JP2006297676A - Method and apparatus for manufacturing thermoplastic elastomer molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of molding the thermoplastic elastomer molded product of high dimensional precision and excellent in productivity, and a manufacturing apparatus therefor. <P>SOLUTION: The manufacturing method of the thermoplastic elastomer molded product comprises an injection molding process for injecting a thermoplastic elastomer in the fluid state in the cavity formed by a core 22 and a first outer mold 30 and subsequently cooling the same in the cavity to mold a parison, a heating process for separating the first outer mold 30 and heating the parison 11 up to a temperature capable of blowing up the parison 11 in the state attached to the core 22, and a blow molding process for putting the parison 11 in a second outer mold 50 in the state attached to the core 22, blowing compressed air in the parison 11 to expand the parison 11 not only to closely bring the parison 11 into contact with the inner wall surface of the second outer mold 50 but also to cool the same to mold the thermoplastic elastomer molded product 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a thermoplastic elastomer molded product that manufactures a molded product by performing blow molding after molding a parison and an apparatus for manufacturing the same.

  Conventionally, blow molding such as press blow, direct blow, and injection blow has been mainly used as a method for producing a hollow molded article (for example, a constant velocity joint boot) made of a thermoplastic elastomer.

  In the case of press blow or direct blow, it is necessary to mold the parison by extruding the elastomer in a fluid state. Therefore, when forming a parison that is an intermediate molded product of a thick product or a product having a bellows shape (for example, a constant velocity joint boot), drawdown and parison swell are likely to occur, and the dimensional accuracy is lowered. End up. Therefore, injection blow molding is more suitable for increasing the dimensional accuracy of these products.

  Injection blow molding is a method in which a parison is formed by injection molding and the shape of the parison is stabilized and then blow molding is performed. Representative examples of injection blow molding (hot parison method and cold parison method) will be described with reference to the drawings.

  First, the hot parison method will be described with reference to FIGS. FIG. 7 is a manufacturing process diagram by the hot parison method. FIG. 8 is a schematic cross-sectional view showing a state immediately after parison molding when the hot parison method is used. FIG. 9 is an external view of a molded product molded using the hot parison method. 9A is an overall external view, and FIG. 9B is an enlarged view of a portion surrounded by a dotted line in FIG.

  The hot parison method is a manufacturing method in which blow-up is performed using the retained heat at the time of injection molding. The manufacturing apparatus used for the hot parison method includes a rotating body 100 having cores 101 at both ends, as shown in FIG. First, the first outer mold 200 for injection molding is closed with respect to the core 101, and the thermoplastic elastomer 501 in a fluid state is injected into the cavity formed by the core 101 and the first outer mold 200 by the injection mechanism 400. (FIG. 7A). When the temperature of the thermoplastic elastomer in the cavity is lowered, the shape is stabilized to some extent, and the parison 502 is formed (FIG. 7B). Thereafter, while the parison 502 has a certain amount of heat, the first outer mold 200 is released and the rotating body 100 is rotated 180 degrees (FIG. 7C). Then, with the parison 502 still attached to the core 101, the second outer mold 300 for blow molding is closed, blow-up is performed, and a molded product 503 is molded (FIG. 7D). Thereafter, the second outer mold 300 is released, and the molded product 503 is released from the core 101 (FIG. 7E).

  When such a hot parison method is used, if the first outer mold 200 is released before the temperature of the thermoplastic elastomer in the cavity is sufficiently lowered, the shape of the parison 502 is not stable, and the first outer mold The parison 502 is deformed such as sticking to 200 (see FIG. 8). On the other hand, if blow-up is performed after the temperature of the parison 502 has decreased too much, the parison 502 does not expand sufficiently and a desired shape cannot be obtained. That is, as shown in FIG. 9B, the shape shown by the dotted line is the desired shape, but the shape shown by the solid line.

