JPH0116574Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a simple injection molding apparatus particularly suitable for insulation treatment and molding of cable connection parts and the like. Generally, when forming connections between rubber/plastic cables such as cross-linked polyethylene insulated cables, the ends of the cables to be connected are sharpened like a pencil, and the conductors are electrically connected using compression sleeves, etc. After that, an internal semiconductive layer was formed by winding a semiconducting tape or covering the connecting conductor with a semiconductive heat-shrinkable tube, and then a crosslinking agent and an antiaging agent were added onto the internal semiconductive layer. A so-called mold joint insulating layer has been formed by winding an insulating tape or by placing a mold over the semiconductive layer and injecting an insulating resin into the mold. In particular, recently, the method of forming an insulating layer by injecting resin into the mold has been attracting attention because foreign matter is likely to get mixed into the tape when using the above-mentioned insulating tape winding method. There are two methods for injecting resin using a mold: a method using an extruder and a method in which a cylinder is filled with resin and the resin is injected into the mold. When using an extruder, the ejection pressure is generally low because the material flows into the mold, and the resin is easily cooled within the mold, resulting in insufficient resin flow within the mold. , there is a problem that so-called blister is likely to occur. One possible countermeasure is to raise the mold temperature and improve the fluidity of the resin, but for example, if a crosslinking agent is added, the crosslinking reaction progresses unnecessarily during extrusion molding, making molding difficult. Sometimes. On the other hand, a method in which the cylinder is directly filled with resin in the form of pellets or with an extruder, etc., then the cylinder is heated and the molten material is filled into the mold with a piston, etc. makes it easier to control the injection speed and prevents the above defects. Although it has the advantage of being easy to clean, it is easy for foreign objects such as metal foreign objects and burnt resin to get mixed in during injection molding, and these foreign objects can cause electrical defects such as treeing within the cable connection, leading to serious insulation breakdown. I felt a deep sense of sadness. As a result of intensive studies to solve this problem, the inventors have made a cartridge by storing the material to be molded in an appropriate container in advance, and loading this cartridge into a protective cylinder with a heating source as appropriate. They discovered that it is effective to melt the above-mentioned material in a cartridge, apply extrusion pressure from the outside, and inject the molten resin from the cartridge into the mold, and completed this invention. That is, this invention consists of a mold for molding an object, which is provided with a material injection port that can be screwed together, and a material pouring nozzle part, which is provided with a threaded part that screws into the material injection port of this mold. A cylindrical main body having a cartridge loading part, a protective cylinder attached to the outer periphery of the main body and containing a heating source for heating the main body, and a protective cylinder that is inserted from the open end of the main body and slides on the inner wall thereof. This injection molding device is comprised of a back pressure applying piston for applying back pressure to the bottom of the cartridge loaded with the injection molding device. The device of the present invention will be explained below with reference to the drawings. The cartridge used in the device of the present invention will be explained. The cartridge 10 for filling the material is first filled with a resin composition 2 which has been blended to a desired composition and has removed foreign substances, air bubbles, and other factors that degrade the properties of the molded product.The cartridge 10 is a cylinder having a nozzle portion 1a at one end and a bottom plug 1b at the other end. shaped container 1
It is made by sealing it inside a container and cooling it to solidify it. The bottom plug 1b of the cartridge 10 is in the shape of a disc that is in contact with the inner surface of the container and is slidable in the direction of the nozzle portion 1a.As will be described later, the bottom plug 1b is moved within the container and the resin heated to a molten state is removed. It is designed to flow out from the nozzle part. These containers,
The bottom plug must have a wall thickness and material that will not deteriorate, deform, or break even under the temperature conditions necessary for resin flow and the pressure during injection molding, and must be made of a material that does not cause any deterioration, deformation, or destruction, and must not contain any additives in the resin composition contained therein. The material must be able to prevent the deterioration of the resin composition, as well as the deterioration of the resin composition due to the permeation of moisture, oxygen, etc. from the outside, such as metals such as iron, stainless steel, copper, and aluminum;
Thermoplastic plastics, ceramics, inorganic polymer materials, etc. with a softening temperature of 130°C or higher measured by the method specified in JISK6870 can be used. The resin composition to be filled is prepared by adding the base resin and necessary additives such as crosslinking agents, reaction accelerators, stabilizers, and other fillers to the base resin, preferably at a temperature below the reaction decomposition temperature and above the flow temperature. After stirring and mixing thoroughly at the bottom, it is filled into the above cylindrical container, cooled,
