HK1207035A1 - Biaxially stretched polyester film for mold release - Google Patents

Abstract

A biaxially stretched polyester film which has a mold release layer on at least one surface of a polyester film base. This biaxially stretched polyester film for mold release is characterized in that: the mold release layer contains 100 parts by mass of an acid-modified polyolefin resin, wherein the ratio of the acid-modified component is 1-10% by mass, and 1-50 parts by mass of a crosslinking agent; the biaxially stretched polyester film has an elongation at break of 350-500% and a breaking stress of 10-30 MPa at 120°C; and the biaxially stretched polyester film has a thickness unevenness of 5% or less.

Description

Biaxially stretched polyester film for mold release

Technical Field

The present invention relates to a biaxially stretched polyester film for mold release, and more particularly to a biaxially stretched polyester film for mold release having excellent mold release properties useful as a process paper to be peeled after molding.

Background

Polyester films represented by polyethylene terephthalate are widely used in industrial fields and industrial fields because of their excellent mechanical properties, heat resistance, and chemical resistance. Among them, films that can be used as release materials have been in wide use in the field of electronics and motors, particularly as process materials and protective materials, and the demand for such films has been remarkably increasing in recent years.

Examples of uses of the release material include a protective material or a process material used for an adhesive surface of an adhesive material such as an adhesive sheet or an adhesive tape, a process material used for manufacturing a printed wiring board, a flexible printed wiring board, a multilayer printed wiring board, or the like, and a protective material for a polarizing plate or a phase difference plate of a liquid crystal display device member, and the release material is also used for molding a structure.

The molding of the structure, which is an example of the use of the release material, includes, for example, in-mold molding in which a printed film is inserted into a mold and decorated at the same time as injection molding, and this molding method is widely used for molding interior parts of automobiles, housings of electronic devices, and the like because it enables beautiful decoration at low cost.

In-mold molding is roughly classified into two types, one in which the film is peeled off after injection molding, and the other in which the film is integrated with the molded article and the film remains in the molded article after injection molding. In the latter method, since the film needs to follow a complicated three-dimensional shape, an acrylic film having extremely high moldability is used.

On the other hand, the former method is widely used because a stretched film of polyester is high in heat resistance, dimensional stability, printability, thickness accuracy and low in cost. However, stretched polyester films may have insufficient moldability and releasability. Accordingly, patent document 1 discloses an unstretched polyester film containing a stretching agent and having a stress of 2 to 20MPa when stretched at 400% in an atmosphere of 120 ℃.

In order to use a polyester film as a release material, generally, a polyester film is used as a base material, and a release layer containing a release agent is laminated to impart releasability to the film. As a method for laminating a release layer, many methods for coating a film surface have been proposed. Lamination by coating is an effective method from the viewpoint of making the release layer thin.

For example, patent document 2 discloses a method of laminating vinyl group-containing polydimethylsiloxane using a solvent-based coating agent, and patent document 3 discloses a method of laminating a fluorine compound.

Further, there is a method of laminating a wax (patent document 4), a low molecular weight organosilicon compound, and a fluorine-based surfactant as a release layer using an aqueous coating agent, but the obtained release material has a problem that the release agent is transferred to an adherend when peeled off, and functions of the adherend, for example, adhesiveness, are lowered.

Accordingly, patent documents 5 and 6 disclose a method of laminating silicone resins, patent document 7 discloses a method of laminating fluorine-containing resins, and patent documents 8 and 9 disclose methods of laminating polyolefin resins having a specific composition.

Documents of the prior art

Patent document

Patent document 1, Japanese patent application laid-open No. 2010-070581

Patent document 2 Japanese laid-open patent publication No. 2002-182037

Patent document 3, Japanese patent laid-open No. 2007-002066

Patent document 4 Japanese examined patent publication No. H05-062897

Patent document 5 Japanese patent application laid-open No. H07-196984

Patent document 6 Japanese laid-open patent publication No. 2005-125656

Patent document 7 Japanese patent laid-open No. 2004-114620

Patent document 8, Japanese patent laid-open No. 2007-031639

Patent document 9 Japanese laid-open patent publication No. 2002-265719

Disclosure of Invention

The polyester film described in patent document 1 is an unstretched film and therefore does not have sufficient thickness accuracy.

The release layer described in patent document 2 needs to be treated at a high temperature for lamination and curing. Further, the resins described in patent documents 3 and 7 are not only expensive, but also difficult to burn and generate toxic gas in waste incineration treatment after use. In addition, there is a problem that a large amount of organic solvent is used to uniformly apply the release agent.

The olefin-based aqueous liquid described in patent document 4 using an aqueous coating agent is substantially obtained by laminating a low molecular weight olefin-based wax, and contains a surfactant, and therefore, there is a possibility that the adherend is contaminated. The release layers described in patent documents 5 and 6 have insufficient adhesion to the base material and insufficient releasability and the like.

In patent document 8, the sheet for mold release is not actually evaluated. And since the coating agent contains a surfactant, the adherend may be contaminated. In addition, since the resin used in patent document 9 is expensive and has a high melting point, it is necessary to perform a treatment at a high temperature in order to form a release sheet.

In order to solve the above problems and obtain sufficient thickness accuracy, the present invention is intended to provide a biaxially stretched polyester film for mold release which is suitable as a mold release material and which can be molded with large deformation even after stretching.

The present inventors have intensively studied to solve the above problems, and as a result, they have found that the above problems can be solved by providing a release layer containing a polyolefin resin having a specific composition and a specific amount of a crosslinking agent on at least one surface of a biaxially stretched polyester film having a specific elongation at break and a specific stress at break, and have completed the present invention.

That is, the gist of the present invention is as follows.

(1) A biaxially stretched polyester film for releasing a mold, which is characterized by comprising a polyester film substrate and a biaxially stretched polyester film having a release layer on at least one side thereof,

the mold release layer contains 100 parts by mass of an acid-modified polyolefin resin having an acid-modifying component content of 1 to 10% by mass and 1 to 50 parts by mass of a crosslinking agent,

the biaxially stretched polyester film has an elongation at break of 350 to 500% at 120 ℃ and a stress at break of 10 to 30MPa,

the biaxially stretched polyester film has a thickness unevenness (み -thick spots) of 5% or less.

(2) The biaxially stretched polyester film for mold release according to (1), wherein the polyester film substrate comprises at least 1 layer each of a copolymerized polyethylene terephthalate layer (layer A) and an amorphous polyester resin layer (layer B) having a diethylene glycol content of 4 to 12 mol%.

(3) The biaxially stretched polyester film for mold release according to (1), wherein the release layer further contains polyvinyl alcohol in an amount of 5 to 200 parts by mass per 100 parts by mass of the acid-modified polyolefin resin.

(4) The biaxially stretched polyester film for mold release according to (2), wherein the layer A contains 0.1 to 1% by mass of an antioxidant.

(5) The biaxially stretched polyester film for mold release according to (2), wherein the copolymerized polyethylene terephthalate constituting the layer A is polymerized by a germanium catalyst.

(6) The biaxially stretched polyester film for mold release according to any one of (1) to (5), wherein the surface magnification of the biaxial stretching is 9.0 to 12.3 times.

