JP2019038938A - Polyamide resin composition and molding thereof - Google Patents

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) 3-30 pts.mass with a density of 0.915-0.975 g/cm, a melt flow rate (190°C, 2.16 kg load) of preferably 0.01-50 g/10 min, and a degree of acid modification of preferably 0.1-5 mass%. There is also provided a molding obtained by molding the polyamide resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a polyamide resin composition excellent in heat aging resistance and a molded body thereof.

  In recent years, in order to reduce the weight of automobiles and improve productivity, automobile parts formed by injection molding of a resin composition are frequently used. Among such automotive parts, particularly high-temperature part cover parts (for example, engine covers) are exposed to a high-temperature environment for a long period of time, so that mechanical properties (for example, impact strength) may decrease due to thermal aging.

  Patent Document 1 discloses an engine cover that has polypropylene and polymethylpentene as main components and is excellent in heat distortion resistance (shape retention) and heat discoloration. However, the problem of mechanical property deterioration due to heat aging as described above has not been sufficiently studied. Also,

JP 2013-227488 A

  Instead of the polypropylene used in Patent Document 1, it is also conceivable to use a polyamide having a higher impact resistance. However, the present inventors considered that it is necessary to further improve the heat aging resistance of polyamide in order to use it as a material for automobile parts, particularly high-temperature part cover parts. That is, the objective of this invention is providing the polyamide resin composition excellent in heat aging resistance, and its molded object.

  As a result of intensive studies to solve the above problems, the present inventors have found that it is very effective to blend a specific amount of a specific acid-modified polyethylene with respect to polyamide, and this is particularly effective for high-temperature parts such as engine covers. The present inventors have found that it is very suitable as a material for cover parts, and have completed the present invention. That is, the present invention is specified by the following matters.

[1] A polyamide resin composition comprising 100 parts by mass of polyamide (A) and 3 to 20 parts by mass of acid-modified polyethylene (E) having a density of 0.915 to 0.975 g / cm ³ .

[2] The polyamide resin composition according to [1], wherein the melt flow rate (190 ° C., 2.16 kg load) of the acid-modified polyethylene (E) is 0.01 to 50 g / 10 min.

[3] The polyamide resin composition according to [1] or [2], wherein the acid-modified polyethylene (E) has an acid modification degree of 0.1 to 5% by mass.

[4] A molded product obtained by molding the polyamide resin composition according to [1].

[5] The molded article according to [4], which is a heat-resistant aging part for high-temperature parts.

[6] The molded article according to [5], which is an automotive part.

[7] The molded article according to [5], which is a cover part for a high temperature part.

[8] The molded article according to [7], which is an engine cover.

  ADVANTAGE OF THE INVENTION According to this invention, even if it exposes to a high temperature environment for a long time, it can provide the resin composition excellent in the heat aging resistance in which mechanical physical properties, such as impact resistance, do not fall easily. Therefore, the molded product obtained from the polyamide resin composition of the present invention is very useful as a part for automobiles, particularly as a cover part for high temperature parts such as an engine cover.

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

  (1) A polycondensation product of an organic dicarboxylic acid having 4 to 12 carbon atoms and an organic diamine having 2 to 13 carbon atoms, for example, polyhexamethylene adipamide which is a polycondensation product of hexamethylenediamine and adipic acid [ 6,6 nylon], polyhexamethylene azelamide [6,9 nylon] which is a polycondensate of hexamethylene diamine and azelaic acid, polyhexamethylene sebacamide which is a polycondensate of hexamethylene diamine and sebacic acid [6,10 nylon], polyhexamethylene dodecanoamide [6,12 nylon], which is a polycondensate of hexamethylene diamine and dodecanedioic acid, semi-condensation product of aromatic dicarboxylic acid and aliphatic diamine Aromatic polyamide (PA6T, PA9T, PA10T, PA11T), bis-p-aminocyclohexylmethane and dode Polybis (4-aminocyclohexyl) methane dodecane which is a polycondensate with candioic acid. Examples of the organic dicarboxylic acid include adipic acid, pimelic acid, suberic acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phenylenedioxydiacetic acid, oxydibenzoic acid, diphenylmethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, and biphenyl. Examples thereof include dicarboxylic acid, sebacic acid, dodecanedioic acid and the like. Examples of the organic diamine include hexamethylene diamine, octamethylene diamine, nonane diamine, octane diamine, decane diamine, undecane diamine, undecane diamine, and dodecane diamine.

