JP2016104539A - Mold releasing biaxial oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold releasing biaxial polyester film excellent in blocking resistance even when winding to a roll state, capable of molding with large deformation even when conducting drawing for obtaining sufficient thickness accuracy and suitable as a mold releasing material.SOLUTION: There is provided a mold releasing biaxial oriented polyester film having a resin layer containing 100 pts.mass of an acid modified ethylene-α-olefin copolymer on at least a single surface of a polyester film substrate and 0.1 to 50 pts.mass of an oxazoline compound and/or a carbodiimide compound as a crosslinking agent and having rupture elongation at 120°C of 350 to 500% and rupture stress of 10 to 30 MPa.SELECTED DRAWING: None

Description

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

Polyester films represented by polyethylene terephthalate are widely used in industrial and industrial fields because they have excellent mechanical properties, heat resistance, and chemical resistance. Among them, demand for process materials has shown remarkable growth in recent years, and in particular, mold release materials, which are one of process materials, are widely used in the field of electronics and electric machinery. Examples of application of mold release materials include: adhesive materials such as adhesive sheets and adhesive tapes, adhesive materials for protecting adhesive surfaces or process materials, process materials for manufacturing printed wiring boards, flexible printed wiring boards, multilayer printed wiring boards, etc. Protective materials for polarizing plates and retardation plates, which are parts for liquid crystal displays, as well as structural body molding applications.

In-mold molding, in which a printed film is inserted into a mold and decorated at the same time as injection molding as a molding application for structures, can be beautifully decorated at low cost. Widely used in housings of equipment and the like. There are two types of in-mold molding, one is a method of peeling the film after injection molding, and the other is a method in which the film remains integrally with the molded product after injection molding. . In the case of the latter method, it is necessary to follow a complicated three-dimensional shape, and an acrylic film having a very high moldability is used. On the other hand, stretched polyester films are widely used because the former method has high heat resistance, dimensional stability, printability, thickness accuracy, and is inexpensive. However, the compatibility of molding processability and releasability is insufficient. Met.

In order to use a polyester film as a mold release material, a film obtained by laminating a mold release layer containing a mold release agent and imparting mold release properties to the substrate surface is generally used. However, since the resin having releasability is generally expensive, the release material obtained by forming into a film becomes expensive. Therefore, many methods have been proposed for forming a release layer by using an inexpensive resin as a base film for obtaining a release material and coating the film surface with a release agent or the like.

However, if waxes, low molecular weight silicone compounds, or fluorosurfactants are used as the release agent, these release agents are transferred to the adherend during peeling, reducing the adherent function such as adhesiveness. There was a problem of letting.
In Patent Documents 1 to 3, an acid-modified ethylene polymer is used without using a release agent such as waxes, a low molecular weight silicone compound, or a fluorosurfactant in which the release agent is easily transferred upon peeling. Has been proposed, and it is disclosed that it exhibits good releasability for various adherends. Patent Document 4 proposes that an acid-modified polybutadiene or acid-modified polyisoprene having a good release property with respect to the pressure-sensitive adhesive is used for the release layer.

Patent Documents 5 and 6 propose release films having releasability and embedding properties (flexibility) that are used when manufacturing circuit boards.

JP 2009-101680 A International Publication No. 2009/025063 International Publication No. 2014/007187 JP 2012-152965 A JP 2007-98816 A JP 2007-84760 A

However, the release sheets of Patent Documents 1 to 3 tend to be slightly peeled from the pressure-sensitive adhesive sheet, and the handling properties when peeling the pressure-sensitive adhesive sheet may not be good. In addition, there was a tendency that the releasability when the heat treatment was performed after bonding with an adhesive material or the like was slightly inferior. In the release sheet of Patent Document 4, since the release layer is soft, when the release sheet is wound into a roll shape, the sheet may be blocked and cannot be unwound from the roll.

Moreover, the release films of Patent Documents 5 to 6 do not have sufficient releasability, heat resistance and flexibility, and when emphasizing releasability and heat resistance, flexibility is sacrificed and precise. The embedding property of the printed circuit board having the pattern tended to be inferior. On the other hand, when emphasis was placed on flexibility, the mold release property and the slipperiness of the film surface deteriorated, and the elastic modulus also decreased. Therefore, the film tended to be stretched and wrinkled at the time of film winding or cutting.
As described above, a release film used for in-mold molding or the like needs to have release properties, heat resistance and flexibility suitable for these, but there is no release film satisfying these.

The present invention eliminates such a problem, and even when wound into a roll, it has excellent blocking resistance and can be molded with large deformation even if stretched to obtain sufficient thickness accuracy, It is an object of the present invention to provide a release film that can protect the adhesive surface of a material and can be easily peeled without degrading the quality of the adhesive material.

As a result of intensive studies to solve the above problems, the present inventors have found that an acid-modified ethylene-α-olefin copolymer is formed on at least one surface of a polyester film having a specific range of breaking elongation and breaking stress at 120 ° C. The present inventors have found that a biaxially stretched polyester film for mold release comprising a resin layer containing a polymer and a specific cross-linking agent solves the above problems, and has reached the present invention.

That is, the gist of the present invention is as follows.
(1) A resin layer containing 100 parts by mass of an acid-modified ethylene-α-olefin copolymer and 0.1 to 50 parts by mass of an oxazoline compound and / or a carbodiimide compound as a crosslinking agent on at least one side of a polyester film substrate. A biaxially stretched polyester film for mold release having a breaking elongation at 120 ° C. of 350 to 500% and a breaking stress of 10 to 30 MPa.
(2) The polyester film substrate comprises a film having at least one copolymer polyester resin layer (A) and a polyester resin layer (B), and biaxial stretching for mold release according to (1) Polyester film.
(3) The copolyester resin layer (A) is made of copolymerized polyethylene terephthalate containing 4 to 12 mol% of a diethylene glycol residue with respect to all glycol components, and biaxial stretching for mold release according to (2) Polyester film.
(4) The mass ratio (ethylene component / α-olefin component) of the ethylene component and the α-olefin component in which the resin layer constitutes the acid-modified ethylene-α-olefin copolymer is 60/40 to 99/1. (2) The biaxially stretched polyester film for release according to any one of (1) to (3).
(5) The content of the acid-modified component constituting the acid-modified ethylene-α-olefin copolymer is less than 1% by mass with respect to the total of the ethylene component and the α-olefin component ( The biaxially stretched polyester film for mold release according to any one of 1) to (4).
(6) The release strength of the resin layer and the acrylic pressure-sensitive adhesive material is 0.5 N / cm or less, and the biaxially stretched polyester film for release according to any one of (1) to (5).

Even when the biaxially stretched polyester film for release of the present invention is rolled up, it can be easily peeled without impairing the quality of the adhesive material because it has excellent blocking resistance and excellent release properties. In addition, since it has excellent heat resistance, it can be easily peeled even after heat treatment. In addition, because it has good thickness accuracy and has a specific breaking elongation and breaking stress, it has good moldability and releasability even when used for in-mold molding, and can be molded with beautiful decoration. It becomes. Furthermore, since the film of the present invention does not require a release agent such as waxes, low molecular weight silicone compounds, and surfactants, it does not contaminate the adherend during peeling, and halogen such as fluorine. Since it is not necessary to use a release agent containing elements, there is little impact on the environment at the time of disposal.

