JP3270768B2 - Two-color container integral molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for integrally molding a two-color container, and more particularly, to forming a two-color container into a sharp straight line without distortion or disturbance when molding a two-color container. The present invention relates to a method for integrally forming a two-color container that can be formed.

[0002]

BACKGROUND OF THE INVENTION In recent years, plastic containers have been widely used as containers for transporting goods such as food.

In particular, in such a plastic container, a stacking / nesting type container which can be easily stacked (stacked) at the time of transportation and overlapped (nested) so as not to be bulky at the time of storage has been developed and used.

In order to identify the direction of a container such as a stacking / nesting-type container at the time of carrying or storing the container, generally, (1) a window or the like is provided in one direction of the container. , A method of identifying using a photoelectric tube, (2) a method of attaching a reflective seal to a part of the container and reading it, (3) identifying the container by stamping or attaching a label, insert piece, etc. And (4) a method of reading the difference between the colors of the two-color container classified into the left and right colors.

[0005] Among these, the two-color container has many advantages such that the direction of the container can be visually identified and the structure can be simplified, so that it is easy to clean. Excellent work efficiency. Such a two-color container is disclosed, for example, in JP-A-60-19515.

A two-color container such as the stacking / nesting type container usually injects a thermoplastic polymer composition such as polypropylene, which is colored to a desired color, into a mold cavity from different directions. It is molded integrally by joining the two colored resins at substantially the center of the cavity.

In the two-color container obtained by the conventional integral molding method, the boundary between the colors (merging line) at the resin merging portion of the container is distorted or disturbed, so that a clear straight line cannot be obtained. there were.

[0008] Such a two-color container in which the merging line is not linear has a poor appearance, and in some cases, it may be a defective product, which lowers the yield during molding of the two-color container. ing.

For this reason, there is a demand for an integrated molding method of a two-color container in which a boundary between colors, that is, a merging line is straight without being distorted or disturbed. The present inventor has conducted research in view of such prior art, and obtained a two-color container after molding using a mold provided with a resin tab void at a resin joining position tip portion in a cavity. When the resin tab was cut off from the two-color container, it was found that the merging line was formed as a clear straight line, and the present invention was completed.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for integrally forming a two-color container in which a two-color merging line of a two-color container classified into two colors can be formed in a sharp straight line.

[0011]

SUMMARY OF THE INVENTION An integrated molding method for a two-color container according to the present invention comprises a two-color container having a bottom plate and side walls erected on a peripheral portion of the bottom plate, and which is color-coded in two colors in the left-right direction. The thermoplastic resins colored differently from each other are injected from separate gates of the mold, and the resins colored differently from each other are merged at almost the center of the cavity in the left-right direction to form a single piece. In doing this, the two-color container is molded using a mold having a resin tab void at the tip of the resin merging position in the cavity, preferably at the tip of the resin final arrival position in the cavity. The resin tab is cut off from the color container.

According to the present invention, it is possible to obtain a two-color container in which two-color merging lines for color separation in the left-right direction are formed in a sharp straight line.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a method for forming a two-color container according to the present invention will be specifically described with reference to the accompanying drawings.

First, the shape of the two-color container formed by the present invention will be described. FIG. 1 is a schematic perspective view of a stacking / nesting type two-color container 1, and FIG.
1 is a longitudinal sectional view of an injection mold used in the present invention. FIG. 3 and FIG. 5 are enlarged longitudinal sectional views of a main part of a molded two-color container with a resin tab. FIG. 3 shows a mode in which a resin tab is provided at the end of the flange, and FIG. 5 shows a mode in which a resin tab is provided between two upper and lower flanges. FIG. 4 is a sectional view taken along the line [IV]-[IV] in FIG. 3, and FIG. 6 is a sectional view [VI]-[VI] in FIG.
FIG.

In FIG. 1, a two-color container 1 includes a bottom plate 3 and a pair of side walls 2 erected on the periphery of the bottom plate 3.
c, 2d and a pair of end walls 2a, 2b. The two-color container 1 is color-coded in two colors by a merging line L on the bottom plate 3 and the side walls 2c and 2d.

