Food-grade antibacterial mildew-proof silica gel cushion filler and preparation method thereof

Abstract

The invention provides a food-grade antibacterial mildew-proof silica gel cushion filler and a preparation method thereof, and belongs to the field of compositions of high-molecular compounds. The preparation method comprises the following steps: reacting chitosan with quaternary ammonium salt to generate chitosan quaternary ammonium salt; then activating the silica gel by using a coupling agent; finally, bridging by utilizing a cross-linking agent; finally, the chitosan quaternary ammonium salt is linked with the silica gel; in addition, the silica gel pad is compatible with inorganic antibacterial agents such as silver ions, so that the silica gel pad with sufficient antibacterial and mildew-proof capabilities is obtained; and the device can be used for multiple different scenes such as food storage, tableware and tap water pipes.

Description

Technical Field

[0001] The present invention belongs to the field of compositions of high molecular compounds, and particularly relates to a food-grade antibacterial and mildew-proof silicone pad filler and a preparation method thereof. Background Art

[0002] Silicone rubber is a high molecular elastomer with a main chain composed of alternating silicon (Si) and oxygen (O) atoms. Usually, two organic groups (such as methyl, vinyl, etc.) are connected to the silicon atoms. The special molecular structure endows it with the characteristics of both organic and inorganic materials. Due to its unique chemical structure, silicone rubber exhibits excellent heat resistance, chemical stability, electrical insulation, and air permeability; thus, it has important applications in multiple fields:

[0003] Industry and electronics: used for cable accessories, composite insulators, heat-conducting materials (such as LED heat dissipation potting) and automotive seals.

[0004] Medical and biological: manufacturing artificial organs (such as blood vessels, trachea), noise-proof earplugs, etc., relying on its biocompatibility and anticoagulant properties.

[0005] Aerospace: high-temperature resistant components (such as engine seals) and radiation-resistant materials.

[0006] Daily life: food-grade silicone is used for kitchen utensils, baby products, and in the construction field for fireproof coatings and sealants.

[0007] Food-grade silicone needs to pass more stringent chemical element control certifications (such as lead and mercury content), while environmental protection grade and medical grade are respectively for industrial seals and higher biocompatibility requirements. And for food-grade or used in related fields such as water pipes, etc., there is the following room for improvement:

[0008] Ability to withstand extreme environments: Food-grade silicone rubber needs to maintain flexibility and stability under extreme conditions such as high temperature (such as baking), low temperature (such as freezing), and chemical corrosion (such as grease), which puts extremely high requirements on the heat resistance, antioxidant property, and tear resistance of the material.

[0009] Low volatile organic compounds (VOCs) control: To ensure that the material is non-toxic and odorless, it is necessary to reduce the release of VOCs during the production process, which poses challenges to the raw material formula and vulcanization process.

[0010] Biocompatibility and safety: Medical and food contact scenarios require the material to pass strict biocompatibility tests and avoid the residue of toxic auxiliaries (such as peroxides). Summary of the Invention

[0011] The first object of the present invention is to provide a preparation method of a food-grade antibacterial and mildew-proof silicone pad filler, including the steps:

[0012] S1: Weigh according to parts by mass:

[0013] Component A:

[0014]

[0015] Component B:

[0016] Vinyl polysiloxane 50 - 60

[0017] Fumed silica 20 - 30

[0018] Silane coupling agent 0.8 - 2.4

[0019] Component C:

[0020] Chitosan 0.75 - 1.20

[0021] Quaternary ammonium salt 0.25 - 0.40

[0022] Silane coupling agent 0.6 - 2.0

[0023] S2: Mix Component A and Component B and then inject them into a mold, heat and hold pressure; obtain a cured silicone component;

[0024] S3: Immerse the silicone component in an ethanol solution of silane coupling agent, clean and dry it to obtain amino-functionalized silica gel;

[0025] S4: React Component C under alkaline conditions to obtain chitosan quaternary ammonium salt;

[0026] S5: The amino-functionalized silica gel and chitosan quaternary ammonium salt undergo a Schiff base reaction under the action of glutaraldehyde; obtain a food-grade antibacterial and antifungal silicone pad filler.

