JP5734018B2 - Injection molding method - Google Patents

Description

  The present invention relates to an injection molding method, and more particularly to an injection molding method in which a molding material containing a large amount of powder is directly put into a cylinder from a hopper.

  One of typical molding methods for resin (plastic) molding is an injection molding method. The injection molding method consists of filling a mold cavity consisting of a male mold and a female mold with a resin molding material melted in a heating cylinder (also simply referred to as a cylinder) with a screw or a plunger, followed by rapid cooling. This is a method of obtaining a molded product by taking it out from the mold.

  The molding cycle of injection molding is generally composed of a measuring process, a mold clamping process, an injection process, a pressure holding process, a cooling process, and a mold releasing process.

  Here, the measurement process will be described in detail. In the measurement process, the molding material supplied into the cylinder is stored at the tip of the cylinder by the rotation of the screw, and the screw is subjected to a predetermined measurement by receiving the pressure of the stored molding material itself. After retreating to the set position, stop the screw rotation and finish weighing. In this case, the hopper is filled with an amount of molding material that exceeds the rotational speed of the screw, that is, the material feeding capacity of the molding material, and the material in the hopper is placed inside the cylinder by the weight of the molding material according to the material feeding capacity of the screw. A normal supply method is generally used. Therefore, when the back pressure set value is constant, the metering time is shortened as the screw rotational speed is high, and the metering time is prolonged as the rotational speed is low. On the contrary, when the screw rotation number is constant, the measurement time becomes shorter as the back pressure is set lower, and the measurement time becomes longer as the back pressure is higher.

  By the way, as a resin molding material used for injection molding, petroleum-based resins have been mainly used conventionally, but problems such as air pollution, global warming, and ozone layer destruction have become obvious. Attempts have been made to build an energy-saving society. As one of them, conversion from petroleum resin molding materials to molding materials of plant resins derived from organisms such as plants has been attempted.

  Plant-based resin molding materials include so-called biomass resins (also referred to as biomass plastics or bioplastics), and attempts have been made to produce various products using these as molding materials.

  Typical examples of biomass resins include polylactic acid (also referred to as polylactic acid resin or PLA) and cellulosic resins. These biomass resins can be expected to eliminate carbon dioxide uptake and generation in the global environment, and this idea is called carbon neutral.

  However, when a molded product is manufactured by injection molding using a biomass resin as a molding material, the low heat resistance of the biomass resin becomes a problem. Biomass resin has a smaller difference between the temperature at which it can be melted by heat and it can easily flow, and the decomposition temperature of the resin, compared to petroleum-based resin, so it can be used in injection molding and pre-processing processes. There is a problem that the setting range is limited. For example, when the biomass resin and the additive are kneaded with a kneader and pelletized in the pretreatment before being supplied to the injection molding apparatus, if the resin is exposed to high heat for a long time, the resin is likely to be colored or reduced in molecular weight. In particular, in order to make the biomass resin flame-retardant, it is necessary to knead a large amount of flame retardant (usually powder) into the biomass resin. The biomass resin and the refractory agent are pelletized with a kneader in advance and then injection molded. It is preferable to supply the apparatus. However, there is a problem that the biomass resin is decomposed during the heat processing in the kneader and the strength of the molded product is lowered.

  In addition, the biomass resin has a brittle property in strength and has a problem that it is difficult to obtain strength. In particular, since the biomass resin needs to incorporate a large amount of flame retardant as described above, it becomes increasingly brittle in strength. For this reason, when a flame retardant is kneaded into the biomass resin to ensure flame retardancy, it is necessary to increase the strength by adding a reinforcing agent.

  As a method for increasing the strength of biomass resin, it can also be achieved by mixing petroleum resin, but this is not an essential solution for reducing environmental burden. As another method, there is a method of adding inorganic fibers such as glass fibers or petroleum-based organic fibers, which is preferable because strength can be obtained without significantly reducing the plantiness of the molded product. As another method, there is a method of adding a natural molding material such as bamboo or kenaf fiber in a fiber form. In this case, the fiber portion can be replaced with a carbon neutral material.

  Thus, in order to use biomass resin as a molding material for injection molding, it is common to add additives such as flame retardants and fibers. And considering the low heat resistance of the biomass resin, the biomass resin and the additive are not directly pretreated for kneading and mixing and pelletized, and the biomass resin and additive are directly fed into the injection molding apparatus. It is preferable for the quality of the molded product to employ a direct injection molding method (direct mixing: DM method).

  However, the injection molding apparatus is originally made as an apparatus premised on supply with pellets. For example, at least among powder materials (including fibers), pellet materials, and liquid materials, at least powder materials and pellets are used. There are the following two problems when the molding material composed of the material is directly supplied into the cylinder via the hopper of the injection molding apparatus.

  The first problem is that when powder material and pellet-like material are directly supplied, clogging occurs in the hopper outlet or in the cylinder due to a bridge caused by compression in the hopper, and so on, and thus there is a problem that stable supply is not possible. Further, even if it can be charged, the powder material and the pellet-like material are easily separated and become non-uniform in the cylinder, and there is a problem that the mixture is not sufficiently uniformly kneaded. In particular, when a large amount of powder material is contained in the molding material, it is difficult to perform uniform kneading by the direct injection molding method. In particular, when the ratio of the powder (including the molding material in a fine fiber state equivalent to the powder) in the molding material exceeds 30% by weight, uniform kneading becomes impossible with the conventional injection molding method.

  The second problem is that, for example, even if each material once mixed by a stirrer or the like is directly supplied to the hopper in order to directly supply the powder material and the pellet-like material, the injection molding apparatus is in the process of repeating the injection molding. Separation due to the vibration of each material, the shape of each material, the difference in specific gravity, and the like. As a result, the powder material and pellet-like material supplied from the hopper into the cylinder do not have the ratio as designed, and it becomes difficult to stably produce a molded product of uniform quality.

  As a technique for solving problems such as clogging and degassing of an injection molding apparatus, there is, for example, Patent Document 1, and as a conventional technique for performing a direct injection molding method, for example, Patent Document 2.

  Patent Document 1 discloses a so-called hungry feed in which a molding material is quantitatively supplied by a quantitative feeder mechanism instead of its own weight so as to form a space for separating a gas component (generated from the molding material) in a cylinder of an injection molding apparatus. Have been described. Thereby, it is supposed that degassing can be reliably performed without clogging the molding material in the cylinder, so that a molded product of good quality can be stably manufactured.

  Further, Patent Document 2 proposes that an additive be directly supplied to the screw portion with respect to the base resin supplied by its own weight in the cylinder of the injection molding apparatus. It is characterized by continuing supply not only in the process but also in the injection process and the pressure holding process. That is, paying attention to the fact that the base resin is supplied also in the injection process, the additive is supplied also in the injection process in a form supplementing it. Thereby, it is said that the concentration unevenness of the additive in the cylinder length direction in the cylinder can be improved.

JP 2005-319813 A JP 2001-277296 A

  However, even if the technique of Patent Document 1 is applied to injection molding of a molding material composed of biomass resin and additives (flame retardant, fiber, etc.), particularly direct injection molding method, it is possible to obtain a molded product of good quality. There is a problem that you can not. Patent Document 1 is based on the premise that the powder is originally supplied to the cylinder in the form of pellets. When a large amount of powder or fiber is supplied as a molding material, even if it is directly supplied from the hopper into the cylinder, it is uniformly kneaded. Therefore, a stable quality molded product cannot be obtained.

  By the way, in Patent Document 2, which is a prior art, additives are metered simultaneously with resin pellets naturally fed by gravity during the metering process, but only the additive is not metered (for example, during the injection process). The metering is continued even when the motor operates without rotating, thereby further stabilizing the amount (unevenness) of the additive in the molded product. When this method is used, the additive is supplied even in a state such as an injection process in which the screw advances without rotating, and it is possible to reduce variations in additive concentration and color unevenness of the colorant compared to conventional methods. Is possible.

  However, for example, while the screw during the injection process is moving forward, unlike the weighing process, the amount of resin pellets to be supplied changes, so the resin pellets that fall due to gravity and the additive that is being metered in The ratio cannot be controlled. Furthermore, since material stays at the material inlet (C2 portion in FIG. 1 in Patent Document 2) tends to increase, re-separation of the material easily occurs. In particular, as in the present invention, when the additive ratio in the molding material, that is, the powder material ratio is large, or when the apparent specific gravity of the powder material is small, the molding material cannot be made sufficiently homogeneous.

  In fact, when a molding material containing a large amount of powdered additive in pellet-shaped biomass resin is inspected by a direct injection molding method using the techniques of Patent Documents 1 and 2, the additive is It is not uniformly dispersed in the biomass resin, and a molded product of the desired quality cannot be obtained.

  From such a background, it is a fact that biomass resin and additives are kneaded in advance with a kneader to form pellets, and the pellets must be put into an injection molding apparatus to be molded.

  However, as described above, the biomass resin has low heat resistance, and high heat is applied in the pretreatment by the kneader, so that the molding material is deteriorated before being supplied to the injection molding apparatus, resulting in a decrease in molecular weight or coloring. End up. As a result, even if the molding material can be processed into a pellet shape suitable for a corner or an injection molding apparatus, the molecular weight of the resin is lowered, the strength of the molded product is not increased, or the molded product is colored and the quality is deteriorated. There is a problem.

  The present invention has been made in view of such circumstances, and can prevent clogging even if a molding material, particularly a molding material containing a large amount of powder, is directly charged into an injection molding apparatus by a direct charging molding method. Since the molding material can be sufficiently uniformly kneaded in the cylinder, for example, an injection molding method capable of stably producing a high-quality molded product even when using a biomass resin having low heat resistance is provided. Objective.

In order to achieve the above object, the injection molding method of the present invention 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 receives the pressure of the stored molding material itself. In the injection molding method comprising a metering step of stopping the rotation of the screw after the screw has moved back to the metering setting position, the molding material is composed of a base resin and an additive, and the base resin and the additive At least one of them is powder, and the molding material is directly supplied into the cylinder without being pelletized. In the measuring step, the back pressure applied to the screw is set to a predetermined value and the screw is rotated. The number is set to a constant rotational speed in the range of 50 rpm or more and 300 rpm or less, and in the measuring step, the screw rotational speed material is set. Supply speed of the molding material supplied into the cylinder when the metering time in the normal supply method in which the molding material is charged into the cylinder by its own weight from the inlet according to the capacity is SN seconds, Adjusting the metering time so that the metering time is not less than twice the SN and not more than 180 seconds, whereby the metering time is controlled independently of the set value of the rotational speed of the screw and the back pressure. To do.

