JP2010203772A - Foam duct - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight foam duct having an excellent heat insulation property and hardly causing dew condensation. <P>SOLUTION: The foam duct 1 includes a three-dimensionally bending bent portion composed of one end bent portion 1b and the other end bent portion 1c which are provided adjacently at both ends of the center 1a. Surface roughness on the outer surface of the foam dust is Rt 45 μm or smaller, and an expansion ratio is within 2.5-5 times. In addition, foamed cells having small diameters are uniformly distributed in the foam duct including a thin-walled portion, and the foam duct has a high expansion ratio, is light in weight and has the excellent heat insulation property. Thereby, when the foam duct is used for an air conditioner or the like for an automobile or the like, the amount of dew condensation is remarkably reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a foam duct that is lightweight and excellent in heat insulation.

  A conventional example of a lightweight and heat-insulating foam duct used for an air conditioner of an automobile will be described.

  The foam duct disclosed in Patent Document 1 is formed by foam blow molding in which a physical foaming agent is added as a foaming agent to a polyolefin resin, and the physical foaming agent includes carbon dioxide gas and nitrogen gas. Inorganic physical foaming agents such as air and organic physical foaming agents such as propane, chlorofluorocarbon and butane are used (see Patent Document 1).

  However, the foam duct disclosed in Patent Document 1 is not only insufficient in heat insulation but also has a large surface roughness. For this reason, when used in the flow path of the cooling medium of the air conditioner, condensation tends to occur on the outer surface, and the flow resistance of the cooling medium is large.

  In addition, if the minimum thickness of the foam duct is less than 0.5 mm, pinholes will occur in the minimum thickness portion during foam blow molding, making foam blow molding impossible. It is necessary to make it thicker and there is a limit to weight reduction.

  In the invention disclosed in Patent Document 2, the problem of deterioration in appearance performance due to surface defects in blow molding is to be solved for the surface quality of ABS.

  In order to improve the appearance, additives such as phenolic antioxidants, phosphite antioxidants, and thioether antioxidants are added. However, even in the examples, the average value of the surface roughness is as small as 1 to 3 μm, and there is no description of the surface roughness (average value is 45 μm) due to the bubbles in the foam blow molding. Further, since ABS has a high molding temperature (270 ° C.), an antioxidant is added to prevent deterioration of the resin, and PP is not described. Since the molding temperature of PP is 200 ° C., which is lower than that of ABS, the deterioration of the surface quality due to the deterioration of the resin is not a problem.

Patent Document 3 describes the production of an ultra-microporous foam material by supplying carbon dioxide in a supercritical state as a foaming agent to the material to be foamed. However, the production of 100-500 μm, which has an average bubble diameter of less than 2 μm (9th bubbles / material cm ³ , 20 to 90% of the total volume is a pore fraction) and a larger bubble diameter, is described It has not been. Moreover, it does not describe foam blow molding.

  Patent Document 4 describes that a product with an average cell diameter of 50 to 100 μm can be obtained by supplying a supercritical foaming agent and a nucleating agent to a material to be foamed for extrusion of a microporous foam. Yes.

  However, there is no description of the determination of the melt tension of the material to be foamed and the average cell diameter of 100 μm or more.

  Patent Document 5 discloses a foamed blow molded product and a production method in which the melt tension at 230 ° C. of the resin is 0.049 N or more and the expansion ratio is 3 or more, regarding polypropylene for foam blowing.

  However, the melt tension at 230 ° C. of the resin is 0.029 to 0.049 N, and there is no description of a foam blown product in which a supercritical foaming agent and a nucleating agent are blended.

JP-A-10-181334 JP-A-7-32454 Japanese Patent No. 2625576 JP-T-2001-527106 WO99 / 28111

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and an object thereof is to provide a foam duct that is light in weight and has excellent heat insulation properties and is unlikely to cause condensation. .

To achieve the above object, the foam duct of the present invention is directed to small foam cells evenly distribution of foamed cell diameter, surface roughness is below Rt45μm the outer surface, an expansion ratio of 2.5 It is within the range of 5 times.