[0027] Preferably, the particle size of the nano silver is 15 nm - 30 nm.

[0028] Preferably, the mass content of platinum in the platinum catalyst ≥ 1000 ppm.

[0029] Preferably, D97 of the fumed silica is 20 μm.

[0030] Preferably, the chitosan is oligochitosan and the viscosity is 200 - 400 Pa·s.

[0031] Preferably, the quaternary ammonium salt is dodecyl dimethyl benzyl ammonium chloride.

[0032] Preferably, in step S3, the coupling agent concentration of the ethanol solution of silane coupling agent is 1 - 5 wt%, heated to 60 ± 2.5 °C, and reacted for at least 6 h.

[0033] Preferably, in the step S4, chitosan and quaternary ammonium salt react under alkaline conditions; the conditions are heating to 60±2.5°C, pH 9-11, and reacting for at least 8 hours.

[0034] Preferably, in the step S5, the aminated silica gel and chitosan quaternary ammonium salt are dispersed in a buffer solution with a pH of 7-8, at least 0.5 wt% of glutaraldehyde is added, and the reaction is carried out for at least 4 hours.

[0035] The present invention also provides a food-grade antibacterial and mildew-proof silica gel pad filler prepared by the foregoing method.

[0036] There are three antibacterial and mildew-proof components in the present invention, namely nano silver, quaternary ammonium salt and chitosan; since nano silver does not need to undergo a chemical reaction and only needs physical mixing to exert its antibacterial effect; it can be mixed as a raw material before the curing of silica gel.

[0037] Silica gel itself is chemically inert and difficult to directly react with quaternary ammonium salt or chitosan. If adsorbed by physical adsorption or electrostatic interaction, it is easy to fall off; it cannot exert a long-term antibacterial and mildew-proof effect. To solve this problem, the present invention first uses chitosan to introduce quaternary ammonium salt groups through quaternization reaction to generate positively charged chitosan quaternary ammonium salt. Then, the surface of silica gel is activated by a coupling agent to introduce amino (-NH 2 ) groups; finally, a cross-linking agent is used to carry out a Schiff base reaction between the aminated silica gel and chitosan quaternary ammonium salt; to achieve the grafting of chitosan quaternary ammonium salt.

[0038] In the present invention:

[0039] Fumed silica is used as a raw material to improve mechanical properties and adsorption capacity.

[0040] The platinum catalyst is used as a catalyst for addition-type silica gel. To ensure its effect, the mass content of platinum needs to be ≥1000 ppm.

[0041] The beneficial technical effects of the present invention are at least as follows:

[0042] In the present invention, chitosan reacts with quaternary ammonium salt to generate chitosan quaternary ammonium salt; then a coupling agent is used to activate silica gel; finally, a cross-linking agent is used for bridging; finally, chitosan quaternary ammonium salt is linked to silica gel; in addition, it is simultaneously compatible with inorganic antibacterial agents such as silver ions to obtain a silica gel pad with sufficient antibacterial and mildew-proof ability; it can be used in multiple different scenarios such as food storage, tableware, and water pipes. Detailed implementation mode

[0043] To better understand the present invention, the present invention will be further described below with specific serial numbers. The terms used in the serial numbers are for describing specific specific implementation schemes and do not constitute a limitation on the protection scope of the present invention.

[0044] In this specific embodiment, without other special circumstances, the components used are as follows:

[0045] Vinyl polysiloxane: viscosity at 25 °C is 5000 mPa·s - 10000 mPa·s; mass percentage of vinyl is ≥0.4.

[0046] Fumed silica: cumulative particle size distribution number D97 = 20 μm.

[0047] Silver nanoparticles: particle size is 15 nm - 30 nm.

