Multidimensional environment impedance POM composite material and preparation method thereof

Abstract

The invention provides a multidimensional environment impedance POM (polyoxymethylene) composite material and a preparation method thereof. The multidimensional environment impedance POM composite material comprises 80-92 parts of copolyformaldehyde resin; 3 to 10 parts of amino functionalized metal organic framework particles; 0.5 to 3 parts of a composite weather-resistant agent; 0.5 to 3 parts of epoxy-terminated short-chain polyether and / or short-chain polyester; 0.2 to 1 part of an antioxidant; and 0.2 to 1 part of a lubricant. Amino-functionalized metal organic framework particles are introduced into a polyformaldehyde matrix and matched with an epoxy-terminated short-chain polymer, a cross-linked shell layer is formed around the metal organic framework particles in situ, and a composite weather-proof agent (a compound of an ultraviolet light absorber and a hindered amine light stabilizer) is enriched in the shell layer area, so that the weather-proof performance of the polyformaldehyde composite material is improved. Therefore, a local weather-proof functional domain is formed in the material. The microstructure is different from a pure homogeneous dispersion auxiliary system in the prior art, free radicals and energy can be more effectively captured under the simultaneous action of light, heat and oxygen, and the weather resistance efficiency and durability of the material are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a POM composite material with multi-dimensional environmental resistance and a preparation method thereof. BACKGROUND

[0002] Polyoxymethylene resin (POM) is widely used in the automotive industry, machinery manufacturing, electronics, precision instruments and other industries due to its high strength, high rigidity, good wear resistance, fatigue resistance, chemical corrosion resistance and dimensional stability. However, when POM materials are exposed to complex multi-dimensional environments such as high temperature and humidity, chemical corrosion, and ultraviolet radiation, their weather resistance becomes a major factor limiting their application.

[0003] The weather resistance defects of POM materials mainly manifest in the following aspects: 1. Sensitivity to ultraviolet aging: POM molecular chains contain a large number of ether bonds (-O-) and methylene groups (-CH2-), which are prone to photo-oxidative degradation under ultraviolet radiation (especially UV-B and UV-A bands with wavelengths of 280-400 nm), resulting in yellowing and loss of gloss on the material surface, and a sharp decline in internal mechanical properties; 2. Poor humidity and temperature cycle stability: under the combined action of alternating high and low temperatures (such as -40℃~80℃) and high humidity (relative humidity ≥85%), the crystallinity of existing POM materials changes repeatedly, resulting in internal stress and cracking, warping and other phenomena; 3. Weak resistance to wet heat aging and chemical medium synergistic corrosion: in outdoor environments, POM materials not only face wet heat aging, but also come into contact with corrosive media such as rainwater, dew, industrial waste gas (such as sulfur dioxide and nitrogen oxides), which can penetrate into the material and accelerate molecular chain degradation and swelling, resulting in a decrease in material hardness and poor dimensional stability.

[0004] To solve the above problems, some POM modification attempts have appeared in the prior art. For example, Chinese patent CN108794664A discloses a weather-resistant POM composite material, which achieves improved weather resistance by adding a benzotriazole ultraviolet absorber and a hindered phenolic antioxidant; however, this solution does not consider the impact of humidity and temperature cycles on material performance, and the ultraviolet absorber is prone to migration and failure under long-term exposure to strong ultraviolet radiation, resulting in insufficient weather resistance durability. Chinese patent CN110156469A discloses an anti-aging POM material, which introduces glass fiber reinforcement to improve mechanical properties; however, the interface between the glass fiber and the POM matrix has poor bonding properties, which can lead to interface peeling in a humid heat environment, thereby exacerbating material performance degradation.

[0005] Therefore, developing a POM material capable of resisting ultraviolet, temperature and humidity cycle, and chemical medium synergistic erosion, and excellent weather resistance durability, to meet the needs of long-term use in harsh environments, has become a technical problem to be solved in the field of high polymer materials. SUMMARY

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a POM composite material with multi-dimensional environmental resistance to solve the problem of insufficient weather resistance of POM materials in multi-dimensional environments. At the same time, the present application also provides a preparation method of a POM composite material with multi-dimensional environmental resistance.

[0007] To achieve the above-mentioned purposes and other related purposes, the present application provides the following technical solutions. In a first aspect of the present application, a POM composite material with multi-dimensional environmental resistance is provided, comprising the following components by weight: Copolyoxymethylene (POM) resin: 80-92 parts; Amino-functionalized metal organic framework particles: 3-10 parts; Composite weathering agent: 0.5-3 parts; Epoxy-terminated short-chain polyether and / or short-chain polyester: 0.5-3 parts; Antioxidant: 0.2-1 part; Lubricant: 0.2-1 part; The amino-functionalized metal organic framework particles form a core, the epoxy-terminated short-chain polyether and / or short-chain polyester compatible with the POM matrix form a cross-linked shell layer around the amino-functionalized metal organic framework particles, and the composite weathering agent preferentially accumulates in the cross-linked shell layer region, thereby forming a multi-phase microstructure of "metal organic framework core-reactive shell-POM matrix" in the POM resin matrix.

