JPH0538738A - Molding machine, plasticization part of which is separated - Google Patents

Abstract

PURPOSE:To inject a resin which is uniformly kneaded and plasticized at a, uniform temperature by separating a molding machine of synthetic resin into a plasticization part, a kneading part and an injection part and injecting the synthetic resin supplied from the plasticization part and the kneading part via a cylinder for injection. CONSTITUTION:A feed zone FZ and a compression zone CZ are made independent of an injection or extrusion zone MZ and formed. Moreover one step, multisteps or the respective steps are constituted so that plasticization of synthetic resin is continuously performed by a screw having a short shaft or many shafts. Further plasticized resin is stored in a resin reservoir PC1 at low pressure. This stored plasticized resin is weight by the screw SC1 of a matering zone MZ (injection or extrusion zone) and injected. Both a plasticization screw SC2 and a hopper H are provided to the feed zone FZ and also a feed plunger P1 is inserted into the compression zone CZ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding machine for synthetic resin, that is, an injection molding machine or an extruder.

[0002]

2. Description of the Related Art Conventional injection molding machines include in-line screw type, screw pre-plastic (abbreviation of pre-plasticizing; hereinafter the same) type, plunger type, plunger pre-plastic type, shear plasticizing type, high pressure There are plasticized types. Among these, the former two screw types are excellent in plasticization and kneading,
Further, the inline screw type has a characteristic that the structure is simple and there are few elements in which molten resin stays or leaks.

Here, the in-line screw type injection molding machine performs plasticization and plunger injection with one screw, and the screw structure is such that one screw is a feed zone. Compression zone
And a zone called a metering zone. The movement of this screw is
The plasticized resin is stored in the resin reservoir between the injection nozzle and the tip of the screw, and the plasticized resin is measured (metering), so that the screw itself moves backward while rotating.

At this time, the resin that first flows into the resin reservoir is the resin that has stayed in the clearance between the screw and the cylinder, and the resin that subsequently flows in has long passed through the feed zone. The resin, which is the resin that flows toward the end, is the resin that has passed through the feed zone for a short period of time.

Therefore, there is a problem that the temperature of the resin flowing into the resin reservoir fluctuates. In this regard, the present inventors have actually confirmed that the temperature of the plasticized resin flowing from the screw into the resin reservoir fluctuates during plasticization and metering. However, if the temperature of the resin stored in the resin reservoir is locally different, the viscosity of the injected resin changes, which is one of the causes of defective molding.

Further, in the case of an in-line screw type injection molding machine, the length of the screw becomes longer than that of the conventional one for the purpose of sufficiently plasticizing and increasing the injection capacity of the resin. Currently, up to 23 times the screw diameter is being used. This causes the length of the injection molding machine to be large and occupies a large installation space, and also causes the cost of the injection molding machine itself to increase with the increase in screw processing cost. Therefore,
The lengthening of the screw is apt to cause temperature unevenness in the plasticized resin, and at the same time, it is a problem to be solved when increasing the injection capacity of the injection molding machine.

Further, in the in-line screw type injection molding machine, the plasticization of the resin is intermittent, that is, when the resin is plasticized between the screw and the cylinder, the passing distance and the passing time are within one cycle. Since it changes, there is a problem that the plasticized state becomes non-uniform. This is screw
The same applies to a pre-plastic type injection molding machine.

In addition, since the conventional injection molding machine cannot sufficiently knead the mixture, the additive and the resin are kneaded into pellets by the extruder in advance, and then the pellets are put into the injection molding machine and injected. Has been taken. This is one of the drawbacks of the in-line screw type injection molding machine.Because only a single screw can be used, it is impossible to use a multi-screw screw with good kneading property. It is due.

On the other hand, the pre-plasticizing type which is a pre-plasticizing type has a drawback that its structure is slightly complicated, but it is said to be an effective injection molding machine for a resin which is easily decomposed by heat. Among them, the screw-pre-plastic type is considered to have the best performance. In addition, in the case of an in-line screw type injection molding machine, since the screw is moved and injected, the relative positional relationship between the resin-supplying hopper and the screw changes, whereas the screw pre-plastic type injection molding The machine is characterized in that the screw fills the plasticized resin in front of the injection piston.

