Flame-retardant antibacterial microspheres, method for preparing the same and application thereof in ABS material

Abstract

This invention belongs to the field of polymer materials technology, specifically relating to a functional polymer microsphere, particularly a flame-retardant and antibacterial microsphere, its preparation method, and its application in ABS materials. The polymer core of this invention is copolymerized from maleic anhydride, C4 / C5 olefins, and a first crosslinking agent, with a crosslinking degree ≥50%. The shell crosslinking network uses a guanidine salt derivative containing unsaturated double bonds as the core second crosslinking agent. The guanidine salt functional groups, as structural units of the crosslinking network, are covalently anchored in the three-dimensional network, rather than being merely surface-grafted. Adding the microspheres of this invention to ABS resin at 0.05~10 parts by weight yields an ABS composition possessing both high-efficiency flame retardancy and broad-spectrum antibacterial properties. Compared with existing surface grafting technologies, the microspheres of this invention significantly reduce the risk of guanidine salt migration and precipitation. After rigorous treatments such as high-temperature aging, damp-heat aging, solvent wiping, and water immersion, they still maintain a V-0 flame retardancy rating and an antibacterial rate of over 99.9%, exhibiting excellent long-term stability and making them suitable for preparing high-requirement engineering plastic products.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a functional polymer microsphere, particularly a flame-retardant and antibacterial microsphere, its preparation method, and its application in ABS materials. Background Technology

[0002] Acrylonitrile-butadiene-styrene copolymer (ABS), as a high-performance thermoplastic engineering plastic, is widely used in household appliances, automotive parts, and electronic device housings due to its good processability, high mechanical strength, and surface gloss. However, ABS resin itself has poor flame retardancy, and its surface is prone to bacterial growth, which is insufficient in some applications with strict requirements for fire safety and hygiene. Therefore, developing ABS materials that combine highly efficient flame retardancy with long-lasting antibacterial properties has significant market value and application prospects.

[0003] In existing technologies, flame-retardant and antibacterial properties are often imparted to ABS matrix by adding functional additives. For example, existing technologies (Chinese invention patent with publication number CN107815066B, publication date 2018-03-20) add inorganic flame retardants to ABS, specifically aluminum hydroxide, magnesium hydroxide, halogen-based or phosphorus-nitrogen-based flame retardants; existing technologies (Chinese invention patent with publication number CN116023747B, publication date 2023-04-28) add silver ions as antibacterial agents. However, these technical solutions usually face the following problems: First, simple physical blending is difficult to achieve synergistic effects of flame retardancy and antibacterial functions, and the addition of multiple additives may also lead to a significant decrease in the mechanical properties of the matrix material, affecting its service durability; second, the migration and precipitation of antibacterial agents in the matrix are the main reasons for the functional decay or failure over time. Due to the limited compatibility between small molecule antibacterial agents and polymer matrices (such as ABS), they are prone to migrate and be lost to the material surface under high temperature, high humidity or long-term use conditions. This not only directly leads to a decrease in antibacterial function, but the released substances may also contaminate the contact surface and even pose health risks. Similar problems exist for flame retardants.

[0004] Some existing technologies have also attempted to load or graft functional molecules onto the surface of microspheres before adding them to polymers to improve the dispersibility of functional molecules. For example, existing technology (Chinese invention patent with publication number CN113549312B, publication date 2021-10-26) discloses a technical solution for grafting guanidine salts onto the surface of cross-linked polymer microspheres, resulting in microspheres that can simultaneously impart flame-retardant and antibacterial properties to ABS materials. However, in this solution, the guanidine salt is fixed on the surface of the microspheres in the form of end grafting. This bonding method still carries the risk of migration and precipitation of antibacterial and flame-retardant active ingredients through molecular chain segment movement during long-term use, especially in high temperature, high humidity, or solvent contact environments, which makes it impossible to effectively guarantee the reliability of the material's long-term performance. Summary of the Invention

[0005] One of the objectives of this invention is to provide a flame-retardant and antibacterial microsphere with a special core-shell cross-linked structure. This microsphere is obtained by chemically anchoring guanidine salts with flame-retardant and antibacterial functions into the three-dimensional cross-linked network of the microsphere shell, thereby achieving a durable, non-precipitated, and highly efficient synergistic microsphere additive.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned flame-retardant and antibacterial microspheres. This method has a simple and controllable process and can effectively form a stable core-shell cross-linked structure.

[0007] The third objective of this invention is to provide a polymeric material composition containing the above-mentioned flame-retardant and antibacterial microspheres, particularly for use in ABS resin. This composition not only initially exhibits excellent flame-retardant, antibacterial, and antistatic properties, but more importantly, it possesses outstanding performance durability. Even under harsh environments such as long-term thermal aging, high humidity, or wiping, it can still maintain a stable and reliable flame-retardant rating and antibacterial rate.

