JPH09119898A - Method for managing impregnating resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize an impregnating resin, by quickly and accurately deciding whether or not an acid anhydride composed of an epoxy resin and a setting agent of the acid anhydride can be used and a usable period of the impregnating resin. SOLUTION: The amount of a free acid promoting a polymerization reaction of an epoxy resin in an acid anhydride is obtained. More specifically, an absorbance A1 corresponding to a wavelength of 1775cm<-1> is obtained by an infrared spectrophotometer 9, and a concentration M1 of the free acid is obtained from a working curve L obtained by measuring an absorbance A of a sample 8 after changing a concentration M of the free acid of the acid anhydride hydrolyzed beforehand with a distilled water. The value is compared with a reference value, thereby to judge whether or not the acid anhydride is usable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the insulation of electric equipment, and in particular to the insulation coil of a rotating electric machine, whether or not the curing agent can be used in an impregnation resin comprising a mixture of an epoxy resin and a curing agent of an acid anhydride, and impregnation. The present invention relates to a method of managing the usable life time of a resin.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of an apparatus for explaining a resin-containing system of a coil of a rotary electric machine. The insulating coil of the rotating electric machine is subjected to resin impregnation insulation treatment so as to prevent the occurrence of partial discharge by improving the electric field resistance by eliminating voids in the coil insulating layer, and to withstand a polluted atmosphere against moisture and dust. For resin impregnation insulation treatment of this coil, the coil is inserted in the iron core slot, the coil and the iron core are integrally impregnated with resin and heat-cured, and the large impregnation of turbine generator, turbine generator, etc. There is a single resin impregnation method in which a single coil of an insulated coil is impregnated with resin and heat-molded with a mold. This method of manufacturing an insulating coil by the resin impregnation method, because the resin is sufficiently impregnated inside the coil insulating layer, a dense insulating layer can be obtained, high insulation reliability can be achieved, and the number of manufacturing steps can be reduced. As described above, the insulation coil of the high-voltage rotating electric machine to which a high voltage is applied is applied from small machines to large machines.

The impregnating resin used for insulation of electrical equipment is
Various curable resins are used properly depending on the required performance of electrical equipment insulation. Especially in coils of rotating machines, a resin in which a predetermined weight of an epoxy resin, an acid anhydride curing agent and a curing accelerator are blended mechanically, It is used because it has excellent thermal properties, and it has a low curing reactivity at room temperature in consideration of resin impregnation workability, and an impregnation made of a resin compounding system that has high curing reactivity when heated and hardened. A resin is selected and used. In the method of manufacturing an insulated coil by this resin-impregnated insulation method,
As shown in FIG. 6, a resin storage tank 1 containing an epoxy resin and a curing agent of an acid anhydride and a curing agent storage tank 2 are pressurized with nitrogen gas by a pressure device 3 and supplied with a predetermined ratio of the epoxy resin. Impregnated resin storage tank 5 for injecting and storing liquid impregnated resin 4 prepared by mixing
From the above, the resin impregnation tank 7 accommodating a plurality of unimpregnated coils 6 is vacuum impregnated with the impregnation resin 4 by the vacuum pump 3a,
Further, the insulating layer of the coil 6 is actually impregnated in order to perform the impregnation process in such a manner that the liquid surface of the impregnating resin 4 is gas-pressurized by the pressure device 3b to impregnate the insulating layer of the coil 6 with the impregnating resin 4. A much larger amount of impregnating resin 4 is required as compared with the amount. Therefore, mix a large amount of impregnating resin 4 at a time,
Since the coil is impregnated by repeatedly using the impregnated resin 4, a stable resin having a small increase in viscosity is selected in order to avoid defective impregnation of the insulating layer of the coil 6 due to an increase in viscosity of the impregnated resin 4 during impregnation. Must.

