JPH035977B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of forming a resin film by thinly and uniformly applying a hot melt resin onto a release paper when manufacturing a hot melt type adhesive or prepreg resin film. Traditionally, hot melt adhesives and resin films for prepregs have been manufactured by coating them on release films using various roll coaters, doctor knife coaters, die coaters, fountain coaters, etc. There are, but
No matter which coater is used, the resin used is quite viscous even under heating, and it is extremely difficult to apply it thinly and uniformly onto the release paper. For example, FIG. 1 is a schematic diagram showing the process of creating a resin film using a fountain coater. In the figure, 1 is a fountain coater, 2 is a back-up roll, 3 is a release paper, and 4 is a resin film coated on the release paper. Figure 2 shows the results of measuring the thickness in the width direction of the resin film coated on the release paper by the method shown in Figure 1, using the fountain coater shown in Figure 1. No matter how accurately the opening width of the lip portion is made uniform, it is impossible to prevent thickness unevenness from occurring in the width direction of the resulting resin film. Therefore, in order to prevent the occurrence of thickness unevenness in the width direction of the film, conventional techniques have been used to improve the width accuracy of the die discharge part and improve the machining accuracy of the back-up roll surface. The occurrence of thickness unevenness in the width direction of the film has been improved to a large extent by improving the accuracy of the film width, improving the temperature distribution of the resin coating part of the die, and adjusting the die slit width using push-pull bolts installed on the die. However, these improvement methods cannot prevent the occurrence of thickness spots on the film as shown in a, b, c, and d of Figure 3. It has been said that it is virtually impossible to suppress it. Therefore, the present inventors investigated to find a method of manufacturing a resin film that could prevent the occurrence of thickness unevenness on the film, and found that even if the molten resin coating part was applied with various improvement methods as described above, It was found that temperature distribution unevenness occurred as shown in the figure, and thickness unevenness occurred in the resulting resin film. Figure 2 shows the thickness in the width direction of the resin film obtained when several strip heaters were installed in the die slit to prevent uneven temperature distribution at the discharge part.
This method requires a lot of effort to eliminate thickness unevenness in the width direction of the film, but is not very effective. Therefore, the present inventors further investigated a method for eliminating thickness unevenness in the width direction of the film, and surprisingly found that the thickness of the resin film obtained by preheating the release film to which the molten resin is applied The present invention was completed by discovering that the occurrence of taste spots was eliminated and a resin film with only thickness spots of 10 μm or less could be obtained. FIG. 5 is a schematic diagram showing an example of the method for forming the resin film of the present invention using a fountain coater as the coater. In the figure, 5 is a heater for heating the release paper. Although the release paper can be heated uniformly, depending on the thickness unevenness development pattern in the width direction of the film as shown in Fig. 3, the release film heating heater may be a multi-stage divided heater to control the thickness of the resin film. It was possible to prevent the occurrence of thickness unevenness in the resin film by heating the part of the release paper that is thicker than other parts so that the temperature of the release paper was higher than that of other parts of the release paper. As for the method of heating the release paper, it is desirable to perform contact heating using plate heaters separated in the width direction, but it is also possible to use a non-contact heating method using a dark infrared heater or the like. The heating section is preferably divided into three or more zones, although it depends on the characteristics of the coater used.
Further, although it is desirable that the temperature of each of the separated heating elements can be controlled independently, it is not necessary that adjacent heaters be completely independent by using a heat insulating material or the like. According to the method of the present invention, in addition to the advantage of correcting the thickness unevenness of the resin film as described above, as an effect of heating the release paper, cooling of the resin during coating can be prevented. Because there is almost no sudden drop in viscosity, a thinner coating film can be obtained at the same resin temperature than without this method, and when applying a coating film of the same thickness, the resin temperature can be lowered. This method has the advantage of being able to be set easily, and is particularly suitable for making resin films from thermosetting resins, which are easily affected by thermal history. If the coating base material is release paper, the heating temperature is 100℃ for a short time.
It can sufficiently withstand heating to a nearby temperature without deteriorating in quality, and even if a thermoplastic resin film is used as a release paper, its effects can be fully demonstrated by appropriately selecting the heating temperature. Furthermore, according to this method, it is also possible to correct uneven resin thickness caused by resin supply methods and resin flow conditions. For example, when using a die coater with a single-sided resin supply system as shown in Figure 5, uneven thickness patterns as shown in Figure 3 c or d tend to occur; By increasing the heating of the release paper compared to other types, uneven thickness can be eliminated. Going further, laser type,
It is easy to automatically control the thickness distribution by combining an automatic continuous thickness measuring device such as a dielectric constant detection type with a control device for the release paper heating element.
Further, the method according to the present invention is an extremely effective method because it can be easily implemented even in an existing coater by simply attaching a part for heating the release paper using a heating element such as a plate heater. The present invention will be explained in more detail below with reference to Examples, but it goes without saying that the present invention is not limited thereto. Example 1 In the fountain coater 1 shown in Fig. 1, a plate heater with a length of 60 cm divided into three parts based on the coating width was installed just before the coating section so that it could contact and heat the release surface of the release paper, and the curing agent was applied. The mixed epoxy resin composition was discharged from the die at a heating medium temperature of 70°C, and coated on the center of a 530 mm wide release paper at a coating width of 500 mm and a coating speed of 10 m/sec without raising the temperature of the plate heater. Perform sampling and measure the thickness of the resin film.
Measurements were taken in 100mm width sections. Further, under the same conditions, the left and right plate heaters were heated to 100°C, and the center plate heater was heated to 80°C, and then sampling was performed again to measure the thickness and basis weight of the resin film. Table 1 shows the results.

[Table] The thickness of the film was calculated by dividing the basis weight of the 100 mm width of the film by the density of the resin, 1.20/cm ² . Example 2 5th plate heater with 3-part heating type plate heater
Using a one-sided resin supply type fountain coater as shown in the figure, the same resin composition as in Example 1 was applied at a heating medium temperature of 75°C without raising the temperature of the plate heater, with a release paper width of 530 mm and a coating width of 500 mm. After coating at a coating speed of 15 m/sec, sampling was performed and the basis weight and film thickness of the resin film were measured every 100 mm width. Furthermore, under the same conditions, the plate heater for resin supply measurement was heated to 100°C, the center part to 90°C, and the opposite side to 80°C, and then sampling was performed again, and the basis weight and film thickness of the resin film were measured at every 100 mm width. .
The results are shown in Table-2.

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a fuauten coater, in which 1 is a die, 2 is a back-up roll, and 3 is a back-up roll.
4 indicates the release paper, and the shaded area 4 indicates the coated resin film. FIGS. 2 and 3 show the measurement results of thickness unevenness of the resin film, and FIG. 4 shows the unevenness of the die slit temperature during resin coating. FIG. 5 shows the production of a resin film using a one-sided supply type Fauten coater, and numeral 5 in the figure indicates a plate heater. This heater is divided into three zones, each of which can be controlled.

Claims (1)

[Scope of Claims] 1. A method for forming a resin film, characterized in that when a heated and melted resin is continuously applied to a release paper, the release paper is heated in the width direction to apply the resin. 2. A release paper The method for forming a resin film according to claim 1, characterized in that the method of heating the resin film uses a means of heating the resin film by dividing it in the width direction.