JP2006150737A - Heat-sealable laminate and package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sealable laminate which has enough heat sealing strength to package a heavy article and good stiffness, can be opened easily owing to its good tearing properties when opened, and is suitable for packaging applications and a package produced by using the laminate. <P>SOLUTION: The multi-layer, heat-sealable laminate is composed of a substrate film and a heat-sealable film. The heat sealing strength of the laminate is at least 8 N/15 mm, the product of tensile moduli of elasticity in the laminate flow direction (MD) and in the direction perpendicular to MD (TD) is 4.0-6.0 (GPa)<SP>2</SP>, and the tear propagation resistance in TD is 120 mN or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sealable laminate and a package, and more specifically, has a heat-seal strength sufficient for packaging heavy objects, has good transparency, and can be suitably used for packaging applications. The present invention relates to a heat-sealable laminate that can be opened without resistance at the time of opening and a package using such a laminate.

Conventionally, as a heat-sealable laminate used for packaging, generally, a stretched polypropylene resin film, a stretched polyethylene terephthalate film or a stretched polyamide film is added to an unstretched polyethylene resin film or a non-stretched polypropylene resin film. Laminated laminates are often used. However, the film laminated in this way has a problem that when the bag is cut in a direction perpendicular to the film flow direction, the film stretches and is difficult to open.
On the other hand, in JP-A-9-48101, a special polyamide film is used for the base film, and the adhesive properties are specified to improve the adhesive force between the base film and the heat-sealable film. A method for improving the cutting property has been proposed. However, in such a method, since the base film and the adhesive are limited, the use is limited and the versatility is inferior. On the other hand, Japanese Patent Laid-Open No. 9-174776 uses a biaxially stretched nylon film as a base film and improves the cut property by laminating a film having a linear ethylene-α-olefin copolymer layer as a sealant film. However, while the linear ethylene-α-olefin copolymer is excellent in impact resistance, there is no feeling in the back of the film, so when handling products packaged using a heat-sealable laminate, it is inferior in handleability. It was a thing.

  The present invention solves the problems of the above conventional heat-sealable laminate, has sufficient heat-seal strength to wrap heavy objects, has a good waist feeling, and has good tearability when opened. An object of the present invention is to provide a heat-sealable laminate that can be easily opened and is suitable for packaging applications, and a package using such a laminate.

In order to achieve the above object, the packaging film of the present invention is a laminate of at least two layers composed of a base film and a heat-sealable film, and has a heat seal strength of 8 N / 15 mm or more. The product of the tensile modulus of elasticity in the flow direction (MD) and the direction (TD) perpendicular to the flow direction is 4.0 to 6.0 (GPa) ² and is perpendicular to the flow direction (MD) of the laminate. The tear propagation resistance in the direction (TD) is 120 mN or less.

  The heat-sealable laminate of the present invention composed of the above-mentioned structure has sufficient heat-seal strength to wrap heavy items, has good bag-making processability, and improves handling and unpackability after product packaging. Can be made.

  In this case, it is preferable that the base film and the heat-sealable film are stretched.

  In this case, the heat-sealable film is composed of three or more layers, a base material layer made of a crystalline polypropylene resin, a heat fusion layer having a melting point of 150 ° C. or less, a base material layer, and a heat fusion layer. It is preferable that the film has at least an intermediate layer therebetween.

Furthermore, in this case, it is preferable that the intermediate layer of the heat-sealable film contains an α-olefin copolymer having a cold xylene-soluble content of 3% by weight or less.
Furthermore, in this case, the package using the heat-sealable laminate can be suitably used for packaging heavy items.

  According to the heat-sealable laminate of the present invention, it has sufficient heat-sealing strength to wrap heavy objects, has a good waist feeling, has no resistance at the time of opening, and can be easily opened from a cut opening. It can be used as a film suitable for packaging applications.

  According to the packaging body of the present invention, it is possible to obtain a packaging body that has sufficient heat seal strength capable of packaging heavy objects, has good waist feeling, is easy to handle, and can be easily opened.

