Thermoplastic resin composition having excellent electrolyte resistance and molded article comprising same

Abstract

The present invention relates to a thermoplastic resin composition having excellent electrolyte resistance and a molded article comprising same and, more specifically, to a thermoplastic resin composition and a molded article (particularly, a cell gasket for a cylindrical battery) comprising same, wherein the thermoplastic resin composition comprises a thermoplastic polyester elastomer and an inorganic nucleating agent in a specific weight ratio together with polybutylene terephthalate, thereby exhibiting both excellent electrolyte resistance and strength (tensile strength, flexural strength, etc.) characteristics and thus being very suitable for use as a cell gasket for a cylindrical battery for electric vehicles, particularly a high-capacity cylindrical battery.

Description

Thermoplastic resin composition with excellent electrolyte resistance and molded article containing the same

[0001] The present invention relates to a thermoplastic resin composition having excellent electrolyte resistance and a molded article containing the same. More specifically, by including a thermoplastic polyester elastomer and an inorganic nucleating agent together with polybutylene terephthalate in a specific weight ratio, the invention simultaneously exhibits excellent electrolyte resistance and strength characteristics (tensile strength, flexural strength, etc.), thereby making it highly suitable for use as a cell gasket for cylindrical batteries for electric vehicles, particularly high-capacity cylindrical batteries, and to a molded article containing the same (particularly a cell gasket for a cylindrical battery).

[0002] While performance improvements in electric vehicle batteries have primarily relied on chemical composition—such as increasing the nickel content of the cathode and adding silicon to the anode—rather than on cell or pack design, much research is currently underway to increase the energy density and capacity of the cell itself by increasing the cell size.

[0003] For example, there is a 'Structural Battery' technology that increases the size of cylindrical battery cells from the current 2170 (diameter 21mm, height 70mm) to 4680 (diameter 46mm, height 80mm) so that the cell itself acts as a structure. When the battery cell size increases in this way, not only does the energy density and capacity of the cell itself increase, but 4680 battery cells can be accommodated in a battery pack layout that previously held 4,416 2170 cells, allowing for a drastic reduction in materials such as wiring connecting the cells, which can help improve manufacturing processes and reduce costs.

[0004] However, as battery cell sizes increase, various problems are expected to arise, one of which is electrolyte leakage. Cylindrical batteries have cell gaskets to prevent electrolyte leakage; while cell gaskets made of conventional materials are suitable for the currently used 2170 cylindrical battery cell size for electric vehicles, the electrolyte leakage prevention function must be further improved when the battery cell size increases to 4680. Furthermore, for the larger battery cell to perform structural functions, the cell gasket also requires higher flexural modulus and tensile properties.

[0005] Resin compositions containing polybutylene terephthalate are known as materials for conventional cell gaskets (e.g., Korean Patent Publication No. 10-2013-0009691, No. 10-2019-0101913, etc.). However, these conventional materials are not suitable for high-capacity cylindrical battery cell structures due to insufficient resistance to electrolytes and strength (tensile, flexural) properties.

[0006] The objective of the present invention is to provide a thermoplastic resin composition that simultaneously exhibits excellent electrolyte resistance and strength characteristics (tensile strength, flexural strength, etc.), and which is highly suitable for use as a cell gasket for cylindrical batteries for electric vehicles, particularly high-capacity cylindrical batteries, and a molded article containing the same (particularly a cell gasket for a cylindrical battery).

[0007] In order to solve the above-mentioned technical problem, the present invention provides a thermoplastic resin composition comprising (1) polybutylene terephthalate (PBT); (2) a thermoplastic polyester elastomer; and (3) an inorganic nucleating agent; wherein, based on 100 parts by weight of the total composition, the content of the thermoplastic polyester elastomer is greater than 3 parts by weight and less than 42 parts by weight, and the content of the inorganic nucleating agent is greater than 0.3 parts by weight and less than 3 parts by weight.

[0008] According to another aspect of the present invention, a molded article comprising the thermoplastic resin composition of the present invention is provided.

[0009] In a preferred embodiment, the molded product is a cell gasket for a cylindrical battery for an electric vehicle.

[0010] The thermoplastic resin composition of the present invention exhibits superior electrolyte resistance and strength (tensile strength, flexural strength, etc.) characteristics compared to conventional PBT resin compositions, and can be very suitable for use as a cell gasket for cylindrical batteries for electric vehicles, particularly high-capacity cylindrical batteries. The cell gasket obtained by molding it exhibits excellent leakage prevention characteristics after assembly into a cylindrical battery for electric vehicles, and at the same time exhibits excellent strength characteristics, allowing the battery cell itself to function as a structure.

