JP2812564B2 - Reverse roll coating method with excellent coating lubricity - Google Patents

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 coating material in a good lubrication state using a reverse roll coater.

[0002]

2. Description of the Related Art Conventionally, it has been difficult to apply a paint having a very low liquid viscosity to a reverse method in which a heavy load is applied to an applicator roll due to poor lubrication between a steel strip and an applicator roll. Natural coating has been performed.

[0003]

However, the natural coating method has a problem that the controllability of the coating film thickness is poor and the coating appearance is poor. Therefore, when attempting to apply this extremely low-viscosity water-based paint by the reverse method, an excessive frictional force is generated due to poor lubrication between the applicator roll and the steel strip as described above, and as a result, the rotation of the applicator roll is caused. May become uneven, causing problems such as uneven coating and damage to the applicator roll surface. In more severe cases, not only was the applicator roll damaged, but also the drive for the applicator roll was broken.

Accordingly, an object of the present invention is to provide a method of applying a coating material in a good lubricating state using a reverse roll coater.

[0005]

In order to improve the lubricity between the applicator roll and the steel strip in a reverse type roll coater, the present inventors have developed a steel strip having a surface roughness σ _S.
The ratio of the surface roughness sigma _A of the applicator roll σ _S / σ _A
And found that there is an interesting relationship between the applicator roll and the lubricity between the steel strip and the present invention. That is, the present invention uses a pick-up roll that picks up paint from a paint pan and a reverse roll coater that includes an applicator roll that transfers paint from the pick-up roll. Is applied to a steel strip to be coated, the ratio σ _S / σ _A of the surface roughness σ _S of the steel strip to the surface roughness σ _A of the applicator roll is adjusted to 3.0 or less. The present invention provides a reverse roll coating method excellent in coating lubrication, characterized by improving the coating lubrication between the roller and the applicator roll.

Hereinafter, the present invention will be described in more detail.

FIG. 1 is a schematic view of a reverse type two-roll roll coater to which the present invention is applied. In FIG. 1, 1 is a paint pan, 2 is a pick-up roll, 3 is an applicator roll, 4 is a backup roll, 5 is a steel strip, and each roll rotates in the direction shown by the arrow. The rotation direction of the applicator roll 3 with respect to the backup roll 4 is the reverse direction (reverse direction).

In general, in the theory of elastohydrodynamic lubrication, if the surface roughness of sliding opposing surfaces, such as a rolling bearing, is σ ₁ and σ ₂ , respectively, the composite surface roughness σ is σ = (σ ₁ ² + Σ ₂ ² ) ^1/2 , but it is considered that the greater the composite surface roughness, the worse the lubricity. However, the present inventors have found that in a reverse roll coater, when the surface roughness of the applicator roll is reduced to reduce the composite surface roughness σ, the lubrication state deteriorates as will be shown in Examples later. Was.

More specifically, when an ultra-low viscosity paint having a liquid viscosity of 5.0 CP or less is applied to a steel strip by a reverse roll coater, the surface roughness σ _S of the steel strip and the surface roughness of the applicator roll are applied. by setting the ratio σ _S / σ _a of is sigma _a to 3.0 or less, the present inventors to be able to greatly improve the coating lubricity between the steel strip and the applicator roll is to that knowledge.

[0010] This phenomenon also occurs because the liquid viscosity of the coating material is 5.
It cannot be seen with medium and high viscosity paints exceeding 0CP,
As will be shown in the examples below, it is considered to be a peculiar phenomenon of the low-viscosity paint.

Σ indicating the surface roughness of the steel strip and the applicator roll is the respective surface roughness Ra.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

(Example 1) A coating lubrication test was conducted using a two-roll reverse roll coater shown in FIG. In this test, the dynamic friction coefficient at the time of coating was measured by using a low-viscosity paint having a liquid viscosity of 1.8 CP while changing the surface roughness of the steel strip and the surface roughness of the applicator roll. Table 1 shows the experimental conditions. FIGS. 2 and 3 show the obtained experimental results.

FIG. 2 is a graph showing the relationship between the measured dynamic friction coefficient and the composite surface roughness (σ _S ² + σ _A ² ) ^1/2 . FIG. 2 shows a clear relationship between the two. Nothing should be recognized.

FIG. 3 is a graph showing the relationship between the ratio σ _S / σ _A of the surface roughness between the steel strip and the applicator roll and the dynamic friction coefficient. From FIG. 3, the coefficient of kinetic friction sharply changes when the value of σ _S / σ _A is 3.0, and σ _S / σ _A ≦ 3.0.
It can be clearly seen that the lubrication state of both is very good in the region of No. Based on this finding, when a steel strip to be coated is coated with a coating material having a low liquid viscosity, σ _S / σ _A ≦ 3.
It has been found that by selecting the roughness of the applicator roll that satisfies the condition of 0, it is possible to perform coating with good lubricity without causing the above-mentioned troubles such as uneven coating and damage to the applicator roll.

[0016]

[0017]

According to the present invention, even for a paint having a low viscosity and poor coating lubricity, the ratio σ _S / σ _A of the surface roughness σ _S of the steel strip to the surface roughness σ _A of the applicator roll can be obtained. 3.0
By doing so, coating lubricity between the steel strip and the applicator roll can be greatly improved, and coating unevenness due to poor rotation of the applicator roll and damage to the applicator roll itself can be prevented.

[0018]

[Brief description of the drawings]

FIG. 1 is a schematic view of a reverse roll coater.

FIG. 2 is a diagram showing a relationship between composite surface roughness and dynamic friction coefficient.

FIG. 3 is a diagram showing the relationship between the ratio of the surface roughness of a steel strip to an applicator roll and the coefficient of dynamic friction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paint pan 2 Pickup roll 3 Applicator roll 4 Backup roll 5 Steel strip

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-8776 (JP, A) JP-A-61-216771 (JP, A) JP-A-54-153842 (JP, A) JP-A-58-1983 98166 (JP, A) Hikaru Hei 3-3466 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B05D 1/28 B05D 7/14 B05C 1/04-1/14

Claims (1)

(57) [Claims] An extremely low-viscosity paint having a liquid viscosity of 5.0 CP or less is obtained by using a reverse roll coater having a pickup roll for picking up paint from a paint pan and an applicator roll for transferring paint from the pickup roll. , upon coating the steel strip which is an object to be coated was a steel strip by the ratio σ _S / σ _a surface roughness sigma _S and the surface roughness of the applicator roll sigma _a of the strip than 3.0 A reverse roll coating method excellent in coating lubrication, characterized by improving coating lubrication between applicator rolls.