JP2782007B2 - Heating method of thermoplastic resin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for heating a thermoplastic resin film, and more specifically, it poses a problem when a thermoplastic resin film is stretched or heated to a heat treatment temperature. The present invention relates to a method for heating a thermoplastic resin film in which static electricity has been eliminated.

[Prior Art] Generally, a plurality of heating rolls are used in a method of preheating a film to a temperature suitable for stretching or heat treatment. Then, the preheated film is stretched by a peripheral speed difference between a plurality of rolls in a stretching step, and is heat-treated by controlling a tension of the film between the plurality of rolls in a heat treatment step.

Conventionally, the above-mentioned heating roll is a metal roll, a roll in which the surface of the metal roll is coated with ceramic or resin, and a roll in which the surface is coated with rubber (rubber roll).
And the like are appropriately used. In practice, a roll surface material is selected so that the film and the roll do not adhere to each other at a desired preheating temperature.

[Problems to be solved by the invention]

However, in the case of a rubber roll, generally, both the thermoplastic resin film and the rubber have poor electric conductivity,
When the film and the surface of the rubber roll come into contact with each other, static electricity is charged on both surfaces, and as a result, various kinds of static electricity damage occur.

For example, when the surface of the film is charged, dust and dust existing in the film manufacturing process adhere to the film surface. In the case of a polyester film for magnetic recording, if the film on which the dust adheres is coated with a magnetic recording layer, the portion forms abnormally high protrusions, and it becomes impossible to perform normal recording and reproduction of signals. Cause quality problems. Furthermore, when winding up a film having a very flat surface, the portion to which dust is attached rises, and the rise extends to the top roll of the product. As a result, the raised portion becomes wrinkled and causes permanent deformation. For example, in the case of a polyester film for CHP, the raised portion is projected as a defect on a screen, and there is a problem that the quality of a product is significantly impaired.

On the other hand, when the rubber roll is charged, if it exceeds the dielectric breakdown voltage of the rubber, cracks may suddenly enter the surface of the rubber roll. And in this case, when a shearing force is acting on the surface like a stretching roll, the rubber wound on the surface layer of the metal roll is broken, and the rubber pieces are scattered and entangled in a sliding portion of a nearby machine. There are problems such as breakage of the machine, breakage of the film and winding around the roll.

Accordingly, the present invention focuses on the above-described problems in rubber rolls, and proposes a method for heating a thermoplastic resin film without electrostatic damage.

[Means for solving the problem]

That is, the gist of the present invention is to use a plurality of heating rolls for an unstretched or at least uniaxially oriented thermoplastic resin film, and to heat the film to a stretching or heat treatment temperature. A method for heating a thermoplastic resin film, comprising using a rubber roll coated with rubber having a volume resistivity of 10 ⁷ Ωcm or less.

The rubber material of the rubber roll used in the present invention is not particularly limited, and silicon, chloroprene, acrylic, ethylene propylene terpolymer, fluorine, natural rubber, chlorosulfonated polyethylene and the like can be used. It is preferred to use rubber.

The rubber roll used in the present invention has a volume resistivity of 10 ⁷ Ωc
m or less, and usually, the rubber material does not satisfy the volume resistivity by itself, therefore,
It is necessary to appropriately impart conductivity. The means for imparting conductivity is not particularly limited, but it is preferable to knead conductive carbon, a metal component, or the like as a conductive agent in a rubber material. These additives are substances having properties different from those of the rubber material, and thus may be detached from the roll surface. Accordingly, for example, in the production of a polyester film for a magnetic tape, it is preferable to use a polyester film having a particle size as small as possible so that even if it adheres to the film, the signal recording is not adversely affected.

The thickness of the rubber coating of the rubber roll used in the present invention is not particularly limited, but if it is too thin, the influence of the core metal extends to the surface and the hardness of the rubber roll surface increases,
It is preferably set to 0.5 mm or more. The rubber hardness is also not particularly limited, but if the hardness is too low and the surface is too soft, friction may occur due to plastic deformation when coming into contact with the film. Further, the coefficient of friction is not particularly limited, but in the stretching portion and the heat treatment portion, it is necessary to set the film so that the film does not slip on the roll due to the stretching force or the shrinking force of the film,
Therefore, a rubber material that does not cause the film to adhere to the roll surface is selected.

