A pk / pa alloy and a method of manufacturing and using the same

Abstract

The present application relates to a kind of PK / PA alloy and its preparation method and application, the PK / PA alloy includes by mass parts: PA6 resin 20-45 parts, PK resin 15-35 parts, ultra-high molecular weight polyethylene 2-5 parts, glass fiber 15-40 parts and flame retardant 8-14 parts.The present application is by formula optimization to PK / PA alloy, effectively reduce the friction between alloy system inside and alloy and processing equipment, reduce the mass generation of free radical from source, can effectively solve the problem that crosslinking, gel even carbonization is caused by free radical in processing, the PK / PA alloy prepared has excellent mechanical property, flame retardancy, heat resistance, processing stability and weather resistance, has wide application prospect in the field such as automobile, electronic appliance.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and in particular to a PK / PA alloy, its preparation method, and its applications. Background Technology

[0002] Polyamide (PA) possesses excellent mechanical and electrical properties and is widely used in the automotive, electronics, and other fields. However, PA molecules contain polar amide groups, which easily form hydrogen bonds with water molecules in the air. This increases the intermolecular distance and the free volume of the material, ultimately resulting in a decrease in product rigidity and significant dimensional changes, making it difficult to meet the requirements of high-precision components.

[0003] Polyketone (PK) is produced by triblock copolymerization of carbon monoxide, ethylene, and a small amount of propylene. Its molecular backbone is predominantly composed of carbon-carbon single bonds and contains numerous carbonyl groups. This structure endows PK with excellent chain mobility, effectively dissipating external loads and resulting in outstanding toughness. Furthermore, PK exhibits extremely low water absorption and good dimensional stability. Due to its high hydrocarbon ratio and excellent char-forming ability, the π electrons of the unsaturated carbonyl groups within the molecule do not form a conjugated system, giving the material a high glow wire ignition temperature (GWIT) and a tracking index (CTI) of 600 V or higher. Only a small amount of flame retardant is needed to achieve the UL94V-0 flame retardant rating. However, PK also has significant drawbacks: poor processing stability and weather resistance, and its overall strength is weaker than that of poly(acetal) with stronger intermolecular forces.

[0004] Blending PK and PA to prepare PK / PA alloys can effectively improve the hydrolysis resistance of PA, further increase the glow wire ignition temperature of the alloy system, enhance material toughness, reduce overall water absorption, and optimize product dimensional stability. However, this blend system still has drawbacks: PK itself has poor processing stability and weather resistance, and the propylene group in the molecular chain contains tertiary carbon atoms, which easily lose hydrogen atoms during processing to generate free radicals; these free radicals can form conjugated structures with carbonyl groups, tending to be stable. In the low-oxygen environment of twin-screw extrusion, the alloy system will generate a large number of carbon-centered alkyl free radicals, which will then trigger partial cross-linking reactions, and in severe cases, gelation and carbonization will occur; after the melt is extruded from the die and comes into contact with air, the free radicals will combine with oxygen to generate peroxy free radicals, further inducing chain degradation reactions. Furthermore, the presence of PA exacerbates the free radical generation tendency of PK / PA alloys: PA molecules can form a large number of hydrogen bonds, and the melt viscosity is higher at processing temperatures, which prolongs the residence time of the originally self-lubricating PK component in the screw. Compared with the pure PK system, the blended material is more likely to generate free radicals, exacerbating thermal degradation and carbonization problems.

[0005] Therefore, how to solve the problems of free radical generation and gel carbonization during the processing of PK / PA blended alloys has become an urgent issue to be addressed. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a PK / PA alloy, its preparation method, and its applications. This PK / PA alloy exhibits excellent mechanical properties, flame retardancy, heat resistance, processing stability, and weather resistance, and has broad application prospects in the automotive, electronics, and other fields.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a PK / PA alloy, wherein the PK / PA alloy comprises, by weight, 20-45 parts of PA6 resin, 15-35 parts of PK resin, 2-5 parts of ultra-high molecular weight polyethylene, 15-40 parts of glass fiber, and 8-14 parts of flame retardant.

