WO2012046780A1 - Easy-to-remove laminate film and use thereof - Google Patents

Abstract

The object of the present invention is to develop an easy-to-remove film in which no stringiness phenomenon occurs and the detachment of a laminate or the breakage of the film does not occur when the hot melting temperature is increased, and which has steady easy-to-remove performance. The present invention relates to: an easy-to-remove laminate film characterized by comprising a hot melt layer and a support layer, wherein the hot melt layer comprises a polyolefin composition (D) comprising 20-70 mass% of a propylene polymer (A), 20-60 mass% of an ethylene polymer (B) and 5-40 mass% of an (ethylene)-(α,β-unsaturated carboxylic acid) copolymer (C) and the support layer comprises a propylene block copolymer (E); and use of the easy-to-remove laminate film.

Description

Easy peelable laminated film and its use

The present invention is easily peelable from a propylene-based polymer layer composed of a composition of an ethylene polymer, a propylene polymer and an ethylene / unsaturated carboxylic acid copolymer, soft feeling at opening, blocking resistance, hygiene The present invention relates to an easily peelable laminated film provided with a heat-fusible layer excellent in film forming workability and laminating workability, a lid made of such an easily peelable laminated film, and a package using the same.

Bottles for packaging of snacks such as rice crackers and potato chips, food packaging such as jelly, milk, yogurt, pudding, tofu and lactic acid beverages, blister packaging, pharmaceuticals, medical equipment packaging, etc. A packaging in which a plastic container such as a cup or a tray-like polypropylene or polystyrene is sealed with a lid made of a plastic laminate film or an aluminum foil laminate film is widely used. What is required for such packaging is mechanical strength that can withstand distribution channels, sealing strength that can maintain hygiene, and good openability during use.

As a film having such an easy-opening property (easy-peeling property), for example, an easy-opening package comprising a mixture layer of a polypropylene resin and a polyethylene resin and a high-density polyethylene resin layer (Patent Document 1: Special). No. 5-64593), a sealant film for a polypropylene container comprising an adhesive layer (easy release layer) made of a mixed resin of polypropylene and polyethylene and a support layer (laminate layer) (Patent Document 2: JP-B-5 No. 6513) has been proposed. However, a film in which a mixture layer of a polypropylene resin and a polyethylene resin is merely a heat-sealing layer is not always satisfactory in terms of the balance between sealing performance and easy opening performance.

As a method for improving such a problem, an easily openable sealing material comprising a polyolefin composition in which an ethylene / α, β-unsaturated carboxylic acid copolymer is added to a propylene polymer and an ethylene polymer has been proposed (patent) Document 3: Japanese Patent No. 2505031). However, as described in the publication, when a film obtained from such a polyolefin composition is dry laminated to a polyethylene terephthalate film as a single layer film and bonded together with a polypropylene sheet, it can be opened. However, it has been found that an unstable peeling state such as a stringing phenomenon occurs. A laminated film obtained by coextrusion molding with such a polyolefin composition and polypropylene can also be opened, but it has been found that when the heat fusion temperature is raised, an unstable peeling state accompanied by delamination or film breakage is found. It was.

Japanese Patent Publication No. 5-64593 Japanese Patent Publication No. 5-6513 Japanese Patent No. 2505031

Therefore, the present inventors have developed an easily peelable film having stable peelability that does not cause delamination or film breakage even when the heat fusion temperature is further increased without causing a stringing phenomenon. As a result, as a result of various studies, a propylene / block copolymer was added to a heat-sealing layer comprising a polyolefin composition in which an ethylene / α, β-unsaturated carboxylic acid copolymer was added to a propylene polymer and an ethylene polymer. By laminating a support layer made of coalescence, it can be seen that it has a stable and easy peelability without causing a stringing phenomenon, and even when the heat fusion temperature is raised, the laminate does not peel off or the film breaks. The invention has been reached.

The present invention comprises 20 to 70% by mass of a propylene polymer (A), 20 to 60% by mass of an ethylene polymer (B) and 5 to 40% by mass of an ethylene / α, β-unsaturated carboxylic acid copolymer (C). It is related with the easily peelable laminated film characterized by comprising the heat-fusible layer which consists of the polyolefin composition (D) of this, and the support layer which consists of a propylene block copolymer (E).

