JP2022187553A - Laminate film - Google Patents

Abstract

To provide a laminate film which, when used as a lid material for a container or the like, has a small change in an opening strength even when a sealing condition changes, and can be easily opened with an appropriate force.SOLUTION: There is provided a laminate film having a heat seal layer and one or more support layers, in which when the heat seal layer and a polypropylene sheet are heat sealed at 200°C for 1 second and at 200°C for 4 seconds, heat seal strengths are both 15 to 27 N/15 mm, and a difference is 7 N/15 mm or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a laminated film having excellent unsealability.

The original purpose of the package is to protect the contents, and it is important that the package resists external forces during transportation and display and is not easily unsealed. On the other hand, it is required to have an easy-to-open property that allows the lid to be opened normally and easily without causing the lid to crack or the like during use.

Especially in recent years, the increase in the elderly population and the tendency to eat individually have increased the demand for convenient and easy-to-open packages. Various easy-open packages have been proposed, and a package called an easy-peel package uses a sealant film imparting openability, and is used for desserts such as jelly, yogurt, and pudding, and cooked rice. , lid materials for cup containers such as side dishes, packs for processed meat products such as ham and bacon, etc.

A coextruded multilayer film composed of a heat-sealable layer obtained by mixing a polypropylene resin and a polyethylene resin in a specific ratio has been proposed as an easy-to-open sealant film. (See Patent Documents 1 and 2, for example)
However, even when the coextruded multilayer film proposed in Patent Documents 1 and 2 is used as a sealant film, when the sealing conditions change, the opening strength increases, and the opening cannot be performed with an appropriate force. There was a problem that the lid was torn in the middle of opening.

JP 2012-144015 A JP 2016-055433 A

The present invention provides a laminated film which, when used as a lid material for a container or the like, exhibits little change in opening strength even when sealing conditions change, and can be easily opened with an appropriate force.

That is, the present invention
A laminated film having a heat-sealing layer and one or more support layers, wherein the heat-sealing strength when heat-sealing the heat-sealing layer and a polypropylene sheet at 200 ° C. for 1 second and at 200 ° C. for 4 seconds is All of them are laminated films having 15 to 27 N/15 mm and a difference of 7 N/15 mm or less.

The laminated film of the present invention can be used as a lid material with little change in opening strength even if the sealing conditions change, and can be easily opened with an appropriate force.

An object of the present invention is to provide a laminated film that can be easily opened with an appropriate amount of force, with little change in opening strength even if the sealing conditions change when a lid member or the like is used for a container. Furthermore, by laminating at least one layer selected from biaxially oriented polyamide film, biaxially oriented polyester film, printed paper, metal foil, etc. on the support layer side of the laminated film, it can be easily opened as a lid material with an appropriate force. It is possible to obtain a package that can

The laminated film of the present invention will be specifically described.

The laminated film of the present invention must be a laminated film having a heat-sealable heat-sealable layer and one or more support layers. Lamination of one or more layers of the support layer is important in order to prevent the lid from tearing and to open the package normally.

The laminated film of the present invention has a heat seal strength when the heat seal layer and the polypropylene sheet are heat sealed at a sealing pressure of 2 kg/cm ² , a sealing temperature of 200° C., and a sealing time of 1 second and 4 seconds (a tensile speed of 300 mm/min. and the peeling angle is 180°) must be in the range of 15 to 27N/15mm, and more preferably in the range of 16 to 25N/15mm.

The difference in heat seal strength between the heat seal layer and the polypropylene sheet at 200° C. for 1 second and 4 seconds is required to be 7 N/15 mm or less, preferably 6 N/15 mm or less. Since the difference between the heat seal strength when heat-sealed at 200°C for 1 second and the heat seal strength when heat-sealed at 200°C for 4 seconds is 7 N/15 mm or less, the unsealability is stable regardless of sealing conditions. Therefore, it becomes good as an easy-peel packaging material.

The heat seal strength at a temperature of 150° C. is preferably in the range of 10 to 20 N/15 mm under the conditions of a sealing pressure of 2 kg/cm ² and a sealing time of 1 second. is preferably 10 N/15 mm or less. This is preferable because the sealing temperature dependence is small, the heat-sealing property is good in a wide temperature range, and the workability in manufacturing the packaging material and filling the packaging material with the contents is improved.

