JPS62180776A - Method and apparatus for coating hot melt adhesive agent - Google Patents

Abstract

PURPOSE:To form stably, uniformly and sharply intermitted coating patterns by adding specific time of the ejection time for hot air before and after the discharge time for a hot melt adhesive agent and spraying the adhesive agent. CONSTITUTION:The hot air is used for the ejection air in an intermittent coating operation of the hot melt adhesive agent by air spray and 1-100msec of the ejection time for the hot air is added before and after the discharge time for the hot melt adhesive agent, then the adhesive agent is sprayed. The continuously generated hot air is released into the atm. or transferred to the other circuit during the intermission of the ejection from a gun nozzle for the hot air. As a result, the stably, uniformly and sharply intermitted coating patterns are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for applying a hot melt adhesive by hot air spray.

Conventional technology Conventionally, when applying true melt adhesive intermittently by air spray, air is continuously jetted from a gun.
Only hot melt adhesive was being discharged intermittently. Specifically, the compressed air supply valve was always open to cause the compressed air to be continuously jetted from the gun, and only the needle valve on the hot melt adhesive discharge path inside the gun was opened and closed. The reason for this was the need to maintain a constant air jet and stabilize the coating pattern.

As a practical matter, the problem to be solved is that in the above conventional method,
Sufficient stabilization of the coating pattern could not be obtained.

This will be explained using drawings. Please refer to Figure 3.

This figure is a cross-sectional view of the gun after the needle valve for discharging hot melt adhesive. E7. In the intermittent application operation of the hot melt adhesive, the discharge of the molten hot melt adhesive HM can be completely interrupted by closing the needle valve 32. At the same time, the closing part of the needle valve 32 (valve note 3
2S), hot melt adhesive remains in the passageway to the tip 31F of the gun body 31, that is, in the discharge hole 34 (H
MZ). However, this residual hot melt adhesive H
Due to the suction effect (Bernoulli's theorem) of continuously ejected air, the MZ is picked up little by little and discharged and sprayed into the atmosphere. We call this the spitting phenomenon. These immediately appear on the spray pattern resulting in an unstable or undesired coating pattern.

Furthermore, when cutting the coating pattern, a sufficient clean cut is not performed, and the outline of the intermittent coating pattern becomes unclear.

Means to solve the problem In the intermittent spray application work of hot melt adhesive,
Needle valve 32 is used to perform a clean cut.
It is sufficient to prevent the remaining hot melt and adhesive HMZ remaining in the passageway after the sheet and the part 32S, that is, the discharge hole 34, from being discharged, and for this purpose, it is necessary to stop the blowout of air. Good (see Figure 3). That is, in addition to stopping the discharge of the hot melt adhesive and cutting off the heat, the air blowout can also be immediately turned off. However, as a practical matter, after the discharge of the hot melt adhesive is "cut off", the residual amount of the hot melt adhesive adheres in an extremely unstable state around the discharge hole 34 (1).
1.1. In order to eliminate this problem, if the air jet is turned off after a period of time (in units of milliseconds) after the hot melt adhesive 1 is broken, the above-mentioned problem will occur within 0 hours. Steady state residual HMZ'
is excluded.

In addition, the air is ejected a little earlier (in milliseconds) than the hot melt adhesive discharge time (in milliseconds). Is it longer than the closing time of the dollar valve?
This is because that. A graph showing the timing comparison of both valves in the intermittent spraying of hot melt adhesive performed in this manner is shown in FIG. 1A.

When the above method, that is, the intermittent opening and closing of the hot melt adhesive valve and the blowing air valve, is carried out using a conventional device, that is, a device equipped with a three-way switching valve 8B as shown in FIG. 2B, the following results are obtained. Problem has occurred.

In the first place, hot air is used as the compressed air to be ejected in this work. The reason is that with compressed air at ambient temperature, when the compressed air is ejected from the nozzle into the atmosphere,
Due to adiabatic expansion, the temperature of the air itself suddenly drops, and if it becomes below the softening point of the adhesive (fosotomel) to be sprayed, sufficient atomization will not be obtained, that is, the desired coating pattern will not be obtained. be. Therefore, the temperature of the hot air being ejected is at least equal to or higher than the softening point of the hot melt adhesive, and the hot air is supplied to the gun and nozzle at a temperature that takes into account the temperature drop caused by adiabatic expansion. It is necessary. In particular, the higher the viscosity of the hot melt adhesive, the more essential the above conditions become.

As shown in FIG. 2A, the hot air is generally heated in the system after the blower 10 or after the compressor. In the figure, heating is performed by a hot air generator 9. Traditionally, hot air was continuously supplied to the gun through this air warmer. However, problems arise when the hot air is supplied intermittently according to the present invention. When the hot air is cut off, the flow of hot air stops and the air warmer overheats, and the hot air in the piping stagnates, causing the temperature to drop.Therefore, in conventional hot air systems, the hot air The desired intermittent jetting could not be achieved. Conventionally, hot air could only be supplied by opening and closing as described above, and a three-way switching valve 8B was provided as shown in FIG. 2B.

In order to solve this problem, the present invention provides a solenoid air type three-way switching valve in the hot air system between the air warmer 9 and the gun 1, as shown in FIG. 2A. Out of the three outlets of the three-way switching valve, one is provided with a pipe 11 which is connected to the gun 1 and the other is opened to the atmosphere or fed back to the inlet of the air warmer 9. Alternatively, the piping may be connected to a heat exchanger for another purpose instead of the air warmer.