However, in the screw-pre-plastic type,
Since the valve between the plunger part and the plasticizing part is closed not only at the time of injection but also at the time of holding pressure, as a result, plasticization is stopped during that time, resulting in intermittent plasticization, In addition, the plasticized resin is intermittently injected into the resin reservoir, which causes a problem of uneven temperature. Therefore, the screw pre-plastic type injection molding machine also has a problem that the temperature of the plasticized resin fluctuates, as in the in-line screw type injection molding machine.

On the other hand, in the conventional extruder, a method of rotating not only a single screw but also a multi-screw screw in the same direction or in different directions to plasticize is adopted, but the thermal stability is not improved. In the case of a bad resin, since the screw diameter is constant, it is difficult to keep the temperature and the pressure until plasticization to be ideal, and as a result, it is difficult to plasticize the resin so that it does not thermally decompose. It was Further, degassing was not always easy by the conventional plasticizing method using an extractor.

Recently, it has been practiced to collect discarded synthetic resin moldings, prepare recycled resin raw materials, and mix them with the original raw resin (virgin raw material). However, if the recycled resin is mixed with the original raw material resin, the melting temperature will be different due to the difference in molecular weight and so on.Therefore, sufficient kneading and plasticization must be performed regardless of the injection method or the extrusion method. There is also a problem that the strength of the molded product is not uniform.

[0013]

In view of the above problems, the present invention makes it possible to shorten the length of the injection molding machine and to keep the temperature of the plasticized resin substantially constant. In addition, when plasticizing, it is possible to avoid the temperature from rising locally and the resin to be pyrolyzed, or to eliminate the gas required for plasticizing, which can be easily released from an injection molding machine or an extruder. The challenge is to develop a plasticization mechanism and an extrusion mechanism. Another object is to reduce the energy consumption overall by omitting the step of kneading the additive and the resin in advance with an extruder to form pellets.

[0014]

The constitution of the present invention made for the purpose of solving the above-mentioned problems is such that plasticization is carried out substantially continuously in accordance with the injection amount, and the plasticized resin is kept at a substantially constant temperature. The plasticizing mechanism or the extruding mechanism of the molding machine is gradually separated from the short feed zone part, the plasticizing part, and the injection part or the extruding part so that the resin is gradually stored in the resin pool and intermittently injected. The forming machine is formed in a mechanism in which the former and the latter are separated from each other, and at the same time, the mechanism is provided with a variable volume resin reservoir for storing the resin to be continuously discharged. Is.

By adopting this structure in the molding machine, it is possible to use not only a single screw but also a multi-screw screw which is said to have good plasticizing ability as a plasticizing method. By using a multi-stage screw, it is possible to gradually plasticize at a low shear rate in the early stage of plasticization, and to heat and knead at a high shear rate when the plasticization is sufficiently advanced. Further, since the pressure can be reduced at each stroke stage, degassing can be easily performed.

That is, in the present invention, each zone of the screw is
The rotation speed, diameter, screw shape, etc. of each screw in each zone can be arbitrarily changed and set according to the action of each zone. This is because plasticization is performed in multiple stages, so that the rotational speed (peripheral speed) of each stage screw and the cylinder diameter and the cylinder temperature can be changed according to the plasticized state and the kneading state. As a result, the plasticized state can be controlled arbitrarily, and the exhaustability is improved.

As a result of observing the plasticizing behavior of the synthetic resin in the plasticizing screw, the inventor of the present invention found that the frictional force between the synthetic resin and the cylinder and between the resin and the screw at the initial stage of plasticization. The resin begins to melt from the rear of the large screw groove, and the molten portion gradually spreads to fill the groove width, but when the screw recedes and plasticizes, the incompletely molten portion flows into the resin pool. I got to know.

That is, since the relative position of the screw and the hopper for supplying the synthetic resin largely changes as the screw retracts, the amount of the synthetic resin heated by shearing or the like depending on the position of the screw supplied from the hopper to the screw. Therefore, it was confirmed that unevenness occurs in the plasticizing temperature. It was also confirmed that even in the extruder, when the temperature and pressure were changed slightly, the position plasticized by the screw was changed significantly and the synthetic resin was thermally decomposed. The present invention pays attention to this point, and performs complete plasticization as a structure in which the plasticized portion is separated from the injection or extruded portion, and is then extruded or injected through a variable-capacity resin reservoir. ..

