JP4036416B2 - Measuring method of silanol group concentration - Google Patents
Measuring method of silanol group concentration Download PDFInfo
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- JP4036416B2 JP4036416B2 JP2000021404A JP2000021404A JP4036416B2 JP 4036416 B2 JP4036416 B2 JP 4036416B2 JP 2000021404 A JP2000021404 A JP 2000021404A JP 2000021404 A JP2000021404 A JP 2000021404A JP 4036416 B2 JP4036416 B2 JP 4036416B2
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- concentration
- silanol group
- fine particles
- silica
- silica fine
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- 125000005372 silanol group Chemical group 0.000 title claims description 56
- 238000000034 method Methods 0.000 title claims description 26
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 97
- 239000000377 silicon dioxide Substances 0.000 claims description 45
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 28
- 239000010419 fine particle Substances 0.000 claims description 27
- 238000010521 absorption reaction Methods 0.000 claims description 15
- 238000002835 absorbance Methods 0.000 claims description 14
- 239000006185 dispersion Substances 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 10
- 150000001283 organosilanols Chemical class 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 2
- 238000011088 calibration curve Methods 0.000 description 13
- 238000005259 measurement Methods 0.000 description 9
- 239000000126 substance Substances 0.000 description 7
- 238000002329 infrared spectrum Methods 0.000 description 5
- AAPLIUHOKVUFCC-UHFFFAOYSA-N trimethylsilanol Chemical compound C[Si](C)(C)O AAPLIUHOKVUFCC-UHFFFAOYSA-N 0.000 description 5
- 239000003960 organic solvent Substances 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- SCPYDCQAZCOKTP-UHFFFAOYSA-N silanol Chemical compound [SiH3]O SCPYDCQAZCOKTP-UHFFFAOYSA-N 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000000862 absorption spectrum Methods 0.000 description 3
- -1 carbon tetrachloride organosilanol Chemical class 0.000 description 3
- 239000013558 reference substance Substances 0.000 description 3
- 238000001507 sample dispersion Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 239000012925 reference material Substances 0.000 description 2
- 239000000741 silica gel Substances 0.000 description 2
- 229910002027 silica gel Inorganic materials 0.000 description 2
- 238000006884 silylation reaction Methods 0.000 description 2
