JP4221581B2 - Compression molding method and apparatus for resin molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a resin in which a molten resin lump having a substantially columnar shape is dropped into a cavity formed in a female mold, and the molten resin lump is compression-molded by cooperation of the female mold and the male mold. The present invention relates to a compression molding method and apparatus for a molded product.
[0002]
[Prior art]
Conventionally, as one method of molding a synthetic resin container such as a PET bottle or a synthetic resin closure for closing the mouth of the container, a molten resin lump is divided into a female mold and a male mold. There is a method of compression molding in cooperation with each other. The molten resin mass is once formed into a preform (hereinafter referred to as “preform”) for the container, and the preform is further blow-molded to form the container. In forming a container or a closure, the molten resin extruded from the extruder is cut into a substantially columnar molten resin lump and dropped into a cavity formed in the female mold. In the case of container molding, the molten resin lump is inserted between the female mold and the male mold by pressing the male mold that is the mold core into the molten resin lump in the cavity and compressing it. It is molded into a preform (see Patent Document 1 for a blow molding preform and its manufacturing method). Also when molding the closure, the molten resin is cut out as a molten resin lump with a reduced thickness compared to the case of the container, the molten resin lump is dropped into the cavity in the female mold, Thereafter, it is formed into a closure in the same manner as in the case of the container.
[0003]
The conceptual diagram of the apparatus used for the conventional compression molding method is shown by FIG. FIG. 4 is a conceptual diagram showing an example of an apparatus in which the outer diameter of the molten resin lump and the inner diameter of the mold cavity are substantially equal. As shown in FIG. 4, the molten resin lump extruder 40 includes a die lip 16 that pushes out the molten resin lump 41, and a female mold 44 disposed below the die lip 16. In order to cut out the molten resin extruded from the die lip 16, a cutter 17 is disposed at the outlet of the die lip 16. The female mold 44 for compression molding has a substantially cylindrical inner surface 44a and a flat bottom surface 44b, and has a shape. In order to form a body portion and a closed bottom portion of a preform 49 which will be described later, these inner surfaces are formed. A cavity 45 having an upper opening is formed by 44a and the bottom surface 44b. Since the extruder 40 and the female mold 44 of the molten resin lump 41 are arranged coaxially in the vertical direction, the melt produced by cutting the molten resin extruded from the extruder 40 by the cutter 17. The resin lump 41 is dropped and thrown into the cavity 45 of the female mold 44. A guide member 43 for guiding the cut out molten resin mass 41 is disposed immediately below the die lip 16 of the extruder 40. Inside the guide member 43, a tapered guide passage 43a aligned with the cavity 45 of the female mold 44 disposed below is formed. Since the upper opening 43b of the guide passage 43a is aligned with the lower end opening of the die lip 16 and is larger than the lower end opening, the cut out molten resin mass 41 can be reliably received. The guide member 43 is lowered while guiding the descending molten resin mass 41 along the center by the centering action of the guide passage 43a (refer to Patent Document 2 as a synthetic resin supply device provided with a synthetic resin guide member). By disposing a holding member below the die lip 16, the molten resin lump cut out by the cutter is held by a holding mechanism (not shown) provided in the conveyance unit, and the molten resin lump is held by the holding mechanism by the operation of the conveyance unit. It can also be transported to a compression molding mechanism including both molds provided at different positions in the same state (refer to Patent Documents 2 and 3 for a synthetic resin supply device including a cutting / holding mechanism). In this case, the compression molding apparatus can be configured, for example, as a rotary type that is arranged at equal intervals on the peripheral edge of the disk that rotates the mold. In order to form a multilayer preform, the extruder 40 forms a molten resin mass 41 in which, for example, a gas barrier resin 42 is wrapped.
