JPH0664018A - Coating method of thermosetting coating and coated matter - Google Patents

Abstract

PURPOSE:To obtain coating composition with a simple device and apply it with good workability by a method wherein the tnermosetting coating composition, which is made of component having the specified ratio or more of solid at normal temperature and which contains no solvent, is supplied to a coater head so as to be spread to the necessary coating width under the molten state having specified viscosity and, after coating, thermally set. CONSTITUTION:Thermosetting coating composition, which is made of component having 95wt.% or more of solid at normal temperature and which contains no solvent, is melted and mixed together at the melting temperature lower than setting temperature and then supplied to a coater head. In this case, the composition is extruded in uniformly distributed state under the viscosity of 4,000-10,000cP, which responds to the necessary coating width, so as to be coated to matter to be coated and finally thermal set. Concretely, stock mixture 13 is introduced from a hopper 14 so as to supply coating composition 16 under molten state obtained from a continuous kneading machine 2 in order to be spread to the necessary coating width by means of a coating flow path 22 and then extruded from a lip-like extrusion port 23 in the form of flat sheet and finally applied to the matter to be coated 4. In addition, in the side wall of the coater head 3, heat medium flow path 26 is provided so as to control the viscosity of the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a thermosetting paint, and more particularly to a method and an article for applying a thermosetting paint suitable for applying a sheet material such as a precoated steel sheet.

[0002]

2. Description of the Related Art Solvent-based paints are generally used as thermosetting paints for precoated steel sheets. The solvent-based coating is applied by coating a coating composition dissolved or dispersed in a solvent on a coating object by a roll coater, brush, etc., and curing by natural drying or baking. However, such a solvent-based paint uses a solvent, and thus has problems such as deterioration of working environment and fire hazard.

On the other hand, powder paint is a non-polluting paint containing no solvent as compared with a solvent type paint, and its coating workability is extremely simple. Therefore, it is applied to molded products such as gates and guardrails. It has been. It has been used for so-called post-coating applications, but recently, in order to rationalize the coating line, powder coating has come to be used also for pre-coating lines such as steel plates for the purpose of improving productivity.

The powder coating material is composed of powder particles having an average particle size of 30-40 μm, and the powder coating is performed by charging the powder particles to an object to be coated. Both postcoats and precoats are typically applied using electrostatic powder coating guns. In this case, the powder coating material is supplied from the powder supply device,
It is mixed with compressed air by an injector and sent to a spray gun via a paint hose. Then, the high voltage obtained by the high pressure generator is applied to the tip of the spray gun to ionize the air around the gun. When passing through the ionized air, the powder particles discharged from the tip of the gun are charged by colliding with the ionized air and are pulled and attached to the grounded object to be coated.

Both the post-coating and the pre-coating are carried out by moving the object to be coated at a high speed, and instead, the coating gun is fixed for coating. When the speed of the object to be coated is increased, the amount of powder coating material supplied from the coating gun cannot keep up, and it is necessary to use a large number of guns. It disturbs the created air and makes uniform coating impossible. In the precoat line, the limit line speed is about 20 m / min.

When a solvent type paint is used in a steel sheet precoat line, it is used at a line speed of 50 m / min or more. However, the lower the line speed, the lower the productivity. Steel plate manufacturing costs are high. For this reason, when a pre-coated steel sheet is manufactured using a powder coating, the increase in production cost has been a major drawback.

Further, the method for producing the powder coating material includes a resin, a pigment,
After preliminarily mixing the curing agent, additives and the like, melt mixing is performed using a kneader, and further cooling, coarse pulverization, fine pulverization, classification and filtration are performed to produce a powder coating material. However, paints have many colors and resin types are different. Therefore, in the manufacturing process of powder coating material, when melt mixing, coarse pulverization, then fine pulverization, classification, and filtration are performed, in order to remove the coating material adhering to the fine pulverizer and classification filter material, Thorough cleaning is required, which increases the cost of manufacturing powder coatings. Further, the powder coating material uses powder particles having an average particle size of 30 to 40 μm, and thus has problems such as blocking during storage and clogging of a hose when the powder particles are conveyed on a coating line.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to improve the problems of conventional solvent-based paints and powder paints, to manufacture paint compositions at low cost with simple equipment and operation, and to handle them easily. The present invention is to propose a novel method for coating a thermosetting coating and a coated article which can be coated with good workability and productivity.

