) of C.I. I. Pigment Red 122 (trade name KetRed 309 manufactured by Dainippon Ink and Chemicals Inc.) is used in the same manner as the cyan-based translucent powder coating material, except that the volume center particle diameter is 13 μm. Was prepared and 0.4 parts by weight of fine powder silica (R972 described above) was mixed with 100 parts by weight of the powder coating material by stirring using the rotary blade type mixer also described above. It was subjected to toning.
<Yellow (Y) -based translucent powder coating>
As a pigment, C.I. I. Pigment Blue 15: 3 and the same amount (3.0 parts by weight) of C.I. I. Pigment Yellow 154 (trade name: Symuler Fast Yellow 4192, manufactured by Ciba Geigy) is used to produce a yellow translucent powder paint having a volume center particle diameter of 13 μm, in the same manner as the cyan translucent powder paint. Then, 0.4 parts by weight of the fine powder silica [R972 described above] is mixed with 100 parts by weight of the powder coating material using the rotary blade type mixer described above, and the mixture is mixed. Was served.
<Red (R) translucent powder coating>
As a pigment, C.I. I. Pigment Blue 15: 3 and the same amount (3.0 parts by weight) of C.I. I. Pigment Red 170 (trade name: Brilliant Carmine 7009, manufactured by Sanyo Dyeing Co., Ltd.), except that a cyan-based translucent powder coating material having a volume center particle diameter of 13 μm is used in the same manner as the cyan-based translucent powder coating material. Was prepared and 0.4 parts by weight of fine powder silica (R972 described above) was mixed with 100 parts by weight of the powder coating material by stirring using the rotary blade type mixer also described above. It was subjected to toning.
<Clear (T) -based translucent powder coating>
Except that the pigment was not blended, a clear translucent powder coating having a volume center particle diameter of 13 μm was produced in the same manner as the cyan translucent powder coating, and based on 100 parts by weight of the powder coating. Then, 0.4 parts by weight of finely divided silica [R972, supra] was stirred and mixed using the above-mentioned rotary blade type mixer, and subjected to toning.
[0089]
<< Toning example 1 >>
The charge amount (value of 30 seconds after stirring, μC / g) of the powder paints of four colors C, M, Y and T among the powder paints of the respective colors produced in the preparation of the powder paint, was measured by blow-off charging. When measured using a volume meter, the values shown in Table 1 below were obtained.
[0090]
[Table 1]

[0091]
From the above measurement results, the maximum charge amount Q_maxIs 23.8 μC / g of cyan powder coating, minimum value Q_minIs 19.2 μC / g of the magenta powder coating material, and the difference ΔQ between the two is 4.6 μC / g._maxOf 20%, that is, less than 4.76 μC / g, and it was confirmed that the above expression was satisfied.
Then, each of the powder coatings was blended at a blending ratio (% by weight) shown in Table 2 below and supplied to a rotary blade type mixer (manufactured by WARING Co., Ltd.) as a mixing device, and dried for 25 seconds. Blended.
[0092]
[Table 2]