The heat seal layer in the present invention is made of a resin composition in which a polyethylene resin and a polypropylene resin are mixed, and the polyethylene resin is quantitatively larger than the polypropylene resin, so that the sealing temperature dependency is small and in a wide temperature range. It is preferable because the heat-sealing property becomes good. It is preferably made of a resin composition in which 51% to 95% by mass of polyethylene resin and 5% to 49% by mass of polypropylene resin are mixed.

Examples of the polyethylene-based resin include at least one of high-pressure low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene/α-olefin random copolymer elastomer, and the like. Among them, a mixed resin composition of linear low-density polyethylene, high-pressure low-density polyethylene, and ethylene/α-olefin random copolymer elastomer is particularly preferable.

It is preferable that the polyethylene-based resin of the heat seal layer in the present invention contains linear low-density polyethylene as a main component. Here, the main component means that it contains 50% by mass or more of the mixed resin composition.

The linear low-density polyethylene has a density of 0.910 to 0.940 g/cm ³ and an MFR (190° C.) of 1.0 to 40.0 g/10 minutes. 880 to 0.930 g/cm ³ , MFR (190°C) in the range of 1.0 to 20.0 g/10 minutes, and the ethylene/α-olefin random copolymer elastomer has a density of 0.865 to 0.895 g/cm In ³ , it is preferable that the MFR (190° C.) is in the range of 0.5 to 10.0 g/10 min because of good mixing properties and moderate dispersibility in the ethylene/propylene random copolymer.

The polypropylene resin of the heat seal layer in the present invention is preferably an ethylene/propylene random copolymer of propylene and a comonomer, and the comonomers are ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. , 1-decene, etc., and those in which the comonomer content is less than 5% by mass are preferred.

The polypropylene resin may be mixed with a polypropylene resin polymerized using a multisite catalyst (Ziegler-Natta catalyst), a metallocene catalyst (Kaminsky catalyst), or the like.

The ethylene/propylene random copolymer has a density of 0.90 to 0.96 g/cm ³ and an MFR (230° C.) of 1 to 30 g/min. is also moderate and desirable.

As described above, the mixing ratio of the resin in the heat seal layer is preferably made of a resin composition in which 51 to 95% by mass of polyethylene resin and 5% to 49% by mass of polypropylene resin are mixed. When used as a lid material, the heat seal layer undergoes cohesive failure, the heat seal strength is in the range of 15 to 27 N/15 mm, and a film with good unsealability without stringiness at the time of opening may be obtained.

The support layer in the present invention is preferably made of a resin composition in which an ethylene/propylene block copolymer and a polyethylene resin are mixed.

The resin constituting the support layer in the present invention is preferably made of a resin composition in which 70 to 97% by mass of the ethylene/propylene block copolymer (a) and 3 to 30% by mass of the polyethylene resin (b) are mixed. If the mixed amount of the polyethylene resin (b) is less than 2% by mass, the flexibility may be lost, and the film may tear at the time of opening. If the content exceeds % by mass, wrinkles may easily occur when the film is wound during film formation, resulting in poor film formability and poor punchability as a lid material.

The propylene/ethylene block copolymer (a) is a copolymer comprising a propylene polymer (a1) and an ethylene-based polymer (a2), and has a density of 0.90 to 0.96 g/cm ³ . is preferred. If the density is less than 0.90 g/cm ³ , the mechanical strength of the film may be low, and the slit property after film formation or the film may stretch during the lamination process, resulting in poor process passability. Moreover, when the density exceeds 0.96 g/cm ³ , the crystallinity of the film may become high, and the lid tear resistance may deteriorate. The polyethylene-based resin is preferably composed of one or more resin compositions selected from ethylene/α-olefin random copolymer elastomer and linear low-density polyethylene.

The ethylene/α-olefin random copolymer elastomer preferably has a density of 0.860 to 0.900 g/cm ³ , more preferably 0.865 to 0.895 g/cm ³ . MFR (190° C.) is preferably 0.2 to 20.0 g/10 minutes, more preferably 0.5 to 10.0 g/10 minutes. The α-olefin can be preferably selected from propylene, 1-butene and 1-octene, and specifically ethylene-propylene copolymer, ethylene-1-butene copolymer and ethylene-1-hexene copolymer. preferable.

