An environmentally friendly waterborne polymerization inhibitor and its preparation method

Abstract

This invention provides an environmentally friendly waterborne polymerization inhibitor and its preparation method, belonging to the field of polymer additive technology. It includes an aqueous phase, an oil phase, an emulsifier, and a polymer stabilizer. The oil phase comprises a polymerization inhibitor monomer and an antioxidant, and the polymerization inhibitor monomer has the chemical structure shown in Structural Formula I. This invention improves the overall performance of waterborne PVC polymerization inhibitors by introducing a smart, responsive polymerization inhibitor monomer based on dynamic covalent bonds.

Description

Technical Field

[0001] This invention belongs to the field of polymer additive technology, specifically relating to an environmentally friendly waterborne polymerization inhibitor and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC), as one of the top three most produced general-purpose thermoplastic polymers globally, is widely used in building materials, medical devices, and other fields. In global industrial-scale production, approximately 80% of PVC resin is synthesized in an aqueous medium via suspension polymerization. In the later stages of this process, when the monomer conversion rate reaches 80% to 85%, a highly efficient polymerization inhibitor (or terminator) must be injected into the reaction system to control the molecular weight distribution of the resin, prevent excessive aggregation of resin particles, and maintain excellent porosity. More importantly, the polymerization inhibitor not only needs to be able to instantly quench residual macromolecular free radicals in the system, but also needs to provide long-lasting thermal stability protection during the subsequent processing and long-term service of the PVC resin.

[0003] The intrinsic structure of PVC makes it highly sensitive to heat and ultraviolet light, making it prone to autocatalytic dechlorination during processing and service. This degradation process follows a zipper-like elimination mechanism, rapidly forming conjugated polyene sequences on the polymer backbone. This not only leads to severe color degradation of the resin but also causes a sharp decline in the material's mechanical properties. Simultaneously, the released hydrogen chloride gas acts as a catalyst, further accelerating the degradation chain reaction and generating a strong autocatalytic effect. Furthermore, peroxide free radicals are formed during photo-oxidative aging, leading to photo-oxidative degradation.

[0004] To address these issues, various waterborne polymerization inhibitors have been developed industrially, but all suffer from significant technical drawbacks: Traditional phenolic compounds (such as bisphenol A) are effective at terminating macroscopic self-polymerization reactions, but residual bisphenol A leads to extremely poor whiteness of the resin during later aging processes. Industrially, acetone thiourea (ATSC) is often combined with bisphenol A to improve aging whiteness, but this inevitably weakens the initial thermal stability of the resin. In the case of α-methylstyrene and dialkyl hydroxylamine, residual α-methylstyrene easily leads to the formation of unplasticizable particles in the final product, accompanied by the risk of toxic substance leaching. Dialkyl hydroxylamine cannot provide long-term antioxidant buffer capacity. Stabilized nitroxide radicals (such as TEMPO) have extremely high free radical scavenging rates, but if introduced directly as free small molecules into the polymerization system, they are easily and ineffectively consumed by trace impurities or dissolved oxygen in the early stages of polymerization. Furthermore, the strong hydrophilicity of TEMPO results in a low partition coefficient in the hydrophobic PVC polymer phase, making it unable to anchor and provide anti-aging protection for a long period during the service life of PVC.

[0005] In summary, existing polyvinyl chloride (PVC) polymerization inhibitors struggle to simultaneously achieve both instantaneous polymerization termination and long-term anti-aging properties of the polymer resin, and suffer from issues such as easy volatilization and release of active ingredients, and poor environmental compatibility. Therefore, there is a need in this field for a novel waterborne polymerization inhibitor system capable of latent shielding of active ingredients and targeted release within the degradation microenvironment, to comprehensively meet the industrial demands for instantaneous polymerization inhibition, long-term anchoring, and non-toxicity and environmental friendliness. Summary of the Invention

[0006] In view of the above situation and to overcome the defects of the prior art, the purpose of this invention is to provide an environmentally friendly waterborne polymerization inhibitor and its preparation method, so as to at least partially solve the problems mentioned in the background art.

[0007] The technical solution adopted in this invention is as follows: The first aspect of this invention provides an environmentally friendly waterborne polymerization inhibitor, comprising: The mixture comprises an aqueous phase, an oil phase, an emulsifier, and a polymeric stabilizer; wherein the oil phase includes a polymerization inhibitor monomer and an antioxidant, and the polymerization inhibitor monomer has the chemical structure shown in Formula I: Structural formula I.

