JPH0367626B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Field of Application> The present invention relates to an easily adhesive polyester film and a method for producing the same, and more specifically to highly processed products such as audio magnetic tape, video magnetic tape, computer magnetic tape,
The present invention relates to a polyester film having excellent adhesiveness and blocking resistance, useful as a base material for floppy disks, X-ray photographic films, telephone cards, membranes, diazo microfilms, etc., 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 its surface is highly crystallized, its surface cohesiveness is high;
For example, it has poor adhesion to paints, adhesives, inks, etc. Therefore, physical treatments such as corona treatment, ultraviolet ray treatment, plasma treatment, EB treatment, flame treatment, etc., or chemical treatments such as alkali, amine aqueous solution, trichloroacetic acid, phenols, etc., are methods for improving this adhesiveness. Are known. However, these methods have practical disadvantages such as deterioration of adhesive strength over time and contamination of the working environment due to volatilization of chemicals. Another known method is to apply an easily adhesive coating agent to the surface of the film in a process other than the usual polyester film forming process to form a primer layer. However, with this method, organic solvents are usually used as coating solvents, and the coating atmosphere is not sufficiently clean, resulting in frequent surface defects on processed products due to dust adhesion, or environmental pollution caused by organic solvents. There are safety and hygiene problems such as deterioration. By the way, if this primer treatment is performed during the polyester film forming process using a water-based coating agent, the film can be formed in a clean environment without dust adhesion, and because it is a water-based solvent, there is no risk of explosion or environmental deterioration. It is advantageous in terms of performance, economy, and safety. Because of these advantages, it has been proposed to use water-soluble or water-dispersible polyester resins or acrylic resins as primers (Japanese Patent Application Laid-open No. 43017/1983, Japanese Patent Publication No. 10243/1973, -19786, JP-A-52-19787, etc.). but,
The above-mentioned polyester resin has the disadvantage of easily causing blocking when the film is wound into a roll, and the above-mentioned acrylic resin has the disadvantage of poor adhesion with the film, mechanical strength, and adhesion with the magnetic layer. be. In order to improve these drawbacks, it has been proposed to use a mixture of the above polyester resin and the above acrylic resin (Japanese Patent Laid-Open No.
No. 58-124651), but the improvement of these drawbacks cannot be said to be sufficient. <Object of the invention> The object of the invention is to provide various coatings applied to polyester films, such as offset inks,
Gravure ink, silk screen ink, UV
Excellent adhesion to inks, magnetic paints, gelatin compositions, adhesives, electrophotographic toners, chemical matte paints, diazo paints, hard coat paints, UV paints, heat-sealable compositions, inorganic film-forming substances, etc. An object of the present invention is to provide an easily adhesive polyester film having a primer layer that has a tackiness and has no tackiness. Another object of the present invention is to provide a preferred method for producing such an easily adhesive polyester film. <Structure/Effects of the Invention> According to the present invention, (1) at least one side of the polyester film,
Water-based polyester in which the trunk polymer is polyester and the branch polymers are acrylic polymers.
An easily adhesive polyester film provided with a primer layer of an acrylic graft polymer, and (2) on at least one side of the polyester film before crystal orientation is completed, the trunk polymer is polyester and the branch polymers are acrylic polymers. This is achieved by a method for producing an easily adhesive polyester film, which comprises applying an aqueous primer solution containing an aqueous polyester-acrylic graft polymer, 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-naphthalenedicarboxylate, 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 crystal orientation is completed is an unstretched film obtained by thermally melting the polymer 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 being finally re-stretched in the vertical or horizontal direction to complete oriented crystallization), etc. This includes: The aqueous primer liquid used in the present invention contains an aqueous polyester-acrylic graft polymer in which the trunk polymer is polyester and the branch polymers are acrylic polymers. The polyester serving as the backbone polymer of this aqueous polyester-acrylic graft polymer is a substantially linear polymer synthesized from a polybasic acid or its ester-forming derivative and a polyol or its ester-forming derivative. Polybasic acid components of this polymer include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid. , dimer acid and the like. Two or more types of these components can be used. Furthermore, in addition to these components, unsaturated polybasic acids such as maleic acid, fumaric acid, itaconic acid, etc., and hydroxycarboxylic acids such as p-hydroxybenzoic acid, p-(β-hydroxyethoxy)benzoic acid, etc. may be used in small proportions. can. The proportion of the unsaturated polybasic acid component and the hydroxycaubonic acid component is at most 10 mol%, preferably 5 mol% or less. In addition, as polyol components, ethylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4
Examples include -cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, poly(ethylene oxide) glycol, poly(tetramethylene oxide) glycol, and the like. Two or more types of these can be used. The backbone polymer is preferably an aqueous polyester, for example, an organic sulfonate, carboxylate, etc.
