JP2014173803A - Dryer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dryer capable of forming a coating film hardly separated from a base material.SOLUTION: A dryer 1 for drying a coating film 3 applied to one surface of a base material 2 includes heating means 12 for heating the base material 2 from a base material surface side to which the coating film 3 to be dried is not applied, and cooling means 13 for cooling a surface of the coating film 3 from the other side of the heating means 12 with the base material 2 in between.

Description

  The present invention relates to a drying apparatus for drying a coating film of a slurry coated on a current collecting electrode substrate in a production process of a non-aqueous electrolyte secondary battery represented by a lithium ion battery.

  Lithium-ion batteries are widely used in electronic information terminal devices such as mobile phones and personal computers, as higher energy density and improved safety are required for secondary batteries as electronic devices become smaller and lighter. It has been. In recent years, the use of secondary batteries has been expanded to nighttime power storage, electric vehicles (EV), hybrid vehicles (HEV), and the like, and demand for high-capacity types has also increased.

  In the production process of such a lithium ion battery cell, as disclosed in Patent Document 1, an active material, a binder, and a conductive auxiliary agent coated on a collecting electrode base material fed by roll-to-roll. The slurry coating containing the solvent and the solvent is dried by a drying device. As a method for drying a coating film using this drying apparatus, a method of heating from the surface side of the coating film with hot air or the like has been conventionally used as described in Patent Document 1.

JP 2012-9717 A

  However, in the drying apparatus described in Patent Document 1, the adhesion between the base material and the coating film becomes weak, and there is a possibility that the battery performance cannot be exhibited. Specifically, in the process of evaporating and drying the solvent in the active material coating film, the binder and the conductive auxiliary agent are segregated on the surface of the coating film by moving through the active material, and the binder and conductive auxiliary agent A so-called migration phenomenon occurs that causes a bias in the content concentration distribution in the coating film. For this reason, after the coating film is dried, the content concentration of the binder in the vicinity of the contact surface with the substrate of the coating film becomes thin, the adhesion force of the coating film becomes weak, and there is a problem that the coating film is easily peeled off. .

  In particular, when producing a battery with a large battery capacity such as a lithium-ion battery for automobiles, the film thickness of the coating film becomes thick, so the temperature difference between the coating film surface and the inside becomes large, and the above problem becomes remarkable. It was appearing.

  Further, when the drying of the surface of the slurry coating progresses, a phenomenon called skinning occurs, further hindering the drying inside the coating.

  On the other hand, by drying at a lower heating temperature, the temperature difference between the coating surface and the interior is reduced, suppressing the segregation of binder on the coating surface and the decrease in adhesion of the coating. However, if the coating film is dried while transporting the substrate, there is a disadvantage that the size of the drying apparatus increases.

  This invention is made | formed in view of the said problem, and it aims at providing the drying apparatus which can form the coating film which is hard to peel from a base material.

  In order to solve the above problems, the drying apparatus of the present invention is a drying apparatus for drying a coating film applied to one side of a substrate, and the substrate on which the coating film to be dried is not applied It has a heating means for heating the substrate from the surface side, and a cooling means for cooling the surface of the coating film from the opposite side of the heating means across the substrate.

  According to the drying apparatus, by having the heating means and the cooling means, it is possible to dry the coating film so that peeling does not easily occur. Specifically, since the coating film is heated by the base material heated by the heating means by having the heating means, the coating film is heated from the contact surface with the base material and dried. As a result, it is possible to prevent segregation of the binder on the surface of the coating film and to prevent a decrease in adhesion between the coating film and the substrate. Moreover, since the temperature difference between the inside and the surface of the coating film can be increased by further providing a cooling means, it is possible to further prevent the binder from segregating on the coating film surface.

  The cooling means may be a blower that blows air toward the coating film.

  By carrying out like this, it is possible to cool the coating-film surface reliably without contact with a coating-film.

  According to the drying apparatus of the present invention, it is possible to form a coating film that is difficult to peel from the substrate.

It is the schematic of the drying apparatus in one Embodiment of this invention. It is the schematic which shows the heating form of the coating film in this embodiment. It is an application example of the drying device in the present embodiment. It is an application example of the drying device in the present embodiment.

  Embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of a drying apparatus according to an embodiment of the present invention.

  The drying apparatus 1 has a housing 11, and the base material 2 coated with the coating film 3 passes through the inside of the housing 11. In addition, heating means 12 and cooling means 13 are provided inside the housing 11, and the heating means 12 heats the base material 2 from the side of the base material surface on which the coating film 3 is not applied, The cooling means 13 cools the surface of the coating film 3 from the opposite side of the heating means 12 with the substrate 2 interposed therebetween, that is, from the side on which the coating film 3 is applied.

  Moreover, in this embodiment, the base material 2 is conveyed in the horizontal direction in the drying apparatus 1 by operation | movement of a winding roller and a winding roller. In the following description, the direction in which the base material 2 is conveyed is the X-axis direction, the direction orthogonal to the X-axis direction on the horizontal plane is the Y-axis direction, and the direction orthogonal to the X-axis direction and the Y-axis direction, that is, the vertical direction is Called the Z-axis direction.

  The base material 2 is a metal foil that serves as a collecting electrode base material for a lithium ion battery, and an aluminum foil or the like is used when forming the positive electrode, and a copper foil or the like is used when forming the negative electrode. This base material 2 has a strip shape that is long in one direction, and is provided with an unwinding roller for unwinding the base material 2 on the upstream side with respect to the drying apparatus 1, and the coating film 3 is applied on the downstream side. The recovery device for recovering the base material 2 is provided, and the unwinding roller and the recovery device are operated in synchronization with each other so that the base material 2 is unrolled while a predetermined tension is applied to the base material 2. To the recovery device.

  The coating film 3 is a slurry containing active materials and solvents for each electrode, and in this embodiment, the coating film 3 is applied to the upper surface of the substrate 2 by a coating device such as a slit die. This slurry contains a binder called a binder in order to improve the binding property between the base material 2 and the active material, and prevents the coating film 3 from peeling off from the base material 2. The slurry also contains a conductive additive that keeps the electrical resistance of the entire coating film 3 low.

  The housing 11 is a rectangular parallelepiped composed of a bottom plate 14, a top plate 15, and side plates 16, and is a hollow metal box.

  The bottom plate 14 is a rectangular flat plate whose plate surface is parallel to the horizontal plane. A plurality of heating means 12 for heating the base material 2 is provided in the vicinity of the upper surface of the bottom plate 14.

  The top plate 15 is a flat plate having the same shape as the bottom plate 14 provided above the bottom plate 14 so as to face the bottom plate 14. In the vicinity of the lower surface of the top plate 15, a plurality of cooling means 13 for cooling the coating film 3 applied to the substrate 2 is provided.

  The side plates 16 are four flat plates connected to the sides of the bottom plate 14 and the top plate 15, and the bottom plate 14, the top plate 15, and the side plates 16 constitute a box. Further, the side plate 16 has a pair of openings 17, and the base material 2 is transported into the housing 11 through the openings 17, and is carried out of the housing 11. .

  In the present embodiment, the heating means 12 is a plurality of hot air sources that generate hot air, and emits hot air upward.

  Here, as described above, since each heating means 12 is provided in the vicinity of the upper surface of the bottom plate 14, the hot air emitted from the heating means 12 heats the substrate 2 from below inside the housing 11. It becomes. That is, the base material 2 is heated from the side where the coating film 3 of the base material 2 is not coated.

  Further, in the present embodiment, the heating means 12 also has a role of floating the base material 2 with the wind pressure of hot air in order to prevent the base material 2 from being bent and transport the base material 2 horizontally.

  In the present embodiment, the cooling means 13 is a blower that blows cool air of about room temperature, and emits cool air downward.

  Here, as described above, since each cooling means 13 is provided in the vicinity of the lower surface of the top plate 15, the cold air emitted from the cooling means 13 was applied to the base material 2 inside the housing 11. The surface of the coating film 3 and the atmosphere in the vicinity thereof are cooled from above.

  Next, the heating mode of the coating film in this embodiment is shown in FIG.

