Apparatus for manufacturing thermoplastic resin molded products and method for manufacturing thermoplastic resin molded products

Abstract

The present invention provides a thermoplastic resin molded product manufacturing apparatus and a thermoplastic resin molded product manufacturing method that can easily manufacture small quantities of parts. [Solution] The thermoplastic resin molded product manufacturing apparatus disclosed in this application comprises a first pressurizer that pressurizes a mold filled with a quantity of thermoplastic resin equal to or greater than the volume of the molded product at a first temperature and a first pressure, and a second pressurizer that pressurizes the mold pressurized by the first pressurizer at a second temperature lower than the first temperature and a second pressure higher than the first pressure. The thermoplastic resin molded product manufacturing method disclosed in this application is a method of filling a mold with a quantity of thermoplastic resin equal to or greater than the volume of the molded product, pressurizing the mold filled with thermoplastic resin at a first temperature and a first pressure, and pressurizing the mold after pressurizing at the first temperature and first pressure at a second temperature lower than the first temperature and a second pressure higher than the first pressure.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for manufacturing a resin molded product, and more particularly, to an apparatus and a method for manufacturing a thermoplastic resin molded product capable of manufacturing a molded product (thermoplastic resin molded product) using a thermoplastic resin.

Background Art

[0002] Conventionally, an injection molding method has been widely and commonly used for manufacturing a molded product using a thermoplastic resin. The injection molding method is a method of obtaining a molded product having a shape inverted from a mold by pouring molten thermoplastic resin (molten resin) into the mold, and a cylinder heated to melt the resin is used.

[0003] A thermoplastic resin is a material having a large specific volume change within the range from the glass transition point to the melting point. When the glass transition point is exceeded, the volume rapidly increases, maximizes near the melting point, and when the melting point is exceeded, the phase changes from a solid to a liquid. Injection molding is a technique for obtaining a target molded product while melting, filling, holding pressure, and cooling the resin by utilizing the characteristics of this thermoplastic resin.

[0004] In order to shape a thermoplastic resin by this method, first, it is necessary to change a solid-phase material (such as pellets) into a liquid phase (melting step). The specific volume of the melted resin in the liquid phase is discontinuously larger compared to the resin before the glass transition point.

[0005] After the material is made into a liquid phase, this molten resin having a large specific volume is poured into a mold and shaped into a target shape (shaping step (injection filling step)). Since the thermoplastic resin that has been shaped greatly changes in specific volume and shrinks when cooled, the target shape cannot be obtained only by pouring the melted resin into the mold.

[0006] Therefore, while the molten resin cools from its solidification point to its glass transition point, it is necessary to constantly replenish the resin in the mold to compensate for shrinkage. In injection molding, the shape of the molded product is maintained by continuously applying strong pressure from the cylinder and supplying resin to match the shrinkage (holding pressure process).

[0007] When a resin is cooled to a temperature below its glass transition temperature, the rate of decrease in specific volume becomes linear, making it less likely for the molded product to deform when removed from the mold (cooling process, removal process). Generally, during removal, the resin is cooled to a temperature below the glass transition temperature, but still at a temperature where sufficient workability can be expected.

[0008] Thus, in injection molding, a molded product of the desired shape is obtained by going through five steps: a melting step, a shaping step (injection filling step), a holding pressure step, a cooling step, and a removal step, in order to shape the thermoplastic resin.

[0009] Conventionally, an injection molding apparatus used in injection molding is known in which resin introduced into a heating cylinder is gradually melted while being transferred to the tip by a screw, and the molten resin is extruded from an extrusion injection nozzle at the tip of the heating cylinder and injected into an injection mold (Patent Document 1). [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2010-131966 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, injection molding has drawbacks such as the need to clean the molds every time the material used is changed, the high cost of the molds, and the time required to master the technique, making it unsuitable for the simple production of small quantities of parts using thermoplastic resins.

[0012] This invention has been made in view of the above circumstances, and its objective is to provide a thermoplastic resin molded product manufacturing apparatus and a thermoplastic resin molded product manufacturing method that can easily manufacture small quantities of parts using thermoplastic resin. [Means for solving the problem]

[0013] The inventors of this case believe that one of the causes of the aforementioned problems lies in the use of a heating cylinder, and after diligent study, have developed the thermoplastic resin molded product manufacturing apparatus and thermoplastic resin molded product manufacturing method disclosed in this application as means of not using a heating cylinder.

