JPS61268383A - Method for control of coating film - Google Patents

Abstract

PURPOSE:To facilitate control, by setting two conditions among three conditions of the amount of supplied air, the temp. of supplied air and the amount of a coating solution in order to set the temp. of exhaust gas to a predetermined amount and calculating the residual one by the heat quantity calculation formula in a heat insulating cooling system based on two set values. CONSTITUTION:In performing the automatic film coating of a tablet, a worker inputs coating conditions. That is, the objective value of exhaust temp. t2, two conditions, for example, the temp. t1 of supplied air and the amount W of a coating solution among three conditions, the ratio (s) of the solvent in the solu tion, the latent heat (r) of evaporation of the solvent and the spray set amount of the solution are inputted. By using these set values, the amount V of supplied air is calculated by formula I and, if the calculated amount V of supplied air is an operable value, coating is performed under the set and calculated conditions. A control apparatus 10 always measure the values on the basis of the outputs of detectors during coating and a coating state is monitored by using the actually measured values.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is intended for use in film coating by spraying a coating liquid onto an object to be coated, such as a tablet or granule, and using ventilation so that the exhaust temperature reaches a predetermined value. Air supply 1! This invention relates to a method of controlling three conditions: I amount, supply air temperature, and coating liquid amount.

Conventional Technology When coating tablets with a film by spraying a coating liquid and using ventilation, the exhaust temperature is an important factor that affects the quality and yield of the product. For this reason, in the past, the target value for the exhaust gas temperature was first determined, and the three conditions of supply air volume, supply air temperature, and coating liquid amount were empirically set so that the exhaust temperature reached the target value, and the condition of the film coating was determined. The monitoring is done by humans. In addition, if it is necessary to change the target value of the exhaust temperature or any of the above three conditions during film coating, determine each condition after the change empirically, and determine the necessary conditions during the process. Manual control is used to change the conditions, or sequence control is used to automatically change the necessary conditions.

Problems to be Solved by the Invention However, in the conventional method, it is necessary to determine in advance the three conditions of supply air flow rate, supply air temperature, and coating liquid amount with respect to the target value of exhaust temperature. If any of the above three conditions is changed, the remaining conditions will also change, so these must be determined separately. therefore,
It is difficult to variously change the target value of the exhaust temperature or the above-mentioned conditions, and it is not always possible to perform film coating under suitable conditions.

In addition, unmanned operation is impossible because the state of the film coating is monitored by humans.

The purpose of this invention is to set a target value of exhaust temperature or supply air volume,
It is an object of the present invention to provide a method that allows film coating to be performed under suitable conditions by appropriately selecting three conditions: supply air temperature and coating liquid amount.

In addition to this, it is an object of the present invention to provide a method by which the state of film coating can be automatically monitored.

Means for Solving the Problems The method according to the first invention is such that when spraying a coating liquid onto an object to be coated and performing film coating by ventilation, the amount of air supplied and the amount of air supplied are adjusted so that the exhaust temperature reaches a predetermined value. This is a method of controlling the three conditions of temperature and coating liquid volume, in which two of the three conditions above are set, and the remaining one condition is determined based on these set values using a formula for calculating the amount of heat in the adiabatic cooling system. This method is characterized in that the image coating is performed under the conditions set and ffi calculated in this way.

In addition to the above, the method according to the second invention provides air supply ffl! at room temperature and on the exhaust side during film coating. , measure the supply air temperature and coating liquid volume, calculate the amount of heat in the adiabatic cooling system based on these measured values, and use these measured values and calculation results to monitor the state of the film coating. This is a characteristic feature.

As a result of repeated research on film coating of tablets, the inventors discovered that the formula for calculating the amount of heat in a ml thermal cooling system in the unit operation of drying also applies to film coating of tablets, and completed this invention.

That is, if the amount of heat (total heat dissipation) lost by the supply air during film coating is Q + (cal/5ec), this is expressed by the following equation (1).

Q+=(j+j2)・V−R...(1) Here,
t, ('C) is the supply air temperature, i2 (℃) is the exhaust side L V
(1/5 ec) is the supply air volume, and R (cal/°C./) is the heat capacity of the air. Note that the supply air volume is controlled to be approximately equal to the exhaust air volume.

The amount of heat required to dry the solvent in the coating liquid (
If the drying heat amount) is 02 (cal/5ec), this is expressed by the following equation (2).

Q2 = W-8-r/60 +・(2) where W (0/5in) is the amount of coating liquid, S is the ratio of solvent in coating liquid, r (cal/(1) is the latent heat of vaporization of solvent It is.

