JP2008082644A - Heating device and manufacturing method of aluminum foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize normal growth of an oxide film on an aluminum foil for electrolytic capacitor when annealed, without being influenced by the air. <P>SOLUTION: An aluminum foil coil 30 manufactured with cold rolling is stored in a main heating chamber 10 of an annealing furnace 1 having a sealed multiple chamber structure with an innermost chamber formed as the main heating chamber 10, and chambers 10, 20 are sealed. Negative pressure and positive pressure are given to the main heating chamber 10 and to a sub heating chamber 20 outside the main heating chamber, respectively, for heating annealing. Thus, annealing is performed in a negative pressure atmosphere without causing the entry of the air into the main heating chamber 10 and a cubic rate is increased while producing the homogeneous oxide film on the aluminum foil. The electrolytic capacitor aluminum foil superior in etching quality is effectively obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating device for heating an aluminum foil coil and the like, and a method for producing an aluminum foil for an electrolytic capacitor using the heating device as an annealing furnace.

  As an electrode of an aluminum electrolytic capacitor, a high-purity aluminum foil having a thickness of 20 to 150 μm and etching in a strong acid solution to expand the surface area is generally used. The aluminum foil is manufactured as a foil having a predetermined thickness through cold rolling using a high-purity aluminum material as a raw material, and then roughened by the etching. Of these aluminum foils, foils used for medium- and high-voltage electrolytic capacitors are made thin by rolling the aluminum foil, and then wound into a coil shape. The etching property is improved by annealing at a high temperature and increasing the cubic crystal ratio to 95% or more.

  In the above annealing, an oxide film grows on the surface of the aluminum foil by heating at a high temperature. However, if this oxide film does not grow normally, the etching property is remarkably lowered. For example, when the oxygen concentration and moisture content in the atmosphere increase, the oxide film grows abnormally and causes defects such as end oxidation. For this reason, normally, annealing is performed in a state where the outside pressure from the outside of the furnace is prevented and the pressure inside the furnace is higher than the atmospheric pressure. However, the rolling oil, moisture, etc. are attached to the surface of the aluminum foil after the foil rolling, and during the annealing, the heated rolling oil and moisture are gasified, contaminating the annealing atmosphere, and the gasified substance is present. When extruded from the center of the coil to the end, it reacts on the surface of the aluminum foil, causing problems such as variations in the oxide film and oxidation of the end. Variation in the oxide film causes variation in the capacitance of the electrolytic capacitor. In addition, the excessively oxidized end portion has poor etching property, and good roughening cannot be performed.

On the other hand, there has been proposed a method for efficiently removing the gasified material of rolling oil or adsorbed water generated from the surface of the foil during annealing and heating by setting the inside of the annealing furnace to a negative pressure. However, when negative pressure annealing is performed, it is easy to invite outside air, so it is necessary to prevent this entry. For example, when gasifying waste, a gasification furnace with a negative pressure inside the furnace introduces exhaust gas into the connection between the gasification furnace and a device for supplying waste to the gasification furnace. Means for preventing intrusion have been proposed (see Patent Document 1). However, in the above annealing furnace, it is impossible to apply the sucked gas again into the furnace because the inside of the furnace is contaminated. Therefore, conventionally, an O-ring is arranged at the boundary between the furnace wall and the opening / closing lid so that the atmosphere does not enter from the periphery of the opening / closing lid for carrying in and out the coil provided in the annealing furnace, and a close contact portion between the O-ring and the furnace Adhesion is improved by using grease.
JP 2003-14218 A

  However, since an annealing furnace is generally heated to 400 ° C. or more and annealed, there is thermal expansion of the furnace and the O-ring, and it is difficult to maintain a close contact state around the open / close lid. For this reason, when annealing is performed under negative pressure, there is a problem that outside air enters the furnace through a minute gap, the oxygen concentration becomes high, abnormal growth of the surface oxide film occurs, and the etching property is impaired.

