Laminated film

Abstract

To provide an environment-compatible laminated film that comprises an inorganic thin film layer and a protective layer in this order on a substrate film layer using a polyester resin recycled from plastic bottles, and that has an excellent barrier property and adhesiveness even after a severe wet heat treatment such as retort sterilization, and that has less deterioration in appearance of a film even after retort treatment.SOLUTION: There is provided a laminated film, comprising an inorganic thin film layer on at least one surface of a substrate film, and a protective layer containing an urethane resin on the inorganic thin film layer. The laminated film satisfies the following requirements (a) to (c). Requirement (a): the substrate film contains 50 wt.% or more of a polyester resin recycled from plastic bottles. Requirement (b): a standard deviation of a haze after retort treatment of the laminated film at 130°C for 30 minutes is 0.5% or less. Requirement (c): an adhesion amount of the protective layer is 0.5 g / m2 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a laminated film used in the packaging field of foods, pharmaceuticals, industrial products, etc. More specifically, it is a laminated film having an inorganic thin film layer and a protective layer in this order on a base film layer made of a polyester resin recycled from PET bottles, which is excellent in barrier properties and adhesiveness, and has excellent gas barrier properties even when used in applications subjected to severe wet heat treatment such as retort sterilization.

Background Art

[0002] In recent years, regulations for reducing the use of disposable plastics have been strengthened in various countries around the world including Europe. The background includes the growing international awareness of resource circulation and the exacerbation of waste problems in emerging countries. Therefore, for plastic packaging materials required for foods, pharmaceuticals, etc., environmentally friendly products are demanded from the perspective of 3R (recycle, reuse, reduce).

[0003] Performance requirements for the above-mentioned environmentally friendly packaging materials include being made of recycled materials, having gas barrier performance that can block various gases and extend the shelf life, using materials with low environmental impact (for example, not using organic solvents or having a small amount of material used), etc.

[0004] As a typical recycled material, a polyester resin recycled from PET bottles is known, and a technology is known to make a polyester film for body wrap labels with less trouble due to static electricity from a polyester resin derived from PET bottles with a low oligomer content without sacrificing productivity and quality (see, for example, Patent Document 1). With the increasing environmental regulations in the future, an expansion in demand for such film applications is expected.

[0005] On the one hand, in food applications that require blocking various gases such as water vapor and oxygen, a gas barrier laminate in which a metal thin film made of aluminum or the like and an inorganic thin film made of an inorganic oxide such as silicon oxide or aluminum oxide are formed on the surface of a base film made of plastic is generally used. Among them, those with a thin film of an inorganic oxide (inorganic thin film layer) such as silicon oxide, aluminum oxide, or a mixture thereof are widely used because there is no need to use aluminum foil and they are transparent and the contents can be confirmed.

[0006] Regarding the gas barrier film composed of the aforementioned recycled material and the inorganic thin film, when a gas barrier laminate film having an inorganic thin film layer and a sealant layer is formed using a polyester resin recycled from a PET bottle and having low heat shrinkage and small thickness unevenness, a laminate film exhibiting good gas barrier properties has been proposed (for example, Patent Document 2). However, in such a conventional technology, no consideration has been given to the interfacial adhesiveness after sterilization treatment such as retort treatment that can extend the shelf life, and the barrier performance after retort treatment has not been examined.

[0007] As a means of maintaining the barrier property and adhesiveness even after retort treatment, it has been reported that a coating layer made of an oxazoline group-containing water-soluble polymer is provided between the base film and an inorganic thin film layer formed by, for example, a vapor deposition method (see, for example, Patent Document 3). Providing a coating layer between the base film and the inorganic thin film can also be performed continuously during the film formation of the base material, and a greater cost reduction can be expected compared to forming a protective layer on the inorganic thin film. However, in the case of the above configuration, the coating layer itself has no gas barrier property, and the contribution to the gas barrier property is mainly due to the inorganic thin film layer only, so there is a problem that the gas barrier property is not sufficient.

[0008] In response to the above problems, attempts have been made to provide a protective layer having gas barrier properties on the inorganic thin film. For example, a method of coating a water-soluble polymer, an inorganic layered compound, and a metal alkoxide or its hydrolyzate on the inorganic thin film to form a composite of an inorganic substance containing the inorganic layered compound and the water-soluble polymer on the inorganic thin film by the sol-gel method, and a laminate in which a metaxylylene group-containing polyurethane is coated on the inorganic thin film (see, for example, Patent Document 4) can be mentioned.

[0009] By providing the coating layer, the inorganic thin film layer, and the protective layer, it is possible to maintain the barrier performance after retort treatment and the adhesiveness at the interfaces of each layer when made into a laminate. However, regarding the base material and the coating material, those with less environmental load have not been used with awareness, and there has been a concern about a large environmental load. Furthermore, the film whitening during retort treatment at high temperature has not been studied. That is, when the film is exposed to high temperature, the film may turn white due to the precipitation of oligomers in the base material and the uneven deformation of the coating / protective layer, which may have an adverse effect on the appearance and printability. In particular, when a film is made using a resin derived from a PET bottle, the haze value may originally be high, and the inventors have found that the haze value further increases after retort.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] In Patent Document 2 mentioned above, the gas barrier properties and adhesiveness after severe wet heat treatment such as retort treatment were not examined. In Patent Document 3 mentioned above, the gas barrier performance was insufficient. In Patent Document 4 mentioned above, the deterioration of the film appearance after retort treatment was not examined.

[0012] The present invention has been made against the background of such problems of the prior art. That is, an environmentally friendly laminated film having an inorganic thin film layer and a protective layer in this order on a base film layer using a polyester resin recycled from a PET bottle, which is excellent in barrier properties and adhesiveness even after severe wet heat treatment such as retort sterilization, and provides a laminated film with little film appearance deterioration even after retort treatment.

Means for Solving the Problems

[0013] The inventors of the present invention have found that by making a laminated film having a structure in which an inorganic thin film layer is sandwiched between a specific coating layer or a specific barrier protective layer excellent in flexibility and adhesiveness, the gas barrier performance before treatment can be improved and the barrier properties and adhesiveness can be maintained even after severe wet heat treatment. Furthermore, by using a polyester resin derived from a PET bottle with a low environmental load as a base material, it has been found that there is little whitening after retort treatment, and the present invention has been completed.

[0014] That is, the present invention has the following configuration. (1) A laminated film having an inorganic thin film layer on at least one side of a base film and a protective layer having a urethane resin on the inorganic thin film layer, wherein the laminated film satisfies the following requirements (a) to (c). (a) The base film contains 50% by weight or more of a polyester resin recycled from a PET bottle. (b) The standard deviation of the haze of the laminated film after retort treatment at 130°C for 30 minutes is 0.5% or less. (c) The coating amount of the protective layer is 0.5 g / m 2 or less. (2) The laminated film according to (1), wherein the protective layer contains an aromatic or araliphatic component as a constituent component. (3) The laminated film according to (1) or (2), wherein the protective layer contains a metaxylylene diisocyanate component as a constituent component. (4) The laminated film according to any one of (1) to (3), having a coating layer between the base film layer and the inorganic thin film layer, wherein the coating layer contains a resin having an oxazoline group or a carbodiimide group as a constituent component. (5) The laminated film according to any one of (1) to (4), wherein the inorganic thin film layer is a layer of aluminum oxide or a composite oxide of silicon oxide and aluminum oxide. (6) A packaging material obtained by laminating a sealant layer on one side of the laminated film according to any one of (1) to (5). [Advantages of the Invention]

[0015] According to the present invention, it has become possible to provide a laminated film that is excellent in barrier properties and adhesiveness even after severe wet heat treatment such as retort sterilization while using recycled materials, and has little deterioration in the appearance of the film even after retort treatment. [Embodiments for Carrying Out the Invention]

[0016] Hereinafter, the present invention will be described in detail. [Base Film Layer] In the present invention, as described later, it is a preferred embodiment to use a recycled polyester resin regenerated from a PET bottle containing an isophthalic acid component as a raw material for the base film. Therefore, the base film is a mixed resin of a recycled polyester resin and a virgin raw material, that is, a resin that has not been recycled. The intrinsic viscosity of the resin constituting the film means a value obtained by measuring the intrinsic viscosity of the mixed resin constituting these films. The lower limit of the intrinsic viscosity of the resin constituting the film obtained by measuring the base film is preferably 0.58 dl / g, more preferably 0.60 dl / g. If it is less than 0.58 dl / g, many recycled resins made of PET bottles have an intrinsic viscosity exceeding 0.68 dl / g. When using it to produce a film, if the viscosity is reduced, uneven thickness defects may occur, which is not preferable. Also, since the film may be colored, it is not preferable. The upper limit is preferably 0.70 dl / g, more preferably 0.68 dl / g. If it exceeds 0.70 dl / g, the resin from the extruder may be difficult to discharge, and productivity may decrease, which is not preferable.

[0017] The lower limit of the thickness of the base film is preferably 8 μm, more preferably 10 μm, and even more preferably 12 μm. If it is less than 8 μm, the strength of the film may be insufficient, which is not preferable. The upper limit is preferably 200 μm, more preferably 50 μm, and even more preferably 30 μm. If it exceeds 200 μm, it may become too thick and difficult to process. Also, an increase in the film thickness is not preferable in terms of environmental load, and it is preferable to reduce the volume as much as possible.

[0018] The lower limit of the refractive index in the thickness direction of the base film is preferably 1.4930, more preferably 1.4940. If it is less than 1.4930, the orientation may not be sufficient, and laminate strength may not be obtained in some cases. The upper limit is preferably 1.4995, more preferably 1.4980. If it exceeds 1.4995, the surface orientation may collapse, and mechanical properties may be insufficient, which is not preferable.

