JP6540999B2 - Moisture content measurement method - Google Patents

Description

  The present invention belongs to a moisture content measurement method.

  Conventionally, in the manufacturing process of industrial products, it is necessary to grasp the moisture content of water adhering to the products. In many cases, the moisture content of the attached water in the sample (hereinafter referred to as "adhesion moisture content") is to grasp the purity, to prevent deterioration of the sample, or to prevent defects in post-processes and products. Measurement is being done for various reasons. The measurement methods include various methods such as loss on drying, colorimetric method, near infrared absorption method, thermogravimetry, Karl Fischer vaporization method, Karl Fischer method using titration of iodine (for example, non-patent document 1), etc. Is used.

Mitsubishi Chemical / APIC Karl Fischer Reagents Technical Manual Mitsubishi Chemical Corporation

  According to the knowledge obtained by the present inventor, when quantifying the attached moisture content, the accuracy of the determination largely changes depending on the compound that constitutes the product of interest.

For example, in the case of quantifying the attached moisture content of a solid powder having high basicity such as metal hydroxide, the accuracy of the determination may be greatly reduced. This is because, as an example, when the moisture content of water adhering to the solid is measured in an open system, carbonation reaction (described below) may occur in the solid.
M (OH) ₂ + H ₂ O + CO ₂ → MCO ₃ + 2 H ₂ O ・ ・ ・ · · · (Equation 1)
In the quantification method by the loss on drying method and the near infrared absorption method, as the above reaction shows, it easily reacts with carbon dioxide in the atmosphere, and the moisture content relatively decreases due to the increase in the amount of samples, It is feared to underestimate the adhesion moisture rate.
Moreover, when measuring with respect to the compound used as a sample, the hydroxyl group and crystal water in a compound will be detected with adhering water, and it is feared to overestimate a moisture content.

  The main object of the present invention is to provide a technology capable of accurately quantifying the moisture content of water adhering to the solid even if it is an alkaline solid.

  The present inventors diligently studied to solve the above problems. An alkaline solid (for example, a metal hydroxide) can easily cause increase or decrease of water due to the hydroxyl group that it has. Therefore, it is difficult to eliminate the possibility that water is generated if the solid itself is measured.

  Therefore, the inventor does not use the solid itself for the measurement of the moisture content, but extracts water attached to the solid into a separately prepared solvent, and then applies the solvent for the measurement of the moisture content. I thought of a timely method. And the method of selecting the solvent which does not react with the said solid as a solvent in that case was considered. By doing this, it is not necessary to subject the solid itself to the measurement of the moisture content, so the influence on the sample like deterioration (increase) of the solid and the composition of the sample like the formation of water from the solid It is possible to eliminate the resulting effects together. As a result, the inventor obtained the knowledge that the moisture content on the solid can be accurately quantified.

Aspects of the present invention made based on the above findings are as follows.
The first aspect of the present invention is
A method of measuring the moisture content of water adhering to an alkaline solid,
Extracting the separated water from the solid and extracting it into the solvent by bringing the solid into contact with a solvent which does not react with the solid and which can dissolve water;
Determining the moisture content of the attached water in the solid from the amount of water extracted into the solvent;
Moisture content measuring method.

In a second aspect of the present invention, in the invention described in the first aspect,
The solid is a powder of metal hydroxide.

A third aspect of the present invention is the invention described in the first or second aspect, wherein
The solid contains water of crystallization.

In a fourth aspect of the present invention, in the invention according to any one of the first to third aspects,
The solvent is methanol,
In the determination step, Karl Fischer method using iodine titration is used.
The Karl Fischer method uses the methanol after the extraction step.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects,
In the extraction step, stirring and extraction in a closed vessel are performed, and then solid-liquid separation by centrifugation is performed.

  According to the present invention, even if it is an alkaline solid, the moisture content of water adhering to the solid can be accurately quantified.

It is a flowchart which shows the outline | summary of the method of specific quantification in a present Example.

Hereinafter, embodiments of the present invention will be described in the following order.
1. Moisture content measuring method 1-1. Preparation process 1-2. Extraction process 1-3. Quantitative process 2. Effect in the embodiment

<1. Moisture content measurement method>
In the present embodiment, the target of quantification is water attached to an alkaline solid capable of generating water and absorbing carbon dioxide. And the moisture content of the water adhering to a solid is quantified by mainly performing the following processes with respect to the said solid.
Extraction step of separating attached water from the solid by extracting the solid from the solid by bringing the solid into contact with a solvent which does not react with the solid and can dissolve water; extracted into the solvent Quantification process to quantify the moisture content on the solid concerned from the amount of water

In addition, "the moisture content of the water adhering to solid" in this embodiment refers to the weight% (wt%) of water with respect to the value which added the weight of water to the weight of solid. On the other hand, the “water attached to solid” is the water adsorbed to the solid to the last, and does not include the water generated by the reaction of the solid (chemical reaction, thermal reaction, etc.).
Each step will be described below.