In the impregnation, a method of heating the impregnating resin 4 to reduce the viscosity to impregnate the resin in consideration of the impregnation property into the coil is generally performed. In this case, as described above, the impregnating resin 4 is impregnated with the impregnating resin 4. For the mixture of the epoxy resin and the acid anhydride, a resin system containing no curing accelerator that accelerates the curing reaction by heating is used, and the mica insulating tape forming the insulating layer of the coil 6 is thermally cured with the resin system described above. A curing accelerator that accelerates the reaction is applied to accelerate the curing reaction of only the impregnated resin impregnated in the coil insulating layer at the time of heat curing. However, when the impregnating resin 4 is repeatedly used for impregnating the coil 6 in a state of being heated to reduce the viscosity as described above,

Embedded image The epoxy group (CH ₂ OCH) of the epoxy resin [I] shown in
-) And a part of the acid anhydride [II] gradually progresses to form an ester compound (COO to [R ']) which is a cured polymer by an ester bond as a cured product [III].
The reaction that occurs occurs.

Embedded image

Further, this reaction is further caused by the presence of a free acid (carboxylic acid: an acid having a carboxyl group, -COOH) produced by hydrolysis of the acid anhydride [II] by reacting with water in the atmosphere. Since it is accelerated, it is necessary to use the acid anhydride used for the impregnating resin that contains as little free acid as possible.

By the way, when the polymerization reaction of the impregnated resin 4 progresses due to the formation of the above-mentioned ester compound, the viscosity of the impregnated resin 4 gradually rises, which causes impregnation into the coil insulating layer and causes impregnation failure. There is a fear. Therefore, the amount of the above-mentioned free acid in the acid anhydride [II] used as the curing agent is monitored to use a curing agent containing no free acid, and the amount of the ester compound in the impregnated resin 4 is changed. Monitoring is performed, and when the amount reaches a predetermined limit value, use of the impregnated resin 4 is stopped and replaced with a new resin.

[0007]

The means for measuring the ester compound, which is the reaction component of the above-mentioned impregnated resin, is as follows:
Previously, the above was done using potassium hydroxide aqueous solution as the impregnating resin.

The free acid generated by the reaction between the ester compound of the cured product [III] of [Chemical formula 1] and water is hydrolyzed, and then titrated with hydrochloric acid or sulfuric acid. The value of the hydration value obtained by back-calculating the amount of potassium hydroxide consumed for the hydrolysis and the free acid produced by hydrolysis by adding distilled water to the impregnated resin are determined by titration with an aqueous potassium hydroxide solution. A method of measuring the acid value and the value of the ester value obtained from the difference between the soap value and the acid value, or by heating the impregnated resin for a certain period. However, a method is known in which the increase in viscosity is obtained from the difference in viscosity before and after that, and the production amount of the ester compound is estimated from the magnitude of the increase value. Also,
The amount of free acid contained in the above-mentioned acid anhydride can be determined by measuring the above-mentioned acid value.

However, these methods have a problem that it takes half a day to one day for measurement, so that by stopping the impregnation process until the measurement result is reached, the process is delayed, or the impregnation failure or the process delay does not occur. In addition, since the impregnating resin 4 is replaced early by terminating the use of the impregnating resin early, a large amount of the impregnating resin 4 cannot be fully utilized until the end of its service life, which is economically disadvantageous. There was a problem and there was a need for improvement.

An object of the present invention is whether or not it can be used by measuring a free acid in an acid anhydride curing agent which solves the above problems,
An object of the present invention is to provide a method for controlling the impregnated resin, which can measure the usable life of the impregnated resin quickly and accurately, eliminate the delay of the resin impregnation step, and can effectively use the impregnated resin.

[0010]

In order to solve the above-mentioned problems, the present invention provides a free acid produced by reacting a part of the acid anhydride of the curing agent constituting the impregnating resin with moisture in the atmosphere. Alternatively, the ester compound produced by repeatedly using an impregnating resin consisting of an epoxy resin and an acid anhydride for a long time, by measuring the absorbance at a wavelength showing a unique absorption spectrum by an infrared spectrophotometer, Whether or not the acid anhydride can be used and the usable life of the impregnated resin can be quickly determined by comparing with the calibration curve obtained with the impregnated resin having a known amount of acid anhydride and ester compound. I did it.

