JPH08219B2 - How to prevent skinning of nozzles, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to preventing skinning around a nozzle and the vicinity including the nozzle in the application of an emulsion type adhesive and a coating agent.

[Conventional technology]

2. Description of the Related Art Conventionally, a room temperature dry type, particularly a solvent type emulsion type coating agent and an adhesive agent have been widely used.

Compared to hot melt type adhesives, these coating agents and adhesives generally have a lower viscosity during application, and since a solvent is included, a thin film is finally obtained, and it is possible to work with a simple device. It is characterized by leading to cost reduction.

On the other hand, these emulsion type coating agents and adhesives (hereinafter referred to as emulsion adhesives) solidify when the solvent evaporates, and require a long time for washing, and therefore a simple method has been required. In particular, emulsion adhesives of vinyl acetate or ethylene vinyl acetate copolymer have strong adhesive strength to paper and are superior in heat resistance to general hot melt adhesives, while the solvent is water When the above solidified, it became impossible to wash with water, and it was necessary to wash with an organic solvent having a strong dissolving power.

In general, an inexpensive and simple method such as an air spray gun has been the mainstream for applying the emulsion adhesive in the packaging field. More recently, automation has progressed, and the need for labor saving is increasing. Emulsion adhesives can be inspected in a later process when the nozzle is completely solidified and not applied, but when it is not completely skinned, it can be applied. The present situation is that the quantity changes and becomes a serious defect in quality, which has a great impact on automation and labor saving.

[Problems to be solved]

The motivation for the present invention was to maximize the advantages of emulsion adhesives while at the same time eliminating their drawbacks.

[Means for solving problems]

An object of the present invention is to perform unattended application of emulsion adhesive under the same conditions without solidifying the emulsion adhesive or the like in the nozzle portion.

First, the conventional basic method will be described. Please refer to FIG. Emulsion adhesive (6) is a pressure tank (5)
Then, the compressed air is pressurized by a desired amount of compressed air and guided to the spray gun (1) by the hose (7). The emulsion adhesive is activated by the operation of the gun (1) and the needle (8
-A) and the sheet (8-B) are discharged to the outside. The gun (1) is operated by compressed air, and when the three-way valve type solenoid valve (2) is opened, preconditioned air passes through the hose (3) and lifts the piston (4). The piston (4) and the needle (8-A) are connected, and the emulsion adhesive is automatically discharged. When the solenoid valve (2) is closed, the air that lifts the piston escapes from the exhaust port of the solenoid valve through the hose (3), and the piston (4) and needle (8-A) are pushed back by the spring (22) and the emulsion The adhesive stops dispensing.

When the desired compressed air is let out through the hose (10) at the same time as the ejection of the emulsion adhesive, or before and after the ejection, the emulsion adhesive is patterned according to the characteristics of the air nozzle (9), It becomes atomized or atomized particles (21).

The solvent (14) in the container (16) can be guided through the tube (13) into the atomizing air hose (10) leading to the gun (1) as shown in FIG. If the container is open,
As shown in Fig. 3, the solvent (14) is the flow of compressed air (18).
It is pulled out by the siphon effect (19) and the fine particles (2
0) and mixed with compressed air to granulate the emulsion. At this time, the emulsion adhesive particles, which are about to adhere to the surfaces of the sheet (8-B) and the air nozzle (9) in FIG. 5, are easily washed away by the force of the solvent and the compressed air. For this reason, the needle (8-A), the seat (8-B) and the air nozzle (9) have no residue of emulsion at all, and therefore are not skinned.

In intermittent spraying of an emulsion adhesive, compressed air for granulation or atomization is mainly jetted intermittently according to opening and closing of the emulsion adhesive from the viewpoint of energy saving. In this case, it is desirable to guide the solvent tube (13) downstream of the solenoid valve (12) for opening and closing the compressed air shown in FIG. This is because in the case of a complicated circuit, the atomized solvent may aggregate to form water droplets, and in this case, a portion where the emulsion adhesive is applied may be diluted. As for the solvent supply method in this case, the solvent (14) is put into the pressure tank (16) and pressurized by a solenoid valve (17) as shown in FIG. But either is fine.

The most ideal method is the two-fluid spray method of emulsion type adhesive, which is a circuit downstream of an on-off valve for supplying compressed gas and which is provided with a solvent liquid by a separate line near the compressed gas ejection nozzle. A certain water or a solvent liquid containing 5% or less of an alcohol solvent in water is introduced, and the solvent liquid is atomized or atomized by jetting the compressed gas, and the gas-liquid mixture is subjected to the emulsion-type adhesion. In synchronization with the opening / closing timing of the needle valve of the agent, when the needle valve is closed, it is supplied to the downstream side of the needle valve to prevent skinning of the nozzle and its vicinity, a method of preventing skinning of the nozzle, etc. Suitable for forming small application patterns with a small amount by high-speed intermittent spraying.

