Polyurea microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a polyurea microcapsule as well as a preparation method and application thereof. The structure of the polyurea microcapsule comprises a capsule wall and a capsule core, the capsule wall is formed by reaction of polyisocyanate and polyamine, the capsule core comprises a flavoring agent and a high-boiling-point organic solvent, and the mass ratio of the flavoring agent to the high-boiling-point organic solvent is 1: 2-1: 5. The polyurea microcapsule is good in thermal stability, good in particle size uniformity and high in coating rate.

Description

Technical Field

[0001] The present invention relates to the technical field of microcapsule preparation, and more specifically, to a polyurea microcapsule and a preparation method and application thereof. Background Art

[0002] Fragrances are often used in daily life to give people a pleasant feeling, and their functions include insect repellent, freshness preservation, disinfection, etc. For example, essential oils have good antibacterial and antioxidant properties, are green and safe, and are widely used in food, medicine and cosmetics. However, natural essential oils contain a large amount of terpene compounds, which are unstable and volatile in light, oxygen, high temperature and humid environments. Therefore, microencapsulation technology is used to solve this problem and play a role in protection and slow release.

[0003] Due to the volatility of essential oils, it is particularly important to be careful when heating is used in the coating process of essential oils, which may reduce the coating efficiency or even fail to coat. Therefore, room temperature or even low temperature reactions are often used. Chinese patent CN106433151A reports a method for preparing clove oil antibacterial microcapsules, which uses lauryl alcohol modified sodium alginate derivatives as wall materials, and self-assembles to form core-shell structure microcapsules with clove oil as the core, which belongs to the sharp hole-condensation method. There is also a patent with publication number CN108479650A reporting a method for preparing silk fibroin microcapsules, which uses silk fibroin as wall material and is prepared by freezing induction method. The capsule has an average particle size of 3.4-5.3 μm and a fragrance loading (covering rate) of 34-47%. These methods have the disadvantages of poor particle size uniformity and poor heat resistance stability.

[0004] Polyurethane and polyurea micro-wall materials have good thermal stability and are also well-known capsule preparation technologies. They are used in various technical fields, including the field of spices. Some prior arts disclose a natural essential oil microcapsule coated with a polyurethane or polyurea-silk fibroin composite wall material and a preparation method thereof. First, diisocyanates are mixed with natural essential oils; polyol or polyamine aqueous solution is added to the obtained emulsion, and a suspension containing polyurethane / polyurea microcapsules is obtained after heating and stirring the reaction. However, heating and stirring are required during the reaction process, resulting in problems with the uniformity of the particle size and coverage of the capsules. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a polyurea microcapsule and a preparation method and application thereof. The polyurea microcapsule has good thermal stability, good particle size uniformity and high coverage rate.

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

[0007] On the one hand, the present invention provides a polyurea microcapsule, wherein the structure of the polyurea microcapsule comprises a capsule wall and a capsule core, wherein the capsule wall is formed by the reaction of polyisocyanate and polyamine, and the capsule core comprises a flavoring agent and a high-boiling point organic solvent, and the mass ratio of the flavoring agent to the high-boiling point organic solvent is 1:2-1:5.

[0008] Furthermore, the molar number of the polyamine is slightly higher than the molar number of the polyisocyanate, which can ensure that the polyisocyanate is completely reacted.

[0009] Furthermore, the capsule wall is formed by reacting polyisocyanate and polyamine in a molar ratio of 1:1-1:2 or 1:1-1:1.5 or 1:1-1:1.2.

[0010] Furthermore, the mass ratio of the capsule wall to the capsule core is 1:1.5-1:3.

[0011] Furthermore, the average particle size of the polyurea microcapsules is 5-15 μm, preferably 8-10 μm, the capsule wall thickness is 0.5-1.0 μm, the thickness ratio of the capsule wall to the capsule core is 1:10-1:20, and the coverage rate of the capsule core is 80-90%.

[0012] Furthermore, the polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane-4,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, D-110N, trimer of hexamethylene diisocyanate, trimer of isophorone diisocyanate, biuret of hexamethylene diisocyanate, polyisocyanurate of toluene diisocyanate, trimethylolpropane adduct of toluene diisocyanate, and trimethylolpropane adduct of xylylene diisocyanate.