The linear low-density polyethylene may be obtained using a single-site or multi-site catalyst, and the comonomers include 1-butene, 1-hexene, 4methyl-1-pentene, 1 - You can choose octene. Linear low-density polyethylene has a higher melting point (Tm) than high-pressure low-density polyethylene, improves the heat resistance of the film, and has excellent cold resistance, resulting in strong lid tear resistance. Generally, the density is preferably 0.905-0.95 g/cm ³ , more preferably 0.910-0.940 g/cm ³ . MFR (190° C.) is preferably 0.5 to 100 g/10 minutes, more preferably 1 to 20 g/10 minutes.

In the support layer and heat seal layer of the present invention, specific additives, specifically erucamide, are added to the extent that the object of the present invention is not impaired, in order to ensure slipperiness suitable for film processing and lamination suitability. Organic lubricants, antioxidants having a molecular weight of 500 or more, inorganic particles such as silica, zeolite and calcium carbonate, and organic particles such as polymethyl methacrylate crosslinked particles may be selected and used. In addition, it may contain an antioxidant, a heat stabilizer, an antistatic agent, and the like, which improve the film formability. Selvages, slit scraps, etc. generated during the production of the laminated film of the present invention can be mixed and used in the support layer, if necessary, as long as they do not impair the effects of the present invention.

Moreover, a plant-derived resin (hereinafter sometimes referred to as a biomass resin) may be selected and used for the purpose of reducing environmental load. At that time, the index representing the ratio (% by mass) of plant-derived raw materials in the total composition is called biomass content, which is contained at a certain concentration in plant-derived raw materials and is almost absent in petroleum-derived raw materials. By measuring the concentration of radioactive carbon (C ¹⁴ ) by accelerator mass spectrometry, the degree of biomass (%) can be calculated. However, in recent years, even without accelerator mass spectrometry of the actual product, the value of the minimum biomass degree of each plant-derived raw material is provided by the raw material manufacturer, so each plant-derived raw material provided by these raw material manufacturers Based on the minimum biomass degree and the blending amount of each plant-derived raw material, the biomass degree, which is the ratio (%) of the plant-derived raw material in the entire composition, can be calculated substantially accurately.

Polyterpene resin is preferable as the plant-derived resin. Polyterpene resins include α-pinene, β-pinene, dipentene, styrene-modified terpene and hydrogenated products thereof.

The content of the plant-derived polyterpene resin is preferably 1 to 50% by mass based on the entire film. If the content is less than 1% by mass, the addition effect may not be obtained, and if the content exceeds 50% by mass, the heat seal strength may decrease.

The biomass content of the laminated film of the present invention is preferably 1% or more and 45% or less, more preferably 3% or more and 40% or less. If the biomass degree is less than 1%, the contribution to reducing the environmental load is low, and the higher the biomass degree, the higher the contribution to reducing the environmental load. may become brittle and workability may deteriorate. The thickness of the laminated film of the present invention is preferably 15-100 μm. The thickness of the support layer is preferably 10 to 70 μm, more preferably 13 to 60 μm, because of good punchability.

The thickness of the heat seal layer is preferably in the range of 1-30 μm, preferably 1.5-20 μm. If the thickness of the heat seal layer exceeds 30 μm, when the heat seal layer is peeled off, appearance defects called stringiness, feathering, and film residue may occur. Seal strength may not be obtained.

Here, stringiness refers to the state in which the film stretches like a thread and peels off when the film is opened, and feathering and film residue refer to the state in which the film remains in the container of the adherend and peels off when the film is opened. Say.

In the laminated film of the present invention, at least one other substrate layer selected from polyamide film, polyester film, printed paper, and metal foil is laminated on the support layer side, alone or in combination, as necessary. preferably used. Polyamide films include nylon 6, nylon 11, nylon 66, etc. Among them, biaxially oriented nylon 66 film is more preferable in terms of heat resistance and moisture resistance. Examples of the polyester film include biaxially stretched polyethylene terephthalate film (hereinafter sometimes abbreviated as PET), biaxially stretched polyethylene naphthalate film, biaxially stretched polybutylene terephthalate film, etc. Among them, biaxially stretched polyethylene terephthalate film. However, it is generally preferable in terms of heat resistance and film price. Examples of the metal foil include aluminum foil and copper foil, with aluminum foil being more preferred. Examples of printing paper include synthetic paper, high-quality paper, medium-quality paper, art paper, coated paper, and raw paper, but art paper is preferable in view of the quality of printing.