The support layer made of the propylene block copolymer of the present invention and the heat fusion layer made of the polyolefin composition of the propylene polymer, the ethylene polymer, and the ethylene / α, β-unsaturated carboxylic acid copolymer. The peelable laminate film itself is excellent in blocking resistance, hygiene, film forming processability, laminate processability, and when such an easily peelable laminate film is heat-sealed with a propylene polymer layer, Stable heat-sealing strength (peeling strength) in a wide temperature range, stable peeling product that does not cause laminate peeling or film breakage even when the stringing phenomenon or heat fusing temperature is increased, and when peeling (when opened) It can be easily peeled off and has a soft feeling.

<Propylene polymer (A)>
The propylene polymer (A), which is a component of the polyolefin composition (D) constituting the heat-sealing layer of the easily peelable laminated film of the present invention, is a resin that is generally manufactured and sold under the name of polypropylene. A single weight of propylene having a density of 0.890 to 0.930 g / cm ³ and an MFR (ASTM D1238 load of 2160 g, temperature of 230 ° C.) of 0.1 to 100 g / 10 min, preferably 0.5 to 70 g / 10 min. A random or block copolymer of a polymer or propylene and another small amount of α-olefin such as ethylene, butene-1, hexene-1, etc., and a random copolymer is particularly preferred. The random copolymer usually has an ethylene or other α-olefin content of 0.5 to 20 mol%, preferably 1 to 10 mol%.

<Ethylene polymer (B)>
The ethylene polymer (B), which is a component of the polyolefin composition (D) constituting the heat-sealing layer of the easily peelable laminated film of the present invention, usually has a density of 0.910 to 0.970 g / cm ³ , Preferably, ethylene homopolymer or ethylene having 0.920 to 0.960 g / cm ³ and MFR (ASTM D1238 load 2160 g, temperature 190 ° C.) of 1 to 30 g / 10 minutes, preferably 1 to 10 g / 10 minutes And a small amount of an α-olefin having 3 to 10 carbon atoms, such as propylene, butene-1, heptene-1, hexene-1, octene-1, 4-methyl-pentene-1, and so-called High pressure low density polyethylene (HP-LDPE), linear or linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene It is a polymer mainly composed of ethylene called HDPE. These ethylene polymers (B) may be a single polymer or a composition (mixture) with two or more kinds of ethylene polymers.

Among these ethylene polymers, ethylene / α− having a density in the range of 0.920 to 0.940 g / cm ³ manufactured and sold under the name of linear low density polyethylene (LLDPE) or medium density polyethylene (MDPE). Olefin random copolymers are preferred.
<Ethylene / α, β-unsaturated carboxylic acid copolymer (C)>
The ethylene / α, β-unsaturated carboxylic acid copolymer (C), which is a component of the polyolefin composition (D) constituting the heat-sealing layer of the easily peelable laminated film of the present invention, is composed of ethylene and α, β -A copolymer with an unsaturated carboxylic acid, and a part or all of the α, β-unsaturated carboxylic acid may be a metal salt. Further, in addition to the α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid ester or a carboxylic acid vinyl ester may be included as a copolymerization component.

Examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, and monomethyl maleate. As the α, β-unsaturated carboxylic acid ester, acrylic acid or methacrylic acid alkyl ester having 1 to 8 carbon atoms such as methyl, ethyl, propyl, n-butyl, isobutyl, 2-ethylhexyl, etc. It can be illustrated. Moreover, as a carboxylic acid vinyl ester, a vinyl acetate ester can be shown as a representative example.

Examples of metal salts include monovalent metal ions such as lithium, sodium, potassium and cesium, divalent metal ions such as zinc, copper, magnesium, calcium, strontium and barium, and trivalent metal ions such as ammonium and iron. Can be used.