  As described above, in the present embodiment, the heating means 12 emits hot air from below the base material 2 (the base material surface side on which the coating film 3 to be applied is not applied), and the base material is generated by the heat. The lower surface of 2 is heated. And the heat which the base material 2 received from the heating means 12 is conducted in the base material 2, and the upper surface (contact surface with the coating film 3) of the base material 2 is heated up with a substantially uniform temperature distribution.

  Thereby, the coating film 3 is heated not from the surface of the coating film but from the contact surface with the substrate 2 by the heat of the upper surface of the substrate 2 whose temperature has been increased. The heat of the base material 2 is transmitted from the contact surface with the base material 2 to the surface of the coating film as indicated by the arrow in FIG. 2, and the drying of the coating film 3 is performed on the surface of the coating film from the contact surface with the base material 2. Proceed in order.

  Here, when heating is performed from the surface of the coating film 3 in the prior art, the binder has been segregated to the surface where the drying proceeds first, but in the present embodiment, drying is performed on the surface of the coating film 3. By the start, drying has already progressed in the coating film 3, particularly in the vicinity of the contact surface with the substrate 2, so that segregation of the binder on the surface of the coating film 3 can be prevented. That is, since it is possible to prevent a decrease in the binder concentration in the vicinity of the contact surface of the coating film 3 with the substrate 2, it is possible to prevent a decrease in the adhesion between the coating film 3 and the substrate 2.

  Further, as described above, the upper surface of the base material 2 (contact surface with the coating film 3) is heated up with a substantially uniform temperature distribution to heat the coating film 3, and thus the contact surface with the base material 2 in the coating film 3 It is considered that the segregation of the binder is less likely to occur.

  Further, by further providing the cooling device 13, the atmosphere in the vicinity of the surface of the coating film 3 is constantly prevented from being heated by the heat of hot air emitted from the heating device 12. Since the temperature difference between the two can be increased, segregation of the binder to the surface of the coating film 3 can be further prevented, and as a result, a decrease in the adhesion of the coating film 3 can be prevented and peeling can be difficult. it can.

  In addition, if the surface of the coating film 3 is dried by heating while the coating film 3 is being dried from the contact surface with the base material 2, there is a risk that skinning, a phenomenon peculiar to slurry, may occur. However, by cooling the surface of the coating film 3, it is possible to prevent the occurrence of skinning and to form a good coating film 3.

  Next, in order to show the effect of the drying apparatus of the present invention, the temperature difference between the temperature at the surface of the coating film 3 and the temperature at the contact surface between the coating film 3 and the substrate 2 and the adhesion force of the coating film 3 The related experimental results are shown in Table 1.

  The evaluation of the adhesion strength of the coating film 3 is performed by evaluating the peel force when the substrate 2 is peeled from the coating film 3 in the upward direction. The higher the peeling force, the more the adhesion strength of the coating film 3 is. Indicates big. In addition, the width | variety (Y-axis direction dimension shown in FIG. 2) of the applied coating film 3 is 20 mm.

  Here, since the temperature of the contact surface between the base material 2 and the coating film 3 cannot be directly measured for the temperature measurement position, the temperature of the lower surface of the base material 2 is measured, and this is used instead of the temperature of the contact surface. It is said. This is because the temperature of the upper surface (contact surface) of the substrate 2 is considered to be substantially equal to the temperature of the lower surface of the substrate 2 because the substrate 2 is sufficiently thin. In addition, the temperature of the surface of the coating film 3 and the lower surface of the base material 2 is measured with a radiation thermometer. Also, the drying time is set to 100 seconds.

  No. in Table 1 5 to No. No. 8 is an example in which the temperature of the lower surface of the substrate 2 is higher than the temperature (surface temperature) on the surface of the coating film 3, and is an example that may occur when the present invention is carried out. 1 and no. Compared with the example which surface temperature is high like 2 and it dries from the surface of the coating film 3, the adhesive force became 2 times or more.

