JP2001002079A - Packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging bag in which it has a superior combination of an opening characteristic attained by tearing action and a rigidity and further it has a superior combination with an anti-environmental stress cracking characteristic. SOLUTION: A packaging bag composed of a laminated film is made such that an inner surface film of the laminated film is a polyethylene-based resin film satisfying an equation of T1<0.0969×E1 -0.0023, where T1 is a tearing strength (kgf) of the inner surface film, E1 is a product of resilient strength (kgf/cm) of the inner film, i.e., a modulus of elasticity (kgf/cm2) and a film thickness (cm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging bag, and more particularly to a packaging bag which is excellent in a combination of tear-openability and rigidity, and moreover excellent in a combination of environmental stress crack resistance. .

[0002]

2. Description of the Related Art Heretofore, packaging bags such as standing pouches have been known in which an inner film of an olefin resin is laminated on a base material such as a biaxially stretched plastic film or aluminum foil.

Japanese Patent Application Laid-Open No. 7-241967 is characterized in that at least the outer film is a biaxially stretched plastic film, and the inner film is a laminated film which is a coextruded film of linear low-density polyethylene having different densities. A standing pouch is described.

Japanese Patent Application Laid-Open No. 7-232418 discloses a packaging material comprising at least a base film layer and a heat-sealing resin layer, wherein the innermost layer of the heat-sealing resin layer is ethylene polymerized by using a single-site catalyst. -A packaging material characterized by being an α-olefin copolymer film is described.

In JP-A-10-24539, a low-density polyethylene layer formed by a single-site catalyst is formed on at least one surface of a base film via a low-density polyethylene or linear low-density polyethylene layer. A tear-resistant packaging material characterized by this is described.

Japanese Patent Application Laid-Open No. 10-86300 discloses a density
Is 0.860 to 0.925 g / cm ³, Weight average molecular weight
/ Linear low-density polyethylene having a number average molecular weight of 1 to 3
A sealing layer having a density of 0.900 to 0.935 g /
cm³Base made of linear low-density polyethylene
Layer, density 0.910 to 0.950 g / cm³The line that is
Layer and biaxial roll made of fibrous low-density polyethylene
Make sure that the stretched plastic film layers are
The characteristic linear low-density polyethylene composite film
It is listed.

JP-A-9-31263 discloses that (A) the density is 0.86 to 0.96 g / cm ³ , the melt flow rate is 0.1 to 200 g / 10 min, and the molecular weight distribution is 1.
4 to 4.5, 98 to 20% by weight of an ethylene / α-olefin copolymer having a specific range of orthodichlorobenzene soluble matter, density and MFR, and (B) other ethylene polymer 2 A polyethylene composition comprising 80% by weight and a container made of the same are described.

[0008]

Although the conventional packaging bag has a satisfactory level of heat sealability and the like, it still has a problem to be solved with respect to the combination of the opening property and rigidity due to tearing of the bag. Have.

[0009] That is, a standing pouch is required to be upright with the contents filled therein. For this purpose, the laminated film or sheet constituting the pouch must have stiffness (rigidity). Required. On the other hand, the polyethylene resin used as the inner film material for heat sealing accounts for the majority of the thickness of the laminated film for pouches, but the elastic modulus of the polyethylene resin is at a smaller level than other resins. Therefore, in order to increase the rigidity, the thickness must be increased.

However, the tearability and rigidity of the bag are incompatible with each other. In the above example, when the thickness of the inner film material of the polyethylene resin is increased, the rigidity is increased, but the tearability is opposite. There is a problem that it decreases.

Another problem with the conventional polyethylene resin inner film material is that it is inferior in resistance to environmental stress cracking as compared with other resins such as polypropylene. In this case, there is a problem that a stress crack is easily generated.

Accordingly, an object of the present invention is to provide a packaging bag which is excellent in combination with the opening property by tearing and rigidity, and further excellent in combination with environmental stress crack resistance.
Another object of the present invention is to provide a packaging bag useful as a standing pouch for filling a liquid detergent or the like.

