Hollow silicone resin particle and preparation method thereof

Abstract

The invention relates to a hollow particle P consisting of a hollow core K and a shell H comprising a silicone resin composition Z comprising a condensation-crosslinked silicone composition X and a particle solid F. The invention further relates to a process for preparing hollow particles P, comprising a first step of mixing a dispersion V comprising a particle solid F and water with a condensation crosslinkable silicone composition X1 to form an aqueous continuous phase and a discontinuous phase comprising a condensation crosslinkable silicone composition X1, a second step of crosslinking the silicone composition X1 in a discontinuous phase to form a silicone composition X, thereby forming hollow particles P, and a third step of forming the hollow particles P, and a fourth step of forming the hollow particles P, and a fourth step of forming the hollow particles P, and a fourth step of forming the hollow particles P, and a fourth step of forming the hollow particles P, and a fourth step of forming the hollow particles P,

Description

Technical Field

[0001] The present invention relates to hollow particles composed of a hollow core and a shell of a condensed crosslinked silicone resin and particulate solids, and to a method for their preparation. Background Art

[0002] Hollow body particles are widely used, for example, as lightweight fillers for reducing the density of polymer or ceramic components, or for absorbing, transporting, and releasing active ingredients, such as fragrances, care substances, or active substances, for example, in cosmetic or medical applications or in household products or detergents.

[0003] The preparation of hollow body particles is very laborious and typically uses hard or soft templates on which the shell is constructed and then removed again very laboriously. These methods are extremely disadvantageous both ecologically and economically.

[0004] WO 2007113095 and WO 2021121562 describe core-shell particles based on polysiloxanes that have very favorable properties in cosmetic applications and are used as additives in many technical applications, where they have advantages particularly due to surface effects. However, the filled structure means that these particles cannot absorb functional substances inside them.

[0005] US2009004418 describes hollow silicone resin particles having a particle size of less than 1 mm, where the shell is formed from a silicone resin composition of SiO 4 / 2 units, RSiO 3 / 2 units, and R2SiO 2 / 2 units. The preparation is very laborious and extremely disadvantageous both ecologically and economically because template particles (such as organic polymer particles) and / or toxic organic solvents (such as toluene or xylene) are initially suspended in water and then coated with reactive silanes to form a silicone resin shell, and the core is removed with an organic solvent in the final step.

[0006] US 9 802 175 B2 describes a method for preparing hollow silicone resin particles composed of RSiO 3 / 2 units and having a particle size of less than 200 nm. The preparation is very laborious and extremely disadvantageous both ecologically and economically because organic template particles, such as polystyrene particles, polyacrylate particles, or polyvinyl acetate particles, are initially prepared, the particles are coated with an alkoxy-functionalized silane in a second step to form a silicone resin shell, and the core is removed with an organic solvent and heating in a third step.

[0007] US 5945043 describes a method for preparing hollow polysiloxane particles having a shell formed of a thermoplastic polysiloxane. The thermoplastic polysiloxane is dissolved in a solvent, and the mixture is dispersed in water. The dispersion is spray-dried, resulting in the removal of the solvent and water and the formation of hollow thermoplastic polysiloxane particles. The polymer shell of the particles is not crosslinked. Thus, such particles are sensitive to temperature and solvents. The use of toxic solvents makes the preparation extremely disadvantageous ecologically and economically.

[0008] WO 14098107 describes a method in which silica particles are used as a template to prepare hollow polysiloxane particles. The silica particles undergo dispersion. On the surface of the template particles, a polysiloxane shell is formed by hydrolysis and condensation of an alkoxy-functionalized silane or siloxane. The template particles are then separated and decomposed. The method is extremely disadvantageous ecologically and economically because the preparation of the silica particles used as a template and separated and decomposed in the final step of the method is very laborious.

[0009] Xue Wang et al. (Journal of Colloid and Interface Science 542 (2019) 144 - 150) describe a method for preparing hollow particles via Pickering emulsions. In this method, a solution of a photopolymerizable compound in an organic oil is emulsified in an aqueous phase, and the boundary phase is stabilized by fine silica particles. In a second process step, the photopolymerizable compound polymerizes at the boundary phase and forms a solid shell together with the silica particles. The use of an organic oil as a template makes the preparation extremely disadvantageous ecologically and economically.

[0010] All of the above methods have the following disadvantages: the use of a solid or liquid template compound to construct a core - shell structure that is coated and then has to be laboriously removed and discarded. Summary of the Invention

[0011] The present invention provides hollow particles P composed of a hollow core K and a shell H comprising a silicone resin composition Z containing a condensed crosslinked silicone composition X and particulate solids F.

[0012] The median particle size d50 of the hollow particles P is in the range from 0.1 to 100 μm, preferably in the range from 0.4 to 60 μm, and preferably in the range from 0.8 to 40 μm.

[0013] The hollow particles P are preferably substantially spherical. The sphericity SPHT3, determinable according to ISO9276 - 6 using a Camsizer X2 from Retsch Technology, is preferably at least 0.8, more preferably at least 0.82.

[0014] The hollow particles P are amphiphilic, have a defined and uniform structure, and can be dispersed in both aqueous and oily media.

[0015] The hollow particles P have additional advantages: their low density as additives in formulations means that they migrate to the surface and thus exhibit enhanced surface effects. They are also suitable as lightweight fillers, for example, for ceramics.

[0016] The hollow particles P can accommodate other substances. Filled particles cannot do this.

[0017] The present invention also provides a simple and inexpensive method for preparing hollow body particles, which does not involve the use of templates.

[0018] The present invention further provides a method for preparing the hollow particles P, wherein in a first step, a dispersion V containing particulate solids F and water is mixed with a condensation-crosslinkable silicone composition X1 to form an aqueous continuous phase and a discontinuous phase containing the condensation-crosslinkable silicone composition X1, the condensation-crosslinkable silicone composition X1 comprising a silicone resin A containing alkoxy groups and a silane B containing alkoxy groups that are liquid at 20 °C, and in a second step, the silicone composition X1 is crosslinked in the discontinuous phase to form a silicone composition X, resulting in the formation of the hollow particles P.