[0019]

Embodiments of the present invention will now be described with reference to the drawings.
Fig. 1 shows the feed zone FZ, which is necessary for plasticizing the resin.
The compression zone CZ is formed independently from the injection or extrusion zone MZ, and is formed in a single stage or multiple stages, or
Synthetic resin is continuously plasticized in each stage using a single-screw or multi-screw screw, and the plasticized resin is stored in the resin reservoir PC1 at a low pressure. FIG. 6 is a cross-sectional view showing an example in which a metering zone MZ (injection or extrusion zone) having the same structure as the metering zone is measured and injected by a screw SC1.
In FIG. 1, SC2 is a plasticizing screw, P1 is a feed plunger, NZ is an injection nozzle, H is a hopper, and PC is a resin pool of a metering zone.

In FIG. 2, a synthetic resin is plasticized on a shaft that is coaxially arranged in a composite manner, and the synthetic resin is continuously supplied to and stored in a resin pool PC, and the volume of the resin pool PC is contracted from the outside. It is sectional drawing of an example of the molding machine which was made to inject by this. In FIG. 2, SC3 is a plasticizing screw, P2 is an injection piston in which the screw-SC3 is installed, CV is a check valve of the plasticizing resin delivery hole PH formed at the tip of the injection piston P2, and IV is an injection cylinder I.
The injection check valve provided in the injection nozzle NZ of C, H is the hopper
Is.

FIG. 3 is a cross-sectional view of an example of an extruder in which the plasticizing portion is divided into a structure having a multi-step process and the synthetic resin sequentially plasticized therein is supplied to the extrusion cylinder CC. In FIG. 3, SC4 and SC5 are plasticizing screws, C1 and C2 are plasticizing cylinders, SC6 is an extruding screw, and H is a hopper. The multi-stage structure of the plasticized portion is not limited to the example shown in FIG. 3 and may have three or more stages.

[0022]

As shown in the above embodiments, in the present invention, the plasticizing portion and the kneading portion in the injection molding machine or the extruder and the injection or extrusion portion are separately formed, and the plasticization is performed. The part and the kneading part are not limited to a single screw, but preferably the screw diameter, length, number of revolutions, etc. are optimally provided to form a multi-stage or multi-screw structure to plasticize the synthetic resin Since the temperature of the plasticized resin at the time of injection or extrusion is made uniform and injection or extrusion is performed in accordance with the degree of,
The resin that has been uniformly kneaded and plasticized at a uniform temperature can be injected or extruded.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of an example of an injection molding machine in which an injection part and a plasticizing part are separated structures by applying the present invention.

FIG. 2 is a cross-sectional view showing a main part of another example of an injection molding machine to which the present invention is applied and which has an injection part and a plasticizing part as separate structures.

FIG. 3 is a cross-sectional view showing a main part of an example of an extruder to which the present invention is applied and which has a structure in which an extruding part and a plasticizing part are separated.

[Explanation of symbols]

FZ Feed Zone CZ Compression Zone MZ Metering Zone PC1, PC Resin Reservoir SC1, SC2, SC3, SC4, SC5, SC6
Screw NZ Injection nozzle P1 Piston IC Injection cylinder-CC Extrusion cylinder-H Hopper-

Claims (4)

[Claims] 1. A synthetic resin supplied from the plasticizing section and the kneading section, which are separately formed from a plasticizing section and a kneading section for melting the synthetic resin and an injection section or an extruding section for injecting the synthetic resin and the like. A molding machine of a type in which a plasticizing part is separated, characterized in that a resin or the like is injected through a cylinder for injection or extrusion. 2. The plasticizing section and kneading section are uniaxial, or
Formed by a multi-axis screw or a multi-stage screw,
A molding machine according to claim 1, wherein the plasticizing part is separated according to the plasticizing temperature and the kneading state so that the plasticizing and kneading can be performed efficiently. 3. A type in which the plasticized portion is separated according to claim 1 or 2 having a structure capable of changing the volume of the resin reservoir portion in order to plasticize and knead synthetic resin or the like constantly or continuously. Molding machine. 4. A molding machine of the type in which the plasticized portion is separated, wherein a structure for temporarily storing the resin is formed between the plasticized portion and the measuring portion.