WO2018181011A1 - Biaxially oriented polypropylene resin film - Google Patents

Abstract

To provide a polypropylene resin film that has heat seal strength and sealing properties adequate for packaging a heavy object and that is also suitable for automatic packaging. A biaxially oriented polypropylene resin film comprising a substrate layer (A), an intermediate layer (B), and a seal layer (C), the melting point of a resin constituting part of the substrate layer (A) and the seal layer (C) being in a specific range, and the thickness of each of the intermediate layer (B) and the seal layer (C) furthermore being set so that the ratio thereof with respect to the thickness of all the layers is in a specific range.

Description

Biaxially oriented polypropylene resin film

The present invention relates to a biaxially oriented polypropylene-based resin film. More specifically, the biaxially oriented polypropylene resin film has sufficient heat seal strength and sealability to package heavy objects and can be suitably used for automatic filling packaging. The present invention relates to a polypropylene resin film.

Conventionally, as a heat-sealable film used for packaging, an unstretched polyethylene resin film, a laminated polypropylene resin film obtained by laminating an unstretched polypropylene resin film and a stretched polypropylene resin film, or a high melting point polypropylene film A laminated polypropylene-based resin film obtained by laminating and extruding a low melting point polyolefin-based resin layer on a resin layer and stretching is widely used.
However, unstretched polyethylene resin film or laminated polypropylene resin film laminated with unstretched polypropylene resin film and stretched polypropylene resin film has sufficient sealing strength, but requires a laminating process using organic solvent It is not preferable from the viewpoint of the influence on the global environment economically.
In addition, a laminated polypropylene resin film obtained by laminating and extruding a low melting point polyolefin resin layer to a high melting point polypropylene resin layer and stretching the laminated polypropylene resin film has some degree of sealing strength, but a heavy product such as water There was no sealing strength until packaging.

By laminating an intermediate layer between a base material layer made of polypropylene resin and a seal layer made of polyolefin resin with a low melting point, the heat seal strength and sealability are improved. It is disclosed that no peeling occurs and the contents do not leak from the seal (see, for example, Patent Document 1).
However, this film is wrinkled in the bag-making product obtained by the so-called automatic packaging process after the contents are packaged, which is continuously heat-sealed. There is a problem that it is not smoothly conveyed.

Japanese Patent No. 4894340

The present invention solves the problems of the above-mentioned conventional laminated polypropylene film, has sufficient heat seal strength and sealability to package heavy objects, can perform automatic packaging smoothly, and can be obtained. It is an object of the present invention to provide a biaxially oriented polypropylene-based resin film that has less wrinkles in a bag product and less air return to a vacuum-degassed bag product.

As a result of intensive investigations in order to achieve such an object, the inventors of the biaxially oriented polypropylene resin film comprising the base material layer (A), the intermediate layer (B) and the seal layer (C) ( A) The melting point of the resin constituting the seal layer (C) is set to a specific range, and the ratio of the thickness of each of the intermediate layer (B) and the seal layer (C) to the total layer thickness and the total film thickness By having a range, it has sufficient sealing strength and sealing properties to package heavy objects, can smoothly transport the film in automatic packaging processing, and it is difficult to wrinkle the obtained bag product In addition, the present inventors have found that there is little return of air to vacuum-degassed bag-making products, which has led to the present invention.

That is, the present invention
1. A biaxially oriented polypropylene resin film comprising a base material layer (A), an intermediate layer (B), and a seal layer (C), which satisfies the following 1) to 5): the film.
1) The resin composition which comprises a base material layer (A) has a polypropylene resin as a main component, and melting | fusing point is 156 degreeC or more.
2) The resin composition constituting the intermediate layer (B) is at least selected from the group consisting of a propylene / ethylene / butene-1 copolymer, a propylene / butene-1 copolymer, and a propylene / ethylene copolymer. One type of copolymer is contained at 30% by weight or more.
3) The resin composition constituting the seal layer (C) is at least one selected from the group consisting of a propylene / butene-1 copolymer, a propylene / ethylene / butene-1 copolymer, and a propylene / ethylene copolymer. It is mainly composed of a seed copolymer, and its melting point is 135 ° C. or lower.
4) The thickness of the sealing layer (C) is 2% or more and 8% or less with respect to the entire film layer.
5) The thickness of the intermediate layer (B) is 5% or more and 18% or less with respect to the entire film layer.
6) The total thickness of the sealing layer (C) and the intermediate layer (B) is 22% or less with respect to the total film layer.
7) The thickness of the entire film layer is 33 μm or less.

