JP2020146625A - Wet powder coating device control program, wet powder coating device and method for producing coating film - Google Patents

Abstract

To provide a wet powder coating device control program, a wet powder coating device and a method for producing a coating film, capable of calculating coating conditions to obtain target weight per unit area when coating wet powder on a base material by using non-constant velocity rolls having different diameters.SOLUTION: In the case where a diameter D1 of a compaction roll, a diameter D2 of a holding roll, a roll speed ratio rBC and powder properties of wet powder are given, a change rate (dσ/dx) of compressive stress σ applied to the wet powder when the wet powder is in a slip section and a change rate (dσ/dx) of the compressive stress σ applied to the wet powder when the wet powder is in a nip section are calculated. Next, from an intersection of the two dσ/dx, a nip angle α is calculated. On the assumption that a product of loose bulk density ρ and micro-volume Vα of the wet powder passing through a position in the vicinity of α and amount Wcalc,a of the wet powder passing through a gap between the rolls are equal to each other, a combination of a roll speed ratio r and a gap G that can obtain target weight per unit area Wc is explored.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wet powder coating device control program, a wet powder coating device, and a method for producing a coating film. More specifically, the present invention uses a plurality of non-constant velocity rolls having different diameters and roll speeds to provide wet powder. A wet powder coating device control program capable of calculating coating conditions for obtaining a target amount of texture when coating a body on a base material, a wet powder provided with such a program. The present invention relates to a coating apparatus and a method for producing a coating film using such a wet powder coating apparatus.

The electrode for a secondary battery generally has a structure in which an active material is applied to the surface of a conductive base material. As a method for manufacturing such an electrode for a secondary battery,
(A) A method of applying an electrode paste containing an active material to the surface of a substrate and drying it.
(B) A method of coating a granulated powder (wet powder) containing an active material on the surface of a base material is known.
Among these, the method of applying the wet powder has advantages such as no need for a solvent drying step and easy control of the amount of the active material applied. Therefore, various proposals have been made conventionally regarding such a method.

For example, Non-Patent Document 1 does not apply a wet powder to the surface of a base material, but the granulated powder is compressed using two constant velocity rolls having the same diameter to form a plate or a plate. A method of calculating the compressive stress acting between rolls is disclosed from the coating conditions such as the roll diameter and the gap and the powder characteristics such as the internal friction angle and the wall surface friction angle in the case of processing into pellets.

In Patent Document 1,
Wet powder that uses three non-constant velocity rolls of the same diameter to coat a wet granule containing a solvent and an active material on a current collector foil to form an electrode mixture layer on the current collector foil. In the film formation method
A method of keeping the viscosity of the solvent used, the contact angle of the active material with respect to the solvent, and the weight ratio of the solid content of the wet granulated product within a predetermined range is disclosed.
The document describes that an electrode mixture layer having a uniform thickness can be formed on the current collector foil by such a method.

In Patent Document 2,
A step of rolling a wet material containing an active material using a first roll and a second roll having the same diameter, and
In a method for manufacturing an electrode including a step of transferring an active material material onto a metal foil using a second roll and a third roll having the same diameter.
(A) Weight W _c , per unit area of active material after transfer,
(B) Weight W _b per unit area of active material on the second roll after rolling,
(C) Ratio V _r (= V _c / V _b ) of the peripheral speed V _c of the third roll to the peripheral speed V _b of the second roll,
(D) Density of active material on the third roll after transfer ρ _C ,
(E) Density of active material material on the second roll after rolling ρ _B , and (f) Maximum allowable density of active material material ρ _M
A method for determining the gap between the second roll and the third roll and the peripheral speed ratio V _r is disclosed so that a predetermined relationship is established between the two rolls.
The document describes that transfer defects can be suppressed by such a method.

Further, Patent Document 3 does not describe a method of applying wet powder to the surface of a base material, but in the case of rolling a metal strip with a rolling mill,
(A) During the rolling of multiple coils, the actual data of the entry side plate thickness, exit side plate thickness, rolling load, advanced rate, and tension of multiple stands or multiple passes are measured.
(B) Using these measured values and the rolling theory formula, the friction coefficient between the rolling roll and the material to be rolled and the two-dimensional average deformation resistance of the material to be rolled are calculated.
(C) The calculation result and the measured value are accumulated for a certain period of time during rolling of a plurality of coils.
(D) The two-dimensional average deformation resistance equation and the friction coefficient equation are learned based on the calculation result and the measured value.
(E) A roll gap setting method for setting a roll gap based on the learning result is disclosed.
The document describes that the plate thickness accuracy is improved and the yield is improved by such a method, and the roll gap setting accuracy is improved.

As disclosed in Patent Documents 1 and 2, by using three non-constant velocity rolls having the same diameter, the granulated powder can be continuously applied to the surface of the conductive base material. .. Further, as described in Patent Document 2, the gap between the second roll and the third roll, and a second roll by controlling the peripheral speed ratio V _r of the third roll, to suppress the transfer failure Can be done. However, with the method described in Patent Document 2, it is difficult to accurately control the basis weight of the granulated powder on the surface of the base material. Further, the methods described in Patent Documents 1 and 2 cannot be directly applied to non-constant velocity rolls having different diameters.

On the other hand, Non-Patent Document 1 describes a method of calculating the compressive stress applied to the granulated powder when the granulated powder is compressed using constant velocity rolls having the same diameter. Using this method, it is possible to estimate the amount of granulated powder to be charged between the constant velocity rolls. However, the method described in Non-Patent Document 1 cannot be applied to compression of granulated powder using non-constant velocity rolls having different diameters.
Similarly, Patent Document 3 discloses a method of setting a roll gap when rolling a metal strip using a constant velocity roll. However, the method described in Patent Document 3 cannot be applied to compression of granulated powder using non-constant velocity rolls having different diameters.