Among these ethylene / α, β-unsaturated carboxylic acid copolymers (C), the ethylene unit is usually 85 to 99.5 mol%, preferably 94 to 99 mol%, and the α, β-unsaturated carboxylic acid unit is Copolymer of 1 to 6 mol%, other monomers of 0 to 10 mol%, especially 0 to 6 mol%, or metal chloride so that the degree of neutralization is 10% or less, particularly 80% or less Is preferred. Specific examples of such copolymers include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-ethyl acrylate-acrylic acid copolymers, ethylene-isobutyl acrylate-methacrylic acid copolymers. A combination or a salt thereof can be used.

The ethylene / α, β-unsaturated carboxylic acid copolymer (C) has a melt flow rate at 190 ° C. of usually 0.1 to 500 g / 10 min, particularly 0.5 to 100 g / 10 min. preferable.

<Polyolefin composition (D)>
The polyolefin composition (D) constituting the heat-sealing layer of the easily peelable laminated film of the present invention has a propylene polymer (A) content of 20 to 70% by mass, preferably 30 to 60% by mass, an ethylene polymer ( B) is composed of 20 to 60% by mass, preferably 25 to 50% by mass, and ethylene / α, β-unsaturated carboxylic acid copolymer (C) is composed of 5 to 40% by mass, preferably 10 to 30% by mass. The

If the amount of the propylene polymer (A) is less than 20% by mass, it may not show an appropriate heat seal strength in a wide temperature range, while if it exceeds 70% by mass, it tends to be inferior in easy-openability, Moreover, there is a possibility that moderate heat seal strength is not exhibited in a wide temperature range.

When the amount of the ethylene polymer (B) is less than 20% by mass, the heat seal strength may be too high or too weak. On the other hand, when it exceeds 60% by mass, the easy-openability tends to be inferior. In addition, there is a possibility that moderate heat seal strength is not exhibited in a wide temperature range.

If the amount of the ethylene / α, β-unsaturated carboxylic acid copolymer (C) is less than the above range, it may not show an excellent easy-opening property, and an appropriate heat seal strength in a wide temperature range. May not show. On the other hand, if it exceeds 40% by mass, the heat seal strength may be too weak.

<Propylene block copolymer (E)>
The propylene block copolymer (E) that forms the support layer of the easily peelable laminated film of the present invention is a crystalline propylene that is a homopolymer of propylene or a random copolymer of propylene and a small amount of α-olefin. The polymer component and the copolymer component which is an amorphous or low crystalline propylene / ethylene random copolymer are usually in a mass ratio of 60:40 to 97: 3, preferably 65:35 to 95: 5, More preferably, the composition is in the range of 70:30 to 89:11, and is usually produced and sold as the name of the propylene block copolymer.

In the propylene block copolymer (E) according to the present invention, since the melting point of the propylene polymer component is as high as 158 to 170 ° C., the support layer does not become a molten state even when subjected to a high temperature retort treatment. There is no possibility of delamination between base materials such as PET and nylon (Ny), and since it has flexibility, it can suppress film breakage even when the heat fusion temperature is raised. I can do it.

The propylene block copolymer (E) according to the present invention is obtained by polymerizing the propylene polymer component and the copolymer component in a plurality of polymerization reactors, respectively, separately polymerized and melt mixed. It can be manufactured by a conventionally known manufacturing method.

The propylene block copolymer (E) according to the present invention may be used as the propylene polymer (A) which is one of the components forming the heat-sealing layer of the easily peelable laminated film of the present invention. .

The MFR (ASTM D1238, load 2160 g, temperature 230 ° C.) of the propylene block copolymer (E) according to the present invention is not particularly limited as long as it has a film forming ability, but usually 0.1 to 100 g / 10 min. Preferably, it is in the range of 0.5 to 70 g / 10 minutes.

<Propylene homopolymer (F)>
The propylene homopolymer (F) constituting the laminate layer of the easily peelable laminated film of the present invention is a crystalline resin, and among the resins generally manufactured and sold under the name of polypropylene, homopolymers, homotypes, etc. It is a resin (polymer) called a propylene homopolymer.

The MFR (ASTM D1238 load 2160 g, temperature 230 ° C.) of the propylene homopolymer (F) according to the present invention is not particularly limited as long as it has a film-forming ability, but is usually 0.1 to 100 g / 10 minutes, preferably It is in the range of 0.5 to 70 g / 10 minutes.

