JP2007320276A - Tenter oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tenter oven which enables a thermoplastic resin film having uniform characteristics and a uniform thickness in the film width direction to be produced by suppressing the generation of a MD flow to reduce a temperature unevenness in the film width direction. <P>SOLUTION: The tenter oven for manufacturing the thermoplastic resin film comprises a plurality of zones connected in the film longitudinal direction, a plurality of air blowing parts in the film longitudinal direction disposed facing to both sides of the film in the zones, and air suction parts around the air blowing parts wherein a suction amount of the air suction parts of a center section is greater than a suction amount of the air suction parts of an inlet section and a suction amount of the air suction parts of an outlet section when at least one zone of the zones is divided into three sections of the inlet section, the center section and the outlet section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tenter oven suitable for use in the production of a thermoplastic resin film.

  As a method for producing a thermoplastic resin film, an unstretched resin sheet is stretched in the longitudinal direction, and then the uniaxially stretched film is stretched in the width direction using a tenter oven, or an unstretched resin sheet. A simultaneous biaxial stretching method is known in which a tenter oven is used to simultaneously stretch in the longitudinal direction and the width direction.

  Tenter ovens used in these production methods are generally composed of a plurality of zones connected in the longitudinal direction of the film, and the film is preheated, stretched and heat treated while maintaining the film at a predetermined temperature in each zone. In addition, it is configured to perform processing such as cooling. The zone is a section corresponding to processing steps such as preheating, stretching, heat treatment, and cooling, and each step is generally called a preheating zone, a stretching zone, a heat treatment zone, a cooling zone, and the like. Moreover, although the said zone may be comprised by one chamber, generally it is divided into several chambers in a film longitudinal direction, and it is comprised so that the setting of temperature can be changed for every chamber. The said chamber is the space where the part other than the opening part provided in order to let a film pass was partitioned off with the wall.

  As a method for keeping the film at a predetermined temperature, an air circulation method is generally adopted. The air circulation system has a plurality of air blowing portions installed in the room in the longitudinal direction of the film facing each side of the film, and has an air suction portion around the air blowing portion. The air controlled to a desired temperature is blown out from the air blowing portion toward the film by a fan and collected from the air suction portion. The film gripped at both ends by the tenter clip is stretched in at least a uniaxial direction while being heated or cooled by heat exchange with air circulating in the room.

  The thermoplastic resin film produced in this way takes advantage of its characteristics such as mechanical properties, optical properties, electrical properties, dimensional stability, flexibility, etc., for magnetic recording media applications, optical applications, packaging applications, card applications, etc. It is used for. Since the film characteristics are determined by the thermal history received in the manufacturing process, the temperature unevenness in the film width direction in the tenter oven causes film characteristic unevenness and deteriorates the quality of the product. Further, the temperature unevenness in the stretching process also causes thickness unevenness and characteristic unevenness, not only lowering the quality of the product, but also severely reducing the productivity by breaking the film in the tenter oven.

Conventionally, as a method of reducing temperature unevenness in the film width direction, a method of increasing the flow rate of circulating air blown out from the air blowing portion at the film end compared to the film center (see, for example, Patent Document 1). There are also known methods for controlling a heat exchanger based on the temperature detected by a temperature sensor (see, for example, Patent Document 2 and Patent Document 3).
JP 5-96619 (page 2-4, Fig. 1-3) JP-A-10-249933 (page 2-7, FIG. 2-3) JP 2002-18970 (page 2-6, Fig. 2-3)

  However, the above method is effective when the air circulation is completed in each room, but the temperature unevenness caused by a part of the circulating air in the adjacent rooms having different set temperatures flows, The temperature uniformity effect cannot be obtained for temperature unevenness caused by the outside air flowing into the oven.

  The flow of circulating air from one room to the adjacent room and the flow of outside air into the tenter oven are both phenomena in which the air flows in the longitudinal direction of the film across the boundary of the room. MD flow (Machine Direction Flow) ). When the MD flow occurs, air having different temperatures flowing from the outside is mixed into the circulating air, which causes a problem that large temperature unevenness occurs. In addition, when air of different temperatures is mixed, there is a problem that the power consumption of the heat exchanger increases and the energy efficiency decreases. Further, since the MD flow is more likely to occur in a wide tenter oven, it tends to be a problem in a large machine aimed at cost reduction by mass production.

