JP2004083839A - Low temperature curable epoxy resin, method for producing the same and composition for powder coating using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for powder coating using a low temperature curable epoxy resin. <P>SOLUTION: This powder coating composition contains 100 pts. wt. low temperature curable epoxy resin expressed by general formula (I) [wherein, (n) is 0 or 1-30 real number; R<SB>1</SB>, R<SB>2</SB>are each independently H, substituted or non-substituted 1-5C alkyl or alkoxy; and X is H or glycidyl and ≥20 % of X is glycidyl] and 30-500 pts. wt. curing agent. Thereby, since the composition is easily cured at a low temperature, it is possible to provide the powder coating capable of being used on a raw material of which temperature can not be easily elevated, or a material sensitive to heat. <P>COPYRIGHT: (C)2004,JPO

Description

（式中、ｎは０．１乃至３０の実数を表し、Ｒ_１及びＲ_２は、独立的に水素、置換又は非置換された炭素原子数１乃至５のアルキル又はアルコキシであり、Ｘは水素原子又はグリシジル基を表すが、Ｘの２０％以上はグリシジル基を表す。）
【００１３】
また、請求項１の構成において、上記一般式（Ｉ）で表される低温硬化性エポキシが、下記式（１）で表されるエポキシ樹脂であることが好ましい。

（式中、ｎは０．１乃至３０の実数を表し、Ｒ_１及びＲ_２は、独立的に水素、置換又は非置換された炭素原子数１乃至５のアルキル又はアルコキシである。）
【００１４】
また、前記式（Ｉ）中、Ｒ_１およびＲ_２が共に水素又はメチルであり、ｎが１乃至１５の実数であるのが好ましい。
【００１５】
本発明の別の実施例によれば、消泡剤０．１乃至２０重量部％と、レベリング剤０．１乃至２０重量％とをさらに含むことが好ましい。
【００１６】
本発明の別の実施例によれば、前記硬化剤はフェノール系硬化剤又はポリエステル系硬化剤であることが好ましい。
【００１７】
本発明の別の実施例によれば、本発明の粉体塗料組成物は前記一般式（Ｉ）で表される低温硬化性エポキシ樹脂１００重量部に対して、エポキシ当量６００乃至１５００ｇ／ｅｑのビスフェノールＡ系凡用粉体塗料用エポキシ樹脂１０乃至２００重量部をさらに含むのが好ましい。
【００１８】
本発明のさらに別の実施例によれば、本発明の粉体塗料組成物は、顔料、酸化防止剤、充填剤、光安定剤、硬化促進剤及び紫外線吸収剤よりなる群から選択された１種以上をさらに含むことが好ましい。
【００１９】
【発明の実施の形態】
以下、本発明をさらに詳細に説明する。
【００２０】
本発明の粉体塗料組成物は、下記一般式（Ｉ）で表されるエポキシ樹脂１００重量部と、硬化剤３０乃至５００重量部とを含むことが必要である。

（式中、ｎは０．１乃至３０の実数を表し、Ｒ_１及びＲ_２は、独立的に水素、置換又は非置換された炭素原子数１乃至５のアルキル又はアルコキシであり、Ｘは水素原子又はグリシジル基を表すが、Ｘの２０％以上はグリシジル基を表す。）
【００２１】
本発明において、一般式（Ｉ）中、Ｒ_１及びＲ_２が共に水素原子又は共にメチル基であることが好ましい。また、上記Ｒ_１及びＲ_２で表される炭素原子数１乃至５のアルキル基としては、例えば、メチル、エチル、プロピル、ブチルなどの基が挙げられる。また、ｎは０．１乃至３０の実数であり、好ましくは１乃至１５の実数を表す。Ｘは水素原子又はグリシジル基を表すが、Ｘの２０％以上、好ましくは２５％以上がグリシジル基である。ここで、ｎおよびＸは平均値を表すものである。本発明において、ｎが０．１未満あるいはＸの２０％未満がグリシジル基である場合には、三官能以上の多官能エポキシ化合物の含有量が少なくなるため、硬化性や塗膜物性が満足できるものが得られなくなる。
【００２２】
本発明の粉体塗料用組成物は、主剤として前記一般式（Ｉ）の低温硬化性エポキシ樹脂を使用する必要があり、前記一般式（１）の低温硬化性エポキシ樹脂であることが好ましい。
【００２３】
また、本発明の粉体塗料用組成物は、硬化剤としてはフェノール系硬化剤又はポリエステル系硬化剤を使用することが好ましい。すなわち、酸無水物やアミンのような一般塗料用硬化剤を使用せずに、低温で加熱することによって前記粉体塗料用組成物を硬化反応せしめ得るように、硬化剤としてフェノール系又はポリエステル系樹脂を使用することが好ましい。
【００２４】
本発明の粉体塗料用組成物で使用される硬化剤の使用量は、前記一般式（Ｉ）の低温硬化性エポキシ樹脂１００重量部に対して３０ないし５００重量部を使用できるが、その理由は、主剤と硬化剤の官能基が当量反応によって完全に反応して未反応官能基が残らないようにするためである。
【００２５】
本発明に使用される一般式（Ｉ）で表されるエポキシ樹脂は、エポキシ当量が２００乃至６００ｇ／ｅｑであることが好ましく、エポキシ当量が６００ｇ／ｅｑを越えるような場合には、硬化物が着色したり、物性が低下するおそれがある。
【００２６】
本発明の粉体塗料用組成物で硬化剤として使用されるポリエステル系硬化剤は、当業界で粉体塗料用組成物に通常的に使用されるものであって、エポキシ樹脂との硬化反応に参与できるカルボキシ基を含有するものなら特に制限はないが、ガラス転移温度が５５ないし６５℃であり、酸価は３０ないし８０程度であるのが好ましい。
【００２７】
商業的に得られる前記ポリエステル系硬化剤の例には、商標名「ＫＰ−３５２０」（国都化学株式会社製）、商標名「ＫＰ−３５３１」（国都化学株式会社製）、商標名「ＫＰ−３６２０」（国都化学株式会社製）、商標名「ＫＰ−３７２０」（国都化学株式会社製）などがある。
【００２８】
また、本発明の粉体塗料用組成物で硬化剤として使用されるフェノール系硬化剤は、当業界で粉体塗料用組成物に通常的に使用されるものであれば特に限定されないが、末端基にＯＨ基を有し、このようなフェノールＯＨ基の当量は２００ないし８００であるのが好ましい。本発明においては、ビスフェノールＡ系硬化剤を使用することが好ましい。
【００２９】
商業的に得られる前記ビスフェノールＡ系硬化剤としては、例えば商標名「ＫＤ−４１０Ｊ」（国都化学株式会社製）、商標名「ＫＤ−４０６」（国都化学株式会社製）、商標名「ＫＤ−４２０」（国都化学株式会社製）、商標名「ＫＤ−４２６」（国都化学株式会社製）などが挙げられる。
【００３０】
本発明の粉体塗料組成物は、エポキシ当量６００ないし１５００ｇ／ｅｑのビスフェノールＡ系凡用粉体塗料用エポキシ樹脂をさらに含むのが好ましいが、これらは粉体塗料が硬化するときフェノール系硬化剤およびポリエステル系硬化剤と反応して硬化物を形成する。前述のような当量６００ないし１５００ｇ／ｅｑのビスフェノールＡ系凡用粉体塗料用エポキシ樹脂は、前記一般式（Ｉ）の低温エポキシ樹脂１００重量部に対して１０ないし２００重量部の含量で添加されるのが好ましく、その含量が１０重量部未満であれば添加に伴う効果が少なく、２００重量部を超えると低温硬化効果がなくなり、かつ機械的物性が低くなるため、好ましくない。
【００３１】
本発明の粉体塗料用組成物は当業界に公知の消泡剤を所定量含有するのが好ましいが、消泡剤は塗膜表面での気泡発生を抑制する役割をし、その含量は粉体塗料組成物総重量を基準に０．１ないし２０重量％であることが好ましい。消泡剤の含量がこの範囲を外れると物性に悪影響を与えることになる。
【００３２】
本発明の粉体塗料用組成物に使用されるレベリング剤は塗膜の平滑性を付与するものであって、その含量は粉体塗料組成物総重量を基準に０．１ないし２０重量％であることが好ましい。レベリング剤の含量がこの範囲を外れる場合もやはり機械的物性に良くない影響を与える。
【００３３】
本発明の前記粉体塗料用組成物は、前記成分以外にも当業界で粉体塗料用組成物に通常的に添加される公知の添加剤をさらに含むことができる。この種の添加剤には顔料、酸化防止剤、充填剤、光安定剤、硬化促進剤及び紫外線吸収剤などがあり、これらからなる群から選ばれる１種以上を、必要に応じて適宜含むことができる。
【００３４】
本発明に使用される一般式（Ｉ）の低温硬化性多官能性エポキシ樹脂は、例えば下記一般式（２）の構造を有するビスフェノールＡ系エポキシ樹脂とエピクロロヒドリンを重合して製造することができる。

