JPS5927693B2 - Method for manufacturing thermoplastic polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing thermoplastic polyester films.

More specifically, it suppresses the reduction in width, non-uniformity of thickness, precipitation of white powder on the surface of the casting drum, etc. that occurs when the thermoplastic polyester melt polymer is cooled and solidified on the surface of the casting drum and formed into a film. The aim is to provide a method to reduce the deterioration of the working environment. Methods for producing films by applying organic liquids to the surface of a casting drum are known.

For example, Japanese Patent Application Laid-open No. 49-99160 discloses that the surface tension of the casting drum is 5 at boiling point of 150 to 220°C.
It has been proposed to apply alcohol with a boiling point of 150 to 220°C and a surface tension of 5.
It has been proposed to apply organic liquids other than alcohol at less than 0 turns/1. However, these alcohols and other organic liquids have a strong odor and are often flammable, which not only significantly degrades the working environment but also makes them uneconomical. Furthermore, JP-A-50-76173 proposes applying an oily substance to the surface of the casting drum, but it is difficult to completely remove the oily substance from the film in subsequent steps, and longitudinal stretching is difficult. In this case, oily substances will accumulate on the surface of the stretching roll.
During lateral stretching, oily substances scatter in the underlayer, causing stains on the film, and post-processing of the resulting film.
For example, it is not preferred because it brings about disadvantageous results when applying magnetic paints, photosensitive agents, pressure-sensitive adhesives, laminating adhesives, and the like.

As a result of extensive research into a method that does not have these drawbacks and suppresses the reduction in width, non-uniformity of thickness, and precipitation of white powder on the surface of the casting drum during film formation, the inventor has found that The inventors have discovered that it is sufficient to apply water on the surface of the casting drum held, and have arrived at the present invention. That is, in the present invention, when a thermoplastic polyester melt extruded from a die is cooled and solidified using a rotating casting drum soil coated with liquid on the surface to form a film, the surface temperature of the casting drum is set at 2°C. As described above, the production of a thermoplastic polyester film is characterized in that the temperature is maintained at a temperature lower than the boiling point of water and at least 3°C lower than the glass transition temperature of the thermoplastic polyester, and water is used as the liquid applied to the drum surface. It's a method.

The thermoplastic polyester used in the method of the present invention is polyethylene terephthalate, polytrimethylene terephthalate,
Polytetramethylene terephthalate, polypentamethylene terephthalate, polyethylene-2,6-naphthalate, polytetramethylene-2,6-naphthalate, polyhexamethylene-2,6-naphthalate, polytrimethylene-2,6-naphthalate, polypenta methylene-2
, 6-naphthalate, etc., and the thermoplastic polyester may be a copolymer or a blend of two or more thermoplastic polyesters.

In the method of the present invention, water is applied to the surface of a rotating casting drum used to cool and solidify the thermoplastic polyester melt extruded from a die.

This is to suppress reduction in film width, non-uniformity in thickness, and precipitation of white powder on the surface of the casting drum during film formation. It is preferable that the temperature of the water applied to the surface of the casting drum be as equal as possible to the surface temperature of the casting drum. The water used here may be of a level generally used in tap water, and if necessary, a small amount of surfactant may be included. The surface temperature of the casting drum is 2° C. or higher, and the glass transition temperature (hereinafter abbreviated as Tg) of the thermoplastic polyester extruded from Calidae.

) and below the boiling point of water. If the surface temperature of the casting drum is lower than 2°C, the casted film that is being cooled will slip on the casting drum soil, resulting in uneven film thickness and width, and This is not preferable because the adhesion to the surface of the casting drum deteriorates, making it impossible to suppress the precipitation of white powder. On the other hand, if the surface temperature of the casting drum is not lower than Tg by 3°C or more, the casted film will stick to the surface of the casting drum, making it impossible to obtain a film with a uniform thickness, which is undesirable. As the surface temperature of the drum, it is preferable to adopt a value measured with a contact type surface thermometer.