[0019] The advantageous method of the present invention differs from the prior art methods particularly in that it does not involve the use of liquid or solid templates. The templates used according to the prior art form cores, and shells are constructed on the surfaces of these cores. The templates are then removed again to form hollow particles.

[0020] According to the method of the present invention, a shell H is formed by condensation-crosslinking the emulsified condensation-crosslinkable silicone composition X1 at the boundary with the aqueous continuous phase of the emulsion E. Thus, the emulsion droplets of the condensation-crosslinkable silicone composition X1 initially form a temporary core, and then the condensation-crosslinkable silicone composition X1 binds to the particulate solids F on the surface of the temporary core to form the shell H during crosslinking to the silicone composition X, forming the hollow particles P. Using the method of the present invention, no separate, expensive, or laborious preparation of templates is required, and the templates must be laboriously separated, recycled, or discarded as waste. Therefore, the method of the present invention is very advantageous both economically and ecologically.

[0021] Based on the total amount of components (A) and (B), the condensation-crosslinkable silicone composition X1 preferably contains respectively:

[0022] -(A) 50 wt% - 90 wt% of at least one silicone resin A composed of units of formulas (Ia), (Ib), (VII), and (Id)

[0023]

[0024] wherein

[0025] R 17 represents the same or independently different monovalent, substituted or unsubstituted organic groups with or without functional groups, or -OH or hydrogen groups,

[0026] provided that

[0027] - at least 20 mol% of the formula (Ia) or (Ib) or a mixture of both is present in (A),

[0028] - not more than 50 mol% of the formula (Ib) is present in (A),

[0029] - the alkoxy group is present in (A) to an extent of at least 5 wt% as R 17

[0030] provided that

[0031] -(A) is a liquid at 20 °C,

[0032] -(B) 10 wt% - 50 wt% of at least one silane B having the following general formula

[0033] R 1 (4-a) Si(OR) a (II),

[0034] wherein,

[0035] R is a hydrocarbon group having 1 to 16 carbon atoms, the carbon chain of which may be interrupted by non-adjacent -O- groups,

[0036] R 1 represents the same or independently different monovalent hydrocarbon groups, and

[0037] a represents the value 2, 3 or 4, wherein

[0038] based on the total mass of all silanes B, at least 20 wt% of the silanes B satisfy the characteristic a = 3 or 4.

[0039] Component (A)

[0040] In each case based on the total amount of components (A) and (B), the condensation-crosslinkable silicone composition X1 used according to the invention preferably comprises 55 wt% - 85 wt%, preferably 60 wt% to 80 wt% of one or more silicone resins A.

[0041] ​Silicone resin A is preferably those with a molecular weight Mw of at least 500, preferably at least 600, more preferably at least 700, and not greater than 5000, preferably not greater than 4000, more preferably not greater than 3000, where the polydispersity does not exceed 20, preferably does not exceed 18, more preferably does not exceed 16, especially does not exceed 15.

[0042] Silicone resin A contains at least 20 mol%, preferably at least 30 mol%, more preferably at least 40 mol%, especially at least 50 mol% of repeating units of formula (Ia) or (Ib) or a mixture of formula (Ia) and (Ib), where the content of the repeating units of formula (Ib) is not greater than 50 mol%, preferably not greater than 40 mol%, more preferably not greater than 20 mol%. In a particularly preferred embodiment, unit (Ib) is absent in silicone resin A.

[0043] The repeating units of formula (Id) can be present in silicone resin A in an amount of up to 80 mol%, preferably up to 70 mol%, more preferably up to 60 mol%, especially up to 50 mol%.

[0044] Silicone resin A contains alkoxy groups as R 17 to an extent of at least 5 wt%, preferably at least 8 wt%, and particularly preferably at least 10 wt%.

[0045] As R 17 Examples of suitable alkoxy groups are hydrocarbonoxy groups having 1 to 16 carbon atoms, which may also be substituted. Particularly suitable and thus preferred are methoxy, ethoxy, isopropoxy, n-butoxy and tert-butoxy and p-nitrophenoxy, especially preferably methoxy and ethoxy.

[0046] All other R 17 can independently of one another be monovalent, substituted or unsubstituted hydrocarbon groups. Preferred are pure hydrocarbon groups, preferably having 1 to 16 carbon atoms. Examples of suitable hydrocarbon group R 17 choices are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl groups, hexyl groups such as n-hexyl groups, heptyl groups such as n-heptyl groups, octyl groups such as n-octyl groups and isooctyl groups such as 2,2,4-trimethylpentyl groups, nonyl, such as n-nonyl; decyl, such as n-decyl; dodecyl, such as n-dodecyl; and octadecyl, such as n-octadecyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl groups, aryl groups such as phenyl, naphthyl, anthracyl and phenanthryl groups, alkaryl groups such as tolyl groups, xylyl groups and ethylphenyl groups, and aralkyl groups such as benzyl groups and β-phenylethyl groups. As R 17Preferred hydrocarbon groups are methyl, n-propyl, isopropyl, phenyl, n-octyl or isooctyl, more preferably methyl, n-propyl, phenyl and isooctyl, and particularly preferably methyl and phenyl.

[0047] Component (B)

[0048] Based in each case on the total amount of components (A) and (B), the condensation-crosslinkable silicone composition X1 preferably comprises 15 wt% - 45 wt%, preferably 20 wt% to 40 wt% of one or more silanes B.

[0049] Preferably, based on the total mass of all silanes B, at least 50 wt%, preferably at least 70 wt%, more preferably at least 90 wt%, particularly preferably at least 95 wt% of the silanes B satisfy the characteristic a = 3 or 4; in a preferred embodiment, in each case based on the total mass of all silanes B, there is at least 30 wt%, preferably at least 40 wt%, more preferably at least 50 wt% of at least one silane B in which a = 4.

[0050] Examples of suitable groups R are hydrocarbon groups having 1 to 16 carbon atoms, which hydrocarbon groups may also be substituted. Particularly suitable and thus preferred are methyl, ethyl, isopropyl and tert-butyl groups and the p-nitrophenyl group, and particularly preferred are methyl and ethyl groups.

