JPH0414426A - Apparatus for molding film or sheet - Google Patents

Abstract

PURPOSE:To enhance a surface state by preventing the entrapment of air while preventing the vibration of a film or sheet by spraying air to the surface opposite to a roll of the film or sheet and sucking the air in the space formed by the film or sheet and a rotary roll. CONSTITUTION:An air knife 3 injects air at uniform flow velocity in the lateral direction of the molten film or sheet 5 flowing out of a die 1 so as to press the film or sheet 5 to a roll 2. In this case, this flow velocity is set so as not to vibrate the film or sheet 5 in an air gap (l). A vacuum chamber 4 is arranged on the side opposite to the air knife 3 so as to hold the film or sheet 5 between the vacuum chamber 4 and the air knife 3 not only to bring the film or sheet 5 into close contact with the roll 2 but also to prevent the drawing of the film or sheet 5 in the rotary direction of the roll 2 in cooperation with the air knife 3. By this method, the air gap (l) is shortened and the entrapment of air between the film or sheet 5 and the roll 2 is prevented. As a result, the surface state of the film or sheet can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a film/sheet forming apparatus which is designed to bring a molten film sheet into close contact with a roll in a plastic film/sheet casting process.

(Prior Art) Conventionally, the air knife method (Fig. 4), electrostatic fixing method (Fig. 5), vacuum suction method (Fig. 6), etc. have been used as means for bringing the molten film/sheet into close contact with the roll. Furthermore, a method combining electrostatic fixation and vacuum suction (FIG. 7) is also disclosed in Japanese Patent Publication No. 55-22257.

(Problems to be Solved by the Invention) First, the conventional air knife method, as shown in FIG. 4, is a method in which a molten film sheet 5 extruded from a die l is pressed against a roll 2 by a high-speed gas jet from an air knife 3. However, as the molding speed increases, it becomes difficult to prevent the air from being entrained, and when the jet speed is increased and the pressing force is increased, air turbulence is generated in the surrounding area, causing the molten film in the air gap to vibrate. It had the disadvantage of uneven thickness and uneven adhesion.

Next, in the electrostatic fixing method, as shown in FIG. 5, static electricity is generated on the molten film sheet 5 by a fixed electrode 15 installed near the film sheet 5, and the molten film sheet 5 is brought into close contact with the electrically grounded roll 2. However, like the air knife method, there is a limit to the molding speed, and at the same time, the generation of static electricity varies depending on the material of the film or sheet, so it has the disadvantage that the target is limited.

In addition, as shown in FIG. 6, the vacuum suction method, contrary to the air knife method, brings the roll 2 and film sheet 5 into close contact by vacuum suctioning the air between the molten film sheet 5 and the roll 2 in a vacuum chamber 4. At the same time, this is a method of preventing air entrapment, but since both ends of the space formed by the film sheet 5 and the roll 2 are open, increasing the degree of vacuum to increase adhesion forces This causes turbulence in the air flowing into the space, which causes vibrations in the molten film sheet 5, causing problems such as uneven thickness and uneven adhesion.

Also, to explain the case of the vacuum suction method in which vacuum suction is performed in the vacuum chamber 4 shown in FIG. Since the electrostatic force (the amount of charge differs depending on the dielectric constant) is different, the adhesion of the film/sheet 5 to the roll 2 is different (-
ET has good adhesion, PP has poor adhesion). For this reason, electrostatic fixing is not often used for PP resins. Also, adding additives to the resin, such as antistatic agents, will weaken the electrostatic force (
This results in poor adhesion. That is, there was a drawback that the resin material was limited.

The present invention aims to solve the above-mentioned conventional problems that occur when the molding speed increases, and aims to prevent the vibration of the film/sheet when increasing the adhesion force, prevent air entrainment, and prevent the material from getting trapped. It is an object of the present invention to provide a film/sheet forming apparatus that is not limited to any limitations.

(Means for Solving the Problems) For this reason, the present invention provides a forming apparatus in which a molten film sheet flowing out from a die exit is cooled and solidified by a rotating roll, and in which air is blown toward the opposite side of the roll surface of the film sheet. This device is equipped with a blowing device and a suction device that faces the space formed by the film sheet and the rotating roll and suctions the air in the same space, and this is used as a means to solve the problem. .

Further, the present invention is provided with a spraying device that sprays water toward the opposite side of the roll of the film/sheet, and this is used as a means for solving the problem.

(Function) The molten film sheet flowing out from the die is pressed against the roll surface by the air blown from the blowing device, and
By suctioning the air that tends to be caught between the film sheet and the roll, the film sheet is prevented from flapping in conjunction with the blowing device, and the film sheet is evenly brought into close contact with the roll. In addition, by installing a spraying device that sprays water toward the anti-roll surface of the film/sheet, the film/sheet can be
In addition to promoting the effect of closely adhering the sheet to the roll,
Films and sheets can be cooled and solidified at high speed.

