JP2008080790A - Method and apparatus for molding resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin molded product excellent in appearance, lightweight properties and rigidity by enhancing the foaming degree of an internal foamed resin covered with a surface layer part comprising a solid resin and avoiding the partial lowering of the rigidity of the surface layer part constituted of a primary hollow molded member. <P>SOLUTION: This molding method of the resin molded product includes a process for molding a parison P from the solid resin, a process for blowing a gas into the molded parison P held in a mold to shape it into a predetermined shape, a process for injecting a foamable resin of a molten state in the obtained hollow molded member in a state that the hollow molded member is left in the mold, and a process for foaming the foamable resin while opening the mold by predetermined quantity after injection to fill the hollow molded member with the resin. The parts X and Y to be stretched of the hollow molded member are preliminarily made thicker than another part in the molding process of the parison P by opening the mold by the predetermined quantity in the filling process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding method and a molding apparatus for a resin molded product, and belongs to the technical field of resin molding.

Conventionally, resin molded products are sometimes used for automobile parts. Especially, from the viewpoint of appearance, lightness and rigidity, resin molded products whose interior is made of foamed resin and whose surface layer is made of solid resin (non-foamed resin) are used. For example, it may be used for an interior / exterior member of an automobile. In this regard, Patent Document 1 discloses that a hollow molded body having a foam layer is filled with a thermoplastic resin foam piece, and the foam piece is heated with a heating medium such as steam to mutually connect the foam pieces. It is disclosed that a foamed article with a skin is obtained by fusing to the surface.
JP2004-284149 (paragraph 0025)

  However, since the technique obtains a foamed molded article covered with the skin of a hollow molded article by heat-sealing the already foamed resin pieces, bubbles are crushed and foamed at the time of heat-sealing. As a result, there is a problem that a sufficiently satisfactory product cannot be obtained in terms of lightness and rigidity. In addition, since the surface layer portion has a foam layer, there is a problem that bubbles appear in the surface layer portion, and a sufficiently satisfactory appearance cannot be obtained.

  On the other hand, in order to ensure good moldability of the primary hollow molded body and to ensure good appearance and rigidity of the final molded product, the primary hollow molded body is molded by blow molding, and this primary hollow molded body is formed. It is conceivable that a foamable resin is injected into the molded body and a predetermined amount of the mold is opened (core back) at the time of foaming. However, in that case, there arises a problem that the primary hollow molded body is partially stretched by the core back of the mold, and the stretched portion is thinned to reduce the rigidity.

  The present invention sufficiently enhances the degree of foaming of the foam resin inside covered with the surface layer portion made of solid resin, and avoids the partial rigidity reduction of the surface layer portion composed of the primary hollow molded body, It is an object to provide a resin molded product having excellent properties, lightness, and rigidity.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a method for molding a resin molded product in which the inside is made of a foamed resin and the surface layer portion is made of a solid resin, and a parison molding step of molding a parison with the solid resin. And a molding process in which a molded parison is sandwiched between molding molds and a gas is blown into the interior to form into a predetermined shape, and a foamed resin in a molten state with the resulting hollow molded body left in the molding mold An injection step of injecting the resin into the hollow molded body, and a filling step of filling the hollow molded body with the foamable resin by foaming the foamable resin while opening a predetermined amount after the injection. The part where the hollow molded body is stretched by opening a predetermined amount of the mold is made thicker in advance than the other parts in the parison molding step.

  Next, the invention described in claim 2 of the present application is the method of molding a resin molded product according to claim 1, wherein one of the molds is the other outer peripheral mating surface of the mold when the mold is clamped. An outer peripheral mold that comes into contact with the outer peripheral mold, and an inner mold that is movable relative to the outer peripheral mold in a direction close to the other of the molding dies or in a direction away from the other of the molding dies, and the shaping step And in the injection step, the mold is clamped in a state in which the internal mold is moved in a direction close to the other of the molds, and in the filling step, the mold is clamped in the state, The inner mold is moved away from the other of the molds, and in the parison molding process, the portion of the parison located at the boundary between the outer peripheral mold and the inner mold is thickened in the filling process. Features.

  Next, the invention described in claim 3 of the present application is the method for molding a resin molded product according to claim 1 or 2, wherein, in the parison molding step, a portion where the hollow molded body is stretched, It is characterized in that it is previously thickened with a solid resin rather than other portions.

  Next, the invention according to claim 4 of the present application is the method for molding a resin molded product according to claim 1 or 2, wherein, in the parison molding step, a portion where the hollow molded body is stretched, A thick foaming resin is interposed in the parison layer of the part and foamed by foaming, so that it is previously thicker than the other part.

  Next, the invention according to claim 5 of the present application is a method for molding a resin molded product according to claim 3, in which the other resin of the parison is used as the base resin in the solid resin for thickening. It is characterized by using the same kind of resin as the base resin in the solid resin for molding the part.

  Next, the invention described in claim 6 of the present application is the method for molding a resin molded product according to claim 4, wherein the base resin in the foamable resin for increasing the thickness is a parison. The same type of resin as the base resin in the solid resin for molding the portion is used.

  Next, the invention according to claim 7 of the present application is the method for molding a resin molded product according to any one of claims 1 to 6, wherein in the injection step, a foamable resin containing reinforcing fibers is used. It is characterized by injecting.