[0019] The lower limit of the heat shrinkage rate of the base film in the longitudinal direction (sometimes referred to as MD) and the transverse direction (sometimes referred to as TD) at 150°C for 30 minutes is preferably 0.1%, more preferably 0.3%. If it is less than 0.1%, the improvement effect will saturate, and in addition, it may become mechanically brittle, which is not preferable. The upper limit is preferably 3.0%, more preferably 2.5%. If it exceeds 3.0%, pitch misalignment or the like may occur due to dimensional changes during processing such as printing, which is not preferable. Also, if it exceeds 3.0%, shrinkage in the width direction or the like may occur due to dimensional changes during processing such as printing, which is not preferable.

[0020] As the raw material of the base film, it is preferable to use a recycled polyester resin made from PET bottles containing an isophthalic acid component as an acid component. For the polyester used in PET bottles, in order to have a good bottle appearance, the crystallinity is controlled. As a result, a polyester containing 10 mol% or less of the isophthalic acid component may be used. In order to utilize recycled resins, materials containing an isophthalic acid component may be used.

[0021] The lower limit of the amount of the terephthalic acid component in all the dicarboxylic acid components constituting the polyester resin contained in the base film is preferably 95.0 mol%, more preferably 96.0 mol%, still more preferably 96.5 mol%, and particularly preferably 97.0 mol%. If it is less than 95.0 mol%, the crystallinity will decrease, and the heat shrinkage rate may increase, which is not very preferable. Also, the upper limit of the amount of the terephthalic acid component in the polyester resin contained in the film is preferably 99.5 mol%, more preferably 99.0 mol%. Since many recycled polyester resins made from PET bottles have dicarboxylic acid components other than terephthalic acid represented by isophthalic acid, for the terephthalic acid component constituting the polyester resin in the film to exceed 99.5 mol% will result in difficulty in manufacturing a polyester film with a high ratio of recycled resin, which is not very preferable.

[0022] The lower limit of the amount of isophthalic acid component in all dicarboxylic acid components constituting the polyester resin contained in the base film is preferably 0.5 mol%, more preferably 0.7 mol%, still more preferably 0.9 mol%, and particularly preferably 1.0 mol%. Since some recycled polyester resins made of PET bottles contain a large amount of isophthalic acid component, if the isophthalic acid component constituting the polyester resin in the film is less than 0.5 mol%, it will be difficult to produce a polyester film with a high ratio of recycled resin as a result, which is not very preferable. The upper limit of the amount of isophthalic acid component in all dicarboxylic acid components constituting the polyester resin contained in the film is preferably 5.0 mol%, more preferably 4.0 mol%, still more preferably 3.5 mol%, and particularly preferably 3.0 mol%. If it exceeds 5.0 mol%, the crystallinity will decrease, and the heat shrinkage rate may increase, which is not very preferable. Also, by setting the content rate of the isophthalic acid component within the above range, it becomes easy to create a film excellent in laminate strength, shrinkage rate, and thickness unevenness, which is preferable.

[0023] The upper limit of the intrinsic viscosity of the recycled resin made of PET bottles is preferably 0.90 dl / g, more preferably 0.80 dl / g, still more preferably 0.77 dl / g, and particularly preferably 0.75 dl / g. If it exceeds 0.9 dl / g, the resin may be difficult to discharge from the extruder, resulting in a decrease in productivity, which is not very preferable.

[0024] The lower limit of the content of the polyester resin recycled from PET bottles in the film is preferably 50% by weight, more preferably 65% by weight, and still more preferably 75% by weight. If it is less than 50% by weight, the utilization of the recycled resin is poor in terms of content and is not very preferable in terms of contribution to environmental protection. Since the recycled resin is produced by solid-phase polymerization, the content of oligomers that can cause film whitening is low. Therefore, the larger the content of the recycled resin, the more likely the film whitening after retort treatment will be improved. If the content of the recycled resin is less than 50%, there is a concern that the uneven whitening of the film after retort treatment will be promoted. On the other hand, the upper limit of the content of the polyester resin recycled from PET bottles is 100% by weight, preferably 99% by weight, more preferably 95% by weight, still more preferably 90% by weight, and particularly preferably 85% by weight. If it exceeds 95% by weight, it may not be possible to sufficiently add lubricants and additives such as inorganic particles for improving the film function, which is not very preferable. In addition, the polyester resin recycled from PET bottles can also be used as a masterbatch (high-concentration-containing resin) used when adding lubricants and additives such as inorganic particles for improving the film function.

[0025] As the lubricant type, in addition to inorganic lubricants such as silica, calcium carbonate, and alumina, organic lubricants are preferred, and silica and calcium carbonate are more preferred. Transparency and slipperiness can be exhibited by these.

[0026] The lower limit of the lubricant content in the base film is preferably 0.01% by weight, more preferably 0.015% by weight, and still more preferably 0.02% by weight. If it is less than 0.01% by weight, the slipperiness may decrease. The upper limit is preferably 1% by weight, more preferably 0.2% by weight, and still more preferably 0.1% by weight. If it exceeds 1% by weight, the transparency may decrease, which is not very preferable.

[0027] The manufacturing method of the base film used in the laminated film of the present invention is not particularly limited. For example, the following manufacturing methods are recommended. The temperature setting for melting and extruding the resin in the extruder is crucial. The basic concept is that (1) since the polyester resin used for PET bottles contains an isophthalic acid component, extrusion is carried out at as low a temperature as possible to suppress degradation, and (2) in order to melt the intrinsic viscosity and fine highly crystalline parts sufficiently and uniformly, there is a part that melts at high temperature and high pressure. The inclusion of the isophthalic acid component results in a decrease in the stereoregularity of the polyester and leads to a decrease in the melting point. Therefore, extrusion at a high temperature causes a significant decrease in the melt viscosity due to heat and degradation, resulting in a decrease in mechanical strength and an increase in degraded foreign substances. Also, simply lowering the extrusion temperature may not enable sufficient melt kneading, and problems such as an increase in thickness unevenness and foreign substances such as fish eyes may occur. From the above, recommended manufacturing methods include, for example, using two extruders in tandem, increasing the pressure in the filter section, and using a screw with a strong shearing force in a part of the screw configuration, etc.

[0028] The lower limit of the set temperature of the resin melting section in the extruder (excluding the maximum set temperature of the compression section of the screw in the extruder) is preferably 270 °C, and the upper limit is preferably 290 °C. If it is less than 270 °C, extrusion is difficult, and if it exceeds 290 °C, resin degradation may occur, which is not very preferable.

[0029] The lower limit of the maximum set temperature of the compression section of the screw in the extruder is preferably 295 °C. Polyester resins used for PET bottles often have high-melting-point crystals (260 °C to 290 °C) in terms of transparency. Also, additives and crystallization nucleating agents are added, and variations are seen in the fine melting behavior within the resin material. If it is less than 295 °C, it becomes difficult to melt them sufficiently, which is not very preferable. The upper limit of the maximum set temperature of the compression section of the screw in the extruder is preferably 310 °C. If it exceeds 310 °C, resin degradation may occur, which is not very preferable.

[0030] The lower limit of the time for the resin to pass through the region of the highest set temperature of the compression section of the screw in the extruder is preferably 10 seconds, more preferably 15 seconds. If it is less than 10 seconds, the polyester resin used for PET bottles cannot be sufficiently melted, which is not very preferable. The upper limit is preferably 60 seconds, more preferably 50 seconds. If it exceeds 60 seconds, the resin is likely to deteriorate, which is not very preferable. By setting the extruder within such a range, it is possible to obtain a film with less thickness unevenness, foreign matters such as fish eyes, and less coloring while using a large amount of recycled polyester resin from PET bottles.

[0031] The resin melted in this way is extruded into a sheet shape on a cooling roll and then biaxially stretched. As the stretching method, a simultaneous biaxial stretching method may be used, but a sequential biaxial stretching method is particularly preferable. These make it easy to satisfy productivity and the quality required by the present invention.

[0032] In the present invention, the film stretching method is not particularly limited, but the following points are important. For stretching a resin having an intrinsic viscosity of 0.58 dl / g or more and containing an isophthalic acid component, the stretching ratio and temperature in the longitudinal direction (MD) and the transverse direction (TD) are important. If the MD stretching ratio and temperature are not appropriate, the stretching force is not applied uniformly, the molecular orientation becomes insufficient, and the thickness unevenness may increase and the mechanical properties may become insufficient. Also, film breakage may occur in the next TD stretching step, or extreme thickness unevenness may increase. If the TD stretching ratio and temperature are not appropriate, the film is not stretched uniformly, the orientation balance in the longitudinal and transverse directions is poor, and the mechanical properties may become insufficient. Also, when proceeding to the next heat setting step in a state where the thickness unevenness is large or the molecular chain orientation is insufficient, relaxation cannot be performed uniformly, and problems such as further increase in thickness unevenness and insufficient mechanical properties occur. Therefore, basically, in MD stretching, the temperature adjustment described below is performed to perform stretching step by step, and in TD stretching, it is recommended to stretch at an appropriate temperature so that the orientation balance does not become extremely poor. Although not limited to the following embodiments, an example will be described for illustration.

[0033] As the longitudinal direction (MD) stretching method, a roll stretching method or an IR heating method is preferred.

[0034] The lower limit of the MD stretching temperature is preferably 100 °C, more preferably 110 °C, and even more preferably 120 °C. If it is less than 100 °C, when stretching a polyester resin with an intrinsic viscosity of 0.58 dl / g or more and molecularly orienting it in the longitudinal direction, film breakage or extreme thickness defects may occur in the subsequent transverse stretching step, which is not preferable. The upper limit is preferably 140 °C, more preferably 135 °C, and even more preferably 130 °C. If it exceeds 140 °C, the orientation of the molecular chains may become insufficient and the mechanical properties may be insufficient, so it is not very preferable.

