JP2008191003A - Surface characteristic evaluation method for power particle - Google Patents
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本発明は、自動車、鉄道車両、産業機械等のブレーキに使用されるブレーキ用摩擦材、構造用接着剤、コンクリート等の建築用構造部材、プラスッチック等の成形材料及び食料品等の粉体粒子原料の表面特性を粉体の状態で評価する手法を提供する。更に詳しくは、粉体粒子の親水化度、疎水化度及び表面張力の推定方法を提供する。 The present invention relates to a friction material for brakes used in brakes for automobiles, railway vehicles, industrial machines, etc., structural adhesives, structural members for construction such as concrete, molding materials such as plastics, and raw material for powder particles such as foodstuffs. A method for evaluating the surface properties of powder in the state of powder is provided. More specifically, the present invention provides a method for estimating the degree of hydrophilization, degree of hydrophobicity and surface tension of powder particles.
固体表面の親水・疎水化度及び表面張力は、表面張力が既知の液体と固体表面のぬれ性評価により求められる。一般的にぬれ性評価は、液体と固体表面の接触角を測定して評価する。この接触角は、固体の表面積により変動するため、測定試料の表面粗さを把握し、測定結果を補正する必要がある。また、一般的に用いられる液滴法では、滴下する液滴の体積が約１μｌであり、液滴の直径は約１・５ｍｍとなるため、固体試料の大きさは、１．５ｍｍ以上でなければならない。このことから、一般的に粉体の状態で評価することは困難であった。 The degree of hydrophilicity / hydrophobicity of the solid surface and the surface tension are determined by evaluating the wettability of the liquid and the solid surface with known surface tension. In general, wettability evaluation is performed by measuring the contact angle between a liquid and a solid surface. Since this contact angle varies depending on the surface area of the solid, it is necessary to grasp the surface roughness of the measurement sample and correct the measurement result. Further, in the generally used droplet method, the volume of the droplet to be dropped is about 1 μl, and the diameter of the droplet is about 1.5 mm. Therefore, the size of the solid sample must be 1.5 mm or more. I must. For this reason, it was generally difficult to evaluate in a powder state.
一方、粉体粒子をゾル−ゲル法などで析出させて作成したセラミックス試料や、カップリング剤コーティング等の２次加工を施した粉体試料でぬれ性を評価する場合、液滴を滴下できるほど大きい試料を作製する必要がある。そのため、焼結体を作製する必要があるが、焼結する際の圧力と熱で表面化学成分が変化し、試料の正確な親水・疎水度及び表面張力を把握することはできない。
また、粉体のぬれ性を評価する手法として毛管法があるが、粉体充填層において仮定する毛細管半径の決定に任意性があることや粉体の均一充填が難しいことなど問題点が多い。
On the other hand, when wettability is evaluated with a ceramic sample prepared by precipitating powder particles by a sol-gel method or a powder sample subjected to secondary processing such as a coupling agent coating, droplets can be dropped. Large samples need to be made. For this reason, it is necessary to produce a sintered body, but the surface chemical components change depending on the pressure and heat during sintering, and the exact hydrophilicity / hydrophobicity and surface tension of the sample cannot be grasped.
In addition, there is a capillary method as a method for evaluating the wettability of the powder, but there are many problems such as an arbitrary determination of the capillary radius assumed in the powder packed bed and difficulty in uniformly filling the powder.
粉体粒子の比表面積を測定する方法としては、ＢＥＴ法が知られている。これは、基本的には被測定試料の入った試料セルに混合ガス（通常、窒素とヘリウム）を流し、試料セルを液体窒素温度に冷却すると、被測定粒子表面に窒素ガスだけが吸着する特性と、この試料セルを常温に戻すと被測定粒子が吸着した窒素ガスが脱離する性質とを利用したものである。窒素ガス吸着量又は脱離量は、熱伝導検出器等で検出し、表面積に換算する。
「特許文献１」では金属化合物粒子粉末の疎水化度として温度２５℃、相対温度９０％時の単位表面積あたりの水蒸気吸着量を使用している。しかし、機能性フィラーや強化繊維としての樹脂との接着性や材料分散性などを考察する場合、疎水化度だけでは、表面特性評価としては不十分である。
In “Patent Document 1”, the water vapor adsorption amount per unit surface area at a temperature of 25 ° C. and a relative temperature of 90% is used as the degree of hydrophobicity of the metal compound particle powder. However, when considering the adhesiveness with a functional filler or a resin as a reinforcing fiber, material dispersibility, etc., the hydrophobization degree alone is not sufficient for surface property evaluation.
