JP2000317993A - Molding die and holding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a resin in a sprue section at the mold melting point viscosity without being cured, use the resin in the following molding and carry out the continuous molding by providing a plurality of recesses and projections on the outer periphery of a sprue bush and a cylindrical heat insulation section on the outer periphery of a space, and making a flow path for a cooling medium small. SOLUTION: A plurality of recesses and projections 14 are formed on the outer periphery of a sprue bush 13, and a cylindrical heat insulation section 10 formed of a material of low thermal conductivity such as a ceramic, a gypsum, a laminate or a plastic is formed inside a cutting face of a mold 7. A cooling medium is brought into contact with the sprue bush 13 with good efficiency, and as a result cooling is carried out effectively to control the resin temperature rise and cool a sprue section 16 uniformly and with good efficiency and cool uniformly without curing the molten resin in the bush. The resin in the sprue bush 13 is kept at the moldable melting viscosity to use the resin in the following molding, carry out the continuous molding and improve the yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for injection molding of a thermosetting resin, in which a molten resin existing in an intermediate portion between an injection molding machine and a mold cavity is maintained at a moldable viscosity without curing. An object of the present invention is to improve the yield of the resin by using the resin in this portion for the next molding.

[0002]

2. Description of the Related Art In injection molding of a thermoplastic resin, the use of an extension nozzle and a hot runner has been studied to improve the yield of the resin (reduction of the amount of resin used). In injection molding, reaction hardening of the resin is a major obstacle, making continuous molding difficult, and is not widely used.

In order to solve these problems, the sprue portion is formed as a bush having a structure independent of the mold body, and the sprue bush is maintained at a constant temperature by using a heating medium such as hot water or hot oil, a heater, or a combination thereof. The method has been performed (for example, described in Japanese Patent Application Laid-Open No. 50-82166). By using such a sprue bush, the thermosetting resin in this portion has a melt viscosity capable of being molded, and the resin in this sprue portion is effectively used for the next molding. In this way, continuous molding of sprues can be performed. However, in order to adjust the heat medium such as hot water or hot oil to a constant temperature (hereinafter referred to as temperature control), a dedicated temperature controller is usually required,
Further, the sprue bush must have a structure in which the heat medium does not leak. Therefore, a dedicated sprue bush (temperature-controlling sprue bush) having a precise structure must be used, which is not preferable in terms of cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve these problems in the injection molding of a thermosetting resin, and has been made as a result of various studies. This is to maintain the melt viscosity at which molding can be performed without curing the resin, and to use this part of the resin for the next molding to commercialize the product. Structure, a plurality of irregularities are provided on the outer periphery of the bush structure, a gap is provided between the outside of the sprue bush and the mold, and
By providing a heat insulating portion in the uneven portion or the void portion on the material inflow side to reduce the flow path of the cooling medium, preferably by providing two or more partition plates in the void portion, the cooling medium can be supplied to the inlet of the void portion. From the rear to reach the gap outlet, is a molding die that allows a non-liquid cooling medium such as air to efficiently flow through this gap, and is a dedicated mold like a conventional temperature control type sprue bush. It enables good continuous molding without the need for a temperature controller and a dedicated sprue bush with a precise structure.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a molding die used for injection molding of a thermosetting resin, wherein a sprue portion has a bush structure and the thermosetting resin is maintained in a molten state. In a molding die having a sprue bushing structure in which a void portion for flowing a cooling medium that is not a liquid such as air is provided between the outside of the sprue bush and the mold, a plurality of irregularities are formed on the outer periphery of the sprue bush. A molding die, wherein a cylindrical heat insulating portion is provided on the outer periphery of the gap to reduce the flow path of the cooling medium, and further, the outer periphery of a sprue bush in the die. The present invention relates to a molding die provided with a plurality of concaves and convexes, and a heat insulating portion provided in a concave or convex portion or a void portion on a material inflow side to reduce a flow path of a cooling medium. Preferably, in the mold, a plurality of irregularities are provided on an outer periphery of the sprue bush, a cylindrical heat insulating portion is provided on an outer periphery of the gap portion, and a heat insulating portion is formed on the material inflow side uneven portion or the gap portion. Further, the molding die having a small flow path for the cooling medium is provided, and more preferably, the gap is formed by a sprue bush so that the cooling medium reaches the rear of the gap after reaching the rear of the gap from the entrance of the gap. The present invention relates to a molding die provided with two or more partition plates in a void portion for dividing in the same direction as a longitudinal direction (flow direction of resin), and a molding method using such a die. It is about.

