Phase change microcapsule antibacterial material based on alkylated chitosan-polystyrene copolymer and preparation method thereof

Abstract

The invention discloses a phase change microcapsule antibacterial material based on an alkylated chitosan-polystyrene copolymer and a preparation method thereof.The material is composed of a core material and a wall material, the core material is an aliphatic hydrocarbon phase change material, the wall material is the alkylated chitosan-polystyrene copolymer, and the alkylated chitosan-polystyrene copolymer is a mixture of the alkylated chitosan-polystyrene copolymer and the alkylated chitosan-polystyrene copolymer. The outer layer of the wall material is an alkylated chitosan-styrene grafted section, and the inner layer of the wall material is a polystyrene cross-linked section; according to the invention, tert-butyl hydrogen sulfate is designed as an amino protective agent for the first time, and amino protective grafting is carried out on chitosan through a path of'protection-grafting-deprotection 'to synthesize alkylated chitosan (ACS); and preparing the phase-change microcapsule antibacterial material with the ACS-g-PSt material as the wall material by using ACS as an emulsifier and a wall material component at the same time through a microemulsion interfacial polymerization method, so that the application research blank of the chitosan grafting material in the field of phase-change microcapsules is filled; and a new technology and direction are provided for industrial application of the phase change microcapsules in the fields of medical treatment and public health and the like.

Description

Technical Field

[0001] The present invention relates to a phase change material coating technology, and particularly to a phase change microcapsule antibacterial material based on an alkylated chitosan-polystyrene copolymer and a preparation method thereof. Background Art

[0002] At present, the wall materials of phase change microcapsule products that have achieved industrial application are usually amino aldehyde resins (such as melamine formaldehyde resin, urea formaldehyde resin, etc.) and polyolefins (such as polystyrene, polymethyl methacrylate, etc.). On the one hand, amino aldehyde resin microcapsules lack hardness, resulting in poor microscopic morphology and overall mechanical properties of the microcapsule products; on the other hand, toxic substances such as formaldehyde will be released during their preparation and use, reducing the safety and environmental friendliness of the products. Polyolefin microcapsules do not involve formaldehyde during the preparation process and have excellent mechanical properties and chemical stability, but due to the lack of toughness, the shell is easy to break, restricting their effects in practical applications.

[0003] Chitosan (CS), as a natural polymer rich in amino groups, itself has toughness, hydrophilicity, antibacterial property and biocompatibility, and has been widely used in the fields of composite material preparation, coating modification, antibacterial material preparation, etc. In recent years, the research and development work on chitosan graft copolymers has become one of the hotspots in the application research of chitosan. Among them, the graft resin structure of chitosan-polystyrene copolymer (CS-g-PSt) is an important research direction of this hotspot. The CS-g-PSt structure contains both the ductile chitosan-styrene (CS-St) graft segment and the rigid self-crosslinked polystyrene (PSt) segment, making the overall material maintain high hardness while having a certain toughness, thereby improving the mechanical properties of the material in aspects such as stretching and extrusion. In addition, the chitosan component in the system can make the material have antibacterial property, hydrophilicity and biocompatibility at the same time, further promoting the application of CS-g-PSt materials in the fields of medical and health, home textiles, food, etc.

[0004] At the same time, the design of amphiphilic chitosan derivatives through hydrophobic modification also has high application value. By esterifying and grafting the methyl hydroxyl group (and hydroxyl group) in chitosan, an alkylated chitosan structure can be obtained, which can be directly used as an emulsifier in the preparation of microemulsions. Inspired by the above two points, the present invention first designs tert-butyl hydrogen sulfate as an amino protecting agent, and conducts amino-protective grafting synthesis of alkylated chitosan (ACS) on chitosan through the "protection-grafting-deprotection" path. Then, using ACS as both an emulsifier and a wall material component, a phase change microcapsule antibacterial material with ACS-g-PSt material as the wall material is prepared by the microemulsion interfacial polymerization method. While filling the blank in the application research of chitosan graft materials in the field of phase change microcapsules, it provides a new technology and direction for the industrial application of phase change microcapsules in the fields of medical and health, etc. Summary of the Invention

