Polyamide resin composition

Abstract

A polyamide resin composition is provided which can be blow molded while concurrently satisfying blow moldability and uniform wall thickness of the molten resin, exhibits excellent thermal stability when the resin composition is accumulated as a melt and thereby gives molded articles with a good surface appearance, and is further excellent in impact resistance at room and low temperatures. The polyamide resin composition includes, based on 100 mass % of the polyamide resin composition, 40 to 84 mass % of a polyamide resin (A), not less than 15 mass % of an olefin-based ionomer (B), 0 to 10 mass % of an impact modifier (C), and 0.1 to 3 mass % of heat resistant agents (D). The polyamide resin (A) includes at least one selected from the group consisting of aliphatic copolyamides (A-1) and aromatic copolyamides (A-2). The heat resistant agents (D) include two or more kinds of organic hindered phenol heat resistant agents (D-1).

Claims

1. A polyamide resin composition comprising, based on 100 mass % of the polyamide resin composition, 40 to 84 mass % of a polyamide resin (A), not less than 15 mass % of an olefin-based ionomer (B), 0 to 10 mass % of an impact modifier (C), and 0.1 to 3 mass % of heat resistant agents (D), wherein the polyamide resin (A) comprises an aliphatic copolyamide (A-1), an aromatic copolyamide (A-2) and an aliphatic homopolyamide (A-3), wherein the heat resistant agents (D) comprises two or more kinds of organic hindered phenol heat resistant agents (D-1), wherein the impact modifier (C) is at least one selected from the group consisting of (ethylene and/or propylene)/α-olefin-based copolymers and (ethylene and/or propylene)/(α,β-unsaturated carboxylic acid and/or unsaturated carboxylic acid ester)-based copolymers, and wherein the impact modifier (C) has at least one group selected from the group consisting of a carboxyl group, an acid anhydride group, a carboxylic acid ester group, a carboxylic imide group, a carboxylic amide group and an epoxy group.

2. The polyamide resin composition according to claim 1, wherein the heat resistant agents (D) further comprise a phosphorus heat resistant agent (D-2).

3. The polyamide resin composition according to claim 2, wherein the olefin-based ionomer (B) has a melting point of 75 to 100° C., a density of 940 to 980 kg/m.sup.3, and a content of zinc element of not less than 3 mass % as measured by inductively coupled plasma-optical emission spectrometry.

4. The polyamide resin composition according to claim 2, wherein when the resin is extruded into a 15 cm strand at a measurement temperature of 250° C. and a shear rate of 121.6 sec.sup.−1 in accordance with ISO 11443 using a capillary rheometer having a capillary die 1.0 mm in inner diameter and 10 mm in length, the strand being then sampled and solidified by cooling at room temperature for 24 hours, the diameter of the strand is less than 3.00 mm.

5. The polyamide resin composition according to claim 1, wherein the olefin-based ionomer (B) has a melting point of 75 to 100° C., a density of 940 to 980 kg/m.sup.3, and a content of zinc element of not less than 3 mass % as measured by inductively coupled plasma-optical emission spectrometry.

6. The polyamide resin composition according to claim 1, wherein when the resin is extruded into a 15 cm strand at a measurement temperature of 250° C. and a shear rate of 121.6 sec.sup.−1 in accordance with ISO 11443 using a capillary rheometer having a capillary die 1.0 mm in inner diameter and 10 mm in length, the strand being then sampled and solidified by cooling at room temperature for 24 hours, the diameter of the strand is less than 3.00 mm.

Description

EXAMPLES

(1) Hereinbelow, the present invention will be described in more detail based on Examples and Comparative Examples. However, it should be construed that the scope of the present invention is not limited to such Examples. In Examples and Comparative Examples, properties of resins and molded articles were evaluated using the following methods.

(2) (Productivity)

(3) Various productivity indexes were checked by performing melt-kneading with twin-screw kneader TEX44HCT having a cylinder diameter of 44 mm and L/D of 35, at a cylinder temperature of 250° C., a screw rotational speed of 120 rpm, and a discharge of 40 kg/hrs.

(4) (1) Resin Temperature

(5) The temperature of the resin in the kneader was measured near the die head before the strand was discharged. An excessively high resin temperature can cause deterioration in quality.

