Degradable Microbeads and Their Preparation Methods and Applications

Abstract

The present application discloses a degradable microbead and its preparation method and application. The degradable microbead is an inorganic nanoparticle coated with a degradable plastic outer layer. Among them, the average particle size D50 of the degradable microbead is 1 μm to 3000 μm, the content of the inorganic nanoparticle is 5 wt% to 15 wt%, the sphericity of the degradable microbead is greater than 0.86, the particle size distribution span span is 0.6 to 2.5, the particle size distribution is narrow and the particle fluidity is good. And a waste-reducing and non-toxic manufacturing method for biodegradable microbeads is provided.

Description

Technical Field

[0001] The present application relates to a degradable microbead, its preparation method and application, specifically to a degradable microbead with a core-shell structure, and provides a waste-reducing and non-toxic manufacturing method for biodegradable microbeads. Background Art

[0002] Microplastics, which are plastic particles with a diameter less than 5 millimeters, are a major carrier of pollution. The small volume of microplastics means a higher specific surface area. The larger the specific surface area, the stronger the ability to adsorb pollutants. However, there are already a large number of persistent organic pollutants such as polychlorinated biphenyls and bisphenol A in the current environment. Once microplastics meet these pollutants, they just gather to form an organic pollution sphere. Microplastics are equivalent to becoming the mounts of pollutants, and the two can wander around in the environment.

[0003] In 2004, the concept of microplastics was first proposed in an article published in Science. And due to the widespread presence of microplastics in the marine environment and various definite and indefinite hazards to organisms, it has received extensive attention from all walks of life.

[0004] Existing plastic microbeads, in applications such as personal cleaning and cosmetics, due to their small particle size and light specific gravity, are not easily intercepted by the sewage system and are directly discharged into the ocean, causing marine organisms to accidentally ingest them, enter the food chain, resulting in a marine biological disaster, and also returning to the human table. Therefore, various countries have promulgated plastic microbead bans.

[0005] Currently, biodegradable plastics or natural materials can be used to make microbeads. The preparation methods are mostly direct grinding, emulsion method or polymerization emulsion method. However, the above methods have the following disadvantages. When using the grinding method, the size and shape of the grinding are not easy to control, and the application is limited; if using the emulsion method or polymerization emulsion method, it can be easily made into spherical shapes, but there are problems of monomer residues and a large amount of organic solvents need to be invested in the production process, and even toxic solvents are used, causing environmental pollution. Summary of the Invention

[0006] In order to solve the above deficiencies in the art, an object of the present application is to provide a degradable plastic microbead, its preparation method and application.

[0007] According to one aspect of the present application, a degradable microbead is provided, and the microbead includes: a degradable plastic and a plurality of inorganic nanoparticles coated on the outer layer of the degradable plastic;

[0008] Wherein, the average particle size D50 of the degradable microbead is 1 micrometer (μm) to 3000 micrometers;

[0009] Based on the total weight of the degradable microspheres, the content of the inorganic nanoparticles is 5 wt% to 15 wt%, preferably 4.7 wt% to 13 wt%.

[0010] According to some embodiments of the present application, taking the geometric center of the degradable microspheres as the center of the sphere, in the outer layer with a depth extending from the outermost edge of the degradable microspheres towards the center of the sphere by 15% to 20%, the content of the inorganic nanoparticles accounts for 95% to 100% of the content of the inorganic nanoparticles in the overall degradable microspheres.

[0011] According to some embodiments of the present application, the sphericity of the degradable microspheres is greater than 0.86, and the particle size distribution span span is 0.6 to 2.5.

[0012] Preferably, the sphericity of the degradable microspheres is 0.86 to 1.

[0013] According to some embodiments of the present application, the particle size of the inorganic nanoparticles coated on the outer layer is less than 100 nanometers (nm), preferably 1 to 100 nanometers, more preferably 1 to 40 nanometers.

[0014] Preferably, the inorganic nanoparticles coated on the outer layer are selected from silicon dioxide, titanium dioxide, aluminum oxide, zinc oxide, iron oxide, cerium oxide, calcium carbonate, barium carbonate, montmorillonite or a combination thereof.

[0015] According to some embodiments of the present application, the degradable plastic is a thermoplastic plastic;

[0016] The melting point of the thermoplastic plastic > 35 degrees Celsius.

[0017] According to some embodiments of the present application, the degradable plastic is selected from degradable synthetic polymers, degradable natural polymers, copolymers of degradable synthetic polymers, copolymers of degradable natural polymers or a combination thereof.

[0018] According to some embodiments of the present application, the degradable plastic is a degradable synthetic polymer, a copolymer of degradable synthetic polymers or a combination thereof.

[0019] Preferably, the degradable synthetic polymer includes: aliphatic polyesters, aromatic / aliphatic polyesters, aliphatic polyamide esters, polyamino acids, polycarbonates, polyester ethers, polyphosphazenes, polyanhydrides and polyurethanes or a combination thereof.

[0020] Preferably, the degradable natural polymer includes: collagen, gelatin, chitin, chitosan, dextran, hyaluronic acid, sodium alginate, starch, cellulose and microcrystalline cellulose or a combination thereof.

[0021] Another object of the present application is to provide a method for preparing the degradable microspheres as described above, including:

[0022] Mix multiple inorganic nanoparticles with a first solvent in a reactor for dispersion;

[0023] Add a molten biodegradable plastic (also known as degradable plastic);

[0024] After stirring, lower the temperature to 20°C to 25°C, and the degradable microbeads will precipitate.

[0025] According to some embodiments of the present application, adding a molten biodegradable plastic includes: adding a biodegradable plastic into the reactor, and while stirring, raising the temperature above the melting point of the biodegradable plastic, or raising the temperature of the reactor above the melting point of the biodegradable plastic, and while stirring, adding the molten biodegradable plastic into the reactor.

[0026] Optionally, add a second solvent, filter and collect the precipitated degradable microbeads, then wash; and dry, pulverize and sieve.

[0027] According to some embodiments of the present application, it is preferred to first add the biodegradable plastic into the reactor, and while stirring, raise the temperature above the melting point of the biodegradable plastic.

[0028] According to some embodiments of the present application, the boiling point of the first solvent is more than 10 degrees higher than the melting point of the biodegradable plastic; and the first solvent is immiscible with the biodegradable plastic.

[0029] According to some embodiments of the present application, the first solvent is immiscible with the molten and / or solid state of the biodegradable plastic.

[0030] That is, the solubility of the biodegradable plastic in the first solvent is between 0 and 0.01 g / 100 g of solvent.

[0031] The first solvent includes silicone oil, glycerol, phenoxy alcohols, diethylene glycol or a combination thereof, preferably diethylene glycol.

