PC / ABS resin and automotive interior component formed therefrom

Abstract

To provide a PC / ABS resin having excellent impact resistance with improved anisotropy, and an automotive interior component formed therefrom.SOLUTION: A PC / ABS resin of the present invention, which is a polymer alloy of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS), is configured such that the PC has a viscosity-average molecular weight of 27,500 or more, the ABS has a melt flow rate of 45 g / 10 min or less as measured according to JIS K 7210 (220°C, 10 kg load), and the PC content is 65 mass% or more relative to the total mass of the PC and the ABS. An automotive interior component 10 is formed from the PC / ABS resin.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to PC / ABS resins and automotive interior parts formed therefrom. [Background technology]

[0002] Automobile interior parts such as instrument panels and door panels require impact resistance, and therefore it is necessary to use resin materials with excellent impact resistance when molding these parts. There are various resin materials with excellent impact resistance, and it is known that a polymer alloy of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS) (hereinafter referred to as "PC / ABS resin") also has high impact resistance (Patent Document 1). This PC / ABS resin is an alloy resin material that combines the excellent impact resistance inherent to PC with the easy moldability and secondary processability (paintability and suitability for plating) that are characteristics of ABS, and is widely used for automobile interior parts, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 38-15225 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inventors of the present application have found that when injection molding automobile interior parts with conventional PC / ABS resin, expected impact resistance cannot be obtained in the direction perpendicular to the resin flow direction (MD direction). As a result of performing a Charpy impact test on test pieces cut in the MD direction and test pieces cut in the TD direction from a flat plate injection molded with a commercially available grade PC / ABS resin, the Charpy impact value of the test pieces in the TD direction was lower than that of the test pieces in the MD direction, and the ratio of the value of the test pieces in the MD direction to the value of the test pieces in the TD direction (MD / TD ratio) was 2.3 to 4.6, showing strong anisotropy. In addition, the fracture mode of the test pieces in the TD direction was complete fracture. Thus, when the impact resistance of the molded product in the TD direction is low and there is strong anisotropy, there are problems such as the position of the gate in the mold for injection molding the automobile interior part being limited, and the design of the automobile interior part itself being restricted.

[0005] In view of the above problems, the present invention has an object to provide a PC / ABS resin having improved anisotropy and excellent impact resistance, and an automobile interior part formed therefrom. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention is a polymer alloy (PC / ABS resin) of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS), in which the viscosity average molecular weight of the PC is 27,500 or more, the melt flow rate of the ABS measured in accordance with JIS K 7210 (220°C, 10 kg load) is 45 g / 10 min or less, and the content of the PC is 65 mass % or more of the total mass of the PC and the ABS.

[0007] In another embodiment, the present invention provides an automobile interior part formed from a polymer alloy (PC / ABS resin) of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS), in which the viscosity average molecular weight of the PC is 27,500 or more, the melt flow rate of the ABS measured in accordance with JIS K 7210 (220°C, 10 kg load) is 45 g / 10 min or less, and the PC accounts for 65 mass % or more of the total mass of the PC and the ABS. Effect of the Invention

[0008] Thus, according to the present invention, it is possible to provide a PC / ABS resin having improved anisotropy and excellent impact resistance, and an automobile interior part formed therefrom. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a front view illustrating an example of an instrument panel. [Diagram 2] 2 is a front perspective view showing a garnish attached to the instrument panel shown in FIG. 1. [Diagram 3] 3 is a rear perspective view illustrating a method of attaching the garnish shown in FIG. 2 to the instrument panel. FIG. [Figure 4] FIG. 2 is a plan view showing the locations where test pieces were taken in the TD direction in the examples. [Diagram 5] FIG. 2 is a plan view showing the locations where test pieces were taken in the MD direction in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a PC / ABS resin according to the present invention and an automobile interior part formed therefrom will be described with reference to the accompanying drawings.

