JP2704605B2 - Thermoplastic resin injection molding apparatus and molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus for a thermoplastic resin capable of molding a large molded article having a high resin density despite being small in size and capable of low pressure molding; The present invention relates to a molding method. More specifically, it is possible to prevent the thermoplastic resin from being thermally decomposed at the time of low-pressure molding of a highly thermally decomposable thermoplastic resin in which the melting temperature and the thermal decomposition temperature are close to each other, and to obtain an excellent molded product of the thermoplastic resin. The present invention relates to an injection molding apparatus and a molding method using the same.

[0002]

2. Description of the Related Art As a thermoplastic resin injection molding machine, a plan in which a molten resin is provided in an apparatus body by a built-in screw in order to speed up a molding cycle, increase an injection amount, and improve quality by uniformly kneading a molten material. An injection molding apparatus having a function of storing a fixed amount in an accumulator having a jar and injecting the molten resin stored by operation of the plunger into a molding die is disclosed in, for example, JP-A-48-73458.
It is known in Japanese Patent Publication No.

[0003]

When an olefin-based resin is used as a thermoplastic resin applied to these injection molding apparatuses, since the decomposition of the molten resin by heat is small, the melt viscosity is reduced at a high temperature. It can be molded, whereby a molded article of excellent quality can be easily obtained. However, when targeting a thermoplastic resin which is easily decomposed by heat, such as a vinyl chloride resin, the molten resin stagnated in a narrow portion or a gap portion of the injection molding device is decomposed by heating, so-called "burn" is caused. Occurs. The raw resin in which this "burn" has occurred is mixed into the molten resin little by little and is injected into the mold, which causes deterioration of the quality of the molded product. In addition, if "burn" due to such decomposition of resin occurs even in a part of the apparatus, this becomes a nucleus and "burn" propagates in a chain form to various parts of the injection molding apparatus,
As a result, the quality of the molded product is acceleratedly degraded, which not only deteriorates the product yield but also causes various troubles such as troublesome disassembly and cleaning of the apparatus. JP 4
Also in the molding apparatus disclosed in JP-A-8-73458, the introduction of the molten resin exiting the screw type extruder into the accumulator and the injection of the molten resin stored in the accumulator into the mold are controlled by a needle valve or the like. Therefore, the above-described problem occurs due to the stagnation of the molten resin in such a valve mechanism and a narrow portion in the vicinity thereof.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional injection molding apparatus, and to provide a thermoplastic resin injection molding apparatus which can sufficiently cope with the use of easily decomposable resins, and a molding method using the same. It does not provide a method. Another object of the present invention is to provide a thermoplastic resin injection molding apparatus capable of easily molding a large-sized molded article of excellent quality by a relatively small plasticizing apparatus, and a molding method using the injection molding apparatus. Things.

[0005]

To achieve the above object, an injection molding apparatus for a thermoplastic resin according to the present invention comprises: a screw tip portion of an apparatus main body having a supply port for an injection material and a screw rotatably built therein. A main accumulator for accumulating molten resin having an injection mechanism by a plunger is provided in the vicinity, and a main accumulator is provided in an apparatus body near an outlet of an injection flow path for injecting the molten resin of the main accumulator into a molding die. And a sub-accumulator capable of blocking or opening the injection flow path of the molten resin injected from the main accumulator.

More specifically, the injection molding apparatus for a thermoplastic resin according to the present invention comprises an injection mechanism using a plunger provided in the vicinity of the screw tip of an apparatus body in which an injection material supply port and a screw are rotatably built. A main accumulator for accumulating molten resin having the following, and the injection flow path can be shut off or opened in an apparatus main body near an outlet of an injection flow path for injecting the molten resin in the main accumulator into a molding die. And a sub-accumulation of molten resin having an injection mechanism with a plunger detachably provided as described above, and the sub-accumulation plunger is injected from the main accumulator through the sub-accumulation toward the molding die. The injection channel of the molten resin is blocked or opened, and the molten resin in the sub-accum is forcibly injected into the molding die. It is characterized in.

