A kind of p-hydroxybenzoic acid and its preparation method and application

Abstract

The present invention relates to the field of chemical process technology, and in particular to a p-hydroxybenzoic acid and a preparation method and application thereof. The preparation method of the p-hydroxybenzoic acid comprises the following steps: step (1) preparing a composite salt of potassium phenolate and phenol; step (2) preparing a p-hydroxybenzoic acid dipotassium salt solution; step (3) adding activated carbon to the p-hydroxybenzoic acid dipotassium salt solution obtained in step (2) for decolorization, and then filtering the activated carbon to obtain a decolorized p-hydroxybenzoic acid dipotassium salt solution; step (4) adding dilute sulfuric acid to the decolorized p-hydroxybenzoic acid dipotassium salt solution obtained in step (3) to adjust the pH value, cooling and centrifuging to filter out potassium sulfate, and then dripping dilute sulfuric acid in the centrifuge to adjust the pH value, cooling and centrifuging to obtain a filter cake, and drying to obtain p-hydroxybenzoic acid. The present invention does not require carbon monoxide for carboxylation reaction, can avoid the safety and environmental hazards caused by carbon monoxide, the technical solution is simple in post-processing, has little environmental pollution, and has a high yield, and the modified p-hydroxybenzoic acid prepared by grafting the p-hydroxybenzoic acid prepared by the present invention has good antibacterial and antioxidant properties.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical processes, and specifically relates to p-hydroxybenzoic acid and a preparation method and application thereof. Background Art

[0002] Parahydroxybenzoic acid has many uses in industry and scientific research, mainly in the following aspects:

[0003] Chemical synthesis: As a starting material or intermediate in organic synthesis, hydroxybenzoic acid can be used to synthesize other organic compounds, such as drugs, dyes, fragrances, etc. Its hydroxyl and carboxyl functional groups give it important reactivity and selectivity in synthetic chemistry. Polymer industry: p-Hydroxybenzoic acid can be used as a monomer or functional additive for polymers. For example, it plays a role in regulating performance in the production of polymer materials such as polyester resins and polyamides. Preservative: Due to its antibacterial properties, hydroxybenzoic acid is often used as a preservative in food and cosmetics to extend the shelf life of the product. Medical field: p-Hydroxybenzoic acid and its derivatives are widely used in drug synthesis, for example, as intermediates or pharmacophores of certain drugs. In short, hydroxybenzoic acid has important application value in many industrial and scientific fields due to its diverse chemical properties and reactivity.

[0004] Therefore, there is an urgent need to optimize the preparation process of p-hydroxybenzoic acid to increase its yield and enhance its application value. Summary of the invention

[0005] The object of the present invention is to provide a p-hydroxybenzoic acid and a preparation method thereof, which has high yield, easy reaction operation, simple post-treatment and little environmental pollution.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing p-hydroxybenzoic acid, comprising the following steps:

[0008] Step (1) potassium hydroxide, phenol and water are mixed in a reaction container, stirred, heated, dehydrated at normal pressure, dehydrated at reduced pressure, dissolved, heated and azeotropically treated, and the dehydration is terminated to obtain a composite salt of potassium phenolate and phenol;

[0009] Step (2) introducing purified anhydrous carbon dioxide into the composite salt of potassium phenolate and phenol obtained in step (1), reacting, recovering phenol under reduced pressure, introducing purified anhydrous carbon dioxide again, performing a second carboxylation reaction, recovering phenol under reduced pressure, maintaining pressure, releasing pressure, draining water, and then adding water to dissolve to obtain a dipotassium p-hydroxybenzoate solution;

[0010] In the above process, when the water is drained, the excess phenol is taken out by the water vapor, and the heat is taken away by the steam to reduce the temperature of the reactor.

[0011] Step (3) adding activated carbon to the dipotassium p-hydroxybenzoate solution obtained in step (2) for decolorization, and then filtering the activated carbon to obtain a decolorized dipotassium p-hydroxybenzoate solution;

[0012] Step (4) adding dilute sulfuric acid to the decolorized dipotassium p-hydroxybenzoate solution obtained in step (3) to adjust the pH, cooling and centrifuging to remove potassium sulfate, and then continuing to dropwise add dilute sulfuric acid to the centrifuge to adjust the pH, cooling and centrifuging to obtain a filter cake, and drying to obtain p-hydroxybenzoic acid.