（式中、ｎは０．１乃至３０の実数を表し、Ｒ_１及びＲ_２は、独立的に水素、置換又は非置換された炭素原子数１乃至５のアルキル又はアルコキシである。）
【００３５】
本発明における一般式（Ｉ）の低温硬化性エポキシ樹脂を製造するために使用されるエピクロロヒドリンは、１，２−エポキシ−３−クロロプロパンとも呼ばれ、下記一般式３のような構造を有し、無色透明な液体であってｄｌ−体とｌ−体が知られているが、通常はｄｌ−体を指す。

【００３６】
前記一般式（２）のビスフェノールＡ系化合物と前記一般式（３）のエピクロロヒドリンを反応させることによって、本発明の前記一般式（Ｉ）の多官能性エポキシ樹脂を製造することができ、その製造方法は具体的に下記の反応式１の通りである。
（反応式１）

【００３７】
前記反応式１に示したように、前記化学式（２）のビスフェノールＡ系エポキシ樹脂を、触媒の存在下に過量の前記化学式（３）のエピクロロヒドリンと反応させて、本発明における一般式（Ｉ）の低温硬化性である多官能性エポキシ系樹脂を得ることができる。このときの反応温度は５０〜８０℃の範囲であることが好ましく、３０〜２５０Ｔｏｒｒの減圧条件下で反応が行われることが好ましい。また、前記反応の反応時間は、２乃至３０時間であることが好ましい。
【００３８】
前記触媒としては、アルカリ、ルイス酸および層間移動触媒が挙げられる。ここで、アルカリとしては、例えば、水酸化ナトリウム、水酸化カリウム、水酸化カルシウムなどが挙げられ、ルイス酸としては、例えば、トリフッ化ホウ素、塩化錫、塩化亜鉛などが挙げられ、層間移動触媒としては、例えば、テトラメチルアンモニウムクロリド、テトラブチルアンモニウムブロミド、メチルトリオクチルアンモニウムクロリド、メチルトリデシルアンモニウムクロリド、Ｎ，Ｎ−ジメチルピロリジニウムクロリド、Ｎ−エチル−Ｎ−メチルピロリジニウムヨージド、Ｎ−ブチル−Ｎ−メチルピロリジニウムブロミド、Ｎ−ベンジル−Ｎ−メチルピロリジニウムクロリド、Ｎ−エチル−Ｎ−メチルピロリジニウムブロミド、Ｎ−ブチル−Ｎ−メチルモルホリニウムブロミド、Ｎ−ブチル−Ｎ−メチルモルホリニウムヨージド、Ｎ−アリル−Ｎ−メチルモルホリニウムブロミド、Ｎ−メチル−Ｎ−ベンジルピペリジニウムクロリド、Ｎ−メチル−Ｎ−ベンジルピペリジニウムブロミド、Ｎ，Ｎ−ジメチルピペリジニウムヨージド、Ｎ−メチル−Ｎ−エチルピペリジニウムアセテート、Ｎ−メチル−Ｎ−エチルピペリジニウムヨージドなどが挙げられるが、これらの中でテトラメチルアンモニウムクロリドが好ましい。
【００３９】
前記反応式１におけるエピクロルヒドリンの使用量は、ジグリシジルエーテルの水酸基１当量に対し、１当量以上で使用されることが好ましく、より好ましくは２〜１０当量の範囲である。
【００４０】
また、前記反応式１において、触媒としてのアルカリの使用量は、グリシジル化される水酸基１当量に対し、０．１〜２．０モル使用されることが好ましく、より好ましくは０．３〜１．５モル使用である。また、前記反応式１において、触媒としての層間移動触媒の使用量は、反応剤の全重量に対し、０．０１〜１０モル％であることが好ましく、より好ましくは０．２〜２モル％である。
【００４１】
また、前記反応は炭化水素、エーテル又はケトンのような溶媒下で行なうこともできるが、過剰のエピクロルヒドリンを溶媒として使用することもできる。また、前記一般式（Ｉ）で表されるエポキシ樹脂は、Ｘの２０％以上がグリシジル基である必要があるが、エピクロルヒドリンの過剰量、反応温度、反応圧力、反応時間、触媒の種類および使用量等の反応条件を調整することにより任意の再エポキシ化率のエポキシ樹脂を製造することができる。
【００４２】
前記反応で得られた本発明の一般式（Ｉ）の低温硬化性である多官能性エポキシ系樹脂は、エポキシ当量が２００乃至６００の値を有し、ｎの値は、１乃至３０の値を有する。
【００４３】
本発明に使用される一般式（１）の低温硬化性である多官能性エポキシ樹脂は、例えば下記一般式（２）の構造を有するビスフェノールＡ系エポキシ樹脂と前記一般式（３）のエピクロロヒドリンを重合して製造することができる。