[0004]
As shown in FIG. 5, the molten resin mass 41 charged into the cavity 45 is lowered in the compression molding process by lowering the core mold arranged coaxially with the female mold 44, that is, the male mold. The preform 49 is compression molded. The molten resin mass 41 is formed in a layer structure in which a gas barrier resin 42 is sandwiched between outer resin layers. FIG. 5 is a schematic diagram showing an example of a male mold and a preform formed around the male mold. The male mold 46 includes a core part 47 to be inserted into the cavity 45, a mouth part disposed on and around the core part 47, and a neck part molding die 48 for molding the neck part. It is possible to move. The neck mold 48 can be opened and closed horizontally, and the neck mold 48 is opened and the core mold 47 is removed, so that the preform 49 having the mouth and neck 50 can be separated from the male mold 46. . The female mold 44 and the male mold 46 can be forcibly cooled from the inside, and supercool the molded preform 49 into an amorphous state. After the cooling of the preform 49 is completed, the male mold 46 is raised and the preform 49 is extracted from the female mold 44.
[0005]
The molten resin mass 41 dropped into the cavity 45 is extruded into a substantially cylindrical shape. As shown in FIG. 4, if the outer diameter of the molten resin lump 41 and the inner diameter of the cavity 45 are substantially equal, after the molten resin lump 41 is dropped into the female mold, the female mold and the molten resin Since the axial centrality with the lump 41 does not collapse, uniform resin flow occurs at any position in the circumferential direction by compression with the mold core, and a good molded product is obtained.
[0006]
However, depending on the form of the molded product to be manufactured, the cavity formed in the female mold may be formed with a wider opening. FIG. 6 is a conceptual diagram illustrating an example of a compression molding apparatus that molds a wide-mouth preform. The same components as those in the compression molding apparatus shown in FIG. As shown in FIG. 6, since the structure of the die lip 16 of the extruder 40 is constant, the inner diameter of the cavity 55 formed in the female mold 54 is equal to the molten resin lump 41 when forming a wide-mouth preform. It becomes larger than the outer diameter. In such a case, the molten resin mass 41 may be tilted in the cavity 55 as indicated by an imaginary line due to its fluidity. When the inclination of the molten resin lump 41 is increased, the center position of the molten resin lump 41 is shifted with respect to the male mold 54. Therefore, when the male mold is pushed in and compression molded, the molten resin lump 41 does not move around the male mold. Uniform resin flow occurs and molding defects occur.
[0007]
A multilayer preform in which an intermediate layer having a relatively low molecular weight is encapsulated in an inner and outer layer resin has been proposed, and includes a molten resin extrusion process, a molten resin cutting process, a compression molding process for molding a multilayer preform, and a molded multilayer. A compression molding apparatus that performs a preform cooling step is disclosed (Patent Document 4). Also, a method for producing a multilayer preform in which a virgin resin and a recycled resin are separately extruded and supplied into the same female mold and compression-molded by the female mold and the male mold has been devised. Various types of molten resin lumps are compression-molded using a male mold and a neck mold to form a multilayer preform (Patent Document 5).
[0008]
[Patent Document 1]
JP 2000-25729 A (paragraphs [0032] to [0038], FIGS. 1 to 4)
[Patent Document 2]
JP 2000-280248 A (paragraphs [0013] and [0017], FIGS. 2, 5, 6, and 9)
[Patent Document 3]
JP 2000-108127 A (paragraphs [0013] to [0015], FIGS. 5 to 7)
[Patent Document 4]
JP 2003-39531 A (paragraphs [0049] to [0057]), FIGS. 1 and 2)
[Patent Document 5]
JP 2002-248675 A (paragraphs [0015] to [0019], FIGS. 4 and 5)
[0009]
[Problems to be solved by the invention]
Therefore, even when the cavity is formed in a female mold in a tapered shape with a wide opening, it is possible to stably hold the cut molten resin mass in the cavity of the female mold. There is a problem to be solved in terms.
[0010]
The object of the present invention is to prevent the molten resin mass from tilting in the cavity formed in the wide mouth of the female mold, and to melt around the male mold when the male mold is pressed and compressed. It is an object of the present invention to provide a compression molding method and apparatus for a resin molded article that makes it possible to prevent molding defects in advance by making the resin flow uniform.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, a resin molding compression molding method according to the present invention drops a molten resin lump having a substantially columnar shape into a cavity formed in a female mold, and the female mold and In the method of compression molding the molten resin mass in cooperation with a male mold, when the molten resin mass is dropped into the cavity, the molten resin mass is removed from the peripheral edge of the columnar tip portion to the female die. It is made to collide with the inclined part of the taper-shaped recessed part which is formed in the metal mold | die and comprises a part of said cavity, and the said molten resin lump is stably supported by the said taper-shaped recessed part.
