JPH0577280A - Multi-layer injection molding - Google Patents

Abstract

(57) [Summary] [Object] To provide a molded article having a higher gas barrier property by suppressing the gas permeation in the gate of a multilayer molded article having a gas barrier property and its vicinity and further devising it. [Structure] An innermost layer and an outermost layer of a molded product made of a polyolefin-based resin, and an adhesive layer made of a thermoplastic resin whose main component is a copolymer obtained by graft-modifying a polyolefine, just inside thereof. In a multilayer injection molding of 3 types and 5 layers including an oxygen gas barrier layer made of an oxygen gas barrier resin inside, the surface of the molded product is entirely made of polyolefin resin, and the end of the oxygen gas barrier layer is formed at the end of the molded product. It is covered with the adhesive layer, the adhesive layer is covered with the polyolefin resin, and the gate cut surface is formed only by the polyolefin resin, and the oxygen gas barrier layer near the gate has an end portion. A multilayer injection-molded article, which does not contain a polyolefin resin and an oxygen gas barrier resin in the adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic multi-layered molded product, and more specifically, a plastic multi-layered container, a cap, and a lid for containing contents such as foods, beverages, cosmetics, etc. which are required to have an oxygen gas barrier property. Etc.

[0002]

2. Description of the Related Art When a container, a lid or the like is produced by using a small amount of a gas barrier resin having a gas barrier property which is relatively expensive and has a gas barrier property required for contents, a multilayer structure including a gas barrier layer is preferred. It is common. When molding a multi-layered container or the like, there are a method of molding the laminated sheet including the gas barrier resin layer by vacuum forming or the like, a blow molding using a multi-layer parison, and the like.

In these methods, at the end of the molded product,
Since the gas barrier resin is exposed on the surface of the molded product and the gas barrier resin absorbs moisture and its performance may be deteriorated, the gas barrier resin layer was made thicker than necessary or a hygroscopic agent was contained on both sides of the gas barrier layer. Various measures have been taken, such as providing a resin layer. Further, in these manufacturing methods, material loss such as burrs is very large. In addition, a method of inserting a laminated film containing a gas barrier resin into a mold and performing injection molding has been considered, but there is a step of manufacturing a laminated film and an injection molding step, and the number of steps increases, resulting in high cost. Become.

In multi-layer injection molding, it is generally difficult to control the position and thickness of each resin layer. Therefore, various molding methods and molding apparatuses have been devised. In these molding methods, the layer structure at the end of the molded product is devised so that the gas barrier layer is not exposed on the surface of the molded product. However,
When the blade is cut, the gas barrier resin may exist on the cut surface. At this time, the gas-barrier resin on the cut surface absorbs moisture, and its performance may be deteriorated. Also, in the case of multi-layer injection molding, the gate becomes relatively thick, but there is no gas barrier resin at the center of the cut surface of the gate, and there is one resin layer forming the surface of the molded product in the central axis direction. More gas is permeable. On the contrary, if the gas barrier resin is not exposed to the cut surface of the gate, the gas barrier resin layer is not located near the gate, and the gas permeation point is taken into consideration.
There is a hole in the vicinity of the hole, which makes it easier for gas to permeate.

[0005]

DISCLOSURE OF THE INVENTION The present invention has the above-mentioned drawbacks, namely, it suppresses gas permeation in the gate of a multilayer molded article having a gas barrier property and in the vicinity thereof, and further devises the gas barrier property to a higher level. An object is to provide a molded product.

