JPH1134126A - Lim molding method by cold runner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep flowability and curability constant, to eliminate necessity of frequent adjustment of a molding condition or the adjustment of the flow rate of a cold runner, and to dispense with skill. SOLUTION: In this molding method, a mold provided with a cold runner is used to perform injection molding. In this case, a liquid silicone rubber two- pack 16 before mixing is held to a temp. of 15 to 40 deg.C and a screw and cylinder part 14 performing mixing or a static mixer and plunger part and a nozzle tip part 15 are cooled to -5 to 20 deg.C. Then, the cold plate part in the mold and a cold runner part are cooled to -5 to 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to injection molding of liquid silicone rubber using a cold runner (hereinafter referred to as LI).
M (Liquid Injection Molding) method.

[0002]

2. Description of the Related Art The LIM molding method for liquid silicone rubber comprises a liquid base polymer having a vinyl group (component A) and a liquid crosslinking agent having a hydrogen atom bonded to a silicon atom (component B), which are stored separately. The liquid is measured in a certain ratio, mixed in a screw and a cylinder or a static mixer and a plunger, and injected under pressure into a mold from a nozzle tip of an injection molding machine. The liquid silicone rubber injected into the mold from the nozzle tip is introduced into the cold runner cooled by the mold body and the insulated cold plate, and is heated from the gate at the tip of the cold runner into the product cavity of the mold body. And is cured.

[0003] In the conventional LIM molding method using a cold runner, the A component and the B component of the liquid silicone rubber before mixing were exposed to the outside temperature throughout the four seasons. At this time, the flowability after mixing is changed due to the difference in the outside temperature of the liquid silicone rubber to which the liquid silicone rubber has been exposed before mixing, and defects such as insufficient hot water (short circuit) and insufficient curing are likely to occur. It was prevented by adjusting the conditions.

[0004] Further, a mixing screw and a cylinder portion or a static mixer and a plunger portion,
Further, the tip of the nozzle was cooled by tap water, groundwater, industrial water, or the like. Therefore, the temperature of the screw and cylinder, the static mixer, the plunger, and the tip of the nozzle often rises to 20 ° C or more depending on the season. Therefore, the yield and productivity have been secured by frequent adjustment of molding conditions.

[0005]

As described above, in the conventional method, the temperature of the liquid silicone rubber rises to 30 to 40 ° C. in summer depending on the storage location, and -10 to +10 in winter.
° C, causing a large temperature difference. For this reason, the flowability of the liquid silicone rubber changes, and it is necessary to adjust the injection pressure and the flow rate of each of the multi-cavity cold runners.

In addition, the temperature of the liquid silicone rubber is
If the temperature is lower than 15 ° C., the molded article becomes uncured and the curing time is increased, so that there is a disadvantage that the cycle time is long and the productivity is deteriorated. Further, when the mold temperature is increased, the flowability changes, and there is a trouble that other conditions must be adjusted.

Furthermore, in winter, the temperature difference between morning and evening is severe, so that molding conditions must be adjusted many times a day, which lowers productivity and lowers yield. The present invention has been made in order to solve the above-mentioned disadvantages of the conventional method, and maintains the flowability and the curability constant, eliminates the need for frequent molding condition adjustments and the adjustment of the flow rate of a multi-cavity cold runner. It is an object of the present invention to provide a method for LIM molding of liquid silicone rubber using a cold runner that does not require a method.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has examined the flowability of the LIM molding method using a cold runner. The present inventors have found that the above-mentioned object can be achieved by setting a specific temperature range for the cooling temperature of the cold portion in the mold, and have completed the present invention.

That is, the present invention uses a molding die provided with a cold runner, keeps the temperature of the liquid silicone rubber two components before mixing, and cools the mixing and the line after mixing and the cold part inside the die. LIM molding method of liquid silicone rubber to perform injection molding by mixing, (A) two liquid silicone rubber liquid before mixing,
(B) cooling the mixing screw and cylinder, or static mixer and plunger, and the tip of the nozzle to -5 to 20 ° C; and (C) a mold. An LIM molding method using a cold runner, wherein an internal cold plate portion and a cold runner portion are cooled to -5 to 20C. According to the method of the present invention, the LIM molding by the cold runner is, in effect, an improvement in productivity, an improvement in yield, a rationalization, and a reduction in cost.

In the present invention, (A) the liquid silicone rubber two component [component A and component B] before mixing is preferably kept at a temperature of 15 to 40 ° C, more preferably 20 to 30 ° C. It is. If the temperature is lower than 15 ° C., the flowability is lowered or uncured, and if it is higher than 40 ° C., the storage stability deteriorates, which is not preferable.

As a method of keeping the heat of (A), there is a method of using a band heater or a tube through steam in a container (a drum, a pail, or the like) filled with the A component and the B component. Occasional removal, ON, O
At the time of FF, heating may advance locally and the condition may not be stable. For this reason, it is preferable to use the apparatus after leaving it in a room at 20 to 30 ° C. for 4 hours or more, or to keep the temperature of the apparatus set in the molding machine using the waste heat of the cold runner cooling device or the air conditioner. This method is economical because it reduces equipment costs and recycles waste heat.

In the present invention, (B) mixing and cooling of the line after mixing are cooling of the mixing screw, the cylinder, the static mixer and the plunger, and the tip of the nozzle. -5 to 20 ° C, preferably 0 to 18 ° C. Further, the temperature at the tip of the nozzle is more preferably 0 to 10 ° C. If the cooling temperature is lower than −5 ° C., the flowability of the material itself is reduced, the curing speed is slowed, and uncured, and if it exceeds 20 ° C., the storage stability is deteriorated. The time during which the operation can be stopped is limited, which is not preferable. As the cooling method (B), it is preferable to use a dedicated cooling device and keep the temperature uniform throughout the year.

