JP2014015007A - Methods of forming film and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that can adhere a film to a chill role while excluding out the air that enters between the film and the chill role and also cooling the film uniformly across the whole area, during the cooling and forming of the film while adhering the film extruded out of a die in molten state to the chill role by blowing an air stream from an air knife.SOLUTION: The problem is solved by having the up and down opening width of the central part of an air blowout port 4 of an air knife 3 which blows an air stream to a film A wide and having it progressively narrow toward both side ends to gradually weaken the wind pressure blowing against the film A along from the central part toward both side ear parts of the film A such that the air existing between the film A and the chill role 2 is excluded out of both side ends by that wind pressure to improve the adherence of the film A to chill role 2, and by having the temperature of the air blowing out from both side ends higher than the central part of an air blowout port 4 such that the film A is cooled uniformly.

Description

  The present invention relates to a molding method for forming a film having a constant thickness by cooling a film in a molten state extruded from a die while being in close contact with a chill roll by blowing hot air from an air knife, and an apparatus for carrying out the method. .

  Conventionally, in order to form a thermoplastic resin melted by an extruder into a sheet or film (hereinafter referred to as a film), for example, as described in Patent Document 1, it is attached to the tip of the extruder. The molten resin is taken into a film from a die which is formed on a chill roll, and cooled and solidified while the molten film is brought into close contact with the chill roll by an air flow blown from an air knife toward the chill roll. At this time, the adhesion between the chill roll and the film is increased by the air pressure blown from the air knife.

JP 2002-96374 A

  However, when the molten film extruded from the die is brought into close contact with the peripheral surface of the chill roll by the air flow from the air knife, air enters between the chill roll and the film, and the film partially lifts against the chill roll. As a result, there is a concern that a poorly adhered portion is generated and uniform cooling cannot be performed, and a high-quality product cannot be manufactured.

  Moreover, in order to improve the production efficiency by rotating the chill roll at high speed, it is necessary to increase the air pressure from the air knife and effectively form the film while firmly pressing the film against the chill roll. When the wind pressure blown out from the air is increased, air easily enters between the chill roll and the film as described above, and thus it is difficult to improve the production efficiency.

  Furthermore, when the melted film is extruded from the die, the ears on both sides of the film shrink in the width direction and become thicker than the central part, so when this film is in contact with the peripheral surface of the chill roll, Even if the ears at both ends are in close contact with the chill roll, a part of the film between the ears is lifted from the peripheral surface of the chill roll, and the adhesiveness with the chill roll is impaired, and the film from the air knife toward the film Even if uniform wind pressure is blown in the width direction, it is difficult to effectively eliminate the air existing between the opposed surfaces of the chill roll and the film, and some air remains as above, and is uniform as above. There is a problem that proper molding is not performed.

  In addition, the melted film extruded from the die generally has a problem in that molding defects such as uneven cooling occur because the central portion in the width direction is hotter than the ears at both ends.

  The present invention has been made in view of such problems, and the object of the present invention is to uniformly adhere a molten film extruded from a die to a chill roll by wind pressure generated by an air flow blown from an air knife. In order to carry out this method and a film forming method capable of producing a high-quality film by eliminating the uneven cooling of the film and improving the production efficiency by enabling the forming by effective cooling as described above To provide the equipment.

  In order to achieve the above object, according to the film forming method of the present invention, a melted film extruded from a die is taken on the chill roll by rotating the chill roll, and an air knife air blower is used. In the film forming method of cooling and forming the above film in close contact with the chill roll by the air flow from the outlet, the air volume per unit area of the air flow blown from the air outlet of the air knife to the central part in the width direction of the film It is characterized by spraying so as to gradually decrease from the central part toward both ears.

  In the film forming method, the invention according to claim 2 is that the temperature of the air flow blown from the air outlet of the air knife to the film is blown with the temperature at the center lower than the temperature of the ears on both sides of the film. Features.

  The invention according to claim 3 relates to an apparatus for carrying out the film forming method, wherein the molten film extruded from the die is brought into close contact with the chill roll by the wind pressure of the air flow from the air outlet of the air knife. In the film forming apparatus for cooling and forming, the air outlet of the air knife opens from the center in the length direction corresponding to the width direction of the film toward both end portions corresponding to the both side ears of the film. The width is formed so as to be gradually reduced.

  In the film forming apparatus configured as described above, the invention according to claim 4 includes a heater disposed in the main body of the air knife, an air outlet at the front end of the main body, and an air supply port at the base end. And an air rectifying chamber in which a wire mesh is stretched between the air supply port and the heater.