[0035] The lower limit of the MD stretching ratio is preferably 2.5 times, more preferably 3.5 times, and even more preferably 4 times. If it is less than 2.5 times, when stretching a polyester resin with an intrinsic viscosity of 0.58 dl / g or more and molecularly orienting it in the longitudinal direction, film breakage or extreme thickness defects may occur in the subsequent transverse stretching step, which is not very preferable. The upper limit is preferably 5 times, more preferably 4.8 times, and even more preferably 4.5 times. If it exceeds 5 times, the effects of improving mechanical strength and thickness unevenness may saturate, and its significance is not very great.

[0036] As the MD stretching method, the above single-stage stretching may be used, but it is more preferable to divide the stretching into two or more stages. By dividing it into two or more stages, it becomes possible to stretch well a polyester resin made of a recycled resin with a high intrinsic viscosity and containing isophthalic acid, and the thickness unevenness, laminate strength, mechanical properties, etc. become good.

[0037] The lower limit of the preferable first-stage MD stretching temperature is 110 °C, more preferably 115 °C. If it is less than 110 °C, there will be insufficient heat and it cannot be stretched sufficiently in the longitudinal direction, resulting in poor planarity, which is not preferable. The upper limit of the preferable first-stage MD stretching temperature is 125 °C, more preferably 120 °C. If it exceeds 125 °C, the orientation of the molecular chains may become insufficient and the mechanical properties may decrease, so it is not very preferable.

[0038] The lower limit of the preferable MD draw ratio in the first stage is 1.1 times, more preferably 1.3 times. When it is 1.1 times or more, by performing weak drawing in the first stage, a polyester resin having an intrinsic viscosity of 0.58 dl / g or more can be sufficiently longitudinally drawn finally, and productivity can be improved. The upper limit of the preferable MD draw ratio in the first stage is 2 times, more preferably 1.6 times. When it exceeds 2 times, the orientation of the molecular chains in the longitudinal direction becomes too high, which may make it difficult to perform drawing in the subsequent second stage and may result in a film with uneven thickness, which is not very preferable.

[0039] The lower limit of the preferable MD draw temperature in the second stage (or the final stage) is preferably 110°C, more preferably 115°C. When it is 110°C or more, a polyester resin having an intrinsic viscosity of 0.58 dl / g or more can be sufficiently longitudinally drawn, transverse drawing in the next step becomes possible, and the thickness unevenness in the longitudinal and transverse directions becomes good. The upper limit is preferably 130°C, more preferably 125°C. When it exceeds 130°C, crystallization is promoted, which may make transverse drawing difficult or may increase the thickness unevenness, which is not very preferable.

[0040] The lower limit of the preferable MD draw ratio in the second stage (or the final stage) is preferably 2.1 times, more preferably 2.5 times. When it is less than 2.1 times, even if a polyester resin having an intrinsic viscosity of 0.58 dl / g or more is drawn and molecularly oriented in the longitudinal direction, film breakage or extreme thickness defects may occur in the subsequent transverse drawing process, which is not very preferable. The upper limit is preferably 3.5 times, more preferably 3.1 times. When it exceeds 3.5 times, the longitudinal orientation becomes too high, which may make it impossible to perform drawing in the second stage and subsequent stages or may result in a film with large thickness unevenness, which is not very preferable.

[0041] The lower limit of the TD stretching temperature is preferably 110°C, more preferably 120°C, and even more preferably 125°C. If it is less than 110°C, the stretching stress in the transverse direction becomes high, and the film may break or the thickness unevenness may become extremely large, which is not very preferable. The upper limit is preferably 150°C, more preferably 145°C, and even more preferably 140°C. If it exceeds 150°C, the orientation of the molecular chains may not increase, resulting in a possible decrease in mechanical properties, which is not very preferable.

[0042] The lower limit of the transverse (TD) stretching ratio is preferably 3.5 times, more preferably 3.9 times. If it is less than 3.5 times, the molecular orientation may be weak and the mechanical strength may be insufficient, which is not very preferable. Also, the orientation of the molecular chains in the longitudinal direction is large, and the balance between the longitudinal and transverse directions becomes poor, resulting in large thickness unevenness, which is not very preferable. The upper limit is preferably 5.5 times, more preferably 4.5 times. If it exceeds 5.5 times, it may break, which is not very preferable.

[0043] In order to obtain the base film used in the laminated film of the present invention, it is desirable to appropriately set the heat setting performed in the tenter continuously after the completion of TD stretching and the conditions when the film is then cooled to room temperature. A polyester film containing a recycled resin made of a PET bottle containing isophthalic acid has lower crystallinity, is more likely to melt extremely slightly, and has lower mechanical strength compared to a normal polyethylene terephthalate film that does not contain isophthalic acid. Therefore, when it is rapidly exposed to a high temperature under tension after the completion of stretching or when it is rapidly cooled under tension after the completion of high-temperature heat setting, the tension balance in the width direction is disturbed due to the inevitable temperature difference in the width direction of the film, resulting in uneven thickness and poor mechanical properties. On the other hand, if the heat setting temperature is lowered to cope with this phenomenon, sufficient laminating strength may not be obtained in some cases. In the present invention, it is recommended to provide a slow cooling process to lower the temperature to room temperature after heat setting 1 at a slightly lower temperature and heat setting 2 (heat setting 3 if necessary) at a sufficiently high temperature after the completion of stretching. However, it is not limited to this method. For example, methods such as controlling the film tension according to the speed of hot air in the tenter and the temperature of each zone, performing a heat treatment with a relatively low temperature with a sufficient furnace length after the completion of stretching, and relaxing with a heating roll after the completion of heat setting are also included.

[0044] As an example, a method by temperature control of the tenter is shown below. Heat settings 1, 2, and 3 are arranged in order from the upstream side in the film flow direction in the heat setting zone in the tenter.

[0045] The lower limit of the temperature of heat setting 1 is preferably 160 °C, more preferably 170 °C. If it is less than 160 °C, the final heat shrinkage rate may increase, and displacement and shrinkage may occur during processing, which is not very preferable. The upper limit is preferably 215 °C, more preferably 210 °C. If it exceeds 215 °C, the film will be rapidly exposed to a high temperature, resulting in a large thickness unevenness and it may break, which is not very preferable.

[0046] The lower limit of the time for heat fixation 1 is preferably 0.5 seconds, more preferably 2 seconds. If it is less than 0.5 seconds, the film temperature may not rise sufficiently. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, the productivity may decrease, which is not very preferable.

[0047] The lower limit of the temperature for heat fixation 2 is preferably 220 °C, more preferably 227 °C. If it is less than 220 °C, the heat shrinkage rate may increase, resulting in deviation or shrinkage during processing, which is not very preferable. The upper limit is preferably 240 °C, more preferably 237 °C. If it exceeds 240 °C, the film may melt, or even if it does not melt, it may become brittle, which is not very preferable.

[0048] The lower limit of the time for heat fixation 2 is preferably 0.5 seconds, more preferably 3 seconds. If it is less than 0.5 seconds, breakage may easily occur during heat fixation, which is not very preferable. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, sagging etc. may occur, resulting in thickness unevenness, which is not very preferable.

[0049] If heat fixation 3 is provided as necessary, the lower limit of the temperature is preferably 205 °C, more preferably 220 °C. If it is less than 205 °C, the heat shrinkage rate may increase, resulting in deviation or shrinkage during processing, which is not very preferable. The upper limit is preferably 240 °C, more preferably 237 °C. If it exceeds 240 °C, the film may melt, or even if it does not melt, it may become brittle, which is not very preferable.

[0050] If heat fixation 3 is provided as necessary, the lower limit of the time is preferably 0.5 seconds, more preferably 3 seconds. If it is less than 0.5 seconds, breakage may easily occur during heat fixation, which is not very preferable. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, sagging etc. may occur, resulting in thickness unevenness, which is not very preferable.

[0051] TD relaxation can be carried out at any point of heat setting. The lower limit is preferably 0.5% and more preferably 3%. If it is less than 0.5%, the lateral heat shrinkage rate will be particularly large, which may cause deviation and shrinkage during processing, and is not very preferable. The upper limit is preferably 10% and more preferably 8%. If it exceeds 10%, sagging etc. may occur and thickness unevenness may occur, which is not very preferable.

[0052] The lower limit of the slow cooling temperature after TD heat setting is preferably 90 °C and more preferably 100 °C. If it is less than 90 °C, since it is a film containing isophthalic acid, thickness unevenness may increase or breakage may occur due to shrinkage etc. caused by a rapid temperature change, which is not very preferable. The upper limit of the slow cooling temperature is preferably 150 °C and more preferably 140 °C. If it exceeds 150 °C, a sufficient cooling effect may not be obtained, which is not very preferable.

[0053] The lower limit of the slow cooling time after heat setting is preferably 2 seconds and more preferably 4 seconds. If it is less than 2 seconds, a sufficient slow cooling effect may not be obtained, so it is not very preferable. The upper limit is preferably 20 seconds and more preferably 15 seconds. If it exceeds 20 seconds, it is likely to be disadvantageous in terms of productivity and is not very preferable.

[0054] The upper limit of the haze per thickness of the base film layer in the present invention is preferably 0.66% / μm, more preferably 0.60% / μm, and still more preferably 0.53% / μm. When printing is performed on a base film layer with 0.66% / μm or less, the quality of the printed characters and images is improved.

[0055] In addition, the base film layer in the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, surface roughening treatment as long as the object of the present invention is not impaired, and known anchor coat treatment, printing, decoration, etc. may also be performed.