[0051] Group R 1 can each independently be a substituted or unsubstituted monovalent hydrocarbon group. Preferred are pure hydrocarbon groups, preferably having 1 to 16 carbon atoms. Examples of suitable hydrocarbon groups R 1 are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl groups, hexyl groups such as n-hexyl groups, heptyl groups such as n-heptyl groups, octyl groups such as n-octyl groups and isooctyl groups such as 2,2,4-trimethylpentyl groups, nonyl, such as n-nonyl; decyl, such as n-decyl; dodecyl, such as n-dodecyl; and octadecyl, such as n-octadecyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl groups, aryl groups such as phenyl, naphthyl, anthracyl and phenanthryl groups, alkaryl groups such as tolyl groups, xylyl groups and ethylphenyl groups, and aralkyl groups such as benzyl groups and β-phenylethyl groups. As R 1 the preferred hydrocarbon groups are methyl, n-propyl, isopropyl, phenyl, n-octyl or isooctyl, more preferably methyl, n-propyl, phenyl and isooctyl, and particularly preferably methyl and phenyl.

[0052] The condensation-crosslinkable silicone composition X1 may comprise other solid or liquid components I, provided that the condensation crosslinking of the silicone composition X1 and the formation of the shell H are not impaired.

[0053] Examples of other component I include catalysts, active and inactive fillers, inhibitors, heat stabilizers, solvents, plasticizers, color pigments, soluble dyes, sensitizers, photoinitiators, adhesion promoters, conductivity additives, cosmetic substances, fragrances, pharmaceutical or cosmetic active substances, fluorescent dyes, fungicides, flavors, rheological additives, corrosion inhibitors, oxidation inhibitors, light stabilizers, heat stabilizers, flame retardants, reagents for influencing electrical properties, and reagents for improving thermal conductivity.

[0054] These components can be retained in the core of the hollow particles P and thus be encapsulated, stored, transported, or selectively released.

[0055] Particulate solid F

[0056] The particulate solid F used according to the invention is preferably in particulate form and is solid at 20 °C and the pressure of the ambient atmosphere (i.e., 1013 hPa).

[0057] The particulate solid F preferably has a solubility in water of less than 0.1 g / l, more preferably less than 0.05 g / l, at pH 7.33, an electrolyte background of 0.11 mol, and a temperature of 37 °C under the pressure of the ambient atmosphere (i.e., 1013 hPa).

[0058] The particulate solid F preferably has a molar mass of greater than 10,000 g / mol, more preferably from 50,000 to 50,000,000 g / mol, especially from 100,000 to 10,000,000 g / mol, in each case preferably measured by static light scattering.

[0059] The particulate solid F preferably has a BET surface area of 30 m 2 / g to 500 m 2 / g, more preferably 100 m 2 / g to 300 m 2 / g. The BET surface area is preferably measured according to known methods, preferably according to German Industrial Standards DIN 66131 and DIN 66132.

[0060] The particulate solid F preferably has a Mohs hardness greater than 1, more preferably greater than 4.

[0061] The particulate solid F used is preferably a metal oxide having a covalently bonded component in the metal-oxygen bond, such as solid oxides of main group and transition group elements, such as one of the third main group, such as boron oxide, aluminum oxide, gallium oxide, or indium oxide, or one of the fourth main group, such as silicon dioxide, germanium dioxide, tin oxide, or stannic oxide, or lead oxide or lead dioxide, or oxides of these transition group elements, such as titanium dioxide, zirconium dioxide, hafnium dioxide, cerium oxide, or iron oxide.

[0062] The metal oxides used according to the invention are preferably aluminum(III), titanium(IV) or silicon(IV) oxides, such as those prepared by wet chemistry, for example precipitated, silica or silica gel, or alumina, titanium dioxide or silica prepared by methods at elevated temperature, such as fumed alumina, titanium dioxide or silica.

[0063] The median particle size of the particulate solid F or the particulate aggregates (if present) is preferably less here than the median diameter d of the emulsion droplets formed according to the method of the invention in the absence of fine-grained particles 50 。

[0064] The median particle size of the particulate solid F is less than 1000 nm, preferably between 10 nm and 800 nm, more preferably between 50 nm and 500 nm, and most preferably between 75 nm and 300 nm, in each case measured as the median hydrodynamic equivalent diameter determined by photon correlation spectroscopy at 173° (backscattering) with a Nanosizer ZS from Malvern.

[0065] The methanol number of the particulate solid F is preferably less than 70, preferably less than 50, more preferably less than 40, and particularly preferably less than 30.

[0066] To determine the methanol number, defined mixtures of water and methanol are prepared and then the surface tension of these mixtures is determined using known methods. In a separate experiment, these water-methanol mixtures are covered with a limited amount of particles and shaken under defined conditions (e.g., gentle manual shaking or shaking with a rotary mixer for about 1 minute). The water-alcohol mixture in which the particles have not settled and the water-alcohol mixture with a higher alcohol content in which the particles have just settled are determined. The surface tension of the latter alcohol-water mixture gives the critical surface energy γ crit , as a measure of the surface energy γ of the particles. The methanol content in water gives the methanol number.

[0067] The carbon content of the particulate solid F measured by elemental analysis on the dry particulate solid is greater than 0 wt%, preferably 0.1 wt% - 4 wt%, more preferably 0.25 wt% - 3.5 wt%, and most preferably 0.5 wt% - 3 wt%.

[0068] In a preferred embodiment, the particulate solid F is silica S.

[0069] Silica S preferably has a surface area of 30 to 500 m 2 / g, more preferably 100 to 300 m 2Partially water-wettable fumed silica and precipitated silica or mixtures thereof having a BET surface area of / g, with fumed silica being particularly preferred. The BET surface area is preferably measured according to known methods, preferably according to German Industrial Standards DIN 66131 and DIN 66132.

[0070] Preferably, the silica S is surface-treated with a suitable hydrophobizing agent and is thus hydrophobic. Hydrophobization must be carried out such that the silica S remains partially water-wettable. According to the present invention, this means that the methanol value of the silica S is less than 70, preferably less than 50, more preferably less than 40, and particularly preferably less than 30. As a result of the surface treatment, the preferred silica S has a carbon content of at least 0.2 wt% to a maximum of 1.5 wt%, preferably between 0.4 wt% and 1.4 wt%, more preferably between 0.6 wt% and 1.3 wt%. The hydrophobic groups are, for example, Si-bonded methyl or vinyl groups. Methods for hydrophobizing silica are known to those skilled in the art.

