CN116887985A - Hollow polyester film - Google Patents

Abstract

The present invention provides an easily adhesive hollow polyester film which contains hollow of optimal size, is light, and has excellent shielding property, whiteness, film forming property and thermal dimensional stability, and has excellent ink adhesion and antistatic property as an information recording material and a printing material. The present invention relates to a void-containing polyester film comprising a layer A, which is a layer containing voids therein, and a layer B, which is a layer containing a polyester resin containing inorganic particles, wherein the layer A contains a composition containing a polyester resin and a polypropylene resin, and wherein the film has a weight deflection in at least one direction of 100mm or less and 60mm or more, and wherein at least one surface of the void-containing polyester film has a surface resistivity of 1.0X10 ¹³ An easy-to-adhere layer having an omega/sq or less.

Description

Hollow polyester film

Technical Field

The present invention relates to an easily bondable void-containing polyester film which contains voids of an optimal size, is lightweight, and is excellent in shielding properties, whiteness, film forming properties, and thermal dimensional stability, and is excellent in ink adhesion and antistatic properties as an information recording material or a printing material.

Background

Synthetic paper, which is a paper substitute mainly composed of synthetic resin, is excellent in water resistance, moisture absorption dimensional stability, surface stability, and the like as compared with natural paper, and is widely used for labels, stickers, posters, recording papers, packaging materials, and the like. Polyethylene resins, polypropylene resins, polyester resins, and the like are used as main raw materials of synthetic papers, and in particular, polyester resins typified by polyethylene terephthalate have been widely used because of their excellent mechanical properties, thermal properties, and the like.

As a method for obtaining a film having a function similar to paper, the following method is generally given: a method of forming a large number of fine voids in the film; a method of roughening a flat film by performing surface treatment such as sandblasting, chemical etching, or matting. Among these, the former method of containing a large number of fine voids in the film is largely employed due to the following advantages: the film itself can be made lightweight, and thus the cost per unit area can be suppressed, while not only the masking property and whiteness of paper can be obtained; since appropriate flexibility and cushioning properties can be obtained, the image clarity at the time of printing is excellent.

As a method for generating fine voids in the film, the following methods are generally mentioned: first, an incompatible thermoplastic resin (hereinafter referred to as an incompatible resin) is mixed with a polyester resin, whereby a melt having a sea-island structure in which the incompatible resin is dispersed in the polyester resin is obtained. Then, an unstretched sheet is formed by extrusion from a die and stretched at least in a uniaxial direction, whereby voids are exhibited by interfacial peeling between the polyester resin and the incompatible resin. As the type of the incompatible resin as the sea component, a polyolefin resin such as a polyethylene resin, a polypropylene resin, and a polymethylpentene resin, and a polystyrene resin are preferably used (for example, refer to patent documents 1 to 3) and a polystyrene resin (for example, refer to patent documents 4 and 5). Among these, polypropylene resins are preferable in view of cavity exhibiting performance and cost performance.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 49-134755

Patent document 2: japanese patent laid-open No. 2-284929

Patent document 3: japanese patent laid-open No. 2-180933

Patent document 4: japanese patent publication No. 54-29550

Patent document 5: japanese patent laid-open No. 11-116716

Patent document 6: japanese patent publication No. 7-17779

Patent document 7: japanese patent laid-open No. 8-252857

Disclosure of Invention

Problems to be solved by the invention

In the case where a conventional polyester synthetic paper is used as a base film in various printing fields such as a label, tag, IC card, magnetic recording material, packaging material, electric insulating material, photosensitive material, graphic material, photo material, etc., there is a concern that the appearance may be impaired if the rigidity is insufficient. For example, the following problems occur: in the case of a label, the film is wrinkled when being sent out, and is greatly affected by the unevenness of the product when being wound around the product, thereby causing dishing and distortion. On the other hand, when the rigidity is too high, the stress applied to the bonded portion increases when the sheet is wound around a product, and the bonded portion may be easily peeled off. Therefore, it becomes important to exhibit rigid self-weight deflection within an appropriate range.

In addition, in the step of performing printing and the adhesive processing for adhering to a container or the like, since the polyester film has high insulation properties, it often occurs that: ink omission caused by adsorption of dust due to static electricity during various processes; poor feeding due to adsorption of films to each other by tribostatic electricity; and the like at the time of printing.

The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a void-containing polyester film which contains voids of an optimal size, is excellent not only in light weight but also in masking properties, whiteness, film forming properties, and thermal dimensional stability, has easy adhesion suitable as an information recording material or a printing material excellent in ink sealing properties, and has antistatic properties which hardly causes problems in processing steps.

Means for solving the problems

The present inventors have conducted intensive studies and as a result, found that: by controlling the specific gravity, the elastic modulus, and the thickness by using the amount of the polypropylene resin to be added and the conditions at the time of stretching, the occurrence of wrinkles and warping can be suppressed by controlling the dead weight deflection and the bending resistance. It was also found that the hollow polyester film was able to be obtained without wrinkling or distortion when the label was fed or wound while maintaining the shielding property and whiteness of the hollow polyester film.

It has also been found that a functional layer having excellent ink-sealing properties and antistatic properties can provide a film which is less likely to cause problems in a processing step in applications such as labels.

That is, the void-containing polyester film of the present invention may comprise the following constitution.

1. A hollow-core-containing polyester film comprising a layer A, which is a layer containing hollow-core inside, and a layer B, which is a layer containing a polyester resin containing inorganic particles,

the layer A comprises a composition containing a polyester resin and a polypropylene resin,

the film in at least one direction has a weight deflection of 100mm or less and 60mm or more,

at least one surface of the hollow polyester film has a surface resistivity of 1.0X10 ¹³ An easy-to-adhere layer having an omega/sq or less.

2. A polyester film containing voids, wherein,

the adhesive layer is formed by curing a composition containing an ion-conductive antistatic agent, a polyester resin, and a polycarbonate urethane resin.

3. The void-containing polyester film according to claim 1, wherein,

make other toThe polyester film contacts the surface of the easy-to-adhere layer at 50 ℃ and 1kg/cm ² After 3 days of holding under pressure, the other polyester film in contact with the surface of the easy-to-adhere layer was measured to obtain a surface resistivity of 1.0X10 ¹⁴ Omega/sq or more.

4. A void-containing polyester film having a residual area of 90% or more of a printed layer in the evaluation of adhesion to a UV ink.

5. The void-containing polyester film according to claim 1 or 2, wherein,

the layer A further contains 5 to 60% by weight of the recycled material of the hollow polyester film.

6. The void-containing polyester film according to claim 1 to 3,

the inorganic particles in the layer B are titanium oxide.

7. The void-containing polyester film according to any one of claims 1 to 4, which has an optical density of 0.55 or more (in terms of thickness 50 μm) and a color tone b value of 4 or less.

8. The void-containing polyester film according to any one of claims 1 to 5, which has an apparent density in the range of 0.8 to 1.2.

Effects of the invention

According to the present invention, a highly rigid synthetic paper which is less likely to cause wrinkles or distortion and which has an easy adhesion property suitable as an information recording material or a printing material having excellent ink sealing properties and an antistatic property which is less likely to cause problems in processing steps can be provided, which can be used for applications represented by labels having excellent shielding properties, whiteness and printability.

Detailed Description

(hollow polyester film)

In the hollow polyester film of the present invention, the polyester resin which is the main component of the layers a and B is a polymer synthesized from a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Typical examples of such polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene 2, 6-naphthalate, and polyethylene terephthalate is preferable from the viewpoints of mechanical properties, heat resistance, cost, and the like.

Further, as long as the object of the present invention is not impaired, these polyester resins may be copolymerized with other components. Specifically, examples of the copolymerization component include isophthalic acid, naphthalene dicarboxylic acid, 4-biphenyldicarboxylic acid, adipic acid, sebacic acid, and ester-forming derivatives thereof as dicarboxylic acid components. Further, as the diol component, diethylene glycol, hexamethylene glycol, neopentyl glycol, and cyclohexanedimethanol may be mentioned. Further, polyoxyalkylene glycol such as polyethylene glycol and polypropylene glycol can be mentioned. The copolymerization amount is preferably 10 mol% or less, more preferably 5 mol% or less, of the repeating units to be constituted.

