Antibacterial room temperature vulcanized silicone rubber and preparation method thereof

Abstract

The invention relates to the technical field of silicone rubber, in particular to antibacterial room-temperature vulcanized silicone rubber and a preparation method thereof.The method comprises the steps that firstly, betaine salt and an esterification reaction catalyst are mixed and activated, quaternary ammonium salt modified chitosan is added, and a quaternary ammonium salt and betaine salt co-modified chitosan auxiliary is obtained after a reaction; and 2, mixing the required amount of RTV silicone rubber, the quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent and the cross-linking agent, adding a cross-linking catalyst, uniformly mixing, forming a film, drying, and curing to obtain the antibacterial room temperature vulcanized silicone rubber. The antibacterial activity of the RTV silicone rubber is mutually promoted by utilizing quaternary ammonium salt and betaine, the quaternary ammonium salt and betaine co-modified chitosan additive has good compatibility and outstanding antibacterial effect, is green and safe, endows the RTV silicone rubber with excellent antibacterial property, and improves the crosslinking property and mechanical property of the RTV silicone rubber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone rubber, and is an antibacterial room temperature vulcanized silicone rubber and a preparation method thereof. BACKGROUND

[0002] At present, silicone rubber is widely used in the field of medical devices due to its excellent high and low temperature resistance, aging resistance, hydrophobicity and good biocompatibility. However, when the silicone rubber is exposed to a microbial environment for a long time, bacteria are easily adsorbed on the surface of the silicone rubber, leading to bacterial proliferation, thereby reducing the function of the medical device, shortening its service life, and possibly causing bacterial infection, which poses a serious threat to human health. The types of antibacterial agents used for modification of silicone rubber mainly include inorganic antibacterial agents and organic antibacterial agents. Inorganic antibacterial agents, such as silver nanoparticles, copper nanoparticles and zinc oxide nanoparticles, have good antibacterial activity, but have problems such as poor biocompatibility, potential toxicity and environmental accumulation, which limit their wide application in medical and daily necessities. In contrast, natural antibacterial materials have gradually attracted the attention of researchers and the industry due to their good biocompatibility, environmental friendliness and harmlessness to the human body, among which natural organic antibacterial agents are particularly valued.

[0003] Chitosan (CS) is a natural polysaccharide with alkaline cationic organic polysaccharide, which is obtained by deacetylation of chitin. It has a wide range of sources, good biocompatibility and natural antibacterial activity, and thus has broad application prospects in the fields of biomedicine, food packaging and environmental engineering. However, chitosan also has some defects, such as low mechanical strength, poor barrier performance, weak antioxidant activity, poor water solubility, and insufficient antibacterial ability. Because chitosan contains a large number of amino and hydroxyl groups, it can be chemically modified by introducing other functional groups to improve its functionality and utilization value. In order to improve the solubility and functional activity of chitosan, hydrophilic groups can be introduced by chemical modification to destroy its original hydrogen bond network structure. The research of Liu et al. (Fangqin L, Dengfeng H, Yunlong Y, et al. Quaternary ammonium salt-based cross-linked micelles to combat biofilm [J]. Bioconjugate chemistry, 2019, 30(3):541-546.) showed that quaternary ammonium salt micelles can be adsorbed on the surface of biofilm by multi-charge interaction, and then penetrate into the interior of the biofilm in the form of nanoparticles. In this process, the extracellular polymeric substances will be widely diffused in the biofilm, effectively destroying the structure of the formed biofilm, and achieving the killing effect on the corresponding bacteria. Quaternization helps to improve the biocompatibility of chitosan, but further improvement of its antibacterial performance is still needed according to different application scenarios.

[0004] Traditional organic antibacterial agents and metal antibacterial agents have potential cytotoxicity and poor biocompatibility, and can only be used for antibacterial modification of materials with active chemical properties, but it is difficult to achieve antibacterial modification for materials with stable chemical properties such as RTV silicone rubber (room temperature vulcanized silicone rubber). Therefore, it is urgent to seek a biocompatible and biocompatible organic antibacterial agent and apply it to the antibacterial modification of RTV silicone rubber to achieve safe and environmentally friendly antibacterial effect.

[0005] Currently, the commonly used antibacterial substances for antibacterial modification of medical devices are metal ions, antibiotics, and small molecule quaternary ammonium salt antibacterial agents. Metal ions such as copper and silver ions have high cytotoxicity and can easily cause inflammation; antibiotics such as cephalosporins and penicillins may cause adverse reactions in the human body and long-term use can lead to bacterial resistance; small molecule quaternary ammonium salts such as benzalkonium chloride and benzalkonium bromide also have high cytotoxicity and may cause hemolysis and other risks.