Further, according to the injection molding method for a thermoplastic resin of the present invention, a molten resin plasticized by a screw incorporated in an apparatus body is fed into a main accumulator provided near a tip of the screw to accumulate a predetermined amount. Then, when the accumulated predetermined amount of the molten resin is injected toward the molding die by the plunger provided in the main accumulator, the molten resin is supplied to the apparatus main body close to the discharge port of the injection flow path of the molten resin communicating with the molding die. Providing a sub-accum having an injection mechanism by a plunger, activating the screw while accumulating the molten resin in the main accumulator, and shutting off the injection channel by operating the plunger of the sub-accum, and accumulating in the main accumulator. When the molten resin is injected into the molding die, the screw is stopped, and the molten resin is injected by a sub-accumulation plunger. Opening the flow path, and is characterized in that injection forced to the mold the molten resin in Sabuakyumu.

More specifically, according to the injection molding method of a thermoplastic resin of the present invention, a molten resin plasticized by a screw incorporated in an apparatus body is fed into a main accumulator provided near a tip of the screw. When a predetermined amount of accumulated molten resin is injected toward a molding die by a plunger provided in the main accumulator, the molding die is set to be slightly open from a predetermined interval, A sub accumulator having an injection mechanism by a plunger is provided in the apparatus main body near the outlet of the injection flow path of the molten resin communicating with the molding die, and the screw is operated while the molten resin is accumulated in the main accumulator, and By operating the plunger of the accumulator, the injection flow path is shut off, and when injecting the molten resin accumulated in the main accumulator into the molding die, the While stopping the screw, the injection channel is opened by the plunger of the sub-accumulation, and the molten resin in the sub-accumulation is forcibly injected into the molding die. It is characterized in that the mold is clamped by using.

As the thermoplastic resin used in the present invention, not only olefin resins such as polyethylene, but also
It is also possible to use a vinyl chloride resin such as a vinyl chloride resin, a vinyl acetate resin, or a polyacetal having a high melting point close to the melting point and a high thermal decomposition property.

The main body of the apparatus basically has a screw rotatably built in a cylinder provided with a hopper for charging a thermoplastic resin as an injection material at an upper part thereof.
A main accumulator is provided in the upper part near the tip of the screw. The main accumulator has a plunger whose base end is operated by an injection cylinder, and the amount of accumulated molten resin can be changed by controlling the position of the plunger.

The sub-accumulation is easily disassembled and cleaned on the apparatus main body near an outlet of an injection flow path for injecting a molten resin into a molding die disposed at a predetermined interval in the apparatus main body. It is attached detachably so that it can be made, and shuts off the injection flow path by controlling the position of the built-in plunger,
It is open.

The molding dies arranged at predetermined intervals in the apparatus main body are preferably set so that the parting line forms an appropriate gap by injection, and the set interval is in the range of 10 mm to 100 mm. , Especially 10-20
It is preferable to be in an open state in the range of mm.

[0013]

The injection molding apparatus for a thermoplastic resin of the present invention, when injecting a predetermined amount of molten resin stored in the main accumulator into a molding die, is attached to and detached from an apparatus body near an outlet of an injection flow path of the molten resin. The injection flow path can be shut off and opened by the plunger operation of a sub accumulator having a freely provided substantially valve mechanism, so that a conventional ordinary switching valve (check valve, ball valve, gate valve, etc.) type In comparison with the above, the molten resin can be injected into the molding die without staying near the valve. When the molten resin from the main accumulator is injected into the molding die, the injection channel is opened by operating the sub-accumulation plunger. By operating the jar, the sub-accumulation can be reliably discharged from the cylinder.