[0056] In addition, a layer of other materials may be laminated on the base film layer in the present invention. As a method, it can be laminated after the production of the base film layer or during film formation.

[0057] [Inorganic thin film layer] The gas barrier laminated film of the present invention has an inorganic thin film layer on the surface of the base film layer. The inorganic thin film layer is a thin film made of a metal or an inorganic oxide. The material for forming the inorganic thin film layer is not particularly limited as long as it can form a thin film. From the viewpoint of gas barrier properties, inorganic oxides such as silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide are preferably mentioned. In particular, from the viewpoint of achieving both flexibility and denseness of the thin film layer, a composite oxide of silicon oxide and aluminum oxide is preferred. In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably in the range of 20 to 70% by mass of Al in terms of the mass ratio of the metal component. When the Al concentration is less than 20% by mass, the water vapor barrier property may be reduced. On the other hand, when it exceeds 70% by mass, the inorganic thin film layer tends to become hard, and there is a risk that the film will be broken during secondary processing such as printing or lamination, resulting in a decrease in gas barrier properties. Here, the silicon oxide referred to herein is various silicon oxides such as SiO or SiO2 or a mixture thereof, and the aluminum oxide is various aluminum oxides such as AlO or Al2O3 or a mixture thereof.

[0058] The film thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 5 to 50 nm. When the film thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain a satisfactory gas barrier property. On the other hand, even if it is excessively thick exceeding 100 nm, the corresponding improvement effect of the gas barrier property cannot be obtained, and it is rather disadvantageous in terms of bending resistance and manufacturing cost.

[0059] The method for forming the inorganic thin film layer is not particularly limited. For example, known vapor deposition methods such as physical vapor deposition (PVD) methods such as vacuum evaporation, sputtering, and ion plating, or chemical vapor deposition (CVD) methods can be appropriately adopted. Hereinafter, a typical method for forming the inorganic thin film layer will be described by taking a silicon oxide-aluminum oxide-based thin film as an example. For example, when adopting the vacuum evaporation method, a mixture of SiO2 and Al2O3, or a mixture of SiO2 and Al, etc. is preferably used as the evaporation raw material. Usually, particles are used as these evaporation raw materials. At this time, the size of each particle is preferably such that the pressure during evaporation does not change, and the preferred particle diameter is 1 mm to 5 mm. For heating, methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be adopted. In addition, it is also possible to introduce reaction gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor, etc., or to adopt reactive evaporation using means such as ozone addition and ion assist. Furthermore, the film formation conditions can be arbitrarily changed, such as applying a bias to the object to be vapor-deposited (the laminated film to be subjected to vapor deposition), or heating or cooling the object to be vapor-deposited. Such evaporation materials, reaction gases, bias of the object to be vapor-deposited, heating and cooling, etc. can be similarly changed when adopting the sputtering method or the CVD method.

[0060] [Coating layer] For the laminated film of the present invention, a coating layer can be provided between the base film layer and the inorganic thin film layer for the purpose of ensuring the gas barrier property and laminate strength after retort treatment. Examples of the resin composition used for the coating layer provided between the base film layer and the inorganic thin film layer include resins such as urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins to which curing agents such as epoxy-based, isocyanate-based, melamine-based, oxazoline-based, and carbodiimide-based are added. The resin composition used for these coating layers preferably contains a silane coupling agent having at least one type of organic functional group. Examples of the organic functional group include an alkoxy group, an amino group, an epoxy group, and an isocyanate group. The addition of the silane coupling agent further improves the laminate strength after retort treatment.

[0061] Among the resin compositions used for the coating layer, it is preferable to use a mixture of a resin containing an oxazoline group or a carbodiimide group, an acrylic resin, and a urethane resin. These functional groups have a high affinity for the inorganic thin film, and can react with the oxygen-deficient portions of the inorganic oxides generated during the formation of the inorganic thin film layer and metal hydroxides, showing strong adhesion to the inorganic thin film layer. Further, the unreacted functional groups present in the coating layer can react with the carboxylic acid terminals generated by the hydrolysis of the base material film layer and the coating layer to form crosslinks.

[0062] In the present invention, it is preferable that the coating amount of the coating layer is 0.010 to 0.200 (g / m 2 ). Thereby, since the coating layer can be uniformly controlled, as a result, it becomes possible to deposit the inorganic thin film layer densely. Further, the cohesive force inside the coating layer is improved, and the adhesion between the base material film - coating layer - inorganic thin film layer is also increased, so that the water-resistant adhesiveness of the coating layer can be enhanced. The coating amount of the coating layer is preferably 0.015 (g / m 2 ) or more, more preferably 0.020 (g / m 2 ) or more, still more preferably 0.025 (g / m 2 ) or more, and preferably 0.190 (g / m 2 ) or less, more preferably 0.180 (g / m 2 ) or less, still more preferably 0.170 (g / m 2 ) or less. When the coating amount of the coating layer exceeds 0.200 (g / m 2 ), the cohesive force inside the coating layer becomes insufficient, and good adhesion may not be exhibited. Further, since the uniformity of the coating layer also decreases, defects may occur in the inorganic thin film layer, and the gas barrier property may decrease. Moreover, the manufacturing cost increases and it becomes economically disadvantageous. On the other hand, when the film thickness of the coating layer is less than 0.010 (g / m 2 ), the base material may not be sufficiently coated, and there is a possibility that sufficient gas barrier property and interlayer adhesion cannot be obtained.

[0063] The method for forming the coating layer is not particularly limited, and conventionally known methods such as a coating method can be employed. Among coating methods, preferred methods include an offline coating method and an inline coating method. For example, in the case of an inline coating method performed in the process of manufacturing the base film layer, the drying and heat treatment conditions during coating depend on the coating thickness and the conditions of the apparatus, but it is preferable to feed it immediately after coating into a stretching step in a right-angle direction and dry it in the preheating zone or stretching zone of the stretching step. In such a case, the temperature is usually preferably about 50 to 250°C. As the solvent used when using the coating method, for example, aromatic solvents such as benzene and toluene; alcohol solvents such as methanol and ethanol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate and butyl acetate; polyhydric alcohol derivatives such as ethylene glycol monomethyl ether, etc. can be mentioned.

[0064] [Protective layer] In the present invention, a protective layer is provided on the inorganic thin film layer. The metal oxide layer is not a completely dense film, and minute defective portions are scattered. By forming a protective layer by applying a specific resin composition for the protective layer described later on the metal oxide layer, the resin in the resin composition for the protective layer penetrates into the defective portions of the metal oxide layer, and as a result, the effect that the gas barrier property is stabilized can be obtained. In addition, by using a material having a gas barrier property also for the protective layer itself, the gas barrier performance of the laminated film is also greatly improved. Furthermore, since the barrier layer prevents the intrusion of hot water into the base material, as a result, the film whitening after retorting described later can also be reduced.

[0065] In the present invention, the adhesion amount of the protective layer is 0.50 (g / m 2 ) or less, and 0.10 to 0.40 (g / m 2It is preferable to set it like this. As a result, the protective layer can be uniformly controlled during coating, resulting in a film with less coating unevenness and defects. Also, the cohesive force of the protective layer itself is improved, and the adhesion between the inorganic thin film layer and the protective layer becomes strong. Furthermore, the protective layer contributes to suppressing the oligomer exposure, and the haze after retort is stabilized. The adhesion amount of the protective layer is preferably 0.13 (g / m 2 ) or more, more preferably 0.16 (g / m 2 ) or more, still more preferably 0.19 (g / m 2 ) or more, and preferably 0.37 (g / m 2 ) or less, more preferably 0.34 (g / m 2 ) or less, still more preferably 0.31 (g / m 2 ) or less. When the adhesion amount of the protective layer exceeds 0.400 (g / m 2 ), the gas barrier property is improved, but the cohesive force inside the protective layer becomes insufficient, and the uniformity of the protective layer also decreases. As a result, unevenness and defects may occur in the coating appearance, and the gas barrier property and adhesiveness may not be fully exhibited. On the other hand, if the film thickness of the protective layer is less than 0.10 (g / m 2 ), there is a risk that sufficient gas barrier property and interlayer adhesiveness cannot be obtained.

[0066] As the resin composition used for the protective layer formed on the surface of the inorganic thin film layer of the laminated film of the present invention include those obtained by adding a curing agent such as an epoxy-based, isocyanate-based, or melamine-based curing agent to resins such as urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based , and polybutadiene-based resins. In particular, the inclusion of urethane resin, in addition to the barrier performance due to the high cohesiveness of the urethane bond itself, the polar group interacts with the inorganic thin film layer and also has flexibility due to the presence of the amorphous part, so it is preferable because it can suppress damage to the inorganic thin film layer even when a bending load is applied. Also, since polyester resin can be expected to have the same effect, it is suitable.

[0067] (Urethane resin) From the viewpoint of improving the barrier property due to cohesive force, the urethane resin used in the present invention preferably has a glass transition temperature (Tg) of 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. However, in order to exhibit adhesion, a flexible resin with a Tg of 100°C or lower and excellent flexibility may be mixed and used. In that case, the addition ratio of the flexible resin is preferably in the range of 0 to 80%. More preferably, it is in the range of 10 to 70%, and even more preferably in the range of 20 to 60%. When the addition ratio is within the above range, both cohesive force and flexibility can be achieved, and the barrier property and adhesion are improved. Note that when the addition ratio exceeds 80%, the film becomes too soft, which may lead to a decrease in barrier performance.

