JP6594280B2 - Copolymer for pH indication in wide range and synthesis method thereof - Google Patents
Copolymer for pH indication in wide range and synthesis method thereof Download PDFInfo
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Description
本発明は広範囲ｐＨ指示用共重合体及びその合成方法に関し，とくに広い範囲にわたるｐＨを測定できる広範囲ｐＨ指示用共重合体に関する。 The present invention relates to a wide-range pH indicating copolymer and a synthesis method thereof, and more particularly to a wide-range pH indicating copolymer capable of measuring pH over a wide range.
河川・湖沼，空気・大気，地質等の環境モニタリングにおいて，例えば所定地点におけるｐＨを長期にわたり継続的にモニタリングすること（ｐＨモニタリング）を求められることがある。従来から一般的なｐＨ測定法は，液体（水溶液等）に接触させたｐＨ指示薬の色調変化を見る比色分析と，液体に浸漬した電極の起電力を計測する電気化学分析である。しかし，従来の比色分析は，紙等に含浸させた低分子のｐＨ指示薬（リトマス試験紙等）を用いるものであり，液体中に長期間浸漬し続けるとｐＨ指示薬が溶出してしまう問題点がある。また電気化学分析は，電極の頻繁なメンテナンスが欠かせないものであり，液体中に電極を長期間浸漬し続けると表面に異物が析出・付着するおそれがあるので，無人化が基本となるような長期のｐＨモニタリングに適用することは難しい。 In environmental monitoring of rivers / lakes, air / air, geology, etc., for example, it may be required to continuously monitor pH at a predetermined point over a long period of time (pH monitoring). Conventionally, a general pH measurement method is a colorimetric analysis in which a color change of a pH indicator brought into contact with a liquid (aqueous solution or the like) is observed, and an electrochemical analysis in which an electromotive force of an electrode immersed in the liquid is measured. However, the conventional colorimetric analysis uses a low molecular pH indicator (such as litmus paper) impregnated in paper or the like, and there is a problem in that the pH indicator is eluted if it is immersed in a liquid for a long period of time. . Electrochemical analysis requires frequent maintenance of the electrode. If the electrode is immersed in a liquid for a long period of time, foreign matter may be deposited on the surface. It is difficult to apply to long-term pH monitoring.
これに対し，ｐＨ指示部位及び重合性部位を有する単量体成分（ｐＨ指示用モノマー）と電気的中性部位及び重合性部位を有する単量体成分（非イオン性モノマー）とを共重合させた色調変化型の高分子材料をｐＨモニタリングに用いることが提案されている（特許文献１及び２参照）。例えば特許文献１は，（２）式に示すように，メチルイエローとメタクリル酸とを反応して得られたジメチルアミノアゾベンゼンアクリレート（ＡＡＢＡＡ）をｐＨ指示用モノマーとし，非イオン性モノマーであるＮ−イソプロピルアクリルアミド（ＮＩＰＡＡｍ）と共重合させた色調変化型共重合体を開示している。
In contrast, a monomer component having a pH indicating site and a polymerizable site (pH indicating monomer) is copolymerized with a monomer component having an electrically neutral site and a polymerizable site (nonionic monomer). It has been proposed to use a color change type polymer material for pH monitoring (see Patent Documents 1 and 2). For example, in Patent Document 1, as shown in the formula (2), dimethylaminoazobenzene acrylate (AABAA) obtained by reacting methyl yellow and methacrylic acid is used as a pH-indicating monomer, and N— which is a nonionic monomer. A color change copolymer copolymerized with isopropylacrylamide (NIPAAm) is disclosed.
（２）式のような色調変化型共重合体は，ｐＨ指示部が強固な共有結合で高分子鎖に担持されており，液体に長期間浸漬してもｐＨ指示部が溶出するおそれがない。また必要に応じて，（２）式のようにイオン性部位及び重合性部位を有する単量体成分（イオン性モノマー）を含めて共重合させ，ｐＨ指示用モノマーが色調変化するｐＨ領域を塩基性側又は酸性側へシフトさせることにより，共重合体の色調変化領域をｐＨ指示用モノマーに固有の変色域から移動させ，色調変化領域を制御することが可能である。 (2) In the color tone changing copolymer as shown in the formula, the pH indicator is supported on the polymer chain by a strong covalent bond, and there is no possibility that the pH indicator will be eluted even if immersed in a liquid for a long period of time. . Further, if necessary, copolymerization is carried out including a monomer component (ionic monomer) having an ionic part and a polymerizable part as shown in the formula (2), and the pH region in which the pH indicator monomer changes color tone is changed to a base. By shifting to the acid side or the acid side, the color tone change region of the copolymer can be moved from the color change region specific to the pH indicating monomer, and the color tone change region can be controlled.
更に，（２）式のような色調変化型共重合体をｐＨモニタリングに適用するため，ｐＨ指示用モノマーの発色からｐＨ値を精度よく測定する方法が提案されている（特許文献３参照）。例えば特許文献３は，ｐＨ指示用モノマーの発色を白色点Ｏが中央に配置された色度図Ｍ（図６（Ａ）参照）上にプロットしてその白色点Ｏが中心の極座標上の発色点Ｃの偏角Ｄを検出し，ｐＨ値の異なる複数の標本に接触させた共重合体の発色点Ｃ１，Ｃ２，……の偏角Ｄ１，Ｄ２，……と各標本のｐＨ値との関係式Ｆ１（図６（Ｂ）及び（Ｃ）参照）を予め設定しておき，測定対象の液体に浸漬させた共重合体の発色から発色点Ｃの偏角Ｄを検出し，その発色点Ｃの偏角Ｄと関係式Ｆ１とから測定対象の液体のｐＨ値を求める方法を開示している。 Furthermore, in order to apply the color tone changing copolymer represented by the formula (2) to pH monitoring, a method of measuring the pH value with accuracy from the color development of the pH indicating monomer has been proposed (see Patent Document 3). For example, in Patent Document 3, the color development of the pH indicating monomer is plotted on a chromaticity diagram M (see FIG. 6A) in which the white point O is arranged at the center, and the color development on the polar coordinate centered on the white point O The deviation angle D of point C is detected, and the deviation angles D1, D2,... Of the color development points C1, C2,. A relational expression F1 (see FIGS. 6B and 6C) is set in advance, and the deviation angle D of the color development point C is detected from the color development of the copolymer immersed in the liquid to be measured. A method for obtaining the pH value of the liquid to be measured from the deviation angle D of C and the relational expression F1 is disclosed.
図６（Ａ）は色度図Ｍの一例であるＣＩＥｘｙ色度図Ｍ１を示している。この色度図Ｍ１には，表色上の３原色の刺激値（Ｘ，Ｙ，Ｚ）に基づき全ての色が２つの数値（ｘ，ｙ）＝（Ｘ／（Ｘ＋Ｙ＋Ｚ），Ｙ／（Ｘ＋Ｙ＋Ｚ））として表現されており，ｐＨ指示用モノマーの発色を２つの数値の発色点Ｃ（ｘ，ｙ）としてプロットすることができる。また，ほぼ中央に白色点Ｏが配置されており，その白色点Ｏを中心とする極座標系を想定することにより，全ての色の数値（ｘ，ｙ）を動径ｒ及び偏角Ｄに変換することができる。図６（Ｂ）はｐＨ値の異なる複数の標本に接触させた色調変化型共重合体の発色点Ｃ１，Ｃ２，……が白色点Ｏを中心として弧を描くように並んでいることを示しており，図６（Ｃ）はそのような各発色点Ｃ１，Ｃ２，……のｐＨ値と偏角Ｄとの関係式Ｆ１の一例を示している。特許文献３は，偏角ＤからｐＨ値を精度よく推定するため，（Ａ）式のようなロジスティックモデル（ロジスティック曲線）で近似した関係式Ｆ１を用いることが有効であることを開示している。
Ｄ＝α／（１＋β・ｅｘｐ（−γ・ｐＨ）） ………………………（Ａ）
FIG. 6A shows a CIExy chromaticity diagram M1, which is an example of the chromaticity diagram M. In this chromaticity diagram M1, all colors are represented by two numerical values (x, y) = (X / (X + Y + Z), Y / (X + Y + Z) based on the stimulus values (X, Y, Z) of the three primary colors on the color. )), And the color development of the pH indicating monomer can be plotted as the two color development points C (x, y). In addition, a white point O is arranged almost at the center, and by assuming a polar coordinate system centered on the white point O, numerical values (x, y) of all colors are converted into a radius vector r and a declination angle D. can do. FIG. 6 (B) shows that the color development points C1, C2,... Of the color change type copolymers brought into contact with a plurality of specimens having different pH values are arranged in an arc with the white point O as the center. FIG. 6C shows an example of a relational expression F1 between the pH value of each of the coloring points C1, C2,. Patent Document 3 discloses that it is effective to use the relational expression F1 approximated by a logistic model (logistic curve) such as the expression (A) in order to accurately estimate the pH value from the declination angle D. .
