阅读说明：本技术 一种浅色化邻苯二酚木质素磺酸盐防晒微胶囊及其制备与应用 (Light-colored catechol lignosulfonate sun-proof microcapsule and preparation and application thereof ) 是由 钱勇 张艾程 邱学青 杨东杰 杨换仙 楼宏铭 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种浅色化邻苯二酚木质素磺酸盐防晒微胶囊及其制备与应用。本发明采用硫化法对木质素磺酸盐进行改性制备邻苯二酚木质素磺酸盐,再将邻苯二酚木质素磺酸盐与防晒剂、表面活性剂进行超声空化制备邻苯二酚木质素磺酸盐/化学防晒剂微胶囊乳液。本发明所述木质素/化学防晒剂微胶囊的制备过程绿色环保,成本低廉而且紫外吸收性能优异,相比于其他木质素基防晒剂颜色更浅,生物粘附性和抗渗透性能良好,解决传统防晒剂耐水性差、制备工艺污染较大、易渗入皮肤伤害人体等问题。(The invention discloses a light-colored catechol lignosulfonate sun-proof microcapsule and preparation and application thereof. The invention adopts a vulcanization method to modify lignosulfonate to prepare catechol lignosulfonate, and then carries out ultrasonic cavitation on the catechol lignosulfonate, a sun-screening agent and a surfactant to prepare catechol lignosulfonate/chemical sun-screening agent microcapsule emulsion. The preparation process of the lignin/chemical sunscreen agent microcapsule is environment-friendly, the cost is low, the ultraviolet absorption performance is excellent, compared with other lignin-based sunscreen agents, the lignin/chemical sunscreen agent microcapsule is lighter in color, good in biological adhesion and anti-permeability performance, and the problems that a traditional sunscreen agent is poor in water resistance, large in pollution of a preparation process, easy to permeate into skin and damage human bodies and the like are solved.)

1. A preparation method of a light-colored catechol lignosulfonate sun-protection microcapsule is characterized by comprising the following steps:

(1) dissolving lignosulfonate and a vulcanizing reagent in an alkali solution, reacting at 40-160 ℃ for 0.1-5 hours, dialyzing, concentrating and drying to obtain catechol lignosulfonate;

(2) dissolving catechol lignosulfonate in an aqueous solution with the pH value of 5-9, adding a sun-screening agent and a surfactant, performing ultrasonic cavitation to obtain catechol lignosulfonate/chemical sun-screening agent microcapsule emulsion, and centrifuging to obtain light-colored catechol lignosulfonate sun-screening microcapsules.

2. The preparation method of the light-colored catechol lignosulfonate sun-blocking microcapsule according to claim 1, wherein the weight ratio of the lignosulfonate to the vulcanizing agent in the step (1) is 1-10: 0.2 to 2; the sulfuration reagent is at least one of sulfite, pyrosulfite, thiosulfate and bisulfite.

3. The method for preparing a light-colored catechol lignosulfonate sunscreen microcapsule according to claim 2, wherein the weight ratio of the lignosulfonate to the vulcanizing agent in the step (1) is 10: 0.7 to 2.

4. The preparation method of the light-colored catechol lignosulfonate sun-screening microcapsule according to claim 1, wherein the weight ratio of the total weight of the solution obtained by dissolving the catechol lignosulfonate in the aqueous solution with the pH value of 5-9 in the step (2) to the sun-screening agent is 1: 1-10: 1;

the addition amount of the surfactant in the step (2) accounts for 1-10 wt% of the total weight of the catechol lignosulfonate, the aqueous solution with the pH value of 5-9 and the sun-screening agent;

the weight ratio of the catechol lignosulfonate to the aqueous solution with the pH value of 5-9 in the step (2) is 1-10: 20 to 100.