[0011] The present invention will be described in more detail below.

[0012] The thermoplastic resin composition of the present invention comprises (1) polybutylene terephthalate (PBT); (2) a thermoplastic polyester elastomer; and (3) an inorganic nucleating agent.

[0013] (1) Polybutylene terephthalate (PBT)

[0014] The polybutylene terephthalate included in the thermoplastic resin composition of the present invention is a thermoplastic resin having repeating units represented by the following chemical formula 1, and having a melting temperature of 215 to 235°C:

[0015] [Chemical Formula 1]

[0016]

[0017] In the above chemical formula 1, n is an integer greater than or equal to 1, and specifically, may be an integer from 50 to 200.

[0018] In one embodiment, the intrinsic viscosity (IV) of the polybutylene terephthalate may be 0.8 to 1.5 dl / g, preferably 0.9 to 1.4 dl / g, and more preferably 1.0 to 1.3 dl / g, but is not limited thereto.

[0019] In one embodiment, the crystallization temperature of the polybutylene terephthalate may be 160 to 200°C, and more specifically 170 to 190°C, but is not limited thereto.

[0020] In one embodiment, the thermoplastic resin composition of the present invention may contain the polybutylene terephthalate in an amount of 55 to 94 parts by weight based on 100 parts by weight of the total composition. If the polybutylene terephthalate content in 100 parts by weight of the total composition is within the above range, the composition may simultaneously exhibit excellent electrolyte resistance and strength (tensile strength, flexural strength, etc.) characteristics.

[0021] More specifically, within a total of 100 parts by weight of the thermoplastic resin composition of the present invention, the polybutylene terephthalate may be included in an amount of, for example, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, 59 parts by weight or more, 60 parts by weight or more, 61 parts by weight or more, 62 parts by weight or more, or 63 parts by weight or more, and may also be included in an amount of 94 parts by weight or less, 93.5 parts by weight or less, 93 parts by weight or less, 92.5 parts by weight or less, or 92 parts by weight or less, but is not limited thereto.

[0022] (2) Thermoplastic polyester elastomer (TPEE)

[0023] The thermoplastic polyester elastomer included in the thermoplastic resin composition of the present invention is a thermoplastic block copolymer comprising a hard segment and a soft segment.

[0024] In one embodiment, the hard segment may comprise a polymerization unit of an aromatic dicarboxylic compound and a diol, and the soft segment may comprise a polymerization unit of a polyalkylene oxide.

[0025] Specifically, the aromatic dicarboxylic compound may be selected from the group consisting of 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 combinations thereof, and preferably may be DMT.

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

[0027] Additionally, specifically, the polyalkylene oxide may be a polyalkylene glycol selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol (PTMEG), and combinations thereof, and preferably may be PTMEG. Also, in one embodiment, the number average molecular weight of the polyalkylene glycol for the soft segment may be, for example, 600 to 3000 g / mol (more specifically 800 to 2000 g / mol, and even more specifically 1000 to 1500 g / mol), but is not limited thereto.

[0028] In one embodiment, the thermoplastic polyester elastomer may be branched by a branching agent to increase melt tension, thereby improving the stability of the strand during TPEE production and increasing productivity. The branching agent may be selected from the group consisting of, for example, glycerol, pentaerythritol, neopentylglycol, and combinations thereof, and preferably may be glycerol.

[0029] The TPEE that can be used in the thermoplastic resin composition of the present invention may generally be produced through melt polymerization consisting of two stages of oligomerization reaction and polycondensation reaction, and preferably may be branched TPEE.

[0030] Branched TPEE can be produced by introducing the above-mentioned components into a reactor and then carrying out melt polymerization consisting of two stages, an oligomerization reaction and a polycondensation reaction, in the presence of a suitable catalyst, such as tetra-n-butoxy titanium (TBT). The oligomerization reaction can be carried out at 140 to 215°C for 3 to 4 hours, and the polycondensation reaction can be carried out at 210 to 250°C for 4 to 5 hours with a stepwise reduction of pressure from 760 torr to 0.3 torr.

[0031] In one embodiment, the soft segment content in the TPEE may be 5 wt% or more, 10 wt% or more, 15 wt% or more, 20 wt% or more, or 25 wt% or more based on 100 wt% of the total TPEE, and may also be 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, or 35 wt% or less, but is not limited thereto.