  (2) Polyundecanamide [11 nylon] which is a polycondensate of ω-amino acid, for example, a polycondensate of ω-aminoundecanoic acid.

  (3) Ring-opening polymer of lactam, for example, polycapramide [6 nylon] which is a ring-opening polymer of ε-aminocaprolactam, ring-opening polymer of ε-aminolaurolactam, polylauric lactam [12 nylon].

  Of these, polyhexamethylene adipamide [6,6 nylon], polyhexamethylene azelamide [6,9 nylon], and polycoupler [6 nylon] are preferable.

  In the present invention, for example, a polyamide resin produced from adipic acid, isophthalic acid, and hexamethylenediamine can be used, and two or more polyamide resins are blended, such as a mixture of 6 nylon and 6,6 nylon. Blends can also be used.

<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 be a copolymer of ethylene and a small amount of an α-olefin within a range not impairing the effects of the present invention.

  Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene and 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-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-dode Emissions include having 3 to 20 carbon atoms α- olefins such as 1-Hekisadodesen. These α-olefins may be used in combination of two or more.

  The acid-modified ethylene polymer (E) is obtained, for example, by graft polymerizing an acid component (for example, maleic acid or its anhydride) to polyethylene in the presence of a radical initiator. In that case, you may add the additive mentioned later as needed. Polyethylene may be previously granulated by a melt kneading method. Further, an acid component may be graft-polymerized to polyethylene in the presence of a radical initiator by using an extruder without using a solvent. The graft polymerization reaction is preferably performed at a temperature equal to or higher than the melting point of polyethylene for 0.5 to 10 minutes.

  The charging amount of the acid component is usually 0.01 to 15 parts by mass, preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of polyethylene before acid modification. The usage-amount of a radical initiator is 0.001-1 mass part normally with respect to 100 mass parts of polyethylene before an acid modification, Preferably it is 0.001-0.3 mass part.

  As the radical initiator, for example, an organic peroxide, an azo compound, or a metal hydride can be used. The radical initiator may be used as it is mixed with the acid component and polyethylene before acid modification, or may be used after being dissolved in a small amount of an organic solvent.

The polyethylene before acid-modified, density 0.940 g / cm ³ or more, 0.975 g / cm ³ or less of high density polyethylene, density of 0.915 g / cm ³ or more, a low density of less than 0.940 g / cm ³ Any of polyethylene can be used. The density of the acid-modified polyethylene (E) is 0.915 to 0.975 g / cm ³ , preferably 0.915 to 0.970 g / cm ³ , more preferably 0.915 to 0.960 g / cm ³ . ³ .

  The melt flow rate (MFR) measured under conditions of 190 ° C. and 2.16 kg load according to ASTM D1238 of acid-modified polyethylene (E) is preferably 0.01 to 50 g / 10 min, more preferably 0.05 to 40 g. / 10 min.

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

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

<Polyamide resin composition>
The polyamide resin composition of the present invention is 3 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 5 to 20 parts by mass, with respect to 100 parts by mass of the polyamide (A). It is a composition containing a part by mass. By blending the acid-modified ethylene polymer (E) at this ratio, it becomes a heat aging polyamide resin composition in which mechanical properties such as impact resistance are unlikely to deteriorate even when exposed to a high temperature environment for a long time.

  The polyamide resin composition of the present invention can be obtained, for example, by melt-mixing polyamide (A), acid-modified polyethylene (E), and other components as necessary. Specifically, each of the above components is simultaneously or sequentially charged and mixed in a mixing apparatus such as a Henschel mixer, a V-type blender, a tumbler mixer, a ribbon blender, etc., and a single-screw extruder, a multi-screw extruder, It can be obtained by melt-kneading with a kneader, Banbury mixer or the like. In particular, when a device excellent in kneading performance such as a multi-screw extruder, a kneader, or a Bannbury mixer is used, a high-quality polyamide resin composition in which each component is more uniformly dispersed can be obtained. In addition, other additives such as an antioxidant may be added at these optional stages as necessary.

