JPH01295816A - Injection molding apparatus - Google Patents

Abstract

PURPOSE:To well perform vulcanization by accurately monitoring the advance state of vulcanization, by providing at least one pressure sensor in a mold. CONSTITUTION:A mold 2 is equipped with a heater 7 and pressure sensors 8, 9 are embedded in the inner wall of the mold to make it possible to measure the pressure of the rubber in a mold cavity. The temp. of the rubber material received in the pot of an injection mechanism 1 is 50-100 deg.C while the mold 2 is heated to 160-200 deg.C. The rubber material injected in the mold 2 receives a temp. rise of about 100 deg.C by the heating due to the heat transfer from the mold 2 and frictional heating and the advance of the vulcanization and solidification thereof accompanied by heating is observed as an increase in pressure by the pressure sensors. By this method, since the state of the rubber material flowing within the mold can be directly measured, a curing time can be known corresponding to the kind and injection molding condition of unvulcanized rubber and molding operation is controlled to make it possible to perform a good injection molding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection molding device, and particularly to an injection molding device that can measure the progress of vulcanization of rubber and thereby perform appropriate vulcanization. Regarding molding equipment.

[Conventional technology]

Generally, rubber is produced by adding a cross-linking agent such as sulfur or peroxide to unvulcanized rubber using a roll or a Banbury mixer, and then applying pressure (50 to 100 kgf/cni) at high temperature (140°C to 200°C) to produce rubber. ) in a mold to form a molded product.

Molding methods include compression molding, transfer molding, injection molding, etc. In recent years, injection molding technology has developed rapidly due to its advantages such as shortening the molding cycle and being completely unmanned. .

Injection molding equipment generally includes an injection mechanism that extrudes unvulcanized rubber material into a mold cavity and a cough mold cavity, and the unvulcanized rubber material is injected into the mold cavity from a nozzle of the injection mechanism at high pressure. Sulfurized rubber is vulcanized under pressure within the mold cavity. After curing, the resulting molded product is removed from the mold by opening it.

By the way, if the rubber is insufficiently vulcanized, desired rubber physical properties cannot be obtained, so it is generally important to accurately monitor the progress of vulcanization of the rubber when molding the rubber. Therefore, devices such as a valkameter, a curometer, a rheometer, and a culastometer are known as devices for measuring the vulcanization state of rubber. All of these are devices that determine the vulcanization state of rubber by applying shear force to the rubber and measuring the stress generated in the rubber at that time.

[Problem that the invention seeks to solve]

However, although the above measurement device is effective in compression molding, it has the problem that the reliability of the judgment results obtained is low in injection molding, where rubber passes through the nozzle and mold at high speed. be. That is, when the rubber material passes through the gate from the nozzle of the injection mechanism to the mold at high speed, heat is generated due to friction, and this heat generation naturally affects vulcanization. Moreover, the temperature of the heat generated at this time is not uniform, as it varies considerably depending on not only the size and shape of the gate opening into the mold cavity of the equipment used, but also the type and composition of the rubber material used for vulcanization. . - For example, it is known that the exothermic temperature under certain conditions varies as shown in the table below (Quirk J, F, + RubberAge
, 99, [10], 84 (1967))
.

Rubber material Exothermic temperature ('C) IR10 Silicone rubber 18 CR23 SBR171225 JIR26 NR35 SBR150038 NBR60 As the vulcanization rate of rubber is affected by various factors, the progress of vulcanization can be accurately determined using the measuring device described above. However, it was not possible to properly control vulcanization.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an injection molding apparatus that can accurately monitor and judge the progress of vulcanization in an injection molding method, and thereby can perform vulcanization well. .

[Means for solving problems]

The present inventors have discovered that by disposing one or more pressure sensors in the mold, it is possible to accurately monitor and determine the progress of vulcanization in an injection molding process.

That is, the present invention provides an injection molding apparatus including an injection mechanism and a mold, characterized in that at least one pressure sensor is provided in the mold.

[For production]

The invention will be explained in detail below with reference to an embodiment shown conceptually in FIG.

The injection molding apparatus in FIG. 1 includes an injection mechanism 1 and a mold 2,
The side 1 of the injection machine consists of a generally cylindrical pot, and a plunger 4 for extruding unvulcanized rubber 3 is provided inside.

A nozzle 5 at the tip of the injection mechanism 1 is connected to a gate 6 of the mold 2. The mold 2 is equipped with a heating heater 7,
Further, pressure sensors 8 and 9 are embedded in the inner wall of the mold so that the pressure of the rubber inside the mold cavity can be measured. Pressure sensors 8 and 9 are connected to a recorder 11 via an amplifier 10, and the outputs of the pressure sensors are recorded.

This injection molding device operates as follows.

The unvulcanized rubber material 3 into which the vulcanizing agent has been kneaded is injected into the mold 2 from the nozzle 5 by the plunger 4, and flows inside the mold in the direction of arrow I2. Among the pressure sensors installed in the mold, the pressure sensor 8 near the gate 6
The initial pressure of the rubber material injected from the nozzle 5 is measured.

The rubber material 13 in the mold 2 gradually progresses in vulcanization while flowing in the direction of the arrow 12, and is finally fixed in the mold 2.

