JP2004143316A - Kneaded product for water-based pigment dispersion, and method for producing water-based pigment dispersion, and ink composition by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique by which an excellent water-based pigment dispersion and an ink composition, containing a stably dispersed pigment (having good dispersion stability) and maintaining the dispersion even after a long-term preservation (having good long-term preservation stability) can be obtained. <P>SOLUTION: The method for producing a solid or semisolid kneaded product for the water-based pigment dispersion involves carrying out kneading of a mixture comprising a resin which at least can be dissolved or self-dispersed in water, and a pigment while adding an energy under a condition of having at least one or more local maximum values to a kneader when producing the solid or semisolid kneaded product for the water-based pigment dispersion by the kneading. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１３】
【表２】

【０１１４】
同様に本実施例及び比較例に使用した樹脂Ｓ及びＴは以下のものである。
樹脂Ｓ　（Ｃ）：モノマー組成比において、
スチレン／メタアクリル酸／アクリル酸＝７７／１３／１０　（質量比）であり、
質量平均分子量１２０００、酸価１５１ｍｇＫＯＨ／ｇ、ガラス転移点１０７℃である樹脂。
樹脂Ｔ　（Ｃ）：モノマー組成比で
スチレン／メタアクリル酸／アクリル酸＝７７／１３／１０　（質量比）とし、
分子量が質量平均分子量で７５００、酸価１５０ｍｇＫＯＨ／ｇ、ガラス転移点１０７℃である樹脂。
【０１１５】
（実施例１）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。なお、プラネタリーミキサーＰＬＭ−Ｖ−５０Ｖにおける高速時（（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）での無負荷運転を行ったときの負荷電流値は５Ａであった。
【０１１６】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　１５００ｇ
カーボンブラック（三菱化学製＃４５Ｌ）　　　　　　５０００ｇ
ＤＥＧ　　　　　　　　　　　　　　　　　　　　３８００ｇ
３４質量％水酸化カリウム水溶液　　　　　　　　　６６６ｇ
【０１１７】
高速への切替時のプラネタリーミキサー負荷電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が１５Ａを示した。最大負荷電流値を示してから３０分間、混練を継続した後、プラネタリーミキサーの負荷電流値は８Ａであった。この様にして得た撹拌槽内の混練物に、イオン交換水を２００ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２００ｇのイオン交換水を加え、同様に均一になるまで混合した。以下同様にして、イオン交換水を２００ｇづつ加え、総量１０００ｇのイオン交換水を加えながら約２時間混練した。
ついで、混練を継続しながら、イオン交換水を加える量を５００ｇ／回にし、上記と同様に均一に混合されたことを確認しながら総量５０００ｇのイオン交換水を加えた。
【０１１８】
イオン交換水の添加が終了した後、プラネタリーミキサーから混練物を取り出した。この混練物の固形分濃度は、３８．１質量％であった。さらに取り出した混練物１０ｋｇに、ジエチレングリコール３７５７ｇ、イオン交換水２３８０ｇを分散撹拌機で撹拌しながら３０分間で少量づつ添加し、粘度調整物を得た。
この粘度調整物を、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて下記条件で分散を実施し、水性カーボンブラック分散液Ｐ１を得た。
【０１１９】
・・分散条件
分散機　　　　　　　ナノミルＮＭ−Ｇ２Ｌ（浅田鉄工製）
ビーズ　　　　　　　φ０．３ｍｍジルコニアビーズ
ビーズ充填量　　　　８５％
冷却水温度　　　　　１０℃
回転数　　　　　　　２６６０ｒｐｍ　　（ディスク周速：１２．５ｍ／ｓｅｃ）
送液量　　　　　　　２００ｇ／ｍｉｎ
なお、分散は上記条件で、４回分散機を通す（４パス）ことで行った。
水性カーボンブラック分散液Ｐ１は、固形分濃度２５．２質量％、カーボンブラック濃度１８．２質量％であった。
【０１２０】
（実施例２）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１２１】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　　　２５００ｇ
ファストゲンブルーＴＧＲ　（Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：３）
（大日本インキ製）　　　　　　　　　　　５０００ｇ
３４質量％水酸化カリウム水溶液　　　　　　　　　　１１０３ｇ
ジエチレングリコール　　　　　　　　　　　　　２３９０ｇ
高速への切替時のプラネタリーミキサー負荷電流値は７Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が１５Ａを示した。最大負荷電流値を示してから１５分後、プラネタリーミキサーの負荷電流値は７．５Ａに低下し安定したこの状態で混練を３時間継続して混練物を得た。
続いて、撹拌槽内の混練物に、イオン交換水を５００ｇ加え、混練を継続し、均一に混合されたことを確認し、さらに５００ｇのイオン交換水を加え、同様に均一に混合されるまで混練し、粘度調整を行った。
【０１２２】
以下同様にして、イオン交換水を５００ｇづつ加え、総量４０００ｇのイオン交換水を加えた。
ついで、混練を継続しながら、イオン交換水を加える量を１０００ｇ／回にし、上記と同様に均一に混合されたことを確認しながらさらに総量４０００ｇのイオン交換水を加えた。
イオン交換水の添加が終了した後、プラネタリーミキサーから粘度調整物を取り出した。
取り出した粘度調整物１０．００ｋｇに、ジエチレングリコール４．００ｋｇ、イオン交換水３．２９ｋｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて下記条件で分散を実施し、顔料分散液Ｐ２を得た。
【０１２３】
・・分散条件
分散機　　　　　　　ナノミルＮＭ−Ｇ２Ｌ（浅田鉄工製）
ビーズ　　　　　　　φ０．３ｍｍジルコニアビーズ
ビーズ充填量　　　　８５％
冷却水温度　　　　　１０℃
回転数　　　　　　　２６６０ｒｐｍ　　（ディスク周速：１２．５ｍ／ｓｅｃ）
送液量　　　　　　　２００ｇ／ｍｉｎ
なお、分散は上記条件で、４回分散機を通す（４パス）ことで行った。
顔料分散液Ｐ２は、固形分濃度２４質量％、顔料濃度１５．２質量％であった。
【０１２４】
（実施例３）
実施例２において、ファストゲンブルーＴＧＲの代わりに、ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　８７００（Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：３）：チバスペシャリティーケミカルス株式会社製とすること以外は実施例１と同様にして、顔料分散液Ａ２を得た。
このとき、プラネタリーミキサー混練時の負荷電流値は、高速での初期７Ａで、その後最大１４Ａまで達し、混練継続に伴い徐々に低下した。
また、ビーズミルでの分散でも実施例２と同様に、４パスを問題無く実施可能であった。
顔料分散液Ｐ３の固形分濃度は２３．９％で、顔料濃度は１５．１％であった。
【０１２５】
（実施例４）
実施例３において、ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　８７００の代わりに、ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　ＧＬＶＯ　（Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：４）：チバスペシャリティーケミカルス株式会社製とし、樹脂Ｔを樹脂Ｓとすること以外は実施例３と同様にして、顔料分散液Ｐ４を得た。ただし、３４質量％水酸化カリウムの添加量は、１１１０．３ｇとした。
このとき、プラネタリーミキサー混練時の負荷電流値は、高速での初期７Ａで、その後最大１４Ａまで達し、混練継続に伴い徐々に低下した。
また、ビーズミルでの分散でも実施例３と同様に、４パスを問題無く実施可能であった。
顔料分散液Ｐ４の固形分濃度は２３．８質量％で、顔料濃度は１５．１質量％であった。
【０１２６】
（実施例５）
下記組成の混合物を、容量５０Ｌのプラネタリーミキサー　ＰＬＭ−Ｖ−５０Ｖ（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１２７】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　　　　２５００ｇ
ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　８７００　（Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：３）
（チバスペシャリティーケミカルス株式会社製）　　　５０００ｇ
ジエチレングリコール　　　　　　　　　　　　　　　３１２５ｇ
プラネタリーミキサーの負荷電流値はスタート時点で６Ａであったが、４５分後には最大の９Ａに到達した。その後徐々に減少し１３５分以降は５．０〜５．５Ａと漸減しつつも安定した。１２０分後以降混練終了近くまでにジエチレングリコールの追加分６８７５ｋｇを少量追加し、２４０分後混練を終了し、粘度調整液を得た。この粘度調整物の固形分濃度は４３質量％であった。
この粘度調整物１０ｋｇ、水７５８３ｇ、３４質量％ＫＯＨ水溶液６３２．４ｇの配合で、分散撹拌機を用いて分散液化した。
この分散液を、実施例３と同様にして分散を行い顔料分散液Ｐ５を得た。
このときのビーズミルでの分散作業は良好で、条件通りに作業することが可能であった。顔料分散液Ｐ５の固形分濃度は２４．９質量％、顔料濃度は１５．８質量％であった。
【０１２８】
（実施例６）
実施例５において、ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　８７００の代わりに、ＩＲＧＡＬＩＴＥ　Ｂｌｕｅ　ＧＬＶＯ　（Ｐｉｇｍｅｎｔ　Ｂｌｕｅ　１５：４）：チバスペシャリティーケミカルス株式会社製とし、樹脂Ｔを樹脂Ｓとすること以外は実施例５と同様にして、顔料分散液Ｐ６を得た。ただし、３４質量％水酸化カリウムの添加量は、６３６．５ｇとした。
このとき、プラネタリーミキサー混練時の状況は、実施例５とほぼ同様な挙動を示し、高速での初期負荷電流値は６Ａであり、その後最大値９Ａを示した後徐々に減少して、５〜５．５Ａで安定した。
また、ビーズミルでの分散状況は、実施例５と同様であった。
顔料分散液Ｐ６の固形分濃度は２３．７質量％で、顔料濃度は１５．７質量％であった。
【０１２９】
（実施例７）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１３０】
樹脂Ｓ　　　　　　　　　　　　　　　　　　　　７５０ｇ
ファストゲンスーパーマゼンタＲＴＳ　　　　　　　５０００ｇ
（大日本インキ化学工業（株）製）
ＤＥＧ　　　　　　　　　　　　　　　　　　　　　３５００ｇ
３４質量％水酸化カリウム水溶液　　　　　　　　　３３３ｇ
イオン交換水　　　　　　　　　　　　　　　　　２００ｇ
高速への切替時のプラネタリーミキサーの負荷電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が２０Ａを示した。最大負荷電流値を示してから１時間、混練を継続した後、プラネタリーミキサーの負荷電流値は１５Ａであった。この様にして得た撹拌槽内の混練物に、イオン交換水を２００ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２００ｇのイオン交換水を加え、同様に均一になるまで混合した。以下同様にして、イオン交換水を２００ｇづつ加え、総量１０００ｇのイオン交換水を加えた。
ついで、混練を継続しながら、イオン交換水を加える量を５００ｇ／回にし、上記と同様に均一に混合されたことを確認しながら総量４０００ｇのイオン交換水を加えた。
イオン交換水の添加が終了した後、プラネタリーミキサーから生成物を取り出した。さらに取り出した生成物１０ｋｇに、ジエチレングリコール４．３９ｋｇイオン交換水５．４３ｋｇを分散撹拌機で撹拌しながら少量づつ添加し、粘度調整物を得た。
【０１３１】
・・分散条件
分散機　　　　　　　ナノミルＮＭ−Ｇ２Ｌ　（浅田鉄工製）
ビーズ　　　　　　　φ０．３ｍｍジルコニアビーズ
ビーズ充填量　　　　８５％
冷却水温度　　　　　１０℃
回転数　　　　　　　２６６０ｒｐｍ　　（ディスク周速：１２．５ｍ／ｓｅｃ）
送液量　　　　　　　２００ｇ／ｍｉｎ
なお、分散は上記条件で、４回分散機を通す（４パス）ことで行った。
顔料分散液Ｐ７は、固形分濃度２０質量％、顔料濃度１７質量％であった。
【０１３２】
（実施例８）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１３３】
樹脂Ｓ　　　　　　　　　　　　　　　　　　　　　２５００ｇ
ＩＲＧＡＰＨＯＲ　Ｙｅｌｌｏｗ　８ＧＣＦ　（Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　１２８）
（チバスペシャリティーケミカルス株式会社製）　　　５０００ｇ
３４質量％水酸化カリウム水溶液（ＫＯＨ）　　　　　　　　１１１８ｇ
ジエチレングリコール　　　　　　　　　　　　　　３０００ｇ
イオン交換水　　　　　　　　　　　　　　　　　　１０００ｇ
高速への切替時のプラネタリーミキサーの負荷電流値は７Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が１２Ａを示した。最大負荷電流値を示してから３０分後、プラネタリーミキサーの負荷電流値は８Ａに低下し安定したこの状態で混練を３時間継続して混練物を得た。
続いて、撹拌槽内の混練物に、混練を継続しながらイオン交換水を１３ｇ／分で１０００ｇのイオン交換水を加えた。その後、混練を継続しながら５０ｇ／分で４８００ｇのイオン交換水を加えた。さらに、１５００ｇのイオン交換水を加え、粘度調整物とし、取出した。
取り出した粘度調整物１０．００ｋｇに、ジエチレングリコール３５１４．４ｇ、イオン交換水２１８４．８ｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、ビーズミル　（浅田鉄工製ナノミル　ＮＭ−Ｇ２Ｌ）にて下記条件で分散を実施し、顔料分散液Ｐ８を得た。
【０１３４】
・・分散条件
分散機　　　　　　　ナノミルＮＭ−Ｇ２Ｌ　（浅田鉄工製）
ビーズ　　　　　　　φ０．３ｍｍジルコニアビーズ
ビーズ充填量　　　　８５％
冷却水温度　　　　　１０℃
回転数　　　　　　　２６６０ｒｐｍ　　（ディスク周速：１２．５ｍ／ｓｅｃ）
送液量　　　　　　　５００ｇ／ｍｉｎ
なお、分散は上記条件で、１回分散機を通す（１パス）ことで行った。
顔料分散液Ｐ８は、固形分濃度２５．４質量％、顔料濃度１６．１質量％であった。
【０１３５】
（実施例９）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１３６】
樹脂Ｓ　　　　　　　　　　　　　　　　　　　　２４００ｇ
Ｆａｓｔ　Ｙｅｌｌｏｗ　７４１０　（Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　７４）
（山陽色素株式会社製）　　　　　　　　　　　　　６０００ｇ
３４質量％水酸化カリウム水溶液（ＫＯＨ）　　　　　　　１１１８ｇ
ジエチレングリコール　　　　　　　　　　　　　３０００ｇ
このとき、プラネタリーミキサー混練時の負荷電流値は、初期７Ａで、その後最大１４Ａまで達し、混練継続に伴い徐々に低下した。
続いて、撹拌槽内の混練物に、混練を継続しながらイオン交換水を２０ｇ／分で１０００ｇのイオン交換水を加えた。その後、混練を継続しながら８０ｇ／分で８０００ｇのイオン交換水を加えた。さらに、２０００ｇのイオン交換水を加え、粘度調整物とし、取出した。
取り出した粘度調整物１０．００ｋｇに、ジエチレングリコール４７７９ｇ、イオン交換水１０５１ｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、ビーズミル　（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて実施例８と同一条件で分散を実施し、顔料分散液Ｐ９を得た。
顔料分散液Ｐ９の固形分濃度は２５．３％で、顔料濃度は１７．３％であった。
【０１３７】
（実施例１０）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１３８】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　　　３０００ｇ
ＮＯＶＯＰＥＲＭ　ＹＥＬＬＯＷ　Ｈ２Ｇ　（Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　１２０）
（クラリアントジャパン株式会社製）　　　　　　５０００ｇ
３４質量％水酸化カリウム水溶液（ＫＯＨ）　　　　　　　１３２３．５ｇ
ジエチレングリコール　　　　　　　　　　　　　３０００ｇ
このとき、プラネタリーミキサー混練時の負荷電流値は、初期７Ａで、その後最大１２Ａまで達し、混練継続に伴い徐々に低下した。
続いて、撹拌槽内の混練物に、混練を継続しながらイオン交換水を２０ｇ／分で１０００ｇのイオン交換水を加えた。その後、混練を継続しながら８０ｇ／分で８０００ｇのイオン交換水を加えた。さらに、２０００ｇのイオン交換水を加え、粘度調整物とし、取出した。
取り出した粘度調整物１０．００ｋｇに、ジエチレングリコール３０００ｇ、イオン交換水１６００ｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて実施例８と同一条件で分散を実施し、顔料分散液Ｐ１０を得た。
顔料分散液Ｐ１０の固形分濃度は２４．９％で、顔料濃度は１４．７％であった。
【０１３９】
（比較例１）
