JPH0222022A - Multilayer injection molded piece and manufacture of hollow vessel - Google Patents

Abstract

PURPOSE:To severely control the disposition of an intermediate layer by coaxially disposing inner layer, the intermediate layer and outer layer resin passages from a center toward an outward direction in a hot runner, initially injection molding the inner layer and the outer layer resin, and coinjecting the intermediate layer resin by slightly delaying in a laminar flow in which the compression force of the circumferential direction is sufficiently alleviated, and early finishing the injection. CONSTITUTION:An inner layer resin passage 54, an intermediate layer resin passage 55 and an outer layer resin passage 56 are coaxially disposed in this sequence from a center toward an outward direction in a hot runner 50, and the inner layer resin and the outer layer resin are initially injected. After a slight delay, the intermediate layer resin is coinjected in the shape of a laminar flow that the circumferential compression force is sufficiently alleviated and sandwiched by the inner and outer layer resins, and the injection of the intermediate layer resin is stopped prior to the end of the injection. The inner and outer layer resins are eventually injected. Thus, since the intermediate layer resin is controlled in a laminar flow thereby to regularly feed the resin layers, the position and disposition of the intermediate layer can be severely controlled in the molded piece.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a multilayer injection molded article, and more specifically, a method for producing a multilayer injection molded article having an outer layer, an intermediate layer, and an inner layer. It relates to a method of manufacturing under strictly controlled conditions. The invention also relates to a method for manufacturing hollow containers from this multilayer injection molded body.

(Prior art and its problems) Unlike metal containers and glass containers, resin containers are
Permeation of gases such as oxygen through the vessel walls occurs on a non-negligible scale, resulting in poor preservation of the contents. In order to solve this problem, multilayer resin containers are widely used in which the inner and outer layers are made of resin with excellent hygienic properties and moisture resistance, and the middle layer is made of resin with excellent gas barrier properties.

Methods for manufacturing this multilayer resin container include a method in which resin is co-injected into multiple layers into an injection mold to directly mold the multilayer container, or a preform is once manufactured by multilayer co-injection, and then this multilayer preform is stretch-blow molded. There are known ways to do this.

When producing multilayer containers and multilayer preforms by these methods using ordinary multilayer injection molding machines, it is difficult to strictly control the position and arrangement of the intermediate layer in the injection molded product. Disadvantages are recognized that the method is branched into more than one layer, or a branched intermediate layer is exposed on the surface of the injection molded product. When the intermediate layer is exposed on the surface of the molded product, the intermediate layer resin absorbs moisture, resulting in deterioration of the elastic properties and delamination between the intermediate layer and the inner and outer layers, that is, delamination.

In particular, in order to prevent the intermediate layer from being exposed at the mouth or bottom of the container, the injection timing of the intermediate layer resin and the injection timing of the inner and outer layer resins are staggered, and the injection timing of the intermediate layer resin is delayed from the injection timing of the inner and outer layer resins. A method has been adopted in which the injection flow of the intermediate layer resin is delayed and the injection of the intermediate layer resin is completed earlier than that of the inner and outer layer resins, so that the intermediate layer is not formed at the mouth and bottom. Therefore, after the injection pressure of the intermediate layer resin is cut off, the intermediate layer resin continues to flow out along with the inner and outer layer resins, resulting in a problem that the intermediate layer is exposed at the bottom.

Therefore, an object of the present invention is to provide a method for producing a multilayer injection molded product which eliminates the above-mentioned problems in the conventional method for producing a multilayer injection molded product and allows strict control of the position and arrangement of the intermediate layer in the injection molded product. It is on offer.

(Means for Solving the Problems) According to the present invention, the first resin constituting the inner layer and the outer layer of the multilayer injection molded article and the second resin constituting the intermediate layer of the multilayer molded article are heated through a hot runner nozzle. In a method for producing a multilayer injection molded body, which comprises co-injecting into an injection mold through the
In a hot runner, the inner layer resin flow path, middle layer resin flow path, and outer layer resin flow path are arranged coaxially in this order from the center outward, and the inner layer resin and outer layer resin are injected first, and there is a slight delay. After that, the intermediate layer resin is co-injected in the form of a laminar flow in which the compressive force in the circumferential direction is sufficiently relaxed and sandwiched between the inner and outer layer resins, and the injection of the intermediate layer resin is stopped before the end of injection. There is also provided a method for producing a multilayer injection molded article, which comprises finally injecting an inner layer resin and an outer layer resin.

