Polyamide resin composition and molded article thereof

Abstract

To provide a polyamide resin composition having excellent thermal aging resistance, and a molding thereof.SOLUTION: A polyamide resin composition contains polyamide (A) 100 pts.mass, and acid-modified polyethylene (E) 3-20 pts.mass with a density of 0.915-0.925 g / cm3 and a melt flow rate (190°C, 2.16 kg load) of 0.01-0.4 g / 10 min. There is also provided a molding obtained by molding made from the polyamide resin composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin composition having excellent heat aging resistance and a molded article thereof. [Background technology]

[0002] In recent years, automobile parts made by injection molding resin compositions have been widely used to reduce the weight of automobiles and improve productivity. Among such automobile parts, cover parts for high-temperature areas (e.g., engine covers) are particularly exposed to high-temperature environments for long periods of time, and their mechanical properties (e.g., impact strength) may deteriorate due to thermal aging.

[0003] Patent Document 1 discloses an engine cover that is made primarily of polypropylene and polymethylpentene and has excellent resistance to heat deformation (shape retention) and heat discoloration, etc. However, the issue of deterioration in mechanical properties due to heat aging as described above is not fully addressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-227488 Summary of the Invention [Problem to be solved by the invention]

[0005] It is also conceivable to use polyamide, which has better impact resistance, instead of the polypropylene used in Patent Document 1. However, the present inventors believe that in order to use it as a material for automobile parts, particularly cover parts for high-temperature sections, it is necessary to further improve the heat aging resistance of polyamide. That is, an object of the present invention is to provide a polyamide resin composition having excellent heat aging resistance and a molded article thereof. [Means for solving the problem]

[0006] As a result of extensive research aimed at solving the above problems, the present inventors have found that blending a specific amount of a specific acid-modified polyethylene with polyamide is extremely effective, and that this is particularly suitable as a material for cover parts for high-temperature areas such as engine covers, and have thus completed the present invention. That is, the present invention is characterized by the following features.

[0007] [1] 100 parts by mass of one or more polyamides (A) selected from the group consisting of polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms (excluding aromatic dicarboxylic acids) and organic diamines having 2 to 13 carbon atoms, polycondensates of ω-amino acids, and ring-opening polymers of lactams, and Density 0.915~0.925g / cm 3 and comprising 3 to 20 parts by mass of an acid-modified polyethylene (E) having a melt flow rate (190°C, 2.16 kg load) of 0.01 to 0.4 g / 10 min.

[0008] [2] The polyamide resin composition according to [1], wherein the degree of acid modification of the acid-modified polyethylene (E) is 0.6 to 5% by mass. [3] A molded article made of the polyamide resin composition according to [1] or [2]. [4] The molded article according to [3], which is an automobile part. [5] The molded article according to [3], which is an engine cover. [Effects of the Invention]

[0009] According to the present invention, a resin composition having excellent heat aging resistance, in which mechanical properties such as impact resistance are not easily deteriorated even when exposed to a high-temperature environment for a long period of time, can be provided. Therefore, a molded article obtained from the polyamide resin composition of the present invention is very useful as an automobile part, particularly as a cover part for a high-temperature portion such as an engine cover. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Polyamide (A)> The polyamide (A) used in the present invention is not particularly limited, and various known polyamide resins can be used without limitation as long as the effects of the present invention are not impaired. For example, an amino acid lactam or a melt-moldable polyamide resin obtained by polycondensation reaction of a diamine and a dicarboxylic acid can be used. Specific examples of the polyamide (A) include the following resins.