[0008] In some embodiments of the present invention, the mass ratio of the aqueous phase, oil phase, emulsifier and polymeric stabilizer is (50-80):(15-40):(2-10):(0.5-5), and the mass ratio of the polymerization inhibitor monomer and the antioxidant in the oil phase is (3-5):1.

[0009] In some embodiments of the present invention, the aqueous phase is an acidic aqueous solution with a pH value of 4.5-5.5.

[0010] In some embodiments of the present invention, the antioxidant includes trinonylphenyl phosphite and dilauryl thiodipropionate.

[0011] In some embodiments of the present invention, the emulsifier includes sorbitan oleate and polyoxyethylene sorbitan monooleate.

[0012] In some embodiments of the present invention, the polymeric stabilizer includes chitosan and hydroxypropyl cellulose.

[0013] A second aspect of this invention provides a method for preparing the above-mentioned environmentally friendly waterborne polymerization inhibitor, comprising the following steps: Eugenol was etherified with glycidyl methacrylate to obtain a monomer precursor; the allyl group of the side chain of the monomer precursor was ozonally oxidized and reduced to obtain an intermediate containing a terminal aldehyde group; the intermediate was condensed with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy radical to obtain a polymerization inhibitor monomer. The polymerization inhibitor monomer, antioxidant and sorbitan oleate are mixed and heated to melt at 40-45°C to obtain an oil phase solution; Polyoxyethylene sorbitan monooleate, chitosan and hydroxypropyl cellulose were dispersed in deionized water, and the pH was adjusted to 4.5-5.5 to obtain an aqueous solution. The oil phase solution is added to the aqueous phase solution, and phase emulsification is carried out under shear cavitation to obtain the environmentally friendly waterborne polymerization inhibitor.

[0014] In some embodiments of the present invention, the etherification reaction is carried out using tetrabutylammonium bromide as a catalyst, the reaction temperature is 85-90°C, and the reaction time is 6-12 hours; the molar ratio of eugenol to glycidyl methacrylate is 1:1. The ozone deoxidation is carried out at a low temperature of -78°C.

[0015] In some embodiments of the present invention, the condensation reaction is carried out under reflux conditions for 12-15 hours with p-toluenesulfonic acid as a catalyst; the molar ratio of the intermediate to 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radical is 1:1.05.

[0016] The third aspect of this invention proposes the application of the above-mentioned environmentally friendly waterborne polymerization inhibitor in the aqueous suspension polymerization reaction of polyvinyl chloride. When the monomer conversion rate in the polyvinyl chloride suspension polymerization reaction system reaches 80% to 85%, the environmentally friendly waterborne polymerization inhibitor is injected into the polymerization system. The amount of the environmentally friendly waterborne polymerization inhibitor added is 0.03% to 0.08% of the mass of liquid vinyl chloride monomer in the polymerization reaction system.

[0017] The beneficial effects achieved by this invention are as follows: This invention improves the overall performance of waterborne PVC polymerization inhibitors by introducing a smart, responsive polymerization inhibitor monomer based on dynamic covalent bonds. The high rigidity and steric hindrance shielding effect of this monomer's macromolecular backbone overcome the migration and ineffective consumption of the active ingredient. Its dynamic imine bonds impart a microenvironment-responsive characteristic, achieving chain blocking through targeted release of highly active TEMPO. Based on this core carrier mechanism, the catalytic cycle driven by the released TEMPO can further synergize deeply with antioxidants, enabling the system to maintain extremely excellent stability even under long-term thermal aging conditions. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this invention.

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] To address the problems raised in the background art, the first aspect of this invention provides an environmentally friendly waterborne polymerization inhibitor comprising an aqueous phase, an oil phase, an emulsifier, and a polymeric stabilizer; wherein the oil phase includes a polymerization inhibitor monomer and an antioxidant, and the polymerization inhibitor monomer has the chemical structure shown in Formula I: Structural formula I.

[0022] In the composition, the aqueous phase serves as a green carrier liquid medium, providing a basic emulsification and dispersion environment; emulsifiers and polymeric stabilizers are used to construct the microenvironment to maintain the interfacial stability of the system; and the polymerization inhibitor monomers and antioxidants in the oil phase are key functional components for achieving breakthroughs in instantaneous polymerization inhibition and long-term thermal stability of PVC resin.

