JP5710813B1 - Injection molding machine screw and injection molding machine - Google Patents

Abstract

A screw for preventing vent-up is provided in an injection molding machine that injects an inert gas into a molten resin and degass and injects the excess inert gas. A high pressure area (9) in which an inert gas is injected on the upstream side and an inert gas on the downstream side in the heating cylinder (2) by a seal structure (27) provided on the screw (3). The screw (3) of the injection molding machine (1) partitioned by the low pressure area (30) from which the gas is deaerated is targeted. In the present invention, a step-down relaxation section (35) is provided downstream of the seal structure (27) of the screw (3). The step-down relaxation section (35) is composed of two or more multi-flight flights, and two or more shallow groove portions (38) having shallow screw grooves are formed in the axial direction. The inert gas is deaerated on the downstream side of the pressure reduction mitigation section (35). [Selection] Figure 1

Description

  In the present invention, the inside of the heating cylinder is partitioned into a high pressure area near the rear and a low pressure area near the front by a seal structure provided at a predetermined position of the screw of the injection molding machine. Is injected and the inert gas is degassed in the low-pressure area.

  When the electroless plating method is performed on plastic molded products molded by injection molding, it is complicated to degrease, etch, wet, catalyst, accelerator, etc. of molded products in order to modify the surface of the molded products. A pretreatment step is required, and after the surface modification, a plating treatment is performed. Such a pretreatment process uses a hazardous substance, so that there is a problem of waste liquid treatment, and there are many processes and high costs. In recent years, there has been proposed an injection method for obtaining a molded article whose surface has been modified only by injection molding, and it has become possible to perform the electroless plating method by omitting such a pretreatment step. Specifically, it is a method of obtaining a molded product by injecting a molten resin to which a surface modifying substance such as a metal complex is added, and the resulting molded product has a surface modified state. In this method, since a small amount of surface modifying material is added to the molten resin, supercritical inert gas is injection-molded so that the surface modifying material can uniformly penetrate and disperse in the molten resin. Inject into the heating cylinder of the machine. When the surface modifying substance uniformly penetrates and disperses in the molten resin, the inert gas is degassed from the heating cylinder. The molten resin in which the surface modifying material is infiltrated and dispersed is injected into the mold. Patent Literatures 1 and 2 propose a screw and an injection molding machine suitable for such an injection method.

Japanese Patent No. 4804557 Japanese Patent No. 4939623

  Both the screw and injection molding machine described in Patent Document 1 and the screw and injection molding machine described in Patent Document 2 are provided with a seal structure including a seal and a predetermined flow control mechanism at a predetermined position of the screw. The heating cylinder is divided into two areas. The screw described in Patent Document 1 and the screw described in Patent Document 2 are almost the same except that the structure of the flow control mechanism is slightly different, and there is no difference in other configurations other than the flow control mechanism. . Therefore, the screw 51 and the injection molding machine 50 described in Patent Document 1 will be briefly described with reference to FIG. The screw 51 is put into the heating cylinder 53 so as to be driven in the rotational direction and the axial direction, and a seal 54 is provided on the outer peripheral surface at a predetermined position. Further, a seal portion 52 is formed near the rear side of the screw 51 so that the flight groove is shallow and has a sealing action. By the seal 54 and the seal portion 52, a first area 55 is formed in the heating cylinder 53 toward the rear, that is, upstream. A second area 56 is formed on the front side, that is, on the downstream side. A flow control mechanism 58 is provided inside the screw 51 in the vicinity of the seal 54. The flow control mechanism 58 includes a communication path that communicates the first and second areas 55 and 56 and a valve structure that opens and closes the communication path, and maintains the pressure of the molten resin in the first area 55 at a predetermined pressure. When the pressure is higher than that, the valve is opened so that the molten resin flows into the second area 56. With this valve structure, the first area 55 is a high pressure area, and the second area is a low pressure area. Further, backflow from the second area 56 to the first area 55 is prevented. The screw 51 has a deep groove at a predetermined position in the first area 55, and the heating cylinder 53 is provided with an inlet 59 at this portion, and the supercritical fluid supply device 60 is provided at the inlet 59. In addition, an inert gas such as carbon dioxide is brought into a supercritical state by raising the temperature and pressure, and a surface modifying substance is added thereto and injected into the heating cylinder 53. A vent portion 62 is provided at a predetermined portion of the heating cylinder 53 corresponding to the second area 56, and the inert gas is deaerated when the valve 63 is opened.

