JP2011231167A - Polyamide resin for automobile component or for electric/electronic component, having small density change by heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin having a small density change after heat treatment as compared with those of conventional aliphatic polyamide resins, without damaging a low water absorptivity, chemical resistance and hydrolysis resistance observed in the aliphatic linear polyoxamide resin.SOLUTION: The polyamide resin for an automobile component or an electric/electronic component having the small change in density by the heat treatment, consisting of oxalic acid as a dicarboxylic acid component and an aliphatic diamine as a diamine component is characterized by having 0.0 to +0.3% density change after the 48 hr treatment at a temperature higher than a glass transition temperature, obtained by a solid viscoelasticity measurement.

Description

  The present invention relates to a polyamide resin for automobile parts or electric / electronic parts. Specifically, it is a polyamide resin whose dicarboxylic acid component is oxalic acid, has a wide moldable temperature range, excellent molding processability, low water absorption, chemical resistance, hydrolysis resistance, etc., especially by heat treatment The present invention relates to a polyamide resin for automobile parts or electric / electronic parts, which has a small density change and requires physical properties and dimensional stability in a high temperature environment.

  Crystalline polyamides typified by nylon 6 and nylon 66 are widely used as textiles for clothing, industrial materials, or general-purpose engineering plastics because of their excellent properties and ease of melt molding.

  On the other hand, problems such as changes in physical properties and dimensions under water absorption and high-temperature environments have been pointed out for parts in the engine compartment of automobiles and parts for electric and electronic equipment. These phenomena are generally considered to be caused by the fact that the crystalline polyamide resin has a high water absorption rate and the density increases due to an increase in crystallinity upon heat treatment. To solve these problems, there are a method of absorbing water up to an equilibrium water absorption rate at the time of actual use before use and a method of performing a heat treatment at a temperature higher than that at the time of actual use. However, productivity decreases due to the above treatment, and the size of the molded product may change or deteriorate in the annealing treatment, and water absorption and annealing treatment are not required. In addition, there is an increasing demand for polyamide resins having excellent dimensional stability.

  As a method for solving the above problems, polyamide resins having improved heat resistance and water resistance have been proposed. For example, Japanese Patent Application Laid-Open No. 2002-220461 (Patent Document 1) discloses a polyamide composed of 1,9-nonanediamine, an aliphatic diamine other than 1,9-nonanediamine, and terephthalic acid. Although these polyamides can provide molded articles with low water absorption and high crystallinity compared to conventional polyamides, crystallization is further promoted when the molded articles are used at high temperatures, and physical properties and May cause dimensional changes.

  On the other hand, a polyamide resin using oxalic acid as a dicarboxylic acid component is called a polyoxamide resin, and is known to have a higher melting point and lower water absorption than other polyamide resins having the same amino group concentration (Patent Document 2). It is expected to be utilized in fields where conventional polyamides are difficult to use due to changes in physical properties and dimensions due to water absorption.

So far, polyoxamide resins using various aliphatic linear diamines as diamine components have been proposed. For example, in WO2008072754A (Patent Document 3), a polyoxamide resin in the case where a mixture in which a molar ratio of 1,9-nonanediamine and 2-methyl-1,8-octanediamine is 6:94 to 99: 1 is used as a diamine component. However, it is possible to increase the molecular weight by melt polymerization, and the temperature range that can be molded is as wide as 90 ° C or more, and it is excellent in melt moldability, and is also excellent in low water absorption, chemical resistance, and hydrolysis resistance. Yes.
However, in the prior literature, regarding the polyoxamide resin, there is no disclosure regarding the stability of the density with respect to the heat treatment.
JP2002-220461 JP 2006-57033 A WO2008072754A

  The problem to be solved by the present invention is the density after heat treatment as compared with conventional aliphatic polyamide resin without impairing the low water absorption, chemical resistance and hydrolysis resistance found in aliphatic linear polyoxamide resins. The object is to provide a polyamide resin with little change.

  As a result of intensive studies to solve the above problems, the present inventors have found that polyoxamido resin is obtained by using an oxalic acid diester as the oxalic acid source and an aliphatic diamine having a diamine component of 6 to 12 carbon atoms. The present inventors have found that a polyamide resin having a small density change after heat treatment can be obtained as compared with conventional polyamide without impairing the low water absorption, chemical resistance and hydrolysis resistance.

