JP2013199128A - Method for molding resin-made air-conditioning duct for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding an air-conditioning duct for a vehicle, particularly required to be superior in lightweight properties, heat insulation properties, rigidity, impact resistance, and durability against changes in temperature and humidity.SOLUTION: A method for molding a resin-made air-conditioning duct for a vehicle is molded with a pair of thermoplastic resin sheets. The pair of thermoplastic resin sheets in a molten state are extruded from an extruder and arranged between a pair of split molds, and a mold frame positioned at a split mold outer periphery is thereafter advanced relative to the split molds to bring the extruded thermoplastic resin sheets and the mold frame into contact with each other. Thereafter, the pair of split molds are closed, and the thermoplastic resin sheets corresponding to cavities of one and the other of the split molds, respectively, are vacuum sucked to form the duct.

Description

  The present invention relates to a method for forming an air conditioning duct for a vehicle formed by a pair of thermoplastic resin sheets.

  Conventionally, as a method of manufacturing an air conditioning duct for a vehicle, two sheets formed in advance between a pair of upper and lower molds are placed in a molten state by reheating, and the mold is clamped and pressurized fluid is blown between the sheets. Thus, a method of forming a duct in which a first half and a second half are integrally welded is known.

  For example, Patent Documents 1 and 2 disclose a so-called sheet blow molding method using a foamed resin sheet. In the sheet blow molding method, two thermoplastic resin sheets cut in advance to a predetermined size are heated by an infrared heater to be softened, and then clamped, pinched off by a mold, and pressurized fluid between the sheets. This is a molding method in which a sheet is brought into close contact with the cavity to form a desired shape. When this molding method is used, a sheet at room temperature prepared in advance is softened by reheating it with radiant heat from an infrared heater or the like during sheet blow molding, particularly when a foamed resin sheet is used. It is difficult to achieve a uniform molten state, and not only has a small amount of heat compared to a melt-extruded sheet, but also has poor followability to the mold cavity, as well as a pinch-off part of two sheets (parting line) The welding strength is insufficient.

JP 2001-239824 A JP 2000-289093 A

  The present invention provides a method for molding a resin vehicle air conditioning duct that is particularly required to be excellent in lightness, heat insulation, rigidity, impact resistance, and durability against changes in temperature and humidity.

  The present invention relates to a method for forming a resin vehicle air conditioning duct that is formed by a pair of thermoplastic resin sheets, after a pair of molten thermoplastic resin sheets are extruded and disposed between a pair of split molds from an extruder. The mold located on the outer periphery of the split mold is moved forward relative to the split mold, the extruded thermoplastic resin sheet and the mold are brought into close contact, and then the pair of split molds are closed and one of the molds is closed. The duct is formed by vacuum-sucking the thermoplastic resin sheets respectively corresponding to the cavities of the split mold and the other split mold.

  According to the present invention, in the above-described method for forming a resin vehicle air conditioning duct, the thermoplastic resin kneaded with the foaming agent supplied from the extruder is stored in the accumulator chamber, and the first and the It is preferable to intermittently extrude as a sheet having a bubble cell by being supplied to the second T die.

  ADVANTAGE OF THE INVENTION According to this invention, the resin-made air conditioning duct for vehicles which is excellent in the lightness, heat insulation, rigidity, impact resistance, durability with respect to the change of temperature and humidity can be obtained.