[0011] (1) Polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms and organic diamines having 2 to 13 carbon atoms, such as polyhexamethylene adipamide [6,6 nylon], which is a polycondensate of hexamethylene diamine and adipic acid, polyhexamethylene azelamide [6,9 nylon], which is a polycondensate of hexamethylene diamine and azelaic acid, polyhexamethylene sebacamide [6,10 nylon], which is a polycondensate of hexamethylene diamine and sebacic acid, and polyhexamethylene dodecanoamide [6,12 nylon], which is a polycondensate of hexamethylene diamine and dodecanedioic acid. , B Polybis(4-aminocyclohexyl)methanedodecane, which is a polycondensate of s-p-aminocyclohexylmethane and dodecanedioic acid. Examples of the organic dicarboxylic acid include adipic acid, pimelic acid, and suberic acid. , Se Examples of the organic diamine include hexamethylenediamine, octamethylenediamine, nonanediamine, octanediamine, decanediamine, undecanediamine, undecanediamine, and dodecanediamine.

[0012] (2) Polycondensation products of ω-amino acids, such as polyundecaneamide [11 nylon], which is a polycondensation product of ω-aminoundecanoic acid.

[0013] (3) Ring-opening polymers of lactams, such as polycapramide [nylon 6], which is a ring-opening polymer of ε-aminocaprolactam, and polylauric lactam [nylon 12], which is a ring-opening polymer of ε-aminolaurolactam.

[0014] Among these, polyhexamethylene adipamide [6,6 nylon], polyhexamethylene azelamide [6,9 nylon], and polycapramide [6 nylon] are preferred.

[0015] In the present invention, for example, polyamide resins produced from adipic acid, isophthalic acid, and hexamethylenediamine can be used, and further, blends of two or more polyamide resins, such as a mixture of nylon 6 and nylon 6,6, can also be used.

[0016] <Acid-modified polyethylene (E)> The acid-modified polyethylene (E) used in the present invention is obtained by acid-modifying polyethylene. The polyethylene before acid-modification is typically an ethylene homopolymer, but may also be a copolymer of ethylene and a small amount of an α-olefin, provided that the effects of the present invention are not impaired.

[0017] Specific examples of α-olefins include propylene, 1-butene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, trimethyl-1-butene, ethyl-1-pentene, 1-octene, methyl-1-pentene, dimethyl-1- Examples of the α-olefins include α-olefins having 3 to 20 carbon atoms, such as hexene, trimethyl-1-pentene, ethyl-1-hexene, methylethyl-1-pentene, diethyl-1-butene, propyl-1-pentene, 1-decene, methyl-1-nonene, dimethyl-1-octene, trimethyl-1-heptene, ethyl-1-octene, methylethyl-1-heptene, diethyl-1-hexene, 1-dodecene, and 1-hexadodecene. Two or more of these α-olefins may be used in combination.

[0018] The acid-modified ethylene polymer (E) can be obtained, for example, by graft polymerizing an acid component (e.g., maleic acid or its anhydride) onto polyethylene in the presence of a radical initiator. At this time, additives described below may be added as needed. The polyethylene may be granulated in advance by a melt-kneading method. Alternatively, the acid-modified ethylene polymer (E) can be granulated into polyethylene in the presence of a radical initiator using an extruder without a solvent. The graft polymerization reaction is preferably carried out at a temperature equal to or higher than the melting point of polyethylene for 0.5 to 10 minutes.

[0019] The amount of the acid component is usually 0.01 to 15 parts by mass, and preferably 0.01 to 5 parts by mass, relative to 100 parts by mass of the polyethylene before acid modification. The amount of the radical initiator used is usually 0.001 to 1 part by mass, and preferably 0.001 to 0.3 part by mass, relative to 100 parts by mass of the polyethylene before acid modification.

[0020] Examples of the radical initiator that can be used include organic peroxides, azo compounds, and metal hydrides. The radical initiator may be used by directly mixing with the acid component and the polyethylene before acid modification, or may be used by dissolving in a small amount of an organic solvent.

[0021] Before acid modification, polyethylene has a density of 0.940 g / cm 3 More than 0.975g / cm 3 High density polyethylene with a density of 0.915 g / cm 3 More than 0.940g / cm 3 Any low density polyethylene having a density of less than 0.915 to 0.975 g / cm can be used. The density of the acid-modified polyethylene (E) is 0.915 to 0.975 g / cm 3 and preferably 0.915 to 0.970 g / cm 3 , more preferably 0.915 to 0.960 g / cm 3 is.