(6) (2) Torque (Electric Current)

(7) The screw current value during kneading was measured to simulate the torque. The lower the current value, the more the screw rotational speed can be increased and the higher the productivity.

(8) (3) Conditions of Strands

(9) The strand conditions were evaluated as good when the surface was smooth without any irregularities, and were evaluated as poor when the surface was irregular or markedly rough.

(10) From the results of the above productivity indexes (1) to (3), the productivity was evaluated based on the following criteria.

(11) ◯: The resin composition satisfied all requirements of 335° C. or lower resin temperature, 134 A or lower torque and good strand conditions.

(12) x: The productivity was judged as x when the resin composition failed to satisfy any one or more of the requirements under the same criteria as ◯.

(13) (Blow Moldability)

(14) Blow moldability was evaluated using accumulator head blow molding machine DA-50 manufactured by PLACO Co., Ltd. Molded articles were obtained under measurement conditions where the cylinder temperature was 250° C., the screw rotational speed was 40 rpm, the die diameter was 50 mm, and the mold was a cylindrical 3-liter bottle mold.

(15) (1) Extrudability

(16) The current value during rotation of the screw was measured as an index of extrudability. The lower the current value, the higher the extrudability, the more the screw rotational speed can be increased, and the shorter the blow molding cycle.

(17) (2) Parison Characteristics

(18) (2-1) Amount of Droop in 5 Seconds (Amount of Drawdown in 5 Seconds after Injection)

(19) A parison was injected from the accumulator and was video-recorded. The length of the resin droop after the lapse of 5 seconds was read on the video. The smaller the amount of droop in 5 seconds, the higher the parison shape retention.

(20) (2-2) Amount of Droop in 2 Seconds (Amount of Drawdown in 2 Seconds after Injection)

(21) The amount of droop in 2 seconds was read on the video in the same manner as the amount of droop in 5 seconds was measured. The smaller the amount of droop in 2 seconds, the higher the parison shape retention.

(22) (3) Conditions of Inner Surface

(23) Blow molded articles were visually evaluated as good when there were no burn marks on all the inner and outer surfaces and the entirety of the molded article was free from yellowing.

(24) (4) Irregularities on Inner Surface Caused by Accumulation

(25) To evaluate the uniformity in wall thickness, the inner surface of a blow molded article produced after accumulation in the apparatus was visually inspected for irregularities and was evaluated based on the following criteria. The less the irregularities, the higher the uniformity in wall thickness.

(26) Absent: The inner surface was free from large irregularities and was uniform and similar in conditions to the outer surface.

(27) Present: The inner surface had large irregularities and was not the same in conditions as the outer surface.

(28) From the results of the above blow moldability indexes (1) to (4), the blow moldability was evaluated based on the following criteria.

(29) ◯: The blow moldability was judged as ◯ when all the following requirements were satisfied. As an index of extrudability, the current value was less than 40 A. The amount of droop in 5 seconds or the amount of droop in 2 seconds was less than 50 cm. The blow molded article had no burn marks on all the inner and outer surfaces and was free from yellowing over the entirety of the molded article, or the blow molded article had burn marks on the inner surface only in some areas at the blown-in portion and the pinched-off portion. There were no irregularities on the inner surface caused by accumulation.

(30) x: The blow moldability was judged as x when any one or more of the requirements were not satisfied under the same criteria as ◯.

(31) (Properties at 23° C. and Properties at −60° C.)

(32) Type-A or type-B test pieces according to ISO standards were fabricated by injection molding and were tested to obtain data of mechanical properties.

(33) (1) Tensile Stress at Yield and Nominal Tensile Strain at Yield, and Nominal Tensile Strain at Break and Tensile Strength

(34) Measurement was performed at 23° C. and −60° C. in accordance with ISO 527-2/1A/50 using an Instron tensile tester, model 5567.

(35) (2) Tensile Modulus

(36) Measurement was performed at 23° C. in accordance with ISO 527-2/1A/1 using an Instron tensile tester, model 5567.

(37) (3) Charpy Impact Strength

(38) In accordance with ISO 179-1/1eA, 4 mm thick test pieces (n=10) having a notch shape A were tested by an edgewise impact test at −40° C. using Charpy impact tester No. 258-PC manufactured by YASUDA SEIKI SEISAKUSHO, LTD.