Not all of the heat in the supplied air is used to dry the solvent, but is lost due to heat radiation from the film coating equipment, etc. The amount of heat lost is Q a (cal/5ec
), this should be theoretically determined by the following equation (3) as stated in the usual literature.

Q3-h-A・Δt...(3) Here, n (cal 7 2nd - sec - °C) is the overall heat transfer coefficient, A (2nd) is the surface area, and Δt is the temperature difference (room temperature standard)
It is.

However, in reality, it is difficult to actually measure the overall heat transfer coefficient and the surface area A.

Therefore, the inventors put effort into finding a realistic way to find the amount of heat loss Q3, and found it in the following manner.

Note that this does not determine the absolute value of the amount of heat loss Q3.

That is, first, the supply air volume (2) is kept constant, and the supply air temperature 11 is varied without spraying the coating liquid to determine the exhaust temperature t2 under each condition and the room temperature 1-. o
(°C). And the amount of heat dissipation Q in each article +1
is calculated using equation (1). This heat radiation amount Q is the loss heat ff
Corresponds to 1Qa. Next, the average temperature difference T
1 - Calculate 4 using the following formula.

"1m-(t+j2)/In(↑l/i2) and the temperature difference (T1
1to) and the amount of heat dissipation Q in rectangular coordinates.

Next, air supply I! The above operation is repeated by changing the l amount v, and a relational expression for each supply air V is determined.

By inputting the relational expression for each supply air flow rate obtained in this way into the storage device, it is possible to calculate the average temperature difference T from the supply air temperature t and the exhaust air temperature t2 during actual film coating.
1m, and calculate the supply air volume (■), the average temperature difference TI-, and the room temperature t. The heat loss IQ3 can be determined from these relational expressions.

According to the measurement results of the inventors, when the supply air volume V is constant, the amount of heat loss Q3 can be approximated by the following equation (4).

C3=f・(T 1m ”o) ・・・(
4) f is a function of the supply air volume V, and when these are plotted on rectangular coordinates, it can be approximated by the following equation.

f=c, ・V + 02 C+ and C2 are constants, and when f is substituted into equation (4), the following equation (5) is obtained.

Qa = (C+ ・V+C2)' (Tl, jo
)...(5) In addition, in the film coating apparatus used by the inventors, C4 was 0.02712 and C2 was 3°98.

The above method does not determine the absolute value of the heat loss IQ3, but can be approximated by using the exhaust temperature II'j2 instead of the average drying surface difference T1. In this case, the amount of heat loss Q3 is expressed by the following equation (6).

C3-(C3・V104)・(12-1o)...(6
) In the device used by the inventors, C3 is 0°0255
3.C4 was 5.16.

If film coating is proceeding smoothly,
The following equation (7) holds true.

Q2=QI Qa (7) Then, by substituting equations (1), (2), and (6) into equation (7), the following equation (8) is obtained.

W-s -r/6O-(t+j2)・V-R-(C3・V104)・(t2-to)...
(8) In equation (8), the ratio S of the solvent in the coating liquid is a constant value determined by the type of coating liquid.

The latent heat of vaporization r of the solvent in the coating liquid is determined by the type of solvent and the supply air temperature t. For example, when water is used as a solvent, the latent heat of vaporization r is determined by the supply air temperature t,
When the supply air temperature t1 is set first, the latent heat of evaporation r can be determined in advance using a humidity chart or the like. Further, when an aqueous ethyl alcohol solution is used as a solvent, the latent heat of vaporization r of water and ethyl alcohol is obtained by determining the respective latent heats of vaporization and sieving them using a weight ratio. Also in this case, when the supply air temperature t1 is set first, the latent heat of vaporization r can be determined in advance. The heat capacity IR of air is determined by the supply air temperature t1 and the absolute humidity, and when the supply air temperature t is set in advance, the heat capacity IR can be determined in advance. Room temperature to is usually held constant and can also be measured during film coating.

Therefore, the target value of the exhaust gas temperature t2 is determined, the remaining supply air 1!1fflV, the supply air temperature t, and the coating liquid M.
By setting two conditions out of the three conditions of W (hereinafter simply referred to as 3 conditions f1), the remaining conditions can be calculated from equation (8).

If film coating is not performed normally, equations (7) and (8) do not hold. For example, is the coating regulation inappropriate or the solvent drying inappropriate? In such a case, the following equation (9) is obtained.

Q2 > Ql - Qa ... (9)
Therefore, by measuring room temperature to, exhaust temperature t2, supply air volume V1, supply air temperature t1, and coating liquid ff1W during film coating, and comparing Q2 calculated using these and (Q, -03), The condition of the film coating can be monitored.

