JP2016093916A - Longitudinally stretching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a longitudinally stretching apparatus capable of conveying an unstretched sheet by adhering to a low speed roll in the longitudinally stretching apparatus even if the unstretched sheet composed of a thermoplastic resin is thick, and effective for maintaining film quality after stretching.SOLUTION: The stretching apparatus for stretching a continuous unstretched sheet composed of a thermoplastic resin while running in a direction continuing the unstretched sheet to produce a longitudinally stretched film includes: a low speed roll group having a function to preliminarily heat the unstretched sheet near to a softening temperature by contacting and passing through a plurality of rolls; a hot stretching part; a high speed roll group along a direction running the unstretched sheet from the upstream to the downstream; and further a non-contact preheating part for heating the unstretched sheet without contacting on an upstream side of the low speed roll group.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a thermoplastic film, and more particularly to a longitudinal stretching apparatus that longitudinally stretches a sheet-like thermoplastic resin to form a longitudinally stretched film.

  Films made of thermoplastic resins such as aromatic polyesters, polyolefins, polyamides, etc., have biaxially stretched films that are stretched in two orthogonal directions, and thus have excellent mechanical strength, etc. It is used.

  An example of a process for producing a biaxially stretched film made of a thermoplastic resin is shown in FIG. In FIG. 4, the thermoplastic resin is supplied from the hopper 10 to the melt extrusion device 20 in the form of chips, heated and melted by the melt extrusion device 20, and continuously extruded from the slit-shaped die 30 to be closely attached onto the casting roll 40. After being cooled, it becomes an unstretched sheet 2. This continuous unstretched sheet 2 is stretched in the continuous direction by a longitudinal stretching apparatus 101 to become a longitudinally stretched film 3, and the longitudinally stretched film 3 is stretched in the width direction by a lateral stretching apparatus 102 to become a biaxially stretched film 4. It is wound around the core material by a winding device.

  Among these, as described in Patent Document 1, the longitudinal stretching apparatus 101 is generally composed of a low-speed roll group, a high-speed roll group, and a heating and stretching unit between both roll groups. An example is shown in FIG. In FIG. 5, the longitudinal stretching apparatus 101 heats the unstretched sheet 2 to a temperature equal to or higher than the softening point temperature (of the thermoplastic resin that is the material) at the heating stretching unit 6, and between the low-speed roll group 5 and the high-speed roll group 7. A circumferential speed difference is provided between them, and the unstretched sheet 2 is stretched by a circumferential speed difference to have a longitudinally stretched film 3. Here, if the unstretched sheet 2 is heated only at the heating and stretching section 6 to a temperature higher than the softening point temperature, heating unevenness or the like occurs. Therefore, the low-speed roll group 5 usually keeps the unstretched sheet 2 close to the softening point temperature. It has a preheating function for heating. Since it is desirable to heat both surfaces of the unstretched sheet 2 evenly during the preliminary heating, the low-speed roll group 5 alternately heats both surfaces of the unstretched sheet 2 with relatively small rolls 5R (5R1 to 5R4). It is the composition to do.

  In addition, since the unstretched sheet 2 is stretched 2 to 4 times by the longitudinal stretching apparatus 101 as described above, the thickness of the longitudinally stretched film 3 is 1/2 to 1/4 of the unstretched sheet 2. Similarly, since the longitudinally stretched film 3 is stretched 2 to 4 times by the transverse stretching device 102, the thickness of the biaxially stretched film 4 is 1/2 to 1/4 of that of the longitudinally stretched film 3. Therefore, the thickness of the biaxially stretched film 4 is approximately 1/10 of that of the unstretched sheet 2. That is, the thickness of the unstretched sheet 2 to be stretched by the longitudinal stretching apparatus 101 is about 10 times the desired thickness as the biaxially stretched film 4.