[0008] Among them, 20-45 portions can be, for example, 20 portions, 25 portions, 30 portions, 35 portions, or 40 portions; 15-35 portions can be, for example, 15 portions, 20 portions, 25 portions, 30 portions, or 35 portions; 2-5 portions can be, for example, 2 portions, 2.5 portions, 3 portions, 3.5 portions, 4 portions, 4.5 portions, or 5 portions; 15-40 portions can be, for example, 15 portions, 20 portions, 25 portions, 30 portions, 35 portions, or 40 portions; 8-14 portions can be, for example, 8 portions, 9 portions, 10 portions, 11 portions, 12 portions, 13 portions, or 14 portions.

[0009] This invention optimizes the formulation of PK / PA alloys by adding glass fiber and flame retardants to improve their mechanical strength, flame retardancy, and heat resistance. UHMWPE is a non-polar PE material with ultra-long molecular chains and a low coefficient of friction, reducing friction between the melt and the screw / barrel. Due to its extremely high molecular weight, a large number of chain segments remain within the melt, forming a protective lubricating layer on the melt surface while also reducing intermolecular forces and improving fluidity. The addition of ultra-high molecular weight polyethylene reduces friction between PK / PA alloy components (the introduction of glass fiber and flame retardants exacerbates internal friction within the alloy system, prolonging the material's residence time in the screw) and between the PK / PA alloy and processing equipment. This allows the alloy to pass through the processing equipment quickly, reducing residence time and preventing the excessive generation of free radicals caused by internal friction within the alloy components and friction between the alloy and equipment. This solves the problems of crosslinking, gelation, and carbonization during alloy processing.

[0010] This invention limits the dosage of each component: if the proportion of PK resin is too low, the alloy GWIT will be difficult to reach temperatures above 750°C, and the amount of flame retardant added needs to be increased to maintain the same flame retardant rating; if the proportion of PK resin is too high, the performance degradation of the material after photoaging will be significantly increased, the weather resistance will be worse, and the initial mechanical strength will be lower. On the other hand, if the amount of ultra-high molecular weight polyethylene added is insufficient, it will not be able to play its role in reducing friction and inhibiting free radicals, while adding too much will significantly weaken the flame retardant performance of the alloy.

[0011] Preferably, the mass ratio of PA6 resin to PK resin is (1-4):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, etc.

[0012] The present invention limits the mass ratio of PA6 resin to PK resin to (1-4):1. By adjusting the ratio of the two, the comprehensive mechanical properties of the alloy can be controlled or the GWIT value can be improved. If the proportion of PK resin in the alloy is too high, the degradation of various properties of the alloy after photoaging will be significantly increased, and the weather resistance stability will be greatly reduced.

[0013] Preferably, the relative viscosity of the PA6 resin is 1.8-2.1, for example, it can be 1.8, 1.85, 1.9, 1.95, 2, 2.05 or 2.1.

[0014] The relative viscosity was tested in accordance with GB / T 1632-93.

[0015] This invention limits the relative viscosity of PA6 resin to 1.8-2.1. If the relative viscosity is too low, the corresponding molecular weight of PA6 resin is too small. Although the melt flow is good, the surface of the product is smooth, and the free radicals generated by the alloy system are less when co-processed with PK alloy, its own toughness is insufficient and cannot meet the requirements of actual use conditions. If the relative viscosity is too high, the PK matrix is ​​prone to gelation and carbonization during processing. In extreme cases, melt foaming problems may occur, which will prevent the granulation process from being carried out normally.

[0016] Preferably, the melt flow index of the PK resin is 50-250 g / 10min, for example, it can be 50 g / 10min, 60 g / 10min, 80 g / 10min, 100 g / 10min, 120 g / 10min, 140 g / 10min, 150 g / 10min, 160 g / 10min, 180 g / 10min, 200 g / 10min, 220 g / 10min, 240 g / 10min or 250 g / 10min, etc.

