JPH06172563A - Antistatic polyester film - Google Patents

Abstract

PURPOSE:To obtain a polyester film excellent in antistatic properties at low humidity, water resistance, and oil resistance by forming a coating film contg. a specific ion-conductive resin on at least one side of a melt-extruded polyester film and then stretching the polyester film. CONSTITUTION:A coating compsn. comprising a water-sol. ion-conductive resin and a thermally crosslinking monomer is applied to at least one side of a melt- extruded nonstretched or monoaxially stretched polyester film, which is then mono- or biaxially stretched. The water-sol. ion-conductive resin is obtd. by copolymerizing a monomer having a cationic quaternary ammonium group in the side chain and a polylmerizable double bond at the molecular end, a hydroxylated difunctional vinyl monomer, and another copolymerizable vinyl monomer. An example of the thermally crosslinking monomer is an epoxy compd. having 2-4 glycidyl groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic polyester film which is transparent and has excellent antistatic properties at low humidity, water resistance and solvent resistance.

[0002]

2. Description of the Related Art Polyester film has a high degree of crystallinity,
It is used in a wide range of applications due to its excellent transparent gloss, mechanical properties, chemical resistance, and heat resistance. But,
Since a general polyester film has a high degree of electrical insulation, it has a drawback that static electricity is likely to be generated and accumulated and various troubles due to electrostatic damage are caused. Such electrostatic damage is a decrease in work efficiency such as winding around a roll, electric shock to a human body, or difficulty in handling in a film forming process, printing, adhesion, bag making, packaging, and other secondary processing processes. Also, it may cause print beards and stains on the film surface, resulting in reduced product value. As a method of preventing such electrostatic damage, there are generally a method of kneading an antistatic agent into a resin to form a film, and a method of applying an antistatic agent to the film surface. When this so-called kneading type antistatic treatment method is applied to a polyester film, the antistatic effect is exerted by the antistatic agent oozing from the inside of the film to the surface. For this reason, after film formation, the antistatic agent does not exude to the film surface at temperatures near room temperature.On the other hand, due to the high film formation temperature conditions and the high reactivity of the polar groups of polyester itself, charging The compounding of the inhibitor causes problems such as deterioration of the polymer at the time of film formation, coloration and deterioration of physical properties. In particular, in the case of a biaxially stretched polyester film, the antistatic agent on the surface of the film often escapes and disappears in the stretching step, and thus often has no antistatic effect. However, it is difficult to put the film into practical use because it significantly reduces the transparency of the film.

For these reasons, a method of applying an anionic compound or a cationic compound as an antistatic agent is widely used as an antistatic method for a biaxially stretched polyester film. As a method for producing a biaxially stretched Porie ester film having a coating layer, there is one called a coating stretching method (in-line coating method) in which a coating solution of an antistatic agent is coated and then the film is stretched and heat-treated. Compared with the method of forming a coating layer by coating the coating liquid of antistatic agent on the polyester film after biaxial stretching, this method performs film formation and coating of the film at the same time. It is a useful method because it is obtained at a relatively low cost, and the adhesiveness between the coating layer and the polyester film of the substrate is good. However, when producing an antistatic polyester film by the in-line coating method, the antistatic agent is generally thermally unstable, so volatilization or thermal decomposition occurs in the stretching and heat treatment steps, and the expected antistatic effect is exhibited. It is often not done.

Therefore, conventionally, a method has been adopted in which an anionic or nonionic compound having good thermal stability is mixed with a binder resin and applied. However, although anionic and nonionic antistatic agents exhibit a practical antistatic property under high humidity, the effect of environmental humidity on the antistatic property is large and the antistatic property under low humidity decreases. There was a problem. Further, the polyester film is extremely rarely used alone and is often used in the form of being laminated with another film or a functional compound. Therefore, the antistatic agent coating layer is required to have properties such as water resistance and solvent resistance in addition to antistatic properties.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a polyester having excellent antistatic property at low humidity, and excellent water resistance and solvent resistance. To provide a film.