[0023] The polymerization inhibitor monomer (Structural Formula I) in the oil phase constitutes the backbone structure of the macromolecular intelligent environmental sensing and targeted release carrier. In this invention, this structure is based on a eugenol precursor with a high aromatic ring density, and is formed by covalently anchoring 4-amino-TEMPO (i.e., 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radical) with extremely rapid free radical scavenging ability through dynamic imine bonds (-C=N-) in the side chain. During the polymerization stage and the latency period of normal storage (neutral pH environment), the larger copolymer backbone can exert a strong steric hindrance shielding effect on the attached TEMPO groups. This spatial configuration avoids the highly active TEMPO from being ineffectively consumed by trace dissolved oxygen or minor impurities in the system during non-critical periods, thereby maintaining the maximum antioxidant reserve of the polymerization inhibitor.

[0024] Compared to traditional free small-molecule polymerization inhibitors (such as free TEMPO or bisphenol A), the polymerization inhibitor monomer of this invention, relying on the double bond of methacrylate, can be covalently anchored extremely firmly in the PVC macromolecular network, completely solving the physical defects of easy migration, volatility, and extraction of the active ingredient. When autocatalytic dechlorination of PVC occurs during high-temperature processing or service life, leading to rapid acidification of the local microenvironment, its dynamic imine bond (-C=N-) is attacked by a large number of H+ protons and hydrolyzes and breaks. This microenvironment response mechanism instantly cuts off the covalent bond, thereby releasing highly active 4-amino-TEMPO free small molecules. The spatially freed TEMPO reaches the degradation site at an extremely high diffusion rate, rapidly capturing carbon centers and peroxide free radicals, thereby breaking the polymer's zipper-like elimination reaction chain.

[0025] The antioxidant, compounded in the oil phase, introduces a non-radical pathway for decomposing peroxides, constructing a logically closed loop for long-term antioxidant protection. The released TEMPO molecules, when capturing free radicals, are involved in a complex redox cycle of nitric oxide radicals, hydroxylamine, and their oxoammonium ions. This mechanism exhibits superoxide dismutase-like catalytic dismutation activity, overcoming the stoichiometric limitations of traditional antioxidants that require a one-to-one consumption ratio, repeatedly scavenging reactive oxygen species in the system. Simultaneously, the antioxidant can reduce and decompose the inevitably generated hydroperoxides (ROOH) on the polymer chain into stable alcohols (ROH) via a non-radical pathway. This comprehensive combination of infinitely cyclical free radical scavenging and peroxide decomposition synergistically inhibits the oxidative degradation of the polymer backbone.

[0026] In summary, this invention improves the overall performance of waterborne PVC polymerization inhibitors by introducing a smart, responsive polymerization inhibitor monomer based on dynamic covalent bonds. The high rigidity and steric hindrance shielding effect of this monomer's macromolecular backbone overcome the migration and ineffective consumption of the active ingredient; its dynamic imine bonds impart a microenvironment-responsive characteristic, achieving chain blocking through targeted release of highly active TEMPO; based on this core carrier mechanism, the catalytic macrocycle driven by the released TEMPO can further form a deep synergy with antioxidants, enabling the system to maintain extremely excellent stability even under long-term thermal aging conditions.

[0027] In some embodiments, the mass ratio of the aqueous phase, oil phase, emulsifier, and polymeric stabilizer is (50-80):(15-40):(2-10):(0.5-5), and the mass ratio of the polymerization inhibitor monomer to the antioxidant in the oil phase is (3-5):1. Within the above ratio range, appropriate amounts of emulsifier and polymeric stabilizer synergistically regulate the oil-water interfacial tension, avoiding foaming of the system due to excessive emulsifier or droplet flocculation and demulsification due to insufficient stabilizer, ensuring that the highly hydrophobic polymerization inhibitor monomer maintains stable micron-level dispersion under high temperature and strong shear. Furthermore, the mass ratio of the polymerization inhibitor monomer to the antioxidant in the oil phase is limited to (3-5):1. At this specific ratio, sufficient polymerization inhibitor monomer is retained to target and release TEMPO to capture free radicals, while an appropriate amount of auxiliary antioxidant is provided to decompose hydrogen peroxide, achieving optimal stoichiometric balance in the synergistic echo stabilization effect, thereby significantly extending the antioxidant life of polyvinyl chloride resin.

[0028] In some embodiments, the aqueous phase is an acidic aqueous solution with a pH of 4.5-5.5. This slightly acidic environment promotes the moderate protonation of amino groups in the polymeric stabilizers (such as chitosan), imparting a strong positive charge to the surface of the oil phase droplets. This effectively inhibits droplet flocculation and aggregation using Coulombic repulsion. Simultaneously, this specific weakly acidic range satisfies the physical stability requirements of the emulsion hydrodynamics while precisely preventing premature hydrolysis of the dynamic imine bonds on the core polymerization inhibitor monomers due to excessive acidity. This ensures the structural integrity of the aqueous polymerization inhibitor during storage and pumping, allowing it to maintain maximum latent shielding and antioxidant reserves before entering the polymerization system.