The thickness of the polyamide film or polyester film is preferably in the range of 10 to 100 μm, and in particular, when it is in the range of 12 to 50 μm, the suitability for printing is good, and when it is used as a lid material, the lid tear resistance and punchability are improved. preferable.

The thickness of the metal foil is preferably in the range of 5 to 30 μm from the standpoint of punchability, handleability and economy when used as a cover material.

The method of laminating these other base material layers on the support layer side is not particularly limited, but a method of laminating via an adhesive, a hot-melt agent, or a low-melting extrusion laminating resin can be mentioned.

Next, an example of the method for producing the laminated film of the present invention will be described.

Using two extruders, from one extruder, ethylene propylene having a density of 0.90 to 0.96 g/cm ³ and an MFR (230° C.) of 1 to 10 g/min as a support layer. A block copolymer and an ethylene/α-olefin random copolymer having a density of 0.865 to 0.895 g/cm ³ and an MFR (190°C) of 0.5 to 10.0 g/10 minutes as a polyethylene resin. A resin composition mixed with a coalesced elastomer is extruded at 200 to 280° C., and a heat seal layer having a density of 0.910 to 0.940 g/cm ³ and an MFR (190° C.) of 1.0 is extruded from another extruder. Linear low density polyethylene in the range of 0 to 40.0 g/10 min, density in the range of 0.880 to 0.930 g/cm ³ and MFR (190°C) in the range of 1.0 to 20.0 g/10 min. and an ethylene/α-olefin random copolymer elastomer having a density of 0.865 to 0.895 g/cm ³ and an MFR (190°C) of 0.5 to 10.0 g/10 min. and an ethylene/propylene random copolymer having a density of 0.90 to 0.96 g/cm ³ and an MFR (230°C) of 1 to 30 g/min are extruded at 200 to 250°C. , laminated with a co-extrusion multilayer die. Here, the film is extruded so that the thickness of the support layer/heat seal layer is, for example, 45 μm/5 μm, cast with cooling rolls at 25 to 50° C., cooled and solidified to form a laminated film. Subsequently, the surface of the support layer is subjected to corona discharge treatment, if necessary.

The present invention will be described based on examples, but the present invention is not limited to these.
Methods for measuring properties and evaluating effects in the present invention are as follows.

(1) Density of Resin Density was measured according to the density gradient tube method specified in JIS K 7112 (1980).

(2) Film thickness Using a dial gauge thickness gauge (JIS B 7509 (1992), stylus 5 mmφ flat type), measure 10 points at intervals of 10 cm in the longitudinal direction and width direction of the film, and the average value and

(3) Thickness of each layer A cross section of the film is cut out with a microtome, and a digital microscope VHX-5000 type (manufactured by Keyence Corporation) is used to observe the cross section at a magnification of 1000 times. The thickness of each layer was obtained by measuring the distance in the thickness direction of each layer and calculating back from the magnification. In determining the thickness of each layer, 5 cross-sectional photographs at 5 locations arbitrarily selected from mutually different measurement fields were used, and the average value thereof was calculated.

(4) Melt flow rate (MFR)
Polyethylene resin was measured at 190°C and polypropylene resin was measured at 230°C according to JIS K 7210 (1999).

(5) Method for preparing composite film for sealing On the support layer side of the laminated film, PET having a thickness of 12 μm was dry-laminated using a polyurethane adhesive at a coating amount of 2 g/m ² , and aged at 40° C. for 72 hours to obtain a sample. A composite film for sealing was used.

(6) Evaluation polypropylene sheet (adherend)
A homopolypropylene (PP-2 described later) resin is melted from an extruder at a temperature of 220 to 230 ° C., extruded from a die into a film, cast with a cooling roll at 25 to 50 ° C., cooled and solidified, and a 300 μm thick polypropylene for evaluation. created a sheet.