D = α / (1 + β · exp (−γ · pH)) ……………………… (A)
上述した（２）式のような色調変化型共重合体を用いると共に，その発色から色度図Ｍ１上の偏角Ｄを介してｐＨ値を求める図６のような測定方法を適用することにより，長期間にわたる継続的な環境中のｐＨモニタリングを実現することが期待できる。しかし，特許文献１の開示するＡＡＢＡＡをｐＨ指示用モノマーとする共重合体は，比較的狭い酸性範囲で色調変化を示すものであり（ｐＨ１．０〜４．０程度，図６（Ｃ）参照），イオン性モノマーを含めて共重合させることで色調変化領域を多少シフトさせることは可能であるものの，測定できるｐＨ範囲が限定的である。環境モニタリング等では酸性から塩基性にわたる広い範囲のｐＨの継続的な測定を求められる場合があり，広いｐＨ範囲で色調変化を示し，広い範囲にわたるｐＨをｖに基づいて測定できる色調変化型共重合体の開発が求められている。 By using a color tone change type copolymer like the above-mentioned (2) formula, and applying the measuring method as shown in FIG. 6 for obtaining the pH value from the color development through the deviation angle D on the chromaticity diagram M1. , It can be expected to realize continuous pH monitoring in the environment over a long period of time. However, the copolymer having AABAA as a pH indicating monomer disclosed in Patent Document 1 exhibits a change in color tone in a relatively narrow acidic range (about pH 1.0 to 4.0, see FIG. 6C). ), It is possible to slightly shift the color change region by copolymerization including the ionic monomer, but the measurable pH range is limited. In environmental monitoring, etc., it may be required to continuously measure pH over a wide range from acidic to basic, and color tone change can be measured based on v over a wide pH range, showing color change over a wide pH range. Development of coalescence is required.
そこで本発明の目的は，広いｐＨ範囲で色調変化を示すｐＨ指示用共重合体を提供することにある。 Accordingly, an object of the present invention is to provide a pH indicating copolymer exhibiting a color change in a wide pH range.
本発明者は，異なるｐＨ範囲で色調変化する複数種類のｐＨ指示用モノマーを共重合させることに着目した。上述したＡＡＢＡＡのように単独のｐＨ指示用モノマーで測定できるｐＨ範囲は限られていても，異なるｐＨ範囲で色調変化する複数種類のｐＨ指示用モノマーを組み合わせて色調変化型共重合とすれば，測定できるｐＨ範囲を広げることが期待できる。ただし，共重合体の色調変化からｐＨ値を求めるためには，共重合体が異なるｐＨ値で同じ色となることを避ける必要がある。例えば図６（Ｃ）のように共重合体の発色から色度図上の偏角Ｄを介してｐＨ値を求めるためには，ｐＨ値の増加に応じて偏角Ｄが増加するように共重合体を色調変化させることが必要となる。本発明者は，ｐＨ値の増加に応じて偏角Ｄが増加するように色調変化させるためには，共重合体をチモールブルーのように２段階で色調変化させることが有効であるとの着想を得，２段階で色調変化する共重合体の研究開発の結果，本発明の完成に至ったものである。 The inventor has focused on copolymerizing a plurality of types of pH indicating monomers that change color tone in different pH ranges. Even if the pH range that can be measured with a single pH indicator monomer such as AABAA described above is limited, by combining a plurality of types of pH indicator monomers that change color tone in different pH ranges, the color change copolymerization is obtained. It can be expected to widen the measurable pH range. However, in order to obtain the pH value from the color tone change of the copolymer, it is necessary to avoid the copolymer from having the same color at different pH values. For example, as shown in FIG. 6C, in order to obtain the pH value from the color development of the copolymer via the deviation angle D on the chromaticity diagram, the deviation angle D increases as the pH value increases. It is necessary to change the color of the polymer. The inventor has the idea that it is effective to change the color tone of the copolymer in two stages like thymol blue in order to change the color tone so that the declination angle D increases as the pH value increases. As a result of research and development of a copolymer that changes its color tone in two stages, the present invention has been completed.
本発明による広範囲ｐＨ指示用共重合体は，第１ｐＨ範囲で色調変化する第１ｐＨ指示部位及び重合性基を含む第１ｐＨ指示用モノマーと，第１ｐＨ範囲と異なる第２ｐＨ範囲で色調変化する第２ｐＨ指示部位及び重合性基を含む第２ｐＨ指示用モノマーと，電気的中性部位及び重合性基を含む非イオン性モノマーとを含めて共重合してなり，第１及び第２ｐＨ範囲の中間域において両ｐＨ指示用モノマーが近似色であるか又は少なくとも一方が無色であり，第１及び第２ｐＨ範囲の両端域において両ｐＨ指示用モノマーが異なる色であるものである。 The wide-range pH indicating copolymer according to the present invention includes a first pH indicating moiety that changes color tone in the first pH range and a first pH indicating monomer that includes a polymerizable group, and a second pH that changes color tone in a second pH range different from the first pH range. In the middle region of the first and second pH ranges, the second pH indicating monomer containing an indicator moiety and a polymerizable group and a nonionic monomer containing an electrically neutral moiety and a polymerizable group are copolymerized. Both pH indicating monomers are approximate colors or at least one is colorless, and both pH indicating monomers are different colors at both ends of the first and second pH ranges.
好ましい実施例では，更にイオン性部位及び重合性基を含むイオン性モノマーを含めて共重合する。例えば，第１ｐＨ指示用モノマーを酸性範囲で色調変化するものとし，第２ｐＨ指示用モノマーを塩基性範囲で色調変化するものとすることができる。 In a preferred embodiment, the copolymerization further includes an ionic monomer containing an ionic moiety and a polymerizable group. For example, the first pH indicating monomer can be changed in color in the acidic range, and the second pH indicating monomer can be changed in color in the basic range.
望ましい実施例では，第１及び第２ｐＨ指示用モノマーの混合比率を，第１及び第２ｐＨ範囲にまたがる複数の異なるｐＨ値におけるｐＨ指示用共重合体の発色を白色点が中央に配置された色度図上にプロットして当該白色点が中心の極座標上の発色点の偏角Ｄを検出したときに，ｐＨ値の増加に応じて各発色点の偏角Ｄが増加するように調整する。 In a preferred embodiment, the mixing ratio of the first and second pH indicating monomers is the color of the pH indicating copolymer at a plurality of different pH values spanning the first and second pH ranges. When the deviation angle D of the coloring point on the polar coordinate centered on the white point is detected by plotting on the degree diagram, adjustment is performed so that the deviation angle D of each coloring point increases as the pH value increases.