- QQQSFSZALRVCSZ-UHFFFAOYSA-N triethoxysilane Chemical compound CCO[SiH](OCC)OCC QQQSFSZALRVCSZ-UHFFFAOYSA-N 0.000 description 2
- 238000004438 BET method Methods 0.000 description 1
- YZCKVEUIGOORGS-OUBTZVSYSA-N Deuterium Chemical group [2H] YZCKVEUIGOORGS-OUBTZVSYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 238000004497 NIR spectroscopy Methods 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 235000013405 beer Nutrition 0.000 description 1
- UAHRFLZYHFOALR-UHFFFAOYSA-N butyl(dihydroxy)silane Chemical compound CCCC[SiH](O)O UAHRFLZYHFOALR-UHFFFAOYSA-N 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 229910001634 calcium fluoride Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 229910052805 deuterium Inorganic materials 0.000 description 1
- DAKRXZUXJUPCOF-UHFFFAOYSA-N diethyl(dihydroxy)silane Chemical compound CC[Si](O)(O)CC DAKRXZUXJUPCOF-UHFFFAOYSA-N 0.000 description 1
- OLLFKUHHDPMQFR-UHFFFAOYSA-N dihydroxy(diphenyl)silane Chemical compound C=1C=CC=CC=1[Si](O)(O)C1=CC=CC=C1 OLLFKUHHDPMQFR-UHFFFAOYSA-N 0.000 description 1
- XCLIHDJZGPCUBT-UHFFFAOYSA-N dimethylsilanediol Chemical compound C[Si](C)(O)O XCLIHDJZGPCUBT-UHFFFAOYSA-N 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- DVSDBMFJEQPWNO-UHFFFAOYSA-N methyllithium Chemical compound C[Li] DVSDBMFJEQPWNO-UHFFFAOYSA-N 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000003333 near-infrared imaging Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000011002 quantification Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- WVMSIBFANXCZKT-UHFFFAOYSA-N triethyl(hydroxy)silane Chemical compound CC[Si](O)(CC)CC WVMSIBFANXCZKT-UHFFFAOYSA-N 0.000 description 1
- NLSXASIDNWDYMI-UHFFFAOYSA-N triphenylsilanol Chemical compound C=1C=CC=CC=1[Si](C=1C=CC=CC=1)(O)C1=CC=CC=C1 NLSXASIDNWDYMI-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N2021/3595—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using FTIR
Description
【０００１】
【発明の属する技術分野】
本発明は、近赤外線を光源とする吸光光度法を利用して、シリカ微粒子中のシラノール基の濃度（mmol／ｇ）を測定する方法に関する。
【０００２】
【従来の技術】
シラノール基を有するシリカの粉体は物質を吸・脱着する性質があるため、これを利用して乾燥剤、吸着剤、クロマトグラフのカラム充填剤など幅広い分野で利用されている材料である。シリカ粉体の性質はその粒子表面に存在するシラノール基の濃度に依存するため、シリカ粒子の品質管理のためには、そのシラノール基濃度を測定する必要がある。
従来、シリカのシラノール基を定量する方法としては、その化学反応性を用いた方法が幾つか提案されている。例えばメチルリチウムをシラノール基と反応させ、発生したメタンを定量することによりシラノールの量を求める方法が知られている〔S.C.Antakli, J.Serpinet, Chromatographia, Vol.23, No.10, p.767-769 (1987) 〕。また、不活性な有機溶剤中にシリカ粒子を分散させ、この分散液に既知量のトリエトキシシランを添加し、それとシラノール基との反応後のトリエトキシシランの濃度をガスクロマトグラフィー等で測定することにより、シラノール基の量を求める方法もある。上記の方法では、シラノール基濃度が0.５mmol／ｇ程度かそれ以上の場合であれば測定可能であるが、それを下回るような量に対しては測定が難しかった。