<Molded body>
The molded body 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. Of these, the injection molding method is preferable.

  Since the molded article of the present invention is excellent in heat aging resistance, it is useful as a heat aging part for high temperature parts, and in particular, a vehicle part (automobile) used in a high temperature part and requiring heat aging resistance. It is very useful as a component for use. Specific examples of vehicle components include engine covers, cylinder head covers, timing belt covers, intercooler housings, thermostat housings, cover parts for high temperature parts such as air ducts, fuel tube tubes, cable ties and other cable ties. . Among them, it is very useful as an engine cover. Further, the present invention is not limited to vehicle parts, and is useful as a cover part for high-temperature parts as, for example, an electrical / electronic equipment part, a mechatronics part, or a home appliance part.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The materials used in Examples and Comparative Examples are as follows.

<Polyamide (A)>
“Polyamide 6 (PA6)” manufactured by Toray Industries, Inc., Amilan (registered trademark) CM1026

<Ethylene polymer before acid modification>
As an ethylene polymer before acid modification, 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), an ethylene-1-butene copolymer (EBR) manufactured by Mitsui Chemicals, Inc. was used. The properties of each ethylene polymer before acid modification are as follows.

“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 ° C., 2.16 kg load) 1.0 g / 10 min
“Ethylene / 1-butene copolymer (EBR)”: ethylene content 85 mol%, density 870 kg / m ³ , MFR (190 ° C., 2.16 kg load) 1.2 g / 10 min

<Preparation of acid-modified polyethylene (E-1)>
10 kg of high density polyethylene (HDPE-1), 120 g of maleic anhydride (MAH) and 6 g of 2,5-dimethyl-2,5-di- (t-butylperoxy) -3-hexyne (trade name perhexine 25B) in acetone The solution dissolved in was blended. The obtained blend was introduced from a hopper of a twin screw extruder (trade name: TEX30SS, manufactured by Nippon Steel Co., Ltd.) with a screw diameter of 30 mm and L / D = 42, a resin temperature of 250 ° C., and a screw rotation speed of 180 rpm. And extruded at a discharge rate of 10 kg / hr. The obtained strand was sufficiently cooled and then granulated to obtain acid-modified polyethylene (E-1).

<Preparation of acid-modified polyethylene (E-2) to (E-5)>
Acid-modified polyethylenes (E-2) to (E-7) were prepared in the same manner as the acid-modified ethylene polymer (E-1) except that each component shown in Table 1 was used.

<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 the acid-modified ethylene polymer (E-1) except that each component shown in Table 1 was used.

  The physical properties of the acid-modified polyethylenes (E-1) to (E-5) and the 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.

(Preparation of measurement press sheet)
Pressure sheet molding was performed at 7.5 MPa using a hydraulic heat press machine manufactured by Shindo Metal Industry Co., Ltd. set at 180 ° C. Specifically, in the case of a sheet having a thickness of 0.5 to 3 mm, the remaining heat is applied for 5 minutes with no load, pressurized at 7.5 MPa for 2 minutes, and then another refined oil set at 20 ° C. The sample for measurement was obtained by compressing at 7.5 MPa using a pressure hot press machine and cooling for 5 minutes. A 5 mm thick brass plate was used as the hot plate. This sample was used for each physical property measurement.

(MFR)
In accordance with ASTM D1238, the melt flow rate (MFR) was measured under conditions of 190 ° C. and 2.16 kg load and 230 ° C. and 2.16 kg load.

(density)
Based on ASTM D1505, the density was measured by a density gradient tube method using a strand resin flowing out by MFR measurement.

(Acid modification degree)
The degree of acid modification (maleic anhydride graft amount) was determined from a calibration curve created based on the wave number 1780 cm ⁻¹ peak intensity attributed to the carbonyl group by FT-IR.

