Long-acting weather-resistant antioxidant composition for polyolefins and use thereof

Abstract

The application relates to the technical field of polyolefin modification, and particularly discloses a long-acting weather-resistant antioxidant composition for polyolefin and application thereof. The composition comprises the following components in parts by weight: 100-150 parts of a polyolefin matrix, 0.10-0.80 parts of component A, a hindered piperidine bifunctional compound, 0.05-0.30 parts of component B, an auxiliary antioxidant, and 0.02-0.30 parts of component C, a lamellar additive. The hindered piperidine bifunctional compound takes a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring as a hindered piperidine skeleton. The auxiliary antioxidant is a phosphite compound. The lamellar additive is selected from layered hydrotalcite or organic montmorillonite monolayer fragments. The composition can be used for pipe materials, cable sheaths, films or injection molding parts, and has the advantages of reduced weathering agent loss rate and prolonged protection period of the polyolefin products.

Description

Technical Field

[0001] This application relates to the field of polyolefin modification technology, and more specifically, to a long-lasting weather-resistant antioxidant composition for polyolefins and its application. Background Technology

[0002] Polyolefin materials, with their excellent mechanical properties, chemical stability, and processability, have been widely used in pipes, cable sheaths, agricultural films, and outdoor injection molded parts. To inhibit molecular chain breakage and cross-linking degradation of polyolefins during processing and long-term use due to thermo-oxidative and photo-oxidative effects, the industry commonly adopts a weather-resistant system that physically combines hindered phenolic antioxidants and hindered amine light stabilizers. In this system, hindered phenols capture peroxide free radicals through hydrogen atom transfer, blocking the thermo-oxidative aging chain reaction; hindered amines continuously capture alkyl free radicals and decompose hydroperoxides through a reversible Denisov cycle. The synergistic effect of the two can simultaneously cover the protection against thermo-oxidative and photo-oxidative aging, and the raw materials are readily available, the cost is moderate, and the processing adaptability is strong, thus improving the basic service life of most general-purpose polyolefin products.

[0003] However, the hindered phenols and hindered amines are structurally independent small molecule compounds with differences in molecular polarity and spatial volume. Their diffusion and migration rates in the nonpolar polyolefin matrix are asynchronous. During long-term use, the components with faster migration rates are more likely to precipitate onto the product surface, volatilize, or be washed away by environmental media, while the components with slower migration rates tend to accumulate locally inside the matrix, resulting in an imbalance in the overall distribution of the weathering agent and a reduction in the effective protective efficiency per unit mass of additive. On the other hand, the phenolic hydroxyl groups of hindered phenols are weakly acidic, and the piperidine nitrogen atoms of hindered amines are basic. During high-temperature processing and long-term storage, the two will undergo an acid-base neutralization reaction, generating salt byproducts with no antioxidant or photostable activity. This further accelerates the functional loss of the weathering agent, making the existing compound system unable to meet the long-term weather resistance requirements of polyolefin products in harsh outdoor environments. Summary of the Invention

[0004] In order to solve the problem that polyolefin products lack long-term weather resistance due to the acid-base neutralization reaction between the phenolic hydroxyl group of the relevant hindered phenol and the nitrogen atom of piperidine, this application provides a long-term weather-resistant antioxidant composition for polyolefins and its application.

[0005] This application provides a long-lasting weather-resistant antioxidant composition for polyolefins, employing the following technical solution: A long-lasting weather-resistant antioxidant composition for polyolefins comprises the following components in parts by weight: 100-150 parts of polyolefin matrix, component A: 0.10-0.80 parts of sterically hindered piperidine bifunctional compound, component B: 0.05-0.30 parts of co-antioxidant, and component C: 0.02-0.30 parts of lamellar additive. The sterically hindered piperidine bifunctional compound uses a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring as its sterically hindered piperidine skeleton. At the 4-position of the piperidine ring, a 2,6-di-tert-butyl-4-hydroxyphenyl antioxidant side chain containing a free phenolic -OH group is covalently linked. The phenolic -OH group exists as a free -OH group and does not participate in the bridging bond of the spacer group. The spacer group does not contain a phenolic -OH oxygen atom, and the side chain of the spacer group has a tertiary amine dangling group: —(CH2). m —N(R)(R′); the auxiliary antioxidant is a phosphite compound; the lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

[0006] By adopting the above technical solution, and using a sterically hindered piperidine bifunctional compound as the core weather-resistant unit, this compound integrates the hindered phenolic antioxidant active center and the hindered amine photostable active center into the same molecule through a covalent spacer group; avoiding the uneven distribution problem caused by the difference in migration rate between the two active components in traditional physical blending systems; the phenolic hydroxyl group exists in a free form to ensure unobstructed hydrogen atom transfer antioxidant channels; the tertiary amine hanging group of the side chain of the spacer group selectively coordinates with the residual catalyst acid microregions inside the matrix during polyolefin melt processing; anchoring the weather-resistant agent molecule to the interface region where degradation reactions are prone to occur; achieving a transformation from uniform dispersion to targeted distribution; and improving the protective efficiency of the additive per unit mass.