（式中、ｎは０．１乃至３０の実数を表し、Ｒ_１及びＲ_２は、独立的に水素、置換又は非置換された炭素原子数１乃至５のアルキル又はアルコキシである。）
【００４４】
前記一般式（２）のビスフェノールＡ系化合物と前記一般式（３）のエピクロロヒドリンを反応させることによって、本発明の前記一般式（１）の多官能性エポキシ樹脂を製造することができ、その製造方法は具体的に下記の反応式２の通りである。
（反応式２）

【００４５】
前記反応式２に表されるように、前記一般式（２）のビスフェノールＡ系エポキシ樹脂を触媒下で、過量の前記一般式（３）のエピクロロヒドリンと反応させて、本発明の一般式（１）の多官能性エポキシ樹脂が得られる。
【００４６】
前記反応において反応温度は５０ないし１８０℃の範囲にあり、３０ないし２５０Ｔｏｒｒの減圧条件下で反応が行われることが好ましい。
【００４７】
前記反応において出発物質として加えられる前記一般式（３）のエピクロロヒドリンは、前記一般式（２）のビスフェノールＡ系エポキシ樹脂に比べて過量加えるのが好ましく、前記一般式（２）のビスフェノールＡ系エポキシ樹脂に対して１：３０ないし１：８０のモル比で加えられるのがよい。
【００４８】
また、前記反応において出発物質として加えられる前記一般式（２）のビスフェノールＡ系エポキシ樹脂は、エポキシ当量が４００ないし２０００の値を有するものが好ましく、４００ないし１０００の値を有するものがより好ましい。
【００４９】
このような前記一般式（２）のビスフェノールＡ系エポキシ樹脂は、市販されている製品を適宜購入して使用することもできるが、下記反応式３の工程にしたがって製造することも可能である。
（反応式３）

（式中、Ｒ_１、Ｒ_２およびｎは前記一般式（Ｉ）での定義と同一である）
【００５０】
前記反応式３に表すように、前記一般式（４）の通常のビスフェノールＡ系化合物と前記一般式（３）のエピクロロヒドリンを反応させて本発明の出発物質として使用される前記一般式（２）のビスフェノールＡ系エポキシ樹脂を製造することができる。
【００５１】
【実施例】
以下、実施例を挙げて本発明をさらに詳細に説明するが、本発明の範疇が下記実施例に限定されるのではない。
【００５２】
１．多官能性エポキシ樹脂の製造
製造例１
ビスフェノールＡ系エポキシ樹脂５００ｇ（エポキシ当量：７００ｇ／ｅｑ、ｎ＝３．７、Ｒ_１：ＣＨ_３、Ｒ_２：ＣＨ_３）とエピクロロヒドリン１３００ｇを、１００Ｔｏｒｒの減圧条件下、６０℃で３時間触媒のＮａＯＨとともに反応させた後、未反応エピクロロヒドリンを分離、除去し、メチルイソブチルケトンを使用して脱塩し、精製水を使用して洗浄することによって所望の多官能性エポキシ樹脂（ＥＰ−１）を得た。
【００５３】
製造例２
ビスフェノールＦ系エポキシ樹脂の５００ｇ（エポキシ当量：１０００ｇ／ｅｑ、ｎ＝６．６、Ｒ_１：Ｈ、Ｒ_２：Ｈ）とエピクロロヒドリン１３００ｇを１００Ｔｏｒｒの減圧条件下、７０℃で３時間触媒のＫＯＨとともに反応させた後、未反応エピクロロヒドリンを分離、除去し、メチルイソブチルケトンを使用して脱塩し、精製水を使用して洗浄することによって所望の多官能性エポキシ樹脂（ＥＰ−２）を得た。
【００５４】
製造例３
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＡ系エポキシ樹脂▲１▼（エポキシ当量：６５０ｇ／ｅｑ、ｎ＝３．４、Ｒ_１：ＣＨ_３、Ｒ_２：ＣＨ_３）６５重量部、エピクロルヒドリン４６．３重量部およびテトラメチルアンモニウムクロライド０．２重量部を仕込み、滴下装置中に水酸化ナトリウム８．５重量部を４８重量％水溶液として入れておく。水酸化ナトリウム水溶液を還流下５０〜６０℃の内部温度で８０Ｔｏｒｒで２時間かけて滴下し、同時に水を共沸蒸留により除去した。その後さらに２時間反応し、冷却、ろ過し、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：３４０ｇ／ｅｑ、Ｇ〔一般式（Ｉ）において、Ｘがグリシジル基である比率〕＝６５％）（ＥＰ−３）を得た。
【００５５】
製造例４
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＡ系エポキシ樹脂▲２▼（エポキシ当量：４７５ｇ／ｅｑ、ｎ＝２．１、Ｒ_１：ＣＨ_３、Ｒ_２：ＣＨ_３）４７．５重量部、エピクロルヒドリン４６．３重量部およびテトラメチルアンモニウムクロライド０．２重量部を仕込み、滴下装置中に水酸化ナトリウム５．５重量部を４８重量％水溶液として入れておく。水酸化ナトリウム水溶液を還流下５０〜６０℃の内部温度で８０Ｔｏｒｒで２時間かけて滴下し、同時に水を共沸蒸留により除去した。その後さらに２時間反応し、冷却、ろ過し、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：３１０ｇ／ｅｑ、Ｇ＝６２％）（ＥＰ−４）を得た。
【００５６】
製造例５
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＡ系エポキシ樹脂▲３▼（エポキシ当量：２０００ｇ／ｅｑ、ｎ＝５．８、Ｒ_１：ＣＨ_３、Ｒ_２：ＣＨ_３）２００重量部、エピクロルヒドリン４６．３重量部およびテトラメチルアンモニウムクロライド０．２重量部を仕込み、滴下装置中に水酸化ナトリウム１５重量部を４８重量％水溶液として入れておく。水酸化ナトリウム水溶液を還流下５０〜６０℃の内部温度で８０Ｔｏｒｒで２時間かけて滴下し、同時に水を共沸蒸留により除去した。その後さらに２時間反応し、冷却、ろ過し、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：４２０ｇ／ｅｑ、Ｇ＝５５％）（ＥＰ−５）を得た。
【００５７】
製造例６
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＡ系エポキシ樹脂▲２▼　４７．５重量部、エピクロルヒドリン９２．５重量部およびテトラメチルアンモニウムクロライド０．４重量部を仕込み、滴下装置中に水酸化ナトリウム水溶液４．９重量部を４８重量％水溶液として入れておく。水酸化ナトリウム水溶液を還流下５０〜６０℃の内部温度で８０Ｔｏｒｒで２時間かけて滴下し、同時に水を共沸蒸留により除去した。その後さらに２時間反応し、冷却、ろ過し、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：２７８ｇ／ｅｑ、Ｇ＝８２％）（ＥＰ−６）を得た。
【００５８】
製造例７
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＡ系エポキシ樹脂▲１▼　６５重量部、エピクロルヒドリン１６２重量部およびジメチルスルホキシド８１．０重量部を仕込んだ。水酸化ナトリウム９．１重量部を７０℃で撹拌しながら序所に添加し、添加後さらに３時間反応させた。次に未反応のエピクロルヒドリンおよびジメチルスルホキシドの大部分を減圧下に留去し、副生塩とジメチルスルホキシドを含む反応性生物をメチルイソブチルケトン１５０重量部に溶解し、さらに３０％水酸化ナトリウム水溶液２重量部を加え、７０℃で２時間反応した。水洗、油水分離後、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：２９５ｇ／ｅｑ、Ｇ＝９０％）（ＥＰ−７）を得た。
【００５９】
製造例８
還流装置、攪拌装置、減圧装置、滴下装置を備えたフラスコ中に、ビスフェノールＦ系エポキシ樹脂５００ｇ（エポキシ当量：１０００ｇ／ｅｑ、ｎ＝６．６、Ｒ_１：Ｈ、Ｒ_２：Ｈ）１００重量部、エピクロルヒドリン４６．３重量部およびテトラメチルアンモニウムクロライド０．４重量部を仕込み、滴下装置中に水酸化ナトリウム水溶液４．９重量部を４８重量％水溶液として入れておく。水酸化ナトリウム水溶液を還流下５０〜６０℃の内部温度で８０Ｔｏｒｒで２時間かけて滴下し、同時に水を共沸蒸留により除去した。その後さらに２時間反応し、冷却、ろ過し、溶媒をエバポレーターで蒸発除去して、目的の多官能性エポキシ樹脂（エポキシ当量：３２０ｇ／ｅｑ、Ｇ＝６５％）（ＥＰ−８）を得た。
【００６０】
前記製造例１〜８で得られたエポキシ樹脂（ＥＰ−１）〜（ＥＰ−８）におけるｎ、Ｒ_１、Ｒ_２について、表１に示す。
【表１】