[0032] According to some embodiments of the present application, the second solvent is miscible with the first solvent, and the second solvent is immiscible with the precipitated degradable microbeads, that is, the solubility of the biodegradable microbeads (also known as degradable microbeads) in the second solvent is between 0 and 0.01 g / 100 g of solvent, and the second solvent is preferably water;

[0033] According to another aspect of the present application, there is provided a composition for skin coating, comprising the above-mentioned degradable microbeads.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] According to an embodiment of the present application, the present application provides a degradable microbead (which may also be referred to as a microbead or a degradable microbead hereinafter), which has a core-shell-like structure, with a degradable plastic as the core and multiple inorganic nanoparticles as the shell-like layer, coated on the outer layer of the degradable plastic (which may also be referred to as a biodegradable plastic hereinafter). The average particle size of the microbead is 1 μm to 3000 μm, and the sphericity is above 0.86.

[0036] The degradable microbead of the present application contains a degradable plastic and multiple inorganic nanoparticles coated on the outer layer of the degradable plastic. Based on the total weight of the degradable microbead, the content of the multiple inorganic nanoparticles is 5 wt% to 15 wt%. The content of the inorganic nanoparticles can be used to control the particle size range of the degradable microbead, so the produced microbeads have a wide particle size range and a narrow particle size distribution.

[0037] The degradable microbead of the present application has a core-shell-like structure, that is: the degradable plastic is the core, and the inorganic nanoparticles are coated on the surface of the degradable plastic in a "particle form" and in a dot-like distribution manner to form an outer layer, rather than being arranged in the form of a "coating film" on the outer layer of the degradable plastic. Therefore, the inorganic nanoparticles do not form a film (or sheet) on the outer layer of the degradable plastic. Since the inorganic nanoparticles are not tightly coated, the inorganic nanoparticles do not affect the environmental degradability of the degradable plastic.

[0038] The degradable microbead of the present application has a core-shell-like structure and is spherical, with good sphericity and uniform particle size distribution. The spherical degradable microbead is analyzed using a focused ion beam-scanning electron microscope-X-ray energy dispersive spectroscopy (FIB-SEM-EDS). Taking the geometric center of the degradable microbead as the center of the sphere, the content of the inorganic nanoparticles in the outer layer with a depth extending from the outermost edge of the degradable microbead towards the center of the sphere by 15% to 20% accounts for 95% to 100% of the content of the inorganic nanoparticles in the overall degradable microbead, preferably 98% to 100%.

[0039] The inorganic nanoparticles are coated on the periphery of the degradable plastic, bringing better fluidity and hardness to the degradable microbead, so that when it is applied to industrial production, the time and cost of the conveying process are reduced, and deformation during operation and application is avoided; compared with the microbeads formed by mixing inorganic nanoparticles or mixing inorganic nanoparticles in the degradable plastic and further using emulsion, meltblowing or rapid freezing, the inorganic nanoparticles of the present application are coated on the periphery, and only a smaller amount of inorganic nanoparticles is required to achieve the same compressive strength. Therefore, the raw material addition cost can be saved, and the preparation process can be reduced.

[0040] In addition, the degradable microbead coated with inorganic nanoparticles on the outer layer of the present application has better fluidity. When it is applied as a skin feel regulator in cosmetics or skin care products, it can achieve better oil control, improve the smoothness, and is easy to spread when applied.

[0041] According to an embodiment of the present application, the present application provides a method for preparing degradable plastic microspheres. The preparation method is simple to operate, does not require a large amount of organic solvents, and the solvents used are non-toxic and have less impact on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of the degradable plastic microspheres of the exemplary embodiment of the present application.

[0043] Figure 2 It is an optical microscope image of the microspheres of the comparative example (no nano-inorganic particles added during the process).

[0044] Figure 3 It is a diagram showing the particle size distribution measurement of Example 3.

[0045] Figure 4 Example 1 - Scanning Electron Microscope (SEM) image.

[0046] Figure 5 Example 2 - SEM image.

[0047] Figure 6 Example 3 - SEM image.

[0048] Figure 7 Example 5 - SEM image.

[0049] Figure 8 Example 5 - SEM magnified image.

[0050] Figure 9 Example 7 - Appearance photo.

[0051] Figure 10 A - Figure 10 D Results of X-ray Photoelectron Spectroscopy (XPS) analysis of Example 4.

[0052] Figure 11 A - Figure 11 B Results of Focused Ion Beam - Scanning Electron Microscope - Energy Dispersive X-ray Spectroscopy (FIB-SEM-EDS) analysis of Example 1.

[0053] Figure 12 Appearance, oil absorption and agglomeration of Example 1 and comparative microspheres.

[0054] Figure 13 Appearance after degradation of the laboratory degradation test of Example 5.

[0055] Figure 14Example 6 Laboratory Degradation Test - Appearance after Degradation.

[0056] Figure 15 Comparative Sample PMMA Laboratory Degradation Test - Appearance after Degradation.

[0057] Figure 16 Example 2 Laboratory Degradation Test - SEM Image after Degradation

[0058] Figure 17 A- Figure 17 Application Example 1 - Powder Cake - Skin Feel Test Results.

[0059] Figure 18 A- Figure 18 Application Example 1 - Cream - Skin Feel Test Results. Detailed Description of the Invention

[0060] As described in the background art above, currently, plastic microbeads, when used in personal care, cosmetics, etc., due to their small particle size and low specific gravity, are not easily intercepted by the sewage system and are directly discharged into the ocean, causing marine organisms to ingest them by mistake and enter the food chain. Moreover, currently, the methods for preparing plastic microbeads using biodegradable plastics or natural materials have many drawbacks. In view of the above problems, the present application provides a degradable microbead, its preparation method, and its application.

[0061] Next, the technical solutions of the present application will be clearly and completely described in conjunction with the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0062] It should be particularly noted that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all considered to be included in the present application. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only some, but not all, of the embodiments of the present application.

[0063] Unless otherwise specified in the present application, all are carried out according to conventional conditions or conditions recommended by the manufacturer. The raw materials or auxiliary materials used, as well as the reagents or instruments used, without indicating the manufacturer, are all conventional products that can be obtained through commercial purchase.

[0064] The following provides a detailed description of the present application.

[0065] Polymer microbeads, common polymer raw materials include polystyrene (PS), polycarbonate (PC), poly(methyl methacrylate) (PMMA), etc. Their application fields include adding to plastic moldings to improve physical properties, light diffusers, coating additives, toner, and other industries. Subsequently, they have gradually been adopted in cosmetics, body cleansing products, and daily chemical products. For example, toothpaste, scrub cream, scrub facial cleanser, foundation, loose powder, lipstick, eyeshadow, etc. However, in recent years, it has been found that these tiny plastic particles are not easily intercepted by sewer or sewage treatment systems and flow into the ocean, causing pollution to marine life. Therefore, laws have been enacted in various countries to prohibit their use, and thus alternative materials to replace plastic microbeads are urgently needed. Since the plastic microbeads used in cosmetics on the current market mainly provide a matte effect, skin feel adjustment, and oil absorption, and their main component is PMMA, alternative materials to replace PMMA microbeads are urgently needed.