[0048] Platinum catalyst: chloroplatinic acid tetramethyldivinyldisiloxane complex, mass content of platinum is ≥1000 ppm.

[0049] Silane coupling agent: 3-aminopropyltriethoxysilane.

[0050] Chitosan: food-grade chitosan oligosaccharide, and viscosity is medium viscosity 200 - 400 Pa·s.

[0051] Quaternary ammonium salt: dodecyl dimethyl benzyl ammonium chloride

[0052] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 1

[0053] Step S1: Weigh the raw materials

[0054] Component A:

[0055]

[0056] Component B:

[0057] Vinyl polysiloxane 50

[0058] Fumed silica 20

[0059] Silane coupling agent 0.8

[0060] Component C:

[0061] Chitosan 0.75

[0062] Quaternary ammonium salt 0.25

[0063] Silane coupling agent 0.6

[0064] S2: Mix Component A and Component B and stir evenly, then inject the mixture into an injection machine, and cure under pressure at the reaction temperature to obtain a cured silica gel component; set the reaction temperature to 170 °C and the vulcanization time to 15 min.

[0065] S3: Soak the silica gel component in an ethanol solution of 1 wt% silane coupling agent, heat it to 60 °C, and keep the temperature fluctuation within ±2.5 °C for 6 h; wash it successively with ethanol and distilled water, and dry it to obtain amino-functionalized silica gel;

[0066] S4: Heat component C to 60 °C, keep the temperature fluctuation within ±2.5 °C, and adjust the pH = 9 with NaOH,

[0067] React for 8 h; obtain quaternary ammonium salt of chitosan;

[0068] S5: Disperse the amino-functionalized silica gel and the quaternary ammonium salt of chitosan in a buffer solution with pH 7 - 8, add 0.5 wt% glutaraldehyde, and react at room temperature for 4 h. After the reaction, wash it successively with ethanol and distilled water, and then dry it with hot air; obtain the food-grade antibacterial and mildew-proof silica gel pad filler

[0069] Example 2 Preparation of food-grade antibacterial and mildew-proof silica gel pad filler

[0070] The difference from Example 1 is that in step S1, the raw materials are weighed according to the following parts by mass

[0071] Component A:

[0072]

[0073] Component B:

[0074] Vinyl polysiloxane 55

[0075] Fumed silica 25

[0076] Silane coupling agent 1.6

[0077] Component C:

[0078] Chitosan 1.00

[0079] Quaternary ammonium salt 0.34

[0080] Silane coupling agent 1.2

[0081] Example 3 Preparation of food-grade antibacterial and mildew-proof silica gel pad filler

[0082] The difference from Example 1 is that in step S1, the raw materials are weighed according to the following parts by mass

[0083] Component A:

[0084]

[0085] Component B:

[0086] Vinyl polysiloxane 60

[0087] Fumed silica 30

[0088] Silane coupling agent 2.4

[0089] Component C:

[0090] Chitosan 1.20

[0091] Quaternary ammonium salt 0.40

[0092] Silane coupling agent 2.0

[0093] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 4

[0094] The difference from Example 1 is that in step S1, Component C is not added, and steps S4 and S5 are not carried out.

[0095] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 5

[0096] The difference from Example 1 is that in step S1, Component A does not contain nano silver.

[0097] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 6

[0098] The difference from Example 1 is that in step S1, Component C is not contained, and an equal amount of chitosan (0.75 parts) in the original Component C is added to Component A.

[0099] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 7

[0100] The difference from Example 1 is that in step S1, Component C is not contained, and an equal amount of quaternary ammonium salt (0.25 parts) in the original Component C is added to Component A.

[0101] Preparation of food-grade antibacterial and mildew-proof silica gel pad filler in Example 8

[0102] The difference from Example 1 is that in step S1, Component C is not contained, and an equal amount of quaternary ammonium salt (0.25 parts) and chitosan (0.75 parts) in the original Component C are added to Component A; and steps S4 and S5 are not carried out.