[0008] The technical solution adopted by the present invention to solve the above problems is: flame-retardant and antibacterial microspheres, comprising: A polymer core composed of a first structural unit, a second structural unit, and a third structural unit, and a guanidine salt crosslinked polymer shell covering the surface of the polymer core; The first structural unit is maleic anhydride, the second structural unit is a C4 and / or C5 olefin, and the third structural unit is a first crosslinking agent; The first crosslinking agent includes divinylbenzene and / or an acrylate crosslinking agent containing at least two acrylate groups; The guanidine salt-crosslinked polymer shell comprises a crosslinked network grafted with a guanidine salt or a polymer thereof, and the crosslinked network comprises a second crosslinking agent; The second crosslinking agent comprises a guanidine salt derivative crosslinking monomer containing unsaturated double bonds, or is composed of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds and at least one of an acrylate crosslinking agent selected from divinylbenzene and containing at least two acrylate groups.

[0009] A further preferred technical solution is that the second crosslinking agent is composed solely of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds.

[0010] A further preferred technical solution is that the crosslinking monomer of the guanidine salt derivative containing unsaturated double bonds is bis(meth)acryloyloxyalkyl guanidine salt or vinylbenzyl guanidine salt.

[0011] A further preferred technical solution is that the bis(meth)acryloyloxyalkylguanidine salt is a phosphate, hydrochloride or hydrobromide of bis(methacryloyloxyethyl)guanidine.

[0012] A further preferred technical solution is that the guanidine salt or its polymer includes at least one of guanidine phosphate, guanidine hydrochloride, guanidine hydrobromide, dihydroguanidine phosphate, diguanidine hydrogen phosphate, polyhexamethylene biguanide hydrochloride, polyhexamethylene biguanide phosphate, and polyhexamethylene biguanide acetate.

[0013] A further preferred technical solution is that the degree of crosslinking of the polymer core is ≥50%, and the degree of crosslinking of the guanidine salt crosslinked polymer shell is ≥30%.

[0014] The preparation method of any of the above flame-retardant and antibacterial microspheres includes the following steps: S1. In the presence of an organic solvent and an initiator, a monomer mixture comprising maleic anhydride, C4 and / or C5 olefins and a first crosslinking agent is subjected to a first polymerization reaction to obtain a first reaction product; S2. Add a mixture of shell monomers containing guanidine salt derivative crosslinking monomers with unsaturated double bonds and an initiator to the first reaction product to carry out a second polymerization reaction, so that the shell monomers are grafted and crosslinked on the surface of the polymer core to form a crosslinked shell coating the surface of the polymer core, and obtain the second reaction product. S3. Add a small molecule guanidine salt or guanidine salt polymer to the second reaction product to carry out a grafting reaction. After the reaction is complete, separate, wash and dry to obtain the flame-retardant and antibacterial microspheres.

[0015] A further preferred technical solution is that, in step S2, the shell monomer mixture further comprises additional maleic anhydride and / or C4 / C5 olefin monomers; the molar ratio of the additional maleic anhydride and / or C4 / C5 olefin monomers to the crosslinking monomer of the guanidine salt derivative containing unsaturated double bonds is (0.1~5):1.

[0016] A further preferred technical solution is that, based on the total moles of maleic anhydride, the amount of the guanidine salt derivative crosslinking monomer containing unsaturated double bonds is 1~40 mol.

[0017] A polymeric material composition comprising an acrylonitrile-butadiene-styrene copolymer resin matrix and any of the above-mentioned flame-retardant and antibacterial microspheres; wherein the amount of flame-retardant and antibacterial microspheres added is 0.05 to 10 parts by weight, based on 100 parts by weight of the total weight of the acrylonitrile-butadiene-styrene copolymer resin matrix.

[0018] In summary, the present invention has the following advantages: 1. This invention creatively designs a core-shell structure with cross-linked guanidine salt derivatives as the key component of the shell. The guanidine salt functional groups are firmly embedded in the three-dimensional cross-linked network of the microsphere shell through covalent bonds, greatly restricting the migration and movement freedom of the functional molecules. This ensures that when the microspheres are added to polymer matrices such as ABS, even under high temperature, high humidity, or long-term friction environments, the guanidine salt is not easily migrated or precipitated onto the material surface, thus guaranteeing the long-term stability of the material's flame-retardant and antibacterial properties.

[0019] 2. Because a large number of guanidine salt crosslinking agents containing reactive double bonds are directly introduced into the network construction during the shell polymerization stage, the density of flame-retardant and antibacterial functional groups on a unit microsphere is higher. Subsequent selective "post-functionalization" can be performed, further grafting guanidine salts to achieve flexible control of the functional loading.

[0020] 3. The core-shell structure of polymer microspheres improves the dispersibility of functional additives in the ABS matrix and prevents aggregation. Simultaneously, the stable structure of chemical cross-linking ensures that functional molecules are not damaged or prematurely degraded during processing. The abundant guanidine salts on the microsphere surface provide highly efficient and broad-spectrum antibacterial activity, while their phosphate groups, halide ions, or polymer backbone synergistically exert excellent flame-retardant effects with the polymer core, achieving "multiple effects from one agent."