[0007] Preferably, the covalent spacer base is selected from any of the following types or a combination thereof: C2-C6 straight-chain alkylene chain: —(CH2) n —, where n = 2 to 6; Oxyalkylene chain: —CH2—CH2—O—CH2—CH2—; Dimethyl divalent silane-alkyl bridge: —Si(CH3)2—CH2CH2—; Carbonate bridge: —O—C(=O)—O—.

[0008] By employing the above technical solutions, the spatial distance and relative orientation between the sterically hindered piperidine backbone and the phenolic side chain are controlled using a specific spacer group structure; the dimethyl divalent silane alkyl bridge provides rigid turns due to the tetrahedral geometry of silicon atoms; it restricts direct contact between the phenolic hydroxyl group and the piperidine nitrogen atom; it blocks the acid-base antagonistic channel between the two from a geometrical perspective; the carbonate bridge has high bond energy and thermal stability; it maintains structural integrity at the conventional processing temperature of polyolefins; its planar zigzag conformation further increases the steric hindrance of the molecule; it reduces the diffusion coefficient of the auxiliary molecule in the nonpolar matrix of polyolefins; and it extends the effective protection period.

[0009] Preferably, the polyolefin matrix is ​​one or more of the following: homopolymer polypropylene, random copolymer polypropylene, impact copolymer polypropylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or polyolefin elastomers and their blends.

[0010] By adopting the above technical solution, due to the selection of the specific type of polyolefin matrix, the composition is adaptable to polymer environments with different crystallinity and polarity; for polypropylene or high-density polyethylene with high crystallinity, the tertiary amine hanging groups in the bifunctional compound are tightly bound to the acid microregions at the grain boundaries; preventing the additives from being excessively enriched or precipitated at the spherulite edges during crystallization and extrusion; for ethylene-vinyl acetate copolymers with strong polarity, the appropriate oxyalkylene or ester bond structure in the spacer group provides a certain polarity match; improving the dispersion uniformity of the bifunctional compound in the non-polar matrix; and avoiding stress concentration or surface defects caused by poor compatibility.

[0011] Preferably, in the tertiary amine suspending group, m = 1 to 4, and R and R′ are H or C. 1-4 Alkyl group, and at least one of which is C 1-4 alkyl.

[0012] By adopting the above technical solution, the carbon chain length and substituents of the tertiary amine suspension group are limited. When the value of m is 2 to 3 and both R and R′ are alkyl, the suspension group has a suitable electron cloud density and steric hindrance. This structure enables the formation of stable coordination complexes with residual metal ions of the catalyst or acidic sites at the edge of layered hydrotalcite. It also avoids hindering the antioxidant and free radical scavenging functions of the phenolic hydroxyl group and piperidine nitrogen due to excessive steric hindrance. At the same time, the tertiary amine structure does not participate in the Denisov cycle of the hindered amine, thus avoiding the introduction of additional basic centers that interfere with the acid-base balance of the system.

[0013] Preferably, component B is selected from one or more combinations of bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, or distearyl pentaerythritol diphosphite.

[0014] By adopting the above technical solution, the use of phosphites with sterically hindered structures as auxiliary antioxidants efficiently decomposes the hydroperoxides generated during the thermo-oxidative aging of polyolefins, converting them into stable alcohols or ketones, and blocking the branching of free radical chain reactions. The sterically hindered phenolic ring structure endows the auxiliary antioxidant with good hydrolysis resistance and thermal stability, making it less prone to decomposition and failure under the high temperature and high shear environment of twin-screw extruders. In addition, this type of auxiliary antioxidant does not contain free phenolic hydroxyl groups and does not undergo acid-base neutralization reactions with the basic nitrogen atoms in sterically hindered piperidine bifunctional compounds, ensuring the chemical stability of the two antioxidant components during storage and processing.

[0015] Preferably, when component C is layered hydrotalcite, its X-ray diffraction (003) plane interplanar spacing d 001 The wavelength is 0.78–0.90 nm; when component C is an organo-modified montmorillonite monolayer fragment, its d 001 The wavelength ranges from 1.5 to 3.0 nm.

[0016] By adopting the above technical solution, due to the control of the interlayer spacing parameter of the layered inorganic material, when component C is hydrotalcite, the smaller d... 001 The value indicates that it is in a collapsed monolayer or low crystallinity state; this morphology maximizes the exposure of Lewis acidic sites at the edges of the lamellar plates; provides more coordination anchoring points for tertiary amine suspension groups; rather than acting as a filler to carry large amounts of water or organic matter; when component C is organic montmorillonite, the larger d 001 It ensures that the organic intercalating agent fully expands the interlayer spacing; allows bifunctional compounds to penetrate into the interlayer domain or be firmly adsorbed on the surface of the laminate; utilizes the dual effects of physical adsorption and chemical coordination to further inhibit the migration of additives; and avoids the dispersion difficulties caused by the tight stacking of laminates.

