JPS62299313A - Preparation of container made of thermoplasltic resin - Google Patents

Abstract

PURPOSE:To prevent the generation of a burr on a rule part and a notch part, by injecting a specific resin in a mold having a specific mold structure to form a developing plate having a specific shape. CONSTITUTION:A developing plate, wherein an area is 100cm<2> or more, an average plate thickness is 0.3-2.0mm, an average thickness of a rule part is 0.15-1.0mm and a notch part is provided, is formed by using a thermoplastic resin of which the melt index is 16-60g/10min. In a mold, one mold A has a wall surface deeper than the objective thickness of a cavity as a recessed mold and the other opposed side mold B being a projected mold having a side wall extending along the wall surface of said mold A is fitted to the mold A to constitute a mold structure forming an objective thickness. When a resin is injected in the cavity and injection pressure is larger than a clamp pressure and a mold open (a) is generated, the engagement part of the molds A, B forms a mold open (b) and relation of b<a is formed. Therefore, the part of the mold open (b) is high in flow resistance to allow an almost unnoticeable penetration and, when the resin is soldified, a longitudinal almost unnoticeable, burr is formed, so it is unnecessary to remove it.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a tape cassette for a video tape recorder, a floppy disk, a magneto-optical disk, a compact disk, a rad disk, an optical disk, a record, a video discs, digital audio discs, and fluorescent screens for X-ray imaging.

Maging Plate This invention relates to a method of manufacturing a thermoplastic resin container for accommodating disc-shaped or sheet-shaped products such as IC printed boards.

[Traditional Hisao]

Thermoplastic resin containers with small volumes such as those mentioned above can be three-dimensionally molded by direct injection molding, but cases that store items larger than a certain volume, such as tape cassettes for video tape recorders, can be molded using direct injection molding. in case of,
Since it is impossible to perform three-dimensional molding by direct injection molding, a method is used in which boxes are manufactured from expandable plates.

Conventionally, the development plate of such a thermoplastic resin container is a flat thermoplastic resin plate of a constant thickness that is extruded from a T-die into a long length.
If necessary, after printing, etc., cut the board to a certain size, and then cut the parts corresponding to the folds (hereinafter referred to as ``key line parts'')
It is called. ) was produced by compressed shading or cutting, punching out the notches, and in some cases foil-stamping or embossing the surface.

However, this conventional manufacturing method requires a large number of man-hours and is inefficient, lacks uniformity in the strength of the silicon wire, surface shape, thickness of the developed plate, etc., and has a high incidence of defective products in terms of quality. In addition, because the wires, grain shapes, and cutting are done with excessive force, wire cracks may occur, the surface of the wire grooves may become rough, and debris may adhere to the cut surface, resulting in poor appearance. Since the cutting allowance and cutting allowance are discarded, there are disadvantages in terms of cost and industrial waste generation. Furthermore, in terms of quality, notches and other punched edges are crushed, resulting in cutting debris that can fall off during use, and in the case of containers containing bidet centrifuges, etc. This caused dropouts (distortion of sound and images).
Furthermore, it was impossible to partially change the thickness for differentiation, or to mold special shapes or fine letters.

In order to eliminate the drawbacks of the prior art as described above, the present inventor first developed a development plate for such a thermoplastic resin container by using a resin with good fluidity and having a wire portion and a cutout portion. It was proposed to be made by injection molding in the form of thin sheets. (Refer to Japanese Patent Application Laid-open No. 15283/1983).

That is, it is a developing plate made mainly of thermoplastic resin and having a diagonal line part and a notch part, and the average thickness of the developing plate is 0.3 to 3 tons.
m, the average thickness of the diagonal line part is 5% or more thinner than the average thickness of the development plate, and the average thickness of the diagonal line part is 0.15 to 1.5
This is a method for manufacturing a thermoplastic resin container, which comprises producing a developing plate (n) by an injection molding method and forming the same into a box.

To explain with a diagram, as shown in Fig. 3, a fourth
The expansion plate 1 shown in Figure (b) is manufactured by making a box.

In Fig. 4(b), the front part 4 degrees and the rear part 5 degrees are on the development plate.
．． Left side part 6. Right side part 7. Bottom part 8° Left side overlapping part 9. Right side overlapping part 10° flap part 11.
By forming these into a box, a thermoplastic resin container top as shown in FIG. 3 is formed.

According to this manufacturing method, the developing plate 1 as shown in FIG. many with
.