5. The preparation method of the light-colored catechol lignosulfonate sun-screening microcapsule according to claim 4, wherein the weight ratio of the total weight of the solution obtained by dissolving the catechol lignosulfonate in the aqueous solution with the pH value of 5-9 in the step (2) to the sun-screening agent is 1: 1-4: 1;

the addition amount of the surfactant in the step (2) accounts for 3-10 wt% of the total weight of the catechol lignosulfonate, the aqueous solution with the pH value of 5-9 and the sun-screening agent;

the weight ratio of the catechol lignosulfonate to the aqueous solution with the pH value of 5-9 in the step (2) is 1: 10 to 33.

6. The method for preparing a light-colored catechol lignosulfonate sunscreen microcapsule according to claim 1, wherein the lignosulfonate of step (1) is at least one of sodium lignosulfonate, magnesium lignosulfonate and calcium lignosulfonate; the lignin in the lignosulfonate is at least one of bamboo pulp lignosulfonate, wheat straw pulp lignosulfonate, reed lignosulfonate, bagasse pulp lignosulfonate, asparagus pulp lignosulfonate and cotton pulp lignosulfonate;

the sun-screening agent in the step (2) is at least one of avobenzone, ethylhexyl methoxycinnamate, homosalate and oxybenzone;

and (3) the surfactant in the step (2) is at least one of tween, alkyl polyglycoside and sucrose ester.

7. The preparation method of the light-colored catechol lignosulfonate sun-blocking microcapsule according to claim 1, wherein the reaction temperature in the step (1) is 70-140 ℃ and the reaction time is 1-2.5 h;

and (3) the power of the ultrasonic cavitation in the step (2) is 200-1500W, and the time is 1-20 min.

8. The preparation method of the light-colored catechol lignosulfonate sun-blocking microcapsule as claimed in claim 1, wherein the alkali solution in the step (1) is 1-20 wt% of sodium hydroxide solution, and the weight ratio of the lignosulfonate to the alkali solution is 1-10: 30, of a nitrogen-containing gas; the dialysis treatment in the step (1) is carried out for 2-8 days, and the dialysate is water.

9. A light-coloured catechol lignosulfonate sunscreen microcapsule obtainable by the process according to any one of claims 1 to 8.

10. Use of a light-coloured catechol lignosulfonate sunscreen microcapsule according to claim 9 in the field of chemical sunscreen.

Technical Field

The invention belongs to the field of fine chemicals, and particularly relates to a light-colored catechol lignosulfonate sun-protection microcapsule as well as preparation and application thereof.

Background

Illumination radiation having a wavelength of 10 to 400nm is internationally called ultraviolet radiation. According to international practice, ultraviolet radiation can be divided into UVA (ultraviolet A) band (320-400 nm), UVB (ultraviolet B) band (290-320 nm), UVC (ultraviolet C) band (200-290 nm) and EUV (ultraviolet light) band (10-100 nm). Prolonged exposure to uv radiation can result in sunburn, aging and even skin cancer. EUV and UVC are already absorbed by the ozone layer in high altitude, while 1% to 10% of UVB and more than about 90% of UVA can still pass through the atmosphere to the earth's surface. Ultraviolet rays in the UVB band have weak penetrating performance, most of the ultraviolet rays are absorbed by epidermal cells of a human body when the ultraviolet rays irradiate the human body, but the ultraviolet rays in the UVB band have relatively high energy, so that the skin is damaged by light, and the phenomena of reddening and blister appear on the skin. If the skin is irradiated for a long time, adverse reactions such as inflammation and aging of the skin can be caused, and skin cancer can be caused in severe cases. Ultraviolet rays in UVA wave band have strong penetrating performance and can reach deep dermis of a human body, so that melanin in the human body is deposited, and the skin of the human body is aged and damaged after long-term accumulation. Reactive Oxygen Species (ROS) induced by UVA and UVB radiation damage various cellular components and induce The formation of immunosuppressive cytokines (The FASEB Journal,2018,32(7): 3700-. Therefore, it is necessary to use an ultraviolet protective agent to prevent ultraviolet damage.