  Hereinafter, embodiments of the heat-sealable laminate and the package of the present invention will be described.

  In the present invention, the substrate film used for the heat-sealable laminate is not particularly limited, but a uniaxially stretched film or a biaxially stretched film is preferably used. In the case of a uniaxially stretched film, a polyolefin is mainly used. In the case of a biaxially stretched film, a biaxially stretched polyester film, a biaxially stretched polypropylene film, a biaxially stretched nylon film, or the like is used. The substrate film only needs to have strength, dimensional stability, and printing and laminating suitability, but considering the film strength and laminating suitability, a biaxially stretched film is desirable.

The heat-sealable film used in the heat-sealable laminate of the present invention uses a base material layer, a heat-sealable layer, and a film having three or more layers in which an intermediate layer is provided between the base material layer and the heat-sealable layer. Is preferred.
The base material layer is preferably made of a crystalline polypropylene resin. The crystalline polypropylene resin used for the base layer of the laminated film of the present invention contains 70% by weight or more of an n-heptane-insoluble isotactic propylene homopolymer or propylene used in ordinary extrusion molding or the like. Any copolymer of polypropylene and another α-olefin may be used.
The insolubility of n-heptane indicates the crystallinity of polypropylene and at the same time indicates safety when used for food packaging. In the present invention, n-heptane insolubility according to Notification No. 20 of the Ministry of Health and Welfare in February 1982 is used. It is a preferred embodiment to use a material that conforms to (the elution amount when extracted at 25 ° C. for 60 minutes is 150 pPm or less [the usage temperature exceeds 100 ° C. is 30 pPm or less]).
The α-olefin as the copolymerization component is preferably an α-olefin having 2 to 8 carbon atoms, such as ethylene, butene-1, pentene-1, hexene-1, 4-methyl-1-pentene. Here, the copolymer includes a random or block copolymer. Moreover, a melt flow rate (MFR) is 0.1-100 g / 10min, Preferably it is 0.5-20 g / 10min, More preferably, the thing of the range of 1.0-10 g / 10min can be illustrated. Furthermore, the crystalline polypropylene resin used here may be a mixture of two or more.

  Further, the resin used for the heat-sealing layer of the heat-sealable film used in the heat-sealable laminate of the present invention is a thermoplastic resin having a melting point of 150 ° C. or less, and ethylene, propylene, butene, pentene, hexene, octene, A random copolymer or block copolymer obtained by polymerizing two or more selected from α-olefin monomers having 2 to 10 carbon atoms, such as decene, is preferable. Can be used.

In particular, the resin constituting the heat-sealing layer preferably contains a propylene-butene copolymer having a high butyne content. Here, the butene content in the propylene-butene copolymer is preferably 20% by mass or more. The upper limit of the butene content is not particularly limited, but if the butene content is too much, the film surface may become sticky, and slipperiness and blocking resistance may be reduced. Good. Examples of the propylene-butene copolymer having a high butene content include “S” manufactured by Sumitomo Chemical Co., Ltd.
PX78J1 "etc. can be illustrated.

The propylene-butene copolymer is preferably blended in an amount of 65% by mass or more in the resin component constituting the heat-sealing layer. More preferably, it is 70% by mass or more, preferably 99% by mass or less, and more preferably 95% by mass or less. When the blending amount of the propylene-butene copolymer is too small, the fusion force at the time of sealing may be low, and it may be difficult to obtain sufficient heat seal energy. Interlaminar strength may decrease.

Furthermore, the melting point of the thermoplastic resin forming the heat-sealing layer is desirably 150 ° C. or less, preferably 60 to 150 ° C. By doing in this way, sufficient heat seal intensity | strength can be given to a heat-sealable laminated body. When the melting point of the thermoplastic resin forming the heat-sealing layer is less than 60 ° C., the heat resistance of the heat seal portion is poor, and when it exceeds 150 ° C., improvement in heat seal strength cannot be expected.
Moreover, MFR is 0.1-100 g / 10min, Preferably it is 0.5-20 g / 10min, More preferably, the thing of the range of 1.0-10 g / 10min can be illustrated.