[0013] Preferably, in the step (1), the amount ratio of potassium hydroxide, phenol and water is 280-560g:470-940g:1-2L; stirring treatment conditions: stirring treatment temperature is 130-140°C, stirring treatment time is 0.3-0.7h; reduced pressure dehydration conditions: reduced pressure dehydration is carried out at a temperature of 130-140°C; dissolution method: after distilling water to a droplet-like state under a pressure of -0.11 to -0.09MPa, 2-4L of phenol is added to dissolve the solvent; heating azeotropic method: heating to 220-240°C to make phenol and water azeotropic; dehydration termination condition: when the liquid changes from milky white to transparent, and there is no flow under the conditions of a temperature of 220-240°C and a pressure of -0.11 to -0.09MPa, the dehydration is terminated.

[0014] Preferably, in the step (2), the temperature of the purified anhydrous carbon dioxide is 220-230°C; the reaction conditions are: the reaction pressure is 0.6-0.8MPa, and the reaction time is 1-2h; the temperature of the purified anhydrous carbon dioxide is 220-230°C; the second carboxylation reaction conditions are: the second carboxylation reaction pressure is 0.6-0.8MPa, and the second carboxylation reaction time is 0.3-0.7h; the pressure holding method is: the steam is introduced to a pressure of 0.1-0.3MPa and the pressure is maintained for 0.3-0.7h; the water is drained off at a pressure of -0.11 to -0.09MPa; the amount of water added for dissolution is 1-2L.

[0015] Preferably, in step (3), the amount of activated carbon used is 5-10 kg.

[0016] Preferably, in the step (4), the method of adding dilute sulfuric acid to the dipotassium p-hydroxybenzoate solution to adjust the pH is as follows: adding 10 wt % dilute sulfuric acid to adjust the pH to 6.6-7; the method of continuing to dropwise add dilute sulfuric acid to the centrifuge solution to adjust the pH is as follows: adding 10 wt % dilute sulfuric acid to adjust the pH to 1.3-1.7; and the drying conditions are as follows: the drying temperature is 95-105° C. and the drying time is 8-12 h.

[0017] The p-hydroxybenzoic acid is prepared by the p-hydroxybenzoic acid preparation method.

[0018] Preferably, the present invention also provides an application of modifying p-hydroxybenzoic acid to obtain modified p-hydroxybenzoic acid, comprising the following steps:

[0019] P1: 110-220 g of p-hydroxybenzoic acid and 30-60 g of the graft copolymer are added to 10-20 L of water, stirred at room temperature for 20-30 min, then 470-940 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 280-560 g of N-hydroxysuccinimide are added, activated for 2-4 h, 32.7-65.4 g of chitosan is added, stirred at room temperature for 20-28 h, centrifuged 3-5 times, and finally freeze-dried at -80 ° C for 40-56 h to obtain grafted p-hydroxybenzoic acid;

[0020] P2: Disperse 100-200g of zinc material in 1-2L of water, ultrasonically treat for 20-30min, then add 50-100g of grafted p-hydroxybenzoic acid, continue ultrasonically treating for 20-30min, irradiate with microwaves at a power of 200-300W at room temperature for 8-12min, filter, wash the filter residue alternately with ethanol and deionized water for 3-5 times, and dry at 45-55°C for 20-28h to obtain modified p-hydroxybenzoic acid.

[0021] The structural formula of modified p-hydroxybenzoic acid is as follows:

[0022]

[0023] Preferably, the method for preparing the graft copolymer comprises the following steps:

[0024] S1: 103-202 g of 4-chloromethylstyrene, 76-152 g of butyl acrylate, 36-72 g of acrylic acid and 2.2-4.4 g of azobisisobutyronitrile were mixed, magnetically stirred in a nitrogen atmosphere at 75-85° C. for 3-5 h, dialyzed with a 3-4 kDa dialysis bag for 10-14 h, and then centrifuged at a speed of 9000-11000 rpm for 4-8 min, and then precipitated with n-hexane 2-4 times, and the precipitate was vacuum dried at 35-45° C. for 8-12 h to obtain a copolymer;

[0025] S2: Dissolve 60-120 g of the copolymer in 0.6-1.2 L of 1,4-dioxane, add 180-360 g of hexadecyldimethylamine, react at 35-45° C. in a nitrogen atmosphere for 20-28 h, dialyze with a 3-4 kDa dialysis bag for 36-54 h, and freeze-dry in vacuum for 10-14 h to obtain a graft copolymer.