[0012]
According to the compression molding method of the resin molded product, the molten resin mass is formed from the peripheral edge of the columnar tip of the tapered concave portion that is formed in the female mold and constitutes a part of the cavity. It is dropped into the cavity in a manner that collides with. The molten resin mass cut into a columnar shape and dropped into the cavity is prevented from falling at an inclined portion that becomes an upward slope regardless of the direction, and is stably supported by the tapered recess. Therefore, the molten resin lump hardly tilts in the cavity, and the molten resin lump is also formed around the male mold when the male mold descends and the molten resin lump is compressed into a preform. The resin flow becomes sufficiently uniform.
[0013]
In order to solve the above-described problem, a compression molding apparatus for a resin molded product according to the present invention is disposed below a supply unit having a supply port for supplying a substantially columnar molten resin lump, A female mold in which a cavity into which the molten resin mass is dropped is formed, and a male mold that compresses the molten resin mass in cooperation with the female die, and the molten resin mass is dropped. When viewed in the insertion direction, the projection position of the peripheral edge of the supply port onto the female die is formed on the inclined portion of the tapered recess that is formed on the female die and forms a part of the cavity. It consists of being located.
[0014]
According to the compression molding apparatus for a resin molded product, the substantially columnar molten resin mass supplied from the supply port by the supply unit is dropped into a cavity formed in the female mold. The projection position of the peripheral edge of the supply port onto the female mold is the inclination of the tapered recess formed in the female mold and constituting a part of the cavity as seen in the dropping direction of the molten resin lump. Since the molten resin mass is dropped, the peripheral edge of the substantially columnar molten resin mass collides with the inclined portion of the tapered recess when the molten resin mass is dropped. Accordingly, since the substantially columnar molten resin lump is supported by the rising slope toward the outside at the periphery of the tip, the fall is suppressed at the inclined portion that becomes the rising slope regardless of the direction, and the tip is tapered. Is stably supported by the concave portion. When the male mold compresses the molten resin mass in cooperation with the female mold, the molten resin mass flows evenly around the male mold, and a good preform is formed. A molten resin lump is usually obtained by cutting out from a continuous molten resin by a cutting mechanism.
[0015]
In this compression molding method, the tapered recess may be a truncated cone-shaped recess or a spherical recess formed in the center of the cavity. When the tapered recess is a truncated cone-shaped recess or a spherical recess formed in the center of the cavity, the cavity can be formed as the surface of the rotating body, so it is easy to rotate the female mold. Can be produced.
[0016]
In this compression molding apparatus, the supply unit includes a holding unit that holds the molten resin lump, and includes a conveyance unit that conveys the molten resin lump to the supply port located directly above the female mold. it can. When the female mold is placed at a position away from the extrusion port of the extruder, such as a rotary type compression molding device that is arranged at equal intervals around the periphery of the rotating disk, it is discharged from the extruder. The molten resin to be cut is cut, and the cut molten resin lumps are individually held by the holding mechanism and conveyed to a supply port located directly above the female mold by the conveyance unit. Since the holding mechanism is provided in the transport unit, when the molten resin mass is held by the holding mechanism, the transport can be started as it is. In this case, the cutter can be provided on the extruder side or on each holding mechanism.
[0017]
In this compression molding method and apparatus, the molten resin lump has the center of gravity located in a cylinder formed by extending the outer shape of the columnar tip in the dropping direction, and the column-shaped axis is dropped. It is preferable to drop in substantially the same direction. If the center of the molten resin mass is outside of the cylinder that extends in the direction of dropping the outer shape of the columnar tip, the column-shaped molten resin mass tends to collapse, but the center of gravity of the molten resin mass is inside the cylinder. It is possible to make it difficult for the molten resin lump to fall down.