[0068] From the aspect of improving the gas barrier property, it is more preferable to use a urethane resin containing an aromatic or araliphatic diisocyanate component as a main constituent. Among them, it is particularly preferable to contain a metaxylylene diisocyanate component. By using the above resin, the cohesive force of the urethane bond can be further enhanced by the stacking effect between aromatic rings, and as a result, a good gas barrier property can be obtained.

[0069] In the present invention, the proportion of aromatic or araliphatic diisocyanate in the urethane resin is preferably in the range of 50 mol% or more (50 to 100 mol%) in 100 mol% of the polyisocyanate component (F). The proportion of the total amount of aromatic or araliphatic diisocyanate is preferably 60 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%. As such a resin, the "Takelac (registered trademark) WPB" series commercially available from Mitsui Chemicals, Inc. can be preferably used. If the proportion of the total amount of aromatic or araliphatic diisocyanate is less than 50 mol%, good gas barrier properties may not be obtained.

[0070] In the urethane resin used in the present invention, for the purpose of improving the cohesive force of the film and the adhesion property to wet heat, various crosslinking agents, such as silicon-based crosslinking agents, may be blended within the range that does not impair the gas barrier property. Examples of the crosslinking agent include, for example, silicon-based crosslinking agents, oxazoline compounds, carbodiimide compounds, epoxy compounds, and the like. Among them, by blending a silicon-based crosslinking agent, the water-resistant adhesion property with an inorganic thin film layer can be particularly improved. From this viewpoint, a silicon-based crosslinking agent is particularly preferable. In addition, as the crosslinking agent, an oxazoline compound, a carbodiimide compound, an epoxy compound, or the like may be used in combination.

[0071] As a silicon-based crosslinking agent, a silane coupling agent is preferred from the viewpoint of crosslinking between inorganic and organic substances. As the silane coupling agent, hydrolyzable alkoxysilane compounds such as halogen-containing alkoxysilanes (chloro C2-4 alkyltri C1-4 alkoxysilanes such as 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc.), alkoxysilanes having an epoxy group [glycidyloxy C2-4 alkyltri C1-4 alkoxysilanes such as 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, etc., glycidyloxydic2-4 alkyldi C1-4 alkoxysilanes such as 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, etc., (epoxycycloalkyl)C2-4 alkyltri C1-4 alkoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)propyltrimethoxysilane, etc.], alkoxysilanes having an amino group [amino C2-4 alkyltri C1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminodic2-4 alkyldi C1-4 alkoxysilanes such as 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., (2-amino C2-4 alkyl)amino C2-4 alkyltri C1-4 alkoxysilanes such as 2-[N-(2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltriethoxysilane, etc., (amino C2-4 alkyl)aminodic2-4 alkyldi C1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane, etc.],Alkoxysilanes having a mercapto group (mercapto C2-4 alkyltri C1-4 alkoxysilanes such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., mercapto C2-4 alkyltri C1-4 alkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.), alkoxysilanes having a vinyl group (vinyltri C1-4 alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.), alkoxysilanes having an ethylenically unsaturated bond group [(meth)acryloxy C2-4 alkyltri C1-4 alkoxysilanes such as 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, etc., (meth)acryloxy C2-4 alkyltri C1-4 alkoxysilanes such as 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, etc.] and the like can be exemplified. These silane coupling agents can be used alone or in combination of two or more. Among these silane coupling agents, silane coupling agents having an amino group are preferred.,

[0072] It is preferable to add 0.25 to 3.00% by mass of the silane coupling agent silicon-based crosslinking agent to the protective layer, more preferably 0.5 to 2.75% by mass, and even more preferably 0.75 to 2.50% by mass. By adding the silane coupling agent, the curing of the film proceeds, the cohesive force is improved, and as a result, a film excellent in water-resistant adhesiveness is obtained, and furthermore, the effect of preventing the exposure of the oligomer can be expected. If the addition amount exceeds 3.00% by mass, the curing of the film proceeds and the cohesive force is improved, but some unreacted portions may also occur, and the adhesiveness between layers may decrease. On the other hand, if the addition amount is less than 0.25% by mass, sufficient cohesive force may not be obtained.,

[0073] (Polyester resin) The polyester resin used in the present invention is produced by polycondensing a polycarboxylic acid component and a polyhydric alcohol component. The molecular weight of the polyester is not particularly limited as long as it can impart sufficient film toughness, coating suitability, and solvent solubility as a coating material, but the number average molecular weight is 1000 to 50000, more preferably 1500 to 30000. There is also no particular limitation on the functional group at the end of the polyester, and it may have an alcohol end, a carboxylic acid end, or both. However, when an isocyanate-based curing agent is used in combination, it is necessary to use a polyester polyol mainly having an alcohol end.

[0074] [Glass transition temperature (Tg) of polyester] The Tg of the polyester used in the present invention needs to be 15°C or higher. If the temperature is lower than this, the resin will have adhesiveness after the coating operation, easily cause blocking, and make the winding operation after coating difficult. This is because when Tg is 15°C or lower, it becomes difficult to prevent blocking even with the addition of an anti-blocking agent under high pressure near the winding core. A more preferable temperature for Tg is 18°C or higher, and even more preferably 25°C or higher.

[0075] The polyester used in the present invention is used by polycondensing a polycarboxylic acid component and a polyhydric alcohol component. [Polycarboxylic acid component] The polycarboxylic acid component of the polyester used in the present invention is characterized by containing at least one of ortho-oriented aromatic dicarboxylic acids or their anhydrides. By making it ortho-oriented, the solubility in the solvent is improved, and it becomes possible to coat the substrate uniformly. The uniformly coated protective layer has less variation in barrier performance, and as a result, it contributes to the suppression of oligomer whitening. Also, by making it ortho-oriented, a film with excellent flexibility is obtained and the interfacial adhesive strength is improved, so that damage to the substrate due to wet heat treatment can be reduced, leading to the suppression of oligomers. Examples of the aromatic polycarboxylic acid or its anhydride in which the carboxylic acid is substituted at the ortho position include phthalic acid or its anhydride, naphthalene 2,3-dicarboxylic acid or its anhydride, naphthalene 1,2-dicarboxylic acid or its anhydride, anthraquinone 2,3-dicarboxylic acid or its anhydride, and 2,3-anthracene dicarboxylic acid or its anhydride. These compounds may have a substituent on any carbon atom of the aromatic ring. Examples of the substituent include a chloro group, a bromo group, a methyl group, an ethyl group, an i-propyl group, a hydroxyl group, a methoxy group, an ethoxy group, a phenoxy group, a methylthio group, a phenylthio group, a cyano group, a nitro group, an amino group, a phthalimide group, a carboxyl group, a carbamoyl group, an N-ethylcarbamoyl group, a phenyl group, or a naphthyl group. Further, a polyester polyol in which the content with respect to 100 mol% of all these polycarboxylic acid components is 70 to 100 mol% is particularly preferable because it has a high effect of improving the barrier property and is excellent in the solvent solubility essential for a coating material.

[0076] In the present invention, other polyvalent carboxylic acid components may be copolymerized as long as the effects of the invention are not impaired. Specifically, examples of the aliphatic polyvalent carboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc.; examples of the unsaturated bond-containing polyvalent carboxylic acid include maleic anhydride, maleic acid, fumaric acid, etc.; examples of the alicyclic polyvalent carboxylic acid include 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, etc.; examples of the aromatic polyvalent carboxylic acid include terephthalic acid, isophthalic acid, pyromellitic acid, trimellitic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, diphenic acid and its anhydride, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid and the anhydride or ester-forming derivative of these dicarboxylic acids; polybasic acids such as p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid and the ester-forming derivative of these dihydroxycarboxylic acids can be used alone or as a mixture of two or more. Among them, from the viewpoints of solubility in organic solvents and gas barrier properties, succinic acid, 1,3-cyclopentanedicarboxylic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalic acid, and diphenic acid are preferred.

[0077] [Polyhydric alcohol component] The polyhydric alcohol component of the polyester used in the present invention is not particularly limited as long as it can synthesize a polyester exhibiting gas barrier filling performance, but it preferably contains a polyhydric alcohol component containing at least one selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, and 1,3-bis(hydroxyethyl)benzene. Among them, since it is presumed that the fewer the number of carbon atoms between oxygen atoms, the less likely the molecular chain becomes overly flexible and the less likely oxygen is to permeate, it is most preferable to use ethylene glycol as the main component.

[0078] In the present invention, it is preferable to use the aforementioned polyhydric alcohol component. In addition, other polyhydric alcohol components may be copolymerized as long as the effects of the present invention are not impaired. Specifically, examples of diols include 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Examples of polyhydric alcohols having three or more hydroxyl groups include glycerol, trimethylolpropane, trimethylolethane, tris(2-hydroxyethyl)isocyanurate, 1,2,4-butanetriol, pentaerythritol, and dipentaerythritol. In particular, among the trihydric alcohols, a polyester obtained by combining glycerol and tris(2-hydroxyethyl)isocyanurate has a moderately high crosslink density due to its branched structure, resulting in good solubility in organic solvents and excellent barrier function, and is particularly preferably used.

[0079] Examples of the catalyst used in the reaction for obtaining the polyester of the present invention include tin-based catalysts such as monobutyltin oxide and dibutyltin oxide, titanium-based catalysts such as tetra-isopropyl-titanate and tetra-butyl-titanate, and acid catalysts such as zirconia-based catalysts such as tetra-butyl-zirconate. It is preferable to use a combination of the above titanium-based catalysts such as tetra-isopropyl-titanate and tetra-butyl-titanate, which have high activity for the esterification reaction, and the above zirconia catalyst. The amount of the catalyst used is 1 to 1000 ppm, more preferably 10 to 100 ppm, based on the total mass of all the reaction raw materials used. If it is less than 1 ppm, it is difficult to obtain the effect as a catalyst, and if it exceeds 1000 ppm, there may be a problem of inhibiting the urethanization reaction when an isocyanate curing agent is used.