[0032] The thermoplastic resin composition of the present invention comprises the TPEE in an amount greater than 3 parts by weight and less than 42 parts by weight, based on 100 parts by weight of the total composition. If the TPEE content in 100 parts by weight of the thermoplastic resin composition of the present invention is 3 parts by weight or less, the mechanical properties of the composition, such as impact resistance and tensile elongation, are reduced, and the electrolyte resistance is also deteriorated; conversely, if the content is 42 parts by weight or more, the mechanical properties of the composition, such as tensile strength and flexural strength, are reduced.

[0033] More specifically, the TPEE content in a total of 100 parts by weight of the thermoplastic resin composition of the present invention may, for example, be more than 3 parts by weight, 3.1 parts by weight or more, 3.5 parts by weight or more, 4 parts by weight or more, 4.5 parts by weight or more, 5 parts by weight or more, 5.5 parts by weight or more, or 6 parts by weight or more, and may also be less than 42 parts by weight, 41 parts by weight or less, 40 parts by weight or less, 39 parts by weight or less, 38 parts by weight or less, 37 parts by weight or less, 36 parts by weight or less, 35 parts by weight or less, or 34 parts by weight or less, but is not limited thereto.

[0034] (3) Weapon nuclear agent

[0035] The thermoplastic resin composition of the present invention includes an inorganic nucleating agent.

[0036] In one embodiment, the inorganic nucleating agent may be selected from the group consisting of talc, kaolin, silica, titanium dioxide, nanoclay, and combinations thereof, and preferably may be talc.

[0037] In one embodiment, the particle size of the inorganic nucleating agent may be 1 to 10 μm, more specifically 2 to 8 μm, and even more specifically 3 to 7 μm, but is not limited thereto.

[0038] The thermoplastic resin composition of the present invention comprises the inorganic nucleating agent in an amount greater than 0.3 parts by weight and less than 3 parts by weight based on 100 parts by weight of the total composition. If the content of the inorganic nucleating agent in 100 parts by weight of the total composition of the present invention is 0.3 parts by weight or less, the mechanical properties of the composition, such as tensile strength and flexural strength, are reduced, and the electrolyte resistance properties are also deteriorated; conversely, if the content is 3 parts by weight or more, the mechanical properties of the composition, such as impact resistance and tensile elongation, are reduced.

[0039] More specifically, the content of an inorganic nucleating agent in a total of 100 parts by weight of the thermoplastic resin composition of the present invention may, for example, be greater than 0.3 parts by weight, 0.4 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, 1.1 parts by weight or more, 1.2 parts by weight or more, 1.3 parts by weight or more, 1.4 parts by weight or more, or 1.5 parts by weight or more, and may also be less than 3 parts by weight, 2.9 parts by weight or less, 2.8 parts by weight or less, 2.7 parts by weight or less, 2.6 parts by weight or less, 2.5 parts by weight or less, 2.4 parts by weight or less, 2.3 parts by weight or less, 2.2 parts by weight or less, 2.1 parts by weight or less, or 2 parts by weight or less, but is not limited thereto.

[0040] According to one embodiment of the present invention, within the scope of achieving the purpose of the present invention, the composition of the present invention may further include a nucleating agent other than the inorganic nucleating agent, and such nucleating agent other than the inorganic nucleating agent may be an organic nucleating agent, an organic-inorganic composite nucleating agent, or a combination thereof, but is not limited thereto. In one embodiment, the organic nucleating agent may be a polymer having a melting point 50 degrees or higher than sodium benzoate, sodium octacosanoate, organic phosphate, carbon fiber, polyphenylene sulfide, polycarbonate, polyphenylene oxide, or polyamide 6, or a combination thereof.

[0041] The thermoplastic resin composition of the present invention may further include one or more additives commonly used in thermoplastic resin compositions in addition to the components described above.

[0042] In one embodiment, the additive may be selected from heat stabilizers, dispersants, antioxidants, lubricants, flame retardants, flame retardant aids, and combinations thereof, and the content of each may be 0.1 to 5 parts by weight or 0.1 to 1 part by weight based on 100 parts by weight of the total composition, but is not limited thereto.

[0043] There are no particular limitations on the method for manufacturing the thermoplastic resin composition of the present invention, and it may be appropriately selected depending on the equipment used and other process elements. According to one embodiment of the present invention, the thermoplastic resin composition may be manufactured in the form of pellets by mixing raw materials and extruding them, but is not limited thereto.

[0044] The thermoplastic resin composition of the present invention, due to its composition comprising the aforementioned specific essential components in a specific content ratio, simultaneously exhibits superior electrolyte resistance and strength characteristics (tensile strength, flexural strength, etc.) compared to conventional PBT resin compositions.

