Silica capsule wall, silica microcapsule and preparation method and application thereof

Abstract

This invention discloses a silica capsule wall, silica microcapsules, their preparation method, and applications. The silica capsule wall of this invention comprises: hydrophobic hollow mesoporous silica and a hydrophilic surfactant. The hydrophobic tail of the hydrophilic surfactant is inserted into the mesopores of the hydrophobic hollow mesoporous silica, while the hydrophilic head of the hydrophilic surfactant remains on the surface of the hydrophobic hollow mesoporous silica. The HLB value of the hydrophilic surfactant is not less than 10. The hydrophobic hollow mesoporous silica includes hollow mesoporous silica and a hydrophobic agent attached to the surface of the hollow mesoporous silica. The silica microcapsules of this invention exhibit good dispersibility in water, high loading capacity, good sustained release, and controllable core material release.

Description

TECHNICAL FIELD

[0001] The present application relates to a silica capsule wall, a silica microcapsule and a preparation method and application thereof. BACKGROUND

[0002] With the progress of nanotechnology and biotechnology, the research on fragrance nanocapsules is also increasing. The low loading capacity and low adsorption rate of conventional nanocarriers have been a bottleneck problem. Hollow mesoporous silica nanoparticles, due to their large internal space and pore structure, can provide high loading capacity and slow release characteristics for guest molecules, which are particularly valuable. However, the encapsulation of guest core materials in hollow mesoporous silica materials is mainly achieved by impregnation method, and the traditional impregnation method has high requirements for the hydrophobicity of the encapsulated guest molecules. Due to the poor impregnation effect of hydrophobic guest materials, a large number of guest molecules are difficult to enter the internal cavity. Although the addition of cosolvents or phase transfer agents can improve the encapsulation efficiency, the introduction of a large amount of synthetic additives has certain environmental hazards, which is not conducive to sustainable development.

[0003] In order to solve the above problems, hydrophobic groups are often introduced into the surface of solid materials to increase their hydrophobicity, thereby improving the adsorption of hydrophobic organic matter in water. However, the increase of hydrophobicity inevitably leads to the decrease of dispersibility in water, limiting its application in aqueous systems (such as cosmetic emulsions, etc.). At the same time, due to the large amount of mesoporous structure in the microcapsule, the core material coated therein is released in a short time, which is difficult to meet the slow release requirement. In addition, the hollow mesoporous silica microcapsule with hydrophobicity can only load the core material in the hollow structure, and the loading capacity of the core material is limited. Therefore, there is an urgent need for a microcapsule with high loading capacity, good slow release and adjustable dispersibility in water system. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects of poor dispersibility in water, low loading capacity, short release time and uncontrollability of the hydrophobic hollow mesoporous silica microcapsule in the prior art, and to provide a silica capsule wall, a silica microcapsule and a preparation method and application thereof. The silica microcapsule of the present application has good dispersibility in water, high loading capacity, good slow release and controllability of core material release.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a kind of silica capsule wall, it includes: hydrophobic hollow mesoporous silica and hydrophilic surfactant, the hydrophilic tail of the hydrophilic surfactant is located in the mesoporous of the hydrophobic hollow mesoporous silica, the hydrophilic head of the hydrophilic surfactant is attached to the surface of the hydrophobic hollow mesoporous silica;The HLB value of the hydrophilic surfactant is not less than 10.

[0007] In the present application, the HLB value of the hydrophilic surfactant is preferably 13-30, more preferably 14-20, for example 15, 16 or 17.

[0008] In the present application, the hydrophilic surfactant can be a conventional hydrophilic surfactant with an HLB value of not less than 10 in the art, preferably one or more of PEG(8) nonylphenol ether, PEG(20) glycerol, monostearate and Tween 80, more preferably Tween 80.

[0009] In the present application, the hydrophobic hollow mesoporous silica can be conventional in the art, and generally includes hollow mesoporous silica and a hydrophobic agent attached to the surface of the hollow mesoporous silica.

[0010] The hydrophobic agent can be conventional in the art, preferably n-octyltrimethoxysilane (OCSS) and / or 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDES), more preferably PDES.

[0011] The hollow mesoporous silica can be conventional in the art.

[0012] The present application also provides a method for preparing the silica capsule wall as described above, which comprises the following steps: mixing the hydrophobic hollow mesoporous silica and the hydrophilic surfactant.

