JP7035974B2 - Laminated film and packaging bag made of it - Google Patents

Description

The present invention relates to a laminated film used in the packaging field of foods, pharmaceuticals, industrial products and the like. More specifically, it is a laminated film composed of a base material layer and a sealant layer, and instead of using a laminated film of a polyester film and a nylon film as the base material layer, one layer of polybutylene terephthalate (hereinafter, may be abbreviated as PBT) film. The present invention relates to a laminated film having excellent puncture resistance and bag tear resistance, straight-line cutability, and excellent self-supporting property for a standing pouch even when the film is replaced with.

Conventionally, in order to prevent deterioration of contents such as foods, packaging materials in which various base materials such as plastic films, papers, and metal foils are laminated have been developed. Generally, a heat seal layer is provided on the innermost layer of these packaging materials, and the bags are manufactured in various forms by superimposing and sealing them. Then, the contents are filled from the opening, heat-sealed and sealed to complete the final packaged product. Especially in food applications, retort pouches are widely known as a packaging form that can be stored for a long period of time, and have already been put into practical use in all fields. Furthermore, in recent years, among the above-mentioned retort pouches, the retort pouch itself has a self-supporting structure so that it can be displayed at the store as it is without putting it in the outer box for the purpose of reducing the packaging material that becomes waste after use. Standing pouches that are used are becoming more popular.

On the other hand, the basic performance required for packaging materials for retort pouches is safety, tasteless and odorless, heat-resistant water, light-shielding, fragrance-retaining, discoloration-resistant, various gas barrier properties, pressure resistance, impact, and strength such as piercing. , Flexibility, airtightness, etc., and the optimum laminating configuration is designed according to the conditions of heat treatment, the type of contents, the content, and the like.
For example, biaxially stretched polyethylene terephthalate film (hereinafter abbreviated as OPET) to impart heat resistance, waist (independence), gloss, printability, and fragrance retention, impact resistance, pinhole resistance, and puncture resistance. Biaxially stretched nylon film (hereinafter abbreviated as ONy) to impart light, aluminum foil or aluminum vapor-deposited film or gas barrier coating layer to block light, oxygen, and water vapor, and unstretched polypropylene film to impart heat sealability. (Hereinafter abbreviated as CPP), polyethylene film, or the like is selected, and a packaging material for retort can be obtained by laminating these materials by dry laminating or the like.

Regarding the laminating composition of the packaging material for retort, for example, the film laminated in the order of OPET / ONy / CPP from the outside, OPET / AL / CPP, OPTET / ONy / AL / CPP, OPTET / AL / ONy / CPP, respectively. A typical configuration is a laminated film or the like. (See Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).
OPET and ONy are generally used as the base material layer of the packaging material for retort pouches, but OPET has the advantage of high heat resistance and water resistance, but has the weaknesses of low impact strength, piercing strength, and pinhole resistance. rice field. On the other hand, although ONy has high impact strength and piercing strength, since the film itself has hygroscopicity, it has a drawback that its strength is lowered by hydrolysis when it comes into contact with hot water. From the above viewpoints, especially in the case of harsh retort conditions of 130 ° C or higher, or when high pressure resistance and impact resistance are required, OPT and ONy are used as base material layers in order to mutually compensate for the shortcomings of both base materials. Is used together.

However, using both OPET and ONy as the base material has problems in terms of resource saving and impact on the environmental load. In addition, since the number of laminating processes is increased, there are problems in terms of economy and workability.
Therefore, in recent years, an attempt has been made to supplement the structure in which OPT and ONy are laminated as described above with a single layer film.
For example, Patent Document 6 and Patent Document 7 disclose biaxially stretched films containing PBT. According to such a technique, since it is excellent in impact resistance and piercing resistance and can withstand harsh heat treatment such as retort treatment, a base material in which OPET and ONy are laminated can be replaced with a single layer film. ..
However, when a film in which the base material layer is made into one layer and laminated with the sealant layer is processed into a packaging bag such as a standing pouch, the standing pouch lacks the independence of the standing pouch because the feeling of waist as a laminated film is insufficient. There was a problem.

Further, when the food contents are taken out from the packaging bag, particularly the retort pouch, the packaging bag is often torn by hand from the notch portion inserted in the seal portion of the packaging bag. At this time, the packaging bag could not be torn straight in the horizontal direction and may be opened diagonally.
When the package is opened at an angle, the laminated film on the front and back of the packaging bag has a phenomenon in which the direction of tearing is reversed, the so-called "breaking up" phenomenon, which makes it difficult to take out the food contents and makes it difficult to take out the food contents. There was a risk of burning hands and clothes, and if the contents were heated.

The reason why it is difficult to tear the packaging bag parallel to one side of the packaging bag is that the base material used for the laminated film is distorted, that is, the molecular orientation axis direction of the biaxially stretched film used for the base material is the packaging. One of the causes is that it is not parallel to one side of the body.

If the molecular orientation axis direction of the biaxially stretched film can be the same as the tearing direction of the packaging bag, such a problem is unlikely to occur. Since the molecular orientation axis direction of the central portion of the wide stretched film produced in the width direction substantially coincides with the traveling direction of the film, it can be torn parallel to one side of the packaging bag. However, since the molecular orientation axis direction is tilted at the widthwise end of the base film, the tearing direction of the packaging bag is tilted. It is not practical to procure a base film that uses the widthwise ends of the base film completely avoiding it. Further, as the production speed of the biaxially stretched film is increased and the width is increased, the inclination in the molecular orientation axis direction at the end in the width direction tends to be further larger than in the conventional case.
Therefore, it is attempted to solve such a problem by devising a sealant film laminated with the base film.

For example, a film obtained by uniaxially stretching a polyolefin-based resin sheet containing an ethylene-propylene block copolymer and an ethylene-propylene random copolymer at a ratio of 3.0 times or less is known (for example, Patent Document 7). reference). It is described that straight-line cutability was obtained by laminating the sealant film and the base film. However, this laminated film may have a weak tear strength or "breaking up" may occur.

Further, a sealant film obtained by uniaxially stretching a sheet composed of a propylene-ethylene block copolymer or a propylene-ethylene random copolymer and a polyolefin resin composition containing a propylene-butene elastomer and / or an ethylene-butene elastomer by about 5 times. Laminated films with base films are known (see Patent Documents 8 and 9). However, this laminated film also has room for improvement in bag breaking when dropped, and has a problem that bag breaking resistance is insufficient at a temperature lower than the operating temperature assumed in Patent Document 10.

Jitsukosho 63-31961 Gazette Japanese Unexamined Patent Publication No. 5-38779 JP-A-2002-326306 Japanese Unexamined Patent Publication No. 2005-178311 JP-A-2017-09946 WO2014 / 077197 Japanese Patent No. 5790497 Special Table 2012-500307 Gazette Japanese Unexamined Patent Publication No. 2014-141302 Japanese Unexamined Patent Publication No. 2018-20844

The present invention has been made in the background of the problems of the prior art. That is, the subject of the present invention is that the amount of the packaging material can be reduced, the impact resistance and the bag breaking resistance are excellent, the straight-line cut property is excellent, and the self-supporting property is sufficient when used as a standing pouch. It is an object of the present invention to provide a laminated film suitable for packaging of retort foods and the like which can be secured, and a packaging bag made of the laminated film.

The present inventors set the rigidity of the laminated film obtained by laminating the film base layer containing PBT resin as the main component and the sealant film layer within a specific range, so that even one base layer has heat resistance and impact resistance. It was found that it is excellent and can secure independence when processed into a standing pouch. At the same time, the laminated film is straightened by a film in which a sealant film containing an ethylene-propylene copolymerized elastomer having excellent compatibility with a polyolefin resin as a main component and a base film of a biaxially stretched film containing a PBT resin as a main component are laminated. The cutability could be improved. We have found that this makes it possible to reduce the amount of packaging material, has excellent impact resistance and bag resistance, has excellent straight-line cutability, and can ensure sufficient independence when used as a standing pouch. The invention was completed.

That is, the present invention has the following configuration.
[1] A biaxially stretched film base material made of a polyester resin composition containing at least (1) a polybutylene terephthalate resin in an amount of 60% by mass or more, and (2) a heat shrinkage in the longitudinal direction of 3% or more and 20% or less. It is a laminated film having a sealant film having a heat shrinkage rate in the width direction of 1% or less and a yield stress in the longitudinal direction of 150 MPa or more and 250 MPa or less, and is characterized by satisfying the following (a) to (c). Laminated film.
(A) The straight-line cutability of the laminated film in the longitudinal direction is 5 mm or less.
(B) The piercing strength of the laminated film is 15 N or more.
(C) The value (A value) obtained by dividing the average value of the loop stiffness in the longitudinal direction and the width direction of the laminated film by the cube of the thickness of the laminated film is 2.5 × 10 ^-4 or more.
[2] The sealant film contains a propylene-ethylene block copolymer of 40% by mass or more and 97% by mass or less, an ethylene-propylene copolymer elastomer of 3% by mass or more and 10% by mass or less, and an ethylene-α-olefin random copolymer. The laminated film according to [1], which is a sealant film comprising a polyolefin resin composition containing 0% by mass or more and 50% by mass or less.
[3] The laminated film according to [1] or [2], which has an inorganic thin film layer on at least one side of the biaxially stretched film base material.
[4] The laminated film according to [1] or [2], wherein the inorganic thin film layer is a layer made of an oxide of silicon oxide and / or aluminum oxide.
[5] The laminated film according to [3] or [4], which has an adhesion layer between the biaxially stretched film base material and the inorganic thin film layer.
[6] The laminated film according to any one of [3] to [5], which has a protective layer on the inorganic thin film layer.
[7] The laminated film according to [1] or [2], wherein an aluminum foil is provided between the biaxially stretched film base material and the sealant film.
[8] A packaging bag made of the laminated film according to any one of [1] to [7].
[9] The packaging bag according to [8] for retort pouches.

INDUSTRIAL APPLICABILITY According to the present invention, the amount of packaging material can be reduced, the impact resistance and bag breaking resistance are excellent, the straight-line cut property is excellent, and the retort food can secure sufficient independence when used as a standing pouch. It has become possible to provide a laminated film suitable for liquid packaging such as and a packaging bag made of the laminated film.

It is a top view which shows the shape of the standing pouch produced by using the laminated film which concerns on this invention. It is a perspective view which shows the shape of the standing pouch produced by using the laminated film which concerns on this invention.

Hereinafter, the present invention will be described in detail.
(Sealant film)
The sealant film in the present invention has a polyolefin-based resin composition containing a propylene-ethylene block copolymer, or a propylene-ethylene block copolymer, at least one propylene-α-olefin random copolymer, and an ethylene-propylene copolymer elastomer. By making a sea-island structure made of a material, good rupture resistance can be exhibited.
At this time, the sea part is composed of a portion of the propylene-ethylene block copolymer containing propylene as a main component, or a portion further containing a propylene-α-olefin random copolymer, and the island portion is an ethylene-propylene copolymer elastomer and propylene-. It consists of a portion of the ethylene block copolymer containing ethylene as a main component.