[0093]
The above-mentioned compounding ratio is derived from the color card manufactured by Toyo Ink Co., Ltd. using CF0461 (purple) as the target color by the automatic color matching system described above, and then automatically weighed based on the result. Value.
<< Toning example 2 >>
For comparison, as a magenta powder coating, a powder having a charge amount of 18.1 μC / g was adjusted with the addition amount of fine powder silica and combined with another powder coating to obtain the same blending ratio as above. A dry-blended product under the same conditions was used as Toning Example 2.
[0094]
In the toning example 2, the maximum value Q of the charge amount_maxIs 23.8 µC / g of cyan powder coating, minimum value Q_minIs 18.1 μC / g of the powder coating of magenta, and the difference ΔQ between the two is 5.7 μC / g, and the value of ΔQ is the maximum value Q_max20%, that is, 4.76 μC / g or more, which corresponds to a conventional formulation that does not satisfy the above formula.
[0095]
<< Toning example 3 >>
For comparison, as a powder coating of cyan, a powder having a charge amount of 25.3 μC / g was adjusted by adding an amount of fine powder silica as a powder coating of cyan and combined with another powder coating to obtain the same compounding as described above. The dry-blended product under the same conditions was designated as Toning Example 3.
In the toning example 3, the maximum value Q of the charge amount_maxIs 25.3 μC / g of cyan powder coating, minimum value Q_minIs 19.2 μC / g of the powder coating of magenta, and the difference ΔQ between the two is 6.1 μC / g, and the value of ΔQ is the maximum value Q_max20%, that is, 5.06 μC / g or more, which is equivalent to the conventional formulation which also does not satisfy the above formula.
[0096]
《Formation of coating film》
Next, each of the three kinds of powder paints toned as described above was first coated on one side of an SPCC steel plate (150 mm in length, 70 mm in width, 40.8 mm in thickness) as an object to be coated in white under the conditions of I below. After the powder coating is electrostatically deposited, the powder coating is electrostatically deposited under the following conditions II, and then baked at 180 ° C. for 20 minutes to form a 30-35 μm-thick white base layer and a thickness of each powder coating. A coating film having a total thickness of 65 μm having a two-layer structure of a colored overcoat layer having a thickness of 30 to 35 μm was prepared.
<Condition I (coating of white underlayer)>
-Powder supply: quantitative feeder [prototype manufactured by Mita Kogyo Co., Ltd.], rotation speed = 380 r. p. m. , Scraper angle = scale 1
・ Conveyance speed of coated object: 50mm / sec
・ Coating machine: manufactured by Barcalizing, INF pressure = 3kg / cm²G, swirling pressure = 3 kg / cm²G, transfer pressure = 3 kg / cm²G
・ Gun: Friction electrification gun, nozzle = fan shape
・ Booth suction wind speed: 0.59m / sec
・ Painting distance: 300mm
・ Adhesion amount to SPCC steel sheet: 0.7g
<Condition II (coating of colored overcoat layer)>
・ Powder supply: Same as above
・ Substrate transfer speed: Same as above
・ Coating machine: Same as above
・ Gun: Corona charging gun, applied voltage = -60 kV
・ Booth suction wind speed: Same as above
・ Painting distance: Same as above
・ Adhesion amount to SPCC steel sheet: 0.5g
The following was used as the white powder coating for the white underlayer.
<White powder paint>
As a pigment, C.I. I. Pigment Blue 15: 3, and cyan-based translucent powder except that 30 parts by weight of titanium oxide (trade name: CR-90, manufactured by Ishihara Techno Co., Ltd.) was used and was not classified after pulverization. A white powder paint having a volume center particle size of 17 μm was produced in the same manner as the paint (I). The white powder coating was used as a base without being subjected to a surface treatment.
[0097]
《Evaluation of toning》
Next, the color of each coating film is measured using the spectrophotometer (X-Rite SP68 manufactured by Kurabo Industries Co., Ltd.), and the colorimetry of the color card as a target color of the colorimetric data is performed. Color difference from data ΔΕ^*And calculate the color difference ΔΕ^*Was evaluated as having no hue shift (o) when the threshold value was 0.8 or less, and as hue shift (x) when exceeding 0.8.
[0098]
In addition, each coating film was visually observed, and the presence or absence of defects such as color segregation, mottle, and shading was observed. As a judgment method, when the coating film was observed from a position of 20 cm, color segregation, mottling, shading, etc. were not seen (good), and when the coating film was observed from a position of 40 cm, the above defect was clearly observed. Observed things were bad (x), and the middle between them, that is, the above-mentioned bad was not seen when the coating film was observed from a position of 40 cm, but something bad when observed from a position of 20 cm was slightly bad (△).
[0099]
Table 3 shows the results.
[0100]
[Table 3]

[0101]
From the table, by setting the charge amount of the powder coating of each color used for toning within the above specified range, color segregation, mottled feeling, coating film having almost uniform shade without defects such as shading It was found that
[0102]
【The invention's effect】
As described in detail above, according to the present invention, despite having dry-blended a powder coating of a plurality of colors, it has substantially uniform shades without defects such as color segregation, mottle, and shading. A unique function and effect is provided in that a novel method for toning a powder coating material capable of forming a coating film can be provided.
[Brief description of the drawings]
FIG. 1 is a flowchart showing each step of an example of a toning method of the present invention.
FIG. 2 is a flowchart showing a process of calculating a calculated reflectance and a tristimulus value from a plurality of basic data measured in advance for each of a plurality of color powder coatings used in the toning method.

Claims (2)

A toning in which a plurality of colored , translucent powder coatings and a colorless and transparent powder coating containing no coloring agent are blended in a predetermined ratio, and then dry-blended using a mixing device to perform the toning. In the method, the difference ΔQ (= Q _max −Q _min ) between the maximum value Q _max and the minimum value Q _min of the charge amount of the powder coating of each color before toning is calculated by the following formula:
ΔQ <| Q _max | × 0.20
A method for toning a powder coating material, wherein the amount of charge of each color powder coating material is adjusted in advance so as to satisfy the following. 2. The method of claim 1, wherein the amount of charge is adjusted by adding a particulate silica-based surface treatment agent to the powder coating of each color before toning.

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