Embodiment FIG. 1 shows the main parts of an automatic film coating device for tablets and its control device (10). The coating device is equipped with a horizontal drum (11) with a large number of ventilation holes (as shown) in the peripheral wall. Rotates around the axis.

A spray gun (13) for spraying the coating liquid onto the tablets (12) is arranged inside the drum (11), and the coating liquid is supplied to the coating liquid supply pipe (14) connected to the spray gun (13). Valve for adjusting the amount (
(Illustrated path) is provided. This valve is controlled by the control lI device (
10) is automatically controlled. Furthermore, the coating liquid supply pipe (14) is provided with a liquid amount detector (16) for detecting the amount of coating liquid, and its output signal line is connected to the control device (
10). A supply cylinder (17) for supplying hot air for drying into the drum (11) and an exhaust pipe (18) for discharging hot air from inside the drum (11) are provided in a position close to the peripheral wall of the drum (11). , these tubes (1701
8) is provided with a fan and a damper (path shown) for adjusting the air volume. These are automatically controlled by the control device (10) so that the supply air [1 and the exhaust air volume are approximately equal to each other. The supply cylinder (17) is equipped with a supply air temperature detector (19), a supply air flow rate detector (23), and an exhaust pipe (18).
) is equipped with an exhaust temperature detector (20) and an exhaust air flow rate detector (24).
), and a coating chamber (2
1) is provided with a room temperature detector (22). And these detectors (19N2ON22H23) (24
) is also connected to the control device (10).

In addition to hot air, indoor air or cold air may be supplied into the drum (11) for drying purposes.

Control equipment m! (10) uses a microcomputer or the like, and the coating conditions are controlled, for example, as follows (see FIGS. 2 and 3).

First, before coating, a message is output to prompt the operator to input coating conditions (step 10).
1).

Next, the operator selects the target value of the exhaust temperature t2, two of the three conditions, for example, the supply air temperature t1 and the coating liquid amount W, the ratio of the solvent in the coating liquid S1, the latent heat of vaporization r of the solvent, and the period until the end of coating. Enter the setting amount etc. of the coating liquid to be sprayed on the surface (step 10).
2).

Next, the air supply air pressure ■ is calculated using equation (8) using the above set values (step 103).

Next, in step 1, it is necessary to judge whether the supply air volume ■ calculated in step 103 can be generated in the actual coating equipment.
04), if this is not possible, return to step 101 and repeat the above operation, and if possible, perform coating under the conditions set and calculated in this way (step 105).

During coating, the control device (10) detects the detector (16)-
1Q - From the output of (19) (20) (22) (23), coating liquid amount W1, supply air temperature t1, exhaust temperature t2, room temperature t. and the supply air volume ■ are constantly measured, and the coating condition is monitored using these measured values as follows.

First, Ql, Q2, and Q3 are calculated from equations (1), (2), and (6) using the above measured values (step 201).

Then, the state of the coating is determined based on the comparison between the target value and the measured value of the exhaust temperature t2, the comparison between Q2 calculated using the measured value and (Q, -03), the change in the exhaust temperature t2, etc. The presence or absence of an abnormality or the possibility of an abnormality occurring is checked (step 202). In this case, for example, when formula (9) is obtained, tablet (12) is already present.
In order to prevent problems, it is preferable to check, for example, the rate of change of Q2/(QI-03).

If the result of the determination in step 202 is normal, it is checked whether coating has been completed (step 203). This is done by comparing the accumulated value of the coating liquid amount from the start of coating with the set amount of coating liquid sprayed, and returns to step 201 and repeats the above operation until the accumulated value reaches the set amount. . When the integrated value reaches the set value, coating is finished and a completion message is output to the operator (step 1).
06).

If the result of the judgment in step 202 is that it is abnormal, it is judged whether or not it is possible to correct the three conditions in the actual coding device (step 204). If it is possible, at least one of the three conditions Modify the conditions (step 205). This correction is performed in the order of first the supply air volume ■, then the supply air volume th, and the coating liquid volume W.
Normally, the supply air volume is set so that the exhaust temperature t2 becomes the target value.
control. Then, the process returns to step 203 and the same operation as above is performed.

If it is not possible to modify the three conditions in the actual coating equipment, first of all, stop spraying the coating liquid, maximize the supply/exhaust flow rate, raise the supply air temperature, etc.
All possible operations necessary to avoid the defective products in step 2) are performed (step 206), an alarm is issued and an abnormality message is output (step 207), and the coating is completed.

Note that it is also possible to automatically proceed to the next step when film coating is successfully completed.

