JP2020055942A - Foam duct - Google Patents

Abstract

To provide a foam duct which has high variability and restorability and is difficult to be damaged, and can also improve conveyance efficiency and fittability.SOLUTION: A foam duct is formed by blow molding of a foam resin containing a polyolefin-based resin and an elastomer. A content of the elastomer is 60 mass% to 85 mass%. An expansion ratio is twice or less. The polyolefin-based resin is, for instance, a polypropylene-based resin. The polypropylene-based resin preferably has a long chain branch structure.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a foam duct, and more particularly to a foam duct formed by molding a resin material containing an elastomer.

  Various air-conditioning ducts mounted in, for example, an instrument panel of an automobile are known as foam blow molded articles. 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 adding a foaming agent to a resin material such as a polyolefin resin, melt-kneading, and blow-molding a foam parison extruded from a die of an extruder.

  Polyolefin resins are widely used as resin materials used for foam blow molded articles, and among them, polypropylene resins are generally used. In recent years, replacement with a polyethylene resin or the like has been studied for the purpose of making the material configuration more inexpensive (see Patent Document 1 and the like).

  Patent Document 1 discloses a high-density polyethylene having a long-chain branched structure, a specific gravity of 0.95 to 0.96, a melt flow rate (MFR) of 3 to 7 g / 10 minutes, and a melt tension of 100 to 250 mN, and a melt flow rate. An automotive duct is disclosed in which a chemical foaming agent is added to a mixed resin obtained by mixing a high density polyethylene (MFR) of 0.3 to 1.0 g / 10 minutes and blow molding is performed.

JP 2011-194700 A

  As described above, usually, a polyolefin resin material such as polypropylene or high-density polyethylene is used as a main material of the foam duct. Here, the reason why the foam duct is adopted is that a weight-reducing effect and high heat insulating property are obtained. On the other hand, when the foam duct is adopted, the mechanical properties are reduced and the fitting portion is deformed. Has been viewed as a problem.

  The blow-molded foam duct has air bubbles inside the resin wall, and as in the case of conventional mass-produced products, when polypropylene or polyethylene is used as a raw material, the air bubbles serve as a starting point of destruction and reduce the strength. Due to the small elastic deformation range of the system material, the product tends to be easily broken. In particular, in a low-temperature environment, cracks in the foam duct and a degree of damage during transportation are likely to occur.

  Under such circumstances, conventionally, a dedicated pass-through box or rack corresponding to the duct shape has been prepared, but this causes a reduction in transport efficiency and an increase in cost.

  The present invention has been proposed in view of such a conventional situation, and has an object to provide a foam duct having high variability and high resilience, which is hardly damaged, and further has a transport efficiency and a fitting property. It is another object of the present invention to provide a foam duct capable of improving the quality.

  In order to achieve the above object, the foam duct of the present invention is a foam duct formed by blow molding a foam resin containing a polyolefin resin and an elastomer, wherein the content of the elastomer is 60% by mass or more. 85% by mass.

  The elastomer has a large elastic deformation range, and by increasing the ratio thereof, when an external force is applied, the foam duct itself deforms and does not break. Further, since the compression portion and the undulation of the flow path are usually provided in the foamed duct, after the external force is removed, an attempt is made to restore the original duct shape. Further, since bubbles are present inside, the stress applied to the resin per unit volume is reduced, and the accumulation of residual stress after the load is removed is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the foam duct with high variability and high resilience, which is hard to break, and it is also possible to improve the transport efficiency and the fitting property.

It is a schematic perspective view which shows an example of a foam duct. It is an outline sectional view showing typically the mode at the time of carrying out blow molding of a duct. It is a photograph of a section of a foam duct containing an elastomer. It is a photograph which shows the form of the foam duct containing an elastomer, (A) shows the form of the duct at the time of no load, (B) shows the form of the duct at the time of bending, and (C) shows the form of the duct at the time of twist.

  Hereinafter, embodiments of a foam duct to which the present invention is applied will be described in detail with reference to the drawings.

  The foam duct 10 is configured such that air-conditioning air supplied from an air-conditioning unit (not shown) is circulated through an internal flow path and is ventilated to a desired portion. In addition, the shape of the foam duct 10 is not limited to the shape shown in FIG. 1, and may be an arbitrary shape according to a use or an installation place.