[0022] The melt flow rate (MFR) of the acid-modified polyethylene (E), measured in accordance with ASTM D1238 at 190° C. under a load of 2.16 kg, is preferably 0.01 to 50 g / 10 min, more preferably 0.05 to 40 g / 10 min.

[0023] The degree of acid modification (amount of acid component grafted) of the acid-modified polyethylene (E) is preferably 0.1 to 5 mass %, more preferably 0.2 to 3 mass %.

[0024] <Other ingredients> The polyamide resin composition of the present invention may contain other components (components other than the polyamide (A) and the acid-modified ethylene polymer (E)) as needed. Specific examples of the other components include: ,acid Examples of other components include antioxidants, heat stabilizers, weather stabilizers, slip agents, antiblocking agents, crystal nucleating agents, pigments, hydrochloric acid absorbers, and copper inhibitors. The amount of other components added is usually 0.01 to 10 parts by mass, and preferably 0.1 to 5 parts by mass, per 100 parts by mass of the polyamide resin composition. The other components may be added at the stage of preparing the polyamide resin composition, or before, during, or after preparing the acid-modified polyethylene (E).

[0025] <Polyamide resin composition> The polyamide resin composition of the present invention is a composition in which 3 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 5 to 20 parts by mass of the acid-modified polyethylene (E) described above is blended with 100 parts by mass of polyamide (A). Blending the acid-modified ethylene polymer (E) in this ratio results in a heat-aging-resistant polyamide resin composition in which mechanical properties such as impact resistance are resistant to deterioration even when exposed to a high-temperature environment for a long period of time.

[0026] The polyamide resin composition of the present invention can be obtained, for example, by melt-mixing polyamide (A), acid-modified polyethylene (E), and, if necessary, other components. Specifically, the above components are simultaneously or sequentially charged into a mixing device such as a Henschel mixer, V-blender, tumbler mixer, or ribbon blender, and then melt-kneaded using a single-screw extruder, multi-screw extruder, kneader, Banbury mixer, or the like. In particular, the use of a device with excellent kneading performance, such as a multi-screw extruder, kneader, or Banbury mixer, allows for the production of a high-quality polyamide resin composition in which the components are more uniformly dispersed. Furthermore, other additives, such as antioxidants, can be added at any of these stages, if necessary.

[0027] <Molded body> The molded article of the present invention can be obtained by molding the polyamide resin composition described above. The molding method is not particularly limited, and various known molding methods can be used. Among them, injection molding is preferred.

[0028] The molded article of the present invention has excellent heat aging resistance and is therefore useful as a heat aging-resistant part for high-temperature areas, and is particularly useful as a vehicle part (such as an automobile part) that is used in high-temperature areas and requires heat aging resistance. Specific examples of vehicle parts include engine covers, cylinder head covers, timing belt covers, intercooler housings, thermostat housings, and air ducts; tubes such as fuel tubes; and cable ties and other binding straps. Among these, the molded article is particularly useful as an engine cover. It is also useful not only for vehicle parts, but also as a high-temperature cover part for electrical / electronic equipment parts, mechatronics parts, and home appliance parts. [Example]

[0029] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0030] <Polyamide (A)> "Polyamide 6 (PA6)": Amilan (registered trademark) CM1026, manufactured by Toray Industries, Inc.