  According to the first aspect of the present invention, the air volume per unit area of the air flow from the air outlet of the air knife that attaches the film to the peripheral surface of the chill roll is the maximum at the center in the width direction of the film, and the center The air pressure that blows to the center in the width direction of the film is the largest, and the wind pressure gradually decreases toward the both ends of the film. The air existing between the film and the chill roll is pushed in the width direction of the film from the width direction central portion side receiving the large wind pressure toward the both side edges of the film, and the air is released to the outside from the both side edges of the film. Can be eliminated smoothly.

  Therefore, both side ears of the film extruded from the die are formed thicker than the central part, and the central part side of the film is difficult to adhere to the entire chill roll, so that air is partly between the film and the chill roll. Even if it exists, the air pressure blown out from the air outlet of the air knife discharges the air existing between the film and the chill roll from both ends of the film and tensions the film in the width direction on the outer peripheral surface of the chill roll. The film can be uniformly cooled and molded with a chill roll without causing uneven thickness by bringing the film into close contact with each other, and a high quality film can be obtained while increasing the wind pressure from the air outlet of the air knife and improving the molding speed. It can be manufactured efficiently.

  Furthermore, according to the invention according to claim 2, since the temperature of the air flow blown to the film from the air outlet of the air knife is blown with the temperature at the central part lower than the temperature of the both side ears of the film, The film in the melted state where the central part is extruded from the die at a higher temperature than the ears on both sides, the width direction in the film by the air flow ejected from the air outlet of the air knife whose central part is low temperature and both side parts are hot The film can be made to have a uniform temperature distribution, and an excellent quality film can be produced while adjusting to the optimum film temperature for molding.

  Moreover, according to the invention which concerns on Claim 3, the shape of the air blower outlet of an air knife is the direction from the center part of the length direction corresponding to the width direction of a film toward the both-ends part corresponding to the both-sides ear | edge part of a film. Since the opening width is formed so as to gradually decrease, the flow rate of air from the central part of the air outlet can be maximized, and the flow rate can be gradually decreased from the central part toward both side ends. Therefore, the wind pressure blown from the central portion of the air outlet to the central portion in the width direction of the film is the largest, and the wind pressure gradually decreases toward the both side ends, and exists between the film and the chill roll as described above. While excluding air from the center in the width direction of the film toward both side edges and while tensioning the film in the width direction, the film is brought into close contact with the outer peripheral surface of the chill roll and is evened by the chill roll. It can be in cooling, to produce efficiently the high quality of the film while improving the forming rate by increasing the wind pressure from the air outlet of the air knife with can be molded.

  According to the invention of claim 4, the heater is disposed in the main body of the air knife, the air outlet is provided at the distal end portion of the main body, the air supply port is provided at the proximal end portion, and the air supply is further provided. Since the air rectifying chamber is formed by extending a wire mesh between the opening and the heater, the air supplied from the air supply port of the air knife into the air knife body is diffused in the air rectifying chamber to While being rectified, it can be always ejected from the air outlet as a constant air flow.

  At this time, the heater disposed in the main body of the air knife is heated so that the air becomes warm air at a predetermined temperature, and the air outlet is in the length direction corresponding to the width direction of the film as described above. Since the opening width is gradually reduced from the central part of the film toward the both side edges corresponding to the both side ears of the film, the flow of air flowing through the central part of the air outlet is fast, The flow of air flowing through the end portion becomes slow, and the time heated by the heater becomes longer than the central portion of the air outlet port, so that the air flowing through both end portions becomes longer. The temperature of the air stream to be blown can be lower in the center than the temperature of the ears on both sides of the film, and the melt in the state where the center in the width direction is pushed out of the die at a temperature higher than the ears of both sides. The temperature of the film in the width direction of the film can be made uniform by the air flow ejected from the air outlet of the air knife whose central part is cold and both sides are hot. An excellent quality film can be produced while adjusting.

The simplified side view of a film forming apparatus. The perspective view of an air knife. The front view which shows the shape of the air blower outlet of an air knife. The cross-sectional view which shows the internal structure of an air knife. Sectional drawing of the film of the molten state extruded from die | dye. Explanatory drawing which shows the state which has stuck the film to the chill roll.

  Next, a specific embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a film forming apparatus includes a die 1 provided at the tip of an extruder (not shown), and a die 1 below. The chill roll 2 disposed in close proximity and the melted film A extruded from the slit-like extrusion port 1a of the die 1 are blown from the air outlet 4 onto the outer peripheral surface of the rotating chill roll 2. And an air knife 3 which is pressed and adhered by wind pressure.

