KR20110100596A - Injection molding method - Google Patents

Abstract

The injection molding method stores the molding material supplied into the cylinder of the injection molding apparatus at the tip of the cylinder by the rotation of the screw, and stops the rotation of the screw after the screw is retracted to the weighing setting position by the pressure from the stored molding material itself. A weighing step of weighing the amount of molding material by stopping. The metering step may include: setting a back pressure applied to the screw to a predetermined value; Setting a rotation speed of the screw to a constant rotation speed within a predetermined range; And adjusting the feed rate of the molding material to a predetermined time so that the feed rate is controlled irrespective of the rotational speed and the back pressure set value of the screw.

Description

Injection molding method {INJECTION MOLDING METHOD}

The presently described subject relates to an injection molding method, more particularly an injection molding method for feeding a molding material containing a large amount of powder directly from a hopper into a cylinder.

One conventional resin (plastic) molding method is an injection molding method. The injection molding method uses a screw or plunger to fill a molten resin molding material in a heating cylinder (also simply referred to as a cylinder) into a cavity of a mold comprising a male mold and a female mold, and then rapidly cools the molded article The method is to remove material from the mold to obtain it.

The injection molding cycle generally includes a metering step, a mold clamping step, an injection step, a dwelling step, a cooling step and a release step.

The weighing step is now described in detail. In the metering step, the molding material supplied into the cylinder is stored at the tip of the cylinder by the rotation of the screw, the screw is pressurized from the stored molding material itself and retracted to the predetermined weighing setting position, after which the rotation of the screw It stops to end. In this case, the normal feeding method is generally performed, in which the molding material is filled in an amount that exceeds the rotational speed of the screw, that is, the material feeding capacity of the molding material into the hopper, and according to the material feeding capacity of the screw, The material in the hopper is fed to fill the cylinder by self-weight. Therefore, when the back pressure set value is constant, the weighing time decreases with the increase in the rotational speed of the screw, and the weighing time increases with the decrease in the rotational speed. Conversely, when the screw rotational speed is constant, the metering time decreases with decreasing back pressure, and the metering time increases with increasing back pressure.

As a resin molding material used for injection molding, petroleum resin is conventionally used. However, problems such as air pollution, global warming, or ozone depletion have emerged, and as a measure against these problems, attempts are being made to build a circulating energy saving society. In one approach, molding materials are converted from petroleum based resins to biological plant based resins derived from plants and the like.

Plant-based resin molding materials include so-called biomass resins (also called biomass plastics or bioplastics), and attempts are made to use biomass resins as molding materials for producing a variety of products.

Typical examples of biomass resins include polylactic acid (also called polylactic acid resin or PLA) or cellulosic resins. Such biomass resins offer the advantage that the release and absorption of carbon dioxide in the global environment is overridden by each other. This idea is called carbon neutral.

However, when the biomass resin is used as a molding material to produce a molded article by injection molding, the low heat resistance of the biomass resin has a difficulty. Biomass resins can be used in the processing step or injection molding as a pretreatment of injection molding because the difference between the temperature at which the biomass resin is thermally melted and easily flows and the decomposition temperature of the biomass resin is smaller than that of petroleum resin. The temperature set range is limited to a narrow range. For example, when biomass resins and additives are kneaded and pelletized by a kneading machine in the pretreatment before the molding material is fed to the injection molding apparatus, the biomass resins are easily exposed to high temperatures for a long time. It is colored or low molecular weight. In particular, in order to provide flame retardancy to the biomass resin, a large amount of flame retardant (generally powder) needs to be kneaded with the bio resin, and the biomass resin and the flame retardant are preferably pelletized in advance by a kneading machine and then injected Supplied to the molding apparatus. However, the biomass resin is decomposed in the heat processing by the kneading machine, thereby reducing the strength of the molded article.

In addition, biomass resins are fragile and difficult to provide sufficient strength. In particular, a large amount of flame retardant needs to be kneaded with the biomass resin as described above, which becomes more fragile. Therefore, when the flame retardant is kneaded with the biomass resin to ensure flame retardancy, it is necessary to add a reinforcing agent to increase the strength.

The strength of biomass resins can be increased by mixing petroleum-based resins, but this does not essentially reduce the environmental load. Another method is to add inorganic fibers such as glass fibers or petroleum organic fibers. This method can provide strength without significantly reducing the bio-content of the molded article and is desirable. Another method is to form a natural molding material such as bamboo or kenaf fibers into fibers and add the natural molding material. In this case, the fiber portion can also be replaced with a carbon neutral material.

Thus, in order to use biomass resins as molding materials for injection molding, additives such as flame retardants or fibers are generally added. In view of the low heat resistance of the biomass resin, no pretreatment for mixing and kneading the biomass resin and additives pelletized for the quality of the molded product is carried out, but the biomass resin and additives are fed directly into the injection molding apparatus for molding. It is preferable to adopt a direct mixing (called a DM method).

However, injection molding apparatus are originally produced for feeding pellets, for example, containing at least a large amount of powder materials (including molding materials such as fine fibers corresponding to powder) and pellet materials among powder materials, pellet materials and liquid materials. There are two problems when the molding material is fed directly into the cylinder through the hopper of the injection molding apparatus.

The first problem is that when powdered and pelleted materials are fed directly, a bridge or the like due to compression of the hopper causes blockage at the hopper outlet port or cylinder to prevent a stable supply. Although the material can be supplied, the powder material and the pellet material are easily separated and become non-uniform in the cylinder and do not knead sufficiently uniformly. In particular, when the molding material contains a large amount of powder material, it is difficult to carry out a uniform dough by direct mixing. In particular, when the powder ratio of the molding material exceeds 30% by weight, uniform dough cannot be performed by conventional injection molding methods.

The second problem is that even if the powdered and pelleted material, once mixed by means of a stirrer or the like, is fed to the hopper, for example for the direct supply of the powdered and pelleted material, the powdered and pelleted materials are subjected to a specific weight or shape of the material during repeated injection molding. Is separated by the difference or vibration of the injection molding apparatus. Therefore, the ratio between the pellet material and the powder material fed from the hopper into the cylinder does not become as designed, which makes it difficult to stably produce a molded product having a uniform quality.

For example, Japanese Patent Application Laid-Open No. 2005-319813 describes a technique for solving the problem of gas separation or clogging of an injection molding apparatus, and Japanese Patent Application Laid-Open No. 2001-277296 describes a conventional direct mixing technique.

Japanese Patent Application Laid-Open No. 2005-319813 discloses a so-called hungry supply where the molding material is constantly supplied by the metering feeder mechanism rather than its own weight so as to form a space for separating gas components (occurring from the molding material) of the cylinder of the injection molding apparatus. hungry feeding). This enables reliable gas separation without clogging of the molding material in the cylinder, thereby enabling the production of molded products of high quality stably.

Japanese Patent Application Laid-Open No. 2001-277296 proposes that the basic resin is supplied by self weight into the cylinder of the injection molding apparatus, and the additive is supplied directly to the screw portion. Such a device is characterized by the fact that the additive is continuously supplied not only in the metering step but also in the injection step or the dwelling step. Specifically, it should be noted that the base resin is also supplied at the injection stage and the additive is also supplied at the injection stage as its supplement. Thus, the nonuniform concentration of the additive in the cylinder longitudinal direction in the cylinder can be improved.

An object of the present invention is to provide an injection molding method capable of stably producing a molded product having a high quality.

However, if the technique of Japanese Patent Application Laid-open No. 2005-319813 is applied to injection molding, in particular, direct mixing of biomass resins and molding materials containing additives (flame retardants, fibers, etc.), molded articles having high quality can be obtained. Can't. Japanese Patent Application Laid-Open No. 2005-319813 is directed to feeding pellets into a cylinder originally, and when a large amount of powder or fiber is supplied as a molding material, even dough can be carried out even if the material is fed directly from the hopper into the cylinder. And molded articles with stable quality cannot be obtained.

For comparison, in Japanese Patent Application Laid-Open No. 2001-277296, additives are metered and added at the same time as the resin pellets are naturally supplied by gravity. In addition, for additives only, the metered addition is carried out continuously while the screw is working without rotation, such as the injection step, as well as the metering step, thereby stabilizing the amount of additives (unevenness) in the molded article. . In this way, the additive is supplied even when the screw is advanced without rotation, such as in the injection step, which can reduce the color heterogeneity of the colorant and the variation of the additive concentration in comparison with the conventional method.

However, while the screw is advanced, for example during the injection step, the feed amount of the resin pellets varies differently than during the metering step. Therefore, it is impossible to control the ratio of the resin pellet falling by gravity and the additive to be weighed and supplied. In addition, because of the tendency of stagnation (holding) of the material in the material inlet port (part C2 of FIG. 1 of Japanese Patent Application Laid-open No. 2001-277296) to be large, the material is easily separated again. In particular, when the additive ratio of the molding material, that is, the powder material ratio is large, or when the apparent specific gravity of the powder material is small, it is impossible to sufficiently uniform the molding material, as in the present invention.

In fact, the techniques of Japanese Patent Application Laid-Open Nos. 2005-319813 and 2001-277296 can be applied to perform injection molding of molding materials containing a large amount of powder additives in pelleted biomass resins by direct mixing and to test the obtained molded products. When added, the additive is not uniformly dispersed in the biomass resin, and a molded article having an intended quality cannot be obtained.

From this background, in practice, the biomass resins and additives must be kneaded in advance by the kneading machine to be formed into pellets, and the pellets must be fed into the injection molding apparatus for molding.

However, as described above, the biomass resin has low heat resistance, and when high heat is applied in the pretreatment by the kneading machine, the molding material is degraded and reduced in molecular weight or colored before being fed into the injection molding apparatus. Thus, even if the molding material can be processed into pellets suitable for an injection molding apparatus, the molecular weight of the resin is reduced and the strength of the molded article cannot be provided, or the molded article is colored and of low quality.

The presently described subject matter is achieved in view of this situation, and molding materials, in particular molding materials containing at least one of powder and pellet materials among powder materials, pellet materials and liquid materials, are introduced into the cylinder through the hopper of the injection molding apparatus for injection molding. Injection molding can prevent the blockage of the cylinder and evenly mold the molding material even when supplied directly, so that, for example, a biomass resin having a low heat resistance can be stably produced with a high quality molded product even when used as a basic resin. It is an object to provide a method.

In order to achieve this object, the presently described subject stores the molding material fed into the cylinder of the injection molding apparatus at the tip of the cylinder by the rotation of the screw, and the screw is stored in the weighing set position by the pressure from the stored molding material itself. Providing a injection molding method comprising a metering step of measuring the amount of molding material by stopping the rotation of the screw after it is retracted, the metering step setting the back pressure applied to the screw to a predetermined value; Setting the rotational speed of the screw at a constant rotational speed within 50-300 rpm; Weighing time is twice the SN second, in which case the metering time in the normal feeding method in which the molding material is fed into the cylinder from the inlet port to fill the cylinder by the self-weight of the molding material according to the material feeding capacity of the screw's rotational speed And adjusting the feed rate of the molding material fed into the cylinder to be above 180 seconds or less, whereby the metering time is controlled irrespective of the rotational speed of the screw and the back pressure setpoint.

Here, the supply speed of the molding material is the supply amount of the molding material per unit time.

According to the presently disclosed subject matter, the metering time is not determined by the rotational speed of the screw, that is, the material supply capacity or the back pressure setting value of the molding material of the cylinder as conventionally, but the feeding speed of the molding material is the rotational speed and the back pressure setting value of the screw. The weighing time is thus controlled independent of the screw's supply capacity and back pressure setpoint (hereinafter referred to as "weighing time control"). Specifically, in the weighing time control, when the back pressure is set to a predetermined value, the rotational speed of the screw is set at a constant rotational speed of 50 to 300 rpm at which high kneading performance can be obtained, and the molding material fed into the cylinder The feed rate of is adjusted so that, in the case of SN, which is the metering time of the normal feeding method in which the cylinder is filled with the molding material, the metering time is not less than twice the SN and not more than 180 seconds.

The rotation speed of the screw is preferably 150 to 200 rpm, and the weighing time is more preferably 5 to 20 times the weighing time SN.

Thus, the screw can be rotated at a rotational speed suitable for the dough, and a long weighing time can be taken. Thus, even when a molding material made of, for example, a large amount of powder or fiber is directly supplied into the cylinder, the rotational speed of the screw or the kneading time required for uniformly kneading the molding material can be sufficiently ensured.

In this case, the rotational speed of the screw is set at 50 to 300 rpm in view of both the improvement of the kneading performance and the deterioration by shear heating. The back pressure set value may be set to a desired value, preferably 5 to 150 kg / cm 2.

In addition, a long metering time can be taken irrespective of the rotational speed of the screw and the back pressure setting value, so that the amount of feed of the molding material can be significantly reduced compared to the material feed capacity of the screw. Thus, even if a molding material containing, for example, a powder which easily causes bridging or clogging is fed directly into the cylinder, no bridging or clogging is caused.

In the presently described subject matter, when the inside of the cylinder is divided in this order from the inlet port of the molding material into three zones: the supply zone, the compression zone, and the metering zone, at least the space before the compression zone is preferably not filled with the molding material. Do.

"Cylinder not filled with molding material" means that the molding material is transferred from the cylinder to a loose state (lean state) rather than the airtight state (dense state), when the airtight state and the loose state are alternately formed in the cylinder. Also included.

This specifies the fullness of the molding material in the cylinder. At least the space before the compression zone is not filled with the molding material, and therefore also in the compression zone, which is a particularly important area for uniform kneading, the amount of material supplied is reduced and it takes a long time to generate the back pressure required for the retraction of the screw. . Specifically, the dough and dispersion time required can be sufficiently ensured. In this case, at the start of the injection molding, a "state at least in which the space before the compression zone is not filled with the molding material" is created, in which the molding material is more than for the average consumption of the molding material in the normal feeding method. It is added from the metered feeder at a low feed rate. Thus, the state where the cylinder is not filled with the molding material at the start of the injection molding can be maintained after the continuous injection molding.

