Halogen-free flame-retardant polyamide composition as well as preparation method and application thereof

Abstract

The invention discloses a halogen-free flame-retardant polyamide composition as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. The halogen-free flame-retardant polyamide composition is prepared from the following components in parts by weight: 34 to 56 parts of polyterephthalamide resin; 33 to 56 parts of poly (m-xylylenediamine adipate) resin; 4-16 parts of an organic hypophosphite flame retardant; 4-52 parts of flat glass fiber; 4-52 parts of a flaky filler; the mass ratio of the flat glass fibers to the flaky filler is (0.6-4): 1; the flatness ratio of the flat glass fibers is (2-6): 1. The halogen-free flame-retardant polyamide composition disclosed by the invention has excellent mechanical properties and cold and hot impact cracking resistance.

Description

Technical Field

[0001] This invention relates to the technical field of polymer materials, and in particular to a halogen-free flame-retardant polyamide composition, its preparation method, and its application. Background Technology

[0002] Currently, the most common halogen-free flame-retardant PPA materials on the market are 30%-45% glass fiber / mineral reinforced, ADP halogen-free flame-retardant PA6T materials, such as DuPont Zytel® HTN52G45HSL and Solvay Amodel® AS-1145. When applied to busbars, these materials are prone to edge cracking under long-term thermal shock conditions due to the significant difference in CLTE between the material and the metal (such as copper), as well as the large difference in CLTE between the transverse and longitudinal directions. This leads to insulation failure and renders the material unusable.

[0003] Currently, no patents mention research on the resistance to thermal shock cracking of halogen-free flame-retardant polyamide (PPA) materials used in the busbar applications of new energy vehicles. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a halogen-free flame-retardant polyamide composition, its preparation method, and its applications. The halogen-free flame-retardant polyamide composition of this invention possesses excellent mechanical properties and resistance to thermal shock cracking.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a halogen-free flame-retardant polyamide composition comprising the following components in parts by weight: 34-56 parts of poly(terephthalamide) resin; 33-56 parts of poly(m-phenylene adipamide) resin; 4-16 parts of organic hypophosphite flame retardant; 4-52 parts of flat glass fiber; 4-52 parts of sheet filler; The mass ratio of the flat glass fiber to the sheet filler is (0.6-4):1; the flatness ratio of the flat glass fiber is (2-6):1.

[0006] This invention achieves a balanced comprehensive performance by using a combination of flat glass fibers and sheet fillers, resulting in high strength, low transverse and longitudinal CLTE, and low internal stress in the composite material.

[0007] If the mass ratio of flat glass fiber to sheet filler is too low, although the anisotropic shrinkage of the composite material is uniform, the strength of the composite material is low. Under long-term thermal shock conditions, even a small interfacial stress can cause the busbar to crack. If the mass ratio of flat glass fiber to sheet filler is too high, although the strength of the composite material is high, the dimensional anisotropy is significantly increased. Under long-term thermal shock conditions, uneven shrinkage in the transverse and longitudinal directions leads to poor flatness, high internal stress, and easy cracking. Therefore, this invention, by controlling the mass ratio of flat glass fiber to sheet filler, is beneficial to improving the mechanical properties and resistance to thermal shock cracking of the composite material, while also exhibiting a low coefficient of linear thermal expansion (CLTE).

[0008] It should be noted that the aspect ratio refers to the ratio of the width to the length of the glass fiber cross-section.

[0009] The testing standard for aspect ratio is ISO 1888:2022.

[0010] Preferably, the flat glass fiber is chopped glass fiber; the chopped length is 2-15 mm.

[0011] Preferably, the short axis of the cross-section of the flat glass fiber is 3-20 μm and the long axis is 5-40 μm.

[0012] Preferably, the mass ratio of the flat glass fiber to the sheet filler is any one or a range of two of the following: 0.6:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, and 4:1.

[0013] Preferably, the flatness ratio of the flat glass fiber is any one or a combination of 2:1, 3:1, 4:1, 5:1, and 6:1.

[0014] Preferably, the mass ratio of the flat glass fiber to the sheet filler is (1-2.5):1.