A conventional temperature control type sprue bush and a molding die having the sprue bush structure of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a molding apparatus using a conventional temperature-controlled sprue bush (one example), and FIG. 2 is a schematic view of a molding apparatus using a molding die (one example) including a sprue bush structure of the present invention. It is an outline sectional view. The thermosetting resin charged into the hopper 1 of the injection molding machine is melted by the cylinder 2 and the screw 3. The molten resin 4 is injected from an injection molding machine, passes through a sprue bush 5 and is injected into a cavity 9 of a mold 8 to form a molded product. In the molds shown in FIGS. 1 and 2, the resin of the sprue portion 6 or 16 of the sprue bush 5 or 13 does not cure and stays in a molten state both during and after the molding.

FIG. 3 is an enlarged sectional view of a sprue bush portion of the molding apparatus of FIG. 1, and FIG. 4 is a front view of the sprue bush of FIG. FIG. 5 is an enlarged sectional view of an example of a sprue bush of the molding apparatus of FIG. 2, and FIG. 6 is a front view of the sprue bush of FIG. FIG. 7 is an enlarged cross-sectional view of another example of the sprue bush portion of the molding apparatus of FIG.
8 is a front view of the sprue bush of FIG. 7, FIG. 9 is a sectional view taken along line AA of FIG. 7, and FIG. 10 is a sectional side view of FIG. FIG.
12 is an enlarged sectional view of still another example of the sprue bush portion of the molding apparatus of FIG. 2, FIG. 12 is a front view of the sprue bush of FIG. 11, FIG. 13 is a sectional view taken along line AA of FIG.
FIG. 12 is a side sectional view of FIG. 11.

In the mold shown in FIG. 3, the outer periphery of the outer cylinder 22 of the sprue portion 6 of the sprue bush 5 is cut to form a spiral groove 23, and a sleeve-like part 24 is formed for sealing the groove. The structure is attached. At the time of molding, the resin in the sprue portion 6 is maintained at a constant temperature by flowing a liquid medium such as hot water or hot oil through the entrances 28 and 29 shown in FIG. In FIG. 4, 27
Is the sprue entrance. Thereby, the retained resin in the sprue portion is maintained at a melt viscosity capable of being molded without being cured, and is filled in the cavity 9 of the mold 8 and molded into a molded product at the next molding.

On the other hand, the dies shown in FIGS. 5 and 6 which are an example of the present invention have a structure in which the sprue bush 13 is inserted into the dies 7. The sprue bush 13 has a sprue 1 in the center.
6 and a plurality of irregularities 14 are formed on the outer periphery. The mold 7 is cut so that a gap is formed between the mold 7 and the outer surface of the sprue bush 13 when the sprue bush 13 is inserted. A cylindrical heat insulating portion 10 is provided on the outer periphery of this gap (inside the cutting surface of the mold 7) in order to prevent heat transfer to the mold. 7 to 10, which are other examples of the present invention, similarly to the mold of FIG. 5, the sprue bush 13 has a sprue portion 16 at the center, and a plurality of irregularities 14 are formed on the outer periphery. The mold 7 is cut so that a gap is formed between the mold 7 and the outer surface of the sprue bush 13. A heat insulating portion 20 is provided in the concave / convex portions or voids on the material inflow side while leaving the flow path of the cooling medium 21.

In the present invention, preferably, as shown in FIGS. 11 to 14, the mold 7 is cut so as to form a gap between the mold 7 and the outer surface of the sprue bush 13. In order to prevent heat transfer to the mold, a cylindrical heat insulating portion 10 is provided on the outer periphery of the mold, and the flow path of the cooling medium 21 ′ is left in the uneven portion or void on the material inflow side. A heat insulating part 20 'is provided. More preferably, in each of the above dies, this void portion is formed as shown in FIGS.
As shown in FIGS. 13 and 14, the gaps 11 and 12 are formed by being divided by the partition plate 15. The gaps 11 and 12 serve as flow paths for the medium. Although the outside of the partition plate 15 is in contact with the mold 7, it does not completely separate the gaps 11 and 12, but instead extends from the fluid inlet / outlet provided on the injection molding machine side of the sprue bush 13 to the deepest parting surface. The near portion is cut out of the partition plate so that the fluid passes between the gaps 11 and 12. The number of the partition plates may be usually two, but may be three or more as necessary in order to increase the cooling efficiency.