JP-A-4-282225

  Conventionally, the base film of recording media such as magnetic tape is mainly used as a biaxially stretched film, and the thickness is mostly several tens of μm or less. Recently, however, the thickness exceeds 100 μm for optical use, industrial use, etc. The ratio is increasing, and depending on the application, there is a demand for products exceeding 300 μm. For this reason, it is necessary to increase the thickness of the unstretched sheet, which is the target of stretching in the longitudinal stretching apparatus.

  However, even an unstretched sheet made of a relatively flexible thermoplastic resin becomes difficult to bend when its thickness increases. As a result, as shown in FIG. 5, when the unstretched sheet 2 is wound around the first low-speed roll 5R1 of the low-speed roll group, the non-stretched sheet 2 and the surface of the low-speed roll 5R1 do not adhere to each other (see FIG. 6). 2d1, 2d2) are more likely to occur. When such a poor adhesion phenomenon occurs, preheating unevenness occurs, or the surface of the unstretched sheet is scratched due to sliding between the unstretched sheet and the low-speed roll, and ultimately the quality of the biaxially stretched film is adversely affected. Effect.

  Corresponding to the increase in thickness of the unstretched sheet, if the roll diameter of the low-speed roll group can be increased, it will be easy to adhere to the roll even if it is difficult to bend, but as described above, both sides of the unstretched sheet are heated evenly. In view of this, it is disadvantageous, and is particularly unsuitable as the thickness of the unstretched sheet is large.

  The present invention has been made in view of the above problems, and even if the thickness of an unstretched sheet made of a thermoplastic resin is large, the unstretched sheet can be transported in close contact with a low-speed roll in a longitudinal stretching apparatus. And a longitudinal stretching apparatus effective for maintaining the film quality after stretching.

In order to solve the above problem, the invention according to claim 1
A longitudinal stretching apparatus that stretches a continuous unstretched sheet made of a thermoplastic resin while traveling in the direction in which the unstretched sheet continues to form a longitudinally stretched film,
Along with the downstream from the upstream of the direction in which the unstretched sheet travels, a low-speed roll group, a heating stretch unit, and a high-speed roll group,
The low-speed roll group has a function of preheating the unstretched sheet to the vicinity of the softening temperature by passing through the plurality of rolls.
A non-contact preheating part for heating the unstretched sheet in a non-contact manner is further provided on the upstream side of the low-speed roll group.

Invention of Claim 2 is the longitudinal stretch apparatus of Claim 1, Comprising:
The non-contact preheating part is characterized in that a heat source is arranged on the side opposite to the surface where the unstretched sheet first contacts the low-speed roll group.

Invention of Claim 3 is the longitudinal stretch apparatus of Claim 1 or Claim 2, Comprising:
The non-contact preheating part is composed of an infrared heater.

Invention of Claim 4 is the longitudinal stretch apparatus of Claim 3, Comprising:
The dominant wavelength of infrared rays emitted from the infrared heater is in the range of 0.8 to 1.6 μm.

Even if the unstretched sheet made of a thermoplastic resin is thick, the longitudinal stretching apparatus of the present invention enables the unstretched sheet to be transported in close contact with a low-speed roll in the longitudinal stretching apparatus, and the film quality after stretching. It is effective for maintenance.

It is a figure explaining one Embodiment of the longitudinal stretch apparatus which has this invention. It is a figure explaining the non-contact preheating part in one Embodiment of the longitudinal stretch apparatus which has this invention. It is a figure explaining the structural example of the non-contact preheating part in one Embodiment of the longitudinal stretch apparatus which has this invention. It is a figure explaining the manufacturing process of the biaxially stretched film which consists of thermoplastic resins. It is a figure explaining the conventional longitudinal stretch apparatus. It is a figure explaining the problem at the time of handling a thick unstretched sheet with the conventional longitudinal stretch apparatus.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view for explaining a longitudinal stretching apparatus 1 for explaining an embodiment of the present invention. While a continuous unstretched sheet 2 supplied from the left side of the diagram is run in a continuous direction, FIG. The film is stretched and supplied as a longitudinally stretched film 3 to the next step on the right side (generally a transverse stretching step). The unstretched sheet 2 has a width of about 0.5 to 2.0 m and a thickness of about 1 to 5 mm, and various thermoplastic resins can be used as a raw material. Generally, polyethylene terephthalate (PET) is used. An aromatic polyester such as polyethylene naphthalate (PEN) is used. In addition, inorganic fine particles or organic fine particles may be dispersed in the thermosetting resin.

