JPS60154024A - Manufacture of thermoplastic resin container - Google Patents

Abstract

PURPOSE:To concurrently form plural developing plates with good efficiency by an injection molding method using a multi-staged mold. CONSTITUTION:A developing plate of an average thickness of 0.3-3mm. is formed of a thermoplastic resin mainly by injection molding using multi-stage molds. The developing plate is printed by hot stamping, etc., as needed and made into a box. The plate is molded through a fixed mold 21 and movable molds 22 and 23 having two cavities 25 and 26. A molten thermoplastic resin is sent under pressures through a gate 27 formed inside of the fixed mold 21 from an injection cylinder 24 into the cavities 25 and 26 for molding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a unit of a certain volume such as a tape cassette for a video tape recorder, a floppy disk, a video disk, a digital audio disk, and a sheet of photosensitive material. The present invention relates to a method of manufacturing a thermoplastic resin container suitable for accommodating products such as film, photographic paper, I(3 printed boards, etc.).

[Prior art]

Thermoplastic resin containers with small volumes such as those mentioned above can be made by direct injection molding or three-dimensional molding, but for cases that store items over a certain volume, such as tape cassettes for video tape recorders. In some cases, it is impossible to perform three-dimensional construction by direct injection molding, so a method of manufacturing a box from a spread plate is used.

Conventionally, the development plate for such synthetic resin containers is made by extruding a long synthetic resin plate from a T-die, printing it if necessary, and then cutting it into a plate of a certain size. , the area corresponding to the fold (hereinafter referred to as the ``key line area'') was compressed or cut, the notch was punched out, and in some cases, the surface was stamped with foil or embossed. .

However, such conventional manufacturing methods require a large number of man-hours and are inefficient, lack uniformity in the strength of the silicon wire, surface shape, thickness of the developed plate, etc., and in terms of quality, the incidence of defective products is low. The height is high, and the wires, shaping, and cutting are done by force, which may result in cracks in the wire, the surface of the wire grooves may become rough, and the appearance is poor due to debris adhering to the cutting surface. Since the cutout and notch allowance are discarded, there are inconveniences in terms of cost and generation of industrial waste. Furthermore, in terms of quality, notches and other punched edges are crushed and cut scraps are generated, which fall off during use, and when storing video cassettes, for example, these adhere to the tape and drop. It was also impossible to change the thickness of parts for differentiation (disturbing the sound and image), or to process special shapes or fine letters or shapes.

In order to eliminate the above-mentioned drawbacks of the prior art, the inventor of the present invention previously proposed that a developing plate of such a synthetic resin container be manufactured by injection force (Japanese Patent Application No. 58-2, 13
No. 007). In other words, it has traditionally been difficult to injection mold a developing plate with a wide area beyond a certain level using resin.
Although it has never been attempted, it is possible to make a developing plate with a cross section or a notch by injection molding, and by doing so, the drawbacks of the prior art as described above can be completely eliminated. I found out that it is possible.

[Purpose of the invention]

As a result of further studies aimed at improving the above method, the inventors of the present invention have found that it is possible to efficiently produce a plurality of expansion plates at the same time by injection molding the expansion plates using a multistage mold.
Furthermore, the present invention was achieved by discovering that developing plates of different colors can be simultaneously produced as required.

Therefore, an object of the present invention is to eliminate the drawbacks of the prior art as described above and to provide a method for efficiently performing the method of manufacturing a thermoplastic container by injection molding previously proposed by the present inventor. be.

[Structure of the invention]

The above-mentioned object of the present invention is to produce a developing plate made mainly of thermoplastic resin and having an average thickness of 0.3 to 3 groups by injection molding using a multi-stage mold, and if necessary, printing, hot stamping, etc. This is achieved by a method for producing a thermoplastic resin container, which is characterized in that the thermoplastic resin container is formed into a box after being applied.

Hereinafter, the present invention will be explained in more detail with reference to the accompanying drawings.

