JP2719952B2 - Polyester film with antistatic effect - Google Patents

Description

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

[Problems to be Solved by the Prior Art and the Invention] A biaxially stretched polyester film containing polyethylene terephthalate as a main component has mechanical properties, chemical resistance,
Because of its excellent properties such as gas barrier properties, transparency and safety, it has been applied to many uses such as magnetic recording media, plate making / photosensitive etching, electrical and packaging.

However, since the polyester film has a high friction coefficient and a high specific electric resistance, there is a problem that it is easily charged by static electricity. The electrostatic charge of the polyester film causes inconveniences such as wrapping around films and winding around rolls in the film formation process and slitting process, and furthermore, this charge also causes safety discharge such as discharge spark to equipment and workers. Not preferred. Also,
Since the charged polyester adheres to dust, dust adheres to the film surface in the printing process and the coating process of the magnetic material, and the adhesion causes whiskers. It is also difficult to make a record.

Numerous technologies have been developed to attempt to prevent electrostatic charging of polyester films, such as a method of applying an antistatic material to the film surface and a method of simultaneously extruding a polyester resin and a resin having an antistatic effect. 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, a method of modifying a polyester resin itself and imparting an antistatic ability has been proposed. This method includes a method of copolymerizing a linear aliphatic diol or a linear aliphatic dicarboxylic acid with a raw material for producing a polyester or a polyester. A method has been proposed in which a polyalkylene glycol and a metal salt of an organic sulfonic acid are added to the mixture. For example, Japanese Patent Publication No. 58-12910 discloses an invention relating to a composition in which a polyester is mixed with polyethylene glycol and a metal sulfonic acid derivative, and Japanese Patent Publication No. 63-3895 discloses an alkali metal of polyethylene glycol and alkylsulfonic acid. There is disclosed an invention relating to a polyester film formed from a composition in which particles insoluble in a salt and polyester are added and mixed. However, although these methods exhibit some antistatic effect, they are not sufficient compared to conventional methods, for example, coating. Furthermore, when actually forming a film using such a modified resin, the polyalkylene glycol in the drying / melting step of the core polyester resin undergoes oxidative decomposition or thermal decomposition, and the resulting polyester film is mechanically processed. However, there are disadvantages such as deterioration of the mechanical strength, coloring, etc., bleed out of the antistatic agent on the polyester film surface, deterioration of the haze of the polyester film, and impairment of the excellent properties peculiar to the polyester film. Was. Further, the polyester to which the polyalkylene glycol is added frequently breaks the film in the film forming process, and it is considered that this is due to the thermal decomposition of the polyalkylene glycol in the polyester composition.

[Means for Solving the Problems] In view of this situation, the present inventors have conducted intensive studies and as a result, by using a polyester resin composition having a specific composition, without impairing the excellent properties unique to a polyester film. The present inventors have found that a film having an extremely good antistatic effect can be industrially produced stably, and the present invention has been completed.

That is, the present invention is based on 100 parts by weight of polyester having ethylene terephthalate as a main repeating unit,
Weight part of polyethylene glycol having a weight average molecular weight of 4,000 to 50,000 a part by weight, alkali metal salt of alkyl sulfonic acid b
Parts by weight and c by weight of an alkali metal salt of alkylbenzenesulfonic acid so that a, b and c satisfy the relations of the formulas (1) to (3). It is a polyester film having.

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 comprises terephthalic acid or a derivative thereof and ethylene glycol. Is a polymer obtained by subjecting an esterification reaction or a transesterification reaction to a polycondensation reaction of an intermediate product thereof, but a conventionally known carboxylic acid component and a glycol component within a range not impairing the effects of the present invention. Copolymerizable, specifically, for example, phthalic acid, isophthalic acid, apicic acid, sebacic acid, naphthalene-1,4- or -2,6-dicarboxylic acid,
Carboxylic acid components such as diphenyl ether-4,4'-dicarboxylic acid; glycol components such as propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, and 2,2-bis (4-hydroxyphenyl) propane; p-oxybenzoic Acids, p-methoxybenzoic acid, oxyacids of p-hydroxyethoxybenzoic acid and the like can be mentioned.

