JP2008290384A - Resin molding, its manufacturing method, and injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a resin molding which is free from surface distortion, a flow mark, a weld mark, a sink, and warpage and good in appearance in a short production time even when it is relatively thick. <P>SOLUTION: The resin molding 11 is divided into two parts 12 and 13, and the parts 12 and 13 are formed from the same thermoplastic resin (PMMA) having translucency. First, a movable mold and a first fixed mold are kept at a temperature of at least the load distortion temperature and below heat decomposition temperature of PMMA, and PMMA is injected into a first cavity formed by both molds to form a first part 12. After the movable mold 9 and the first fixed mold 4 are cooled, a second cavity is formed by the movable mold holding the first part and a second fixed mold. The movable mold is kept at a low temperature. While the temperature of the second fixed mold is again raised to be at least the load distortion temperature and below heat decomposition temperature of PMMA, PMMA is injected into the second cavity to form a second part 13. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a resin molded product, a manufacturing method thereof, and an injection molding apparatus.

Since a thermoplastic resin is lighter than inorganic materials such as metal and glass, when a thick product is required, a resin molded product made of such a thermoplastic resin is often used. In particular, when manufacturing a product having translucency, if glass is used as a material, it is disadvantageous in that it is not only heavy but is easily damaged, and the degree of freedom in shape is poor. Therefore, when manufacturing a translucent and thick product, injection molding of a thermoplastic resin is often used (see Patent Document 1).
JP 2000-229343 A

  When a thick resin molded product is manufactured by a normal injection molding method, it takes time to fill the resin into the cavity, and the resin near the mold surface cools down during the filling process and a solidified layer is formed. Sometimes. If a part of the resin being filled becomes a solidified layer, there is a possibility that the resin in the vicinity of the central portion still flowing moves the solidified layer. When the resin solidified to some extent is moved, the trace may remain as a flow mark, or the force generated by the movement of the solidified resin may remain as surface distortion or warp. In particular, when a resin molded product having translucency is distorted, optical distortion is caused, so that the desired performance of the resin molded product may not be obtained. Further, in the case of a resin molded product having a hole, if a part of the resin being filled becomes a solidified layer, a weld mark is likely to occur, and the product value is significantly reduced. Therefore, when manufacturing a thick resin molded product having a hole, conventionally, a hole is formed by cutting machining after injection molding a resin molded product without a hole. Thereby, the manufacturing cost is very high.

  As described above, when a solidified layer is formed at a position in contact with the mold surface during resin filling, the solidified layer starts to cool quickly, whereas the molten resin in the central portion is cooled after the injection is completely completed. Since it is started, a difference in cooling time occurs in part. As a result, a difference in volume shrinkage partially occurs in the resin molded product, and as a result, sink marks are likely to occur in the resin molded product. If the filling pressure is reduced so that the solidified layer does not move so much, the time required for filling becomes further longer.

  Therefore, conventionally, by increasing the resin temperature and the mold temperature, it has been attempted to make the thermoplastic resin difficult to solidify even on the mold surface, suppress the occurrence of a solidified layer, and eliminate the above-mentioned problems. . However, if the resin temperature and the mold temperature are increased, the cooling time after completion of the injection is further increased, so that the time required for producing the resin molded product is increased and the efficiency is deteriorated. Such a long cooling time is disadvantageous from the viewpoint of manufacturing efficiency and is not preferable.

  Patent Document 1 discloses a special injection compression molding method for solving the problem of sink marks and distortion, but this is not easy because the process becomes very complicated, such as control of compression force.

  Also, it is a relatively thin resin molded product that is divided into a plurality of portions in the in-plane direction instead of the thickness direction, and is formed first in the case of a resin molded product molded by a multicolor molding method. There may be a problem that the first part is reheated when the second part is molded. For example, when the movable mold holding the first part formed earlier is reheated during molding of the second part, the first part sticks to the cavity surface of the movable mold by heat. There is a risk that. In this case, if the mold is opened after the second part is molded and the molded product is taken out, the first part attached to the cavity surface of the movable mold is peeled off, and the surface state is deteriorated. That is, the transfer failure of the surface of the first portion of the molded product.

  The purpose of the present invention is to form a resin that has a relatively good thickness and does not increase the time required for production, suppresses surface distortion, prevents flow marks, weld marks, sink marks, warpage, and other appearance defects, and has good transferability. It is to provide a product, a manufacturing method thereof, and an injection molding apparatus.

  The method for producing a resin molded product of the present invention is formed by dividing a resin molded product into a plurality of portions in the thickness direction, each of the plurality of portions being formed from the same thermoplastic resin, and the movable side mold and the first mold. The fixed mold is closed by closing the movable mold and the first fixed mold in a state where the cavity surface of the fixed mold is maintained at a temperature higher than the deflection temperature of the thermoplastic resin and less than the thermal decomposition temperature. Injecting a thermoplastic resin into one cavity and cooling the cavity surfaces of the movable mold and the first fixed mold after completion of the injection to a temperature lower than the deflection temperature of the thermoplastic resin to form a first portion And a step of moving the formed movable mold holding the first portion from a position facing the first fixed mold to a position facing the second fixed mold. Movable mold with the first part held The cavity surface of the second fixed mold is kept at a temperature equal to or higher than the load deflection temperature of the thermoplastic resin and lower than the thermal decomposition temperature while keeping the cavity surface below the thermoplastic resin load deflection temperature. The thermoplastic resin is injected into the second cavity formed by closing the movable movable mold and the second fixed mold in the held state, and the cavity surface of the second fixed mold is completed after the injection is completed. Forming a second part joined to the first part, wherein a signal indicative of the position or movement of the movable mold is detected and the signal is Based on the above, the heating or cooling of the movable mold is controlled.