In the present invention, the two-color container 1 as described above is used.
Using a mold having a cavity shape corresponding to the shape of a container as shown in FIG. 2, a two-color thermoplastic resin as described later is injected and integrally molded.

In the injection mold shown in FIG. 2, a cavity 10 having a shape corresponding to the container 1 as described above is formed by a movable mold (male mold) 8 and a fixed mold (female mold) 9. ing. A runner block 11 is fixed to one side of the fixed mold 9, and an end (sprue) of the runner block 11 is connected to the nozzles 13a and 13b of the injection devices 15a and 15b at the center of the runner block 2. Book passages 12a, 1
2b is drilled. In the runner block, two runners 11a and 11b communicating with these passages 12a and 12b respectively extend in opposite directions so as to be substantially parallel to the cavity 10. Further, the runners 11a, 11b communicate with the cavity 10 by gates (passages) 16a, 16a, 16b, 16b provided at two locations, respectively. Further, the portion where the resin in the cavity 10 merges (finally) arrives,
For example, a resin tab gap (not shown) for forming resin tabs 30a and 30b as illustrated in FIG. 3 or FIG. ) Is provided.

In the above description, an example in which the two-color container 1 is integrally molded using the injection mold shown in FIG. 2 has been described. However, the injection mold used in the present invention is not limited to this example. Not something.

For example, the number of gates communicating with the cavity may be such that at least one gate communicates with each injection device, and the number is not limited when a plurality of gates are provided. The position of such a gate is appropriately set depending on the shape of the container to be obtained.For example, in the case of obtaining a substantially symmetrical container, the gates of the resin of each color are joined to the merging line of the two colors. It is preferable that they are provided substantially line-symmetrically to the left and right. The injection device may be a screw type or a plunger type as described above.

In order to integrally mold the two-color container 1 using the above-described injection molding apparatus, the two-color container 1 is first melted separately,
Heating cylinders 14a and 14b are formed by operating the screws (not shown) in the injection devices 15a and 15b, respectively, with resins colored in different colors as described below.
From the nozzles 13a and 13b of the
a, 12b. The resin injected into the mold flows from the passages 12a, 12b into the runners 11a, 11b, and is pressed into the cavity 10 from the gates 16a, 16a, 16b, 16b. The two-color resin press-fitted into the cavity gradually flows into the resin tab 30a (30b) space provided at the end of a portion corresponding to substantially the center of the flange portion 20 of the two-color container in the cavity 10. Eventually, the resin reaches the cavity for the resin tab 30a (30b) provided at the tip of the portion (the portion corresponding to 40a in FIG. 3) where the two colors of resin merge in the cavity 10.

By forming the resin tabs 30a (30b) at the end portions 40a (40b) at the positions where the two colors of resin merge, the merge line L formed when the two colors of resin merge is formed. It can be formed in a straight line without disturbance or distortion. This is considered for the following reason. That is, when the resin tabs 30a (30b) are not formed, the pressure inside the cavity suddenly increases due to the inflowing resin at the merging end of the resin (for example, at a position in the cavity corresponding to the flange 20). Therefore, the merging line L of the two colors of resin may be disturbed. However, the tip position of the resin merging end 20 (for example, 40 in FIG. 3)
(a position in the cavity corresponding to a)
When the space for (30b) is formed, the resin tab portion 30a (3
0b) Although the cavity internal pressure sharply increases in the cavity for use, the convergence line L of the obtained two-color container may be disturbed, but the cavity internal pressure does not increase abruptly at the merging end of the resin. Therefore, it is considered that the convergence line is hardly disturbed at the merging end of the resin.

That is, when the merging line L of the flange portion 20 of the container 1 is formed in this manner, the flow of the resin in the flange portion 20 is not disturbed or distorted, and the merging line L is formed in a straight line.

Next, by cutting off the resin tabs 30a (30b) of the two-color container with a resin tab removed from the mold, a two-color container in which the merging line L is formed in a straight line is obtained. The means for cutting the resin tabs 30a (30b) is not particularly limited, and may be cut using a blade or the like, or may be removed by melting.

