JP2013202985A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film that has a coating layer having superior adhesion, especially, to a polypropylene among polyolefins at high level, and is suitably usable for extrusion lamination on a polyolefin, and the like.SOLUTION: There is provided a laminated polyester film having a coating layer, the coating film being formed by applying a coating agent composition containing carboxyl group containing polyurethane, a polyolefin, and one or more kinds of crosslinking agents.

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 the characteristics capable of 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, the polyester film and the polyolefin have poor adhesion, and it is generally necessary to further provide an adhesive layer to form a laminated film of the polyester film and the polyolefin, resulting in productivity hindrance and cost increase.

  As shown in Patent Documents 1 and 2 and the like, a technique for forming an easily adhesive film by providing an adhesion modified layer on a polyester film has been widely used, but satisfactory adhesion with polyolefin is obtained. Not.

  Patent Document 3 discloses a water-based paint that modifies the adhesion of polyolefin, but is not necessarily 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, wherein the coating layer is formed by coating a coating composition containing a carboxyl group-containing polyurethane, a polyolefin, and one or more crosslinking agents. It exists in the laminated polyester film characterized by this.

  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.

  The coating layer of the present invention can be obtained by coating, drying, and curing a coating solution containing a carboxyl group-containing polyurethane, polyolefin, and one or more crosslinking agents on a film.

  The carboxyl group-containing polyurethane can be obtained by using a polyol component containing a carboxyl group as a urethane component.

  Examples of the carboxyl group-containing polyol component include the following. That is, for example, 2,2′-dimethylolpropionic acid, 2,2′-dimethylolbutanoic acid, 2,2′-dimethylolbutyric acid, 2,2′-dimethylolvaleric acid and the like can be used. Dimethylolpropionic acid and dimethylolbutanoic acid are preferably used.

  The amount of the hydrophilic group in the carboxyl group-containing polyurethane is preferably 0.05% by weight to 8% by weight. When the amount of the hydrophilic group is small, the water solubility or water dispersibility of the polyurethane is poor, and when the amount of the hydrophilic group is large, the water resistance of the coating layer after coating is poor, or the film tends to stick to each other due to moisture absorption. Because there are things.

  As the polyol used for the production of the carboxyl group-containing polyurethane resin, other polyols (for example, polyether diol, polyester diol, polycarbonate diol) and the like may be contained as necessary in addition to the carboxyl group-containing polyol. .

  Examples of the polycarbonate polyol include those obtained by using a transesterification reaction between a diol and a lower dialkylene carbonate such as diethyl carbonate or a carbonate such as diphenyl carbonate and a diol directly with the diol. . In the present invention, as the diol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Polycarbonate polyols using diol, neopentyl glycol, 3-methyl-1.5-pentanediol, 3,3-dimethylol heptane and the like can be used. Among these polycarbonate polyols, those using 1,6-hexanediol as the diol are particularly preferable because they have good adhesion and are easily industrially available.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.) and those having derivative units of lactone compounds such as polycaprolactone.

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Next, the polyisocyanate component of the carboxyl group-containing polyurethane in the present invention will be described.

The isocyanate component in the present invention is preferably composed mainly of aliphatic and alicyclic groups.
Specifically, it is preferable that 50 mol% or more of all the polyisocyanate components is aliphatic or alicyclic polyisocyanate.

  Examples of polyisocyanate components include isophorone diisocyanate, 1,6-hexamethylene diisocyanate, triene diisocyanate, hydrogenated diphenylmethane diisocyanate, trans-1,4-cyclohexylene diisocyanate, 4,7-dimer acid diisocyanate, lysine diisocyanate, 1, 6-diisocyanato-2,2,4-trimethylhexane, cyclohexane-1,3-diyl diisocyanate, cyclohexane-1,4-diyl diisocyanate, cyclohexane-1,3-diylbis (methyl isocyanate), 1-methylcyclohexane-2, Examples include 4-diyl diisocyanate, methyl 2,6-diisocyanatohexanoate, and tetramethylene diisocyanate.