  An object of the present invention is to provide a tenter oven that suppresses the occurrence of MD flow to reduce temperature unevenness in the film width direction and enables the production of a thermoplastic resin film having uniform characteristics and thickness in the film width direction. It is to provide.

  In order to solve the above problems, the inventor has found a configuration capable of suppressing the occurrence of MD flow by paying attention to the intake amount balance of the air suction portion. That is, according to the present invention, a plurality of zones are connected in the longitudinal direction of the film, and the zones have a plurality of air blowing portions installed in opposite directions on both sides of the film in the longitudinal direction of the film. In a tenter oven for producing a thermoplastic resin film having an air suction portion in the periphery, when at least one of the zones is divided into three portions of an inlet portion, a central portion, and an outlet portion at equal intervals in the film longitudinal direction MD that flows between zones when the air intake amount in the air suction portion in the central portion is larger than the air intake amount in the air suction portion in the inlet portion and larger than the air intake amount in the air suction portion in the outlet portion A zone center suction reinforced tenter oven is provided that has a flow-preventing effect.

  The temperature of the air circulating in the zone is controlled to a desired temperature by one or more heat exchangers. Each zone may be composed of one chamber, or may be composed of a plurality of chambers in the longitudinal direction of the film. For example, when the thermoplastic resin film is a film made of a resin mainly composed of polyethylene terephthalate, the stretching zone is usually set to 80 to 120 ° C., and the heat treatment zone is set to 180 to 240 ° C. Further, when the heat treatment zone is composed of three chambers, for example, the heat treatment first chamber is set to 190 ° C., the heat treatment second chamber is set to 195 ° C., and the heat treatment third chamber is set to 220 ° C. for each chamber. The temperature can be changed.

  As another preferred embodiment of the present invention, a plurality of zones are connected in the longitudinal direction of the film, and at least one of the zones is composed of a plurality of chambers. In a tenter oven for producing a thermoplastic resin film having a plurality of air blowing portions in the longitudinal direction of the film and having an air suction portion around the air blowing portion, at least one of the chambers is equally spaced in the longitudinal direction of the film. When it is divided into an inlet, center, and outlet, the air intake in the air intake in the center is greater than the air intake in the air intake and in the outlet. When the air intake amount is larger than the air intake amount in the room, a suction suction strengthened tenter oven at the center of the room having an effect of preventing the MD flow flowing between the rooms is provided.

  Further, as another preferred embodiment of the present invention, a plurality of zones are connected in the film longitudinal direction, and the zone has a plurality of air blowing portions installed in opposite directions on both sides of the film in the film longitudinal direction, In a tenter oven for manufacturing a thermoplastic resin film having an air suction portion around an air blowing portion, at least one of the zones is divided into three portions, an inlet portion, a central portion, and an outlet portion, at equal intervals in the film longitudinal direction. When divided, if the total area of the air suction holes in the center is larger than the total area of the air suction holes in the inlet and larger than the total area of the air suction holes in the outlet, A zone central suction hole enlarged tenter oven having an effect of preventing a flowing MD flow is provided.

  In general, the suction surface of the air suction portion is made of a plate (such as a punching plate or a wire mesh) having a plurality of air suction holes. If the total area of the air suction holes existing on the suction surface of the air suction portion is increased, the resistance when air passes through the suction surface is reduced, and the amount of intake of the air suction portion is increased. In the present invention, the total area of the air suction holes in the central portion of the zone is made larger than that of other regions (inlet portion and outlet portion), so that air can be easily sucked from the central portion.

  As another preferred embodiment of the present invention, a plurality of zones are connected in the longitudinal direction of the film, and at least one of the zones is composed of a plurality of chambers. In a tenter oven for producing a thermoplastic resin film having a plurality of air blowing portions in the longitudinal direction of the film and having an air suction portion around the air blowing portion, at least one of the chambers is equally spaced in the longitudinal direction of the film. When divided into an inlet part, a central part, and an outlet part, the total area of the air suction holes in the central part is larger than the total area of the air suction holes in the inlet part, and the air suction holes in the outlet part When the area is larger than the total area, a tenter oven with an enlarged suction hole at the center of the chamber having an effect of preventing an MD flow flowing between the chambers is provided. That.

