JP4033523B2 - Water-based block polyisocyanate composition - Google Patents

Description

【００２６】
本発明に用いるポリイソシアネート組成物Ａのイソシアネート基平均官能基数は４．５〜２０である。前記官能基数が４．５未満の場合は、良好な塗膜が得られない。また、前記官能基数が２０を越えると、塗膜の機械的物性が劣る。好ましくは６〜１５である。
この様にして得られたポリイソシアネート組成物Ａの２５℃における粘度は、５，０００〜１００，０００ｍＰａ・ｓ、イソシアネート濃度２〜２０重量％、である。
【００２７】
得られたポリイソシアネート組成物Ａに活性水素とエチレンオキサイド単位を有する化合物を付加する。この化合物としては、メタノール、エタノール、ブタノール等のモノアルコールにエチレンオキサイドを付加して得られる。得られた化合物中のエチレンオキサイド含有量は５０重量％以上が好ましく、数平均分子量は２００〜１，０００が好ましい。この化合物はプロピレンオキサイドを含んでも良い。
【００２８】
活性水素とエチレンオキサイド単位を有する化合物のポリイソシアネート組成物Ａに対する付加量（ポリエーテル鎖単位／イソシアネート基（モル／モル））は、ポリイソシアネート組成物の全イソシアネート基の２〜４０％、好ましくは２〜３０％である。２％未満であるとポリイソシアネート組成物の水分散性が低下し、４０％を越えると塗膜物性が低下する。前記化合物とポリイソシアネート組成物Ａの反応は、溶剤を用いて行うこともできる。この場合に使用する溶剤は、イソシアネートに対して不活性であるものがよい。
【００２９】
反応温度は、４０〜１５０℃、好ましくは６０〜１２０℃である。必要に応じてジブチル錫ジラウレート等の錫化合物等の塩基性化合物を反応触媒に使用しても良い。得られたポリイソシアネート組成物に前記化合物が付加されていないポリイソシアネート組成物Ａを混合することもできる。この場合、全イソシアネートに対する前記化合物の付加する割合も２〜４０％が好ましい。
【００３０】
かくして得られたポリイソシアネート組成物のイソシアネート基とブロック剤を反応し、熱解離性ブロックイソシアネート基を得る。
本発明に用いるブロック剤としては、例えば、フェノール系、活性メチレン、メルカプタン系、酸アミド系、酸イミド系、イミダゾール系、尿素系、オキシム系、アミン系、イミド系化合物等があり、これらを単独あるいは、混合して使用してもよい。より具体的なブロック剤の例を下記に示す。
【００３１】
１）フェノール系；フェノール、クレゾール、エチルフェノール、ブチルフェノール等。
２）活性メチレン系；マロン酸ジエステル（マロン酸ジメチル、マロン酸ジエチル、マロン酸ジｎ−ブチル、マロン酸ジ２−エチルヘキシル、マロン酸メチルｎ−ブチル、マロン酸エチルｎ−ブチル、マロン酸メチルｓｅｃ−ブチル、マロン酸エチルｓｅｃ−ブチル、マロン酸メチルｔ−ブチル、マロン酸エチルｔ−ブチル、メチルマロン酸ジエチル、マロン酸ジベンジル、マロン酸ジフェニル、マロン酸ベンジルメチル、マロン酸エチルフェニル、マロン酸ｔ−ブチルフェニル、イソプロピリデンマロネート）、アセト酢酸エステル（アセト酢酸メチル、アセト酢酸エチル、アセト酢酸ｎ−プロピル、アセト酢酸イソプロピル、アセト酢酸ｎ−ブチル、アセト酢酸ｔ−ブチル、アセト酢酸ベンジル、アセト酢酸フェニル）アセチルアセトン等。
【００３２】
３）メルカプタン系；ブチルメルカプタン、ドデシルメルカプタン等。
４）酸アミド系；アセトアニリド、酢酸アミド、ε−カプロラクタム、δ−バレロラクタム、γ−ブチロラクタム等。
５）酸イミド系；コハク酸イミド、マレイン酸イミド等。
６）イミダゾール系；イミダゾール、２−メチルイミダゾール等。
【００３３】
７）尿素系；尿素、チオ尿素、エチレン尿素等。
８）オキシム系；ホルムアルドオキシム、アセトアルドオキシム、アセトオキシム、メチルエチルケトオキシム、シクロヘキサノンオキシム等。
９）アミン系；ジフェニルアミン、アニリン、カルバゾール等。
１０）イミン系；エチレンイミン、ポリエチレンイミン等。
【００３４】
１１）重亜硫酸塩；重亜硫酸ソーダ等。
１２）ピラゾール系；ピラゾール、３−メチルピラゾール、３，５−ジメチルピラゾール等。
１３）トリアゾール系；１，２，４−トリアゾール等。
これらのうち、活性メチレン系、オキシム系、酸アミド系が好ましく、更に好ましくはアセトオキシム、メチルエチルケトオキシム、マロン酸ジエステル、アセト酢酸エステルであり、特に、マロン酸ジエステル１種以上とアセト酢酸エステル１種以上を併用することが好ましい。その併用割合は、モル比で、マロン酸ジエステル／アセト酢酸エステル＝５／１〜１／５が好ましく、前記値が５／１を越えると、ブロックポリイソシアネートの結晶化が生ずる場合があり、１／５未満であると、塗膜の硬化時の黄変などを生ずる場合がある。
【００３５】
ポリイソシアネート組成物とブロック剤との反応は溶剤の存在の有無に関わらず行うことができる。溶剤を用いる場合、イソシアネート基に対して不活性な溶剤を用いるのがよい。
ブロック化反応に際して、触媒として前記ジイソシアネートとポリオールの反応触媒を用いることが出来る。用いた触媒が塗料物性に悪影響を及ぼす可能性がある場合は、該触媒を酸性化合物などで中和することが好ましい。この場合の酸性化合物としては、例えば、塩酸、亜燐酸、燐酸などの無機酸、メタンスルホン酸、ｐ−トルエンスルホン酸、ｐ−トルエンスルホン酸メチルエステル、ｐ−トルエンスルホン酸エチルエステル等のスルホン酸またはその誘導体、燐酸エチル、燐酸ジエチル、燐酸イソプロピル、燐酸ジイソプロピル、燐酸ブチル、燐酸ジブチル、燐酸２−エチルヘキシル、燐酸ジ（２エチルヘキシル）、燐酸イソデシル、燐酸ジイソデシル、オレイルアシッドホスフェート、テトラコシルアシッドホスフェート、エチレングリコールアシッドホスフェート、ピロリン酸ブチル、亜燐酸ブチル等があり、これらは２種以上を併用しても良い。