The method for producing the polyester resin of the present invention includes: first, the above dicarboxylic acid or an ester-forming derivative thereof and the diol or an ester-forming derivative thereof are used as main starting materials, and the process is carried out by performing an esterification or transesterification reaction according to a conventional method, and then further performing a polycondensation reaction at a high temperature under reduced pressure.

The limiting viscosity of the polyester resin pellet of the present invention is preferably in the range of 0.50 to 0.9dl/g from the viewpoints of film forming property, recyclability and the like. More preferably in the range of 0.55 to 0.85 dl/g.

Next, the incompatible resin used in the present invention will be described. As thermoplastic resins that are incompatible with the polyester-based resins used in the present invention, the following resins are used: the polypropylene resin is uniformly mixed in a dispersed state into the polyester resin, and is peeled off at the interface with the base resin during stretching to form a void.

The preferable amount of the incompatible resin is also varied depending on the amount of voids to be formed, stretching conditions, etc. required for the finally obtained film, and is usually selected from the range of 3 mass% or more and less than 40 mass%, more preferably 5 to 30 mass% in terms of the ratio of the total amount of the resin composition. If the amount is 3% by mass or more, the amount of voids generated in the stretching step can be sufficiently ensured, and satisfactory light weight, flexibility, drawing property, writing property and the like can be obtained. On the other hand, if it is less than 40 mass%, a significant decrease in stretchability can be avoided, and excellent heat resistance, strength, and strength of stiffness (elastic force) can be exhibited.

In addition, a small amount of other polymers, antioxidants, heat stabilizers, delustrants, pigments, ultraviolet absorbers, optical brighteners, plasticizers, other additives, and the like may be contained in these polyester-based resins or polypropylene-based resins within a range that does not impair the object of the present invention. In particular, in order to suppress oxidative deterioration of the polypropylene resin, an antioxidant or a heat stabilizer is preferably contained. The types of the antioxidant and the heat stabilizer are not particularly limited, and examples thereof include hindered phenol type, phosphorus type, hindered amine type, and the like, which may be used alone or in combination. The amount to be added is preferably in the range of 1 to 50000 ppm.

In the present invention, the void-containing polyester film may contain inorganic particles in the polyester resin or in the incompatible resin as necessary for the purpose of improving the masking property and whiteness. Examples of the inorganic particles include silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, titanium oxide, zinc sulfide, and the like, and titanium oxide, calcium carbonate, and barium sulfate are preferable from the viewpoints of shielding property and whiteness. These inorganic particles may be used alone or in combination of two or more. These particles may be contained in the film by being added to the polyester resin or the incompatible resin in advance.

In the present invention, the method of mixing inorganic particles into the polyester resin or the incompatible resin is not particularly limited, and examples thereof include: a method of dry-mixing a polyester resin and an incompatible resin and then directly feeding the dry-mixed polyester resin and the incompatible resin into a film forming machine; and a method in which a polyester resin and an incompatible resin are dry-blended and then melt-kneaded by using various general kneaders to obtain a master batch.

The hollow-core-containing polyester film of the present invention has a laminated structure as a layer structure as follows: a laminated structure in which a layer (layer B) containing a polyester resin containing inorganic particles is laminated on both surfaces of a layer (layer a) containing a hollow and containing a composition containing a polyester resin and an incompatible resin. When the a layer containing the incompatible resin is exposed on the surface, some particles of the exposed incompatible resin may cause contamination of the roll, for example, in the process. When the layer a contains the recovered raw material, the layer B containing the inorganic pigment is covered, thereby preventing the whiteness from being lowered.

The ratio of the sum of thicknesses of the B layers laminated on both sides of the a layer is preferably in the range of 1 to 40%, more preferably 5 to 30%, relative to the thickness of the entire film from the viewpoints of void-exhibiting property and suppression of exposure of the incompatible resin. When the sum of the thicknesses of the B layers is 1% or more, exposure of the incompatible resin can be suppressed, which is preferable. On the other hand, when the sum of the thicknesses of the B layers is 40% or less, a cavity for obtaining sufficient lightweight and cushioning properties can be formed.

In the present invention, examples of the inorganic particles contained in the B layer include silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, titanium oxide, zinc sulfide, and the like, and titanium oxide, calcium carbonate, and barium sulfate are preferable, and titanium oxide is particularly preferable from the viewpoints of shielding property and whiteness. In addition, these inorganic particles may be used alone, or two or more kinds may be used in combination. These particles may be contained in the film by being added to the polyester resin in advance.

The upper limit of the average particle diameter of the inorganic particles contained in the layer B is preferably 5.0 μm, more preferably 3.0 μm, and particularly preferably 2.5 μm, from the viewpoint of print quality such as setting a print layer in post-processing. In view of the slidability and the shielding property in the film production step and the post-processing step, the lower limit value of the average particle diameter of the inorganic particles is preferably 0.1 μm, and particularly preferably 0.2 μm.

The amount of the inorganic particles added to the layer B is preferably 5 mass% or more and 40 mass% or less, and more preferably 7 to 30 mass%. When the amount is 5% by mass or more, the masking property and whiteness can be improved. On the other hand, when the amount of the additive is 40% by weight or less, deterioration of film forming property can be avoided, and deterioration of mechanical strength of the film can be avoided, which is preferable. The content of the inorganic particles in the layer B is preferably 1 mass% or more and 30 mass% or less, and more preferably 2 to 20 mass% relative to the entire film. When the amount of the additive is 1 mass% or more, the masking property and whiteness can be improved, and when the amount of the additive is 30 mass% or less, deterioration of the film forming property can be avoided, and significant deterioration of the mechanical strength of the film can be avoided.

The void-containing polyester film thus obtained can be used in layer a: the self-regenerated raw material (Japanese: self-regenerated raw material) contains an ear portion generated in the film forming step and a broken film generated due to a breakage problem or the like. The amount of the self-regenerating raw material to be added is preferably 5 to 60% by weight based on the total amount of the components in the layer a from the viewpoints of reduction in raw material cost, whiteness and film formability. In addition, although the layer B may contain a self-regenerating raw material, it is preferable not to contain the self-regenerating raw material from the viewpoints of deterioration of whiteness and exposure of an incompatible resin in the self-regenerating raw material.

(easy adhesive layer)

In order to improve the back surface mobility of the antistatic agent and the adhesion to UV ink, an easily adhesive layer formed by curing a composition containing an ion-conductive antistatic agent, a polycarbonate urethane resin, and a polyester resin is laminated on at least one side of the easily adhesive polyester film of the present invention. By providing such a layer, the ink sealing performance is improved, and problems such as dust adsorption due to electrification in various use steps can be suppressed, and further, adsorption of films to each other is suppressed, so that in addition to the effect due to the rigidity of the films, the handling performance is also improved in applications including printed labels and the like.

Although the adhesive layer is thought to be formed by curing a cationic antistatic agent or an anionic antistatic agent, a polycarbonate urethane resin, or a polyester resin, it is difficult to exhibit the chemical structure itself after curing, and therefore, it is considered that: the composition containing the cationic or anionic antistatic agent, the polycarbonate urethane resin and the polyester resin is cured. The easy-to-adhere layer may be provided on both sides of the polyester film base material, or may be provided on only one side of the polyester film base material, and may be provided with a different type of resin coating layer on the other side.

In the present invention, it is preferable that the surface resistivity of the surface of the easy-to-adhere layer of the easy-to-adhere polyester film is 1.0X10 ¹³ Antistatic properties of Ω/sq or less. If the surface resistivity of the surface of the easy-to-adhere layer is 1.0X10 ¹³ Omega/sq or less is preferable because dust adsorption by static electricity generated during rubbing and peeling does not occur, print quality is improved, and scattering of toner particles by a laser printer method does not occur. Further, if electrostatic adsorption of the films occurs, it is preferable to prevent occurrence of a phenomenon such as handling failure (japanese trouble) or overlapping feeding at the time of conveyance and feeding. The surface resistivity of the surface of the easy-to-adhere layer is more preferably 5.0X10 ¹² Omega/sq or less, more preferably 1.0X10 ¹² Omega/sq or less. On the other hand, if the surface resistivity is 1.0X10 ⁸ The polarity is preferably not too high because of the fact that the ratio of Ω/sq is not too high, and the adhesion to various inks and the like is good. Further preferably 5.0X10 ⁸ Omega/sq or more, particularly preferably 1.0X10 ⁹ Omega/sq or more.