(39) From the results of the properties (1) and (2) at 23° C. and −60° C., the properties at 23° C. and at −60° C. were evaluated based on the following criteria.

(40) ◯: The test pieces satisfied all of 100% or more nominal tensile strain at break at 23° C., more than 17% nominal tensile strain at break at −60° C. and 1500 MPa or more tensile modulus at 23° C.

(41) x: The properties were judged as x when the test pieces failed to satisfy any one or more of the requirements under the same criteria as ◯.

(42) (Quality)

(43) (1) Melt Viscosity

(44) The melt viscosity was measured in accordance with ISO 11443 using Capilograph 1D, model P-C, manufactured by Toyo Seiki Seisaku-sho, Ltd. The measurement temperature was 250° C., and the orifice used was 1.0 mm in hole diameter and 10 mm in length (L/D=10). The melt viscosity was measured at each of the shear rates of 12.16 sec.sup.−1, 60.8 sec.sup.−1 and 121.6 sec.sup.−1. Excessively high melt viscosity increases the load on the kneader and the blow molding machine and causes a limitation on discharge, thus being not preferable in terms of productivity.

(45) (2) Strand Diameter

(46) Similarly to the measurement of melt viscosity, the resin was extruded at a measurement temperature of 250° C. and each of the shear rates of 12.16 sec.sup.−1, 60.8 sec.sup.−1 and 121.6 sec.sup.−1, using a capillary die 1.0 mm in inner diameter and 10 mm in length. The strand that had been extruded 15 cm was sampled and solidified by cooling at room temperature for 24 hours. The diameter of the central portion was measured with a caliper to determine the strand diameter. An excessive increase in strand diameter is undesirable for the reason that a swell cannot be controlled during blow molding and a molded article will be out of a target size.

(47) (3) Measurement of Melting Point Tm and Crystallization Temperature Tc

(48) Measurement was performed in a nitrogen atmosphere in accordance with ISO 11357-3 at a heat-up rate of 20° C./min using PYRIS Diamond DSC manufactured by PerkinElmer Co., Ltd.

(49) (4) Heat Resistance

(50) Type-A test pieces according to ISO standards were fabricated by injection molding and were tested to obtain data of heat resistance. The test pieces were heat treated in a hot air oven preset to 200° C., and were taken out 4.5 hours later. After being cooled, the test pieces were tested in accordance with ISO 527-2/1A/50 using Instron tensile tester, model 5567, at −60° C. to determine the tensile stress at yield and the tensile strain at break.

(51) (5) Blister Resistance

(52) A 4 mm thick blow molded article was placed into an autoclave filled with high-pressure hydrogen gas at 87.5 MPa and 85° C., and was held therein for more than 20 hours. The autoclave was decompressed in 0.5 min, and the molded article was taken out. The test piece was visually inspected for the presence or absence of blister-like appearance abnormality.

(53) From the results of the above quality tests (1) to (5), the quality was evaluated based on the following criteria.

(54) ◯: The quality was judged as ◯ when all the following requirements were satisfied. The melt viscosity at a shear rate of 12.16 sec.sup.1 was less than 15,000. The strand diameter at a shear rate of 121.6 sec.sup.−1 was less than 2.7 mm. The difference between the melting point Tm and the crystallization temperature Tc was more than 45° C. The heat resistance satisfied more than 15% tensile strain at break in the tensile test at −60° C. after treatment at 200° C. for 4.5 hours. No blisters were found in the blister resistance test.

(55) x: The quality was judged as x when any one or more of the requirements were not satisfied under the same criteria as ◯.

Examples 1 to 14 and Comparative Examples 1 to 11

(56) Target polyamide resin composition were prepared as pellets by melt kneading the components shown in Table 1 using twin-screw kneader TEX44HCT having a cylinder diameter of 44 mm and L/D of 35, at a cylinder temperature of 250° C., a screw rotational speed of 120 rpm, and a discharge of 40 kg/hrs.

(57) The unit for the composition in the table is mass % relative to the whole resin composition taken as 100 mass %.

