JP2016083859A - Blow molding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blow molding method and apparatus in which a good deburring can be implemented while achieving a reduction in the cooling time.SOLUTION: Provided is a blow molding method and apparatus in which a foam blow molding is carried out within a mold, and in which the cooling efficiency is improved by positively bringing the burrs into contact with the mold, thereby improving the cooling efficiency of the burrs. The method for positively bringing the burrs into contact with the mold includes a method for bringing burrs into contact with mold by vacuum suction. Alternatively, the burrs may be brought into contact with the mold by a vacuum suction and an air blow.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a blow molding method and a blow molding method for molding a foam duct and the like, and more particularly to an improvement for improving productivity.

  For example, various air-conditioning ducts that are mounted in an instrument panel of an automobile are known as foam blow molded products. For these air conditioning ducts, foam ducts formed by molding a foamed resin material are widely used. The foam duct is lightweight and can be easily manufactured by, for example, adding a foaming agent to a resin material such as polyolefin resin, melt-kneading, and blow-molding a foam parison extruded from a die of an extruder.

  In the duct for ventilating the air from the air conditioner, it is possible to realize a lightweight duct having excellent heat insulation by using a tubular foamed molded body. Further, such a duct is more effective because it can further improve heat insulation and light weight by increasing the foaming ratio at the time of manufacture and increasing the number of bubbles inside the foam.

  As a method for producing such a foam-molded product, a method of molding a molten resin by clamping with a split mold is widely known. In recent years, with the improvement of molding technology, mass production with an increased foaming ratio of a foam molded product is becoming possible.

  Further, as a technology previously filed by the present applicant, foam molding having a tubular portion and a plate-like portion is performed by clamping a resin sheet made of foamed resin and a resin sheet made of unfoamed resin with a split mold. Some manufacture products (see, for example, Patent Document 1).

JP 2011-131777 A

  By the way, in the foam molded product (foam duct) subjected to the above-described foam blow molding, burrs are formed around the clamped mold, and removing this is an essential process. In general, deburring after blow molding is often performed using a press machine, and burrs around the mold are collectively removed by punching out the burrs with the press machine.

  At this time, it is necessary that the burrs are sufficiently cooled. If the burrs are not sufficiently cooled, the burrs are deteriorated and the burrs cannot be removed cleanly. For example, when polypropylene is blown by blow molding, the upper limit of the burr temperature at which burr can be punched with a press machine is about 100 ° C. If punching is performed at a temperature higher than this, it is difficult to remove the burr.

  Therefore, in the above-described foam blow molding, after the burrs are sufficiently cooled, the burrs are punched out by a press machine, which causes a large time loss and is a factor that impairs productivity.

  After deburring, large burrs are processed by a series of processes in which they are roughly crushed and crushed by a pulverizer, etc., mixed with a predetermined amount of virgin material, and charged again from the hopper to the extruder. If the large burrs remain in a high temperature state, it may cause clogging in the pulverizer or the conveying path. Therefore, large burrs are supplied after being cooled with a blower or the like, but the required cooling time varies depending on the expansion ratio, set wall thickness, etc., and it is difficult to determine the cooling time. Further, cooling here also leads to a decrease in productivity.

  The present invention has been proposed in view of such a conventional situation, and provides a blow molding method and a blow molding apparatus capable of performing good deburring while shortening the cooling time. It is an object to provide a blow molding method and a blow molding apparatus capable of producing a high-quality molded product with high productivity.

  In order to achieve the above-mentioned object, the blow molding method of the present invention is a blow molding method in which foam blow molding is performed in a mold, wherein the burr is cooled by being brought into contact with the mold. Moreover, the part b row molding apparatus of the present invention is a blow molding apparatus that performs foam blow molding in a mold, and is characterized by cooling by bringing a burr into contact with the mold.

  If the burr is brought into contact with the mold and cooled, the burr cooling time is greatly shortened. Therefore, the time required for a series of steps from blow molding to deburring is short, and productivity is improved. Further, there is no need to cool the burr after deburring, and it can be immediately pulverized and reused.