  The deflection temperature under load is defined by the international standard ISO 75 (JIS 7191) load 1.8 MPa.

  In this method, a resin molded product is manufactured by a multicolor molding method. Usually, the multicolor molding method is used to integrally form a plurality of parts having different colors or characteristics using different resins, but in the present invention, a resin molded product made of a single thermoplastic resin is used. By manufacturing using this multicolor molding method, the manufacturing time can be shortened while improving the appearance. In the resin molding village manufactured in this way, a difference in partial cooling time hardly occurs, and the problem of sink marks and warpage hardly occurs. Moreover, when the first portion is formed, the surface of the cavity is higher than the deflection temperature under load of the thermoplastic resin, so that the thermoplastic resin has good fluidity and fills the entire first cavity. As a result, a resin molded product in which the occurrence of weld marks and flow marks is suppressed can be manufactured, and the appearance transfer is good and distortion is small. Further, when the second part is formed, the first part held by the movable side mold is kept at a low temperature, and the second fixed side mold is at a high temperature, so that the thermoplastic fluid flows in the second cavity. The resin flows better in the portion closer to the second fixed mold than in the portion close to the first portion and the intermediate portion, and the movable mold is lower than the deflection temperature under load of the first thermoplastic resin. Therefore, the first part is not redissolved, and the first part is not moved by the flow of the thermoplastic resin as the second part.

  The resin molded product of the present invention includes a first part formed by injection molding of a thermoplastic resin and a second part laminated on the first part by injection molding of the same thermoplastic resin as the first part. It is characterized by including. Conventionally, it was natural to manufacture a resin molded product made of a single resin material by a single injection molding, but in the present invention, a plurality of parts made of the same resin material are individually formed by injection molding. Yes. As a result, in particular, a thick resin molded product in which the total thickness of the first part and the second part laminated is 3 mm or more, particularly 4 mm or more can be produced in a relatively short time, and warpage is prevented. The appearance can be improved.

  The “cavity” in this specification is a space between molds in a clamped state, excluding sprues and runners, that can be filled with resin, and refers to a space corresponding to the shape of each molded product. The “cavity surface” refers to the mold surface that defines the cavity.

  According to the present invention, even a relatively thick (for example, 3 mm or more) resin molded product can be manufactured in a short time, and it can prevent warpage, weld marks, flow marks, surface distortion, and have a good appearance. be able to. In particular, in the case of a resin molded product having translucency, the optical characteristics can be improved by suppressing the surface distortion to a small value.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is suitable for manufacturing a relatively thick resin molded article 11 (see FIG. 1) having a thickness of 3 mm or more, particularly 4 mm or more, and is divided into a plurality of parts in the thickness direction. To form. First, this point will be described.

  As described above, conventionally, in order to suppress the surface distortion of a thick resin molded product, to prevent appearance defects such as flow marks, weld marks, sink marks and warpage, and to improve transferability, the resin temperature and gold during molding are required. It was considered to increase the mold temperature. However, along with this, the cooling time of the resin becomes longer, resulting in the disadvantage that the time required for the production is long and the production efficiency is poor. Therefore, in order to solve all of these problems, the present applicant considered that the resin molded product was divided into a plurality of portions in the thickness direction and formed in stages. That is, the resin molded product 11 shown in FIG. 1 has a configuration in which a first part (first layer) 12 and a second part (second layer) 13 having the same shape are laminated, and the first part 12 and the second part. 13 consists of the same thermoplastic resin.

  As an example, the resin molded product 11 is made of a translucent acrylic resin (PMMA: deflection temperature under load of 90 ° C.), and has a square shape with a planar shape of 100 mm × 100 mm and a hole portion 11a with a diameter of 10 mm. The total thickness of the first portion 12 (thickness 3 mm) and the second portion (thickness 3 mm) is 6 mm. And in this invention, it formed using the multicolor molding method conventionally used when the resin molded product was made into the multilayered structure and several types of resin from which a color and a material differ were used as a material conventionally. In addition, the translucency said in this specification means that haze is 30% or less.