[0008] Further, the melt index of the copolyoxymethylene resin is 5-15 g / 10 min (190°C, 2.16 kg), preferably 8-12 g / 10 min. Compared with homopolyoxymethylene resin, the copolyoxymethylene resin selected by the present application introduces a small amount of copolymer units into the molecular chain, which can reduce the regularity of the molecular chain and reduce the crystallinity, thereby improving the impact resistance and wet heat aging resistance of the material; at the same time, its alkali resistance and processing stability are better, which provides guarantee for the basic performance of the material.

[0009] Further, the amino-functionalized metal organic framework particles are selected from one or more of Zr-based or Fe-based metal organic framework compounds containing amino ligands. The metal organic framework particles have a specific surface area of 500-1200 m 2 / g, a pore size range of 0.3-1.2 nm, and a bulk median particle size of 0.1-5 μm.

[0010] Further, the amino-functionalized metal-organic framework particles are preferably NH2-UiO-66 and / or NH2-MIL-101.

[0011] Further, the epoxy-terminated short-chain polyether and / or short-chain polyester has 2-3 epoxy end groups and a number average molecular weight of 500-3000, preferably 800-2000. The epoxy-terminated polymer can adduct or condense with the amino groups on the surface of the amino-functionalized metal-organic framework particles, the hydroxyl / terminal groups at the ends of the polyformal chain, and small molecules such as formaldehyde adsorbed in the pores of the metal-organic framework, forming a reaction-type crosslinked shell rich in C–N–C and C–O–C bonds around the metal-organic framework particles.

[0012] Further, the mass ratio of the amino-functionalized metal-organic framework particles to the epoxy-terminated short-chain polyether and / or short-chain polyester is 1:(0.1-0.5).

[0013] Further, the composite weathering agent is compounded from an ultraviolet absorber and a hindered amine light stabilizer. The weight fraction of the ultraviolet absorber is 0.2-2 parts, and the weight fraction of the hindered amine light stabilizer is 0.1-1 part. The mass ratio of the ultraviolet absorber to the hindered amine light stabilizer is 1:1-3:1, preferably 2:1.

[0014] Further, the ultraviolet absorber is preferably a triazine or benzotriazole ultraviolet absorber, such as 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole (UV-328), 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole (UV-327), and the like.

[0015] Further, the hindered amine light stabilizer is selected from a low-molecular-weight hindered amine light stabilizer or a high-molecular-weight hindered amine light stabilizer. The low-molecular-weight hindered amine light stabilizer includes bis(2,2,6,6-tetramethylpiperidyl)sebacate (HALS-770); the high-molecular-weight hindered amine light stabilizer is preferably a polymeric hindered amine light stabilizer, such as HALS-944 or HALS-622, and has a number average molecular weight of preferably 2000-10000.

[0016] Further, the antioxidant is preferably a compounded system of hindered phenolic antioxidant and phosphite antioxidant, and the mass ratio of the two is 1:1; wherein the hindered phenolic antioxidant is preferably pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenylpropionate)] (antioxidant 1010), and the phosphite antioxidant is preferably tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168). The hindered phenolic antioxidant can capture free radicals generated during material degradation, and the phosphite antioxidant can decompose hydroperoxides, and the two work together to effectively inhibit the thermal oxidative degradation of the material, complement the composite weathering agent, and improve the stability of the material in a high-temperature environment.

[0017] Further, the lubricant is preferably ethylene bis-stearamide (EBS) and / or polytetrafluoroethylene micro powder and a mixture thereof. It has excellent internal and external lubricating properties, can reduce the melt viscosity of the material during forming processing, reduce equipment wear, and at the same time can improve the surface gloss of the material and avoid material degradation caused by frictional heat during processing.

[0018] In a preferred embodiment, the POM material of the multi-dimensional environmental resistance further comprises 1-3 parts of a reinforcing modifier and 0.5-2 parts of an interfacial compatibility agent.

[0019] Further, the reinforcing modifier is selected from nano-montmorillonite surface treated by a silane coupling agent, and the particle size is 50-100 nm. The silane coupling agent is preferably KH-550. The high specific surface area of the nano-montmorillonite can form a dense network structure with the POM matrix, improving the rigidity and dimensional stability of the material; the surface treatment of the silane coupling agent can enhance the interfacial bonding with the matrix, and the nanoparticles can scatter ultraviolet rays, further improving the ultraviolet resistance of the material; in addition, the lamellar structure can block the diffusion of oxygen and moisture into the interior, and at the same time improve the bending modulus by 10-15%.