  According to the blow molding method and the blow molding apparatus of the present invention, the burr cooling time can be significantly shortened, and a high-quality foam molded product can be manufactured with high productivity. In addition, according to the present invention, even when a large-sized burr is reused, the burr cooling time can be shortened and the extrusion can be stabilized.

It is a schematic plan view which shows an example of a foam duct. It is a bottom view of the foam duct shown in FIG. It is a schematic sectional drawing which shows typically the aspect at the time of blow-molding a foam duct. It is a schematic plan view which shows the foaming duct before removing a burr | flash. It is a schematic sectional drawing which shows a burr | flash punching process. It is a schematic sectional drawing which shows an example of the metal mold | die which provided the burr escape space. It is a schematic sectional drawing which shows an example of a metal mold | die with a shallow burr escape space. It is a schematic sectional drawing which shows an example of the metal mold | die provided with the vacuum suction mechanism for making a burr | flash contact a metal mold | die. It is a schematic sectional drawing which shows an example of the metal mold | die provided with the vacuum suction mechanism and air blowing mechanism for making a burr | flash contact a metal mold | die.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a blow molding method and a blow molding apparatus to which the present invention is applied will be described in detail with reference to the drawings, taking as an example the production of a foam duct.

  FIG.1 and FIG.2 shows the example of the shape of the foaming duct 1 blow-molded. In the foamed duct 1 of this example, a supply port 3 for connection to an air conditioner unit (not shown) is opened at the center on the bottom side of the pipe part 2, and a plurality of duct parts (here 4 The open ends of the duct portions 4, 5, 6 and 7 are provided with fitting portions 4 a, 5 a, 6 a and 7 a, respectively. Each of the duct parts 4, 5, 6, and 7 is formed in a cylindrical shape so as to have a flow path for circulating a fluid, so that cool and warm air introduced from the air conditioner unit can be circulated through the supply port 3. Yes. Therefore, in the foamed duct 1 of this embodiment, the said pipe part 2 and the duct parts 4, 5, 6, and 7 correspond to a pipe main body, and an internal space becomes a mainstream part of a cool / warm air.

  In the foamed duct 1 of the present example, a plurality of locations of the duct portions 4, 5, 6, and 7, which are pipe bodies, are used for the purpose of structural reinforcement of the duct itself and reinforcement at the time of attachment to other parts. In addition, the flange portion 8 (plate-like portion) is provided so as to be connected to the outside of the pipe body (duct portions 4, 5, 6, 7). These flange portions 8 are formed as compression portions obtained by overlapping and crushing two foam parisons.

  In the case of the foamed duct 1 of this example, the flange portion 8 includes the branched portions of the duct portions 4 and 5, the branched portions of the duct portions 6 and 7, and the middle portions of the duct portions 4, 5, 6, and 7. In the vicinity of the tip, it is formed at a position necessary for reinforcement and mounting and fixing. Each flange portion 8 is provided with fixing holes (not shown) as required. By passing bolts or the like through these fixing holes and tightening with nuts, other tubular members or the vehicle body can be provided. It fixes to the provided support part etc.

  The foam duct 1 having the above-described form is formed by, for example, clamping a thermoplastic resin mixed with a foaming agent with a split mold and blow-molding the thermoplastic resin. Here, examples of the thermoplastic resin include a polypropylene resin, and a blend in which 1 to 20% by mass of a polyolefin polymer and 5 to 40% by mass of a hydrogenated styrene thermoplastic elastomer are mixed. Resins and the like can also be used.

  As said polypropylene resin, the polypropylene whose melt tension in 230 degreeC is in the range of 30-350 mN is preferable. In particular, the polypropylene resin is preferably a propylene homopolymer having a long-chain branched structure, and more preferably an ethylene-propylene block copolymer is added.

  The hydrogenated styrene thermoplastic elastomer blended with the polypropylene resin is preferably 5 to 40% by mass with respect to the polypropylene resin in order to improve impact resistance and maintain rigidity as a tubular foamed molded article. Is preferably added in the range of 15 to 30% by mass.