Moreover, in the cross section of the said foam duct, the said foam cell is elliptical shape, The length of the average ellipse long diameter of the said foam cell may be 100 micrometers-500 micrometers.

Further , it may be molded using polypropylene having a melt tension at 230 ° C. within the range of 0.029N to 0.049N.

  Since this invention is comprised as mentioned above, there exists an effect as described below.

  Throughout the entire foam duct, the foam cells having a small foam cell diameter are uniformly distributed including the thin-walled portion, and the foaming ratio is large, which is lightweight and excellent in heat insulation. In addition, the surface roughness Rt of the outer surface is 45 μm or less, and when used in an air conditioner or the like of an automobile in which a cooling medium having a temperature lower than the outside air temperature flows, the amount of condensation is significantly reduced.

It is a model perspective view of the foam duct by one embodiment. It is the photograph of the magnification 100 which image | photographed the cross section which cut | disconnected the foam duct which concerns on this invention with the CCD camera. It is the photograph of the magnification 100 which image | photographed the cross section which cut | disconnected the foam duct which concerns on a prior art example with the CCD camera.

  FIG. 1 is a schematic perspective view of a foam duct according to an embodiment of the present invention.

  The foam duct 1 according to the present embodiment has a bent portion that has a rectangular cross-sectional shape and is bent three-dimensionally. One end side bent portion 1b continuously provided on one end side of the central portion 1a is bent in an arc shape with respect to the central portion 1a (X-axis side in the drawing), and the opposite central portion side is more than the central portion 1a. A bulging portion 2 having an enlarged cross-sectional shape in which a slightly high step 2a is formed is continuously provided. The other end side bent portion 1c connected to the other end side of the central portion 1a is bent in an L shape with respect to the central portion 1a (bent to the Z axis side in the drawing and then bent to the Y axis side in the drawing). The connecting portion 3 having a pair of protrusions 3a and 3b formed on the outer surface at a predetermined interval is connected to the anti-central portion side, and the anti-central portion side of the connecting portion 3 is closed. The part 4 is continuously provided.

  The foam duct 1 is not limited to a total burr type in which burrs are generated in all parts of the parting line 5, but is a type of blowing in which burrs are generated only in the parts of the parting line 5 in the bulging part 2 and the closing part 4. Foam blow molding can be performed using a mold.

  When the foam duct is molded by the foam blow molding method disclosed in Patent Document 1, the foam cell diameter becomes large with a size of 1500 μm or more and the distribution of the foam cells becomes non-uniform, and the expansion ratio is as small as about 2 times. It becomes a thing. For this reason, the heat insulating property is insufficient and the surface roughness becomes rough, and when it is used in an air conditioner, condensation tends to occur. Moreover, since the foam cell diameter is large, if the minimum thickness of the foam duct is 0.5 mm or less, a pinhole is generated in the minimum thickness portion, resulting in a molding failure.

  Therefore, as a result of repeated experiments, an extruder using a supercritical fluid, which has been attracting attention in foam extrusion molding, as a blowing agent was used to mold a molten parison in which supercritical fluid was added as a blowing agent to a thermoplastic resin. By forming the parison by blow molding with a blow mold, the surface roughness Rt (maximum height) on the outer surface of the foam duct is 45 μm or less, and the foaming ratio is within the range of 2.5 to 5 times. A superior foam duct was obtained.

As the supercritical fluid, carbon dioxide gas or nitrogen gas, which are inert gases, which are not toxic or flammable and can easily be brought to a supercritical state at a supercritical pressure and a supercritical temperature may be used. Incidentally, carbon dioxide (CO ₂ ) becomes a supercritical fluid at a critical temperature of 31 ° C. and a critical pressure of 7.4 MPa or more.

  Moreover, by making the addition amount of the nucleating agent within the range of 2.5 to 7% by weight, the foamed cells having a foamed cell diameter of 500 μm or less (small foamed cell diameter) are uniformly distributed, and the foaming ratio is increased. It turns out that you can.