The sealant film in the present invention contains a propylene-ethylene block copolymer of 40% by mass or more and 97% by mass or less, an ethylene-propylene copolymer elastomer of 3% by mass or more and 10% by mass or less, and an ethylene-α-olefin random copolymer of 0. It comprises a polyolefin-based resin composition containing in an amount of mass% or more and 50% by mass or less. Within this range, the packaging bag has excellent tear resistance and bag-making finish, sufficient tear strength can be obtained, and the amount of crying at the time of opening is small and good.

In the sealant film of the present invention, when the ratio of the propylene-α-olefin random copolymer exceeds 50% by mass, the tear resistance of the packaging bag is deteriorated, the tear strength is lowered, and the amount of tearing at the time of opening is large. May become. It is preferably 40% by mass or less, more preferably 35% by weight or less.
From the viewpoint of the heat seal start temperature, the ratio of the propylene-α-olefin random copolymer is preferably 10% by mass or more, more preferably 20% by mass or more.

(Propene-ethylene block copolymer)
In the present invention, a propylene-ethylene block copolymer can be used as the main component of the sealant film. The propylene-ethylene block copolymer in the present invention has a first-stage polymerization step consisting of a large amount of propylene and a small amount of ethylene copolymerization component and a second-stage polymerization step consisting of a small amount of propylene and a large amount of ethylene copolymerization component. It is a multi-stage copolymer composed of the polymerization steps of. Specifically, as shown in Japanese Patent Application Laid-Open No. 2000-186159, it is preferable to use one that has undergone vapor phase polymerization. That is, in the first step, the polymer portion (component A) mainly composed of propylene is polymerized in the absence of a substantially inert solvent, and then in the second step, the ethylene content is 20 to 50% by mass in the gas phase. Examples thereof include block copolymers obtained by polymerizing a copolymer portion (B component) of propylene and ethylene, but the present invention is not limited thereto.

The melt flow rate (MFR) (230 ° C., load 2.16 kg measurement) of the propylene-ethylene block copolymer is not particularly limited, but is preferably 1 to 10 g / 10 minutes, more preferably 2 to 7. If it is less than 1 g / 10 minutes, the viscosity is too high and it is difficult to extrude with a T-die. On the contrary, if it exceeds 10 g / 10 minutes, the stickiness of the film and the impact strength (impact strength) of the film are inferior. This is because problems such as occur.

In the present invention, the xylene-soluble portion at 20 ° C. is referred to as CXS, and the xylene-insoluble portion at 20 ° C. is referred to as CXIS. In the propylene-ethylene block copolymer used in the present invention, CXS is mainly composed of a rubber component (component B), and CXIS is mainly composed of a polypropylene component (component A). Assuming that the respective ultimate viscosities are [η] CXS and [η] CXIS, the values of [η] CXS and [η] CXIS are not particularly limited, but [η] CXS is in the range of 1.8 to 3.8 dl / g. Is preferable, and more preferably, it is in the range of 2.0 to 3.0 dl / g. If it exceeds 3.0 dl / g, fish eyes are likely to occur in the polyolefin resin film. On the other hand, if it is 1.8 dl / g or less, the heat seal strength between the polyolefin resin films may be significantly lowered. On the other hand, [η] CXIS is preferably in the range of 1.0 to 3.0 dl / g. If it exceeds 3.0 dl / g, the viscosity may be too high and it may be difficult to extrude with a T-die. On the contrary, if it is less than 1.0 dl / g, the film may become sticky or the film may be impact resistant. This is because problems such as inferior strength (impact strength) may occur.

The above [η] CXS and [η] CXIS are values measured by the following measuring methods. After completely dissolving 5 g of the sample in 500 ml of boiling xylene, the temperature was lowered to 20 ° C., and the mixture was allowed to stand for 4 hours or more. Next, this was separated into a filtrate and a precipitate, and the component (CXS) obtained by drying the filtrate and the precipitate were dried at 70 ° C. under reduced pressure to obtain the ultimate viscosity ([]. η]) was measured in 135 ° C. tetralin using a Ubbelohde viscometer.

In general, it is known that the MFR and the ultimate viscosity η of the entire film are correlated. By knowing the η of the film, the MFR of the resin used can be roughly known. η is a guideline for the molecular weight. The larger the value, the larger the molecular weight, and the smaller the value, the smaller the molecular weight. MFR is a measure of molecular weight. The smaller the value, the larger the molecular weight, and the larger the value, the smaller the molecular weight.
Further, as the propylene-ethylene block copolymer, the copolymerization ratio of the ethylene component in the propylene-ethylene block copolymer is preferably 1 to 15% by mass, and preferably 3 to 10% by mass. The copolymerization ratio of the propylene component in the propylene-ethylene block copolymer is preferably 85 to 99%, preferably 90 to 97% by mass.
Specifically, for example, a block copolymer polypropylene resin (230 ° C., load) having an ethylene content of 6.5% by mass, a propylene content of 93.5% by mass, and a CXS extreme viscosity η = 2.5 dl / g. MFR = 3.0 g / 10 minutes at 2.16 kg, WFS5293-22) manufactured by Sumitomo Chemical Co., Ltd., ethylene content is 5.7% by mass, propylene content is 94.3% by mass, and the ultimate viscosity η of CXS. = 2.3 dl / g block copolymer polypropylene resin (MFR = 3.0 g / 10 minutes at 230 ° C. and a load of 2.16 kg, WFS5293-29 manufactured by Sumitomo Chemical Corporation).

(Ethylene-propylene copolymer elastomer)
In the present invention, the ethylene-propylene copolymer elastomer is used as one component of the raw material of the polyolefin-based resin film of the present invention for the purpose of enhancing the drop-breaking resistance of the packaging bag of the present invention.
The ethylene-propylene copolymer elastomer is a copolymerized polymer obtained by copolymerizing ethylene and propylene, which is amorphous or has low crystallinity and exhibits rubber-like elasticity at around room temperature.

The ethylene-propylene copolymer elastomer in the present invention is not particularly limited, but the melt flow rate (MFR) at 230 ° C. and a load of 2.16 kg is 0.2 to 5 g / 10 minutes, the density is 820 to 930 kg / m ³ , and the GPC method. It is a desirable form to use one having a molecular weight distribution (Mw / Mn) of 1.3 to 6.0.
When the melt flow rate (MFR) of the ethylene-propylene copolymerized elastomer in the present invention at 230 ° C. and a load of 2.16 kg is less than 0.2 g / 10 minutes, uniform kneading becomes insufficient and fish eyes are likely to occur. Further, if it exceeds 5 g / min, it is not preferable from the viewpoint of bag breaking resistance.

Further, the ultimate viscosity [η] of the ethylene-propylene copolymerized elastomer in the present invention is preferably 1.0 to 5.0 from the viewpoints of heat seal strength retention, impact strength retention, and bag drop strength, and is preferable. It is 1.2 to 3.0. If the ultimate viscosity [η] is less than 1.0, uniform kneading becomes insufficient and fish eyes are likely to occur, and if it exceeds 5.0, it is not preferable from the viewpoint of bag breaking resistance and heat seal strength. ..
The ethylene-propylene copolymer elastomer in the present invention preferably has a copolymerization ratio of the propylene component in the ethylene-propylene copolymer elastomer of 15 to 45% by mass, preferably 20 to 40% by mass. The copolymerization ratio of the ethylene component in the ethylene-propylene copolymerized elastomer is preferably 55 to 85% by mass, and preferably 60 to 80% by mass.
Specifically, for example, an ethylene-propylene copolymer elastomer having a density of 870 kg / m ³ , MFR (230 ° C., 2.16 kg) of 1.8 g / 10 minutes and a propylene content of 93.5% by mass (Mitsui Chemicals, Inc.) Toughmer P0480,) and the like.

(Propene-α-olefin random copolymer)
In the present invention, a propylene-α-olefin random copolymer may be added for the purpose of lowering the heat-sealing temperature of the polyolefin-based resin film.
Examples of the propylene-α-olefin random copolymer include a copolymer of propylene and at least one α-olefin having 2 to 20 carbon atoms other than propylene. As the α-olefin monomer having 2 to 20 carbon atoms, ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1 and the like can be used. Although not particularly limited, it is preferable to use ethylene from the viewpoint of compatibility with the propylene-ethylene block copolymer. Further, at least one type may be used, and two or more types may be mixed and used as needed. Particularly suitable is a propylene-ethylene random copolymer.

The lower limit of the melt flow rate (MFR) of the propylene-α-olefin random copolymer at 230 ° C. and a load of 2.16 kg is not particularly limited, but is preferably 0.6 g / 10 min, and more preferably 1.0 g / 10 min. It is more preferably 1.2 g / 10 minutes. If it is less than the above, the compatibility with the propylene-ethylene block copolymer is low and the film may be whitened. The upper limit of the melt flow rate of the propylene-α-olefin random copolymer is not particularly limited, but is preferably 8.0 g / 10 minutes, more preferably 7.0 g / 10 minutes, and further preferably 5.0 g / 10 minutes. Minutes. Specific examples of the propylene-α-olefin random copolymer include S131 manufactured by Sumitomo Chemical Co., Ltd. (density 890 kg / m ³ , 230 ° C., MFR 1.5 g / 10 minutes at a load of 2.16 kg, melting point 132 ° C.). Can be mentioned.

The lower limit of the melting point of the propylene-α-olefin random copolymer is not particularly limited, but is preferably 120 ° C. and more preferably 125 ° C. If it is less than the above, the heat resistance is impaired, and the inner surfaces of the bags may be fused to each other during the retort treatment. The upper limit of the melting point of the propylene-α-olefin random copolymer is not particularly limited, but is preferably 145 ° C, more preferably 140 ° C. If it is more than the above, the effect of lowering the heat seal temperature may be small.