[0009]

SUMMARY OF THE INVENTION The present invention is the following method for coating a thermosetting coating material and a coated article. (1) A thermosetting coating composition containing 95% by weight or more of a solid component at room temperature and containing substantially no solvent is supplied to a coater head in a state of being melt-mixed at a melting temperature lower than the curing temperature. Then, the thermosetting coating composition is characterized in that it is spread to a required coating width in a molten state having a viscosity of 4,000 to 100,000 centipoise, is extruded in a uniform distribution state, is applied to an object to be coated, and is then heated to a curing temperature to be cured. How to paint. (2) The thermosetting coating composition melt-mixed by a kneading machine,
The molten state is supplied to the coater head, or it is cooled and coarsely pulverized and then remelted and supplied to the coater head for coating on the object to be coated.
The described coating method. (3) The coating method according to (1) above, wherein the article to be coated is a sheet material. (4) A coated article coated by the method described in (1) to (3) above.

The thermosetting coating composition used in the present invention is
A thermosetting resin that is composed of components that are 95% by weight or more solid at room temperature, does not substantially contain a solvent, and can be applied by extrusion in a melt-mixed state, and has been conventionally used as a powder coating powder. The thermosetting coating composition for paint can be used as it is. Examples of such thermosetting coating compositions include polyester resin-based, epoxy resin-based, epoxy-polyester resin-based, acrylic resin-based, fluororesin-based, phenol resin-based, polyurethane resin-based and other thermosetting coating compositions. can give. As the thermosetting coating composition for a precoated steel sheet, a polyester resin-based or epoxy / polyester resin-based thermosetting coating composition that can obtain a coating film excellent in processability is preferable.

These thermosetting coating compositions include a leveling agent, a pigment dispersant, an ultraviolet absorber, a light stabilizer, and a heat stabilizer, in addition to the above-mentioned thermosetting resin, a curing agent and a pigment which are coating film forming components. It is obtained by blending additives such as a foaming inhibitor.
This thermosetting coating composition does not substantially contain a solvent such as water or an organic solvent, and the content of liquid components at room temperature such as a leveling agent is 5% by weight or less.

In the present invention, such a thermosetting coating composition is used in a melting temperature lower than the curing temperature, preferably 50 to 20.
It is melt-mixed at 0 ° C. and supplied to a coater head. In this case, the thermosetting coating composition melt-mixed with a kneader or the like may be directly supplied to the coater head in a molten state, but it may be cooled and coarsely pulverized to have a particle size of about 3 to 30 mm, and then melt-mixed again with a kneader or the like. Then, when the pigment is supplied to the coater head, the pigment dispersion can be made more uniform, and the toning accuracy is improved.

The coater head maintains a melting temperature lower than the curing temperature of the coating composition and has a viscosity of 4000 to 10000.
In a molten state of 0 centipoise, the coating is spread to a required coating width, extruded in a uniformly distributed state to be applied to an object to be coated, and then heated to a curing temperature to be cured to form a cured coating film to obtain a coated object.

Suitable materials to be coated are sheet materials such as steel plates and resin sheets, and long materials such as strips, pipes and profile materials, but are not limited to these. Of these, sheet-like materials such as steel plates are suitable for use as an object to be coated, as they can be rolled out as they are by sending out a molten coating composition in a planar shape for coating and curing, while sending out at a predetermined speed. There is.

The coated article thus produced is used as it is as a conventional coated article, but the coated article coated on a sheet material such as a pre-coated steel sheet is subjected to post-processing such as bending and drawing. It can be molded into any shape.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments of the drawings. FIG. 1 is a configuration diagram showing a coating method of an embodiment, and FIG. 2 is a front view of a coater head. In the figure, 1 is a high-speed mixer, 2 is a continuous kneader, 3 is a coater head, 4 is a sheet-shaped object to be coated (steel plate), 5 is a backup roll, 6 is a pressure roll, 7 is a baking device, and 8 is a coated object. , 9 and 10 are coils.

