Moisture-proof antibacterial hot melt adhesive and preparation method thereof

Abstract

The invention relates to the technical field of hot melt adhesives, in particular to a damp-proof antibacterial hot melt adhesive and a preparation method thereof. 100 parts of a vinyl acetate copolymer, 20-40 parts of fluorosilicone resin, 5-8 parts of modified silver sodium zirconium phosphate and 0.5-2 parts of an antioxidant; the preparation method of the modified silver sodium zirconium phosphate comprises the following steps: A1, adding silver sodium zirconium phosphate into an ethanol solution, dropwise adding an amino silane modifier, stirring and reacting at 25-35 DEG C for 3-5 hours, filtering, washing and drying to obtain amino modified silver sodium zirconium phosphate; a2, adding the amino modified silver sodium zirconium phosphate into absolute ethyl alcohol, stirring and dispersing, then adding vanillin, stirring and reacting at 60-70 DEG C for 3-5 hours, filtering, washing and drying to obtain the modified silver sodium zirconium phosphate. According to the invention, ethylene is scientifically compounded; the hot melt adhesive which is damp-proof, hydrophobic, anti-fouling, antibacterial and mildew-proof is prepared from the raw materials, vinyl acetate copolymer, fluorosilicone resin and modified silver sodium zirconium phosphate.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesives, and in particular to a moisture-proof and antibacterial hot melt adhesive and a preparation method thereof. Background Art

[0002] EVA hot melt adhesive is a solid fusible polymer without solvents and water. It is solid at room temperature and becomes a flowable melt when heated to a certain temperature. It has advantages such as environmental protection, high adhesion performance, and barrier properties, and is widely used in fields such as packaging, bookbinding, furniture making, rubber bonding, and electronic components. In a humid environment, EVA hot melt adhesive is prone to breeding bacteria and molds, and cannot meet the application requirements in fields such as packaging, textiles, and furniture.

[0003] In order to meet the market demand for antibacterial hot melt adhesives, various antibacterial hot melt adhesives have emerged in an endless stream. For example, the invention patent with the application number CN201710511775.9 discloses an antibacterial hot melt adhesive and a preparation method thereof. By adding zinc oxide and nano-titanium dioxide to the adhesive material, its antibacterial performance is improved. As is well known, nano-titanium dioxide, as a photocatalyst, is prone to cause oxidative decomposition of the hot melt adhesive when in long-term contact with it.

[0004] Silver zirconium sodium phosphate is a silver-based inorganic antibacterial agent with layered zirconium phosphate as the carrier. It uses silver ions as antibacterial ions and has advantages such as high safety and good heat resistance. It can be added to various resins to play a broad-spectrum antibacterial role. Therefore, the prior art is also keen to use silver zirconium sodium phosphate as an antibacterial agent for hot melt adhesives or organic composite materials. For example, the invention patent with the application number CN202210553433.4 discloses a preparation method and application of an antibacterial agent and a composite material containing the antibacterial agent. By compounding and plasticizing a thermoplastic elastomer material with a porous material-supported guanidine salt antibacterial agent, a silver-loaded zirconium sodium phosphate antibacterial agent, etc., and then extruding and pelletizing, a composite antibacterial masterbatch is prepared. For example, the invention patent with the application number CN202410889003.9 discloses a sustained-release antibacterial masterbatch and a preparation method thereof, using a composition containing layered zirconium phosphate and a compound containing an antibacterial metal element as the antibacterial component.

[0005] However, silver zirconium sodium phosphate inhibits and kills bacteria by releasing silver ions. However, as the silver ions are gradually consumed, the antibacterial effect will gradually weaken. Therefore, how to improve the antibacterial performance of silver zirconium sodium phosphate and extend its sustained-release antibacterial time limit is of great significance for the long-term antibacterial of hot melt adhesives. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a moisture-proof and antibacterial hot melt adhesive and its preparation method. On the one hand, the present invention is committed to developing a new type of modified sodium zirconium phosphate silver to enhance its antibacterial performance, avoid the loss of antibacterial performance of traditional sodium zirconium phosphate silver due to silver ion loss, and extend its slow-release antibacterial time to a certain extent; on the other hand, the present invention first applies the new type of modified sodium zirconium phosphate silver to the hot melt adhesive material to prepare a hot melt adhesive with high-efficiency and long-lasting antibacterial properties. Based on the above object, the present invention provides a moisture-proof and antibacterial hot melt adhesive, which comprises the following raw materials in parts by mass: 100 parts of ethylene-vinyl acetate copolymer, 20-40 parts of fluorosilicone resin, 5-8 parts of modified sodium zirconium phosphate silver, and 0.5-2 parts of antioxidant; The preparation method of the modified sodium zirconium phosphate silver comprises the following steps: A1: Add sodium zirconium phosphate silver to an ethanol solution, dropwise add an amino silane modifier, and stir and react at 25-35 °C for 3-5 h. After filtration, washing, and drying, amino-modified sodium zirconium phosphate silver is obtained; A2: Add the amino-modified sodium zirconium phosphate silver to absolute ethanol, stir and disperse it, then add vanillin, and stir and react at 60-70 °C for 3-5 h. After filtration, washing, and drying, modified sodium zirconium phosphate silver is obtained.