Depending on the mechanism of protection, protective agents can be divided into two broad categories, physical and chemical sunscreens. Physical sunscreens are relatively thick and heavy, have poor feel in use, and are susceptible to photocatalytic reactions. Therefore, most of the chemical sun-screening agents are used in the market, and common chemical sun-screening additives in the market comprise benzophenone-3, dimethylbenzene, avobenzone, cinnamate and the like. But after the reaction, the small molecules are absorbed by the skin, penetrate further through the stratum corneum, or enter the epidermal cells through the follicles, and cause allergic reactions or even destroy the DNA. And under uv radiation, even small amounts of chemical, physical sunscreens penetrate the skin, generating Reactive Oxygen Species (ROS) leading to cell and tissue damage and ultimately to a range of skin and systemic diseases (Advanced Functional Materials,2018,28, 1802127). The permeation problem of the small molecule sunscreen has attracted people's close attention, and Deng et al effectively prevent the sunscreen from permeating by using aldehyde hyperbranched polyglycidyl ether with biological adhesive property as a wall material to wrap the small molecule sunscreen to form microcapsules (Nature Materials,2015,14, 1278). But its uv resistance is limited and it is difficult to satisfy the use conditions in severe environments.

The nature has abundant lignin, and the lignin is the second natural high molecular compound in nature and is also the highest natural high molecular polymer containing benzene rings. It can protect the tissues inside the plant from being damaged by ultraviolet radiation. The reason is that after the ultraviolet rays irradiate the plants, the lignin in the plants generates the phenylpropane conjugate, so that the ultraviolet rays can be effectively shielded. Lignin contains a large number of phenolic hydroxyl groups, benzene rings, carbonyl groups, methoxy groups, etc., which can effectively absorb ultraviolet rays and can also scavenge free radicals to play a role in oxidation resistance (Industrial crops and products,2011,33, 259-276).

Although the sun-screening performance of lignin is limited, the lignin and the chemical sun-screening agent have a synergistic effect, so that the sun-screening performance of the commercial sun-screening cream can be effectively improved, and meanwhile, the photolysis resistance of the chemical sun-screening agent can also be improved (Green Chemistry,2015,17: 320-324). Therefore, the lignin/sunscreen composite nanocapsule is prepared by wrapping avobenzone and cinnamate with lignin, the ratio of the lignin and the sunscreen is regulated to strengthen the synergistic effect of the lignin and the sunscreen, the SPF value of the sunscreen obtained by adding 10 wt% of the lignin and mixing the lignin with blank hand cream can reach 408 at most, and the sunscreen can show good ultraviolet protection performance within 8 hours (ACS Applied Bio Materials,2018,1, 1276).

The nano-scale lignin capsule provides a new direction for the development of natural high-efficiency sunscreen cream due to the excellent and long-acting ultraviolet protection performance. However, the lignin microcapsules have relatively small particle size and little bioadhesive properties, and thus still pose the potential for skin penetration. Therefore, lignin needs to be modified to increase the content of phenolic hydroxyl in lignin, so that the bioadhesion capability of lignin and lignin microcapsules is enhanced, and the safety and the use performance of sodium lignosulfonate for an ultraviolet protective agent are improved.

The existing lignin-based sunscreen cream is mainly prepared by using alkali lignin and enzymatic hydrolysis lignin as raw materials, the two lignins are relatively dark in color, lignosulfonate has a lighter color compared with the alkali lignin and the enzymatic hydrolysis lignin, but the lignosulfonate easily causes the phenomenon of demulsification of a cream body, so that the prepared sunscreen agent is poor in stability compared with a common lignin sunscreen agent, and the application of the sunscreen agent in the sunscreen field is limited. In addition, lignosulfonate has low content of phenolic hydroxyl groups, so that the free radical scavenging capacity is poor, and the absorption capacity in the ultraviolet region is limited.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a preparation method of a light-colored catechol lignosulfonate sun-screening microcapsule.