[0017] The melt flow rate was tested according to ASTM D1238-23 at a temperature of 240°C and a load of 2.16 kg.

[0018] This invention limits the melt flow index of PK resin to 50-250 g / 10min. When the melt flow index is too high, the resin melt has excellent fluidity, but the overall mechanical properties are insufficient and the raw material cost is also higher. When the melt flow index is too low, the melt fluidity is insufficient. Although its negative impact is not as great as that caused by the viscosity fluctuation of PA6 resin, it will still promote the generation of a large number of free radicals in the alloy system, which will damage the performance and color stability of the alloy.

[0019] Preferably, the ultra-high molecular weight polyethylene has a weight-average molecular weight of 8.0 × 10⁻⁶. 6 ~10×10 6 g / mol, for example, could be 8.0 × 10⁻⁶ g / mol. 6 g / mol, 8.2×10 6 g / mol, 8.4×10 6 g / mol, 8.5×10 6 g / mol, 8.6×10 6 g / mol, 8.7×10 6 g / mol, 9.0×10 6 g / mol, 9.2×10 6 g / mol, 9.4×10 6 g / mol, 9.5×10 6 g / mol, 9.6×10 6 g / mol, 9.8×10 6 g / mol or 10×10 6 g / mol, etc.

[0020] Preferably, the diameter of the glass fiber monofilament is 8-15 μm, for example, it can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc.

[0021] Preferably, the chopped length of the glass fiber is 2.5-5 mm, for example, it can be 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, etc.

[0022] Preferably, the flame retardant comprises an organophosphonate flame retardant.

[0023] Preferably, the organophosphonate flame retardant comprises alkylphosphonates.

[0024] Preferably, the alkylphosphinate includes any one or a combination of at least two of aluminum diethylphosphinate, aluminum methyl ethylphosphinate, aluminum diisobutylphosphinate, or aluminum diethylphosphinate combined with aluminum phosphite, and more preferably aluminum diethylphosphinate.

[0025] Currently, mainstream halogen-free and red phosphine-free flame retardant systems on the market are divided into three categories: pure aluminum diethyl phosphonate (ADP), aluminum diethyl phosphonate combined with melamine polyphosphonate (MPP), and aluminum diethyl phosphonate combined with aluminum phosphonite (AHP). Among them, melamine polyphosphonate has the potential for excessive melamine release during use, and its application scenarios continue to be limited under increasingly stringent environmental regulations. At the same time, the flame retardant system of aluminum diethyl phosphonate combined with melamine polyphosphonate is prone to forming scale on the mold surface during injection molding, and the additives may migrate and precipitate under humid and hot conditions, resulting in poor product stability. Considering the above defects, this invention preferably uses aluminum diethyl phosphonate as the flame retardant. By weight, the PK / PA alloy can contain 8-10 parts of aluminum diethyl phosphonate, which can achieve the technical effect of GWIT≥750℃ in the PK / PA alloy system. If the flame retardant system of aluminum diethyl phosphonate combined with melamine polyphosphonate and other flame retardants are selected, the filler content needs to be further increased.

[0026] Preferably, the PK / PA alloy further comprises, by weight, any one or a combination of at least two of the following: 0.1-0.3 parts of primary antioxidant, 0.1-0.3 parts of secondary antioxidant, 0.2-0.4 parts of ultraviolet absorber, or 0.2-0.4 parts of light stabilizer.

[0027] Among them, 0.1-0.3 parts can be, for example, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, or 0.3 parts; 0.2-0.4 parts can be, for example, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, or 0.4 parts.

[0028] Preferably, the primary antioxidant comprises hindered phenolic antioxidants.

[0029] Preferably, the hindered phenolic antioxidant includes any one or a combination of at least two of N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide), β-(3,5-di-tert-butyl-4-hydroxyphenyl)octadecyl ester or tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)pentaerythritol ester, and more preferably N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide).

[0030] Preferably, the auxiliary antioxidant includes phosphonates as antioxidants.