[0020] Further, the interfacial compatibility agent is selected from maleic anhydride grafted polyoxymethylene (MAH-g-POM), and the grafting rate is 0.8%-1.2%. The polyoxymethylene in the molecular chain can form good compatibility with the matrix, the maleic anhydride groups can chemically react with the hydroxyl groups on the surface of the reinforcing modifier, and the interfacial bonding force between the matrix and the reinforcing modifier is improved, avoiding interfacial peeling in a complex environment. Among them, the nano-montmorillonite and the maleic anhydride grafted polyoxymethylene can synergistically form a layered barrier phase, improving the barrier ability of the material to moisture and corrosive media.

[0021] In a second aspect of the present application, a preparation method of a POM composite material with multi-dimensional environmental resistance is provided, comprising the following steps: S100, raw material pretreatment, comprising: S101, vacuum drying the amino-functionalized metal organic framework particles at 80-110 DEG C for 4-8 hours to obtain dried particles, mixing the dried particles with epoxy-terminated short-chain polyether and / or short-chain polyester at a mass ratio of 1:(0.1-0.5), stirring at 80-100 DEG C for 20-40 minutes to allow addition reaction of part of the epoxy end groups with the amino groups on the surface of the amino-functionalized metal organic framework particles to form a preliminary cross-linked shell layer; continuing to add part or all of the composite weathering agent, maintaining 80-100 DEG C stirring for 10-30 minutes to obtain a metal organic framework pre-mixture pre-coated with a weathering agent; S102, air-drying the copolymerized formaldehyde resin at 80-90 DEG C for 4-6 hours to remove moisture in the resin to avoid bubbles and hydrolysis during molding; S200, raw material mixing, comprising: adding the copolymerized formaldehyde resin of step S102, the metal organic framework pre-mixture pre-coated with a weathering agent obtained in step S101, the balance of the composite weathering agent, the antioxidant, the lubricant, and optionally the reinforcing modifier and the interfacial compatibility agent into a high-speed mixer, mixing at a rotation speed of 800-1000 r / min and a temperature of 50-60 DEG C for 15-20 minutes to uniformly disperse the components to obtain a pre-mixture; S300, melt blending and extrusion: adding the pre-mixture into a twin-screw extruder for melt blending and extrusion, setting the temperature of each section of the twin-screw extruder as follows: 140-150 DEG C for the feeding section, 160-170 DEG C for the first section, 170-180 DEG C for the second section, 180-190 DEG C for the third section, 175-185 DEG C for the fourth section, and 180-190 DEG C for the die head; the screw rotation speed is 200-300 r / min, and the vacuum degree is -0.08~-0.06 MPa; precisely controlling the extrusion temperature to avoid overheating degradation of the POM resin while ensuring sufficient melting and dispersion of the components; S400, granulation and drying: cutting the extruded melt through an underwater pelletizer to obtain primary particles; drying the primary particles in an air-drying oven at 70-80 DEG C for 2-3 hours to remove surface moisture to obtain a POM composite material with multi-dimensional environmental impedance.

[0022] Further, in step S101, the addition amount of part of the composite weathering agent is 20-70% of the total amount.

[0023] As described above, the POM composite material with multi-dimensional environmental impedance and the preparation method thereof have the following beneficial effects: 1、The present application introduces amino-functionalized metal-organic framework particles into the polyoxymethylene matrix, and cooperates with short-chain epoxy-terminated polymers to form a cross-linked shell layer around the metal-organic framework particles, and makes the composite weathering agent (a compound of ultraviolet absorber and hindered amine light stabilizer) enriched in the shell layer region, thereby forming a local weathering functional domain inside the material. This microstructure is different from the simple homogeneous dispersion of the auxiliary system in the prior art, and can more effectively capture free radicals and energy under the simultaneous action of light, heat and oxygen, thereby significantly improving the weathering efficiency and durability of the material.

[0024] 2、The amino-functionalized metal-organic framework itself has a high specific surface area and a rich pore structure, and can selectively adsorb small molecules such as formaldehyde and moisture; at the same time, the short-chain epoxy-terminated polymer reacts with the amino groups on the surface of the metal-organic framework, the polyoxymethylene chain ends and the adsorbed small molecules during melt blending to form a cross-linked shell layer, and part of the degradation products are sealed near the shell layer; thereby reducing the migration concentration of the degradation products in the matrix in space, inhibiting the chain degradation expansion, and improving the anti-degradation performance of the material in a humid and alkaline environment.