  The present invention has been made against the background of the above circumstances. A heating device that can maintain a negative pressure atmosphere in the heating chamber and effectively prevent the intrusion of the air, and a uniform oxidation on the aluminum foil by using the heating device. It aims at providing the manufacturing method of the aluminum foil for electrolytic capacitors which can improve etching property by annealing, forming a membrane | film | coat.

That is, among the heating devices of the present invention, the invention according to claim 1 is characterized by having a sealed multiple chamber structure in which the innermost chamber is the main heating chamber.
According to a second aspect of the present invention, there is provided a heating apparatus according to the first aspect, wherein each chamber can be independently adjusted in atmosphere.
According to a third aspect of the present invention, there is provided a heating apparatus according to the first or second aspect, wherein the main heating chamber can be adjusted to a negative pressure, and the sub-heating chamber outside the main heating chamber is adjusted to a positive pressure. It is possible.

  The invention of the method for manufacturing an aluminum foil for electrolytic capacitors according to claim 4 is an aluminum foil manufactured by cold rolling in the main heating chamber of an annealing furnace having a sealed multi-chamber structure having the innermost chamber as a main heating chamber. The coil is housed, each chamber is sealed, the main heating chamber is set to a negative pressure, and the sub-heating chamber outside the main heating chamber is set to a positive pressure and heat annealing is performed.

In the heating device of the present invention, the main heating chamber in the innermost chamber is separated from the atmosphere by other multiple chambers, the atmosphere of the main heating chamber is maintained well, and the influence of the atmosphere outside the heating device is minimized. be able to. Moreover, the atmosphere of the main heating chamber can be set and maintained more appropriately by making each chamber independently adjustable. In particular, the main heating chamber can be adjusted to a negative pressure, and the outer sub-heating chamber can be adjusted to a positive pressure to reliably prevent the atmosphere from entering the heating device, while the main heating chamber Then, it is possible to secure a negative pressure environment by eliminating air intrusion. However, since the invasion of atmospheric gas from the positive-pressure sub-heating chamber to the negative-pressure main heating chamber is expected, it is desirable to adjust the atmosphere of the sub-heating chamber assuming this.
Note that the heating device of the present invention can be applied in various applications for performing heat treatment, and is not limited to use in a specific application. Preferably, it is suitable for a heating furnace, particularly an annealing furnace that requires strict atmosphere adjustment.

  Moreover, in the manufacturing method of the aluminum foil for electrolytic capacitors of this invention, air | atmosphere penetration | invasion in the main heating chamber made into the negative pressure is prevented by using the said heating apparatus as an annealing furnace. As a result, the gasified material by the rolling oil and adsorbed water generated from the foil surface during annealing is efficiently removed from the main heating chamber to prevent these materials from reattaching to the aluminum foil coil. Further, increase of oxygen and moisture into the atmosphere due to air intrusion is prevented, and annealing is performed while the oxide film grows normally.

The negative-pressure force of the main heating chamber is desirably maintained at ^{0.5 × 10 5 Pa~0.9 × 10 5} Pa. If the negative pressure is excessively reduced, the gasified substance is rapidly discharged out of the coil, causing coil misalignment and close contact between aluminum foils. Further, the atmospheric gas concentration is lowered, the thermal conductivity is lowered, and the annealing rate is remarkably slowed. From these points, the negative pressure is preferably 0.5 × 10 ⁵ Pa or more. Further, when the negative pressure is not sufficiently low, the gasification substance is not sufficiently discharged, and the main heating chamber is easily contaminated. From these points, the negative pressure is preferably 0.9 × 10 ⁵ Pa or less. The negative pressure may be constant within the pressure range, or the pressure may be varied within the pressure range.

The positive-pressure force of the main heating chamber outer is desirably maintained within the range of ^{1.013 × 10 5 Pa~1.1 × 10 5} Pa. By setting the pressure to 1.013 × 10 ⁵ Pa or more, the sub-heating chamber can be set to a positive pressure (atmospheric pressure or more). In addition, when the positive pressure is excessively high, atmospheric gas easily enters the main heating chamber from the sub-heating chamber, and the atmosphere in the main heating chamber becomes unstable. From these points, it is desirable to set the positive pressure within the above range.
The negative pressure and the positive pressure may be maintained until the end of annealing, but it is desirable to maintain the pressure until the coil temperature reaches 200 ° C. at least when the temperature is lowered. This is because gas is generated from the coil up to about 200 ° C. even during the temperature drop, and it is desirable to maintain the positive pressure and the negative pressure in order to effectively discharge the gas and keep the inside of the furnace clean. Because. In the case where a plurality of sub-heating chambers are provided in multiple, the positive pressures of the sub-heating chambers may be different from each other.