実施例１で３４質量％水酸化カリウム水溶液の替わりに、純水を４４０ｇとして、実施例１と同様に容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１４０】
高速への切替時のプラネタリーミキサー負荷電流値は５Ａであった。その後、混練を継続したがプラネタリーミキサーの負荷電流値は５〜６Ａであり最大負荷電流値を示すことが無く３０分間、混練を継続した。このときの内容物は、塊状とはならず、粉体状であった。この様にして得た撹拌槽内の混練物に、イオン交換水を２５０ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２５０ｇのイオン交換水を加え、同様に均一になるまで混合した。以下同様にして、イオン交換水を２５０ｇづつ加え、総量１０００ｇのイオン交換水を加えながら約２時間混練した。
混練を継続しながら、イオン交換水を加える量を５００ｇ／回にし、上記と同様に均一に混合されたことを確認しながらさらに総量５０００ｇのイオン交換水を実施例１とほぼ同じ時間をかけて加えた。
【０１４１】
イオン交換水の添加が終了した後、プラネタリーミキサーから内容物を取り出した。内容物は、樹脂、カーボンブラックともに未分散状態で、粒子形状が認められた。また、この内容物の固形分を測定したところ、３９．０質量％であった。
取り出した内容物１０．００ｋｇに、ジエチレングリコール６０００ｇ、イオン交換水５８４４ｇ、３４質量％水酸化カリウム水溶液３９８．８ｇを分散撹拌機で撹拌しながら３０分間で少量づつ添加して、分散させ分散液を得た。
【０１４２】
この分散液を、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて実施例１と同一条件で分散の実施を試みたが、１パス目で、分散機への送液圧力が上がり、送液量を低下させても送液圧力が適正圧力まで下げられず本分散できなかった。
また、分散攪拌機で攪拌した分散液を１昼夜放置したところ、容器底部にかなりの量の沈降物が発生していた。
【０１４３】
（比較例２）
実施例１でカーボンブラックを三菱化学製＃４５Ｌの代わりに三菱化学製＃９６０にし、３４質量％水酸化カリウム水溶液の替わりに、純水を４４０ｇとして、実施例１と同様に容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１４４】
高速への切替時のプラネタリーミキサー負荷電流値は５Ａであった。その後、混練を継続したがプラネタリーミキサーの負荷電流値は５〜６Ａであり最大負荷電流値を示すことが無く３０分間、混練を継続した。このときの内容物は、塊状とはならず、粉体状であった。この様にして得た撹拌槽内の混練物に、ジエチレングリコール（ＤＥＧ）を２５０ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２５０ｇのＤＥＧを加え、同様に均一になるまで混合した。以下同様にして、ＤＥＧを２５０ｇづつ加え、総量１０００ｇのＤＥＧを加えながら約２時間混練した。このときのプラネタリーミキサーの負荷電流値はやや増加し、８Ａを示した。
混練を継続しながら、ＤＥＧを加える量を５００ｇ／回にし上記と同様に均一に混合されたことを確認しながらさらに総量５０００ｇのＤＥＧを実施例２とほぼ同じ時間をかけて加えた。
ＤＥＧの添加が終了した後、プラネタリーミキサーから内容物を取り出した。内容物は、樹脂、カーボンブラックともに未分散状態で、粒子形状が認められた。また、この内容物の固形分を測定したところ、３８．９質量％であった。
【０１４５】
取り出した内容物１０．００ｋｇに、ジエチレングリコール１２０ｇ、イオン交換水５８２８ｇ、３４質量％水酸化カリウム水溶液３９８ｇを分散撹拌機で撹拌しながら３０分間で少量づつ添加して、分散させ分散液を得た。
この分散液を、ビーズミル（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて実施例１と同一条件で分散の実施を試みたが、１パス目で、分散機への送液圧力が上がり、送液量を４０ｇ／ｍｉｎまで低下させて分散実施した。２パス目以降は、通常の２００ｇ／ｍｉｎで分散実施し、水性カーボンブラック分散液Ｒ２を得た。
【０１４６】
（比較例３）
実施例２において、３４質量％水酸化カリウム水溶液の替わりにイオン交換水とすること以外は、実施例２と全く同様にしてプラネタリーミキサーを用いて、粘度調整物を得た。
このプラネタリーミキサーでの混練時の状態は、実施例２と異なり、明確な負荷電流値の変化が無く、７〜８Ａで推移した。
得られた粘度調整物１０ｋｇにジエチレングリコール４ｋｇ、３４質量％水酸化カリウム水溶液５５１．５ｇ、イオン交換水２．９３ｋｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、実施例２と全く同様にしてビーズミルで分散を実施したが、分散１パス目において、分散機への送液圧力が上昇し、２００ｍｌ／ｍｉｎでは送液できないため、５０ｍｌ／ｍｉｎまで送液量を低下させて行った。
２パス目以降からは、２００ｍｌ／ｍｉｎで送液することが可能であり、４パスまで実施し、顔料分散液Ｒ３を得た。
顔料分散液Ｒ３の固形分濃度は２３．５質量％で、顔料濃度は１４．９質量％であった。
【０１４７】
（比較例４）
実施例７と同様に下記組成の混合物（実施例７で３４質量％ＫＯＨ水溶液をイオン交換水とした）を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１４８】
樹脂Ｓ　　　　　　　　　　　　　　　　　　　　　７５０ｇ
ファストゲンスーパーマゼンタＲＴＳ　　　　　　　　５０００ｇ
（大日本インキ化学工業（株）製）
ＤＥＧ　　　　　　　　　　　　　　　　　　　　　　３５００ｇ
イオン交換水　　　　　　　　　　　　　　　　　　５３３ｇ
高速への切替時のプラネタリーミキサーの負荷電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が６Ａを示した。その後混練を実施してから１時間、混練を継続した後、プラネタリーミキサーの負荷電流値に変化は無かった。この様にして得た撹拌槽内の混練物に、イオン交換水を２００ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２００ｇのイオン交換水を加え、同様に均一になるまで混合した。以下同様にして、イオン交換水を２００ｇづつ加え、総量１０００ｇのイオン交換水を加えた。
ついで、混練を継続しながら、イオン交換水を加える量を５００ｇ／回にし、上記と同様に均一に混合されたことを確認しながら総量４０００ｇのイオン交換水を加えた。
【０１４９】
イオン交換水の添加が終了した後、プラネタリーミキサーから生成物を取り出した。さらに取り出した生成物１０ｋｇに、ジエチレングリコール４３９０ｇ、イオン交換水５２０８ｋｇ、３４質量％水酸化カリウム溶液２２２．４ｇを分散撹拌機で撹拌しながら少量づつ添加し、粘度調整物を得た。
この粘度調整物を、実施例７と同様な条件でビーズミル　（浅田鉄工製ナノミルＮＭ−Ｇ２Ｌ）にて分散を実施したところ、１パス目において、ビーズミルへの送液圧力が上昇し２００ｍｌ／ｍｉｎでは送液できないため、５０ｍｌ／ｍｉｎまで送液量を低下させて行った。２パス目以降からは、２００ｍｌ／ｍｉｎで送液することが可能であり、４パスまで実施し、顔料分散液Ｒ４を得た。
顔料分散液Ｒ４は、固形分濃度１９．８質量％、顔料濃度１７．１質量％であった。
【０１５０】
（比較例５）
下記組成の混合物を、容量５０ＬのプラネタリーミキサーＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、実施例７と同様に混練を行った。
【０１５１】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　１０００ｇ
ＣＲＯＭＯＰＨＴＡＬ　ＰｉｎｋＰＴ　　　　　　　　　　　　　５０００ｇ
（チバスペシャリティーケミカル（株）製）
ジエチレングリコール（ＤＥＧ）　　　　　　　　　３０００ｇ
イオン交換水　　　　　　　　　　　　　　　　４４１．２ｇ
プラネタリーミキサー回転数を高速へ切替時のプラネタリーミキサーの負荷電流値は５Ａであった。その後、混練を継続し、プラネタリーミキサーの最大負荷電流値が８Ａを示した。その後混練を実施してから１時間、混練を継続した後、プラネタリーミキサーの負荷電流値に変化は無かった。この様にして得た撹拌槽内の混練物に、ジエチレングリコール（ＤＥＧ）を２００ｇ加えて混練を継続し、均一に混合されたことを確認して、さらに２００ｇのＤＥＧを加え、同様に均一になるまで混合した。以下同様にして、ＤＥＧを２００ｇづつ加え、総量１０００ｇＤＥＧを加えた。
【０１５２】
さらに混練を継続しながら、ＤＥＧの加える量を５００ｇ／回にし、上記と同様に均一に混合されたことを確認しながら総量４０００ｇのＤＥＧを加えた。
この混練物１０ｋｇにＤＥＧ１３８５ｇ、イオン交換水９８１８ｇ、３４質量％水酸化カリウム溶液３０５．６ｇを分散撹拌機で撹拌しながら少量づつ添加し、粘度調整物を得た。
この粘度調整物を、ビーズミル（浅田鉄工製ナノミル　ＮＭ−Ｇ２Ｌ）にて実施例７と同一条件で分散を実施し、顔料分散液Ｒ５を得た。
顔料分散液Ｒ５の固形分濃度は１９．９質量％、顔料濃度は１６．２質量％であった。
【０１５３】
（比較例６）
実施例８において、３４質量％水酸化カリウム水溶液の替わりにイオン交換水とすること以外は、実施例８と全く同様にしてプラネタリーミキサーを用いて、粘度調整物を得た。
このプラネタリーミキサーでの混練時の状態は、実施例８と異なり、明確な負荷電流値の変化が無く、７〜８Ａで推移した。
得られた粘度調整物１０ｋｇにジエチレングリコール３５１４．４ｇ、３４質量％水酸化カリウム水溶液５６１．２ｇ、イオン交換水１７４９．２ｇを分散撹拌機で撹拌しながら少量づつ添加して、分散させた。さらに、実施例８と全く同様にしてビーズミルで分散を実施したが、分散機への送液圧力が上昇し、５００ｍｌ／ｍｉｎでは送液できないため、３０ｍｌ／ｍｉｎまで送液量を低下させ分散を実施し、顔料分散液Ｒ６を得た。
顔料分散液Ｒ６の固形分濃度は２５．１質量％で、顔料濃度は１５．９質量％であった。
【０１５４】
（比較例７）
下記組成の混合物を、容量５０Ｌのプラネタリーミキサー　ＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１５５】
樹脂Ｓ　　　　　　　　　　　　　　　　　　　　２４００ｇ
Ｆａｓｔ　Ｙｅｌｌｏｗ　７４１０　（Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　７４）
（山陽色素株式会社製）　　　　　　　　　　　　　６０００ｇ
イオン交換水　　　　　　　　　　　　　　　　　１１１８ｇ
ジエチレングリコール　　　　　　　　　　　　　３０００ｇ
プラネタリーミキサーの負荷電流値は高速開始時で６Ａであった。高速での混練を３０分間実施し、その後ジエチレングリコールを、５０ｇ／分で２０００ｇ加えた。その間の負荷電流値は、８Ａを示し安定した。この状態で１時間混練を継続後、ジエチレングリコール／イオン交換水＝３０００ｇ／３５００ｇの混合液を１００ｇ／分で加えた。混合液の添加終了後、３０分間混練を継続し、粘度調整物を取出した。
【０１５６】
この粘度調整物１０ｋｇに、ジエチレングリコール１９０３．１ｇ、イオン交換水４２００ｇ、３４質量％ＫＯＨ水溶液５１０．６ｇを、分散撹拌機を用いて少量づつ添加し分散液化した。
得られた分散液を実施例２と全く同様にしてビーズミルで分散を実施したが、分散機への送液圧力が上昇し、５００ｍｌ／ｍｉｎでは送液できないため、５０ｍｌ／ｍｉｎまで送液量を低下させ分散を実施し、顔料分散液Ｒ７を得た。
顔料分散液Ｒ７の固形分濃度は２５．３質量％、顔料濃度は１７．３質量％であった。
【０１５７】
（比較例８）
実施例１０の３４質量％水酸化カリウム水溶液をイオン交換水とした下記組成の混合物を、容量５０Ｌのプラネタリーミキサー　ＰＬＭ−Ｖ−５０Ｖ　（株式会社井上製作所製）に仕込み、ジャケットを加温し、内容物温度が６０℃になるまで低速（自転回転数：２１ｒｐｍ，公転回転数：１４ｒｐｍ）で混練を行い、内容物温度が６０℃に達した後、高速（自転回転数：３５ｒｐｍ，公転回転数：２４ｒｐｍ）に切替、混練を継続した。
【０１５８】
樹脂Ｔ　　　　　　　　　　　　　　　　　　　　　　３０００ｇ
ＮＯＶＯＰＥＲＭ　ＹＥＬＬＯＷ　Ｈ２Ｇ　（Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ　１２０）
（クラリアントジャパン株式会社製）　　　　　　　　５０００ｇ
イオン交換水　　　　　　　　　　　　　　　　　　　　１３２３．５ｇ
ジエチレングリコール　　　　　　　　　　　　　　　　３０００ｇ
プラネタリーミキサーの負荷電流値は高速開始時で６Ａであった。高速での混練を３０分間実施し、その後ジエチレングリコールを、５０ｇ／分で２０００ｇ加えた。その間の負荷電流値は、８Ａを示し安定した。この状態で１時間混練を継続後、ジエチレングリコール／イオン交換水＝３０００ｇ／３５００ｇの混合液を１００ｇ／分で加えた。混合液の添加終了後、３０分間混練を継続し、粘度調整物を取出した。
この粘度調整物１０ｋｇに、ジエチレングリコール９６０ｇ、イオン交換水３８３３ｇ、３４質量％ＫＯＨ水溶液６３５．６ｇを、分散撹拌機を用いて少量づつ添加し分散液化した。
【０１５９】
得られた分散液を実施例１０と全く同様にしてビーズミルで分散を実施したが、分散機への送液圧力が上昇し、５００ｍｌ／ｍｉｎでは送液できないため、５０ｍｌ／ｍｉｎまで送液量を低下させ分散を実施し、顔料分散液Ｒ８を得た。
顔料分散液Ｒ８の固形分濃度は２６．５質量％で、顔料濃度は１５．７質量％であった。
上記実施例、比較例で作製した分散体について、混練時の負荷電流値の極大値、最小値及び混練時の回転数での無負荷電流値を表３に示す。
【０１６０】
【表３】

【０１６１】
（水性顔料分散液の評価）
上述の様にして得られた実施例、比較例の水性顔料分散液について、それぞれ顔料濃度が１４．５質量％になるように、イオン交換水を加えて濃度調整を行った。顔料濃度を調整した水性カーボンブラック分散液について、マイクロトラックＵＰＡ粒度分析計（Ｌｅｅｄｓ　＆　Ｎｏｒｔｈｒｕｐ社製）で粒径測定を実施した。その際、粒径測定サンプルは粒径測定可能な濃度となるように、イオン交換水で適宜希釈した。
【０１６２】
また、調整した水性顔料分散液をスライドグラス上に極少量採取し、スライドグラス上の分散液滴に空気を巻き込まないようにカバーグラスを乗せ、分散液膜厚を一定にした状態で、２００倍の倍率で透過光による顕微鏡観察を行い、粗大粒子の観察を行った。
【０１６３】
顔料濃度の調整を行った分散液について、スクリュー管等のガラス容器に密栓し、６０℃の恒温器で１週間の加熱試験を行い、加熱試験前後の粒径変化及び沈殿の有無等の分散液状態を目視で観察することにより、分散安定性の評価を実施した。
結果を表４に示した。
【０１６４】
【表４】

【０１６５】
（分散判定方法）
○：顕微鏡観察において１〜５μｍの粗大粒子が数個、視野に観察される。
△：顕微鏡観察において１〜５μｍのの粗大粒子が数十個以上、５μｍ以上の粒子が数個、視野に観測される。
×：５μｍ以上の粗大粒子が数十個以上視野に観察される。
××：分散不可。
【０１６６】
（沈降物量）
○：沈降物は認められない
△：底部によどみがある（沈降物はない）
×　：沈降物がはっきりと確認できる
【０１６７】
同一顔料種（色）内での分散顔料の平均粒径、顕微鏡観察結果比較より、本発明に係る実施例においては、負荷電流において混練時に明確な極大値を示さない比較例の方法と比較して、顕著に粒径も細かくすることができ、粗大粒子についてはその残存量を少なくすることができることが判った。ただし、シアンの分散粒径では、顔料を同一製品とした場合は前述の通りの結果を示す（実施例２と比較例３の比較）が、顔料が他品番となる場合（実施例３、４、５）は、一見本発明の効果は発揮されていない結果となっているが、これは使用する顔料そのものの粒径によるものと推定される。しかし、粗大粒子の発生は、比較例以上の効果を発揮している。
【０１６８】
分散液を一定温度で保存し、平均粒径変化、沈降物の有無を観察した結果では同一顔料種（色）内での比較で、本発明に係る実施例においては、負荷電流において混練時に明確な極大値を示さない比較例の方法と比較して、加熱試験後の平均粒径の増加が少ないことは明白であり、また比較例では沈降物の発生が認められることに対し、実施例では沈降物の発生がないことから、本発明の係る実施例ではより分散安定性が良好であることが判った。
【０１６９】
（インク組成物の調整）
上記実施例、比較例で得られた分散液を下記配合にて調整し、それぞれの色調によりおおよそ３〜５質量％のインク組成物を作製した。配合表を表５に示す。
【０１７０】
【表５】

【０１７１】
（印字試験）
得られた表５のインク組成物を、ＥＮＣＡＤ社製ＮＯＶＡＪＥＴ　ＰＲＯに搭載し、印字試験を実施した。
具体的には、Ａ４の印字用紙（ユポインクジェット専用紙）４枚に、ベタ印字と細線印字を行い、インクの吐出状態を確認した。
結果を表６に示した。
【０１７２】
【表６】

【０１７３】
◎：全ての印字サンプルで均一なベタ印字、細線部でも吐出不良、印字位置ズレ無し。
○：全ての印字サンプルで均一なベタ印字、細線部では吐出不良は無いが、印字位置ズレが見られる。
△：初期印字では問題無いが、印字途中より吐出不良発生。
×：初期より吐出不良による濃度ムラがベタ印字見られる。細線部でも初期より吐出不良による印字抜けが顕著。
【０１７４】
この表６の結果より、本発明の実施例では初期印字では全て問題無い画像が得られており、これに対し比較例では、全て初期印字からインクの吐出が不安定であり、インクの吐出安定性で大きな差が発生していることから、本発明実施例が格段に優れた吐出安定性があることが判る。
【０１７５】
【発明の効果】
少なくとも水に溶解または自己分散可能な樹脂、及び顔料を含む混合物を混練し、固体もしくは半固体状の水性顔料分散液用混練物を製造する際、混練機に付与するエネルギーに少なくとも１回以上の極大値を持つ条件とすることを特徴とする水性顔料分散液用混練物の製造方法を提供することができた。
【図面の簡単な説明】
【図１】プラネタリーミキサーの構成の一例を示した斜視図。
【図２】プラネタリーミキサーの一部拡大図。
【図３】プラネタリーミキサーにおける撹拌羽根の軌跡を示した説明図。
【図４】混練時間と負荷電流値の変化の例（極大値が一つの場合）
【図５】混練時間と負荷電流値の変化の例（極大値が複数の場合）
【図６】混練時間と負荷電流値の変化の例（極大値が一つの場合）
【符号の説明】
１…撹拌槽
２…撹拌槽の上部
３…撹拌槽の下部
４及び５…撹拌羽根
６…ローター
Ａ…混練開始、
Ｂ、Ｂ１、Ｂ２…負荷電流値が極大値を示した位置、
Ｃ…水、水溶性溶剤等の添加開始、
Ｄ…混練物もしくは顔料分散液取り出し
Ｅ…混練時の回転数での無負荷運転時の負荷電流値
Ｆ…負荷電流値が極大値が複数ある場合の極小位置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a kneaded product for an aqueous pigment dispersion, and a method for producing an aqueous pigment dispersion and an ink composition using the same, and is particularly suitable for inkjet recording.