[0029] In some embodiments, the antioxidant comprises trinonylphenyl phosphite and dilaurate thiodipropionate. With this configuration, the two compounds act as a synergistic antioxidant system, constructing a non-radical pathway for the decomposition of hydroperoxides. During the cascade degradation of polyvinyl chloride (PVC), both compounds synergistically reduce and decompose the highly unstable hydroperoxides (ROOH) generated on the polymer macromolecular chains into stable alcohols (ROH). This non-radical decomposition mechanism is deeply intertwined with the free radical capture catalytic cycle driven by the targeted burst release of TEMPO from the polymerization inhibitor monomer, thereby achieving a dual defense of infinite free radical scavenging and peroxide decomposition. This significantly enhances the antioxidant buffer capacity of the system under long-term thermo-oxidative aging conditions and effectively delays the color degradation of the resin material.

[0030] In some embodiments, the emulsifier comprises sorbitan oleate and polyoxyethylene sorbitan monooleate. This configuration, combining sorbitan oleate (Span 80) with a low hydrophilic-lipophilic balance (HLB) value with polyoxyethylene sorbitan monooleate (Tween 80) with a high HLB value, precisely matches the microscopic thermodynamic requirements of highly hydrophobic monomers, finely controlling the overall HLB value of the system to the optimal range. This compound system achieves the lowest oil-water interfacial tension during spontaneous microemulsification, thereby not only endowing the aqueous polymerization inhibitor emulsion with excellent basic thermodynamic stability but also effectively preventing the aggregation and phase separation of hydrophobic polymerization inhibitor monomers in the aqueous phase, ensuring efficient dispersion of the agent.

[0031] In some embodiments, the polymeric stabilizer includes chitosan and hydroxypropyl cellulose. Chitosan, as a natural polycationic polysaccharide, undergoes amino protonation in a slightly acidic environment and tightly adsorbs at the oil-water interface, effectively inhibiting droplet flocculation and aggregation through strong Coulombic repulsion. Hydroxypropyl cellulose, with its flexible hydrophilic segments extending into the aqueous phase, forms a thick hydration layer shield, providing excellent steric hindrance. This deep synergy between the two allows the aqueous polymerization inhibitor emulsion to perfectly resist the high temperatures and strong fluid shear forces in the reactor during the later stages of suspension polymerization, effectively preventing demulsification and stratification under extreme conditions. This ensures the instantaneous and uniform dispersion of the polymerization inhibitor droplets in the complex polymerization system.

[0032] A second aspect of this invention provides a method for preparing the above-mentioned environmentally friendly waterborne polymerization inhibitor, comprising the following steps: Eugenol was etherified with glycidyl methacrylate to obtain a monomer precursor; the allyl group of the side chain of the monomer precursor was ozonally oxidized and reduced to obtain an intermediate containing a terminal aldehyde group; the intermediate was condensed with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy radical to obtain a polymerization inhibitor monomer. The polymerization inhibitor monomer, antioxidant and sorbitan oleate are mixed and heated to melt at 40-45°C to obtain an oil phase solution; Polyoxyethylene sorbitan monooleate, chitosan and hydroxypropyl cellulose were dispersed in deionized water, and the pH was adjusted to 4.5-5.5 to obtain an aqueous solution. The oil phase solution is added to the aqueous phase solution, and phase emulsification is carried out under shear cavitation to obtain the environmentally friendly waterborne polymerization inhibitor.

[0033] This setup, at the molecular synthesis level, employs a specific reaction sequence of etherification, ozone oxidation-reduction, and condensation to prepare a polymerization inhibitor monomer framework containing dynamic imine bonds and anchored to TEMPO. This modification pathway effectively protects the key active groups at both ends of the monomer. At the formulation engineering level, the functional oil phase is gently melted at 40-45℃ and then incorporated into an aqueous phase at a specific pH value, where reverse emulsification is performed using strong shear cavitation. The mechanical shearing and cavitation bursting effects under high-pressure turbulent flow forcefully tear and encapsulate the highly hydrophobic functional oil phase into the aqueous phase, prompting the emulsifier and polymeric stabilizer to rapidly lock the oil-water interface. Thus, this method not only ensures the precise realization of the core monomer's intelligent response topology but also successfully prepares micron-sized emulsions with uniform particle size and high demulsification resistance, guaranteeing the instantaneous uniform distribution and efficient reaction of the final polymerization inhibitor product in an industrial-grade PVC suspension polymerization reactor.