粉末粒子の表面特性としては、疎水化度以外に、細孔分布、親水化度あるいは表面張力等の各種性質を総合的に把握しておくことが粉末粒子を複合材料の配合材として使用するときには重要である。
従って、本発明は、同一の測定装置を用い、複数の測定条件を設定するだけで簡単に被測定粉体粒子の疎水化度、親水化度あるいは表面張力を推定し得る粉体粒子の表面特性評価方法を得ることを課題としている。
As surface characteristics of powder particles, it is necessary to comprehensively grasp various properties such as pore distribution, degree of hydrophilicity or surface tension in addition to the degree of hydrophobicity when using powder particles as a compounding material for composite materials. is important.
Therefore, the present invention uses the same measuring apparatus and can easily estimate the degree of hydrophobicity, degree of hydrophilicity or surface tension of the powder particles to be measured simply by setting a plurality of measurement conditions. The task is to obtain an evaluation method.
本発明の課題は、下記の手段により解決された。
（１）被測定粉体粒子について、窒素ガス吸着によるＢＥＴ比表面積を測定しておき、表面張力が既知の水蒸気及び少なくとも一種の有機溶剤蒸気吸着によるＢＥＴ比表面積を測定し、それらの比表面積の比率を算出することにより該粉体粒子の親水化度・疎水化度評価及び／又は表面張力を推定することを特徴とする粉体粒子の表面特性評価方法。
（２）前記粉体粒子表面をカップリング剤により疎水化した場合、カップリング剤の疎水基より大きい表面張力を持つ物質の蒸気の吸着によるＢＥＴ比表面積を比較することにより、疎水基の被覆割合を推定することを特徴とする上記（１）記載の粉体粒子の表面特性評価方法。
The problems of the present invention have been solved by the following means.
(1) For the powder particles to be measured, the BET specific surface area by nitrogen gas adsorption is measured, the BET specific surface area by water vapor with known surface tension and at least one organic solvent vapor adsorption is measured, A method for evaluating the surface properties of powder particles, characterized by calculating the ratio of hydrophilicity / hydrophobicity of the powder particles and / or estimating the surface tension by calculating the ratio.
(2) When the powder particle surface is hydrophobized with a coupling agent, the coating ratio of the hydrophobic group is determined by comparing the BET specific surface area due to vapor adsorption of a substance having a surface tension larger than the hydrophobic group of the coupling agent. The method for evaluating the surface characteristics of powder particles according to (1), wherein
本発明によれば、粉体粒子の表面特性評価を粉体の状態で評価できる。また、吸着ガス分子のサイズが非常に小さいので、表面粗さの影響を無視できる。
更に、粉体粒子の２次加工を行った場合の表面化学特性の変化を知る手段として有効であり、被測定粉体粒子の疎水化度、親水化度あるいは表面張力等の粉体粒子の複数の表面特性項目を同一の測定装置により評価出来るので、分析に要する時間を短縮することができる。
According to the present invention, it is possible to evaluate the surface characteristics of powder particles in a powder state. Further, since the size of the adsorbed gas molecules is very small, the influence of the surface roughness can be ignored.
Furthermore, it is effective as a means for knowing the change in surface chemical characteristics when secondary processing of powder particles is performed, and a plurality of powder particles such as the degree of hydrophobicity, the degree of hydrophilicity or the surface tension of the powder particles to be measured. Since the surface characteristic items can be evaluated by the same measuring device, the time required for analysis can be shortened.
