JPS6231989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating curing device, and more particularly to a coating curing device for curing a coating containing a prepolymer containing free isocyanate groups in an amine atmosphere.

Traditionally, the formation of coatings presents various problems in terms of thermal energy, pollution, and productivity. In the coating film forming method most commonly employed in industry, after a substrate article is coated, the coated article is transported into a baking oven and the coating film is baked at high temperature. This baking requires a large amount of thermal energy, and an expensive exhaust treatment system is required to remove harmful components such as solvents and paint tar generated during baking of the paint film from the exhaust gas. In addition, in the case of painting woodwork, etc., where the paint film cannot be baked at high temperatures, the paint film must be cured by air drying, which requires an extremely long time to harden, and during which time the wet paint cannot be used. Strict management is required to prevent dust from adhering to the membrane.

In recent years, a method for drying a coating film that does not require heat curing has been proposed, and Japanese Patent Publication No. 13038/1983 describes a method in which a vehicle containing a prepolymer containing free isocyanate groups is applied onto a substrate. A method for forming a dry coating is described, which consists in subsequently treating this vehicle with an agent consisting of ammonia or an amine in the vapor phase.

However, this ammonia or amine has a very strong odor, and its presence in very small amounts causes discomfort to humans. Therefore, when such a method is adopted, the airtightness of the device becomes an important issue.

The present invention relates to an apparatus for carrying out the above method, and in particular, an apparatus for efficiently baking or curing a coating film by the above method using an amine continuously and in a substantially closed system. Regarding.

That is, an object of the present invention is to provide an apparatus for continuously curing coating films containing free isocyanate groups with amines in a closed system.

Another object of the present invention is to eliminate the need for high-temperature baking operations and allow the coating film to be cured in an extremely short period of time.As a result, the equipment is compact and has high productivity, and the equipment is easy to maintain. The purpose of the present invention is to provide a coating film curing device.

Still other objects of the present invention include woodwork, hydraulic equipment,
It is an object of the present invention to provide an apparatus capable of curing a coating film in an extremely short time even on articles for which it has been difficult to bake the coating film by heat, such as articles having an extremely large heat capacity.

According to the invention, there is provided an apparatus for curing a coating film containing a prepolymer having free isocyanate groups by contacting it with an amine in the gas phase, comprising: a curing chamber; and a coated article in the curing chamber. an inlet passageway having an inlet for carrying in the amine; an outlet passageway having an outlet for carrying out the amine; a steam generator for generating an airflow containing amine vapor; and an airflow from the steam generator. It consists of a circulation system that supplies the gas to the curing chamber and circulates the gas after contact with the coated article to the steam generator, and a mechanism that seals the inlet and outlet to the curing chamber to prevent leakage of amine vapor. There is provided a coating film curing apparatus, wherein the curing chamber is located at a lower portion than the inlet and the outlet.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing an outline of the coating film curing device of the present invention, and FIG. 2 is an A of the curing device of FIG. 1.
-A cross-sectional view is shown.

In FIG. 1 and FIG. 2, the coating film curing apparatus of the present invention generally includes a curing chamber 1, a carry-in passage 2a having a carry-in port 5, and a carry-out passage 2b having a carry-in port 6. , a steam generator 3, a curing airflow circulation system 4, and a sealing mechanism 7 provided at an inlet 5 and an outlet 6.

Further, FIG. 3 is a diagram showing an example of a planar arrangement in which this coating film curing device is combined with an attached painting room and a post-curing room.

In the specific example shown in FIG. 3, a coating chamber 8 is disposed upstream of the curing chamber 1, and a post-curing chamber 9 is disposed downstream of the curing chamber 1, and a conveyance system 100 is provided to pass through these. It is being

The painting room 8 contains articles (substrates) to be painted.
10 is for applying a specific paint, that is, a paint containing a prepolymer containing free isocyanate groups, and, like a normal simple painting booth, there is an entrance 11 into which the substrate 10 is brought in, and an entrance 11 through which the coated substrate is taken out. An application mechanism 13 such as a spray gun for applying the paint onto the substrate is provided on one side of the movement path of the substrate 10.
Further, on the other side, an exhaust suction duct 15 is provided via a paint mist collection mechanism 14 such as a filter, if necessary.

