Polyamide resin composition

Abstract

The present invention relates to a polyamide resin composition, and more particularly, to a polyamide resin composition and a molded article (in particular, an inner liner of a gas storage container) comprising the same, the present invention relates to a polyamide resin composition comprising a polyamide resin, a thermoplastic polyester elastomer (TPEE), an impact modifier, and a nucleating agent in a specific weight ratio, which can simultaneously exhibit excellent gas barrier properties and excellent impact resistance (particularly high low-temperature impact resistance), further, the material has excellent mechanical and physical properties such as tensile strength and heat resistance, and thus can be very suitably applied to inner liners of gas storage containers.

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition, and more particularly, to a polyamide resin composition and a molded product comprising the polyamide resin composition (particularly, a liner of a gas storage container). The polyamide resin composition comprises a polyamide resin, a thermoplastic polyester elastomer (TPEE), an impact modifier and a nucleating agent in a specific weight ratio. The polyamide resin composition can simultaneously exhibit excellent gas barrier properties and excellent impact resistance (particularly high low-temperature impact resistance), and has excellent mechanical and physical properties such as tensile strength and heat resistance, and can therefore be very suitably applied to the liner of a gas storage container. Background Art

[0002] Polyamide resin has excellent heat resistance, mechanical physical properties, oil resistance, chemical resistance, etc., and is widely used in electrical and electronic industrial parts and automotive industrial parts, etc., and a composition containing polyamide resin requires various physical properties according to its specific use. In particular, in order to be used as a liner of a gas storage container, a polyamide resin composition needs to have both excellent impact resistance and excellent gas barrier properties.

[0003] However, existing polyamide resin compositions have limitations in satisfying both excellent impact resistance and excellent gas barrier properties. For example, the polyamide resin composition disclosed as a hydrogen tank lining material in Japanese Patent No. 4588078 has excellent low-temperature impact resistance, but has the disadvantage of reduced gas barrier properties. On the other hand, the polyamide resin composition disclosed as a gas tank lining material in Korean Patent No. 10-2189936 has excellent gas barrier properties, but has the disadvantage of reduced low-temperature impact resistance.

[0004] Therefore, for use in gas storage container liners, there is a need to develop a polyamide resin composition that exhibits both excellent gas barrier properties and excellent impact resistance (particularly high low-temperature impact resistance) at suitable levels. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] An object of the present invention is to provide a polyamide resin composition which exhibits both excellent gas barrier properties and excellent impact resistance (particularly, high low-temperature impact resistance) and is suitable for use as a lining material for a gas storage container.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a polyamide resin composition, which comprises: (1) a polyamide resin; (2) a thermoplastic polyester elastomer; (3) an impact modifier and (4) a nucleating agent. Based on 100 parts by weight of the composition in total, the content of the thermoplastic polyester elastomer is more than 0.5 parts by weight but less than 20 parts by weight, the content of the impact modifier is more than 11 parts by weight but less than 34 parts by weight, and the content of the nucleating agent is more than 0 parts by weight but less than 3 parts by weight.

[0009] According to another aspect of the present invention, a molded article comprising the polyamide resin composition of the present invention is provided.

[0010] In a specific embodiment, the molded article is a liner of a gas storage container.

[0011] (III) Beneficial effects

[0012] The polyamide resin composition of the present invention simultaneously exhibits excellent gas barrier properties and excellent impact resistance (especially high low-temperature impact resistance) that cannot be achieved by existing polyamide resin compositions, and also has excellent mechanical physical properties such as tensile strength and heat resistance. In particular, it can simultaneously exhibit the high level of gas barrier properties and low-temperature impact resistance required for the use of linings for gas storage containers, and therefore can be very suitably used for the use of linings for gas storage containers. DETAILED DESCRIPTION

[0013] Hereinafter, the present invention will be described in more detail.

[0014] In this specification, the term "gas" is a concept including various gaseous substances. Specific examples include hydrogen, methane, butane, propane, helium, nitrogen and oxygen, but the present invention is not limited to these.

[0015] The polyamide resin composition of the present invention contains a polyamide resin.

[0016] As the polyamide resin, any polyamide resin generally used in the art may be used without particular limitation.

[0017] In a specific embodiment, the polyamide resin may be an aliphatic polyamide homopolymer, an aliphatic polyamide copolymer, or a combination thereof.

