JP3604404B2 - Two-color container integral molding method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for integrally forming a two-color container, and more particularly, to a method for forming a two-color merging portion in a clear straight line without distortion or disturbance when molding left and right color-coded containers. The present invention relates to a method for integrally forming a color container.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
BACKGROUND ART In recent years, plastic containers have been widely used as containers for transporting products such as foods.
[0003]
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.
[0004]
By the way, in order to identify the direction of a container such as a stacking / nesting type container at the time of work such as transportation and storage, generally,
(1) A method of providing a window or the like in one direction of a container and using a photoelectric tube for identification;
(2) A method of attaching a reflective sticker to a part of the container and reading it,
(3) Mark the container with a stamp or attach a label, insert piece, etc. to identify it.
(4) A method such as a method of reading a color difference between two-color containers that are color-coded into left and right colors is used.
[0005]
Of these, the two-color container has many advantages, such as being able to visually identify the direction of the container and being able to simplify the structure and thus being easy to clean. Are better. Such a two-color container is disclosed, for example, in JP-A-60-19515.
[0006]
Two-color containers including this stacking nesting type container are usually injection-molded into a cavity in a mold from a thermoplastic polymer composition such as polypropylene, each colored in a desired color, from different directions, The two colored resins are merged at a substantially central portion of the cavity to be integrally formed. A grid-like rib is usually formed at the bottom of the bottom of such a two-color container for reinforcement of the bottom and stability of sitting.
[0007]
By the way, in a two-color container obtained by a conventional integral molding method, a boundary between colors (merging line) is distorted or disturbed, and thus a clear straight line may not be obtained. Such a two-color container in which the merging lines do not have a straight line shape is inferior in appearance, and in some cases, may be a defective product, thereby lowering the yield at the time of molding the two-color container.
[0008]
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 straightened without being distorted or disturbed.
The present inventor has studied in view of such a conventional technique, and as a result, the joining of the two differently colored resins injected into the cavity in the mold from different directions is parallel to the end wall. It has been found that, when the process is performed at a portion where no rib is provided, a merging line is formed as a clear straight line, and the present invention has been completed.
[0009]
[Object of the invention]
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 that is color-coded in the left-right direction can be formed in a clear straight line.
[0010]
Summary of the Invention
The method of integrally molding a two-color container according to the present invention comprises:
Consists square or a rectangular bottom plate portion, and the bottom plate portion a pair of side walls and a pair of end walls erected on the periphery of,
On the bottom surface of the bottom plate portion, a grid-like rib composed of a horizontal rib parallel to the pair of side walls and a vertical rib parallel to the pair of end walls is formed,
The bottom plate portion and the pair of side walls are merged lines formed so as to be located at a substantially central portion from the pair of end walls, and are color-coded in the left-right direction when viewed from the side wall side,
In the bottom plate portion, the merging line is located at a portion where a vertical rib parallel to the end wall is not provided,
A method of integrally molding a two-color container, wherein the pair of end walls are color-coded according to the color of the side wall,
A mold in which a mold cavity portion corresponding to a vertical rib parallel to an end wall of the container is not formed substantially at the center of the mold cavity corresponding to the bottom plate portion of the container in the left-right direction. ,
While injecting thermoplastic resins colored differently from each other into the mold cavity from separate gates of the mold ,
The injected two-color resin is joined at a portion of the mold cavity corresponding to the bottom plate portion, where a mold cavity portion corresponding to a vertical rib parallel to an end wall of the container is not formed. Features.
[0011]
Furthermore, in the method for integrally forming a two-color container according to the present invention,
In the bottom plate portion, a distance between longitudinal ribs parallel to the end wall adjacent to each other with a merging line interposed therebetween is P ₂ [cm],
In the bottom plate portion, when a distance between longitudinal ribs parallel to the end wall adjacent to each other without interposing a merging line is P ₁ [cm],
P _2> P ₁
It is preferable that
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for forming a two-color container according to the present invention will be described with reference to the drawings.
First, the shape of the two-color container formed by the present invention will be described.
[0013]
FIG. 1 is a schematic perspective view of the stacking / nesting type two-color container 1, and FIG. 2 is a perspective view of a bottom part of the two-color container 1.