(7) Dependence of heat seal strength on seconds The composite film for sealing prepared in (5) was cut into 100 mm × 15 mm, and the heat seal layer was laminated on the 300 μm polypropylene sheet for evaluation prepared in (6), and the tester A flat plate heat seal tester (TP-701B) manufactured by Sangyo Co., Ltd. was used under conditions of a sealing temperature of 200° C., a sealing pressure of 2 kg/cm ² , and a sealing time of 1 second and 4 seconds. A sample heat-sealed by heating one side from the PET side at a tensile speed of 300 mm / min using Tensilon (RTC-1210A) manufactured by Orientec Co., Ltd. at a room temperature of 23 ° C. Heat when peeled 180 ° Seal strength was measured. At that time, the average value of the measured values of n number 10 is taken for one sample, and those with heat seal strength in the range of 15 to 27 N / 15 mm are evaluated as good sealability and peelability, and those outside this range. was x. In addition, under the conditions of 1 second and 4 seconds at 200° C., samples with a difference in heat seal strength of 7 N/15 mm or less were evaluated as having good opening stability, and were evaluated as x.

(8) Temperature dependence of heat seal strength Cut out the composite film for sealing prepared in (5) to 100 mm × 15 mm, put the heat seal layer on the polypropylene sheet for evaluation of 300 μm prepared in (6), and tester industry Using a flat plate heat seal tester (TP-701B) manufactured by Co., Ltd., the sealing temperature was 150° C. and 200° C., the sealing pressure was 2 kg/cm ² , and the sealing time was 1 second. A sample heat-sealed by heating one side from the PET side at a tensile speed of 300 mm / min using Tensilon (RTC-1210A) manufactured by Orientec Co., Ltd. at a room temperature of 23 ° C. Heat when peeled 180 ° Seal strength was measured. At that time, the average value of the measured values of n number 10 is taken for one sample, and the heat seal strength at a heat seal temperature of 150 ° C. is in the range of 10 to 20 N / 15 mm, and the heat seal strength at a heat seal temperature of 200 ° C. is 15 to 27 N / Those in the range of 15 mm were rated as good in sealing and peeling properties, and those outside the range were rated as x. Those having a seal temperature stability of 15 mm or less were evaluated as ◯, and those outside this range were evaluated as x.

(9) Punchability The composite film for sealing prepared in (5) was sampled to 50 mm × 50 mm, set in a sample holder with a hole of 20 mm in diameter, and Tensilon (RTC-1210A) manufactured by Orientec Co., Ltd. was used. A needle (diameter 1.0 mm, tip shape 0.5 mm) was pierced at a speed of 50±5 mm per minute, and the elongation of the film was measured at the time of piercing. When the elongation of the film was less than 3 mm, it was evaluated as ◯, and when it was 3 mm or more, it was evaluated as x.

(10) Peeling Appearance When the heat seal strength measurement sample prepared in (7) was peeled by hand, the peeling appearance was visually evaluated, and stringiness and film residue were determined as follows.

◯: No stringiness or film residue is observed. x: Long stringiness of 1.5 mm or more and film residue remain.

(11) Lid Tearability A sample of 100 mm × 100 mm was cut from the composite film for sealing prepared in (5), and the heat seal layer and a polypropylene container (95φ × 61.9H, manufactured by Tokan Kogyo Co., Ltd.) were overlapped, Using a hand sealer manufactured by Ashinpak Kogyo Co., Ltd., a heat-sealed sample was prepared under the conditions of a heat-sealing temperature of 200 ° C., a sealing pressure of 0.3 MPa, and a sealing time of 2 seconds. When the composite film was not torn, it was evaluated as ◯, and when the composite film was torn, it was evaluated as x.

(12) Film formability When the laminated film is formed and wound up, the film is not torn, the winding tension is easy to adjust, and wrinkles do not occur. , and the case where the breaking elongation or breaking strength of the film was low and the film was broken during film formation was evaluated as x.