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

  According to the present invention, the measurement time is not determined by the rotational speed of the screw, i.e., the material feeding ability and the back pressure setting value for feeding the molding material in the cylinder as in the prior art, but the rotational speed and back pressure setting of the screw. By adjusting the molding material supply speed completely independently of the value, the metering time is controlled in a way that is independent of the screw feed capacity and back pressure setting value (hereinafter referred to as “metering time control”). . That is, in the metering time control, when the back pressure is set to a predetermined value, the rotational speed of the screw is set to a constant rotational speed at which high kneading performance of 50 rpm or more and 300 rpm or less is obtained, while the molding material supplied into the cylinder Was adjusted so that the metering time was not less than twice the metering time SN and 180 seconds or less of the metering time SN in the normal feeding method in which the molding material was filled in the cylinder.

  As a screw rotation speed, 150-200 rpm is more preferable, and as metering time, it is more preferable that it is 5 times or more SN and 20 times or less SN.

  As a result, the number of rotations of the screw can be rotated at a speed suitable for kneading, and the measurement time can be increased. For example, a molding material composed of a large amount of powder, fibers, etc. can be directly supplied into the cylinder. However, it is possible to sufficiently secure the screw rotation speed and the necessary kneading time necessary for uniformly kneading the molding material.

In this case, the rotation speed of the screw is set to a rotation speed of 50 rpm or more and 300 rpm or less in consideration of both improvement in kneading performance and deterioration due to shear heat generation. In addition, about a back pressure setting value, although it can set to a desired value, the range of 5-150 kg / m < ² > is preferable.

  Furthermore, since the metering time can be increased regardless of the number of rotations of the screw and the set value of the back pressure, the supply amount of the molding material can be greatly reduced with respect to the material feeding capability of the screw. Thereby, for example, even if a molding material containing powder that easily causes bridging or clogging is supplied directly into the cylinder, bridging or clogging does not occur. Note that the molding material containing powder includes not only a part of the molding material is powder but also 100% powder.

In the present invention, when the inside of the cylinder is divided into three zones of a supply zone, a compression zone, and a metering zone in order from the injection port of the molding material, it is preferable that at least the supply zone is not filled with the molding material. .

  Here, not filling the molding material means that the molding material is transported in a sparse state rather than a dense state in the cylinder, and a dense state and a sparse state may be alternately formed in the cylinder. Including.

This prescribes the degree of filling of the molding material in the cylinder. In the compression zone, which is an important zone especially for uniform kneading, the molding material is not filled at least before the compression zone. The material supply is reduced, and it takes a long time for the back pressure necessary for the backward movement of the screw. That is, the necessary kneading and dispersing time can be secured sufficiently. In this case, at the start of the injection molding, “ at least the supply zone is not filled with the molding material” is formed, and in this state, the average consumption of the molding material by the normal supply method is less than the constant supply method. The molding material is replenished into the cylinder at a supply speed of Thereby, the state which is not filled with the molding material at the time of the start of injection molding can be maintained even after continuing injection molding.

  In particular, in the case of a molding material containing a large amount of powder, the molding material in the vicinity of the screw shaft remains unmelted in the compression zone, and is easily sent to the measuring zone while being wound around the screw shaft. As a result, the molding material that is not sufficiently uniformly kneaded reaches the measuring zone, so that the quality of the injected molded product is deteriorated.

  In the present invention, the amount of molding material supplied can be made smaller than the material feeding ability of the molding material by the screw rotation speed by setting the metering time to be not less than twice the metering time SN in the normal supply method and not more than 180 seconds. Accordingly, the degree of fullness of the molding material in the compression zone can be reduced to suppress excessive shearing heat generation, and a longer kneading time can be taken, so even a molding material containing a large amount of powder can be uniformly kneaded. Is possible.

  In the present invention, the metering time is preferably controlled according to the required kneading time of the molding material. Here, as described above, the necessary kneading time of the molding material means a time required until the molding material is uniformly kneaded in the cylinder, and can be obtained by a preliminary test or the like. However, when the necessary kneading time exceeds 180 seconds, it is set to 180 seconds.

  Moreover, in this invention, it is preferable to control metering time according to the time from the cooling process start to the completion | finish of a mold release process among injection molding cycles. Thereby, it is not necessary to provide time (waiting process) during which the rotation of the screw stops from the start of the cooling process to the end of the mold release process. Therefore, not only the molding material can be sufficiently kneaded but also the uneven heating of the molding material due to the stoppage of the screw can be prevented.

  The present invention can also be applied to a molding material in the form of a pellet. The molding material is composed of a base resin and an additive, and at least one of the base resin and the additive is a powder, and the molding material is pelletized. It is preferable to supply directly into the cylinder without making it. In particular, it is preferable that 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. In this case, the ratio of the biomass resin in the molding material is preferably 30% by weight or more, and particularly preferably 50% by weight or more. This is because it can contribute to reducing the environmental load.

  Here, supplying the molding material directly into the cylinder means that the pre-processing for pelletizing the molding material by kneading and mixing in advance with a kneader or the like is not performed.

  In this way, when a biomass resin having low heat resistance and a powdery or fibrous additive (for example, a flame retardant or fiber) that is added in a large amount and difficult to uniformly knead are directly supplied to a cylinder for injection molding This is because a high-quality molded product can be stably produced.

  In the molding material, the powder ratio is preferably 30% by weight or more. This is because the present invention is particularly effective at such a high powder ratio. In particular, the powder ratio is preferably 50% by weight or more.

  In the present invention, it is preferable to adjust the supply speed by continuously supplying a small amount of the molding material into the cylinder or intermittently supplying the molding material into the cylinder.

  As a result, the supply speed can be slowed, and the supply speed can be easily equalized, so that variations in kneading in the weighing process are unlikely to occur.

  According to the injection molding method of the present invention, a molding material, particularly a molding material containing a large amount of powder can be prevented from being clogged even if it is directly fed into an injection molding apparatus by a direct feeding molding method, and molded in a cylinder. Since the materials can be sufficiently uniformly kneaded, a high-quality molded product can be stably produced even when, for example, a biomass resin having low heat resistance is used.

Schematic configuration diagram of an injection molding apparatus for carrying out the injection molding method of the present invention Explanatory drawing explaining the zone composition of an injection molding device Explanatory drawing explaining a general injection molding cycle Explanatory drawing explaining the general relationship between the rising speed of back pressure and screw rotation speed Explanatory drawing explaining the behavior in the compression zone when 100% pellet molding material is injection molded Explanatory drawing explaining the behavior in the compression zone when injection molding a molding material containing 30% by weight or more of powder Explanatory drawing explaining the position of the screw in the measurement process of the present invention Table showing injection conditions and results in Examples of Test A Table showing injection conditions and results in Comparative Example of Test A A photograph comparing the adhesion of the powder material to the screw shaft in Test A between Example and Comparative Example Table showing injection conditions and results in Examples of Test B Table showing injection conditions and results in comparative example of test B Explanatory drawing explaining normal supply Explanatory drawing explaining Hungry Feed Explanatory drawing explaining “Flip-Floating” in the present invention Explanatory diagram of the further advanced state of “Flip-Floating” in the present invention Explanatory drawing of the limit state of “Flip-Floating” in the present invention

  Hereinafter, preferred embodiments of the injection molding method of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing an example of an injection molding apparatus for carrying out the injection molding method of the present invention.

  As shown in FIG. 1, the injection molding apparatus 10 includes a cylinder 14 having a nozzle 12 at the tip, and a screw 16 is rotatably disposed in the cylinder 14. At the opposite end of the nozzle 12 and at the rear end of the screw 16, the motor 16 that rotates the screw 16 and the screw 16 are fixed in the axial direction (the left-right direction in FIG. 1) based on the set values of pressure and speed. A motor / piston device 22 including a piston device 20 that moves forward and backward by a stroke is provided. The piston device 20 causes the screw 16 to advance leftward in FIG. Further, the piston device 20 is provided with a back pressure sensor 17 for detecting a back pressure at which the screw 16 moves backward in the measuring step, and a measured value is input to a controller 41 described later. The controller 41 receives a measurement signal from the motor / piston device 22 to notify the start and end of the measurement process.

  A heater 24 is wound around the outer periphery of the cylinder 14, and the cylinder 14 is heated to a predetermined temperature based on a melting temperature (plasticization temperature) of a molding material to be injection molded. The tip of the nozzle 12 is connected to a gate 32 of a mold 30 that forms a cavity 28 therein. The mold 30 includes a fixed mold 30A and a movable mold 30B, and the movable mold 30B opens and closes the fixed mold 30A.

  In the longitudinal direction of the cylinder 14, an inlet 25 for supplying a base resin, an additive, and the like, which are molding materials, into the cylinder 14 is formed at the opposite end of the nozzle 12, and a hopper 26 is formed in the inlet 25. It is attached.

  As shown in FIG. 2, the inside of the cylinder 14 is divided into three zones of a supply zone, a compression zone, and a metering zone in order from the molding material inlet 25. The molding material charged into the supply zone from the hopper 26 through the charging port 25 is transported in the cylinder 14 to the screw tip side by the rotation of the screw 16. The molding material conveyed in the cylinder 14 is gradually melted by the shear heat generated between the surface of the rotating screw 16 and the inner surface of the cylinder 14 and the heat from the heater 24 provided on the outer periphery of the cylinder 14. Melting and kneading of the molding material is started in the compression zone. The molding resin melt-kneaded in the compression zone is further conveyed forward and reaches the measurement zone. Then, as the melt-kneaded molding material accumulates at the tip of the cylinder 14, the screw 16 moves backward, and when it reaches the measurement setting position, the backward movement stops.

  The material supply device 34 mainly includes a mixer 36 for mixing, for example, a base resin and additives constituting the molding material, a powder and granular quantity supply device 38, a metering control feeder 40, and a controller for controlling the supply of the molding material. 41. The mixer 36 may be any as long as it can uniformly mix the base material and the additive, and a stirring method, a vibration method, an air flow method, or the like can be used. Moreover, as the powder and granular constant supply machine 38, there are a table feeder, a belt feeder, a screw feeder, a rotary feeder, a bin discharger, a circle feeder, and the like, which can be appropriately used in the properties of the molding material.

  A predetermined amount of the molding material in which the base resin and the additive are mixed in the mixer 36 is cut out by the powder particle quantity supply unit 38. The cut molding material is sent to the weighing control feeder 40 via the shooter 42. The measurement control feeder 40 is provided with a sensor 44, and the sensor 44 detects whether or not the molding material is stored in the measurement control feeder 40 and transmits it to the controller 41. The controller 41 is necessary for one cycle of the metering process from the powder quantitative supply unit 38 to the metering control feeder 40 in the time zone in which the metering control feeder 40 is waiting, that is, the time zone in which the metering control feeder 40 is not stored. A certain amount of molding material is fed.

  The controller 41 includes a type of molding material (type of resin, type of additive, etc.), shape of the material (powder, granule, liquid, pellet), mixing ratio (ratio of base resin and additive), injection Depending on various factors such as molding conditions (injection amount per shot, cylinder heating temperature, screw rotation speed, back pressure setting value, etc.), the necessary kneading time data required for uniform and sufficient mixing of the molding material Have been entered. These necessary kneading time data can be obtained in advance by a preliminary test or the like. In addition, the controller 41 is input with the relationship between the metering time for securing the necessary kneading time and the supply speed of the molding material from the metering control feeder 40.