  Such an injection molding machine 50 can select, for example, a surface modifying substance as an additive and perform injection molding as follows. That is, when the heating cylinder 53 is heated to rotate the screw 51 and the resin material is supplied from the rear hopper 64, the resin material is melted and stored in the first area 55. The supercritical fluid supply device 60 generates an inert gas in a supercritical state to which the surface modifying substance is added, and supplies this through the inlet 59. As a result, the molten resin in the first area 55 becomes highly fluid due to the inert gas in a supercritical state, and the surface modifying material penetrates and disperses quickly and uniformly in the molten resin. At this time, since the inside of the first area 55 is maintained at a high pressure by the flow control mechanism 58, the inert gas maintains a supercritical state and is not gasified. When the pressure of the molten resin in the first area 55 exceeds a predetermined pressure, the valve of the flow control mechanism 58 is opened and the molten resin flows into the second area 56, that is, the low pressure area. When the pressure is reduced in the second area 56, the inert gas is vaporized. The valve 63 is opened to degas the inert gas. As a result, a molten resin in which the surface modifying substance is uniformly permeated and dispersed is obtained. When such molten resin is measured at the tip of the screw 51, the screw 51 is driven in the axial direction as is well known in the art, and is injected into a mold (not shown). When the mold is opened after cooling and solidification, a molded product having a modified surface is obtained.

  An injection molding machine equipped with such a screw is also suitable for foam molding using a physical foaming agent, that is, an inert gas. In foam molding, an inert gas is injected into a molten resin under a predetermined pressure so as to reach a saturation solubility, and this is injected into a cavity in a mold to drive a core in the cavity or mold a predetermined amount. Open to increase cavity volume. Alternatively, a small amount of molten resin is injected into the cavity. If it does so, the inert gas in molten resin will foam in a cavity, and a foaming molded product will be obtained. In such foam molding, it is necessary to inject an inert gas so as to have a saturated solubility accurately in the molten resin to be injected so that there is no variation in product quality. However, it is difficult to accurately measure the inert gas to be injected without excess or deficiency. If an injection molding machine as shown in FIG. 3 is used, a molten resin into which an inert gas having a saturated solubility is accurately injected can be obtained. Specifically, the injection molding machine 50 shown in FIG. 3 is modified as follows. First, instead of the supercritical fluid supply device 60, an inert gas supply device is provided at the injection port 59 so that an inert gas such as carbon dioxide and nitrogen can be injected into the first area 55 at a high pressure such as 10 MPa. . The vent 62 is provided with a back pressure valve that is set to be opened at a predetermined pressure, for example, 5 MPa. In such an injection molding machine, an inert gas is injected into the molten resin in the first area 55 which is a high-pressure area so as to be slightly excessive. Then, the pressure is reduced to a predetermined pressure in the second area 56 which is a low pressure area, and excess inert gas is vaporized and degassed from the vent portion 62. Then, in the second area 56, the molten resin is in a state in which an inert gas having a saturated solubility under a predetermined pressure is melted. When this is injected, a foamed molded product with uniform quality is obtained.