[0018] More specifically, the polyamide resin may be selected from the group consisting of polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 6 / 66, polyamide 66 / 6, polyamide 66 / 612, and combinations thereof.

[0019] In addition, in a specific embodiment, the relative viscosity of the polyamide resin may be in the range of 2.3-4.0. When the relative viscosity of the polyamide resin is too low compared to the above level, the tensile strength, impact strength and heat resistance of the composition may be reduced. On the other hand, when the relative viscosity is too high compared to the above level, the composition has insufficient fluidity during molding, and the problem of reduced injection molding processability may occur.

[0020] In a specific embodiment, the polyamide resin composition of the present invention may include 30-88 parts by weight of the polyamide resin based on a total of 100 parts by weight of the composition. When the content of the polyamide resin in the total of 100 parts by weight of the polyamide resin composition of the present invention is too less than the above level, the mechanical strength of the composition may be reduced, and on the other hand, when the content of the polyamide resin is too much compared to the above level, the impact resistance of the composition may be insufficient.

[0021] More specifically, the polyamide resin content in a total of 100 parts by weight of the polyamide resin composition of the present invention can be, for example, 30 parts by weight or more, 32 parts by weight or more, 35 parts by weight or more, 37 parts by weight or more, 40 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 45 parts by weight or more, 47 parts by weight or more, 50 parts by weight or more, 52 parts by weight or more, 55 parts by weight or more, 57 parts by weight or more, 60 parts by weight or more, 62 parts by weight or more, or 63 parts by weight or more, and can be 88 parts by weight or less, 87 parts by weight or less, 86 parts by weight or less, 85 parts by weight or less, 84 parts by weight or less, 83 parts by weight or less, 82 parts by weight or less, 81 parts by weight or less, or 80 parts by weight or less, but is not limited thereto.

[0022] The polyamide resin composition of the present invention further comprises a thermoplastic polyester elastomer (TPEE).

[0023] The thermoplastic polyester elastomer is a thermoplastic block copolymer including a rigid hard segment and a flexible soft segment.

[0024] In a specific embodiment, the hard segment may include polymerization units of an aromatic dicarboxylic acid compound and a diol, and the soft segment may include polymerization units of a polyalkylene oxide.

[0025] Specifically, the aromatic dicarboxylic acid compound can be selected from terephthalic acid (TPA), isophthalic acid (IPA), 1,5-naphthalenedicarboxylic acid (1,5-NDCA), 2,6-naphthalenedicarboxylic acid (2,6-NDCA), dimethyl terephthalate (DMT), dimethyl isophthalate and a combination thereof, preferably DMT.

[0026] In addition, specifically, the diol can be a linear or cyclic aliphatic diol having 2 to 8 carbon atoms, more specifically can be selected from ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and combinations thereof, preferably 1,4-butanediol.

[0027] In addition, specifically, the polyalkylene oxide may be selected from polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol (PTMEG) and a combination thereof, and may preferably be PTMEG.

[0028] In a specific embodiment, the thermoplastic polyester elastomer can be branched by a branching agent to increase the melt tension and improve the stability of its strand when producing TPEE, thereby improving productivity. The branching agent can be selected from, for example, glycerol, pentaerythritol, neopentyl glycol, and combinations thereof, preferably glycerol.

[0029] The TPEE that can be used for the polyamide resin composition of the present invention can be prepared by melt polymerization generally consisting of two steps of oligomerization and polycondensation, and can preferably be a branched TPEE.

[0030] After adding the above ingredients to the reactor, branched TPEE is prepared by melt polymerization consisting of two steps of oligomerization and polycondensation in the presence of a suitable catalyst, for example, tetra-n-butoxytitanium (TBT). The oligomerization reaction can be carried out at 140-215° C. for 3-4 hours, and the polycondensation reaction can be carried out by gradually reducing the pressure from 760 torr to 0.3 torr at 210-250° C. for 4-5 hours.

[0031] Taking impact resistance and heat resistance into consideration, the soft segment content in the TPEE is preferably 5-75% by weight, more preferably 30-70% by weight, based on 100 parts by weight of TPEE in total. When the soft segment content in TPEE is too low, the hardness of TPEE increases, and it is difficult to expect an improvement in impact resistance. On the other hand, when the polyalkylene oxide content is too high, heat resistance may decrease.