【００３６】
ブロック化反応は、一般に−２０〜１５０℃で行うことが出来るが、好ましくは０〜１００℃である。１００℃を越えると副反応を起こす可能性があり、他方、あまり低温になると反応速度が小さくなり不利である。
この様に、ブロック剤と反応したイソシアネート基の濃度を潜在イソシアネート濃度と言い、１分子中に統計的に有するブロック剤と反応したイソシアネート官能基の数をブロックイソシアネート基平均官能基数と言う。
【００３７】
イソシアネート基とブロック剤の反応、イソシアネート基とエチレンオキサイド付加物の反応は、いずれか一方を先行させることもできるし、同時に行うことも出来る。
この様にして得られた本発明の水系ブロックポリイソシアネート組成物は下記の特徴を有する。
（ａ）分子内にイオン性基を含まない。
（ｂ）ポリエーテル鎖単位／イソシアネート基＝２／９８〜４０／６０（モル／モル）。
（ｃ）ブロックイソシアネート平均官能基数が３．５〜１８。
（ｄ）数平均分子量が１，０００〜１０，０００。
（ｅ）潜在イソシアネート濃度が２〜１９重量％。
【００３８】
更に目的に応じて、アニオン系、カチオン系、ノニオン系、両イオン系界面活性剤を添加することができる。界面活性剤の具体例としては、例えば、カルボン酸、スルホン酸、硫酸エステル、燐酸エステル、重合型高分子のナトリウム、カリウム等のアニオン系、第４級アンモニウム塩、ポリエチレンアミン誘導体等のカチオン系、エーテル系、エステル系、エステルエーテル系、含窒素系等のノニオン系、カルボキシベタイン、アミノカルボン酸、スルホベタイン、アミノ硫酸エステル、イミダゾリン等の両イオン系界面活性剤がある。
【００３９】
本発明においては、貯蔵安定性を向上するために１価アルコール系化合物を含むことが好ましい。該１価アルコール系化合物としては、脂肪族、脂環族、芳香族などがあり、脂肪族が好ましい。炭素数１〜２０が好ましく、例えば、メタノール、エタノール、ｎ−プロパノール、イソプロパノール、ｎ−ブタノール、ｓｅｃ−ブタノール、ｔｅｒｔ−ブタノール、２−メチル−１−プロパノール、ｎ−アミルアルコール、２−ペンタノール、３−ペンタノール、２−メチル−１−ブタノール、３−メチル−１−ブタノール、２−メチル−２−ブタノール、３−メチル−２−ブタノール、２，２，−ジメチル−１−プロパノール等の飽和アルコール、２−メトキシエタノール、２−エトキシエタノール、２−ブトキシエタノール、３，６−ジオキサ−１−ヘプタノール等のエーテルアルコール等がある。その添加量は、熱解離性ブロックイソシアネート基に対して、０．２〜１０倍モル量が好ましい。
【００４０】
このようにして調整された低温硬化性の水系ブロックポリイソシアネート組成物は、水親和性ポリオールと共に混合され水性塗料組成物の主要構成成分を形成する。
本発明に使用する水親和性ポリオールとしては、通常、水性塗料用に用いられているものであれば特に制限なく使用可能であり、アニオン系、カチオン系、両性イオン系でも、またイオン性を持たないものであってもよい。アルキド系、ポリエステル系、エポキシ系、フッ素系、アクリル系等がある。該ポリオールの樹脂分水酸基価は１０〜２００ｍｇＫＯＨ／ｇであり、水を主たる成分とする分散媒に、溶解または分散されているものである。樹脂分水酸基価１０ｍｇＫＯＨ／ｇ未満の場合には、イソシアネート成分との反応によるウレタン架橋の密度が減少して、本発明の物性を達成することが出来ず、樹脂水酸基価が２００ｍｇＫＯＨ／ｇを超えると、逆に架橋密度が増大し、塗膜の機械的物性が低下し好ましくない。
【００４１】
溶解型のポリオールとしては、数平均分子量２，０００〜１００，０００が好ましく、例えば、特開昭６３−２９５６８０号公報、特開昭６３−１７５０５９号公報、特開昭６２−２１６６７１号公報、特開平２−１９１６９２号公報等にその製造方法が開示されている。分散型のポリオールとしては、水酸基を含有するラテックスであり、その製法としては、例えば、特開昭５６−１５７３５８号公報等に開示されている。
【００４２】
ヒドロキシル基を有するフッ素共重合体であるフッ素ポリオールとしては、特開昭５７−３４１０７号公報、特開昭６１−２３１０４４号公報、特開平３−３７２５２号公報等にその製造方法が開示されている。
本発明の水性塗料組成物において、熱解離性ブロックイソシアネート基と水親和性ポリオールの水酸基の当量比は通常、１０：１〜１：１０に設定される。
【００４３】
硬化剤として、ブロックポリイソシアネート以外の硬化剤、例えば、メラミン系硬化剤等を併用することもできる。メラミン系硬化剤としては、ヘキサメトキシメチロールメラミン、メチル・ブチルエーテル化メラミン等が代表的なものとして例示される。
また、必要に応じて酸化防止剤、紫外線吸収剤、顔料、アルミ等の金属粉顔料、ジブチル錫ジラウレート等の有機金属化合物等の架橋促進剤、レベリング剤、レオロジーコントロール剤、溶剤等を添加してもよい。
【００４４】
通常は、水親和性ポリオール、硬化剤、添加剤等を混合し、水を主成分とする媒体を添加し、塗装方法に応じた塗料粘度に調整することにより水性塗料組成物となる。
この様に調整した水系塗料は、スプレー塗装、ロール塗装、シャワー塗装、浸漬塗装等の方法で金属、プラスチック、無機材料等に塗装され、耐チッピング塗料、プレコートメタル用塗料等としても有用である。
【００４５】
本発明の低温硬化性の水系ブロックポリイソシアネート組成物は、塗料以外に、インキ、接着剤、繊維、フィルム、セラミック等の無機材料、紙、木材、樹脂等の改質剤、表面処理剤、バインダーとしても有用である。
【００４６】
【発明の実施の形態】
以下に、実施例に基づいて本発明を更に詳細に説明するが、本発明は、以下の実施例に限定されるものではない。
なお、部、％は重量基準である。評価は下記に従い行った。
（数平均分子量の測定）
数平均分子量は、下記の装置を用いたゲルパーミエーションクロマトグラフ（以下、ＧＰＣと称す）測定によるポリスチレン基準の数平均分子量である。