[0013] In the present application, the method for preparing the hydrophobic hollow mesoporous silica can be conventional in the art, and generally can be hydrophobic modification of hollow mesoporous silica.

[0014] The method for preparing the hollow mesoporous silica can be conventional in the art, and preferably comprises the following steps:

[0015] S1: mixing a cationic surfactant, solid silica nanoparticles (sSiO2) and tetraethoxysilane (TEOS) in a solvent under alkaline conditions to obtain a core / shell composite structure composed of SiO2, the cationic surfactant and sSiO2 from outside to inside;

[0016] S2: selectively etching the sSiO2 core of the core / shell composite structure obtained in S1 to remove the cationic surfactant.

[0017] The cationic surfactant forms liquid micelle individuals on the surface of sSiO2, and these micelle individuals combine to form a positively charged surface. In an alkaline environment, the free silicate formed by the hydrolysis of TEOS is negatively charged. According to the electrostatic adsorption theory, the electrostatic attraction will cause a large amount of free silicate fragments to automatically deposit on the surface of the cationic surfactant micelles until a SiO2-cationic surfactant shell is formed.

[0018] In S1, the solvent can be a solvent commonly used in the art that is compatible with the TEOS, and is preferably an ethanol aqueous solution.

[0019] In the ethanol aqueous solution, the volume ratio of ethanol to water can be conventional in the art, and is preferably (1-10):1, and more preferably 7:1.

[0020] In S1, the cationic surfactant can be conventional in the art, and is preferably cetyltrimethylammonium bromide (CTAB).

[0021] In S1, the concentration of the cationic surfactant in the solvent is preferably 4-7 mg / mL, and more preferably 5-6 mg / mL.

[0022] TEOS forms an oil-in-water emulsion system in the solvent, and the solvent of the ethanol aqueous solution, the concentration of the above ethanol aqueous solution, and the concentration of the cationic surfactant help to improve the stability of the oil droplets, thereby improving the monodispersity of the oil droplets. The dispersity of the mesoporous silica formed on this basis is also good.

[0023] In S1, the volume ratio of the TEOS to the solvent can be conventional in the art, and is preferably 1:(80-150), and more preferably 1:106.7.

[0024] In S1, the alkaline environment can be a pH>7 that is conventional in the art, and is preferably a pH of 9-10.

[0025] In S1, the alkaline environment can be formed by adding a base commonly used in the art to the solvent, and is preferably by adding ammonia.

[0026] In S1, the preparation method of the sSiO2 can be conventional in the art, and preferably includes the following steps:

[0027] In a solvent, TEOS is added and reacted in an alkaline environment, and the sSiO2 is obtained.

[0028] In the preparation method of the sSiO2, the solvent can be a solvent commonly used in the art that is compatible with the TEOS, and is preferably an ethanol aqueous solution.

[0029] In the method for preparing the sSiO2, the pH value of the alkaline environment can be conventional in the art, preferably 8-10, more preferably 9.5.

[0030] In the method for preparing the sSiO2, the alkaline environment is preferably provided by ammonia.

[0031] In the method for preparing the sSiO2, the temperature of the reaction can be conventional in the art, preferably 20-30°C, for example 25°C.

[0032] In the method for preparing the sSiO2, the time of the reaction can be conventional in the art, preferably 40-80 min, more preferably 50-70 min, for example 60 min.

[0033] In the method for preparing the sSiO2, the reaction is generally carried out under stirring.

[0034] Under the catalysis of alkali, TEOS is first replaced by -OH to generate a large amount of silicic acid. The silicic acid is polymerized to form Si-O-Si, and as the concentration increases, it gradually reaches saturation, i.e. the silica nucleus is aggregated, and the polymer and silicic acid molecules continuously react and aggregate on the surface of the silica nucleus, and finally the silica nanoparticles are obtained.

[0035] In the method for preparing the sSiO2, after the reaction, preferably, the method further comprises the steps of solid-liquid separation, washing and drying.

[0036] The solid-liquid separation can be carried out by a method conventional in the art, preferably by centrifugation.

[0037] The washing can be carried out by a method conventional in the art, preferably by washing with water and ethanol in sequence, more preferably by washing with water three times and then washing with ethanol three times.

[0038] The temperature of the drying can be conventional in the art, preferably 40-80°C, for example 65°C.

[0039] The time of the drying can be conventional in the art, preferably not less than 6 h, more preferably 10-15 h, for example 12 h.

