Hollow silicone resin particles and method for producing the same

Abstract

The present invention provides hollow particles P comprising a hollow core K and a shell H comprising a silicone resin composition Z containing a condensation-crosslinked silicone composition X and a particulate solid F. The present invention further provides a method for producing a dispersion of a particulate solid (F) and water, comprising: mixing a dispersion (V) containing a particulate solid (F) and water with a condensation-crosslinkable silicone composition (X1) that is liquid at 20°C and contains an alkoxy-containing silicone resin (A) and an alkoxy-containing silane (B), to form a continuous water-containing phase and a discontinuous phase containing the condensation-crosslinkable silicone composition (X1); In a second step, the silicone composition X1 is crosslinked in the discontinuous phase to form the silicone composition X, and the hollow particles P are formed.

Description

[Technical Field]

[0001] The present invention relates to hollow particles comprising a hollow core and a shell of condensation-crosslinked silicone resin and particulate solids, and a process for producing the same. [Background technology]

[0002] Hollow body particles are widely used, for example, in cosmetic or medical applications, or in household products or detergents, as lightweight fillers, for example to reduce the density of polymeric or ceramic components, or to absorb, transport and release active ingredients, such as fragrances, care substances or actives.

[0003] The production of hollow particles is very laborious and typically involves the use of a hard or soft template on which a shell is built, followed by the subsequent, again very laborious, removal of the template, which is highly disadvantageous both ecologically and economically.

[0004] WO2007113095 and WO2021121562 describe polysiloxane-based core-shell particles that have very advantageous properties as additives in cosmetic applications and in many technical applications, and which have advantages, in particular, due to their surface effects. However, the packed structure means that these particles cannot absorb functional substances inside.

[0005] US2009004418 describes hollow silicone resin particles having a particle size of less than 1 mm, the shell of which is SiO 4 / 2 Units, RSiO 3 / 2 Units and R2SiO 2 / 2 The production is very laborious and ecologically and economically disadvantageous, since template particles, such as organic polymer particles, and / or toxic organic solvents, such as toluene or xylene, are first suspended in water and then coated with a reactive silane to form a silicone resin shell, and the core is removed together with the organic solvent in a final step.

[0006] US9802175B2 is RSiO 3 / 2 This paper describes a method for producing hollow silicone resin particles composed of units with a particle size of less than 200 nm. The production process is very laborious and ecologically and economically disadvantageous. This is because organic template particles, such as polystyrene particles, polyacrylate particles, or polyvinyl acetate particles, are first produced, which are then coated with an alkoxy-functional silane in a second step to form a silicone resin shell, and the core is removed in a third step using an organic solvent and heat.

[0007] US5945043 describes a method for producing hollow polysiloxane particles having a shell formed from a thermoplastic polysiloxane. The thermoplastic polysiloxane is dissolved in a solvent and the mixture is dispersed in water. The dispersion is sprayed in a spray dryer, 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. As a result, such particles are sensitive to temperature and solvents. The use of toxic solvents makes production extremely unfavorable ecologically and economically.

[0008] WO14098107 describes a method of using silica particles as templates for producing hollow polysiloxane particles. The silica particles are dispersed. A polysiloxane shell is formed on the surface of the template particles by hydrolysis and condensation of alkoxy-functional silanes or siloxanes. The template particles are then removed and destroyed. This process is ecologically and economically very disadvantageous, since the silica particles used as templates and removed and destroyed in the final step of the process are very laborious to produce.

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

[0010] All of the above processes have the disadvantage of using solid or liquid templating compounds to build core-shell structures that must be coated and then laboriously removed and disposed of. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2007 / 113095 [Patent Document 2] International Publication No. 2021 / 121562 [Patent Document 3] US Patent Application Publication No. 2009 / 004418 [Patent Document 4] U.S. Patent No. 9,802,175 [Patent Document 5] U.S. Patent No. 5,945,043 [Patent Document 6] International Publication No. 14098107 [Non-patent literature]

[0012] [Non-Patent Document 1] Xue Wang et al., Journal of Colloid and Interface Science 542 (2019) 144-150 Summary of the Invention

[0013] The present invention provides hollow particles P comprising a hollow core K and a shell H comprising a silicone resin composition Z containing a condensation-crosslinked silicone composition X and a particulate solid F.

[0014] The median particle size d50 of the hollow particles P is in the range of 0.1 to 100 μm, preferably in the range of 0.4 to 60 μm, and more preferably in the range of 0.8 to 40 μm.

[0015] The hollow particles P are preferably substantially spherical, with a sphericity SPHT3 of preferably at least 0.8, more preferably at least 0.82, measurable according to ISO 9276-6 using a Camsizer X2 from Retsch Technology.

[0016] The hollow particles P are amphiphilic, have a defined uniform structure and can be dispersed in aqueous and oily media.

[0017] Hollow particles P have the additional advantage that their low density as additives in formulations means that they migrate to the surface, thereby exhibiting improved surface effects. They are also suitable for use as lightweight fillers, for example in ceramics.

[0018] Hollow particles P can hold other substances; filled particles cannot do this.

