Method of measuring amount of hydroxyl groups in inorganic materials

Abstract

To provide a method of measuring the amount of hydroxyl groups in inorganic materials such as silica, alumina, zirconia, and titanium.SOLUTION: A method of measuring the amount of hydroxyl groups in an inorganic material is provided, the method involving deriving the amount of adsorbed water in the inorganic material using the temperature programmed desorption mass spectrometry (TPD-MS), and determining the amount of hydroxyl groups in the inorganic material on the basis of the amount of the adsorbed water using the time domain nuclear magnetic resonance (TD-NMR).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the amount of hydroxyl groups in inorganic materials such as silica, alumina, zirconia, and titanium. [Background technology]

[0002] Inorganic materials such as silica are essential for the production of various functional materials, including materials for electronic components and semiconductor devices, fillers for reinforcing resin materials, and heat dissipation materials.

[0003] The key to improving adhesion between these inorganic materials and resin materials is the hydroxyl group, which acts as a reaction site for imparting functionality to silane coupling agents, etc. Therefore, evaluation of the amount of hydroxyl groups contained in inorganic materials is required for technological development to improve the properties of the materials.

[0004] For the above reasons, it is necessary to evaluate the amount of hydroxyl groups in inorganic materials such as silica, alumina, zirconia, and titanium. For example, in the case of silica, 29 The amount of hydroxyl groups was calculated from the ratio of Q1 structure, Q2 structure, Q3 structure, and Q4 structure of silica (silicon dioxide) shown in Figure 1 by applying the Si NMR method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-231694 Summary of the Invention [Problem to be solved by the invention]

[0006] however, 29 Since the sensitivity of Si nuclei is very poor, measurements over 24 hours were required to obtain a spectrum with a sufficient S / N ratio for the analysis shown in Figure 2.

[0007] The present invention has been made in consideration of the problems of the prior art, and relates to a method for measuring the amount of hydroxyl groups in inorganic materials such as silica, alumina, zirconia, and titanium, using TPD-MS and TD-NMR, which can shorten the time required for each analysis to about one hour and provide a highly sensitive method. 1 TD-NMR measurements are performed using H nuclei, providing highly accurate results. [Means for solving the problem]

[0008] That is, the measurement method of the present invention is as follows. (1) A method for measuring the amount of hydroxyl groups in an inorganic material, which involves determining the amount of adsorbed water in the inorganic material using thermally evolved gas mass spectrometry (hereinafter sometimes referred to as TPD-MS), and then determining the amount of hydroxyl groups in the inorganic material using time-domain nuclear magnetic resonance (hereinafter sometimes referred to as TD-NMR) based on the amount of adsorbed water; (2) The method for measuring the amount of hydroxyl groups in an inorganic material according to (1), wherein the ratio of the amount of hydroxyl groups in the inorganic material to the amount of adsorbed water is quantified using time-domain nuclear magnetic resonance (TD-NMR). (3) The method for measuring the amount of hydroxyl groups in an inorganic material according to (1), wherein the inorganic material is one selected from the group consisting of silica, alumina, zirconia, and titanium. (4) A method for measuring the amount of hydroxyl groups in an inorganic material according to (1), in which hydrogen atoms of the adsorbed water and / or the hydroxyl groups are exchanged for deuterium atoms, and the amount of hydrogen nuclei resulting from the chemical exchange is evaluated from the decrease in response intensity using time-domain nuclear magnetic resonance (TD-NMR). [Effects of the Invention]

[0009] The measurement method of the present invention can be used to evaluate the amount of hydroxyl groups in inorganic materials such as silica, alumina, zirconia, and titanium. Furthermore, by using heavy water to exchange the hydrogen atoms of the adsorbed water and / or hydroxyl groups with deuterium atoms and then applying the measurement method of the present invention, the amount of hydrogen nuclei that are resistant to chemical exchange can be evaluated. Hereinafter, this process may be referred to as deuterium exchange treatment or HD exchange treatment. Note that hydrogen nuclei that are resistant to chemical exchange refer to, for example, hydroxyl groups or adsorbed water that exist inside an inorganic material sample and are difficult to contact even when heavy water is added. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram of the chemical structure of silica (silicon dioxide) [Figure 2] Solid-state 29Si NMR spectrum of silica [Figure 3] TD-NMR relaxation response and analysis results of silica in Example 1. [Figure 4] FIG. 1 shows the relaxation response of silica in Example 2 before and after deuterium exchange treatment. [Figure 5] FIG. 10 shows the analysis results of the relaxation response of silica after deuterium exchange treatment in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] TPD-MS method In this invention, the TPD-MS method is a technique in which a mass spectrometer (MS) is directly connected to a special heating device with a temperature controller, and the concentration change of the gas evolved from a heated sample is tracked as a function of temperature or time according to a predetermined heating program. In quantifying adsorbed water using TPD-MS, the evolved water is detected by observing the molecular ions and fragment ions with a mass-to-charge ratio of m / z 18 (water ions have an original molecular weight of 18 and a charge of +1, so m / z 18).

