JP4904624B2 - Paint composition - Google Patents

Description

乳化重合中のｐＨは２．０〜８．５、好ましくは４．０〜８．０、より好ましくは４．０〜７．５であることが推奨される。乳化重合中のｐＨ調整は、よく知られているように炭酸水素ナトリウム等のｐＨ緩衝剤（調節剤）を乳化重合時に添加することにより実施され、本発明でも好適に適用される。乳化重合中のｐＨが２．０未満では、水酸基やエポキシ基などの官能基の保護作用が十分でなく、重合後に官能基の一部または全部が消失する場合がある。乳化重合中のｐＨが８．５を超える場合にも同様となり、官能基が消失することがある。
【００２５】
さらに望ましくは、乳化重合中の酸素濃度が０．０〜２０％、より好ましくは５〜１５％であることが推奨される。乳化重合中に酸素が存在しない場合には、アクリル系エマルジョン（Ａ）の粒子径コントロールが不可能となり、密着性、塗膜外観が悪化する場合がある。また、酸素濃度が２０％を超える場合には、引火性の高い不飽和単量体類を使用するため、安全上深刻な問題を引き起こす可能性がある。
【００２６】
本発明で用いられる３級アミノ基およびカルボキシル基を有する水性アクリル樹脂（Ｂ）は、水性媒体中で３級アミノ基含有不飽和単量体（ｄ）、カルボキシル基含有不飽和単量体（ｅ）、不飽和単量体（ｆ）をラジカル共重合することにより製造する。水性アクリル樹脂（Ｂ）は溶液状であっても、乳化・分散状であってもその形態を問わない。
【００２７】
ここに、水性媒体とは、主として水をさすが、メチルアルコール、エチルアルコール、イソプロピルアルコール、ｎ−ブチルアルコール等のアルコール類、エチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル等、水に可溶性の有機溶剤であっても、該有機溶剤が混合された水であってもよい。
【００２８】
３級アミノ基含有不飽和単量体（ｄ）は、Ｎ，Ｎ−ジメチルアミノエチルアクリレートである。
【００２９】
３級アミノ基含有不飽和単量体（ｄ）は、水性アクリル樹脂（Ｂ）を構成する不飽和単量体中０．０２〜５０重量％、好ましくは０．５〜２５重量％共重合されることが望ましい。共重合量が０．０２重量％未満では、塗料の硬化性がやや悪化することがあり、耐薬品性や塗膜硬度が不足する場合がある。また、５０重量％を超えて共重合される場合には、塗料の耐水性、耐薬品性など化学的性質がやや悪化することがある。
【００３０】
カルボキシル基含有不飽和単量体（ｅ）は、メタクリル酸である。
【００３１】
カルボキシル基含有不飽和単量体（ｅ）は、水性アクリル樹脂（Ｂ）の酸価が０．１〜１５０ｍｇＫＯＨ、好ましくは１〜１００ｍｇＫＯＨとなるように共重合されることが望ましい。酸価が０．１ｍｇＫＯＨ未満では、塗料の硬化性が不足する場合があり、塗膜硬度７や着性など物理的性質がやや悪化することがある。また、酸価が１５０ｍｇＫＯＨを超える場合には、塗料の耐水性や耐薬品性など化学的性質がやや悪化することがある。また、塗料のポットライフ（仮死時間）が短くなりすぎる傾向にあり、塗装作業性が悪くなることがある。
【００３２】
不飽和単量体（ｆ）は、アクリル酸ブチル、メタクリル酸メチル、メタクリル酸ブチル、スチレンである。不飽和単量体（ｆ）は、単独でも２種類以上の混合物であってもよい。
【００３３】
本発明で用いられる水性アクリル樹脂（Ｂ）は、一例を挙げると以下のようにして製造することができる。
【００３４】
（１）溶液重合で製造する場合
イソプロピルアルコール、ｎ−ブチルアルコール、ブチルセロソルブあるいはプロピレングリコールモノメチルエーテル等の有機溶剤（水性媒体）を溶媒として使用し、３級アミノ基含有不飽和単量体（ｄ）、カルボキシル基含有不飽和単量体（ｅ）、および必要であればその他の不飽和単量体（ｆ）を、重合温度４０〜１５０℃で、ラジカル（共）重合することにより製造することができる。
【００３５】
このとき、α，α−アゾビスイソブチロニトリル、過酸化ベンゾイルなどの有機アゾ系化合物や有機過酸化物などの重合開始剤、ドデシルメルカプタンやアルファメチルスチレンダイマー等の重合度調節剤を使用することができる。また、製造された水性アクリル樹脂（Ｂ）の着色を防ぐため、重合は不活性ガス雰囲気で行なうことが好ましく、より好ましくは、重合中の酸素濃度が８％未満で製造されることが推奨される。重合中の酸素濃度が８％を超える場合には、水性アクリル樹脂（Ｂ）が黄色に着色することがあり、クリア塗料や淡色系塗料の製造に支障を来す場合がある。
【００３６】
（２）乳化重合で製造する場合
例えば、水（好ましくはｐＨ＝６〜７／２５℃のイオン交換水）を分散媒体とし、ポリオキシエチレンノニルフェニルエーテルやドデシルメルベンゼンスルホン酸などの乳化剤を使用し、重合開始剤として過硫酸カリウムや過硫酸アンモニウム等を使用し、重合温度４０〜１００℃、好ましくは６０〜９０℃で、３級アミノ基含有不飽和単量体（ｄ）、カルボキシル基含有不飽和単量体（ｅ）、および必要であればその他の不飽和単量体（ｆ）を乳化重合し製造される。
【００３７】
本発明では、乳化剤として反応性乳化剤が好適に用いられ、乳化重合中のｐＨが２．０〜８．５、好ましくは４．０〜８．０、より好ましくは４．０〜７．５であることが推奨される。
【００３８】
すなわち、乳化剤としてより好ましくは、下記構造式で示されるような反応性乳化剤を示すことができる。下記構造式で示される反応性乳化剤の一例を挙げれば、α−スルホ−ω−（１−（ノニルフェノキシ）メチル−２−（２−プロペニルオキシ）エトキシ−ポリ（オキシ−１，２−エタンジイル）のアンモニウム塩を挙げることができる。
【００３９】
反応性乳化剤、好ましくは下記構造式で示される反応性乳化剤を使用すれば、粒子径が均一で、乳化重合時に凝集物が少ないアクリル系エマルジョン（Ａ）を製造することができる。さらに、該エマルジョンから得られる塗膜は耐水性、耐薬品性、耐溶剤性、耐候性など種々塗料性能が優れたものとなる。
【００４０】
さらに言えば、アクリル系エマルジョン（Ａ）と水性アクリル樹脂（Ｂ）を所定割合で混合し、塗料用組成物を製造する際、アクリル系エマルジョン（Ａ）と水性アクリル樹脂（Ｂ）はよく混合される必要があり、この観点からも下記構造式で示される反応性乳化剤が好適に使用される。
【００４１】
【化２】

同様な理由で、乳化重合中のｐＨは２．０〜８．５、好ましくは４．０〜８．０、より好ましくは４．０〜７．５であることが推奨される。乳化重合中のｐＨ調整は、よく知られているように炭酸水素ナトリウム等のｐＨ緩衝剤（調節剤）を乳化重合時に添加することにより実施することができる。乳化重合中のｐＨが２．０未満では、塗料用組成物の硬化性が悪くなる傾向にあり、耐水性、耐薬品性などが悪化する場合がある。また、乳化重合中のｐＨが８．５を超える場合には、アクリル系エマルジョン（Ａ）と水性アクリル樹脂（Ｂ）とを混合し塗料用組成物を製造した際、アクリル系エマルジョン（Ａ）のエポキシ基が単独で反応し、消滅する傾向にあって、アクリル系エマルジョン（Ａ）と水性アクリル樹脂（Ｂ）とを混合し、相互に作用、反応することで発現される優れた諸機能、性能が失われる傾向にある。
【００４２】
さらに望ましくは、乳化重合中の酸素濃度が０．０〜２０％、より好ましくは５〜１５％であることが推奨される。乳化重合中に酸素が存在しない場合には、アクリル系エマルジョン（Ａ）の粒子径コントロールが不可能となり、密着性、塗膜外観が悪化する場合がある。酸素濃度が２０％を超える場合には、引火性の高い不飽和単量体類を使用するため、安全上深刻な問題を引き起こす可能性がある。
【００４３】
アクリル系エマルジョン（Ａ）と水性アクリル樹脂（Ｂ）は、重量比で９０／１０で配合される。さらに、驚くべきことに、本配合比で塗料が作製されるとき、アクリロニトリル−スチレン−ブタジエン樹脂（ＡＢＳ樹脂）、ポリカーボネート樹脂（ＰＣ樹脂）等のプラスチック類、ガラス、石綿セメントスレート、モルタル等の無機物、鉄、アルミニウム、マグネシウム、亜鉛等の金属および合金類等の種々基材に対する密着性が大いに改善、向上する。
【００４４】
本発明の塗料組成物は、側鎖に水酸基とエポキシ基を有するアクリル系エマルジョン（Ａ）と、側鎖に３級アミノ基およびカルボキシル基を有する水性アクリル樹脂（Ｂ）とを均一になるよう混合できれば、どのような製造方法で作製してもよい。また、必要であれば、酸価チタン、炭酸カルシウム、雲母、アルミニウムあるいはカーボンブラックなどの顔料類、好ましくは水性媒体であるがトルエン、キシレン、酢酸エチル、酢酸ブチル、メチルアルコール、エチルアルコール、イソプロピルアルコール、ノルマルプロピルアルコール、ノルマルブチルアルコール、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル、γ−ブチルラクトンあるいはメチルイソブチルケトンなどの有機溶剤類、造膜助剤、沈殿防止剤、レベリング剤、スリップ防止剤、消泡剤、防かび剤、防藻剤、防錆剤などの種々塗料添加剤、その他の塗料に配合される樹脂類、可塑剤、添加剤、酸化防止剤（フェノール系または燐酸系が好ましく使用できる）、光安定剤（塩基定数（ＰＫｂ）が８以上のヒンダードアミン系（ＨＡＬＳ）が好ましい。ｐＫｂが８以上のＨＡＬＳは乳化重合時に添加しておくことが好ましい。さらに、モノマー類と混合し、乳化重合を実施し、配合することが推奨される。このとき、ＨＡＬＳとしての効果がより顕著に発揮される場合がある。）などを配合することができる。