With this device, the air warmer can be operated continuously even when hot melt is intermittent, so problems such as fluctuations in hot air temperature, which are conventional, do not occur.

Operation First, the timing of intermittent operation of the hot melt adhesive needle valve and the hot air air solenoid type three-way switching valve according to the method of the present invention will be described. 1st
Please refer to Figure A. The vertical axis shows the opening and closing of both valves, and the horizontal axis shows time T (milliseconds). The operating waveform of the hot melt adhesive needle valve (hereinafter abbreviated as NB) is set to “N”°, and the three-way switching valve for hot air (hereinafter referred to as AB
(abbreviated as ) is assumed to be "A'".

All have the same waveform. An enlarged view of the operating waveform "N" of NB and the corresponding operating waveform "A" of AB is shown in FIG. 1B.

On each of the above waveforms (note, the unit is milliseconds) n, ... NB's "open" start n2... Similarly, "open end n3... NB's" Beginning of "closed" n4... Similarly, end of "'closed"a,...
・AB's"open" start a2...Similarly, "open" end a3...AB's "close" start a4...Similarly, "close" end δn... ...Time δn of n+ -n 2 on waveform "°N", ...Time of same<ns→n □
δa... Time δa from a1 to a2 on waveform "A"
′,... Same<a3→a, time α...
...Allowance β of AB operation error...
・・Transmission time γ of hot air from the valve of AB to the nozzle ・・・・Time to remove unstable residue HMZ/ around the discharge hole 34 of the gun Tゎ ・・・・・AB and NB The time difference Tf between the start of operation and
l+... Sufficient time Ta before hot air blows out hot melt adhesive... Time difference T between NB and AB end of operation
a, . . . If the sufficient time for hot air injection after the end of discharging the hot melt adhesive is taken as T, =α−δn+β+δ3 T, =α+β.

T3-α-L l1γ+δa.

T, = α + γ.

If γ=10, then 8 m5 (T,) at the beginning of dispensing hot melt adhesive
Open the three-way hot air switching valve before opening, and then turn off the
Sometimes 14m5 (T
), just close the hot air three-way switching valve.

, The above figures are hypothetical figures for explanation purposes, and in reality they will fluctuate significantly more than the above. That is, the shape and dimensions of the gun and nozzle, the viscosity of the hot melt adhesive, the temperature of the hot air,
Their discharge, ejection amount, speed, etc. are major factors.

Next, the operation of the device according to the present invention will be explained. Please refer to Figure 2. In the intermittent spray operation of gun 1,
The supply of hot air is carried out by opening and closing the three-way switching valve 8, but when the three-way switching valve 8 is closed, the hot air is released to the atmosphere or switched to another circuit, so that the hot air generator can be operated continuously. Therefore, the operation of the hot air generator is not interrupted, that is, it can be operated continuously at all times, so there is no problem such as overheating of the air warmer or a drop in the temperature of the hot air in the circuit piping. , the conventional problems will no longer occur.

Effects of the Invention As described above, the method and apparatus of the present invention can provide a stable, uniform, and sharp discontinuous coating pattern in hot air intermittent spray application of true melt adhesives.

[Brief explanation of drawings]

Fig. 1A is a correlation diagram between the opening/closing timing waveform 11N I+ of the hot melt adhesive need valve according to the method of the present invention and the corresponding opening/closing timing waveform 11N I+ of the three-way switching valve for hot air according to the method of the present invention. N''
An explanatory diagram of the correlation between the waveform and the “A” waveform. Fig. 2A is a system diagram of the device of the present invention. Fig. 2B is a conventional three-way switching valve for hot air in section B of the above figure. Fig. 3 is a discharge hole in the side. Explanatory diagram of the state of hot melt adhesive remaining inside Explanation of main symbols 1.31...Gun (body) 5.35.
... Nozzle 6 ... Hot melt applicator 8 ... Three-way switching valve for hot air
9... Air warmer 23... Timer 32... Needle valve 33...
...Air blowout passage 34...HMZ...
Residue of hot melt adhesive in discharge hole HMZ'・
・・・・・・Unstable residual amount of hot melt adhesive attached around the discharge hole HA・・・・・・Hot air

Claims (1)

[Claims] 1. In the intermittent application work of hot melt adhesive by air spray, the jetting air is hot air, and the jetting time of the hot air is set to 1 millisecond before and after the hot melt adhesive jetting time, respectively. A hot melt adhesive application method characterized by spraying with an additional spray time of 1 to 100 milliseconds. 2. The hot melt adhesive coating method according to claim 1, wherein the number of interruptions is 100 times/min or more. 3. The method for applying a hot melt adhesive according to claim 1, wherein the temperature of the hot air at the time of ejection is at least higher than the softening point of the hot melt adhesive. 4. In the intermittent application work of hot melt adhesive by air spray, the blowing air is hot air, and the blowing time of the hot air is added from 1 millisecond to 100 milliseconds before and after the hot melt adhesive discharge time, respectively. A method for applying a hot melt adhesive, characterized in that the continuously generated hot air is discharged into the atmosphere or transferred to another circuit when jetting of the hot air from a gun nozzle is interrupted. 5. A hot melt adhesive coating device, characterized in that a three-way switching valve 8 is provided on the hot air supply piping 7 to the gun 1 in a hot air supply system consisting of a hot air generator. 6. The method for applying a hot melt adhesive according to any one of claims 1 to 4, and the apparatus for applying a hot melt adhesive according to claim 5, wherein the hot air is a heated gas.