Since the charging phenomenon is caused by the contact between the film and the roll regardless of the conditions, the rubber roll of the present invention is not only used as a heating roll, but also when the heating roll itself is simultaneously stretched or heat-treated. It can also be used effectively when acting as a roll.

The heating method of the present invention is typically used when stretching or heat-treating a polyester film, but it is needless to say that the heating method can be applied to similar heating of other thermoplastic films. Further, the film may be an unstretched or stretched film.

〔Example〕

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

The volume resistivity of the rubber material of the rubber roll used was measured by the following method.

<Method of Measuring Volume Resistivity> A rubber test piece having a length of 100 mm, a width of 100 mm and a thickness of 3 mm was used. As shown in FIGS. 2 and 3, the main electrode ( 20) and a guard electrode (30) are provided, and a lower electrode (40) is provided on the other surface.

All the electrodes are made of metal foil, and are bonded to each other with conductive paint (Dohite manufactured by Fujikura Electric Wire Co., Ltd.) so that their centers are aligned. The diameter of the main electrode (20) is 50 ± 0.5 mm, the inner diameter of the guard electrode (30) is 70 ± 0.5 mm, the outer diameter is 80 ± 0.5 mm, and the diameter of the lower electrode (40) is 70 ± 0.5 mm. .

In an atmosphere at a temperature of 20 ° C. and a relative humidity of 65%, a DC voltage of 500 V is applied between the main electrode and the lower electrode for 1 minute to charge the battery. Then, the resistance value is measured, and the volume resistivity (ρ ) Is calculated.

ρ = 19.6 R / t (Ωcm) In the above equation, R represents the measured resistance value (Ω), and t represents the thickness (mm) of the test piece.

Example In the stretching and heat treatment step of the film having the roll arrangement shown in FIG. 1, stretching and heat treatment of a polyethylene terephthalate unstretched film (sheet) were performed.

In FIG. 1, the unstretched film (A) includes heating rolls (1) to (4), stretching rolls (5) and (5 '), heat treatment rolls (6) and (6'), and a cooling roll (7). ,
Processed through (7 ').

For the rolls (1), (2) and (7), (7 '), use metal rolls having a hard chrome plating finish. A rubber roll was used in which chlorosulfonated polyethylene having a ratio of 1 × 10 ⁵ (Ωcm) was covered with a thickness of 3 mm on the surface of a metal roll.

The processing conditions were as follows, and Nicarlico was sprayed on the film to be processed and each roll, and the presence or absence of electrification was evaluated by observing the state of adhesion.

Roll surface temperature: (1), (2) 85 ° C (3), (4) 100 ° C (5), (5 ') 100 ° C (6), (6') 98 ° C (7), (7 ') 20 ° C. Stretching magnification: 3.5 times Relaxing tension: 150 kg Film thickness: 800 μm before stretching 100 μm after stretching For comparison, in the process shown in FIG. An unstretched polyethylene terephthalate film was treated in the same manner as in the above example, except that a rubber roll was partially used, and the film and each roll were evaluated for the presence or absence of charging.

 The evaluation results are summarized in Table 1.

As is clear from the results in Table 1, in the case of a rubber roll having a volume resistivity satisfying the specified value of the present invention, no electrostatic charge is recognized on any of the roll and the film.

〔The invention's effect〕

According to the present invention described above, a simple configuration in which a rubber roll coated with a rubber having a specific volume resistivity is used as a heating roll can solve electrostatic problems which are a problem in heating a thermoplastic film at once. Therefore, the industrial value of the present invention is remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of roll arrangement in a film stretching and heat treatment step, where (A) is an unstretched film, and (1) to (1).
(4) is a heating roll, (5) and (5 ') are stretching rolls,
(6) and (6 ′) are heat treatment rolls, and (7) and (7 ′) are cooling rolls. 2 and 3 are explanatory diagrams showing a method of measuring the volume resistivity of a rubber material. (10) is a rubber test piece, (20) is a main electrode, (30) is a guide electrode, and (40) Is a lower electrode.

Claims (1)

(57) [Claims] 1. A method of heating an unstretched or at least uniaxially oriented thermoplastic resin film to a stretching or heat treatment temperature by using a plurality of heating rolls, wherein the heating roll has a volume resistivity on a metal roll surface. Is 10
^A method for heating a thermoplastic resin film, comprising using a rubber roll coated with a rubber having a resistivity of ⁷ Ωcm or less.