JPH03153327A - Vessel body and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain both characteristics of a resin for a skin and a resin for a core simultaneously, and to thin the thickness of a resin layer for the core by preparing a vessel body composed of distinct five layers in which the resins for the skins and the resins for the cores are laminated alternately. CONSTITUTION:Polypropylene is injected into a mold 8 at specified injection speed and a fixed injection time from the resin cylinder 4 for a skin of a co- injection molding machine 1 first. An ethylene-vinyl alcohol copolymer is injected into the mold 8 from the resin cylinder 3 for a core of the co-injection molding machine 1. The injection speed is made faster than the injection speed of a first process and the injection time is made shorter than the injection time of the first process in this case. Lastly, polypropylene is injected into the mold 8 from the resin cylinder 4 for the skin of the co-injection molding machine 1. The injection speed and injection time of polypropylene are made approximately the same as the injection speed and injection time of the first process at that time. Accordingly, a vessel body 11 consisting of the distinct five layers of polypropylene 21/an ethylene-vinyl alcohol copolymer 22/polypropylene 23/an ethylene-vinyl alcohol copolymer 24/polypropylene 25 is prepared.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a multilayer plastic container body manufactured by injection molding and a method for manufacturing the same, particularly for manufacturing a container with a metal lid. The present invention relates to a container body used for and a method of manufacturing the same.

(Prior Art) Conventionally, methods for producing a multilayer plastic container body by injection molding include (2) a two-color molding method using rotating molds or a core pack, and (2) a sandwich molding method.

However, in the case of the two-color molding method, there is a problem in that the container body only has two layers. In addition, when a container body is made from two parts, for example, an outer heat-resistant layer and an inner gas barrier layer, by two-color molding, the inner gas barrier layer protrudes from the outer surface, which is inconvenient when performing retort processing, hot filling, etc. may occur. Furthermore, in the case of a two-color molding method, the thickness of each layer must be increased to some extent.

On the other hand, the sandwich molding method
A three-layer structure (a three-layer structure made of two types of materials) is possible. However, for example, when the intermediate layer is a gas barrier layer, this layer may become unnecessarily thick, resulting in high cost.

Incidentally, in recent years, instead of metal cans as food storage containers, containers with metal lids, in which the peripheral edge of a metal lid is wrapped around the flange of a plastic container body, have been considered. The container body used for such containers with metal lids is required to be heat resistant and made of a gas barrier material, and in order to perform accurate seaming work, dimensional accuracy such as flange wall thickness and external dimensions is required. . As a method of manufacturing a container body that improves the dimensional accuracy of the flange portion, injection molding is generally said to be superior to a method of manufacturing by thermoforming a sheet plate.

(Problems to be Solved by the Invention) As described above, methods for manufacturing a multilayer plastic container body by injection molding include (1) two-color molding method, (2) sandwich molding method, and the like. However, at present, in either case, there is a problem that a low-cost multilayer container cannot be manufactured. Furthermore, when the sheet plate is thermoformed, there is a problem in that it is not possible to manufacture a container body with higher dimensional accuracy than when injection molding is used.

The present invention has been made in consideration of these points,
The object of the present invention is to provide a plastic container body with a clear multilayer structure and a method for manufacturing the same.

[Structure of the invention]

(Means for Solving Problems) The present invention provides a method for manufacturing a container body in which a plastic container body is manufactured by injecting two different types of resins, in which skin resin is injected at a predetermined injection speed and for a predetermined injection time. a first step of injecting the core resin into the mold at a faster injection speed and a shorter injection time than the skin resin; and a second step of injecting the skin resin into the mold at a faster injection speed and shorter injection time than the skin resin. and a third step of injecting into the mold at an injection speed and time of -, and the container body consists of five layers: skin resin, core resin, skin resin, core resin, and skin resin. and a plastic container body obtained by the above-described manufacturing method, consisting of five layers: resin for skin, resin for core, resin for skin, resin for core, and resin for skin.

(Function) According to the present invention, since it is possible to create a container body consisting of five distinct layers in which skin resin and core resin are alternately laminated, the characteristics of both the skin resin and the core resin can be obtained. It is possible to obtain a multilayer injection molded container main body which has both of the following properties and can reduce the thickness of the core resin layer.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

1 to 5 are diagrams showing an embodiment of a container body and a method for manufacturing the same according to the present invention.