When the container 1 is viewed from the back side of the bottom plate, the merging line L may be formed on the left or right of the container 1 which is color-coded left and right. The two-color thermoplastic resin colored in different colors and used when integrally forming such a two-color container usually contains a thermoplastic resin and a pigment (dye).

As the thermoplastic resin, a resin widely used in injection molding of plastic is generally used without any particular limitation. Examples include polypropylene (PP), polyethylene (PE), ABS resin, polystyrene (PS), polycarbonate (PC), polyvinyl acetate (EVA resin), polyamide (PA), and polyacetal (POM).

The thermoplastic resins to be charged into the injection devices 15a and 15b are different in color, that is, different only in pigment (dye) or composition ratio thereof, and it is preferable to use the same resin.

As the pigment compounded in the resin, pigments or dyes generally used for coloring plastics are used without any particular limitation. Further, the thermoplastic resin, depending on the intended use of the resulting container,
Additives such as heat stabilizers and weather stabilizers, and fillers such as glass fibers and fillers are appropriately blended.

Such a thermoplastic resin is generally injection-molded under conditions such as a melting temperature and a pressure at the time of injection-molding a plastic. In the present invention, as described above, injection is performed from different directions. The injection is performed while adjusting the injection pressure and the like such that the melted resin merges at a desired position where the shielding plate is provided, generally at the center of the cavity.

In the above description, the stacking / nesting type container has been described as an example. However, the present invention is not limited to the above-described example, and can be applied to various two-color injection molded articles.

In the above-described two-color container, for example, a rib may be provided on the bottom surface, and its shape may be parallel or oblique linear to any side, or two adjacent sides. May be provided so as to be orthogonal to each other. Further, the side wall portions 2c and 2d, the bottom plate portion 3
For example, a plurality of holes for draining or the like may be provided.

Further, in the above-mentioned mold, the position of the void for the resin tab is not limited to the mode of being provided at the front end portion 40a (40b) of the flange portion of the container 1 in the cavity as shown in the above example. Depending on the shape of the cavity, the gate position for press-fitting the resin, and the like, the design can be appropriately changed in accordance with the merging position of the two colors of resin, preferably the final resin reaching position.

[0032]

According to the method for integrally forming a two-color container according to the present invention, a two-color merging line of a two-color container classified into two different colors, left and right, can be obtained in a straight line without distortion or disturbance.

Therefore, according to the present invention, the two-color container can be integrally formed with an excellent yield.

[Brief description of the drawings]

FIG. 1 shows a perspective view of a stacking nesting type two-color container obtained by the present invention.

FIG. 2 is a longitudinal sectional view of an injection mold used in the present invention.

FIG. 3 is an enlarged vertical sectional view of a main part of a molded two-color container with a resin tab. FIG. 3 shows an embodiment in which a resin tab is provided at the tip of the flange.

FIG. 4 is a sectional view taken along the line [IV]-[IV] in FIG.

FIG. 5 is an enlarged vertical sectional view of a main part of a molded two-color container with a resin tab. FIG. 5 shows an embodiment in which a resin tab is provided between two upper and lower flanges.

FIG. 6 is a sectional view taken along the line [VI]-[VI] in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Two-color container, 2a, 2b ... End wall, 2c, 2d ... Side wall, 3 ... Bottom plate part, 8 ... Movable mold, 9 ... Fixed mold, 30a, 30b ... Resin tab (small piece), 40a , 40b: tip of the resin merging end, PL: mold joining surface, L: merging line.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/16 B29C 45/26 B65D 6/04

Claims (2)

(57) [Claims] 1. A two-color container comprising a bottom plate portion and side walls erected on a peripheral portion of the bottom plate portion, which is colored in two colors in the left-right direction, is made of a thermoplastic resin colored in different colors from each other. Injected from different gates of the mold, and at the center of the left and right direction, when the resins colored in different colors are merged and molded together, a resin tab at the tip of the resin merging position in the cavity After molding a two-color container using a mold with a void,
An integrated molding method for a two-color container, wherein a resin tab is cut from the obtained two-color container. 2. The method according to claim 1, wherein the cavity for the resin tab uses a mold provided at the front end of the resin merging position in the cavity corresponding to the flange of the two-color container.