[0006] Generally, the antibacterial properties of silicone rubber are improved by adding antibacterial agents or surface modification. For example, the addition of nano-silver particles or quaternary ammonium salts can effectively inhibit bacterial growth, but some antibacterial agents (such as nano-silver) may be released into the environment during use, potentially harming the ecosystem, and there are some defects and challenges in terms of antibacterial performance, biocompatibility, physical and chemical properties, environmental issues, and technical bottlenecks. Chinese patent document CN2778285Y discloses a design of a urinary catheter, the antibacterial layer is composed of nano-silver, the bactericidal effect is significant, and the nano-silver layer as an antibacterial layer has the antibacterial property of no drug resistance. However, there are some limitations in the actual application of this urinary catheter. First, the manufacturing process is relatively complex, resulting in high production costs. Second, the continuous release and accumulation of antibacterial metal ions or nanoparticles disrupt the balance of the microenvironment of surrounding tissues, interfere with the normal growth of surrounding cells, produce cytotoxicity, and have poor biocompatibility. Since the patent document uses a surface silver ion smearing method, the antibacterial duration is relatively short. At the same time, Zheng et al. (Chenlong Z, Guangfu W, Yingjie Ch, et al. RTV silicone rubber surface modification for cell biocompatibility by negative-ion implantation. Nuclear Inst. and Methods in physics Research, B, 370, 73-78.) disclosed a surface modification method for antibacterial treatment of products made of silicone rubber materials. This method forms an antibacterial coating on the surface of the silicone rubber product by treating its surface with low-temperature oxygen plasma under high-frequency electromagnetic radiation conditions, effectively improving the antibacterial performance. However, surface modification has the problems of large engineering quantity and high cost. In addition, since the surface of the organic silicone rubber material needs to be in contact with the tissue, it must itself have good cell affinity, which may to some extent lead to the degradation of antibacterial performance. Chinese patent document CN114316597A discloses a Eucommia rubber antibacterial silicone rubber, which has excellent and durable antibacterial performance and significantly improved mechanical properties through the processing method of blending Eucommia rubber, nano-calcium carbonate, and silicone rubber. It can be further applied to antibacterial medical devices. However, there is a problem of insufficient cell affinity. Although Eucommia rubber itself has good biocompatibility, after blending with silicone rubber and nano-calcium carbonate, the surface properties of the material may change, affecting its cell affinity. This may cause the material to trigger certain immune responses when in contact with tissues.Cao (Cao Q, Preparation and Performance of Surface Antimicrobial Silicone Rubber Material[D]. South China University of Technology, 2018) used vacuum ultraviolet to activate the surface of silicone rubber, then used silane coupling agent and ultraviolet curing reaction to chemically graft zwitterionic 3-((3-methacryloylpropyl) dimethylamino) propyl-1-sulfonic acid inner salt on the surface of silicone rubber, obtaining surface grafted comb zwitterionic silicone rubber and surface grafted crosslinked zwitterionic silicone rubber with different crosslinking degrees, which showed good antimicrobial performance. However, the zwitterionic polymer in aqueous solution has strong intermolecular and intramolecular dipole interactions due to its high dipole moment, leading to reversible self-association of polymer chains. This self-association behavior may affect the stability and durability of its antimicrobial performance, so it has poor durability. Yin et al. (Yin GD, Huang DQ, Liang Y, et al. Application of Surface Modification in Preparation of Silver-containing Antimicrobial Coating on Silicone Rubber Surface and Study on Antimicrobial Performance[J]. New Chemical Materials, 2025, 53(07):231-236+242.) used plasma technology to modify the surface of silicone rubber, and used silver as an antimicrobial agent and polydopamine (PDA) as a "coupling agent" to prepare a silver antimicrobial coating on the surface of silicone rubber by chemical plating method. Although this method provides a new technology for preparing antimicrobial medical materials, it also has some potential drawbacks. First, the chemical plating method may result in insufficient bonding strength between the antimicrobial coating and the silicone rubber substrate, affecting the stability and durability of the coating. In addition, the slow-release performance of the antimicrobial coating may not be ideal, and the release rate of silver ions may be too fast or too slow, affecting its antimicrobial effect. Furthermore, the use of silver may cause bacterial resistance, immune response, inflammation, and toxicity, making it unsuitable for complex environments in the body. Dai et al. (Dai FL, Fu ZN, Jiang JB, et al. Study on Long-acting Antimicrobial Performance of Room Temperature Cured Silicone Rubber[J]. Chinese Adhesives, 2021, 30(12):32-36.) modified PHMG with isocyanate propyl trialkoxy silane to make it a special curable antimicrobial agent, and incorporated it into the three-dimensional structure of silicone sealant cured material to improve the antimicrobial retention rate of RTV silicone sealant. However, the synthesis of isocyanate propyl trialkoxy silane requires the use of phosgene or solid phosgene (highly toxic), or a multi-step reaction (such as the carbamate method), resulting in high raw material costs, and unbound PHMG may be dissolved, posing a potential toxicity risk when in contact with drinking water.Li Fei et al. (Li Fei, Li Lina, Jiang Feiyuan, et al. Antimicrobial properties of different antimicrobial agents in medical silicone rubber [J]. Guangdong Chemical Industry, 2019, 46(17): 65-66+50.) used three kinds of antimicrobial agents, namely isothiazolinone, nano ionic antimicrobial agent and silver series antimicrobial agent. The isothiazolinone antimicrobial effect is remarkable, but the isothiazolinone high concentration, long-term contact or sensitive population (such as allergic constitution) may cause skin irritation, allergic reaction and even systemic toxicity. The other two kinds of antimicrobial effect is not good, the nano ionic type has no antimicrobial property to two kinds of bacteria, the reason may be that compared with organic antimicrobial agent and silver series antimicrobial agent, nano ionic antimicrobial agent may interact with silicone rubber, and is not easy to migrate to the surface. Therefore, although the above method provides a new way for the preparation of antimicrobial medical materials, but in the practical application, it may need to be further optimized to solve the above problems. SUMMARY