The weight average molecular weight of the polyethylene glycol used in the present invention is preferably in the range of 4000 to 50000, more preferably 1
A range from 0000 to 30000 is preferred. Weight average molecular weight is 4
From the polyester composition to which less than 000 was added, a film in which the effect of improving the antistatic property was not obtained,
Further, it is difficult to obtain a polyester film having good mechanical properties and haze from a polyester composition to which a polyester having a weight average molecular weight exceeding 50,000 is added, and the film is frequently broken during the film forming process. The amount of the polyethylene glycol is preferably 0.1 to 3 parts by weight, more preferably 0.5 to 2.5 parts by weight, based on 100 parts by weight of the polyester. A film having a sufficient antistatic effect cannot be obtained from a polyester composition in which the amount of polyethylene glycol added is less than 0.1 part by weight, and a polyester film made from a polyester composition in excess of 3 parts by weight has a haze. In addition to the deterioration of the mechanical properties, the film becomes colored and odorous, and the film is frequently broken during the film forming process.

The alkali metal salt of an alkyl sulfonic acid and the alkali metal salt of an alkyl benzene sulfonic acid used in the present invention include: an alkali metal salt of an alkyl sulfonic acid: R-SO ₃ M an alkali metal salt of an alkyl benzene sulfonic acid: (R and R 'are alkyl groups having 10 to 16 carbon atoms, M
And M 'are represented by Li, Na, K). Polyester films obtained by synthesizing these metal salts with polyethylene glycol exhibit an excellent antistatic effect.

Although the alkali metal salt of alkyl sulfonic acid has an excellent antistatic effect, it has a low compatibility with polyethylene terephthalate. The salt bleeds out onto the film surface and the haze of the film is extremely reduced.

On the other hand, the alkali metal salt of alkyl benzene sulfonic acid has a lower antistatic effect than the alkali metal salt of alkyl sulfonic acid, but has excellent compatibility with polyethylene terephthalate.

The polyester film of the present invention is made from a polyester composition in which both the above-mentioned alkali metal salt of alkylsulfonic acid and alkali metal salt of alkylbenzenesulfonic acid are blended in a specific amount of polyester.

The compounding amount of the alkali metal salt of alkyl sulfonic acid is preferably 0.01 part by weight or more and less than 0.1 part by weight based on 100 parts by weight of the polyester. The film made from the polyester composition having a compounding amount of less than 0.01 does not have sufficient antistatic effect, and the compounding amount of the metal salt is 0.1% by weight or more. Bleed-out and haze of the film are deteriorated.

The compounding amount of the alkali metal salt of alkylbenzenesulfonic acid is preferably in the range of 0.05 to 1.0 part by weight based on 100 parts by weight of the polyester. Films made from the polyester composition having a compounding amount of less than 0.05 do not have sufficient antistatic effect, and films made from the polyester composition having the compounding amount of the metal salt of 1.0 part by weight or more have a bleed of the metal salt. Out and the haze of the film are deteriorated.

In practicing the present invention, it is preferable to add an antioxidant in order to prevent thermal decomposition of polyethylene glycol added to the polyester. As antioxidants, butylated hydroxytoluene, n-octadecyl-β- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate, triethylene glycol bis-3- (3-t
-Butyl-4-hydroxy-5-methylphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzyl,
Tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 1,3,5-tris (3,5-di-t-butyl-4-hydroxy (Benzyl) -s-triazine-2,4,6 (1H, 3H, 5H)
A so-called hindered phenolic compound such as trione, or dilauryl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, tetrakis [methylene-3- (dodecylthio) propionate] methane, etc. Sulfur compound, distearyl pentaerythritol diphosphite or cyclic neopentane terayl bis (octadecyl phosphite), 1,1,3-tris (2-methyl-4-di-tridecyl phosphite-5-t-) And phosphorus compounds such as a mixture of (butylphenyl) butane and phenylphosphite. The compounding amount is preferably in the range of 0.05 to 1.0 part by weight based on 100 parts by weight of the polyester resin, and is preferably 5% by weight or more based on the compounding amount of polyethylene glycol. If the amount of these antioxidants is less than 0.05 part by weight based on 100 parts by weight of the polyester resin, it is difficult to prevent the thermal decomposition of polyethylene glycol, and 1.
A film obtained from a polyester composition exceeding 0 parts by weight is liable to cause coloring, increase in haze, bleed out of a stabilizer, and the like.