In the injection molding method of a thermoplastic resin according to the present invention, when the molten resin accumulated in the main accumulator provided in the apparatus main body is injected into a molding die, the molten resin is placed near an outlet of an injection flow path. Since it is performed through a sub-accumulation provided with the provided plunger, molding can be performed at a low pressure of about 1/5 to 1/10 as compared with a normal injection molding method. Further, by such low-pressure molding, the mold clamping force of the mold can be reduced to 1/10 to 1/100 as compared with the ordinary molding method, and molding can be performed. A large molded product can be easily obtained by molding.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a thermoplastic resin injection molding apparatus and a molding method according to the present invention will be specifically described below with reference to the accompanying drawings. The thermoplastic resin injection molding apparatus 1 of the present invention basically includes a hopper 5 for supplying an injection material at an upper portion, and a screw 4 for melt-plasticizing and transporting the thermoplastic resin therein. The apparatus main body 2 includes a horizontally long cylinder 3 provided rotatably, and a main accumulator 6 and a sub-accumulation 10 provided in the apparatus main body 2.

The main accumulator 6 is provided vertically above the tip of the screw 4 built in the horizontally long apparatus main body 2, and includes a cylinder 7 communicating with the cylinder 3 of the apparatus main body 2, and a drive provided therein. The plunger 8 is composed of a mechanism 9 and an interlocking plunger 8, and the plunger 8 is slid up and down along the inner peripheral wall of the cylinder 7 by a hydraulic or pneumatic driving mechanism 9, and the plunger 8 is retracted (elevated). Thus, a space portion having a predetermined volume is formed in the lower portion of the cylinder 7, and the volume of the space portion is reduced by advancing (falling), so that the space portion does not exist at the maximum advance position. The main accumulator 6 incorporates a temperature control mechanism to maintain the molten resin in the cylinder 7 at a predetermined temperature.

The sub-accumulation unit 10 is detachably mounted on the upper portion of the apparatus main body 2 by bolts or the like at an upper portion of the molten resin injection passage near the discharge port so that the inside can be easily and easily cleaned. , A cylinder 11 and a plunger 12 interlocked with a driving mechanism 13 provided therein
The plunger 12 is slid up and down along the inner peripheral wall of the cylinder 11 by a hydraulic or pneumatic drive mechanism 13, and the plunger 12 is retracted (ascended) to a predetermined volume below the cylinder 11. Is formed, and the volume of this space is narrowed by forward movement (downward), so that there is no space at the maximum forward position. The sub-accumulator 10 is smaller than the main accumulator 6, and its size is such that the amount of the molten resin accumulated in the main accumulator 6 for one time is directed to the molding die 16 through the sub-accumulator 10. Any size is acceptable as long as it does not hinder the distribution for sending. Further, a temperature control mechanism is also incorporated in the sub-accumulation unit 10 so as to maintain the molten resin in the cylinder 11 at a predetermined temperature.

The sub-accumulation 10 has an injection path 14 for receiving the molten resin from the main accumulator 6 and a discharge path 15 for injecting the molten resin from the sub-accumulation 10 into the molding die 16. It is provided in the middle of the flow path, and is configured such that the introduction path 14 and the discharge path 15 are simultaneously blocked or opened by the action of the plunger 12. That is, when the plunger 12 in the sub-accumulation unit 10 retreats (rises), the injection flow path including the introduction path 14 and the discharge path 15 is opened, and when the plunger 12 reaches the maximum forward position (maximum descending position), the introduction path starts. The injection flow path including the path 14 and the discharge path 15 is shut off.

A molding die 16 is provided in the apparatus main body 2 at an end portion (discharge port) of the discharge path constituting the injection flow path via an injection nozzle 17, and molten resin is injected into the cavity. It is configured as follows. This molding die 16
When the molten resin is injected into the molding die 16, the parting line is set to 10 to 100 mm by the injection pressure.
The mold is automatically opened to the extent that when the injection is completed, it is automatically closed by the mold clamping force to set the mold to a regular mold clamping state.