[0013]

According to the present invention, in a packaging bag made of a laminated film, the inner film of the laminated film has the following formula (1) T ₁ <0.0969 × E ₁ −0.0023 {(1) In the formula, T ₁ is the tear strength (kgf) of the inner film, and E ₁ is the elastic strength (kgf / c) of the inner film.
m), that is, the product of the elastic modulus of the film (kgf / cm ² ) and the thickness of the film (cm). A packaging bag characterized by being a polyethylene resin film satisfying the following. In the packaging bag of the present invention, the laminated film has the following formula (2): T ₂ <0.0884 × E ₂ −1.9131 (2) where T ₂ is the tear strength (kgf) of the laminated film. , _{E 2} is the elastic strength of the laminate film (kgf / c
m), that is, the elastic modulus (kgf / cm ² ) of the laminated film
And a thickness of the laminated film (cm). In addition, the innermost film is an innermost layer of an ethylene / butene-1 copolymer produced using a metallocene-based catalyst,
A laminate comprising an intermediate layer of 1 copolymer or an intermediate layer of a blend of ethylene / butene-1 copolymer and high-density polyethylene or low-density polyethylene, and a bonding layer of ethylene / hexene-1 copolymer Is preferred. When the density of the resin of each layer of the inner film is d _I , the density of the resin of the innermost layer is d _M , the density of the resin of the intermediate layer is d _M, and the density of the bonding layer is d _L , these densities are expressed by the following equation. is preferably in the relationship satisfying the _M> d _L and _{d L>} d _I. The inner film is formed by co-extrusion, and the innermost layers (a) 10 to 4 are formed.
5%, intermediate layer (b) 10-80% and bonding layer (c) 10
It preferably has a thickness ratio of ~ 45%.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The packaging bag of the present invention is made of a laminated film and is provided with a polyethylene resin film as an inner film, and this inner film has the following formula (1) T ₁ <0.0889 × E ₁ −0.0023 ‥ (1) where T ₁ is the tear strength (kgf) of the inner film, and E 1 is the elastic strength (kgf / c) of the inner film.
m), that is, a product of the modulus of elasticity of the film (kgf / cm ² ) and the thickness of the film (cm). It is possible to improve the rigidity of the laminated film while maintaining the tear strength in a low range.

The straight line A in FIG. 1 of the accompanying drawings shows, for a known polyethylene resin film, the elasticity (kgf / cm) of the film and the tear strength (k) of the film.
gf) is plotted, and this straight line corresponds to the following equation (1a): T ₁ = 0.0969 × E ₁ −0.0023 (1a). On the other hand, a straight line B in FIG. 1 indicates the elastic strength (kgf / kg) of the polyethylene-based resin inner surface film (see the example for details) of the example described later.
cm) and the tear strength (kgf) of this film are plotted.
b) T ₁ = 0.0889 × E ₁ −0.1595 Equivalent to (1b).

From these plots, the elastic strength (kgf / cm) and the tear strength (kgf) of the polyethylene resin film are in a linear relationship, and the elastic strength (kgf / cm)
It can be seen that the tear strength (kgf) increases as the size (cm) increases. Also, elastic strength (kgf / cm)
Is the elastic modulus of the film (Kgf / c)
Since m ² ) is the product of the film thickness (cm), it indicates that as the film thickness eventually increases, the tear strength of the film increases linearly.

On the other hand, the straight line A in FIG. 2 of the accompanying drawings shows the elastic strength of the laminated film obtained by laminating a polyethylene resin film having the strength characteristics shown by the straight line A in FIG. 1 on a biaxially stretched nylon film. kgf / c
m) and the tear strength (kgf) of the laminated film are plotted, and this straight line corresponds to the following formula (2a): T ₂ = 0.0884 × E ₂ −1.9131 ‥ (2a) I do. On the other hand, a straight line B in FIG. 2 indicates a laminated film in which a polyethylene-based resin film having the strength characteristics shown by the straight line B in FIG. 1 is similarly laminated on a biaxially stretched nylon film (for details, see Examples). It is a plot of the relationship between the elastic strength (kgf / cm) of the laminated film and the tear strength (kgf) of the laminated film. The straight line B is expressed by the following equation (2b): T ₂ = 0.0194 × E ₂ − 0.4382 ‥ (2b).

A comparison of these plots of FIGS. 1 and 2 reveals the following surprising fact. That is, in FIG. 1, even though the straight line B is located below the straight line A, and the gradient of the straight line B (dependence of the tear strength on the elastic strength) is smaller than that of the straight line A, the difference in the gradient is compared. In contrast to this, a great difference is recognized in the strength characteristics of the laminated film of FIG. To explain this point, also in FIG. 2, the straight line B is located below the straight line A, and the gradient of the straight line B (dependence of the tear strength on the elastic strength) is smaller than that of the straight line A. The difference is that the straight line A is 0.0884 and the straight line B is 0.0194, which is a very large difference.

