JPS599350B2 - multilayer container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coextruded multilayer container consisting of at least two layers, a thermoplastic saturated polyester resin and a polyolefin resin, with improved adhesion between the two layers.

Conventionally, even when containers with a multilayer structure of polyester resin and polyolefin resin were formed by blow molding, pipe molding, or sheet film molding, the former was highly polar and the latter was non-polar, so it had poor adhesion and was easy to separate when molded. .

In such an extreme case, the properties would be no worse than those of a single layer of each resin, and it could not be used as a product. Therefore, in order to obtain a laminated sheet or film that joins the two, it is necessary to form a single-layer sheet or film that has been formed in advance, apply an adhesive or a treatment agent, and then extrusion coat or bond the formed sheet or film together. .

According to this method, there were many molding steps, the molding efficiency was not good, and it was more difficult to mold containers. Alternatively, modified polyolefins in which polar groups are introduced into polyolefin resins have been used to improve adhesion.

However, because modified polyolefins are expensive, it has been difficult to commercialize them. In addition, several proposals have been made to improve adhesion by adding polyolefin to thermoplastic saturated polyester, but this impairs the excellent gas barrier properties of thermoplastic saturated polyester and does not provide the desired adhesive strength. I couldn't help it.

Furthermore, attempts have been made to add ionomer resins and ethylene-vinyl acetate copolymers to polyolefins to improve adhesion, but when these resins are added, the drop impact strength is insufficient due to poor compatibility. Therefore, the function as a hollow container was lacking.

The present invention aims to improve such conventional drawbacks, to obtain a coextruded multilayer container consisting of a thermoplastic saturated polyester resin layer and a polyolefin resin layer, with improved adhesiveness between the two, and which can withstand harsh usage conditions. This is the purpose.

The present invention is a coextruded multilayer container comprising a thermoplastic saturated polyester resin layer and a polyolefin resin layer, and is made by adding 2 to 45% by weight of a polyurethane resin to the polyolefin resin.

Here, if the amount added is less than 2% by weight, no improvement in adhesion is observed, and if it is more than 45% by weight, the compatibility is poor,
Mechanical properties deteriorate.

Since the container of the present invention has the above-described structure, the thermoplastic saturated polyester and polyolefin resin are strongly bonded to each other, so there is no need to use an adhesive as in the past, so coextrusion can be performed without using an adhesive. Because it is possible, the manufacturing process can be simplified, and the container can withstand severe usage conditions such as bending, squeezing, and dropping impact, so it has great practical value. ．．・. In addition, thermoplastic saturated polyester has excellent gas permeability, mechanical properties, water resistance, good preservability of contents (1), and excellent shape retention. Furthermore, since each layer is strongly bonded, it is possible to reuse the recycled product, which reduces the price of the product and has great economic value.

In addition, simply adding it is enough, and since polyolefins and polyesters are different from those that are chemically modified, the price of the resin does not increase. The present invention will be explained in detail based on examples.

Example 1 Low density polyethylene (d; 0.920, MI
22.0) A resin prepared by adding 5% by weight of polyurethane (Paraprene 22S Nippon Polyurethane Co., Ltd.) to 95% by weight is kneaded and melted in an extruder, and then supplied to a blow molding machine at 200°C.

Furthermore, polybutadiene phthalate (Mitsubishi Kasei★2:.
PBT5OlO (manufactured by Mitsubishi Chemical Corporation) is melted in a separate extruder and fed to a die at 200°C.

Inside the die, concentric resin passages were provided, and polyethylene resin (thickness 0.511 mm) was coextruded on the inside and polybutadiene phthalate (0.1 ml) was extruded on the outside to form a two-layer hollow container. (d is the density, M represents melt index) Comparative example 1 Low density polyethylene (d: 0.920,
MI; 2.0) as an inner layer (thickness 0.51!), 95% by weight of polybutadiene terephthalate (Mitsubishi Kasei PBT5OlO manufactured by Mitsubishi Kasei Corporation) and 5% by weight of the above low density polyethylene.
The added resin was used as the outer layer (thickness 0.111), and Example 1
A hollow container was obtained in the same manner.

Comparative Example 2 The same low density polyethylene as in Example 1 was used as the inner layer (thickness 0.5
1t! 11), 3% of the same low density polyethylene as in Example 1 was added to 70% by weight of the same polybutadiene phthalate as in Example 1.
A hollow container was obtained in the same manner as in the example except that the resin added in an amount of 0% by weight was used as an outer layer (thickness: 0.f1).

Comparative Example 3 Same low density polyethylene as Example 1, thickness 0.61! A recommended hollow-molded container was obtained.

Claims (1)

[Claims] 1. A coextruded multilayer container consisting of at least two layers: a thermoplastic saturated polyester resin layer and a polyolefin resin layer, with 2 to 45% by weight of a polyurethane resin added to the polyolefin resin layer.