【００６１】
２．粉体塗料組成物の製造
実施例１〜３
前記製造例１で得られた多官能性エポキシ樹脂を使用して下記表２に記載された組成を有する各々の成分を配合した後、ヒーティングされた押出機ＺＳＫ２５（Ｗ＆Ｐ社製、Ｍａｉｎ　ｓｃｒｅｗ　ｒｐｍ：２５０）に通過させて完全に配合した。得られた物質を微細粒子に粉砕し、ＧＥＭＡ社製静電機スプレーガン（６０〜８０ＫＶ）を使用して金属表面上に塗布して塗膜を形成した。該粉体塗膜の形成された該金属を１４０℃で硬化させた。
【００６２】
比較例１
下記表２に記載された組成を有する粉体塗料用組成物を、前記実施例１に記載された方法によって製造した。
【００６３】
【表２】

＊表１において、各単位は重量部を表す。
【００６４】
前記表２の成分のうち、商標名「ＫＤ−２４２Ｇ」（国都化学株式会社製）は６５０−７２５ｇ／ｅｑのビスフェノールＡ系凡用粉体塗料用エポキシ樹脂を表し、商標名「ＫＰ−３５２０」（国都化学株式会社製）は粉体塗料用ポリエステル樹脂であり、硬化剤として使用された。
【００６５】
ベンゾインと商標名「ＰＶ５」（Ｗｏｌｅｅ社製）は各々消泡剤とレベリング剤の用途に使用され、ＢａＳＯ_４は充填剤、ＴｉＯ_２は顔料、２−メチルイミダゾールは硬化促進剤の用途に使用された。
【００６６】
実施例４〜１２
製造例３〜８で得られた多官能性エポキシ樹脂（ＥＰ−３〜ＥＰ−８）を用いて、下記表３に記載された組成を有する粉体塗料組成物を、実施例１と同様にして製造した。
【表３】

＊表２において、各単位は、重量部を示す。
【００６７】
３．試験方法
（１）衝撃性試験
実施例１〜１２、比較例１で得られた粉体塗料組成物について、ＡＳＴＭ　Ｄ２７９４に基づいて行い、下記の基準に基づいて評価した。
○：良好
△：微細クラックの発生
×：クラック発生
【００６８】
（２）エリクセン試験
実施例１〜１２、比較例１で得られた粉体塗料組成物について、ＩＳＯ１５２０に基づいて行い、下記の基準に基づいて評価した。
○：良好
△：微細クラックの発生
×：クラック発生
【００６９】
（３）ゲル化時間測定試験
実施例１〜１２、比較例１で得られた粉体塗料組成物について、ゲル化に要する時間を測定した。
【００７０】
前記試験（１）〜（３）の結果を表４、５に示す。なお、表４に記載したゲル化時間に対する各温度別測定値を図１に示す。
【００７１】
【表４】