In addition, it is desirable to use the same atmospheric gas in the main heating chamber and the sub-heating chamber. As a result, even when the atmospheric gas in the sub-heating chamber of the positive pressure enters the main heating chamber of the negative pressure, the main heating chamber is not contaminated by the penetration and the atmosphere of the main heating chamber is stably maintained. Can do.
Incidentally, the atmospheric gas, so as to be suitable for annealing, can be used Ar, N ₂ Hitoshifu active gas, alone or mixed gas of a reducing gas such as H _2. In addition, atmospheric gas may change a component with progress of annealing.

  As described above, according to the heating device of the present invention, since it has a sealed multiple chamber structure in which the innermost chamber is the main heating chamber, the influence of the atmosphere on the main heating chamber is minimized to maintain a stable atmosphere. It becomes possible.

  Moreover, according to the manufacturing method of the aluminum foil for electrolytic capacitors of this invention, the aluminum foil manufactured by cold rolling in the said main heating chamber of the annealing furnace which consists of a sealed multi-chamber structure which uses an innermost chamber as a main heating chamber The coil is housed to seal each chamber, the main heating chamber is set to a negative pressure, and the sub-heating chamber outside the main heating chamber is set to a positive pressure for heat annealing. Therefore, annealing can be performed in a negative pressure atmosphere, and the cubic crystal ratio can be increased while forming a uniform oxide film on the aluminum foil, and an aluminum foil for electrolytic capacitors excellent in etching property can be obtained. Etching using the aluminum foil makes it possible to obtain a roughened surface. By using the aluminum foil, there is an effect that there is no variation and an electrolytic capacitor excellent in capacitance per unit area can be obtained.

Below, the actual form of the heating apparatus of this invention and the manufacturing method of the aluminum foil for electrolytic capacitors using this heating apparatus is demonstrated based on FIG.
An annealing furnace 1 corresponding to a heating device has a double chamber structure having an inner main heating chamber 10 surrounded by a furnace wall and a sub-heating chamber 20 surrounded by the furnace wall that covers the main heating chamber 10 from the outside. Each chamber includes open / close lids 11 and 21 for carrying the aluminum foil coil 30 in and out. By closing the open portions 12 and 22 of the chambers with the opening and closing lids 11 and 21, the chambers are sealed. In addition, in this embodiment, although the heating apparatus of the double chamber structure which consists of the main heating chamber 10 and the subheating chamber 20 is demonstrated, it is not limited to this as this invention, A triple chamber You may consist of the above structures. Moreover, it is not necessary for the surroundings to be completely separated from each other by a space, as long as each chamber is separated by a space covering at least the open portion.

Atmospheric gas supply pipes 13 and 23 are connected to the main heating chamber 10 and the sub-heating chamber 20, respectively. The atmospheric gas supply pipes 13 and 23 are connected to gas tanks 2 and 3 respectively storing atmospheric gases. ing. Note that a common gas tank may be used for the atmosphere gas supply pipes 13 and 23. Each atmospheric gas supply pipe 13 and 23 is provided with on / off valves 13a and 23a, pressure reducing valves 13b and 23b, and pressure gauges 13c and 23c sequentially from the upstream side, and an atmospheric gas of a predetermined pressure is arbitrarily selected as the main gas. Supply to the heating chamber 10 and the sub-heating chamber 20 is possible.
Further, exhaust pipes 15 and 25 are connected to the main heating chamber 10 and the sub-heating chamber 20, and the exhaust pipes 15 and 25 are joined together and connected to the exhaust pump 4. On the exhaust pipes 15 and 25, on-off valves 15a and 25a and a relief valve 25b are provided in this order from the downstream side. The relief valve 25b can be adjusted so that the pressure in the sub-heating chamber 20 does not exceed a predetermined value.
The annealing furnace 1 is provided with a heating means (not shown), and the internal atmosphere can be adjusted to a desired temperature.