[0002]
[Prior art]
Conventionally, an aqueous pigment dispersion in which a pigment is dispersed in a liquid medium containing water as a main component has been proposed, and an ink composition has been manufactured by diluting the aqueous pigment dispersion.
In producing an aqueous pigment dispersion, it is common to mix a pigment, water, an organic solvent, a dispersant, and an alkaline agent, and to perform a pigment dispersion treatment using a disperser. As a result, an aqueous pigment dispersion in which a plurality of resin-coated particles in which a particulate pigment is coated with a resin is dispersed in a water-soluble solvent is obtained.
[0003]
On the other hand, when an aqueous pigment dispersion is used to prepare an ink composition for ink jet recording, an ink composition having much better light resistance, water resistance, and the like than those using a conventional dye can be obtained.
In the ink composition for ink jet recording, stability when ejected from an ink jet (ejection stability), long-term storage stability, and the like are extremely strictly required as compared with other uses. That is, it is necessary that fine pigment particles having a uniform particle diameter as much as possible are stably dispersed in the liquid medium for a long time in a state of being coated with the dispersant. In order to satisfy these requirements, it is necessary that the aqueous pigment dispersion has good dispersion stability and long-term storage stability.
[0004]
Therefore, recently, various studies have been started on the aqueous pigment dispersion liquid, such as a composition suitable for inkjet recording and a method of dispersing the pigment.
For example, an aqueous solution in which a water-soluble resin and an alkali component are dissolved in water is prepared, and the pigment is added thereto and sufficiently stirred, and then further dispersed using a high-speed sand mill or the like having a high dispersion efficiency to obtain an aqueous pigment dispersion. A method has been proposed.
[0005]
A method for preparing a dispersion by dispersing a pigment and a polymer dispersant in a water-based carrier medium after obtaining a dispersion by kneading the pigment and a polymer dispersant with each other is disclosed (for example, Patent Documents 1 and 2). And Patent Document 3). According to an embodiment, a pigment, a polymer dispersant, and a solvent are treated by a 2-roll milling apparatus to obtain a pigment dispersion, and then mixed with potassium hydroxide as a neutralizing agent and water to obtain a pigment dispersion. is there.
[Patent Document 1]
JP-A-6-157954
[Patent Document 2]
JP-A-2000-80299
[Patent Document 3]
JP 2001-81390 A
[0006]
[Problems to be solved by the invention]
However, in the above-described production method, the pigment is finely refined and the dispersibility in an aqueous carrier medium can be improved by kneading in advance in a two-roll milling apparatus as compared with the unkneaded one, but the pigment and the polymer dispersant are kneaded. There was a problem that it was not possible to completely prevent pigment aggregates generated when dispersing the resulting dispersion in an aqueous carrier medium.
In addition, this method has a problem that the dispersion time is long and the production efficiency is low. Also, the aqueous pigment dispersion obtained in this way still had insufficient dispersion stability.
[0007]
On the other hand, it is common practice to produce an aqueous pigment dispersion with a dispersing machine using a medium such as a sand mill, but usually a low-viscosity liquid to be dispersed having a low solid content ratio such as a pigment and a dispersant is used. Done. Therefore, there is a problem that it is difficult to efficiently apply the pulverizing energy to the pigment, and it takes much time to pulverize the pigment particles. Improvements have been made such as using a medium with a large specific gravity such as zirconia and increasing the pigment grinding efficiency by reducing the particle size. However, the weight of one medium is reduced, so the grinding energy is reduced. At present, it is not always sufficient to improve the efficiency of pulverization / dispersion of pigments, for example, the pigment content increases and adversely affects product quality. The aqueous pigment dispersion thus obtained contains a considerable amount of coarse particles having a particle diameter of 1 μm or more even after dispersion. In addition, since the ejection stability of the ink jet cannot be ensured as it is, a step of removing the coarse particles by centrifugation, filtration, or the like is required, and there is a problem that the production efficiency is further reduced and the yield is further reduced.
[0008]
The present invention has been made in view of the above circumstances, and is finer and more stablely dispersed (having good dispersion stability) than a pigment dispersion produced by a conventional method, and is maintained even during long-term storage. It is an object of the present invention to provide a technique capable of obtaining an aqueous pigment dispersion and an ink composition having good long-term storage stability.
Another object of the present invention is to provide a method for producing an aqueous pigment dispersion liquid and an ink composition which has a short production time such as a dispersion time and a high production efficiency.
Another object of the present invention is to provide a method for producing an aqueous pigment dispersion and an ink composition having a high yield.
In particular, it is an object of the present invention to provide a technique capable of obtaining an ink composition for inkjet recording having excellent ejection characteristics.
[0009]
[Means for Solving the Problems]
The present inventors have solved the above-mentioned problems, and in order to efficiently prepare an aqueous pigment dispersion having good dispersion stability, a mixture containing a dispersion resin and a pigment is blended, and the mixture is kneaded with high viscosity to obtain a kneaded product. It has been found that it is preferable to adjust the energy applied to the kneading machine during the production, and a novel aqueous pigment dispersion kneaded material and a method for producing an aqueous pigment dispersion and an ink composition using the same are completed. Reached.
[0010]
That is, in order to solve the above-mentioned problem, the present inventors knead at least a resin-soluble or self-dispersible resin, a mixture containing a pigment, and produce a solid or semi-solid aqueous pigment dispersion kneaded product. Wherein the mixture is kneaded such that the value (I / v) obtained by dividing the load current (I) of the kneader by the shear rate (v) of the kneader increases with time and then decreases. Provided is a method for producing a kneaded product for an aqueous pigment dispersion.
[0011]
Further, the present inventors, by the method for producing a kneaded product for aqueous pigment dispersion, the step of producing the kneaded product for aqueous pigment dispersion, and dispersing the kneaded product in a solution containing water as a main component. Producing a water-based pigment dispersion.
[0012]
In the present specification, in the process of producing a kneaded product for an aqueous pigment dispersion, a mixture before kneading is referred to as a mixture, and a mixture during or after kneading is referred to as a kneaded product.
Further, the present invention provides a method for producing an ink composition, comprising a step of producing the aqueous pigment dispersion, and a step of diluting the aqueous pigment dispersion with a water-soluble solvent to obtain an ink composition.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
At least a resin that can be dissolved or self-dispersed in water, and a mixture containing a pigment, if necessary, is provided with mechanical energy using a kneader in a state where a solvent or the like is added, and the resin is mixed and kneaded. And the pigment are efficiently melted and mixed. At this time, the pigment is miniaturized by the mechanical energy of the kneading machine, and at the same time, the resin adsorption on the micronized pigment surface progresses, and the high viscosity maintaining the state in which the resin is adsorbed on each fine pigment particle surface is maintained. It becomes a lump.
[0014]
Furthermore, in the method for producing a kneaded material for an aqueous pigment dispersion, the kneaded material may be kneaded so that the energy applied to the kneader has a maximum value of at least one or more times. It has been found that it is preferable in reducing the dispersed particle size of the pigment and also preferable in increasing the dispersion stability. Further, even when the kneaded material is dispersed in ion-exchanged water or a mixture of water and a water-soluble organic solvent, the condition that the energy imparted to the kneader has a maximum value of at least one or more times is set as coarse particles. It has been found that it is effective in preventing generation and is useful in increasing production efficiency.
[0015]
The mixture supplied to the kneader is subjected to various forces such as shearing force and pressure by the kneader, and is kneaded under an action such as "mixed, stretched, kneaded, and cut". . The mixture becomes a solid or semi-solid kneaded material, and a state where sufficient force and energy can be received from the kneader, and sufficient force and energy are applied to the kneaded material from the kneader to effectively promote kneading. be able to.
Considering the form of the kneaded material, at the start of kneading, the resin and the pigment are mixed in water, the viscosity is relatively low, and the force and energy from the kneader are hard to be given.
[0016]
However, when the viscosity is increased by kneading these materials, the force and energy from the kneading machine can be sufficiently applied to the kneaded material. In this state, if the kneader is kneaded so as to give sufficient power and energy to the kneaded material, the pigment is finely refined under the action of “mixing, stretching, kneading, and cutting”, and at the same time, finely divided. Adsorption of the resin to the surface of the pigmentized pigment proceeds, and a high-viscosity mass maintaining the state where the resin is adsorbed to the surface of each fine pigment particle is formed.
Further kneading proceeds, the pigment adsorbed on the surface of the resin is suitably dispersed in water, the viscosity of the kneaded material is reduced again, it becomes difficult to apply force or energy to the kneaded material, excessive pulverization of the pigment hardly occurs Become. Then, if excessive force or energy is not applied from the kneading machine, the dispersion system reaches a certain dispersion state after decreasing the viscosity.
[0017]
An aqueous pigment dispersion and an ink having good long-term storage stability, which are finely and stably dispersed (having good dispersion stability) by a production method providing such a kneading step, and are maintained even during long-term storage. A composition can be obtained.
[0018]
The force and energy given to the kneaded material by the kneader are obtained by dividing the load current (I) (unit: A) of the kneader by the shear rate (v) (unit: m / sec) of the kneader (I / v). ) (Unit: A · sec / m) can be used to control the kneader. Specifically, the I / v can be controlled by controlling the rotation speed and the shearing speed of a roll or a stirrer as a kneader. In addition, when the stirring is performed while the rotation speed of the stirrer is substantially constant, I / v is proportional to the load current (I), so that the increase / decrease of I / v can be regarded as the increase / decrease of the load current (I).
[0019]
As described above, in the kneading process, the adjustment so that the mixture and the kneaded material have preferable kneading behavior can be achieved by appropriately selecting the types of water, resin, and pigment, and adjusting the amount of addition. The same adjustment can be performed in a system containing a base.
[0020]
When the kneading step is performed using an open kneader such as a two-roll or three-roll mill, kneading is performed at an appropriate viscosity at which pigment dispersion is most efficiently performed. At that time, if the kneaded material contains water or a water-soluble organic solvent, the water in the kneaded material or the water-soluble organic solvent evaporates due to the temperature rise during kneading, and the solid content ratio of the kneaded material increases. Remarkable. As a result, the solid content ratio rises remarkably at the end of kneading, so that after the kneading operation is completed, the cooled one has a dry surface of the kneaded material and becomes a robust mixture. Also, in the case of kneading with an open kneader such as a two-roll or three-roll mill, the viscosity of the kneaded material is determined by the temperature of the kneaded material and the solid concentration, and is considered to be substantially constant or increase during kneading. Can be Therefore, the power consumption of the kneading machine and the energy applied to the kneading machine when the rotation speed is constant at the roll rotation speed used for the kneading are constant during the kneading step, or show an increasing tendency (the kneading machine has When the applied voltage is constant, an increase in power consumption means an increase in the load current value.)
[0021]
However, if too much water is lost in the kneading step, and in the subsequent dispersing step, when preparing an aqueous pigment dispersion, water or a water-soluble organic solvent is further added to the kneaded substance to form a solid chip. Grinding, dissolving and dispersing the pigment must be performed. Therefore, a load is imposed on the dispersing step following the roll meat, and there is a very high possibility that the dispersing time is prolonged, and even if the dispersing is performed for a long time, coarse particles remain.
[0022]
On the other hand, when kneading is performed such that the mass of the mixture does not substantially change, a kneaded product for an aqueous pigment dispersion is obtained without causing problems such as an increase in the viscosity of the kneaded material and an increase in the solid content ratio. be able to.