[0034] In some embodiments, the etherification reaction is catalyzed by tetrabutylammonium bromide, the reaction temperature is 85-90°C, and the reaction time is 6-12 hours; the molar ratio of eugenol to glycidyl methacrylate is 1:1; by reacting eugenol and glycidyl methacrylate (GMA) in an equimolar ratio of 1:1 under the catalysis of tetrabutylammonium bromide and at 85-90°C, it is possible to ensure that the active phenolic hydroxyl groups in the eugenol molecule undergo efficient and directional addition with the epoxy groups of GMA, completely converting eugenol into an aryl-alkyl ether structure with higher thermodynamic rigidity, providing a stable skeletal basis for subsequent covalent anchoring.

[0035] The ozone deoxidation is carried out at a low temperature of -78°C. Specifically, the ozone deoxidation is limited to this extremely low temperature of -78°C. Under this specific low-temperature condition, ozone molecules can selectively attack the allyl double bond of the eugenol side chain, converting it into a reactive aldehyde group, while effectively preventing the oxidative dissociation or self-polymerization of the extremely fragile methacrylate double bond at the other end of the molecule.

[0036] In some embodiments, the condensation reaction is catalyzed by p-toluenesulfonic acid and carried out under reflux for 12-15 hours; the molar ratio of the intermediate to the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radical is 1:1.05. By using p-toluenesulfonic acid as a catalyst and reacting under reflux, the aldehyde group at the end of the intermediate can be effectively activated, and the byproduct water generated in the reaction can be continuously removed by azeotropic distillation, strongly driving the Schiff basification reaction in the forward direction according to the principle of chemical equilibrium shift. In addition, limiting the molar ratio of the intermediate to 4-amino-TEMPO to 1:1.05, the slight excess of the amine component ensures the complete conversion of the aldehyde group in the intermediate, thereby improving the efficiency of dynamic imine bond construction.

[0037] The third aspect of this invention proposes the application of the above-mentioned environmentally friendly waterborne polymerization inhibitor in the aqueous suspension polymerization reaction of polyvinyl chloride. When the monomer conversion rate in the polyvinyl chloride suspension polymerization reaction system reaches 80% to 85%, the environmentally friendly waterborne polymerization inhibitor is injected into the polymerization system. The amount of the environmentally friendly waterborne polymerization inhibitor added is 0.03% to 0.08% of the mass of liquid vinyl chloride monomer in the polymerization reaction system.

[0038] The present invention will be described below through specific embodiments. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0039] Example 1: The weight ratio of each component in this embodiment is as follows: 65g of aqueous phase, 25g of oil phase, 7.5g of emulsifier, and 2.5g of polymeric stabilizer.

[0040] Preparation of the polymerization inhibitor monomer: 16.4 g eugenol (0.1 mol) and 14.2 g glycidyl methacrylate (0.1 mol) were added to a reaction vessel. 0.32 g tetrabutylammonium bromide was added as a phase transfer catalyst. Stirring was started, and the system was slowly heated to 88 °C under nitrogen purging, and the reaction was continued for 9 hours. After the reaction was completed, the monomer precursor was obtained by cooling, extraction with anhydrous diethyl ether, washing with saturated brine, drying with anhydrous magnesium sulfate, and vacuum rotary evaporation.

[0041] The prepared monomer precursor was dissolved in 150 mL of anhydrous dichloromethane, and ozone gas was bubbled through it under a low temperature of -78 °C and continuous nitrogen protection until the solution turned slightly blue. Then, dimethyl sulfide reducing agent was added dropwise, and the mixture was stirred in an ice-water bath for 3 hours. After washing with water and removing the solvent by rotary evaporation, an intermediate containing a terminal aldehyde group was obtained.

[0042] The intermediate was co-dissolved with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radical in anhydrous ethanol / toluene (1:2) mixed solvent at a molar ratio of 1:1.05. 0.5 mol% p-toluenesulfonic acid was added, and the reaction was carried out under reflux for 14 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by silica gel column chromatography to obtain the polymerization inhibitor monomer.

