JPH02232257A - Polyester film having anti-static effect - Google Patents

Abstract

PURPOSE:To obtain the title film with improved antistatic characteristics and excellent mechanical characteristics, heat resistance, transparency, etc., by making a film from a compsn. prepd. by compounding a specified polyester, a polyethylene glycol and two kinds of alkali metal salt so as to satisfy specified relations. CONSTITUTION:The title film is obtd. from a polyester compsn. prepd by compounding 100 pts.wt. (hereinbelow described as pts.) polyester wherein ethylene terephthalate is a main repeating unit, (a) pts. polyethylene glycol with a wt. average MW of 4,000-50,000, (b) pts. alkali metal salt of an alkyl-sulfonic acid and (c) pts. alkali metal salt of alkylbenzene-sulfonic acid so as to satisfy reactions of formula I-III between a, b and c. This film not only has original mechanical characteristics, heat resistance, chem. resistance, transparency, gas barrier characteristics, etc., but exhibits excellent anti-static properties and adhesiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention has particularly improved antistatic properties,
and mechanical properties, heat resistance, slipperiness, transparency, surface gloss,
This invention relates to a polyester film with excellent chemical resistance and gas barrier properties.

[Prior art and problems to be solved by the invention] A biaxially oriented polyester film containing polyethylene terephthalate as its main component has excellent properties such as mechanical properties, chemical resistance, gas barrier properties, transparency, and safety. Because of this, it is used in a wide variety of applications, including magnetic recording media, plate making/photosensitive etching, electrical applications, and packaging.

However, since polyester films have a high coefficient of friction and high specific electrical resistance, they have the problem of being easily charged by static electricity. Static electricity on polyester film can cause inconveniences during the film forming and slitting processes, such as the films clinging to each other and wrapping around the roll.Furthermore, the static electricity on the film can cause sparks to the equipment and workers, which is a safety issue. Not desirable. In addition, since dust adheres to charged polyester, dust adheres to the film surface during the printing process and the magnetic material coating process, and this adhesion causes the formation of whiskers, which can affect the aesthetic quality of printed materials and recording characteristics. Another reason is that it is difficult to make good recording media.

A number of techniques have been developed to try to prevent static electricity from forming on polyester films, such as applying an antistatic agent to the surface of the film and extruding polyester resin and a resin that has an antistatic effect at the same time. A polyester film having a somewhat satisfactory antistatic effect can be obtained. However, these methods have low film production efficiency and cannot avoid an increase in cost, and cannot be said to be industrially and economically effective methods. On the other hand, by modifying the polyester resin itself,
Methods of imparting antistatic properties have been proposed, including methods of copolymerizing linear aliphatic diols or linear aliphatic dicarboxylic acids with raw materials for polyester production, and methods of copolymerizing polyester with polyalkylene glycol and organic sulfonic acid metal salts. Methods have been proposed that include the addition of For example,
Japanese Patent Publication No. 8-12910 discloses an invention relating to a composition in which polyester is mixed with polyethylene glycol and a sulfonic acid metal salt derivative, and Japanese Patent Publication No. 1983-3895 discloses an invention in which polyethylene glycol, an alkali metal salt of an alkyl sulfonic acid, and polyester are mixed. An invention related to a polyester film formed from a composition in which insoluble particles are added and mixed is disclosed. However, although these methods achieve some degree of antistatic effect, they are not as sufficient as conventional methods, such as coating. Furthermore, when actually forming a film using such a modified resin, the polyalkylene glycol during the drying and melting process of the polyester resin may undergo oxidative decomposition or thermal decomposition.
The mechanical strength of the resulting polyester film may decrease, discoloration may occur, the antistatic agent may bleed out onto the surface of the polyester film, the haze of the polyester film may worsen, and the excellent properties unique to polyester film may There was a drawback that it was damaged. In addition, polyesters to which polyalkylene glycol has been added frequently break the film during the film forming process, and this is thought to be caused by thermal decomposition of the polyalkylene glycol in the polyester composition.

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive research and found that by using a polyester resin composition with a specific composition, the excellent properties unique to polyester films are not impaired. They discovered that it is possible to industrially and stably produce a film that has an antistatic effect comparable to that of the very good antistatic effect, and completed the present invention.

That is, the present invention uses 100 parts by weight of polyester containing ethylene terephthalate as a main repeating unit.
Parts by weight of polyethylene glycol a having a weight average molecular weight of 4,000 to 50,000, parts by weight of an alkali metal salt of an alkylsulfonic acid B, and parts by weight of an alkali metal salt of an alkylbenzenesulfonic acid, where a, b and C are represented by formulas (1) to (3).
This is a polyester film having an antistatic effect formed from a polyester composition blended so as to satisfy the following relationship.