[0103] Preparation of silica gel pad filler in Example 9

[0104] The difference from Example 1 is that in step S1, the weighing amount of Component C is modified to:

[0105] Chitosan 0.45

[0106] Quaternary ammonium salt 0.10

[0107] Silane coupling agent 0.4.

[0108] Preparation of silica gel pad filler in Example 10

[0109] The difference from Example 1 is that in step S1, nano silver in component C and component A is not added; and steps S4 and S5 are not carried out.

[0110] Performance Test

[0111] I. Antibacterial Performance

[0112] Referring to the standard of GB / T21510-2024 "Test Method for Antibacterial Properties of Nano-Inorganic Materials Appendix B - Oscillation Method", the antibacterial rate of the antibacterial silica gel was detected; the test time was 24h.

[0113] The test strains were: Candida albicans, 9.9X10 5 CFU / mL

[0114] Escherichia coli, 2.3X10 5 CFU / mL

[0115] Staphylococcus aureus, 3.5X10 5 CFU / mL.

[0116] II. Persistent Antibacterial Performance

[0117] After boiling the sample in a constant temperature water bath at 55°C for 15 days, referring to the standard of GB / T21510-2024 "Test Method for Antibacterial Properties of Nano-Inorganic Materials Appendix B - Oscillation Method", the antibacterial rate of the antibacterial silica gel was detected; the test time was 24h.

[0118] III. Safety Detection

[0119] Detection Conclusion: According to the "Hygienic Safety Evaluation Specification for Drinking Water Distribution Equipment and Protective Materials"

[0120] (2001), "Hygienic Standard for Drinking Water" (GB 5749-2022) and "Standard Test Methods for Drinking Water" (GB / T5750-2023), the hygienic safety of the accepted samples was tested.

[0121] The test methods adopted were "Standard Test Methods for Drinking Water Part 4: Sensory Characteristics and Physical Indexes" (GB / T5750.4-2023), "Standard Test Methods for Drinking Water Part 6: Metal and Metalloid Indexes" (GB / T5750.6-2023), "Standard Test Methods for Drinking Water Part 7: Comprehensive Indexes of Organic Substances" (GB / T5750.7-2023), "Standard Test Methods for Drinking Water Part 8: Organic Substance Indexes"

[0122] (GB / T5750.8-2023), "Standard Test Methods for Drinking Water Part 10: Disinfection By-Product Indexes" (GB / T5750.10-2023):

[0123] The sample treatment method is carried out in accordance with Appendix A of the "Hygienic Safety Evaluation Specification for Drinking Water Distribution Equipment and Protective Materials" (2001); the sample immersion water is prepared according to Section A1.3.1 of Appendix A; the immersion time is 24 h ± 1 h, and the immersion temperature is 25°C ± 5°C.

[0124] The test results are shown in Table 1 and Table 2 below respectively.

[0125] Table 1 Test Results of Antibacterial Performance and Persistent Antibacterial Performance

[0126]

[0127]

[0128] Table 2 Safety Detection

[0129]

[0130]

[0131] Antibacterial conclusion: As shown in the results of Table 1, in the formulation of the present invention, the dosages of the three different antibacterial components are relatively low; the absence of any one antibacterial component will lead to a significant decrease in antibacterial performance (Examples 4 and 5); and the results of Example 9 show that there is a lower limit for the addition amount of the antibacterial component of the present invention, and if it is lower than the lower limit, it will lead to insufficient antibacterial performance; the results of Example 10 show that

[0132] From the comparison between Examples 6, 7 and Example 1, it can be seen that in the case of the same addition amount of antibacterial components, the absence of quaternary ammonium salt or chitosan will lead to the antibacterial performance not meeting the relevant requirements. And the results of Example 10 show that the microporous structure and air permeability of silica gel may reduce the environment for bacterial growth (such as adsorbing moisture or organic matter), but this belongs to passive inhibition, not active antibacterial; the experimental results are also consistent with the conclusion in "Preparation of Rare Earth-Zinc Antibacterial Silica Gel and Its Application in Silicone Rubber, Zhang Bin, Mao Huaming, etc., Rare Earth Compounds and Applications" that pure silica gel itself has no bactericidal ability.