[0066] This application uses a Pickering emulsion-like method to manufacture degradable microbeads with a nanoparticle-coated outer layer by a melt-emulsification method. Using nano-inorganic particles as emulsifiers, the molten degradable plastic is emulsified in an immiscible solvent. After cooling to room temperature and solidifying, degradable microbeads with a nanoparticle-coated outer layer are prepared. It has the advantages of not requiring additional emulsifier addition, being environmentally friendly, having low toxicity to humans, and good stability. In addition, the particle size of the degradable microbeads obtained by this manufacturing method is easy to control, and can be prepared from the micron level to the millimeter level, and the degradable microbeads have a high sphericity.

[0067] In addition, due to the addition of the coating of inorganic nanoparticles, the smoothness and fluidity of the degradable micro-powder can be enhanced, which is suitable for applications with high requirements for fluidity and smoothness. However, since the nano-inorganic particles do not completely coat the degradable plastic, it does not affect its degradation. The inorganic nanoparticles coated on the outer layer provide fluidity and compression modulus for the degradable microbeads, but do not affect the adhesion of the degradable microbeads to the skin and the oil absorption amount, and provide good ductility, which is suitable for replacing PMMA as an environmentally friendly skin feel regulator.

[0068] The degradable microbeads of this application include: a degradable plastic and a plurality of inorganic nanoparticles coated on the outer layer of the degradable plastic;

[0069] Among them, the average particle size D50 of the microbeads is 1 micron to 3000 microns;

[0070] The content of the inorganic nanoparticles coated on the outer layer is 5 wt% to 15 wt%, based on the total weight of the degradable microspheres. The sphericity of the degradable microspheres is greater than 0.86, and the particle size distribution span (span) is 0.6 - 2.5. If the content of the inorganic nanoparticles is less than 5 wt%, the sphericity of the obtained powder (microspheres) is poor and the size is uneven; if the content of the inorganic nanoparticles is higher than 15 wt%, there is almost no change in the sphericity and size of the obtained microspheres, that is, the content higher than 15 wt% is not beneficial to the improvement of the sphericity and size of the microspheres. In a preferred embodiment, the sphericity of the microspheres is 0.86 to 1. In some embodiments, the particle size of the inorganic nanoparticles is less than 100 nanometers. If the particle size of the nano-inorganic particles is less than 1 nanometer, the self-aggregation is too strong and it is not easy to form an emulsifying effect, and it is not easy to form microspheres. If the particle size of the nano-inorganic particles is greater than 100 nanometers, the surface roughness is too large, the fluidity becomes poor, and the skin feel is not good; through the induction of the results of countless experimental tests, it is preferably 1 nanometer to 40 nanometers. When the particle size of the nano-inorganic particles is 1 nanometer to 40 nanometers, the inorganic nanoparticles coated on the outer layer can provide better fluidity and stronger compression modulus for the degradable microspheres, without affecting the adhesion of the microparticles to the skin and the oil absorption amount, and providing good ductility.

[0071] The degradable microspheres of the present application have a narrow particle size distribution, and the average particle size of the degradable microspheres can be controlled by adjusting the addition amount of the nanoparticles and the mechanical force; when the addition amount of the nanoparticles reaches up to 15 wt%, the particle size can reach the minimum, and the particle size of the degradable microspheres prepared gradually increases as the addition amount decreases. Another feature is that the selection of the degradable plastic is not restricted, and its selectivity is high. The degradable microspheres coated with nanoparticles made of a suitable degradable plastic can be selected according to its physical properties, so it is possible to replace the polymer microparticles used in the past and can be used very effectively and practically in industries and various applications.

[0072] The degradable microspheres were analyzed by focused electron beam - scanning electron microscope - X - ray energy dispersive spectroscopy (FIB - SEM - EDS) to understand the distribution relationship of multiple inorganic nanoparticles on the surface of the degradable plastic. The FIB can etch the cross - section of the degradable microspheres. After sorting out the analysis results, it is found that with the geometric center of the degradable microspheres as the center of the sphere, the content of inorganic nanoparticles in the outer layer with a depth extending from the outermost edge of the degradable microspheres towards the center of the sphere and accounting for 15% to 20% of the depth accounts for 95% to 100% of the total inorganic nanoparticles in the whole degradable microspheres, preferably 98% to 100%, that is, more than 95% of the inorganic nanoparticles are distributed in the depth range of 15% to 20% of the outermost layer of the degradable microspheres. In addition, for the multiple inorganic nanoparticles of the present application, based on the total weight of the degradable microspheres, the content of the multiple inorganic nanoparticles is 5 wt% to 15 wt%. Therefore, by reasonable calculation, based on the total weight of the degradable microspheres, the content of inorganic nanoparticles in the depth range of 15% to 20% of the outermost layer of the degradable microspheres is 4.75 wt% to 15 wt%, preferably 4.9 wt% to 15 wt%.

[0073] In addition, the degradable microspheres were analyzed by X - ray photoelectron spectroscopy (XPS). X - ray photoelectron spectroscopy (XPS) analysis can perform elemental analysis on the surface of the degradable microspheres about 10 nm deep. The molecular formula of the inorganic nanoparticles of the present application is MxNyOz, where M is a metal or metalloid atom. In some embodiments, M is Si (silicon), Al (aluminum), Zn (zinc), Ti (titanium), Fe (iron), Ce (cerium), Ba (barium), Ca (calcium), etc. In some embodiments, N is N (nitrogen), C (carbon), etc. In some embodiments, N is not an essential atom, and O is an O (oxygen) atom. The degradable plastic is mainly judged by the proportion of its C(1s) element in the XPS analysis, the S - orbital electrons of C (carbon). In some embodiments, after sorting out the analysis results of the degradable microspheres, the surface of the degradable microspheres has a detectable amount of inorganic nanoparticle M accounting for 3.0% to 25% by atoms x O y and as the D50 particle size of the degradable microspheres increases, the inorganic nanoparticle M x O yThe smaller the detectable amount of M, and the ratio (C / M) of the detectable amount of degradable plastic C(1s) to the detectable amount of M can be arranged to be 0.5 to 20. The smaller the ratio, the more inorganic nanoparticles there are. In some embodiments, the inorganic nanoparticles are silica. The analysis result shows that there is 3.0% to 25% of Si element on the surface of the degradable microbeads, and the ratio (C / M) of C(1S) / Si is 0.5 to 20. By converting the atomic ratio analysis of the X-ray photoelectron spectroscopy (XPS) of the degradable microbeads, the weight percentage of the inorganic nanoparticles is 10% to 80%, and the ratio is lower in the inner layer. In some embodiments, the inorganic nanoparticles are silica (molecular weight 60.08), and the degradable plastic is PLA (repeating unit molecular weight 72.06). Convert the atomic ratio measured by XPS to the weight percentage of the inorganic nanoparticles and the degradable plastic. The weight percentage result of nano-silica is 10% to 80%. The larger the average particle size of the degradable microbeads, the lower the weight percentage of silica, and after XPS etching, the lower the weight percentage of silica in the inner layer.