[0021] 4. The microspheres of the present invention have good compatibility with the ABS matrix. Adding a small amount can achieve the ideal flame retardant and antibacterial effect, with little impact on the mechanical properties and processing fluidity of the matrix, thus maintaining the inherent advantages of ABS material.

[0022] 5. The preparation method is based on a mature stepwise suspension polymerization process. After the original polymer core synthesis, the shell copolymerization grafting is carried out directly. The process is continuous, simple to operate, and easy to achieve large-scale production. Detailed Implementation

[0023] The specific components of flame-retardant and antibacterial microspheres.

[0024] In this embodiment, a flame-retardant and antibacterial microsphere is disclosed, comprising: A highly cross-linked polymer core composed of a first structural unit, a second structural unit, and a third structural unit, and a guanidine salting cross-linked polymer shell coating the surface of the polymer core; The first structural unit is maleic anhydride, the second structural unit is a C4 and / or C5 olefin, and the third structural unit is a first crosslinking agent; The first crosslinking agent includes divinylbenzene and / or an acrylate crosslinking agent containing at least two acrylate groups; The guanidine salt-crosslinked polymer shell comprises a crosslinked network grafted with a guanidine salt or a polymer thereof, and the crosslinked network comprises a second crosslinking agent; The second crosslinking agent comprises a guanidine salt derivative crosslinking monomer containing unsaturated double bonds, or is composed of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds and at least one of an acrylate crosslinking agent selected from divinylbenzene and containing at least two acrylate groups.

[0025] Specifically, the microsphere is a core-shell structured polymer microsphere, whose core components include: Highly cross-linked polymer core: serving as the framework and supporting structure for microspheres.

[0026] Guanidinized crosslinked polymer shell: Coated on the surface of the polymer core, serving as a key layer that imparts flame retardant and antibacterial functions to the microspheres.

[0027] The polymer core is formed from the following three structural units through copolymerization and crosslinking reactions: 1. First structural unit: provided by maleic anhydride.

[0028] 2. Second structural unit: provided by C4 and / or C5 olefins (e.g., butene, isobutene, pentene, etc.).

[0029] 3. Third structural unit (first crosslinking agent): provided by the first crosslinking agent, used to construct a highly crosslinked network. Specifically, it includes: divinylbenzene and / or acrylate crosslinking agents containing at least two acrylate groups.

[0030] The guanidine salt-based crosslinked polymer shell is a crosslinked polymer network grafted with guanidine salt functional groups, and its chemical composition includes: 1. Second crosslinking agent: The core crosslinking agent constituting the shell crosslinking network, specifically: a guanidine salt derivative crosslinking monomer containing unsaturated double bonds, such as: bis(meth)acryloyloxyalkyl guanidine salt or vinylbenzyl guanidine salt, or a mixture of the above-mentioned guanidine salt derivative crosslinking monomer with at least one of divinylbenzene or an acrylate crosslinking agent containing at least two acrylate groups. Preferably, the second crosslinking agent is composed solely of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds.

[0031] 2. Grafted guanidine salts or their polymers: Functional molecules grafted onto a shell network via chemical bonds, including: Small molecule guanidine salts: such as guanidine phosphate, guanidine hydrochloride, guanidine hydrobromide, dihydroguanidine phosphate, and diguanidine hydrogen phosphate. Guanidine salt polymers: such as polyhexamethylene biguanide hydrochloride, polyhexamethylene biguanide phosphate, and polyhexamethylene biguanide acetate. Preferably, it can be a combination of at least one of the above.

[0032] In constructing the shell, in addition to the second crosslinking agent, additional maleic anhydride and / or C4 / C5 olefin monomers may be added to adjust the shell properties.

[0033] The degree of crosslinking of the polymer core should be ≥50% to ensure the mechanical strength and stability of the core. The degree of crosslinking of the guanidine salt-crosslinked polymer shell should be ≥30% to ensure a dense shell, effectively immobilize the guanidine salt, and prevent migration. The degree of crosslinking refers to the percentage of gel content in the polymer microspheres that is insoluble in good solvents relative to the total polymer mass. It is a core indicator characterizing the degree of crosslinking network formation, and the measurement method used is the industry-standard Soxhlet extraction method.

[0034] The flame-retardant and antibacterial microspheres of this embodiment are composite microspheres with a core of a highly cross-linked polymer composed of maleic anhydride, C4 / C5 olefins and a first cross-linking agent, such as divinylbenzene, and a shell of a guanidine salt derivative containing unsaturated double bonds, such as bis(methacryloyloxyethyl)guanidine salt, as the key cross-linking agent and grafted with a cross-linked polymer of guanidine salt or its polymer, such as polyhexamethylene biguanide phosphate. The aim is to firmly anchor the flame-retardant and antibacterial functional groups through chemical cross-linking, thereby obtaining long-lasting and stable performance.

[0035] The specific preparation steps of flame-retardant and antibacterial microspheres.