[0007] Further, the amino silane modifier is selected from one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0008] Further, the concentration of the ethanol solution is 30-50 wt%.

[0009] Further, the mass ratio of the sodium zirconium phosphate silver, the ethanol solution, and the amino silane modifier is 1:10:(0.2-0.3).

[0010] Further, the mass ratio of the amino-modified sodium zirconium phosphate silver, absolute ethanol, and vanillin is 1:10:(0.1-0.2).

[0011] Further, the antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and distearyl pentaerythritol diphosphite.

[0012] The present invention further provides the preparation method of the moisture-proof and antibacterial hot melt adhesive, which comprises the following steps: S1: Mix and knead the ethylene-vinyl acetate copolymer, the fluorosilicone resin, and the antioxidant to obtain a mixture; S2: At a certain temperature, mix the mixture with the modified sodium zirconium phosphate silver evenly, and then extrude and mold to obtain the moisture-proof and antibacterial hot melt adhesive.

[0013] Furthermore, the mixing and kneading temperature is 180 - 210 °C, and the rotation speed is 80 - 100 r / min.

[0014] Furthermore, the mixing temperature of the mixture and the modified sodium zirconium phosphate silver is 160 - 180 °C.

[0015] Furthermore, the extrusion molding temperature is 130 - 150 °C.

[0016] Advantages of the present invention: The present invention first applies a novel modified sodium zirconium phosphate silver antibacterial agent to hot melt adhesive materials. The modified sodium zirconium phosphate is sodium zirconium phosphate silver grafted with vanillin - amino - silane Schiff base. Compared with traditional sodium zirconium phosphate silver, the modified sodium zirconium phosphate silver has more excellent antibacterial properties, with a longer antibacterial time effect, stronger sterilization performance, and effectively delays the loss of silver ions.

[0017] The present invention prepares a moisture - proof, hydrophobic, stain - resistant, antibacterial and mildew - resistant hot melt adhesive by scientifically compounding ethylene - vinyl acetate copolymer, fluorosilicone resin, and modified sodium zirconium phosphate silver. Among them, ethylene - vinyl acetate copolymer and fluorosilicone resin serve as the hot melt adhesive substrate. The fluorosilicone resin has excellent waterproof and hydrophobic properties, endowing the hot melt adhesive with moisture - proof performance, and its low surface tension gives the hot melt adhesive certain stain - resistant properties. The modified sodium zirconium phosphate silver serves as an active antibacterial component, endowing the hot melt adhesive with long - lasting antibacterial properties.

[0018] The present invention conducts amination modification on sodium zirconium phosphate silver, grafts an amino - silane chain onto the sodium zirconium phosphate silver particles, and then further undergoes a Schiff base reaction with vanillin to generate modified sodium zirconium phosphate silver. Compared with traditional sodium zirconium phosphate silver, the modified sodium zirconium phosphate silver can antibacterial persistently and efficiently. After the hot melt adhesive prepared with it is treated in an environment with a relative humidity of 95% and a temperature of 30 °C for 90 days, it can still maintain an antibacterial rate of more than 96.87% against Escherichia coli and more than 97.22% against Staphylococcus aureus. The reason for the analysis may be that The structure of the external vanillin-aminosilane Schiff base grafted on its exterior also has a certain protective effect on the loaded silver ions, inhibiting their slow release. On the other hand, the Schiff base has a chelating effect on the excess free silver ions released during slow release, forming a Schiff base-silver ion complex structure. From this aspect, the "recovery and reuse" of silver ions is achieved, delaying the loss of silver ions, and thus significantly improving the antibacterial performance and prolonging the antibacterial time limit. At the same time, vanillin-aminosilane Schiff base and silver sodium zirconium phosphate have a synergistic antibacterial effect. The reason may be that vanillin itself has antibacterial properties and reacts with the amino groups on the surface of silver sodium zirconium phosphate to form a vanillin Schiff base structure with dual synergistic antibacterial effects, further improving its antibacterial performance. Combining with the silver ions in the innermost layer, an antibacterial agent similar to the multi-layer synergistic antibacterial effect of vanillin-Schiff base-silver ions is created, thereby effectively improving the antibacterial performance of the hot melt adhesive. Detailed implementation mode