[0017] Preferably, it further comprises: 0.01 to 0.25 parts of ultraviolet absorber, wherein the ultraviolet absorber is selected from benzotriazole or triazine ultraviolet absorbers; and 0 to 1.0 parts of other processing aids, wherein the processing aids are one or more combinations of self-lubricating agents, nucleating agents or antistatic agents.

[0018] By adopting the above technical solutions, a multi-dimensional protection system is constructed by introducing ultraviolet absorbers and conventional processing aids. Benzotriazole or triazine ultraviolet absorbers preferentially absorb high-energy ultraviolet rays and convert them into harmless heat energy, reducing the total amount of ultraviolet radiation reaching the polyolefin matrix and alleviating the light-stabilizing load of sterically hindered piperidine bifunctional compounds. Conventional processing aids, such as self-lubricants, reduce melt viscosity, reduce shear heat generation during processing, and prevent thermal oxidation degradation of the matrix due to local overheating. Nucleating agents regulate crystal morphology, refine grains, and indirectly improve the physical barrier ability of composite materials against the migration of additives.

[0019] Preferably, the self-lubricant is one or a combination of calcium stearate, zinc stearate, or polyethylene wax.

[0020] By adopting the above technical solutions, fatty acid salts or low molecular weight polymers are used as self-lubricants, which are uniformly dispersed in the polyolefin melt to form a lubricating interface; calcium stearate and zinc stearate have the function of capturing metal ions; neutralizing trace amounts of metal ions released in the processing equipment; preventing them from catalyzing the degradation of polyolefins; and polyethylene wax, with its good compatibility with polyolefins and low surface energy characteristics, improves the flow behavior of materials between the screw and the barrel; reduces processing torque; and avoids the thermal decomposition or oxidation of the tertiary amine hanging groups in the sterically hindered piperidine bifunctional compound due to excessive frictional heat.

[0021] Preferably, the nucleating agent is a sorbitol-based nucleating agent or an aryl phosphate nucleating agent; the antistatic agent is glyceryl monostearate or ethoxylated alkylamine.

[0022] By adopting the above technical solutions, due to the selection of the specific types of nucleating agents and antistatic agents, sorbitol-based nucleating agents induce polyolefins to form fine pseudo-hexagonal cell structures; increase grain boundary density; and provide more physical barriers along the grain boundaries for sterically hindered piperidine bifunctional compounds; aryl phosphate nucleating agents increase crystallization temperature and crystallinity through interaction with polyolefin molecular chains; the densified crystal structure blocks the diffusion and penetration of oxygen into the material interior; the addition of antistatic agents forms conductive pathways on the material surface by absorbing trace amounts of moisture in the environment; timely releases static charges generated by friction; prevents surface deterioration caused by static dust adsorption; and avoids localized oxidation reactions caused by discharge sparks.

[0023] Secondly, this application provides an application of a long-lasting weather-resistant antioxidant composition for polyolefins, employing the following technical solution: An application of a long-lasting weather-resistant antioxidant composition for polyolefins involves premixing the components of the composition with a polyolefin matrix, followed by melt blending and molding to obtain weather-resistant polyolefin products; the weather-resistant polyolefin products are pipes, cable sheaths, films, or injection molded parts.

[0024] By adopting the above technical solution, due to the use of melt blending molding process, under the high-temperature shearing action of the twin-screw extruder, the tertiary amine suspension group in the sterically hindered piperidine bifunctional compound undergoes in-situ coordination assembly with the lamellar additive of component C; this assembly process occurs in the molten state of the polymer melt with low viscosity; ensuring that the bifunctional compound is precisely guided to the surface of the acid micro-region or the edge of the layered material; forming a weather-resistant agent enrichment zone with the acid micro-region as the core; subsequently, during the cooling and shaping process, as the crystallinity of the polyolefin increases, these enrichment zones are fixed in the spherulite interface or the gaps in the layered structure; the resulting pipes, cable sheaths and other products exhibit long-term weather resistance stability and surface smoothness.

[0025] In summary, this application has the following beneficial effects: 1. Since this application uses a sterically hindered piperidine bifunctional compound as a weather-resistant component, the hindered phenolic antioxidant active center and the hindered amine photostable active center are integrated into the same molecule through a covalent spacer group, thereby avoiding the independent migration and acid-base antagonism of the two active components, and achieving the effect of reducing the weather-resistant agent consumption rate and extending the protection period of polyolefin products.

[0026] 2. In this application, a bifunctional compound structure with tertiary amine suspension groups is preferably used, and layered hydrotalcite or organo-modified montmorillonite with specific interlayer spacing is used as a lamellar additive. The tertiary amine suspension groups can selectively coordinate with the residual acid micro-regions of the catalyst in the polyolefin matrix or the edges of the layered materials. Through chemical coordination anchoring and lamellar barrier, the migration and precipitation rate of the weathering agent and environmental damage are reduced, the retention time of the weathering active ingredients in the weathering agent is increased during long-term use, and the weather protection cycle and outdoor service life of the polyolefin products are further extended.