The lignin contains a plurality of methoxyl groups in the molecule, and the potential methoxyl groups and SO in the lignosulfonate can be modified by a vulcanization method₃ ^2-Nucleophilic substitution reactions occur to convert to hydroxyl groups. The process of the vulcanization method is improved, the reaction conditions are relatively milder, the molecular weight can not be obviously reduced when the vulcanization method is used for treatment, and the molecular structure of the lignosulfonate is proved not to be obviously damaged. The phenolic hydroxyl content in the lignosulfonate after demethylation treatment is obviously improved, so that the structure of catechol and resorcinol appears in the structure of lignin, the bioadhesion capability of the lignosulfonate is improved, the problem of poor compatibility of the lignosulfonate and frost can be solved, a stable lignin microcapsule can be formed, and the ultraviolet compatibility of the lignosulfonate is improvedThe application possibility in the field of protective agents. The process is adopted for demethylation treatment, the reaction is carried out in an all-water phase system, the reaction process is relatively more environment-friendly and green, the reaction cost is lower, and the subsequent industrial production has better application potential.

The invention also aims to provide a light-colored catechol lignosulfonate sun-protection microcapsule prepared by the method.

The invention further aims to provide application of the light-colored catechol lignosulfonate sun-protection microcapsule.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a light-colored catechol lignosulfonate sun-protection microcapsule comprises the following steps:

(1) dissolving lignosulfonate and a vulcanizing reagent in an alkali solution, reacting at 40-160 ℃ for 0.1-5 hours, dialyzing, concentrating and drying to obtain catechol lignosulfonate;

(2) dissolving catechol lignosulfonate in an aqueous solution with the pH value of 5-9, adding a sun-screening agent and a surfactant, performing ultrasonic cavitation to obtain catechol lignosulfonate/chemical sun-screening agent microcapsule emulsion, and centrifuging to obtain light-colored catechol lignosulfonate sun-screening microcapsules.

Preferably, the weight ratio of the lignosulfonate to the vulcanizing agent in the step (1) is 1-10: 0.2 to 2; more preferably 10: 0.7 to 2; most preferably 8:1 to 5: 1.

Preferably, the sulfuration reagent of step (1) is at least one of sulfite, pyrosulfite, thiosulfate and bisulfite.

Preferably, the lignosulfonate of step (1) is at least one of sodium lignosulfonate, magnesium lignosulfonate and calcium lignosulfonate.

More preferably, the lignin in the lignosulfonate is at least one of bamboo pulp lignosulfonate, wheat straw pulp lignosulfonate, reed lignosulfonate, bagasse pulp lignosulfonate, asparagus pulp lignosulfonate and cotton pulp lignosulfonate.

The lignin obtained by industrially treating and separating it using different treatment means is generally called industrial lignin. The division and naming is generally based on the different ways of processing and separation of the lignin. Different lignins differ greatly in structure, reactive functional group content and species. Industrial lignin can be divided into four major groups: enzymatic hydrolysis of lignin: the enzymatic hydrolysis lignin is lignin which is obtained by depolymerizing and dissolving lignin raw materials by using cellulase and hemicellulose, alkali lignin: the alkali lignin mainly comes from waste liquid of alkaline pulping such as sulfate method and alkyl-alkali method, organic solvent lignin: the organic solvent lignin is lignin extracted from plants by organic reagents such as methanol, ethanol, acetone and the like under a high-temperature environment, and is characterized in that lignin sulfonate: the lignosulfonate is derived from sulfite pulping waste liquor, and has good water solubility and wide application prospect.

Preferably, the alkali solution in the step (1) is 1-20 wt% of sodium hydroxide solution, more preferably 1.5-15 wt% of sodium hydroxide solution, and most preferably 5-15 wt% of sodium hydroxide solution; the weight ratio of the lignosulfonate to the alkali solution is 1-10: 30.

preferably, the reaction temperature in the step (1) is 70-140 ℃ and the reaction time is 1-2.5 h.

Preferably, the dialysis treatment in the step (1) is carried out for 2-8 days, more preferably for 4-6 days, and the dialysate is water.