【００７２】
【表５】

【００７３】
表４、５および図１に表されているように、本発明の低温硬化性エポキシ樹脂を使用して得られた実施例１〜１２の粉体塗料組成物は、同一硬化条件下で比較例１に比べて硬化物性、つまり衝撃性およびエリクセン試験に際しての機械的物性にさらに優れていることがわかる。
【００７４】
【発明の効果】
以上の如く、本発明による多官能性エポキシ樹脂を含む粉体塗料用組成物は、低温硬化性に極めて優れているため、短時間で昇温し難い金属系の厚い塗装物および熱に敏感な素材などに使用することができ、小さいエネルギーでも十分な硬化が得られ、結果としてエネルギー節減および環境保護にさらに寄与できる。
【図面の簡単な説明】
【図１】図１は、実施例１〜３および比較例１で得られた粉体塗料用組成物の温度別ゲル化速度を表すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a powder coating composition using a low-temperature curable epoxy resin, and more particularly, because it is easily cured at a low temperature, it is difficult to raise the temperature, and a low-temperature material that can be used even for a heat-sensitive material. The present invention relates to a composition for powder coating using a curable epoxy resin.
[0002]
[Prior art]
An epoxy resin is a compound having two or more epoxy groups in a molecule, and is a kind of a thermosetting resin having a three-dimensional structure at room temperature or by heating in the presence of a catalyst or a curing agent. However, it is distinguished from other thermosetting resins in that it is not cured when heated without adding a curing agent or a catalyst. The cured epoxy resin has excellent adhesive strength, mechanical properties, electrical performance, chemical resistance, and the like, and is therefore widely used in mold products, molded products, paints, and the like.
[0003]
In particular, epoxy resins having excellent adhesion, water resistance, and chemical resistance to various materials including metals and excellent toughness of coating films are widely used in place of alkyd and phenol resin paints.
[0004]
Powder coating, after applying the powder-forming film-forming composition to the surface of the object to be coated without using a volatile dispersion medium such as an organic solvent or water, the coating used in the method of heating and melting. means. Unlike liquid paints, powder paints do not require a solvent, a thick coating can be obtained with only one application, and polymer resins that are not dissolved in solvents can be used. Applications and demands for pipes, mechanical parts, electronic products, iron furniture and the like are increasing.
[0005]
Thermosetting powder coatings are generally heated to 80 to 130 ° C in a blender such as an extruder or high-temperature roll mill together with a curing agent, a pigment, additives, and the like, and then melt-mixed. Manufactured by grinding. As another method, it can be manufactured by mixing components at room temperature using a mixer such as a ball mill or a ribbon blender.
[0006]
Powder coatings can be applied by a variety of coating methods, such as thermal spraying, fluidized bed or electrostatic coating, but electrostatic coating is the most widely used.
[0007]
On the other hand, polyfunctional bisphenol-type epoxy resins obtained by reacting epichlorohydrin with secondary hydroxyl groups of diglycidyl ether of ordinary bisphenol compounds are used for sealing materials for electric and electronic parts, laminates, etc. It is proposed to be useful (for example, see Patent Documents 1 to 4). However, these publications do not describe anything about producing a powder coating using the same.
[0008]
Resins used for powder coatings are broadly classified into epoxy resins and polyester resins. As the epoxy resin, a bisphenol A epoxy resin produced by reacting bisphenol A with epichlorohydrin in the presence of a base or an acid catalyst is usually used. The problem is that a large amount of heat energy must be applied to thick metallic coatings, which are difficult to heat up in a short time, resulting in large energy loss and difficult to apply to heat-sensitive materials. There was a point.
[0009]
[Patent Document 1]
U.S. Pat. No. 4,623,701
[Patent Document 2]
JP-A-5-5020
[Patent Document 3]
JP-A-6-248055
[Patent Document 4]
JP-A-6-298904
[0010]
[Problems to be solved by the invention]
Therefore, the present invention has been devised to solve the above-mentioned problems, and a powder using a low-temperature-curable epoxy resin that can be cured even at a low temperature while maintaining corrosion resistance, which is a physical property inherent to an epoxy resin. It is an object to provide a coating composition.
[0011]
[Means for Solving the Problems]
In order to improve the shortcomings of general epoxy resins that have excellent corrosion resistance but are cured at high temperatures, in the powder coating composition of the present invention, the above-mentioned general epoxy resin is given a multifunctionality. The use of the low-temperature curable epoxy resin of the formula (I) has complemented the low-temperature curability while maintaining the existing corrosion resistance.
[0012]
That is, the present invention provides a powder coating composition comprising 100 parts by weight of an epoxy resin represented by the following general formula (I) and 30 to 500 parts by weight of a curing agent.

(Where n represents a real number from 0.1 to 30; ₁ And R ₂ Is independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms, X represents a hydrogen atom or a glycidyl group, and 20% or more of X represents a glycidyl group. )
[0013]
In the constitution of the first aspect, the low-temperature-curable epoxy represented by the general formula (I) is preferably an epoxy resin represented by the following formula (1).

(Where n represents a real number from 0.1 to 30; ₁ And R ₂ Is independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms. )
[0014]
In the above formula (I), R ₁ And R ₂ Are both hydrogen or methyl, and n is preferably a real number of 1 to 15.
[0015]
According to another embodiment of the present invention, the composition preferably further comprises 0.1 to 20% by weight of an antifoaming agent and 0.1 to 20% by weight of a leveling agent.
[0016]
According to another embodiment of the present invention, the curing agent is preferably a phenolic curing agent or a polyester curing agent.
[0017]
According to another embodiment of the present invention, the powder coating composition of the present invention has an epoxy equivalent of 600 to 1500 g / eq per 100 parts by weight of the low-temperature curable epoxy resin represented by the general formula (I). It is preferable to further include 10 to 200 parts by weight of a bisphenol A-based epoxy resin for powder coating.
[0018]
According to yet another embodiment of the present invention, the powder coating composition of the present invention is a powder coating composition selected from the group consisting of pigments, antioxidants, fillers, light stabilizers, curing accelerators and UV absorbers. It is preferred to further include more than one species.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
[0020]
The powder coating composition of the present invention needs to contain 100 parts by weight of the epoxy resin represented by the following general formula (I) and 30 to 500 parts by weight of a curing agent.