2. Item 2. The polypropylene resin film according to Item 1, wherein the seal layer (C) contains an antifogging agent.

According to the present invention, the bag making has a sufficient sealing strength and sealing property for packaging heavy objects, can perform automatic packaging smoothly, and has less wrinkles in the obtained bag making product, and is vacuum degassed. A biaxially oriented polypropylene-based resin film that returns less air to the product can be provided.

It is the schematic of the shape of the bag created in the Example, and the test piece for heat seal strength measurement. It is a schematic diagram of the sealing performance evaluation method.

Detailed Description of the Invention

Hereinafter, embodiments of the biaxially oriented polypropylene resin film of the present invention will be described.
(Base material layer (A))
The resin composition used for the base material layer (A) is mainly composed of a polypropylene resin. The polypropylene resin here is selected from the group consisting of an n-heptane insoluble isotactic propylene homopolymer and a copolymer of propylene and other α-olefins containing 70 mol% or more of propylene. It is preferably made of at least one resin.
Such a polypropylene resin is preferably contained in an amount of 80% by weight or more, more preferably 90% by weight or more based on the resin composition constituting the base material layer (A).
The melting point of the polypropylene resin used for the base material layer (A) needs to be 156 ° C. or higher. Melting | fusing point is measured by the method as described in the Example mentioned later. When the melting point is less than 156 ° C., the film cannot be conveyed more smoothly in the automatic packaging process, and the obtained bag-making product is more likely to wrinkle.
The insolubility of n-heptane indicates the crystallinity of polypropylene and 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]).

As an α-olefin copolymer component of a copolymer of propylene and another α-olefin, an α-olefin having 2 to 8 carbon atoms such as ethylene, butene-1, pentene-1, hexene-1, 4 -Methyl-1-pentene and the like are preferable. Here, the copolymer is preferably a random or block copolymer obtained by polymerizing one or more of the α-olefins exemplified above with propylene.
When propylene homopolymerization and a copolymer of propylene and other α-olefins containing 70 mol% or more of propylene are mixed and used, the total resin composition used for the base material layer (A) Thus, it is desirable that the content of a copolymer of propylene containing 70 mol% or more of propylene and another α-olefin is 20 wt% or less. More preferably, it is 10% by weight or less.

(Intermediate layer (B))
The resin composition constituting the intermediate layer (B) is at least one selected from the group consisting of propylene / ethylene / butene-1 copolymers, propylene / butene-1 copolymers, and propylene / ethylene copolymers. It is necessary to contain 30% by weight or more of a copolymer. As a result, the seal arrival strength and the sealing performance can be improved. Preferably it is 65 weight% or more, More preferably, it is 80 weight% or more, Most preferably, it is 90 weight% or more.
Further preferred forms of the propylene-butene-1 copolymer, propylene / ethylene / butene-1 copolymer, and propylene / ethylene copolymer are described in the following 1) to 3).

1) Propylene / ethylene / butene-1 copolymer The butene content in the propylene / ethylene / butene-1 copolymer is preferably 5% by weight or more. When the butene content is 5 mol% or more, the adhesion between the layers with the seal layer (C) is improved, and the heat seal strength and the sealing property are easily improved.
The upper limit of the butene content is not particularly limited, but if the butene content is too high, crystallization is excessively suppressed, and the crystallinity is lower than that of the propylene homopolymer, resulting in a reduction in the back feeling of the film. .
Examples of the propylene / ethylene / butene-1 copolymer having a high butene content include “FSX66E8” manufactured by Sumitomo Chemical Co., Ltd.
The propylene / ethylene / butene-1 copolymer is preferably blended in an amount of 65% by weight or more in the resin component constituting the intermediate layer (B). More preferably, it is 70 weight% or more, and it is still more preferable that it is 99 weight% or less, More preferably, it is 95 weight% or less. By increasing the blending strength of the propylene / ethylene / butene-1 copolymer to 65% by weight or more, the interlaminar strength with the seal layer (C) is increased, so that the heat seal strength can be increased and the sealing performance can be further enhanced. On the other hand, the interlayer strength with the base material layer (A) can be increased by setting it to 95% by weight or less.