[0012] This method can be used to quantify the amount of water adsorbed on inorganic materials such as silica.

[0013] First, a calibration curve is created from the peak area value of m / z 18 observed in TPD-MS measurements performed on known amounts of inorganic salt hydrates.

[0014] Next, for inorganic materials such as silica, the m / z 18 ion is observed using TPD-MS. Based on the created calibration curve, the amount of adsorbed water can be calculated from the observed peak intensity of m / z 18. The amount of adsorbed water may also be determined by a method such as the Karl Fischer method.

[0015] TD-NMR Next, TD-NMR mainly 1 This is a measurement method that measures H nuclei (hydrogen nuclei) and evaluates the relaxation time of hydrogen nuclei in a substance. A feature of TD-NMR is that it can evaluate relaxation times with high reproducibility and precision. Hydroxyl groups, such as those in silica, are bound to the surface of inorganic materials, resulting in low molecular mobility. Adsorbed water is weaker in binding than hydroxyl groups, resulting in higher molecular mobility than hydroxyl groups. The T2 relaxation time, which is the time constant for the process by which magnetization perpendicular to the static magnetic field (transverse magnetization) relaxes and decays, becomes shorter the lower the molecular mobility, so the T2 relaxation time of hydroxyl groups is observed to be shorter than the relaxation time of adsorbed water.

[0016] In the present invention, it is preferable to perform two-component analysis of the relaxation response by TD-NMR, and the response can be separated because the component with a short relaxation time can be attributed to hydroxyl groups and the component with a long relaxation time can be attributed to adsorbed water. Since the initial intensity of each response corresponds to the amount of hydrogen nuclei, the amounts of hydroxyl groups and adsorbed water can be evaluated.

[0017] The procedure for quantifying the ratio of hydroxyl groups to adsorbed water by TD-NMR is as follows.

[0018] The sample is loaded into a TD-NMR sample tube. It is preferable that the humidity does not change, and the sample tube is capped and used for TD-NMR measurement. For sampling, the inner tube used for TD-NMR samples can also be used. TD-NMR measurement should be performed at around room temperature to prevent adsorbed water from evaporating.

[0019] TPD-MS and TD-NMR measurements In order to align the sample conditions, it is desirable to perform the TPD-MS measurement and the TD-NMR measurement within a short period of time, that is, on the same day, although this is not necessarily a requirement.

[0020] The amount of hydroxyl groups contained in the inorganic material is calculated based on the amount of adsorbed water contained in the inorganic material obtained from analysis by TPD-MS and the ratio of the amount of adsorbed water to hydroxyl groups obtained from analysis by TD-NMR. The method for calculating hydroxyl groups is as follows.

[0021] The amount of adsorbed water obtained from TPD-MS is x percent, the ratio of hydroxyl groups to adsorbed water obtained from TD-NMR is y:(100-y), and the molar ratio of SiO2 to hydroxyl groups is z. That is, the molar ratio of hydroxyl groups, water, and SiO2 can be expressed as hydroxyl groups:water:SiO2 = y:(100-y) / 2:z.

[0022] When the partial molecular weight or molecular weight is 18.0 for H2O (adsorbed water) and 17.0 for OH (hydroxyl group) of SiOH (i.e., 16.0 + 1.0), the hydroxyl group content (wt%) can be expressed by the following formula: Hydroxyl group content (wt%) = x × {17.0 × y} / {18.0 × (100 - y) / 2} [Formula 1]

[0023] If the partial molecular weights or molecular weights are SiO2 60.1, H2O (absorbed water) 18.0, and the molecular weight of OH (hydroxyl group) of SiOH 9.0 (i.e. 16.0 / 2 + 1.0), the following equation holds: Note that in the silica structure, the oxygen atom of SiOH is counted as half because it is shared with silicon and hydrogen. x / 100={18×(100-y) / 2} / {60.1×z+18.0×(100-y) / 2+9.0×y} [Formula 2]

[0024] Assuming that SiOH has only a Q3 structure (one OH bonded to Si), the ratio of Q3 structures to the total Q structures can be expressed by the following formula using the value of z calculated by [Formula 2]. Ratio of Q3 (mol%) = y / z × 100 [Equation 3].

[0025] Hydrogen-deuterium exchange process In the hydrogen-deuterium exchange process (hereafter referred to as HD exchange), heavy water is added to the sample, replacing easily exchangeable hydrogen atoms in adsorbed water and hydroxyl groups with deuterium atoms. In this state, excess heavy water is removed by freeze-drying or in a moisture-free environment, and the sample is sealed in a state where it is not exposed to external atmospheres such as air, and then TD-NMR measurements are performed. TD-NMR measurements are performed under the same conditions as those before HD exchange, and the amount of hydrogen atoms that did not exchange with heavy water can be estimated from the response intensity.

