JPH05154442A - Continuously coating method for belt like material - Google Patents

Abstract

PURPOSE:To provide a simply coating means to stably realize a smoothed surface of a coating film free uneven defect of coating film such as a roll grain in a continuously coating of a belt like material. CONSTITUTION:In the continuously coating of the belt like material 7, pressure inclination is generated at the vicinity of the coating film 14 to accelerate leveling effect by allowing an ejecting gas from a nozzle to come in collision with the unhardened coating film 14 (coating film in wet state) applied on the surface of the belt like material 7. Furthermore, leveling speed is more improved by controlling temp. and/or ejecting pressure of the ejecting gas from the nozzle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously coating a strip material for obtaining a smooth coated surface.

[0002]

2. Description of the Related Art Conventionally, as a means for continuously applying a coating liquid to a strip-shaped material such as a steel plate, a roll coating method, a curtain flow coating method, an extrusion coating method ( Die coating, slit coating
(Also referred to as coating, fountain coating, or slot orifice coating method) has been developed. Especially, the history of the roll coating method has a long history, and it has become a current mainstream technology, and there are very few proposals related to it. There are many.

For example, FIG. 7 is a schematic view of a typical roll coater used in the roll coating method, in which a part of the roll coater is immersed in the paint 2 contained in a paint pan 1. The pick-up roll 3 is arranged in the same manner, and the metering roll 4 is provided on the "roller peripheral surface portion of the pick-up roll 3 which rotates out of the paint 2 and rotates upward". The term "roll 4" refers to the applicator rolls 5 which are arranged facing each other in the circumferential direction of the pickup roll at a predetermined distance from each other with a slight distance therebetween or in a pressed state. In addition, the application roll 5
Are arranged so as to be in rolling contact with the surface of the strip-shaped material 7 wound around the backup roll 6 and transferred.

Now, the coating on the belt-shaped material by the roll coater is performed as follows. That is, the pick-up roll 3 around which the paint 2 in the paint pan 1 is attached is in the middle of the mail.
After adjusting the amount of paint adhered by the taling roll 4,
The remaining adhered paint is transferred to the applicator roll 5. Next, the application roll with the paint transferred and attached.
The roll 5 transfers / applies the adhered paint onto the surface of the strip-shaped material 7 which is wound around the backup roll 6 and transferred. After that, the band-shaped material 7 is transferred to a drying furnace and the attached paint is cured.

However, in such a roll coating method, ridge-like irregularities called "roll eyes" as shown in FIG. 8 are formed on the coated surface along the traveling direction of the strip-shaped material. It tended to happen. The rolls are caused by the instability of the paint flow between the rolls constituting the roll coater, but they remain after the drying oven and cause serious defects on the surface of the coating film. In order to remain, the development of the preventive measures has become an urgent issue.

However, the irregularities on the surface of the coating film such as the above-mentioned "roll eyes" are not limited to the case of the roll coating method, and the flow of the coating material becomes unstable even in the other coating methods described above. The problem is that similar defects caused by them tend to appear.

However, looking only at the roll-coating method, recently, some proposals which are considered to be promising as a measure for preventing the occurrence of the "roll eye" have been found. For example, as disclosed in Japanese Unexamined Patent Publication No. 63-143962, the roll coater structure is devised so that the transfer roll 8 is closely arranged with a required gap in the applicator roll 5 as shown in FIG. In addition, a doctor roll 9 is disposed in close proximity to the transfer roll 8 with a required clearance, and a blade 10 is provided so that the cutting edge is in contact with the doctor roll 9. What you have done is proposed. And this rollco
In the computer, the three rolls other than the pickup roll 3 and the backup roll 6 all rotate in the same direction.

That is, the roll coater proposed above is
By rotating the three rolls other than the pickup roll 3 and the backup roll 6 in the same direction, the rolls are rotated.
Prevents the instability of paint flow between the rolls and at the same time prevents paint unevenness by allowing the applicator roll 5 to be supplied with double paint from the pickup roll 3 and the transfer roll 8. , Aiming for uniform coating.

However, it is generally difficult to adjust the thickness of the coating film by reverser coating in which the rolls rotate in the same direction, and when the number of rolls is large, setting operating conditions becomes complicated. Because of the unavoidable circumstances, the above proposal cannot be said to be fully satisfactory in practice.

Further, as Japanese Patent Laid-Open No. 63-143961, there is a proposal of a roll coater for preventing roll eyes. In this proposal, as shown in Fig. 10, "Blade 10 for guiding the flowing paint flow to the application roll"
Is arranged so that the lower end is close to the surface of the applicator roll 5, and the transfer roll 8 is arranged in contact with the upper end of the blade 10, and further the transfer roll 8 is arranged.
A doctor that rotates in the same direction as the doctor
A roll coater structure in which rolls 9 are closely arranged is disclosed, and it is intended to suppress an unstable phenomenon of paint flow between the rolls and perform uniform coating.