2) Propylene / butene-1 copolymer The butene content in the propylene / butene-1 copolymer is preferably 20 mol% or more. When the butene content is 20 mol% or more, the adhesion between the layers with the seal layer (C) is improved, and the heat seal strength and the sealing performance are improved.
The upper limit of the butene content is not particularly limited, but if the butene content is too high, crystallization is excessively suppressed, and the crystallinity is lower than that of the propylene homopolymer, resulting in a reduction in the back feeling of the film. .
Examples of the propylene / butene-1 copolymer having a high butene content include “SPX78J1” manufactured by Sumitomo Chemical Co., Ltd. and “XR110H” manufactured by Mitsui Chemicals, Inc.
The propylene / butene-1 copolymer is preferably blended in an amount of 65% by weight or more in the resin component constituting the intermediate layer (B). More preferably, it is 70 weight% or more, and it is still more preferable that it is 99 weight% or less, More preferably, it is 95 weight% or less. By increasing the blend strength of the propylene / ethylene / butene-1 copolymer to 65% by weight or more, the interlayer strength with the seal layer (C) is increased, thereby making it easy to increase the heat seal strength or to improve the sealing performance. On the other hand, the interlayer strength with the base material layer (A) can be increased by setting it to 95% by weight or less.

3) Propylene / ethylene copolymer The propylene / ethylene copolymer preferably has an ethylene content of 4 mol% or more. When the ethylene content is 4 mol% or more, the adhesion between the layers with the seal layer (C) is improved, and the heat seal strength and the sealability are improved.
The upper limit of the ethylene content is not particularly limited, but if the ethylene content is too high, crystallization is suppressed too much and the crystallinity is lower than that of the propylene homopolymer, resulting in a reduction in the feeling of the film. .
Examples of the propylene / ethylene copolymer having a high ethylene content include “PC540R” manufactured by Sun Allomer Co., Ltd. and “VM3588FL” manufactured by Mitsui Chemicals, Inc.
The propylene / ethylene copolymer is preferably blended in an amount of 65% by weight or more in the resin component constituting the intermediate layer (B). More preferably, it is 70 weight% or more, and it is still more preferable that it is 99 weight% or less, More preferably, it is 95 weight% or less. By increasing the blending ratio of propylene / ethylene: butene-1 copolymer to 65% by weight or more, the interlayer strength with the seal layer (C) is increased, so that the heat seal strength can be increased or the sealing performance can be easily improved. On the other hand, the interlayer strength with the base material layer (A) can be increased by setting it to 95% by weight or less.

The propylene copolymer 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 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 weight 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.
At this time, the cold xylene soluble content (CXS) of the entire intermediate layer is preferably 2.5% by weight or less, and more preferably 2.4% by weight or less. Furthermore, it is more preferable that it is 2.2 weight% or less.

(Sealing layer (C))
The resin composition constituting the seal layer (C) is at least one selected from the group consisting of a propylene / butene-1 copolymer, a propylene / ethylene / butene-1 copolymer, and a propylene / ethylene copolymer. The copolymer is mainly used, and the melting point of the copolymer needs to be 135 ° C. or less. Melting | fusing point is measured by the method as described in the Example mentioned later. When the melting point exceeds 135 ° C., improvement in heat seal and heat seal strength cannot be expected.
Further preferred forms of propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer, and propylene / ethylene copolymer will be described in the following 1) to 3).

1) The butene content in the propylene / butene-1 copolymer is preferably 20 mol% or more. By making it 20 mol% or more, it is easy to increase the heat seal strength or to improve the sealing performance.
The upper limit of the butene content is not particularly limited, but if the butene content is too high, the film surface may become sticky, and slipperiness and blocking resistance may be reduced. Examples of the propylene / butene-1 copolymer having a high butene content include “SPX78J1” manufactured by Sumitomo Chemical Co., Ltd. and “XR110H” manufactured by Mitsui Chemicals, Inc.
The propylene / butene-1 copolymer is preferably blended in an amount of 65% by weight or more in the resin component constituting the seal layer (C). More preferably, it is 70% by weight or more. 99% by weight or less, and more preferably 95% by weight or less. By making the blend of propylene / butene copolymer 65% by weight or more, it is easy to increase the heat seal strength or to improve the sealing performance. On the other hand, by setting it to 95% by weight or less, the interlayer strength with the intermediate layer (B) can be increased.

2) Propylene / ethylene / butene-1 copolymer The butene content in the propylene / ethylene / butene-1 copolymer is preferably 5 mol% 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 / ethylene / butene-1 copolymer having a high butene content include “FSX66E8” manufactured by Sumitomo Chemical Co., Ltd.

3) Propylene / ethylene copolymer The propylene / ethylene copolymer preferably has an ethylene content of 4 mol% or more. The upper limit of the ethylene content is not particularly limited, but if the ethylene content is too high, the film surface may become sticky, and slipperiness and blocking resistance may decrease. Good. Examples of the propylene / ethylene copolymer having a high ethylene content include “PC540R” manufactured by Sun Allomer Co., Ltd. and “VM3588FL” manufactured by Mitsui Chemicals, Inc.