[0040] In S1, the sSiO2 is preferably first dispersed in water to form a suspension of sSiO2 nanoparticles, and then mixed with the cationic surfactant and the TEOS.

[0041] In S1, the mixing can be carried out by a method conventional in the art, preferably, in the solvent, the cationic surfactant is first added and mixed, then the sSiO2 is added and mixed, and then the TEOS is added and mixed.

[0042] The mixing method is preferably stirring.

[0043] The mixing time after adding the cationic surfactant can be conventional in the art, preferably 10-50 min, more preferably 30 min.

[0044] The mixing time after adding the sSiO2can be conventional in the art, preferably 40-100 min, more preferably 60 min.

[0045] The mixing time after adding the TEOS can be conventional in the art, preferably 3-8 h, more preferably 5-7 h, for example 6 h.

[0046] In S1, the preparation method of the core / shell composite structure preferably further comprises a separation, washing and drying step.

[0047] The separation method can be conventional in the art, preferably centrifugation.

[0048] The washing method can be conventional in the art, preferably washing with ethanol.

[0049] The drying temperature can be conventional in the art, preferably 50-80°C, for example 65°C.

[0050] The drying is preferably vacuum drying.

[0051] In S2, the method of selectively etching the sSiO2core can be conventional in the art, preferably heating the core / shell composite structure obtained in S1 in an alkaline solution.

[0052] The alkaline solution can be conventional in the art, preferably an aqueous Na2CO3solution.

[0053] The heating temperature can be conventional in the art, preferably 60-100°C, more preferably 70-90°C, for example 80°C.

[0054] The heating time can be conventional in the art, preferably 30-60 min, more preferably 35-50 min, for example 40 min.

[0055] In S2, the method of removing the cationic surfactant can be conventional in the art, preferably heating in an alcohol acid solution.

[0056] The method of removing the cationic surfactant, the alcohol acid solution can be conventional in the art, generally comprising ethanol and a mineral acid. The mineral acid is preferably hydrochloric acid.

[0057] The method for removing the cationic surfactant, the volume ratio of the inorganic acid to the ethanol in the alcohol acid solution can be conventional in the art, preferably (0.5-1.5):100, for example 0.8:100.

[0058] The method for removing the cationic surfactant, the temperature of the heating is preferably 100-140℃, more preferably 110-130℃, for example 120℃.

[0059] The method for removing the cationic surfactant, the time of the heating is preferably 2-4h, for example 3h.

[0060] The method for removing the cationic surfactant, the heating process preferably needs to be cooled to reflux.

[0061] The hydrophobic modification can be performed by conventional methods in the art, preferably by Method One or Method Two as follows:

[0062] Method One, the hydrophobic agent is mixed with the components in S1, and the mixing is completed.

[0063] Method Two, the hollow mesoporous silica obtained in S2 is mixed with the hydrophobic agent, and the mixing is completed.

[0064] In the hydrophobic modification, the hydrophobic agent can be as described above.

[0065] In Method One of the hydrophobic modification, the hydrophobic agent is mixed with the TEOS to obtain a mixed solution, and the mixed solution is mixed with the cationic surfactant and the solid silica nanoparticles (sSiO2).

[0066] The volume ratio of the hydrophobic agent to the TEOS can be conventional in the art, preferably 1:(1-30), more preferably 1:(2.5-20), for example 1:9.

[0067] The present application also provides a silica capsule wall prepared by the preparation method as described above.

[0068] The present application also provides a silica microcapsule, which comprises a plurality of silica capsule walls agglomerated into a hollow spherical capsule, and the hollow spherical capsule and the silica capsule wall are both filled with a core material in the cavity.

[0069] In the present application, the core material can be conventional in the art, preferably an oil-soluble compound or an oil-soluble mixture, more preferably a fragrance, a flavoring agent or a drug; further more preferably one or more of jasmine essence, sweet orange essence and lavender essence.

[0070] In the present application, the mass ratio of the core material to the silica microcapsule is preferably 30% to 50%, more preferably 40% to 45%, for example, 43.6%.

[0071] In some preferred embodiments of the present application, the core material is a fragrance, and the mass ratio of the fragrance to the silica microcapsule is 40% to 45%, for example, 43.6%.

[0072] The present application also provides a preparation method of the silica microcapsule as described above, which comprises the following steps:

[0073] S1: mixing the core material and the hydrophobic hollow mesoporous silica;

[0074] S2: mixing the solid obtained in S1 and the hydrophilic surfactant;

[0075] S3: mixing the solid obtained in S2 and the core material.