  Next, as a preferred embodiment in any one of the zone center suction enhanced tenter oven, the chamber center suction enhanced tenter oven, the zone center suction hole enlarged tenter oven, and the chamber center suction hole enlarged tenter oven, In one, the blowing direction of the air blowing part closest to the zone inlet among the air blowing parts in the zone is inclined to the zone outlet direction, and the blowing direction of the air blowing part closest to the zone outlet is inclined to the zone inlet direction. An inclined blowout tenter oven is provided.

  Further, as another preferred aspect of the chamber central portion suction reinforced tenter oven or the chamber central portion suction hole expansion tenter oven, in at least one of the chambers, the air blowing portion closest to the chamber inlet of the indoor air blowing portions An inclined blowing tenter oven is provided in which the blowing direction is inclined toward the chamber outlet, and the blowing direction of the air blowing portion closest to the chamber outlet is inclined toward the chamber inlet.

  Furthermore, as a preferred embodiment in any one of the zone center suction enhanced tenter oven, the chamber center suction enhanced tenter oven, the zone center suction hole enlarged tenter oven, the chamber center suction hole enlarged tenter oven, the inclined blowing tenter oven, In the air suction section, there is provided a width direction suction adjustment tenter oven having means for changing the area or distribution density of the air suction holes in the film width direction so that the air intake amount in the film width direction becomes uniform.

  The tenter ovens described above are all suitable for use in a film-forming apparatus for producing a thermoplastic resin film, and can be used for either a sequential biaxial stretching machine or a simultaneous biaxial stretching machine.

  According to the tenter oven of the present invention, by suppressing the occurrence of MD flow, it is possible to reduce the temperature unevenness in the width direction in the tenter oven and produce a thermoplastic resin film having uniform characteristics and thickness in the width direction. It is possible to improve product quality and secure process stability by reducing film breakage.

  Further, it becomes possible to widen the tenter oven, which has been difficult since MD flow is likely to occur, and it is possible to reduce the manufacturing cost by mass production.

  Moreover, since it is excellent in temperature uniformity, the power consumption of the heat exchanger required when circulating and using air is reduced, and there is an energy saving effect.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of a zone or a chamber constituting the tenter oven of the present invention. 2 is a cross-sectional view showing an example of the arrow AA in FIG. 1, and FIG. 3 is a cross-sectional view showing an example of the arrow BB in FIG.

  As shown in FIG. 2, the film 2 held at both ends so as to be substantially horizontal by the tenter clip 8 is inserted into the zone 1, and the air blowing section 3 is installed facing both surfaces of the film 2. . As shown in FIG. 1, a plurality of air blowing portions 3 are installed in the longitudinal direction of the film, and there are air suction portions 4 around the air blowing portions 3, and the circulation connecting the air suction portions 4 and the air blowing portions 3. The path has a heat exchanger 5 and a fan 6. The temperature and wind speed of the circulating air blown out from the air blowing unit 3 toward the film 2 and collected from the air sucking unit 4 are controlled by the heat exchanger 5 and the fan 6, respectively. The film 2 to be processed is heated or cooled by the air blown out from the air blowing section 3 while moving in the longitudinal direction in the zone 1.

  As shown in FIG. 3, the zone 1 is divided into three regions at equal intervals in the film longitudinal direction, and each region is referred to as an inlet portion, a central portion, and an outlet portion along the moving direction of the film 2. The suction surface of the air suction part 4 is made of a punching plate having a plurality of air suction holes 9, and the total area of the air suction holes 9 in the central part is larger than the total area of the air suction holes 9 in the inlet part, and It is larger than the total area of the air suction holes 9 in the outlet.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
Zone 1 for the MD flow measurement test configured as shown in FIG. 4 was created. The external dimensions of the zone 1 were 3.3 m in the film longitudinal direction, 9.9 m in the film width direction, and 3.3 m in the height direction. The wall of the zone 1 has openings 7 at the entrance and exit surfaces of the film 2, respectively. The shape of the opening 7 is 6.0 m in the film width direction and the film 2 in the vertical direction. A rectangle of 0.27 m is formed on the upper side and the lower side from the position where is located.