[0133] The results of Example 8 show that when chitosan and quaternary ammonium salt are directly mixed and added to the formulation, the antibacterial performance meets the relevant requirements in the initial stage, but its attenuation is extremely rapid and drops to the same level as that of only adding nano-silver; it can be seen that when no specific grafting reaction is carried out, it cannot be retained in silica gel for a long time; nor can it achieve the corresponding antibacterial function.

[0134] Safety conclusion: The results show that: color, turbidity, odor and taste, visible substances to the naked eye, pH, total dissolved solids, permanganate index (in terms of O 2The indicators of arsenic, cadmium, chromium (hexavalent), aluminum, lead, mercury, chloroform and volatile phenols (calculated as phenol) all meet the requirements of the "Hygienic Safety Evaluation Specification for Drinking Water Distribution Equipment and Protective Materials" (2001) and the "Hygienic Standard for Drinking Water" (GB5749-2022) for drinking water distribution equipment.

[0135] It should be noted that the above-described work process is only illustrative and does not limit the protection scope of the present invention. In actual applications, those skilled in the art can select some or all of them according to actual needs to achieve the purpose of the solution of this embodiment, and no limitation is made here.

[0136] In addition, for the technical details not described in detail in this embodiment, reference can be made to the parameter operation method provided in any embodiment of the present invention, and no further elaboration will be made here.

[0137] It should be noted that in this article, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or system. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or system including that element.

[0138] The serial numbers of the above embodiments of the present invention are only for description and do not represent the superiority or inferiority of the embodiments.

[0139] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the specification of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing food-grade antibacterial and mildew-proof silica gel padding, characterized in that: Includes steps: S1: Weigh by weight: Component A: Component B: Vinyl polysiloxane 50-60 White carbon black 20-30 Silane coupling agent 0.8-2.4 C component: Chitosan 0.75-1.20 Quaternary ammonium salt 0.25-0.40 Silane coupling agent 0.6-2.0 S2: Mix component A and component B and inject them into the mold, heat and maintain pressure to obtain a cured silicone component; S3: The silica gel element is soaked in an ethanol solution of a silane coupling agent with silica gel, and then washed and dried to obtain amino silica gel; S4: Component C reacts under alkaline conditions to obtain chitosan quaternary ammonium salt; S5: Aminated silica gel and chitosan quaternary ammonium salt react with glutaraldehyde to produce a Schiff base reaction; a food-grade antibacterial and anti-mildew silica gel padding is obtained.

2. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: The particle size of the nano silver is 15nm-30nm.

3. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: The mass content of platinum in the platinum catalyst is ≥1000ppm.

4. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: The D97 of the white carbon is 20 μm.

5. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: The chitosan is oligomeric chitosan, and has a viscosity of 200-400 Pa.s.

6. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: The quaternary ammonium salt is dodecyl dimethyl benzyl ammonium chloride.

7. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: In step S3, the silane coupling agent concentration of the ethanol solution is 1-5 wt %, and the solution is heated to 60±2.5° C. and reacted for at least 6 hours.

8. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: In step S4, chitosan reacts with quaternary ammonium salt under alkaline conditions; the conditions are heating to 60±2.5° C., pH 9-11, and reacting for at least 8 hours.

9. The method for preparing the food-grade antibacterial and mildew-proof silica gel padding according to claim 1, characterized in that: In the step S5, the amino silica gel and the chitosan quaternary ammonium salt are dispersed in a buffer solution with a pH of 7 to 8, and at least 0.5 wt % of glutaraldehyde is added to react for at least 4 hours.

10. A food-grade antibacterial and mildew-proof silica gel padding, made by the preparation method according to any one of claims 1 to 9.

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