（ジイソシアネート環状３量体濃度）
前記ＧＰＣ測定で得られるジイソシアネート環状３量体相当の分子量（例えば、ＨＭＤＩであれば５０４）のピーク面積％で表した。
【００４７】
（アロファネート結合濃度の測定）
日本電子のＦＴ−ＮＭＲ「ＦＸ９０Ｑ」を用い、溶媒はアセトン−ｄ６を使用し、Ｈ−ＮＭＲ測定の結果、アロファネート結合／（アロファネート結合＋ウレタン結合）で表した値が、０．９以上は◎、０．９未満０．１以上は○、０．１未満は×で示した。
【００４８】
（粘度測定）
エミラ型回転粘度計を用いて２５℃で測定した。
（ゲル分率）
硬化塗膜を、アセトンに２０℃で２４時間浸漬した時の未溶解部分重量の浸漬前に対する値を計算し、８５％未満は×、８５％以上は○で表した。
【００４９】
（ブロックポリイソシアネート組成物の水分散性評価）
ブロックポリイソシアネート組成物と純水を重量比２：１０で混合し、その後の溶液状態を肉眼で観察した。混合液が均一で沈降物のない状態を「良好」と評価した。
【００５０】
【製造例１】
（ポリイソシアネート組成物の製造）
撹拌機、温度計、還流冷却管、窒素吹き込み管、滴下ロートを取り付けた４ツ口フラスコ内を窒素雰囲気にし、ＨＭＤＩを６００部、４価アルコールであるポリエーテルポリオール（旭電化の商標「アデカニューポリオールＷＲ−４７４」）１６９部を仕込み、撹拌下反応器内温度を１２０℃５時間保持した。反応液温度を下げ、薄膜蒸発缶を用いて未反応ＨＭＤＩを除去した。
【００５１】
反応生成物の分子量をＧＰＣで測定し、アロファネート結合濃度をＨ−ＮＭＲで測定し、イソシアネート濃度を滴定で測定することにより、本発明のポリイソシアネート組成物が生成していることを確認した。
得られたポリイソシアネート組成物の２５℃における粘度は２０，０００ｍＰａ・ｓ、イソシアネート濃度は１３．２％、数平均分子量は１，６９０であり、イソシアネート平均官能基数は５．３、ジイソシアネート環状３量体濃度は１．７％であった。また、このポリイソシアネート組成物のアロファネート結合濃度は○であった。
【００５２】
【製造例２〜５及び参考製造例１、２】
製造例１と同様の装置を用いて、表１に示す反応条件で反応を行い、製造例１と同様の方法で未反応ＨＭＤＩを除去した。ポリイソシアネート組成物の物性を表２に示す。
【００５３】
【参考製造例３】
製造例１と同様の装置に、ＨＭＤＩを６００部、１，３−ブタンジオール１１部を仕込み、窒素雰囲気下、反応器内温度を８０℃に２時間保持した。その後、反応器内温度を６０℃に保持し、イソシアヌレート化反応触媒としてテトラメチルアンモニウムカプリエートを加え、収率が２８％になった時点で燐酸を添加し反応を停止した。反応液を濾過した後、薄膜蒸発缶を用いて未反応のＨＭＤＩを除去した。得られたポリイソシアネート組成物の物性を表２に示す。
【００５４】
【実施例１】
（水系ブロックポリイソシアネート組成物の製造）
撹拌機、温度計、還流冷却管、窒素吹き込み管、滴下ロートを取り付けた４ツ口フラスコ内を窒素雰囲気にし、製造例１で得られたポリイソシアネート組成物１００部、分子量６００のメトキシポリエチレングリコール（日本油脂の商標「ユニオックスＭ６００」）１９部（ポリイソシアネートの全イソシアネート基の１０％と反応する）、溶剤としてプロピレングリコールモノメチルエーテルアセテート４７部を仕込み、８０℃で７時間保持した。反応器内温度を５０℃に下げメチルエチルケトオキシム２６部を滴下し、赤外スペクトルによるイソシアネート基の特性吸収が消失したことを確認した。
【００５５】
樹脂固形分７５重量％の水系ブロックポリイソシアネート組成物溶液が得られた。得られた水系ブロックポリイソシアネート組成物の水分散性を評価したところ良好であった。
【００５６】
【実施例２〜７】
（水系ブロックポリイソシアネート組成物の製造）
表３に記載した以外は、実施例１と同様に行った。結果を表３に示す。
【００５７】
【比較例１〜３】
参考製造例１で得られたポリイソシアネート組成物を用い、表４に示した以外は、実施例１と同様に行った。結果を表４に示す。
【００５８】
【製造例６】
（水親和性ポリオールの製造）
撹拌機、温度計、還流冷却管、滴下ロートを取り付けた４ツ口フラスコ内にイソプロピルアルコール１００部を仕込み、８０℃に昇温した。スチレン２２部、メタクリル酸メチル２２部、アクリル酸ｎ−ブチル２１部、メタクリル酸２−ヒドロキシエチル２４部、アクリル酸１１部、アゾビス（イソブチロニトリル）３部を滴下ロートに仕込み、３．５時間かけてフラスコに滴下した。
【００５９】
滴下後、２時間保持し、樹脂分水酸基価１０４ｍｇＫＯＨ／ｇ、樹脂分酸価８６ｍｇＫＯＨ／ｇの水親和性ポリオールを得た。
【００６０】
【実施例８〜１４】
（水性塗料組成物）
製造例６で得られた水親和性ポリオールをジメチルエタノールアミンで中和したものと、実施例１〜７で得られた水系ブロックポリイソシアネート組成物とを、イソシアネート基／水酸基の当量比が１／１になるように混合した。更に水を添加し、塗料粘度が、フォードカップＮｏ．４で３０秒になるように調整した。この塗料をアプリケータ塗装し、１３０及び１００℃、３０分で硬化させた。塗膜焼き付け条件、評価結果を表５に示す。
【００６１】
【比較例４〜６】
比較例１〜３で得られた水系ブロックポリイソシアネートを用いた以外は実施例６と同様に行った。結果を表６に示す。
【００６２】
【表１】