JP-A-2018-113112 Japanese Unexamined Patent Publication No. 2017-091987 Japanese Unexamined Patent Publication No. 08-090023

J. R. Johanson, J. Appl. Mechanics, 32 (4), pp. 842-848

The problem to be solved by the present invention is to calculate the coating conditions for obtaining the target basis weight when the wet powder is coated on the base material using non-constant velocity rolls having different diameters. To provide a wet powder coating device control program capable of.
Another problem to be solved by the present invention is to provide a wet powder coating apparatus provided with such a program.
Furthermore, another problem to be solved by the present invention is to provide a method for producing a coating film using such a wet powder coating apparatus.

In order to solve the above problems, the wet powder coating device control program according to the present invention comprises a computer for performing the following procedure.
(A) To the operator
(A) Compression coefficient K of wet powder, internal friction angle δ, wall friction angle φ, and looseness density ρ,
(B) The target value W _c of the basis weight of the wet powder, which is compressed by the consolidation roll and the holding roll and transferred to the surface of the base material by the transfer roll, and
(C) The diameter D _{1 of the} consolidation roll, the diameter D _{2 of the} holding roll (where D ₂ / D ₁ ≧ 1.01), and the roll speed V of the transfer roll relative to the roll speed V _B of the holding roll. Ratio of _C r _BC (= V _C / V _B > 1)
Procedure A in which the input of is requested and these input variables are stored in the memory.
(B) The roll speed ratio r is the ratio of the roll speed V _B of the holding roll to the roll speed V _A of the compacted roll (= V _B / _VA > 1), and the gap G is defined as the compacted roll and the holding. Step B to calculate the given roll speed ratio r and the nip angle α corresponding to the gap G based on the input variable when the gap with the roll is set, and store this in the memory. ..
(C) the inputted variables, and based on the calculated alpha, the basis weight of the 'calculates the W _c' estimate W _c procedure to store in the memory C.
(D) the difference between the W _c 'and the W _c epsilon, in case of the threshold epsilon _c of the epsilon, until epsilon ≦ epsilon _c when a epsilon> epsilon _c, or, When ε ≧ ε _c , the procedure D in which the r and / or the G is changed and the procedure B and the procedure C are repeated until ε <ε _c .
(E) When ε ≦ ε _c or ε <ε _c , the r and the G at that time are set as the fixed roll speed ratio r _f and the fixed gap G _f , respectively, and the procedure E for storing these in the memory. ..

The wet powder coating apparatus control program according to the present invention may further include the following procedure.
(F) If the condition that ε ≦ ε _c or ε <ε _c cannot be found even after searching for all the combinations of r and S, the operator (a) Changes to D ₁ , D ₂ , and / or r _BC ,
(B) Changes to K, δ, φ, and / or ρ, and
(C) A procedure F in which any one or more selected from the group consisting of changes in W _c is obtained, and the steps B to E are repeated based on the changed variables.

The wet powder coating apparatus according to the present invention has the following configurations.
(1) The wet powder coating device is
With a consolidation roll for compressing wet powder,
A holding roll for holding a molded product made of the compressed wet powder, and
A transfer roll for transferring the molded product adhering to the surface of the holding roll to the surface of the base material,
A drive device for rotating the consolidation roll, the holding roll, and the transfer roll in opposite directions and at the same time adjusting the gap between the rolls.
A wet powder supply device for supplying wet powder to the gap G between the consolidation roll and the holding roll,
A base material supply device for supplying a base material to the transfer roll, and
It is provided with a control device for controlling the operation of the wet powder coating device.
(2) The diameter of the consolidation roll is D ₁ , and the diameter of the holding roll is D ₂ (where D ₂ / D ₁ ≧ 1.01).
(3) the drive roll speed V _A of the compaction rolls, the roll speed V _B of the holding roll, a roll speed of said transfer roll when the _{V C, V A <V B} <V C The compaction roll, the holding roll, and the transfer roll can each be rotated at a non-constant speed so as to be such.
(4) The wet powder coating device control program according to the present invention is stored in the memory of the control device.

Furthermore, the gist of the method for producing a coating film according to the present invention is to apply a wet powder to the surface of a base material by using the wet powder coating apparatus according to the present invention.

Using the formula described later, when compressing the wet powder using non-constant velocity rolls (consolidated roll and holding roll) having different diameters, the roll velocity ratio is r and the gap is G. The nip angle α at a certain time can be obtained. Also, alpha when is found, it is possible from a calculation to be described later, and calculates the estimated value of the corresponding basis weight in alpha W _c '.
Therefore, the diameter D ₁ of the compaction rolls, the holding roll diameter D _2, a roll speed ratio r _BC, and properties of the wet powder (K, δ, φ, ρ ) in the case where given, roll speed ratio r and repeating the calculation by changing the gap G, the basis weight of the estimated value W _c 'becomes equal to the target value W _c basis weight optimum coating conditions (i.e., combination of r and G needed to obtain a W _c) Can be sought.

Also, under the given conditions, even if the optimum coating conditions could not be found, D ₁ , D ₂ , and / or r _BC were changed and the type of wet powder was changed (ie, K, Optimal coating conditions can be obtained by changing δ, φ, and ρ) or by changing W _c and repeating the same calculation.

It is a schematic diagram of the wet powder coating apparatus which concerns on this invention. It is sectional drawing of a pair of non-constant velocity rolls having different diameters. FIG. 3A is a schematic view of the direction of the principal stress when slip occurs between the powder and the roll surface. FIG. 3B is a schematic diagram of the direction of the principal stress assuming that a force is applied at an average angle. It is a flow chart of the wet powder coating apparatus control program which concerns on this invention. It is a continuation of the flow chart shown in FIG. FIG. 6A shows wet conditions under the condition that A roll diameter <B roll diameter <C roll diameter, and the rotation speed of B roll, the rotation speed of C roll, and the gap G between A and B rolls are constant. It is a figure which shows the relationship (Example 1) of the rotation speed of A roll and the electrode grain amount at the time of applying a powder. FIG. 6B shows the rotation speed of the A roll and the basis weight of the electrodes when the wet powder was applied under the same conditions as in the first embodiment, except that the rotation speed of the B roll was made faster than that of the first embodiment. It is a figure which shows the relationship (Example 2).

