JPS6216146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method for an apparatus for heating and melting a thermoplastic resin to give it fluidity and applying it to an adherend as an instant adhesive/adhesive.

There is an apparatus for applying this type of resin called hot melt adhesive having a structure as shown in FIG. According to FIG. 1, the coating device is
Melting tank 1 that holds thermoplastic resin in a molten state
It is equipped with An electric heater 2 is buried in the bottom of the melting tank 1. A gear pump 3 is provided at the bottom of the melting tank 1.
A heater 4 is also embedded within the main body of the heater. The gear pump 3 is connected to a suitable drive motor 5. The outlet of the gear pump 3 is connected to a manifold 7 via a filter 6. This manifold 7
A heater 8 is also embedded in the main body. Manifold 7 communicates with melting tank 1 via pressure regulating orifice 9 . A flexible hose 10 is connected to the outlet of the manifold 7. The flexible hose 10 includes a heater 11 and a heat insulator 12
The inner wall is lined with polyfluoroethylene to prevent adhesion of molten resin. A gun 13 that injects molten resin is connected to the outlet of the flexible hose 10. This gun 13 is also provided with a heater 14. Gun 13 has needle valve 15 and valve seat 16
and a nozzle 17, and further includes a needle valve 1.
It has a pneumatic nozzle opening/closing device 18 for controlling 5. A line filter 19 is also provided at the inlet of the gun 13.

The thermoplastic resin charged into the melting tank 1 is heated to a constant temperature and melted by a heater 2 and a thermostat (not shown). This molten resin is sucked in and pressurized by the gear pump 3, which is kept at a constant temperature by a heater 4 and a thermostat (not shown). Next, impurities are removed from the molten resin by a filter 6, and the molten resin is fed under pressure to a manifold 7 kept at a constant temperature by a heater 8 and a thermostat (not shown). The pressure in the manifold 7 is regulated by a pressure regulating orifice 9 communicating with the melting tank 1. Further, the molten resin is supplied to the gun 13 via a heated flexible hose 10. The gun 13, which is kept at a constant temperature by a heater 14 and a thermostat (not shown), filters the supplied molten resin with a line filter 19, and then injects it from a nozzle 17 in response to opening/closing of a needle valve 15 to remove deposits (not shown). Apply to the body.

In the conventional coating device as described above, since the resin solidifies at room temperature, the melting tank 1, which is the inlet of the resin,
heaters 2, 4, 8,
11 and 14 are provided to heat and melt the resin at all times, and the heating temperature of each heater is controlled independently by a thermostat associated with each heater using a preset system. The preset values for each temperature are determined by the type of resin used.

The problem here is the heating state of the melting tank 1. That is, the melting tank 1 heats and melts the solid thermoplastic resin and at the same time maintains the molten state, and this temperature is controlled independently of the coating state of the coating device. Therefore, when the amount of molten resin applied is small (including when the coating apparatus is stopped), the resin is kept in a heated and molten state for a long time. Therefore, the surface of the high-temperature molten resin exposed to air in the melting tank 1 will undergo thermal deterioration, alteration, and discoloration. In order to avoid this, there is a conventional method in which the melting tank 1 is filled with an inert gas such as nitrogen gas to shut off air. However, it is known that even if the resin does not come into contact with air, as heating temperature and heating time increase, property deterioration, such as a decrease in adhesive ability, is accelerated.

The present invention has been made in view of the above-mentioned circumstances, and is a coating device that lowers the temperature of the resin heated and melted in the melting tank 1 of the coating device as much as possible to prevent thermal deterioration of the thermoplastic resin. The purpose is to provide a temperature control method.

According to the present invention, it is desired that the application temperature of the molten resin finally applied to the adherend is maintained at a desired temperature in the application device, and therefore,
The melting tank 1 is heated to a temperature as low as possible without causing any change in the coating temperature. That is, the heating temperature of the melting tank 1 is feedback-controlled based on the coating temperature.