[0045] For example, but not limited to, the thermoplastic resin composition of the present invention has a strength of 600 kgf / cm² 2 Above (more specifically, 600 to 700 kgf / cm²) 2 ) tensile strength, tensile elongation of 80% or more (more specifically, 80 to 150%), 800 kgf / cm 2 Above (more specifically, 800 to 1000 kgf / cm²) 2 Flexural strength of ), and 25,000 kgf / cm 2 Above (more specifically, 25,000 to 30,000 kgf / cm²) 2 It can exhibit a flexural modulus of ), and preferably, even after exposure to the electrolyte, one or more of the above properties, preferably two or more (e.g., 600 kgf / cm²) 2 It can exhibit tensile strength and tensile elongation of 80% or more. Here, 'electrolyte exposure' means exposure for 7 days to an electrolyte in which LiPF6 is dissolved at a concentration of 1.0 M in an EC (ethylene carbonate)-EMC (ethyl methyl carbonate)-DMC (dimethyl carbonate) mixed electrolyte (EC:EMC:DMC = 2:4:4 weight ratio).

[0046] As such, since the thermoplastic resin composition of the present invention simultaneously exhibits excellent electrolyte resistance and strength (tensile strength, flexural strength, etc.) characteristics, it can be very suitable for use as a cell gasket for cylindrical batteries for electric vehicles, particularly high-capacity cylindrical batteries. The cell gasket obtained by molding it exhibits excellent leakage prevention characteristics after assembly into a cylindrical battery for electric vehicles, and at the same time exhibits excellent strength characteristics, allowing the battery cell itself to function as a structure.

[0047] Accordingly, according to another aspect of the present invention, a molded article comprising the thermoplastic resin composition of the present invention is provided, and in a preferred embodiment, the molded article is a cell gasket of a cylindrical battery for an electric vehicle.

[0048] The above-mentioned molded article may be an extrusion-molded article or an injection-molded article of the thermoplastic resin composition of the present invention, and in one embodiment, the molding process method may be extrusion, injection, blow molding, rotational molding, etc., but is not limited thereto.

[0049] The present invention will be explained in more detail below through examples. However, the scope of the present invention is not limited to these examples.

[0050] [Example]

[0051] Examples 1 to 7 and Comparative Examples 1 to 8

[0052] <Preparation of Thermoplastic Resin Composition>

[0053] Resin compositions for each example and comparative example were prepared with the compositions shown in Table 1 below. Specifically, the raw material components described below were mixed in a super mixer for about 2 minutes and fed into an extruder hopper to produce pellets. A 12-barrel 30 mm extruder (Japan Steel Works) was used. The RPM was set to 250, and the melting temperature was set to 235°C as a standard for each section. After the extrusion process, the composition was cooled in a cooling bath to produce pellets of the resin composition.

[0054] <Ingredient Description>

[0055] A. Polybutylene terephthalate (PBT)

[0056] (A-1) PBT resin with intrinsic viscosity of 0.85 dl / g (211M, Changchun)

[0057] (A-2) PBT resin with intrinsic viscosity of 1.1 dl / g (211H, Changchun)

[0058] B. Thermoplastic Polyester Elastomer (TPEE)

[0059] (B-1) TPEE containing 25 wt% of polyoxytetramethylene glycol (PTMEG) with a number average molecular weight of 1000 g / mol as a soft segment (TRIEL 5639, Samyang Corporation)

[0060] (B-2) TPEE containing 35 wt% of polyoxytetramethylene glycol (PTMEG) with a number average molecular weight of 1000 g / mol as a soft segment (TRIEL 5552, Samyang Corporation)

[0061] C. Weapon Nuclear Agents

[0062] Talc with particle size of 3~7㎛ (KCM6300, KOCH)

[0063] D. Organic nucleating agents

[0064] Sodium octacosanoate (NAV101, Clariant)

[0065] E. Heat stabilizer

[0066] (E-1) Primary: Phenolic antioxidant (SONGNOX®1010, Songwon Industrial)

[0067] (E-2) Secondary: Phosphorus-based antioxidant (Doverphos®S-9228, Dover chemical)

[0068] F. Dispersant

[0069] Ester wax (Licowax®E, Clariant)

[0070] <Measurement and Evaluation of Physical Properties>

[0071] The following physical properties were measured and evaluated for the thermoplastic resin composition prepared as described above, and the results are summarized in Table 1 below.

