JP2000168003A - Easily-peelable multilayered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging film excellent in easy peelability, easy in the control of peel strength having a heat sealing condition range and good appearance and capable of fixing a peel place. SOLUTION: An easily-peelable multilayered film with the total thickness of 0.015-2 mm is obtained by a method wherein a surface layer with a thickness of 2-30 μm comprising a resin compsn. containing 2-40 wt.% of a polybutene resin and 98-60 wt.% of a polyolefinic resin other than the polybutene resin and an inner layer with a thickness of 2 μm or more composed of a polyolefinic resin other than the polybutene resin are formed so as to be adjacent to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an easy-peelable multilayer film. More specifically, the present invention relates to a packaging film having an excellent peel property and a good appearance of a peel portion.

[0002]

2. Description of the Related Art Polyolefin resins have been widely used as packaging films for foods, pharmaceuticals, medical instruments, daily necessities and the like. When a pouch, cup, container, or the like is packaged using such a packaging film, it is usually sealed by heat sealing. However, conventionally, when taking out the contents, this sealing strength (heat sealing strength)
Is too strong, and it is not easy to peel off the heat-sealed part and open it. If you try to open it by force, a part other than the heat-sealed part may be broken. There were things.

[0003] In order to solve such a problem, it has been proposed to use various polyolefin resins as a material for a packaging film. However, if the same resin material is heat-sealed, the sealing strength cannot be increased and the purpose of facilitating peeling cannot be achieved.On the other hand, between different resin materials, the sealing strength between films can be sufficiently secured. In any case, it was difficult to control the sealing strength and the peel strength (peel strength) in a well-balanced manner. In addition, there are also problems that a good appearance cannot be obtained in the peeled portion, such as swelling or stringing in the peeled portion after peeling, and a problem that the condition range of the heat seal is narrowed.

On the other hand, a polybutene resin is used as a resin having excellent heat sealing properties and easy peel properties,
It has been proposed to use it by blending it with polyethylene or the like (Japanese Patent Application Laid-Open No. Hei 4-211442).

However, even if such a blend of polybutene resin is used, the poor appearance of the peeled portion is not sufficiently eliminated, and the peeled portion is peeled from a portion other than a predetermined portion, making it difficult to fix the peeled portion. There was a problem. In other words, when trying to peel the heat-sealed portion, the force applied to the heat-sealed portion causes destruction at any of the film thickness portions other than the heat-sealed portion, and the peeled portion is in an upside-down state or the broken portion is in the form of a thread. The appearance of the peeling part becomes poor due to the stringing state, or the resin broken finely in the form of a thread is mixed with the opened food or the like, resulting in a state unfavorable for food hygiene, or causing a reduction in commercial value A problem arose.

Therefore, a certain peel strength (sealing strength)
It has been desired to develop a packaging film having excellent peelability, which can be easily peeled off when necessary, and which has a good appearance of the peel portion.

[0007]

DISCLOSURE OF THE INVENTION The present invention has excellent easy-peeling properties, easy control of peeling strength, a wide range of heat sealing conditions, good appearance of peeled parts,
Another object of the present invention is to provide a packaging film capable of fixing a peeled portion.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problems can be solved by forming a laminate having a certain resin material and a certain layer thickness.
The present invention has been completed.

That is, the present invention is a multilayer film including a surface layer and an inner layer adjacent to the surface layer, wherein the surface layer is composed of a polybutene resin: 2 to 40% by weight and a polyolefin other than the polybutene resin. System resin: 98% by weight to 6
0-30% by weight of a resin composition containing 0% by weight
Wherein the inner layer is a layer made of a polyolefin resin other than the polybutene-based resin and having a thickness of 2 μm or more.

The present invention is also a multilayer film comprising a surface layer, an inner layer and a back layer laminated in this order, wherein both the surface layer and the back layer are made of the resin composition, and the inner layer is The present invention provides the easy-peelable multilayer film comprising the polyolefin-based resin.

Further, the present invention provides the easy-peelable multilayer film, wherein the thickness of the entire film is 0.015 to 2 mm. Also, the present invention
The present invention provides the easy-peelable multilayer film, which is a non-stretched film.

In the present invention, the film has a multilayer structure,
In addition, by reducing the thickness of the surface layer, the peeled portion after peeling is in an interfacial peeling state (considered as a state of fine cohesion failure on the surface), and the appearance is good and the stringing state does not occur. That is, peeling occurs substantially at the interface of the heat seal portion, and the peeled portion is fixed.