In the present invention, a thermoplastic resin container 1 in the shape of a rectangular parallelepiped with an open opening on the negative side as shown in FIG. 1 is manufactured by box-forming the expandable plate 2 shown in FIG.

In FIG. 2, the development plate 2 includes a front part 4, a back part 5, a left side part 6, a right side part 7, a bottom part 8, and a left side overlapping part 9.
, the right side overlapping part 10, the flap 11.11α, and the key line part 12, and by making these into a box, the first
A thermoplastic resin container 1 as shown in the figure is formed. 1st
In the figure, the correspondence of each part of the expansion plate in FIG.

Conventionally, a thermoplastic resin container 1 as shown in FIG. 1 has a T.
A synthetic resin flat plate of a constant thickness extruded into a long length from a die is printed in multiple layers, dried, and then cut. After punching with lines or making a rectangular plate with no cutout, the cutout part 12 is formed by compression shading or cutting, and then the cutout part 13° 14 with diagonal lines is formed. ．．
15.16 is punched and in some cases, the front part 4
etc., to create a development plate, which was then manufactured into a box.

According to the present invention, the developing plate 2 as shown in FIG. 2 is formed by injection molding into a polygonal shape having a cutout portion, a diagonal line portion 12, and, depending on the case, an uneven front portion. After the container is prepared and subjected to printing or the like if necessary, it is made into a box to create a thermoplastic resin container 1 as shown in FIG.

In the method of the present invention, various thermoplastic resins can be used as the thermoplastic resin used in injection molding, and in particular, polyion fin thermoplastic resins (including copolymers with other thermoplastic resins), or polystyrene thermoplastic resins can be used. A resin, an ABS thermoplastic resin, or a mixed resin of two or more of these thermoplastic resins are used, and various polypropylene resins, especially propylene/ethylene random copolymer resins containing 0.01 to 2 parts by weight of various nucleating agents, are used. It is suitable in terms of cost, printability, manufacturing accuracy, dimensional fixability, wire strength, surface strength, rigidity, suitability for injection molding, etc. These thermoplastic resins contain various blowing agents, white pigments (titanium oxide, talc, mica, calcium carbonate, clay, etc.), various carbon blacks, various coloring pigments, and various metal powders (
aluminum powder, tin powder, aluminum paste, etc.)
, various organic or inorganic fiber substances such as various metal fibers, glass fibers, and carbon fibers, various other coloring dyes, various antistatic agents, various silicones, surfactants, stearic acid, etc. Various additives such as lubricants and antioxidants can be added.

Furthermore, when injection molding is performed in the method of the present invention, the injection port (gate) for the molten thermoplastic resin is not limited to one location, but can be provided at a plurality of locations. By doing so, the flow of the thermoplastic resin improves during injection molding, and it is possible to prevent the occurrence of a weld line where the flow of the thermoplastic resin merges. These injection ports (gates) are shown in Fig. 2 on the inside of the container to improve the fluidity of the thermoplastic resin in terms of the appearance of the container and in the structure where the diagonal line is provided only on the surface of the container as shown in Fig. 3. Ta Xl.

x2gX3IYIIY3 It is desirable to form the thermoplastic resin at one or more locations, preferably in the vicinity of horizontally or vertically symmetrical positions, where the thermoplastic resin can flow in a square shape in approximately the same amount of time. It is particularly desirable to provide the injection port (gate) for the thermoplastic resin at only one location, x2Y2 in FIG. Moreover, if it is provided in two places, it is provided at the positions Yl and Y3 in FIG.

As another example of providing two locations, it is also desirable to provide locations X1 and X3 in FIG. Although there are various known shapes of the resin injection port (gate), which will be described later, a pin gate is preferred from the viewpoint of leaving no marks on the appearance. Another desirable position for the resin injection port (gate) is the notch 13° 1-4-. 15, 16 product ends are desirable;
Other desirable locations for using pin gates or other gates are locations where the resin injection port does not appear on the surface after forming the box, such as the overlapping portions 9 and 10 of the left and right sides of the expansion plate shown in FIG. 2 or the flaps. 11.11 (It is desirable to provide it at one or more locations on the front, back, or end of the Z, preferably near the horizontally or vertically symmetrical positions as described above.

