JPS5947994B2 - Multilayer extrusion molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer extrusion molded article comprising a gas permeation resistant layer made of a saponified ethylene-vinyl acetate copolymer and a polyolefin layer, which have excellent gas permeation resistance and interlayer adhesion.

Conventionally, polyolefins have been widely used as packaging materials due to their excellent moisture permeability, chemical resistance, transparency, hygiene, and the like.

However, polyolefins have the disadvantage of high permeability to gases such as oxygen gas and carbon dioxide gas, and the long-term storage stability of the contents is poor, so they are not completely satisfactory in this respect.
On the other hand, the ethylene content is low (ethylene content 25-50
Saponified ethylene-vinyl acetate copolymer (hereinafter referred to as saponified material A) with a high degree of saponification (96% or more) has the advantage of having significantly lower gas permeability to oxygen gas than polyolefin. However, on the other hand, since it is hydrophilic, it has a high gas permeability to water vapor, and when exposed to a high humidity atmosphere, it has a drawback that it has a high gas permeability to oxygen gas and the like.

Therefore, as a packaging material that has both the properties of the polyolefin and the properties of saponified product A, a multilayer extrusion molded product with two or more layers, in which a layer of polyolefin is laminated on at least one side of the layer of saponified product A, is suitable, especially on both sides of the saponified product A. A multilayer container consisting of three or more layers protected by a layer of polyolefin is desired.

However, when a multilayer container is manufactured by extruding the layer of saponified material A and the layer of polyolefin using a coextrusion method, the adhesion between each layer is insufficient because the saponified material A and the polyolefin have no affinity. It peels off and is often impractical. In order to solve this problem, it is possible to mix saponified material A with a polymer that has excellent affinity with saponified material A and polyolefin, but if the above polymer is mixed with saponified material A, However, there was a problem in that the gas permeability resistance was reduced.

In view of the above, as a result of research and experiments, the present invention has been developed by combining a saponified substance A with excellent gas permeation resistance, a polymer with excellent affinity between this saponified substance A and polyolefin, and polyvinyl alcohol. It has been discovered that by constructing a multilayer container with a gas permeable layer and a polyolefin layer, a multilayer extrusion molded product with excellent gas permeability resistance and interlayer adhesion can be produced by coextrusion.

That is, the ethylene content is low (ethylene content 25
~50 mol%), ethylene monovinyl acetate copolymer with a high saponification degree (saponification degree of 96% or more), saponified product 1 (saponified product A), and a high ethylene content (ethylene content 60 mol%)
~95 mol%) and saponified ethylene monovinyl acetate copolymer with a low saponification degree (saponification degree of 50% or more) (hereinafter referred to as saponified material B) at a weight ratio of A:B = 95:5 to 50:50. Mix and total amount of the saponified product (A.B) 10
0 parts by weight, a mixture of 5 to 100 parts by weight, preferably 10 to 95 parts by weight, of polyvinyl alcohol having an average degree of polymerization of 300 to 2000 and a degree of saponification of 70% or more is used as a gas permeation-resistant layer, and at least one side of this is coated with polyolefin. The layers were laminated adjacently to form a multilayer extrusion.

The saponified material A used in the present invention has an ethylene content of 25 to
A saponified ethylene monovinyl acetate copolymer with a saponification degree of 50 mol%, preferably 25 to 45 mol 5%, a saponification degree of 96 (!) or higher, preferably 98 (f:) or higher, and an ethylene content of 25 (Ft) or higher. When the ethylene content is lower than 50%, the hydrophilicity increases and the water vapor permeability increases, and the processability by extrusion molding decreases, and when the ethylene content exceeds 50%, the permeability to gases such as oxygen gas is lost.

On the other hand, if the degree of saponification is lower than 96%, the permeability to gases such as oxygen gas will be lost, so the degree of saponification must be 96% or more.
Saponified product B is mixed with saponified product A for affinity with polyvinyl alcohol and polyolefin, and has an ethylene content of 60 to 95 mol%, preferably 70 to 90 mol%.
Mol%, saponification degree of 50% or more, preferably 65 to 99%
It is a saponified ethylene monovinyl acetate copolymer.

Polyvinyl alcohol has an average degree of polymerization of 300 to 2000,
Fully saponified products and partially saponified products with a saponification degree of 70% or more are preferred.

On the other hand, the polyolefin may be any polymer or copolymer of olefin that can protect the gas permeation-resistant layer of the mixture, and is not particularly limited, but one with low moisture permeability is preferred.

Examples include low, medium, and high density polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-11, polybenzene-11, and the like. Of course, the polyolefin used in the present invention may contain small amounts of other copolymer components as long as the properties of the polyolefin are not impaired. Examples include ethylene monovinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and the like. The mixing ratio of the mixture constituting the gas permeation resistant layer of the present invention is extremely important; saponified substance B is an indispensable component for improving the interlayer adhesion with the polyolefin layer; The mixing ratio is 95:5-5 by weight.
It is necessary to set the time to 0:50.

