JPH028786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved coating method that provides a cured product free of shot marks and with uniform appearance and physical properties. The present invention also relates to a method for eliminating surface defects that occur in a cured product when a reactively curable resin liquid is discharged continuously or intermittently from a mixing device.

The reactive hardening resin liquid is measured and mixed using a compounding machine, etc.
It is discharged onto a sheet material such as paper, cloth, plastic film, or metal foil, or onto a base material such as a wooden board, metal plate, or plastic board, and then coated with a spreading coating device such as a knife coater. After that,
Common processing methods include leaving the product at room temperature or passing it through an oven, heat plate, or other curing device to obtain a cured product. In such a processing method, only the portions of the surface of the cured product where the liquid has been discharged and flowed appear to have an appearance that is different from the rest of the surface.
This surface pattern is called a “shot mark”.
This not only significantly reduces the aesthetic value of the cured product, but also significantly impairs its commercial value due to its non-uniform surface properties. These shot marks are thought to be caused by differences in physical properties and reactivity between the liquid flowing down and the liquid that has already been discharged and remains in the coater's pool, but they are unavoidable in the processing method described above. Ta.

On the other hand, in order to eliminate this shot mark, there is a method of eliminating the need for a continuous coating device such as a knife coater and letting the discharged liquid flow down a die strip in the form of a thin film, but in this case, strict die design is required to ensure uniform coating thickness. This is essential, and it is necessary to pay sufficient attention to the delivery of the ejected liquid and its viscosity range. Therefore, such coating equipment is very expensive, and coating conditions etc. must be strictly controlled.

The present invention is a coating method using a continuous coating device such as a knife coater, which has a simple mechanism and easy coating management.
The object of the present invention is to provide an improved coating method that allows a cured product with uniform appearance and physical properties to be obtained without shot marks.

When coating with a spreading coating device such as a knife coater, a barrier such as a knife is placed in a direction perpendicular to the coating direction, so a portion of the liquid discharged in front of this barrier is dammed up. The liquid accumulates and forms a puddle. This pooled liquid rotates with a rotation axis perpendicular to the direction of movement as the substrate advances while contacting the knife barrier. The upper surface of the puddle liquid, when viewed from the front in the direction of travel, wraps around from the top to the bottom, contacts and adheres to the base material, and sinks into the puddle. In this way, a portion of the pooled liquid passes through the gap at the tip of the knife blade or the like and is applied, but this reduced amount is supplied continuously or intermittently from the liquid outlet.

Therefore, when discharging a reaction-curable resin liquid directly onto a substrate or discharging it down onto a liquid pool as in the past, there is a difference between the liquid that has already been discharged and remains in the pool and the liquid that is newly discharged and flowing down. It is thought that shot marks are produced because the liquid comes into contact with the substrate without being sufficiently diffused and mixed.

As a result of a detailed study on the retention of liquid puddles, we found that when applying reactive curing resin liquid that is continuously or intermittently discharged from a mixing device with a continuous coating device such as a knife coater, The following improved coating method has been invented which has no shot marks and has uniform appearance and physical properties. That is, in a knife coater or the like, a liquid discharge port is located near the central axis of rotation of a rotating liquid pool, and the coating is performed by reciprocating the liquid from side to side in the direction along a barrier such as a knife in the liquid pool. . In this case, the liquid discharged from the mixing device is constantly supplied over the entire axial direction of the rotating liquid pool near the rotation center axis.

In carrying out the present invention, the mixing device includes:
A gear pump such as a urethane foaming machine is used to continuously send the liquid to the mixing head, where it is rotated and stirred, and the liquid is immediately discharged. Alternatively, a plunger, which is often used as a compounding machine for epoxy resin, etc., is used to intermittently send the liquid to the mixing head. Devices that mix and discharge through guided static mixing elements, or combinations thereof, can be used. Among these, a device that continuously feeds the liquid with a gear pump and continuously mixes and discharges the liquid is particularly preferred.

As a spreading coating device such as a knife coater, any device that coats while creating a liquid pool with a scraper plate or scraper may be used, but a knife coater is generally preferred. The knife coater may be of any type, such as a floating knife, knife over roll, knife over blanket, etc., and the knife shape may be an arc knife, a hook knife, a weir knife, a spanishing knife, a cow nose knife, or a round knife. Any shape such as a stick knife can be used, and the selection thereof may be made according to the coating purpose and conditions such as coating amount, liquid viscosity, and coating speed.

In addition, a method of introducing a discharge port into a liquid pool and causing it to reciprocate from side to side is to insert the discharge port of the mixing head into the liquid pool and connect the two together to a traverse device driven by hydraulic pressure or an electric motor. There is a method of moving the fluid, and a method of connecting a flexible hose to the discharge port of a stationary mixing head and introducing the end of this hose into a liquid pool and traversing it.