  As the thermoplastic resin, high-density polyethylene, polyolefin such as polypropylene, polystyrene, or the like can be used. As the nucleating agent, known materials such as talc, calcium carbonate, titanium oxide, barium sulfate and the like can be used.

  Next, a foam duct according to another embodiment of the present invention will be described.

  In general, air conditioning ducts that supply cooled air or clean air need to be provided along the wall surface around the ducts or avoid the surrounding positions, so that supply passage Often has a twisted shape. Accordingly, the air-conditioning duct is generally constituted by a plurality of divided ducts having a meandering shape as a whole and connected to form a single duct. In particular, in an air conditioning duct in which an air supply passage is bent in a three-dimensional direction, it is difficult to integrally form the duct, and therefore, a divided structure of the duct is generally adopted. That is, when manufacturing a duct for air conditioning bent in a three-dimensional direction by blow molding, it is difficult to arrange a tubular parison at an appropriate position of the mold cavity, thereby, on the wall surface of the blow molded duct, There is a problem that a gap between a high blow ratio and a low blow ratio becomes sharp, which causes a thin portion and further a pinhole.

  Therefore, when the gap of the blow ratio as described above is large, the set thickness of the blow molding is generally increased to prevent pinholes. In particular, when blow-molding a foamable resin, the parison elongation is lower than in the case of a non-foamed resin, so a thick wall thickness is set to prevent pinholes.

  Means for improving the above problem will be described below.

  That is, the foam duct according to the present embodiment is an air-conditioning foam duct integrally blow-molded with a foamable resin in which the axis of the internal air supply passage is bent in a three-dimensional direction, and the parison at the time of blow molding Is bent in a three-dimensional direction and the foam duct for air conditioning has an average thickness of 0.5 to 1.5 mm, The foam cells having a small foam cell diameter are uniformly distributed, the surface roughness on the outer surface is Rt 45 μm or less, and the foaming ratio is within the range of 2.5 to 5 times.

  The foam duct according to the present embodiment is lightweight and excellent in heat insulation, and further excellent in thickness uniformity, light weight, and economy. The relationship between configuration and effect will be described below.

  (1) The parting line 5 formed by the mold pinch-off of the split type with the parison being sandwiched during blow molding is for adjusting and suppressing the blow ratio of the parison.

  (2) Since the parison is appropriately arranged along the air supply passage by bending the parting line 5 in the three-dimensional direction, and the parison expands starting from the parting line 5, the wall thickness of the duct wall surface Uniformity can be ensured.

  (3) A foam duct for air conditioning that is integrally blow-molded in which the axis of the internal air supply passage is bent in a three-dimensional direction has a reduced manufacturing process as compared with a configuration in which many conventional divided ducts are assembled.

  (4) Since the thickness uniformity is ensured even if the average thickness is relatively thin with a thickness of 0.5 to 1.5 mm, the heat insulation can be maintained.

  (5) Since the foam cells having a small foam cell diameter are uniformly distributed, the surface roughness on the outer surface is Rt 45 μm or less, and the foaming ratio is within the range of 2.5 to 5 times, the conventional foam duct Condensation is superior compared to.

  In the production of the air-conditioning foam duct having the above-described configuration, the foam blow molding in which a supercritical fluid is added as a foaming agent to a thermoplastic resin is preferable, but the foam blow molding in which a supercritical fluid is not added as a foaming agent. Even if it exists, it is applicable.

  Moreover, it is not necessary for the parison to be sandwiched over the entire length of the parting line, and it is sufficient that the parison is substantially sandwiched around the part that causes the problem of thickness uniformity.

Foam blow molding machine (P-50-L / D34, manufactured by Nippon Steel Works, Ltd.) equipped with a screw type extruder having a gas supply port in a cylinder using polypropylene (New Former FB3312 manufactured by Nippon Polypro Co., Ltd.) as a molding material. A supercritical fluid of carbon dioxide (CO ₂ ) is added from the gas supply port, and a foam duct sample having a three-dimensionally bent portion similar to that shown in FIG. Foam blow molding was performed by changing the expansion ratio under molding conditions.