It is sectional drawing which shows an example of the shaping | molding apparatus which enforces the shaping | molding method of the air conditioning duct for vehicles which concerns on this invention. FIG. 2 is a partial cross-sectional view showing a process in which a pair of thermoplastic resin sheets are disposed in a pair of split molds in the molding apparatus of FIG. 1 and a space between each thermoplastic resin sheet and a corresponding mold cavity is closed by a mold frame. is there. FIG. 3 is a partial cross-sectional view showing a process in which each thermoplastic resin sheet is vacuum-sucked into a corresponding mold cavity from the embodiment shown in FIG. 2 in the molding apparatus of FIG. 1. FIG. 4 is a partial cross-sectional view showing a process of closing and molding a mold from the embodiment shown in FIG. 3 in the molding apparatus of FIG. 1. FIG. 5 is a partial cross-sectional view showing a step of opening a mold and taking out a molded product from the embodiment of FIG. 4 in the molding apparatus of FIG. 1. It is a perspective view of the vehicle air-conditioning duct shape | molded in the shaping | molding apparatus of FIG. It is an expanded sectional view same as the above.

  1 to 5, 1 is a first accumulator, 2 is a second accumulator, 3 is a first plunger, 4 is a second plunger, 5 is a first T die, and 6 is a second accumulator. T die, 7 is a first extruder, 8 is a second extruder, 9 is a first thermoplastic resin supply hopper, 10 is a second thermoplastic resin supply hopper, and 11 and 11 are a first pair of Rollers, 12 and 12 are a second pair of rollers, 13 and 13 are a pair of split molds, 14 and 14 are cavities, 15 and 15 are pinch-off forming portions, and 16 and 16 are thermoplastic resin sheets. Reference numerals 17 and 17 denote mold frames, which are located on the outer periphery of the pair of split molds 13 and 13.

  The vehicle air-conditioning duct 18 shown in FIGS. 6 and 7 is a lightweight air-conditioning duct for allowing the air-conditioning air supplied from the air-conditioning unit to flow to a desired part. This vehicle air-conditioning duct 18 is constituted by foamed wall surfaces (first wall surface 19 and second wall surface 20, the same applies hereinafter), and has a closed cell structure (independent cell structure) having a plurality of cell cells with a foaming ratio of 2.0 times or more. The bubble ratio is 70% or more. 21 is a parting line, and 22 is a mounting piece. The average wall thickness of the wall surface is 3.5 mm or less, and the average cell diameter of the cell in the thickness direction of the wall surface is less than 300 μm, preferably less than 100 μm. The vehicle air-conditioning duct 18 is made of a polypropylene resin, and is preferably composed of a blend resin in which 1 to 20 wt% of a polyethylene resin and / or 5 to 40 wt% of a hydrogenated styrene thermoplastic elastomer is mixed. The tensile elongation at break at −10 ° C. is 40% or more, and the tensile modulus at normal temperature is 1000 kg / cm 2 or more. Further, the tensile fracture elongation at −10 ° C. is preferably 100% or more.

Tensile elongation at break: After cutting out the wall surface of the vehicle air-conditioning duct 18 obtained by the molding method according to the present invention and storing it at minus 10 ° C., the tensile speed is 50 mm / min as a No. 2 type test piece according to JIS K-7113. Measurements were made.
Tensile modulus: Wall surface 18 of a vehicle air-conditioning duct obtained by the molding method according to the present invention is cut out at room temperature (23 ° C.) as a No. 2 test piece according to JIS K-7113 at a pulling speed of 50 mm / min. Measurements were made.
Foaming ratio: A value obtained by dividing the density of the thermoplastic resin used in the molding method according to the present invention by the apparent density of the wall surface of the vehicle air-conditioning duct obtained by the molding method according to the present invention was defined as the foaming ratio.
Melt flow rate (MFR): A propylene-based resin and a styrene-based elastomer and an ethylene-based polymer blended therein were measured at a test temperature of 230 ° C. and a test load of 2.16 kg according to JIS K-7210.
Izod impact strength: The wall surface of the vehicle air-conditioning duct 18 obtained by the molding method according to the present invention is cut out, stored at minus 20 ° C., cut out as a test piece of 80 × 10 (length × width mm), and has a thickness of 4 mm. The test pieces cut out so as to be stacked were used and measured according to JIS K-7110 (with notch).