[0074] The average particle size D50 of the degradable microbeads of the present application is from 1 micron (μm) to 3000 microns, so the application distribution is quite wide. Generally, 1 micron to 30 microns can be used in cosmetics and daily chemical products to provide a delicate skin feel or an optical matte effect. In some embodiments of the present application, the particle size of the inorganic nanoparticles is from 1 nanometer to 40 nanometers. When the average particle size of the degradable microbeads is in the range of 1 micron to 30 microns, it can replace PMMA as an environmentally friendly skin feel regulator; 1 micron to 500 microns can be used in coatings, varnishes, grinding, adhesives, etc.; 500 to 3000 microns can be used in products such as automobiles and buildings that require mechanical structures, etc.; specifically, it can be used as an additive for skin care products such as facial cleanser, sunscreen, makeup remover, lotion, essence, cream, cold cream, aftershave lotion, shaving soap, oil blotting paper, oil control and skin cleansing agent, etc.; foundation, powder, liquid foundation, mascara, face powder, oil pastel, concealer, eyebrow pencil, mascara, eyeliner, eyeshadow, eyeshadow primer, nose shadow, lipstick, lip gloss, blush, toothblackening agent, nail polish, nail polish top coat, etc. cosmetics or their modifiers; additives for hair products such as shampoo, dry shampoo, hair conditioner, hair dye, 2-in-1 shampoo, hair care agent, hair growth promoter, hair styling agent, hair oil, hair grease, hair dye, etc.; additives for comfort products such as deodorant, baby powder, toothpaste, mouthwash, lip balm, soap, etc.; additives for toner; rheology modifiers for coatings, etc.; medical diagnostic agents, mechanical property improvers for molded products such as automotive materials and building materials, etc.; mechanical property improvers for membranes, fibers, etc.; raw materials for resin molded bodies for rapid prototyping and rapid manufacturing, materials for flash prototyping, resin pastes for plastisols, powder adhesives, powder flowability improvers, lubricants, rubber compounding agents, abrasives, tackifiers, filter agents and filter aids, gelling agents, flocculants, additives for coatings, oil absorbents, mold release agents, slip property improvers for plastic films - sheets, anti-blocking agents, gloss regulators, matting agents, light diffusing agents, surface high hardness improvers, toughness improvers, etc. various modifiers, spacers for liquid crystal display devices, packing materials for chromatography, base materials - additives for cosmetic foundations, auxiliaries for microcapsules, medical materials such as drug delivery systems - diagnostic drugs, sintering materials for ceramic processing, standard particles for measurement and analysis, particles for the food industry field, materials for powder coatings, toner for electrophotographic development, etc.

[0075] Nomenclature Definition:

[0076] D50: The average particle size D50 of the particles, also known as the median particle size, refers to the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that 50% of the particles have a particle size larger than it, and 50% of the particles have a particle size smaller than it.

[0077] Sphericity: A parameter characterizing the morphology of particles. The closer a particle is to a sphere in morphology, the closer its sphericity is to 1, which is the ratio of the surface area of a sphere with the same volume as the object to the surface area of the object. The sphericity of a sphere is equal to 1, and the sphericity of other objects is less than 1.

[0078] The sphericity formula for any particle is Y = As / Ap (where Ap is the surface area of particle p and As is the surface area of sphere s with the same volume as particle p); under two-dimensional measurement, it can be equivalent to the projected area of the particle.

[0079] Particle size distribution span: A measure of the width of the particle size distribution of a sample. Generally, span = (D90 - D10) / D50, where D90 and D10 refer to the particle sizes corresponding to when the cumulative particle size distribution percentage reaches 90% and 10% respectively. The closer the span is to 0, the more uniform the particle size and the higher the size consistency.

[0080] The biodegradable plastics mentioned in this application are also called biodegradable plastics, which are defined as plastics that can be degraded by the action of naturally occurring microorganisms in nature such as soil or sand, or under specific conditions such as industrial / home composting conditions, anaerobic digestion conditions, aqueous culture solutions, or marine environments, and finally completely degraded into carbon dioxide or / and methane, water, mineral salts of the elements contained therein, and new biomass.

[0081] Biodegradable plastics are classified into two types according to the raw material sources: bio-based and petroleum-based. The biodegradable plastics are selected from biodegradable synthetic polymers, biodegradable natural polymers, copolymers of biodegradable synthetic polymers, copolymers of biodegradable natural polymers, or combinations thereof.

[0082] According to some embodiments of the present application, the biodegradable plastics are biodegradable synthetic polymers, copolymers of biodegradable synthetic polymers, or combinations thereof.

[0083] The biodegradable synthetic polymer refers to a polymer obtained by chemically synthesizing petrochemical product monomers, including: aliphatic polyesters, such as polycaprolactone (PCL), polybutylene succinate (PBS), aromatic / aliphatic polyesters, such as polybutylene adipate terephthalate (PBAT), aliphatic polyamide esters, polyamino acids, polycarbonates, polyester ethers, polyphosphazenes, polyanhydrides, carbon dioxide copolymers (polypropylene carbonate, PPC), and polyurethanes, or combinations thereof.

[0084] The biodegradable natural polymers are mainly made from natural macromolecules, including: collagen, gelatin, chitin, chitosan, dextran, hyaluronic acid, sodium alginate, starch, cellulose, and microcrystalline cellulose, or their combinations, which are made into biodegradable polymers through microbial fermentation or synthesis, such as thermoplastic starch plastics, aliphatic polyesters, or aromatic-aliphatic polyesters like polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyethylene 2,5-furanoate (PEF), polylactic acid (PLA), starch / polyvinyl alcohol, aliphatic polyamide esters, polyester ethers, polyurethanes, polyphosphazenes, polyanhydrides, etc. These are all such plastics, polymers directly synthesized by microorganisms; polyhydroxyalkanoates (PHA), which include polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx or PGBHHx), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), etc.

[0085] The biodegradable microspheres with an inorganic nanoparticle coating in this application have a wide D50 particle size range and high sphericity. In some embodiments, the biodegradable plastic is a thermoplastic biodegradable plastic, and the melting point of this thermoplastic biodegradable plastic is greater than 35 degrees Celsius. The biodegradable plastic includes polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), polyethylene 2,5-furanoate (PEF), polylactic acid (PLA), polyhydroxyalkanoates (PHA), or their combinations. According to some more preferred embodiments of this application, the biodegradable plastic is PLA (polylactic acid), PCL (polycaprolactone), PHBV poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PBAT (aromatic-aliphatic copolyester of butanediol, adipic acid, and terephthalic acid), or their combinations.

[0086] The average particle size D50 of the degradable microbeads of the present application is from 1 to 3000 microns, and small particle sizes from 1 to 30 microns can be achieved. They can be used in cosmetics and daily chemical products to provide a delicate skin feel or an optical matte effect, and have a high sphericity. Therefore, they have good fluidity and smoothness. The nanoparticles on the surface provide high compressive strength at small particle sizes, and also enhance the fluidity and smoothness.