[0013]

Embodiments of the present invention will be described below. The multilayer film of the present invention comprises a laminate including at least a surface layer and an inner layer.

(1) Surface Layer The surface layer of the present invention comprises a resin composition containing a polybutene resin and a polyolefin resin other than the polybutene resin.

Polybutene Resin The polybutene resin used in the present invention includes a homopolymer of butene-1 or a copolymer of butene-1. As the copolymer of butene-1, a copolymer of butene-1 with ethylene or an α-olefin other than butene-1, specifically, butene-1-ethylene, butene-1-
Copolymers of propylene, butene-1 and an α-olefin having 5 to 8 carbon atoms are exemplified. The ratio of butene-1 unit in the polybutene-based resin is not particularly limited, but is preferably from 60 to 100% by weight.

The polybutene-based resin is the product of a stereospecific polymerization process and is referred to as an "isotactic" or "stereospecific" polymer, where the repeating units of the polymer chain are all It has the same stereochemical configuration along the chain. This is in contrast to "atactic" polymers, where the repeating units of the polymer chain vary in an irregular arrangement along the chain.

The "isotactic" polybutene resin used in the present invention is produced by stereospecific polymerization of monomeric butene-1. Methods for performing such polymerization steps are known and typical steps are described in U.S. Pat. No. 3,197,4.
No. 52, German Patent Application No. 6507546. In these steps, monomeric butene-1 is generally polymerized in the presence of a polymerization initiator and a preferred catalyst system to produce a high molecular weight polymer.

Preferred catalyst systems include metal alkyl compounds such as aluminum triethyl, and IV to VI of the periodic table such as titanium, vanadium, chromium, zirconium, molybdenum and tungsten.
There are reaction products with heavy metal compounds such as group trihalides. Therefore, the formation of a polymer exhibiting substantially isotactic properties and molecular weight fluctuation usually depends on the properties of the polymerization catalyst, the properties of the co-reactant in the system, the reaction conditions, and the like.

The MFR of the polybutene-based resin is not particularly limited as long as it can be formed into a film or sheet, but is generally 0.1 to 300 g / 10 min, preferably 0.5 to 30 g / 10 min. More preferably 1 to
10 g / 10 min. The MFR of the polybutene resin is JIS-K7210 (190 ° C., 2.
16 kg load).

Polyolefin Resin The polyolefin resin other than the polybutene resin used in the present invention (hereinafter, simply referred to as "polyolefin resin") includes polyethylene resin and polypropylene resin. Of these, polyethylene resins are preferred.

Examples of the polyethylene resin include ethylene polymers such as low-density polyethylene, high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene. Further, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl methacrylate copolymer,
Ethylene-methyl methacrylate copolymer, ethylene-
Ethylene copolymers such as an ethyl acrylate copolymer and an ethylene-methyl acrylate copolymer can also be exemplified. Further, modified resins obtained by modifying these ethylene-based polymers or copolymers (preferable ratio of ethylene units: 70 to 100% by weight) with maleic acid or the like can be also exemplified. Further, these resins may be used alone or in combination of two or more. Of these, particularly preferred is low density polyethylene.

The MFR of the polyethylene resin is not particularly limited as long as it can be formed into a film or sheet, but is generally 0.1 to 300 g / 10 min, preferably 0.5 to 30 g / 10 min. More preferably, 1
〜１０10 g / 10 min. The MFR of the polyethylene resin is JIS-K7210 (190 ° C,
2.16 kg load).

Examples of the polypropylene resin usable in the present invention include a propylene homopolymer and a propylene / α-olefin copolymer.

In the case of the propylene / α-olefin copolymer, the α-olefin to be copolymerized is selected from ethylene or those having 4 or more, preferably 6 or more carbon atoms. Specific examples of such α-olefins include ethylene,
-Butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, hexadecene and the like. The proportion of propylene units in such a copolymer is preferably at least 70% by weight.

The MFR of the polypropylene resin is not particularly limited as long as it can be formed into a film or a sheet, but is generally 0.1 to 300 g / 10 min.
Preferably it is 0.5 to 30 g / 10 min, more preferably 1 to 10 g / 10 min. The MFR for this polypropylene resin is JIS-K7210 (230
C., 2.16 kg load).

The polyolefin resin blended with the resin composition of the surface layer may be the same as or different from the polyolefin resin forming the inner layer, but the difference in melting point between the surface layer and the inner layer is large (particularly, the inner layer (The melting point of the resin is low.)
Therefore, it is preferable to use the same resin because the heat-sealing property tends to be deteriorated, and it is preferable to use the same resin also from the viewpoint of the adhesion between the surface layer and the inner layer.