[0031] <Ethylene polymer before acid modification> The ethylene polymers used before acid modification were two types (HDPE-1) and (HDPE-2) of high-density polyethylene "Hizex (registered trademark)" manufactured by Prime Polymer Co., Ltd., linear low-density polyethylene "Evolue (registered trademark)" (LLDPE), and ethylene-1-butene copolymer (EBR) manufactured by Mitsui Chemicals, Inc. The properties of each ethylene polymer before acid modification are as follows:

[0032] "High-density polyethylene (HDPE-1)": density 964 kg / m 3 MFR (190°C, 2.16 kg load) 5.0 g / 10 min "High density polyethylene (HDPE-2)": density 950 kg / m 3 MFR (190°C, 2.16 kg load) 0.8 g / 10 min "Linear low-density polyethylene (LLDPE)": density 925 kg / m 3 , MFR (190℃, 2.16kg load) 1.0g / 10min "Ethylene-1-butene copolymer (EBR)": ethylene content 85 mol%, density 870 kg / m 3 MFR (190℃, 2.16kg load) 1.2g / 10min

[0033] <Preparation of Acid-Modified Polyethylene (E-1)> 10 kg of high-density polyethylene (HDPE-1) was blended with a solution of 120 g of maleic anhydride (MAH) and 6 g of 2,5-dimethyl-2,5-di-(t-butylperoxy)-3-hexyne (trade name: Perhexyne 25B) dissolved in acetone. The resulting blend was then fed into the hopper of a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., trade name: TEX30SS) with a screw diameter of 30 mm and an L / D ratio of 42 mm, and extruded into strands at a resin temperature of 250°C, a screw rotation speed of 180 rpm, and a throughput of 10 kg / hr. The resulting strands were thoroughly cooled and then granulated to obtain acid-modified polyethylene (E-1).

[0034] <Preparation of Acid-Modified Polyethylenes (E-2) to (E-5)> Acid-modified polyethylenes (E-2) to (E-5) were prepared in the same manner as for the acid-modified ethylene polymer (E-1), except that the components shown in Table 1 were used instead.

[0035] <Preparation of Acid-Modified Elastomers (E'-1) to (E'-2)> Acid-modified elastomers (E'-1) to (E'-2) were prepared in the same manner as for the acid-modified ethylene polymer (E-1), except that the components shown in Table 1 were used.

[0036] The physical properties of the acid-modified polyethylenes (E-1) to (E-5) and acid-modified elastomers (E'-1) to (E'-2) obtained as described above were measured by the following methods. The results are shown in Table 1.

[0037] (Preparation of measurement press sheet) Using a hydraulic heat press manufactured by Shinto Metal Industries Co., Ltd. set at 180°C, pressure sheet molding was performed at 7.5 MPa. Specifically, for sheets with thicknesses of 0.5 to 3 mm, the sheets were preheated without load for 5 minutes, pressed at 7.5 MPa for 2 minutes, and then compressed at 7.5 MPa using another hydraulic heat press manufactured by Shinto Metal Industries Co., Ltd. set at 20°C, and cooled for 5 minutes to obtain a measurement sample. A 5 mm thick brass plate was used as the hot plate. This sample was used to measure various physical properties.

[0038] (MFR) The melt flow rate (MFR) was measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg and 230°C and a load of 2.16 kg.

[0039] (density) In accordance with ASTM D1505, the density was measured by the density gradient tube method using the strand resin that flows out during the MFR measurement.

[0040] (Acid denaturation degree) The degree of acid modification (maleic anhydride graft amount) was measured by FT-IR at a wave number of 1780 cm -1 The values ​​were determined from a calibration curve prepared based on peak intensities.

[0041] [Table 1]

[0042] [Reference example 1] 90 parts by mass of polyamide 6 (Amilan (registered trademark) CM1026, manufactured by Toray Industries, Inc.) and 10 parts by mass of an acid-modified ethylene polymer (E-1) were mixed using a Henschel mixer to obtain a dry blend. This dry blend was fed into a twin-screw extruder (L / D = 42, 30 mmφ) set at 245°C and extruded at a screw rotation speed of 180 rpm to produce pellets of a polyamide resin composition. The pellets were dried at 80°C for 12 hours and then injection molded under the following conditions to prepare test pieces for physical property testing.