The constituent components of the adhesive layer will be described in detail below.

(ion-conductive antistatic agent)

As the antistatic agent, an antistatic agent capable of suppressing mobility to the back surface of another article or the film itself in contact is preferable. For example, examples of the functional group include: nonionic systems such as sorbitol anhydride type, ether type, ester type, sorbitol type, glucose type, quaternary ammonium salt type, quaternary ammonium resin type, imidazoline type, a type コ, a type and other cationic systems, anionic systems such as alkyl sulfate type, alkyl phosphate type, sulfate type and other amphoteric surfactant type or polymer type, betaine type, amino acid type, amino sulfate type and other amphoteric systems, and the like.

Among the above antistatic agents, the counter ion of the quaternary ammonium salt group (Japanese 4. Sup. Frame-type) is not particularly limited as long as it is an anionic compound, and is preferably ethyl sulfate from the viewpoint of stability of surface resistivity, stability of coating liquid, ink sealing property, and suppression of mobility of the antistatic agent to other articles and the back surface, and can be suitably selected from halogen ions, mono-or polyhaloalkyl ions, nitrate ions, sulfate ions, alkyl sulfate ions, sulfonate ions, and alkyl sulfonate ions.

Further, there may be mentioned: polyethyleneimine, polydimethyldiallylammonium salt, polyalkylene polyamine dicyanodiamide ammonium condensate, polyvinyl pyridine halide (japanese) polymer, polyethylene (meth) acrylic acid alkyl quaternary ammonium salt, (meth) acrylamide alkyl quaternary ammonium salt, ω -chloro-poly (oxyethylene-polymethylene-alkyl quaternary ammonium salt), polyvinyl benzyl trimethylammonium salt, polystyrene cationic polymer, poly (meth) acrylic acid cationic polymer (methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate, trimethylaminoethyl chloride methacrylate, etc.), polyvinyl pyridine polymer, cyclic integral (japanese) polymer, linear integral (i) polymer, pendant (japanese: quaternary) polymer of aromatic vinyl monomer having 2 or more ammonium groups, main chain polymer of aromatic vinyl monomer having pyrrolidinium ring, etc. These polymers may be homopolymers or copolymers. For producing these polymers, known monomers capable of copolymerization can be used. From the viewpoint of controlling the mixing property of the coating liquid and the amount of the antistatic agent component present on the surface of the easy-to-adhere layer, an antistatic agent having a linear alkyl group is preferable, and an antistatic agent having a linear alkyl group and having a quaternary ammonium salt group is more preferable.

Therefore, in the antistatic agent having a linear alkyl group and having a quaternary ammonium salt group, the number of carbon atoms of the alkyl chain is preferably 10 to 25, more preferably 12 to 19, particularly preferably 14 to 18. The above range is preferable in consideration of the interaction with the molecule and the inhibition of the back mobility due to the molecular length.

The molecular weight of the quaternary ammonium salt group having a linear alkyl group is preferably 200 or more, and preferably 700 or less. More preferably 400 to 600. When the molecular weight is 200 or more, the surface resistivity can be exhibited, and the back surface movement can be suppressed with good balance. If the molecular weight is 700 or less, surface resistivity can be exhibited, and occurrence of aggregation due to interaction with a resin functional group can be suppressed at the time of coating liquid dispensing.

In addition, the molecular structure of the cationic antistatic agent having a nitrogen element may include at least 1 amide bond, urethane bond, or the like between the linear alkyl chain and the quaternary ammonium salt group.

(polycarbonate urethane resin)

The urethane resin having a polycarbonate structure in the present invention preferably has at least a urethane bond part structure derived from a polycarbonate polyol component and a polyisocyanate component, and further contains a chain extender as needed. In addition, by providing 3 or more terminal functional groups of any of the above-described raw material components constituting the molecular chain, a branched molecular chain structure can be formed after synthesis and polymerization, and thus a polyisocyanate having a branched structure can be appropriately introduced.

The lower limit of the number of terminal functional groups in the molecular chain is preferably 3, more preferably 4, in the polycarbonate urethane resin of the present invention and the urethane resin in the case of having a branched structure, depending on the branched structure. If the amount is 3 or more, the blocking resistance at the time of water adhesion can be improved, and thus it is preferable. The upper limit of the number of terminal functional groups in the molecular chain of the urethane resin having a polycarbonate structure in the present invention is preferably 6 depending on the branched structure thereof. If the amount is 6 or less, the resin can be stably dispersed in the aqueous solution, which is preferable.

The polycarbonate polyol component used for synthesizing and polymerizing the polycarbonate urethane resin in the present invention preferably contains an aliphatic polycarbonate polyol excellent in heat resistance and hydrolysis resistance. The aliphatic polycarbonate polyol includes aliphatic polycarbonate diols, aliphatic polycarbonate triols, and the like, and aliphatic polycarbonate diols are preferably used. Examples of aliphatic polycarbonate diols used for synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention include: aliphatic polycarbonate diols obtained by reacting one or more of glycols such as ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 1, 6-hexanediol, 1, 9-nonanediol, 1, 8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, and the like with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene, and the like.

The number average molecular weight of the polycarbonate polyol in the present invention is preferably 1000 to 3000. More preferably 1200 to 2900, and most preferably 1500 to 2800. If it is 1000 or more, the ink-tightness can be improved, so that it is preferable. If it is 3000 or less, the back surface mobility of the antistatic agent can be suppressed, which is preferable.

Examples of the synthetic and polymerized polyisocyanate used in the present invention for the polycarbonate urethane resin include: aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4, 4-dicyclohexylmethane diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2, 4-trimethylhexamethylene diisocyanate, or polyisocyanates obtained by preliminarily adding one or more of these compounds to trimethylolpropane or the like. In the case of using the above aromatic aliphatic diisocyanate, alicyclic diisocyanate, aliphatic diisocyanate, or the like, yellowing is not a problem, and is preferable. In addition, the coating film does not become too hard, and is preferable in that the surface resistivity is excellent by the antistatic agent.

The chain extender may be: glycols such as ethylene glycol, diethylene glycol, 1, 4-butanediol, neopentyl glycol and 1, 6-hexanediol, polyols such as glycerol, trimethylolpropane and pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine and piperazine, aminoalcohols such as monoethanolamine and diethanolamine, thioglycols such as thiodiethylene glycol, or water.

In order to form a branched structure in the urethane resin, for example, it is preferable to employ: and a method in which the polycarbonate polyol component, the polyisocyanate and the chain extender are reacted by setting an appropriate temperature and time, and then a compound having a hydroxyl group or an isocyanate group having 3 or more functions is added to further react.

Specific examples of the compound having a hydroxyl group of 3 or more functions include caprolactone triol, glycerin, trimethylolpropane, butanetriol, hexanetriol, 1,2, 3-pentanetriol, 1,3, 4-hexanetriol, 1,3, 4-pentanetriol, 1,3, 5-hexanetriol, 1,3, 5-pentanetriol, polyether triol and the like. Examples of the polyether triol include: and a compound obtained by polyaddition of 1 or 2 or more monomers such as ethylene oxide, propylene oxide, butylene oxide, tetrahydropyran, glycidyl ether, methyl glycidyl ether, t-butyl glycidyl ether, phenyl glycidyl ether, or the like, using 1 or 2 or more compounds having 3 active hydrogens such as an alcohol such as glycerin or trimethylolpropane, diethylenetriamine, or the like as an initiator.

As a specific example of the compound having an isocyanate group of 3 or more functions, a polyisocyanate compound having at least 3 isocyanate (NCO) groups in 1 molecule may be used. In the present invention, examples of the isocyanate compound having 3 or more functions include: biuret, cyanurate, adduct, and the like obtained by modifying an isocyanate monomer such as an aromatic diisocyanate, an aliphatic diisocyanate, an aromatic aliphatic diisocyanate, or an alicyclic diisocyanate having 2 isocyanate groups.

Examples of the aromatic diisocyanate include: 1, 3-phenylene diisocyanate, 4 '-diphenyl diisocyanate, 1, 4-phenylene diisocyanate, 4' -diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 4 '-toluidine diisocyanate, dianisidine diisocyanate, 4' -diphenyl ether diisocyanate, and the like.