First, a container body according to the present invention and a container with a metal lid using this container body will be explained with reference to FIG. Fourth
As shown in the figure, the container body 11 is composed of a body portion 12a having an upper end opening, a bottom portion 12b, and a flange portion 13 provided at the periphery of the upper end opening of the body portion 12a and protruding outward in the radial direction. 11 is made of multilayer plastic as a whole.

A container 10 with a metal lid is obtained by storing a high-temperature content 19 inside the container body 11 having such a structure, and wrapping the peripheral edge 17 of the metal lid 16 made of aluminum around the flange portion 13.

Next, a manufacturing apparatus for the plastic container body 11 will be described.

The container body according to this embodiment is manufactured by using a sandwich-type co-injection molding machine 1 as shown in FIG. molded.

First, according to FIG. 3, the sandwich type co-injection molding machine 1 is
I will explain about it. This co-injection molding machine 1 has a piston 3
a core resin cylinder 3 and a piston 4a
Skin resin cylinders 4 for what purpose are arranged in parallel, and these core resin cylinders 3 and skin resin cylinders 4
The nozzle 2 is connected to the nozzle 2 via a connector piece 5. In this co-injection molding machine 1,
The core resin is injected from the core resin cylinder 3 into the mold 8 through the connector piece 5 and the nozzle 2, and the skin resin from the skin resin cylinder 4 is injected into the mold 8 through the connector piece 5 and the nozzle 2. It is designed to be ejected.

The mold 8 has a male mold 8a and a female mold 8b as shown in FIG.
It consists of

Next, a method for manufacturing the container body will be described.

Co-injection molding is carried out using ethylene-vinyl alcohol copolymer (EVOH) as the core resin and polypropylene as the skin resin under the molding conditions shown in FIGS. 1 and 5. Here, FIG. 1 is a diagram showing the injection speed of resin, and FIG. 5 is a schematic diagram of the flow of resin within the mold.

Note that olefins other than polypropylene can be used as the skin resin. Examples include olefin homopolymers, olefin copolymers, and mixtures thereof. Furthermore, as an olefin homopolymer,
Examples include high density polyethylene, low density polyethylene, linear low density polyethylene, polybutene-1, porin 4-methylpentene-1, and the like. Examples of olefin copolymers include copolymers of ethylene and small amounts of propylene, butyne, hexane, and the like. Among these, particularly preferred resins are high density polyethylene and polypropylene.

First, as shown in FIG. 1, polypropylene is first injected from the skin resin cylinder 4 of the co-injection molding machine 1 into the mold 8 at a predetermined injection speed and a predetermined injection time (first step). The state of this first step is shown in FIG. 1A and FIG. 5(a).

Next, from the core resin cylinder 3 of the co-injection molding machine 1,
The ethylene-vinyl alcohol copolymer is injected into the mold 8 (second step). In this case, the injection speed is faster than the injection speed in the first step, and the injection time is shorter than the injection time in the first step. The injection time T in the second step is preferably 1/20 to 1/1O second. In the second step, by reducing the injection speed of polypropylene from the resin cylinder 4 for the skin, the resin cylinder 3 for the core is
It is desirable to have a large difference in injection speed between the ethylene-vinyl alcohol copolymer and the ethylene-vinyl alcohol copolymer. The state of this second step is shown in FIG. 1B and FIG. 5(b).

Finally, polypropylene is injected into the mold 8 from the skin resin cylinder 4 of the co-injection molding machine 1 (third step). In this case, the injection speed and injection time of polypropylene are
The injection speed and injection time are approximately the same as those of the first step. This third step is shown in FIG. 1C and FIG. 5(C). Next, the first figure and FIG. 5(d) show the end of release.

In this way, as shown in FIG. 2, the container body 11 is made up of five distinct layers: polypropylene 21/ethylene-vinyl alcohol copolymer 22/polypropylene 23/ethylene-vinyl alcohol copolymer 24/polypropylene 25. Created.