Thus, in the case of the hot parison method, the timing of performing each manufacturing process (particularly, the process of releasing the first outer mold 200 and the process of blow-up) is the same as that of the material after injection (thermoplastic elastomer). Must be suitable for temperature. However, the temperature of the material after injection is greatly influenced by various influences such as ambient environmental temperature and various settings in the manufacturing apparatus. Therefore, it is difficult to set various conditions of the manufacturing apparatus and to manage the time of the manufacturing process, and it is difficult to stably obtain a molded product having a desired size and shape.

  Next, the cold parison method will be described with reference to FIGS. FIG. 10 is a manufacturing process diagram by the cold parison method. FIG. 11 is an explanatory diagram of a parison when the cold parison method is used. FIG. 11A is a schematic cross-sectional view showing a state where the parison is released, and FIG. 11B is an external view of the parison (defective product).

  The cold parison method is a process in which the parison is reheated before blow-up. First, a thermoplastic elastomer in a fluidized state is injected into the cavity formed by the first outer mold 250 and the core 150 for injection molding, and the parison 550 is molded by cooling the thermoplastic elastomer. (FIG. 10A). After the material is sufficiently cooled and the shape of the parison 550 is stabilized, the parison 550 is released from the core 150 and the first outer mold 250 (FIG. 10B). Then, heating members 601 and 602 are disposed on the outer side and the inner side of the parison 550, respectively, and the parison 550 is heated to a temperature at which blowup can be performed by radiant heat generated by the heating members 601 and 602 (FIG. 10C). Next, the heating members 601 and 602 are removed, and the parison 550 is placed in the second outer mold 350 for blow molding (FIG. 10D), and blow-up is performed (FIG. 10E). Thereafter, the molded product 551 is released from the second outer mold 350 (FIG. 10F).

  In the case of this cold parison method, after cooling until the shape of the parison 550 is sufficiently stabilized, blow molding is performed by reheating, so that the shape of the molded product can be stabilized. However, the parison 550 must be cooled sufficiently until the shape of the parison 550 is stabilized, the parison 550 is released from the core 150, and then the parison 550 must be reheated to a temperature at which blowup can be performed again. Therefore, if the product is thin (for example, a PET bottle), it is effective because the cooling time and reheating time are short. However, if the product is thick, the cooling time and reheating time are long. Therefore, there are problems that cycle time is long and productivity is poor.

  Note that if the parison 550 is released before the temperature of the parison 550 is sufficiently lowered, the parison 550 is deformed. That is, when releasing the parison 550, as shown in FIG. 11A, the core 150 and the first outer mold 250 are removed from the parison 550 in the directions of the arrows in the drawing. If the temperature of the parison 550 is not sufficiently lowered, the parison 550 adheres to the core 150 and the first outer mold 250, and deformation is caused as indicated by a dotted line shown in FIG. It will occur. For example, when a parison for a constant velocity joint boot is molded, it is necessary to set the parison surface temperature at the time of mold release to 120 ° C. or less in order to prevent deformation.

  In injection blow molding, if the temperature of the parison at the time of blow-up is low, or if the thermoplastic elastomer that is the material is rapidly heated or cooled rapidly, a large residual stress remains in the molded product. Therefore, in particular, in the case of a product having a bellows shape, there is a problem, so that residual stress must be removed. For example, Patent Document 1 discloses a technique for removing residual stress by performing annealing after molding, but there is a problem that the number of manufacturing steps increases.

Moreover, there exists a technique disclosed by patent documents 2-6 as a related technique.
JP-A-4-173226 Japanese Patent No. 2845072 Japanese Patent No. 3037988 JP-A-6-206249 JP-A-9-187859 JP-A-5-138725

  An object of the present invention is to provide a method for manufacturing a thermoplastic elastomer molded product that can form a molded product with high dimensional accuracy and is excellent in productivity, and a manufacturing apparatus therefor.

  The present invention employs the following means in order to solve the above problems.