A raw material 11 such as a thermosetting resin, a curing agent, a pigment, and other additives which are components of the thermosetting coating composition is introduced into the high speed mixer 1, and a stirring blade of the high speed mixer 1 (shown in the figure) is driven by a motor 12. (Omitted) is rotated to uniformly mix the raw material 11. The raw material mixture 13 obtained by the high-speed mixer 1 is introduced into the hopper 14 of the continuous kneader 2.

The continuous kneading machine 2 maintains the melting temperature lower than the hardening temperature of the thermosetting resin, and the kneading roll (not shown) is rotated by the motor 15 to introduce the raw material mixture 13 from the hopper 14, The mixture is kneaded in a molten state to obtain a thermosetting coating composition 16 that is uniformly melt-mixed. At this time, the temperature of the coating composition 16 is 50 to 200 ° C. and the viscosity is 4
000 to 100,000 centipoise, preferably a temperature of 80 to 200 ° C. and a viscosity of 8,000 to 80,000 centipoise.

In the conventional powder coating, the melt-mixed coating composition is cooled, coarsely pulverized, finely pulverized, classified and filtered to produce a powder coating, and the powder coating is applied by electrostatic coating or the like. After that, it was heated and melted and cured to form a coating film to obtain a coated object, but in the present invention, the molten and mixed coating composition is supplied to the coater head 3 in a molten state, and extruded in a molten state for coating. I do.

In the example of FIG. 1, the molten coating composition 16 obtained from the continuous kneading machine 2 is supplied to the coater head 3 as it is, but the coating composition 16 obtained from the continuous kneading machine 2 is shown. It is also possible to cool and coarsely pulverize and re-melt and supply to the coater head 3.

In the coater head 3, as shown in FIGS. 1 and 2, the molten coating composition 16 is introduced from a pipe-shaped inlet 21, and a fan-shaped coating passage 22 expands to a required coating width. It is spread and extruded in the form of a flat plate from the lip-shaped extrusion port 23 to coat the article 4 to be coated. The paint flow path 22 is provided with a storage section 24 and a throttle section 25, and has an extrusion port 23.
The coating material extruded from is extruded in a uniform flow over the entire width. A pattern can be formed on the coating film by partially extruding the paint by closing a part of the extrusion port 23 that opens in a lip shape. On the side wall of the coater head 3, the paint flow path 2
The heating medium flow paths 26 are provided so as to sandwich the two, and heating is performed by introducing the heating medium from the heating medium inlet 27 and discharging it from the heating medium outlet 28 to remove the coating composition in the coating fluid channel 22. Extrude at a temperature of 50 to 200 ° C. and a viscosity of 4000 to 100000 centipoise.

A steel sheet is used as the article to be coated 4 in the embodiment, and while being sent out from the coil 9 and backed up by the backup roll 5, it is coated with the coating composition 16 extruded from the coater head 3 to form a coating film 31. To form. The coating film 31 is pressure-bonded by the pressure-bonding roll 6, and then heated in the baking device 7 to the curing temperature of the coating composition to be cured, whereby the coated article 8 having the cured coating film is completed. Paint 8 is roll 10
It is rolled up into a product. The curing temperature will vary depending on the type of resin and curing agent in the coating composition, but is generally 12
It is 0 to 300 ° C.

The above-mentioned coating method is fundamentally different from the conventional electrostatic coating method using powder coating, and since it is not necessary to create an ionized air flow, the object to be coated is moved at a speed of 50 m / min or more. However, it can be applied uniformly. The coating thickness may be adjusted by changing the amount extruded from the continuous kneader,
It can also be adjusted by changing the amount of extrusion from the extrusion port of the coater head. Also crush like powder paint,
Since there is no need for classification, filtration, cleaning, etc., the manufacturing cost of the coating composition can be reduced.

The coating composition used in the present invention is 50
At a melting temperature of ℃ to 200 ℃, it is preferable that the melt viscosity is low, and the viscosity between this temperature is preferably 4,000 to 100,000 centipoise. If the temperature at the time of kneading is less than 50 ° C, the coating composition is not sufficiently melted, and if it exceeds 200 ° C, the reaction between the thermosetting resin and the curing agent tends to occur rapidly. May increase viscosity.