[0006]

Means for Solving the Problems The present invention is to solve the above-mentioned problems and comprises an innermost layer and an outermost layer of a molded product made of a polyolefin resin, and a polyolefin resin having a polyolefin modified immediately inside thereof. A multilayer injection molded product of 3 types and 5 layers, which has an adhesive layer made of a thermoplastic resin containing a polymer as a main component, and includes an oxygen gas barrier layer made of an oxygen gas barrier resin inside the adhesive layer. All are made of polyolefin resin, the end of the oxygen gas barrier layer is covered with the adhesive layer at the end of the molded product, and the adhesive layer is covered with the polyolefin resin.
The cut surface is formed only by the polyolefin resin, the oxygen gas barrier layer does not have an end portion in the vicinity of the gate,
Provided is a multilayer injection-molded article containing a polyolefin resin and an oxygen gas barrier resin in the adhesive layer, and the multilayer injection molding wherein the oxygen gas barrier layer is made of a resin containing an ethylene-vinyl alcohol copolymer. It is to provide things.

[0007]

Detailed Description Performance deterioration of the gas barrier resin is promoted by the moisture absorption of the gas barrier resin. In order to prevent this performance deterioration, a method has been considered in which a gas barrier resin is sandwiched between moisture-proof resins to form a multilayer structure. However, in blow molded products and sheet molded products, the gas barrier resin may be exposed on the surface of the molded product at the ends of the molded product. In the case of multi-layer injection molding, many methods have been published that can solve the above problems at the end of the molded product. However, in injection molding, a gate is always present, but the gas barrier property deteriorates depending on the layer structure in the vicinity of this gate. That is, the gas barrier layer is exposed on the gate cut surface.

However, in the multilayer injection-molded article of the present invention, since the gas barrier resin layer is not exposed on the cut surface of the gate, deterioration of the gas barrier property due to moisture absorption does not occur. Further, in the vicinity of the gate, a continuous resin layer having no end face is formed on the gas barrier resin layer. In other words, it has a layer structure that must cross the gas barrier layer when passing from the surface of the molded product to the other surface (including the gate cut surface) in the vicinity of the gate. Therefore, the gas barrier property has the same performance as other parts of the molded product. Further, since there is an adhesive layer immediately outside the gas barrier layer and the surface layer of the molded article and the gas barrier layer do not come into direct contact with each other, peeling between layers does not occur.

That is, the multilayer injection-molded container according to the present invention has the same gas barrier property as the vacuum molding at the bottom, and the gas barrier performance is less deteriorated at the end. further,
Since the adhesive layer preferably contains recycled gas barrier resin, water vapor permeated from the surface is absorbed by this resin. Therefore, the amount of water vapor reaching the central gas barrier layer is reduced, and the performance of the oxygen barrier is less likely to deteriorate.

[0010]

The multilayer injection-molded article of the present invention has a structure in which the oxygen gas layer is covered with the adhesive layer without breaks even at the end and in the vicinity of the gate, and the adhesive layer is covered with the polyolefin resin of the surface layer. Furthermore, since the adhesive layer contains a polyolefin resin and an oxygen gas barrier resin, the water vapor that has permeated from the surface is absorbed by the adhesive layer, and a multi-layer injection-molded article having a better oxygen gas barrier property is obtained. ..

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The multilayer container of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view of a cross section of a multilayer container showing one embodiment of the multilayer injection-molded article of the present invention. This container is cup-shaped and has a flange 1 formed at the opening. The outer container layer 2 and the inner container layer 9 are made of the same polyolefin resin having a low water vapor permeability and high strength. Immediately inside the outer layer and the inner layer, there is a polyolefin having an adhesive force with the inner and outer container layers and the gas barrier resin. There is an adhesive layer 3 composed mainly of a copolymer obtained by graft-modifying fins and made of a recycled polyolefin resin and a thermoplastic resin containing a gas barrier resin. The interface between the outer container layer 2 and the inner container layer 9 and the adhesive layer 3 is smooth, and the adhesive layer 3 in the flange portion 1 is covered with the polyolefin resin forming the outer container layer 2 and the inner container layer 9. Is not exposed on the outer surface of the container.

