JP2996037B2 - Multilayer plastic container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a multilayer plastic container, and more particularly to a multilayer plastic container having excellent surface gloss and impact resistance.

[0002]

2. Description of the Related Art Polyolefin resins such as polyethylene and polypropylene are used in plastic hollow molded containers from the viewpoints of hygiene, moisture resistance and material cost. 2. Description of the Related Art In recent years, a hollow container having a glossy outer surface has been desired for the purpose of improving the commercial value of the container.
As a grade of resin used for a container made of polypropylene, an ethylene-propylene block copolymer is often used because of its high drop impact strength.

[0003] However, such a resin is effective in terms of the drop impact strength, but the molded container has a poor surface gloss, and when filled with contents, does not have a high-grade feeling and has a poor commercial value. There was a disadvantage that it becomes. Therefore, as a means to provide the molded product with sufficient drop impact strength and to give the container excellent surface gloss, the container has a multilayer structure, the outer layer is made of resin with excellent gloss, and the inner layer is dropped impact. It has been proposed to use a polypropylene block copolymer resin having excellent properties. In addition, as the resin having excellent glossiness used for the outer layer, a polypropylene homopolymer or a polypropylene random copolymer is used.

[0004]

However, although the surface gloss of the container is improved by the above-mentioned method, the drop impact strength is not yet sufficiently strong at present. In addition, it is a required performance that the bottle surface is not easily damaged when the container is transported or the contents are filled. Accordingly, an object of the present invention is to provide a multilayer plastic container having excellent surface gloss, hygienic properties, drop impact resistance, and having a bottle surface that is not easily damaged.

[0005]

In order to solve the above-mentioned problems, the present invention provides a multilayer plastic container having a structure in which at least two or more resin layers are laminated, wherein the outer layer comprises a polypropylene homopolymer and an ethylene-α-olefin. A multilayer plastic container characterized by being a mixture with a polymer, wherein the inner layer is a polypropylene block copolymer. In order to obtain more excellent drop impact resistance, the ethylene-α-olefin copolymer α-olefin should have a carbon number of 4 or more, and the outermost layer should have a thickness ratio of 5 to 20% of the total thickness. Preferably it is present.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 showing an example of a multilayer plastic container of the present invention, a container 1 is connected to a body 2, a bottom 3 formed by pinching off a parison, and a bottom 3 and a body 2 connected to the lower end of the body 2. It consists of a mouth and neck 5 connected to the upper end via a shoulder 4, and this mouth and neck 5 has a lid (not shown).
There is provided a mouth portion 6 which is sealingly engaged with the mouth portion, and a lid mounting portion 7 including a screw, a beat, a flange, a shoulder, or the like below the mouth portion 6. In FIG. 2, which is an enlarged cross-sectional view of the container wall of part A of the multilayer plastic container, the container wall is formed of a mixture of the outermost layer 10 made of a mixture of the polypropylene homopolymer of the present invention and an ethylene-α-olefin copolymer and a polypropylene block. It comprises a base layer 11 made of a polymer. Further, a scrap resin layer such as a burr of the present container may be provided as an intermediate layer in the configuration of FIG.

An important feature of the multilayer plastic container according to the present invention is that a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer is used for the outermost layer. Heretofore, a polypropylene homopolymer or a polypropylene random copolymer has been used alone for the outermost layer of such a container having excellent gloss. However, while these resins are excellent in glossiness, the impact resistance at drop impact, particularly at low temperatures, is very weak, and even if it is multilayered with a polypropylene block copolymer having excellent impact resistance, the impact resistance is not sufficient. . The present invention uses a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer for the outermost layer and a polypropylene block copolymer for the inner layer, thereby significantly improving the impact resistance of the multilayer plastic container. It is based on the knowledge of gaining.

[0008] It is also important that the bottle surface is hardly damaged in the transfer line and the filling line. Polypropylene homopolymer has higher surface hardness and lower coefficient of friction than polypropylene random copolymer, and therefore is less likely to be scratched. That is, in the present invention, by using a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer as the resin constituting the outermost layer, it is possible to prevent the bottle surface from being damaged. As the α-olefin of the ethylene-α-olefin copolymer, it is preferable to use one having 4 or more carbon atoms such as butene and hexene for improving the impact strength.
It is also preferable that the outermost layer has a thickness ratio of 5 to 20% of the entire thickness in order to impart impact resistance. That is, if it is 5% or less, it is difficult to uniformly cover the outer surface, and if it is 20% or more, the impact resistance becomes poor.