Therefore, according to the present invention, it is possible to increase the rigidity of the laminated film while maintaining the tear strength of the packaging bag made of the laminated film at a small value, and to improve the openability by tearing the packaging bag. In addition, it is possible to increase the rigidity (lumbar) required for the packaging bag. In addition, since the thickness of the film required to obtain a certain rigidity can be reduced, the cost required for manufacturing the packaging bag can be reduced, and it is suitable for the purpose of resource saving and waste reduction.

The packaging bag of the present invention comprises a laminated film,
Although a polyethylene resin film is used as the inner film, a single-layer film or a multilayer film may be used as long as it has the strength characteristics defined by the above formula (1), and the chemical composition and the like are not particularly limited. .

Generally speaking, it is not easy to obtain a polyethylene resin alone having the strength characteristics of the above formula (1), so that a combination of two or more polyethylene resins or a olefin for reforming is used. It is appropriate to use a combination with a system resin.

In this case, it is desirable that the thickness of the inner film is generally in the range of 20 to 200 μm, particularly 50 to 150 μm. If the thickness is less than the above range, the heat sealing workability may be reduced, or the final packaging bag may have a reduced thickness. If the waist tends to decrease, on the other hand, if the thickness exceeds the above range, the tearability tends to decrease, which is not preferable.

However, in the packaging bag of the present invention, as shown in FIG. 3, a stretched plastic film base 2 and an inner film 3 of linear low-density polyethylene provided on the inner side of the film base 2 are used. The low-density polyethylene inner film 3 is made up of an innermost layer 4 of an ethylene / butene-1 copolymer, an intermediate layer 5 of an ethylene / butene-1 copolymer, and an ethylene / butene-1 copolymer produced using a metallocene catalyst.
It is preferable to form a laminate of the bonding layer 6 of hexene-1 copolymer.

As the inner film 3 laminated on the stretched plastic film 2, three types of linear low-density polyethylenes having different comonomer constitutions and different polymerization catalysts are laminated to provide excellent sealing properties. A combination of easy opening by tearing, resistance to environmental stress cracking, and appropriate waist (rigidity) suitable for a standing pouch or the like can be achieved.

In the inner layer film 3 of the packaging bag 1 of the present invention, the ethylene / butene-1 copolymer produced by using a metallocene catalyst is used as the innermost layer (heat sealing layer) 4. The specific linear low-density polyethylene not only has a good heat-sealing property but also has a good tearing property, which is because it is particularly suitable for the innermost surface layer 4. Further, as a characteristic of the linear low-density polyethylene produced by using the metallocene-based catalyst, the linear low-density polyethylene has excellent resistance to environmental stress cracking and has an advantage in terms of resistance to contents.

The ethylene-hexene-1 copolymer is used as the bonding layer 6 to be bonded to the stretched plastic film 2 because the copolymer has excellent lamination strength with the stretched plastic film substrate. Along with
Due to its excellent flexibility. That is, when sufficient lamination strength is not obtained between the stretched plastic film 2 and the linear low-density polyethylene-based inner layer film 3, the gap between the tearing direction of the base material and the tearing direction of the inner surface material at the time of opening by tearing. There is a tendency for misalignment to occur, which often results in a loss of tear relief. On the other hand, when the lamination strength of both films is high, the tear start points coincide and are fixed at one point, and in this case, the tearing of the film becomes much easier. In the bonding layer 6 used in the present invention, it is considered that the branched chains in the copolymer derived from the hexene-1 comonomer contribute to increasing the laminate strength and imparting flexibility.

Further, the ethylene / butene-1 copolymer is interposed between the innermost layer 4 and the bonding layer 6 as the intermediate layer 5 because the intermediate layer 5 is suitable for a standing pouch or the like. It has excellent waist (rigidity) and excellent tearability.

In the inner film 3 of the packaging bag 1 of the present invention,
As the innermost surface layer 4, the intermediate layer 5, and the bonding layer 6, linear low-density polyethylene having good tearability is selected and combined, but the innermost surface layer 4 has a heat sealing property, and the intermediate layer 5 has a rigid and bonding layer. In No. 6, the combination characteristics described above are achieved by selecting the copolymer composition of the ethylene / α-olefin copolymer in consideration of the laminate strength and flexibility.