[0036] In this embodiment, a method for preparing flame-retardant and antibacterial microspheres is disclosed, comprising the following steps: S1. Preparation of polymer core: In the presence of an organic solvent and an initiator, a monomer mixture containing maleic anhydride, C4 and / or C5 olefins and a first crosslinking agent is subjected to a first polymerization reaction to obtain a first reaction product; S2. Construction of the guanidine salt crosslinked polymer shell: Add a mixture of shell monomers containing guanidine salt derivative crosslinked monomers with unsaturated double bonds and an initiator to the first reaction product to carry out a second polymerization reaction, so that the shell monomers are grafted and crosslinked on the surface of the polymer core to form a crosslinked shell covering the surface of the polymer core, and obtain the second reaction product. S3. Optional post-functionalization: A small molecule guanidine salt or guanidine salt polymer is added to the second reaction product for grafting reaction. After the reaction is complete, the product is separated, washed, and dried to obtain the flame-retardant and antibacterial microspheres.

[0037] In step S1, the first structural unit is maleic anhydride, the second structural unit is a C4 and / or C5 olefin, such as butene, isobutene, pentene, etc., and the third structural unit is divinylbenzene and / or an acrylate crosslinking agent containing at least two acrylate groups, such as ethylene glycol dimethacrylate, trimethylolpropane triacrylate, etc., specifically the first crosslinking agent. The above monomer mixture is added to a reaction vessel containing an organic solvent and a free radical initiator, such as azobisisobutyronitrile, benzoyl peroxide, etc. The mixture is stirred at a first polymerization reaction temperature to carry out the first polymerization reaction. This reaction copolymerizes and crosslinks the monomers through free radical polymerization, forming a polymer microsphere suspension with a crosslinking degree of not less than 50%, which is the first reaction product, specifically the polymer core. Preferably, the first polymerization reaction temperature is 60~80℃.

[0038] Step S2 is crucial for forming a stable core-shell structure, firmly fixing the flame-retardant and antibacterial functional groups to the microsphere surface through chemical cross-linking. This includes: Shell material preparation: Prepare a mixture of shell monomers, the core component of which is a guanidine salt derivative crosslinking monomer containing unsaturated double bonds, such as bis(methacryloyloxyethyl)guanidine phosphate or hydrochloride. This monomer possesses both polymerizable double bonds and guanidine salt functional groups. Preferably, to adjust the shell thickness and properties, the shell mixture may also contain additional maleic anhydride and / or additional C4 / C5 olefin monomers. The recommended molar ratio of the additional monomers to the guanidine salt derivative crosslinking monomer is (0.1~5):1.

[0039] Shell polymerization: The first reaction product obtained in the previous step, i.e., the polymer core suspension, is then added to the aforementioned shell monomer mixture and a new initiator.

[0040] Second polymerization reaction: The second polymerization reaction is carried out at a suitable temperature. During this reaction, the shell monomers, especially guanidine salt derivatives containing double bonds, undergo graft copolymerization and crosslinking reactions on the surface of the polymer core, thereby forming a polymer shell with a crosslinking degree of not less than 30%, and anchoring the guanidine salt groups in this three-dimensional network by chemical bonds. After the reaction is complete, the second reaction product is obtained. Preferably, throughout the entire preparation process, based on the total moles of maleic anhydride in all steps, the amount of crosslinking monomers containing unsaturated double bonds of guanidine salt derivatives is 1~40 mol%.

[0041] Step S3 aims to further increase the functional loading of the microspheres. This includes: Grafting reaction: Adding a small molecule guanidine salt, such as guanidine hydrochloride, guanidine phosphate, or guanidine salt polymer, such as polyhexamethylene biguanide hydrochloride, to the product of the second reaction.

[0042] Functionalization: Maleic anhydride groups that may remain in the polymer core and shell are reacted with added guanidine salts to further graft them onto microspheres.

[0043] Purification: After the reaction is complete, the final flame-retardant and antibacterial microspheres can be obtained through conventional post-processing steps such as separation, filtration, centrifugation, washing and drying.

[0044] This embodiment uses shell construction to chemically immobilize guanidine salt functional groups as part of a cross-linking network, rather than through simple physical adsorption or end grafting. This fundamentally solves the problem of easy migration and loss of active ingredients in traditional functional microspheres, thereby ensuring that the materials prepared from it have long-lasting and stable flame-retardant and antibacterial properties.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below with reference to specific embodiments and comparative examples. It should be understood that the following description is for illustrative purposes only and is not intended to limit the scope of the invention.

[0046] The raw materials used in the examples and comparative examples are shown in Table 1: Table 1. Sources of raw materials for the examples and comparative examples.

[0047] Synthetic Example 1: Preparation of bis(glycidyl methacrylate)guanidine hydrochloride (hereinafter referred to as DG-GMA): In a 500 mL four-necked flask equipped with a stirrer, thermometer, and reflux condenser, 47.5 g (0.5 mol) of guanidine hydrochloride, 142.0 g (1.0 mol) of glycidyl methacrylate (GMA), 0.25 g of hydroquinone (polymer inhibitor), and 200 mL of anhydrous ethanol were added. Under nitrogen protection, the mixture was stirred and heated to 60 °C, and reacted at this temperature for 8 hours. During the reaction, the epoxy group of GMA underwent a ring-opening addition reaction with the amino group of guanidine to generate a guanidine salt derivative containing two methacrylate double bonds. After the reaction was completed, the solvent ethanol was removed by vacuum distillation to obtain approximately 168 g of a pale yellow viscous liquid, DG-GMA, with a yield of approximately 89%. The structure was confirmed by ¹H NMR spectroscopy.