  The polyamide resin of the present invention is excellent in low water absorption, chemical resistance, and hydrolysis resistance, particularly has a small density change after heat treatment, and is excellent in physical properties and dimensional stability under a high temperature environment.

(1) Constituent Component of Polyamide Resin The polyamide of the present invention is a polyamide resin obtained by condensing the dicarboxylic acid component and the diamine component, wherein the dicarboxylic acid component is oxalic acid, the diamine component is an aliphatic diamine.

  As the oxalic acid source used in the production of the polyamide of the present invention, oxalic acid diesters are used, and these are not particularly limited as long as they have reactivity with amino groups. Dimethyl oxalate, diethyl oxalate, di-n-oxalate ( Or i-) propyl, oxalic acid diester of aliphatic monohydric alcohol such as di-n- (or i-, or t-) butyl oxalate, oxalic acid diester of alicyclic alcohol such as dicyclohexyl oxalate, aromatic alcohol such as diphenyl oxalate And oxalic acid diesters.

  Among the above oxalic acid diesters, oxalic acid diesters of aliphatic monohydric alcohols having more than 3 carbon atoms, oxalic acid diesters of alicyclic alcohols, and oxalic acid diesters of aromatic alcohols are preferred, and among them, dibutyl oxalate and diphenyl oxalate are particularly preferred.

  As the diamine component, an aliphatic diamine having 6 to 12 carbon atoms, preferably an aliphatic diamine having 9 to 12 carbon atoms, more preferably an aliphatic diamine having 9 to 10 carbon atoms, is used to polymerize, thereby reducing water absorption and chemical resistance. Thus, a polyamide having a hydrolysis resistance, in particular, a small density change due to heat treatment is obtained.

(2) Manufacture of polyamide resin The polyamide resin of this invention can be manufactured using the arbitrary methods known as a method of manufacturing polyamide. According to the study by the present inventors, it can be obtained by subjecting diamine and oxalic acid diester to a polycondensation reaction in a batch or continuous manner. Specifically, it is preferable to carry out in the order of (i) pre-polycondensation step and (ii) post-polycondensation step as shown by the following operations.

  (I) Pre-polycondensation step: First, the inside of the reactor is purged with nitrogen, and then diamine (diamine component) and oxalic acid diester (oxalic acid source) are mixed. When mixing, a solvent in which both the diamine and the oxalic acid diester are soluble may be used. The solvent in which both the diamine component and the oxalic acid source are soluble is not particularly limited, but toluene, xylene, trichlorobenzene, phenol, trifluoroethanol, and the like can be used, and particularly, toluene can be preferably used. For example, after heating the toluene solution which melt | dissolved diamine to 50 degreeC, oxalic acid diester is added with respect to this. At this time, the charging ratio of the oxalic acid diester and the diamine is oxalic acid diester / the diamine, 0.8 to 1.5 (molar ratio), preferably 0.91 to 1.1 (molar ratio), more preferably 0. .99 to 1.01 (molar ratio).

  The temperature in the reactor charged in this way is increased under normal pressure while stirring and / or nitrogen bubbling. The reaction temperature is preferably controlled so that the final temperature reaches 80 to 150 ° C., preferably 100 to 140 ° C. The reaction time at the final temperature reached is 3-6 hours.

  (Ii) Post-polycondensation step: In order to further increase the molecular weight, the polymer produced in the pre-polycondensation step is gradually heated in the reactor under normal pressure. In the temperature rising process, the final temperature of the prepolycondensation step, that is, from 80 to 150 ° C, is finally 220 ° C to 300 ° C, preferably 230 ° C to 280 ° C, more preferably 240 ° C to 270 ° C. Let reach the range. It is preferable to carry out the reaction for 1 to 8 hours including the temperature raising time, preferably 2 to 6 hours. Furthermore, in the post-polymerization step, polymerization can be performed under reduced pressure as necessary. The preferable final ultimate pressure in the case of performing the vacuum polymerization is less than 0.1 MPa to 13.3 Pa.

