JP2001187436A - Multi-layer film and heat-sealable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer film for packaging, having heat sealing property and hot tack property best suited for rapid filling of liquid. SOLUTION: This multi-layer film is structured of two different kinds of ethylene/α-olefin copolymers (a) and (b) as a layer A and a layer B respectively, formed and laminated on each other. The copolymer (a) used has one melt point peak at 85-100 deg.C and the copolymer (b) likewise used has one or more melt point peaks at 85-105 deg.C and 106-125 deg.C respectively. The layer A serves as a heat-sealable face showing hot-tack properties and in order to enhance the hot tack, the copolymer (a) may be blended with an amorphous ethylene/α- olefin copolymer, an amorphous ethylene/vinyl acetate copolymer or a high pressure process low-density polyethylene. In addition, the layer B may be formed in a two-tier fashion with the copolymer (b) of a different density. Further, this multi-layer film may be formed as a heat-sealable film by laminating a base material layer on one multi-layer film. A polyamide film, a polyester film or a polypropylene film is preferably used as the base material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film and a heat-sealable film using the same, and more particularly, to at least two types of ethylene-.alpha.
The present invention relates to a multilayer film excellent in heat sealability in which an olefin copolymer forms each layer, and a heat sealable film further added with a base layer. The present invention also relates to a package using the heat sealable film.

[0002]

2. Description of the Related Art The packaging work of liquid soup used for instant foods and the like is performed through a process in which a continuously supplied plastic film forms a packaging bag and at the same time a liquid soup is rapidly filled therein. Has been done. The film properties required during the high-speed filling and packaging are mainly heat sealing properties and hot tack properties. Linear low-density polyethylene (L-LDPE) films have been more widely used than ever, but the demands for higher heat-sealing properties and hot-tack properties have been increasing in response to increasingly faster filling speeds. It is growing.

[0003] Recently, a new polyethylene produced by using a metallocene catalyst has been distributed in a field where L-LDPE has been used so far, which is expected to contribute to cost reduction and to develop a new application. . But,
In the case of the polyethylene single film, it is practically difficult to satisfy the above-mentioned advanced heat sealing property and hot tack property at the same time while satisfying the mechanical strength as a film. As a solution, improvement by forming a film with a blend resin and forming a composite film with another film has been studied.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been undertaken to develop a technology from the viewpoint of forming a composite film, and to provide a multilayer packaging film having heat sealing properties and hot tack properties suitable for high-speed liquid filling. Aim.

[0005]

That is, the present invention provides an A layer and a B layer in which two types of ethylene / α-olefin copolymers (a) and (b) are independently in contact with each other. The copolymer (a) has a single melting point peak as measured by DSC, and the copolymer (b) relates to a multilayer film having two or more melting point peaks.

The copolymer (a) has a melting point peak in the range of 85 to 100 ° C., and the copolymer (b) has a melting point peak in the range of 85 to 105 ° C. It is preferable that at least one of them exists in the range of -125 ° C, and that the copolymer (a) has a density of 0.890-0.902 (g / cm ³ ),
The copolymer (b) has a density of 0.903 to 0.940.
(G / cm ³ ).

[0007] The layer A is at least one selected from the group consisting of a copolymer (a), an amorphous ethylene / α-olefin copolymer, an ethylene / vinyl acetate copolymer and a high-pressure low-density polyethylene. It may be formed of a resin composition comprising one kind of polymer. In the case of such a resin composition, 60 to 95% by weight of the copolymer (a) and 5 to 40% by weight of the above polymer %.

The B layer is a (B-1) layer in contact with the A layer.
And layer (B-2) located on the opposite side to layer A.
The (B-1) layer may be formed at that time.
Resin density is higher than the resin density forming the (B-2) layer.
It is desirable to be small, for example, to form the (B-1) layer.
Resin density is 0.903 to 0.912 (g / cm^Three)so
Yes, the density of the resin forming the (B-2) layer is 0.913 to
0.940 (g / cm ^Three) Is preferable.

[0009] Further, the present invention provides a heat sealing method wherein the above-mentioned multilayer film is laminated and integrated on at least one surface of a film serving as a base material layer through a B layer, and the A layer can be used as a heat sealing surface. Related to rubble film. Here, as a usable substrate layer, a polyamide film,
Examples thereof include a polyester film and a polypropylene film. Further, the present invention relates to a package using such a heat-sealable film, forming a packaging bag by heat sealing between the layers A, and containing therein a content such as a liquid material. .