【００６３】
【表２】

【００６４】
【表３】

【００６５】
【表４】

【００６６】
【表５】

【００６７】
【表６】

【００６８】
【発明の効果】
本発明の水系ブロックポリイソシアネート組成物を用いた水性塗料組成物は、硬化性が優れ、かつ耐候性を有する水性一液型熱硬化性塗料組成物である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous block polyisocyanate composition using a polyisocyanate composition obtained from an aliphatic or alicyclic diisocyanate, and an aqueous coating composition using the same.
[0002]
[Prior art]
In recent years, water-based paints have attracted attention from the viewpoints of the global environment, safety, and hygiene. It has come to be used for industrial coatings such as for building cans and coil coatings from building exteriors. Furthermore, there are many proposals regarding one-component paints for automobiles that require high quality such as weather resistance, chemical resistance, impact resistance, etc., as disclosed in JP-A-56-157358, JP-A-63-175079, Japanese Patent Application Laid-Open No. 63-193968 discloses a water-based paint. Many of the curing agents used here are alkyl etherified melamines.
[0003]
In addition, the coatings obtained from urethane-based paints that are cross-linked with isocyanate have very excellent wear resistance, chemical resistance, and stain resistance, and are made from aliphatic and alicyclic diisocyanates as isocyanate components. By using the non-yellowing polyisocyanate, the weather resistance is further improved, and the demand is increasing.
Therefore, development of water-based urethane paints capable of crosslinking with isocyanate has been actively conducted. When a one-component property such as a line paint is required, the isocyanate group of the polyisocyanate is usually blocked with a heat dissociable blocking agent and used as a blocked polyisocyanate.
[0004]
As an aqueous technology for block polyisocyanate, for example, JP-A-52-59657 uses a surfactant to make the block polyisocyanate aqueous. JP-A-56-151753 uses polyethylene oxide containing a higher fatty acid having 7 to 26 carbon atoms, and block polyisocyanate can be made aqueous by blocking the isocyanate group of polyisocyanate with sodium bisulfite. I have to.
[0005]
Japanese Patent Application Laid-Open No. 61-31422 discloses a technique in which a specific polyoxyethylene, which is a hydrophilic group, is reacted with polyisocyanate to prevent elution of a hydrophilic component and to make it aqueous using a high-speed stirring group or the like.
Techniques for making a polyisocyanate block having a heat resistant isocyanurate structure aqueous are disclosed in JP-A-62-151419 and JP-A-2-3465.
[0006]
JP-A-62-151419 adds a polyoxyethylene group to a part of polyisocyanate and further mixes a water-soluble polymer compound such as polyethylene glycol, a copolymer of ethylene oxide and propylene oxide. .
In JP-A-2-3465, hydrophilicity is imparted by hydroxycarboxylic acid.
[0007]
However, when these water-based block polyisocyanates are used to form a crosslinked coating film, high-temperature baking is required, and there is a limit to use for plastics and the like that are not heat resistant. Moreover, high temperature baking requires a large energy cost.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide an aqueous block polyisocyanate composition having excellent weather resistance and low temperature curability, and a coating composition containing the same.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention.
That is, the present invention is as follows.
[1] It has a thermally dissociable blocked isocyanate group and a nonionic hydrophilic group in one molecule,
(A) no ionic group in the molecule;
(B) Polyether chain unit / block Isocyanate group = 2 / 98-40 / 60 (mol / mol),
(C) Block isocyanate group average functional group number is 3.5-18,
(D) a number average molecular weight of 1,000 to 10,000,
(E) The latent isocyanate concentration is 2 to 19% by weight,
Water-based block polyisocyanate composition satisfying the above-mentioned conditions, and the precursor of the block polyisocyanate composition is the polyisocyanate composition A shown in the following (1), which can be dissolved or dispersed in water Block polyisocyanate composition.
[0010]
(1) A precursor polyisocyanate composition A is obtained by reacting at least one of aliphatic and / or alicyclic diisocyanates with a polyhydric alcohol,
(1) Isocyanate group average functional group number is 4.5-20,
(2) Viscosity at 25 ° C. of 5,000 to 100,000 mPa · s,
(3) The isocyanate concentration is 2 to 20% by weight,
(4) Diisocyanate cyclic trimer concentration is 10% or less,
(5) Concentration of allophanate bond / (allophanate bond + urethane bond) is 10% or more (however, all of (1) to (5) are substantially free of diisocyanate and solvent).
[0011]
[2] The water-based block polyisocyanate composition as described in 1 above, wherein the polyhydric alcohol is a 3 to 10 valent polyester and / or polyether.
[3] An aqueous coating composition comprising a water-affinity polyol having a resin hydroxyl value of 10 to 200 mg KOH / g and the water-based block polyisocyanate composition described in 1 or 2 above.
[0012]
In the above (1) to (5), “substantially free of diisocyanate and solvent” refers to a state in which the diisocyanate and solvent are removed using an industrial separation apparatus. In general, they are 1% by weight or less.
Hereinafter, the present invention will be described in detail.
The diisocyanates used in the present invention are aliphatic and alicyclic diisocyanates. Aliphatic diisocyanates having 4 to 30 carbon atoms are preferred, and alicyclic diisocyanates having 8 to 30 carbon atoms are preferred. For example, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1 , 6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, lysine diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 1,3-bis (Isocyanate methyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate and the like can be mentioned. Of these, 1,6-hexamethylene diisocyanate (hereinafter referred to as HMDI) and isophorone diisocyanate (hereinafter referred to as IPDI) are preferable from the viewpoint of weather resistance and industrial availability. May be.
[0013]
The polyhydric alcohol used in the present invention is preferably an alcohol having a valence of 3 or more, particularly preferably a valence of 3 to 20 and even more preferably a valence of 3 to 10.
Examples of the low molecular weight polyhydric alcohol include trimethylolpropane, glycerin, and pentaerythritol.
[0014]
Examples of the high molecular weight polyhydric alcohol include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine polyols, and acrylic polyols.