(3) Properties and properties of polyamide resin There is no particular limitation on the molecular weight of the polyamide resin obtained from the present invention, but the relative value measured at 25 ° C. using a 96% concentrated sulfuric acid solution with a polyamide resin concentration of 1.0 g / dl. The viscosity ηr is in the range of 1.8 to 6.0. Preferably it is 2.0-5.5, and 2.5-4.5 is especially preferable. If ηr is lower than 1.8, the molded product becomes brittle and the physical properties deteriorate. On the other hand, if ηr is higher than 6.0, the melt viscosity becomes high, and the molding processability deteriorates.

The polyamide resin of the present invention can be polymerized using oxalic acid as the carboxylic acid component and an aliphatic diamine having 6 to 12 carbon atoms as the diamine component, thereby increasing the relative viscosity, that is, increasing the molecular weight. Is possible. The moldable temperature range represented by the difference (Td−Tm) between the 1% weight loss temperature (hereinafter abbreviated as Td) and the melting point (hereinafter abbreviated as Tm), which is a substantial thermal decomposition index, is oxalic acid. And a polyamide composed of 1,9-nonanediamine, preferably 60 ° C. or higher, more preferably 70 ° C. or higher, and even 90 ° C. or higher. The polyamide resin of the present invention has a Td of preferably 300 ° C. or higher, more preferably 320 ° C. or higher, and has high heat resistance.

  The polyamide resin of the present invention has a density change after heat treatment in the range of 0.0% to + 0.3%, preferably in the range of 0.0% to + 0.2%, and more preferably in the range of 0.0% to 0.00. The range is 1%. When the density change after heat treatment is within the above range, a polyamide resin excellent in physical properties and dimensional stability against heat treatment can be obtained.

(4) Components that can be blended with the polyamide resin The polyamide resin obtained according to the present invention can be mixed with other dicarboxylic acid components as long as the effects of the present invention are not impaired. Examples of dicarboxylic acid components other than succinic acid include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, 3, Aliphatic dicarboxylic acids such as 3-diethylsuccinic acid, azelaic acid, sebacic acid and suberic acid, alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and terephthalic acid , Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, dibenzoic acid Acid, 4,4′-oxydibenzoic acid, diphenylmethane-4,4′-dicarboxylic acid, diphenyls Hong-4,4'-dicarboxylic acid, 4,4'-biphenyl and the like alone aromatic dicarboxylic acids such as dicarboxylic acids, or may be added to any mixture thereof during the polycondensation reaction. Furthermore, polyvalent carboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid can be used as long as melt molding is possible.

  The polyamide resin obtained from the present invention can be mixed with other diamine components as long as the effects of the present invention are not impaired. Other diamine components include ethylenediamine, propylenediamine, 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-decanediamine, 1,12-dodecanediamine, and 3-methyl. Fats such as -1,5-pentanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, 5-methyl-1,9-nonanediamine Group diamines, alicyclic diamines such as cyclohexanediamine, methylcyclohexanediamine, and isophoronediamine, p-phenylenediamine, m-phenylenediamine, p-xylenediamine, m-xylenediamine, 4,4′-diaminodiphenylmethane, 4 , 4′-Diaminodiphenylsulfone, 4,4 - it can be added alone and aromatic diamines, such as diaminodiphenyl ether, or any mixture thereof during the polycondensation reaction.

  In the present invention, other polyoxamides, polyamides such as aromatic polyamides, aliphatic polyamides, and alicyclic polyamides can be mixed within a range not impairing the effects of the present invention. Furthermore, thermoplastic polymers other than polyamide, elastomers, fillers, reinforcing fibers, and various additives can be similarly blended.

  Furthermore, the polyamide resin obtained according to the present invention may optionally contain a stabilizer such as a copper compound, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, and a crystallization accelerator. Glass fiber, plasticizer, lubricant and the like can be added during or after the polycondensation reaction.

(5) Polyamide resin molding process The polyamide resin molding method obtained by the present invention includes all known molding process methods applicable to polyamide, such as injection, extrusion, hollow, press, roll, foaming, vacuum / pressure, and stretching. The film can be processed into a film, a sheet, a molded product, a fiber, or the like by these molding methods.