According to the present invention, there is also provided a method for producing a multilayer hollow container, which comprises stretching the glyph 4-me of the multilayer injection molded product obtained by the above-described production method in the axial direction and blow-stretching it in the circumferential direction in a blower. is provided.

(Function) In the present invention, an inner layer resin flow path, an intermediate layer resin flow path, and an outer layer resin flow path are arranged coaxially in this order from the center to the outside in a hot runner. Inject the outer layer resin. Once the amount of resin corresponding to the mouth portion has been injected, the injection of the intermediate layer resin is also started. At this time, in the present invention, the intermediate layer resin is co-injected in the form of a laminar flow in which compressive stress in the circumferential direction is sufficiently relaxed and sandwiched between the inner and outer layer resins, so that the intermediate layer is not exposed to the inner and outer surfaces. This is an important feature for

In other words, by controlling the intermediate layer resin to form a laminar flow, each resin layer flows in an orderly manner without exchanging positions, even though they may slide against each other. Therefore, branching or separation of the intermediate layer can be prevented in the injection molded product. It is possible to effectively prevent this from occurring, and also to precisely control the leading and trailing ends of the intermediate layer.

In conventional injection machines, the resin flow path is tapered near the tip of the nozzle, so in this tapered part, the circumferential flow path of each resin layer is narrowed and the resin flows inward. Therefore, compressive stress is applied to the entire resin flow in the circumferential inner direction, and it is thought that this compressive stress causes the resin flow to become turbulent. Controlling the intermediate layer resin flow into a laminar flow is made possible by sufficiently relaxing this compressive stress in the circumferential direction.

(Preferred Embodiment of the Invention) An example of a method for sufficiently relaxing compressive stress in the circumferential direction is a method using a multilayer injection molding nozzle as shown in FIG.

In FIG. 1, this nozzle 1 consists of a nozzle outer cylinder 2, a large diameter sleeve 3 inside the outer cylinder, and a small diameter sleeve 4 inside the large diameter sleeve, which are provided coaxially with each other. The nozzle outer cylinder 2 is tapered, and an orifice 5 is provided at the center of its tip. Nozzle outer cylinder 2 and large diameter sleeve 3
An outer resin channel 6 is provided between the large diameter sleeve 3 and the small diameter sleeve 4, an intermediate resin channel 7 is provided between the large diameter sleeve 3 and the small diameter sleeve 4, and an inner resin channel 8 is provided inside the small diameter sleeve 4. ing.

The inner surface of the nozzle outer cylinder 2 consists of a cylindrical surface 9 and a tapered surface 10, and a large diameter sleeve 3 corresponds to the cylindrical surface 9 and the tapered surface 10.
The inner surface also consists of a cylindrical surface 11 and a tapered surface 12.

The inner surface of the large-diameter sleeve 3 consists of a relatively large-diameter cylindrical surface 13, a tapered surface 14, and a relatively small-diameter cylindrical surface 15 with a small axial dimension. It also consists of a cylindrical surface 16 with a relatively large diameter, a tapered surface 17, and a cylindrical surface 18 with a relatively small diameter and small axial dimension. That is, the intermediate layer resin flow path 7 in this nozzle has a tapered flow path defined by surfaces 14 and 17, followed by a straight resin flow path (land portion) defined by surfaces 15 and 18. It is a characteristic. The tip of the small diameter sleeve 4 is cut at right angles to the axial direction to form a circular tip surface 19.

Also inside the small diameter sleeve 4, there is a relatively large diameter cylindrical surface 20,
There is an inner layer resin flow path 8 defined by a tapered surface 21 and a cylindrical surface 22 having a relatively small diameter.

The circular distal end surface 19 of the small diameter sleeve 4 is located at a position slightly recessed from the rear end of the orifice 5, and a truncated conical small space 23 is formed between the orifice 5 and the small diameter sleeve 4.

With the above structure, the outer layer resin flow path 6 and the intermediate layer resin flow path 7
It will be understood that each tip of the inner layer resin channel 8 is located in substantially the same plane as the circular tip surface 19.