Hereinafter, the present invention will be described in detail.
The biaxially stretched polyester film for mold release according to the present invention has a release layer containing an acid-modified ethylene-α-olefin copolymer and a crosslinking agent on at least one surface of a polyester film substrate, at 120 ° C. The breaking elongation is 350 to 500%, the breaking stress is 10 to 30 MPa, and the thickness unevenness is 5% or less.

In the biaxially stretched polyester film for release of the present invention, the elongation at break at 120 ° C. needs to be 350 to 500% as described above, preferably 370 to 500%, preferably 400 to 500%. % Is more preferable. When the elongation at break is less than 350%, the film may not follow when it is subjected to in-mold molding, and may be broken or torn, which may impair the appearance of the molded product. Although it is preferable that the elongation at break is high, in a stretched film stretched to a surface magnification of 9.0 times or more, thickness accuracy may not be obtained with a film produced so that the break elongation exceeds 500%.

In the biaxially stretched polyester film for release of the present invention, the breaking stress at 120 ° C. needs to be 10 to 30 MPa as described above, preferably 10 to 25 MPa, and preferably 10 to 20 MPa. Is more preferable. When the breaking stress is less than 10 MPa, the film may break when in-mold molding is performed, and the appearance of the molded product may be impaired. When the breaking stress exceeds 30 MPa, the resin injected to every corner of the mold does not reach when molding is performed, and the obtained molded product tends to have a defective shape.

The thickness unevenness of the biaxially stretched polyester film for release according to the present invention is preferably 5% or less, more preferably 4% or less. If the thickness unevenness exceeds 5%, when the in-mold molding is performed, the deformation will occur on the film and the design printed on the film will also be distorted. There is. In addition, the measuring method of thickness spots is mentioned later.

In order to make the thickness unevenness 5% or less, the polyester film needs to be biaxially stretched. The method for biaxial stretching of the polyester film can be selected within the scope of known techniques such as sequential biaxial stretching, tenter simultaneous biaxial stretching, and inflation simultaneous biaxial stretching. The range of the surface magnification of the biaxial stretching is preferably 9.0 times to 12.3 times, and preferably 9.7 times to 10 times in order to achieve thickness spots and a breaking elongation at 120 ° C. of 350% or more. More preferably, it is 0.0 times. If the surface magnification of biaxial stretching exceeds 12.3 times, it may be difficult to make the breaking elongation at 120 ° C. 350% or more, and if the surface magnification is less than 9.0 times, May be difficult to be 5% or less.

In the biaxial stretching, the ratio of the stretching ratio in the machine direction (MD) and the transverse direction (TD) is preferably 0.8 to 1.2. Outside this range, the anisotropy of the breaking elongation and breaking stress at 120 ° C. increases, and when in-mold molding is performed, distortion occurs in the printed design resulting in deformation spots on the film. The resulting molded product is detrimental to aesthetics.

Biaxial stretching is usually performed at a temperature higher than the glass transition temperature (Tg) of the polyester, but as long as the thickness variation is 5% or less, the higher the stretching temperature, the higher the breaking elongation at 120 ° C. It is preferable in that it can be increased. However, when the stretching temperature exceeds Tg + 30 ° C., it may be 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% when treated at 160 ° C for 15 minutes, and is -0.3 to 0.5%. More preferably. The dry heat shrinkage rate of the film is preferably in the above range in both the machine direction (MD) and the transverse direction (TD). If it is out of the above range, when it is subjected to in-mold molding, deformation spots are produced on the film and the printed design is also distorted, so that the aesthetics of the obtained molded product are impaired.

The biaxially stretched polyester film for release of the present invention has a polyester film substrate and a release layer. This polyester film substrate has a copolymer polyester resin layer (A) in which the proportion of the diethylene glycol component is 4 to 12 mol% and a breaking stress of 10 to 30 MPa in order to set the elongation at break to 350 to 500% at 120 ° C. Therefore, it is preferable to have at least one polyester resin layer (B).

As the resin constituting the copolymerized polyester resin layer (A), copolymerized polyethylene terephthalate is preferable. In the copolymerized polyethylene terephthalate, the proportion of the diethylene glycol component is 4 to 12 mol%, preferably 6 to 10 mol%, based on the total glycol component. When the ratio of the diethylene glycol component is less than 4 mol%, it may be difficult for the resulting biaxially stretched polyester film to have a breaking elongation at 120 ° C. exceeding 350%. On the other hand, when the ratio of the diethylene glycol component exceeds 12 mol%, the resulting polyester film substrate has low thermal stability and may be foamed by pyrolysis gas during film formation.

The copolymerized polyethylene terephthalate is polymerized using a known polymerization catalyst, but is preferably polymerized using a germanium catalyst. Since the polyester resin polymerized using the germanium catalyst has low crystallinity, the breaking elongation at 120 ° C. can be increased in the obtained biaxially stretched polyester film.

The copolymerized polyethylene terephthalate copolymerizes a diethylene glycol component, but other monomer components may be copolymerized as long as the effects of the present invention are not hindered.
For example, as an acid component, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, anhydrous Examples include maleic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, and dicarboxylic acids such as cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid.
Examples of alcohol components include 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. And ethylene oxide adducts of bisphenol A and bisphenol S.
Further, a small amount of trifunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, pentaerythritol, and the like may be used. Two or more of these copolymer components may be used in combination.

The copolymerized polyester resin 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, as a result, the breaking elongation of the film is increased, and the upper limit of the ratio of the diol component can be increased.

As the antioxidant, a hindered phenol-based antioxidant can be suitably used. For example, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 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, pentaerythrityl-tetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylylene-di-phosphonite, triethylene glycol-bis-3- ( 3-t-butyl-4-hydroxy-5-methyl-phenyl) propionate and the like.
In the present invention,
N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t-tyl-4-hydroxy-benzyl phosphonate-diethyl ester 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxy-benzyl) benzene and pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate] is preferably selected from the group consisting of at least one compound.

As resin which comprises a polyester resin layer (B), the amorphous polyester resin which does not show crystallinity substantially is preferable. That is, it means a resin having a crystallinity of 5% or less when the resin is allowed to stand for a sufficiently long time in an arbitrary temperature range from the glass transition temperature to the melting point. The degree of crystallinity is obtained from the X-ray diffraction intensity of the crystal part and the X-ray diffraction intensity of the amorphous part.
As an amorphous polyester resin, for example, a polyalkylene terephthalate resin such as polyethylene terephthalate or a polyalkylene-2,6-naphthalate resin such as polyethylene-2,6-naphthalate is acid-modified and / or diol-modified amorphous. Preferred are copolyesters.