The paint used in the apparatus of the present invention is a paint containing a prepolymer containing free isocyanate groups, and is cured by contact with a gaseous amine, which will be described in detail later. Suitable examples of such coatings are those called isocyanate group-terminated prepolymers, such as polyester polyols, polyether polyols, hydroxyl group-containing acrylic resins, hydroxyl group-containing vinyl resins, alkyd resins, polyamides, etc. A reactive oligomer or polymer is reacted with a polyisocyanate such as tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, or diphenylmethane diisocyanate, and the isocyanate is reacted with the oligomer or polymer through urethane bonds, urea bonds, etc. It is used attached to a skeleton. Of course, the above-mentioned oligomer or polymer reactive with isocyanate groups and the polyisocyanate may be reacted in advance or partially reacted in the form of a mixture, and this coating material may be used in combination with multiple polyisocyanates. It may be a mixture of different resins. In summary, it should be understood that any coating material may be used for purposes of the present invention as long as it contains a sufficient amount of free isocyanate groups to be cured with a gas phase amine.

The concentration of free isocyanate groups is generally determined by the resin content.
A range of 10 to 500 mmol, particularly 30 to 300 mmol per 100 g is preferred.

This paint can be used as a solvent-free paint if it is a liquid with a viscosity suitable for painting, or it can be used as a solution-type paint in which the prepolymer is diluted with a solvent. Of course, this paint contains components known per se, such as pigments, plasticizers,
It is blended with surfactants, anti-sag agents, rust preventive agents, etc. in known proportions. Suitable coatings have a non-volatile concentration of 20 to 100% by weight and a kinematic viscosity (foed cup #4) of 15 to 150 seconds.

Substrates 10 to be coated include, in addition to substrates formed from ordinary steel plates or surface-treated steel plates, manufactured products whose paint film is difficult to bake due to heat, textile products, plastic products, hydraulic equipment products, and castings with a large heat capacity. Particularly in the case of the latter substrates, the significant advantages of the present invention are achieved in that no thermal baking is necessary and the coating film hardens quickly.

As the coating mechanism 13, a spray coating mechanism such as an air spray gun, an airless spray gun, a rotary atomization coating device, etc., including non-electrostatic type and electrostatic type, is suitably used. Of course, other coating methods such as dip coating, roller coating, flow coating, etc. may also be employed depending on the type of substrate.

Returning again to FIGS. 1 and 2, the curing chamber 1 is for bringing the coated article 10' from the coating chamber 8 into contact with a gaseous amine to effect a curing reaction of the formed coating film. , a carry-in passage 2a having a carry-in port 5 for carrying the coated article 10' into the room and a carry-out passage having a carry-out port 6 for carrying out the article after contact with the amine, in order to enable continuous processing. 2
It is equipped with b.

The coating film curing apparatus of the present invention includes a curing chamber 1, an amine steam generator 3 for curing, and a curing chamber 1, an amine vapor generator 3 for curing, and a curing chamber 1, a curing amine vapor generator 3, A circulation system 4 for the air flow is provided in connection with which it will be explained in more detail below.

First, the curing chamber 1 is provided with an air supply duct 16 having a spray port 16a on the bottom wall in order to uniformly and uniformly supply a curing gas (airflow) containing amine and spray it onto the coated article 10'. An air supply duct 17 having a large number of fins 17a is provided on both side walls, and a curing gas is sprayed onto the coating article 10' which is rotating and moving.

These ducts 16 and 17 are connected to the curing steam generator 3 via a supply duct 18.
This curing steam generator is for sending amines in a gaseous phase to the curing chamber 1. In the specific example shown in the drawings, amines are supplied by a spray device 20 into a carrier gas such as air or nitrogen sent by a fan 19. The curing steam is generated by spraying.

The curing chamber 1 is provided with an exhaust duct 21 having an exhaust port 21a, and is connected to the suction side of the fan 19 via an exhaust duct 22 and, if necessary, a supercleaning mechanism 23 such as a filter. .