[0027] 3. The method of this application utilizes the side chain coordination characteristics of bifunctional compounds to perform in-situ assembly with lamellar additives in the melt blending process, so that the weather-resistant agent enrichment area is locked in the spherulite interface or the gap of the layered structure during the cooling crystallization process, thus obtaining weather-resistant polyolefin products with both high surface smoothness and long-term thermo-oxidative stability.

[0028] 4. In this application, ultraviolet absorbers, nucleating agents with specific structures, and antistatic agents are preferably introduced. By constructing an auxiliary protection system that combines ultraviolet shielding, grain boundary blocking, and static electricity elimination, polyolefin products can achieve the effects of resisting surface powdering, antistatic adsorption, and stress cracking in complex outdoor environments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the test results of long-term thermo-oxidative stability and antioxidant depletion rate of the embodiments and comparative examples proposed in this application. Figure 2 This is a schematic diagram showing the test results of artificial accelerated photoaging, surface chalking, and gloss retention in the embodiments and comparative examples proposed in this application. Figure 3 This is a schematic diagram showing the test results of the targeted enrichment effect and extraction resistance of the layered medium in the embodiments and comparative examples proposed in this application. Figure 4 This is a schematic diagram showing the antistatic performance test results of the embodiments and comparative examples proposed in this application; Figure 5 This is a schematic diagram showing the environmental stress cracking test results of the embodiments and comparative examples proposed in this application. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] This application discloses a long-lasting weather-resistant antioxidant composition for polyolefins and its application. It comprises the following components in parts by weight: 100-150 parts of a polyolefin matrix; component A: 0.10-0.80 parts of a sterically hindered piperidine bifunctional compound; component B: 0.05-0.30 parts of a co-antioxidant; and component C: 0.02-0.30 parts of a lamellar additive. The sterically hindered piperidine bifunctional compound has a sterically hindered piperidine backbone of 2,2,6,6-tetramethylpiperidine or 1,2,2,6,6-pentamethylpiperidine; the co-antioxidant is a phosphite compound; and the lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

[0032] This application uses a sterically hindered piperidine bifunctional compound as a weather-resistant component, integrating the hindered phenolic antioxidant active center and the hindered amine photostable active center into the same molecule through a covalent spacer group, thereby avoiding the independent migration and acid-base antagonism of the two active components, and achieving the effect of reducing the weather-resistant agent wear rate and extending the protection period of polyolefin products.

[0033] Example 1: This example provides a long-lasting weather-resistant antioxidant composition for polyolefins, comprising the following components in parts by weight: 100 parts of polyolefin matrix, component A: 0.10 parts of sterically hindered piperidine bifunctional compound, component B: 0.05 parts of co-antioxidant, and component C: 0.02 parts of lamellar additive.

[0034] Among them, the sterically hindered piperidine bifunctional compound has a sterically hindered piperidine skeleton with a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring. The 4-position of the piperidine ring is connected by a covalent spacer group to a 2,6-di-tert-butyl-4-hydroxyphenyl antioxidant side chain containing a free phenol-OH group. The phenol-OH group exists in the form of a free phenol-OH group and does not participate in the bridging bond of the spacer group. The spacer group does not contain a phenol-OH oxygen atom, and the side chain of the spacer group has a tertiary amine dangling group. The co-antioxidant is a phosphite compound. The lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

[0035] The covalent spacer group is selected from one or more of the following: a C2 straight-chain alkylene chain, an oxyalkylene chain, a dimethyl divalent silane alkylene bridge, or a carbonate bridge.

[0036] The polyolefin matrix is ​​one or a combination of homopolymer polypropylene, random copolymer polypropylene, or impact copolymer polypropylene.

[0037] In the tertiary amine suspending group, m = 1, R is H and R′ is C. 1-4 alkyl.

[0038] Component B is bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite.

[0039] When component C is layered hydrotalcite, its X-ray diffraction (003) plane interplanar spacing d 001 The wavelength is 0.78 nm; when component C is an organo-modified montmorillonite monolayer fragment, its d 001 It is 1.5nm.

[0040] It also contains 0.01 parts of ultraviolet absorber, which is selected from benzotriazole ultraviolet absorbers; and 0.5 parts of other processing aids, which are one or more combinations of self-lubricating agents, nucleating agents or antistatic agents.

[0041] The self-lubricant is calcium stearate, the nucleating agent is sorbitol-based nucleating agent, and the antistatic agent is glyceryl monostearate.

[0042] Example 2: This example provides a long-lasting weather-resistant antioxidant composition for polyolefins, comprising the following components in parts by weight: 125 parts of polyolefin matrix, component A: 0.45 parts of sterically hindered piperidine bifunctional compound, component B: 0.175 parts of co-antioxidant, and component C: 0.16 parts of lamellar additive.