Examples of aliphatic diisocyanates include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1, 2-propylene diisocyanate, 2, 3-butylene diisocyanate, 1, 3-butylene diisocyanate, dodecamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate, and the like.

Examples of the aromatic aliphatic diisocyanate include: xylylene diisocyanate, ω' -diisocyanate-1, 4-diethylbenzene, 1, 4-tetramethylxylylene diisocyanate, 1, 3-tetramethylxylylene diisocyanate, and the like.

Examples of the alicyclic diisocyanate include: 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate (alias: IPDI, isophorone diisocyanate), 1, 3-cyclopentane diisocyanate, 1, 3-cyclohexane diisocyanate, 1, 4-cyclohexane diisocyanate, methyl-2, 6-cyclohexane diisocyanate, 4' -methylenebis (cyclohexyl isocyanate), 1, 4-bis (isocyanatomethyl) cyclohexane, and the like.

The biuret is a self-condensate having a biuret bond formed by self-condensing an isocyanate monomer, and examples thereof include a biuret of hexamethylene diisocyanate.

The cyanurate means a terpolymer of isocyanate monomers, and examples thereof include: a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, a trimer of toluene diisocyanate, and the like.

The adducts are 3-or higher-functional isocyanate compounds obtained by reacting the above isocyanate monomers with 3-or higher-functional low-molecular active hydrogen-containing compounds, and examples thereof include: a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with toluene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, a compound obtained by reacting trimethylolpropane with isophorone diisocyanate, and the like.

As the chain extender having a functional group number of 3 or more, trimethylolpropane, pentaerythritol and other alcohols having a hydroxyl group of 3 or more are suitable in the description of the chain extender.

The adhesive layer in the present invention is preferably provided by a line coating method (japanese: bilrun コ) described later using an aqueous coating liquid. Therefore, the urethane resin of the present invention is expected to have water solubility or water dispersibility. The term "water-soluble or water-dispersible" as used herein means: dispersed in water or an aqueous solution containing less than 50 mass% of a water-soluble organic solvent.

In order to impart water dispersibility to the urethane resin, a (co) sulfonic acid (salt) group or a carboxylic acid (salt) group may be introduced into the urethane molecular skeleton. In order to maintain moisture resistance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group, and it is also preferable to suppress interaction (gelation) with a cationic antistatic agent. Nonionic groups such as polyoxyalkylene groups may be further introduced.

In order to introduce a carboxylic acid (salt) group into the urethane resin, for example, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutyric acid is introduced as a copolymerization component, and neutralization is performed by a salifying agent. Specific examples of the salt former include: trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-N-propylamine and tri-N-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of 2 or more.

In order to impart water dispersibility, when a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is preferably 3 to 60 mol%, and preferably 5 to 40 mol%, based on 100 mol% of the total polyisocyanate component of the urethane resin. When the above composition molar ratio is 3 mol% or more, water dispersibility can be obtained, which is preferable. In addition, when the above composition molar ratio is 60 mol% or less, the moisture and heat resistance can be obtained while maintaining the water resistance, and thus it is preferable.

In order to improve the strength, the urethane resin in the present invention may have a blocked isocyanate (Japanese-style) structure at the end.

(crosslinking agent)

In the present invention, a blocked isocyanate may be added as a crosslinking agent to the composition for forming an easy-to-adhere layer. Further, blocked isocyanates having 3 or more functions are preferable, and blocked isocyanates having 4 or more functions are particularly preferable. This suppresses the antistatic property of the surface of the easy-to-adhere layer and suppresses the back surface mobility of the antistatic agent.

In the blocked isocyanate of the present invention, a hydrophilic group may be introduced into the polyisocyanate as a precursor in order to impart water solubility or water dispersibility. Examples of the hydrophilic group include: (1) quaternary ammonium salts of dialkylaminoalcohols, quaternary ammonium salts of dialkylaminoalkylamines, and the like, (2) sulfonates, carboxylates, phosphates, and the like, (3) polyethylene glycols, polypropylene glycols, and the like, which are end-capped with an alkyl group. When the hydrophilic site is introduced, the composition becomes (1) cationic, (2) anionic, and (3) nonionic. Among them, other water-soluble resins are usually anionic, and therefore, anionic and nonionic resins that can be easily compatible are preferable. In addition, since the anionic property is excellent in compatibility with other resins and the nonionic property does not have an ionic hydrophilic group, it is also preferable in order to improve the wet heat resistance.

The anionic hydrophilic group preferably has: hydroxyl groups for introducing into the polyisocyanate, and carboxylic acid groups for imparting hydrophilicity. Examples include: glycolic acid, lactic acid, tartaric acid, citric acid, oxobutyric acid, oxovaleric acid, hydroxypivalic acid, dimethylol acetic acid, dimethylol propionic acid, dimethylol butyric acid, polycaprolactone having a carboxylic acid group. For neutralizing the carboxylic acid groups, organic amine compounds are preferred. Examples include: and hydroxyl-containing amines such as straight-chain or branched primary, secondary or tertiary amines having 1 to 20 carbon atoms, such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexyl amine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine, etc., cyclic amines such as morpholine, N-alkylmorpholine, pyridine, etc., monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, triethanolamine, etc.

The nonionic hydrophilic group is preferably a polyethylene glycol, polypropylene glycol, or polypropylene glycol having a single terminal end-capped with an alkyl group, and the repeating unit of ethylene oxide and/or propylene oxide is preferably 3 to 50, more preferably 5 to 30. When the repeating unit is small, the compatibility with the resin is poor, and when the repeating unit is large, the haze is high, and when the repeating unit is large, the adhesiveness at high temperature and high humidity is sometimes low. For the blocked isocyanate of the present invention, nonionic, anionic, cationic, and amphoteric surfactants may be added to improve water dispersibility. Examples thereof include nonionic surfactants such as polyethylene glycol and polyol fatty acid esters, anionic surfactants such as fatty acid salts, alkyl sulfates, alkylbenzenesulfonates, sulfosuccinates, and alkyl phosphates, cationic surfactants such as alkylamine salts and alkylbetaine, and surfactants such as carboxylate amine salts, sulfonate amine salts, and sulfate salts.

In addition, water may be contained in addition to water, and a water-soluble organic solvent may be contained. For example, an organic solvent used in the reaction may be added, or the organic solvent may be removed and other organic solvents may be added.

As a method for improving the adhesion, other disclosed compounds may be added. In order to improve the adhesion durability of the adhesive layer, the adhesion at high temperature and high humidity can be further improved even with other crosslinking agents. Specific examples of the crosslinking agent include urea-based, epoxy-based, melamine-based, oxazoline-based, and carbodiimide-based. In order to promote the crosslinking reaction, a catalyst or the like may be used as needed.

(polyester resin)

The polyester resin used for forming the easy-to-adhere layer in the present invention may be linear, and more preferably a polyester resin containing a dicarboxylic acid and a diol having a branched structure as constituent components. The dicarboxylic acid mentioned here is mainly terephthalic acid, isophthalic acid or 2, 6-naphthalene dicarboxylic acid, and examples thereof include aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and 2, 6-naphthalene dicarboxylic acid. Further, branched diols refer to diols having branched alkyl groups, and examples thereof include: 2, 2-dimethyl-1, 3-propanediol, 2-methyl-2-ethyl-1, 3-propanediol, 2-methyl-2-butyl-1, 3-propanediol, 2-methyl-2-propyl-1, 3-propanediol, 2-methyl-2-isopropyl-1, 3-propanediol, 2-methyl-2-n-hexyl-1, 3-propanediol, 2-diethyl-1, 3-propanediol, 2-ethyl-2-n-butyl-1, 3-propanediol, 2-ethyl-2-n-hexyl-1, 3-propanediol, 2-di-n-butyl-1, 3-propanediol, 2-n-butyl-2-propyl-1, 3-propanediol, 2-di-n-hexyl-1, 3-propanediol, and the like.