  The controller 41 sets the back pressure to a predetermined value and sets the rotational speed of the screw 16 to a constant rotational speed in the range of 50 rpm to 300 rpm, while feeding the molding material in accordance with the material feed capability of the screw rotational speed. When the metering time in the normal supply method that fills the cylinder 14 with its own weight from the mouth 25 is SN seconds, the supply speed of the molding material supplied into the cylinder 14 is not less than twice SN and not more than 180 seconds. Adjust the weighing time. That is, the controller 41 adjusts the supply speed of the molding material supplied into the cylinder 14 from the measurement control feeder 40 via the hopper 26 regardless of the rotational speed of the screw 16 and the back pressure setting value, thereby measuring the measurement process. Is controlled in accordance with the required kneading time of the molding material within the range of not less than twice SN and not more than 180 seconds (“metering time control”). A more preferable metering time in the metering time control is in the range of 5 times SN to 20 times SN.

  As a result, the number of rotations of the screw can be rotated at a speed suitable for kneading, and the measurement time can be increased. For example, a molding material composed of a large amount of powder, fibers, etc. can be directly supplied into the cylinder. However, it is possible to sufficiently secure the screw rotation speed and the necessary kneading time necessary for uniformly kneading the molding material.

  In this case, it is preferable to set the rotation speed of the screw to 50 rpm or more and 300 rpm or less in consideration of both improvement in kneading performance and deterioration due to shear heat generation. More preferably, it is set in the range of 150 to 200 rpm. If the screw speed is less than 50 rpm, uniform kneading cannot be performed sufficiently, and if it exceeds 300 rpm, the molding material may be deteriorated by shearing heat generation. In particular, when the base resin of the molding material is a biomass resin, the risk of deterioration increases when it exceeds 300 rpm.

  Moreover, uniform kneading cannot be performed if the supply speed of the molding material supplied into the cylinder is less than twice the measuring time SN in the normal supply method for filling the cylinder with the molding material. On the other hand, if the metering time is longer than 180 seconds, even if uniform kneading is possible, the molecular weight is lowered due to decomposition of the base resin, and the strength of the molded product obtained by injection molding is reduced. Therefore, if the necessary kneading time obtained by the preliminary test exceeds 180 seconds, it is preferably set to 180 seconds.

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

  The injection molding cycle generally includes a measuring process, a mold clamping process, an injection process, a pressure holding process, a cooling process, and a mold releasing process.

  In the metering step, the molding material supplied into the cylinder 14 heated from the hopper 26 is kneaded and melted (plasticized) by the rotation of the screw 16, and the molten molding material is stored in the cylinder tip 14A. To go. Then, under the pressure of the stored molding material itself, the screw 16 moves backward while rotating, and when reaching a preset measurement value, the screw stops rotating and the measurement is finished. The time required for the weighing process is called weighing time.

  The mold clamping process is a process of closing the mold 30 between the movable mold 30B and the fixed mold 30A in the mold open state, and the movable mold 30B is moved to the fixed mold 30A by a mold clamping cylinder (not shown). The mold 30 is closed by moving it to the contact position.

  In the injection process (also referred to as a filling process), the molding material melted and fluidized in the cylinder 14 is injected into the mold 30 through the nozzle 12 as the screw 16 advances. Thereby, the molten molding material is filled in the cavity 28 of the mold 30.

  In the pressure holding process, pressure is applied to the cavity 28 by the screw 16 even after the molding material melted in the injection process is filled in the cavity 28 of the mold 30. Thereby, the molding material in the cavity 28 is formed into a cavity shape.

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

  In the mold release step, the mold 30 is opened by moving the movable mold 30B away from the fixed mold 30A by the mold clamping cylinder. Thereby, the molded product is released from the mold 30.

  In each of the above steps, after the pressure holding is completed, the screw 16 can freely move. Therefore, as shown in FIG. 3, the n + 1 cycle measuring step exceeds the n + 1 cycle cooling step as much as possible. The efficiency of the molding cycle is improved by lapping.

  FIG. 4 is a diagram showing a general relationship between the increasing speed of the back pressure and the number of rotations of the screw 16 in the above-described measuring process. As can be seen from the straight line rising upward in FIG. 4, the higher the rotational speed of the screw 16, the faster the back pressure increases. Therefore, if the rotational speed of the screw 16 is increased to increase the shearing force on the molding material, the back pressure rises in a short time, and the measuring process ends. Thereby, a long time for kneading the molding material cannot be secured.

  On the contrary, if the rotational speed of the screw 16 is lowered, the time for increasing the back pressure can be delayed and the kneading time can be secured long. However, since the rotational speed of the screw 16 is low, the shearing force for sufficiently kneading the molding material is increased. Cannot be granted.

  Therefore, in the conventional injection molding method in which the metering time of the metering process is determined based on the rotation speed of the screw 16 and the back pressure setting value, a long kneading time cannot be ensured. When the cooling time required for the cooling process is longer than the measuring time of the measuring process, as shown in the injection molding cycle of FIG. 3, the waiting process after the measuring process is completed between the measuring process and the mold clamping process. Is required. The waiting process is a state in which the metering process is completed and the screw 16 is stopped, so that the kneading is stopped. Thereby, there is a possibility that a sufficient kneading time of the molding material cannot be secured, and when the screw 16 is stopped, the heating of the molding material is unevenly distributed, and a plastic distribution is likely to occur.

  Especially in the case of molding materials that require a large amount of additives such as flame retardants and fibers to improve quality, such as biomass resin, it is necessary to sufficiently stir and knead the materials in the metering process, and the cooling process starts. It is important to make full use of the time from the start to the end of the mold release process for kneading.

  Therefore, as shown in the A zone in FIG. 4, both the high shearing force and the kneading time can be satisfied if the back pressure rise rate can be slow despite the high rotation speed of the screw 16. it can.

  Therefore, in the injection molding method of the present invention, as described above, the required kneading time is adjusted by adjusting the supply speed of the molding material supplied from the hopper 26 into the cylinder 14 regardless of the rotational speed of the screw 16 or the back pressure setting value. The metering time was controlled according to.

  That is, when the above-described factors such as the type of molding material and molding conditions are input to the controller 41, the controller 41 selects a measurement time required for the molding material from the input necessary kneading time data. Further, the controller 41 calculates a supply speed for the required kneading time from the start of measurement to the end of the molding material stored in the measurement control feeder 40 for one cycle. Set to control feeder 40. Thereby, the measurement control feeder 40 supplies the molding material for one cycle into the cylinder 14 via the hopper 26 based on the calculated supply speed.

  For example, if the necessary kneading time required for kneading the biomass resin and the additive (flame retardant + glass fiber) uniformly and sufficiently is 20 seconds, the weighing time in the weighing process is at least 20 seconds or more. Thus, the supply speed of the molding material for one cycle stored in the weighing control feeder 40 is controlled. In this case, the supply rate from the start of the weighing process to the end of the weighing process is preferably as uniform as possible. Therefore, a small amount continuous supply method (pull-filling) in which the molding material is continuously and gradually dropped from the measurement control feeder 40 to the hopper 26, or intermittent supply in which a constant amount is intermittently dropped from the measurement control feeder 40 to the hopper 26 at regular intervals. It is preferable to adopt the method.

  As a result, the rotational speed of the screw 16 can be rotated at a high speed suitable for kneading, and the measuring time during which the screw 16 is rotating can be lengthened. For example, a molding material composed of a large amount of powder or fiber Even if it is directly supplied into the cylinder 14, sufficient kneading can be performed.

  Further, since the metering time can be increased regardless of the number of rotations of the screw 16, even if a molding material containing powder is directly supplied into the cylinder 14, the material feed of the screw 16 relative to the molding material supply speed is achieved. Since the capacity is far greater, the molding material is not clogged at the outlet of the hopper 26 or in the cylinder 14.

  In particular, when the proportion of powder in the molding material is 30% by weight or more, uniform injection can be performed by performing the injection molding method of the present invention, and the molding material can be discharged into the outlet of the hopper 26 or in the cylinder 14. It becomes possible to perform injection molding without clogging.

  In other words, it has good heat resistance like petroleum-based resin, and even if it has a powder material as an additive, it can be pelletized by a kneader as a pretreatment for injection molding, so all the molding material is put into the cylinder 14 in the pellet state. It becomes possible to do. However, when the heat resistance is poor like biomass resin and it has a large amount of powder material as an additive, it cannot be pelletized in a kneader as a pretreatment for injection molding, It is directly put into the cylinder 14 as it is.

  Then, when a molding material of 100% pellets is directly put into the cylinder 14 (DM method), and a molding material containing 30% by weight or more, especially 50% by weight or more of powder is directly put into the cylinder 14 (DM method). ), The melting behavior of the molding material in the compression zone is quite different. That is, most of powder materials (including fibrous materials) such as flame retardants, compatibilizers, and decomposition inhibitors used as additives do not melt. For this reason, even when shearing is applied in the same manner as when the resin pellets are sheared, the resin deteriorates due to sudden heat generation due to friction between the powder material and the inner wall surface of the cylinder. Further, since the powder material is bulkier than the pellet and easily forms a gap in the cylinder, the heat of the heater 24 provided on the outer periphery of the cylinder is not easily transmitted. For this reason, in the compression zone, only the molding material near the inner wall surface of the cylinder 14 becomes hot and melts, but heat is not easily transmitted to the molding material on the shaft side of the screw 16 and is difficult to melt. Therefore, in a short time measurement, the molding material near the shaft side of the screw 16 is sent to the screw tip through the measurement zone without being melted. As a result, the molding material containing a large amount of the powder material cannot be uniformly kneaded, and the quality (strength, flame retardancy, appearance color, etc.) of the molded product obtained by injection molding is reduced. In fact, when a molding material containing 30% by weight or more of the powder material is molded by a conventional molding method and then the screw 16 is pulled out of the cylinder 14 and observed, the molding material near the inner wall surface of the cylinder 14 at the end of the compression zone is Although it is melted, the molding material in the vicinity of the shaft of the screw 16 remains as a powder without melting. This will be described in detail with reference to FIGS.

  FIG. 5 shows the melting behavior of the molding material in the compression zone when 100% pellets of the molding material are supplied into the cylinder by the conventional normal supply method of supplying the molding material into the cylinder 14 in a full manner. As shown in FIG. 5A, an unmelted molding material forms a solid bed layer S and a melt film layer M in which the molding material is melted is formed on the inner wall surface portion of the cylinder 14 at the compression zone inlet portion. When this melt film layer M is formed, the solid bed layer S is melted by heat generated by shear energy, and an unmelted molding material is dispersed in the central portion of the compression zone as shown in FIG. 5B. P is formed. As shown in FIG. 5C, almost no unmelted molding material is left in the melt pool P at the exit portion of the compression zone. Thereby, uniform kneading can be performed.