In these figures, the two-color container 1 includes a bottom plate 3, a pair of side walls 2c and 2d erected on the peripheral edge of the bottom plate 3, and a pair of end walls 2a and 2b. The two-color container 1 is color-coded left and right on the side wall.
[0014]
The bottom plate part 3 is composed of a flat plate 3a and lattice-shaped ribs 4 formed on the bottom surface side thereof. The lattice-shaped rib 4 is composed of a longitudinal rib 4a parallel to the end walls 2a, 2b and end walls 2a, 2b. And a transverse rib 4b perpendicular to the horizontal direction.
[0015]
In the present invention, the two-color container 1 is integrally molded by injecting a two-color thermoplastic resin using an injection mold having a cavity corresponding to such a container shape.
[0016]
FIG. 3 shows a vertical sectional view of the injection mold.
In the mold, 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. 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 and 12b are formed. In the runner block, two runners 11a and 11b communicating with the 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.
[0017]
Resin colored in different colors, which have been melted separately, are advanced from the respective nozzles 13a, 13b of the heating cylinders 14a, 14b into the mold by advancing screws (not shown) in the injection devices 15a, 15b, respectively. It is injected into the passages 12a and 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 through the gates 16a, 16a, 16b, 16b.
[0018]
In the present invention, an example in which the injection molding die shown in FIG. 3 is used to integrally mold the two-color container 1 has been described, but the injection molding die used in the present invention is not limited to this example. For example, the number of gates communicating with the cavity may be such that at least one gate communicates with each injection device. Even when a plurality of gates are provided, the number is not limited. 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 connected to the merging line of the two colors. It is preferable that they are provided substantially line-symmetrically to the left and right. Further, the injection device may be of a screw type or a plunger type, and its operating mechanism is not limited.
[0019]
In the present invention, a molten thermoplastic resin colored in different colors is simultaneously injected into the injection mold as described above, and the resins are merged at a substantially horizontal center in the cavity 10 to merge. A line C is formed, and the container 1 which is color-coded left and right with different colors from the merging line C is integrally formed.
[0020]
The merging line C may be formed on the left or right of the container 1 when the container 1 is viewed from the side wall surface side.
The thermoplastic resins colored differently from each other usually consist of a thermoplastic resin and a pigment (dye).
[0021]
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).
[0022]
The thermoplastic resins charged into the injection devices 15a and 15b are different in color, that is, different only in pigment (dye), and it is preferable to use the same resin.
As the pigment to be mixed with the resin, pigments or dyes generally used for coloring plastics are used without any particular limitation.
[0023]
Further, additives such as heat stabilizers and weather stabilizers, fillers such as glass fibers and fillers, etc. are appropriately blended with the thermoplastic resin according to the intended use of the obtained container.
[0024]
Injection molding of such a thermoplastic resin is generally performed under conditions such as melting temperature and pressure during injection molding of plastic, but in the present invention, a molten resin injected from different directions, It is carried out while adjusting the injection pressure and the like so that it merges at a desired position, usually at substantially the center of the cavity.
[0025]
In the present invention, during such injection integral molding, resins of different colors flowing from different directions as described above are merged substantially at the center of the container. In the present invention, in the bottom plate portion 3, resins of different colors flowing opposite to each other are joined at a portion where the longitudinal rib 4 a parallel to the end wall is not provided.
[0026]
FIG. 4 is an explanatory diagram showing the flow of the resin in the mold near the resin merging portion of the bottom plate portion 3 when the container 1 is integrally molded.
In the drawing, different colors are indicated by a dot pattern and a hatched pattern.
[0027]
In the present invention, the joining of the resins in the bottom plate portion 3 is performed at a portion where the longitudinal ribs 4a parallel to the end walls 2a and 2b are not provided.
In the vicinity of the merging line C between the two-color resins, the resin flows from both directions toward the merging line C (in the direction of the arrow in the figure).
[0028]
Therefore, according to the method of the present invention, there is no disturbance or distortion in the resin flow at the merging line C, and the merging line C is formed in a straight line.
FIG. 5 shows a case where two colors of resin are joined at a portion where the longitudinal ribs 4a are provided.
[0029]
The two colors of resin flowing from the left and right directions to the vicinity C of the merging line come to the vertical ribs 4a provided in the direction perpendicular to the direction of travel of the resin, and bend perpendicularly to the direction of travel. At this time, the resins whose directions have been changed influence each other, and the flow of the resins is disturbed. For this reason, when the resins are merged on the longitudinal ribs 4a, the merged line C is distorted or disturbed.