For polyester resins, it can be said that: the branched diol component as a more preferable embodiment is contained in the total diol component in a proportion of preferably 10 mol% or more, and more preferably 20 mol% or more. If it is 10 mol% or more, crystallinity does not become too high, and adhesion of the adhesive layer becomes good, which is preferable. The upper limit of the diol component in the total diol components is preferably 80 mol% or less, more preferably 70 mass%. If the amount is 80 mol% or less, the concentration of the oligomer as a by-product can be suppressed, and the transparency of the adhesive layer is good, which is preferable. The diol component other than the above-mentioned compounds is most preferably ethylene glycol. If it is small, diethylene glycol, propylene glycol, butylene glycol, hexylene glycol, 1, 4-cyclohexanedimethanol, or the like may be used.

The dicarboxylic acid as a constituent of the polyester resin is most preferably terephthalic acid or isophthalic acid. In addition to the dicarboxylic acid, in order to impart water dispersibility to the copolyester-based resin, 5-sulfoisophthalic acid and the like are preferably copolymerized in a numerical range of 1 to 10 mol%, and examples thereof include: sulfoterephthalic acid, 5-sulfoisophthalic acid, isophthalic acid-5-sodium sulfonate, and the like. The polyester resin containing a dicarboxylic acid having a naphthalene skeleton may be used, and the proportion of the amount thereof is preferably 5 mol% or less based on the total carboxylic acid components, or may be omitted, in order to suppress the decrease in adhesion with UV ink.

The constituent components of the polyester resin may include triols and tricarboxylic acids to such an extent that the properties of the polyester resin are not impaired.

The polyester resin may contain a polar group other than a carboxyl group. Examples thereof include sulfonate metal salts, phosphate groups, etc., and these may have 1 or 2 or more. The method of introducing a sulfonate group includes: in the range of 10 mol% or less, preferably 7 mol% or less, and more preferably 5 mol% or less of the total of the polycarboxylic acid component and the polyol component, a sulfonic acid metal salt-containing dicarboxylic acid or diol such as a metal salt of 5-sulfoisophthalic acid, 4-sulfonaphthalene-2, 7-dicarboxylic acid, 5- [ 4-sulfophenoxy ] isophthalic acid, or a metal salt of 2-sulfo-1, 4-butanediol, 2, 5-dimethyl-3-sulfo-2, 5-hexanediol is used. If the amount exceeds 10 mol%, hydrolysis resistance of the resin itself and water resistance of the coating film tend to be lowered.

The resin solid content concentration in the coating liquid is the sum of the solid content concentrations of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent. It is desirable to adjust the concentration of the resin solid content in the coating liquid at 5 to 17%. If the resin solid content is 5% or more, the thickness of the dried and cured adhesive layer will not be too thin, and various adhesive properties such as UV curable ink will be good, which is preferable. On the other hand, if the resin solid content concentration is 17% or less, sufficient crosslinking properties can be obtained when the crosslinking agent is contained, and migration of the antistatic agent to other articles or the back surface can be suppressed, and blocking phenomenon can be suppressed, which is preferable.

When the total of the solid components contained in the composition for forming an adhesive layer is 100% by mass, it is desirable to contain 1 to 8% by mass of the ion-conductive antistatic agent. If the prescribed range is satisfied, antistatic performance can be obtained. In addition, the antistatic component is preferably not moved to other articles or the back surface after the heating or the wet heat treatment.

The content of the urethane resin having a polycarbonate structure is preferably 5 to 50% by mass, based on 100% by mass of the total of the 3 solid contents of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent. When the content satisfies the above range, the affinity with various materials and UV ink is good, and the adhesion can be achieved, which is preferable. When the content is within the above-mentioned predetermined range, the antistatic agent is excellent in adhesion and antistatic property, and can inhibit the migration of the antistatic agent to other articles and the back surface even under wet heat resistance, and is preferable.

The upper limit of the content of the crosslinking agent is preferably 50% by mass, based on 100% by mass of the total of the 3 solid contents of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent. When the above range is satisfied, the crosslinking property of the adhesive layer is high, the affinity with UV ink or the like is good, and the antistatic property is also easily exhibited, which is preferable. Further, the strength of the adhesive layer in the moisture-resistant treatment can be maintained, and the mobility of the antistatic agent to other articles and the back surface can be suppressed, which is preferable.

The content of the polyester resin is preferably 10 to 70 mass% when the total of the solid contents of 3 types of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent is 100 mass%. When the above range is satisfied, the affinity with various materials and UV ink is good, and the adhesion can be achieved. In particular, the adhesion to the polyester film substrate is improved, and is preferable. In addition, in the case of using a cationic antistatic agent, gelation of the coating liquid due to interaction can be suppressed, which is preferable.

(additive)

In the present invention, a known additive such as a surfactant, a Ph adjuster, an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic slip agent, a pigment, a dye, organic or inorganic particles, an antistatic agent, a nucleating agent, or the like may be added to the easy-to-adhere layer in a range not to impair the effect of the present invention.

The above surfactant may be used in a manner that the effects of a solubilizer, a dispersant, an antifoaming agent, a wettability aid and the like are expected. The hydrophilic portion of the surfactant is divided into an ionic (cationic, anionic, amphoteric) portion and a nonionic portion. In the case of producing an aqueous coating material, a polyester film used as a base material is used because of its low surface energy and lack of wettability. Therefore, the aqueous coating composition is often used as a surface tension adjusting and wettability auxiliary agent for aqueous coating materials. The surfactant is not particularly limited, but is preferably a surfactant capable of reducing the surface tension of the coating liquid to 50dyne/cm or less, preferably 40dyne/cm or less, and promoting wetting of the polyester film, and examples thereof include: alkyl trimethylammonium salts, dialkyl dimethylammonium salts, alkyl benzyldimethylammonium salts, monoalkyl sulfates, alkyl polyoxyethylene sulfates, alkylbenzenesulfonates, monoalkyl phosphates, alkyl dimethylamine oxides, alkyl carboxybetaines, polyoxyethylene alkyl ethers, fatty acid sorbitan esters, alkyl polyglucosides, fatty acid diethanolamides, alkyl monoglycidyl ethers, and the like, with polyether modified silicones being preferred.

When the total mass of the solid components in the coating liquid is 100% by mass, the amount of the surfactant added is preferably 0.1% by mass or more and 1.0% by mass or less. More preferably, the content is in the range of 0.2 to 0.8 mass%. If it is 0.1 mass% or more, the wettability effect as a surfactant can be obtained, and is preferable. In addition, if it is 1.0 mass% or less, the adhesion can be maintained satisfactorily, and it is preferable.

Among the above additives, a pH adjuster is also sometimes used. As the acid for adjusting the pH, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as oxalic acid, formic acid, citric acid, and acetic acid can be used, and examples of the alkali adjustment include sodium carbonate, sodium bicarbonate, and sodium phosphinate. In the adjustment of the aqueous coating material, the degree of neutrality is preferably adjusted to a pH in the range of 5 to 9, and more preferably adjusted to a pH of 6 to 8.5. If the pH is 5 or less, there is a concern that the coating machine is corroded, and in the case where a blocked isocyanate is selected as the crosslinking agent, the blocking agent release promoting effect is lowered. In addition, if the pH is 9 or more, the polyester resin used as the resin binder is hydrolyzed, and the adhesiveness and durability are impaired, which is not preferable.

In order to reduce the glossiness of the easy-to-adhere layer, inactive particles may be contained in the easy-to-adhere layer.

In order to impart slidability, matting property, ink absorbency, and the like to the surface, lubricant particles may be contained in the easy-to-adhere layer. The particles may be inorganic particles or organic particles, and are not particularly limited, but examples thereof include: (1) Silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium oxide, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, barium sulfate, and the like, (2) organic particles of acrylic acid or methacrylic acid, vinyl chloride, vinyl acetate, nylon, styrene/acrylic acid, styrene/butadiene, polystyrene/acrylic acid, polystyrene/isoprene, methyl methacrylate/butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, polyester, and the like, and silica is particularly preferably used for imparting moderate sliding properties to the easy-to-adhere layer.

The average particle diameter of the inactive particles is preferably 0.1 μm or more and 2.4 μm or less, and more preferably 0.3 to 2.0 μm. If the average particle diameter of the inactive particles is 0.04 μm or more, an excessive increase in the glossiness of the film surface can be suppressed. On the other hand, if the particle size is 2.4 μm or less, the particles can be prevented from falling off from the adhesive layer, and powder falling during various steps such as film running can be avoided.