  Both the injection molding machine 50 described in Patent Document 1 and the injection molding machine described in Patent Document 2 permeate and disperse a desired additive such as a surface modification material made of a metal complex in a molten resin. And a molded product having desired properties can be obtained. In particular, even when the additive is in a small amount, the additive can be efficiently and uniformly permeated and dispersed in the molten resin by injecting the supercritical inert gas in the first area. It can be said that the inert gas which has become unnecessary in the area can be appropriately degassed and is excellent. Moreover, foam molding using a physical foaming agent can be performed by such an injection molding machine, and a high-quality foam molded product can be obtained. That is, the injection molding machine having the first and second areas has no particular problem with respect to its basic structure. However, there are also problems to be solved. Specifically, there are problems with degassing of inert gas in the second area. In the injection molding machine described in Patent Document 1 or Patent Document 2, since the vent portion is opened to atmospheric pressure, the inert gas is quickly vaporized and degassed from the vent portion in the second area. However, at this time, the molten resin may be vented up at the vent portion, which may close the vent portion or flow out to the outside. This is caused when the valve structure of the flow control mechanism is opened and the high-pressure molten resin in the first area flows into the second area, and the molten resin is strongly pushed toward the vent portion due to the large pressure difference. . Moreover, there is a possibility of being extruded by the pressure of gas vaporized from the molten resin. Even when the molten resin does not flow out from the vent portion, when the molten resin rises in the vent portion, the molten resin is solidified at this portion. If it does so, the efficiency of deaeration will fall and quality will fall. If the vent part is provided in the second area in the downstream direction as much as possible, the bent-up of the molten resin can be prevented. In other words, if the vent portion is provided at a position separated from the seal 54, the molten resin reaches the vent portion after being sent a predetermined distance through the second area, so the pressure gradually decreases to prevent vent-up. it can. However, if this is done, the screw length and the machine length become longer and the cost becomes higher. This is not an effective solution. There is a similar problem in foam molding. Although a predetermined pressure is maintained in the second area, the second area is at a lower pressure than the first area, so the vent may vent up. Because there is.

  An object of the present invention is to provide an injection molding machine screw and an injection molding machine that solve the above-described problems. Specifically, the inside of a heating cylinder is formed by a seal structure provided in the screw. When degassing inert gas in an injection molding machine that is partitioned into a high-pressure area and a low-pressure area, in which an inert gas is injected in the high-pressure area, and where the inert gas is degassed in the low-pressure area It is an object of the present invention to provide an injection molding machine screw and an injection molding machine that can prevent vent-up safely and reliably.

In order to achieve the above object, the present invention is provided with a seal structure at a predetermined position, whereby the heating cylinder is partitioned into a high pressure area near the rear and a low pressure area near the front, and the molten resin is inactive in the high pressure area. It is configured for a screw of an injection molding machine that is sent to a low-pressure area after the gas is injected and the inert gas is deaerated in the low-pressure area. The present invention, on the downstream side of the seal structure in such a screw, provided buck relaxation section and screw groove shallow shallow groove and deep deep groove portion is formed at least axially beyond the respective two locations between flights. Moreover, this step-down mitigation section is composed of two or more multi-flight flights. And an inert gas is comprised so that it may deaerate in the downstream of such a pressure | voltage fall relaxation area.

Thus, in order to achieve the above object, the heating cylinder is partitioned into a high pressure area near the rear and a low pressure area near the front by a seal structure provided at a predetermined position of the screw. The molten resin is a screw of an injection molding machine in which an inert gas is injected in a high-pressure area and then sent to a low-pressure area, and the inert gas is degassed in the low-pressure area. the downstream side of the seal structure prescribed antihypertensive relaxation period provided, the buck relaxation interval a screw groove is deep deep groove portion and a shallow shallow groove portion between flights is formed at least in the axial direction than each of two locations, inert gas is configured as a screw of the injection molding machine, characterized in that is adapted to be degassed in a downstream side of the step-down relaxation interval.
According to a second aspect of the present invention, the screw according to the first aspect is configured as a screw of an injection molding machine, wherein the step-down relaxation section is composed of two or more multi-flight flights.
The invention according to claim 3 is the screw according to claim 1 or 2, wherein the seal structure is fitted into the reduced diameter portion with a reduced diameter portion where the screw is reduced in diameter and a predetermined gap. And a seal ring that is liquid-tightly slid with respect to the bore of the heating cylinder, and a tapered surface on which the seal ring is seated is formed at the reduced diameter portion, and the screw When rotating in the direction, the seal ring is separated from the tapered surface and the high pressure area and the low pressure area communicate with each other through the gap, and when rotated in the opposite direction, the seal ring is seated on the tapered surface and the high pressure area And the low-pressure area are blocked from communicating with each other.
According to a fourth aspect of the present invention, in the screw according to the first or second aspect, the seal structure includes a seal that liquid-tightly partitions the high pressure area and the low pressure area, and the high pressure area and the low pressure area. An injection molding machine comprising: a communication path that communicates; and a valve mechanism that closes the communication path and causes the molten resin in the high-pressure area to flow into the low-pressure area when the molten resin exceeds a predetermined pressure. Configured as a screw.