[0026] The structural formula of the graft copolymer is as follows:

[0027]

[0028] Through the above technical scheme, the synthesized ternary polymer is smoother but has sharper edges. The acrylic acid monomer mainly gives the polymer chain hydrophilicity and rigidity, while the butyl acrylate monomer provides elasticity and hydrophobicity to the polymer chain.

[0029] Preferably, the method for preparing the zinc material comprises the following steps:

[0030] 280-560 g of zinc chloride and 340-680 g of pyridine-2,6-dicarboxylic acid are added to 40-80 L of water, and microwave irradiation is performed at room temperature at a power of 200-300 W for 10-20 min, and the filter residue is washed alternately with ethanol and deionized water for 3-5 times, and then dried at 45-55° C. for 20-28 h to obtain a zinc material.

[0031] The structural formula of zinc material is as follows:

[0032]

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] 1. The present invention does not need to use carbon monoxide for carboxylation reaction, which can avoid the safety and environmental hazards caused by carbon monoxide. The technical solution is simple to post-process and has little pollution to the environment, and has a high yield.

[0035] 2. In the present invention, acrylic acid, butyl acrylate and 4-chloromethylstyrene are used as monomers to synthesize a terpolymer by solution polymerization, and then the terpolymer is reacted with hexadecyl dimethyl tertiary amine to obtain a more hydrophilic antibacterial graft copolymer, and the graft copolymer is covalently cross-linked with chitosan, p-hydroxybenzoic acid and zinc material to prepare a modified p-hydroxybenzoic acid containing a quaternary ammonium group; further grafting of the graft copolymer not only effectively improves the hydrophilicity of the structure, but also imparts antibacterial activity to the cationic group; the carboxyl group of the hydrophilic graft copolymer and the carboxyl group of p-hydroxybenzoic acid are combined with the amino bond of chitosan, and the p-hydroxybenzoic acid is grafted and modified to improve the water dispersibility, antibacterial activity stability and antioxidant property of the p-hydroxybenzoic acid; the bioactive metal zinc material prepared by the microwave method has good antibacterial and antioxidant properties, and the modified p-hydroxybenzoic acid is further improved. The antibacterial and antioxidant properties of hydroxybenzoic acid; the reactive oxygen species (ROS) catalyzed by modified p-hydroxybenzoic acid can effectively kill bacteria roaming in the surrounding environment, and the positively charged components further prevent bacteria from proliferating on its surface and even forming biofilms. Moreover, the modified p-hydroxybenzoic acid catalysis has a larger active specific surface area to kill bacteria adsorbed on its surface, and at the same time has a mechanical damage effect on the bacterial cell membrane and exerts antibacterial activity in a physical way; p-hydroxybenzoic acid grafted chitosan significantly improves the ability of chitosan to scavenge hydroxyl radicals, which is compatible with free radical adduct formation (RAF). Since the electrophilic free radical OH in MHBA is more likely to participate in the RAF reaction than the non-electrophilic free radical, thereby scavenging free radicals, the electron-isolated aromatic core structure is conducive to the reaction, and the free radical product is more stable through the resonance effect of the aromatic core. Modified p-hydroxybenzoic acid has multiple antibacterial modes, can protect and kill bacteria from different dimensions and levels, and has significant advantages over other single active materials in long-term antibacterial activity and drug resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is a process flow chart of the preparation of p-hydroxybenzoic acid of the present invention;

[0038] Figure 2 is a bar graph of the antibacterial rate of the modified p-hydroxybenzoic acid of the present invention;

[0039] Figure 3 It is a line graph of the antioxidant activity of the modified p-hydroxybenzoic acid of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] See also Figure 1 As shown, this embodiment discloses a method for preparing p-hydroxybenzoic acid, comprising the following steps:

[0043] Step (1) 420 g potassium hydroxide, 705 g phenol and 1.5 L water are mixed in a reaction vessel, stirred at 100 ° C for 0.5 h, heated, and then dehydrated at normal pressure. When the temperature is 135 ° C, dehydrate under reduced pressure. When water is evaporated to a droplet-like state under a pressure of -0.1 MPa, 3 L of phenol is added as a solvent to dissolve. The temperature is then raised to 230 ° C to make azeotropy of phenol and water. When the liquid changes from milky white to transparent, dehydration is terminated when there is no flow under the conditions of a temperature of 230 ° C and a pressure of -0.1 MPa to obtain a composite salt of potassium phenolate and phenol.