The average particle diameter may be determined from the results of morphological observation by a microscope using a scanning electron microscope, a transmission electron microscope, or the like. Specifically, in these microscopic observations, an average value of diameters of 20 particles arbitrarily selected was employed. The shape of the particles is not particularly limited as long as the object of the present invention is satisfied, and spherical particles or irregular non-spherical particles may be used. The particle size of the irregular particles can be calculated as the equivalent circle diameter. The equivalent circle diameter is a value obtained by dividing the area of the observed particle by pi, calculating the square root, and multiplying by 2 times.

In the case where the gloss of the easy-to-adhere layer is to be increased, it is preferable that the easy-to-adhere layer contains no particles.

(film-forming of hollow polyester film)

Next, a film forming method of the hollow polyester-based film of the present invention will be described, but is not particularly limited. For example, a mixture containing the above composition is dried by a usual method, and then melt-extruded in a sheet form from a T-shaped tube head, and then brought into close contact with a casting drum by an electrostatic application method or the like, and cooled and solidified to obtain an unstretched film. Next, the unstretched film is subjected to stretching and orientation, and a method of stretching the unstretched film in the longitudinal direction and then stretching the unstretched film in the transverse direction, which is the most commonly used sequential biaxial stretching method, will be described below. First, in the longitudinal stretching step in the longitudinal direction, the film is heated and stretched between two or more rolls having different peripheral speeds to 1.0 to 5.0 times. The heating method may be a method using a heating roller, a method using a non-contact heating medium, or a combination of these methods, and the temperature of the film is preferably in the range of (Tg-10 ℃) to (Tg+50℃). Next, the uniaxially stretched film is introduced into a tenter, and stretched at a temperature of (Tg-10 ℃) of Tm-10 ℃ or lower to 1.0 to 6.0 times in the width direction, thereby obtaining a biaxially stretched film. Wherein Tg is the glass transition temperature of the polyester resin, and Tm is the melting point of the polyester. The film obtained by the above-described operation is preferably heat-treated as needed, and the treatment temperature is preferably in the range of (Tm-60 ℃) Tm.

The easy-to-adhere layer may be provided after the film is manufactured or in the manufacturing process. In particular, from the viewpoint of productivity, it is preferable to form the easy-to-adhere layer by applying the coating liquid to at least one side of the PET film after the film production process, that is, after the stretching or uniaxial stretching.

The method for applying the coating liquid to the polyester film may be any known method. Examples thereof include reverse roll coating, gravure coating, kiss coating, die coating, roll brushing, spray coating, air knife coating, bar coating, tubular doctor blade (japanese) coating, dip coating, curtain coating, and the like. These methods may be applied alone or in combination.

In the present invention, the thickness of the adhesive layer may be appropriately set in the range of 0.001 to 2.00. Mu.m. In order to achieve both workability and adhesion, the range of the polymer is preferably 0.01 to 1.00. Mu.m, more preferably 0.02 to 0.80. Mu.m, and still more preferably 0.05 to 0.50. Mu.m. The thickness of the adhesive layer is preferably 0.001 μm or more, since the adhesion is good. If the thickness of the easy-to-adhere layer is 2.00 μm or less, other articles or the back surface of the antistatic agent can be suppressed from moving, which is preferable.

The void-containing polyester film of the present invention preferably has an optical density (OD value) of 0.55 or more, more preferably 0.6 or more. When the OD value is 0.55 or more, sufficient shielding properties can be obtained, and when the ink is used for a label or the like, sharpness of an image at the time of printing can be maintained well, and a value can be added to a commodity. The upper limit of the OD value is preferably 1.5. When 1.5 or less, the whiteness is not saturated, and a sufficient whiteness can be exhibited, which is also preferable in terms of cost. The OD value is a value obtained by a measurement method described in the evaluation method described later, and is calculated by conversion of 50. Mu.m.

The void-containing polyester film of the present invention preferably has a color tone b value of 4.0 or less, more preferably 3.0 or less. When the b value is 4.0 or less, good whiteness can be exhibited, and when a label or the like is produced, high definition can be maintained after printing, and a value can be added to a commodity. The lower limit of the hue b value is preferably-5.0. When the b value is-5.0 or more, the blue feel of the film can be prevented from becoming strong, and the resolution can be satisfied in a good balance when the film is used as a printing substrate.

In the hollow-core-containing polyester film of the present invention, when used as a roll label, the deflection due to the self weight of a sample having a length of 130mm is 100mm or less and 60mm or more, whereby it is possible to realize: the film can be used as a label which does not cause wrinkles or distortion when the label is fed out or wound around a product. If the thickness is 100mm or less, the rigidity can be sufficiently maintained, and even after the label is attached to a product, the label can be kept in an upright state, and an excellent appearance can be imparted to the label. For example, it is possible to avoid wrinkling when the label is fed out, and to avoid problems such as sagging and distortion, without being greatly affected by the irregularities of the product when the label is wound around the product.

On the other hand, if the weight deflection is 60mm or more, excessive increase in rigidity can be avoided, increase in stress applied to the bonded portion when the product is wound can be avoided, and the bonding can be suppressed from being easily peeled off. Therefore, it becomes important that the self-weight deflection is in an appropriate range. The self-weight deflection can be effectively adjusted by the specific gravity, thickness, and elastic modulus in the deflection direction.

The thickness of the hollow polyester film of the present invention is preferably 20 to 300. Mu.m, more preferably 50 to 120. Mu.m. The influence of the thickness on the self-weight deflection is large, and by increasing the thickness, the film can have bending rigidity, and the self-weight deflection can be suppressed to a small level, and if the thickness is kept at a necessary level or more, the self-weight deflection becomes small, and the handling property as a label becomes poor.

The elastic modulus in the deflection direction of the hollow-core-containing polyester film of the present invention is preferably 2500MPa or more, more preferably 3500MPa or more, although it depends on the thickness of the film. When the elastic modulus is 2500MPa or more, wrinkling during transportation of the roll label can be suppressed. Even when the thickness of the film cannot be increased, the elastic modulus of the film can be increased to adjust the film to an appropriate amount of self-weight deflection. The elastic modulus can be effectively adjusted by the stretching ratios in the longitudinal direction and the width direction and the heat treatment conditions.

The apparent density of the void-containing polyester film of the present invention is preferably 0.8g/cm ³ Above and 1.3g/cm ³ Hereinafter, more preferably 0.90g/cm ³ Above and 1.2g/cm ³ The following is given. At an apparent density of 0.8g/cm ³ In the above case, excessive increase of voids can be suppressed, and the operability of light control can be exhibited at the time of post-processing such as printing processing and at the time of use. At 1.3g/cm ³ In the following cases, sufficient lightweight and cushioning properties can be obtained.

In addition, the influence on the deflection by weight was 1.3g/cm ³ In the following cases, even with the same thickness, the weight is prevented from becoming large, and the weight deflection can be prevented from becoming excessively large. The apparent density is a value obtained by a measurement method described in an evaluation method described later.

In one embodiment, the present invention may be recovered and used as a recycled polyester raw material, and for example, a film may be formed from the recycled raw material.

Examples

The present invention will be specifically described below with reference to examples. The present invention is not limited to the examples described below. The evaluation items in examples and comparative examples were measured by the following methods.

(1) Limiting viscosity [ eta ]

The solution was dissolved in a mixed solvent of phenol/tetrachloroethane=60/40 (mass ratio), and the measurement was performed at 30 ℃ using an ostwald viscometer. The measurement was performed 3 times, and the average value was obtained.

(4) Apparent density of

4 pieces of square 5.0cm square were cut out from the film, 4 pieces were overlapped, and 10 points were measured using a micrometer at a position where the total thickness was changed by a 4-digit effective number, and the average value of the thicknesses of the 4 pieces overlapped was obtained. The effective number was rounded to 3 bits by dividing the average by 4 as the average thickness of each piece (t: μm). The mass (w: g) of 4 pieces of the same sample was measured with an automatic plate-loading balance in 4-digit significant numbers, and the apparent density was determined by the following formula. The apparent density was rounded to 3 significant digits.

Apparent Density (g/cm) ³ )＝w/(5.0×5.0×t×10 ^-4 ×4)

(5) Optical density (OD value)

The film was measured using a transmission densitometer "Ihac-T5" manufactured by itone electronics corporation, and converted to a film thickness of 50 μm. The higher the value of the optical density, the greater the shielding property.