[0006]

The polyester film of the present invention comprises a melt-extruded unstretched polyester film or a uniaxially stretched polyester film having at least one surface thereof a cationic type quaternary ammonium salt group as a side chain and a terminal. A monomer (X) having a polymerizable double bond,
Water-soluble ion conductive resin (A) obtained by copolymerizing a bifunctional vinyl monomer (Y) having a hydroxyl group and another polymerizable vinyl monomer (Z) copolymerizable with these monomers And an antistatic polyester film obtained by applying a coating film-forming composition comprising a heat-crosslinkable monomer (B) and then biaxially or uniaxially stretching the coated film. .

In the present invention, the polyester is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4)
-Cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalene dicarboxylate and the like. These copolymers or their blends with a small proportion of other resins are also included. The polyester may contain a small amount of inorganic or organic fine particles to improve slipperiness. Such particles include
Inorganic filler such as titanium oxide, calcium carbonate, barium sulfate, silicone, acrylic resin, benzoguanamine,
Organic fillers such as Teflon and epoxy resin can be used.

A polyester film is obtained by melt-extruding this polyester into a film by a conventional method, and further, oriented crystallization by biaxial stretching in the longitudinal and transverse directions and crystallization by heat treatment.

The monofunctional vinyl monomer (X) having a cationic type quaternary ammonium base in the side chain and a polymerizable double bond at the terminal in the ion conductive resin (A) in the present invention is For example, dimethylaminoethyl acrylate quaternary product, dimethylaminoethyl methacrylate 4
Graded product, diethylaminoethyl acrylate quaternized product,
Examples thereof include diethylaminoethyl methacrylate quaternized product, methylethylaminoethyl acrylate quaternized product, methylethylaminoethyl methacrylate quaternized product, dimethylaminostyrene quaternized product, methylethylaminostyrene quaternized product, and the like. Two or more can be used.

On the other hand, examples of the bifunctional vinyl monomer (Y) having a hydroxyl group include polyglycerol diacrylate, polyglycerol dimethacrylate, polyglyceride propylene glycol diacrylate and polyglyceride propylene glycol dimethacrylate.

Other polymerizable vinyl monomers (Z) copolymerizable with these monomers include methyl acrylate, alkyl acrylates such as ethyl acrylate, methyl methacrylate, ethyl methacrylate. Examples thereof include alkyl methacrylic acid esters such as styrene, vinyl monomers such as styrene, vinyltoluene, and vinyl acetate.

A monofunctional vinyl monomer (X) having a cation type quaternary ammonium base in a side chain and a polymerizable double bond at a terminal in the ion conductive resin (A) of the present invention.
And the ratio of the bifunctional vinyl monomer (Y) having a hydroxyl group and the other polymerizable vinyl monomer (Z) copolymerizable with these monomers is (Y + Z) / X The ratio is preferably in the range of 2/1 to 5/1, and the polymerization ratio is 5
If it exceeds / 1, the water solubility of the ion conductive resin (A) will be reduced, or a monofunctional vinyl monomer having a cationic quaternary ammonium base in the side chain and a polymerizable double bond at the end. As a result, the ratio of (X) decreases, so that a coating film having excellent antistatic properties cannot be obtained. On the other hand, when the polymerization ratio is less than 2/1, the water resistance of the coating film tends to decrease and the stickiness and blocking property of the obtained coating film increase.

The polymerization ratio of (X + Z) / Y is 30.
/ 1 to 100/1 is preferable, and the polymerization ratio is 1
If it exceeds 00/1, the amount of the bifunctional vinyl monomer (Y) having a hydroxyl group becomes small, and when the thermally crosslinkable monomer (B) is added, the crosslinkability becomes insufficient as a result. Property and solvent resistance are reduced, and the spreadability of the coating film is reduced, causing film breakage during in-line coating. on the other hand,
When the polymerization ratio is less than 30/1, the amount of the bifunctional vinyl monomer (Y) having a hydroxyl group increases, the partial crosslink density of the water-soluble conductive resin (A) increases, and the water solubility of the resin (A) increases. It becomes too low to obtain an aqueous solution.

The thermally crosslinkable monomer (B) in the present invention is
Specifically, it is an epoxy compound having 2 to 4 glycidyl groups, and examples of the epoxy compound include ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol. Examples thereof include diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, and the like.
One kind or two or more kinds can be used.