[0087] A degradable microbead of the present application, the degradable microbead includes: 85wt% to 95wt% of a degradable plastic and 5wt% to 15wt% of inorganic nanoparticles coated on the outer layer of the degradable plastic. In some embodiments, the degradable plastic is polylactic acid (PLA), and the inorganic nanoparticles are silica nanoparticles. For the degradable microbeads with silica nanoparticles coated on PLA, its oil absorption is equivalent to that of the current 7μm PMMA microbeads (45ml / 100g), which is 58ml / 100g. And the coating of inorganic nanoparticles provides a compressive modulus and enhances the drop resistance after making into powder compacts, providing an environmentally friendly material that can be directly replaced for the cosmetics industry. And the preparation method is simple, without using a large amount of toxic solvents, with low energy consumption and environmental protection.

[0088]

Degradable Microbeads Coated with Inorganic Nanoparticles

[0089] Figure 1 It is a degradable plastic microbead of the present application, and the microbead includes a degradable plastic and inorganic nanoparticles coated on the outer layer of the degradable plastic. The average particle size of the degradable microbead is from 1 to 3000 microns, the sphericity is above 0.86, and the particle size distribution span span is from 0.6 to 2.5. It contains 85wt% to 95wt% of a biodegradable plastic, and the outer circle of the biodegradable plastic is coated with inorganic nanoparticles, and the content of the inorganic nanoparticles accounts for 5wt% to 15wt%.

[0090]

Preparation Method of Degradable Microbeads Coated with Inorganic Nanoparticles

[0091] The preparation method of the degradable microbeads of the present application is to use inorganic nanoparticles as a solid emulsifier and prepare them by the melting-emulsification method. The inorganic nanoparticles are mixed with a high-boiling solvent that is immiscible with the degradable plastic (for example, the solubility of the molten and solid degradable plastic in this high-boiling solvent is between 0 and 0.01 g / 100 g of solvent) in a reactor. At room temperature, the degradable plastic masterbatch is then added to the reactor and stirred. The temperature is raised above the melting temperature of the degradable plastic (for example, above the melting point of the degradable plastic, preferably 3 °C or more above the melting point of the degradable plastic, more preferably 5 °C or more above the melting point of the degradable plastic and below the melting point of the degradable plastic plus 35 °C, or below the boiling point of the high-boiling solvent), or the biodegradable plastic is heated above its melting point and the reactor is also heated above the melting point of the biodegradable plastic. Under stirring, the molten biodegradable plastic is added to the reactor, and the stirring shear force is increased to stir into an emulsion state. Then, the temperature is lowered to shape the plastic polymer. At this time, the degradable microbeads precipitate. Then, a large amount of solvent is added, where the solvent is miscible with the aforementioned high-boiling solvent, and the solubility of the degradable microbeads in this solvent is between 0 and 0.01 g / 100 g of solvent (for example, adding water with the same volume as the solvent). The precipitated degradable microbeads are filtered and collected to remove the solvent, and are washed and filtered multiple times (for example, 2 to 3 times of washing and filtering), and then dried, crushed, and sieved to obtain powdery degradable microbeads.

[0092] The following is a detailed description of the present application in conjunction with specific embodiments.

[0093] Example 1

[0094] Preparation of the degradable microbeads of the present application:

[0095] (1) 15 g of inorganic nanoparticles are mixed evenly with 400 g of diethylene glycol.

[0096] (2) 100 g of PLA masterbatch is added to the mixture in step (1) and stirred continuously, and the temperature is raised to 180 °C.

[0097] (3) The stirring speed is increased to 1000 rpm. After stirring for 20 min, the heating is turned off and the temperature is lowered to room temperature (20 °C to 25 °C).

[0098] (4) The mixture in step (3) is filtered to remove the solvent and washed with a certain amount of water.

[0099] (5) Step (4) is repeated 2 times.

[0100] (6) It can be dried, crushed, and sieved.

[0101] Example 2

[0102] Preparation of the degradable microbeads of the present application:

[0103] (1) Mix 10 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0104] (2) Take 100 g of PLA masterbatch and add it to the mixture in step (1), then continue stirring and heat up to 180 °C.

[0105] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0106] (4) Filter the mixture in step (3) to remove the solvent, and wash it with a certain amount of water.

[0107] (5) Repeat step (4) twice.

[0108] (6) Dry, crush and sieve it to obtain the product.

[0109] Example 3

[0110] Preparation of the degradable microbeads of the present application:

[0111] (1) Mix 8 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0112] (2) Take 100 g of PLA masterbatch and add it to the mixture in step (1), then continue stirring and heat up to 180 °C.

[0113] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0114] (4) Filter the mixture in step (3) to remove the solvent, and wash it with a certain amount of water.

[0115] (5) Repeat step (4) twice.

[0116] (6) Dry, crush and sieve it to obtain the product.

[0117] Example 4

[0118] Preparation of the degradable microbeads of the present application:

[0119] (1) Mix 15 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0120] (2) Take 100 g of PCL masterbatch and add it to the mixture in step (1), then continue stirring and heat up to 80 °C.

[0121] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0122] (4) Filter the mixture in step (3), remove the solvent, and wash with a certain amount of water.

[0123] (5) Repeat step (4) twice.

[0124] (6) Just dry, crush and sieve.

[0125] Example 5

[0126] Preparation of the degradable microbeads of the present application:

[0127] (1) Mix 15 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0128] (2) Take 100 g of PHBV masterbatch and add it to the mixture in step (1), continue stirring, and heat up to 180 °C.

[0129] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0130] (4) Filter the mixture in step (3), remove the solvent, and wash with a certain amount of water.

[0131] (5) Repeat step (4) twice.

[0132] (6) Just dry, crush and sieve.

[0133] Example 6

[0134] Preparation of the degradable microbeads of the present application:

[0135] (1) Mix 15 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0136] (2) Take 100 g of PBAT masterbatch and add it to the mixture in step (1), continue stirring, and heat up to 180 °C.

[0137] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0138] (4) Filter the mixture in step (3), remove the solvent, and wash with a certain amount of water.

[0139] (5) Repeat step (4) twice.

[0140] (6) Just dry, crush and sieve.

[0141] Example 7

[0142] Preparation of the degradable microbeads of the present application:

[0143] (1) Mix 5 g of inorganic nanoparticles evenly with 400 g of diethylene glycol.

[0144] (2) Take 100 g of PBAT masterbatch and add it to the mixture in step (1), then continue stirring and heat up to 180 °C.

[0145] (3) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0146] (4) Filter the mixture in step (3) to remove the solvent, and wash it with a certain amount of water.

[0147] (5) Repeat step (4) twice.

[0148] (6) Dry, crush and sieve it to obtain the product.