  Eight air blowing portions 3 were installed on the upper side and the lower side of the film, respectively, with a pitch of 0.3 m in the longitudinal direction of the film. The shape of the blowing surface of the air blowing unit 3 was a rectangle of 0.01 m in the film longitudinal direction and 6.0 m in the film width direction. The blowing surface was fixed in parallel with the film surface at a position 0.27 m away from the position where the film 2 is located on the upper side and the lower side, respectively. Zone 1 has a vertically symmetric structure with film 2 as a symmetry plane.

As shown in FIG. 4, zone 1 is equally divided into three in the longitudinal direction of the film, the first area up to 1.1 m in the longitudinal direction from the wall on the film entrance side is the inlet section, and the next area up to 1.1 m is the central section. The next area up to 1.1 m was taken as the outlet. The total area of the air suction holes in each region, the inlet section 0.37 m ^2, the central portion 0.7 m ^2, was an outlet section 0.37 m ^2.

  In order to carry out the test simply and inexpensively, the film was not formed and the zone 1 was operated alone. As a substitute for the film 2, a veneer plate having a film width direction of 5.0 m and a film longitudinal direction of 4.0 m was fixed at a position where the film 2 is located. The upper and lower flow fields were separated by the plywood, and the state during film formation was simulated.

  The fan 6 was operated so that the average value of the blowing wind speed on the blowing surface of the air blowing unit 3 was about 25 m / sec. However, since it is difficult to make the blowing wind speed from all the air blowing portions uniform, the wind speed variation within ± 2 m / sec with respect to the average wind speed was allowed. Further, the heat exchanger 5 was not operated and air at room temperature was circulated.

  The wind speed measurement position of the MD flow will be described with reference to FIG. The measurement was performed at five points P1 to P5 provided at almost equal intervals in the film width direction immediately below the veneer plate of the opening 7. Since zone 1 has a vertically symmetric structure and the air flow is also substantially vertically symmetric, measurement of the wind speed above the plywood plate is omitted. A vane anemometer P having a diameter of 80 mm was used for the measurement. By measuring the observation surface of the vane anemometer P in the longitudinal direction of the film, the wind velocity component (air velocity of MD flow) of the air crossing the opening 7 in the longitudinal direction of the film was measured. Since the wind speed of the MD flow fluctuates with time, the sampling interval is set to 1 second, and the average value when measured continuously for 15 seconds. The measurement results are shown in Table 1. Compared with Comparative Example 1, the wind speed of the MD flow was significantly reduced, and a suitable zone configuration was obtained for use in a tenter oven for producing a thermoplastic resin film.

[Comparative Example 1]
In Zone 1 of Example 1, the inlet portion, a central portion, the total area of the air intake holes 9 in the outlet portion, respectively 0.37 m ^2, 0.37 m ^2, was 0.37 m ^2. Other conditions are the same as those in the first embodiment. The measurement results are shown in Table 1.

  The flow of Comparative Example 1 is indicated by arrows in FIG. Circulating air flows out from the opening on one side of the zone 1, and outside air flows in from the opening facing the zone 1. In such a flow field, since the outside air flowing in from the opening flows in the longitudinal direction of the film near the surface of the film 2, it mixes with the air blown out from the air blowing portion 3 to generate temperature unevenness, and the film 2 is made to have a desired shape. Unable to heat or cool to temperature. In addition, since outside air is mixed into the air sucked from the air sucking section 4, when the heat exchanger 5 has a low capacity, the air blown out from the air blowing section 3 cannot be controlled to a desired temperature, and the heat exchanger 5 has the capacity. There is also a problem that the power consumption increases even if it is sufficient.