In addition, the heat-sealable film used in the heat-sealable laminate of the present invention includes a resin comprising a base material layer and a propylene-α-olefin copolymer between the base material layer and the heat-sealing layer. It is preferable to provide an intermediate layer containing The compounding quantity of resin which consists of resin which comprises a base layer and a propylene-alpha-olefin copolymer here is not specifically limited, You may contain the same kind polypropylene resin and another thermoplastic resin. A preferable blending amount of the resin constituting the base layer is 10% to 90% by weight, and if it is less than 10%, there is a tendency to lose elasticity, which is not preferable in terms of handling the product. On the other hand, if it exceeds 90%, the adhesion between the base material layer and the heat-sealing layer becomes insufficient, and the sealing strength may be lowered. Similarly, the blending amount of the resin made of the propylene-α-olefin copolymer is 10% by weight to 90% by weight, and if it is less than 10%, the adhesion between the base material layer and the heat fusion layer becomes insufficient. , The sealing strength may decrease, which is not preferable. On the other hand, if it exceeds 90%, the waist tends to be lost, which is not preferable in handling the product.
The propylene-α-olefin copolymer used here is not particularly limited, but is preferably a propylene-α-olefin copolymer having a cold xylene soluble content (CXS) of 3% by weight or less. . When a propylene-α-olefin copolymer having a cold xylene soluble content (CXS) exceeding 3% by weight is used, it is not preferable because it tends to lose elasticity.

  The α-olefin copolymer is excellent in mechanical strength such as impact strength and tearing properties, low temperature properties, weather resistance, and the like, and by blending such components, excellent properties can be imparted to the laminated film. it can. However, since the α-olefin copolymer has a structure in which different α-olefins are randomly introduced as the second component or the third component in the main α-olefin molecular chain, Is suppressed, and the crystallinity is low as compared with a homopolymer of α-olefin fin such as homopolypropylene, and the blending of the α-olefin copolymer results in lowering the feeling of the back of the film.

The above-mentioned “cold xylene-soluble matter” indicates the amount of amorphous part contained in the α-olefin copolymer, and it is said that “cold xylene-soluble matter is 3% by mass or less” It means an α-olefin copolymer having few crystal parts and high crystallinity.
Here, the cold xylene-soluble component means that 1 g of a sample is completely dissolved in 100 ml of boiling xylene, then cooled to 20 ° C., left for 4 hours, and then separated into a precipitate and a solution. The weight is determined by measuring the weight when the liquid is dried and dried at 70 ° C. under reduced pressure.

Examples of the α-olefin having a cold xylene soluble content of 3% by mass or less include JP-A-2003-277.
Examples of the polymer synthesized by the continuous gas phase polymerization method described in No. 412 include, for example, “FS
X66E8 "(manufactured by Sumitomo Chemical Co., Ltd.) can be used.

The heat-sealable laminate in the present invention has a film flow direction (MD) measured in accordance with JIS-K-7127 and a direction perpendicular to this (TD) from the viewpoint of ensuring handling at the time of product packaging. ) Is required to be 4.0 (GPa) ² or more and 6.0 (GPa) ² or less. Preferably it is 4.2 (GPa) ² or more, more preferably 4.5 (GPa) ² or more, preferably 5.9 (GPa) ² or less, more preferably 5.8 (GPa) ² or less.

  In general, it is known that the tensile elastic modulus of a heat-sealable laminate used as a packaging material has a correlation with the feeling of waist when handling the packaging material. In the present invention, the product of the tensile elastic modulus in MD and TD, not the tensile elastic modulus, is used as a criterion for judging the waist feeling of the film laminate. For example, the film laminate is formed into a bag-like shape. This is because when used as a packaging body, both the flow direction (MD) of the film laminate and the direction (TD) perpendicular thereto are required.

