JP2011230502A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film which has a coating layer suitable for extrusion laminating a polyolefin and excellent in bonding property with the polyolefin, and particularly a coating layer remarkably excellent in the bonding property with a polypropylene.SOLUTION: In the polyester film having the coating layer, the coating layer is made by applying a coating composition containing a modified polyolefin having two melting points and one kind or more crosslinking agents on one side of the film and drying the coating composition in the laminated polyester film.

Description

  The present invention relates to a laminated polyester having a coating layer excellent in adhesion to polyolefin, particularly polypropylene.

  Polyester films are used in a wide range of fields because they are excellent in mechanical properties and processing properties and are relatively inexpensive. A laminate of a polyester film and a polyolefin is widely used for packaging materials and the like because of its excellent film strength and gas barrier properties and heat sealing. In recent years, it has begun to be used for automobiles and solar cells. For the production of such a laminate, there are a method of extrusion laminating polyester and polyolefin, a method of heat sealing, and the like. However, polyester film and polyolefin have poor adhesion, and it is generally necessary to provide an additional adhesive layer to form a laminated film of polyester film and polyolefin, resulting in productivity hindrance and cost increase. . In addition, as shown in Patent Documents 1 and 2, etc., a method of providing an adhesion-modifying layer on a polyester film to make an easy-adhesive film is widely performed. Not obtained.

  Further, Patent Document 3 discloses a water-based paint for modifying the adhesion of polyolefin, but it is not always sufficient for improving the adhesion between the polyester film and the polyolefin.

JP 2004-256625 A Japanese Patent Laid-Open No. 8-31121 Japanese Patent No. 3759160

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the laminated polyester film which has a coating layer excellent in adhesiveness with polyolefin, especially polypropylene.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a coating layer containing a specific type of compound, and the present invention has been completed.

  That is, the gist of the present invention is a polyester film having a coating layer, and the coating layer includes a coating composition containing a modified polyolefin having two melting points and one or more crosslinking agents on one side of the film. It exists in the laminated polyester film characterized by being apply | coated and drying.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated polyester film which has a coating layer excellent in adhesiveness with polyolefin, especially polypropylene can be provided, and the industrial value of this invention is high.

The base film of the coated film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.
For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles used are selected according to the use and purpose of the film, but the average particle size is usually in the range of 0.01 to 5.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film becomes too rough, or the particles are likely to fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained. About particle | grain content, it is 0.0003 to 1.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 0.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 1.0% by weight, the transparency of the film is poor. It may be enough. In addition, when it is particularly desired to ensure transparency, smoothness, etc. of the film, it can also be configured so as not to substantially contain particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

  The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on the purpose.

  The polyester film of the present invention has an easily adhesive coating layer on at least one surface, but even if a similar or other coating layer or functional layer is provided on the opposite surface of the film, it is naturally included in the concept of the present invention. is there.

  The easy-adhesion coating layer of the present invention is obtained by coating a coating composition on a polyester film. Various methods can be applied to the coating, but a so-called in-line coating in which a coating layer is provided during film formation, particularly a coating stretching method in which stretching is performed after coating is preferably used.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent. According to such a method, since film formation and coating layer coating can be performed simultaneously, there is an advantage in manufacturing cost, and since stretching is performed after coating, a uniform coating with a thin film is achieved, so that adhesion performance is stabilized. . Moreover, the polyester film before biaxially stretching is first covered with an easy-adhesive resin layer, and then the film and the coating layer are stretched simultaneously, whereby the base film and the coating layer are firmly adhered. In addition, biaxial stretching of the polyester film is achieved by stretching the film in the lateral direction while holding the film edge with a tenter, so that the film is constrained in the longitudinal / lateral direction. High temperature can be applied while maintaining Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. As an easily-adhesive polyester film, the uniformity of the coating layer, the improvement of the film-forming property, and the adhesion between the coating layer and the film often produce favorable characteristics.

  In this case, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, and water as the main medium, as long as it does not exceed the gist of the present invention. An organic solvent may be contained.

  Next, the coating layer provided on the film in the present invention will be described.

  The (A) polyolefin contained in the coating layer in the present invention is a polymer obtained by polymerizing alkenes such as ethylene and propylene, and includes a copolymer having such a structure. The polyolefin used in the present invention is preferably a polypropylene polymer.