[0013] Further, the polyamine is selected from one or more of hexamethylenediamine, tetraethylenepentamine, ethylenediamine, hexamethylenediamine, triethylamine, pentaethylenehexamine, diphenylmethanediamine, diethyltoluenediamine, dimethylthiotoluenediamine, 1,3-diaminopropane, 1,4-diaminobutane, diethylenetriamine, pentaethylenehexamine, bis(3-aminopropyl)amine, bis(hexamethylene)triamine, tris(2-aminoethyl)amine, triethylenetetramine, N,N′-bis(3-aminopropyl)-1,3-propylenediamine, pentaethylenehexamine, polyetheramine, 1,2-cyclohexanediamine, N,N′-dimethyl-1,2-cyclohexanediamine, chitosan, nisin, gelatin, 1,3-diaminoguanidine, 1,1-dimethylbiguanidine, guanidine, arginine, lysine, and ornithine.

[0014] Furthermore, the flavoring agent is selected from one or more of alcohols, aldehydes, ketones, esters, ethers, acetates, nitriles, terpenoids, nitrogen-containing or sulfur-containing heterocyclic compounds and essential oils.

[0015] Furthermore, the essential oil is selected from natural essential oils, specifically selected from one or more of clove oil, peppermint oil, lavender oil, thyme oil, eucalyptus oil, and ginger oil.

[0016] Furthermore, the flavoring agent is selected from one or more of limonene, orange essential oil, eucalyptus oil, osmanthus essence, thyme oil, eucalyptus oil, clove oil, lavender oil, and ginger oil.

[0017] Furthermore, the high boiling point solvent refers to an organic solvent that is insoluble in water and has a high boiling point and a high flash point.

[0018] Furthermore, the high boiling point solvent is selected from one or more of dimethyl phthalate, diethyl phthalate, isopropyl myristate, benzyl benzoate, and ethyl citrate.

[0019] In another aspect, the present invention provides a method for preparing the polyurea microcapsule as described above, the preparation method comprising the following steps:

[0020] Mixing the fragrance, the high boiling point solvent and the polyisocyanate uniformly to obtain an oil phase;

[0021] Dissolve the surfactant in water and mix well to obtain an aqueous phase;

[0022] The water-soluble resin is first dissolved in water to prepare a resin aqueous solution, and then a polyamine is added and mixed evenly to obtain a wall-forming reaction solution;

[0023] The oil phase is added to the water phase to obtain a water-oil mixture, which is placed in an ice bath, the temperature of the water-oil mixture is adjusted to ≤10°C, and high-speed shearing and emulsification are started to obtain a low-temperature emulsion;

[0024] Under ice bath and stirring conditions, the wall-forming reaction liquid is added dropwise to the low-temperature emulsion. During the adding process, the temperature of the low-temperature emulsion is maintained at ≤15°C. The wall-forming reaction liquid is added dropwise at a speed of 20-60 minutes. After the wall reaction liquid is added dropwise, the ice bath is removed, and the reaction is stirred at room temperature until the isocyanate peak of the multifunctional isocyanate compound in the reaction liquid disappears as detected by infrared spectroscopy, thereby obtaining the polyurea microcapsules.

[0025] In the present technical solution, slowly dropping the wall-forming reaction liquid at low temperature is the key to maintaining good uniformity of the particle size of the product capsules; and low-temperature dropping and room-temperature reaction are the keys to improving the coverage rate.

[0026] Furthermore, the surface tension of the water phase is 15-30 N / m.

[0027] Furthermore, the surfactant consists of a fluorine surfactant and a fluorine-free surfactant.

[0028] Furthermore, in the water phase, the amount of fluorine surfactant added is 0.01-0.05 wt % of water, and the amount of non-fluorine-containing surfactant added is 0.1-1.0 wt % of water.

[0029] Furthermore, in the wall-forming reaction solution, the concentration of the water-soluble resin is 1-5wt%.

[0030] In this technical solution, the water-soluble resin does not participate in the reaction, that is, the final product polyurea microcapsule does not contain water-soluble resin. The water-soluble resin is an additive in the reaction process. For example, the subsequent water phase also contains fluorinated surfactants and non-ionic surfactants, which are additives in the reaction and do not appear in the final product.