  Here, the overall structure of the injection molding apparatus of the present invention will be described. As shown in FIGS. 2 and 3, the injection molding apparatus includes a fixed side plate 1 and a movable side plate 2 that moves toward and away from the fixed side plate 1 along the guide 3 by driving means (not shown). Yes. A first fixed mold 4 and a second fixed mold 5 are attached to the surface of the fixed plate 1 facing the movable plate 2 side. As will be described later, the first fixed side mold 4 and the second fixed side mold 5 are different in the shapes of the cavities 14 and 17 and the positions of the sprues 15 and 18 and the runners 16 and 19 (FIG. 5). , 6), and the other configuration is substantially the same. In FIGS. 2 and 3, two injection mechanisms 6 and 7 are attached to the fixed side plate 1, although they are illustrated separately for the sake of clarity. Although not described in detail, the injection mechanisms 6 and 7 are respectively connected to the sprues 15 and 18 of the fixed molds 4 and 5, and molten thermoplastic resin is passed through the sprues 15 and 18 and the runners 16 and 19. Are injected into the cavities 14 and 17, respectively. Both injection mechanisms 6 and 7 can be supplied with the same thermoplastic resin having translucency. Note that there may be only one injection mechanism as long as the thermoplastic resin can be injected into both the first cavity 14 and the second cavity 17.

  A rotating plate 8 that is rotated by driving means (not shown) is attached to the surface of the movable side plate 2 facing the fixed side plate 1, and two movable side molds 9 are attached to the rotating plate 8. ing. The two movable-side molds 9 have the cavity shapes that are upside down, but the other configurations are the same, and can be opposed to the first fixed-side mold 4 and the second fixed-side mold 5 respectively. Placed in position.

  Each mold 4, 5, 9 is provided with a plurality of flow path pipes 10. Each channel tube 10 is arranged in the vicinity of each cavity 14, 17, and a cooling medium such as cold water or a heating medium such as hot water can be introduced from the temperature control mechanism 20. In each drawing, for the sake of simplicity, the temperature control mechanism 20 is illustrated as if all the flow pipes 10 are connected by a single line. The cooling medium or the heating medium can be supplied to the flow path pipe 10 independently every time.

  Further, in FIG. 3, the molds 4, 5, and 9 are illustrated as having a nested structure. With this configuration, resin molded products having different shapes can be manufactured by exchanging the nested parts. Easy to do. However, it does not necessarily have a nested structure.

  Next, an embodiment of the method of the present invention for producing the resin molded product 11 shown in FIG. 1 using the injection molding apparatus shown in FIGS. 2 and 3 will be described below along the flowchart of FIG.

  First, as shown in FIG. 5, the movable mold 9 is brought into contact with the first fixed mold 4 to form a first cavity 14 therebetween (step S1). The first cavity 14 has the same shape as the first portion 12 shown in FIG. Then, the temperature control mechanism 20 receives the signal indicating that the movable mold 9 is at the position facing the first fixed mold 4 in this way, and based on the signal, the temperature control mechanism 20 and the first mold A heating medium such as hot water is supplied to the flow path pipe 10 provided in the one fixed-side mold 4. This signal may be a signal for driving the rotating plate 8 to rotate by a driving means (not shown), or a signal output by a sensor (not shown) detecting the attitude of the rotating plate 8, that is, the rotating plate. 8 may be a signal indicating that the movable mold 9 is in a posture facing the first fixed mold 4.

  As described above, the heating medium is supplied to the flow path pipes of the movable mold 9 and the first fixed mold 4 so that the cavity surface temperature is equal to or higher than the load deflection temperature of the thermoplastic resin (PMMA) and the thermal decomposition temperature. The temperature is raised to 100 ° C., which is lower than that, and held (step S2). Therefore, a predetermined amount of molten PMMA is injected from the first injection mechanism 6 shown in FIGS. 2 and 3 into the first cavity 14 via the sprue 15 and the runner 16, so that the first part having a thickness of 3 mm is obtained. 12 is formed (step S3). When the injection of PMMA is completed, the temperature control mechanism 20 stops the supply of the heating medium to the flow path pipe 10 provided in the movable mold 9 and the first fixed mold 4, and instead of cold water or the like Supply cooling medium. Thereby, the cavity surface temperature of the movable mold 9 and the first fixed mold 4 is lowered to 50 ° C., and the first portion 12 is solidified (step S4). Thus, the 1st part 12 is shape | molded by what is called a heat cycle shaping | molding method which raises / lowers the temperature of the metal mold | die 4 and 9. FIG.

  Then, the movable side plate 2 is opened away from the fixed side plate 1, and the rotary plate 8 (see FIGS. 2 and 3) is rotated 180 degrees to hold the formed first portion 12. The mold 9 is moved from a position facing the first fixed side mold 4 to a position facing the second fixed side mold 5 (step S5). In this state, as shown in FIG. 6, the movable plate 2 is brought into contact with the fixed plate 1, the movable die 9 is brought into contact with the second fixed die 5, and the first Two cavities 17 are formed (step S6). The second cavity 17 is formed by the second fixed mold 5, the movable mold 9 and the first part 12, and has the same shape as the second part 13 shown in FIG. In addition, the state which abbreviate | omitted the 1st part 12 from FIG. 6 is shown in FIG.

