JPH09290477A - Film of barrier properties and packaging material using the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide superior gas barrier properties and good bonding properties with an OPP base. SOLUTION: A deposited layer 14 composed of an inorganic oxide is formed on a face not being in contact with a core layer of a skin layer of a coextruded polypropylene biaxially oriented film 13 composed of a homopolymer type polypropylene core layer 11 and a copolymer type polypropylene skin layer 12 not containing an antistatic agent nor a slip agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrier packaging material for packaging snacks and pharmaceuticals which are required to have an oxygen barrier property and a water vapor barrier property, and more specifically, a polypropylene film deposited with an inorganic oxide or a vapor deposited layer thereof. The present invention relates to a barrier film having a coating layer composed of a metal alkoxide and a water-soluble resin applied thereon and a packaging material using the same.

[0002]

2. Description of the Related Art Conventionally, when stretched polypropylene (hereinafter abbreviated as OPP) consisting of a homopolymer type polypropylene simple substance is subjected to vapor deposition processing, the adhesion at the interface is maintained when metal aluminum is vapor deposited, but it is oxidized. Silicon,
When an inorganic oxide such as aluminum oxide or magnesium oxide is deposited, sufficient adhesion at the interface cannot be maintained.
This means that flexible metallic aluminum can also adhere to the solid surface of the homopolymer-type-polypropylene layer, but the rigid inorganic compound cannot pierce on the solid surface, resulting in sufficient adhesion. It is considered that this is not possible.

Further, the OPP consisting of a copolymer type polypropylene alone has an inferior heat resistance because it contains an ethylene component, and OPP is caused by a heat load during vapor deposition processing.
Causes thermal contraction and induces defects such as cracks in the deposited film. Such defects impede the barrier property originally possessed by the deposited film, particularly the oxygen barrier property.

An antistatic agent or a slip agent may be added to OPP, but such an organic additive is not compatible with polypropylene, so that it bleeds out on the OPP surface and functions as such. Express. Therefore, if the OPP containing such an additive is directly subjected to the vapor deposition process, there is a problem that the adhesion between the OPP and the vapor deposited film deteriorates with time due to the bleed-out of the additive component.

Further, a film having a barrier property obtained by applying a barrier resin solution to OPP is PVDC.
It has already been completed for coated products and EVOH coated products. However, since PVDC contains chlorine as a component, it has a problem of pollution at the time of incineration, and EVOH has problems of insufficient steam barrier property and poor moisture resistance.

For the above-mentioned reasons, a polyethylene terephthalate film, which has good adhesion to inorganic compounds and excellent heat resistance, is widely used as a substrate for vapor deposition of inorganic compounds used for packaging materials. A thickness of 12 μm is often used because of its price.
However, there has been a demand for a barrier film that is more flexible than the polyethylene terephthalate film, has a high flexibility, and is inexpensive.

[0007]

The present invention has been made in order to eliminate the above-mentioned problems associated with OPP used as a substrate for vapor deposition of inorganic oxides, and has excellent gas barrier properties and OPP substrate. It is an object of the present invention to provide a low-cost barrier film having good adhesion with and a packaging material using the barrier film.

[0008]

Means for Solving the Problems A first invention of the present invention is:
A coextruded polypropylene biaxially stretched film comprising a homopolymer type polypropylene core layer and a copolymer type polypropylene skin layer containing no antistatic agent or slip agent, which is not in contact with the core layer of the skin layer. It is a barrier film characterized in that a vapor deposition layer made of an inorganic oxide is provided on its surface.

A second invention is a barrier film according to the first invention, characterized in that a coating layer comprising a metal alkoxide and a water-soluble resin is provided on the vapor deposition layer.

Furthermore, a third invention is a barrier film according to the first and second inventions, wherein the copolymer type polypropylene is an ethylene-propylene copolymer (ethylene component 1 to 50%). is there.

