JP2924140B2 - Quantitative analysis method of zinc in my car tape by ICP method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to a high frequency inductively coupled plasma emission method (hereinafter, IC).
P method) for quantitative analysis of zinc in car tape.

B. Summary of the Invention The present invention relates to a method for quantitative analysis of zinc in a mica tape, adding nitric acid to the mica tape, decomposing it by heating, and analyzing a mixture of a filtrate obtained by filtering the decomposed solution and a washing solution for analysis. By measuring the luminescence intensity by the ICP method, the zinc in the mica tape is quantitatively determined with high sensitivity, whereby the zinc in the mica tape, especially the composition and properties of the zinc naphthenate as a curing accelerator in the mica tape, In addition to clarifying the relationship, it is possible to improve the quality control and process control of the curing accelerator in the my car tape.

C. Prior Art At present, the stator coil of a large rotating machine, for example, a water turbine generator, is a portion that becomes the heart of the generator, and this coil generates a high voltage and a large current. Therefore, an insulating impregnating agent has been used for the stator coil. The inside of the slot of the stator coil using the insulating impregnating agent is composed of wires, insulation between turns, insulation to ground, and the like. The strands are configured to prevent skin effect and eddy current loss due to current, and are insulated from each other. As the strand, there are a case where a covered electric wire is used and a case where a bare copper wire is formed and then insulated. When the latter copper wire is formed and then insulated, a mica tape of the same system as that used for insulation between turns or insulation to ground is used. In general, a thin mica for strand insulation is used, and is insulated for each stage. When the wire insulation is completed, there is a work of solidifying many wires together. This operation includes a single-turn operation and a multi-turn operation. In the case of a single-turn operation, there is no insulation. However, in the case of a multi-turn operation, insulation is performed using a mica tape.

Mica tape is a convenient material for winding a backing material such as thin paper or a thin glass cloth and pasting a piece of cast mica or laminated mica (known as pulp mica, mica mat, samaica, etc.) with a synthetic resin adhesive. It is cut to an appropriate width as described above. Generally, both paper mica are used, and a mica adhesive that is compatible with the impregnated varnish is selected.

Mica has long been used in stator coils of generators because mica is very corona resistant and is indispensable for stator coils that generate high voltages.

In the case of a multi-turn coil, the insulation between the turns is completed, and in the case of the single-turn coil, the wire insulation work and the forming work are completed, and then the ground insulation is performed. After the insulation between turns is completed, the turns are collectively tightened with a glass tape or the like, and the mica tape is wound. The mica tape used for ground insulation is the same as that between turns, but a relatively thick one is used. When the mica tape is wound to a certain extent, the mica tape alone tends to loosen, so it is fastened with a glass tape or the like, and finally the surface protection tape is wound.

After that, the coil is placed in a vacuum tank and dried under vacuum, and then the vacuum-dried coil is vacuum impregnated with an insulating varnish (synthetic resin varnish). After completion of the vacuum impregnation, a resin curing operation for curing the varnish is performed, and the varnish is cured by heating until the optimal mechanical performance and electrical performance of the coil insulating layer are obtained.

The fact that mica has excellent dielectric strength is described in "Handbook of Electrical Insulating Materials, issued August 31, 1965". In addition, a class B insulating varnish is used as the insulating varnish of the stator coil of the generator.

D. Problems to be Solved by the Invention As described above, an insulating configuration for upgrading a coil insulating varnish of a large rotating machine from Class B to Class F is being developed. Also, this coil manufacturing method has been improved from the above-mentioned heating method to a drying method. However, in this drying method, a phenomenon that a resin (insulating varnish) flows out during coil curing (during drying) occurred. For this reason, there is a means for increasing the amount of the curing accelerator to accelerate the curing speed as a means for preventing the resin from flowing out. However, when the amount of the curing accelerator is increased and added to the resin, the pot life of the resin is shortened, and it becomes difficult to reuse the resin. Was reduced. However, since there is a delicate relationship between the amount of the curing accelerator and the electrical characteristics, the amount of the curing accelerator (zinc naphthenate is used for this curing accelerator) in the mica tape, that is, naphthene It has become necessary to accurately and quantitatively grasp the amount of zinc acid.

