JP2788066B2 - Mold for molding synthetic resin products with hinges - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a hollow molding of a synthetic resin product in which hollow main body parts are connected by an integrally molded hinge, such as a folding container for cooling and keeping heat. TECHNICAL FIELD The present invention relates to a hinged synthetic resin product molding die used when molding by a method.

[Conventional technology]

There are various types of synthetic resin products having a hinge, and a folding container used for distribution or the like will be described below as a representative example.

Containers used for logistics are required to be foldable in order to increase the transportation efficiency when no objects are placed.

Cardboard boxes are disposable and folded until used for packaging, so they are widely used for transportation and stock efficiency. However, due to poor water resistance, low strength, and hygiene problems, folding containers made of a synthetic resin that can be used repeatedly have been increasingly used.

The folding container is, as shown in FIG.
The injection molded thermoplastic resin plate 1 is used as a main body part.
These are connected using a metal hinge 2. When this is used, a box is formed by the plate 1 and a stop frame 3 is fitted to the upper end edge to be used as the box 4. However, there is a disadvantage in that the injection molded plate 1 is connected with the metal hinge 2 and the post-process requires manpower and the cost is increased. In particular, cold storage containers used for cold storage are made of a plate with an empty space inside and filled with foamed resin etc. to increase the heat insulation of the plate, but the parts connected by hinges In addition, there was a problem that a gap 5 was formed in the slab, and the cooling effect was reduced.

In order to solve the above problem, a hinge made of a thin synthetic resin integrally formed with a hollow plate 1 'as shown in FIGS. 3 (a) and 3 (b), instead of the metal hinge 2 connecting the respective plates. The hinged one having 6 is made by the hollow molding method and is partially commercialized. This eliminates the need for a post-processing step for attaching the hinge 2 and, in addition, FIG.
As shown in (b), if the hinge 6 is bent, the gap 5 is eliminated, so that the cooling and warming effect is improved.

In order to produce a synthetic resin product whose development is shown in FIG. 3 (a), as shown in FIGS. 5 (a) and 5 (b),
After the parison (not shown) is clamped by the left and right dies 9, 10 attached to the clamping plate 8 at the tip of the clamping cylinder 7, which moves forward and backward, and the hinge 6 is formed by the projecting portion 11. The parison is brought into close contact with the inner surfaces of the dies 9 and 10 by air blowing.

When the air blow is performed, the air blowing blow needle attached to the die for each plate 1 'is closed when the mold is clamped so that the air blow is performed for each plate 1' divided by the hinge. Air blow through parison.

[Problems to be solved by the invention]

However, the hinge 6
In the case of a hollow molded product with a large area, the mold clamping force of the hollow molding machine is small, so that it is not enough to press the parison with poor flow to crush the hinge 6 to the desired thickness. The flexibility and durability when flexing and extending the hinge
Did not reach satisfactory performance.

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the hinge 6 does not become thin because of the poor slip due to the rough surface of the mold and the cooling of the mold. If the protruding portion touches the resin, the temperature of this portion is lowered, and it is considered that the portion is hardly deformed.

The present invention has been made based on the above idea, and has as its object to provide a mold for forming a hinged synthetic resin product, which can form a thin hinge.

[Means for solving the problem]

In order to achieve the above object, the method of the present invention comprises connecting a thermoplastic resin molded body to be a main body part by hollow molding, and having a hinge made of a thin synthetic resin molded integrally with the main body part. In a synthetic resin molding die with a hinge used for molding a resin product, a protruding portion for molding a hinge of the die is coated with Teflon having a thickness of 2 mm or less.

[Action]

Since the method of the present invention has the above configuration, the parison has a good slip when pressed by the protruding portion, and the resin comes into contact with the protruding portion via the highly heat-insulating Teflon coating and instantly contacts the protruding portion. Due to the deformation, there is almost no drop in temperature during the deformation.

