JPS5941772A - Method of continuously drying organic solvent applied material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] It is coated with a paint such as resin or fine metal powder. The present invention relates to a method for rapidly drying a paint by heating objects of various shapes to vaporize the organic solvent in the paint.

Generally a solvent or diluent. Pigments, dyes, paints, and inks that use organic solvents as spreading materials. Surface treatment agent.

The surface of the object to be treated is coated with a coating material made of resin, fine metal powder, ceramic powder, etc. by means such as coating, spraying, electrostatic coating, impregnation, printing, etc. When drying, the organic solvent evaporates and evaporates. generates explosive gas. Such drying is usually carried out by transporting the object to be processed into a restricted space, such as a drying chamber, and irradiating the heated airflow there with pulses or infrared rays. It is necessary to suppress the organic solvent gas concentration to approximately ≠ below the lower limit of the explosion limit, and therefore the drying chamber is ventilated using an exhaust fan with a sufficiently large ventilation capacity. The organic solvent gas concentration inside the room or exhaust duct is detected, and when the concentration rises above the lower explosive limit, an alarm is issued, and at the same time, the supply of the object to be treated is stopped and the ventilation damper is automatically activated. Safety measures have been taken to reduce the concentration by opening the air.

However, in the conventional method described above, the capacity of the exhaust fan is designed based on the amount of gas generated at the maximum load of the drying room, that is, the maximum processing time assumed in the design, and the Since a method has been adopted in which the exhaust fan is constantly operated at a constant rotation speed of 5 at maximum load, the load on the drying room is reduced by changing the amount of coating or changing the supply speed of the object to be processed. In such cases, even though the amount of organic solvent gas generated naturally decreased, ventilation continued to be more than necessary. As a result, the amount of heat added to the drying chamber is wasted and is emitted outside the prefecture, which not only significantly reduces drying efficiency, but also wastes electricity to drive the exhaust fan, resulting in large economic sacrifices. The current situation is that excessive safety measures are being taken than necessary.

The present invention is the result of intensive research aimed at solving the problems of the prior art as described above, and its purpose is to significantly reduce energy consumption of heat, air, etc. , organic solvent coated materials can be continuously dried with high drying efficiency and complete safety.

That is, the method of the present invention is characterized by continuously supplying the object coated with a paint containing an organic solvent into a predetermined restricted space and heating it within the restricted space. After gasifying the organic solvent and drying the paint, in the suspender method, the object to be treated is continuously taken from all of the above-mentioned limits,
When the processing amount of the object to be treated in the restricted space reaches the maximum value 2, the concentration of the solvent gas generated under elevated temperature from the organic solvent carried along with the VC@processing object is sufficiently higher than the lower explosive limit value. The air flow rate 2 flowing through the restricted space 2 is predetermined so as to be an appropriate value set low, and the organic solvent gas concentration inside the restricted space or in the air flow discharge part is detected and the value is set as above. The purpose is to maintain the organic solvent gas concentration in the restricted space at the set value by comparing it with the set value and controlling the air flow rate 2 in proportion to the difference between them.

The following apparatus can be used for the tMLvC of the above-mentioned method of the present invention.

That is, a drying chamber having a supply port and a discharge port 2 for the object to be treated coated with a paint containing an organic solvent gas, and a heating means for heating the object to be treated; In the continuous drying device for organic solvent gases, which includes a transfer device that continuously passes through the drying chamber, an exhaust fan is provided to exhaust the gas in the drying chamber, and the concentration of the organic solvent gas at appropriate locations in the drying chamber is further controlled. a gas detector that detects the gas concentration, a gas concentration indicator and alarm that receives a signal from the gas detector and displays the gas concentration and outputs a voltage proportional to the gas concentration, and a gas concentration indicator that rotates the exhaust fan in accordance with the output. Equipped with a gas concentration detection control mechanism consisting of a gas concentration regulator for controlling the number of particles or adjusting the damper, the organic solvent gas concentration in the drying chamber is set to be sufficiently lower than the lower explosive limit when the object to be treated is at maximum load. The rotation speed of the exhaust fan is set to an appropriate value, and during normal operation, the rotation speed of the exhaust fan is automatically controlled to maintain the organic solvent gas concentration at the set value. It is a device.