  Polyolefin, which is a component constituting the coating layer in the present invention, has two melting points (Tm). Regarding the two melting points, the low-temperature side melting point Tm1 is preferably in the range of 0 to 50 ° C, and the high-temperature side melting point Tm2 is preferably in the range of 50 to 180 ° C. More preferably, Tm2 is 50 to 100 ° C.

  For example, such polyolefin can be obtained by copolymerizing a compound having a melting point of 0 to 50 ° C. with an olefin polymer, preferably a propylene polymer. The copolymerizable compound is preferably hydrophilic because it is difficult to disperse water if it is hydrophobic. Polyalkylene oxide and polyalkyleneimine are preferably used as the hydrophilic compound, and examples thereof include polyethylene oxide, polypropylene oxide, and polyethyleneimine.

  In the present invention, a sample obtained by vacuum drying a polyolefin solution or water dispersion is heated from −100 ° C. to 200 ° C. at a rate of 10 ° C. per minute by DSC measurement (differential thermal analysis), and then −100 ° C. Then, the temperature indicated by the endothermic peak when the temperature is raised again to 200 ° C. at 10 ° C. per minute is defined as the melting point.

  Hereinafter, the polypropylene polymer will be described in detail.

The propylene polymer used in the present invention is not particularly limited as long as the effects of the present invention are not significantly impaired, and various known propylene polymers and modified propylene polymers can be used. It may be a propylene polymer having a reactive group or a propylene polymer having no reactive group.

Examples of the propylene polymer having no reactive group include a propylene homopolymer, a copolymer of ethylene and propylene, propylene and other comonomers such as 1-butene, 1-pentene, 1-hexene and 1-heptene. , 1-octene, cyclopentene, cyclohexene and other α-olefin comonomers having 2 or more carbon atoms, or copolymers of two or more of these comonomers can be used. Specific examples of the propylene polymer include polypropylene,
Ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer, propylene-hexene copolymer, chlorinated polypropylene, chlorinated ethylene-propylene copolymer, chlorinated propylene-butene copolymer Such as coalescence.

  The copolymer may be a random copolymer or a block copolymer, but is preferably a random copolymer that can lower the melting point of the copolymer more effectively. Lowering the melting point is advantageous in that heat sealing is possible at a low temperature.

Examples of the propylene-based polymer having a reactive group include a copolymer (a) obtained by copolymerizing an unsaturated compound having no reactive group and an unsaturated compound having a reactive group at the time of polymerization, or a reactive group. A polymer (b) obtained by graft polymerization of a radical polymerizable unsaturated compound having a propylene-based polymer can be used.
The copolymer (a) is obtained by copolymerizing an unsaturated compound having no reactive group and an unsaturated compound having a reactive group, and the unsaturated compound having a reactive group is inserted into the main chain. Copolymer. For example, an α-olefin such as ethylene, propylene, or butene and an α, β-unsaturated carboxylic acid or anhydride such as acrylic acid or maleic anhydride can be obtained as a copolymer. Specific examples of the copolymer include a propylene-acrylic acid copolymer and a propylene-acrylic acid ester-maleic anhydride copolymer. The copolymer (b) is obtained by graft polymerization of a prepolymerized propylene polymer with a radically polymerizable unsaturated compound having a reactive group, and the unsaturated compound having a reactive group is grafted to the main chain. Yes. For example, (meth) acrylic acid, fumaric acid, maleic acid or its anhydride, itaconic acid or its anhydride, crotonic acid, (meth) acrylic acid 2-propylene polymer such as polypropylene and propylene-butene copolymer Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, (dimethylamino) ethyl (meth) acrylate, glycidyl (meth) acrylate, ethyl (meth) acrylate (2-isocyanate), etc. A grafted polymer. These may be used singly or in combination of two or more. The propylene polymer may be linear or branched.

  Examples of reactive groups used in polypropylene polymers having reactive groups include carboxylic acid groups, dicarboxylic anhydride groups, and carboxylic anhydride monoester groups, hydroxyl groups, amino groups, epoxy groups, and isocyanate groups. Can be mentioned. More preferably, the propylene-based polymer has at least one selected from the group consisting of carboxylic acid derivative groups, that is, carboxylic acid groups, dicarboxylic anhydride groups, and dicarboxylic anhydride monoester groups. These carboxylic acid groups and the like have high reactivity and are easy to bond with various polymers, and many unsaturated compounds having these groups are easily copolymerized or graft-reacted to a propylene polymer.