[0032] In a specific embodiment, the Shore hardness of the TPEE that can be used in the polyamide resin composition of the present invention may be D20 to D40.

[0033] The polyamide resin composition of the present invention contains the TPEE in an amount of more than 0.5 parts by weight to less than 20 parts by weight based on a total of 100 parts by weight of the composition. When the TPEE content in the polyamide resin composition of the present invention is less than 0.5 parts by weight, the heat resistance of the composition is reduced, and the impact resistance or gas barrier properties are deteriorated. On the other hand, when the TPEE content is more than 20 parts by weight, the impact resistance and gas barrier properties of the composition are reduced.

[0034] More specifically, the TPEE content in a total of 100 parts by weight of the polyamide resin composition of the present invention may be, for example, more than 0.5 parts by weight, 0.6 parts by weight or more, 0.8 parts by weight or more, 1 part by weight or more, 1.2 parts by weight or more, 1.4 parts by weight or more, 1.5 parts by weight or more, 1.6 parts by weight or more, 1.8 parts by weight or more, or 2 parts by weight or more, and may be less than 20 parts by weight, 19.9 parts by weight or less, 19 parts by weight or less, 18 parts by weight or less, 17 parts by weight or less, 16 parts by weight or less, 15 parts by weight or less, 14 parts by weight or less, 13 parts by weight or less, 12 parts by weight or less, 11 parts by weight or less, 10 parts by weight or less, 9 parts by weight or less, or 8 parts by weight or less, but is not limited thereto.

[0035] The polyamide resin composition of the present invention further comprises an impact modifier.

[0036] In a specific embodiment, the impact modifier can be selected from maleic anhydride grafted polyolefin elastomer rubber (POE-MAH), maleic anhydride grafted ethylene propylene rubber (EPDM-MAH), styrene-ethylene-butylene-styrene rubber (SEBS), maleic anhydride grafted styrene-ethylene-butylene-styrene rubber (SEBS-MAH), random terpolymer of ethylene, acrylic esterand glycidyl methacrylate, ethylene-acrylic acid rubber, ethylene-glycidyl methacrylate and combinations thereof. From the viewpoint of low-temperature impact resistance and heat resistance, maleic anhydride grafted polyolefin elastomer rubber can be preferably used as the impact modifier.

[0037] The polyamide resin composition of the present invention may contain the impact modifier in an amount of more than 11 parts by weight to less than 34 parts by weight based on a total of 100 parts by weight of the composition. When the content of the impact modifier in a total of 100 parts by weight of the polyamide resin composition of the present invention is 11 parts by weight or less, the impact resistance of the composition is reduced, and on the other hand, when the content of the impact modifier is 34 parts by weight or more, the gas barrier properties and heat resistance of the composition are reduced.

[0038] More specifically, the content of the impact modifier in a total of 100 parts by weight of the polyamide resin composition of the present invention may be, for example, more than 11 parts by weight, 11.1 parts by weight or more, 11.5 parts by weight or more, 12 parts by weight or more, 12.5 parts by weight or more, 13 parts by weight or more, 13.5 parts by weight or more, 14 parts by weight or more, 14.5 parts by weight or more, 15 parts by weight or more, 15.5 parts by weight or more, or 16 parts by weight or more, and may be less than 34 parts by weight, 33.9 parts by weight or less, 33 parts by weight or less, 32 parts by weight or less, 31 parts by weight or less, 30 parts by weight or less, 29 parts by weight or less, 28 parts by weight or less, 27 parts by weight or less, 26 parts by weight or less, 25 parts by weight or less, or 24 parts by weight or less, but is not limited thereto.

[0039] The polyamide resin composition of the present invention further comprises a nucleating agent.

[0040] In a specific embodiment, the nucleating agent can be an inorganic nucleating agent, an organic nucleating agent, an organic-inorganic composite nucleating agent or a combination thereof, more specifically an organic-inorganic composite nucleating agent, but is not limited thereto.