In particular, for molding materials containing a large amount of powder, the molding material around the screw shaft remains unmelted in the compression zone and tends to wind around the screw shaft and feed into the metering zone. Thus, the molding material which has not been kneaded sufficiently uniformly reaches the metering zone, thereby lowering the quality of the injection molded product.

In the presently described subject matter, the weighing time is more than twice and less than 180 seconds of the weighing time SN of the normal feeding method, so that the supply amount of the molding material can be reduced with respect to the material feeding capacity of the molding material by the rotational speed of the screw. have. Thus, the fullness of the molding material of the compression zone is reduced to prevent excessive shear heating, and a long kneading time can be taken. Therefore, even a molding material containing a large amount of powder can be uniformly kneaded.

In the presently described subject matter, the metering time is preferably controlled according to the required kneading time of the molding material. The required kneading time of the molding material is the time required for the molding material to be kneaded uniformly in the cylinder, as described above, and can be calculated by preliminary tests or the like. However, when the required dough time exceeds 180 seconds described above, the required dough time is set to 180 seconds.

In the presently described subject matter, the metering time is preferably controlled in accordance with the time from the start of the cooling phase of the injection molding cycle to the end of the release phase. Therefore, there is no need to provide time (waiting step) when the rotation of the screw is stopped from the start of the cooling step to the end of the release step. Thus, the molding material can be kneaded sufficiently, and heterogeneous heating of the molding material by the stop of the screw can be prevented.

While the presently described subject matter can be applied to molding materials in pellet form, it is preferred that the molding material contains a base resin and additives, the at least one base resin and additives are powders, and the unpelleted molding material is fed directly into the cylinder. Do. In particular, the basic resin is at least one of a polylactic acid resin and a cellulose resin, and the additive is preferably at least one of a flame retardant and a fiber. In this case, the ratio of the biomass resin of the molding material is preferably at least 30% by weight, particularly preferably at least 50% by weight. This can contribute to reducing environmental load.

The fact that the molding material is fed directly into the cylinder means that the pretreatment processing in which the molding material is kneaded in advance by a kneading machine or the like and then pelletized is not performed.

High quality molded articles are stable when biomass resins with low heat resistance and additives in the form of powders or fibers (such as flame retardants or fibers) that are added in bulk and are difficult to homogeneously knead directly into the cylinder for injection molding Can be produced.

The ratio of the powder of the molding material is preferably at least 30% by weight, since the presently described subject matter is particularly effective by this high powder ratio. The powder ratio is particularly preferably 50% by weight or more.

In the presently disclosed subject matter, it is preferable that a small amount of molding material is continuously fed into the cylinder or the molding material is fed intermittently into the cylinder to adjust the feed rate.

This can reduce the feed rate and make it easy to equalize the feed rate, thereby preventing the change in the dough of the weighing step.

In the presently described subject matter, the molding material is a molding material containing at least the powder material and the pellet material among the powder material, the pellet material and the liquid material, and one injection shot of each material is fed into the cylinder using a separate metering feeder and supplied. The feeding time period from the start to the end of is synchronized at least 60% and the feeding is preferably terminated within the metering time of the metering phase of the injection molding cycle.

In addition to "measurement time control", a "synchronization feed" is thus performed in which the material is synchronized at least 60%. Thus, even if the molding material contains a high powder ratio, a more uniform dough can be performed.

In order to achieve the above object, the presently disclosed subject matter provides an injection molding method in which a molding material containing at least the powder material and the pellet material among the powder material, the pellet material and the liquid material is fed directly into the cylinder of the injection molding apparatus for injection molding. And the method comprises: feeding one injection shot of each material into the cylinder using a separate metering feeder such that the feed time period from start of feed to end is synchronized by at least 60%; And ending the supply within the metering time of the metering step of the injection molding cycle.

This aspect takes the " synchronized supply " described above as one feature, and the advantages of the presently described subject matter can be achieved by performing only synchronous supply without performing metering time control.

The powder material includes fine fibers corresponding to the powder and the like, and the pellet material includes granular material having a larger size than the powder.

According to the synchronous feeding of the injection molding method of the presently described subject matter, one injection shot of each molding material containing at least powder material and pellet material is weighed separately so that the feeding time period from the start of the feeding to the end is synchronized by 60% or more. Supplied by the feeder (hereinafter referred to as "synchronized feed"). The feeding time period is more preferably at least 90% synchronized. Thus, the feeding time period is synchronized by 60% or more, so that the molding material can be uniformly kneaded in the cylinder even if the molding material contains powder material and pellet material having different shapes or specific gravity. The fact that the feed time period of the material is synchronized more than 60% means that the overlap of the feed time period of the material is more than 60%.

In Japanese Patent Application Laid-Open No. 2001-277296 as a prior art, the additives added and metered simultaneously with the resin pellets are spontaneously driven by gravity in the weighing step when the screw is not rotated but is operated in addition to the weighing step (eg, injection step). It is continuously metered and added to the resin pellets fed into it, thereby stabilizing the amount (heterogeneity) of the additives in the molded article. By this method, the additive is supplied even when the screw is not rotated as in the injection stage but advanced, and the variation of the additive concentration or the color irregularity of the colorant can be reduced when compared with the conventional method.

However, for example during the advancement of the screw in the injection step, the feed amount of the resin pellets varies differently than in the metering step. Therefore, the ratio between the resin pellets dropped by gravity and the additives constantly supplied cannot be controlled. Also, a large amount of material tends to accumulate at the material inlet port (C2 portion of FIG. 1 of Japanese Patent Application Laid-Open No. 2001-277296), and the material is easily separated again. In particular, as in the presently described subject matter, when the additive ratio, ie the powder material ratio of the molding material is high, or the apparent specific gravity of the powder material is low, the molding material cannot be made sufficiently uniform.

In contrast, in the presently described subject matter, additives are supplied upon supply of resin pellets, and the ratio between the additives and the resin pellets can be kept constant. A level sensor of the molding material is provided in close contact with the screw (just above), thereby reducing the amount of molding material that accumulates. This substantially prevents uneven separation of the molding material before it is fed into the screw and makes it possible to obtain a stable injection molded product.

Thus, according to the presently disclosed subject matter, even if materials such as pellet materials and powder materials having different shapes or specific gravity are fed directly into the cylinder through the hopper, the ratio between the powder material and the pellet materials becomes as easy as designed, thereby It makes it possible to stably produce molded articles with uniform quality.

It is also preferred that the metering time control described above is combined with the "synchronized feed" of the presently described subject matter as described above. Also in "synchronized feed", it is preferable that the molding material contains a base resin and an additive, the base resin is at least one of a polylactic acid resin and a cellulose resin, and the additive is at least one of a flame retardant and a fiber.

According to the injection molding method of the presently disclosed subject matter, weighing time control is performed, so that even if a molding material, especially a molding material containing a large amount of powder, is directly supplied into the injection molding apparatus by direct mixing, clogging can be prevented, The molding material may be kneaded sufficiently uniformly in the cylinder.

According to the injection molding method of the presently disclosed subject matter, a synchronous feed is carried out, and thus a molding material containing at least the powder material and the pellet material among the powder material, the pellet material and the liquid material is cylinderd for injection molding through the hopper of the injection molding apparatus. Even if fed directly in, the molding material can be kneaded uniformly in the cylinder.

Therefore, even if a biomass resin having low heat resistance is used as the base resin, molded articles having high quality can be stably produced.

In addition, metering time control and synchronized feed can be combined to provide better benefits.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure diagram of the injection molding apparatus which implements the injection molding method which concerns on the 1st Embodiment of the presently described subject matter.
2 is a diagram showing a zone configuration of an injection molding apparatus.
3 is a view showing a general injection molding cycle.
4 is a diagram showing a general relationship between a back pressure increase rate and a screw rotation speed.
5 is a view showing the behavior of the compression zone when the molding material containing 100% pellets is injection molded.
6 is a view showing the behavior of the compression zone when a molding material containing at least 30% by weight of powder is injection molded.
7 (a) to 7 (c) are views showing the position of the screw in the weighing step of the presently described subject matter.
8 is a diagram showing a schematic configuration diagram of an injection molding apparatus for executing an injection molding method according to the second embodiment of the presently described subject matter.
9 is a diagram illustrating synchronization supply.
10A is a table showing the injection conditions and results of the Examples of Test A. FIG.
10B is a table showing the injection conditions and results of the comparative example of Test A. FIG.
11A and 11B are photographs each showing a comparison of the adhesion state of the powder material to the screw shaft between the Example of Test A and the Comparative Example.
12A is a table showing the injection conditions and results of the Examples of Test B. FIG.
12B is a table showing the injection conditions and results of the comparative example of test B. FIG.
13A is a diagram illustrating a normal supply.
13B is a diagram illustrating a Hungry feed.
FIG. 13C shows a “scattering feed” of the presently described subject matter. FIG.
FIG. 13D illustrates a further advanced state of "scattering supply" of the presently described subject matter.
13E is a diagram showing the extreme state of "scattering supply" of the presently described subject matter.
14 is a table showing Examples and Comparative Examples of Test C. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the presently described injection molding method will now be described with reference to the accompanying drawings. In addition, the numerical range expressed using "-" in this description means the range containing the numerical value described before and after "-".

[First embodiment]

A first embodiment of the presently described subject matter relates to the metering time control of an injection molding method.

1 is a schematic structural diagram of an embodiment of an injection molding apparatus for implementing the presently described injection molding method.

As shown in FIG. 1, the injection molding mechanism 10 includes a cylinder 14 having a nozzle 12 at the tip, and the screw 16 is provided to the cylinder 14 in a rotational manner. At the end opposite to the nozzle 12 and at the rear end of the screw 16, a motor / piston device 22 is provided, which sets the motor 18 for rotating the screw 16 and the set values of pressure and speed. Basically it comprises a piston device 20 for advancing and retracting the screw 16 in the axial direction (the transverse direction in FIG. 1) with a constant stroke. The piston device 20 causes the screw 16 to advance to the left in FIG. 1 to perform the injection operation. In the piston device 20, a back pressure sensor 17 is provided for detecting back pressure which causes the screw 16 to retract in the metering step, and the measured value is input to the controller 41 described later. The controller 41 is input from the motor / piston device 22 to signal the start and end of the weighing step.

The heater 24 is wound around the outer periphery of the cylinder 14, and the cylinder 14 is heated to a predetermined temperature based on the melting temperature (plasticization temperature) or the like of the molding material to be injection molded. The tip of the nozzle 12 is connected to the gate 32 of the mold 30 forming a cavity 28 therein. The mold 30 includes the stationary mold 30A and the movable mold 30B, and the movable mold 30B is opened and closed with respect to the stationary mold 30A.

In the longitudinal direction of the cylinder 14, an inlet port 25 for supplying a base resin, additives, and the like as a molding material into the cylinder 14 is formed at an opposite end of the nozzle 12, and the hopper 26 is an inlet port. It is attached to 25.

As shown in FIG. 2, the inside of the cylinder 14 is divided in this order from the inlet port 25 of the molding material into three zones: the supply zone, the compression zone and the metering zone. The molding material fed from the hopper 26 into the feed zone via the inlet port 25 is transferred from the cylinder 14 to the tip side of the screw by the rotation of the screw 16. Molding material transferred from the cylinder 14 is transferred to the heat of shear generated between the inner surface of the cylinder 14 and the surface of the rotating screw 16 and from the heater 24 provided around the outer periphery of the cylinder 14. Gradually melted. In the compression zone, melting and kneading of the molding material begins. The molded resin melted and kneaded in the compression zone is further forwarded and reaches the metering zone. Since the molten and kneaded molding material accumulates at the tip of the cylinder 14, the screw 16 is retracted, and the retraction is stopped when the screw 16 reaches the metering setting position.

The material supply device 34 is mainly a mixer 36 for mixing the additives and the base resin constituting the molding material, the granular material metering feeder 38, the metering control feeder 40 and the controller for controlling the supply of the molding material, for example. (41). Mixer 36 may include a stirred mixer, a vibrating mixer, an airflow mixer, and the like, capable of uniformly mixing the base material and the additives. The granular material metering feeder 38 includes a table feeder, a belt feeder, a screw feeder, a rotary feeder, a bin discharger, a circular feeder, and the like, which are suitably used according to the properties of the molding material.

The molding material containing the additive and base resin mixed in the mixer 36 is cut into a predetermined amount by the granular material metering feeder 38. The cut molding material is supplied to the metering control supply 40 through the launcher 42. A sensor 44 is provided to the metering control supply 40, which detects whether the molding material is stored in the metering control supply 40 and sends the result to the controller 41. The controller 41 has a fixed amount of time required for one cycle of the weighing step in the time period when the weighing control supply 40 is at standby, ie, when the molding material is not stored in the weighing control supply 40. Molding material is supplied from the granular material metering feeder 38 to the metering control feeder 40.

Type of molding material (type of resin, type of additive, etc.), shape of material (powder, granule, liquid, pellet), mixing ratio (ratio between base resin and additive), injection molding conditions (injection amount of 1 shot, cylinder Kneading time data required for the molding material to be uniformly and sufficiently kneaded is input to the controller 41 according to various factors such as heating temperature, screw rotation speed, back pressure set value, and the like. The required dough time data can be obtained in advance by preliminary tests or the like. In addition, the relationship between the weighing time to ensure the required dough time and the feed rate of the molding material from the weighing control feeder 40 is input to the controller 41.

The controller 41 sets the back pressure to a predetermined value and sets the rotation speed of the screw 16 to a constant rotation speed within 50 to 300 rpm. In the meantime, when the metering time of the normal supply in which the molding material is supplied from the inlet port 25 into the cylinder 14 to fill the cylinder 14 by its own weight according to the material feeding capacity of the screw rotational speed, the controller ( 41) adjusts the feed rate of the molding material fed into the cylinder 14 so that the weighing time is more than twice the SN second and less than 180 seconds. Specifically, the controller 41 adjusts the feed rate of the molding material from the metering control feeder 40 through the hopper 26 to the cylinder 14 irrespective of the back pressure set value and the rotational speed of the screw 16, The controller 41 thereby controls the metering time of the metering step from 2 times to 180 seconds of SN depending on the required kneading time of the molding material ("metering time control"). A more preferable weighing time in weighing time control is 5 to 20 times SN second.