  Moreover, what combined the acidic group with the propylene-type polymer can also be used as a polymer as it is. The propylene polymer may be linear or branched.

  The most preferred polyolefin in the present invention is a copolymer having a polypropylene structure and a polyethylene oxide structure, and a copolymer obtained by grafting polyethylene oxide to a polymer having a polypropylene structure.

The coating layer of the present invention contains (B) a crosslinking agent as an essential component.
The crosslinking agent in the present invention refers to a compound that undergoes a crosslinking reaction by heat, such as oxazoline, epoxy, isocyanate, carbodiimide, and the like. Since the crosslinking point (crosslinking density) varies depending on the type of the crosslinking agent, the optimum addition amount varies.

The oxazoline-based crosslinking agent in the present invention is a compound having an oxazoline group in the molecule. In particular, a polymer synthesized using a monomer containing an oxazoline compound as at least one of the raw material monomers is preferable. Examples of the oxazoline compound include 2-oxazoline, 3-oxazoline, and 4-oxazoline compound, and any of them may be used. In particular, the 2-oxazoline compound is rich in reactivity and has been industrially put into practical use.
For example, 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-vinyl-5,6- Dihydro-4H-1,3-oxazine, 4,4,6-trimethyl-2-vinyl-5,6-dihydro-4H-1,3-oxazine, 2-isopropenyl-2-oxazoline, 4,4-dimethyl- 2-Isopropenyl-2-oxazoline, 4-acryloyl-oxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyl-oxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyl-oxymethyl-2 -Phenyl-4-methyl-2-oxazoline, 2- (4-vinylphenyl) -4,4-dimethyl-2-oxazoline, 4-ethyl- - hydroxymethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-ethoxymethyl-2-isopropenyl-2-but-oxazoline, and the like, but is not limited thereto.
The polymer containing an oxazoline group used in the present invention may be copolymerized with any other copolymerizable monomer.

  The blending ratio of the oxazoline-based crosslinking agent is preferably olefin / oxazoline = 87/7 to 10/84, more preferably 87/7 to 50/44, and particularly preferably 80/14 to 70/44. 34. Moreover, you may use together with an epoxy-group containing crosslinking agent.

The isocyanate crosslinking agent used in the present invention is not particularly limited as long as it has an isocyanate group as a functional group in the compound, and a known polyisocyanate crosslinking agent can be used. Specifically, generally used water-dispersed polyisocyanate crosslinking agents can be used. The water-dispersible polyisocyanate-based crosslinking agent is a polyisocyanate polymer having a hydrophilic group introduced therein, and can be dispersed in water as fine particles when added to water and stirred.
Examples of the polyisocyanate constituting the water-dispersible polyisocyanate include aliphatic isocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, lysine diisocyanate, and dimer acid diisocyanate; Isocyanate, diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, 1,5-phthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether isocyanate, (m- or p-) phenylene Diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-biphenyl Aromatic polyisocyanates such as diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate); hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methyl Cyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, Examples thereof include alicyclic diisocyanate compounds such as 1,2-cyclohexane diisocyanate. As such a polyisocyanate compound, a polyisocyanate compound having an isocyanurate structure, a urethane structure, a biuret structure, an allophanate structure, a uretdione structure, a trimer structure, or the like can also be used. So-called blocked isocyanates in which isocyanate groups are blocked with active hydrogen groups may be used.

  Moreover, olefin / isocyanate = 80/14 to 30/64 is preferable, and more preferably 80/14 to 40/54 in terms of weight ratio with respect to the isocyanate-based crosslinking agent.

  The carbodiimide-based crosslinking agent used in the present invention is a compound having a carbodiimide group in the molecule. In particular, polycarbodiimide compounds having two or more carbodiimide groups in the molecule are suitable. For example, as shown in JP-A-10-316930 and JP-A-11-140164, organic polyisocyanates are particularly preferable. Is produced using organic diisocyanate as the main synthetic raw material.

Further, the weight ratio of carbodiimide-based crosslinking agent is preferably olefin / carbodiimide = 80/14 to 30/64, and more preferably 60/34 to 40/54.
In addition, any of the above cross-linking agents cannot be used as an easy-adhesion layer with good adhesion to polyolefin, and must be used in combination with olefin.

  In the present invention, particles may be contained in the coating layer in order to give film slipperiness and to reduce blocking. If the content of the particles is too large, the transparency of the coating layer may decrease, the continuity of the coating layer may be impaired, the coating strength may decrease, and the easy adhesion may decrease. Less than 10% by weight is preferable. Moreover, there is no limitation in particular about the minimum of particle content.