(Where n represents a real number from 0.1 to 30; ₁ And R ₂ Is independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms, X represents a hydrogen atom or a glycidyl group, and 20% or more of X represents a glycidyl group. )
[0021]
In the present invention, in the general formula (I), R ₁ And R ₂ Are preferably both hydrogen atoms or both methyl groups. In addition, the above R ₁ And R ₂ Examples of the alkyl group having 1 to 5 carbon atoms represented by include groups such as methyl, ethyl, propyl, and butyl. In addition, n is a real number of 0.1 to 30, and preferably represents a real number of 1 to 15. X represents a hydrogen atom or a glycidyl group, and 20% or more, preferably 25% or more of X is a glycidyl group. Here, n and X represent average values. In the present invention, when n is less than 0.1 or less than 20% of X is a glycidyl group, the content of the trifunctional or higher polyfunctional epoxy compound is reduced, so that the curability and physical properties of the coating film can be satisfied. You won't get anything.
[0022]
The composition for a powder coating material of the present invention needs to use the low-temperature-curable epoxy resin of the general formula (I) as a main component, and is preferably the low-temperature-curable epoxy resin of the general formula (1).
[0023]
In the powder coating composition of the present invention, it is preferable to use a phenol-based curing agent or a polyester-based curing agent as a curing agent. That is, without using a curing agent for general paints such as acid anhydrides and amines, a phenolic or polyester-based curing agent is used as a curing agent so that the powder coating composition can be cured by heating at a low temperature. Preferably, a resin is used.
[0024]
The amount of the curing agent used in the powder coating composition of the present invention may be 30 to 500 parts by weight based on 100 parts by weight of the low-temperature curable epoxy resin of the general formula (I). The reason is that the functional groups of the main agent and the curing agent are completely reacted by an equivalent reaction so that no unreacted functional groups remain.
[0025]
The epoxy resin represented by the general formula (I) used in the present invention preferably has an epoxy equivalent of 200 to 600 g / eq, and when the epoxy equivalent exceeds 600 g / eq, the cured product is hardened. There is a possibility that coloring or physical properties may be reduced.
[0026]
The polyester-based curing agent used as a curing agent in the powder coating composition of the present invention is one commonly used in powder coating compositions in the art, and is used for curing reaction with an epoxy resin. There is no particular limitation as long as it contains a carboxy group that can participate, but it is preferable that the glass transition temperature is 55 to 65 ° C. and the acid value is about 30 to 80.
[0027]
Examples of the commercially available polyester-based curing agent include a trade name “KP-3520” (manufactured by Kokuto Chemical Co., Ltd.), a trade name “KP-3531” (manufactured by Kokuto Chemical Co., Ltd.), and a trade name “KP- 3620 "(manufactured by Kokuto Chemical Co., Ltd.) and the trade name" KP-3720 "(manufactured by Kokuto Chemical Co., Ltd.).
[0028]
The phenolic curing agent used as a curing agent in the powder coating composition of the present invention is not particularly limited as long as it is generally used in the art for powder coating compositions in the art. The group has an OH group and the equivalent of such a phenolic OH group is preferably from 200 to 800. In the present invention, it is preferable to use a bisphenol A-based curing agent.
[0029]
Examples of commercially available bisphenol A-based curing agents include, for example, trade names “KD-410J” (manufactured by Kokuto Chemical Co., Ltd.), trade names “KD-406” (manufactured by Kokuto Chemical Co., Ltd.), and trade name “KD- 420 "(manufactured by Kokuto Chemical Co., Ltd.) and the trade name" KD-426 "(manufactured by Kokuto Chemical Co., Ltd.).
[0030]
The powder coating composition of the present invention preferably further comprises a bisphenol A-based epoxy resin for powder coatings having an epoxy equivalent of 600 to 1500 g / eq, which is a phenolic curing agent when the powder coating is cured. And a polyester-based curing agent to form a cured product. The bisphenol A-based epoxy resin for powder coating having an equivalent weight of 600 to 1500 g / eq as described above is added in an amount of 10 to 200 parts by weight based on 100 parts by weight of the low-temperature epoxy resin of the formula (I). If the content is less than 10 parts by weight, the effect of the addition is small, and if it exceeds 200 parts by weight, the low-temperature curing effect is lost and the mechanical properties are unfavorably reduced.
[0031]
The composition for a powder coating of the present invention preferably contains a predetermined amount of an antifoaming agent known in the art, but the antifoaming agent has a role of suppressing the generation of air bubbles on the surface of the coating film. It is preferably 0.1 to 20% by weight based on the total weight of the body coating composition. If the content of the antifoaming agent is out of this range, physical properties are adversely affected.
[0032]
The leveling agent used in the powder coating composition of the present invention imparts smoothness to the coating film, and its content is 0.1 to 20% by weight based on the total weight of the powder coating composition. Preferably, there is. When the content of the leveling agent is out of this range, the mechanical properties are also adversely affected.
[0033]
The composition for a powder coating of the present invention may further include known additives commonly added to the composition for a powder coating in the art in addition to the above components. This type of additive includes a pigment, an antioxidant, a filler, a light stabilizer, a curing accelerator, an ultraviolet absorber, and the like, and optionally contains at least one selected from the group consisting of these. Can be.
[0034]
The low-temperature curable polyfunctional epoxy resin of the general formula (I) used in the present invention is produced, for example, by polymerizing a bisphenol A-based epoxy resin having a structure of the following general formula (2) with epichlorohydrin. Can be.

(Where n represents a real number from 0.1 to 30; ₁ And R ₂ Is independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms. )
[0035]
Epichlorohydrin used for producing the low-temperature curable epoxy resin of the general formula (I) in the present invention is also called 1,2-epoxy-3-chloropropane and has a structure represented by the following general formula 3. It is a colorless and transparent liquid having a dl-form and an 1-form, and usually refers to a dl-form.

[0036]
By reacting the bisphenol A-based compound of the general formula (2) with epichlorohydrin of the general formula (3), the polyfunctional epoxy resin of the general formula (I) of the present invention can be produced. The production method is specifically as shown in the following reaction formula 1.
(Reaction formula 1)

[0037]
As shown in the reaction formula 1, the bisphenol A-based epoxy resin of the formula (2) is reacted with an excessive amount of epichlorohydrin of the formula (3) in the presence of a catalyst to obtain a compound of the general formula The low-temperature curable polyfunctional epoxy resin (I) can be obtained. The reaction temperature at this time is preferably in the range of 50 to 80 ° C., and the reaction is preferably performed under a reduced pressure condition of 30 to 250 Torr. Further, the reaction time of the reaction is preferably 2 to 30 hours.
[0038]
Examples of the catalyst include an alkali, a Lewis acid and an interlayer transfer catalyst. Here, examples of the alkali include, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like. Examples of the Lewis acid include, for example, boron trifluoride, tin chloride, and zinc chloride. Is, for example, tetramethylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride, methyltridecylammonium chloride, N, N-dimethylpyrrolidinium chloride, N-ethyl-N-methylpyrrolidinium iodide, N -Butyl-N-methylpyrrolidinium bromide, N-benzyl-N-methylpyrrolidinium chloride, N-ethyl-N-methylpyrrolidinium bromide, N-butyl-N-methylmorpholinium bromide, N-butyl -N-methylmorpholinium iodide N-allyl-N-methylmorpholinium bromide, N-methyl-N-benzylpiperidinium chloride, N-methyl-N-benzylpiperidinium bromide, N, N-dimethylpiperidinium iodide, N- Examples thereof include methyl-N-ethylpiperidinium acetate and N-methyl-N-ethylpiperidinium iodide, and among them, tetramethylammonium chloride is preferable.
[0039]
The amount of epichlorohydrin used in the reaction formula 1 is preferably 1 equivalent or more, more preferably 2 to 10 equivalents, per 1 equivalent of the hydroxyl group of diglycidyl ether.
[0040]
In the reaction formula 1, the amount of the alkali used as the catalyst is preferably 0.1 to 2.0 mol, more preferably 0.3 to 1 mol, per equivalent of the hydroxyl group to be glycidylated. 0.5 mol used. In the reaction formula 1, the amount of the interlayer transfer catalyst used as the catalyst is preferably 0.01 to 10 mol%, more preferably 0.2 to 2 mol%, based on the total weight of the reactants. It is.
[0041]
The above reaction can be carried out in a solvent such as hydrocarbon, ether or ketone, but an excess of epichlorohydrin can be used as a solvent. In the epoxy resin represented by the general formula (I), at least 20% of X needs to be a glycidyl group. However, the excess amount of epichlorohydrin, the reaction temperature, the reaction pressure, the reaction time, the type of the catalyst and the use thereof By adjusting the reaction conditions such as the amount, an epoxy resin having an arbitrary epoxidation ratio can be produced.
[0042]
The low-temperature curable polyfunctional epoxy resin of the general formula (I) of the present invention obtained by the above reaction has an epoxy equivalent value of 200 to 600 and a value of n of 1 to 30. Having.
[0043]
The low-temperature curable polyfunctional epoxy resin of the general formula (1) used in the present invention includes, for example, a bisphenol A-based epoxy resin having a structure of the following general formula (2) and an epichloroform of the general formula (3). It can be produced by polymerizing hydrin.