[0015] Preferably, the flatness ratio of the flat glass fiber is (3-4):1.

[0016] Preferably, the relative viscosity of the poly(terephthalamide) resin is greater than 1.6, and the relative viscosity of the poly(m-phenylene adipamide) is less than 3.0.

[0017] More preferably, the relative viscosity of the poly(terephthalamide) resin is in the range of 1.8-2.8.

[0018] More preferably, the relative viscosity of the poly(m-phenylene adipamide) is in the range of 1.8-2.8.

[0019] More preferably, the relative viscosity ratio of the poly(terephthalamide) resin and the poly(m-phenylene adipamide) resin is (0.7-1.25):1, and even more preferably (0.9-1.1):1.

[0020] The test method for the relative viscosity of the polyamide resin described in this invention is as follows: the test is carried out in accordance with GB12006.1-89. The specific test method is as follows: the relative viscosity ηr of the polyamide with a concentration of 0.25 g / dl is measured in 98% concentrated sulfuric acid at 25±0.01℃.

[0021] Preferably, the diamine unit in the poly(terephthalamide) resin is derived from an aliphatic diamine; the aliphatic diamine unit has ≥8 carbon atoms; preferably, the aliphatic diamine has 9-12 carbon atoms.

[0022] More preferably, the poly(terephthalamide) resin includes at least one of poly(octyl terephthalamide), poly(nonyl terephthalamide), poly(decyl terephthalamide), poly(undecyl terephthalamide), and poly(dodecanoyl terephthalamide).

[0023] Preferably, the flat glass fiber is a chopped fiber; the cross-section of the flat glass fiber is substantially rectangular.

[0024] Preferably, the sheet-like filler includes at least one of talc, mica, and boron nitride.

[0025] Preferably, the particle size range of the sheet-like filler is 5-50 μm, more preferably 5-15 μm.

[0026] Preferably, the diameter-to-thickness ratio of the sheet-like filler is (2-15):1.

[0027] The particle size of the sheet-like filler described in this invention was measured by laser diffraction, and the aspect ratio of the sheet-like filler was measured by microscopic image analysis (SEM scanning electron microscopy).

[0028] Preferably, the organic hypophosphite flame retardant includes at least one of aluminum diethylphosphinate, zinc diethylphosphinate, aluminum methyl ethylphosphinate, aluminum ethyl butylphosphinate, and aluminum ethylhexylphosphinate.

[0029] More preferably, the organophosphite flame retardant is aluminum diethylphosphinate.

[0030] Preferably, the halogen-free flame-retardant polyamide composition comprises the following components in parts by weight: 40-50 parts of poly(terephthalamide) resin; 40-50 parts of poly(m-phenylene adipamide) resin; 6-12 parts of organic hypophosphite flame retardant; 10-40 parts of flat glass fiber; 10-40 parts of sheet filler.

[0031] Preferably, in the halogen-free flame-retardant polyamide composition, the total mass percentage of poly(terephthalamide) resin and poly(m-phenylene adipamide) resin is not less than 25%.

[0032] Preferably, the total mass percentage of the sheet filler and flat glass fiber in the halogen-free flame-retardant polyamide composition of the present invention is in the range of 25-40%.

[0033] Preferably, the halogen-free flame-retardant polyamide composition further includes 0-5 parts of other additives, including but not limited to lubricants, antioxidants, light stabilizers, etc.

[0034] Preferably, the lubricant comprises at least one of fluoropolymers, linear low-density polyethylene (LLDPE), silicone oil, metal stearate, alkyl stearate, metal montanic acid, montanic ester wax, or polyethylene wax. Specifically, the lubricant may include solid paraffin, liquid paraffin, polyolefin wax, calcium stearate, magnesium stearate, zinc stearate, barium stearate, ethylene glycol stearate, glyceryl stearate, pentaerythritol stearate, erucamide, methylene bis-stearamide, N,N-ethylene bis-stearamide, and combinations thereof.