Preferably, the weight ratio of the total weight of the solution obtained by dissolving the catechol lignosulfonate in the step (2) in an aqueous solution with the pH value of 5-9 to the sunscreen agent is 1: 1-10: 1; more preferably 1:1 to 4:1, most preferably 7: 3.

preferably, the surfactant in the step (2) is added in an amount of 1-10 wt% of the total weight of the catechol lignosulfonate, the aqueous solution with the pH value of 5-9 and the sunscreen agent; more preferably 3 to 10 wt%.

Preferably, the weight ratio of the catechol lignosulfonate to the aqueous solution with the pH value of 5-9 in the step (2) is 1-10: 20-100 parts of; more preferably 1: 10 to 33.

Preferably, the pH range of the solution obtained after the catechol lignosulfonate is dissolved in the aqueous solution in the step (2) should be 6-8.

Preferably, the sunscreen agent of step (2) is at least one of a UVA and UVB type sunscreen agent; more preferably at least one of avobenzone, ethylhexyl methoxycinnamate, homosalate and oxybenzone; when more than one sunscreen agent is used, good miscibility is required.

Preferably, the surfactant in step (2) is at least one of tween, alkyl polyglycoside and sucrose ester.

Preferably, the power of the ultrasonic cavitation in the step (2) is 200-1500W, and the time is 1-20 min; more preferably, the ultrasonic cavitation is performed for 3-10 min under 400-1000W.

Preferably, the catechol lignosulfonate/chemical sunscreen microcapsule emulsion in the step (2) can be washed by centrifugal water to remove excessive catechol lignosulfonate, so as to obtain catechol lignosulfonate/chemical sunscreen microcapsule.

More preferably, the speed of the centrifugation is 5000-15000 r/min, and the time of the centrifugation and water washing is 20-40 min.

The invention provides a light-colored catechol lignosulfonate sun-protection microcapsule prepared by the method.

The light-colored catechol lignosulfonate sun-protection microcapsule disclosed by the invention is of an amphiphilic spherical structure, has the particle size of 100-1000nm, is excellent in ultraviolet absorption performance and good in stability, and has excellent water resistance and anti-permeability.

The invention provides an application of the light-colored catechol lignosulfonate sun-screening microcapsule in the field of chemical sun-screening. The chemical sun protection does not take a living body as a sun protection object.

More preferably in the preparation of sunscreens.

The lignin is a natural macromolecular ultraviolet protective agent in plants, has good ultraviolet absorption and oxidation resistance functions, and also has good biocompatibility. The demethylated lignin after chemical modification contains more phenolic hydroxyl groups, so that a crosslinking reaction is easier to occur when the chemical sun-screening agent is embedded by ultrasonic cavitation, and the added surfactant is beneficial to the nano-scale reduction of the microcapsule size prepared by oil phase dispersion, so that the ultraviolet scattering effect can be enhanced. On the basis, the pyrocatechol and resorcinol structures distributed on the surface of the bioadhesive microcapsule of the pyrocatechol lignosulfonate/chemical sun-screening agent endow the microcapsule with good water resistance and permeation resistance, and the use efficiency and safety are improved. The preparation process of the biological adhesion type microcapsule of the catechol lignosulfonate/chemical sun-screening agent is green and environment-friendly, the product is safe and efficient, the application of lignin which is a renewable resource in the field of daily chemicals is promoted, the problems of insufficient crosslinking capacity of the lignosulfonate and the like are solved, and the biological adhesion type microcapsule has a wide application prospect.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the lignosulfonate has good ultraviolet resistance and oxidation resistance, has good biocompatibility, has numerous phenolic hydroxyl active sites in molecules after chemical modification, is beneficial to free radical crosslinking in an ultrasonic cavitation process, can effectively embed a small-molecule chemical sunscreen agent for synergistic sun protection, improves the photolysis resistance of the small-molecule chemical sunscreen agent, and realizes lasting sun protection.

(2) The demethylation process of the lignosulfonate is green and environment-friendly, the whole reaction process is carried out in a water phase, an organic solvent is not used, the reaction process is safe and environment-friendly, the reaction flow is simple, mass preparation is easy to realize, and the lignosulfonate has a good industrial prospect.