[0018]
In this compression molding method and apparatus, the center of gravity of the molten resin mass has an elevation angle of 82 degrees or less as viewed from the position where the peripheral edge of the columnar tip collides with the inclined portion of the tapered recess. Is preferred. Even if the molten resin mass is elongated substantially vertically, if the elevation angle of the center of gravity defined in this way is 82 degrees or less, it can be made difficult to fall down when dropped into the female mold.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a compression molding method and apparatus for resin moldings according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a conceptual view showing an embodiment of a resin molding compression molding apparatus according to the present invention. In the resin molded product compression molding apparatus shown in FIG. 1, the same components as those used in the conventional resin molded product compression molding apparatus shown in FIG. Is omitted.
[0020]
A compression molding apparatus 1 for a resin molded product shown in FIG. 1 is disposed below an extruder 2 and an extruder 2 that supply molten resin by cutting it out from a die lip 3 that is a supply port as a substantially column-shaped molten resin lump 11. A female mold 4 in which a cavity 5 into which the molten resin lump 11 is dropped is formed, and a male mold (not shown) that compresses the molten resin lump 11 in cooperation with the female mold 4. It has. The molten resin mass 11 is cut out by enclosing a gas barrier resin 12. The cavity 5 of the female mold 4 is a space defined by a tapered recess 6 having a bottom portion 7 and an inclined portion 8 extending continuously upward from the bottom portion 7. The center line 9 of the recess 6 coincides with the vertical axis in the dropping direction of the molten resin mass 11. The bottom portion 7 may be circular or square, and the inclined portion 8 may accordingly be a conical surface or a truncated pyramid surface.
[0021]
The tip portion 13 of the molten resin mass 11 having a substantially columnar shape is set to be larger than the bottom surface 7. That is, the projection position 8 a of the mouth rim 3 a of the die lip 3 onto the female mold 4 is on the inclined portion 8 of the tapered recess 6 of the female mold 4. In the molten resin mass 11 dropped into the cavity 5, first, the peripheral edge portion 13 a of the tip portion 13 collides with the inclined portion 8. Since the molten resin lump 11 has fluidity, the molten resin lump 11 is deformed so as to fill a space between the bottom portion 7 of the tapered recess 6 and the tip end portion 13 of the molten resin lump 11. The melted resin mass 11 dropped into the cavity 5 is supported by the inclined portion 8 in the tapered recess 6, that is, the inclined surface that rises outward, regardless of the direction of the collapse. It becomes difficult and is supported stably. Therefore, the molten resin mass 11 without almost inclined in the cavity 5, bias figure during introduction into the cavity 5 is substantially maintained.
[0022]
The molten resin mass 11 held in the cavity 5 is then compression molded into a preform by lowering the male mold. In the compression molding apparatus 1, since the center positions of the male mold and the female mold 4 are adjusted with each other, the gap formed around both molds is determined in advance, for example, to be uniform in the circumferential direction. Gap. As the male mold descends, the molten resin lump 11 is pushed away by the male mold substantially uniformly around the periphery, and the pushed molten resin lump 11 flows through the gap in a substantially uniform manner at any position in the circumferential direction. And rise. Therefore, the molten resin mass 11 stably supported in the cavity 5 flows evenly around the male mold when the male mold is compression-molded in cooperation with the female mold 4, and is made of resin. A pre-molded body for the container and a resin closure are formed.
[0023]
FIG. 2 is a conceptual diagram showing a female mold as another embodiment of the resin molding compression molding apparatus according to the present invention. In the resin molding product compression molding apparatus shown in FIG. 2, the same components as those used in the resin molding compression molding apparatus shown in FIG. To do. The cavity 25 of the female mold 24 used in the resin molding compression molding apparatus 20 shown in FIG. 2 is a space defined by a spherical tapered recess 26, and the center of the tapered recess 26. The line 29 coincides with the vertical axis in the dropping direction of the molten resin mass 11. The projection position 28 a of the mouth rim 3 a of the die lip 3 onto the female mold 24 is on the inclined portion 28 of the tapered recess 26 of the female mold 24. The molten resin mass 11 dropped into the cavity 25 is first supported by colliding with a slope portion 28 inclined in an upward curved shape at the peripheral edge portion 13a of the tip end portion 13 toward the outside in the tapered recess portion 26. Therefore, it is supported stably. Therefore, the molten resin mass 11, without hardly inclined at the cavity 25 inside, attitude upon introduction into the cavity 25 is substantially maintained. The compression molding to the preform by the lowering of the male mold is substantially the same as the case of the compression molding apparatus 1 shown in FIG.