[0071] As the silica S, silylated fumed silica having a methanol value of less than 70, preferably less than 50, more preferably less than 40, and particularly preferably less than 30 is preferred.

[0072] Very particularly preferred is the partially water-wettable silica as described in EP 1433749 A1 and DE 10349082 A1.

[0073] Hollow core K

[0074] The separated and dried hollow particles P retain the hollow core K. The average ratio of the average diameter of the hollow core K to the average diameter of the hollow particles P is preferably greater than 0.2, preferably greater than 0.3, in each case determined as the average of at least 5 individual particles from an electron microscope image (e.g., TEM or SEM micrograph). The hollow core K can consist of a single cavity or multiple individual cavities.

[0075] The hollow core K is adapted to accommodate other components I.

[0076] Shell H

[0077] The shell H comprises a silicone resin composition Z formed from a condensed crosslinked silicone composition X and a particulate solid F. The shell H is formed by condensing and crosslinking the emulsified condensable crosslinkable silicone composition X1 at the boundary with the aqueous continuous phase of the emulsion. The boundary phase is stabilized by the particulate solid F, and the particulate solid F is physically and / or chemically incorporated into the developing shell H during the condensation crosslinking process.

[0078] The shell H preferably has an average diameter of at least 50 nm, preferably at least 70 nm, in each case determined as the average of at least 5 individual particles by electron microscope images (e.g., TEM or SEM micrographs).

[0079] Catalyst K

[0080] In the case of the less reactive condensation crosslinkable silicone composition X1, if desired, a catalyst K is required to cause the hydrolysis and condensation of silicone resin A and silane B. Such catalysts are known to those skilled in the art. They can be acid or base or metal catalysts, such as Group IV transition metal catalysts, tin catalysts, such as those commonly used to accelerate hydrolysis, condensation reactions or transesterification reactions. As acids or bases, in addition to the known inorganic acids and metal salts, acidic or basic silanes or siloxanes can also be considered.

[0081] Preferred basic catalysts are NaOH, KOH, ammonia and NEt3. When using the basic catalyst K, the pH of the reaction mixture is preferably in the range of pH 8 to pH 12.

[0082] Preferred acidic catalysts K are p-toluenesulfonic acid, aqueous or gaseous HCl, and sulfuric acid. When using an acidic catalyst, the pH of the reaction mixture is preferably in the range of pH 1 to pH 5.

[0083] Hollow particle P

[0084] Hollow silicone resin particles of the prior art have a silicone resin shell obtained by coating and subsequently removing a liquid or solid template. The silicone resin shell is hydrophobic and not suitable for use in hydrophilic formulations and products, especially not suitable as an additive in aqueous formulations.

[0085] The hollow particle P of the present invention has an amphiphilic shell H of a silicone resin composition Z formed from a condensation crosslinked silicone composition X and a partially water-wettable solid F. The hollow particle P of the present invention preferably has a methanol value of less than 80, preferably less than 60, more preferably less than 50, and particularly preferably less than 40. Therefore, the hollow particle P of the present invention can be easily processed in hydrophilic and hydrophobic formulations and products.

[0086] The hollow particle P of the present invention preferably has a BET of greater than 4 m 2 / g, preferably greater than 10 m 2 / g, preferably greater than 20 m 2 / g.

[0087] The hollow particle P of the present invention preferably has a density of less than 0.28 g / cm 3 、preferably less than 0.25 g / cm 3The bulk density

[0088] Method for preparing hollow particles P

[0089] The continuous phase preferably comprises at least 80 wt%, in particular at least 90 wt%, of water.

[0090] Preferably, a three-phase mixture is formed in which an emulsion of a micro-water-soluble and water-immiscible condensable crosslinkable silicone composition X1 is prepared, and the emulsion is stabilized in the aqueous phase by partially hydrophobized silica (Pickering emulsion). After emulsification, the condensable crosslinkable silicone composition X1 undergoes crosslinking in a process suitable for preparing particles P. For example, if it comprises alkoxy- or acetoxy-substituted silanes or siloxanes, it may be necessary to hydrolyze the condensable crosslinkable silicone composition X1. If the silicone composition X1 has sufficient reactivity, the water already present can cause hydrolysis and subsequent condensation. The process must be carried out in such a way that no significant crosslinking occurs during the emulsification process, because otherwise a finely dispersed emulsion will not be formed. In the case of a less reactive condensable crosslinkable silicone composition X1, a catalyst K is required, if necessary, to cause hydrolysis and condensation of the siloxanes and silanes.

[0091] The second step of the process must be carried out such that the condensable crosslinkable silicone composition X1 forming the discontinuous phase reacts with the condensable crosslinking reaction at the interface with the aqueous continuous phase to form the shell H of the hollow particles P, which is accompanied by physical and / or chemical bonding to the particulate solid F of the stabilizing boundary phase.

[0092] Those skilled in the art know that before the first drying, the newly formed hollow particles P in the dispersion are filled with the condensable crosslinked liquid cleavage products and / or the aqueous continuous phase.

[0093] The size of the hollow particles P can be determined, for example, by emulsification techniques, thus, for example, by variables such as the input shear energy, the volume fraction of the silicone composition X1, the amount of the particulate solid F, the pH and the ionic strength, viscosity, feeding sequence, feeding rate of the continuous aqueous phase, or by the reaction scheme, that is, for example, by the reaction temperature, reaction time, and the concentration of the raw materials used. The choice and amount of any hydrolysis / condensation catalyst used also have an impact on the particle size.

[0094] If there are other optional solid or liquid components I, these are preferably homogeneously mixed with the condensable crosslinkable silicone composition X1 in the first step to form a mixture B, which is then emulsified with the dispersion V in a further step and subsequently crosslinked to form the hollow particles P. This ensures that all optional solid or liquid components I are present inside the droplets after emulsification and inside the hollow particles P after crosslinking.

[0095] The Pickering emulsion E of mixture B is preferably substantially free of conventional organic surface-active substances that are non-particulate liquids and solids at room temperature and ambient atmospheric pressure, such as non-ionic, cationic, and anionic emulsifiers ("organic emulsifiers").