[0007] The present application provides an antibacterial room temperature (RTV) vulcanized silicone rubber, which overcomes the shortcomings of the prior art and effectively solves the problems of poor compatibility and potential toxicity of organic antimicrobial agents in the modification process of existing silicone rubber.

[0008] One of the technical solutions of the present application is realized by the following measures: a preparation method of an antibacterial room temperature vulcanized silicone rubber, comprising the following steps: In the first step, the betaine salt and esterification catalyst are mixed, activated, then the quaternary ammonium salt modified chitosan is added, and the quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent (HTCC-Bet) is obtained after reaction; In the second step, the required amount of RTV silicone rubber, quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent and crosslinking agent are mixed, the crosslinking catalyst is added, and the antibacterial room temperature vulcanized silicone rubber is obtained after mixing, drying and curing.

[0009] The following is a further optimization or / and improvement of the above-mentioned technical solutions of the application: In the above-mentioned first step, the quaternary ammonium salt modified chitosan is 2,3- glycidyltrimethylammonium chloride grafted chitosan.

[0010] The above-mentioned 2,3-glycidyltrimethylammonium chloride grafted chitosan is prepared by the following method: The required amount of activated chitosan and 2,3-glycidyltrimethylammonium chloride (GTMAC) are added to the reaction solvent, and the 2,3-glycidyltrimethylammonium chloride grafted chitosan is obtained after amidation reaction; The reaction temperature of the amidation reaction is 60-80℃, and the time is 10-24h; The mass ratio of chitosan to 2,3-glycidyltrimethylammonium chloride is (1-16):4; The activated chitosan is prepared by the following steps: dissolving chitosan (CS) in an acidic aqueous solution, adjusting the pH value of the solution to 9-11 by NaOH, washing and drying the chitosan after precipitation, and obtaining the activated chitosan; the acidic aqueous solution is an aqueous hydrochloric acid solution, an aqueous acetic acid solution or an aqueous sulfuric acid solution, and the volume fraction of the acidic aqueous solution is 1%-5%. The reaction solvent is a mixture of acetic acid and isopropyl alcohol in a volume ratio of 1-2:100.

[0011] In the first step, the esterification reaction catalyst is one or more of dicyclohexyl carbodiimide (DCC), dimethylpyridine (DMAP), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS).

[0012] The esterification reaction catalyst is a mixture of dicyclohexyl carbodiimide (DCC) and dimethylpyridine (DMAP) in a mass ratio of 2:0.7.

[0013] In the first step, the mass ratio of the quaternary ammonium salt modified chitosan, the betaine salt and the esterification reaction catalyst is 2:(1-8):(2-8).