【００４５】
さらに本発明では、ＡＢＳ樹脂、ＰＣ樹脂、ノリル樹脂、ポリアミド樹脂、ＡＢＳ−ＰＣアロイ樹脂、ポリエステル樹脂（ＰＥＳ）、ポリスチレン、ポリメタクリル酸メチル等のプラスチック類、不飽和ポリエステル、エポキシ樹脂等の熱硬化性樹脂等、ガラス、石綿セメントスレート、モルタル等の無機物、鉄、アルミニウム、マグネシウム、亜鉛等の金属および合金類等の種々基材（被塗物）に対する密着性を改善し、向上するために、一分子中にエポキシ基またはアミノ基を有するシラン化合物（Ｃ）を配合することができる。さらに驚くべきことに、シラン化合物（Ｃ）を配合することにより、種々被塗物への密着性が向上するだけでなく、被塗物がアルミニウム合金、マグネシウム合金などの電気伝導性がよく、腐食されやすい金属の場合には、該金属の電気腐食を防止し耐水性や、耐塩水性などの悪環境化での密着性が飛躍的に改善され、向上する。これは、シラン化合物（Ｃ）のアルコキシシラン基が加水分解され、シラノール基となって金属表面の水酸基と相互に反応し、金属表面を不動化、安定化し、一方では、残る官能基であるアミノ基またはエポキシ基が、塗膜マトリックス中に取り込まれて架橋構造を形成するためと考えられる。結果として、シラン化合物（Ｃ）は、金属表面を悪環境に対し不導体化、安定化する作用とともに、表面に強固な保護相を形成する作用を有するものとなる。
【００４６】
一分子中にエポキシ基を有するシラン化合物（Ｃ）としては、３−グリシドキシプロピルトリメトキシシラン、３−グリシドキシプロピルトリエトキシシラン、３−グリシドキシプロピルメチルジメトキシシラン、γ−（３，４−エポキシシクロヘキシル）エチルトリエトキシシラン、および該化合物の加水分解物、縮合物などを例示することができる。該シラン化合物（Ｃ）は、単独でももしくは２種類以上の混合物であってもよい。
【００４７】
一分子中にエポキシ基またはアミノ基を有するシラン化合物（Ｃ）は、塗料用組成物中に、３．９〜７．６重量％含有される。
【００４８】
シラン化合物（Ｃ）は、塗料用組成物に添加し、均一になるまで攪拌、混合するだけでもよいが、本発明では以下に述べる方法に従い製造、配合することが望ましい。
【００４９】
すなわち、アクリル系エマルジョン（Ａ）を製造する際、シラン化合物（Ｃ）の存在下に乳化重合し、シラン化合物（Ｃ）が配合されたアクリル系エマルジョン（Ａ）を製造することが推奨される。
【００５０】
より具体的には、アクリル系エマルジョン（Ａ）の製造時、水酸基含有不飽和単量体（ａ）、エポキシ基含有不飽和単量体（ｂ）およびその他の不飽和単量体（ｃ）の混合物に、シラン化合物（Ｃ）を混合し、このものを乳化重合し製造する。あるいは、水性アクリル樹脂（Ｂ）の製造時、３級アミノ基含有不飽和単量体（ｄ）、カルボキシル基含有不飽和単量体（ｅ）およびその他の不飽和単量体（ｆ）の混合物に、シラン化合物（Ｃ）を混合し、このものを重合し製造する。
【００５１】
また、アクリル系エマルジョン（Ａ）の製造と同様に、乳化剤として反応性乳化剤が好適に用いられ、乳化重合中のｐＨは２．０〜８．５、好ましくは４．０〜８．０、より好ましくは４．０〜７．５であることが推奨される。
【００５２】
本発明の塗料用組成物に対して、上記の成分の他に、水性媒体が好ましいが、トルエン、キシレン、酢酸ブチル、メチルイソブチルケトン、イソプロピルアルコール、ブチルセロソルブなどの有機溶剤、二酸化チタン、炭酸カルシウム、カーボンブラック、パール顔料などの顔料、造膜助剤、顔料分散剤、消泡剤、沈殿防止剤、レベリング剤などの塗料添加剤など、塗料に一般的に配合されるものを配合することにより、塗料とすることができる。
【００５３】
本発明では、より好ましく配合される添加剤として、シリカゾルやアルミナゾルなどの無機微粒子を例示することができる。シリカゾルやアルミナゾルなどの無機微粒子の配合により、塗膜強度と硬度を高めることができ、塗膜の耐傷つき性、耐摩耗性を向上することが可能となる。シリカゾル、アルミナゾルとしては、「オルガノシリカゾルＭＡ−ＳＴ」、「オルガノシリカゾルＩＰＡ−ＳＴ」（以上、日産化学工業（株）の製品）、「アルミナゾル−１０」、「アルミナゾル−２０」（以上、川研ファインケミカル（株）の製品）などを例示することができる。シリカゾルとアルミナゾルは、塗料用組成物１００重量部に対し、０．０２〜５０重量％配合することが推奨される。配合量が０．０２重量％未満では、塗膜のアップ、耐傷つき性向上に顕著な効果が見られない場合がある。また、５０重量％を超えて配合される場合には、塗料の貯蔵安定性がやや悪化する場合があり、また塗膜外観がやや損なわれる傾向にある。
【００５４】
塗料の塗装方法としては、スプレー塗装、ロールコート塗装および静電塗装などの一般的な塗装方法を適用することができる。
【００５５】
本発明の塗料が適用できる被塗物としては、アクリロニトリル−スチレン−ブタジエン樹脂（ＡＢＳ）、ポリスチレン樹脂（ＰＳ）、アクリル樹脂等のプラスチック製品類や、鉄やアルミニウムなどの金属類、合金、モルタルおよび石綿セメントなどの無機建材などを例示することができる。より好ましく適用できる被塗物としては、マグネシウム合金、アルミニウム合金、ステンレススチールが例示できる。
【００５６】
本発明の塗料組成物は、ことさら、携帯電話やパソコン（ＰＣ）筐体などの（移動用）情報機器端末に多用されているマグネシウム合金用塗料として好適である。マグネシウム合金はリサイクルが容易であること、軽量であること、強度が大きいこと、資源埋蔵量が豊富であることから、近年上記用途等に多用されている。本発明の塗料組成物は、難接着性合金とされるマグネシウム合金に極めて良好な密着性を与えるとともに、防食性に優れ、塗膜強度、硬度が高く、かつ美麗な塗装外観を得ることができる。この効果は、本願の塗料組成物が、エポキシ基、水酸基、アミノ基等の（ポリマーが有する）官能基を必須成分とし有機的かつ効果的に組み合わせていること、ポリマー（アクリル系エマルジョン（Ａ））／ポリマー（水性アクリル樹脂（Ｂ））の架橋反応により塗膜に強靱で、耐薬品性、耐水性など諸性能に優れたネットワーク構造が付与されることを主要因としている。さらに、シラン化合物（Ｃ）の配合により、悪環境下での密着性、塗膜強度および硬度をさらに高めることができる。
【００５７】
以下に、実施例をもって本発明をさらに詳細に説明するが、その前にアクリル系エマルジョン（Ａ）および水性アクリル樹脂（Ｂ）の製造例を示す。なお、特に断りがなければ、数字は重量部を、また割合は重量％を示す。
【００５８】
［アクリル系エマルジョン（Ａ）の製造例］
（Ａ−１）の製造例
（１）撹拌装置、温度計、窒素ガス導入管を備えた２Ｌ四つ口フラスコに、イオン交換水（ｐＨ＝６．８／２５℃）４６２．２ｇ、炭酸水素ナトリウム２．１ｇ、「アデカリアソーブＳＥ−１０２５Ａ」（α−スルホ−ω−（１−（ノニルフェノキシ）メチル−２−（２−プロペニルオキシ）エトキシ−ポリ（オキシ−１，２−エタンジイル）のアンモニウム塩／２５％水溶液、反応性乳化剤、旭電化工業（株）の製品）１４．０ｇ、過硫酸アンモニウム０．２ｇを仕込み、これを攪拌しながら、窒素ガスと空気を吹き込み、フラスコ内の酸素濃度が８．０％になるようにコントロールした。
【００５９】
（２）１Ｌガラスビーカーに、メタクリル酸メチル（ＭＭＡ）／メタクリル酸ｎ−ブチル（ＢＭＡ）／アクリル酸ｎ−ブチル（ＢＡ）／グリシジルメタクリレート（ＧＭＡ）／メタクリル酸２−ヒドロキシエチル（ＨＥＭＡ）（＝４０／２０／２０／１０／１０）の混合モノマー６００ｇと「ＳＨ−６０４０」（３−グリシドキシプロピルトリメトキシシラン、エポキシ基を有するシラン化合物、東レ・ダウコーニングシリコーン（株）の製品）６０ｇとを仕込み、攪拌して均一溶液とした。さらにこれにイオン交換水１５４．１ｇ、過硫酸アンモニウム１．６ｇ、「ＳＥ−１０２５Ａ」７０ｇの混合物を添加し、窒素ガスと空気を吹き込みながらビーカー内の酸素濃度を８％に調整し、ゆっくりとかき混ぜてモノマーと「ＳＨ−６０４０」が水中に乳化されたモノマーエマルジョンを作製した。
【００６０】
（３）モノマーエマルジョンの１０％をフラスコ内に添加し、８０℃まで昇温を行なう。８０℃で３０分間、プレチャージしたモノマーエマルジョンの乳化重合を行なった後、モノマーエマルジョンを３時間かけてフラスコ内に滴下した。
【００６１】