In the present invention, the cooling of the cold portion inside the mold in (C) is the cooling of the cold plate portion and the cold runner portion, and the cooling temperature range is -5 to 20 ° C, preferably 5 to 18 ° C. It is. If the cooling temperature is lower than −5 ° C., the flowability of the material itself is reduced, it is difficult to control the flow rate of multi-cavity, the curing speed is slow, and the gate portion is uncured. On the other hand, if the cooling temperature exceeds 20 ° C., the storage stability deteriorates, and in particular, the time during which the molding machine can be stopped is limited, which is not preferable.

As for the cooling method (C), it is preferable to use a dedicated cooling device and keep it uniform throughout the year.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an overall view of a 100-ton horizontal injection molding machine in which the cold runner LIM molding method of the present invention is carried out (the vertical direction in the drawing is the horizontal plane of the molding machine). The cylinder 14 and the nozzle tip 15 are cooled to a certain temperature by a cooling device, and the liquid silicone rubber LIM material 16 is cooled.
[Two cans of component A and component B] were used after being stored at 25 ° C. for one day, and after setting in a molding machine, the temperature was maintained by waste heat of a cooling device. The set LIM material 16 is sent to the cylinder portion 14 for mixing and mixing by a series of devices illustrated in the middle of the cylinder portion 14 for mixing.

FIG. 2 is a sectional view of a main part of a mold in which the LIM molding method using the cold runner of the present invention is performed. In FIG. 1, a cold plate 11 and a cold runner portion 12 are referred to as a mold cold portion, and these are maintained at a constant temperature by using a cooling device.

The mold of FIG. 2 used in this embodiment uses the anode cap 13 as a product, and has a cold runner structure of 10 pieces using the largest mold attached to a 100 ton horizontal injection molding machine. However, the present invention
The present invention is not limited by the products, mold structures, and the like shown in this embodiment.

Next, the molding process in the mold of FIG. 2 will be described. An LIM material (16 in FIG. 1) such as an additional liquid silicone rubber is brought into contact with a mold at a nozzle tip (15 in FIG. 1) of the injection molding machine, and the cold runner 12 is pressed.
To form the anode cap. Subsequently, the mold is opened, and the anode cap 13 is taken out of the mold using a stripper plate, an air blow, an ejector, a blade, or the like.

At this time, the temperature of the liquid silicone rubber two liquids (16 in FIG. 1) before mixing is kept at 20 to 30 ° C., and a screw and a cylinder part (FIG.
14) and the nozzle tip (1 in FIG. 1)
Cool the temperature of 5) to 0-15 ° C. Further, by cooling the temperature of the cold plate (11 in FIG. 2) and the cold runner portion (12 in FIG. 2) of the mold to 5 to 18 ° C., variations in flowability and curability between seasons and material lots are reduced. Control and improve productivity and yield.

The injection molding method according to the above embodiment is shown for each season, and the effect is evaluated for each season.
It was shown to. Similarly, the results of the injection molding method of the present invention were confirmed by comparing the results of Table 1 with those of the conventional example.

[0022]

[Table 1] * 1: In the examples, the storage was performed at 25 ° C for one day and then used. The conventional example is used while exposed to the outside air. * 2: The embodiment uses a cooling device to keep the temperature constant, and the conventional example uses tap water for cooling water. * 3: The actual value that has been operating for 10 hours a day and averaged over three months. * 4: Measured using Asker Micro Rubber Hardness Tester MD-1 manufactured by Kobunshi Keiki Co., Ltd.

[0023]

As apparent from the above description and Table 1, the effects of the present invention can be enumerated as follows.

By maintaining the temperature of the liquid silicone rubber two-part liquid and mixing it and cooling the cold part in the mold, there is no large difference in temperature of the material itself due to seasons as in the prior art. Is maintained constant, and frequent adjustment of molding conditions and adjustment of the flow rate of the cold runner, which has been performed many times, are no longer required, and skill is not required. Further, the variation of the material lot was suppressed, and the molding was performed under almost constant conditions. In addition, productivity was improved, and there was almost no variation in productivity throughout the year, yield was improved, material loss was reduced, and molding by cold runner could be fully utilized. In particular, adjustment of molding conditions for multi-cavity becomes easy, and the use of LIM molding by a cold runner is further expanded. Since the molding conditions are almost constant, the mold can be automatically demolded by providing a simple take-out facility, the number of personnel can be reduced, and a molded product having excellent characteristics and excellent quality can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall view of an injection molding machine in which an LIM molding method using a cold runner of the present invention is performed (the vertical direction in the drawing is the horizontal plane of the molding machine).

FIG. 2 is a sectional view of a main part of a molding die in which the LIM molding method using the cold runner of the present invention is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Cold plate 12 Cold runner part 13 Anode cap 14 Cylinder part 15 Nozzle tip part 16 LIM material [A component, B component]

Claims (1)

[Claims] 1. Injection molding by using a molding die provided with a cold runner, keeping the liquid silicone rubber two liquids before mixing, cooling the mixing and the line after mixing and the cold part inside the die. (A) keeping the liquid silicone rubber two liquids before mixing at 15-40 ° C., (B) a screw and cylinder part or static mixer for mixing. The plunger and the nozzle tip are cooled to -5 to 20C, and (C) the cold plate and cold runner inside the mold are cooled to -5 to 20C. LIM molding method by cold runner.