【０００３】
一方、赤外吸収スペクトル法により3000〜3700cm-1におけるシラノール基の赤外線吸収を利用して、シラノール基濃度を測定することも原理的には可能である。しかしながら、上記波数領域における赤外線吸収は、水のヒドロキシ基による吸収と重なりなり表面吸着水の影響を受けるために、シリカ粒子表面に存在するシラノール基を正確に測定することはできない。
これに対して近赤外吸収帯を利用すると、水の吸収は5100〜5200cm-1に、またシラノール基の吸収は4500cm-1および7200cm-1付近に観測され、それぞれは分離する。従来、近赤外法によるシラノール基の定量は、主にシリル化反応等においてシラノール基の相対量をモニターする手段として利用されていた。
シラノール基の絶対量を測定した例としては、比表面積が100 〜300m2 /gのクロマトグラフ用シリカゲルを四塩化炭素中に分散させ、その分散液の近赤外線吸光度を測定し、別途作成した検量線により定量したという報告がある〔S.G.Bosh, J.W.Jorgenson, J.Chromatogr., Vol.503, No.1, p.69-91 (1990) 〕。この方法では、検量線の作成のために用いるシリカゲル試料について、そのシラノール基の絶対量をシリル化反応法または重水素置換法にて求める必要があり、この点でやはり低濃度のシラノール基の測定には制約があった。
【０００４】
【発明が解決しようとする課題】
本発明においては、低濃度たとえば0.１mmol／ｇ以下の濃度の測定が可能で、かつ操作の簡便なシラノール基濃度の測定方法の提供を目的とした。
【０００５】
【課題を解決するための手段】
本発明者らは、上記課題を解決するために鋭意検討した結果、シリカ微粒子の表面に存在するシラノール基の濃度を測定するために、粒径が２０μ m 以下のシリカ微粒子の四塩化炭素分散液を試料として、透過法による近赤外線吸光光度法を適用し、得られた吸光度をオルガノシラノールの標準溶液で作成した検量線によりシラノール基濃度に変換することにより、低濃度のシラノール基の濃度を相対値ながら容易に数値化できることを見出した。検量線の作成にシラノール基濃度が既知なシリカ微粒子を使用せずに、オルガノシラノールの四塩化炭素溶液を使用する点で、得られるシラノール濃度は相対値であるものの、本測定法で得られるシラノール基の濃度数値はシリカ微粒子の物性から予測されるシラノール基濃度と良好な相関関係があることも見出した。
【０００６】
すなわち、本発明は、近赤外線を光源とする吸光光度法により粒径２０μｍ以下のシリカ微粒子中のシラノール基の濃度（mmol／ｇ）を測定するに当たり、シリカ微粒子を四塩化炭素に分散させ、得られる分散液を試料として透過法により４３８５〜４８００cm-1吸収帯の吸光度を測定し、得られたピーク面積／シリカ濃度の直線関係の勾配値をシラノール基濃度が既知のオルガノシラノールの四塩化炭素溶液のピーク面積／シラノール基濃度の直線関係の勾配値と対比させることによりシラノール基濃度に変換させることを特徴とするシリカ微粒子中のシラノール基濃度の測定方法である。
上記本発明によれば、粒径が２０μｍ以下のシリカ微粒子中のシラノール基濃度を数値化でき、しかもその数値によりシリカ微粒子の物性を管理できるという優れた効果が奏される。
【０００７】
【発明の実施の形態】
本発明においては、粒径が２０μｍ以下のシリカ微粒子の四塩化炭素分散液を試料として、透過法により近赤外線の吸光度を測定する。用いる近赤外線の波数としては、シラノール基の特性吸収帯である４３８５〜４８００cm-1が好ましい。近赤外線の吸光度の測定で光路にセットする試料セルの長さ（一般に光路長またはセル長と称される）としては、２〜１０ｍｍが好ましい。本発明による測定の対象となるシリカ微粒子の粒径としては、２０μｍ以下であり、その下限は０．１μｍが好ましい。さらに好ましい粒径は１〜１０μｍである。シリカ微粒子の粒径が２０μｍを越えると、シリカ微粒子による近赤外線の屈折および散乱等が無視できなくなり、測定誤差すなわちシラノール基の吸光以外の作用により吸光度が変動を受け易い。
【０００８】
シリカ微粒子の分散液を得るために用いる媒体は四塩化炭素である。四塩化炭素は、４２００〜４８００ cm -1 の波数領域を含む近赤外領域に吸収を持たない点で好ましく使用できる。さらに、四塩化炭素（以下有機溶剤ということがある）は、屈折率がシリカの屈折率（１．４５）と近似している点で好ましい。使用する媒体とシリカの屈折率が大幅に異なると、試料セルに当てられた入射光がそのまま直進せず屈折するため、かかる屈折が起こる分だけ透過光が減少し、その結果測定のノイズが大きくなる。測定に供するシリカ微粒子の分散液中の好ましいシリカ濃度は、０．１〜１ｇ／mlである。
【０００９】
本発明においては、オルガノシラノールを基準物質として使用する。種々のオルガノシラノールを用いることができ、具体的にはトリメチルシラノール、トリエチルシラノール、ジメチルシランジオール、ジエチルシランジオール、1,1,2,2,- テトラメチル-1,2- ジヒドロキシジシロキサン、ジターシャリブチルシランジオール、トリフェニルシラノールまたはジフェニルシランジオール等が挙げられる。