A copolymer of a hydrophilic group-containing compound such as diethylene glycol, polyethylene glycol, polytetramethylene glycol, etc. is advantageous for preparing an aqueous dispersion and is therefore preferred. Introducing this carboxylic acid salt usually uses a trifunctional or higher-functional carboxylic acid, but this carboxylic acid undergoes branching during the polymerization process.
Since it is easy to gel, it is desirable to reduce the copolymerization ratio. In this respect, the introduction of hydrophilic groups using sulfonate salts, diethylene glycol, polyalkylene ether glycol, etc. is more advantageous since the problems that occur when using carboxylate salts do not occur. In order to introduce a sulfonate group into the polyester molecule, for example, 5-Na sulfoisophthalic acid, 5-ammonium sulfoisophthalic acid, 4-
Na sulfoisophthalic acid, 4-methylammonium sulfoisophthalic acid, 2-Na sulfoterephthalic acid, 5-K sulfoisophthalic acid, 4-K sulfoisophthalic acid, 2-K sulfoterephthalic acid, Na
It is preferable to use a sulfonic acid alkali metal salt type compound such as sulfosuccinic acid or a sulfonic acid amine salt type compound. The polycarboxylic acid or polyhydric alcohol having a sulfonate group preferably accounts for 0.5 to 20 mol%, more preferably 1 to 18 mol%, of the total polycarboxylic acid component or polyhydric alcohol component. In addition, in order to introduce a carboxylic acid group into the polyester molecule, for example, trimellitic anhydride,
Compounds such as trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, and dimethylolpropionic acid can be used. Further, a carboxylic acid salt can be obtained by neutralizing a carboxylic acid with an amino compound, ammonia, an alkali metal, or the like. When introducing a hydrophilic group-containing compound into a polyester molecule, various known methods can be employed. To further explain the case of introducing a carboxylate or organic sulfonate group, for example, a method for synthesizing polyester using a compound having a carboxylate or organic sulfonate group in the molecule as one of the starting materials, a molecule. A method such as synthesizing a polyester using a compound having three or more carboxylic acid groups as one component as a starting material, and then neutralizing free carboxyl groups in the polyester in a medium with ammonia, amines, alkali metal compounds, etc. There is. To further explain the method, for example, trimellitic anhydride is added to one of the polyester raw materials.
Aqueous polyester can be produced by using it as a component to produce a polymer having free carboxyl groups in the side chain, and after the reaction is completed, aqueous ammonia is added to neutralize it. Preferably, the polyester is produced by a melt polymerization method. The branch polymer of the aqueous polyester-acrylic graft polymer is an acrylic polymer, and monomers of the acrylic polymer include, for example, alkyl acrylate, alkyl methacrylate (alkyl groups include methyl group, ethyl group, n-propyl group, and isopropyl group). , n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.): 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2
- Hydroxy-containing monomers such as hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide,
N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N-
Amide group-containing monomers such as methylolmethacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-phenylacrylamide; N,N-diethylaminoethyl acrylate, N,N-diethylamino Amino group-containing monomers such as ethyl methacrylate; Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; Containing carboxyl groups or their salts such as acrylic acid, methacrylic acid and their salts (sodium salt, potassium salt, ammonium salt) Examples include monomers that These can be used in combination with other types of monomers. Examples of other monomers include epoxy group-containing monomers such as allyl glycidyl ether; monomers containing sulfonic acid groups or their salts such as styrene sulfonic acid, vinyl sulfonic acid, and their salts (sodium salts, potassium salts, ammonium salts, etc.) ; Monomers containing carboxyl groups or salts thereof such as crotonic acid, itaconic acid, maleic acid, fumaric acid and their salts (sodium salt, potassium salt, ammonium salt, etc.); acid anhydrides such as maleic anhydride, itaconic anhydride, etc. Monomers containing: vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, alkyl itaconic acid monoester , vinylidene chloride, vinyl acetate, vinyl chloride, and the like. The above-mentioned monomers can be copolymerized using one type or two or more types. Hydroxyl groups, amide groups, carboxyl groups, or their salts (sodium salts, potassium salts, ammonium salts, etc.) are recommended from the viewpoint of imparting hydrophilicity to the acrylic copolymer, dispersion stability of aqueous liquids, adhesion to polyester films, etc. Preferably, those having functional groups such as A known graft polymerization method can be used to graft the acrylic polymer onto the polyester (stem polymer). There are three main methods: (A) A method of graft polymerizing acrylic monomers by generating reaction initiation sites such as radicals, cations, or anions in the backbone polymer. (B) A method of graft polymerizing acrylic monomers by generating reaction initiation sites such as radicals, cations, or anions in the backbone polymer. A method of graft polymerizing system monomers (C) A method of reacting a trunk polymer having a functional group in its side chain with a branch polymer having a group that reacts with the functional group at the end As a more specific method of the above (A), For example, light
A radical polymerization method in which radicals are generated in the backbone polymer by heat or radiation and then graft polymerized with monomers; a cationic group is generated in the backbone polymer using a catalyst such as AlCl ₃ or TiCl ₄ , or metal Na, metal Examples include cationic polymerization or anionic polymerization in which anionic groups are generated in the backbone polymer using Li or the like and then graft polymerization is performed with monomers. In addition, as a more specific method of (B) above, for example, glycidyl methacrylate is added to a polyester having a carboxyl group or a hydroxyl group in the side chain.