[0005] The present invention provides a phase change microcapsule antibacterial material based on an alkylated chitosan-polystyrene copolymer and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] A phase change microcapsule antibacterial material based on an alkylated chitosan-polystyrene copolymer, which is composed of a core material and a wall material. The core material is a fatty hydrocarbon phase change material, and the wall material is an alkylated chitosan-polystyrene copolymer;

[0008] Among them,

[0009] The core material fatty hydrocarbon phase change material is selected from one or more of n-tetradecane, n-hexadecane, and n-octadecane;

[0010] The wall material alkylated chitosan-polystyrene copolymer is obtained by interfacial polymerization of alkylated chitosan and styrene under the initiation of persulfate ions; and the outer layer of the wall material is an alkylated chitosan-styrene graft segment, and the inner layer is a polystyrene cross-linked segment.

[0011] The preparation method of the phase change microcapsule antibacterial material based on an alkylated chitosan-polystyrene copolymer of the present invention is as follows:

[0012] (1) Mix an H2SO4 solution, tert-butanol, and hydrogen peroxide, react at 40-50 °C for 3-10 h, and adjust the pH = 2-4 to obtain a tert-butyl hydrogen sulfate (TBHS) solution;

[0013] Preferably, the mass fraction of the H2SO4 solution is 40-70%;

[0014] Preferably, the molar ratio of H2SO4 to tert-butanol is 1-1.1:1;

[0015] Adjust the pH to 2-4 by dropwise addition of 0.1 M H2SO4 as needed;

[0016] (2) Add chitosan to the tert-butyl hydrogen sulfate solution obtained in step (1), stir to dissolve, then add a fatty acid monomer and mix evenly. Stir and react at 60-80 °C under a nitrogen atmosphere for 3-10 h, adjust the pH = 7-9, centrifuge to collect the precipitate, wash and dry to obtain alkylated chitosan (ACS);

[0017] Preferably, the molar ratio of amino groups in chitosan to tert-butanol in step (1) is 1-1.2:1;

[0018] The fatty acid monomer is selected from one or more of alkyl acids with a fatty chain length of C5-C15;

[0019] Preferably, the molar ratio of the carboxyl group in the fatty acid to the amino group in the chitosan is 1 to 1.2:1;

[0020] The pH is adjusted to 7 to 9 by adding an alkali solution, and the alkali solution is, for example, one or more of an NaOH solution, a KOH solution, an alkaloid solution, and an ammonia water;

[0021] (3) Add the alkylated chitosan obtained in step (2) (simultaneously used as an emulsifier), styrene, a fatty hydrocarbon phase change material, and a diene crosslinking agent to deionized water, and stir and emulsify the mixed system in a nitrogen atmosphere at 40 to 60 °C for 10 to 30 min to form a stable oil-in-water microemulsion;

[0022] Preferably, in the mixed system, the mass fraction of the alkylated chitosan is 1 to 10%, the mass fraction of the styrene is 1 to 10%, the mass fraction of the fatty hydrocarbon phase change material is 5 to 20%, and the mass fraction of the diene crosslinking agent is 0.5 to 1%;

[0023] Preferably, the total mass ratio of the fatty hydrocarbon phase change material (core material), styrene and alkylated chitosan (wall material raw material) is 1 to 5:1;

[0024] The diene crosslinking agent is selected from one or more of divinylbenzene (DVB), diallyl phthalate (DAP), pentaerythritol acrylate (PETA), and ethylene glycol diacrylate (EGDMA);

[0025] Preferably, the stirring and emulsifying rate is 600 to 5000 r / min;

[0026] (4) In a nitrogen atmosphere, dropwise add an aqueous solution of an initiator to the microemulsion in step (3) to start an interfacial polymerization reaction, control the reaction temperature at 50 to 80 °C and the stirring rate at 100 to 600 r / min, and obtain a suspension containing the product after 5 to 12 h. After dehydration and drying treatment, the phase change microcapsule antibacterial material based on the alkylated chitosan-polystyrene copolymer is obtained;

[0027] Preferably, the dropping rate of the aqueous solution of the initiator is 0.1 to 2 mL / s;

