JPH0367624B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an easily adhesive polyester film and a method for producing the same, and more specifically, the present invention relates to an easily adhesive polyester film and a method for producing the same, and more specifically, a primer layer having excellent adhesiveness and solvent resistance made by reacting an aqueous polyester resin with an epoxy crosslinking agent is applied to a polyester film. The present invention relates to an easily adhesive polyester film characterized in that it is provided on at least one surface, and a method for producing the same. <Prior Art> It is known to melt-extrude thermoplastic polyesters, such as polyethylene terephthalate or its copolymers, polyethylene naphthalate or its copolymers, or blends of these with small proportions of other resins, to form films. be. It is also known that the resulting biaxially stretched and heat-set polyester film has better heat resistance, gas barrier properties, electrical properties, and chemical resistance than films made of other resins. However, since the surface is highly crystal oriented, the surface has high cohesion and poor solubility for paints, adhesives, inks, etc. Therefore, when a synthetic resin layer is provided on the surface of such a polyester film, the surface of the film is activated by corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, or flame treatment in order to strengthen the adhesion between the two. A means of coating with a synthetic resin coating has been applied. However, although these methods of activating the film surface can be expected to improve adhesion to the coating layer by increasing the secondary bonding force due to wetting, the activity decreases over time. Therefore, these means of activating the film surface are not necessarily satisfactory. As another approach to increasing the receptivity of polyester film surfaces, etching methods have been proposed in which the surface is swollen or partially dissolved with various agents. This involves etching the film surface by bringing it into contact with chemicals such as acid, alkali, amine aqueous solution, trichloroacetic acid, or phenols, decomposing, dissolving, and relaxing the crystal orientation near the surface, and at the same time reducing cohesion. This is intended to increase the adhesiveness with the binder resin by reducing the
The effect is most reliable, and the adhesion between the film and the layer provided thereon, such as a synthetic resin coating layer, becomes strong. However, some of the chemicals used in this method are harmful, and there is a risk that they may be dangerous to handle, or that volatile substances from the chemicals may be released into the atmosphere. There are various disadvantages in practical terms, such as the need for extreme caution. A method similar to this method is to form a primer layer (undercoat layer) on the surface of the film in advance, form a thin surface layer that is different from the base film, and then cover it with a desired layer, such as a synthetic resin. be. When forming the undercoat layer, a coating process is usually performed in a process different from the polyester film forming process. However, advanced processed film products such as audio magnetic tape, video magnetic tape, computer magnetic tape,
In applications such as floppy discs, X-ray photographic films, photographic films for printing, and diazo microfilms where precision and delicate quality must be maintained, even if an easily adhesive surface is successfully formed, the resulting film If there are surface defects due to dust, the base film cannot be used for these purposes, but this defect is likely to occur in this separate process. Therefore, it is desirable to perform the undercoating process in an atmosphere as free from dust as possible. There is a polyester film forming process that satisfies these conditions, and if undercoating is performed in this process, a product that can be fully used for the above-mentioned advanced film processed products can be obtained. On the other hand, in the prior art, the method of modifying the surface of a polyester film to make it easily adhesive by treating the surface with a primer is often achieved by coating the surface layer of the film with a composition dissolved in an organic material. I came. When such a method is carried out during film production, contamination of the surrounding environment by fugitive organic solvents,
resulting in unfavorable safety and hygiene conditions,
The use of organic solvents should be kept to a minimum as much as possible since they adversely affect the film forming process. Therefore, when performing in-line subbing treatment in the film forming process, it is preferable to use a composition using water as a solvent from the viewpoints of process, economy, and safety. Therefore, many primer compositions using water as a solvent have been proposed, and in particular, many proposals have been made for aqueous solutions or dispersions of polyurethane or polyester. However, these primer compositions have poor water resistance and solvent resistance, have poor blocking properties when exposed to wet heat, or swell or dissolve in the solvent of a coating that is further applied onto the primer layer, resulting in poor adhesion performance. There is a problem with the decline. <Object of the invention> The object of the invention is to provide various coatings applied to polyester films, such as cellophane ink,
It has excellent adhesion to UV inks, magnetic paints, gelatin compositions, offset inks, electrophotographic toners, chemical matte paints, diazo paints, heat-sealable compositions, inorganic film-forming substances, etc.