[0043] Among them, the sterically hindered piperidine bifunctional compound has a sterically hindered piperidine skeleton with a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring. The 4-position of the piperidine ring is connected by a covalent spacer group to a 2,6-di-tert-butyl-4-hydroxyphenyl antioxidant side chain containing a free phenol-OH group. The phenol-OH group exists in the form of a free phenol-OH group and does not participate in the bridging bond of the spacer group. The spacer group does not contain a phenol-OH oxygen atom, and the side chain of the spacer group has a tertiary amine dangling group. The co-antioxidant is a phosphite compound. The lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

[0044] The covalent spacer group is selected from one or more of the following: a C4 straight-chain alkylene chain, an oxoalkylene chain, a dimethyl divalent silane alkylene bridge, or a carbonate bridge.

[0045] The polyolefin matrix is ​​high-density polyethylene or linear low-density polyethylene.

[0046] In the tertiary amine suspending group, m = 2, and R is C 1-4 Alkyl group, where R′ is H.

[0047] Component B is tris(2,4-di-tert-butylphenyl) phosphite.

[0048] When component C is layered hydrotalcite, its X-ray diffraction (003) plane interplanar spacing d 001 The wavelength is 0.82 nm; when component C is an organo-modified montmorillonite monolayer fragment, its d 001 It is 2.0nm.

[0049] It also contains 0.13 parts of ultraviolet absorber, which is selected from triazine ultraviolet absorbers; and 0.75 parts of other processing aids, which are one or more combinations of self-lubricating agents, nucleating agents or antistatic agents.

[0050] The self-lubricant is zinc stearate, the nucleating agent is an aryl phosphate nucleating agent, and the antistatic agent is an ethoxylated alkylamine.

[0051] Example 3: This example provides a long-lasting weather-resistant antioxidant composition for polyolefins, comprising the following components in parts by weight: 150 parts of polyolefin matrix, component A: 0.80 parts of sterically hindered piperidine bifunctional compound, component B: 0.30 parts of co-antioxidant, and component C: 0.30 parts of lamellar additive.

[0052] Among them, the sterically hindered piperidine bifunctional compound has a sterically hindered piperidine skeleton with a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring. The 4-position of the piperidine ring is connected by a covalent spacer group to a 2,6-di-tert-butyl-4-hydroxyphenyl antioxidant side chain containing a free phenol-OH group. The phenol-OH group exists in the form of a free phenol-OH group and does not participate in the bridging bond of the spacer group. The spacer group does not contain a phenol-OH oxygen atom, and the side chain of the spacer group has a tertiary amine dangling group. The co-antioxidant is a phosphite compound. The lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

[0053] The covalent spacer group is selected from one or more of the following: a C6 straight-chain alkylene chain, an oxoalkylene chain, a dimethyl divalent silanealkylene bridge, or a carbonate bridge.

[0054] The polyolefin matrix is ​​an ethylene-vinyl acetate copolymer or a polyolefin elastomer and its blends.

[0055] In the tertiary amine suspending group, m = 4, and both R′ and R are C. 1-4 alkyl.

[0056] Component B is distearyl pentaerythritol diphosphite.

[0057] When component C is layered hydrotalcite, its X-ray diffraction (003) plane interplanar spacing d 001 The wavelength is 0.90 nm; when component C is an organo-modified montmorillonite monolayer fragment, its d 001 It is 3.0nm.

[0058] It also contains 0.25 parts of ultraviolet absorber, which is selected from benzotriazole ultraviolet absorbers; and 1.0 part of other processing aids, which are one or more combinations of self-lubricating agents, nucleating agents or antistatic agents.

[0059] The self-lubricant is polyethylene wax, the nucleating agent is a combination of sorbitol nucleating agents and aryl phosphate nucleating agents, and the antistatic agent is a combination of glyceryl monostearate and ethoxylated alkylamine.

[0060] Comparative Example 1: This comparative example is the same as that in Example 1, except that component A was not added.

[0061] Comparative Example 2: This comparative example refers to the content of Example 1, except that component A is replaced with an equal weight of a conventional physical blending system, and the rest is the same as Example 1.

[0062] Comparative Example 3: This comparative example is the same as Example 1, except that component C was not added.

[0063] Comparative Example 4: This comparative example is the same as that in Example 1, except that the spacer side chain of component A does not have a tertiary amine dangling group. The rest of the contents are the same as in Example 1.

[0064] Comparative Example 5: This comparative example is the same as that in Example 1, except that component B is replaced with an equal weight of hindered phenolic co-antioxidant.

[0065] Comparative Example 6: This comparative example is the same as Example 1, except that no ultraviolet absorber was added.