Propylene polymer (A), ethylene polymer (B) and ethylene / α, β-unsaturated carboxylic acid copolymer (C), polyolefin composition (D), propylene block copolymer (E) according to the present invention ) Or propylene homopolymer (F), as long as the object of the present invention is not impaired, various known additives that are usually added to polyolefins, for example, antioxidants, weathering stabilizers, antistatic agents, antifogging agents. An agent, an antiblocking agent, a slip agent (lubricant) and the like can be blended as necessary.

<Easily peelable laminated film>
The easily peelable laminated film of the present invention comprises a propylene polymer (A) 20 to 70% by mass, an ethylene polymer (B) 20 to 60% by mass and an ethylene / α, β-unsaturated carboxylic acid copolymer (C). It consists of a heat-sealing layer made of 5 to 40% by mass of the polyolefin composition (D) and a support layer made of the propylene block copolymer (E).

Moreover, the easily peelable laminated film of the present invention comprises a laminate layer / support layer / a laminate layer comprising a propylene homopolymer (F) on the surface of the support layer on which the heat-sealing layer is not laminated. A three-layer structure of a heat fusion layer may be used. In addition, each of the laminate layer, the support layer, and the heat sealing layer may be a single layer or two or more layers.

In order to improve the adhesive strength when the support layer made of the propylene block copolymer (E) or the laminate layer made of the propylene homopolymer (F) is bonded to the base material layer (G) described later, The surface may be subjected to surface activation treatment such as corona treatment, flame treatment, plasma treatment, undercoat treatment, primer coat treatment, and flame treatment.

The thickness of the easily peelable laminated film of the present invention can be appropriately determined according to the application, but usually the thickness of the heat-sealing layer is 2 to 20 μm, preferably 2 to 15 μm, and the thickness of the support layer is 16 to In the case of having a laminate layer as an easily peelable laminated film, the thickness of the laminate layer is in the range of 2 to 20 μm, preferably in the range of 2 to 15 μm. Further, the thickness of all layers of the easily peelable laminated film of the present invention is usually in the range of 20 to 110 μm, preferably 20 to 80 μm.

The easily peelable laminated film of the present invention can be produced by various known methods. For example, when producing a film having two or more laminate layers, a multilayer film molding machine equipped with three or more extruders is used, and a polyolefin composition (D The propylene polymer (A), ethylene polymer (B), and ethylene / α, β-unsaturated carboxylic acid copolymer (C), which are components of The propylene block copolymer (E) that constitutes the support layer and the propylene homopolymer (F) that constitutes the laminate layer are introduced into another extruder, and a T-die, a cyclic die, etc. are used. A predetermined amount of a propylene polymer (A), an ethylene polymer (B) and an ethylene / α, β-unsaturated carboxylic acid copolymer (C). Mixed and pressed After obtaining polyolefin composition (D) was melt-kneaded in the machine or the like, T-die method to laminate film of two or more layers by using a circular die or the like can be exemplified.
<Base material layer (G)>
In the easily peelable laminated film of the present invention, various known base material layers (G) may be laminated on the support layer or the laminate layer depending on the application.

The base material layer (G) according to the present invention is made of a sheet or film made of thermoplastic resin, paper, aluminum foil or the like. As the thermoplastic resin, various known thermoplastic resins such as polyolefin (polyethylene, polypropylene, poly-4-methyl / 1-pentene, polybutene, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (Nylon-6, nylon-66, polymetaxylene adipamide, etc.), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymer or saponified product thereof, polyacrylonitrile, polycarbonate, polystyrene, ionomer, or a mixture thereof Can be illustrated. Of these, thermoplastic resins having good stretchability and transparency, such as polypropylene, polyethylene terephthalate, and polyamide, are preferable. Further, the substrate made of such a thermoplastic resin film may be an unstretched film or a stretched film, and a laminate of one or more coextruded products, extruded laminate products, dry laminate products, etc. It may be the body. Also, for example, corona treatment, flame treatment, plasma treatment, undercoat treatment, primer coat treatment to improve the adhesion of one or both sides of the base material layer (G) with the laminate layer of the easily peelable laminated film. Alternatively, surface activation treatment such as frame treatment may be performed. The thickness of the base material layer (G) is usually in the range of 5 to 1000 μm, preferably 9 to 100 μm.