The mixing ratio of the ion conductive resin (A) and the heat-crosslinkable monomer (B) in the coating film forming composition of the present invention is (A) / (B) 70 by weight. /30-99.5/
A range of 0.5 is preferred. When the compounding ratio is less than 70/30, the heat-crosslinkable monomer (B) becomes excessive, so that the water resistance and solvent resistance of the resulting coating film are improved, but the antistatic property is deteriorated or the antistatic property is deteriorated. And the spreadability of the coating film are reduced. If the blending ratio exceeds 99.5 / 0.5, the amount of the heat-crosslinkable monomer (B) decreases and the crosslinking reactivity decreases, so that the water resistance and solvent resistance of the coating film deteriorate.

When a coating film is formed using the coating film forming composition of the present invention, in order to accelerate the crosslinking reaction of the epoxy compound constituting the thermally crosslinkable monomer (B), Or an inorganic alkaline compound, such as an amine,
It is desirable to use a small amount of a cross-linking curing agent composed of polyamine, amidoamine, polyamidoamine, imidazole, alkali metal carbonate, and derivatives thereof.

The coating film forming composition of the present invention is used in a liquid state, but since the ion conductive resin (A) is water-soluble, it is preferably used in an aqueous solution. In this case, an organic solvent such as alcohol may be used together for the purpose of improving the wettability with polyester. Further, other cross-linking agents, catalysts, wetting agents and the like can be added if necessary. Further, an ultraviolet absorber, a pigment, an organic filler, an inorganic filler, a lubricant, an antiblocking agent and the like may be used in combination unless the object of the present invention is impaired. Further, other binder resins may be used together to improve properties such as adhesiveness and blocking property.

The polyester film coated with the solution of the coating film forming composition thus obtained is preferably a melt-extruded unstretched film or a uniaxially stretched film. In particular, it is preferable to carry out the stretching treatment in a state in which the water content of the coating film after coating is 10% or more after the raw material for casting or uniaxial stretching. It is not preferable to apply it to the biaxial film because the film is wide and the traveling speed of the film is high, so that it is difficult to apply it uniformly. As a method for applying the coating layer on the polyester film, a known method can be applied. For example, a spray coating method, an air knife method, a reverse roll coating method, a kiss roll coating method, a gravure coating method, a Meyer bar method, a roll brushing method and the like can be applied.

The coating amount of the aqueous solution of the coating film forming composition applied to the polyester film is 0.01 to 5 g / m as solid content as the amount present on the film after biaxial stretching.
^{Is 2} . If the coating amount is less than 0.01 g / m ² , sufficient antistatic properties cannot be obtained. If 5 g / m ² or more is applied, blocking becomes a problem.

Before applying the solution of the composition for forming a coating film, for example, pretreatment such as corona discharge treatment may be applied to the polyester film to improve the coatability of the solution or to form the polyester film and the coating film. The adhesion between the can be improved. The wettability and adhesiveness of the film surface can be improved by subjecting the coating layer after in-line coating or after biaxial stretching to corona discharge treatment, corona discharge treatment in a nitrogen atmosphere, ultraviolet irradiation treatment and the like. The film coated with the coating film forming composition is further biaxially or uniaxially stretched by a conventional method.

The coated polyester film produced by the above method is particularly useful as a base material for magnetic recording media such as video tapes, audio tapes, computer tapes and floppy disks. Also, general industrial films, such as membranes, telephone cards, labels, microfilms, diazo films,
It is also useful as a base material for OHP films and the like.

[0022]

EXAMPLES Next, examples and comparative examples of the present invention will be shown. In addition, in these examples, evaluation of various properties was performed by the following methods. (1) Surface resistance Takeda Riken Co., Ltd. applied resistance measuring device 500V, 2
It was measured under the conditions of 3 ° C. and 40% RH. (2) Evaluation of water resistance and solvent resistance The film was immersed in each solvent and the surface resistance was measured after standing at room temperature (26 ° C) for 16 hours.