[0028] The initiator is selected from potassium persulfate, sodium persulfate, ammonium persulfate, etc.;

[0029] Preferably, the mass ratio of the alkylated chitosan to the initiator in step (3) is 10 to 50:1;

[0030] The dehydration and drying treatment method can be natural drying method, heating drying method, freeze drying method, spray drying method, etc. The heating drying method is preferred. The specific operation is as follows: Centrifuge the suspension containing the product at a rotational speed of 1000 - 5000 r / min for 5 - 30 min to obtain a light yellow phase change microcapsule solid sample. Then wash the phase change microcapsule solid sample with a detergent 1 - 5 times. Finally, place the washed phase change microcapsule solid sample in an oven at 20 - 80 °C for heating and drying for 2 - 8 h to obtain a phase change microcapsule powder sample; wherein the detergent is a liquid ether reagent, preferably petroleum ether.

[0031] The technical principle of the present invention includes:

[0032] First, through the catalytic action of hydrogen peroxide, sulfuric acid (H2SO4) and tert-butanol (TBA) undergo an esterification reaction to generate tert-butyl hydrogen sulfate (TBHS) as an amino protecting agent and an organic acid. Then, under the conditions of acidity, heating and nitrogen atmosphere, TBHS, CS and fatty acids are mixed for a hydrophobic modification reaction. After the reaction is completed, a deprotection reaction of the amino group is carried out by adding an alkali solution, and then the precipitate in the reaction solution is separated and dried to obtain ACS powder. Under heating conditions, ACS, styrene, aliphatic hydrocarbon phase change material and a crosslinking agent are dispersed in deionized water to prepare a microemulsion. Then, an initiator is added to the microemulsion under a nitrogen atmosphere to start a polymerization reaction. Under the action of the initiator, the -NH2 of ACS is activated into a -HN· active group, which can undergo a grafting reaction with the carbon-carbon double bond in the styrene structure in the oil phase at the oil-water interface to generate a (R 1,2,3 )3-C· group, and this active group can continue to react with the styrene monomer in the oil phase to generate a polystyrene crosslinked structure. Finally, a phase change microcapsule antibacterial material with an outer ACS-St grafting segment and an inner PSt crosslinked segment ACS-g-PSt copolymer shell structure is formed. Moreover, the proportion of the grafting segment and the crosslinked segment in the copolymer system can be controlled by adjusting the dosage ratio of chitosan and styrene, so as to prepare phase change microcapsule antibacterial materials with different mechanical strengths and antibacterial properties.

[0033] Compared with the prior art, the present invention has the following outstanding effects:

[0034] By subjecting chitosan to amino-protective hydrophobic modification, an amphiphilic polymer chitosan alkyl derivative ACS is synthesized, which can simultaneously serve as a wall material component and an emulsifier for preparing phase change microcapsules. A phase change microcapsule antibacterial material with a novel ACS-g-PSt shell structure is prepared by the microemulsion interfacial polymerization method; the outer layer of the shell structure is mainly an ACS-St graft segment with high toughness, antibacterial property, hydrophilicity and biocompatibility, and the inner layer is mainly a PSt self-crosslinked segment with high hardness and high density. This novel ACS-g-PSt shell structure enhances the toughness while ensuring the hardness of the phase change microcapsule material, thereby improving the overall mechanical strength and impact resistance of the microcapsule material, and effectively solving the problem of rupture of the phase change microcapsules due to extrusion, friction, etc. in practical applications.

[0035] The outer layer of the shell of the phase change microcapsule antibacterial material prepared by the present invention is mainly an ACS-St graft structure. In this structure, a small part of -NH2 reacts with the carbon-carbon double bond in styrene to form a -NH-CH2- structure, and most of the -NH2 is concentrated on the outer layer of the shell, which can fully exert the contact killing effect of the quaternary ammonium salt structure on bacteria and improve the overall antibacterial effect of the phase change microcapsules. In addition, due to the high hydrophilicity and biocompatibility of the ACS-St graft structure on the outer layer of the shell, the phase change microcapsule antibacterial material prepared by the present invention has advantages and application potential that cannot be achieved by traditional phase change microcapsule materials in application scenarios such as medical and health, food processing and storage, and next-to-skin fabrics that are in direct contact with the human body.