  Next, the invention according to claim 8 of the present application is the method for molding a resin molded product according to any one of claims 1 to 7, wherein the foaming resin contains a physical foaming agent in the injection step. It is characterized by injecting.

  Next, the invention according to claim 9 of the present application is the method for molding a resin molded product according to claim 8, wherein, in the injection step, foaming containing a fluid in a supercritical state as the physical foaming agent. It is characterized by injecting a functional resin.

  On the other hand, the invention described in claim 10 of the present application is a molding apparatus for a resin molded product in which the inside is made of foamed resin and the surface layer portion is made of solid resin, and the parison molding means for molding the parison with the solid resin, A molding die sandwiched between the parisons formed by the parison molding means, a shaping means for blowing a gas into the inside of the parison sandwiched between the molding dies and shaping into a predetermined shape, and obtained by this shaping means An injection means for injecting a molten foamable resin into the hollow molded body in the mold, and after the injection of the foamable resin by the injection means, the foamable resin is foamed while opening the mold by a predetermined amount. A filling means for filling the hollow molded body with the resin, and a portion where the hollow molded body is stretched by opening a predetermined amount of the mold by the filling means, is a parison formed by the parison molding means. During molding, characterized in that it includes a thickening means to keep thickening than previously other portions.

  Next, the invention according to claim 11 of the present application is the apparatus for molding a resin molded product according to claim 10, wherein one of the molds is the other outer peripheral mating surface of the mold during clamping. An outer peripheral mold that is in contact with the outer peripheral mold, and an inner mold that is movable relative to the outer peripheral mold in a direction close to the other of the molding dies or in a direction away from the other of the molding dies, At the time of shaping by the shaping means and at the time of injection by the injection means, the inner mold is moved in a direction close to the other of the molding dies, so that the mold is clamped. At the time of filling, the inner mold moves in a direction away from the other of the molding dies in the mold-clamped state, and the thickening means is a boundary between the outer peripheral mold and the inner mold at the time of filling by the filling means. Department of Parison located in Characterized by thickening the.

  Next, the invention according to claim 12 of the present application is the apparatus for molding a resin molded article according to claim 10 or 11, wherein the thickening means includes a portion where the hollow molded body is stretched. Further, it is characterized in that it is thickened with a solid resin more than other portions in advance.

  Next, the invention according to claim 13 of the present application is the apparatus for molding a resin molded product according to claim 10 or 11, wherein the thickening means includes a portion where the hollow molded body is stretched. In the parison layer of this part, a foamed resin in a molten state is interposed and foamed to make it thicker than other parts in advance.

  Next, an invention according to claim 14 of the present application is the molding apparatus for a resin molded product according to claim 12, wherein the thickening means is a base material in a solid resin for thickening. The resin is characterized by using the same type of resin as the base resin in the solid resin for molding the other part of the parison.

  Next, an invention according to claim 15 of the present application is the molding apparatus for a resin molded product according to claim 13, wherein the thickening means is a base in the foamable resin for thickening. As the material resin, the same kind of resin as the base resin in the solid resin for molding the other part of the parison is used.

  Next, an invention according to claim 16 of the present application is the apparatus for molding a resin molded product according to any one of claims 11 to 15, wherein the injection means is a foamable resin containing a physical foaming agent. It is characterized by injecting.

  Next, an invention according to claim 17 of the present application is the apparatus for molding a resin molded article according to claim 16, wherein the injection means is a foam containing a supercritical fluid as the physical foaming agent. It is characterized by injecting a functional resin.

  First, according to the invention described in claim 1 or claim 10, in order to ensure good moldability of the primary hollow molded body and to ensure good appearance and rigidity of the final molded product, a solid resin is used. Injecting a foamed resin in a molten state into a hollow molded body in a state where a hollow molded body obtained by sandwiching a molded parison between molding molds and blowing a gas into the interior to be shaped into a predetermined shape is left in the mold, Thereafter, the foamable resin is foamed while the mold is opened by a predetermined amount, and the resin is filled into the hollow molded body. Therefore, foaming of the foamed resin is sufficiently promoted, and lightness and rigidity are improved. Furthermore, since the surface layer portion is made of a solid resin (non-foamed resin), bubbles do not appear in the surface layer portion, and the appearance can be improved.

  In addition, by opening the molding die by a predetermined amount (core back), the portion where the hollow molded body is stretched and thinned (the stretched portion of the hollow molded body, the thinned portion) is made thicker than other portions in advance. As a result, even if the surface layer portion formed of the hollow molded body is partially stretched, it is possible to easily and effectively prevent the stretched portion from being thinned and the rigidity from being lowered. Therefore, the degree of foaming of the internal foamed resin covered with the surface layer part made of solid resin is sufficiently increased, and the surface layer part is partially thinned and thus the rigidity is prevented from being lowered, and the appearance, lightness and rigidity are excellent. A resin molded product can be obtained easily and reliably.

  Next, according to the invention described in claim 2 or claim 11, one of the molding dies is an outer peripheral die that comes into contact with the other outer peripheral mating surface of the molding die when the mold is clamped. An inner mold that is relatively movable in a direction close to the other of the molds or a direction away from the other of the molds, and when the parison is molded and the foamable resin is injected, the inner mold is The mold is clamped in a state of being moved in the direction close to the other, and when foaming resin is filled and filled, the inner mold is moved away from the other of the molds while the mold is clamped As a result, it is possible to open the mold by a predetermined amount (core back) with a simple configuration without complicating the structure of the mold and its driving mechanism.