And invention of Claim 5 is equipped with the screw in any one of Claims 1-4, and the said heating cylinder is a supercritical state in which the additive melt | dissolved in the predetermined position corresponding to the said high voltage | pressure area. The injection molding machine is characterized in that an injection hole for injecting an inert gas is formed, and a deaeration hole for degassing the inert gas is formed at a predetermined position corresponding to the low pressure area.
A sixth aspect of the present invention includes the screw according to any one of the first to fourth aspects, wherein the heating cylinder injects a high-pressure inert gas into a predetermined position corresponding to the high-pressure area. And a deaeration hole for degassing the inert gas is opened at a predetermined position corresponding to the low pressure area, and a valve opened at a predetermined pressure is provided in the deaeration hole. Configured as an injection molding machine.

According to the above, the present invention divides the inside of the heating cylinder into the high-pressure area near the rear and the low-pressure area near the front by the seal structure provided at a predetermined position of the screw, and the molten resin contains the inert gas in the high-pressure area. It is intended for an injection molding machine screw that is injected into the low-pressure area and in which the inert gas is deaerated in the low-pressure area. In other words, an injection molding machine that can efficiently infiltrate and disperse additives such as surface modifying substances made of metal complexes in the molten resin, or injection that can perform foam molding with a physical foaming agent made of inert gas. Intended for screws of molding machines. And according to the present invention, the screw, a predetermined step-down relaxation section provided on the downstream side of the seal structure, the step-down relaxation interval each screw groove deep deep groove portion and a shallow shallow groove and at least axial direction between the flight 2 More than one place is formed, and the inert gas is deaerated on the downstream side of the pressure reduction mitigation section. That is, the step-down relaxation section is located in the low-pressure area, and two or more shallow groove portions that can reduce the pressure by the throttling action are provided in the axial direction. Since it is configured in this way, even when the molten resin flows from the high pressure area to the low pressure area, the molten resin flows through the pressure reduction relaxation section, and the resin pressure gradually decreases. And since inert gas is deaerated after that, the vent up in the vent part, ie, the deaeration hole provided in the heating cylinder, can be prevented reliably. According to another invention, the step-down mitigation section is composed of two or more multi-flight flights. A molten resin into which an inert gas is injected at a high pressure, particularly a molten resin into which an inert gas in a supercritical state is injected has low viscosity and high fluidity. According to the invention in which the pressure reduction mitigation section is composed of two or more multi-flight flights, even a highly fluid molten resin is appropriately sent downstream of the screw without backflow, and the pressure reduction mitigation section is smooth in the pressure reduction mitigation section. It is guaranteed that the resin pressure will drop. As a result, vent-up can be reliably prevented.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the injection molding machine which concerns on 1st Embodiment provided with the screw which concerns on embodiment of this invention, The (a) is side sectional drawing of an injection molding machine, The (a) (c) is They are a partial side view of a screw and a partial side cross-sectional view of a screw, in which the portions indicated by reference signs X and Y in (a) are enlarged. It is side surface sectional drawing which shows the injection molding machine which concerns on 2nd Embodiment provided with the screw which concerns on embodiment of this invention. It is side surface sectional drawing which shows the conventional injection molding machine.