  At this time, a signal for rotationally driving the rotating plate 8 or a signal output by detecting by a sensor (not shown) that the rotating plate 8 has been rotated 180 degrees is supplied to the temperature control mechanism 20. . Based on this signal, the temperature control mechanism 20 stops the supply of the cooling medium to the flow path pipe 10 provided in the movable side mold 9 and the first fixed side mold 4, and the second fixed side. Supply of the heating medium to the flow path tube 10 of the mold 5 is started. In this way, the cavity surface temperature of the second fixed-side mold 5 is 100 ° C. which is not less than the load deflection temperature of PMMA and less than the thermal decomposition temperature while maintaining the cavity surface temperature of the movable-side mold 9 at 50 ° C. (Step S7). As will be described later, when the first portion 12 of the next resin molded product 11 is molded in the first cavity 14 simultaneously with the molding of the second portion 13 of the resin molded product 11, the first The supply of the heating medium to the flow path pipe 10 of the fixed side mold 4 is resumed.

  In the flowchart shown in FIG. 4, for convenience, it is described that the steps are performed in the order of step S5, step S6, and step S7, but the order of these three steps is not limited. For example, the order of step S6 and step S7 may be switched. Furthermore, the cooling in step S7 may be started simultaneously with the start of the movement of the movable mold 9 in step S5 (rotation of the rotating plate 8). This is a signal used by the temperature control mechanism 20 to control heating or cooling (a signal for rotating the rotating plate 8 or the rotating plate 8 rotated 180 degrees). In some cases, it is determined by whether or not a sensor (not shown) detects that the posture has been reached and outputs it.

  Next, a predetermined amount of molten PMMA is injected into the second cavity 17 through the sprue 18 and the runner 19 from the second injection mechanism 7 shown in FIGS. The part 13 is formed (step S8). When the injection of PMMA is completed, the temperature control mechanism 20 stops the supply of the heating medium to the flow path pipe 10 of the second fixed mold 5 and supplies a cooling medium such as cold water instead. Thereby, the cavity surface temperature of the second stationary mold 4 is lowered to 50 ° C., similarly to the cavity surface temperature of the movable mold 9, and the second portion 13 shown in FIG. 8 is solidified (step S9). .

  Thus, the resin molded product 11 shown in FIG. 1 is manufactured, the movable side plate 2 is separated from the fixed side plate 1 and the mold is opened, and the resin molded product 11 is taken out (step S10).

  Table 1 shows the results of studying the resin molded product 11 manufactured according to the present embodiment described above in comparison with Comparative Examples 1 to 4 described later.

  The “weld mark” in Table 1 represents the presence or absence of occurrence of a visible weld mark on the surface of the resin molded product 11 (particularly around the hole 11a). The “flow mark” indicates whether or not a flow mark that can be visually recognized is generated on the surface of the resin molded product 11. “Surface distortion” represents the presence or absence of visible distortion on the surface of the resin molded article 11 in contact with the mold. “Sink” represents the presence or absence of a sinkable mark in the resin molded product 11. “Warpage” represents the shape and size of warpage in the resin molded product 11. “Manufacturing time” represents the time from the start of molding of the first portion (start of injection) until the cooled and solidified resin molded product 11 is taken out.

  As can be seen from Table 1, according to the present embodiment, good results were obtained in any of the weld mark, flow mark, surface distortion, sink mark, and warp, and the manufacturing time was as short as 45 seconds.

  The present applicant conducted a comparative experiment for comparison with the present embodiment. Hereinafter, those comparative examples will be described. In all the following comparative examples, a resin molded product having the same shape is manufactured using the same thermoplastic resin as that of the above-described embodiment. Further, in Comparative Examples 1 and 2, the same injection molding apparatus as in the above-described embodiment is used.

[Comparative Example 1]
In Comparative Example 1, the cavity surface temperatures of the movable mold 9 and the first fixed mold 4 were maintained at 100 ° C., which is higher than the deflection temperature of the thermoplastic resin (PMMA) and lower than the thermal decomposition temperature. The first portion 12 having a thickness of 3 mm was formed by injecting PMMA into the first cavity 14. Then, after the cavity surface temperature of the movable side mold 9 and the first fixed side mold 4 is lowered to 50 ° C. to solidify the first part 12, the movable part in a state where the formed first part 12 is held. The side mold 9 was moved and brought into contact with the second fixed side mold 5. Then, the cavity surface temperature of the movable side mold 9 and the second fixed side mold 5 is increased to 100 ° C. which is higher than the deflection temperature under load of PMMA and lower than the thermal decomposition temperature. Was injected to form a second portion 13 having a thickness of 3 mm. Thereafter, the cavity surface temperature of the movable mold 9 and the second fixed mold 5 was lowered to 50 ° C., and the resin molded product was solidified. The results of studying the resin molded product having a thickness of 6 mm manufactured in this way are shown in Table 1 described above. In Comparative Example 1, there was no problem with respect to the weld mark, flow mark, and sink mark, and the manufacturing time was short, but surface distortion occurred and a concave warp of 0.1 mm also occurred.