Further, in detecting and measuring the ester compound of the impregnated resin by the above infrared spectrophotometer, the free acid and the ester compound are separated and extracted from the impregnated resin under test by using a liquid chromatograph in advance, By adopting a method of measuring the absorbance of the extract with an infrared spectrophotometer, the absorbance of the ester compound can be measured more accurately, and the usable life of the impregnated resin can be quantitatively and accurately determined. As a result, the free acid of the acid anhydride of the curing agent and the ester compound of the impregnating resin can be quantitatively measured quickly, so that the impregnation process which has been a problem is affected by adopting the conventional measuring method. It becomes possible to effectively utilize the useful life of the impregnated resin.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIGS. 1 to 3 show a method for measuring a free acid of an acid anhydride showing a first embodiment of the present invention. FIG. 1 shows absorption of an acid anhydride by an infrared spectrophotometer. Spectrum, FIG. 2 is a calibration curve showing the relationship between the concentration of free acid in the acid anhydride and the absorbance,
FIG. 3 is a process diagram for determining the usable state as a curing agent by generating a free acid of an acid anhydride. Acid anhydrides having two or more carbonyl groups (= CO) in the molecule, such as methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride, which are used as curing agents for epoxy resins, are
As shown by the arrow P in FIG. 1, wavelengths 1700 to 1700 in the infrared region
It has two absorptions at 1800 cm ^-1 due to the molecular structure produced by dehydration of the intramolecular carboxylic acid. On the other hand, the free acid generated by the reaction of the acid anhydride with water has a wavelength of 1700 as described above.
It has one absorption shown by Q arrow due to carboxylic acid (carboxyl group) generated by hydrolysis of acid anhydride at ˜1800 cm ⁻¹ . Since the absorption of these two acid anhydrides and the absorption of the free acid appear at different wavelengths in the above-mentioned wavelength region, the free acid in the acid anhydride can be detected by using an infrared spectrophotometer.

A calibration curve for determining the concentration of free acid in the acid anhydride from the above-mentioned detection data was prepared as follows. Distilled water (60 mL) was added to methylhexaphthalic anhydride (10 g) as an acid anhydride, and the mixture was boiled for 4 hours, cooled to room temperature, filtered, and precipitated crystals were filtered and washed thoroughly with distilled water. Dry and cool to room temperature in a dessicator. The crystals thus produced are dissolved in trichloromethane (chloroform) to a concentration of 0.1 mg / ml, and this solution is used as a standard solution obtained by 100% free oxidation of acid anhydride. Then, prepare a sample in which this standard solution was diluted with chloroform to change the concentration, and the infrared spectrophotometer measured 1500 to 2000 cm.
The absorption spectrum of ^-1 was measured to show the formation of free acid 1
The absorbance A at the wavelength of 775 cm ^-1 is determined, and this absorbance A
Then, the calibration curve L is obtained from the relationship between the absorbance A and the free acid concentration M as shown in FIG.

Next, as shown in FIG. 3, a sample 8 of methylhexaphthalic anhydride stored from a pipe communicating with the curing agent storage tank 2 shown in FIG. Is dissolved in chloroform so that the concentration becomes 0.1 mg / ml, the absorption spectrum shown in FIG. 1 is obtained by the infrared spectrophotometer 9, the absorbance A ₁ at the wavelength of 1775 cm ⁻¹ is obtained, and the calibration is performed. From the line L (see FIG. 2), the concentration M _{1 of the} free acid is determined and compared with the reference value to determine whether or not it can be used as a curing agent.