[0014] [Thermoplastic resin molded product manufacturing equipment] The thermoplastic resin molded product manufacturing apparatus disclosed herein comprises a first pressurizer that pressurizes a mold filled with a quantity of thermoplastic resin equal to or greater than the volume of the molded product at a first temperature and a first pressure, and a second pressurizer that pressurizes the mold pressurized by the first pressurizer at a second temperature lower than the first temperature and a second pressure higher than the first pressure.

[0015] [Thermoplastic resin molded product manufacturing method] The thermoplastic resin molded article manufacturing method disclosed herein involves filling a mold with a thermoplastic resin in an amount greater than or equal to the volume of the molded article, pressurizing the mold filled with the thermoplastic resin at a first temperature and a first pressure, and then pressurizing the mold after pressurizing at the first temperature and first pressure at a second temperature lower than the first temperature and a second pressure higher than the first pressure. [Effects of the Invention]

[0016] According to the thermoplastic resin molded product manufacturing apparatus and thermoplastic resin molded product manufacturing method disclosed in this application, small quantities of parts using thermoplastic resin can be easily manufactured. [Brief explanation of the drawing]

[0017] [Figure 1] A front view showing an example of a thermoplastic resin molded product manufacturing apparatus. [Figure 2](a) is a view taken along the line IIa-IIa of FIG. 1, and (b) is a view taken along the line IIb-IIb of (a). [Figure 3] (a) is an explanatory view of the state where the mold is on the elliptical roll, and (b) is an explanatory view of the state where the mold is on the lower plate. [Figure 4] (a) is an explanatory view of the process of transferring the mold to a predetermined position of the first pressurizer, and (b) is an explanatory view of the process of pressurizing the mold with the first pressurizer. [Figure 5] (a) is an explanatory view of the process of transferring the mold to a predetermined position of the second pressurizer, and (b) is an explanatory view of the process of pressurizing the mold with the second pressurizer. [Figure 6] Explanatory view of the process of sending out the mold from the second pressurizer. [Figure 7] (a) is an explanatory view of the state where the mold is set at a predetermined position of the first pressurizer, (b) is an explanatory view of the state of the thermoplastic resin when the mold is pressurized with the first pressurizer, and (c)(d) are explanatory views of the change in the state of the thermoplastic resin when the mold is cooled with the second pressurizer.

Mode for Carrying Out the Invention

[0018] (Embodiment) An example of an embodiment of the present invention will be described with reference to the drawings. The thermoplastic resin molding apparatus of this embodiment (hereinafter simply referred to as "manufacturing apparatus") is an apparatus capable of realizing shaping of a resin using a thermoplastic resin.

[0019] As an example, the manufacturing apparatus shown in FIGS. 1 to 3(a)(b) includes a first pressurizer 10, a second pressurizer 20, and a mold transfer device 30. In this embodiment, the first pressurizer 10 and the second pressurizer 20 are arranged side by side at the same height, and the mold transfer device 30 is provided so as to straddle both of them.

[0020] <The First Pressurizer> The first pressurizer 10 is a compression mechanism that pressurizes a mold M filled with a thermoplastic resin in an amount greater than the volume of the molded product at a first temperature and a first pressure, and comprises an upper plate (hereinafter referred to as the "first upper plate") 11 and a lower plate (hereinafter referred to as the "first lower plate") 12 that are positioned opposite each other with a gap between them in the vertical direction. The first upper plate 11 and the first lower plate 12 cooperate to clamp the mold M, and together they function as a single clamping device (the first clamping device).

[0021] An air cylinder 13 is connected to the first upper plate 11, and the first upper plate 11 is configured to move up and down by the power of the air cylinder 13. Other means besides the air cylinder can also be used to drive the first upper plate 11. Between the first upper plate 11 and the first lower plate 12, a guide column (hereinafter referred to as the "first guide column") 14 is provided to guide the first upper plate 11 as it moves up and down.

