JPH029927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an amorphous polyester film, and more particularly, the present invention relates to a method for producing an amorphous polyester film, and more particularly, extruding molten polyester through a die orifice, forming the film into a film, and adhering the film to a moving cooling surface.
During cooling and solidification, from the uncooled polymer surface,
A method of manufacturing polyester film that reduces the deposition of low molecular weight substances on cooling surfaces. When melt-extruding crystalline thermoplastic resins such as polyethylene terephthalate, it is necessary to rapidly cool the molten polymer below its glass transition temperature to minimize crystallization. Excessive crystallization in a polyester film can cause embrittlement, interfere with subsequent film manufacturing operations such as stretch orientation, and cause haze and thickness unevenness in the oriented product. The polyester film is then rapidly solidified by pouring the molten polymer onto a cold moving surface such as a rotating drum. However, when polymer films are exposed to high temperatures, low molecular weight substances precipitate on the film surface or sublimate from the film surface, so when the film is brought into close contact with a moving cooling surface, low molecular weight substances adhere to the moving cooling surface. become contaminated. This low molecular weight substance may be contained in the polymer, or may be hydrolyzed by surrounding moisture during melting. When low-molecular-weight substances adhere and accumulate on the moving cooling surface, irregular irregularities occur on the cooling surface, causing irregular irregularities and non-uniform physical properties on the surface of the product film. Further, cooling efficiency may be lowered, and some of the deposits may peel off from the moving cooling surface and adhere to the film, causing surface defects on the film and reducing product value. Furthermore, this deposit becomes increasingly difficult to remove as the operation continues because the hot sheet burns it onto the cooling surface. This deposit of low-molecular-weight sublimate adheres not only to the moving cooling surface but also to the surface of the linear electrode in the electrostatic adhesion method that is commonly used to improve the adhesion between the cooling surface and the film. Significantly reduces the effectiveness of static electricity adhesion. In order to remove this deposit, in the prior art, it was necessary to stop the equipment and clean the surface, resulting in a decrease in productivity. The present inventors have completed the present invention as a result of intensive studies regarding such problems. That is, in the present invention, when producing an amorphous polyester film in which molten polyester is extruded into a film through a die orifice, brought into close contact with a moving cooling surface, and solidified by cooling, an aliphatic monocarboxylic acid having 8 to 32 carbon atoms is added to the polyester. , their esters, and liquid paraffin. The present invention will be explained in more detail below. The polyester referred to in the present invention refers to a polyester obtained using terephthalic acid or its alkyl ester and ethylene glycol as main starting materials, but other third components may be used as part of the raw materials. As the third component, one or more kinds of isophthalic acid, naphthalene dicarboxylic acid, or their alkyl esters are used as an aromatic dicarboxylic acid component, and as a glycol component,
One or more polyalkylene glycols such as propylene glycol, tetramethylene glycol, and polyethylene glycol can be used. In any case, the polyester of the present invention refers to a polyester in which at least 80% of the repeating structural units are polyethylene terephthalate units. Examples of the aliphatic monocarboxylic acid having 8 to 32 carbon atoms used in the present invention include cabric acid, myristic acid, stearic acid, behenic acid, and montanic acid. Examples of the ester include glycerol stearate and ethylene glycol mono- or diester of montanic acid. As the liquid paraffin, paraffin that is liquid at room temperature and is represented by CnH ₂ n+ ₂ can be used. The amount of such a compound added is 10 to 1000 ppm, preferably 50 to 550 ppm, based on the polyester resin.