In this case, there is no concern that the solvent will agglomerate in the atomizing compressed air hose (10), the solvent may be in a very small amount, and the particles may be fine or saturated to have a relative humidity of 99% in the case of an aqueous system.
All you need to do is the above.

The application in this case is not possible until now, as described above, when it is necessary to maintain a constant coating amount at a high speed and with a small coating amount, for example, in the packaging field, for coating vinyl acetate emulsion by high-speed cartoning. Optimal.

The present invention can also be applied to airless air spray. In this method, as shown in FIG. 9, when airless spraying, tails (2
It is used in the industry to reduce or eliminate the liquid atomization resistance called 5) which is difficult to atomize. However, even in this method, the flow of air is caused by jetting the compressed air, and the residue (26) of the jetted liquid dries around the orifice of the airless nozzle and is immediately skinned. Airless spray has a relatively high hydraulic pressure (20 kg / cm ² ~ 15
Since it is sprayed at 0 kg / cm ² ), it can be sprayed with a small amount of skin, but the residue or the emulsion adhesive that has adhered near this nozzle is ejected together and is called a gob. Since it adheres to the coating film as a foreign substance, it causes a fatal coating film defect in the coating.
According to the present invention, this problem can be solved easily. Next, as a typical example of the contact type, coating with a slot nozzle will be described with reference to FIG.

Since the gun mechanism of the slot nozzle is generally the same as that of the air spray gun and the airless spray gun, it is omitted. When an open signal is input to the gun, the needle or ball (26) rises, and the emulsion adhesive pressurized by the pump passes through a narrow slit groove (29) and then a thin coating film ( 30) is formed. Particularly, in intermittent coating, the emulsion adhesive adhered to the slot nozzle portion (32), and it was difficult to form a good pattern. In the present invention, in order to prevent the emulsion adhesive from adhering to the slot nozzle portion, it was examined that compressed air is applied to the slot nozzle to prevent the adhesion.

However, the compressed air dries the adhered emulsion adhesive, so that good results were not obtained. Therefore,
A liquid adhesive or coating agent containing the solvent of the present invention,
In a method of spraying from a slot nozzle provided with an assist air spray port and applying to a substrate, a solvent liquid is introduced into an assist air spray conduit, and the solvent liquid is atomized or atomized by the spray of the assist air. The gas-liquid mixed fluid is jetted toward the tip of the slot nozzle that jets the liquid adhesive or coating agent containing the solvent, and the liquid adhesive or coating agent containing the solvent is jetted and applied to the substrate. This problem could be easily solved by adopting the above-described method of preventing skinning of the nozzle or the like.

Although the solvent ejection timing is preferably the timing shown in FIG. 8A in all cases, good results are also obtained in FIGS. 8B, 8C and 8D in the extrusion discharge method and the airless spray method.

〔effect〕

As described above, according to the present invention, it is possible to prevent the skin adhering phenomenon of the same on the two-fluid spray nozzles for various emulsion adhesives or coating agents and to contribute to the improvement of work efficiency. is there.

[Brief description of drawings]

FIG. 1 is an explanatory view of a basic system in a two-fluid spray. FIG. 2 is an explanatory view of a state in which a solvent tube is provided downstream of an opening / closing valve on a compressed air pipe in the two-fluid spray according to the present invention. FIG. 3 is a siphon of a solvent tube. Fig. 4 is an explanatory view in the case of using a pipe. Fig. 4 is an explanatory view in the case of using the solvent tube for solvent pressure feeding. Fig. 5 is an explanatory view in the case of introducing the end of the solvent tube in the vicinity of the nozzle in the same. Fig. 6 is the same as above. Piping explanatory drawing FIG. 7 is an explanatory drawing when applied on the slot nozzle of the present invention. FIGS. 8A to 8D are timing charts for discharging adhesive, compressed air, solvent, etc. FIG. 9 is a conventional two-fluid spray nozzle. Illustration of state of residue generated on top Explanation of main symbols 10 …… Compressed air piping, 13 …… Solvent tube

Claims (1)

[Claims] 1. A two-fluid spraying method for an emulsion type adhesive, wherein water as a solvent liquid is supplied through an independent pipe line in the circuit downstream of an on-off valve for supplying compressed gas and near the compressed gas ejection nozzle. Alternatively, a solvent liquid containing 5% or less of an alcohol solvent in water is introduced, and the solvent liquid is atomized or atomized by jetting the compressed gas, and the gas-liquid mixture is mixed with the emulsion-type adhesive. A method for preventing skinning of a nozzle or the like, which is synchronized with the opening / closing timing of the needle valve and is supplied to the downstream side of the needle valve when the needle valve is closed to prevent skinning of the nozzle and its vicinity.