The raw materials used in this example are as follows.
(1) Ethylene/propylene block polymer (BPP-1)
MFR = 2.5 g/10 minutes, density = 0.900 g/cm3 ^, Tm = 163°C
(2) Ethylene-α-olefin random copolymer elastomer (E-1)
MFR = 3.6 g/10 min, density = 0.885 g/ ^cm3
(3) 1-butene copolymer linear low-density polyethylene (LL-1)
MFR=8.0 g/10 min, Density=0.920 g/cm ³ , Tm=123° C.
(4) 1-octene copolymer linear low density polyethylene (LL-2)
MFR = 2.2 g/10 min, density = 0.921 g/ ^cm3 , Tm = 120°C
(5) High pressure low density polyethylene (LD-1)
MFR = 7.0 g/10 minutes, density 0.919 g/cm ³ , Tm = 106°C
(6) Ethylene/propylene random copolymer (PP-1)
MFR = 6.0 g/10 min, density = 0.900 g/ ^cm3 , Tm = 145°C
(7) homopolypropylene (PP-2)
MFR = 8.0 g/10 min, density = 0.900 g/ ^cm3 , Tm = 163°C
(8) Plant-derived polyterpene resin (PT-1)
Softening point = 115°C, degree of biomass = 90%.

Example 1
As the support layer, a resin composition in which 95% by mass of ethylene/propylene polymer (BPP-1) and 5% by mass of ethylene-α-olefin random copolymer elastomer (E-1) are mixed is used, and as the heat seal layer, ethylene 30% by mass of propylene random copolymer (PP-1), 60% by mass of linear low-density polyethylene (LL-1), 5% by mass of high-pressure low-density polyethylene (PE-1), and ethylene-α-olefin random copolymer A resin composition mixed with 5% by mass of the combined elastomer (E-1) was charged into two extruders of a two-kind two-layer nonstretching film molding machine, and the support layer was heated at 260°C and the heat seal layer at 200°C. After melt-kneading at the extrusion temperature, the mixture was extruded through a two-kind, two-layer T-die at 230°C, quenched with a casting roll at 40°C to form a laminated film, and the support layer was subjected to corona discharge treatment. The total thickness of the laminated film obtained was 50 μm, and the thickness of the heat seal layer was 5 μm. The film formability was good, and there was no curling of the edge during casting, and no wrinkles during winding, and the film could be wound stably. All the properties required for the laminated film of the present invention were satisfied.

Example 2
A laminated film was obtained in the same manner as in Example 1, except that the total thickness of the laminated film was 25 µm and the thickness of the heat seal layer was 5 µm. All the properties required for the laminated film of the present invention were satisfied.

Example 3
A laminated film was obtained in the same manner as in Example 1 except that linear low density polyethylene (LL-1) in the heat seal layer of Example 1 was changed to linear low density polyethylene (LL-2). All the properties required for the laminated film of the present invention were satisfied.

Example 4
The heat seal layer is composed of 40% by mass of ethylene/propylene random copolymer (PP-1), 55% by mass of linear low-density polyethylene (LL-1), and 5% by mass of ethylene-α-olefin random copolymer elastomer (E-1). A laminated film was obtained in the same manner as in Example 1, except that the resin composition was mixed by %. All the properties required for the laminated film of the present invention were satisfied.

Example 5
In the same manner as in Example 1, except that the support layer is made of a resin composition obtained by mixing 80% by mass of an ethylene/propylene polymer (BPP-1) and 20% by mass of an ethylene-α-olefin random copolymer elastomer (E-1). A laminated film was obtained. All the properties required for the laminated film of the present invention were satisfied.

Example 6
A laminated film was obtained in the same manner as in Example 1 except that the support layer was made of a resin composition obtained by mixing 80% by mass of ethylene/propylene polymer (BPP-1) and 20% by mass of linear low-density polyethylene (LL-2). rice field. All the properties required for the laminated film of the present invention were satisfied.

Example 7
The support layer is a mixture of 85% by mass of ethylene/propylene polymer (BPP-1), 5% by mass of ethylene-α-olefin random copolymer elastomer (E-1), and 10% by mass of plant-derived polyterpene resin (PT-1). A laminated film was obtained in the same manner as in Example 1, except that the resin composition was prepared in the same manner as in Example 1. All the properties required for the laminated film of the present invention were satisfied.

Comparative example 1
A laminated film was obtained in the same manner as in Example 1, except that the heat seal layer was made of 60% by mass of ethylene/propylene random copolymer (PP-1) and 40% by mass of linear low-density polyethylene (LL-1). The resulting film was evaluated in the same manner as in Example 1. A large amount of ethylene-propylene random copolymer is added to the heat seal layer, and regarding the heat seal strength depending on the number of seconds, the strength after heat sealing at a sealing temperature of 200 ° C. for 4 seconds is high, and the strength difference from heat sealing for 1 second is large. In addition, the difference in strength between heat-sealing at sealing temperatures of 150° C. and 200° C. for 1 second was large, and the required properties of the present invention were not satisfied.