(Additive)
The sealant film in the present invention may contain an anti-blocking agent. The compounded anti-blocking agent is not particularly limited, but is limited to inorganic particles such as calcium carbonate, silicon dioxide, titanium dioxide, barium sulfate, magnesium oxide, talc, and zeolite, and acrylic, styrene, and styrene / butadiene polymers. Further, organic particles made of these crosslinked bodies and the like can be mentioned. Considering the ease of controlling the particle size distribution, the dispersibility, the ease of maintaining the optical appearance, and the prevention of the particles from falling off from the film, the organic particles made of a crosslinked body are preferable. As the crosslinked product, a crosslinked acrylic polymer composed of an acrylic monomer such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester is particularly preferable, and crosslinked polymethylmethacrylate is more preferable. Recommended. The surface of these particles may be coated with various coatings for the purpose of dispersibility and prevention of falling off. Further, the shape of these particles may be amorphous, spherical, elliptical sphere, rod-shaped, square, polyhedron, conical, or porous shape having cavities on the surface or inside of the particles.
The anti-blocking agent preferably has an average particle size of 3 to 12 μm from the viewpoint of the appearance of the film and the blocking resistance. Although it is effective to use only one type of anti-blocking agent, it is more effective to mix two or more types of inorganic particles having different particle sizes and shapes to form more complicated protrusions on the film surface and to have a higher blocking prevention effect. May be able to be obtained. When the block copolymer is used as the main constituent resin, surface irregularities may be formed due to the dispersion of the polymer, and a high blocking resistance effect may be obtained without adding an anti-blocking agent.

An organic lubricant may be added to the sealant film in the present invention. The slipperiness and blocking prevention effect of the laminated film are improved, and the handleability of the film is improved. It is considered that the reason is that the organic lubricant bleeds out and is present on the film surface, so that the lubricant effect and the mold release effect are exhibited. Further, it is preferable to add an organic lubricant having a melting point of room temperature or higher. Examples of suitable organic lubricants include fatty acid amides and fatty acid esters. More specifically, there are oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, ethylene bisoleic acid amide and the like. These may be used alone, but it is preferable to use two or more of them in combination because it may be possible to maintain the slipperiness and the blocking prevention effect even in a harsher environment.

The sealant film in the present invention is used as an appropriate amount of antioxidant, antistatic agent, antistatic agent, neutralizing agent, nucleating agent, colorant, and other additives as long as the object of the present invention is not impaired. An inorganic filler or the like can be blended. Examples of the antioxidant include the single use and combined use of phenol-based and phosphite-based agents, and the single use of those having a phenol-based and phosphite-based skeleton in one molecule.

(Sealant film consisting of multiple layers)
The sealant film in the present invention may be a single layer or may be composed of a plurality of layers. For example, by adopting a three-layer structure consisting of a seal layer, an intermediate layer, and a laminate layer, and adding pellets obtained by recycling the film to the intermediate layer, the cost can be reduced without impairing the heat seal energy and the rupture resistance, or propylene. By adding the -α-olefin random copolymer only to the seal layer and using the propylene-ethylene block copolymer as the main component for the intermediate layer and the laminate layer, it is possible to suppress the decrease in impact resistance. When it is composed of a plurality of layers, it is preferable that each layer has the composition ratio described in the above [2].

(Manufacturing method of sealant film)
As the method for forming the sealant film in the present invention, for example, an inflation method and a T-die method can be used, but the T-die method is preferable in order to improve transparency and to make drafting easy. In the inflation method, the cooling medium is air, whereas in the T-die method, a cooling roll is used, which is an advantageous manufacturing method for increasing the cooling rate of the unstretched sheet. By increasing the cooling rate, crystallization of the unstretched sheet can be suppressed, so that high transparency can be obtained and the load applied to stretching in the subsequent step can be easily controlled, which is advantageous. For this reason, it is more preferable to mold by the T-die method.

The lower limit of the temperature of the cooling roll when casting the molten raw material resin to obtain an unoriented sheet is not particularly limited, but is preferably 15 ° C., more preferably 20 ° C. If it is less than the above, dew condensation occurs on the cooling roll, and the unstretched sheet and the cooling roll become insufficiently adhered, which may cause a poor thickness. The upper limit of the cooling roll is not particularly limited, but is preferably 50 ° C. and more preferably 40 ° C. If it exceeds the above, the transparency of the sealant film may deteriorate.

The method of stretching the non-oriented sheet is not particularly limited, and for example, an inflation method and a roll stretching method can be used, but the roll stretching method is preferable because of the ease of controlling the orientation.
By stretching the non-oriented sheet in the longitudinal direction under appropriate conditions, straight-line cutability is exhibited. This is because the molecular chains are regularly arranged in the stretching direction. In the present invention, the direction in which the film travels in the film manufacturing process is referred to as the longitudinal direction, and the direction perpendicular to the longitudinal direction is referred to as the width direction.
The lower limit of the draw ratio in the longitudinal direction is not particularly limited, but is preferably 3.3 times. If it is smaller than this, the yield stress may decrease, the tear strength in the longitudinal direction may increase, or the straight-line cutability may be inferior. It is more preferably 3.5 times, still more preferably 3.8 times.
The upper limit of the draw ratio in the longitudinal direction is not particularly limited, but is preferably 5.5 times. If it is larger than this, the orientation may be excessively advanced, the sealing energy may be lowered, and the bag-breaking resistance at the time of dropping may be deteriorated. More preferably, it is 5.0 times.

The lower limit of the roll temperature in the longitudinal stretching is not particularly limited, but is preferably 80 ° C. If it is lower than this, the stretching stress applied to the film becomes high, and the thickness of the film may fluctuate. More preferably, it is 90 ° C.
The upper limit of the stretching roll temperature is not particularly limited, but is preferably 140 ° C. If it exceeds this, the stretching stress applied to the film is lowered, the tear strength of the film is lowered, and the film may be fused to the stretched roll, which may make the production difficult. It is more preferably 130 ° C, still more preferably 125 ° C, and particularly preferably 115 ° C.

Before introducing the unstretched sheet into the stretching step, it is preferable to bring the unstretched sheet into contact with the preheating roll to raise the sheet temperature.
The lower limit of the preheating roll temperature when stretching the non-oriented sheet is not particularly limited, but is preferably 80 ° C, more preferably 90 ° C. If it is less than the above, the stretching stress becomes high and the thickness may fluctuate. The upper limit of the preheating roll temperature is not particularly limited, but is preferably 140 ° C, more preferably 130 ° C, and even more preferably 125 ° C. If it is more than the above, the heat shrinkage rate and the retort shrinkage rate may increase. This is because thermal crystallization before stretching can be suppressed and residual stress after stretching can be reduced.

The sealant film that has undergone the stretching step is preferably subjected to a treatment for promoting crystallization (hereinafter referred to as annealing treatment) in order to suppress heat shrinkage. The annealing method includes a roll heating method, a tenter method, and the like, but the roll heating method is preferable because of the simplicity of the equipment and the ease of maintenance. By reducing the internal stress of the film by the annealing treatment, it is possible to suppress the thermal shrinkage of the film and further improve the easy tearability. Since the anneal treatment can further improve the tearability, it is not necessary to increase the draw ratio in order to improve the tearability as in the conventional case, so that the retort shrinkage rate and the heat seal strength after retort are sacrificed. There is nothing to do.

The lower limit of the annealing treatment temperature is not particularly limited, but is preferably 80 ° C. If it is less than the above, the heat shrinkage rate becomes high, and the finish of the packaging bag after bag making or retort may be deteriorated, or the tear strength may be increased. More preferably, it is 100 ° C, and 110 ° C is particularly preferable.
The upper limit of the annealing treatment temperature is not particularly limited, but is preferably 140 ° C. The higher the annealing treatment temperature, the lower the heat shrinkage rate tends to be, but if it exceeds this, uneven film thickness may occur or the film may be fused to the manufacturing equipment. It is more preferably 135 ° C., and particularly preferably 130 ° C.

In the present invention, it is preferable to activate the surface of the laminated surface of the sealant film described above by corona treatment or the like. By this correspondence, the laminating strength with the base film is improved.

(Characteristics of sealant film)
<Thickness of sealant film>
The thickness of the sealant film in the present invention is not particularly limited, but the lower limit is preferably 10 μm, more preferably 30 μm, still more preferably 40 μm, and particularly preferably 50 μm. If it is less than the above, it becomes relatively thin with respect to the thickness of the base film, so that the straight-line cutability of the laminated film may deteriorate, the firmness of the film may be too weak, and it may be difficult to process. Impact resistance may decrease and bag tear resistance may deteriorate. The upper limit of the film thickness is preferably 200 μm, more preferably 130 μm, preferably 100 μm, and particularly preferably 80 μm. If it exceeds the above, the film may be too stiff and difficult to process, and it may be difficult to manufacture a suitable package.

<Heat shrinkage of sealant film>
The upper limit of the heat shrinkage rate at 120 ° C. in the longitudinal direction of the sealant film in the present invention is preferably 20%. If it exceeds the above, the tear strength increases, and at the same time, the retort shrinkage of the package during heat sealing increases, which may impair the appearance of the package. It is more preferably 17% and even more preferably 14%.
The lower limit of the heat shrinkage in the longitudinal direction of the sealant film in the present invention is preferably 2%. If it is made smaller than this, the annealing temperature and the annealing time need to be remarkably increased, so that the bag resistance and the appearance may be remarkably deteriorated.
The upper limit of the heat shrinkage rate in the width direction of the sealant film in the present invention is preferably 1%. If it exceeds the above, the tear strength in the longitudinal direction becomes large, or the straight-line cutability is inferior. More preferably, it is 0.5%. The lower limit of the heat shrinkage in the width direction of the sealant film in the present invention is preferably -3%. If it is less than the above, the heat seal may be stretched and the appearance of the package may be deteriorated. It is preferably -2%.

<Yield stress of sealant film>
The yield stress in the longitudinal direction of the sealant film in the present invention is preferably 150 MPa or more. If it is smaller than this, the straight cut property in that direction is inferior. It is more preferably 160 MPa or more, and even more preferably 170 MPa or more.
The yield stress in the longitudinal direction of the sealant film in the present invention is preferably 250 MPa or less. If it is larger than this, the sealing energy of the film is lowered, and the bag breaking resistance may be deteriorated.

Further, the ratio of the yield stress in the longitudinal direction and the width direction of the sealant film in the present invention is not particularly limited, but is preferably 4.0 or more, more preferably 6.0 or more. When the ratio of the yield stress in the longitudinal direction and the yield stress in the width direction is 4.0 or more, the straight-line cutability is likely to be improved without insufficient orientation in the longitudinal direction.
The ratio of the yield stress in the longitudinal direction and the width direction is not particularly limited, but is preferably 14.0 or less, more preferably 12.0 or less. When the ratio of the yield stress in the longitudinal direction and the yield stress in the width direction is 14.0 or less, the orientation in the longitudinal direction is not excessive and a suitable heat seal strength can be obtained, so that the bag resistance is likely to be improved. ..

<Tear strength of sealant film>
The upper limit of the tear strength in the longitudinal direction of the sealant film in the present invention is not particularly limited, but is preferably 0.2N. If it exceeds this, it may be difficult to tear the laminated film. More preferably, it is 0.16N.
The lower limit of the tear strength in the longitudinal direction of the sealant film in the present invention is not particularly limited, but is preferably 0.02N. If it is smaller than this, the bag resistance may deteriorate. More preferably, it is 0.03N.