[0011] As an example of an automobile interior part, Fig. 1 shows an instrument panel for a right-hand drive vehicle provided at the front of the passenger compartment. As shown in Fig. 1, an instrument panel (not shown) including a speedometer, a fuel gauge, etc. is provided on the right side of an instrument panel main body 1, a design panel covering the periphery thereof, a so-called cluster panel 2, and an upper storage box 3 is provided on the left side. A car navigation system 4 is installed in the center, and a design panel covering the periphery thereof, a so-called garnish 10, is provided. A design panel for an air conditioning device such as an air conditioner or a heater, a so-called heater control panel 5, is provided below the garnish 10. In addition, a center louver mechanism 7 serving as an air conditioning device outlet in the center of the passenger compartment is provided on both sides of the garnish 10.

[0012] Automobile interior parts such as the cluster panel 2, storage box 3, garnish 10, and heater control panel 5 are each molded from resin and positioned so as to protrude further into the interior than the center louver mechanism 7, and are configured with hollow spaces in their internal cross sections to provide a cushioning effect for absorbing shocks.

[0013] Moreover, these automobile interior parts are generally configured to be removable to allow for maintenance and replacement. For example, the garnish 10 is a thin frame that surrounds the display of the car navigation system 4, and is configured to protrude from the instrument panel main body 1 to the interior of the vehicle, as shown in Fig. 2. The garnish 10 is removably provided on the instrument panel main body 1, and is configured so that the mounting portion of the in-vehicle device can be exposed by removing the garnish 10 prior to removing the in-vehicle device.

[0014] As shown in Fig. 3, the garnish 10 is mainly composed of an upper frame body 11, a lower frame body 12, a right side frame body 13, and a left side frame body 14, which define a central opening, as viewed from inside the vehicle compartment. The longitudinal direction of the garnish 10 is along the vehicle width direction, i.e., the upper frame body 11 and the lower frame body 12 are longer than the left and right side frame bodies 13, 14. The garnish 10 is attached to the instrument panel body by inserting a positioning pin 15 protruding from the garnish 10 into a positioning hole 7 of a bracket 6 of the instrument panel body, and fastening the garnish 10 by inserting a screw 17 into a mounting hole (not shown) of the garnish 10. The garnish 10 is also fixed by inserting a clip 16 of the garnish 10 into a locking hole (not shown) of the instrument panel body.

[0015] Although such garnish 10 is integrally molded from PC / ABS resin and has excellent impact resistance, conventional PC / ABS resin has low impact resistance in the direction perpendicular to the resin flow direction (MD direction) (TD direction) and has strong anisotropy, so that if an occupant were to collide with the garnish 10 in an accident or the like, it is thought that the collision would be likely to occur against the upper side of the upper frame 11. Therefore, in order to prevent this part from being in the TD direction during injection molding, it was necessary to provide the gate of the mold on the right side frame 13 side or the left side frame 14 side of the garnish 10. If the position of the gate in the mold is limited in this way, the design of the garnish 10 itself would be restricted.

[0016] Thus, the PC / ABS resin of this embodiment contains PC with a viscosity average molecular weight of 27500 or more and ABS with a melt flow rate (MFR) of 45 g / 10 min or less as measured by JIS K 7210 (220°C, 10 kg load), with PC being 65 mass% or more of the total mass of PC and ABS. By using the PC / ABS resin of this embodiment, the ratio of the Charpy impact value in the MD direction to the Charpy impact value in the TD direction (MD / TD ratio) in the molded product can be made 2.0 or less, improving anisotropy.

[0017] Although this is currently speculation, PC / ABS resin has a sea-island structure, where ABS, which has good fluidity, usually shows a continuous structure, with PC scattered as islands in the sea of ​​ABS. In this embodiment, by increasing the mass ratio of PC to 65% or more, the sea-island relationship is reversed, with PC showing a continuous structure, and the structure changes to one where ABS is scattered as islands in the sea of ​​PC, and it is believed that the good impact resistance of PC is expressed and the anisotropy is improved.

[0018] In this embodiment, the ABS used must have a high viscosity, with an MFR of 45 g / 10 min or less. It is generally known that a low-viscosity material with good fluidity is likely to form a sea structure, and in this embodiment, by using a high-viscosity ABS, the reversal of the sea-island structure can be caused even when the mass % of PC is relatively low. The MFR of the ABS is preferably 40 g / 10 min or less, and more preferably 35 g / 10 min or less. The lower limit of the MFR of the ABS is not particularly limited, but may be, for example, 20 g / 10 min or more, or may be 25 g / 10 min or more.