[0048] Synthetic Example 2: Preparation of Vinylbenzylguanidine hydrochloride (hereinafter referred to as VBG): In a 500 mL four-necked flask equipped with a stirrer and thermometer, 47.5 g (0.5 mol) of guanidine hydrochloride, 76.3 g (0.5 mol) of p-chloromethylstyrene (CMS), 69.1 g (0.5 mol) of anhydrous potassium carbonate, and 200 mL of N,N-dimethylformamide (DMF) were added. Under nitrogen protection, the mixture was stirred and heated to 80 °C, and reacted at this temperature for 12 hours. After the reaction was complete, the inorganic salts were removed by filtration, and the DMF was recovered by vacuum distillation of the filtrate to obtain crude VBG. The crude product was recrystallized from ethanol / water (1:1 v / v) and dried under vacuum to give approximately 78 g of white solid VBG, with a yield of approximately 74%. The structure was confirmed by ¹H NMR spectroscopy.

[0049] Example 1: Preparation of core-shell structured flame-retardant and antibacterial microspheres (MC-1).

[0050] (1) Preparation of polymer core: In a 2L high-pressure reactor, 98.0g (1.0mol) of maleic anhydride, 112.0g (2.0mol) of isobutylene, 26.0g (0.2mol) of divinylbenzene (DVB), 800mL of ethyl acetate, and 3.0g of initiator AIBN were added. The reactor was sealed, and after purging with nitrogen, the mixture was stirred and heated to 70°C, and the first polymerization reaction was carried out at this temperature for 6 hours. After the reaction was completed, a white suspension of polymer cores with a high degree of crosslinking (approximately 62%) was obtained, which is the first reaction product.

[0051] (2) Construction of the guanidine salting crosslinked polymer shell: While maintaining the temperature of the above reaction system at 70°C, and under stirring conditions, simultaneously add the following two solutions dropwise to the first reaction product through a constant-pressure dropping funnel: Shell monomer solution: 57.0 g (about 0.15 mol) of DG-GMA prepared in Synthesis Example 1 was dissolved in 200 mL of ethyl acetate.

[0052] Initiator solution: 1.5g of AIBN dissolved in 50mL of ethyl acetate.

[0053] The dropping time was controlled at 2 hours, and after the dropping was completed, the reaction was continued at a constant temperature of 70°C for 4 hours. During this process, DG-GMA underwent graft copolymerization and cross-linking reactions on the surface of the polymer core, forming a guanidine salt cross-linked shell (cross-linking degree of approximately 48%). After the reaction was completed, the second reaction product was obtained.

[0054] (3) Post-functionalization: The second reaction product was cooled to 60°C, and 200g of a 20wt% aqueous solution of polyhexamethylene biguanide phosphate (PHMB-P) was added to the reaction system. The mixture was stirred at 60°C for 5 hours to allow the residual anhydride groups to fully react with PHMB-P. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the solid product was obtained. The solid product was washed three times each with deionized water and ethanol, and then dried under vacuum at 80°C for 12 hours to obtain approximately 185g of white powdery core-shell structured flame-retardant and antibacterial microspheres MC-1.

[0055] Example 2: Preparation of core-shell structured flame-retardant and antibacterial microspheres (MC-2).

[0056] (1) Preparation of polymer core: The polymer core suspension was prepared in the same manner as in step (1) of Example 1.

[0057] (2) Construction of the guanidine salting crosslinked polymer shell: Maintain the reaction system temperature at 70℃, and simultaneously add the following two solutions dropwise to the first reaction product through a constant pressure dropping funnel: Shell monomer solution: 42.3 g (about 0.2 mol) of VBG and 19.6 g (0.2 mol) of maleic anhydride prepared in Synthesis Example 2 were dissolved in 250 mL of ethyl acetate.

[0058] Initiator solution: 2.0 g of AIBN dissolved in 50 mL of ethyl acetate.

[0059] The dropping time was controlled at 2 hours, and after the dropping was completed, the reaction continued at 70℃ for 4 hours. VBG and maleic anhydride copolymerized and crosslinked on the core surface to form a shell (crosslinking degree of about 42%).

[0060] (3) Post-functionalization: The reaction system was cooled to 60°C, and 100 mL of an aqueous solution of 47.8 g (0.5 mol) guanidine hydrochloride was added. The reaction was continued at 60°C for 5 hours. The post-treatment steps were the same as in Example 1, yielding approximately 172 g of white powdery microspheres MC-2.

[0061] Example 3: Preparation of core-shell structured flame-retardant and antibacterial microspheres (MC-3).

[0062] (1) Preparation of polymer core: Same as step (1) in Example 1.