  The longitudinal stretching apparatus 1 includes a low-speed roll group 5, a heating stretching unit 6, a high-speed roll group 7, and a non-contact preheating unit 8 as basic components.

  The low-speed roll group 5 is composed of a plurality of low-speed rolls 5R (symbols when 5R1 to 5R4 are not individually identified), and the unstretched sheets 2 are arranged so that both surfaces are alternately in close contact with the surface of the low-speed roll 5R. In FIG. 1, the low-speed roll group 5 includes four low-speed rolls 5R, but the number of low-speed rolls 5R is not limited to four and may be further increased. The low-speed roll 5R is a metal roll having a diameter of 200 to 400 mm, and may be subjected to surface treatment such as hard chrome plating treatment, tungsten carbide thermal spraying, fluororesin coating, or ceramic coating. Each low-speed roll 5R includes a heating means and a temperature measuring means for measuring the roll surface temperature, and also has a temperature control function for heating and maintaining the roll surface temperature at a predetermined value. Here, as the heating means, there is used hot water, pressurized hot water, circulation of a heat medium such as heating oil, induction heating, a roll built-in cartridge heater, or the like. In controlling the temperature of each low-speed roll 5R, it is desirable to gradually raise the set temperature from the upstream side to the downstream side (heating and stretching unit 6 side) rather than setting all to the same set temperature. Although specific temperature changes also with kinds of thermoplastic resin, in the case of PET resin, it is 60-80 degreeC with the low-speed roll 5R1 of the most upstream side of the low-speed roll group 5, the most downstream side (just before the heating extending part 6, In FIG. 1, it is about 100-120 degreeC in 5R4).

  Each low-speed roll 5R of the low-speed roll group 5 rotates at a predetermined peripheral speed so as to convey the unstretched sheet 2 at a predetermined speed. Therefore, all the low-speed rolls 5R are drive rolls that are driven at a predetermined rotation speed. Although it is desirable, only some low-speed rolls may be drive rolls and others may be free rolls.

  The heating and stretching unit 6 has a heating function for heating the unstretched sheet 2 to a temperature equal to or higher than the softening point of the thermoplastic resin that is the material. The unstretched sheet 2 is stretched in the longitudinal direction, that is, in the traveling direction by the difference in peripheral speed between the low-speed roll group 5 and the high-speed roll group 7, so that the traveling speed is changed in the heating and stretching unit 6. . For this reason, if the heating function is to contact and heat the unstretched sheet 2 (or longitudinally stretched film 3), the surface of the unstretched sheet 2 (or longitudinally stretched film 3) may be scratched due to friction. . For this reason, the heating function is preferably a non-contact type, and an infrared heater is generally used.

  The high-speed roll group 7 is composed of a plurality of high-speed rolls 7R (symbol when 7R1 and 7R2 are not individually identified), and is disposed so that both surfaces of the longitudinally stretched film 2 are in close contact with the high-speed roll surface alternately. In FIG. 1, the low-speed roll group is constituted by two high-speed rolls 7R, but the high-speed roll 7R is not limited to two. The high-speed roll 7R is a metal roll having a diameter of 200 to 400 mm like the low-speed roll, and the roll surface may be subjected to surface treatment such as resin coating, ceramic coating, or chrome plating. The high-speed roll 7 </ b> R is provided with a cooling means for lowering the temperature of the longitudinally stretched film 3, which has been heated by the heating / stretching unit 6, below the glass transition point. Here, a cooling water circulation is generally used as the cooling means.