  When an aromatic polyisocyanate is used in an amount of 50 mol% or more of all the polyisocyanate components, the adhesiveness, appearance, and transparency tend to be poor.

  The carboxyl group-containing polyurethane in the present invention may be one having a solvent as a medium, but is preferably one having water as a medium. In order to disperse or dissolve polyurethane in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into a polyurethane resin, and a water-soluble type. In particular, the self-emulsification type in which a hydrophilic group is introduced into the skeleton of the polyurethane resin is preferable because of excellent storage stability of the liquid and water resistance and transparency of the resulting coating layer.

  Examples of the hydrophilic group to be introduced include various groups such as a carboxyl group, a sulfone group, phosphoric acid, phosphonic acid, quaternary ammonium, and polyethylene glycol.

  The polyolefin contained in the coating layer in the present invention is a polymer obtained by polymerizing an alkene such as ethylene or propylene, and includes a copolymer having such a structure.

  The structure of these copolymers is not particularly limited, such as random copolymerization, graft copolymerization, and block copolymerization.

  For example, homopolymers and copolymers such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene can be used. Specifically, polyethylene, Polypropylene, polybutadiene, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, t-butyl peroxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane , Di (t-butyl) peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, 1,1-bis (t-butylperoxy) -3,3,5 -Trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, methyl ethyl ketone -Oxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, t-butyl hydroperoxide, p-menthane hydroperoxide, benzoyl peroxide, p-chlorobenzoyl peroxide, t-butyl peroxyisobuty Examples thereof include rate, hydroxyheptyl peroxide, dichlorohexanone peroxide, ethylene-propylene copolymer, natural rubber, synthetic isopropylene rubber, and ethylene-vinyl acetate copolymer. When the polyolefin resin is a copolymer, it 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. It is advantageous in that heat sealing can be performed at a low temperature by lowering the melting point.

  The mass ratio ((A) / (B)) of the carboxyl group-containing polyurethane (A) and the polyolefin (B) contained in the nonvolatile component of the coating solution is preferably in the range of 5/5 to 9/1. More preferably, it is the range of 6/4-8/2. When outside this range, the appearance and adhesion of the coating layer obtained may be inferior.

  The coating composition used for providing the coating layer of the present invention contains 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, and details thereof are as follows.

  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, -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-4 Hydroxymethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-ethoxymethyl-2-isopropenyl-2-oxazoline and the like, but not limited thereto.

  The polymer containing an oxazoline group used in the present invention may be copolymerized with any other copolymerizable monomer.

  Further, the dispersion ratio of the carboxyl group-containing polyurethane (A) and the polyolefin (B) / oxazoline group-containing crosslinking agent (C1) = 50/10 to 70/5 is preferable in terms of the mixing ratio of the oxazoline-based crosslinking agent. 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-naphthalene 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'-biphe Aromatic polyisocyanates such as nylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenyl isocyanate); hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4′-methylene bis (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.

  Further, the dispersion of the carboxyl group-containing polyurethane resin (A) and the polyolefin (B) / isocyanate (C2) = 60/34 to 80/14 is preferable in terms of the weight ratio of 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 dispersion of the carboxyl group-containing polyurethane resin (A) and the polyolefin (B) / carbodiimide (C3) = 60/34 to 80/14 is preferable in terms of the weight ratio of the carbodiimide-based crosslinking agent.

  Examples of the epoxy-based crosslinking agent in the present invention include a compound having an epoxy group in the molecule, a prepolymer and a cured product thereof. Examples include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, and polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. is there. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compound such as N, N, N ′, N ′,-tetraglycidyl-m-. Examples include xylylenediamine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  Further, the dispersion of the carboxyl group-containing polyurethane resin (A) and the polyolefin (B) / epoxy (C4) = 50/10 to 70/5 is preferable in terms of the weight ratio of the epoxy-based crosslinking agent.

