Antibacterial acrylic material and preparation method thereof

Abstract

The invention discloses an antibacterial acrylic material and a preparation method thereof. The antibacterial acrylic material is prepared from the following raw materials: 90 to 100 parts of methyl methacrylate, 0.4 to 1.0 part of antibacterial liquid and 0.01 to 1.0 part of initiator, wherein the antibacterial liquid comprises the following raw materials: modified nano-zinc oxide, an ether ester solvent and an auxiliary agent, the content of the modified nano-zinc oxide in the antibacterial liquid is 35wt%-45wt%, and the modified nano-zinc oxide is nano-zinc oxide of which the surface is grafted with a silane coupling agent. Through specific nano-zinc oxide surface grafting modification and an optimized antibacterial liquid formula, the contradiction between antibacterial durability and high-temperature yellowing resistance is synergistically solved, the antibacterial liquid ensures good dispersion of nano-particles, the problem of nonuniformity caused by agglomeration in a matrix is avoided, and the service life of the nano-particles is prolonged. The grafting modified nano zinc oxide not only ensures the compatibility with the matrix, but also avoids the generation of obvious catalytic thermal degradation side effects.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an antibacterial acrylic material and its preparation method. Background Technology

[0002] Acrylic material, chemically known as polymethyl methacrylate (PMMA), is widely used in bathroom products and other fields due to its excellent transparency, weather resistance, and processing properties. However, in the humid and enclosed environment of a bathroom, bacteria can easily grow on the surface of acrylic products, affecting human health. Therefore, endowing acrylic material with long-lasting antibacterial properties is of great significance.

[0003] Antibacterial agents are added to acrylic sheets, generally falling into two categories: organic and inorganic antibacterial systems. Organic antibacterial agents are easy to process, disperse well, and are highly efficient, but they are prone to migration and precipitation under long-term use in hydrothermal environments, resulting in a short lifespan. They also face safety evaluation issues, as organic antibacterial agents cannot obtain the corresponding certifications under the SIAA and CIAA certification systems. Inorganic antibacterial agents are mainly composites of glass (silicate, borate) or zirconium phosphate carriers with silver, zinc particles, and corresponding metal oxides. Inorganic antibacterial agents generally exist in powder form. The significant polarity difference between inorganic antibacterial agent powders and PMMA leads to poor compatibility and a tendency for phase separation. These factors result in uneven distribution of inorganic antibacterial agent powders within the polymethyl methacrylate matrix. For example, in one antibacterial dispersion system, instability during polymerization caused severe agglomeration of nano-zinc oxide, forming micron-sized clusters, resulting in a white, opaque sample. In addition to dispersion issues, a more prominent problem with inorganic antibacterial agents during use is yellowing. Under high-temperature processing conditions (such as the approximately 200°C required for vacuum forming), the surface activity of semiconductor materials like nano-zinc oxide catalyzes the thermal degradation of the PMMA matrix, leading to PMMA matrix degradation and a significant increase in color difference (ΔE), severely affecting the product's appearance. This phenomenon may be due to the photocatalytic degradation properties of the antibacterial particles (such as nano-zinc oxide). Nano-zinc oxide is a wide-bandgap semiconductor; when exposed to light with energy greater than its bandgap (especially ultraviolet light), it generates photogenerated electrons and holes. These electrons and holes possess strong reducing and oxidizing capabilities, reacting with water molecules and oxygen in the air to generate reactive oxygen species such as hydroxyl radicals and superoxide radicals. Under high-temperature processing conditions, the increased mobility of the polymer chains makes it easier for free radicals to contact and react with the polymer chains. Ultimately, these degradation products form chromophores such as conjugated double bonds, which macroscopically manifest as the material yellowing. Summary of the Invention