However, this means is also disclosed in the above-mentioned JP-A-63-1.
As in the case of the proposal relating to No. 43962, it is difficult to control the thickness of the coating film, and the coating material flows down the blade surface, so that it is impossible to apply high viscosity coating material. So, I was not satisfied enough.

In view of the above, the object of the present invention is to provide a simple and stable coating film surface free from irregularities such as rolls in the continuous coating of a strip material. It was to establish the means of painting.

[0013]

The present invention has been completed based on the results of research by the present inventor conducted while repeating many experiments to achieve the above object,
"When continuously coating the strip-shaped material, the gas sprayed from the nozzle collides with the coating film before curing (wet coating film) applied to the surface of the strip-shaped material to generate a pressure gradient near the surface of the coating material. It has a major feature in that "the leveling effect is promoted and a smooth coating film surface can be stably ensured." Furthermore, "either the temperature of the" gas injected from the nozzle "or the injection pressure or both" is controlled. This also improves the leveling speed and ensures the smooth coating film surface more reliably. "

Here, the gas to be sprayed for the leveling of the coating film is not particularly specified, and inexpensive gas such as air is sufficient. The leveling effect is affected by the jet pressure of the gas, and if the jet pressure is increased in a range where the coating film does not have a dent, a good result can be obtained in improving the leveling effect. In addition, the resin generally used as a paint has a tendency that the viscosity decreases as the temperature rises,
Therefore, it is also preferable to inject the heated gas from the nozzle to raise the temperature of the applied coating material in order to increase the leveling effect.

Further, it is desirable that the gas which has collided with the coating surface for leveling is recovered and circulated after the collision. This is because the paint solvent mixes with the gas that has collided with the coating surface before curing, but by collecting and circulating it, it is possible to effectively prevent the paint solvent from escaping into the atmosphere. , Can prevent environmental problems. Moreover, when the heated gas is used, the energy saving effect is increased, and when the inert gas or the like is applied, the gas consumption rate is suppressed.

In order to collect and circulate the gas to be sprayed for leveling the coating film, it is effective to use a gas spraying device in which a slit-shaped nozzle is sandwiched by slit-shaped exhaust holes.

Hereinafter, the present invention will be described in detail with its operation based on the drawings.

FIG. 1 is a schematic view of a main part (nozzle part) of a "gas injection device (a leveling device) in which a slit-shaped nozzle is sandwiched by slit-shaped exhaust holes" suitable for carrying out the method of the present invention. , A slit-shaped air intake hole 12 is provided so as to sandwich the slit-shaped gas ejection portion 11 from both sides.
Is defined by a straightening plate 13 provided so that the ejected gas is not diffused into the atmosphere.

In the continuous coating process of the strip-shaped material, this nozzle portion is arranged to face the "pre-cured coating film 14 on the coated strip-shaped material 7" with an appropriate gap.

The gas injection device illustrated in FIG. 1 is equipped with the injection gas circulation system shown in FIG. That is,
A part of the gas ejected and collected by the nozzle portion passes through the solvent treatment device 16 via the pump 15, the paint solvent mixed therein is removed, and the gas is exhausted to the atmosphere. The remaining collected gas is taken into the circulation system by the circulating gas pump 17, mixed with the “gas containing no paint solvent” taken by the pump 18, and if necessary heated by the heating device 19 to an appropriate temperature,
The pressure pump 20 again feeds the nozzle portion.

Now, when the "gas pressurized to an appropriate pressure" is blown against the coating film before curing (wet) by the gas injection device (leveling device) having the above-mentioned structure to make it collide, the coating film surface becomes uneven. If there is, a pressure distribution of the sprayed gas is generated in the vicinity of the surface of the coating film, thereby promoting the leveling of the coating film.

That is, taking the gas injection device shown in FIG. 1 as an example, the gas injected from the gas injection portion is as shown in FIG.
The flow becomes as shown in (1), a high pressure is generated in the convex portion on the surface of the coating film 14, and the pressure decreases in the concave portion. Due to such a pressure gradient, the coating material on the convex portions of the coating film is swept into the concave portions. For this reason, the leveling of the coating film is promoted, and a smooth coating film surface on which irregularities such as rolls do not remain can be easily realized.

Here, when the temperature of the coating film before curing is raised by heating the gas sent to the nozzle portion, the viscosity of the coating material is lowered, leveling is promoted, and the smoothing effect is increased. As I did.

Next, the effects of the present invention will be described more specifically with reference to Examples.