[0022] The first upper plate 11 and the first lower plate 12 of the first pressurizer 10 can be adjusted to a predetermined resin melting temperature by a temperature controller (first temperature control device) or the like. In addition to an electric heater, a medium-circulating type temperature controller that circulates a medium such as oil or steam to control the temperature can be used.

[0023] The first pressurizer 10 is a mechanism for heating and melting the thermoplastic resin filled in the mold M, and is configured to continuously press down on the mold M while heating it with a low pressure (first pressure). The low pressure (first pressure) referred to here is 1 kgf / cm². 2 This refers to a pressure above the specified level, but not exceeding the second pressure described later. However, this value is just an example, and the first pressure may vary depending on the material viscosity at the time of melting, the size of the molded product, and the size of the mold, which may be 1 kgf / cm². 2 It can also be expressed as less than.

[0024] In the first pressurizer 10, when pressurized, the heat from the heated first upper plate 11 and first lower plate 12 is transferred to the mold M, and pressure is applied such that the resin inside the mold M and the inner surface of the mold M are in close contact, and the outer surface of the mold M and the first upper plate 11 and first lower plate 12 are in close contact.

[0025] Furthermore, the first pressurizer 10 may also be equipped with a mechanism (first pressure control device) that automatically releases the pressure from the first upper plate 11 and the first lower plate 12 when heating and pressurization are completed (i.e., when the melting of the thermoplastic resin is complete). In this case, for example, it is possible to determine that heating and pressurization have been completed when a preset time has elapsed, and to automatically release the pressure from the first upper plate 11 and the first lower plate 12.

[0026] The completion of heating and pressurizing can also be determined by other methods. For example, if the density of the thermoplastic resin inside the mold M changes due to melting, the depth to which the mold closes (the gap between the upper mold M1 and the lower mold M2) changes. Therefore, the completion of heating and pressurizing can be determined based on the gap between the upper mold M1 and the lower mold M2.

[0027] Specifically, the gap between the upper mold M1 and the lower mold M2 is photographed with a camera or the like, and when the width of the gap falls below a preset threshold, it is determined that heating and pressurization have finished, and the pressurization by the first upper plate 11 and the first lower plate 12 is automatically released.

[0028] <Second pressurizer> The second pressurizer 20 is a compression mechanism that pressurizes the mold M at a second temperature lower than the first temperature and a second pressure higher than the first pressure, and comprises an upper plate (hereinafter referred to as the "second upper plate") 21 and a lower plate (hereinafter referred to as the "second lower plate") 22 that are positioned opposite each other with a gap between them in the vertical direction. The second upper plate 21 and the second lower plate 22 cooperate to clamp the mold M, and together they function as a single clamping device (second clamping device).

[0029] A hydraulic cylinder 23 is connected to the second upper plate 21, and the second upper plate 21 is configured to move up and down by the power of the hydraulic cylinder 23. Other means besides a hydraulic cylinder can also be used to drive the second upper plate 21. Between the second upper plate 21 and the second lower plate 22, a guide column (hereinafter referred to as the "second guide column") 24 is provided to guide the second upper plate 21 as it moves up and down.

[0030] Similar to the first upper plate 11 and the first lower plate 12, the second upper plate 21 and the second lower plate 22 can also be adjusted to a predetermined cooling temperature by a temperature controller (second temperature control device), etc. A medium circulation type temperature controller that circulates a medium such as water, oil, or steam can be used for temperature control. The temperature controller can be shared with the temperature controller of the first upper plate 11 and the first lower plate 12, or a separate temperature controller can be used.

[0031] The second pressurizer 20 is a mechanism for compressing and cooling the thermoplastic resin, and is configured to rapidly cool the mold M, which is sandwiched under high pressure (second pressure), while continuously applying high pressure. The high pressure (second pressure) referred to here is 20 kgf / cm². 2 This refers to the pressure above. However, this value is just one example; the second pressure is 20 kgf / cm². 2 It can also be expressed as less than.

[0032] In the second pressurizer 20, when pressurized, the mold M is cooled by the cooled second upper plate 21 and second lower plate 22, so that the outer surface of the mold M and the cooled second upper plate 21 and second lower plate 22 are in close contact, and pressure is applied to the extent that the molten resin inside the mold M and the inner surface of the mold M are in close contact (enough to tighten the mold M).