  FIG. 5 shows an ideal flow field conceivable in the zone 1 configured as in the comparative example 1. If the balance in the longitudinal direction of the film is not lost, the air blown from the air blowing section 3 is divided into left and right after colliding with the film 2 and flows near the film surface, which collides with the air blown from the adjacent air blowing section 3 Then, it should be sucked in from the air sucking portion 4. At this time, a part of the air blown out from the air blowing portion 3 closest to the opening flows out in the opening of the zone 1, and outside air flows in instead. In this case, although it does not become a big problem like the comparative example 1, when the capability of the heat exchanger 5 is low again, the air blown out from the air blowing part 3 cannot be controlled to a desired temperature, and the capability of the heat exchanger 5 is sufficient. Even if it exists, power consumption increases. However, the ideal flow field as shown in FIG. 5 is vulnerable to disturbances such as flapping of the film and pressure fluctuation outside the tenter oven, and immediately collapses to the flow field as shown in FIG. In Comparative Example 1, the flow field of FIG. 5 could not be formed.

  Further, when considering a tenter oven in which a plurality of zones 1 forming the flow field of FIG. 5 are connected in the longitudinal direction of the film, the air flowing out from the opening of the zone 1 flows into adjacent zones. When the set temperatures of the zones are different, temperature unevenness occurs. Accordingly, the flow field of FIG. 5 is insufficient to eliminate temperature unevenness, and it is necessary to eliminate the flow (MD flow) passing through the opening in the longitudinal direction of the film.

[Example 2]
In the zone 1 of Example 1, the air blowing direction of the air blowing portion 3 closest to the opening serving as the inlet of the film 2 is tilted by 20 ° toward the outlet of the film 2 and the air blowing closest to the opening serving as the outlet of the film 2 The blowing direction of the part 3 was tilted by 20 ° toward the entrance direction of the film 2. Other conditions are the same as those in the first embodiment. The measurement results are shown in Table 1. Compared with Example 1, the wind speed of MD flow was further reduced, and a more suitable zone configuration was obtained by using it in a tenter oven for producing a thermoplastic resin film.

[Example 3]
In the zone 1 of Example 2, the area of the air suction hole 9 was changed in the film width direction so that the air suction amount of the air suction portion 4 was uniform. Other conditions are the same as those in the first embodiment. The measurement results are shown in Table 1. Compared with Example 2, the wind speed of the MD flow was further reduced, and a state with almost no MD flow was obtained.

  The air intake amount distribution in the film width direction of the air suction portion 4 varies depending on the flow rate of the circulating air. Therefore, when there is a possibility of changing the flow rate of the circulating air, which is the production condition, the area or distribution of the air suction holes 9 is adjusted so that the air intake amount in the film width direction becomes uniform at the changed flow rate. It is necessary to have a means for changing the density in the film width direction.

  A means for changing the area or distribution density of the air suction holes 9 is shown in FIG. (A) changes an opening area by fixing a board to the suction surface which has the big air suction hole 9. FIG. (B) changes the distribution density of the air suction holes 9 by fixing a small plate to the suction surface. (C) divides the plate itself forming the suction surface in the film width direction so that it can be replaced. If a plurality of plates having different areas and distribution densities of the air suction holes 9 are prepared, the suction balance in the film width direction can be adjusted by replacing the plates.

In this example, the method (a) was adopted. Table 2 shows the area distribution and the flow rate distribution of the air suction holes 9 in the air suction portion 4 in the film width direction. In Examples 1 and 2, the flow rate of the air suction hole 9 up to 0.227m ³ / s, the minimum 0.049m ³ / s, whereas the flow rate difference in the width direction was 0.178m ³ / s In Example 3, the maximum was 0.175 m ³ / s, the minimum was 0.143 m ³ / s, and the flow rate difference in the width direction was 0.032 m ³ / s, and the flow rate unevenness in the film width direction was greatly reduced. By adjusting the area of the air suction hole 9 so that the air intake amount in the film width direction is uniform, a more suitable zone configuration was obtained for use in a tenter oven for producing a thermoplastic resin film.