【Example】

[Example 1] In this example, a coating material having a viscosity of 500 cp and a surface tension of 34 dyn / cm was applied to a strip-shaped material (steel strip) having a width of 1000 mm by roll coating at an average film thickness of 40 µm. The coating film leveling method according to the present invention was applied to roll eyes (uneven defects on the coating film surface). In addition,
The roll pattern generated during the above-mentioned roll coating has an irregularity period of 1.2 to 1.5 mm and an irregularity amplitude of 30 to 50 μm.
Met.

For coating film leveling, a gas injection device of the type shown in FIG. 1 (nozzle width: 1100 m) is used.
m) was used, and as shown in FIG. 4, this was installed so that the nozzle slit crossed at right angles the roll eyes formed along the traveling direction of the strip-shaped material 7. The cross section of the nozzle of the gas injection device used had the shape and dimensions shown in FIG.

The air used as the working gas was jetted under the conditions shown in Table 1 onto the coating film surface of the strip-shaped material immediately after the roll coating moving at a speed of 60 m / min by the above gas spraying device, and A leveling test was conducted.

After passing through the gas injection device, the coating film surface shape after entering the drying furnace and curing the coating film was measured, and the leveling effect was evaluated by the amplitude of the unevenness. The results are shown in Table 1.

[0027]

[Table 1]

The results shown in Table 1 also show that the method of the present invention significantly improves the smoothness of the coating surface as compared with the conventional method (no nozzle in Table 1) in which the leveling measure by gas injection is not applied. It is clear that

[Embodiment 2] Embodiment 1 is the same as embodiment 1 except that the strip material immediately after roll coating under the same conditions is heated with circulating air as the working gas (injection gas).
A leveling test of the coating film was performed under the same conditions as described above. However, at this time, the gas flow velocity at the tip of the nozzle of the gas injection device is 10 m.
/ s, the distance between the tip of the nozzle and the surface of the coating film was set to 10 mm, and the level of the air was controlled by controlling the temperature of the blast air.

The "temperature-viscosity characteristic" of the coating material used here is shown in FIG. 6. The viscosity tends to decrease as the temperature rises. It was possible to reduce it to / 3 to 1/5.

Then, after passing through the gas injection device, the coating film surface shape after entering the drying furnace and curing the coating film was measured, and the leveling effect was evaluated by the period of the irregularities. The results are shown in Table 2.

[0032]

[Table 2]

From the results shown in Table 2, it can be seen that Test No. 14 in which air at a temperature at which the viscosity of the coating material is most significantly lowered (see FIG. 6) is injected has a particularly large leveling effect.

Table 2 also shows the results when the gas injection device (leveling nozzle) is installed at two places. The result is that installing the leveling nozzle at two places means that gas from the nozzles is discharged. This suggests that it is effective in improving the leveling effect when the temperature is low.

[0035]

[Summary of Effects] As described above, according to the present invention, the unevenness of the coating film surface generated in the continuous coating process of the strip-shaped material is easily and surely removed, and a smooth coating film surface is stably secured. It will be possible to bring about useful effects in industry.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part (nozzle part) of a gas injection device (leveling device) suitable for carrying out the method of the present invention.

FIG. 2 is an explanatory diagram relating to a circulation system of an injection gas in the gas injection device illustrated in FIG.

FIG. 3 is an explanatory diagram related to a flow state of gas in a nozzle portion of the gas injection device illustrated in FIG. 1.

FIG. 4 is an explanatory view showing an arrangement state of the gas injection device in the embodiment.

FIG. 5 is a shape / dimension explanatory view of a cross section of a nozzle portion of the gas injection device used in the embodiment.

FIG. 6 is a graph showing “temperature-viscosity characteristics” of paints used in Examples.

FIG. 7 is a schematic view showing a typical example of a roll coater used in a roll coating method.

FIG. 8 is an explanatory view of irregularities (roll eyes) generated on the surface of the coating film by roll coating.

FIG. 9 is an explanatory view of a conventionally proposed roll coater.

FIG. 10 is an explanatory diagram relating to another example of a conventionally proposed roll coater.

[Explanation of symbols]

 1 Paint pan 2 Paint 3 Pickup roll 4 Metering roll 5 Applicator roll 6 Backup roll 7 Strip material 8 Transfer roll 9 Doctor roll 10 Blade 11 Gas ejection part 12 Air intake hole 13 Current plate 14 Coating film 15 Pump 16 Solvent treatment device 17 Circulating gas pump 18 Pump 19 Heating device 20 Pressurizing pump

Claims (2)

[Claims] 1. When continuously coating a strip-shaped material, jet gas from a nozzle collides with the coating film before curing applied to the surface of the strip-shaped material to generate a pressure gradient in the vicinity of the surface of the coating material, thereby achieving a leveling effect. A continuous coating method for strip-shaped materials, which is characterized by accelerating. 2. The continuous coating method for a belt-shaped material according to claim 1, wherein the leveling speed is improved by controlling either or both of the temperature and the injection pressure of the gas ejected from the nozzle.