Examples of acid-modifying components used in amorphous polyester resins include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, and adipine Dicarboxylic acids such as acid, sebacic acid, dodecanedioic acid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, ε-caprolactone, Examples thereof include oxycarboxylic acids such as lactic acid, and polyfunctional compounds such as trimellitic acid, trimesic acid, and pyromellitic acid. These acid-modifying components may be used alone or in combination of two or more.
Examples of the diol-modified 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, trimethylolpropane, glycerin, pentaerythritol, etc. And the like. These diol-modified components may be used alone or in combination of two or more.

The amorphous polyester resin is preferably an amorphous copolyester obtained by modifying polyethylene terephthalate with 1,4-cyclohexanedimethanol from the viewpoint of heat resistance, mechanical properties, transparency, etc., and 1,4-cyclohexanedimethanol It is preferable that the ratio of a component is 10-70 mol% with respect to all the glycol components.

The glass transition temperature of the amorphous polyester resin is preferably lower than “glass transition temperature of copolymerized polyethylene terephthalate constituting layer A + 10 ° C.”. If the glass transition temperature of the amorphous polyester resin is higher than this, it may be difficult to biaxially stretch the laminated film containing the A layer and the B layer. The glass transition temperature of the amorphous polyester resin can be adjusted by adjusting the proportion of the copolymer component, and sebacic acid is preferably used as the copolymer component.

The polyester resin layer (B) may contain other polymer components as long as the effects of the present invention are not impaired.

The thickness of the polyester film substrate constituting the biaxially stretched polyester film for release of the present invention is preferably 30 to 200 μm, and preferably 40 to 150 μm, since the breaking stress can be easily controlled within a predetermined range. Is more preferable.
The ratio of the thickness of the polyester resin layer (B) to the thickness of the polyester film substrate (the total thickness in the case where there are a plurality of B layers) is preferably 50 to 95%, and preferably 65 to 85%. Is more preferable. When the thickness ratio of the polyester resin layer (B) exceeds 95%, the contribution of the copolyester resin layer (A) is reduced, so that the resulting biaxially stretched polyester film has heat resistance, mechanical properties, elongation at break. Degree and thickness accuracy may not be obtained. On the other hand, when the thickness ratio of the polyester resin layer (B) is less than 50%, the obtained biaxially stretched polyester film for release may not have a breaking stress within the range specified in the present invention.

Specific layer configurations of the polyester film substrate in the present invention include A layer / B layer, A layer / B layer / A layer, B layer / A layer / B layer, A layer / B layer / A layer. / B layer / A layer and the like. In order to prevent the polyester resin as the B layer from sticking to the mold, a configuration in which the B layer is not a surface layer, that is, a configuration in which the copolymer polyester resin layer as the A layer is a surface layer is preferable. / B layer / A layer. Moreover, you may laminate | stack the adhesive agent layer for providing interlayer adhesiveness, etc. other than the layer which consists of said A layer and B layer in the polyester film base material in this invention.

The polyester film substrate in the present invention may contain known additives and stabilizers such as antistatic agents, plasticizers, lubricants, antioxidants, pinning agents and the like. Moreover, silica, alumina, etc. may be vapor-deposited, and other layers, such as a barrier layer, an easily bonding layer, an antistatic layer, and an ultraviolet absorption layer, may be laminated. In order to improve adhesion when laminated with other materials, the surface of the polyester film may be subjected to corona treatment, plasma treatment, ozone treatment, chemical treatment, solvent treatment, etc. as pretreatment.

The biaxially stretched polyester film for mold release of the present invention has a resin layer containing an acid-modified ethylene-α-olefin copolymer and a crosslinking agent on at least one surface of a polyester film substrate.

The acid-modified ethylene-α-olefin copolymer is obtained by acid-modifying an ethylene-α-olefin copolymer, and the ethylene-α-olefin copolymer comprises an ethylene component and one or more α-olefin components. Containing.
Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like can be mentioned. Among these, propylene and 1-butene are preferable from the viewpoints of economy and availability.

In the ethylene-α-olefin copolymer, the mass ratio of the ethylene component to the α-olefin component (ethylene component / α-olefin component) is preferably 60/40 to 99/1, and 70/30 to 97. / 3 is more preferable, and 80/20 to 95/5 is still more preferable. When the mass ratio of the ethylene component and the α-olefin component is outside this range, the obtained biaxially stretched polyester film for release may have a reduced release property and may have a reduced high-speed peelability.

The ethylene-α-olefin copolymer is preferably produced using a metallocene catalyst. The ethylene-α-olefin copolymer produced by this method has a narrow molecular weight distribution and a small amount of low molecular weight components, and becomes a uniform copolymer.

In the present invention, the ethylene-α-olefin copolymer is acid-modified from the viewpoint of improving the adhesion between the resulting resin layer and the substrate and improving the heat resistance by reacting with a crosslinking agent. is necessary. The acid modification of the ethylene-α-olefin copolymer can be performed, for example, by introducing an unsaturated carboxylic acid component into the ethylene-α-olefin copolymer.
In the present invention, the content of the acid-modified component constituting the acid-modified ethylene-α-olefin copolymer is less than 1% by mass with respect to the total amount of the olefin component, that is, the total of the ethylene component and the α-olefin component. Is preferably 0.01% by mass or more and less than 1% by mass, more preferably 0.05% by mass or more and less than 1% by mass, and further preferably 0.1% by mass or more and less than 1% by mass. It is particularly preferable that the content is 0.2% by mass or more and less than 1% by mass. When the content of the acid-modified component is less than 0.01% by mass, the adhesion to the substrate may be insufficient, or the reaction with the crosslinking agent may be insufficient, resulting in poor heat resistance. On the other hand, when the content of the acid-modifying component is 1% by mass or more, the releasability tends to decrease. When a polyolefin resin that normally contains an ethylene component is acid-modified, the cross-linking reaction proceeds in concert. Therefore, it may be substantially difficult to produce a product having a high acid modification amount from the viewpoint of operability.

Specific examples of the unsaturated carboxylic acid component introduced into the ethylene-α-olefin copolymer include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, aconitic acid, aconitic anhydride, In addition to fumaric acid, crotonic acid, citraconic acid, mesaconic acid, allyl succinic acid, etc., at least one carboxyl group or acid anhydride in the molecule (in the monomer unit) such as half ester or half amide of unsaturated dicarboxylic acid The compound which has a physical group is mentioned. Of these, maleic anhydride, acrylic acid and methacrylic acid are preferred, and maleic anhydride is more preferred from the viewpoint of ease of introduction into the ethylene-α-olefin copolymer.
The unsaturated carboxylic acid component only needs to be copolymerized in the ethylene-α-olefin copolymer, and the form thereof is not limited, and examples thereof include random copolymerization, block copolymerization, and graft copolymerization. It is done.

The method for introducing the unsaturated carboxylic acid unit into the ethylene-α-olefin copolymer is not particularly limited. For example, in the presence of a radical generator, an ethylene-α-olefin copolymer and an unsaturated carboxylic acid are heated and melted to a temperature equal to or higher than the melting point of the ethylene-α-olefin copolymer, or an ethylene-α-olefin is reacted. After dissolving the copolymer and the unsaturated carboxylic acid in an organic solvent, the unsaturated carboxylic acid is added to the ethylene-α-olefin copolymer by a method of reacting by heating and stirring in the presence of a radical generator. A method of graft copolymerization may be mentioned. The former method is preferable because the operation is simple.
Examples of the radical generator used for graft copolymerization include di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, tert-butyl cumyl peroxide, benzoyl peroxide, dilauryl peroxide, Examples thereof include organic peroxides such as cumene hydroperoxide, tert-butyl peroxybenzoate, ethyl ethyl ketone peroxide, and di-tert-butyl diperphthalate, and azonitriles such as azobisisobutyronitrile. These may be appropriately selected and used depending on the reaction temperature.

