JPH03229672A - Roller curtain coating method - Google Patents

Abstract

PURPOSE:To prevent the cutting of a paint curtain due to the transfer inferiority of the paint from a doctor roll to a coating roll and to stably perform coating even when the peripheral speed of the coating roll is increased by forming the surface of the coating roll into a uniform rough surface. CONSTITUTION:The paint T supplied to the surface of a doctor roll 2 is transferred to the surface of a coating roll 1 arranged at a predetermined roll surface interval so that the shaft thereof is in parallel to the roll 2 to be supported on the surface of the coating roll 1 and the paint T downwardly emitted from the gap between both rolls is scraped off by the doctor blade 3 provided in contact with the lower part of the coating roll 1 to be allowed to freely fall downwardly in a curtain state. An object 6 to be coated is passed under both rolls to be coated with the freely falling curtain (d) of the paint. At this time, the coating roll 1 whose surface is uniformly made rough is used. As a result, the cutting of the paint curtain due to the paint transfer inferiority from the doctor roll to the coating roll is prevented and coating can be stably performed even when the peripheral speed of the coating roll is increased.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a roller curtain coating method.

The roller curtain coating method is a method in which paint is supplied between a paint roll and a doctor roll whose axes are arranged parallel to each other at a predetermined spacing between the rolls, and the paint is carried on the paint roll surface and discharged downward from between the two rolls. is scraped off with a doctor plate installed in contact with the bottom of the coating roll, guided downward and allowed to fall freely in a curtain-like manner, and the object to be coated is passed under both of the rolls to be coated with the free-falling curtain of the paint. It's a method. The paint roll is a roll that carries paint on its rotating roll surface and continuously supplies the paint to the paint curtain via a doctor plate.

The doctor roll usually rotates in the opposite direction to the paint roll, and is a roll that pulls back the paint carried on the paint roll and limits the amount of paint carried downward from between the two rolls to a predetermined amount. be. The amount of paint supplied to the paint curtain is mainly adjusted by the distance between the two rolls and the peripheral speed of rotation.

Roller curtain painting, like other curtain painting methods such as slit type and overflow type, can virtually eliminate paint loss compared to brush painting methods, spray painting methods, dipping painting methods, etc. It has excellent advantages such as extremely high capacity (and a very good finish on the painted surface), and compared to other curtain coating methods, it allows for many adjustment factors such as the amount of paint supplied, making it suitable for small-lot, high-mix production. It has the great advantage of being able to respond quickly to painting.

In recent years, home appliances, office equipment, etc. in particular have become extremely diverse depending on their uses and customer requests.
As the variety of products (board width), colors, and types of coatings are diversifying to meet individual requirements, the superiority of the roller curtain coating method, which can relatively easily accommodate the production of a wide variety of products in small quantities, is attracting even more attention. .

[Conventional technology]

In the roller curtain painting method, for example,
As disclosed in Japanese Utility Model Publication No. 1-178972 and Japanese Utility Model Application No. 63-63163, when the paint is supplied between the coating roll and the doctor roll, the paint is supplied directly between these two rolls, A paint puddle had formed there.

However, in the above method, the liquid level of the paint pool bulges under the paint supply nozzle, or a so-called "dancing phenomenon" occurs in which the liquid surface waves over the entire surface, causing uneven coating. As a method for preventing such uneven coating, the present inventor has already proposed a method of supplying the paint onto the coating roll surface or doctor roll surface without forming a paint pool ("Roller Curtain Coating Method"). 1990 under the name of
(Apply on March 31st)

In the method proposed above, the paint is supplied onto the doctor roll surface and then supported (transferred) onto the coating roll surface.
When this method is used, the coating roll surface needs to have sufficient wettability for the paint. If the wettability is insufficient, a slip phenomenon will occur between the paint and the coating roll surface, and the paint on the doctor roll surface will not be sufficiently transferred to the coating roll surface, eventually causing the paint curtain to break. This slip phenomenon becomes particularly noticeable as the coating roll circumferential speed (strictly speaking, the coating roll circumferential speed relative to the doctor roll circumferential speed) increases, and becomes an obstacle to coating film thickness controllability.