  Specifically, a hydrogenated polymer such as a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, or a styrene-butadiene random copolymer is used. The hydrogenated styrene thermoplastic elastomer has a styrene content of less than 30% by mass, preferably less than 20% by mass, MFR at 230 ° C. (test temperature 230 ° C. according to JIS K-7210, test load) (Measured at 2.16 kg) is 10 g / 10 min or less, preferably 5.0 g / 10 min or less and 1.0 g / 10 min or more.

The polyolefin polymer blended with the polypropylene resin is preferably a low-density ethylene-α-olefin, and is preferably blended in the range of 1 to 20% by mass. As the low density ethylene-α-olefin, one having a density of 0.91 g / cm ³ or less is preferably used, and ethylene-α- obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. Olefin copolymers are preferred and include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4-methyl-1-pentene. 4-methyl-1-hexene and the like, and 1-butene, 1-hexene, 1-octene and the like are particularly preferable. Further, the α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more. The content of the monomer unit based on ethylene in the ethylene-α-olefin copolymer is preferably in the range of 50 to 99 mass% with respect to the ethylene-α-olefin copolymer. Moreover, it is preferable that content of the monomer unit based on an alpha olefin is the range of 1-50 mass% with respect to an ethylene-alpha-olefin copolymer. In particular, it is preferable to use a linear ultra-low density polyethylene polymerized using a metallocene catalyst, an ethylene elastomer, or a propylene elastomer.

  Examples of the foaming agent include physical foaming agents, chemical foaming agents, and mixtures thereof. Physical foaming agents include inorganic physical foaming agents such as air, carbon dioxide, nitrogen gas, and water, organic physical foaming agents such as butane, pentane, hexane, dichloromethane, dichloroethane, and their supercritical fluids. Can be applied. As the supercritical fluid, carbon dioxide, nitrogen or the like is preferably used. If nitrogen, the critical temperature is 149.1 ° C. and the critical pressure is 3.4 MPa or more. If carbon dioxide, the critical temperature is 31 ° C., the critical pressure. It can be made by setting it to 7.4 MPa or more.

  The expansion ratio of the foam duct 1 formed by blow molding is, for example, 2.5 times or more, and is configured by a closed cell structure having a plurality of cell cells (closed cell ratio is 70% or more). The present invention is effective in forming a tubular foamed molded article having a high expansion ratio. From this viewpoint, the effect is high when the expansion ratio is 3 times or more. The average cell diameter of the cell in the thickness direction is, for example, less than 300 μm, and preferably less than 100 μm.

The foamed duct 1 formed by blow molding preferably has a tensile fracture elongation at −10 ° C. of 40% or more and a tensile elastic modulus at room temperature of 1000 kg / cm ² or more. Furthermore, it is preferable that the tensile fracture elongation at −10 ° C. is 100% or more. In addition, the definition of each term of the said expansion ratio, tensile fracture elongation, and a tensile elasticity modulus is as follows.

Foaming ratio: A value obtained by dividing the density of the thermoplastic resin by the apparent density in the tube body of the foamed duct obtained by blow molding.
-Tensile fracture elongation: The tube body of the foamed duct obtained by blow molding was cut out, stored at -10 ° C, and then measured as a No. 2 test piece according to JIS K-7113 at a tensile rate of 50 mm / min. Value.
-Tensile elastic modulus: A tube body of a foam duct obtained by blow molding was cut out and measured at room temperature (23 ° C) as a No. 2 type test piece according to JIS K-7113 at a tensile speed of 50 mm / min. Value.

  Next, the blow molding method for the foam duct 1 and the blow molding apparatus used therefor will be described. FIG. 3 is a view showing an embodiment when the foam duct 1 is blow-molded.

  In blow molding, first, a resin material used for molding is kneaded in an extruder to produce a base resin. In the case of molding using only the virgin resin, a modifier is added to the virgin resin of the above-described resin material as necessary and kneaded to prepare a base resin. When the recovered resin material is used, a predetermined ratio of virgin resin is added to the pulverized recovered resin material and kneaded to prepare a base resin.