In the present invention, the melt flow rate of the acid-modified ethylene-α-olefin copolymer as the resin layer production raw material is not particularly limited, but is preferably 0.01 to 500 g / 10 min at 230 ° C. and 2160 g load. 0.1 to 100 g / 10 min is more preferable, and 0.3 to 10 g / 10 min is further preferable. An acid-modified ethylene-α-olefin copolymer having a melt flow rate of less than 0.01 g / 10 min is difficult to dissolve in a solvent, whereas the melt flow rate of the acid-modified ethylene-α-olefin copolymer is difficult. Is 500 g / 10 min or more, the resulting resin layer may have poor adhesion to the substrate, and migration of low molecular weight components tends to occur on the adherend such as an adhesive.

A commercially available ethylene-α-olefin copolymer can be used as the ethylene-α-olefin copolymer for acid modification. Examples of commercially available ethylene-α-olefin copolymers include Esprene series manufactured by Sumitomo Chemical Co., Ltd. and Tuffmer series manufactured by Mitsui Chemicals. An acid-modified ethylene-α-olefin copolymer can be obtained by performing acid modification by the above-described method using such a commercially available ethylene-α-olefin copolymer.
A commercially available acid-modified ethylene-α-olefin copolymer may be used. Examples of commercially available acid-modified ethylene-α-olefin copolymers include MP-0620, MH-7020, MA-8510, etc., manufactured by Mitsui Chemicals, Inc.

The resin layer in the biaxially stretched polyester film for release of the present invention contains a crosslinking agent. As the crosslinking agent, a compound having a plurality of functional groups that react with the acid-modified ethylene-α-olefin copolymer in the molecule is used. From the viewpoint of reactivity, at least one kind selected from an oxazoline compound and a carbodiimide compound is used. It must be a crosslinking agent. When a compound other than an oxazoline compound or a carbodiimide compound is used as the cross-linking agent, the resulting resin layer has a reduced heat resistance and a tendency to lower the releasability after heat treatment.

The oxazoline compound is not particularly limited as long as it has two or more oxazoline groups in the molecule. For example, 2,2'-bis (2-oxazoline), 2,2'-ethylene-bis (4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis (2-oxazoline) , A compound having an oxazoline group such as bis (2-oxazolinylcyclohexane) sulfide, an oxazoline group-containing polymer, and the like. These 1 type (s) or 2 or more types can be used. Among these, an oxazoline group-containing polymer is preferable because of ease of handling.
The oxazoline group-containing polymer is obtained by polymerizing an addition polymerizable oxazoline such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. Other monomers may be copolymerized as necessary. The polymerization method of the oxazoline group-containing polymer is not particularly limited, and various known polymerization methods can be employed.
Examples of commercially available products of the oxazoline group-containing polymer include EPOCROSS series manufactured by Nippon Shokubai Co., Ltd., and specifically, water-soluble type “WS-500”, “WS-700”, and solid type “RPS-”. 1005 "and the like.

The carbodiimide compound is not particularly limited as long as it has at least two or more carbodiimide groups in the molecule. For example, 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 polycarbodiimide which is a polymer having a carbodiimide group. These 1 type (s) or 2 or more types can be used. Among these, polycarbodiimide is preferable from the viewpoint of ease of handling.
The method for producing polycarbodiimide is not particularly limited. Polycarbodiimide can be produced, for example, by a condensation reaction involving decarbonization of an isocyanate compound. The isocyanate compound is not limited, and any of aliphatic isocyanate, alicyclic isocyanate, and aromatic isocyanate may be used. The isocyanate compound may be copolymerized with a polyfunctional liquid rubber or polyalkylene diol as necessary.
Examples of commercially available products of polycarbodiimide include carbodilite series manufactured by Nisshinbo Co., Ltd. Specifically, water-soluble types “SV-02”, “V-02”, “V-02-L2”, “ V-04 ", organic solution type" V-01 "," V-03 "," V-07 "," V-09 ", solventless type" V-05 ", and the like.

The content of the crosslinking agent comprising the oxazoline compound and / or carbodiimide compound needs to be 0.1 to 50 parts by mass with respect to 100 parts by mass of the acid-modified ethylene-α-olefin copolymer. It is preferably 30 parts by mass, more preferably 2 to 20 parts by mass. When the content of the cross-linking agent is less than 0.1 parts by mass, the effect of addition is poor and the releasability may deteriorate over time, or sufficient heat resistance may not be obtained. Moreover, when content exceeds 50 mass parts, mold release property may fall. A plurality of types of crosslinking agents can be used simultaneously. When used at the same time, the total amount of the crosslinking agent only needs to satisfy the range of the content of the crosslinking agent.

  As described above, the resin layer constituting the biaxially stretched polyester film for mold release according to the present invention contains an acid-modified ethylene-α-olefin copolymer and a crosslinking agent. Various agents such as agents, antifoaming agents, anti-waxing agents, antistatic agents, pigment dispersants, UV absorbers, and pigments or dyes such as titanium oxide, zinc white, and carbon black may be contained. In addition, organic or inorganic compounds other than those described above can be added to the liquid material and contained in the resin layer as long as the stability of the liquid material for forming the resin layer described later is not impaired.

The resin layer in the biaxially stretched polyester film for mold release according to the present invention may be formed on at least one side of the polyester film substrate, but the resin layer is applied to the polyester film substrate in which both the A layer and the B layer appear on the surface. When forming one layer, it is preferable to form a resin layer on the surface of the B layer. When a resin layer having releasability is formed on the surface of the A layer, the surface of the B layer is arranged so that the surface of the B layer is in contact with the mold at the time of molding. There is a risk of fusing to the mold.

The thickness of the resin layer is preferably 0.01 to 5.0 μm, more preferably 0.03 to 3.0 μm, and still more preferably 0.05 to 1.0 μm. If the thickness of the resin layer is less than 0.01 μm, sufficient releasability may not be obtained. On the other hand, if the thickness exceeds 5.0 μm, the cost increases, which is not preferable.

In the present invention, the method for providing the resin layer on the polyester film substrate is not particularly limited. For example, a method of preparing a liquid material containing an acid-modified ethylene-α-olefin copolymer, a crosslinking agent, and a medium, applying the liquid material on a substrate, and drying the medium is the thickness of the resin layer. It is preferable in that it can be easily made uniform and mass production is possible. Alternatively, a resin layer may be formed by melt-extruding a mixture of an acid-modified ethylene-α-olefin copolymer and a crosslinking agent onto a polyester film substrate. Moreover, you may obtain the biaxially-stretched polyester film for mold release by coextruding the resin material which comprises a polyester film base material, and resin layer forming material.