In an example of a molding die having a sprue bush structure according to the present invention, a plurality of irregularities 14 are provided on the outer periphery of a sprue bush 13, and ceramic, gypsum, laminated A cylindrical heat insulating portion 10 made of a material having low thermal conductivity, such as a material or plastic, is provided. More preferably, the gap is divided by the partition plate 15, thereby effectively preventing heat conduction from the mold as compared to a case where only a plurality of irregularities are provided on the outer periphery of the sprue bush, The unevenness on the outer periphery of the sprue bush effectively cools the resin with the cooling medium.
Furthermore, it is preferable to provide an air gap between the mold 7 and the heat insulating portion 10 in order to more effectively perform heat insulation. Further, by providing the partition plate, the surface area of the outer periphery of the bush is increased, and the cooling efficiency is further improved.

In another example of the molding die having the sprue bush structure of the present invention, the sprue bush 13
A plurality of irregularities 14 are provided on the outer periphery of the ceramic, gypsum, laminated material,
A heat insulating portion 20 made of a material having a low thermal conductivity such as plastic,
20 'is provided to reduce the size of the cooling medium flow paths 21, 21'. More preferably, the gap is divided by the partition plate 15, so that the cooling efficiency of the medium is not large in the portion near the inlet / outlet of the cooling medium (the portion near the injection cylinder), so that the sprue portion is too cold and the resin material is solidified. In other words, the resin temperature tends to increase in a portion far from the inlet / outlet of the cooling medium (a portion close to the parting surface) due to heat from the cavity mold 8, but the cooling medium is efficiently connected to the sprue bush 13. Since the contact and the cooling can be performed effectively, the rise in the resin temperature can be suppressed, and the resin temperature in the bush can be kept uniform. Therefore, the cooling of the sprue portion 16 is performed more uniformly and efficiently. In addition,
Irregularities may not necessarily be formed in the sprue bush portion provided with the heat insulating portion.

The entrances and exits 18 and 19 of the medium leading to the gaps 11 and 12 are usually provided as shown in FIGS. 6, 8 and 12.
The sprue bush 13 is provided on the injection molding machine side surface. This entrance may be provided in the mold 7 outside the sprue bush. In FIG. 6, reference numeral 17 denotes a sprue entrance. In this manner, the resin in the sprue portion 16 is maintained at a constant temperature by flowing a non-liquid cooling medium such as air through the gap between the sprue bush 13 and the mold 7. Thereby, the resin of the retained sprue portion is filled into the cavity 9 of the mold 8 at the next molding, and molded into a molded product.

The molding die of the present invention has the above-described structure, so that the cooling of the sprue portion 16 can be performed more uniformly.
Since it is performed efficiently, the molten resin in the bush is uniformly cooled without solidification. Therefore, good continuous molding is possible, and the resin in the sprue portion, which has conventionally been discarded for each molding, can be minimized or completely eliminated, and the amount of resin used per molding can be reduced.

Further, since the mold structure is simple and a non-liquid such as air is used as a cooling medium, a special sprue bush having a precise structure with no liquid leakage, such as a conventional temperature control type sprue bush, is used. There is no need for a dedicated temperature controller for liquids. Therefore, there is little occurrence of trouble during molding. Also, a trouble occurs during molding, and the resin in the sprue portion 16 of the sprue bush is hardened (or solidified).
Even in this case, the cured product (or solidified product) can be easily protruded from the parting surface side. Further, the sprue bushing of the present invention has a simple structure and is light in weight, so that it is easy to handle. After the molding is completed, the sprue bush is pulled out to easily remove the residue (hardened material or solidified material) in the sprue. can do.

[0016]

According to the molding die of the present invention, the sprue portion has a bush structure, a plurality of irregularities are provided on the outer periphery of the sprue bush, and a gap is provided between the outside of the sprue bush and the die. By providing a cylindrical heat insulating portion on the outer periphery of the void portion and / or by providing a heat insulating portion in the uneven portion or the void portion on the material inflow side, the flow path of the cooling medium is reduced, and preferably, the void portion is divided. Therefore, two or more partition plates are provided in the gap, and a cooling medium that is not a liquid such as air is circulated in the gap, so that the resin in the sprue bush can be molded. By using this resin as a molded product in the next molding while maintaining a high melt viscosity, the resin yield can be improved.