The biaxially stretched polyester film for mold release of the present invention has good thickness accuracy and specific elongation at break and stress at break, and therefore, even when used for in-mold molding, it has good moldability and mold release properties and can be molded with beautiful decoration. Further, the biaxially stretched polyester film for releasing of the present invention does not need to contain a release agent such as wax, a low molecular weight organosilicon compound, or a surfactant, and therefore, does not contaminate an adherend during release, and does not contain a release agent containing a halogen element such as fluorine, and therefore, it is less environmentally friendly to dispose of.

Detailed Description

The biaxially stretched polyester film for releasing is a polyester film having a release layer on at least one surface of a polyester film substrate, and has an elongation at break at 120 ℃ of 350 to 500%, a stress at break of 10 to 30MPa, and a thickness variation of 5% or less.

The biaxially stretched polyester film for releasing a mold of the present invention has an elongation at break at 120 ℃ of 350 to 500%, preferably 370 to 500%, and more preferably 400 to 500%, as described above. When the elongation at break is less than 350%, the film is not followed during the in-mold molding, and the film may be broken, thereby impairing the appearance of the molded article. The elongation at break is preferably high, but thickness accuracy may not be obtained in a film produced so that the elongation at break exceeds 500%.

The biaxially stretched polyester film for releasing a mold of the present invention has a breaking stress at 120 ℃ of 10 to 30MPa, preferably 10 to 25MPa, and more preferably 10 to 20 MPa. When the breaking stress is less than 10MPa, the film may break during the in-mold molding, which may impair the appearance of the molded article. When the breaking stress exceeds 30MPa, the resin injected during molding cannot spread over the corners of the mold, and the resulting molded article tends to have a defective shape.

The thickness unevenness of the biaxially stretched polyester film for mold release of the present invention is preferably 5% or less, more preferably 4% or less. If the thickness unevenness rate exceeds 5%, the film may be deformed unevenly (deformed spots) during in-mold molding, and the design pattern printed on the film may be deformed, which may impair the appearance of the molded article obtained by transferring the design pattern. The method of measuring the thickness unevenness is described later.

In order to reduce the thickness unevenness to 5% or less, the polyester film needs to be a biaxially stretched film. As a method for biaxially stretching the polyester film, known methods such as sequential biaxial stretching, tenter type simultaneous biaxial stretching, and expanding type simultaneous biaxial stretching can be selected.

In the biaxial stretching, the surface magnification is preferably 9.0 to 12.3 times, and more preferably 9.7 to 10.0 times. If the area magnification is less than 9.0 times, it may be difficult to make the thickness unevenness rate 5% or less. On the other hand, if the surface magnification exceeds 12.3 times, it may be difficult to set the elongation at break at 120 ℃ to 350% or more.

In the biaxial stretching, the ratio of the stretching ratio in the Machine Direction (MD) to the stretching ratio in the Transverse Direction (TD) is preferably 0.8 to 1.2. If the amount is outside this range, anisotropy of elongation at break and stress at break at 120 ℃ becomes large, and when in-mold molding is performed, the film is deformed unevenly, and the printed design pattern is also deformed, so that the molded article obtained is impaired in appearance.

The stretching temperature in the biaxial stretching is set to a temperature higher than the glass transition temperature (Tg) of the polyester, but it is preferable that the stretching temperature is as high as possible from the viewpoint of being able to increase the elongation at break at 120 ℃ as long as the thickness unevenness is 5% or less. If the stretching temperature exceeds (Tg +30 ℃), it becomes difficult to make the thickness unevenness 5% or less.

The biaxially stretched polyester film for mold release of the present invention preferably has a dry heat shrinkage of-0.5 to 1.0%, more preferably-0.3 to 0.5%, when treated at 160 ℃ for 15 minutes. The dry heat shrinkage of the film is preferably within the above range in both the Machine Direction (MD) and the Transverse Direction (TD). If the amount is outside the above range, the film is deformed unevenly when the in-mold molding is performed, and the printed design is also deformed, so that the appearance of the molded article obtained is impaired.

The biaxially stretched polyester film for releasing has a base material and a release layer. The substrate is required to be a film made of a polyester resin, and the polyester film substrate preferably contains at least 1 layer of a copolymerized polyethylene terephthalate layer (layer A) having a breaking elongation at 120 ℃ of 350 to 500% and a diethylene glycol component content of 4 to 12 mol%, and preferably contains at least 1 layer of an amorphous polyester resin layer (layer B) so that the breaking stress is 10 to 30 MPa.

In the copolymerized polyethylene terephthalate constituting the layer A, the proportion of the diethylene glycol component is 4 to 12 mol%, preferably 6 to 10 mol%, based on the total glycol components. If the proportion of the diethylene glycol component is less than 4 mol%, the elongation at break at 120 ℃ of the obtained biaxially stretched polyester film may be difficult to exceed 350%. On the other hand, if the proportion of the diethylene glycol component exceeds 12 mol%, the thermal stability of the polyester film substrate obtained may be low, and foaming may occur due to thermal decomposition gas during film formation.

The copolymerized polyethylene terephthalate constituting the layer a is polymerized using a known polymerization catalyst, but is preferably polymerized using a germanium catalyst. Since the polyester polymerized using the germanium catalyst has low crystallinity, the elongation at break of the obtained biaxially stretched polyester film at 120 ℃ can be improved.

The copolymerized polyethylene terephthalate is obtained by copolymerizing diethylene glycol, and other monomer components may be copolymerized within a range not to impair the effects of the present invention.

Examples of the acid component include isophthalic acid, phthalic acid, 2, 6-naphthalenedicarboxylic acid, isophthalic acid-5-sodium sulfonate, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, and dicarboxylic acids such as cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, -caprolactone, and lactic acid.

Examples of the alcohol component include 1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 1, 6-hexanediol, cyclohexanedimethanol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene oxide adducts of bisphenol a and bisphenol S.

In addition, a small amount of a trifunctional compound such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerol, pentaerythritol, or the like can be used.

These copolymerization components may be used in combination of 2 or more.

The layer A preferably contains 0.1 to 1% by mass of an antioxidant for improving thermal stability. Since the generation of bubbles is suppressed by the antioxidant, the elongation at break of the film is increased as a result, and the upper limit of the proportion of the diethylene glycol component can be increased.

As the antioxidant, a hindered phenol-based antioxidant can be preferably used. Examples thereof include N, N '-hexamethylenebis (3, 5-di-tert-butyl-4-hydroxy-phenylacrylamide), 3, 5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxy-benzyl) benzene, pentaerythrityl-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], tetrakis (2, 4-di-tert-butylphenyl) -4, 4' -biphenylene-di-phosphonite, triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate and the like, particular preference is given to at least 1 compound selected from the group consisting of N, N' -hexamethylenebis (3, 5-di-tert-butyl-4-hydroxy-phenylacrylamide), 3, 5-di-tert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxy-benzyl) benzene and pentaerythrityl-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

The amorphous polyester resin constituting the B layer means a polyester resin which does not substantially exhibit crystallinity. That is, the term means a resin having a crystallinity of 5% or less in an arbitrary temperature range from the glass transition temperature to the melting point when the resin is left for a sufficiently long time. The crystallinity is determined from the X-ray diffraction intensity of the crystalline portion and the X-ray diffraction intensity of the amorphous portion.