[0063] (2) Construction of the guanidine salting crosslinked polymer shell: Maintaining the reaction system temperature at 70°C, the shell monomer solution (DG-GMA 38.0 g, approximately 0.1 mol; DVB 6.5 g, 0.05 mol; ethyl acetate 200 mL) and initiator solution (AIBN 1.2 g / ethyl acetate 50 mL) were added dropwise over 2 hours, and the reaction was carried out at 70°C for 4 hours (shell crosslinking degree approximately 55%). Subsequent functionalization steps were the same as in Example 1, yielding approximately 178 g of microspheres MC-3.

[0064] Comparative Example 1: Blank ABS (without microspheres added) It is injection molded directly using pure ABS resin (PA-757) without adding any microspheres.

[0065] Comparative Example 2: Surface-grafted guanidine salt microspheres (MC-C1).

[0066] (1) Preparation of cross-linked polymer microspheres: Same as step (1) in Example 1.

[0067] (2) Surface grafting of guanidine salt (no shell crosslinking step): The polymer microsphere suspension obtained in step (1) was cooled to 60°C, and 200g of PHMB-P aqueous solution (20wt%) was directly added. The mixture was reacted at 60°C for 5 hours to perform surface grafting. The post-treatment was the same as in Example 1, and about 160g of surface-grafted microspheres MC-C1 were obtained.

[0068] Key difference: The guanidine salt of MC-C1 is attached to the surface of the microspheres only through end grafting, without forming a shell containing a guanidine salt cross-linked network.

[0069] Comparative Example 3: Post-grafted microspheres with guanidine salt cross-linked shells (MC-C2).

[0070] (1) Preparation of polymer core: Same as step (1) in Example 1.

[0071] (2) Construction of conventional cross-linked shell (without guanidine salt cross-linking agent): Add 200 mL of shell monomer solution (containing only 19.6 g maleic anhydride and 26.0 g DVB in ethyl acetate solution) and initiator solution, react at 70 °C for 4 hours to form a conventional cross-linked shell without guanidine salt.

[0072] (3) Post-functionalization: Same as step (3) in Example 1, graft PHMB-P. Approximately 170g of microspheres MC-C2 were obtained.

[0073] Key difference: The shell crosslinking network of MC-C2 does not contain guanidine salt derivative crosslinking monomers; guanidine salts are only introduced through post-functionalization grafting.

[0074] Taking the polymer core crosslinking degree measurement in Example 1 as an example, the specific steps are as follows: 1. Sample pretreatment: Take the polymer core suspension obtained after the reaction in step (1) of Example 1, take out about 5g of the product, separate it by centrifugation to obtain solid polymer, wash it repeatedly with acetone 3 times to remove unreacted monomers and soluble oligomers, and then place it in an 80℃ vacuum oven to dry to constant weight to obtain the dried sample to be tested.

[0075] 2. Soxhlet extraction process: Accurately weigh the dried sample and record the mass as m0. Wrap the sample in filter paper and place it in a Soxhlet extractor. Use acetone as the extraction solvent and perform continuous extraction in an 80℃ oil bath for 24 hours to ensure that all soluble oligomers and uncrosslinked linear polymers are fully extracted.

[0076] 3. Drying and weighing the remaining gel: After extraction, remove the remaining insoluble cross-linked gel from the filter paper packet in the extractor, transfer it to a weighing bottle, and dry it in an 80℃ vacuum oven until constant weight. The mass of the insoluble gel obtained is recorded as m1.

[0077] 4. Crosslinking Degree Calculation: The crosslinking degree (gel content) is calculated using the following formula: Crosslinking Degree (%) = (m1 / m0) 100%.

[0078] To verify that small molecule guanidine salts can be effectively grafted onto the microsphere shell using the method of this invention, the MC-2 microspheres prepared in Example 2 (grafting of small molecule guanidine hydrochloride) were subjected to elemental analysis and X-ray photoelectron spectroscopy (XPS) characterization. The results are as follows: 1. Elemental Analysis: The nitrogen content of the dried MC-2 microspheres was determined using an elemental analyzer. The results showed that the nitrogen mass fraction of the MC-2 microspheres was 3.21 wt%, while the nitrogen mass fraction of the blank microspheres (containing only VBG in the shell and without post-functionalization) was only 1.34 wt%. The significantly increased nitrogen content proves that the small molecule guanidine salt was successfully grafted onto the microspheres.

[0079] 2. X-ray photoelectron spectroscopy (XPS) analysis: A full-spectrum scan of the MC-2 microsphere surface revealed a distinct guanidine N1s characteristic peak at a binding energy of ~400 eV; a narrow-spectrum scan of Cl element detected a Cl2p characteristic peak at a binding energy of ~199 eV, proving that guanidine hydrochloride molecules are chemically grafted into the microsphere structure in the form of hydrochloride salt.

[0080] 3. Grafting rate calculation: Based on the elemental analysis results, the grafting rate of small molecule guanidine hydrochloride in MC-2 microspheres was calculated to be approximately 1.2 mmol / g, proving that small molecule guanidine salts can be stably grafted through the method described in this invention, and the grafting amount can meet the functional requirements of antibacterial and flame retardant.