[0019] The present invention also provides a simple and inexpensive process for producing hollow body particles that does not involve the use of templates.

[0020] Furthermore, in a first step, a dispersion V containing a particulate solid F and water is mixed with a condensation-crosslinkable silicone composition X1 that is liquid at 20°C and contains an alkoxy group-containing silicone resin A and an alkoxy group-containing silane B to form a continuous water-containing phase and a discontinuous phase containing the condensation-crosslinkable silicone composition X1; In a second step, the silicone composition X1 is crosslinked in the discontinuous phase to form the silicone composition X, which provides a process for producing hollow particles P.

[0021] The advantageous process of the present invention differs from prior art processes in particular in that it does not involve the use of a liquid or solid template. The template used according to the prior art forms a core on the surface of which a shell is built. The template is then removed again, forming hollow particles.

[0022] According to the process of the present invention, shell H is formed by condensation crosslinking of emulsified condensation-crosslinkable silicone composition X1 at the boundary phase with the continuous water-containing phase of emulsion E. Thus, emulsified droplets of condensation-crosslinkable silicone composition X1 first form temporary cores on the surface of which condensation-crosslinkable silicone composition X1 then combines with particulate solid F to form shell H during crosslinking to silicone composition X, forming hollow particles P. Using the process of the present invention, there is no need for any separate, expensive, or labor-intensive process to produce templates that must be laboriously separated, reused, or disposed of as waste. This makes the process of the present invention highly advantageous economically and ecologically. DETAILED DESCRIPTION OF THE INVENTION

[0023] The condensation-crosslinkable silicone composition X1 preferably contains, based on the total amount of components (A) and (B), (A) 50 to 90% by weight of at least one silicone resin A composed of units of formulae (Ia), (Ib), (VII), and (Id); [R 17 SiO 3 / 2 ][SiO 4 / 2 ][R 17 3SiO 1 / 2 ][R 17 2SiO 2 / 2 ] (Ia) (Ib) (VII) (Id) [In the formula, R 17 represent the same or independently different monovalent substituted or unsubstituted organic groups with or without functional groups, or -OH or hydrogen groups; however, - at least 20 mol % of formula (Ia) or (Ib) or a combination of the two is present in (A); - 50 mol % or less of formula (Ib) is present in (A); - The alkoxy group is R in (A). 17 to the extent of at least 5% by weight as however, - (A) is a liquid at 20°C. (B) 10 to 50% by weight of at least one silane B of the following general formula: R 1 (4-a) Si(OR) a (II), [In the formula, R is a hydrocarbon group having 1 to 16 carbon atoms, the carbon chain of which may be interrupted by non-adjacent -O- groups; R 1 represent the same or independently different monovalent hydrocarbon groups, a represents the value 2, 3 or 4, At least 20 wt. % of silane B, based on the total mass of all silanes B, satisfies characteristic a=3 or 4. Includes.

[0024] <Component (A)> The condensation-crosslinkable silicone composition X1 used in the present invention preferably contains 55 to 85% by weight, and more preferably 60 to 80% by weight, of one or more silicone resins A, based on the total amount of components (A) and (B) in either case.

[0025] Silicone resin A has a molecular weight Mw of at least 500, preferably at least 600, more preferably at least 700, and not more than 5000, preferably not more than 4000, more preferably not more than 3000, and a polydispersity of not more than 20, preferably not more than 18, more preferably not more than 16, and especially not more than 15.

[0026] Silicone resin A contains at least 20 mol%, preferably at least 30 mol%, more preferably at least 40 mol%, and in particular at least 50 mol% of repeating units of formula (Ia) or (Ib) or a combination of formula (Ia) and (Ib), with repeating units of formula (Ib) being present in an amount of not more than 50 mol%, preferably not more than 40 mol%, and more preferably not more than 20 mol%. In a particularly preferred embodiment, silicone resin A is free of units (Ib).

[0027] The repeat unit of formula (Id) may 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 %.

[0028] Silicone resin A is R 17 The alkoxy group content is at least 5% by weight, preferably at least 8% by weight, and particularly preferably at least 10% by weight.

[0029] R 17 Examples of suitable alkoxy groups are hydrocarbonoxy groups having 1 to 16 carbon atoms, which may be substituted. Particularly suitable and therefore preferred are methoxy, ethoxy, isopropoxy, n-butoxy and tert-butoxy groups, and p-nitrophenoxy groups, and particularly preferred are methoxy and ethoxy groups.

[0030] All other R 17 may be, independently of each other, substituted or unsubstituted monovalent hydrocarbon groups. Preferably, pure hydrocarbon groups having 1 to 16 carbon atoms are preferred. Suitable hydrocarbon groups R 17Selected examples of R are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl groups such as n-hexyl, heptyl groups such as n-heptyl, octyl groups such as n-octyl and isooctyl, nonyl groups such as n-nonyl, decyl groups such as n-decyl, dodecyl groups such as n-dodecyl, and octadecyl groups such as n-octadecyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl, aryl groups such as phenyl, naphthyl, anthryl, and phenanthryl, alkaryl groups such as tolyl, xylyl, and ethylphenyl, and aralkyl groups such as benzyl and β-phenylethyl. 17 Preferred hydrocarbon groups for are methyl, n-propyl, isopropyl, phenyl, n-octyl or isooctyl, with methyl, n-propyl, phenyl and isooctyl being more preferred, and methyl and phenyl being particularly preferred.