The amorphous polyester resin is preferably an amorphous copolyester obtained by acid-modifying and/or diol-modifying a polyalkylene terephthalate resin such as polyethylene terephthalate or a polyalkylene 2, 6-naphthalate resin such as polyethylene 2, 6-naphthalate.

Examples of the acid-modifying component used in the amorphous polyester resin include isophthalic acid, phthalic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, isophthalic acid-5-sodium sulfonate, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, dicarboxylic acids such as cyclohexanedicarboxylic acid, oxycarboxylic acids such as 4-hydroxybenzoic acid, -caprolactone, and lactic acid, and polyfunctional compounds such as trimellitic acid, trimesic acid, and pyromellitic acid. These acid-modified components may be used alone or in combination of 2 or more.

Examples of the diol-modifying component used in the amorphous polyester resin include 1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 1, 4-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1, 2-cyclohexanedimethanol, 1, 6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycols such as ethylene oxide adducts of bisphenol a and bisphenol S, and polyfunctional compounds such as trimethylolpropane, glycerol, and pentaerythritol. These diol-modifying components may be used alone or in combination of 2 or more.

The non-crystalline polyester resin is preferably a non-crystalline copolyester obtained by modifying polyethylene terephthalate with 1, 4-cyclohexanedimethanol, and the proportion of the 1, 4-cyclohexanedimethanol component is preferably 10 to 70 mol% based on the total diol components, from the viewpoints of heat resistance, mechanical properties, transparency, and the like.

The glass transition temperature of the amorphous polyester resin constituting the layer B is preferably lower than "the glass transition temperature of the copolymerized polyethylene terephthalate constituting the layer A +10 ℃. If the glass transition temperature of the amorphous polyester resin is higher than this, it becomes difficult to biaxially stretch a laminated film comprising the a layer and the B layer. The glass transition temperature of the amorphous polyester resin can be adjusted by adjusting the ratio of the copolymerization component, and sebacic acid is preferably used as the copolymerization component.

The layer B contains an amorphous polyester resin, and may contain other polymer components within a range not impairing the necessary characteristics. From the viewpoint of molecular theory, other polymer components may be compatible with or incompatible with the amorphous polyester resin.

The thickness of the polyester film substrate is preferably 30 to 200 μm, and more preferably 40 to 150 μm, from the viewpoint of easily controlling the breaking stress within a predetermined range.

The polyester film substrate comprises at least 1 layer each of the above-mentioned layer A and layer B.

The ratio of the thickness of the B layer (the total thickness when the B layer is a plurality of layers) to the thickness of the polyester film substrate is preferably 50 to 95%, and more preferably 65 to 85%. If the thickness ratio of the layer B exceeds 95%, the effect of the layer A comprising copolymerized polyethylene terephthalate is reduced, and the resulting biaxially stretched polyester film may not have heat resistance, mechanical properties, elongation at break and thickness accuracy. On the other hand, if the thickness ratio of the B layer is less than 50%, the obtained biaxially stretched polyester film cannot obtain the breaking stress in the above range.

Specific layer configurations of the polyester film substrate are represented by layer a/layer B, layer a/layer B/layer a, and examples thereof include layer B/layer a/layer B, layer a/layer B/layer a. The layer structure is preferably a structure in which the layer B is not a surface layer, that is, a structure in which the layer a is a surface layer, because the non-crystalline polyester resin layer (layer B) can be prevented from sticking to the mold, a structure formed by the layer a/the layer B/the layer a is particularly preferable.

The polyester film substrate may be laminated with an adhesive layer or the like for providing interlayer adhesiveness, as a layer other than the a layer and the B layer.

The biaxially stretched polyester film for releasing has a releasing layer on at least one surface of the polyester film substrate.

The release layer may be formed on at least one surface of the polyester film substrate, and when 1 release layer is formed on the polyester film substrate having both the a layer and the B layer exposed on the surface, the release layer is preferably formed on the surface of the B layer. If a release layer having releasability is formed on the surface of the layer a, the surface of the layer B is placed in contact with the mold during molding, and therefore, when the layer B is softened, the surface of the layer B may be fused with the mold.

The thickness of the release layer is not particularly limited, but is preferably 0.01 to 1.0 μm, and more preferably 0.05 to 0.5 μm, from the viewpoint of film-forming properties and economy when the liquid substance for forming the release layer is applied.

In the present invention, the releasing layer contains an acid-modified polyolefin resin and a crosslinking agent.

The acid-modified polyolefin resin needs to contain an olefin component as a main component. The olefin component is not particularly limited, but is preferably an olefin having 2 to 6 carbon atoms such as ethylene, propylene, isobutylene, 2-butene, 1-pentene, 1-hexene, and the like, and may be a mixture thereof, and among these, an olefin having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, 1-butene, and the like is more preferable, ethylene and propylene are further preferable, and ethylene is most preferable.

The proportion of the acid-modifying component in the acid-modified polyolefin resin is desirably 1 to 10% by mass, more preferably 2 to 10% by mass, and still more preferably 2 to 9% by mass.

When the proportion of the acid-denatured component is less than 1% by mass, the proportion of the polar group contained in the release layer is reduced, and therefore sufficient adhesion between the release layer and the polyester film substrate may not be obtained, and there is a possibility that the adherend may be contaminated. In addition, in the preparation of a liquid substance for forming a release layer, which will be described later, it tends to be difficult to stably disperse an acid-modified polyolefin resin in an aqueous phase. On the other hand, when the proportion of the acid-denatured component exceeds 10% by mass, the proportion of the polar group contained in the release layer increases, so that the adhesiveness between the release layer and the polyester film substrate becomes sufficient, but the adhesiveness between the release layer and the adherend also increases, so that the releasability from the adherend tends to decrease.

Examples of the acid-modifying component constituting the acid-modified polyolefin resin include unsaturated carboxylic acid components. Examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, and a half ester and a half amide of an unsaturated dicarboxylic acid. Among them, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferable, and acrylic acid, methacrylic acid, and maleic anhydride are particularly preferable, from the viewpoint of dispersion stability of the resin. These acid-modified components may be contained in the acid-modified polyolefin resin in an amount of 2 or more.

In addition, the acid-modified polyolefin resin preferably contains an ethylenically unsaturated component having an oxygen atom in the side chain, for the reason of further improving the adhesion to the polyester film substrate.

The side chain contains an ethylenically unsaturated component containing an oxygen atom, and has a polar group in the molecule, as in the acid-modified component. Therefore, when the acid-modified polyolefin resin contains an ethylenically unsaturated component having an oxygen atom in the side chain, the adhesion between the release layer and the polyester film substrate is improved. On the other hand, if the amount of the side chain ethylenically unsaturated component containing an oxygen atom is too large, the properties of the olefin-derived resin are lost, and the releasability between the release layer and the adherend may be lowered. The proportion of the side chain oxygen atom-containing ethylenically unsaturated component contained in the acid-modified polyolefin resin is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, even more preferably 3 to 30% by mass, and particularly preferably 6 to 18% by mass.

Examples of the ethylenically unsaturated component having an oxygen atom in the side chain include esters of (meth) acrylic acid and alcohols having 1 to 30 carbon atoms, and esters of (meth) acrylic acid and alcohols having 1 to 20 carbon atoms are preferable from the viewpoint of easy availability. Specific examples of such a compound include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, and octadecyl (meth) acrylate. Mixtures thereof may be used. Among them, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl acrylate, octyl acrylate are more preferable, ethyl acrylate, butyl acrylate are still more preferable, and ethyl acrylate is particularly preferable, from the viewpoint of adhesiveness to the substrate film. "(meth) acrylic acid" means "acrylic acid" or methacrylic acid ".