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Wet powder]
[1.1. composition]
In the present invention, the term "wet powder" is used.
(A) Containing at least powder and liquid (dispersion medium, etc.)
(B) The solid volume integral ratio is 50% or more and less than 100%, and
(C) A powder composition that does not have fluid properties in a stationary state.

The wet powder may contain an additive in addition to the powder and the liquid (that is, a powder / liquid / additive mixed system). The "additive" refers to a solid component other than powder particles such as a thickener and a binder. The additive is added as a powder or a dispersion liquid in which the powder is dispersed in a solvent. Since the solid component of the additive adheres to the powder particles to exhibit its function, the solid component can be regarded as a part of the powder. However, the solvent component of the dispersion liquid is regarded as a liquid.

The composition of the powder contained in the wet powder is not particularly limited. As a powder, for example
(A) Positive electrode active material of secondary battery (for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO _4, etc., which are positive electrode active materials of lithium ion secondary battery),
(B) Negative electrode active material of secondary battery (for example, graphite, Si, Ge, etc., which are negative electrode active materials of lithium ion secondary battery),
(C) Metal powder, ore powder, polymer beads, starch granules and the like.

The wet powder preferably contains an active material for a secondary battery, a conductive material, a binder, and a solvent. When the present invention is applied to such a wet powder, the amount of powder supplied between the rolls (or the surface of the base material) when a predetermined amount of the active material is transferred to the surface of the conductive base material. The amount of powder texture) can be controlled accurately. The details of the powder amount control method will be described later.

[1.2. Particle size]
It is preferable to select an optimum value for the primary particle size of the powder according to the purpose. In general, if the primary particle size is too small, it becomes difficult to produce a granule. Therefore, the primary particle diameter is preferably 1 μm or more. The primary particle size is preferably 3 μm or more, more preferably 5 μm or more.
On the other hand, if the primary particle diameter becomes too large, the surface area decreases and it becomes difficult to adsorb the particles. In addition, it becomes difficult to produce a thin film. Therefore, the primary particle size is preferably 100 μm or less. The primary particle size is preferably 50 μm or less, more preferably 30 μm or less.

It is preferable to select an optimum value for the particle size (secondary particle size) of the wet powder according to the purpose. Generally, if the secondary particle diameter becomes too small, it becomes difficult to form a film by roll compression. Therefore, the secondary particle diameter is preferably 50 μm or more. The secondary particle size is preferably 100 μm or more, more preferably 200 μm or more.
On the other hand, if the secondary particle size becomes too large, the film thickness and density of the completed film tend to vary. Therefore, the secondary particle diameter is preferably 6 mm or less. The secondary particle diameter is preferably 4 mm or less, more preferably 2 mm or less.
The "particle size" refers to the median diameter (d ₅₀ ) measured by the laser diffraction / scattering method.

[2. Wet powder coating equipment]
FIG. 1 shows a schematic view of a wet powder coating apparatus according to the present invention. In FIG. 1, the wet powder coating device 10 is
A consolidation roll (A roll) 12 for compressing the wet powder and
A holding roll (B roll) 14 for holding the molded product 22 made of the compressed wet powder, and
A transfer roll (C roll) 16 for transferring the molded product 22 adhering to the surface of the holding roll 14 to the surface of the base material 20 and
A drive device (not shown) for rotating the consolidation roll 12, the holding roll 14, and the transfer roll 16 in opposite directions and at the same time adjusting the gap between the rolls.
A wet powder supply device (not shown) for supplying wet powder to the gap G between the consolidation roll 12 and the holding roll 14 and
A base material supply device (not shown) for supplying the base material 20 to the transfer roll 16 and
It is provided with a control device (not shown) that controls the operation of the wet powder coating device 10.

[2.1. Consolidation roll, retention roll, and transfer roll]
The consolidation roll 12 and the holding roll 14 are arranged in the horizontal direction at predetermined intervals. On the other hand, the transfer rolls 16 are arranged below the holding rolls 14 at predetermined intervals. The consolidation roll 12, the holding roll 14, and the transfer roll 16 are each connected to a driving device (not shown) so as to rotate in opposite directions.
Since it is necessary to uniformly supply the powder to the gap G, the consolidation roll 12 and the holding roll 14 need to be aligned in the horizontal direction. On the other hand, the transfer roll 16 need only be in a position where the molded product 22 can be transferred to the surface of the base material 20, and is not necessarily arranged below the holding roll 14.

The consolidation roll 12 is for compressing the wet powder. The holding roll 14 is for holding a molded product 22 made of compressed wet powder on its surface. Each of these has a different diameter. Further, the consolidation roll 12 and the holding roll 14 are rolls (a pair of non-constant velocity rolls) having different roll speeds (peripheral speeds) from each other.
Here, "different diameters" means that the ratio (= D ₂ / D ₁ ) of the diameter D ₂ of the holding roll 14 to the diameter D ₁ of the consolidation roll 12 is 1.01 or more.
The larger the D ₂ / D ₁ ratio, the easier it is to transfer the powder to the holding roll 14. The D ₂ / D ₁ ratio is preferably 1.1 or more, more preferably 1.5 or more.
On the other hand, if the D ₂ / D ₁ ratio becomes too large, it may not be possible to supply a sufficient amount of wet powder between the gaps G. The D ₂ / D ₁ ratio is preferably 5.0 or less, more preferably 3.0 or less.
The shortest distance between the surface of the consolidation roll 12 and the surface of the holding roll 14 corresponds to the "gap G". Further, the ratio of the roll speed V _B of the holding roll (high speed roll) 14 to the roll speed V _A of the consolidation roll (low speed roll) 12 (= V _B / V _A > 1) corresponds to the “roll speed ratio r”. .. The gap G and the roll speed ratio r are optimized by using the method described later.