Close-up and Kei line portion 12. Further, depending on the case, a container 1 made of thermoplastic resin is formed by injection molding so as to have unevenness on the front surface, etc., and after printing or the like is applied to this if necessary, the container is manufactured into a box as shown in FIG. 3. You can.

Note that (1) the shape of the expansion plate l is not symmetrical; for example, the shape of the front part 4 and the shape of the back part 5 may be different.

(2) Side parts 6, 7. Even if the thickness is the same as the remaining thickness of the silicon wire portion 12, the strength can be maintained by overlapping and joining.

(3) Notches 13.14, 15.16. The shape can be a rectangle, a square trapezoid, a semicircle, a semiellipse, an equilateral triangle, an isosceles triangle, an arrow shape, etc.

(4) The residual thickness of the wire portion 12 may be partially increased to improve the flow of resin during injection molding.

(5) In addition, the surface of the mold may be processed to provide a transparent window in one or more places on the development plate, or the product name, company name, picture, etc. may be printed on the inside and outside surfaces of the case, or the surface may have a silky, sandy, or rope pattern. .

It can also have shapes (texturing) such as vertical stripes, horizontal stripes, lattice patterns, fine-grain surface textures, etc.

(6) As disclosed in Japanese Patent Application Laid-Open No. 61-78617, etc.
It is also possible to create delivery expansion plates using an injection molding delivery system.

In this manufacturing method, various thermoplastic resins can be used as the thermoplastic resin used in injection molding, but polyolefin thermoplastic resins (including copolymers with other thermoplastic resins) or polystyrene thermoplastic resins are particularly suitable. Plastic resin or ABS thermoplastic resin A mixed resin of two or more of these thermoplastic resins is used, and various polypropylene resins, especially various nucleating agents, are mixed with 0. A propylene/ethylene random copolymer resin containing 1 to 2 O by weight is superior in terms of cost, printability, manufacturing accuracy, dimensional stability, wire strength, surface strength, rigidity, injection moldability, etc.

Furthermore, one or more colored pigments or dyes can be added to these thermoplastic resins.

In addition, after the development plate is injection molded, printing and labeling processes can be selectively added before and after the box manufacturing process, making it possible to add marks and letters.This is an excellent manufacturing method for thermoplastic resin containers. be. An embodiment of the injection molding apparatus used in this manufacturing method is shown in FIG.

[Problem that the invention seeks to solve]

However, in this manufacturing method, as shown in FIG. 2, when a highly fluid resin is used to injection mold a thin sheet-like expansion plate with a large projected area, and the thickness is further thinned in the diagonal line part 12. , especially the flap part 11 which is subjected to high injection pressures. There is a problem in that the resin gets around the gap between the parting lines of the lla, causing so-called "paris 17".

This Paris 17 has a thickness of 5/100 tm or less, and in large parts, it occurs in the width of 3 dragons, which makes automatic box making not easy and the appearance is not good, so it is necessary to remove the Paris. However, this requires a large number of processing steps, and the excellent effects of the process are diminished.

The present invention has been made to eliminate the above-mentioned drawbacks and to bring out the effects of this manufacturing method.
-The average plate thickness is 0.3 to 2. On.

The average thickness of the silicon wire is 0.15 to 1. A developing plate with a notch and a melt index of 16 to 60 g/
When manufacturing by injection molding method (including whole-mold vacuum injection molding method) using high-flow thermoplastic resin for 10 minutes, it is important to avoid the occurrence of paris at the parting line, which is particularly susceptible to high injection pressure. It is an object of the present invention to provide a method for stably producing a developing plate having a cutout portion and a cutout portion at low cost, and manufacturing a thermoplastic resin container with good quality.

[Means and effects for solving the problems] The present invention provides a plate having an area of 100 cIa or more and an average thickness of 0.3 to 2.0 m.
, the average thickness of the line part is 0.15 to 1.0 mm, and the melt index is 16 to 6.
In a method for manufacturing a thermoplastic resin container, which involves making a thermoplastic resin container by injection molding using a thermoplastic resin of 0 g/10 min, and forming the container into a box, at least the cavity portion of the mold that is susceptible to particularly high injection pressure. This is a method for manufacturing a thermoplastic resin container, characterized in that the parting line has a cylindrical alloy type structure.

The injection molding method of the present invention includes an in-mold vacuum injection molding method and a stack molding method.