  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 or reduce blocking. If the particle content is too large, the transparency of the coating layer may decrease, the continuity of the coating layer may be impaired, and the coating strength may decrease, or the easy adhesion may decrease. 15% by weight or less, more preferably 10% by weight or less. 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 diameter is too small, the effect of reducing blocking is difficult to obtain, and if it is too large, the coating film easily falls off. 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.).

  The coating solution for providing an easy-adhesive coating layer contains the carboxyl group-containing polyurethane (A), polyolefin (B) and one or more crosslinking agents (C) as essential components and contains other components. Can do. 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 coated layer surface and a non-stretched homopolypropylene film (thickness 60 μm, melting point = 168 ° C., melt flow rate = 15 g / 10 min) are overlapped, and an untreated polyester film is overlapped on the overlapped polyolefin. . The superimposed 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 adhesion interface between the polyester coating layer and the unstretched film of homo PP with both hands. The judgment criteria are as follows.
A: Strongly adhered and the film breaks when it is peeled off ○: The heat-sealed part can be peeled off a little, but it breaks immediately △: It can be peeled off by hand, but it adheres strongly XX: Easy to peel off XX: Don't stick

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

Moreover, the following was used as a coating composition. However, “part” in the text represents the weight ratio in the resin solid content.
(A1): A polyester polyol comprising 1330 parts of terephthalic acid as an acid component, 1163 parts of isophthalic acid, 1167 parts of diethylene glycol as a glycol component, and 497 parts of ethylene glycol is polymerized. Polyurethane resin (A2) obtained by adding 445 parts of isophorone diisocyanate as an isocyanate component and 137 parts of dimethylolpropionic acid and subjecting it to a urethanization reaction: 4123 parts of polyhexamethylene carbonate diol as a diol component, and 252 parts of polypropylene polyol Then, 476 parts of a hydroxyl-terminated polyolefin polyol comprising 224 parts of polyisobutene polyol is mixed. Polyurethane resin obtained by adding 1251 parts of hydrogenated diphenylmethane diisocyanate and 160 parts of dimethylolpropionic acid as an isocyanate component and subjecting it to a urethanization reaction.

(B) A polyolefin random copolymer obtained by polymerizing 1890 parts of polypropylene and 1066 parts of poly-1-butene.
(C1): Copolymer-type crosslinking agent aqueous solution of 2-isopropenyl-2-oxazoline and acrylic monomer, oxazoline group amount = 4.5 mmol / g
(C2): Blocked isocyanate-based crosslinking agent aqueous dispersion Nippon Polyurethane Industry Co., Ltd. Development BWD-102 (having blocked isocyanate group in polymer skeleton)
(C3): Carbodiimide resin crosslinker aqueous dispersion Nisshinbo Chemical Co., Ltd. Trade name Carbodilite (registered trademark)
(C4): Polyglycerol polyglycidyl ether

Examples 1-6:
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. The coating composition as shown in Table 1 was applied to one side of this uniaxially oriented film. Next, this film was guided to a tenter stretching machine, and the coating composition was dried using the heat, while being stretched 4.0 times in the width direction at 100 ° C., and further subjected to heat treatment at 230 ° C. A coated film having a coating layer containing (A1) polyurethane resin, (B) polyolefin resin, and (C1) a cross-linking agent having an oxazoline group as shown in Table 1 on a μm biaxially oriented polyethylene terephthalate film Got. The film properties are shown in Table 1.

Examples 7-8:
In the same process as in Example 1, a coating layer containing (A1) a polyurethane resin, (B) a polyolefin resin, and (C2) a crosslinking agent having an isocyanate group as described in Table 1 on a base film. The coating film which provided was obtained. The properties of this film are shown in Table 1.