[0031] Preferably, the phosphonite antioxidant includes any one or a combination of at least two of tris(2,4-di-tert-butylphenyl)phosphonite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphonite, trinonylphenyl phosphonite, triphenyl phosphonite or pentaerythritol bisoctadecyl phosphonite, and more preferably tris(2,4-di-tert-butylphenyl)phosphonite.

[0032] Preferably, the ultraviolet absorber includes a triazine ultraviolet absorber.

[0033] Preferably, the triazine-based ultraviolet absorber includes 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octoxy)phenol and / or 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol, more preferably 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-octoxyphenol.

[0034] Preferably, the light stabilizer includes hindered amine light stabilizers.

[0035] Preferably, the hindered amine light stabilizer comprises N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide and / or bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, more preferably N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

[0036] Because the molecular chains of PK / PA alloys contain ethylene and propylene structures, they easily form carbonyl conjugated systems after the generation of free radicals. The continuous accumulation of conjugated structures causes the light absorption band to shift from red to the visible light region, resulting in yellowing of the product. At the same time, the oxidation chain reaction initiated by free radicals can also destroy the integrity of the matrix molecular chain during processing, significantly reducing the alloy's weather resistance. This invention further adds antioxidants, ultraviolet absorbers, and light stabilizers, which can not only eliminate melt free radicals and reduce the initial ignition point of oxidation chain reactions during the high-temperature extrusion processing stage, ensuring the integrity of the PK / PA molecular structure, but also pre-absorb ultraviolet light to avoid ultraviolet light exciting resin segments to generate free radicals and reduce the formation of conjugated color-emitting structures. It can also continuously inhibit the generation of free radicals in the local high-temperature environment generated by the conversion of light energy into heat energy by ultraviolet absorbers.

[0037] In a second aspect, the present invention provides a method for preparing the PK / PA alloy as described in the first aspect, the method comprising the following steps: The components of the PK / PA alloy are melt-blended, extruded, and granulated to obtain the PK / PA alloy.

[0038] Preferably, the melt blending is carried out in a twin-screw extruder.

[0039] Preferably, the PA resin, PK resin, ultra-high molecular weight polyethylene, antioxidant, ultraviolet absorber, light stabilizer, and flame retardant in the PK / PA alloy are mixed and then fed into a twin-screw extruder through the main feed port.

[0040] Preferably, the glass fibers in the PK / PA alloy are fed into the twin-screw extruder via a side feed port.

[0041] Preferably, the temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 280-300℃; Zone 2: 280-300℃; Zone 3: 280-300℃; Zone 4: 280-300℃; Zone 5: 260-280℃; Zone 6: 170-190℃; Zone 7: 170-190℃; Zone 8: 180-200℃; and Zone 9: 170-190℃.

[0042] Among them, 280-300℃ can be, for example, 280℃, 285℃, 290℃, 295℃ or 300℃; 260-280℃ can be, for example, 260℃, 265℃, 270℃, 275℃ or 280℃; 170-190℃ can be, for example, 170℃, 175℃, 180℃, 185℃ or 190℃; 180-200℃ can be, for example, 180℃, 185℃, 190℃, 195℃ or 200℃.

[0043] Preferably, the die head temperature of the twin-screw extruder is 240-255℃, for example, it can be 240℃, 245℃, 250℃ or 255℃.

[0044] Preferably, the screw speed of the twin-screw extruder is 350-450 r / min, for example, it can be 350 r / min, 360 r / min, 380 r / min, 400 r / min, 420 r / min, 440 r / min or 450 r / min, etc.

[0045] Thirdly, the present invention provides an application of the PK / PA alloy as described in the first aspect in automobiles and electronic appliances.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects: (1) By optimizing the formula of PK / PA alloy, this invention effectively reduces the friction between the alloy system and the processing equipment, thereby reducing the generation of free radicals from the source. It can effectively solve the problems of crosslinking, gelation and even carbonization caused by free radicals during processing. The resulting PK / PA alloy has excellent mechanical properties, flame retardancy, heat resistance, processing stability and weather resistance, and has broad application prospects in the fields of automobiles, electronics and electrical appliances.