Resin Composition The resin composition of the present invention comprises the above polybutene resin in an amount of 2 to 4
0% by weight, preferably 3 to 30% by weight, and 98% to 60% by weight, preferably 97 to 70% by weight of the polyolefin resin. If the amount of the polybutene-based resin is less than the above range, it is not preferable because the easy-peeling property is reduced.

Further, in addition to the above essential components, other additional components can be added to the resin composition of the present invention as long as the effects of the present invention are not significantly impaired. Such optional components include antioxidants, crystal nucleating agents, light stabilizers, ultraviolet absorbers, lubricants, antiblocking agents, antistatic agents, antifogging agents, and neutralizing agents used in ordinary polyolefin resin materials. Metal deactivators, coloring agents such as pigments and dyes, dispersants, peroxides, fillers, fluorescent brighteners, and extenders.

The resin composition of the present invention can be obtained by melt-kneading the above components by a conventionally known method. Melt kneading, for example, powder, pellets and other components in a single or twin screw extruder, Henschel mixer, super mixer, V blender, tumbler mixer, ribbon blender, Banbury mixer, kneader blender,
It can be performed using a known kneading machine such as a Brabender plastograph, a small batch mixer, a continuous mixer, and a mixing roll.

Surface Layer The surface layer of the multilayer film of the present invention comprises the above resin composition and has a thickness of 2 to 30 μm, preferably 2 to 20 μm.
m, more preferably 5 to 10 μm. If the thickness is less than the above range, the peel strength becomes partially unstable, and the easy peelability becomes unstable, so that it is not preferable.If the thickness exceeds the above range, stringing or crushing occurs in the peel portion after peeling,
It is not preferable because the appearance becomes poor.

(2) Inner Layer The inner layer in the multilayer film of the present invention is made of a polyolefin resin other than the polybutene resin. Such a polyolefin-based resin can be selected from the same range as those usable as the polyolefin-based resin blended with the above-described resin composition for forming the surface layer. Preferably, it is a polyethylene resin, particularly preferably low density polyethylene. The polyolefin resin used for the inner layer may be the same as or different from the polyolefin resin used for the resin composition forming the surface layer, but the difference in melting point between the surface layer and the inner layer is large (particularly, the inner layer resin (The melting point is low), the heat sealing properties tend to deteriorate, so that it is preferable to use the same resin, and it is preferable to use the same resin also from the viewpoint of the adhesion between the surface layer and the inner layer.

Further, in addition to the above-mentioned polyolefin resin, other additional components can be added to the resin material for forming the inner layer, as long as the effects of the present invention are not significantly impaired. Such optional components can be selected from the same ranges as the additional components that can be used in the resin composition forming the surface layer.

As an optional component, a resin other than the above-mentioned polyolefin-based resin, for example, an olefin-based elastomer can be blended. Polybutene-based resin can also be blended as a resin other than the polyolefin-based resin, but in that case, the content of the polybutene-based resin contained in the resin composition of the surface layer should be smaller, preferably, in the resin composition. 3% by weight or less than the amount of the polybutene resin.

The thickness of the inner layer is at least 2 μm, preferably at least 10 μm. If it is less than 2 μm, stringing, swelling and the like will occur at the peeled portion after peeling, which will cause poor appearance of the peeled portion. The upper limit of the thickness of the inner layer is not particularly limited,
Preferably, it is 100 μm or less.

(3) Multilayer Film The multilayer film of the present invention contains at least the above-mentioned surface layer and inner layer, and the surface layer and the inner layer need to be adjacent to each other. The layer structure is not particularly limited, and may be, for example, a two-layer structure including only the surface layer and the inner layer, or a three-layer structure including the surface layer, the inner layer, and the back layer.

When a multilayer film having a three-layer structure is formed by laminating a surface layer, an inner layer, and a back layer in this order, only the surface layer is formed of the resin composition, and the inner layer is formed of the polyolefin resin. However, it is preferable that both the front layer and the back layer are formed of the resin composition, and that the inner layer is formed of the polyolefin resin.

The multilayer film further comprises an adhesive layer for imparting various functions as needed within a range not impairing the above-mentioned layer structure, in addition to the above-mentioned surface layer and inner layer and an optional back layer. A layer such as a gas barrier layer can be optionally provided.