<Wet tension of sealant film>
The lower limit of the wetting tension of the surface of the sealant film in the present invention to be laminated with the biaxially stretched film base material made of a polyester resin composition containing 60% by mass or more of polybutylene terephthalate resin is not particularly limited, but is preferably 30 mN / m. Yes, more preferably 35 mN / m. If it is less than the above, the laminate strength may decrease. The upper limit of the wetting tension is not particularly limited, but is preferably 57 mN / m, and more preferably 50 mN / m. If it exceeds the above, blocking of the roll of the sealant film may occur.

<Puncture strength of sealant film>
The lower limit of the puncture strength of the sealant film in the present invention is not particularly limited, but is preferably 7.8N, more preferably 9N. If it is less than the above, pinholes may occur when the protrusion hits the package. The upper limit of the puncture strength is not particularly limited, but is preferably 24N, more preferably 19N. If it exceeds the above, the feeling of elasticity is too strong, and it may be difficult to handle the film or laminated film.

(Biaxially stretched film made of a polyester resin composition containing 60% by mass or more of PBT resin)
The biaxially stretched film (hereinafter, may be abbreviated as biaxially stretched PBT film) made of a polyester resin composition containing 60% by mass or more of the PBT resin used in the present invention contains 60% by mass or more of the PBT resin.
When the content of the PBT resin is less than 60% by mass, the features of the biaxially stretched PBT film, which are excellent in dimensional stability, workability, bag breakage resistance, chemical resistance, and pinhole resistance at low temperature, are lost.

The biaxially stretched PBT film used in the present invention may contain other resins and additives as long as the PBT resin is not less than 60% by mass.
The PBT resin in the present invention preferably contains terephthalic acid in an amount of 90 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more, and most preferably 100 mol% as a dicarboxylic acid component. Is. As the glycol component, 1,4-butanediol is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 97 mol% or more.
The PBT resin in the present invention may be copolymerized within the above range. However, the biaxially stretched PBT film layer of the present invention needs to contain 60% by mass or more of PBT repeating units.

The components that copolymerize with the PBT resin include isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, dicarboxylic acids such as sebacic acid, ethylene glycol, and 1,3-propylene glycol. , 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol, polycarbonate diol and the like.

The biaxially stretched PBT film layer used in the present invention can contain a polyester resin other than the PBT resin for the purpose of adjusting the film-forming property at the time of biaxial stretching and the mechanical properties of the obtained film.
Examples of the polyester resin other than the PBT resin include polyethylene terephthalate (hereinafter referred to as PET) resin and polyethylene naphthalate (PEN) resin.
Polyester resins other than PBT resin may be copolymerized. For example, as the components to be copolymerized with the PET resin, dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, and sebacic acid, butylene glycol, 1,3-. Examples thereof include diol components such as propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol, and polycarbonate diol. ..

The lower limit of the intrinsic viscosity of the PBT resin used in the present invention is preferably 0.9 dl / g, more preferably 0.95 dl / g, and further preferably 1.0 dl / g.
When the intrinsic viscosity of the PBT resin is less than 0.9 dl / g, the intrinsic viscosity of the film obtained by forming the film may decrease, and the puncture strength, impact strength, rupture resistance and the like may decrease.
The upper limit of the intrinsic viscosity of the PBT resin is preferably 1.3 dl / g. If it exceeds the above, the stress at the time of stretching becomes too high, and the film forming property may deteriorate. In addition, since the melt viscosity is high, it is necessary to raise the extrusion temperature to a high temperature, and decomposition products may be easily generated during extrusion.

When a PET resin is used, the lower limit of the intrinsic viscosity of the polyester resin other than the PBT resin used in the present invention is preferably 0.5 dl / g, more preferably 0.6 dl / g.
If the intrinsic viscosity of the polyester resin other than the PBT resin is less than 0.9 dl / g, the intrinsic viscosity of the film obtained by forming the film may decrease, and the puncture strength, impact strength, rupture resistance, etc. may decrease. ..
The upper limit of the intrinsic viscosity of the polyester resin other than the PBT resin is preferably 1.2 dl / g when the PET resin is used. If it exceeds the above, the stress at the time of stretching becomes too high, and the film forming property may deteriorate. In addition, since the melt viscosity is high, it is necessary to raise the extrusion temperature to a high temperature, and decomposition products may be easily generated during extrusion.

It is effective to add an antioxidant to the biaxially stretched PBT film layer for the purpose of reducing the eluate after the retort treatment of the packaging bag of the present invention. This is to suppress a decrease in the molecular weight of the resin in the resin extrusion step and reduce the amount of 1,4-butanediol and THF remaining in the obtained film. Further, since PBT gradually decomposes by heating, it is also effective in suppressing the thermal decomposition that occurs during the retort treatment of the film.

Antioxidants used in the biaxially stretched PBT film layer in the present invention include a primary antioxidant (which has a phenolic or amine-based radical scavenging and chain arresting action) and a secondary antioxidant (which has a chain terminator effect). Has a peroxide-decomposing action such as phosphorus-based and sulfur-based), and any of these can be used. Specific examples include phenolic antioxidants (eg, phenol type, bisphenol type, thiobisphenol type, polyphenol type, etc.), amine-based antioxidants (eg, diphenylamine type, quinoline type, etc.), and phosphorus-based antioxidants (eg, diphenylamine type, quinoline type, etc.). For example, a phosphite type, a phosphonite type, etc.), a sulfur-based antioxidant (for example, a thiodipropionic acid ester type, etc.) can be mentioned.
Specifically, n-octadecyl-β- (4'-hydroxy-3,5'-di-t-butylphenyl) propionate, tetrakis [methylene-3- (3', 5'-di-t-butyl-) 4'-Hydroxyphenyl) propionate] (which is commercially available as "Irganox 1010" (trade name)), 1,1,3-Tris (2-methyl-4-hydroxy-5-t-butylphenyl). ) Butane, 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -S-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (which is commercially available as "Irganox 1330" (trade name)), Tris ( Mixed mono and / or dinonylphenyl) phosphite, cyclic neopentanetetraylbis (octadecylphosphite), tris (2,4-di-t-butylphenylphosphite), 2,2-methylenebis (4, 6-di-t-butylphenyl) octylphosphite, di-lauryl-thiodipropionate, di-myristyl-thiodipropionate, di-stearyl-thiodipropionate and the like can be mentioned. These antioxidants may be used alone or in combination of two or more. Among these, n-octadecyl-β- (4'-hydroxy (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] (Irganox 1010) from the viewpoint of availability and food hygiene. Is preferable.

The upper limit of the antioxidant concentration is preferably 2000 ppm, more preferably 1000 ppm. If it exceeds the above, the added antioxidant itself may become an eluate.

If necessary, the biaxially stretched PBT film layer in the present invention may contain conventionally known additives such as lubricants, stabilizers, colorants, antistatic agents, and ultraviolet absorbers.

Examples of the lubricant include inorganic particle lubricants such as silica, calcium carbonate and alumina, and organic lubricants. Silica and calcium carbonate are preferable, and porous silica is particularly preferable in that haze is reduced. These can be expressed as transparent and slippery.

The lower limit of the lubricant concentration is preferably 100 ppm, more preferably 500 ppm, still more preferably 800 ppm. If it is less than the above, the slipperiness of the film may decrease. The upper limit of the lubricant concentration is preferably 20000 ppm, more preferably 10000 ppm, still more preferably 1800 ppm. If it exceeds the above, transparency may deteriorate.

The production method for obtaining the biaxially stretched PBT film layer in the present invention will be specifically described. It is not limited to these.

The lower limit of the resin melting temperature is preferably 200 ° C, more preferably 250 ° C, and even more preferably 260 ° C. If it is less than the above, the discharge may become unstable. The upper limit of the resin melting temperature is preferably 280 ° C, more preferably 270 ° C.
Since PBT has a high crystallization rate, crystallization proceeds even during casting. At this time, when cast in a single layer without multi-layering, these crystals grow into spherulites having a large size because there is no barrier that can suppress the growth of the crystals. As a result, the yield stress of the obtained unstretched sheet becomes high, and not only is it easy to break during biaxial stretching, but also the flexibility of the obtained biaxially stretched film is impaired, resulting in pinhole resistance and breakage resistance. The film will have insufficient properties.

As a specific method of multi-layering, a general multi-layering device (multi-layer feed block, static mixer, multi-layer multi-manifold, etc.) can be used, and for example, two or more extruders are used to deliver from different flow paths. It is possible to use a method of laminating the obtained thermoplastic resin in multiple layers using a feed block, a static mixer, a multi-manifold die, or the like. In the case of multi-layering with the same composition as in the present invention, the object of the present invention is achieved by introducing the above-mentioned multi-layering device into the melt line from the extruder to the die using only one extruder. It is also possible to fulfill.

The lower limit of the cooling roll temperature is preferably −10 ° C. If it is less than the above, the effect of suppressing crystallization may be saturated. The upper limit of the cooling roll temperature is preferably 40 ° C. If it exceeds the above, the crystallinity may become too high and stretching may become difficult. When the temperature of the cooling roll is within the above range, it is preferable to lower the humidity of the environment near the cooling roll in order to prevent dew condensation.

In casting, the temperature of the surface of the cooling roll rises because the high temperature resin comes into contact with the surface. Normally, the cooling roll is cooled by flowing cooling water through the piping inside, but the cooling roll is cooled by ensuring a sufficient amount of cooling water, devising the arrangement of the piping, and performing maintenance to prevent sludge from adhering to the piping. It is necessary to reduce the temperature difference in the width direction of the surface. At this time, the thickness of the unstretched sheet is preferably in the range of 15 to 2500 μm.

The casting in the multilayer structure described above is performed with at least 60 layers or more, preferably 250 layers or more, and more preferably 1000 layers or more. If the number of layers is small, the effect of improving stretchability is lost.

Next, the stretching method will be described. The stretching method can be either simultaneous biaxial stretching or sequential biaxial stretching, but in order to increase the puncture strength, it is necessary to increase the plane orientation coefficient, and the film forming speed is high and the productivity is high. In the above, sequential biaxial stretching is most preferable.

The lower limit of the stretching temperature in the longitudinal direction is preferably 55 ° C, more preferably 60 ° C. If the temperature is lower than 55 ° C., not only the fracture may easily occur, but also the orientation in the longitudinal direction becomes stronger due to the stretching at a low temperature. The strain may increase, resulting in reduced straight-line tearability in the longitudinal direction. The upper limit of the longitudinal stretching temperature is preferably 100 ° C, more preferably 95 ° C. If the temperature exceeds 100 ° C., the mechanical properties may deteriorate because the orientation is not applied.

