JP5523153B2 - Method for determination of benzotriazole on metal powder surface - Google Patents

Description

  The present invention relates to a method for quantitative analysis of benzotriazole (also referred to as BTA) and benzotriazole salt (also referred to as BTA salt) present on the surface of a metal powder.

  In order to improve the characteristics of the metal powder, there is a technique for attaching one or more of BTA and BTA salt to the surface of the metal powder. For example, Patent Document 1 describes a technique for producing silver powder having a surface moisture amount suitable for a conductive paste using an organic solvent having high water solubility by attaching BTA or a BTA salt to the surface of silver powder. Yes. Here, BTA or BTA salt is made to adhere to the surface of silver powder by adding to the wet reaction system which produces | generates silver powder.

  Patent Document 2 describes a technique for increasing the sintering start temperature of copper powder by attaching BTA to the surface of the copper powder. Here, adhesion of BTA to the copper powder surface is performed by immersing the copper powder in a solvent in which BTA is dissolved and then drying.

JP 2008-88453 A JP 2006-117959 A

  Conventionally, as a method of measuring the amount of organic matter attached to the surface of metal powder such as silver powder or copper powder, there was a method using a trace carbon sulfur analyzer, but according to this method, if some organic matter is used, Even when measured for metal powder to which BTA and BTA salt are not added at all in the production process, naturally, the organic matter is quantified, and the amount of BTA on the surface of the metal powder cannot be quantified. There was no method for measuring (quantifying) the amount of BTA or BTA salt adhering to the surface of a metal powder such as silver powder or copper powder.

  For this reason, it was unclear whether or not the amount of BTA and BTA salt adhered on the surface of the metal powder could be sufficiently managed (controlled). Specifically, if there is a change in the application characteristics of metal powder (sintering start temperature, viscosity of paste manufactured using metal powder, etc.), grasp the relationship with the amount of BTA and BTA salt attached. Therefore, there has been a demand for a method for measuring (quantifying) the amount of BTA and BTA salt adhering to the surface of a metal powder such as silver powder or copper powder.

One or more of BTA and BTA salts are mixed with an aqueous hydrochloric acid solution at a predetermined concentration, heated and dissolved in the solution, and the absorbance is measured with a spectrophotometer, and a calibration curve or a relational expression between the BTA and BTA salt concentrations and absorbance is obtained. Ask for.
Next, a metal powder (sample metal powder) on which one or more of BTA and BTA salts are present is mixed with a hydrochloric acid aqueous solution and heated to dissolve the BTA and BTA salts in the liquid, and the resulting slurry is subjected to solid-liquid separation. Then, the absorbance of the liquid obtained is measured with a spectrophotometer, and the BTA and BTA salt concentrations of the liquid are determined from the absorbance measurement value and the calibration curve or the relational expression. From this concentration value and the amount of liquid obtained by solid-liquid separation and the amount of sample metal powder, the BTA and BTA salt abundance (mass) per unit metal powder unit mass can be calculated.

According to the present invention, BTA and BTA salt present on the surface of metal powder can be efficiently quantitatively analyzed.
Furthermore, according to the method of the present invention, it is possible to manage and control the amount of BTA and BTA salt attached in the process of attaching one or more of BTA and BTA salt to the surface of the metal powder in order to improve the properties of the metal powder. Became.