  As shown in FIG. 1, the non-contact preheating unit 8 is disposed on the upstream side of the low-speed roll group 5 over the entire width of the unstretched sheet 2 as shown in FIG. 2 and heats the unstretched sheet 2 to soften it. have. As a heating means of the non-contact preheating part 8, in order to soften the unstretched sheet 2 having a thickness of several mm, it is desirable to heat the unstretched sheet 2 and an infrared heater or a microwave heater is preferable. It is. In the case of an infrared heater, the wavelength is desirably 0.8 to 1.6 μm, which is easily absorbed by the thermoplastic resin, and more desirably within a range of 1.1 to 1.5 μm.

  In addition, when the unstretched sheet 2 is in contact with the first low-speed roll 5R1 of the low-speed roll group 5, the heat between the unstretched sheets 2 is higher when the temperature of the surface that does not contact the roll is higher than the surface that contacts the roll. Due to the expansion difference, it becomes easy to bend along the roll surface. For this reason, it is preferable to arrange | position the heat source 81 on the opposite side (upper side of the unstretched sheet | seat 2 in FIG. 1) of the surface which contacts the first low-speed roll 5R1 of the low-speed roll group 5 (FIG. 3 (a)). However, when the thickness of the unstretched sheet 2 is large, a heat source 82 having a heating capability lower than that of the heat source 81 may be disposed on the opposite side across the unstretched sheet 2 (FIG. 3B). Instead of this, a heat ray reflecting mirror 8r may be arranged (FIG. 3C). As the mirror 8r, a mirror that effectively reflects heat rays and hardly deforms due to thermal distortion is desirable, and a stainless steel polishing plate or the like can be used.

  With the above configuration, even if the thickness of the unstretched sheet 2 made of thermoplastic resin is large, it adheres to the first low-speed roll 5R1 of the low-speed roll group 5 over the entire width, and also adheres to the subsequent low-speed roll 5R and heats it. Therefore, the unstretched sheet 2 can be longitudinally stretched in a state in which both surfaces are preheated without heating unevenness.

  In addition, although this invention is suitable for production of a biaxially stretched film, only longitudinal stretching is performed and it is effective also in production of a longitudinally stretched film.

  It can be used for production of a stretched film made of a thermoplastic resin, and is particularly suitable for producing a thick film with high quality.

DESCRIPTION OF SYMBOLS 1 Longitudinal stretching apparatus 2 Unstretched sheet 3 Longitudinal stretched film 4 Biaxially stretched film 5 Low speed roll group 5R Low speed roll 5R1 First low speed roll 6 Heating stretch part 7 High speed roll group 7R High speed roll 8 Non-contact preheating part 81 Heat source 82 Heat source

Claims (4)

A longitudinal stretching apparatus that stretches a continuous unstretched sheet made of a thermoplastic resin while traveling in the direction in which the unstretched sheet continues to form a longitudinally stretched film,
Along with the downstream from the upstream of the direction in which the unstretched sheet travels, a low-speed roll group, a heating stretch unit, and a high-speed roll group,
The low-speed roll group has a function of preheating the unstretched sheet to the vicinity of the softening temperature by passing through the plurality of rolls.
A longitudinal stretching apparatus, further comprising a non-contact preheating unit that heats the unstretched sheet in a non-contact manner on the upstream side of the low-speed roll group. The longitudinal stretching apparatus according to claim 1,
The non-contact preheating unit is characterized in that a heat source is arranged on the opposite side of the surface where the unstretched sheet first contacts the low-speed roll group. The longitudinal stretching apparatus according to claim 1 or 2, wherein
The non-contact preheating part consists of an infrared heater, The longitudinal drawing apparatus characterized by the above-mentioned. The longitudinal stretching apparatus according to claim 3,
A longitudinal stretching apparatus characterized in that the dominant wavelength of infrared rays irradiated from the infrared heater is in the range of 0.8 to 1.6 μm.

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