  FIG. 6 shows a melting behavior of the molding material in the compression zone when a molding material containing 30% by weight or more of powder (the rest is in a pellet state) is supplied into the cylinder 14 by a conventional normal supply method. As shown in FIG. 6A, at the compression zone inlet portion, the powder and pellets are separated during the conveyance of the screw 16, the pellet layer X is formed on the cylinder 14 side, and the powder layer is formed on the shaft side of the screw 16. Y is formed. And it fuse | melts from the pellet layer X near the cylinder 14 side, and forms the melt film layer M like FIG. 6 (B). However, when the powder layer Y is present, the melt pool P is not formed in the entire compression zone like 100% pellets, and heat transfer to the entire compression zone is deteriorated. As a result, as shown in FIG. 6C, the powder layer Y adheres to the vicinity of the shaft of the screw 16 also at the outlet of the compression zone, and is sent to the measuring zone while being wound around the shaft of the screw 16. As a result, the molding material that is not sufficiently uniformly kneaded reaches the measuring zone, so that the quality of the injected molded product is deteriorated.

  Further, when a biomass resin such as polylactic acid is used as the base resin, the melting point of polylactic acid is around 170 ° C., but the decomposition starts rapidly from around 220 ° C. Thus, since melting | fusing point temperature and decomposition temperature are close, heating and melting are very difficult. Since the fluidity is very poor near the melting point, it is desired to melt it by raising the temperature as much as possible. In particular, a molding material containing 30% by weight or more of a powder that is difficult to melt as described above in a base resin of polylactic acid cannot be melted by heating unless the molding set temperature is raised to about 200 ° C. However, the molding material containing a large amount of the powder material rises by 15 to 25 ° C. from the molding set temperature of the cylinder 14 due to shear heat generation, and the cylinder internal temperature is heated to about 220 ° C.

  However, even when a molding material containing 30% by weight or more of powder is directly supplied into the cylinder, the screw required for kneading is ensured by ensuring a long measurement time regardless of the screw rotation speed and back pressure setting value. It is possible to significantly reduce the molding material density in the cylinder 14, particularly in the compression zone, while ensuring the rotational speed. Thereby, since excessive shearing is not applied to the molding material, the temperature rise of the cylinder internal temperature due to shearing heat generation can be suppressed. Further, even if the molding material density in the cylinder is low, by ensuring a long metering time, heat on the cylinder 14 side is slowly transmitted to the shaft side of the screw 16, and the screw rotation speed can be increased while ensuring a long metering time. Since it can be increased, the kneading efficiency is improved. Thereby, even if it is a molding material which contains 30 weight% or more of powders, since it is easy to form the melt pool P in the whole compression zone, uniform kneading can be performed without generating the quality degradation of a molded product.

  For uniform kneading without causing deterioration of the quality of the molded product, when the back pressure is set to a predetermined value, the rotation speed of the screw 16 is set to a constant rotation speed of 50 to 300 rpm suitable for kneading. Regardless of the rotation speed of the screw 16 or the back pressure setting value, the material supply speed is adjusted so that the measurement time is not less than twice the measurement time SN in the normal supply method and not more than 180 seconds. It can be achieved by securing.

  In this case, it is preferable to supply the molding material so that the molding material is not filled at least before the compression zone in the three zones of the supply zone, the compression zone, and the metering zone in the cylinder. That is, at the start of injection molding, a state in which the molding material is not filled at least before the compression zone is formed, and in this state, molding is performed at a supply speed that is less than the average consumption of the molding material by the normal feeding method from the quantitative feeder 40. It is preferable to replenish the material. Thereby, the state which is not filled with the molding material at the time of the start of injection molding can be maintained even after continuing injection molding.

  In particular, in the compression zone, by not filling the molding material, heat transfer from the cylinder 14 side to the shaft side of the screw 16 is improved, thereby promoting melting of the powder layer formed on the shaft side.

  The number of required metering times to be set within the range of not less than twice the metering time SN and not more than 180 seconds can be appropriately determined by a test or the like in advance depending on the composition of the molding material and the conditions of the injection molding apparatus. Also, the measurement time SN of 2 seconds to 180 seconds is within the range where there is no problem even with a molding material containing 30% by weight or more of powder, and the molding conditions are not strict like the molding material of 100% pellets. Of course, it can be applied to.

  The metering time controlled according to the necessary kneading time can be arbitrarily set by confirming the mixing of the materials within the total time of the cooling step and the release step, but the cooling step and the release step. When the total time is set to coincide with the above, it is preferable because higher kneading performance can be obtained.

  Thereby, since the above-mentioned waiting process can be eliminated, the state where the screw 16 is always rotated can be maintained during the measuring process.

  If the metering time is longer than the total time, it is preferable to select a condition in which the number of rotations of the screw 16 is increased from the necessary kneading time data so that the metering time matches the total time.

  FIG. 7 is a diagram showing an image of the measurement process when the measurement time controlled according to the necessary kneading time coincides with the total time of the cooling process and the release process. The supply rate of the molding material at this time is assumed to be Qg per minute. FIG. 7A shows the start of the cooling process, FIG. 7B shows the end of the cooling process, and FIG. 7C shows the end of the mold release process. Of the stroke in which the screw 16 advances and retreats, the most advanced position (left side position in FIG. 7) is shown as the X position, and the most backward position is shown as the Y position.

  Simultaneously with the start of the cooling process in FIG. 7A, the molding material is supplied into the cylinder 14 at a supply rate of Qg / min, and the metering process is started. The position of the screw 16 at this time is the X position on the most nozzle side in the forward / backward stroke of the screw.

  As the molding material is supplied, the back pressure rises, and the back pressure gradually moves back while rotating the screw 16. Then, as shown in FIG. 7B, at the end of the cooling step, the screw 16 is positioned slightly closer to the Y side than the middle between the X position and the Y position. Further, as the supply of the molding material continues, the screw moves backward, and reaches the Y position simultaneously with the end of the mold release process as shown in FIG.

  Thus, in the injection molding method of the present invention, the metering time can be controlled according to the required kneading time, so even a molding material that requires a long time for kneading can be kneaded uniformly and sufficiently. it can. Therefore, the present invention is particularly effective as a molding method for injection molding by the direct supply method of biomass resin.

  Next, preferable conditions for the molding material used in the present invention will be described.

  The present invention is applicable to petroleum resins, but is preferably applied to biomass resins such as polylactic acid resins and cellulose resins.

  Various types of polylactic acid resins can be used, and examples thereof include lactic acid homopolymer resins and lactic acid copolymer resins. Also, the lactic acid component that is a raw material of the polylactic acid resin is not particularly limited. For example, L-lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof, or L-lactide or D-lactide that is a lactic acid cyclic dimer. , Meso-lactide, or mixtures thereof.

  The production method of the polylactic acid resin used in the present invention is not particularly limited, and various resins synthesized by a conventionally known method can be used. The lactic acid homopolymer resin is, for example, L-lactic acid, D-lactic acid, DL-lactic acid or the like, or a mixture thereof directly dehydrated or condensed, or L-lactide, D-lactide, meso-lactide, or these It can be obtained by ring-opening polymerization of a mixture or the like. The lactic acid copolymer resin can be obtained, for example, by copolymerizing a lactic acid monomer or lactide and another component copolymerizable with the monomer. Examples of other copolymerizable components include dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones, etc. having two or more ester bond-forming functional groups in the molecule, and various constituents thereof. And various polyesters, various polyethers, and various polycarbonates.

  Further, the weight average molecular weight of the polylactic acid-based 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 preferable because the strength of the obtained molded product of the present invention is further increased. A weight average molecular weight of 500,000 or less is preferable because the molding material used for injection molding tends to be uniform, and the strength of the molded product obtained thereby tends to increase.

  The cellulose resin is not particularly limited, but diacetyl cellulose (DAC), triacetyl cellulose (TAC), cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP) can be preferably used. The particle size of the cellulosic resin supplied from the cellulosic resin manufacturer is generally supplied to the user as an irregular granule in the range of 1 to 30 mm.

  In the present invention, the content of the biomass resin that is the base resin of the molding material supplied to the injection molding apparatus is preferably 30% by mass or more, and more preferably 50% by mass or more. By setting it as such a structure, the outstanding environmental performance can be provided to the shape | molded fiber containing injection molded product.

  The flame retardant (flame retardant) used as an additive in the present invention is not particularly limited, and various known flame retardants used for flame-retarding a resin (molded product) can be used. Examples include brominated flame retardants, chlorine-based flame retardants, phosphorus-containing flame retardants, silicon-containing flame retardants, nitrogen compound-based flame retardants, and inorganic flame retardants. Among these, phosphorus-containing flame retardants that have little flame retardant effect and have little possibility of adversely affecting the environment when incineration and disposal of molded products with less corrosion of equipment and molds during kneading and molding with resins Is preferred.

  There is no limitation in particular as a phosphorus containing flame retardant, A well-known thing can be used. For example, organic phosphorus compounds such as phosphoric acid esters, phosphoric acid condensed esters, and polyphosphates are exemplified. Specifically, as the phosphate ester, as an example, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, Tris (isopropylphenyl) phosphate, tris (phenylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl (2-ethylhexyl) phosphate, di (isopropylphenyl) phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate Diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dimelamine phosphate, melamine pyrophosphate, triphenylphosphine oxide, tricresylphosphine oxide, diphenyl methanephosphonate, phenylphosphonic acid Examples include diethyl and the like.

  Examples of phosphoric acid condensed esters include resorcinol polyphenyl phosphate, resorcinol poly (di-2,6-xylyl) phosphate, bisphenol A polycresyl phosphate, hydroquinone poly (2,6-xylyl) phosphate, and these Aromatic phosphoric acid condensed esters such as condensates are exemplified.

  Furthermore, the polyphosphate which consists of a salt with phosphoric acid, polyphosphoric acid, a periodic table group IA-IVB group metal, ammonia, an aliphatic amine, and an aromatic amine can also be mentioned.

  As typical salts of polyphosphates, lithium salts, sodium salts, calcium salts, barium salts, iron (II) salts, iron (III) salts, aluminum salts, etc. as metal salts, methylamine salts as aliphatic amine salts, Examples include ethylamine salts, diethylamine salts, triethylamine salts, ethylenediamine salts, piperazine salts, and examples of aromatic amine salts include pyridine salts and triazines.

  Moreover, in this invention, you may use another flame retardant other than these phosphorus containing flame retardants and silicon containing flame retardants as needed. For example, magnesium hydroxide, aluminum hydroxide, antimony trioxide, antimony pentoxide, sodium antimonate, zinc hydroxystannate, zinc stannate, metastannic acid, tin oxide, tin oxide salt, zinc sulfate, zinc oxide, first oxide Iron, ferric oxide, stannous oxide, stannic oxide, zinc borate, ammonium borate, ammonium octamolybdate, metal salt of tungstic acid, complex oxide acid of tungsten and metalloid, ammonium sulfamate, Inorganic flame retardants such as ammonium bromide, zirconium compounds, guanidine compounds, fluorine compounds, graphite, and swellable graphite can be used.