  After the foaming agent is added to the base resin thus prepared and mixed in the extruder, it is stored in an in-die accumulator (not shown). Subsequently, after a predetermined amount of resin is stored, a ring-shaped piston (not shown) ) In a direction perpendicular to the horizontal direction (vertical direction). And it extrudes between the split molds 21 and 22 which comprise the mold clamping apparatus 20 as the cylindrical parison P from the die slit of the cyclic | annular die | dye 11 shown in FIG. Thereafter, the split molds 21 and 22 are clamped to hold the parison P, and air is blown into the parison P in a pressure range of 0.05 to 0.15 MPa to form the foam duct 1.

  After molding, parts other than the finished product (burrs) in the cooled and solidified resin material are crushed into a recovered resin material, and the same blow molding is performed again using a mixed resin obtained by adding a predetermined ratio of virgin resin to the recovered resin material. I do. By repeating such a manufacturing cycle, the foam duct 1 can be mass-produced.

  When molding a resin molded product by general blow molding, mold the molten resin material into the shape of the mold surface, release it from the mold in a cooled and solidified state, and remove burrs around the molded product. The finished product is obtained by cutting out the opening with a cutter or the like.

  FIG. 4 is a view showing a state where the foam duct 1 after blow molding is opened from the split molds 21 and 22 and taken out. The foamed duct 1 after blow molding has a burr 31 larger than the product around the foamed duct 1 to be a product, and it is necessary to cut and remove this.

  FIG. 5 is a view showing a burr punching process by the press machine, and the foaming duct 1 and the burr 31 are made a boundary line by the punching blades 32 and 33 which are respectively provided on the upper platen and the lower platen of the press machine and face each other. Cut along.

  In a general blow molding apparatus, as shown in FIG. 6, the split molds 21 and 22 are provided with cavities 21a and 22a for molding the foam duct 1, and are provided with pinch portions 21b and 22b on the outer peripheral portion thereof. Then, the parison is crushed by the pinch portions 21b and 22b. This part becomes the parting line. Excess foamed resin (burr 31) is present outside the parting line, but the split molds 21 and 22 are provided with burr relief recesses 21c and 22c to form a burr escape space.

  Although the burr 31 is housed in the burr escape space of the divided molds 21 and 22, contact with the divided molds 21 and 22 is insufficient. Since the burr 31 after molding shrinks with the passage of time, if the burr escape space is wide (deep), the adhesion with the divided molds 21 and 22 is deteriorated. In some cases, the burr 31 may not contact the split mold. Therefore, it takes time until the burr 31 is cooled, leading to a decrease in productivity.

  In order to solve this problem, for example, as shown in FIG. In the example shown in FIG. 7, the burr relief recesses 21c and 22c of the divided molds 21 and 22 are retracted from the pinch parts 21b and 22b to form shallow portions 21g and 22g, thereby narrowing the burr relief space of these portions. As a result, the burr 31 can easily come into contact with the divided molds 21 and 22 to improve the cooling efficiency and shorten the cooling time.

  However, if the burr relief space is made shallow, the resin material crushed by the pinch portions 21b and 22b loses the escape space, and the inner surface near the parting line of the foam duct 1 becomes thick (wall) or balloon-like. There is a risk of problems such as the generation of bubbles.

  Therefore, in the blow molding method and blow molding apparatus of this embodiment, as shown in FIG. 8, a frame-shaped portion 22d is provided outside the burr escape space of one split mold 22 so as to close the burr escape space. Furthermore, air vents 21e and 22e are provided as vacuum suction mechanisms corresponding to the burr relief recesses 21c and 22c of the divided molds 21 and 22, respectively, so that the burr 31 is forcibly brought into contact with the divided molds 21 and 22. ing. In the case of this embodiment, ventilation members 22h and 22h are installed at the inlet side end portions of the air vents 21e and 22e, and the insides of the recesses 21c and 22c are vacuum-sucked by the air vents 21e and 22e via the ventilation members 21h and 22h. It is configured. The ventilation members 21h and 22h are, for example, a porous plate having a large number of fine holes communicating with the front and back, a plate-like member having one or more through holes, and the like. The timing of idle suction in the air vents 21e and 22e is the same as the timing of air blowing when the foam duct 1 is blow-molded, for example.