Although FIG. 3 shows the case where the key line portion is provided only on one side of the expansion plate, it is of course possible to provide it on both sides.

In any case, in the present invention, the number and position of resin injection ports (gates) are determined depending on the shape of the developing plate, the fluidity (melt index) of the thermoplastic resin, the ease of generating gate marks, the ease of generating weld lines, etc. The present invention is not limited to the above description because the resin injection ports (gates) can be placed in any position on the expansion plate in any number and shape, and the resin injection ports (gates) can be used in any number and shape of the container during injection molding and box manufacturing. It is desirable to prevent it from appearing on the surface (visible surface), both from the viewpoint of appearance and the fluidity of the resin.

A feature of the present invention is that a developing plate made mainly of thermoplastic resin and having an average thickness of 0.3 to 3111 mm is manufactured by injection molding using a multi-stage mold as shown in FIGS. 5 to 7. As a result, the molding capacity in a -cycle can be increased by at least 2 to 10 times the conventional single stack mold (compared to the conventional single stack mold).

In addition, in the present invention, if the so-called in-mold vacuum injection molding method is adopted in which the inside of the mold is evacuated in advance and then filled with thermoplastic resin in a predetermined injection control (ξ turn) and then molded at low pressure, the The molding capacity of the conventional machine is much improved compared to the conventional single stack mold, making it possible to improve productivity and reduce costs.

FIG. 4 is a schematic cross-section showing an example of a double stacked mold used in the present invention, and is a type of mold in which an injection tube is provided at the upper part of the mold.

The mold shown in the figure includes a fixed mold 21, two movable molds 22 and 23 located on both sides thereof, and one injection cylinder 24 provided in the center.
It's getting better. The fixed mold 21 and the movable mold 2'2, 23 form two cavities 25, 26 for forming the expansion plate. A runner (runner) 27 inside the fixed mold 21
is formed, and the molten thermoplastic resin from the injection cylinder 24 is pumped into the respective cavities 25 and 261C to be molded. In addition, micro holes for air venting are formed in the matching parts of the molds of each cavity 25 and 26, and the fixed mold 21 p+''.

In this case, heat-retaining medium passages and cooling water passages are appropriately provided, and hot water at, for example, about 80° C. can be flowed during pouring, and cold water can be flowed during molding.

In the illustrated example, each molded product has one gate, but an appropriate number of gates can be provided by increasing the number of runners.

FIG. 5 is a schematic diagram showing an example of a quadruple stacked mold, in which movable molds 32, 33, and 34 are provided on both sides of a fixed mold 31, respectively. The size of the movable mold 33 and the central mold 34 is large, with one molding cavity 35.36 (37.38 in the other).
) is formed.

A double-headed nozzle injection tube 39 is installed above the center, and 4
Molten resin is pumped into two cavities to form a development plate.

FIG. 6 is a schematic diagram showing an example of a four-chamfer mold in which double-stacked molds are provided on the upper and lower sides, and movable molds 43 are provided on both sides of a fixed mold 41 and 42, and the fixed mold and the movable mold A total of four developing plate molding cavities 45 are formed between the two. Injection cylinders 46 and 47 are provided on the upper and lower sides of the mold, and the molten resin is sent from the runners provided in the fixed molds 41 and 42, respectively, to the upper and lower parts.
Pressure-feed into two cavities and mold.

In this example, if the upper and lower materials are made of different colors, it is possible to make two development plates with different colors.

The above is just a few examples of the multi-tiered molds used in the present invention, and the present invention is not limited to these types.
Various variants are possible. For example, by increasing the number of movable molds of the type shown in FIG. 6, it is also possible to produce a larger number of developing plates.