(58) The pellets obtained were used for the evaluation of the properties described above. The results obtained are described in Table 1.

(59) The abbreviations in the table are as follows.

(60) (Polyamide Resins)

(61) PA6: Polyamide 6, product name “1030B” manufactured by UBE INDUSTRIES, LTD.

(62) PA6/66: Polyamide 6/66, product name “5034B” manufactured by UBE INDUSTRIES, LTD.

(63) Aromatic PA6T/6I: Polyamide 6T/6I, product name “Grivory G21” manufactured by EMS-CHEMIE (Japan) Ltd.

(64) (Olefin-Based Ionomers)

(65) Ionomer-1: Density: 960 kg/m.sup.3, melting point: 88° C., melt flow rate: 0.9 g/10 min, zinc content: 3.4 mass %, ethylene-methacrylic acid copolymer, metal ion: zinc, product name “HIMILAN (registered trademark) 1706” manufactured by DOW-MITSUI POLYCHEMICALS CO., LTD.

(66) Ionomer-2: Density: 950 kg/m.sup.3, melting point: 96° C., melt flow rate: 1.0 g/10 min, zinc content: 2.9 mass %, ethylene-methacrylic acid copolymer, metal ion: zinc, product name “HIMILAN (registered trademark) AM7328T” manufactured by DOW-MITSUI POLYCHEMICALS CO., LTD.

(67) Ionomer-3: Density: 960 kg/m.sup.3, melting point: 95° C., melt flow rate: 1.0 g/10 min, zinc content: 2.9 mass %, ethylene-methacrylic acid copolymer, metal ion: zinc, product name “HIMILAN (registered trademark) 1554W” manufactured by DOW-MITSUI POLYCHEMICALS CO., LTD.

(68) Ionomer-4: Density: 950 kg/m.sup.3, melting point: 101° C., melt flow rate: 1.1 g/10 min, zinc content: 1.6 mass %, ethylene-methacrylic acid copolymer, metal ion: zinc, product name “HIMILAN (registered trademark) AM7326” manufactured by DOW-MITSUI POLYCHEMICALS CO., LTD.

(69) (Impact Modifiers)

(70) m-EBR: Maleic anhydride-modified ethylene-butene copolymer, product name “TAFMER (registered trademark) MH5020” manufactured by Mitsui Chemicals, Inc.

(71) m-LLDPE: Maleic anhydride-modified linear low-density polyethylene, product name “UBE BOND F3000” manufactured by UBE-MARUZEN POLYETHYLENE.

(72) (Heat Resistant Agents)

(73) Heat resistant agent 1: Phenolic antioxidant (N,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), product name “Irganox 1098” manufactured by BASF.

(74) Heat resistant agent 2: Phenolic antioxidant (3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane), product name “Sumilizer GA-80” manufactured by Sumitomo Chemical Co., Ltd.

(75) Heat resistant agent 3: Phosphorus antioxidant (tris(2,4-di-t-butylphenyl) phosphite), product name “Irgafos 168” manufactured by BASF.

(76) Heat resistant agent 4: Phenolic antioxidant (pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]), product name “Irganox 1010” manufactured by BASF.

(77) (Dispersant)

(78) Dispersant: Nonionic activator, product name “Value-7220” manufactured by Marubishi Oil Chemical Corporation.