通常、粉体粒子の表面積の測定は窒素吸着によるＢＥＴ法比表面積を測定することで、粉体粒子試料の比表面積を算出することにより行う。具体的には、窒素ガス分子の吸着断面積（ＡＣＳ）は０．１６ｎｍ２であるという基本的な数値から、固体試料１ｇあたりの比表面積を測定することが出来る。
一方、粉体及び多孔質材料の比表面積や細孔分布の測定技術及び測定装置の進歩は著しく、定容量法ガス吸着法により吸脱着等温線を自動測定し、簡単に比表面積（ＢＥＴ法等）あるいは細孔分布（マクロ気孔、メソ気孔等）を解析することが可能となった。又、比較的比表面積が小さい試料から多孔質の比表面積が大きな試料まで多種類の粉体材料の測定が可能である。
Usually, the surface area of powder particles is measured by calculating the specific surface area of a powder particle sample by measuring the BET specific surface area by nitrogen adsorption. Specifically, the specific surface area per 1 g of the solid sample can be measured from the basic numerical value that the adsorption cross section (ACS) of nitrogen gas molecules is 0.16 nm 2 .
On the other hand, the measurement technology and measuring device for specific surface area and pore distribution of powders and porous materials are remarkably advanced, and adsorption / desorption isotherms are automatically measured by the constant volume method gas adsorption method, and the specific surface area (BET method etc. ) Or pore distribution (macropores, mesopores, etc.) can be analyzed. In addition, various types of powder materials can be measured from a sample having a relatively small specific surface area to a sample having a porous specific surface area.
従って、本発明の表面特性評価方法で扱う粉体粒子の比表面積は、通常０．１〜５００ｍ２／ｇの範囲であれば推定評価の対象とすることができる。
吸着ガスとしては窒素ガスを使用する。吸着ガスとして他に一酸化炭素、二酸化炭素、ヘリウムあるいはアルゴン等の非腐食性ガスを使用することも考えられるが、前記した理由で窒素ガスを使用することが最適である。次いで、水あるいは有機溶剤の蒸気吸着により比表面積を測定するが、有機溶剤としてはメタノール、エタノール、メトキシエタノール、エチレングリコール、アセトン、ベンゼン、ペンタン、ヘキサン、ピリジン等が使用されるが、限定されるものではない。測定精度が高いなどの点からメタノールが好ましい。
Therefore, if the specific surface area of the powder particles handled by the surface property evaluation method of the present invention is usually in the range of 0.1 to 500 m 2 / g, it can be an object of estimation evaluation.
Nitrogen gas is used as the adsorption gas. It is conceivable to use other non-corrosive gases such as carbon monoxide, carbon dioxide, helium or argon as the adsorbed gas, but it is optimal to use nitrogen gas for the reasons described above. Next, the specific surface area is measured by vapor adsorption of water or an organic solvent. As the organic solvent, methanol, ethanol, methoxyethanol, ethylene glycol, acetone, benzene, pentane, hexane, pyridine and the like are used, but are limited. It is not a thing. Methanol is preferable from the viewpoint of high measurement accuracy.
被測定粉体粒子の表面は親水的であるか疎水的であるかによって、水及び有機溶剤蒸気の粒子表面に対する蒸気の吸着量は異なってくる。すなわち、表面が親水的な粒子を疎水化剤等で疎水化すると、疎水化度が大きくなるに従って水蒸気のＢＥＴ吸着比表面積は減少する。これとは異なり、疎水性の高い有機溶剤蒸気を粒子表面に吸着させる場合、粒子表面の疎水化度が大きくなるにつれても比表面積は変わらないが、疎水化度がある値を越えると、そこから比表面積は減少していく。比表面積は減少しはじめる疎水化度の値は有機溶剤の種類によって異なっている。水蒸気と有機溶剤蒸気では、粒子表面に対する疎水化度の変化に対し、両者の比表面積が互いに変化する態様を図１にモデル的に示した。 Depending on whether the surface of the powder particle to be measured is hydrophilic or hydrophobic, the adsorption amount of the vapor of water and organic solvent vapor on the particle surface varies. That is, when particles having a hydrophilic surface are hydrophobized with a hydrophobizing agent or the like, the BET adsorption specific surface area of water vapor decreases as the degree of hydrophobicity increases. Unlike this, when adsorbing highly hydrophobic organic solvent vapor on the particle surface, the specific surface area does not change as the particle surface becomes more hydrophobic, but if the degree of hydrophobicity exceeds a certain value, Specific surface area decreases. The value of the degree of hydrophobicity at which the specific surface area begins to decrease varies depending on the type of organic solvent. In the case of water vapor and organic solvent vapor, the mode in which the specific surface area of both changes with respect to the change in the degree of hydrophobicity with respect to the particle surface is shown as a model in FIG.