[0035] The halogen-free flame-retardant polyamide composition of the present invention may include antioxidants, and suitable antioxidants may include, but are not limited to, thioester antioxidants, hindered phenolic antioxidants, hydroxylamine antioxidants, phosphite antioxidants, phosphate antioxidants, and combinations thereof.

[0036] Preferably, the thioester antioxidant includes at least one of dialkyl thiodipropionate or pentaerythritol tetra(3-lauryl thiopropionate).

[0037] Preferably, the hindered phenolic antioxidant comprises at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, vinyl bis(oxyvinyl)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] or 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0038] Preferably, the hydroxylamine antioxidant includes bis(octadecyl)hydroxylamine.

[0039] Preferably, the phosphite antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol dibis(2,4-tert-butylphenyl) phosphite.

[0040] Preferably, the phosphate antioxidant includes bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate.

[0041] Secondly, the present invention also discloses a method for preparing a halogen-free flame-retardant polyamide composition, comprising the following steps: The components are mixed and added to a twin-screw extruder, and after extrusion and granulation, a halogen-free flame-retardant polyamide composition is obtained.

[0042] Preferably, the temperature of the twin-screw extruder is 250-350℃, and the screw speed is 200-600 rpm.

[0043] Thirdly, the present invention also discloses the application of a halogen-free flame-retardant polyamide composition in the preparation of automotive parts, specifically applicable to bus connectors in new energy vehicle battery systems.

[0044] Fourthly, the present invention also discloses an automotive component, preferably a bus connector, specifically a bus connector in a new energy battery system.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves a composite material with high strength, low transverse and longitudinal CLTE, and balanced comprehensive performance by using flat glass fiber and sheet filler in combination and controlling their mass ratio. This results in a halogen-free flame-retardant polyamide composition with excellent mechanical properties and resistance to thermal shock cracking, as well as a low linear coefficient of thermal expansion. Detailed Implementation

[0046] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0047] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0048] Examples 1-12 Examples of the halogen-free flame-retardant polyamide composition and its preparation method according to the present invention are shown in Table 1.

[0049] The method for preparing the halogen-free flame-retardant polyamide composition includes the following steps: The components are mixed and added to a twin-screw extruder. After granulation and cooling, a halogen-free flame-retardant polyamide composition is obtained.

[0050] The temperature of the twin-screw extruder is 250-350℃, and the screw speed is 200-600 rpm.

[0051] Comparative Examples 1-8 The only difference between the comparative examples and the embodiments is the type and ratio of components, as shown in Table 2.

[0052] In the components described in each embodiment and comparative example: The poly(terephthalamide) resin 1 is PA10T:KFHP11, manufactured by Kingfa Science & Technology, with a relative viscosity of 2.2. The poly(terephthalamide) resin 2 is PA12T: Henan Junheng Industrial Group Biotechnology Co., Ltd., with a relative viscosity of 2.1.

[0053] The poly(terephthalamide) resin 3 is PA10T, KFHP11-0, manufactured by Kingfa Science & Technology, with a relative viscosity of 1.6. The poly(terephthalamide) resin 4 is PA6T: Amodel A-4000, manufactured by Solvay, USA.

[0054] The poly(m-phenylene adipamide) resin 1:S6007, Mitsubishi Gas, has a relative viscosity of 2.6; The poly(m-phenylene adipamide) resin 2:1022F, Mitsubishi Gas, has a relative viscosity of 2.2. The poly(m-phenylene adipamide) resin 3: PA MXD6, manufactured by Qicai Chemicals, has a relative viscosity of 3.0.

[0055] The flat glass fiber 1 is TFG432, Taishan Glass Fiber, with a flatness ratio of 1.8:1; The flat glass fiber 2 is TFG436, Taishan Glass Fiber, with a flatness ratio of 2.5:1; The flat glass fiber 3 is TFG835, Taishan Glass Fiber, with a flatness ratio of 4:1; The flat glass fiber 4 is TFG950, Taishan glass fiber, with a flatness ratio of 6:1; The flat glass fiber 5 is JD-FB60, manufactured by Jiangsu Jiuding, with a flatness ratio of 8:1. The circular glass fiber: ECS301HP-3-H, Chongqing International.