[0076] In the present application, after the above-mentioned S1 step, the core material is coated in the cavity of the hydrophobic hollow mesoporous silica; the obtained solid is mixed with the hydrophilic surfactant, i.e., the hydrophilic modification is performed, the hydrophobic tail of the hydrophilic surfactant is inserted into the mesopore of the hydrophobic hollow mesoporous silica, and the hydrophilic head is left on the surface of the silica; the surface of the obtained solid is hydrophilic, and then the hydrophobic core material is mixed to form an oil-in-water system.

[0077] In the present application, it can be routinely understood by those skilled in the art that the steps of S1 and S2 and the steps of S2 and S3 can further comprise a solid-liquid separation step.

[0078] The method of solid-liquid separation can be routine in the art, and is preferably suction filtration.

[0079] In S2, the mixing step is preferably performed by shaking. The shaking device can be routine in the art, and is preferably a shaker.

[0080] In S2, the mixing time can be routine in the art, and is preferably 1 to 3 hours, more preferably 2 hours.

[0081] The present application also provides a silica microcapsule obtained by the above-mentioned preparation method.

[0082] The present application also provides the use of the above-mentioned silica microcapsule as an additive in food or daily chemicals.

[0083] On the basis of common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain each preferred embodiment of the present application.

[0084] The reagents and raw materials used in the present application are commercially available.

[0085] The positive progress effect of the present application is that:

[0086] (1) The surface of the silica microcapsule of the present application forms a hydrophilic valve, improving the sustained-release characteristics of the core material and the controllability of the release, and the core material can be released through human friction and the like;

[0087] (2) The silica microcapsule with a hydrophilic valve can perform secondary embedding of the core material, forming a Pickering emulsion, improving the embedding efficiency, and the core material loading capacity can be as high as 43.6%;

[0088] (3) The silica microcapsule of the present application has a complete structure, is non-toxic, has good biocompatibility, and has high thermal stability;

[0089] (4) In the preparation of the silica microcapsule of the present application, the core material is embedded by using an adsorption method, and no additional additives are needed, which is green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0090] Figure 1 is a schematic diagram of double embedding of the silica microcapsule of the present application, and Fig. b is a partial enlarged view of Fig. a;

[0091] Figure 2 is a transmission electron microscope photograph of the hollow mesoporous silica prepared in Example 2;

[0092] Figure 3 is a hydrophobic angle test photograph of the hydrophobic hollow mesoporous silica prepared in Example 1, and the hydrophobic angle thereof is 141.4°;

[0093] Figure 4 a and Figure 4 b are dispersion test diagrams of the silica microcapsule of Comparative Example 1 and the silica microcapsule of Example 1 in water;

[0094] Figure 5 a and Figure 5 b are aroma fingerprint diagrams of a direct perfuming skin layer of an essential oil Figure 5 b is a partial enlarged view of a; Figure 5 a;

[0095] Figure 6 c and Figure 6 d are aroma fingerprint diagrams of a perfuming skin layer of a silica fragrance microcapsule Figure 6 d is a partial enlarged view of c; Figure 6 c;

[0096] Figure 7 The curves a, b and c of Fig. are respectively the thermal stability test result diagrams of the silica fragrance microcapsule of Example 1, the silica capsule wall of Example 5 and the sweet orange essential oil. DETAILED DESCRIPTION

[0097] The present application is further illustrated by the following examples without thereby limiting the application to the examples described. The experimental methods in the following examples, where no specific conditions are indicated, were carried out according to conventional methods and conditions, or according to the instructions of the commercial suppliers.

[0098] The product specifications and manufacturers of the main raw materials used in the following examples and comparative examples are shown in Table 1, and other raw materials are commercially available.

[0099] Table 1 Details of main raw materials used in examples and comparative examples

[0100]

[0101]

[0102] Example 1

[0103] Step 1: Preparation of sSiO2:

[0104] Deionized water 10 mL, ethanol 70 mL, ammonia water (25%-28wt%) 1.6 mL were mixed uniformly in a conical flask with a magnetic stirrer at a speed of 800 rpm / min, then 2 mL of tetraethoxysilane (TEOS) was added, stirred at room temperature for 1 h, a milky white silica colloidal suspension was formed, centrifugal separation was carried out at a speed of 13000 rpm / min, silica particles were collected, and washed with deionized water and ethanol three times each, vacuum dried at 65°C for 12 h, to obtain solid SiO2 nanospheres, namely sSiO2.