  Moreover, since the part of the parison located at the boundary between the outer peripheral mold and the inner mold is made thicker, it is sure to aim at the appropriate part of the parison (the stretched part of the hollow molded body, the thinned part). Therefore, it is possible to more effectively prevent a reduction in the thickness of the surface layer portion and a reduction in rigidity.

  In that case, according to the invention described in claim 3 or claim 12, the portion where the hollow molded body is stretched is thickened with a solid resin having a relatively high rigidity. It is possible to more effectively prevent a decrease in rigidity after stretching.

  On the other hand, according to the invention described in claim 4 or claim 13, the portion where the hollow molded body is stretched is foamed by interposing a foamable resin in a molten state in the parison layer of the portion and foaming. Since it is made thicker, the part tends to extend when the core is back, and the boundary between the part and another part (non-thickened part) adjacent to the part (part where the thickness changes greatly: stress tends to concentrate) ) Is stretched well without being cut, and the followability of the hollow molded body to the mold for core back does not decrease. In addition, after stretching, the portion has a closed cross-sectional structure in which the parison layer is filled with foamed resin, so that high rigidity is ensured.

  Next, according to the invention described in claim 5 or claim 14, the base resin in the solid resin for thickening, and the base resin in the solid resin for molding the other part of the parison Since they are the same type, the configuration of the molding method or molding apparatus is simplified. Further, the conformability between the two resins does not decrease, and problems such as delamination between the two resins are suppressed.

  On the other hand, according to the invention described in claim 6 or claim 15, the base resin in the foamable resin for thickening and the base resin in the solid resin for molding the other part of the parison. Since they are the same type, the configuration of the molding method or molding apparatus is simplified. Further, the conformability between the two resins does not decrease, and problems such as delamination between the two resins are suppressed.

  Next, according to the seventh aspect of the invention, when the foamable resin is injected, the foamable resin containing the reinforcing fiber is injected, so that the spring of the reinforcing fiber when the mold is opened by a predetermined amount. By the back phenomenon, it becomes possible to further promote the foaming of the foamed resin.

  Next, according to the invention described in claim 8 or claim 16, when the foamable resin is injected, the foamable resin containing the physical foaming agent is injected. The foamed cell diameter inside the molded product can be made small, and the rigidity of the resin molded product can be further improved.

  Next, according to the invention described in claim 9 or claim 17, when the foamable resin is injected, the foamable resin containing the fluid in the supercritical state is injected. With this function, the foamed cell diameter inside the molded product can be made to be a finer diameter, and the rigidity of the resin molded product can be further improved. Hereinafter, the present invention will be described in more detail through the best mode for carrying out the invention.

<First Embodiment>
FIG. 1 is a longitudinal sectional view showing a configuration of an extruding apparatus (parison forming means) 1 for a parison P according to the present embodiment. The accumulator head 2 of the device 1 has a cylinder 3, a ring piston 4 and a core 5. A resin storage chamber 6 is formed below the ring piston 4. The resin storage chamber 6 is connected to an extruder 8 of a solid resin N (see FIG. 5) that is a raw material of the parison P via an upper annular communication path 7.

  A die 9 is provided at the lower end of the cylinder 3. A core support 10 is provided at the lower end of the core 5. A core 11 is fitted to the core support 10 so as to be movable up and down. An annular die slit 12 is formed between the die 9 and the core 11. The die slit 12 communicates with the resin storage chamber 6. The parison P is extruded from the die slit 12 in a tube shape and hangs down.

  The core 11 is moved up and down by a core driving hydraulic cylinder (thickening means) 14 via a core driving rod 13. Thereby, the space | interval of the die slit 12, ie, the thickness of the parison P extruded from the die slit 12 and drooping is adjusted.

  The ring piston 4 is moved up and down by a ring piston driving hydraulic cylinder 16 via a ring piston driving rod 15. Thereby, the accumulator which pumps the resin in the resin storage chamber 6 to the die slit 12 side is constituted.

  2 is a cross-sectional view taken along line II-II in FIG. On the outer peripheral surface of the core 11, two concave grooves (thickening means) 21 and 21 are provided to extend vertically at a predetermined interval. As a result, as shown in FIG. 3, the parison P hanging down in a tube shape has two vertical thickenings at the same interval as the concave grooves 21 and 21 and having a larger radial thickness than the other portions. The portions Y and Y are formed extending vertically. In addition, the parison P is also formed with annular laterally thickened portions X and X that extend in the circumferential direction, which is also thicker in the radial direction than other portions. The laterally thickened portion X is formed by adjusting the distance between the die slits 12 by the vertical movement of the core 11.

  Here, the laterally thickened portions X and X and the vertical thickened portions Y and Y are positioned at the boundary between the outer peripheral die 34 and the internal die 35 of the second mold 33 in the mold 31 described later. (See, for example, FIG. 6). And the area | region S enclosed with the oblique line in FIG. 3 is a core back contact surface contact | abutted to the internal type | mold 35 of the 2nd shaping | molding die 33 mentioned later.