According to this example, the ethylene-vinyl alcohol copolymer is injected in the second step at a higher injection speed than the first step.
The injection time is shorter than the injection time of the first step, and the first
By injecting polypropylene at the same injection speed and injection time as in the first step, a clear ethylene-vinyl alcohol 8m combined layer is formed on the outside of the polypropylene layer injected in the first step, and a clear polypropylene layer is further formed on the outside of the polypropylene layer. layers can be formed. That is, for example, the second
If the injection speed of the step is slower than the injection speed of the first step, the ethylene-vinyl alcohol copolymer will not reach the end of the container, and the ethylene-vinyl alcohol copolymer layer will become unclear. By creating a container body consisting of five layers, it is possible to obtain a container body having the strength and heat resistance of polypropylene and the gas barrier properties of ethylene-vinyl alcohol copolymer.

In addition, in the above embodiment, the plastic container body 1
An example is shown in which the container 10 with a metal lid is manufactured by wrapping the peripheral edge 17 of the metal lid 16 around the flange 13 of the container 1 (FIG. 4).
However, the present invention is not limited to this, and as shown in FIG. 6, a plastic lid member 36 is heat-sealed to the flange portion 13 of the plastic container body 11.

The plastic container 30 may also be manufactured by doing so.

(Concrete example) Next, specific examples of the present invention will be shown.

i Co-injection molding machine 1-1 The specifications of the co-injection molding machine used are as follows.

Sandwich type co-injection molding machine manufactured by Battenfelt,
BM-72400/ 2X1000UNI LOG80
00 Mold clamping force 240t1-2 The temperature of the co-injection molding machine was set as shown in Table-1.

Table 1 1i mold A mold for a small (200ml) container with 4 cavities.

I11 molding conditions The molding conditions are as shown in Table-2 and Table-3.

Table 2 In addition, the piston stroke of the resin cylinder for the skin and the piston stroke of the resin cylinder for the core have the values shown in Table 4.

Table 4 Table 3 Iv Resin Material XK6449 (Ml-7,0) manufactured by Chisso Kagaku Co., Ltd. was used as the polypropylene resin for the skin.

Further, as the ethylene-vinyl alcohol copolymer of the core resin, EVAL and EP-E manufactured by Kuraray were used.

When a container body was produced under each of the above conditions, a container body clearly separated into five layers was obtained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to create a container body consisting of five distinct layers in which the skin resin and the core resin are alternately laminated. It is possible to obtain a multilayer injection molded container body that has both the above characteristics and allows the thickness of the core resin layer to be reduced.

Therefore, a container body with higher dimensional accuracy than thermoforming can be manufactured at a lower cost, and this container body can be used to manufacture a high quality container with a metal lid.

[Brief explanation of the drawing]

1 to 5 are diagrams showing an embodiment of the container body and its manufacturing method according to the present invention, FIG. 1 is a diagram showing molding conditions of a co-injection molding machine, and FIG. Figure 3 is a sectional view showing the co-injection molding machine, Figure 4 is a side sectional view of a container with a metal lid, and Figure 5 is a schematic diagram showing the flow of resin. , FIG. 6 is a side view of the plastic container. DESCRIPTION OF SYMBOLS 1... Sandwich type co-injection molding machine, 2... Nozzle, 3... Resin cylinder for core, 4... Resin cylinder for skin, 5... Connector piece, 8... Mold, 1
o... Container with metal lid, 11... Container body, 21...
- Polypropylene, 22... Ethylene vinyl alcohol copolymer, 25... Polypropylene, 30... Plastic container.

Claims (1)

[Claims] In a method for manufacturing a container body in which a plastic container body is manufactured by injecting 1 or 2 different types of resin, skin resin is injected into a mold at a predetermined injection speed and for a predetermined injection time. The first step is to inject the core resin into the mold at a higher injection speed and shorter injection time than the skin resin.
and a third step of injecting the skin resin into the mold at approximately the same injection speed and approximately the same injection time as the first step, and the skin resin, the core resin, the skin resin, the core. A method for manufacturing a container body comprising five layers of a skin resin and a skin resin. 2. The method for manufacturing a container body according to claim 1, wherein a polyolefin is used as the resin for the skin, and an ethylene-vinyl alcohol copolymer is used as the resin for the core. 3. A plastic container body obtained by the manufacturing method according to claim 1, comprising five layers: skin resin, core resin, skin resin, core resin, and skin resin.