In the acid-modified polyolefin resin, other monomers may be copolymerized in a small amount. Examples of the other monomer include dienes, (meth) acrylonitrile, vinyl halides, vinylidene halides, carbon monoxide, and sulfur dioxide.

The components constituting the acid-modified polyolefin resin may be copolymerized in the acid-modified polyolefin resin, and the mode is not limited. Examples of the copolymerization mode include random copolymerization, block copolymerization, and graft copolymerization (graft modification).

The melting point of the acid-modified polyolefin resin is preferably 80 to 150 ℃, and more preferably 90 to 130 ℃. In addition, the Vicat softening point of the acid-modified polyolefin resin is preferably 50 to 130 ℃, more preferably 53 to 110 ℃, and further preferably 55 to 90 ℃.

If the melting point and vicat softening point of the acid-modified polyolefin resin are each higher than the above range, a high-temperature treatment may be required to form a resin layer on the surface of the polyester film substrate. On the other hand, if the melting point and vicat softening point of the acid-modified polyolefin resin are each lower than the above range, the release layer formed on the polyester film substrate is easily melted, adhesion to the adherend is improved, and releasability is lowered.

The melt flow rate of the acid-modified polyolefin resin is preferably 1 to 1000g/10 min, more preferably 1 to 500g/10 min, and still more preferably 1 to 100g/10 min at 190 ℃ under a load of 2160 g. If the melt flow rate of the acid-modified polyolefin resin is less than 1g/10 minutes, it becomes difficult to produce an aqueous dispersion having excellent dispersion stability as described later. On the other hand, if the melt flow rate exceeds 1000g/10 min, the adhesion between the resin layer and the polyester film substrate may be reduced.

Examples of the acid-modified polyolefin resin usable in the present invention include NEWCREL series (trade name) as an acid-modified polyolefin resin manufactured by DUPONT-MITSUI POLYCHEMICALS, and REXPEARL series (trade name) as an acid-modified Polyethylene resin manufactured by Japan Polyethylene. Specific trade names include "AN 42115C", "N1050H", "N1110H" of NEWCREL series, and "a 210K" of REXPEARL series.

Further, as the acid-modified polyolefin resin containing an ethylenically unsaturated component having an oxygen atom in a side chain which can be used in the present invention, BONDINE series (trade name) as a maleic anhydride-modified polyolefin resin manufactured by Arkema company is exemplified. Specific trade names include "LX-4110", "HX-8210", "HX-8290", "TX-8030" and "AX-8390".

The release layer contains a crosslinking agent in addition to the acid-modified polyolefin resin.

By containing the crosslinking agent, various properties such as cohesive force and water resistance of the release layer can be further improved. The amount of the crosslinking agent to be added is 1 to 50 parts by mass, preferably 2 to 40 parts by mass, and more preferably 2 to 30 parts by mass, per 100 parts by mass of the acid-modified polyolefin resin.

As the crosslinking agent, a crosslinking agent having self-crosslinking property, a compound having a plurality of functional groups reacting with carboxyl groups in the molecule, and the like can be used, and among them, an isocyanate compound, a melamine compound, a urea compound, an epoxy compound, a carbodiimide compound, a compound containing a carbodiimide compound, and the like are preferableOxazoline-based compounds, etc., especiallyWhich are effective as a carbodiimide compound,An oxazoline compound. These crosslinking agents may be used in combination.

The carbodiimide compound is not particularly limited as long as it has 1 or more carbodiimide groups in the molecule. The carbodiimide compound forms an ester with 2 carboxyl groups in the acid-modified portion of the acid-modified polyolefin resin at 1 carbodiimide portion, and crosslinking is achieved.

Specific examples of the carbodiimide compound include compounds having a carbodiimide group such as p-phenylene-bis (2, 6-xylylcarbodiimide), tetramethylene-bis (t-butylcarbodiimide), cyclohexane-1, 4-bis (methylene-t-butylcarbodiimide), and polycarbodiimides which are polymers having a carbodiimide group. 1 or 2 or more of them may be used. Among them, polycarbodiimide is preferable from the viewpoint of easy handling.

Commercially available products of polycarbodiimide include CARBODILITE series available from Nisshinbo Co., Ltd, and more specifically, water-soluble types "SV-02", "V-02-L2" and "V-04"; emulsion type "E-01", "E-02"; "V-01", "V-03", "V-07", "V-09" of the organic solution type; "V-05" of the solvent-free type.

As long as the oxazoline compound has 2 or more atoms in the moleculeThe oxazoline group is not particularly limited.2 oxazoline compoundsThe oxazoline moiety forms amide esters with 1 carboxyl group in the acid-modified moiety of the acid-modified polyolefin resin, respectively, to effect crosslinking.

AsSpecific examples of the oxazoline compound include, for example, 2' -bis (2-)Oxazoline), 2 '-ethylene-bis (4, 4' -dimethyl-2-Oxazoline), 2' -p-phenylene-bis (2-Oxazoline), bis (2-Oxazoline cyclohexane) sulfides, etc. havingOxazoline-based compounds containingAn oxazoline-based polymer. 1 or 2 or more of them may be used. Among them, from the viewpoint of easy handling, it is preferable to containAn oxazoline-based polymer.

As containingCommercially available oxazoline-based polymers include the EPOCROS series manufactured by NIPPONSHOKUBA, and more specifically, water-soluble polymers such as "WS-500" and "WS-700"; emulsion type "K-1010E", "K-1020E", "K-1030E", "K-2010E "," K-2020E "," K-2030E ", and the like.

In the present invention, the releasing layer preferably contains polyvinyl alcohol. The polyvinyl alcohol is dispersed in the acid-modified polyolefin resin in the release layer, and thus the polyvinyl alcohol functions by appropriately reducing the releasability of the acid-modified polyolefin resin and also exhibits the adhesion by itself. Further, since the polyvinyl alcohol forms fine protrusions on the surface of the release layer together with the crosslinking agent used in combination, the slipperiness of the release layer can be remarkably improved, and the transportation and winding properties of the obtained release film can be improved.

The content of the polyvinyl alcohol is preferably 5 to 200 parts by mass, more preferably 10 to 100 parts by mass, and still more preferably 20 to 50 parts by mass, based on 100 parts by mass of the acid-modified polyolefin resin. If the content of polyvinyl alcohol is 5 parts by mass or more, the influence of the heat treatment temperature (drying temperature) on the releasability at the time of forming the release layer can be further reduced, while if it is 200 parts by mass or less, the stability of the liquid substance for forming the release layer can be favorably maintained, and the occurrence of coating unevenness can be suppressed.

The polyvinyl alcohol is not particularly limited, and examples thereof include those in which a polymer of a vinyl ester is completely or partially gelled.

The average polymerization degree of the polyvinyl alcohol is not particularly limited, and may be, for example, 300 to 5000, and preferably 300 to 2000 from the viewpoint of improving the stability of the liquid material for forming a release layer.

As described below, in order to use a liquid substance for forming the release layer, it is preferable that the polyvinyl alcohol has water solubility.