[0072] (1) Impact strength (notch impact strength) (Kgfcm / cm): Measured according to ASTM D256.

[0073] (2) Tensile strength (kgf / cm²) 2 ): Measured according to ASTM D638.

[0074] (3) Tensile elongation (%): Measured according to ASTM D638.

[0075] (4) Flexural strength (kgf / cm²) 2 ): Measured according to ASTM D790.

[0076] (5) Flexural modulus (kgf / cm²) 2 ): Measured according to ASTM D790.

[0077] (6) Evaluation of internal electrolyte characteristics

[0078] According to the Environmental Stress Cracking Test (ESCR) method, the specimen was exposed to the electrolyte for 7 days under the following conditions, and if no cracks were found upon visual inspection, a tensile test was performed.

[0079] - Electrolyte: An electrolyte in which LiPF6 is dissolved at a concentration of 1.0 M in an EC (ethylene carbonate)-EMC (ethylmethyl carbonate)-DMC (dimethyl carbonate) mixed electrolyte (EC:EMC:DMC = 2:4:4 by weight ratio).

[0080] - Test specimen: Tensile specimen according to ASTM 638 standard

[0081] - Test Method: After applying the electrolyte at Strain (ε=1.5), expose for 7 days, then perform a tensile test.

[0082] - Equipment used: Environmental Stress Cracking Test Equipment (ESCR)

[0083]

[0084]

[0085] As can be seen from Table 1 above, the thermoplastic resin compositions according to Examples 1 to 7 have a density of 600 kgf / cm² 2 Tensile strength greater than or equal to, tensile elongation of 80% or greater, 800 kgf / cm² 2 Flexural strength of the above, and 25,000 kgf / cm² 2 Excellent mechanical properties with the above flexural modulus were exhibited, and 600 kgf / cm² even after electrolyte exposure. 2 Excellent electrolyte resistance characteristics were exhibited by maintaining the above tensile strength and tensile elongation of 80% or more. A resin composition exhibiting such excellent electrolyte resistance characteristics and strength (tensile strength, flexural strength, etc.) characteristics simultaneously can be very suitable for use as a cell gasket for cylindrical batteries for electric vehicles, particularly high-capacity cylindrical batteries, and the cell gasket obtained by molding it exhibits excellent leakage prevention characteristics after assembly into a cylindrical battery for electric vehicles, while also exhibiting excellent mechanical properties, allowing the battery cell itself to function as a structure.

[0086] On the other hand, in the case of the comparative example compositions, one or more of the mechanical properties of the test items were inferior compared to the example, and physical properties deteriorated after exposure to electrolyte. These resin compositions are insufficient to function as gaskets for preventing electrolyte leakage, particularly when the cell size of a cylindrical battery increases from 2170 (diameter 21 mm, height 70 mm) to 4680 (diameter 46 mm, height 80 mm), as it is difficult to maintain their shape.

Claims

1. As a thermoplastic resin composition, (1) Polybutylene terephthalate; (2) thermoplastic polyester elastomer; and (3) Includes weapon nucleation agent; and Based on a total of 100 parts by weight of the composition, the content of the thermoplastic polyester elastomer is greater than 3 parts by weight and less than 42 parts by weight, and the content of the inorganic nucleating agent is greater than 0.3 parts by weight and less than 3 parts by weight, Thermoplastic resin composition.

2. A thermoplastic resin composition according to claim 1, wherein the intrinsic viscosity (IV) of the polybutylene terephthalate is 0.8 to 1.5 dl / g.

3. A thermoplastic resin composition according to claim 1, wherein the thermoplastic polyester elastomer is a thermoplastic block copolymer comprising a hard segment and a soft segment.

4. A thermoplastic resin composition according to claim 3, wherein the hard segment comprises a polymerization unit of an aromatic dicarboxylic compound and a diol, and the soft segment comprises a polymerization unit of a polyalkylene oxide.

5. In Paragraph 4, An aromatic dicarboxylic compound is selected from the group consisting of 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 combinations thereof, and The diol is selected from the group consisting of ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, and combinations thereof, and The polyalkylene oxide is selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol (PTMEG), and combinations thereof, Thermoplastic resin composition.

6. A thermoplastic resin composition according to claim 1, wherein the inorganic nucleating agent is selected from the group consisting of talc, kaolin, silica, titanium dioxide, nano clay, and combinations thereof.

7. A molded article comprising a thermoplastic resin composition according to any one of claims 1 to 6.

8. A molded product, wherein the cell gasket of a cylindrical battery for an electric vehicle, in paragraph 7.

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