[0036] The phase change microcapsule antibacterial material prepared by the present invention does not contain components harmful to the human body and the environment, does not have the potential hazards of flammability, explosiveness, and corrosion, and is not prone to phenomena harmful to the human body and the environment such as formaldehyde release and microplastics during use; the preparation method described in the present invention does not involve rare and expensive raw materials, does not involve extreme, harsh, and complex process conditions, and no toxic substances and substances that require special treatment are generated during the preparation process. The above characteristics of the present invention meet the requirements of safety, green environmental protection in industrial production and have high industrial application value. Description of the Drawings

[0037] Figure 1 : Antibacterial test results of the phase change microcapsule sample.

[0038] Figure 2 : DSC characterization results; the blue line is the 30% chitosan sample, and the red line is the 20% chitosan sample. Detailed Embodiments

[0039] The present invention will be further described below through specific embodiments, but the protection scope of the present invention is not limited thereto.

[0040] In the following examples, the chitosan product of Shanghai Reagent Co., Ltd. has a deacetylation degree of 80-95% and a viscosity of 50-800 mPa·s; the tert-butanol is the product of Shanghai Reagent Co., Ltd. with a purity of ≥99.5%; the H2SO4 is the product of Shanghai Reagent Co., Ltd. with a mass concentration of 50%; the H2O2 is the product of Shanghai Reagent Co., Ltd. with a mass concentration of 30%; the lauric acid is the product of TCI with a purity of 98%; the styrene is the product of Shanghai Reagent Co., Ltd. with a purity of ≥99.5% and contains about 0.0015% p-tert-butylcatechol as a polymerization inhibitor; the n-octadecane is the product of TCI with a purity of 98%; the K2S2O8 is the product of Shanghai Reagent Co., Ltd. with a purity of ≥99.5%; the DVB is the product of TCI containing the stabilizer TBC; the PETA is the product of Wokai with a purity of 96%; the petroleum ether is the product of Acros; the genipin is the product of Wokai with a purity of 95%; the hydroxypropyl cellulose is the product of TCI with a viscosity of 150-400 mPa·s. Other reagents are all conventional laboratory reagents without specific specification requirements.

[0041] Example 1: Preparation of tert-butyl hydrogen sulfate (TBHS) amino protecting agent

[0042] Slowly add 7.4 g of tert-butanol to 20 g of a 50% H2SO4 solution and mix well. Then add 10 mL of H2O2 and mix well. Place the mixed solution under the condition of 45 °C and react for 6 h to obtain a TBHS solution, and adjust the pH of the solution to 3.5 by dropwise adding 0.1 M H2SO4 as needed.

[0043] Example 2: Preparation of lauric acid-O-chitosan ester (LA-O-CSE) powder

[0044] Dissolve 20 g of chitosan in the TBHS solution prepared in Example 1 and stir for 60 min to completely dissolve it. Then add 20 g of lauric acid and mix well. Place the mixed solution under a nitrogen atmosphere and at 70 °C and react for 5 h. After the reaction, adjust the pH to 7.5 with 0.1 M NaOH solution to obtain a LA-O-CSE precipitate, and then successively carry out centrifugal separation at 3000 rpm, wash with ethanol and deionized water, and dry at 45 °C for 5 h to obtain LA-O-CSE powder.

[0045] Example 3: Preparation of a high-toughness phase change microcapsule antibacterial material powder sample with 30% chitosan component (calculated based on the dosage of chitosan raw material)