The density of the resin in each layer of the inner film 3 also
There is an optimum density range in terms of the above combination characteristics. When the density of the resin of the innermost layer 4 is d _I , the density of the resin of the intermediate layer 5 is d _M, and the density of the bonding layer 6 is d _L , it is preferable that the density is in the relation satisfying the formula d _{M> d L} and _{d L>} d _I.

The inner film formed by co-extrusion has an innermost layer 4 of 10 to 45% and an intermediate layer 5 of 10 to 8%.
It is preferable in terms of combination characteristics that 0% and the bonding layer 6 have a thickness ratio of 10 to 45%.

[Inner Film] (1) Innermost Layer Resin The resin used for the innermost layer 4 in the present invention is a polymer obtained by polymerizing a mixture of ethylene and α-olefin, especially butene-1, in the presence of a metallocene catalyst. It is obtained by doing.

The metallocene catalyst is a metallocene, that is, a transition metal component composed of a complex composed of two substituted or unsubstituted cyclopentadienyl rings and various transition metals, an organoaluminum component, especially aluminoxane. The transition metal component is a metal of Group IVb, Vb or VIb of the periodic table, particularly titanium or zirconium. As a transition metal component in the catalyst, generally, in the following formula (Cp) ₂ MR ₂ , Cp is a substituted or unsubstituted cyclopentadienyl ring, M is a transition metal, and R is a halogen atom or an alkyl group. Is generally used.

The aluminoxane is obtained by reacting an organic aluminum compound with water, and includes a linear aluminoxane and a cyclic aluminoxane. These aluminoxanes can be used alone or in combination with other organic aluminum.

A method for polymerizing ethylene or ethylene and an α-olefin using a metallocene catalyst is disclosed in
-19309 and other publications, which are synthesized by polymerization in an organic solvent, in a liquid monomer or in a gas phase method in the presence of the metallocene catalyst.
Any of these known methods that satisfy the above conditions can be used for the purpose of the present invention.

As the resin for the innermost surface layer 4, a resin containing butene-1 as an α-olefin comonomer and polymerized with a metallocene catalyst is used because of the combination of heat sealability and tearability. And also has resistance to contents such as detergents, which are liable to cause environmental stress cracking.

The resin of the innermost surface layer 4 preferably has a density in the range of 0.860 to 0.925 g / cm ³ in terms of heat sealability, tearability, and moldability. If it is out of the range, the heat sealing property and the tear property tend to be poor.

(2) Intermediate Layer Resin The resin used for the intermediate layer 5 is an ethylene / butene-1 copolymer produced using a usual Ziegler catalyst, and has a density higher than the density dI of the innermost layer resin. In particular, it is preferable to have a density 0.2 g / cm ³ or more higher than the density of the resin of the innermost surface layer 4.

The resin of the intermediate layer 5 should have a density in the range of 0.91 to 0.95 g / cm ³ in terms of the waist (rigidity) required for the standing pouch, the tearing property, and the moldability. Preferably, if the density is below the above range, the rigidity tends to decrease, and if the density exceeds the above range, the tearability tends to decrease.

In order to further improve the tearability,
In the mid layer 5, the ethylene / butene-1 copolymer was added in an amount of 0.1%.
High-density polyethylene or low-density polyethylene may be blended at a ratio of 1 to 80% by weight, preferably 5 to 50% by weight. When the proportion of the high-density polyethylene or the low-density polyethylene is less than 0.1% by weight, substantially no further improvement in the tearing property is observed, and when it exceeds 80% by weight, the drop strength decreases.

The reason why the high-density polyethylene or the low-density polyethylene is blended with the ethylene / butene-1 copolymer to improve the tear property is that the compatibility between the ethylene / butene-1 copolymer and these polyethylene resins is poor. This results in a non-uniform structure.

In the present invention, the use of the above resin as the intermediate layer 5 is also important from the viewpoint of the coextrusion moldability of the laminate. The ethylene / butene-1 copolymer produced using a metallocene catalyst used for the innermost layer 4 has a narrow molecular weight distribution and is difficult to mold. By performing co-extrusion on the resin, the moldability can be improved. This applies to the bonding layer 6 as well.

(3) Resin for bonding layer The resin used for the bonding layer 6 is a copolymer obtained by copolymerizing hexene-1 with ethylene among α-olefins.
It has high lamination strength with a stretched plastic film and is flexible, and has a function of absorbing the impact of the composite film and improving the delamination resistance upon impact.