The melting point of the polypropylene resin constituting the seal layer (C) of the present invention needs to be 135 ° C. or lower. Melting | fusing point is measured by the method as described in the Example mentioned later. When the melting point exceeds 135 ° C., improvement in heat seal and heat seal strength cannot be expected.

In the present invention, in the resin forming each layer, various additives and fillers, for example, an antifogging agent, a heat stabilizer, an antioxidant, a light stabilizer, as long as the properties of each layer are not impaired as required. Antistatic agent, lubricant, nucleating agent, flame retardant, pigment, dye, calcium carbonate, barium sulfate, magnesium hydroxide, mica, talc, clay, zinc oxide, magnesium oxide, aluminum oxide, antibacterial agent, antifogging agent, natural decomposition Additives that impart properties 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 film of the present invention.

(Biaxially oriented polypropylene resin film)
The polypropylene resin film of the present invention comprises the above-mentioned base material layer (A), intermediate layer (B), and seal layer (C).

The thickness of the sealing layer (C) needs to be 2% or more and 8% or less with respect to the entire film layer.
Here, when the thickness of the seal layer (A) is less than 5%, sufficient heat seal strength and sealability cannot be obtained. When the thickness of the sealing layer (A) exceeds 8%, the film can be smoothly conveyed in the automatic packaging process, and wrinkles are hardly formed in the obtained bag-making product. More preferably, it is 2% or more and 5% or less.

The thickness of the intermediate layer (B) needs to be 5% or more and 18% or less with respect to the entire film layer.
Here, when the thickness of the intermediate layer (B) is less than 5%, sufficient strength and sealability cannot be obtained. When the thickness of the intermediate layer (B) is 18% or less, the film can be smoothly conveyed in the automatic packaging process, and wrinkles are unlikely to occur in the obtained bag-made product. More preferably, it is 5% or more and 15% or less.

It is necessary that the sum of the thickness of the intermediate layer (B) and the thickness of the sealing layer (C) is 7% or more and 22% or less with respect to the thickness of the entire film layer. When the sum of the thickness of the intermediate layer (B) and the thickness of the seal layer (C) is 7% or more with respect to the thickness of the entire film layer, the return of air to the vacuum-deaerated bag-making product is reduced. When the sum of the thickness of the intermediate layer (B) and the thickness of the seal layer (C) is 22% or less with respect to the thickness of the entire film layer, the film can be transported more smoothly in the automatic packaging process. Wrinkles are more difficult to enter into the bag-made products. Preferably they are 10% or more and 22% or less. More preferably, it is 10% or more and 20% or less, and particularly preferably 15% or more and 18% or less.

The thickness of the biaxially oriented polypropylene resin film of the present invention needs to be 15 μm or more and 33 μm or less. In the case of this range, the balance between the lower back and the reduction of air return to the vacuum-deaerated bag making product is balanced. More preferably, it is 15 μm or more and 30 μm or less, and particularly preferably 15 μm or more and 28 μm or less.

(Production method)
The biaxially oriented polypropylene-based resin film of the present invention can be manufactured by the following film forming method, but is not limited thereto.
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 tubular stretching method.
Here, if the conditions at the time of manufacturing by a sequential biaxial stretching method are illustrated, the resin melt-extruded from the T-shaped die is cooled and solidified by a casting machine to produce a raw sheet.
The temperature at the time of melt lamination is preferably set in the range of 240 ° C. to 300 ° C. with reference to the melting point of the raw material resin used for each layer. The casting roll temperature 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. The stretching temperature is also preferably set between 100 ° C. and 150 ° C. in view of stable production without unevenness of stretching.
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. The stretching temperature is also preferably set between 130 ° C. and 180 ° C. in view of stable production without unevenness of stretching.
Finally, it is preferable to perform the heat setting treatment in the range of 150 ° C to 200 ° C.

The biaxially oriented polypropylene resin film of the present invention can be subjected to a surface treatment in order to improve printability, laminating properties and the like. 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 carried out continuously and can be easily carried out before the winding step of the film production process.

(Film characteristics)
(Anti-fogging property)
The polypropylene resin film of the present invention preferably has an antifogging evaluation of rank 3 or higher obtained by a measurement method described later. More preferably, it is rank 2 or higher, and further preferably rank 1.

(Heat seal rise temperature)
The biaxially oriented polypropylene-based resin film of the present invention preferably has a heat seal rising temperature obtained by a measurement method described later of 120 ° C. or lower. More preferably, it is 115 degrees C or less.