The transfer roll 16 is for transferring the molded product 22 adhering to the surface of the holding roll 14 to the surface of the base material 20. The diameter D of the transfer roller 16 'and the roll velocity V _C, and the shortest distance between the surface of the holding roll 14 and the surface of the transfer roll 16 (gap G') is a molded product 22 uniformly to the substrate 20 surface It is not particularly limited as long as it can be transferred.
Furthermore, the ratio of roll speed V _C of the transfer roll 16 against roll speed V _B of the holding roll _{14 (= V C / V B} > 1) corresponds to "roll speed ratio r _BC".

[2.2. Drive device]
The driving device (not shown) is for rotating the consolidation roll 12, the holding roll 14, and the transfer roll 16 in opposite directions, and at the same time, adjusting the gaps G and G'between the rolls. Also, the drive, the roll speed V _A of the compaction roll 12, the roll speed V _B of the holding roll 14, a roll speed of the transfer roll when the V _C, so as to be V _A <V _B <V _C In addition, the consolidation roll 12, the holding roll 14, and the transfer roll 16 are each capable of rotating at a non-constant speed. Drive, roll speed V _A of each roll, V _B, V _C, gap G, G ', and the roll speed ratio r, in as far as it is capable of controlling the r _BC, not particularly limited.

[2.3. Wet powder supply device]
The wet powder supply device (not shown) is for supplying the wet powder to the gap G between the consolidation roll 12 and the holding roll 14. The wet powder supply device is not particularly limited as long as it can supply an appropriate amount of wet powder to the gap G in a timely manner.

[2.4. Base material supply device]
The base material supply device (not shown) is for supplying the base material 20 to the transfer roll 16. The base material supply device is not particularly limited as long as the required amount of the base material 20 can be supplied to the transfer roll 16.

[2.5. Control device]
The control device (not shown) is for controlling the operation of the wet powder coating device 10. The control device includes a memory in addition to a mechanism for controlling the general operation of the wet powder coating device 10. The wet powder coating device control program according to the present invention is stored in the memory. The wet powder coating device control program is a program for calculating the gap G and the roll speed ratio r for obtaining the target powder amount (weighting amount). The details of the program will be described later.

[3. Manufacturing method of coating film]
The gist of the method for producing a coating film according to the present invention is to apply a wet powder to the surface of a base material by using the wet powder coating apparatus 10 shown in FIG. Specifically, the coating film is produced as follows.

[3.1. Coating method]
First, the base material 20 is wound around the transfer roll 16. Next, the wet powder is charged between the consolidation roll 12 and the holding roll 14. When the consolidation roll 12, the holding roll 14 and the transfer roll 16 are rotated in opposite directions in this state, the wet powder is compressed between the consolidation roll 12 and the holding roll 14 and formed into a sheet.
At this time, if the roll speed V _B of the holding roll 14 is made larger than the roll speed V _A of the consolidation roll 12, the sheet-shaped molded product 22 is conveyed to the transfer roll 16 while remaining attached to the surface of the holding roll 14. The molded product 22 conveyed to the transfer roll 16 is continuously transferred to the surface of the base material 20 while being compressed between the holding roll 14 and the transfer roll 16.

[3.2. Coating film thickness]
When the wet powder is applied using the wet powder coating apparatus according to the present invention, it is preferable to select the optimum thickness of the coating film according to the purpose. In general, if the coating film is too thin, scoring is likely to occur. Therefore, the thickness of the coating film is preferably 5 μm or more. The thickness is preferably 10 μm or more, more preferably 20 μm or more.
On the other hand, if the coating film becomes too thick, cracks are likely to occur. Therefore, the thickness of the coating film is preferably 300 μm or less. The thickness is preferably 200 μm or less, more preferably 150 μm or less.

[4. Calculation method of roll speed ratio and gap]
[4.1. Definition of terms]
The powder supplied between the rolls is first compressed by friction with the roll surface while the powder slips on the roll surface. As a result, the density of the powder gradually increases. As the density increases further, the roll speed and the powder movement speed become almost equal. As a result, the powder is compressed without slipping on the roll surface.
The “slip section” refers to a section in which slip occurs between the powder and the roll and the powder is slightly compressed.
The "nip section" means a section in which the powder is compressed without slipping.
The "nip angle" means the rotation angle of the B roll at the point where the nip section starts.

FIG. 2 shows a schematic cross-sectional view of a pair of non-constant velocity rolls having different diameters. In FIG. 2, the A roll and the B roll are non-constant velocity rolls having diameters D ₁ and D ₂ (> D ₁ ), respectively, and rotating in opposite directions. The x-axis is an axis perpendicular to the line connecting the centers of the A roll and the B roll. σ represents the compressive stress acting between the A roll and the B roll. σ is a function of x.
α represents the nip angle. α is specifically
(A) The line connecting the centers of the A roll and the B roll,
(B) Represents the angle formed by the line connecting the center of the B roll and the point on the surface of the B roll where the nip section starts.

G represents the gap between the A roll and the B roll. r represents the ratio (= V _B / V _A ) of the roll speed V _B of the B roll (high speed roll) to the roll speed V _A of the A roll (low speed roll). For example, when the B roll rotates by an angle α (or an angle θ), the A roll rotates by an angle D ₁ α / D ₂ r (or D ₁ θ / D ₂ r).
V _θ (or V _α ) is the powder that passes through the position of angle θ (or angle α) when the B roll advances by a minute length ΔL at the position of angle θ (or angle α). Represents a small volume.
W _calc represents the amount of powder that passes through the position where the inter-roll distance is the minimum (that is, the gap between the rolls) when the B roll advances by a minute length ΔL at the position where the inter-roll distance is the minimum. .. W _{calc, a} represents an estimated value of the amount of powder obtained by the calculation described later.