A second aspect of the present invention will be described in detail below with reference to the attached drawing 2.

The figure is a schematic diagram illustrating one embodiment of an apparatus for carrying out the method of the invention. In the figure, a drying chamber (1) is provided with a supply port (2) and a discharge port (3) for the object to be processed on its front and rear walls, respectively, and is made of glass wool.

A restricted space is defined inside by a peripheral wall covered with a heat insulating material such as rock wool. In this example, the object to be processed (
Since 4) is a continuous long sheet-like material, the supply port (2) and discharge port (3) are formed in a slit shape. If the material is to be transferred, install a conduit at each of the supply and discharge ports, and form an air curtain in the gap.
The internal restricted space can be substantially isolated from the outside. - The object to be treated (4) is fed out from the supply roll (5), coated with a paint containing organic solvent 2 by the coater (6), and then transferred from the supply port (2) into the drying chamber fil. The paper is then sent out from the discharge port (3) and wound up onto the winding roll (7). The object to be treated (4) is dried while being transported through the drying chamber (1) by adding an organic solvent 2 to the paint, but in order to dry the object in a short time, In the illustrated embodiment, the air taken out from the drying room fi+ by the air fan (8) is heated by the heater (9), and then heated to the drying room + 11 yen of the object to be processed. It is supplied to ducts +101 and [101' equipped with jetting beaks facing each other across a passage, and is blown onto the object to be processed (4) from the jetting beaks to heat the object.

The heater (9) can use a heat source such as steam, electric heat, or combustion gas, and the heating temperature of the object to be treated depends on the organic solvent, paint, type of object to be treated, and coating layer thickness.

Although it varies depending on the drying time, etc., it is usually 50°C or higher, and may reach up to 300°C.

To prevent migration, it is preferable to dry rapidly at high temperatures, but blisters may occur if the holder is kept at high temperatures for a long period of time, so the drying chamber should be divided into multiple sections in the direction of transport of the objects to be processed. We recommend a design in which the temperature is divided and the temperature is high on the inlet side, and the temperature gradually decreases toward the outlet.

It goes without saying that in addition to the heating method described above, direct heating using known infrared radiation can also be applied.

The present invention further includes an exhaust fan (11) for discharging the organic solvent gas from the vicinity of the upper part of the restricted space, that is, the drying chamber [+1] to the outside. By operating the exhaust fan, the organic solvent gas concentration in the drying chamber is maintained at a value sufficiently lower than the lower explosive limit, but a negative pressure is formed in the drying chamber and the material to be processed is supplied. Outside air flows in through the slits of the opening (2) and the discharge opening (3), which not only changes the temperature conditions in the drying chamber but also impedes the smooth running of the objects being transported, which may cause wrinkles. Therefore, in order to eliminate these inconveniences, it is necessary to take in outside air from the conduit (I2) connected to the suction side of the air supply fan (8) and supply it to the drying room (1) through the ducts Oo) and Ool'. If the temperature condition is kept normal, the negative pressure can be reduced at 1, and excessive outside air suction from the supply port (2) and the discharge port (3) can be prevented. However, if the negative pressure inside the drying chamber becomes extremely small or becomes positive, the solvent gas will leak out from the supply port (2) and discharge port (3), etc., resulting in a slight suction state. If the air curtain 2 is provided, the capacity and air suction amount of each fan may be determined so that a portion of the air flows into the drying chamber.