Furthermore, a fourth invention is a packaging material according to the first invention, wherein a sealant layer is laminated on the vapor deposition layer surface of the barrier film.

Furthermore, a fifth invention is a packaging material according to the second invention, wherein a sealant layer is laminated on the coating layer surface of the barrier film.

As described above, according to the present invention, a homopolymer type-polypropylene core layer and a copolymer type-polypropylene containing no antistatic agent or slip agent, particularly ethylene-propylene copolymers (ethylene components 1 to 1). 50%), a coextruded polypropylene biaxially stretched film comprising a skin layer is provided with a vapor deposition layer comprising an inorganic oxide on the surface of the skin layer which is not in contact with the core layer. A barrier film having excellent properties and good adhesion to an OPP substrate can be obtained. Further, since the sealant layer is laminated on the vapor deposition surface of this barrier film, it is possible to produce a packaging material having a good gas barrier property.

Furthermore, since a coating layer composed of a metal alkoxide and a water-soluble resin is provided on the vapor-deposited layer, a barrier film having further excellent barrier properties and water vapor barrier properties can be obtained.

Furthermore, the coating layer composed of the metal alkoxide and the water-soluble resin is excellent in environmental friendliness.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments. The base film of the barrier film of the present invention is composed of a homopolymer type-polypropylene core layer and a copolymer type-polypropylene skin layer. For example, polypropylene obtained by fusing the core layer and the skin layer by a coextrusion laminating method. Is a biaxially stretched film. This production method will be described in detail.First, homopolymer type-polypropylene and copolymer type-polypropylene are fed to separate extruders, melt-extruded,
For example, in a die, the core layer and the skin layer are merged so as to form the core layer / skin layer or the skin layer / core layer / skin layer, and the mixture is extruded from a slit, wrapped around a cooling roll, cooled and solidified into a roll shape, and an unstretched film. And afterwards,
Using a stretching machine by a known method this unstretched film,
It is a biaxially oriented polypropylene film.

As the copolymer type polypropylene, propylene copolymers such as polypropylene-α-olefin copolymer, polypropylene-acrylic acid copolymer and polypropylene-maleic anhydride copolymer are preferred. In particular, from the viewpoint of price and processability, ethylene-propylene copolymer (ethylene component is 1 to 50%) can be preferably used. The coextruded polypropylene biaxially stretched film as a base material has a two-layer structure of homopolymer type-polypropylene / copolymer type-polypropylene, and a three-layer structure of copolymer type-polypropylene / homopolymer type-polypropylene / copolymer type-polypropylene. It can be preferably used.

Here, it is important not to add an organic molding aid such as an antistatic agent or a slip agent to the copolymer type polypropylene used for the skin layer. In particular, an antistatic agent and a slip agent should not be included on the surface of the inorganic oxide, which will be described later, for vapor deposition processing. If the antistatic agent or the slip agent is contained, the antistatic agent or the slip agent bleeds out, and the adhesion between the skin layer and the vapor deposition layer deteriorates over time.

The ratio of the thickness of the core layer to the thickness of the skin layer is 20 /
About 1 to 2/1 is preferably used, and the total thickness of the substrate is preferably about 20 μm.

An inorganic oxide having a thickness of 100 to 100 is formed on the skin layer surface of the coextruded polypropylene biaxially stretched film containing no antistatic agent or slip agent by a known method.
About 0Å is vapor-deposited to produce a barrier film which is an inorganic oxide vapor-deposited polypropylene film. As the inorganic oxide, silicon oxide, aluminum oxide, magnesium oxide and the like can be preferably used.

When further gas barrier properties and water vapor barrier properties are required, it is advisable to provide a coating layer comprising a metal alkoxide and a water-soluble resin on the above-mentioned inorganic oxide vapor deposition layer.