The lower limit of the longitudinal draw ratio is preferably 2.6 times, particularly preferably 2.8 times. If it is less than the above, the orientation is not applied, and the mechanical properties and thickness unevenness may deteriorate. The upper limit of the longitudinal draw ratio is preferably 4.3 times, more preferably 4.0 times, and particularly preferably 3.8 times. If it exceeds the above, not only the effect of improving the mechanical strength and the thickness unevenness may be saturated, but also the orientation in the longitudinal direction becomes stronger. The strain may increase, resulting in a decrease in longitudinal straight tearability.

The lower limit of the stretching temperature in the width direction is preferably 60 ° C., and if it is lower than the above, fracture may easily occur. The upper limit of the width stretching temperature is preferably 100 ° C., and if it exceeds the above, orientation may not be applied and the mechanical properties may deteriorate.

The lower limit of the draw ratio in the width direction is preferably 3.5 times, more preferably 3.6 times, and particularly preferably 3.7 times. If it is less than the above, the orientation is not applied, and the mechanical properties and thickness unevenness may deteriorate. The upper limit of the width stretching ratio is preferably 5 times, more preferably 4.5 times, and particularly preferably 4.0 times. If it exceeds the above, the effect of improving the mechanical strength and thickness unevenness may be saturated.

The lower limit of the heat fixing temperature in the width direction is preferably 190 ° C., more preferably 205 ° C. If it is less than the above, the heat shrinkage rate becomes large, and deviation or shrinkage during processing may occur. The upper limit of the width heat fixing temperature is preferably 240 ° C., and if it exceeds the above range, the film melts, and even if it does not melt, it may become extremely brittle.

The lower limit of the relaxation rate in the width direction is preferably 3%, and if it is less than the above, fracture may easily occur during heat fixing. The upper limit of the width relaxation rate is preferably 12%, and if it exceeds the above, not only slack may occur and thickness unevenness may occur, but also the shrinkage in the longitudinal direction at the time of heat fixing becomes large, and as a result, the end portion Distortion of molecular orientation may increase and straight-line tearability may decrease.

The lower limit of the thickness of the biaxially stretched PBT film in the present invention 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.
The upper limit of the film thickness is preferably 25 μm, more preferably 18 μm, and even more preferably 16 μm. If it exceeds 25 μm, it becomes too thick, which is economically disadvantageous and may deteriorate the processability and productivity at the time of bag making.

The upper limit of the orientation axis angle of the biaxially stretched PBT film is not particularly limited, and it is possible to obtain a tear straight-line cut property when tearing in the longitudinal direction, but it is preferably 30 °, more preferably 28 °. More preferably, it is 25 °.

The lower limit of the impact strength of the biaxially stretched PBT film is preferably 0.05 J / μm. If it is less than the above, the strength of the packaging bag may be insufficient.
The upper limit of the impact strength of the biaxially stretched PBT film layer is preferably 0.2 J / μm. If it exceeds the above, the effect of improvement may be saturated.

The upper limit of the haze per thickness of the biaxially stretched PBT film is preferably 0.66% / μm, more preferably 0.60% / μm, and even more preferably 0.53% / μm.
If it exceeds the above, the quality of the printed characters and images may be impaired when the biaxially stretched PBT film is printed.

The lower limit of the heat shrinkage rate after heating at 150 ° C. for 15 minutes in the longitudinal direction and the width direction of the biaxially stretched PBT film is preferably −1.0%. If it is less than the above, the effect of improvement is saturated and it may become mechanically brittle.

The upper limit of the heat shrinkage rate after heating at 150 ° C. for 15 minutes in the longitudinal direction and the width direction of the biaxially stretched PBT film is preferably 4.0%, more preferably 3.0%. If it exceeds the above, pitch deviation may occur due to dimensional changes during processing such as printing. Further, in general, the heat shrinkage rate of the film is adjusted by the processing temperature in the heat fixing process in the width direction and the relaxation rate in the width direction.

The biaxially stretched PBT film can be imparted with excellent gas barrier properties by forming a laminated film having an inorganic thin film layer on at least one side thereof.
As the inorganic thin film layer laminated on the biaxially stretched PBT film, a thin film made of a metal or an inorganic oxide is preferably used.
The material for forming the inorganic thin film layer is not particularly limited as long as it can be made into a thin film, but from the viewpoint of gas barrier properties, inorganic oxidation such as silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide. Things are preferred. In particular, a composite oxide of silicon oxide and aluminum oxide is preferable from the viewpoint of achieving both flexibility and denseness of the thin film layer.
In this composite oxide, the mixing ratio of silicon oxide and aluminum oxide is preferably in the range of 20 to 70% for Al in terms of the mass ratio of the metal content. If the Al concentration is less than 20%, the water vapor barrier property may be lowered. On the other hand, if it exceeds 70%, the inorganic thin film layer tends to be hard, and the film may be destroyed during secondary processing such as printing or laminating, and the barrier property may be deteriorated. The silicon oxide referred to here is various silicon oxides such as SiO and SiO ₂ or a mixture thereof, and the aluminum oxide is various aluminum oxides such as AlO and Al ₂ O ₃ or a mixture thereof.

The film thickness of the inorganic thin film layer is usually 1 to 800 nm, preferably 5 to 500 nm. If 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 the thickness exceeds 800 nm, the corresponding improvement effect of the gas barrier property can be obtained. However, it is disadvantageous in terms of bending resistance and manufacturing cost.

The method for forming the inorganic thin film layer is not particularly limited, and is known, for example, a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical vapor deposition method (CVD method). The method may be adopted as appropriate. Hereinafter, a typical method for forming an inorganic thin film layer will be described using a silicon oxide / aluminum oxide thin film as an example. For example, when the vacuum vapor deposition method is adopted, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al is preferably used as the vapor deposition raw material. Particles are usually used as these vapor deposition raw materials, but at that time, it is desirable that the size of each particle is such that the pressure at the time of vapor deposition does not change, and the preferable 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. Further, it is also possible to introduce oxygen, nitrogen, hydrogen, argon, carbon dioxide gas, water vapor or the like as the reaction gas, or to adopt reactive vapor deposition using means such as ozone addition and ion assist. Further, the film forming conditions can be arbitrarily changed, such as applying a bias to the film to be vapor-deposited (laminated film to be subjected to vapor deposition) or heating or cooling the film to be vapor-deposited. Such a vapor deposition material, a reaction gas, a bias of the vapor-film-deposited body, heating / cooling, and the like can be similarly changed when the sputtering method or the CVD method is adopted.

An adhesion layer can be provided between the biaxially stretched PBT film layer and the inorganic thin film layer in order to secure the gas barrier property and the laminating strength after the retort treatment.
The adhesive layer provided between the biaxially stretched PBT film layer and the inorganic thin film layer includes urethane-based, polyester-based, acrylic, titanium-based, isocyanate-based, imine-based, polybutadiene-based resins, epoxy-based, and isocyanate-based resins. Examples thereof include those to which a curing agent such as a system or a melamine system is added. Examples of the solvent (solvent) include 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; ethylene. Examples thereof include polyhydric alcohol derivatives such as glycol monomethyl ether. The resin composition used for these adhesion layers preferably contains a silane coupling agent having at least one organic functional group. Examples of the organic functional group include an alkoxy group, an amino group, an epoxy group, an isocyanate group and the like. By adding the silane coupling agent, the laminating strength after the retort treatment is further improved.

Among the resin compositions used for the adhesion layer, it is preferable to use a mixture of a resin containing an oxazoline group, an acrylic resin and a urethane resin. The oxazoline group has a high affinity with the inorganic thin film, and can react with the oxygen-deficient portion of the inorganic oxide generated during the formation of the inorganic thin film layer and the metal hydroxide, and exhibits strong adhesion to the inorganic thin film layer. .. Further, the unreacted oxazoline group present in the coating layer can react with the carboxylic acid terminal generated by the hydrolysis of the biaxially stretched PBT film layer and the coating layer to form a crosslink.

The method for forming the adhesion layer is not particularly limited, and a conventionally known method such as a coating method can be adopted. Among the coating methods, the offline coating method and the inline coating method can be mentioned as preferable methods. For example, in the case of the in-line coating method performed in the process of manufacturing a biaxially stretched PBT film, the conditions of drying and heat treatment at the time of coating are transferred to the stretching process in the width direction immediately after coating, although it depends on the coating thickness and the conditions of the apparatus. It is preferable to dry in the preheating zone or the stretching zone in the stretching step, and in such a case, the temperature is usually preferably about 50 to 250 ° C.

(Aluminum foil layer)
As the material of the aluminum foil, a general soft aluminum foil can be used, but it is preferable to use an aluminum foil containing iron for the purpose of further imparting pinhole resistance and ductility during molding. The iron content is preferably 0.1 to 9.0% by mass, more preferably 0.5 to 2.0% by mass in 100% by mass of the aluminum foil. If the lower limit of the iron content is less than the above value, pinhole resistance and ductility cannot be sufficiently imparted, while if the upper limit is more than the above value, flexibility is impaired. The thickness of the aluminum foil is preferably 5 to 12 μm, more preferably 7 to 9 μm in consideration of barrier properties, pinhole resistance, and processability.

It is desirable to pretreat the aluminum foil from the viewpoint of adhesion and acid resistance. As the pretreatment, degreasing, acid cleaning, alkaline cleaning and the like can be performed. The pretreatment can be broadly classified into a wet type and a dry type. In the wet type, acid cleaning and alkaline cleaning can be mentioned. Examples of the acid used for acid cleaning include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid, and these acids may be used alone or in combination of two or more. Further, from the viewpoint of improving the etching effect of the aluminum foil, various metal salts serving as a supply source such as Fe ions and Ce ions may be blended as needed. Examples of the alkali used for alkaline cleaning include a strong etching type such as sodium hydroxide. Further, a weak alkaline type or a material containing a surfactant may be used. These degreasings are performed by a dipping method or a spraying method.
As one of the dry type methods, there is a method of performing degreasing treatment in the step of annealing aluminum.
In addition to the above, examples of the degreasing treatment include frame treatment and corona treatment. Further, there is also a degreasing treatment in which pollutants are oxidatively decomposed and removed by active oxygen generated by irradiating ultraviolet rays having a specific wavelength.

(Adhesive layer)
The adhesive layer provided between the biaxially stretched PBT film layer and the polyolefin-based resin film, between the biaxially stretched PBT film and the aluminum foil, and between the aluminum foil and the polyolefin-based resin film is urethane-based or polyester. Examples thereof include those obtained by adding an epoxy-based, isocyanate-based, melamine-based or the like curing agent to a resin such as an acrylic-based, acrylic-based, titanium-based, isocyanate-based, imine-based, or polybutadiene-based resin. Examples of the solvent (solvent) include 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; ethylene. Examples thereof include polyhydric alcohol derivatives such as glycol monomethyl ether. As the adhesive layer, a polyurethane-based adhesive containing a polyester polyol, a polyether polyol, or an acrylic polyol as a main component is preferable. The thickness of the adhesive layer 15 is preferably 1 to 10 μm, more preferably 3 to 7 μm.