(3) Compared with the traditional sulfurization demethylation method, the reaction conditions used in the method are milder, the preparation cost is lower, the used sulfurization reagents are inorganic sulfides, the method is more environment-friendly, the methyl in the lignosulfonate can be removed at lower cost, and the construction of the catechol lignosulfonate is effectively promoted.

(4) The structure of catechol, resorcinol and the like distributed on the surface of the biological adhesion type microcapsule of the catechol lignosulfonate/chemical sun-screening agent endows the microcapsule with good adhesion performance and permeation resistance, improves the use efficiency and safety, solves the problems that the traditional sun-screening agent has poor water resistance, is easy to permeate into skin to hurt human bodies and the like, and realizes safe and efficient sun-screening and skin care.

Drawings

FIG. 1 is a bioadhesive microcapsule emulsion of catechol lignosulfonate/chemical sunscreen obtained by ultrasonic cavitation in step (2) of example 1.

Figure 2 is a photograph of the original sodium lignosulfonate (left) and the sodium catechol lignosulfonate made in example 1 (right) when tested in the forrinol test.

FIG. 3 is an ultraviolet spectrum of the bioadhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent and the ultraviolet spectrum of the lignosulfonate/chemical sunscreen agent microcapsule sunscreen cream in the range of 260-400 nm, which are obtained in example 1.

FIG. 4 is a laser confocal test chart of bioadhesive microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen obtained in example 1 and of sodium lignosulfonate/chemical sunscreen microcapsule sunscreen cream.

FIG. 5 is data relating to particle size testing of bioadhesive microcapsules of catechol lignosulfonate/chemical sunscreen obtained in example 1 and of sodium lignosulfonate/chemical sunscreen microcapsules.

FIG. 6 is the catechol lignosulfonate ultrasonic cavitation emulsion obtained in comparative example 1.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.

Example 1

(1) Dissolving 10g of sodium lignosulfonate and 1.5g of sodium sulfite in 30ml of 10 wt% NaOH solution, carrying out condensation reflux reaction at 90 ℃ for 1 hour, cooling to room temperature after the reaction is finished, carrying out dialysis purification treatment on the reaction solution in pure water, and concentrating and drying the sample solution after the dialysis is finished to obtain catechol lignosulfonate solid powder.

(2) Dissolving 0.21g of catechol lignosulfonate in 6.79g of ultrapure water to prepare a 5 wt% solution, adding a mixture of 3g of ethylhexyl methoxycinnamate and avobenzone (the mass ratio is 4:1) and 0.7g of tween, carrying out ultrasonic cavitation for 3min under the condition that the ultrasonic power is 400W to obtain a bioadhesive microcapsule emulsion of catechol lignosulfonate/chemical sun-screening agent, and centrifuging for 30min at 10000r/min to obtain the bioadhesive microcapsule of catechol lignosulfonate/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent.

FIG. 1 is an ultrasonic cavitated emulsion of catechol lignosulfonate/chemical sunscreen prepared in step (2). The ultrasonic cavitation emulsion obtained after demethylation is seen to have good stability.

FIG. 2 is a photograph of original sodium lignosulfonate and catechol lignosulfonate from step (1) when subjected to the Folin phenol test. The absorption value of original sodium lignosulfonate at 760nm on the left side is 0.216, the absorption value of modified sodium lignosulfonate at 760nm reaches 0.3739, the content of phenolic hydroxyl groups is increased from original 0.631mmol/g to 1.234mmol/g, which is increased by 95.5%, and the test solution of sodium lignosulfonate after demethylation reaction is darker in color, which can also be shown to show that the content of phenolic hydroxyl groups is increased.