  Embodiments of the present invention will be described below. The injection molding machine according to the first embodiment of the present invention is an injection molding that efficiently penetrates and disperses using a supercritical inert gas when a desired additive is infiltrated and dispersed in a molten resin. It is configured as a machine. Therefore, the configuration is similar to the injection molding machine described in Patent Document 1 and Patent Document 2. That is, the injection molding machine 1 according to the present embodiment is also provided so as to be able to be driven in the rotation direction and the axial direction within the heating cylinder 2 as shown in FIG. It is comprised from the screw 3 currently made. A plurality of band heaters are wound around the outer peripheral surface of the heating cylinder 2, but these are not shown in the figure.

  Similarly to the screw described in Patent Document 1, the screw 3 according to the present embodiment also has a specific structure suitable for using the supercritical inert gas. That is, the screw 3 is provided with the first seal structure 7 and the second seal structure 27 at predetermined positions. As a result, as will be described later, the inside of the heating cylinder 2 is divided into three areas, and a high pressure area for injecting an inert gas and a low pressure area for degassing the inert gas are formed. Yes.

  The first seal structure 7 includes a seal 5 and a flow control mechanism 6 that exerts a pressure adjusting action. As shown in detail in FIG. 1C, the seal 5 is provided in a groove having a predetermined width formed on the outer peripheral surface of the screw 3, and slides in contact with the bore of the heating cylinder 2 smoothly. The molten resin is prevented from flowing on this outer peripheral surface. That is, the inside of the heating cylinder 2 is liquid-tightly divided by the seal 5 into a first area 8 on the upstream side and a second area 9 on the downstream side. The first seal structure 7 is provided with one or a plurality of flow control mechanisms 6. One flow control mechanism 6 is provided in the screw 3 so as to communicate the first and second areas 8 and 9. And a valve mechanism 11 that opens and closes the communication path 10. A midway portion of the communication path 10 is tapered so that a tapered seating surface 13 is formed. When the head 15 of the poppet valve 14 constituting the valve mechanism 11 is seated on the seating surface 13, the communication path 10 is closed. The poppet valve 14 is composed of an umbrella-shaped head portion 15 and a shaft portion 16, and a plurality of disc springs 18, 18,. As described above, the poppet valve 14 provided with the disc springs 18, 18,... Is placed in a retainer 19 having a bottomed hole. The retainer 19 is fixed by being screwed into a female screw formed on the inner peripheral surface of the communication path 10 by a male screw formed on the outer peripheral surface thereof. Therefore, the poppet valve 14 is urged by the disc springs 18, 18,..., The head 15 is pressed against the seating surface 13, and the communication path 10 is closed. When the molten resin in the first area 8 reaches a predetermined pressure, the poppet valve 14 moves backward against the bias of the disc springs 18, 18,..., And the first and second areas 8, 9 communicate with each other. Thus, the molten resin flows into the second area 9. The resin path 20 is opened in the retainer 19, and when the first and second areas 8 and 9 communicate with each other, the molten resin flows from the resin path 20 to the second area 9. When the pressure of the molten resin in the first and second areas 8 and 9 is equal, or when the pressure in the second area 9 is higher, the poppet valve 14 is seated on the seating surface 13 and communication is cut off. The backflow of the molten resin from the second area 9 to the first area 8 is completely prevented.