(Structure and manufacturing method of laminated film)
The laminated film of the present invention uses the polyolefin-based resin film as a sealant and contains at least a biaxially stretched PBT film as a base material. Further, as a known technique, those base films coated or vapor-deposited for the purpose of imparting adhesiveness and barrier properties may be used, or aluminum foil may be further laminated.
Specifically, for example, biaxially stretched PBT film / aluminum foil / sealant, biaxially stretched PBT film / vapor deposition layer / sealant, biaxially stretched PBT film / easy adhesive coat layer / vapor deposition layer / sealant, biaxially stretched PBT film / The composition such as a print layer / sealant can be mentioned.
As a laminating method, known methods such as a dry laminating method and an extrusion laminating method can be used, and any laminating method can be used to produce a laminated film having good straight-line cutting properties.

(Characteristics of laminated film)
<Tear strength of laminated film>
The upper limit of the tear strength in the longitudinal direction of the laminated film of the present invention is not particularly limited, but is preferably 0.4N. If it exceeds this, it may be difficult to tear the laminated film. It is more preferably 0.35N, still more preferably 0.3N. 0.1N is sufficient.

<Straight cutability of laminated film>
The upper limit of the straight-line cutability in the longitudinal direction of the laminated film of the present invention is preferably 5 mm, more preferably 3 mm, still more preferably 2 mm, and particularly preferably 1 mm. If it exceeds the above, the package may cry. 1 mm is sufficient.

<Retort shrinkage rate of laminated film>
The upper limit of the retort shrinkage rate of the laminated film of the present invention is not particularly limited, but is 10%. If this is exceeded, the appearance of the package after retort may be deteriorated. More preferably, it is 7%. The lower limit of the retort shrinkage rate in the longitudinal direction is not particularly limited, but is -1%. If it is less than this, the elongation after retort is large, which may cause bag breakage.

<Heat seal strength of laminated film>
The lower limit of the heat seal strength of the laminated film of the present invention before retort is not particularly limited, but is preferably 30 N / 15 mm, more preferably 35 N / 15 mm. If it is less than the above, the bag resistance may deteriorate. It is preferable that the heat seal strength is maintained at 35 N / 15 mm or more even after the retort treatment at 121 ° C. for 30 minutes. The upper limit of the heat seal strength is not particularly limited, but is preferably 60 N / 15 mm. In order to exceed the above, it is necessary to increase the thickness of the film, which may increase the cost.

<Seal energy of laminated film>
The lower limit of the sealing energy of the laminated film of the present invention is not particularly limited, but is preferably 0.9J / 150mm ² , more preferably 1.0J / 150mm ² , and even more preferably 1.2J / 150mm ² . .. If it is less than the above, the bag resistance may be deteriorated.

<Puncture strength of laminated film>
The lower limit of the puncture strength of the laminated film of the present invention before retort is not particularly limited, but is preferably 12.0 N, more preferably 15.0 N. If it is less than the above, it may become a pinhole when the protrusion comes into contact with the packaging bag. The upper limit of the puncture strength is not particularly limited, but is preferably 45.0N, more preferably 30.0N. If it exceeds the above, the thickness of the laminated film may be too strong and handling may be difficult.

<Loop stiffness of laminated film>
The lower limit of the loop stiffness value (mN / 25 mm) of the laminated film of the present invention is preferably 80, more preferably 90, and most preferably 100.
Here, the loop stiffness refers to the repulsive force of a loop measured in a state where a loop is formed by using a film cut into strips of a predetermined size and the loop is crushed by a predetermined amount in the radial direction, and the rigidity of the film. It is an index showing.
If the loop stiffness of the laminated film is less than the above, it is not possible to secure the independence of the standing pouch even when the content is small, and problems such as crushing during display at the store occur. The higher the loop stiffness value, the higher the rigidity of the film. The method for measuring the loop stiffness will be described later.

(Packaging bag)
The laminated film arranged so as to wrap around the contents is called a packaging bag for the purpose of protecting the contents such as food from dust and gas in the natural world. The packaging bag is manufactured by cutting out the laminated film and adhering the inner surfaces to each other with a heated heat seal bar or ultrasonic waves to form a bag. For example, two rectangular laminated films are laminated so that the sealant side is on the inside. A four-way seal bag with heat-sealed four sides is widely used. It may have a shape other than a rectangle, such as a standing pouch or a pillow wrapping bag, which has folds on the bottom of the bag so that it can stand on its own.
Further, a packaging bag capable of withstanding the heat of heat sterilization with hot water whose boiling point is raised to 100 ° C. or higher by pressurizing or the like is called a packaging bag for retort pouch. Further, a film for the purpose of providing the packaging bag is called a retort film.

(Amount of crying wrapping bag)
The upper limit of the amount of crying of the packaging bag obtained from the laminated film of the present invention is not particularly limited, but is preferably 5 mm, more preferably 4 mm, still more preferably 3 mm, and particularly preferably 2 mm. .. If it exceeds the above, the contents may spill when the package is torn. 1 mm is sufficient.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. The characteristics obtained in each example were measured and evaluated by the following methods. At the time of evaluation, the longitudinal direction of the film-forming film was defined as the longitudinal direction (also referred to as MD direction), and the width direction was defined as the width direction (also referred to as TD direction).

[Measuring method of biaxially stretched PBT film]
The biaxially stretched PBT film was evaluated by the following measurement method.
(1) Thickness of biaxially stretched PBT film Measured using a dial gauge in accordance with JIS K7130-1999 A method.

(2) Heat shrinkage rate of biaxially stretched PBT film The heat shrinkage rate of the polyester film is the dimensional change test method described in JIS-C-2151-2006.21 except that the test temperature is 150 ° C. and the heating time is 15 minutes. It was measured.
The test piece was used according to the description in 21.1 (a).

(3) Impact Strength of Biaxially Stretched PBT Film The strength of the film against impact punching in an atmosphere of 23 ° C. was measured using an impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. according to JIS K7160-1996. The impact spherical surface used was one with a diameter of 1/2 inch. The unit is J / μm.

(4) Puncture strength of biaxially stretched PBT film "2. Strength test method" in "Standards for Foods, Additives, etc. 3: Instruments and Containers and Packaging" (Notification No. 20 of the Ministry of Health and Welfare, 1982) in the Food Sanitation Law. Was measured in accordance with. A needle with a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength at which the needle penetrated the film was measured and used as the piercing strength. The measurement is performed at room temperature (23 ° C.), and the unit is N.

[Measuring method of sealant film]
Hereinafter, a method for measuring the sealant film will be described.
(1) Resin density JIS K7112: The density was evaluated according to the 1999 D method (density tube).
The measurement was performed at N = 3, and the average value was calculated.

(2) Melt flow rate (MFR)
The measurement was carried out at 230 ° C. and a load of 2.16 kg based on JISK-7210-1. The measurement was performed at N = 3, and the average value was calculated.

(4) Puncture strength Sealant film or laminated film is used in "2. Strength, etc." of "Standards for Foods, Additives, etc. 3: Instruments and Containers and Packaging" (Notification No. 20 of the Ministry of Health and Welfare, 1982) in the Food Sanitation Law. The puncture strength was measured at 23 ° C. according to the "Test Method". A needle having a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm / min, and the strength when the needle penetrated the film was measured. The obtained measured value was divided by the thickness of the film to calculate the puncture strength [N / μm] per 1 μm of the film. The measurement was performed at N = 3, and the average value was calculated.
The same measurement was performed after the laminated film was retort-treated with hot water at 121 ° C. for 30 minutes.

(5) Tear strength The tear strength was measured according to JIS K7120-1: 1998. The sealant film before laminating and the laminated film were each evaluated. Measurements were made at N = 3 in the longitudinal direction and the width direction, respectively, and the average value was calculated.

(6) Yield stress The sealant film was cut into strips having a width of 15 mm. A tensile test was conducted with a universal material testing machine 5965 manufactured by Instron Instruments, with a distance between marked lines of 20 mm and a crosshead speed of 1000 mm / min. The tensile stress at the time when the slope in the stress-strain curve first became 0 was yield stressed. When the draw ratio is high, the point with a slope of 0, which is generally called the upper yield point, disappears. In this case as well, the point where the slope first becomes 0 near the fracture point is defined as the yield stress. Measurements were made at each N = 3 in the longitudinal direction and the width direction, and the average value of each was calculated.

(7) Heat shrinkage rate A sealant film was cut out in 120 mm square. Marked lines were drawn so that the intervals were 100 mm in each of the longitudinal direction (flow direction of film forming) and the width direction (direction perpendicular to the longitudinal direction). The sample was hung in an oven kept at 120 ° C. and heat-treated for 30 minutes. The distance between the marked lines was measured, and the heat shrinkage was calculated according to the following formula. The measurement was performed at N = 3, and the average value was calculated.
Heat shrinkage rate = (mark line length before heat treatment-mark line length after heat treatment) / mark line length before heat treatment x 100 (%)

[Measurement method of laminated film]
Hereinafter, the evaluation method and the measurement method of the laminated film will be shown.
(1) Straight cut property The straight cut property indicates the ability to tear a sealant film or a laminated film straight in the longitudinal direction when it is torn. The measurement was performed by the following method. In this example, since it was stretched in the longitudinal direction, the straight-line cutability was evaluated only in the longitudinal direction.
The laminated film was cut into strips having a length of 150 mm and a width of 60 mm, and a notch of 30 mm was made along the length from the center of the short side. The sample was torn according to JIS K7128-1: 1998. The distance traveled in the width direction was measured at the time of tearing 120 mm in the longitudinal direction, not including the notch of 30 mm, and the absolute value was recorded. Both the case where the right side section was sandwiched between the upper grippers and the case where the left side section was sandwiched between the upper grippers were measured at each N = 3, and the average value of each was calculated. Of the measurement results on the right and left sides, the one with the larger numerical value was adopted.

(2) Retort shrinkage rate The laminated film was cut out in 120 mm square. Marked lines were drawn so that the intervals were 100 mm in each of the longitudinal direction and the width direction. The retort treatment was performed with hot water at 121 ° C. for 30 minutes. The distance between the marked lines was measured, and the retort shrinkage rate was measured according to the following formula. Measurement was performed at each N = 3, and the average value was calculated.
Retort shrinkage rate = (mark line length before treatment-mark line length after treatment) / mark line length before treatment x 100 (%)

(3) Heat seal strength The heat seal conditions and strength measurement conditions are as follows. That is, the sealant film sides of the laminated films obtained in Examples and Comparative Examples are overlapped with each other, heat-sealed at a pressure of 0.2 MPa for 1 second at a seal bar width of 10 mm and a heat-sealing temperature of 220 ° C., and then allowed to cool. did. Test pieces of 80 mm in the longitudinal direction and 15 mm in the width direction were cut from the heat-sealed film at each temperature, and the peel strength of each test piece was measured when the heat-sealed portion was peeled off at a crosshead speed of 200 mm / min. As the testing machine, a universal material testing machine 5965 manufactured by Instron Instruments was used. The measurement was performed at each N = 3 times, and the average value was calculated. It was measured before and after the retort treatment with hot water at 121 ° C. for 30 minutes.

