JPH0229692B2 - SEIDENSEIHORIESUTERUFUIRUMU - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a polyester film with excellent antistatic properties and good surface properties. [Prior art] Polyester film generally exhibits high crystallinity and high melting point, and is known to have excellent properties such as heat resistance, chemical resistance, strength, and elastic modulus, and is used for magnetic tape, drafting, and electrical applications. It has many uses such as for commercial use and packaging. However, polyester films are easily charged, and the accumulation of static electricity often causes various problems during the film forming process, processing process, and use. For example, problems include wrapping of film around rolls during the film forming and processing process, electric shock to workers, dirt on the film surface due to dirt and dust being sucked in, printing defects, and clinging between films. As a method to prevent static electricity on polyester film,
A commonly used method is to apply an antistatic agent to the surface of the film, but since this method requires a coating process, it is not only complicated and economically disadvantageous, but also causes friction on the film surface. There is a drawback that the antistatic agent easily falls off and the antistatic effect is reduced. On the other hand, many methods have been proposed in which an antistatic agent is added to polyester, which is the raw material for the film.
For example, JP-A-52-47071 discloses that a polyalkylene glycol soluble in polyester is blended with a salt of an alkylated aromatic sulfonic acid; It has been shown that a combination of a soluble low molecular weight polyalkylene glycol and a salt of an alkyl sulfonic acid can be formulated. In these methods, polyalkylene glycol is combined in order to improve the dispersibility of the sulfonic acid metal salt derivative compound that acts as an antistatic agent, but it is difficult to avoid significantly roughening the surface of the film. First, it is difficult to use it in magnetic applications, where flatness of the base film surface is required to prevent recording disturbances. [Object of the Invention] The present invention provides a polyester film that has excellent antistatic properties and good surface properties, particularly a polyester film that has surface flatness sufficient to withstand use in high-grade magnetic applications, and has sufficient antistatic properties. An object of the present invention is to provide a biaxially oriented polyester film having the following properties. [Structure/Effects of the Invention] The object of the present invention is to provide 100 parts by weight of a polyester whose main repeating unit is an ethylene terephthalate unit, and (a) 0.1 to 10 parts by weight of a sulfonic acid metal salt derivative and (b) a higher fatty acid metal. This is achieved by an antistatic polyester film characterized in that the salt is blended in an amount of 0.1 to 2 times the weight of the sulfonic acid metal salt derivative, biaxially oriented, and heat-set. The polyester that is the base material of the polyester film of the present invention is a polyester having ethylene terephthalate units as the main repeating unit, and dicarboxylic acids other than the terephthalic acid component include fatty acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid. group dicarboxylic acids; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid; aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenylsulfone dicarboxylic acid, and benzophenone dicarboxylic acid; and/or glycol other than ethylene glycol component, 1,
3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, etc. may be copolymerized. The content of these copolymerization components is preferably 15 mol% or less, more preferably 10 mol% or less, based on the total repeating units. Among these, polyethylene terephthalate is preferred. The polyester may also contain additives such as stabilizers, colorants, etc., which are usually added to polyethylene terephthalate. Such polyesters can typically be produced by melt polymerization of conventionally stored polyesters. For example, terephthalic acid or its lower alkyl ester is subjected to an esterification or transesterification reaction with ethylene glycol to form a monomer or an initial polymer, which is then heated at a temperature above its melting point under vacuum or under an inert gas flow. It is manufactured by a method in which a polycondensation reaction is carried out while stirring until the intrinsic viscosity becomes about 0.45 to 0.75. On this occasion,
Additives such as catalysts can be used as desired. In the present invention, examples of the sulfonic acid metal salt derivative to be blended into the polyester as an antistatic property improver include compounds represented by the following structural formulas (1), (2), and (3). Here, R is an alkyl group having 8 to 20 carbon atoms,
Specific examples include octyl, nonyl, decyl, undecyl, dodecyl, and octadecyl. Further, Me is an alkali metal or an alkaline earth metal, and examples of the alkali metal include lithium, sodium, potassium, etc., and examples of the alkaline earth metal include calcium, barium, magnesium, etc. Specific examples of such compounds include sodium octylsulfonate, sodium octylbenzenesulfonate, sodium dodecylsulfonate, lithium dodecylsulfonate, sodium dodecylbenzenesulfonate, lithium dodecylbenzenesulfonate, sodium dodecylnaphthalenesulfonate, and dodecyl sulfonate. Examples include potassium naphthalene sulfonate. The amount of the sulfonic acid metal salt derivative blended into the polyester film is 0.1 to 10 parts by weight, preferably 0.5 to 5.0 parts by weight, per 100 parts by weight of polyester. This amount is