[0041] More specifically, the inorganic nucleating agent can be talc, kaolin, silica, titanium dioxide, nanoclay or a combination thereof, the organic nucleating agent can be sodium benzoate, organic phosphate, carbon fiber, polyphenylene sulfide, polycarbonate, polyphenylene ether, a polymer having a melting point 50 degrees higher than that of polyamide 6 or a combination thereof, and the organic-inorganic composite nucleating agent can be a mixture of a polyamide component and a silicate component that are advantageously dispersed in a nylon phase (for example, Bruggolen P22 (polyamide 22 + aluminum silicate) of Brüggemann), but is not limited thereto.

[0042] The polyamide resin composition of the present invention contains the nucleating agent in an amount of more than 0 parts by weight to less than 3 parts by weight based on a total of 100 parts by weight of the composition. When the content of the nucleating agent in a total of 100 parts by weight of the polyamide resin composition of the present invention is 0, that is, when the composition does not contain the nucleating agent, the impact resistance of the composition becomes very poor, and on the other hand, when the content of the nucleating agent is 3 parts by weight or more, the impact resistance and heat resistance of the composition are reduced.

[0043] More specifically, the content of the nucleating agent in a total of 100 parts by weight of the polyamide resin composition of the present invention can be, for example, more than 0 parts by weight, 0.001 parts by weight or more, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, or 0.05 parts by weight or more, and can be less than 3 parts by weight, less than 2.9 parts by weight, less than 2.8 parts by weight, less than 2.5 parts by weight, less than 2.3 parts by weight, less than 2 parts by weight, less than 1.8 parts by weight, or less than 1.5 parts by weight, but is not limited thereto.

[0044] The polyamide resin composition of the present invention may further contain one or more additives generally used in polyamide resin compositions in addition to the above-mentioned components.

[0045] In a specific embodiment, the additive can be selected from a heat stabilizer, an antioxidant, a lubricant, a flame retardant, a flame retardant aid and a combination thereof. Based on a total of 100 parts by weight of the composition, the content of the additive can be 0.1-20 parts by weight or 1-10 parts by weight, but is not limited thereto.

[0046] The polyamide resin composition of the present invention contains the above-mentioned specific essential components in combination at specific content ratios, and can simultaneously exhibit excellent gas barrier properties and low-temperature impact resistance at a high level required for use as a lining for gas storage containers.

[0047] For example, although not limited thereto, the polyamide resin composition of the present invention may simultaneously exhibit a gas permeability of 170 cm / s at a thickness of 3 mm measured at 80° C. according to ISO 15105. 3 / (m 2 24h atm) or less, 165cm 3 / (m 2 24h atm) or less, 160cm 3 / (m 2 24h atm) or less or 155cm 3 / (m 2 Excellent gas barrier properties of less than 24h·atm) and a -40℃ Charpy notched impact strength of 20kJ / m measured according to ISO179 2 Above, 25kJ / m 2 Above, 30kJ / m 2 Above or 35kJ / m 2 Excellent low temperature impact resistance.

[0048] In addition, for example, although not limited thereto, the polyamide resin composition of the present invention can exhibit excellent heat resistance by having a tensile strength of 80% or more of the tensile strength before treatment even after treatment at 120° C. for 3000 hours (i.e., a tensile strength retention of 80% or more).

[0049] In this way, the polyamide resin composition of the present invention can simultaneously exhibit excellent gas barrier properties and excellent impact resistance (especially high low-temperature impact resistance) that cannot be achieved by existing polyamide resin compositions, and can also exhibit excellent mechanical physical properties such as tensile strength and heat resistance, and therefore can be very suitable for use as linings for gas storage containers.

[0050] The method for preparing the polyamide resin composition of the present invention is not particularly limited and can be appropriately selected according to the equipment used and other process elements. According to a specific embodiment of the present invention, the raw materials are mixed and added to the extruder hopper, the melt temperature at this time is set to 200-300° C., and the RPM is set to 150 to 250 to extrude the mixture, thereby preparing polyamide resin pellets, but it is not limited thereto.

[0051] Therefore, according to another aspect of the present invention, a molded article comprising the polyamide resin composition of the present invention is provided. In a preferred embodiment, the molded article is a liner of a gas storage container.

[0052] The molded product can be an extrusion molded product or an injection molded product of the polyamide resin composition of the present invention. In a specific embodiment, the molding process can be extrusion, injection molding, blowing (hollow molding), rotational molding, etc., but is not limited thereto.

[0053] Hereinafter, the present invention will be described in more detail by way of examples, but the scope of the present invention is not limited to these examples.