  The vehicle air-conditioning duct 18 shown in FIGS. 5 and 6 is formed according to the embodiment shown in FIGS. That is, the thermoplastic resin sheets 16 and 16 having two cells for forming the first wall 19 and the second wall 20 of the air conditioning duct 18 for a vehicle and having bubble cells are respectively formed in the first T-die. 5 and the second T die 6 are extruded and suspended between the pair of split molds 13 and 13. A shape along the cavity shape is obtained by vacuum-sucking two thermoplastic resin sheets 16 and 16 each having a bubble cell in a suspended molten state into the cavities 14 and 14 of the pair of split molds 13 and 13, respectively. To do. Thereafter, the vehicle air conditioning duct 18 cooled in the pair of split molds 13 and 13 is formed by removing burrs at the outer periphery of the parting line 21 formed by the pinch-off forming portions 15 and 15 after being released from the mold. The

  The two foamed thermoplastic resin sheets 16, 16 suspended between the pair of split molds 13, 13 have a sheet thickness to prevent variation in thickness due to drawdown, neck-in, or the like. It is necessary to separately adjust the extrusion speed, the thickness distribution in the extrusion direction, and the like. The foamed thermoplastic resin sheets 16 and 16 are respectively melted and kneaded with a thermoplastic resin to which a foaming agent has been added by the first extruder 7 and the second extruder 8, and then the accumulator chamber of the first accumulator 1. , Temporarily stored in the accumulator chamber of the second accumulator 2, and at regular intervals to the first T die 5 by the first plunger 3 and to the second T die 6 by the second plunger 4, respectively. Supplied. The foamed thermoplastic resin sheets 16 and 16 extruded from the first T die 5 and the second T die 6 are sandwiched between a first pair of rollers 11 and 11 and a second pair of rollers 12 and 12, respectively. It is pressed and arrange | positioned between a pair of split metal molds 13 and 13. At this time, the thickness and thickness distribution of the foamed thermoplastic resin sheets 16 and 16 are adjusted separately.

  Specifically, first, extrusion speeds are set separately by the first accumulator 1 and the second accumulator 2, the first T die 5 and the second T die 6, respectively. The extrusion capability of the first extruder 7 and the second extruder 8 connected to the first accumulator 1 and the second accumulator 2 can be selected as appropriate according to the size of the air conditioning duct 18 for the vehicle. However, it is preferably 50 kg / hour or more from the viewpoint of shortening the molding cycle. Further, from the viewpoint of preventing the occurrence of drawdown, the extrusion process of the thermoplastic resin sheets 16 and 16 from the first T die 5 and the second T die 6 is completed within 40 seconds, more preferably within 30 seconds. There is a need. Therefore, the thermoplastic resin stored in the accumulator chamber of the first accumulator 1 and the second accumulator chamber of the second accumulator 2 per 1 cm 2 from the opening of the slits of the first T die 5 and the second T die 6. Extrusion is performed at 50 kg / hour or more, preferably 60 kg / hour or more. At this time, the influence of the drawdown can be minimized by changing the slit gaps of the first T die 5 and the second T die 6 together with the extrusion of the thermoplastic resin sheets 16 and 16. That is, the thickness of the thermoplastic resin sheet 16 is increased by gradually widening the slit gap from the start of extrusion against the thickness of the thermoplastic resin sheet 16, 16 that is drawn down and thinned by its own weight due to the drawdown phenomenon. , 16 can be adjusted to a uniform thickness from the upper side to the lower side of the thermoplastic resin sheets 16, 16 by extruding thicker toward the upper side. Further, the first pair of rollers 11, 11 and the second pair of rollers 12, with respect to the extrusion speed of the thermoplastic resin sheets 16, 16 extruded from the first T die 5 and the second T die 6, 12 by changing the rotational speed of the first T die 5 due to the difference between the extrusion speed of the thermoplastic resin sheets 16 and 16 from the first T die 5 and the second T die 6 and the feed speed by the roller. The thermoplastic resin sheets 16 and 16 are stretched between the fifth and second T dies 6, the first pair of rollers 11 and 11, and the second pair of rollers 12 and 12 to adjust the thickness of the sheet to be thin. it can.