As commercially available polyvinyl alcohols, trade names such as "JC-05", "VC-10", "ASC-05X", "UMR-10 HH" specific trade names of "J-POVAL" available from JAPANVAM & POVAL company; specific trade names of "KURARAAY POVAL" by KURARAAY corporation of "PVA-103", "PVA-105", and specific trade names of "EXCEVAL" of "AQ 4104", "HR 3010"; specific trade names of "DENKA POVAL" of the electric chemical industry Co., Ltd. "PC-1000", "PC-2000", and the like.

In the present invention, the release layer may contain inorganic particles and/or organic particles as a roughening substance, but does not necessarily have to contain them. In general, in order to impart slip properties to a film, inorganic particles such as calcium carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, silicon oxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide, tin oxide, antimony trioxide, carbon black, molybdenum disulfide, and organic particles such as acrylic crosslinked polymer, styrene crosslinked polymer, silicone resin, fluororesin, benzoguanamine resin, phenol resin, nylon resin, polyethylene wax are often added.

However, inorganic particles have problems such as generation and sedimentation of coarse particles due to coagulation of the particles in an aqueous dispersion, and falling off of the particles from the surface of the release layer. The inorganic particles are preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, and particularly preferably not contained, per 100 parts by mass of the acid-modified polyolefin resin.

On the other hand, in the organic particles, the addition of an organic silicon compound, a fluorine compound, a wax, and a surfactant significantly improves the smoothness of the film, but has the following problems: the low-molecular-weight component bleeds out at the interface between the polyester film base and the release layer and at the surface of the release layer, and the adhesion between the polyester film base and the release layer is lowered or the adherend at the time of peeling is contaminated. Therefore, the organic particles are preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and particularly preferably not contained, per 100 parts by mass of the acid-modified polyolefin resin.

The wax is selected from vegetable wax, animal wax, mineral wax, petrochemical wax, etc. with number average molecular weight of 10000 or less. Specific examples thereof include candelilla wax, carnauba wax, rice bran wax, wood wax, fruit wax (ベリーワックス), jojoba wax, shea butter, beeswax, shellac wax, lanolin wax, spermaceti wax, montan wax, ceresin wax, paraffin wax, microcrystalline wax, synthetic polyethylene wax, synthetic polypropylene wax, and synthetic ethylene-vinyl acetate copolymer wax.

Examples of the surfactant include cationic surfactants, anionic surfactants, non-ionic (non-ionic) surfactants, amphoteric surfactants, fluorine-based surfactants, and reactive surfactants. In general, the emulsion polymerization contains an emulsifier in addition to the substances used in the emulsion polymerization.

Examples of the anionic surfactant include higher alcohol sulfate ester salts, higher alkylsulfonic acids and salts thereof, alkylbenzenesulfonic acids and salts thereof, polyoxyethylene alkylsulfate ester salts, polyoxyethylene alkylphenyl ether sulfate ester salts, and vinylsulfosuccinate esters.

Examples of the nonionic surfactant include compounds having a polyoxyethylene structure such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, ethylene oxide-propylene oxide block copolymers, polyoxyethylene fatty acid amides, and ethylene oxide-propylene oxide copolymers, and sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters.

Examples of the amphoteric surfactant include dodecyl betaine and lauryl dimethylamine oxide.

Examples of the reactive surfactant include compounds having a reactive double bond such as an alkylphenylpolyoxyethylene adduct (アルキルプロペニルフェノールポリエチレンオキサイド adduct) and a sulfate ester thereof, an allylalkylphenol polyoxyethylene adduct (アリルアルキルフェノールポリエチレンオキサイド adduct) and a sulfate ester thereof, and an allyldialkylphenol polyoxyethylene adduct (アリルジアルキルフェノールポリエチレンオキサイド adduct) and a sulfate ester salt thereof.

In the present invention, the release layer can be industrially easily formed by a method of coating a liquid material containing an acid-modified polyolefin resin, a crosslinking agent and a liquid medium on a polyester film substrate and then drying the coated liquid material.

The liquid medium constituting the liquid substance is preferably an aqueous medium.

In the present invention, the aqueous medium refers to a solvent containing water and an amphiphilic organic solvent, and the water content is 2% by mass or more, and may be water alone.

The amphiphilic organic solvent refers to an organic solvent having a solubility in water in an organic solvent of 5 mass% or more at 20 ℃ (the solubility in water in an organic solvent at 20 ℃) is described in, for example, a literature such as "solvent handbook" (Kodansha Scientific, 10 th edition 1990). Specific examples of the amphiphilic organic solvent include alcohols such as methanol, ethanol, n-propanol and isopropanol, tetrahydrofuran and 1, 4-bis (tert-butyl ether)Ethers such as alkanes, ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate, N-propyl acetate, isopropyl acetate, methyl propionate, ethyl propionate and dimethyl carbonate, organic amine compounds such as diethylamine, triethylamine, diethanolamine, triethanolamine, N-dimethylethanolamine, N-diethylethanolamine and N-diethanolamine containing ammonia, lactams such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and the like.

The liquid material may further contain an antioxidant, an ultraviolet absorber, a lubricant, a colorant, and the like, as long as the properties thereof are not impaired.

The liquid material can be obtained by mixing the acid-modified polyolefin resin, the crosslinking agent and the liquid medium, and in this mixing, a previously prepared liquid material of the acid-modified polyolefin resin may be used, or an aqueous dispersion of the acid-modified polyolefin resin may be used. The method for dispersing the acid-modified polyolefin resin in an aqueous solution is not particularly limited, and examples thereof include the method described in International publication WO 02/055598. Examples of the aqueous medium constituting the aqueous dispersion of the acid-modified polyolefin resin include the aqueous media exemplified above as liquid materials.

The number average particle diameter of the dispersed particle diameter of the acid-modified polyolefin resin in the aqueous medium is preferably 1 μm or less, more preferably 0.8 μm or less, from the viewpoints of stability when mixed with other components and storage stability after mixing. Such a dispersed particle size can be achieved by the production method described in WO 02/055598. The number average particle diameter of the acid-modified polyolefin resin was measured by a dynamic light scattering method.

The solid content of the aqueous dispersion of the acid-modified polyolefin resin is not particularly limited, but is preferably 1 to 60% by mass, more preferably 5 to 30% by mass, in order to appropriately maintain the viscosity of the aqueous dispersion.

The solid content of the liquid substance obtained by mixing the aqueous dispersion of the acid-modified polyolefin resin with the crosslinking agent may be appropriately selected depending on the lamination conditions, the target thickness, the performance, and the like, and is not particularly limited. However, in order to form a uniform release layer while maintaining the viscosity of the liquid material appropriately, the solid content of the liquid material is preferably 2 to 30 mass%, and more preferably 3 to 20 mass%.

Examples of the method for applying the liquid substance to the polyester film substrate include known methods such as gravure roll coating, reverse roll coating, wire bar coating, die lip coating, air knife coating, curtain flow coating, spray coating, dip coating, and brush coating.

The release layer can be formed by a method of coating a liquid substance for forming a release layer on a polyester film substrate which has been biaxially stretched and drying the coating. The method of drying the liquid material after the liquid material is applied includes a method of blowing hot air at 40 to 180 ℃ for 3 to 60 seconds.