[4.2. Calculation of nip angle]
In order to calculate the estimated value W _{calc, a} (that is, the estimated value of the amount of powder on the surface of the substrate) of the amount of powder passing between non-constant velocity rolls, it is first necessary to know the nip angle α. There is. α is the properties of the powder (K: compression coefficient, δ: internal friction, φ: wall friction angle, ρ: looseness density), A roll diameter D ₁ , B roll diameter D ₂ , gap G, and It depends on the roll speed ratio r.

FIG. 3A shows a schematic diagram of the direction of the principal stress when slip occurs between the powder and the roll surface. FIG. 3B shows a schematic diagram of the direction of the principal stress when it is assumed that a force is applied at an average angle.
In order to calculate the nip angle α, it is necessary to know the principal stress applied to the powder by the left and right rolls. Strictly speaking, when the roll diameters are different on the left and right, the direction of the principal stress due to the left and right rolls is different. Specifically, as shown in FIG. 3 (A), the angle formed by the direction of the principal stress due to the A roll and the x-axis is expressed as sin ^-1 {(D ₁ / D ₂ ) sin θ} + ν. On the other hand, the angle formed by the direction of the principal stress due to the B roll and the x-axis is expressed as ν + θ. Further, ν is expressed as {π-arcsin (sinφ / sinδ) −φ} / 2.

However, in the present invention, the direction of this principal stress is assumed to be the average of the left and right. In this case, as shown in FIG. 3B, the angle formed by the direction of the principal stress due to the A roll or the B roll and the x-axis is [sin ^-1 {(D ₁ / D ₂ ) sin θ} + θ + 2 ν], respectively. It is expressed as / 2.

The compressive stress σ applied to the powder differs depending on whether the powder is in the slip section or the nip section. The following equation (1) shows the general equation of dσ / dx when the powder is in the slip section when the above assumption is made. The following equation (2) represents the general equation of dσ / dx when the powder is in the nip section when the above assumption is made.

However,
r is the ratio of the roll speed of the high speed roll to the roll speed of the low speed roll,
G is the gap between non-constant velocity rolls,
σ is the compressive stress acting between non-constant velocity rolls,
dσ / dx is the rate of change of σ (the slope of σ with respect to the x-axis) when the direction perpendicular to the line connecting the centers of the non-constant velocity rolls is the x-axis.
C ₀ is an arbitrary constant.

When equations (1) and (2) are drawn with θ on the horizontal axis and dσ / dx on the vertical axis, the coordinates (θ, dσ / dx) of the intersections of the two equations can be obtained. Θ at this intersection is the nip angle α.
Here, the compression coefficient K of the powder can be obtained from the relationship between stress and volume, which can be obtained from the powder compression test. The internal friction angle δ of the powder and the wall surface friction angle φ of the powder can be obtained by a powder layer shear test. Further, the looseness density ρ can be determined by a well-known method (for example, a method of measuring using a measuring cylinder).
Therefore, given the powder properties (K, δ, φ, ρ), D ₁ , D ₂ , r, and G, the nip angle α can be obtained from the intersection of equations (1) and (2). it can.

[4.3. Calculation of estimated powder amount W _{calc, a} and estimated weight W _c ']
In the compression of powder using a non-constant velocity roll, assuming that the product of looseness density ρ and minute volume V _α and the amount of powder W _{calc, a} are equal, the following equation (3) is derived. Therefore, by substituting the nip angle α into the equation (3), the powder amount W _{calc, a} under the given conditions can be obtained. Furthermore, W _calc, by substituting the equation (4) to _a, basis weight of the estimated value W _c 'is obtained.
Note that ΔL in the equation (3) is a variable that determines the number of divisions of the integration interval when calculating the powder amount W _{calc, a} . The smaller the value of ΔL, the more accurate the powder amount can be calculated, but if it is too small, the calculation takes time. Therefore, it is preferable to set ΔL in the range of 0.05 mm <ΔL <0.5 mm.

However,
H is the coating width,
ΔL is a minute length.

[4.4. Calculation of fixed roll speed ratio and fixed gap]
Basis weight of the estimated value W _c 'when is calculated, W _c' for comparing the target value W _c of the basis weight. Then, the deviation between the W _c 'and W _c epsilon, when the epsilon Noshiiki value was epsilon _c, when an epsilon ≦ epsilon _c or epsilon <epsilon _c is the r and G at that time, _{Let the} fixed roll speed ratio r _f and the fixed gap G _f , respectively. The optimum value of ε _c can be selected according to the required coating accuracy.

On the other hand, when ε> ε _c , the same applies until ε ≤ ε _c , or when ε ≥ ε _c , ε <ε _c , by changing the roll speed ratio r and / or the gap G. Repeat the calculation. As a result, when a combination of r and G such that ε ≦ ε _c or ε <ε _c is found, r and G at that time are set to r _f and G _f , respectively. Further, when r _f and G _f are calculated, the powder is applied under these conditions. As a result, the powder can be applied to the surface of the base material with a predetermined coating accuracy.

[4.5. Conditions change]
In the wet powder coating apparatus according to the present invention, the roll speed ratio r and the gap G can be changed. However, in general, the changeable range of r and G is limited. Therefore, even if all possible combinations of r and G are calculated, it may not be possible to find a combination of r and G such that ε ≦ ε _c or ε <ε _c .

In such a case
(A) A roll diameter D ₁ , B roll diameter D ₂ , and / or roll speed ratio r _BC ,
(B) Properties of the powder (that is, the compression coefficient K of the powder, the internal friction angle δ, the wall friction angle φ, and / or the looseness density ρ), or
(C) Target value of basis weight W _c
Any one or more of the above may be changed and the same calculation may be repeated.

When changing the conditions, which parameter should be prioritized can be arbitrarily selected according to the purpose. Generally, it is easiest to change the roll diameters D ₁ , D ₂ , and roll rate ratio r _BC , so it is preferable to change D ₁ , D ₂ , and / or r _{BC first} . If the optimum conditions cannot be found even after changing D ₁ , D ₂ , and r _BC , it is preferable to change the properties of the powder next. Nevertheless, when the optimum conditions cannot be found, it is preferable to change the target value W _c of the basis weight.