或いは，イオン性モノマーを含めて共重合させる場合に，イオン性モノマーの混合比率を，第１及び第２ｐＨ範囲にまたがる複数の異なるｐＨ値におけるｐＨ指示用共重合体の発色を白色点が中央に配置された色度図上にプロットして当該白色点が中心の極座標上の発色点の偏角Ｄを検出したときに，ｐＨ値の増加に応じて各発色点の偏角Ｄが増加するように調整することも可能である。 Alternatively, when copolymerizing including ionic monomers, the mixing ratio of the ionic monomers is such that the color of the pH indicating copolymer at a plurality of different pH values spanning the first and second pH ranges is centered on the white point. When the deviation angle D of the color development point on the polar coordinates centered on the white point is detected by plotting on the arranged chromaticity diagram, the deviation angle D of each color development point increases as the pH value increases. It is also possible to adjust to.
本発明による広範囲ｐＨ指示用共重合体は，第１ｐＨ範囲で色調変化する第１ｐＨ指示用モノマーと，第１ｐＨ範囲と異なる第２ｐＨ範囲で色調変化する第２ｐＨ指示用モノマーとを共重合させると共に，第１及び第２ｐＨ範囲の中間域において両ｐＨ指示用モノマーを近似色とするか又は少なくとも一方を無色とし，第１及び第２ｐＨ範囲の両端域において異なる色とするので，ｐＨ値の増加に応じて２段階で色調変化させることができ，その色調変化から広い範囲にわたるｐＨを測定することができる。また，複数の異なるｐＨ値における発色を白色点が中央に配置された色度図上にプロットして当該白色点が中心の極座標上の発色点の偏角Ｄを検出したときに，各ｐＨ値の発色点を色度図Ｍ１上に白色点Ｏを中心として弧を描くように，すなわちｐＨ値の増加に応じて偏角Ｄが増加するように並べることができ，発色点の偏角ＤからｐＨ値を測定することができる。 The wide-range pH indicating copolymer according to the present invention is a copolymer of a first pH indicating monomer that changes color tone in the first pH range and a second pH indicating monomer that changes color tone in a second pH range different from the first pH range, Since both pH indicating monomers are approximate colors in the middle range of the first and second pH ranges, or at least one is colorless and different colors at both ends of the first and second pH ranges, the pH value increases. The color tone can be changed in two stages, and the pH over a wide range can be measured from the color tone change. Further, when the color development at a plurality of different pH values is plotted on a chromaticity diagram in which the white point is arranged at the center, and the deviation angle D of the color development point on the polar coordinate centered on the white point is detected, each pH value Can be arranged on the chromaticity diagram M1 so as to draw an arc centering on the white point O, that is, the declination D increases as the pH value increases. The pH value can be measured.
ｐＨ値の増加に応じてｐＨ指示用共重合体の色度図Ｍ１上の発色点の偏角Ｄの減少が発生するような場合は，第１及び第２ｐＨ指示用モノマーの混合比率を調整することにより偏角Ｄの減少を避け，ｐＨ値の増加に応じて色度図Ｍ１上の各発色点の偏角Ｄが増加するようなｐＨ指示用共重合体とすることができる。また，イオン性部位及び重合性部位を有するイオン性モノマーを含めて共重合させることにより，第１ｐＨ指示用モノマー及び第２ｐＨ指示用モノマーの色調変化領域を制御することが可能であり，ｐＨ値の増加に応じてｐＨ指示用共重合体の色度図Ｍ１上の発色点の偏角Ｄの減少が発生するような場合は，イオン性モノマーの混合比率を調整することにより偏角Ｄの減少を避けることも可能である。 If the declination angle D of the color development point on the chromaticity diagram M1 of the pH indicating copolymer is generated as the pH value increases, the mixing ratio of the first and second pH indicating monomers is adjusted. Thus, a decrease in the deflection angle D can be avoided, and a pH indicating copolymer can be obtained in which the deflection angle D of each color development point on the chromaticity diagram M1 increases as the pH value increases. In addition, by copolymerization including an ionic monomer having an ionic part and a polymerizable part, it is possible to control the color change region of the first pH indicating monomer and the second pH indicating monomer. If the declination angle D of the coloring point on the chromaticity diagram M1 of the pH indicating copolymer increases with the increase, the declination angle D can be reduced by adjusting the mixing ratio of the ionic monomers. It is also possible to avoid it.
以下，添付図面を参照して本発明を実施するための形態及び実施例を説明する。
本発明は，異なるｐＨ範囲で色調変化する第１ｐＨ指示用モノマー及び第２ｐＨ指示用モノマーを共重合させて，２段階で色調変化するような広範囲ｐＨ指示用共重合体としたものである。そのような第１及び第２ｐＨ指示用モノマーの一例は，特定のｐＨ領域で色調変化を示す従来の低分子のｐＨ指示薬をｐＨ指示部位として，その特定部位に重合性基を導入して合成したモノマーである。従来の代表的な低分子のｐＨ指示薬は黄色を示すものが多く，例えば表１に示すように，色調変化を示すｐＨ領域の低ｐＨ側（酸性側）で黄色を示すＡ群，色調変化を示すｐＨ領域の高ｐＨ側（塩基性側）で黄色を示すＢ群，色調変化をするが黄色を示さないＣ群に分類することができる。 In the present invention, a first pH indicating monomer and a second pH indicating monomer that change color tone in different pH ranges are copolymerized to obtain a wide pH indicating copolymer that changes color tone in two stages. One example of such first and second pH indicating monomers was synthesized by using a conventional low molecular weight pH indicator showing a color change in a specific pH region as a pH indicating site and introducing a polymerizable group into the specific site. Monomer. Many of the conventional representative low molecular pH indicators show a yellow color. For example, as shown in Table 1, a group A showing a yellow color on the low pH side (acid side) of the pH range showing a color tone change, a color tone change. It can be classified into Group B showing yellow on the high pH side (basic side) of the pH range shown, and Group C showing a color change but not showing yellow.
また本発明は，第１ｐＨ指示用モノマーを色調変化させる第１ｐＨ範囲と第２ｐＨ指示用モノマーを色調変化させる第２ｐＨ範囲との中間域（両ｐＨ範囲が重なる領域を含む）において両ｐＨ指示用モノマーが近似色であり，第１ｐＨ範囲及び第２ｐＨ範囲の両端域において両ｐＨ指示用モノマーが異なる色であるような，複数種類のｐＨ指示用モノマーを共重合させたものである。例えば表１において，Ｂ群のメチルイエロー（色調変化ｐＨ範囲が酸性）をｐＨ指示部位とする第１ｐＨ指示用モノマーと，Ａ群のブロモチモールブルー（色調変化ｐＨ範囲が中性）をｐＨ指示部位とする第２ｐＨ指示用モノマーとが合成できた場合に，両モノマーは色調変化ｐＨ範囲の中間域において近似色（黄色）である。また，色調変化ｐＨ範囲の一端の低ｐＨ側（酸性側）においてメチルイエローは赤色であるのに対し，色調変化ｐＨ範囲の他端の高ｐＨ側（塩基性側）においてブロモチモールブルーは青色であるから，両モノマーは色調変化ｐＨ範囲の両端域において異なる色である。従って，そのようなメチルイエローをｐＨ指示部位とする第１ｐＨ指示用モノマーと，ブロモチモールブルーをｐＨ指示部位とする第２ｐＨ指示用モノマーとを共重合させて，本発明の広範囲ｐＨ指示用共重合体とすることができる。 Further, the present invention provides both pH indicating monomers in an intermediate range (including a region where both pH ranges overlap) between a first pH range in which the first pH indicating monomer changes its color tone and a second pH range in which the second pH indicating monomer changes its color tone. Is a color obtained by copolymerizing a plurality of types of pH indicating monomers such that both pH indicating monomers are different colors at both ends of the first pH range and the second pH range. For example, in Table 1, the first pH indicating monomer having methyl yellow of group B (color tone change pH range is acidic) and the bromothymol blue (color change pH range neutral) of group A as pH indicating sites. When the second pH indicating monomer is synthesized, both monomers are approximate colors (yellow) in the middle of the color change pH range. Also, methyl yellow is red on the low pH side (acid side) at one end of the color change pH range, whereas bromothymol blue is blue on the high pH side (basic side) at the other end of the color change pH range. Therefore, both monomers have different colors at both ends of the color change pH range. Therefore, the first pH indicating monomer having such a methyl yellow as the pH indicating site and the second pH indicating monomer having the bromothymol blue as the pH indicating site are copolymerized to produce the broad pH indicating copolymer of the present invention. Can be combined.