  FIG. 4 is a longitudinal sectional view showing the configuration of the injection molding apparatus 30 according to this embodiment. The injection molding apparatus 30 has a molding die 31. The mold 31 includes a first mold 32 and a second mold 33. Connected to the first mold 32 is an injection machine (injection means) 40 of a foamed resin M (see FIG. 5), which is a raw material inside the molded product. Further, the first mold 32 is provided with a hollow blow pin (shaping means) 41 for blowing gas into the parison P sandwiched between the molds 31 so as to freely advance and retract. Here, the first mold 32 has a built-in block body 43 that opens and closes the injection port 40 a of the resin injection machine 40. The block body 43 is moved up and down by an appropriate actuator (for example, an electromagnetic valve) 42. The illustrated example shows a state in which the block body 43 is moved to the upper position and the injection port 40a is closed. The inner surface of the block body 43 faces a recessed hole 44 formed in the first mold 32.

  On the other hand, the second molding die 33 of the molding die 31 includes an outer peripheral die 34 that contacts the outer peripheral mating surface of the first molding die 32 at the time of clamping, and a direction close to the first molding die 32 with respect to the outer peripheral die 34 or An internal die 35 that is relatively movable in a direction away from the first molding die 32 is provided.

  Next, a method for molding the resin molded product A according to this embodiment will be described. Here, the resin molded product A according to the present embodiment is used, for example, for an interior / exterior member of an automobile, and as shown in FIG. 5, the inside is a foamed resin M (resin after being foamed). In addition, the code | symbol M 'is used for resin (foamable resin) before foaming (refer FIG.8 and FIG.9), and a surface layer part consists of solid resin N. FIG. First, in the extrusion molding apparatus 1 shown in FIG. 1 and FIG. 2, a tube-shaped parison P in a molten state is molded from a solid resin N as a raw material (see FIG. 3: parison molding process).

  Next, as shown in FIG. 6, the molded parison P is sandwiched between the molding dies 31. That is, the first mold 32 and the second mold 33 are clamped. Next, as shown in FIG. 6, gas is blown into the inside of the parison P sandwiched between the molding dies 31 and shaped into a predetermined shape (shaping step).

  Here, the blow pin 41 advances into the cavity as indicated by an arrow a, and gas (typically air) is blown into the parison P. A part of the swelled parison P enters the concave hole 44 formed in the first mold 32 and is thinly stretched. As described above, the thickened portions X, X and Y, Y of the parison (only the thickened portions X, X are shown in the figure) are the inner periphery of the second mold 33 in the mold 31 and the inside. It is located at the boundary with the mold 35. The core back contact surface S of the parison P is in contact with the internal mold 35 of the second mold 33.

  Next, as shown in FIG. 7, the actuator 42 is operated to move the block body 43 to the lower position as indicated by the arrow b. Thereby, it enters into the concave hole 44 formed in the first mold 32, and a part of the parison P that has been thinly stretched is further thinned and ruptured, and the resin injection machine 40 is placed inside the hollow molded body. A hole for injecting the foamable resin M is generated through the injection port 40a.

  Next, as shown in FIG. 8, the foamed resin M ′ in a molten state is injected into the hollow molded body while leaving the obtained hollow molded body inside the molding die 31 (injection step). At this time, the foamable resin M ′ in the melted state is blown from the resin injection machine 40 through the injection port 40a, the recessed hole 44, and a hole formed by rupturing a part of the hollow molded body. It is injected into the body. At this stage, the blow pin 41 is retracted from the cavity as indicated by an arrow c.

  Next, as shown in FIG. 9, after injection of the molten foamable resin M ′, the foamable resin M ′ is foamed while the mold 31 is opened by a predetermined amount, and the resin M ′ is filled into the hollow molded body. (Filling step). That is, in FIG. 6 to FIG. 8, the mold 31 is clamped in a state where the inner mold 35 of the second mold 33 is moved in the direction close to the first mold 32, but in FIG. In a state where the mold 31 is clamped (that is, in a state where the first mold 32 and the outer peripheral mold 34 of the second mold 33 are in contact with each other), only the inner mold 35 is separated from the first mold 32 (arrow) e) is moved by a predetermined amount (core back) (not shown, but the device that cores the mold 31 in this way corresponds to “filling means” in the claims). By performing this core back, the thickness of the molded product increases and the specific gravity decreases, and the foaming of the foamed resin M is promoted, and fine bubbles are uniformly dispersed inside the molded product. Thereby, the rigidity of a molded product improves and weight reduction is achieved.

  In addition, the core back extends a portion located at the boundary between the outer peripheral die 34 and the inner die 35 of the second molding die 33 in the hollow molded body. However, as described above, this stretched portion is thickened in advance in the parison P forming step compared to other portions (thickened portions X and Y: see FIG. 3). As a result, as shown in FIG. 9, the thickened portions X and Y are extended (only the elongated lateral thickened portions X ′ and X ′ are shown in the figure), and the hollow made of the solid resin N is formed. The surface layer part comprised by a molded object becomes uniform thickness. That is, even if a part of the hollow molded body is stretched by the core back, the surface layer portion is not partially thinned, and a decrease in rigidity of the surface layer portion of the resin molded product A is avoided. Furthermore, since the surface layer portion is composed of the solid resin (non-foamed resin) N, bubbles do not appear in the surface layer portion, and the appearance of the finally obtained resin molded product A can be improved.