Furthermore, in carrying out the present invention, the organic gas is extracted by sampling the gas through the gas suction hole (13) provided at an appropriate location near the top of the drying chamber or in the exhaust duct of the exhaust fan (11). A gas detector (14) for detecting the concentration, and when receiving the signal sent from the gas detector and indicating or displaying the gas concentration, it outputs an electrical voltage proportional to the gas concentration. A gas concentration indicating alarm (15) that records the gas concentration according to the output signal, and an exhaust fan (1 G) that records the gas concentration based on the output signal. The above gas detector (0) to which a gas concentration detection control mechanism is applied, which includes a gas concentration regulator (18) that controls the rotation speed of the exhaust damper (17) and a damper adjustment of the air intake conduit (12). 1
4) is, for example, a known gas concentration detector such as a catalytic combustion type or a semiconductor type, and an ultrasonic type can also be applied depending on the case. Also, gas concentration indicator (15) a detected gas concentration O~100%K proportional, 0~l Om V,
D. Gives an output of 0. Furthermore, the gas concentration regulator (18) compares the gas concentration converted into an electric signal with a set value, and in proportion to the difference, a frequency converter connected to the exhaust fan (11) driving motor (19); That is, it acts on the inverter (20), controls the rotation speed of the exhaust fan (11) by 2, adjusts the exhaust damper (+7), and further controls the flow rate in the drying chamber. A conduit for outside air intake (
12) Also has the function of adjusting the damper.

The most distinctive feature of the present invention when using a device such as a diagonal top is that it indicates the maximum amount of objects to be processed within all of the above limits, and when the load on the drying chamber reaches its maximum, it specifies When the transport speed of the object to be treated is maximum and the amount of paint applied is the maximum, the organic solvent gas generated by heating is generated from the organic solvent brought into the drying chamber along with the object to be treated. The rotational speed of the exhaust fan and the damper are adjusted in advance so that the concentration in the drying room is sufficiently low than the lower explosive limit □, that is, an appropriate value preferably set at about 20-25% of the lower explosive limit. (17) and the opening degree of the damper of the conduit (12), the air flow rate flowing through the drying chamber is determined, and the organic gas concentration in the drying chamber is determined by the gas detector at all times during normal operation. By forming a loop that connects to the gas concentration regulator, the concentration within the dryer is always maintained at a predetermined level.

Although the concentration of organic solvent gas in the drying room is better from a safety standpoint, it should be within 1 B of the lower explosive limit; It can be said that it is sufficient if it is about 25% or less of the lower limit value.

However, when K is diluted at a high concentration, it is necessary to increase the ventilation volume of the drying room, that is, the air flow velocity flowing across the restricted space of the drying room, and as a matter of course, the power consumption increases due to the increase in the rotation speed of the exhaust fan by 2. It becomes necessary. In addition,
As the exhaust volume increases, the amount of heat released outside the drying chamber increases, which causes an inconvenient phenomenon in which the humidity of the object to be treated decreases and the drying efficiency decreases, so the gas concentration is below the lower explosive limit. From an economic standpoint, it is preferable to set it to about 20% or more.

As mentioned above, if the air flow rate, that is, the rotation speed of the exhaust fan and the damper opening when the load of the drying chamber is at its maximum, are set to correspond to the values in the gas concentration range, in most cases Is the coating amount less than the setting conditions?
Since the drying chamber is operated with a reduced supply amount of objects to be treated, the load on the drying chamber is less than the maximum value, and therefore the organic solvent gas concentration in the drying chamber is lower than the set value.

-10,000, is the gas detector the gas concentration in the drying room? directly detect,
A detection signal is sent to the gas concentration indicator and alarm, and after being converted into an electrical output by the gas concentration indicator and alarm, it is compared with the preset concentration in the gas concentration controller, and it immediately acts on the inverter according to the difference. However, in this case, the detected concentration is smaller than the set concentration by V, so the inverter acts to reduce the rotation speed of the exhaust fan motor, and the damper is rotated in the closing direction.

The organic solvent gas concentration in the drying chamber returns to the set value. Even if the concentration rises and exceeds the set value, it can be easily lowered by a slight increase in the air flow rate, since the concentration is fluctuating within a range that does not reach the maximum load of the drying chamber.