The resin of the bonding layer 6 is less dense than the density d _M of the resin of the intermediate layer 5, in particular having a density less 0.1 g / cm ³ or more than the density of the resin of the intermediate layer 5, and most it is preferred to have a density greater than the density d _I of the resin of the inner surface layer 4.

Generally, the resin of the bonding layer 6 has a density of 0.9.
The density is preferably in the range of 0 to 0.935 g / cm ³ in terms of lamination strength and flexibility, and furthermore, moldability. When the density is lower than the above range, the lamination strength is reduced, and when the density is higher than the above range, the flexibility is higher. Tends to decrease.

(4) Inner Film Material The inner film 3 used in the present invention is produced by co-extruding the innermost layer 4, the intermediate layer 5, and the bonding layer 6 described above. The overall thickness of the inner film 3 composed of the laminate varies depending on the application, but generally ranges from 20 to 20.
It is preferably in the range of 0 μm, especially 50 to 150 μm. That is, when the thickness exceeds the above range, the flexibility of the laminate of the inner film 3 tends to be lost, while when the thickness is below the above range, the rigidity of the film is lost or the heat sealing property is impaired. Tend.

The ratio of the thickness of each layer in the inner film 3 composed of the laminated body is 10 to 45% for the innermost layer 4, especially 15 to 45%.
Preferably, the intermediate layer 5 is in the range of 10 to 80%, especially 20 to 70%, and the bonding layer 6 is in the range of 10 to 45%, especially 15 to 40%. When the thickness ratio of the innermost surface layer 4 is less than the above range, the heat sealability tends to decrease, and
When the intermediate layer 5 falls below the above range, the stiffness (rigidity) of the inner film 3 tends to decrease, and when the bonding layer 6 falls below the above range, the lamination strength of the inner film tends to decrease. When the thickness ratio of each layer of the inner film 3 is within the above range, the most excellent tear openability and the balance of each property can be obtained.

The inner film 3 made of a laminate by coextrusion is manufactured by using an extruder corresponding to the type of each resin layer.
This is performed by superimposing the melts of the respective resins in a multilayer multiplex die and extruding the melt from a die orifice. This inner surface film material can be formed into a film in advance by a T-die method, an inflation film forming method, or the like, and used for lamination with a stretched plastic film, or can be extrusion-coated on a stretched plastic film in a molten web form. You can also.

The other substrate 2 on which the inner film 3 is laminated
Examples thereof include various stretched plastic films and metal foils other than polyethylene. Polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, ethylene terephthalate / isophthalate copolymer: nylon 6,
Polyamide (Ny) such as nylon 6,6, nylon 11, nylon 12, nylon 6 / nylon 6,6 copolymer
Film: Propylene polymer film (PP): Polyvinyl chloride film: Polyvinylidene chloride film: Ethylene vinyl alcohol copolymer film (EVOH)
And the like. These films may be uniaxially stretched or biaxially stretched.

Among the above stretched films, biaxially stretched polyethylene terephthalate film is a material having excellent mechanical strength, pinhole resistance, crack resistance and heat resistance.
Particularly suitable as the outermost layer of a packaging container. On the other hand, a stretched polyamide film is excellent in gas barrier properties and barrier properties against aroma components, but is more sensitive to humidity components and tends to have lower barrier properties due to moisture absorption. . Further, the uniaxially stretched polypropylene film has an effect of imparting tearing properties in the stretching direction. This uniaxially stretched polypropylene film is preferably provided on the side joined to the inner surface material.
Its thickness is generally 3 to 50 μm, especially 5 to 40 μm.
m is desirable.

The above-mentioned stretched plastic films can be used alone or in combination of two or more. For example, by combining two or more kinds of stretched plastic films having different properties, it is possible to obtain a desired combination property in the composite film.

To bond a plurality of stretched plastic films, an adhesive known per se, for example, an isocyanate-based adhesive, an epoxy-based adhesive, an acid-modified olefin-based resin, a polyester-based adhesive, and a polyamide-based adhesive are used. be able to.

Further, these stretched plastic films may be printed, metal-deposited, or formed with a silicon oxide (SiOx) -deposited layer before or after lamination with the inner film made of a laminate. It can be performed. For example, when using a laminate of a stretched PET film and a stretched polyamide film,
This is convenient because the above-described printing, metal deposition, formation of a silicon oxide (SiOx) deposition layer, and the like can be performed on the inner surface side of the stretched PET film as the outermost surface layer.