Example 1 Methyl methacrylate / ethyl acrylate / polyglycerol diacrylate / dimethylaminoethyl methacrylate quaternary compound was used in a conventional manner in a weight composition ratio of 4
Copolymerization was carried out at a ratio of 8/20/2/30 to obtain a copolymer aqueous solution. To this aqueous solution of the copolymer, glycerol polyglycidyl ether as an epoxy compound was added in an amount of 4% by weight based on the solid content of the copolymer, and 2% as a crosslinking curing agent.
-Methylimidazole was added to 2.5% by weight of the glycerol polyglycidyl ether and mixed to obtain a solid content of 7%.
An aqueous solution of the composition for forming a coating film by weight% was obtained. Intrinsic viscosity 0.
65 polyethylene terephthalate at 280-300 ° C
Melt-extruded with, and cooled with a cooling roll at 15 ° C. to obtain an unstretched film.
After stretching 3.5 times in the machine direction between a pair of rolls at 5 ° C.,
An aqueous solution of the composition for forming a coating film was applied by a kiss roll coating method at 10 g / m ² and dried with hot air at 70 ° C. to make the water content of the coating film about 25%, and then at 10 ° C. with a tenter. Was stretched 3.5 times in the direction, and heat-set at 200 to 210 ° C. to obtain a biaxially stretched coated polyester film having a thickness of 100 μm.

Examples 2 to 8 The same procedure as in Example 1 was repeated except that the composition of the coating film forming composition was changed as shown in Table 1.

Example 9 28 polyethylene terephthalate having an intrinsic viscosity of 0.65 was used.
It is melt-extruded at 0 to 300 ° C. and cooled by a cooling roll at 15 ° C. to obtain an unstretched film. An aqueous solution of the same coating film forming composition as in Example 1 is applied to this unstretched film by a kiss roll coating method at 10 g / m ^{2 was} applied. After coating, the coating is passed through a 90 ° C preheat zone to have a water content of about 15%, stretched 3.2 times in the transverse direction at 100 ° C, and further stretched 4 times in the longitudinal direction between a pair of rolls at 85 ° C with different peripheral speeds. After stretching 2 times, 200 to 2
It was heat set at 10 ° C. to obtain a biaxially stretched coated polyester film having a thickness of 7 μm.

Comparative Examples 1 to 4 and 6 to 8 Comparative Examples 1 to 4 and 6 to 8 were carried out in the same manner except that the composition of the coating film forming composition of Example 1 was changed as shown in Table 1.

Comparative Example 5 Example 1 except that a mixed solution of a resin (A) of Comparative Example 2 in Table 1 and a commercially available anionic antistatic agent consisting of sodium sulfonate at a ratio of 8/2 was used as a coating solution. I went in the same way.

Comparative Example 9 The procedure of Example 1 was repeated except that the aqueous solution of the coating film forming composition was not applied.

The characteristics of the films obtained in the above Examples and Comparative Examples are shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

As shown in Table 2, the antistatic films of the examples have small surface resistance even at low humidity and have excellent antistatic properties.
It also has excellent water resistance and solvent resistance. On the other hand, Comparative Example 1
Since it has no cationic group, it cannot provide antistatic properties.
In Comparative Examples 2 and 3, the spreadability of the coating film is poor, a uniform coating film cannot be formed, and antistatic properties cannot be imparted. Comparative Example 4,
Nos. 5 and 6 have good antistatic properties but poor water resistance and solvent resistance. In Comparative Example 7, the partial crosslinking reaction proceeded and an aqueous solution was not obtained. Comparative Example 8 is excellent in water resistance and solvent resistance, but inferior in antistatic property at low humidity. Comparative Example 9 has a large surface resistance and is inferior in antistatic property.

[0033]

As described above, the antistatic polyester film of the present invention is excellent in antistatic property at low humidity, and also excellent in water resistance and solvent resistance. It can be widely and suitably used as a film for packaging and a film for various packaging.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B29L 7:00 4F (72) Inventor Kazuhiro Abe 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Co., Ltd. (72) Inventor Koji Yamada 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. (72) Inventor Mutsuyuki Kawaguchi 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Koji Co., Ltd. Research Institute (72) Inventor Toshitake Suzuki 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Institute

Claims (1)

[Claims] 1. A monomer having a cationic quaternary ammonium salt group as a side chain and a polymerizable double bond at an end on at least one surface of a melt-extruded unstretched polyester film or uniaxially stretched polyester film. (X), a bifunctional vinyl monomer having a hydroxyl group (Y), and a water-soluble ionic conductor obtained by copolymerizing these monomers with another polymerizable vinyl monomer (Z) An antistatic polyester film obtained by coating a coating film-forming composition comprising a polymerizable resin (A) and a heat-crosslinkable monomer (B), and then biaxially or uniaxially stretching the coated film.