Fig. 3 is an ultraviolet spectrum of the bioadhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent obtained in this example 1 and an ultraviolet spectrum of the sodium lignosulfonate/chemical sunscreen agent microcapsule sunscreen cream prepared by replacing catechol lignosulfonate with sodium lignosulfonate in step 2 of example 1 in the range of 290-400 nm, which are measured by a japanese shimadzu UV-2600 ultraviolet-visible spectrophotometer, and it can be seen that the ultraviolet transmittance of the bioadhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent is obviously smaller than that of the sodium lignosulfonate/chemical sunscreen agent microcapsule sunscreen cream, which indicates that more ultraviolet rays can be blocked. Converted to the ultraviolet protection index (SPF), the SPF of the catechol lignosulfonate/chemical sunscreen bioadhesive microcapsule sunscreen cream is 116, while the SPF of the sodium lignosulfonate/chemical sunscreen microcapsule sunscreen cream is only 39.

FIG. 4 is a laser confocal test chart of bioadhesive microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen obtained in example 1 and of sodium lignosulfonate/chemical sunscreen microcapsule sunscreen cream. The adhesion performance of the biological adhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent and the adhesion performance of the sodium lignosulfonate/chemical sunscreen agent microcapsule sunscreen cream to skin are tested by using a laser confocal microscope. The adhesion performance of the sodium lignosulfonate/chemical sunscreen agent microcapsule sunscreen cream prepared by replacing catechol lignosulfonate with the original sodium lignosulfonate in the step 2 in the embodiment 1 is poor, a blue fluorescence signal of surface lignin is weak, so that the microcapsules adhered to the surface of the skin are proved to be washed away, the biological adhesion type microcapsule sunscreen cream of the catechol lignosulfonate/chemical sunscreen agent can still keep a strong fluorescence signal after washing, and the condition that phenolic hydroxyl groups on the surface of the sodium lignosulfonate are increased after demethylation compared with the original sodium lignosulfonate is proved, and the adhesion performance is obviously improved.

Figure 5 is data relating to particle size testing of bioadhesive microcapsules of catechol lignosulfonate/chemical sunscreen agent obtained from example 1 according to the malvern laser particle sizer test. The size of the microcapsules has a great influence on the storage stability thereof at normal temperature, and the larger the particle size, the less easily the microcapsules can be stored. From the figure, the average particle size of the biological adhesion type microcapsule of the catechol lignosulfonate/chemical sun-screening agent is about 300nm, the median particle size of the sodium lignosulfonate/chemical sun-screening agent microcapsule is 350nm, the particle size distribution of the biological adhesion type microcapsule of the catechol lignosulfonate/chemical sun-screening agent is narrower, and the uniformity of the product obtained after demethylation treatment is proved to be better. Therefore, the preparation method of the invention can obviously improve the storage time and stability of the microcapsule.

Example 2

(1) Dissolving 10g of magnesium lignosulfonate and 2g of sodium sulfite in 30mL of 15 wt% NaOH solution, carrying out condensation reflux reaction at 120 ℃ for 1 hour, cooling to room temperature after the reaction is finished, carrying out dialysis purification treatment on the reaction solution in pure water, and concentrating and drying the sample solution after the dialysis is finished to obtain catechol lignosulfonate solid powder.

(2) Dissolving 0.21g of catechol lignosulfonate in 6.79g of ultrapure water to prepare a 3 wt% solution, adding 4g of a mixture of homosalate and avobenzone (the mass ratio is 4:1) and 1g of tween, carrying out ultrasonic cavitation for 5min under the condition that the ultrasonic power is 600W, and centrifuging at 8000r/min for 30min to obtain the bioadhesive microcapsule of catechol lignosulfonate/chemical sunscreen agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent.

The same microcapsule preparation process, uv-vis spectroscopy, laser confocal test, and particle size test as in example 1 were used. The results are essentially the same as in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, respectively. The SPF value of the bioadhesive microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent is 98.

Example 3

(1) Dissolving 10g of sodium lignosulfonate and 0.7g of sodium metabisulfite in 40mL of 5 wt% NaOH solution, carrying out condensation reflux reaction at 70 ℃ for 2.5 hours, cooling to room temperature after the reaction is finished, carrying out dialysis purification treatment on the reaction solution in pure water, and concentrating and drying the sample solution after the dialysis is finished to obtain catechol lignosulfonate solid powder.