[0014] In the first step, the activation is mixing at room temperature for 20 min to 45 min.

[0015] In the first step, the reaction temperature is 60-80℃, and the time is 4-12 h.

[0016] In the second step, the crosslinking agent is one or both of methyl high hydrogen-containing silicone oil and hydroxyl-terminated silicone oil.

[0017] In the second step, the crosslinking catalyst is one or more of dibutyltin dilaurate, bis(acetylacetone) dibutyltin and isopropyl titanate.

[0018] In the second step, the mass ratio of the RTV silicone rubber, the quaternary ammonium salt betaine salt co-modified chitosan auxiliary, the crosslinking agent and the crosslinking catalyst is 10:(1-4):(0.2-0.3):(0.03-0.07).

[0019] In the second step, the curing temperature is 25-70℃.

[0020] The second technical solution of the application is an antibacterial room temperature vulcanized silicone rubber prepared by the preparation method of the antibacterial room temperature vulcanized silicone rubber.

[0021] The application discloses an antibacterial room temperature vulcanized silicone rubber and a preparation method thereof, and utilizes quaternary ammonium salt and betaine to promote the antibacterial activity of each other, and the quaternary ammonium salt betaine co-modified chitosan auxiliary agent has good compatibility and outstanding antibacterial effect, is green and safe, and can endow the RTV silicone rubber with excellent antibacterial property and improve the crosslinking property and mechanical property of the RTV silicone rubber. BRIEF DESCRIPTION OF DRAWINGS

[0022] BRIEF DESCRIPTION OF DRAWINGS Figure 1 The SEM image of the antibacterial quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent in Example 13 of the application.

[0023] BRIEF DESCRIPTION OF DRAWINGS Figure 2 The SEM image of the antibacterial quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent in Example 13 of the application. 13 C NMR spectrum.

[0024] BRIEF DESCRIPTION OF DRAWINGS Figure 3 The SEM of the antibacterial quaternary ammonium salt betaine hydrochloride co-modified chitosan composite RTV silicone rubber in Example 13 of the application. DETAILED DESCRIPTION

[0025] The application is not limited by the following examples, and the specific implementation manners can be determined according to the technical scheme of the application and the actual situation. The various chemical reagents and chemical products mentioned in the application are all common chemical reagents and chemical products known in the prior art unless otherwise specified; the percentages in the application are all mass percentages unless otherwise specified; the solution in the application is all aqueous solution with water as a solvent unless otherwise specified, for example, the hydrochloric acid solution is an aqueous hydrochloric acid solution; the normal temperature and room temperature in the application generally refer to the temperature of 15 DEG C to 25 DEG C, and are generally defined as 25 DEG C.

[0026] The application will be further described in combination with the following examples: Example 1: the preparation method of the antibacterial room temperature vulcanized silicone rubber, comprising the following steps: Firstly, the betaine salt and an esterification reaction catalyst are mixed, the modified chitosan is added after activation, and a quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent (HTCC-Bet) is obtained after reaction; Secondly, the required amount of RTV silicone rubber, the quaternary ammonium salt betaine salt co-modified chitosan auxiliary agent and a crosslinking agent are mixed, a crosslinking catalyst is added, and the antibacterial room temperature vulcanized silicone rubber is obtained after film forming, drying and curing.

[0027] Example 2: as the optimization of the above example, in the first step, the quaternary ammonium salt modified chitosan is 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan.

[0028] Example 3: As an optimization of the above-mentioned Example 2, 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan is prepared by the following method: A desired amount of activated chitosan and 2,3-epoxypropyl trimethyl ammonium chloride (GTMAC) are added to a reaction solvent, and after amidation reaction, 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan is obtained; The reaction temperature of the amidation reaction is 60-80°C, and the time is 10-24h; The mass ratio of chitosan to 2,3-epoxypropyl trimethyl ammonium chloride is (1-16):4; The activated chitosan is prepared by the following steps: chitosan (CS) is dissolved in an acidic aqueous solution, the pH of the solution is adjusted to 9-11 with NaOH, and after chitosan is precipitated, it is washed and dried to obtain the activated chitosan; the acidic aqueous solution is an aqueous hydrochloric acid solution, an aqueous acetic acid solution, or an aqueous sulfuric acid solution, and the volume fraction of the acidic aqueous solution is 1-5%; The reaction solvent is a mixture of acetic acid and isopropyl alcohol in a volume ratio of 1-2:100.

