JPH074569B2 - Drying method for alkyd resin paint - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for drying an ordinary temperature drying type or forced drying type coating which is dried and cured at ordinary temperature or forced drying such as an alkyd resin coating.

[Conventional technology]

Usually, a continuous drying oven is often used to dry the coated article. The coated article is fed from one port (inlet) of the oven, and is heated and dried or cured in the oven, and then the other port of the oven is dried. It comes out from the (exit).

However, in order to dry large paints such as construction machinery, heavy vehicles, large vehicles, and heavy electrical equipment products, a large drying oven is required in the above continuous drying oven, and the product portion cannot withstand relatively high temperatures. Since there are some places and there is a large part of the heat capacity and it takes a long time to heat and dry, it is dry and hardened (oxidative polymerization or oxidative hardening) in air like alkyd resin paints and urethane resin paints at room temperature. Dry or forced drying paints are used.

This alkyd resin paint (including its modified resin paint)
Since it is an oxidative polymerization type coating, it takes a long time to dry when left at room temperature, and it may take several days for complete curing. Therefore, a certain amount of time is required until the coating film is touch-dried, which is the minimum required to transfer the coated product to the next step.

As a practical matter, taping for masking or the like may be necessary in the case of top-coating in the case of painting in a production line. Further, if the drying time is long, dust adheres and the device occupies long time. Therefore, the tact of the production line is improved,
Forced drying was required to reduce the time required for taping and to prevent dust from adhering until drying.

[Problems to be solved by the invention]

Regarding the forced drying of this large product, heating by an electric infrared furnace or an electric far infrared furnace has been widely adopted in the conventional production line. However, when this electric infrared method or electric far infrared method is used, the power consumption is enormous and it is against energy saving. Also, since the infrared ray is a straight type, the shadowed part cannot be heated and must be completely dried by heating. Further, since the alkyd resin paint and the like are of an oxidative polymerization type, it is necessary to bring oxygen into contact with the surface of the coating film, so that it took a long time to dry.

For the above reasons, there has been a demand for a method of drying an oxidation-polymerization type coating material in a simple drying furnace in a short time with good finish.

[Means for solving problems]

The present inventors have focused on the present invention by focusing on the point that contacting with a sufficient amount of oxygen, particularly contact with cold air after heating is important for drying the oxidative polymerization type paint, only by heating. completed.

The method for drying a room-temperature-drying type or forced-drying-type coating material according to the present invention is a method of drying a coated article to which a room-temperature-drying type or forced-drying type coating material such as an alkyd resin coating material (or its modified resin) coating material and a urethane resin coating material is applied. It is characterized in that it is configured such that combustion heating air is fed into the drying chamber to heat the coated article to a predetermined temperature, and then air is fed into the drying chamber to cool the coated article.

In the present invention, any coating can be applied as long as it is an oxidative polymerization type or a room temperature drying type or a forced drying type coating in which the coating film "clamps" when heated and cooled. Alkyd resin and urethane resin coatings such as

The present invention uses a one-room type drying chamber, for example, a gas combustion hot air circulation type batch furnace, in which the coating material is put in one furnace and combustion heating air (hot air) by a gas burner is supplied. Introduces and circulates in the furnace to uniformly heat the coated object in a short time, and after a certain period of time, closes the hot air circulation path,
Open the outside air introduction damper and open the large-volume exhaust duct, cool a large amount of cold air of the outside air to the coating object (product) to cool, and exhaust the heated air in the furnace to the outside of the furnace by the large-volume exhaust duct. Done by.

In the drying furnace used in the present invention, the same blower can be used both for heating and for air cooling, and a large-capacity circulation fan (blower) is used to form one fan. be able to.

For the heating of coated objects such as large heavy vehicles and large heavy electrical equipment, in the case of alkyd resin paint, the entire coated object can be heated in about 20 to 30 minutes in a short-time baking hot air oven at about 90 ° C. .

According to the coating material drying method of the present invention, in addition to heating and cooling the coating material in the drying furnace, the temperature in the drying chamber of the drying furnace itself can be rapidly heated to a predetermined temperature and cooled.

Therefore, according to the present invention, combustion heating air is further fed into the drying chamber to heat the chamber to a predetermined temperature when required such as when drying a coated object, and when the drying chamber is cooled, air outside the drying chamber is fed into the chamber. The present invention relates to a rapid heating-cooling method in a drying chamber.

〔Example〕

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

FIG. 1 is a front sectional view of the drying furnace, FIG. 2 is a plan view, 1 is a drying furnace main body, 2 is a hot air inlet duct, 3 is a hot air circulation duct, 4 is an outside air intake duct, 5a, 5b is a damper, 6 is an exhaust duct, 7 is a burner combustion device, 8 is a painted object, 9 is a blower, 10 is a motor, and 21 is a hot air outlet.

Drying was performed as follows.