[0149] Note: In Example 7, the particles were too large to be suspended for measuring the scattering particle size distribution. Therefore, only 20 samples were taken to measure the particle size with a vernier caliper, and the average particle size value was taken, as shown in Figure 9.

[0150] Comparative Example

[0151] (1) Take 100 g of PLA and mix it evenly with 400 g of diethylene glycol, then heat up to 180 °C;

[0152] (2) Increase the stirring speed to 1000 rpm. After stirring for 20 min, turn off the heating and cool down to room temperature (20 °C to 25 °C).

[0153] (3) Filter the mixture in step (2) to remove the solvent, and wash it with a certain amount of water.

[0154] (4) Repeat step (3) twice.

[0155] (5) Dry, crush and sieve it to obtain the product.

[0156] Experimental Example: Through the following measurement methods, the properties of the degradable microbeads are summarized in Table 1-3:

[0157] (1) Average particle size D50 and span of the degradable microbeads:

[0158] The average particle size D50 is the equivalent diameter of the larger particles when the cumulative distribution in the particle size distribution curve is 50%. The D90 particle size, D50 particle size, and D10 particle size are the equivalent diameters (average particle sizes) of the larger particles when the cumulative distributions in the distribution curve are 90%, 50%, and 10% respectively. span=(Dv90 - Dv10) / Dv50, which refers to the distribution condition of the particle size. The closer the span is to 0, the more uniform the fineness and the higher the size consistency. D97 is the equivalent diameter when the cumulative distribution in the distribution curve is 97%, representing the size of the coarse particle size in the particle size distribution; the D97 data provided in Table 1 is to illustrate the size of the coarse particles in the results of each embodiment of the present application, providing, in addition to the particle distribution span span, another corroboration of the microbead particle distribution situation.

[0159] The particle size distributions of each embodiment were measured using the laser diffraction method, and D50, D97, and Span expressed in terms of the median particle size were obtained from the particle size distributions as follows Figure 3 . In the measurement of the particle size distribution based on the laser diffraction method, a laser diffraction / scattering type particle size distribution measuring device LA_950v2 (manufactured by Horiba, Ltd.) was used.

[0160] (2) Sphericity:

[0161] Testing with reference to the standard GB / T 32661-2016, using a scanning electron microscope (SU3800 manufactured by Hitachi, Ltd.), taking photos, measuring the projected area and perimeter length of the particles in the photos, calculating the area of the true circle with the same perimeter from the perimeter length, and the sphericity value is the ratio of the projected area of the particles to the area of the true circle with the same perimeter; Method: The arithmetic mean of the sphericities of 50 complete particles randomly selected in the image, and the particles with incomplete edges in the image are not measured.

[0162] (3) Powder flowability:

[0163] Measured with a powder flow meter, also called a Hall flowmeter, by measuring the time for 50 g of powder to flow through a funnel. The shorter the time, the better the flowability, and the unit is s / 10 g.

[0164] (4) Powder compression modulus:

[0165] Taking 5 microbead particles in the range of the average particle size ±0.5 μm as samples, using a micro compression testing machine (manufactured by Shimadzu Corporation, MCT-211), applying a load to the sample at a certain load rate, calculating the compression modulus by taking 30% of the maximum compression amount, and calculating the average compression modulus (GPa).

[0166] (5) X-ray photoelectron spectroscopy (XPS) measurement:

[0167] XPS mainly analyzes the elemental composition of the object surface from about 0 nm to 10 nm; in order to prove that the nano-inorganic powder is coated on the outer layer of the degradable microspheres, the samples of Examples 1 to 4 were sent for testing, and the samples of Examples 1 and 2 were analyzed after different etching depths by XPS. The detection basis: GB / T19500-2004, the detection equipment: Thermo Fisher ESCALAB 250Xi, as shown in Tables 4 and 5 and Figures 10A to 10D below. Among them, Figures 10A to 10D are the energy spectra of the sample of Example 4. Figure 10A presents the measurement results of the overall energy spectrum, and Figure 10B is the fine spectrum of Figure 10A, which presents the measurement results of the 1s orbital of carbon element (C1s); Figure 10C is the fine spectrum of Figure 10A, which presents the measurement results of the 2p orbital of silicon element (Si2p); and Figure 10D is the fine spectrum of Figure 10A, which presents the measurement results of the 1s orbital of oxygen element (O1s).

[0168] Focused Ion Beam-Scanning Electron Microscope (FIB-SEM), combined with Energy-dispersive X-ray spectroscopy (EDS) for elemental analysis of the cross-section of microspheres: Detection equipment: Thermo Fisher Helios G4 UX. The samples of Example 1 were selected for degradable microspheres with a particle size of 10 μm. After gold plating, they were etched with an ion beam until the maximum diameter of the sphere, and EDS elemental analysis was carried out from the periphery of the sphere towards the center of the sphere, as shown in Figures 11A and 11B.

[0169] (7) Determination of oil absorption:

[0170] Based on the method for determining oil absorption in JIS K 5101, dimethyl silicone oil commonly used in cosmetics was selected; about 100 mg of fine particles were precisely weighed on a watch glass, and dimethyl silicone oil was slowly added drop by drop with a burette and kneaded with a palette knife. Before the sample agglomerated, the dropping-kneading was repeated, and the point where the paste became smooth and hard was taken as the end point. The oil absorption (ml / 100 g) was calculated from the amount of dimethyl silicone oil used for dropping; the oil absorption of the degradable microspheres obtained in Example 1 was measured. In addition, for comparison, the oil absorption of commercially available PMMA microspheres for cosmetics and their possible substitutes - natural material substitutes was measured in the same way. The sources of commercially available PMMA microspheres and natural material substitutes are shown in Table 6.

[0171] (8) Agglomeration property after oil absorption:

[0172] An appropriate amount of oil was added to the microspheres, and dimethyl silicone oil was used as the oil. A spatula was used to stir and mix, and the appearance agglomeration characteristics were observed from the photos. This characteristic is for confirmation before the application example.

[0173] (9) Degradability:

[0174] With the aim of simulating seawater degradation, place the microbead samples in a petri dish filled with seawater. Under the conditions of an ultraviolet chamber, at 25 °C, age for 30 days. After 30 days, confirm the degradation situation by photos or SEM.