[0023]
Furthermore, in the method for producing a kneaded product for an aqueous pigment dispersion, it is preferable to knead the mixture using a kneader having a stirring tank and a stirring blade. In such a kneader, unlike the above-mentioned roll kneader, it is possible to seal the stirring tank, to prevent evaporation of water or a water-soluble organic solvent during kneading, and to reduce the mass of the mixture during kneading. Can be substantially unchanged.
[0024]
For this reason, the solid content ratio of the kneaded material is not excessively increased, and water for dilution added for moving to a dispersion step, or can be easily mixed and dispersed in a water-soluble solvent, to efficiently prepare a dispersion liquid. be able to.
[0025]
Further, it is preferable that the kneading machine is a planetary mixer. The planetary mixer has a structure in which the kneaded material in the stirring tank is stirred and kneaded using two or more stirring blades that rotate and revolve with each other, so that the stirring blade does not reach the stirring tank. There is little space. In addition, the shape of the blade is thick and a high load can be applied. On the other hand, the blade can be used like an ordinary stirrer which rotates a stirring blade in a stirring tank. For this reason, from the high load region to the low load region, the range of the kneaded material that can be processed is wide, and the kneaded material after completion of kneading is directly added with water or a water-soluble organic solvent or both, and diluted and stirred. All dispersing operations can be performed in the same mixer without removing the kneaded material from the planetary mixer.
[0026]
Various blade shapes such as hook type, frame type, and twist type have been proposed for the blades used in the planetary mixer, but any blade can be used and specified in this patent. However, it is necessary to have a strength that can withstand the viscosity of the kneaded material, and a frame type is preferable in terms of strength, kneading properties, and the like.
[0027]
In addition, when the aqueous pigment dispersion is kneaded with the aqueous pigment dispersion and dispersed in a water-soluble solvent to prepare an aqueous pigment dispersion, it is preferable that the aqueous pigment dispersion is dispersed with a disperser using a medium. By using such a disperser, it is possible to simultaneously reduce the particle size by crushing the pigment and adsorb the resin onto the surface of the pigment.
[0028]
The shear rate in the present invention is the maximum shear rate generated by a kneader stirring blade (blade) during kneading. In the case of one blade, it is the peripheral speed of the blade. In the case of two blades, the peripheral speed is indicated by the sum of the peripheral speeds or the peripheral speed of one blade according to the rotation direction of the two blades.
[0029]
Hereinafter, examples of the shear rate are shown.
1. For two rolls
・ In the case of two rolls, the peripheral speed difference between the two rolls
2. Single-axis rotating device (Henschel mixer, etc.)
・ The peripheral speed of the blade (at the maximum diameter position)
3. Two-axis rotating device (Kneeder etc.)
・ In the case of two axes rotating in the same direction, twice the peripheral speed of the blade
・ In the case of two-axis reverse rotation, the peripheral speed of the blade
4. Equipment with a planetary motion axis (such as a planetary mixer)
・ When the revolution / rotation is in the same direction, the speed that is the sum of the revolution speed and the revolution speed (at the maximum diameter position) or twice the revolution speed (at the revolution blade maximum diameter position) is large.・ When the revolution / rotation is in the opposite direction, the difference between the revolution speed and the revolution speed (at the maximum diameter position) or twice the revolution speed (at the rotation blade maximum diameter position) is large.
[0030]
In the aqueous pigment dispersion, the dispersion state of the pigment is affected by the particle size of the pigment, the particle size of the resin-coated particles in which the pigment is coated on the resin, the ratio of the pigment to the resin, the composition of the resin and the water-soluble solvent, and the like. You. The fine resin-coated particles in which the surface of the fine pigment particles are thinly and uniformly coated with the resin are stably dispersed in the water-soluble solvent, and the dispersed state is maintained even after long-term storage. In the ink composition for inkjet recording, it is preferable to obtain effects such as ejection stability.
In the present invention, the term “water-soluble solvent or aqueous medium” refers to water or an aqueous solution containing a water-soluble organic solvent that easily mixes with water.
[0031]
Hereinafter, the method of producing a kneaded product for an aqueous pigment dispersion, the method of producing an aqueous pigment dispersion, and the method of producing an ink composition of the present invention will be described in detail with reference to examples in order.
[0032]
(1) Method for producing kneaded product for aqueous pigment dispersion
In the production of the kneaded material for aqueous pigment dispersion, at least
(1) Water-soluble or self-dispersible resin
(2) pigment,
Is kneaded to produce a solid or semi-solid kneaded material for an aqueous pigment dispersion.
[0033]
The solid content ratio of (1) the resin and (2) the pigment is preferably from 60 to 80% by mass in the obtained kneaded product for an aqueous pigment dispersion. When the solid content ratio is less than 50% by mass, the viscosity of the mixture is reduced, so that kneading is not sufficiently performed, and sufficient energy for disintegrating the pigment is not applied to the kneaded material, and a large amount of coarse particles remains, which is preferable. Absent. Then, by increasing the solid content ratio in this way, the viscosity of the kneaded material during kneading is kept moderately high, the shearing force applied to the kneaded material from the kneading machine during kneading is increased, and the pigment in the kneaded material is pulverized. The coating of the pigment with the resin can proceed simultaneously. If the solid content ratio exceeds 80% by mass, kneading becomes difficult even if the resin is sufficiently softened by heating. Further, it may be difficult to dissolve or disperse the pigment in a water-soluble solvent during the production of the aqueous pigment dispersion, or it may be difficult to reduce the viscosity by the water-soluble solvent.
[0034]
Hereinafter, each configuration will be described in detail.
▲ 1 ▼ Resin
The resin is soluble or self-dispersible in water, and is obtained by polymerizing a monomer component having at least one or more anionic groups, or a monomer component having at least one or more cationic groups, Both monomers may be used in combination. Further, it may be obtained by polymerizing a monomer containing a monomer component having at least one or more hydroxyl groups, wherein the monomer containing an anionic group, the monomer containing a cationic group, and the monomer component containing a hydroxyl group are each a hydrophilic group. Function as
[0035]
In addition, it is preferable that the other monomer used for polymerization contains a hydrophobic monomer having a hydrophobic group. As a resin that can be dissolved or self-dispersed in water, a monomer component having a hydrophilic group selected from at least one or more anionic group, cationic group, and hydroxyl group and a monomer component having a hydrophobic group coexist. It is preferable to use a resin.
[0036]
Examples of such a resin include a styrene resin, an acrylic resin, a maleic resin, a polyvinyl acetate resin, a polyvinyl sulfonic acid resin, an alkyd resin, an epoxy resin, an amine resin, a polyester resin, and a polyurethane resin. Resin, polyamide resin, polyvinyl alcohol resin, polypyrrolidone resin, cellulose resin, and the like.
[0037]
As the hydrophobic monomer having a hydrophobic group used for the resin,
Methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, Octadecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, 2,3-epoxypropyl acrylate, 2,3-epoxybutyl acrylate, 2,3-epoxycyclohexyl acrylate, vinyl acrylate, methyl methacrylate , Ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate , Dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, vinyl methacrylate, dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl itaconate, benzyl itaconate, etc. Unsaturated fatty acid esters;
[0038]
Acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-dimethylacrylamide, N-diethylacrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-propylmethacrylamide, N- Unsaturated fatty acid amides such as dimethyl methacrylamide, N-diethyl methacrylamide, maleamide, N, N-dimethylmaleamide, fumaramid, N, N-dimethylfumaramide;
[0039]
Unsaturated nitriles such as acrylonitrile and methacrylonitrile;
Carboxylic acids such as vinyl acetate, vinyl propionate, vinyl butanoate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl octadecanoate, vinyl benzoate, allyl acetate, allyl propionate, allyl hexanoate, allyl decanoate, etc. Saturated esters;
Unsaturated ethers such as ethyl vinyl ether and butyl vinyl ether;
[0040]
Styrenes such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 4-methoxystyrene, 4-chlorostyrene, etc .; ethylene, propylene, 1-butene , 1-octene, vinylcyclohexane, 4-vinylcyclohexene, and other unsaturated hydrocarbons;
[0041]
Unsaturated halogenated hydrocarbons such as vinyl chloride, vinylidene chloride, tetrafluoroethylene, and 3-chloropropylene;
Vinyl-substituted heterocyclic compounds such as 4-vinylpyridine, N-vinylcarbazole, N-vinylpyrrolidone;
A reaction product of a monomer having a substituent having an active hydrogen such as a carboxyl group, a hydroxyl group, or an amino group in the above-described exemplified monomers with an epoxide such as ethylene oxide, propylene oxide, or shikilohexene oxide;
[0042]
Examples of the reaction product include a reaction product of a monomer having a substituent having a hydroxyl group, an amino group, or the like in the above-described exemplary monomers with a carboxylic acid such as acetic acid, propionic acid, butanoic acid, hexanoic acid, decanoic acid, or dodecanoic acid.
Among them, styrene monomers, and more preferably styrene monomers are preferred.
These can be used alone or in combination of two or more.
In addition, (meth) acrylate shows acrylate and / or methacrylate, and (meth) acrylic acid shows acrylic acid and / or methacrylic acid.
[0043]
Examples of the monomer having an anionic group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid and 4-vinylbenzoic acid; vinyl succinate, allyl maleate and vinyl terephthalate And polybasic acid unsaturated esters such as allyl trimellitate. Examples of the sulfonic acid group-containing monomer include unsaturated sulfo-substituted alkyl or aryl esters such as 2-sulfoethyl acrylate and 4-sulfophenyl methacrylate; and unsaturated sulfocarboxylic acids such as vinyl sulfosuccinate. Sulfostyrenes such as styrene-4-sulfonic acid;
[0044]
Particularly, from the viewpoint of dispersion stability and long-term storage stability, a monomer containing a carboxyl group is preferable, and examples thereof include vinyl monomers such as (meth) acrylic acid and maleic anhydride.
[0045]
As the monomer having a cationic group, a monomer containing a primary amine, a secondary amine, a tertiary amine, or the like is preferable, and examples thereof include aminoethyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.
[0046]
As the monomer having a hydroxyl group, a monomer having at least one hydroxyl group in the molecule is preferable, and 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxy Examples thereof include butyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 2-hydroxy (meth) acrylate, glycerin (meth) acrylate, and polyethylene glycol mono (meth) acrylate.
As the hydrophilic group, a group selected from an anionic group, a cationic group, and a hydroxyl group can be appropriately selected and used, and can be used in various combinations.
[0047]
In the present invention, from the viewpoint of dispersion stability and long-term storage stability, it is particularly preferable to use a (meth) acrylic acid-based monomer having a structure derived from (meth) acrylic acid.
Further, from the viewpoint of dispersion stability and long-term storage stability, the resin having an anionic group is preferably a copolymer resin composed of a styrene monomer component which is a hydrophobic monomer component and a monomer component having an anionic group.
At this time, the monomer having an anionic group is preferably a hydrophilic monomer.
[0048]
In a copolymer resin comprising a styrene monomer component and a monomer component having an anionic group, the styrene monomer component is preferably at least 50% by mass, more preferably at least 70% by mass, and preferably at least 70% by mass, from the viewpoint of dispersion stability and long-term storage stability. It is preferable that the content is 95% by mass or less.
[0049]
By setting the content of the styrene monomer component in the copolymer resin to 50% by mass or more, the hydrophobicity of the copolymer resin is increased, and in an aqueous system, the pigment is more strongly coated with the resin. As a result, even when the resin-coated particles are heated when the ink composition prepared via the aqueous pigment dispersion is used for inkjet, the particle size is stable and the particle size stability is improved. Then, the ejection stability is improved, and a high print density is obtained. Further, it is also effective for improving the durability of the coating film on the recording medium. If the content exceeds 95% by mass, the content of the monomer component having an anionic group contributing to dispersion may decrease, and the dispersion stability in water and the long-term storage stability may decrease.
[0050]
In the present invention, the term “monomer” refers to a monomer before polymerization, and the term “monomer component” refers to a structure derived from a monomer contained in a resin.
From the viewpoint of long-term storage stability, the acid value of the resin is in the range of 60 to 300 mgKOH / g, preferably 100 to 180 mgKOH / g, and more preferably 120 to 170 mgKOH / g. The acid value is the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize 1 g of the resin, and is an amount represented by mgKOH / g.
[0051]
If the acid value is less than 60, the hydrophilicity may be reduced, and the dispersion stability of the pigment may be reduced. On the other hand, when the acid value is larger than 300, aggregation of the pigment is likely to occur, and the water resistance of a printed product using the ink composition may be reduced.
[0052]
The resin having an anionic group has a mass average molecular weight of 3,000 to 50,000, more preferably 4,000 to 400,000, and still more preferably 5,000 to 30,000. The reason why the molecular weight is set to 3000 or more is that the lower the molecular weight, the better the initial dispersibility, but the longer-term storage stability tends to decrease. If it exceeds 50,000, not only does the viscosity of the aqueous pigment dispersion increase, but also the dispersibility and solubility of the resin tend to decrease.
[0053]
By using a resin having a weight average molecular weight in the above preferred range, it is possible to achieve both the stability of the pigment in the water-soluble solvent and the durability of the coating film formed on the recording medium.
The glass transition point of the resin is 90 ° C. or higher, preferably 100 ° C. or higher, and substantially 150 ° C. or lower.
When the glass transition point is 90 ° C. or higher, the durability of an image formed by the ink composition is improved, and the thermal stability of the ink composition is improved. Therefore, even if the aqueous ink composition for ink jet recording prepared from the aqueous pigment dispersion is used for thermal jet type ink jet recording, it does not cause a change in characteristics that would cause a discharge failure due to heating, which is preferable. The glass transition point of the resin can be adjusted by changing the molecular weight and the like.
[0054]
(2) Pigment
Known pigments can be used without particular limitation.
Examples of the inorganic pigment include carbon black, titanium black, titanium white, zinc sulfide, and red iron oxide.
[0055]
Examples of organic pigments include C.I. I. Quinacridone pigments such as CI Pigment Red 122, Red 202, Red 207, Red 209 and Violet 19;
C. I. Quinacridonequinone pigments such as CI Pigment Orange 48 and Orange 49;
C. I. Dioxazine pigments such as CI Pigment Violet 23 and Violet 37;
C. I. Pigment Blue 15, Blue 15: 1, Blue 15: 2, Blue 15:
3, phthalocyanine pigments such as Blue 15: 4, Blue 15: 6, Blue 16, Blue 68, Green 7, Green 36, etc .;
C. I. Anthrapyrimidine pigments such as CI Pigment Yellow 108;
C. I. Pigments such as CI Pigment Orange 77 and Red 168;
C. I. Pigment blue 60 and other indanthrone-based pigments;
C. I. Flavanthrone-based pigments such as CI Pigment Yellow 24;
C. I. Anthraquinone pigments such as CI Pigment Yellow 196 and Red 177;
C. I. Perylene pigments such as CI Pigment Red 123, Red 149, Red 178, Red 179, Red 190, and Red 224;
C. I. Perinone pigments such as CI Pigment Yellow 196 and Orange 43;
C. I. Quinophthalone pigments such as CI Pigment Yellow 138;
C. I. Diketopyrrolopyrrole pigments such as CI Pigment Orange 71, Orange 73, Red 254, Red 255, Red 264, Red 272;
C. I. Thioindigo pigments such as CI Pigment Red 88, Red 181 and Brown 27;
C. I. Isoindoline-based pigments such as CI Pigment Yellow 139, Yellow 185, Orange 69, and Red 260;
C. I. Isoindolinone pigments such as CI Pigment Yellow 109, Yellow 110 and Yellow 173;
C. I. Azomethine pigments such as CI Pigment Yellow 101, Yellow 129 and Orange 65;
C. I. Benzimidazolone pigments such as CI Pigment Yellow 151, Yellow 154, Yellow 175, Yellow 180, Yellow 181, Orange 36, Red 175, Red 176, Red 185;
C. I. Pigment Yellow 1, Yellow 65, Yellow 73, Yellow 74, Yellow 116, Red 3, Red 48: 1, Red 48: 2, Red 48: 3, Red 53: 1, Red Monoazo pigments such as 57: 1 and Red 115;
C. I. Disazo pigments such as CI Pigment Yellow 12, Yellow 13, Yellow 17, Yellow 81, Yellow 83, Orange 13, Orange 16;
C. I. Pigment Yellow 93, Yellow 95, Yellow 128, Red 144, Red 166, Red 220, Red 221 and the like.
[0056]
The pigment may be a powdery, granular or massive dry pigment, or may be a wet cake or slurry.