Inside the adhesive layer 3, there is a gas barrier layer 4 made of a gas barrier resin, and the flange portion 1 is covered with the adhesive resin forming the adhesive layer 3. At the body and bottom of the container, an inner adhesive layer 7 and an outer adhesive layer 8 are provided on both sides of the gas barrier layer 4, and an outer container layer 2 and an inner container layer 9 are provided on the outer side of the gas barrier layer 4 to form a three-kind five-layer structure.

The gate 5 is located at the center of the bottom of the container, and a cut surface 6 is formed by cutting the gate after injection molding. The gate cut surface 6 is made of a polyolefin resin forming the outer layer 2 of the container.
The layer structure near the gate 5 has the same layer structure as the container body. That is, there is a continuous gas barrier layer 4 having no end face in the center of the wall thickness of the container, and the adhesive layers 3 immediately on both sides thereof,
The outer adhesive layer 7 and the inner adhesive layer 8 are not in contact with each other, the outer container layer 2 is outside the outer adhesive layer 7, and the inner container layer 9 is outside the inner adhesive layer 8. The container outer layer 2 and the container inner layer 9 are not in contact with each other. As described above, the layer structure in the vicinity of the gate 5 has the same layer structure as the body and bottom of the container, so that the gas barrier property is the same as that of the other parts. In addition, since the gas barrier resin is not exposed on the gate cut surface 6, the performance of the gas barrier resin is not deteriorated.

FIG. 2 is a cross-sectional view of a conventional multi-layer injection molded article in the vicinity of the gate. In FIG. 2, the three-kind five-layer structure extends to the sprue, the center of the sprue is a polyolefin resin layer 11 communicating with the container inner layer 9, the outside thereof is an adhesive layer 12 communicating with the inner adhesive layer 8, and the outside thereof. Gas barrier layer 1
3, the adhesive layer 1 communicating with the outer adhesive layer 7 on the outside thereof
4 and a polyolefin resin layer 15 communicating with the outer layer 2 of the container on the outer side thereof has a quintuple structure.

Gate formed by gate cutting after injection molding
The gas barrier layer 13 is exposed on the surface of the cut surface 16. Therefore, the gas barrier resin absorbs moisture due to water vapor or the like in the air and its performance is deteriorated. Furthermore, there is no gas barrier layer near the central axis of the gate cut surface 16, that is, inside the gas barrier layer 13 on the cut surface, and oxygen can easily pass through the container in this region.
That is, the conventional multi-layer container having the layer structure as shown in FIG. 2 in the vicinity of the gate has a poor gas barrier property due to the deterioration of the performance of the gas barrier resin and the existence of the region where the gas barrier layer is not formed.

FIG. 3 is also a sectional view in the vicinity of the gate of a conventional multi-layer injection molded product. In FIG. 3, a three-kind five-layer structure is used.
It is not formed in the vicinity. The container body and the bottom have a three-layer, five-layer structure of an inner and outer layer of the container, an inner and outer adhesive layer, and a gas barrier layer, but the gas barrier layer 21 near the gate.
Is broken. The details will be described below. Gas barrier layer 2
1 has an inner adhesive layer 22 and an outer adhesive layer 23 on both sides, and has a container inner layer 24 and a container outer layer 25 on the outside thereof. The end portion 26 of the gas barrier layer 21 is covered with an adhesive resin 27.

The inner adhesive layer 22 and the outer adhesive layer 23 communicate with each other at the end portion of the gas barrier layer 21.
1 and its end 28 is covered with a polyolefin resin forming the inner and outer layers of the container. The container inner layer 24 and the container outer layer 25 communicate with each other at the adhesive layer end portion 28. Since only the polyolefin resin is present on the sprue center axis, the gas barrier resin is not exposed on the gate cut surface 29. In this case, the gas barrier resin absorbs less moisture and its performance is less likely to deteriorate. However, a circular region 30 where the gas barrier layer 21 does not exist is wide near the gate, and oxygen gas easily permeates through this region 30. In such a multi-layer container having a layer structure near the gate as shown in FIG. 3, the gas barrier resin is less deteriorated, but there is a region without a gas barrier layer, and the gas barrier property of the container is poor. In some cases, the end 28 of the adhesive layer extends into the sprue, and the sprue has a triple structure of an adhesive resin and a polyolefin resin, but the gas barrier property is also inferior.

