JPH051164A - Antistatic polyester film - Google Patents

Abstract

PURPOSE:To obtain the transparent film excellent in the antistatic nature at low humidity, water resistance and solvent resistance by coating one or both of the surfaces of a polyester film with a composition comprising a water-soluble ionically conductive resin and a thermocrosslinkable monomer followed by drawing. CONSTITUTION:The objective film can be obtained by coating one or both of the surfaces of a melt-extruded undrawn polyester film or uniaxially drawn polyester film with a coating film-forming composition comprising (A) a water- soluble ionically conductive resin prepared by copolymerization between (1) a monomer having in the side chain cationic quaternary ammonium base(s) and at the end(s) polymerizable double bond(s), (2) a hydroxyl group-contg. monofunctional vinyl monomer and (3) another vinyl monomer copolymerizable with both the components A and B and (B) a thermocrosslinkable monomer such as ethylene glycol glycidyl ether, followed by further biaxial or uniaxial drawing.

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. For example, in the film forming process, printing, adhesion, bag making, packaging, and other secondary processing processes, winding around a roll, electric shock to the human body, reduction in work efficiency such as difficulty in handling, occurrence of print whiskers, It may cause a decrease in product value such as dirt on the film surface. As such an antistatic method, there are generally a method in which an antistatic agent is kneaded into a resin to form a film, and a method in which an antistatic agent is applied to the film surface. Regarding polyester films, this so-called kneading-type antistatic treatment method exerts an antistatic effect by bleeding the antistatic agent from the inside of the film to the antistatic effect, whereas the polyester resin has a high second-order transition temperature. After film formation, the antistatic agent does not exude to the film at temperatures near room temperature, while the antistatic agent is compounded due to the high film forming temperature conditions and the high reactivity of the polar groups of the polyester itself. However, there have been problems such as deterioration of the polymer during 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. It is difficult to put it into practical use because the composition of (1) extremely 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 polyester film having such a coating layer, there is one called a coating stretching method (in-line coating method) in which a coating solution is coated and then the film is stretched and heat-treated. Compared with the method of forming a coating layer by coating a coating solution on a polyester film after biaxial stretching, this method performs film formation and coating at the same time, so a wide product can be obtained at a relatively low cost. Not only that, it is a useful method because it has characteristics such that the adhesiveness between the coating layer and the polyester film as 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 thereof is to have excellent antistatic property at low humidity and excellent water resistance and solvent resistance. To provide a polyester 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 side 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 monofunctional 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 the 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. Examples of such fine particles include inorganic fillers such as titanium oxide, calcium carbonate and barium sulfate, and organic fillers such as silicone, acrylic resin, benzoguanamine, Teflon and epoxy resin. This polyester is melt-extruded into a film by a conventional method, and then oriented and crystallized by biaxial stretching in the longitudinal and transverse directions and crystallized by heat treatment to obtain a polyester film. The coating film-forming composition in the present invention is applied to an unstretched film after melt extrusion or a film after uniaxial stretching.

In the ion-conductive resin (A) of the present invention, the monofunctional vinyl monomer (X) having a cationic type quaternary ammonium base in the side chain and a polymerizable double bond in the terminal is: For example, dimethylaminoethyl acrylate quaternized product, dimethylaminoethyl methacrylate quaternized product, diethylaminoethyl acrylate quaternized product, diethylaminoethyl methacrylate quaternized product, methylethylaminoethyl acrylate quaternized product, methylethylaminoethyl methacrylate quaternized product, dimethyl Examples thereof include aminostyrene quaternary compounds and methylethylaminostyrene quaternary compounds, and these can be used alone or in combination of two or more. On the other hand, examples of the monofunctional vinyl monomer (Y) having a hydroxyl group include 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. Other polymerizable vinyl monomers (Z) copolymerizable with these monomers include methyl acrylate,
Examples thereof include alkyl acrylates such as ethyl acrylate, methyl methacrylates, methacrylic acid alkyl esters such as ethyl methacrylate, and 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.
The copolymerization ratio of the monofunctional vinyl monomer (Y) having a hydroxyl group and the other polymerizable vinyl monomer (Z) copolymerizable with these monomers is (Y + Z) / X. The polymerization ratio is preferably in the range of 5/1 to 2/1, and the polymerization ratio is 5
When the ratio exceeds / 1, the water solubility of the ion conductive resin (A) is decreased, or a monofunctional vinyl monomer having a cationic doublet quaternary ammonium salt group on the side chain and a polymerizable double bond at the end. As a result, the ratio of (X) becomes small, so that a coating film excellent in antistatic property 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 10
The range of / 1 to 15/1 is preferable, and the polymerization ratio is 15
When it exceeds / 1, the monofunctional vinyl monomer (Y) having a hydroxyl group is reduced, and when the heat-crosslinkable monomer (B) is added, the crosslinkability is insufficient as a result. And the solvent resistance decreases. On the other hand, the polymerization ratio is 10/1
When it is less than 1, the amount of the monofunctional vinyl monomer (Y) having a hydroxyl group increases, and the water resistance and solvent resistance of the coating film decrease. The heat-crosslinkable monomer (B) of the present invention is specifically 2
An epoxy compound having 4 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 diglycidyl ether, Glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether and the like can be mentioned, and one or more of these 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. The range of / 30 to 97/3 is preferable. When the blending 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,
Spreadability of the coating film decreases. If the blending ratio exceeds 97/3, 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, and the cause is unknown. The spreadability of the coating film decreases and the antistatic property deteriorates. 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), an organic or inorganic organic compound is used. Alkaline compounds such as amines, polyamines, amidoamines, polyamidoamines, imidazoles,
It is desirable to use a small amount of a cross-linking curing agent and the like, and alkali metal carbonates, and derivatives thereof. The solution for forming a coating film in the present invention is an ion conductive resin (A).
Is suitable for use in an aqueous solution because it is water-soluble,
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.