By the way, the temperature of the rubber material in the pot of the injection mechanism 1 is 50~100℃, while the temperature of the mold 2 is 160''~200℃.
It is heated to ℃. The rubber material injected into the mold 2 experiences a temperature rise of nearly 100°C due to heat conduction from the mold and heating due to friction, resulting in vulcanization and
Furthermore, fixation (reduction in fluidity and expansion) by vulcanization proceeds simultaneously.

The progress of this vulcanization is observed by a pressure sensor as an increase in pressure, as illustrated in FIG. 2, for example. In FIG. 2, area A is the increase in injection pressure due to the plunger, and area B is the increase in pressure due to vulcanization. If the rubber material does not contain a vulcanizing agent, vulcanization will not proceed, and the fluidity of the rubber material will increase as the temperature increases, so no pressure increase will occur in zone B. Since the rubber material has, for example, a coefficient of thermal expansion shown in the table below, the above pressure increase due to vulcanization, fixation, and expansion can be sufficiently measured.

Ethylene propylene- silicone rubber 8.5 xlO-'/'C
Silicone rubber 9.5 Xl0-'/'C
Butal rubber 1.8 xto-'/'c
Chloroprene rubber 2. OXl0-'/'C Natural rubber 1.5-1.8 Xl0-'/'C
Therefore, the above transition from area A to area 8, and
The progress of vulcanization can be determined from the behavior of pressure changes in the zone. That is, it can be determined that vulcanization is complete when the pressure increase reaches the maximum in the 8 zones, and the curing time can be measured as the time up to this point.

In the device of the invention at least one, preferably one or two pressure sensors are provided. Since the vulcanization rate varies depending on the position within the mold, it is advantageous to provide a plurality of pressure sensors at different positions in order to accurately determine the vulcanization rate of the entire mold.

As the pressure sensor used in the device of the present invention, for example, a quartz pressure sensor can be used, and the measured pressure may be recorded by, for example, an analyzing recorder, an analog recorder, an oscilloscope, or the like.

〔Example〕

Next, the present invention will be specifically explained using examples.

In the following description, "part" means part by weight.

Example 1 Spiral flow 21 shown in FIG. 3 was used as an injection molding device.
An injection molding mechanism (manufactured by Sensing Seisakusho, shown in the diagram) was used. On the inner wall of the spiral flow 21, pressure sensors 22 and 23 (
(manufactured by Kistler) is buried, and these pressure sensors are connected to an analyzing recorder (manufactured by Yokogawa Electric Corporation).

2 parts of cross-linking agent C-8 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts of thermosetting silicone rubber KE951U (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) using a roll, and kneaded. A vulcanized rubber material was prepared. This unvulcanized rubber material was molded at a mold temperature of 170°C in the injection molding apparatus mentioned above.
, when injection was performed under the conditions of injection pressure 102102O/cot, the pressure sensors 22 and 23 detected, respectively,
The behavior of pressure changes was measured as curves a and b shown in FIG. The measurement results showed that this unvulcanized rubber cured in 25 seconds under the above conditions.

Further, when injection molding was performed in the same manner as above except that the mold temperature was 180° C., it was found that the curing time was 15 seconds.

Example 2 The unvulcanized rubber material had the following composition: EPT3045 (Mitsui Petrochemical) 10
0 parts Asahi Carbon #70 (manufactured by Asahi Carbon Co., Ltd., 50 parts carbon black) Sambar 2280 (manufactured by Nippon Sun Oil, 20 parts process oil) ZnO 5 parts Stearic acid 1 part Dicumyl peroxide 2.7 parts EPDM (
When injection molding was performed in the same manner as in Example 1 except that the composition was used with an iodine value of 12) and the mold temperature was 170°C, it was found that the composition was cured in 33 seconds based on the behavior of pressure increase.

Example 3 The unvulcanized rubber material had the following composition: Natural rubber 100 parts Asahi Carbon #70 (manufactured by Asahi Carbon Co., Ltd., carbon black)
30 parts ZnO 5 parts stearic acid 3 parts sulfur
265 part accelerator DM
(Kawaguchi Kagaku Kogyo Co., Ltd., 0.7 part vulcanization accelerator) was used for injection molding in the same manner as in Example 1 except that the mold temperature was 170°C. It was found that it hardened in 35 seconds after rising.

〔Effect of the invention〕

According to the injection molding apparatus of the present invention, unlike conventional rheometers, it is possible to directly measure the state of the rubber material flowing inside the mold, and measurement can be performed without external influences. The progress of sulfur can be accurately monitored and determined. Therefore, the curing time can be determined according to the type of unvulcanized rubber to be molded and the injection molding conditions, and by controlling the injection molding operation,
Good injection molding can be performed.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an example of the device of the present invention. FIG. 2 shows the change in pressure inside the mold as measured by the device of the invention. FIG. 3 is part of the apparatus used in the example, and shows a spiral flow equipped with a sensor. FIG. 4 shows a curve showing the pressure change measured in Example 1. Agent Patent Attorney Shushi Iwamiya Figure 1 10]] Figure 2

Claims (2)

[Claims] (1) An injection molding apparatus comprising an injection mechanism and a mold, characterized in that at least one pressure sensor is provided within the mold. (2) A method for measuring vulcanization of rubber using the apparatus according to claim 1.