  As the particles, for example, inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles can be used. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  If the particle size is too small, it is difficult to obtain an effect of reducing blocking, and if it is too large, the particles are likely to fall off the coating film. The average particle size is preferably about 1/2 to 10 times the thickness of the coating layer. Furthermore, if the particle size is too large, the transparency of the coating layer may be inferior, so the average particle size is preferably 300 nm or less, and more preferably 150 nm or less. The average particle diameter of the particles described here can be obtained by measuring the 50% average diameter of the number average of the particle dispersion with Microtrac UPA (Nikkiso Co., Ltd.).

  In the coating liquid for providing the easily adhesive coating layer, the above-described components are essential, and other components can be included. For example, surfactants, other binders, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments, and other crosslinking agents. These additives may be used alone or in combination of two or more as necessary.

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may give a chemical process, a corona discharge process, a plasma process, etc. to a film before application | coating.
The lower limit of the coating amount of the coating layer provided on the polyester film 0.005 g / ^{m 2,} more preferably 0.01 g / ^{m 2,} particularly preferably 0.02 g / ^{m 2.} The upper limit is 0.1 g / m ² , preferably 0.08 g / m ² , particularly preferably 0.06 g / m ² .

The coating amount tends to be insufficient adhesion between when the olefin is less than 0.005 g / ^{m 2,} when more than 0.1 g / m ² are likely to occur deterioration of coating appearance.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example and a comparative example is as follows.

(1) Adhesiveness For the evaluation of adhesiveness, a heat seal sample was prepared under the following conditions. That is, a polyester film coating layer surface and a homopolypropylene unstretched film (thickness 60 μm, melting point = 168 ° C., melt flow rate = 15 g / 10 min) are overlapped, and an untreated polyester film is placed on the overlapped polypropylene. Overlapping. The superposed sample was pressed for 2 minutes under the conditions of a heat seal temperature of 160 ° C. and a press pressure of 5 kg / cm ² to prepare a sample for evaluation having a heat seal width of 1.5 cm. Thereafter, the adhesion was evaluated by slowly tearing the adhesive interface between the polyester coating layer and the unstretched film of homopolypropylene with both hands. The judgment criteria are as follows.
A: Strongly adhered, and the film breaks when peeled off. ○: The heat-sealed part can be peeled off a little, but it breaks immediately. Δ: It can be peeled by hand, but it adheres strongly. Can be peeled off by hand XX: Not tight

(2) Appearance Using a halogen light, the appearance of the coating was visually determined according to the following criteria.
○: Appearance is good ○ △: Unevenness is slightly visible on part of the coating surface △: Unevenness is slightly visible on the entire coating surface △: Unevenness is visible on the entire coating surface ×: Unevenness is clearly visible on the entire coating surface

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1): Polyethylene terephthalate having an intrinsic viscosity of 0.66 substantially free of particles (Polyester 2): containing 0.6 parts by weight of amorphous silica having an average particle diameter of 2.5 μm 66 polyethylene terephthalate The following was used as the coating composition. However, “part” in the text represents the weight ratio in the resin solid content.
(A1): Polypropylene modified with polyethylene glycol at two points, Tm1 = about 20 ° C., Tm2 = about 70 ° C. (A2): Two points of melting point, Tm1 = about 30 ° C. Tm2 = Polypropylene (A3) having a melting point of about 150 ° C. One point of melting point, modified polypropylene (B1) having Tm = 160 ° C .: Oxazoline group-containing crosslinking agent: WS-500: (Nippon Catalyst)
(B2): Epoxy group-containing crosslinking agent: EX-521 (Nagase Kasei)
(B3): Isocyanate-based crosslinking agent: BWD102 (Nippon Polyurethane)
(B4): Carbodiimide group-containing crosslinking agent: E02 (Nisshinbo)

Examples 1-8:
Polyester 1 and polyester 2 are blended at a weight ratio of 95/5, dried thoroughly, melted by heating to 280-300 ° C., extruded into a sheet form from a T-shaped die, and the surface using an electrostatic adhesion method It cooled and solidified, making it closely_contact | adhere to the mirror surface cooling drum of temperature 40-50 degreeC, and the unstretched polyethylene terephthalate film was created. This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. A coating composition as shown in Table 1 below was applied to one side of the uniaxially oriented film. Next, this film was guided to a tenter stretching machine, and the coating composition was dried using the heat, and stretched 4.0 times in the width direction at 100 ° C., and further heat-treated at 230 ° C., and the film thickness was 38 μm. 0.02 g containing an olefin (A1) having melting points Tm1 = 20 ° C. and Tm2 = 70 ° C. on the biaxially oriented polyethylene terephthalate film and a cross-linking agent having an oxazoline group (B1) as shown in Table 1. A coating film provided with a coating layer of / m ² was obtained. It shows in Table 1 about the addition amount and film characteristic of a crosslinking agent.