The "film" in the present invention includes a relatively thick film generally called a "sheet". The multilayer film of the present invention has an overall thickness of preferably 0.015 to 2 mm, more preferably 0.015 to 2 mm. Preferably 0.025 to
0.5 mm. If the thickness of the entire film is less than the above range, the protective property of the package contents is lowered due to insufficient strength of the film, which is not preferable. If the thickness is more than that, the rigidity becomes too high and the easy-peel property becomes unstable, which is not preferable.

The method for producing the multilayer film of the present invention may be any of the conventionally known methods for producing a laminated film, and is not particularly limited. Specifically, a known multi-layer co-extrusion blown film forming method, a multi-layer co-extrusion cast film (T-die) or sheet forming method, a multi-layer co-extrusion laminate (coating) forming method, an extrusion laminate forming method, and the like can be used.

The multilayer film of the present invention may be stretched or unstretched. However, if the heat shrinkage at the time of heat sealing is high, easy peeling becomes unstable, and problems such as poor appearance arise. It is preferable to use a non-stretched film.

The multilayer film of the present invention includes a substrate made of other plastic films such as nylon film, polyester film, OPP film, vapor-deposited film such as metal and glass, paper, nonwoven fabric, metal foil such as aluminum foil. It can be suitably used as a laminate film. Further, the multilayer film of the present invention may be subjected to a known surface treatment such as a corona discharge treatment and an ozone treatment as necessary.

The multilayer film of the present invention is easily peeled and easily opened at a heat-sealed portion (heat-sealed portion) between the multilayer films or with another polyolefin resin film or sheet. Therefore, food, medicine,
It is suitable as a packaging film for medical instruments and daily necessities.

[0043]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In addition, the evaluation method of the physical property in the following Examples is as follows.

(1) Heat Seal Strength The heat seal strength was measured using a heat sealer.
140 ° C.-1 kg / cm for No. 1 and Comparative Examples 1-3
Was heat sealed under the conditions of ² -1 seconds, T-peel strength (tensile speed: 300 mm / min) was measured. Example 12 was heat-sealed under the conditions of 180 ° C.-1 kg / cm ² -1 second, and the T-peel strength (tensile speed: 300 mm / min) was measured.

(2) Easy peelability A test piece having a width of 30 mm was prepared by heat sealing in the same manner as in the method for measuring heat seal strength, and the sensory evaluation when peeled by hand was performed according to the following criteria. ：: good easy peelability ×: bad easy peelability

(3) Appearance of Peel Part The appearance of the peel part after measuring the heat seal strength was visually observed and evaluated according to the following criteria. ：: No stringing, no scabs, etc., excellent in appearance. ：: A little scum is recognized, but the appearance is good. ×: Many strings or scabs were observed, and the appearance was poor.

[0047]

Example 1 (1) Production of multilayer film As a resin material for the inner layer, a low-density polyethylene having an MFR of 2.2 g / 10 min and a density of 0.923 g / cm ³ was used. The same low-density polyethylene as used in the above: 85% by weight and MFR of 2.0
A resin composition was used in which polybutene-1 having a density of 0.900 g / cm < ³ > and a weight ratio of 0.910 g / cm < ³ > was mixed.

Using an inflation coextrusion multilayer molding machine, a processing temperature of 160 ° C., a blow ratio of 2.0, and a folding diameter of 700 m
m, a multilayer tubular film having an overall thickness of 30 μm (inner layer thickness: 28 μm, surface layer thickness: 2 μm) was formed. Next, the folded portions at both ends are continuously cut into two flat shapes, and then the inner layer is subjected to corona discharge treatment (wetting index according to JIS-K6768-1977 immediately after treatment is 4).
5 dyn / cm) to produce a multilayer film.

(2) Production of Laminate Film Using an extrusion laminator equipped with an extruder having a diameter of 90 mm, a polyester film (hereinafter referred to as “PET # 12”) having a thickness of 12 μm was wound from one side, and the PET # was wound.
12 was anchor-coated with a polyurethane-based two-pack primer. From the other side, the multilayer film obtained in the above item (1) was wound so that the corona-treated surface became the bonding surface.

Next, a low-density polyethylene (abbreviated as “LDPE”, MFR = 4 g / 10 min, density =
0.918 g / cm ³ ) at a resin temperature of 320 ° C.
PET # 1 at a thickness of 15 μm and a speed of 100 m / min.
2 (anchor coating surface is a bonding surface) and the multilayer film are sandwich-laminated, and PET # 12 / L
A laminated film having a structure of DPE (15 μm) / multilayer film (30 μm) was obtained.