(Where n represents a real number from 0.1 to 30; ₁ And R ₂ Is independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms. )
[0044]
By reacting the bisphenol A compound of the general formula (2) with epichlorohydrin of the general formula (3), the polyfunctional epoxy resin of the general formula (1) of the present invention can be produced. The production method is specifically as shown in the following reaction formula 2.
(Reaction formula 2)

[0045]
As shown in the reaction formula 2, the bisphenol A-based epoxy resin of the general formula (2) is reacted with an excessive amount of epichlorohydrin of the general formula (3) under a catalyst to give a general compound of the present invention. A polyfunctional epoxy resin of the formula (1) is obtained.
[0046]
In the above reaction, the reaction temperature is in the range of 50 to 180 ° C., and the reaction is preferably performed under a reduced pressure of 30 to 250 Torr.
[0047]
The epichlorohydrin of the general formula (3) added as a starting material in the reaction is preferably added in excess compared to the bisphenol A-based epoxy resin of the general formula (2), and the bisphenol A of the general formula (2) is preferably added. It is preferable to add it in a molar ratio of 1:30 to 1:80 with respect to the epoxy resin A.
[0048]
Further, the bisphenol A-based epoxy resin of the general formula (2) added as a starting material in the reaction preferably has an epoxy equivalent of 400 to 2,000, more preferably 400 to 1,000.
[0049]
Such a bisphenol A-based epoxy resin of the general formula (2) can be appropriately purchased and used as a commercially available product, but can also be produced according to the following reaction formula 3.
(Reaction formula 3)

(Where R ₁ , R ₂ And n are the same as defined in the general formula (I).
[0050]
As shown in the reaction formula 3, the general formula (4) is used as a starting material of the present invention by reacting a normal bisphenol A-based compound of the general formula (3) with epichlorohydrin of the general formula (3). The bisphenol A-based epoxy resin of (2) can be produced.
[0051]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.
[0052]
1. Manufacture of multifunctional epoxy resin
Production Example 1
Bisphenol A-based epoxy resin 500 g (epoxy equivalent: 700 g / eq, n = 3.7, R ₁ : CH ₃ , R ₂ : CH ₃ ) And 1300 g of epichlorohydrin were reacted with NaOH as a catalyst at 60 ° C. for 3 hours under reduced pressure of 100 Torr. Then, unreacted epichlorohydrin was separated and removed, and desalted using methyl isobutyl ketone. Then, the desired polyfunctional epoxy resin (EP-1) was obtained by washing with purified water.
[0053]
Production Example 2
500 g of bisphenol F epoxy resin (epoxy equivalent: 1000 g / eq, n = 6.6, R ₁ : H, R ₂ : H) and 1300 g of epichlorohydrin were reacted with KOH as a catalyst at 70 ° C. for 3 hours under a reduced pressure of 100 Torr. Then, unreacted epichlorohydrin was separated and removed, and then removed using methyl isobutyl ketone. The desired polyfunctional epoxy resin (EP-2) was obtained by salting and washing using purified water.
[0054]
Production Example 3
Bisphenol A-based epoxy resin (1) (epoxy equivalent: 650 g / eq, n = 3.4, R ₁ : CH ₃ , R ₂ : CH ₃ ) 65 parts by weight, 46.3 parts by weight of epichlorohydrin and 0.2 parts by weight of tetramethylammonium chloride are charged, and 8.5 parts by weight of sodium hydroxide are put in a dropping device as a 48% by weight aqueous solution. An aqueous sodium hydroxide solution was added dropwise at reflux at an internal temperature of 50 to 60 ° C. at 80 Torr over 2 hours, and at the same time, water was removed by azeotropic distillation. Thereafter, the mixture was reacted for further 2 hours, cooled, filtered, and the solvent was removed by evaporation using an evaporator. The target polyfunctional epoxy resin (epoxy equivalent: 340 g / eq, G [in the general formula (I), X represents a glycidyl group, [A certain ratio] = 65%) (EP-3) was obtained.
[0055]
Production Example 4
Bisphenol A-based epoxy resin (2) (epoxy equivalent: 475 g / eq, n = 2.1, R ₁ : CH ₃ , R ₂ : CH ₃ ) 47.5 parts by weight of epichlorohydrin, 46.3 parts by weight of epichlorohydrin and 0.2 parts by weight of tetramethylammonium chloride are charged, and 5.5 parts by weight of sodium hydroxide are placed in a dropping device as a 48% by weight aqueous solution. An aqueous sodium hydroxide solution was added dropwise at reflux at an internal temperature of 50 to 60 ° C. at 80 Torr over 2 hours, and at the same time, water was removed by azeotropic distillation. Thereafter, the reaction was further continued for 2 hours, cooled, filtered, and the solvent was removed by evaporation using an evaporator to obtain a target polyfunctional epoxy resin (epoxy equivalent: 310 g / eq, G = 62%) (EP-4).
[0056]
Production Example 5
In a flask equipped with a reflux device, a stirring device, a decompression device, and a dropping device, bisphenol A-based epoxy resin (3) (epoxy equivalent: 2000 g / eq, n = 5.8, R ₁ : CH ₃ , R ₂ : CH ₃ ) 200 parts by weight, 46.3 parts by weight of epichlorohydrin and 0.2 parts by weight of tetramethylammonium chloride are charged, and 15 parts by weight of sodium hydroxide are placed in a dropping apparatus as a 48% by weight aqueous solution. An aqueous sodium hydroxide solution was added dropwise at reflux at an internal temperature of 50 to 60 ° C. at 80 Torr over 2 hours, and at the same time, water was removed by azeotropic distillation. Thereafter, the reaction was further performed for 2 hours, cooled, filtered, and the solvent was removed by evaporation using an evaporator to obtain a target polyfunctional epoxy resin (epoxy equivalent: 420 g / eq, G = 55%) (EP-5).
[0057]
Production Example 6
In a flask equipped with a reflux device, a stirring device, a decompression device, and a dropping device, 47.5 parts by weight of bisphenol A epoxy resin (2), 92.5 parts by weight of epichlorohydrin, and 0.4 parts by weight of tetramethylammonium chloride were charged. Then, 4.9 parts by weight of an aqueous sodium hydroxide solution is put as a 48% by weight aqueous solution in a dropping device. An aqueous sodium hydroxide solution was added dropwise at reflux at an internal temperature of 50 to 60 ° C. at 80 Torr over 2 hours, and at the same time, water was removed by azeotropic distillation. Thereafter, the mixture was reacted for further 2 hours, cooled, filtered, and the solvent was removed by evaporation using an evaporator to obtain a target polyfunctional epoxy resin (epoxy equivalent: 278 g / eq, G = 82%) (EP-6).
[0058]
Production Example 7
In a flask equipped with a reflux device, a stirring device, a decompression device, and a dropping device, 65 parts by weight of bisphenol A epoxy resin (1), 162 parts by weight of epichlorohydrin, and 81.0 parts by weight of dimethyl sulfoxide were charged. 9.1 parts by weight of sodium hydroxide were added at the beginning while stirring at 70 ° C., and the mixture was further reacted for 3 hours. Next, most of the unreacted epichlorohydrin and dimethyl sulfoxide are distilled off under reduced pressure, and the reactive product containing by-product salt and dimethyl sulfoxide is dissolved in 150 parts by weight of methyl isobutyl ketone. The reaction mixture was reacted at 70 ° C. for 2 hours. After washing with water and oil-water separation, the solvent was removed by evaporation using an evaporator to obtain a target polyfunctional epoxy resin (epoxy equivalent: 295 g / eq, G = 90%) (EP-7).
[0059]
Production Example 8
In a flask equipped with a reflux device, a stirring device, a decompression device, and a dropping device, 500 g of a bisphenol F epoxy resin (epoxy equivalent: 1000 g / eq, n = 6.6, R ₁ : H, R ₂ : H) 100 parts by weight, 46.3 parts by weight of epichlorohydrin and 0.4 parts by weight of tetramethylammonium chloride are charged, and 4.9 parts by weight of an aqueous sodium hydroxide solution is placed in a dropping apparatus as a 48% by weight aqueous solution. An aqueous sodium hydroxide solution was added dropwise at reflux at an internal temperature of 50 to 60 ° C. at 80 Torr over 2 hours, and at the same time, water was removed by azeotropic distillation. Thereafter, the reaction was further continued for 2 hours, followed by cooling and filtration, and the solvent was removed by evaporation using an evaporator to obtain a target polyfunctional epoxy resin (epoxy equivalent: 320 g / eq, G = 65%) (EP-8).
[0060]
N, R in the epoxy resins (EP-1) to (EP-8) obtained in the above Production Examples 1 to 8 ₁ , R ₂ Is shown in Table 1.
[Table 1]