(Achieved heat seal strength)
The biaxially oriented polypropylene resin film of the present invention preferably has an ultimate heat seal strength of 4.5 N / 15 mm or more obtained by a measurement method described later. More preferably, it is 5N / 15mm or more, More preferably, it is 6N / 15mm ° C or more.

(Sealing)
In the biaxially oriented polypropylene-based resin film of the present invention, it is preferable that the evaluation of the sealing property obtained by the measurement method described later is rank 3 or higher. More preferably, it is rank 2 or higher, and further preferably rank 1.

(Bag-made products)
The biaxially oriented polypropylene-based resin film of the present invention preferably has a rank of 3 or more in terms of evaluation of bag feeling obtained by a measurement method described later. More preferably, it is rank 2 or higher, and further preferably rank 1.

(Automatic packaging suitability)
In the biaxially oriented polypropylene-based resin film of the present invention, it is preferable that the evaluation of the automatic packaging suitability obtained by the measurement method described later is ◯ or Δ. More preferably, it is (circle).

(Air return after deaeration packaging)
In the biaxially oriented polypropylene-based resin film of the present invention, the evaluation of air return after vacuum deaeration packaging obtained by a measurement method described later is preferably ◎ or ◯. More preferable is ◎.
Air return is related to the above-mentioned sealing property, and is an evaluation of suitability for vacuum packaging at a practical level.

(Use)
Since the biaxially oriented polypropylene-based resin film of the present invention has sufficient heat seal strength to wrap heavy objects, it also has excellent handling properties and good sealing properties. Cereals such as wheat, root vegetables such as potatoes, radish and carrots, plates and yarn konnyakus, various pickles such as takuan pickles, soy sauce pickles, Nara pickles, various miso soups, dashi source, noodle soup, soy sauce Alternatively, it can be suitably used as a packaging material for various seasonings such as sauces, ketchup, mayonnaise, or a packaging material for collective packaging in which several individual packages such as ramen are packaged together.
Moreover, since it is excellent in the conveyance property of a film, it can be used suitably also for the packaging material used for automatic packaging of vegetables etc.

Hereinafter, specific examples of the present invention will be further described by way of 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.

(1) Melting point Tm
In accordance with JIS K 7121, measurement was performed with a differential scanning calorimeter (DSC).
As a condition adjustment, the temperature was increased from room temperature to 200 ° C. at 30 ° C./min, held at 200 ° C. for 5 minutes, cooled to −100 ° C. at 10 ° C./min, held at −100 ° C. for 5 minutes, and then endothermic. As a measurement of the curve, the temperature was increased from −100 ° C. to 200 ° C. at 10 ° C./min.
When there were a plurality of melting peaks, in the case of the heat seal layer (C), the melting peak with the maximum temperature was taken as the melting point. In the case of the base material layer (A), the melting peak having the minimum temperature was taken as the melting point.

(2) Layer thickness A sample film was cut into a size of 1 cm x 1 cm, embedded in a UV curable resin, and irradiated with UV for 5 minutes to solidify. Thereafter, a cross-sectional sample was prepared with a microtome and observed with a differential interference microscope, and the thicknesses of the intermediate layer (B) and the seal layer (C) were measured. Samples were measured at five points, and the average value was calculated.

(3) Anti-fogging property 1) Put 300 cc of hot water at 50 ° C. into a 500 cc top open container.
2) The container opening is sealed with the film with the antifogging measurement surface of the film facing inside.
3) Leave in a cold room at 5 ° C.
4) The state of dew adhesion on the film surface was evaluated in five stages while the hot water in the container was completely cooled to the ambient temperature.
Rank 1: No dew on the entire surface (attachment area 0)
Rank 2: Slight dew adhesion (up to 1/4 adhesion area)
Rank 3: About 1/2 dew adhesion (up to 2/4 adhesion area)
Rank 4: almost dew adhesion (up to 3/4 adhesion area)
Rank 5: Dew adhesion on the entire surface (adhesion area 3/4 or more)

(4) Heat seal rise temperature The heat seal layers of the sample film are stacked face to face, and using a thermal tilt tester (manufactured by Toyo Seiki Co., Ltd.), the heat seal pressure is 1 kg / cm ² , the time is 1 second, and the temperature is This refers to the temperature at which the heat seal strength is 1 N / 15 mm when heat-sealed at 80 ° C. to 5 ° C., and the heat seal layer surfaces of a 5 cm × 20 cm film face each other, and the temperature is set at a pitch of 5 ° C. Heat seal bars (seal surface 1cm x 3cm) are heat-sealed at the same time, the central part is cut to a width of 15mm, attached to the upper and lower chucks of a tensile tester, and pulled at a pulling speed of 200mm / min. The heat seal strength was calculated (unit: N / 15 mm).
A linear graph with temperature on the horizontal axis and heat seal strength on the vertical axis was drawn, and the temperature at which the heat seal strength exceeded 2.5 N / 15 mm was defined as the heat seal rising temperature.