Thus, the screw 16 can be rotated at a rotational speed suitable for the dough, and a long weighing time can be taken. Thus, for example, when a molding material containing a large amount of powder or fiber is fed directly into the cylinder, the screw rotation speed or the required kneading time required for uniformly kneading the molding material can be sufficiently ensured.

In this case, the rotational speed of the screw is preferably set at 50 to 300 rpm in view of both deterioration by shear heating and improvement of the kneading performance. More preferably, the rotational speed of the screw is 150-200 rpm. At screw rotation speeds of less than 50 rpm, uniform kneading cannot be performed sufficiently, and at screw rotation speeds above 300 rpm, shear heating may degrade the molding material. In particular, when the base resin of the molding material is a biomass resin, screw rotation speeds exceeding 300 rpm are likely to deteriorate the molding material.

When the feed rate of the molding material fed into the cylinder is set such that the weighing time is less than twice when the weighing time of the normal feeding method in which the cylinder is filled with the molding material, the uniform dough cannot be performed. In the meantime, when the metering time is increased to exceed 180 seconds, uniform dough can be performed, but low molecular weight by decomposition of the base resin occurs to reduce the strength of the molded article obtained by injection molding. Therefore, if the required kneading time obtained by the preliminary test exceeds 180 seconds, the required kneading time is preferably set to 180 seconds.

Now, the injection molding cycle of the injection molding apparatus will be described with reference to FIG. 3.

The injection molding cycle generally includes a metering step, a mold clamping step, an injection step, a dwelling step, a cooling step, and a release step.

In the metering step (also called the plasticizing step), the molding material fed from the hopper 26 into the heated cylinder 14 is kneaded, melted (plasticized) and pressure feed by the rotation of the screw 16. And the molten molding material is stored in the cylinder tip 14A. The screw 16 is rotated and retracted by the pressure received from the stored molding material itself, and when the preset weighing value is reached, the rotation of the screw is stopped and the metering ends. The time required for the weighing step is called the weighing time.

In the mold clamping step, the mold 30 including the fixed mold 30A and the movable mold 30B in the open state is closed, and the mold clamping cylinder (not shown) moves the movable mold 30B to the fixed mold 30A. It is moved toward the fixing mold 30A so as to be in contact with, thereby closing the mold 30.

In the injection step (also called the filling step), the molding material molten in the liquid state in the cylinder 14 is injected into the mold 30 through the nozzle 12 by the advancement of the screw 16. Thus, the molten molding material is filled into the cavities 28 of the mold 30.

In the dwelling step, the screw 16 pressurizes into the cavity 28 even after the molten molding material is filled into the cavity 28 of the mold 30 in the injection step. Thus, the molding material of the cavity 28 is formed in the shape of the cavity.

In the cooling step, the molding material is cooled and solidified so that the molded article has sufficient rigidity when released from the mold.

In the release step, the mold clamping cylinder moves the movable mold 30B in a direction away from the stationary mold 30A to open the mold 30. Thus, the molded article is released from the mold 30.

In the step described above, the screw 16 is freely movable after completion of the dwelling. Thus, as shown in FIG. 3, the metering step of the n + 1th cycle overlaps as much as possible with the cooling step of the nth cycle to increase the efficiency of the molding cycle.

4 is a diagram showing a general relationship between the rotational speed of the screw 16 and the increase rate of back pressure in the above-described metering step. As is evident from the straight line constantly increasing from left to right in FIG. 4, the back pressure increase rate increases with increasing rotation speed of the screw 16. Therefore, if the rotational speed of the screw 16 is increased to increase the shear force of the molding material, the back pressure increases in a short time, and the metering step ends. Thus, a long time for kneading the molding material cannot be guaranteed.

In contrast, if the rotational speed of the screw 16 is reduced, the time required to increase the back pressure is extended to ensure a long kneading time. However, because the rotation speed of the screw 16 is low, shearing force for sufficient dough cannot be applied to the molding material.

Therefore, in the conventional injection molding method in which the weighing time of the weighing step is determined with reference to the rotational speed and the back pressure set value of the screw 16, a long dough time cannot be guaranteed. If the cooling time required in the cooling step is longer than the metering time of the weighing step, a waiting step after the end of the weighing step is required between the weighing step and the mold clamping step, as shown in the injection molding cycle of FIG. The waiting step is a state where the weighing step is finished and the screw 16 is stopped, and thus waiting is performed with the dough stopped. Thus, the kneading time of the molding material cannot be sufficiently ensured, and there is a possibility that the screw 16 is stopped and inhomogeneously heats the molding material, thereby easily causing a plastic distribution.

In particular, for molding materials such as biomass resins that require the addition of a large amount of additives such as flame retardants or fibers to improve quality, the materials need to be sufficiently stirred and kneaded in the metering step, It is important to fully use the time from the start to the end of the release phase.

Therefore, if the rate of back pressure increase is low despite the high rotational speed of the screw 16 as in zone A of FIG. 4, both high shear force and kneading time can be satisfied.

Thus, as described above, in the presently described subject injection molding method, the feed rate of the molding material from the hopper 26 into the cylinder 14 is required regardless of the rotational speed and the back pressure set value of the screw 16. It is adjusted to control the weighing time according to the dough time.

Specifically, when factors such as the type of molding material or molding conditions are input to the controller 41, the controller 41 selects the weighing time required for the molding material from the required dough time data input. The controller 41 also calculates the feed rate of the molding material for one cycle stored in the weighing control feeder 40 so that the weighing time from the start of the weighing to the end becomes the required dough time, and the feed rate is supplied to the weighing control feeder. Set to (40). Thus, the metering control feeder 40 supplies the molding material for one cycle through the hopper 26 into the cylinder 14 on the basis of the calculated feed rate.

For example, when the kneading time required for uniformly and sufficiently kneading the biomass resin and the additives (flame retardant and glass fiber) is 20 seconds, the feed rate of the molding material for one cycle stored in the metering control feeder 40 is measured. The metering time of the step is controlled to be at least 20 seconds or more. In this case, the feed rate from the start to the end of the metering step is preferably as same as possible. Therefore, a small amount of continuous supply method (scattering supply) in which a small amount of molding material is continuously dropped from the metering control supply 40 onto the hopper 26 in a scattering manner, or a constant amount of molding material is removed from the metering control supply 40. It is preferable to adopt an intermittent feeding method which intermittently falls onto the hopper 26 at regular intervals.

Thus, the screw 16 can be rotated at a suitable high speed for the dough, and a long metering time can be taken when the screw 16 is operated in rotation. Thus, even if a molding material containing a large amount of powder or fibers is fed directly into the cylinder 14, sufficient dough can be performed.

The long metering time can be taken irrespective of the rotational speed of the screw 16, so that even if the molding material containing the powder is fed directly into the cylinder 14, the material feeding capacity of the screw 16 is equal to the feed rate of the molding material. It is definitely higher when compared. This prevents clogging of the molding material in the cylinder 14 or at the outlet port of the hopper 26.

In particular, when the powder ratio of the molding material is 30% by weight or more, the presently disclosed injection molding method enables uniform dough, and injection without clogging of the molding material in the cylinder 14 or at the outlet port of the hopper 26. To enable molding.

Specifically, even if the molding material contains a petroleum-based resin having high heat resistance and a powder material as an additive, the molding material can be pelletized by the kneading machine as a pretreatment of the injection molding, so that all the molding material is pelletized into a cylinder ( 14) Can be supplied in However, even if the molding material contains a large amount of powder material as biomass resin and additives having low heat resistance, the molding material cannot be pelletized by the kneading machine as a pretreatment of injection molding, so that the bulk additive in powder form (14) is fed directly into.

The melting behavior of the molding material in the compression zone is determined when the molding material containing 100% pellets is fed directly into the cylinder 14 (DM method), and molding containing at least 30% by weight of powder, in particular at least 50% by weight of powder. It is completely different from when the material is fed directly into the cylinder 14 (DM method). Specifically, most powder materials (including fiber materials), such as flame retardants, compatibilizing agents, or stabilizers used as additives, do not melt. Thus, even if shear is applied to the powder material in the same manner as when shear is applied to the resin pellets, heat is rapidly generated by friction between the powder material and the cylinder inner wall surface to degrade the resin. In addition, the powder material is bulkier than pellets and easily causes gaps in the cylinder, and heat from the heater 24 provided around the outer circumference of the cylinder is not easily transferred. Thus, in the compression zone, only the molding material near the inner wall surface of the cylinder 14 is heated and melted to a high temperature, and heat is not easily transferred to the molding material on the shaft side of the screw 16, and the molding material is Does not melt easily Therefore, in short time metering, the molding material near the shaft side of the screw 16 is supplied to the tip of the screw through the metering zone without melting. Therefore, uniform kneading of the molding material containing a large amount of powder material cannot be performed, and the quality (strength, flame retardancy, color of appearance, etc.) of the molded product obtained by injection molding is lowered. In fact, when a molding material containing 30% by weight or more of powder material is molded by a conventional molding method, the screw 16 is pulled out of the cylinder 14 and observed at this time, and near the inner wall surface of the cylinder 14. Of the molding material is melted at the end position of the compression zone, and the molding material near the shaft of the screw 16 remains unmelted in powder form. This will be explained in more detail with reference to FIGS. 5 and 6.

5 shows the melting behavior of the molding material in the compression zone when the molding material containing 100% pellets is fed into the cylinder by a conventional normal feeding method of feeding the molding material into the cylinder 14 to fill the cylinder 14. It is a figure which shows. At the inlet of the compression zone, as shown by part A of FIG. 5, a solid bed layer S of unmolded molding material is formed, and a molten film layer M of molten molding material is formed inside the cylinder 14. It is formed on the wall surface. When the molten film layer M is formed, the heat generated by the shear energy melts the solid bed layer S, and as shown in part B of FIG. 5, a molten pool in which unmolded molding material is dispersed ( melt pool (P) forms in the center of the compression zone. As shown in part C of FIG. 5, at the outlet of the compression zone, there is little unmelted molding material in the melt pool P. This allows for a uniform dough.

FIG. 6 is a diagram showing the melting behavior of the molding material in the compression zone when molding material containing 30% by weight or more of powder (the remaining pellets) is fed into the cylinder 14 by a conventional normal feeding method. At the inlet of the compression zone, as shown in part A of FIG. 6, the powder and pellets are separated during the delivery of the screw 16, the pellet layer X is formed on the cylinder 14 side, and the powder layer Y ) Is formed on the shaft side of the screw 16. The pellet layer X close to the cylinder 14 is first melted to form a molten film layer M as shown in part B of FIG. 6. However, with the powder layer Y, the melt pool P is not formed over the compression zone as in the case of 100% pellets, thereby reducing heat transfer to the entire compression zone. Thus, as shown in part C of FIG. 6, also at the outlet of the compression zone, the powder layer Y is attached around the shaft of the screw 16 and wound around the shaft of the screw 16 and fed to the metering zone. do. Thus, the molding material that has not been kneaded sufficiently uniformly reaches the metering zone, thereby lowering the quality of the injection molded product.

When a biomass resin such as polylactic acid is used as the base resin, the melting point of the polylactic acid is around 170 ° C., but decomposition starts rapidly around 220 ° C. Melting point temperature and decomposition temperature are close and therefore heating and melting are very difficult. Since the fluidity is very low around the melting point, it is desirable to melt the molding material at as high a temperature as possible. In particular, molding materials containing at least 30% by weight of powders and polylactic acid based resins which are not easily melted as described above can only be heated and melted when the molding set temperature is increased to around 200 ° C. However, in a molding material containing a large amount of powder material, the temperature is increased by 15 to 25 ° C. above the molding set temperature of the cylinder 14 by shear heating, and the temperature of the cylinder is increased to around 220 ° C.

However, even when the molding material containing 30% by weight or more of powder is directly supplied into the cylinder 14, a long weighing time is ensured regardless of the screw rotational speed and the back pressure setting value, thereby ensuring the screw rotational speed required for the dough, This significantly reduces the density of the molding material in the cylinder 14, in particular in the compression zone. Therefore, excessive shear is not applied to the molding material, thereby preventing an increase in the temperature of the cylinder due to shear heating. Even at the low density of the molding material of the cylinder, a long metering time is ensured so that the heat on the cylinder 14 side is slowly transferred to the shaft side of the screw 16 and the screw rotational speed is increased with the long metering time guaranteed. Can thereby increase the dough efficiency. Therefore, even in a molding material containing 30% by weight or more of powder, the melt pool P is easily formed over the compression zone, thereby enabling uniform dough without lowering the quality of the molded product.

For uniform dough that does not lower the quality of the molded product, when the back pressure is set to a predetermined value, the rotational speed of the screw 16 is set at a constant speed of 50 to 300 rpm suitable for the dough, and the feed rate of the molding material is adjusted. It can be achieved by ensuring twice the weighing time SN seconds (SN is the weighing time of the normal supply method) to 180 seconds, regardless of the back pressure setpoint and the rotational speed of the screw 16 to ensure the weighing time. .

In this case, the molding material is preferably supplied so that at least one of the three zones of the cylinder 14: the supply zone, the compression zone, and the metering zone is not filled with the molding material. That is, at the start of injection molding, a state is formed in which at least the space before the compression zone is not filled with the molding material, in which state the molding material is at a lower feed rate than for the average consumption of the molding material of the normal feeding method. It is preferably added from the metering feeder 40. Thus, the state where the cylinder 14 is not filled with the molding material at the start of injection molding can be maintained after subsequent injection molding.

In particular, the compression zone is not filled with the molding material, so heat transfer from the cylinder 14 side to the shaft side of the screw 16 is increased, thereby facilitating the melting of the powder layer formed on the shaft side.

The required metering time of twice to 180 seconds of the metering time SN can be determined in advance by testing or the like from the composition of the molding material or the conditions of the injection molding apparatus or the like. The range of 2 times to 180 seconds of the metering time SN is no problem for molding materials containing 30% by weight or more of powder, and can be applied to molding materials containing 100% pellets with less stringent molding conditions.

