JPS5829233B2 - Sekisou Film Oyobi Sonoseizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a laminated film having ethylene-propylene random copolymer resin on one surface and having excellent gas barrier properties, water vapor barrier properties, heat sealability, and excellent scratch resistance, and a method for producing the same. It is related to.

Conventionally, it has been known to use a vinylidene chloride resin as a surface layer or an intermediate layer as a barrier layer against gas and moisture in a laminated film.

For example, gases with excellent mechanical strength, transparency, etc.
There is a method of coating a two-wheel stretched polypropylene film, which has poor moisture barrier properties, with a vinylidene chloride resin as a paint or emulsion, or laminating a vinylidene chloride resin film using an adhesive.

However, the former coating method not only requires a large amount of capital for equipment such as drying equipment and solvent recovery equipment, but is also performed in a completely separate process from the preparatory process, which avoids high costs in terms of the number of operating personnel, yield, etc. I couldn't.

The latter method, in which a polypropylene film and a vinylidene chloride resin film are laminated via an adhesive, is complicated in that it requires surface treatment of the polypropylene sheet and adhesive application, but is easy to manufacture. Not.

Further, in both cases, there was a drawback that the vinylidene chloride resin located on the inner surface of the bag after making the bag did not have scratch resistance against the contents of the package, such as rice crackers and hail.

Moreover, in general, it is extremely difficult to melt-extrude vinylidene chloride resin into a film with a thickness of 5 microns or less due to extrusion die design, and compared to other resins, the monomer manufacturing process is much more complicated. 1. Easy to form a film because it is expensive.
0: It is difficult to use it for the same purpose as inexpensive films such as polyethylene, polypropylene, and nylon that are thicker than chlorine, and even if they have highly superior properties in terms of gas barrier and water vapor barrier properties, they are not suitable for the industry due to price. The reality is that the barrier layer is avoided, so it was completely inconceivable that a film laminated with this as a barrier layer would be accepted by the industry.

The present invention purposefully combines a vinylidene chloride copolymer resin layer, an ethylene-propylene random copolymer resin layer, and an isotactic polypropylene resin layer, and has almost no heat shrinkage, transparency, toughness, and gas resistance. The purpose of this film is to provide an ideal packaging film with excellent moisture barrier properties, easy heat-sealing properties, and surface scratch resistance.

The present invention provides (1) a vinylidene chloride copolymer resin layer stretched axially or biaxially at an area ratio of preferably 5 times or more; An ethylene-propylene random copolymer resin layer that is biaxially stretched, preferably at an area ratio of 5 times or more, and an isotactic propylene resin layer that is uniaxially or biaxially stretched and laminated on one side of the multilayer film. and (2) a non-stretched vinylidene chloride copolymer resin layer and a non-stretched ethylene-propylene random copolymer layer laminated directly or via an adhesive resin layer on both surfaces thereof. After that, isotactic polypropylene is laminated on one side of the multilayer film by melt extrusion or laminated in film form, and the laminate is uniaxially or biaxially D-shaped.
This is a method for producing a laminated film characterized by O-thermal stretching.

In the present invention, the vinylidene chloride-based copolymer resin includes vinylidene chloride in an amount of 70% by weight (t-g) as a copolymer component, and includes vinyl chloride, acrylonitrile,
It is a copolymer containing 30% by weight or less of vinyl acetate, acrylic acid, and one or more esters of an alcohol having an alkyl group having 1 to 18 carbon atoms and acrylic acid or methacrylic acid.

In addition, ethylene-propylene random copolymerized Ti fat refers to one with an ethylene content of 1.0 to 20% by weight and a randomness index of 1.5 or less, and isotactic polypropylene refers to one in which the intrinsic viscosity of a tetralin solution at 135°C is 1. .2 to 4.0, preferably 1.5 to 35 isotactic polypropylene.

The present inventors believe that if the vinylidene chloride copolymer resin layer is stretched uniaxially or biaxially, even if the thickness is 1 micron or less, the barrier property required by the market, that is, the oxygen permeability of 100 (cc/m. 24Hr, 23℃) or less, water vapor transmission rate 8. o (g/m-24Hr) or more, and has several times the blocking effect compared to commonly used packaging films such as polypropylene, polyethylene, and nylon, and must be stretched in an aO heat zone. It has been found that if the material is heated and heat-set at that temperature, almost no heat shrinkage remains.