[0033] Similar to the first pressurizer 10, the second pressurizer 20 can also be equipped with a mechanism (second pressure control device) that automatically releases the pressure from the second upper plate 21 and the second lower plate 22 when cooling and pressurization are complete. In this case, for example, it is possible to determine that cooling and pressurization are complete when a preset time has elapsed, and to automatically release the pressure from the second upper plate 21 and the second lower plate 22. Determining the end of cooling and pressurization can also be done by other methods.

[0034] <Mold Transfer Machine> The mold transfer machine 30 is a conveyor for transferring the mold M. The mold transfer machine 30 transfers the mold M filled with thermoplastic resin to a predetermined position in the first pressurizer 10, transfers the mold M after pressurization in the first pressurizer 10 to a predetermined position in the second pressurizer 20, and delivers the mold M from the predetermined position in the second pressurizer 20.

[0035] In this embodiment, two roller conveyors are used as the mold transfer machine 30, which are spaced apart and arranged parallel to each other. Each roller conveyor comprises opposing support members 31a and 31b, and a plurality of elliptical rolls 32 rotatably supported between the two support members 31a and 31b. The plurality of elliptical rolls 32 are connected by a coupling such as a belt so that they rotate synchronously by a single drive source (not shown).

[0036] As shown in Figures 2(a) and 2(b), in this embodiment, two grooves 12a and 22a are formed in the first lower plate 12 and the second lower plate 22, respectively, and one roller conveyor fits into each groove 12a and 22a.

[0037] As shown in Figures 3(a) and 3(b), the mold M transported by the mold transfer machine 30 is separated from the first lower plate 12 and the second lower plate 22 when the elliptical roll 32 is oriented vertically, and supported by the first lower plate 12 and the second lower plate 22 when the elliptical roll 32 is oriented horizontally. Therefore, by oriented the elliptical roll 32 horizontally, the mold M can be pressed without the elliptical roll 32 interfering with anything.

[0038] The configuration of this embodiment is an example, and the manufacturing apparatus of the present invention is not limited to the configuration of the embodiment described above. The manufacturing apparatus of the present invention can be modified as appropriate, such as by adding, replacing, or omitting components, to the extent that the intended purpose can be achieved.

[0039] For example, in this embodiment, from the viewpoint of thermal efficiency, the first pressurizer 10 and the second pressurizer 20 are shown as being installed on separate tables, but the first pressurizer 10 and the second pressurizer 20 can also be installed on a single table.

[0040] Furthermore, in the above embodiment, the arrangement of the first pressurizer 10 and the second pressurizer 20 side by side is given as an example, but the arrangement of the first pressurizer 10 and the second pressurizer 20 may be other than this, for example, the first pressurizer 10 and the second pressurizer 20 may be arranged facing each other.

[0041] Furthermore, in the above embodiment, one example is a case in which the mold transfer machine 30 is composed of two roller conveyors equipped with elliptical rolls 32, but the mold transfer machine 30 can also be equipped with a roller conveyor equipped with cylindrical rolls (with a perfectly circular or nearly circular cross-sectional shape).

[0042] In this case, the mold transfer machine 30 is not structured to fit into the grooves 12a and 22a of the first lower plate 12 and the second lower plate 22, but can be installed in front of the first pressurizer 10 and the second pressurizer 20 which are arranged side by side.

[0043] In such a configuration, it is necessary to provide a mechanism for sending the mold M from the mold transfer machine 30 to a predetermined position in the first pressurizer 10 or the second pressurizer 20, and a mechanism for sending the mold M from the predetermined position in the first pressurizer 10 or the second pressurizer 20 back to the mold transfer machine 30.

[0044] Furthermore, in the above embodiment, one example is a case in which the first presser 10 is equipped with a first guide column 14 and the second presser 20 is equipped with a second guide column 24. However, the first presser 10 and the second presser 20 can also be presses that do not have columns corresponding to the first guide column 14 and the second guide column 24 (so-called C-type presses).