[0019] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0020] Example 1 A method for preparing a moisture-proof and antibacterial hot melt adhesive includes the following steps: S1: Add silver sodium zirconium phosphate to a 30 wt% ethanol solution, dropwise add γ-aminopropyltrimethoxysilane, and stir and react at 25 °C for 3 h. After filtration, washing and drying, amino-modified silver sodium zirconium phosphate is obtained; the mass ratio of silver sodium zirconium phosphate, ethanol solution, and γ-aminopropyltrimethoxysilane is 1:10:0.2; S2: Add amino-modified silver sodium zirconium phosphate to absolute ethanol, stir and disperse it, then add vanillin, and stir and react at 60 °C for 3 h. After filtration, washing and drying, modified silver sodium zirconium phosphate is obtained; the mass ratio of amino-modified silver sodium zirconium phosphate, absolute ethanol, and vanillin is 1:10:0.1; S3: Prepare materials according to the following mass parts: 100 parts of ethylene-vinyl acetate copolymer, 20 parts of fluorosilicone resin, 5 parts of modified silver sodium zirconium phosphate, and 0.5 part of 2,6-di-tert-butyl-p-cresol; S4: Under the conditions of a temperature of 180 °C and a rotation speed of 80 r / min, mix and knead the ethylene-vinyl acetate copolymer, fluorosilicone resin, and 2,6-di-tert-butyl-p-cresol to obtain a mixture; S5: At 160 °C, mix the mixture with modified silver sodium zirconium phosphate evenly, and then extrude and mold at 130 °C to obtain a moisture-proof and antibacterial hot melt adhesive.

[0021] Example 2 A method for preparing a moisture-proof and antibacterial hot melt adhesive includes the following steps: S1: Add silver sodium zirconium phosphate to a 40 wt% ethanol solution, dropwise add γ-aminopropyltriethoxysilane, and stir and react at 30 °C for 4 h. After filtration, washing, and drying, obtain amino-modified silver sodium zirconium phosphate; the mass ratio of silver sodium zirconium phosphate, ethanol solution, and γ-aminopropyltriethoxysilane is 1:10:0.25; S2: Add amino-modified silver sodium zirconium phosphate to absolute ethanol, stir and disperse, then add vanillin, and stir and react at 60 - 70 °C for 3 - 5 h. After filtration, washing, and drying, obtain modified silver sodium zirconium phosphate; the mass ratio of amino-modified silver sodium zirconium phosphate, absolute ethanol, and vanillin is 1:10:0.15; S3: Prepare materials according to the following mass parts: 100 parts of ethylene-vinyl acetate copolymer, 30 parts of fluorosilicone resin, 7 parts of modified silver sodium zirconium phosphate, and 1 part of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; S4: Under the conditions of a temperature of 200 °C and a rotation speed of 100 r / min, mix and knead the ethylene-vinyl acetate copolymer, fluorosilicone resin, and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to obtain a mixture; S5: At 170 °C, mix the mixture with modified silver sodium zirconium phosphate evenly, and then extrude and mold at 135 °C to obtain a moisture-proof and antibacterial hot melt adhesive.

[0022] Example 3 A method for preparing a moisture-proof and antibacterial hot melt adhesive, comprising the following steps: S1: Add silver sodium zirconium phosphate to a 50 wt% ethanol solution, dropwise add N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and stir and react at 35 °C for 5 h. After filtration, washing, and drying, obtain amino-modified silver sodium zirconium phosphate; the mass ratio of silver sodium zirconium phosphate, ethanol solution, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is 1:10:0.3; S2: Add amino-modified silver sodium zirconium phosphate to absolute ethanol, stir and disperse, then add vanillin, and stir and react at 70 °C for 5 h. After filtration, washing, and drying, obtain modified silver sodium zirconium phosphate; the mass ratio of amino-modified silver sodium zirconium phosphate, absolute ethanol, and vanillin is 1:10:0.2; S3: Prepare materials according to the following mass parts: 100 parts of ethylene-vinyl acetate copolymer, 40 parts of fluorosilicone resin, 8 parts of modified silver sodium zirconium phosphate, and 2 parts of distearyl pentaerythritol diphosphite; S4: Under the conditions of a temperature of 210 °C and a rotation speed of 100 r / min, mix and knead the ethylene-vinyl acetate copolymer, fluorosilicone resin, and distearyl pentaerythritol diphosphite to obtain a mixture; S5: At 180 °C, after uniformly mixing the mixture with silver-modified sodium zirconium phosphate, extrude it at 140 °C to obtain a moisture-proof and antibacterial hot melt adhesive.