[0056] The sheet-like filler 1 is phlogopite with a diameter-to-thickness ratio of 2:1 to 3:1, KM-20, manufactured by Asahi Kasei.

[0057] The sheet filler 2 is talc powder with a diameter-to-thickness ratio of 5:1 to 8:1, MKMN-T01, Hebei Maikeman Mineral Co., Ltd.

[0058] The organic hypophosphite flame retardant is aluminum diethylphosphinate: OP 1230, Clariant Chemicals.

[0059] The lubricant is LLDPE7042, manufactured by Guangzhou Petrochemical.

[0060] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0061] Table 1 Table 2 To verify the performance of the halogen-free flame-retardant polyamide composition of the present invention, the halogen-free flame-retardant polyamide compositions prepared in the various examples and comparative examples were injection molded into specimens for testing the following properties.

[0062] Performance testing methods: 1. Linear thermal expansion coefficient (CLTE in the vertical flow direction): Tested according to ISO 11359-1 / -2 standard.

[0063] 2. Tensile properties: Tested according to ISO 527-4-2023 standard, the tensile rate is 10 mm / min.

[0064] 3. Crack Resistance: The prepared halogen-free flame-retardant polyamide composition was injection molded into M8 busbars (150*28*35mm) at an injection temperature of 315-335℃. Standard busbars were obtained and stored at -40℃ for 60 minutes, then transferred to 150℃ within 3 minutes, and stored at 150℃ for another 60 minutes, then transferred to -40℃ within 3 minutes, for a total of 500 cycles. After cooling to room temperature, the cracking of the busbars was observed.

[0065] 4. Flame retardant performance: Tested in accordance with UL 94 flame retardant performance test method and standard.

[0066] The performance parameters obtained from the above tests are shown in Table 3.

[0067] Table 3 As shown in Table 3, the halogen-free flame-retardant polyamide composition of the present invention has a CLTE of less than 70, a tensile strength of greater than 120 MPa, and a flame retardant rating of V-0, indicating that the halogen-free flame-retardant polyamide composition of the present invention has excellent mechanical properties, low CLTE, resistance to thermal shock cracking, and flame retardant properties.

[0068] Comparing Comparative Examples 1-2 with Example 1, it can be seen that in Comparative Example 1, the aspect ratio of the flat glass fibers is too small, resulting in a significant fiber reinforcement effect, but no significant effect on reducing CLTE. This leads to excessive interference stress during thermal shock, causing cracking. In Comparative Example 2, the aspect ratio of the flat glass fibers is too large, and although CLTE is controlled to be relatively low, cracking still occurs. Therefore, by controlling the aspect ratio of the flat glass fibers to (2-6):1, the present invention enables the halogen-free flame-retardant polyamide composition to possess excellent mechanical properties, low CLTE, and resistance to thermal shock cracking.

[0069] Comparing Comparative Examples 3-4 with Example 1, it can be seen that in Comparative Example 3, the mass ratio of flat glass fiber to sheet filler was too small. Although the CLTE was controlled to be low, the fiber reinforcement effect was significantly weakened, leading to cracking. In Comparative Example 4, the mass ratio of flat glass fiber to sheet filler was too large. Although the fiber reinforcement effect was enhanced, the sheet filler's effect on improving CLTE was greatly reduced. Therefore, by controlling the mass ratio of flat glass fiber to sheet filler to (0.6-4):1, the present invention enables the halogen-free flame-retardant polyamide composition to possess excellent mechanical properties, low CLTE, and resistance to thermal shock cracking.

[0070] Comparing Comparative Examples 5-6 with Example 1, it can be seen that Comparative Example 5, lacking the addition of flat glass fibers, exhibits significantly reduced material strength, leading to cracking. Comparative Example 6, lacking the addition of sheet fillers, fails to effectively reduce transverse and longitudinal CLTE, resulting in excessive interference stress during thermal shock and consequently, cracking. Therefore, this invention, by employing a combination of flat glass fibers and sheet fillers, enables the halogen-free flame-retardant polyamide composition to possess excellent mechanical properties, low CLTE, and resistance to thermal shock cracking.