A method of injection molding a thermoplastic resin using the thermoplastic resin injection molding apparatus 1 of the present invention will be described below. First, a thermoplastic resin as an injection material is supplied to a hopper 5.
When supplied into the cylinder 3 constituting the apparatus main body 2 through the
And the rotation of the screw 4 is fed to the tip side of the screw 4 as a molten resin plasticized. At this time, since the injection pressure is not acting on the plunger 8 of the main accumulator 6, the plunger 8 is in a free state. On the other hand, since a load acts on the plunger of the sub-accumulation 10, the plunger 12 is at the maximum forward position, and the introduction path 14 and the discharge path 15 are blocked on the sub-accumulation 10 side. The molten resin cannot be received in the accumulator 10. Therefore, the molten resin in the apparatus main body 2 is conveyed while receiving a load on the distal end side by the rotation of the screw 4 and introduced into the main accumulator 6, and a predetermined amount is accumulated in the main accumulator 6 while pushing up the plunger 8. You.

When the amount of molten resin necessary for injection into the molding die 16 is accumulated in the main accumulator 6, the screw 4 is automatically stopped, and at the same time, the sub accumulator 10 is stopped.
Since the load acting on the plunger 12 is released, the plunger 12 is in a free state. When the injection pressure is applied to the plunger 8 of the main accumulator 6 in this state, the plunger 8 starts to move forward (down), and the molten resin in the main accumulator 6 moves from the introduction passage 14 to the sub-accum 10 by the pressing force. While being pushed up, the plunger 12 of the sub-accumulator 10 is injected into the molding die 16 through the sub-accumulator 10, the discharge path 15, and the injection nozzle 17. At this time, since the molding die 16 is opened at predetermined intervals (about 10 to 20 mm in the embodiment), the molding surface of the molding die 16 is closed by the injection pressure of the molten resin. 10-20m against
It is automatically opened by about m and formed into a predetermined shape.

When the plunger 8 of the main accumulator 6 reaches the maximum forward position and the injection of the molten resin is completed, when an injection pressure is applied to the plunger 12 of the sub-accumulator 10, it is pushed up by the pressure of the molten resin and retreats. The plunger 12 of the sub-accumulation 10 at the position moves forward (down) to discharge the molten resin in the cylinder 11 to the discharge path 15.
And starts to be injected into the cavity A of the molding die 16. And plunger 1 of sub-accumulation 10
2 moves forward and reaches the maximum advance position, the molten resin in the sub-accumulation 10 is completely sent out from the sub-accumulation 10 to the discharge path 15, and at the same time, the discharge path 15 for feeding the molten resin into the molding die 16 The introduction path 14 for sending the molten resin from the main accumulator 8 to the sub-accum 10 is simultaneously shut off. Then, plunger 12 of sub-accumulation 10
, While maintaining the state where the injection pressure is applied, and the state where the injection flow path is closed. When the injection of the molten resin is completed, the load on the plunger 8 in the main accumulator 6 is automatically eliminated and the plunger 8 is in a free state. After that, a predetermined amount is accumulated, and thereafter, through a similar process, the molten resin is injected into a molding die.

When the injection flow path of the molten resin by the plunger 12 of the sub-accumulation unit 10 is completed, the injection of the molten resin into the molding die 16 is completed, and the molding metal opened by the injection pressure of the molten resin. The mold 16 is automatically closed and brought into a regular mold clamping state, whereby a dense molded product can be obtained. After the molded product is taken out by cooling and opening the molding die 16, molding can be performed one after another in a cycle similar to the above.

[0024]

According to the thermoplastic resin injection molding apparatus of the present invention, the main accumulator is provided at the tip of the screw of the apparatus main body containing the screw, and the sub-accumulation is provided at the apparatus main body near the outlet of the molten resin injection flow path. And an injection passage composed of an introduction passage for sending the molten resin from the main accumulator to the sub-accum and a discharge passage for sending the molten resin from the sub-accumulation to the molding die by the action of the plunger provided on the sub-accumulation, and opening the opening. With such a configuration, the sub-accumulation effectively has the function of a switching valve. Therefore, compared to conventional check valves, ball valves, and switching valves such as gate valves, there is no narrow portion where molten resin stays in the injection flow path of molten resin. Therefore, the number of times of disassembly and cleaning is greatly reduced, and the sub-accum serving as the switching valve can be disassembled and assembled, and the structure is extremely simple. Can be achieved. Therefore, it is possible to easily form not only resins having no thermal decomposition property but also thermally decomposable resins such as vinyl chloride resin, vinyl acetate resin, and polyacetal resin, and can be widely used for molding various resins. is there.