Specific examples of the aliphatic hydrocarbon polyols include terminal hydroxylated polybutadiene and hydrogenated products thereof. As the polyether polyols, for example, a single or mixture of polyhydric alcohols such as propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitol is added alone or a mixture of alkylene oxides such as ethylene oxide and propylene oxide. In addition, polyether polyols obtained by adding alkylene oxides alone or in mixture to polyfunctional compounds such as ethylenediamine and ethanolamine, and acrylamide etc. are polymerized using these polyethers as a medium. And so-called polymer polyols, polytetramethylene glycols, and the like obtained in the above manner.
[0015]
Polyester polyols include, for example, dibasic acids selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid or the like. Polyester polyol resins obtained by a condensation reaction of a polyhydric alcohol selected from the group of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin and the like alone or a mixture thereof, and, for example, ε -Polycaprolactones obtained by ring-opening polymerization of caprolactone using a polyhydric alcohol.
[0016]
Examples of epoxy resins include novolak type, β-methyl epichloro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compound, epoxidized fatty acid ester type, polyvalent carboxylic acid ester type, Examples thereof include aminoglycidyl type, halogenated type, and resorcin type epoxy resins.
[0017]
Examples of the acrylic polyol include acrylic acid esters having active hydrogen, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, or monoester or methacrylic acid glycerol. Acid monoester, trimethylolpropane acrylic acid monoester or methacrylic acid monoester alone or in mixture and methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-butyl, acrylic acid-2 -Acrylic esters such as ethylhexyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, methacrylic acid- -Methacrylic acid ester having active hydrogen such as hydroxybutyl, or methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, -n-butyl methacrylate, isobutyl methacrylate, -n-hexyl methacrylate, lauryl methacrylate, etc. A single or mixture selected from the group of methacrylic acid esters as essential components, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, and unsaturated such as acrylamide, N-methylol acrylamide and diacetone acrylamide Polymerized in the presence or absence of amide and glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, other polymerizable monomers such as dibutyl fumarate, alone or in a mixture It is an acrylic polyol resin.
[0018]
Among these polyols, preferred are the above-mentioned polyester polyols and polyether polyols, particularly preferred are polycaprolactone-based polyester polyols and polypropylene-based polyether polyols, and more preferably those having a number average molecular weight of 200 to 5,000. . These may be used alone or in combination of two or more.
[0019]
When the diisocyanate and the polyhydric alcohol are reacted, the equivalent ratio of the isocyanate group of the diisocyanate to the hydroxyl group of the polyhydric alcohol is preferably 2/1 to 30/1. If it is less than 2/1, the viscosity of the reaction solution after the reaction increases, and the capital investment for industrial production increases, and if it exceeds 30/1, the productivity tends to decrease. Preferably it is 5/1-20/1. The diisocyanate and the polyhydric alcohol may be charged into the reactor at the same time, or only the diisocyanate may be charged first, and after reaching a predetermined temperature, the polyhydric alcohol may be added all at once or in divided portions.
[0020]
The diisocyanate and the polyhydric alcohol are reacted to convert at least a part of the formed urethane bond into an allophanate bond.
A solvent may be used for the reaction. In that case, it is preferable to use a solvent inert to the isocyanate group.
The reaction temperature is 60 to 200 ° C, preferably 130 to 180 ° C. If it is less than 60 degreeC, the reaction rate is slow and the increase in the number of average functional groups of an isocyanate group estimated to be due to the allophanatization reaction hardly occurs. When it exceeds 200 ° C., an undesirable side reaction tends to occur such as coloring of the resulting polyisocyanate composition.
[0021]
While the reaction time varies depending on the reaction temperature, it is 1 to 8 hours, preferably 2 to 6 hours.
A catalyst can also be used in the reaction. As the catalyst, those having basicity are generally preferred. (A) Tetraalkylammonium hydroxide and quaternary amine compounds such as organic weak acid salts such as acetic acid and capric acid, Octylamine, 1,4-diazabicyclo (2,2,2) octane, 1,8-diazabicyclo (5,4,0) undecene-7, 1,5-diazabicyclo (4,3,0) nonene-5, etc. Tertiary amine compounds (c) Catalysts that promote allophanatization reactions such as metal organic weak acid salts such as zinc, tin, lead, and iron, such as acetylacetone metal salts such as zinc, are effective.
[0022]
The catalyst concentration is usually selected from the range of 10 ppm to 1.0% with respect to all isocyanate compounds charged into the reactor.
Part of the urethane bond formed by the reaction of the diisocyanate and the polyhydric alcohol is converted to an allophanate bond, and the resulting polyisocyanate composition A has an allophanate bond. The conversion of urethane bonds to allophanate bonds is 10% or more, preferably 20% or more. If the value is less than 10%, it is difficult to increase the number of isocyanate average functional groups, and the viscosity of the polyisocyanate composition may become too high.
[0023]
Moreover, the diisocyanate cyclic trimer density | concentration of the obtained polyisocyanate composition A is 10% or less. The concentration in this case is the ratio of the diisocyanate cyclic trimer peak area to the total peak area as measured by gel permeation chromatography. When the concentration of the diisocyanate cyclic trimer exceeds 10%, the number of isocyanate functional groups hardly increases, and the diisocyanate cyclic trimer may deteriorate the physical properties of the coating film when imparted with hydrophilicity described later. That is, a component having a low number of isocyanate functional groups, such as a diisocyanate cyclic trimer, is further reduced in the number of isocyanate functional groups by imparting hydrophilicity, resulting in a decrease in crosslinkability.
[0024]
The yield is approximately 20% to 70% by weight.
Unreacted diisocyanate and solvent are removed, and a precursor polyisocyanate composition A having an allophanate bond used in the present invention is obtained.
The number of isocyanate average functional groups of the polyisocyanate composition is the number of isocyanate functional groups statistically possessed by one molecule of polyisocyanate, and can be calculated from the number average molecular weight of the polyisocyanate composition and the isocyanate concentration by the following formula.
[0025]
[Expression 1]