[Comparative Example 2]
In Comparative Example 2, PMMA was injected into the first cavity 14 while maintaining the cavity surface temperatures of the movable mold 9 and the first fixed mold 4 at 60 ° C., which is lower than the deflection temperature of PMMA. Thus, the first portion 12 having a thickness of 3 mm was formed. When the injection of PMMA is completed, the first part 12 is naturally solidified, and then the movable mold 9 holding the formed first part 12 is moved so as to contact the second fixed mold 5 I let you. Then, while keeping the cavity surface temperatures of the movable mold 9 and the second fixed mold 5 at 60 ° C., PMMA is injected into the second cavity 17 to form a second part having a thickness of 3 mm. 13 was formed. The resin molded product 11 was naturally solidified. The results of studying the resin molded product having a thickness of 6 mm manufactured in this way are shown in Table 1 described above. In Comparative Example 2, good results were obtained with respect to surface distortion and sinking, and the manufacturing time was short, but a weld mark and a flow mark were generated, and a convex warp of 0.1 mm was also generated.

[Comparative Example 3]
In Comparative Example 3, a similar resin molded product was manufactured by a normal molding method instead of performing the multicolor molding method using the injection molding apparatus shown in FIGS. That is, a single-layer resin molded product having a thickness of 6 mm was manufactured. Specifically, the cavity surface temperature of the movable side mold and the fixed side mold is increased to 100 ° C. which is higher than the deflection temperature under load of PMMA and lower than the thermal decomposition temperature, and PMMA is injected into the cavity to obtain a thickness. A 6 mm resin molded product was formed. When the injection of a predetermined amount of PMMA was completed, the cavity surface temperature of the movable mold and the fixed mold was lowered to 50 ° C., and the resin molded product was solidified. The results of studying the resin molded product thus manufactured are shown in Table 1 above. In Comparative Example 3, good results were obtained with respect to the weld mark, flow mark, and surface distortion, but there was a sink, a large convex warp of 0.7 mm, and a manufacturing time of 110 seconds. there were.

[Comparative Example 4]
In Comparative Example 4, as in Comparative Example 3, a single-layer resin molded product was produced not by a multicolor molding method but by normal molding. That is, the cavity surface temperature of the movable mold and the fixed mold was maintained at 60 ° C., which is lower than the deflection temperature under load of PMMA, and PMMA was injected into the cavity to form a resin molded product having a thickness of 6 mm. And the resin molded product was naturally solidified. The results of studying the resin molded product thus manufactured are shown in Table 1 above. In Comparative Example 4, the weld mark, flow mark, surface distortion, and sink mark all had bad results, a large convex warp of 0.8 mm was generated, and the manufacturing time was as long as 120 seconds.

[Verification of Embodiment of the Present Invention and Comparative Examples 1 to 4]
As can be seen from Table 1, in the embodiment of the present invention, good results were obtained in any of weld marks, flow marks, surface distortion, sink marks, and warpage, and the manufacturing time was as short as 45 seconds.

  In contrast, in Comparative Example 1, surface distortion and small warpage occurred. This is because when the second portion 13 is formed, the movable side mold 9 holding the first portion 12 is heated, and the resin of the second portion 13 flows into the place where the first portion 12 is remelted. This is considered to be caused by the fact that one part 12 was dragged.

  In Comparative Example 2, a small warp occurred between the weld mark and the flow mark. This is because the temperature (60 ° C.) of the cavity surface of each mold 4, 5, 9 is lower than the load deflection temperature of PMMA when the first portion 12 is formed and when the second portion 13 is formed. is there. That is, a solidified layer is likely to occur near the mold surface during resin filling.

  In Comparative Example 3, sink marks and large warpage occur, and the manufacturing time is as long as 110 seconds. This is because a molded product having a thickness of 6 mm was manufactured by a single injection molding, and therefore, it took a long time to cool and solidify at the center of the molded product, and the difference in cooling time was likely to occur. This is because a difference occurs.

  In Comparative Example 4, there is a large warp and warpage for the same reason as in Comparative Example 3, resulting in a longer manufacturing time, and further, a weld mark, a flow mark, and surface distortion. The reason for the latter is that, as in Comparative Example 2, the temperature (60 ° C.) of the cavity surface of each mold is lower than the load deflection temperature of PMMA during molding, and a solidified layer is formed near the mold surface during resin filling. It is because it is easy to occur.

  From the above verification, in order to generate a large warp and shorten the manufacturing time, it is effective to form a resin molded product in a multi-layered structure in stages (for example, in a 2-layer structure in two stages). I know that there is. In order to prevent weld marks and flow marks, it is effective to increase the cavity surface temperature of the mold during molding higher than the deflection temperature under load of the thermoplastic resin. Furthermore, as described above, when forming the resin molded product in a multi-layered structure in steps (for example, in a two-layered structure in two steps), in order to prevent surface distortion of the resin molded product, The temperature of the movable mold holding the first part already formed is set lower than the deflection temperature under load of the thermoplastic resin, and only the second fixed mold opposite thereto is made of the thermoplastic resin. It can be seen that it is effective to make the temperature higher than the deflection temperature under load.

  Therefore, according to the embodiment of the present invention, it is possible to obtain a resin molded product that satisfies all of these requirements, has no weld mark, flow mark, surface distortion, sink mark, warp, etc., has a good appearance, and has a short manufacturing time. In particular, when the resin molded product is thick, it has conventionally been liable to cause appearance defects such as warping and sink marks, and the manufacturing time (especially the cooling time) tends to be long. Can be manufactured in a short time and the appearance can be improved. Furthermore, it is particularly effective to apply the present invention so that the surface distortion is reduced even for a resin molded product having translucency that has a large influence when surface distortion occurs.