[0023] Comparative Example 1 is the same as Example 1, except that: silver sodium zirconium phosphate is used to replace the silver-modified sodium zirconium phosphate in Example 1. Its preparation method includes the following steps: S1: Prepare materials according to the following parts by mass: 100 parts of ethylene-vinyl acetate copolymer, 20 parts of fluorosilicone resin, 5 parts of silver sodium zirconium phosphate, and 0.5 part of 2,6-di-tert-butyl-p-cresol; S2: Under the conditions of a temperature of 180 °C and a rotation speed of 80 r / min, mix and knead the ethylene-vinyl acetate copolymer, fluorosilicone resin, and 2,6-di-tert-butyl-p-cresol to obtain a mixture; S3: At 160 °C, after uniformly mixing the mixture with silver sodium zirconium phosphate, extrude it at 130 °C to obtain a moisture-proof and antibacterial hot melt adhesive.

[0024] Comparative Example 2 is the same as Example 1, except that: propyltrimethoxysilane is used to replace γ-aminopropyltrimethoxysilane in Example 1. Its preparation method includes the following steps: S1: Add silver sodium zirconium phosphate to a 30 wt% ethanol solution, dropwise add propyltrimethoxysilane, and stir and react at 25 °C for 3 h. After filtration, washing, and drying, obtain silane-modified silver sodium zirconium phosphate; the mass ratio of silver sodium zirconium phosphate, ethanol solution, and propyltrimethoxysilane is 1:10:0.2; S2: Add the silane-modified silver sodium zirconium phosphate to anhydrous ethanol, stir and disperse it, then add vanillin, and stir and react at 60 °C for 3 h. After filtration, washing, and drying, obtain silver-modified sodium zirconium phosphate; the mass ratio of silane-modified silver sodium zirconium phosphate, anhydrous ethanol, and vanillin is 1:10:0.1; S3: Prepare materials according to the following parts by mass: 100 parts of ethylene-vinyl acetate copolymer, 20 parts of fluorosilicone resin, 5 parts of silver-modified sodium zirconium phosphate, and 0.5 part of 2,6-di-tert-butyl-p-cresol; S4: Under the conditions of a temperature of 180 °C and a rotation speed of 80 r / min, mix and knead the ethylene-vinyl acetate copolymer, fluorosilicone resin, and 2,6-di-tert-butyl-p-cresol to obtain a mixture; S5: At 160 °C, after uniformly mixing the mixture with silver-modified sodium zirconium phosphate, extrude it at 130 °C to obtain a moisture-proof and antibacterial hot melt adhesive.

[0025] Antibacterial performance test: Add the sterilized nutrient agar medium to a petri dish, cover and flatten it, and add 1×10 6Suspensions of Escherichia coli and Staphylococcus aureus at CFU / mL were respectively spread evenly on the culture medium to form a bacterial liquid film. The hot-melt adhesive materials of Examples 1-3 and Comparative Examples 1-2 were added to the petri dishes, and the petri dishes were placed in a constant temperature incubator at 37°C for 24 h. The colony concentration was observed and recorded, and the initial antibacterial rate was calculated. Then, the hot-melt adhesive materials of Examples 1-3 and Comparative Examples 1-2 were respectively placed in an environment with a relative humidity of 95% and a temperature of 30°C. After standing for 30 d and 90 d, the surface of the hot-melt adhesive material was rinsed and wiped clean, and then the antibacterial rate was determined according to the above antibacterial performance test.

[0026] The test results are shown in the following table: As can be seen from the above table, the moisture-proof and antibacterial hot-melt adhesive prepared by the present invention has excellent antibacterial properties. After being treated in an environment with a relative humidity of 95% and a temperature of 30°C for 90 d, it can still maintain an antibacterial rate of more than 96.87% against Escherichia coli and more than 97.22% against Staphylococcus aureus. After being treated for 90 d, the antibacterial rates of Comparative Example 1 and Comparative Example 2 against Escherichia coli and Staphylococcus aureus dropped sharply. Especially for Comparative Example 1 using silver zirconium sodium phosphate as the antibacterial agent, the reason may be that the silver zirconium sodium phosphate in Comparative Example 1 has no surface treatment or protection, and the silver ions in it can be released faster under wet conditions. While the silver zirconium sodium phosphate in Comparative Example 2 is surface-treated with propyltrimethoxysilane, which is equivalent to having an additional silane protective film. Therefore, to a certain extent, the release of silver ions is inhibited.