[0080] In the present invention, when a polyester resin is used as the main component of the coating agent constituting the protective layer, an isocyanate-based curing agent must be used to form a urethane resin. In this case, since the coating layer becomes a crosslinked type, there are advantages such as improved heat resistance, abrasion resistance, and rigidity. Therefore, it is also easy to use for boil-in-bag or retort packaging. On the other hand, after mixing the curing agent, the liquid cannot be reused, and there is also a problem that a curing (aging) process is essential after coating.

[0081] When the polyester has a hydroxyl group, at least a part of the polyisocyanate compound used in the present invention reacts to form a urethane structure, thereby highly polarizing as a resin component and further strengthening the gas barrier function by aggregating between polymer chains. Also, when the resin of the coating material is a linear resin, heat resistance and abrasion resistance can be imparted by crosslinking with a polyisocyanate having a trivalent or higher valence. The polyisocyanate compound used in the present invention may be any of diisocyanates, polyisocyanates having a trivalent or higher valence, low molecular weight compounds, and high molecular weight compounds, but it is preferable from the viewpoint of improving the gas barrier function that it contains an aromatic ring or an aliphatic ring in a part of the skeleton. For example, as isocyanates having an aromatic ring, there are toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, and as isocyanates having an aliphatic ring, there are hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, or trimers of these isocyanate compounds, and terminal isocyanate group-containing compounds obtained by reacting an excess amount of these isocyanate compounds with low molecular weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, or high molecular weight active hydrogen compounds such as various polyester polyols, polyether polyols, and polyamides.

[0082] The coating method of the resin composition for the protective layer is not particularly limited as long as it is a method of forming a layer by coating the film surface. For example, ordinary coating methods such as gravure coating, reverse roll coating, wire bar coating, die coating, etc. can be adopted.

[0083] When forming the protective layer, it is preferable to heat and dry after applying the resin composition for the protective layer. The drying temperature at that time is preferably 110 to 190 °C, more preferably 130 to 185 °C, and even more preferably 150 to 180 °C. If the drying temperature is less than 110 °C, insufficient drying may occur in the protective layer, or film formation of the protective layer may not proceed, resulting in a decrease in cohesive force and water-resistant adhesiveness, and as a result, the barrier property and cut-off property may decrease. On the other hand, if the drying temperature exceeds 190 °C, the film may be overheated, making the film brittle and reducing the puncture strength, or it may shrink and deteriorate the processability. In particular, by drying at 150 °C or higher, preferably 160 °C or higher, film formation of the protective layer proceeds effectively, and the adhesive area between the resin of the protective layer and the inorganic thin film layer becomes larger, so the water-resistant adhesiveness can be improved. It is particularly preferable that the protective film first volatilizes the solvent under relatively low temperature conditions of 90 °C to 110 °C immediately after coating, and then dries at 150 °C or higher, so that a uniform film can be obtained. In addition to drying, applying additional heat treatment in the lowest possible temperature range is even more effective in promoting film formation of the protective layer.

[0084] From the above, the laminated film of the present invention is excellent in gas barrier performance before treatment, can maintain its barrier property and adhesiveness even after severe damp heat treatment, and further has the characteristic of less whitening after retort treatment by using a polyester resin derived from a PET bottle with less environmental load as the base material.

[0085] [Packaging material] When the laminated film of the present invention is used as a packaging material, it is preferable to form a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually provided on an inorganic thin film layer, but may also be provided on the outer side of the base film layer (the surface opposite to the coating layer forming surface). The formation of the heat-sealable resin layer is usually carried out by an extrusion lamination method or a dry lamination method. As the thermoplastic polymer for forming the heat-sealable resin layer, any polymer can be used as long as it can sufficiently exhibit sealant adhesiveness, such as polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin, etc.

[0086] [Adhesive layer] As the adhesive layer used in the present invention, general-purpose laminating adhesives can be used. For example, (solventless) solvent-based, aqueous-based, and hot-melt adhesives mainly composed of poly(ester)urethane-based, polyester-based, polyamide-based, epoxy-based, poly(meth)acrylic-based, polyethyleneimine-based, ethylene-(meth)acrylic acid-based, polyvinyl acetate-based, (modified) polyolefin-based, polybutadiene-based, wax-based, casein-based, etc. can be used. Among these, considering the moisture and heat resistance that can withstand retort processing and the flexibility that can follow the dimensional changes of each base material, urethane-based or polyester-based is preferable. As the lamination method of the above adhesive layer, for example, it can be applied by a direct gravure coating method, a reverse gravure coating method, a kiss coating method, a die coating method, a roll coating method, a dip coating method, a knife coating method, a spray coating method, a fountain coating method, or other methods. In order to exhibit sufficient adhesiveness after retort, the coating amount after drying is preferably 1 to 8 g / m 2 is preferable. More preferably 2 to 7 g / m 2 , even more preferably 3 to 6 g / m 2 . If the coating amount is less than 1 g / m 2 , it becomes difficult to bond over the entire surface and the adhesive strength decreases. Also, if it exceeds 8 g / m 2 , it takes time for the film to completely cure, unreacted substances tend to remain, and the adhesive strength decreases.

[0087] Furthermore, in the laminated film of the present invention, at least one layer or more of a printing layer, other plastic substrates, and / or paper substrates may be laminated between or outside the inorganic thin film layer or the base film layer and the heat-sealable resin layer.

[0088] As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks can preferably be used. Examples of the resin used in the printing ink here include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoaming agents, crosslinking agents, antiblocking agents, antioxidants, etc. The printing method for providing the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. For drying the solvent after printing, known drying methods such as hot air drying, hot roll drying, and infrared drying can be used.

[0089] The laminate of the present invention preferably has a standard deviation of haze of 0.5% or less after retort treatment at 130°C for 30 minutes. Within this range, the whitening unevenness of the film is not noticeable even after retort treatment, and a good appearance can be maintained. The reason is not clear, but generally, recycled resins derived from PET bottles adjust the intrinsic viscosity to a predetermined value by solid-phase polymerization when resinifying. Therefore, there is a tendency for the amount of oligomers to be less than that of general film-recovered resins. As a result, it is considered that whitening of the film after retort can be suppressed. In addition, crystallization is suppressed by the inclusion of isophthalic acid, and a synergistic effect of suppressing whitening can also be expected. Furthermore, when a barrier film is formed, the barrier layer suppresses the appearance of oligomers, so a greater effect can be expected. The standard deviation of haze is preferably 0.4% or less, more preferably 0.35% or less, and even more preferably 0.3% or less. If the standard deviation of haze is 0.5% or more, there is a risk of deterioration of the appearance after retort, and if oligomers appear, it may lead to deterioration of adhesion and barrier properties, which is not preferable.

[0090] The evaluation method of the haze standard is as follows: After subjecting a laminated film with a size of 30 cm in the vertical direction × 21 cm in the horizontal direction to retort treatment at 130°C for 30 minutes, the surface moisture is wiped off, and the standard deviation is calculated using the data obtained by measuring the haze at 10 points at arbitrary locations with a haze meter.

[0091] For the laminate of the present invention, it is preferable in terms of exhibiting good gas barrier properties that the oxygen permeability under the conditions of 23°C × 65% RH before and after retort treatment is both 10 ml / m 2 ·d·MPa or less. Furthermore, by controlling the inorganic thin film layer component and the adhesion amount as described above, preferably 7.5 ml / m 2 ·d·MPa or less, more preferably 5 ml / m 2 ·d·MPa or less can be achieved. When the oxygen permeability exceeds 10 ml / m 2 ·d·MPa, it becomes difficult to meet the applications that require high gas barrier properties. On the other hand, when the oxygen permeability before and after retort treatment is both less than 1 ml / m 2 ·d·MPa, although it has excellent barrier performance, the residual solvent is less likely to permeate to the outside of the bag, and there is a possibility that the amount of migration to the contents relatively increases, so it is not preferable. The preferable lower limit of the oxygen permeability is 1 ml / m 2 ·d·MPa or more.

[0092] For the laminate of the present invention, it is preferable in terms of exhibiting good gas barrier properties that the water vapor permeability under the conditions of 40°C × 90% RH before and after retort treatment is both 2.0 g / m 2 ·d or less. Furthermore, by controlling the inorganic thin film layer component and the adhesion amount as described above, preferably 1.5 g / m 2 ·d or less, more preferably 1.0 g / m 2 ·d or less can be achieved. When the water vapor permeability exceeds 2.0 g / m 2 ·d, it becomes difficult to meet the applications that require high gas barrier properties. On the other hand, when the water vapor permeability before and after retort treatment is both 0.1 g / m 2If it is less than this value, although the barrier performance is excellent, the residual solvent becomes less likely to permeate to the outside of the bag, and there is a risk that the amount of migration into the contents relatively increases, which is not preferable. The preferable lower limit of the water vapor permeability is 0.1 g / m 2 ·d or more.

[0093] In the laminate of the present invention, it is preferable that the wet lamination strength under the conditions of 23°C × 65% RH before and after retort treatment is 1.0 N / 15 mm or more, more preferably 1.5 N / 15 mm or more, and even more preferably 2.0 N / 15 mm or more. If the lamination strength is less than 1.0 N / 15 mm, peeling may occur due to the bending load or the liquid contents, and there is a risk that the barrier property deteriorates or the contents leak out. Furthermore, there is also a risk that the cutability deteriorates.

Examples

[0094] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. The evaluation of the film was carried out by the following measurement methods.