  In addition, when filling the foamable resin M ′, as shown by an arrow d in FIG. 9, the air is removed from the hollow molded body through the hollow blow pin 41 in the retracted state.

  In addition, the resin injection machine 40 and the injection port 40 a or the recessed hole 44 are disposed in the central portion of the first mold 32. As a result, as shown in FIGS. 8 and 9, the foamable resin M ′ is injected from the front portion of the mold 31. Thereby, the flow distance in the cavity of the injected foamable resin M ′ is averaged, and the foamed resin M is uniformly filled inside the hollow molded body.

  As described above, as shown in FIG. 5, the resin molded product A having the inside made of the foamed resin M and the surface layer portion made of the solid resin N is finally molded.

  Thus, in this embodiment, in order to ensure good moldability of the primary hollow molded body and to ensure good appearance and rigidity of the final molded product A, the parison P ( 3) is sandwiched between molds 31 and a hollow molded body (see FIGS. 6 and 7) obtained by blowing gas into the interior and shaping into a predetermined shape is left in the mold 31 in a molten state. The foamable resin M ′ is injected into the hollow molded body (see FIG. 8), and then the foamable resin M ′ is foamed while the molding die 31 is opened (core back) to hollow the resin M ′. Since the molded body is filled (see FIG. 9), foaming of the foamable resin M ′ is sufficiently promoted, and lightness and rigidity are improved. Moreover, since the portion where the hollow molded body is stretched by opening the molding die 31 by a predetermined amount is made thicker than other portions in advance (thickened portions X and Y), the hollow molded body is constituted. It is possible to effectively prevent the surface layer portion from being partially thinned and the rigidity from being lowered. Furthermore, since the surface layer portion is made of solid resin (non-foamed resin) N, bubbles do not appear in the surface layer portion, and the appearance can be improved. Therefore, the degree of foaming of the internal foamed resin M covered with the surface layer portion made of the solid resin N is sufficiently increased, and partial thinning of the surface layer portion is prevented, and the appearance, lightness, and rigidity are excellent. The resin molded product A can be obtained easily and reliably. [Configuration equivalent to claim 1]

  In addition, one of the molds 31 (second mold 33) has an outer peripheral mold 34 that contacts the outer peripheral mating surface of the other mold 31 (first mold 32) when the mold is clamped. It has an internal mold 35 that is relatively movable in the direction close to the first mold 32 or in the direction away from the first mold 32, and when the parison P is shaped (see FIGS. 6 and 7) and foaming At the time of injection of the expandable resin M ′ (see FIG. 8), the mold 31 is clamped in a state where the internal mold 35 is moved in the direction close to the first mold 32, and the foaming resin M ′ is expanded. At the time of filling (see FIG. 9), since the inner mold 35 is moved in the direction (arrow e) away from the first mold 32 while the mold 31 is clamped, the structure of the mold 31 and its Without complicating the drive mechanism and the like, the mold 31 is opened by a predetermined amount with a simple configuration. The core back) it becomes possible. In addition, since the portion of the parison P located at the boundary between the outer peripheral die 34 and the inner die 35 is thickened (thickening portions X and Y: see, for example, FIG. 6), the parison P is appropriate. Therefore, it is possible to increase the thickness of such a portion, and to effectively prevent partial thinning of the surface layer portion. [Configuration equivalent to claim 2]

  Here, it is preferable that reinforcing resin such as glass fiber is contained in the foamable resin M ′. When the mold 31 is core-backed, a springback phenomenon of the reinforcing fiber occurs, and thereby foaming of the foamed resin M is further promoted. [Configuration corresponding to claim 7]

  The foamable resin M ′ preferably contains a physical foaming agent. Due to the effect of the physical foaming agent, the foamed cell diameter inside the molded product A can be made smaller, and the rigidity of the resin molded product A is further improved. [Configuration corresponding to claim 8]

  In that case, it is preferable to use a fluid in a supercritical state as the physical foaming agent. By the function of the fluid in the supercritical state, the diameter of the foam cell inside the molded product A can be made to be a finer diameter, and the rigidity of the resin molded product A is further improved. [Configuration equivalent to claim 9]

  Here, the fluid in a supercritical state is a fluid that exceeds a limit temperature (critical temperature) and pressure (critical pressure) at which gas and liquid can coexist, and the critical temperature is, for example, carbon dioxide The critical pressure is, for example, 7.4 MPa for carbon dioxide and 3.4 MPa for nitrogen. A fluid in a supercritical state has a density close to that of a liquid and has a fluidity similar to that of a gas. As a result, it can move actively in the molten resin, and can be diffused and penetrated deeply into the resin molecules to become a fine foam seed.

  For the solid resin N that is the raw material of the parison P and the foamable resin M that is the raw material inside the molded product, thermoplastic resins are preferably used. For example, polyethylene (PE), polypropylene (PP), ABS resin, nylon resin Etc. are suitable.

  4 and 6 to 9, originally, the laterally thickened portions X and X of the parison P are also provided on the side of the first mold 32 opposite to the core back contact surface S. Although it appears, the thickened portion on that side is not a feature of the present invention, so illustration is omitted.