(4) Heat seal start temperature The heat seal start temperature is an item related to productivity when continuous production with a bag making machine is assumed. Good bag-making suitability means that sufficient sealing performance can be obtained in a temperature range in which the biaxially stretched film of the base material does not shrink or break. The heat seal start temperature was evaluated as follows.
In the measurement of the heat seal strength, the temperature of the heat seal bar was changed at a pitch of 5 ° C., and the heat seal strength was measured at N = 3, respectively. It was calculated by weighted averaging the heat seal strength at the temperature immediately before the heat seal strength exceeded 30 N and the heat seal strength at the temperature immediately after the heat seal strength exceeded 30 N.

(5) Seal energy When measuring the heat seal strength of the laminated film before retort, the graph area from the start of peeling to the break is analyzed for Instron in the measurement chart with the horizontal axis as the peeling distance and the vertical axis as the peeling strength. The seal energy was calculated by analysis with soft blue hill3. Measurement was performed at each N = 3, and the average value was calculated.

(6) Amount of crying The laminated films were heat-sealed with the sealant films facing each other to prepare a four-way seal bag having an inner dimension of 120 mm in the longitudinal direction and 170 mm in the width direction. A notch was made at the end of the 4-way seal bag and torn by hand in the longitudinal direction. The cut was advanced to the opposite end, and the deviation of the tear line of the film on the front side and the back side of the bag was measured. The average value measured at each N = 3 was calculated for both the direction in which the right hand side was in front and the direction in which the left hand side was in front, and the larger measured value was adopted.
(7) Loop Stiffness of Laminated Film As a sample for measuring loop stiffness, a strip-shaped film having a width of 25.4 mm and a width of 110 mm was cut out from the laminated laminated film prepared in Examples and Comparative Examples. At this time, the longitudinal direction of the strip-shaped film coincided with the direction of the measurement target. The cut strip-shaped film was set in a loop stiffness tester manufactured by Toyo Seiki Co., Ltd., and the repulsive force was measured. The measurement frequency was 50 Hz. The value of the repulsive force (mN) obtained by the measurement was taken as the loop stiffness.
(8) Independence of packaging bag <Making packaging bag>
Using the laminated laminates shown in Examples and Comparative Examples described later, a standing pouch having the shape shown in FIG. 1 was produced.
The external dimensions of the pouch body were 160 mm in width, 230 mm in length, and 90 mm in folding at the bottom.
The heat-sealed part at the bottom has a curved part with a downward warp at the top like a normal standing pouch, the lower side of the curved part is heat-sealed, and the bottom of the curved part is a heat with a length of 5 mm to the lower end of the pouch. The bottom portion was formed by heat-sealing with a pattern having a sealing portion, and the body portion was formed by heat-sealing both the left and right sides of the pouch with a heat-sealing width of 5 mm.
The unsealed upper part was opened as an opening for filling the contents.
Then, 250 ml of water was filled as the content from each unsealed upper opening, and then the opening was degassed and sealed to seal the pouch to prepare a standing pouch for independence evaluation.
The temperature at the time of heat sealing when producing the standing pouch was 200 ° C. × 1 second in the case of the unstretched polypropylene film.
<Evaluation of independence>
The evaluation criteria for independence and moldability are as follows.
・ Independence ○: The bottom of the standing pouch did not bend, and the independence was maintained.
Δ: Although the bottom of the standing pouch was slightly deformed, the self-standing state was maintained.
×: The bottom of the standing pouch was bent and could not maintain its independence.

The details of the raw material resin and the coating liquid used in this example and the comparative example are described below.
1) PBT resin: As the PBT resin used in the film production of the substrate layer films A1 to A3 described later, 1100-211XG (CHANG CHUN PLASTICS CO., LTD., Intrinsic viscosity 1.28 dl / g) was used.
2) PET resin: The PET resin used in the production of the base material layer films A1 to A3 described later was a PET resin manufactured by Toyobo Co., Ltd. and having an intrinsic viscosity of 0.62 dl / g.

3) Resin having an oxazoline group for an easy-adhesion layer (A): As a resin having an oxazoline group, a commercially available water-soluble oxazoline group-containing acrylate (“Epocross (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.

4) Acrylic resin (B) for easy-adhesive layer: As an acrylic resin, a 25% by mass emulsion of a commercially available acrylic acid ester copolymer (“Mobile (registered trademark) 7980” manufactured by Nichigo Vinyl Co., Ltd.) was prepared. The acid value (theoretical value) of this acrylic resin (B) was 4 mgKOH / g.

5) Urethane resin (C) for easy-adhesion layer: As a urethane resin, a commercially available polyester urethane resin dispersion (“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. The ratio of aromatic diisocyanate or aromatic aliphatic diisocyanate to the total polyisocyanate component measured by 1H-NMR was 55 mol%.

6) Urethane resin (D) for the protective layer ;: As the urethane resin, a commercially available dispersion of a urethane resin containing a metaxylylene group (“Takelac (registered trademark) WPB341” 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 130 ° C. The ratio of aromatic diisocyanate or aromatic aliphatic diisocyanate to the total polyisocyanate component measured by ¹ H-NMR was 85 mol%.

7) Coating liquid 1 (coat 1) used for the easy-adhesion layer
Each material was mixed at the following blending ratio to prepare a coating liquid (resin composition for easy adhesive layer).
Water 54.40% by mass
Isopropanol 25.00% by mass
Oxazoline group-containing resin (A) 15.00% by mass
Acrylic resin (B) 3.60% by mass
Urethane resin (C) 2.00% by mass

8) Coating liquid 2 (coat 2) used for the protective layer
The following coating agents were mixed to prepare a coating liquid 2. Here, the mass ratio of the urethane resin (E) in terms of solid content is as shown in.
Water 60.00% by mass
Isopropanol 30.00% by mass
Urethane resin (D) 10.00% by mass

(Example 1)
(Preparation of biaxially stretched PBT film)
As PBT resin 1, 1100-211XG (CHANGE CHUN PLASTICS CO., L width., Intrinsic viscosity 1.28 dl / g) was used.
Using a uniaxial extruder, 80 parts by mass of PBT resin and 20 parts by mass of PET resin having an intrinsic viscosity of 0.62 dl / g consisting of terephthalic acid // ethylene glycol = 100 // 100 (mol%), averaged as inert particles. After melting a mixture of porous silica particles having a particle size of 2.4 μm so as to have a silica concentration of 1600 ppm, a melt line was introduced into a 12-element static mixer. As a result, the melt of PBT resin was divided and laminated to obtain a multilayer melt made of the same raw material. It was cast from a T-die at 265 ° C. and adhered to a cooling roll at 15 ° C. by an electrostatic adhesion method to obtain an unstretched sheet.
Then, it was rolled 3.0 times in the longitudinal direction at 70 ° C., then passed through a tenter and stretched 4.0 times in the lateral direction at 90 ° C., and was subjected to tension heat treatment at 200 ° C. for 3 seconds and 1% for 1 second.
After the relaxation treatment of the above, the grips at both ends were cut and removed by 10% to obtain a biaxially stretched PBT film having a thickness of 15 μm.

(Preparation of sealant film)
MFR 3.0 g / 10 min propylene-ethylene block copolymer at resin density 891 kg / m ³ , 230 ° C, 2.16 kg (WFS5293-22 manufactured by Sumitomo Chemical Co., Ltd., propylene content 93.5% by mass) 94% by mass On the other hand, an ethylene-propylene copolymer elastomer resin (manufactured by Mitsui Chemicals Co., Ltd., Toughmer P0480, propylene content: 27% by mass) at an MFR of 1.8 g / 10 min at a resin density of 870 kg / m ³ , 230 ° C. and 2.16 kg was 6 Mass% mixed.

(Melting extrusion)
A 3-stage single-screw extruder with a screw diameter of 90 mm for mixed polyolefin resin, with a width of 800 mm and two stages of preland, and the shape of the stepped portion is curved so that the flow of the molten resin becomes uniform. It was introduced into a T-slot type die designed so that the flow was uniform, and the outlet temperature of the die was extruded at 230 ° C.

(cooling)
The molten resin sheet coming out of the die was cooled with a cooling roll at 21 ° C. to obtain an unstretched polyolefin resin film having a layer thickness of 270 (μm). When cooling with the cooling roll, fix both ends of the film on the cooling roll with an air nozzle, press the entire width of the molten resin sheet against the cooling roll with an air knife, and at the same time operate a vacuum chamber between the molten resin sheet and the cooling roll. Prevented air from getting into the air. The air nozzles were installed in series at both ends in the film traveling direction. The area around the die was surrounded by a sheet to prevent the molten resin sheet from being exposed to wind.

(Preheat)
The unstretched sheet was guided to a group of heated rolls, and the sheet was preheated by bringing the sheet into contact with the roll. The temperature of the preheating roll was 105 ° C. Both sides of the film were preheated using multiple rolls.
(Stretching)
The unstretched sheet was guided to a roll stretching machine and stretched 4.0 times in the longitudinal direction due to the difference in roll speed to have a thickness of 60 μm. The temperature of the stretched roll was 105 ° C.

(Annealing process)
Heat treatment was performed at 130 ° C. using an annealing roll. Both sides of the film were heat treated using multiple rolls.
(Corona processing)
One side (laminated side) of the film was subjected to corona treatment.

(Winding)
The film formation speed was 20 m / min. The ears of the film-formed film were trimmed, rolled, and wound.

(Preparation of laminated film)
The obtained biaxially stretched PBT film (thickness 15 μm, orientation angle is 30 ° with respect to the longitudinal direction) and a polyolefin resin film are combined with an ester-based dry laminating adhesive (TM569, manufactured by Toyo Morton Co., Ltd.) in an amount of 33.6 parts by mass. An ester-based adhesive obtained by mixing 4.0 parts by mass of (CAT10L, manufactured by Toyo Morton Co., Ltd.) and 62.4 parts by mass of ethyl acetate was used as a curing agent, and the amount of the adhesive applied was 3.0 g. It was dry-laminated to a ratio of / m ² . The laminated laminated film was kept at 40 ° C. and aged for 3 days to obtain a laminated film.