  The thermoplastic resin respectively supplied to the first T die 5 and the second T die 6 is extruded as a sheet from a slit through a resin flow path from a manifold of each T die body (not shown). Each T-die body is formed by superimposing one die and the other die, and one die lip and the other die lip are opposed to each other with a slit gap at the tip portion of each T-die body. It is set by the preparation device 23. The thickness of the extruded sheet is determined by the slit gap, and specifically, the thermoplastic resin sheet having a thickness of 0.6 to 6.0 mm from the first T die 5 and the second T die 6 respectively. 16 and 16 are extruded. In the above description, the case where the thermoplastic resin supply paths to the first T die 5 and the second T die 6 are independent from each other has been described. However, the first T die 5 and the second T die are used. It is also possible to supply a thermoplastic resin to each T die by providing a branch path at the tip of the accumulator using one extruder and one accumulator connected thereto for 6. Further, as the type of accumulator, a side accumulation method or a ring accumulation method can be used.

  The slit gap is adjusted for uniformity in the width direction of the sheet by a known slit gap adjusting device. Further, the other die lip is varied from the start to the end of extrusion of the sheet that is intermittently extruded by a slit clearance driving device (not shown) to adjust the thickness of the sheet in the extrusion direction.

  As the slit gap adjusting device, there are a thermal expansion type and a mechanical type, and it is preferable to use a device having both functions. A plurality of slit gap adjusting devices are arranged at equal intervals along the width direction of the slit, and the slit gap is narrowed or widened by each slit gap adjusting device to make the sheet thickness uniform in the width direction. To do.

  The slit clearance adjusting device has a die bolt provided so as to be able to advance and retreat toward one die lip, and an adjustment shaft is disposed at the tip of the die bolt via a pressure transmission unit. An engagement piece is coupled to the adjustment shaft by a fastening bolt, and the engagement piece is connected to one die lip. When the die bolt is moved forward, the adjustment shaft is pushed out in the distal direction through the pressure transmission portion, and one die lip is pressed. As a result, the die lip is deformed at the portion of the concave groove, and the slit gap is narrowed. To widen the slit gap, the die bolt is moved backward.

  Furthermore, the slit gap can be adjusted with high accuracy by using a thermal expansion type adjusting means in accordance with the mechanical adjusting means. Specifically, one die lip is pressed by heating the adjustment shaft by an electric heater (not shown) to cause thermal expansion, thereby narrowing the slit gap. In order to widen the slit gap, the electric heater is stopped, and the adjusting shaft is cooled and contracted by a cooling means (not shown).

  The sheet extruded from the T-die is preferably adjusted so that the thickness in the extrusion direction becomes uniform when the sheet is suspended between the divided molds, that is, when the mold is clamped. In this case, the slit gap is gradually widened from the start of extrusion and is varied so as to become maximum at the end of extrusion. As a result, the thickness of the sheet extruded from the T-die gradually increases from the start of extrusion, but the sheet extruded in the molten state is stretched by its own weight and gradually decreases from the bottom to the top of the sheet, thus widening the slit gap. The thickly extruded portion and the thinned and thinned portion due to the drawdown phenomenon are offset, and the sheet can be adjusted to have a uniform thickness from the top to the bottom.

  As the foaming agent used in the present invention, any of physical foaming agents, chemical foaming agents and mixtures thereof may be used. As physical foaming agents, inorganic physical foaming agents such as air, carbon dioxide, nitrogen gas, and water, and organic physical foaming agents such as butane, pentane, hexane, dichloromethane, dichloroethane, and their supercritical fluids are used. be able to. As the supercritical fluid, carbon dioxide, nitrogen or the like is preferably used. If nitrogen is used, the critical temperature is 149.1 ° C. and the critical pressure is 3.4 MPa or more. If carbon dioxide is used, the critical temperature is 31 ° C. and the critical pressure is 7 It is obtained by setting it to 4 MPa or more.