[0066] Performance testing Sample preparation: Following the component ratios given in the examples and comparative examples, accurately weigh the polyolefin matrix, component A (hindered piperidine bifunctional compound), component B (phosphite-based antioxidant), component C (lamellar additive), and optional UV absorbers and processing aids. Add each component to a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. Add the premix to the main feed port of a co-rotating twin-screw extruder. Set the appropriate melt processing temperature range according to the type of polyolefin matrix. After shearing and dispersing by the screw, extrude, water-cool, and pelletize to obtain composite granules. Vacuum dry the granules at 80°C for 4 hours, then injection mold them using a precision injection molding machine at the standard injection temperature corresponding to the matrix to prepare standard test strips and samples for various performance tests. The injection mold temperature is controlled between 30°C and 60°C.

[0067] Long-term thermo-oxidative stability and antioxidant depletion rate test: Type 1 dumbbell-shaped tensile specimens obtained from injection molding were suspended in a forced-ventilation circulating thermal aging test chamber at a test temperature of 150℃ for a period of more than 60 days. Every few days, five specimens were taken out and conditioned for 24 hours in a standard environment of 23℃ and 50% relative humidity. Subsequently, a portion of the aged specimens were taken, and the oxidation induction time was measured using a differential scanning calorimeter in an oxygen atmosphere to characterize the residual thermo-oxidative protection capability of the samples. The remaining aged specimens were tested for tensile strength and fracture rate according to tensile test standards. Elongation test was conducted to evaluate the time-dependent decay of its mechanical properties. Simultaneously, to directly compare the loss rate of the weathering agent, another sample taken at the same aging point was used. The central portion was cut off, ground into powder, and ultrasonically extracted with dichloromethane at 40°C for 6 hours. The content of component A in the extract was determined by high-performance liquid chromatography (HPLC). A curve showing the change in the residual rate of component A over aging time was plotted, and its half-life was calculated. Oxidation induction time was tested according to ISO 11357-6 standard, tensile properties were tested according to ISO 527-2 standard, and the residual rate of component A was determined using an internal HPLC quantitative method.

[0068] Artificial accelerated photoaging, surface chalking, and gloss retention tests: Square samples (60mm × 60mm × 2mm) obtained from injection molding were placed in a xenon arc lamp accelerated weathering test chamber equipped with a water-cooling system. Exposure was conducted for over 3000 hours according to Method A of GB / T16422.2, with the irradiance set at 0.5 W / m² at 340 nm. 2 The blackboard temperature was 65℃ and the relative humidity was 50%. Every 500 hours, three samples were taken out and conditioned in a standard environment away from light. The color difference of the samples was measured using a spectrophotometer and the yellowness index was calculated. The surface gloss was measured using a gloss meter under 60° geometric conditions. The chalking level of the sample surface was visually evaluated according to GB / T1766 standard. A chalking level of 0 indicates no chalking, and a level of 5 indicates severe chalking. This was to verify the inhibitory effect of the protective system constructed with the assistance of UV absorbers on surface chalking. The color difference and yellowness index were tested according to ISO7724 standard, the 60° gloss was tested according to ISO2813 standard, and the chalking level was evaluated according to GB / T1766 standard.

[0069] Verification of Targeted Enrichment Effect and Extraction Resistance of Layered Media: To further verify the targeted enrichment effect produced by the selective coordination between component C (layered additive) and component A (tertiary amine suspension group), a solvent resistance extraction test was conducted. Films with a thickness of 0.5 mm obtained from injection molding were cut into 50 mm × 50 mm squares, accurately weighed, and placed in screw-capped glass bottles. Sufficient n-hexane was added as the extraction solvent, and extraction was carried out continuously with shaking in a 50°C constant-temperature water bath shaker for 24 h. The membranes were then removed, quickly rinsed with fresh n-hexane, and dried to constant weight in a vacuum oven at 40°C. Fourier transform infrared spectroscopy was used in attenuated total reflectance mode to determine the concentration of components in the membranes before and after extraction. The area of ​​the characteristic absorption peak of the phenolic hydroxyl group of component A was used to calculate the extraction resistance retention rate of component A in each sample. The higher the retention rate, the stronger the in-situ anchoring and targeted enrichment effect of the lamellar additive on the weathering agent molecules. At the same time, the film after ultrathin frozen sectioning was observed by scanning transmission electron microscopy, and the surface distribution map of nitrogen element was collected by energy dispersive X-ray spectroscopy to visually observe whether the nitrogen-containing sterically hindered piperidine groups were directionally enriched in the edge region of layered hydrotalcite or montmorillonite monolayer fragments. The extraction resistance retention rate of component A was determined according to the extraction method specified in ASTM D7210 standard and combined with the Fourier transform infrared spectroscopy internal standard method. The energy dispersive X-ray spectroscopy elemental distribution analysis was performed according to ISO 22309 standard.

[0070] Antistatic performance test: 100mm diameter and 2mm thick disc samples obtained from injection molding were conditioned for 48 hours in a standard environment of 23℃ and 50% relative humidity. Using a high-resistivity meter and a concentric three-electrode system, the surface resistivity of the samples was tested according to GB / T1410 standard under an applied voltage of 500V. Five different locations were tested for each sample, and the average value was taken. The lower the surface resistivity value, the more significant the effect of the antistatic agent migrating to the surface and eliminating electrostatic adsorption, directly verifying the auxiliary protective ability against electrostatic adsorption described in the beneficial effects. Surface resistivity was tested according to GB / T1410 standard.