[0010]

DETAILED DESCRIPTION OF THE INVENTION Next, the constitution of the multilayer film, the heat-sealable film and the package using the same according to the present invention will be specifically described.

Ethylene / α-olefin copolymer As the ethylene / α-olefin copolymer used in the present invention, at least two types (a) and (b) are used. Is a copolymer with an α-olefin. The two types of copolymers (a) and (b) have the α-
It can be produced by adjusting the type and content of the olefin and adjusting the polymerization conditions.

Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-heptene.
Examples thereof include octene and 1-decene, and among them, 1-hexene, 4-methyl-1-pentene and 1-octene are preferable. One of these comonomers may be used in the copolymerization, or two or more thereof may be used in combination. The ethylene content in the copolymer is
80 to 99.9, preferably 90 to 99.5, more preferably 95 to 99 (mol%), the α-olefin content is
When the content is 0.1 to 20, preferably 0.5 to 10, and more preferably 1 to 5 (mol%), and the content of the copolymer component is within this range, the polymer is crystalline and has high transparency. Can be obtained.

One type of ethylene / α-olefin copolymer
(A) shows the melting point peak detected by DSC measurement.
One, and its peak is preferably in the range of 85 to 100 ° C.
Exists in the enclosure. The preferred density range is 0.8
90 to 0.902 (g / cm ^Three) And ASTM
190 ° C under 2.16 kg load according to D-1238
Melt flow rate value measured in 0.5 to 10 (g
/ 10 minutes).

The other ethylene / α-olefin copolymer (b) has two or more melting point peaks detected by DSC, and these peaks are in the range of 85 to 105 ° C. and 106 to 125 ° C. It is preferred that at least one is present. Also, the density of this copolymer is
0.890 to 0.902 (g / cm ³ ),
It is desirable that the MFR be in the range of 0.5 to 20 (g / 10 minutes).

Here, for the DSC measurement, about 5 mg of a sample was packed in an aluminum pan using a differential scanning calorimeter DSC220 type device manufactured by Seiko Denshi Kogyo KK at a rate of 10 ° C./min.
Temperature, and kept at 180 ° C. for 5 minutes.
The temperature is lowered to room temperature at a rate of 10 ° C./min, and the temperature is increased again at a rate of 10 ° C./min. The melting point is determined from the position of the peak appearing in the measured endothermic curve. The density is
The strand obtained at the time of measuring the melt flow rate (MFR) is heat-treated at 120 ° C. for 1 hour, then slowly cooled to room temperature over 1 hour, and the sample is measured by using a density gradient tube.

Ethylene having the above-mentioned composition and physical properties
The α-olefin copolymers (a) and (b) can be produced using an olefin stereoregular polymerization catalyst including a metallocene catalyst. The metallocene catalyst is
Usually, a metallocene catalyst component comprising a transition metal compound of Group IVB of the Periodic Table having at least one ligand having a cyclopentadienyl skeleton, an organic aluminum oxy compound catalyst component, a particulate carrier, an organic aluminum compound, an ionized ion It is formed by appropriately combining the active compounds. In the presence of such a catalyst, ethylene and α-olefin are copolymerized under the conditions of a gas phase, a slurry state or a solution state of a liquid phase to obtain ethylene / α-olefin.
-Olefin copolymers (a) and (b) can be obtained. A metallocene catalyst and a polymerization method using the same are described in, for example, JP-A-6-9724 and JP-A-6-1.
No. 36195, JP-A-6-136196, and JP-A-6-207057.

The ethylene / α-olefin copolymer produced in the presence of the above-mentioned metallocene catalyst is characterized in that its molecular weight distribution and composition distribution are narrower than those of the copolymers used so far. is there. Therefore, the amount of solvent extraction derived from low molecular weight components is small, and there is no stickiness on the film surface, which is suitable for the production of packaging films.

Various additives can be appropriately added to the ethylene / α-olefin copolymer without departing from the object of the present invention. For example, phenolic or phosphorus antioxidants, heat stabilizers, antistatic agents,
Examples include anti-blocking agents, slip agents, anti-fogging agents, and coloring agents.