[4.6. Other calculation methods]
Alpha described above and W _c 'calculation method is one in which an improvement Johanson method (see Non-Patent Document 1), alpha and W _c' can also be calculated by other methods.
As another calculation method of α and / or W _c ', for example,
(A) Method using the slab method (see References 1 and 2),
(B) Method obtained by simulation using FEM or DEM,
(C) Method of statistically predicting using machine learning,
and so on.

Of these, the slab method requires the nip angle to be determined experimentally. The simulation method takes too much time to calculate. In addition, machine learning methods require large amounts of experimental data. On the other hand, the above-mentioned calculation method does not have such a drawback, and is therefore suitable as a calculation method for α and W _c '.
[Reference 1] Katashinskii VP and Shtern, MB, Stress-Strained State of Powder Being Rolled in the Densificatiion Zone. I. Mathematical Model of Rolling in the Densificfation Zone. Poroshkovaya Metallurgiya, 1983, 11 (251), pp. 17- twenty one
[Reference 2] Katashinskii VP and Shtern, MB, Stress-Strained State of Powder Being Rolled in the Densification Zone. II Distribution of Density, Longitudinal Strain and Contact Stress in the Densification Zone. Poroshkovaya Metallurgiya, 1983, 12 (252), pp. 9-13

[5. Wet powder coating device control program]
FIG. 4 shows a flow chart of a wet powder coating apparatus control program according to the present invention. FIG. 5 shows a continuation of the flow chart shown in FIG.
First, in step 1 (hereinafter, simply referred to as “S1”), the operator is asked to (a) the compression coefficient K of the wet powder, the internal friction angle δ, the wall surface friction angle φ, and the looseness density ρ.
(B) The target value W _c of the basis weight of the wet powder that is compressed by the consolidation roll and the holding roll and transferred to the surface of the substrate by the transfer roll, and
(C) the diameter D ₁ of the compaction rolls, the diameter D ₂ of the holding roll, and the ratio r _BC roll velocity V _C of the transfer roll relative to the roll velocity V _B of the holding roll _{(= V C / V B>} 1)
Is requested, and these input variables are stored in the memory (procedure A).

Next, in S2, the initial value "1" is substituted for the variable (variable representing the number of selectable Gs) m used when exploring the gap G. Next, in S3, the initial value "1" is substituted for the variable (variable representing the number of selectable r) n used when searching for the roll speed ratio r. Further, in S4, the nth (here, the first) numerical value r _n is substituted for the roll speed ratio r. Similarly, the m-th (here, the first) numerical value G _m is substituted for the gap G.

Next, in S5, the nip angle α corresponding to the given roll speed ratio r and the gap G is calculated based on the input variable, and this is stored in the memory (procedure B).
Specifically, the calculation of α
(A) The above-mentioned equations (1) and (2) are stored in the memory in advance.
(B) With the given roll speed ratio r and gap G, the coordinates (θ, dσ / dx) of the intersections of equations (1) and (2) are obtained.
(C) The θ at the intersection is stored in the memory as the nip angle α.
It is done by.
The details of the method for calculating α are as described above, and thus the description thereof will be omitted.

Next, in S6, the input variables, and based on the α was calculated, 'calculates, W _c' basis weight of the estimated value W _c is stored in the memory (Step C).
Specifically, the calculation of W _c'is
(A) The above-mentioned equations (3) and (4) are stored in the memory in advance.
(B) By substituting α into the equation (3), the estimated powder amount W _{calc, a} is calculated.
(C) W _calc, by substituting the equation (4) and _a, to calculate the basis weight of the estimated value W _c ',
(C) This is performed by storing the calculated W _{c'in the} memory.
The details of the calculation method of W _c'are as described above, and thus the description thereof will be omitted.

Next, the process proceeds to S7. In S7, when the deviation between the estimated value W _{c'of the} basis weight and the target value W _c of the basis weight is ε and the threshold value of ε is ε _c , ε ≤ ε _c (or ε <ε). It is determined whether or not _c ). When ε> ε _c (or ε ≧ ε _c ) (S7: NO), change r and / or G until ε ≦ ε _c (or ε <ε _c ) to change α. The calculation (procedure B) and the calculation of W _c '(procedure C) are repeated (procedure D).

Specifically, when ε> ε _c (or ε ≧ ε _c ) (S7: NO), the process proceeds to S10. In S10, it is determined whether or not the variable n is less than the maximum value n _max . When n is less than n _max (S10: YES), it means that r that can be selected remains. In such a case, the process proceeds to S11, and 1 is added to the variable n. After that, it returns to S4. Then, the calculation of α (S5) and the calculation of W _c '(S6) are repeated based on the newly selected nth r _n and other variables stored in the memory.
On the other hand, in S10, when n is not less than n _max (S10: NO), it means that no selectable r remains. In such a case, the process proceeds to S12.

In S12, it is determined whether or not the variable m is less than the maximum value m _max . When m is less than m _max (S12: YES), it means that selectable G remains. In such a case, the process proceeds to S13, and 1 is added to the variable m. After that, it returns to S3. Then, the calculation of α (S5) and the calculation of W _c '(S6) are repeated based on the newly selected m-th G _m and other variables stored in the memory.
In the examples shown in FIGS. 4 and 5, the search for r is performed first, and then the search for G is performed, but the search order may be reversed.

Given roll diameters D ₁ , D ₂ , roll velocity ratio r _BC , and powder properties (K, δ, φ, ρ), r ε ≤ ε _c (or ε <ε _c ) When a combination of and G is found, the process proceeds to S8, and r and G at that time are set as a fixed roll speed ratio r _f and a fixed gap G _f , respectively, and these are stored in the memory (procedure E). Further, the process proceeds to S9, and the coating is performed under the determined conditions.
On the other hand, when all the combinations of r and G cannot be found even if the combination of ε ≦ ε _c (or ε <ε _c ) is found (S10: NO, S12: NO), To the operator
(A) Changes to D ₁ , D ₂ , and / or r _BC ,
(B) Change of powder properties (K, δ, φ, and / or ρ), and
(C) One or more selected from the group consisting of changes in W _c is obtained, and steps B to E are repeated based on the changed variables (step F).