[Example 1]
90 parts by mass of polyamide 6 (manufactured by Toray Industries, Inc., Amilan (registered trademark) CM1026) and 10 parts by mass of acid-modified ethylene polymer (E-1) were mixed using a Henschel mixer, and a dry blend product was obtained. Obtained. This dry blend was supplied to a twin-screw extruder (L / D = 42, 30 mmφ) set at 245 ° C., and extruded under the condition of a screw rotation speed of 180 rpm to produce polyamide resin composition pellets. After the pellets were dried at 80 ° C. for 12 hours, injection molding was performed under the following conditions to prepare test pieces for physical property tests.

(Injection molding conditions)
Injection molding machine with a clamping force of 50 tons (MEIKI M50)
Cylinder temperature: 245 ° C
Injection pressure: 400 kg / cm ²
Mold temperature: 80 ℃

[Examples 2 to 5]
Except having used each component shown in Table 2, the pellet of the polyamide resin composition was produced like Example 1, and the test piece for a physical property test was produced using the pellet.

[Comparative Examples 1-3]
Except having used each component shown in Table 3, the pellet of the polyamide resin composition was produced like Example 1, and the test piece for a physical property test was produced using the pellet.

  The heat aging resistance of the test pieces of Examples 1 to 5 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.

(1) Izod impact test Notched Izod impact strength was measured at 23 ° C. and −40 ° C. in accordance with ASTM D256 using a test piece having a thickness of 1/8 ″. The test piece was prepared in a dry state at a temperature of 23 ° C. for 2 days.

(2) Thermal aging test The test piece was stored in the gear oven set to 160 degreeC. After 500 hours from the start of heating, the test piece was taken out, and the notched Izod impact strength was measured again at 23 ° C. and −40 ° C. as in (1) above.

(3) Heat aging resistance (impact strength maintenance rate)
As an index of heat aging resistance, the maintenance ratio of Izod impact strength was defined by the following equation.
(Impact strength maintenance rate) = (Izod impact strength after 500 hours of thermal aging test) / (Izod impact strength before thermal aging test) × 100 (%)

  As is clear from Tables 2 and 3, the polyamide resin compositions of Examples 1 to 5 had a high impact strength maintenance rate after being exposed to an environment of 160 ° C. for 500 hours and were excellent in heat aging resistance.

  The polyamide (PA6) simple substance of Comparative Example 1 was inferior in heat aging resistance to the polyamide resin compositions of Examples 1 to 5.

  The polyamide resin composition of Comparative Example 2 is obtained by blending acid-modified elastomer (E′-1) having a low density with polyamide (PA6), and has a heat aging resistance higher than that of the polyamide resin compositions of Examples 1 to 5. It was inferior.

  The polyamide resin composition of Comparative Example 3 is obtained by blending an acid-modified elastomer (E′-2) containing an antioxidant and a relatively low density into polyamide (PA6). This is inferior in heat aging resistance to the polyamide resin compositions of Examples 3 and 5 in which polyethylene (E-3) and (E-5) having a relatively high density containing an antioxidant are blended with polyamide (PA6). It was.

  Since the polyamide resin composition of the present invention is excellent in heat aging resistance, the molded product is useful as a heat aging part for high temperature parts in the fields of vehicle parts, electrical / electronic equipment parts, mechatronic parts, home appliance parts, etc. .

Claims (8)

A polyamide resin composition comprising 100 parts by mass of polyamide (A) and 3 to 30 parts by mass of acid-modified polyethylene (E) having a density of 0.915 to 0.975 g / cm ³ .   The polyamide resin composition according to claim 1, wherein the acid-modified polyethylene (E) has a melt flow rate (190 ° C., 2.16 kg load) of 0.01 to 50 g / 10 min.   The polyamide resin composition according to claim 1 or 2, wherein the acid-modified polyethylene (E) has an acid modification degree of 0.1 to 5% by mass.   The molded object formed by shape | molding the polyamide resin composition of Claim 1.   The molded article according to claim 4, which is a heat-resistant aging part for high-temperature parts.   The molded article according to claim 5, which is an automotive part.   The molded article according to claim 5, which is a cover part for a high-temperature part.   The molded article according to claim 7, which is an engine cover.