<Heat seal layer>
The propylene-based polymer constituting the heat sealing layer composed of the propylene-based polymer layer facing the heat-sealing layer of the easily peelable laminated film of the present invention is a polymer in the same category as the propylene polymer (A). However, the individual physical properties may be the same or different. Such a heat seal layer can be formed into various shapes such as a film, a sheet, a tray, a cup, and a bottle by using a propylene polymer according to a known method in accordance with the material to be packaged. In the case of a film or sheet, it can be produced by the same method as the above easily peelable laminated film. In the case of a tray or a cup, it can be produced by once producing a sheet by the above method and then forming a container such as a tray or a cup by thermoforming such as vacuum forming or pressure forming. In the case of a cup or bottle, it can be molded as a container by injection molding, injection hollow molding (injection blow), hollow molding or the like. Further, depending on the application, a propylene-based polymer may be laminated by extrusion lamination or extrusion coating, dry lamination, or the like on the base material layer such as paper.

<Cover material>
The lid material of the present invention has the heat-sealing layer of the easily peelable laminated film as the innermost layer. When it is used as a lid, the various materials exemplified as the base material layer are usually laminated on the easily peelable laminated film.

The sheet, tray, cup, bottle or the like facing the lid material of the present invention has a heat sealing layer made of a propylene-based polymer layer on the surface facing the heat fusion layer of the lid material.

<Packaging body>
The packaging body of the present invention is composed of a packaging body in which the heat-sealing layers of the easily peelable laminated film are combined with each other, or the heat-sealing layer and the propylene-based polymer layer of the easily peelable laminated film. A package including a heat sealing layer. The shape of the package of the present invention can take various shapes depending on the shape, form or application of the material to be packaged. For example, a three-sided or four-sided sealed package in which a heat-sealed layer of easily peelable laminated films is combined and a packaging material is filled in a two-sided or three-sided sealed bag, and then the mouth is heat sealed. As a package, a four-sided seal is formed by filling a packaging material into a three-sided sealing bag made of an easily peelable laminated film and a film having a heat sealing layer made of a propylene-based polymer layer, and then heat-sealing the mouth. A package, a sheet, a tray, a cup, a bottle or the like having a heat sealing layer made of a propylene-based polymer layer, filled with a material to be packaged, and then a lid that has a heat-sealing layer of an easily peelable laminated film as the innermost layer Examples include a package formed by sealing the upper surface with a material (sealant).

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

The raw materials used in Examples and Comparative Examples are as follows.
(1) Propylene / ethylene random copolymer (R-PP): manufactured by Prime Polymer Co., Ltd., propylene / ethylene random copolymer (trade name: Prime Polypropylene F327; density: 0.91 g / cm ³ , MFR; 6.0 g) / 10 min, melting point; 138 ° C).
(2) Medium density polyethylene (MDPE): Prime polymer, medium density polyethylene (trade name: Neozex: NZ3510F; density; 0.935 g / cm ³ , MFR; 1.6 g / 10 min).
(3) Ethylene / methacrylic acid copolymer (EMC): methacrylic acid content; 9% by mass, MFR; 3 g / 10 min.
(4) Propylene block copolymer (B-PP): MFR: 3.2 g / 10 min, melting point: 164 ° C., 86% by mass of propylene polymer component and 14% by mass of propylene / ethylene random copolymer component (ethylene Content 26.6 mol%, intrinsic viscosity [η] 3.1 dl / g).
(5) Propylene homopolymer (H-PP): manufactured by Prime Polymer Co., Ltd., propylene homopolymer polymer (trade name: Prime Polypro F704NP; density: 0.90 g / cm ³ , MFR: 7.0 g / 10 min, melting point 160 ° C.).