The method for molding a multi-layered container of the present invention uses an injection molding machine equipped with three injection devices, and a polyolefin resin forming the outer layer of the container in each injection device, a recycled polyolefin resin and a gas barrier resin. Adhesive resin and gas barrier resin containing are added. First, the polyolefin resin is injected, and before the polyolefin resin is completely solidified in the cavity, the above 3
The seed resin is injected into a quintuple tube structure. At this time, the pressure and flow rate of each resin are controlled by the viscosity of each resin and the thickness of each layer. The layer structure near the gate is formed by changing the pressure of each resin immediately before the cavity is filled with the resin. More specifically, the injection pressure of the gas barrier resin is reduced to about 1/3 after a while while the above three kinds of resins are injected into a quintuple pipe structure, and then the injection pressure of the polyolefin resin is changed to about 3 minutes. Lower to 1. After that, only the polyolefin resin is injected. As the multilayer injection molding machine used for this molding, a molding machine according to Japanese Patent Application No. 02-035819 was used.

[0019]

EFFECTS OF THE INVENTION The present invention is constructed as described above. However, since the gas barrier resin is not exposed on the cut surface of the gate, moisture absorption by the recycled gas barrier resin in the adhesive layer is prevented. Therefore, the gas barrier property is not deteriorated by the moisture absorption of the gas barrier resin, and the layer structure in the vicinity of the gate has a three-kind five-layer structure like the other parts of the molded product, so that a region having extremely high gas permeability is formed. Therefore, a molded product having a high gas barrier property can be provided by a method with less waste of materials and fewer steps.

[0020]

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer container according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the conventional multi-layer container and its vicinity.

FIG. 3 is a partially enlarged cross-sectional view of a conventional multi-layer container and its vicinity.

[Explanation of symbols]

1 ... Flange 2, 25 ... Container outer layer 3 ... Adhesive layer
4, 21 ... Gas barrier layer 5 ... Gate 6, 16, 29 ... Gate cut surface 7, 23
Outer adhesive layer 8, 22 ... Inner adhesive layer 9, 24 ... Container inner layer 11 ... Polyolefin resin layer 12 ... Adhesive layer
Reference numeral 13 ... Gas barrier layer 14 ... Adhesive layer 15 ... Polyolefin resin layer 26 ... Gas barrier layer end 27 ... Adhesive resin 28 ... Adhesive layer end 30 ... Region without gas barrier layer

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location B32B 27/32 E 8115-4F // B29K 23:00 B29L 9:00 4F 22:00 4F 31:56 4F

Claims (2)

[Claims] 1. An innermost layer and an outermost layer of a molded product made of a polyolefin-based resin, and an adhesive layer made of a thermoplastic resin whose main component is a copolymer obtained by graft-modifying polyolefin olefin, immediately inside thereof. In a multilayer injection molding of 3 types and 5 layers including an oxygen gas barrier layer made of an oxygen gas barrier resin inside the adhesive layer, the surface of the molded product is entirely formed of a polyolefin resin, and the end of the oxygen gas barrier layer is formed at the end of the molded product. A part is covered with the adhesive layer, the adhesive layer is covered with the polyolefin resin, and the gate cut surface is formed only with the polyolefin resin.
A multilayer injection-molded article, characterized in that the oxygen gas barrier layer does not have an end portion in the vicinity of the temperature, and the adhesive layer contains a polyolefin resin and an oxygen gas barrier resin. 2. The multilayer injection molded article according to claim 1, wherein the oxygen gas barrier layer is made of a resin containing an ethylene-vinyl alcohol copolymer.