(5) Heat seal ultimate strength Heat seal layers of the sample film are stacked face to face, using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.), heat seal pressure 1 kg / cm ² , time is 1 second, temperature is Heat seal strength from 80 ° C to 150 ° C at a high temperature in increments of 5 ° C, cut the center part to a width of 15mm, attached to the upper and lower chucks of a tensile tester, and from the heat seal strength when pulled at a tensile speed of 200mm / min Calculated (unit: N / 15 mm).
The numerical value that reached the maximum strength when the upper limit of the seal temperature was 150 ° C. was defined as the ultimate heat seal ultimate strength.

(6) Sealing property Red ink (RECORDER made by CHUGAI KASEI CO. LTD) is formed in the overlapping portions of the length direction (MD) and width direction (TD) seal portions of the bag prepared in the same manner as the above heat seal strength measurement method. INK) was hung from the inner side of the bag and the degree of removal from the inner side of the bag was evaluated.
Rank 1: Ink accumulates inside the bag, does not penetrate the seal, and does not leak outside the bag. Rank 2: There is a slight penetration of the ink into the seal, but does not leak outside the bag. Rank 3: Ink seal penetrates but does not leak to the outside of the bag Rank 4: Ink seal penetrates to the outside of the bag and there is a slight leak outside the bag Rank 5: Ink Leak out of the bag.

(7) Looseness of bag-made products In a bag made in the same manner as the above heat seal strength measurement method, a rice cake having a weight of about 4 g and a size of 25 mm × 75 mm is a polyethylene film having a thickness of 25 μm and a size of 80 mm × 140 mm. The product was twisted and packaged to evaluate the handling of the product.
Rank 1: The film has a waist, can be packed, boxed, and displayed easily. Rank 2: When you have a bag, you can feel it a little bit, but you can work without problems. Rank 3: You feel that you are not waisted. ： Feels a little harder to work when held in the hand. Rank 4: Has less waist and feels more difficult to work when held in the hand. Rank 5: Has no waist and difficult to work.

(8) Automatic packaging suitability Using a horizontal pillow bag making machine (manufactured by Kyoei Printing Machinery Materials Co., Ltd .: PP500 type), a pillow package was produced.
conditions:
Fusing blade; Blade angle 60 °
Sealing temperature: 370 ° C
Number of shots: 120 bags / minute Evaluation was made in the following three stages from the smoothness during film conveyance and the degree of wrinkles of the bag-made product.
○: Film transportability is good and there is no wrinkle in the bag product △: Either film transport property or bag product wrinkle is defective ×: Film transportability is defective or bag product wrinkle is present

(9) Air return after deaeration packaging When making a bag in the same manner as in the above automatic packaging suitability measurement method, 2 pieces of glass repellency (diameter 1.5 cm) were enclosed. Thereafter, the air inside was removed with a syringe and a tape was applied to the needle hole to create a vacuum state. After 24 hours, the degree of air return was evaluated by the ease of movement of the repellency.
A: The vacuum state is maintained and there is no air return.
○: A vacuum state is maintained, but a slight return of air is confirmed.
Δ: A vacuum state is partially maintained, but air return is confirmed.
X: The vacuum state is not maintained.

(Used polypropylene resin)
The polypropylene resin constituting each layer used in the examples is as follows.
[PP-1]: Propylene homopolymer: “FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd., MFR: 2.5 g / 10 min, melting point: 158 ° C.
[PP-2]: Propylene / ethylene / butene random copolymer: “FSX66E8” manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 2.5 mol%, butene content: 7 mol%, MFR: 3.1 g / 10 minutes, melting point: 133 ° C
[PP-3]: Propylene / butene-1 copolymer: “SPX78J1” manufactured by Sumitomo Chemical Co., Ltd., butene content: 25 mol%, MFR: 8.5 g / 10 min, melting point: 128 ° C.

Example 1
The resin composition constituting each layer used in Example 1 is as follows.
(1) Base layer (A) Constituent resin composition [PP-1], 0.16% by weight of glycerin monostearate (Matsumoto Yushi Seiyaku Co., Ltd., TB-123) as an antifogging agent, polyoxyethylene (2) 0.2% by weight of stearylamine (Matsumoto Yushi Seiyaku Co., Ltd., TB-12), 0.6% polyoxyethylene (2) stearylamine monostearate (Matsumoto Yushi Seiyaku Co., Ltd., Elex 334) The material added by weight% was used as [PP-4], and 100 weight% was used as the base layer (A) constituting resin composition.