The metering time controlled according to the kneading time required can be set within the total time of the cooling step and the releasing step in view of the mixing properties of the materials. The metering time is preferably matched to the total time of the cooling step and the releasing step, since higher dough performance can be obtained.

This can eliminate the waiting step described above, so that the rotational state of the screw 16 can always be maintained in the metering step.

When the weighing time is longer than the total time, it is preferable that the condition with the increased rotational speed of the screw 16 is selected from the dough time data required, and the weighing time matches the total time.

7 (a) to 7 (c) are diagrams showing images of the weighing step when the weighing time controlled according to the required dough time matches the total time of the cooling step and the releasing step. The feed rate of the molding material at this time is Q grams per minute (g / min). FIG. 7A is a view showing the start of the cooling step, FIG. 7B is a view showing the end of the cooling step, and FIG. 7C is a view showing the end of the release step. In the forward and backward strokes of the screw 16, the most advanced position (left position in FIG. 7) is the X position and the most retracted position is the Y position.

At the same time as the start of the cooling step in FIG. 7A, the molding material is fed into the cylinder 14 at a feed rate of Q g / min to start the metering step. The position of the screw 16 at this time is the X position of the side closest to the nozzle in the forward and backward strokes of the screw 16.

When the molding material is supplied, the back pressure is increased, and the screw 16 is rotated by the back pressure and gradually retracted. Then, as shown in Fig. 7B, at the end of the cooling step, the screw 16 is located slightly closer to the Y side than the middle between the X position and the Y position. In addition, when the molding material is continuously supplied, the screw is retracted, and as shown in Fig. 7C, the screw 16 reaches the Y position at the same time as the end of the release step.

Thus, in the injection molding method according to the first embodiment of the presently described subject matter, the weighing time can be controlled according to the required dough time. Therefore, in the molding material which requires a long time for the dough, a uniform and sufficient dough can be performed. Accordingly, the presently described subject matter is particularly effective as an injection molding method by direct mixing of biomass resins.

Second Embodiment

A second embodiment of the presently described subject matter relates to the synchronized supply of injection molding methods.

The presently-synchronized supply of the subject matter is such that molding material containing at least powder and pellet material among the powder material, pellet material and liquid material is introduced into the cylinder 14 through the hopper 26 of the injection molding apparatus 10 for injection molding. Even when directly supplied, it can be performed to prevent clogging and to knead the molding material of the cylinder 14 uniformly.

However, needless to say, the synchronization feed is combined with the "metering time control" described above to further provide the benefits of the synchronization feed.

FIG. 8 is a diagram showing a schematic configuration diagram showing an embodiment of an injection molding apparatus capable of executing synchronization supply. FIG. The basic configuration of the injection molding apparatus 10 is the same as that of FIG. 1, and the material supply apparatus 134 is configured to perform synchronous supply.

Therefore, the structure of the injection molding main main body of the injection molding mechanism 10, and description of FIGS. 2-7 overlap and are abbreviate | omitted here.

The synchronized feed of this embodiment will be explained by an example of injection molding using two kinds of materials: powder material and pellet material, but it can also be applied to three kinds of materials: powder material, pellet material and liquid material. .

The material supply device 134 mainly includes a powder supply device 135 for supplying the powder material to the hopper 26, and a pellet supply device 137 for supplying the pellet material to the hopper 26.

The powder supply device 135 includes a powder mixing tank 135B including an agitator 135A and a drying device (not shown), and a powder metering feeder 135C for supplying the powder material to the hopper 26. In the molding material, various kinds of powder materials, which are powders or materials corresponding to the powder (e.g., fibers), are dry blended in advance in the powder mixing tank 135B, and then the molding material for one injection shot is supplied with a powder metering feeder ( 135C) is supplied to the hopper 26.

The pellet feed device 137 includes a pellet mixing tank 137B including a stirrer 137A and a drying device (not shown), and a pellet metering feeder 137C. In the molding material, various kinds of pellet materials, which are pellets or materials corresponding to the pellets (large-sized granules), are dry blended in advance by the pellet mixing tank 137B, and then the molding material for one injection shot is pelleted. It is supplied to the hopper 26 by the metering feeder 137C. Dry blending refers to blending the material while it is drying.

In Fig. 8, the powder metering feeder 135C and the pellet metering feeder 137C are shown as screw feeders, but table feeders, belt feeders, rotary feeders, barrel ejectors, circular feeders, vibratory cutting devices using shearing forces, and the like are employed. And they are suitably used according to the properties of the molding material.

In the hopper 26, an upper limit level sensor 140 and a lower limit level sensor 143 are provided for detecting the storage amount of the molding material in the hopper 26. The level signal H from the upper limit level sensor 140 and the level signal L from the lower limit level sensor 143 are input to the controller 139 via a signal cable or without wires. The controller 139 controls the feed time and feed rate of the pellet metering feeder 137C and the powder metering feeder 135C based on the level signals H and L so that the storage amount of the molding material in the hopper 26 is at an upper limit level. It becomes between the sensor 140 and the lower limit level sensor 143. Specifically, the time when the powder material and pellet material for one injection shot supplied to the hopper 26 from the powder metering feeder 135C and the pellet metering feeder 137C is stored in the hopper 26 is as short as possible. . This prevents the molding material from accumulating in the hopper 26 and separating the powder material and the pellet material.

Hopper 26 need not have the function of storing material, but may have a small size that prevents the material from overflowing. Thus, the hopper 26 in the synchronization feed can have a size about half the size of the hopper 26 shown in FIG. 7.

In this embodiment, the injection molding apparatus transfers one injection shot of the dry blended powder material of the powder mixing tank 135B and one injection shot of the dry blended pellet material of the pellet mixing tank 137B to the hopper 26. The feeding time period from the beginning to the end of the feeding of the material used to feed is synchronized at least 60%, preferably at least 90%. This supply method of synchronous method is called "synchronized supply".

FIG. 9 shows an embodiment of a synchronized supply of powder material and pellet material having different shapes, with part A of FIG. 9 representing 100% synchronization and part B of FIG. 9 representing 50% synchronization.

Thus, by 60% or more synchronization, the blend ratio between the powder material and the pellet material is easily obtained, even if a material such as powder material and pellet material having a different shape or specific gravity is directly supplied into the cylinder 14 through the hopper 26. It can be as designed.

The controller 139 molds from the hopper 26 into the cylinder 14 within the weighing time of the weighing step of the injection molding cycle based on the weighing signal informing the start and end of the weighing step from the motor / piston device 22. Supply of material is terminated. Thus, powder material and pellet material having different shapes can be smoothly taken from the inlet port 25 into the cylinder 14 during the rotation of the screw, thereby preventing the separation of the material taken.

Thus, one injection shot of each material having a different shape or specific gravity is fed into the cylinder 14 using separate metering feeders 135C and 137C so that the supply time period from the start to the end of the feed is synchronized by at least 60%. And the supply is terminated within the metering time of the metering step of the injection molding cycle, thereby making it possible to stably produce a molded product having a uniform quality.

In this embodiment, a molding material feeder 141 of the table feeder type is provided in the lower part of the hopper 26 and is supplied into the cylinder 14 from the hopper 26 by the instruction from the controller 139. A " measurement time control " in which the feed rate of is controlled regardless of the rotational speed of the screw 16 and the back pressure set value is combined.

Weighing time control has been described in the first embodiment and description thereof will be omitted here. In the second embodiment, the kneading time data required for uniformly and sufficiently kneading the molding material includes the type of molding material (type of resin, type of additive, etc.), shape of the material (powder, granule, or pellet), mixing ratio (The ratio between the base resin and the additive) and the injection molding conditions (injection amount of one shot, the heating temperature of the cylinder, the rotational speed of the screw, the back pressure set value, etc.) are input to the controller 139 according to various factors.

When factors such as the type of molding material or molding conditions are input to the controller 139, the controller 139 selects a weighing time required for the molding material from the inputted dough time data input. The controller 139 also calculates the feed rate of the molding material stored in the weighing control feeder 141 so that the weighing time from the start of the weighing to the end is required dough time, and the speed is transferred to the weighing control feeder 141. Set it. Accordingly, the metering control feeder 141 feeds the molding material stored in the hopper 26 into the cylinder 14 on the basis of the calculated feed rate.

Thus, the screw 16 can be rotated at a suitable high speed for the dough, and a long metering time can also be taken when the screw 16 is operated rotationally. Thus, for example, a molding material containing a large amount of powder or fibers is fed directly into the cylinder 14, and sufficient dough can be performed. A long metering time can be taken irrespective of the rotational speed of the screw 16, so that even if the molding material containing powder is fed directly into the cylinder 14, the feeding capacity of the screw 16 can be compared with the feeding speed of the molding material. When it is definitely higher. This prevents clogging of the molding material in the cylinder 14 or at the outlet port of the hopper 26.

Synchronous feeding of the second embodiment is particularly effective when the direct mixing (DM method) is carried out using a molding material having a powder ratio of at least 30% by weight, more preferably at least 50% by weight. This is because powder material having a specific gravity and shape different from the pellet material is easily separated by time in the hopper 26, and the synchronization feed is extremely effective in preventing separation.

Next, preferable conditions of the molding material used in the first and second embodiments of the presently described subject matter will be described.

The presently described subject matter can be applied to petroleum based resins, but is preferably applied to biomass resins such as polylactic acid resins or cellulose based resins.

For example, various polylactic acid resins can be used, including lactic acid homopolymer resins and lactic acid copolymer resins. The lactic acid component which is a raw material of the polylactic acid resin is not particularly limited, but for example, L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, lactic acid cyclic dimmer meso-lactide, or mixtures thereof) may be used.

The production method of the polylactic acid used in the presently described subject is not particularly limited, but various kinds of resins synthesized by conventionally known methods can be used. Lactic acid homopolymer resins are, for example, direct dehydration and condensation of L-lactic acid, D-lactic acid, DL-lactic acid, or mixtures thereof, or of L-lactide, D-lactide, meso-lactide, or mixtures thereof It can be obtained by ring-open polymerization. Lactic acid copolymer resins can be obtained, for example, by copolymerizing lactic acid monomers or lactide with other components that can be copolymerized with monomers. Other components that can be copolymerized are, for example, dicarboxylic acids, polyalcohols, hydroxycarboxylic acids, or lactones having two or more ester bond forming functional groups in the molecule, various kinds of polyesters containing various components, various kinds Polyethers, or various kinds of polycarbonates.

The weight average molecular weight of the polylactic acid resin is not particularly limited, but is preferably 50,000 to 500,000, and more preferably 100,000 to 250,000.

A weight average molecular weight of 50,000 or more is preferred because of the increased strength of the resulting molded articles of the presently described subject matter. A weight average molecular weight of 500,000 or less is preferred because the molding material used for injection molding can easily be uniform, and the strength of the molded article obtained by injection molding tends to be increased.

The cellulose resin is not particularly limited, but diacetyl cellulose (DAC), triacetyl cellulose (TAC), cellulose acetate butyrate (CAB), or cellulose acetate propionate (CAP) may be preferably used. Cellulose resins supplied from cellulosic resin manufacturers are generally supplied to the user in the form of heterogeneous granules having a particle size of 1 to 30 mm.

In the presently described subject matter, the content of the biomass resin as the base resin of the molding material supplied to the injection molding apparatus is preferably at least 30% by weight, more preferably at least 50% by weight. Such a configuration can provide high environmental performance for molded fiber containing injection molded articles.

The flame retardants used as additives in the presently described subject matter are not particularly limited, but various kinds of known flame retardants used for flame retardation of resins (molded articles) can be used. For example, flame retardants include bromine flame retardants, chlorine flame retardants, phosphorus-containing flame retardants, silicon-containing flame retardants, nitrogen compound flame retardants, inorganic flame retardants and the like. Among the flame retardants, a phosphorus-containing flame retardant having a high flame retardant effect, which prevents corrosion of the device or mold during kneading or molding with a resin, has little effect on the environment when incinerated and discarded the molded product, is preferred.

Phosphorus-containing flame retardants are not particularly limited, but known phosphorus-containing flame retardants may be used. Organic phosphorus compounds such as, for example, phosphate esters, condensed phosphate esters and polyphosphates. Specifically, the phosphate ester is, for example, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixenyl phosphate, tris (Isopropyl phenyl) phosphate, tris (phenylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl (2-ethylhexyl) phosphate, di (isopropyl phenyl) phenyl phosphate , Monoisodecyl phosphate, 2-acryloyloxy ethyl acid phosphate, 2-methacryloyloxy ethyl acid phosphate, diphenyl-2-acryloyloxy ethyl phosphate, diphenyl-2-methacryloyloxy ethyl Phosphate, melamine phosphate, dimelamine phosphate, melamine pyro-phosphate, triphenyl phosph Fin oxide, tricresyl phosphine oxide, methane phosphonic acid diphenyl and phenyl phosphonic acid diethyl.

Condensed phosphate esters include, for example, resorcinol polyphenyl phosphate, resorcinol poly (di-2,6-xylyl) phosphate, bisphenol A polycresyl phosphate, hydroquinone poly (2,6-xylyl) phosphate and these Aromatic condensed phosphate esters such as condensates thereof.

Condensed phosphate esters may also include polyphosphates containing phosphoric acid, polyphosphoric acid and salts of metals of Groups IA to IVB of the periodic table, ammonia, aliphatic amines, aromatic amines.

Conventional salts of polyphosphates are lithium salts, sodium salts, calcium salts, barium salts, ferrous salts, ferric salts and aluminum salts as metal salts, methylamine salts as aliphatic amine salts, ethylamine Salts, diethylamine salts, triethylamine salts, ethylenediamine salts and piperazine salts, and pyridine salts and triazines as aromatic amine salts.