[0031] <Ingredient (B)> The condensation-crosslinkable silicone composition X1 preferably contains 15 to 45% by weight, preferably 20 to 40% by weight, of one or more silanes B, in each case based on the total amount of components (A) and (B).

[0032] Preferably, at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight and particularly preferably at least 95% by weight of the silanes B, based on the total weight of all silanes B, satisfy the characteristic a=3 or 4; in a preferred embodiment, at least 30% by weight, preferably at least 40% by weight and more preferably at least 50% by weight of at least one silane B (a=4) is present, in each case based on the total weight of all silanes B.

[0033] Examples of suitable radicals R are hydrocarbon radicals having 1 to 16 carbon atoms, which may be substituted. Particularly suitable and therefore preferred are the methyl, ethyl, isopropyl and tert-butyl radicals and the p-nitrophenyl radical, particularly preferred are the methyl and ethyl radicals.

[0034] base R 1 may be, independently of each other, substituted or unsubstituted monovalent hydrocarbon groups. Preferably, pure hydrocarbon groups having 1 to 16 carbon atoms are preferred. Suitable hydrocarbon groups R 1 Selected examples of R are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl groups such as n-hexyl, heptyl groups such as n-heptyl, octyl groups such as n-octyl and isooctyl, nonyl groups such as n-nonyl, decyl groups such as n-decyl, dodecyl groups such as n-dodecyl, and octadecyl groups such as n-octadecyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and methylcyclohexyl, aryl groups such as phenyl, naphthyl, anthryl, and phenanthryl, alkaryl groups such as tolyl, xylyl, and ethylphenyl, and aralkyl groups such as benzyl and β-phenylethyl. 1 Preferred hydrocarbon groups for are methyl, n-propyl, isopropyl, phenyl, n-octyl or isooctyl, with methyl, n-propyl, phenyl and isooctyl being more preferred, and methyl and phenyl being particularly preferred.

[0035] The condensation-crosslinkable silicone composition X1 may contain a further solid or liquid component I, provided that the condensation crosslinking of the silicone composition X1 and the formation of the shell H are not hindered.

[0036] Examples of further components I include catalysts, active and inert fillers, inhibitors, heat stabilizers, solvents, plasticizers, color pigments, soluble dyes, sensitizers, photoinitiators, adhesion promoters, conductive additives, cosmetic substances, fragrances, pharmaceutical or cosmetic active substances, fluorescent dyes, fungicides, fragrances, rheological additives, corrosion inhibitors, antioxidants, light stabilizers, heat stabilizers, flame retardants, agents for influencing electrical properties, and agents for improving thermal conductivity.

[0037] These components can remain within the core of the hollow particles P, thereby encapsulating, storing, transporting, or selectively releasing them.

[0038] <Particulate solid F> The particulate solid F used according to the invention is preferably in the form of particles that are solid at 20° C. and at the pressure of the ambient atmosphere, ie 1013 hPa.

[0039] 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 the pressure of the ambient atmosphere, i.e. 1013 hPa, at pH 7.33, at a 0.11 molar electrolyte background and at a temperature of 37°C.

[0040] The particulate solid F preferably has a molar mass of more than 10 000 g / mol, more preferably of between 50 000 and 50 000 000 g / mol, in particular of between 100 000 and 10 000 000 g / mol, in each case preferably determined by static light scattering.

[0041] The solid fine particles F preferably have a particle size of 30 to 500 m 2 / g, more preferably 100 to 300m 2 / g The BET specific surface area is preferably determined according to known methods (German Industrial Standards DIN 66131 and DIN 66132).

[0042] The particulate solid F preferably has a Mohs hardness of greater than 1, more preferably greater than 4.

[0043] The particulate solid F used is preferably a metal oxide having a covalent component in the metal-oxygen bond, for example a solid oxide of a main group element or an element of the transition group, for example one of main group 3, such as boron oxide, aluminum oxide, gallium oxide or indium oxide, or one of main group 4, such as silicon dioxide, germanium dioxide, tin oxide or tin dioxide, or lead oxide or lead dioxide, or an oxide of an element of the transition group, such as titanium dioxide, zirconium dioxide, hafnium dioxide, cerium oxide or iron oxide.

[0044] The metal oxides used according to the invention are preferably oxides of aluminium (III), titanium (IV) or silicon (IV), such as aluminium oxide, titanium dioxide or silicon dioxide produced by wet chemical processes, e.g. precipitated silica or silica gel, or by processes at high temperatures, e.g. fumed aluminium oxide, titanium dioxide or silica.

[0045] The median particle size of the particulate solid F or of the particle agglomerates, if present, is preferably less than the median diameter d of the droplets of the emulsion formed according to the process of the present invention in the absence of fine particulate particles. 50 is less than.

[0046] The particulate solid F has a median particle size of 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 by photon correlation spectroscopy at 173° (backscattering) using a Nanosizer ZS from Malvern.