[0105] Step 2: Preparation of hydrophobic hollow mesoporous silica

[0106] Deionized water 10 mL, ethanol 70 mL and ammonia water (25-28 wt%) 3 mL were mixed homogeneously in a conical flask with a magnetic stirrer, 6 mL of TEOS was added, stirred at room temperature for 1 h, then 450 mg of cetyltrimethylammonium chloride (CTAC) was added, sSiO2 (300 mg, ultrasonic dispersion in 60 mL of deionized water) was added and dispersed by ultrasonic, stirred for 30 min, then 3.5 mL of TEOS:PDES = 2.5:1 mixture was added, stirred at 35°C for 1.5 h with a magnetic stirrer, the obtained solid was washed with ethanol for three times, and finally vacuum dried at 65°C for 12 h to obtain a core-shell structure of SiO2, CTAC and sSiO2 from outside to inside, which was recorded as SiO2-CTAC@SiO2. 100 mg of SiO2-CTAC@SiO2 was dispersed in 100 mL of sodium carbonate aqueous solution, after 50 min at 80°C, centrifugation, washing, and removal of CTAC by refluxing in 100 mL of 0.2 mol / L anhydrous ethanol containing 4 mL of hydrochloric acid at 80°C for 24 h, centrifugation, washing, and vacuum drying, hydrophobic hollow mesoporous silica was obtained, which was recorded as HMSN-PDES.

[0107] Step 3: embedding fragrance

[0108] The HMSN-PDES obtained in step 2 was mixed with jasmine fragrance, adsorbed, and then suction filtered.

[0109] Step 4: hydrophilic modification

[0110] The solid obtained in step 3 was added to Tween 80, shaken on a shaker at room temperature for 2 h, and then suction filtered.

[0111] Step 5: secondary embedding

[0112] The solid obtained in step 4 was mixed with jasmine fragrance, and then suction filtered, and the obtained solid was silica microcapsule with jasmine fragrance as the core material.

[0113] Example 2

[0114] Step 1: preparation of sSiO2

[0115] Step 1 was the same as example 1, and solid SiO2 nanospheres, i.e. sSiO2, were obtained.

[0116] Step 2: preparation of hydrophobic hollow mesoporous silica

[0117] Deionized water 10 mL, ethanol 70 mL and ammonia water (25-28 wt%) 3 mL were mixed in a flask with a magnetic stirrer, 450 mg of CTAC was added and stirred for 30 min, then sSiO2 (300 mg dispersed in 60 mL deionized water by ultrasonic) was added and stirred for 1 h, then 0.75 mL of TEOS was added and stirred for 6 h. The obtained solid was washed with ethanol for three times, and finally dried at 65 °C under vacuum for 12 h to obtain a core-shell structure of SiO2, CTAC and sSiO2 from outside to inside, which was recorded as SiO2-CTAC@SiO2. 100 mg of SiO2-CTAC@SiO2 was dispersed in 100 mL of 0.2 mol / L Na2CO3 aqueous solution, and sSiO2 was etched away after stirring at 80 °C for 40 min. The obtained solid was washed by centrifugation. The CTAC was removed by refluxing the obtained solid with 0.8 mL of hydrochloric acid and 100 mL of absolute ethanol at 120 °C for 3 h to obtain hollow mesoporous silica. The hollow mesoporous silica was dispersed in an ethanol solution containing PDES, where the volume of PDES and ethanol was 1 mL and 15 mL respectively, and stirred at room temperature at a speed of 800 rpm for 10 h. The obtained solid was washed by centrifugation and dried to obtain hydrophobic hollow mesoporous silica, which was recorded as HMSN-PDES.

[0118] Steps 3-5 were the same as those in Example 1 to obtain silica microcapsules.

[0119] Example 3

[0120] The lavender fragrance was loaded in step 3, and other steps were the same as those in Example 2 to obtain silica microcapsules.

[0121] Example 4

[0122] Step 1: The same as step 1 in Example 1.