Multilayer Film The multilayer film according to the present invention is a laminate in which at least two types of ethylene / α-olefin copolymers form separate independent layers and are in contact with each other. FIG. 1 is a cross-sectional view of the multilayer film. The multilayer film 1 is composed of an A layer 2 formed from an ethylene / α-olefin copolymer (a) and an ethylene / α-olefin copolymer (b). This indicates that the A layer 2 and the B layer 3 are adjacent to each other in the lamination relationship.

The thickness of the multilayer film is not particularly limited, but is preferably in the range of 30 to 100 μm. The thicknesses of the A layer and the B layer constituting the multilayer film are preferably such that the A layer is thinner or substantially equal in thickness to the B layer, and the thickness ratio is (A) / (B ), 10/90 to 50 /
It is particularly preferred that it is in the range of 50.

The layer A is formed from a low melting point ethylene / α-olefin copolymer (a) as described later,
Since the film has a soft waist, blocking is likely to occur, and its mechanical suitability is not very good. In order to improve this point, a formulation containing a large amount of additives is generally used, but the low-temperature sealability is impaired. However, in a preferred embodiment of the present invention, when the layer A and the layer B are provided within the above-mentioned thickness range, the multilayer film exhibits good mechanical suitability.

The ethylene / α-olefin copolymer (a) forming the layer A has one melting point peak, preferably in the range of 85 to 100 ° C., and has a relatively low melting point. Is a copolymer of Further, it is a low-density copolymer having a density preferably in the range of 0.890 to 0.902 (g / cm ³ ). Since the copolymer (a) has such physical properties, it is possible to form a surface heat seal layer having good hot tack even if the layer thickness is reduced.

The resin forming the layer A may be composed of only the above-mentioned ethylene / α-olefin copolymer (a), or may be formed by heating the ethylene / α-olefin copolymer (a) Resins, elastomers, additives, and the like that further improve the sealing property and hot tack property can be used.

A particularly preferred compounding polymer is at least one polymer selected from the group consisting of an amorphous ethylene / α-olefin copolymer, an ethylene / vinyl acetate copolymer and a high-pressure low-density polyethylene. is there. Such a polymer has good compatibility with the ethylene / α-olefin copolymer (a). When the polymer is blended and used as a resin composition, the composition ratio is such that the copolymer (a) is 60 to 95, preferably 70 to 90% by weight,
The amount of the polymer to be blended is desirably 5 to 40, preferably 10 to 30% by weight. When the component content of the composition is within the above range, the heat sealing temperature can be lowered, the heat sealing strength can be improved, and furthermore, so-called thinning during heat sealing can be prevented, so that the high heat sealing strength There is an advantage that the thickness of the layer A which is the heat seal layer can be further reduced while maintaining the above.

Here, the amorphous ethylene / α-olefin copolymer includes ethylene and an α-olefin having 3 to 10 carbon atoms such as ethylene / propylene copolymer and ethylene / 1-butene copolymer. Is a low crystalline or amorphous copolymer containing 10 to 50 (mol%). The ethylene / vinyl acetate copolymer is a copolymer having a vinyl acetate content of 3 to 20% by weight. High pressure method low density polyethylene
General grades can be used. These amorphous ethylene / α-olefin copolymers, ethylene / vinyl acetate copolymers and high-pressure low-density polyethylenes are available from ASTM D
The melt flow rate measured at 190 ° C under a load of 2.16 kg is 0.5 to 20 (g / 1
0 minutes).

The resin forming the layer B has two or more melting point peaks, and has a preferable density of 0.903 to 0.940.
(G / cm ³ ) in the range of ethylene / α-olefin copolymer (b), which is on the higher density side than ethylene / α-olefin copolymer (a). The layer B has an effect of maintaining the mechanical strength of the multilayer film and further improving the heat sealing property of the layer A acting as a heat sealing surface. Various resin modifiers and additives may be added to the resin forming the layer B as long as the object of the present invention is not impaired.

Further, the B layer is not limited to one layer but can be formed in two or more layers. FIG. 2 is a cross-sectional view showing one example of a multilayer film in which the B layer is composed of two layers. The multilayer film 4 includes an A layer 2 and a (B-1) layer 3 adjacent to the A layer.
1. A laminate comprising a (B-2) layer 32 disposed on the side opposite to the A layer, wherein the A layer, the (B-1) layer, and the (B-2) layer are laminated in this order. And integrated.