[0026]
The isocyanate group average functional group number of the polyisocyanate composition A used for this invention is 4.5-20. When the number of functional groups is less than 4.5, a good coating film cannot be obtained. If the number of functional groups exceeds 20, the mechanical properties of the coating film are inferior. Preferably it is 6-15.
The viscosity at 25 ° C. of the polyisocyanate composition A thus obtained is 5,000 to 100,000 mPa · s and the isocyanate concentration is 2 to 20% by weight.
[0027]
A compound having active hydrogen and ethylene oxide units is added to the resulting polyisocyanate composition A. This compound can be obtained by adding ethylene oxide to a monoalcohol such as methanol, ethanol, or butanol. The content of ethylene oxide in the obtained compound is preferably 50% by weight or more, and the number average molecular weight is preferably 200 to 1,000. This compound may contain propylene oxide.
[0028]
The addition amount of the compound having active hydrogen and ethylene oxide unit to polyisocyanate composition A (polyether chain unit / isocyanate group (mol / mol)) is 2 to 40% of the total isocyanate groups of the polyisocyanate composition, preferably 2-30%. If it is less than 2%, the water dispersibility of the polyisocyanate composition is lowered, and if it exceeds 40%, the physical properties of the coating film are lowered. The reaction of the compound and polyisocyanate composition A can also be performed using a solvent. The solvent used in this case is preferably inert to isocyanates.
[0029]
The reaction temperature is 40 to 150 ° C, preferably 60 to 120 ° C. If necessary, a basic compound such as a tin compound such as dibutyltin dilaurate may be used for the reaction catalyst. Polyisocyanate composition A to which the compound is not added can be mixed with the obtained polyisocyanate composition. In this case, the ratio of the compound to the total isocyanate is preferably 2 to 40%.
[0030]
The isocyanate group of the polyisocyanate composition thus obtained is reacted with a blocking agent to obtain a thermally dissociable blocked isocyanate group.
Examples of the blocking agent used in the present invention include phenolic, active methylene, mercaptan, acid amide, acid imide, imidazole, urea, oxime, amine, and imide compounds. Or you may use it, mixing. Examples of more specific blocking agents are shown below.
[0031]
1) Phenol type; phenol, cresol, ethylphenol, butylphenol and the like.
2) Active methylene series: Malonic acid diester (dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-2-ethylhexyl malonate, methyl n-butyl malonate, ethyl n-butyl malonate, methyl sec-malonate sec -Butyl, ethyl sec-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, diethyl methyl malonate, dibenzyl malonate, diphenyl malonate, benzyl methyl malonate, ethyl phenyl malonate, t malonic acid t -Butylphenyl, isopropylidenemalonate), acetoacetate (methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, benzyl acetoacetate, acetoacetic acid Phenyl) acetylacetone .
[0032]
3) Mercaptan series; butyl mercaptan, dodecyl mercaptan, etc.
4) Acid amide system; acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam and the like.
5) Acid imide type: succinimide, maleic imide and the like.
6) Imidazole series; imidazole, 2-methylimidazole and the like.
[0033]
7) Urea type; urea, thiourea, ethylene urea and the like.
8) Oxime type: formaldoxime, acetaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc.
9) Amine type; diphenylamine, aniline, carbazole and the like.
10) Imine type; ethyleneimine, polyethyleneimine and the like.
[0034]
11) Bisulfite; sodium bisulfite and the like.
12) Pyrazole type; pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and the like.
13) Triazole type; 1,2,4-triazole and the like.
Of these, active methylene, oxime, and acid amide are preferable, and acetooxime, methyl ethyl ketoxime, malonic acid diester, and acetoacetate are particularly preferable. One or more malonic acid diesters and one acetoacetate are particularly preferable. It is preferable to use the above in combination. The combination ratio is preferably a malonic acid diester / acetoacetate ester = 5/1 to 1/5 in terms of molar ratio. If the above value exceeds 5/1, crystallization of the block polyisocyanate may occur. If it is less than / 5, yellowing or the like may occur when the coating film is cured.
[0035]
The reaction between the polyisocyanate composition and the blocking agent can be performed regardless of the presence or absence of a solvent. When using a solvent, it is preferable to use a solvent inert to the isocyanate group.
In the blocking reaction, the reaction catalyst of diisocyanate and polyol can be used as a catalyst. When the used catalyst may adversely affect the physical properties of the paint, it is preferable to neutralize the catalyst with an acidic compound or the like. Examples of acidic compounds in this case include inorganic acids such as hydrochloric acid, phosphorous acid, and phosphoric acid, and sulfonic acids such as methanesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid methyl ester, and p-toluenesulfonic acid ethyl ester. Or its derivatives, ethyl phosphate, diethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphate, dibutyl phosphate, 2-ethylhexyl phosphate, di (2 ethylhexyl) phosphate, isodecyl phosphate, diisodecyl phosphate, oleyl acid phosphate, tetracosyl acid phosphate, There are ethylene glycol acid phosphate, butyl pyrophosphate, butyl phosphite, etc., and these may be used in combination of two or more.
[0036]
The blocking reaction can be generally carried out at -20 to 150 ° C, preferably 0 to 100 ° C. If the temperature exceeds 100 ° C., side reactions may occur. On the other hand, if the temperature is too low, the reaction rate is low, which is disadvantageous.
Thus, the density | concentration of the isocyanate group reacted with the blocking agent is called a latent isocyanate concentration, and the number of isocyanate functional groups reacted with the blocking agent statistically contained in one molecule is called the blocked isocyanate group average functional group number.
[0037]
Either the reaction of the isocyanate group and the blocking agent, or the reaction of the isocyanate group and the ethylene oxide adduct can be preceded or can be performed simultaneously.
The aqueous block polyisocyanate composition of the present invention thus obtained has the following characteristics.
(A) No ionic group is contained in the molecule.
(B) Polyether chain unit / isocyanate group = 2/98 to 40/60 (mol / mol).
(C) The block isocyanate average functional group number is 3.5-18.
(D) Number average molecular weight is 1,000 to 10,000.
(E) The latent isocyanate concentration is 2 to 19% by weight.
[0038]
Furthermore, an anionic, cationic, nonionic or amphoteric surfactant can be added depending on the purpose. Specific examples of the surfactant include, for example, carboxylic acid, sulfonic acid, sulfuric acid ester, phosphoric acid ester, anionic polymer such as sodium and potassium of polymerization type polymer, quaternary ammonium salt, cationic system such as polyethyleneamine derivative, There are nonionic surfactants such as ether-based, ester-based, ester-ether-based, nitrogen-containing, and the like, and zwitterionic surfactants such as carboxybetaine, aminocarboxylic acid, sulfobetaine, aminosulfate, and imidazoline.
[0039]
In the present invention, it is preferable to include a monohydric alcohol compound in order to improve storage stability. Examples of the monohydric alcohol compound include aliphatic, alicyclic, and aromatic, with aliphatic being preferred. C1-C20 is preferable, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, 2-methyl-1-propanol, n-amyl alcohol, 2-pentanol, Saturation of 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2, -dimethyl-1-propanol There are ether alcohols such as alcohol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, and 3,6-dioxa-1-heptanol. The addition amount is preferably 0.2 to 10 times the molar amount with respect to the thermally dissociable blocked isocyanate group.
[0040]
The low-temperature curable water-based block polyisocyanate composition thus prepared is mixed with a water-affinity polyol to form a main component of the aqueous coating composition.
The water-affinity polyol used in the present invention can be used without particular limitation as long as it is usually used for water-based paints, and can be anionic, cationic or zwitterionic and has ionicity. It may not be. There are alkyd, polyester, epoxy, fluorine, acrylic and the like. The polyol has a hydroxyl group value of 10 to 200 mgKOH / g and is dissolved or dispersed in a dispersion medium containing water as a main component. When the resin hydroxyl value is less than 10 mgKOH / g, the density of urethane crosslinking due to the reaction with the isocyanate component is reduced, and the physical properties of the present invention cannot be achieved, and the resin hydroxyl value exceeds 200 mgKOH / g. On the contrary, the crosslink density increases, and the mechanical properties of the coating film decrease, which is not preferable.
[0041]
As the soluble polyol, a number average molecular weight of 2,000 to 100,000 is preferable. For example, JP-A 63-295680, JP-A 63-175059, JP-A 62-216671, A manufacturing method thereof is disclosed in, for example, Japanese Laid-Open Patent Application No. 2-191692. The dispersion type polyol is a latex containing a hydroxyl group, and its production method is disclosed in, for example, JP-A-56-157358.
[0042]
As a fluoropolyol which is a fluorocopolymer having a hydroxyl group, its production method is disclosed in JP-A-57-34107, JP-A-61-231044, JP-A-3-37252 and the like. .
In the water-based coating composition of the present invention, the equivalent ratio of the thermally dissociable blocked isocyanate group to the hydroxyl group of the water-soluble polyol is usually set to 10: 1 to 1:10.
[0043]
As the curing agent, a curing agent other than the block polyisocyanate, for example, a melamine-based curing agent can be used in combination. Typical examples of the melamine curing agent include hexamethoxymethylol melamine and methyl / butyl etherified melamine.
If necessary, add antioxidants, ultraviolet absorbers, pigments, metal powder pigments such as aluminum, cross-linking accelerators such as organometallic compounds such as dibutyltin dilaurate, leveling agents, rheology control agents, solvents, etc. Also good.
[0044]
Usually, an aqueous coating composition is obtained by mixing a water-affinity polyol, a curing agent, an additive, and the like, adding a medium containing water as a main component, and adjusting the coating viscosity according to the coating method.
The water-based paint adjusted in this way is applied to metals, plastics, inorganic materials, etc. by methods such as spray coating, roll coating, shower coating, and immersion coating, and is useful as a chipping-resistant coating material, a pre-coated metal coating material, and the like.
[0045]
The low-temperature curable water-based block polyisocyanate composition of the present invention includes, in addition to paints, inorganic materials such as inks, adhesives, fibers, films, and ceramics, modifiers such as paper, wood, and resins, surface treatment agents, and binders. It is also useful.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.
Parts and% are based on weight. Evaluation was performed according to the following.
(Measurement of number average molecular weight)
The number average molecular weight is a polystyrene-based number average molecular weight determined by gel permeation chromatograph (hereinafter referred to as GPC) measurement using the following apparatus.