シラノール基は一般に反応性が高く水分の存在下にそれが自己縮合反応を起こすとその量が変動し、かかるシラノール基を有するオルガノシラノールは基準物質として使用し難い。従って、反応性の低い程、基準物質として好ましく使用することができ、その点で、トリメチルシラノール、1,1,2,2,- テトラメチル-1,2- ジヒドロキシジシロキサンまたはジターシャリブチルシランジオールが特に好ましい。
【００１０】
本発明においては、試料分散液から得られた吸光度をシラノール基濃度が既知のオルガノシラノール（以下基準物質ということがある）の有機溶剤溶液の吸光度と対比させるが、かかる対比に際しては、基準物質で作成した検量線を利用することが好ましい。
後記した具体例における検量線は、トリメチルシラノールの四塩化炭素溶液（シラノール基濃度; 0.００５６mol/L 〜0.１７mol/L ）を使用し、以下の測定装置によって作成した。吸光度としては、４８００〜４３８５cm-1の波数領域における吸光度を積算したものすなわち吸光度を縦軸として吸光スペクトルにおける吸収ピーク面積を採用したが、特定の波数における吸光度すなわちピーク高さを採用することもできる。
使用装置：Nicolet 製MAGNA750型フーリエ変換赤外分光光度計
［光源：タングステンハロゲンランプ、ビームスプリッタ：フッ化カルシウム、検出器：DTGS］
測定用セル：5mm （液体用石英セル）
測定波数領域：8000〜4000cm-1
波数分解能：8cm -1
積算回数：32回
測定時の温度：25℃
【００１１】
試料分散液から得られた吸光度を上記方法によって作成された検量線に適用することにより、試料分散液中のシラノール基濃度が求められる。シリカ微粒子が有機溶剤に溶解しておらず、固形物のシリカ微粒子により近赤外線の試料セル透過が多少とも影響を受けるとすれば、本方法で真値を得ることは理論上無理であるが、シリカ微粒子の物性の管理にとって十分な基準物質換算のシラノール基濃度を求めることができる。
シリカ微粒子の表面に存在するシラノール基の量は、シリカ微粒子を加熱することにより減少させることもできるし、またシリカ微粒子は周囲の空気中の水分を吸って表面シラノール基の量が徐徐に増加する。そして、前述のとおり、そのシラノール基の濃度によりシリカ微粒子の実用物性が異なるのである。本発明の方法によってシリカ微粒子中のシラノール基の量が管理できれば、シリカ微粒子を使用する者にとって好都合である。
以下に、実施例に基づいて本発明を具体的に説明する。
【００１２】
＜検量線の作成方法＞標準物質のオルガノシラノール化合物としてトリメチルシラノール〔信越化学工業（株）製〕を選択し、検量線用標準近赤外吸収スペクトルを測定した。得られた近赤外スペクトルを図１に示した。シラノール基の吸収帯4800〜4385cm-1 のピーク面積を計算してトリメチルシラノール、すなわちシラノール基のモル濃度に対してこれをプロットすると、図２の検量線が得られた。
【００１３】
【化１】
【化２】
【実施例２】
平均粒子径５μｍ、比表面積250m2/g（BET法）の粉末状シリカＡ（東亞合成株式会社製）0.205gを5mmのセルに採取し、四塩化炭素1.0mLを加えて攪拌してシリカの分散液を調製した（試料濃度；0.164g/mL）。積算回数を500 回にしたこと以外は＜検量線の作成方法＞と同様の分析条件とし、シリカＡ分散液の近赤外吸収スペクトルを測定した。濃度を0.364g/mL、0.423g/mL、0.439g/mL、0.559g/mLに調製したシリカＡ分散液についても同様にスペクトル測定を実施した。四塩化炭素中に種々の濃度で分散させた粉末状シリカＡの近赤外スペクトルを図３に示した。シラノール基の吸収ピークが4700〜4300cm-1に観測され、これらのピーク面積を分散液の濃度Cwに対してプロットすると図４が得られた。濃度と面積は比例関係が成立しており、Beerの法則に従うことが確認できた。＜検量線の作成方法＞よりシラノール基のモル濃度Cm[mol/L]と近赤外スペクトルのピーク面積Sとの関係式は、
S＝６９．９０×Cm・・・・・・・＜１＞
であり、本実施例から粉末状シリカＡの分散重量濃度Cw[g/mL]と近赤外スペクトルのピーク面積Sとの関係式は、
S＝４２．０７×Cw・・・・・・・＜２＞
であるので、粉末状シリカＡのシラノール基濃度C[mmol/g]は、
C＝Cm/Cw＝（Ｓ／６９．９０）／（Ｓ／４２．０７）＝０．６０２[mmol/g]と求められた。
【００１６】
【化３】
【化４】
【実施例３】
実施例２の被検試料である粉末状シリカＡを1000℃で１時間熱処理してシラノール基の脱水縮合を行った比表面積が1.9m2/gである試料（以下、粉末状シリカＢと言う）を用い、濃度Cwを0.381g/mL、0.454g/mL、0.594g/mL、0.620g/mLに調製した四塩化炭素分散液について実施例２と同様にして近赤外スペクトルの測定を行った。Cwとシラノール基吸収ピークの面積は図５のように比例関係が確認され、粉末状シリカＢのシラノール基濃度は＜検量線の作成方法＞に基づく検量線式＜１＞より0.012[mmol/g]と求められた。
【００１９】
【化５】
【発明の効果】
本発明の方法によれば、粉末状シリカ中のシラノール基濃度を簡便な近赤外分光法で迅速に測定することができ、水分が共存しても極めて低濃度のシラノール量まで定量することできる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the concentration (mmol / g) of silanol groups in silica fine particles using an absorptiometric method using near infrared rays as a light source.