Conventionally, hard rolls such as chrome-plated steel rolls have been used as coating rolls, but the roll surface has been mirror-finished to ensure close contact with the cutting edge of the doctor plate. Such a mirror-like roll surface has poor wettability with paint, and there is a problem in that paint curtain breakage is likely to occur due to poor paint transfer from the doctor roll surface.

[Problems to be Solved by the Invention] The present invention provides a roller curtain coating method that prevents paint curtain breakage due to poor paint transfer from a doctor roll to a coating roll, and allows stable coating even when the peripheral speed of the coating roll is increased. The purpose is to provide.

[Means to solve the problem]

According to the present invention, the above object is to transfer the paint supplied on the doctor roll surface onto the coating roll surface whose axis is parallel to this and arranged at a predetermined distance between the roller surfaces, and to transfer the coating material onto the coating roll surface. The paint discharged downward from between the two rolls is scraped off with a doctor plate installed in contact with the lower part of the coating roll, and allowed to fall freely downward in a curtain-like manner, and the object to be coated is passed under the two rolls. This is achieved by a roller curtain coating method characterized by using a coating roll with a uniformly roughened roll surface.

[Effect]

The roller curtain coating method of the present invention has a uniform rough surface on the coating roll surface, which improves the wettability of the paint compared to a conventional mirror-like coating roll, and prevents paint curtain breakage due to poor transfer to the coating roll. Since this can be prevented, stable coating can be performed even at high peripheral speeds of the coating roll.

The roll surface roughness and uniformity of the coating roll are determined by the viscosity of the paint used, the dry coating thickness, and the paint solid content (N.

■Set in advance by testing according to the conditions such as 0%), etc.

In order to obtain uniform roughness, it is appropriate to roughen the roll surface by shot blasting or laser treatment with an appropriate particle size.

The present invention will be explained in more detail with reference to Examples below.

[Example] Referring to FIG. 1 (a) sectional view, (b) front view, and (C) perspective view, a doctor roll surface was An example of a roller curtain coating method in which paint is supplied onto the roller curtain will be explained.

A coating roll 1 with a uniformly roughened roll surface 7 and a doctor roll 2 are arranged with their axes parallel to each other at a predetermined distance between the roll surfaces. The roll surface spacing is set in relation to a predetermined coating film thickness, rotational speed of the coating roll and doctor roll, traveling speed of the object to be coated, etc., paint viscosity, paint specific gravity, coating film specific gravity, etc. The coating roll 1 and the doctor roll 2 are rotated in the directions indicated by arrows by a roll drive device (not shown). The object to be coated 6 moves below both rolls in the direction of the arrow.

A paint supply jig 5 placed above the paint roll 1 and doctor roll 2 temporarily stores paint T from a paint supply source (not shown), and distributes the paint depending on the opening of the discharge port extending in the width direction at the bottom. The supply amount can be adjusted.

The jig 5 is arranged so that its discharge port is also parallel to the axes of both rolls 1.2 and positioned above the doctor roll 2.

The paint adjusted to a predetermined amount is supplied from the discharge port t onto the roll surface of the doctor roll 2 in the form of a curtain having a predetermined width W substantially parallel to the roll width W, as shown by a.

The paint supplied onto the 2nd side of the doctor roll is
．． The coating material is transferred onto the surface of the coating roll 1 between 2 and 2, guided downward by the doctor plate 3 disposed in contact with the lower part of the coating roll, and freely falls as a coating curtain d, and is coated on the object 6 to be coated, such as a strip-shaped steel plate.

The roll surface roughness of the coating roll 1 is set to be rough enough to prevent slippage between the roll surface and the paint.
If it's too rough, it may cause streak-like uneven coating and make it difficult to scrape it off uniformly from the coating roll.
Set according to the relationship with N, V, %), etc. For example, using a pre-coated paint, the dry coating thickness is 10 to 30 μm, N
.