  As shown in detail in FIG. 1A, the second seal structure 27 is provided with a reduced diameter portion 28 obtained by reducing the diameter of the screw 3 and a predetermined gap provided in the reduced diameter portion 28. And a seal ring 29. The seal ring 29 has an outer peripheral surface that is in smooth contact with the bore of the heating cylinder 2 so that the molten resin does not flow from the outer peripheral surface. That is, the inside of the heating cylinder 2 is liquid-tightly divided into the second area 9 on the upstream side and the third area 30 on the downstream side by the seal ring 29. The diameter-reduced portion 28 into which the seal ring 29 is fitted with a gap is expanded on the upstream side to form a tapered surface 31, and the upstream end of the seal ring 29 is also tapered. ing. When the tapered end portion of the seal ring 29 is separated from the tapered surface 31, the second and third areas 9 and 30 communicate with each other through the gap between the reduced diameter portion 28 and the seal ring 29, and the molten resin. If the end of the seal ring 29 is seated on the tapered surface 31, the communication is blocked and the flow of the molten resin is hindered. The reduced diameter portion 28 is provided with a pin 32 so that a locking portion formed on the seal ring 29 is locked. When the screw 3 is rotated in the forward direction in the measuring step, the seal ring 29 is locked to the pin 32 to secure a flow path of the molten resin, and the molten resin is sent to the third area 30. When the reverse rotation is made to the extent, the locked state is released and the seal ring 29 is seated on the tapered surface 31. That is, communication is blocked. If it does so, even if the pressure of the molten resin of the 2nd area 9 becomes high, the flow of the molten resin to the 3rd area 30 can be prevented reliably. Moreover, the backflow of the molten resin from the third area 30 to the second area 9 can be prevented at the time of injection or the like.

  As described above, the inside of the heating cylinder 2 is partitioned into the first to third areas 8, 9, and 30 by the first and second seal structures 7 and 27, but the first area 8 is melted to melt the resin of the material. It is an area. The high-pressure area in the claims is the second area 9 where an inert gas is injected into the molten resin at a high pressure, and the low-pressure area is a third area for degassing the inert gas from the molten resin. 27 corresponds to each. Further, the seal structure in the claims corresponds to the second seal structure 27 which is a seal structure in which the high pressure area and the low pressure area are divided.

  Next, the flight of the screw 3 according to the present embodiment will be described. In the first area 8 of the screw 3, that is, on the upstream side of the first seal structure 7, a single flight of a general pitch and lead is formed, and the resin of the material is melted and sent forward. The second area 9 of the screw 3, that is, the high pressure area is a mixing section 34, which is formed from a multi-strip flight called a so-called barrier shape and is efficiently mixed. An injection hole 21 is provided in the heating cylinder 2 so as to correspond to the second area 9. An additive injection device 23 is connected to the injection hole 21. The additive injection device 23 puts an inert gas such as carbon dioxide supplied from the gas cylinder 24 into a supercritical state, and adds an additive such as a surface modifying material supplied from the additive supply tank 25 to the supercritical state. It is a device that is dissolved in an active gas and supplied to the heating cylinder 2.

  In the third area 30 of the screw 3, that is, the low pressure area, a step-down relaxation section 35 having a flight unique to the present invention is provided. The flight in the step-down mitigation section 35 is the same as a general flight with a lead, but consists of a multi-flight flight consisting of a plurality of flights. In this embodiment, it is composed of two-flight flights. Thus, since it comprises a plurality of flights, the molten resin sent out in the pressure reduction relaxation section 35 is smoothly sent downstream without turbulent flow or reverse flow even if the viscosity is small. In such a step-down relaxation section 35, deep groove portions 37, 37 having deep screw grooves and shallow shallow groove portions 38, 38 are formed in at least two places in the axial direction. That is, two or more shallow groove portions 38 are formed. The shallow groove portions 38 and 38 have a squeezing action, and appropriately reduce the pressure when the molten resin flows.

  The downstream side of the step-down relaxation section 35 of the screw 3 corresponding to the low pressure area is formed in a general single flight. The heating cylinder 2 is provided with a deaeration hole 40 for degassing an inert gas at a portion corresponding to the single flight. That is, the inert gas is degassed on the downstream side of the pressure reduction mitigation section 35. The deaeration hole 40 is opened and closed by a deaeration valve 41.