It is preferable that the solution of the coating film-forming composition thus obtained is applied to at least one side of a polyester film for an unstretched film in which polyester is melt extruded or a uniaxially stretched film. .. It is not preferable to apply it to a biaxially stretched film, because the film is wide and the running speed of the film is high, so it is difficult to apply it uniformly. A known method can be applied to apply the coating liquid on the polyester film. For example, a spray coating method, an air knife method, a river coating method, a kiss coating method, a gravure coating method, a Meyer bar method, a roll brush 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 ² as the solid content as the amount present on the film after biaxial stretching. 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 the solution of the composition for forming a coating film is applied, for example, the polyester film is subjected to corona discharge treatment to improve the coatability of the solution or the adhesion between the polyester film and the coating film. It is possible to employ means for doing so. 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 polyester film produced by the above method is particularly useful as a base material for porcelain recording media such as video tapes, audio tapes, computer tapes and floppy disks. It is also useful as a substrate for general industrial films such as membranes, telephone cards, labels, microfilms, diazo films, OHP films and the like.

[0015]

EXAMPLES Next, examples and comparative examples of the present invention will be shown. Various evaluations were made by the following methods. (1) Surface resistance Takeda Riken Co., Ltd. applied resistance 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 / 2-hydroxyethyl methacrylate / dimethylaminoethyl methacrylate quaternary compound was copolymerized by a conventional method at a weight composition ratio of 47/21/7/25 to obtain a copolymer. An aqueous polymer solution was obtained. To the 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-methylimidazole as a crosslinking curing agent was added to the glycerol polyglycidyl ether at 2. 5 wt% was added and mixed to obtain an aqueous solution of a solid content of 7 wt% coating film forming composition. 280-30 polyethylene terephthalate with an intrinsic viscosity of 0.65
After melt-extruding at 0 ° C. and cooling with a cooling roll at 15 ° C. to obtain an unstretched film, the unstretched film was stretched 3.5 times in the machine direction between a pair of rolls at 85 ° C. having different peripheral speeds, An aqueous solution of the composition for forming a coating film was applied by a kiss coat method at 10 g / m ² , dried with hot air at 70 ° C., and then stretched 3.5 times in the transverse direction at 98 ° C. with a tenter, and further 2
It was heat-set at 00 to 210 ° C. to obtain a biaxially stretched coated polyester film having a thickness of 100 μm. The characteristics of the obtained film are shown in Table 2.

Examples 2 to 5 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 6 28 polyethylene terephthalate having an intrinsic viscosity of 0.65
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 coating method at 10 g / m ^2. Applied. After coating, the mixture is passed through a preheat zone of 90 ° C., stretched 3.2 times in the transverse direction at 100 ° C., further stretched 4.2 times in the longitudinal direction between a pair of rolls at 85 ° C. having different peripheral speeds, and then 200 to 210. A biaxially stretched coated polyester film having a pressure of 7 μm was obtained by heat setting at ℃.

Comparative Examples 1 to 3 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. Comparative Example 4 Same as Example 1 except that a mixed solution of the 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.

Comparative Example 5 The same procedure was carried out except that the aqueous solution of the coating film forming composition of Example 1 was not applied. As shown in Table 2, the antistatic films of the examples of the present invention have small surface resistance even at low humidity, excellent antistatic properties, and excellent water resistance and solvent resistance. On the other hand, in Comparative Example 1, the spreadability of the coating film is poor, a uniform coating film cannot be formed, and antistatic properties cannot be imparted. Comparative Example 2 has good antistatic properties but poor water resistance and solvent resistance. Comparative Example 3 has a large surface resistance and is inferior in antistatic property. Comparative Example 4 is inferior in antistatic property, water resistance and solvent resistance.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

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 code Internal reference number FI Technical display location // C08L 63/00 NJN 8416-4J C09D 163/00 PKD 8416-4J B29K 69:00 4F B29L 7 : 00 4F (72) Inventor Masaru Ito 3-63 Esaki, Tsurumi-ku, Yokohama-shi, Kanagawa Nippon Pure Chemical Co., Ltd. Tsurumi factory

Claims (1)

Claims: 1. A melt-extruded unstretched polyester film or uniaxially stretched polyester film having a cationic quaternary ammonium salt group on its side chain and a polymerizable diamine at its end on at least one side thereof. By copolymerizing a monomer (X) having a heavy bond, a monofunctional vinyl monomer (Y) having a hydroxyl group, and another polymerizable vinyl monomer (Z) copolymerizable with these monomers A charging obtained by applying a coating film-forming composition comprising the resulting water-soluble ion-conductive resin (A) and a heat-crosslinkable monomer (B), and then biaxially or uniaxially stretching the coated film. Preventive polyester film.