また，表１において，Ｃ群のメチルオレンジ（色調変化ｐＨ範囲が酸性）をｐＨ指示部位とする第１ｐＨ指示用モノマーと，Ａ群のクレゾールレッド（色調変化ｐＨ範囲が塩基性）をｐＨ指示部位とする第２ｐＨ指示用モノマーとが合成できた場合に，両モノマーは色調変化ｐＨ範囲の中間域において近似色（黄色と橙色）である。また，色調変化ｐＨ範囲の一端の低ｐＨ側（酸性側）においてメチルオレンジは赤色であるのに対し，色調変化ｐＨ範囲の他端の高ｐＨ側（塩基性側）においてクレゾールレッドは赤紫色であるから，両モノマーは色調変化ｐＨ範囲の両端域において異なる色である。従って，そのようなメチルオレンジをｐＨ指示部位とする第１ｐＨ指示用モノマーと，クレゾールレッドをｐＨ指示部位とする第２ｐＨ指示用モノマーとを共重合させて，本発明の広範囲ｐＨ指示用共重合体とすることができる。 Further, in Table 1, the first pH indicating monomer having the group C methyl orange (color change pH range is acidic) as the pH indicating site and the group A cresol red (color change pH range being basic) are indicated as the pH indicating site. When the second pH indicating monomer is synthesized, both monomers are approximate colors (yellow and orange) in the middle of the color change pH range. Also, methyl orange is red on the low pH side (acidic side) at one end of the color change pH range, whereas cresol red is reddish purple on the high pH side (basic side) at the other end of the color change pH range. Therefore, both monomers have different colors at both ends of the color change pH range. Therefore, the first pH indicating monomer having the methyl orange as the pH indicating site and the second pH indicating monomer having the cresol red as the pH indicating site are copolymerized to obtain the wide range pH indicating copolymer of the present invention. It can be.
表１に示すｐＨ指示薬をｐＨ指示用モノマーとするために導入する重合性基は，例えば（メタ）アクリルロイル基，（メタ）アクリルロイルオキシ基，ビニル基のように不飽和結合で付加重合できる基，又は，アミノ基，カルボキシル基，アルデヒド基，環状エーテル基のように縮合重合できる基等を重合性基とすることができる。また，ｐＨ指示薬と重合性基とは，直接結合させることも可能であるが，アルキレン基，エーテル結合，カルボニル基，アミド結合（−ＣＯ−ＮＨ−）の少なくとも一種を介して結合させることもできる。 The polymerizable group introduced to make the pH indicator shown in Table 1 into a pH indicator monomer can be addition-polymerized with an unsaturated bond such as a (meth) acryloyl group, a (meth) acryloyloxy group, or a vinyl group. A polymerizable group such as an amino group, a carboxyl group, an aldehyde group, or a cyclic ether group can be used as the polymerizable group. Further, the pH indicator and the polymerizable group can be directly bonded, but can also be bonded via at least one of an alkylene group, an ether bond, a carbonyl group, and an amide bond (—CO—NH—). .
もっとも，一般的に色調変化を示す低分子のｐＨ指示薬は重合性基を導入すると類似の色調変化を示さなくなることがあり，表１に示す低分子のｐＨ指示薬の示す色調変化は，必ずしもそのｐＨ指示薬をｐＨ指示部位として合成したｐＨ指示用モノマーの色調変化を示すものではない。合成したｐＨ指示用モノマーの色調変化を確認したうえで本発明に用いることが必要である。以下の説明では，表１のうち重合性基を導入してｐＨ指示用モノマーとしても類似の色調変化を示すことが確認された２種類のｐＨ指示薬，すなわちＢ群のメチルイエロー（酸性ｐＨ範囲が色調変化）をｐＨ指示部位として合成されたジメチルアミノアゾベンゼンアクリレート（ＡＡＢＡＡ）を第１ｐＨ指示用モノマーとし，Ａ群のαナフトールフタレイン（α−ＮＰ，塩基性ｐＨ範囲で色調変化）をｐＨ指示部位として合成された６ビニルナフトールフタレイン（６ビニル−αＮＰ）を第２ｐＨ指示用モノマーとした実施例について説明する。ただし，本発明は表１に示すｐＨ指示薬から合成されたｐＨ指示用モノマーの使用に限定されるわけではなく，所定ｐＨ範囲で色調変化する他のｐＨ指示用モノマーを使用することも可能である。 However, in general, a low molecular pH indicator exhibiting a color tone change may not exhibit a similar color tone change when a polymerizable group is introduced, and the color tone change indicated by the low molecular pH indicator shown in Table 1 is not necessarily the pH value. It does not indicate a change in color tone of a pH indicator monomer synthesized using an indicator as a pH indicator site. It is necessary to use in the present invention after confirming the color change of the synthesized pH indicating monomer. In the following description, two kinds of pH indicators that have been confirmed to exhibit a similar color change as a pH-indicating monomer by introducing a polymerizable group in Table 1, that is, group B methyl yellow (with acidic pH range). Dimethylaminoazobenzene acrylate (AABAA) synthesized using pH change site as the pH indicator site is used as the first pH indicator monomer, and α-naphtholphthalein (α-NP, color tone change in basic pH range) of Group A is used as the pH indicator site. An example using 6 vinyl naphtholphthalein (6 vinyl-αNP) synthesized as a second pH indicating monomer will be described. However, the present invention is not limited to the use of a pH indicator monomer synthesized from the pH indicator shown in Table 1, and it is also possible to use other pH indicator monomers that change color tone within a predetermined pH range. .
（１）第１ｐＨ指示用モノマーの作製及び色調変化の確認
第１ｐＨ指示用モノマーとして，表１のＢ群のメチルイエローをｐＨ指示部位とし，メタクリル酸と反応させて重合性基を導入したジメチルアミノアゾベンゼンアクリレート（ＡＡＢＡＡ）を作製した（（２）式参照）。そして，作製したＡＡＢＡＡを，表２の重合条件で非イオン性モノマーであるＮ−イソプロピルアクリルアミド（ＮＩＰＡＡｍ）及び架橋剤であるＮ，Ｎ−メチレンビスアクリルアミド（ＭＢＡＡｍ）と共重合させてｐＨ指示用共重合体（ＮＩＰＡＡｍ−ＡＡＢＡＡ）を作製した。
(1) Preparation of first pH indicating monomer and confirmation of change in color tone As the first pH indicating monomer, dimethylamino introduced with a polymerizable group by reacting with methacrylic acid using methyl yellow of group B in Table 1 as a pH indicating site. Azobenzene acrylate (AABAA) was prepared (see formula (2)). Then, the prepared AABAA was copolymerized with N-isopropylacrylamide (NIPAAm) as a nonionic monomer and N, N-methylenebisacrylamide (MBAAm) as a crosslinking agent under the polymerization conditions shown in Table 2. A polymer (NIPAAm-ABAAA) was produced.