[0027] In addition, by comparing the data of Example 1 and Comparative Example 2, it can be seen that the initial antibacterial rate of Example 1 is also significantly higher than that of Comparative Example 2. The reason may be that in Example 1, the silver zirconium sodium phosphate is amino-modified, an amino-silane chain is grafted on the silver zirconium sodium phosphate particles, and then a Schiff base reaction is further carried out with vanillin to generate a vanillin Schiff base structure with a dual synergistic antibacterial effect. Combining with the silver ions in the innermost layer, an antibacterial agent similar to a multi-layer synergistic antibacterial structure of vanillin-Schiff base-silver ions is created, thereby effectively improving the antibacterial performance of the hot-melt adhesive. At the same time, compared with Comparative Example 2, Example 1 still has a high-level antibacterial effect after being treated for 90 d, indicating that the moisture-proof and antibacterial hot-melt adhesive prepared by the present invention can also have long-lasting antibacterial properties in a humid environment. The reason may be that on the one hand, the structure of vanillin Schiff base of amino-silane grafted on the outside of silver zirconium sodium phosphate also has a certain protective effect on the loaded silver ions, inhibiting their slow release. On the other hand, the Schiff base has a chelating effect on the excess free silver ions released, forming a structure of Schiff base-silver ion complex, realizing the "recovery and reuse" of silver ions, delaying the loss of silver ions, and thus greatly improving the antibacterial performance and prolonging the antibacterial time limit.

[0028] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0029] The present invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A moisture-proof and antibacterial hot melt adhesive, characterized in that: The method comprises the following raw materials in parts by weight: 100 parts of ethylene-vinyl acetate copolymer, 20-40 parts of fluorosilicone resin, 5-8 parts of modified sodium zirconium phosphate silver, and 0.5-2 parts of antioxidant; The preparation method of the modified sodium silver zirconium phosphate comprises the following steps: A1: Add sodium zirconium silver phosphate to an ethanol solution, dropwise add an aminosilane modifier, stir and react at 25-35°C for 3-5 hours, filter, wash and dry to obtain amino-modified sodium zirconium silver phosphate; A2: Add amino-modified sodium zirconium silver phosphate into anhydrous ethanol, stir and disperse, then add vanillin, stir and react at 60-70°C for 3-5h, filter, wash and dry to obtain modified sodium zirconium silver phosphate.

2. The moisture-proof and antibacterial hot melt adhesive according to claim 1, characterized in that: The aminosilane modifier is selected from one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

3. The moisture-proof and antibacterial hot melt adhesive according to claim 1, characterized in that: The concentration of the ethanol solution is 30-50wt%.

4. The moisture-proof and antibacterial hot melt adhesive according to claim 1, characterized in that: The mass ratio of the sodium silver zirconium phosphate, the ethanol solution and the aminosilane modifier is 1:10:(0.2-0.3).

5. The moisture-proof and antibacterial hot melt adhesive according to claim 1, characterized in that: The mass ratio of the amino-modified sodium silver zirconium phosphate, anhydrous ethanol and vanillin is 1:10:(0.1-0.2).

6. The moisture-proof and antibacterial hot melt adhesive according to claim 1, characterized in that: The antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and dioctadecyl pentaerythritol diphosphite.

7. A method for preparing a moisture-proof and antibacterial hot melt adhesive according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: mixing and kneading ethylene-vinyl acetate copolymer, fluorosilicone resin and antioxidant to obtain a mixture; S2: At a certain temperature, the mixture is mixed evenly with modified sodium silver zirconium phosphate, and then extruded to obtain a moisture-proof and antibacterial hot melt adhesive.

8. The method for preparing moisture-proof and antibacterial hot melt adhesive according to claim 7, characterized in that: The mixing and kneading temperature is 180-210° C. and the rotation speed is 80-100 r / min.

9. The method for preparing moisture-proof and antibacterial hot melt adhesive according to claim 7, characterized in that: The mixing temperature of the mixture and the modified sodium silver zirconium phosphate is 160-180°C.

10. The method for preparing moisture-proof and antibacterial hot melt adhesive according to claim 7, characterized in that: The extrusion molding temperature is 130-150°C.

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