The pigment is preferably blended in the mixture in an amount of 15 to 80% by mass. Generally, in order to obtain an ink composition having a certain pigment concentration by diluting an aqueous pigment dispersion, production at the highest possible concentration in the aqueous pigment dispersion requires production efficiency because more ink compositions can be produced. It is more advantageous. However, increasing the pigment concentration deteriorates the storage stability of the aqueous pigment dispersion, and therefore, substantially from the viewpoint of securing the dispersion stability of the pigment and the stability of the kneaded product for the aqueous pigment dispersion, 75 mass%. %, Preferably 40 to 60% by mass.
[0057]
In addition, a pigment derivative of the pigment to be used can be used in combination to stabilize the dispersion of the pigment, as usually used in pigment dispersion. Examples of these derivatives include compounds in which a sulfone group, a carboxyl group, a phosphoric acid group, a chlorosulfonyl group, a phthalimidomethyl group, a chloromethyl group, an amino group, an amide group, and the like are partially substituted for the pigment structure.
[0058]
Further, with respect to the mass ratio of the pigment to the resin (Resin), it is sufficient if the resin is present in an amount necessary to stably coat the pigment surface, and the content of the resin exceeding that amount is rather undesirable. When the resin is present in an excessive amount, the amount of free resin that does not adsorb to the pigment increases when an aqueous pigment dispersion or an ink composition is prepared. The ink is likely to adhere to the ink and cause ink ejection failure. In particular, in a thermal jet printer, there is a high risk that the problem of the ejection failure occurs.
[0059]
Therefore, in the production of the kneaded product for aqueous pigment dispersion of the present invention, the mass ratio of resin / pigment in the kneaded product for aqueous pigment dispersion is preferably 1/20 to 2/1, and 1/10 to 10/1. More preferably, it is 1/1.
[0060]
The kneaded product for an aqueous pigment dispersion needs to contain an amount of resin capable of uniformly covering the surface of the pigment. For this reason, if the mixing ratio of the pigment is too large, the pigment is not sufficiently covered with the resin, and the dispersion stability and long-term storage stability may be reduced. However, if a large amount of excess resin exceeding the required amount is contained, the amount of resin present in water or a water-soluble organic solvent in a particle state or a dissolved state increases without adhering to the surface of the pigment. This is not preferred because it causes an increase in viscosity.
[0061]
(3) Basic compounds, acidic compounds
The ionic group-containing resin in the aqueous pigment dispersion of the present invention has a form in which at least a part of the ionic group is ionized (neutralized) by an ionic substance (counter ion) opposite to the ionic group. This is preferred in terms of exhibiting dispersibility and dispersion stability.
[0062]
When the ionic group-containing resin is an anionic group, the optimal ratio of ionized groups among the anionic groups is uniquely limited because it changes depending on the composition, molecular weight, acid value, etc. of the anionic group-containing resin used. The neutralization ratio is not particularly limited as long as the desired dispersibility and dispersion stability are exhibited, and the neutralization ratio is preferably set in the range of 20 to 200%. Here, the neutralization ratio is a value calculated by the following equation.
Neutralization rate (%) = ((mass of basic compound (g) × 56 × 1000) / (resin acid value × equivalent of basic compound × resin amount (g))) × 100
When the neutralization ratio (%) is 100% or more, it means that an excess base is used which is at least the base theoretically necessary to neutralize the acid value of the resin.
As described above, as the basic compound used to ionize at least a part of the anionic group of the anionic group-containing resin, either an inorganic basic compound or an organic basic compound can be used. In terms of easy adjustment of alkali strength, inorganic basic compounds are more preferable.
[0063]
Examples of the organic basic compound include ammonia and organic amines (including a basic nitrogen-containing heterocyclic compound). For example, common amines such as aqueous ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, and triethylamine can be exemplified. Since the amine is generally in a liquid state, it can be used as it is.
[0064]
Examples of the inorganic basic compound include hydroxides and alkali hydroxides of alkali metals such as potassium and sodium; carbonates of alkali metals such as potassium and sodium; carbonates of alkaline earth metals such as calcium and barium; Examples can be given.
Among the above, strong alkalis are preferable because they are effective in increasing the dispersibility of the resin by neutralizing the resin containing an anionic group. Specifically, alkalis such as potassium hydroxide and sodium hydroxide are preferable. Metal hydroxides are preferred.
[0065]
When the basic compound is added to the aqueous pigment dispersion kneaded material or the aqueous pigment dispersion, a) a method of adding the kneaded material at the stage of producing the kneaded material; b) a mixture of water or a water-soluble solvent and water There is a method of adding it when dispersing in a liquid.
[0066]
a) Method of adding at the stage of producing a kneaded material
By mixing a resin having an anionic group and a basic compound, a kneaded product for an aqueous pigment dispersion in which the anionic group has been neutralized can be obtained. As a result, the affinity between the kneaded product for aqueous pigment dispersion and water is improved, and the kneaded product for aqueous pigment dispersion is rapidly dispersed in water during the production of the aqueous pigment dispersion, thereby improving the production efficiency. Further, the dispersion state of the resin-coated pigment in the aqueous pigment dispersion becomes more stable, and the dispersion stability and long-term storage stability are also improved.
[0067]
When a basic compound is blended, the pigment can be kneaded in a state where the pigment is easily coated on the resin by the interaction between the basic compound and the resin having an anionic group. Therefore, the pigment is finely pulverized during the kneading, and the coarse particles are easily reduced, and the step of removing the coarse particles in the subsequent step can be omitted, and the effect of improving the yield can be obtained.
[0068]
The basic compound is suitably added as an aqueous solution in order to efficiently obtain the above effects. Therefore, a water-soluble basic compound is preferably used.
The inorganic basic compound is usually used in the form of an aqueous solution having a concentration of about 20 to 50% by mass from the viewpoint of improving the mixing property.
[0069]
Regarding the method of adding the basic compound, the basic compound may be added all at once, or may be added plural times during kneading. However, from the viewpoint of easiness of work and stabilization of the kneading conditions, it is preferable to knead by adding them all at once in the initial stage of compounding.
[0070]
The compounding amount of the basic compound is preferably such that the neutralization ratio of the resin having an anionic group is 20% or more, and substantially has dispersion stability during long-term storage, In order to prevent gelation, the content is preferably 200% or less, particularly preferably 80 to 120%. By setting the content in a preferable range, the dispersion speed in a water-soluble solvent, the dispersion stability, and the long-term storage stability are further improved.
[0071]
Further, it is preferable that the basic compound is mixed at once with the other components to be mixed into the mixture to form a mixture before kneading.
For example, the mixture is divided into a plurality of stages by preparing a resin aqueous solution by previously mixing a resin containing an anionic group, water and a basic compound, and adding this to another compounding component such as a pigment. It can be mixed and produced, but it is preferable to prepare a mixture for kneading by blending the basic compound and other components at once since the adsorption of the resin onto the surface of the pigment proceeds efficiently. .
[0072]
b) A method of adding the kneaded material to water or a mixed solution of a water-soluble solvent and water. When dispersing the kneaded material in water or a mixed solution of a water-soluble solvent and water, add water or a water-soluble solvent to water. A necessary amount of a basic compound is previously dissolved in a mixed solution of the above, and the kneaded product is dispersed in an aqueous solution containing the basic compound by mixing and stirring to obtain an aqueous pigment dispersion. At that time, it is preferable to warm the aqueous solution containing the basic compound because the dispersion time is shortened.
When the kneaded material that has been kneaded is not to be taken out from the kneader, there is a method in which an aqueous solution containing a basic compound is added while kneading is continued.
[0073]
When the ionic group-containing resin is a cationic group, it can be carried out in the same manner as described above, and the appropriate neutralization ratio is usually 20 to 200%. The neutralization ratio in that case is a numerical value calculated by the following equation.
Neutralization ratio (%) = ((mass of acidic compound (g) × 56 × 1000) / (resin amine value × equivalent of acidic compound × resin amount (g))) × 100
When the neutralization ratio (%) is 100% or more, it means that an excess acid is used which is more than the acid theoretically necessary to neutralize the amine value of the resin.
As described above, as the acidic compound used to ionize at least a part of the cationic group of the cationic group-containing resin, either an inorganic acidic compound or an organic acidic compound can be used.
[0074]
Examples of the organic acidic compound include acetic acid, acrylic acid, propionic acid, and methacrylic acid. In the case of an organic acidic compound, it is generally a liquid or a solid, and both can be used. However, those soluble in water have good dispersibility in the cationic group-containing resin used, and can be suitably used.
[0075]
Examples of the inorganic acidic compound include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and the like.
Of these, acidic compounds such as acetic acid, hydrochloric acid, and nitric acid are preferred as acids effective for enhancing the dispersibility of the resin containing a cationic group by neutralizing the resin.
[0076]
(4) Water-soluble organic solvent
In producing the kneaded product for an aqueous pigment dispersion, it is preferable to knead the mixture in the presence of a certain amount of solvent. If the solvent is not present, kneading cannot be performed sufficiently, or the surface of the pigment does not wet, so that the resin coating may be insufficient.
[0077]
Therefore, when a water-soluble organic solvent is added to the kneaded product for an aqueous pigment dispersion, the resin is dissolved, partially dissolved or swelled in the water-soluble organic solvent, so that a uniform coating of the resin is formed on the surface of the pigment particles. Can be formed. As a result, the dispersion stability of the aqueous pigment dispersion and the ink composition can be further improved.
[0078]
In addition, when an aqueous solution of a basic compound or an acidic compound is used, or when the basic compound or the acidic compound is an organic compound such as an amine or acetic acid and is in a liquid state, since these serve as the solvent, the In some cases, it is not necessary to add a neutral organic solvent.
[0079]
Known water-soluble organic solvents can be used without any particular limitation. Glycols such as, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol and polypropylene glycol;
Diols such as butanediol, pentanediol, hexanediol and diols homologous thereto;
Glycol esters such as propylene glycol laurate;
Diethylene glycol ethers such as ethylene glycol monobutyl ether and carbitol;
Monoglycol ethers such as cellosolve, including diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl, propylene glycol ether, dipropylene glycol ether, and triethylene glycol ether;
Alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, pentyl alcohol, and alcohols homologous thereto;
Alternatively, lactones such as sulfolane, ester, ketone, and γ-butyrolactone, lactams such as N- (2-hydroxyethyl) pyrrolidone, glycerin and derivatives thereof, and other various solvents known as water-soluble organic solvents. Can be mentioned.
[0080]
These water-soluble organic solvents can be used alone or in combination of two or more.
The selection of the water-soluble organic solvent depends on the resin to be used, but preferably has a certain degree of solubility, and the amount added is adjusted by the solubility of the resin.
[0081]
The water-soluble organic solvent also serves as an anti-drying agent in the aqueous pigment dispersion or the ink composition, and therefore a polyhydric alcohol having a high boiling point, a low volatility, and a high surface tension is preferable, and particularly, diethylene glycol and triethylene. Glycols such as glycols are preferred. In general, glycols are often contained in the ink composition, and there is no problem if they remain in the final product.
[0082]
The water-soluble organic solvent varies depending on the resin to be used, but is usually mixed in the charged mixture in an amount of 10 to 50% by mass, preferably 20 to 40% by mass. The amount of addition is about 1/2 to 5 times the amount of the resin, and preferably about 1 to 4 times the amount of the resin. When the amount of the water-soluble organic solvent is less than 1/2 of the amount of the resin, the resin cannot be dissolved, partially dissolved, or swelled, and the dispersion stability of the pigment may be reduced. On the other hand, when the ratio exceeds 5 times, the viscosity of the kneading mixture decreases, and sufficient kneading cannot be performed. Therefore, the dispersibility of the pigment decreases, and the ink composition may cause a deterioration in image quality such as discharge failure. In addition, as described above, in the case where another compound that plays a role of a solvent derived from an organic compound or the like is further compounded, it is preferable to determine the compounding amount of the water-soluble organic solvent in consideration of this.
[0083]
Further, it is preferable that the water-soluble organic solvent is blended with the pigment in a mass ratio of 1/5 or more, preferably 1/3 to 1 times. As a result, the kneading process proceeds while the resin is always in a semi-dissolved or swollen state, and the resin coating on the pigment surface is favorably performed. If the ratio is less than 1/5, the surface of the pigment cannot be sufficiently wetted in the initial stage of kneading, or the resin cannot be dissolved, partially dissolved, or swelled, and the effect may not be sufficiently obtained. .
[0084]
▲ 5 ▼ Kneading method
In the present invention, instead of directly dispersing the pigment in the water-soluble solvent, the pigment is first kneaded with a resin or the like, and then dispersed in the water-soluble solvent. Therefore, the pigment is finely pulverized during the kneading, so that coarse particles can be reduced.
At this time, it is preferable to add the above-mentioned basic compound or acidic compound, and at this time, coarseness is also caused by the interaction between the basic compound and the resin having an anionic group or between the acidic compound and the resin having a cationic group. Particles are significantly reduced.
Therefore, the step of removing the coarse particles can be omitted, and the production efficiency can be improved and the yield can be improved.
[0085]
In the present invention, kneading is preferably performed such that the mass of the mixture (kneaded material) does not substantially change so that water and water-soluble organic solvent do not evaporate during kneading. Therefore, when an appropriate solvent is used, from the start to the end of kneading, a constant amount of solvent is always present in the mixture, and the solvent that wets the surface of the pigment in the initial kneading is preferably dissolved by the solvent, The resin is replaced with the resin which has swollen or partially dissolved, and the coating of the pigment with the resin proceeds more efficiently, and the pigment is sufficiently coated. As a result, the dispersion stability and long-term storage stability of the aqueous pigment dispersion and the ink composition are significantly improved.
[0086]
Further, even after the completion of the kneading, almost the same amount of the solvent remains as at the start of the kneading, and the dissolution and dispersion of the kneaded mixture can be advanced in an extremely short time.
For this purpose, a kneader that performs kneading in a closed system is preferable, and it is preferable to use a kneader equipped with a stirring tank and a single-shaft or multi-shaft stirring blade. The number of stirring blades is not particularly limited, but two or more stirring blades are preferable in order to obtain a high kneading action.
[0087]
By using a kneader having such a configuration, after a kneaded product for an aqueous pigment dispersion is produced, the kneaded product is continuously diluted directly with a water-soluble solvent after the kneading step in the same stirring tank, and dispersed. A dispersion can be produced.
[0088]
In addition, that the mass does not substantially change means that the weight of the kneaded material during or after kneading is preferably maintained in a range of preferably 90% by mass or more with respect to the charged amount of the mixture before kneading. And
[0089]
Examples of such an apparatus include a Henschel mixer, a pressure kneader, a Banbury mixer, and a planetary mixer, and a planetary mixer is particularly preferable. In the present invention, the kneading is preferably performed in a state where the pigment concentration and the solid content composed of the pigment and the resin are high, so that the viscosity of the kneaded material varies over a wide range depending on the kneading state of the kneaded material. This is because the Lee mixer can handle a wide range from low viscosity to high viscosity.
[0090]
1 to 3 show an example of the configuration of a planetary mixer. In the figure, reference numeral 1 denotes a stirring tank, and this hollow cylindrical stirring tank 1 is shown in an enlarged view in FIG. In addition, stirring blades 4 and 5 composed of frame type blades are rotatably provided.