[0047] (2) The PK / PA alloy provided by this invention has a tensile strength of 133.01-146.96 MPa, a tensile modulus of 10076.75-10962.85 MPa, an elongation at break of 2.9-3.7%, a bending strength of 177.22-214.6 MPa, a bending modulus of 7191.56-7800.70 MPa, and a notched impact strength of 11.25-17.89 kJ / m. 2 The impact strength of a cantilever beam without a notch can reach 42.03-62.4 kJ / m. 2 It exhibits flame retardancy up to UL 94 V-1 and V-0 standards, a GWIT of 750-800℃, a ΔE of 4.10-7.39 after light aging, a tensile strength of 85.85-119.88 MPa after light aging, and an elongation at break of 1.8-3.0% after light aging. It possesses excellent mechanical properties and weather resistance, with a GWIT ≥ 750℃, making it suitable for unattended applications and situations requiring precise dimensional accuracy. Detailed Implementation

[0048] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0049] The specific information of the materials used in the following specific embodiments of the present invention is as follows: PA6 resin, BL3180 (relative viscosity 1.85±0.05), purchased from Baling Petrochemical; PA6 resin, BL3200 (relative viscosity 2.05±0.05), purchased from Baling Petrochemical; PA6 resin, BL3240 (relative viscosity 2.45±0.05), purchased from Baling Petrochemical; PA66 resin, EP1106 (relative viscosity 2.28), purchased from Zhejiang Huafeng Group; PK resin, M330A (melt flow rate of 60 g / 10min), was purchased from Hyosung, South Korea. PK resin, M930A (melt flow rate 200 g / 10min), was purchased from Hyosung, South Korea. PK resin, M630V (melt flow rate of 6 g / 10min), was purchased from Hyosung, South Korea. Ultra-high molecular weight polyethylene, GUR4150 (weight average molecular weight 8.7 × 10⁻⁶) 6 g / mol), purchased from Celanese; Polytetrafluoroethylene, PTFE-0143, purchased from Nanjing Tianshi New Material Technology Co., Ltd. Glass fiber, 301HP (monofilament diameter 10 μm, chopped length 3 mm), purchased from Chongqing Composite Materials. Flame retardant, aluminum diethylphosphinate OP-1230, purchased from Clariant; Flame retardant, aluminum diethylphosphinate compounded with aluminum phosphite OP-1400, purchased from Clariant; The main antioxidants, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide) and antioxidant 1098, were purchased from Rion. Co-antioxidant, tris(2,4-di-tert-butylphenyl)phosphonite, antioxidant 168, purchased from Rion; Ultraviolet absorber, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-(octyloxy)phenol, UV-1164, purchased from Rianlong; Light stabilizer, N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide, UV-660, purchased from Rion.

[0050] Examples 1-13, Comparative Examples 1-5 Examples 1-13 and Comparative Examples 1-5 respectively provide a PK / PA alloy and its preparation method. The specific composition of the PK / PA alloy is shown in Tables 1-3 (the amount of each component in the table is by mass), where "--" indicates that the component was not added.

[0051] The preparation method of the PK / PA alloy includes: PA resin, PK resin, UHMWPE, primary antioxidant, secondary antioxidant, UV absorber, and light stabilizer were added to a high-speed mixer according to their mass ratios and mixed at 100 rpm for 5 min to obtain mixture A. The flame retardant was designated as component B. Mixture A and component B were fed into a twin-screw extruder through the main feed port, while glass fiber was fed into the twin-screw extruder through the side feed port for melt blending. The twin-screw extruder temperatures were: zone 1 290℃, zone 2 290℃, zone 3 290℃, zone 4 290℃, zone 5 290℃, zone 6 180℃, zone 7 180℃, zone 8 190℃, zone 9 180℃, die head temperature 250℃, and screw speed 400 r / min. After extrusion, the mixture was cooled, dried, and pelletized to obtain the PK / PA alloy.