Molding conditions Outer diameter of parison: 120mm
Resin temperature at die outlet: 172 ° C
Parison wall thickness: 5mm
Wall thickness of the thinnest part of the foam duct 0.3mm

Condensation rate is determined by filling the foam duct with 0 ° C cold water and leaving it in a constant temperature bath at a temperature of 40 ° C and a humidity of 90% for 10 minutes, and then condensing and dripping water on the outer surface of the foam duct. It is a value obtained by measuring the change in weight (condensation amount) by impregnation and converting the measured dew amount (g) per unit area (cm ² ) of the surface of the foam duct.

  The foam cell diameter of the foam cell was measured by cutting the foam duct with a microtome (LEICA RM2145) and photographing the cut section with a CCD camera (Keyence VH-6300). And the length of the average elliptical major axis of the foam cell was taken as the foam cell diameter.

  FIG. 2 is a photograph of 100 times the magnification of the foam cell in the cut surface of the foam duct of the present invention. The foam cell diameter is 500 μm or less.

  FIG. 3 is a photograph of the foam cell at a magnification of 100 on the cut surface of the foam duct of the comparative example. The foam cell diameter is 1500 μm or more.

  The surface roughness of each sample of the foam duct indicates Rt (maximum height) measured using a surface roughness measuring machine (Surfcom 470A manufactured by Tokyo Seimitsu Co., Ltd.). The measurement part of the surface roughness of the foam duct is a part corresponding to the front side where the surface roughness of the outer surface is rougher than the rear side in the extrusion direction of the parison (the other end side bent portion 1c shown in FIG. 1). did.

(Comparative Example 1)
A foam duct sample was foamed and blown in the same manner as in Example 1 except that carbon dioxide gas was added as a foaming agent instead of adding a carbon dioxide supercritical fluid as a foaming agent. Was measured.

  The results are shown in Table 1.

  A foam duct sample was foam blow molded in the same manner as in Example 1 except that the nucleating agent was added.

(Comparative Example 2)
A foam duct sample was foam blow molded as in (Comparative Example 1) except that the nucleating agent was added.

  The results are shown in Table 2.

  A foam duct sample was blow-molded in the same manner as in Example 1 except that polypropylene was used as the molding material and the melt tension at 230 ° C. was changed.

(Comparative Example 3)
A foam duct sample was foam blow molded in the same manner as Comparative Example 1 except that polypropylene was used as the molding material.

  The results are shown in Table 3.

  As is clear from the respective data of Samples 1 to 6 and Samples 7 to 10 in Tables 1 to 3, the foam duct according to the present invention has a surface roughness Rt of 45 μm or less on its outer surface and a foaming ratio of 2. It is a necessary condition to be within a range of 5 to 5 times. If the surface roughness is greater than Rt 45 μm, condensation tends to occur.

DESCRIPTION OF SYMBOLS 1 Foam duct 1a Center part 1b One end side bending part 1c Other end side bending part 2 Swelling part 3 Connection part 4 Closure part 5 Parting line

Claims (5)

  A foam duct characterized in that foam cells having a small foam cell diameter are uniformly distributed, the surface roughness on the outer surface is Rt 45 μm or less, and the foaming ratio is within a range of 2.5 to 5 times. 2. The foam duct according to claim 1 , wherein in the cross section of the foam duct, the foam cell has an elliptical shape, and an average length of a major axis of the foam cell is 100 μm to 500 μm . The foam duct according to claim 1 or 2, wherein the foam duct is formed using polypropylene having a melt tension at 230 ° C within a range of 0.029N to 0.049N. The foam duct according to any one of claims 1 to 3, further comprising a bent portion that is bent three- dimensionally. It claims 1-4 foam duct according to any one of the flat HitoshinikuAtsu is characterized in that Ru 0.5~1.5mm der.