[0091]
Then, at the time of stirring, the upper member 2 and the lower member 3 are integrated to form a closed system. Inside the upper member 2 of the stirring tank 1, stirring blades 4 and 5 composed of frame-shaped blades are held by one rotor 6 as shown in an enlarged view in FIG. When the rotor 6 rotates (revolves), the stirring blades 4 and 5 rotate (rotate) in the same direction. Then, as shown in FIG. 3, the kneading object loaded in the stirring tank 1 is a so-called planetary movement (planetary movement) in which the two stirring blades 4 and 5 rotate in rotation with the revolving movement of the rotor. Is kneaded. FIG. 3 shows the trajectory of the tip of the two stirring blades 4 and 5 in one revolution of the stirring tank 1.
[0092]
In the planetary mixer, a strong shearing force acts between the stirring blades 4 and 5 and between the stirring blades 4 and 5 and the inner surface of the stirring tank 1 due to the planetary movement of the stirring blades 4 and 5. High degree of stirring, kneading and dispersing effects can be obtained.
In addition, when kneading using a closed kneader such as a planetary mixer, the load current gradually increases with time, usually reaches a maximum value within 30 minutes, and then gradually decreases.
[0093]
That is, when the mixture is heated and heated to a predetermined temperature (for example, 40 to 70 ° C., depending on the type of the resin), the resin becomes viscous and is mixed with the pigment. A large load is applied to the rotation of the blades 4,5. At this time, a large shearing force is applied to the material between the stirring blades 4 and 5 and between the stirring blades 4 and 5 and the stirring tank 1, so that the pigment is finely pulverized efficiently and the pigment is mixed with the material. Inside, it is sufficiently dispersed, mixed and covered with a resin. In particular, when a closed kneader such as a planetary mixer is used, effective kneading is performed, so that the resin, pigment, and water-soluble organic solvent are almost completely mixed within 30 minutes, and the stirring blade 4, The load on 5 is reduced. Therefore, the load current gradually decreases.
[0094]
As described above, in the present invention, when mixing is performed using a closed kneader such as a planetary mixer, the kneading time and the kneading machine (planetary) are mixed in a state where the number of revolutions of the kneader (kneading blade) is substantially constant. In the graph of the relationship with the load current value of the (mixer), one or more load current values have a maximum value. This is because the surface of the pigment is efficiently coated with the resin by kneading with a substantially closed kneader, and it is presumed to be caused by a change in the phase structure of the resin during kneading. Furthermore, the load current value can also be adjusted by adding water or water and a water-soluble organic solvent during kneading, and the anionic group or the cationic group contained in the resin is dispersed in a dispersion medium (water or water). And a water-soluble organic solvent).
[0095]
4 to 6 show examples of changes in the kneading time and the load current value. FIG. 4 shows a general change in kneading time and load current value. A is a point at which the charging of the raw materials is completed, the temperature in the stirring tank substantially reaches a predetermined temperature, and the stirring blade starts rotating at the number of revolutions at the time of kneading (start of kneading). Thereafter, the load current value sharply increases and reaches a maximum value (point B). In this state, the resin is in a molten state, is integrated with the pigment or the like, and is kneaded in a lump. Thereafter, as the kneading proceeds, the load current value decreases. In the state where C has been reached, the kneading step is almost completed, and after the dilution step (water, water-soluble solvent), it is taken out at D and the series of steps is completed. Here, between B and C, water and a water-soluble solvent may be appropriately added. The load current value when the kneader was operated at no load at the number of revolutions at the time of kneading is indicated by a broken line E.
[0096]
FIG. 5 is an example of a diagram showing a change in the kneading time and the load current value when the maximum value of the load current value occurs a plurality of times. After the first maximum value B1, the load current value decreases (F), and the maximum value B2 occurs again. Thereafter, the mixture is kneaded to C, and after the dilution step, it is taken out at D. In order to obtain such a maximum value a plurality of times, the stirring tank is opened with F, or the stirring tank is evacuated to a reduced pressure to remove water and a water-soluble solvent in the kneaded material. It can be done easily. In order to reduce the load current after B2, water and a water-soluble solvent can be added again.
[0097]
FIG. 6 shows an example in which the maximum value of the load current value is large, and the load current decreases little after the maximum value B. After the maximum value B, water and a water-soluble solvent are added at a very early stage C, and kneading is performed. Then, after the dilution process, the sample is taken out at D.
When kneading in a closed system in this way, the mass of the kneaded material does not substantially change during the kneading with respect to the mass of the charged mixture, and a kneaded material for an aqueous pigment dispersion having the same composition as the charged is obtained. And the production stability is improved.
[0098]
In addition, since kneading is performed in a state where the pigment concentration and the solid content concentration are high from the initial stage of kneading, the pigment is crushed by the shearing force applied by kneading, and undispersed coarse particles are reduced. As a result, it is not necessary to remove coarse particles in a later step, and the yield is improved.
In addition, when removing a water-soluble organic solvent, it can also remove by heating and drying after kneading.
[0099]
During kneading with an planetary mixer or the like described herein, a large load current value is observed when a shear force is applied to the kneaded material between the stirring blades / stirring blades or between the stirring blades / stirring tanks. When the voltage is not applied (when the stirring blade is present in the gap of the stirring tank), a current value close to the load current value when there is no load is observed. Therefore, the kneading is continued with the load current value fluctuating, and the fluctuation range of the load current value increases as the kneaded material viscosity increases. In the present invention, the maximum value of the load current is determined by observing the behavior of the maximum value of the load current fluctuation, and the maximum load current value also indicates the maximum value of the load current fluctuation.
[0100]
(2) Method for producing aqueous pigment dispersion
The kneaded material for an aqueous pigment dispersion is usually a semi-solid or solid kneaded product. Thus, the aqueous pigment dispersion kneaded product is dispersed in water or a mixture of water and a water-soluble organic solvent to produce an aqueous pigment dispersion. The pigment in the aqueous pigment dispersion kneaded material is already crushed at the time of production of the aqueous pigment dispersion kneaded material, and is covered with the dispersing resin, so that the dispersion time for obtaining the aqueous pigment dispersion is short. The manufacturing efficiency is improved.
In addition, the kneaded product for aqueous pigment dispersion of the present invention has good solubility and dispersibility in water due to the interaction between the resin having an anionic group and the basic compound, so that it is rapidly dissolved and dispersed. It is a great feature of the aqueous pigment dispersion kneaded product of the present invention that it is rapidly dispersed and dissolved in water and is stably maintained.
[0101]
In the present invention, the water-soluble solvent includes water or a water-soluble organic solvent that easily mixes with water. Examples of the water-soluble organic solvent used herein include lower alcohols such as ethanol and isopropyl alcohol; ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether; and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. Is mentioned.
[0102]
The disperser can use a known one, for example, in the case of using a medium, an ultrasonic homogenized bain shaker, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, Spike mills, agitator mills and the like can be mentioned. Examples of the apparatus that does not use a medium include an ultrasonic homogenizer, a nanomizer, a dissolver, a disper, and a high-speed impeller disperser. Among them, a disperser using a medium is preferable because of its high dispersing ability. After the dispersion, the concentration may be adjusted with a water-soluble solvent, if necessary.
[0103]
Further, when preparing the aqueous pigment dispersion, if necessary, various known additives such as an alkali agent and an acid agent can be further blended. The addition of an alkali agent and an acid agent is preferable because dispersion stability and the like are improved.
In addition, depending on the type of the disperser or the like to be used, a water-soluble solvent is added to the kneaded material for an aqueous pigment dispersion as needed before mixing (permanent dispersion) with the disperser, followed by mixing and dilution. It is preferable to adjust the viscosity to a value suitable for processing with a disperser (hereinafter, this viscosity-adjusted product may be referred to as a viscosity-adjusted product).
For example, when a sand mill is used, it is preferable to dilute the solid content to a concentration of 10 to 40% by mass, adjust the viscosity to tens to several hundreds mPa · s, and then drive the sand mill to perform dispersion.
[0104]
In the present invention, for example, after obtaining a kneaded material by performing kneading with a kneader equipped with a stirring tank and a stirring blade described above, by adding a water-soluble solvent to the kneaded material in this stirring tank, by mixing, Viscosity adjustment can be performed. Therefore, from the production of the kneaded material to the adjustment of the viscosity can be continuously performed by one apparatus, and the production efficiency can be improved. The viscosity-adjusted product is taken out of the stirring tank, for example, if necessary, and dispersed by the above-mentioned disperser to obtain an aqueous pigment dispersion.
After adjusting the viscosity to a predetermined value in the stirring tank, further take out from the stirring tank, and mixed with a water-soluble solvent to adjust the viscosity to obtain a viscosity-adjusted product, which is further dispersed in a water-soluble solvent to obtain an aqueous solution. It can also be a pigment dispersion.
[0105]
(3) Method for producing ink composition
The ink composition can be produced by further diluting the aqueous pigment dispersion obtained as described above with a water-soluble solvent. The concentration of the pigment contained in the ink composition is preferably about 2 to 10% by mass.
[0106]
It is preferable that a water-soluble organic solvent is added to the water-soluble solvent for diluting the aqueous pigment dispersion, because it contributes to prevention of drying, viscosity adjustment, and density adjustment in the ink composition. Examples of the water-soluble organic solvent include those similar to those used for dispersing the above-mentioned kneaded material for aqueous pigment dispersion.
[0107]
Further, it is preferable that a water-soluble organic solvent exhibiting permeability to the recording medium is added, since the ink composition can be provided with permeability. In the ink composition, the permeability is a characteristic necessary for adjusting the permeability of the ink composition (pigment) into the recording medium and the dot diameter on the recording medium.
[0108]
Examples of the water-soluble organic solvent exhibiting permeability include lower alcohols such as ethanol and isopropyl alcohol; ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether; and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. And the like.
[0109]
The ink composition may contain, for example, known additives and the like in addition to the water-soluble solvent and the kneaded product for the aqueous pigment dispersion.
Examples of compounds that can be added include alkali agents, pH adjusters, surfactants, preservatives, chelating agents, plasticizers, antioxidants, ultraviolet absorbers, and ultraviolet curable resins.
[0110]
In the present invention, an ink composition can be produced by, for example, adding an aqueous pigment dispersion, a water-soluble solvent, and various additives as necessary, and stirring the mixture uniformly.
This ink composition can be suitably used as an ink for inkjet recording. The inkjet system to be applied is not particularly limited, but examples include known systems such as a continuous injection type (charge control type, spray type, etc.) and an on-demand type (piezo type, thermal type, electrostatic suction type, etc.). can do.
And, when this ink composition is applied to these various ink jet systems, extremely stable ink ejection becomes possible.
[0111]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
Unless otherwise specified, “parts” is “parts by mass” and “%” is “% by mass”.
The pigments used in the examples and comparative examples are as follows.
[0112]
[Table 1]

[0113]
[Table 2]

[0114]
Similarly, the resins S and T used in this example and comparative examples are as follows.
Resin S (C): In monomer composition ratio,
Styrene / methacrylic acid / acrylic acid = 77/13/10 (mass ratio),
A resin having a weight average molecular weight of 12,000, an acid value of 151 mg KOH / g, and a glass transition point of 107 ° C.
Resin T (C): In monomer composition ratio
Styrene / methacrylic acid / acrylic acid = 77/13/10 (mass ratio)
A resin having a molecular weight of 7,500 in terms of mass average molecular weight, an acid value of 150 mgKOH / g, and a glass transition point of 107 ° C.
[0115]
(Example 1)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed (rotational rotation speed: 21 rpm, 21 rpm, 60 ° C.). After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued. In addition, the load current value when performing no-load operation at high speed ((rotational speed: 35 rpm, revolution speed: 24 rpm)) in the planetary mixer PLM-V-50V was 5A.
[0116]
1500g of resin T
5000g carbon black (Mitsubishi Chemical's # 45L)
DEG 3800g
666 g of 34 mass% aqueous potassium hydroxide solution
[0117]
The planetary mixer load current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer showed 15A. After the kneading was continued for 30 minutes after showing the maximum load current value, the load current value of the planetary mixer was 8A. 200 g of ion-exchanged water was added to the kneaded material in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 200 g of ion-exchanged water was further added, and the mixture was uniformly mixed. Mix until complete. Similarly, 200 g of ion-exchanged water was added in the same manner, and kneaded for about 2 hours while adding a total of 1000 g of ion-exchanged water.
Next, while the kneading was continued, the amount of ion-exchanged water was increased to 500 g / time, and a total of 5000 g of ion-exchanged water was added while confirming uniform mixing in the same manner as described above.
[0118]
After the addition of the ion-exchanged water was completed, the kneaded material was taken out of the planetary mixer. The solid content concentration of this kneaded product was 38.1% by mass. Further, to 10 kg of the removed kneaded product, 3577 g of diethylene glycol and 2380 g of ion-exchanged water were added little by little over 30 minutes while stirring with a dispersion stirrer to obtain a viscosity-adjusted product.
This viscosity-adjusted product was dispersed in a bead mill (Nanomill NM-G2L manufactured by Asada Iron Works) under the following conditions to obtain an aqueous carbon black dispersion P1.
[0119]
..Dispersion conditions
Disperser Nanomill NM-G2L (made by Asada Iron Works)
Beads φ0.3mm zirconia beads
Bead filling 85%
Cooling water temperature 10 ℃
Rotation speed 2660 rpm (disk peripheral speed: 12.5 m / sec)
200g / min
The dispersion was performed by passing through a disperser four times (four passes) under the above conditions.
The aqueous carbon black dispersion P1 had a solid content concentration of 25.2% by mass and a carbon black concentration of 18.2% by mass.
[0120]
(Example 2)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed (rotational rotation speed: 21 rpm, 21 rpm, 60 ° C.). After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0121]
2500g of resin T
Fastogen Blue TGR (Pigment Blue 15: 3)
(Dai Nippon Ink) 5000g
1103 g of 34 mass% aqueous potassium hydroxide solution
2,390 g of diethylene glycol
The planetary mixer load current value at the time of switching to high speed was 7A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer showed 15A. Fifteen minutes after the maximum load current value was shown, the load current value of the planetary mixer dropped to 7.5 A, and kneading was continued for 3 hours in this stable state to obtain a kneaded material.
Subsequently, 500 g of ion-exchanged water was added to the kneaded material in the stirring tank, kneading was continued, and it was confirmed that the mixture was uniformly mixed. Then, 500 g of ion-exchanged water was further added, and the mixture was similarly uniformly mixed. The mixture was kneaded and the viscosity was adjusted.
[0122]
In the same manner as above, ion-exchanged water was added in increments of 500 g, and a total amount of 4000 g of ion-exchanged water was added.
Then, while kneading was continued, the amount of ion-exchanged water was increased to 1000 g / time, and a total of 4000 g of ion-exchanged water was further added while confirming uniform mixing in the same manner as described above.
After the addition of ion-exchanged water was completed, the viscosity-adjusted product was taken out of the planetary mixer.
4.00 kg of diethylene glycol and 3.29 kg of ion-exchanged water were added little by little to 10.00 kg of the viscosity-adjusted product taken out while stirring with a dispersion stirrer, and dispersed. Further, dispersion was performed with a bead mill (Nanomill NM-G2L manufactured by Asada Iron Works) under the following conditions to obtain a pigment dispersion P2.
[0123]
..Dispersion conditions
Disperser Nanomill NM-G2L (made by Asada Iron Works)
Beads φ0.3mm zirconia beads
Bead filling 85%
Cooling water temperature 10 ℃
Rotation speed 2660 rpm (disk peripheral speed: 12.5 m / sec)
200g / min
The dispersion was performed by passing through a disperser four times (four passes) under the above conditions.
The pigment dispersion P2 had a solid content of 24% by mass and a pigment concentration of 15.2% by mass.
[0124]
(Example 3)
In Example 2, a pigment dispersion liquid A2 was obtained in the same manner as in Example 1 except that IRGALITE Blue 8700 (Pigment Blue 15: 3): manufactured by Ciba Specialty Chemicals Co., Ltd. instead of Fastogen Blue TGR. Was.
At this time, the load current value at the time of kneading the planetary mixer was 7 A at the initial stage at a high speed, and thereafter reached a maximum of 14 A, and gradually decreased as the kneading continued.
Also, in the case of dispersion using a bead mill, four passes could be performed without any problem, as in Example 2.