[0019] The mass ratio of PC is preferably 67% or more, more preferably 69% or more. The upper limit of the mass ratio of PC is not particularly limited, but may be, for example, 80% or less, or 75% or less. In addition, by using PC having a viscosity average molecular weight of 27500 or more, the impact resistance of the PC itself having a sea structure can be increased, and therefore the anisotropy of the PC / ABS resin can be improved. The viscosity average molecular weight of PC is preferably 28000 or more, more preferably 29000 or more. From the viewpoint of fluidity described later, the upper limit of the viscosity average molecular weight of PC is, for example, preferably 40000 or less, more preferably 35000 or less. In this specification, the viscosity average molecular weight is calculated by inserting the specific viscosity (ηSP) calculated from a solution in which 0.7 g of polycarbonate resin is dissolved in 100 ml of methylene chloride at 20° C. into the following formula. ηSP / c=[η]+0.45×[η]2c (where [η] is the intrinsic viscosity) [η]=1.23×10 -4 M 0.83 c=0.7

[0020] It is preferable to use PC with a high viscosity, with an MFR of 6 g / 10 min or less. Usually, the higher the viscosity average molecular weight of PC, the higher the viscosity tends to be. It is possible to use a PC with a low viscosity so that the PC has a sea structure, but as mentioned above, it is necessary to increase the impact resistance of the PC itself, so that a PC with a high viscosity average molecular weight, i.e., a high viscosity PC is used. However, if the viscosity of PC is too high, the flowability during injection molding is poor, so the lower limit of the MFR of PC is preferably 2 g / 10 min or more, more preferably 3 g / 10 min or more.

[0021] By using PC having a predetermined viscosity average molecular weight and ABS having a predetermined MFR in a predetermined mass ratio, a PC / ABS resin having excellent impact resistance with improved anisotropy and an MD / TD ratio of 2.0 or less in the Charpy impact value can be obtained. The MD / TD ratio of the Charpy impact value is preferably 1.8 or less, more preferably 1.6 or less. The lower limit of the MD / TD ratio of the Charpy impact value is not particularly limited, but may be, for example, 1.0 or more, or 1.2 or more. In addition, by using this PC / ABS resin with improved anisotropy for automobile interior parts such as instrument panel garnishes, the degree of freedom of the gate position in the mold can be increased, and the degree of freedom of the design of the automobile interior parts can also be increased. EXAMPLES

[0022] [Example 1] Polycarbonate (PC) was a linear aromatic polycarbonate resin with a viscosity average molecular weight of 30,000 (Teijin, grade: K-1300Y, MFR: 3g / 10min), and acrylonitrile-butadiene-styrene copolymer (ABS) was an ABS resin with an MFR of 31g / 10min (Santac, Japan A&L, grade: AT-07). The PC / ABS was mixed in a mass ratio of 70 / 30 by a twin-screw kneader, and then injection molded at a resin temperature of 240°C to produce a flat-plate-shaped PC and ABS polymer alloy (PC / ABS resin) (80mm x 87mm x thickness 3mm, Finegate flat plate). Then, strip test pieces (10mm x 80mm x thickness 3mm) in the resin flow direction (MD direction) and perpendicular direction (TD direction) were cut out from this PC / ABS resin flat molded product by an automatic sample molding machine. The sampling locations of the test specimens in the MD direction are shown in Fig. 4, and the sampling locations of the test specimens in the TD direction are shown in Fig. 5.

[0023] As shown in FIG. 4, the flat plate molded product 30 was molded by resin flowing from the gate 33 of the injection molding machine in the direction of the arrow. The strip test piece 31 in the MD direction was cut out from the flat plate molded product 30 so that its longitudinal direction was the flow direction indicated by the arrow. The distances a from the center line of the flat plate molded product 30 to the center lines of the five test pieces (MD1 to MD5) in the MD direction were 32 mm, 16 mm, 0 mm, 16 mm, and 32 mm. On the other hand, as shown in FIG. 5, the strip test piece 32 in the TD direction was cut out so that the longitudinal direction of the strip test piece was perpendicular to the flow direction. The distances b from the end face on the gate 33 side of the flat plate molded product 30 to the center lines of the test pieces (TD1 to TD5) in the TD direction were 15 mm, 31 mm, 47 mm, 63 mm, and 79 mm.