On the other hand, the reaction-curable resin liquid in the present invention is as follows:
Urethane resin, epoxy resin, silicone resin, unsaturated polyester resin, polydiene liquid rubber,
It is like curing liquid resin such as polysulfide resin by reaction with a curing agent or a reaction initiator.
The viscosity of these mixed liquids must be 100 to 100,000 in order to perform coating with a spreading coating device such as a knife coater.
Centipoise, especially 1000 to 10000 centipoise, is desirable.

The present invention provides high quality products with excellent appearance, such as laminated products such as woven fabrics with foam packing, transportation belts, sheet products such as packing sheets, waterproof materials, and coated products such as decorative panels, synthetic leather, and tarpaulins. is obtained, so
Extremely useful.

Examples and comparative examples of the present invention are shown below.

Example 1 A satin woven glass cloth EC#181VT (manufactured by Nitto Boseki Co., Ltd.) whose ends were gripped with a clip tenter was set in a coating device equipped with a knife-over bracket coater and a 6 m long oven, and 30 kg/g was applied in the direction of travel. A glass cloth was placed under tension and interposed between the hook knife and the blanket. After increasing the oven temperature to 120℃, apply silicone resin KE1204 (A-
B) Autospenser LTV (manufactured by Shin-Etsu Chemical Co., Ltd.)
Weigh and mix using an EP201S compounding machine (manufactured by Automachine Kaihatsu Co., Ltd.), and while dispensing at a rate of 430 g/min.
The discharge port was traversed over a width of m at a speed of 6 m/min to create a pool of liquid in front of the knife barrier. At the same time, an edge dam was installed so that the coating width was 1.2 m, and 2
When the glass cloth is fed at a speed of m/min, the liquid pool is approximately 30 m/min.
It is rolled into a roll with a diameter of mm and is applied by rotating while adhering to the knife barrier. Next, the discharge port was inserted into the liquid pool from above and positioned near the central axis of rotation of the liquid pool, and thereafter coating was continued in this state.

When we examined the surface of the cured coated product, we found that before the discharge port was inserted into the liquid pool, there were zigzag-like shot marks along the traversed route, but when the discharge port was inserted into the liquid pool, the center of rotation of the product was observed. After positioning it nearby, I could not see any shot marks at all.
The surface was smooth and beautiful.

Example 2 Process paper EK subjected to mold release treatment using a coating device with a knife over roll coater and a 6m long oven.
-120D ₂ (manufactured by Soken Kako Co., Ltd.) was set, and the gap between the arc knives was set to 0.5 mm. Oven temperature 135
℃, then measure and mix the urethane resin Adiprene L-315/Kaitiyur 21 (manufactured by Dupont) on process paper using an Auto Spencer EP201S compounding machine (Developed by Auto Machine Co., Ltd.), and dispense it at a rate of 520 g/min for 1 m. The discharge port was traversed across the width at a speed of 6 m/min to create a pool in front of the knife barrier.
At the same time, an edge dam is installed so that the coating width is 1.2 m, and when the process paper is fed at a speed of 1.2 m/min, the pooled liquid becomes a flat elliptical column with a height of about 20 mm and a width of about 100 mm, forming a knife barrier. It rotates while adhering and is coated. Next, insert the discharge port into the liquid pool from above and position it near the central axis of rotation of the liquid pool (this can be found by observing the cross section of the rotating body through a transparent edge dam plate). After that, coating was continued in this state.

When the surface of the cured coated product was examined, a zigzag-like shot mark was seen along the traversed route before the discharge port was inserted into the liquid pool, but when the discharge port was inserted into the liquid pool as the center of rotation, After positioning it near the axis, no shot marks were visible at all.
The surface was smooth and beautiful.

Example 3 In Example 1, only the blender was changed to an intermittent metering and mixing type Twin Flow (manufactured by Naka Seiki Co., Ltd.), and the mixture was discharged at 205 g/shot. The number of shots is approximately 2 per minute.
It was hot. In this case as well, no shot marks were observed in the cured product coated by inserting the discharge port into the liquid pool.

Comparative Example In Examples 1, 2, and 3, when coating was performed while inserting the discharge port into the liquid pool, when the traverse of the discharge port was stopped, thick linear shot marks appeared on the cured product.

[Brief explanation of drawings]

Figure 1 is a perspective view of the coating equipment, which is an example of a floating knife coater. Explanation of the symbols of the main parts, ...mixing head, ...knife coater, ...edge dam, ...
Liquid reservoir,...discharge port,...substrate to be coated. FIG. 2 is an enlarged sectional view of the main part, showing the position of the discharge port in the liquid pool. Explanation of the symbols of the main parts, ...mixing head, ...knife coater, 3' ...discharge port, ...liquid reservoir, 5' ...substrate to be coated, 6' ...back roll.

Claims (1)

[Claims] 1. When applying a reactive hardening resin liquid that is continuously or intermittently discharged from a mixing device using a spreading coating device such as a knife coater, the liquid is discharged near the central axis of rotation of the liquid puddle that rotates at the corner. A coating method characterized by locating an outlet and causing the liquid to reciprocate from side to side in a direction along a barrier such as a knife in a liquid pool.