In the present invention, the polyester film is preferably produced by a so-called inline coating method (インラインコート method) in which the liquid substance is coated on an unstretched polyester film substrate or a uniaxially stretched polyester film substrate in a stretching step of the polyester film substrate, and then the coating is stretched and dried to form a release layer. The instant coating method can promote the crosslinking of the release layer by the temperature of the heat treatment after the film stretching.

Examples

The present invention will be specifically described with reference to examples.

The raw materials and characteristic values of the films in examples and comparative examples were measured as follows.

Copolymerized polyethylene terephthalate for layer A formation

(1)DEG10

Ethylene glycol as a diol component, diethylene glycol 9.5 mol% based on the total diols, and terephthalic acid as an acid component were charged into an esterification tank and reacted at 275 ℃ for 3 hours to obtain an esterified product. Next, pentaerythrityl-tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] (Irganox 1010, BASF) as an antioxidant was added in an amount of 0.6 mass% based on the polyester after polymerization, and melt polymerization was carried out at 300 ℃ under a reduced pressure of 1.3hPa in the presence of a germanium catalyst to obtain a copolymerized polyethylene terephthalate (DEG10) having a relative viscosity of 1.38, a melting point of 238 ℃ and a glass transition temperature of 70 ℃. The proportion of the diethylene glycol component to the total glycol component was 9.5 mol%.

(2)DEG14、DEG12、DEG8、DEG4、DEG2

In the above (1), a copolymerized polyethylene terephthalate (DEG14, DEG12, DEG8, DEG4, and DEG2) was obtained in the same manner as in (1) except that the charging ratio of diethylene glycol to the entire glycol components was changed to 13.5 mol%, 11.5 mol%, 7.5 mol%, 3.5 mol%, and 1.5 mol%, respectively.

Melting points of 234 ℃, 236 ℃, 241 ℃, 248 ℃ and 252 ℃, glass transition temperatures of 67 ℃, 68 ℃, 70 ℃, 74 ℃ and 76 ℃, respectively, and the ratios of the diethylene glycol component to the total glycol component are 14.2 mol%, 12.1 mol%, 8.1 mol%, 3.7 mol% and 2.2 mol%, respectively.

(3)DEG8-2

The preparation of a copolymerized polyethylene terephthalate (DEG8-2) having a relative viscosity of 1.38, a melting point of 240 ℃ and a glass transition temperature of 70 ℃ was carried out in the same manner as DEG8 except that Irganox1010 was not added to the above (2). The proportion of the diethylene glycol component to the total glycol component was 8.1 mol%.

Non-crystalline polyester resin (PETG) for forming B layer

Ethylene glycol as a diol component, cyclohexanedimethanol in an amount of 34.5 mol% based on the total diol component, and terephthalic acid as an acid component were fed into an esterification vessel and reacted at 275 ℃ for 3 hours to obtain an esterified product. Irganox1010 (manufactured by BASF) was added to the polyester after polymerization in an amount of 0.6 mass%, and melt polymerization was carried out at 300 ℃ under reduced pressure of 1.3hPa in the presence of a germanium catalyst to obtain an amorphous polyester resin (PETG) having a relative viscosity of 1.38 and a glass transition temperature of 75 ℃. The proportion of the cyclohexanedimethanol component to the whole diol component was 30 mol%.

3. Acid-modified polyolefin resin aqueous dispersion

(1)O-1

60.0g of "BONDINE LX-4110" (maleic anhydride-modified polyolefin resin manufactured by Arkema corporation, 60.0g of isopropyl alcohol (IPA)), 3.0g of Triethylamine (TEA) and 147.0g of distilled water were charged into a glass container using a stirrer equipped with a heater and having a pressure-proof glass container with a capacity of 1 liter. Then, the rotation speed of the stirring blade was set to 300rpm, the temperature in the system was maintained at 140 to 145 ℃, and the mixture was stirred for 30 minutes. Thereafter, the mixture was immersed in a water bath and cooled to room temperature (about 25 ℃) while stirring at a rotation speed of 300 rpm. 180g of distilled water and 3.0g of N, N-Dimethylethanolamine (DMEA) were put into a 0.5L two-necked round-bottomed flask, a mechanical stirrer and a Liebig type cooler were installed, and the flask was heated by an oil bath to distill off the aqueous medium. After about 180g of water and IPA were distilled off, heating was completed, and the mixture was cooled to room temperature. After cooling, the liquid contents in the flask were subjected to pressure filtration (air pressure 0.2MPa) using a 300-mesh stainless steel filter (wire diameter 0.035mm, plain weave) to obtain a milky-white acid-modified polyolefin resin aqueous dispersion (O-1). The content of the organic solvent in the aqueous medium was 1.0 mass%.

(2)O-2

The same procedure as in the production of the aqueous dispersion (O-1) was carried out using "BONDINE HX-8210" (maleic anhydride-modified polyolefin resin, manufactured by Arkema) as the acid-modified polyolefin resin to obtain an aqueous acid-modified polyolefin resin dispersion (O-2).

(3)O-3

The same procedure as in the production of the aqueous dispersion (O-1) was carried out using "BONDINE AX-8390" (maleic anhydride-modified polyolefin resin, manufactured by Arkema) as the acid-modified polyolefin resin to obtain an aqueous acid-modified polyolefin resin dispersion (O-3).

(4)O-4

30.0g of "REXPEARLEAA A210K" (manufactured by Japan Polyethylene Co., Ltd., acrylic acid-modified Polyethylene resin), 105.0g of n-propanol (NPA), 7.8g of TEA and 157.2g of distilled water were put into a glass vessel using a stirrer equipped with a heater and having a pressure-resistant 1-liter glass vessel, and the rotational speed of the stirring blade was set to 300 rpm. The temperature in the system was then kept at 170 ℃ and stirred for 30 minutes. The mixture was cooled to room temperature (about 25 ℃ C.) while maintaining the rotation speed at 300 rpm. 180g of distilled water and 3.0g of DMEA were put into a 0.5L 2-neck round-bottom flask, a mechanical stirrer and a Liebig type cooler were installed, and the flask was heated with an oil bath to distill off the aqueous medium. After about 180g of water and NPA were distilled off, heating was terminated and cooling was carried out to room temperature. After cooling, the liquid contents in the flask were subjected to pressure filtration (air pressure 0.2MPa) using a 300-mesh stainless steel filter (wire diameter 0.035mm, plain weave) to obtain a milky-white acid-modified polyolefin resin aqueous dispersion (O-4). The content of the organic solvent in the aqueous medium was 1.0 mass%.

(5)O-5

60.0g of "PRIMACOR 5980I" (manufactured by Dow Chemical Co., Ltd., acrylic acid modified polyolefin resin), 16.8g of TEA, and 223.2g of distilled water were charged into a glass container using a stirrer equipped with a heater and having a pressure-resistant, sealable glass container with a volume of 1 liter. Then, the rotation speed of the stirring blade was set to 300rpm, the temperature in the system was maintained at 140 to 145 ℃, and the mixture was stirred for 30 minutes. Thereafter, the mixture was immersed in a water bath and cooled to room temperature (about 25 ℃) while stirring at a rotation speed of 300 rpm. Then, the mixture was filtered (air pressure: 0.2MPa) through a 300-mesh stainless steel filter (wire diameter: 0.035mm, plain weave) to obtain a slightly cloudy aqueous dispersion (O-5). At this time, almost no resin remained on the filter.