Since it is difficult to directly measure the curing accelerator (zinc naphthenate) in the mica tape, the curing accelerator was indirectly determined by quantifying zinc. As this method, first, an epoxy resin + zinc naphthenate is extracted with an organic solvent from a sample in which mica is impregnated with epoxy resin + zinc naphthenate (curing accelerator), and mica is removed. Thereafter, the organic solvent in the extracted sample is removed only by heating and vacuum. The residue (solid) is measured by X-ray fluorescence, infrared spectroscopy, and atomic absorption.

 In the fluorescent X-ray method, the peak intensity of the Zn wavelength is measured.

In infrared spectroscopy, the peak intensity at the wavelength of the -C = 02-Zn group is measured.

In the atomic absorption method, after a sample is incinerated, alkalis are melted to dissolve metals, and the peak intensity of the Zn wavelength in the dissolved solution is measured.

As described above, there are three methods for quantifying zinc, but there is no method based on the ICP method.

The present invention has been made in view of the above circumstances,
ICP for highly sensitive determination of curing accelerators in my car tape
The present invention provides a method for quantitative analysis of zinc in mica tape by the method.

E. Means and Action for Solving the Problems That is, the present invention relates to a filtrate obtained by adding nitric acid to a mica tape, decomposing the mica tape by heating, cooling, and then filtering the decomposition liquid. By adding strontium as a standard substance to a mixed solution with a washing solution obtained by washing the precipitate with nitric acid, making a fixed amount with water, and measuring the luminescence intensity using the ICP method as a sample solution. The solution.

 Hereinafter, the present invention will be described in more detail.

First, when carrying out the method according to the present invention, the mica tape as a sample is well decomposed.

Although this decomposition is performed using nitric acid, it is preferable to measure with a whole pipette, a micropipette or the like in order to perform the analysis method according to the present invention with higher accuracy.

Next, the necessity of heating and stirring the mica tape as a sample in the presence of the above-mentioned nitric acid is collected in a conical beaker, and thermally decomposed.

Further, the decomposed solution obtained above is cooled, filtered with a filter paper or the like, the filtrate is received in a volumetric flask or the like, and then the residue is mixed with a washing solution obtained by washing with nitric acid.

Next, strontium as a standard substance is added to this mixed solution, and water is added to make a fixed amount, and this is used as a sample solution in a method for quantitative analysis of zinc in a mica tape by an ICP method. In addition, it is preferable to use ion-exchange water as water used.

F. Examples Hereinafter, the details of the method for quantitatively analyzing zinc in a mica tape by the ICP method according to the present invention will be described based on examples.

[1] Operating procedure of analytical method [Sample decomposition and preparation method] (1) Collect a sample in a conical beaker.

(2) Add a rotor and nitric acid and stir on a stirrer.

(3) After heating in a thermostat, stir on a stirrer.

(4) After cooling, the solution is filtered using filter paper, the filtrate is placed in a volumetric flask, and the residue is washed with nitric acid and mixed with the obtained filtrate.

(5) Add strontium and adjust to constant volume with ion exchanged water.

[Preparation Method of Calibration Curve Solution] (1) 0.25 m of mica tape and 10 ml of nitric acid were added to a conical beaker to decompose by heating, and 25 ml of ion-exchanged water was added.

(2) A mixture of a filtrate of the decomposition solution and a residue obtained by adding 25 ml of nitric acid (1 + 5) to a 100 ml volumetric flask, 1.0 mg of strontium, and 1,3,5,7 mg of zinc were added.
The volume was kept constant at 100 ml with ion-exchanged water.

[2] Example 1. Analyzer and reagent 1.1 Analyzer and measurement conditions As an ICP emission spectrometer, an ICPS-1000II manufactured by Shimadzu was used. Table 1 shows the measurement conditions.