A method of reacting 2-hydroxyethyl acrylate, acrylic acid, etc. to introduce an unsaturated group into the side chain of the polyester, and polymerizing this with a monomer;
Examples include a method of reacting an acrylic monomer with a polyester in which an unsaturated group is introduced into the polymer main chain using an unsaturated compound such as fumaric acid as one component of the synthetic raw material. Furthermore, as a specific method for the above (C), for example, a polyester (stem polymer) having a hydrogen donating group such as -OH, -SH, -NH ₂ , -COOH, -CONH ₂ etc. in the side chain and one terminal is a hydrogen-accepting group such as -N=C=O, -C=C=O,
A method of reacting an acrylic polymer (branch polymer) such as -CH - OCH ₂ or -CH - SCH ₂ with a polyester (stem polymer) having a hydrogen-accepting group in the side chain and a hydrogen-donating group at one end. Examples include a method of reacting with an acrylic polymer (branch polymer). Other combinations of functional groups include -COOH and -COCl, -COOH and -
Examples include combinations of OH, -COOH and _-NH2 , and _-NH2 and -OH. The weight ratio of the trunk polymer to the branch polymer in the graft polymer is preferably 5:95 to 95:5, more preferably 10:90 to 90:10. The molecular weight of the trunk polymer is preferably 5,000 to 200,000, more preferably 10,000 to 100,000, and the molecular weight of the branch polymer is 500 to 50,000.
Furthermore, 1000 to 10,000 is preferable. In the present invention, the aqueous primer liquid contains the above-mentioned aqueous polyester-acrylic graft polymer, and is obtained by dissolving and dispersing the graft polymer in an aqueous medium. This aqueous primer solution may contain a small amount of organic solvent as long as it does not affect the graft polymer or other additives. Any method can be used to produce such an aqueous primer liquid, such as a method in which an aqueous polyester-acrylic graft polymer is synthesized in an organic solvent, and then part or all of the organic solvent is replaced with an aqueous medium to make it water-dispersed. Preferable examples include a method of dispersing the backbone polymer and monomer in water and carrying out emulsion polymerization. To further explain the former method, after transesterifying the polyol constituting the polyester and the polycarboxylic acid lower alkyl ester, a polycondensation reaction is initiated at a temperature of 250 to 300°C under normal pressure, and finally under vacuum. The reaction proceeds to obtain a polyester with a predetermined degree of polymerization, and then this polyester and an acrylic polymer or acrylic monomer are dissolved in an organic solvent, a polymer reaction or a radical reaction is performed to obtain a graft polymer liquid, and this graft polymer liquid is dissolved in water. An example of this method is to mix the organic solvent with a medium and then remove the organic solvent. The aqueous primer liquid may be used by adding a necessary amount of a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant. Such a surfactant is preferably one that can lower the surface tension of the aqueous coating solution to 40 dyne/cm or less and promotes wetting to the polyester film, such as polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan, etc. Fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate,
Examples include alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts, and alkylamine hydrochloric acids. 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 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 trap 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 liquid to one or both sides of the polyester film before the crystal orientation is completed during this step. In this case, the solid content concentration of the aqueous primer liquid is usually 30% by weight or less, more preferably 10% by weight or less. The coating amount is based on the running film 1.