[0047] The particulate solid F preferably has a methanol number of less than 70, preferably less than 50, more preferably less than 40, and particularly preferably less than 30.

[0048] To determine the methanol number, defined mixtures of water and methanol are prepared, and the surface tension of these mixtures is then measured using known methods. In separate experiments, these water-methanol mixtures are overlaid with a defined amount of particles and shaken under defined conditions (e.g., gentle manual shaking or shaking with a tumble mixer for about 1 minute). Water-alcohol mixtures in which the particles have not yet sunk and water-alcohol mixtures with higher alcohol contents in which the particles just sunk are determined. The surface tension of the latter alcohol-water mixtures is calculated using the critical surface energy γ as a measure of the particle's surface energy γ. crit The methanol content in the water gives the methanol number.

[0049] The carbon content of the particulate solid F is greater than 0 wt. %, preferably 0.1 to 4 wt. %, more preferably 0.25 to 3.5 wt. %, and most preferably 0.5 to 3 wt. %, as determined by elemental analysis of the dry particulate solid.

[0050] In a preferred embodiment, the particulate solid F is silica S.

[0051] Silica S is preferably 30 to 500 m 2 / g, more preferably 100 to 300m 2 Partially water-wettable fumed silica and precipitated silica or mixtures thereof having a BET specific surface area of ​​1 / g, fumed silica being particularly preferred. Preferably, the BET specific surface area is measured according to known methods (German Industrial Standards DIN 66131 and DIN 66132).

[0052] Preferably, the silica S is surface-treated with a suitable hydrophobizing agent, resulting in hydrophobicity. The hydrophobization must be carried out so that the silica S is still partially water-wettable. According to the present invention, this means that the methanol number 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% and at most 1.5% by weight, preferably between 0.4% and 1.4% by weight, and more preferably between 0.6% and 1.3% by weight. The hydrophobic group is, for example, a Si-bonded methyl or vinyl group. Methods for hydrophobizing silica are known to those skilled in the art.

[0053] Silica S is preferably a silanized fumed silica having a methanol number of less than 70, preferably less than 50, more preferably less than 40, and particularly preferably less than 30.

[0054] Very particular preference is given to the partially water-wettable silicas described in EP 1 433 749 A1 and DE 10 349 082 A1.

[0055] <Hollow Core K> The isolated and dried hollow particles P maintain a hollow core K, wherein 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 measured as an average value of at least 5 individual particles by electron microscope imaging, e.g. TEM or SEM micrographs; the hollow core K can consist of a single cavity or of several separate cavities).

[0056] The hollow core K is suitable for holding a further component I.

[0057] <Shell H> Shell H comprises silicone resin composition Z formed from condensation-crosslinked silicone composition X and particulate solid F. Shell H is formed by condensation-crosslinking emulsified condensation-crosslinkable silicone composition X1 at the boundary phase with the water-containing continuous phase of the emulsion. The boundary phase is stabilized by particulate solid F, which is physically and / or chemically incorporated into the growing shell H during condensation crosslinking.

[0058] The shell H preferably has an average diameter of at least 50 nm, preferably at least 70 nm (in each case measured as the average value of at least 5 individual particles by electron microscope imaging, for example TEM or SEM micrographs).

[0059] <Catalyst K> In the case of a less reactive condensation-crosslinkable silicone composition X1, a catalyst K is required to bring about the hydrolysis and condensation of silicone resin A and silane B, if necessary. Such catalysts are known to those skilled in the art. The catalyst can be either an acid or a base, or a metal catalyst, such as a Group IV transition metal catalyst, or a tin catalyst, such as those commonly used to promote hydrolysis, condensation reactions, or transesterification reactions. In addition to known mineral acids and metal salts, acidic or basic silanes or siloxanes can also be considered as acids or bases.

[0060] Preferred basic catalysts are NaOH, KOH, ammonia and NEt3. When the basic catalyst K is used, the pH of the reaction mixture is preferably in the range of pH8 to pH12.

[0061] Preferred acid catalysts K are p-toluenesulfonic acid, aqueous or gaseous HCl, and sulfuric acid. When an acid catalyst is used, the pH of the reaction mixture is preferably in the range of pH1 to pH5.

[0062] <Hollow particle P> Prior art hollow silicone resin particles have a silicone resin shell obtained by coating with a liquid or solid template and subsequent removal, which is hydrophobic and unsuitable for use in hydrophilic formulations and products, particularly as an additive in aqueous formulations.

[0063] The hollow particles P of the present invention have 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 particles P of the present invention preferably have a methanol number of less than 80, preferably less than 60, more preferably less than 50, and particularly preferably less than 40. This allows the hollow particles P of the present invention to be easily processed in both hydrophilic and hydrophobic formulations and products.

[0064] The hollow particles P of the present invention are preferably 4 m 2 / g, preferably above 10m 2 / g, preferably above 20m 2 / g.

[0065] The hollow particles P of the present invention preferably have a density of 0.28 g / cm 3 less than 0.25 g / cm 3 It has a bulk density of less than 10 ...

[0066] <Hollow particle P manufacturing process> The continuous phase preferably contains at least 80% by weight, especially at least 90% by weight, of water.