(6) Use of polyamide molded product The polyamide molded product obtained by the present invention has an intake manifold, an air cleaner, a resonator, a fuel rail, a throttle body and a valve, which require physical properties and dimensional stability under a high temperature environment. Air flow meter, harness connector, engine cover, cylinder head cover, timing belt (chain cover), timing chain (belt) tensioner and guide, alternator cover, distributor cover, brake master cylinder, oil pump, oil filter, engine mount, etc. Parts used in the engine room, radiator core parts such as radiator core, radiator tank top and base, coolant reserve tank, water -Suitable for automotive underhood parts such as engine cooling system parts such as pipes, water pump housings, water pump impellers, water jacket spacers, valves and thermostat cases, and electrical and electronic parts such as connectors, cable ties, motor cases, gears and cams Can be used.

[Physical property measurement, molding, evaluation method]
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, density measurement, film forming, and heat treatment were performed by the following methods.

(1) Film molding A 50 mm x 50 mm x about 0.15 mm thick sheet was compression molded using a vacuum press TMB-10 manufactured by Toho Machinery Co., Ltd. After being melted by heating at 260 ° C. for 5 minutes in a reduced pressure atmosphere of 500 to 700 Pa, pressing was performed at 10 MPa for 1 minute to form. Next, the reduced-pressure atmosphere was returned to normal pressure, and then cooled and solidified at room temperature of 5 MPa for 1 minute to obtain a sample.

(2) A sheet obtained by molding the heat-treated polyamide resin under the condition (1) was treated at 140 ° C. for 48 hours in a reduced pressure atmosphere of 500 to 700 Pa.

(3) Density measurement The density of the sample molded under the condition (1) and the sample heat-treated by the method (2) were measured by the density gradient tube method of JIS K7112.

[Example 1]
(I) Pre-polycondensation step: The interior of a 500 ml separable flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and raw material inlet is replaced with nitrogen gas having a purity of 99.9999% for dehydration. 200 ml of used toluene and 24.9530 g (0.1577 mol) of 2-methyl-1,8-octanediamine were charged. The separable flask was placed in an oil bath and the temperature was raised to 50 ° C., and 31.88849 g (0.1577 mol) of dibutyl oxalate was charged. Next, the temperature of the oil bath was raised to 130 ° C., and the reaction was carried out for 5 hours under reflux. Note that all operations from preparation of raw materials to completion of the reaction were performed under a nitrogen stream of 50 ml / min.

  (Ii) Post-polycondensation step: The prepolymer obtained by the above operation is charged into a glass reaction tube having a diameter of about 35 mmφ equipped with a stirrer, an air cooling tube, and a nitrogen introduction tube, and the pressure inside the reaction tube is reduced to 13.3 Pa or less. Then, the operation of introducing nitrogen gas to normal pressure was repeated five times, and then the mixture was transferred to a salt bath maintained at 210 ° C. under a nitrogen stream of 50 ml / min, and temperature increase was immediately started. The temperature of the salt bath was adjusted to 260 ° C. over 1 hour, and the reaction was further continued for 2 hours. The polyamide resin was obtained by removing from the salt bath and cooling to room temperature under a nitrogen stream of 50 ml / min. The obtained polyamide was a tough polymer.

[Example 2]
(I) Pre-polycondensation step: A raw material feed pump was directly connected by a stirrer, a thermometer, a torque meter, a pressure gauge, a nitrogen gas inlet, a pressure outlet, a polymer outlet, and a pipe made of SUS316 having a diameter of 1/8 inch. After charging 1048.87 g (5.18616 mol) of dibutyl oxalate into a 5 L pressure vessel equipped with a raw material inlet, the inside of the pressure vessel was pressurized to 3.0 MPa with 99.9999% purity nitrogen gas, Next, the operation of releasing nitrogen gas to normal pressure was repeated five times, and then the system was heated under a sealing pressure. After the internal temperature was raised to 100 ° C. over 20 minutes, a mixture of 49.26 g (0.3112 mol) of 1,9-nonanediamine and 771.74 g (4.8756 mol) of 2-methyl-1,8-octanediamine (4.8756 mol) The molar ratio of 1,9-nonanediamine and 2-methyl-1,8-octanediamine was 6:94) was poured into the reaction vessel over 17 minutes at a flow rate of 13 ml / min by a raw material feed pump, and the temperature was increased. The internal pressure in the pressure vessel immediately after injection of the whole amount increased to 0.35 MPa by 1-butanol generated by the polycondensation reaction, and the internal temperature increased to 168 ° C.