  The die 1 has the extrusion port 1a opened downward toward the outer peripheral surface of the chill roll 2, and the molten thermoplastic resin supplied from the extruder has a certain width and thickness from the extrusion port 1a. The film A is configured to be extruded toward the outer peripheral surface of the chill roll 2 facing the air knife 3 while being formed into the film A, and the chill roll 2 has a rotational peripheral speed higher than an extrusion speed from the extrusion port 1a of the die 1. The film A is in close contact with the outer peripheral surface of the film A while being stretched, and the film A is cooled and solidified to be taken to the take-out machine (not shown) side. The number of chill rolls 2 is not limited to one, and two or more chill rolls 2 may be provided in parallel.

  As shown in FIGS. 2 and 3, the air knife 3 has a main body 30 integrally connected between upper and lower wall plate portions 31 and 32 and both side ends of the upper and lower wall plate portions 31 and 32. , 33, and the upper and lower wall plate portions 31 and 32 and the both side wall plate portions 33 and 33, the cross-sectionally oblong rectangular interior of the hollow interior is a base end side opening opposite to the front end side facing the film A It is formed in a hollow box shape by the rear wall plate part 34 whose end is sealed, and further, the upper and lower widths of the upper and lower wall plate parts 31 and 32 are gradually increased toward the front end facing the film A. The air blower outlet 4 having a slit shape that is long in the width direction of the main body 30 is formed at the tip thereof, and the air flow blown out from the air blower outlet 4 is brought into close contact with the outer peripheral surface of the chill roll 2. Directed to film A.

  The air outlet 4 has a length between both side ends thereof, that is, between the front ends of the side wall plate portions 33 and 33 in the main body 30 parallel to the width direction of the film A, and the upper and lower walls in the main body 30. The air corresponding to the central portion A1 in the width direction of the film A is formed by curving at least the front end portions of the plate portions 31 and 32 in a gentle arc shape from the central portion toward both side ends in a direction in which the opposing surfaces are separated from each other. The opening width of the central portion 4a in the length direction of the air outlet 4 is set to the largest opening width, and the opening extends from the center portion 4a toward both side end portions in the length direction corresponding to both side ear portions A2 and A2 of the film A. The width is gradually reduced, and the opening widths of the side end portions 4b and 4b are formed to the minimum opening width.

  Further, as shown in FIG. 4, a fine metal mesh 5 is stretched in the rear end portion of the hollow interior of the main body 30 of the air knife 3 so that the rear end side center between the metal mesh 5 and the rear wall plate portion 34 is stretched. The inside is formed in an air rectifying chamber 3a, and a heater 6 is disposed in the hollow interior between the wire mesh 5 and the air outlet 4 to form the hollow interior in the hot air generating chamber 3b. The air supply port 7 is connected to and communicated with the central portion of the rear wall plate portion 34.

  Next, the operation of the film forming apparatus of the embodiment of the present invention provided with the air knife 3 formed in this manner will be described. The film A made of a thermoplastic resin in a molten state extruded from the extrusion port 1a of the die 1 is as follows. The chill roll 2 is drawn toward the chill roll 2 while being drawn toward the chill roll 2 according to the speed difference between the rotational speed of the chill roll 2 and the extrusion speed from the die 1, and is wound around the outer peripheral surface of the chill roll 2 according to the rotation of the chill roll 2. The film A is brought into close contact with the peripheral surface of the chill roll 2 by the wind pressure of the air flow that is taken by the air knife 3 and ejected from the air outlet 4 of the air knife 3.

  At this time, as described above, the air outlet 4 of the air knife 3 has the maximum opening width of the central portion 4a in the longitudinal direction of the air outlet 4 corresponding to the central portion A1 in the width direction of the film A. The unit of air flow from the air outlet 4 is gradually narrowed from the portion 4a toward the both side end portions 4b, 4b in the length direction corresponding to the both side ears A2, A2 of the film A. The air volume per area is maximum at the central portion 4a and gradually decreases from the central portion 4a toward the side end portions 4b and 4b. Therefore, as shown by the lengths of the arrows in FIG. The wind pressure of the airflow that spills into the center is the largest, and the wind pressure gradually decreases toward the ends on both sides of the film, so that the center A1 in the width direction of the film A is firmly attached to the chill roll 2 and both ears Adhesion gradually weakens toward A2 and A2.