[0123] Step 2: Preparation of hydrophobic hollow mesoporous silica

[0124] The 540 mL of deionized water, 540 mL of ethanol and 9.9 mL of ammonia water were mixed in a triangular flask with a magnetic stirrer, 2.7 g of CATC was added and stirred for 30 min, sSiO2 (1.8 g of sSiO2 was ultrasonically dispersed in 360 mL of deionized water) ultrasonically dispersed in deionized water was added, stirred for 1 h, then 45 mL of TEOS and OCSS mixture (the volume ratio of TEOS to OCSS was 9:1) was added, stirred for 6 h, after centrifugation, the obtained solid was washed with ethanol for three times, and finally vacuum dried (0.8 MPa, 65°C) for 12 h. 0.6 g of the product was dispersed in 100 mL of 0.2 mol / L Na2CO3 aqueous solution, stirred at 80°C for 40 min, then centrifuged and washed. Vacuum drying obtained hydrophobic hollow mesoporous silica (hydrophobic agent was OCSS), marked as HMSN-OCSS.

[0125] Steps 3-5 are the same as those in Example 1.

[0126] Example 5

[0127] Steps 3 and 5 are not performed, and other steps are the same as those in Example 1, to obtain a silica capsule wall.

[0128] Comparative Example 1

[0129] Only steps 1-3 of Example 1 are included, steps 4 and 5 are not performed, to obtain a silica microcapsule.

[0130] Comparative Example 2

[0131] Steps 1-3 are the same as those in Example 1, the modifier in step 4 is changed from Tween 80 to oleic acid, and other steps are the same as those in Example 1, to obtain a silica microcapsule.

[0132] Effect Example

[0133] 1. Structural schematic diagram

[0134] The schematic diagram of the silica microcapsule double-embedded obtained by Examples 1-4 of the present application is shown in Figure 1 . Figure 1 b is Figure 1 a local enlarged view. Figure 1 The small ball with a tail in b represents a hydrophilic surfactant, the hydrophobic tail of which is inserted into the mesopore of the hydrophobic hollow mesoporous silica, and the hydrophilic head is left on the surface of the silica. The cavity of the hydrophobic hollow mesoporous silica is filled with a core material.

[0135] 2. TEM test

[0136] The hollow mesoporous silica obtained in Example 2 was subjected to TEM test, and the transmission electron microscope was JEOL-2100F of Japan Electron Corporation, and the result is shown inFigure 2 As shown in Figure 2 It can be seen that the particle diameter is about 402 nm, the wall thickness is about 38 nm, the structure of the particle is complete, and the sphericity is good.

[0137] 3. Hydrophobic angle test

[0138] The hydrophobicity of the hollow mesoporous silica obtained in Example 1 and Example 4 was tested.

[0139] Specifically, the water contact angle was measured on a Theta flex optical contact angle instrument (Biolin scientific AB, Sweden) by the sessile drop method, the droplet volume was 5 μL, and the angle accuracy was ± 0.5°. Before testing, the silica capsule wall was pressed into a uniform sheet at a pressure of 20 MPa using a tablet press, and a photograph was taken for testing. The test method was a three-point measurement method, and the included angle between the tangent of the droplet and the bottom surface was taken. In order to make the measurement result more accurate, multiple samples were selected during the experiment, and then the contact angle was measured at multiple sites on the silica capsule wall. After the measurement was completed, the average value was calculated. The test results of the hydrophobic hollow mesoporous silica of Example 1 are shown in Figure 3 As shown in Figure 3 It can be seen that the hydrophobic angle is about 141.4°. The hydrophobic angle of the hydrophobic hollow mesoporous silica of Example 4 is 75.9°. It can be seen from the hydrophobic angle test results that the hydrophobic agent PDES of Example 1 has a better hydrophobic modification effect on the hollow mesoporous silica than the hydrophobic agent OCSS of Example 4, thereby improving the dispersibility of the hollow mesoporous silica in the perfume and having a higher perfume loading capacity.

[0140] 4. Dispersion test

[0141] The dispersion of the silica perfume microcapsules of Example 1 and Comparative Example 1 in water at room temperature was tested, and the results are shown in Figure 4 b and a of Figure 4 It can be seen that the silica microcapsules of Comparative Example 1 float in water and have poor dispersion; the silica microcapsules of the present application can be uniformly dispersed in water.

[0142] 5. Release test

[0143] The fragrance retention ability of the perfume oil directly added with fragrance and the silica perfume microcapsules obtained in Example 1 was tested using a Heracles II ultra-fast gas chromatograph type electronic nose, and the results are shown in Figure 5 a, 5b (perfume oil directly added with fragrance skin layer, b is an enlarged view of a), and Figure 6c, 6d (perfumed leather coated with silica microcapsules, wherein d is a magnified view of c) and the radar chart shown. This electronic nose is used to generate the aroma fingerprint by separating the compounds using different polarity chromatographic columns and identifying them by FID detector. 1 g of perfumed leather with dimensions of 0.5*0.5 cm was placed in a headspace bottle with a lid.