[0029] Example 4: As an optimization of the above-mentioned Example, in the first step, the esterification reaction catalyst is one or more of dicyclohexyl carbodiimide (DCC), dimethyl pyridine (DMAP), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC), and N-hydroxysuccinimide (NHS). Optimized, the esterification reaction catalyst is a mixture of dicyclohexyl carbodiimide (DCC) and dimethyl pyridine (DMAP) in a mass ratio of 2:0.7.

[0030] Example 5: As an optimization of the above-mentioned Example, in the first step, the mass ratio of quaternary ammonium salt modified chitosan, betaine salt, and esterification reaction catalyst is 2:(1-8):(2-8).

[0031] Example 6: As an optimization of the above-mentioned Example, in the first step, the activation is mixed at room temperature for 20-45 min.

[0032] Example 7: As an optimization of the above-mentioned Example, in the first step, the reaction temperature is 60-80°C, and the time is 4-12h.

[0033] Example 8: As an optimization of the above-mentioned Example, in the second step, the crosslinking agent is one or both of methyl high hydrogen-containing silicone oil and hydroxyl-terminated silicone oil.

[0034] Example 9: As an optimization of the above-mentioned Example, in the second step, the crosslinking catalyst is one or more of dibutyltin dilaurate, bis(acetylacetone) dibutyltin, and isopropyl titanate.

[0035] Example 10: As an optimization of the above examples, in the second step, the mass ratio of RTV silicone rubber, quaternary ammonium betaine salt co-modified chitosan auxiliary, crosslinking agent and crosslinking catalyst is 10: (1 to 4): (0.2 to 0.3): (0.03 to 0.07).

[0036] Example 11: As an optimization of the above examples, in the second step, the curing temperature is 25 to 70°C.

[0037] Example 12: Preparation of 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan: Dissolve chitosan in a 2% volume fraction of an aqueous acetic acid solution, adjust the pH of the solution to 9 with NaOH, and after the chitosan precipitates, stand for 12 h, then extract and wash with ethanol 3 times to obtain activated chitosan; Add the activated chitosan and 2,3-epoxypropyl trimethyl ammonium chloride in a mass ratio of 1:4 to a mixture of acetic acid and isopropyl alcohol in a volume ratio of 1:100, and react at 70°C for 12 h. The reaction product is precipitated with anhydrous ethanol, extracted and washed with ethanol 3 times, and vacuum dried at 60°C for 12 h to obtain 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan (HTCC).

[0038] Example 13: Preparation of an antibacterial room temperature vulcanized silicone rubber: First step, mix 2 parts of dicyclohexyl carbodiimide, 0.7 parts of dimethylpyridine and 8 parts of betaine hydrochloride uniformly, activate the carboxyl group at room temperature for 30 min, then add 2 parts of 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan, and react at 75°C for 6 h to obtain a quaternary ammonium betaine salt co-modified chitosan auxiliary.

[0039] Second step, mix 10 parts of RTV silicone rubber, 1 part of quaternary ammonium betaine salt co-modified chitosan auxiliary and 0.25 parts of methyl high hydrogen silicone oil uniformly, then add 0.05 parts of dibutyltin dilaurate and mix again, pour into a teflon mold and flow into a film, first place in a vacuum drying oven at room temperature, vacuum for 15 min, then cure and form on a 65°C flat plate heating table to obtain an antibacterial room temperature vulcanized silicone rubber.

[0040] Example 14: Preparation of an antibacterial room temperature vulcanized silicone rubber: First step, mix 4 parts of dicyclohexyl carbodiimide, 2 parts of dimethylpyridine and 2 parts of betaine hydrochloride uniformly, activate the carboxyl group at room temperature for 30 min, then add 2 parts of 2,3-epoxypropyl trimethyl ammonium chloride grafted chitosan, and react at 85°C for 6 h to obtain a quaternary ammonium betaine salt co-modified chitosan auxiliary.

[0041] Second step, 10 parts of RTV silicone rubber, 2 parts of quaternary ammonium salt betaine co-modified chitosan auxiliary and 0.25 parts of methyl high hydrogen-containing silicone oil were uniformly mixed, then 0.05 parts of titanium isopropylate was added, and the mixture was uniformly mixed again, and then was poured into a teflon mold to flow into a film. The film was first placed in a vacuum drying oven at room temperature, vacuumed for 15 min, and then cured and formed on a flat heating table at 60°C to obtain an antibacterial room temperature vulcanized silicone rubber.