[0096] The meaning of "organic emulsifier" here is not particulate and colloidal, but molecules and polymers according to the definitions of molecules, polymers, colloids, and particles given in "Dispersions and emulsions", G. Lagaly, O. Schulz, R. Zindel, Steinkopff, Darmstadt 1997, ISBN 3-7985-1087-3, pp. 1-4.

[0097] Generally, these organic emulsifiers have a size of less than 1 nm, a molar mass of < 10,000 g / mol, a carbon content of > 50 wt% (determinable by elemental analysis), and a Mohs hardness of less than 1.

[0098] At the same time, the organic emulsifiers that are substantially absent in the emulsion of the present invention generally have a solubility in water in a homogeneous or micellar form of > 1 wt% at 20 °C and the pressure of the ambient atmosphere (i.e., 900 to 1100 hPa).

[0099] The Pickering emulsion E of mixture B can contain such organic emulsifiers up to a maximum concentration of less than 0.1 times, preferably less than 0.01 times, more preferably less than 0.001 times, especially less than 0.0001 times the critical micelle concentration of these organic emulsifiers in the aqueous phase; this corresponds to a concentration of these organic emulsifiers of less than 10 wt%, preferably less than 2 wt%, more preferably less than 1 wt%, especially 0 wt% based on the total weight of the dispersion of the present invention.

[0100] In order to prepare the particle-stabilized Pickering emulsion E in the first step, any method known to those skilled in the art for preparing emulsions can be used. However, it has been found that an emulsion particularly suitable for preparing hollow particles P can be obtained according to the following process:

[0101] Process 1:

[0102] - First, add the highly concentrated dispersion V, initially adding a volume such that it contains the total amount of the required solid F and only a part of the volume of water.

[0103] - Slowly metering in the total volume of mixture B under constant homogenization, for example, by a high-speed stirrer, a high-speed dissolver, or a rotor-stator system.

[0104] - Then, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, the remaining desired volume of water is slowly metered in, optionally under constant homogenization.

[0105] Process 2:

[0106] - First, Dispersion V is added, with an initial added volume such that it contains the total amount of the required solid F and water.

[0107] - The total volume of Mixture B is slowly metered in, for example, using a high-speed stirrer, a high-speed dissolver, a rotor-stator system or a capillary emulsifier, under constant homogenization.

[0108] Process 3:

[0109] - First, the total volume of Mixture B is added.

[0110] - The highly concentrated Dispersion V is slowly metered in, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, under constant homogenization, with a metered-in volume such that it contains the total amount of the required solid F and only a part of the volume of water.

[0111] - Then, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, the remaining desired volume of water is slowly metered in, optionally under constant homogenization.

[0112] Process 4:

[0113] - First, the total volume of Mixture B is added.

[0114] - Dispersion V is slowly metered in, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, under constant homogenization, with a metered-in volume such that it contains the required solid F and the total amount of water.

[0115] Process 5:

[0116] - First, the total volume of Mixture B and the total volume of Dispersion V are added, with an initial added volume such that it contains the total amount of the required solid F and water.

[0117] - The two are homogenized together, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0118] Process 6:

[0119] - First, the total volume of Mixture B and the total volume of the highly concentrated Dispersion V are added, with an initial added volume such that it contains the total amount of the required solid F and a part of the volume of water.

[0120] - The two are homogenized together, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0121] - Then, for example, using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, optionally under constant homogenization, slowly metering in the remaining desired volume of water.

[0122] Processes 1, 2, 5 and 6 are preferred, with processes 2 and 5 being particularly preferred.

[0123] Homogenization is preferably carried out for at least 30 seconds, preferably at least 1 minute, in at least one process step.

[0124] In principle, a dispersion V of particulate solid F in water that is homogeneous in the emulsion according to the invention can be prepared according to known methods for preparing particulate dispersions, for example using a combination of stirrers that generate high shear (such as high-speed stirrers, high-speed dissolvers, rotor-stator systems, ultrasonic dispersers or ball / pearl mills).

[0125] The concentration of particulate solid F in dispersion V is hereby between 1 wt% and 80 wt%, preferably between 10 wt% and 60 wt%, more preferably between 10 wt% and 40 wt%, and most preferably between 12 wt% and 30 wt%.

[0126] In an optional process step, the Pickering emulsion E is diluted with water, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, optionally under constant homogenization.

[0127] The processes described can be carried out continuously or discontinuously.

[0128] The temperature in the first step of emulsification is between 0 °C and 80 °C, preferably between 10 °C and 50 °C.

[0129] The emulsification process can be carried out at standard pressure, i.e., between 900 and 1100 hPa, at elevated pressure, or under reduced pressure. The process is preferably carried out at atmospheric pressure.

[0130] The concentration of particulate solid F in the three-phase mixture of dispersion V and mixture B from the first step is hereby between 1 wt% and 80 wt%, preferably between 2 wt% and 50 wt%, more preferably between 3 wt% and 30 wt%, and most preferably between 4 wt% and 20 wt%.

[0131] The concentration of the condensable crosslinkable silicone composition X1 in the three-phase mixture of dispersion V and mixture B from the first step is hereby between 1 wt% and 80 wt%, preferably between 20 wt% and 76 wt%, more preferably between 40 wt% and 72 wt%, and most preferably between 50 wt% and 70 wt%.

[0132] The concentration of water in the three-phase mixture of dispersion V and mixture B from the first step is herein between 5 wt% and 80 wt%, preferably between 10 wt% and 70 wt%, more preferably between 15 wt% and 60 wt%, and most preferably between 20 wt% and 40 wt%.

[0133] Starting from the three-phase mixture described above, hollow particles P can be obtained in a second step according to the following process:

[0134] The three-phase mixture is preferably diluted by adding water to a water mass fraction of from 50 wt% to 90 wt%, preferably from 60 wt% to 80 wt%.

[0135] In the second step, preferably at low shear, the three-phase mixture is stirred, for example, by a slowly operating dissolver, rotor-stator or paddle stirrer, or shaken by a suitable unit until the internal crosslinking of the hollow particles P is completed.

[0136] The duration of the second process step is preferably less than 120 h, preferably between 0 h and 48 h, more preferably 0.1 h to 24 h, and in a specific embodiment, 0.25 h to 12 h.