[0046] Under the conditions of 60 °C and in a nitrogen atmosphere, 150 g of deionized water, 10 g of the LA-O-CSE powder prepared in Example 2, 45 g of n-octadecane, 10 g of styrene, and 3 g of DVB were successively added to a three-necked flask and emulsified for 30 min at 4500 r / min to prepare a microemulsion. 1 mL of a K2S2O8 solution with a concentration of 0.06 g / mL was added to the microemulsion at a dropping rate of 0.1 mL / s to initiate the interfacial polymerization reaction. During the entire reaction process, the reaction temperature was controlled at 60 °C and the stirring rate was 300 r / min. After 7 h, a suspension containing the phase change microcapsule product was obtained. The phase change microcapsule suspension was centrifuged at 3000 r / min for 10 min to obtain a light yellow solid sample of the phase change microcapsules. The solid sample was washed twice with petroleum ether, and finally the washed solid sample of the phase change microcapsules was placed in an oven at 60 °C and heated and dried for 5 h to obtain a powder sample of a high-toughness phase change microcapsule antibacterial material with 30% chitosan component (calculated based on the dosage of the chitosan raw material).

[0047] Example 4: Preparation of a powder sample of a high-hardness phase change microcapsule antibacterial material with 20% chitosan component (calculated based on the dosage of the chitosan raw material)

[0048] Under the conditions of 70 °C and in a nitrogen atmosphere, 8 g of the LA-O-CSE powder prepared in Example 2, 150 g of deionized water, 45 g of n-octadecane, 10 g of styrene, and 2 g of PETA were successively added to a three-necked flask and emulsified for 30 min at 4500 r / min to prepare a microemulsion. 1 mL of a K2S2O8 solution with a concentration of 0.06 g / mL was added to the microemulsion at a dropping rate of 0.1 mL / s to initiate the interfacial polymerization reaction. During the entire reaction process, the reaction temperature was controlled at 70 °C and the stirring rate was 300 r / min. After 6 h, a suspension containing the phase change microcapsule product was obtained. The phase change microcapsule suspension was centrifuged at 3000 r / min for 10 min to obtain a light yellow solid sample of the phase change microcapsules. The solid sample was washed twice with petroleum ether, and finally the washed solid sample of the phase change microcapsules was placed in an oven at 60 °C and heated and dried for 5 h to obtain a powder sample of a high-hardness phase change microcapsule antibacterial material with 20% chitosan component (calculated based on the dosage of the chitosan raw material).

[0049] Example 5: Antibacterial detection of a phase change microcapsule antibacterial material sample with 20% chitosan component (calculated based on the dosage of the chitosan raw material)

[0050] Referring to "GB / T 20944.3-2008 Evaluation of antibacterial properties of textiles - Part 3: Oscillation method", the CFU of Escherichia coli was detected for the phase change microcapsule antibacterial material sample prepared in Example 4, and the results are as Figure 1 shown. No bacterial plaques were observed in all the sample media, indicating that the antibacterial rate of the microcapsule sample against Escherichia coli was 100%.

[0051] Example 6: Detection of Phase Change Performance of Phase Change Microcapsule Antibacterial Material Samples

[0052] DSC heating and cooling curves were respectively characterized for the microcapsule samples with 20% and 30% chitosan content prepared in Example 4 and Example 3, and the results are as Figure 2 shown in Table 1. No split peaks appeared in the crystallization exothermic curves of all samples, indicating that the core materials were evenly and fully distributed in the microcapsules. The analysis results show that the phase change performance indexes (phase change enthalpy, supercooling degree) of all microcapsule samples meet the relevant requirements of "T-CTES-1005-2017 Phase Change Temperature-Regulating Microcapsules for Textiles and Their Application Function Evaluation", indicating that the phase change microcapsules prepared by the present invention meet the product application standards.

[0053] Table 1 Phase Change Performance Parameters of Samples

[0054]

[0055]

[0056] Example 7: Preparation of Phase Change Microcapsule Cooling Antibacterial Fabric

[0057] Take 20 g of the phase change microcapsules prepared in Example 3 or Example 4, 5.8 g of genipin, 3 g of waterborne polyurethane, 0.5 g of hydroxypropyl cellulose and 10 g of water, and stir evenly under the condition of a rotation speed of 600 rpm to prepare a microcapsule coating. Use a screen printing machine to perform screen printing coating finishing on the polyester fabric, control the scraper angle at 80°, and the number of printing times is 2 times. Take down the fabric and bake it at 95 °C for 30 min to obtain a cooling antibacterial fabric.