[0042] Example 15: Preparation of an antibacterial room temperature vulcanized silicone rubber First step, 2 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), 2 parts of N-hydroxysuccinimide (NHS) and 4 parts of betaine hydrochloride were uniformly mixed, and the carboxyl group was activated at room temperature for 30 min. Then 2 parts of 2,3-epoxypropyltrimethylammonium chloride grafted chitosan was added, and the reaction was carried out at 70°C for 8 h to obtain a quaternary ammonium salt betaine co-modified chitosan auxiliary.

[0043] Second step, 10 parts of RTV silicone rubber, 3 parts of quaternary ammonium salt betaine co-modified chitosan auxiliary and 0.25 parts of hydroxyl-terminated silicone oil were uniformly mixed, then 0.05 parts of bis(acetylacetone) dibutyl tin was added, and the mixture was uniformly mixed again, and then was poured into a teflon mold to flow into a film. The film was first placed in a vacuum drying oven at room temperature, vacuumed for 15 min, and then cured and formed on a flat heating table at 65°C to obtain an antibacterial room temperature vulcanized silicone rubber.

[0044] Example 16: The difference from example 13 is that the mass fractions of RTV silicone rubber, quaternary ammonium salt betaine co-modified chitosan auxiliary and methyl high hydrogen-containing silicone oil are 10 parts, 2 parts and 0.25 parts respectively.

[0045] Example 17: The difference from example 13 is that the mass fractions of RTV silicone rubber, quaternary ammonium salt betaine co-modified chitosan auxiliary and methyl high hydrogen-containing silicone oil are 10 parts, 3 parts and 0.25 parts respectively.

[0046] Example 18: The difference from example 13 is that the mass fractions of RTV silicone rubber, quaternary ammonium salt betaine co-modified chitosan auxiliary and methyl high hydrogen-containing silicone oil are 10 parts, 4 parts and 0.25 parts respectively.

[0047] Comparative example 1: The difference from example 13 is that the mass fractions of RTV silicone rubber, quaternary ammonium salt betaine co-modified chitosan auxiliary and methyl high hydrogen-containing silicone oil are 10 parts, 0 parts and 0.25 parts respectively (i.e. no quaternary ammonium salt betaine co-modified chitosan auxiliary is added).

[0048] Comparative example 2: The difference from example 13 is that in the first step, betaine hydrochloride is replaced by L-glutamic acid.

[0049] The raw material parts in the above examples 13 to 18 and comparative examples are all mass parts.

[0050] Test Example 1: The nitrogen content, Zeta potential and water solubility of the quaternary ammonium betaine salt co-modified chitosan adjuvant prepared in the first step of Example 13 and the activated chitosan were tested, and the test results are shown in Table 1.

[0051] As can be seen from Table 1, the quaternary ammonium betaine salt co-modified chitosan adjuvant has significantly higher water solubility (33.79 mg / mL) than chitosan (insoluble in water). This indicates that the grafting reaction effectively improves the hydrophilicity of the material and enhances its suitability in a biological environment. At the same time, the Zeta potential of chitosan is -4.933 ± 1.23 mV, and the Zeta potential of the quaternary ammonium betaine salt co-modified chitosan adjuvant is 35.15 ± 1.69 mV. The significant increase in Zeta potential shows that the surface is positively charged. This change can lead to better stability and interaction ability of the material in the body, such as enhanced binding ability to cell membranes or other biological molecules.

[0052] Test Example 2: The SEM images of the quaternary ammonium betaine salt co-modified chitosan adjuvant prepared in the first step of Example 13 and 13 CNMR spectrum is shown in Figure 1 and Figure 2 .

[0053] Test Example 3: The SEM images of the antibacterial room temperature vulcanized silicone rubber prepared in Example 13 are shown in Figure 3 .

[0054] Test Example 4: The mechanical properties of the antibacterial room temperature vulcanized silicone rubber prepared in Examples 13, 16, 17, 18 and the silicone rubber obtained in Comparative Examples 1 and 2 were tested.

[0055] According to ISO 37:2005, the tensile strength of the above silicone rubber samples was measured using an INSTRON 5967 electronic universal material testing machine (USA). The test specimen type was dumbbell type I, and the crosshead speed was set to 500 mm / min. Each sample was tested at least five times to calculate the average value, and the test results of the mechanical properties of each sample are shown in Table 2.

[0056] Test Example 5: The surface hydrophobicity of the antibacterial room temperature vulcanized silicone rubber prepared in Examples 13, 16, 17, 18 and the silicone rubber obtained in Comparative Example 1 was tested.