That is, the method for producing the thermoplastic elastomer molded article of the present invention includes:
An injection molding step of injecting a thermoplastic elastomer in a fluid state into a cavity formed by the core and the first outer mold, and then cooling the thermoplastic elastomer in the cavity to mold a parison;
A heating step of releasing the first outer mold and heating the parison to a temperature at which blow-up can be performed while the parison is attached to the core;
The parison is placed in the second outer mold while being attached to the core, and compressed air is blown into the inside of the parison to inflate it, closely contact the inner wall surface of the second outer mold, and cool the molded product. And a blow molding step of molding.

  According to the present invention, since there is a step of reheating in the middle, the first outer mold can be released after the shape of the parison is stabilized. Thereby, the deformation | transformation of a parison can be suppressed. In addition, it is only necessary to reheat the parison in the heating process with the parison attached to the core, so even if the inner temperature of the parison is high to some extent, the parison will be deformed if the outer surface temperature is sufficiently lowered. The first outer mold can be released without any problem. Therefore, compared with the case where both the core and the first outer mold are released, the inner temperature of the parison when releasing the first outer mold may be kept relatively high, and the heating process may be performed again. The time required for heating can be shortened. Moreover, since it is reheated on the way, the rapid temperature change of a parison can be suppressed and a residual stress can be reduced.

Moreover, the manufacturing apparatus of the thermoplastic elastomer molded article of the present invention is:
The core that forms the inner shape of the parison,
A first outer mold that forms the outer shape of the parison;
An injection mechanism for injecting a thermoplastic elastomer in a fluid state into a cavity formed by the core and the first outer mold;
A heating mechanism for heating the parison as it is attached to the core after injection molding;
A second outer mold for shaping the outer shape of the molded product;
A blow-up mechanism that blows compressed air into the inside of the parison that is still attached to the core after heating, and closes it to the inner wall surface of the second outer mold;
And a rotation mechanism for rotating the core to an injection molding position by an injection mechanism and a first outer mold, a heating position by a heating mechanism, and a blow-up mechanism and a blow molding position by a second outer mold. And

  The above manufacturing method can be realized by such a manufacturing apparatus.

  As described above, according to the present invention, a molded product with high dimensional accuracy can be formed, and productivity can be increased.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

  With reference to FIGS. 1-6, the manufacturing method and its manufacturing apparatus of the thermoplastic elastomer molded article which concern on the Example of this invention are demonstrated. In the present embodiment, a case of a constant velocity joint boot will be described as an example of a molded product. FIG. 1 is a schematic view of a manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is an external view of a molded product manufactured by the manufacturing method according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a blow molding portion of the manufacturing apparatus according to the embodiment of the present invention. FIG. 4 is an operation explanatory view of the core in the manufacturing apparatus according to the embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of the heating mechanism according to the embodiment of the present invention. FIG. 6 is an external view of the molded product. 6A is an external view of a molded product manufactured by using the manufacturing method according to the present embodiment, and FIG. 6B is an external view of a molded product manufactured without reheating.

<Manufacturing equipment>
In particular, a manufacturing apparatus according to an embodiment of the present invention will be described with reference to FIG. The manufacturing apparatus 1 according to the embodiment of the present invention includes three cores 22 that form the inner shape of the parison 11. In addition, the manufacturing apparatus 1 includes a rotation mechanism 21 that rotates the three cores 22. The core 22 is provided at three positions at an equal angle (120 °) with respect to the rotation center. In addition, the manufacturing apparatus 1 injects a thermoplastic elastomer in a fluid state into a cavity formed by the first outer mold 30 for injection molding that forms the outer shape of the parison 11 and the core 22 and the first outer mold 30. An injection mechanism 31, a heating mechanism 40 for heating the parison 11, and a blow molding second outer mold 50 that forms the outer shape of the molded product 12 are provided.

  The rotation mechanism 21 rotates the core 22 to an injection molding position by the injection mechanism 31 and the first outer mold 30, a heating position by the heating mechanism 40, and a blow molding position by a blow-up mechanism and the second outer mold 50 described later. It is configured so that it can be moved. The first outer mold 30, the heating mechanism 40, and the second outer mold 50 are configured to be movable to a position that does not hinder the rotation when the core 22 is rotated by the rotation mechanism 21. In this embodiment, in order to reduce the installation space, the rotating mechanism 21 rotates the core 22 in the vertical direction (height direction).