[0044] Step (2) introducing purified anhydrous carbon dioxide into the composite salt of potassium phenolate and phenol obtained in step (1) at 225° C., reacting at a pressure of 0.7 MPa for 1.5 h, recovering phenol under reduced pressure, introducing purified anhydrous carbon dioxide again at 225° C., carrying out a second carboxylation reaction at a pressure of 0.7 MPa for 0.5 h, recovering phenol under reduced pressure, introducing steam to a pressure of 0.2 MPa and maintaining the pressure for 0.5 h, releasing the pressure, draining water at -0.1 MPa, and adding 1.5 L of water to dissolve, thereby obtaining a dipotassium p-hydroxybenzoate solution;

[0045] Step (3) adding 7.5 kg of activated carbon to the dipotassium p-hydroxybenzoate solution obtained in step (2) for decolorization, and then filtering the activated carbon to obtain a decolorized dipotassium p-hydroxybenzoate solution;

[0046] Step (4) adding 10 wt % dilute sulfuric acid to the decolorized dipotassium p-hydroxybenzoate solution obtained in step (3) to adjust the pH to 6.8, cooling and centrifuging to remove potassium sulfate, and then continuing to dropwise add 10 wt % dilute sulfuric acid to the centrifuge to adjust the pH to 1.5, cooling and centrifuging to obtain a filter cake, and drying the filter cake at 100° C. for 10 hours to obtain p-hydroxybenzoic acid with a yield of 82.1%.

[0047] Example 2

[0048] See also Figure 1As shown, this embodiment discloses a method for preparing p-hydroxybenzoic acid, comprising the following steps:

[0049] Step (1) 280g potassium hydroxide, 940g phenol and 1L water are mixed in a reaction vessel, stirred at 110°C for 0.3h, heated, and then dehydrated under normal pressure, dehydrated under reduced pressure at 140°C, and added with 4L phenol solvent to dissolve the mixture under a pressure of -0.11MPa until the water flow is in a drop shape, and then heated to 220°C to make azeotropy of phenol and water, and when the liquid changes from milky white to transparent, dehydrate is terminated when there is no flow under the conditions of 240°C and -0.11MPa to obtain a composite salt of potassium phenolate and phenol;

[0050] Step (2) introducing purified anhydrous carbon dioxide into the composite salt of potassium phenol and phenol obtained in step (1) at 220-230° C., reacting at a pressure of 0.8 MPa for 1-2 h, recovering phenol under reduced pressure, introducing purified anhydrous carbon dioxide again at 220-230° C., carrying out a second carboxylation reaction at a pressure of 0.6 MPa for 0.7 h, recovering phenol under reduced pressure, introducing steam to a pressure of 0.1 MPa and maintaining the pressure for 0.7 h, releasing the pressure, draining water at -0.11 MPa, and adding 2 L of water to dissolve, thereby obtaining a dipotassium p-hydroxybenzoate solution;

[0051] Step (3) adding 5 kg of activated carbon to the dipotassium p-hydroxybenzoate solution obtained in step (2) for decolorization, and then filtering the activated carbon to obtain a decolorized dipotassium p-hydroxybenzoate solution;

[0052] Step (4) adding 10 wt % dilute sulfuric acid to the decolorized dipotassium p-hydroxybenzoate solution obtained in step (3) to adjust the pH to 7, cooling and centrifuging to remove potassium sulfate, and then continuing to dropwise add 10 wt % dilute sulfuric acid to the centrifuge to adjust the pH to 1.3, cooling and centrifuging to obtain a filter cake, and drying the filter cake at 105° C. for 8 h to obtain p-hydroxybenzoic acid with a yield of 72.5%.