  It is preferable that the fiber used as an additive in the injection molding method of the present invention is formed by bonding or embedding in a pellet form having a length of 3 to 10 mm. Moreover, it is preferable that resin used for adhesion | attachment or embedding contains biomass resin. As the fiber, any of synthetic fiber and inorganic fiber can be used. Among these, synthetic fibers such as polyester fibers, polyarylate fibers, polyamide fibers, polyolefin fibers, etc. are preferable in that stable quality can be obtained and the functions are sufficiently exhibited. Among these, polyester fibers are more preferable.

  If a heat-meltable synthetic fiber is used as a fiber to reinforce the molded product, when the molded product is ignited, the fiber shrinks due to melting and does not protrude onto the molded product surface, preventing the uniform formation of a carbonized layer. This is preferable in that it is not present.

  The polyester resin means a general term for polymer compounds having an ester bond as the main bond chain of the main chain. Accordingly, as the polyester resin, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PTT (polytrimethylene terephthalate), PBT (polybutylene terephthalate), PPT (polypentamethylene terephthalate), PHT (polyhexamethylene). Includes not only terephthalate), PBN (polybutylene naphthalate), PES (polyethylene succinate), PBS (polybutylene succinate), but also all polymer compounds obtained by polycondensation reaction of dicarboxylic acid component and diol component It is.

  The dicarboxylic acid component is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, oxycarboxylic acids, and polyfunctional acids. Of these, aromatic dicarboxylic acids are preferred.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfoisophthalic acid.

  Among these, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are preferable, and terephthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are more preferable.

  Examples of the aliphatic dicarboxylic acid include oxalic acid, succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, fumaric acid and the like. As an alicyclic dicarboxylic acid, cyclohexane dicarboxylic acid etc. are illustrated as an example. Among such aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, succinic acid, adipic acid and cyclohexanedicarboxylic acid are preferable, and succinic acid and adipic acid are more preferable.

  As an oxycarboxylic acid, p-oxybenzoic acid etc. are illustrated as an example.

  Furthermore, examples of the polyfunctional acid include trimellitic acid and pyromellitic acid.

  On the other hand, the diol component is not particularly limited and can be appropriately selected according to the purpose. Examples include aliphatic diols, alicyclic diols, aromatic diols, diethylene glycol, polyalkylene glycol, and the like, among which aliphatic diols are preferred.

  Examples of the aliphatic diol include ethylene glycol, propane diol, butane diol, pentane diol, hexane diol, neopentyl glycol, triethylene glycol and the like. Among them, propane diol, butane diol, pentane diol, hexane diol are exemplified. Particularly preferred.

  As an alicyclic diol, cyclohexane dimethanol etc. are illustrated as an example. Furthermore, as an aromatic diol, bisphenol A, bisphenol S, etc. are illustrated as an example.

  The degree of polymerization of the polyester fiber used in the present invention is not particularly limited, but an intrinsic viscosity of 0.50 dL / g or more is preferable, and 0.70 dL / g or more is more preferable when exhibiting excellent mechanical properties. The upper limit of the intrinsic viscosity is about 3.00 dL / g.

  Further, the polyester resin used as the fiber in the present invention has an intrinsic viscosity of 0.36 to 1.60 dL / g, particularly 0.52 to 1.35 dL / g, when an o-chlorophenol solution is measured at 25 ° C. Are preferred. Use of a polyester resin having such an intrinsic viscosity is preferable in terms of mechanical properties and moldability.

  In the present invention, such a fiber preferably has a tensile strength of 2 cN / dtex or more, and more preferably 5 cN / dtex or more.

  By using such a fiber, the strength of the resulting fiber-containing injection-molded product can be improved. In particular, even in the case where 40% or more of bioresin is contained in the mixture, in the Charpy test according to JISK7110, The molded product of the mixture is preferable in that the impact strength of 4 KJ / m 2 or more can be maintained.

Moreover, there is no limitation in particular in the cross-sectional shape of the fiber used in this invention. As an example, it may be circular, and in this case, the production cost of the fiber is reduced, and in addition, the dispersibility in the resin composition is increased, which is preferable. Alternatively, it may be an atypical cross section such as a star shape, a polygonal shape, an indeterminate shape, or an uneven shape, or an atypical cross section composite cross section. In this case, in the mixture, the contact area with the resin is increased, the adhesiveness is increased, and the strength of the fiber-containing injection-molded product of the present invention tends to increase, which is preferable. In addition, in the case of the fiber whose cross-sectional shape is not circular, as an example, it shall mean an area circle equivalent diameter (Heywood diameter).

  In the present invention, the thickness of the fiber is not particularly limited, and those used in a resin molded product reinforced with fibers may be used. For example, the use of an injection molded product, an injection molding device to be used, a resin pellet An appropriate thickness may be selected as appropriate in accordance with the size and the like.

  In the present invention, the material supplied to the injection molding apparatus may contain a nucleating agent. By including the nucleating agent, moldability, heat resistance, and product strength can be improved. There is no limitation in particular in the nucleating agent to be used, The well-known thing mix | blended as a nucleating agent of 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, oxidation Examples thereof include metal salts of aluminum, neodymium oxide and phenylphosphonate.

  On the other hand, as organic nucleating agents, sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, calcium oxalate, lauric acid Sodium, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacosanoate, calcium octacosanoate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, montan Acid sodium, calcium montanate, sodium toluate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum Organic carboxylic acid metal salts such as dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalate, sodium cyclohexanecarboxylate, organic sulfonates such as sodium p-toluenesulfonate, sodium sulfoisophthalate, stearamide, Carboxylic acid amides such as ethylenebislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide, trimesic acid tris (t-butylamide), benzylidene sorbitol and its derivatives, sodium-2,2′-methylenebis (4 Phosphorus compound metal salts such as 6-di-t-butylphenyl) phosphate, sodium 2,2-methylbis (4,6-di-t-butylphenyl) and the like.

  These inorganic nucleating agents and organic nucleating agents may be used alone or in combination of two or more. A mixture of inorganic and organic materials may be used.

  When a nucleating agent is contained as a molding material used in the injection molding method of the present invention, the content is preferably 0.005 to 5 parts by mass with respect to 100 parts by mass of a resin such as polylactic acid resin. The ratio of 1-1 mass part is still more preferable.

  Moreover, the molding material used for the injection molding method of the present invention may contain a plasticizer.

  The plasticizer to be used is not particularly limited, and various plasticizers generally used for resin molding can be used. For example, polyester plasticizer, glycerin plasticizer, polyvalent carboxylic acid ester plasticizer. Examples thereof include a polyalkylene glycol plasticizer and an epoxy plasticizer.

  Examples of the polyester plasticizer include acid components such as adipic acid, sebacic acid, terephthalic acid / isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, rosin, propylene glycol, 1,3-butanediol, 1,4. Examples include polyesters composed of diol components such as butanediol, 1,6-hexanediol, ethylene glycol and diethylene glycol, and polyesters composed of hydroxycarboxylic acids such as polycaprolactone.

  These polyesters may be end-capped with a monofunctional carboxylic acid or monofunctional alcohol, or may be end-capped with an epoxy compound or the like.

  Examples of the glycerin plasticizer include glycerin monoacetomonolaurate, glycerin diacetomonolaurate, glycerin monoacetomonostearate, glycerin diacetomonooleate, and glycerin monoacetomonomontanate. be able to.

  Examples of polyvalent carboxylic acid plasticizers include phthalate esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dihexyl phthalate, dibenzyl phthalate, and butyl benzyl phthalate. Trimellitic acid esters such as tributyl meritate, trioctyl trimellitic acid, trihexyl trimellitic acid, diisodecyl adipate, n-octyl-a monodecyl adipate, methyl diglycol butyl diglycol adipate, benzyl methyl diglycol adipate Adipic acid esters such as benzylbutyl diglycol adipate, citrate esters such as triethyl acetylcitrate and tributyl acetylcitrate, azelaic acid esters such as di-2-ethylhexyl azelate, seba Phosphate dibutyl and sebacic acid di 2-ethylhexyl, and the like.

  Examples of the polyalkylene glycol plasticizer include polyethylene glycol, polypropylene glycol, poly (ethylene oxide / propylene oxide) block and / or random copolymer, polytetramethylene glycol, ethylene oxide addition polymer of bisphenols, and bisphenols. Examples thereof include polyalkylene glycols such as propylene oxide addition polymers and tetrahydrofuran addition polymers of bisphenols, or terminal epoxy-modified compounds thereof, terminal ester-modified compounds, and terminal ether-modified compounds.

  The epoxy plasticizer generally refers to an epoxy triglyceride composed of an alkyl epoxy stearate and soybean oil, but there are also so-called epoxy resins mainly made of bisphenol A and epichlorohydrin. Can be used.

  In addition, as a plasticizer, in addition to this, benzoic acid esters of aliphatic polyols such as neopentyl glycol dibenzoate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl propylate, fatty acid amides such as stearic acid amide, Examples also include aliphatic carboxylic acid esters such as butyl oleate, oxyacid esters such as methyl acetylricinoleate and butyl acetylricinoleate, pentaerythritol, and various sorbitols.

  When a plasticizer is contained in the molding material used in the injection molding method of the present invention, the content is preferably 1 to 30 parts by mass with respect to 100 parts by mass of a resin such as polylactic acid, and 5 to 10 parts by mass. Part is more preferred. When the molding material contains a plasticizer with a content in the above preferred range, the molding temperature can be reduced by about 10 ° C. during the production of the molded product of the present invention.

  In the molding material used in the injection molding method of the present invention, in addition to the nucleating agent and the plasticizer, if necessary, a surfactant, an elastomer, an antioxidant, a thermal stabilizer, an ultraviolet absorber, a light stabilizer, Components such as antistatic agents, neutralizers, colorants such as pigments, dispersants, rosins, synthetic rubbers, inorganic additives, antibacterial agents, fragrances, mold release agents, and hydrolysis inhibitors may be included.

  In the molding material used in the present invention, the components other than the resin, the flame retardant, and the fiber are preferably 20% by mass or less in total, and more preferably 10% by mass or less.

  Although the injection molding method of the present invention has been described in detail above, the present invention is not limited to the above-described examples, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

[Test A]
Next, specific examples of the injection molding method of the present invention will be described by Test A.

[Molding materials]
・ Polylactic acid resin (pellet shape): 100 parts by weight of LACEA H100 manufactured by Mitsui Chemicals ・ Compatibilizer (powder type): 20 parts by weight of Ravitor FP110 manufactured by Fushimi Pharmaceutical
・ Decomposition prevention agent (powder): Nisshinbo Carbodilite LA1 5 parts by weight Flame retardant (powder): ADEKA Adekastab FP2100 35 parts by weight Glass fiber: Owens Corning FT592 15 parts by weight (fibers consolidated into pellets) )
<Total> 175 parts by weight The polylactic acid resin used was previously dried in a hot air dryer at 80 ° C. for 5 hours. Moreover, the flame retardant used beforehand was dried under reduced pressure at 80 ° C. for 5 hours with a vacuum dryer. The powder ratio of the molding material is 34% by weight.