[0004] This invention aims to at least partially solve one of the aforementioned technical problems in related technologies. To this end, this invention proposes an antibacterial acrylic material and its preparation method. This solution synergistically resolves the contradiction between antibacterial durability and high-temperature resistance to yellowing through specific nano-zinc oxide surface grafting modification and an optimized antibacterial liquid formulation. The antibacterial liquid ensures good dispersion of nanoparticles, avoiding the unevenness caused by agglomeration in the matrix. Meanwhile, the grafted zinc oxide must ensure compatibility with the matrix while avoiding significant catalytic thermal degradation side effects.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The first aspect of this invention provides an antibacterial acrylic material, comprising, by weight, the following raw materials:

[0007] 90-100 parts methyl methacrylate, 0.4-1.0 parts antibacterial solution, 0.01-1.0 parts initiator;

[0008] The antibacterial solution comprises the following raw materials: modified nano zinc oxide, ether ester solvent and additives. The modified nano zinc oxide in the antibacterial solution has a content of 35wt%-45wt%, and the modified nano zinc oxide is nano zinc oxide with surface grafted silane coupling agent.

[0009] In some embodiments of the present invention, the preparation of the modified nano zinc oxide includes the following steps: (1) dispersing nano zinc oxide in an alcohol solution and ultrasonically treating it to obtain a zinc oxide dispersion; (2) adding a silane coupling agent to a mixed solution of alcohol and water with a pH of 4-5 for hydrolysis to obtain a silane coupling agent solution; (3) adding the zinc oxide dispersion to the silane coupling agent solution and heating it under a protective atmosphere. After the reaction is completed, the solid and liquid are separated to obtain the modified nano zinc oxide. Further, in step (1), the alcohol solution is anhydrous ethanol or isopropanol. In step (2), the hydrolysis reaction time is 30 min-60 min. In step (3), the heating reaction temperature is 60℃-80℃, the reaction time is 4 h-8 h, and the protective atmosphere is nitrogen or argon. Reaction equations (taking KH-570 as an example): Hydrolysis: KH-570 + H2O → HO-Si-(OR)2(OH) + CH3OH; Condensation: HO-Si-(OR)2(OH) + ZnO-OH → ZnO-O-Si-(OR)2(OH) + H2O.

[0010] In some embodiments of the present invention, the additives include dispersants, defoamers, and anti-settling agents. Further, the dispersant is an organosilicon dispersant or an acrylic resin dispersant, preferably an organosilicon dispersant. The defoamer is an organosilicon defoamer or acetylenic diol, preferably an organosilicon defoamer. The anti-settling agent is bentonite.

[0011] In some embodiments of the present invention, the content of dispersant in the antibacterial liquid is 1wt%-2wt%, the content of defoamer is 0.1wt%-1wt%, and the content of antisettling agent is 0.5wt%-2wt%.

[0012] In some embodiments of the present invention, the preparation of the antibacterial solution includes the following steps: (1) dissolving the dispersant in a portion of the ether ester solvent to obtain solution A; (2) adding the modified nano zinc oxide to solution A to obtain mixture B; (3) sequentially adding the defoamer, anti-settling agent, and the remaining ether ester solvent to mixture B, stirring, and grinding to obtain the antibacterial solution. Further, in step (3), the stirring is performed using a high-speed mixer for 5-10 minutes, and the grinding is performed using a grinding media for 1-3 hours.

[0013] In some embodiments of the present invention, the particle size of the nano zinc oxide is 20nm-80nm.

[0014] In some embodiments of the present invention, the ether ester solvent is selected from one or more of ethylene glycol butyl ether acetate, propylene glycol butyl ether acetate, propylene glycol ethyl ether acetate, or propylene glycol methyl ether acetate. Preferably, the ether ester solvent is selected from propylene glycol methyl ether acetate.

[0015] In some embodiments of the present invention, the silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, or γ-aminopropyltriethoxysilane. The preferred silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH-570).

[0016] In some embodiments of the present invention, the raw materials of the antibacterial acrylic material further include plasticizer and color paste, wherein the amount of plasticizer is 2-5 parts and the amount of color paste is 1-3 parts.

[0017] A second aspect of the present invention provides a method for preparing the antibacterial acrylic material, comprising the following steps:

[0018] S1: Methyl methacrylate is mixed with a portion of the initiator and heated to react, yielding a prepolymer.

