JP3483369B2 - Coextrusion multilayer film for deep drawing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coextrusion multilayer film for deep drawing, which can be suitably used for packaging trays and the like which are required to have high gas barrier properties and strength.

[0002]

2. Description of the Related Art Conventionally, various packaging trays have been formed by a deep-drawing method, and as a film to be used (hereinafter, also including a relatively thick sheet), there is a multi-layered film having various layers. . The functions required for such a multilayer film are processability, strength, transparency, gas barrier properties, aroma retention, heat resistance, sealing properties, etc., and a multilayer film having a layer structure as necessary is selected.

Generally, as a method for obtaining a multilayer film, a dry laminating method in which each layer is formed into a film and then laminated with an adhesive, or a method in which any material is used as a substrate for extrusion laminating or coating, There is a coextrusion method.

In the methods for obtaining these multilayer films, in the dry laminating method, extrusion laminating method and coating method, the productivity is deteriorated due to the complicated laminating process,
There is a problem that the manufacturing cost is high.

Also in the coextrusion method, the appearance is good and
In order to obtain a multilayer film in which each layer has a uniform thickness and is excellent in deep drawability, manufacturing conditions specific to the coextrusion method, such as coextrusion temperature, spinneret temperature, spinneret structure, casting temperature, and take-off There is a problem in that the layer structure and the raw material resin that match the optimum combination of molding conditions such as speed are limited.

[0006] The largest cause of the defects is a defect at the resin interface due to the stability of the multilayer flow of the resin in the die in the coextrusion molding method. This is a problem peculiar to the co-extrusion molding method, and is particularly remarkable in a multi-layer film having a resin composition with uneven flow characteristics. Phenomenon instability occurs at the interface between the resins in the flow of multi-layered resin, and a fine wavy pattern occurs on the inner surface of the film.In severe cases, unevenness occurs on the entire surface of the film, resulting in holes. There is also. When such a film is post-processed such as deep drawing, the degree of defects tends to be further promoted.

[0007]

DISCLOSURE OF THE INVENTION The present invention has found a coextrusion multilayer film for deep drawing, in which a polyester resin layer having the above-mentioned problems is provided as the outermost layer, and the gist thereof is , The first layer is a polyester resin layer,
The second layer is an adhesive resin layer, the third layer is a saponified ethylene vinyl acetate copolymer layer, the fourth layer is an adhesive resin layer, and the fifth layer is a sealing resin layer. The intrinsic viscosity (IV) of the polyester resin of the layer is 0.65
0.85, the thickness ratio to the total thickness of the first layer is in the range of 0.75 to 0.92, and the melt index (MI) of the resin other than the first layer is 5.0 to 35.
It is a coextrusion multilayer film for deep drawing, which is characterized by 0.

The polyester resin used in the first layer of the multilayer film of the present invention is provided to impart rigidity, strength and secondary processability. Specific resins include polyethylene terephthalate resin (PET) and poly Butylene terephthalate resin (PBT) can be preferably used.

The polyester resin of the first layer has an intrinsic viscosity (IV) of 0.65 to 0.85, preferably 0.7 to
Use the one in the range of 0.8. Here, the intrinsic viscosity (I
V) is measured by using 300 mg of resin as a sample and 30 m of solvent as the solvent.
It was dissolved in 1 (phenol, 1,1,2,2-tetrachloroethane weight ratio of 1: 1) and the sample drop time was measured using an Uberose viscometer to calculate the IV value.

When IV is less than 0.65, there is no effect of improving rigidity and strength, and when IV exceeds 0.85, there is a problem that productivity is poor. Further, the thickness ratio to the total thickness of the first layer needs to be in the range of 0.75 to 0.92. If it is less than 0.75, there is no improvement effect on rigidity and strength, and if it exceeds 0.92, it is molded. There is a problem of poor sex.

The adhesive resin used for the second layer and the fourth layer is for improving the adhesive force between the layers, and the adhesive resin used is at least one kind selected from unsaturated carboxylic acids or their derivatives. A modified polyolefin resin grafted with a monomer can be preferably used, and the thickness of each adhesive resin layer may be in the range of 5 to 20 μm.