For measuring the glass transition temperature Tg in the present invention, a differential calorimeter (ie, DSC-1B manufactured by DSC Perkin Elmer Co., Ltd.) was used.
) was rapidly cooled by pouring the molten resin as a sample into ice water in the sample pan 107! ! f and the temperature increase rate is 32℃/! Draw the endothermic/exothermic curve with E and pace/
The value obtained from the rise of the line is used. When a plurality of Tg's are measured (for certain types of homopolymers, copolymers, blends, etc.), the lowest value is taken as the Tg in the method of the present invention. In the method of the present invention, in order to apply water to the surface of the rotating casting drum, it is necessary to apply water to the entire width of the casting drum or to the part of the drum where the polymer melt thin film or the solidified thin film is not attached. Water may be applied to the area to which it is attached using a known application means such as spraying, a doctor knife, a brush, or the like.

Alternatively, a considerable effect can be obtained by applying water only to the portions of the drum surface where the left and right ends (direction perpendicular to the extrusion direction) of the film are attached. The method of the present invention includes other methods to help the polyester melt adhere to the casting drum. means, such as blowing a uniform stream of air onto the melt, suctioning air interposed between the melt and the drum, or electrostatically creating an attractive force between the melt and the drum. Needless to say, it is possible to use other means such as adding the information. According to the method of the present invention, when manufacturing a film by extruding a polyester melt through a die and cooling and solidifying it on the surface of a casting drum, the film width is reduced, the thickness of the film becomes uneven, and white powder is deposited on the drum surface. It suppresses adhesion, is safe and economical, and does not deteriorate the working environment.

Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 Polyethylene terephthalate having an intrinsic viscosity (measured at 25°C using 0-chlorophenol as a solvent) of 0.640 was melted by heating at 280°C in an extruder, extruded through an extrusion die with a width of 320 mm, and the surface temperature was 40°C. The mixture was quenched on the surface of a casting drum (634 nm in diameter), turned into a film with a thickness of 170 μm, and taken off at a speed of 30 m/meter.

At this time, water was applied to the entire surface of the casting drum by bringing a cloth pad impregnated with 40° C. water into contact with the entire width of the rotating casting drum. As a result, the width of the produced film is 2351z
1&, the thickness variation rate was ±1.6%. Even after one hour of continuous operation, no white powder was observed on the surface of the casting drum.

The obtained unstretched film was biaxially stretched at a longitudinal stretching temperature of 85° C., a longitudinal stretching ratio of 3.6 times, a transverse stretching temperature of 100° C., and a transverse stretching ratio of 3.9 times, and then heat treated at 200° C. for 10 seconds.
No water remained on the film surface.

Example 2 Polytetramethylene terephthalate having an intrinsic viscosity (measured at 25°C using 0-chlorophenol as a solvent) of 1.10 was melted by heating at 270°C in an extruder, extruded through an extrusion die with a width of 320ml, and the surface temperature was 5. Casting drum (diameter 63411) on surface, chilled, thickness 250 °C
15m/M7 with μ film! It was picked up at a speed of

At this time, water was applied to the surface of the casting drum by bringing a cloth pad impregnated with water at 5° C. into contact with the entire width of the rotating casting drum. As a result, the width of the formed film was 255 mm, and the thickness variation rate was ±1.8%. Most of the water on the film surface evaporated immediately after leaving the casting drum. Even after one hour of continuous operation, no white powder was observed on the surface of the casting drum.

After biaxial stretching and heat treatment under exactly the same conditions as in Example 1, no water remained on the film surface. Comparative example 1
Film formation, biaxial stretching, and heat treatment were performed in the same manner as in Example 1 except that no liquid was applied to the surface of the casting drum.

The width of the unstretched film thus formed was 1901 tm, and the thickness variation rate was ±29%.

From this result, it can be seen that in this example, the width of the unstretched film relative to the width of the extrudate was greatly reduced, and the rate of variation in the thickness of the film was also large, compared to the example. Also, on the surface of the casting drum, 5 minutes after the start of continuous operation,
White powder was observed to adhere to the drum surface.

Claims (1)

[Claims] 1. When the thermoplastic polyester melt extruded from the die is cooled and solidified on a rotating casting drum whose surface is coated with a liquid and formed into a film, the surface temperature of the casting drum is kept at 2°C or more, and water is A method for producing a thermoplastic polyester film, characterized in that the temperature is kept below the boiling point and at least 3°C lower than the glass transition temperature of the thermoplastic polyester, and water is used as a liquid applied to the drum surface.