Taper angle (θ1
, angle from the horizontal axis), taper angle (θ2) of intermediate layer resin flow path 14-17, straight flow path (land) 15-
18 axial dimensions (g,.

mm) and diameter (d, mm) vary depending on the size of the injection molded product, etc., but are generally preferably within the following ranges.

2" L frying" L dish 40-70" 50-80° 1-20 mm 0.5-3ff1m Preferred range 55-60° 70-80° 3-10 mm 0.5-1.5 mm In the present invention, A multilayer injection molded body and a multilayer preform are molded using an injection molding apparatus using the above-described multilayer injection molding nozzle as shown in Figure 2.This apparatus includes a nozzle 1, a hot runner block 50, an injection mold 51
, outer layer and inner layer resin injection machine 52 and middle layer resin injection machine 5
Consists of 3. The hot runner block 50 has a solid flow path 54 for the inner layer resin at the center, an annular inner annular flow path 55 for the intermediate layer resin around the solid flow path 54, and an outer annular flow path 56 for the outer layer resin around the outer circumference thereof. Each of these channels is connected to each resin channel of the hot runner nozzle 1. Further, the injection machine 52 for the inner and outer layers is connected to the corresponding channels 54 and 56 via branch channels 57 and 58, and the injection machine 53 for the intermediate layer is connected to the channel 55 for the intermediate layer via a nozzle 59.

The injection machines 52 and 53 have screws 61 and 6, respectively.
2 is provided.

The injection mold 51 consists of a cavity mold 63 and a core mold 64, and a cavity 65 is provided between the two. The cavity mold 63 has a gate 66 leading to the cavity 65.
is provided, and the orifice 5 of the nozzle 1, the goo 1-66, and the cavity 65 communicate with each other in the mold-clamped state.
: Sea urchins are turning.

When injection molding the resin, the screw 61 of the injection machine 52 for the inner and outer layers is advanced to start injecting a certain amount of the resin for the inner and outer layers. The screw 62 of the intermediate layer injection machine 53 is moved forward with a slight delay from this timing, and the intermediate layer resin is injected in parallel with the inner and outer layers. Nearing the end of injection,
The screw 62 of the intermediate layer resin injection machine 53 is stopped to stop the injection of the intermediate layer resin. After this stoppage, the injection of the inner and outer layer resin continues for a while, and then the screw 61 of the inner and outer layer resin injection machine 52 is stopped, and the injection molding cycle is completed.

As the inner and outer layer resins, olefin resins such as polyethylene and polypropylene, styrene resins, polyester resins, etc. are used, and as the intermediate layer resins, ethylene-vinyl alcohol copolymers, vinylidene chloride resins, xylylene group-containing polyamides, and casbarriers are used. Polymer 17 ester resin or the like is used.

The method of the invention is also applicable to multilayer resin injection molding with more than three layers. For example, in the multilayer injection molding nozzle shown in FIG. 3, the large diameter sleeve is coaxial with the first sleeve 3.
a and a second sleeve 3b, the first sleeve 3
An outer adhesive layer resin channel 24 is provided between the first sleeve 4 and the second sleeve 3b, and the small diameter sleeve is coaxial with the first sleeve 4.
an inner adhesive layer resin flow path 25 is provided between the first sleeve 4a and the second sleeve 4b, and the tips of the outer layer side and inner layer side adhesive layer resin flow paths also have the circular shape. It is located on the same plane as one tip surface.

In the present invention, it is possible to directly obtain a multilayer injection molded product, but it is also possible to first mold a multilayer preform and then uniaxially stretch it by blow molding to form a hollow container. Conventionally known methods can be used for blow molding, but
An example thereof will be explained using FIG.

] 2 Insert the mandrel 101 into the mouth of the preform 100, and insert the mouth into the pair of split molds 102a and 102b.
Hold it between the two. A stretching rod 103 that is vertically movable coaxially with the mandrel 101 is provided, and an annular passage 1 for blowing fluid is provided between the stretching rod 103 and the mandrel 10.
There is 04.

The tip 105 of the stretching rod 103 is applied to the inside of the bottom 106 of the preform 100, and by moving the stretching rod 103 downward, it is stretched in the axial direction, and the inside of the preform 100 is drawn through the fluid injection passage 104. A hollow container is obtained by blowing fluid into the glyph and expanding and stretching it in the circumferential direction using the fluid pressure.