[0052] Table 1 Table 2 Table 3 Test methods The PK / PA alloys provided in the examples and comparative examples were subjected to the following performance tests: (1) Tensile strength (MPa): Tested according to ISO 527-2, using type 1A specimens, and at a test speed of 5 mm / min; (2) Tensile modulus (MPa): Tested according to ISO 527-2, using type 1A specimen, at a test speed of 5 mm / min; (3) Elongation at break (%): The test was conducted in accordance with ISO 527-2, using type 1A specimens and a test speed of 5 mm / min; (4) Bending strength (MPa): The test was conducted in accordance with ISO 178. The PK / PA alloy was cut into strips with dimensions of 80 mm × 10 mm × 4 mm, and the test speed was 2 mm / min. (5) Bending modulus (MPa): The test was conducted in accordance with ISO 178. The PK / PA alloy was cut into strips with dimensions of 80 mm × 10 mm × 4 mm, and the test speed was 2 mm / min. (6) Cantilever beam notch impact (kJ / m) 2 According to ISO 180, the PK / PA alloy was cut into strips with dimensions of 80mm × 10mm × 4mm and a notch of 2mm. The impact energy was 2.75 J. (7) Cantilever beam impact without notch (kJ / m 2 ): The test was conducted according to ISO 180. The PK / PA alloy was cut into strips with dimensions of 80 mm × 10 mm × 4 mm, and the impact energy was 5.5 J. (8) Flame retardancy: Tested according to UL 94, the PK / PA alloy was cut into strips with dimensions of 125 mm × 13 mm × 1.5 mm; (9) Glow wire ignition temperature (GWIT, °C): Tested according to IEC 60695, the PK / PA alloy was cut into strips with dimensions of 60 mm × 60 mm × 2 mm; (10) Xenon arc lamp acceleration experiment: The test was conducted according to VS-99.01-L-08004, using 340 nm ultraviolet light at 0.55 W / m 2 Irradiation intensity reached 488 kJ / m 2 The color difference value ΔE, tensile strength after aging (MPa), and elongation at break (%) were tested.

[0053] The test results are shown in Tables 4-6 below: Table 4 Table 5 Table 6 The test results show that: (1) As can be seen from Examples 1-13, this invention effectively reduces friction within the alloy system and between the alloy and processing equipment by optimizing the formulation of the PK / PA alloy, thereby reducing the generation of a large number of free radicals from the source. This effectively solves the problems of crosslinking, gelation, and even carbonization caused by free radicals during processing. The obtained PK / PA alloy has a tensile strength of 133.01-146.96 MPa, a tensile modulus of 10076.75-10962.85 MPa, an elongation at break of 2.9-3.7%, a flexural strength of 177.22-214.6 MPa, a flexural modulus of 7191.56-7800.70 MPa, and a cantilever beam notched impact strength of 11.25-17.89 kJ / m. 2 The impact strength of a cantilever beam without a notch can reach 42.03-62.4 kJ / m. 2 It has flame retardancy up to UL 94 V-1 and V-0 standards, GWIT of 750-800℃, ΔE of 4.10-7.39 after light aging, tensile strength of 85.85-119.88MPa after light aging, and elongation at break of 1.8-3.0% after light aging.

[0054] (2) As can be seen from Examples 1-3, the present invention can achieve better mechanical properties or higher GWIT by adjusting the mass ratio of PA to PK. However, if the proportion of PK resin in the alloy is too high, the degradation of various properties of the alloy after photoaging will increase significantly and the weather resistance stability will decrease.

[0055] (3) As can be seen from Examples 1 and 4-5, the present invention can synergistically balance the mechanical properties and weather resistance of the alloy by controlling the amount of ultra-high molecular weight polyethylene (UHMWPE) added. When the amount of UHMWPE added is too high, the flame retardant properties and mechanical strength of the alloy both decrease, but the weather resistance of the alloy is improved; if the amount of UHMWPE added is insufficient, the weather resistance of the alloy deteriorates. This confirms that UHMWPE can maintain the integrity of the internal structure of the alloy during processing and effectively inhibit the generation of free radicals in the alloy system.