[0144] Preparation method of perfumed leather: (1) Pretreatment of leather surface: ammonia: anhydrous ethanol: deionized water = 1:2:17 (w / w / w) were stirred uniformly to obtain a leather surface cleaning solution, which was bottled for later use. Then the whole grain cowhide was cut into uniform small pieces of 3*3 cm. Dry gauze dipped in the cleaning solution was used to wipe the leather and remove dirt and dust. The clean leather was placed in a dry and ventilated place to dry, and then packed in a bag for later use; (2) The silica microcapsules of Example 1 and sandalwood essential oil (specifically including 5wt% sandalwood essential oil, 15wt% finishing agent and 80wt% water) were added to different spraying machines respectively, and were sprayed on the leather surface treated by the cleaning solution, with the same spraying amount. Then the wet leather was placed in a dry and ventilated place to dry for 24h to obtain the silica microcapsule perfumed leather and the essential oil directly perfumed leather.

[0145] Detection condition parameters: injection port pressure 10 KPa, trapping temperature 80°C, injection speed 125 μL / s, trapping time 16 s, injection volume 800 μL, injection port temperature 200°C, data acquisition time 138 s, injection time 11 s.

[0146] Figure 5 The electronic nose sensors of Figure 6 recorded the changes of aroma intensity of two different perfumed leather samples at different times through the aroma fingerprint. Through the comparison of the aroma fingerprints, the slow-release results of the two different perfumed leathers were obtained. The area size of the fingerprint region was positively correlated with the intensity of the aroma. As time went on, the area of the radar region became smaller and smaller due to the volatilization of the aroma of the perfumed leather, which indicated that the aroma intensity of the leather became weaker and weaker. From Figure 5 and Figure 6 it can be seen that the aroma of the silica microcapsule perfumed leather was released slowly, and the aroma of the essential oil directly perfumed leather was quickly volatilized and released. The reason may be that the essential oil molecules in the silica microcapsules are not only wrapped by the hollow mesoporous silica particles, but also adsorbed in the cavities of the particles, so the essential oil molecules are protected, and therefore the aroma release speed is relatively slow. After 90 days, the aroma of the silica microcapsule perfumed leather was far greater than that of the essential oil directly perfumed leather, and the silica microcapsule perfumed leather had a more durable aroma retention ability.

[0147] 6. Loading capacity and thermal stability test

[0148] The loading amount is the mass percentage of the core material in the microcapsule, which is an important index in industrial production.

[0149] The silica wall material obtained in Example 5 was dried in a freeze dryer for 24 h to obtain a white powder, which was used as a blank wall material for comparison. Then, 3-5 mg of the silica microcapsule of Example 1, the blank wall material powder and sweet orange oil were weighed into platinum sample pans, respectively, and were placed in a thermal gravimetric analyzer (Q5000, TA Instruments, USA). The samples were heated from 25 to 600℃ at a heating rate of 10℃ / min under a nitrogen atmosphere at a flow rate of 20 mL / min. The thermal gravimetric curves of the silica microcapsule, the blank wall material and the sweet orange oil were obtained from the changes in the sample mass with the increase in temperature, as shown in curves a, b and c, respectively, in FIG. 2. The loading amount can be calculated from the data in the thermal gravimetric curve using the following equation: Figure 7 (η2-LC) / (100-η1-LC)=η2’ / (100-η1’)

[0150] (η2-LC) / (100-η1-LC)=η2’ / (100-η1’)

[0151] η1 is the weight loss rate of the silica microcapsule between 25 and 100℃, which is 2%;

[0152] η1’ is the weight loss rate of the blank wall material between 25 and 100℃, which is 7%;

[0153] η2 represents the weight loss rate of the silica microcapsule between 100 and 600℃, which is 60%,

[0154] η2’ represents the weight loss rate of the blank wall material between 100 and 600℃, which is 28%;

[0155] LC is the loading amount of the silica microcapsule, and the calculation result is 43.6%.

