JPS6234617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extruded tube container made of plastic that has excellent content preservation and functionality.

Conventionally, when the content is an aqueous paste such as toothpaste, special preservation performance of the content is required.
For this reason, thin-walled aluminum impact-molded tubes are mainly used.

Aluminum has excellent storage stability because it is not gas permeable, but it is prone to deformation after filling, bending deformation and cracking due to squeezing during use, which reduces the product value in terms of usability and appearance. It's summery.

On the other hand, laminate tubes, which are made from multilayer sheets made by laminating aluminum foil, paper, and polyethylene, have attracted attention and are gradually replacing aluminum tubes. However, this laminate tube uses aluminum foil for the tube body, so it has excellent gas barrier properties, but since it is molded from a sheet, it always has a back sheet part. In addition, the manufacturing machinery and equipment become larger, and the cost becomes higher unless a small number of products are produced in large quantities.All of these tube forms have a cylindrical main body with a mouth at the top, and the contents are filled from the bottom.
It uses heat to seal the ends. Therefore, the form and design of the container itself are also determined by its manufacturing method.

In addition, although this type of laminate tube improves the drawbacks of aluminum tubes in terms of usability, the mouth part is obtained by injection molding of polyethylene after inserting the main body part, but the mouth part is obtained from the shoulder part by injection molding of polyethylene. As mentioned above, since the film is made of polyethylene alone, which has high gas permeability, it must be said that there remains a problem in storage performance due to the reduction in gas barrier properties at this location.

The present invention solves the above-mentioned problems and has excellent gas and water vapor barrier properties and squeezing properties.
It also has many characteristics in terms of design such as container form. Another object of the present invention is to obtain an extruded tube having a characteristic inner resin layer to prevent the content from becoming rough, which is important for the shelf life of toothpaste.

The extruded tube container according to the present invention has a multilayer structure made entirely of plastic, with the outer layer being made of low density polyethylene graft-modified with maleic anhydride in a range of 0.1 to 15% by weight, and the middle layer having an ethylene content of 20 to 70% by weight. The inner layer is made of saponified ethylene-vinyl acetate copolymer with a saponification degree of 90% or more, and the inner layer is made of maleic anhydride-grafted modified low-density polyethylene similar to the outer layer, with an ethylene content of 20 to 70 mol%.
One or both of the saponified ethylene-vinyl acetate copolymers with a saponification degree of 90% or more, or modified polyvinyl alcohols such as saponified polyvinyl acetate with a saponification degree of 30 to 40%.
This is an extruded tube container with a 3-layer structure made of 3 types of resins, each consisting of a polymer blend layer in the range of ~30% by weight.

In addition, the saponified ethylene-vinyl acetate copolymer in the middle layer has the best gas barrier properties among thermoplastic plastics, and is suitable for use in toothpastes.
The thickness may be in the range of 100μ, and the layer thickness may be thinner than the inner and outer layers. In addition, the present invention is particularly intended for use in toothpaste, and is characterized by excellent preservability of its contents.

Generally, paste-like toothpaste contains a powder base, a humectant, a binder, a foaming agent, a flavoring agent, a sweetener, a medicinal agent, pure water, etc. Among these, the humectant is used to maintain the proper wettability of the toothpaste. At the same time, moisturizing stabilizes the properties of the toothpaste, and the binder keeps the powder base and liquid components homogeneous, preventing separation and adjusting the properties. This is especially true for general-purpose low-density polyethylene, which is commonly used in plastics, because of its hydrophobicity, which reduces its effectiveness and tends to cause cracking of toothpaste, liquid separation, and rough skin on the contact surface.

In the present invention, in order to improve these phenomena, the resin of the inner layer has characteristics, and by using a modified resin that is a polymer blend of modified polyvinyl alcohol having a hydrophilic hydroxyl group in polyethylene graft-modified with maleic anhydride. This is something that can be fully dealt with. The surface tension of these inner layer resins is in the range of 35 to 75 dynes/cm, which is considerably higher than the 30 dynes/cm of ordinary polyethylene.
The wetting of the interface is improved and the effects of wetting agents and binders are sufficiently maintained.

The structure of the extruded tube container of the present invention (immediately after blow molding) is shown in FIG.
The structure is shown in the partially cutaway side view of the figure (with the end sealed after filling the contents), and Fig. 3 is an enlarged cross-sectional view of the mouth (X section), and Fig. 4 is the tube container body ( It is an enlarged cross-sectional view of the fifth
The figure is an enlarged sectional view of the bottom end seal part (Z part). A is the trunk body, B is the mouth, C is the bottom, 1 is the inner layer, 2 is the middle layer, and 3 is the outer layer.

The method for manufacturing the three-layer extruded tube of the present invention is carried out by a coextrusion three-layer blow molding method. A conventional blow molding machine is equipped with three extruders and a three-layer blow die head at the tip. After installing the tube-shaped mold shown in Figure 1 and blow molding,
The desired container is obtained by cutting the bottom. At this time, each of the three types of resin is completely adhered in the die head and extruded as a single parison, and the inner surface of the molded tube container is entirely made of the resin for the inner layer, which is conventionally used in the manufacture of plastic tubes. Compared to the general extrusion molding method, it is characterized by a continuous structure with the same quality as the main body with gas barrier properties at the mouth. This manufacturing method based on multilayer blow molding has the great advantage that conventional molding machines can be applied as is, allowing production from small quantities to large quantities with a small investment in equipment.

Example: For the outer layer of a multilayer blow molding machine equipped with a three-layer die head, maleic anhydride-modified polyethylene (MI = 1.0), saponified ethylene-vinyl acetate copolymer (MI = 1.5, mp = 180°C) for the middle layer, For the inner layer, a modified resin consisting of 3% by weight of saponified ethylene-vinyl acetate copolymer and 5% by weight of saponified vinyl acetate (saponification degree 25%) is supplied to maleic anhydride-modified polyethylene, and the outer layer/middle layer/inner layer is The weight ratio
A tube-shaped container made of 50/15/35% is formed,
After cutting the bottom, the contents were filled and the end was sealed to obtain the container shown in FIG. 2.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a tube-shaped container of the present invention obtained by three-layer blow molding, and FIG. 2 shows the container shown in FIG. 1 after cutting the bottom and filling the container with contents.
FIG. 3 is a partially enlarged sectional view of the mouth of the container; FIG. 4 is a partially enlarged sectional view of the body;
FIG. 5 is a partially enlarged sectional view of the bottom end seal portion. 1...inner layer, 2...middle layer, 3...outer layer, A...body,
B...mouth part, C...bottom part.

Claims (1)

[Scope of Claims] 1. A multilayer extruded tube container made of plastic, in which the outermost layer is maleic anhydride-modified low-density polyethylene, the middle layer is a saponified ethylene-vinyl acetate copolymer, and the inner layer is maleic-anhydride-modified low-density polyethylene-vinyl acetate copolymer. compound or saponified polyvinyl acetate, or both are 1
Extruded tube container with three layers of layers containing ~30% by weight. 2. The extruded tube container according to claim 1, wherein the middle layer is the thinnest layer compared to both the inner and outer layers in the extruded multilayer plastic tube container. 3 In a plastic multilayer extruded tube container, the surface tension of the innermost layer of the tube container is 35 to 75.
An extruded tube container according to claim 1 in the dynes/cm range. 4. An extruded multilayer tube container made of plastic, characterized in that the inner layer resin according to claim 1 is continuous on the entire inner surface including the mouth of the tube container.