According to the injection molding method of a thermoplastic resin of the present invention, the molten resin accumulated in the main accumulator provided in the apparatus main body is injected into the molding die via the sub-accum. It is injected in two stages by the accumulator plunger and the sub-accumulation plunger and hardly remains in the apparatus main body, and can be injected into the molding die very smoothly to obtain a high quality molded product. Can be done. In addition, when the molten resin is injected into the molding die, the molding die set to be opened at regular intervals is used, so that the molten resin is opened at predetermined intervals by the injection pressure, and the mold is clamped after the injection. By returning the mold to a normal mold clamping state by force, a dense large-sized molded product can be efficiently obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an injection molding apparatus showing a state of accumulating molten resin.

FIG. 2 is a longitudinal sectional view of an injection molding apparatus showing a state of injection of a molten resin into a molding die.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection molding apparatus for thermoplastic resin 2 apparatus main body 4 screw 5 hopper 6 main accumulator 10 sub-accum 14 molten resin introduction path 15 molten resin discharge path 16 molding die

Claims (4)

(57) [Claims] A main accumulator for accumulating molten resin having an injection mechanism by a plunger is provided in the vicinity of the screw tip of an apparatus main body having a supply port for an injection material and a screw rotatably built therein, and a main accumulator. The main body has the same structure as the main accumulator in the apparatus main body near the outlet of the injection flow path for injecting the molten resin into the molding die, and the injection flow path of the molten resin injected from the main accumulation is shut off or An injection molding apparatus for a thermoplastic resin, comprising a sub-accumulation that can be opened. 2. A main accumulator for accumulating molten resin having an injection mechanism by a plunger provided in the vicinity of the screw tip of an apparatus body in which an injection material supply port and a screw are rotatably built, and a molten resin of the main accumulator. Resin having an injection mechanism with a plunger removably provided in an apparatus body near an outlet of an injection flow path for injecting the injection flow into a molding die so that the injection flow path can be blocked or opened. The sub-accum is provided, and the operation of the plunger of the sub-accum shuts off or opens the injection flow path of the molten resin injected from the main accumulator through the sub-accum toward the molding die, and within the sub-accum. Wherein the molten resin is forcibly injected into the molding die. 3. A molten resin plasticized by a screw incorporated in an apparatus body is fed into a main accumulator provided near a tip of the screw to accumulate a predetermined amount, and the accumulated predetermined amount of the molten resin is accumulated in the main accumulator. A sub-accum having an injection mechanism by a plunger is provided in the middle of the injection flow path of the molten resin communicating with the molding die when injecting the molten resin toward the molding die by the plunger provided in the main accumulator. Activate the screw during accumulation in
And, by operating the plunger of the sub-accumulation, the injection flow path is shut off, and upon injection of the molten resin accumulated in the main accumulation into the molding die, the screw is stopped, and the plunger of the sub-accumulation is used. An injection molding method for a thermoplastic resin, characterized by opening an injection flow path and forcibly injecting a molten resin in a sub-accumulation into the molding die. 4. A molten resin plasticized by a screw incorporated in an apparatus main body is fed into a main accumulator provided near a tip end of the screw to accumulate a predetermined amount, and the accumulated predetermined amount of the molten resin is accumulated in the main accumulator. When injecting toward the molding die by the plunger provided at the same time, the molding die is set to be slightly opened from a predetermined interval, and in the middle of the injection flow path of the molten resin communicating with the molding die. Provide a sub-accumulation with a plunger injection mechanism,
During the accumulation of the molten resin in the main accumulator, the screw is operated, and the injection flow path is shut off by operating the plunger of the sub-accumulation, and when the molten resin accumulated in the main accumulation is injected into the molding die. Stopping the screw, opening the injection flow path by the plunger of the sub-accumulation, and forcibly injecting the molten resin in the sub-accumulation into the molding die. An injection molding method for a thermoplastic resin, wherein the mold is self-clamped.