1-1. Preparation Step In this step, preparation for performing the above extraction step and quantification step is performed.
The solid in the present embodiment is not particularly limited as long as water may adhere.

  In addition, when the said solid is a powder of a metal hydroxide, since the surface area of a metal hydroxide becomes large, reaction which produces | generates water will occur easily. However, by adopting the method according to the present embodiment described below, the adhesion water is extracted to the solvent and then the measurement is performed to the solvent, so that even if it is a powder of metal hydroxide, the adhesion water is The rate can be quantified accurately.

  In addition, even when the solid contains water of crystallization, a reaction to generate water is likely to occur, but by employing the method of the present embodiment described below, it is possible to quantify the moisture content with high accuracy. .

  Of course, when the solid is a powder of metal hydroxide and contains crystal water, it is extremely difficult to determine the moisture adhesion rate in the prior art, but by employing the method of the present embodiment, the moisture adhesion rate is It becomes possible to quantify accurately.

  Moreover, as a solvent (extraction solvent) for extracting adhesion water, it is a solvent which does not react with the said solid, and if it can dissolve water, there will be no limitation in particular. That is, a combination of a solid and a solvent is employed such that no reaction (dissolution of solid, etc.) occurs when the solid and the solvent contact each other. More specifically, a solvent is prepared which has a good balance of "solubility in water" and "polarity which does not dissolve solid". By this, for example, the solvent can be prevented from dissolving the solid, and the solvent and solid after water extraction can be separated easily and reliably by the solid-liquid separation, and as a result, in the solvent Only the adhesion water is included, and it becomes possible to reliably grasp the amount of adhesion water.

  In the present embodiment, when a powder of metal hydroxide containing water of crystallization is used as a solid, chemical reaction or thermal reaction on the powder is less likely to occur, and adhesion water extracted from the powder to a solvent is used. Preferably, an organic solvent (hydrocarbon or hydrogen substitute) is used as the solvent to keep the solvent in the solvent.

  Furthermore, in the case where Karl Fischer's method (iodine KF method) using titration of iodine is employed in the determination step described later, it is highly preferable to use methanol as the solvent. This is because it is possible to use, as methanol used in the iodine KF method, a solvent (methanol) after extracting attached water from the powder.

Incidentally, although methanol is an organic solvent, it has a certain degree of solubility in water. Of course, the moisture content of the solvent before the extraction step described later is preferably as low as possible (for example, 0.001 wt% or less). Therefore, it is preferable to dehydrate the solvent. In addition, since methanol is an organic solvent, the powder is hardly dissolved in methanol. As a result, only the adhesion water is contained in the solvent, and the amount of adhesion water can be reliably grasped.
Hereinafter, in the present embodiment, the combination of powder of metal hydroxide containing crystal water and methanol is exemplified.

1-2. Extraction Step In this step, by bringing the powder into contact with methanol, water attached to the powder is separated from the powder and extracted into methanol. Specifically, the powder is added to methanol. By doing this, the adhering water is separated from the powder, and the adhering water is extracted into methanol.

  In addition, you may employ | adopt a well-known series of apparatuses and operation | work used in this process. For example, as shown in the below-mentioned Example, powder may be measured in an airtight container, methanol may be added in the said container, and it may shake and stir. Then, after stirring, solid-liquid separation may be performed by centrifugation, filter filtration or the like. The solid in the solid-liquid separation referred to here corresponds to a solid (powder of metal hydroxide containing water of crystallization) after the adhesion water is extracted, and the liquid is extracted by the solvent (methanol) and the solvent It corresponds to the adhesion water.

1-4. Determination Step In this step, the attached moisture content of the solid is determined from the amount of water extracted to the solvent. Moreover, in this process, the case where the iodine KF method is used is illustrated, and it measures with respect to methanol (adhesion water is included) after an extraction process. In addition, although the method of a nonpatent literature 1 may be employ | adopted as a concrete method of the iodine KF method, it is as follows as a summary.