Moreover, if it is possible to form a vinylidene chloride-based resin layer as an extremely thin barrier layer, that is, 3 microns or less, it will be welcomed by the industry in terms of cost, considering the above-mentioned barrier effect. It was expected that it would be something.

The present invention makes it possible to stretch the vinylidene chloride resin layer by making it into an unstretched film, and also converts the unstretched vinylidene chloride resin layer into a thicker ethylene-propylene film. By keeping it inseparably adhered to the random copolymer resin layer, it is possible to achieve more uniform stretching and prevent the layer from tearing due to stretching (stretching). We succeeded in making it thicker.

A stretched ethylene-propylene random copolymer resin layer, preferably thicker than this, directly or via an adhesive resin layer on both sides of the extremely thin layer of the stretched vinylidene chloride resin layer of the present invention, preferably having a thickness of 3 microns or less. As a method for producing a laminated film having a layer structure in which a stretched crystalline polypropylene layer is further arranged on one outer surface, for example, each resin is simultaneously arranged in the above layer structure using a T-die or an annular die and laminated. The extruded product may be stretched uniaxially or biaxially, but preferably a vinylidene chloride resin is used as the inner layer, and a thicker ethylene-propylene random resin layer is preferably used on both sides of the inner layer, either directly or through an adhesive resin layer. A polymeric resin layer is arranged and laminated and extruded from a T-die to form a non-stretched film, and then, at a necessary point, a resin to be made into a surface layer is melt-extruded and laminated onto the film and DO hot-stretched, or the surface layer and The desired film is laminated onto the above film and stretched uniaxially or biaxially through a heating zone, preferably at an area ratio of 5 times or more.

That is, when it is desired to obtain the above-mentioned laminated film of the present invention, polypropylene is laminated by melt extrusion on the above film and then heated and stretched, or a polypropylene film is laminated on the above film and then stretched by force.

It is preferable that the vinylidene chloride resin does not contain a plasticizer in terms of gas and moisture barrier properties, but in order to facilitate stretchability, it is preferable to contain a low-molecular plasticizer such as dibutyl sebacate, dioctyl adipate, etc. Good too.

The heating temperature for stretching is preferably above the melting point of the ethylene-propylene copolymer resin.

The vinylidene chloride resin and the ethylene-propylene random copolymer resin may be directly laminated and extruded, but they may also be extruded with, for example, ethylene-vinyl acetate interposed therebetween.

When extruding and stretching with the desired layer configuration from the beginning, even if they are directly laminated, there is adhesion between both layers due to melting, which causes friction between the layers during stretching, which hinders the stretching of the vinylinodene chloride resin layer. However, if you create a film by directly laminating both layers of -tan, then laminating a molten polypropylene resin or film thereon and stretching the film, the vinylidene chloride copolymer resin layer and the ethylene-propylene random copolymer resin layer will be used. It is preferable to interpose the above-mentioned ethylene-vinyl acetate or the like between the two layers since the surface adhesion between the two layers is weakened.

Next, a practical example of the present invention will be described.

Actual example l Vinylidene chloride 83.0%, vinyl chloride 17.
A 6 micron inner layer of vinylidene chloride copolymer resin containing 100 parts by weight of 0% copolymer (1.5 parts of dioctyl adipate and 2.5 parts of dibutyl sebacate) and its both sides (ethylene-vinyl A 5 micron layer of acetate, on both outer sides of which has a 19 micron layer with an intrinsic viscosity of 1.6 in tetralin solution at 135°C, an ethylene content of 5 weight percent, and a randomness index of 0.4.
5 ethylene propylene random copolymer resin is arranged and T
A non-stretched film A was obtained by laminating and extruding from a die.

On the other hand, isotactic polypropylene having an intrinsic viscosity of 2.5 in a tetralin solution at 135°C was extruded into a film and stretched five times in the straight direction to form a film B of 270 microns, which was then laminated onto film A. 160
2x in the longitudinal direction and 4x in the lateral direction in the thermal zone of ℃
Stretching was performed by a total of 8 times.