In the above embodiment, the supply air volume is reduced by setting the supply air temperature and the coating liquid volume among the three conditions, but the supply air temperature can be calculated by setting the supply air volume and the coating liquid volume. Alternatively, it is also possible to calculate the coating liquid amount by setting the supply air flow rate and supply air temperature. For example, set the target value of exhaust temperature to 38℃, and set the supply air volume and coating liquid volume to 8m3/1lli each.
n and 60 (1/n+in), calculated the supply air temperature so that the exhaust temperature would reach the target value, and performed film coating while changing the set value of the supply air temperature as necessary. As shown in FIG. 4, the exhaust temperature was maintained at approximately the target value, and the film coating was in good condition.

Furthermore, the target value of the exhaust gas temperature or the set values of two of the three conditions can also be changed during the process.

In this case, the target value of the exhaust gas temperature after the change, the set values of the two conditions, and the change timing are input into the control device (10) in advance.

When the time for change is reached, the remaining conditions are calculated in the same manner as above using these target values and set values, and coating is continued under the conditions set and calculated in this way. In addition, the state of the coating after the change is monitored in the same manner as above.

Note that it is of course possible to perform such changes two or more times during coating.

Further, in the above embodiment, control is performed so that the supply air volume 1!1ffi and the exhaust air volume are approximately equal, but the method according to the present invention can also be applied to cases where the supply air volume and the exhaust air volume are different.

Effects of the Invention According to the first invention, when spraying the coating liquid onto the object to be coated and performing film coating by ventilation, the supply air volume, supply air temperature, and coating liquid volume are adjusted so that the exhaust temperature becomes a predetermined value. This is a method of controlling the three conditions described above, in which two of the three conditions are set, and the remaining one condition is calculated based on these set values using the formula for calculating the amount of heat in the adiabatic cooling system. Since film coating is performed under conditions set and calculated using However, the remaining conditions can be easily determined, so that it is possible to appropriately select these conditions and perform film coating under suitable conditions. Furthermore, since the calorific value formula is used to calculate the conditions, it is not only possible to use water as the solvent for the coating liquid.
It can also be applied when using an organic solvent.

According to the second invention, in addition to the above, the room temperature, exhaust temperature, air supply air volume, supply air temperature, and coating liquid amount are measured during film coating, and the adiabatic cooling system is adjusted based on these actual measured values. Calories are calculated at , Therefore, unmanned operation of the film coating apparatus becomes possible.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram showing the main parts of an automatic film coating apparatus and its control device, and FIGS. 2 and 3 show the operation of the control device, that is, one of the methods of the present invention. FIG. 4 is a flowchart showing an example, and is a graph showing the measurement results of the supply air temperature and the exhaust temperature when the supply air temperature is calculated by setting the supply air flow rate and the coating liquid amount. (10)...control device, (12)...tablet, (13
)...Spray gun, (16)...Liquid level detector, (
17)... Supply cylinder, (18)... Exhaust pipe, (19)
...Intake air tli[detector, (20)...Exhaust temperature detector, (22)...Room temperature detector, (23)...Intake air 1! II detector, (24)...Exhaust J! 1m detector. Figure 2: 4 people other than the above

Claims (3)

[Claims] (1) A method of controlling the three conditions of air supply air volume, air supply temperature, and coating liquid volume so that the exhaust temperature reaches a predetermined value when spraying the coating liquid onto the object to be coated and performing film coating by ventilation. Therefore, two of the three conditions above are set, and the remaining one is calculated using the formula for calculating the amount of heat in the adiabatic cooling system based on these set values.
1. A method for controlling film coating, comprising calculating two conditions and performing film coating under the thus set and calculated conditions. (2) A method of controlling the three conditions of air supply air volume, air supply temperature, and coating liquid volume so that the exhaust temperature reaches a predetermined value when spraying the coating liquid onto the object to be coated and performing film coating by ventilation. Then, two of the three conditions above are set, and the remaining one is calculated using the formula for calculating the amount of heat in the adiabatic cooling system based on these set values.
Film coating is performed under the conditions set and calculated in this way, and during film coating, room temperature, exhaust humidity, air supply air volume, air supply temperature, and coating liquid volume are measured, and these actual measurements are performed. A method for controlling film coating, characterized in that the amount of heat in an adiabatic cooling system is calculated based on the value, and the state of the film coating is monitored using these measured values and calculation results. (3) Determine whether the above film coating condition is normal or abnormal based on the actual measurement values and calorific value calculation results, and if abnormal, modify the three conditions of supply air volume, supply air temperature, and coating liquid volume. If modification is possible, at least one of these three conditions shall be determined.
3. The method of controlling film coating according to claim 2, wherein one condition is corrected and, if correction is impossible, film coating is terminated.