[0025] 3、Under the combined action of the metal-organic framework micropore domestication, the reaction shell sealing and the optional nano-montmorillonite barrier layer, the POM composite material of the present application realizes the comprehensive balance of mechanical properties, color difference, dimensional stability and mass change rate under the conditions of ultraviolet light irradiation, humid heat cycle and alkaline solution immersion. Compared with the polyoxymethylene material only added with traditional ultraviolet absorber and antioxidant, the material of the present application shows higher performance retention rate and smaller appearance and size decay in xenon lamp aging, humid heat treatment and alkaline immersion tests.

[0026] 4、The present application selects nano-montmorillonite treated with silane coupling agent as a reinforcing modifier, and cooperates with maleic anhydride grafted polyoxymethylene as an interfacial compatibilizer, so that the nano-montmorillonite layers and MAH-g-POM cooperatively form a layered barrier phase, which not only improves the flexural modulus and dimensional stability, but also significantly blocks the diffusion of moisture and corrosive medium into the interior.

[0027] 5、The present application forms a multi-phase microstructure of "core-shell-barrier phase-matrix" through a specific process sequence, so that the core-shell structure, the shell weathering zone and the layered barrier phase cooperatively build in the POM matrix, and realize the comprehensive impedance ability to multi-dimensional environment. DETAILED DESCRIPTION

[0028] The following specific examples illustrate the embodiments of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure.

[0029] Example 1 The present embodiment provides a POM composite material for multi-dimensional environmental impedance, which comprises the following components by weight: Polyoxymethylene copolymer resin (melt index 10 g / 10 min): 90 parts; Amino-functionalized metal-organic framework particles (NH2-UiO-66, Zr-based, average particle size 1 pm, specific surface area about 900 m 2 / g): 5 parts; Composite weathering agent (UV-327: HALS-944 = 1:1): 2 parts; Epoxy-terminated short-chain polyether EPE-1 (number average molecular weight 1000, terminal epoxy equivalent weight about 500 g / eq): 2 parts; Antioxidant (antioxidant 1010: antioxidant 168 = 1:1): 0.5 parts; Lubricant (EBS): 0.5 parts.

[0030] The embodiment also provides a preparation method of the POM material of the multi-dimensional environmental impedance, comprising the following steps: S100, raw material pretreatment, comprising: S101, 5 parts of amino-functionalized metal-organic framework particles NH2-UiO-66 are vacuum dried at 100°C for 6 hours to obtain dried particles, the dried particles are mixed with epoxy-terminated short-chain polyether EPE-1 at a mass ratio of 1:0.4, and stirring is performed at 90°C for 30 minutes to make part of the epoxy terminal groups react with the amino groups on the surface of the amino-functionalized metal-organic framework particles to form a preliminary cross-linked shell layer; 1 part of a composite weathering agent is continuously added, and stirring is performed at 90°C for 20 minutes to obtain a metal-organic framework pre-mixture coated with a weathering agent; S102, 90 parts of polyoxymethylene copolymer resin are air-dried at 85°C for 5 hours to remove water in the resin, so as to avoid bubbles and hydrolysis caused by water in the molding process; S200, raw material mixing, comprising: The polyoxymethylene copolymer resin of step S102, the metal-organic framework pre-mixture coated with a weathering agent obtained in step S101, the remaining 1 part of the composite weathering agent, 0.5 parts of the antioxidant, and 0.5 parts of the lubricant are added into a high-speed mixer, and mixing is performed at a rotation speed of 900 r / min and a temperature of 55°C for 18 minutes, so that the components are uniformly dispersed to obtain a pre-mixture; S300, melt blending and extrusion: The pre-mixture is added into a twin-screw extruder for melt blending and extrusion, and the temperature of each section of the twin-screw extruder is set as follows: the feeding section is 145°C, the first section is 165°C, the second section is 175°C, the third section is 185°C, the fourth section is 180°C, and the die head is 185°C; the screw rotation speed is 250 r / min, the vacuum degree is-0.07 MPa, and the extrusion melt is obtained; the extrusion temperature is accurately controlled to avoid overheating degradation of the POM resin, and at the same time, the components are fully melt-dispersed; S400, granulation and drying: The extruded melt is cut by underwater pelletizer to obtain primary particles; the primary particles are placed in a forced air drying oven and dried at 75°C for 2.5 hours to remove surface moisture to obtain a POM composite material with multi-dimensional environmental impedance.

[0031] The prepared POM composite material with multi-dimensional environmental impedance is detected, and the performance test results are as follows: Tensile strength 78 MPa, elongation at break 40%, impact strength (notched) 13 kJ / m², flexural modulus 2600 MPa; After xenon lamp aging for 1000h: color difference ΔE = 1.0, tensile strength retention rate 92.3%, elongation at break retention rate 87.5%, impact strength retention rate 90.9%; After 50 cycles of temperature and humidity: tensile strength retention rate 94.9%, elongation at break retention rate 95%, impact strength retention rate 95.5%, no cracking; After 5% sodium hydroxide solution immersion for 30 days: mass change rate 0.25%, tensile strength retention rate 89.7%, elongation at break retention rate 80%, impact strength retention rate 86.4%.