[Injection molding equipment]
The injection molding apparatus used for the test was α50-A manufactured by FANUC, and a mold capable of simultaneously injection-molding Charpy test pieces and UL test pieces (thickness 1.6 mm) was set in this injection molding apparatus. The heater temperature of the injection molding apparatus was set to 195 ° C.-195 ° C.-190 ° C.-180 ° C.-30 ° C. from the nozzle side. In addition, the injection amount per shot was set to 25 g.

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

(Charpy impact test)
Charpy impact test piece according to JISK-7111, length 80mm ± 2mm, width 10mm ± 0.2mm, thickness 4mm ± 0.2mm, notch processing (notch radius 0.25mm ± 0.05mm, notch Width 8.0 mm ± 0.2 mm). The mass of the notched test piece was 4.2 g. The test apparatus used was IMPACTTESTER (analog type) manufactured by TOYOSEIKI. And the test piece obtained by said Example and comparative example was used for the Charpy impact test according to JISK-7111, and 5 (KJ / m < ² >) or more was set as the pass.

(Flammability 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 plastic parts and the like, and the degree of combustion of the test piece is examined by applying a flame of a gas burner to a test piece having a specified size. The grades are 5VA, 5VB, V-0, V-1, V-2, and HB in descending order of flame retardancy, and pass flame retardance of V-1 or higher (5VA to V-1). It was.

(Dispersibility test)
The test piece used was an injection-molded test piece having a length of 127 mm, a width of 12.7 mm, and a thickness of 1.6 mm according to UL94. This 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 transmitted light transmitted through the test piece. Then, the following five-step evaluation of A to XX was performed.

    A: Aggregates are not observed in the test piece, and the color is uniform.

    ○: Aggregates are not observed in the test piece, but unevenness is observed in color.

    Δ: Minute aggregates having a length of 0.5 mm or more are slightly observed in the test piece.

    X: Five or more aggregates having a length of 0.5 mm or more are observed in the test piece.

    XX: Ten or more aggregates having a length of 1 mm or more are observed in the test piece.

(Judgment)
When all the above-mentioned three evaluation items passed, it evaluated that it was pass in determination, and when there was even one failure, it evaluated that it failed in determination.

[Injection molding conditions and results of Examples and Comparative Examples in Test A]
The injection molding conditions and results of the examples are shown in FIG. 8 (A), and the injection molding conditions and results of the comparative example are shown in FIG. 8 (B).

Example 1
In Example 1, a small weighing feeder was attached to the injection molding apparatus, and the molding material having the above composition was put in a plastic bag, well shaken and uniformly mixed, and then put into the weighing feeder. Then, the back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 200 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 20 seconds. That is, Example 1 is a case where the measuring time of the measuring process is controlled to 20 seconds by adjusting the supply speed of the molding material supplied into the cylinder irrespective of the rotational speed of the screw and the back pressure setting value. is there. As a result, the uniform kneading of the pellet-like material and the powder-like material was sufficient, resulting in a Charpy impact test result of 7.1 (KJ / m ² ), flame retardancy of V-0, dispersibility. Was ◎, and the judgment was acceptable. FIG. 9A is a photograph of the screw shaft of the injection molding apparatus in Example 1, and the portion that appears white is the powder material adhering to the shaft. As can be seen from FIG. 9A, almost no adhesion of the powder material to the shaft was observed in the compression zone, and it was found that the molding material was sufficiently uniformly kneaded.

Incidentally, Comparative Example 1, which will be described later, is a measuring time SN in normal supply at a back pressure set value of 30 kg / cm ² and a screw rotation speed of 200 rpm, and the measuring time SN is 4 seconds.

(Example 2)
In Example 2, injection molding was performed in the same manner as in Example 1 except that the back pressure was increased to 150 kg / cm ² . That is, in Example 2, the effect on the present invention when the back pressure is set large with the screw rotation speed and the metering time being the same as in Example 1 was examined. As a result, the Charpy impact test result was 6.9 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ◎, and the determination was acceptable. Further, it was found that even if the back pressure set value was increased from 30 kg / cm ² to 150 kg / cm ² , the quality of the molded product was hardly affected if the screw rotation speed and the measuring time were set to the conditions of the present invention. . From this, the back pressure can be set to a predetermined value. Incidentally, Comparative Example 2 to be described later is a measuring time SN in normal supply at a set value of 150 kg / cm ² and a screw rotation speed of 200 rpm, and the measuring time SN is 7 seconds.

(Example 3)
The back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 50 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 40 seconds. Other conditions are the same as in the first embodiment. That is, in Example 3, the decrease in kneading performance due to the slow screw rotation speed is compensated by increasing the metering time to 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 ◎, and the determination was acceptable.

Example 4
The back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 200 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 8 seconds. Other conditions are the same as in the first embodiment. That is, in Example 4, the back pressure set value and the screw rotation speed are the same as those in Example 1, and the measurement time is set to the lower limit of the present invention. As a result, the Charpy impact test result was 6.0 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ○, and the determination was acceptable.

(Example 5)
The back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 200 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 180 seconds. Other conditions are the same as in the first embodiment. That is, in the fifth embodiment, the back pressure set value and the screw rotation speed are the same as those in the first embodiment, and the measurement time is set to the upper limit of the present invention. As a result, the Charpy impact test result was 5.1 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ◎ and the determination was acceptable, but the Charpy impact test result was due to the long measurement time. Was near the pass line. This is considered to be due to the low molecular weight due to the decomposition of the polylactic acid resin due to the long measurement time.

(Example 6)
The back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 300 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 20 seconds. Other conditions are the same as in the first embodiment. That is, in the sixth embodiment, the back pressure set value and the metering time are the same as those in the first embodiment, and the screw rotation speed is set to the upper limit of the present invention. As a result, the Charpy impact test result was 5.5 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ○, and the determination was acceptable. However, because the screw rotation number was high, the Charpy impact test The result was near the pass line. This is considered to be due to the fact that shear heat generation is greatly generated due to the high screw rotation speed, and that the molecular weight is lowered due to the decomposition of the polylactic acid resin.

(Comparative Example 1)
The back pressure is set to 30 kg / cm ² , the number of rotations of the screw is set to 200 rpm, and the molding material having the above composition is put into a mini hopper having a capacity of 50 mL without using a measuring feeder, and the molding material is put in the cylinder by its own weight. The normal supply method was used for full supply. The measuring time at this time was 4 seconds. That is, in Comparative Example 1, the molding time is 4 seconds because the molding material is supplied into the cylinder in conjunction with the rotational speed of the screw, that is, the material feeding ability of the molding material. As a result, the metering time was too short and the uniform kneading of the pellet-like material and the powder-like material was insufficient, resulting in a Charpy impact test result of 4.7 (KJ / m ² ), flame retardancy. Was V-2, dispersibility was x, and the determination was unacceptable.

  FIG. 9B is a photograph of the screw shaft of the injection molding apparatus in Comparative Example 1, and the portion that appears white is the powder material adhering to the shaft. As can be seen from FIG. 9 (B), it can be seen that much adhesion of the powder material to the shaft is observed in the compression zone, and the uniform kneading of the molding material is insufficient.

(Comparative Example 2)
The back pressure is set to 150 kg / cm ² , the number of rotations of the screw is set to 200 rpm, and the molding material having the above composition is put into a mini hopper having a capacity of 50 mL without using a measuring feeder, and the molding material is put in the cylinder by its own weight. The normal supply method was used for full supply. The measuring time at this time was 7 seconds. In other words, in Comparative Example 2, the molding time is 7 seconds by supplying the molding material into the cylinder in conjunction with the rotational speed of the screw, that is, the material feeding ability of the molding material. In this case, by increasing the setting of the back pressure from 30 kg / cm ² in Comparative Example 1 to 150 kg / cm ² , the measurement time in the normal supply method was increased from 4 seconds in 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 xx, and the determination was unacceptable.

(Comparative Example 3)
As in Example 1, the back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 200 rpm, and the molding material having the above composition was put in a mini hopper having a capacity of 50 mL without using a measuring feeder. It was made to supply in the cylinder with its own weight. As a result, the molding material was blocked and clogged at the cylinder inlet, and a stable molded product sample could not be taken. Thus, when a large amount of powder is included in the molding material, clogging occurs due to some cause.

(Comparative Example 4)
Comparative Example 4 was tested according to the Hungry Feed of Patent Document 1. That is, the back pressure was set to 30 kg / cm ² , the number of rotations of the screw was set to 200 rpm, and the molding material was supplied so that the screw was hidden by ¼ to ¾ while looking at the inlet of the cylinder. When the measurement time at this time was measured, it was the same as the measurement time of 4 seconds in the normal supply method of Comparative Example 1. As a result, the measurement time was too short and the uniform kneading of the pellet material and the powder material was insufficient, so the Charpy impact test result was 5.5 (KJ / m ² ). However, the flame retardancy was V-2, the dispersibility was x, and the judgment was rejected.

(Comparative Example 5)
Comparative Example 5 was tested according to Patent Document 2. That is, the back pressure is set to 30 kg / cm ² , the rotation speed of the screw is set to 200 rpm, the quantitative feeder F3 of Toyo Seiki Seisakusho is manually turned on and off, and the molding material is put into the cylinder by the supply method of Patent Document 2. Supplied. The measurement time at this time was measured and found to be 5 seconds. As a result, the measurement time was too short and the uniform kneading of the pellet-like material and the powder-like material was insufficient, and the Charpy impact test result was 5.2 (KJ / m ² ). However, the flame retardancy was V-2, the dispersibility was x, and the determination was unacceptable.

(Comparative Example 6)
Comparative Example 6 was performed in the same manner as in Example 1 except that the molding material was supplied into the cylinder at a supply speed at which the metering time was 200 seconds. That is, in Comparative Example 6, the back pressure set value and the screw rotation speed satisfy the present invention, but the metering time is longer than the upper limit of the present invention. As a result, the flame retardancy was V-1, the dispersibility was ◎, and the determination was acceptable, but because the measurement time was too long, the Charpy impact test result was 4.5 (KJ / m ² ) below the acceptable line. Became. This is considered to be caused by excessively low molecular weight due to decomposition of the polylactic acid resin because the measurement time is too long.

(Comparative Example 7)
In Comparative Example 7, the same procedure as in Example 1 was performed except that the screw rotation speed was set to 350 rpm. That is, Comparative Example 7 is such that the back pressure set value and the metering time satisfy the present invention, but the screw rotation speed exceeds the upper limit of the present invention. As a result, the flame retardancy was V-1, the dispersibility was ◎ and the determination was acceptable, but the screw rotation number was high, so the Charpy impact test result was 4.2 (KJ / m ² ) below the acceptable line. Became. It is considered that this is due to excessive generation of shear heat due to excessively high screw rotation speed, resulting in low molecular weight due to decomposition of the polylactic acid resin.