[0019] S2: Add the remaining initiator, plasticizer, colorant and antibacterial liquid to the prepolymer to obtain a mixture;

[0020] S3: Place the mixture in a mold and degas it under vacuum. Then, perform low-temperature polymerization at 50℃-60℃ and high-temperature polymerization at 100℃-120℃. After polymerization, cool and demold to obtain the antibacterial acrylic material.

[0021] In some embodiments of the present invention, in step S1, the heating reaction is to heat to boiling and maintain for 5-10 minutes.

[0022] In some embodiments of the present invention, in step S3, the low-temperature polymerization time is 2h-3h, and the high-temperature polymerization time is 2h-3h.

[0023] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0024] 1. Improved antibacterial durability: The modified nano zinc oxide has greatly improved compatibility with the PMMA matrix, is evenly dispersed and firmly bound, and is not easy to dissolve or agglomerate in boiling water, thus achieving long-lasting and highly effective antibacterial performance.

[0025] 2. Solving the Yellowing Problem During High-Temperature Processing: Surface grafting modification of nano-zinc oxide using a silane coupling agent effectively coats and neutralizes the highly active sites on the zinc oxide surface through covalent bonding, significantly inhibiting its photocatalytic activity. This is equivalent to establishing a physical barrier layer between the zinc oxide particles and the PMMA matrix, thus preventing degradation and yellowing of the PMMA matrix during high-temperature processing. Furthermore, after grafting silane molecules onto ZnO, the silane molecules remain reactive and can continue to undergo reverse polymerization with MMA monomers, increasing the molecular weight and further improving temperature resistance. However, in practical applications, yellowing still occurs when the amount of antibacterial solution exceeds a certain value. This is partly due to the conversion rate issue in the grafting reaction, which prevents complete reaction, leaving a small amount of ungrafted nano-zinc oxide in the antibacterial solution. Another reason is that excess zinc oxide does not copolymerize with methyl methacrylate monomers, meaning it does not enter the molecular chain and exists in a free state within the PMMA matrix, thus enhancing thermo-oxidative degradation. Therefore, the amount of antibacterial solution used needs to be controlled within a reasonable range to maintain long-lasting and efficient antibacterial performance while also being able to withstand high-temperature processing without yellowing.

[0026] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0027] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment prepares an antibacterial acrylic sheet, and the specific process is as follows:

[0030] I. Preparation of Modified Nano Zinc Oxide

[0031] (1) Pretreatment: 100g of nano zinc oxide with an average particle size of 30nm was dispersed in 500mL of anhydrous ethanol and ultrasonically treated for 30 minutes to fully disperse and activate the surface hydroxyl groups to obtain zinc oxide dispersion.

[0032] (2) Hydrolysis: Add 15g of KH-570 silane coupling agent to a mixed solution consisting of 150mL ethanol and 50mL deionized water (adjusted to pH 4.5 with acetic acid), and hydrolyze for 45 minutes under magnetic stirring to obtain a silane coupling agent solution.

[0033] (3) Grafting reaction: The pretreated zinc oxide dispersion was slowly added dropwise to the hydrolyzed silane coupling agent solution. Under nitrogen protection, the mixture was refluxed at 70°C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 80°C for 12 hours to obtain modified nano zinc oxide with KH-570 grafted on the surface.

[0034] II. Preparation of Antibacterial Solution

[0035] Antibacterial liquid composition (by weight percentage): 40% modified nano zinc oxide, 1.5% organosilicon dispersant, 0.5% organosilicon defoamer, 1.5% bentonite, and 56.5% propylene glycol methyl ether acetate (PMA).

[0036] Preparation method: Dissolve the organosilicon dispersant in about half of the amount of PMA and stir until uniform to obtain solution A. Add modified nano zinc oxide to solution A and mix initially to obtain mixture B. Add defoamer, anti-settling agent and the remaining PMA to mixture B in sequence, place in a high-speed mixer and mix for 8 minutes, then transfer to a rod mill and use 0.2 mm zirconia beads as the grinding medium to mill for 2 hours to obtain an antibacterial solution with a solid content of 40%.