  Therefore, even if air enters between the chill roll 2 and the film A, the air is pushed toward the both side ears A2, A2 of the film A by the wind pressure acting on the film A, and the both side ears A2, The film A is extruded to the outside from both ends of A2, and the film A can be brought into close contact with the peripheral surface of the chill roll 2 while being tensioned in the width direction.

  Further, when the melted film is extruded from the die 1, both end portions of the film A contract in the width direction, and as shown in FIG. 5, the ears A2 and A2 are formed thicker than the central portion. Then, when this film A is brought into close contact with the peripheral surface of the chill roll 2, a space part where air exists between the film A between the two side ears A2 and A2 and the peripheral surface of the chill roll 2 is partially generated. However, a part of the film A is lifted from the chill roll 2 by this space portion, and the adhesion to the chill roll 2 is impaired. However, as described above, the air existing in the space portion is formed on both sides from the central portion 4a. By the air flow from the air outlet 4 where the wind force becomes weaker toward the ends 4b and 4b, the film A is pushed toward the both side ears A2 and A2 of the film A to the outside from both side ends of the both side ears A2 and A2. Can be discharged.

  Further, a fine metal mesh 5 is stretched in the rear end portion of the hollow inside of the main body 30 of the air knife 3, and the center inside of the rear end side between the metal mesh 5 and the rear wall plate portion 34 is formed in the air rectifying chamber 3a. Since the heater 6 is disposed in the hollow interior between the wire mesh 5 and the air outlet 4 and this hollow interior is formed in the hot air generating chamber 3b, it is connected to the rear wall plate portion 34 of the main body 30. The air supplied through the air supply port 7 into the air rectifying chamber 3a flows into the hot air generating chamber 3b while being rectified by the wire mesh 5, and is heated by the heater 6 in the hot air generating chamber 3b. Hot air is blown out toward the film A from the air outlet 4.

  At this time, at least the front end portion of the hot air generating chamber 3b is the same as the air outlet 4, and the central portion of the air outlet 4 is gradually narrowed as the vertical width of the central portion becomes wider and toward both ends. The heater of the air flowing from the central part of the hot air generating chamber 3b toward the central part 4a of the air outlet 4 has the largest flow speed of the air ejected from 4a and becomes slower as it goes toward both end parts 4b and 4b. 6, the contact time with the heater 6 for the air flowing from the both end portions of the hot air generating chamber 3 b toward the both end portions 4 b and 4 b of the air outlet 4 is increased.

  Therefore, the temperature of the hot air blown from the central portion 4a of the air blower outlet 4 of the air knife 3 toward the central portion A1 of the film A is lowered, and the both end portions 4b and 4b of the air blower outlet 4 are both ears of the film A. The temperature of the hot air blown toward A2 and A2 can be higher than that of the central part 4a, and the central part A1 in the width direction is in a molten state that is extruded from the die 1 at a higher temperature than both ears A2 and A2. The film A is chill-rolled while the temperature distribution in the width direction of the film A is made uniform by an air flow ejected from the air outlet 4 of the air knife 3 in which the central portion 4a has a low temperature and both end portions 4b and 4b have a high temperature. 2 can be brought into close contact with each other.

  In this way, the film A is cooled and solidified while uniformly and firmly adhering to the outer peripheral surface of the rotating chill roll 2 by the wind pressure of the airflow ejected from the air knife 3, and the film A having a predetermined thickness is formed at high speed. Then, a take-up machine (not shown) is taken up.

A film 1 die 2 chill roll 3 air knife 4 air outlet 5 wire mesh 6 heater
30 Air knife body

Claims (4)

  In a film forming method, a molten film extruded from a die is taken on the chill roll by rotation of the chill roll, and cooled and molded while the film is closely attached to the chill roll by an air flow from an air blower outlet of the air knife. The air flow per unit area of the air flow blown from the air outlet to the film is blown so that the central part in the width direction of the film is maximum and gradually decreases from the central part toward both ears. Film forming method.   2. The film forming method according to claim 1, wherein the temperature of the air flow blown to the film from the air outlet of the air knife is blown with the temperature at the center part lower than the temperature of the ears on both sides of the film.   In a film forming apparatus for cooling and forming a molten film extruded from a die in close contact with a chill roll by air pressure from an air outlet of an air knife, the air outlet of the air knife is arranged in the width direction of the film. An apparatus for forming a film, characterized in that the opening width is gradually reduced from a corresponding central portion in the length direction toward both end portions corresponding to both side ear portions of the film.   The air knife has a heater in its main body, an air outlet at the tip, an air supply port at the base, and a wire mesh between the air supply and the heater. The film forming apparatus according to claim 3, wherein an air rectifying chamber is provided.

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