As the thermoplastic resin of the present invention, various known thermoplastic resins can be used, but one of various polyolefin resins can be used.
A species or a mixture of two or more kinds of resins, particularly preferably a random copolymer resin of propylene and α-olefin, or a blend resin of various polypropylene resins and linear low density polyethylene resins are used.

In the present invention, the parting line in the cavity part of the mold that is susceptible to particularly high injection pressure is the parting line in the notch 15, which is related to the thin wire part that is difficult for resin to pass through.
．． There are 16 related parting lines.

In the present invention, the parting line of the cavity part is made into a cylindrical alloy type structure, which means that the thickness and depth of the conventional cavity are completely dependent on one mold, and the other mold is made of a flat surface. Unlike this method, one mold is a concave mold with a wall surface deeper than the target thickness (depth) of the cavity, and a convex mating mold with side walls that follow the wall surface is inserted to form a predetermined cavity. This means creating a mold structure that forms the target thickness.

The present invention will be explained based on the drawings. Figure 1 shows injection molding magnet 1 "mold opening J-Na2r mold clamping" - patient 3 "injection process J-
It is a figure explaining the relationship between the shape and structure of the mold which forms a cavity by process, and the injection molding situation in the order of ``Na4r holding pressure process J-11h5r cooling process''. The injection molding situation of the present invention is shown in the left column (a), and the injection molding situation of the conventional method is shown in the right column (b) for comparison. .

In the "mold opening" of the Nll process, in the mold of the present invention, mold A is concave and mold B is convex, whereas in conventional molds, mold A is concave and mold B is flat.

In the "mold clamping" stage 2 process, the present invention creates a cavity with a thickness t by making molds A and B into a mating structure, but the conventional mold has a concave surface of mold A. The depth becomes the cavity thickness t. In the case of the present invention, the appropriate angle between the fitting portion and the vertical line is α=40” to L15°, preferably α=j3° to L18°.

In the third step, the "injection step," thermoplastic resin is injected into the cavity.

In the "pressure holding process" of the 4th process, when the injection pressure becomes greater than the mold clamping pressure, a slight mold opening a occurs between mold A and mold B. In the case of the present invention, mold opening a occurs. When a occurs, b opens at the fitting portion of molds A and B, resulting in a baa relationship. Therefore, when the thermoplastic resin intrudes into the mold opening b of the present invention, the flow resistance is greater than in the conventional mold opening a, and the infiltration is almost invisible. In the conventional method, an infiltration with a thickness of a is performed.

In the "cooling process" of 11h5, the mold opening contracts slightly and becomes a-mu a and b-Δb. The thermoplastic resin solidifies, but in the case of the present invention, the vertical burrs are almost invisible and do not need to be removed, but in the conventional case, as mentioned above, the horizontal burrs are as thick as 5/100. This occurs over a width of 3 m, which poses a practical problem and requires many man-hours to remove the burrs.

〔Example〕

Next, in order to further clarify the effects of the present invention, examples are listed below.

+11 A two-stage, four-cavity mold for injection molding of a developing plate as shown in FIG. 5 was used. FIG. 5 is a schematic diagram showing the mold in an open state, and four development plates can be molded at the same time. The mold consists of a fixed mold 41 and a movable mold including an intermediate plate 42 and a movable core 43.

The fixed mold 41 has a sprue bush insertion opening 44 for the intermediate plate, and two cavities 45a and 4 for molding the expansion plate.
5b, a gas vent hole 46 and a gas vent slit 47 for vacuum and air blow are provided. These are connected to external vacuum equipment or pressurized gas supply surfaces by gas vent outlets.

The intermediate plate 42 is provided with a spool bush 49 provided with a spool for molten resin, a manifold 50 for molten resin, and a gate 51.

The movable core 43 is provided with a development plate molding cavity 45, a gas vent hole 46, and a gas vent slit 47 similar to those of the fixed mold 41, and act in the same manner (simultaneously) as the fixed mold 41.

When in use, the fixed mold and the movable mold are closed, the injection tube 52 is set, and four sheets are produced by the injection control pattern of vacuum operation, injection, molding, opening, gas blow (molded product eject), cotton opening, and vacuum operation. The development plate is molded at the same time.

In addition, in this apparatus, after the first injection molding is completed, molten resin exists in the manifold 50 and is maintained in a molten state, and the next vacuum operation causes the resin to pass through the gate 51 and enter the cavity 45. .45a.