[0026] That is, when the ratio of hydroxyl groups to adsorbed water obtained from TD-NMR after HD exchange is defined as y':y", the ratio of hydroxyl groups that are resistant to HD exchange and the ratio of adsorbed water that are resistant to HD exchange can be calculated as follows. Ratio of hydroxyl groups that are resistant to HD exchange (%) = y' / y × 100 (Equation 4-1) Ratio of adsorbed water that is difficult for HD exchange to occur (%) = y" / (100-y) x 100 (Equation 4-2) [Example]

[0027] The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[0028] Example 1 Measurements were performed using TPD-MS on a known amount of calcium oxalate, and a calibration curve was created from the peak area value of m / z 18 observed. Next, TPD-MS measurements were performed on silica, and the m / z 18 ion was observed. The amount of adsorbed water was calculated using the calibration curve, and the amount was found to be 1.5 wt%. The analytical conditions for TPD-MS measurements are listed below. Heating rate: 10℃ / min Temperature range: Room temperature to 250°C.

[0029] Next, to perform TD-NMR measurements, silica was filled into the inner tube of a TD-NMR sample tube and capped with silicone rubber. The inner tube filled with the sample was placed in the TD-NMR sample tube, placed in an apparatus stabilized at 30°C, and left for at least 15 minutes to stabilize the temperature, after which the T1 relaxation time, which is the relaxation time occurring in the longitudinal direction, was measured. Next, the T2 relaxation time was measured with a pulse repetition time (2 seconds) that was at least five times the obtained T1 relaxation time. The analytical conditions are listed below. Device: mq-20 (Bruker) Measurement method: Solid echo method (T2 relaxation time measurement) Resonance frequency: 20MHz Repeat Time: 2 seconds Measurement temperature: 30℃.

[0030] The results of the TD-NMR measurements and analysis are shown in Figure 3. As a result of the analysis, the ratio of the response resonances of hydroxyl groups to adsorbed water was 64.7:35.3. Therefore, by substituting the values ​​x = 1.5 wt%, y = 64.7, and 100 - y = 35.3 from the above amount of adsorbed water of 1.5 wt% into [Equation 1], the hydroxyl group content (wt%) is calculated to be 5.2 wt%, as shown below. Hydroxyl group content (wt%) = 1.5 × (17.0 × 64.7) / (18.0 × 35.3 / 2) = 5.2 [Equation 1]

[0031] Next, from [Equation 2], z, which relates to the molar ratio of SiO2, is found to be 337.4. 1.5 / 100=(18.0×35.3 / 2) / (60.1×z+18.0×35.3 / 2+9.0×64.7) [Formula 2]

[0032] Finally, from [Equation 3], the ratio of Q3 structure is calculated as 19 mol% as follows. Q3 ratio (%) = 64.7 / 337.4 × 100 = 19 [Equation 3].

[0033] Example 2 HD exchange was performed on the silica shown in Example 1. HD exchange was performed by continuously adding heavy water to the silica in a glove box filled with nitrogen gas to dry it, and the TD-NMR sample tube was sealed with a lid. Measurement and analysis were performed in the same manner as in Example 1. The results obtained, as shown in Figure 4, indicate that the response intensity decreased due to HD exchange. The analysis results are shown in Figure 5.

[0034] As a result of the analysis, y' = 0.4 and y" = 17.1, and therefore, from [Equation 4-1] and [Equation 4-2], the ratio of hydroxyl groups that are resistant to HD exchange is determined to be 1%, and the ratio of adsorbed water that is resistant to HD exchange is determined to be 48%. Ratio of hydroxyl groups that are resistant to HD exchange (%) = 0.4 / 64.7 × 100 (Equation 4-1) Ratio of adsorbed water that is less likely to undergo HD exchange (%) = 17.1 / 35.3 x 100 (Equation 4-2)

Claims

1. A method for measuring the amount of hydroxyl groups in an inorganic material, which involves determining the amount of adsorbed water in the inorganic material using thermally evolved gas mass spectrometry (TPD-MS), and then determining the amount of hydroxyl groups in the inorganic material using time-domain nuclear magnetic resonance (TD-NMR) based on the amount of adsorbed water.

2. 2. The method for measuring the amount of hydroxyl groups in an inorganic material according to claim 1, wherein the ratio of the amount of hydroxyl groups in the inorganic material to the amount of adsorbed water is quantified using time-domain nuclear magnetic resonance (TD-NMR).

3. 2. The method for measuring the amount of hydroxyl groups in an inorganic material according to claim 1, wherein the inorganic material is one selected from the group consisting of silica, alumina, zirconia, and titanium.

4. 2. The method for measuring the amount of hydroxyl groups in an inorganic material according to claim 1, wherein hydrogen atoms of the adsorbed water and / or the hydroxyl groups are exchanged with deuterium atoms, and the amount of hydrogen nuclei resulting from the chemical exchange is evaluated from the decrease in response intensity using time-domain nuclear magnetic resonance (TD-NMR).

Images