Another object of the present invention is to provide an easily adhesive polyester film coated with a primer layer having high solvent resistance that is not affected by the solvents of these coatings. A second object of the present invention is to provide a preferable method for producing such an easily adhesive polyester film. <Structure/Effects of the Invention> According to the present invention, an aqueous polyester film having (1) at least one of a free carboxylic acid group and a carboxylic acid group in its molecule, is provided on at least one side of the polyester film. Polyester resin and (2)2
An easily adhesive polyester film provided with a primer layer reacted with a crosslinking agent having at least 3 epoxy groups, and optionally in the presence of (3) a reaction accelerating compound, and On at least one side of the polyester film, (1) an aqueous polyester resin having at least one of a free carboxylic acid group and a carboxylic acid group in the molecule, (2) a crosslinking agent having two or more epoxy groups, and as necessary. depending on
(3) This is achieved by a method for producing an easily adhesive polyester film, which is characterized by applying an aqueous primer coating solution containing a reaction accelerating compound, followed by drying, stretching, and heat treatment to complete crystal orientation. In the present invention, the polyester constituting the polyester film 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 copolymers of these polyesters. It also includes combinations or blends of these with small proportions of other resins. The polyester film of the present invention is obtained by melt-extruding such a linear saturated polyester resin, forming it into a film by a conventional method, and subjecting it to oriented crystallization and heat treatment crystallization. This polyester film has crystal orientation to such an extent that the heat of crystal fusion measured by a differential scanning calorimeter in a nitrogen stream [at a heating rate of 10°C/min] is usually 4 cal/g or more. Preferably. In the present invention, a polyester film before completion of crystal orientation refers to an unstretched film obtained by thermally melting the polyester and forming it into a film as it is; an unstretched film oriented in either the vertical direction or the horizontal direction. Uniaxially stretched film; furthermore, one that has been stretched and oriented at a low magnification in both the vertical and horizontal directions (biaxially stretched film before finally being re-stretched in the vertical or horizontal direction to complete oriented crystallization), etc. This includes: The aqueous primer coating solution used in the present invention includes (1) an aqueous polyester resin having at least one free carboxylic acid group and carboxylic acid group in its molecule, (2) a crosslinking agent having two or more epoxy groups, and the necessary components. (3) Contains a reaction accelerating compound depending on the conditions. This aqueous primer coating liquid may be an aqueous solution, emulsion or aqueous dispersion. In order to introduce a carboxylic acid group into the molecule of this aqueous polyester resin, for example, a polyhydric compound such as trimellitic anhydride, trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid, etc. is preferably used as one of the raw materials for polymer production. Further, a carboxylic acid salt can be introduced by neutralizing the carboxylic acid group introduced into the polymer with an amino compound, ammonia, an alkali metal, or the like. When introducing a carboxylate group, other known methods can be employed. For example, there is a method of synthesizing polyester using a compound having a carboxylate group in the molecule as a raw material. A polyester having free carboxyl groups is produced using trimellitic anhydride as a polyester raw material, and after the reaction is completed, aqueous ammonia is added to neutralize it, thereby producing an aqueous solution of the polyester resin used in the present invention. In addition to the above-mentioned polyhydric compounds, acid components forming the aqueous polyester resin include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, Examples include sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, and itaconic acid. The ratio of the above polyhydric compound to the total acid component is 0.5
~30 mol%, particularly 1-10 mol% is preferred. 0.5
If it is less than mol %, the hydrophilicity will be poor, and if it exceeds 30 mol %, the water resistance will be poor and the coating will become brittle. In addition, the polyhydric alcohol components that form the aqueous polyester resin include ethylene glycol,
1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane,
Trimethylolethane, pentaerythritol,
Examples include poly(ethylene oxide) glycol and poly(tetramethylene oxide) glycol. In addition to these components, hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-(β-hydroxyethoxy)benzoic acid, benzoic acid, monocarboxylic acids such as fatty acids, and esters such as linseed oil can also be used. The aqueous polyester resin is synthesized from a polyhydric carboxylic acid or its ester-forming derivative and a polyhydric alcohol or its ester-forming derivative by a known method. The methods for making an aqueous solution of aqueous polyester resin include (1) dissolving the polyester resin in water; (2)