(Diisocyanate cyclic trimer concentration)
The molecular weight (for example, 504 in the case of HMDI) corresponding to the diisocyanate cyclic trimer obtained by the GPC measurement was expressed as a peak area%.
[0047]
(Measurement of allophanate binding concentration)
JEFT's FT-NMR “FX90Q” was used, the solvent was acetone-d6, and as a result of H-NMR measurement, the value represented by allophanate bond / (allophanate bond + urethane bond) was 0.9 or more. , Less than 0.9 and 0.1 or more are indicated by ◯, and less than 0.1 are indicated by ×.
[0048]
(Viscosity measurement)
It measured at 25 degreeC using the Emira type | formula rotational viscometer.
(Gel fraction)
When the cured coating film was immersed in acetone at 20 ° C. for 24 hours, the value of the undissolved part weight relative to that before immersion was calculated, and less than 85% was indicated by x and 85% or more was indicated by ◯.
[0049]
(Evaluation of water dispersibility of block polyisocyanate composition)
The block polyisocyanate composition and pure water were mixed at a weight ratio of 2:10, and the subsequent solution state was observed with the naked eye. A state in which the liquid mixture was uniform and no precipitate was evaluated as “good”.
[0050]
[Production Example 1]
(Production of polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel is placed in a nitrogen atmosphere, 600 parts of HMDI is a polyether polyol (trademark “Adecan New” from Asahi Denka) 169 parts of polyol WR-474 ") was charged, and the temperature in the reactor was kept at 120 ° C for 5 hours with stirring. The reaction liquid temperature was lowered and unreacted HMDI was removed using a thin film evaporator.
[0051]
The molecular weight of the reaction product was measured by GPC, the allophanate bond concentration was measured by H-NMR, and the isocyanate concentration was measured by titration to confirm that the polyisocyanate composition of the present invention was produced.
The resulting polyisocyanate composition had a viscosity at 25 ° C. of 20,000 mPa · s, an isocyanate concentration of 13.2%, a number average molecular weight of 1,690, an isocyanate average functional group number of 5.3, and a diisocyanate cyclic 3 content. The body concentration was 1.7%. Moreover, the allophanate bond density | concentration of this polyisocyanate composition was (circle).
[0052]
[Production Examples 2 to 5 and Reference Production Examples 1 and 2]
Using the same apparatus as in Production Example 1, the reaction was carried out under the reaction conditions shown in Table 1, and unreacted HMDI was removed by the same method as in Production Example 1. Table 2 shows the physical properties of the polyisocyanate composition.
[0053]
[Reference Production Example 3]
In the same apparatus as in Production Example 1, 600 parts of HMDI and 11 parts of 1,3-butanediol were charged, and the temperature in the reactor was maintained at 80 ° C. for 2 hours in a nitrogen atmosphere. Thereafter, the temperature in the reactor was kept at 60 ° C., tetramethylammonium capriate was added as an isocyanuration reaction catalyst, and phosphoric acid was added to stop the reaction when the yield reached 28%. After the reaction solution was filtered, unreacted HMDI was removed using a thin film evaporator. Table 2 shows the physical properties of the resulting polyisocyanate composition.
[0054]
[Example 1]
(Production of water-based block polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, 100 parts of the polyisocyanate composition obtained in Production Example 1, methoxypolyethylene glycol having a molecular weight of 600 ( 19 parts (reacted with 10% of all isocyanate groups of polyisocyanate) 19 parts (trade name “Niox M600” of Nippon Oil & Fats) and 47 parts of propylene glycol monomethyl ether acetate as a solvent were kept at 80 ° C. for 7 hours. The temperature inside the reactor was lowered to 50 ° C., and 26 parts of methyl ethyl ketoxime was added dropwise to confirm that the characteristic absorption of isocyanate groups by infrared spectrum disappeared.
[0055]
An aqueous block polyisocyanate composition solution having a resin solid content of 75% by weight was obtained. When the water dispersibility of the obtained aqueous block polyisocyanate composition was evaluated, it was good.
[0056]
Examples 2-7
(Production of water-based block polyisocyanate composition)
The same procedure as in Example 1 was performed, except that it was described in Table 3. The results are shown in Table 3.
[0057]
[Comparative Examples 1-3]
The same procedure as in Example 1 was carried out except that the polyisocyanate composition obtained in Reference Production Example 1 was used and that it was shown in Table 4. The results are shown in Table 4.
[0058]
[Production Example 6]
(Production of water affinity polyol)
100 parts of isopropyl alcohol was charged into a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, and the temperature was raised to 80 ° C. 22 parts of styrene, 22 parts of methyl methacrylate, 21 parts of n-butyl acrylate, 24 parts of 2-hydroxyethyl methacrylate, 11 parts of acrylic acid and 3 parts of azobis (isobutyronitrile) were charged into a dropping funnel, 3.5 It was added dropwise to the flask over time.
[0059]
After dropping, the mixture was held for 2 hours to obtain a water-affinity polyol having a resin partial hydroxyl value of 104 mgKOH / g and a resin partial acid value of 86 mgKOH / g.
[0060]
Examples 8 to 14
(Water-based paint composition)
The water-soluble polyol obtained in Production Example 6 was neutralized with dimethylethanolamine and the water-based block polyisocyanate composition obtained in Examples 1 to 7 having an isocyanate group / hydroxyl equivalent ratio of 1 / 1 to mix. Water was further added and the paint viscosity was 4 was adjusted to 30 seconds. The paint was applied with an applicator and cured at 130 and 100 ° C. for 30 minutes. Table 5 shows the baking conditions and the evaluation results.
[0061]
[Comparative Examples 4-6]
It carried out similarly to Example 6 except having used the water-system block polyisocyanate obtained by Comparative Examples 1-3. The results are shown in Table 6.
[0062]
[Table 1]