[0056] (4) As can be seen from Examples 1 and 6-7, if the PK / PA alloy is not compounded with a primary antioxidant and a secondary antioxidant, the free radicals generated during the processing stage cannot be captured and removed in time, which will directly damage the initial mechanical properties of the alloy. At the same time, during the photo-aging stage, the ultraviolet absorber and the light stabilizer can only convert light energy into heat energy, which can easily cause local thermal aging. Moreover, the efficiency of the light stabilizer in capturing free radicals is much lower than that of the hindered phenolic primary antioxidant, which ultimately leads to a significant decrease in the overall performance of the alloy after aging. If no ultraviolet absorber and light stabilizer are added to the alloy, although the initial performance and appearance color of the alloy after processing and forming are not obviously abnormal, the mechanical properties will be greatly reduced after photo-aging treatment, and the color difference of the product will be significantly increased.

[0057] (5) As can be seen from Examples 1 and 8-11, if PA6 resin with a relatively high viscosity is selected, the overall performance of the alloy will decrease. This is because after the melt viscosity increases, the material stays in the screw for a longer time, which makes it easy for excessive cross-linking to occur, ultimately causing the alloy strength and weather resistance to deteriorate simultaneously. If PK resin with a low melt index is selected, the overall viscosity of the processing system will also be high, which will induce the alloy system to generate more free radicals and damage the overall performance of the alloy.

[0058] (6) As can be seen from Examples 1 and 12-13, although the composite flame retardant system of diethyl aluminum hypophosphite and aluminum phosphite used in this invention has excellent weather resistance, the amount required to add it is higher than that of pure diethyl aluminum hypophosphite for the same flame retardant level. The reason is that aluminum phosphite relies on the formation of a dense ceramic layer for flame retardancy during combustion, while PK has a loose char layer and cannot work together to exert a flame retardant effect. Excessive addition will reduce the mechanical strength and toughness of the material and worsen the processing fluidity. Moreover, if the flame retardant is added in excess, it will also reduce the overall mechanical strength and toughness of the alloy, while affecting the processing fluidity of the material and increasing the generation of free radicals.

[0059] (7) As can be seen from Example 1 and Comparative Examples 1-3, if ultra-high molecular weight polyethylene is not added, the composite material made by using PA6 alone has outstanding mechanical properties, but low flame retardancy and low GWIT; the composite material made by using PK alone has poor rigidity and serious weathering degradation; the PA / PK alloy without ultra-high molecular weight polyethylene has insufficient toughness and large color difference after aging. None of the three can achieve excellent mechanical properties, aging resistance and flame retardancy at the same time.

[0060] (8) As can be seen from Example 1 and Comparative Example 4, if PA is replaced with PA66, due to the high density of hydrogen bonds between PA66 molecules, the processing temperature is higher, the melt viscosity is larger, the PK / PA66 alloy moves slowly in the screw, the PK phase undergoes severe thermal aging, generates a large number of free radicals, combines with oxygen to form a series of conjugated structures, making the alloy initially yellow, with poor resistance to light aging, resulting in the alloy initially being even yellower and severe yellowing.

[0061] (9) As can be seen from Example 1 and Comparative Example 5, if ultra-high molecular weight polyethylene is replaced with polytetrafluoroethylene, the CF bond energy in polytetrafluoroethylene is large, and the whole is non-polar. It is not wear-resistant and is easy to form a transfer film on the surface of the screw and barrel during processing, causing the screw to slip, the melt to be poorly conveyed, the flame retardant to be difficult to disperse evenly, and the material to stay in the screw for a longer time, resulting in a decline in the flame retardant grade, mechanical properties and photo-aging strength of the material. In contrast, ultra-high molecular weight polyethylene has a very high molecular weight and can form an entangled structure inside the melt, which can exist stably in the alloy system and effectively avoid slippage defects.

[0062] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A PK / PA alloy, characterized in that, The PK / PA alloy comprises, by weight, 20-45 parts PA6 resin, 15-35 parts PK resin, 2-5 parts ultra-high molecular weight polyethylene, 15-40 parts glass fiber, and 8-14 parts flame retardant.