[0058] After testing, the instantaneous contact cooling performance of the prepared fabric is 0.36, the wicking height is 109 mm, the moisture permeability is 10500 g / (m 2 ·d), the contact wetting time is 0.5 s, the water droplet diffusion time is 1.7 s, and the moisture evaporation rate is 0.28 g / h. The test results show that the prepared microcapsule cooling antibacterial fabric has good temperature-regulating and breathable properties and meets the performance indexes of cooling clothing.

Claims

1. A phase change microcapsule antibacterial material based on alkylated chitosan-polystyrene copolymer, characterized in that, It consists of a core material and a wall material. The core material is a fatty hydrocarbon phase change material, and the wall material is an alkylated chitosan-polystyrene copolymer; Among them, The fatty hydrocarbon phase change material of the core material is selected from one or more of n-tetradecane, n-hexadecane, and n-octadecane; The alkylated chitosan-polystyrene copolymer of the wall material is obtained by interfacial polymerization of alkylated chitosan and styrene under the initiation of persulfate ions; moreover, the outer layer of the wall material is an alkylated chitosan-styrene graft segment, and the inner layer is a polystyrene cross-linked segment.

2. The preparation method of the phase change microcapsule antibacterial material based on alkylated chitosan-polystyrene copolymer as claimed in claim 1, characterized in that The preparation method is as follows: (1) Mix the H2SO4 solution, tert-butanol, and hydrogen peroxide, react at 40-50 °C for 3-10 h, adjust the pH = 2-4 to obtain a tert-butyl hydrogen sulfate solution; (2) Add chitosan to the tert-butyl hydrogen sulfate solution obtained in step (1), stir to dissolve, then add fatty acid monomers and mix evenly, stir and react at 60-80 °C under a nitrogen atmosphere for 3-10 h, adjust the pH = 7-9, centrifuge to collect the precipitate, wash and dry to obtain alkylated chitosan; The fatty acid monomers are selected from one or more of alkyl acids with a fatty chain length of C5-C15; (3) Add the alkylated chitosan, styrene, fatty hydrocarbon phase change material, and diene cross-linking agent obtained in step (2) to deionized water, and the mixed system is stirred and emulsified at 40-60 °C under a nitrogen atmosphere for 10-30 min to form a stable oil-in-water microemulsion; The diene cross-linking agents are selected from one or more of divinylbenzene, diallyl phthalate, pentaerythritol acrylate, and ethylene glycol diacrylate; (4) Under a nitrogen atmosphere, drop the aqueous solution of the initiator into the microemulsion in step (3) to start the interfacial polymerization reaction, control the reaction temperature at 50-80 °C and the stirring rate at 100-600 r / min, and obtain a suspension containing the product after 5-12 h. After dehydration and drying treatment, the phase change microcapsule antibacterial material based on the alkylated chitosan-polystyrene copolymer is obtained; The initiators are selected from potassium persulfate, sodium persulfate, and ammonium persulfate.

3. The preparation method according to claim 2, characterized in that, In step (1), the mass fraction of the H2SO4 solution is 40-70%.

4. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of H2SO4 to tert-butanol is 1-1.1:

1.

5. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of the amino group contained in chitosan to tert-butanol in step (1) is 1-1.2:

1.

6. The preparation method according to claim 2, wherein In step (2), the molar ratio of the carboxyl group in the fatty acid to the amino group in chitosan is 1-1.2:

1.

7. The preparation method according to claim 2, wherein In the mixed system of step (3), the mass fraction of alkylated chitosan is 1-10%, the mass fraction of styrene is 1-10%, the mass fraction of fatty hydrocarbon phase change material is 5-20%, and the mass fraction of diene cross-linking agent is 0.5-1%.

8. The preparation method according to claim 2, characterized in that, In step (3), the mass ratio of the fatty hydrocarbon phase change material of the core material, the wall material raw material styrene, and alkylated chitosan is 1-5:

1.

9. The preparation method according to claim 2, wherein In step (3), the stirring and emulsifying rate is 600-5000 r / min.

10. The preparation method according to claim 2, characterized in that, In step (3), the mass ratio of alkylated chitosan to the initiator in step (4) is 10-50:1.

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