First, the iodine KF method measures water in a closed system using the reaction of iodine and water. Then, heat is applied to the object to be measured in an electric furnace under an atmosphere of dry nitrogen gas or the like. In the present embodiment, the measurement target is not a solid, but a solvent (methanol) after extraction of the attached water. By applying heat, the water in methanol is volatilized. The volatilized water is introduced into a mixture of iodine, sulfur dioxide, pyridine and methanol in a container which is shut off from the atmosphere. And the reaction shown below arises. Base refers to pyridine which is an amine.
I ₂ + SO ₂ + H ₂ O + 3Base + CH ₃ OH
→ 2Base · HI + Base · HSO ₄ CH ₃ ... (Equation 2)

  Water and iodine react equimolarly by the reaction of the above (formula 2). Therefore, it becomes possible to quantify the moisture content from the amount of iodine consumed. And if it is this embodiment, it becomes possible to use methanol which is a solvent after extraction of adhesion water as methanol of the above (formula 2). With this method, the pretreatment (thermal reaction, addition of a new reagent, etc.) for the iodine KF method becomes unnecessary, and the accuracy of the determination of the attached water is improved. Specifically, it becomes possible to measure the moisture content in the order of one decimal place. Moreover, it is not necessary to separately prepare methanol for iodine KF method, and extra work is not necessary.

  In the case of the conventionally known iodine KF method, the measurement object is the sample itself which is a solid. This has not changed in the past even though it is an alkaline solid capable of generating water and absorbing carbon dioxide. However, according to the present embodiment, the measurement target is not the sample itself but the solvent after extracting the attached water. Therefore, it is possible to eliminate the possibility that water is generated by thermal decomposition of the OH group in the powder of the metal hydroxide containing crystal water. Similarly, it is also possible to eliminate the possibility of water being generated from crystal water. As a result, according to this process, it is possible to accurately determine the adhering moisture percentage to the powder.

  In the iodine KF method, it is considered that the metal element (here, metal ion) inhibits the reaction of the above (formula 2). That is, when performing the iodine KF method, it is preferable to remove the metal element as much as possible. Also in this respect, the method of the present embodiment is excellent. As described above, in the present embodiment, the iodine KF method is not the sample itself but the solvent after extracting the adhering water, and the solvent hardly contains the metal element. As a result, it is possible to improve the accuracy of the determination result of the attached moisture content obtained by the iodine KF method.

  Moreover, although quantification using the iodine KF method was illustrated in said example, you may employ | adopt the method of other than that.

<2. Effect in the embodiment>
According to the present embodiment, the following effects are mainly achieved.
First, the alkaline solid itself is not subjected to the measurement of the moisture content, but the water adhering to the solid is extracted into a separately prepared solvent, and the solvent is subjected to the measurement of the moisture content. By doing this, it is not necessary to subject the solid itself to measurement of moisture content. Therefore, even if a hydroxyl group or crystal water is contained in the compound to be the solid, it is possible to pay for the influence thereof, and the reaction with carbon dioxide in the atmosphere hardly occurs. As a result, it is possible to suppress the possibility of an increase in the amount of solid and an underestimate of the moisture content attached.

  As a result of the above, according to this embodiment, even if it is an alkaline solid, the moisture content of water adhering to the solid can be quantified with high accuracy.

  Hereinafter, the present embodiment will be described. The technical scope of the present invention is not limited to the following examples.

(Previous example 1)
Before carrying out the present example, the following test was conducted to confirm whether the thing to be measured is really water.
Of the metal hydroxides (samples A to N described later, samples A to N are the same type) which were samples to be used in the examples described later and were at the present inventor's hand, the samples A were dried. Under varying conditions (drying time and temperature), the moisture content was measured after sample A was directly applied to the iodine KF method as in the prior art. As a result, as shown in the following table, the moisture content decreased when the degree of drying was increased. In addition, about drying conditions (middle), two examples were performed.
From the above results, it has become clear that the value measured by the iodine KF method is the moisture content with certainty.

(Pre-example 2)
Next, the methanol which did not perform the extraction process described in the embodiment was used as a blank, and the measurement using the iodine KF method used in the below-mentioned Example was performed. As a result, it was confirmed how much the moisture content fluctuates in the work related to the iodine KF method. The results are shown in the following table.
As a result, it was found that in the work related to the iodine KF method, there is only an influence of two decimal places on the moisture adhesion rate. As the below-mentioned Example shows, since the adhesion moisture content obtained by the Example is around 1%, the measurement of the adhesion moisture content in the Example performed by this item has maintained sufficient accuracy.

(Example)
In the present example, the water attached to the above samples A to I was extracted into methanol, and then the methanol was subjected to the iodine KF method. Thereby, the adhesion moisture content of sample AI was quantified.

  The specific quantitative method is as described in the above embodiment, but the outline is shown in FIG. As shown in FIG. 1, 5 g of each sample was weighed and inserted into a 50 mL vial. Then, 50 mL of superdehydrated methanol (water content less than 0.001%) (manufactured by Wako Pure Chemical Industries, Ltd.) was added. Then, shaking and stirring, stationary, transfer to a 10 mL styrene tube, centrifugation and membrane filtration were performed. And the adhesion water of sample AI was quantified using the iodine KF method.