  In the present embodiment, a single flat resin molded product made of a single thermoplastic resin, not a complicated shape, is manufactured using the same thermoplastic resin by the multicolor molding method. Each of the plurality of shape portions is injection-molded. This method has the advantages described above, and is particularly effective in producing a thick resin molded product having translucency. Usually, the multicolor molding method is used when manufacturing a resin molded product including a plurality of types of resins having different colors and properties. By using it for a new application that deviates from the above-mentioned application, an advantage not found in the past was derived.

  However, since the present invention uses a multicolor molding method, the shape of the first cavity 14 that forms the first portion 12 and the shape of the second cavity 17 that forms the second portion 13 can be freely changed. You can also. In addition, since different cavities are used when the first portion 12 is formed and when the second portion 13 is formed, the resin can be injected into the cavities 14 and 17 simultaneously. That is, the movable side mold 9 holding the already formed first portion 12 is brought into contact with the second fixed side mold 5 and the second thermoplastic resin is injected into the second cavity 17 at the same time. Then, another movable mold 9 is brought into contact with the first fixed mold 4 and the first thermoplastic resin is injected into the first cavity 14 to start manufacturing the next resin molded article 11. be able to. That is, the first portion 12 of the next resin molded product 11 can be molded in the first cavity 14 simultaneously with the molding of the second portion 13 of the resin molded product 11. In this way, the manufacturing cycle of the resin molded product can be shortened, which is suitable for mass production.

  The above description describes an example in which a resin molded product is divided into a plurality of layers in the thickness direction, that is, a first portion (first layer) 12 and a second portion (second layer) 13. . However, the injection molding apparatus of the present invention is also applicable to the case where the resin molded product is divided into a plurality of parts other than the thickness direction, that is, in the in-plane direction (for example, the length direction or the width direction) and manufactured by multicolor molding. Can be used. Even in that case, when the movable side mold holding the first molded part is joined to the second fixed side mold and the thermoplastic resin is injected, the cavity surface of the movable side mold is formed. It is effective to keep the temperature below the deflection temperature under load of the thermoplastic resin and keep the cavity surface of the second fixed mold at or above the deflection temperature under load of the thermoplastic resin and below the heat decomposition temperature. This is because the first part molded first does not stick to the cavity surface of the movable mold by heat, so that the appearance of the resin molded product can be kept good.

  Here, the temperature control mechanism 20 of the present invention will be described. In the following description, for the sake of convenience, a pair of movable molds are distinguished by reference numerals 9a and 9b, respectively. However, as described above, there is no structural difference between the movable molds 9a and 9b. As an example of the temperature control mechanism 20, as shown in FIG. 9, each of the heating medium supply mechanism 20 a and the cooling medium connected to each mold 4, 5, 9 a, 9 b through an independent valve (not shown). The medium supply mechanism 20b may be included. In that case, in the manufacturing method described above, when the movable side mold 9a reaches the position facing the first fixed side mold 4, between the movable side mold 9a and the heating medium supply mechanism 20a. The valve is opened, and a heating medium is supplied to the flow path tube 10 of the movable mold 9a to heat it. When the injection of the resin from the first injection mechanism 6 to the first cavity 14 is completed, the valve between the movable mold 9a and the cooling medium supply mechanism 20b is opened, and the movable mold 9a is opened. A cooling medium is supplied to the channel tube 10 and cooled. When the movable mold 9a is at a position facing the second fixed mold 5, the valve between the movable mold 9a and the cooling medium supply mechanism 20b is opened, and the movable mold 9a is opened. Alternatively, a cooling medium may be supplied to the channel tube 10 for cooling, or all the valves between the movable side mold 9a and the temperature control mechanism 20 are closed, and the flow of the movable side mold 9a is closed. Nothing may flow through the road pipe 10. Such temperature control applies to both the pair of movable molds 9a and 9b.

  On the other hand, the first and second fixed molds 4, 5 both have their fixed molds 4, 5 and the heating medium supply mechanism 20a when the movable molds 9a, 9b reach the opposing positions. And the heating medium is supplied to the flow pipes 10 of the fixed molds 4 and 5 to heat them. When the injection of the resin from the first and second injection mechanisms 6 and 7 to the first and second cavities 14 and 17 is completed, the fixed-side molds 4 and 5 and the cooling medium supply mechanism 20b The valve is opened, and a cooling medium is supplied to the flow path pipes 10 of the fixed molds 4 and 5 to cool them. Such temperature control applies to both of the two fixed molds 4 and 5.

  As a modification, the order in which the movable molds 9a and 9b facing the first and second fixed molds 4 and 5 are connected to the medium supply mechanism 20 can be reversed.

  As described above, in the present invention, as one of the factors for controlling the heating or cooling of each mold 4, 5, 9a, 9b, a signal indicating the position or movement of the movable mold 9 (for example, A signal for rotationally driving the rotating plate 8 or a signal (detected and output by a sensor not shown) that the rotating plate 8 has been rotated 180 degrees is used.