（４）モノマーエマルジョン滴下終了後、さらに１時間乳化重合を継続し、アクリル系エマルジョン（Ａ−１）を製造した。
【００６２】
（５）アクリル系エマルジョン（Ａ−１）の固形分は５０％、エポキシ当量は１４２０、水酸基価は４３ｍｇＫＯＨであった。また、重合中のｐＨは５．６／２５℃、重合後のｐＨは５．８／２５℃であった。
【００６３】
（Ａ−２）の製造例
（１）アクリル系エマルジョン（Ａ−１）において、「ＳＨ−６０４０」の配合量を１２０ｇに変えたこと以外は、（Ａ−１）と同様にしてアクリル系エマルジョン（Ａ−２）を製造した。
【００６４】
（２）アクリル系エマルジョン（Ａ−２）の固形分は５３％、エポキシ当量は１４２０、水酸基価は４３ｍｇＫＯＨであった。また、重合中のｐＨは５．３／２５℃、重合後のｐＨは５．５／２５℃であった。
【００６５】
（Ａ−３）の製造例
（１）撹拌装置、温度計、窒素ガス導入管を備えた２Ｌ四つ口フラスコに、イオン交換水（ｐＨ＝６．８／２５℃）４６２．２ｇ、炭酸水素ナトリウム２．１ｇ、「アデカリアソーブＳＥ−１０２５Ａ」１４．０ｇ、過硫酸アンモニウム０．２ｇを仕込み、これを攪拌しながら、窒素ガスと空気を吹き込み、フラスコ内の酸素濃度が８．０％になるようコントロールした。
【００６６】
（２）１ＬガラスビーカーにＭＭＡ／ＢＭＡ／ＢＡ／ＧＭＡ／ＨＥＭＡ（＝４０／２０／２０／１０／１０）の混合モノマー６００ｇと「ＳＨ−６０４０」６０ｇ、「サノールＬＳ−２６２６」（１−［２−〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオニルオキシ〕エチル］−４−〔３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオニルオキシ〕−２，２，６，６−テトラメチルピペリジン、ｐＫｂ＝１２（ｐＫｂが８以上のＨＡＬＳ、三共（株）の製品）１２ｇとを仕込み、攪拌して均一溶液とした。さらにこれにイオン交換水１５４．１ｇ、過硫酸アンモニウム１．６ｇ、「ＳＥ−１０２５Ａ」７０ｇの混合物を添加し、窒素ガスと空気を吹き込みながらビーカー内の酸素濃度を８％に調整し、ゆっくりとかき混ぜてモノマーと「ＳＨ−６０４０」が水中に乳化されたモノマーエマルジョンを作製した。
【００６７】
（３）モノマーエマルジョンの１０％をフラスコ内に添加し、８０℃まで昇温を行なう。８０℃で３０分間、プレチャージしたモノマーエマルジョンの乳化重合を行なった後、モノマーエマルジョンを３時間かけてフラスコ内に滴下した。
【００６８】
（４）モノマーエマルジョン滴下終了後、さらに１時間乳化重合を継続し、アクリル系エマルジョン（Ａ−３）を製造した。
【００６９】
（５）アクリル系エマルジョン（Ａ−３）の固形分は５０％、エポキシ当量は１４２０、水酸基価は４３ｍｇＫＯＨであった。また、重合中のｐＨは５．８／２５℃、重合後のｐＨは６．０／２５℃であった。
【００７０】
［水性アクリル樹脂（Ｂ）の製造例］
（Ｂ−１）の製造例
（１）撹拌装置、温度計、窒素ガス導入管を備えた２Ｌ四つ口フラスコに、エチレングリコールモノブチルエーテル（ＢＣ）／イソプロピルアルコール（ＩＰＡ）（＝８０／２０）４３５ｇを仕込み、フラスコ内を十分に窒素ガス置換した後、９０℃に昇温した。また、重合中は窒素ガスを吹き込んだ。
【００７１】
（２）１ＬビーカーにＭＭＡ／スチレン（ＳＴ）／ＢＭＡ／ＢＡ／Ｎ．Ｎ−ジメチルアミノエチルメタクリレート（ＭＬＤＡ）／メタクリル酸（ＭＡＡ）（＝２６／２０／２０／２０／６／８）５００ｇ、ｎ−ドデシルメルカプタン（ＤＭ）２０ｇ、α，α−アゾビスイソブチロニトリル（ＡＩＢＮ）１５ｇを仕込み、均一になるまで攪拌した。（⇒モノマー混合液とする）
（３）滴下ポンプ（定流量ポンプ）を使用し、モノマー混合液をフラスコ内に４時間で滴下した。滴下終了後、１時間重合を継続し、１時間毎６回に分けＩＰＡ５０ｇ、ＡＩＢＮ１ｇの混合スラリーを添加する。この後、さらに１時間重合を続け、４０℃に冷却した後Ｎ，Ｎ−ジメチルアミノエタノール３０ｇ、イオン交換水２０ｇの混合溶液を添加しアクリル樹脂（Ｂ−１）を製造した。
【００７２】
（４）水性アクリル樹脂（Ｂ−１）の固形分は５０％、酸価は５２．２ｍｇＫＯＨ、数平均分子量は３０００であった。
【００７３】
（Ｂ−２）の製造例
（１）撹拌装置、温度計、窒素ガス導入管を備えた２Ｌ四つ口フラスコに、イオン交換水（ｐＨ＝６．８／２５℃）４６２．２ｇ、炭酸水素ナトリウム２．１ｇ、「アデカリアソーブＳＥ−１０２５Ａ」１４．０ｇ、過硫酸アンモニウム０．２ｇを仕込んだ。これを攪拌しながら、窒素ガスと空気を吹き込み、フラスコ内の酸素濃度が８．０％になるようコントロールした。
【００７４】
（２）１ＬガラスビーカーにＭＭＡ／ＳＴ／ＢＭＡ／ＢＡ／ＭＬＤＡ／ＭＡＡ（＝２６／２０／２０／２０／６／８）６００ｇを仕込み、攪拌して均一溶液とする。さらにこれにイオン交換水１５４．１ｇ、過硫酸アンモニウム１．６ｇ、「ＳＥ−１０２５Ａ」７０ｇの混合物を添加し、窒素ガスと空気を吹き込みながらビーカー内の酸素濃度を８％に調整し、ゆっくりとかき混ぜてモノマーが水中に乳化されたモノマーエマルジョンを作製した。
【００７５】
（３）モノマーエマルジョンの１０％をフラスコ内に添加し、８０℃まで昇温を行なう。８０℃で３０分間、プレチャージしたモノマーエマルジョンの乳化重合を行なった後、モノマーエマルジョンを３時間かけてフラスコ内に滴下した。
【００７６】
（４）モノマーエマルジョン滴下終了後、さらに１時間乳化重合を継続し、アクリル系エマルジョン（Ｂ−２）を製造した。
【００７７】
（５）アクリル系エマルジョン（Ｂ−２）の固形分は５０％、酸価は５２．２ｍｇＫＯＨであった。また、重合中のｐＨは６．０／２５℃、重合後のｐＨは６．２／２５℃であった。
【００７８】
【実施例】
（実施例１）
アクリル系エマルジョン（Ａ−１）９０ｇと水性アクリル樹脂（Ｂ−１）１０ｇとを、ディスパーを使用し均一になるまで混合し、実施例１の塗料用組成物を製造した。さらに、これに水を加えフォードカップＮｏ．４での粘度が１５秒（２５℃）となるように希釈して、実施例１の塗料組成物を使用した塗料を作製した。
【００７９】
（実施例２）
実施例１において、アクリル系エマルジョン（Ａ−１）の代わりにアクリル系エマルジョン（Ａ−２）を用いたこと以外は、実施例１と同様にして、実施例２の塗料用組成物と塗料を製造した。
【００８０】
（実施例３）
実施例１で、アクリル系エマルジョン（Ａ−１）の代わりにアクリル系エマルジョン（Ａ−３）を用いたこと以外は、実施例１と同様にして、実施例３の塗料用組成物と塗料を製造した。
【００８１】
（実施例４）
アクリル系エマルジョン（Ａ−１）９０ｇと水性アクリル樹脂（Ｂ−２）１０ｇとを、ディスパーを使用し均一になるまで混合して、実施例４の塗料用組成物を製造した。さらに、これに「ＣＳ−１２」（２，２，４−トリメチル−１，３−ペンタンジオール モノイソブチレート、造膜助剤、チッソ石油化学（株）の製品）１０ｇを添加し、ディスパーで均一になるまで攪拌、混合し、さらに、水を加えフォードカップＮｏ．４での粘度が１５秒（２５℃）となるように希釈し、実施例４の塗料組成物を使用した塗料を作製した。
【００８２】
（比較例１）
実施例１において、水性アクリル樹脂（Ｂ−１）を使用しないこと以外は、実施例１と同様にして、比較例１の塗料用組成物と塗料を製造した。
【００８３】
（比較例２）
水性アクリル樹脂（Ｂ−１）１００ｇに「ＳＨ−６０４０」１０ｇを配合し均一になるまで混合して比較例２の塗料用組成物を製造した。これをＢＣ／水（＝９０／１０）の混合溶剤で、フォードカップＮｏ．４での粘度が１５秒（２５℃）となるよう希釈し、比較例２の塗料用組成物を使用した塗料を作製した。
【００８４】
［試験用塗装板の作製］
上記の各実施例および比較例の塗料用組成物を使用した各塗料を使用し、試験用の塗装板を作製した。
〔付着性および耐水性試験用塗装板の作製〕
（１）各塗料をＡＢＳ板に塗膜厚が３０μｍになるようスプレー塗布し、８０℃で３０分間焼き付けを行ない、さらに、室温で３日間乾燥し試験用塗装板と
した。
（２）各塗料を、マグネシウム合金（ＪＩＳ ＡＺ９１Ｄ）に塗膜厚が３０μｍになるよう塗布し、１２０℃で３０分間焼き付けを行う。さらに、室温で３
日間乾燥し試験用塗装板とした。
【００８５】
〔硬化性試験用塗装板の作製〕
（１）各塗料をポリプロピレン板に塗膜厚が３０μｍになるよう塗布し、１００℃で３０分間焼き付けを行ない、さらに、室温で１週間乾燥し試験用塗装板
とした。
【００８６】
［試験結果］
上記の各実施例および比較例の塗料組成物を用い、各種試験を行なった。試験結果を表１に示す。なお、試験方法と評価結果の判定は、下記のとおりとする。
【００８７】
【表１】

１．付着性
ＪＩＳ Ｋ ５４００ 付着性（碁盤目テープ法）に従い試験を行なう。
【００８８】
１００／１００で合格とした。
【００８９】
２．耐水性