[0045] In this case, the mold transfer machine 30 can be of any type other than those with the various structures described above, or it can be a type that utilizes a ball screw. Specifically, a mold press can be attached to the nut of the ball screw, and the mold M can be transferred by the mold press.

[0046] Next, a method for manufacturing thermoplastic resin molded products (hereinafter simply referred to as "manufacturing method") will be described. Here, we will use the manufacturing apparatus of this embodiment as an example.

[0047] (1) First, thermoplastic resin (pellets) is placed between the upper mold M1 and the lower mold M2 that make up the mold M. In order to obtain sufficient holding pressure, the amount of thermoplastic resin in the mold M is greater than the volume of the product (for example, about 105-120% of the volume of the product). (2) The mold M into which the thermoplastic resin has been placed is transferred by the mold transfer machine 30 to a predetermined position between the first upper plate 11 and the first lower plate 12 of the first pressurizer 10 (Figure 4(a)). (3) After the mold M is transferred to a predetermined position in the first pressurizer 10, the first upper plate 11 is pushed down by the air cylinder 13, and the mold M is pressurized and heated by the first upper plate 11 and the first lower plate 12 (Figure 4(b)). At this time, the upper mold M1 and lower mold M2 of the mold M are not completely closed, and are pressurized to the extent that a gap remains between them. In addition, the first upper plate 11 and the first lower plate 12 are heated to a temperature slightly above the melting temperature of the pellets inside the mold M so that the pellets inside the mold M can be melted. (4) After pressurization and heating in the first pressurizer 10 are completed, the pressurization of the mold M by the first upper plate 11 and the first lower plate 12 is released, and the mold M is transferred by the mold transfer machine 30 to a predetermined position between the second upper plate 21 and the second lower plate 22 of the second pressurizer 20 (Figure 5(a)). (5) After the mold M is transferred to a predetermined position in the second pressurizer 20, the second upper plate 21 is pushed down by the hydraulic cylinder 23, and the mold M is pressurized and cooled by the second upper plate 21 and the second lower plate 22 (Figure 5(b)). At this time, the upper mold M1 and lower mold M2 of the mold M are pressurized to the extent that they are completely closed. In addition, the second upper plate 21 and the second lower plate 22 are, in principle, temperature-controlled so that the temperature of the molded product inside the mold M is below the glass transition temperature. (6) After pressurization and cooling in the second pressurizer 20 are completed, the pressurization of the mold M by the second upper plate 21 and the second lower plate 22 is released, and the mold M is discharged to the other side of the second pressurizer 20 by the mold transfer machine 30 (Figure 6). (7) After the mold M is discharged to the front of the second pressurizer 20, the upper mold M1 and lower mold M2 of the discharged mold M are opened to remove the molded product inside, and finishing work is performed to complete the thermoplastic resin molded product.

[0048] In the above manufacturing process, as shown in Figures 7(a) and 7(b), the mold M is heated in the first pressurizer 10 while being sandwiched between the first upper plate 11 and the first lower plate 12 under weak pressure (first pressure), and the thermoplastic resin heated together with the mold M is melted. By compressing at low pressure, the molten resin is gradually filled into the voids inside the mold. As the entire thermoplastic resin melts, the resin melting and shaping by the mold occur.

[0049] In the first pressurizer 10, the heated first upper plate 11 and first lower plate 12 remain in close contact with the outer surface of the mold M, transferring heat to the mold M. This heat causes the thermoplastic resin inside the mold M to melt sequentially. However, because the pressurizing force is weak, the mold M does not completely close even after all the thermoplastic resin inside has melted.

[0050] Subsequently, in the second pressurizer 20, as shown in Figures 7(c) and 7(d), the mold M, which has been melted and shaped in the first pressurizer 10, is cooled while being squeezed under strong pressure (second pressure) by the second upper plate 21 and the second lower plate 22. At this time, the excess molten resin inside the mold M seeps out due to the high-pressure compression. The operation of the second pressurizer 20 then performs holding pressure and cooling.