  The operation of the injection molding machine 1 according to the first embodiment of the present invention will be described. The heating cylinder 2 is heated to rotate the screw 3 in the forward direction, and the resin material is supplied from a hopper not shown in the drawing. The supplied resin material is melted in the first area 8 by the heat of the heating cylinder 2 and the heat generated by the shearing force of the rotation of the screw 3, and is sent to the second area 9, that is, the high-pressure area.

  When the molten resin sent to the second area 9 reaches a predetermined amount, the rotation of the screw 3 is stopped and reversely rotated by about a half turn. Then, the lock by the pin 32 is released in the second seal structure 27 and the seal ring 29 rotates relative to the screw 3 by a half circumference. Then, the seal ring 29 is seated on the tapered surface 31 and the communication between the second and third areas 9 and 30 is blocked. The additive injection device 23 injects an additive such as a surface modifying substance made of a metal complex and an inert gas in a supercritical state into the second area 9 of the heating cylinder 2, that is, the high pressure area. Since the high-pressure area is completely sealed by the first and second sealing structures 7 and 27, the molten resin is also in the first area 8 and in the low-pressure area even when the inert gas is injected and the pressure is increased. There is no leakage in the third area 30. When an inert gas in a supercritical state is injected, the viscosity of the molten resin decreases and the fluidity increases, and the additive quickly penetrates and disperses in the molten resin.

  The screw 3 is rotated in the forward direction. Then, in the second seal structure 27, the seal ring 29 is separated from the tapered surface 31, and the second and third areas 9, 30, that is, the high pressure area and the low pressure area communicate with each other. Since the deaeration valve 41 is opened, the vicinity of the deaeration hole 40 in the low pressure area is close to the atmospheric pressure. Then, the molten resin in the high pressure area is strongly pushed away to the low pressure area side. However, when the molten resin is sent from the high-pressure area to the low-pressure area, the molten resin flows through the pressure reduction mitigation section 35, so that vent-up does not occur when the inert gas is degassed in the deaeration holes 40. More specifically, the molten resin is smoothly sent downstream in the step-down relaxation zone 35 by two flights. And the pressure of molten resin falls by two groove shallow parts 38 and 38. FIG. In other words, the two shallow groove portions 38, 38 serve as the flow resistance of the molten resin, and increase in the flow rate is suppressed. As described above, in the screw 3 according to the present embodiment, the pressure of the molten resin is gradually reduced by the pressure reduction relaxation section 35 and the flow rate is suppressed, so that the molten resin is gently sent downstream. This prevents the molten resin from being vented up in the deaeration holes 40. The inert gas is degassed from the deaeration holes 40 to obtain a molten resin in which additives such as surface modifying substances are uniformly dispersed. When a predetermined amount of molten resin is weighed, the screw 3 is driven in the axial direction and injected as conventionally known.

  Next, an injection molding machine 1 'according to a second embodiment will be described. The injection molding machine 1 ′ according to the second embodiment is configured as an injection molding machine that obtains a foam molded product using a physical foaming agent made of an inert gas. As shown in FIG. 2, the injection molding machine 1 'is configured in substantially the same manner as the injection molding machine 1 according to the first embodiment. The same members as those of the injection molding machine 1 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the injection molding machine 1 ′ according to the second embodiment, the injection hole 21 is provided with an inert gas injection device 43 for injecting an inert gas. A back pressure valve 44 is provided in the deaeration hole 40 so that the valve opens when the pressure in the deaeration hole 40 becomes a predetermined pressure, for example, 5 MPa or more. That is, the vicinity of the deaeration hole 40 is maintained at a constant pressure.