[0063]
[Table 2]

[0064]
[Table 3]

[0065]
[Table 4]

[0066]
[Table 5]

[0067]
[Table 6]

[0068]
【The invention's effect】
The aqueous coating composition using the water-based block polyisocyanate composition of the present invention is an aqueous one-component thermosetting coating composition having excellent curability and weather resistance.

Claims (3)

It has a thermally dissociable blocked isocyanate group and a nonionic hydrophilic group in one molecule,
(A) no ionic group in the molecule;
(B) polyether chain unit / block isocyanate group = 2/98 to 40/60 (mol / mol),
(C) Block isocyanate group average functional group number is 3.5-18,
(D) a number average molecular weight of 1,000 to 10,000,
(E) The latent isocyanate concentration is 2 to 19% by weight,
Water-based block polyisocyanate composition satisfying the above-mentioned conditions, and the precursor of the block polyisocyanate composition is the polyisocyanate composition A shown in the following (1), which can be dissolved or dispersed in water Block polyisocyanate composition.
(1) A precursor polyisocyanate composition A is obtained by reacting at least one of aliphatic and / or alicyclic diisocyanates with a polyhydric alcohol,
(1) Isocyanate average functional group number is 4.5-20,
(2) Viscosity at 25 ° C. of 5,000 to 100,000 mPa · s
(3) The isocyanate concentration is 2 to 20% by weight,
(4) Diisocyanate cyclic trimer concentration is 10% or less,
(5) The allophanate bond / (allophanate bond + urethane bond) concentration is 10% or more (however, (1) to (5) are substantially free of diisocyanate and solvent).   The aqueous block polyisocyanate composition according to claim 1, wherein the polyhydric alcohol is a trivalent to trivalent polyester and / or polyether.   An aqueous coating composition comprising a water-affinity polyol having a resin hydroxyl value of 10 to 200 mgKOH / g and the water-based block polyisocyanate composition according to claim 1 or 2.