Further, since the cooling efficiency is improved and the uniformity of the cooling is improved, when a medium such as air is cooled and used, the degree of cooling is reduced and the medium can be circulated at a temperature close to room temperature. It becomes possible. Furthermore, unlike the conventional temperature control type sprue bush, there is no need for a special sprue bush having a precise structure, and no special temperature controller is required. Further, since a non-liquid cooling medium such as air is used, there is no risk of water leakage, oil leakage, rust, dirt, and the like, and it is suitably used in injection molding of a thermosetting resin.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a molding apparatus (one example) having a conventional temperature control type sprue bush structure.

FIG. 2 is a schematic cross-sectional view of a molding device (one example) having a sprue bush structure of the present invention.

FIG. 3 is an enlarged sectional view of a sprue bush portion of the molding apparatus of FIG.

FIG. 4 is a front view of the sprue bush of FIG. 3;

FIG. 5 is an enlarged sectional view of a sprue bush portion of the molding apparatus of FIG. 2;

FIG. 6 is a front view of the sprue bush of FIG. 5;

FIG. 7 is an enlarged cross-sectional view of a sprue bush portion of a molding device (other example) having a sprue bush structure of the present invention.

FIG. 8 is a front view of the sprue bush of FIG. 7;

FIG. 9 is a cross-sectional view of the sprue bush AA of FIG. 7;

FIG. 10 is a side sectional view of the sprue bush of FIG. 7;

FIG. 11 is an enlarged cross-sectional view of a sprue bush portion of a molding device (other example) having a sprue bush structure of the present invention.

FIG. 12 is a front view of the sprue bush of FIG. 11;

FIG. 13 is a sectional view of the sprue bush taken along the line AA in FIG. 11;

FIG. 14 is a side sectional view of the sprue bush of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hopper 2 Cylinder 3 Screw 4 Molten resin 5 Sprue bush 6 Sprue part 7,8 Die 9 Cavity 10 Heat insulation part 11,12 Void part (medium flow path) 13 Sprue bush 14 Irregularity 15 Partition plate 16 Sprue part 17 Sprue entrance 18, 19 Medium inlet / outlet 20, 20 'Insulating part 21, 21' Cooling medium flow path 22 Outer cylinder 23 Groove 24 Sleeve 27 Sprue inlet 28, 29 Medium inlet / outlet

Claims (5)

[Claims] 1. A molding die used for injection molding of a thermosetting resin, wherein a sprue portion has a bush structure, and an outer side of the sprue bush and a mold for maintaining the thermosetting resin in a molten state. In a molding die having a sprue bushing structure provided with a gap for flowing a cooling medium that is not a liquid such as air between the sprue bush, a plurality of irregularities are provided on the outer periphery of the sprue bush, A molding die characterized in that a cooling medium flow path is reduced by providing a cylindrical heat insulating portion on the outer periphery. 2. A molding die used for injection molding of a thermosetting resin, wherein a sprue portion has a bush structure, and an outer side of the sprue bush and a die for maintaining the thermosetting resin in a molten state. In a molding die having a sprue bushing structure provided with a gap for flowing a cooling medium that is not a liquid such as air between the sprue bush, a plurality of irregularities are provided on the outer periphery of the sprue bush, and a material inflow side A molding die characterized in that a heat insulating portion is provided in an uneven portion or a void portion to reduce a flow path of a cooling medium. 3. The molding die according to claim 1, wherein a heat-insulating portion is provided in the uneven portion or void on the material inflow side to reduce the flow path of the cooling medium. 4. A gap portion for dividing the gap portion in the same direction as the longitudinal direction of the sprue bush (flow direction of the resin) so that the cooling medium reaches the gap portion outlet from the gap portion inlet and then to the gap portion outlet. The molding die according to claim 1, 2 or 3, further comprising two or more partition plates. 5. Injection of a thermosetting resin, wherein the mold is formed using a mold according to claim 1, 2, 3, or 4 while flowing a cooling medium that is not a liquid such as air through the gap. Molding method.