  (Ii) Post-polycondensation step: Distillation of butanol produced immediately after injection was started, and the internal temperature was maintained at 235 ° C. over 2 hours while maintaining the internal pressure at 0.25 MPa. Immediately after the internal temperature reached 235 ° C., 1-butanol produced by the polycondensation reaction was extracted from the pressure release port over 20 minutes. After releasing the pressure, the temperature was raised under a nitrogen stream of 260 ml / min. The internal temperature was raised to 260 ° C. over 1 hour, and the reaction was carried out at 260 ° C. for 0.5 hour. Thereafter, the stirring was stopped, the inside of the system was pressurized to 3 MPa with nitrogen and allowed to stand for 10 minutes, and then released to an internal pressure of 0.5 MPa, and the polymer was extracted from the lower part of the pressure vessel in a string shape. The string-like polymer was immediately cooled with water, and the water-cooled string-like polymer was pelletized with a pelletizer. The obtained polymer was a tough polymer.

[Example 3]
In the prepolymerization step, 9.6777 g (0.0611 mol) of 1,9-nonanediamine, 22.58581 g (0.1425 mol) of 2-methyl-1,8-octanediamine (1,9-nonanediamine and 2-methyl- A polyamide was obtained in the same manner as in Example 1 except that the molar ratio of 1,8-octanediamine was 30:70) and 41.1781 g (0.2036 mol) of dibutyl oxalate was charged. The obtained polyamide was a tough polymer.

[Example 4]
In the prepolymerization step, 16.129 g (0.1018 mol) of 1,9-nonanediamine and 16.129 g (0.1018 mol) of 2-methyl-1,8-octanediamine (1,9-nonanediamine and 2-methyl- Polyamide was obtained by carrying out the reaction in the same manner as in Example 1 except that the molar ratio of 1,8-octanediamine was 50:50) and 41.1781 g (0.2036 mol) of dibutyl oxalate was charged. The obtained polyamide was a tough polymer.

[Example 5]
(I) Pre-polycondensation step: The inside of a separable flask having a volume of 5 liters equipped with a stirrer, an air cooling tube, a nitrogen inlet tube, and a raw material inlet is replaced with nitrogen gas having a purity of 99.9999%, and oxalic acid 1211 g (5.99871 mol) of dibutyl was charged. While maintaining this container at 20 ° C., 807.6 g (5.102 mol) of 1,9-nonanediamine and 142.5 g (0.9004 mol) of 2-methyl-1,8-octanediamine were added while stirring (1,004 mol). The molar ratio of 9-nonanediamine and 2-methyl-1,8-octanediamine was 85:15), and the polycondensation reaction was performed. Note that all operations from preparation of raw materials to completion of the reaction were performed under a nitrogen stream of 200 ml / min.

(Ii) Post-polycondensation step: The prepolymer obtained by the above operation is charged into a 5 L pressure vessel equipped with a stirrer, thermometer, torque meter, pressure gauge, nitrogen gas inlet and polymer outlet, and the inside of the pressure vessel Was maintained under a pressure of 3.0 MPa or more and then the operation of releasing nitrogen gas to normal pressure was repeated five times, and then the system was heated under a nitrogen stream and normal pressure. The internal temperature was raised to 120 ° C. over 1.5 hours. At this time, distillation of butanol was confirmed. While distilling butanol, the temperature was raised to 260 ° C. over 5 hours and reacted for 2 hours. Thereafter, the temperature in the system was lowered to 250 ° C., the stirring was stopped, and the mixture was allowed to stand for 25 minutes. The string-like polymer was immediately cooled with water, and the water-cooled string-like polymer was pelletized with a pelletizer. The obtained polymer was a tough polymer.

[Example 6]
In the prepolymerization step, polyamide was obtained by reacting in the same manner as in Example 1 except that 26.1474 g (0.1652 mol) of 1,9-nonanediamine and 33.4111 g (0.1652 mol) of dibutyl oxalate were charged. . The obtained polyamide was a tough polymer. A film was formed in the same manner except that the temperature was 270 ° C. in the method (1), and the density of this film and the film heat-treated by the method (2) were measured.