  As the driving mechanism for moving the first outer mold 30, the heating mechanism 40, and the second outer mold 50, a known technique may be adopted as appropriate, and the description thereof is omitted. In addition, the rotation mechanism 21 and the injection mechanism 31 itself may appropriately employ known techniques, and the description thereof is omitted. Furthermore, as for the mold clamping and mold opening mechanisms of the first outer mold 30 and the second outer mold 50, known techniques may be adopted as appropriate, and the description thereof is omitted.

<Manufacturing method>
A manufacturing method according to an embodiment of the present invention will be described in the order of manufacturing steps. The manufacturing process according to the present embodiment includes an injection molding process, a heating process, and a blow molding process, and a molded product is manufactured in this order.

<< Injection molding process >>
The injection mechanism 31 injects the thermoplastic elastomer in a fluid state into a cavity formed by the core 22 and the first outer mold 30 that are clamped. When the temperature of the thermoplastic elastomer in the cavity is lowered, the fluidity is lost and the thermoplastic elastomer is cured, and the parison 11 is formed.
Then, after the temperature of the outer surface of the parison 11 is lowered to such an extent that it is not deformed by mold release, the first outer mold 30 is released (opened).

  Here, in the present embodiment, since the parison 11 is moved to the next process while being attached to the core 22, the temperature of the inner surface of the parison 11 may remain high to some extent. In other words, if the parison 11 is released from the core 22, the temperature at which the parison 11 is deformed may be used. Rather, in order to shorten the time required for heating in the next heating step, it is desirable that the temperature of the inner surface of the parison 11 is somewhat high. Therefore, it is desirable to maintain the temperature of the inner surface of the parison 11 at a certain level by a heating means (not shown) provided on the core 22 side. For example, when the temperature of the outer surface of the parison 11 is set to 155 ° C. or less as the measured value of the parison 11 and the temperature of the inner surface of the parison 11 is set to 170 ° C. or less as the measured value of the surface of the core 22, The mold 30 can be released.

  Then, after releasing the first outer mold 30, the core 22 is rotated by 120 ° by the rotation mechanism 21, and the next heating process is performed. At this time, the first outer mold 30, the heating mechanism 40, and the second outer mold 50 are retracted to a position that does not hinder the rotation of the core 22.

<< Heating process >>
After the core 22 is rotated to a predetermined position, the heating mechanism 40 is placed so as to cover the entire parison 11. Then, the parison 11 is heated to a temperature at which the parison 11 can be blown up by the heating mechanism 40 while the parison 11 is attached to the core 22.

  Here, although a well-known technique can be suitably employed for the heating mechanism 40, a suitable example will be described with reference to FIG. The illustrated heating mechanism 40 includes a plurality of annular heating bodies 41, fixing members 42 and 43 for fixing the plurality of heating bodies 41 at both ends, an annular band heater 44 wound around the outer periphery of each heating body 41, A plurality of heat insulating members 45 provided between the heating bodies 41 and the like for suppressing escape of heat are provided. The heating body 41 is made of a material having heat conductivity (for example, metal). Further, the inner circumference of the heating mechanism 40 is tapered so as to follow the shape of the parison 11, and an infrared surface treatment 46 is applied to the inner circumference of each heating body 41. With the above configuration, by operating the band heater 44, heat is transmitted through the heating body 41, infrared rays are generated toward the inner peripheral side of the heating mechanism 40, and the parison 11 is heated by radiant heat. The heating temperature is appropriately set according to the radiation rate of the heating body 41, the distance between the heating body 41 and the parison 11, the heating time, and the like. For example, in order to complete the heating for 5 to 20 seconds with a radiation rate of 0.9 to 0.95, a distance of 1 to 2 mm between the heating body 41 and the parison 11, the heating temperature is in the range of 150 ° C to 400 ° C. It is good to set. The heating time varies depending on the temperature to be heated and other conditions, but is set in a range of 3 to 60 seconds when the heating mechanism 40 configured as shown in FIG. 5 is used.

