JPH0952291A - Manufacture of plastic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of foreign matter accumulated on the surface of a film such as dust and a film composition by treating, at least, one of the surfaces of the film in a manufacturing step using an ultrasonic dust remover generating an air knife flow. SOLUTION: An ultrasonic dust remover removes foreign matter and dust accumulated on the surface of a film, in a manufacturing step, without damaging the surface of the film, by making the dust afloat with an ultrasonic pressure air ejected, in the form of an air knife flow, from a slit on a cleaner head. At the same time, microparticle dust is also removed by the ultrasonic effect. It is effective in the removal of foreign matter accumulated on the surface of the film to perform a discharging treatment prior to the ultrasonic dust removal. It is also desirable for the removal of dust when manufacturing the film to perform the ultrasonic dust removal with a film winder and in a slitter device, immediately before the film is wound in roll. In addition, the ultrasonic dust remover preferably has a three-layer construction consisting of an air blower part, a suction part and an air blower part arranged in the longitudinal direction of the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a plastic film, and more particularly to a production method for reducing dusts and deposits containing a film composition on the surface of a plastic film.

[0002]

2. Description of the Related Art Plastic films are widely used in various applications. Among them, polyester film
Because of its excellent physical and chemical properties, it is also used for magnetic tapes, floppy disks, photographs, capacitors, packaging, and films such as roentgen films and microfilms. In particular, it is indispensable as a base film for magnetic recording media.

In any of these applications, the presence of deposits on the film surface causes product defects. Especially when used as a magnetic tape coated with a magnetic material, the coating roll or coating die and the film surface are close to each other when the magnetic material is coated, and if there is an adhered substance on the film surface, the magnetic coating becomes uneven and the product yields. Is reduced. In addition, the deposit itself causes the dropout.
Further, in the use of capacitors as well, defective withstand voltage occurs due to insulation defects. In optical applications, it becomes a defective product due to poor photosensitivity and opacity.

In order to solve such problems, as a method of removing the film surface deposits, a method of installing a roll surface cleaning tool on a roll that comes into contact with the film, and a non-woven fabric made of polyester short fibers are brought into contact with the film and removed. Japanese Patent Publication No. 59-47703 and Japanese Examined Patent Publication No. 06-098699 propose a method of contacting a film with a cleaner made of long-fiber woven or knitted fabric. However, in the conventional method, there are drawbacks such as the limit of the size of the deposit that can be removed and scratches on the film surface because the removal method is a contact type, and the deposit removed by the cleaner is transferred to the film surface again. there were.

[0005]

That is, the present invention relates to a method for producing a plastic film, characterized in that at least one surface of the plastic film is treated by an air knife type ultrasonic dust remover in the process of producing the plastic film. In a preferred embodiment, static elimination is performed immediately before the ultrasonic dust remover treatment, and / or the ultrasonic dust remover is installed in a film winder and / or a slitter device, and / or the structure of the ultrasonic dust remover is a film It has a three-layer structure of an air blowing part / a suction part / air blowing part in the longitudinal direction.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The plastic film in the present invention includes, but is not limited to, a single layer or a laminated product of polyethylene terephthalate, polyethylene, polystyrene, nylon and the like. The air knife flow ultrasonic dust remover referred to in the present invention is an air knife flow by ejecting ultrasonic pressure air from the slit portion of the cleaner head to float surface deposits and is a non-contact type. Therefore, unlike the prior art, the problem that the contact-type cleaner scratches the film surface does not occur. Further, it is characterized by being effective in removing fine particle dust (1 to 50 μm) by the ultrasonic effect. Ultrasound here is 5-80kHz
It is an ultrasonic wave having a frequency band with a peak of, and an average output of 50 dB to 200 dB is more effective.

Further, in the case of a plastic film, since static electricity is easily charged, it was found that the static elimination treatment just before the ultrasonic dust remover is effective for removing the deposits on the film surface. The static elimination method creates an unequal electric field between the high-voltage cable and the grounded electrode needle, accelerates corona discharge, ionizes the air around the static elimination bar, and causes excess charged objects in the ion path. The method of neutralizing and removing the charges is the most preferable, but the method is not limited to this.

In general, a film is rolled up into a product to be a product. Therefore, it is desirable to perform ultrasonic dust removal treatment in a step immediately before winding up, that is, in a so-called film winder and / or a slitter device. The reason for this is that when manufacturing a plastic film, it is under dry heat and high temperature, specifically about 80
Even if oligomers are deposited by the process of exposure to ~ 220 ° C, or environmental dust or chips generated in the film cutting process are attached to the film surface, the deposit is weak because it is not rolled up and the surface is easily removed by the ultrasonic dust remover. This is because deposits are removed and a roll film product with less deposits is obtained.

The structure of the ultrasonic dust remover has a three-layer structure of an air blowing part / aspirating part / air blowing part in the longitudinal direction of the film, which is the most effective in removing dust, and a structure in which the order of these three layers is different or 2 It was found to be superior to the layered ultrasonic dust remover. This is especially effective for partially adhered adherents because ultrasonic air is blown against the film adherents from both sides (in the film flow direction), and the separated adherents are turbulent flows generated by the air knife. This is because it is removed from the suction section by riding on the board. Air blowing pressure = 800 to 2 as a condition for obtaining the effect of each layer
The range of 000 mmAq is preferable, and 1000 is more preferable.
~ 1800 mmAq. The pressure of the suction part is -100 to-
The range of 500 mmAq is preferable, and more preferably -300.
~ -500mmAq is excellent in dust removal rate.