作製したｐＨ指示用共重合体（ＮＩＰＡＡｍ−ＡＡＢＡＡ）を用いて複数の試験片（１×１ｃｍ）を成形し，各試験片をｐＨ１間隔で調製した異なるｐＨ値０〜８の水溶液にそれぞれ浸漬して発色させ，上述した特許文献３の場合と同様に，各試験片の発色を白色点Ｏが中央に配置された図６（Ａ）の色度図Ｍ１上にプロットしてその白色点Ｏが中心の極座標上の発色点Ｃの偏角Ｄを検出し，各試験片の発色点Ｃの偏角ＤとｐＨ値との関係をロジスティックモデル（ロジスティック曲線）で近似した関係式Ｆ１を求めた。求めた関係式Ｆ１を図１に示す。 A plurality of test pieces (1 × 1 cm) are formed using the prepared pH indicating copolymer (NIPAAm-ABAAA), and each test piece is immersed in an aqueous solution having different pH values of 0 to 8 prepared at pH 1 intervals. As in the case of Patent Document 3 described above, the color of each test piece is plotted on the chromaticity diagram M1 in FIG. 6A in which the white point O is arranged at the center. The deviation angle D of the coloring point C on the central polar coordinates was detected, and a relational expression F1 that approximated the relationship between the deviation angle D of the coloring point C and the pH value of each test piece with a logistic model (logistic curve) was obtained. The obtained relational expression F1 is shown in FIG.
図１の関係式Ｆ１は，ＡＡＢＡＡを用いた色調変化型ｐＨ指示用共重合体が，ｐＨ２〜７の酸性領域において赤色から黄色に色調変化しており，ｐＨが増加すると偏角Ｄも増加しながら上に凹の状態から凸の状態に変わる曲線となっており，変曲点におけるｐＨ（＝ｐＫａ）が約３.３であることを示している。なお，ＡＡＢＡＡとＮＩＰＡＡｍと共に，イオン性部位及び重合性部位を有するイオン性モノマーを含めて共重合させることにより，関係式Ｆ１の色調変化するｐＨ領域を塩基性側又は酸性側へシフトさせることもできる。 The relational expression F1 in FIG. 1 shows that the color-changing pH indicating copolymer using AABAA changes from red to yellow in the acidic region of pH 2 to 7, and the declination angle D increases as the pH increases. However, the curve changes from a concave state to a convex state, indicating that the pH (= pKa) at the inflection point is about 3.3. In addition, by co-polymerizing with AABAA and NIPAAm including an ionic monomer having an ionic part and a polymerizable part, the pH range where the color tone of the relational formula F1 changes can be shifted to the basic side or the acidic side. .
（２）第２ｐＨ指示用モノマーの作製及び色調変化の確認
第２ｐＨモノマーとして，（６）式に示すように，表１のＡ群のαナフトールフタレイン（α−ＮＰ）をｐＨ指示部位とし，そのイソベンゾフラン縮合環の６位に重合性基としてビニル基を導入した６ビニルナフトールフタレイン（６ビニル−αＮＰ）を作製した。そして，作製した６ビニル−αＮＰを，表３の重合条件で非イオン性モノマーであるＮＩＰＡＡｍ及び架橋剤であるＭＢＡＡｍと共重合させてｐＨ指示用共重合体（ＮＩＰＡＡｍ−６ビニルαＮＰ）を作製した。
(2) Preparation of second pH indicating monomer and confirmation of change in color tone As the second pH monomer, as shown in the formula (6), α-naphtholphthalein (α-NP) of Group A in Table 1 is used as the pH indicating site, 6 vinyl naphtholphthalein (6 vinyl-αNP) in which a vinyl group was introduced as a polymerizable group at the 6-position of the isobenzofuran condensed ring was produced. Then, the produced 6 vinyl-αNP was copolymerized with NIPAAm, which is a nonionic monomer, and MBAAm, which is a crosslinking agent, under the polymerization conditions shown in Table 3 to produce a pH indicating copolymer (NIPAAm-6 vinyl αNP). .
次いで，作製したｐＨ指示用共重合体（ＮＩＰＡＡｍ−６ビニルαＮＰ）を用いて複数の試験片（１×１ｃｍ）を成形し，各試験片をｐＨ１間隔で調製した異なるｐＨ値６〜１２の水溶液にそれぞれ浸漬して発色させ，上述した第１ｐＨ指示用モノマーの場合と同様に，各試験片の発色を図６（Ａ）の色度図Ｍ１上にプロットしてその白色点Ｏが中心の極座標上の発色点Ｃの偏角Ｄを検出し，各試験片の発色点Ｃの偏角ＤとｐＨ値との関係をロジスティックモデル（ロジスティック曲線）で近似した関係式Ｆ２を求めた。求めた関係式Ｆ２を，関係式Ｆ１と共に図１に示す。 Next, a plurality of test pieces (1 × 1 cm) were formed using the prepared pH indicating copolymer (NIPAAm-6 vinyl αNP), and aqueous solutions having different pH values of 6 to 12 were prepared at pH 1 intervals. In the same way as in the case of the first pH indicating monomer described above, the color development of each test piece is plotted on the chromaticity diagram M1 in FIG. 6A and the white point O is the central polar coordinate. The deviation angle D of the upper coloring point C was detected, and a relational expression F2 that approximated the relationship between the deviation angle D of the coloring point C and the pH value of each test piece with a logistic model (logistic curve) was obtained. The obtained relational expression F2 is shown in FIG. 1 together with the relational expression F1.
図１の関係式Ｆ２は，６ビニル−αＮＰを用いた色調変化型ｐＨ指示用共重合体が，ｐＨ６〜１２の塩基性領域において黄色から青色（ライトブルー）に色調変化しており，ｐＨが増加すると偏角Ｄも増加しながら上に凹の状態から凸の状態に変わる曲線となっており，変曲点におけるｐＨ（＝ｐＫａ）が約９．９であることを示している。なお，６ビニル−αＮＰとＮＩＰＡＡｍと共に，イオン性部位及び重合性部位を有するイオン性モノマーを含めて共重合させることによりに，関係式Ｆ２の色調変化するｐＨ領域を塩基性側又は酸性側へシフトさせることができる。 The relational expression F2 in FIG. 1 shows that the color changing pH-indicating copolymer using 6 vinyl-αNP changes in color from yellow to blue (light blue) in the basic region of pH 6-12. As the declination D increases, the curve changes from a concave state to a convex state while increasing, indicating that the pH (= pKa) at the inflection point is about 9.9. By co-polymerizing with 6 vinyl-αNP and NIPAAm including an ionic monomer having a ionic site and a polymerizable site, the pH range where the color tone of relational formula F2 changes is shifted to the basic side or acidic side. Can be made.
（３）第１ｐＨ指示用モノマー及び第２ｐＨ指示用モノマーを共重合したｐＨ指示用共重合体の作製
上述した第１ｐＨ指示用モノマー（ＡＡＢＡＡ）と第２ｐＨ指示用モノマー（６ビニル−αＮＰ）とは，各モノマーの色調変化ｐＨ範囲の中間域，すなわち中性域において近似色（黄色）である。また，色調変化ｐＨ範囲の一端の低ｐＨ側（酸性側）において第１ｐＨ指示用モノマー（ＡＡＢＡＡ）は赤色であるのに対し，色調変化ｐＨ範囲の他端の高ｐＨ側（塩基性側）において第２ｐＨ指示用モノマー（６ビニル−αＮＰ）は青色（ライトブルー）であるから，両モノマーは色調変化ｐＨ範囲の両端域において異なる色である。従って，この第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとは，本発明の共重合条件を満たしている。
(3) Production of pH-indicating copolymer obtained by copolymerizing first pH-indicating monomer and second pH-indicating monomer What are the first pH-indicating monomer (AABAA) and the second pH-indicating monomer (6 vinyl-αNP)? The color change of each monomer is an approximate color (yellow) in the middle range of the pH range, that is, in the neutral range. The first pH indicating monomer (AABAA) is red on the low pH side (acid side) at one end of the color change pH range, whereas it is on the high pH side (basic side) at the other end of the color change pH range. Since the second pH indicating monomer (6 vinyl-αNP) is blue (light blue), both monomers have different colors at both ends of the color change pH range. Therefore, the first pH indicating monomer and the second pH indicating monomer satisfy the copolymerization conditions of the present invention.