  Therefore, when the product of the tensile elastic modulus is less than the above range, the back feeling of the film laminate is lowered, and the handleability of the package tends to be deteriorated. On the other hand, when the above range is exceeded, the film laminate tends to become hard, and cracks entering the film laminate tend to propagate when the package is opened, and it tears in an unintended direction. There is a risk of spilling.

  If the product of tensile elastic modulus is included in the above range, the value of the tensile elastic modulus of each of MD and TD is not particularly limited, but the tensile elastic modulus in MD is preferably 1.40 GPa or more, More preferably, it is 1.45 GPa, and the tensile elastic modulus at TD is preferably 2.25 GPa or more, more preferably 2.35 GPa or more.

In the heat-sealable laminate of the present invention, it is necessary that the heat-seal strength of the film laminate is 8 N / 15 mm or more. “When the MD and TD of the film are sealed so that the heat seal strength is 8 N / 15 m blood or more”, the provision of “when the heat seal strength is 8 N / 15 mm or more is sufficient for packaging heavy items. It can be judged that it has. This is because, in specifying the heat seal temperature, the above heat seal strength may be difficult to obtain depending on the type of resin constituting each layer constituting the laminated film and the thickness of the layer.
Therefore, when the heat seal strength is less than the above value, when the film laminate is used as a bag-like package, the sealed portion may be broken due to vibration or impact during transportation or dropping during distribution. There is. This phenomenon is particularly remarkable when heavy objects are packaged. Therefore, in the present invention, a regulation of 8 N / 15 mm or more is provided as a value of heat seal strength that the package can withstand heavy weight packaging.

The regulation of heat seal strength in the present invention means a value measured by the following measuring method.
Heat seal strength: Heat seal (seal width: 10 mm) so that the sample cut out in such a way that the film flow direction is the length direction of the bag has a T-shaped cross section of the seal portion of the bag as shown in FIG. ) (Center joint seal type) to create a center press seal bag of size 185 mm × 255 mm. Heat sealing is performed under conditions of a sealing temperature of 150 ° C., a pressure of 2 kg / cm ² , and a heat sealing time of 2 seconds.

A test piece having a width of 15 mm and a length of 50 mm is cut out from the seal portion parallel to the length direction (MD) and the width direction (TD) of the obtained bag. Next, after leaving this test piece in an atmosphere of a temperature of 20 ° C. and a humidity of 65% RH for 24 hours, using “Tensilon” (UTM-IIIL) manufactured by Toyo Seiki Co., Ltd., the distance between chucks was set to 20 mm (heat seal portion). The strength when peeled 180 degrees at a speed of 200 mm / min (chart speed of 200 mm / min) was measured to obtain a heat seal strength [N / 15 mm]. The schematic of the shape of the bag produced in FIG. 1 and the test piece for heat seal strength measurement is shown.

  Furthermore, the heat-sealable laminate of the present invention is intended for easy opening, particularly when a bag formed by a three-side sealing machine or the like is cut in a direction perpendicular to the film flow direction. In order to obtain a good cut property, the tear propagation resistance value in the direction (TD) perpendicular to the flow direction of the heat-sealable laminate measured in accordance with JIS-P-8116 needs to be 120 mN or less. Preferably, it is 115 mN or less, More preferably, it is 110 mN or less, Preferably, it is 85 mN or more, More preferably, it is 86 mN or more. When the tear propagation resistance value in the TD direction exceeds 120 mN, the cut property is insufficient, and when it is less than 85 mN, there is a fear of bag breakage due to vibration, impact, etc. during transportation as a package. On the other hand, the tear propagation resistance value in the flow direction (MD) of the heat-sealable laminate is not particularly specified, but in order to reduce the risk of bag breakage due to transportation vibration, impact, etc., as in the TD direction. Is preferably 85 mN or more.