<Example 1>
A polyolefin composition obtained by dry blending R-PP; 40% by mass, MDPE; 50% by mass and EMC; 10% by mass as a heat-fusible layer, B-PP as a support layer, and H-PP as a laminate layer, Each laminate is supplied to a separate extruder, and a laminated film composed of a three-layer coextruded film with the structure of heat-fusion layer / support layer / laminate layer is formed by the T-die method, and corona treatment is applied to the laminate layer. gave. The total thickness of the film was 30 μm, and the thickness of each layer was heat fusion layer / support layer / laminate layer = 4.5 / 21.0 / 4.5 μm.

<Example 2>
The same procedure as in Example 1 was performed except that a polyolefin composition obtained by dry blending R-PP; 40% by mass, MDPE; 40% by mass and EMC; 20% by mass was used in place of the heat-sealing layer of Example 1. A three-layer film was obtained.

<Example 3>
The same procedure as in Example 1 was performed except that a polyolefin composition obtained by dry blending R-PP; 30% by mass, MDPE; 40% by mass and EMC; 30% by mass was used instead of the heat-sealing layer of Example 1. A three-layer film was obtained.

<Comparative example 1>
A three-layer film was obtained in the same manner as in Example 1 except that H-PP used in the laminate layer of Example 1 was used instead of B-PP used in the support layer of Example 1.

<Comparative example 2>
A three-layer film was obtained in the same manner as in Example 1 except that a polyolefin composition obtained by dry blending R-PP; 70% by mass and MDPE; 30% by mass was used in place of the heat-sealing layer of Example 1. It was.

The easy peelability of the three-layer films obtained in Examples and Comparative Examples was evaluated by the following method.
(1) Evaluation of easy peelability In order to evaluate easy peelability, the bilayer stretched polyethylene terephthalate film (PET) having a thickness of 12 μm was subjected to the corona of the three-layer film obtained in each of the above examples and comparative examples. A laminated film was prepared by laminating the treated surface by dry lamination using a urethane adhesive, and a polypropylene sheet having a thickness of 300 μm was prepared as a heat seal layer.

Next, the heat-sealing layer and the polypropylene sheet of each laminated film were overlapped, and sealed at a predetermined temperature shown in Table 1 at a pressure of 0.2 MPa for 1 second using a sealer having a width of 5 mm. And then left to cool. A 15 mm wide test piece was cut out and the heat seal portion was peeled off at a cross bed speed of 500 mm / min, and the strength was set as the heat seal strength (N / 15 mm).

Evaluation of easy peelability is performed by confirming the peeled state in addition to heat seal strength, ○ for a stable peeled state, x for laminate peeling or film breakage, and x for those with stringing. It was.

The results are shown in Table 1.

The easily peelable laminated film of the present invention is suitable as a packaging film, particularly as a cover material for polypropylene sheets, trays, cups, bottles, etc., for snack confectionery packaging such as rice crackers and potato chips, or jelly, milk, It can be suitably used as a packaging material for food packaging such as yogurt, pudding, tofu and lactic acid beverages, packaging for pharmaceuticals, medical instruments, blister packaging, and other daily necessities and miscellaneous goods.

Claims (6)

Polyolefin composition comprising propylene polymer (A) 20 to 70% by mass, ethylene polymer (B) 20 to 60% by mass and ethylene / α, β-unsaturated carboxylic acid copolymer (C) 5 to 40% by mass An easily peelable laminated film comprising a heat-sealing layer comprising (D) and a support layer comprising a propylene block copolymer (E). The easily peelable laminate film according to claim 1, wherein a laminate layer made of a propylene homopolymer (F) is laminated on the surface of the support layer where the heat-sealing layer is not laminated. The easily peelable laminated film according to claim 1 or 2, wherein the base material layer (G) is laminated on the support layer or the laminate layer. The easily peelable laminated film according to any one of claims 1 to 3, wherein the layer facing the heat-sealing layer comprising the polyolefin composition (D) is a propylene polymer layer. A lid material comprising the easily peelable laminated film according to any one of claims 1 to 3. 4. A package comprising a heat-sealing layer comprising a propylene-based polymer layer on a surface facing the heat-sealing layer of the easily peelable laminated film according to any one of claims 1 to 3.