Claims

1. A silica capsule wall, characterized in that, It comprises: hydrophobic hollow mesoporous silica and hydrophilic surfactant, the hydrophilic head of the hydrophilic surfactant is attached to the surface of the hydrophobic hollow mesoporous silica, the hydrophilic tail of the hydrophilic surfactant is located in the mesoporous of the hydrophobic hollow mesoporous silica; the HLB value of the hydrophilic surfactant is not less than 10; the hydrophobic hollow mesoporous silica comprises hollow mesoporous silica and hydrophobic agent attached to the surface of the hollow mesoporous silica; The hydrophobic agent is PDES, and the hydrophilic surfactant is Tween 80.

2. A process for the preparation of a silica capsule wall as claimed in claim 1, characterized in that, It comprises the following steps: mixing the hydrophobic hollow mesoporous silica and the hydrophilic surfactant.

3. The production method according to claim 2, wherein The preparation method of the hydrophobic hollow mesoporous silica is to hydrophobically modify the hollow mesoporous silica. The preparation method of the hollow mesoporous silica comprises the following steps: S1: mixing cationic surfactant, sSiO2 and TEOS in a solvent under alkaline environment to obtain a core / shell composite structure comprising sSiO2, the cationic surfactant and SiO2 from inside to outside; S2: selectively etching the sSiO2 core of the core / shell composite structure obtained in S1 to remove the cationic surfactant.

4. The production method according to claim 3, wherein The preparation method of the hollow mesoporous silica satisfies one or more of the following conditions: (1) In S1, the solvent is an ethanol aqueous solution; the volume ratio of ethanol to water in the ethanol aqueous solution is (1-10):1; (2) In S1, the concentration of the cationic surfactant in the solvent is 4-7 mg / mL; (3) In S1, the volume ratio of the TEOS to the solvent is 1:(80-150); And (4) In S1, the pH value of the alkaline environment is 9-10.

5. The production method according to claim 4, wherein In S1, the volume ratio of ethanol to water in the ethanol aqueous solution is 7:1; And / or, in S1, the concentration of the cationic surfactant in the solvent is 5-6 mg / mL; And / or, in S1, the volume ratio of the TEOS to the solvent is 1:106.

7.

6. The production method according to claim 3, wherein The hydrophobic modification method is method one or method two as follows: Method one, mixing the hydrophobic agent with each component in S1; Method two, mixing the hollow mesoporous silica obtained in S2 with the hydrophobic agent; Wherein, the volume ratio of the hydrophobic agent to the TEOS is 1:(1-30).

7. The production method according to claim 6, wherein The volume ratio of the hydrophobic agent to the TEOS is 1:(2.5-20).

8. The production method according to claim 7, wherein The volume ratio of the hydrophobic agent to the TEOS is 1:

9.

9. A silica capsule wall characterized by, It is obtained by the preparation method in any one of claims 2-8.

10. A silica microcapsule characterized in that, It comprises the hollow capsule formed by the agglomeration of the silica capsule wall in claim 1 or 9, and the cavity of the hollow capsule and the cavity of the silica capsule wall are both filled with core material.

11. The silica microcapsule of claim 10, wherein the silica shell has a thickness of 5 to 50 nm. The mass ratio of the core material to the silica microcapsule is 30%-50%; And / or, the core material is an oil-soluble compound or an oil-soluble mixture.

12. The silica microcapsule of claim 11, wherein, The mass ratio of the core material to the silica microcapsule is 40-45%; And / or, the core material is perfume, flavoring agent and drug.

13. The silica microcapsule of claim 12, wherein the silica shell has a thickness of 5 to 50 nm. The mass ratio of the core material to the silica microcapsule is 43.6%; And / or, the core material is one or more of jasmine essence, sweet orange essence and lavender essence.

14. A process for the preparation of the silica microcapsules according to any one of claims 10 to 13, characterized in that, It comprises the following steps: S1: mixing the core material and the hydrophobic hollow mesoporous silica; S2: mixing the solid obtained in S1 and the hydrophilic surfactant; S3: mixing the solid obtained in S2 with the core material, and the process is completed.

15. The method for producing the silica microcapsules according to claim 14, wherein In S2, the mixing is carried out by shaking; And / or, in S2, the mixing time is 1-3 hours.

16. The method for producing the silica microcapsules according to claim 15, wherein In S2, the mixing time is 2 hours.

17. A silica microcapsule characterized in that, It is obtained by the preparation method of claim 14 or 15.

18. Use of the silica microcapsule of any one of claims 10-13 or 17 as an additive in food or daily chemicals; When the silica microcapsule of claim 12 is used as an additive, the core material is essence or flavoring.

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