<Second Embodiment>
FIG. 10 is a longitudinal sectional view showing a configuration of a characteristic part of an extruding apparatus (parison forming means) 1 of a parison P according to the second embodiment of the present invention. Hereinafter, the same or similar members as those in the first embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only characteristic portions of the second embodiment are described. The extrusion molding apparatus 1 according to the second embodiment includes first, second, and third annular communication passages 7a, 7b, and 7c from the central rod 13 or core 5 side toward the outer peripheral side. Is provided. Accordingly, the first, second, and third resin storage chambers 6a, 6b, and 6c and the first, second, and third ring pistons 4a, 4b, and 4c are provided.

  Both the first annular communication passage 7a and the third annular communication passage 7c are supplied with a solid resin in a molten state from the same raw material supply source, and the second annular communication passage 7b is provided with a foaming property in a molten state from different raw material supply sources. Resin is supplied. Each ring piston 4a, 4b, 4c can be driven individually, and the solid resin is always sent out to the die slit 12 side from the first resin storage chamber 6a and the third resin storage chamber 6c. From 6b, the foamable resin is sent out to the die slit 12 side only when the laterally thickened portion X is formed. Instead of the ring pistons 4a, 4b, and 4c, an on-off valve that opens and closes the resin passage from the resin storage chambers 6a to 6c to the die slit 12 may be used.

  As a result, as shown in FIG. 11, in the parison molding step, a portion where the hollow molded body is stretched is foamed by interposing a foamed resin in a molten state in the parison P layer of the portion. It can be made thicker than other parts. [Configuration corresponding to claim 4]

  That is, a laterally thickened portion X extending in the circumferential direction is formed on the inner peripheral surface of the cylindrical parison P. The laterally thickened portion X is formed from the second annular communication passage 7b between the solid resin layer supplied from the first annular communication passage 7a and the solid resin layer supplied from the third annular communication passage 7c. It is the structure thickened by interposing the supplied foamable resin partially.

  Therefore, as shown in FIG. 12, when the molded parison P is sandwiched between the molds 31, that is, when the first mold 32 and the second mold 33 are clamped, the thickened portion X of the parison P Is located at the boundary between the outer peripheral die 34 and the inner die 35 of the second molding die 33 in the molding die 31. As shown in FIG. 13, when the inner die 35 is core-backed in the direction of arrow e, the portion of the parison P located at the boundary between the outer die 34 of the second molding die 33 and the inner die 35 in the hollow molded body. Is stretched (stretched thickened portion X ′). However, since the portion to be stretched is thicker than the other portions in advance (thickened portion X), as shown in FIG. 13, the thickened portion X is stretched ( In the figure, the elongated thickened portion X ′ is shown), and the surface layer portion formed of the hollow molded body made of the solid resin N has a uniform thickness.

  Moreover, in that case, the portion where the hollow molded body is stretched is made thicker by interposing a foamed resin in a molten state in the parison P layer of the portion and foaming, so that the portion Is easy to extend when the core is back, and the boundary between the part and the other part (non-thickened part) adjacent to the part (the part where the thickness changes greatly: stress tends to concentrate) is improved without cutting the part. The followability of the hollow molded body to the mold (internal mold 35) that is stretched and core-back does not deteriorate. Moreover, after extending | stretching, as shown in FIG. 13, since this part becomes a closed cross-section structure with which the parison P layer was filled with foamed resin, high rigidity is ensured.

  Here, if the base resin in the foamable resin for thickening and the base resin in the solid resin for molding other parts of the parison P are of the same type, the molding method according to this embodiment or The configuration of the molding apparatus is simplified. Further, the conformability between the two resins does not decrease, and problems such as delamination between the two resins are suppressed. [Configuration equivalent to claim 6]

  In addition, although the above demonstrated the case where the horizontal thickening part X was formed with the extrusion molding apparatus 1 shown in FIG. 10, according to this, the vertical thickening part of the same structure was simultaneously made into the parison P. Can be formed.

  Further, in order to form the thickened portion so as to protrude from the inner peripheral surface of the cylindrical parison P, and to make the outer peripheral surface of the parison P closely contact the molding die, a solid resin layer outside the parison P (The solid resin layer supplied from the third annular communication passage 7c in FIG. 10) is thickened, and the solid resin layer inside the parison P (the same, the solid resin layer supplied from the first annular communication passage 7a). This is achieved by thinning (see the enlarged view in a circle in FIG. 11).

  Further, instead of the above, molten solid resin may be supplied also from the second annular communication passage 7b of FIG. As a result, in the parison molding step, the portion where the hollow molded body is stretched can be made thicker in advance with the solid resin than other portions. [Configuration equivalent to claim 3]

  In that case, a reduction in rigidity after stretching of the portion where the hollow molded body is stretched can be prevented more effectively than when foamable resin is used.

  Here, if the base resin in the solid resin for thickening and the base resin in the solid resin for molding other parts of the parison P are of the same type, the molding method or molding according to the present embodiment The configuration of the apparatus is simplified. Further, the conformability between the two resins does not decrease, and problems such as delamination between the two resins are suppressed. [Configuration corresponding to claim 5]

  The above embodiment is the best embodiment of the present invention, but it goes without saying that various modifications and changes may be made without departing from the scope of the claims.