[0053] Example 3

[0054] See also Figure 1 As shown, this embodiment discloses a method for preparing p-hydroxybenzoic acid, comprising the following steps:

[0055] Step (1) 560g potassium hydroxide, 470g phenol and 2L water are mixed in a reaction vessel, stirred at 90°C for 0.7h, heated, and then dehydrated under normal pressure. When the temperature is 130°C, dehydrate under reduced pressure. When water is evaporated to a droplet shape under a pressure of -0.09MPa, 2L phenol is added as a solvent to dissolve. The temperature is then raised to 240°C to make azeotropy of phenol and water. When the liquid changes from milky white to transparent, dehydration is terminated when there is no flow under the conditions of a temperature of 220°C and a pressure of -0.09MPa to obtain a composite salt of potassium phenolate and phenol.

[0056] Step (2) introducing purified anhydrous carbon dioxide into the composite salt of potassium phenolate and phenol obtained in step (1) at 220° C., reacting at a pressure of 0.8 MPa for 1 hour, recovering phenol under reduced pressure, introducing purified anhydrous carbon dioxide again at 230° C., carrying out a second carboxylation reaction at a pressure of 0.6 MPa for 0.7 hour, recovering phenol under reduced pressure, introducing steam to a pressure of 0.1 MPa and maintaining the pressure for 0.7 hour, releasing the pressure, draining water at -0.09 MPa, and adding 1 L of water to dissolve, thereby obtaining a dipotassium p-hydroxybenzoate solution;

[0057] Step (3) adding 10 kg of activated carbon to the dipotassium p-hydroxybenzoate solution obtained in step (2) for decolorization, and then filtering the activated carbon to obtain a decolorized dipotassium p-hydroxybenzoate solution;

[0058] Step (4) adding 10 wt % dilute sulfuric acid to the decolorized dipotassium p-hydroxybenzoate solution obtained in step (3) to adjust the pH to 6.6, cooling and centrifuging to remove potassium sulfate, and then continuing to dropwise add 10 wt % dilute sulfuric acid to the centrifuge to adjust the pH to 1.7, cooling and centrifuging to obtain a filter cake, and drying the filter cake at 95° C. for 12 h to obtain p-hydroxybenzoic acid with a yield of 78.2%.

[0059] Example 4

[0060] This embodiment discloses a method for preparing a graft copolymer, comprising the following steps:

[0061] S1: 150 g of 4-chloromethylstyrene, 105 g of butyl acrylate, 54 g of acrylic acid and 3.3 g of azobisisobutyronitrile were mixed, magnetically stirred in a nitrogen atmosphere at 80° C. for 4 h, dialyzed with a 3.5 kDa dialysis bag for 12 h, and then centrifuged at a speed of 10000 rpm for 6 min, and then precipitated with n-hexane for 3 times, and the precipitate was vacuum dried at 40° C. for 10 h to obtain a copolymer;

[0062] S2: 90 g of the copolymer was dissolved in 0.9 L of 1,4-dioxane, and then 270 g of hexadecyldimethylamine was added. The mixture was reacted at 40° C. for 24 h in a nitrogen atmosphere, and finally dialyzed with a 3.5 kDa dialysis bag for 48 h and vacuum freeze-dried for 12 h to obtain a graft copolymer.

[0063] Example 5

[0064] This embodiment discloses a method for preparing the zinc material, comprising the following steps:

[0065] 420 g of zinc chloride and 510 g of pyridine-2,6-dicarboxylic acid were added to 60 L of water, and microwave irradiated at a power of 250 W for 15 min at room temperature. The residue was filtered, and the residue was washed alternately with ethanol and deionized water for 4 times, and then dried at 50° C. for 24 h to obtain a zinc material.

[0066] Example 6

[0067] This embodiment discloses a method for preparing modified p-hydroxybenzoic acid, comprising the following steps:

[0068] P1: 160 g of p-hydroxybenzoic acid and 45 g of the graft copolymer were added to 15 L of water, stirred at room temperature for 25 min, then 705 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 420 g of N-hydroxysuccinimide were added, activated for 3 h, 49 g of chitosan was added, stirred at room temperature for 24 h, centrifuged 4 times, and finally freeze-dried at -80 ° C for 48 h to obtain grafted p-hydroxybenzoic acid;

[0069] P2: Disperse 150 g of zinc material in 1.5 L of water, ultrasonically treat for 25 min, add 75 g of grafted p-hydroxybenzoic acid, continue ultrasonically treating for 25 min, irradiate with microwaves at a power of 250 W for 10 min at room temperature, filter, wash the residue alternately with ethanol and deionized water for 4 times, and dry at 50 ° C for 24 h to obtain modified p-hydroxybenzoic acid.