[0054] [Example]

[0055] Examples 1 to 6 and Comparative Examples 1 to 10

[0056] <Preparation of polyamide resin composition>

[0057] The resin compositions of the embodiments and comparative examples were prepared according to the compositions shown in Table 1 below. That is, the raw materials consisting of the polyamide, thermoplastic polyester elastomer, impact modifier, nucleating agent, etc. specified in the following ingredient description were mixed in a super mixer for about 2 minutes and added to the extruder hopper to prepare pellets. The extruder used a 30 mm extruder with 12 barrels (Japan Steel Works). The RPM was set to 250, and the melt temperature was set at 260° C. for each part. The composition after the extrusion process was cooled in a cooling tank, and then pellets of the polyamide resin composition were prepared.

[0058] <Ingredients>

[0059] (1) Polyamide resin: polyamide 6 with a relative viscosity of 2.7 (KP Chemtech EN350AA)

[0060] (2) Thermoplastic polyester elastomer (TPEE): TPEE with a Shore hardness of D30 was prepared by the following preparation method and used:

[0061] 29.39 parts by weight of dimethyl terephthalate (DMT), 18.77 parts by weight of 1,4-butanediol, 51.64 parts by weight of polyoxytetramethylene glycol (PTMEG) with a molecular weight of 2000 and 0.065 parts by weight of glycerol were placed in an oligomerization reactor, to which 0.025 parts by weight of tetra-n-butoxytitanium (TBT) was added as a catalyst. The reaction temperature was raised from 140°C to 215°C within 120 minutes, and further reacted for 120 minutes while maintaining 215°C. The amount of methanol as the reaction effluent was converted into a reaction rate, and the reaction was terminated when the reaction rate was 99% or more. After that, 0.04 parts by weight of TBT as a catalyst and 0.07 parts by weight of a heat stabilizer (Irganox 1010) were further added and a polycondensation reaction was carried out. The polycondensation reaction was carried out as follows: the temperature was raised from 215°C to 250°C within 120 minutes, and further reacted for 120 minutes while maintaining 250°C. At this time, the pressure is reduced from 760 Torr to 0.3 Torr for 1 hour, and the remaining 3 hours are carried out under a vacuum condition of less than 0.3 Torr, and the final pressure reduction is adjusted to less than 0.3 Torr, thereby preparing TPEE with a Shore hardness of D30. The intrinsic viscosity (IntrinsicViscosity) of the TPEE prepared in this way is 1.9-2.0 dl / g when measured in a solvent of phenol / tetrachloroethane (TCE) = 50 / 50.

[0062] (3) Impact modifier: maleic anhydride grafted polyolefin elastomer (W1A, XIAMEN COACE PLASTIC)

[0063] (4-1) Nucleating agent 1: organic-inorganic composite nucleating agent (polyamide 22 + aluminum silicate) (Bruggolen P22, Brüggemann)

[0064] (4-2) Nucleating agent 2: Inorganic nucleating agent (talc) (KCM 2000C, KOCH)

[0065] (5) Nanoclay: Layered silicate (Closite 93A)

[0066] (6) Reinforcement filler: Wollastonite (Nyglos 4W)

[0067] (7) Aliphatic polyamide copolymer: Novamid 2430A (PA6 / 66 copolyamide, DSM Engineering Materials)

[0068] (8) Others: Based on a total of 100 parts by weight of the composition, 2 parts by weight of a heat stabilizer, an antioxidant, a lubricant, etc. were added to each experimental group.

[0069] [Table 1]

[0070]

[0071] <Measurement and evaluation of physical properties>

[0072] With respect to the polyamide resin composition prepared as described above, the following physical property items were measured and evaluated, and the results are shown in Table 2 below.

[0073] (1) Low-temperature impact strength: A test piece was prepared according to ISO 179, placed in a low-temperature refrigerator at -40°C for 4 hours, taken out and the Charpy notched impact strength was measured within 5 seconds.

[0074] (2) Gas transmission rate (GTR): Gas permeability is measured using a plastic test piece according to ISO 15105. The test piece is installed to form a barrier between two chambers of a gas transmission unit. One chamber contains a high-pressure test gas, and the other chamber collects the permeated gas and detects it. The gas permeation test is performed using hydrogen at a temperature of 80°C. The unit for expressing the permeability is cm 3 / (m 2 ·24h·atm).