0.1≦a≦3 (1) 0.01≦b
<0.1 (2) 0.05≦c≦1.0
(3) The polyester having ethylene terephthalate as a main repeating unit used in the present invention can be obtained by subjecting terephthalic acid or a derivative thereof to an esterification reaction or transesterification reaction with ethylene glycol, and then subjecting the intermediate product to a polycondensation reaction. However, conventionally known carboxylic acid components and glycol components can be copolymerized within a range that does not impair the effects of the present invention. Specifically, for example, phthalic acid, isophthalic acid, adivic acid, Sebacic acid, naphthalene-1.4-moshi《ha-2.6
-Carboxylic acid components such as dicarboxylic acid, diphenyl ether-4.4°-dicarboxylic acid: brobylene glycol,
Glycol components such as butylene glycol, neopentyl glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)brobanane; oxyacids such as p-oxybenzoic acid, p-methoxybenzoic acid, and p-hydroxyethoxybenzoic acid etc.

The weight average molecular weight of the polyethylene glycol used in the present invention is preferably in the range of 4000 to 50000,
A range of 10,000 to 30,000 is more preferable.

Polyester compositions containing polyesters with a weight average molecular weight of less than 4,000 cannot produce films that exhibit an antistatic property improvement effect, while polyester compositions containing polyesters with a weight average molecular weight of more than 50,000 cannot be obtained. It is difficult to make a polyester film with good mechanical properties and haze, and the film often breaks during the film forming process. The amount of polyethylene glycol to be blended is preferably 0.1 to 3 parts by weight, more preferably 0.5 to 2.5 parts by weight, per 100 parts by weight of polyester. Polyester compositions containing less than 0.1 parts by weight of polyethylene glycol cannot produce films with sufficient antistatic effect, and polyester films made from polyester compositions containing more than 3 parts by weight cannot be obtained. In addition to causing deterioration of haze and mechanical properties, the film becomes colored and has an odor, and the film frequently breaks during the film forming process.

The alkali metal salt of alkylsulfonic acid and the alkali metal salt of alkylbenzenesulfonic acid used in the present invention are as follows: Alkali metal salt of alkylsulfonic acid: R-So. M is represented by alkylbenzenesulfonic acid (R and R' are alkyl groups having 10 to 16 carbon atoms, M and M' are Li s Na % K ). These metal salts have a synergistic effect with polyethylene glycol, and the resulting polyester film exhibits an excellent antistatic effect.

Although alkali metal salts of alkyl sulfonic acids have excellent antistatic effects, they have low compatibility with polyethylene terephthalate. As the salt bleeds out onto the film surface, the haze of the film is extremely reduced.

On the other hand, although alkali metal salts of alkylbenzenesulfonic acids have inferior antistatic effects to alkali metal salts of alkylsulfonic acids, they have excellent compatibility with polyethylene terephthalate.

The polyester film of the present invention is made from a polyester composition in which specific amounts of both the alkali metal salt of alkyl sulfonic acid and the alkali metal salt of alkylbenzene sulfonic acid as described above are blended into polyester.

The amount of alkali metal salt of alkyl sulfonic acid blended is 0 with respect to 100 parts by weight of polyester.

The amount is preferably 0.01 part by weight or more and less than 0.1 part by weight. A film made from a polyester composition containing less than 0.01 part of the metal salt will not have sufficient antistatic effect, and a film made from a polyester composition containing 0.1 part by weight or more of the metal salt will not have sufficient antistatic effect. Metal salt bleed-out and film haze become worse.

The amount of the alkali metal salt of alkylbenzenesulfonic acid is 0.05 to 1.0 parts by weight per 100 parts by weight of polyester.
A range of 0 parts by weight is preferred. A film made from a polyester composition containing less than 0.05 parts by weight of the metal salt does not have sufficient antistatic effect, and a film made from a polyester composition containing 1.0 parts by weight or more of the metal salt does not have sufficient antistatic effect. Metal salt bleed-out and film haze become worse.