  By performing vacuum suction from the air vents 21e and 22e, the adhesion between the burr 31 and the divided molds 21 and 22 can be improved, the cooling efficiency of the burr 31 can be improved, and the cooling time can be shortened. At this time, evacuation is performed by air vents 21e and 22e to release the burrs 31 and pre-shape them along the recesses 21c and 22c. Thereafter, mold clamping is performed, and an air blowing needle is inserted into the burrs 31 to blow air. It is also possible to improve the cooling performance by making the burr 31 hollow.

Usually, in foam blow molding, it is necessary to set the blow pressure to 1 kg / cm ² or less and lower than general blow molding in order not to crush the foam layer with the blow pressure. Different blow pressures can be set on the product side (foam duct 1 side) and the burr 31 side. Therefore, by selectively blowing only at the burr 31 side at a high pressure (for example, 10 kg / cm ² ), it is possible to make the expansion ratio lower than that of the product and further improve the cooling efficiency.

  Furthermore, as shown in FIG. 9, one split mold 21 is provided with an air vent 21e for vacuum suction, and the other split mold 22 is provided with an air vent 22f for air blowing. It is also possible to press 31 against one split mold 21 side to make contact. However, the contact area of the burr 31 with the mold is larger in the example shown in FIG. 8, and the configuration shown in FIG. 8 is better in terms of cooling efficiency.

  In the blow molding method and blow molding apparatus of this embodiment, as described above, the burr 31 is positively brought into contact with the mold to improve the cooling efficiency, so the time from product removal to burr punching can be shortened. And productivity can be improved. Further, when the burr 31 is reused, the cooling time of the burr 31 can be shortened without being affected by the physical properties of the foam molded product, and the apparent specific gravity of the pulverized material can be increased. Therefore, it is possible to stabilize extrusion.

  As mentioned above, although embodiment which applied this invention has been described, it cannot be overemphasized that this invention is not what is limited to the above-mentioned embodiment, In the range which does not deviate from the summary of this invention, a various change can be added. Is possible.

Hereinafter, specific examples of the present invention will be described based on experimental results.

Blow molding conditions The blow molding conditions in this example are as follows.
・ Product weight 484g
・ Burr weight 2810g
・ Burr ratio: 85.30%
・ Mold temperature 21.6 ℃
・ Resin temperature 179.5 to 180 ° C
・ Gas concentration 0.278wt%
・ Set foaming ratio: 3 times ・ Set wall thickness: 2-2.5 mm
・ Blow pressure 0.5kg / cm ²
・ Clamping force 10ton (10%)

Difference due to presence / absence of burr cooling Under the above-mentioned blow conditions, burr cooling was performed in the embodiment shown in FIG. The experiment was performed by changing the cooling time (blowing time) (50 seconds and 30 seconds), and each was performed a plurality of times. The results are shown in Table 1. In Table 1, in addition to the blowing time and the presence / absence of burr cooling, the temperature of the product part and the burr part (temperature immediately after removal), the average specific gravity of the product, the expansion ratio, the weight, and the wall thickness are also shown.

  It can be seen from Table 1 that the burr break condition is improved by bringing the burr into contact with the mold by vacuum suction to improve the cooling efficiency. If burr cooling is not performed, a good burr break state cannot be obtained within the set cooling time.

DESCRIPTION OF SYMBOLS 1 Foam duct 2 Pipe part 3 Opening part 4,5,6,7 Duct part 8 Flange part 21,22 Split mold 21b, 22b Pinch part 21c, 22c Burr relief recessed part 22d Frame-shaped part 21e, 22e Air vent (vacuum suction)
22f Air vent (air blowing)

Claims (6)

  A blow molding method for performing foam blow molding in a mold, wherein the burr is cooled by bringing it into contact with the mold.   2. The blow molding method according to claim 1, wherein the burr is brought into contact with the mold by vacuum suction.   2. The blow molding method according to claim 1, wherein the burr is brought into contact with the mold by vacuum suction and air blowing.   A blow molding apparatus for performing foam blow molding in a mold, wherein the blow molding apparatus is cooled by bringing a burr into contact with the mold.   The blow molding apparatus according to claim 4, further comprising a vacuum suction mechanism for bringing the burr into contact with the mold.   The blow molding apparatus according to claim 4, further comprising a vacuum suction mechanism and an air blowing mechanism for bringing the burr into contact with the mold.

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