[0057] The water contact angle of the above vulcanized silicone rubber samples was measured by a contact angle tester OCA15EC Dataphysis (Germany). Each sample was tested at least five times to calculate the average value, and the test results of the contact angle of each sample are shown in Table 2.

[0058] Test Example 6: The expansion degree test (ASTM D471) was performed on the antibacterial room temperature vulcanized silicone rubber prepared in Examples 13, 16, 17, 18 and the silicone rubber obtained in Comparative Example 1.

[0059] The above vulcanized silicone rubber samples were made into test samples (20 mm long x 20 mm wide x 2 mm thick) and immersed in toluene at room temperature for 70 hours according to ASTM D471, and the expansion degree was measured. The expansion degree (Q) was calculated as shown in Formula 1: Q = (V2-V1) / V1x100% In the formula, V1 and V2 are the volumes of the original and expanded test samples, respectively, obtained by water displacement method. V1 is obtained by V1 = (M2-M1) / p w , where M1 and M2 are the masses of the original test sample in air and distilled water, respectively, and p w is the density of water. After immersion in toluene, V2 was obtained in the same way. The swelling degree results of each sample are shown in Table 2.

[0060] Test Example 7: The hardness test was performed on the antibacterial room temperature vulcanized silicone rubber prepared in Examples 13, 16, 17, 18 and the silicone rubber obtained in Comparative Examples 1 and 2.

[0061] The hardness of the rubber vulcanized rubber was measured using a SHS-1 Shore hardness tester (GB / T 531.1-2008), each sample was tested at least five times and the average value was calculated, and the hardness test results of each sample are shown in Table 2.

[0062] Test Example 8: The antibacterial property test was performed on the antibacterial room temperature vulcanized silicone rubber prepared in Examples 13, 16, 17, 18 and the silicone rubber obtained in Comparative Examples 1 and 2.

[0063] The antibacterial property of the above silicone rubber samples was determined by the inhibition zone method, under sterile conditions, three parallel samples were made for each group, after the LB plate medium was prepared, a 6mm punch was punched, and a 6mm antibacterial silicone rubber was clamped with sterile tweezers, then 10 7 CFU / mL of E. coli and 10 8 CFU / mL of S. aureus were coated, and cultured at (37±1)℃ for 24 h, the antibacterial band width of each sample was measured, H=(D-d) / 2 (in the formula: H is the antibacterial band width, D is the average value of the outer diameter of the inhibition zone, and d is the diameter of the sample, all in millimeters mm), and the results of the antibacterial performance of each sample are shown in Table 2.

[0064] From the above examples and test examples, the technical scheme of the present application has the following beneficial effects: (1) The present application uses naturally degradable chitosan as a modified carrier of antibacterial additives, and 2,3-epoxypropyl trimethyl ammonium chloride is used to modify chitosan through amidation reaction, so that chitosan has good water solubility, effectively overcomes the defect of poor solubility of natural chitosan, is conducive to subsequent functionalization and composite processing, and improves the controllability and efficiency of the preparation process.

[0065] (2) The present application introduces 2,3-epoxypropyl trimethyl ammonium chloride, betaine salt and other functional materials with high safety to modify chitosan, and the obtained antibacterial quaternary ammonium salt betaine co-modified chitosan additive has excellent biocompatibility and is more suitable for the development of human body contact or degradable materials.

[0066] (3) The present application grafts betaine to chitosan grafted with 2,3-epoxypropyl trimethyl ammonium chloride through esterification reaction, so that the chitosan has more spectrum efficient antibacterial activity, and the obtained antibacterial quaternary ammonium salt betaine co-modified chitosan gives RTV silicone rubber excellent antibacterial ability after being blended with RTV silicone rubber, effectively inhibits bacterial growth, and is suitable for medical, food contact and other high hygiene requirement fields.

[0067] (4) The preparation process of the present application adopts conventional chemical reaction and physical mixing process, the reaction condition is mild, the raw materials are easy to obtain, and the production can be easily scaled up, so it has good industrial application prospect. The proportion of each component, reaction time and temperature can be flexibly adjusted, so that the material properties such as antibacterial strength and mechanical properties can be optimized as needed to meet the needs of various scenes. The obtained quaternary ammonium salt betaine salt co-modified chitosan additive can form a uniform composite material after being mixed with RTV silicone rubber, avoiding the problem of phase separation, and ensuring the balance of mechanical properties and antibacterial properties.