Table 1 Measurement conditions Output 1.2KW Ar gas flow rate Cooling gas 15.0l / min Plasma gas 1.2l / min Sample gas 1.0l / min Purge gas 3.5l / min Analysis line Zn 213.856nm HV10 Internal standard substance (Sr) 421.552nm Torch observation Height 15mm 2. Decomposition and preparation method of sample 2.1 Ashing method A method was considered in which a mica tape was ashed in a platinum evaporating dish and then dissolved with an acid. That is, in this method, a solution containing 50 ppm of zinc was ashed, hydrochloric acid was added to make a constant volume of 100 ml with ion-exchanged water, and the measured value of zinc and the like were examined using this as a sample.
Table 2 shows the results. As shown in Table 2, the measured value of zinc was 37.2 ppm, and it was found that about 25% or more was volatilized during incineration. Therefore, the following wet decomposition method was used.

2.2 Wet decomposition method The degree of decomposition of the resin by hydrochloric acid, nitric acid, aqua regia and sulfuric acid was examined. As a result, it was found that hydrochloric acid could not be completely decomposed. In contrast, good results were obtained for nitric acid, aqua regia, and sulfuric acid. Therefore, it was decided to use nitric acid which is easy to handle.

First, 0.5 m of the mica tape was cut into small pieces, placed in a conical beaker, and decomposed by heating with 20 ml of nitric acid. The heating was stopped when nitrous acid gas was almost completely discharged, about 50 ml of ion-exchanged water was added, and the mixture was filtered with a No. 5C filter paper. Next, the residue was treated with nitric acid (1+
5) Wash well with 50 ml of water and add 2.0 mg of strontium to add 20 ml.
The test solution was kept constant at 0 ml.

3.Experiment and results 3.1 Selection of analysis line In order to select the analysis line most suitable for zinc analysis,
Analysis lines were qualitatively selected using a 50 ppm solution and a strontium 10 ppm solution. The results are shown in FIGS. From these figures, no emission spectrum of strontium is observed at any wavelength.

Therefore, the highest emission intensity of 213.856 nm was adopted as the analysis line.

3.2 Selection of Sensitivity (HV) Sensitivity (HV) is the high voltage applied to Photomaru.
There is an optimal HV depending on the concentration.

For this reason, HV was selected using a 50 ppm zinc concentration solution. The results are shown in FIGS.

From these figures, the emission intensity is saturated at the sensitivity of 20. Therefore, 10 was adopted as HV.

3.3 Selection of internal standard substance and its wavelength Strontium, which is easy to handle, was used as the internal standard substance. To select a strontium analysis line,
Three typical wavelengths of strontium (216.596 nm, 407.7
(71 nm, 421.522 nm) was measured qualitatively. The results are shown in FIGS. From these figures, any wavelength can be used as an analysis line only with the spectrum of strontium. Here, a wavelength of 421.552 nm having a high emission intensity was used as the analysis line.

3.4 Accuracy of calibration curve The zinc concentration in the test solution prepared by decomposing and preparing the sample described in 2.2 above is 5 mg / 200 ml. Therefore, zinc concentration 0-10p
The accuracy of the calibration curve was confirmed within the range of pm / 200 ml. The results are shown in FIG. The calibration curve almost passes the origin and the correlation coefficient is 0.
9998, the standard deviation is 0.00675 ppm, indicating that the accuracy is very good.

3.5 Influence of reagents Nitric acid, mica tape and strontium were added stepwise to a 100 ppm zinc solution, and the effects were quantitatively investigated. The results are shown in FIG.

Nitric acid reduced the recovery of zinc in proportion to the amount added. The cause of the decrease in the recovery is that the coexistence of the reagent increases the viscosity of the solution, decreases the amount of sample sucked in, and lowers the luminescence intensity. Therefore, the influence was suppressed by making the concentrations of the reagents in the calibration curve preparation solution and the test solution the same. In contrast,
My car tape showed a positive effect. This is due to the effect of increasing or decreasing the resin content in the my car tape. Therefore, the influence was suppressed by adding the same amount of mycar tape to the calibration curve solution.