Along with polyester resin and water, emulsifiers, dispersants,
Make an emulsion or suspension using a suspension stabilizer, etc.; (3) Dissolve the polyester resin in a medium other than water, add it to make an emulsion or suspension, and remove the medium; (4) Heat and melt the polyester resin, contact and disperse it with water or other media, and then remove unnecessary media; (5) Prepare fine particles of polyester resin in advance and stabilize the particles by dispersing them in water. etc. can be exemplified. Next, as the crosslinking agent having two or more epoxy groups used in the present invention, for example, and water-soluble or water-dispersible epoxy compounds such as addition condensates of bisphenol A and epichlorohydrin. Compounds that promote the reaction between aqueous polyester resin and epoxy crosslinking agent (reaction promoting compounds) include:
Examples include compounds containing a tertiary amino group, compounds having a nitrogen-containing ring structure and salts thereof, and quaternary ammonium salt compounds. More specifically, 3
Examples of compounds containing a class amino group include trimethylamine, triethylamine, tri-n-butylamine, dimethylaminobenzene, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and nitrogen-containing compounds. Examples of compounds having a ring structure and salts thereof include imidazole compounds such as 2-methylimidazole, 2-methyl-4-ethylimidazole, 2-ethylimidazole, 2-isopropylimidazole, and 2-phenyl-4-methylimidazole; ,8-diazo-bicyclo(5,4,
0) Undecene-7 and their hydrochlorides, carbonates, etc. can be mentioned. Examples of the quaternary ammonium salt compound include triethylbenzylammonium chloride and tetramethylammonium chloride. Among these, compounds containing a tertiary amino group and compounds having a nitrogen-containing ring structure are preferred. Particularly preferred are 2,4,6-tris(dimethylaminomethyl)phenol, 2-methylimidazole, and 2-methyl-4-ethylimidazole. The ratio of the aqueous polyester resin to the epoxy crosslinking agent is preferably 1 to 40 parts by weight, more preferably 2 to 30 parts by weight, per 100 parts by weight of the former. If the proportion of the epoxy crosslinking agent is too high, the adhesion performance will decrease, and if it is too low, the solvent resistance will decrease, making it difficult to obtain a good coated surface when applying the coating, which is the object of the present invention, so it is preferable. do not have. In addition, the ratio of the epoxy crosslinking agent to the reaction accelerating compound is 100 parts by weight of the former, 0 to 60 parts by weight of the latter,
Preferably it is 5 to 50 parts by weight. If the proportion of this reaction accelerating compound is too large, it becomes difficult to control the reaction and the stability of the coating liquid decreases. The aqueous primer coating solution is made by dissolving or dispersing the above two components, preferably the above three components, in an aqueous medium, and further contains a necessary amount of a surfactant such as an anionic surfactant or a nonionic surfactant. It can be used as Such surfactants are preferably those that can lower the surface tension of the aqueous coating solution to 40 dyne/cm or less and promote wetting to the polyester film, such as polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan, etc. fatty acid ester,
Examples include glycerin fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfonates, and alkyl sulfosuccinates. Furthermore, other additives such as antistatic agents, ultraviolet absorbers, pigments, organic fillers, inorganic fillers, lubricants, and antiblocking agents may be mixed within a range that does not impair the effects of the present invention. The aqueous primer coating solution may be applied to the polyester film in a normal coating process, that is, in a process in which the biaxially stretched and heat-set polyester film is coated separately from the film manufacturing process. However, this process tends to introduce dirt, dust, etc., and it is desirable to apply the coating in a clean atmosphere for advanced products such as magnetic tapes and floppy disks. From this point of view, coating during the polyester film manufacturing process is preferable. In particular, it is preferable to apply an aqueous primer coating liquid to one or both sides of the polyester film before the crystal orientation is completed during this step. At that time, the solid content concentration of the aqueous primer coating solution is usually 30% by weight or less,
More preferably, it is 10% by weight or less. The amount of coating is 0.5 to 20 g ^per square meter of running film, and more preferably 1 to 10 g.
g is preferred. Any known coating method can be used as the coating method. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating, an air knife coating, an impregnation method, a curtain coating method, etc. may be applied alone or in combination. The polyester film coated with the aqueous coating solution is dried and subjected to processes such as stretching and heat setting. For example, vertical 1 coated with water-based primer coating liquid.