試験用塗装板を５０℃イオン交換水中に４８時間放置した後、室温で１日間乾燥する。外観を判定した後、付着性試験を行う。外観評価は膨れ、白化など外観変化がない場合を合格とした。付着性（耐水後２次密着性）は１００／１００で合格とした。
【００９０】
３．硬化性
塗料をポリプロピレン（ＰＰ）板に塗装し、１００℃で３０分間焼き付けを行なう。さらに室温で１週間乾燥の後、塗膜をＰＰ板からはがし試験を実施した。硬化性の試験は、塗膜（Ｘｇ）をソックスレー抽出器を使用し、 アセトン／メタノール（＝５０／５０ｖｏｌ％）の混合溶媒を還流下に３ 時間抽出試験を行ない未抽出塗膜を取り出す。これを真空乾燥機で２４時 間乾燥した後重量を測定（Ｙｇ）し、ゲル分率を次式により算出する。
ゲ ル分率が高いほど硬化性が優れており、８０％以上で合格とした。
ゲル分率＝（Ｙ／Ｘ）× １００ （％）
【００９１】
【発明の効果】
本発明は、側鎖にエポキシ基と水酸基を有するアクリル系エマルジョン（Ａ）と側鎖に３級アミノ基およびカルボキシル基を有する水性アクリル樹脂（Ｂ）とが、有機的かつ効果的に配合されるため、種々の基材に対する密着性、耐水性などの耐薬品性、塗料の硬化性に優れている。
【００９２】
とりわけ、難接着性金属とされるマグネシウム合金に対する密着性に優れ、耐水性後２次密着性なども良好である。さらに、ヌレ性、塗膜外観などで水系塗料の適用が芳しくないプラスチック基材に対しても、良好な密着性と塗装外観を示し環境対応上極めて望ましいといえる。
【００９３】
また、塗料のレベリング性および製膜性が良好であり、均一でムラのない美麗な塗装外観が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating composition having excellent adhesion to various objects (substrates). More specifically, the present invention relates to a coating composition having excellent adhesion to difficult-to-adhere metals such as magnesium alloy, aluminum alloy or stainless steel and various plastics.
[0002]
[Prior art]
The functions of the paint are adhesion to the object to be coated, protection of the object to be coated and aesthetics. Various paints having these functions have been developed and put into practical use.
[0003]
In addition, the base material on which the paint is applied changes rapidly with the passage of time, and in recent years, not only high strength but also complex performance due to lightness, flame retardancy, recyclability, easy biodegradability, safety, etc. And functions are being demanded. From this point of view, lightweight, high-strength, high-resource reserves such as aluminum alloy and magnesium alloy for structural materials, and easy recycling, and high-strength, excellent transparency such as polycarbonate for glass replacement applications In applications such as plastics and household electrical appliances, plastics such as Noryl are increasingly used to impart flame retardancy.
[0004]
However, such a base material is generally difficult to adhere, and in particular, a base material containing a metal atom such as Al, Zn, Cr or the like as a constituent component such as an aluminum alloy, a magnesium alloy, or stainless steel is difficult to adhere. . From the standpoint of paints, these are difficult-to-adhere base materials, and widely used acrylic melamine resin paints, acrylic urethane resin paints, acrylic silicone resin paints, etc. do not adhere and require a so-called dedicated primer. To do.
[0005]
To make matters worse, the metals that make up these base materials belong to the most basic category in terms of electrical conductivity, and when paint or paint is not appropriate, they cause electrical corrosion and environmental tests such as water resistance. The film may swell or may easily peel off.
[0006]
2. Description of the Related Art Conventionally, in order to improve and secure adhesion, a coating method in which an epoxy resin paint having good adhesion or adhesion is applied as a primer (primer) has been widely practiced. Thereafter, the epoxy resin coating is baked and cured, and a top coating (such as acrylic melamine resin coating or acrylic urethane resin coating) is applied, baked and cured.
[0007]
Although this coating method has excellent performance supported by the excellent adhesion and corrosion resistance of epoxy resin, the so-called 2C2B (painted twice and baked twice), 3C3B (painted three times) It is often applied when the appearance of the paint is unintended, and the paint workability is extremely poor, and the yield of the paint is also low. As a result, a great deal of time is required for the painting work, which not only increases the cost of painting, but also the production efficiency of the final product is extremely poor. Moreover, since the epoxy resin forms a strongly crosslinked coating film, the recoat adhesion is insufficient.