  In addition, the adhesion force was higher as the temperature of the lower surface of the substrate 2 was higher than the surface temperature of the coating film 3. However, the adhesion is No. 7 and no. 8, there is no big difference, and when the temperature of the coating film 3 exceeds 150 ° C., the binder in the coating film 3 may be decomposed. Accordingly, when the temperature of the lower surface of the substrate 2 is higher than the surface temperature of the coating film 3 by 85 ° C. or more in a range where the temperature of the coating film 3 does not exceed 150 ° C., that is, the contact between the substrate 2 and the coating film 3 It can be said that when the surface temperature is higher than the surface temperature of the coating film 3 by 85 ° C. or more, the coating film 3 having strong adhesion can be obtained.

  Next, application examples of the drying apparatus in the present embodiment are shown in FIGS.

  FIG. 3 is an example of application to what is called single manufacturing, in which a coating film is formed only on one side of a substrate. This single manufacturing is a comparative example for mobile devices in the field of lithium ion battery production. Used for manufacturing batteries with low power.

  In this single production, the coating film 3 is applied to one surface of the substrate 2 unwound from the unwinding roller 21 and conveyed by a coating device 4 such as a slit die, and the coating film 3 is dried. The apparatus 1 heats the base material 2 from the surface side opposite to the coating surface of the coating film 3 to dry the coating film 3. And the base material 2 with which the coating film 3 which completed drying was bound is continuously sent to a downstream process.

  Here, with respect to the number of drying apparatuses 1, only one drying apparatus 1 having a furnace length capable of completing the drying of the coating film 3 may be provided to dry the coating film 3, but as shown in FIG. The individual drying apparatuses 1 may be arranged side by side to dry the coating film 3. In this case, the drying speed may be controlled by changing the set temperatures of the heating means 12 and the cooling means 13 between the respective drying apparatuses. For example, in the most upstream drying apparatus 1, the temperature of the heating means 12 may be set high to perform preheating.

  FIG. 4 is an application example to what is called tandem manufacturing, in which coating and drying are performed on each side of the substrate, and finally a coating film is formed on both sides of the substrate.

  In this configuration, coating and drying are performed in such a manner that the single production described above is performed twice. Specifically, first, the coating film 3 is applied to one side of the substrate 2 unwound from the unwinding roller 21 and conveyed, and the drying apparatus 1a is applied to the coating film 3. The base material 2 is heated from the surface side opposite to the coating surface of the coating film 3, and the coating film 3 is dried. After the drying of the coating film 3 is completed, a coating film 6 is applied by the coating device 5 to the surface of the substrate 2 on which the coating film 3 is not applied. Thus, the drying device 1b starts from the surface side opposite to the coating surface of the coating film 6 (the base material surface side where the coating film 6 is not applied, that is, the coating surface side of the coating film 3). The material 2 is heated and the coating film 6 is dried.

  That is, the drying apparatus 1a of the present invention dries the coating film 3, and the drying apparatus 1b of the present invention dries the coating film 6, thereby forming a substrate on which the coating film is formed on both surfaces. Can be manufactured. By applying this manufacturing method to a cell production process of a lithium ion battery, a battery having a large battery capacity such as a lithium ion battery for automobiles can be produced.

  With the above drying apparatus, it is possible to form a coating film that is difficult to peel off from the substrate.

  In the above description, the heating means 12 is used as a hot air source, and the substrate 2 is heated with hot air. However, the substrate 2 is not limited to hot air but is heated with infrared heating, induction heating, steam overheating, or the like. May be used.

  Further, regarding the cooling means 13, in the above description, the surface of the coating film 3 is cooled by cold air, but not limited thereto, a water-cooled metal plate or the like is brought close to the coating film 3 and in the vicinity of the surface of the coating film 3. A method of constantly cooling the atmosphere may be used.

DESCRIPTION OF SYMBOLS 1 Drying apparatus 1a Drying apparatus 1b Drying apparatus 2 Base material 3 Coating film 4 Coating apparatus 5 Coating apparatus 6 Coating film 11 Case 12 Heating means 13 Cooling means 14 Opening part 21 Unwinding roller

Claims (2)

It is a drying device that dries the coating film applied to one side of the substrate,
Heating means for heating the substrate from the side of the substrate surface on which the coating film to be dried is not applied;
A cooling means for cooling the surface of the coating film from the opposite side of the heating means across the substrate,
A drying apparatus comprising:   The drying apparatus according to claim 1, wherein the cooling unit is a blower that blows air toward the coating film.

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