[0081] It is evident that both small molecule guanidine salts (such as guanidine hydrochloride and guanidine phosphate) and guanidine salt polymers (such as polyhexamethylene biguanide phosphate) can be stably introduced into the core-shell microsphere structure using the "post-functionalization grafting of residual anhydride groups" method described in this invention.

[0082] Application example: Preparation of ABS compositions.

[0083] The microspheres prepared in the above examples and comparative examples were mixed with ABS resin and processing aids according to the formulation in Table 1, melt-blended and granulated in a twin-screw extruder (temperature in each zone 180-230℃), and then injection molded into standard test strips.

[0084] Basic formulation (parts by weight): 100 parts ABS resin (PA-757), 0.3 parts composite antioxidant (Irganox 1076 / Irgafos 168 = 1:1). Microsphere addition amount is shown in Table 2.

[0085] Table 2. Microsphere addition amounts in Examples 4-7 and Comparative Examples 4-6.

[0086] The above embodiments and comparative examples were tested, and the test methods are shown in Table 3: Table 3. Examples and comparative test methods.

[0087] The test results of the initial performance of Examples 4-7 and Comparative Examples 4-5 are shown in Table 4: Table 4. Test results of the initial performance of Examples 4-7 and Comparative Examples 4-5.

[0088] As shown in Table 4, Examples 4-7 and Comparative Examples 5-6 of the present invention can impart excellent initial flame retardant properties (UL 94 V-0 rating) and high antibacterial rate (>99.9%) to ABS materials, while keeping the impact on the mechanical properties of the matrix within an acceptable range. Comparative Example 4 (pure ABS) has no flame retardant or antibacterial effects.

[0089] Table 5 shows the performance retention rate test results of Examples 4-6 and Comparative Examples 5-6 after aging in hot air at 85°C for 1000 hours: Table 5. Performance retention rate test results of Examples 4-6 and Comparative Examples 5-6 after aging in hot air at 85°C for 1000 hours.

[0090] As shown in Table 5, after 1000 hours of heat aging at 85°C, the flame retardant rating of Comparative Example 5 (MC-C1, surface-grafted type) and Comparative Example 6 (MC-C2, guanidine salt-free cross-linked shell) decreased from V-0 to V-1, and the antibacterial retention rate also dropped significantly to less than 86%. This is because the guanidine salt molecules grafted on the surface migrated and were lost under long-term heat. In contrast, in Examples 4-6 of this invention, because the guanidine salt is anchored in the cross-linked network of the shell in the form of chemical bonds, its migration is greatly restricted. Therefore, the flame retardant rating is still maintained at V-0, and the antibacterial retention rate is as high as 99.3% or more.

[0091] The performance retention test results of Examples 4-6 and Comparative Examples 5-6 after 1000 hours of damp heat aging at 85℃ / 85%RH are shown in Table 6: Table 6. Performance retention test results of Examples 4-6 and Comparative Examples 5-6 after 1000 hours of damp heat aging at 85℃ / 85%RH.

[0092] As shown in Table 6, under high temperature and high humidity coupling conditions, the penetration and plasticizing effect of water molecules accelerate the migration of guanidine salts. The antibacterial retention rate of Comparative Example 5 drops sharply to approximately 65%, and the flame retardant rating decreases to V-2. However, the embodiments of this invention maintain excellent antibacterial retention rate and a V-0 flame retardant rating, demonstrating the superior stability of the core-shell cross-linked structure under harsh humid and hot environments.

[0093] Table 7 shows the performance comparison results of Example 4 and Comparative Example 5 after 5000 alcohol wipes and 168 hours of immersion in 70°C hot water: Table 7. Performance comparison results of Example 4 and Comparative Example 5 after 5000 alcohol wipes and 168 hours of immersion in 70°C hot water.

[0094] Table 7 shows that the wiping and immersion tests simulated real-world scenarios where the material might come into contact with solvents or humid environments during use. The results again demonstrate that the microspheres of this invention, thanks to their innovative design of locking guanidine salt functional groups within a cross-linked shell, can effectively resist functional loss caused by solvent wiping and water immersion. In Comparative Example 5, because the guanidine salt is only surface-attached, a large number of functional molecules detached after repeated mechanical wiping and hot water immersion, resulting in almost half of the antibacterial performance.

[0095] The surface ATR-FTIR analysis results of Example 4 and Comparative Example 5 before and after aging are shown in Table 8: Table 8. ATR-FTIR analysis results of the surfaces before and after aging in Example 4 and Comparative Example 5.

[0096] As shown in Table 8, the ATR-FTIR results directly confirm from the perspective of molecular spectroscopy that the intensity of the characteristic peak of the guanidine group on the surface of Comparative Example 5 (surface-grafted microspheres) decreased significantly after aging, indicating that the guanidine salt was severely lost; while the peak intensity of the guanidine group in Example 4 of the present invention only decreased slightly, proving that the guanidine salt functional group was stably fixed in the material.