[0031] Furthermore, the water-soluble resin is selected from one or more of polyvinyl alcohol, polyvinyl pyrrolidone, N-vinyl pyrrolidone and vinyl acetate copolymer (referred to as VA resin), N-vinyl pyrrolidone and (methyl) acrylate copolymer, N-vinyl pyrrolidone and (methyl) acrylamide copolymer, N-vinyl pyrrolidone and styrene copolymer, gelatin and cellulose derivatives.

[0032] Furthermore, the emulsification time is 5-15 minutes.

[0033] Furthermore, the fluorinated surfactant can be nonionic, anionic or cationic, without limitation. Low temperature shearing and the use of fluorinated surfactant can make the emulsion more stable, thereby making the particle size uniformity of the final microcapsules good.

[0034] Furthermore, the non-fluorinated surfactant is a non-ionic surfactant in order to be well miscible with the fluorinated surfactant, and the HLB value is greater than or equal to 10. Under this condition, it is well miscible with the fluorinated surfactant.

[0035] Furthermore, the fluorine-free surfactant is selected from one of AEO-9, OP-10, O-15 and the like.

[0036] Furthermore, the wall-forming reaction liquid is dripped at a speed of 30-40 minutes, at which time the reaction stability and reaction efficiency are better.

[0037] In another aspect, the present invention provides the use of the polyurea microcapsules described above in the preparation of cosmetics, personal care products, fabric care products, detergents, and deodorants.

[0038] The beneficial effects of the present invention are as follows:

[0039] The polyurea microcapsules provided in the present invention have photothermal properties, as well as high particle size uniformity, stability and coverage rate; in the preparation method of the polyurea microcapsules provided in the present invention, the emulsification temperature, the speed of adding the wall-forming reaction liquid dropwise, and the preparation conditions are mild, and the prepared microcapsules have high particle size uniformity, stability and coverage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0041] Figure 1 The infrared absorption spectrum of the polyurea microcapsules prepared in Example 1 is shown.

[0042] Figure 2 The scanning electron microscope image of the polyurea microcapsules prepared in Example 1 is shown.

[0043] Figure 3 The transmission electron microscope image of the polyurea microcapsules prepared in Example 1 is shown.

[0044] Figure 4 The thermogravimetric curve of the polyurea microcapsules prepared in Example 1 is shown. DETAILED DESCRIPTION

[0045] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0046] Implementation Example 1-Example 10

[0047] The raw materials of the polyurea microcapsules encapsulating the fragrance agent of Examples 1 to 10 are shown in Table 1, and the preparation method comprises the following steps:

[0048] Weigh 3.3 g of water-soluble resin, 322.2 g of deionized water, and 15.12 g of polyamine respectively, add them into a 500 mL beaker, stir evenly, and fully dissolve to obtain a transparent wall-forming reaction solution;

[0049] Weigh out an equal molar amount of polyisocyanate to the polyamine, 65.92 g of a high boiling point solvent, and 16.48 g of a flavoring agent, stir well, and obtain an oil phase.

[0050] Weigh 1.6g OP-10, 0.12g fluorinated surfactant FC-203 and 305g deionized water respectively, add into a 1000mL beaker, stir evenly to obtain an aqueous phase;

[0051] Pour the oil phase into the water phase and place it in an ice bath. When the temperature of the water-oil mixture is 10°C, emulsify it under high-speed shear for 10 minutes at a shear speed of 10,000RPM. Then change to a mechanical stirring device and add the wall-forming material reaction liquid dropwise while stirring. After 30 minutes of addition, remove the ice bath and continue stirring at room temperature. The reaction end point is when the isocyanate peak of the wall-forming material A in the reaction liquid disappears as detected by infrared spectroscopy.

[0052] The infrared absorption curve of the polyurea microcapsules coated with the flavoring agent prepared in Example 1 is as follows: Figure 1 shown.

[0053] The scanning electron microscopy and transmission electron microscopy images of the polyurea microcapsules prepared in Example 1 are as follows: Figure 2 and Figure 3 As shown, the thermal gravimetric curve is Figure 4 shown.