  In the present invention, the film forming the heat-sealable laminate or each layer thereof may include various additives, fillers such as heat stabilizers and antioxidants as long as the properties of the film and each layer are not impaired as required. , Light stabilizers, antistatic agents, lubricants, nucleating agents, flame retardants, pigments, dyes, antibacterial agents, UV absorbers, UV screening agents, infrared absorbers, calcium carbonate, barium sulfate, magnesium hydroxide, mica, talc, Clay, zinc oxide and the like can be added. Furthermore, other thermoplastic resins, thermoplastic elastomers, rubbers, hydrocarbon resins, petroleum resins and the like may be blended within a range that does not impair the characteristics of the heat-sealable laminate of the present invention.

The thickness constitution of the base film used in the heat-sealable laminate of the present invention is not particularly limited, but from 20 μm to 60 μm biaxially stretched polypropylene film, 12 μm to 25 μm biaxially stretched polyester film, 15 μm A 25 μm biaxially stretched nylon film can be exemplified.
The thickness constitution of the heat-sealable film used in the heat-sealable laminate of the present invention is not particularly limited, but the total layer thickness is 15 μm to 50 μm. Among them, the base material layer has a total layer thickness. It is preferable to set in the range of 10 to 50%, the heat-sealing layer in the range of 1 to 20%, and the intermediate layer in the range of 30 to 89%. More preferable ranges are 15 to 45% of the total thickness of the base material layer, 1.5 to 15% of the heat fusion layer, and 40 to 83.5% of the intermediate layer. When the thickness ratio of the base material layer is small, the waist is lost, and when the thickness ratio is large, the sealing strength may not be obtained. On the other hand, if the thickness ratio of the heat-sealing layer and the intermediate layer is small, sufficient seal strength may not be obtained, and if it is large, the cut property may be insufficient or the waist may be lost.

Please write the drawing temperature, magnification, etc. in a little more detail. Make sure that you understand the meaning of each condition in the example.
The base film and the heat sealable film used in the heat sealable laminate of the present invention can be arbitrarily produced by a method known per se, and are not particularly limited. For example, after melt lamination by T-die method or inflation method using an extruder suitable for the number of layers, it is cooled by a cooling roll method, water cooling method or air cooling method to form a laminated film, sequentially biaxial stretching method, simultaneous biaxial Examples of the stretching method include a stretching method and a tube stretching method.
Here, the conditions when the resin is produced by the sequential biaxial stretching method are exemplified. The resin melt-extruded from a T-shaped die is cooled and solidified by a casting machine to produce an original fabric sheet. At this time, the roll temperature for melt casting is preferably set between 15 ° C. and 40 ° C. for the purpose of suppressing crystallization of the resin and improving transparency. Next, after heating the raw sheet to a temperature suitable for stretching, the sheet is stretched in the flow direction of the sheet using the difference in speed between the stretching rolls. Considering this, it is preferable to set between 3 and 6 times. Next, both ears of the longitudinally stretched sheet are gripped by a tenter clip, and stretched while being sequentially expanded in a direction perpendicular to the flow of the sheet while being heated to a temperature suitable for stretching with hot air. In this case, the transverse draw ratio is preferably set between 7 times and 10 times in consideration of thickness variation and productivity.
In addition, the method for bonding the base film and the heat-sealable film in the heat-sealable laminate of the present invention is not particularly limited, and dry lamination is performed using an adhesive typified by a urethane-based adhesive. Examples thereof include a method and a method of extrusion laminating a heat-sealable film on a substrate film.

  The base film and heat sealable film used in the heat-sealable laminate of the present invention have gas barrier properties such as a polypropylene resin layer, a saponified ethylene-vinyl acetate copolymer, and polyvinyl alcohol, as long as the properties are not impaired. A resin layer may be laminated, or may be one obtained by carrying out transparent vapor deposition such as aluminum vapor deposition or silicon oxide. In addition, when the base film and the heat-sealable film are bonded together, another material such as an aluminum foil may be sandwiched.