[0032] Example 2 The present embodiment provides a POM composite material with multi-dimensional environmental impedance, comprising the following components by weight: Copolymerized formaldehyde resin (melt index 10 g / 10 min): 87 parts; Amino-functionalized metal-organic framework particles (NH2-MIL-101(Fe), average particle size 2 μm, specific surface area about 1500 m 2 / g): 5 parts; Composite weathering agent (UV-327: HALS-944 = 1:1): 2 parts; Epoxy-terminated short-chain polyester: 2 parts; Antioxidant (antioxidant 1010: antioxidant 168 = 1:1): 0.5 parts; Lubricant (EBS): 0.5 parts; KH-550 surface treated nano-montmorillonite MMT: 2 parts; Maleic anhydride grafted polyoxymethylene (MAH-g-POM): 1 part.

[0033] The present embodiment also provides a preparation method of the POM material with multi-dimensional environmental impedance, comprising the following steps: S100, raw material pretreatment, comprising: S101、vacuum drying 5 parts of amino-functionalized metal-organic framework particles NH2-MIL-101(Fe) at 100℃ for 6 hours to obtain dried particles, mixing the dried particles with epoxy-terminated short-chain polyester at a mass ratio of 1:0.4, stirring at 90℃ for 30 minutes to allow addition reaction between part of the epoxy end groups and the amino groups on the surface of the amino-functionalized metal-organic framework particles to form a preliminary cross-linked shell layer; continue to add 1 part of a composite weathering agent, and keep stirring at 90℃ for 20 minutes to obtain a metal-organic framework pre-mixture pre-coated with a weathering agent; S102、blowing and drying 87 parts of copolymerized formaldehyde resin at 85℃ for 5 hours to remove water in the resin to avoid bubbles and hydrolysis during molding; S200、raw material mixing includes: adding the copolymerized formaldehyde resin of step S102, the metal-organic framework pre-mixture pre-coated with a weathering agent obtained in step S101, the remaining 1 part of a composite weathering agent, 0.5 parts of an antioxidant, 0.5 parts of a lubricant, 2 parts of KH-550 surface-treated nano-montmorillonite, and 1 part of maleic anhydride grafted polyformaldehyde into a high-speed mixer, mixing at a rotation speed of 900 r / min and a temperature of 55℃ for 18 minutes to uniformly disperse each component, and obtaining a pre-mixture; S300、melt blending and extrusion: adding the pre-mixture into a twin-screw extruder for melt blending and extrusion, setting the temperature of each section of the twin-screw extruder as follows: 145℃ for the feeding section, 165℃ for the first section, 175℃ for the second section, 185℃ for the third section, 180℃ for the fourth section, and 185℃ for the die head; the screw rotation speed is 250 r / min, the vacuum degree is -0.07 MPa, and the extruded melt is obtained; the extrusion temperature is accurately controlled to avoid overheating degradation of the POM resin, while ensuring sufficient melting and dispersion of each component; S400、granulation and drying: cutting the extruded melt into primary particles through an underwater pelletizer; drying the primary particles in a blowing and drying oven at 75℃ for 2.5 hours to remove surface moisture, and obtaining a POM material with multi-dimensional environmental resistance.

[0034] The prepared POM composite material with multi-dimensional environmental resistance is detected, and the performance test results are as follows: tensile strength 80 MPa, elongation at break 38%, impact strength (notched) 11 kJ / m 2 ; after xenon lamp aging for 1000 hours: color difference ΔE = 0.9, tensile strength retention rate 92.5%, elongation at break retention rate 89.5%, and impact strength retention rate 92.7%; after 50 cycles of temperature and humidity cycles: tensile strength retention rate 95%, elongation at break retention rate 94.7%, impact strength retention rate 95.5%, and no cracking; 5% sodium hydroxide solution immersion for 30 days: mass change rate 0.2%, tensile strength retention rate 90%, elongation at break retention rate 86.8%, impact strength retention rate 90.9%.

[0035] Example 3 The present example provides a multi-dimensional environmental impedance POM composite material, comprising the following components by weight: Copolymerized formaldehyde resin (melt index 12 g / 10 min): 90 parts; Amino-functionalized metal organic framework particles (NH2-UiO-66, Zr-based, average particle size 1 μm, specific surface area about 900 m 2 / g): 5 parts; Composite weathering agent (UV-327: HALS-944 = 2:1): 2 parts; Epoxy-terminated short-chain polyether EPE-1 (number average molecular weight 1000, terminal group epoxy equivalent weight about 500 g / eq): 2 parts; Antioxidant (antioxidant 1010: antioxidant 168 = 1:1): 0.5 parts; Lubricant (EBS): 0.5 parts.