[0067] Preferably, a three-phase mixture is formed, during which an emulsion of the sparingly water-soluble and water-immiscible condensation-crosslinkable silicone composition X1 is produced. This is stabilized in the aqueous phase by partially hydrophobized silica (Pickering emulsion). After emulsification, the condensation-crosslinkable silicone composition X1 is crosslinked by a process suitable for producing particles P. The condensation-crosslinkable silicone composition X1 may need to be hydrolyzed, for example, if it contains alkoxy- or acetoxy-substituted silanes or siloxanes. If the silicone composition X1 is sufficiently reactive, the water already present may cause hydrolysis and subsequent condensation. The process must be carried out in such a way that significant crosslinking does not occur during emulsification, otherwise a finely divided emulsion would not be formed. In the case of a less reactive condensation-crosslinkable silicone composition X1, a catalyst K is required to bring about the hydrolysis and condensation of the siloxanes and silanes as needed.

[0068] The second step of the process must be carried out so that the condensation-crosslinkable silicone composition X1 forming the discontinuous phase reacts and condenses at the interface with the continuous water-containing phase to form shells H of hollow particles P, which are physically and / or chemically bonded to the particulate solids F that stabilize the interphase.

[0069] Those skilled in the art will recognize that before being dried for the first time, the newly formed hollow particles P in the dispersion will be filled with liquid cleavage products of the condensation crosslinks and / or a continuous water-containing phase.

[0070] The size of the hollow particles P can be determined, for example, by emulsification techniques, and thus by variables such as the input shear energy, the volume fraction of the silicone composition X1, the amount of particulate solid F, the pH of the continuous aqueous phase and its ionic strength, viscosity, dosing sequence, dosing rate, etc., or by the reaction regime, i.e., for example, the reaction temperature, reaction time, and concentrations of the raw materials used. The choice and amount of any hydrolysis / condensation catalyst used also influences the particle size.

[0071] If further optional solid or liquid components I are present, these are preferably mixed homogeneously with the condensation-crosslinkable silicone composition X1 in a first step to form mixture B, and then emulsified in a further step with dispersion V and subsequently crosslinked to form 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.

[0072] Pickering emulsion E of mixture B is preferably essentially free of conventional organic surface-active substances that are non-particulate liquids and solids at room temperature and ambient atmospheric pressure, such as nonionic, cationic, and anionic emulsifiers ("organic emulsifiers").

[0073] By organic emulsifiers is meant here not particles and colloids, but molecules and polymers according to the definition of molecules, polymers, colloids and particles given in "Dispersionen und Emulsionen" (Dispersions and emulsions), G. Lagaly, O. Schulz, R. Zindel, Steinkopff, Darmstadt 1997, ISBN 3-7985-1087-3, pp. 1-4.

[0074] Generally, these organic emulsifiers have a size of less than 1 nm, a molar mass of less than 10,000 g / mol, a carbon content of more than 50% by weight (measurable by elemental analysis), and a Mohs hardness of less than 1.

[0075] At the same time, the organic emulsifiers essentially absent from the emulsions of the invention generally have a solubility in water in homogeneous or micellar form of more than 1% by weight at 20° C. and the pressure of the ambient atmosphere, i.e., 900-1100 hPa.

[0076] 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, and in particular less than 0.0001 times the critical micelle concentration of these organic emulsifiers in the aqueous phase, which corresponds to a concentration of these organic emulsifiers of less than 10% by weight, preferably less than 2% by weight, more preferably less than 1% by weight, and in particular 0% by weight, based on the total weight of the dispersion of the invention.

[0077] Any emulsion manufacturing method known to those skilled in the art can be used to prepare the particle-stabilized Pickering emulsion E in the first step. However, it has been found that an emulsion that is particularly suitable for producing hollow particles P can be obtained by the following process.

[0078] Process 1: The concentrated dispersion V is charged first, the volume charged first being such that it contains only a part of the total amount of solids F required and the volume of water. - The total volume of mixture B is slowly metered in under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system. The remainder of the desired volume of water is then slowly metered in, optionally under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0079] Process 2: Firstly, dispersion V is charged, the volume initially charged being such that it contains the total amount of solids F and water required. - The total volume of mixture B is slowly metered in under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver, a rotor-stator system or a capillary emulsifier.

[0080] Step 3: - The total volume of Mixture B is filled first. - The highly concentrated dispersion V is slowly metered in under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, the metered-in volume being such that it contains the total amount of solids F required and only a portion of the volume of water. The remainder of the desired volume of water is then slowly metered in, optionally under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0081] Step 4: - The total volume of Mixture B is filled first. - Dispersion V is slowly metered in under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system, the metered-in volume being such that it contains the total amount of solids F and water required.

[0082] Process 5: The total volume of mixture B and dispersion V is initially charged, the volume initially charged being such as to contain the total amount of solid F and water required. Both homogenizations are carried out together, for example, by means of a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0083] Step 6: The total volume of mixture B and concentrated dispersion V is initially charged, the volume initially charged being such that it contains the total amount of solid F required and part of the volume of water. Both homogenizations are carried out together, for example, by means of a high-speed stirrer, a high-speed dissolver or a rotor-stator system. The remainder of the desired volume of water is then slowly metered in, optionally under constant homogenization, for example using a high-speed stirrer, a high-speed dissolver or a rotor-stator system.