  For example, another method for forming a hole in the hollow molded body for injecting the foamable resin M ′ in the hollow molded body is shown in FIGS. 14 and 15 (the same reference numerals are used for the same or similar members as described above). Use). FIG. 14 shows that the protrusion 32a is raised around the recessed hole 44 of the first mold 32, and a part of the hollow molded body is meandered to be thin (the state shown in FIG. 14 (a)). By pulling 43 as shown by the arrow f (state of FIG. 14 (b)), a part of the hollow molded body is more reliably ruptured, and the hollow molded body is inserted through the generated holes and the injection port 40a. A foamable resin M ′ is injected inside. FIG. 15 shows the same concept, but in the case of FIG. 14, a part of the hollow molded body is stretched in the same direction in the state of FIG. 14 (a) and the state of FIG. 14 (b) to be ruptured. On the other hand, in the case of FIG. 15, the tip of the block body 43 is protruded from the protrusion 32a, and a part of the hollow molded body is reversed in the state of FIG. 15 (a) and the state of FIG. It is different in that it is stretched to burst.

  FIGS. 16, 17 and 18 show a method of forming holes in the hollow molded body for venting air in the hollow molded body when foaming resin M ′ is foamed and filled (the same or similar members as described above). 16, the air discharge passage 51 and the movable body 52 having the projecting pins 53... 53 are built in the first mold 32, and gas is blown into the parison P by the blow pins 41. When projecting (arrow a), the projecting pins 53... 53 project into the cavity to make a hole in the hollow molded body (as shown in FIG. 16A), and move during injection to filling of the foamable resin M ′. The body 52 is retracted as indicated by an arrow g, and the protruding pins 53... 53 are retracted from the cavity (the state shown in FIG. 16B), and the holes formed in the hollow molded body and the through holes 54 of the pins 53. 54 through the air discharge passage 51 17 and 18, the air discharge path forming hole 61 or the air discharge path forming recess 71 is formed in a molding die (first molding in the illustrated example). 17 is provided on the outer peripheral mating surface portion of the mold 32. In the case of Fig. 17, the core columnar body 62 is inserted into the air discharge passage forming hole 61 (the state of Fig. 17A), and this state Then, mold clamping to air blow (state of FIG. 17 (b)), the core columnar body 62 is pulled out at the time of injection of the foamable resin M ′ (state of FIG. 17 (c)), and air is released from the hole. On the other hand, in the case of Fig. 18, the pin bodies 72 ... 72 are inserted into the upper surface portion of the air discharge passage forming recess 71 (the state of Fig. 18 (a)), and in this state, Clamping and air blowing (state shown in FIG. 18B), injection of foamable resin M ′ Are by far the pin body 72 ... 72 (state of FIG. 18 (c)), from the loophole and the pin holes 73 ... 73 to perform air bleeding on.

  As described above in detail with reference to specific examples, the present invention sufficiently enhances the degree of foaming of the internal foamed resin covered with the surface layer portion made of the non-foamed resin, and is constituted by the primary hollow molded body. Because it is a technique that can provide a resin molded product that is excellent in appearance, light weight, and rigidity by avoiding partial reduction in rigidity of the surface layer and avoiding the appearance of bubbles in the surface layer. In the technical field of resin molding, a wide range of industrial applicability is expected.

It is a longitudinal cross-sectional view which shows the structure of the extrusion molding apparatus of the parison which concerns on 1st Embodiment of this invention. It is the II-II sectional view taken on the line of FIG. 1 is a perspective view of a parison according to a preferred embodiment of the present invention. It is a longitudinal section showing the composition of the injection molding device concerning the best embodiment of the present invention. 1 is a partially cutaway perspective view showing the structure of a resin molded product according to a best embodiment of the present invention. FIG. 5 is a longitudinal sectional view similar to FIG. 4 for explaining the molding method of the resin molded product step by step, and shows the next step of FIG. 4. FIG. 9 is a longitudinal sectional view similar to FIG. 4 and showing the next stage of FIG. 6. FIG. 9 is a longitudinal sectional view similar to FIG. 4 and showing the next stage of FIG. 7. FIG. 9 is a longitudinal sectional view similar to FIG. 4, showing the next stage of FIG. 8. It is a longitudinal cross-sectional view which shows the principal part structure of the extrusion molding apparatus of the parison based on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view similar to FIG. 4 which shows the structure of the thickening part in 2nd Embodiment. It is a longitudinal cross-sectional view similar to FIG. 6 which shows the state which pinched | interposed the parison in 2nd Embodiment with the shaping | molding die. It is a longitudinal cross-sectional view similar to FIG. 9 which shows the state at the time of the core back in 2nd Embodiment. It is explanatory drawing of another method of forming the hole for injecting a foamable resin inside a hollow molded object in a hollow molded object. It is explanatory drawing similar to FIG. It is explanatory drawing of the method of forming the hole for performing air bleeding in a hollow molded object at the time of foaming and filling of a foamable resin in a hollow molded object. It is explanatory drawing similar to FIG. It is explanatory drawing similar to FIG.