[0036] The present example also provides a preparation method of the multi-dimensional environmental impedance POM material, comprising the following steps: S100, raw material pretreatment, comprising: S101, vacuum drying 5 parts of amino-functionalized metal organic framework particles NH2-UiO-66 at 100°C for 6 hours to obtain dried particles, mixing the dried particles with epoxy-terminated short-chain polyether EPE-1 at a mass ratio of 1:0.4, stirring at 90°C for 30 minutes to allow addition reaction between part of the epoxy terminal groups and the amino groups on the surface of the amino-functionalized metal organic framework particles to form a preliminary cross-linked shell layer; continue to add 1 part of a composite weathering agent, and keep stirring at 90°C for 18 minutes to obtain a metal organic framework pre-mixture coated with a pre-coated weathering agent; S102, air-drying 90 parts of copolymerized formaldehyde resin at 85°C for 5 hours to remove water in the resin to avoid bubbles and hydrolysis during molding; S200, raw material mixing, comprising: adding the copolymerized formaldehyde resin of step S102, the metal organic framework pre-mixture coated with a pre-coated weathering agent obtained in step S101, the remaining 1 part of a composite weathering agent, 0.5 parts of an antioxidant, and 0.5 parts of a lubricant into a high-speed mixer, and mixing at a rotation speed of 900 r / min and a temperature of 55°C for 18 minutes to uniformly disperse the components to obtain a pre-mixture; S300, melt blending and extrusion: The premix is added into a twin-screw extruder for melt blending extrusion, and the temperature of each section of the twin-screw extruder is set as follows: feeding section 145℃, first zone 165℃, second zone 175℃, third zone 185℃, fourth zone 180℃, and head 185℃; the screw rotation speed is 250r / min, the vacuum degree is -0.07MPa, and the extrusion melt is obtained; the extrusion temperature is precisely controlled to avoid overheating degradation of the POM resin, while ensuring that the components are fully melted and dispersed; S400, granulation and drying: The extruded melt is cut by an underwater cutter to obtain primary particles; the primary particles are placed in a forced air drying oven and dried at 75℃ for 2.5 hours to remove surface moisture, thereby obtaining a POM material with multi-dimensional environmental impedance.

[0037] The prepared POM composite material with multi-dimensional environmental impedance is detected, and the performance test results are as follows: Tensile strength 77MPa, elongation at break 39%, impact strength (notched) 10.8kJ / m 2 ; After xenon lamp aging for 1000h: color difference ΔE=0.8, tensile strength retention rate 92.2%, elongation at break retention rate 87.2%, and impact strength retention rate 90.7%; After 50 cycles of temperature and humidity cycle: tensile strength retention rate 94.8%, elongation at break retention rate 94.9%, impact strength retention rate 94.4%, and no cracking; After soaking in 5% sodium hydroxide solution for 30 days: mass change rate 0.27%, tensile strength retention rate 89.6%, elongation at break retention rate 79.5%, and impact strength retention rate 86.1%.

[0038] Comparative Example 1 This comparative example provides a POM composite material comprising the following components by weight: Copolymerized formaldehyde resin (melt index 10g / 10min): 90 parts; Composite weathering agent (UV-327: HALS-944=1:1): 2 parts; Antioxidant (antioxidant 1010: antioxidant 168=1:1): 0.5 parts; Lubricant (EBS): 0.5 parts.

[0039] The preparation process comprises the following steps: (1) 90 parts of copolymerized formaldehyde resin, 2 parts of composite weathering agent, 0.5 parts of antioxidant, and 0.5 parts of lubricant are added into a high-speed mixer and mixed at a rotation speed of 900r / min and a temperature of 55℃ for 18 minutes to uniformly disperse the components, thereby obtaining a premix; (2) The premix is added into a twin-screw extruder for melt blending and extrusion. The temperature of each section of the twin-screw extruder is set as follows: feeding section 145°C, first zone 165°C, second zone 175°C, third zone 185°C, fourth zone 180°C, and die head 185°C; the screw rotation speed is 250 r / min, the vacuum degree is -0.07 MPa, and the extrusion melt is obtained; the extrusion temperature is precisely controlled to avoid overheating degradation of the POM resin and ensure sufficient melting and dispersion of the components; (3) The extruded melt is cut into primary particles by an underwater pelletizer. The primary particles are dried in a forced air drying oven at 75°C for 2.5 hours to remove surface moisture, thereby obtaining a POM composite material.