Embodiment 2 FIG. 4 is a process diagram showing the second embodiment of the present invention for determining the usable life of the impregnated resin. The ester compound produced by repeatedly using the impregnating resin, which is a mixture of the epoxy resin and the acid anhydride, is caused by the ester group (COO-) in the infrared region of the wavelength of 1700 to 1800 cm ^-1 , similarly to the above. Has absorption to
Similar to Embodiment 1, the impregnated resin used repeatedly was sampled and the absorbance was measured with an infrared spectrophotometer. The viscosity was increased in advance by the formation of an ester compound and the ester value reached the use limit. The pot life of the impregnated resin can be determined from the calibration curve showing the relationship between the absorbance and the ester value obtained for the impregnated resin and the impregnated resin having the ester value before and after the usage limit.

Further, as described above, the absorption wavelength region due to the ester group of the ester compound of the impregnated resin consisting of the epoxy resin and the acid anhydride and the absorption wavelength region of the free acid of the acid anhydride are distinguished from each other. Because it can be difficult,
A liquid chromatograph is used to separate and extract the free acid and the ester compound from the impregnated resin, and the absorbance of this extract is measured.

Extraction of the ester compound of the impregnated resin by liquid chromatography and determination of the usable life are performed as follows. The resin storage tank 1 shown in FIG. 6 in which an impregnating resin composed of a mixture of bisphenol A type epoxy resin and methyltetraphthalic anhydride, which is usually used as an insulating coil of a rotating machine, is stored, or after impregnation of the coil. A sample 10 is taken from the resin impregnation tank 7, and dichloromethane and isopropanol are mixed in a ratio of 1: 1 according to the process chart of FIG.
Dissolve in the solvent compounded in step 1, and add a solvent of normal hexane and dichloromethane 3: 1 to give a concentration of 0.125.
Filter to 0.5 mg / ml with a 0.5 μm filter. A liquid chromatograph 14 consisting of a pump 11, a column 12 and a UV detector 13 was added to the column 12 with a solvent prepared by mixing normal hexane and normal butanol at 97: 3 with 0.05% tetrafluoroacetic acid as a mobile phase. While flowing, the above-mentioned filtered sample is injected, and the separated components flowing out from the column 12 are monitored by the UV detector 13 set to the detection wavelength of 215 nm, and the fraction collector 15 separates each component into the fraction 16. A solution containing is collected. The solution containing the ester compound therein was transferred from the fraction 16 to the liquid cell of the infrared spectrophotometer 9 to obtain a liquid of 1500 to 200
The absorption spectrum at 0 cm ^-1 was measured to be 1710 cm ^-1.
Determine the absorbance B ₁ of.

Then, as described above, the ester compound is separated by the liquid chromatograph 14 from the impregnated resin whose ester value has reached the use limit (for example, 20) and the impregnated resin whose ester value is around 20. From the calibration curve L ₁ consisting of the absorbance B and the ester value E obtained by the above, the ester value E ₁ of the absorbance B ₁ of the impregnated resin measured above
Is determined and the usable life time of the impregnated resin is determined by comparing with the above-mentioned use limit value 20.

Embodiment 3 FIG. 5 is a process diagram for determining the usable life time of the impregnated resin according to the third embodiment of the present invention. The difference between the third embodiment and the second embodiment is that the infrared spectrophotometer 9 is directly used as the detector 13 shown in FIG. 4 for detecting the separated component flowing out from the liquid chromatograph 14. Especially. That is, the liquid cell for sample measurement of the infrared spectrophotometer 9 of FIG. 4 is a liquid flow cell capable of measurement while flowing the liquid sample, and this is also used as the detector 13 of the liquid chromatograph 14. It was done. As a result, as shown in FIG. 5, the solution is collected from the fraction 16 collected by the fraction collector 15, and the separated component flowing out from the column 12 of the liquid chromatograph 14 is not measured by the infrared spectrophotometer 9. Since it is possible to measure continuously, the absorbance B ₂ of the ester compound in the impregnated resin to be measured and the ester value E according to the calibration curve L ₁ can be measured.
_The work of determining the usable life of the impregnated resin by determining ₂ can be performed more quickly.