On the other hand, an aluminum foil can be used as the metal foil, and its thickness is preferably in the range of 5 to 30 μm. The lamination of the inner surface film composed of the laminate and the stretched plastic film or metal foil can be performed by means known per se, such as extrusion coating, sandwich lamination, dry lamination, and the like. In the extrusion coating method, a urethane-based or titanate-based anchoring agent or a corona discharge treatment can be applied to the surface on the side where the laminated inner surface material is applied, in order to increase the adhesive strength. In sandwich lamination, an inner film material composed of a laminate is divided into two layers, and one of the divided layers is formed into a film in advance. Between the film, melt extruded the other split resin layer,
The film of one of the divided layers and the stretched plastic film are joined via the other divided resin layer,
It is a composite film. Also in this case, it is needless to say that the inner surface material of the formed composite film must have the above-mentioned laminated structure. Furthermore, in dry lamination, a urethane-based inner film and a stretched plastic film made of a laminate formed in advance are used.
Adhesion is performed using an adhesive such as titanate.

Suitable examples of the laminated film of the packaging bag include a polyethylene-based resin inner film as PE, a two-layer structure: PE / Ny, PE / PET, PE / OPP, and a three-layer structure: PE / Ny / PET. , PE / Al / PET,
PE / EVOH / Ny, PE / EVOH / PET, PE
/ EVOH / OPP, four-layer structure: PE / PET / Al / PET.

In the present invention, the laminated film thus formed has the following formula (2): T ₂ <0.0884 × E ₂ −1.9131 (2) where T ₂ is the tear strength (kgf) of the laminated film. ), and, _{E 2} is the elastic strength of the laminate film (kgf / c
m), that is, the elastic modulus (kgf / cm ² ) of the laminated film
And the product of the thickness of the laminated film (cm).

The packaging bag of the present invention can be used as various types of packaging bags by utilizing the above-mentioned excellent properties, and the bag can be produced by a bag production method known per se. Examples include ordinary pouches with three-sided or four-sided seals, pouches with gussets, standing pouches, pillow packaging bags, and the like, but are not limited to these examples.

[0057]

EXAMPLE (Example 1) The innermost layer had a density of 0.910 g /
cm ³ of ethylene / butene-1 copolymer, the intermediate layer is a 0.935 g / cm ³ density of ethylene / butene-1 copolymer, and the bonding layer is a density of 0.920 g / cm ³ of ethylene / hexene-1 copolymer. The united product was co-extruded to produce a 70-μm-thick three-layer co-extruded polyethylene resin film. At this time, the thickness ratio of each layer was 25%: 50%: 25%. Example 2 Example 1 except that the thickness was 120 μm.
The same co-extruded polyethylene resin film was prepared. (Example 3) A 15 μm biaxially stretched nylon film and the co-extruded polyethylene resin film produced in Example 1 were laminated with a corona-treated surface of the nylon film and a joint layer of the co-extruded polyethylene resin film by a dry lamination method. To produce a laminated film. (Example 4) The coextruded polyethylene resin film produced in Example 2 was laminated with a biaxially stretched nylon film in the same manner as in Example 3 to produce a laminated film.

(Comparative Example 1) Linear low density polyethylene 40
A single-layer polyethylene resin film having a thickness of 130 μm was prepared from a blend of 30% by weight of low-density polyethylene and 30% by weight of ethylene / butene-1 copolymer. Comparative Example 2 Comparative Example 2 except that the thickness was 150 μm.
The same polyethylene-based resin film was produced. Comparative Example 3 A 15 μm biaxially stretched nylon film and the polyethylene resin film produced in Comparative Example 1 were laminated by a dry lamination method to produce a laminated film. (Comparative Example 4) The polyethylene resin film produced in Comparative Example 2 was laminated with a biaxially stretched nylon film in the same manner as in Comparative Example 3 to produce a laminated film.

[0059]

Table 1 Elastic strength (kgf / cm) Tear strength (kgf) Example 1 9.07 0.68 Example 2 16.53 1.42 Example 3 27.44 0.10 Example 4 33.950 .22 Comparative Example 1 8.41 0.81 Comparative Example 2 10.20 0.99 Comparative Example 3 23.77 0.19 Comparative Example 4 25.18 0.34

[Comparative Test] (1) Elastic strength Using a Tensilon universal testing machine, a tensile speed of 300 mm /
It is obtained by multiplying the elastic modulus obtained in min by the total thickness of the test piece. (2) Tear strength Using a tear tester manufactured by Tester Sangyo, a tear speed of 30 was used.
It was measured at 00 mm / min.