[Example 7]
(I) Pre-polycondensation step: A raw material feed pump was directly connected by a stirrer, a thermometer, a torque meter, a pressure gauge, a nitrogen gas inlet, a pressure outlet, a polymer outlet, and a pipe made of SUS316 having a diameter of 1/8 inch. A 5 L pressure vessel equipped with a raw material inlet is charged with 875.0 g (5.081 mol) of decanediamine and the inside of the pressure vessel is pressurized to 3.0 MPa with nitrogen gas having a purity of 99.9999%. After repeating the operation of releasing nitrogen gas to normal pressure 5 times, the system was heated up under a sealing pressure. After the internal temperature was raised to 190 ° C. over 45 minutes, dibutyl oxalate was poured into the reaction vessel over 17 minutes at a flow rate of 65 ml / min by a raw material feed pump, and the temperature was raised at the same time. The internal pressure in the pressure vessel immediately after injection of the whole amount increased to 0.65 MPa by 1-butanol generated by the polycondensation reaction, and the internal temperature increased to 198 ° C.

(Ii) Post-polycondensation step: Distillation of butanol generated immediately after injection was started, and the internal temperature was increased to 250 ° C. over 3 hours while maintaining the internal pressure at 0.5 MPa. Immediately after the internal temperature reached 250 ° C., 1-butanol produced by the polycondensation reaction was extracted from the pressure release port over 20 minutes. After releasing the pressure, the internal temperature was raised to 270 ° C. over 1.5 hours under a nitrogen stream of 260 ml / min, and then reacted at 270 ° C. for 0.5 hours. Thereafter, the stirring was stopped, the inside of the system was pressurized to 3 MPa with nitrogen and allowed to stand for 10 minutes, and then released to an internal pressure of 0.5 MPa, and the polymer was extracted from the lower part of the pressure vessel in a string shape. The string-like polymer was immediately cooled with water, and the water-cooled string-like polymer was pelletized with a pelletizer. The obtained polymer was a tough polymer. A film was formed in the same manner except that the temperature was set to 270 ° C. in the method (1), and the density of this film and the material heat-treated by the method (2) was measured.

[Comparative Example 1]
A film was formed with a T-die extruder using nylon 9T (Kuraray, N1000D-H) instead of the polyamide resin of the present invention. The obtained nylon 9T film was a tough film. The density of this film and the film heat-treated by the method (2) were measured.

[Comparative Example 2]
In place of the polyamide resin of the present invention, a film was formed using nylon 12 (Ube Industries, UBESTA 3030XA). The obtained nylon 12 film was a tough film. The density of this film and the film heat-treated by the method (2) were measured.

Table 1 shows changes in density due to heat treatment with the polymers obtained in Examples 1 to 7 and Comparative Examples 1 and 2. Since the polymers obtained in Examples 1 to 7 have a smaller density change amount after heat treatment (density difference before and after heat treatment) than the polymers obtained in Comparative Examples 1 and 2, the polyamide resin of the present invention has a density change due to heat treatment. small.

  The polyamide resin of the present invention is excellent in low water absorption, chemical resistance, hydrolysis resistance, etc., is excellent in melt molding processability, and especially has a small density change due to heat treatment. it can. It can also be used for various automotive parts, electrical / electronic parts, and the like that require physical properties and dimensional stability in a high temperature environment.

Claims (5)

  A polyamide resin in which the dicarboxylic acid component is composed of oxalic acid and the diamine component is composed of an aliphatic diamine, and the density change after treatment for 48 hours at a temperature higher than the glass transition temperature determined by solid viscoelasticity measurement is 0.0 to + A polyamide resin for automobile parts or electrical / electronic parts that has a small density change due to heat treatment, characterized by being 0.3%. The polyamide for automobile parts or electric / electronic parts according to claim 1, wherein the diamine component comprises a linear aliphatic diamine having 5 to 12 carbon atoms and / or an aliphatic diamine having 6 to 12 carbon atoms having a side chain. resin.   A molded article comprising the polyamide resin according to claim 1. An automobile part or an electric / electronic part comprising the polyamide resin according to claim 1. A part for an automobile engine room, a radiator tank part, or a connector for electrical and electronic equipment, comprising the polyamide resin according to claim 1 or 2.