[0009]

According to the present invention, the surface gloss and the impact resistance are remarkably improved by using a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer for the outer layer and a polypropylene block copolymer for the inner layer. It is possible to obtain a container that is hardly damaged. By setting the thickness ratio of the outermost layer to 5 to 20%, it is possible to improve the impact resistance of the container and uniformly cover the outer surface.

[0010]

EXAMPLES Examples of the present invention and comparative examples are shown below. (Example 1) MFR (JIS K67) was used as a container outer layer.
58) A mixture of a polypropylene homopolymer of 5.0 g / 10 min and an ethylene-butene copolymer resin at a ratio of 9: 1 is supplied to an extruder for an outer layer, and an MFR of 0.5 g is used as an inner layer.
/ 10 minute ethylene-propylene block copolymer is supplied to an inner layer extruder to extrude a two-layer molten parison, and the parison is blow-molded in a blow mold to obtain an average body thickness of 700 μm and an inner volume of 800 ml. Bottles were molded.
The thickness of each layer of this bottle is 100 μm for the outer layer and 6 μm for the inner layer.
It was set to 00 μm. The results of gloss measurement and drop test of this bottle are shown in (Table 1).

(Example 2) MFR 8.0 as a container outer layer
A bottle was formed in the same manner as in Example 1, except that a mixture of a polypropylene homopolymer of g / 10 minutes, a copolymer resin of ethylene, butene and hexene at a ratio of 9: 1 was used as the outer layer. The results of gloss measurement and drop test of this bottle are shown in (Table 1).

Comparative Example 1 A bottle was formed in the same manner as in Example 1 except that the polypropylene homopolymer having an MFR of 5.0 g / 10 minutes used in Example 1 was used as the outer layer of the container. The results of gloss measurement and drop test of this bottle are shown in (Table 1).

Comparative Example 2 MFR 8.0 as an outer layer of a container
A bottle was formed in the same manner as in Example 1 except that a polypropylene random copolymer of g / 10 minutes was used. Table 1 shows the gloss measurement results and the drop test results of this bottle.

[0014]

[Table 1]

The glossiness in Table 1 is based on JIS K
According to 7105, incident angle 60 °, drop test result: 10 bottles filled with 800 ml of water, stored at 5 ° C for 12 hours, and then dropped on concrete upright 10 times from a height of 1 m. The number of cracks is shown.

[0016]

According to the present invention, in a multilayer plastic container having a structure in which two or more resin layers are laminated, a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer is used as the outermost layer, and a polypropylene block is used as the inner layer. By using the copolymer, the insufficient drop impact can be improved, and the glossiness of the container (according to JIS K 7105, incident angle 60 °) is also 70.
% Or more, it is possible to obtain a multilayer plastic container having excellent surface glossiness of not less than 10%.

[0017]

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of a multilayer plastic container of the present invention.

FIG. 2 is an enlarged explanatory view of a portion A of FIG. 1 which is an embodiment of the multilayer plastic container of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Container 2 ... Body 3 ... Bottom part 4 ... Shoulder part 5 ... Mouth and neck part 6 ... Mouth 7 ... Lid attachment part 10 ... Outermost layer 11 ... Base material layer

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 1/00-35/00 B65D 1/00-1/48

Claims (3)

(57) [Claims] 1. A multilayer plastic container having a structure in which at least two or more resin layers are laminated, wherein the outer layer is a mixture of a polypropylene homopolymer and an ethylene-α-olefin copolymer, and the inner layer is a polypropylene block copolymer. A multilayer plastic container characterized by the following. 2. The multilayer plastic container according to claim 1, wherein the α-olefin of the ethylene-α-olefin copolymer has 4 or more carbon atoms. 3. The multilayer plastic container according to claim 1, wherein the outermost layer is present in a thickness ratio of 5 to 20% of the total thickness.