[0002]
[Prior art]
Silica powder having a silanol group has a property of adsorbing and desorbing substances. Therefore, it is a material used in a wide range of fields such as a desiccant, an adsorbent, and a chromatographic column filler. Since the properties of silica powder depend on the concentration of silanol groups present on the surface of the particles, it is necessary to measure the silanol group concentration for quality control of the silica particles.
Conventionally, several methods using the chemical reactivity have been proposed as methods for quantifying the silanol group of silica. For example, a method for determining the amount of silanol by reacting methyllithium with a silanol group and quantifying the generated methane is known [SCAntakli, J. Serpinet, Chromatographia, Vol. 23, No. 10, p.767- 769 (1987)]. In addition, silica particles are dispersed in an inert organic solvent, a known amount of triethoxysilane is added to the dispersion, and the concentration of triethoxysilane after reaction with the silanol group is measured by gas chromatography or the like. There is also a method for determining the amount of silanol groups. In the above method, measurement is possible if the silanol group concentration is about 0.5 mmol / g or more, but it was difficult to measure the amount below that.
[0003]
On the other hand, it is also possible in principle to measure the silanol group concentration by utilizing infrared absorption of silanol groups at 3000 to 3700 cm −1 by infrared absorption spectroscopy. However, since the infrared absorption in the wave number region overlaps with the absorption by the hydroxyl group of water and is affected by the surface adsorbed water, the silanol group present on the surface of the silica particles cannot be accurately measured.
By using near-infrared absorption bands contrast, the absorption of water in 5100～5200Cm -1, also absorption of silanol group is observed near 4500cm -1 and 7200cm -1, respectively separated. Conventionally, the quantification of silanol groups by the near infrared method has been utilized as a means for monitoring the relative amount of silanol groups mainly in silylation reactions and the like.
As an example of measuring the absolute amount of silanol groups, a silica gel for chromatography having a specific surface area of 100 to 300 m 2 / g was dispersed in carbon tetrachloride, and the near-infrared absorbance of the dispersion was measured. There is a report that it was quantified by lines [SGBosh, JW Jorgenson, J. Chromatogr., Vol. 503, No. 1, p. 69-91 (1990)]. In this method, it is necessary to determine the absolute amount of silanol groups in the silica gel sample used for preparing a calibration curve by the silylation reaction method or the deuterium substitution method. There were limitations.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for measuring a silanol group concentration that can measure a low concentration, for example, a concentration of 0.1 mmol / g or less and is easy to operate.
[0005]
[Means for Solving the Problems]
The present inventors have made intensive studies in order to solve the above problems, in order to measure the concentration of silanol groups present on the surface of the silica fine particles having a particle size of less silica fine 20 [mu] m carbon tetrachloride dispersion Using the near-infrared absorptiometry by the transmission method as a sample, and converting the resulting absorbance to a silanol group concentration using a calibration curve prepared with a standard solution of organosilanol, the relative concentration of low-concentration silanol groups It was found that it was easy to digitize the value. Although silanol concentration obtained is a relative value in using a carbon tetrachloride solution of organosilanol without using silica fine particles with a known silanol group concentration for the preparation of a calibration curve, the silanol obtained by this measurement method is used. It was also found that the group concentration value had a good correlation with the silanol group concentration predicted from the physical properties of the silica fine particles.