Examples 9-10:
In the same process as in Example 1, (A1) polyurethane resin, (B) polyolefin resin, and (C3) carbodiimide group-containing cross-linking agent were provided on the base film as shown in Table 1. A film was obtained. The properties of this film are shown in Table 1.

Example 11:
In the same process as Example 1, (A1) polyurethane resin), (B) polyolefin resin, (C1) an oxazoline group-containing crosslinking agent as a crosslinking agent component, and (C4) epoxy group-containing crosslinking on the base film. The coating film which provided the coating layer which used the agent together as described in Table 1 was obtained. The film properties are shown in Table 1.

Examples 12-16:
In the same process as in Example 1, a coating layer containing (A2) a polyurethane resin, (B) a polyolefin resin, and (C1) a cross-linking agent having an oxazoline group on a base film as described in Table 1. The coating film which provided was obtained. The properties of this film are shown in Table 1.

Examples 17-18:
In the same process as in Example 1, a coating layer containing (A2) a polyurethane resin, (B) a polyolefin resin, and (C2) a crosslinking agent having an isocyanate group as described in Table 1 on a base film. The coating film which provided was obtained. The properties of this film are shown in Table 1.

Examples 19-20:
In the same process as in Example 1, a coated film in which (A2) polyurethane resin, (B) polyolefin resin, and (C3) carbodiimide group-containing crosslinking agent were provided on the base film as shown in Table 1. Got. The properties of this film are shown in Table 1.

Example 21:
In the same process as in Example 1, (A2) polyurethane resin, (B) polyolefin resin, (C1) oxazoline group-containing crosslinking agent, and (C4) epoxy group-containing crosslinking on the base film as a crosslinking agent component. The coating film which provided the coating layer which used the agent together as described in Table 1 was obtained. The film properties are shown in Table 1.

Comparative Example 1:
In the same process as Example 1, the coating film which provided the coating layer of 0.02 g / m < ² > which does not contain a crosslinking agent on a base film, and contains only (A1) polyurethane resin and (B) polyolefin resin. Obtained. As described in Examples 1 to 11, the samples used in combination with various crosslinking agents had good adhesion, but the coating layer containing no crosslinking agent did not provide adhesion.

Comparative Example 2:
In the same process as Example 1, the coating film which provided the coating layer of 0.02 g / m < ² > which contains only (A1) polyurethane resin on the base film was obtained. As described in Examples 1 to 11, the sample used in combination with the olefin resin and various crosslinking agents had good adhesion, but (A1) the result that the adhesive layer was not obtained with the coating layer of only the polyurethane resin. It became.

Comparative Example 3:
In the same process as Example 1, the coating film which provided the coating layer of 0.02 g / m < ² > which does not contain a crosslinking agent on a base film, and contains only (A2) polyurethane resin and (B) polyolefin resin. Obtained. As described in Examples 12 to 21, the samples used in combination with various crosslinking agents had good adhesion, but the coating layer containing no crosslinking agent did not provide adhesion.

Comparative Examples 4-6:
In the same steps as in Example 1, only one type of crosslinking agent selected from (C1) an oxazoline group-containing crosslinking agent, (C2) an isocyanate group-containing crosslinking agent, and (C3) a carbodiimide group-containing crosslinking agent is shown in Table 1. The coating film which provided the coating layer contained as mentioned above was obtained. In the case of the coating layer containing only the crosslinking agent, a coating layer excellent in adhesiveness with PP was not obtained.

Comparative Example 7:
In the same process as Example 1, the film which does not provide a coating layer on a base film was obtained. Adhesiveness could not be obtained with a film having no coating layer.

  The obtained results are summarized in Table 1 below. In Table 1, as for the component ratio, the non-volatile content of each component in the coating solution is described by weight ratio.

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

Claims (1)

A polyester film having a coating layer, wherein the coating layer is formed by coating a coating composition containing a carboxyl group-containing polyurethane, a polyolefin, and one or more crosslinking agents.