(Example 2)
A biaxially stretched PBT film having a thickness of 15 μm was obtained in the same manner as in Example 1 described above.
In the film forming step of the biaxially stretched film of the base material layer film, the resin composition for the easy adhesive layer (coating liquid 1) was applied by the fountain bar coating method after stretching in the MD direction. Then, it was guided to a tenter while being dried, stretched in the TD direction under the above-mentioned film forming conditions, heat-treated and relaxed to obtain a laminated film A2 in which an easy-adhesive layer was formed on one side of a PBT film having a thickness of 20 μm.
<Formation of composite oxide (SiO ₂ / Al ₂ O ₃ ) inorganic thin film layer M1 of silicon dioxide and aluminum oxide>
As the inorganic thin film layer M1, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the base films A-1 to A-3 of the examples by an electron beam vapor deposition method. As the vapor deposition source, particulate SiO ₂ (purity 99.9%) and A1 ₂ O ₃ (purity 99.9%) having a purity of about 3 mm to 5 mm were used. The film thickness of the inorganic thin film layer (SiO ₂ / A1 ₂ O ₃ composite oxide layer) in the film (inorganic thin film layer / film containing an easily adhesive layer) thus obtained was 13 nm. The composition of this composite oxide layer was SiO ₂ / A1 ₂ O ₃ (mass ratio) = 60/40.

<Formation of aluminum oxide (Al ₂ O ₃ ) inorganic thin film layer M2>
As the inorganic thin film layer M2, aluminum oxide was vapor-deposited on the base film. The method of depositing aluminum oxide on a base film 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 the film. At this time, the pressure of the continuous vacuum deposition machine is reduced to 10 ^-4 Torr or less, metallic aluminum with a purity of 99.99% is loaded into an alumina crucible from the bottom of the cooling drum, and the metallic aluminum is heated and evaporated into the steam. Oxygen was supplied and deposited on the film while undergoing an oxidation reaction to form an aluminum oxide film having a thickness of 30 nm.
<Formation of protective layer>
The coating liquid 2 was applied by the wire bar coating method on the inorganic thin film layer formed on the base material layer film, and dried at 200 ° C. for 15 seconds to obtain a protective layer. The coating amount after drying was 0.190 g / m ² (Dry).

(Preparation of sealant film)
A sealant film was produced in the same manner as in Example 1 described above.

(Preparation of laminated film)
The biaxially stretched PBT film and the sealant film obtained by laminating the easy-adhesive layer, the inorganic thin film layer and the protective layer obtained above were dry-laminated by the same method as in Example 1 described above to obtain a laminated laminated film. ..

(Example 3)
In the manufacturing process of the biaxially stretched PBT film of Example 1 described above, the thickness of the biaxially stretched PBT film is 20 μm and the thickness is 60 μm in the same manner as in Example 1 except that the discharge amount of the resin is adjusted to the target thickness. Obtained a sealant film.
On the biaxially stretched PBT film obtained above, aluminum foil (8079 material, thickness 7 μm) is applied to a urethane-based two-component curable adhesive (Mitsui Chemicals, Inc. "Takelac (registered trademark) A525S" and "Takenate (registered)". A50 ”was mixed in a ratio of 13.5: 1 (mass ratio)) to dry-laminate to prepare a biaxially stretched PBT film / aluminum foil laminate.
Next, using the same adhesive as above, the sealant film obtained by the same method as in Example 1 was attached to the aluminum foil side of the biaxially stretched PBT film / aluminum foil laminate obtained above, and 40 The laminated film of Example 3 was obtained by aging at ° C. for 4 days.

(Example 4)
In Example 1, the mixing ratio of the propylene-ethylene block copolymer (WFS5283-22 manufactured by Sumitomo Chemical Co., Ltd.) and the ethylene-propylene copolymer copolymer (Toughmer P0480 manufactured by Mitsui Chemicals Co., Ltd.) was set to 96% by mass of the propylene-ethylene block copolymer. A laminated film was obtained by the same method except that the ethylene-propylene copolymer elastomer (manufactured by Mitsui Chemicals, Toughmer P0480) was adjusted to 4% by mass.

(Example 5)
In Example 1, the mixing ratio of the propylene-ethylene block copolymer (WFS5293-22 manufactured by Sumitomo Chemical Co., Ltd.) and the ethylene-propylene copolymer elastomer was 90% by mass of the propylene-ethylene block copolymer, and the ethylene-propylene copolymer elastomer (WFS5293-22). A laminated film was obtained by the same method except that Tuffmer P0480) manufactured by Mitsui Kagaku Co., Ltd. was set to 10% by mass.

(Example 6)
In Example 1, the mixing ratio of the resin was 64% by mass of the propylene-ethylene block copolymer, 6% by mass of the ethylene-propylene copolymer elastomer (Toughmer P0480, manufactured by Mitsui Chemicals, Inc.), and the density was 890 kg / m ³ MFR 1.5 g / 10. Minutes (230 ° C, 2.16 kg measurement), propylene-ethylene random copolymer (S131 manufactured by Sumitomo Chemical Co., Ltd.) with a melting point of 132 ° C, 30% by mass, and the same method except that the annealing roll temperature was 120 ° C. A laminated film was obtained in.

(Example 7)
In Example 6, a laminated film was obtained in the same manner except that the stretching ratio in the longitudinal direction was 4.5 times and the temperature of the annealing roll was 130 ° C.

(Example 8)
In Example 6, a laminated film was obtained in the same manner except that the temperature of the annealing roll was set to 130 ° C.

(Example 9)
In Example 7, the mixing ratio of the resin was 74% by mass of the propylene-ethylene block copolymer (WFS5293-22 manufactured by Sumitomo Chemical Co., Ltd.) and 6% by mass of the ethylene-propylene copolymer elastomer (Toughmer P0480 manufactured by Mitsui Chemicals Co., Ltd.). A laminated film was obtained by the same method except that the propylene-ethylene random copolymer (S131 manufactured by Sumitomo Chemical Co., Ltd.) was 20% by mass.

(Comparative Example 1)
In the manufacturing process of the sealant film of Example 4, the stretching roll speed in the longitudinal direction was increased to 1.0 times (unstretched) by changing the cooling roll speed of casting without changing the stretching roll speed, and the annealing treatment was not performed. A laminated film was obtained in the same manner except for the above.

(Comparative Example 2)
A biaxially stretched PBT film having a thickness of 20 μm was obtained by the same method as in Example 3 described above.
Next, a sealant film having a thickness of 60 μm was obtained by the same method as in Comparative Example 1 described above.
On the biaxially stretched PBT film obtained above, aluminum foil (8079 material, thickness 7 μm) is applied to a urethane-based two-component curable adhesive (Mitsui Chemicals, Inc. "Takelac (registered trademark) A525S" and "Takenate (registered)". A50 ”was mixed in a ratio of 13.5: 1 (mass ratio)) to dry-laminate to prepare a biaxially stretched PBT film / aluminum foil laminate.
Next, using the same adhesive as above, the sealant film obtained by the same method as in Example 1 was attached to the aluminum foil side of the biaxially stretched PBT film / aluminum foil laminate obtained above, and 40 By aging at ° C. for 4 days, a laminated film of Comparative Example was obtained.

Tables 1 and 2 show the evaluation results of the films and laminated films obtained in the above Examples and Comparative Examples.

As shown in Tables 1 and 2, the laminated films of Examples 1 to 9 obtained by the present invention are not only excellent in straight-line cutability, but also have a piercing strength of the laminated film as compared with the case of using a conventional sealant. It was confirmed that it is possible to improve the feeling of waist and waist.
On the other hand, in Comparative Example 1, since the straight-line cut property is inferior, the crying part is large, and since the sealant film described in the present invention is not used, the piercing strength and the feeling of waist as a laminated film are low, and the conventional method. It is disadvantageous when an attempt is made to reduce the volume of a single layer of a biaxially stretched PBT film in an application in which PET is used by laminating ONy.
Further, also in Comparative Example 2, although the waist feeling of the laminated film is increased by the presence of the aluminum foil, the piercing strength and the straight-line cut property are not improved because the sealant film of the present invention is not used.

In Tables 1 and 2, when the evaluation result is "unmeasurable", it means that the film or the laminated film was torn in the longitudinal direction during the characteristic evaluation and the measured value could not be obtained. Further, the longitudinal direction is abbreviated as MD and the width direction is abbreviated as TD.

According to the present invention, it is possible to reduce the amount of packaging material, it is excellent in rupture resistance, it is excellent in straight-line cutability at the time of opening, and it is possible to secure sufficient independence even when it is used as a standing pouch. , A laminated film suitable for liquid packaging of retort foods and the like can be obtained.
According to the present invention, a packaging bag such as a standing pouch, which has been conventionally made of a laminated film of a sealant film using a base film in which OPT and ONy are laminated, is laminated with one layer of a base film made of PBT and a sealant film. Since it can be produced from a film, it can be widely applied as a material for food packaging.

1: Storage part 2: Side seal part 3: Top seal part 4: Bottom 5: Length 6: Width 7: Bottom fold

Claims (8)

A biaxially stretched film substrate made of a polyester resin composition containing at least (1) a polybutylene terephthalate resin in an amount of 60% by mass or more, and (2) a heat shrinkage in the longitudinal direction of 3% or more and 20% or less in the width direction. A laminated film having a sealant film having a heat shrinkage rate of 1% or less and a breakdown stress in the longitudinal direction of 150 MPa or more and 250 MPa or less.
The sealant film contains 40% by mass or more and 97% by mass or less of the propylene-ethylene block copolymer, 3% by mass or more and 10% by mass or less of the ethylene-propylene copolymerized elastomer, and 0% by mass of the ethylene-α-olefin random copolymer. A uniaxially stretched film made of a polyolefin resin composition containing 50% by mass or less.
A laminated film characterized by satisfying the following (a) to (c).
(A) The straight-line cutability of the laminated film in the longitudinal direction is 5 mm or less.
(B) The piercing strength of the laminated film is 15 N or more.
(C) The value (A value) obtained by dividing the average value of the loop stiffness in the longitudinal direction and the width direction of the laminated film by the cube of the thickness of the laminated film is 2.5 × 10-4 or more. The laminated film according to claim 1 , wherein the biaxially stretched film base material has an inorganic thin film layer on at least one surface thereof. The laminated film according to claim 2 , wherein the inorganic thin film layer is a layer made of an oxide of silicon oxide and / or aluminum oxide. The laminated film according to claim 2 or 3 , wherein an adhesive layer is provided between the biaxially stretched film base material and the inorganic thin film layer. The laminated film according to any one of claims 2 to 4, wherein the protective layer is provided on the inorganic thin film layer. The laminated film according to claim 1 , wherein an aluminum foil is provided between the biaxially stretched film base material and the sealant film. A packaging bag made of the laminated film according to any one of claims 1 to 6 . The packaging bag according to claim 7 , which is for retort pouch.

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