As the metal alkoxide, tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ], triisopropoxyaluminum [Al (O-2′-C ₃ H ₇ ) ₃ ] and other general formulas, M (OR) _n (M: metal such as Si, Ti, Al, Zr, R: CH ₃ ,
And an alkyl group such as C ₂ H ₅ ). Among them, tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

Examples of the water-soluble resin include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like.

The coating liquid for forming the coating layer comprises the above water-soluble resin and the above metal alkoxide directly,
Alternatively, it is formed by coating a solution obtained by mixing treatments such as hydrolysis in advance on the vapor deposition layer of the barrier film and heating and drying.

As a method of applying the coating liquid, conventionally known means such as a dipping method, a roll coating method, a screen printing method and a spray method which are usually used can be used. The thickness of the coating layer varies depending on the type of coating liquid, but the thickness after drying is about 0.01 to 100 μm.
However, if the thickness is 50 μm or more, cracks are easily generated in the coating layer, and therefore 0.01 to 50 μm.
m is desirable.

The vapor-deposited layer surface of the finished barrier film and a plastic film such as an unstretched polypropylene film (hereinafter abbreviated as CPP) are dry-laminated using, for example, a polyurethane adhesive to form a packaging material. When further gas barrier property and water vapor barrier property are required, the coating layer surface of the barrier film provided with the coating layer and the CPP film are dry laminated to form a packaging material.

[0027]

EXAMPLES Examples of the present invention will be described below more specifically. <Example 1> The barrier film of the present invention is shown in FIG.
As shown in FIG.
The structure is such that a vapor deposition layer 14 of silicon oxide or the like is formed on the skin layer surface of PP 13.

OP comprising core layer 11 and skin layer 12
P13 is produced as follows. That is, homopolymer type polypropylene forming the core layer 11 and ethylene type propylene copolymer (copolymer type polypropylene forming the skin layer 12) (ethylene component 5%) are supplied to separate extruders, and 230 to 280 are supplied.
It is melt extruded at a temperature of ° C, the core layer and the skin layer are merged in the die and extruded from the slit, and the final thickness is the core layer 1
5 μm, 5 μm skin layer, 20 μm total thickness, wound around a cooling roll, cooled and solidified into a film to form an unstretched film, and then using a stretching machine according to a known method to obtain OPP13 having a thickness of 20 μm. It should be noted that an organic molding aid such as an antistatic agent or a slip agent should not be added to the ethylene-propylene copolymer.

The skin layer 1 of the OPP 13 produced in this way
2, a barrier film 10 is prepared by vapor-depositing silicon oxide (SiO) 400Å by a known method using a roll-up type vapor deposition machine to form a vapor deposition layer 14 and vapor-depositing an inorganic oxide (silicon oxide). It

A silicon oxide deposition surface of the inorganic oxide (silicon oxide) deposition barrier film 10 and a CP having a thickness of 30 μm
P15 and dry-laminated with urethane adhesive, and OPP (20 μm thick) (a *) 13 / deposition layer (Si
O 400Å thickness) 14 / DL / CPP (30 μm thickness) 1
A packaging material 1 having 5 configurations was produced. However, a *: core layer (15 μm thickness, homopolymer type-polypropylene) 11 / skin layer (5 μm thickness, ethylene-propylene copolymer (ethylene component 5%) 12 DL: bonded by a dry lamination method using a urethane adhesive Means to do.

Example 2 OPP (20 μm thick) (a *) / deposited layer (Al ₂ ) was prepared in the same manner as in Example 1 except that aluminum oxide (Al ₂ O ₃ ) was used as the inorganic oxide.
A packaging material having a structure of O ₃ 400Å thickness) / DL / CPP (30 μm thickness) was manufactured (detailed manufacturing method is omitted).

Example 3 OPP (20 μm thick) (a *) / deposited layer (MgO) was prepared in the same manner as in Example 1 except that the inorganic oxide was magnesium oxide (MgO).
A packaging material having a structure of 400Åthickness / DL / CPP (thickness of 30 μm) was manufactured (detailed manufacturing method is omitted).