The antioxidant used in the present invention can be arbitrarily selected in consideration of other properties, but at least one selected from the above hindered phenol compounds and at least one selected from a sulfur compound or a phosphorus compound are used in combination. Then, an extremely high antioxidant effect is exhibited by synergism, which is preferable.

Further, a conventionally known additive may be added to the polyester composition to the extent that the characteristics of the present invention are not impaired. Examples of the 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, ultraviolet absorbers, release agents, flame retardants and the like. .

The polyester film of the present invention can be easily produced by a conventionally known method. Therefore, polyethylene glycol, an alkali metal salt of an alkyl sulfonic acid, an alkali metal salt of an alkyl benzene sulfonic acid, and an antioxidant can be added to the polyester at any stage, that is, before the start of the esterification or transesterification of the polyester raw material. , During, after, or before or during the start of the polycondensation reaction. Alternatively, an ordinary polyester resin may be manufactured, and the pellets and the additives used in the present invention may be mixed by 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 time point closest to the end time when the raw material polyester resin is produced. This method is most effective in exhibiting an antistatic effect when the additive is dispersed in the resin, and the decomposition of polyethylene glycol is the least, which is advantageous for obtaining the desired film performance.

As the film forming method, any conventionally known method can be selected. That is, a method in which a polyester resin is melted by an extruder, extruded from a die having an appropriate slit, and then stretched uniaxially or biaxially, and then wound into a film product. Further, heat setting or corona treatment can be performed as necessary.

For the stretching method, uniaxial and biaxial directions can be arbitrarily selected, and in the case of biaxial stretching, the order of stretching can be arbitrarily set. Although the stretching ratio and the stretching speed can be appropriately selected, they may be in accordance with ordinary polyester films.

Polyester film of the present invention, excellent mechanical properties of polyethylene terephthalate film that has been conventionally developed, without impairing transparency, heat resistance, etc.,
It exhibits excellent antistatic properties. The polyester film of the present invention can be subjected to conventionally known processing in order to further impart specific performance. Examples of processing include UV,
Irradiation with α-rays, γ-rays or electron beams, surface treatments such as corona treatment, flame treatment and plasma treatment, application of resins such as vinylidene chloride, polyvinyl alcohol, polyamide, and polyolefin, lamination, and metal deposition, etc. .

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples. In addition,
Each physical property value in the examples is measured by the following method.

(1) Haze Measured according to JIS K6714.

[Judgment] ：: Haze hardly increases compared to polyethylene terephthalate film △: Less than 50% increase observed ×: 50% or more increase observed (2) Mechanical strength Based on JIS C-2318 Using Tensilon manufactured by Orientec Co., Ltd., a tensile test was performed on a film having a width of 1 cm and a length of 10 cm (the machine axis direction was defined as the longitudinal direction). At this time, the mechanical strength was measured based on the breaking strength and elongation and Young's modulus.

[Judgment｝]: Neither the breaking elongation nor the Young's modulus is reduced substantially as compared with the polyethylene terephthalate film.

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

X: A significant decrease is observed in both the breaking elongation at break and the Young's modulus.

(3) Antistatic property Surface resistance value Measured by Toa Denpa Kogyo's Extreme Insulation Meter SM-10E.

Half-life of charged voltage was measured using a static honestometer S-5109 manufactured by Shishido Shokai. The voltage was applied at 12 KV from a position 2 mm above the sample.

All of these measurements were performed in an atmosphere at 25 ° C. and 65% RH.

(4) Bleed-out The infrared absorption spectra of the sample film and the film immersed in acetone at room temperature for 30 seconds and dried by ATR were compared, and bleed-out was determined from the difference spectrum between them.

[Judgment] A: Bleed-out hardly exists.

Δ: Bleed-out is slightly present.