The substrate film and heat sealable film used in the heat-sealable laminate of the present invention are preferably subjected to a surface treatment in order to improve the wet tension. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, and acid treatment, and are not particularly limited. It is preferable to perform a corona discharge treatment, a plasma treatment, and a flame treatment that can be continuously performed and can be easily performed before the winding process in the film production process. Depending on the application, the film may be subjected to special processing such as drilling. For example, a film subjected to 1 to 500 μm perforation can be used as a freshness-keeping package for fruits and vegetables.

  The heat-sealable laminate of the present invention has sufficient heat-seal strength for packaging heavy objects and easy tearability at the time of opening, and has good transparency, such as grains such as flour, rice and wheat, It is suitable as a packaging material for various kinds of pickles such as Itokonjac, takuan pickles, soy sauce pickles, Nara pickles, various miso, dashimoto, noodle soup, soy sauce, sauce, ketchup, mayonnaise, etc. It can be used as a package for paper cartons, tubes, bags, cups, standing packs, trays, and the like.

  Hereinafter, specific examples of the present invention will be further described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the characteristic in this specification evaluated by the following method.

(Heat seal strength)
A sample cut out from the heat-sealable laminate obtained in the following experiment in such a manner that the flow direction of the laminate film is in the length direction of the bag, a cross section of the seal portion of the bag as shown in FIG. A center press seal bag having a size of 185 mm × 255 mm was prepared by heat sealing (sealing width: 10 mm) so as to form a letter shape (central palm seal type). The heat sealing was performed using a sealer “Test Sealer” manufactured by Seibu Kikai Co., Ltd. under the conditions of a sealing temperature of 150 ° C., a pressure of 196 kPa (2 kg / cm ² ), and a heat sealing time of 2 seconds.
A test piece having a width of 15 mm and a length of 50 mm is cut out from the seal portion parallel to the length direction (MD) and the width direction (TD) of the obtained bag. Next, after leaving this test piece in an atmosphere of a temperature of 20 ° C. and a humidity of 65% RH for 24 hours, using “Tensilon” (UTM-IIIL) manufactured by Toyo Seiki Co., Ltd., the distance between chucks was set to 20 mm (heat seal portion). The strength when peeled 180 degrees at a speed of 200 mm / min (chart speed of 200 mm / min) was measured to obtain a heat seal strength [N / 15 mm]. The schematic of the shape of the bag produced in FIG. 1 and the test piece for heat seal strength measurement is shown.

(Tensile modulus)
According to the JIS-K-7127 method, the tensile modulus (GPa) of the film flow direction (MD) and the film flow orthogonal direction (TD) was measured. The measurement was performed three times in each direction, and the average value of these values was taken as the tensile elastic modulus in each direction.

(Tear propagation resistance)
The tear propagation resistance (mN) in the film flow direction (MD) and in the film flow orthogonal direction (TD) was measured according to the JIS-P-8116 method. The measurement was performed three times in each direction, and the average of these values was taken as the tear propagation resistance in each direction.

(Product handling)
In a bag made in the same manner as the above heat seal strength measurement method, put a rice confection with a weight of about 4 g and a size of 25 mm × 75 mm twisted with a polyethylene film with a thickness of 25 μm and a size of 80 mm × 140 mm. The handling of the product was evaluated.
Grade 5: The film has a waist and can be packed, boxed, and displayed easily. Grade 4: The bag feels a little bit, but the work can be done without problems. However, it feels a little bit more difficult to hold when it is held in the hand. Grade 2: It is hard to work when it is held in the hand. Difficult to work

(Easily tearable)
For the heat-sealable laminate film obtained in the following experiment, two sheets cut into 170 mm (MD) × 130 mm (TD) were prepared, and the heat seal surfaces were combined as inner surfaces. Was used to obtain a bag which was heat-sealed in a width of 10 mm on four sides under conditions of a sealing temperature of 150 ° C., a pressure of 196 kPa (2 kg / cm ² ), and a heat sealing time of 2 seconds. 10 bags each with a 1 mm deep notch formed near the center of the long side heat seal part of the obtained bag were prepared, and when teared by hand parallel to TD from the notch part, 10 times smoothly without resistance Those that were torn were evaluated as ◯, those that slightly felt resistance were evaluated as Δ, and those that felt strong resistance and were difficult to avoid were evaluated as ×. Here, the notch means a cut end.