[0075] (3) Evaluation of long-term heat resistance by measuring tensile strength and impact strength: Test pieces were prepared according to ISO 527-2, and then the initial tensile strength was measured. The same test piece was placed in an oven set at 120°C for 3000 hours, and the test piece was taken out after 3000 hours, and the tensile strength was measured in the same manner, and compared with the initial value to calculate the tensile strength retention rate (%), thereby evaluating the long-term heat resistance.

[0076] [Table 2]

[0077]

[0078] As can be seen from Table 2, the polyamide resin compositions according to Examples 1 to 6 simultaneously exhibit excellent gas barrier properties and low-temperature impact resistance at high levels required for use in linings of gas storage containers.

[0079] On the other hand, the compositions of Comparative Examples 1, 3 to 6, 9 and 10 have excellent gas barrier properties, but poor low-temperature impact resistance, and are therefore not suitable as materials for hydrogen tanks used in a temperature range including low temperatures (-40°C to 80°C). The compositions of Comparative Examples 2, 7 and 8 have excellent low-temperature impact resistance, but poor gas barrier properties, and are therefore not suitable as materials for hydrogen tanks. In addition, the compositions of Comparative Examples 1 to 4, 5, 7, 8 and 10 also have poor long-term heat resistance.

Claims

1. A polyamide resin composition comprising: (1) a polyamide resin; (2) a thermoplastic polyester elastomer; (3) an impact modifier and (4) a nucleating agent, in, Based on 100 parts by weight of the composition, The content of the thermoplastic polyester elastomer is more than 0.5 parts by weight and less than 20 parts by weight, The content of the impact modifier is more than 11 parts by weight and less than 34 parts by weight, The content of the nucleating agent is more than 0 parts by weight to less than 3 parts by weight.

2. The polyamide resin composition according to claim 1, wherein The polyamide resin is an aliphatic polyamide homopolymer, an aliphatic polyamide copolymer or a combination thereof.

3. The polyamide resin composition according to claim 1, wherein The thermoplastic polyester elastomer is a thermoplastic block copolymer comprising a rigid hard segment and a flexible soft segment.

4. The polyamide resin composition according to claim 3, wherein The hard segment includes polymerization units of an aromatic dicarboxylic acid compound and a diol, and the soft segment includes polymerization units of a polyalkylene oxide.

5. The polyamide resin composition according to claim 4, wherein The aromatic dicarboxylic acid compound is selected from terephthalic acid (TPA), isophthalic acid (IPA), 1,5-naphthalene dicarboxylic acid (1,5-NDCA), 2,6-naphthalene dicarboxylic acid (2,6-NDCA), dimethyl terephthalate (DMT), dimethyl isophthalate and combinations thereof, The diol is selected from ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and combinations thereof, The polyalkylene oxide is selected from polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol (PTMEG) and combinations thereof.

6. The polyamide resin composition according to claim 1, wherein The impact modifier is selected from maleic anhydride grafted polyolefin elastomeric rubber (POE-MAH), maleic anhydride grafted ethylene propylene diene rubber (EPDM-MAH), styrene-ethylene-butylene-styrene rubber (SEBS), maleic anhydride grafted styrene-ethylene-butylene-styrene rubber (SEBS-MAH), random terpolymer of ethylene-acrylate-glycidyl methacrylate, ethylene-acrylic acid rubber, ethylene-glycidyl methacrylate and combinations thereof.

7. The polyamide resin composition according to claim 1, wherein The nucleating agent is selected from an inorganic nucleating agent, an organic nucleating agent, an organic-inorganic composite nucleating agent or a combination thereof.

8. The polyamide resin composition according to claim 7, wherein The inorganic nucleating agent is talc, kaolin, silicon dioxide, titanium dioxide, nano clay or a combination thereof. The organic nucleating agent is sodium benzoate, organic phosphate, carbon fiber, polyphenylene sulfide, polycarbonate, polyphenylene ether, a polymer with a melting point 50 degrees higher than that of polyamide 6, or a combination thereof. The organic-inorganic composite nucleating agent is a mixture of a polyamide component and a silicate component. 9 . A molded article comprising the polyamide resin composition according to claim 1 .

10. The molded article according to claim 9, wherein The molded product is a liner of a gas storage container.

Images