The composition and physical properties of the acid-modified polyolefin resin and the physical properties of the resulting aqueous dispersion are shown in table 1.

[ Table 1]

4. Measurement method

(1) Composition of acid-modified polyolefin resin

It was determined by 1H-NMR analysis (GEMINI 2000/300, manufactured by Varian corporation, 300 MHz). The measurement was carried out at 120 ℃ using o-dichlorobenzene (d4) as a solvent.

(2) Melt Flow Rate (MFR) of acid-modified polyolefin resin

The measurement was carried out by the method described in JIS K6730 (190 ℃, 2160g load).

(3) Melting Point of acid-modified polyolefin resin

A sample of 10mg of the resin was measured at a temperature rise rate of 10 ℃ per minute using a differential scanning calorimeter (DSC 7, Perkinelmer Co., Ltd.), and the melting point was determined from the obtained temperature rise curve.

(4) Vicat softening point of acid-modified polyolefin resin

The measurement was carried out by the method described in JIS K7206.

(5) Solid content ratio of aqueous dispersion

An appropriate amount of the aqueous dispersion was weighed and heated at 150 ℃ until the mass of the residue (solid content) became constant, and the solid content was determined.

(6) Organic solvent content of aqueous dispersion

The aqueous dispersion or a product obtained by diluting the aqueous dispersion with water was directly charged into an apparatus using a gas chromatograph GC-8A manufactured by Shimadzu corporation to determine the content of the organic solvent. The detection limit was 0.01 mass%.

The detailed conditions of the gas chromatography are as follows.

A detector: FID, carrier gas: nitrogen, column packing (GL Sciences corporation): PEG-HT (5%) -Uniport HP (60/80 mesh), column size: diameter 3mm × 3m, sample input temperature (injection temperature): 150 ℃, column temperature: 60 ℃, internal standard: n-butanol.

(7) Number average particle diameter of acid-modified polyolefin resin particles

The number average particle diameter was determined using a Microtrac particle size analyzer UPA150(MODEL No.9340, dynamic light scattering method) manufactured by Nikkiso K.K. The refractive index of the resin used in the calculation of the particle diameter was 1.50.

(8) Rate of thickness unevenness

The thickness of the obtained biaxially stretched polyester film for mold release was measured at 5mm intervals in the Transverse Direction (TD), and the thickness unevenness was calculated by the following formula using the obtained average value (Tave), maximum value (Tmax) and minimum value (Tmin).

Thickness unevenness ratio (%) - (Tmax-Tmin)/Tave × 100

(9) Elongation at break and stress at break

The elongation at break and the stress at break were measured using a tensile tester (manufactured by shimadzu corporation) in which a heating chamber was used to cover the jig portion. From the obtained biaxially stretched polyester film for mold release, a sample of MD100mm × TD10mm was collected as an evaluation sample in the Machine Direction (MD), and a sample of TD100mm × MD10mm was collected as an evaluation sample in the Transverse Direction (TD), and the samples were held and fixed by a jig set at an interval of 50 mm. Then, the sample was maintained in an atmosphere of 120 ℃ by using a heating chamber provided in the grip portion of the tensile tester. The sample was stretched at a rate of 200 mm/min, and the load was measured with a load cell attached to the tester.

The load at break of the load elongation curve (a load-elongation curve) was read, and the load was divided by the cross-sectional area of the sample before the stretching to calculate the breaking stress (MPa).

The elongation at break (%) was calculated from the initial clip spacing (L0) and the clip spacing at break (L1) using the following formula.

Elongation at break (%) - (L1-L0)/L0X 100

Each sample in the Machine Direction (MD) and the Transverse Direction (TD) was measured with the test number n of 5, and the average value of all the measurement results of the stress and elongation at break was obtained.

(10) Formability

The obtained biaxially stretched polyester film for releasing was set in the cavity of the lower cavity of a differential pressure molding die so that the surface on which the release layer was not formed was in contact with the cavity surface of the die, and then fixed to the inner wall of the die by suction through the die, and then the polypropylene resin was injected over the lower cavity to mold the part. The member was formed into a cup shape having a bottom surface with a diameter of 50mm, an opening surface with a diameter of 60mm, and a depth of 30 mm. The film and part were removed from the mold and the film was peeled off the part. The mold release layer of the peeled film was observed, and the moldability of the biaxially stretched polyester film for mold release was evaluated by the presence or absence of film breakage and the presence or absence of cracks.

(11) Peel strength

A polyester adhesive tape (No. 31B/acrylic adhesive manufactured by Ridong electric engineering Co., Ltd.) having a width of 50mm and a length of 150mm was pressure-bonded to the release layer side of the obtained biaxially stretched polyester film for release by a rubber roll to prepare a sample. The sample was held between a metal plate/a rubber plate/a sample/a rubber plate/a metal plate, left under a load of 2kPa at 70 ℃ for 20 hours, and then cooled for 30 minutes or more to return to room temperature to obtain a sample for measuring peel strength. The peel strength between the adhesive tape and the release film of the sample for peel strength measurement was measured in a thermostatic chamber at 25 ℃ by a tensile tester (model 2020 precision Universal Material tester manufactured by Intesco corporation). The peel angle was set to 180 degrees, and the peel speed was set to 300 mm/min.

(12) Residual adhesion rate

The polyester adhesive tape peeled from the surface of the release biaxially stretched polyester film by the peel strength test was adhered to the corona-treated surface of a biaxially stretched polyester resin film (EmbletPET-12, thickness 12 μm, manufactured by Youngco Co., Ltd.), and allowed to stand at room temperature under a load of 2kPa for 20 hours. Thereafter, the peel strength between the polyester adhesive tape and the film was measured in a constant temperature room at 25 ℃ by a tensile tester (model 2020 precision Universal Material tester manufactured by Intesco corporation). The peel angle was set to 180 degrees, and the peel speed was set to 300 mm/min. The peel strength obtained by this measurement was designated as F1.

On the other hand, a polyester adhesive tape (No. 31B/acrylic adhesive manufactured by Nidong electric Co., Ltd.) having a width of 50mm and a length of 150mm was attached to a corona-treated surface of a biaxially stretched polyester resin film ("EmbletPET-12" manufactured by Youngco, having a thickness of 12 μm), and the biaxially stretched polyester resin film was left to stand at room temperature under a load of 2kPa for 20 hours. Thereafter, the peel strength between the polyester adhesive tape and the film was measured in a constant temperature room at 25 ℃ by a tensile tester (model 2020 precision Universal Material tester manufactured by Intesco corporation). The peel angle was set to 180 degrees, and the peel speed was set to 300 mm/min. The peel strength obtained by this measurement was designated as F2.

The residual adhesion ratios were obtained from the obtained peel strengths F1 and F2 according to the following formulas.

Residual adhesion ratio (%) (F1/F2) × 100

When the adhesive surface of the adhesive tape is contaminated with the release layer of the release film, the re-adhesiveness of the adhesive tape is lowered, and the performance as the adhesive tape is impaired. Therefore, the higher the residual adhesion rate, the better.