(2) Dissolving 0.6g of catechol lignosulfonate in 6.4g of ultrapure water to prepare a solution with the weight percent of 3, adding a mixture of 3g of ethylhexyl methoxycinnamate and avobenzone (the mass ratio is 4:1) and 0.3g of sucrose ester, carrying out ultrasonic cavitation for 3min under the condition that the ultrasonic power is 400W, and centrifuging for 40min at 5000r/min to obtain the bioadhesive microcapsule of catechol lignosulfonate/chemical sunscreen agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent.

The same microcapsule preparation process, uv-vis spectroscopy, laser confocal test, and particle size test as in example 1 were used. The results are essentially the same as in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, respectively. The bioadhesive microcapsule sunscreen of catechol lignosulfonate/chemical sunscreen had an SPF value of 104.

Example 4

(1) Dissolving 7g of calcium lignosulfonate and 1.5g of sodium thiosulfate in 20mL of 2.5 wt% NaOH solution, carrying out condensation reflux reaction at 140 ℃ for 1.5 hours, cooling to room temperature after the reaction is finished, carrying out dialysis purification treatment on the reaction solution in pure water, and concentrating and drying the sample solution after the dialysis is finished to obtain catechol lignosulfonate solid powder.

(2) Dissolving 0.21g of catechol lignosulfonate in 6.79g of ultrapure water to prepare a 3 wt% solution, adding a mixture of 3g of homosalate and avobenzone (the mass ratio is 4:1) and 0.4g of alkyl polyglycoside, carrying out ultrasonic cavitation for 5min under the condition that the ultrasonic power is 700W, and centrifuging for 30min at 10000r/min to obtain the bioadhesive microcapsule of the catechol lignosulfonate/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol lignosulfonate/chemical sunscreen agent.

The same microcapsule preparation process, uv-vis spectroscopy, laser confocal test, and particle size test as in example 1 were used. The results are essentially the same as in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, respectively. The bioadhesive microcapsule sunscreen of catechol lignosulfonate/chemical sunscreen had an SPF value of 113.

Comparative example 1

(1) Dissolving 10g of sodium lignosulfonate in 30ml of 10 wt% NaOH solution, carrying out condensation reflux reaction at 90 ℃ for 1 hour in a nitrogen atmosphere, cooling to room temperature after the reaction is finished, carrying out dialysis purification treatment on the reaction solution in pure water, and concentrating and drying the sample solution after the dialysis is finished to obtain catechol lignosulfonate solid powder.

(2) 0.21g of catechol lignosulfonate was dissolved in 6.79g of ultrapure water to prepare a 5 wt% solution, and 3g of a mixture of ethylhexyl methoxycinnamate and avobenzone (mass ratio 4:1) and 0.7g of tween were added and subjected to ultrasonic cavitation at an ultrasonic power of 400W for 3 min. Obtaining the sodium lignosulfonate/chemical sunscreen agent ultrasonic cavitation emulsion.

FIG. 6 is the catechol lignosulfonate ultrasonic cavitation emulsion obtained in this comparative example. From the figure, it can be seen that the obtained ultrasonic cavitation emulsion has a very obvious phenomenon of delamination. The reason is that the proper amount of the surfactant can reduce the interfacial tension of water and oil, increase the specific surface area of oil drops and help sodium lignosulfonate to be adsorbed and crosslinked on the surfaces of the oil drops. However, the excessive surfactant is added, so that the excessive surfactant can interact with the surfactant to cause droplet polymerization, and the prepared microcapsule has an excessively large particle size, is unstable and then breaks emulsion.

When the chemical sunscreen agent and the surfactant are added in the subsequent process to prepare the microcapsule, the microcapsule is basically prepared in a non-existent way or the prepared microcapsule is very easy to break emulsion. The further explanation shows that the demethylation treatment is carried out by a vulcanization method, so that the stability of the modified lignosulfonate in the preparation of the microcapsule is obviously improved.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.