According to the present invention, a thermoplastic resin is heated and melted,
In a resin temperature control method for a device that applies pressure to an adherend, the application temperature of the molten resin to be applied is detected, and this application temperature is set at a predetermined application temperature centered around the optimum application temperature. When the upper limit of the range is reached, the temperature at which the resin is heated and melted is controlled to a predetermined temperature range with the softening point of the resin as the lower limit temperature, and when the coating temperature reaches the lower limit of the coating temperature range, the resin is heated and melted. Provided is a temperature control method for a thermoplastic resin coating apparatus, which comprises controlling the temperature at which the thermoplastic resin is heated and melted to a predetermined temperature range around the optimum coating temperature.

The present invention will be described in detail below based on a preferred embodiment of the present invention illustrated in FIG.

In order to implement the temperature control method for a coating apparatus according to the present invention, it is necessary to detect the temperature of each part of the apparatus. Therefore, in the coating apparatus shown in FIG. 1, the temperature sensor 20 for temperature detection of the melting tank 1, the temperature sensor 21 for temperature detection of the gear pump 3, and the
A temperature sensor 22 for detecting the temperature of the flexible hose 10, a temperature sensor 23 for detecting the temperature of the gun 13, and a temperature sensor 24 for detecting the temperature of the molten resin are provided. It is provided at the outlet portion of the hose 10.

FIG. 2 shows an example of temperature control of the main parts of the coating device. Curve A represented by a solid line represents the temperature change in the melting tank 1, and curve B represented by a broken line represents the temperature change of the flexible hose 10. The dashed line represents the temperature change. curve C
indicates the temperature change of the gun 13, and the curve D indicated by the two-dot chain line indicates the coating temperature of the molten resin measured by the temperature sensor 24, respectively.

The example in Figure 2 is when using a resin whose optimal application temperature is 170°C, softening point (temperature at which melting begins) is 110°C, and thermal stability limit temperature (limit temperature at which deterioration occurs) is 220°C. It shows.

In FIG. 2, time t ₀ is the start time of warm-up operation of the coating device, and at this time, each part of the coating device is at room temperature and the resin is solidified. At the start of this warm-up operation, we originally do not want to expose the resin to high temperatures, but because we want to start the coating process quickly, we rapidly heat the melting tank 1 and adjust the temperature within the temperature control range of 180℃ to 220℃. do. Also, although not shown, the flexible hose 10 and gun 13,
The gear pump 3 and manifold 7 are similarly rapidly heated and their respective temperatures are adjusted within the range of 160°C to 180°C. These temperature adjustments are performed independently by respective temperature sensors, similar to conventional temperature control. This warm-up operation continues until time _t1 . This period t ₀ -t ₁ differs depending on the type of resin, and its setting is performed by a variable timer.

After the warm-up period has passed, the temperature control of the present invention based on the coating temperature (curve D) by the temperature sensor 24 starts.

The coating temperature reaches the upper limit of the coating temperature range at time _t2 .
When the temperature reaches 180℃, the temperature of the melting tank 1 (curve A) decreases from 110℃ to the lower limit of the resin softening point (110℃).
Start temperature adjustment within the temperature control range of 120℃. This is because when the amount of coating is small, each heater up to the temperature sensor 24 can slowly heat the molten resin to the optimum coating temperature.

If the coating temperature reaches 160°C, the lower limit of the coating temperature range, due to an increase in the amount of coating (time t ₃ ), each heater other than melting tank 1 has a small heat capacity, so the resin is heated in melting tank 1. There is a need.
Therefore, at this time, temperature adjustment of the melting tank 1 is started within the temperature control range of 160°C to 170°C, which is close to the coating temperature.

When the coating temperature reaches the coating temperature range upper limit of 180°C again (time t ₄ ), the temperature of the melting tank 1 is adjusted within the temperature control range of 110°C to 120°C until the coating temperature reaches the lower limit temperature of 160°C. It will be done like this.