[0095] (1) Intrinsic viscosity (IV) of the raw material resin and the resin constituting the film After drying the sample in vacuo at 130°C for one day and night, it was pulverized or cut, 80 mg of which was precisely weighed and heated and dissolved in a mixed solution of phenol / tetrachloroethane = 60 / 40 (volume ratio) at 80°C for 30 minutes. After heating and dissolving at 80°C, it was cooled to room temperature, and the mixed solvent prepared at the above ratio was added in a volumetric flask to make 20 ml, and then measured at 30°C (unit: dl / g). An Ostwald viscometer was used for the measurement of the intrinsic viscosity.

[0096] (2) Content ratios of terephthalic acid and isophthalic acid components contained in the raw material polyester and the polyester constituting the film A sample solution was prepared by dissolving a raw material polyester resin or polyester film in a solvent obtained by mixing chloroform D (manufactured by Eurisop) and trifluoroacetic acid D1 (manufactured by Eurisop) at a volume ratio of 10:1. Subsequently, the prepared sample solution was measured for the NMR of protons under the measurement conditions of a temperature of 23°C and an integration number of 64 times using an NMR apparatus (Nuclear Magnetic Resonance Analyzer: GEMINI-200 manufactured by Varian). In the NMR measurement, the peak intensity of a predetermined proton was calculated, and the contents (mol%) of terephthalic acid component and isophthalic acid component in 100 mol% of the acid component were calculated.

[0097] (3) Thickness of the base film Measured using a dial gauge in accordance with Method A of JIS K7130-1999.

[0098] (4) Thermal shrinkage rate in the longitudinal and transverse directions of the base film For the base film, samples were taken with a width of 10 mm, marked with scale lines at intervals of 200 mm at room temperature (27°C), and the interval between the scale lines was measured (L0). Then, the film was sandwiched between papers and placed in a hot air oven controlled at a temperature of 150°C for 30 minutes. After taking it out, the interval between the scale lines was measured (L), and the thermal shrinkage rate was determined from the following formula. Samples were taken and implemented for both the longitudinal and transverse directions of the biaxial direction. Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100

[0099] (5) Refractive index in the thickness direction of the base film In accordance with JIS K7142, the refractive index (Nz) in the thickness direction was determined using an Abbe refractometer NAR-1T (manufactured by Atago Co., Ltd.). The light source was sodium D line, a test piece with a refractive index of 1.74 was used, and methylene iodide was used as the intermediate liquid.

[0100] (6) Composition and film thickness of the inorganic thin film layer For the laminated films obtained in the examples and comparative examples (after thin film lamination), the film thickness composition was measured using a fluorescent X-ray analyzer ("ZSX100e" manufactured by Rigaku Corporation) according to a calibration curve prepared in advance. The conditions of the excitation X-ray tube were set to 50 kV and 70 mA.

[0101] (7) Adhesion amount of the protective layer In each example and comparative example, each laminated film obtained at the stage of laminating the protective layer on the base film was used as a sample. A 100 mm × 100 mm test piece was cut out from this sample, and the protective layer was wiped off with 1-methoxy-2-propanol or dimethylformamide. The adhesion amount was calculated from the mass change of the film before and after wiping. (8) Standard deviation of haze after retort treatment of the laminated film After subjecting a laminated film with a size of 30 cm in the longitudinal direction and 21 cm in the transverse direction to a retort treatment at 130 °C for 30 minutes, the surface moisture was wiped off, and the haze at 10 points at an arbitrary location was measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136. The standard deviation was calculated using the obtained data.

[0102] [Production of laminated laminate] On the laminates obtained in the examples and comparative examples, a urethane two-component curable adhesive (a mixture of "Takelac (registered trademark) A525S" and "Takenate (registered trademark) A50" manufactured by Mitsui Chemicals, Inc. at a ratio of 13.5:1 (mass ratio)) was used to laminate a 15-μm-thick nylon film ("N1100" manufactured by Toyobo Co., Ltd.) by the dry lamination method. Then, on the nylon film, a 70-μm-thick non-stretched polypropylene film ("P1146" manufactured by Toyobo Co., Ltd.) as a heat-sealable resin layer was laminated by the dry lamination method using the same urethane two-component curable adhesive as above, and aging was carried out at 40 °C for 4 days to obtain a laminated gas barrier laminate for evaluation (hereinafter sometimes referred to as "laminated laminate A"). The thickness of the adhesive layer formed by the urethane two-component curable adhesive after drying was about 4 μm in each case.

[0103] (9) Method for Evaluating Oxygen Permeability For the laminate produced in the above [Production of Laminate], in accordance with JIS-K7126 B method, using an oxygen permeability measuring device ("OX-TRAN (registered trademark) 1 / 50" manufactured by MOCON), the normal oxygen permeability was measured under an atmosphere of 23°C and 65% RH. The measurement of oxygen permeability was carried out in the direction in which oxygen permeates from the base film side of the laminate to the heat-sealing resin layer side. On the other hand, for the laminate produced in the above [Production of Laminate], a hydrothermal treatment of holding in hot water at 120°C for 30 minutes was performed, dried at 40°C for 1 day (24 hours), and the oxygen permeability (after retort) of the obtained laminate after hydrothermal treatment was measured in the same manner as above.

[0104] (9) Method for Evaluating Water Vapor Permeability For the laminate produced in the above [Production of Laminate], in accordance with JIS-K7129 B method, using a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON), the normal water vapor permeability was measured under an atmosphere of 40°C and 90% RH. The measurement of water vapor permeability was carried out in the direction in which water vapor permeates from the heat-sealing resin layer side of the laminate to the base film side. On the other hand, for the laminate produced in the above [Production of Laminate], a hydrothermal treatment of holding in hot water at 120°C for 30 minutes was performed, dried at 40°C for 1 day (24 hours), and the water vapor permeability (after retort) of the obtained laminate after hydrothermal treatment was measured in the same manner as above.

[0105] (10) Method for Evaluating Laminating Strength The laminate laminate prepared above was cut into test pieces with a width of 15 mm and a length of 200 mm, and the laminate strength (normal state) was measured using a tensilon universal material testing machine ("Tensilon UMT-II-500 type" manufactured by Toyo Baldwin Co., Ltd.) under the conditions of a temperature of 23°C and a relative humidity of 65%. In addition, for the measurement of the laminate strength, the tensile speed was set to 200 mm / min, and water was applied between the laminate film layer and the heat-sealing resin layer of each laminated film obtained in the examples and comparative examples, and the strength when peeled at a peeling angle of 90 degrees was measured. On the other hand, the laminate laminate prepared above was subjected to a retort treatment of holding in pressurized hot water at a temperature of 120°C for 30 minutes, and immediately after that, test pieces were cut out from the obtained laminate laminate after the retort treatment in the same manner as above, and the laminate strength (after the retort treatment) was measured in the same manner as above.

[0106] The details of the coating liquids used in the present examples and comparative examples are described below. Note that they were used in Examples 1 to 11 and Comparative Examples 1 to 4 and are shown in Table 1.

[0107] [Carbodiimide-based crosslinking agent (A)] As the carbodiimide-based crosslinking agent, commercially available "Carbodilite (registered trademark) SV-02" manufactured by Nisshinbo Co., Ltd.; solid content 40%) was prepared. [Resin (B) having an oxazoline group] As the resin having an oxazoline group, commercially available water-soluble oxazoline group-containing acrylate ("Epocros (registered trademark) WS-300" manufactured by Nippon Shokubai Co., Ltd.; solid content 10%) was prepared. The amount of oxazoline groups in this resin was 7.7 mmol / g.

[0108] [Acrylic resin (C)] As the acrylic resin, a 25 mass% emulsion of a commercially available acrylate copolymer ("Movinyl (registered trademark) 7980" manufactured by Nitto Kasei Co., Ltd.) was prepared. The acid value (theoretical value) of this acrylic resin was 4 mgKOH / g.

[0109] [Urethane resin (D)] As the urethane resin, a dispersion of a commercially available polyester urethane resin ("Takelac (registered trademark) W605" manufactured by Mitsui Chemicals, Inc.; solid content 30%) was prepared. The acid value of this urethane resin was 25 mgKOH / g, and the glass transition temperature (Tg) measured by DSC was 100°C. Also, the ratio of aromatic or araliphatic diisocyanate to the whole polyisocyanate component measured by 1H-NMR was 55 mol%. [Silane coupling agent (E)] As the silane coupling agent, a commercially available "(registered trademark) KBM903" manufactured by Shin-Etsu Chemical Co., Ltd.; solid content 100%) was prepared. At the time of use, it was diluted with water to a 2% aqueous solution.

[0110] [Urethane resin (F)] Into a four-necked flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer, 143.95 parts by mass of metaxylylene diisocyanate, 25.09 parts by mass of 4,4'-methylenebis(cyclohexyl isocyanate), 28.61 parts by mass of ethylene glycol, 5.50 parts by mass of trimethylolpropane, 12.37 parts by mass of dimethylolpropionic acid, and 120.97 parts by mass of methyl ethyl ketone as a solvent were mixed, and stirred at 70 °C under a nitrogen atmosphere until it was confirmed that the reaction solution reached a predetermined amine equivalent. Next, after cooling the reaction solution to 35 °C, 9.14 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 794.97 parts by mass of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, adjusted to 15 °C, and while stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. An aqueous amine solution prepared by mixing 22.96 parts by mass of 2-[(2-aminoethyl)amino]ethanol and 91.84 parts by mass of water was added. Next, an aqueous amine solution prepared by mixing 2.38 parts by mass of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (trade name; KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) and 9.50 parts by mass of water was added to carry out a chain extension reaction. Then, under reduced pressure, a part of methyl ethyl ketone and water was removed to obtain a polyurethane dispersion (E) having a solid content of 25% by mass and an average particle diameter of 70 nm. The Si content (by charge calculation) of the obtained polyurethane dispersion (D-1) was 1200 mg / 1 kg, and the metaxylylene group content (by charge calculation) was 32% by mass.