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems. That is, the object of the present invention is to use a specific acrylic resin that is balanced in various performances and is excellent as a paint binder, and to difficult-to-adhere materials, particularly difficult-to-adhere metals such as magnesium alloy, aluminum alloy or stainless steel. The object is to provide a paint having excellent adhesion.
[0009]
Another object of the present invention is to provide a coated article coated with the coating material, particularly a coated article comprising a magnesium alloy and various plastics as its constituent elements.
[0010]
The coated article coated with the coating composition of the present invention has a number of excellent properties such as adhesion, corrosion resistance, and scratch resistance as well as a beautiful appearance. Furthermore, since the dispersion medium (or diluting solvent) of the coating composition of the present invention is aqueous, it has a low environmental burden and is suitable for the future.
[0011]
  The present invention aims to achieve the above object, and the coating composition of the present invention comprises a hydroxyl group-containing unsaturated monomer (a), an epoxy group-containing unsaturated monomer (b), andBadObtained by emulsion polymerization of saturated monomer (c)specificAcrylic emulsion (A) with tertiary amino group and carboxyl group in side chainspecificIt is a composition for coating materials containing a water-based acrylic resin (B).
[0012]
  BookThe coating composition of the present invention is particularly suitably used for coating difficult-to-adhere substances such as magnesium alloys and aluminum alloys or various plastic substrates.
[0013]
  The coating composition of the present invention comprises a hydroxyl group-containing unsaturated monomer (a), an epoxy group-containing unsaturated monomer (b), andBadObtained by emulsion copolymerization of saturated monomer (c)specificAcrylic emulsion (A) with tertiary amino group and carboxyl group in side chainspecificIt is a composition for coating materials containing a water-based acrylic resin (B).
[0014]
The acrylic emulsion (A) comprises a hydroxyl group-containing unsaturated monomer (a), an epoxy group-containing unsaturated monomer (b), andBadProduced by emulsion copolymerization of saturated monomer (c)The
[0015]
  Hydroxyl-containing unsaturated monomer (a)Is2-hydroxyethacrylic acidLeRu. DPoxy group-containing unsaturated monomer (b)TheLysidyl methacrylateIs.
[0016]
  Also,BadSaturated monomer (c)IsButyl crylate, MeMethyl tacrylate, MeButyl tacrylate, SuChileNTheBadThe saturated monomer (c) may be a single type or a mixture of two or more types.
[0017]
The acrylic emulsion (A) used in the present invention is recommended to have a hydroxyl value of 1-150 mgKOH, preferably 5-100 mgKOH. When the hydroxyl value is less than 1 mgKOH, the adhesion to the article to be coated may be slightly deteriorated. On the other hand, when the hydroxyl value exceeds 150 mgKOH, the storage stability and chemical resistance of the emulsion paint may be slightly deteriorated.
[0018]
In the acrylic emulsion (A), the epoxy group of the epoxy group-containing unsaturated monomer (b) to be copolymerized is preferably left, and the epoxy equivalent is 200 to 15000, preferably 450 to 5000. Is recommended. When the epoxy equivalent is less than 200, the storage stability of the paint tends to deteriorate. When the epoxy equivalent exceeds 15000, the crosslinkability of the coating is deteriorated, and the chemical resistance, solvent resistance, and weather resistance of the coating film may be slightly deteriorated.
[0019]
Furthermore, it is recommended that the acrylic emulsion (A) has an acid value of 0 to 50 mgKOH, preferably 0 to 35 mgKOH. The acid value can be imparted by copolymerizing a monomer having a carboxyl group and a radical polymerizable double bond in a molecule such as acrylic acid or methacrylic acid during emulsion polymerization. When the acid value exceeds 50 mgKOH, the dispersed particles of the acrylic emulsion (A) cause an intraparticle cross-linking reaction, and the film-forming property and leveling property of the paint may be deteriorated, so that a sufficient coating appearance may not be obtained. .
[0020]
The acrylic emulsion (A) is preferably a hydroxyl group-containing unsaturated monomer (a), an epoxy group-containing unsaturated monomer (b), and other unsaturated monomers in the presence of a reactive emulsifier. It is produced by emulsion copolymerizing the body (c).
[0021]
The acrylic emulsion (A) uses, for example, water (preferably ion exchange water having a pH of 6 to 7/25 ° C.) as a dispersion medium and uses an emulsifier such as polyoxyethylene nonylphenyl ether and dodecyl merbenzene sulfonic acid. In addition, potassium persulfate, ammonium persulfate or the like is used as the polymerization initiator, and the polymerization temperature is 40 to 100 ° C., preferably 60 to 90 ° C., the hydroxyl group-containing unsaturated monomer (a), the epoxy group-containing unsaturated monomer ( It is produced by emulsion polymerization of b) and other unsaturated monomers (c).
[0022]
In the present invention, a reactive emulsifier is suitably used as the emulsifier, and the pH during emulsion polymerization is 2.0 to 8.5, preferably 4.0 to 8.0, more preferably 4.0 to 7.5. It is recommended that there be.
[0023]
That is, a reactive emulsifier represented by the following structural formula (1) can be more preferably used as the emulsifier. An example of the reactive emulsifier represented by the structural formula (1) is α-sulfo-ω- (1- (nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-1,2- Ammonium salt of ethanediyl) A reactive emulsifier, preferably a reactive emulsifier represented by the following structural formula, is used to provide an acrylic emulsion (A Furthermore, the coating film obtained from the coating composition containing the acrylic emulsion has excellent coating performance such as water resistance, chemical resistance, solvent resistance and weather resistance. Furthermore, it is desirable that the acrylic emulsion (A) has a hydroxyl group and an epoxy group as functional groups in the acrylic polymer side chain even after emulsion polymerization. Therefore, a reactive emulsifier represented by the following structural formula is preferably used.
[0024]
[Chemical 1]

It is recommended that the pH during emulsion polymerization be 2.0 to 8.5, preferably 4.0 to 8.0, more preferably 4.0 to 7.5. As is well known, pH adjustment during emulsion polymerization is carried out by adding a pH buffering agent (regulator) such as sodium hydrogencarbonate during emulsion polymerization, which is also preferably applied in the present invention. When the pH during emulsion polymerization is less than 2.0, the protective function of functional groups such as hydroxyl groups and epoxy groups is not sufficient, and some or all of the functional groups may disappear after polymerization. The same applies when the pH during emulsion polymerization exceeds 8.5, and the functional group may disappear.
[0025]
More desirably, it is recommended that the oxygen concentration during emulsion polymerization be 0.0 to 20%, more preferably 5 to 15%. When oxygen is not present during emulsion polymerization, the particle size of the acrylic emulsion (A) cannot be controlled, and the adhesion and the coating film appearance may be deteriorated. Further, when the oxygen concentration exceeds 20%, highly flammable unsaturated monomers are used, which may cause serious safety problems.
[0026]
  The aqueous acrylic resin (B) having a tertiary amino group and a carboxyl group used in the present invention comprises a tertiary amino group-containing unsaturated monomer (d) and a carboxyl group-containing unsaturated monomer (e ),BadProduced by radical copolymerization of saturated monomer (f)TheThe aqueous acrylic resin (B) may be in the form of a solution or an emulsified / dispersed form.
[0027]
Here, the aqueous medium mainly refers to water, but is an organic solvent that is soluble in water, such as alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and the like. Alternatively, water mixed with the organic solvent may be used.
[0028]
  Tertiary amino group-containing unsaturated monomer (d)IsN, N-dimethylaminoethyl acrylateIt is.
[0029]
The tertiary amino group-containing unsaturated monomer (d) is copolymerized in the unsaturated monomer constituting the aqueous acrylic resin (B) in an amount of 0.02 to 50% by weight, preferably 0.5 to 25% by weight. It is desirable. If the copolymerization amount is less than 0.02% by weight, the curability of the coating may be slightly deteriorated, and chemical resistance and coating film hardness may be insufficient. In addition, when the copolymerization exceeds 50% by weight, chemical properties such as water resistance and chemical resistance of the paint may be slightly deteriorated.
[0030]
  Carboxyl group-containing unsaturated monomer (e)IsTakrillIt is an acid.
[0031]
The carboxyl group-containing unsaturated monomer (e) is desirably copolymerized so that the acid value of the aqueous acrylic resin (B) is 0.1 to 150 mgKOH, preferably 1 to 100 mgKOH. When the acid value is less than 0.1 mg KOH, the curability of the coating may be insufficient, and physical properties such as coating film hardness 7 and wearability may be slightly deteriorated. In addition, when the acid value exceeds 150 mgKOH, chemical properties such as water resistance and chemical resistance of the paint may be slightly deteriorated. In addition, the pot life (tentative death time) of the paint tends to be too short, and the paint workability may deteriorate.