Of course, flexible hose 10 after time t ₁
The temperature of the gun 13 is individually adjusted within the temperature range of 170°C to 180°C, and the temperature of the gun 13 is similarly adjusted within the temperature range of 160°C to 170°C. Similarly, the temperature of the gear pump 3 and the manifold is individually adjusted within an appropriate temperature range of 160°C to 180°C.

In addition, in the above warm-up operation, the temperature was rapidly heated to the thermal stability limit temperature (220℃), but another method of warm-up operation is to increase the temperature of the melting tank 1 to 110℃, which is the softening point of the resin. If exceeds, time t ₃ ~ _{t 4}
As well as the temperature control of the melting tank 1 during
The temperature may be adjusted within a temperature control range of 160°C to 170°C. According to this method, thermal deterioration of the resin can be completely eliminated.

A control device (not shown) that adjusts the temperature of each part is
In the event of abnormal heating (above 250°C) or abnormally low temperature (below 100°C, heater disconnection), an alarm or display will notify you of this and stop the operation of the coating device.

As described above, according to the present invention, when the coating amount of resin is small and the coating temperature rises, the heating melting temperature of the resin is lowered to near its softening point, and conversely, when the coating amount is large and the coating temperature rises, the heating melting temperature of the resin is lowered to near its softening point. When the temperature drops, the heating melting temperature is temporarily and rapidly raised to around the optimum coating temperature of 170°C to quickly control the coating temperature to the appropriate temperature, so the coating temperature is always constant regardless of the amount of resin coated. is obtained. In addition, since the heating and melting temperature of the melting tank 1 is raised only to the minimum necessary temperature, not only thermal deterioration of the resin but also deterioration and discoloration will not occur at all, and therefore there is no need to fill the melting tank 1 with inert gas. It is. Furthermore, since the heater 2 of the melting tank 1, which has a relatively large heat capacity, requires minimal heating (usually within a temperature range of 110°C to 120°C), the power consumed by the heater 2 can be significantly reduced. I can do it.

Although the present invention has been described below in detail with reference to its preferred embodiment, the present invention is not limited to this specific embodiment and can be modified in many ways without departing from the spirit of the invention. For example, the method of the present invention involves temperature control when applying hot-melt adhesive, including the size of the applicator, the type of applicator (nozzle type, wheel type, jet type, etc.), and the application of the adhesive (sealing, fixing, fixing, etc.). There are no restrictions on insulation, filling, coating, etc.).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a coating apparatus to which the control method according to the present invention is applied, and FIG. 2 is a graph illustrating temperature changes in main parts of the coating apparatus shown in FIG. 1 to which the control method according to the present invention is applied. 1...Melting tank, 2...Heater, 3...Gear pump, 4...Heater, 5...Motor, 6...Filter, 7
...Manifold, 8...Heater, 9...Pressure adjustment orifice, 10...Flexible hose, 11...Heater, 12...Insulation material, 13...Gun, 14...Heater,
15... Needle valve, 16... Valve seat, 1
7... Nozzle, 18... Nozzle opening/closing device, 19... Line filter, 20, 21, 22, 23, 24... Temperature sensor.

Claims (1)

[Claims] 1. In a resin temperature control method for a device that heats and melts a thermoplastic resin and applies pressure to an adherend, the application temperature of the melted resin to be applied is detected, and this application temperature is determined to be the optimum application temperature. Controlling the temperature at which the resin is heated and melted when the upper limit of a predetermined coating temperature range centered on the temperature is reached within a predetermined temperature range with the softening point of the resin as the lower limit temperature,
A temperature control method for a thermoplastic resin coating apparatus, characterized in that when the coating temperature reaches the lower limit of the coating temperature range, the temperature at which the resin is heated and melted is controlled to a predetermined temperature range near the optimum coating temperature. .