[0071] Comparing Comparative Example 7 with Example 1, it can be seen that in Comparative Example 7, an equal amount of PA6T was used to replace PA10T. Due to its hygroscopicity and secondary crystallization, PA6T resin exhibited significantly lower dimensional stability during thermal shock than PAXT resin, which has 8 or more carbon atoms in its diamine, leading to cracking. Therefore, this invention does not demonstrate that selecting any polyterephthalamide resin will necessarily result in a halogen-free flame-retardant polyamide composition with excellent mechanical properties, low CLTE, and resistance to thermal shock cracking.

[0072] By comparing Comparative Example 8 with Example 1, the applicant hypothesizes that if the glass fiber cross-section is circular, the material exhibits significant two-dimensional anisotropy and a large difference in shrinkage rates between the transverse and longitudinal directions, leading to noticeable warping and poor dimensional stability. Conversely, if the glass fiber is flat, the two-dimensional anisotropy is significantly reduced, the difference in shrinkage rates between the transverse and longitudinal directions is smaller, resulting in less warping and improved dimensional stability. Therefore, the present invention selects a combination of flat glass fiber and sheet filler, which is beneficial for improving the dimensional stability of the halogen-free flame-retardant polyamide composition.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A halogen-free flame-retardant polyamide composition, characterized in that, Includes the following components in parts by weight: 34-56 parts of poly(terephthalamide) resin; 33-56 parts of poly(m-phenylene adipamide) resin; 4-16 parts of organic hypophosphite flame retardant; 4-52 parts of flat glass fiber; 4-52 parts of sheet filler; The mass ratio of the flat glass fiber to the sheet filler is (0.6-4):1; the flatness ratio of the flat glass fiber is (2-6):

1.

2. The halogen-free flame-retardant polyamide composition according to claim 1, characterized in that, The relative viscosity of the poly(terephthalamide) resin is greater than 1.6, and the relative viscosity of the poly(m-phenylene adipamide) is less than 3.

0.

3. The halogen-free flame-retardant polyamide composition according to claim 2, characterized in that, The relative viscosity range of the poly(terephthalamide) resin is 1.8-2.8, and the relative viscosity range of the poly(m-phenylene adipamide) is 1.8-2.

8.

4. The halogen-free flame-retardant polyamide composition according to claim 1, characterized in that, The diamine unit in the poly(terephthalamide) resin is derived from an aliphatic diamine; the aliphatic diamine unit has ≥8 carbon atoms; Preferably, the polyterephthalamide resin includes at least one of poly(octyl terephthalamide), poly(nonyl terephthalamide), poly(decyl terephthalamide), poly(undecyl terephthalamide), and poly(dodecanoyl terephthalamide).

5. The halogen-free flame-retardant polyamide composition according to claim 1, characterized in that, The organophosphite flame retardant includes dialkylphosphinates; preferably, the dialkylphosphinates include at least one of aluminum diethylphosphinate, zinc diethylphosphinate, aluminum methyl ethylphosphinate, aluminum ethyl butylphosphinate, and aluminum ethylhexylphosphinate.

6. The halogen-free flame-retardant polyamide composition according to claim 1, characterized in that, The sheet-like filler includes at least one of talc, mica, and boron nitride.

7. The halogen-free flame-retardant polyamide composition according to claim 1, characterized in that, The halogen-free flame-retardant polyamide composition also includes 0-5 parts of lubricant.

8. A method for preparing a halogen-free flame-retardant polyamide composition according to any one of claims 1-7, characterized in that, Includes the following steps: The components are mixed and added to a twin-screw extruder, and after extrusion and granulation, a halogen-free flame-retardant polyamide composition is obtained.

9. The use of a halogen-free flame-retardant polyamide composition as described in any one of claims 1-7 in the preparation of automotive parts.

10. An automotive component, characterized in that, Includes the halogen-free flame-retardant polyamide composition as described in any one of claims 1-7.

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