The solid content concentration of the pigment dispersion P3 was 23.9%, and the pigment concentration was 15.1%.
[0125]
(Example 4)
In Example 3, in place of IRGALITE Blue 8700, IRGALITE Blue GLVO (Pigment Blue 15: 4): manufactured by Ciba Specialty Chemicals Co., Ltd. A pigment dispersion P4 was obtained. However, the addition amount of 34% by mass potassium hydroxide was 1110.3 g.
At this time, the load current value at the time of kneading the planetary mixer was 7 A at the initial stage at a high speed, and thereafter reached a maximum of 14 A, and gradually decreased as the kneading continued.
Also, in the case of dispersion using a bead mill, four passes could be performed without any problem, as in Example 3.
The solid content concentration of the pigment dispersion P4 was 23.8% by mass, and the pigment concentration was 15.1% by mass.
[0126]
(Example 5)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed until the content temperature reached 60 ° C. After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0127]
2500g of resin T
IRGALITE Blue 8700 (Pigment Blue 15: 3)
(Ciba Specialty Chemicals Co., Ltd.) 5000g
3125 g of diethylene glycol
The load current value of the planetary mixer was 6 A at the start, but reached a maximum of 9 A after 45 minutes. After that, it gradually decreased and became stable after 135 minutes, gradually decreasing to 5.0 to 5.5 A. After 120 minutes, a small additional amount of 6875 kg of diethylene glycol was added until the end of kneading, and kneading was completed after 240 minutes to obtain a viscosity adjusting liquid. The solid content concentration of this viscosity-adjusted product was 43% by mass.
Using a dispersion stirrer, 10 kg of this viscosity adjuster, 7583 g of water, and 632.4 g of a 34 mass% KOH aqueous solution were mixed to form a dispersion.
This dispersion was dispersed in the same manner as in Example 3 to obtain a pigment dispersion P5.
The dispersion operation in the bead mill at this time was good, and it was possible to operate according to the conditions. The solid content concentration of the pigment dispersion P5 was 24.9% by mass, and the pigment concentration was 15.8% by mass.
[0128]
(Example 6)
In Example 5, in place of IRGALITE Blue 8700, IRGALITE Blue GLVO (Pigment Blue 15: 4): manufactured by Ciba Specialty Chemicals Co., Ltd. A pigment dispersion P6 was obtained. However, the addition amount of 34% by mass potassium hydroxide was 636.5 g.
At this time, the state at the time of kneading the planetary mixer shows almost the same behavior as in Example 5, the initial load current value at high speed is 6 A, and then gradually decreases after showing the maximum value of 9 A. Stable at ~ 5.5A.
The state of dispersion in the bead mill was the same as in Example 5.
The solid content concentration of the pigment dispersion P6 was 23.7% by mass, and the pigment concentration was 15.7% by mass.
[0129]
(Example 7)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed until the content temperature reached 60 ° C. (rotation speed: 21 rpm, After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0130]
750 g of resin S
Fastgen Super Magenta RTS 5000g
(Dai Nippon Ink Chemical Industry Co., Ltd.)
DEG 3500g
333 g of 34 mass% aqueous potassium hydroxide solution
200 g of ion exchange water
The load current value of the planetary mixer at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer was 20 A. After the kneading was continued for 1 hour after showing the maximum load current value, the load current value of the planetary mixer was 15A. 200 g of ion-exchanged water was added to the kneaded material in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 200 g of ion-exchanged water was further added, and the mixture was uniformly mixed. Mix until complete. In the same manner as above, ion-exchanged water was added in 200 g increments, and a total amount of 1000 g of ion-exchanged water was added.
Next, while the kneading was continued, the amount of ion-exchanged water was increased to 500 g / time, and a total amount of 4000 g of ion-exchanged water was added while confirming uniform mixing as described above.
After the addition of the ion-exchanged water was completed, the product was taken out of the planetary mixer. Further, 4.39 kg of diethylene glycol and 5.43 kg of ion-exchanged water were added little by little to 10 kg of the product taken out while stirring with a dispersion stirrer to obtain a viscosity-adjusted product.
[0131]
..Dispersion conditions
Disperser Nano Mill NM-G2L (made by Asada Iron Works)
Beads φ0.3mm zirconia beads
Bead filling 85%
Cooling water temperature 10 ℃
Rotation speed 2660 rpm (disk peripheral speed: 12.5 m / sec)
200g / min
The dispersion was performed by passing through a disperser four times (four passes) under the above conditions.
The pigment dispersion P7 had a solid content of 20% by mass and a pigment concentration of 17% by mass.
[0132]
(Example 8)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed until the content temperature reached 60 ° C. (rotation speed: 21 rpm, After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0133]
Resin S 2500g
IRGAPHOR Yellow 8GCF (Pigment Yellow 128)
(Ciba Specialty Chemicals Co., Ltd.) 5000g
1118 g of 34% by mass aqueous potassium hydroxide solution (KOH)
3000 g of diethylene glycol
Ion exchange water 1000g
The load current value of the planetary mixer at the time of switching to high speed was 7A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer showed 12 A. Thirty minutes after the maximum load current value was shown, the load current value of the planetary mixer dropped to 8 A, and kneading was continued for 3 hours in this stable state to obtain a kneaded material.
Subsequently, 1000 g of ion-exchanged water was added to the kneaded material in the stirring tank at a rate of 13 g / min while the kneading was continued. Thereafter, 4800 g of ion-exchanged water was added at 50 g / min while continuing kneading. Further, 1500 g of ion-exchanged water was added to obtain a viscosity-adjusted product, which was taken out.
3514.4 g of diethylene glycol and 2184.8 g of ion-exchanged water were added little by little to 10.00 kg of the removed viscosity-adjusted product while stirring with a dispersion stirrer, and dispersed. Further, dispersion was performed with a bead mill (Nanomill NM-G2L manufactured by Asada Iron Works) under the following conditions to obtain a pigment dispersion P8.
[0134]
..Dispersion conditions
Disperser Nano Mill NM-G2L (made by Asada Iron Works)
Beads φ0.3mm zirconia beads
Bead filling 85%
Cooling water temperature 10 ℃
Rotation speed 2660 rpm (disk peripheral speed: 12.5 m / sec)
500g / min
The dispersion was performed by passing the dispersion machine once (1 pass) under the above conditions.
The pigment dispersion P8 had a solid content of 25.4% by mass and a pigment concentration of 16.1% by mass.
[0135]
(Example 9)
A mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho) having a capacity of 50 L, and the jacket was heated. After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0136]
Resin S 2400g
Fast Yellow 7410 (Pigment Yellow 74)
(Sanyo Dye Co., Ltd.) 6000g
1118 g of 34% by mass aqueous potassium hydroxide solution (KOH)
3000 g of diethylene glycol
At this time, the load current value at the time of kneading the planetary mixer was 7 A at the initial stage, and thereafter reached a maximum of 14 A, and gradually decreased as the kneading continued.
Subsequently, 1000 g of ion-exchanged water was added at a rate of 20 g / min to the kneaded material in the stirring tank while the kneading was continued. Thereafter, 8000 g of ion-exchanged water was added at 80 g / min while continuing kneading. Further, 2000 g of ion-exchanged water was added to obtain a viscosity-adjusted product, which was taken out.
47.9 g of diethylene glycol and 1051 g of ion-exchanged water were added little by little to 10.00 kg of the viscosity-adjusted product taken out while stirring with a dispersion stirrer, and dispersed. Further, dispersion was performed with a bead mill (Nanomill NM-G2L manufactured by Asada Iron Works) under the same conditions as in Example 8, to obtain a pigment dispersion P9.
The solid content concentration of the pigment dispersion P9 was 25.3%, and the pigment concentration was 17.3%.
[0137]
(Example 10)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, the jacket was heated, and the content was cooled at a low speed (rotational rotation speed: 21 rpm, 21 rpm, 60 ° C.). After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0138]
3000g of resin T
NOVOPERM Yellow H2G (Pigment Yellow 120)
(Made by Clariant Japan KK) 5000g
1323.5 g of a 34% by mass aqueous solution of potassium hydroxide (KOH)
3000 g of diethylene glycol
At this time, the load current value at the time of kneading the planetary mixer was 7 A in the initial stage, then reached a maximum of 12 A, and gradually decreased as the kneading continued.
Subsequently, 1000 g of ion-exchanged water was added at a rate of 20 g / min to the kneaded material in the stirring tank while the kneading was continued. Thereafter, 8000 g of ion-exchanged water was added at 80 g / min while continuing kneading. Further, 2000 g of ion-exchanged water was added to obtain a viscosity-adjusted product, which was taken out.
3000 g of diethylene glycol and 1600 g of ion-exchanged water were added little by little to 10.00 kg of the viscosity-adjusted product taken out while stirring with a dispersion stirrer and dispersed. Further, dispersion was performed with a bead mill (Nanomill NM-G2L manufactured by Asada Iron Works) under the same conditions as in Example 8, to obtain a pigment dispersion P10.
The solid content concentration of the pigment dispersion P10 was 24.9%, and the pigment concentration was 14.7%.
[0139]
(Comparative Example 1)
In Example 1, pure water was set to 440 g in place of the 34% by mass aqueous solution of potassium hydroxide, and a 50 L capacity planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) was charged in the same manner as in Example 1, and a jacket was placed. The mixture is heated and kneaded at a low speed (rotational speed: 21 rpm, revolution speed: 14 rpm) until the content temperature reaches 60 ° C., and after the content temperature reaches 60 ° C., high speed (rotation speed: 35 rpm). , Revolution speed: 24 rpm), and the kneading was continued.
[0140]
The planetary mixer load current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, but the load current value of the planetary mixer was 5 to 6 A, and the kneading was continued for 30 minutes without showing the maximum load current value. At this time, the content was not a lump but a powder. 250 g of ion-exchanged water was added to the kneaded product in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 250 g of ion-exchanged water was further added, and the mixture was uniformly mixed. Mix until complete. Similarly, 250 g of ion-exchanged water was added in the same manner, and kneading was performed for about 2 hours while adding a total of 1000 g of ion-exchanged water.
While kneading was continued, the amount of ion-exchanged water was added to 500 g / time, and a total of 5000 g of ion-exchanged water was further added over approximately the same time as in Example 1 while confirming uniform mixing as described above. added.
[0141]
After the addition of the ion-exchanged water was completed, the contents were taken out of the planetary mixer. As for the content, both the resin and the carbon black were in an undispersed state, and the particle shape was recognized. The solid content of the content was measured to be 39.0% by mass.
To 10.00 kg of the content taken out, 6000 g of diethylene glycol, 5844 g of ion-exchanged water, and 398.8 g of a 34% by mass aqueous potassium hydroxide solution were added little by little over 30 minutes while stirring with a dispersion stirrer, and dispersed to obtain a dispersion. Was.
[0142]
The dispersion was dispersed in a bead mill (Nanomill NM-G2L manufactured by Asada Tekko) under the same conditions as in Example 1. However, in the first pass, the pressure of the liquid to the disperser was increased, and the amount of the liquid was increased. However, the liquid sending pressure could not be reduced to an appropriate pressure even if the pressure was lowered, and the dispersion could not be carried out.
Further, when the dispersion stirred by the dispersion stirrer was allowed to stand for one day and night, a considerable amount of sediment was generated at the bottom of the container.
[0143]
(Comparative Example 2)
In Example 1, the carbon black was changed to Mitsubishi Chemical # 960 instead of Mitsubishi Chemical # 45L, and pure water was set to 440 g in place of the 34 mass% aqueous potassium hydroxide solution. The mixture was charged into a mixer PLM-V-50V (manufactured by Inoue Seisakusho Co., Ltd.), the jacket was heated, and kneaded at a low speed (rotation speed: 21 rpm, revolution speed: 14 rpm) until the content temperature reached 60 ° C. After the temperature of the contents reached 60 ° C., the speed was switched to high speed (rotational rotation speed: 35 rpm, revolving rotation speed: 24 rpm), and kneading was continued.
[0144]
The planetary mixer load current value at the time of switching to high speed was 5A. Thereafter, the kneading was continued, but the load current value of the planetary mixer was 5 to 6 A, and the kneading was continued for 30 minutes without showing the maximum load current value. At this time, the content was not a lump but a powder. 250 g of diethylene glycol (DEG) was added to the kneaded product in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 250 g of DEG was further added, and the mixture became similarly uniform. Until mixed. Similarly, 250 g of DEG was added in a similar manner, and kneading was performed for about 2 hours while adding a total of 1000 g of DEG. At this time, the load current value of the planetary mixer slightly increased to 8 A.
While kneading was continued, the amount of DEG added was set to 500 g / time, and a total of 5000 g of DEG was further added over substantially the same time as in Example 2 while confirming that the mixing was uniform as described above.
After the addition of DEG was completed, the contents were taken out of the planetary mixer. As for the content, both the resin and the carbon black were in an undispersed state, and the particle shape was recognized. The solid content of the content was measured to be 38.9% by mass.
[0145]
To 10.00 kg of the content taken out, 120 g of diethylene glycol, 5828 g of ion-exchanged water, and 398 g of a 34% by mass aqueous solution of potassium hydroxide were added little by little over 30 minutes while stirring with a dispersion stirrer, and dispersed to obtain a dispersion.
The dispersion was dispersed in a bead mill (Nanomill NM-G2L manufactured by Asada Tekko) under the same conditions as in Example 1. However, in the first pass, the pressure of the liquid to the disperser was increased, and the amount of the liquid was increased. Was reduced to 40 g / min. In the second and subsequent passes, dispersion was performed at a normal rate of 200 g / min to obtain an aqueous carbon black dispersion R2.
[0146]
(Comparative Example 3)
A viscosity-adjusted product was obtained using a planetary mixer in exactly the same manner as in Example 2, except that ion-exchanged water was used instead of the 34% by mass aqueous solution of potassium hydroxide.
The state at the time of kneading with this planetary mixer was different from that of Example 2, and there was no clear change in the load current value, and the state changed at 7 to 8A.
4 kg of diethylene glycol, 551.5 g of a 34% by weight aqueous solution of potassium hydroxide, and 2.93 kg of ion-exchanged water were added little by little to 10 kg of the obtained viscosity-adjusted product while stirring with a dispersion stirrer, and dispersed. Further, the dispersion was carried out by a bead mill exactly in the same manner as in Example 2. However, in the first pass of the dispersion, the liquid sending pressure to the dispersing machine increased, and the liquid could not be sent at 200 ml / min. Performed with reduced volume.
From the second pass, it is possible to feed the solution at 200 ml / min, and the process was performed up to four passes to obtain a pigment dispersion R3.
The solid content concentration of the pigment dispersion R3 was 23.5% by mass, and the pigment concentration was 14.9% by mass.
[0147]
(Comparative Example 4)
In the same manner as in Example 7, a mixture having the following composition (a 34 mass% KOH aqueous solution was used as ion-exchanged water in Example 7) was charged into a 50 L capacity planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho). The jacket is heated and kneaded at a low speed (rotation speed: 21 rpm, revolution speed: 14 rpm) until the content temperature reaches 60 ° C., and after the content temperature reaches 60 ° C., high speed (rotation speed) : 35 rpm, revolution number of revolutions: 24 rpm) and kneading was continued.
[0148]
750 g of resin S
Fastgen Super Magenta RTS 5000g
(Dai Nippon Ink Chemical Industry Co., Ltd.)
DEG 3500g
533g of ion exchange water
The load current value of the planetary mixer at the time of switching to high speed was 5A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer showed 6A. Thereafter, after the kneading was performed, the kneading was continued for 1 hour, and there was no change in the load current value of the planetary mixer. 200 g of ion-exchanged water was added to the kneaded material in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 200 g of ion-exchanged water was further added, and the mixture was uniformly mixed. Mix until complete. In the same manner as above, ion-exchanged water was added in 200 g increments, and a total amount of 1000 g of ion-exchanged water was added.
Next, while the kneading was continued, the amount of ion-exchanged water was increased to 500 g / time, and a total amount of 4000 g of ion-exchanged water was added while confirming uniform mixing as described above.