The resin forming the layer (B-1) and the layer (B-2) is also the ethylene / α-olefin copolymer (b) within the range of the physical properties of the resin forming the layer B. However, when the resin density constituting the (B-1) layer is smaller than the resin density constituting the (B-2) layer, the heat sealing property and the hot tack property of the A layer are improved, and the mechanical strength is improved. Excellent effect of enhancing. Particularly, the density of the resin constituting the (B-1) layer is 0.903 to 0.912 (g / c).
m ³ ), and the density of the resin constituting the layer (B-2) is 0.1.
It is preferably from 913 to 0.940 (g / cm ³ ). Even when the B layer has three or more layers, it is preferable to provide a density gradient such that the resin density increases from the A layer on the front surface to the back layer.

The multilayer film composed of the layer A and the layer B can be formed by a known method such as a method in which a resin film constituting each layer is formed in advance and bonded by heating, and a method in which one film is extruded and laminated on another film. The method can be used. Among them, a preferable molding method is to supply a resin for forming the layer A and a resin for forming the layer B to separate extruders, and join the respective molten resins with a co-extrusion T-die or a circular die to form a co-extruded film. It is a method of molding as. This makes it possible to favorably manufacture multilayer films having different thickness configurations and a small overall thickness. For the production of a multilayer film of three or more layers,
Particularly, the coextrusion molding method is suitable.

The multilayer film described above can be used not only as a packaging film having good heat sealing properties by itself, but also as a plastic material such as other films, a metal material such as aluminum foil, paper, wood, By laminating with ceramics or the like, it can be used in a wide range of fields. For example, a heat sealable film, which is a laminate with a special film described later, is suitable for liquid packaging.

The heat sealing is performed by further providing a base layer C on the B layer side of the multilayer film composed of the heat sealable film A layer and the B layer, or by laminating the multilayer film on both sides of the base layer C. It is possible to obtain a heat syllable film having properties and adding functions such as mechanical strength. FIG. 3 is a sectional view showing an example of the heat sealable film. The heat sealable film 6 has a heat sealable surface A
The layer 2, the B layer 3, and the base material layer C5 are laminated and integrated in this order to form a packaging film.

The base material layer C is a layer mainly responsible for functions such as mechanical strength and gas barrier properties of the film, and preferably has a thickness of 5 to 50 μm. The film layer forming the base layer is a functional film having physical properties such as high mechanical strength, high gas barrier properties, and high heat resistance. In particular, a polyamide film such as nylon 6, nylon 6,6, a polyester film such as polyethylene terephthalate or polybutylene terephthalate, or a polypropylene film is suitable, and this film layer is formed of an unstretched film, a uniaxially stretched film, or a biaxially stretched film. It may be an axially stretched film.

The heat-sealable film composed of the layers A, B and C can be produced by laminating the films forming each layer sequentially or simultaneously, and for example, a co-extrusion molding method can be used. In addition, the preformed A layer and B layer
It can be manufactured by joining a multilayer film composed of layers and a film that becomes the substrate layer C by dry lamination or extrusion lamination. In the case of dry lamination, a urethane-based or isocyanate-based adhesive is applied to one of the adhesive surfaces, and if necessary, one or both adhesive surfaces are subjected to corona discharge treatment, flame treatment,
If bonding is performed after an oxidation treatment or the like, strong bonding can be achieved. In the case of extrusion lamination, it is possible to similarly strongly adhere by extruding molten polyethylene or adhesive polyethylene between both layers.

Using the heat-sealable film, a package of a liquid food or the like can be manufactured. First, as an example, two heat-sealable films are arranged and layered so that the A layers face each other, and the A layers are firmly bonded to each other on the outer periphery of the packaging bag by a heat sealing method. A seal part is formed, and a packaging bag is formed as a whole. When a liquid food or the like is supplied while forming the packaging bag, a package is completed at once.

In this package, the base material layer C having functions such as high gas barrier property and high mechanical strength plays a role of protecting the contents from invasion of external oxygen, impact and the like. Since the resin forming the layer A exhibits high heat sealing strength and hot tackiness with the help of the resin forming the layer B, this heat sealable film is used for packing the contents at a high speed while sealing the contents. It is a packaging film that is convenient for the system. That is, in high-speed filling packaging of liquid,
Since a packaging method is used in which a packaging bag is produced by heat-sealing the periphery of the film and the liquid is immediately filled, the excellent hot tack property of the heat-sealable film is extremely effective. Therefore, bags made from this heat-sealable film are suitable for high-speed packaging of liquid contents such as liquid soups for instant foods using a high-speed filling machine.