The criterion for determining the effect of the reagent was ± 2.0% of the recovery rate of zinc (measured value × 100 / addition amount), and is indicated by a broken line as an allowable range in the figure.

3.6 Effects of coexisting elements on strontium internal standard substance The effects of nitric acid, mica tape and zinc were added stepwise to a 10 ppm strontium solution, and the effects were quantitatively investigated. The results are shown in FIG. As a result, it was found that zinc had no effect within the range shown by the broken line. On the other hand, the measured value of strontium decreased as the amount of nitric acid increased. This is because the coexistence of the reagent increases the viscosity of the sample, decreases the amount of sample sucked, and lowers the luminescence intensity. My car tape showed positive interference due to the effect of increase and decrease.

Therefore, the same amount of nitric acid and mica tape as the test solution was added to the standard solution for preparing the calibration curve to suppress the influence.

3.7 Verification of Analysis Accuracy by Synthetic Solution In order to verify the analysis accuracy under the conditions studied above, measurement was performed according to the following procedure. First add 0.25m of my car tape and 3mg of zinc, add 10ml of nitric acid and heat, 50ml of ion exchange water
And filtered using a filter paper of NO.5C, and then the filtrate and the residue obtained by washing the residue with 25 ml of nitric acid (1 + 5) are mixed. Further, 1.0 mg of strontium is added to the mixture, and The measured value of zinc, the coefficient of variation, and the recovery were measured with 100 ml being kept constant with ion-exchanged water. As a result, the recovery rate of zinc was 100.4%, the coefficient of variation was 0.86%, and the measured value was 30.13 ppm.

 Hereinafter, the measurement results are shown in Table 3.

4. Discussion From the above results, the following findings were obtained by examining the method for analyzing zinc by the ICP method according to the present invention.

1) Decomposition method of sample In the dry ashing method, zinc evaporates during incineration, and the measured value becomes low. Therefore, a method of decomposing with nitric acid was adopted.

2) Influence of coexisting substances Nitric acid showed negative interference due to viscosity effect, and mycar tape showed positive interference due to sensitization effect. To suppress this effect, nitric acid and mica tape were added to the solution for preparing the calibration curve in the same amounts as the test solution to suppress the effect.

3) Analysis accuracy The variation coefficient of the synthesis solution was 0.86%, and the recovery rate was 100.4%, both of which were sufficiently satisfactory for practical use.

4) Others This analysis method can be applied to the analysis of Zn in Zn naphthenate and Zn in epoxy resin.

G. Effect of the Invention According to the ICP method according to the present invention, zinc in the mica tape is quantified with high sensitivity, thereby clarifying the relationship between the composition and properties of the curing accelerator in the mica tape,
It is possible to improve the quality control and process control of the curing accelerator in the my car tape.

[Brief description of the drawings]

1 to 3 are graphs showing emission spectra of various elements, FIGS. 4 to 6 are graphs showing selection of sensitivity (HV),
7 to 9 are graphs showing a profile of a coexisting substance with strontium (Sr), FIG. 10 is a graph showing a calibration curve of zinc, FIG. 11 is a graph showing an influence of the coexisting substance, and FIG.
The figure is a graph showing the effect of coexisting substances on strontium.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-120446 (JP, A) JP-A-60-190839 (JP, A) JP-A-60-205240 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) G01N 1/00-1/34 G01N 21/62-21/74

Claims (1)

(57) [Claims] 1. A method of adding nitric acid to a mica tape, decomposing the mica tape by heating, cooling, and then washing the filtrate and the precipitate obtained by filtering the decomposition solution with nitric acid. A strontium as a standard substance is added to a mixed solution with a liquid, and then the solution is made a fixed amount with water, and the luminescence intensity is measured using a high frequency inductively coupled plasma emission method as a sample solution. Method for quantitative analysis of zinc in tape.