(6) Tone b value

The color tone b value was measured by JIS-8722 using a color difference meter (ZE 6000) manufactured by Nippon electric color Co., ltd, and converted into a film thickness of 50. Mu.m. The smaller the b value, the higher the whiteness and the weaker the yellow feeling.

(7) Deflection by self weight

A specimen (10) having a deflection direction of 150mm and a width of 20mm was prepared, and the specimen was fixed by a magnet (13) so that the sagging length from the horizontal plane became 130 mm. The distance between the front end of the sagging portion of the film and the vertical direction of the film fixing portion at this time is referred to as the dead weight deflection.

(8) Bending resistance

The bending resistance was calculated by using the weight deflection obtained by the above method as δ and using a mathematical formula. The average dead weight deflection of 3 sheets was determined as δ.

Br＝WL ⁴ /8δ

Br: bending resistance (mN cm)

W: gravity per unit area (mN/cm) of test piece ² )

L: length of test piece (cm)

Delta: dead weight deflection (cm)

(9) Antistatic surface resistivity

The film was cut into 3 pieces of square 5.00cm square, and the square was used as a sample. The surface resistivity was measured using a surface resistance measuring device (HIRESTA MCP-HT800, manufactured by Nittoseiko Analytech) under conditions of an applied voltage of 500V, 23 ℃ and 65% humidity according to JIS K6911, and the average value was obtained.

(10) Adhesion to UV ink

UV ink [ T ] is used for the easy-to-adhere layer of the easy-to-adhere polyester film&KTOKA Co., ltd., trade name "BEST CURE UV161 blue S"]Manufactured by the Ming's printer (product name "RI Tester"):]printing was performed, and then the film coated with the ink layer was irradiated with 40mJ/cm using a high-pressure mercury lamp ² The ultraviolet curable ink is cured by ultraviolet rays of (a). Next, a cellophane adhesive tape (CT 405 AP-24) made of nichiba was used, and the tape was cut out to have a width of 24mm and a length of 50mm, and was completely attached by a portable rubber roll so that air was not mixed into the surface of the ink layer. Then, the cellophane adhesive tape was peeled off vertically, and the remaining area of the printed layer was observed in a region of 24mm×50mm, and the judgment was made according to the following criteria.

O: the remaining area of the printed layer was 99% or more of the entire area, and the printed layer was acceptable.

Delta: the remaining area of the printed layer was 90% or more and less than 99% of the whole, and was found to be acceptable.

X: the remaining area of the printed layer was less than 90% of the total area, and the printed layer was found to be unacceptable.

Films of the following examples and comparative examples were produced using the raw materials shown in table 1, the following pellets and the coating liquid.

(cationic antistatic agent)

An esterification reaction was carried out at 100℃for 10 hours in a nitrogen atmosphere using 116g of N, N-dimethyl-1, 3-propanediamine and 285g of stearic acid having 17 carbon atoms, tetrahydrofuran was added as a quaternizing solvent, a predetermined amount of dimethyl sulfate was added to the target amine, and the reaction was carried out at 70℃for about 10 hours. After the reaction, the solvent was distilled off under reduced pressure, and then isopropyl alcohol was added thereto to adjust the concentration of the desired solid content, thereby obtaining an isopropyl alcohol solution of the cationic antistatic agent having quaternary ammonium ethyl sulfate.

(polymerization of urethane resin having polycarbonate Structure)

22 parts by mass of 4, 4-dicyclohexylmethane diisocyanate and a number average molecular weight were charged into a four-necked flask equipped with a stirrer, a Dimarote condenser, a nitrogen gas introduction tube, a silica gel drying tube and a thermometer20 parts by mass of polyethylene glycol monomethyl ether in an amount of 700, 53 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2100, 5 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were stirred under a nitrogen atmosphere at 75℃for 3 hours, and it was confirmed that the reaction solution reached a predetermined amine equivalent. Then, 16 parts by mass of a polyisocyanate compound having an isocyanurate structure (produced by Asahi chemical Co., ltd., DURANATE TPA, 3 function) was charged as a raw material, and the mixture was stirred under a nitrogen atmosphere at 75℃for 1 hour to confirm that the reaction solution had reached a predetermined amine equivalent. Then, the temperature of the reaction solution was lowered to 50℃and 7 parts by mass of methyl ethyl ketoxime was added dropwise. And cooling the reaction solution to 40 ℃ to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a high-speed stirring homogenizer, and the temperature was adjusted to 25℃for 2000 minutes ^-1 The polyurethane prepolymer solution was added while stirring and mixing, and water was dispersed. Then, a portion of the acetone and water was removed under reduced pressure, whereby a solution of 35 mass% of the solid content of the water-dispersible urethane resin was prepared.

(polymerization of blocked isocyanate crosslinking agent)

100 parts by mass of a polyisocyanate compound having an isocyanurate structure (DURANATE TPA, manufactured by Asahi chemical Co., ltd.), 55 parts by mass of propylene glycol monomethyl ether acetate, 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) and the like were placed in a flask equipped with a stirrer, a thermometer and a reflux condenser, and the flask was kept at 70℃for 4 hours in a nitrogen atmosphere. Then, the temperature of the reaction solution was lowered to 50℃and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm the disappearance of the absorption of isocyanate groups, and 210 parts by mass of water was added to obtain an aqueous dispersion having a solid content of 40% by mass of an oxime-blocked isocyanate crosslinking agent. The blocked isocyanate crosslinking agent has a functional group number of 3 and an NCO equivalent of 170.

(polymerization of polyester resin)

Into a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux cooler, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate and 5-sodium isophthalate sulfonate (Japanese) 14.8 parts by mass of Yi Zhi Ji Zhi Di Lou, 185 parts by mass of neopentyl glycol, 188 parts by mass of ethylene glycol and 0.2 part by mass of tetra-n-butyl titanate were added, and transesterification was carried out at 160 to 220℃for 4 hours. Then, the temperature was raised to 255℃and the reaction system was gradually depressurized, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin. The resulting copolyester resin was pale yellow transparent. The reduced viscosity of the copolyester resin was measured and found to be 0.40dl/g. The glass transition temperature based on DSC was 65 ℃.

[ production of titanium oxide masterbatch pellet (M1) ]

50 mass% of anatase type titanium dioxide having an average particle diameter of 0.3 μm (electron microscopic method) was mixed with 50 mass% of a polyethylene terephthalate resin having a melt viscosity of 200 Pa.s, and the resultant was fed to a vented twin screw extruder and kneaded to prepare master batch pellets (M1) containing titanium oxide.

Example 1

The solid content in the coating liquid of the compound constituting the coating layer is as follows.

[ constitution of coating layer (coating liquid A) ]

The total of the solid components contained in the coating layer was set to 100 mass%.

Cationic antistatic agent: 6.2 mass%

Urethane resin having a polycarbonate structure: 25.5% by mass

Blocked isocyanate crosslinker: 10.9% by mass

Polyester resin: 54.6% by mass

Silicone-based surfactant: 0.4 mass%

pH adjuster (sodium bicarbonate): 2.4% by mass

The mass ratio of the solid components of the urethane resin/the crosslinking agent/the polyester resin was 28/12/60.

[ production of unstretched film ]

The raw material for the hollow polyester A layer was prepared by mixing 74% by mass of a polyethylene terephthalate resin having a melt viscosity of 200 Pa.s, 21% by mass of a polypropylene resin having a melt viscosity of 500 Pa.s, and 5% by mass of the above-mentioned master batch pellet (M1) containing titanium oxide, followed by vacuum drying. On the other hand, the above-mentioned master batch pellets (M1) containing titanium oxide were mixed with 70 mass% of polyethylene terephthalate resin having a melt viscosity of 200 Pa.s to prepare a raw material for the polyester B layer containing inorganic particles by vacuum drying. These raw materials were fed to respective extruders, melted at 280℃and laminated in the order of B/A/B so that the thickness ratio became 10/80/10 by means of a feed head, and then extruded from a T die onto a cooling drum adjusted to 30℃to produce 2 kinds of 3-layer unstretched films.