As the saponified ethylene vinyl acetate copolymer used for the third layer (hereinafter referred to as "EVOH"), those having an ethylene content of 30 to 60 mol% and a saponification degree of 95% or more may be used as moldability and It is preferable in terms of gas barrier properties, and the layer thickness may be in the range of 5 to 50 μm.

Further, as the sealing resin used for the fifth layer, an ionomer resin, polyethylene, or a copolymer of ethylene and other components such as ethylene-vinyl acetate copolymer can be used, and the thickness is 20 to 150 μm. It can be suitably used in the range.

In the multilayer film of the present invention, the melt index (MI) of the resin used in the layers other than the first layer other than the above layer structure and the thickness structure of each layer is 5.0 to 35.0,
It is necessary to use the thing of 10.0-20.0 preferably. Melt index (MI) is JISK6760
When the MI is less than 5.0, there is a problem that fine wavy patterns are generated on the inner surface of the film after coextrusion and the product is not good, and when it exceeds 35.0. There is a problem of poor film forming property.

Here, in the multi-layer film having the above-mentioned structure, uneven flow or defective adhesion occurs between the first polyester resin layer and the second adhesive resin layer depending on the manufacturing conditions during coextrusion molding. In some cases, this may cause poor appearance and delamination. Therefore, the above problem can be solved by interposing an amorphous polyethylene terephthalate resin layer between the first layer and the second layer.

As a concrete layer structure, the first layer is a polyethylene terephthalate resin layer, the second layer is an amorphous polyethylene terephthalate resin layer, the third layer is an adhesive resin layer, and the fourth layer is ethylene vinyl acetate copolymer. The multi-layer film is composed of a combined saponified layer, the fifth layer is an adhesive resin layer, and the sixth layer is a sealing resin layer. The contents other than the second layer are the same as those of the above-mentioned multi-layer film.

As the amorphous polyethylene terephthalate resin used for the second layer, a polyethylene terephthalate resin having an alcohol component of 1,4 cyclohexanedimethyl alcohol and ethylene glycol and an acid component of terephthalic acid can be preferably used. Thickness range is 10
If the thickness is less than 10 μm, there is no flow unevenness improving effect, and if it exceeds 100 μm, the rigidity of the film tends to be too strong, which is not preferable.

In the multilayer film having the above-mentioned amorphous polyethylene terephthalate resin layer, IV of the polyester resin of the first layer and the second layer is 0.65 to 0.85, preferably 0.7 to 0.8. Use the one in the range. IV
If less than 0.65, there is no improvement effect on rigidity and strength, and if more than 0.85, there is a problem that productivity is poor. Further, the thickness ratio with respect to the total thickness of the first layer and the second layer needs to be in the range of 0.75 to 0.92,
If it is less than 0.75, there is no improvement effect on rigidity and strength,
If it exceeds 0.92, there is a problem that the moldability is poor.

Further, it is necessary to use a resin other than the first layer and the second layer having MI of 5.0 to 35.0, preferably 10.0 to 20.0. If the MI is less than 5.0, there is a problem in that a fine wavy pattern is generated on the inner surface of the film after coextrusion and a good product cannot be obtained. If the MI exceeds 35.0, there is a problem that the film forming property is poor.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to Examples. Example 1 Layer structure: Outermost layer (first layer): polyethylene terephthalate resin (PET), second layer: carboxylic acid-modified linear low-density polyethylene (AD), third layer: saponified ethylene vinyl acetate copolymer ( EVOH), the fourth layer: a carboxylic acid-modified ethylene-vinyl acetate copolymer (AD), and the fifth layer: a linear low-density polyethylene (LLDPE). PET / AD / EVOH / AD / LLDPE IV = 0.8 / MI = 15 / MI = 6.4 / MI = 15 / MI = 12 295 μm / 10 μm / 12 μm / 5 μm / 33 μm Ratio of the PET resin layer to the total thickness = 0.83 The multilayer film having the above structure was formed into a film by a coextrusion molding method. Then, using this multi-layer film, deep drawing was carried out with a deep drawing machine (R-7000) manufactured by Multibag Co., Ltd., and it was found that the moldability was good, and the strength and appearance of the resulting molded product were not a problem. There wasn't.