[0040] The prepared POM composite material is detected, and the performance test results are as follows: Tensile strength 77 MPa, elongation at break 35%, impact strength (notched) 10 kJ / m²; After xenon lamp aging for 1000 h: color difference ΔE = 2.5, tensile strength retention rate 84.4%, elongation at break retention rate 77.1%, and impact strength retention rate 80%; After 50 cycles of temperature and humidity cycles: tensile strength retention rate 90%, elongation at break retention rate 85.7%, impact strength retention rate 85%, and no cracking; After 30 days of immersion in 5% sodium hydroxide solution: mass change rate 0.7%, tensile strength retention rate 77.9%, elongation at break retention rate 65.7%, and impact strength retention rate 75%.

[0041] Comparative Example 2 This comparative example provides a POM composite material comprising the following components by weight: Copolymerized formaldehyde resin (melt index 10 g / 10 min): 90 parts; Amino-functionalized metal-organic framework particles (NH2-UiO-66, Zr-based, average particle size 1 μm, specific surface area about 900 m 2 / g): 5 parts; Composite weathering agent (UV-327: HALS-944 = 1:1): 2 parts; Antioxidant (antioxidant 1010: antioxidant 168 = 1:1): 0.5 parts; Lubricant (EBS): 0.5 parts.

[0042] The preparation process comprises the following steps: (1) 90 parts of copolymerized formaldehyde resin, 5 parts of amino-functionalized metal-organic framework particles, 2 parts of composite weathering agent, 0.5 parts of antioxidant, and 0.5 parts of lubricant are added into a high-speed mixer and mixed at a rotation speed of 900 r / min and a temperature of 55°C for 18 minutes to uniformly disperse the components, thereby obtaining a premix; (2) The premix is added into a twin-screw extruder for melt blending extrusion, and the temperature of each section of the twin-screw extruder is set as follows: 145℃ for the feeding section, 165℃ for the first section, 175℃ for the second section, 185℃ for the third section, 180℃ for the fourth section, and 185℃ for the head; the screw rotation speed is 250r / min, the vacuum degree is -0.07MPa, and the extrusion melt is obtained; the extrusion temperature is precisely controlled to avoid overheating degradation of the POM resin, while ensuring sufficient melting and dispersion of the components; (3) The extruded melt is cut into primary particles by an underwater pelletizer; the primary particles are dried in a forced air drying oven at 75℃ for 2.5 hours to remove surface moisture, and a POM composite material is obtained.

[0043] The prepared POM composite material is detected, and the performance test results are as follows: The tensile strength is 78MPa, the elongation at break is 36%, and the impact strength (notched) is 10.2kJ / m²; After xenon lamp aging for 1000h: the color difference ΔE is 1.8, the tensile strength retention rate is 87.2%, the elongation at break retention rate is 83.3%, and the impact strength retention rate is 84.3%; After 50 cycles of temperature and humidity cycles: the tensile strength retention rate is 91%, the elongation at break retention rate is 91.7%, the impact strength retention rate is 88.2%, and there is no cracking; After 30 days of immersion in 5% sodium hydroxide solution: the mass change rate is 0.5%, the tensile strength retention rate is 80.8%, the elongation at break retention rate is 69.4%, and the impact strength retention rate is 78.4%.

[0044] Through comparison of the examples and the comparative examples, it can be seen that the present application introduces amino-functionalized metal organic framework particles and constructs a reactive shell layer with an epoxy end group short-chain polymer to form a specific heterogeneous microstructure, thereby achieving synergistic regulation and inhibition of the degradation process under the coupling action of ultraviolet light, humidity and alkaline medium, and excellent comprehensive aging resistance effect is achieved.

[0045] Tests show that the performance of Comparative Example 2 under some working conditions is better than that of Comparative Example 1, but still lower than that of Example 1, and the material surface layer has a local powdering tendency after xenon lamp aging, indicating that the introduction of MOF particles alone without constructing a reactive shell layer has limited ability to domesticate and fix degradation small molecules and weathering aids.

[0046] In summary, the present application introduces amino-functionalized metal-organic framework particles into the polyformaldehyde matrix, and cooperates with the epoxy end group short chain polymer to form a crosslinked shell layer around the metal-organic framework particles in situ, and makes the composite weathering agent (a compound of ultraviolet absorber and hindered amine light stabilizer) enriched in the shell layer region, thereby forming a local weathering functional domain inside the material. This microstructure is different from the simple homogeneous dispersion of the auxiliary system in the prior art, and can more effectively capture free radicals and energy under the simultaneous action of light, heat and oxygen, significantly improving the weathering efficiency and durability of the material. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has high industrial utilization value.

[0047] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present application should be covered by the claims of the present application.