An organic solvent capable of dissolving or dispersing the acid-modified ethylene-α-olefin and the crosslinking agent as a medium for producing the liquid material containing the acid-modified ethylene-α-olefin copolymer and the crosslinking agent, Those that can be removed by drying in the course of film formation can be used. From the viewpoint of efficient removal from the coating film, the boiling point of the organic solvent is preferably 150 ° C. or lower. An organic solvent having a boiling point of more than 150 ° C. tends to be difficult to scatter from the coating film by drying, and in particular, the adhesion property and content resistance of the coating film may decrease.
Examples of the organic solvent include acetone, methyl ethyl ketone, diethyl ketone (3-pentanone), methyl propyl ketone (2-pentanone), isobutyl ketone, methyl isobutyl ketone (4-methyl-2-pentanone), 2-hexanone, 5- Ketones such as methyl-2-hexanone, 2-heptanone, 3-heptanone, 4-heptanone, cyclopentanone, cyclohexanone; aromatic hydrocarbons such as toluene, xylene, benzene, Solvesso 100, Solvesso 150; Aliphatic hydrocarbons such as butane, pentane, hexane, cyclohexane, heptane, octane, nonane; methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, o -Dichlorobenzene, m-dic Halogen-containing compounds such as lobenzene and p-dichlorobenzene; methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, acetic acid isobutyl, acetic acid-sec-butyl, acetic acid-tert-butyl, acetic acid- Esters such as 3-methoxybutyl, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, isophorone; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, ethyl Alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether; ethers such as tetrahydrofuran and 1,4-dioxane; dimethylformamide, dimethylacetamide, diacetone alcohol, acetonitrile, In addition, ammonia, diethylamine, triethylamine, diethanolamine, triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N-diethanolamine, 3-methoxypropylamine, 3-diethylaminopropylamine, dimethylamino Organic amine compounds such as propylamine; and the like.
Among them, from the viewpoint of obtaining a stable liquid material and facilitating coating, aromatic hydrocarbons such as toluene, xylene, benzene, Solvesso 100, Solvesso 150, butane, pentane, hexane, cyclohexane, heptane, octane, nonane Aliphatic hydrocarbons such as toluene are preferred, and toluene is particularly preferred from the viewpoint of solubility.

Two or more kinds of the above organic solvents may be used in combination from the viewpoints of improving the stability of the liquid, improving the solubility, coating properties to the substrate, and improving the coating appearance. When two or more types of organic solvents are used, it is preferable to use a combination of aromatic hydrocarbons and alcohols and / or ketones. In the case of using two or more kinds of organic solvents, the aromatic hydrocarbons are preferably toluene, xylene and the like, and the alcohols are preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and the like, ketones As the class, acetone, methyl ethyl ketone, isobutyl ketone, methyl isobutyl ketone and the like are preferable.
By using these solvents in combination, leveling properties can be improved, interference fringes of the coating film can be eliminated, and a biaxially stretched polyester film excellent in coating appearance can be obtained. When a biaxially stretched polyester film having interference fringes is used, the interference fringes may be transferred to the surface of the pressure-sensitive adhesive or the like, and may not be used for optical materials.
The mixing ratio in the case of mixing two or more organic solvents is not particularly limited, but the mass ratio of (aromatic hydrocarbon solvent) / (alcohol) to the aromatic hydrocarbon solvent and alcohols and / or ketones. And / or ketones)) is preferably 99/1 to 50/50, more preferably 97/3 to 70/30, and even more preferably 95/5 to 80/20.

As a method of producing a liquid material containing an acid-modified ethylene-α-olefin copolymer, a crosslinking agent, and a medium, an acid-modified ethylene-α-olefin copolymer and a crosslinking agent are added to an organic solvent serving as a medium. The method of dissolving is mentioned.
Moreover, as a method for producing a liquid material, a method in which an acid-modified ethylene-α-olefin copolymer is made into an aqueous dispersion and a crosslinking agent is mixed can be mentioned. A method for dispersing the acid-modified ethylene-α-olefin copolymer in an aqueous medium to obtain an aqueous dispersion is not particularly limited. For example, the acid-modified ethylene-α-olefin copolymer, an organic solvent, Examples thereof include a method of introducing an aqueous dispersion by charging raw materials such as water and stirring while maintaining the temperature in the tank at a temperature of about 40 to 150 ° C. For example, the method described in the pamphlet of International Publication No. 02/0555598 can be mentioned, and a good aqueous dispersion can be obtained by neutralizing an acid-modified ethylene-α-olefin copolymer with a basic compound in an aqueous medium. Is obtained.

The solid content in the liquid material can be appropriately selected depending on the formation conditions, thickness, performance, and the like of the resin layer, and is not particularly limited. In order to form a layer, 1-60 mass% is preferable and 2-20 mass% is more preferable.

In the method of forming a resin layer by applying a liquid material on a substrate, known methods such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dipping A uniform resin layer is obtained by uniformly applying a liquid material to the surface of the substrate by coating, brushing, etc., setting it at around room temperature as necessary, and then subjecting it to drying treatment or heat treatment for drying. Can be formed in close contact with the substrate.

After forming the resin layer on the polyester film substrate in the present invention, in order to promote the reaction between the acid-modified ethylene-α-olefin copolymer and the crosslinking agent, an aging treatment is performed in an environment controlled at a constant temperature. You may do. The aging temperature is preferably relatively low from the viewpoint of reducing damage to the substrate, but it is preferable to treat at a high temperature from the viewpoint of allowing the reaction to proceed sufficiently and rapidly. The aging treatment is preferably performed at 20 to 100 ° C, more preferably at 30 to 70 ° C, and further preferably at 40 to 60 ° C.

The biaxially stretched polyester film for release of the present invention may be dried and heat-treated after applying a liquid material to the biaxially stretched polyester film substrate, and unstretched or uniaxially stretched before the orientation is completed. The liquid material may be applied to the polyester film substrate and dried after heating and stretched, or may be heated and stretched simultaneously with drying to complete the orientation. The method of applying the liquid material to the latter unstretched film or the film after completion of uniaxial stretching, followed by drying and stretching orientation is preferable from the viewpoint of cost because a resin layer can be laminated simultaneously with film formation.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

(1) Unsaturated carboxylic acid component content of acid-modified ethylene-α-olefin copolymer The content of the unsaturated carboxylic acid component relative to the total amount of the olefin component is determined using the method (A) or (B) shown below. It was.
(A): The acid value of the acid-modified ethylene-α-olefin copolymer was measured in accordance with JIS K5407, and the content (graft ratio) of the unsaturated carboxylic acid was determined from the following formula.
Content (mass%) = (mass of grafted unsaturated carboxylic acid) / (mass of raw material polyolefin resin) × 100
(B): Infrared absorption spectrum analysis (Perkin Elmer Fourier transform infrared spectrophotometer System-2000, resolution 4 cm ⁻¹ ) was performed to determine the content of the unsaturated carboxylic acid component.