Example 4 OPP (20 μm thick) (a *) / deposition layer (Si) was prepared by the same material and method as in Example 1 except that a coating layer having the following formulation was provided on the vapor deposition layer.
O 400Å thickness) / Coating layer (500Å thickness) / D
A packaging material 1a having an L / CPP (thickness of 30 μm) structure was manufactured (detailed manufacturing method is omitted). However, the coating layer was formed by applying a coating liquid having the following composition with a bar coater and drying it with a dryer at 90 ° C. for 1 minute.

Composition of coating liquid Tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] 10.
89.6 g of 0.1N hydrochloric acid was added to 4 g, and the mixture was hydrolyzed by stirring for 30 minutes to give a hydrolysis solution (A) having a solid content of 3 wt% (SiO conversion) and 3.0 wt% of polyvinyl alcohol.
Of water / isopropyl alcohol (90/10) solution (B).

Example 5 OPP (20 μm thick) (a *) / deposited layer (Al ₂ ) was prepared in the same manner as in Example 4 except that the inorganic oxide was aluminum oxide (Al ₂ O ₃ ).
O ₃ 400Å thickness) / Coating layer (500Å thickness) / D
A packaging material having an L / CPP (thickness of 30 μm) structure was manufactured (detailed manufacturing method is omitted).

Example 6 OPP (20 μm thick) (a *) / deposited layer (MgO) was prepared in the same manner as in Example 4 except that the inorganic oxide was magnesium oxide (MgO).
400Å thickness) / Coating layer (500Å thickness) / DL /
A packaging material having a CPP (thickness of 30 μm) structure was manufactured (detailed manufacturing method is omitted).

Example 7 OPP (20 μm thick) (a *) was prepared by the same material and method as in Example 4 except that the laminating method of the OPP film and the sealant layer was changed from DL to PE extruder laminating method. ) /
Deposition layer (SiO 400Å thickness) / Coating layer (50
0Å thickness) / Ext. A packaging material having a / PE (thickness of 30 μm) configuration was produced (detailed production method is omitted). However, Ext. That means that the urethane-based anchor coating agent is used for adhesion by an extrusion laminating method (extrusion temperature: 320 ° C.).

<Comparative Examples 1, 2, 3> OPP of homopolymer type-polypropylene resin single layer having a thickness of 20 μm
In the same manner as in Examples 1, 2, and 3, a vapor deposition layer (400 Å thickness) of an inorganic oxide (silicon oxide, aluminum oxide, magnesium oxide) is formed on (hereinafter abbreviated as homo OPP),
As in Example 1, CPP (30 μm thick) was formed on the surface of the deposited layer.
Was dry-laminated with a urethane adhesive to prepare a packaging material having the following constitution. Comparative Example 1; Homo OPP (20 μm thick) / deposited layer (SiO
400 Å thickness) / DL / CPP (30 μm thickness) Comparative Example 2; Homo OPP (20 μm thickness) / vapor deposition layer (Al ₂
O ₃ 400Å thickness) / DL / CPP (thickness of 30 μm) Comparative example 3; Homo OPP (thickness of 20 μm) / deposition layer (MgO)
400Å thickness) / DL / CPP (30 μm thickness)

<Comparative Example 4> Example 1 except that the material and method for laminating with OPP as the base film was changed to the extruder lamination method using polyethylene.
A packaging material having the following constitution was produced by the same material and method as in. Comparative Example 4; OPP (20 μm thick) (B *) / deposited layer (S
iO 400Å thickness) / Ext. / PE (30 μm thickness)

In order to evaluate the gas barrier properties and the adhesion of the vapor-deposited layer (or coating layer) to the substrate film of the 11 kinds of packaging materials produced, oxygen gas permeability, water vapor permeability, OPP and CPP (PE) Three points of adhesive strength were measured according to the following measuring method. Table 1 shows the results.