Claims

1. A POM composite of multi-dimensional environmental impedance, characterized in that, The components include the following weight parts: Copolyformaldehyde resin: 80-92 parts; Amino-functionalized metal organic framework particles: 3-10 parts; Composite weathering agent: 0.5-3 parts; Epoxy-terminated short-chain polyether and / or short-chain polyester: 0.5-3 parts; Antioxidant: 0.2-1 part; Lubricant: 0.2-1 part; The amino-functionalized metal organic framework particles are the core, the epoxy-terminated short-chain polyether and / or short-chain polyester compatible with the POM matrix form a cross-linked shell layer around the amino-functionalized metal organic framework particles, and the composite weathering agent preferentially enriches in the cross-linked shell layer region.

2. The POM composite of multi-dimensional environmental impedance according to claim 1, characterized in that, The amino-functionalized metal organic framework particles are selected from one or more of Zr-based or Fe-based metal organic framework compounds containing amino ligands.

3. The POM composite of multi-dimensional environmental impedance according to claim 2, characterized in that, The amino-functionalized metal organic framework particles are NH2-UiO-66 and / or NH2-MIL-101.

4. The POM composite of multi-dimensional environmental impedance according to claim 1, characterized in that, The epoxy-terminated short-chain polyether and / or short-chain polyester has 2-3 epoxy end groups and a number average molecular weight of 500-3000.

5. The POM composite of multi-dimensional environmental impedance according to claim 1, characterized in that, The composite weathering agent is compounded from an ultraviolet absorber and a hindered amine light stabilizer; the ultraviolet absorber is a triazine or benzotriazole ultraviolet absorber; and the hindered amine light stabilizer is selected from a low-molecular hindered amine light stabilizer or a high-molecular hindered amine light stabilizer.

6. The POM composite of multi-dimensional environmental impedance according to claim 5, characterized in that, The mass ratio of the ultraviolet absorber and the hindered amine light stabilizer is 1:1-3:

1.

7. The POM composite of multi-dimensional environmental impedance according to claim 1, characterized in that, The melt index of the copolyformaldehyde resin is 5-15 g / 10 min.

8. The POM composite of multi-dimensional environmental impedance according to claim 1, characterized in that, The POM composite material of the multi-dimensional environmental impedance further includes 1-3 parts of a reinforcing modifier and 0.5-2 parts of an interfacial compatibility agent.

9. A method of preparing a POM composite material of the multi-dimensional environmental impedance according to any one of claims 1 to 8, characterized in that, The method includes the following steps: S100, raw material pretreatment includes: S101, vacuum drying the amino-functionalized metal organic framework particles at 80-110°C for 4-8 hours to obtain dried particles, mixing the dried particles with the epoxy-terminated short-chain polyether and / or short-chain polyester at a mass ratio of 1:(0.1-0.5), stirring at 80-100°C for 20-40 minutes to allow addition reaction of part of the epoxy end groups with the amino groups on the surface of the amino-functionalized metal organic framework particles to form a preliminary cross-linked shell layer, and continuously adding part or all of the composite weathering agent and stirring at 80-100°C for 10-30 minutes to obtain a metal organic framework pre-mixture pre-coated with the weathering agent; S102, blowing dry the copolyformaldehyde resin at 80-90°C for 4-6 hours to remove water in the resin and avoid bubbles and hydrolysis during molding; S200, raw material mixing includes: adding the copolyformaldehyde resin of step S102, the metal organic framework pre-mixture pre-coated with the weathering agent obtained in step S101, the remaining composite weathering agent, the antioxidant, the lubricant, and optionally the reinforcing modifier and the interfacial compatibility agent into a high-speed mixer, mixing at a rotation speed of 800-1000 r / min and a temperature of 50-60°C for 15-20 minutes to uniformly disperse the components and obtain a pre-mixture; S300, melt blending and extrusion: The premix is added into a twin-screw extruder for melt blending extrusion, and the temperature of each section of the twin-screw extruder is set as follows: the feeding section 140-150 DEG C, the first section 160-170 DEG C, the second section 170-180 DEG C, the third section 180-190 DEG C, the fourth section 175-185 DEG C, and the head 180-190 DEG C; the screw rotation speed is 200-300 r / min, and the vacuum degree is -0.08 to -0.06 MPa; the extrusion temperature is accurately controlled to avoid overheating degradation of the POM resin and ensure that the components are fully melted and dispersed; S400, granulation and drying: The extruded melt is cut by an underwater pelletizer to obtain primary particles; the primary particles are placed in a blast drying oven and dried at 70-80 DEG C for 2-3 hours to remove surface moisture, thereby obtaining a POM composite material with multi-dimensional environmental impedance.

10. The method for preparing the multidimensional environmental impedance POM composite material according to claim 9, characterized in that, In step S101, the addition amount of the part of the composite weathering agent is 20-70% of the total amount.