If the amount added is less than 10 ppm, the effect of reducing the accumulation of low molecular weight sublimate due to decomposition of polyester on the moving cooling surface cannot be obtained. Even if it is used in excess of 1000 ppm, no further improvement effect will be obtained, and instead the viscosity of the resulting polyester film will decrease, coloration, and
This is not preferable because it causes a decrease in transparency. Addition of such compounds to polyester resins
This can be carried out at any stage before melt extruding the polyester resin. For example, it is added during the polycondensation reaction when producing polyester resin,
Either it is added directly to polyester resin pellets and adhered to the pellet surface and then melt-extruded, or the pellets and the compound are melt-mixed together in an extruder in advance to produce a so-called masterbatch containing a high concentration of the compound. and compound-free pellets can be blended to a predetermined concentration and extruded. In particular, it is more effective to add it after polyester polymerization and before extrusion. Melt extrusion is carried out at a temperature range of 280-310°C. The molten material extruded into a film from the die orifice is brought into close contact with a moving cooling surface whose surface temperature is maintained at 30 to 70°C, where it is cooled and solidified. At this time, methods such as electrostatic adhesion can be used to improve adhesion. The reason why the deposition of low molecular weight polyester substances on the moving cooling surface is suppressed in the present invention is presumed to be as follows. That is, between the unstretched film melt-extruded from the die orifice and the moving cooling surface, extremely small voids are locally formed, which is thought to be due to insufficient adhesion, and the low molecular weight polyester material is Deposition occurs. This means, for example, the moving speed of the cooling surface (rotational speed of the cooling drum)
It can be assumed from the fact that if the unstretched film and the cooling surface are made to have a sufficient adhesion by reducing the amount of the unstretched film, the accumulation of the above-mentioned low molecular weight substances will be reduced. All of the additives used in the present invention are compounds whose main structure is a hydrocarbon chain, and since these compounds have a relatively low molecular weight when blended with polyester, they do not adhere to the surface of the polyester film at high temperatures. This bleeds out, but this further fills the microscopic voids mentioned above, and as a result,
It is thought that the deposition of low molecular weight compounds of polyester is suppressed. The present invention will be explained below with reference to Examples. Note that "parts" and "%" in Examples are "parts by weight" and "% by weight." Example 1 A polyethylene terephthalate resin having an intrinsic viscosity [η] of 0.66 was vacuum dried at 160° C. for 6 hours.
100 ppm of behenic acid was added to the dried resin, extruded through a slit die using an extruder, and cooled and solidified on a rotating cooling drum kept at 60°C to obtain an amorphous polyester film with a thickness of 210 microns.
After 1.5 hours of operation, the polished surface of the chill roll was still clean and free of low molecular weight compounds. Example 2 Polyethylene terephthalate resin with intrinsic viscosity [η] of 0.66, vacuum dried at 160°C for 6 hours
100 parts, 1 part ethylene glycol distearate
1% masterbatch of ethylene glycol distearate was prepared by melt-kneading at 280° C. using an extruder. Next, 5 parts of the masterbatch pellets and 95 parts of polyethylene terephthalate resin were blended and vacuum-dried at 160°C for 6 hours. This dry resin was used in Example 1.
An amorphous polyester film having a thickness of 210 μm was obtained using an extruder in the same manner as above. Even after 1.5 hours of operation, the polished surface of the cooling roll is still clean and
No attachment of low molecular weight compounds was observed. Example 3 In the same manner as in Example 1 except that liquid paraffin was used instead of behenic acid, the state of attachment of low molecular weight compounds to the moving cooling surface was observed. 1.5
No adhesion was observed even after hours of operation. Comparative Example 1 The same polyethylene terephthalate resin used in Example 1 was treated with 160%
After drying at ℃ for 6 hours, the mixture was melt-extruded using an extruder to obtain an amorphous polyester film with a thickness of 210 μm. After one hour of operation, the polished surface of the cooling surface was heavily streaked with a coating of low molecular weight compounds. In place of behenic acid in Example 1, Hoechstwax S (montanic acid), polyethylene glycol dilaurate, and Hoechstwax E (montanic acid ester) were used to observe the adhesion of low molecular weight compounds to the moving cooling surface. In either case,
No adhesion was observed even after 1.5 hours of operation. The obtained results are summarized in Table 1. 【table】

Claims (1)

[Claims] 1 Extrude the molten polyester into a film through a die orifice, bring it into close contact with the moving cooling surface,
Production of an amorphous polyester film characterized by adding one or more selected from aliphatic monocarboxylic acids having 8 to 32 carbon atoms, their esters, and liquid paraffin to the polyester when producing the amorphous polyester film which is solidified by cooling. Method.