(2) Intermediate layer (B) Organic resin fine particles (CS30: Sumitomo Chemical Co., Ltd .: particle size 3.5 μm) 1.5% by weight in the constituent resin composition [PP-2], glycerin monostea as an antifogging agent The rate (Matsumoto Yushi Seiyaku Co., Ltd., TB-123) was melt-mixed at 0.45% by weight so that the resin temperature was 240 ° C. and pelletized.
This raw material was used as [PP-5], and 100% by weight was used as the resin composition constituting the intermediate layer (B).

(3) Seal layer (C) Organic resin fine particles (CS30: Sumitomo Chemical Co., Ltd .: particle size 3.5 μm) 1.5% by weight in the resin composition [PP-3], glycerin monostea as an antifogging agent [PP-6] was a raw material in which 0.50% by weight of a rate (Matsumoto Yushi Seiyaku Co., Ltd., TB-123) was melt-mixed at a resin temperature of 240 ° C. and pelletized.
A mixture of 50% by weight of [PP-3] and 50% by weight of [PP-6] was used as the resin composition constituting the sealing layer (C).
Using three melt extruders, the base layer (A) constituent resin composition is melt-extruded from the first extruder at a resin temperature of 280 ° C., and the intermediate layer (B) constituent resin composition is used by the second extruder. The resin composition is melt-extruded at a resin temperature of 250 ° C., and the resin composition constituting the seal layer (C) is melt-extruded from the third extruder at a resin temperature of 250 ° C. In the order of material layer (A) / seal layer (C), the thickness ratio in the T-die is such that the base layer (A) / intermediate layer (B) / seal layer (C) = 21/3/1. It laminated | stacked and extruded, it cooled and solidified with the 30 degreeC cooling roll, and the unstretched sheet was obtained. Subsequently, the metal roll heated to 130 ° C. was stretched 4.5 times in the longitudinal direction using the peripheral speed difference, and further introduced into a tenter stretching machine, and stretched 9.5 times in the transverse direction. . The preheating part temperature of the tenter stretching machine was 168 ° C., and the stretching part temperature was 155 ° C.

Furthermore, in the latter half of the tenter stretching machine, after heat setting at 163 ° C., the surface of the base material layer (A) was subjected to corona discharge treatment using a corona discharge treatment machine manufactured by Kasuga Denki Co., Ltd. In the same manner as in C), a corona discharge treatment was performed, and the film was wound with a film winder to obtain a polypropylene resin film. The final film thickness was 25 μm, and the thickness of each layer was substrate layer (A) / intermediate layer (B) / seal layer (C) = 21/3/1 (μm), respectively.
The obtained film satisfies the requirements of the present invention, has sufficient heat seal strength and ultimate strength at low temperatures, and has airtightness, suitability for automatic packaging, bag feeling, and air after deaeration packaging. It came to be compatible with the return. In addition, the anti-fogging property was at a level with no problem in the fruit and vegetable packaging. Table 1 shows the film composition and physical property results.

(Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the constituent resin composition of the intermediate layer (B) was a mixture of 10% by weight of [PP-1] and 90% by weight of [PP-5]. The obtained laminated film has sufficient heat-sealing strength and ultimate strength at a low temperature as in Example 1, and achieves both airtightness, suitability for automatic packaging, bag feeling, and air return after deaeration packaging. It became something to do. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 3)
A laminated film was obtained in the same manner as in Example 1 except that the constituent resin composition of the intermediate layer (B) was a mixture of 50% by weight of [PP-1] and 50% by weight of [PP-5]. The obtained laminated film has sufficient heat-sealing strength and ultimate strength at a low temperature as in Example 1, and achieves both airtightness, suitability for automatic packaging, bag feeling, and air return after deaeration packaging. It became something to do. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

Example 4
A laminated film was obtained in the same manner as in Example 1 except that the constituent resin composition of the intermediate layer (B) was a mixture of 70% by weight of [PP-1] and 30% by weight of [PP-5]. Although the obtained laminated film has a slight decrease in sealing performance, it has sufficient heat seal strength and ultimate strength at low temperatures as in Example 1, and is suitable for automatic packaging, feeling of bag making, after degassing packaging. The air return was compatible. In addition, the anti-fogging property was at a level with no problem in the fruit and vegetable packaging. Table 1 shows the film composition and physical property results.