Thus, the curing steam circulation system 4 in the coating film curing apparatus of the present invention includes the exhaust duct 21 equipped with the exhaust port 21a, the exhaust duct 22, the fan 19, the supply duct 18, and the supply air ducts 16, 17. It will be understood that it is configured. This circulation system 4 can be provided with a curing gas heating mechanism (not shown) if necessary, and during the winter when the temperature drops, the temperature of the curing gas is kept at the same level as room temperature, that is, room temperature or The temperature can be maintained at around 30℃.

Further, an important feature of the present invention is that the curing chamber 1 is located at a lower portion than the entrance 5 and the exit 6. That is, although amine is used as a curing agent in the present invention, the vapor of this amine is heavier than air, so by locating the curing chamber 1 in the lower part as described above, the amine vapor flows into the inlet 5 and the outlet. 6 into the outside air can be more effectively prevented.

In addition, in the curing steam supply port or in the curing chamber,
An amine concentration detection mechanism 25a is provided, and this detection signal controls the valve 26 of the spray device 20 via the concentration control circuit 25, so that the amine concentration in the curing chamber can always be set to a predetermined value.

In addition to primary, secondary, or tertiary monoamines, the amines used in the present invention may be polyvalent amines, such as methylamine, ethylamine, propylamine, diethylamine, triethylamine, piperidine, morpholine, Examples include one or a combination of two or more of piperazine, ethanolamine, diethanolamine, triethanolamine, cyclohexylamine, ethylenediamine, tetramethylethylenediamine, ethylenetriamine, and the like.

The amine can be present in the form of undiluted vapor in the curing air stream, but from the standpoint of ease of operation and economic efficiency, it is preferred to include it in the air stream at a concentration of 50 to 50,000 ppm, particularly 100 to 10,000 ppm. This is desirable.

In the present invention, furthermore, in order to completely prevent leakage of amine vapor, the inlet 5 of the inlet passage 2a is
A sealing mechanism 7 generally indicated by 7 is provided at the exit 6 of the exit passage 2b.

In order to explain the configuration of the sealing mechanism 7, with reference to FIG. 4 showing a BB sectional view and a partial plan view of the device in FIG.
and a partition plate or flap 27 provided at the exit 6 to allow passage of articles, and an intake duct 2
8 and a continuous circumferential intake port 29.

That is, the partition plate or flap 27 is slidable or rotatable, and the article 1 passing therethrough is
Various shapes of passage ports can be formed depending on the shape of 0', and leakage of amine vapor can be effectively prevented by adjusting the area of the passage holes.

Furthermore, an air seal is formed by suctioning the air near the inlet and outlet through the intake port 29, completely preventing amine vapor from leaking into the outside air.

Note that a part of the gas discharged from the intake duct 28 and the curing gas taken out from the exhaust duct 30 connected to the above-mentioned circulation system is passed through a scrubber, an adsorption device,
It can be released into the atmosphere as a substantially odorless and harmless gas through an exhaust treatment device 31 such as a catalytic cracker. It goes without saying that the amine collected by the adsorption device can be recovered by desorption and reused for the purpose of curing.

The time that the coated article is in contact with the amine varies depending on the type and thickness of the paint, the concentration in the curing gas, and the temperature, but generally speaking it is 10 to 600 seconds, especially 20 to 300 seconds. It only takes a very short time.

According to the present invention, the above-described configuration makes it possible to continuously perform curing treatment of a coating film using an amine in a closed system without leaking harmful amine vapor to the outside. Moreover, by supplying the amine vapor as an air stream into the virtually sealed curing chamber and circulating this air stream through a steam generator, the coating film and the vapor come into contact evenly, uniformly, and closely. As a result, the curing reaction of the coating film is carried out effectively and within a short period of time. Moreover, by circulating the steam in a closed system, an economical curing process is possible while preventing loss of amine.

In the specific example shown in FIG. 3, in the curing chamber 1,
The coated article 10'', which has been in contact with the amine-containing curing gas, is contacted with a stream of air in the post-curing chamber 9.

In other words, a paint film that has just come into contact with amines will easily be scratched if you rub it with your fingernail, even if the hardening process is progressing. Contact with air is required for continued curing of the coating as measured by pencil hardness.