[0097] Based on the test results of the above embodiments and comparative examples, it can be clearly concluded that: The core-shell structured flame-retardant and antibacterial microspheres of the present invention use guanidine salt derivatives containing unsaturated double bonds (such as DG-GMA and VBG) as building units of the shell crosslinking network, and deeply anchor the guanidine salt functional groups in a chemical bond manner, fundamentally solving the technical problem of easy migration and loss of functional molecules in traditional surface-grafted microspheres.

[0098] The ABS compositions using the microspheres of this invention (Examples 4-6) maintain a flame retardant rating of V-0 and an antibacterial rate retention rate of over 99% under harsh conditions such as 1000 hours of heat aging at 85°C, 1000 hours of damp heat aging at 85°C / 85%RH, 5000 solvent wiping cycles, and 168 hours of immersion in hot water at 70°C, demonstrating excellent long-term durability, which cannot be achieved in comparative studies.

[0099] The present invention has a simple process, and the microspheres have good compatibility with the ABS matrix. While achieving high efficiency and long-lasting function, it has little impact on the mechanical properties of the matrix and has significant prospects for industrial application.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles defined in the claims of the present invention should be included within the protection scope of the present invention.

Claims

1. Flame-retardant antimicrobial microspheres, characterized in that, include: A polymer core composed of a first structural unit, a second structural unit, and a third structural unit, and a guanidine salt crosslinked polymer shell covering the surface of the polymer core; The first structural unit is maleic anhydride, the second structural unit is a C4 and / or C5 olefin, and the third structural unit is a first crosslinking agent; The first crosslinking agent includes divinylbenzene and / or an acrylate crosslinking agent containing at least two acrylate groups; The guanidine salt-crosslinked polymer shell comprises a crosslinked network grafted with a guanidine salt or a polymer thereof, and the crosslinked network comprises a second crosslinking agent; The second crosslinking agent comprises a guanidine salt derivative crosslinking monomer containing unsaturated double bonds, or is composed of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds and at least one of an acrylate crosslinking agent selected from divinylbenzene and containing at least two acrylate groups.

2. The flame retardant antimicrobial microspheres according to claim 1, wherein, The second crosslinking agent is composed solely of a guanidine salt derivative crosslinking monomer containing unsaturated double bonds.

3. The flame-retardant antimicrobial microspheres according to claim 2, wherein, The crosslinking monomer of the guanidine salt derivative containing unsaturated double bonds is a bis(meth)acryloyloxyalkyl guanidine salt or a vinylbenzyl guanidine salt.

4. The flame-retardant antimicrobial microspheres according to claim 3, wherein The bis(meth)acryloyloxyalkylguanidine salt is a phosphate, hydrochloride, or hydrobromide of bis(methacryloyloxyethyl)guanidine.

5. The flame retardant antimicrobial microspheres according to claim 1, wherein, The guanidine salt or its polymer includes at least one of guanidine phosphate, guanidine hydrochloride, guanidine hydrobromide, dihydroguanidine phosphate, diguanidine hydrogen phosphate, polyhexamethylene biguanide hydrochloride, polyhexamethylene biguanide phosphate, and polyhexamethylene biguanide acetate.

6. The flame retardant antimicrobial microspheres according to claim 1, wherein, The degree of crosslinking of the polymer core is ≥50%, and the degree of crosslinking of the guanidine salt crosslinked polymer shell is ≥30%.

7. A process for the preparation of the flame retardant antimicrobial microspheres according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. In the presence of an organic solvent and an initiator, a monomer mixture comprising maleic anhydride, C4 and / or C5 olefins and a first crosslinking agent is subjected to a first polymerization reaction to obtain a first reaction product; S2. Add a mixture of shell monomers containing guanidine salt derivative crosslinking monomers with unsaturated double bonds and an initiator to the first reaction product to carry out a second polymerization reaction, so that the shell monomers are grafted and crosslinked on the surface of the polymer core to form a crosslinked shell coating the surface of the polymer core, and obtain the second reaction product. S3. Add a small molecule guanidine salt or guanidine salt polymer to the second reaction product to carry out a grafting reaction. After the reaction is complete, separate, wash and dry to obtain the flame-retardant and antibacterial microspheres.

8. The preparation method according to claim 7, characterized in that, In step S2, the shell monomer mixture further comprises additional maleic anhydride and / or C4 / C5 olefin monomers; the molar ratio of the additional maleic anhydride and / or C4 / C5 olefin monomers to the guanidine salt derivative crosslinking monomer containing unsaturated double bonds is (0.1~5):

1.

9. The preparation method according to claim 7, characterized in that, Based on the total moles of maleic anhydride, the amount of the guanidine salt derivative crosslinking monomer containing unsaturated double bonds is 1~40 mol.

10. A polymer material composition, characterized in that, The product comprises an acrylonitrile-butadiene-styrene copolymer resin matrix and flame-retardant and antibacterial microspheres according to any one of claims 1 to 6; the amount of flame-retardant and antibacterial microspheres added is 0.05 to 10 parts by weight, based on 100 parts by weight of the total weight of the acrylonitrile-butadiene-styrene copolymer resin matrix.

Images