The axially stretched polyester film is guided into a stenter, where it is laterally stretched and heat set. During this time, the coating solution dries and further undergoes a crosslinking reaction, forming a continuous film on the film. Heat for the crosslinking reaction is usually supplied by heat during stretching or heat setting. For example, 200℃ for about 10 seconds, 150℃ for about 1 minute, 120℃
You can heat it for about 15 minutes at 220℃ for about 8 seconds, etc.
It may also be heated under more severe or less severe conditions. Conditions for oriented crystallization of the polyester film, such as stretching, heat setting, etc., can be carried out under conditions conventionally accumulated in the art. The polyester film having the primer layer thus obtained can be used for cellophane ink,
It exhibits high adhesion to a wide range of paints such as UV inks, magnetic paints, gelatin compositions, electrophotographic toner compositions, chemical matte paints, and diazo paints, and also exhibits high adhesion to methyl ethyl ketone, toluene, ethyl acetate, butyl acetate, and ethanol. , dioxane,
Shows excellent solvent resistance to organic solvents such as tetrahydrofuran, cyclohexanone, and cyclohexane. Therefore, the polyester film of the present invention can be used for film processing products such as audio and video applications.
It is useful as a base material for computer magnetic tapes, floppy disks, X-ray photographic films, diazo films, membranes, OHP films, hard coat films, abrasive tapes, adhesive tapes, labels, etc. <Examples> The present invention will be further explained below with reference to Examples.
Note that "parts" in the examples mean "parts by weight." Moreover, each characteristic of the film was measured by the following method. 1 Adhesion Apply UV Shine Beni T (manufactured by Moroboshi Ink Co., Ltd.) to a thickness of 4μ on a primer-coated polyester film, irradiate it with ultraviolet rays for 5 minutes using a 1.5KW ultra-high pressure mercury lamp, and then apply Scotch Tape No. 600 (3M). company)
Adhere a piece of tape with a width of 19.4 mm and a length of 15 cm so as not to create any air bubbles, smooth it with a manual load roll as described in JIS, C2701 (1975), and cut it into a tape width. Rapidly peel off this sample with the polyester film facing up and observe how the UV ink is peeled off. Most of the UV ink has transferred to the adhesive tape: × Half of the UV ink remains on the polyester film: △ All of the UV ink remains on the polyester film: 〇2 Solvent resistance Primer-coated polyester film Apply 5 drops of tetrahydrofuran (approx.
0.1cc), place gauze on top, and add 200ml
Place a weight of g on it and move the gauze at a speed of approximately 1000 mm/min. After drying at room temperature, interference micrographs of those not treated with tetrahydrofuran and those treated with tetrahydrofuran are compared at 400x magnification, and the state of surface change of the primer is judged as follows. Items with almost no primer: × Items with almost no change in primer: 〇 Items with slight changes in surface morphology in between
：〇〜△ Those with a considerable change in surface morphology ：×〜△ Those with an intermediate change in surface morphology ：△ 3 Blocking property Polyester film was cut into a piece of 10 x 15 cm with the primer-coated sides together, and 6 kg/
A load of cm is applied and this state is maintained in an atmosphere of 40°C x 80% RH for 17 hours, after which the peel strength of a 10cm width is measured. When this peel strength increases, blocking occurs between the films, causing a so-called delamination phenomenon. Example 1 Preparation of polyester resin aqueous liquid Terephthalic acid (80 mol%) - Isophthalic acid (15
mol%) - trimellitic acid (5 mol%) - ethylene glycol (90 mol%) - diethylene glycol (10 mol%) copolymerized polyester is neutralized with aqueous ammonia equivalent to the free carboxylic acid group of trimellitic acid to reduce the solid content. A 2wt% aqueous polyester resin liquid was obtained. To 680 parts of this aqueous polyester resin solution, 3.0 parts of glycerin triglycidyl ether, 2, 4, 6
-tris(dimethylaminomethyl)phenol
Add and dissolve 0.4 parts of polyoxyethylene nonyl phenyl ether [HLB12.8, Nonion NS208.5: manufactured by Nippon Oil & Fats Co., Ltd.], and then add 313.6 parts of distilled water.