Test Example 1 58 parts of polyester resin ER-6620 (trade name) manufactured by Nippon Ester Co., Ltd. and blocked isocyanate B manufactured by Huls Co.
-12 parts of -1065 (trade name) and 30 parts of titanium dioxide were uniformly mixed with a Hensyl mixer (manufactured by Mitsui Miike Co., Ltd.) for about 1 minute, and then an extrusion kneader (manufactured by Buss) at a temperature condition of 150 ° C. , Busco Kneader PR-46), and the coating composition discharged from the die and having a melt viscosity of 75,000 centipoise is sent directly to a coater head equipped with a lip-shaped extrusion port capable of being spread to a width of 80 cm, and extruded from the extrusion port. The coating composition was directly coated on a steel plate (hot dip galvanized steel plate) sent at 60 m / min.

The coated steel sheet was kept in a baking apparatus designed to have a temperature of 260 ° C. for 50 seconds to obtain a coated precoated steel sheet. Painted film thickness is 40-50μ
m, the pencil hardness was 2H, the bending workability was OT, the edge test was 100/100 (cellophane tape peeling), the Erichsen test was 7 mm, and the physical properties and appearance were good.

Test Example 2 35 parts by weight of polyester resin ER-8105 (trade name) manufactured by Nippon Ester Co., 35 parts of epoxy resin Epute 1004 (trade name) manufactured by Yuka Shell Co., and 25 parts of titanium dioxide.
Parts and 5 parts of cyanine blue are uniformly mixed with a Hensyl mixer (manufactured by Mitsui Miike Co., Ltd.) for about 1 minute, and then an extrusion kneader (Bus company, Busco Kneader PR-46) is used at a temperature of 100 ° C. And kneaded. The coating composition discharged from the die was cooled to 40 ° C. using a cooling conveyor, and coarsely pulverized to a size of 3 mm square using a crusher.

The coarsely pulverized coating composition was melted at 150 ° C. using a twin-screw rudder of Toshiba Machine Co., Ltd.
The coating composition discharged by centipoise was directly fed to a coater head equipped with a lip-shaped extrusion port capable of being expanded to a width of 60 cm, and the coating composition extruded from the extrusion port was 50
It was directly coated on a steel plate (used in Test Example 1) sent at m / min. The coated steel sheet was kept in a baking apparatus designed to have a temperature of 250 ° C. for 50 seconds to obtain a coated precoated steel sheet. Painted film has a thickness of 50-60
.mu.m, the results of the pencil hardness, the goggles test and the Erichsen test were almost the same as those of Test Example 1, the toning accuracy was higher than that of Test Example 1, and the physical properties and appearance were excellent.

[0029]

INDUSTRIAL APPLICABILITY According to the present invention, a thermosetting coating composition can be produced at a low cost with a simple apparatus and operation, and the coating composition can be used for coating with good handleability, workability and productivity. It can be carried out, and a coated article having an excellent coating film can be obtained efficiently and at low cost. In this case, when the coating composition melt-mixed by the kneader is supplied to the coater head in a molten state to perform coating, the coating process is simplified and the coating cost is further reduced. Further, when the melt-mixed coating composition is cooled and coarsely pulverized and then remelted and supplied to the coater head for coating, the toning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a coating method according to an embodiment.

FIG. 2 is a front view of a coater head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-speed mixer 2 Continuous kneader 3 Coater head 4 Object to be coated 5 Backup roll 6 Crimping roll 7 Baking device 8 Painted material 9, 10 Coil 11 Raw material 13 Raw material mixture 14 Hopper 16 Paint composition 22 Paint channel 23 Extrusion port 26 Heat Medium channel 31 Coating film

Claims (4)

[Claims] 1. A coater head in which 95% by weight or more of a thermosetting coating composition consisting of components that are solid at room temperature and containing substantially no solvent is melt-mixed at a melting temperature lower than the curing temperature. The viscosity of 4000 to 100,000
A method for coating a thermosetting coating material, which comprises spreading the coating width to a required coating width in a state of being melted in centipoise, extruding the coating material in a uniform distribution state, applying the coating material to a coating object, and then heating to a curing temperature to cure the coating material. 2. A thermosetting coating composition melt-mixed by a kneader is supplied to a coater head in a molten state, or is cooled and coarsely pulverized and then remelted and supplied to a coater head to be coated. The coating method according to claim 1, characterized in that the coating method is applied to. 3. The coating method according to claim 1, wherein the article to be coated is a sheet material. 4. A coated article coated by the method according to claim 1.