[0043] Preparation of environmentally friendly water-based polymerization inhibitors: The above-prepared 20g polymerization inhibitor monomer, 5g composite antioxidant (trinonylphenyl phosphite and dilaurate thiodipropionate in a mass ratio of 1:1) and 2.5g sorbitan oleate were mixed and heated to melt and homogenize at 42°C to obtain an oil phase solution. 5g of polyoxyethylene sorbitan monooleate, 1.5g of chitosan and 1g of hydroxypropyl cellulose were dispersed in 65g of deionized water, and the pH was adjusted to 4.9 with acetic acid to obtain an aqueous solution. Under high shear conditions of 10,000 rpm, the oil phase solution is slowly added to the aqueous phase solution for phase inversion emulsification to obtain an environmentally friendly waterborne polymerization inhibitor.

[0044] Application testing: In PVC suspension polymerization, when the monomer conversion rate reaches 82%, the above emulsion is injected, and the amount added is 0.05% of the mass of vinyl chloride monomer.

[0045] Example 2: Consistent with Example 1, except for some process parameters: The mixture consisted of 50g of aqueous phase, 15g of oil phase, 2g of emulsifier (0.5g of sorbitan oleate and 1.5g of polyoxyethylene sorbitan monooleate), and 0.5g of polymeric stabilizer (0.3g of chitosan and 0.2g of hydroxypropyl cellulose). The oil phase contained 11.25g of polymerization inhibitor monomer and 3.75g of composite antioxidant. The pH of the aqueous phase was adjusted to 4.5. The etherification reaction was carried out at 85℃ for 6 hours, and the condensation reaction for 12 hours. In application testing, the addition amount was 0.03% of the vinyl chloride monomer mass.

[0046] Example 3: Consistent with Example 1, except for some process parameters: The mixture consisted of 80g of aqueous phase, 40g of oil phase, 10g of emulsifier (3.5g of sorbitan oleate and 6.5g of polyoxyethylene sorbitan monooleate), and 5g of polymeric stabilizer (3g of chitosan and 2g of hydroxypropyl cellulose). The oil phase contained 33.3g of polymerization inhibitor monomer and 6.7g of composite antioxidant. The pH of the aqueous phase was adjusted to 5.5. The etherification reaction was carried out at 90℃ for 12 hours; the condensation reaction was carried out for 15 hours. In application testing, the addition amount was 0.08% of the vinyl chloride monomer mass.

[0047] Example 4: Consistent with Example 1, except for some process parameters: The total amount of oil phase remains unchanged at 25g, of which 18.75g is the polymerization inhibitor monomer and 6.25g is the composite antioxidant.

[0048] Example 5: Consistent with Example 1, except for some process parameters: The total amount of oil phase remained unchanged at 25g, of which 20.83g was the polymerization inhibitor monomer and 4.17g was the composite antioxidant.

[0049] Example 6: Consistent with Example 1, except that: In the aqueous phase preparation stage, acetic acid is used to precisely adjust the pH of the deionized water containing the polymeric stabilizer to the upper limit of 5.5 permitted by the claims.

[0050] Comparative Example 1: The difference from Example 1 is that, in preparing the oil phase, 15g of conventional bisphenol A and 5g of free 4-hydroxy-TEMPO small molecules were used to replace the original 20g of polymerization inhibitor monomer. All other components and processes remained the same as in Example 1.

[0051] Comparative Example 2: The difference from Example 1 is that 5g of the composite antioxidant (trinonylphenyl phosphite and dilaurate thiodipropionate) was removed from the oil phase configuration and replaced with an equal amount of 5g of polymerization inhibitor monomer (i.e., the oil phase consists entirely of polymerization inhibitor monomer, totaling 25g). All other steps and parameters are consistent with Example 1.

[0052] Comparative Example 3: The difference from Example 1 is that acetic acid was not added to adjust the system to a slightly acidic state when preparing the aqueous phase; instead, it was kept neutral or slightly alkaline (pH=7.5).

[0053] Test method: 1. Emulsion particle size analysis: Referring to GB / T19077-2016 "Particle size analysis by laser diffraction", the volume cumulative particle size distribution of the aqueous polymerization inhibitor emulsion was determined using a laser diffraction particle size analyzer, and the average particle size (D50) was recorded.

[0054] 2. Emulsion centrifugation stability test: Referring to the stability test specifications in GB / T11175-2002 "Test Methods for Synthetic Resin Emulsions", the polymerization inhibitor emulsion was placed in a centrifuge and centrifuged at 3000 r / min for 30 minutes. The bottom or top layer of the tube was observed and recorded visually to see if stratification, precipitation or demulsification occurred.

[0055] 3. Aggregation termination response time: Record the response time from when the pressure inside the reactor stops decreasing and begins to stabilize after injection, to when the reactor temperature drops sharply. This indicator is a measured process parameter verified in industrial trials; the shorter the response time, the higher the polymerization inhibition efficiency.