(Example 5)
A laminated film was obtained in the same manner as in Example 2 except that the thickness of the base material layer (A) was 22.5 μm and the thickness of the intermediate layer (B) was 1.5 μm. The resulting laminated film had a slight decrease in hermeticity, but had sufficient heat-sealing strength and ultimate strength at low temperatures as in Example 2. The air return was compatible. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 6)
A laminated film was obtained in the same manner as in Example 2 except that the thickness of the base material layer (A) was 20.5 μm and the thickness of the intermediate layer (B) was 3.5 μm. Although the obtained laminated film had a slightly reduced feeling of bag-making product, it had sufficient heat-sealing strength and ultimate strength at a low temperature as in Example 2, and had sealing properties, automatic packaging suitability, and bag-making product waist. Both feeling and air return after deaeration packaging are achieved. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1 except that the thickness of the base material layer (A) was 24 μm and the intermediate layer (B) was not installed. The obtained laminated film was inferior in sealing performance and air return after deaeration packaging. Table 2 shows the film composition and physical property results.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the thickness of the base material layer (A) was 22 μm, the intermediate layer (B) was not installed, and the thickness of the seal layer (C) was 3 μm. The obtained laminated film was inferior in sealing performance and air return after deaeration packaging. Table 2 shows the film composition and physical property results.

(Comparative Example 3)
A laminated film was obtained in the same manner as in Example 2 except that the thickness of the base layer (A) was 15 μm, the thickness of the intermediate layer (B) was 4 μm, and the thickness of the seal layer (C) was 1 μm. The obtained laminated film was inferior to the bag feeling of the bag-made product. Table 2 shows the film composition and physical property results.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 2 except that the constituent resin composition of the base layer (A) was changed to 100% by weight of [PP-5]. The obtained laminated film was inferior to the bag feeling of the bag-made product. Table 2 shows the film composition and physical property results.

(Comparative Example 5)
A laminated film was obtained in the same manner as in Example 1 except that the constituent resin composition of the intermediate layer (B) was changed to 100% by weight of [PP-4]. The obtained laminated film was inferior in sealing performance, automatic packaging suitability, and air return after deaeration packaging. Table 2 shows the film composition and physical property results.

(Comparative Example 6)
A laminated film was obtained in the same manner as in Example 1 except that the thickness of the base material layer (A) was 23 μm, the thickness of the intermediate layer (B) was 1 μm, and the thickness of the seal layer (C) was 1 μm. The obtained laminated film was inferior in sealing performance, automatic packaging suitability, and air return after deaeration packaging. Table 2 shows the film composition and physical property results.

(Comparative Example 7)
A laminated film was obtained in the same manner as in Example 1 except that the thickness of the base material layer (A) was 35 μm, the thickness of the intermediate layer (B) was 5 μm, and the thickness of the seal layer (C) was 2 μm. The obtained laminated film was inferior in sealing performance and air return after deaeration packaging. Table 2 shows the film composition and physical property results.

The polypropylene-based resin film of the present invention has sufficient sealing strength and sealing properties to package heavy objects, can perform automatic packaging smoothly, has less wrinkles in the resulting bag-making product, and is vacuum-released. It is possible to provide a biaxially oriented polypropylene-based resin film with less air return to the packaged product.

Claims (2)

A biaxially oriented polypropylene resin film comprising a base material layer (A), an intermediate layer (B), and a seal layer (C), which satisfies the following 1) to 5): the film.
1) The resin composition constituting the base material layer (A) is mainly composed of a polypropylene resin and has a melting point of 156 ° C. or higher.
2) The resin composition constituting the intermediate layer (B) is at least selected from the group consisting of a propylene / ethylene / butene-1 copolymer, a propylene / butene-1 copolymer, and a propylene / ethylene copolymer. One type of copolymer is contained at 30% by weight or more.
3) The resin composition constituting the seal layer (C) is at least one selected from the group consisting of a propylene / butene-1 copolymer, a propylene / ethylene / butene-1 copolymer, and a propylene / ethylene copolymer. It is mainly composed of a seed copolymer, and its melting point is 135 ° C. or lower.
4) The thickness of the sealing layer (C) is 2% or more and 8% or less with respect to the entire film layer.
5) The thickness of the intermediate layer (B) is 5% or more and 18% or less with respect to the entire film layer.
6) The total thickness of the sealing layer (C) and the intermediate layer (B) is 22% or less with respect to the total film layer.
7) The thickness of the entire film layer is 33 μm or less. The polypropylene resin film according to claim 1, wherein the seal layer (C) contains an antifogging agent.

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