[0137] Optionally, a catalyst K for accelerating and completing crosslinking can be added to the three-phase mixture of dispersion V and mixture B from the above first step. These can be added directly to the discontinuous or continuous phase before preparing the three-phase mixture, added during the emulsification process, or added after preparing the three-phase mixture.

[0138] The amount of the optionally added catalyst is within the typical range of catalyst amounts.

[0139] The reaction temperature in the second step is between 0 °C and 100 °C, preferably between 10 °C and 90 °C, and more preferably between 20 °C and 80 °C.

[0140] The reaction can optionally be carried out under an atmosphere of an inert gas such as nitrogen, argon or carbon dioxide. In this case, the oxygen content is less than 15 vol%, preferably less than 10 vol%, and more preferably less than 5 vol%.

[0141] Optionally, a water-soluble organic solvent (such as alcohols like methanol, ethanol or isopropanol, or ketones like acetone or MEK, or ethers like THF, etc.) can be added to the three-phase mixture. These can be added in the first step or before or during the second step.

[0142] Optionally, a dispersion aid, protective colloid and / or surfactant can be added to the three-phase mixture. These can be added in the first step or before or during the second step.

[0143] The three-phase mixture preferably contains less than 5 wt%, more preferably less than 1 wt%, and especially less than 0.1 wt% of dispersants, protective colloids, and surfactants. In a specific embodiment, the three-phase mixture does not contain dispersing aids, protective colloids, and surfactants.

[0144] The three-phase mixture may optionally contain inorganic or organic electrolytes. These can be added after the first step, during the second step, or after the end of the second step.

[0145] In this case, the ionic strength of the three-phase mixture is between 0.01 mmol / l and 1 mol / l, preferably between 0.1 mmol / l and 500 mmol / l, and more preferably between 0.5 mmol / l and 100 mmol / l.

[0146] The surface of the hollow particles P can optionally be modified by treatment with reactive silanes or siloxanes. These can be added after the end of the preparation of the Pickering emulsion in the first step, during the reaction stage, or after the end of the reaction stage in the second step, before separating the hollow particles P, or immediately after separating the particles in the liquid or solid phase. The treatment must be carried out such that the silane or siloxane forms a covalent chemical bond with the particles. Suitable methods and processes are known to those skilled in the art.

[0147] The solid content of the hollow particles P in the three-phase mixture, which consists of the sum of the solids used and the polymerization products of the addition-polymerizable, condensation-polymerizable, or polymerizable materials, is 5 wt% - 70 wt%, preferably 10 wt% - 50 wt%, and more preferably 20 wt% - 40 wt%.

[0148] The three-phase mixture after the second step can optionally be stored for a continuous period of time under stirring. This can be done, for example, by a paddle stirrer or an anchor stirrer.

[0149] In a preferred embodiment, the hollow particles P are preferably separated by precipitation, filtration, or centrifugation, more preferably by filtration or centrifugation, and especially preferably by centrifugation.

[0150] After separation, the hollow particles P are preferably washed with a washing liquid, which is preferably selected from softened water, methanol, ethanol, and mixtures thereof.

[0151] In a preferred embodiment, the hollow particles P are separated from the aqueous phase in powder form. This can be done, for example, by filtration, precipitation, centrifugation, or by drying in an oven or a dryer, or by spray drying, or by applying an appropriate reduced pressure to remove volatiles.

[0152] Spray drying allows for very high fineness to be achieved in the particles P without further treatment. The hollow particles P dried statically tend to form loose aggregates, which can be deaggregated by a suitable grinding process such as a ball mill or an air jet mill.

[0153] An aqueous dispersion of the hardened hollow particles can be used for all purposes for which the aqueous dispersion has hitherto also been used. The aqueous dispersion can be used in cosmetic and pharmaceutical applications, cleaning and cleaning compositions or applications involving changing the interfacial properties of solid and liquid substrates (such as water repellents, adhesion promoters, mold release agents, paper coatings or foam control agents), for the preparation of w / o / w or o / w / o multiple emulsions (such as as a controlled release system) or for the separation of reactive substances.

[0154] The hardened hollow particles P are particularly used in cosmetics and pharmaceuticals and as lightweight fillers in the fields of plastics and ceramics.

[0155] The hollow particles P exhibit very advantageous properties, especially for cosmetic applications. They are not prone to aggregation or blocking and are therefore extremely easy to spread and give the skin a smooth and soft feel.

[0156] Compared with filled particles of the prior art that do not have a hollow core, the hollow particles P have a lower density or can be filled with other functional substances, such as active ingredients, such as fragrances, care substances, vitamins, UV absorbers or active substances, in the core and are capable of transporting and releasing the substances in a controlled manner.

[0157] Compared with hollow particles of the prior art that do not have an amphiphilic shell H formed by the silicone resin composition Z, the silica-coated hollow particles can absorb a larger amount of functional substances, such as fragrances, care substances, vitamins or UV absorbers, or medicinal active substances, on the silica surface and are capable of transporting and releasing the substances in a controlled manner.

[0158] Compared with particles of the prior art that do not have an amphiphilic shell H formed by the silicone resin composition Z, the silica-coated particles exhibit amphiphilic behavior, i.e., they can be easily dispersed in both oily and aqueous liquids.

[0159] Compared with particles of the prior art that do not have an amphiphilic shell H formed by the silicone resin composition Z, the surface of the hollow particles of the present invention is more easily wetted by liquids. Therefore, they can be more easily and quickly dispersed in liquids, such as in cosmetic formulations, and they also absorb liquids on the surface significantly faster and more easily, such as they absorb sebum when applied cosmetically to the skin.

[0160] Measurement method

[0161] - Molecular weight distribution:

[0162] The molecular weight distribution was determined using gel permeation chromatography (GPC) or size exclusion chromatography (SEC) with polystyrene standards and a refractive index detector (RI detector) as the weight average Mw and number average Mn. Unless otherwise stated, THF was used as the eluent and DIN 55672-1 was followed. The polydispersity is the ratio Mw / Mn.

[0163] - Solids content: 10 g of the aqueous dispersion was mixed with an equal amount of ethanol in a porcelain dish and evaporated to constant weight in a drying oven flushed with N2 at 150 °C. According to the following expression, the mass m of the dry residue s gives the solids content: Solids content / % = m s * 100 / 10 g.