  In addition, as another one of the factors for controlling the heating or cooling of the respective molds 4, 5, 9a, 9b, the timing of completion of the injection of the resin from the first and second injection mechanisms 6, 7 Is also used, but this is automatically determined by a preset program. However, for example, it is determined by detecting an injection completion signal from the first and second injection mechanisms 6 and 7 or a signal indicating a predetermined resin pressure from a sensor in the first and second cavities 14 and 17. May be.

  For example, as shown in FIGS. 2 and 3, the injection mechanism in the above-described injection molding apparatus is arranged such that two or more injection mechanisms are arranged horizontally, or one injection mechanism is set up vertically and the other injection mechanism is arranged horizontally. It is conceivable to arrange two or more injection devices horizontally and orthogonally to each other, or arrange two or more injection mechanisms so as to face each other with a mold interposed therebetween. In the present invention, any of the above-described arrangement methods may be adopted, and molding can be performed by setting molding conditions independently for each injection mechanism.

  In the above-described embodiment, the rotating plate 8 to which the plurality of movable molds 9 are attached rotates, so that the movable mold 9 becomes the first fixed mold 4 and the second fixed mold 5. It is the structure which moves between. In this way, instead of the core rotation system in which the entire movable mold 9 or at least its core part rotates, a core moving system in which the entire movable mold 9 or at least its core part moves in parallel can be used. Moreover, the core back | bag system which can enlarge a cavity by moving at least one part of a core part without moving the movable die 9 whole can also be used. In the case of the core back method, since only one fixed side mold is required, the entire injection molding apparatus can be used without reducing the number of resin molded products manufactured compared to the case of normal injection molding which is not multicolor molding. There is no need to increase the size. Further, there is an advantage that the configuration of the injection molding apparatus is simple and the manufacture thereof is easy as compared with a configuration that requires a plurality of fixed side molds. In the case of the core back type injection molding apparatus, instead of a signal indicating the position or movement of the movable mold 9, a signal indicating the position or movement of the core portion is used to Heating and cooling may be controlled. For example, the heating may be started when the core portion moves forward to form the first cavity, and the cooling may be started when the injection of the resin from the injection mechanism is completed. However, when the core part is retracted, only cooling is continued.

(A) The front view of the resin molded product manufactured by this invention, (b) is the side sectional drawing. It is a figure which shows the injection molding apparatus of this invention. FIG. 3 is a cross-sectional view of a mold part of the injection molding apparatus shown in FIG. 2. It is a flowchart which shows the manufacturing method of the resin molded product of this invention. It is an expanded sectional view of the metal mold | die part for demonstrating the manufacturing method shown in FIG. It is an expanded sectional view of the metal mold | die part for demonstrating the manufacturing method shown in FIG. It is an expanded sectional view of the metal mold | die part for demonstrating the manufacturing method shown in FIG. It is an expanded sectional view of the metal mold | die part for demonstrating the manufacturing method shown in FIG. It is a schematic diagram which shows an example of the temperature control mechanism of the injection molding apparatus of this invention.

Explanation of symbols

1 fixed side plate 2 movable side plate 3 guide 4 first fixed side mold 5 second fixed side mold 6 first injection mechanism 7 second injection mechanism 8 rotating plates 9, 9a, 9b movable side mold DESCRIPTION OF SYMBOLS 10 Flow path pipe 11 Resin molded product 11a Hole 12 1st part 13 2nd part 14 1st cavity 15, 18 Sprue 16, 19 Runner 17 2nd cavity 20 Temperature control mechanism

Claims (9)