[0030]
In the method of the present invention, the resin of the bottom plate portion 3 is joined at the portion where the longitudinal ribs 4a are not provided as described above. A more preferable embodiment of the present invention is shown in FIG. .
[0031]
In the present invention, in the lattice-shaped rib 4 formed on the bottom plate portion 3 as described above,
The distance between the ribs 4a, 4a (vertical direction) parallel to the merge line adjacent to the merge line is P ₂ [cm],
When the distance between the ribs 4a, 4a (vertical direction) parallel to the adjacent merging line without sandwiching the merging line is P ₁ [cm],
P _2> P ₁
It is preferable that
[0032]
By making the interval (pitch) between the vertical ribs 4a, 4a sandwiching the merging line C longer than the interval (pitch) between the other vertical ribs 4a, 4a, the merging line C becomes more disordered. Not straight.
[0033]
Although the two-color container obtained by the present invention has been described above, the case where the bottom plate portion 3 shown in FIGS. 1 and 2 is formed from the flat plate 3a and the grid-like ribs 4 formed on the bottom surface side thereof has been described. The shape of the bottom plate 3 is not limited to this example.
[0034]
Another two-color container obtained according to the present invention is shown in FIG.
In FIG. 7, the bottom plate portion 3 does not have the flat plate 3a, but is formed by a stitch-like shape formed by the vertical ribs 4a, the horizontal ribs 4b, and the openings 4c formed by the vertical and horizontal ribs (lattice-shaped ribs) 4. Is formed.
[0035]
In such a stitched bottom plate portion 3 as well, the two-color resins are joined not at the vertical ribs 4a parallel to the end walls 2a and 2b but at the horizontal ribs 4b.
[0036]
The two-color container obtained by the present invention as described above is preferably used particularly as a stacking / nesting type container, but need not always be used as a stacking / nesting type container.
[0037]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the integral molding method of the two-color container which concerns on this invention, the two-color container from which the mutually different left and right two-color merging lines are linear is obtained.
[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 bottom perspective view of the two-color container obtained by the present invention.
FIG. 3 is a horizontal sectional view of the injection mold used in the present invention as viewed from a side wall of the two-color container of FIG. 1 ;
FIG. 4 is a schematic diagram showing a flow of resin in the vicinity of a resin merging line in the present invention .
FIG. 5 is a schematic diagram showing a flow of resin near a resin merging line in a comparative example.
FIG. 6 is a schematic diagram showing a flow of resin near a resin merging line in a more preferred embodiment of the present invention.
FIG. 7 shows a bottom view of another two-color container obtained by the present invention.

Claims (2)

Consists square or a rectangular bottom plate portion, and the bottom plate portion a pair of side walls and a pair of end walls erected on the periphery of,
On the bottom surface of the bottom plate portion, a grid-like rib composed of a horizontal rib parallel to the pair of side walls and a vertical rib parallel to the pair of end walls is formed,
The bottom plate portion and the pair of side walls are merged lines formed so as to be located at a substantially central portion from the pair of end walls, and are color-coded in the left-right direction when viewed from the side wall side,
In the bottom plate portion, the merging line is located at a portion where a vertical rib parallel to the end wall is not provided,
A method of integrally molding a two-color container, wherein the pair of end walls are color-coded according to the color of the side wall,
A mold in which a mold cavity portion corresponding to a vertical rib parallel to an end wall of the container is not formed substantially at the center of the mold cavity corresponding to the bottom plate portion of the container in the left-right direction. ,
While injecting thermoplastic resins colored differently from each other into the mold cavity from separate gates of the mold ,
The injected two-color resin is joined at a portion of the mold cavity corresponding to the bottom plate portion, where a mold cavity portion corresponding to a vertical rib parallel to an end wall of the container is not formed. Characteristic integrated molding method for two-color containers. In the bottom plate portion, a distance between longitudinal ribs parallel to the end wall adjacent to each other with a merging line interposed therebetween is P ₂ [cm],
In the bottom plate portion, when a distance between longitudinal ribs parallel to the end wall adjacent to each other without interposing a merging line is P ₁ [cm],
P _2> P ₁
The method for integrally molding a two-color container according to claim 1, wherein:

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