[0071] Environmental stress cracking resistance test: The long strips obtained from each injection molding process that meet the specifications are subjected to environmental stress cracking resistance test according to GB / T1842 standard; after mechanically scoring the strips, they are bent and fixed on the specimen holder, so that the scored surface is under tension, and then completely immersed in a nonylphenol polyoxyethylene ether active solution at a constant temperature of 50℃; the time when visible cracks appear on each strip is observed and recorded, and the median cracking time of each group of parallel specimens is calculated; the longer the cracking time, the stronger the stress cracking resistance obtained by the crystal morphology regulated by the specific nucleating agent and the synergy with the long-lasting antioxidant system; the environmental stress cracking resistance time is tested according to GB / T1842 standard.

[0072] Table 1: Results of Long-Term Thermo-Oxidative Stability and Antioxidant Depletion Rate Tests Example 1 82.5 87.3 79.6 48.7 Example 2 96.3 91.8 84.2 55.2 Example 3 113.7 94.5 88.9 63.8 Comparative Example 1 12.4 43.1 31.5 — Comparative Example 2 67.8 76.2 68.4 36.4 Comparative Example 3 71.3 80.5 72.1 42.9 Comparative Example 4 74.6 83.7 75.8 44.3 Comparative Example 5 58.9 69.4 60.7 45.1 Comparative Example 6 80.1 86.2 78.3 47.8 Table 2: Results of Artificial Accelerated Photoaging, Surface Chalking, and Gloss Retention Rate Testing Example 1 8.7 82.4 1 Example 2 6.3 88.6 0 Example 3 4.8 91.7 0 Comparative Example 1 26.4 38.2 4 Comparative Example 2 14.2 69.5 2 Comparative Example 3 11.9 74.8 2 Comparative Example 4 10.5 78.3 2 Comparative Example 5 13.8 71.6 3 Comparative Example 6 15.3 65.4 3 Table 3: Results of Targeted Enrichment Effect and Extraction Resistance Tests of Layered Media Example 1 8.7 82.4 Example 2 6.3 88.6 Example 3 4.8 91.7 Comparative Example 1 26.4 38.2 Comparative Example 2 14.2 69.5 Comparative Example 3 11.9 74.8 Comparative Example 4 10.5 78.3 Comparative Example 5 13.8 71.6 Comparative Example 6 15.3 65.4 Table 4: Results of Antistatic Performance Test Example 1 <![CDATA[4.6×10 11 ]]> Example 2 <![CDATA[2.8×10 10 ]]> Example 3 <![CDATA[1.3×10 10 <!-- 8 -->]]> Comparative Example 1 <![CDATA[7.9×10 15 ]]> Comparative Example 2 <![CDATA[5.2×10 15 ]]> Comparative Example 3 <![CDATA[6.8×10 14 ]]> Comparative Example 4 <![CDATA[8.3×10 14 ]]> Comparative Example 5 <![CDATA[9.1×10 14 ]]> Comparative Example 6 <![CDATA[3.7×10 11 ]]> Table 5: Results of Environmental Stress Cracking Test Example 1 387 Example 2 462 Example 3 538 Comparative Example 1 86 Comparative Example 2 241 Comparative Example 3 298 Comparative Example 4 312 Comparative Example 5 276 Comparative Example 6 375 Example Conclusion: See appendix Figure 1 - Appendix Figure 5 The differences between each embodiment and the comparative example are as follows: As can be seen from Examples 1-3 and Comparative Example 1, and Tables 1, 2, 4 and 5, the sterically hindered piperidine bifunctional compound is the functional component of this polyolefin long-lasting weather-resistant antioxidant composition. Its absence will lead to a fundamental deterioration in the long-term thermal and oxygen stability, photo-aging protection performance, antistatic performance and environmental stress cracking resistance of polyolefin products, which cannot meet the actual use requirements of long-lasting weather resistance.

[0073] As can be seen from Examples 1-3 and Comparative Example 2, and Tables 1, 2 and 5, the bifunctional structure that integrates the hindered phenolic antioxidant active center and the hindered amine photostable active center into the same molecule through covalent bonds can effectively avoid the independent migration and acid-base antagonism of the two active components compared with the traditional physical blending system. This significantly reduces the loss rate of weathering agent during use, greatly extends the protection period of polyolefin products, and simultaneously improves their mechanical property retention rate and resistance to environmental stress cracking.

[0074] Based on Examples 1-3 and Comparative Example 3, and in conjunction with Tables 1, 2, and 3, it can be seen that there is a significant synergistic effect between the sheet additive and the sterically hindered piperidine bifunctional compound. The former can guide the weathering agent molecules to be directionally enriched at the high-risk degradation interface in the polyolefin matrix through selective coordination with the bifunctional compound, while enhancing the weathering agent's resistance to extraction in the matrix, thereby comprehensively improving the long-term thermo-oxidative stability and photo-aging protection effect of the product.