In the presently described subject matter, other flame retardants besides phosphorus containing flame retardants or silicon containing flame retardants may be used as required. For example, magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony pentaoxide, sodium antimonate, hydroxy zinc stannate, zinc stannate, meta-tartrate, tin oxide, tin oxide salt, zinc sulfate, zinc oxide, ferrous oxide, oxidation Ferric iron, tin oxide, tin oxide, zinc borate, ammonium borate, ammonium octamolybdate, metal salt of tungstic acid, complex oxide acid of tungsten and metalloid, ammonium sulfamate, ammonium bromide, zirconium compounds, Inorganic flame retardants such as guanidine-based compounds, fluorine-based compounds, graphite and expandable graphite may be used.

The fibers used as additives in the injection molding process of the presently described subject are preferably formed into pellets having a length of 3 to 10 mm by joining or sandwiching. Resins used for bonding or embedding preferably include biomass resins. Both synthetic and inorganic fibers can be used. For synthetic fibers, polyester fibers, polyarylate fibers, polyamide fibers and polyolefin fibers can provide stable quality, and polyester fibers are more preferred to provide sufficient functionality.

It is desirable to use hot melt synthetic fibers as the fibers for reinforcing the molded article, which, upon ignition of the molded article, the fibers shrink by melting and do not protrude on the surface of the molded article, and do not interfere with the uniform generation of a carbide layer. Because it does not.

Polyester resin represents the generic name of the high molecular compound which has an ester bond as a bond chain of a main chain. Accordingly, the polyester resin is PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PTT (polytrimethylene terephthalate), PBT (polybutylene terephthalate), PPT (poly-pentamethylene terephthalate), PHT (Polyhexamethylene terephthalate), PBN (polybutylene naphthalate), PES (polyethylene succinate), PBS (polybutylene succinate) and also obtained by polycondensation reaction of dicarboxylic acid component and diol component All high molecular compounds are included.

The dicarboxylic acid component is not particularly limited but may be selected according to the intended use. Dicarboxylic acid components include, for example, aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, oxycarboxylic acids and multifunctional acids. Especially, aromatic dicarboxylic acid is preferable.

Aromatic dicarboxylic acids include, for example, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenyl sulfone dicarboxylic acid, naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid and 5-sodium sulfoisophthalic acid. Include.

Among them, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid and naphthalene dicarboxylic acid are preferable, and terephthalic acid, diphenyldicarboxylic acid and naphthalene dicarboxylic acid are more preferable.

Aliphatic dicarboxylic acids include, for example, oxalic acid, succinic acid, eicosane, adipic acid, sebacic acid, dimer acid, dodecanedioxane, maleic acid and fumaric acid. Alicyclic dicarboxylic acid includes, for example, cyclohexane dicarboxylic acid. Among the aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, succinic acid, adipic acid and cyclohexane dicarboxylic acid are preferable, and succinic acid and adipic acid are more preferable.

Oxycarboxylic acids include, for example, p-oxybenzoic acid.

Multifunctional acids also include, for example, trimellitic acid and pyromellitic acid.

The diol component is not particularly limited but may be selected according to the intended use. Diol components include, for example, aliphatic diols, cycloaliphatic diols, aromatic diols, diethylene glycol, polyalkylene glycols. Especially, aliphatic diol is preferable.

Aliphatic diols include, for example, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol and triethylene glycol. Especially, propanediol, butanediol, pentanediol, and hexanediol are especially preferable.

Alicyclic diols include, for example, cyclohexane dimethanol. Aromatic diols also include, for example, bisphenol A and bisphenol S.

Although the degree of polymerization of the polyester fibers used in the presently described subjects is not particularly limited, intrinsic viscosity of at least 0.5 dl / g is preferred, and at least 0.70 dl / g is more preferred to provide high mechanical properties. The upper limit of the intrinsic viscosity is about 3.00 dl / g.

The polyester resins used as fibers in the presently described subjects preferably have an intrinsic viscosity of 0.36 to 1.60 dl / g, in particular 0.52 to 1.35 dl / g when the aqueous o-chlorophenol solution is metered at 25 ° C. . Polyester resins having such an intrinsic viscosity are preferably used in terms of mechanical properties and formability.

In the presently described subjects, such fibers preferably have a tensile strength of at least 2 cN / dtex, more preferably at least 5 cN / dtex.

Such fibers can be used to increase the strength of the resulting fiber containing injection molded articles. In particular, if the mixture contains 30% by weight or more of the bio resin, the molded article of the mixture can maintain an impact strength of 4 KJ / m 2 or more in the Charpy test according to JISK7110.

The cross-sectional shape of the fibers used in the presently described subjects is not particularly limited. By way of example, the fibers may have a circular cross section. In this case, the production cost of the fiber is reduced, and the dispersibility of the resin composition is increased, which is preferable. Alternatively, the fibers may have irregular cross-section composite cross sections, such as irregular cross-sections or shapes having a star shape, polygonal shape, irregular shape or irregularities. In this case, in mixing, the contact area of the resin with the fiber is increased to increase the sealability, and the strength of the fiber-containing injection molded article of the presently described subject is increased, which is desirable. The diameters of the fibers that do not have a circular cross section are represented, for example, by the same circular area diameter (Heywood diameter).

In the presently described subject matter, the thickness of the fiber is not particularly limited, but a fiber used in a resin molded article reinforced by the fiber may be used. For example, the appropriate thickness may be selected according to the use of the injection molded product, the injection molding apparatus used, the size of the resin pellet, and the like.

In the presently described subject matter, the material supplied to an injection molding apparatus may contain a nucleating agent. Materials containing nucleating agents can improve moldability, heat resistance and product strength. The nucleating agent used is not particularly limited, but known agents which are blended as nucleating agents of the resin (polymer) can be used. The nucleating agent may be an inorganic nucleating agent or an organic nucleating agent.

Inorganic nucleating agents include talc, kaolinite, montmorillonite, synthetic mica, clay, zeolite, silica, graphite, carbon black, zinc oxide, magnesium oxide, titanium oxide, calcium sulfide, boron nitride, calcium carbonate, barium sulfate, aluminum oxide , Metal salts of neodium oxide and phenyl phosphonate, and the like.

The organic nucleating agent is sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, terephthalate lithium, terephthalate sodium, terephthalate potassium, calcium oxalate, sodium laurate, potassium laurate, sodium myristate Potassium myristic acid, calcium myristic acid, sodium octamate, calcium octakorate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, sodium montate, mon Organic carboxylic acid metal salts such as calcium carbonate, sodium toluate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalate and sodium cyclohexane carboxylic acid; organic sulfonates such as p-toluenesulfonic acid sodium and sodium sulfoisophthalate; Carboxylic acid amides such as stearic acid amide, ethylenebislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide and trimesic acid tris (t-butylamide), benzylidene sorbitol and derivatives thereof ; Phosphorus compound metal salts such as sodium-2,2'-methylenebis (4,6-di-t-butylphenyl) phosphate and 2,2-methylbis (4,6-di-t-butylphenyl) sodium and the like do.

The inorganic nucleating agent and the organic nucleating agent may be used alone or in combination of two or more thereof.

When the molding material used in the injection molding method of the presently disclosed subject matter contains a nucleating agent, the content is preferably 0.005 to 5 parts by weight, more preferably 0.1 to 1 part by weight per 100 parts by weight of a resin such as polylactic acid resin. to be.

The molding materials used in the injection molding methods of the presently described subject matter may contain plasticizers.

The plasticizer used is not particularly limited, but various plasticizers generally used for molding the resin can be used. For example, plasticizers include polyester plasticizers, glycerol plasticizers, polyvalent carboxylic acid ester plasticizers, polyalkylene glycol plasticizers, epoxy plasticizers, and the like.

Polyester plasticizers include, for example, acidic components such as adipic acid, sebacic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and rosin and propylene glycol, 1,3-butanediol, 1,4 Polyesters formed from diol components such as butanediol, 1,6-hexanediol, ethylene glycol and diethylene glycol, and polyesters formed from hydroxycarboxylic acids such as polycaprolactone.

Such polyesters may be end-capped with monofunctional carboxylic acids or monofunctional alcohols, or with epoxy compounds or the like.

Glycerol-based plasticizers include, for example, glycerol monoacetomonolaurate, glycerol diacetomonolaurate, glycerol monoacetomonostearate, glycerol diacetomonolate and glycerol monoacetomonomonate.

Polyhydric carboxylic acid plasticizers include, for example, phthalate salts such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diheptyl phthalate, dibenzyl phthalate, dibenzyl phthalate and butylbenzyl phthalate, trimellitic acid tributyl, trimellitic acid trioctyl And trimellitic acid salts such as trimellitic acid trihexyl, adipic acid diisodecyl, adipic acid n-octyl-n-decyl, adipic acid methyl diglycol butyl diglycol, adipic acid benzylmethyl diglycol and adipic acid Adipic acid salts, such as benzylbutyl diglycol dibasic, citrate salts such as acetyl triethyl and tributyl acetyl citrate, azelate salts such as di-2-ethylhexyl azelate, dibutyl sebacate and di-2- sebacic acid Ethylhexyl.

Polyalkylene glycol plasticizers include, for example, polyethylene glycol, polypropylene glycol, poly (ethylene oxide-propylene oxide) blocks and / or random copolymers, polytetramethylene glycol, bisphenol-ethylene oxide addition polymers, bisphenol-propylene oxide addition polymers And polyalkylene glycols such as bisphenol-tetrahydrofuran addition polymers, and terminal epoxidized compounds, terminal esterified compounds and terminal etherified compounds of polyalkylene glycols.

Epoxy plasticizers generally refer to epoxy triglycerides formed from alkyl stearic acid and soybean oil. In addition, so-called epoxy resins made mainly of bisphenol A and epichlorohydrin can be used.

Other plasticizers are benzoates of aliphatic polyols such as neopentyl glycol dibenzoate, diethylene glycol dibenzoate and triethylene glycol di-2-ethyl butyrate, fatty acid amides such as stearic acid amide, aliphatic carboxyl such as butyl oleate Acid salts, acetyl ricinolic acid methyl, oxyacid esters such as acetyl ricinolic acid butyl, pentaerythritol, various sorbitols, and the like.

When the molding material used in the injection molding method of the presently disclosed subject matter contains a plasticizer, the content is preferably 1 to 30 parts by weight, more preferably 5 to 10 parts by weight per 100 parts by weight of a resin such as polylactic acid resin. to be. When the molding material contains a plasticizer in the desired range of content, the molding temperature can be reduced by about 10 ° C. in the production of the shaped articles of the presently described subject matter.

The molding materials used in the injection molding methods of the presently disclosed subject matter include, in addition to nucleating agents and plasticizers, colorants such as surfactants, elastomers, antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, antistatic agents, neutralizers, pigments, Components such as dispersants, rosin, synthetic rubber, mineral additives, antibacterial agents, fragrances, mold release agents, hydrolysis inhibitors and the like.

In the molding materials used in the presently described subjects, the total content of components other than resins, flame retardants and fibers is preferably at most 20% by weight, more preferably at most 10% by weight.

The injection molding method of the presently described subject matter has been described in detail above. The presently described subject matter is not limited to the embodiments described above, and of course, various improvements or changes may be made without departing from the spirit of the presently disclosed subject matter.

[Example]

[Test A]

Next, a specific example of the injection molding method of the first embodiment of the presently described subject will be described by test A.

[Molding material]

ㆍ Polylactic acid resin (pellet) ... 100 parts by weight of LACEA H100 produced by Mitsui Chemicals, Inc

ㆍ Commercial (Powder) ... FUSHIMI Pharmaceutical Co., Ltd. 20 parts by weight of Rabitle FP110 produced by

ㆍ Stabilizer (Powder) ... Nisshinbo Chemical Inc. 5 parts by weight of CARBODILITE LA1 produced by

ㆍ Flame Retardant (Powder) ... 35 parts by weight of ADK STAB FP2100 produced by ADEKA CORPORATION

Glass fiber 15 parts by weight of FT592 produced by Owens Corning (pellet compressed fiber)

<Total> 175 parts by weight

A polylactic acid resin previously dried at 80 ° C. for 5 hours by a hot air dryer was used. A flame retardant dried in advance for 5 hours at 80 ° C. by a reduced pressure drier was used. The powder ratio of the molding material was 34% by weight.

Injection Molding Mechanism

50-A 가 시험에서 사용되었고, 샤르피 시험편과 UL 시험편 (1.6 ㎜ 의 두께) 의 사출 성형을 동시에 수행할 수 있는 몰드가 사출 성형 기구에 세트되었다. 사출 성형 기구의 가열 온도는 노즐 측으로부터 195℃, 195℃, 190℃, 180℃, 그리고 30℃ 로 설정되었다. 1 발사분의 사출량은 25 g 으로 설정되었다. 사출 성형 기구 (10) 가 도 8 에서 3 개의 히터 (24) 를 포함하지만, 사출 성형 기구는 이러한 시험 A 에 이용되었다. Injection molding apparatus, produced by FANUC CORPORATION

50-A was used in the test, and a mold capable of simultaneously performing injection molding of the Charpy test piece and the UL test piece (thickness of 1.6 mm) was set in the injection molding apparatus. The heating temperature of the injection molding apparatus was set to 195 ° C, 195 ° C, 190 ° C, 180 ° C, and 30 ° C from the nozzle side. The injection volume of one shot was set at 25 g. Although the injection molding apparatus 10 includes three heaters 24 in FIG. 8, the injection molding apparatus was used for this test A.

In the test pieces molded under the injection molding conditions of Examples 1 to 6 and Comparative Examples 1 to 7 described later, three items: “Charpy impact”, “combustibility” and “dispersibility” were evaluated. The test method for evaluation is as described below.

(Charpy impact test)

The Charpy impact test piece was formed to have a length of 80 mm ± 2 mm, a width of 10 mm ± 0.2 mm, a thickness of 4 mm ± 0.2 mm according to JISK-7111, and a notching (notch radius of 0.25 mm ± 0.05 mm, 8.0 mm). Width of the notched portion of ± 0.2 mm). The mass of the test piece with a notch was 4.2 g. As a test device, TOYO SEIKI SEISAKU-SHO, LTD. Produced by IMPACT TESTER (analog) was used. The test piece obtained by the Example and the comparative example received the Charpy impact test according to JISK-7111, and 5 (KJ / m <2>) or more was the pass.