  As the polypropylene resin used for the blend resin constituting the vehicle air conditioning duct according to the present invention, polypropylene having a melt tension at 230 ° C. in the range of 30 to 350 mN is used. 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 resin is 5 to 40 wt%, preferably 15 with respect to the polypropylene resin in order to improve impact resistance and maintain rigidity as an air conditioning duct. It is added in a range of ˜30 wt%. 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-based thermoplastic elastomer has a styrene content of less than 30 wt%, preferably less than 20 wt%, and an MFR at 230 ° C of 10 g / 10 min or less, preferably 5.0 g / 10 min or less. And 1.0 g / 10 min or more.

  Moreover, as a polyolefin-type polymer blended with the said resin, a low density ethylene-alpha olefin is preferable and can be mix | blended in 1-20 wt%. A low density ethylene-α olefin having a density of 0.91 g / cm 3 or less is used, and an ethylene / α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms is used. Propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 4-methyl- Examples include 1-hexene, and preferably 1-butene, 1-hexene, and 1-octene are used. Moreover, said C3-C20 alpha olefin may be used independently and may use 2 or more types together. Content of the monomer unit based on ethylene in the ethylene / α-olefin copolymer is in the range of 50 to 99 wt% with respect to the ethylene / α-olefin copolymer. The content of the monomer unit based on the α-olefin is in the range of 1 to 50 wt% with respect to the ethylene / α-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.

  A sheet that hangs in a pair of split molds prevents the occurrence of wall thickness variation due to drawdown, neck-in, etc., and obtains a duct having good light weight and heat insulation properties by having a high expansion ratio Therefore, it is necessary to use a material having a high melt tension. Specifically, the MFR at 230 ° C. (measured at a test temperature of 230 ° C. and a test load of 2.16 kg according to JIS K-7210) is 5.0 g / 10 min or less, more preferably 1.5 to 3.0 g / 10 minutes. In general, from the viewpoint of extruding thinly from a slit of a T die, MFR at 230 ° C. is larger than 3.0 g / 10 minutes, specifically, 5.0 to 10.0 g / 10 minutes is used for molding of a film or the like. It has been.

DESCRIPTION OF SYMBOLS 1 1st accumulator 2 2nd accumulator 3 1st plunger 4 2nd plunger 5 1st T die 6 2nd T die 7 1st extruder 8 2nd extruder 9 1st Thermoplastic resin supply hopper 10 Second thermoplastic resin supply hopper 11, 11 First pair of rollers 12, 12 Second pair of rollers 13, 13 Pair of split molds 14, 14 Cavity 15, 15 Pinch-off forming part 16, 16 Thermoplastic resin sheet 17, 17 Mold 18 Air conditioning duct for vehicle 19 First wall surface 20 Second wall surface 21 Parting line 22 Mounting piece 23 Slit gap adjusting device

Claims (2)

A molding method for a resin vehicle air conditioning duct molded by a pair of thermoplastic resin sheets,
After extruding and arranging a pair of molten thermoplastic resin sheets between a pair of split molds from an extruder, the mold frame located on the outer periphery of the split mold is moved forward relative to the split molds, Adhering the extruded thermoplastic resin sheet and the mold,
Next, the pair of split molds are closed, and a duct is formed by vacuum-sucking the thermoplastic resin sheets respectively corresponding to the cavities of the one split mold and the other split mold. A method for forming an air conditioning duct for a vehicle.   The thermoplastic resin kneaded with the foaming agent supplied from the extruder is stored in the accumulation chamber, and is supplied to the first and second T dies using a plunger at regular intervals. The method for forming a resin vehicle air-conditioning duct according to claim 1, wherein the sheet is intermittently extruded as a sheet having slag.

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