The post-curing chamber 9 has a tunnel-like shape with an inlet 32 and an outlet 33 for the coated article 10'', and inside the post-curing chamber 9, along the movement path of the coated article,
A porous partition wall 34 is provided. There is an air passage 35 through this partition wall 34, and the air introduced into the passage 35 is blown onto the coated article 10'' through the partition wall 34, thereby proceeding with the post-curing of the coating film.Air passage 35 is connected to a blower fan 37 via a supply duct 36, while the airflow after contacting the coating in the post-curing chamber is directed to an exhaust duct 38.
From there, it is circulated to the suction side of the fan 37 via the supercleaning mechanism 39 and the heating mechanism 40.

Room temperature is sufficient for post-curing air, but in order to accelerate post-curing, it is advantageous to heat the air to a temperature of about 50°C.

In this embodiment, the transport mechanism 100 is arranged to pass sequentially through the painting chamber 8, the curing chamber 1, and the post-curing chamber 9 via a series of wheels or sprockets 41, and is continuously or Driven intermittently. In this embodiment, the transport mechanism 100 is an endless overhead conveyor, and the articles 10 to be painted are placed at a loading position 4.
3, the coated product 10a is removed from the conveyor at an unloading position 44.

In the present invention, if it is acceptable to take a certain amount of time to post-cure the coating film, a method may be adopted in which the post-curing chamber 9 is omitted and the semi-cured coated article is left in the air. Further, it is also possible to separate from the coating room 8 and provide a conveyance system only in the coating film curing device.

According to the device of the invention as described above, the following significant advantages are additionally achieved. That is, although the furnace for drying and baking the paint film in the painting equipment consumes a huge amount of thermal energy, according to the present invention, baking at high temperatures is not necessary, resulting in significant energy savings. . In addition, it is possible to cure the coating film in a short time even on items for which it is difficult to bake the coating film at high temperatures.Furthermore, because the curing time is short, the equipment can be small-sized and production capacity can be significantly improved. .
Furthermore, since it is operated at or near room temperature, there is no danger of fire, and there is no need to clean tar as in conventional baking furnaces, making maintenance easy.

In the above specific example, an example was shown in which the curing device of the present invention was applied as a continuous type curing device, but it is also possible to apply this curing device as a so-called batch type curing device. In this case, a passageway for carrying in and out the article having a coating film to be cured may be provided above the curing chamber, and preferably a sealing door may be provided at the carrying-in/outlet. It will be appreciated that this will more effectively prevent heavy amine vapors from escaping through the upper passage even when the door is open.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an outline of the curing device of the present invention, FIG. 2 is an AA sectional view of the device in FIG. 1,
FIG. 3 is a plan layout diagram showing the curing apparatus of FIG. 1 together with an attached coating station and a post-curing chamber. FIG. 4 shows a BB sectional view and a partial plan view of the device shown in FIG. 1. 1 is a curing chamber, 2a is a carry-in passage, 2b is a carry-out passage, 3 is a steam generator, 4 is a curing airflow circulation system, 5 is a carry-in port, 6 is a carry-out port, 7 is a sealing mechanism,
8 is a painting room, 9 is a post-curing room, 10, 10', 1
0'' is a painted article (substrate), 10a is a painted product, 13
1 is a coating mechanism, 16 and 17 are air supply ducts, 18 is a supply duct, 19 is a fan, 20 is a spray device, 21 is an exhaust duct, 22 is an exhaust duct, 28
29 is an intake duct, 29 is a circumferential intake port, 31 is an exhaust treatment device, and 100 is a conveyance system.

Claims (1)

[Scope of Claims] 1. An apparatus for curing a coating film containing a prepolymer having free isocyanate groups by bringing it into contact with a gaseous amine, comprising: a curing chamber; and a coating inside the curing chamber. A carry-in passageway having an inlet for carrying in articles, a conveyance passageway having an outlet for carrying out goods, a steam generation device for generating an airflow containing amine vapor, and an airflow from the steam generation device. A circulation system that supplies amine vapor to the curing chamber and circulates the gas after contact with the coated article to a steam generator, and a mechanism that seals the inlet and outlet to the curing chamber to prevent leakage of amine vapor. A coating film curing apparatus characterized in that the curing chamber is located at a lower portion than an inlet and an outlet.