It is a graph of a calibration curve showing the relationship between BTA concentration (mg / liter) and absorbance. As shown in FIG. 1, the determination coefficient R ² that is the square of the correlation coefficient R was 0.9999, and there was substantially no error between the measured value and y = 0.065x. . It is a graph which shows the absorptivity spectrum of the liquid obtained using the below-mentioned sample 2 silver powder (horizontal axis: nm, vertical axis: absorbance). It is a graph which shows the gas chromatograph mass spectrometry result of the below-mentioned sample A solution (horizontal axis: mass number, vertical axis: signal intensity). It is a graph which shows the gas chromatograph mass spectrometry result of the below-mentioned sample B solution (horizontal axis: mass number, vertical axis: signal intensity). It is a graph which shows the TG-DTA measurement result of the below-mentioned sample 0 silver powder (horizontal axis: temperature ° C, left vertical axis 1 (TG): mass (mg), left vertical axis 2 (DTG): differential thermogravimetric (mg / s), right vertical axis (DTA): temperature difference with reference material (thermocouple electromotive force μV)). It is a graph which shows the TG-DTA measurement result of the below-mentioned sample 1 silver powder (horizontal axis: temperature ° C, left vertical axis (TG): mass (mg), right vertical axis (DTA): temperature difference with reference material (thermoelectric Counter electromotive force μV)). It is a graph which shows the TG-DTA measurement result of below-mentioned sample 2 silver powder (Abscissa: temperature ° C, left ordinate (TG): mass (mg), right ordinate (DTA): temperature difference with reference material (thermoelectric Counter electromotive force μV)). It is a graph which shows the TG-DTA measurement result of the below-mentioned sample 3 silver powder (Abscissa: temperature ° C, left ordinate (TG): mass (mg), right ordinate (DTA): temperature difference with reference material (thermoelectric Counter electromotive force μV)). It is a graph which shows the TG-DTA measurement result of the below-mentioned sample 2 residue (horizontal axis: time (min), left vertical axis (TG): mass (mg), right vertical axis 1: temperature (° C), right vertical axis. 2 (DTA): temperature difference from the standard substance (thermocouple electromotive force μV)).

1. Measurement procedure of sample metal powder 1-1. Sample metal powder In this invention, the metal powder which does not melt | dissolve substantially in hydrochloric acid aqueous solution, such as copper powder and silver powder, can be made into a measuring object. Examples of the metal powder that can be applied as a measurement target include metal powders such as copper and silver, alloy powders of copper and silver, and alloy powders whose content of these metal elements exceeds 50% by mass. The amount of the sample metal powder is not particularly limited, but if the amount is too small, the accuracy of quantification may decrease. Conversely, if the amount is too large, it becomes uneconomical. Is preferred.

  Examples of the BTA salt to be quantitatively analyzed according to the present invention include benzotriazole sodium salt and benzotriazole potassium salt, but are not limited to a specific benzotriazole salt.

1-2. Hydrochloric acid aqueous solution The hydrochloric acid concentration of the hydrochloric acid aqueous solution of the present invention is preferably 5% by mass or more, more preferably 18 to 37% by mass. When the hydrochloric acid concentration is less than 5% by mass, BTA (salt) on the metal powder may not be sufficiently dissolved.
The amount of the hydrochloric acid aqueous solution is not particularly limited, but it is preferable that the amount of the slurry remains without evaporating to dryness even after heating the slurry after mixing with the sample metal powder.

1-3. Mixing of sample metal powder and aqueous hydrochloric acid solution The sample metal powder and the aqueous hydrochloric acid solution are mixed in a mixing vessel to obtain a mixed slurry. Although a mixing container is not specifically limited, What is necessary is just to endure the heating of a post process, for example, a glass container can be used.

1-4. Heating The mixed slurry is heated. The heating is preferably 45 ° C. or higher, and more preferably heated to a temperature at which the mixed slurry boils. When the temperature is lower than 45 ° C., BTA and BTA salt on the surface of the sample metal powder may not be sufficiently dissolved.
The heating time at the heating temperature is not particularly limited, but is preferably 1 minute or longer. If it is less than 1 minute, the BTA and BTA salt on the surface of the metal powder may not be sufficiently dissolved.

1-5. Solid-liquid separation and dilution The mixed slurry after heating is subjected to solid-liquid separation by filtering with a filter paper, and the volume of the liquid (filtrate) is measured. The obtained solution is used as a measurement sample solution for absorbance measurement. If the BTA or BTA salt concentration of this solution exceeds the concentration range of the calibration curve described later, this solution is diluted with pure water or aqueous hydrochloric acid solution. Use the measurement sample solution. The solution used for dilution is particularly preferably an aqueous hydrochloric acid solution. This is because when a very small amount of silver is dissolved in the form of a complex in the liquid, when diluted with pure water, the dissolved silver is precipitated as silver chloride, and the liquid may become cloudy. Because there is.

1-6. Absorbance measurement The peak position of the absorption wavelength and the peak absorbance of the measurement sample solution are measured using a spectrophotometer. The spectrophotometer uses a device capable of measuring the absorbance of ultraviolet light.
The peak position of the absorption wavelength of BTA and BTA salt is 272.8 nm.