[0111] [Polyester resin (G)] As the polyester component, a polyester polyol (DIC Corporation's "DF-COAT GEC-004C": solid content 30%) was used.

[0112] [Polyisocyanate crosslinking agent (H)] As the polyisocyanate component, a trimethylolpropane adduct of metaxylylene diisocyanate (Mitsui Chemicals, Inc.'s "Takenate D-110N": solid content 75%) was used.

[0113] [Silane coupling agent (I)] As the silane coupling agent, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane ("KBM-603" manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0114] [Gas barrier vinyl alcohol-based resin (J)] As the vinyl alcohol-based resin having gas barrier properties, a commercially available water-soluble vinyl alcohol resin ("Nichigo G-Polymer (registered trademark) OKS-8049" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.; powder) was dissolved in water to prepare an aqueous solution with a solid content of 5%.

[0115] [Coating liquid 1 used for the coating layer] Each material was mixed at the following mixing ratios to prepare a coating liquid (resin composition for the coating layer). Water 54.40 mass% Isopropanol 25.00 mass% Oxazoline group-containing resin (A) 15.00 mass% Acrylic resin (B) 3.60 mass% Urethane resin (C) 2.00 mass%

[0116] [Coating liquid 2 used for the coating layer] Each material was mixed at the following mixing ratios to prepare a coating liquid (resin composition for the coating layer). Water 57.80 mass% Isopropanol 25.00 mass% Carbodiimide-based crosslinking agent (A) 2.10 mass% Urethane resin (F) 8.00 mass% Silane coupling agent (E) 7.10 mass%

[0117] [Coating liquid 3 used for coating the protective layer] The following coating agents were mixed to prepare coating liquid 3. Water 22.00 mass% Isopropanol 30.00 mass% Urethane resin (F) 48.00 mass%

[0118] [Coating Liquid 4 for Coating the Protective Layer] A solution (15% wt) of a silane coupling agent (I) dissolved in acetone and an isocyanate (G) were mixed at the following ratio and stirred for 10 minutes using a magnetic stirrer. The resulting formulation was diluted with methyl ethyl ketone, and further a polyester resin (G) was added to obtain a coating liquid. The mixing ratio is shown below. Polyester resin (G) 4.90% by mass Isocyanate (H) 1.87% by mass Silane coupling agent (I)※Acetone-diluted solution 0.85% by mass Methyl ethyl ketone 92.39% by mass

[0119] [Coating Liquid 5 for Coating the Protective Layer] The following coating agents were mixed to prepare Coating Liquid 5. Water 20.00% by mass Isopropanol 10.00% by mass Gas barrier vinyl alcohol-based resin (J) 70.00% by mass

[0120] The manufacturing method of the laminated film used in each of the following Examples and Comparative Examples is described below. Note that it was used in Examples 1 to 11 and Comparative Examples 1 to 4 and is shown in Table 1.

[0121] (Adjustment of Polyester Resin Recycled from PET Bottles) After rinsing off foreign substances such as the remaining beverage from a PET bottle for beverages, the flakes obtained by pulverizing were melted with an extruder, and the filter was changed to a finer one with a smaller mesh size in sequence to filter out finer foreign substances twice more. At the third time, it was filtered with a filter having the smallest mesh size of 50 μm to obtain a polyester recycled raw material. The composition of the obtained resin was terephthalic acid / isophthalic acid / / ethylene glycol = 97.0 / 3.0 / / 100 (mol%), and the limiting viscosity of the resin was 0.70 dl / g. This is designated as Polyester A.

[0122] (Manufacture of the Base Film) As polyester B, a polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g consisting of terephthalic acid / ethylene glycol = 100 / 100 (mol%) was prepared as a masterbatch containing 0.3% of amorphous silica with an average particle diameter of 1.5 μm as polyester C. Each raw material was dried at 125°C for 8 hours under a reduced pressure of 33 Pa. A mixture of them in a weight ratio of A / B / C = 70 / 20 / 10 was put into a single-screw extruder. The temperature was set so that the resin temperature would be 280°C from the extruder to the melt line, filter, and T-die. However, the resin temperature was set to 305°C for 30 seconds from the starting point of the compression section of the extruder screw, and then it was set to 280°C again.

[0123] The melt extruded from the T-die was brought into close contact with a cooling roll to form an unstretched sheet, which was then continuously stretched 1.41 times in the longitudinal direction (MD1) using rolls with a circumferential speed difference heated to 118°C, and further stretched 2.92 times in the longitudinal direction (MD2) using rolls with a circumferential speed difference heated to 128°C. The longitudinally stretched sheet was guided into a tenter, and the coating liquid 1 was coated on one side of the film by the fountain bar coating method. While being dried and guided into the tenter, after preheating at 121°C, it was stretched 4.3 times in the transverse direction at 131°C. Subsequently, as heat setting, it was carried out at 180°C without relaxation (0%) for 2.5 seconds (TS1), then at 231°C with 5% relaxation for 3.0 seconds (TS2), and then at 222°C without relaxation for 2.5 seconds (TS3). Subsequently, in the same tenter, cooling was carried out at 120°C for 6.0 seconds, and finally, a biaxially stretched polyester film with a thickness of 12 μm was obtained by winding it with a winder.

[0124] In preparing the base film layers described in each example and comparative example, a laminated film was produced and evaluated in the same manner except that the blending amounts of resins A / B / C or the coating liquid constituting the coating layer were changed as shown in Table 1.

[0125] The method for producing the inorganic thin film layer used in each example and comparative example is described below. Examples 1 to 9 and used in Comparative Examples 1 to 9, as shown in Table 1. (Formation of Inorganic Thin Film Layer M-1) As the inorganic thin film layer M-1, aluminum oxide was vapor-deposited on the base film layer. The method of vapor-depositing aluminum oxide on the base film layer is to set the film on the unwinding side of a continuous vacuum vapor deposition machine and run it through a cooling metal drum to wind up the film. At this time, the continuous vacuum vapor deposition machine was depressurized to 10-4 Torr or less, and metal aluminum with a purity of 99.99% was loaded into an alumina crucible from below the cooling drum. The metal aluminum was heated and evaporated, and oxygen was supplied into the vapor to cause an oxidation reaction while depositing and adhering it onto the film to form an aluminum oxide film with a thickness of 10 nm.

[0126] (Formation of Inorganic Thin Film Layer M-2) As the inorganic thin film layer M-2, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the base film layer by electron beam evaporation. As the evaporation sources, particulate SiO2 (purity 99.9%) and A12O3 (purity 99.9%) of about 3 mm to 5 mm were used. The film thickness of the inorganic thin film layer (SiO2 / A12O3 composite oxide layer) in the film (film containing the inorganic thin film layer / coating layer) thus obtained was 13 nm. Also, the composition of this composite oxide layer was SiO2 / A12O3 (mass ratio) = 60 / 40.

[0127] (5) Coating of Coating Liquid 3 on the Vapor-Deposited Film (Lamination of the Protective Layer) The prepared coating liquid 3 was applied onto the inorganic thin film layer of the obtained vapor-deposited film by the gravure roll coating method, pre-dried at 110 °C, and then dried at 160 °C to obtain a protective layer. The coating amount after drying was 0.15 g / m 2 (Dry). Thereafter, a post-heat treatment at 40 °C for 2 days was performed. The coating liquid constituting the protective layer, and the temperature of the said main drying and the post-heat treatment conditions were changed as shown in Table 1 for each Example and Comparative Example.

[0128] As described above, a laminated film provided with a coating layer / inorganic thin film layer / protective layer was produced on the base film. The obtained laminated film was evaluated. The results are shown in Table 1.

[0129]

Table 1

Industrial Applicability

[0130] According to the present invention, by forming a laminated film having a structure in which an inorganic thin film layer is sandwiched between a specific coating layer or a specific barrier protection layer excellent in flexibility and adhesiveness, it has been found that the gas barrier performance before treatment can be improved and the barrier property and adhesiveness can be maintained even after severe damp heat treatment. Furthermore, by using a polyester resin derived from a PET bottle with a low environmental load as a base material, it has been found that there is little whitening after retort treatment, and the present invention has been completed. Moreover, since the laminated film of the present invention has few processing steps and can be easily manufactured, it is excellent in both economic efficiency and production stability, and can provide a gas barrier film with uniform characteristics.

Claims

1. A laminated film having an inorganic thin film layer on at least one side of a base film, and having a protective layer containing a urethane resin containing an aromatic component or an aromatic aliphatic component as a constituent component on the inorganic thin film layer, wherein the laminated film satisfies the following requirements (a) to (c). (a) The base film contains 50% by weight or more of a polyester resin recycled from a PET bottle. (b) The standard deviation of the haze after retort treatment of the laminated film at 130 ° C. for 30 minutes is 0.5% or less. (c) The adhesion amount of the protective layer is 0.5 g / m ２ or less.

2. The laminated film according to claim 1, wherein the protective layer contains a meta-xylylene diisocyanate component as a constituent component.

3. The laminated film according to claim 1 or 2, having a coating layer between the base film layer and the inorganic thin film layer, wherein the coating layer contains a resin having an oxazoline group or a carbodiimide group as a constituent component.

4. The laminated film according to any one of claims 1 to 3, wherein the inorganic thin film layer is an aluminum oxide layer or a layer of a composite oxide of silicon oxide and aluminum oxide.

5. A packaging material obtained by laminating a sealant layer on one side of the laminated film according to any one of claims 1 to 4.

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