[0175] Table 1

[0176] Sample Degradable material D50 (μm) D97 (μm) Span (D90 - D10 / D50) Sphericity Example 1 PLA 7.9 25.9 2.1511 0.9773 Example 2 PLA 50.3 91.5 0.8634 0.9702 Example 3 PLA 102.4 183.2 0.6822 NA Example 4 PCL 15.8 31.8 1.4874 0.9886 Example 5 PHBV 7.6 22.2 1.9512 0.9897 Example 6 PBAT 18.8 37.7 1.1777 0.8664 Example 7 PBAT 1004 -- -- --

[0177] Table 2

[0178] Sample Sample material Flowability (s / 10g) Control sample PMMA 45 Example 1 PLA 46 Example 4 PCL 49 Example 6 PBAT 47

[0179] Table 3

[0180]

[0181]

[0182] Table 4

[0183]

[0184] Table 5

[0185]

[0186]

[0187] Table 6

[0188]

[0189] Application Example - Cosmetics Application Example 1 - Powder Puff: Made of PLA microbeads prepared in Example 1

[0190] Table 7

[0191]

[0192] Application Comparative Example - Powder Puff: Made of commercially available PMMA microbeads

[0193] Table 8

[0194]

[0195]

[0196] Application Comparative Example - Powder Puff: Made of commercially available porous silica

[0197] Table 9

[0198]

[0199] Cosmetic Application Example 2 - Cream Prepared with PLA Microbeads from Example 1

[0200] Table 10

[0201]

[0202] Application Comparative Example - Cream Prepared with Commercially Available PMMA Microbeads:

[0203] Table 11

[0204]

[0205]

[0206] Application Comparative Example - Cream Prepared with Commercially Available Porous Silica:

[0207] Table 12

[0208]

[0209] Table 13 - Application Example - Evaluation of the Skin Feel of Powder Puff

[0210]

[0211]

[0212] Table 14 - Application Example - Evaluation of the Skin Feel of Cream

[0213]

[0214] Explanation of the Example:

[0215] The comparative example is a comparison with Example 1. Without adding nano - silica, an emulsion was prepared and filtered and dried in the same manner. By observing its appearance with an Optical Microscope (OM) diagram, although this manufacturing method can also form emulsion particles, it was found that the sphericity of the particles is poor and the particle size is uneven, as Figure 2 , which can illustrate the contribution of nano - silica to sphericity and particle size uniformity.

[0216] Sorted from Table 1, PLA, PBAT, PCL, and PHBV microspheres coated with nanoparticles in Examples 1 to 7 were respectively prepared. From Examples 1 to 3, it can be understood that by controlling the amount of nanoparticles, PLA microspheres coated with nano-silica with different D50 particle sizes were finally prepared. Its characteristic is that the span of the microsphere particle size distribution is small, indicating that the particle sizes of the prepared microspheres are concentrated. When the type of degradable polymer is changed, this property still exists, and the sphericity range is greater than 0.86. The closer the sphericity is to 1, the closer the shape of the prepared degradable microspheres coated with nano-silica is to a sphere. When the type of degradable polymer is changed, this property still exists. Figures 4 to 8 , the actual appearance of the finished products of the embodiments of the present application will be illustrated by electron microscope images. Figure 3 The results of the measured laser diffraction / scattering particle size distribution of Example 3 are presented.

[0217] As shown in Table 2, the fluidity of commercially available PMMA microspheres for cosmetics and the microspheres of the present application was compared. The product number information of the comparative sample PMMA is shown in Table 6. It was found that under the condition of similar D50 particle sizes, the PLA microspheres coated with nano-silica in Example 1 were similar to the commercially available PMMA microspheres, and the fluidity did not deteriorate significantly as the particle size increased, such as in Examples 4 and 6. It is speculated that the outer nanoparticles and sphericity provide the main contribution, and the good fluidity provides better controllability for industrial applications; as shown in Table 3, the compression modulus of the microspheres of the examples and commercially available PMMA microspheres was compared. It can be seen from the results of Examples 1 to 3 that the larger the microspheres, the smaller the compression modulus, indicating that the microspheres are softer and have lower hardness. This can correspond to the volume ratio of the surrounding nanoparticles. The microspheres are small and there are many nanoparticles. Therefore, the PLA microspheres coated with nano-silica in Example 1 have a large compression modulus and are larger than the commercially available PMMA microspheres. Therefore, the microspheres coated with inorganic nanoparticles of the present application can provide better shape retention and will not be deformed by external forces during the manufacturing process; and the particles of Example 1 can be compared with the anti-drop property of the powder cake application example to provide the stress-bearing characteristics of the end product.

[0218] To prove that the nano-inorganic particles are coated on the outer layer of the degradable microspheres, the samples of Examples 1 to 4 were subjected to XPS surface element analysis with an analysis depth of about 10 nm. The results are shown in Table 4. For the samples of Examples 1 to 3, the degradable plastic is PLA. Under the same process conditions, by adding nano-silica particles with weight percentages of 13.04%, 9.09%, and 4.76% of the total microspheres respectively, degradable microspheres with D50 particle sizes of 7.9 μm, 50.3 μm, and 102.4 μm were obtained. The XPS analysis results of the degradable microspheres show that the C element ratios are 17.54%, 35.2%, and 73.14% respectively, and the Si element ratios are 22.6%, 21%, and 3.98% respectively. Based on the molecular weight of the repeating unit C3H4O2 of PLA, the weight ratios of SiO2 in the outer layer of about 10 nm depth of the microspheres in Examples 1 to 3 are 76.3%, 59.8%, and 11.9% in sequence, while the weight ratios of PLA are 23.6%, 40.1%, and 88.0% in sequence. It can be proved that most of the silica is distributed on the outer layer of the microspheres. And as the average particle size of the microspheres increases, the Si element ratio in XPS decreases, the weight ratio of SiO2 decreases, and the PLA content in the outer layer of the microspheres calculated from the carbon signal in XPS is higher. Even though the calculated weight ratio of PLA in the outer layer of the degradable microspheres in Example 1 is 23.6%, it means that the silica does not completely and tightly coat the degradable plastic. Therefore, it is speculated that the degradation ability of the degradable plastic is not affected, and the subsequent degradation test also confirmed this speculation and the XPS experimental results. For Example 4, the XPS test results can also be compared with Example 1, except that the degradable plastic is PCL and the repeating unit is C6H 10 O2, the C element ratio is 20.16%, and the Si element ratio is 25.03%. After calculation, the weight ratio of SiO2 in the outer layer of about 10 nm depth of the microspheres in Example 4 is 63.2%, and the weight ratio of PCL is 63.2%. Therefore, it can be concluded that the characteristics of the degradable microspheres of this application are that there is 3.0% to 25% of Si element on the surface and the ratio of C(1S) / Si is 0.5 to 20.

[0219] After the samples of Examples 1 and 2 were etched to different depths with high-energy electron beams and then subjected to XPS surface element analysis, the results are shown in Table 5 below. As the etching depth increases, the C element ratio increases and the Si element ratio decreases. After etching to a depth of 630 nm, the degradable microspheres melted and deformed due to their intolerance to the high-energy bombardment of the electron beam and could not be etched further.

[0220] To confirm the distribution of the overall inorganic nanoparticles in the degradable microspheres, the sample of Example 1 was etched cross-sectionally with FIB, and then detailed element analysis was carried out with SEM and EDS, as Figure 11 A, Figure 11 B, from Figure 11It can be seen that the Si element signal is approximately 1.3 - 1.5 μm deep from the outer layer to the inner layer of the microbeads, that is, it presents close to about 0.1 - 0.3%, almost approaching the measurement limit of the machine. It can be determined that there is almost no SiO2 after a depth of 1.5 μm from the outer layer of the degradable microbeads. At the same time, it can be confirmed from the analysis of the sample profile that the outer layer of the degradable microbeads still contains the C element, indicating that the nano-silica particles do not completely coat the degradable microbeads.