Oxygen gas permeability ... MOCON OXTR
Using an AN 10/50 oxygen gas permeability measuring device (manufactured by Modern Control Co., Ltd.), 30 ° C., 70% RH. Measured in the atmosphere. Water vapor permeability ··········· PARMATRAN W600 water vapor permeability measuring device (manufactured by Modern Control Co., Ltd.), 40 ℃, 90% RH. Measured in the atmosphere. Adhesive strength between OPP and CPP: 40 ° C, 90% RH.
Immediately after being exposed to the atmosphere described above, the adhesive strength between OPP and CPP (partly PE) was peeled off by T-type peeling (crosshead speed 300 mm / min. Sample width 15m
Measured in m).

[0042]

[Table 1]

Considering from Table 1, by using a homopolymer type-polypropylene base and a coextruded polypropylene biaxially stretched film having an ethylene-propylene copolymer as a skin layer on at least the vapor deposition surface as a base material, silicon oxide and aluminum oxide can be obtained. It became possible to maintain the adhesive strength at the interface when an inorganic oxide such as magnesium oxide was deposited (Examples 1 to 7). It is considered that this is because the surface to be vapor-deposited is changed from the homopolymer type to the copolymer type, so that the surface becomes soft and the effect of increasing the adhesiveness due to the piercing effect of the inorganic oxide is enhanced. It can also be said that it is possible to improve the heat resistance as compared with the copolymer alone, suppress the heat shrinkage during the vapor deposition process, and form a crack-free vapor deposition film. OPP / CPP
Since no deterioration of the adhesive strength with time was observed, it was possible to suppress the bleed-out of the additive to the vapor deposition interface after vapor deposition and to eliminate the deterioration of the adhesive strength at the interface.

[0044]

As described above, according to the present invention, a co-extruded polypropylene biaxially stretched film which is a homopolymer type polypropylene base and has a skin layer containing a copolymer containing no antistatic agent or slip agent at least on the vapor deposition surface. By vapor-depositing an inorganic oxide such as silicon oxide, it became possible to produce an OPP-based barrier film having good gas barrier properties and adhesion, and at low cost. Further, by providing a coating layer made of a mixture of a metal alkoxide and a water-soluble resin on the vapor deposition layer, it became possible to produce an OPP-based barrier film having further gas barrier properties. Furthermore, by laminating a sealant layer such as CPP on the vapor deposition surface (or coating surface) of this barrier film,
It has become possible to manufacture relatively low-cost packaging materials with excellent water vapor barrier properties.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of a barrier film of the present invention and a packaging material using the same.

FIG. 2 is a cross-sectional explanatory view showing another example of the barrier film of the present invention and the packaging material using the same.

[Explanation of symbols]

 1, 1a ... packaging material 10, 10a ... barrier film 11 ... core layer 12 ... skin layer 13 ... OPP 14 ... vapor deposition layer 15 ... CPP 16 ... coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // B29K 23:00 B29L 9:00

Claims (5)

[Claims] 1. A core layer of a skin layer of a co-extruded polypropylene biaxially stretched film comprising a homopolymer type polypropylene core layer and a copolymer type polypropylene skin layer containing no antistatic agent or slip agent. A barrier film having a vapor-deposited layer made of an inorganic oxide on a surface not in contact with the barrier film. 2. The barrier film according to claim 1, wherein a coating layer composed of a metal alkoxide and a water-soluble resin is provided on the vapor deposition layer. 3. The copolymer type polypropylene is an ethylene-propylene copolymer (ethylene components 1 to 5).
It is 0%), The barrier film of Claim 1 or 2 characterized by the above-mentioned. 4. A packaging material obtained by laminating a sealant layer on the vapor-deposition layer surface of the barrier film according to claim 1. 5. A packaging material obtained by laminating a sealant layer on the coating layer surface of the barrier film according to claim 2.