2. The PK / PA alloy according to claim 1, characterized in that, The mass ratio of PA6 resin to PK resin is (1-4):

1.

3. The PK / PA alloy according to claim 1 or 2, characterized in that, The relative viscosity of the PA6 resin is 1.8-2.1; Preferably, the melt flow index of the PK resin is 50-250 g / 10min.

4. The PK / PA alloy according to any one of claims 1-3, characterized in that, The weight-average molecular weight of the ultra-high molecular weight polyethylene is 8.0 × 10⁻⁶. 6 ~10×10 6 g / mol.

5. The PK / PA alloy according to any one of claims 1-4, characterized in that, The diameter of the glass fiber monofilament is 8-15 μm; Preferably, the chopped length of the glass fiber is 2.5-5 mm.

6. The PK / PA alloy according to any one of claims 1-5, characterized in that, The flame retardant includes an organophosphonate flame retardant; Preferably, the organophosphate flame retardant includes alkyl hypophosphite; Preferably, the alkyl hypophosphite includes any one or a combination of at least two of diethyl aluminum hypophosphite, methyl ethyl aluminum hypophosphite, diisobutyl aluminum hypophosphite, or a mixture of diethyl aluminum hypophosphite and aluminum phosphite, and more preferably diethyl aluminum hypophosphite.

7. The PK / PA alloy according to any one of claims 1-6, characterized in that, The PK / PA alloy further comprises, by weight, any one or a combination of at least two of the following: 0.1-0.3 parts of primary antioxidant, 0.1-0.3 parts of secondary antioxidant, 0.2-0.4 parts of ultraviolet absorber, or 0.2-0.4 parts of light stabilizer; Preferably, the primary antioxidant comprises a hindered phenolic antioxidant; Preferably, the hindered phenolic antioxidant includes any one or a combination of at least two of N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide), β-(3,5-di-tert-butyl-4-hydroxyphenyl)octadecyl ester or tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)pentaerythritol ester, and more preferably N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide); Preferably, the auxiliary antioxidant includes phosphite antioxidants; Preferably, the phosphite antioxidant includes any one or a combination of at least two of tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, trinonylphenyl phosphite, triphenyl phosphite, or pentaerythritol bisoctadecyl phosphite, and more preferably tris(2,4-di-tert-butylphenyl) phosphite; Preferably, the ultraviolet absorber includes a triazine ultraviolet absorber; Preferably, the triazine-based ultraviolet absorber comprises 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octoxy)phenol and / or 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol, more preferably 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-octoxyphenol; Preferably, the light stabilizer includes a hindered amine light stabilizer; Preferably, the hindered amine light stabilizer comprises N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide and / or bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, more preferably N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-phenylenediamide.

8. A method for preparing a PK / PA alloy as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: The components of the PK / PA alloy are melt-blended, extruded, and granulated to obtain the PK / PA alloy.

9. The method for preparing the PK / PA alloy according to claim 8, characterized in that, The melt blending is carried out in a twin-screw extruder; Preferably, the PA resin, PK resin, ultra-high molecular weight polyethylene, antioxidant, ultraviolet absorber, light stabilizer and flame retardant in the PK / PA alloy are mixed and then fed into a twin-screw extruder through the main feed port. Preferably, the glass fibers in the PK / PA alloy are fed into the twin-screw extruder via a side feed port; Preferably, the temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 280-300℃; Zone 2: 280-300℃; Zone 3: 280-300℃; Zone 4: 280-300℃; Zone 5: 260-280℃; Zone 6: 170-190℃; Zone 7: 170-190℃; Zone 8: 180-200℃; Zone 9: 170-190℃. Preferably, the die head temperature of the twin-screw extruder is 240-255°C; Preferably, the screw speed of the twin-screw extruder is 350-450 r / min.

10. The application of a PK / PA alloy as described in any one of claims 1-7 in automobiles and electronic appliances.

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