[0054] Embodiment 11

[0055] In Example 1, the oil phase was poured into the water phase and emulsified for 15 minutes, and the rest remained unchanged. The raw materials were as shown in Table 1, and polyurea microcapsules were prepared.

[0056] Example 12

[0057] In Example 1, the time for the dropwise addition of the wall-forming reaction was 60 minutes, and the rest remained unchanged. The raw materials were as shown in Table 1, and microcapsules were prepared.

[0058] Example 13

[0059] In Example 1, the amount of the flavoring agent was changed to 18.73 g, and the rest remained unchanged. The raw materials were as shown in Table 1, and microcapsules were prepared.

[0060] Table 1 Raw material composition of each embodiment and comparative example

[0061]

[0062]

[0063] Comparative Example 1

[0064] In Comparative Example 1, no high boiling point solvent was added, and the rest remained unchanged. The raw materials were shown in Table 1 to prepare microcapsules. The average particle size of the microcapsules was 2 um, and the morphology was irregular, with most of them being concave and deflated.

[0065] Comparative Example 2

[0066] In Comparative Example 2, the wall-forming reaction liquid was added dropwise very slowly, and the addition was completed in 80 minutes, and the rest remained unchanged. The raw materials were shown in Table 1, and microcapsules were prepared. The particle size uniformity of the microcapsules was poor.

[0067] Comparative Example 3

[0068] In comparative example 3, after the wall reaction liquid was added dropwise, the reaction was heated to 60°C and stirred until the isocyanate group disappeared, which was the end point of the reaction. The raw materials were shown in Table 1 to prepare microcapsules. The microcapsules had irregular morphology, and most of them were concave and deflated.

[0069] Comparative Example 4

[0070] In Comparative Example 4, the wall-forming reaction solution was added dropwise without ice bath, and the microcapsules were prepared at room temperature according to conventional reaction methods, and the rest was the same as in Example 1. The raw materials are shown in Table 1. The microcapsules had irregular morphology, and most of them were concave and deflated.

[0071] Comparative Example 5

[0072] In Comparative Example 5, the wall-forming reaction liquid was added to the emulsion quickly under stirring, and the addition was completed in about 5 minutes, and the rest remained unchanged. The raw materials are shown in Table 1, and microcapsules were prepared. The particle size uniformity of the microcapsules was poor.

[0073] The coverage rate refers to the mass percentage of the capsule core composed of the flavoring agent and the high boiling point solvent in the capsule. The higher the coverage rate, the stronger the ability of the polyurea microcapsule provided by the present invention to encapsulate the flavoring agent.

[0074] Test method for coverage:

[0075] The polyurea microcapsules were dried at 50°C to obtain microcapsule powder. A small amount was scraped and placed on a flat aluminum sheet. The mass m1 of the aluminum sheet and the mass m2 of the microcapsule powder were weighed respectively. They were placed on a hot table and heated at a constant temperature of 300°C for 30 min. The total mass m3 of the aluminum sheet and the sample was weighed again. The coverage rate = 1-[(m3-m1) / m2].

[0076] The properties of the polyurea microcapsules prepared in the above embodiments and comparative examples are shown in Table 2 below.

[0077] Table 2 Properties of polyurea microcapsules prepared in Examples and Comparative Examples

[0078]

[0079] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A polyurea microcapsule, characterized in that: The structure of the polyurea microcapsule comprises a capsule wall and a capsule core, wherein the capsule wall is formed by the reaction of polyisocyanate and polyamine, and the capsule core comprises a flavoring agent and a high-boiling-point organic solvent, wherein the mass ratio of the flavoring agent to the high-boiling-point organic solvent is 1:2-1:

5.

2. The polyurea microcapsule according to claim 1, characterized in that The mass ratio of the capsule wall to the capsule core is 1:1.5-1:3; Preferably, the average particle size of the polyurea microcapsules is 5-15 um, the capsule wall thickness is 0.5-1.0 um, the thickness ratio of the capsule wall to the capsule core is 1:10-1:20, and the coverage rate of the capsule core is 80-90%.