[0010]

Next, examples of the present invention and comparative examples will be described. The present invention is not limited to the examples below.
The characteristic values in the examples and comparative examples are as follows.

(1) Amount of deposits on film surface A sample was sampled from a film roll in a clean room of 100 to 1000 class cleanliness, and the obtained film sheet was immersed in ultrapure water and subjected to ultrasonic treatment. The ultrapure water used here had an electric resistance of 18 MΩcm or more and 2 to 4 μm size impurities of 15 pieces / 20 ml or less. The particles in the ultrapure water after removing the film were measured with a particle counter (KP-100 manufactured by KURABO). The measurement conditions are set to 2 to 20 μm, 1 to 2 μm,
The amount of particles having a size of 3 to 4 μm (pieces / 20 ml) was determined.

(2) Scratches on the film surface Regarding the scratches on the film surface, aluminum was vacuum-deposited on the surface opposite to the observation surface, and the presence or absence of scratches was visually evaluated at about 30 times using a stereoscopic microscope.

(3) Preparation of magnetic paint for dropout evaluation Co-γ-Fe ₂ O ₃ (BET specific surface area 30 m ² / g) 100 parts Vinyl chloride / vinyl acetate copolymer 15 parts Urethane-modified saturated polyester resin 15 parts α-alumina (average particle size 0.5 μm) 3 parts Carbon black (average particle size 0.08 μm) 2 parts Toluene 105 parts Methyl ethyl ketone 105 parts Cyclohexanone 105 parts After about 12 hours of mixing and dispersing with a ball mill with the above raw material mixture, this Palmitic acid (1 part) dodecyl stearate (2 parts) oleic acid (2 parts) was added and the mixture was further mixed for 30 minutes. 10 parts of a 75% solid content ethyl acetate solution of the tolylene diisocyanate compound was added and further mixed for 1 hour to obtain a magnetic paint. The magnetic coating material was applied so as to have a thickness of 2.0 μm after dried, subjected to magnetic field orientation treatment, dried at 60 ° C., calendered at 100 ° C., and further cured at 60 ° C. for 72 hours. . This film was slit into a ½ inch width, leader tapes were adhered to both ends and inserted into a cassette to prepare a test VHS cassette tape. Signals are recorded / reproduced on these cassette tapes using a VHS deck for measurement, and dropouts of 15 μsec * 16 dB or more and 5 μ * 10 dB or more are counted for 60 minutes by a dropout counter, and the average value per minute is displayed. did.

(4) Number of defects detected 800 μm by an in-line light-blocking detector,
The amount of deposits on the surface of the film having a size of 1300 μm was evaluated.

[Examples] Examples of embodiments of the present invention will be described below based on examples. Example 1 A polyethylene terephthalate polymer obtained by a known method was dried and extruded into a sheet at 290 ° C.
It was stretched 3.6 times in the machine direction at 0 ° C. and 3.7 times in the cross direction at 110 ° C. After that, heat treatment at 220 ℃, thickness 14.5
A μm biaxially oriented polyethylene terephthalate film was produced. Using a film winder equipped with an ultrasonic dust remover, an ultrasonic dust-free polyethylene terephthalate film was wound up under the following conditions. Dust removal conditions Film traveling speed: 170 m / min Ultrasonic dust remover head configuration: Air blower / suction /
Air blowing part Treatment surface: Both sides Air blowing part pressure: 1500 mmAq Suction part pressure: -350 mmAq Ultrasonic dust remover Installation place: Film winder No scratch was observed on the surface of the obtained film.
It was also confirmed that the amount of the film surface deposit was small and the dropout was also small.

In the same manner as in Examples 2 to 7, the effect was observed when the ultrasonic dust remover was treated on only one side, when the ultrasonic dust remover was installed in the film slitter, and when the material of the film to be treated was different. . The processing conditions are shown in Table 1.

Comparative Examples 1 and 2 Approximately twice as many deposits were detected on the film using the conventional contact type cleaner without using the ultrasonic dust remover. Furthermore, the effect is inferior to that of the embodiment even when the ultrasonic dust remover is installed in a process of a two-layer head structure, a film winder, or a process other than the film slitter, and there is no static eliminator.

[0018]

According to the method of the present invention, it is possible to reduce dust on the surface of the plastic film, deposits containing the film composition and the like, and the non-contact method does not scratch the film surface. It is possible to solve the problem that the removed deposits transfer to the film surface again.

[0019]

[Table 1]

Claims (4)

[Claims] 1. A method for producing a plastic film, characterized in that at least one side of the plastic film is treated with an air knife flow ultrasonic dust remover in the step of producing the plastic film. 2. The method for producing a plastic film according to claim 1, wherein the static elimination treatment is performed immediately before the treatment with the ultrasonic dust remover. 3. The method for producing a plastic film according to claim 1, wherein the ultrasonic dust remover is installed in a film winder and / or a slitter device. 4. The structure of an ultrasonic dust remover has three structures of an air blowing part / a suction part / air blowing part in the longitudinal direction of the film.
The method for producing a plastic film according to claim 1, which has a layered structure.