Next, the manufacturing method of the aluminum foil for electrolytic capacitors using the said annealing furnace 1 is demonstrated.
The aluminum foil for electrolytic capacitors can be preferably manufactured using an aluminum material having an aluminum purity of 99.9% or more. The aluminum material may be one to which various trace elements are added in order to improve the etching property.
In the above production, an aluminum foil having a predetermined thickness (generally 20 to 150 μm thickness) is obtained through melting, homogenization treatment (can be omitted) by casting, hot rolling, and cold rolling. Moreover, an aluminum foil may be manufactured by cold rolling after continuous casting and rolling. However, in the present invention, the composition of the aluminum material used for the aluminum foil and the manufacturing method up to annealing are not particularly limited, and the thickness of the aluminum foil is not limited to the above.

The aluminum foil obtained by the cold rolling is wound up to form an aluminum foil coil 30. During annealing, the opening / closing lid 11 and the opening / closing lid 21 of the annealing furnace 1 are opened, the aluminum foil coil 30 is carried into the main heating chamber 10 through the opening / closing portions 22 and 12, and then the lids 11 and 21 are closed to close the main heating chamber. 10 and the sub-heating chamber 20 are sealed.
Before the annealing, as shown in FIG. 2, the exhaust pipes 15 and 25 are opened, the on-off valves 15 a and 25 a are opened, and the inside of the main heating chamber 10 and the sub-heating chamber 20 is preferably vacuumed to 100 Pa or less by the exhaust pump 4. It is desirable to exhaust and sufficiently reduce the oxygen partial pressure in the furnace. Desirably, it is more effective to perform this evacuation twice or more.

After evacuation, the on-off valves 15a and 25a are closed, the on-off valves 13a and 23a are opened, and the atmosphere gas is supplied from the gas tanks 2 and 3 through the atmosphere gas supply pipes 13 and 23 as shown in FIG. Introduce into the heating chamber 20. The atmospheric gas is adjusted to a predetermined pressure by the pressure reducing valves 13b and 23b and supplied to each chamber. The pressure in each chamber can be measured with pressure gauges 13c and 23c. When H ₂ gas is used as the atmospheric gas, it is desirable to introduce H ₂ gas after filling with an inert gas such as Ar or N ₂ after the evacuation. In addition, when an inert gas such as Ar or N ₂ is used as the atmosphere, the gas can be filled immediately after the evacuation.

At the time of filling of the atmospheric gas, with sub-heating chamber 20 side, positive-pressure force remain closed off valve 25a was set sub-heating chamber ^{20 (1.013 × 10 5 Pa~1.1 ×} 10 5 Pa ) To control the supply of atmospheric gas. Excessive pressure is blocked by the relief valve 25b. On the other hand, in the main heating chamber 10, upon filling of the atmospheric gas in the vicinity negative pressure pressure set ^{(0.5 × 10 5 Pa~0.9 × 10} 5 Pa), discharge pump 4 by opening the on-off valve 15a Then, the atmospheric gas is continuously supplied while evacuating in order to maintain the inside of the main heating chamber 10 at the negative pressure set above.

Moreover, in the annealing furnace 1, as shown in FIG. 2, heating is started with the introduction of the atmospheric gas, the temperature is raised to a predetermined temperature, and annealing is performed at the predetermined temperature for a predetermined time. The annealing time can be determined in consideration of the size of the coil, the annealing temperature, the progress of discharge of impurity gas generated from the coil, etc., and the present invention is limited to a specific one including the annealing temperature. However, for example, an annealing temperature of 200 to 580 ° C. and an annealing time of 2 to 36 hours can be mentioned. When the temperature is lowered after being held at a predetermined temperature for a predetermined time, gasification occurs even at a low temperature. Therefore, it is desirable to continue the control of the positive pressure and the negative pressure until the coil temperature reaches 200 ° C.
After the heating is finished, after the aluminum foil coil 30 has become 200 ° C. or less, the open / close lids 21 and 11 are opened, and the aluminum foil coil 30 is taken out of the annealing furnace 1 through the open portions 11 and 21 to finish the annealing.