[0061]

According to the present invention, it is possible to increase the rigidity of the laminated film while maintaining the tear strength of the packaging bag made of the laminated film at a small value, and to improve the openability by tearing the packaging bag. In addition, the rigidity (lumbar) required for the packaging bag can be increased. In addition, since the thickness of the film required to obtain a certain rigidity can be reduced, the cost required for manufacturing a packaging bag can be reduced,
Further, resource saving and waste reduction can be achieved. In particular, the inner film is a linear low-density polyethylene-based laminate, an innermost resin layer of an ethylene / butene-1 copolymer using a metallocene-based catalyst, an intermediate layer of an ethylene / butene-1 copolymer,
And a bonding layer of ethylene-hexene-1 copolymer to provide excellent sealing properties, easy opening by tearing, environmental stress cracking resistance, and moderate waist (rigidity) suitable for standing pouches. Packaging bag.

[Brief description of the drawings]

FIG. 1 Elastic strength (kgf / c) of inner film
3 is a graph showing the relationship between m) and tear strength (kgf).

FIG. 2 Elastic strength (kgf / c) of a laminated film
3 is a graph showing the relationship between m) and tear strength (kgf).

FIG. 3 is a sectional view showing a sectional structure of the packaging bag of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Packaging bag 2 Base material 3 Inner film 4 Innermost layer 5 Intermediate layer 6 Joining layer

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[Procedure amendment]

[Submission date] August 10, 1999 (1999.8.1
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The packaging bag of the present invention comprises a laminated film and a polyethylene resin film as an inner surface film. The inner surface film has the following formula (1) T ₁ < 0.0969 × E ₁ −0.0023 ‥ (1) where T ₁ is the tear strength (kgf) of the inner film, and E 1 is the elastic strength (kgf / c) of the inner film.
m), that is, a product of the modulus of elasticity of the film (kgf / cm ² ) and the thickness of the film (cm). It is possible to improve the rigidity of the laminated film while maintaining the tear strength in a low range.

Claims (6)

[Claims] 1. A packaging bag comprising a laminated film,
The inner film of the laminated film has the following formula (1) T ₁ <0.0969 × E ₁ −0.0023 (1) where T ₁ is the tear strength (kgf) of the inner film, and E ₁ is the inner film. Is the product of the elastic modulus (kgf / cm ² ) of the film and the thickness (cm) of the film. A packaging bag characterized by being a polyethylene resin film satisfying the following. Wherein in said laminate film is represented by the following formula _{(2) T 2 <0.0884 ×} E 2 -1.9131 ‥ (2) equation, _{T 2} is the tear strength of the laminated film (kgf), _{E 2} Is a laminated film satisfying the elastic strength (kgf / cm) of the laminated film, that is, the product of the elastic modulus (kgf / cm ² ) of the laminated film and the thickness (cm) of the laminated film. The packaging bag according to claim 1, wherein 3. An inner film comprising an innermost layer of an ethylene / butene-1 copolymer, a middle layer of an ethylene / butene-1 copolymer, and an inner layer of an ethylene / hexene-1 copolymer using a metallocene catalyst. 3. The packaging bag according to claim 1, comprising a laminate of a bonding layer. 4. An inner film comprising an innermost layer of an ethylene / butene-1 copolymer using a metallocene catalyst, an intermediate layer of a blend of the ethylene / butene-1 copolymer and a high-density polyethylene or a low-density polyethylene, The packaging bag according to claim 1, comprising a laminate of a bonding layer of ethylene and hexene-1 copolymer. 5. The resin density of each layer of the inner film is d _I , the resin density of the innermost layer is d _I , and the resin density of the intermediate layer is d _M.
And when the density of the bonding layer was _{d L,} claim 3 packaging bag according to a relationship in which these densities satisfy the formula d _{M> d L} and _{d L>} d _I. 6. The inner film is formed by co-extrusion,
Innermost layer (a) 10-45%, middle layer (b) 10-80
The packaging bag according to claim 3 or 4, which has a thickness ratio of 10% to 45% of the bonding layer (c).