Specifically, when the combination of r and G such that ε ≦ ε _c (or ε <ε _c ) cannot be found (S10: NO, S12: NO), the process proceeds to S14. In S14, it is determined whether or not the roll diameters D ₁ , D ₂ , and / or the roll speed ratio r _BC can be changed. If it is possible to change D ₁ , D ₂ , and / or r _BC (S14: YES), the process proceeds to S15. In S15, re-entering D _1, D _2, and / or r _BC to the operator, D _1, D ₂ which is re-entered, and / or r _BC is stored in the memory. After that, it returns to S2. Then, each step of S2 to S15 described above is repeated until a combination of r and G such that ε ≦ ε _c (or ε <ε _c ) is found (procedure F1).
On the other hand, if D ₁ , D ₂ , and r _BC cannot be changed, or even if D ₁ , D ₂ , and r _BC are changed, ε ≤ ε _c (or ε <ε _c ). If it cannot be found (S14: NO), the process proceeds to S16.

In S16, it is determined whether or not the powder properties can be changed. If the powder properties can be changed (S16: YES), the process proceeds to S17. In S17, the operator is requested to re-input K, δ, φ, and / or ρ, and the re-input powder properties are stored in the memory. After that, it returns to S2. Then, each step of S2 to S17 described above is repeated until a combination of r and G such that ε ≦ ε _c (or ε <ε _c ) is found (procedure F2).
On the other hand, when the powder properties cannot be changed, or when the combination of ε ≤ ε _c (or ε <ε _c ) or less cannot be found even after changing the powder properties (S16: NO). Proceeds to S18.

In S18, it is determined whether or not W _c can be changed. If W _c can be changed (S18: YES), the process proceeds to S19. In S19, the operator is requested to re-input W _{c, and} the re-input W _c is stored in the memory. After that, it returns to S2. Then, each step of S2 to S19 described above is repeated until a combination of r and G such that ε ≦ ε _c (or ε <ε _c ) is found (procedure F).
On the other hand, if W _c cannot be changed, or if a combination such that ε ≤ ε _c (or ε <ε _c ) cannot be found even after changing W _c (S18: NO), the coating is applied. It means that the target cannot be achieved only by changing the construction conditions. In such a case, the process proceeds to S20, an error is displayed, and the control is terminated.

[6. Action]
By using a coating device in which three non-constant velocity rolls having the same diameter are arranged in a horizontal row, the granulated powder can be continuously coated on the surface of the base material. However, with the conventional coating apparatus, it is difficult to accurately control the basis weight of the granulated powder on the surface of the base material. Further, the conventional method cannot be directly applied to non-constant velocity rolls having different diameters.

On the other hand, when the formulas (1) and (2) are used, when the wet powder is compressed by using non-constant velocity rolls (consolidation roll and holding roll) having different diameters, the roll velocity ratio is r. It is possible to obtain the nip angle α when there is and the gap is G. Also, alpha when is found from equation (3) and (4), it is possible to calculate the estimated value W _c 'of basis weight corresponding to the alpha.
Therefore, the diameter D ₁ of the compaction rolls, the holding roll diameter D _2, a roll speed ratio r _BC, and properties of the wet powder (K, δ, φ, ρ ) in the case where given, roll speed ratio r and repeating the calculation by changing the gap G, it is possible to obtain the optimum coating conditions W _c 'is equal to W _c (i.e., combination of r and G needed to obtain a W _c).

Also, under the given conditions, even if the optimum coating conditions could not be found, D ₁ , D ₂ , and / or r _BC were changed and the type of wet powder was changed (ie, K, Optimal coating conditions can be obtained by changing δ, φ, and ρ) or by changing W _c and repeating the same calculation.

Once the physical properties of the powder (internal friction angle δ, wall friction angle φ, compression coefficient K, looseness density ρ) are known, the optimum process conditions (roll speed ratio r, gap G) for realizing W _c with that material are known. ) Can be specified from the theoretical formula. If coating is performed under the specified conditions, an electrode having a basis weight (weight per unit area) corresponding to W _c can be produced. Conventionally, when wet powder is applied using non-constant velocity rolls having different diameters, a method of calculating the amount of powder supplied between the rolls from the powder characteristics and process conditions is not known. According to the present invention, the optimum coating conditions for coating a specific material with a certain basis weight W _c can be calculated in the shortest time.

(Examples 1 and 2)
[1. Test method]
The wet powder coating device 10 shown in FIG. 1 was used to coat the surface of the base material with the wet powder. In order to keep the nip angle α constant, the same powder was used, and coating was performed by changing only the rotation speed of the A roll. As the wet powder, a powder having a solid content volume concentration of 56 vol% was used. The rotation speed of the B roll was 2.5 rpm, and the rotation speed of the C roll was 6.1 rpm. Aluminum foil was used for the substrate. Further, the diameter D _{1 of the} A roll <the diameter D _{2 of the} B roll <the diameter D'of the C roll. The gap G was set to 60 μm (Example 1).
Further, the coating was performed under the same conditions as in Example 1 except that the rotation speed of the B roll was set to 2.7 rpm (Example 2).
After coating, the electrode was punched to a diameter of 16 mm, and the weight of the electrode (weight) was measured. Furthermore, using the foregoing equation (1) to (4) to calculate the basis weight of the estimated value W _c '.