[Results and discussion of test A]
As can be seen from the comparison between Example 1 and Comparative Example 1 and the comparison between Example 2 and Comparative Example 2, the molding material is controlled so that the metering time is controlled regardless of the screw rotation speed and the back pressure setting value. By performing the injection molding method of the present invention for adjusting the supply speed of the resin, good results can be obtained in all points of Charpy impact test, flame retardancy, and dispersibility.

  Further, in Comparative Examples 4 and 5 which seem to be close to the injection molding method of the present invention, although the Charpy impact test is improved as compared with Comparative Examples 1 to 3, it is carried out in terms of flame retardancy and dispersibility. It was inferior to Examples 1 to 3, and satisfactory results were not obtained.

  It was also found that when the screw rotation speed exceeded 300 rpm or the metering time exceeded 180 seconds, the polylactic acid resin was lowered in molecular weight even if uniform kneading could be achieved, and the Charpy impact test result deteriorated. Therefore, the rotation speed of the screw is set to a constant rotation speed in the range of 50 rpm (minimum rotation speed at which sufficient kneading can be performed) to 300 rpm, and the supply speed of the molding material supplied into the cylinder is measured in normal supply. It is necessary to control the time SN to be not less than twice the time SN and not more than 180 seconds.

  In this embodiment, polylactic acid resin (PLA) having poor heat resistance is used as the base resin, but the present invention can of course be applied to a base resin having better heat resistance than polylactic acid resin.

[Test B]
Test B was performed by changing the molding material and the injection molding apparatus from Test A.

[Molding materials]
・ Polylactic acid resin (granular) ... Natural Works 4032D 100 parts by weight ・ Refractory agent (powder) ... ADEKA Adeka Stub FP2200 40 parts by weight ・ Compatibilizer (powder) ... Fushimi Pharmaceutical Ravitor FP110 20 parts by weight
・ Decomposition inhibitor (powder): 5 parts by weight of Mitsubishi Rayon Metablen W600A ・ PTFE drip inhibitor (powder): 0.5 parts by weight of FA500H made by Daikin Industries ・ Hydrolysis inhibitor (powder): Rhein Chemie Stubbaxol 1FL 3 parts by weight / filler (fine powder): P3 8 parts by weight manufactured by Nippon Talc Kogyo Co., Ltd. <Total> 176.5 parts by weight Polylactic acid resin previously dried in a hot air dryer at 80 ° C. for 5 hours was used. Moreover, the difficult agent used previously dried under reduced pressure with a vacuum dryer at 80 ° C. for 5 hours. The powder ratio of the molding material is 43% by weight.

[Injection molding equipment]
SG150U-3 manufactured by Sumitomo Heavy Industries, Ltd. is used as the injection molding device for the test, and a Charpy test piece and a mold capable of simultaneously injection-molding a UL test piece (thickness 1.6 mm) are set in this injection molding device. did. The heater temperature of the injection molding apparatus was set to 195 ° C.-195 ° C.-190 ° C.-180 ° C.-30 ° C. from the nozzle side. In addition, the injection amount per shot was set to 120 g.

  And like Test A, when satisfying this invention, it implemented about the case where it is not satisfied, and evaluated three items, the Charpy impact test, a flame retardance test, and a dispersibility test. The test methods and evaluation criteria for the three items are the same as in Test A.

[Injection molding conditions and results of Examples and Comparative Examples in Test B]
The injection molding conditions and results of the examples are shown in FIG. 10 (A), and the injection molding conditions and results of the comparative example are shown in FIG. 10 (B).

(Example 1-1)
In Example 1-1, a small weighing feeder was attached to the injection molding apparatus, and the molding material having the above composition was put in a plastic bag, well shaken and uniformly mixed, and placed in the weighing feeder. Then, the back pressure was set to 5 kg / cm ² , the number of rotations of the screw was set to 150 rpm, and the molding material was supplied into the cylinder at a supply speed at which the measurement time was 40 seconds. That is, in Example 1-1, the measurement time of the measurement process was controlled to 40 seconds by adjusting the supply speed of the molding material supplied into the cylinder regardless of the number of rotations of the screw and the back pressure setting value. Is the case. As a result, the uniform kneading of the pellet-like material and the powder-like material was sufficient, resulting in a Charpy impact test result of 6.4 (KJ / m ² ), flame retardancy of V-1, and dispersibility. Was ◎, and the judgment was acceptable.

Incidentally, Comparative Example 1 to be described later is a measuring time SN in normal supply at a back pressure set value of 5 kg / cm ² and a screw rotation speed of 150 rpm, and the measuring time SN is 3 seconds.

(Example 2-1)
In Example 2-1, a small weighing feeder was attached to the injection molding apparatus, and the molding material having the above composition was put in a plastic bag, well shaken and uniformly mixed, and placed in the weighing feeder. Then, the back pressure was set to 25 kg / cm ² , the number of rotations of the screw was set to 150 rpm, and the molding material was supplied into the cylinder at a supply speed at which the metering time was 60 seconds. That is, in Example 2-1, the measurement time of the measurement process was controlled to 60 seconds by adjusting the supply speed of the molding material supplied into the cylinder irrespective of the number of rotations of the screw and the back pressure setting value. Is the case. As a result, the uniform kneading of the pellet-like material and the powder-like material was sufficient, resulting in a Charpy impact test result of 6.8 (KJ / m ² ), flame retardancy of V-0, and dispersibility. Was ◎, and the judgment was acceptable.

(Example 3-1)
In Example 3-1, it carried out similarly to Example 1-1 except having set the screw rotation speed to 50 rpm which is the minimum of this invention. As a result, the Charpy impact test result was 6.1 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ◎, and the determination was acceptable. Thereby, although screw rotation speed was set to 50 rpm which is the minimum of this invention, it turns out that the pellet-form material and the powder-form material are fully knead | mixed uniformly.

(Example 4-1)
In Example 4-1, it carried out similarly to Example 1-1 except having set the screw rotation speed to 300 rpm which is the upper limit of this invention. As a result, the Charpy impact test result was 5.5 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ◎, and the determination was acceptable. By setting the screw rotation speed to 300 rpm which is the upper limit of the present invention, it is considered that shear heat generation occurred, the molecular weight was lowered due to decomposition of the polylactic acid resin, and the Charpy impact test result was somewhat deteriorated.

(Example 5-1)
In Example 5-1, it carried out similarly to Example 1-1 except having set the measurement time to 180 seconds which is the upper limit of this invention. As a result, the Charpy impact test result was 5.4 (KJ / m ² ), the flame retardancy was V-1, the dispersibility was ◎, and the determination was acceptable. Since the metering time was increased to 180 seconds, which is the upper limit of the present invention, the molecular weight was lowered due to the decomposition of the polylactic acid resin, and it is considered that the Charpy impact test result was somewhat deteriorated.

(Example 6-1)
In Example 6-1, the measurement was performed in the same manner as Example 1-1 except that the measurement time was set to 6 seconds, which is twice the measurement time SN in normal supply, which is the lower limit of the present invention. Incidentally, Comparative Example 1-1 is a metering time in normal supply, which 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 ○, and the determination was acceptable. Although the measurement time was as short as 6 seconds, which is the lower limit of the present invention, uniform kneading to such an extent that the Charpy impact test, flame retardancy, and dispersibility were acceptable could be achieved.

(Comparative Example 1-1)
The back pressure is set to 5 kg / cm ² , the number of rotations of the screw is set to 150 rpm, and the molding material having the above composition is put into a mini hopper having a capacity of 250 mL without using a weighing feeder, and the molding material is put in the cylinder by its own weight. The normal supply method was used for full supply. The measuring time at this time was 3 seconds. That is, in Comparative Example 1-1, the molding time is 3 seconds by supplying the molding material into the cylinder in conjunction with the rotational speed of the screw, that is, the material feeding ability of the molding material. As a result, the metering time was too short and the uniform kneading of the pellet-like material and the powder-like material was insufficient, resulting in a Charpy impact test result of 4.3 (KJ / m ² ), flame retardancy. Was V-2, dispersibility was x, and the determination was unacceptable.

(Comparative Example 2-1)
In Comparative Example 2-1, the same procedure as in Example 1-1 was performed except that the measurement time was 200 seconds. That is, Comparative Example 2-1 is a case where the measurement time is longer than the upper limit of the present invention. As a result, the dispersibility was ◎ and passed, but the Charpy impact test result was 3.2 (KJ / m ² ), the flame retardancy was V-2, and the determination was unacceptable. This is considered to be because the measurement time was too long as 200 seconds, resulting in an excessive decrease in molecular weight due to decomposition of the polylactic acid resin, and the Charpy impact test result being rejected.

(Comparative Example 3-1)
In Comparative Example 3-1, the same procedure as in Example 1-1 was performed except that the screw rotation speed was 350 rpm. That is, Comparative Example 3-1 is a case where the screw rotation speed is higher than the upper limit of the present invention. As a result, the dispersibility was ◎ and passed, but the Charpy impact test result was 3.5 (KJ / m ² ), the flame retardancy was V-2, and the determination was unacceptable. It is considered that this is because the screw rotation speed was too high, resulting in excessive reduction in molecular weight due to decomposition of the polylactic acid resin, and the Charpy impact test result being rejected.

(Comparative Example 4-1)
Comparative Example 4-1 was tested according to the hungry feed of Patent Document 1. That is, the back pressure was set to 5 kg / cm ² , the rotation speed of the screw was set to 150 rpm, and the molding material was supplied so that the screw was hidden by ¼ to ¾ while looking at the cylinder inlet. When the measurement time at this time was measured, it was the same as the measurement time of 3 seconds in the normal supply method of Comparative Example 1-1. As a result, the metering time was too short and the uniform kneading of the pellet-like material and the powder-like material was insufficient, resulting in a Charpy impact test result of 4.5 (KJ / m ² ), flame retardancy. Was V-2, dispersibility was x, and the determination was unacceptable.

(Comparative Example 5-1)
Comparative Example 5-1 was tested according to Patent Document 2. That is, the back pressure is set to 5 kg / cm ² , the number of rotations of the screw is set to 150 rpm, the quantitative feeder F3 of Toyo Seiki Seisakusho is manually turned on and off, and the molding material is put into the cylinder by the supply method of Patent Document 2. Supplied. The measurement time at this time was measured and found to be 4 seconds. As a result, the metering time was too short and the uniform kneading of the pellet-like material and the powder-like material was insufficient, resulting in a Charpy impact test result of 4.3 (KJ / m ² ), flame retardancy. Was V-2, dispersibility was x, and the determination was unacceptable.

[Consideration of test results]
The results of Test B also have the same tendency as Test A, and it was found that the difference in molding material and injection molding apparatus does not affect the present invention.

  From the results of tests A and B, as in the injection molding method of the present invention, the screw rotation speed and the back pressure set value are measured while the rotation speed of the screw is high-speed rotation in the range of 50 rpm to 300 rpm. Regardless of the control, the metering time is more than twice the SN (measuring time of normal supply) and 180 seconds or less, so even if a molding material containing a large amount of powder is put directly into the cylinder from the hopper, It was proved that uniform kneading can be performed.