That is, if the saponified substance B is less than 5% by weight, the interlayer adhesion will be weak, and if it exceeds 50% by weight, the interlayer adhesion will be improved, but the gas permeation resistance will be significantly lowered. Further, polyvinyl alcohol is an indispensable component in order to improve gas permeability, which decreases when saponified substance B is mixed. Gas permeation resistance improves as the mixing ratio of polypynyl alcohol increases, but if it exceeds 100 parts by weight based on 100 parts by weight of the total amount of saponified substance AB, extrusion processability deteriorates and is not good. It is difficult to form a layer consisting of a saponified material A. B mixture 100
It is necessary that the amount of polyvinyl alcohol per part by weight is 5 to 100 parts by weight, preferably 10 to 95 parts by weight. In addition, in order to maintain a high degree of gas permeation resistance in the above-mentioned mixture consisting of the three components of saponified substance A, saponified substance B, and polyvinyl alcohol, the vinyl alcohol concentration should be set to 60% by weight or more, preferably 70% by weight. desirable.

Further, an ethylene monovinyl acetate copolymer or a modified polyolefin may be blended in an amount of up to 20 parts by weight per 100 parts by weight of the mixture. The multilayer extrusion molded article according to the present invention is a bottle, tank, chew, film sheet, pipe, etc. manufactured by a coextrusion method, and is used for packaging of general foods, industrial chemicals, gasoline, chemicals, pharmaceuticals, etc. The present invention will be described above with reference to Examples.

Example 1 The mixing ratio (weight ratio) of saponified product A with ethylene content of 40 mol% and saponification degree of 98% and saponified product B with ethylene content of 80 mol% and saponification degree of 80% is 100:0195:5
, 80:20 150:50, 40:60 mixture 100
A gas-permeable layer consisting of a mixture of 5, 50, 95, and 1001120 parts by weight of polyvinyl alcohol with an average degree of polymerization of 500 and a degree of saponification of 98% per part by weight is placed in the middle, and on both sides of this layer is a gas-permeable layer with a density of 0.93y/CCl melt index. A three-layer bottle consisting of a low-density polyethylene layer with a thickness of 0.47/10 min was manufactured using a coextrusion blow molding machine with two extruders and a three-layer coextrusion die.

The resulting three-layer bottle has a weight of 300CC. The capacity is cylindrical, the weight is 15y, and the weight ratio of the middle layer to the inner and outer layers is 1:15. The body of this three-layer bottle was cut and the peel strength of a 25Tfr1fL width was measured to evaluate interlayer adhesion.

Further, the oxygen permeability of this three-layer bottle at room temperature was measured using an oxygen permeation meter to evaluate the gas permeability. The measurement results are shown in Table 1. As shown in Table 1, adding saponified substance B to saponified substance A increases peel strength, that is, interlayer adhesion, and furthermore, by adding polyvinyl alcohol, oxygen permeability decreases and gas permeation resistance increases. Improved.

Example 2 Saponified product A with ethylene content of 28 mol% and saponification degree of 99 (:!) and saponified product A with ethylene content of 90 mol% and saponification degree of 75
The mixing ratio (weight ratio) of (!) with saponified substance B is 100:0
, per 100 parts by weight of the mixture of 90:10, 70:30,
Completely saponified polyvinyl alcohol with an average degree of polymerization of 750 and a saponification degree of 98% and an average degree of polymerization of 1000 and a saponification degree of 87%.
and partially saponified polyvinyl alcohol in a weight ratio of 1:1.
polyvinyl alcohol mixed with 10, 30, 100
, 120, and 200 parts by weight of a mixture, and a polypropylene layer having a density of 0.90 t/Cc3 melt index of 89/10 min. A two-layer film was produced using a coextrusion inflation molding machine. .

The resulting two-layer film had a thickness of approximately 50μ, with the outer layer having a thickness of 15μ.

Claims (1)

[Claims] 1. Ethylene content 25-50 mol%, saponification degree 96%
The above saponified ethylene-vinyl acetate copolymer (saponified product A), ethylene content 60 to 95 mol%, saponification degree 5
0% or more of a saponified ethylene-vinyl acetate copolymer (saponified product B) is mixed at a weight ratio of A:B = 95:5 to 50:50, and the total amount of the saponified products (A, B) Multilayer extrusion in which a gas permeation-resistant layer is made of a mixture of 5 to 100 parts by weight of polyvinyl alcohol with an average degree of polymerization of 300 to 2,000 and a degree of saponification of 70% or more per 100 parts by weight, and a polyolefin layer is laminated adjacently on at least one side of the mixture. Molded object.