The obtained film has excellent transparency and gloss, and extremely high barrier properties with an oxygen permeability of 52 (cc/m" 24Hr, 23°C) and a water vapor permeability of 3.0 (g/m 24Hr). And the heat seal strength is at a hot plate temperature of 15
The peel strength of the sealed part was 620g/Cr/L1 at 0℃, pressure 1kg/75, and sealing time 0.5 seconds.
It showed a high value.

Actual foil example 2 8 made of a vinylidene chloride copolymer resin in which 2.3 parts of dibutyl sebacate and 2.0 parts of acetyl tributyl citrate were added to 100 parts by weight of a copolymer of 85% vinylidene chloride and 15% vinyl chloride. Ethylene content 4 with an inner layer of 26 microns and an intrinsic viscosity of 1.6 in tetralin solution at 135°C on both sides
Mold weight percent, ethylene with randomness index 0.48
A propylene random copolymer resin was arranged and laminated and extruded from a T-die to obtain an unstretched film A'.

- Isotactic polypropylene having an intrinsic viscosity of 2.3 in tetralin solution at 135°C is melt extruded to 330 microns and laminated to film A' at 160°C.
The film was stretched three times in each of the two axial directions while passing through a heating zone.

The obtained film had excellent transparency and gloss, and exhibited extremely high barrier properties with an oxygen permeability of 50 (cc/m''·24Hr, 23°C) and a water vapor permeability of 30 (fi/m″·24Hr).

Moreover, the heat sealing strength showed a high peel strength of 630 g/h.

Leprosy example 3 Intrinsic viscosity in tetralin solution at 135°C is 2
．． 5 was extruded into a film and stretched 5 times in the warp direction (stretched to form a film B' of 250 microns), which was then laminated on film A of Example 1 and transversely in a 770 heat zone at 160°C. It was stretched 8 times in the force direction and subjected to tension heat treatment at 170°C.

The obtained film has excellent transparency and gloss, and has an oxygen permeability of 40 (/, -24Hr, 23°C) and a water vapor permeability of 2.8.
It has an extremely high blocking property (24 hours) and 9
It exhibited a low heat shrinkage of less than 2 in hot water at 5°C for 30 minutes, and a high heat seal strength of 50og/cm width.

In the laminated film of the present invention, the outer surface has excellent scratch resistance due to polypropylene, and the inner surface has excellent heat sealability and scratch resistance due to the cotylene-propylene copolymer resin.

In addition, the polyvinylidene chloride resin contained therein provides excellent gas and moisture barrier properties, and all three of these resins have excellent gloss and transparency, making the laminated film extremely aesthetically pleasing in this respect.

This laminated film is epoch-makingly excellent for contents that easily damage the inner surface of the film bag, such as graupel, rice crackers, etc., or contents that are easily perishable, such as fresh confectionery, processed seafood, and meat products.

In addition, in the production method of the present invention, a multilayer film (formed in this way) in which vinylidene chloride resin, which is excellent as a barrier layer, is sandwiched between resin layers that are stretchable and have good adhesion to polypropylene and high heat sealability. In order to be
Polypropylene can be laminated and stretched at any time to form any barrier packaging material, and the vinylidene chloride copolymer resin layer can now be stretched very uniformly and easily.

Claims (1)

[Scope of Claims] A uniaxially or biaxially stretched vinylidene chloride copolymer resin layer, and a uniaxially or biaxially stretched ethylene content laminated on both sides thereof directly or via an adhesive resin layer. l
A laminated film comprising an ethylene-propylene random copolymer resin layer of ~20 weight mass and a uniaxially or biaxially stretched isotactic polypropylene resin layer laminated on one side of the multilayer film. 2. A non-stretched vinylidene chloride copolymer resin layer and a non-stretched ethylene-propylene random copolymer resin layer having an ethylene content of 1 to 20% by weight laminated on both sides thereof directly or via an adhesive resin layer. A multilayer film is formed, then isotactic polypropylene is laminated on one side of the multilayer film by melt extrusion or in the form of a film, and the laminate is uniaxially or biaxially heated and stretched. Film manufacturing method.