[0084] Processes 1, 2, 5 and 6 are preferred, with processes 2 and 5 being particularly preferred.

[0085] Homogenization is preferably carried out for at least 30 seconds, preferably at least 1 minute, in at least one process step.

[0086] The dispersion V of particulate solid F in water which forms a homogeneous phase in the emulsion of the invention can in principle be prepared according to known methods for preparing particle dispersions, for example by incorporation using agitators which generate high shear, such as high-speed stirrers, high-speed dissolvers, rotor-stator systems, ultrasonic dispersers or ball / bead mills.

[0087] Here, the concentration of the particulate solid F in the dispersion V is between 1% and 80% by weight, preferably between 10% and 60% by weight, more preferably between 10% and 40% by weight, and most preferably between 12% and 30% by weight.

[0088] In an optional process step, Pickering Emulsion E is optionally diluted with water under constant homogenization, for example using a high speed stirrer, a high speed dissolver or a rotor-stator system.

[0089] The described process can be carried out either continuously or discontinuously.

[0090] The temperature in the first step of emulsification is between 0°C and 80°C, preferably between 10°C and 50°C.

[0091] The emulsification process can be carried out at normal pressure, i.e. 900-1100 hPa, at elevated pressure or under reduced pressure. The process is preferably carried out at normal pressure.

[0092] Here, the concentration of particulate solid F in the three-phase mixture of dispersion V and mixture B from the first step is between 1% and 80% by weight, preferably between 2% and 50% by weight, more preferably between 3% and 30% by weight, and most preferably between 4% and 20% by weight.

[0093] Here, the concentration of condensation-crosslinkable silicone composition X1 in the three-phase mixture of dispersion V and mixture B from the first step is between 1% and 80% by weight, preferably between 20% and 76% by weight, more preferably between 40% and 72% by weight, and most preferably between 50% and 70% by weight.

[0094] Here, the concentration of water in the three-phase mixture of dispersion V and mixture B from the first step is between 5% and 80% by weight, preferably between 10% and 70% by weight, more preferably between 15% and 60% by weight, and most preferably between 20% and 40% by weight.

[0095] Starting from the above three-phase mixture, hollow particles P can be obtained in a second step by the following process:

[0096] The three-phase mixture is preferably diluted by adding water to a water mass fraction of 50% to 90% by weight, preferably 60% to 80% by weight.

[0097] In a second step, the three-phase mixture is stirred, preferably under low shear, for example using a slowly operating dissolver, rotor-stator or paddle stirrer, or shaken using a suitable unit, until the internal crosslinking of the hollow particles P is complete.

[0098] The duration of the second process step is preferably less than 120 hours, preferably between 0 hours and 48 hours, more preferably between 0.1 hours and 24 hours, and in a specific implementation between 0.25 hours and 12 hours.

[0099] Catalysts K, which promote crosslinking to complete crosslinking, can optionally be added to the three-phase mixture of dispersion V and mixture B from the first step as described above. They can be added directly to the discontinuous or continuous phase before the formation of the three-phase mixture, during emulsification, or added later to the prepared three-phase mixture.

[0100] The amount of catalyst used, if any, is within the range typical for catalyst amounts.

[0101] 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.

[0102] The reaction can optionally be carried out under an inert gas atmosphere such as nitrogen, argon, carbon dioxide, etc. In this case, the oxygen content is less than 15% by volume, preferably less than 10% by volume, more preferably less than 5% by volume.

[0103] A water-soluble organic solvent, such as an alcohol such as methanol, ethanol, or isopropanol, or a ketone such as acetone or MEK, or an ether such as THF, may optionally be added to the triphasic mixture in the first step or before or during the second step.

[0104] Dispersing aids, protective colloids and / or surfactants may optionally be added to the three-phase mixture, which may be added in the first step or before or during the second step.

[0105] The three-phase mixture preferably contains less than 5% by weight, more preferably less than 1% by weight, and particularly less than 0.1% by weight of dispersants, protective colloids, and surfactants. In a specific implementation, the three-phase mixture does not contain dispersants, protective colloids, or surfactants.

[0106] The three-phase mixture optionally includes an inorganic or organic electrolyte, which can be added either after the first step, during the second step, or after the second step is completed.

[0107] 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, more preferably between 0.5 mmol / l and 100 mmol / l.

[0108] The surface of the hollow particles P may optionally be modified by treatment with reactive silanes or siloxanes. These may be added immediately after the preparation of the Pickering emulsion in the first step, during the reaction stage, after the reaction stage in the second step, before isolation of the hollow particles P, or after isolation of the particles in the liquid or solid phase. The treatment must be carried out so as to result in a covalent chemical bond between the silane or siloxane and the particles. Suitable methods and processes are known to those skilled in the art.