  And after heating the parison 11 to the temperature which can be blown up, the heating mechanism 40 etc. are evacuated to the position which does not prevent rotation of the core 22. Thereafter, the core 22 is rotated by 120 ° by the rotation mechanism 21 to shift to the next blow molding process.

<< Blow molding process >>
After the core 22 is rotated to a predetermined position, the second outer mold 50 is clamped. Thereafter, compressed air is blown into the interior of the parison 11 that remains attached to the core 22 to be inflated and brought into close contact with the inner wall surface of the second outer mold 50. After the swelled parison 11 is in close contact with the inner wall surface of the second outer mold 50, the temperature is lowered, the shape is stabilized, and the molded product 12 is obtained.

Here, the blow-up mechanism for performing the above blow-up will be described with reference to FIGS. 3 and 4 in particular. In the present embodiment, the core 22 is a first having a through hole in the center.
A core 23 and a second core 24 including a shaft portion that is inserted into the through hole of the first core 23 and a substantially truncated cone portion that forms most of the inner shape of the parison 11 are provided. The second core 24 is configured to reciprocate in the axial direction with respect to the first core 23. A passage 25 through which compressed air passes is provided inside the first core 23 and between the inner peripheral portion of the through hole of the first core 23 and the outer peripheral portion of the shaft portion of the second core 24. .

  With the above configuration, when compressed air is not sent, for example, at the time of injection molding, as shown in FIG. 4 (A), the tip surface 23a of the first core 23 and the substantially truncated cone portion of the second core 24 The bottom surface 24a is closely attached. In addition, as a means to contact | adhere in this way, the 2nd core 24 is urged | biased by the 1st core 23 side by urging means, such as a spring, the self-weight of the 2nd core 24 is utilized, An appropriate method may be adopted. In this way, by keeping the tip surface 23a and the bottom surface 24a in close contact with each other, it is possible to prevent the thermoplastic elastomer in a fluid state from entering between the tip surface 23a and the bottom surface 24a during injection molding.

  Then, when compressed air is sent from the passage 25 during blow molding, the pressure causes the second core 24 to move in a direction in which the bottom surface 24a of the substantially truncated cone part is separated from the front end surface 23a of the first core 23. . Thereby, the front end surface 23a of the first core 23 and the bottom surface 24a of the substantially truncated cone portion of the second core 24 are separated from each other, and a gap 26 is formed (FIG. 4B). Therefore, the compressed air flows from the gap 26 to the outside of the core 22.

  The compressed air is blown into the inside of the parison 11 as described above.

<Excellent points of this embodiment>
According to the method and apparatus for manufacturing a thermoplastic elastomer molded article according to the present embodiment, there is a heating step for reheating the parison 11 between the injection molding step and the blow molding step, so the shape of the parison 11 Is sufficiently stable, the first outer mold 30 can be released. Thereby, the deformation | transformation of the parison 11 can be suppressed. In addition, in order to prevent the deformation of the parison, when using the retained heat as in the hot parison method, the first outer mold is released at the severe timing that the temperature of the parison is not too high and not too low. In the case of the present embodiment, there are no such severe restrictions.

  Further, since the parison 11 may be reheated in the heating process while the parison 11 is attached to the core 22, even if the temperature inside the parison 11 is high to some extent, if the outer surface temperature is sufficiently lowered, the parison 11 The first outer mold 30 can be released without being deformed. Therefore, compared to the case where both the core and the first outer mold are released as in the cold parison method, in this embodiment, the inner side of the parison 11 when the first outer mold 30 is released. Since the reheating can be performed in the heating process while the temperature of the is relatively high, the time required for the reheating can be shortened.

  Further, unlike the cold parison method, it is not necessary to release the parison from the core in the middle, so that the manufacturing process can be simplified as compared with the cold parison method.