[0043] (Injection molding conditions) 50-ton injection molding machine (MEIKI M50) Cylinder temperature: 245℃ Injection pressure: 400 kg / cm 2 Mold temperature: 80℃

[0044] [Reference Examples 2 and 3, Examples 1 and 2] Pellets of the polyamide resin composition were prepared in the same manner as in Reference Example 1, except that the components shown in Table 2 were used, and test pieces for physical property tests were prepared using the pellets.

[0045] [Comparative Examples 1 to 3] Pellets of the polyamide resin composition were prepared in the same manner as in Reference Example 1, except that the components shown in Table 3 were used, and test pieces for physical property tests were prepared using the pellets.

[0046] The heat aging resistance of the test pieces of Reference Examples 1 to 3, Examples 1 and 2, and Comparative Examples 1 to 3 obtained as described above was evaluated by the following methods (1) to (3). The results are shown in Tables 2 and 3.

[0047] (1) Izod impact test Notched Izod impact strength was measured at 23°C and -40°C according to ASTM D256 using 1 / 8" thick test specimens. The test specimens were conditioned dry at 23°C for 2 days.

[0048] (2) Heat aging test The test specimens were stored in a gear oven set at 160° C. After 500 hours had passed since the start of heating, the test specimens were taken out and the notched Izod impact strength was measured again at 23° C. and −40° C. in the same manner as in (1) above.

[0049] (3) Heat aging resistance (impact strength retention rate) As an index of heat aging resistance, the retention rate of Izod impact strength was defined by the following formula. (Impact strength retention rate) = (Izod impact strength after 500 hours of heat aging test) / (Izod impact strength before heat aging test) × 100 (%)

[0050] [Table 2]

[0051] [Table 3]

[0052] As is clear from Tables 2 and 3, the polyamide resin compositions of Examples 1 and 2 and Reference Examples 1 to 3 had high impact strength retention after being exposed to an environment of 160°C for 500 hours and were excellent in heat aging resistance.

[0053] The polyamide (PA6) alone of Comparative Example 1 was inferior to the polyamide resin compositions of Examples 1-2 and Reference Examples 1-3 in heat aging resistance.

[0054] The polyamide resin composition of Comparative Example 2 was prepared by blending a low-density acid-modified elastomer (E'-1) with polyamide (PA6), and had inferior heat aging resistance to the polyamide resin compositions of Examples 1-2 and Reference Examples 1-3.

[0055] The polyamide resin composition of Comparative Example 3 was prepared by blending a relatively low-density acid-modified elastomer (E'-2) containing an antioxidant with polyamide (PA6). This composition had poorer heat aging resistance than the polyamide resin compositions of Example 2 and Reference Example 1, which were prepared by blending relatively high-density polyethylenes (E-3) and (E-5) containing antioxidants with polyamide (PA6). [Industrial Applicability]

[0056] The polyamide resin composition of the present invention has excellent heat aging resistance, and thus molded articles thereof are useful as heat aging-resistant parts for high-temperature use in fields such as vehicle parts, electric / electronic equipment parts, mechatronics parts, and home appliance parts.

Claims

1. 100 parts by mass of one or more polyamides (A) selected from the group consisting of polycondensates of organic dicarboxylic acids having 4 to 12 carbon atoms (excluding aromatic dicarboxylic acids) and organic diamines having 2 to 13 carbon atoms, polycondensates of ω-amino acids, and ring-opening polymers of lactams; and Density is 0.915 to 0.925 g / cm ３ and comprising 3 to 20 parts by mass of an acid-modified polyethylene (E) having a melt flow rate (190°C, 2.16 kg load) of 0.01 to 0.4 g / 10 min and an acid modification degree of 0.6 to 5 mass%, Does not contain semi-aromatic polyamides A polyamide resin composition containing no resin components other than the polyamide (A) and the acid-modified polyethylene (E).

2. A molded article made from the polyamide resin composition according to claim 1.

3. The molded article according to claim 2, which is an automobile part.

4. 3. The molded article according to claim 2, which is an engine cover.

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