[2. result]
FIG. 6A shows wet conditions under the condition that A roll diameter <B roll diameter <C roll diameter, and the rotation speed of B roll, the rotation speed of C roll, and the gap G between A and B rolls are constant. The relationship between the rotation speed of the A roll and the amount of electrode grain when the powder is applied is shown (Example 1). FIG. 6B shows the rotation speed of the A roll and the basis weight of the electrodes when the wet powder was applied under the same conditions as in the first example, except that the rotation speed of the B roll was made faster than that of the first embodiment. Relationship (Example) 2 is shown.
From FIG. 6, it can be seen that the calculated values can reproduce the tendency of the experimental values. However, the experimental values do not completely match the calculated values. It is considered that this is because the looseness density ρ of the powder at the nip angle α is assumed to be 1.0. Since the looseness density of the powder is actually about 0.7, it is considered that the looseness density of the powder at the nip angle α is 1.0 or less. Therefore, it is considered that the calculated value of the basis weight is calculated to be larger than the measured value.
From the above results, it was found that the supply amount can be predicted in the film formation of wet powder using rolls having different diameters by using the method according to the present invention.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

The wet powder coating device control program, the wet powder coating device, and the method for manufacturing a coating film according to the present invention can be used for manufacturing electrodes of a lithium secondary battery.

Claims (7)

A wet powder coating device control program that allows a computer to perform the following steps:
(A) To the operator
(A) Compression coefficient K of wet powder, internal friction angle δ, wall friction angle φ, and looseness density ρ,
(B) The target value W _c of the basis weight of the wet powder, which is compressed by the consolidation roll and the holding roll and transferred to the surface of the base material by the transfer roll, and
(C) The diameter D _{1 of the} consolidation roll, the diameter D _{2 of the} holding roll (where D ₂ / D ₁ ≧ 1.01), and the roll speed V of the transfer roll relative to the roll speed V _B of the holding roll. Ratio of _C r _BC (= V _C / V _B > 1)
Procedure A in which the input of is requested and these input variables are stored in the memory.
(B) The roll speed ratio r is the ratio of the roll speed V _B of the holding roll to the roll speed V _A of the compacted roll (= V _B / _VA > 1), and the gap G is defined as the compacted roll and the holding. Step B to calculate the given roll speed ratio r and the nip angle α corresponding to the gap G based on the input variable when the gap with the roll is set, and store this in the memory. ..
(C) the inputted variables, and based on the calculated alpha, the basis weight of the 'calculates the W _c' estimate W _c procedure to store in the memory C.
(D) the difference between the W _c 'and the W _c epsilon, in case of the threshold epsilon _c of the epsilon, until epsilon ≦ epsilon _c when a epsilon> epsilon _c, or, When ε ≧ ε _c , the procedure D in which the r and / or the G is changed and the procedure B and the procedure C are repeated until ε <ε _c .
(E) When ε ≦ ε _c or ε <ε _c , the r and the G at that time are set as the fixed roll speed ratio r _f and the fixed gap G _f , respectively, and the procedure E for storing these in the memory. .. In step B,
The following equations (1) and (2) are stored in the memory in advance.
With the given roll speed ratio r and the gap G, the coordinates (θ, dσ / dx) of the intersections of the equations (1) and (2) are obtained.
The wet powder coating apparatus control program according to claim 1, wherein θ at the intersection is stored in the memory as a nip angle α.

However,
r is the ratio of the roll speed V _B of the holding roll to the roll speed V _A of the consolidation roll (= V _B / V _A > 1).
G is the gap between the consolidation roll and the holding roll.
σ is the compressive stress acting between the consolidation roll and the holding roll.
dσ / dx is the rate of change of the σ when the direction perpendicular to the line connecting the centers of the consolidation roll and the center of the holding roll is the x-axis.
C ₀ is an arbitrary constant. The procedure C is
The following equations (3) and (4) are stored in the memory in advance.
By substituting the α into the equation (3), an estimated value W _{calc, a} of the amount of powder passing between the consolidation roll and the holding roll was calculated.
Wherein W _calc, by substituting the equation _a (4), to calculate the basis weight of the estimated value W _c ',
The wet powder coating apparatus control program according to claim 2, wherein the W _c'is stored in the memory.

However,
H is the coating width,
ΔL is a minute length,
V _α is a minute volume of the wet powder that passes through the position of α when the holding roll advances by ΔL at the position of α. The wet powder coating apparatus control program according to any one of claims 1 to 3, further comprising the following procedure.
(F) If the condition that ε ≦ ε _c or ε <ε _c cannot be found even after searching for all the combinations of r and S, the operator (a) Changes to D ₁ , D ₂ , and / or r _BC ,
(B) Changes to K, δ, φ, and / or ρ, and
(C) A procedure F in which any one or more selected from the group consisting of changes in W _c is obtained, and the steps B to E are repeated based on the changed variables. Wet powder coating equipment with the following configurations.
(1) The wet powder coating device is
With a consolidation roll for compressing wet powder,
A holding roll for holding a molded product made of the compressed wet powder, and
A transfer roll for transferring the molded product adhering to the surface of the holding roll to the surface of the base material,
A drive device for rotating the consolidation roll, the holding roll, and the transfer roll in opposite directions and at the same time adjusting the gap between the rolls.
A wet powder supply device for supplying wet powder to the gap G between the consolidation roll and the holding roll,
A base material supply device for supplying a base material to the transfer roll, and
It is provided with a control device for controlling the operation of the wet powder coating device.
(2) The diameter of the consolidation roll is D ₁ , and the diameter of the holding roll is D ₂ (where D ₂ / D ₁ ≧ 1.01).
(3) the drive roll speed V _A of the compaction rolls, the roll speed V _B of the holding roll, a roll speed of said transfer roll when the _{V C, V A <V B} <V C The compaction roll, the holding roll, and the transfer roll can each be rotated at a non-constant speed so as to be such.
(4) The wet powder coating device control program according to any one of claims 1 to 4 is stored in the memory of the control device. A method for producing a coating film in which a wet powder is applied to the surface of a base material by using the wet powder coating apparatus according to claim 5. The method for producing a coating film according to claim 6, wherein the wet powder contains an active material for a secondary battery, a conductive material, a binder, and a solvent.

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