(Combustion test: UL94-V)

As the test piece, an injection molded test piece having a length of 127 mm, a width of 12.7 mm, and a thickness of 1.6 mm was used. UL94-V is the most basic flammability test for plastics, etc., and checks the flammability of the test piece by applying the flame of the gas burner to a test piece having a specific size. The levels of flame retardance were 5VA, 5VB, V-0, V-1, V-2, and HB in descending order, and the flame retardance of V-1 or more (5VA-V-1) was the pass.

(Dispersibility test)

As the test piece, an injection molded test piece having a length of 127 mm, a width of 12.7 mm, and a thickness of 1.6 mm was used according to UL94. The test piece was placed on a light table (white light) having an illuminance of 3800 Lx to 4200 Lx, and the dispersibility was visually observed by the light transmitted through the test piece. Thereafter, the following five levels of evaluation of A to E were performed.

A ... No agglomerates were found in the specimen, and the color was uniform.

B ... No agglomerates were found in the specimens, but color heterogeneity was observed.

C ... fine aggregates having a length of 0.5 mm or more were observed in the test piece.

D ... Five or more aggregates with a length of 0.5 mm or more were observed in the test pieces.

E ... Ten or more aggregates having a length of at least 1 mm were observed in the test pieces.

(Judgment)

When all three evaluation items passed, it was evaluated as passing in the judgment, and if any of the evaluation items failed, the evaluation was judged as failing.

[Injection Molding Conditions and Results of Examples and Comparative Examples in Test A]

10A is a view showing injection molding conditions and results of an example, and FIG. 10B is a view showing injection molding conditions and results of a comparative example.

(Example 1)

In Example 1, a small metering feeder was mounted in the injection molding apparatus, and the molding material having the composition was placed in a plastic bag, sufficiently shaken and mixed uniformly, and then placed in the metering feeder. The back pressure was set at 30 kg / cm 2, the rotation speed of the screw was set at 200 rpm, and the molding material was fed into the cylinder at a feed rate with a weighing time of 20 seconds. Specifically, in Example 1, the feed rate of the molding material fed into the cylinder was adjusted irrespective of the rotational speed of the screw and the back pressure setting value, and thus the weighing time of the weighing step was controlled to 20 seconds. As a result, uniform mixing of the powder material and the pellet material was sufficiently performed, the Charpy impact test result was 7.1 (KJ / m 2), the flame retardancy was V-0, the dispersibility was A, and it was determined to pass. Fig. 11A shows a photograph showing a screw shaft of the injection molding apparatus of Example 1, and a white portion is a powder material adhering to the shaft. As is apparent from FIG. 11A, less powder material was attached to the shaft in the compression zone, and uniform dough of the molding material was performed sufficiently.

In Comparative Example 1 described later, the weighing time was SN and the weighing time SN was 4 seconds in a normal feed with a back pressure setpoint of 30 kg / cm 2 and a screw rotation speed of 200 rpm.

(Example 2)

In Example 2, injection molding was performed as in Example 1 except that the back pressure was increased to 150 kg / cm 2. Specifically, in Example 2, the same screw rotation speed and metering time as Example 1 were set and the influence on the presently described subject matter was checked when the back pressure was greater than Example 1. As a result, the Charpy impact test result was 6.9 (KJ / m 2), the flame retardancy was V-1, and the dispersibility was A, and it was determined to pass. Even if the back pressure setting was increased from 30 kg / cm 2 to 150 kg / cm 2, the influence on the quality of the molded article was small as long as the screw rotation speed and the metering time were set under the conditions of the presently described subject matter. Therefore, the back pressure can be set to a predetermined value. In Comparative Example 2 described later, the weighing time was SN and the weighing time SN was 7 seconds in a normal supply having a back pressure setpoint of 150 kg / cm 2 and a screw rotation speed of 200 rpm.

(Example 3)

The back pressure was set at 30 kg / cm 2, the rotation speed of the screw was set at 50 rpm, and the molding material was fed into the cylinder at a feed rate with a metering time of 40 seconds. Other conditions were the same as in Example 1. Specifically, in Example 3, the lowering of the kneading performance by the reduced screw rotation speed is offset by increasing the weighing time by 40 seconds. As a result, the Charpy impact test result was 6.5 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass.

(Example 4)

The back pressure was set at 30 kg / cm 2, the rotational speed of the screw was set at 200 rpm, and the molding material was fed into the cylinder at a feed rate with a weighing time of 8 seconds. Other conditions are the same as in Example 1. Specifically, in Example 4, the back pressure set value and the screw rotation speed were set in the same manner as in Example 1, and the metering time was set to the lower limit of the presently described subject matter. As a result, the Charpy impact test result was 6.0 (KJ / m 2), the flame retardancy was V-1, the dispersibility was B, and it was determined to pass.

(Example 5)

The back pressure was set at 30 kg / cm 2, the rotation speed of the screw was set at 200 rpm, and the molding material was fed into the cylinder at a feed rate with a weighing time of 180 seconds. Other conditions were the same as in Example 1. Specifically, in Example 5, the back pressure set value and the screw rotation speed were set in the same manner as in Example 1, and the metering time was set to the upper limit of the presently described subject matter. As a result, the Charpy impact test result was 5.1 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass. However, due to the long weighing time, Charpy impact test results are close to the pass line. This is because a long metering time can cause low molecular weight by decomposition of the polylactic acid resin.

(Example 6)

The back pressure was set at 30 kg / cm 2, the rotational speed of the screw was set at 300 rpm, and the molding material was fed into the cylinder at a feed rate with a weighing time of 20 seconds. Other conditions were the same as in Example 1. Specifically, in Example 6, the back pressure set value and the metering time were set in the same manner as in Example 1, and the screw rotation speed was set to the upper limit of the presently described subject matter. As a result, the Charpy impact test result was 5.5 (KJ / m 2), the flame retardancy was V-1, the dispersibility was B, and it was determined to pass. However, due to the high screw rotation speed, Charpy impact test results are close to the pass line. This is because a high screw rotational speed may cause excessive shear heating, leading to low molecular weight due to decomposition of the polylactic acid resin.

(Comparative Example 1)

The back pressure was set to 30 kg / cm 2, the rotational speed of the screw was set to 200 rpm, and the molding material having the above composition was placed into a mini hopper having a capacity of 50 ml without using a metering feeder, and fed into a cylinder to form The normal feeding method of filling the cylinder by the weight of the material was performed. The weighing time at this time was measured and this was 4 seconds. Specifically, in Comparative Example 1, the molding material was fed into the cylinder according to the rotational speed of the screw, that is, the material feeding capability of the molding material, and thus the weighing time was 4 seconds. As a result, the Charpy impact test result was 4.7 (KJ / m 2), the flame retardancy was V-2, the dispersibility was D, and failed because the weighing time was too short and uniform dough of the powder material and the pellet material was insufficiently performed. Was determined to be.

FIG. 11B shows a photograph showing a screw shaft of the injection molding apparatus of Comparative Example 1, wherein a white portion is a powder material attached to the shaft. FIG. As is apparent from FIG. 11B, many powder materials are attached to the shaft in the compression zone, and uniform kneading of the molding material is performed insufficiently.

(Comparative Example 2)

The back pressure was set at 150 kg / cm 2, the rotation speed of the screw was set at 200 rpm, and the molding material having the composition was placed into a mini hopper having a capacity of 50 ml without using a metering feeder, and fed into a cylinder to form The normal feeding method of filling the cylinder by the weight of the material was performed. The weighing time at this time was measured and this was 7 seconds. Specifically, in Comparative Example 2, the molding material was fed into the cylinder according to the rotational speed of the screw, that is, the material feeding capability of the molding material, and thus the weighing time was 7 seconds. In this case, since the back pressure was increased from 30 kg / cm 2 of Comparative Example 1 to 150 kg / cm 2, the metering time of the normal feeding method was increased from 4 seconds of Comparative Example 1 to 7 seconds. As a result, the Charpy impact test result was 5.1 (KJ / m 2), the flame retardancy was V-2, the dispersibility was E, and it was determined to fail.

(Comparative Example 3)

The back pressure was set to 30 kg / cm 2 as in Example 1, the rotational speed of the screw was set to 200 rpm, and the molding material having the above composition was placed into a mini hopper having a capacity of 50 ml without using a metering feeder, It was fed into the cylinder and fed into the cylinder by the weight of the molding material. As a result, the inlet port of the cylinder was blocked and blocked by the molding material, it was impossible to obtain a stable sample of the molded article, and the test was stopped. Therefore, when the molding material contains a large amount of powder, clogging may be caused by any factor.

(Comparative Example 4)

In Comparative Example 4, the test was carried out according to the Hungry supply of Japanese Patent Application Laid-open No. 2005-319813. Specifically, the back pressure was set to 30 kg / cm 2, the rotational speed of the screw was set to 200 rpm, and the molding material was supplied such that 1/4 to 3/4 of the screw was covered while the inlet port of the cylinder was checked. The weighing time at this time was measured, which was the same as the weighing time of 4 seconds in the normal feeding method of Comparative Example 1. As a result, the Charpy impact test result was 5.5 (KJ / m2) and passed because the weighing time was too short and uniform dough of the powder material and the pellet material was insufficient, but the flame retardancy was V-2, the dispersibility was D , They were rejected, which was determined to fail.

(Comparative Example 5)

In Comparative Example 5, the test was performed according to Japanese Patent Application Laid-Open No. 2001-277296. Specifically, the back pressure was set to 30 kg / ㎠, the rotation speed of the screw was set to 200 rpm, TOYO SEIKI SEISAKU-SHO, LTD. The metering feeder F3 by was turned on / off manually and the molding material was fed into the cylinder by the feeding method of Japanese Patent Application Laid-open No. 2001-277296. The weighing time at this time was measured and was 5 seconds. As a result, the Charpy impact test result was 5.2 (KJ / m2) and passed because the weighing time was too short and uniform dough of the powder material and pellet material was insufficient, but the flame retardancy was V-2 and the dispersibility was D It was determined that the test failed.

(Comparative Example 6)

In Comparative Example 6, injection molding was performed as in Example 1 except that the molding material was fed into the cylinder at a feed rate with a weighing time of 200 seconds. Specifically, in Comparative Example 6, the back pressure set point and the screw rotational speed satisfied the presently described subject matter, and the metering time was longer than the upper limit of the presently described subject matter. As a result, the flame retardance was V-1, the dispersibility was A, and it was judged as passing. However, because of the too long weighing time, the Charpy impact test result was 4.5 (KJ / m 2) lower than the pass line. This may be because too long metering time causes excessive low molecularization by decomposition of the polylactic acid resin.

(Comparative Example 7)

In Comparative Example 7, injection molding was performed as in Example 1 except that the rotational speed of the screw was set to 350 rpm. Specifically, in Comparative Example 7, the back pressure set point and metering time met the presently described subject matter, but the screw rotational speed was higher than the upper limit of the presently described subject matter. As a result, the flame retardance was V-1, the dispersibility was A, and it was judged as passing. However, due to the high screw rotational speed, the Charpy impact test result was 4.2 (KJ / m 2) lower than the pass line. This may be because too high screw rotation speeds result in excessive shear heating resulting in low molecular weight by decomposition of the polylactic acid resin.

[Result and Discussion of Test A]

As is evident from the comparison between Example 1 and Comparative Example 1 described above and the comparison between Example 2 and Comparative Example 2, the presently described injection molding method is performed by adjusting the feed rate of the molding material so that the metering time is It is controlled regardless of the screw rotational speed and back pressure setpoint, so good results can be obtained in both Charpy impact tests, combustibility and dispersibility.

In addition, in Comparative Examples 4 and 5, which appear close to the injection molding method of the presently described subject matter, the Charpy impact test was improved compared to Comparative Examples 1 to 3, but the flame retardancy and dispersibility were lower than Comparative Examples 1 to 3, and satisfactory The result could not be obtained.

In addition, if the rotational speed of the screw exceeds 300 rpm or the metering time exceeds 180 seconds, uniform dough can be achieved, but low molecular weight of the polylactic acid resin occurs, affecting the Charpy impact test results. Therefore, the rotational speed of the screw is set at a constant rotational speed within 50 rpm (lowest rotational speed at which sufficient kneading can be performed) to 300 rpm, and the supplying speed of the molding material into the cylinder is determined by the weighing time of the normal supply ( It is necessary that it can be adjusted to be more than twice or less than 180 seconds (SN seconds).

In this embodiment, polylactic acid resin (PLA) having low heat resistance was used as the base resin, but the presently described subject matter can be applied to a base resin having higher heat resistance than polylactic acid resin as well.

[Test B]

Test B was performed using a different injection molding tool and molding material than test A.

[Molding material]

ㆍ polylactic acid resin (granule) ... 4032D 100 parts by weight produced by NatureWorks LLC

ㆍ Flame Retardant (Powder) ... 40 parts by weight of ADK STAB FP2200 produced by ADEKA CORPORATION

ㆍ Commercial (Powder) ... FUSHIMI Pharmaceutical Co., Ltd. 20 parts by weight of Rabitle FP110 produced by

ㆍ Stabilizer (Powder) ... MITSUBISHI RAYON CO., LTD. 5 parts by weight of METABLEN W600A produced by

ㆍ PTFE anti-drip agent (powder) ... DAIKIN INDUSTRIES, LTD. 0.5 parts by weight of FA500H produced by

ㆍ Hydrolytic inhibitor (powder) ... 3 parts by weight of Stabaxol 1FL produced by Rhein Chemie Rheinau GmbH

ㆍ Filler (Fine Powder) ... Nippon Talc Co., Ltd. Produced by P3

8 parts by weight

<Total> 176.5 parts by weight

A polylactic acid resin previously dried at 80 ° C. for 5 hours by a hot air dryer was used. A flame retardant dried in advance for 5 hours at 80 ° C. by a reduced pressure drier was used. The powder ratio of the molding material was 43% by weight.