In the present invention, it is also possible to mold a developing plate without wires or notches and then provide the wires or notches after molding, but it is not possible to mold a developing plate with wires or notches. preferable.

In addition, it is possible to change the plate thickness of the developing plate, the shape of the shading, the shape of the developing plate, the flap shape, the notch shape, etc. for each cavity by considering the injection molding control pattern, gate diameter, etc. .

Historically, lubricants such as silicon compounds such as polydimethylsiloxane, surfactants such as saponin, or higher fatty acid metal salts such as sodium stearate are added to thermoplastic resins at 0.1%.
By adding up to 5% by weight, fluidity, moldability, and mold releasability during molding, as well as slipperiness after molding, can be improved. Additionally, by adding an antistatic agent to the thermoplastic resin, it is possible to make it difficult for dirt and dust to adhere to the container, or by adding a foaming agent to the thermoplastic resin, the appearance of the container can be changed to improve its feel and make it lighter. It may also be optionally possible to do so. Further, if necessary, a transparent window may be attached to the developing plate, or printing, hot stamping, surface shading, etc. may be applied to the front and back of the developing plate.

When manufacturing a thermoplastic resin container 1 as shown in FIG. 1 by the method of the present invention, the developing plate 2 as shown in FIG. 2 has a cross-sectional shape as shown in FIG. 3 or 4. is preferred. The plate thickness t is generally from about 0.3 mm to about 3IIIK, and the wire section is 5% of the average plate thickness t of the developed plate.
By making the thickness preferably 15% or more, most preferably 30% or more, the printing ink can be rapidly fixed to the development plate having the notch and the diagonal line by drying or chemical reaction after printing. The occurrence of warping and twisting is small, making it easier to form boxes. In the present invention, the thickness of the developing plate 2, which is an injection molded product, is limited to 0.3 to 3 mm to ensure cooling efficiency, prevention of warping, sink marks, and twisting, and ensuring strength. In order to prevent sink marks, ensure the fluidity of the thermoplastic resin, and at the same time facilitate box manufacturing, it is necessary to reduce the thickness of the plate by at least 5%, preferably at least 15%, most preferably at least 30%, and reduce the strength. at least 0.1 from the point
It is necessary to ensure a thickness of 6 or more.

Before manufacturing the box, embossing, grooving, and unevenness are applied to the front and back surfaces or the outer or inner surfaces of the front section 4, back section 5, left side section 6, right side section 7, bottom section 8, etc. It is also selectively applied to improve the appearance and ease of handling. In conventional manufacturing methods, these were performed by embossing, but in the method of the present invention, these surface treatments can also be performed during injection molding.

〔Example〕

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

(1) The developing plate injection mold shown in Fig. 2 was made into a two-cavity mold using the stack mold shown in Fig. 4.The dimensions of each developing plate were as follows. (The mold was designed so that the thermoplastic resin injection ports (gates) were placed at two locations at "1.Y3" on the inside of the expansion plate (inner bottom surface in contact with the product).

Vertical and horizontal dimensions of the expansion plate: The longest part is 247 Satoshi x 237 heads The thickness of the expansion plate is 20. Dimensions of the 8-double line part: rjl 1.51nn, depth 0.25 mm Cross-sectional shape of the line part: Dimensions of the notches 13 and 14 shown in Fig. 3: Length approximately 70 m, width 20 m Dimensions of the notches 15 and 16: Polygonal with the longest part measuring 37 mm x 28 mm (2) This mold is A molten thermoplastic resin having the following composition was injection molded using: Holipropylene resin manufactured by Mikata Petrochemical Co., Ltd., Great!
No-J-950D (MI-40&/10 minutes)...
・・・・・・・・・・・・・・・・・・・・・・・・
96.8% by weight Shin-Etsu silicone (lead dimethylpolysiloxane, KF-96 (trade name))...
・・・・・・0.1% by weight Titanium oxide・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
2% by weight Kao soap (lead antistatic agent, Electrosuritsu Mo (product name))
...0.1% by weight (3) Print characters in two colors, black and red, using a silk screen printing method on two injection-molded development plates, dry with hot air at 50°C, and apply the printing ink to the development plates. It stuck to. Next, after pressurizing with a hot plate at 80℃ and stamping the product name with aluminum foil, assemble it and weld the overlapping parts with an ultrasonic welder to create a product with approximate dimensions of 192m1X.
Two cases for videotape cassettes of 105 trays x 28 trays were manufactured.