[0024]
Specific numerical examples of the compression molding method and apparatus for resin moldings according to the present invention will be described below. The molten resin mass 11 has a length (or a long diameter when the molten resin mass 11 has a droplet shape) and a diameter (a short diameter when the molten resin mass 11 has a droplet shape). It is assumed that there is a relationship of the following formula (1) with Z.
0.5 ≦ Y / Z ≦ 6 Formula (1)
Further, regarding the female mold 4 shown in FIG. 1, it is assumed that there is a relationship of the following equation (2) between the mouth portion diameter D and the bottom portion diameter Db. Further, the height of the cavity 5 of the female mold 4 is defined as (L).
Db <0.5D Formula (2)
When the height position where the inner diameter of the cavity 5 is Z is Lz, it is preferable to satisfy the relationships of the following formulas (3) to (5).
0.25D ≦ Z <D Formula (3)
Y ≦ 1.5L (4)
Lz ≦ 0.5L (5)
[0025]
FIG. 3 shows examples of numerical values (ratio) that can be applied in the compression molding method and apparatus for resin moldings according to the present invention. As shown in the upper part of FIG. 3, the melted resin mass 11 is from a flat shape whose length Y is about half of the diameter Z to an elongated shape whose length Y is 6 times the diameter Z from the formula (1). It can be seen that can be the target. When the value of Y / Z is 1/4, even if the molten resin lump 11 falls down, there is no practical problem. The center of gravity G of the molten resin mass 11 has an elevation angle θ of 82 degrees or less as viewed from the position 8a (see FIG. 1) where the peripheral edge of the columnar shape collides with the inclined portion of the tapered recess. As long as the elevation angle θ is 82 degrees or less, even when dropped into the female container, it can be stably held in the female container without tilting. The lower part of FIG. 3 shows the ratio of the height L of the cavity 5 to the mouth diameter D of the female mold 4. From equation (2), the tapered recess 6 of the female mold 4 is intended for a shape that is narrowed to a diameter smaller than half. Further, from the expression (3), the diameter Z of the molten resin mass 11 is assumed to be a quarter or more in relation to the mouth diameter D of the female mold 4. Further, from the formula (4), the height Y of the molten resin mass 11 is assumed to be 1.5 times or less the height L of the cavity 5 of the female mold 4. Furthermore, from the equation (5), the point where the peripheral edge portion 13 a of the top portion 13 of the molten resin mass 11 collides with the inclined portion 8 is set to be half or less of the height L of the cavity 5 from the bottom portion 7.
[0026]
In the above embodiment, the case where a multilayer preform having an intermediate layer such as a gas barrier layer is formed in the synthetic resin layer has been described as an example. However, as the preform, a single type of synthetic resin is used as the preform. It may be a layer preform. Further, it goes without saying that the compression molding of the resin molding according to the present invention can also be applied to the compression molding of a multilayer cap as a closure and a multilayer compression molding. Although the resin lump cut out from the molten resin has a substantially columnar shape, it can be expressed as a drop shape or a spheroid shape depending on temperature and viscosity. Further, in the above embodiment, an example in which the resin mold is dropped directly from the extruder into the female mold has been described, but the compression molding technique of the resin molding according to the present invention is an extruder as described in the prior art. The present invention can also be applied to the case where the synthetic resin cut out from is gripped and conveyed by the conveyance unit, and the conveyed synthetic resin mass is dropped into the female mold.