[0032]
  BadSaturated monomer (f)IsButyl crylate, MeMethyl tacrylate, MeButyl tacrylate, SuChileNTheBadThe saturated monomer (f) may be a single monomer or a mixture of two or more.
[0033]
The aqueous acrylic resin (B) used in the present invention can be produced as follows, for example.
[0034]
(1) When manufacturing by solution polymerization
Using an organic solvent (aqueous medium) such as isopropyl alcohol, n-butyl alcohol, butyl cellosolve or propylene glycol monomethyl ether as a solvent, a tertiary amino group-containing unsaturated monomer (d), a carboxyl group-containing unsaturated monomer (E) and, if necessary, other unsaturated monomer (f) can be produced by radical (co) polymerization at a polymerization temperature of 40 to 150 ° C.
[0035]
At this time, polymerization initiators such as organic azo compounds such as α, α-azobisisobutyronitrile and benzoyl peroxide and organic peroxides, and polymerization degree regulators such as dodecyl mercaptan and alphamethylstyrene dimer are used. be able to. In order to prevent coloring of the produced aqueous acrylic resin (B), the polymerization is preferably performed in an inert gas atmosphere, and more preferably, the oxygen concentration during the polymerization is preferably less than 8%. The When the oxygen concentration during polymerization exceeds 8%, the aqueous acrylic resin (B) may be colored yellow, which may hinder the production of clear paints and light-colored paints.
[0036]
(2) When manufacturing by emulsion polymerization
For example, water (preferably ion exchange water having a pH of 6 to 7/25 ° C.) is used as a dispersion medium, an emulsifier such as polyoxyethylene nonylphenyl ether or dodecyl mer benzene sulfonic acid is used, and potassium persulfate is used as a polymerization initiator. A tertiary amino group-containing unsaturated monomer (d), a carboxyl group-containing unsaturated monomer (e), and a polymerization temperature of 40 to 100 ° C., preferably 60 to 90 ° C. If necessary, it is produced by emulsion polymerization of another unsaturated monomer (f).
[0037]
In the present invention, a reactive emulsifier is suitably used as the emulsifier, and the pH during emulsion polymerization is 2.0 to 8.5, preferably 4.0 to 8.0, more preferably 4.0 to 7.5. It is recommended that there be.
[0038]
That is, a reactive emulsifier represented by the following structural formula can be more preferable as an emulsifier. An example of a reactive emulsifier represented by the following structural formula is α-sulfo-ω- (1- (nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-1,2-ethanediyl). The ammonium salt can be mentioned.
[0039]
If a reactive emulsifier, preferably a reactive emulsifier represented by the following structural formula, is used, an acrylic emulsion (A) having a uniform particle size and few aggregates during emulsion polymerization can be produced. Furthermore, the coating film obtained from the emulsion has excellent paint performance such as water resistance, chemical resistance, solvent resistance and weather resistance.
[0040]
Furthermore, when the acrylic emulsion (A) and the aqueous acrylic resin (B) are mixed at a predetermined ratio to produce a coating composition, the acrylic emulsion (A) and the aqueous acrylic resin (B) are mixed well. From this viewpoint, a reactive emulsifier represented by the following structural formula is also preferably used.
[0041]
[Chemical 2]

For the same reason, it is recommended that the pH during emulsion polymerization be 2.0 to 8.5, preferably 4.0 to 8.0, more preferably 4.0 to 7.5. As is well known, pH adjustment during emulsion polymerization can be carried out by adding a pH buffer (regulator) such as sodium hydrogencarbonate during emulsion polymerization. When the pH during emulsion polymerization is less than 2.0, the curability of the coating composition tends to deteriorate, and the water resistance, chemical resistance and the like may deteriorate. Further, when the pH during emulsion polymerization exceeds 8.5, the acrylic emulsion (A) and the aqueous acrylic resin (B) are mixed to produce a coating composition. Epoxy group reacts and tends to disappear, mixing various acrylic emulsion (A) and water-based acrylic resin (B), interacting and reacting, excellent functions and performance Tend to be lost.
[0042]
More desirably, it is recommended that the oxygen concentration during emulsion polymerization be 0.0 to 20%, more preferably 5 to 15%. When oxygen is not present during emulsion polymerization, the particle size of the acrylic emulsion (A) cannot be controlled, and the adhesion and the coating film appearance may be deteriorated. If the oxygen concentration exceeds 20%, highly flammable unsaturated monomers are used, which may cause serious safety problems.
[0043]
  Acrylic emulsion (A) and aqueous acrylic resin (B)90/10It is blended with. Furthermore, surprisingly, when a paint is prepared with this blending ratio, plastics such as acrylonitrile-styrene-butadiene resin (ABS resin) and polycarbonate resin (PC resin), inorganic substances such as glass, asbestos cement slate, and mortar Adhesion to various base materials such as metals, alloys such as iron, aluminum, magnesium and zinc is greatly improved and improved.Do.
[0044]
In the coating composition of the present invention, an acrylic emulsion (A) having a hydroxyl group and an epoxy group in the side chain and an aqueous acrylic resin (B) having a tertiary amino group and a carboxyl group in the side chain are mixed uniformly. If possible, any manufacturing method may be used. If necessary, pigments such as acid value titanium, calcium carbonate, mica, aluminum or carbon black, preferably an aqueous medium, but toluene, xylene, ethyl acetate, butyl acetate, methyl alcohol, ethyl alcohol, isopropyl alcohol , Organic solvents such as normal propyl alcohol, normal butyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, γ-butyl lactone or methyl isobutyl ketone, film-forming aids, precipitation inhibitors, leveling agents Various anti-slip agents, anti-foaming agents, anti-fungal agents, anti-algae agents, anti-rust agents, and other paint additives, resins incorporated in other paints, plasticizers, additives, antioxidants (phenolic or Phosphoric acid is preferred And a light stabilizer (preferably a hindered amine type (HALS) having a base constant (PKb) of 8 or more. HALS having a pKb of 8 or more is preferably added during the emulsion polymerization. It is recommended to carry out emulsion polymerization and blend it, and at this time, the effect as HALS may be exhibited more significantly).
[0045]
Furthermore, in the present invention, ABS resin, PC resin, Noryl resin, polyamide resin, ABS-PC alloy resin, polyester resin (PES), polystyrene, polymethyl methacrylate and other plastics, unsaturated polyester, epoxy resin, etc. In order to improve and improve the adhesion to various base materials (coating materials) such as inorganic resins such as glass, asbestos cement slate, mortar, metals and alloys such as iron, aluminum, magnesium and zinc, A silane compound (C) having an epoxy group or an amino group in one molecule can be blended. Surprisingly, by adding the silane compound (C), not only the adhesion to various objects to be coated is improved, but also the objects to be coated have good electrical conductivity such as aluminum alloy, magnesium alloy, and corrosion. In the case of a metal that is easily applied, the metal is prevented from being electrically corroded, and the adhesion in adverse environments such as water resistance and salt water resistance is drastically improved and improved. This is because the alkoxysilane group of the silane compound (C) is hydrolyzed to form a silanol group, which reacts with the hydroxyl group on the metal surface to immobilize and stabilize the metal surface, while the remaining functional group is amino. This is thought to be because groups or epoxy groups are incorporated into the coating matrix to form a crosslinked structure. As a result, the silane compound (C) has an effect of forming a strong protective phase on the surface as well as an effect of making the metal surface non-conductive and stable against an adverse environment.
[0046]
  Epoxy in one moleculeGroupExamples of the silane compound (C) include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and γ- (3,4-epoxycyclohexyl) ethyl. TriethoxysilaNExamples thereof include hydrolysates and condensates of the compounds. The silane compound (C) may be a single compound or a mixture of two or more.
[0047]
  The silane compound (C) having an epoxy group or amino group in one molecule is a coating composition.Inside, 3.9-7.6weight%ContainsIs done.
[0048]
The silane compound (C) may be added to the coating composition and only stirred and mixed until uniform, but in the present invention, it is desirable to produce and blend according to the method described below.
[0049]
That is, when the acrylic emulsion (A) is produced, it is recommended to produce an acrylic emulsion (A) in which the silane compound (C) is blended by emulsion polymerization in the presence of the silane compound (C).
[0050]
More specifically, during the production of the acrylic emulsion (A), the hydroxyl group-containing unsaturated monomer (a), the epoxy group-containing unsaturated monomer (b), and other unsaturated monomers (c) A silane compound (C) is mixed with the mixture, and this is emulsion-polymerized to produce. Alternatively, a mixture of a tertiary amino group-containing unsaturated monomer (d), a carboxyl group-containing unsaturated monomer (e), and other unsaturated monomers (f) during the production of the aqueous acrylic resin (B) In addition, the silane compound (C) is mixed and polymerized to produce.