In carrying out the present invention, it is preferable to add an antioxidant to the polyester in order to prevent thermal decomposition of the polyethylene glycol added to the polyester. Antioxidants include butylated hydroxytoluene, n-octadecyl-β-(4゜-hydroxy-3゜5゛-di-t-butylphenyl)probionate, triethylene glycol bis-3- (3-t
-butyl-4-hydroxy-5-methylphenyl)probionate, 1,3.5-1-limethyl-2.4.6-
tris(3,5-di-t-butyl-4-hydroxybenzyl)benzyl, tetrakis[methylene-3- (3'
．． 5'-di-t-butyl-4'-hydroxyphenyl)probionate]methane, 1,3.5-tris(3.
So-called hindered phenolic compounds such as 5-di-t-butyl-4-hydroxybenzyl)-s-triazine-2.4.6 (LH,3H,5H)-1 ion, or dilauryl 3,3'-thiodibrobionic acid. ,3
, 3-thiodibrobionic acid distearyl, sulfur-based compounds such as tetrakis[methylene-3-(dodecylthio)probionate]methane, or distearylpentaerythritol diphosphite or cyclic neopentanteryl bis(octadecylphosphite), 1 , 1.3-1 phosphorus compounds such as a mixture of lis(2-methyl-4-ditridecylphosphite-5-t-butylphenyl)butane and phenylphosphite. Further, the blending amount thereof is in the range of 0.05 to 1.0 parts by weight based on 100 parts by weight of the polyester resin, and is preferably 5% by weight or more relative to the blending amount of polyethylene glycol. If the amount of these antioxidants is less than 0.05 parts by weight based on 100 parts by weight of the polyester resin, it will be difficult to prevent thermal decomposition of polyethylene glycol, and if the amount of these antioxidants is more than 1.0 parts by weight, Films that have been used for this purpose are susceptible to discoloration, increased haze, and stabilizer bleed-out.

The antioxidant used in the present invention can be arbitrarily selected while taking other performance into consideration, but at least one selected from the aforementioned hindered phenol compounds and at least one selected from sulfur-based compounds or phosphorus-based compounds are used in combination. This is preferable because an extremely high antioxidant effect is exhibited due to synergistic action.

Moreover, conventionally known additives may be added to the polyester composition to the extent that the features of the present invention are not impaired.

Examples of additives include resins such as polyamide and polyolefin, inorganic particles such as silica, talc, kaolin, and calcium carbonate, pigments such as titanium oxide and carbon black,
Examples include ultraviolet absorbers, mold release agents, and flame retardants.

The polyester film of the present invention can be easily produced by conventionally known methods. Therefore, polyethylene glycol, alkali metal salts of alkylsulfonic acids, alkali metal salts of alkylbenzenesulfonic acids, and antioxidants can be added to polyester at any stage, i.e., before the start of the esterification reaction or transesterification reaction of the polyester raw materials. , during, after the completion of the polycondensation reaction, or before or during the start of the polycondensation reaction. Alternatively, an ordinary polyester resin may be produced in advance, and the pellets and the additive used in the present invention may be mixed in an extruder. Among these, the most preferable addition method is a method in which all additives are simultaneously added to the reaction vessel during the polycondensation reaction and at the point closest to the end of the polycondensation reaction when producing the raw material polyester resin. This method is advantageous in obtaining the desired film performance because the additive is best dispersed in the resin and the polyethylene glycol is least degraded.

Regarding the film forming method, any conventionally known method can be selected. That is, polyester resin is melted in an extruder and extruded through a die with appropriate slits.
Immediately after that, the film is uniaxially or biaxially stretched, heat-set and corona treated, and then wound to form a film product.

As for the stretching method, uniaxial or biaxial stretching can be arbitrarily selected, and in the case of biaxial stretching, the stretching order can be arbitrarily set. The stretching ratio and stretching speed can be selected as appropriate, but may be the same as those for ordinary polyester films.

The polyester film of the present invention exhibits excellent antistatic properties without impairing the excellent mechanical properties, transparency, heat resistance, etc. of conventionally developed films made of polyethylene terephthalate. The polyester film of the present invention can be further subjected to conventionally known processing in order to impart specific properties. Examples of processing include ultraviolet rays, α
Irradiation with rays, gamma rays or electron beams, vinylidene chloride,
Examples include coating of resin such as polyvinyl alcohol, polyamide, polyolefin, etc., lamination, or vapor deposition of metal.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, each physical property value in an Example was measured by the following method.

(1) Hayes Measured in accordance with JIS K6714.

[Judgment] ○: There is almost no increase in haze compared to polyethylene terephthalate film △: An increase of less than 50% is observed. A tensile test was conducted on a film with a width of 1 cm and a length of 10 cm (with the machine axis direction as the longitudinal direction) using Tensilon manufactured by Orientech Co., Ltd. Mechanical strength was measured by breaking strength and elongation and Young's modulus at this time.

[Judgment] O: Both breaking strength and elongation and Young's modulus are hardly reduced compared to polyethylene terephthalate film.