  The foam duct 10 of the present embodiment is obtained by sandwiching a foam parison formed by extruding a foam resin from a die of an extruder with a mold and performing blow molding. Both ends of the duct immediately after blow molding are in a closed state, and both ends are cut by trimming after blow molding to form an open shape.

  The foam duct 10 of the present embodiment is formed of a hollow foamed resin molded product whose pipe wall is formed of a foam layer. By making the foamed layer have a closed cell structure, it is possible to make the duct lightweight and excellent in heat insulation. The closed cell structure is a structure having a plurality of independent cell cells and has a closed cell ratio of at least 70%. With such a configuration, even when cooling air is circulated in the foam duct 10, the possibility of dew condensation can be almost eliminated.

  The foam duct 10 of the present embodiment basically uses a polypropylene resin or a polyolefin resin such as high-density polyethylene as a foam resin material. Among them, the polypropylene resin is optimized in terms of physical properties and the like. It is characterized by being easy and having good foam moldability.

  Examples of the polypropylene resin to be used include a propylene homopolymer or a random or block copolymer of propylene and another α-olefin. Other α-olefins copolymerized with propylene include ethylene, butene, pentene, hexene, octene, methylpentene and the like. The amount of the α-olefin to be copolymerized with propylene is arbitrary, but is preferably, for example, about 0.1 to 20% by mass in order to maintain excellent physical properties of polypropylene.

  Further, the polypropylene resin preferably has a long-chain branched structure. Polypropylene resins have the disadvantage that the melt tension at the time of melting is low and the formability in foam molding is inferior, but by introducing a long-chain branched structure, the melting characteristics can be improved, Can be eliminated.

  It is important that the foam duct 10 of the present embodiment contains an elastomer in addition to the polyolefin-based resin.

  Here, examples of the elastomer used include a styrene-based elastomer, an ethylene / α-olefin random copolymer, a polyethylene-based elastomer, and the like. Representative examples of styrene elastomers include a polybutadiene block segment, a block copolymer comprising a styrene / butadiene copolymer block segment or a hydrogenated product thereof, a polyisoprene block segment, and a styrene / isoprene copolymer block segment. Or a hydrogenated product thereof, a block copolymer composed of a polymer block mainly composed of styrene and a polymer block mainly composed of a conjugated diene compound, and a random copolymer of styrene and a conjugated diene compound Alternatively, a hydrogenated product thereof, a block copolymer composed of a polymer block mainly composed of styrene and a polymer block mainly composed of a conjugated diene compound, or a hydrogenated product thereof may be used. Polyethylene-based elastomers are fine dispersions of olefin-based rubber in a matrix of polyethylene-based resin, have excellent compatibility with polypropylene-based resin, and impart rubber elasticity to the resin material to improve impact resistance. The feature is that it can be.

  The proportion of the elastomer in the resin material is preferably from 60% by mass to 85% by mass. If the proportion of the elastomer is less than 60% by mass, the variability and the restoring property may be insufficient. Further, in order to suppress whitening and wrinkling of the resin that occurs at the time of bending, the proportion of the elastomer is preferably set to 60% by mass or more. Conversely, if the proportion of the elastomer exceeds 85% by mass, it may be difficult to maintain the original duct shape.

  Various additives can be added to the foamed resin material as needed. For example, an antioxidant such as a phosphorus-based antioxidant or a phenol-based antioxidant may be added. Phosphorus-based antioxidants have excellent resistance to hydrolysis and volatilization, and have a function of reacting with a resin bonded to oxygen and preventing oxidative deterioration by a chain reaction. A phenolic antioxidant is an antioxidant that is effective in improving the heat resistance of various resins and elastomers. Since it has a high molecular weight, it has low extractability and low volatility.

  Although the expansion ratio of the foam duct 10 of the present embodiment is arbitrary, it is preferable to suppress the expansion ratio to 2 times or less because the raw resin contains a large amount of elastomer and has poor melt spreadability. Thereby, it is possible to obtain the foam duct 10 having deformability and shape restoring property, and having rigidity capable of maintaining the shape even when it is cantilevered.