(Effects of the Invention) According to the present invention, the intermediate layer resin can be injected in a laminar flow without generating turbulence in the intermediate layer, so that branching of the intermediate layer and This makes it possible to effectively prevent separation and the like, and also to precisely control the leading and trailing ends of the intermediate layer.

Therefore, the injection molded article and hollow container obtained by the method of the present invention have particularly excellent impact resistance and deformation resistance.

(Example) Example and Comparative Example Using the injection molding apparatus shown in FIG.
is supplied, and metaxylylene group-containing polyamide (MXN) is supplied to an injection machine for intermediate layer.

First, a hot runner nozzle (O,
=60°, θ2-75°, , 9 layers 7mm, d=1
The primary injection of molten PET from the injection machine for the inner and outer layers was performed at a pressure of about 60 Kg/cm2 through the injection mold (mm), and about 1.4 seconds later than the injection of the PET, the PET
A predetermined amount of molten MXN is co-injected in 0.8 seconds from the intermediate layer injection machine at a pressure of approximately 100 Kg/cm2, which is higher than the primary injection, and the injection of MXN is stopped prior to the end of the injection, and the next injection is performed. Then, PET was secondarily injected using an injection machine for inner and outer layers at a pressure lower than the primary injection pressure to mold a multilayer preform of two types and three layers with a wall thickness of 4 mm.

This multilayer preform is heated to about 105°C and the length is about 2.
Biaxially stretched and blown to 5 times and about 3.5 times in width to an internal volume of 100.
A 0cc multilayer bottle was molded.

For comparison, a multilayer preform was made by co-injection molding under the same conditions as the example using the method disclosed in JP-A-61-173924 (comparative example). A multilayer bottle was molded.

The results are shown in Table 1. From this result, the example is the outer layer,
While all the middle and inner layers are uniformly distributed,
The comparative example has poor performance because the thickness of the intermediate layer is different at the top, center, and bottom, and the intermediate layer is biased toward the inner layer, resulting in a turbulent flow in multiple layers.

[Brief explanation of the drawing]

FIG. 1 shows a multilayer injection molding nozzle as an example for achieving the object of the present invention, and FIG. 2 is a schematic layout diagram of an injection molding apparatus equipped with the multilayer injection molding nozzle of FIG. 1. 3 is a sectional view of another example of a multilayer injection molding nozzle, and FIG. 4 is a diagram for explaining blow molding. 1 is a nozzle, 2 is a nozzle outer cylinder, 3 is a large diameter sleeve, 4 is a small diameter sleeve, 5 is an orifice, 6 is a multilayer resin flow path, 7
1 is an intermediate layer resin flow path, 8 is an inner layer resin flow path, 14 and 17 are tapered surfaces, 15 and 18 are cylindrical surfaces with a relatively small diameter, 19 is a circular tip surface of a small diameter sleeve, and 23 is a truncated conical space. be. ■ Figure diagram

Claims (3)

[Claims] (1) Multilayer injection molding consisting of co-injecting a first resin constituting the inner and outer layers of the multilayer injection molded article and a second resin constituting the intermediate layer of the multilayer molded article into an injection mold through a hot runner nozzle. In the method of manufacturing the body, an inner layer resin flow path, an intermediate layer resin flow path, and an outer layer resin flow path are arranged coaxially in this order from the center outward in a hot runner, and the inner layer resin and outer layer resin are first injected. After a slight delay, the intermediate layer resin is co-injected in the form of a laminar flow in which the compressive force in the circumferential direction is sufficiently relaxed and sandwiched between the inner and outer layer resins. A method for producing a multilayer injection molded article, which comprises stopping the injection of resin and finally injecting the inner layer resin and the outer layer resin. (2) A claim in which the first resin is made of thermoplastic polyester or polypropylene, and the second resin is a xylylene group-containing polyamide, an ethylene-vinyl alcohol copolymer, a gas barrier polyester resin, or a vinylidene chloride copolymer. 1. The manufacturing method described in 1. (3) A method for producing a multilayer hollow container, which comprises stretching a preform of a multilayer injection molded article obtained by the production method according to claim 1 in the axial direction and blow-stretching it in the circumferential direction in a blow mold.