[0024] Both the TD and MD test pieces were notched (R=0.25) so that the remaining width was 8 mm. Then, a Charpy impact test was performed to measure the Charpy impact value of each test piece. The Charpy impact test was performed in accordance with JIS K 7111 using a Charpy impact tester (manufactured by Toyo Seiki Co., Ltd., model IMPACT TESTER IT). The test temperature was 23°C, and the hammer was 4J. In addition, the fracture morphology of the test pieces in the TD direction after the Charpy impact test was observed. The results are shown in Table 1.

[0025] [Comparative Examples 1 to 4] A PC / ABS resin plate was molded in the same manner as in Example 1, except that, in addition to the above-mentioned K-1300Y, a linear aromatic polycarbonate resin with a viscosity average molecular weight of 25,000 (Teijin's Panlite, grade: L-1250Z, MFR: 9g / 10min) was used as the PC, in addition to the above-mentioned AT-07, an ABS resin with an MFR of 58g / 10min (Nippon A&L's Santac, grade: AT-05) was used as the ABS, and the PC / ABS ratio was set to the ratio shown in Table 1. Test pieces cut from the molded flat plates were subjected to Charpy impact tests. The results are shown in Table 1.

[0026] [Table 1]

[0027] The Charpy impact values ​​in Table 1 are expressed as the ratio of the average of five test pieces in the MD direction to the average of five test pieces in the TD direction (MD / TD ratio), and the relative value (MD relative value) of the average of five test pieces in the MD direction of other Examples and Comparative Examples when the average of the five test pieces in the MD direction of Comparative Example 4 is set to 1. Conventionally, with PC / ABS resin, the Charpy impact value of the test pieces in the TD direction was significantly lower than that of the test pieces in the MD direction, as in Comparative Examples 1 to 4, and the MD / TD ratio exceeded 2. In contrast, the MD / TD ratio of the Charpy impact value of Example 1 was 1.4, and anisotropy could be improved. Moreover, the Charpy impact value in the MD direction of Example 1 was 1.12 when the Charpy impact value of Comparative Example 4 was set to 1, and excellent impact strength was maintained.

[0028] The fracture morphology was evaluated into four categories: complete fracture (the test piece was broken into two or more pieces), hinge fracture (incomplete fracture in which only a thin hinge-like surface layer with low bending strength remained together as a test piece that could not be separated), partial fracture (incomplete fracture that does not meet the definition of hinge fracture), and non-fracture (the test piece was simply bent on the test piece support base and did not break). In Comparative Examples 1 to 4, the test pieces in the TD direction were all completely fractured. In contrast, in Example 1, both the test pieces in the MD and TD directions were partially fractured. [Explanation of symbols]

[0029] 1. Instrument Panel 10 Garnish 11 Upper frame 12 Lower frame 13 Right side frame 14 Left side frame 30 Flat plate molded products 31, 32 Test pieces Gate 33

Claims

1. A polymer alloy (PC / ABS resin) of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS), The viscosity average molecular weight of the PC is 27,500 or more, The melt flow rate of the ABS measured according to JIS K 7210 (220° C., 10 kg load) is 45 g / 10 min or less, A PC / ABS resin, in which the PC accounts for 65 mass % or more of the total mass of the PC and the ABS.

2. An automobile interior part formed of a polymer alloy (PC / ABS resin) of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS), The viscosity average molecular weight of the PC is 27,500 or more, The melt flow rate of the ABS measured according to JIS K 7210 (220° C., 10 kg load) is 45 g / 10 min or less, The automobile interior part, wherein the PC accounts for 65 mass% or more of the total mass of the PC and the ABS.

3. 3. The automobile interior part according to claim 2, wherein the automobile interior part is a frame-shaped garnish that covers a periphery of an in-vehicle device disposed in the center of an instrument panel.

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