[0051] When the mold M is transferred to the second pressurizer 20, the inside of the mold M is filled with molten resin that is slightly above its melting point. In this state, the mold M is rapidly cooled and its temperature drops as it comes into contact with the second upper plate 21 and the second lower plate 22 of the second pressurizer 20. At this time, the molten resin inside is cooled sequentially from the part in contact with the mold M (the part in contact with the inner surface of the mold), but because the temperature of the molten resin is near its melting point, it shrinks rapidly, causing its specific volume to decrease.

[0052] The resin closer to the mold M has a smaller specific volume and higher viscosity, resulting in lower fluidity. Conversely, the resin further away from the mold M has a larger specific volume and lower viscosity. Therefore, the molten resin inside, which is hotter and more fluid, attempts to flow out of the mold M. As it does so, the more fluid resin fills any insufficient areas, while the excess flows out. As a result, the resin solidifies inside the mold M due to cooling, and pressure is maintained by filling the shrinkage areas with material.

[0053] (Comparison with conventional technology) A compression molding apparatus, used for thermosetting rubber and the like, exists as an apparatus that is superficially similar to the manufacturing apparatus of this embodiment. However, the compression molding apparatus is intended to shape thermosetting rubber that cross-links through heating and does not deform after cross-linking, and therefore its essential purpose and function differ from that of the manufacturing apparatus of this embodiment. In particular, it does not have a structure that satisfies the function of holding pressure.

[0054] In addition, because thermoplastic rubber is soft, the mold will not be damaged even if it is compressed under strong pressure before melting. Furthermore, the pressure only needs to be strong enough to close the mold, so there is no need to vary the pressure. Also, since crosslinking and hardening proceed only by heating, there is no need to consider a cooling function to remove the molded product from inside.

[0055] Thus, since the manufacturing apparatus of this embodiment and the conventional compression molding apparatus have clear functional differences, the novelty and inventive step of the manufacturing apparatus disclosed in this application cannot be denied based on the conventional compression molding apparatus.

[0056] Furthermore, heat-and-cool molding is a conventional method known as one of the injection molding methods. Heat-and-cool molding is merely a form of injection molding and differs from the manufacturing apparatus of this embodiment in that it uses a cylinder for melting and holding pressure.

[0057] Thus, the manufacturing apparatus of this embodiment and the heat-and-cool molding method have clear functional differences, and the novelty and inventive step of the manufacturing apparatus disclosed in this application cannot be denied based on the conventional heat-and-cool molding method.

[0058] (Effects of the manufacturing apparatus of this embodiment) In conventional injection molding, thermoplastic resin is melted in a heated cylinder while an internal rotating screw rotates to break the resin. While this method is suitable for efficiently melting thermoplastic resin, the synergistic effect of shear heat generated during resin breakdown and the heating cylinder makes it prone to overshoot, and controlling the heat is difficult.

[0059] In contrast, in the manufacturing apparatus of this embodiment, temperature control is performed solely by the heating mechanism of the apparatus, so shear heat generation does not occur, and the melting temperature of the resin can be accurately controlled. Since it is possible to maintain a temperature slightly above the melting point of the thermoplastic resin, there is no need to worry about the thermoplastic resin in the mold M becoming excessively hot and degrading the material, and the technical expertise required in the resin melting process is not as high as in injection molding.

[0060] In injection molding, in order to fill the mold with molten resin in a short time, it is necessary to completely melt the resin and give it sufficient fluidity. This often requires heating the resin to a temperature well above its melting point, which frequently leads to degradation of the thermoplastic resin.

[0061] In contrast, in the method using the manufacturing apparatus of this embodiment, the molded product is shaped around the melting point of the resin, and heating significantly above this point is unlikely to occur, thus reducing the likelihood of deterioration of the thermoplastic resin.

[0062] In injection molding, molten resin is filled into the mold at high pressure and for a short time, which makes it easy for stress to remain inside the molded product. In particular, it is difficult to prevent the molded product, such as long flat plates, from warping in one direction.

[0063] In contrast, the method using the manufacturing apparatus of this embodiment ensures that melting and cooling are performed uniformly, and residual stress during filling is less likely to occur, thus reducing the likelihood of warping or distortion in the resulting molded product.