If the amount is less than 0.1 part by weight, the antistatic properties will hardly be improved, while if it exceeds 10 parts by weight, the film surface will become rough. In the present invention, the metal salt of higher fatty acid blended as a dispersibility improver in the polyester antistatic agent is a compound represented by the following general formula (4). (RCOO) ₂ Me'...(4) Here, R is the same as the above definition, and Me' is a metal of groups a and b of the periodic table. Specific examples of this compound include magnesium stearate, calcium stearate, zinc stearate, calcium palmitate, calcium arachidate, and the like. The amount of the higher fatty acid metal salt is 0.1 to 2 times the weight, preferably 0.3 to 1.5 times the weight of the sulfonic acid metal salt derivative blended into the polyester film. If the amount of the higher fatty acid metal salt is less than 0.1 times the amount of the sulfonic acid metal salt derivative, the effect of improving the dispersibility of the sulfonic acid metal salt derivative in the polyester will hardly appear. Furthermore, even if the amount is more than twice that of the sulfonic acid metal salt derivative, the dispersibility improvement effect of the sulfonic acid metal salt derivative will not be increased, and on the contrary, it will have adverse effects such as thermal deterioration of the polyester and deterioration of its physical properties during film formation. occurs. By combining a sulfonic acid metal salt derivative and a higher fatty acid metal salt, an antistatic film whose surface is not roughened can be obtained. If only a sulfonic acid metal salt derivative is blended, antistatic properties can be imparted, but the film surface becomes rough, and if only a metal salt of a higher fatty acid is blended, antistatic properties cannot be imparted to the film. In the present invention, the sulfonic acid metal salt derivative and the higher fatty acid metal salt can be blended at any stage of polyester film production. For example, it can be added before starting the polymerization reaction, during the polymerization reaction, or at the end of the polymerization reaction when the raw material polyester is still in a molten state. Further, the polyester and these compounds may be mixed using an extruder, or may be directly blended into the raw material polyester when forming a film. Furthermore, it is also possible to produce a polyester film having a desired blending amount by preparing so-called master chips containing these blends at high concentrations and mixing these as appropriate. The polyester film of the present invention can be manufactured by conventional film forming methods. For example, T-
The polymer is melt-extruded by a die method, an inflation method, or the like, and then stretched simultaneously or sequentially in two axial directions to form a biaxially oriented film, which is then heat-set. The stretching temperature may be approximately the same as that for polyethylene terephthalate alone, but it is preferable to select an appropriate temperature depending on the amount of the blend. The stretching temperature is
Near or above the glass transition temperature of polyester, for example, longitudinal stretching temperature 60 to 100℃, transverse stretching temperature 80℃
It can take ~120℃. Further, the stretching ratio is usually 2.5 to 5 times in the machine direction and 2.5 to 5 times in the transverse direction. Heat setting can be performed at any temperature as long as it is higher than the final stretching temperature, but it is usually 180 to 240°C, and the time is from several seconds to several tens of minutes. The polyester film may further contain suitable antioxidants, ultraviolet absorbers, colorants, etc., if necessary. The antistatic agent used in the present invention has very good dispersibility in polyester, and does not roughen the film surface or roughens the film surface to a very small extent. Therefore, the polyester film of the present invention has excellent flatness and It has excellent antistatic properties and can be widely used in fields that require antistatic properties. [Example] The present invention will be described below with reference to Examples. Note that "parts" in the text represent parts by weight. In addition, various physical property values and characteristics in the examples were measured by the following methods. (1) Surface specific resistance Takeda Riken Co., Ltd. Vibratory capacitance type micropotential ammeter TR-
Measured with 84M model. (20℃, 65%RH) (2) Charge potential half-life time Shishido Shokai Static Honest Meter S-
Using Model 4104, apply a voltage of -5KV to the upper part of the sample.
This is the time (seconds) it takes for the potential generated on the sample to decay to 1/2 of its value when applied for 30 seconds from cm.
(20℃, 65%RH) (3) Film surface roughness CLA [Center Line Average]
According to JIS B 0601, using a stylus surface roughness meter (SURFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd., a chart was applied under the conditions of a needle radius of 2 μm and a load of 0.07 g to measure the film surface roughness. Cut out a part of measurement length L from the curve in the direction of its center line, set the center line of this cut out part as the X axis, and the direction of vertical magnification as the Y axis.
When the roughness curve is expressed as Y=f(x) as an axis, the value given by the following formula is expressed in μm. R _CLA = 1/L∫ ^L ₀ |f(x)|dx In this measurement, 8 measurements were taken with the reference length as 0.25 mm, and the average value of 5 measurements excluding 3 from the largest value is expressed. Examples 1 to 6 and Comparative Examples 1 to 5 Polyethylene terephthalate was polymerized according to a conventional method using manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, and trimethyl phosphate as a heat stabilizer. At this time, in the latter half of the polycondensation reaction, sulfonic acid metal salt derivatives and higher fatty acid metal salts (see Table 1 for types and amounts added)
was added. The resulting polyethylene terephthalate with an intrinsic viscosity of 0.650 was dried and put into the popper of an extruder, melted at 300°C for 5 minutes, extruded into a thin film through a die slit, and placed on a cooling roll whose surface temperature was kept at 40°C. It was cast to. The thickness of the unstretched film after cooling was 350μ. The unstretched film was stretched in the longitudinal direction (MD) at a magnification of 3.7 times using rolls heated to 75°C, and then
Width direction (TD) in a tenter heated to 110℃
The film was stretched at a magnification of 4.0 times and heat treated at 230°C for 5 seconds. The thickness of the biaxially oriented film thus obtained is
It was 25μ. Table 1 shows the physical properties of these films.
Shown below.

[Table] From the above table, it is recognized that by using a sulfonic acid metal salt derivative and a higher fatty acid metal salt in combination, the film can be made antistatic without roughening the film surface. On the other hand, the film of Comparative Example 5 has surface properties,
Although the antistatic property is good, the physical properties of the film are significantly deteriorated and it is not practical.

Claims (1)

[Scope of Claims] 1. (a) 0.1 to 10 parts by weight of a sulfonic acid metal salt derivative and (b) a higher fatty acid metal salt based on 100 parts by weight of a polyester whose main repeating unit is an ethylene terephthalate unit. An antistatic polyester film that is blended in a weight of 0.1 to 2 times the weight of a salt derivative, biaxially oriented, and heat-set.