[0109] The solid content of the hollow particles P in the three-phase mixture consisting of the total of the solids used and the polymerization product of the polyaddition-reactive, polycondensation-reactive or polymerizable material is between 5% and 70% by weight, preferably between 10% and 50% by weight, and more preferably between 20% and 40% by weight.

[0110] The three-phase mixture after the second step can optionally be stored under continuous stirring, which can be done, for example, with a paddle or anchor stirrer.

[0111] In a preferred embodiment, the hollow particles P are isolated, preferably by sedimentation, filtration or centrifugation, more preferably by filtration or centrifugation, particularly preferably by centrifugation.

[0112] After isolation, the hollow particles P are preferably washed with a washing liquid, preferably selected from demineralized water, methanol, ethanol, and mixtures thereof.

[0113] In a preferred embodiment, the hollow particles P are isolated from the aqueous phase in powder form, for example by filtration, sedimentation, centrifugation, or by removing volatile substances by drying in an oven or oven, or by spray drying, or by applying a suitable reduced pressure.

[0114] Spray drying allows a very high degree of fineness to be achieved in the particles P without further processing. Static dried hollow particles P tend to form loose agglomerates, which can be deagglomerated by a suitable comminution process, such as a ball mill or an air jet mill.

[0115] The aqueous dispersions of the hardened hollow particles can be used for all the purposes for which aqueous dispersions have been used to date: for the preparation of w / o / w or o / w / o multiple emulsions, in cosmetic and pharmaceutical applications, in cleaning and washing compositions, or in applications involving modifying the interfacial properties of solid and liquid substrates, such as hydrophobizing agents, adhesion promoters, release agents, paper coatings or foam control agents, e.g., as controlled release systems or for the separation of reactive substances.

[0116] The hardened hollow particles P are used in particular in cosmetics and pharmaceuticals, as well as as lightweight fillers in the plastics and ceramics sector.

[0117] The hollow particles P exhibit very advantageous behavior, especially for cosmetic applications: they are less prone to agglomeration or blockage and therefore spread easily and provide a velvety feel on the skin.

[0118] Compared to non-inventive filled particles that do not have a hollow core, the hollow particles P have a lower density or can be filled with other functional substances, for example active ingredients such as fragrances, care substances, vitamins, UV absorbers or active substances, in the core and can transport and release said substances in a controlled manner.

[0119] Compared to non-inventive hollow particles that do not have an amphiphilic shell H formed from 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 pharmaceutical active substances, onto the silica surface and can transport and release the substances in a controlled manner.

[0120] Compared to non-invention particles that do not have the amphiphilic shell H formed from the silicone resin composition Z, the silica-coated particles exhibit amphiphilic behavior, i.e., they are readily dispersible in both oil-based and aqueous liquids.

[0121] Compared with non-invention particles that do not have the amphiphilic shell H formed from the silicone resin composition Z, the surfaces of the hollow particles of the present invention are more easily wettable by liquids. As a result, they can be dispersed much more easily and rapidly in liquids, for example, in cosmetic formulations, and they also absorb liquids on their surfaces significantly more quickly and readily, for example, absorbing sebum when cosmetically applied to the skin.

[0122] <Measurement method> - Molecular weight distribution: The molecular weight distribution is measured as weight average Mw and number average Mn using the method of gel permeation chromatography (GPC or size exclusion chromatography (SEC)) using polystyrene standards and a refractive index detector (RI detector). Unless otherwise specified, THF is used as the eluent and DIN 55672-1 is followed. Polydispersity is the ratio Mw / Mn.

[0123] - Solid content: 10 g of the aqueous dispersion are mixed in a porcelain dish with the same amount of ethanol and evaporated to constant weight in a N2 flash drying oven at 150 ° C. The mass of the dry residue m s is the formula: solid content / %=m s *Give solid content according to 100 / 10g.

[0124] - Median particle size (d50 value) and particle size: d 50 The values ​​were measured using a Camsizer X2 manufactured by 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).

[0125] - Carbon content %C determined by elemental analysis of carbon: Combustion of the sample at over 1000°C in O2 flow, detection and quantification of the resulting CO2 in a Leco 244 IR analyzer.

[0126] - Methanol number: For the determination of the methanol number, defined mixtures of water and methanol are prepared. In separate experiments, these water-methanol mixtures are overlaid with an equal volume of dry particles and shaken under defined conditions (e.g., by gentle shaking by hand or in a tumble mixer for about 1 minute). Water-alcohol mixtures in which the particles have not yet sunk and water-alcohol mixtures with a higher alcohol content in which the particles just sunk are determined. The methanol content of the latter in water gives the methanol number.

[0127] - The kinematic viscosity is measured at 25°C according to DIN 53019.

[0128] In the following examples, all amounts and percentages are by weight, all pressures are 0.10 MPa (absolute) and all temperatures are 20° C. unless otherwise stated in any case. [Example]

[0129] [Example 1] Preparation of aqueous silica dispersion 200m 2 1300 g of partially hydrophobic fumed silica with a residual silanol content of 71% and a carbon content of 0.95% by weight, obtained by reacting hydrophilic starting silica (available under the designation HDK®N20 from Wacker-Chemie GmbH, Munich) with dimethyldichlorosilane according to EP 1433749 A1, having a BET specific surface area of ​​1 / g, is gradually stirred into 5200 g of demineralized water in a dissolver at 650 rpm. At the end of the silica addition, the mixture is further dispersed at 650 rpm for another 60 minutes. A highly viscous dispersion with a solids content of 20% and a pH of 4.2 is obtained.