[0020]

As described above, in the present invention, the free acid which promotes the reaction with the epoxy resin produced by the coexistence of water in the acid anhydride used as the curing agent for the epoxy resin constituting the impregnating resin. Was quantified with an infrared spectrophotometer, so that it was possible to determine whether or not to use the acid anhydride curing agent during storage. Further, the ester compound as a reaction component produced by being used for repeated impregnation of the impregnating resin for a long time, the accuracy of measurement by an infrared spectrophotometer is increased by separating the impregnating resin with a liquid chromatograph. And it became possible to measure quickly. As a result, it is possible to eliminate the delay of the resin impregnation process due to the time required to determine the renewal time of the impregnated resin, which is a problem in the conventional management method, and the waste due to the early replacement of the impregnated resin, and the curing agent By adopting a control method that detects the free acid of an acid anhydride and judges whether or not it can be used, the pot life of the impregnated resin can be set longer and the impregnated resin can be used more economically and effectively. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing an absorption spectrum of an acid anhydride by an infrared spectrophotometer for explaining a first embodiment of the present invention.

FIG. 2 is a diagram showing a calibration curve of the concentration of free acid in an acid anhydride and the absorbance.

FIG. 3 is a process diagram for determining usableness as a curing agent by generating a free acid of an acid anhydride.

FIG. 4 is a process diagram for determining the usable life time of the impregnated resin according to the second embodiment of the present invention.

FIG. 5 is a process diagram showing the third embodiment of the present invention, which is different from the second embodiment and determines the usable life time of the impregnating resin.

FIG. 6 is a configuration diagram of an apparatus for explaining a resin-containing method of a coil of a rotating electric machine.

[Explanation of symbols]

 1 Resin Storage Tank 2 Curing Agent Storage Tank 3 Pressurizing Device 4 Impregnation Resin 5 Impregnation Resin Storage Tank 7 Resin Impregnation Tank 9 Infrared Spectrophotometer 11 Pump 12 Column 13 UV Detector 14 Liquid Chromatograph 15 Fraction Collector 16 Fraction

Claims (3)

[Claims] 1. A method for controlling an impregnating resin impregnated in a winding of an electric device, which comprises a mixture of an epoxy resin and an acid anhydride curing agent, wherein a curing agent before being mixed is extracted, The absorbance of the free acid produced by reacting with the acid anhydride and water is measured by an infrared spectrophotometer, and the free acid produced by adding a predetermined amount of distilled water to the acid anhydride in advance. Compared with a calibration curve obtained by measuring the absorbance, the amount of free acid present in the acid anhydride is quantified, the impregnating resin characterized by determining the availability of the impregnating resin as a curing agent Management method. 2. A method of controlling an impregnating resin impregnated in a winding of an electric device, which comprises a mixture of an epoxy resin and an acid anhydride, which comprises extracting the impregnating resin containing a mixture of an epoxy resin and a curing agent for a long period of time. , The ester compound which increases the ester value generated in the resin is separated by liquid chromatography, the absorbance of the separated ester compound is measured by an infrared spectrophotometer, and the value of the ester value is a predetermined value. Characterized by determining the usable life of the impregnated resin by comparing with a calibration curve consisting of the ester value and the absorbance, which was measured by using the impregnated resin that reached or reached the usage limit of the viscosity value. Control method for impregnated resin. 3. The method for controlling the impregnated resin according to claim 2, wherein a detector for detecting the eluate from the liquid chromatograph is provided with a liquid flow cell capable of performing measurement while allowing the measurement sample portion to flow the eluate. Using an infrared spectrophotometer with
A method for controlling an impregnated resin, which comprises continuously measuring the absorbance of the ester compound without separating the ester compound separated by the liquid chromatograph from the liquid chromatograph.