(2) Constitution of acid-modified ethylene-α-olefin copolymer other than unsaturated carboxylic acid component In orthodichlorobenzene (d ₄ ), at 120 ° C., ¹ H-NMR, ¹³ C-NMR analysis (manufactured by Varian) , 300 MHz). ^{In 13} C-NMR analysis, measurement was performed using a gated decoupling method in consideration of quantitativeness.

(3) Melt flow rate of acid-modified ethylene-α-olefin copolymer Measured by a method based on JIS K7210 (230 ° C., 2160 g load).

(4) Thickness unevenness Calculated by using the following formula where the average value when measuring the thickness at 5 mm intervals in the width direction of the obtained biaxially stretched polyester film for release is Tave, the maximum value is Tmax, and the minimum value is Tmin. did.
Thickness unevenness (%) = (Tmax−Tmin) / Tave × 100
The thickness spots are preferably less than 5% practically.

(5) Tensile test The breaking stress and breaking elongation of the biaxially stretched polyester film for release were measured using a tensile tester (manufactured by Shimadzu Corporation) with the chuck portion covered with a heating chamber as a measuring device. From the biaxially stretched polyester film for release, samples of 100 mm in the longitudinal direction and 10 mm in the width direction were taken in the machine direction (MD) and the transverse direction (TD), respectively, and fixed with a chuck set at a spacing of 50 mm. At that time, the atmosphere in which the sample exists was maintained at 120 ° C. by a heating chamber installed in the chuck portion of the tensile tester. Pulling was performed at a speed of 200 mm / min, and the load was measured with a load cell attached to the testing machine. The load at the time of breaking of the unloading curve was read, and the breaking stress (MPa) was calculated by dividing by the sample cross-sectional area before tension. The breaking elongation was calculated from the initial chuck interval (L0) and the chuck interval (L1) at the time of breaking using the following formula, and was defined as the breaking elongation (%).
Elongation at break (%) = (L1-L0) / L0 × 100
Measurement in each of the machine direction (MD) and the transverse direction (TD) was performed with the number of tests n = 5, and average values of all measurement results of stress and elongation at break were obtained.

(6) Peel strength (25 ° C)
A polyester adhesive tape (Nitto Denko No. 31B / acrylic adhesive) having a width of 50 mm and a length of 150 mm was pressure-bonded to the resin layer side of the release biaxially stretched polyester film with a rubber roll to prepare a sample. The sample was sandwiched in the form of a metal plate / rubber plate / sample / rubber plate / metal plate and allowed to stand in an atmosphere of 2 kPa load and 25 ° C. for 20 hours to obtain a sample for peel strength measurement. The peel strength between the adhesive tape and the release biaxially stretched polyester film of the peel strength measurement sample was measured with a tensile tester (precision universal material tester type 2020 manufactured by Intesco) in a constant temperature room at 25 ° C. The peeling angle is 180 degrees and the peeling speed is 300 mm / min.
Practically, the peel strength is less than 1.0 N / cm, so that the film can be peeled without resistance, and it is particularly preferably 0.5 N / cm or less.

(7) Peel strength (70 ° C)
The peel strength was measured by the method described in (6) above except that the sample was pressure-bonded with a rubber roll under the conditions of 2 kPa load and 70 ° C. for 20 hours, then cooled to room temperature for 30 minutes or more. A sample was obtained. The peel strength between the adhesive tape of the peel strength measurement sample and the release biaxially stretched polyester film was measured by the method described in (6) above.
Practically, the peel strength is less than 1.0 N / cm, so that the film can be peeled without resistance, and it is particularly preferably 0.5 N / cm or less.

(8) Moldability evaluation After the obtained biaxially stretched polyester film for release was placed in the cavity of the lower female mold of the differential pressure mold so that the printing side of the label was in contact with the cavity surface of the mold, The mold was fixed to the inner wall of the mold by suction, and then a polypropylene resin was injected over the lower female mold to form a member. The shape of the member was a cup shape having a bottom surface diameter of 50 mm, an opening surface diameter of 60 mm, and a depth of 30 mm. The film and member were taken out from the mold, and the film was peeled off from the member.
About the moldability, the resin layer of the peeled film was observed, and it evaluated by the presence or absence of the fracture | rupture of a film.
Formability evaluation:
○: No break ×: With break

(9) Blocking resistance Two pieces of the obtained biaxially stretched polyester film were cut into a size of 50 mm × 50 mm, overlapped so that the resin layer and the opposite surface of the resin layer were in contact, and a load of 10 kPa was applied at 60 ° C. After being allowed to stand for 24 hours, the load was removed and the mixture was cooled to room temperature, and then the adhesion between the resin layer and the opposite surface of the resin layer was examined.
○: Adhesion is not observed between the two films, or the two films are easily peeled off, and no change such as whitening is observed in the resin layer.
X: The resin layer causes cohesive failure, or the resin layer after the two films are peeled off is entirely white.

1. Copolyester resin for layer A construction (1) DEG10
Ethylene glycol as a glycol component and 9.5 mol% of diethylene glycol with respect to all glycols and terephthalic acid as an acid component were charged into an esterification tank and reacted at 275 ° C. for 3 hours to obtain an esterified product. Next, Irganox 1010 (manufactured by BASF) was added to 0.6% by mass with respect to the polyester after polymerization, and melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under a germanium catalyst. Copolymer polyethylene terephthalate (DEG10) having a melting point of 238 ° C. and a glass transition temperature of 70 ° C. was obtained. The diethylene glycol residue relative to the total glycol component was 9.5 mol%.

(2) DEG14, DEG12, DEG8, DEG4, DEG2
(1) and (1) except that the charge ratio of diethylene glycol to the total glycol component was changed to 13.5 mol%, 11.5 mol%, 7.5 mol%, 3.5 mol%, and 1.5 mol%, respectively. The same operation was performed to obtain copolymerized polyethylene terephthalate (DEG14, DEG12, DEG8, DEG4, DEG2), respectively.
The diethylene glycol residues of DEG14, DEG12, DEG8, DEG4, and DEG2 are 14.2 mol%, 12.1 mol%, 8.1 mol%, 3.7 mol%, 2.2 mol% with respect to the total glycol component, respectively, and the melting point is Respectively, 234 degreeC, 236 degreeC, 241 degreeC, 248 degreeC, 252 degreeC and the glass transition temperature were 67 degreeC, 68 degreeC, 70 degreeC, 74 degreeC, and 76 degreeC, respectively.

(3) DEG8-2
Polymerization was carried out in the same manner as DEG8 except that Irganox 1010 was not added to obtain a copolymerized polyethylene terephthalate (DEG8-2) having a relative viscosity of 1.38, a melting point of 240 ° C., and a glass transition temperature of 70 ° C. The diethylene glycol residue with respect to all glycol components was 8.1 mol%.

(4) Hytrel 6347
Polyether PBT elastomer (Tm = 221 ° C., Tg = 3 ° C.) manufactured by Toray DuPont was used.