  A person skilled in the art can easily understand it, and thus will not be described in detail. To obtain a foamed molded article by the injection molding machine 1 ′ according to the second embodiment, the following is performed. The screw is rotated to send the molten resin to the second area 9, that is, the high pressure area. The screw is reversely rotated by about a half turn to block communication in the second seal structure 27. In this state, a slightly larger amount of inert gas is injected into the high-pressure area. If it does so, the pressure of molten resin will rise to 10 Mpa etc., for example. When the screw is rotated in the forward direction, the second seal structure 27 is communicated, and the molten resin is sent to the third area 30, that is, the low pressure area while being kneaded in the mixing section 34. Since the low pressure area is controlled to 5 MPa by the back pressure valve 44, the molten resin is strongly sent out from the high pressure area to the low pressure area. The vent-up at 40 is suppressed. When the inert gas is degassed from the deaeration holes 40, a molten resin in which the inert gas is dissolved at a saturated solubility under a pressure of 5 MPa is obtained in the second area 30. When this is injected, a foam molded product is obtained.

  This embodiment can be variously modified. For example, the first and second seal structures 7 and 27 may be composed of other structures as long as they have a sealing action and can cause the molten resin to flow under predetermined conditions. For example, the second seal structure 27 may be the same as the first seal structure 7. Other points can be modified. For example, the flights in the first and second areas 8 and 9 are not necessarily limited to the present embodiment, and can be replaced with other types of flights.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Heating cylinder 3 Screw 5 Seal 6 Flow control mechanism 7 1st seal structure 8 1st area 9 2nd area 10 Communication path 11 Valve mechanism 13 Seating surface 14 Poppet valve 21 Injection hole 23 Additive supply 23 Device 27 Second seal structure 30 Third area 34 Mixing section 35 Depressurization relaxation section 37 Deep groove section 38 Shallow groove section 40 Deaeration hole 44 Back pressure valve

Claims (6)

The inside of the heating cylinder is divided into a high-pressure area near the rear and a low-pressure area near the front by a seal structure provided at a predetermined position of the screw, and the molten resin is injected into the low-pressure area after inert gas is injected in the high-pressure area. A screw of an injection molding machine that is sent and degassed with inert gas in a low pressure area,
Formed on the screw, the downstream side of the seal structure prescribed antihypertensive relaxation period provided, the buck relaxation section has screw groove between flight deep deep grooves and shallow shallow groove and at least axially to each at two or more by screw of the injection molding machine the inert gas is characterized in that is adapted to be degassed in a downstream side of the step-down relaxation interval.   The screw according to claim 1, wherein the step-down relaxation section is composed of two or more multi-strip flights.   3. The screw according to claim 1, wherein the seal structure includes a reduced diameter portion in which the screw has a reduced diameter, and a fit in the reduced diameter portion with a predetermined gap therebetween. A seal ring that is slid in a liquid-tight manner with respect to the bore, and a tapered surface on which the seal ring is seated is formed in the reduced diameter portion, and when the screw is rotated in a predetermined direction, the seal ring is The high pressure area and the low pressure area communicate with each other through the gap apart from the taper surface, and when rotating in the opposite direction, the seal ring is seated on the taper surface and the communication between the high pressure area and the low pressure area is cut off. A screw for an injection molding machine characterized by being configured to be   The screw according to claim 1 or 2, wherein the seal structure includes a seal that liquid-tightly partitions the high-pressure area and the low-pressure area, a communication path that connects the high-pressure area and the low-pressure area, and the communication path. And a valve mechanism that causes the molten resin to flow into the low pressure area when the molten resin in the high pressure area exceeds a predetermined pressure. A screw according to any one of claims 1 to 4,
The heating cylinder has an injection hole for injecting an inert gas in a supercritical state in which an additive is dissolved at a predetermined position corresponding to the high pressure area, and the inert gas at a predetermined position corresponding to the low pressure area. An injection molding machine characterized in that a deaeration hole for degassing is formed. A screw according to any one of claims 1 to 4,
The heating cylinder has an injection hole for injecting a high-pressure inert gas at a predetermined position corresponding to the high-pressure area, and a deaeration hole for degassing the inert gas at a predetermined position corresponding to the low-pressure area. An injection molding machine characterized by being provided with a valve opened at a predetermined pressure in the deaeration hole.

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