〔Example〕

FIG. 1 shows an embodiment of a synthetic resin product with a hinge according to the present invention, in which a protruding portion 11 of a mold has a diameter of 2 mm or less, generally 5 μm to 1.5 mm, preferably 10 μm to 1.5 m.
m, preferably 10 μm to 1.0 mm Teflon coating 12.

If the Teflon coating 12 exceeds 2 mm, the effect is not improved, and the coating requires human labor and is not economical.

When the above-mentioned coating is thin, the effect on slip does not change and the heat insulating effect is reduced, but the deformation is instantaneous, so that the parison is deformed more smoothly than when the parison directly contacts the mold.

In the conventional mold, even if the thickness of the hinge part is targeted at 0.3 mm, the thickness is about 0.6 mm, and a stable thickness cannot be obtained.However, when the mold of the present invention is used, the thickness is set to 0.3 mm. If it does, the thickness of 0.3mm can be obtained stably.

Therefore, the flexibility of the hinge 6 is improved, and the durability in the durability test of the hinge by the low-temperature hinge repeated bending tester is remarkably improved.

The same effect can be obtained by attaching a Teflon tape to the protruding portion of the mold instead of the Teflon coating.

In addition, it is easy to reduce the thickness of only an optional portion of the hinge.

Example 1 and Comparative Example 1 Using a mold having a 0.5 mm Teflon coating on the protruding portion of the present invention and a conventional mold having no Teflon coating, a third molding was performed by a hollow molding method under the same conditions. The folding container shown in FIG.

(1) The dimensions of the molded container are 300 x 450 x 300m
m, product weight is 2.5kg, (2) Material is 5/5 of polypropylene / polyethylene
(3) Molding conditions: mold clamping pressure: 30 ton, resin temperature: 210 ° C
And

Using the prepared container, a low-temperature hinge repeated bending test was performed under the conditions of a temperature of -40 ° C and a bending angle of 180 °. The results are shown in Table 1.

[Effects of the Invention] As described above, by using the hinged synthetic resin product molding die of the present invention, the thickness of the hinge can be set to a predetermined size without performing a complicated die structure or post-processing. Because it can be made thinner, the flexibility during bending and stretching is improved, and the durability is greatly improved. Therefore, when this mold is used, for example, for manufacturing folding containers and the like, which are required to maintain heat retention, sanitary, corrosion-resistant, and excellent durability can be obtained at a low price, and the economic effect is low. Extremely large.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a protruding portion, showing one embodiment of a hinged synthetic resin product molding die according to the present invention.
FIGS. 3A and 3B are perspective views showing an example of a conventional container, and FIGS. 3A and 3B are perspective views showing an example of a container having an integrally formed hinge. FIG. FIG. 3 (b) is a view showing an assembled state, FIG. 4 (a) is a sectional view taken along the line IV-IV of FIG. 3 (a), and FIG. 4 (b) is a view showing a bent state. 5 (a) and 5 (b) are longitudinal sectional views showing left and right molds, FIG. 5 (a) is a view showing a state where the mold is opened, and FIG. 5 (b) is a state where the mold is closed. FIG. 1 ... thermoplastic resin plate (plate), 1 '... hollow plate (plate), 2 ... hinge, 3 ... frame, 4,4' ... box, 5 ...
Gap, 6: Synthetic resin hinge (hinge), 7: Clamp cylinder, 8: Clamp plate, 9: Left mold, 10: Right mold, 11: Protruding part, 12 ... ... Teflon coating.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Hasegawa 3-2 Chidoricho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Electric Works Co., Ltd. Kawasaki Resin Laboratory (56) References JP-A-56-13140 (JP, A) JP-A-62-85924 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 49/48-49/60 B29C 33/38-33/42 B29C 53/06

Claims (1)

(57) [Claims] 1. A hinge used for forming a synthetic resin product having a hinge made of a thin synthetic resin integrally formed with the main body part by connecting a thermoplastic resin molded body serving as a main body part by hollow molding. In the synthetic resin molding die with a thickness of 2 m,
A mold for molding synthetic resin products with hinges, characterized by having a Teflon coating of m or less.