Resins constituting each layer used in the following production examples are as follows.
Propylene homopolymer: “FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd., MFR: 2.5
g / 10 min, melting point: 158 ° C., cold xylene solubles (CXS): 3.3% by mass
Propylene / Ethylene / Butene Random Copolymer 1: “FSX6” manufactured by Sumitomo Chemical Co., Ltd.
6E8 ", ethylene content: 2.5 mol%, butene content: 7 mol%, MFR: 3.1 g
/ 10 minutes, melting point: 133 ° C., cold xylene solubles (CXS): 1.6% by mass
Propylene / Ethylene / Butene Random Copolymer 121 “W171” manufactured by Sumitomo Chemical Co., Ltd.
”, Ethylene content: 4.6 mol%, butene content: 4.2 mol%, MFR: 4.6 g /
10 minutes, melting point: 128 ° C., cold xylene solubles (CXS): 4.6% by mass
Propylene / Ethylene / Butene Random Copolymer 1: “WF58” manufactured by Sumitomo Chemical Co., Ltd.
4S ", ethylene: 2.6 mol%, butene content: 15.4 mol%, MFR: 4. O
g / 10 minutes, melting point: 135 ° C., cold xylene solubles (CXS): 3.6% by mass (produced by solution polymerization method)
Propylene / Butene Copolymer 1: RSPX78J1 manufactured by Sumitomo Chemical Co., Ltd., butene content: 25 mol%, MFR: 8.5 g / 10 min, melting point: 128 ° C., cold xylene solubles (C
XS): 14. O mass%
Propylene / butene copolymer 1-2: “SP8932” manufactured by Sumitomo Chemical Co., Ltd., butene content: 33 mol%, MFR: 9.0 g / 10 min, melting point: 130 ° C.

Example 1
(Method for producing heat-sealable film)
Using three melt extruders, the propylene homopolymer (density 0.90 g / cm ³ , MFR 2.5 g / 10 min, melting point 157 ° C., cold xylene soluble content 3.3 wt% in the first extruder ) As a base material layer A, in a second extruder, a propylene / ethylene / butene random copolymer (density 0.89 g / cm ³ , MFR 3.1 g / 10 min, melting point 133 ° C., cold xylene solubles) 1.6 wt%) 10 wt%, propylene / butene random copolymer density 0.89 g / cm ³ , MFR 9.0 g / 10 min, melting point 130 ° C., cold xylene soluble content 14.0 wt%) In the third extruder, a mixed resin having a weight% of heat as the heat-fusible layer C was mixed with a propylene / ethylene / butene random copolymer (density 0.89 g / cm ³ , MFR 3.1 g / 10 min, melting point 133 ° C. , 1.6x cold xylene solubles %) 50 wt%, a propylene homopolymer (density 0.90g / cm ^3, MFR2.5g / 10 min, melting point 157 ° C., a cold xylene-soluble portion 3.3 wt%) to 50 wt% and the mixed resin As a layer B positioned between the base material layer and the heat-sealable layer, it is melt-coextruded by the T-die method so as to be A / B / C in the die, and then cooled and solidified with a chill roll at 20 ° C. The laminated film was stretched 4.5 times in the longitudinal direction and 8 times in the transverse direction, and the thickness of the A / B / C structure was 6 μm, 12 μm, and 2 μm, respectively. The surface of the base layer A of the obtained heat-sealable film was subjected to corona discharge treatment so that the wetting tension of the surface of the base layer A after the corona discharge treatment was 37 mN / m.