また，図１の関係式Ｆ１，Ｆ２は，共にｐＨが増加すると偏角Ｄも増加しながら上に凹の状態から凸の状態に変わる曲線となっており，第１ｐＨ指示用モノマーのｐＫａが約３.３であるのに対し，第２ｐＨ指示用モノマーのｐＫａが約９．９であることを示しているので，両者を含めて同一高分子鎖に共重合すれば，変曲点を２つ持つような色調変化型ｐＨ指示用共重合体が合成できることを示唆している。そこで，異なるｐＨ領域で色調変化する第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとを，表４の条件で非イオン性モノマーであるＮＩＰＡＡｍと共重合させてｐＨ指示用共重合体（８）を作製した。
Also, the relational expressions F1 and F2 in FIG. 1 are curves that change from a concave state to a convex state while the declination angle D increases as the pH increases, and the pKa of the first pH indicating monomer is about This indicates that the pKa of the second pH indicating monomer is about 9.9, while it is 3.3, so if both are copolymerized into the same polymer chain, two inflection points will be obtained. This suggests that a color-change-type pH indicating copolymer such as that possessed can be synthesized. Therefore, the pH indicating copolymer (8) is obtained by copolymerizing the first pH indicating monomer and the second pH indicating monomer, which change color tone in different pH ranges, with NIPAAm which is a nonionic monomer under the conditions shown in Table 4. Produced.
（４）ｐＨ指示用共重合体の色調変化の確認
作製したｐＨ指示用共重合体を用いて複数の試験片（２×２ｃｍ）を成形し，各試験片をｐＨ１間隔で調製した異なるｐＨ値０〜１２の水溶液にそれぞれ浸漬して発色させ，上述した第１及び第２ｐＨ指示用モノマーの場合と同様に，各試験片の発色を白色点Ｏが中央に配置された図２（Ａ）の色度図Ｍ１上にプロットしてその白色点Ｏが中心の極座標上の発色点Ｃの偏角Ｄを検出した。図２（Ａ）の色度図Ｍ１は，図６（Ａ）の色度図と同じものである。そして，図２（Ａ）のようにプロットした各試験片の発色点Ｃの偏角ＤとｐＨ値との関係をロジスティックモデル（ロジスティック曲線）で近似した関係式Ｆ３を求めた。求めた関係式Ｆ３を図３に示す。
(4) Confirmation of change in color tone of pH indicating copolymer Different pH values obtained by molding a plurality of test pieces (2 × 2 cm) using the prepared pH indicating copolymer, and preparing each test piece at pH 1 intervals. As shown in FIG. 2A, the white point O is arranged at the center in the same manner as in the case of the first and second pH indicating monomers described above. Plotting on the chromaticity diagram M1, the deviation angle D of the coloring point C on the polar coordinates centered on the white point O was detected. The chromaticity diagram M1 in FIG. 2A is the same as the chromaticity diagram in FIG. And the relational expression F3 which approximated the relationship between the deflection angle D of the coloring point C of each test piece plotted as shown in FIG. 2A and the pH value by a logistic model (logistic curve) was obtained. The obtained relational expression F3 is shown in FIG.
図６の関係式Ｆ３は，６ビニル−αＮＰを用いた第１ｐＨ指示用モノマーとＡＡＢＡＡを用いた第２ｐＨ指示用モノマーとを共重合させたｐＨ指示用共重合体が，ｐＨ２〜７の酸性領域において赤色から黄色に色調変化しており，ｐＨ２〜３において第１の変曲点が存在することを示している。また，ｐＨ７〜１２の塩基性領域において黄色から青色に色調変化しており，ｐＨ９〜１０において第２の変曲点が存在することを示している。すなわち，第１ｐＨ指示用モノマー（ＡＡＢＡＡ）と第２ｐＨ指示用モノマー（６ビニル−αＮＰ）とを共重合させることにより，ｐＨ２〜３とｐＨ７〜１２と２つの変色点を有し，赤色から黄色を経て青色になる２段階の色調変化を示すｐＨ指示用共重合体とすることができ，単独の共重合体で酸性から塩基性にわたる広いｐＨ範囲のｐＨモニタリングが実現できることを確認することができた。 The relational expression F3 in FIG. 6 shows that the pH indicating copolymer obtained by copolymerizing the first pH indicating monomer using 6 vinyl-αNP and the second pH indicating monomer using AABAA has an acidic region of pH 2 to 7. The color tone changes from red to yellow at pH 2, and the first inflection point is present at pH 2 to 3. Further, the color changes from yellow to blue in the basic region of pH 7 to 12, indicating that the second inflection point exists at pH 9 to 10. That is, by copolymerizing the first pH indicating monomer (AABAA) and the second pH indicating monomer (6 vinyl-αNP), pH 2 to 3 and pH 7 to 12 have two color change points. It was possible to obtain a pH-indicating copolymer showing a two-stage color change that turns blue, and it was confirmed that a single copolymer could realize pH monitoring in a wide pH range from acidic to basic. .
（５）ｐＨ指示用共重合体の色調変化の調整
上述した第１ｐＨ指示用モノマー（ＡＡＢＡＡ）と第２ｐＨ指示用モノマー（６ビニル−αＮＰ）との共重合体は，酸性域で赤色，中性域で黄色，塩基性域で青色という２段階の色調変化を示しており，例えばそのような色調変化を目視で観察することにより，ｐＨ２〜１２の広い範囲にわたるｐＨ測定に利用することができる。ただし，図３の関係式Ｆ３から分かるように，ｐＨ５〜８の中性域から塩基性域において，共重合体の発色点の色度図Ｍ１上の偏角ＤがｐＨ値の増加に応じて減少する傾向がみられた。この偏角Ｄの減少の原因は，図２（Ｂ）の色度図Ｍ１の拡大図に示すように，酸性域から中性域において赤色から濃い黄色（橙色に類似）を経て薄い黄色に色調が変化するのに対し，中性域から塩基性域において薄い黄色から再び濃い黄色（橙色に類似）を経て青色に色調が変化しており，薄い黄色と濃い黄色との間で色調変化が往復していることにあると考えられる。
(5) Adjustment of color tone change of pH indicating copolymer The copolymer of the first pH indicating monomer (AABAA) and the second pH indicating monomer (6 vinyl-αNP) is red, neutral in the acidic range. It shows a two-stage color change, yellow in the region and blue in the basic region. For example, by visually observing such a color change, it can be used for pH measurement over a wide range of pH 2-12. However, as can be seen from the relational expression F3 in FIG. 3, in the neutral region to the basic region of pH 5 to 8, the declination angle D on the chromaticity diagram M1 of the color development point of the copolymer depends on the increase of the pH value. There was a tendency to decrease. As shown in the enlarged view of the chromaticity diagram M1 in FIG. 2 (B), the cause of the decrease in the deviation angle D is from red to dark yellow (similar to orange) to light yellow from acid to neutral. Change from light yellow to dark yellow (similar to orange) again to blue from neutral to basic, and the color change between light yellow and dark yellow reciprocates. It is thought that there is in doing.