[0036]

EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples. First, the various resins used are as follows. (1) Copolymer <a>: Ethylene / α-olefin copolymer manufactured using a metallocene catalyst Kernel KF-360 (trade name, manufactured by Nippon Polychem Co., Ltd.) Density = 0.898 MFR = 3.5 Melting point peak 91 ° C. (2) Copolymer <b>: ethylene / 1-hexene copolymer produced using a metallocene catalyst Density = 0.913 MFR = 4.0 Melting point peak 99, 120 ° C.

(3) Copolymer <c>: Ethylene / 1-hexene copolymer produced using a metallocene catalyst Density = 0.903 MFR = 4.0 Melting point peak 92, 120 ° C. Combined <d>: Amorphous ethylene / 1-octene copolymer Density = 0.870 MFR = 4 No melting point

(5) EVA: Ethylene / vinyl acetate copolymer (vinyl acrylate content: 19 wt%) Density = 0.940 MFR = 15.0 No melting point

(Example 1) Copolymer <a> was converted to 40 mmφ
(L / D = 28: manufactured by Modern Machinery) while the copolymer <b> was fed to another 40 mmφ extruder (L / D = 28: manufactured by Modern Machinery) The molten resin was guided to a co-extrusion die and taken up as a two-layer film. The total thickness of the co-extruded film was 50 μm, of which the layer (A) of the copolymer <a> was 25 μm,
The layer (B-1) of b> was 25 μm.

Next, a 15 μm-thick biaxially stretched nylon film (Ny) (C layer) was dry-laminated on one surface layer (B-1) of this co-extruded film using an isocyanate-based adhesive. A three-layer film having a / B-1 / C configuration was obtained.

The A layer surfaces of the two three-layer films were faced to each other, and heat sealing was performed at a sealing temperature of 80 ° C. to 120 ° C. every 10 ° C. The measurement of this heat seal was performed using a hot-tack heat sealer tester HT manufactured by THELER ENGINEERING Co., Ltd., and the seal conditions were a seal time of 300 msec and a seal pressure of 2 kg / cm ² . Then, the peel strength (N / in
ch) was obtained, and the value was used for evaluation of hot tack strength. Table 1 shows the measurement results.

(Examples 2 to 4) Example 1 was repeated except that the total thickness of the layer A and the layer (B-1) was changed to 50 μm and the thickness ratio was changed as shown in Table 1. And a two-layer film was formed. Next, the two-layer film and the biaxially stretched nylon film (C layer) were laminated to obtain a three-layer film. The hot tack strength was measured and is also shown in Table 1.

(Examples 5 to 6) A two-layer film was obtained in the same manner as in Example 4, except that the resin composition constituting the layer A was changed as shown in Table 1. Thereafter, it was laminated with a biaxially stretched nylon film (C layer), and the hot tack strength of this three-layer film was measured. The results are shown in Table 1.

Example 7 Coextrusion molding to a thickness of 50
A three-layer film having a (A / B-1 / B-2) configuration of μm was produced. The resin constituting each layer and the thickness configuration were as shown in Table 1. A biaxially stretched nylon film (C layer) was dry-laminated on the (B-2) layer surface of the three-layer film to obtain a four-layer film having an (A / B-1 / B-2 / C) configuration. The hot tack strength of this four-layer film was measured, and the measurement results are shown in Table 1.

[0045]

[Table 1]

As is clear from the hot tack strength described in Table 1, the three- to four-layer films obtained in Examples 1 to 7
It shows high hot tack strength at 90 to 110 ° C.
The fact that the three- or four-layer film exhibits a high hot tack strength at a low temperature means that the heat sealing time can be shortened, and is suitable for a high-speed packaging operation. Also,
Showing a high hot tack strength in a wide sealing temperature range means that, for example, even if the sealing bar temperature of the packaging machine fluctuates somewhat, it can sufficiently cope with it, and the packaging operation can be facilitated.

[0047]

In the multilayer film according to the present invention, the resin forming the layer A has a high hot tack property even at the time of low-temperature sealing, and the resin forming the layer B holds the layer A. Thus, a film having excellent heat sealing properties can be obtained.