[0064] Generally, thick-walled shapes are avoided in injection molding of thermoplastic resins. In injection molding, the surface in contact with the mold solidifies instantly, but no additional resin is added to compensate for shrinkage inside the thick wall. As a result, internal solidification shrinkage can pull on the solidified surface, causing indentations (sink marks) and vacuum bubbles.

[0065] In contrast, in the method using the manufacturing apparatus of this embodiment, resin is continuously supplied and pressure is maintained inside the molded product until the temperature falls below the solidification point. Therefore, even with thick-walled shapes, sink marks and vacuum bubbles are less likely to occur, and it is possible to mold products without sink marks or vacuum bubbles.

[0066] Generally, in injection molding of thermoplastic resins, parts with uneven wall thickness, where thick and thin sections coexist, are avoided because they are prone to deformation due to the different timing of filling and solidification shrinkage, and are also prone to sink marks.

[0067] In contrast, with the manufacturing apparatus of this embodiment, the entire contents of the mold are melted and filled simultaneously regardless of thickness, so there are no problems with filling. Furthermore, the holding pressure is evenly supplied with resin throughout and pressure is applied, making insufficient filling, shrinkage, and distortion less likely to occur.

[0068] In general, injection molding involves filling and holding pressure within an extremely short timeframe, often less than one second. Since the entire composition of the molded product is determined by the timing of this process, the injection molding machine must control every moment. Acquiring these skills is difficult, and it is said that it takes 5 to 10 years to become a top-tier molding technician.

[0069] In contrast, the method using the manufacturing apparatus of this embodiment does not involve melting and filling problems, and at the same time, there is a time leeway of several tens of seconds for the solidification and shrinkage process, making it easier to acquire molding skills compared to injection molding.

[0070] In injection molding, it is necessary to extrude all the resin in the heating cylinder and replace it with new resin each time the mold is changed. This process is extremely cumbersome and also requires a large amount of material for cleaning the heating cylinder.

[0071] In contrast, in the method using the manufacturing apparatus of this embodiment, the resin exists only within the mold, and therefore, in principle, cleaning is not required. For this reason, it is possible to change the filler material for each shot without any special cleaning, and there is no need for setup. As a result, multi-color single-piece production, which is almost impossible with injection molding, can be easily performed.

[0072] In injection molding, to prevent deformation of the mold while subjected to high pressure during filling, a mold body far larger than the molded product itself is used, and the mold is manufactured using high-strength mold steel that can withstand strong pressure. Because the resin flow path also requires careful consideration, mold costs are extremely high.

[0073] In contrast, the mold used in the manufacturing apparatus of this embodiment is sandwiched between compression devices and does not require the high rigidity of molds used in injection molding. Furthermore, since it does not need to withstand high-speed injection of resin, it does not require the strength of injection molding die steel, and even soft materials such as aluminum are acceptable. In fact, it is preferable to make it thin to increase thermal conductivity, which significantly reduces mold costs. For this reason, it is suitable for small-scale production where amortizing initial costs is difficult.

[0074] Film insert molding is considered difficult in injection molding, and it is particularly challenging to integrally mold thin films over large areas. This is because designing the resin flow path to prevent the film from being damaged or deformed by the high-speed, high-pressure resin requires a high level of expertise.

[0075] In contrast, the method using the manufacturing apparatus of this embodiment makes it easier to perform such film inserts because excessive pressure is less likely to be applied to the film due to resin flow.

[0076] In injection molding, there are very few cases where fibers or fabrics are inserted and molded as a single piece in one go. This is partly because injection molding fills the mold with resin at high speed and high pressure, making it difficult to fill the mold with resin without moving the fibers or fabrics from their initial fixed position, thus making it difficult to evenly integrate the fibers or fabrics with the resin.

[0077] Furthermore, in injection molding, where the material is filled at high speed and solidifies instantly, it is difficult to completely fill the voids in fibers and fabrics with resin and integrate them seamlessly. For this reason, only materials in which short fibers are kneaded into resin pellets and then subjected to conventional injection molding have been put into practical use.

[0078] However, it has been found that compositing fibers and textiles in their original state dramatically improves the strength and toughness of resin-molded products, so there is an extremely high demand for such materials.