図２（Ｂ）の中性域において色調が薄い黄色に変化する理由は，図１の関係式Ｆ２に示すように，第２ｐＨ指示用モノマー（６ビニル−αＮＰ）の中性域における薄い黄色が強く反映された結果と考えられる。そこで，中性域における薄い黄色への色調変化を低減するため，表５の条件で第１ｐＨ指示用モノマー（ＡＡＢＡＡ）と第２ｐＨ指示用モノマー（６ビニル−αＮＰ）と非イオン性モノマーであるＮＩＰＡＡｍとを共重合させたｐＨ指示用共重合体（８）を作製した。表５では，表４の場合に比して第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとの混合比率を変え，第１ｐＨ指示用モノマーの混合割合を高くし，第２ｐＨ指示用モノマーの混合割合を低くした。 The reason why the color tone changes to light yellow in the neutral range of FIG. 2B is that the light yellow color in the neutral range of the second pH indicating monomer (6 vinyl-αNP) is shown in the relational expression F2 in FIG. The result is strongly reflected. Therefore, in order to reduce the color tone change to light yellow in the neutral range, the first pH indicating monomer (AABAA), the second pH indicating monomer (6 vinyl-αNP), and the nonionic monomer NIPAAm are used under the conditions shown in Table 5. And a pH indicating copolymer (8) was prepared. In Table 5, the mixing ratio of the first pH indicating monomer and the second pH indicating monomer is changed as compared with Table 4, the mixing ratio of the first pH indicating monomer is increased, and the mixing ratio of the second pH indicating monomer is increased. Was lowered.
表５の条件で作製したｐＨ指示用共重合体を用いて複数の試験片（２×２ｃｍ）を成形し，各試験片をｐＨ値０〜１２の水溶液にそれぞれ浸漬して発色させ，図４に示すように各試験片の発色を白色点Ｏが中央に配置された色度図Ｍ１上にプロットして各発色点Ｃの極座標上の偏角Ｄを検出した（図４のプロットＦ４参照）。図４の色度図Ｍ１は，図２（Ａ）の色度図と同じものであり，対比のため表４の条件で作製したｐＨ指示用共重合体の発色点（プロットＦ３）も併せて示してある。そして，プロットした各試験片の発色点Ｃの偏角ＤとｐＨ値との関係をロジスティックモデル（ロジスティック曲線）で近似した関係式Ｆ４を求めた。求めた関係式Ｆ４を図５に示す。図５には，対比のため，図３の関係式Ｆ３も併せて示してある。 A plurality of test pieces (2 × 2 cm) were molded using the pH indicating copolymer prepared under the conditions shown in Table 5, and each test piece was immersed in an aqueous solution having a pH value of 0 to 12 to develop a color. As shown in Fig. 4, the color development of each test piece is plotted on a chromaticity diagram M1 in which the white point O is arranged at the center to detect the polar angle D of each color development point C (see plot F4 in Fig. 4). . The chromaticity diagram M1 of FIG. 4 is the same as the chromaticity diagram of FIG. 2 (A), and the coloring point (plot F3) of the pH indicating copolymer prepared under the conditions of Table 4 is also shown for comparison. It is shown. And the relational expression F4 which approximated the relationship between the deviation angle D of the coloring point C and pH value of each plotted test piece with a logistic model (logistic curve) was obtained. The obtained relational expression F4 is shown in FIG. FIG. 5 also shows the relational expression F3 of FIG. 3 for comparison.
図５から分かるように，ｐＨ５〜８の中性域から塩基性域において，関係式Ｆ３では共重合体の発色点の色度図Ｍ１上の偏角ＤがｐＨ値の増加に応じて減少する傾向がみられたが，関係式Ｆ４では共重合体の発色点の色度図Ｍ１上の偏角Ｄがほぼ一定となっており，減少する傾向は見られない。減少する傾向が見られない原因は，第１ｐＨ指示用モノマー（ＡＡＢＡＡ）の混合割合を相対的に高くし，第２ｐＨ指示用モノマー（６ビニル−αＮＰ）の混合割合を相対的に低くしたことにより，第２ｐＨ指示用モノマーの中性域における色調（薄い黄色）の反映が低く抑えられ，薄い黄色と濃い黄色との間で不安定な色調変化の往復を避けることができたことにあると考えられる。 As can be seen from FIG. 5, in the neutral region to the basic region of pH 5 to 8, in the relational expression F3, the deviation angle D on the chromaticity diagram M1 of the color development point of the copolymer decreases as the pH value increases. Although a tendency was observed, in the relational expression F4, the declination angle D on the chromaticity diagram M1 of the color development point of the copolymer is almost constant, and no tendency to decrease is observed. The reason why the tendency to decrease is not seen is that the mixing ratio of the first pH indicating monomer (AABAA) is relatively high and the mixing ratio of the second pH indicating monomer (6 vinyl-αNP) is relatively low. , The reflection of the color tone (light yellow) in the neutral range of the second pH indicating monomer was kept low, and it was thought that it was possible to avoid reciprocal unstable color change between light yellow and dark yellow. It is done.
すなわち，第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとを共重合させる本発明では，第１及び第２ｐＨ指示用モノマーの混合比率の調整によってｐＨ値に対する偏角Ｄの変化を制御することが可能であり，ｐＨ値の増加に応じて色度図Ｍ１上の各発色点の偏角Ｄが増加するようなｐＨ指示用共重合体を合成できることを確認することができた。なお，図５の関係式Ｆ４は，関係式Ｆ３よりも色調変化の幅（偏角Ｄの最大値と最小値との差）が小さくなっており，第１及び第２ｐＨ指示用モノマーの混合比率の調整により，ｐＨ値に対する偏角Ｄの変化だけでなく，偏角Ｄの最大値と最小値との差を制御できることもできることが分かる。従って，第１及び第２ｐＨ指示用モノマーの混合比率は，ｐＨ値に対する偏角Ｄの変化の最適化と，色調変化の幅の最適化とを共に考慮して，設計することが重要である。 That is, in the present invention in which the first pH indicating monomer and the second pH indicating monomer are copolymerized, it is possible to control the change in the deviation angle D with respect to the pH value by adjusting the mixing ratio of the first and second pH indicating monomers. Thus, it was confirmed that a pH indicating copolymer can be synthesized such that the deviation angle D of each color development point on the chromaticity diagram M1 increases as the pH value increases. Note that the relational expression F4 in FIG. 5 has a smaller change in color tone (difference between the maximum value and the minimum value of the deflection angle D) than the relational expression F3, and the mixing ratio of the first and second pH indicating monomers. It can be seen that not only the change of the deflection angle D with respect to the pH value but also the difference between the maximum value and the minimum value of the deflection angle D can be controlled by adjusting the above. Therefore, it is important to design the mixing ratio of the first and second pH indicating monomers by taking into consideration both the optimization of the change of the deviation angle D with respect to the pH value and the optimization of the width of the color tone change.
本発明による広範囲ｐＨ指示用共重合体は，ｐＨ値の増加に応じて２段階で色調変化させることができ，その色調変化から広い範囲にわたるｐＨを測定することができる。また，複数の異なるｐＨ値における発色を白色点が中央に配置された色度図上にプロットして当該白色点が中心の極座標上の発色点の偏角Ｄを検出したときに，各ｐＨ値の発色点を色度図Ｍ１上に白色点Ｏを中心として弧を描くように，すなわちｐＨ値の増加に応じて偏角Ｄが増加するように並べることができ，発色点の偏角ＤからｐＨ値を測定することができる。 The wide-range pH indicating copolymer according to the present invention can change color tone in two steps according to an increase in pH value, and can measure pH over a wide range from the color tone change. Further, when the color development at a plurality of different pH values is plotted on a chromaticity diagram in which the white point is arranged at the center, and the deviation angle D of the color development point on the polar coordinate centered on the white point is detected, each pH value Can be arranged on the chromaticity diagram M1 so as to draw an arc centering on the white point O, that is, the declination D increases as the pH value increases. The pH value can be measured.
こうして本発明の目的である「広いｐＨ範囲で色調変化を示すｐＨ指示用共重合体」の提供を達成することができる。 Thus, the provision of “a pH indicating copolymer exhibiting a color change in a wide pH range”, which is an object of the present invention, can be achieved.