[0149]
After the addition of the ion-exchanged water was completed, the product was taken out of the planetary mixer. Further, to 10 kg of the product taken out, 4390 g of diethylene glycol, 5208 kg of ion-exchanged water, and 222.4 g of a 34% by mass potassium hydroxide solution were added little by little while stirring with a dispersion stirrer to obtain a viscosity-regulated product.
This viscosity-adjusted product was dispersed in a bead mill (Nanomill NM-G2L manufactured by Asada Tekko Co., Ltd.) under the same conditions as in Example 7. As a result, in the first pass, the liquid sending pressure to the bead mill increased, and at 200 ml / min, Since the liquid could not be sent, the amount of the liquid was reduced to 50 ml / min. From the second pass onward, it is possible to feed the solution at 200 ml / min, and the process was performed up to four passes to obtain a pigment dispersion R4.
The pigment dispersion R4 had a solid content of 19.8% by mass and a pigment concentration of 17.1% by mass.
[0150]
(Comparative Example 5)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho) having a capacity of 50 L, and kneaded in the same manner as in Example 7.
[0151]
Resin T 1000g
CROMOPHTAL PinkPT 5000g
(Made by Ciba Specialty Chemical Co., Ltd.)
3000 g of diethylene glycol (DEG)
Ion exchange water 441.2g
The load current value of the planetary mixer when the rotation speed of the planetary mixer was switched to high speed was 5A. Thereafter, the kneading was continued, and the maximum load current value of the planetary mixer showed 8A. Thereafter, after the kneading was performed, the kneading was continued for 1 hour, and there was no change in the load current value of the planetary mixer. 200 g of diethylene glycol (DEG) was added to the kneaded product in the stirring tank thus obtained, and kneading was continued. After confirming that the mixture was uniformly mixed, 200 g of DEG was further added, and the mixture became similarly uniform. Until mixed. In the same manner, DEG was added in 200 g increments, and a total amount of 1000 g DEG was added.
[0152]
While the kneading was continued, the amount of DEG added was set to 500 g / time, and a total amount of 4000 g of DEG was added while confirming uniform mixing in the same manner as described above.
1385 g of DEG, 9818 g of ion-exchanged water, and 305.6 g of a 34% by mass potassium hydroxide solution were added little by little to 10 kg of the kneaded material while stirring with a dispersion stirrer to obtain a viscosity-adjusted product.
This viscosity-adjusted product was dispersed under the same conditions as in Example 7 using a bead mill (Nanomill NM-G2L manufactured by Asada Tekko) to obtain a pigment dispersion R5.
The solid content concentration of the pigment dispersion R5 was 19.9% by mass, and the pigment concentration was 16.2% by mass.
[0153]
(Comparative Example 6)
A viscosity-adjusted product was obtained using a planetary mixer in exactly the same manner as in Example 8, except that ion-exchanged water was used instead of the 34% by mass aqueous solution of potassium hydroxide.
The state at the time of kneading with this planetary mixer was different from that of Example 8, and there was no clear change in the load current value, and the state changed at 7 to 8A.
3514.4 g of diethylene glycol, 561.2 g of a 34% by mass aqueous solution of potassium hydroxide, and 1749.2 g of ion-exchanged water were added little by little to 10 kg of the obtained viscosity-adjusted product while stirring with a dispersion stirrer, and dispersed. Further, the dispersion was carried out in the same manner as in Example 8 using a bead mill. However, since the liquid sending pressure to the dispersing machine increased and the liquid could not be sent at 500 ml / min, the liquid sending amount was reduced to 30 ml / min to perform the dispersion. This was performed to obtain a pigment dispersion R6.
The solid content concentration of the pigment dispersion R6 was 25.1% by mass, and the pigment concentration was 15.9% by mass.
[0154]
(Comparative Example 7)
The mixture having the following composition was charged into a planetary mixer PLM-V-50V (manufactured by Inoue Mfg. Co., Ltd.) having a capacity of 50 L, and the jacket was heated. After kneading at a revolution speed of 14 rpm, and the temperature of the content reached 60 ° C., the kneading was switched to a high speed (rotation speed: 35 rpm, revolution speed: 24 rpm) and kneading was continued.
[0155]
Resin S 2400g
Fast Yellow 7410 (Pigment Yellow 74)
(Sanyo Dye Co., Ltd.) 6000g
1118g of ion exchange water
3000 g of diethylene glycol
The load current value of the planetary mixer was 6 A at the start of high speed. The kneading at a high speed was carried out for 30 minutes, after which 2000 g of diethylene glycol was added at 50 g / min. During this period, the load current value was 8 A and was stable. After continuing kneading for 1 hour in this state, a mixed liquid of diethylene glycol / ion exchange water = 3000 g / 3500 g was added at 100 g / min. After completion of the addition of the mixed solution, kneading was continued for 30 minutes, and the viscosity-adjusted product was taken out.
[0156]
1903.1 g of diethylene glycol, 4200 g of ion-exchanged water, and 510.6 g of a 34% by mass KOH aqueous solution were added little by little to 10 kg of the viscosity-adjusted product using a dispersion stirrer to form a dispersion.
The obtained dispersion was dispersed in a bead mill exactly in the same manner as in Example 2. However, the pressure of the liquid sent to the dispersing machine increased and the liquid could not be sent at 500 ml / min. The dispersion was carried out by lowering to obtain a pigment dispersion R7.
The solid content concentration of the pigment dispersion R7 was 25.3% by mass, and the pigment concentration was 17.3% by mass.
[0157]
(Comparative Example 8)
A mixture having the following composition in which the 34% by mass aqueous potassium hydroxide solution of Example 10 was used as ion-exchanged water was charged into a 50 L planetary mixer PLM-V-50V (manufactured by Inoue Seisakusho), and the jacket was heated. Kneading is performed at a low speed (21 rpm, revolution speed: 14 rpm) until the content temperature reaches 60 ° C., and after the content temperature reaches 60 ° C., high speed (rotation speed: 35 rpm, revolution speed) : 24 rpm) and kneading was continued.
[0158]
3000g of resin T
NOVOPERM Yellow H2G (Pigment Yellow 120)
(Made by Clariant Japan KK) 5000g
1323.5 g of ion exchange water
3000 g of diethylene glycol
The load current value of the planetary mixer was 6 A at the start of high speed. The kneading at a high speed was carried out for 30 minutes, after which 2000 g of diethylene glycol was added at 50 g / min. During this period, the load current value was 8 A and was stable. After continuing kneading for 1 hour in this state, a mixed liquid of diethylene glycol / ion exchange water = 3000 g / 3500 g was added at 100 g / min. After completion of the addition of the mixed solution, kneading was continued for 30 minutes, and the viscosity-adjusted product was taken out.
960 g of diethylene glycol, 3833 g of ion-exchanged water, and 635.6 g of a 34% by mass KOH aqueous solution were added little by little to 10 kg of this viscosity-adjusted product using a dispersion stirrer to form a dispersion.
[0159]
The obtained dispersion was dispersed in a bead mill exactly in the same manner as in Example 10. However, since the pressure of the liquid sent to the dispersing machine increased and the liquid could not be sent at 500 ml / min, the amount of the liquid sent was reduced to 50 ml / min. The dispersion was lowered and dispersion was performed, whereby a pigment dispersion R8 was obtained.
The solid content concentration of the pigment dispersion R8 was 26.5% by mass, and the pigment concentration was 15.7% by mass.
Table 3 shows the maximum and minimum values of the load current value during kneading and the no-load current values at the number of revolutions during kneading for the dispersions prepared in the above Examples and Comparative Examples.
[0160]
[Table 3]

[0161]
(Evaluation of aqueous pigment dispersion)
The aqueous pigment dispersions of Examples and Comparative Examples obtained as described above were each adjusted to have a pigment concentration of 14.5% by mass by adding ion-exchanged water. The particle size of the aqueous carbon black dispersion having the adjusted pigment concentration was measured with a Microtrac UPA particle size analyzer (manufactured by Leeds & Northrup). At that time, the particle size measurement sample was appropriately diluted with ion-exchanged water so that the concentration could be measured.
[0162]
In addition, a very small amount of the prepared aqueous pigment dispersion was collected on a slide glass, and a cover glass was placed thereon so that air was not entrained in the dispersion droplets on the slide glass. Microscopic observation with transmitted light was performed at a magnification of, and coarse particles were observed.
[0163]
The dispersion having the adjusted pigment concentration is sealed in a glass container such as a screw tube, and subjected to a heating test for one week in a thermostat at 60 ° C. The dispersion stability was evaluated by visually observing the state.
The results are shown in Table 4.
[0164]
[Table 4]

[0165]
(Dispersion determination method)
：: Several coarse particles having a size of 1 to 5 μm are observed in the visual field by microscopic observation.
Δ: Several tens or more coarse particles of 1 to 5 μm are observed in the visual field by microscopic observation.
×: Dozens or more of coarse particles of 5 μm or more are observed in the visual field.
XX: Cannot be dispersed.
[0166]
(Amount of sediment)
○: No sediment is observed
△: Stagnation at bottom (no sediment)
×: The sediment can be clearly confirmed.
[0167]
From the comparison of the average particle size of the dispersed pigment within the same pigment type (color) and the result of microscopic observation, the example according to the present invention is compared with the method of the comparative example which does not show a clear maximum value at the time of kneading at the load current. As a result, it was found that the particle size can be remarkably reduced, and the residual amount of coarse particles can be reduced. However, in the case of the dispersed particle diameter of cyan, the same result is obtained when the pigment is the same product (comparison between Example 2 and Comparative Example 3), but when the pigment has another product number (Examples 3 and 4). Although the results of (5) seemingly did not exert the effect of the present invention, it is presumed that this is due to the particle size of the pigment used. However, the generation of the coarse particles exerts the effect more than that of the comparative example.
[0168]
When the dispersion was stored at a constant temperature and the average particle size change and the presence or absence of sediment were observed, the results were compared within the same pigment type (color). In comparison with the method of Comparative Example which does not show a maximum value, it is apparent that the increase in the average particle size after the heating test is small, and the generation of sediment is observed in Comparative Example, whereas in the Example, Since no sediment was generated, it was found that the examples according to the present invention had better dispersion stability.
[0169]
(Adjustment of ink composition)
The dispersions obtained in the above Examples and Comparative Examples were adjusted according to the following formulation, and approximately 3 to 5% by mass of an ink composition was prepared according to each color tone. The composition table is shown in Table 5.
[0170]
[Table 5]

[0171]
(Printing test)
The obtained ink composition of Table 5 was mounted on NOVAJET PRO manufactured by ENCAD, and a printing test was performed.
Specifically, solid printing and fine line printing were performed on four A4 printing papers (paper dedicated to YUPO inkjet), and the ink ejection state was confirmed.
The results are shown in Table 6.
[0172]
[Table 6]

[0173]
：: Uniform solid printing on all print samples, ejection failure even at thin line portions, no print position shift.
：: uniform solid printing in all print samples, no ejection failure in thin line portion, but printing position shift is observed.
Δ: No problem in initial printing, but discharge failure occurred during printing.
×: Solid printing with density unevenness due to discharge failure was observed from the beginning. Even in the thin line portion, printing omission due to defective discharge is remarkable from the beginning.
[0174]
From the results shown in Table 6, in the examples of the present invention, images without any problem were obtained in the initial printing. In contrast, in the comparative examples, the ink ejection was unstable from the initial printing, and the ink ejection was stable. Since there is a large difference in the discharge characteristics, it can be understood that the embodiment of the present invention has remarkably excellent ejection stability.
[0175]
【The invention's effect】
When kneading a mixture containing at least a resin which can be dissolved or self-dispersible in water, and a pigment, and producing a kneaded product for a solid or semi-solid aqueous pigment dispersion, the energy imparted to the kneading machine is at least one or more times. A method for producing a kneaded product for an aqueous pigment dispersion, which is characterized by having a condition having a maximum value, can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of the configuration of a planetary mixer.
FIG. 2 is a partially enlarged view of a planetary mixer.
FIG. 3 is an explanatory diagram showing a locus of a stirring blade in a planetary mixer.
FIG. 4 shows an example of a change in kneading time and load current value (in the case of one maximum value)
FIG. 5 shows an example of a change in kneading time and load current value (when there are a plurality of maximum values).
FIG. 6 shows an example of changes in kneading time and load current value (when there is only one maximum value)
[Explanation of symbols]
1 ... stirring tank
2: Upper part of the stirring tank
3. Lower part of the stirring tank
4 and 5 ... stirring blades
6 ... rotor
A: Start kneading,
B, B1, B2: positions where the load current value shows the maximum value,
C: Addition of water, water-soluble solvent, etc. started
D: Removal of kneaded material or pigment dispersion
E: Load current value during no-load operation at rotational speed during kneading
F: The minimum position when the load current value has a plurality of maximum values

Claims (16)

In a method of producing a kneaded product for a solid or semi-solid aqueous pigment dispersion by kneading a mixture containing at least a resin and a pigment which can be dissolved or self-dispersed in water, the load current (I) of the kneader is adjusted by the kneading machine. A method for producing a kneaded product for an aqueous pigment dispersion, comprising: kneading the mixture such that the value (I / v) divided by the shear rate (v) increases with time and then decreases. When the value (I / v) obtained by dividing the load current (I) of the kneader by the shear rate (v) of the kneader becomes a maximum value, the I / v value of the kneader is equal to the unloaded kneader. 2. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 1, wherein the value exceeds 1.6 times the I / v value when operated in a state. The method according to claim 1 or 2, wherein the resin has at least an anionic group and / or a cationic group. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 3, wherein the resin is a resin having at least an anionic group. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 4, wherein the resin having an anionic group has an acid value of 60 to 300 mgKOH / g. 6. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 4, wherein a mixture containing a basic compound in addition to a resin and a pigment having at least an anionic group is kneaded during the kneading. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 6, wherein the basic compound is used in such an amount that the degree of neutralization of the resin having an anionic group becomes 20% or more. The method for producing a kneaded product for an aqueous pigment dispersion according to any one of claims 1 to 7, wherein the mass ratio of the resin / pigment in the kneaded product for the aqueous pigment dispersion is 1/20 to 5/1. The method for producing a kneaded product for an aqueous pigment dispersion according to any one of claims 1 to 8, wherein the resin has a weight average molecular weight of 3,000 to 50,000. The method for producing an aqueous pigment kneaded product according to any one of claims 1 to 9, wherein the resin has a glass transition point of 90 ° C or higher. The method for producing a kneaded material for an aqueous pigment dispersion according to any one of claims 1 to 10, wherein the kneading is performed using a kneader having a stirring tank and a stirring blade, and the stirring tank having a substantially closed structure. A method for producing a kneaded product for an aqueous pigment dispersion. The method for producing a kneaded product for an aqueous pigment dispersion according to claim 11, wherein the kneading machine is a planetary mixer. A step of obtaining a kneaded product for an aqueous pigment dispersion by the method for producing a kneaded product for an aqueous pigment dispersion according to any one of claims 1 to 12, and mixing the kneaded product for an aqueous pigment dispersion in a water-soluble solvent. Dispersing to obtain an aqueous pigment dispersion. A process for producing a kneaded product for aqueous pigment dispersion in a stirring tank by the method for producing a kneaded product for aqueous pigment dispersion according to claim 11 or 12, and the kneaded product for aqueous pigment dispersion in the stirring tank. Adjusting the viscosity of the aqueous pigment dispersion kneaded product in the stirring tank by adding a water-soluble solvent to the aqueous pigment dispersion. The method for producing an aqueous pigment dispersion according to claim 13 or 14, wherein the kneaded product for the aqueous pigment dispersion is dispersed in a water-soluble solvent using a disperser using a medium, a collision type disperser, and an ultrasonic disperser. A method for producing an aqueous pigment dispersion, wherein the dispersion is performed using at least one disperser selected from a group of dispersers. A method for producing an ink composition, comprising diluting an aqueous pigment dispersion obtained by the method for producing an aqueous pigment dispersion according to any one of claims 13 to 15 with a water-soluble solvent to produce an ink composition.

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