本発明による粉体粒子の表面特性評価方法の手順としては、最初に、窒素吸着による被測定粉体粒子のＢＥＴ比表面積を測定することで、粉体粒子試料の比表面積を算出する。次に、前記窒素ＢＥＴ比表面積と、表面張力が既知の水蒸気及び有機溶剤蒸気吸着によるＢＥＴ比表面積を測定して比較することによって、蒸気分子が粉体粒子表面に吸着できる割合（「比表面積割合」という）を算出する。有機溶剤の多くは表面張力が既知であり、例えば、水７２．２ｍＮ／ｍ、ベンゼン２８．９ｍＮ／ｍ、メタノール２２．６ｍＮ／ｍあるいはペンタン１６．０ｍＮ／ｍ等である。 As a procedure of the method for evaluating the surface characteristics of powder particles according to the present invention, first, the specific surface area of the powder particle sample is calculated by measuring the BET specific surface area of the powder particles to be measured by nitrogen adsorption. Next, by measuring and comparing the nitrogen BET specific surface area and the BET specific surface area by vapor and organic solvent vapor adsorption with known surface tension, the ratio of vapor molecules that can be adsorbed on the powder particle surface ("specific surface area ratio") "). Many organic solvents have known surface tensions, such as water 72.2 mN / m, benzene 28.9 mN / m, methanol 22.6 mN / m, or pentane 16.0 mN / m.
その際、表面張力が異なる少なくとも二種類の蒸気を用いて蒸気分子が粉体粒子表面に吸着できる割合を比較すれば、表面張力を推定することが可能となる。
また、カップリング剤コーティング等の２次加工により粉体粒子表面を変化させ、疎水化した場合、カップリング剤の疎水基よりも大きい表面張力を持つ蒸気の吸着によるＢＥＴ比表面積と窒素ＢＥＴ比表面積を比較することで被覆割合を推定することができる。カップリング剤の疎水基よりも大きい表面張力を持つ物質としては、一般的に水が挙げられる。
At that time, it is possible to estimate the surface tension by comparing the ratio of vapor molecules that can be adsorbed on the surface of the powder particles using at least two kinds of vapors having different surface tensions.
In addition, when the powder particle surface is changed and made hydrophobic by secondary processing such as coupling agent coating, the BET specific surface area and nitrogen BET specific surface area due to adsorption of vapor having a surface tension larger than the hydrophobic group of the coupling agent Can be estimated. As the substance having a surface tension larger than the hydrophobic group of the coupling agent, water is generally used.
以下に、具体例を挙げ本発明を更に詳細に説明するが、本発明の範囲は実施例に限定されるものではない。
試料Ａとして雲母、試料Ｂとして雲母をシランカップリング剤としてメチルトリメトキシシランを窒素雰囲気下でコーティング処理した試料を使用した。窒素ガス吸着及び水蒸気吸着、メタノール蒸気吸着等温線測定はガス・蒸気吸着装置ＢＥＬＳＯＲＰ（日本ベル（株）製）で行った。窒素吸着によるＢＥＴ比表面積と各種蒸気吸着によるＢＥＴ比表面積の割合を第１表に示す。
Hereinafter, the present invention will be described in more detail with specific examples, but the scope of the present invention is not limited to the examples.