Example 1

Using DEG10 as a resin constituting the a layer, the resin was melted at 270 ℃ by an extruder, and using PETG as a resin constituting the B layer, the resin was melted at 270 ℃ by another extruder, and the melts were merged at a composite splicer, extruded through a T-die, and rapidly cooled by a cooling drum to obtain an unstretched laminated film composed of 3 layers of a layer a/B/a layer. At this time, the discharge rate of each extruder was adjusted so that the thickness composition ratio was 1/4/1.

The acid-modified polyolefin resin aqueous dispersion (O-1) is used as a crosslinking agentAn aqueous solution of oxazoline compound (EPOCROS WS-700 manufactured by NIPPON SHOKUBAI corporation, solid content concentration 25 mass%) and an aqueous solution of polyvinyl alcohol (JAPAN VAM)&"VC-10" manufactured by POVAL, polymerization degree 1000, solid content concentration 10% by mass) was mixed so that the solid content ratio of each component became the value shown in Table 2, and then diluted with water to obtain a liquid material (E-3) having a solid content of 8% by mass.

The unstretched laminate film was first stretched to 3.0 times at 80 ℃ in the longitudinal direction by a roll stretching method, and the liquid material (E-3) was formed into 5g/m by using a 120-mesh gravure roll²After coating the longitudinally stretched film, the film was passed through a hot air drying oven at 50 ℃ for 20 seconds.

Next, the longitudinally stretched film having the liquid substance applied and dried was stretched to 3.3 times at 100 ℃ in the transverse direction by a tenter stretching method, and then heat-treated at 225 ℃ while 3% relaxation was performed in the transverse direction. The film was further cooled and wound into a roll by a winder to obtain a biaxially stretched polyester film for releasing having a thickness of 50 μm.

[ Table 2]

Examples 2 to 6 and comparative examples 1 to 2

A biaxially stretched polyester film for releasing was obtained in the same manner as in example 1, except that the composition of the polyester film base material was changed as shown in table 3.

Comparative example 3

DEG8, which is a resin constituting the a layer, was melted at a temperature of 270 ℃ by an extruder, and the melt was extruded from a T-die and rapidly cooled by a cooling drum to obtain an unstretched monolayer film. The liquid material (E-3) was wound with a Meyer bar (マイヤーバー) to a density of 4.5g/m²After coating the polyester film on the undrawn film, the film was dried in a hot air drying oven at 120 ℃ for 90 seconds to obtain an undrawn polyester film having a thickness of 50 μm.

The films obtained in examples 1 to 6 and comparative examples 1 to 3 were evaluated for elongation at break, stress at break, and thickness unevenness. The results are shown in Table 3.

[ Table 3]

The biaxially stretched polyester films for mold release obtained in examples 1 to 6 were suitable for molding, since they had low breaking stress and high elongation at break, and thus no film breakage occurred even when molding was performed.

The film of the biaxially stretched release polyester obtained in example 2 was improved in breaking stress and elongation at break by adding an antioxidant, as compared with the film of example 4 in which the layer a of the polyester film substrate did not contain an antioxidant.

The film of comparative example 1 has a low elongation at break because the proportion of diethylene glycol component in the copolymerized polyethylene terephthalate constituting the layer a of the substrate is small, while the film of comparative example 2 has a high proportion and has a low elongation at break because bubbles enter the film due to thermal decomposition, and the position of the break can be observed in a part of the film in any molding.

The film of comparative example 3 has a high breaking stress because it does not have the B layer as a base material, and the film does not follow the mold during molding, resulting in molding failure.

Examples 7 to 14 and comparative examples 4 to 6

An aqueous dispersion of an acid-modified polyolefin resin,The aqueous solution of the oxazoline compound and the polyvinyl alcohol aqueous solution were mixed so as to have a solid content ratio shown in table 2, and diluted with water so as to have a solid content ratio shown in table 2, to obtain each liquid material. A biaxially stretched polyester film for releasing was obtained in the same manner as in example 1, except that the obtained liquid substance was used and the thickness of the release layer was changed to a value shown in table 4. Since the liquid materials (E-1) and (E-11) containing no polyvinyl alcohol had poor coatability on the polyester film substrate, a liquid material to which acetylene glycol was added as a surfactant in an amount of 0.1 mass% based on the liquid material was used.

Example 15

In example 1, the step of applying the liquid material (E-3) was omitted, and a biaxially stretched polyester film substrate on which no release layer was formed was obtained. The liquid material (E-3) was wound with a Meyer bar (マイヤーバー) to a density of 4.5g/m²The coating liquid was applied to the obtained biaxially stretched polyester film substrate, and dried in a hot air drying oven at 120 ℃ for 90 seconds to obtain a biaxially stretched polyester film for mold release having a thickness of 50 μm.

The films obtained in examples 1, 7 to 15 and comparative examples 4 to 6 were evaluated for mold release properties. The results are shown in Table 4.

[ Table 4]

The biaxially stretched polyester films for mold release obtained in examples 1 and 7 to 13 were excellent in peel strength and residual adhesion as an index of mold release property, and therefore the films could be easily peeled after molding. Further, no cracks were observed in the release layer of the peeled film.

The biaxially stretched polyester films for releasing obtained in examples 14 and 15 were slightly inferior to example 1 in which a releasing layer having the same composition was formed on the same polyester film substrate in peel strength and residual adhesion rate as indices of releasability, and therefore, the films were slightly peeled after molding, and the barrier was slightly felt. No cracks were observed in the release layer of the peeled film.

The films of comparative example 4 had a high ratio of the acid-modified component of the acid-modified polyolefin resin constituting the release layer, and the films of comparative examples 5 and 6 had a higher peel strength, a lower residual adhesion rate, and a lower releasability, and had portions where the films could not be peeled after molding, as compared with the films of release layers having the same thickness, because the release layers did not contain a crosslinking agent. Further, cracks were observed in the release layer of the peeled film.

Claims (6)

1.A biaxially stretched polyester film for releasing a mold, which is characterized by comprising a polyester film substrate and a biaxially stretched polyester film having a release layer on at least one side thereof,

the mold release layer contains 100 parts by mass of an acid-modified polyolefin resin having an acid-modifying component content of 1 to 10% by mass and 1 to 50 parts by mass of a crosslinking agent,

the biaxially stretched polyester film has an elongation at break of 350 to 500% at 120 ℃ and a stress at break of 10 to 30MPa,

the biaxially stretched polyester film has a thickness unevenness of 5% or less.

2. The biaxially stretched polyester film for releasing mold according to claim 1, wherein the polyester film substrate comprises at least 1 layer each of a layer A of copolymerized polyethylene terephthalate having a diethylene glycol content of 4 to 12 mol% and a layer B of an amorphous polyester resin.

3. The biaxially stretched polyester film for releasing mold according to claim 1, wherein the releasing layer further contains 5 to 200 parts by mass of polyvinyl alcohol per 100 parts by mass of the acid-modified polyolefin resin.

4. The biaxially stretched polyester film for mold release according to claim 2, wherein the layer A contains 0.1 to 1% by mass of an antioxidant.

5. The biaxially stretched polyester film for mold release according to claim 2, wherein the copolymerized polyethylene terephthalate constituting the layer a is polymerized by a germanium catalyst.

6. A biaxially stretched polyester film for releasing mold according to any one of claims 1 to 5, wherein the surface magnification of the biaxial stretching is 9.0 to 12.3 times.