Injection Molding Mechanism

As an injection molding apparatus, Sumitomo Heavy Industries, Ltd. The SG150U-3 produced by the US was used in the test, and a mold capable of simultaneously performing injection molding of the Charpy test piece and the UL test piece (thickness of 1.6 mm) was set in the injection molding apparatus. The heating temperature of the injection molding apparatus was set to 195 ° C, 195 ° C, 190 ° C, 180 ° C, and 30 ° C from the nozzle side. The injection quantity of one shot was set to 120 g. Although the injection molding apparatus 10 includes three heaters 24 in FIG. 8, the injection molding apparatus was used for this test B.

As in Test A, it was performed when the presently described subject was satisfied and when the currently described subject was not satisfied, and three items: Charpy impact test, flame retardancy test, and dispersibility test were evaluated. The test methods and evaluation criteria for the three items are the same as for test A.

[Injection Molding Conditions and Results of Examples and Comparative Examples of Test B]

12A is a view showing injection molding conditions and results of an example, and FIG. 12B is a view showing injection molding conditions and results of a comparative example.

(Example 1-1)

In Example 1-1, a small metering feeder was mounted in the injection molding apparatus, and the molding material having the composition was placed in a plastic bag, sufficiently shaken and mixed uniformly, and then placed in the metering feeder. The back pressure was set at 5 kg / cm 2, the rotational speed of the screw was set at 150 rpm, and the molding material was fed into the cylinder at a feed rate with a metering time of 40 seconds. Specifically, in Example 1-1, the feed rate of the molding material fed into the cylinder was adjusted irrespective of the rotational speed of the screw and the back pressure setting value, and thus the weighing time of the weighing step was controlled to 40 seconds. As a result, uniform mixing of the powder material and the pellet material was sufficiently performed, and the Charpy impact test result was 6.4 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass.

In Comparative Example 1-1 described later, the weighing time was SN and the weighing time SN was 3 seconds in a normal supply having a back pressure set value of 5 kg / cm 2 and a screw rotation speed of 150 rpm.

(Example 2-1)

In Example 2-1, a small metering feeder was mounted in the injection molding apparatus, and the molding material having the composition was placed in a plastic bag, sufficiently shaken and mixed uniformly, and then placed in the metering feeder. The back pressure was set at 25 kg / cm 2, the rotational speed of the screw was set at 150 rpm, and the molding material was fed into the cylinder at a feed rate with a weighing time of 60 seconds. Specifically, in Example 2-1, the feed rate of the molding material fed into the cylinder was adjusted irrespective of the rotational speed of the screw and the back pressure setting value, and thus the weighing time of the weighing step was controlled to 60 seconds. As a result, uniform mixing of the powder material and the pellet material was sufficiently performed, the Charpy impact test result was 6.8 (KJ / m 2), the flame retardancy was V-0, the dispersibility was A, and it was determined to pass.

(Example 3-1)

In Example 3-1, injection molding was performed as in Example 1-1 except that the screw rotational speed was set at 50 rpm as the lower limit of the presently described subject matter. As a result, the Charpy impact test result was 6.1 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass. Thus, it was found that uniform kneading of the powder material and the pellet material was sufficiently performed even if the screw rotational speed was set at 50 rpm as the lower limit of the presently described subject matter.

(Example 4-1)

In Example 4-1, injection molding was performed as in Example 1-1 except that the screw rotational speed was set to 300 rpm as the upper limit of the presently described subject matter. As a result, the Charpy impact test result was 5.5 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass. This is because the screw rotational speed was set at 300 rpm as the upper limit of the presently described subject matter, so that shear heating occurred, causing low molecular weight by decomposition of the polylactic acid resin, which had some influence on the Charpy impact test results. Can be.

(Example 5-1)

In Example 5-1, injection molding was performed as in Example 1-1 except that the metering time was set to 180 seconds as the upper limit of the presently described subject matter. As a result, the Charpy impact test result was 5.4 (KJ / m 2), the flame retardancy was V-1, the dispersibility was A, and it was determined to pass. This may be due to the metering time being set to 180 seconds, like the upper limit of the presently described subject matter, so that low molecular weight was caused by the decomposition of the polylactic acid resin, thereby slightly affecting the Charpy impact test results.

(Example 6-1)

In Example 6-1, injection molding was performed as in Example 1-1 except that the metering time was set to 6 seconds, which is twice the metering time SN of the normal feed as the lower limit of the presently described subject. The weighing time of Comparative Example 1-1 is the weighing time of the normal supply and is 3 seconds. As a result, the Charpy impact test result was 6.0 (KJ / m 2), the flame retardancy was V-1, the dispersibility was B, and it was determined to pass. Although the metering time was set to 6 seconds equal to the lower limit of the presently described subject matter, a uniform dough was achieved so that all Charpy impact tests, flame retardancy and dispersibility were accepted.

(Comparative Example 1-1)

The back pressure was set at 5 kg / cm 2, the rotational speed of the screw was set at 150 rpm, and the molding material having the above composition was placed into a mini hopper having a capacity of 250 ml without using a metering feeder, and fed into a cylinder to form The normal feeding method of filling the cylinder by the weight of the material was performed. The weighing time at this time was measured and this was 3 seconds. Specifically, in Comparative Example 1-1, the molding material was supplied into the cylinder according to the rotational speed of the screw, that is, the material feeding capability of the molding material, and thus the weighing time was 3 seconds. As a result, the Charpy impact test result was 4.3 (KJ / m2), the flame retardancy was V-2, the dispersibility was D, and failed because the weighing time was too short and uniform dough of the powder material and the pellet material was insufficiently performed. Was determined to be.

(Comparative Example 2-1)

In Comparative Example 2-1, injection molding was performed as in Example 1-1 except that the weighing time was 200 seconds. Specifically, in Comparative Example 2-1, the metering time was longer than the upper limit of the presently described subject matter. As a result, the dispersibility was A and passed, but the Charpy impact test result was 3.2 (KJ / m 2) and the flame retardancy was V-2, which was determined to be rejected. This may be because the metering time is 200 seconds and too long, excessive low molecular weight was caused by the decomposition of the polylactic acid resin, and the Charpy impact test results failed.

(Comparative Example 3-1)

In Comparative Example 3-1, injection molding was performed as in Example 1-1 except that the screw rotational speed was 350 rpm. Specifically, in Comparative Example 3-1, the screw rotation speed was higher than the upper limit of the presently described subject matter. As a result, the dispersibility was A and was passed, but the Charpy impact test result was 3.5 (KJ / m 2) and the flame retardancy was V-2, and it was determined to fail. This may be because too high screw rotational speed caused excessive low molecularization by decomposition of the polylactic acid resin, and the Charpy impact test results failed.

(Comparative Example 4-1)

In Comparative Example 4-1, the test was carried out according to the Hungry supply of Japanese Patent Application Laid-open No. 2005-319813. Specifically, the back pressure was set to 5 kg / cm 2, the rotational speed of the screw was set to 150 rpm, and the molding material was supplied such that 1/4 to 3/4 of the screw was covered with the inlet port of the cylinder checked. The weighing time at this time was measured, which was the same as the weighing time of 3 seconds in the normal feeding method of Comparative Example 1-1. As a result, the Charpy impact test result was 4.5 (KJ / m 2), the flame retardancy was V-2, and the dispersibility was D, because the weighing time was too short and the uniform dough of the powder material and the pellet material was insufficiently performed. It was determined that it failed.

(Comparative Example 5-1)

In Comparative Example 5-1, the test was performed according to Japanese Patent Application Laid-Open No. 2001-277296. Specifically, the back pressure was set to 5 kg / ㎠, the rotational speed of the screw was set to 150 rpm, TOYO SEIKI SEISAKU-SHO, LTD. The metering feeder was manually turned on / off and the molding material was fed into the cylinder by the feeding method of Japanese Patent Application Laid-open No. 2001-277296. The weighing time at this time was measured and was 4 seconds. As a result, the Charpy impact test result was 4.3 (KJ / m 2), the flame retardancy was V-2 and the dispersibility was D, because the weighing time was too short and uniform dough of the powder material and the pellet material was insufficiently performed. Was determined to be.

[Review of Test Results]

The results of test B were similar to those of test A, and it was found that the difference between the molding material and the injection molding apparatus did not affect the presently described subject matter.

The results of tests A and B showed that, as in the injection molding method of the presently described subject, high speed rotation was performed at a rotational speed of the screw of 50 to 300 rpm, and the weighing time was independent of the rotational speed of the screw and the back pressure setting value. It was controlled and set to twice the SN (metering time in normal feed) to 180 seconds, so that a uniform dough can be performed even if a molding material containing a large amount of powder is fed directly from the hopper into the cylinder.

The metering time of the Hungry feed performed as a comparative example is similar to the metering time in normal feed and is shorter than the metering time of the presently described topic of "scattering feeding".

In this regard, with reference to FIGS. 13A-13E, the differences between "normal supply", "hungry supply", and "scattering supply" of the presently described subject will be described.

13A to 13E show examples of resin pellets as molding materials, reference numeral A denotes pellets, and reference numeral A1 denotes molten resin that is molten pellets.

(Measurement step)

In general, the plasticization performed in the metering step of the injection molding is carried out by the pellet A of the cylinder 14 forwarded by the screw 16, and the frictional heat (shear energy) between the pellet A and the cylinder 14 It melt | dissolves uniformly by the heat transmitted from the heater 24 of the outer side, and a predetermined fixed amount of molten resin A1 is stored in the tip part of the cylinder 14.

Specifically, when the screw 16 is rotated and the molten resin A1 starts to be stored at the tip of the cylinder 14, the screw 16 is screwed if the molten resin A1 does not leak from the tip. It is retracted by the pressure of the pellet (A) itself which is continuously supplied by the rotation of. In this case, the amount of the pellets A supplied increases with increasing rotational speed of the screw 16 (with increasing rotational speed), and the speed of retraction of the screw 16 increases.

Thus, if a signal for stopping the rotation of the screw is provided at a predetermined amount of stroke position (measurement setting position), the retraction of the screw 16 is stopped at that position. This is the weighing step.

Therefore, under the same material and under the same conditions, the time to reach a predetermined constant amount of stroke position, that is, the time to complete the metering, is substantially constant according to the constant rotational speed of the screw 16.

When the rotational speed of the screw 16 increases, the feed amount of the pellet A increases, thereby reducing the time to reach the same stroke position, that is, the time for completing weighing.

Based on the above description, the differences between "normal feed", "hungry feed", and "scatter feed" of the presently described subject matter will be compared.

(Normal supply)

First, the "normal supply" in which pellet A is accumulated in the hopper 26 mounted to the injection molding apparatus will be described. The feed amount of the pellet A into the hopper 26 can be adjusted using the metering feeder 40 (quantitative feeding device). Before the injection molding starts, the hopper 26 is filled with pellets A. The general state of the pellet A in the thread groove of the hopper 26 or the screw 16 is shown in FIG. 13A (conceptual diagram in which a valve or the like is omitted).

As is apparent from FIG. 13A, the thread groove of the screw 16 is always filled with molten resin A1, which is a pellet A or a molten molding material, and the screw 16 is used for feeding the pellet A forward. Force is always generated and metering is completed in a short time. Therefore, the level of the pellets A stored in the hopper 26 is gradually reduced by the consumption of the pellets A.

When the level of pellet A is reduced to the bottom of hopper 26 (position H in FIG. 13A), pellet A is at a feed rate higher than the consumption rate of pellet A consumed in the injection molding cycle. Feeded into the hopper 26 and the hopper 26 is filled back into the pellets A. Therefore, in the normal supply, the consumption and filling of the pellets A of the hopper 26 are repeated with reference to the position H in FIG. 13A.

(Hungry supply)

Next, the "hungry feed" will be described.

From the state where the injection molding continues in the "normal supply" state, the pellet A is gradually consumed. When the pellet A reaches the lower end of the hopper 26 (position H in FIG. 13A), the pellet A ) Is added and the storage level of the hopper 26 is increased again, which is a "normal supply".

However, in the Hungry feed, even if pellet A reaches the bottom of hopper 26 (position H in FIG. 13A), pellet A is not added to hopper 26 but injection molding continues for a while. . Thereafter, the level of the pellets A decreases further from the bottom of the hopper 26 and reaches below the inlet port 25 (position L in FIG. 13A). In this state, the metering feeder 40 supplies the pellet A to the hopper 26 in an amount equal to the average consumption of the pellet A. Specifically, the average consumption amount (average consumption rate) of the pellets A becomes equal to the average supply amount (average supply rate) of the pellets A. Therefore, the rear end position of the pellet A of the cylinder 14 reaches the position shown in FIG. 13B in accordance with the intermittent consumption of the pellet A. FIG. Therefore, when the state of the inlet port 25 is observed from the side of the hopper 26, the pellet A can be seen sometimes. In other words, the screw 16 can sometimes be seen (it can be seen at a point). This is the Hungry supply.

Thus, in the Hungry feed, pellet A sometimes does not exist in the feed path below the hopper 26 and inlet port 25, but when pellet A is fed into the hopper 26, pellet A is It is continuous with the rear end position of the pellet A of the cylinder 14. Specifically, the molten resin A1 stored at the tip of the screw 16 is always continuously supplied in the amount required by the pellet A of the screw groove of the screw. In other words, the state in which a sufficient amount of the pellets A required for the retraction of the screw 16 can be supplied is maintained as in the "normal supply".

The "hungry feed" increases the gap from the screw 16 to the hopper 26 as described above, so that water or cracked gas, which is a problem in the hungry feed, is easily outward from the inlet port 25. It is different from the "normal supply" that it can be released.

(Scattering supply)

Next, the "scattering feed" of the presently described subject will be described.

First, in view of the state of FIG. 13B of the hungry feed, the supply of the pellets A in the "scattering feed" is once stopped in this state. Thereafter, the pellet A or the molten resin A1 of the screw groove of the screw 16 is further consumed by injection molding, and brought into the state of FIG. 13C or 13D, and even if the screw 16 is rotated, the resin pellets And molten resin is not easily fed forward. Specifically, the feed zone, or the section from the feed zone to the compression zone, is not filled with pellets (A). In fact in FIG. 13C, when a loose-tight state (rare-dense state) of the molding material inside the cylinder 14 is observed from the inlet port 25 after removal of the hopper 26, the state of the molding material is loose (rare). State), there is no signal indicating the fullness of the molding material.