X: Bleed-out is remarkably present.

Examples 1 to 7 Terephthalic acid was used as the dicarboxylic acid component, and ethylene glycol was used as the diol component. These were charged into a reaction vessel, and the esterification reaction was allowed to proceed at 240 ° C. under pressure.
The point at which almost no water distilling was observed was regarded as the substantial end point of the esterification reaction.

Then, 500 ppm of antimony trioxide (II) was added to terephthalic acid as a polycondensation catalyst, and the particle size was further reduced to 1.5 μm.
Was added as a lubricant to 500 ppm of terephthalic acid.

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

At 60 minutes after the polycondensation reaction substantially started, polyethylene glycol, sodium alkyl sulfonate (average carbon number of alkyl 13), dodecylbenzenesulfonic acid were added to 100 parts by weight of polyethylene terephthalate in the kettle. Sodium and antioxidants 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 (dissolved in a mixed solution of an equal weight of phenol and tetrachloroethane and measured at 25 ° C.) reached 0.80, it was taken out of the kettle.

A biaxially stretched film was produced using the polyester resin produced by the above method as a raw material and evaluated. The production of the biaxially stretched film was performed by the following sequential biaxial stretching method. That is, the polyester resin was heated at a T
After being melt-extruded at 5 ° C and forming an unstretched film having a thickness of about 130μ at a casting roller temperature of 40 ° C, the longitudinal stretching temperature is 90 to 100 ° C in the longitudinal stretching section composed of a low drive roll and a high drive roll. The film was longitudinally stretched so as to have a longitudinal stretching ratio of 2.8 in the range described above, and then transversely stretched by a tenter so as to have a transverse stretching temperature (tenter oven temperature) of 85 to 95 ° C. and a transverse stretching ratio of 3.8. Then heat set at 210 ° C,
A biaxially stretched film having a thickness of 12 μ was obtained. Table 1 shows the results of evaluation of this film by the above method.

Comparative Examples 1 to 10 Except that the composition of the polyester resin was out of the range of the present invention shown in Table 2, films were produced in exactly the same manner as in Examples 1 to 7, and the obtained films were evaluated. The results are shown in Table 2.

Comparative Example 11 A film was produced in the same manner as in Example 3 except that sodium alkylsulfonate was not added, and the obtained film was evaluated.

The results were haze ○, mechanical properties 、, bleed-out 、, and charged voltage half-life 13.1 seconds.

In Examples 1 to 7 of the present invention, it can be seen that each of the films exhibits a high antistatic effect without impairing the excellent characteristics (Comparative Example 1) inherent to the polyethylene terephthalate film.

On the other hand, in Comparative Examples 2 to 6 in which the amount of sodium alkylsulfonate or sodium alkylbenzenesulfonate was out of the range of the present invention, the antistatic properties were not sufficiently exhibited, or the haze, mechanical properties, and bleed-out were not observed. And other drawbacks. Similar problems also occur in Comparative Examples 7, 8, 9, and 10 in which the amount of added polyethylene glycol or the weight average molecular weight is out of the range of the present invention.

[Effects of the Invention] The polyester film obtained by the present invention has excellent antistatic properties without impairing its original excellent properties, that is, mechanical properties, heat resistance, gas barrier properties, chemical resistance, transparency and the like. This is one in which adhesiveness is developed. Therefore, despite having the same performance as a conventional coated product, it is advantageous in terms of price and can be used in fields that could not be applied until now, so that the industrial contribution is high.

Claims (1)

(57) [Claims] 1. A 100 parts by weight of polyester containing ethylene terephthalate as a main repeating unit, a part by weight of polyethylene glycol having a weight average molecular weight of 4000 to 50,000, b parts by weight of an alkali metal salt of alkyl sulfonic acid, and alkali of alkyl benzene sulfonic acid. A polyester film having an antistatic effect obtained by forming a polyester composition formed by mixing c parts by weight of a metal salt such that a, b and c satisfy the relations of the formulas (1) to (3). 0.1 ≦ a ≦ 3 (1) 0.01 ≦ b <0.1 (2) 0.05 ≦ c ≦ 1.0 (3)