By repeating these operations, the manufacturing cost was reduced to 40% compared to the conventional manufacturing method with cutting and punching processes when the number of boxes manufactured was 300,000 pieces, and the incidence of defective products was reduced. was 1% in the method of the present invention, compared to 11% in the conventional method.

According to the method of the present invention, not only the number of man-hours is reduced as described above, but also the warping and twisting of the printed development plate is greatly reduced, the flatness is improved, and the molding capacity in one cycle is greatly improved, so it can be manufactured. In addition to greatly reducing costs and stabilizing the process, there are no gate marks on the surface, which improves quality in terms of appearance, precision, and finished surface, automates work, and eliminates wire cracks and cut scraps. It is possible to obtain significant effects such as a drastic reduction in dropouts and a reduction in industrial waste.

The present invention is not limited to the embodiments, and can be widely applied, for example, as shown below.

(1) The shape of the expansion plate is not symmetrical; for example, the shape of the front part and the shape of the back part may be different.

(2) Even if the thickness of the side part is the same as the remaining thickness of the silicon wire part, the strength can be maintained by overlapping and joining.

(3) The shape of the notch is rectangular, square, trapezoidal, semicircular,
It can have various shapes such as semi-ellipse, equilateral triangle, isosceles triangle, and arrow shape.

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

(5) Processing the surface of the mold to create a transparent window in one or more places on the expansion plate, or marking the product name, company name, picture, etc. on the inner and outer surfaces of the case with grain, grain, rope, vertical, or horizontal stripes.・It can be made to have a pattern (texturing) such as a lattice pattern or fine-grain surface texture. More than 210 types of concrete textured samples include the ``6 Pairon Grain'' published by Tokyo Bearon (a).

(6) During injection molding, thermoplastic resins are copolymers, 2
It can be a mixed resin of more than one type of thermoplastic resin.

(7) One or more types of colored pigments or colored dyes can be added to the thermoplastic resin.

(8) Injection molding of the development plate (including vacuum injection molding in the entire mold)
After that, printing and labeling processes can be selectively added before and after the box manufacturing process to add marks and letters.

(9) As an injection molding method, in addition to the well-known general injection molding method widely used in the market, the inside of the mold is sealed from the outside air, the inside of the mold is evacuated in advance, and then the determined injection molding is performed. It is effective to use an all-in-mold vacuum injection molding method in which the thermoplastic resin is filled at high speed in a controlled pattern and pressed to form at low pressure.

[Brief explanation of the drawing]

Fig. 1 is an external view showing an example of a thermoplastic resin container manufactured according to the present invention, Fig. 2 is a plan view of a developing plate of the container shown in Fig. 1, and Fig. 3 is a plane A-B in Fig. 2. 4 to 6 are schematic sectional views showing several examples of the multilayer mold used in the present invention. 1... Thermoplastic resin container 2... Expansion plate 12...
・K line part 13, 14, 15, 16... Notch part X1
．． X2. X3. Yl, Y3...Gate 21.41...
・Fixed type 22.23, 32, 33, 34.43...Movable type 24
．． 39, 46.47... Injection tube 25. 26, 35, 36, 37, 38.45... Cavity 27 for molding the expansion plate... Runway Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) It is mainly made of thermoplastic resin and has an average thickness of 0.
Multi-tiered (double stacked) or more 3~3■ expansion plates (2-tiered)
1. A method for manufacturing a thermoplastic resin container, which comprises manufacturing the container by injection molding using a multi-layered mold, and forming the container into a box.