[0164] - Median particle size (d50 value) and particle size:

[0165] The d 50 value was determined using a Camsizer X2 from Retsch Technology (measurement principle: dynamic image analysis according to ISO 13322-2, measurement range: 0.8 μm to 8 mm, analysis type: dry measurement of powders and granules, dispersion pressure = 2 bar).

[0166] - Carbon content %C determined by elemental analysis of carbon; the sample was burned in an O2 stream at over 1000 °C and the resulting CO2 was detected and quantified in a Leco 244IR analyzer.

[0167] - Methanol value: To determine the methanol value, a defined mixture of water and methanol was prepared. In a separate experiment, these water-methanol mixtures were covered with the same volume of dry granules and shaken under defined conditions (e.g., gently shaken by hand or with a tumble mixer for about 1 minute). The water-alcohol mixture in which the granules had not completely settled and the water-alcohol mixture with a higher alcohol content in which the granules had just settled were determined. The methanol content in water of the latter gave the methanol value.

[0168] - The kinematic viscosity was measured according to DIN 53019 at 25 °C.

[0169] In the following examples, unless otherwise stated in each case, all amounts and percentages are by weight, all pressures are 0.10 MPa (absolute), and all temperatures are 20 °C. Detailed Description

[0170] Example 1: Preparation of an aqueous silica dispersion

[0171] 1300 g of a partially hydrophobic fumed silica having a residual silanol content of 71 wt% and a carbon content of 0.95 wt% (obtained by reacting a hydrophilic starting silica having a BET surface area of 200 m 2 / g (purchased from Wacker-Chemie GmbH, Munich, under the name N20) with dimethyldichlorosilane) was added portionwise with stirring at 650 rpm to 5200 g of softened water in a dissolver. At the end of the addition of the silica, the mixture was further dispersed for an additional 60 minutes at 650 rpm. A highly viscous dispersion with a solids content of 20% and a pH of 4.2 was obtained.

[0172] Example 2: General procedure for preparing a Pickering emulsion of a condensation-crosslinkable silicone composition X1 Step 1: Weigh out the silica dispersion described in Example 1 in a suitable 1000 ml stainless steel container and stir with

[0173] T50 at 10,000 rpm for 10 min. During this operation, the viscosity of the dispersion decreases. Optionally, softened water is added and mixed homogeneously. The components of the condensation-crosslinkable silicone composition X1 according to Examples 4 to 7 are mixed using a laboratory stirrer and added to the stirred silica dispersion and then homogenized using an Ultra-Turrax at 10,000 rpm under ice cooling for a total of 10 min. During this operation, the temperature of the mixture should not rise above 35 °C. If the temperature exceeds 35 °C, mixing is stopped to cool. Care must also be taken to ensure that the emulsion formed remains flowable. If necessary, small amounts (about 50 ml) of dilution water are added several times as needed. A white, highly viscous material (emulsion (E)) is obtained. Step 2: The highly viscous material from Step 1 is diluted to a silicone oil content of 30% by adding three equal portions of softened water. After each portion of softened water, the mixture is stirred at 6000 rpm for 3 min. A freely mobile white O / W emulsion is formed.

[0174] Example 3: General procedure for preparing hollow particles from Examples 4 to 7 of the present invention and Comparative Examples V1 to V3 of the present invention

[0175] 1.5 g of p-toluenesulfonic acid was added to 250 g of the condensable Pickering emulsion (E) prepared according to the general procedure of Example 2. The reaction mixture was stirred at room temperature for 24 h. A white, freely mobile dispersion was produced. The particles were filtered out and dried in an oven at 60 °C for 24 h. A fine white powder was obtained.

[0176] ​

[0177] Silicone resin S1: An oligomeric condensation product of methyltrimethoxysilane containing methoxy groups, having a methoxy content of about 30 wt% and a composition [MeSiO 3 / 2 26 [MeO 1 / 2 23 (Molecular weight according to SEC (eluent: toluene): Mw = 2300 g / mol; Mn = 600 g / mol; viscosity (kinematic, DIN 51562, 25 °C) 25 mm 2 / s).

[0178] Silicone resin S2: An oligomeric condensation product of methyltriethoxysilane containing ethoxy groups, having an ethoxy content of about 36 wt% and a composition [MeSiO 3 / 2 23 [MeO 1 / 2 27 (Molecular weight according to SEC (eluent: toluene): Mw = 2560 g / mol; Mn = 900 g / mol; viscosity (kinematic, 25 °C) 22 mm 2 / s).

[0179] Silicone resin S3: An oligomeric condensation product of phenyltrimethoxysilane and dimethyldimethoxysilane containing methoxy groups, having an average molecular weight Mw of 1030 g / mol (number-average molecular weight Mn = 730; polydispersity 1.4) and a viscosity of 140 mm 2 / s (25 °C), having 12.3 wt% of Si-bonded methoxy groups and 0.24 wt% of Si-bonded OH groups on the surface, and consisting of an average of 59 mol% of PhSiO 3 / 2 units and 41 mol% of Me2SiO 2 / 2 units, with the methoxy groups being distributed in the structural units.

[0180] The properties and results of these examples are summarized in Table 1. The compositions of the silicone resin component (A) and the silane component (B) are given in parts by weight:

[0181] Table 1

[0182]

[0183] Use Examples

[0184] Example 8: Use in coatings

[0185] Prepare a silicone coating according to the present invention. This is done by using a dissolver to stir 2 parts of the hollow particles of the present invention from Example 4 with 98 parts of ​​​​RT 601A / B (a pourable, addition-crosslinkable two-component silicone rubber curable at room temperature, obtained from Wacker Chemie AG, Munich, Germany) was mixed homogeneously while maintaining the temperature at 20 °C. The resulting material was applied to a glass plate using a 10 μm doctor blade. A transparent and smooth coating was obtained.

[0186] Example 9: Optical evaluation in cosmetic use

[0187] 100 mg of the hollow particles of the invention from Example 5 were evenly distributed over a circular area with a diameter of 4 cm on the unwashed forearm of a human test subject. A dry, uniform, optically homogeneous and slightly whitened skin surface was obtained. This is a sign that the sebum present has been completely adsorbed from the skin surface.