2. Polyester resin for B layer construction (1) PETG
Ethylene glycol as a glycol component and 34.5 mol% of cyclohexanedimethanol with respect to all glycol components and terephthalic acid as an acid component were charged in an esterification tank and reacted at 275 ° C. for 3 hours to obtain an esterified product. Next, Irganox 1010 (manufactured by BASF) was added to 0.6% by mass with respect to the polyester after polymerization, and melt polymerization was performed at 300 ° C. under a reduced pressure of 1.3 hPa under a germanium catalyst. 38. An amorphous polyester resin (PETG) having a glass transition temperature of 75 ° C. was obtained. The cyclohexanedimethanol residue with respect to all the glycol components was 30 mol%.

(2) PBT
Novaduran 5010CS (Tm = 221 ° C., Tg = 34 ° C.) manufactured by Mitsubishi Engineering Plastics was used.

As the resin layer constituting the biaxially stretched polyester film for release, the following was used.
P-1:
100 g of an ethylene-propylene copolymer (ethylene / propylene = 75/25% by mass) was dissolved in 400 g of xylene heated to 130 ° C. in a four-necked flask under a nitrogen atmosphere. Next, 10 g of a toluene solution of maleic anhydride (5% by mass) and 5 g of a toluene solution of dicumyl peroxide (10% by mass) were respectively added to this solution over 30 minutes, and then the system was kept at 130 ° C. The reaction was performed for 4 hours. After completion of the reaction, the obtained reaction product is put into a large amount of acetone, the resin is precipitated, and further washed with acetone several times to remove unreacted maleic anhydride, followed by drying under reduced pressure to acid-modified ethylene. An α-olefin copolymer P-1 was obtained.

P-2:
In the production of P-1, except that the ethylene-propylene copolymer (ethylene / propylene = 75/25 mass%) was changed to the ethylene-butene copolymer (ethylene / 1-butene = 70/30 mass%), The same operation was performed to obtain an acid-modified ethylene-α-olefin copolymer P-2.

P-3:
In the production of P-1, the same except that the ethylene-propylene copolymer (ethylene / propylene = 75/25 mass%) was changed to the ethylene-propylene copolymer (ethylene / propylene = 90/10 mass%). Operation was performed to obtain an acid-modified ethylene-α-olefin copolymer P-3.

P-4:
In the production of P-1, the same operation was performed except that the amount of the maleic anhydride toluene solution (5% by mass) was changed to 20 g to obtain an acid-modified ethylene-α-olefin copolymer P-4. .

P-5:
In the production of P-1, the same operation was carried out except that the amount of the maleic anhydride toluene solution (5% by mass) was changed to 3 g to obtain an acid-modified ethylene-α-olefin copolymer P-5. .

P-6:
In the production of P-1, the same except that the ethylene-propylene copolymer (ethylene / propylene = 75/25% by mass) was changed to the ethylene-propylene copolymer (ethylene / propylene = 55/45% by mass). The acid-modified ethylene-α-olefin copolymer P-6 obtained by the operation was used.

P-7:
In the production of P-1, the same operation was carried out except that the amount of the maleic anhydride toluene solution (5% by mass) was changed to 40 g and the amount of the dicumyl peroxide toluene solution (10% by mass) was changed to 7 g. The acid-modified ethylene-α-olefin copolymer P-7 obtained above was used.

P-8:
In the production of P-1, except that ethylene-propylene copolymer (ethylene / propylene = 75/25 mass%) was changed to propylene-1-butene copolymer (propylene / 1-butene = 70/30 mass%). Carried out the same operation to obtain an acid-modified propylene-α-olefin copolymer P-8.

P-9:
Bondine “LX-4110” (maleic anhydride-modified polyethylene resin) manufactured by Arkema Inc. was used.

P-10:
Claprene “LIR-403” (acid-modified polyisoprene, number average molecular weight 34000, acid value 9 to 11 mgKOH / g) manufactured by Kuraray Co., Ltd. was used.

P-11:
A non-acid-modified ethylene-propylene copolymer (ethylene / propylene = 70/30% by mass) was used.

Table 1 shows the compositions and characteristics of the resins P-1 to P-11 constituting the resin layer.

Example 1
Using DEG-10 as the resin constituting the A layer, PETG as the resin constituting the B layer is melted at 270 ° C. by separate extruders, and the melts are merged by the composite adapter and then extruded from the T die. Then, it was quenched with a cooling drum to obtain an unstretched laminated film having a three-layer structure of A layer / B layer / A layer. At this time, the discharge amount of each extruder was adjusted so that the thickness composition ratio would be 1/4/1.
The unstretched laminated film was first stretched 3.0 times at 80 ° C. in the longitudinal direction by a roll stretching method. Next, the film was stretched 3.3 times in the transverse direction at 100 ° C. by a tenter stretching method, and then heat-treated at a temperature of 225 ° C. while relaxing 3% in the transverse direction. Further, after cooling the film, the film was wound into a roll by a winder to obtain a laminated biaxially stretched polyester film having a thickness of 50 μm.
On the other hand, an acid-modified ethylene-α-olefin copolymer P-1 was dissolved in toluene so as to be 2% by mass to prepare a solution. The solution and the solution of the oxazoline compound (Nippon Shokubai Co., Ltd., Epocross “WS-500”, solid content concentration: 39% by mass, diluted with isopropyl alcohol), the solid content of the oxazoline compound is acid-modified ethylene-α- A liquid obtained by mixing 2 parts by mass with respect to 100 parts by mass of the olefin copolymer was coated on a biaxially stretched polyester film using a Meyer bar, and then dried at 140 ° C. for 15 seconds. After forming a 0.2 μm thick resin layer on the film, aging was performed at 50 ° C. for 2 days to obtain a release biaxially stretched polyester film.

Examples 2-6, 15, 17, Comparative Examples 1-2
The same procedure as in Example 1 was performed except for the changes shown in Table 2.

Comparative Example 3
DEG-8 was melted by an extruder at a temperature of 270 ° C., and the melt was extruded from a T die and rapidly cooled by a cooling drum to obtain an unstretched monolayer film. Other than that was carried out in the same manner as in Example 1.

Examples 7-14, 16, 18-20 Comparative Examples 4, 7, 10
Except that the type of acid-modified ethylene-α-olefin copolymer and the type and content of the crosslinking agent were changed as shown in Table 2, the same operation as in Example 1 was carried out, and biaxial stretching for mold release was performed. A polyester film was obtained. In Examples 11, 12, 14, 16 and 18, instead of the solution of the oxazoline compound in Example 1, a carbodiimide compound (Carbodilite “V-03” manufactured by Nisshinbo Co., Ltd., solid content concentration: 50% by mass) was mixed with isopropanol. The solution diluted with was used.

Comparative Example 5
60.0 g of maleic anhydride-modified polyethylene resin P-9 (manufactured by Arkema, Bondine “LX-4110”), 90.0 g Isopropyl alcohol, 3.0 g of triethylamine, and 147.0 g of distilled water were charged into a glass container, and the rotation speed of the stirring blade was set to 300 rpm. Then, the system temperature was kept at 140 to 145 ° C. and further stirred for 30 minutes. Then, after putting in a water bath and cooling to room temperature (about 25 ° C.) while stirring at a rotational speed of 300 rpm, pressure filtration (air pressure 0.2 MPa) with a 300 mesh stainless steel filter (wire diameter 0.035 mm, plain weave) Thus, a milky white uniform acid-modified polyethylene resin aqueous dispersion E-1 was obtained.
The obtained acid-modified polyethylene resin aqueous dispersion E-1 and the oxazoline compound solution were mixed so that the solid content of the oxazoline compound was 5 parts by mass with respect to 100 parts by mass of the acid-modified polyethylene resin. A biaxially stretched polyester film for mold release was obtained in the same manner as in Example 1 except that the obtained liquid was applied to the biaxially stretched polyester film.