Explanation of symbols

1 Extrusion molding equipment (Parison molding means)
8 Solid resin extruder 12 Die slit 14 Core drive hydraulic cylinder (thickening means)
21 Groove (thickening means)
30 Injection molding apparatus 31 Mold 32 First mold (the other mold)
33 Second mold (one of the molds)
34 Peripheral mold 35 Internal mold 40 Foamable resin injection machine (injection means)
41 Blow pins (shaping means)
P Parison X, Y Thickening part

Claims (17)

A molding method of a resin molded product in which the inside is made of foamed resin and the surface layer part is made of solid resin,
A parison molding process for molding a parison with the solid resin;
A shaping process in which the molded parison is sandwiched between molds and a gas is blown into the interior to form a predetermined shape;
An injection step of injecting a molten foamable resin into the hollow molded body, with the obtained hollow molded body left in the mold,
And after filling, filling the hollow molded body with the foamable resin by foaming the foamable resin while opening the molding die by a predetermined amount,
A portion of the hollow molded body that is stretched by opening a predetermined amount of the mold in the filling step is made thicker than other portions in the parison molding step in advance. Molding method. A method for molding a resin molded product according to claim 1,
One of the molding dies is in contact with the other outer peripheral mating surface of the molding die at the time of clamping, and is separated from the outer die in a direction adjacent to the other of the molding dies or the other of the molding dies. It has an internal mold that is relatively movable in the direction,
In the shaping step and the injection step, the mold is clamped in a state where the internal mold is moved in a direction close to the other of the molds,
In the filling step, in a state in which the mold is clamped, the internal mold is moved in a direction away from the other of the molds,
In the parison molding step, the parison portion located at the boundary between the outer peripheral mold and the inner mold is thickened in the filling step, and the resin molded product molding method is characterized in that: A method for molding a resin molded product according to claim 1 or 2,
In the parison molding step, a portion where the hollow molded body is stretched is previously thickened with a solid resin more than other portions, and a method for molding a resin molded product is provided. A method for molding a resin molded product according to claim 1 or 2,
In the parison molding step, the portion where the hollow molded body is stretched is made thicker than other portions in advance by interposing a foamed resin in a molten state in the parison layer of the portion and foaming. A method for molding a resin molded product. A method for molding a resin molded product according to claim 3,
A method for molding a resin molded product, comprising using, as a base resin in a solid resin for thickening, a resin of the same type as the base resin in a solid resin for molding other parts of a parison. A method for molding a resin molded product according to claim 4,
A method for molding a resin molded product, comprising using, as a base resin in a foamable resin for thickening, the same type of resin as a base resin in a solid resin for molding other parts of a parison. A method for molding a resin molded product according to any one of claims 1 to 6,
In the injection step, a foamable resin containing reinforcing fibers is injected, and a method for molding a resin molded product is provided. A method for molding a resin molded product according to any one of claims 1 to 7,
In the injection step, a foamable resin containing a physical foaming agent is injected. A method for molding a resin molded product according to claim 8,
In the injection step, a foamable resin containing a fluid in a supercritical state is injected as the physical foaming agent. A molding device for a resin molded product, the inside of which is made of foamed resin and the surface layer portion is made of solid resin,
A parison molding means for molding a parison with the solid resin;
A mold that sandwiches the parison molded by this parison molding means,
Shaping means for blowing gas into the inside of the parison sandwiched between the molding dies and shaping it into a predetermined shape;
Injection means for injecting a foamed resin in a molten state into a hollow molded body in the mold obtained by the shaping means;
After the injection of the foamable resin by the injection means, a filling means for filling the hollow molded body with the foamable resin by foaming the foamable resin while opening the molding die by a predetermined amount;
Thickening means for thickening the part where the hollow molded body is stretched by opening the molding die by a predetermined amount by this filling means, in advance, when parison molding by the parison molding means, than other parts. An apparatus for molding a resin molded product, comprising: A molding apparatus for a resin molded product according to claim 10,
One of the molding dies is in contact with the other outer peripheral mating surface of the molding die at the time of clamping, and is separated from the outer die in a direction adjacent to the other of the molding dies or the other of the molding dies. It has an internal mold that is relatively movable in the direction,
The molding die is in a mold-clamping state in a state where the internal die moves in a direction close to the other of the molding die at the time of shaping by the shaping means and at the time of injection by the injection means,
When the mold is filled by the filling means, the inner mold moves away from the other of the molds in the clamped state,
The apparatus for molding a resin molded product, wherein the thickening means thickens a portion of a parison located at a boundary between the outer peripheral mold and the internal mold when filling by the filling means. A molding apparatus for a resin molded product according to claim 10 or 11,
The apparatus for molding a resin molded product, wherein the thickening means thickens a portion where the hollow molded body is stretched in advance with a solid resin rather than other portions. A molding apparatus for a resin molded product according to claim 10 or 11,
The thickening means is made thicker than the other parts in advance by foaming the part where the hollow molded body is stretched by interposing a foamed resin in a molten state in the parison layer of the part. An apparatus for molding a resin molded product characterized by comprising: A molding apparatus for a resin molded product according to claim 12,
The thickening means uses a resin of the same type as the base resin in the solid resin for molding the other part of the parison as the base resin in the solid resin for increasing the thickness. Product molding equipment. A molding apparatus for a resin molded product according to claim 13,
The thickening means uses a resin of the same type as the base resin in the solid resin for molding other parts of the parison as the base resin in the foamable resin for thickening Molding device. A molding apparatus for a resin molded product according to any one of claims 11 to 15,
The said injection | pouring means inject | pours the foamable resin containing a physical foaming agent, The molding apparatus of the resin molded product characterized by the above-mentioned. A molding apparatus for a resin molded product according to claim 16,
The said injection | pouring means inject | pours the foamable resin containing the fluid of a supercritical state as the said physical foaming agent, The molding apparatus of the resin molded product characterized by the above-mentioned.

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