Further, the heat-sealable film according to the present invention in which the base material layer C is provided on the back surface of the layer B, has the excellent hot tack property of the layer A, and the resin forming the layer B is composed of the layer A and the base. The material layer C is retained, and the functions of the base layer C such as high gas barrier property and mechanical strength increase are added.
A high-performance film with excellent heat sealing properties can be obtained. Therefore, this heat sealable film is suitable as a high-speed filling packaging material for liquids.

[Brief description of the drawings]

FIG. 1 is a sectional view of a two-layer film according to the present invention.

FIG. 2 is a sectional view showing an example of a three-layer film according to the present invention.

FIG. 3 is a cross-sectional view showing one example of a heat sealable film according to the present invention.

[Explanation of symbols]

 1 ... 2 layer film 2 ... A layer 3 ... B layer 31 ... (B-1) layer 32 ... (B-2) layer 4 ... 3 layer film 5: Base layer C 6: Heat-sealable film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shuichi Kinoshita Inventor F-term (reference) 3E086 AD01 BA04 BA15 BB51 BB90 CA01 DA08 4F100 AK01C AK06A AK07C AK41C AK46C AK48 AK51GBAKA AK62D AK68A BA04 BA07 BA10A BA10C BA15 CB00 GB15 JA04A JA04B JA04D JA12A JA13A JA13B JA13D JA20C JD02 JL12 JL13A YY00 YY00A YY00B YY00C YY00D

Claims (13)

[Claims] 1. An ethylene / α-olefin copolymer (a) and (b) each independently form an A layer and a B layer which are in contact with each other, and the copolymer (a) has a DSC
A multilayer film having one melting point peak when measured, and the copolymer (b) having two or more melting point peaks. 2. The copolymer (a) has a melting point peak of 85.
The polymer (b) has a melting point peak in the range of 85 to 105 ° C and at least one melting point peak in the range of 106 to 125 ° C. The multilayer film according to the above. 3. The copolymer (a) has a density of 0.890.
~0.902 (g / cm ³⁾ a and a copolymer density of claim 1 or 2, characterized in that the 0.903~0.940 (g / cm ³⁾ of (b) Multilayer film. 4. The multilayer film according to claim 1, wherein said copolymers (a) and (b) are polymers produced by using a metallocene catalyst. 5. The layer A is selected from the group consisting of a copolymer (a), an amorphous ethylene / α-olefin copolymer, an ethylene / vinyl acetate copolymer and a high-pressure low-density polyethylene. 5. A resin composition comprising at least one polymer.
The multilayer film according to any one of the above. 6. The composition according to claim 1, wherein the layer A comprises a copolymer (a) 60 to 95.
% By weight and an amorphous ethylene / α-olefin copolymer,
2. A resin composition comprising 5 to 40% by weight of at least one polymer selected from the group consisting of ethylene / vinyl acetate copolymer and high-pressure low-density polyethylene. 5. The multilayer film according to any one of items 1 to 4. 7. The method according to claim 1, wherein said multilayer film has a thickness of 30 to 100.
7. The multilayer film according to claim 1, wherein the thickness ratio between the layer A and the layer B (A) / (B) is 10/90 to 50/50. 8. The B layer is formed of two layers: a (B-1) layer in contact with the A layer, and a (B-2) layer located on the opposite side of the A layer. The multilayer film according to any one of claims 1 to 7, wherein the resin density forming the (1) layer is lower than the resin density forming the (B-2) layer. 9. The resin for forming the layer (B-1) has a density of:
0.903 to 0.912 (g / cm ^Three) And (B−
2) The density of the resin forming the layer is 0.913 to 0.940.
(G / cm^Three9. The method according to claim 8, wherein
Multilayer film. 10. A multilayer film according to any one of claims 1 to 9, wherein said multilayer film is laminated and integrated on at least one surface of a film serving as a base material layer with said layer B as a bonding surface, and said layer A is a heat-sealing surface. A heat sealable film characterized in that it can be used as a heat sealable film. 11. The method according to claim 11, wherein the base material layer is a polyamide film,
The heat-sealable film according to claim 10, wherein the heat-sealable film is a film selected from the group consisting of a polyester film and a polypropylene film. 12. The heat-sealable film according to claim 10, wherein said base material layer has a thickness of 5 to 50 μm. 13. A heat sealable film according to any one of claims 10 to 12, wherein the periphery of the packaging bag is sealed by heat sealing between the layer A surfaces, and the contents are stored in the packaging bag. Packaging.