(Method for producing heat-sealable laminate)
A biaxially stretched polypropylene film (trade name Pyrene P2161 (manufactured by Toyobo Co., Ltd.)) having a thickness of 20 μm was prepared as a base film, and the heat-sealable film obtained by the above method was used as a polyester adhesive (trade name TM590). / CAT56 (manufactured by Toyo Morton Co., Ltd., coating amount: 3.0 g (dry) / m ² ) and then bonded by a dry lamination method, and then subjected to aging treatment at 40 ° C. for 72 hours to produce a heat-sealable laminate The evaluation results are shown in Table 1. The obtained heat-sealable laminate has sufficient heat-seal strength, low back, and easy tearability, and is easy to handle and easy to open at the time of product opening. It was excellent.

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1 except that an unstretched polypropylene film (trade name: Pyrene P1128 20 μm (manufactured by Toyobo Co., Ltd.)) was used as the heat-sealable film in Example 1. The obtained laminated film had no waist and was inferior in handleability and was not satisfactory in tearability.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Example 1 except that a biaxially stretched polypropylene film (trade name: Pyrene P3162 20 μm (manufactured by Toyobo Co., Ltd.)) was used as the heat-sealable film in Example 1. . The obtained laminated film had low heat seal strength, and was broken from the seal portion during transportation and handling of the actual bag-making package, and had a problem in practical use.

(Example 2)
In Example 1, instead of the polyester adhesive, a polyether polyurethane adhesive (trade name TM329 / CAT8B (manufactured by Toyo Morton Co., Ltd., coating amount: 2.0 g (dry) / m ² )) A laminated film was obtained in the same manner as in Example 1 except that the lamination was performed by a dry lamination method, and the obtained heat-sealable laminate had sufficient heat-sealing strength, low back feeling, and easy tearing. It was excellent in all of the opening properties at the time of product opening.

(Comparative Example 3)
In Example 2, a laminated film was obtained in the same manner as in Example 2 except that an unstretched polypropylene film (trade name Pyrene P1128 20 μm (manufactured by Toyobo Co., Ltd.)) was used as the heat-sealable film. . The obtained laminated film peeled off at the adhesive interface between the base film and the heat-sealable film at the time of evaluation of tearability, and the tearability was remarkably poor, and the openability was problematic.

  The results are shown in Table 1.

The heat-sealable laminate of the present invention has sufficient heat-seal strength to wrap heavy objects, as well as excellent handleability and good transparency, so that flour, rice, wheat Cereals such as potatoes, radish and carrots, root vegetables; savory konnyakus; various pickles such as takuan pickles, soy sauce pickles, and nara pickles; various miso soups; It is suitable for a packaging material for collective packaging in which several packagings such as exterior materials such as ketchup and mayonnaise and ramen are packaged together. In particular, it can be used as a packaging material optimal for packaging of cut vegetables for business use that requires anti-fogging properties.

The laminated film of the present invention can also be used as a package for paper parkons, tubes, bags, cups, standing packs, trays, and the like.

It is a schematic diagram of the test piece for the shape of the bag created in the Example, and heat seal strength measurement. It is an example of the chart at the time of heat seal intensity | strength measurement.

Claims (5)

A laminate of at least two layers composed of a base film and a heat-sealable film, having a heat seal strength of 8 N / 15 mm or more, a flow direction (MD) of the laminate, and a direction perpendicular to the flow direction ( The product of the tensile modulus of TD) is 4.0 to 6.0 (GPa) ² and the tear propagation resistance in the direction (TD) perpendicular to the flow direction (MD) of the laminate is 120 mN or less. A heat-sealable laminate characterized by the above. The heat-sealable laminate according to claim 1, wherein the substrate film and the heat-sealable film are stretched. The heat-sealable film is composed of three or more layers, and an intermediate layer is formed between the base material layer made of crystalline polypropylene resin, the heat sealing layer having a melting point of 150 ° C. or less, and the base material layer and the heat sealing layer. The heat-sealable laminate according to claim 1, wherein the heat-sealable laminate is at least a film. The heat-sealable laminate according to claim 1, 2, or 3, wherein the intermediate layer of the heat-sealable film comprises an α-olefin copolymer having a cold xylene soluble content of 3% by weight or less. A package comprising the heat-sealable laminate according to claim 1, 2 or 3.

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