By a large amount of pellets A or molten resin A1 filled into the screw grooves of the screw 16, the pellets A or molten resin A1 are easily fed forward by the force of the screw grooves. However, in the "scattering supply", even if an extremely small amount of molding material is present in the thread groove, and the screw 16 is rotated, the pellet A or the molten resin A1 is not easily fed forward. In the state of FIG. 13E, since the molding material is not naturally fed forward, no back pressure is applied to the screw 16, and thus the screw 16 no longer retracts. Therefore, it is required to be filled with a molding material to some extent at least inside the screw groove of the screw 16. Thereafter, the screw 16 does not stop rotation until the screw 16 is retracted to a specific stroke position, so that the addition of the pellet A causes the screw 16 to be pellets A or a molten resin ( Wait while it is being rotated to knead A1). Specifically, in the " scattering feed ", at the start of injection molding, the pellet A or molten resin A1 is not easily fed forward even if the screw 16 is rotated, ie as in FIGS. 13C and 13D. A state is formed in which at least the supply zone of the supply zone, the compression zone, and the metering zone is not filled by the pellets (A). In this state, pellet A is added from quantitative feeder 40 to hopper 26 at a feed rate lower than the average consumption rate of pellet A in "normal feed". Thus, pellet A or molten resin A1 is filled into the screw groove of the screw 16 to gradually increase the back pressure of the tip of the screw, and the screw 16 is slowly retracted. Thus, in the " scattering feed ", the state in which the addition of the pellets A is awaited continues while the screw 16 is rotated, and thus a long metering time can be taken.

The filling position of the pellets A which enables the retraction of the screw 16 differs depending on the injection molding conditions, in particular the back pressure, the screw shape, or the properties of the molding material, but the presently described subject matter is shown in FIGS. 13C to 13D. Can be achieved in any state of 13e. At least the amount of pellets A in the feed zone needs to be significantly reduced, which changes the degree of pressing of the pellets A or molten resin A1 in the compression zone. This can reduce excessive shearing of the compression zone and prevent the actual temperature from significantly exceeding the control temperature to deteriorate the pellets (A). In addition, when the molding material contains pellets and powder, the dough dispersibility of the powder is prevented from being reduced by a sharp decrease in the resin viscosity.

[Exam C]

Next, specific examples of the injection molding method of the second embodiment of the presently described subject will be described by test C. FIG.

[Molding material]

ㆍ polylactic acid resin (pellets) ... UNITIKA. 100 parts by weight of TERRAMAC TE7000 produced by LTD

ㆍ Ammonium polyphosphate flame retardant (powder) ... 40 parts by weight of AP423 produced by Clariant

ㆍ Commercial agent (phosphazene derivative) (powder) ... FUSHIMI Pharmaceutical Co., Ltd. Rabitle FP110 10 parts by weight produced by

ㆍ Antioxidant (Powder) ... Chiba Specialty Chemicals Inc. 0.5 parts by weight of Irganox 245 produced by

ㆍ Hydrolysis Agent (Powder) ... Nisshinbo Chemical Inc. 3 parts by weight of CARBODILITE LA1 produced by

ㆍ Elastomers (pellets) ... MITSUBISHI RAYON CO., LTD. METABLEN SRK200 15 parts by weight produced by

Among the materials, for the elastomer, melt extrusion of the powdered elastomer was performed in advance and formed into pellets for use.

Among the materials, the polylactic acid resin in the pellet state and the elastomer corresponding to the pellets were previously blended in the pellet mixing tank 37B and used as the pellet material (A). The volume specific gravity of the pellet material (A) was 1.31.

Ammonium polyphosphate-based flame retardants, compatibilizers, antioxidants and hydrolysis inhibitors were previously dry blended in the powder mixing tank 35B and used as powder material (B). The volume specific gravity of the powder material (B) was 0.83.

In addition, the pellet material (A) was shaped to reduce the volume specific gravity to 1.10 and was used as the pellet material (A1).

Injection Molding Mechanism

As the injection molding apparatus 10, Sumitomo Heavy Industries, Ltd. A 150t injection molding apparatus (SG150U) produced by was used for the test. A material supply device 34 having the configuration shown in FIG. 1 was used. The hopper 26 mounted on the injection molding apparatus 10 is not a large hopper for storing general materials, and a hopper having a small capacity is used. The upper limit level sensor 140 and the lower limit level sensor 143 are mounted on the hopper 26, and the storage amount of the molding material in which the controller 139 is stored in the hopper 26 is the upper limit level sensor 140 and the lower limit level sensor. The feed amount of one injection shot of each powder metering feeder 135C and pellet metering feeder 137C was controlled so as to be between 143. The feed amount was controlled by driving the powder metering feeder 135C and the pellet metering feeder 137C on / off.

A mold 30 capable of simultaneously performing injection molding of the Charpy test piece and the UL test piece (thickness of 1.6 mm) was set in the injection molding apparatus 10. Heating temperature of the injection molding apparatus was set to 195 degreeC, 195 degreeC, 190 degreeC, 180 degreeC, and 30 degreeC from the nozzle 12 side. The injection volume of one shot was set at 25 g. Although the injection molding apparatus 10 includes three heaters 24 in FIG. 8, the injection molding apparatus was used for this test C. In addition, in this test, the molding material was fed into the cylinder 14 by the weight of the molding material without using the metering control feeder 141 of the table feeder type provided in the hopper 26.

In the test specimens of 20 samples continuously molded in the 11th to 13th firing powders under the injection molding conditions of Examples 1 to 4 and Comparative Examples 1 to 3 described later, four items: "weight of the test specimen (Change) "," Charpy impact "," combustibility "and" dispersibility "were evaluated.

Test methods for evaluation of "weight (change) of specimen", "Charpy impact", "combustibility" and "dispersibility" are as described below.

(Weight (change) of test piece)

When the standard deviation of the weights of the 20 measured samples was sigma, a standard deviation (sigma) of less than 0.8 was a pass (pass), and a standard deviation (sigma) of 0.08 or more was fail (drop out).

(Charpy impact test)

The Charpy impact test was the same as in Test A and Test B.

(Combustion test: UL94-V)

The combustibility test was the same as in the test A and the test B of the first embodiment, the flame retardancy of V-1 or more was passed (passed) and the flame retardancy of less than V-2 was rejected (dropped).

(Dispersibility test)

The dispersibility test was the same as in the test A and the test B of the first embodiment.

(Judgment)

When all four evaluation items passed the test, it was determined to be a pass (pass), and when any one of the evaluation items failed, it was determined to be a fail (dropout).

[Injection Molding Conditions and Test Results of Examples and Comparative Examples]

The table of FIG. 14 shows injection molding conditions and test results of the examples and comparative examples of Test C. FIG.

(Example 1)

In Example 1, the pellet material A and the powder material B were fed into the hopper 26 to be 100% synchronized by the pellet metering feeder 137C and the powder metering feeder 135C. As a result, "weight (change) of the test piece" was pass and "dispersibility" was A which is the highest evaluation, and it was discovered that the pellet material (A) and the powder material (B) were mixed uniformly. As a result of the uniform mixing, the evaluation of both "Charpy impact" and "combustibility" was a pass, and the overall evaluation was also a pass.

(Example 2)

In Example 2, the pellet material A and the powder material B were fed into the hopper 26 to be 60% synchronized by the pellet metering feeder 137C and the powder metering feeder 135C. As a result, the evaluation of "dispersibility" and the value of "Charpy impact" were slightly lower than Example 1 of 100% synchronization, but a pass level was obtained without any problem in quality.

(Example 3)

In Example 3, the pellet material A1 and the powder material B were fed into the hopper 26 to be 100% synchronized by the pellet metering feeder 137C and the powder metering feeder 135C. As a result, as in Example 1, "weight (change) of the test piece" was pass and "dispersibility" was A which is the highest evaluation.

The evaluation of "Charpy impact" and "combustibility" was also higher than Example 1, which was 100% synchronized. This was because the difference in volume specific gravity between the pellet material A1 and the powder material (B) of Example 3 was lower than the difference between the pellet material (A) and the powder material (B) of Example 1.

(Example 4)

In Example 4, the pellet material A1 and the powder material B were fed into the hopper 26 to be 60% synchronized by the pellet metering feeder 137C and the powder metering feeder 135C. As a result, the evaluation of "dispersibility" and the value of "Charpy impact" were slightly lower than Example 3 of 100% synchronization, but a pass level was obtained without any problem in quality. In addition, in Example 4, the difference in volume specific gravity is also lower than in Example 2, which is also 60% synchronized, and higher results than in Example 2 in the values of "dispersibility" and "Charpy impact" were obtained.

(Comparative Example 1)

In Comparative Example 1, the pellet material A and the powder material B were fed into the hopper 26 to be 50% synchronized by the pellet metering feeder 137C and the powder metering feeder 135C. As a result, evaluation of "weight (change) of the test piece" was pass, but evaluation of "Charpy impact", "combustibility", and "dispersibility" was rejected or D, and the comprehensive evaluation was also rejected.

(Comparative Example 2)

In Comparative Example 2, the pellet material (A) and the powder material (B) were not separately dry blended in the pellet mixing tank 137B and the powder mixing tank 135B as in Examples 1 to 4 and Comparative Example 1 , Dry blended together in powder mixing tank 135B and fed into hopper 26 by powder metering feeder 135C. As a result, all four evaluation items failed or were D, and the result of each item was lower than the comparative example 1. As shown in FIG. In particular, the evaluation of "dispersibility" was E, the lowest result.

(Comparative Example 3)

In Comparative Example 3, the test was performed according to Japanese Patent Application Laid-Open No. 2005-319813. Specifically, TOYO SEIKI SEISAKU-SHO, LTD. The metering feeder F3 by was turned on / off manually and the molding material was fed into the cylinder by the feeding method of Japanese Patent Application Laid-open No. 2005-319813. As a result, the evaluation of Comparative Example 3 was higher than other Comparative Examples 1 and 2, but lower than Examples 2 to 4 of 60% synchronization, and the comprehensive evaluation was failed. In particular, for dispersibility with an evaluation of D, in Comparative Example 3, the additive was continuously fed in the metering step and also in the injection step and the dwelling step in which the screw does not rotate after the metering step, which may affect the dispersibility. have.

[Review of the Results of Test C]

As is evident from the test results, the pellet material (A) (or A1) and the powder material (B) are fed directly into the cylinder of the injection molding apparatus for injection molding. In order to mix uniformly), it is important to satisfy the following three conditions.

(1) One injection shot of each material is fed into the hopper using a separate metering feeder.

(2) The material is supplied so that the supply time period from the start of the supply to the end is synchronized at least 60%.

(3) The supply ends in the weighing time of the weighing step of the injection molding cycle.

Claims (12)

By storing the molding material supplied into the cylinder of the injection molding apparatus at the tip of the cylinder by the rotation of the screw and stopping the rotation of the molding material after the screw is retracted to the weighing setting position by the pressure from the stored molding material itself. An injection molding method comprising a metering step of weighing an amount,
The weighing step is:
Setting a back pressure applied to the screw to a predetermined value;
Setting a rotation speed of the screw to a constant rotation speed within 50 to 300 rpm; And
Molding supplied into the cylinder when the molding time is represented by SN as the metering time of the normal feeding method in which the molding material is fed into the cylinder from the inlet port to fill the cylinder by the weight of the molding material according to the material feeding capacity of the screw's rotational speed. Adjusting the feed rate of the material such that the weighing time is more than twice the SN seconds and less than 180 seconds,
Thereby the weighing time is controlled irrespective of the rotational speed of the screw and the back pressure set value. The method of claim 1,
And at least the space before the compression zone is not filled with the molding material when the inside of the cylinder is divided in this order from the inlet port of the molding material into three zones: the supply zone, the compression zone, and the metering zone. The method of claim 2,
At the beginning of the injection molding, a state is created in which at least the space before the compression zone is not filled with the molding material, in which the molding material is quantified at a feed rate lower than the average consumption rate of the molding material in the normal feeding method. Injection molding method added from the supply device. The method according to any one of claims 1 to 3,
Wherein the molding material contains a base resin and an additive, at least one of the base resin and the additive is a powder, and the unpelleted molding material is fed directly into the cylinder. The method according to any one of claims 1 to 3,
Injection molding method in which a small amount of the molding material is continuously fed into the cylinder to adjust the feed rate. The method according to any one of claims 1 to 3,
And the molding material is intermittently fed into the cylinder to adjust the feed rate. The method according to any one of claims 1 to 3,
The molding material contains at least a powder material and a pellet material among the powder material, the pellet material and the liquid material,
One injection shot of each material is fed into the cylinder using a separate metering feeder in such a way that the feed time period from the start to the end of the feed is synchronized by at least 60%, the feed being metered in the metering phase of the injection molding cycle. Injection molding method finished in time. An injection molding method in which a molding material containing at least powder material and pellet material among powder material, pellet material and liquid material is directly supplied into a cylinder of an injection molding apparatus for injection molding, wherein the injection molding method is:
Feeding one injection shot of each material into the cylinder using a separate metering feeder in such a way that the feed time period from the start to the end of the feed is synchronized by at least 60%;
An injection molding method in which the supply is terminated within the metering time of the metering of the injection molding cycle. The method according to any one of claims 1 to 3 and 8,
The metering time is controlled in accordance with the required kneading time of the molding material. The method according to any one of claims 1 to 3 and 8,
The injection molding cycle comprises the steps of metering the molding material, clamping the mold, injection of molten resin from the cylinder into the mold, dwelling to dwell the pressure of the mold, cooling to cool the mold and to remove the molded article. A release step of releasing the mold,
The metering time is controlled in accordance with the time from the start of the cooling step of the injection molding cycle to the end of the release step. The method according to any one of claims 1 to 3 and 8,
Injection ratio of the powder of the molding material is 30% by weight or more. The method according to any one of claims 1 to 3 and 8,
The molding material contains a base resin and an additive, the base resin is at least one of a polylactic acid resin and a cellulose resin, and the additive is at least one of a flame retardant and a fiber.

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