(79) TABLE-US-00001 TABLE 1 Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. Units 1 2 3 4 5 6 7 8 9 10 11 12 13 Formu- Compound formulation lation PA6 1030B mass % 53.8 48.8 38.8 48.8 48.8 48.8 48.8 49.3 48.8 58.8 49.0 48.8 48.8 PA6/66 5034B mass % 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Aromatic Grivory mass % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 PA 6T/6I G21 Ionomer-1 Himilan mass % 20.0 25.0 35.0 22.5 20.0 17.5 15.0 25.0 25.0 15.0 25.0 1706 Ionomer-2 Himilan mass % 25.0 AM7328T Ionomer-3 Himilan mass % 25.0 1554W Ionomer-4 Himilan mass % AM7326 m-EBR Tafmer mass % 2.5 5.0 7.5 10.0 MH5020 m-LLDPE F3000 mass % Heat Irganox mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 resistant 1098 agent 1 Heat Sumilizer mass % 0.50 0.50 resistant GA-80 agent 2 Heat Irgafos168 mass % 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 resistant agent 3 Heat Value- mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 1.00 0.50 0.50 0.50 0.50 resistant 7220 agent 3 Dispersant Value- mass % 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 7220 Produc- Compunding Resin ° C. 314 315 305 319 325 318 334 315 315 314 315 306 308 tivity status temperature TEX44HCT Torque Amp 119 118 114 120 122 125 130 117 117 118 118 113 115 (electric current) Discharge of Strand Good Good Good Good Good Good Good Good Good Good Good Good Good 40 kg/hrs conditions Rotational speed 120 rpm Judge ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Shaping Blow moldability proper- Extrudability Extruder A 30 37 33 35 37 39 39 36 34 32 37 32 31 ties Screw torque- rotation (rated ampere: 56 A) Parison Drawdown cm 30 5 5 10 15 15 15 5 5 >50 20 >50 >50 characteristics in 5 sec and and after fell fell injection 1 m retention Drawdown cm 10 5 0 5 5 5 5 5 5 35 5 5 5 in 2 sec after injection Other — molding defects Molded Inner — Good Good Good Good Good Good Good Good Good Good Local Good Good article surface bum quality conditions marks at pinched- off portion Irregularities — Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent on inner surface by accumulation Judge ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Quality Properties at 23° C. (proper- Tensile stress ISO 527-2/ MPa 58 54 42 55 52 50 48 54 52 62 55 57 56 ties at yield 1A/50 Norminal ISO 527-2/ % 5 5 6 4 5 5 5 5 5 5 5 4 4 tensile strain 1A/50 at yield Norminal ISO 527-2/ % 140 220 235 183 175 200 157 220 240 132 160 234 217 tensile strain 1A/50 at break Tensile ISO527-2/ MPa 64 66 66 65 62 61 58 65 63 62 55 72 71 strength 1A/50 Tensile ISO527-2/ MPa 2,100 2,019 1,553 1,861 1,806 1,810 1,671 2,050 2,000 2,251 2,100 1,935 1,943 modulus 1A/1 Charpy ISO179-1/ kJ/m.sup.2 29 33 56 35 42 51 88 32 30 24 30 27 29 notched 1eA impact strength at −40° C. Quality Extremely cold tensile (low properties at −60° C. temper- Tensile stress ISO 527-2/ MPa 110 108 97 101 98 95 92 107 105 113 109 103 103 ature at yied 1A/50 Norminal ISO 527-2/ % 11 11 15 11 11 11 11 11 10 10 10 10 10 tensile strain 1A/50 at yield Norminal ISO 527-2/ % 23 25 34 27 23 25 25 27 25 19 22 24 21 tensile strain 1A/50 at break Tensile ISO527-2/ MPa 110 108 97 101 98 95 92 107 105 113 109 103 103 strength 1A/50 Judge ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Quality Fluidity, thermal (other characteristics, heat proper- resistance ties) Melt Capilo 12.16 Pa .Math. s 4,710 5,517 6,597 6,580 7,550 8,655 9,720 5,680 5,396 4,892 5,230 3,393 3,440 viscosity graph sec.sup.−1 L/D10, 0.02 60.8 Pa .Math. s 2,600 3,000 3,345 3,370 3,654 4,062 4,460 3,090 2,936 2,638 2,920 2,012 1,949 250° C. or less sec.sup.−1 water 121.6 Pa .Math. s 1,943 2,132 2,329 2,370 2,578 2,789 3,075 2,195 2,085 2,004 2,010 1,477 1,416 content sec.sup.−1 Strand 12.16 mm 1.55 1.60 1.70 1.60 1.55 1.50 1.50 1.60 1.60 1.60 1.60 diam- sec.sup.−1 eter 60.8 mm 2.40 2.45 2.55 2.35 2.30 2.20 2.10 2.45 2.45 2.65 2.70 sec.sup.−1 121.6 mm 2.50 2.55 2.65 2.45 2.35 2.30 2.20 2.55 2.55 3.00 3.05 sec.sup.−1 Thermal characteristics Melting point ISO — ° C. 217 217 215 215 215 216 215 217 216 217 217 217 (DSC Tm- 11357- 2nd) 3 Solidifying ISO — ° C. 162 161 155 165 164 164 165 160 163 165 168 167 point 11357- 3 Melting — ° C. 55 55 61 50 51 51 50 57 53 52 49 50 point- Solidifying point Heat Tensile MPa 107 97 108 resistance stress at yield Tensile tested at Tensile % 31 30 8 −60° C. after heat stress treated at 200° C. for at 4.5 hrs break Blister resistance Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent 87.5 MPa H.sub.2 gas, presoaked (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) for more than 20 h, evacuated in 0.5 min, one cycle Molding method in parentheses Judge ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ x x x Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- Com- parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. parative. Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. ple. Units 14 1 2 3 4 5 6 7 8 9 10 11 Formu- Compound formulation lation PA6 1030B mass % 48.8 73.8 48.8 49.3 58.8 53.8 48.8 58.8 53.8 48.8 48.8 73.8 PA6/66 5034B mass % 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Aromatic Grivory mass % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 PA 6T/6I G21 Ionomer-1 Himilan mass % 25.0 25.0 7.5 25.0 1706 Ionomer-2 Himilan mass % AM7328T Ionomer-3 Himilan mass % 1554W Ionomer-4 Himilan mass % 25.0 AM7326 m-EBR Tafmer mass % 15.0 20.0 25.0 17.5 MH5020 m-LLDPE F3000 mass % 15.0 20.0 25.0 Heat Irganox mass % 0.50 0.50 1.00 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 resistant 1098 agent 1 Heat Sumilizer mass % resistant GA-80 agent 2 Heat Irgafos168 mass % 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 resistant agent 3 Heat Value- mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 resistant 7220 agent 3 Dispersant Value- mass % 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 7220 Produc- Compunding Resin ° C. 305 319 315 310 329 344 340 338 349 362 340 305 tivity status temperature TEX44HCT Torque Amp 111 120 118 118 130 135-138 130 130 135 140 135 105 (electric current) Discharge of Strand Good Good Good Good Good Poor Poor Good Good Poor Good Good 40 kg/hrs conditions Rotational speed 120 rpm Judge ○ ○ ○ ○ ○ x x x x x x ○ Shaping Blow moldability proper- Extrudability Extruder A 30 35 38 33 36 40 48 40 46 52 53 30 ties Screw torque- rotation (rated ampere: 56 A) Parison Drawdown cm >50 >50 10 10 >50 35 8 >50 45 15 15 >50 characteristics in 5 sec and after fell injection 1 m retention Drawdown cm 5 >50 5 5 >50 15 5 >50 25 5 5 >50 in 2 sec after injection Other — Much Much Much Much molding smoke smoke smoke smoke defects Molded Inner — Good Good Bum Bum Yellow- Yellow- Yellow- Yellow- Yellow- Yellow- Yellow- Good article surface marks marks ing ing ing ing ing ing ing quality conditions on on inner inner surface surface Irregularities — Absent Absent Absent Absent Absent Present Present Absent Present Present Present Absent on inner surface by accumulation Judge ○ x x x x x x x x x x x Quality Properties at 23° C. (proper- Tensile stress ISO 527-2/ MPa 57 78 54 55 60 54 50 51 45 39 40 59 ties at yield 1A/50 Norminal ISO 527-2/ % 4 5 5 5 5 5 5 4 4 5 5 5 tensile strain 1A/50 at yield Norminal ISO 527-2/ % 233 26 221 220 148 205 156 158 145 159 167 110 tensile strain 1A/50 at break Tensile ISO527-2/ MPa 70 78 67 66 60 62 55 55 50 49 52 59 strength 1A/50 Tensile ISO527-2/ MPa 1,958 2,766 2,030 2,010 2,165 1,966 1,809 1,957 1,651 1,450 1,515 2,250 modulus 1A/1 Charpy ISO179-1/ kJ/m.sup.2 20 7 34 34 18 18 19 32 76 100 105 28 notched 1eA impact strength at −40° C. Quality Extremely cold tensile (low properties at −60° C. temper- Tensile stress ISO 527-2/ MPa 103 129 109 108 107 101 96 95 87 80 85 112 ature at yied 1A/50 Norminal ISO 527-2/ % 9 9 11 11 9 9 9 10 11 11 11 10 tensile strain 1A/50 at yield Norminal ISO 527-2/ % 25 13 23 24 16 16 18 20 23 27 27 18 tensile strain 1A/50 at break Tensile ISO527-2/ MPa 103 129 109 109 107 101 96 95 87 80 85 112 strength 1A/50 Judge ○ x ○ ○ x x ○ ○ ○ x ○ ○ Quality Fluidity, thermal (other characteristics, heat proper- resistance ties) Melt Capilo 12.16 Pa .Math. s 3,158 6,213 5,612 5,488 9,367 10,490 13,650 8,129 14,260 16,140 15,730 4,400 viscosity graph sec.sup.−1 L/D10, 0.02 60.8 Pa .Math. s 1,774 3,244 3,177 2,912 4,375 4,951 5,518 3,842 6,585 6,724 6,548 2,400 250° C. or less sec.sup.−1 water 121.6 Pa .Math. s 1,281 2,324 2,200 2,070 2,976 3,296 3,650 2,649 4,449 4,545 4,316 1,700 content sec.sup.−1 Strand 12.16 mm 1.65 1.30 1.40 1.40 1.50 diam- sec.sup.−1 eter 60.8 mm 2.70 1.40 1.50 1.55 1.65 sec.sup.−1 121.6 mm 3.10 1.45 1.55 1.60 1.75 sec.sup.−1 Thermal characteristics Melting point ISO — ° C. 217 214 217 217 214 215 215 213 214 214 216 (DSC Tm- 11357- 2nd) 3 Solidifying ISO — ° C. 168 160 163 162 169 171 171 168 170 171 168 point 11357- 3 Melting — ° C. 49 55 53 54 46 43 44 45 43 43 48 point- Solidifying point Heat Tensile MPa 80 81 91 95 82 84 resistance stress at yield Tensile tested at Tensile % 5 4 24 23 29 37 −60° C. after heat stress treated at 200° C. for at 4.5 hrs break Blister resistance Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent Absent 87.5 MPa H.sub.2 gas, presoaked (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) (Blow) for more than 20 h, evacuated in 0.5 min, one cycle Molding method in parentheses Judge x ○ x x ○ x x x x x x ○