1-7. BTA, BTA salt concentration in the sample solution to be measured, BTA, BTA salt adhesion amount of the sample metal powder From the relationship between the absorbance of the calibration curve described later and the BTA, BTA salt concentration, BTA and BTA corresponding to the measured values of the peak absorbance described above The salt concentration is obtained, and this value is used as the BTA and BTA salt concentration of the measurement sample solution. The mass of BTA and BTA salt present on the surface of the sample metal powder is obtained from the product of the BTA and BTA salt concentrations obtained here, the dilution rate of the measurement sample solution, and the volume of the obtained liquid.
By dividing the BTA and BTA salt mass by the mass of the sample metal powder, the mass of BTA and BTA salt per unit mass of the sample metal powder can be obtained.

2. Calibration curve preparation method BTA, BTA salt and hydrochloric acid aqueous solution are mixed to prepare three or more solutions having different BTA and BTA salt concentrations within the range of 1 to 14 mg / L (liter).
Absorbance measurement is performed on these three or more types of solutions in the same manner as in 1-4 to 1-6.
From the peak absorbance and the BTA and BTA salt concentrations, a calibration curve and a relational expression of the BTA and BTA salt concentrations and the absorbance are obtained using the least square method.

1. Preparation of calibration curve 2.6766 g of benzotriazole (1,2,3-benzotriazole, manufactured by Kawaguchi Chemical Industry Co., Ltd.) was weighed. By diluting concentrated hydrochloric acid (manufactured by Kanto Chemical Co., Ltd., special grade) with pure water, an 18% by mass hydrochloric acid aqueous solution was prepared. 2.6768 g of this benzotriazole and 1 L of the aqueous hydrochloric acid solution were mixed to obtain a BTA solution (stock solution). By diluting the BTA solution (stock solution) with an 18% by mass hydrochloric acid aqueous solution, BTA solutions having the BTA concentrations shown in Samples 2 to 6 in Table 1 were obtained.

20 mL of a total of 6 types of solutions of 18 mass% hydrochloric acid solution (sample 1) obtained by diluting the 5 types of BTA solutions and concentrated hydrochloric acid (special grade, manufactured by Kanto Chemical Co., Ltd.) with pure water, were made of glass. Placed in a container and heated to boiling. After starting boiling, the mixture was heated for 15 minutes and continued to boil. During this heating, an 18% by mass aqueous hydrochloric acid solution was added so that the solution did not evaporate to dryness after the start of boiling and was not in excess of the liquid volume before heating.
After the heating, each solution was cooled to 25 ° C., and an 18 mass% hydrochloric acid aqueous solution was added to make the volume of the solution 20 mL.

The absorbance of these six kinds of measurement sample solutions was measured with a spectrophotometer (manufactured by Hitachi, U-3210), and the absorbance of a peak having a peak wavelength at 272.8 nm ± 0.5 nm was measured. The results are shown in Table 1. The calibration curve of FIG. 1 was created from the BTA concentration and the absorbance at the peak wavelength using the least square method. The relationship between the BTA concentration (mg / L) (x) and the absorbance (y) was as shown in Formula 1.
y = 0.065x Equation 1
As described above, the determination coefficient R ² that is the square of the correlation coefficient R between x and y is 0.9999, and there is substantially no error between the measured value of y = 0.065x and the measured value. It was.

2. Measurement of silver powder 2-1. Preparation of Sample Silver Powder A slurry containing silver powder was produced by a method of adding a reducing agent to a solution containing silver. After adding the BTA to the slurry containing silver powder, the sample silver powder to which BTA was adhered was obtained by filtering, washing, drying and crushing. 0.13 mass% (sample 1), 0.26 mass% (sample 2), 0.39 mass% (sample) with respect to the mass of silver contained in the initial solution containing silver. 3 types of silver powders obtained as 3) were obtained and used as sample silver powders 1 to 3, respectively. Moreover, the silver powder (sample silver powder 0) manufactured by the method similar to the above was also set as sample silver powder except not adding the said BTA. Sample silver powders 0 to 3 are shown in Table 2.