In the method of manufacturing a resin molded product,
The resin molded product is formed by dividing into a plurality of parts in the thickness direction, and the plurality of parts are each formed from the same thermoplastic resin,
In a state where the cavity surfaces of the movable side mold and the first fixed side mold are maintained at a temperature equal to or higher than the deflection temperature under load of the thermoplastic resin and lower than the thermal decomposition temperature, the movable side mold and the first fixed side mold The thermoplastic resin is injected into a first cavity formed by closing the mold, and after completion of the injection, the cavity surface of the movable mold and the first fixed mold is loaded with the thermoplastic resin. Forming a first portion that cools below a deflection temperature;
Moving the movable mold in a state of holding the formed first part from a position facing the first fixed mold to a position facing the second fixed mold;
The cavity surface of the second stationary mold is held in the thermoplastic resin while the cavity surface of the movable mold holding the formed first portion is kept below the deflection temperature under load of the thermoplastic resin. A second structure is formed by closing the movable mold and the second fixed mold in a state of maintaining the first portion formed while maintaining a temperature equal to or higher than the deflection temperature of the resin and lower than the thermal decomposition temperature. The thermoplastic resin is injected into the cavity of the second portion, and after completion of the injection, the cavity surface of the second fixed mold is cooled to a temperature lower than the deflection temperature under load of the thermoplastic resin. Forming a part;
Including
A method for manufacturing a resin molded product, comprising: detecting a signal indicating the position or movement of the movable mold and controlling the heating or cooling of the movable mold based on the signal. The movable side mold is mounted on a rotating plate, and the movable side mold is located between a position facing the first fixed side mold and a position facing the second fixed side mold. The movement is performed by rotating the rotating plate 180 degrees,
The signal indicating the position or movement of the movable mold is a signal for rotationally driving the rotating plate or a signal representing the attitude of the rotating plate. Based on the signal, the movable mold is The manufacturing method of the resin molded product of Claim 1 which starts the heating of the said movable side metal mold | die when it reaches | attains a position facing 1 fixed side metal mold | die. A pair of the movable molds;
When one of the pair of movable molds is in a position opposite to one of the first movable mold and the second movable mold, the pair of movable molds At the same time as the other of the molds is at a position opposite to the other of the first movable side mold and the second movable side mold, the second part of the resin molded product is formed. The method for producing a resin molded product according to claim 1, wherein a plurality of resin molded products are continuously produced by forming the first portion of the resin molded product. In the method of manufacturing a resin molded product,
The resin molded product is formed by dividing into a plurality of parts in the thickness direction, and the plurality of parts are each formed from the same thermoplastic resin,
By closing the movable side mold and the fixed side mold in a state where the cavity surfaces of the movable side mold and the fixed side mold are maintained at a temperature equal to or higher than the load deflection temperature of the thermoplastic resin and lower than the thermal decomposition temperature. Injecting the thermoplastic resin into the configured first cavity, and cooling the cavity surfaces of the movable side mold and the fixed side mold to less than a load deflection temperature of the thermoplastic resin after the completion of the injection; Forming a part;
Between the movable side mold and the second fixed side mold in a state where the core part inside the movable side mold or the fixed side mold is moved to hold the formed first part. Configuring the second cavity to:
The cavity surface of the fixed mold is kept under the load of the thermoplastic resin while the cavity surface of the movable mold in a state of holding the formed first portion is kept below the deflection temperature of the thermoplastic resin. The thermoplastic resin is injected into the second cavity in a state where the temperature is not less than the deflection temperature and less than the thermal decomposition temperature, and the cavity surface of the stationary mold is less than the deflection temperature load of the thermoplastic resin after the injection is completed. Cooling to a second portion joined to the first portion;
Including
A method for producing a resin molded product, comprising: detecting a signal indicating the position or movement of the core portion, and controlling heating or cooling of the movable mold based on the signal.   Based on the signal indicating the position or movement of the core portion, heating of the movable mold is started when the first cavity is formed between the movable mold and the fixed mold. The manufacturing method of the resin molded product of Claim 4.   A first portion formed by injection molding of a thermoplastic resin, and a second portion laminated on the first portion by injection molding of the same thermoplastic resin as the first portion, the first portion, The resin molded product, wherein the total thickness of the second portions laminated is 3 mm or more. A first fixed mold, a second fixed mold, and a movable mold movable between the first fixed mold and the second fixed mold; In injection molding equipment for the production of resin molded products,
The first fixed-side mold has a first cavity having the same shape as the first part of the plurality of parts into which the resin molded product to be manufactured is joined when joined to the movable-side mold. Configure
When the second fixed side mold is joined to the movable side mold in a state of holding the formed first part, among the plurality of parts into which the manufactured resin molded product is divided Forming a second cavity having the same shape as the second part of
When a signal indicating the position or movement of the movable mold is detected and the movable mold is at a position facing the first fixed mold, the first fixed mold and the movable mold are moved. The cavity surface of the side mold is maintained at a temperature equal to or higher than the load deflection temperature of the thermoplastic resin and lower than the thermal decomposition temperature, and after the injection of the thermoplastic resin into the first cavity is completed, the movable side mold and the first fixed The cavity surface of the side mold is cooled to below the deflection temperature under load of the thermoplastic resin, a signal indicating the position or movement of the movable side mold is detected, and the movable side mold is moved to the second fixed side mold. When in the position facing the mold, the cavity surface of the movable mold is kept below the deflection temperature under load of the thermoplastic resin, and the cavity surface of the second fixed mold is deflected under load of the thermoplastic resin. Over temperature Temperature control that keeps the temperature below the thermal decomposition temperature and cools the cavity surface of the second fixed mold after the completion of the injection of the thermoplastic resin into the second cavity below the deflection temperature under load of the thermoplastic resin. An injection molding apparatus for producing a resin molded product characterized by having a mechanism. A rotating plate to which the movable mold is attached;
The movable side mold moves between a position facing the first fixed side mold and a position facing the second fixed side mold by the rotation of the rotating plate by 180 degrees,
The signal indicating the position or movement of the movable mold is a signal for rotating the rotating plate or a signal representing the attitude of the rotating plate,
The temperature control mechanism, when the movable mold reaches a position facing the first fixed mold based on a signal for rotating the rotating plate or a signal representing the attitude of the rotating plate The injection molding apparatus for manufacturing a resin molded product according to claim 7, wherein heating of the movable mold is started. A pair of the movable molds;
When one of the pair of movable molds is in a position opposite to one of the first movable mold and the second movable mold, the pair of movable molds The other of the molds is at a position facing the other of the first movable side mold and the second movable side mold, and the formation of the second part of the resin molded product and the next resin molding The injection molding apparatus for manufacturing a resin molded product according to claim 7 or 8, wherein the first portion of the product can be formed simultaneously.

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