As sample A, mica was used, and as sample B, mica was used as a silane coupling agent and methyltrimethoxysilane was coated in a nitrogen atmosphere. Nitrogen gas adsorption, water vapor adsorption, and methanol vapor adsorption isotherm measurement were performed with a gas / vapor adsorption apparatus BELSORP (manufactured by Nippon Bell Co., Ltd.). The ratio of the BET specific surface area by nitrogen adsorption and the BET specific surface area by various vapor adsorption is shown in Table 1.
比表面積の測定結果から、試料Ａは水蒸気吸着による比表面積の割合が９６％と窒素吸着による比表面積のほとんどを占めており、表面張力が水より大きいことを示している。
一方で試料Ｂは、水蒸気吸着による比表面積の割合が１１％で、窒素吸着による比表面積と比較して小さいのに対し、メタノール吸着による比表面積では窒素吸着による比表面積のほとんどを占めており、表面張カがメタノールより大きく、水より小さいことを示している。表面張力は水が７２．２ｍＮ／ｍであるのに対し、メチル基の表面張力は、２４ｍＮ／ｍである。
From the measurement result of the specific surface area, the ratio of the specific surface area by the water vapor adsorption of the sample A is 96%, which occupies most of the specific surface area by the nitrogen adsorption, indicating that the surface tension is larger than that of water.
On the other hand, in the sample B, the ratio of the specific surface area by water vapor adsorption is 11%, which is smaller than the specific surface area by nitrogen adsorption, whereas the specific surface area by methanol adsorption occupies most of the specific surface area by nitrogen adsorption. The surface tension is larger than methanol and smaller than water. The surface tension of water is 72.2 mN / m, whereas the surface tension of methyl groups is 24 mN / m.
また、第１表から試料Ｂのカップリング剤被覆面積の割合は、約９０％であると推定できる。それ故、予め比表面積の割合とカップリング処理による疎水化度の相関から検量線を作成しておけば、カップリング剤の配合量から疎水化度を推定することもできる。
このことから、本発明の評価方法を用いることにより、粉体粒子の表面特性評価を粉体の状態で評価することが可能となる。また、室素ガス吸着によるＢＥＴ比表面積と、表面張力が既知の水及び有機溶剤の蒸気吸着によるＢＥＴ比表面積を比較することで、試料の表面張力を推定することができる。さらに、粉体粒子の２次加工を行つた場合の表面化学特性の変化を知る手段として有効である。
Moreover, it can be estimated from Table 1 that the ratio of the coating agent coating area of Sample B is about 90%. Therefore, if a calibration curve is created in advance from the correlation between the ratio of the specific surface area and the degree of hydrophobicity due to the coupling treatment, the degree of hydrophobicity can also be estimated from the blending amount of the coupling agent.
From this, by using the evaluation method of the present invention, it becomes possible to evaluate the surface characteristics of the powder particles in a powder state. Further, the surface tension of the sample can be estimated by comparing the BET specific surface area due to adsorption of the elemental gas and the BET specific surface area due to vapor adsorption of water and an organic solvent having a known surface tension. Furthermore, it is effective as a means for knowing the change in surface chemical characteristics when secondary processing of powder particles is performed.
本発明の表面特性評価方法は、比表面積が小さい試料から多孔質の比表面積が大きな試料まで広範囲の粉体材料の測定に利用できるので、同一装置で短時間に、成形材料からその粉末状の配合原料まで分析評価することが可能である。 The surface property evaluation method of the present invention can be used to measure a wide range of powder materials from samples having a small specific surface area to samples having a large porous specific surface area. It is possible to analyze and evaluate even the blended raw materials.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111366502A (en) * | 2020-05-13 | 2020-07-03 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Method for evaluating hydrophobicity of composite insulator |
| CN116008129A (en) * | 2023-03-28 | 2023-04-25 | 叙镇铁路有限责任公司 | Negative pressure detection device in water distribution is divided to cement-based material surface hydrophobe |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111366502A (en) * | 2020-05-13 | 2020-07-03 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Method for evaluating hydrophobicity of composite insulator |
| CN116008129A (en) * | 2023-03-28 | 2023-04-25 | 叙镇铁路有限责任公司 | Negative pressure detection device in water distribution is divided to cement-based material surface hydrophobe |
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