[0061]
2. Manufacture of powder coating composition
Examples 1-3
After using the polyfunctional epoxy resin obtained in Preparation Example 1 to mix each component having the composition shown in Table 2 below, a heated extruder ZSK25 (Main screw rpm, manufactured by W & P) was used. : 250) and completely blended. The obtained substance was pulverized into fine particles and applied on a metal surface using an electrostatic machine spray gun (60 to 80 KV) manufactured by GEMA to form a coating film. The metal on which the powder coating was formed was cured at 140 ° C.
[0062]
Comparative Example 1
A powder coating composition having the composition shown in Table 2 below was produced by the method described in Example 1.
[0063]
[Table 2]

* In Table 1, each unit represents parts by weight.
[0064]
Among the components in Table 2, the brand name “KD-242G” (manufactured by Kokuto Chemical Co., Ltd.) represents 650-725 g / eq of bisphenol A-based epoxy resin for general powder coating, and the brand name “KP-3520” (Kokuto Chemical Co., Ltd.) is a polyester resin for powder coatings and was used as a curing agent.
[0065]
Benzoin and the brand name "PV5" (Wollie) are used for defoaming and leveling agents respectively, ₄ Is a filler, TiO ₂ Is used as a pigment and 2-methylimidazole is used as a curing accelerator.
[0066]
Examples 4 to 12
Using the polyfunctional epoxy resins (EP-3 to EP-8) obtained in Production Examples 3 to 8, powder coating compositions having the compositions shown in Table 3 below were prepared in the same manner as in Example 1. Manufactured.
[Table 3]

* In Table 2, each unit indicates parts by weight.
[0067]
3. Test method
(1) Impact test
The powder coating compositions obtained in Examples 1 to 12 and Comparative Example 1 were evaluated according to the following criteria based on ASTM D2794.
：: good
Δ: occurrence of fine cracks
×: Cracks occurred
[0068]
(2) Erichsen test
The powder coating compositions obtained in Examples 1 to 12 and Comparative Example 1 were evaluated based on ISO 1520 based on the following criteria.
：: good
Δ: occurrence of fine cracks
×: Cracks occurred
[0069]
(3) Gelation time measurement test
With respect to the powder coating compositions obtained in Examples 1 to 12 and Comparative Example 1, the time required for gelation was measured.
[0070]
Tables 4 and 5 show the results of the tests (1) to (3). In addition, the measured value at each temperature with respect to the gelation time described in Table 4 is shown in FIG.
[0071]
[Table 4]

[0072]
[Table 5]

[0073]
As shown in Tables 4 and 5, and FIG. 1, the powder coating compositions of Examples 1 to 12 obtained by using the low-temperature curable epoxy resin of the present invention are comparative examples under the same curing conditions. It can be seen that the cured physical properties, that is, the impact properties and the mechanical properties at the time of the Erichsen test are more excellent than those of No. 1.
[0074]
【The invention's effect】
As described above, the powder coating composition containing the polyfunctional epoxy resin according to the present invention is extremely excellent in low-temperature curability, so that it is difficult to raise the temperature in a short time. It can be used for materials and the like, and sufficient curing can be obtained even with small energy, and as a result, it can further contribute to energy saving and environmental protection.
[Brief description of the drawings]
FIG. 1 is a graph showing the gelation rate at different temperatures of the powder coating compositions obtained in Examples 1 to 3 and Comparative Example 1.

Claims (7)

A powder coating composition comprising 100 parts by weight of a low-temperature curable epoxy resin represented by the following general formula (I) and 30 to 500 parts by weight of a curing agent.

(Wherein, n represents a real number of 0.1 to 30, R ₁ and R ₂ are each independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms, and X is hydrogen Represents an atom or a glycidyl group, and 20 mol% or more of X represents a glycidyl group.) The composition for a powder coating according to claim 1, wherein the low-temperature-curable epoxy resin represented by the general formula (I) is a low-temperature-curable epoxy resin represented by the following formula (1).

(In the formula, n represents a real number of 0.1 to 30, and R ₁ and R ₂ are each independently hydrogen, substituted or unsubstituted alkyl or alkoxy having 1 to 5 carbon atoms.) 3. The composition for powder coating according to claim 1, wherein in the formula (I), R ₁ and R ₂ are both hydrogen atoms or both methyl, and n is a real number of 1 to 15. 4. . 4. The powder coating composition according to claim 1, further comprising 0.1 to 20% by weight of an antifoaming agent and 0.1 to 20% by weight of a leveling agent based on the total weight of the powder coating composition. Composition. The composition for powder coating according to any one of claims 1 to 4, wherein the curing agent is a phenol-based curing agent or a polyester-based curing agent. It is characterized by further comprising 10 to 200 parts by weight of an epoxy resin for bisphenol A-based powder coating having an epoxy equivalent of 600 to 1500 g / eq with respect to 100 parts by weight of the low-temperature curable epoxy resin represented by the general formula (I). The composition for a powder coating according to any one of claims 1 to 5, wherein The powder coating composition according to any one of claims 1 to 6, further comprising at least one selected from the group consisting of pigments, antioxidants, fillers, light stabilizers, curing accelerators, and ultraviolet absorbers. object.

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