[0188] Example 10: Use as a light filler

[0189] 5 parts of the hollow particles of the invention from Example 5 and 95 parts of LR 3003 / 40A / B (a paste addition-crosslinkable two-component silicone rubber, obtained from Wacker Chemie AG, Munich, Germany) were mixed homogeneously. Then, test samples with a diameter of 4 cm and a height of 0.6 cm were cured in a suitable mold at 165 °C for 30 minutes. The density of the test samples determined according to DIN EN ISO 1183-1A was 1.01 g / ml.

[0190] Comparative Example V4:

[0191] Test samples were prepared in a manner similar to Example 10, but without adding the hollow particles of the invention. The density of the reference test samples measured according to DIN EN ISO 1183-1A was 1.09 g / ml.

Claims

1. A hollow particle P composed of a hollow core K and a shell H, wherein the shell H comprises a silicone resin composition Z containing a condensed crosslinked silicone composition X and a particulate solid F.

2. The hollow particle P according to claim 1, measurable using a Camsizer X2 from Retsch Technology (measurement principle: dynamic image analysis according to ISO 13322-2, measurement range: 0.8 μm to 8 mm, analysis type: dry measurement of powders and particles, dispersion pressure = 2 bar), wherein the median particle size d50 of the hollow particle P is in the range of 0.1 - 100 μm.

3. The hollow particle P according to claim 1 or 2, having a sphericity SPHT3 of at least 0.8 determinable using a Camsizer X2 from Retsch Technology according to ISO 9276-6.

4. The hollow particle P according to any one of the preceding claims, wherein the shell H of the hollow particle P has an average diameter of at least 50 nm, determined in each case as the average of at least 5 individual particles by electron micrographs such as TEM or SEM micrographs.

5. The hollow particle P according to any one of the preceding claims, wherein the average ratio of the average diameter of the hollow core K to the average diameter of the hollow particle P is greater than 0.2, determinable as the average of at least 5 individual particles by electron micrographs such as TEM or SEM micrographs.

6. The hollow particle P according to any one of the preceding claims, wherein the particulate solid F is selected from aluminum(III) oxide, titanium(IV) oxide, and silicon(IV) oxide.

7. The hollow particle P according to any one of the preceding claims, wherein the particulate solid F is a partially water-wettable fumed silica or precipitated silica or a mixture thereof having a BET surface area of 30 to 500 m 2 / g measurable according to German Industrial Standards DIN 66131 and DIN 66132.

8. The hollow particle P according to any one of the preceding claims, wherein the methanol value of the particulate solid F is less than 70, wherein a defined mixture of water and methanol is prepared for the determination of the methanol value, and in a separate experiment, these water - methanol mixtures are covered with the same volume of dry particles and shaken under defined conditions, and the water - alcohol mixture in which the particles have not completely settled and the water - alcohol mixture with a higher alcohol content in which the particles have just settled are determined, and the methanol content in water of the latter gives the methanol value.

9. A method for preparing the hollow particles P according to any one of claims 1 to 8, wherein, In a first step, a dispersion V containing the particulate solid F and water is mixed with a condensation - crosslinkable silicone composition X1 containing an alkoxy - containing silicone resin A and an alkoxy - containing silane B that are liquid at 20 °C to form an aqueous continuous phase and a discontinuous phase containing the condensation - crosslinkable silicone composition X1, and in a second step, the silicone composition X1 is crosslinked in the discontinuous phase to form the silicone composition X, resulting in the formation of the hollow particle P.

10. The method according to claim 9, wherein, Respectively based on the total amount of component (A) and component (B), the condensation - crosslinkable silicone composition X1 comprises: (A) 50 wt% - 90 wt% of at least one silicone resin A composed of units of formula (Ia), (Ib), (VII), and (Id), wherein R 17 represents the same or independently different monovalent, substituted or unsubstituted organic groups with or without functional groups, or -OH or hydrogen groups, the condition is - at least 20 mol% of formula (Ia) or (Ib) or a mixture of both is present in (A), - There is no more than 50 mol% of formula (Ib) in (A), - an alkoxy group as R 17 is present in (A) to an extent of at least 5 wt%, provided that - (A) is liquid at 20 °C, (B) 10 wt% - 50 wt% of at least one silane B of the following general formula R 1 (4-a) Si(OR) a (II), wherein, R is a hydrocarbon group having 1 to 16 carbon atoms, and the carbon chain of the hydrocarbon group may be interrupted by non-adjacent -O- groups, R 1 represents monovalent hydrocarbon groups that are the same as or independently different from each other, and a represents the value 2, 3 or 4, wherein based on the total mass of all silanes B, at least 20 wt% of the silanes B satisfy the characteristic a = 3 or 4.

11. The method according to one or more of claims 9 to 10, wherein, The alkoxy group R of the silicone resin A 17 is selected from methoxy, ethoxy, isopropoxy, n-butoxy, and tert-butoxy.

12. The method according to one or more of claims 9 to 11, wherein the group R of the silane B is selected from methyl, ethyl, isopropyl and tert-butyl.

13. The method according to one or more of claims 9 to 12, wherein the particulate solid F is selected from aluminum(III) oxide, titanium(IV) oxide and silicon(IV) oxide.

14. The method according to one or more of claims 9 to 13, wherein Measured by photon correlation spectroscopy as the median hydrodynamic equivalent diameter at 173° (backscattering) with a Nanosizer ZS from Malvern, the median particle size of the particulate solid F is less than 1000 nm.

15. The method according to one or more of claims 9 to 14, wherein the particulate solid F is a partially water-wettable fumed silica or precipitated silica having a BET surface area measurable according to German Industrial Standards DIN 66131 and DIN 66132 of 30 to 500 m 2 / g or a mixture thereof.

16. The method according to one or more of claims 9 to 15, wherein the particulate solid F has a methanol number less than 70, wherein a defined mixture of water and methanol is prepared for the determination of the methanol number, and in a separate experiment, these water-methanol mixtures are covered with the same volume of dry particles and shaken under defined conditions, and the water-alcohol mixture in which the particles have not completely settled and the water-alcohol mixture with a higher alcohol content in which the particles have just settled are determined, and the methanol content of the latter in water gives the methanol number.

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