[0051]
Similarly to the production of the acrylic emulsion (A), a reactive emulsifier is suitably used as an emulsifier, and the pH during emulsion polymerization is 2.0 to 8.5, preferably 4.0 to 8.0. It is recommended that it is preferably 4.0 to 7.5.
[0052]
For the coating composition of the present invention, in addition to the above components, an aqueous medium is preferable, but organic solvents such as toluene, xylene, butyl acetate, methyl isobutyl ketone, isopropyl alcohol, butyl cellosolve, titanium dioxide, calcium carbonate, By blending pigments such as carbon black and pearl pigments, film-forming aids, pigment dispersants, antifoaming agents, precipitation inhibitors, paint additives such as leveling agents, etc. It can be a paint.
[0053]
In the present invention, inorganic fine particles such as silica sol and alumina sol can be exemplified as an additive that is more preferably blended. By blending inorganic fine particles such as silica sol and alumina sol, the strength and hardness of the coating film can be increased, and the scratch resistance and abrasion resistance of the coating film can be improved. As silica sol and alumina sol, “organo silica sol MA-ST”, “organo silica sol IPA-ST” (product of Nissan Chemical Industries, Ltd.), “alumina sol-10”, “alumina sol-20” (above, Kawaken) Fine chemicals product) and the like. It is recommended that the silica sol and the alumina sol are mixed in an amount of 0.02 to 50% by weight based on 100 parts by weight of the coating composition. If the blending amount is less than 0.02% by weight, there may be a case where a remarkable effect is not seen in improving the coating film and improving scratch resistance. Moreover, when it mix | blends exceeding 50 weight%, the storage stability of a coating material may deteriorate a little, and it exists in the tendency for the coating-film external appearance to be impaired a little.
[0054]
As the coating method of the paint, general coating methods such as spray coating, roll coating and electrostatic coating can be applied.
[0055]
Examples of articles to which the paint of the present invention can be applied include plastic products such as acrylonitrile-styrene-butadiene resin (ABS), polystyrene resin (PS), acrylic resin, metals such as iron and aluminum, alloys, mortar, and the like. Examples thereof include inorganic building materials such as asbestos cement. Examples of the coated material that can be more preferably applied include magnesium alloy, aluminum alloy, and stainless steel.
[0056]
In particular, the coating composition of the present invention is suitable as a coating for magnesium alloy that is frequently used in (mobile) information equipment terminals such as mobile phones and personal computer (PC) housings. Magnesium alloys are frequently used in the above applications in recent years because they are easy to recycle, are lightweight, have high strength, and have abundant resource reserves. The coating composition of the present invention gives extremely good adhesion to a magnesium alloy which is a hardly adhesive alloy, has excellent anticorrosion properties, high coating film strength and hardness, and can provide a beautiful coating appearance. . This effect is due to the fact that the coating composition of the present application combines an organic and effective functional group (having a polymer) such as an epoxy group, a hydroxyl group, and an amino group as an essential component, and a polymer (acrylic emulsion (A)). ) / Polymer (water-based acrylic resin (B)) cross-linking reaction gives the coating film a strong network structure with excellent performance such as chemical resistance and water resistance. Furthermore, the adhesiveness in a bad environment, coating-film intensity | strength, and hardness can further be improved by mix | blending a silane compound (C).
[0057]
Hereinafter, the present invention will be described in more detail with reference to examples, but before that, production examples of an acrylic emulsion (A) and an aqueous acrylic resin (B) will be shown. Unless otherwise specified, the numbers indicate parts by weight and the ratios indicate weight percent.
[0058]
[Production Example of Acrylic Emulsion (A)]
Production example of (A-1)
(1) In a 2 L four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube, 462.2 g of ion-exchanged water (pH = 6.8 / 25 ° C.), 2.1 g of sodium hydrogen carbonate, “Adeka Resorb SE -1025A "(α-sulfo-ω- (1- (nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-1,2-ethanediyl) ammonium salt / 25% aqueous solution, reactive emulsifier , Product of Asahi Denka Kogyo Co., Ltd.) 14.0 g and ammonium persulfate 0.2 g were added, and while stirring this, nitrogen gas and air were blown in to control the oxygen concentration in the flask to 8.0%. did.
[0059]
(2) In a 1 L glass beaker, methyl methacrylate (MMA) / n-butyl methacrylate (BMA) / n-butyl acrylate (BA) / glycidyl methacrylate (GMA) / 2-hydroxyethyl methacrylate (HEMA) (= 40/20/20/10/10) 600 g of mixed monomer and 60 g of “SH-6040” (3-glycidoxypropyltrimethoxysilane, silane compound having an epoxy group, product of Toray Dow Corning Silicone Co., Ltd.) And stirred to obtain a homogeneous solution. Furthermore, a mixture of 154.1 g of ion-exchanged water, 1.6 g of ammonium persulfate and 70 g of “SE-1025A” was added, and the oxygen concentration in the beaker was adjusted to 8% while blowing nitrogen gas and air, and the mixture was slowly stirred. A monomer emulsion in which the monomer and “SH-6040” were emulsified in water was prepared.
[0060]
(3) Add 10% of the monomer emulsion into the flask and raise the temperature to 80 ° C. After emulsion polymerization of the precharged monomer emulsion at 80 ° C. for 30 minutes, the monomer emulsion was dropped into the flask over 3 hours.
[0061]
(4) After completion of dropping the monomer emulsion, emulsion polymerization was continued for another hour to produce an acrylic emulsion (A-1).
[0062]
(5) The acrylic emulsion (A-1) had a solid content of 50%, an epoxy equivalent of 1420, and a hydroxyl value of 43 mgKOH. The pH during the polymerization was 5.6 / 25 ° C., and the pH after the polymerization was 5.8 / 25 ° C.
[0063]
Production example of (A-2)
(1) In the acrylic emulsion (A-1), an acrylic emulsion (A-2) was produced in the same manner as (A-1) except that the blending amount of “SH-6040” was changed to 120 g. .
[0064]
(2) The solid content of the acrylic emulsion (A-2) was 53%, the epoxy equivalent was 1420, and the hydroxyl value was 43 mgKOH. The pH during the polymerization was 5.3 / 25 ° C., and the pH after the polymerization was 5.5 / 25 ° C.
[0065]
Production example of (A-3)
(1) In a 2 L four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas introduction tube, 462.2 g of ion-exchanged water (pH = 6.8 / 25 ° C.), 2.1 g of sodium hydrogen carbonate, “Adeka Resorb SE −1025A ”14.0 g and ammonium persulfate 0.2 g were charged, and while stirring the mixture, nitrogen gas and air were blown in to control the oxygen concentration in the flask to 8.0%.
[0066]
(2) 600 g of MMA / BMA / BA / GMA / HEMA (= 40/20/20/10/10) mixed monomer, 60 g of “SH-6040”, “Sanol LS-2626” (1- [ 2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy ] -2,2,6,6-tetramethylpiperidine, 12 g of pKb = 12 (HALS having a pKb of 8 or more, product of Sankyo Co., Ltd.), and stirred to obtain a homogeneous solution. Add a mixture of 154.1 g of water, 1.6 g of ammonium persulfate and 70 g of “SE-1025A” and adjust the oxygen concentration in the beaker to 8% while blowing nitrogen gas and air. , Monomer and "SH-6040" is to prepare a monomer emulsion, which is emulsified in water and stir slowly.
[0067]
(3) Add 10% of the monomer emulsion into the flask and raise the temperature to 80 ° C. After emulsion polymerization of the precharged monomer emulsion at 80 ° C. for 30 minutes, the monomer emulsion was dropped into the flask over 3 hours.
[0068]
(4) After completion of dropping of the monomer emulsion, the emulsion polymerization was further continued for 1 hour to produce an acrylic emulsion (A-3).
[0069]
(5) The acrylic emulsion (A-3) had a solid content of 50%, an epoxy equivalent of 1420, and a hydroxyl value of 43 mgKOH. The pH during the polymerization was 5.8 / 25 ° C., and the pH after the polymerization was 6.0 / 25 ° C.
[0070]
[Production Example of Aqueous Acrylic Resin (B)]
Production example of (B-1)
(1) 435 g of ethylene glycol monobutyl ether (BC) / isopropyl alcohol (IPA) (= 80/20) is charged into a 2 L four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas introduction tube, and the flask is fully filled After nitrogen gas substitution, the temperature was raised to 90 ° C. Further, nitrogen gas was blown during the polymerization.