[0056] 4. Ultimate thermal stability (Congo red method): Referring to GB / T2917.1-2002 "Determination of thermal stability of homopolymers and copolymers and their compounds mainly composed of vinyl chloride - Part 1: Congo red method and pH method", a quantitatively prepared polyvinyl chloride resin sample was placed in a glass test tube and heated in a constant temperature oil bath at 180℃. The static thermal stability time when the Congo red indicator paper changed from red to bright blue was recorded.

[0057] 5. Oxidation Induction Time (OIT): Referring to GB / T19466.6-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 6: Determination of Oxidation Induction Time (Isothermal OIT)," the sample was placed in a differential scanning calorimeter, and the time span from the introduction of oxygen to the occurrence of a violent autocatalytic oxidation exothermic peak was recorded under a constant temperature of 200℃ in a pure oxygen atmosphere.

[0058] 6. Accelerates photo-oxidative aging and whiteness retention: First, referring to GB / T16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", the resin and plasticizer were mixed, pressed into tablets, and placed in an accelerated aging test chamber for continuous exposure for 300 hours at a specified wavelength (290-400nm). Then, referring to GB / T15595-2008 "Test Method for Thermal Stability of Polyvinyl Chloride Resin - Whiteness Method", the initial whiteness and the whiteness after aging of the sample were determined using a colorimeter (characterized by the L* lightness value in the CIELAB color space; industry standard: the aged whiteness should not be less than 88).

[0059] The data from the above tests were statistically analyzed, and the results are shown in Tables 1 and 2.

[0060] Table 1. Physical stability and instantaneous inhibition efficiency of waterborne polymerization inhibitors

[0061] Table 2. Long-term oxidation aging resistance and ultimate thermal stability of PVC resin

[0062] Comparing the data from Example 1 and Comparative Example 3, it can be seen that the emulsion of Example 1 (aqueous phase pH=4.9) has an extremely fine average particle size (D50) of only 9.8 μm, and shows no stratification or demulsification under centrifugation at 3000 r / min. In contrast, Comparative Example 3, due to the failure to adjust the aqueous phase to a slightly acidic state (pH=7.5) during preparation, resulted in a dramatic increase in its D50 to 58.2 μm, leading to severe demulsification and flocculation. This precipitous performance difference confirms the necessity of limiting the aqueous phase pH (4.5-5.5) in this invention. In a slightly acidic environment, chitosan in the polymeric stabilizer can undergo amino protonation, imparting a strong positive charge to the surface of the droplets. Combined with the steric hindrance of the hydration layer of hydroxypropyl cellulose (HPC), a robust binary stable network is constructed. A neutral environment (Comparative Example 3) leads to the absence of Coulombic electrostatic repulsion, thereby causing system collapse. Examples 2 to 6 underwent extreme value tests within the component ratios and pH ranges defined in the claims. The results showed that the D50 of each emulsion remained in the excellent range of 8.4-16.3 μm, the centrifugal stability met the standard, and the modified PVC resin cross-sections retained the complete core-shell microporous structure as observed by electron microscopy, proving that the formulation system of the present invention has extremely high industrial tolerance and morphology fidelity.

[0063] In Example 1, the reaction pressure was completely stabilized and the reactor temperature dropped sharply within just 12 seconds after injection into the reactor, demonstrating extremely high polymerization inhibition efficiency. In contrast, Comparative Example 1 (using conventional bisphenol A + free 4-hydroxy-TEMPO) had a polymerization termination response time as long as 45 seconds, and due to uneven dispersion of the polymerization inhibitor, there were obvious lumps in the resin. Free TEMPO molecules are easily and ineffectively consumed by trace amounts of oxygen and impurities during the early stages of polymerization or during storage. The polymerization inhibitor monomer of this invention encapsulates the attached TEMPO groups through a highly rigid macromolecular skeleton, generating a strong steric hindrance shielding effect. This allows the active ingredient to remain latent during the non-critical period before injection, thus unleashing maximum effectiveness at the moment when polymerization inhibition is truly needed.

[0064] The Congo red thermal stability time of Example 1 reached 94 minutes, and the whiteness (L value) remained at a high level of 91.5 after aging for 300 hours. In contrast, Comparative Example 1, which used a traditional polymerization inhibitor system, had a Congo red stability time of only 35 minutes, and the resin turned severely yellow and black after aging (the L value plummeted to 68.2). Traditional bisphenol A is prone to color degradation during thermal aging, and its free small molecules are easily volatilized and migrated. The polymerization inhibitor monomer of this invention is firmly covalently anchored in the PVC network by a highly rigid bio-based framework; when the resin loses HCl during aging, leading to local microenvironment acidification, the dynamic imine bonds, acting as a smart switch, rapidly hydrolyze and break, releasing highly active free TEMPO molecules in situ and in a targeted manner.