Δ: A significant decrease is observed in either the breaking strength and elongation or Young's modulus.

×: Significant decrease in both breaking strength and elongation or Young's modulus is observed.

(3) Antistatic property ■Surface resistance value Measured using an ultimate insulation meter SM-1 0E manufactured by Toa Denpa Kogyo.

■ Half-life of frictional charging voltage Measured using a static honest meter model S-5109 manufactured by Shishido Shokai. Voltage application is 12KV above the sample.
The measurement was performed from the mm position.

Note that all these measurements were performed in an atmosphere of 25° C. and 65% RH.

(4) The infrared absorption spectra of the surface of the bleed-out sample film and the film immersed in acetone at room temperature for 30 seconds were compared using the ATR method, and bleed-out was determined from the difference spectra.

[judgement] O: Almost no bleed-out.

△: Slight bleed-out is present.

×: Significant bleed-out exists.

Examples 1 to 7 As a dicarboxylic acid component. Using terephthalic acid and ethylene glycol as the diol component, these were charged into a reaction vessel, and the esterification reaction was allowed to proceed under pressure at 260°C. The point at which almost no water was distilled out was considered to be a substantial esterification reaction. It was set as the end point. Next, 500 ppm of antimony trioxide (II) was added to terephthalic acid as a polycondensation catalyst, and the particle size was
, 5μm silica as a lubricant against terephthalic acid.
00 ppm was added.

Thereafter, the pressure inside the pot was reduced, and the polycondensation reaction was allowed to proceed under a vacuum of 0.5 torr.

After 60 minutes have passed after the polycondensation reaction has substantially started, polyethylene glycol, sodium alkyl sulfonate (average carbon number of alkyl is 13), and dodecylbenzenesulfone are added to 100 parts by weight of polyethylene terephthalate in the pot. Sodium acid and antioxidant were added in the proportions shown in Table 1. After the addition was completed, the polycondensation reaction was allowed to proceed again, and when the intrinsic viscosity (measured at 25° C. after being dissolved in an equal weight mixed solution of phenol and tetrachloroethane) reached 0.80, the solution was taken out of the pot.

A biaxially stretched film was produced using the polyester resin produced by the above method as a raw material, and evaluated. The biaxially stretched film was produced by the following sequential biaxial stretching method. That is, the polyester resin is heated to a T-die temperature of 28
Melt extrusion at 5℃ and cast roller temperature 40℃
After forming an unstretched film with a thickness of about 130μ under
The film was then longitudinally stretched using a tenter at a transverse stretching temperature (tenter oven temperature) of 85 to 95°C and a transverse stretching ratio of 3.8. Thereafter, it was heat set at 210° C. to obtain a biaxially stretched film with a thickness of 12 μm. Table 1 shows the results of evaluating this film using the method described above.

Comparative Examples 1 to 10 Films were produced in exactly the same manner as Examples 1 to 7, except that the composition of the polyester resin was outside the scope of the present invention shown in Table 2. It is shown in Table 2.

It can be seen that in Examples 1 to 7 of the present invention, all the films exhibited high antistatic effects without impairing the excellent properties inherent to polyethylene terephthalate films (Comparative Example 1).

On the other hand, in Comparative Examples 2 to 6, in which the amount of sodium alkylsulfone or sodium alkylbenzene sulfonate added was outside the range of the present invention, antistatic properties were not sufficiently expressed, haze, mechanical properties, and bleed-out. There are also some drawbacks. Similar problems also occur in Comparative Examples 7, 8, 9, and 10 in which the amount of polyethylene glycol added or the weight average molecular weight is outside the range of the present invention.

[Effects of the Invention] The polyester film obtained by the present invention has excellent antistatic properties and adhesion without impairing its original excellent properties, such as mechanical properties, heat resistance, gas barrier properties, chemical resistance, and transparency. It is a manifestation of sexuality. Therefore, although it has the same performance as conventional coated products, it is advantageous in price and can be used in fields that have not been applicable up to now, making it a high contribution to industry.

Claims (1)

[Claims] Based on 100 parts by weight of polyester whose main repeating unit is ethylene terephthalate, the weight average molecular weight is 40.
00 to 50,000 parts by weight of polyethylene glycol a, parts by weight of alkali metal salt of alkyl sulfonic acid b, and parts by weight of alkali metal salt of alkylbenzenesulfonic acid, where a, b and c satisfy the relationships of formulas (1) to (3). A polyester film having an antistatic effect made of a polyester composition blended so as to. 0.1≦a≦3 (1) 0.01≦b<0.1 (2) 0.05≦c≦1.0 (3)