[0221] Before applying to cosmetics, in response to the needs of cosmetic formulation, it is necessary to confirm the oil absorption and agglomeration properties of the microbead powder. Since the PLA microbeads coated with silica nanoparticles in Example 1 have a D50 particle size of 7 μm, which is similar to the particle size of the PMMA microbeads, the most commonly used material in the industry before the plastic ban in the comparative example, it can be used in cosmetics. Other comparative samples are known natural materials used to replace PMMA microbeads after the plastic ban, such as porous silica, rice starch, modified rice starch, and modified cellulose. Their properties are presented in Table 6. The OM observations, agglomeration, and oil absorption after individual oil absorption are organized as Figure 12 , It can be seen from the OM observation that except for PMMA, Example 1, and porous silica, which are true spherical, the other three natural materials show irregular or fibrous shapes. In terms of agglomeration, PMMA, porous silica, modified cellulose, and Example 1 have better agglomeration. However, the agglomerated porous silica is too hard and slightly transparent, while the agglomerated modified cellulose is too soft and flaccid and slightly white. Only Example 1 is similar to the PMMA microspheres, and the oil absorption is also similar to that of PMMA. The oil absorption of PMMA is 45 ml per 100 g, and the oil absorption of Example 1 is 58 ml.

[0222] To prove that the outer coating of silica nanoparticles in this application does not affect the degradation characteristics, Examples 2, 5, and 6 and the comparative sample PMMA were placed in a petri dish filled with seawater and aged for 30 days at 25°C under ultraviolet conditions, as Figures 13 to 15 , It can be seen that the PBHV and PBAT microbeads coated with silica nanoparticles in Examples 5 and 6 have become moldy and turbid, as Figure 13 , 14 , and in Example 2, microbead breakdown was observed under SEM, as Figure 16 , while the comparative sample showed the original white turbidity before aging without any special changes, as Figure 15 , indicating that the degradable microbeads coated with inorganic nanoparticles in this application can indeed degrade in seawater, achieving the purpose of reducing environmental pollution.

[0223] Application examples take powder compacts and creams as examples, and the comparison samples are commercially available PMMA and porous silica. The powder compacts and creams are prepared in the same preparation method according to the compounding ratios (weight %) shown in Tables 7 to 12. Sensory tests are carried out by 20 members of the expert group. For the powder compact, in terms of the uniform spreading and smearing feeling during skin coating, moist feeling, smoothness, and the smooth feeling, soft feeling, soft focus effect, oil control effect of the makeup film after skin coating, the sticking property of the powder puff and the drop resistance of the powder compact itself, seven evaluation items are investigated through interviews and evaluated based on the evaluation score benchmark table; for the cream, in terms of the uniform spreading property during skin coating, and the soft and moist feeling, smoothness, absorption speed and retention feeling of the maintenance film after skin coating, five evaluation items are investigated through interviews and evaluated based on the evaluation score benchmark table. As shown in Tables 13 to 14, the results are as Figure 17 A, 17B, 18A, 18B. In Example 1, the PLA microspheres coated with silica nanoparticles are applied to the powder compact. Except that the sticking property is slightly poor, the porous silica has poor drop resistance, and the overall performance is close to that of the commercially available PMMA and porous silica. In the application of creams, the overall performance of the comparative sample PMMA and the PLA microspheres coated with silica nanoparticles in Example 1 is similar, while the performance of the comparative sample porous silica in creams is poor. Therefore, the degradable microspheres with an outer layer coated with inorganic nanoparticles of the present application can replace the plastic microparticles PMMA that pollute the ocean, and have excellent points such as drop resistance, soft and moist feeling, smoothness, absorption speed and smearing property compared with the alternative material of the natural material porous silica, and have competitive advantages and are worthy of promotion.

[0224] According to the examples and comparative examples (samples), the degradable microspheres of the present application have good sphericity, uniform particle size distribution, and can be made with a wide range of particle sizes. Its preparation method is simple and does not require a large amount of organic solvents.

[0225] The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A degradable microbead, characterized in that, The microbeads include: a degradable plastic and a plurality of inorganic nanoparticles coated on the outer layer of the degradable plastic; Among them, the average particle size D50 of the microbeads is 1 micron to 3000 microns; The content of the inorganic nanoparticles is 7.4 wt% to 15 wt%, based on the total weight of the degradable microbeads; The particle size of the inorganic nanoparticles is 1 to 100 nanometers; The material of the inorganic nanoparticles is silica; the degradable microbeads are of a core-shell-like structure and are spherical.

2. The degradable microbeads according to claim 1, characterized in that, The sphericity of the degradable microbeads is greater than 0.86, and the particle size distribution span is 0.6 to 2.

5.

3. The degradable microbeads according to claim 1, characterized in that, The inorganic nanoparticles are spherical silica with a particle size of 1-40 nanometers.

4. The degradable microbeads according to claim 1, characterized in that, The material of the inorganic nanoparticles is selected from silica, titanium dioxide, aluminum oxide, zinc oxide, iron oxide, cerium oxide, calcium carbonate, barium carbonate, montmorillonite or a combination thereof.

5. The degradable microbeads according to claim 1, characterized in that, The degradable plastic is selected from degradable synthetic polymers, degradable natural polymers, copolymers of degradable synthetic polymers, copolymers of degradable natural polymers or a combination thereof.

6. The degradable microbeads according to claim 5, wherein, The degradable synthetic polymers are selected from aliphatic polyesters, aromatic / aliphatic polyesters, aliphatic polyamide esters, polyamino acids, polycarbonates, polyester ethers, polyphosphazenes, polyanhydrides and polyurethanes or a combination thereof.

7. The degradable microbeads according to claim 5, characterized in that, The degradable natural polymers are selected from collagen, gelatin, chitin, chitosan, dextran, hyaluronic acid, sodium alginate, starch, cellulose and microcrystalline cellulose or a combination thereof.

8. A method for preparing the degradable microbeads as described in claim 1, characterized in that, Comprising: Mixing and dispersing the plurality of inorganic nanoparticles with a solvent in a reactor; Adding the molten degradable plastic; After stirring, the temperature is reduced to 20°C to 25°C, and the degradable microbeads precipitate.

9. The preparation method of the degradable microbeads according to claim 8, characterized in that, The boiling point of the solvent is more than 10 degrees higher than the melting point of the degradable plastic; The solubility of the degradable plastic in the solvent is between 0 and 0.01 g / 100 g of solvent; The solvent is selected from silicone oil, glycerol, phenoxy alcohols, diethylene glycol or a combination thereof.

10. A composition for skin coating, characterized in that, Comprising the degradable microbeads according to any one of claims 1-7.

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