When coating with V of about 30 to 50%, the surface roughness of the coating roll is suitably 5 μm or less. In this case, the uniformity of roughness can be evaluated by the uniformity of the distribution of the roughness waveform, as illustrated in the roughness meter chart in Figure 2. If it is double, it can be considered as uniform in practical terms.

Table 1 summarizes the results of coating pretreated electrogalvanized steel sheets using the roller curtain coating apparatus shown in FIG. 1 and varying the surface roughness of the coating roll 1. The roll surface was roughened as follows. In other words, JIS
R based on G5903 and JIS R6001
In order to obtain a roughness within the range of a O, 075 to 100 m,
Conditions such as the number of abrasive materials such as steel grids and alumina glass beads, blasting time, blasting amount, and blasting distance were selected, and shot blasting was performed on the roll surface that had been ground to a smooth finish. In addition, for the rough-surfaced roll with a rounded bottom and a corrugated bottom, the smooth-finished roll surface was laser-processed to give it a rough surface. The coating conditions are as described in (Note 2) below.

Margin below (Note 1) The higher the value, the better the surface wettability.

(Note 2) Paint nib record paint (manufactured by Dainippon Ink ■), paint viscosity = 40-100 seconds/25'C (Ford Cup #4), dry film thickness = 20 μm Coverability Bunkyu Conforms to row cropping JIS K6768. (Wettability test reagent: standard reagent of formamide/ethylene glycol ether) When the coated roll 1 with uniform and appropriate roughness according to the present invention was used (Examples 1 to 3), the wettability of the roll surface was good. and the ratio of the circumferential speed (va) of the coating roll 1 to the circumferential speed (vd) of the doctor roll 2 (va / v d
) was approximately 70 or higher, no streaky coating unevenness occurred, the scraping property was good, and the coating could be performed without slippage between the coating material and the coating roll.

On the other hand, in the case of Comparative Example 1, in which a coated roll with too rough a roll surface was used, the roll surface had good wettability, but streaky coating unevenness occurred and the evenness of spreading was poor. , it was not possible to perform a good coating.

On the other hand, in the case of Comparative Example 2, in which the roll surface was kept mirror-finished as in the past, the wettability of the painted roll surface was poor, and even though the circumferential speed ratio was low at about 20 or less, it was difficult to coat the paint. The paint curtain broke due to slipping between the parts.

[Effects of the Invention] As explained above, according to the roller curtain coating method of the present invention, even if the circumferential speed ratio of the coating roll is increased, the slip phenomenon between the coating roll and the paint can be prevented, and the scraping performance is improved evenly. By ensuring sufficient amount of paint, it is possible to perform high-quality coating without uneven coating.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are (a) a cross-sectional view, (b) a front view, and (c) for explaining one embodiment of the roller curtain coating method according to the present invention. ) Perspective view, FIG. 2 is a graph showing roughness meter charts for various roll surface roughnesses. l: Paint roll, 2: Doctor roll, 3: Doctor blade, 4: Doctor knife, 5: Paint supply jig, 6:
Object to be coated, 7: Paint roll surface with uniform roughness, a: Paint supply curtain, d: Free-falling paint curtain.

Claims (1)

[Scope of Claims] 1. The paint supplied on the doctor roll surface is transferred onto the paint roll surface whose axis is parallel to this and is arranged at a predetermined distance between the roll surfaces, and the paint is carried on the paint roll surface and both of the above rolls are transferred. The paint discharged downward from between the rolls is scraped off by a doctor plate installed in contact with the lower part of the coating roll, and allowed to fall freely downward in the form of a curtain, and the object to be coated is passed under both of the rolls, thereby forming a free-falling curtain of the paint. A roller curtain coating method characterized by using a coating roll with a uniformly roughened roll surface.