In this way, in the method of the present invention, the air flow rate is changed (reduced) in accordance with the fluctuation (reduction) in the load of the drying chamber, so that the amount of heat released from the dryer during operation is suppressed to an appropriate amount. This not only saves thermal energy and reduces running costs, but also shortens the temperature rise time during no-load conditions before starting operation, saving time and energy. Even if the system is temporarily stopped due to switching or an accident, the exhaust gas is automatically stopped, resulting in energy savings as well. Also, by controlling the exhaust air volume,
In addition to reducing the power consumption of exhaust fan motors, etc., which has a large power saving effect, the concentration of solvent gas in the exhaust gas is not unduly diluted when the exhaust gas is led to a solvent collecting device to recover the solvent. , there is also the advantage of improved recovery efficiency.

Although the method of the present invention has been described above from the economic standpoint, it is important to ensure safety when handling organic solvent gases that generate explosive gases.

In the method of the present invention, the organic solvent gas concentration at maximum load is set to be less than the lower explosive limit μ, especially about 20 to 25%, so there is a sufficient guarantee that the concentration will not exceed this value. can be said to be given. However, from the perspective of double and triple consideration for safety, in preparation for unexpected abnormal situations, the organic solvent gas concentration detected by the gas detector exceeded approximately 25% of the lower explosive limit. The gas concentration indicating alarm will immediately act on alarm devices such as buzzers and bells, emitting an alarm sound, and furthermore, the gas concentration indicator will immediately act on alarm devices such as buzzers and bells, and furthermore, about 33% of the lower explosive limit (
1/3), the gas concentration regulator acts on the transfer device of the object to be processed to reduce the transfer speed, that is, the supply speed of the object to be processed. If %L<, the gas concentration regulator either stops the drying chamber or closes the wall surface of the drying chamber. The organic solvent gas can be rapidly removed by either widening the opening, or by attempting to increase the air flow velocity (exhaust volume) beyond the set value, or by performing one or more of the above three actions. It would be desirable to devise ways to dilute it. Performing the above operations using the electrical signals or electrical outputs generated by the gas concentration indicator and alarm device and the gas concentration controller requires the use of ordinary electrical engineering design knowledge or the application of known techniques. According to the method of the present invention described in detail above, when a coated article coated with a paint containing an organic solvent is heated and dried, the vaporized organic solvent gas is removed. It is completely safe with no risk of explosion, provides high drying efficiency, and has succeeded in significantly reducing energy consumption such as heat and electricity, so it has great industrial value. .

[Brief explanation of the drawing]

The figure is a schematic diagram showing an example of an apparatus used to carry out the method of the present invention. (11... Drying room, (4)... Object to be treated. (6)... Coater, +8)... Air supply fan. (9)...Heater, (0)...Exhaust fan. (14)...Gas detector. 06)...Gas concentration indicator alarm. (18)...Gas concentration regulator, (20)...Inverter.

Claims (1)

[Claims] / A workpiece coated with a paint containing organic solvent B is continuously supplied into a predetermined restricted space, and heated within the restricted space to remove the organic solvent. In the method of continuously lifting the object to be treated from the restricted space after drying the paint, when the amount of the object to be treated in the restricted space reaches the maximum value, the amount of the object attached to the object to be treated is suspended. The air flow rate flowing through the restricted space is adjusted in advance so that the concentration of the solvent gas generated from the organic solvent brought in as the temperature rises is an appropriate value that is set sufficiently lower than the lower explosive limit. and detecting the organic solvent gas concentration inside the restricted space or at the air flow outlet, comparing that value with the set value, and controlling the air flow rate in proportion to the difference therebetween. A continuous drying method for an organic solvent coated product, wherein the organic solvent gas concentration in the space is maintained at the set value of 2%. 2 The set value of the concentration of the solvent gas is approximately 2 of the lower explosive limit value.
A continuous drying method for an organic solvent coated material according to claim 1, wherein the concentration is 0 to 25%. 3. If the detected concentration of organic solvent gas exceeds approximately 25% of the lower explosive limit, an alarm will sound immediately, and if the concentration reaches approximately 33% of the lower limit, @ will open the restricted space. ,
Claims for rapidly diluting the organic solvent gas by one or more of reducing or stopping the supply of the whole, or increasing the air flow rate above the predetermined value. 2. The continuous drying method for an organic solvent coated product according to item 2.