Open the entrance door and open the furnace door 1 of the product (product) 8 that has been painted with phthalic resin paint, such as alkyd resin paint.
After carrying in the inside and closing the door, the pilot burner and the main burner of the burner combustion device 7 are ignited by the push button operation of the operation panel to generate hot air, and the generated hot air is fed into the hot air feeding duct 2 in the furnace main body. Send within 1. The hot air blown into the furnace from the hot air outlet 21 of the duct 2 transfers heat directly or indirectly to the coating object 8 and is sucked from the hot air circulation duct 3 and passes through the burner combustor 7 and the hot air inlet duct 2 It is again fed into the furnace body 1. During this time, the damper 5a of the outside air intake duct 4 and the damper (not shown) of the exhaust duct 6 are kept "closed".

In the case of this example, the temperature controller in the furnace is set to 90 ° C., and after raising the temperature to 90 ° C. and holding at this temperature for 25 minutes, the main burner,
The pilot burner stopped burning, then the damper 5b of the circulation circuit was "closed" and the dampers of the outside air intake duct and the exhaust duct were each "open", and the coated object 8 was air-cooled. In this example, the air cooling time was 20 minutes.

After the outside air is sent into the furnace body 1 for a predetermined time to cool the coated object 8 by air, the dampers of the outside air intake duct and the exhaust duct are “closed”, and the damper 5b of the circulation circuit is “open”. And complete all operations. It should be noted that it is advantageous to automatically control the operation of the burner combustion device and the blower, and the opening / closing of each damper.

In the case of this example, it takes about 40 to 45 minutes from the heating to the end of the air cooling operation, which is much shorter than the conventional method,
The alkyd resin paint on the surface of the product after the drying process "tightens" very well due to the contact with heated oxygen and the cooling effect after that, and the curing is good, and not only the taping (masking) after that but also the productivity A coating film excellent in improvement, durability and weather resistance was obtained.

〔The invention's effect〕

According to the drying method of the present invention, since hot air is sent into the drying chamber to heat the coated article, there is no shadowed portion as in conventional infrared heating, and the entire coated article can be heated uniformly. You can

Since the gas combustion air is directly used as the heating source, the energy loss is small, and the hot air is directly applied to the coated surface, so that the heating time can be further shortened. It is also advantageous from this point that the oxidative polymerization will proceed further by applying a large amount of heating and cooling air to the coating film.

In the case of oxidative polymerization type paint, it is not necessary to heat it to a high temperature, and the heating-cooling time can be shortened by the air flow rate,
It is sufficient to switch hot air and cold air in a one-room type drying room. As described above, since heating is performed in a batch type drying chamber for a short period of time and air cooling is performed, adhesion of dust and the like is not observed, gloss of the coating film is not lost, and a finished product having good sharpness can be obtained.

According to the rapid heating-cooling method of the drying chamber of the present invention, since the drying chamber can be rapidly heated to a predetermined temperature and cooled to a predetermined temperature, one unit is used regardless of whether the furnace is a batch system or a tunnel system. In this drying furnace, it is possible to bake / dry various paints having different baking temperatures, and it is also possible to bake / dry paints having different drying properties such as forced-drying type paints and baking-drying type paints. In addition, the inside of the furnace can be rapidly cooled, for example, when a worker enters the furnace due to the fall of coated objects (products) in the tunnel furnace, and then the temperature can be quickly returned to a predetermined temperature. ,
It has many advantages. Due to the nature of the present invention, the tunnel furnace is a furnace of which both ends are shielded from the outside air by an appropriate means such as an air curtain.

Since the equipment is a one-room drying room, no special air-cooling device is required, and only three automatic dampers, outside air intake ducts, and large-capacity exhaust ducts need to be installed in the conventional furnace. It has the advantages of low cost and no special space required.

[Brief description of drawings]

 FIG. 1 is a front sectional view showing an example of a drying furnace, and FIG. 2 is a plan view of the drying furnace. In the figure, 1 ... Drying oven main body, 2 ... Hot air inlet duct 3, Circulation duct, 4 ... Outside air intake duct 5a, 5b ... Damper, 6 ... Exhaust duct 8 ... Painted object,

Claims (6)

[Claims] 1. An article coated with an oxidative polymerization type paint such as an alkyd resin paint (including its modified resin paint) and a urethane resin paint is placed in a drying chamber, and combustion heating air is fed into the drying chamber. After heating the coated object to the specified temperature,
A method for drying an oxidative polymerization type coating material, characterized in that air outside the drying room is sent into the drying room to cool the coated article and oxidatively cure it. 2. The drying method according to claim 1, wherein the drying chamber comprises one chamber. 3. The drying method according to claim 1, wherein the oxidative polymerization type paint is an alkyd resin paint such as a phthalic acid resin paint. 4. The drying method according to claim 1, wherein the combustion heating air is fed into the drying chamber and the air outside the drying chamber is fed by one large capacity circulation fan. 5. The drying method according to claim 1, wherein the combustion heating air is gas combustion heating air by a burner. 6. The drying method according to claim 1, wherein the inside of the drying chamber is rapidly cooled by sending in air outside the drying chamber by a large capacity circulation fan.