[0037] III. Preparation of Antibacterial Acrylic Sheets

[0038] (1) Prepolymerization: Add 95 parts by weight of methyl methacrylate (MMA) and 0.1 parts by weight of azobisisobutyronitrile (AIBN) to the reactor, heat it to boiling and maintain it for 8 minutes, and then cool it naturally to room temperature to obtain the prepolymer material;

[0039] (2) Mixing: Add 0.2 parts by weight of AIBN, 3 parts by weight of dioctyl terephthalate (plasticizer DOTP), 1 part by weight of titanium white paste and 0.6 parts by weight of antibacterial liquid to the prepolymer, and mechanically stir for 15 minutes to obtain a uniform mixture.

[0040] (3) Degassing and polymerization: The mixture is poured into a flat mold and placed in a vacuum drying oven for degassing for 30 minutes. Then the mold is moved to a 60°C water bath for low-temperature polymerization for 2.5 hours. After that, it is transferred to an oven for high-temperature polymerization at 110°C for 2 hours.

[0041] (4) Cooling and demolding: After polymerization, the mold is cooled to room temperature and demolded to obtain an antibacterial acrylic sheet with a thickness of about 3 mm.

[0042] Example 2

[0043] This embodiment prepares an antibacterial acrylic sheet using the same preparation method as in Example 1, except that the amount of antibacterial liquid is changed to 1 part.

[0044] Example 3

[0045] This embodiment prepares an antibacterial acrylic sheet using the same preparation method as in Example 1, except that the amount of antibacterial liquid is changed to 0.4 parts.

[0046] Comparative Example 1

[0047] This comparative example prepared an antibacterial acrylic sheet. The difference from Example 1 is that unmodified nano zinc oxide was used to disperse in dioctyl terephthalate (DOTP) to prepare an antibacterial solution (without adding other additives). The rest is the same as in Example 1.

[0048] Comparative Example 2

[0049] This comparative example prepared an antibacterial acrylic sheet. The difference from Example 1 is that the antibacterial liquid used was unmodified nano zinc oxide, while the rest was the same as in Example 1.

[0050] Comparative Example 3

[0051] This comparative example prepared an antibacterial acrylic sheet, which differs from Example 1 in that the solvent for the antibacterial solution is dioctyl terephthalate (DOTP), otherwise it is the same as Example 1.

[0052] Comparative Example 4

[0053] This comparative example prepared an antibacterial acrylic sheet, which differs from Example 1 in that the amount of antibacterial liquid used is 1.2 parts, and the rest is the same as in Example 1.

[0054] Test case

[0055] This experiment tested the performance of the antibacterial acrylic sheets prepared in Examples 1-3 and Comparative Examples 1-4, and the results are shown in Table 1.

[0056] Table 1

[0057]

[0058] Antibacterial rate: Refer to QB / T 2591-2003 "Test methods and antibacterial effects of antibacterial plastics", the test species are Escherichia coli and Staphylococcus aureus.

[0059] Durable antibacterial rate: The antibacterial rate of the sample after immersion in a constant temperature water bath at 55℃ for 360 hours.

[0060] ΔE: The color change before and after treatment in a 200℃ oven for 5 minutes was measured using a colorimeter.

[0061] Appearance after boiling: 80℃ / 100h, to determine whether the color change of the test plate before and after boiling is obvious (change in brightness or yellowing). Boiling at 80℃ is used as the whole bathtub test condition to consider the stability of the material under hydrothermal conditions. When a substance is hydrolyzed or oxidized, the material will undergo macroscopic discoloration.