なお，以上の説明では，第１ｐＨ指示用モノマーを色調変化させる第１ｐＨ範囲と第２ｐＨ指示用モノマーを色調変化させる第２ｐＨ範囲との中間域において両ｐＨ指示用モノマーが近似色である場合に本発明を適用できるとしたが，第１ｐＨ範囲及び第２ｐＨ範囲の中間域において少なくとも一方のｐＨ指示用モノマーが無色である場合にも本発明を適用することが可能であり，そのような両ｐＨ指示用モノマーの共重合により，ｐＨ値の増加に応じて２段階で色調変化するような広範囲ｐＨ指示用共重合体を作製することができる。中間域において，何れか一方のｐＨ指示用モノマーの発色と他方のｐＨ指示用モノマーの発色とが干渉することがなくなるので，ｐＨ値の増加に応じて滑らかな色調変化（滑らかな偏角Ｄの増加）が期待できる。 In the above description, when both pH indicating monomers are approximate colors in the intermediate range between the first pH range in which the color tone of the first pH indicating monomer is changed and the second pH range in which the color tone of the second pH indicating monomer is changed. Although the invention can be applied, the present invention can also be applied when at least one of the pH indicating monomers is colorless in the intermediate range between the first pH range and the second pH range. By copolymerizing the monomer for use, it is possible to produce a copolymer for indicating a wide range of pH that changes its color tone in two steps as the pH value increases. In the intermediate range, the color development of one of the pH indicating monomers and the color development of the other pH indicating monomer do not interfere with each other, so that a smooth color change (smooth declination D of smooth declination D) occurs as the pH value increases. Increase).
例えば表１において，Ｂ群のメチルイエロー（色調変化ｐＨ範囲が酸性）をｐＨ指示部位とする第１ｐＨ指示用モノマーと，Ｃ群のチモールフタレイン（色調変化ｐＨ範囲が塩基性）をｐＨ指示部位とする第２ｐＨ指示用モノマーとが合成できた場合に，それらの色調変化ｐＨ範囲の中間域，すなわち中性域において一方の第２ｐＨ指示用モノマーは無色である。また，色調変化ｐＨ範囲の一端の低ｐＨ側（酸性側）においてメチルイエローは赤色であるのに対し，色調変化ｐＨ範囲の他端の高ｐＨ側（塩基性側）においてチモールフタレインは青色であるから，両モノマーは色調変化ｐＨ範囲の両端域において異なる色である。従って，メチルイエローをｐＨ指示部位とする第１ｐＨ指示用モノマーと，チモールフタレインをｐＨ指示部位とする第２ｐＨ指示用モノマーとを共重合させることにより，ｐＨ値の増加に応じて２段階で色調変化するような本発明の広範囲ｐＨ指示用共重合体とすることができる。 For example, in Table 1, the first pH indicating monomer having methyl yellow of group B (the color change pH range is acidic) and the thymolphthalein of group C (basic change pH range is basic) as the pH indicating site When the second pH indicating monomer is synthesized, one of the second pH indicating monomers is colorless in the middle range of the color change pH range, that is, in the neutral range. In addition, methyl yellow is red on the low pH side (acid side) at one end of the color change pH range, whereas thymolphthalein is blue on the high pH side (basic side) at the other end of the color change pH range. Therefore, both monomers have different colors at both ends of the color change pH range. Therefore, by copolymerizing the first pH indicator monomer having methyl yellow as the pH indicator site and the second pH indicator monomer having thymolphthalein as the pH indicator site, the color tone is increased in two stages according to the increase in pH value. The wide range pH indicating copolymer of the present invention can be changed.
異なるｐＨ範囲で色調変化する第１ｐＨ指示用モノマー及び第２ｐＨ指示用モノマーを共重合させて２段階で色調変化するような広範囲ｐＨ指示用共重合体とする本発明において，更にイオン性部位及び重合性部位を有するイオン性モノマーを含めて共重合させ，高分子主鎖周りのイオン濃度を変化させることにより，共重合体の色調変化領域を塩基性側又は酸性側へシフトさせることができる。 In the present invention, a first pH indicating monomer and a second pH indicating monomer that change color tone in different pH ranges are copolymerized to obtain a wide pH indicating copolymer that changes color tone in two stages. By changing the ion concentration around the main chain of the polymer by copolymerization including an ionic monomer having a neutral site, the color change region of the copolymer can be shifted to the basic side or the acidic side.
イオン性部位は，陰イオン性部位又は陽イオン性部位とすることができ，陰イオン性部位としては，次の式（Ｉ）〜（ＶＩ）で表す陰イオンの何れかが陽イオンと塩を形成している基であることが望ましい。ここで，式（ＩＩ）のＲ１はアルキル基及び水素原子の何れかであり，式（ＩＶ）のＲ２〜Ｒ４の何れか一つは単結合であり，残りの二つは同一又は異なるアルキル基であり，式（Ｖ）のＲ５はアルキル基である。
The ionic site can be an anionic site or a cationic site, and any one of the anions represented by the following formulas (I) to (VI) can be a cation and a salt. It is desirable that it is a forming group. Here, R 1 in formula (II) is either an alkyl group or a hydrogen atom, any one of R 2 to R 4 in formula (IV) is a single bond, and the other two are the same or It is a different alkyl group, and R 5 in formula (V) is an alkyl group.
イオン性部位が陽イオン性部位である場合は，−ＮＲｎＨ（３−ｎ） ＋（Ｒはアルキル基，ｎは０〜３の整数）が陰イオンと塩を形成している基，又は陽イオン化したヘテロ環と陰イオンとが塩を形成している基であることが望ましい。 When the ionic moiety is a cationic moiety, a group in which —NR n H (3-n) + (R is an alkyl group, n is an integer of 0 to 3) forms a salt with an anion, or It is desirable that the cationized heterocycle and an anion form a salt.
更に，イオン性モノマーを含めて共重合させる場合は，上述した第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとの混合比率の調整に代えて，或いは第１ｐＨ指示用モノマーと第２ｐＨ指示用モノマーとの混合比率の調整に加えて，イオン性モノマーの混合比率を調整することによってｐＨ値に対する色調変化を制御することも期待できる。すなわち，図３の関係式Ｆ３に示すように，例えば特定の色調変化領域において共重合体の発色点の不所望な色調変化（色度図Ｍ１上の偏角ＤがｐＨ値の増加に応じて減少する傾向等）がみられた場合に，イオン性モノマーの混合比率を調整することにより，第１ｐＨ指示用モノマーを色調変化させる第１ｐＨ範囲と第２ｐＨ指示用モノマーを色調変化させる第２ｐＨ範囲との中間域における色調変化（ｐＨ値に対する偏角Ｄの変化）を制御することが可能であり，不所望な色調変化を改善することによって色度図Ｍ１上の偏角ＤがｐＨ値の増加に応じて増加するようなｐＨ指示用共重合体とすることが期待できる。 Further, when copolymerizing including an ionic monomer, instead of adjusting the mixing ratio of the first pH indicating monomer and the second pH indicating monomer described above, or the first pH indicating monomer and the second pH indicating monomer, In addition to the adjustment of the mixing ratio, it is also expected to control the color tone change with respect to the pH value by adjusting the mixing ratio of the ionic monomer. That is, as shown by the relational expression F3 in FIG. 3, for example, an undesired color tone change of the color development point of the copolymer in a specific color tone change region (the declination angle D on the chromaticity diagram M1 corresponds to an increase in pH value). A first pH range in which the color tone of the first pH indicating monomer is changed and a second pH range in which the color tone of the second pH indicating monomer is changed by adjusting the mixing ratio of the ionic monomer when a tendency to decrease is observed. It is possible to control the color tone change (change in the declination angle D with respect to the pH value) in the middle range of the image, and by improving the undesired color tone change, the declination angle D on the chromaticity diagram M1 increases the pH value. It can be expected to be a pH indicating copolymer that increases accordingly.
Ｃ…発色点 Ｄ…偏角
Ｆ…関係式 Ｍ…色度図
Ｏ…白色点
C ... Color development point D ... Deflection angle F ... Relational expression M ... Chromaticity diagram O ... White point
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