[0006]
That is, in the present invention, when measuring the concentration (mmol / g) of silanol groups in silica fine particles having a particle diameter of 20 μm or less by an absorptiometry using a near infrared light source, the silica fine particles are dispersed in carbon tetrachloride. the dispersion was measured absorbance at 4385 ~4800cm -1 absorption band by a transmission method as a sample to be, carbon tetrachloride organosilanol gradient values silanol group concentration of the known linear relationship of the peak area / silica concentrations obtained solution This is a method for measuring the silanol group concentration in silica fine particles, wherein the concentration is converted to a silanol group concentration by comparing with the gradient value of the linear relationship of the peak area / silanol group concentration .
According to the present invention, the silanol group concentration in the silica fine particles having a particle diameter of 20 μm or less can be quantified, and the excellent effect that the physical properties of the silica fine particles can be managed by the numerical values is exhibited.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the absorbance of near infrared rays is measured by a transmission method using a carbon tetrachloride dispersion of silica fine particles having a particle size of 20 μm or less as a sample. The wave number of the near infrared ray to be used is preferably 4 385 to 4800 cm −1 which is a characteristic absorption band of a silanol group. The length of the sample cell (generally referred to as optical path length or cell length) set in the optical path in the measurement of near-infrared absorbance is preferably 2 to 10 mm. The particle diameter of the silica fine particles to be measured according to the present invention is 20 μm or less, and the lower limit is preferably 0.1 μm. A more preferable particle size is 1 to 10 μm. If the particle size of the silica fine particles exceeds 20 μm, near infrared refraction and scattering by the silica fine particles cannot be ignored, and the absorbance is likely to fluctuate due to measurement errors, that is, actions other than the absorption of silanol groups.
[0008]
The medium used to obtain the dispersion of silica fine particles is carbon tetrachloride. Carbon tetrachloride can be preferably used in that it has no absorption in the near infrared region including the wave number region of 4200 to 4800 cm −1 . Further, carbon tetrachloride (hereinafter sometimes referred to as an organic solvent) is preferable in that the refractive index approximates that of silica (1.45). If the refractive index of the medium used and the silica are significantly different, the incident light applied to the sample cell will be refracted without going straight, so the transmitted light will be reduced by the amount of such refraction, resulting in a large measurement noise. Become. A preferable silica concentration in the dispersion of silica fine particles used for the measurement is 0.1 to 1 g / ml.
[0009]
In the present invention, organosilanol is used as a reference substance. Various organosilanols can be used, such as trimethylsilanol, triethylsilanol, dimethylsilanediol, diethylsilanediol, 1,1,2,2, -tetramethyl-1,2-dihydroxydisiloxane, ditertiary. Examples include butylsilane diol, triphenylsilanol, diphenylsilane diol, and the like.
Silanol groups are generally highly reactive and their amount varies when they undergo a self-condensation reaction in the presence of moisture, and organosilanols having such silanol groups are difficult to use as reference materials. Therefore, the lower the reactivity, the more preferable it can be used as a reference substance. In that respect, trimethylsilanol, 1,1,2,2, -tetramethyl-1,2-dihydroxydisiloxane or ditertiarybutylsilanediol Is particularly preferred.
[0010]
In the present invention, the absorbance obtained from the sample dispersion is compared with the absorbance of an organic solvent solution of organosilanol having a known silanol group concentration (hereinafter sometimes referred to as a reference substance). It is preferable to use the prepared calibration curve.
The calibration curve in the specific examples described later was prepared by the following measuring apparatus using a carbon tetrachloride solution of trimethylsilanol (silanol group concentration; 0.0022 mol / L to 0.17 mol / L). As the absorbance, the absorbance in the wave number region of 4800 to 4385 cm −1 is integrated, that is, the absorption peak area in the absorption spectrum is used with the absorbance as the vertical axis, but the absorbance at a specific wave number, that is, the peak height can also be adopted. .
Equipment used: Nicolet MAGNA750 Fourier transform infrared spectrophotometer [Light source: tungsten halogen lamp, beam splitter: calcium fluoride, detector: DTGS]
Measurement cell: 5mm (Quartz cell for liquid)
Measurement wave number range: 8000-4000cm -1
Wave number resolution: 8cm -1
Integration count: 32 times Measurement temperature: 25 ° C
[0011]
By applying the absorbance obtained from the sample dispersion to the calibration curve created by the above method, the silanol group concentration in the sample dispersion is determined. If the silica fine particles are not dissolved in the organic solvent and the near-infrared sample cell transmission is somewhat affected by the solid silica fine particles, it is theoretically impossible to obtain a true value by this method. It is possible to obtain a silanol group concentration in terms of a reference material sufficient for management of physical properties of silica fine particles.