[0062] As shown in Table 1, Example 1 exhibits excellent antibacterial properties, and the color difference ΔE is controlled within 0.5 after high-temperature treatment, indicating stable quality. Comparative Examples 1 and 2 both used unmodified nano-zinc oxide, and Comparative Example 1's antibacterial solution did not use other additives, leading to nanoparticle aggregation. Consequently, its durable antibacterial rate was only 39.5%, due to performance imbalance caused by the inhomogeneity of the nanoparticles. Although Comparative Example 2 adjusted the solvent and dispersion system of its antibacterial solution compared to Comparative Example 1, its high-temperature resistance to yellowing still did not meet the requirements for molding and processing. Comparative Example 3 used modified nano-zinc oxide, and its initial and durable antibacterial rates both met the requirements, indicating improved compatibility and dispersibility. However, its high-temperature resistance remained unresolved, possibly due to the plasticizing effect of DOTP itself, which reduced the material's temperature resistance. Comparative Example 4 increased the amount of antibacterial solution. While the antibacterial performance was maintained, the high-temperature resistance decreased, indicating that excessive nano-zinc oxide promoted the thermo-oxidative degradation of acrylic. In summary, modified nano zinc oxide can improve its compatibility with PMMA matrix, thereby enhancing antibacterial durability. At the same time, modified nano zinc oxide also improves the material's resistance to high-temperature yellowing, but its usage should be controlled within a reasonable range.

[0063] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An antibacterial acrylic material, characterized in that, By weight, it includes the following ingredients: 90-100 parts methyl methacrylate, 0.4-1.0 parts antibacterial solution, 0.01-1.0 parts initiator; The antibacterial solution comprises the following raw materials: modified nano zinc oxide, ether ester solvent and additives. The modified nano zinc oxide has a content of 35wt%-45wt% in the antibacterial solution, and the modified nano zinc oxide is nano zinc oxide with surface grafted silane coupling agent.

2. The antibacterial acrylic material according to claim 1, characterized in that, The preparation of the modified nano zinc oxide includes the following steps: (1) dispersing nano zinc oxide in an alcohol solution and ultrasonically treating it to obtain a zinc oxide dispersion; (2) adding a silane coupling agent to a mixed solution of alcohol and water with a pH of 4-5 for hydrolysis to obtain a silane coupling agent solution; (3) adding the zinc oxide dispersion to the silane coupling agent solution and heating it under a protective atmosphere. After the reaction is completed, the solid and liquid are separated to obtain the modified nano zinc oxide.

3. The antibacterial acrylic material according to claim 1, characterized in that, The additives include dispersants, defoamers, and antisettling agents.

4. The antibacterial acrylic material according to claim 3, characterized in that, The antibacterial liquid contains 1wt%-2wt% dispersant, 0.1wt%-1wt% defoamer, and 0.5wt%-2wt% antisettling agent.

5. The antibacterial acrylic material according to claim 3, characterized in that, The preparation of the antibacterial liquid includes the following steps: (1) dissolving the dispersant in part of the ether ester solvent to obtain solution A; (2) adding the modified nano zinc oxide to solution A to obtain mixture B; (3) adding the defoamer, antisettling agent and the remaining ether ester solvent to mixture B in sequence, stirring and grinding to obtain the antibacterial liquid.

6. The antibacterial acrylic material according to claim 1, characterized in that, The particle size of the nano zinc oxide is 20nm-80nm.

7. The antibacterial acrylic material according to claim 1, characterized in that, The ether ester solvent is selected from one or more of ethylene glycol butyl ether acetate, propylene glycol butyl ether acetate, propylene glycol ethyl ether acetate, or propylene glycol methyl ether acetate.

8. The antibacterial acrylic material according to claim 1, characterized in that, The silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, or γ-aminopropyltriethoxysilane.

9. The method for preparing the antibacterial acrylic material according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Methyl methacrylate is mixed with a portion of the initiator and heated to react, yielding a prepolymer. S2: Add the remaining initiator, plasticizer, colorant and antibacterial liquid to the prepolymer to obtain a mixture; S3: Place the mixture in a mold and degas it under vacuum. Then, perform low-temperature polymerization at 50℃-60℃ and high-temperature polymerization at 100℃-120℃. After polymerization, cool and demold to obtain the antibacterial acrylic material.

10. The preparation method according to claim 9, characterized in that, In step S3, the low-temperature polymerization time is 2h-3h, and the high-temperature polymerization time is 2h-3h.

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