[0070] Example 7

[0071] This embodiment discloses a method for preparing modified p-hydroxybenzoic acid, comprising the following steps:

[0072] P1: 110 g of p-hydroxybenzoic acid and 60 g of the graft copolymer were added to 10 L of water, stirred at room temperature for 30 min, then 470 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 560 g of N-hydroxysuccinimide were added, activated for 2 h, 65.4 g of chitosan was added, stirred at room temperature for 20 h, centrifuged 5 times, and finally freeze-dried at -80 ° C for 40 h to obtain grafted p-hydroxybenzoic acid;

[0073] P2: Disperse 200g of zinc material in 1L of water, ultrasonically treat for 30min, then add 50g of grafted p-hydroxybenzoic acid, continue ultrasonically treating for 30min, irradiate with microwaves at a power of 200W for 12min at room temperature, filter, wash the residue alternately with ethanol and deionized water for 3 times, and dry at 55°C for 20h to obtain modified p-hydroxybenzoic acid.

[0074] Example 8

[0075] This embodiment discloses a method for preparing modified p-hydroxybenzoic acid, comprising the following steps:

[0076] P1: 220 g of p-hydroxybenzoic acid and 30 g of the graft copolymer were added to 20 L of water, stirred at room temperature for 20 min, and then 940 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 280 g of N-hydroxysuccinimide were added. After activation for 4 h, 32.7 g of chitosan was added. After stirring at room temperature for 28 h, the mixture was centrifuged 3 times and finally freeze-dried at -80 ° C for 56 h to obtain grafted p-hydroxybenzoic acid;

[0077] P2: Disperse 100 g of zinc material in 2 L of water, ultrasonically treat for 20 min, then add 100 g of grafted p-hydroxybenzoic acid, continue ultrasonically treating for 20 min, irradiate with microwaves at a power of 300 W for 8 min at room temperature, filter, wash the filter residue alternately with ethanol and deionized water for 5 times, and dry it at 45 ° C for 28 h to obtain modified p-hydroxybenzoic acid.

[0078] Comparative Example 1

[0079] Comparative Example 1 Compared with Example 6, in the process of preparing modified p-hydroxybenzoic acid in Comparative Example 1, no graft copolymer was added, and other conditions remained unchanged.

[0080] Comparative Example 2

[0081] Compared with Example 6, in Comparative Example 2, no zinc material was added during the preparation of modified p-hydroxybenzoic acid, and other conditions remained unchanged.

[0082] Experimental example

[0083] The properties of the modified p-hydroxybenzoic acid prepared in Examples 6-8 and Comparative Examples 1-2 were tested.

[0084] 1. Antibacterial Test

[0085] After subculturing, the strains (Bacillus subtilis ATCC 11774, Pseudomonas aeruginosa ATCC 25923, Staphylococcus aureus ATCC 11632 and Escherichia coli ATCC 25922) were inoculated into Mueller-Hinton (MH) broth (25 g / L, pH 7.2) and cultured at 37°C for about 8 hours. Subsequently, the obtained culture was diluted with MH broth to a final OD600 of 0.1 (equivalent to ~108 CFU / mL), which was used for the subsequent determination of the inhibition rate. The test results are shown in Table 1:.

[0086] Table 1

[0087] Group Escherichia coli Staphylococcus aureus Pseudomonas aeruginosa Bacillus subtilis Example 6 99.95 99.91 99.98 99.92 Example 7 99.87 99.85 99.91 99.85 Example 8 99.75 99.70 99.82 99.73 Comparative Example 1 86.57 86.19 88.32 87.24 Comparative Example 2 87.32 87.05 89.79 87.18

[0088] From the test results in Table 1, it can be seen that the modified p-hydroxybenzoic acid prepared in Examples 6-8 of the present invention has good antibacterial properties. From the comparison between Comparative Example 1 and Example 6, it can be seen that the antibacterial properties of the modified p-hydroxybenzoic acid can be improved by adding the graft copolymer in the present invention; from the comparison between Comparative Example 2 and Example 6, it can be seen that the antibacterial properties of the modified p-hydroxybenzoic acid can be improved by adding the zinc material in the present invention.