0.5 to 20 g, more preferably 1 to 10 g per m ² . 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 method, an air knife coating method, an impregnation method, a curtain coating method, etc. may be applied alone or in combination. The polyester film coated with the aqueous primer solution and before crystal orientation is completed is dried and subjected to processes such as stretching and heat setting. For example, a longitudinally uniaxially stretched polyester film coated with an aqueous primer solution is guided into a stenter, where it is laterally stretched and heat-set. During this time, the coating solution dries and forms a continuous film on the film. Drying is preferably carried out before or during stretching. Conditions for oriented crystallization of the polyester film, such as stretching, heat setting, etc., can be those conventionally accumulated in the art. The polyester film having the primer layer obtained in this manner solves the problems when using conventional water-based polyester resins or acrylic resins, and furthermore, the problems when using a blend of these resins. , cellophane ink, magnetic paint, gelatin composition, electrophotographic toner composition, chemical matte paint, diazo paint,
It exhibits high adhesion to a wide variety of paints such as UV inks, and exhibits good blocking resistance without stickiness. <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 polyester film or primer-treated 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 ( (manufactured by 3M) 19.4 mm wide and 15 cm long, glue it so that there are no air bubbles, and then apply JIS
C2701 (1975), use a manual load roll to flatten the tape and cut it out to the width of the tape. 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 migrated 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 Blocking property Place the primer-coated sides of the polyester film together. Then cut into 10cm x 15cm squares and use
A load of 6 kg/cm ² was applied for 17 hours in an atmosphere of 55° C. and 80% RH, and then the peel strength of this 10 cm width was measured. The peeling speed at this time was 100 mm/min. Example 1 The acid component consists of terephthalic acid (50 mol%), isophthalic acid (45 mol%) and trimellitic acid (5 mol%), and the glycol component consists of ethylene glycol (80 mol%) and ethylene glycol (20 mol%). (intrinsic viscosity measured in O-chlorophenol at 25°C = 0.28) consisting of 3 parts of methyl methacrylate (48 mol%), ethyl acrylate (47 mol%) and 2-hydroethyl acrylate (5 mol%) Acrylic copolymer 6
9 parts of a graft polymer obtained by polymer-reacting 9 parts of the graft polymer were dissolved in 90 parts of tetrahydrofuran, and 1 part of a nonionic surfactant [HLB12.8] was added thereto. 490 parts of water was gradually added to this solution while stirring at high speed, followed by heating and distillation to remove the tetrahydrofuran and obtain an aqueous primer solution. 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 stretched in the machine axis direction. After stretching the film by 3.5 times, the aqueous primer solution was applied to both sides of the uniaxially stretched film using a kiss coating method. The average coating amount at this time was 50 mg/m ² in terms of solid content. Subsequently, it was stretched 3.9 times in the transverse direction at 105°C, and then heat treated at 210°C to increase the thickness.
A 75 μm double-sided primer-coated biaxially oriented polyester film was obtained. Example 2 The acid component consists of terephthalic acid (49 mol%), isophthalic acid (49 mol%), and 5-sodium sulfoisophthalic acid (2 mol%), and the glycol component consists of ethylene glycol (50 mol%) and neopentyl glycol. (45 mol%) and trimethylolpropane (5 mol%), methyl methacrylate (50 mol%), ethyl acrylate (37 mol%), butyl acrylate (8 mol%) and acrylic acid (5 mol%). %) of acrylic polymer was subjected to a polymer reaction to obtain a graft polymer. This graft polymer was made into an aqueous primer solution in exactly the same manner as in Example 1, and a primer-coated polyester film was obtained in the same manner as in Example 1 except that this primer solution was used. Comparative Example 1 Thickness 75μm without primer treatment for comparison
Various evaluations were conducted using polyethylene terephthalate film. Comparative Example 2 The acid component consists of terephthalic acid (49 mol%), isophthalic acid (49 mol%) and 5-sodium sulfoisophthalic acid (2 mol%), and the glycol component consists of ethylene glycol (50 mol%) and neopentyl glycol. An aqueous primer solution was prepared using a blend of 5.4 parts of polyester (50 mol%) and 3.6 parts of the acrylic polymer of Example 2. A primer-coated polyester film was obtained in a similar manner. The performance of the polyester films and primer-coated polyester films obtained in the above Examples and Comparative Examples was evaluated. The results are shown in Table 1.

[Table] As is clear from Table 1, the primer-coated polyester film of the present invention has excellent adhesion and blocking properties.

Claims (1)

[Claims] 1. On at least one side of the polyester film,
An easily adhesive polyester film comprising a primer layer of an aqueous polyester-acrylic graft polymer in which the trunk polymer is polyester and the branch polymers are acrylic polymers. 2. An aqueous primer solution containing an aqueous polyester-acrylic graft polymer in which the trunk polymer is polyester and the branch polymers are acrylic polymers is applied to at least one side of the polyester film before crystal orientation is completed, and then dried and stretched. A method for producing an easily adhesive polyester film, which comprises completing a crystal orientation by heat treatment.