[0065] The oxidation induction time (OIT) of Example 1 reached 42.5 minutes. As a highly convincing control, Comparative Example 2 showed a significantly reduced OIT value of 16.8 minutes and exhibited a slight reddish-brown tinge after aging (L* value 79.5). This comparison demonstrates that a long-lasting antioxidant defense relies on a logical closed loop of two main modules. While the released TEMPO can rapidly capture free radicals through a catalytic macrocycle, it cannot eliminate the hydroperoxides (ROOH) already generated on the polymer backbone. The addition of the auxiliary antioxidant system in Example 1 successfully opened up a non-radical pathway for the decomposition of hydroperoxides. The deep interplay between these two components constitutes an echo stabilization effect, breaking through the stoichiometric limitations of traditional antioxidants and achieving a significant improvement in the performance of the polymerization inhibitor.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. An environmentally friendly water-based polymerization inhibitor, characterized in that, include: The mixture comprises an aqueous phase, an oil phase, an emulsifier, and a polymeric stabilizer; wherein the oil phase includes a polymerization inhibitor monomer and an antioxidant, and the polymerization inhibitor monomer has the chemical structure shown in Formula I: Structural formula I.

2. The environmentally friendly waterborne polymerization inhibitor according to claim 1, characterized in that, The mass ratio of the aqueous phase, oil phase, emulsifier and polymeric stabilizer is (50-80):(15-40):(2-10):(0.5-5), and the mass ratio of the polymerization inhibitor monomer to the antioxidant in the oil phase is (3-5):

1.

3. The environmentally friendly waterborne polymerization inhibitor according to claim 1, characterized in that, The aqueous phase is an acidic aqueous solution with a pH value of 4.5-5.

5.

4. The environmentally friendly water-based polymerization inhibitor according to claim 1, characterized in that, The antioxidants include trinonylphenyl phosphite and dilaurate thiodipropionate.

5. The environmentally friendly waterborne polymerization inhibitor according to claim 1, characterized in that, The emulsifiers include sorbitan oleate and polyoxyethylene sorbitan monooleate.

6. The environmentally friendly waterborne polymerization inhibitor according to claim 1, characterized in that, The polymeric stabilizers include chitosan and hydroxypropyl cellulose.

7. A method for preparing the environmentally friendly waterborne polymerization inhibitor according to any one of claims 1 to 6, characterized in that, Includes the following steps: Eugenol was etherified with glycidyl methacrylate to obtain a monomer precursor; the allyl group of the side chain of the monomer precursor was ozonally oxidized and reduced to obtain an intermediate containing a terminal aldehyde group; the intermediate was condensed with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy radical to obtain a polymerization inhibitor monomer. The polymerization inhibitor monomer, antioxidant and sorbitan oleate are mixed and heated to melt at 40-45°C to obtain an oil phase solution; Polyoxyethylene sorbitan monooleate, chitosan and hydroxypropyl cellulose were dispersed in deionized water, and the pH was adjusted to 4.5-5.5 to obtain an aqueous solution. The oil phase solution is added to the aqueous phase solution, and phase emulsification is carried out under shear cavitation to obtain the environmentally friendly waterborne polymerization inhibitor.

8. The method according to claim 7, characterized in that, The etherification reaction is carried out using tetrabutylammonium bromide as a catalyst at a reaction temperature of 85-90℃ for 6-12 hours; the molar ratio of eugenol to glycidyl methacrylate is 1:

1. The ozone deoxidation is carried out at a low temperature of -78°C.

9. The method according to claim 7, characterized in that, The condensation reaction was carried out under reflux for 12-15 hours with p-toluenesulfonic acid as a catalyst; the molar ratio of the intermediate to 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radical was 1:1.

05.

10. The application of an environmentally friendly waterborne polymerization inhibitor as described in any one of claims 1 to 6 in the aqueous suspension polymerization reaction of polyvinyl chloride, characterized in that, When the monomer conversion rate in the polyvinyl chloride suspension polymerization reaction system reaches 80% to 85%, the environmentally friendly waterborne polymerization inhibitor is injected into the polymerization system. The amount of the environmentally friendly waterborne polymerization inhibitor added is 0.03% to 0.08% of the mass of liquid vinyl chloride monomer in the polymerization reaction system.

Images