Examples 9-13:
In the same process as in Example 1, the olefin (A1) having melting points Tm1 = 20 ° C. and Tm2 = 70 ° C. and the cross-linking agent (B1) having an oxazoline group on the base film as shown in Table 1 The coating film which provided the coating layer of 0.005 g / m < ² > to contain was obtained. Table 1 shows the amount and characteristics of the crosslinking agent added to the film.

Examples 14-20
In the same process as in Example 1, an olefin (A1) having melting points Tm1 = 20 ° C. and Tm2 = 70 ° C., an oxazoline group-containing crosslinking agent (B1), an epoxy group-containing crosslinking agent (B2) on the base film. The coating film which provided the coating layer which used together as shown in Table 1 was obtained.
The film thickness was changed as shown in Table 1 at a weight ratio of olefin / oxazoline / epoxy = 60/24/10. In Examples 18 to 20, since the film thickness was thick, uneven coating was conspicuous, and the appearance was slightly inferior. Other film properties are shown in Table 1.

Examples: 21-24:
In the same process as in Example 1, an olefin (A1) having a melting point Tm1 = 20 ° C. and Tm2 = 70 ° C. and a crosslinking agent (B3) having an isocyanate group are contained on the base film as shown in Table 1. A coated film provided with a coating layer of 0.015 g / m ² was obtained. It shows in Table 1 about the addition amount of a crosslinking agent, and a film characteristic.

Examples 25-28:
In the same process as in Example 1, an olefin (A1) having a melting point Tm1 = 20 ° C. and Tm2 = 70 ° C. and a crosslinking agent (B4) having a carbodiimide group on the base film as shown in Table 1. The coating film which provided the coating layer of 0.015 g / m < ² > containing was obtained. The amount of crosslinking agent added and film characteristics are shown in Table 1.

Comparative example: 1
In the same process as Example 1, a 0.02 g / m ² coating layer containing only an olefin (A1) having a melting point Tm1 = 20 ° C. and Tm2 = 70 ° C. containing no crosslinking agent on the base film. The provided coating film was obtained. As described in Examples 1 to 24, the samples used in combination with various crosslinking agents had good adhesion, but the coating layer containing no crosslinking agent did not provide adhesion.

Examples: 29-31
In the same process as in Example 1, an olefin (A2) having melting points Tm1 = 30 ° C. and Tm2 = 150 ° C. is used, and an oxazoline group-containing crosslinking agent (B1), an isocyanate group-containing crosslinking agent (B3), and a carbodiimide group are contained. A coating film provided with a coating layer containing one crosslinking agent selected from the crosslinking agents (B4) as shown in Table 1 was obtained.

Comparative examples: 2-4
In the same process as in Example 1, a polyolefin (A3) having a melting point Tm1 = 160 ° C. was used, an oxazoline group-containing crosslinking agent (B1), an isocyanate group-containing crosslinking agent (B3), and a carbodiimide group-containing crosslinking agent (B4). The coating film which provided the coating layer which contains 1 type of crosslinking agents chosen from inside as Table 1 was obtained. Since these coating layers used olefin having only one melting point, the adhesion was insufficient regardless of the type of crosslinking agent.

Comparative examples: 5-7
In the same process as Example 1, the coating film which did not contain an olefin on the base film and provided the coating layer 0.02g / m < ² > of only a crosslinking agent was obtained. A coating layer excellent in adhesiveness with polypropylene could not be obtained with only the crosslinking agent.

  The film of the present invention is a biaxially stretched polyester film excellent in adhesion to polyolefin, and can be suitably used for extrusion lamination with polyolefin and the like.

Claims (1)

A polyester film having a coating layer, wherein the coating layer is formed by coating a coating composition containing a modified polyolefin having two melting points and one or more cross-linking agents on one side of the film and drying. A laminated polyester film characterized.