2-2. Processing and measurement of sample silver powder About the four types of sample silver powder of Table 2, the following processes were performed, the measurement sample solution was obtained, and the light absorbency measurement was performed.
0.2 g of each sample silver powder 0 to 3 shown in Table 2 was weighed. By diluting concentrated hydrochloric acid (manufactured by Kanto Chemical Co., Ltd., special grade) with pure water, an 18% by mass hydrochloric acid aqueous solution was prepared. 0.2 g of this sample silver powder and 20 mL of hydrochloric acid aqueous solution were put into a 100 mL glass beaker, heated and boiled. After starting boiling, the mixture was heated for 15 minutes and continued to boil. During this heating, 18% by mass of hydrochloric acid aqueous solution was added within the range not exceeding the amount of liquid before heating so that the solution would not evaporate to dryness after the start of boiling.
Each solution after completion of heating is cooled to 25 ° C. and filtered. The filtrate has a volume of 20 mL for the sample 0 and sample 1 filtrates, 54 mL for the sample 2 filtrate, and 60 mL for the sample 3 filtrate. Then, a 18% by mass hydrochloric acid aqueous solution was added to make a constant volume, and a measurement sample solution was prepared.

  The absorbance of these four kinds of measurement sample solutions was measured with a spectrophotometer (manufactured by Hitachi, Ltd., U-3210), and the absorbance of a peak having a peak wavelength at 272.8 nm ± 0.5 nm was measured. From this absorbance value, the BTA concentration in the measurement sample solution was determined using Equation 1, and the amount of BTA adhering to the silver powder surface (ratio of BTA mass to silver powder mass) was determined from the BTA concentration. The results are shown in Table 2.

2-3. Confirmation of repeatability of quantitative analysis Regarding the steps after the weighing of the sample silver powder of 2-2, the sample 0 was performed twice, the sample 1 was performed 15 times, the sample 2 was performed 11 times, and the sample 3 was adhered 4 times. The amount of BTA was determined. The results are shown in Table 3. The standard deviation values of Samples 1 to 3 were 3% or less of the average value. FIG. 2 shows an absorptiometric spectrum measured by the spectrophotometer of Sample 2.

3. Confirmation of organic substance in measurement sample solution In order to confirm the organic substance in the measurement sample solution, the following two samples were prepared, and a gas chromatograph mass spectrometer (manufactured by HP, HP 6890 Series GC System (GC), HP 5973 Mass) Mass spectrometry was performed using Selective Detector (MS).
Sample A: Sample 1 Solution obtained by heating and drying the measurement sample solution prepared using silver powder, and adding toluene to the obtained solid Sample B: Solution obtained by adding the BTA to toluene Sample The gas chromatograph mass spectrometry results of A and Sample B are shown in FIGS.
The peak positions and heights in FIGS. 3 and 4 are substantially the same, and it was confirmed that the organic substance contained in the measurement sample solution prepared using the sample 1 is the BTA.

4). TG-DTA measurement results Total of 4 types of silver powder samples of samples 0 to 3 and solid (silver powder) (referred to as sample 2 residue) obtained by filtration when preparing a measurement sample solution from sample 2 silver powder. TG-DTA measurement was performed on five types of silver powder samples. The measurement was performed using a differential thermal balance (Rigaku Co., Ltd., Thermo Plus 8120) at a sample heating rate of 20 ° C./min. The results are shown in FIGS.
Here, in the TG-DTA measurement, the sample and the standard substance are heated and the mass change with time is measured. In the present application, the heating atmosphere was air, and the standard material was alumina.

In FIGS. 6 to 8 where silver powder containing BTA was used as a sample, an exothermic peak was obtained together with a reduction in weight. This is considered to be an exothermic peak caused by burning without being able to volatilize because the binding energy of Ag and BTA is high. Moreover, the exothermic peak temperature became higher as the BTA amount increased. This is presumably because the interaction between adjacent BTAs became stronger and the retention on the silver powder surface became stronger as the amount of BTA adhering to the silver powder surface increased. On the other hand, in FIG. 9 as a result of measuring the residue of Sample 2, no exothermic peak as described above was observed, and most of the BTA adhering to the surface of the silver powder was removed from the silver powder by heating in the hydrochloric acid aqueous solution. It is shown that.
On the other hand, in FIG. 5 where the sample 0 was measured, the clear exothermic peak observed in FIGS. 6 to 8 was not recognized. In the case of sample 0, this is presumed to be due to the fact that organic substances having a single composition such as BTA are not attached to the surface.