The surface layer of the multilayer film in the laminated film and a separately prepared sandwich laminated film [Constitution: PET # 12 / LDPE (15 μm) /
LDPE film (MFR = 1 g / 10 min, density = 0.
920 g / cm ³ : 50 μm)], and heat-sealed, and evaluated for various physical properties (heat-sealing strength, easy-peeling property, and appearance of peeled portion). Table 1 shows the physical property evaluation results.

[0052]

Examples 2 to 6 A multilayer film and a laminated film were produced in the same manner as in Example 1 except that the thicknesses of the inner layer and the surface layer were changed as shown in Table 1, and various physical properties were evaluated. Table 1 shows the results.

[0053]

Examples 7 to 10 A multilayer film and a laminated film were produced in the same manner as in Example 1 except that the composition of the polybutene resin in the surface layer was changed as shown in Table 1, and various physical properties were evaluated. Was. Table 1 shows the results.

[0054]

EXAMPLE 11 The resin of the inner layer and the surface layer and the resin composition were the same as those of Example 11 shown in Table 1, and a multilayer film was produced in the same manner as in Example 1 (the processing temperature was 190 ° C.). Physical properties were evaluated. However, the separately prepared sandwich laminated film is [Construction: PE
T # 12 / LDPE (15 μm) / LLDPE film (MFR = 2 g / 10 min, density = 0.915 g / c
m ³ : 50 μm)]. Table 1 shows the physical property evaluation results.

[0055]

Example 12 The resin and the resin composition of the inner layer and the surface layer were the same as those of Example 12 shown in Table 1, except that the resin temperature was 250 ° C. and a T-die co-extrusion multilayer molding machine was used. In the same manner as described above, a multilayer film (in which the inner layer was subjected to corona discharge treatment in the same manner as in Example 1) was obtained.
Next, a laminated film was obtained. Table 1 shows the results of the physical property evaluation performed in the same manner as in Example 1. However, the separately prepared sandwich laminated film is [Construction: PE
T # 12 / LDPE (15 μm) / PP film (propylene / ethylene random copolymer, MFR = 4 g /
10 minutes, density = 0.90 g / cm ³ : 25 μm)].

[0056]

Comparative Examples 1 to 3 A multilayer film and a laminated film were obtained in the same manner as in Example 1 except that the composition of the surface layer and the thickness constitution of the inner layer and the surface layer were as shown in Table 1. Table 1 shows the results of the physical property evaluation performed in the same manner as in Example 1.

[0057]

[Table 1]

In Table 1, LDPE is low-density polyethylene, LLDPE is linear low-density polyethylene, PP is polypropylene (random copolymer with ethylene),
PB-1 represents polybutene-1.

[0059]

The multilayer film of the present invention has a predetermined peel strength (sealing strength), and is excellent in easy peelability that can be easily peeled off when necessary, easy in controlling the peel strength, The sealing condition range is wide, the appearance is good, and the peeling point can be fixed, so that the peeling property is excellent. Therefore, it is suitable as a packaging film for foods, pharmaceuticals, medical instruments, daily necessities and the like.

Continued on the front page F-term (reference) 4F071 AA14 AA21 AF29 AF53 BC02 4F100 AK03A AK03B AK03C AK06 AK09A AK09C AK62A AK62B AK62C AK66A AK66B AK66C AL05A AL05C BA02 BA03 BA20 J15 DA02 E15 BB001 BB172 GF00

Claims (4)

[Claims] 1. A multilayer film comprising a surface layer and an inner layer adjacent to the surface layer, wherein the surface layer is composed of 2 to 40% by weight of a polybutene resin and 98 of a polyolefin resin other than the polybutene resin. A layer having a thickness of from 2 to 30 μm, comprising a resin composition containing at least about 60% by weight, and wherein the inner layer is a layer having a thickness of at least 2 μm, comprising a polyolefin-based resin other than the polybutene-based resin. , Easy peel multilayer film. 2. A multilayer film in which a surface layer, an inner layer and a back layer are laminated in this order, wherein both the surface layer and the back layer are made of the resin composition, and the inner layer is made of the polyolefin resin. The easy-peelable multilayer film according to claim 1, comprising: 3. The thickness of the entire film is 0.015 to 2 m.
3. The easy-peelable multilayer film according to claim 1, wherein m is m. 4. The easy-peelable multilayer film according to claim 1, which is a non-stretched film.