Comparative Example 6
A biaxially stretched polyester film for mold release was obtained in the same manner as in Example 1 except that no crosslinking agent was added.

Comparative Example 8
A biaxially stretched polyester film for mold release was obtained in the same manner as in Example 1 except that the acid-modified ethylene-α-olefin copolymer was not added.

Comparative Example 9
60.0 g of acid-modified polyisoprene P-10 (manufactured by Kuraray Co., Ltd., Claprene “LIR-403”), 60.0 g of isopropanol, 15 g of triethylamine and 165 g of distilled water were charged into a glass container and heated while stirring at a rotation speed of a stirring blade of 300 rpm, and the system temperature was kept at 120 ° C. and further stirred for 60 minutes. Then, after cooling to room temperature (about 25 ° C.) while stirring with air cooling, pressure filtration (air pressure 0.2 MPa) with a 300 mesh stainless steel filter (wire diameter 0.035 mm, plain weave), milky white uniform An acid-modified polyisoprene aqueous dispersion was obtained. Except that the obtained acid-modified polyisoprene aqueous dispersion and the oxazoline compound solution were mixed so that the solid content of the oxazoline compound was 5 parts by mass with respect to 100 parts by mass of the acid-modified polyisoprene resin. The same operation as in Example 1 was performed to obtain a release biaxially stretched polyester film.

Comparative Example 11
In Example 1, instead of the solution of the oxazoline compound, a solution obtained by diluting an isocyanate compound (BASFAT, Basonat “HW-100”, solid content concentration: 100% by mass) with isopropanol was used. A biaxially stretched polyester film for mold release was obtained by performing the same operation except that the acid-modified ethylene-α-olefin copolymer was mixed in an amount of 10 parts by mass with respect to 100 parts by mass.

Comparative Example 12
In Example 1, in place of the solution of the oxazoline compound, a solution obtained by diluting an epoxy compound (manufactured by DIC, EPICLON “860-90X”, solid content concentration: 90 mass%) with isopropanol was used, and the solid content of the epoxy compound The same operation was performed except that 5 parts by mass was mixed with 100 parts by mass of the acid-modified ethylene-α-olefin copolymer to obtain a release biaxially stretched polyester film.

Comparative Example 13
In Example 1, instead of the oxazoline compound solution, a solution obtained by diluting a melamine compound (Nippon Cytec Industries, Cymel “325”, solid content concentration: 80% by mass) with isopropanol was used. A biaxially stretched polyester film for mold release was obtained by performing the same operation except that the mixture was mixed so that the content was 10 parts by mass with respect to 100 parts by mass of the acid-modified ethylene-α-olefin copolymer.

The biaxially stretched polyester films for release obtained in Examples 1 to 20 were excellent in blocking resistance, and excellent in release properties at room temperature and release properties after heat treatment. Further, since the breaking elongation and breaking stress at 120 ° C. were within the range defined by the present invention, the film was not broken even when evaluated for molding, and was a film suitable for in-mold molding. In Example 19, since the mass ratio of the ethylene component and the α-olefin component constituting the acid-modified ethylene-α-olefin copolymer was not in the preferred range, the releasability was slightly lowered. In Example 20, since the content of the acid-modified component constituting the acid-modified ethylene-α-olefin copolymer was not in the preferred range, the releasability was slightly lowered.

Comparative Example 1 had a low elongation at break, and Comparative Example 2 had a low elongation at break because there were bubbles in the film due to thermal decomposition.
In Comparative Example 3, a monolayer of copolymerized polyethylene terephthalate was used as the substrate. As a result, the breaking stress was high, and the film did not follow the mold in the molding evaluation, resulting in molding failure.
In Comparative Examples 4 and 5, since a resin different from the polyolefin resin specified in the present invention was used for the resin layer, the obtained biaxially stretched polyester film for release was inferior in releasability at room temperature or after heat treatment. Met.
Since Comparative Example 6 did not contain a cross-linking agent in the resin layer, it had a tendency to be inferior in heat resistance and inferior in releasability after heat treatment at 70 ° C.
In Comparative Example 7, since the content of the crosslinking agent component in the resin layer exceeded the amount specified in the present invention, the obtained biaxially stretched polyester film for release had insufficient releasability. There was a tendency to be inferior in releasability after heat treatment at 70 ° C.
In Comparative Example 8, the resin layer could not be uniformly applied to the polyolefin film substrate, the measurement was not possible in the peel strength evaluation, and the moldability evaluation was inferior.
Comparative Example 9 is a case where acid-modified polyisoprene is used as the resin constituting the resin layer, and the obtained biaxially stretched polyester film for release was excellent in releasability and heat resistance, The blocking resistance was significantly reduced.
Comparative Example 10 is a case where an acid-modified ethylene-α-olefin copolymer was used for the resin layer, and the obtained biaxially stretched polyester film for release was inferior in heat resistance and was released by heat treatment. The property decreased significantly.
Comparative Examples 11 to 13 are cases where a crosslinking agent different from the crosslinking agent defined in the present invention was used, and the obtained biaxially stretched polyester film for release was inferior in heat resistance and had releasability by heat treatment. Remarkably reduced.

Claims (6)

Polyester having a resin layer containing 100 parts by mass of an acid-modified ethylene-α-olefin copolymer and 0.1 to 50 parts by mass of an oxazoline compound and / or a carbodiimide compound as a crosslinking agent on at least one side of a polyester film substrate A biaxially stretched polyester film for mold release having a breaking elongation at 120 ° C of 350 to 500% and a breaking stress of 10 to 30 MPa. 2. The biaxially stretched polyester film for mold release according to claim 1, wherein the polyester film substrate comprises a film having at least one copolymer polyester resin layer (A) and a polyester resin layer (B). The biaxially stretched polyester film for mold release according to claim 2, wherein the copolymerized polyester resin layer (A) is made of copolymerized polyethylene terephthalate containing 4 to 12 mol% of diethylene glycol residue with respect to all glycol components. The mass ratio (ethylene component / α-olefin component) of the ethylene component and the α-olefin component constituting the acid-modified ethylene-α-olefin copolymer in the resin layer is 60/40 to 99/1. The biaxially stretched polyester film for mold release according to any one of claims 1 to 3. The content of the acid-modified component constituting the acid-modified ethylene-α-olefin copolymer is less than 1% by mass with respect to the total of the ethylene component and the α-olefin component. The biaxially stretched polyester film for release according to any one of 4. The release strength of the resin layer and the acrylic adhesive material is 0.5 N / cm or less, and the biaxially stretched polyester film for mold release according to any one of claims 1 to 5.