3. The polyurea microcapsule according to claim 1, characterized in that The polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane-4,4 diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, D-110N, trimer of hexamethylene diisocyanate, trimer of isophorone diisocyanate, biuret of hexamethylene diisocyanate, polyisocyanurate of toluene diisocyanate, trimethylolpropane adduct of toluene diisocyanate, and trimethylolpropane adduct of xylylene diisocyanate; and / or The polyamine is selected from one or more of hexamethylenediamine, tetraethylenepentamine, ethylenediamine, hexamethylenediamine, triethylamine, pentaethylenehexamine, diphenylmethanediamine, diethyltoluenediamine, dimethylthiotoluenediamine, 1,3-diaminopropane, 1,4-diaminobutane, diethylenetriamine, pentaethylenehexamine, bis(3-aminopropyl)amine, bis(hexamethylene)triamine, tris(2-aminoethyl)amine, triethylenetetramine, N,N′-bis(3-aminopropyl)-1,3-propylenediamine, pentaethylenehexamine, polyetheramine, 1,2-cyclohexanediamine, N,N′-dimethyl-1,2-cyclohexanediamine, chitosan, nisin, gelatin, 1,3-diaminoguanidine, 1,1-dimethylbiguanidine, guanidine, arginine, lysine, and ornithine.

4. The polyurea microcapsule according to claim 1, characterized in that: The flavoring agent is selected from one or more of alcohols, aldehydes, ketones, esters, ethers, acetates, nitriles, terpenoids, nitrogen-containing or sulfur-containing heterocyclic compounds and essential oils; and / or The high boiling point solvent is selected from one or more of dimethyl phthalate, diethyl phthalate, isopropyl myristate, benzyl benzoate and ethyl citrate.

5. The method for preparing polyurea microcapsules according to any one of claims 1 to 4, characterized in that: The steps include: Mixing the fragrance, the high boiling point solvent and the polyisocyanate uniformly to obtain an oil phase; Dissolve the surfactant in water and mix well to obtain an aqueous phase; The water-soluble resin is first dissolved in water to prepare a resin aqueous solution, and then a polyamine is added and mixed evenly to obtain a wall-forming reaction solution; The oil phase is added to the water phase to obtain a water-oil mixture, which is placed in an ice bath, the temperature of the water-oil mixture is adjusted to ≤10°C, and high-speed shearing and emulsification are started to obtain a low-temperature emulsion; Under ice bath and stirring conditions, the wall-forming reaction liquid is added dropwise to the low-temperature emulsion. During the adding process, the temperature of the low-temperature emulsion is maintained at ≤15°C. The wall-forming reaction liquid is added dropwise at a speed of 20-60 minutes. After the wall reaction liquid is added dropwise, the ice bath is removed, and the reaction is stirred at room temperature until the isocyanate peak of the multifunctional isocyanate compound in the reaction liquid disappears as detected by infrared spectroscopy, thereby obtaining the polyurea microcapsules.

6. The preparation method according to claim 5, characterized in that: The surface tension of the aqueous phase is 15-30 N / m; Preferably, the surfactant consists of a fluorinated surfactant and a non-fluorinated surfactant; Preferably, in the water phase, the amount of fluorinated surfactant added is 0.01-0.05 wt % of water, and the amount of non-fluorinated surfactant added is 0.1-1.0 wt % of water.

7. The preparation method according to claim 5, characterized in that: In the wall-forming reaction solution, the concentration of the water-soluble resin is 1-5wt%.

8. The preparation method according to claim 5, characterized in that: The water-soluble resin is selected from one or more of polyvinyl alcohol, polyvinyl pyrrolidone, N-vinyl pyrrolidone and vinyl acetate copolymer (referred to as VA resin), N-vinyl pyrrolidone and (methyl) acrylate copolymer, N-vinyl pyrrolidone and (methyl) acrylamide copolymer, N-vinyl pyrrolidone and styrene copolymer, gelatin and cellulose derivatives.

9. The preparation method according to claim 5, characterized in that: The emulsification time is 5-15 minutes.

10. Use of the polyurea microcapsule according to any one of claims 1 to 4 in the preparation of cosmetics, personal care products, fabric care products, detergents and deodorants.

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