[0071]
(2) MMA / styrene (ST) / BMA / BA / N. 500 g of N-dimethylaminoethyl methacrylate (MLDA) / methacrylic acid (MAA) (= 26/20/20/20/6/8), 20 g of n-dodecyl mercaptan (DM), α, α-azobisisobutyronitrile (AIBN) 15 g was charged and stirred until uniform. (⇒ Use monomer mixture)
(3) A dropping pump (constant flow pump) was used, and the monomer mixture was dropped into the flask in 4 hours. After completion of dropping, polymerization is continued for 1 hour, and a mixed slurry of 50 g of IPA and 1 g of AIBN is added in 6 times every hour. Thereafter, the polymerization was further continued for 1 hour, and after cooling to 40 ° C., a mixed solution of 30 g of N, N-dimethylaminoethanol and 20 g of ion-exchanged water was added to produce an acrylic resin (B-1).
[0072]
(4) The solid content of the aqueous acrylic resin (B-1) was 50%, the acid value was 52.2 mgKOH, and the number average molecular weight was 3000.
[0073]
Production example of (B-2)
(1) In a 2 L four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube, 462.2 g of ion-exchanged water (pH = 6.8 / 25 ° C.), 2.1 g of sodium hydrogen carbonate, “Adeka Resorb SE −1025A ”14.0 g and ammonium persulfate 0.2 g were charged. While stirring this, nitrogen gas and air were blown into the flask to control the oxygen concentration in the flask to 8.0%.
[0074]
(2) A 1 L glass beaker is charged with 600 g of MMA / ST / BMA / BA / MLDA / MAA (= 26/20/20/20/6/8) and stirred to obtain a homogeneous solution. Furthermore, a mixture of 154.1 g of ion-exchanged water, 1.6 g of ammonium persulfate and 70 g of “SE-1025A” was added, and the oxygen concentration in the beaker was adjusted to 8% while blowing nitrogen gas and air, and the mixture was slowly stirred. A monomer emulsion in which the monomer was emulsified in water was prepared.
[0075]
(3) Add 10% of the monomer emulsion into the flask and raise the temperature to 80 ° C. After emulsion polymerization of the precharged monomer emulsion at 80 ° C. for 30 minutes, the monomer emulsion was dropped into the flask over 3 hours.
[0076]
(4) After completion of dropping of the monomer emulsion, the emulsion polymerization was continued for another hour to produce an acrylic emulsion (B-2).
[0077]
(5) The solid content of the acrylic emulsion (B-2) was 50%, and the acid value was 52.2 mgKOH. The pH during the polymerization was 6.0 / 25 ° C., and the pH after the polymerization was 6.2 / 25 ° C.
[0078]
【Example】
Example 1
90 g of the acrylic emulsion (A-1) and 10 g of the aqueous acrylic resin (B-1) were mixed until uniform using a disper to produce the coating composition of Example 1. Furthermore, water was added to this, and Ford Cup No. The coating composition using the coating composition of Example 1 was prepared by diluting so that the viscosity at 4 was 15 seconds (25 ° C.).
[0079]
(Example 2)
In Example 1, except that the acrylic emulsion (A-2) was used instead of the acrylic emulsion (A-1), the coating composition and paint of Example 2 were used in the same manner as in Example 1. Manufactured.
[0080]
(Example 3)
In Example 1, except that the acrylic emulsion (A-3) was used instead of the acrylic emulsion (A-1), the coating composition and paint of Example 3 were used in the same manner as in Example 1. Manufactured.
[0081]
Example 4
90 g of the acrylic emulsion (A-1) and 10 g of the aqueous acrylic resin (B-2) were mixed until uniform using a disper to produce the coating composition of Example 4. Furthermore, 10 g of “CS-12” (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, film-forming aid, product of Chisso Petrochemical Co., Ltd.) was added thereto, Stir and mix until uniform, then add water and add Ford cup no. 4 was diluted so that the viscosity at 4 was 15 seconds (25 ° C.), and a coating material using the coating composition of Example 4 was prepared.
[0082]
(Comparative Example 1)
In Example 1, the coating composition and the coating material of Comparative Example 1 were produced in the same manner as in Example 1 except that the aqueous acrylic resin (B-1) was not used.
[0083]
(Comparative Example 2)
A coating composition of Comparative Example 2 was produced by blending 10 g of “SH-6040” with 100 g of the aqueous acrylic resin (B-1) and mixing them until uniform. This was a mixed solvent of BC / water (= 90/10). 4 was diluted so that the viscosity at 4 was 15 seconds (25 ° C.), and a coating material using the coating composition of Comparative Example 2 was prepared.
[0084]
[Preparation of test paint plate]
A paint plate for a test was prepared using each paint using the paint composition of each of the above Examples and Comparative Examples.
[Preparation of coated plates for adhesion and water resistance tests]
(1) Each paint is spray-applied on an ABS plate to a coating thickness of 30 μm, baked at 80 ° C. for 30 minutes, and further dried at room temperature for 3 days.
did.
(2) Each paint is applied to a magnesium alloy (JIS AZ91D) so that the coating thickness is 30 μm, and baked at 120 ° C. for 30 minutes. In addition, at room temperature 3
It dried for the day and it was set as the coating board for a test.
[0085]
[Preparation of paint plate for curability test]
(1) Each paint is applied to a polypropylene plate so that the coating thickness is 30 μm, baked at 100 ° C. for 30 minutes, and further dried at room temperature for 1 week to be a test coating plate
It was.
[0086]
[Test results]
Various tests were performed using the coating compositions of the above Examples and Comparative Examples. The test results are shown in Table 1. The test method and evaluation results are determined as follows.
[0087]
[Table 1]

1. Adhesiveness
The test is performed according to JIS K 5400 adhesion (cross cut tape method).
[0088]
It was considered as passing at 100/100.
[0089]
2. water resistant
The test plate is left in ion exchange water at 50 ° C. for 48 hours and then dried at room temperature for 1 day. After the appearance is judged, an adhesion test is performed. Appearance evaluation was passed when there was no change in appearance such as swelling and whitening. Adhesiveness (secondary adhesion after water resistance) was 100/100 and passed.
[0090]
3. Curability
The paint is applied to a polypropylene (PP) plate and baked at 100 ° C. for 30 minutes. Furthermore, after drying at room temperature for 1 week, the coating film was peeled off from the PP plate, and the test was carried out. In the curing test, the coating film (Xg) was subjected to an extraction test for 3 hours under reflux using a mixed solvent of acetone / methanol (= 50/50 vol%) using a Soxhlet extractor, and the unextracted coating film was taken out. After drying this with a vacuum dryer for 24 hours, the weight is measured (Yg), and the gel fraction is calculated by the following equation.
The higher the gel fraction, the better the curability, and 80% or more passed.
Gel fraction = (Y / X) × 100 (%)
[0091]
【The invention's effect】
In the present invention, an acrylic emulsion (A) having an epoxy group and a hydroxyl group in the side chain and an aqueous acrylic resin (B) having a tertiary amino group and a carboxyl group in the side chain are blended organically and effectively. Therefore, it is excellent in adhesion to various substrates, chemical resistance such as water resistance, and curability of the paint.
[0092]
In particular, it has excellent adhesion to a magnesium alloy that is regarded as a difficult-to-adhere metal, and has good secondary adhesion after water resistance. Furthermore, it can be said that it is extremely desirable from the standpoint of environmental friendliness and coating appearance even for plastic substrates that are poor in application of water-based paints due to wettability and coating film appearance.
[0093]
In addition, the leveling property and film forming property of the paint are good, and a uniform and beautiful coating appearance without unevenness can be obtained.

Claims (3)

Acrylic emulsion (A) obtained by emulsion copolymerization of hydroxyl group-containing unsaturated monomer (a), epoxy group-containing unsaturated monomer (b), and unsaturated monomer (c), and side chain And a water-based acrylic resin (B) having a tertiary amino group and a carboxyl group, wherein the hydroxyl group-containing unsaturated monomer (a) is 2-hydroxyethyl methacrylate, and an epoxy group The contained unsaturated monomer (b) is glycidyl methacrylate, the unsaturated monomer (c) is at least one selected from butyl acrylate, methyl methacrylate, and butyl methacrylate, and 3 in the side chain. Aqueous acrylic resin (B) having a tertiary amino group and a carboxyl group is a tertiary amino group-containing unsaturated monomer (d), a carboxyl group-containing unsaturated monomer (e), an unsaturated monomer in an aqueous medium. body( ), And the tertiary amino group-containing unsaturated monomer (d) is N, N-dimethylaminoethyl acrylate, and the carboxyl group-containing unsaturated monomer (e) is Methacrylic acid, unsaturated monomer (f) is at least one selected from butyl acrylate, methyl methacrylate, butyl methacrylate and styrene, and silane compound (C) having an epoxy group in one molecule and in the coating composition and also contains 3.9 to 7.6 wt%, acrylic emulsion (a) and aqueous acrylic resin (B), but is blended with 90/10 weight ratio A coating composition.   A magnesium alloy product coated with the coating composition according to claim 1.   An ABS product coated with the coating composition according to claim 1.