It is a schematic block diagram of the zone or chamber which comprises the tenter oven which concerns on one Embodiment of this invention. It is a schematic block diagram of the AA arrow of FIG. It is a schematic block diagram of the BB arrow of FIG. It is a schematic block diagram of the zone or chamber which comprises the tenter oven which concerns on one Embodiment of this invention. It is a general form of a zone or chamber constituting a tenter oven that has been conventionally used. It is a general form of a zone or chamber constituting a tenter oven that has been conventionally used. It is a schematic block diagram of CC view of FIG. 1 or FIG. It is an example of the change means of an air suction part opening area.

Explanation of symbols

1: Zone (or room)
2: Film 3: Air blowing part 4: Air suction part 5: Heat exchanger 6: Fan 7: Opening part 8: Tenter clip 9: Air suction hole 10: Clip rail cover P: Vane type anemometer P1-P5: MD Wind speed measurement position

Claims (8)

  A plurality of zones are connected in the longitudinal direction of the film, the zone has a plurality of air blowing portions arranged in the film longitudinal direction so as to face both sides of the film, and an air suction portion around the air blowing portion. In a tenter oven for producing a thermoplastic resin film having at least one of the zones divided into three portions of an inlet portion, a central portion, and an outlet portion at equal intervals in the longitudinal direction of the film, air suction in the central portion The tenter oven is characterized in that the intake air amount of the air intake portion is larger than the intake air amount of the air suction portion in the inlet portion and larger than the intake air amount of the air suction portion in the outlet portion.   A plurality of zones are connected in the longitudinal direction of the film, and at least one of the zones is composed of a plurality of chambers, and the chamber has a plurality of air blowing portions arranged opposite to both sides of the film in the longitudinal direction of the film. In the tenter oven for producing a thermoplastic resin film having an air suction portion around the air blowing portion, at least one of the chambers is provided at three intervals of an inlet portion, a central portion, and an outlet portion at equal intervals in the film longitudinal direction. When the air suction section is divided into two, the air intake amount of the air suction portion in the central portion is larger than the air intake amount of the air suction portion in the inlet portion and larger than the air intake amount of the air suction portion in the outlet portion. Tenter oven.   A plurality of zones are connected in the longitudinal direction of the film, the zone has a plurality of air blowing portions arranged in the film longitudinal direction so as to face both sides of the film, and an air suction portion around the air blowing portion. In a tenter oven for producing a thermoplastic resin film having at least one of the zones divided into three portions of an inlet portion, a central portion, and an outlet portion at equal intervals in the longitudinal direction of the film, air suction in the central portion A tenter oven characterized in that the total area of the holes is larger than the total area of the air suction holes in the inlet part and larger than the total area of the air suction holes in the outlet part.   A plurality of zones are connected in the longitudinal direction of the film, and at least one of the zones is composed of a plurality of chambers, and the chamber has a plurality of air blowing portions arranged opposite to both sides of the film in the longitudinal direction of the film. In the tenter oven for producing a thermoplastic resin film having an air suction portion around the air blowing portion, at least one of the chambers is provided at three intervals of an inlet portion, a central portion, and an outlet portion at equal intervals in the film longitudinal direction. The total area of the air suction holes in the central part is larger than the total area of the air suction holes in the inlet part and larger than the total area of the air suction holes in the outlet part. Tenter oven.   In at least one of the zones, the blowing direction of the air blowing portion closest to the zone inlet among the air blowing portions in the zone is inclined toward the zone outlet direction, and the blowing direction of the air blowing portion closest to the zone outlet is set to the zone inlet direction. The tenter oven according to any one of claims 1 to 4, wherein the tenter oven is inclined.   In at least one of the chambers, of the indoor air blowing portions, the blowing direction of the air blowing portion closest to the chamber inlet is inclined toward the chamber outlet, and the blowing direction of the air blowing portion closest to the chamber outlet is inclined toward the chamber inlet. The tenter oven according to claim 2 or 4, wherein the tenter oven is provided.   7. The air suction part according to claim 1, further comprising means for changing the area or distribution density of the air suction holes in the film width direction so that the air intake amount in the film width direction is uniform. Tenter oven as described in.   A film forming apparatus comprising the tenter oven according to any one of claims 1 to 7.

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