Comparative example 2
The heat seal layer is made of 60% by mass of homopropylene (PP-2) and 40% by mass of linear low density polyethylene (LL-1), the total thickness of the laminated film is 50 μm, and the thickness of the heat seal layer is 30 μm. obtained a laminated film in the same manner as in Example 1. The resulting film was evaluated in the same manner as in Example 1. Since the melting point of homopolypropylene is high, the strength after heat-sealing at 150°C for 1 second is weak, and the heat-sealing strength, which is dependent on the number of seconds, is higher after heat-sealing at a sealing temperature of 200°C for 4 seconds, and the heat-sealing strength is higher for 1 second. In addition, since the heat seal layer is thick, severe stringiness occurs when peeled from the adherend, and the peeled appearance is poor.

Comparative example 3
A laminated film was obtained in the same manner as in Example 1, except that the heat seal layer was composed of 1% by mass of ethylene/propylene random copolymer (PP-1) and 99% by mass of linear low-density polyethylene (LL-1). The resulting film was evaluated in the same manner as in Example 1. The amount of ethylene-propylene random copolymer added to the heat-sealing layer was too small, and the heat-sealing strength was too weak to satisfy the properties required by the present invention.

Comparative example 4
As the support layer, a resin composition in which 50% by mass of ethylene/propylene polymer (BPP-1) and 50% by mass of ethylene-α-olefin random copolymer elastomer (E-1) are mixed is used, and as the heat seal layer, ethylene A laminated film was obtained in the same manner as in Example 1, except that the propylene random copolymer (PP-1) was 60% by mass and the linear low-density polyethylene (LL-1) was 40% by mass. Many ethylene/propylene random copolymers are added to the heat seal layer, and the heat seal strength, which depends on the number of seconds, increases. Since the proportion of the copolymer elastomer (E-1) was large, wrinkles occurred during winding, and since there was no rigidity, punchability was poor, and the required properties of the laminated film were not satisfied.

Comparative example 5
95% by mass of homopolypropylene (PP-2) and 5% by mass of ethylene-α-olefin random copolymer elastomer (E-1) as a support layer, and 60% by mass of ethylene/propylene random copolymer (PP-1) as a heat seal layer A laminated film was obtained in the same manner as in Example 1 except that the content was 40% by mass and the linear low density polyethylene (LL-1) was 40% by mass. Since the homopolypropylene (PP-2) of the support layer has high crystallinity, film tearing occurs during film formation, resulting in poor film-forming properties. However, the addition of ethylene-propylene random copolymer to the heat-sealing layer was large, and the heat-sealing strength dependent on the number of seconds increased, resulting in a large difference in strength, which did not satisfy the properties required by the present invention.

Claims (6)

A laminated film having a heat-sealing layer and one or more support layers, wherein the heat-sealing strength when heat-sealing the heat-sealing layer and a polypropylene sheet at 200 ° C. for 1 second and at 200 ° C. for 4 seconds is Laminated films each having 15 to 27 N/15 mm and a difference of 7 N/15 mm or less. A heat seal strength of 10 to 20 N/15 mm when the heat seal layer and the polypropylene sheet are heat sealed at 150° C. for 1 second, and the difference between the strength when heat sealed at 200° C. for 1 second is 10 N/15 mm or less. 2. The laminated film according to 1. 1. The heat seal layer is made of a resin composition in which a polyethylene resin and a polypropylene resin are mixed, and the polyethylene resin is 51% by mass to 95% by mass and the polypropylene resin is 5% by mass to 49% by mass. 3. or the laminated film according to 2. 4. The laminated film according to any one of claims 1 to 3, wherein the support layer comprises a resin composition obtained by mixing an ethylene/propylene block copolymer and a polyethylene resin. 4. The laminate film according to claim 3, wherein the polyethylene-based resin of the heat-seal layer is mainly composed of linear low-density polyethylene. The laminated film according to any one of claims 1 to 5, which has a thickness of 15 to 100 µm.