[0075] Based on Examples 1-3 and Comparative Example 4, and in conjunction with Tables 1, 2 and 3, it can be seen that the tertiary amine suspending group on the spacer side chain of the sterically hindered piperidine bifunctional compound is the key structural unit for achieving targeted coordination in acid microregions. Its absence will prevent the weathering agent from forming an effective enrichment in high-risk degradation areas, thereby significantly weakening the composition's long-lasting thermo-oxidative protection and photo-aging inhibition effect.

[0076] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Tables 1, 2 and 5, it can be seen that there is a unique synergistic antioxidant effect between phosphite-based auxiliary antioxidants and sterically hindered piperidine bifunctional primary antioxidants. Replacing them with other types of auxiliary antioxidants will significantly reduce the thermo-oxidative stability and photo-aging protection of the composition, and will also be detrimental to improving the environmental stress cracking resistance of polyolefin products.

[0077] As can be seen from Examples 1-3 and Comparative Example 6, and Tables 2 and 5, the UV absorber can synergistically construct a complete multi-level UV shielding protection system with the main weather-resistant system, effectively inhibiting surface yellowing and chalking of polyolefin products during long-term outdoor use, improving surface gloss retention, and also having a certain auxiliary effect on improving the environmental stress cracking resistance of the products.

[0078] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A long-lasting weather-resistant antioxidant composition for polyolefins, characterized in that, It contains the following components in parts by weight: 100-150 parts of polyolefin matrix, component A: 0.10-0.80 parts of sterically hindered piperidine bifunctional compound, component B: 0.05-0.30 parts of co-antioxidant, and component C: 0.02-0.30 parts of sheet additive; The sterically hindered piperidine bifunctional compound uses a 2,2,6,6-tetramethylpiperidine ring or a 1,2,2,6,6-pentamethylpiperidine ring as its sterically hindered piperidine skeleton. At the 4-position of the piperidine ring, a 2,6-di-tert-butyl-4-hydroxyphenyl antioxidant side chain containing a free phenolic -OH group is covalently linked. The phenolic -OH group exists as a free -OH group and does not participate in the bridging bond of the spacer group. The spacer group does not contain a phenolic -OH oxygen atom, and the side chain of the spacer group has a tertiary amine dangling group: —(CH2). m —N(R)(R′); the auxiliary antioxidant is a phosphite compound; the lamellar additive is selected from layered hydrotalcite or organo-modified montmorillonite monolayer fragments.

2. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, The covalent spacer base is selected from any of the following types or a combination thereof: C2-C6 straight-chain alkylene chain: —(CH2) n —, where n = 2 to 6; Oxyalkylene chain: —CH2—CH2—O—CH2—CH2—; Dimethyl divalent silane-alkyl bridge: —Si(CH3)2—CH2CH2—; Carbonate bridge: —O—C(=O)—O—.

3. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, The polyolefin matrix is ​​one or more of the following: homopolymer polypropylene, random copolymer polypropylene, impact copolymer polypropylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or polyolefin elastomers and their blends.

4. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, In the tertiary amine suspension group, m = 1 to 4, and R and R′ are H or C. 1-4 Alkyl group, and at least one of which is C 1-4 alkyl.

5. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, The phosphite compounds are selected from one or more combinations of bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, or distearyl pentaerythritol diphosphite.

6. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, When component C is layered hydrotalcite, its X-ray diffraction (003) interplanar spacing d 001 The wavelength is 0.78–0.90 nm; when component C is an organo-modified montmorillonite monolayer fragment, its d 001 The wavelength ranges from 1.5 to 3.0 nm.

7. The long-lasting weather-resistant antioxidant composition for polyolefins according to claim 1, characterized in that, It also contains: 0.01 to 0.25 parts of ultraviolet absorber, wherein the ultraviolet absorber is selected from benzotriazole or triazine ultraviolet absorbers; and 0 to 1.0 parts of other processing aids, wherein the processing aids are one or more combinations of self-lubricating agents, nucleating agents or antistatic agents.

8. A long-lasting weather-resistant antioxidant composition for polyolefins according to claim 7, characterized in that, The self-lubricating agent is one or more of calcium stearate, zinc stearate, or polyethylene wax.

9. A long-lasting weather-resistant antioxidant composition for polyolefins according to claim 7, characterized in that, The nucleating agent is a sorbitol-based nucleating agent or an aryl phosphate nucleating agent; the antistatic agent is glyceryl monostearate or ethoxylated alkylamine.

10. The application of a long-lasting weather-resistant antioxidant composition for polyolefins, characterized in that, The long-lasting weather-resistant antioxidant composition for polyolefins according to any one of claims 1-9 is prepared by premixing each component of the composition with a polyolefin matrix and then melt-blending and molding to obtain a weather-resistant polyolefin product; the weather-resistant polyolefin product is a pipe, cable sheath, film or injection molded part.

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