5. Organic matter measurement of silver powder using trace carbon sulfur analyzer (comparative example)
For the four types of silver powder samples of Samples 0 to 3, the amount of carbon in the sample silver powder was measured using a trace carbon sulfur analyzer (manufactured by Horiba, EMIL-U510). The measurement was performed at a sample temperature of 1350 ° C. Table 4 shows the measurement results. The values in Table 4 are large values compared to the amount of BTA added during the silver powder production process (the ratio of the mass of BTA to silver), and the amount of BTA attached to the metal powder could not be quantified.

Claims (6)

A metal powder containing a total of more than 50% by mass of one or two kinds of copper and silver having at least one of benzotriazole and benzotriazole salt on the surface is mixed with an aqueous hydrochloric acid solution having a concentration of 5% by mass or more , The obtained liquid was heated at a temperature of 45 ° C. or more, and the absorbance was measured with a spectrophotometer. From the absorbance measurement value, a calibration curve or a relational expression of the concentration and absorbance of benzotriazole or benzotriazole salt, A method for quantitative analysis of benzotriazole and benzotriazole salt on the surface of metal powder, wherein the concentration of benzotriazole and benzotriazole salt in the liquid is obtained and the amount of benzotriazole and benzotriazole salt on the surface of the metal powder is calculated. A metal powder containing a total of more than 50% by mass of one or two kinds of copper and silver having at least one of benzotriazole and benzotriazole salt on the surface is mixed with an aqueous hydrochloric acid solution having a concentration of 5% by mass or more , The liquid obtained by solid-liquid separation of the slurry obtained by heating at a temperature of 45 ° C. or higher was measured for absorbance using a spectrophotometer, and the absorbance measurement value, the concentration of benzotriazole and benzotriazole salt and absorbance were measured. The concentration of benzotriazole and benzotriazole salt in the liquid is calculated from the calibration curve or the relational expression, and the amount of benzotriazole and benzotriazole salt on the surface of the metal powder is calculated. Benzotriazole and benzotriazole on the surface of the metal powder Salt quantitative analysis method. One or more of benzotriazole and benzotriazole salt is mixed with hydrochloric acid aqueous solution at a predetermined concentration, heated, and the absorbance is measured with a spectrophotometer to obtain a calibration curve or a relational expression between the concentration and absorbance of the benzotriazole or benzotriazole salt. And a metal powder containing a total of more than 50% by mass of one or two of copper and silver in which at least one of benzotriazole and benzotriazole salt is present on the surface, and a hydrochloric acid aqueous solution having a concentration of 5% by mass or more Mix , heat at a temperature of 45 ° C. or higher, measure the absorbance of the resulting liquid with a spectrophotometer, and use the measured value of the absorbance and the calibration curve or relational expression to determine the benzotriazole and benzotriazole salts of the liquid. And determining the amount of benzotriazole and benzotriazole salt on the surface of the metal powder. Zotoriazoru, quantitative analysis method of benzotriazole salt. One or more of benzotriazole and benzotriazole salt is mixed with hydrochloric acid aqueous solution at a predetermined concentration, heated, and the absorbance is measured with a spectrophotometer to obtain a calibration curve or a relational expression between the concentration and absorbance of the benzotriazole or benzotriazole salt. And a metal powder containing a total of more than 50% by mass of one or two of copper and silver in which at least one of benzotriazole and benzotriazole salt is present on the surface, and a hydrochloric acid aqueous solution having a concentration of 5% by mass or more Mix , heat at a temperature of 45 ° C. or higher, and measure the absorbance of the liquid obtained by solid-liquid separation of the obtained slurry using a spectrophotometer. From the absorbance measurement value and the calibration curve or the relational expression, The concentration of benzotriazole and benzotriazole salt in the liquid is obtained, and the amount of benzotriazole and benzotriazole salt on the surface of the metal powder is calculated. A step, benzotriazole metal powder surface, quantitative analysis method of benzotriazole salt.   The quantitative analysis method according to claim 1, wherein the metal powder is silver powder or copper powder.   The quantitative analysis method according to claim 1, wherein the absorbance is measured after the obtained liquid is diluted with water or an aqueous hydrochloric acid solution.