[0027]
【The invention's effect】
As described above, the compression molding method and apparatus for a resin molded product according to the present invention includes, as a method, dropping a molten resin lump into the cavity from the peripheral edge of the columnar tip when the molten resin lump is dropped into the cavity. It collides with the inclined portion of the tapered recess that forms part of the cavity, and the molten resin lump is stably supported by the tapered recess, and the molten resin lump is dropped as a device. When viewed in the direction, the projection position of the peripheral edge of the supply port onto the female mold is positioned on the inclined portion of the tapered recess formed on the female mold and constituting a part of the cavity. Because of this configuration, even when the cavity is formed in a female mold with a wide opening and a tapered shape, the molten resin lump that is cut out is an inclined portion that becomes an upward slope regardless of which direction it falls. Tilt is suppressed and can be stably supported in the tapered recess of the female mold. Therefore, according to the compression molding method and apparatus for resin moldings according to the present invention, even if the cavity formed in the female mold has a wide mouth, the molten resin lump is prevented from tilting in the cavity. When a male mold compresses a molten resin mass in cooperation with a female mold, the flow of the molten resin is made uniform around the male mold to prevent molding defects such as preforms. This can be prevented in advance.
[Brief description of the drawings]
FIG. 1 is a conceptual view showing an embodiment of a resin molding compression molding apparatus according to the present invention.
FIG. 2 is a conceptual view showing a female mold as another embodiment of the resin molding compression molding apparatus according to the present invention.
FIG. 3 is a diagram showing examples of numerical values (ratio) that can be applied in the compression molding method and apparatus for resin moldings according to the present invention.
FIG. 4 is a conceptual diagram showing an example of a conventional apparatus in which the outer diameter of a molten resin lump and the inner diameter of a mold cavity are substantially equal.
FIG. 5 is a schematic view showing an example of a male mold and a preform formed around the male mold.
FIG. 6 is a conceptual diagram showing an example of a conventional compression molding apparatus that molds a wide-mouth preform.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,20 Compression molding apparatus 2 Extruder 3 Die lip 3a Periphery | periphery edge 4,24 Female die 5,25 Cavity 6,26 Tapered recessed part 7 Bottom face 8,28 Inclined part 8a, 28a Projection position 11 Molten resin lump 12 Gas barrier resin 13 Tip portion 13a Peripheral portion 17 of tip portion 13 Cutter 18 Holding member 46 Male mold 47 Core portion 48 Neck mold 49 Preform 50 Mouth

Claims (8)

In a method of dropping a molten resin lump having a substantially column shape into a cavity formed in a female mold, and compressing the molten resin lump by cooperation of the female mold and the male mold, When the molten resin mass is dropped into the cavity, a tapered concave portion is formed in the female mold from the peripheral edge of the columnar tip and forms a part of the cavity. A method of compression molding a resin molded product, wherein the molten resin lump is made to collide with an inclined portion of the resin and the molten resin mass is stably supported by the tapered recess. The compression molding method according to claim 1, wherein the tapered recess is a truncated cone-shaped recess or a spherical recess formed in the center of the cavity. The molten resin mass is dropped with the column-shaped axis line substantially aligned with the dropping direction in a posture in which the center of gravity exists in a cylinder extending in the dropping direction with the outer shape of the columnar tip. The compression molding method according to claim 1, comprising: The said gravity center of the said molten resin lump consists of the elevation angle seen from the position where the peripheral edge of the said columnar shape collides with the said inclined part of the said tapered recess is 82 degrees or less. Compression molding method. Supply unit having a supply port for supplying a substantially columnar molten resin lump, a female mold in which a cavity into which the molten resin lump is dropped is formed, and the molten resin in cooperation with the female mold A male mold for compressing the lump, and a projection position of the peripheral edge of the supply port onto the female mold as viewed in the dropping direction of the molten resin lump is formed on the female mold; A compression molding apparatus for a resin molded product, which is located at an inclined portion of a tapered concave portion constituting a part of a cavity. The said supply part is equipped with the holding mechanism which hold | maintains the said molten resin lump, It has a conveyance part which conveys the said molten resin lump to the said supply port located just above the said female metal mold | die. Compression molding equipment. The molten resin mass is dropped with the column-shaped axis line substantially aligned with the dropping direction in a posture in which the center of gravity exists in a cylinder extending in the dropping direction with the outer shape of the columnar tip. The compression molding apparatus according to claim 5, comprising: 8. The center of gravity of the molten resin mass has an elevation angle of 82 degrees or less as viewed from a position where a peripheral edge of the columnar tip collides with the inclined portion of the tapered recess. Compression molding device.

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