[0089] 2. Antioxidant Determination

[0090] The test method for the ability to scavenge DPPH free radicals is as follows: prepare the sample with different concentrations (0.1, 0.2, 0.3, 0.4, 0.5 mg / mL) with distilled water, take 2 mL of sample solution and incubate with 4 mL of ethanol DPPH solution (180 mL) for 20 minutes. The control group uses 4.00 mL of anhydrous ethanol instead of the sample solution, and the blank group uses 2.00 mL of deionized water instead of the sample solution. Then measure the absorbance of the solution at 517 nm. The DPPH free radical scavenging rate is calculated by the following formula:

[0091] DPPH free radical scavenging rate (%) = (A0-A1) / A0×100%, where A0 and A1 represent the absorbance values ​​of the supernatant in the blank group and the sample tube, respectively. The test results are shown in Table 2:

[0092] Table 2

[0093] Group DPPH free radical scavenging rate (%) Example 6 93.5 Example 7 92.4 Example 8 92.1 Comparative Example 1 80.2 Comparative Example 2 81.6

[0094] From the test results in Table 2, it can be seen that the modified p-hydroxybenzoic acid prepared in Examples 6-8 of the present invention has antibacterial properties. From the comparison between Comparative Example 1 and Example 6, it can be seen that the antioxidant property of the modified p-hydroxybenzoic acid can be improved by adding the graft copolymer in the present invention; from the comparison between Comparative Example 2 and Example 6, it can be seen that the antioxidant property of the modified p-hydroxybenzoic acid can be improved by adding the zinc material in the present invention.

[0095] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0096] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing modified p-hydroxybenzoic acid, characterized in that: The following steps are involved: P1: 110-220 g of p-hydroxybenzoic acid and 30-60 g of the graft copolymer are added to 10-20 L of water, stirred at room temperature for 20-30 min, then 470-940 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 280-560 g of N-hydroxysuccinimide are added, activated for 2-4 h, 32.7-65.4 g of chitosan is added, stirred at room temperature for 20-28 h, centrifuged 3-5 times, and finally freeze-dried at -80 ° C for 40-56 h to obtain grafted p-hydroxybenzoic acid; P2: Disperse 100-200 g of zinc material in 1-2 L of water, perform ultrasonic treatment for 20-30 min, then add 50-100 g of grafted p-hydroxybenzoic acid, continue ultrasonic treatment for 20-30 min, irradiate with microwaves at a power of 200-300 W for 8-12 min at room temperature, filter, wash the filter residue alternately with ethanol and deionized water for 3-5 times, and dry at 45-55 ° C for 20-28 h to obtain modified p-hydroxybenzoic acid; The preparation method of the graft copolymer comprises the following steps: S1: 103-202 g of 4-chloromethylstyrene, 76-152 g of butyl acrylate, 36-72 g of acrylic acid and 2.2-4.4 g of azobisisobutyronitrile were mixed, magnetically stirred in a nitrogen atmosphere at 75-85° C. for 3-5 h, dialyzed with a 3-4 kDa dialysis bag for 10-14 h, and then centrifuged at a speed of 9000-11000 rpm for 4-8 min, and then precipitated with n-hexane 2-4 times, and the precipitate was vacuum dried at 35-45° C. for 8-12 h to obtain a copolymer; S2: Dissolve 60-120 g of the copolymer in 0.6-1.2 L of 1,4-dioxane, add 180-360 g of hexadecyl dimethyl tertiary amine, react at 35-45° C. in a nitrogen atmosphere for 20-28 h, and finally dialyze with a 3-4 kDa dialysis bag for 36-54 h, and freeze-dry in vacuum for 10-14 h to obtain a graft copolymer; The preparation method of the zinc material comprises the following steps: 280-560 g of zinc chloride and 340-680 g of pyridine-2,6-dicarboxylic acid are added to 40-80 L of water, and microwave irradiation is performed at room temperature at a power of 200-300 W for 10-20 min, and the filter residue is washed alternately with ethanol and deionized water for 3-5 times, and then dried at 45-55° C. for 20-28 h to obtain a zinc material.

2. A modified p-hydroxybenzoic acid prepared according to the method for preparing modified p-hydroxybenzoic acid according to claim 1.

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