(Embodiments) The present invention will be described below with reference to embodiments of the drawings. FIGS. 1, 2, and 3 are the embodiments of the present invention. Second. A third example is shown. First, the first embodiment shown in FIG. 1 will be explained.
Air is ejected 6 at a uniform velocity in the width direction so as to press the sheet 5 against the roll 2. However, this flow rate is
It must be at a level that does not vibrate the film sheet 5 between the two. The vacuum chamber 4 is installed on the opposite side of the air knife 3 and the film sheet 5, and the air knife 3
By cooperating with the film sheet 5 to bring the film sheet 5 into close contact with the roll 2 and at the same time preventing the film sheet 5 from being pulled in the rotational direction of the roll 2, the air gap 7'j2 is shortened and the film sheet 5 is To prevent air from getting caught between the rolls 2. For that, die 1 and roll 2
It is necessary to maintain the space formed under the atmospheric pressure or lower, and the gaps between the die 1 and the vacuum chamber 4, and the gaps between the roll 2 and the vacuum chamber 4 need to be made small so as to provide sufficient resistance to the flow of air. In addition, as a method for uniformly jetting air 6, there is a method of inserting a diagonal cutout into the chamber of the air knife 3 to rectify the flow.

Next, the second embodiment shown in FIG. 2 will be described. This is a combination of an air chamber 8 and a suction nozzle 11. In this embodiment, good adhesion between the film sheet 5 and the roll 2 can be obtained at a conventional level of air pressure even though the molding is performed at high speed. That is, the suction nozzle 11 removes air that is about to be caught between the film sheet 5 and the roll 2 in advance, and helps eliminate the air that is caught when the air chamber 8 is used alone.

Furthermore, since there is no need to increase the air pressure in the air chamber 8, the above-mentioned problems regarding the air chamber 8 do not occur. If there is no air entrapped between the film/sheet 5 and the roll 2, sufficient adhesion can be obtained by the action of the air chamber 8.

Next, the third embodiment shown in FIG. 3 will be described. The air knife 3 blows out air at a uniform velocity in the width direction so as to press the molten film sheet 5 flowing out from the die 1 against the cooling roll 2. However, this flow rate must be at a level that does not vibrate the film sheet 5 between the air gears 712.

Vacuum chamber 4 includes air knife 3 and film sheet 5
It is installed on the opposite side to sandwich the film, and works together with the air knife 3 to bring the film sheet 5 into close contact with the cooling roll 2, and at the same time,
By preventing the film sheet 5 from being pulled in the direction of rotation of the cooling roll 2, the air gap l is shortened and air is prevented from being caught between the film sheet 5 and the cooling roll 2. To do this, it is necessary to maintain the space formed by the die 1 and the cooling roll 2 below atmospheric pressure, and the die I
and vacuum chamber 4, cooling roll 2 and vacuum chamber 4
The gap between the two must be small enough to provide sufficient resistance to air flow. The jet generator 6 compensates for the lack of cooling capacity of the cooling roll 2 and enables high-speed, rapid cooling by cooling the film/sheet 5 from both sides.

(Effects of the Invention) As explained above in detail, the present invention combines an air blowing device and an air suction device, so it is not limited by the material of the film or sheet, and while preventing vibration of the film or sheet. , generates a large adhesion force, and together with the effect of the suction device, prevents air from being drawn in between the roll and the film/sheet, and improves the surface condition of the film/sheet. In addition, the combination of the blowing device and the suction device has the effect of shortening the air gap 2, which reduces the vibration of the film/sheet and at the same time reduces the amount of neck-in (a phenomenon in which the width of the sheet becomes narrower than the width of the die). This prevents the edge of the film/sheet from becoming thicker, leading to an improvement in the yield of the film/sheet. In addition, the effect of shortening the air gap enables stable molding at high speeds and rapid cooling, thereby improving the transparency and physical properties of films and sheets. Furthermore, by providing a spraying device that sprays water toward the opposite side of the film/sheet, the above-mentioned effect is further promoted and the film/sheet is sprayed with water.
The sheet can be cooled and solidified at high speed.

[Brief explanation of the drawing]

1, 2, and 3 are side sectional views of molding apparatuses according to the first, second, and third embodiments of the present invention, respectively, and FIG. 4 is a side sectional view of a molding apparatus using the conventional air knife method. , Fig. 5 is a side sectional view of a molding device using a conventional electrostatic fixing method, Fig. 6 is a side sectional view of a forming device using a conventional vacuum suction method, and Fig. 7 is a side sectional view of a molding device using a conventional vacuum suction method and an electrostatic fixing method. It is a side sectional view of the molding device by the combination. Explanation of the main parts of the diagram Die rotating roll air knife (spray device) Vacuum chamber (suction device) Film/sheet air chamber (spray device) ・Suction nozzle (suction device) Jet stream generator (spray device) Fig. 2 Fig. 4 Figure 6 Figure 5 Figure 7

Claims (2)

[Claims] (1) In a forming device that cools and solidifies the molten film sheet flowing out from the die exit with a rotating roll, a blowing device that blows air toward the opposite side of the film sheet and the rotating roll is installed. 1. A film/sheet forming apparatus characterized by being provided with a suction device that faces a space formed by and sucks air in the space. (2) The film/sheet forming apparatus according to claim 1, further comprising a spraying device for spraying water toward the opposite side of the film/sheet.