[ production of hollow-containing polyester film ]

The unstretched film a was uniformly heated to 70℃using a heated roll and stretched longitudinally to 1.4 times between two pairs of nip rolls having different peripheral speeds. In this case, as an auxiliary heating device for the film, an infrared heating heater (rated value of 20W/cm) having a gold reflective film in the middle of the nip roller was provided so as to face both sides of the film and be 1cm away from the film surface, and the film was heated. The uniaxially stretched film thus obtained was coated on one side by the reverse gravure coating method using the coating composition described above so that the WET coating amount was 7g/m ² After the coating was carried out in the manner of (a) and then was introduced into a tenter, heated to 140℃and stretched transversely to 4.0 times, the width was fixed and heat-setting treatment was carried out at 240℃and further relaxed by 3% in the width direction at 210℃to obtain a void-containing polyester film (B/A/B) having a thickness of 50. Mu.m. The evaluation results of example 1 are shown in Table 1. As shown in Table 1, since the film of example 1 uses the raw resin satisfying the above-mentioned elements (1) to (3), the dispersion particle size of the polypropylene resin was controlled to be an appropriate size, 20. Mu.m ² The above number of voids is also large, and the apparent density, OD (shading), hue b, heat shrinkage (MD and TD), and film forming properties are all good. Details are shown in the table below.

Example 2

A void-containing polyester film having a thickness of 50 μm was obtained in the same manner as in example 1 except that the amount of the polypropylene resin added to the unstretched film was 30% by mass and the transverse stretching ratio was 3.8 times.

Example 3

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 1 except that the longitudinal stretching ratio was 3.2 times.

Example 4

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3, except that the solid content of the compound constituting the coating layer was changed as described below.

[ constitution of coating layer (coating liquid B) ]

The total of the solid components contained in the coating layer was set to 100 mass%.

Cationic antistatic agent: 6.2 mass%

Urethane resin having a polycarbonate structure: 36.4 mass%

Blocked isocyanate crosslinker: 0 mass%

Polyester resin: 54.6% by mass

Silicone-based surfactant: 0.4 mass%

pH adjuster (sodium bicarbonate): 2.4% by mass

The mass ratio of the solid components of the urethane resin/the crosslinking agent/the polyester resin was 40/0/60.

Example 5

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3 except that the amount of the polypropylene resin added to the unstretched film was 15% by mass.

Example 6

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3 except that the amount of the polypropylene resin added to the unstretched film was 30% by mass.

Example 7

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 1 except that the transverse stretching ratio was set to 3.8 times.

Example 8

A hollow polyester film having a thickness of 100 μm was obtained in the same manner as in example 3.

Example 9

A hollow-containing polyester film having a thickness of 100 μm was obtained in the same manner as in example 1, except that the longitudinal stretching magnification was 2.5 times and the transverse stretching magnification was 2.5 times.

Example 10

A hollow-core polyester film having a thickness of 100 μm was obtained in the same manner as in example 1, except that the amount of the polypropylene resin added to the unstretched film was 15% by mass and the longitudinal stretching ratio was 3.5 times.

Example 11

A hollow-core polyester film having a thickness of 100 μm was obtained in the same manner as in example 3, except that the amount of the polypropylene resin added to the unstretched film was 30% by mass.

Comparative example 1

A void-containing polyester film having a thickness of 50 μm was obtained in the same manner as in example 1 except that the transverse stretching ratio was set to 3.8 times.

Comparative example 2

A void-containing polyester film having a thickness of 50 μm was obtained in the same manner as in example 1, except that the longitudinal stretching magnification was 3.2 times and the transverse stretching magnification was 4.0 times.

Comparative example 3

A polyester film having a thickness of 75 μm was obtained in the same manner as in example 1.

Comparative example 4

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 1, except that the longitudinal stretching magnification was 2.5 times and the transverse stretching magnification was 2.5 times.

Comparative example 5

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3, except that the solid content of the compound constituting the coating layer was changed as described below.

[ constitution of coating layer (coating liquid C) ]

The total of the solid components contained in the coating layer was set to 100 mass%.

Cationic antistatic agent: 0 mass%

Urethane resin having a polycarbonate structure: 27.2% by mass

Blocked isocyanate crosslinker: 11.6% by mass

Polyester resin: 58.2 mass%

Silicone-based surfactant: 0.4 mass%

pH adjuster (sodium bicarbonate): 2.6% by mass

The mass ratio of the solid components of the urethane resin/the crosslinking agent/the polyester resin was 28/12/60.

Comparative example 6

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3, except that the solid content of the compound constituting the coating layer was changed as described below.

[ constitution of coating layer (coating liquid D) ]

The total of the solid components contained in the coating layer was set to 100 mass%.

Cationic antistatic agent: 6.2 mass%

Urethane resin having a polycarbonate structure: 0 mass%

Blocked isocyanate crosslinker: 36.4 mass%

Polyester resin: 54.6% by mass

Silicone-based surfactant: 0.4 mass%

pH adjuster (sodium bicarbonate): 2.6% by mass

The mass ratio of the solid components of the urethane resin/the crosslinking agent/the polyester resin was 0/40/60.

Comparative example 7

A void-containing polyester film having a thickness of 75 μm was obtained in the same manner as in example 3, except that the solid content of the compound constituting the coating layer was changed as described below.

[ constitution of coating layer (coating liquid E) ]

The total of the solid components contained in the coating layer was set to 100 mass%.

Cationic antistatic agent: 6.2 mass%

Urethane resin having a polycarbonate structure: 63.7% by mass

Blocked isocyanate crosslinker: 27.3% by mass

Polyester resin: 0 mass%

Silicone-based surfactant: 0.4 mass%

pH adjuster (sodium bicarbonate): 2.6% by mass

The mass ratio of the solid components of the urethane resin/the crosslinking agent/the polyester resin was 70/30/0.

Comparative example 8

A hollow-containing polyester film having a thickness of 100 μm was obtained in the same manner as in example 1 except that the transverse stretching ratio was set to 3.8 times.

Comparative example 9

A hollow-containing polyester film having a thickness of 100 μm was obtained in the same manner as in example 1 except that the longitudinal stretching ratio was set to 3.5 times.

The deflection of comparative examples 1 to 4 was outside the range of the present invention, and wrinkles and adhesion delamination occurred. The surface resistivity of comparative examples 5 to 7 was outside the range of the present invention, and dust adsorption by static electricity occurred at the time of printing or the like, and the printing quality was poor. In comparative examples 8 and 9, the amount of deflection was outside the range of the present invention, and adhesion delamination occurred.

Industrial applicability

According to the present invention, even when an inexpensive polypropylene resin is used as a void-generating agent, a void-containing polyester film having excellent light weight, excellent cushioning properties, shielding properties, whiteness, thermal dimensional stability and film forming properties can be provided.

Claims (8)

1. A hollow-core-containing polyester film comprising a layer A, which is a layer containing hollow-core inside, and a layer B, which is a layer containing a polyester resin containing inorganic particles,

the layer A comprises a composition containing a polyester resin and a polypropylene resin,

the film in at least one direction has a weight deflection of 100mm or less and 60mm or more,

at least one side of the hollow polyester film has a surface resistivity of 1.0X10 ¹³ An easy-to-adhere layer having an omega/sq or less.

2. The void-containing polyester film according to claim 1, wherein,

the easy-to-adhere layer is formed by curing a composition containing an ion-conductive antistatic agent, a polyester resin and a polycarbonate urethane resin.

3. The void-containing polyester film according to claim 1 or 2, wherein,

contacting the other polyester film with the surface of the easy-to-adhere layer at 50deg.C, 1kg/cm ² After 3 days of holding under pressure, the other polyester film in contact with the surface of the easy-to-adhere layer was measured to obtain a surface resistivity of 1.0X10 ¹⁴ Omega/sq or more.

4. The void-containing polyester film according to any one of claim 1 to 3,

in the evaluation of adhesion to UV ink, the remaining area of the printed layer was 90% or more.

5. The void-containing polyester film according to any one of claims 1 to 4,

the layer A further contains 5 to 60% by weight of the recycled material of the hollow polyester film.

6. The void-containing polyester film according to any one of claims 1 to 5,

the inorganic particles in the layer B are titanium oxide.

7. The void-containing polyester film according to any one of claims 1 to 6, which has an optical density of 0.55 or more in terms of a thickness of 50 μm and a color tone b value of 4 or less.

8. The void-containing polyester film according to any one of claims 1 to 7, which has an apparent density in the range of 0.8 to 1.2.