[0068] In summary, the present application takes environment-friendly and biocompatible chitosan as an antibacterial skeleton, grafts quaternary ammonium salt and betaine hydrochloride on the basis of chitosan, synthesizes a new type of chitosan derivative organic antibacterial agent, and utilizes the mutual promotion of quaternary ammonium salt and betaine to antibacterial activity. The quaternary ammonium salt betaine co-modified chitosan additive is blended with RVT silicone rubber to obtain antibacterial silicone rubber with excellent antibacterial performance. The quaternary ammonium salt betaine co-modified chitosan additive has good compatibility and outstanding antibacterial effect, is green and safe, and improves the crosslinking performance and mechanical properties of RTV silicone rubber.

[0069] The above technical features respectively constitute each embodiment of the present application, which has strong adaptability and implementation effect, and unnecessary technical features can be added or reduced according to actual needs to meet the needs of different situations.

Claims

1. A method for preparing an antibacterial room temperature vulcanized silicone rubber, characterized in that The following steps are involved: The first step is to mix betaine salt and esterification catalyst, activate them, add quaternary ammonium salt to modify chitosan, and obtain quaternary ammonium salt betaine salt co-modified chitosan additive after reaction; In the second step, the required amount of RTV silicone rubber, quaternary ammonium betaine salt co-modified chitosan additive and cross-linking agent are mixed, a cross-linking catalyst is added, and the mixture is evenly mixed to form a film, dried and cured to obtain the antibacterial room temperature vulcanized silicone rubber.

2. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to claim 1, characterized in that In the first step, the quaternary ammonium salt-modified chitosan is chitosan grafted with 2,3-epoxypropyltrimethylammonium chloride.

3. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to claim 2, wherein Chitosan grafted with 2,3-epoxypropyltrimethylammonium chloride was prepared by the following method: Adding a required amount of activated chitosan and 2,3-epoxypropyltrimethylammonium chloride into a reaction solvent, and performing an amidation reaction to obtain chitosan grafted with 2,3-epoxypropyltrimethylammonium chloride; The reaction temperature of the amidation reaction is 60°C to 80°C, and the time is 10h to 24h; The mass ratio of the chitosan to 2,3-epoxypropyltrimethylammonium chloride is 1 to 16:4; The activated chitosan is prepared according to the following steps: dissolving chitosan in an acidic aqueous solution, adjusting the pH value of the solution to 9 to 11 with NaOH, and washing and drying the chitosan after precipitation to obtain activated chitosan; the acidic aqueous solution is a hydrochloric acid aqueous solution, an acetic acid aqueous solution or a sulfuric acid aqueous solution, and the volume fraction of the acidic aqueous solution is 1% to 5%; The reaction solvent is a mixture of acetic acid and isopropanol in a volume ratio of 1 to 2:

100.

4. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 3, characterized in that In the first step, the esterification reaction catalyst is one or more of dicyclohexylcarbodiimide, lutidine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and N-hydroxysuccinimide.

5. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to claim 4, characterized in that The esterification reaction catalyst is a mixture of dicyclohexylcarbodiimide and lutidine in a mass ratio of 2:0.

7.

6. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 5, characterized in that In the first step, the mass ratio of the quaternary ammonium salt modified chitosan, the betaine salt and the esterification reaction catalyst is 0.2:0.1 to 0.8:0.2 to 0.

8.

7. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 6, characterized in that In the first step, activation is performed by mixing and activating at room temperature for 20 to 45 minutes; Or / and, in the first step, the reaction temperature is 60° C. to 80° C., and the reaction time is 4 h to 12 h.

8. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 7, characterized in that In the second step, the crosslinking agent is one or both of methyl high hydrogen silicone oil and hydroxyl terminated silicone oil; or / and, in the second step, the cross-linking catalyst is one or more of dibutyltin dilaurate, dibutyltin bis(acetylacetonate), and isopropyl titanate; or / and, in the second step, the curing temperature is 25°C to 70°C.

9. The method for preparing the antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 8, characterized in that In the second step, the mass ratio of the RTV silicone rubber, the quaternary ammonium salt betaine salt co-modified chitosan additive, the crosslinking agent and the crosslinking catalyst is 10:1 to 4:0.2 to 0.3:0.03 to 0.

07.

10. An antibacterial room temperature vulcanized silicone rubber prepared according to the method for preparing antibacterial room temperature vulcanized silicone rubber according to any one of claims 1 to 9.

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