(Comparative example)
In the present comparative example, the adhesion moisture percentage was tried to be measured by the loss on drying method with respect to the samples A to I separately prepared. Specifically, it was dried at 105 ° C. for 8 hours by a drier, and the measurement of the adhesion moisture percentage was tried from the increase and decrease of the weight.

The results of the above examples and comparative examples are shown in the following table.
As the above-mentioned table shows, the result of the comparative example showed 10 to 30% lower adhesion moisture rate than the result of an example. The reason for this is considered to be that, in the comparative example, the samples A to I of the metal hydroxide were affected by carbon dioxide in the atmosphere. On the other hand, according to the method of the embodiment, even an alkaline solid during measurement can be excluded from the influence of causing carbonation to cause increase or decrease of water. The following verification tests were conducted to show this.

(Verification test showing that the difference between the result of the example and the result of the comparative example is due to carbonation)
As described in the subject of the present invention, when the moisture content of water attached to the samples A to I of the metal hydroxide is measured in an open system, a carbonation reaction (described below) occurs in the solid. There is a risk of
M (OH) ₂ + H ₂ O + CO ₂ → MCO ₃ + 2 H ₂ O ・ ・ ・ · · · (Equation 1)
In the conventional method of loss on drying and near infrared absorption determination, as the above reaction shows, it easily reacts with carbon dioxide in the atmosphere, and the moisture content decreases relatively due to the increase in the amount of samples. It is estimated that there is a concern that the attached moisture rate is underestimated.
Therefore, in this verification test, T-C (estimate of weight increase or decrease due to carbonation) was measured as a marker of carbonation amount before and after the dry weight method. Here, metal hydroxides (samples J to N) of the same type as samples A to I were used. The results of the TC measurements are shown in the following table.
As a result, before and after weight loss on drying, it increased by 500 ppm (2500 ppm in terms of CO ₃ ), and when calculated on the weight balance, the weight increase rate was 0.10 to 0.17 wt%. That is, in the conventional loss-on-drying method (ie, the comparative example), in the samples A to I which are metal hydroxides, the amount of the sample itself increases before and after the measurement of the attached moisture percentage, and hence the attached moisture percentage Means to be underestimated. As a result, compared with the result of the example, in the result of the comparative example, the adhesion moisture percentage is lowered by an amount of 0.10 to 0.17 wt% corresponding to the weight increase rate of the sample.
From the above contents, it can be seen that while the influence on the quantitative result by the carbonation occurs in the comparative example, the influence can be excluded in the example.

(The presence or absence of the influence on the iodine KF method by the metal element in the example)
Incidentally, among the metal hydroxides used in the examples, metal elements were quantified with respect to methanol before performing the iodine KF method and after extracting the adhesion water in the samples A and B. As described above, in the case of the iodine KF method, it is considered that the metal element inhibits the reaction of the formula (2) related to the iodine KF method, so when performing the iodine KF method, the metal element is to be measured It is preferable to eliminate as much as possible. In addition, as a specific method of the determination of the metal element, in samples A and B, nitric acid is added to methanol which has been extracted and dried before performing the iodine KF method and after the attached water is extracted, Analysis was performed using an ICP (Inductively Coupled Plasma) emission spectrometer (SPS 3000 manufactured by Seiko Instruments Inc.). The results are shown below.
As the above table shows, at least samples A and B contained almost no metal element that would inhibit the reaction of the iodine KF method. As a result, it is considered that in the examples including the other samples C to I, it is possible to improve the accuracy of the determination result of the attached moisture content obtained by the iodine KF method.

(Summary)
As a result of the above, it was found that, in this example, even if it is an alkaline solid, the moisture content of water adhering to the solid can be accurately quantified.

Claims (2)

A method for measuring the moisture content of water attached to an alkaline solid which is a powder of a metal hydroxide containing crystal water ,
By bringing the solid into contact with a solvent which does not react with the solid and which can dissolve water, it does not thermally decompose the OH group in the solid and does not produce water from the water of crystallization; Extracting the separated water for extraction into the solvent;
Determining the moisture content of the attached water in the solid from the amount of water extracted into the solvent;
I have a,
The solvent is methanol,
In the determination step, Karl Fischer method using iodine titration is used.
A method of measuring moisture content using the methanol after the extraction step in the Karl Fischer method. The moisture content measuring method according to claim 1, wherein solid-liquid separation by centrifugation is performed after stirring and extraction in a closed vessel in the extraction step.