(80) The composition obtained in Examples attained excellent results in productivity, blow moldability, molded article quality, properties at room and low temperatures, and other properties. The comparison of Example 2 to Examples 4 to 7 shows that the Charpy impact strength at −40° C. is enhanced when not only an olefin-based ionomer but also a specific amount of an impact modifier are added to the polyamide resin. From the comparison of Example 2 to Example 11, the addition of a phosphorus antioxidant as a heat resistant agent results in a molded article having better conditions of the inner surface and higher heat resistance. From the comparison of Comparative Example 1, Examples show that the polyamide resin composition is deteriorated in parison characteristics and also in nominal tensile strain at break when containing no ionomers and no impact modifiers. From the comparison of Example 2 to Examples 12 to 14, good parison characteristics are obtained and an excessive increase in strand diameter is avoided when the melting point or zinc content of the olefin-based ionomer falls in the specified range. The comparison of Example 2 with Comparative Examples 2 and 3 shows that burn marks occur on the inner surface and also the heat resistance is poor when the heat resistant agents include only one organic hindered phenol heat resistant agent. By comparing Examples 1 and 2 with Comparative Examples 4 to 9, it is shown that the polyamide resin composition containing an impact modifier and no ionomers exhibits a high viscosity and is poor in blow moldability and in the quality and productivity of molded articles. Further, when the amount of the impact modifier is large, the tensile modulus at room temperature is low. The comparison of Examples with Comparative Example 10 shows that the polyamide resin composition, when containing an ionomer and an impact modifier and the amount of the ionomer is less than the specified range, exhibits a high viscosity and is poor in blow moldability and in the quality and productivity of molded articles. From the comparison of Example 2 with Comparative Example 11, parison characteristics are deteriorated and molded articles cannot be obtained with a uniform wall thickness when the polyamide resins do not include at least one selected from the group consisting of aliphatic copolyamides and aromatic copolyamides.