Let solidify. When stirring and mixing, care must be taken to perform this stirring and mixing in a completely sealed atmosphere to prevent deterioration of the resin or additives due to oxygen, moisture, etc. contained in the outside air, contamination of foreign substances, and generation of air bubbles. Usually, extrusion filling is carried out using an extruder, but if a container equipped with a stirrer is used, it is preferably carried out in a high vacuum state or in an inert gas atmosphere. Next, the injection molding apparatus of this invention is constructed as shown in FIG. That is, the material inlet 12 that can be screwed together
A mold 11 for molding an object and this mold 1 provided with
A cylindrical main body 14 having a material pouring nozzle part 13 provided with a threaded part to be threaded into the material inlet 12 of the first material injection port 1, and a loading part of the cartridge 10; a protective cylinder 16 containing a heating source 15 for heating the main body; and a piston 17 for applying back pressure to the bottom of the loaded cartridge 10 inserted from the open end of the main body and sliding on the inner wall. It consists of: In the figure, 11a is the inner cavity of the mold, 18 is the cable, and 18a is the connection part. In cast molding using the device of the present invention, the above-mentioned cartridge 10 is heated with a protective tube 16 into a cylindrical body 1.
4 with the nozzle 1a facing the pouring nozzle 13 side, and the protective cylinder 16 is heated from outside by the coil 15 to melt the resin inside the cartridge. Next, back pressure is applied by the piston 17 from the rear of the cartridge 10, and the molten resin 2 is injected into the mold 11, and the resin is solidified around the cable connection part 18a, thereby obtaining a resin molded product by molding. be. In this injection molding apparatus, the cartridge is replaced every time injection is performed. In this invention, the heating coil is not particularly limited to the above structure in terms of structure, and it is also possible to heat the cartridge from outside the protective tube, or directly heat the cartridge while it is inscribed inside the protective tube. Further, the heating method is not particularly limited, and a liquid heat medium such as external oil for electric heating, a gas heat medium such as air, nitrogen gas, etc. may be used. Furthermore, the above-mentioned back pressure method is not particularly limited, and any method such as gas pressure, spring pressure, or hydraulic pressure may be used. The materials used in this injection molding apparatus include the above-mentioned rubbers and ethylene-based resin rubbers which have excellent electrical insulation properties in plastic electrical cable connection parts. Molecular weight for ethylene resin is 5000~
100,000 ethylene alone and ethylene copolymers. If the molecular weight is less than 5,000, the mechanical strength of the cable connection part is too small to be used, and the molecular weight
If it exceeds 100,000, it will be almost impossible to eject, so be careful. Specifically, polyethylene, ethylene-
Carboxylic acid vinyl esters, ethylene-acrylic acid alkyl esters, ethylene-methacrylic acid alkyl esters, ethylene resins such as ethylene copolymers such as ethylene-α-olefin,
Rubbers such as EPM, EPDM, polyisobutylene, isobutylene-isoprene copolymer, and polybutadiene may be mentioned. As is clear from the examples below, the device of the present invention replaces the cartridge each time injection molding is performed, so there is no risk of foreign matter getting into the molded product, and the device is compact and has excellent portability. In addition, the material replenishment using the cartridge enables work to be carried out in a flexible manner, which is extremely effective in solving the above-mentioned problems. This will be explained in detail below using examples. Example 1, Comparative Examples 1 and 2 In order to confirm the effects of the injection molding apparatus of the present invention,
A conventional screw-type extruder (Comparative Example 1), a non-cartridge injection molding machine (Comparative Example 2), and the injection molding apparatus of the present invention described above (Example 1) were used to produce a conductor with a cross-sectional area of 2000 mm ² insulation. Polyethylene containing cross-linking agent (manufactured by Nippon Unicar Co., Ltd.
HFOJ4201E) was cast to a thickness of 25 mm using the conventional method, and their properties were compared and the results are shown in the table. The specifications and resin injection method for the screw type extruder non-cartridge injection molding and the injection molding of the present invention are as follows. (1) Screw extrusion Using an extruder with a cylinder diameter of 30φL/D=20,

[Table] According to the results shown in the above table, it is clear that by using the injection molding machine of the present invention, it is possible to mold a cable connection part with very stable characteristics and no voids or foreign matter.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a cartridge used in the present invention, and FIG. 2 is a schematic sectional view of the injection molding apparatus of the present invention. 1... Cylindrical container, 1a... Nozzle portion of the cylindrical container, 1b... Bottom stopper, 10... Cartridge,
11... Mold, 12... Material injection port, 13... Material pouring nozzle part, 14... Cylindrical body, 15... Heating coil, 16... Protection tube, 17... Piston,
18a... Cable connection part.

Claims (1)

[Scope of utility model registration request] A mold for molding an object that is provided with a material injection port that can be screwed together, a material pouring nozzle part that is provided with a threaded part that screws into the material injection port of this mold, and a cartridge loading part. a cylindrical body having a cylindrical body, a protective tube attached to the outer periphery of the body and containing a heating source for heating the body, and a cartridge inserted from the open end of the body and loaded by sliding on the inner wall thereof. An injection molding device consisting of a back pressure applying piston for applying back pressure to the bottom of the machine.