[0079] In contrast, the method using the manufacturing apparatus of this embodiment is less likely to generate forces that move the fabric or fibers from their predetermined positions within the mold, and is easy to control. Furthermore, because resin fills the spaces between the fibers during the long holding pressure period, adhesion is enhanced, allowing for easy integral molding without requiring any particularly difficult techniques for fixing the fibers or fabrics.

[0080] When different types of plastics are molded together using methods other than injection molding, the joining of the two materials often fails. In injection molding, the resin fills the mold in a fluid state called fountain flow, which forms a surface skin layer and an internal core layer. The skin layer, being relatively cold, is in a state where it is difficult to bond with the insert material. The other insert material is also cold and has low molecular activity, so even if the two materials come into contact under high pressure for a short period of time, sufficient adhesion and intermolecular forces are difficult to exert.

[0081] In contrast, when inserting using the manufacturing apparatus of this embodiment, the insert is heated to a certain temperature or higher, and the molten resin, in a molecularly activated state, is pressed against it for a certain period of time. As a result, sufficient adhesion occurs between the two, and intermolecular forces act, as well as bonding through the anchoring effect. This makes it possible to bond resins that hardly bond in injection molding with extremely high strength.

[0082] It should be noted that the effects exemplified here are effects that the manufacturing apparatus of this embodiment may achieve, and it is not the case that all of these effects will always be achieved. The manufacturing apparatus of the present invention also includes those that do not achieve these effects.

[0083] The embodiments and modifications disclosed herein are illustrative and not intended to restrict the technical scope of the present invention. The technical scope of the present invention is defined by the claims, and includes equivalents to the claims. [Industrial applicability]

[0084] The manufacturing apparatus and manufacturing method of the present invention can be used for molding various resins, and can be particularly suitable for manufacturing molded products using thermoplastic resins. [Explanation of symbols]

[0085] 10 First pressurizer 11. Upper plate (first upper plate) 12 Lower plate (first lower plate) 12a groove 13 Air Cylinder 14 Guide posts (first guide post) 20 Second pressurizer 21 Upper plate (second upper plate) 22 Lower plate (second lower plate) 22a groove 23 Hydraulic Cylinder 24 Guide posts (second guide posts) 30 Mold transfer machine 31a, 31b Support 32 elliptical rolls M mold M1 upper mold M2 lower mold

Claims

1. In a manufacturing apparatus for molded products using thermoplastic resin, A first pressurizer that pressurizes a mold filled with a quantity of thermoplastic resin exceeding the volume of the molded product at a first temperature and a first pressure, The mold pressurized by the first pressurizer is further pressurized by a second pressurizer at a second temperature lower than the first temperature and a second pressure higher than the first pressure. A thermoplastic resin molded product manufacturing apparatus characterized by the following features.

2. In the thermoplastic resin molded product manufacturing apparatus according to claim 1, The system includes a mold transfer machine that transfers a mold filled with thermoplastic resin to a predetermined position in a first pressurizer, and transfers the mold, after pressurization in the first pressurizer, to a predetermined position in a second pressurizer. A thermoplastic resin molded product manufacturing apparatus characterized by the following features.

3. In the thermoplastic resin molded product manufacturing apparatus according to claim 1, The first pressurizer comprises a first clamping device for clamping a mold, a first temperature control device for controlling the temperature of the first clamping device, and a first pressure control device for controlling the pressure applied to the first clamping device. A thermoplastic resin molded product manufacturing apparatus characterized by the following features.

4. In the thermoplastic resin molded product manufacturing apparatus according to claim 1, The second pressurizer comprises a second clamping device for holding the mold, a second temperature control device for controlling the temperature of the second clamping device, and a second pressure control device for controlling the pressure applied to the second clamping device. A thermoplastic resin molded product manufacturing apparatus characterized by the following features.

5. In a method for manufacturing molded products using thermoplastic resins, A thermoplastic resin is filled into the mold in an amount exceeding the volume of the molded product. The mold filled with the thermoplastic resin is pressurized at a first temperature and a first pressure. The mold, after being pressurized at the first temperature and first pressure, is then pressurized again at a second temperature lower than the first temperature and a second pressure higher than the first pressure. A method for manufacturing a thermoplastic resin molded product, characterized by the features described herein.

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