  The foam duct 10 is manufactured by supplying a resin material containing the above-described polyolefin-based resin (polypropylene-based resin) or elastomer to a blow molding apparatus. In the blow molding, foaming is performed using a foaming agent. As the foaming agent, any of a physical foaming agent and a chemical foaming agent may be used.For example, inorganic foaming agents such as air, carbon dioxide gas, nitrogen gas, and water, and organic foaming agents such as butane, pentane, hexane, dichloromethane, and dichloroethane may be used. A system foaming agent and the like can be used.

  The foamed duct 10 is formed by blow molding the foamed resin material by a known method. FIG. 2 is a diagram illustrating an aspect when the foam duct 10 is blow-molded.

  At the time of blow molding, first, a resin material used for molding is kneaded in an extruder to prepare a base resin. After adding a foaming agent to such a base resin and mixing in an extruder, the resin is stored in an accumulator in a die (not shown), and after a predetermined amount of resin is stored, a ring-shaped piston (not shown) is removed. Push down in the direction perpendicular to the horizontal direction (vertical direction).

  The accumulator type molding machine may be a conventional hydraulic machine or an all-electric motor. In hydraulic machines, the accumulator is operated by sending oil to the cylinder.By controlling this oil pressure, back pressure is applied to the accumulator, suppressing cell expansion in the head and achieving a high parison expansion ratio of the parison. ing.

  In the case of an all-electric motor, an accumulator for storing resin is operated by a ball screw and a servomotor, but it is difficult to increase the foaming of the parison. However, in the molding of the foam duct 10 of the present embodiment, the foaming ratio is 2 times or less as described above, and the molding can be sufficiently performed even by the accumulator type all-motor.

  As described above, the foam duct of the present invention has high variability and restorability, and has good fitting properties. Further, the foaming duct of the present invention is hard to be damaged, and it is not necessary to prepare a dedicated pass-through box or rack, so that the transfer efficiency is good.

  The embodiment to which the present invention is applied has been described above. However, it is needless to say that the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. It is possible.

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

Using a polypropylene-based resin and an elastomer as raw materials for producing the foam duct , the foam duct was blow-molded with the composition shown in Table 1 (Examples 1 to 4, Comparative Examples 1 to 3). The raw materials used are as follows.
・ Polypropylene resin: WB140 (trade name, manufactured by Boreales Co., Ltd.)
-Elastomer: manufactured by Kuraray Plastics Co., Ltd., trade name Arneston-Chemical blowing agent CF40E-J (master batch of a mixture of baking soda and citric acid, 4 parts by mass based on 100 parts by mass of polypropylene resin + elastomer)
・ No colorant

The foam ducts thus evaluated were evaluated for flexibility, torsion, whitening and wrinkling after bending, and rigidity (maintaining shape). Table 1 shows the results.

  As is evident from Table 1, when the blending amount of the elastomer is small, the variability such as flexibility and torsion is insufficient (see Comparative Examples 2 and 3). Further, in the sample in which the proportion of the elastomer was 50% by mass, whitening and wrinkling were observed after bending. The sample having 90% by mass of the elastomer (Comparative Example 1) had a problem that the shape could not be maintained.

  On the other hand, as shown in Examples 1 to 4, by setting the proportion of the elastomer to 60% by mass to 85% by mass, good variability can be realized, and the resilience and rigidity (maintaining shape). Was also good.

  FIG. 3 is a cross-sectional image of a sample (foam duct) having 70% by mass of an elastomer (Example 3). The expansion ratio of this sample is 1.8 times, and the cell diameter is 189 μm.

  FIG. 4 shows the form of a sample (foam duct) in which the proportion of the elastomer is 70% by mass (Example 3), (A) the form of the duct when no load is applied, and (B) the duct when bent. (C) shows the form of the duct when twisted. When the load was released after bending or twisting, the state of (A) was quickly restored.

Reference Signs List 10 foam duct 21 annular die 30 mold clamping device 31, 32 split mold P parison

Claims (4)

A foam duct formed by blow molding a foamed resin containing a polyolefin resin and an elastomer,
The foam duct, wherein the content of the elastomer is from 60% by mass to 85% by mass.   The foam duct according to claim 1, wherein the foaming ratio is 2 times or less.   3. The foam duct according to claim 1, wherein the polyolefin resin is a polypropylene resin.   4. The foam duct according to claim 3, wherein the polypropylene resin has a long-chain branched structure.