A 2wt% aqueous primer solution was obtained. This primer solution was applied onto a 75 μm biaxially stretched polyethylene terephthalate film by gravure coating, and then heat treated at 120° C. for 5 minutes to obtain a primer-coated polyester film with an average dry coating amount of 50 mg/m ² . Example 2 Polyethylene terephthalate (containing lubricant) with an intrinsic viscosity of 0.65 measured in O-chlorophenol at 25°C was melt-extruded onto a rotating cooling drum maintained at 20°C to obtain an unstretched film with a thickness of 950 μm, and then machined. After stretching 3.5 times in the axial direction, a coating solution identical to the coating solution prepared in Example 1 was applied to both sides of the uniaxially stretched film by a kiss coating method. The average coating amount at this time was 50 mg/m ² in terms of solid content. Subsequently, the film was stretched 3.9 times in the transverse direction at 105°C and further heat-treated at 210°C to obtain a polyester film coated with primer on both sides and having a thickness of 75 μm. Example 3 Carboxyamine salt-containing aqueous polyester resin liquid [TK Set 113B; 20wt% manufactured by Takamatsu Yushi Co., Ltd.]
360 parts was dissolved in 4612 parts of water, and further 10 parts of glycerin triglycidyl ether, 3 parts of 2,4,6-tris(dimethylaminomethyl)phenol, and the nonionic surfactant NS208.5 [NOF] used in Example 1 were added. Co., Ltd.] was dissolved to obtain an aqueous primer solution. A primer-coated polyester film was obtained in exactly the same manner as in Example 2 except for using this primer solution. Example 4 A primer solution was prepared in the same manner as in Example 3 except that 2-methylimidazole was used instead of 2,4,6-tris(dimethylaminomethyl)phenol in Example 3. A primer-coated polyester film was obtained in the same manner as in Example 2 except for using the following. Example 5 A primer solution was prepared in the same manner as in Example 3, except that sorbitol tetraglycidyl ether was used instead of glycerin triglycidyl ether in Example 3, and in the same manner as in Example 2, except that this primer solution was used. A primer-coated polyester film was obtained. Comparative Example 1 Various evaluations were conducted using a 75 μm thick polyethylene terephthalate film that was not subjected to primer treatment. Comparative Example 2 42.5 parts of the aqueous polyester resin and 1.5 parts of the surfactant NS208.5 in Example 2 were dissolved in 456 parts of water to obtain an aqueous primer liquid. A primer-coated polyester film was obtained in exactly the same manner as in Example 2 except for using this primer solution. The adhesiveness, solvent resistance, and blocking properties of the polyester films of Examples 1 to 5 and Comparative Examples 1 to 2 were evaluated. The results are summarized in Table 1.

[Table] From Table 1, it is clear that the polyester film of the present invention has excellent performance in adhesiveness, solvent resistance, and blocking property.

Claims (1)

[Claims] 1. On at least one side of the polyester film, (1)
(2) an aqueous polyester resin having at least one type of free carboxylic acid group and carboxylic acid group in the molecule;
An easily adhesive polyester film comprising a primer layer made by reacting a crosslinking agent having two or more epoxy groups, optionally in the presence of (3) a reaction accelerating compound. 2. On at least one side of the polyester film before crystal orientation is completed, (1) an aqueous polyester resin having at least one of a free carboxylic acid group and a carboxylic acid group in the molecule, and (2) two or more epoxy groups. An easily adhesive polyester film characterized in that it is coated with an aqueous primer coating solution containing a crosslinking agent having the following properties and, if necessary, (3) a reaction accelerating compound, and then dried, stretched, and heat-treated to complete crystal orientation. manufacturing method.