45b, and new molten resin is supplied to the injection tube 5.
Supplied from 2. In this case, the diameter of the gate 51 is very small, and the molten resin can pass through when an exhaust force is applied from the outside, but when there is no exhaust force, there is almost no leakage of the molten resin. The gap in the gas vent slit 47 is extremely small, allowing air to pass through, but not allowing the molten resin supplied to the cavity 45 by vacuum operation to pass through.

Also in this case, when the mold is opened, the gas vent and the cavity 45 are connected to the vacuum system, and the back side of the molded product is held under negative pressure to be held on the fixed mold 41 and movable core 43 side. There is.

In this case, the mold was designed so that the dimensions of the expansion plate were as follows. The thermoplastic resin injection port (gate) is shown in Figure 4 (b).
) inside the development plate (inner bottom surface in contact with the product) Y, Y
There were two locations.

Vertical and horizontal dimensions of the expansion plate: The longest part is 2471 mm x 237 mm Thickness of the expansion plate: 20.9 mm Dimensions of the cross section: Medium 1.5 mm, depth 0.25 m Cross-sectional shape of the cross section: No. 4 Notch 1 shown in Figure (a)
Dimensions of 3.14: Length approx. 70mm, medium 20m Dimensions of notch 15.16: Polygon whose longest part is 37n+x28n+ Note that the parting line of the cavity corresponding to the periphery of notch 15.16 is It has a koi alloy type structure.

(2) Using this mold, a molten thermoplastic resin having the following composition was injection molded: Mitsui Petrochemical (Polypropylene) H resin, (M!-4)
0g/10min)...97.8% by weight Shin-Etsu silicone side type dimethylpolysiloxane, KF-96 (product name)
...0.1% by weight titanium oxide ...
・ 2.0% by weight Electroslipper, an antistatic agent made of Hanatamaishi M■...0.1% by weight (3) Assemble the injection molded development plates and weld the overlapping parts using an ultrasonic welding machine. Approximate dimensions are 192ws
A case for a video tape cassette measuring 105 III x 28 m was manufactured.

With the present invention, the generation of flakes during injection molding is almost eliminated, resulting in a significant reduction in the occurrence of defective products, lowering manufacturing costs, and stabilizing the process, as well as improving appearance and accuracy.

We were able to obtain significant effects such as improving the quality of finished surfaces, automating tasks, and reducing industrial waste.

〔Effect of the invention〕

According to the present invention, the parting line of the cavity part of the mold, which is particularly susceptible to high injection pressure, has a cylindrical alloy type structure, thereby creating a thin-walled developing plate with a large projected area and a diagonal line part and a notch part. Even when injection molded using thermoplastic resin with a high melt index, no flaking occurs and warpage does not occur.

It is now possible to produce high-quality developing plates without twisting or short shots with high efficiency, and by taking advantage of the excellent effects of producing developing plates using the injection molding method, it is possible to reduce the cost and improve the quality of thermoplastic resin containers. contributed greatly.

[Brief explanation of drawings]

Figure 1 is Arashi 1 "Mold Opening" for detailed explanation of the present invention.
Block 2 "Mold clamping" - Box 3 "Injection process" - Box 4 "Pressure holding process J-
The relationship between the mold shape and structure and the resin molding situation in each injection molding process in the order of "11kL5r cooling process" are described in the present invention (a
) column is a comparative explanatory diagram for the conventional method (b) column, FIG. 2 is a plan view of the occurrence of paris in the conventional manufacturing method, and FIG.
The figure is a perspective view of an example of a thermoplastic resin container manufactured according to the present invention, and FIG. FIG. 5 is a schematic sectional view of an embodiment of an injection molding apparatus used in an embodiment of the present invention. Top...Thermoplastic resin container 1...Development plate 11, lla...Flap portion 12...K line portions 13.14, 15.16...Notch portion 17...Paris 41...・Fixed mold 42...Intermediate plate 43...Movable core 45...
・Cavity 46... Gas vent hole 47... Gas vent slit 501... Manifold 51... Gate Figure 1 Figure 2 Figure 4 (b)

Claims (1)

[Claims] Area is 100cm^2 or more, average plate thickness is 0.3 to 2.0
mm, the average thickness of the wire part is 0.15 to 1.0 mm, and the melt index is 16.
In a method for manufacturing a thermoplastic resin container, which involves making a thermoplastic resin container by injection molding using a thermoplastic resin of ~60 g/10 min, and forming the container into a box, the cavity portion of the mold is susceptible to at least particularly high injection pressure. A method for manufacturing a thermoplastic resin container, characterized in that the parting line of the container has a cylindrical alloy type structure.