Example 2 Layer Structure: Outermost layer (first layer): polyethylene terephthalate resin (PET), second layer: amorphous polyethylene terephthalate resin (PETG), third layer: carboxylic acid modified vertical chain low density polyethylene (AD), 4th layer: saponified ethylene vinyl acetate copolymer (EVOH), 5th layer: carboxylic acid-modified ethylene-vinyl acetate copolymer (AD), 6th layer:
A structure in which linear low density polyethylene (LDPE) is arranged.

PET / PETG / AD / EVOH / AD / LLDPE IV = 0.755 / IV = 0.75 / MI = 15 / MI = 5.5 / MI = 15 / MI = 23 255 μm / 43 μm / 15 μm / 14 μm / 5 μm / 32 μm PET + PETG Ratio of layer to total thickness = 0.82 The multilayer film having the above structure was formed into a film by a coextrusion molding method. Then, using this multi-layer film, deep drawing was carried out by a deep drawing machine (R-7000) manufactured by Multibag Co., Ltd., and the moldability was good, and the strength and surface unevenness of the obtained molded product were excellent. There was no problem in appearance.

Comparative Example 1 A multilayer film having the following constitution was obtained and evaluated in the same manner as in Example 1.

PET / AD / EVOH / AD / LLDPE IV = 0.63 / MI = 3.4 / MI = 2.5 / MI = 3.4 / MI = 3.5 281 μm / 13 μm / 19 μm / 13 μm / 65 μm Ratio of PET layer to total thickness = 0 .72 The multilayer film having the above structure was formed into a film by a coextrusion molding method. Flow unevenness was found in the obtained film. Then, using this multilayer film, deep drawing was carried out in the same manner as in Example 1, and the transparency and strength of the obtained molded product were poor and there was a practical problem.

Comparative Example 2 A multilayer film having the following constitution was obtained and evaluated in the same manner as in Example 1.

PET / AD / EVOH / AD / LLDPE IV = 0.8 / MI = 3.4 / MI = 2.5 / MI = 1.5 / MI = 7.0 280 μm / 5 μm / 15 μm / 10 μm / 60 μm Ratio of PET layer to total thickness = 0 .76 The multilayer film having the above structure was formed into a film by a coextrusion molding method. The appearance of the obtained film was good. Then, using this multilayer film, deep drawing was carried out in the same manner as in Example 1. As a result, a fine wavy pattern was found on the obtained molded product, which was a problem in practical use.

[0027]

As described above, the coextruded multilayer film of the present invention has a high gas barrier property and strength, and can be suitably used for various packaging trays by deep drawing.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-7-96582 (JP, A) JP-A-63-270140 (JP, A) JP-A-7-108655 (JP, A) JP-A-6- 226930 (JP, A) Actual development Sho 56-163533 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A first layer is a polyester resin layer, a second layer is an adhesive resin layer, a third layer is a saponified ethylene vinyl acetate copolymer layer, a fourth layer is an adhesive resin layer, and a fifth layer is A multilayer film having a sealing resin layer, wherein the polyester resin of the first layer has an intrinsic viscosity (IV) of 0.65 to 0.85.
And the thickness ratio to the total thickness of the first layer is 0.75
A coextrusion multilayer film for deep drawing, wherein the melt index (MI) of the resin other than the first layer is in the range of 0.92 and is 5.0 to 35.0. 2. A first layer is a polyethylene terephthalate resin layer, a second layer is an amorphous polyethylene terephthalate resin layer, a third layer is an adhesive resin layer, a fourth layer is a saponified ethylene vinyl acetate copolymer layer, and A multi-layer film comprising five layers of an adhesive resin layer and a sixth layer of a sealing resin layer,
The intrinsic viscosity (IV) of the polyester resin of the first layer and the second layer is 0.65 to 0.85, and the ratio of the total thickness of the first layer and the second layer to the total thickness is 0.75 to 0.92. A coextrusion multilayer film for deep drawing, characterized in that the melt index (MI) of the resin other than the first layer and the second layer is in the range of 5.0 to 35.0.