The amount of silanol groups present on the surface of the silica fine particles can be reduced by heating the silica fine particles, and the silica fine particles absorb the moisture in the surrounding air and the amount of surface silanol groups gradually increases. . As described above, the practical physical properties of the silica fine particles differ depending on the concentration of the silanol group. If the amount of silanol groups in the silica fine particles can be controlled by the method of the present invention, it is convenient for those who use the silica fine particles.
Hereinafter, the present invention will be specifically described based on examples.
[0012]
<Method for preparing calibration curve> Trimethylsilanol [manufactured by Shin-Etsu Chemical Co., Ltd.] was selected as the organosilanol compound of the standard substance, and a standard near infrared absorption spectrum for a calibration curve was measured. The obtained near-infrared spectrum is shown in FIG. The peak area of the silanol group absorption band 4800-4385 cm-1 was calculated and plotted against the molar concentration of trimethylsilanol, that is, silanol group, the calibration curve of FIG. 2 was obtained.
[0013]
[Chemical 1]
[Chemical 2]
[Example 2]
0.205 g of powdered silica A (manufactured by Toagosei Co., Ltd.) having an average particle size of 5 μm and a specific surface area of 250 m 2 / g (BET method) was sampled in a 5 mm cell, added with 1.0 mL of carbon tetrachloride and stirred. A dispersion was prepared (sample concentration: 0.164 g / mL). The near-infrared absorption spectrum of the silica A dispersion was measured under the same analysis conditions as in <Method for creating calibration curve> except that the number of integrations was 500. Spectral measurements were similarly performed on silica A dispersions prepared at concentrations of 0.364 g / mL, 0.423 g / mL, 0.439 g / mL, and 0.559 g / mL. FIG. 3 shows near-infrared spectra of powdered silica A dispersed at various concentrations in carbon tetrachloride. Absorption peaks of silanol groups were observed at 4700-4300 cm-1, and when these peak areas were plotted against the concentration Cw of the dispersion, FIG. 4 was obtained. Concentration and area are in a proportional relationship, confirming that Beer's law is obeyed. <Method for preparing calibration curve> From the relationship between the molar concentration Cm [mol / L] of the silanol group and the peak area S of the near infrared spectrum,
S = 69.90 × Cm ・ ・ ・ ・ ・ ・<1>
From this example, the relationship between the dispersion weight concentration Cw [g / mL] of the powdered silica A and the peak area S of the near-infrared spectrum is
S = 42.07 x Cw ... <2>
Therefore, the silanol group concentration C [mmol / g] of the powdered silica A is
C = Cm / Cw = (S / 69.90) / (S / 42.07) = 0.602 [mmol / g].
[0016]
[Chemical 3]
[Formula 4]
[Example 3]
A sample having a specific surface area of 1.9 m 2 / g (hereinafter referred to as powdered silica B) obtained by subjecting the powdered silica A, which is a test sample of Example 2, to heat treatment at 1000 ° C. for 1 hour to perform dehydration condensation of silanol groups. ), And measuring the near-infrared spectrum of the carbon tetrachloride dispersion prepared at concentrations Cw of 0.381 g / mL, 0.454 g / mL, 0.594 g / mL, and 0.620 g / mL in the same manner as in Example 2. It was. The area of the Cw and silanol group absorption peak has a proportional relationship as shown in FIG. 5, and the silanol group concentration of the powdered silica B is 0.012 [mmol / g from the calibration curve formula <1> based on the <calibration curve creation method>. I was asked.
[0019]
[Chemical formula 5]
【The invention's effect】
According to the method of the present invention, the concentration of silanol groups in powdered silica can be quickly measured by simple near infrared spectroscopy, and even in the presence of moisture, it can be quantified to a very low concentration of silanol. .
Claims (1)
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