  It should be noted that the weighing time of the hungry feed performed as a comparative example was not different from the weighing time in the normal supply, and was shorter than the “para-para feeding” in the present invention.

  With respect to this point, the difference between “normal supply”, “hungry feed”, and “para-para supply” in the present invention will be described with reference to FIGS.

  In FIGS. 11A to 11E, an example of a resin pellet will be described as a molding material, the pellet is indicated by A, and the molten resin in which the pellet is melted is indicated by A1.

(Weighing process)
In general, plasticization performed in a metering process in injection molding means that the pellet A in the cylinder 14 is conveyed forward by the screw 16 while heat transfer from the heater 24 outside the cylinder 14 and frictional heat between the pellets A ( It means that the molten resin is uniformly melted by the shearing energy) and a predetermined amount of the molten resin A1 is stored at the tip of the cylinder.

  That is, when the molten resin A1 starts to be stored at the tip of the cylinder 14 by the rotation of the screw 16, if the molten resin A1 does not leak from the tip, the pressure of the pellet A itself that is sequentially fed by the rotation of the screw 16 The screw 16 moves backward. In this case, the faster the rotation of the screw 16 (the higher the rotation speed), the more pellets A are fed, and the speed at which the screw 16 moves backward increases.

  Thereby, if a screw rotation stop signal is given to a predetermined stroke position (measurement setting position) set in advance, the backward movement of the screw 16 stops at that position. This is the weighing process.

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

  Further, if the rotational speed of the screw 16 is increased, the feed amount of the pellet A is increased. Therefore, the time until the same stroke position is reached, that is, the time until the measurement is completed is shortened.

  Based on the above description, the difference between “normal supply”, “hungry feed”, and “para-fill” of the present invention will be compared.

(Normal supply)
First, “normal supply” in which pellets A are stacked in the hopper 26 attached to the injection molding apparatus will be described. The supply of pellets A to the hopper 26 can be arbitrarily adjusted by using a quantitative feeder 40 (quantitative supply device). Before the injection molding is started, the pellet A is supplied to the hopper 26 in a full tank. FIG. 11A shows a schematic state of the pellet A in the screw groove of the screw 16 and the hopper 26 at this time (a conceptual diagram in which valves and the like are omitted).

  As can be seen from FIG. 11 (A), the screw groove of the screw 16 is always filled with the molten resin A1 in which the pellet A and the molding material are melted, and the force for feeding the pellet A forward by the screw 16 is always generated. The weighing is completed in a short time. Thereby, the level of the pellet A stored in the hopper 26 is gradually lowered by the consumption of the pellet A.

  Then, when the level of the pellet A decreases to the lower end of the hopper 26 (H position in FIG. 11A), the pellet A is fed to the hopper 26 at a supply speed faster than the amount of pellet A consumed in the injection molding cycle. Supply and fill again. Thus, the normal supply repeats the consumption of the pellet A and the full tank in the hopper 26 with the H position in FIG. 11A as a reference.

(Hungry feed)
Next, “Hungry Feed” will be described.

  The pellet A is gradually consumed from the state where the injection molding is continued in the “normal supply” state. Then, when the pellet A is replenished with the pellet A at the lower end of the hopper 26 (H position in FIG. 11A) and the storage level in the hopper 26 is increased again, “normal supply” is obtained.

  However, in the case of the hungry feed, even if the pellet A comes to the lower end of the hopper 26 (H position in FIG. 11A), the injection molding is continued for a while without replenishing the hopper 26 with the pellet A. Then, the level of the pellet A is further lowered from the lower end of the hopper 26, and reaches below the insertion port 25 (L position in FIG. 11A). In this state, a quantity of pellets A equal to the average consumption of pellets A is supplied to the hopper 26 by the quantitative feeder 40. That is, the average consumption of pellets A and the average supply of pellets A are made equal. Therefore, the rear end position of the pellet A in the cylinder 14 comes to the position shown in FIG. 11B according to the intermittent consumption of the pellet A. Thereby, when the state of the insertion port 25 is observed from the hopper 26 side, the pellet A is visible and hidden. In other words, the screw 16 is visible and hidden. This is the state of the hungry feed.

  Therefore, in the hungry feed, the pellet A may not exist in the charging path to the inside of the hopper 26 and to the bottom of the charging port 25, but when the pellet A is supplied to the hopper 26, the rear end of the pellet A in the cylinder 14 is present. It becomes a continuous state with the position. That is, the molten resin A1 stored at the tip of the screw 16 is always supplied in a required amount by the pellet A in the screw groove of the screw without interruption of continuity. In other words, a state in which a sufficient amount of pellets A necessary for the retraction of the screw 16 can be supplied is maintained in the same manner as “normal supply”.

  The difference from “normal supply” is that the gap from the screw 16 to the hopper 26 increases as described above, so that moisture and decomposition gas, which is a problem with hungry feed, can easily escape from the inlet 25 to the outside. This is the point.

(Flip through)
Then, what is the “flip” in the present invention will be explained.

  First, considering the state of FIG. 11 (B) in the above-described hungry feed, “filling” temporarily stops the supply of pellets A in this state. Then, the pellet A and the molten resin A1 in the screw groove of the screw 16 are further consumed by the injection molding, and the state becomes as shown in FIGS. 11C and 11D, and the screw 16 rotates. A state is formed in which the resin pellets and the molten resin are hardly sent forward. That is, a state where the pellet A is not filled from the supply zone or from the supply zone to the compression zone is formed. Actually, in FIG. 11C, the hopper 26 was removed and the density of the molding material inside the cylinder 14 was observed from the inlet 25, but it was sparse and there was no state of fullness.

  The pellet A and the molten resin A1 are more likely to be fed forward by the force of the screw groove if they are contained in a larger amount in the screw groove of the screw 16. However, in the case of “filling”, since the molding material existing in the thread groove is extremely small, even if the screw 16 is rotated, the pellet A and the molten resin A1 are hardly fed forward. As a matter of course, when the state shown in FIG. 11E is reached, the molding material is no longer sent forward, so that the back pressure can no longer be established and the screw 16 cannot be retracted. Therefore, it is necessary that the molding material is filled up to a certain level in at least the thread groove of the screw 16. Then, since the screw 16 does not stop rotating until the screw 16 moves back to a certain stroke position, the screw 16 rotates and waits for the replenishment of the pellet A while kneading the pellet A and the molten resin A1 in the thread groove. Become. That is, in the case of “filling”, at the start of injection molding, even if the screw 16 is rotated, the pellet A or the molten resin A1 is hardly fed forward, that is, at least in the supply zone, the compression zone, and the metering zone. The state as shown in FIG. 11C or FIG. 11D where the pellet A is not filled in the supply zone is created. In this state, the pellet A is supplied to the hopper 26 from the quantitative feeder 40 at a supply speed that is less than the average consumption of the pellet A during “normal supply”. As a result, since the pellet A and the molten resin A1 are filled in the screw groove of the screw 16 and the back pressure at the tip of the screw gradually increases, the screw 16 moves backward slowly. As described above, in the “filling”, since the state of waiting for the replenishment of the pellet A continues even if the screw 16 is rotating, the measurement time can be increased.

  The position to which the screw 16 can be retracted when the pellet A is filled depends on the injection molding conditions, particularly the back pressure, the screw shape, and the properties of the molding material, but from FIG. 11 (C) to FIG. The present invention can be achieved in any state from (D) to FIG. 11 (E). At least the amount of pellets A in the supply zone needs to be considerably reduced, which changes how the pellets A and molten resin A1 are pushed in the compression zone. Thereby, excessive shear in the compression zone can be reduced, and the actual temperature does not greatly exceed the control temperature and the pellet A is not deteriorated. Moreover, also when it has a pellet and powder as a molding material, it can suppress that the kneading | mixing dispersibility of a powder falls by the rapid fall of resin viscosity.

  DESCRIPTION OF SYMBOLS 10 ... Injection molding apparatus, 12 ... Nozzle, 14 ... Cylinder, 16 ... Screw, 17 ... Back pressure sensor, 18 ... Hydraulic motor, 20 ... Injection cylinder, 22 ... Motor cylinder set, 24 ... Heater, 26 ... Hopper, 28 ... Cavity, 30 ... Mold, 32 ... Gate, 34 ... Material supply device, 36 ... Mixer, 38 ... Powder and powder quantitative supply machine, 40 ... Measuring feeder, 42 ... Shooter, 44 ... Sensor

Claims (9)

The molding material supplied into the cylinder of the injection molding apparatus is stored at the tip of the cylinder by the rotation of the screw, and the rotation of the screw after receiving the pressure of the stored molding material itself and retreating to the measurement setting position. In the injection molding method provided with a weighing process to stop
The molding material is composed of a base resin and an additive, and at least one of the base resin and the additive is a powder, and the molding material is directly supplied into the cylinder without being pelletized.
In the measuring step, the back pressure applied to the screw is set to a predetermined value, and the rotational speed of the screw is set to a constant rotational speed in the range of 50 rpm to 300 rpm,
In the metering step, when the metering time in the normal feeding method in which the molding material is filled and filled in the cylinder by its own weight from the input port in accordance with the material feeding capability of the screw rotation speed is SN seconds, Adjusting the supply speed of the molding material to be supplied to the metering time not less than twice the SN and not more than 180 seconds,
Thereby, the metering time is controlled independently of the set value of the rotational speed of the screw and the back pressure. The inside of the cylinder is divided into three zones of a supply zone, a compression zone, and a metering zone in order from the molding material inlet, and at least the supply zone is not filled with the molding material. 1. An injection molding method of 1. At the start of injection molding, a state in which the at least the supply zone is not filled with the molding material is formed, and in this state, the supply rate becomes lower than the average consumption of the molding material in the normal supply method from the constant supply device. 3. The injection molding method according to claim 2, wherein a molding material is supplied into the cylinder.   The injection molding method according to any one of claims 1 to 3, wherein the measuring time is controlled according to a necessary kneading time of the molding material.   The injection molding cycle includes the molding material metering process, the mold clamping process, the molten resin injection process from the cylinder to the mold, the pressure holding process for maintaining the pressure inside the mold, and the cooling process for cooling the mold. And a mold release step for releasing the mold and taking out the molded product, and the measuring time is controlled according to the time from the start of the cooling step to the end of the mold release step in the injection molding cycle. The injection molding method according to any one of claims 1 to 3. Among the molding material, any one of the injection molding method of claim 1, wherein the ratio of the powder is 30 wt% or more. The injection molding according to any one of claims 1 to 6, wherein the base resin is at least one of a polylactic acid resin and a cellulosic resin, and the additive is at least one of a flame retardant and a fiber. Method. By continuously supplying a small amount of the molding material in the cylinder, an injection molding method according to any one of claims 1 to 7, wherein adjusting the feed rate. By intermittently supplying the molding material in the cylinder, an injection molding method according to any one of claims 1 to 7, wherein adjusting the feed rate.