Moreover, the in-furnace situation at the time of the said annealing is demonstrated.
During annealing, impurity gas is generated by rolling oil or the like in the coil as described above due to heating. This impurity gas is discharged out of the aluminum foil coil 30 by maintaining the furnace pressure at a negative pressure. This impurity gas is exhausted as the atmospheric gas in the main heating chamber 10 is exhausted out of the annealing furnace 1 through the exhaust pipe 15.

On the other hand, the pressure of the sub-heating chamber 20 is kept high between the sub-heating chamber 20 and the main heating chamber 10, and the atmosphere gas on the sub-heating chamber 20 side may enter the main heating chamber 10 side. The atmosphere on the side of the sub-heating chamber 20 is an adjusted atmosphere unlike the atmosphere, and in this embodiment, the same type of atmospheric gas as that on the side of the main heating chamber 10 is used. There is no fear of atmospheric contamination in the heating chamber 10, and good annealing is performed.
Further, between the sub-heating chamber 20 and the outside of the annealing furnace 1, the sub-heating chamber 20 side is set to the same pressure or a higher pressure, so that no air enters the sub-heating chamber 20 side, and the sub-heating chamber 20 The atmosphere on the side is also kept clean.
By the above pressure control, the impurity gas generated in the aluminum foil coil 30 can be quickly discharged out of the coil without causing winding displacement or adhesion of the aluminum foil coil 30, and the impurity gas forms on the surface of the aluminum foil. There is no abnormality in the oxidized film. As a result, it is possible to obtain an annealed coil with excellent uniformity that suppresses abnormal oxidation of the coil end face and abnormal growth of the oxide film on the surface of the aluminum foil.

The aluminum foil for electrolytic capacitors obtained by the annealing is subjected to etching. The etching may be electrolytic etching or chemical etching, and a desired etching method can be employed. In the etching, a uniform oxide film is formed on the surface of the aluminum foil without any variation. Therefore, good etching is uniformly performed, and a high and uniform roughening rate is obtained. An electrolytic capacitor using the aluminum foil for electrolytic capacitors as an electrode can obtain an excellent electrostatic capacity.
As described above, the present invention has been described based on the above embodiments, but the present invention is not limited to the contents of the above description, and appropriate modifications can be made without departing from the scope of the present invention. .

It is the schematic which shows the annealing furnace in one Embodiment of this invention. It is the same figure which shows the pressure and heating pattern at the time of annealing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Annealing furnace 2 Gas tank 3 Gas tank 4 Exhaust pump 10 Main heating chamber 11 Opening and closing cover 12 Opening part 13 Atmospheric gas supply pipe 13a Opening and closing valve 13b Pressure reducing valve 13c Pressure gauge 15 Exhaust pipe 15a Opening and closing valve 15b Relief valve 20 Subheating chamber 21 Opening and closing cover 22 Opening portion 23 Atmospheric gas supply pipe 23a Open / close valve 23b Pressure reducing valve 23c Pressure gauge 25a Open / close valve 25b Relief valve

Claims (4)

  A heating apparatus comprising a sealed multiple chamber structure in which the innermost chamber is a main heating chamber.   The heating apparatus according to claim 1, wherein each chamber is capable of adjusting the atmosphere independently.   The heating apparatus according to claim 1 or 2, wherein the main heating chamber can be adjusted to a negative pressure, and the sub-heating chamber outside the main heating chamber can be adjusted to a positive pressure.   An aluminum foil coil manufactured by cold rolling is accommodated in the main heating chamber of an annealing furnace having a closed multiple chamber structure in which the innermost chamber is the main heating chamber, each chamber is sealed, and the main heating chamber is negatively charged. A method for producing an aluminum foil for an electrolytic capacitor, characterized in that the subheating chamber outside the main heating chamber is heated to a positive pressure while being heated and annealed.

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