  Further, in this embodiment, blow molding is performed after the temperature of the parison 11 is increased by reheating, so that blow-up can be sufficiently performed and the dimensional accuracy of the blow molded product can be increased.

  Moreover, since it is reheated on the way, the rapid temperature change of the parison 11 can be suppressed, and a residual stress can be reduced. This eliminates the need for a process for removing residual stress.

As described above, according to the present embodiment, the deformation of the parison 11 molded by injection molding and the molded product 12 molded by subsequent blow molding can be suppressed, and the molded product 12 with high dimensional accuracy can be obtained. Can be molded. In addition, the number of manufacturing steps is small, and the time required for each step is short, so that productivity can be improved. Furthermore, strict management of the manufacturing process is not necessary. FIG. 6A shows an external view of a molded product manufactured by the manufacturing method according to the present example, and FIG. 6B shows a heating process in the manufacturing process of the present example. The external view of the molded product when the process is omitted is shown. From these figures, it can be seen that in the case of the present embodiment, a molded product without deformation is molded, but when reheating is not performed in the middle, the molded product is deformed.

<Others>
In the above embodiment, the case where the core is rotated vertically (in the height direction) by the rotation mechanism has been described. However, the core may be rotated horizontally (in the horizontal direction) using a rotary table or the like. Moreover, in the said Example, although the case of the constant velocity joint boot was demonstrated as an example as a molded article, the molded article is not restricted to this, If it is a hollow thing (for example, dust cover), it is applicable.

FIG. 1 is a schematic view of a manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is an external view of a molded product manufactured by the manufacturing method according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a blow molding portion of the manufacturing apparatus according to the embodiment of the present invention. FIG. 4 is an operation explanatory view of the core in the manufacturing apparatus according to the embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of the heating mechanism according to the embodiment of the present invention. FIG. 6 is an external view of the molded product. FIG. 7 is a manufacturing process diagram by the hot parison method. FIG. 8 is a schematic cross-sectional view showing a state immediately after parison molding when the hot parison method is used. FIG. 9 is an external view of a molded product molded using the hot parison method. FIG. 10 is a manufacturing process diagram by the cold parison method. FIG. 11 is an explanatory diagram of a parison when the cold parison method is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 11 Parison 12 Molded article 21 Rotating mechanism 22 Core 23 1st core 23a Front end surface 24 2nd core 24a Bottom face 25 Path | passage 26 Gap | interval 30 First outer mold 31 Injection mechanism 40 Heating mechanism 41 Heating bodies 42, 43 Fixed member 44 Band heater 45 Thermal insulation member 46 Infrared surface treatment 50 Second outer mold

Claims (2)

An injection molding step of injecting a thermoplastic elastomer in a fluid state into a cavity formed by the core and the first outer mold, and then cooling the thermoplastic elastomer in the cavity to mold a parison;
A heating step of releasing the first outer mold and heating the parison to a temperature at which blow-up can be performed while the parison is attached to the core;
The parison is placed in the second outer mold while being attached to the core, and compressed air is blown into the inside of the parison to inflate it, closely contact the inner wall surface of the second outer mold, and cool the molded product. A method for producing a thermoplastic elastomer molded article, comprising: a blow molding step for molding. The core that forms the inner shape of the parison,
A first outer mold that forms the outer shape of the parison;
An injection mechanism for injecting a thermoplastic elastomer in a fluid state into a cavity formed by the core and the first outer mold;
A heating mechanism for heating the parison as it is attached to the core after injection molding;
A second outer mold for shaping the outer shape of the molded product;
A blow-up mechanism that blows compressed air into the inside of the parison that is still attached to the core after heating, and closes it to the inner wall surface of the second outer mold;
And a rotation mechanism for rotating the core to an injection molding position by an injection mechanism and a first outer mold, a heating position by a heating mechanism, and a blow-up mechanism and a blow molding position by a second outer mold. Production equipment for thermoplastic elastomer molded products.

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