[0130] Example 2 General Procedure for Preparing a Pickering Emulsion of Condensation-Crosslinkable Silicone Composition X1 Using Ultra-Turrax® Step 1: The silica dispersion described in Example 1 is weighed into a suitable 1000 ml stainless steel container and stirred for 10 minutes at 10,000 rpm using an Ultra-Turrax® T50. The viscosity of the dispersion decreases during this operation. Demineralized water is optionally added and mixed until homogeneous. 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, which is then homogenized using an Ultra-Turrax at 10,000 rpm for a total of 10 minutes while cooling with ice. The temperature of the mixture must not rise above 35°C during this operation. If the temperature exceeds 35°C, mixing is stopped to allow for cooling. Care must be taken to ensure that the resulting emulsion remains fluid. If necessary, small amounts (approximately 50 ml) of dilution water are added, multiple times as necessary. A white, highly viscous mass (emulsion (E)) is obtained.

[0131] Step 2: The highly viscous mass from step 1 is diluted to a silicone oil content of 30% by adding three equal portions of demineralized water. After each portion of demineralized water, the mixture is stirred for 3 minutes at 6000 rpm. A freely mobile white O / W emulsion results.

[0132] Example 3: General procedure for producing hollow particles of inventive examples 4-7 and non-inventive comparative examples V1-V3 1.5 g of p-toluenesulfonic acid is added to 250 g of polycondensable Pickering emulsion (E) prepared according to the general procedure of Example 2. The reaction mixture is stirred at room temperature for 24 hours. A white, freely mobile dispersion is obtained. The particles are filtered off and dried in a drying oven at 60°C for 24 hours. A fine white powder is obtained.

[0133] Silicone resin S1: methoxy group content of about 30 wt% and composition [MeSiO 3 / 2 ] 26 [MeO 1 / 2 ] 23Methoxy group-containing oligomeric condensation product of methyltrimethoxysilane (molecular weight by SEC (eluent: toluene): Mw = 2300 g / mol, Mn = 600 g / mol, viscosity (kinematic viscosity, DIN 51562, 25 °C) 25 mm 2 / sec)

[0134] Silicone resin S2: Ethoxy group content of about 36 wt% and composition [MeSiO 3 / 2 ] 23 [MeO 1 / 2 ] 27 Ethoxy group-containing oligomer condensate of methyltriethoxysilane (molecular weight by SEC (eluent: toluene): Mw = 2560 g / mol, Mn = 900 g / mol, viscosity (kinematic viscosity, 25 °C) 22 mm 2 / sec).

[0135] Silicone resin S3: average molecular weight Mw of 1030 g / mol (number average Mn=730, polydispersity 1.4) and 140 mm 2 / sec (25°C), and had 12.3 wt% Si-bonded methoxy groups and 0.24 wt% Si-bonded OH groups on the surface, with an average of 59 mol% PhSiO 3 / 2 units and 41 mol% MeSiO 2 / 2 units, the methoxy groups being distributed among the structural units described.

[0136] Properties and results of the examples are summarized in Table 1. Constituents of the silicone resin component (A) and the silane component (B) are given in parts by weight.

[0137] [Table 1]

[0138] Usage example [Example 8] Use in coating A silicone coating according to the invention was produced by homogeneously mixing 2 parts of the hollow particles according to Example 4 with 98 parts of Elastosil® RT 601 A / B (a room-temperature vulcanizable, pourable, addition-crosslinked, two-component silicone rubber, available from Wacker Chemie, Munich, Germany), stirring with a dissolver at 6000 rpm for 10 minutes and maintaining the temperature at 20°C. The resulting mass was applied to a glass plate using a 10 μm doctor blade. A clear, smooth coating was obtained.

[0139] [Example 9] Optical evaluation in cosmetic applications 100mg of the hollow particles of the present invention from Example 5 is evenly distributed on a circular area of ​​4cm diameter on the unwashed forearm of a human subject. A dry, uniform, optically homogeneous, slightly whitish skin surface is obtained. This indicates that the existing sebum is completely absorbed from the skin surface.

[0140] [Example 10] Use as a lightweight filler Five parts of the hollow particles of the invention from Example 5 and 95 parts of Elastosil® LR 3003 / 40 A / B (a paste-like, addition-crosslinked, two-component silicone rubber available from Wacker Chemie, Munich, Germany) were mixed to homogeneity using a laboratory stirrer. Test specimens 4 cm in diameter and 0.6 cm in height were then cured in suitable molds at 165°C for 30 minutes. The density of the test specimens was 1.01 g / ml, measured according to DIN EN ISO 1183-1A.

[0141] [Comparative Example V4] The test specimen was produced in a manner similar to that of Example 10, but without the addition of hollow particles according to the invention. The density of the reference test specimen is 1.09 g / ml, measured according to DIN EN ISO 1183-1A.

Claims

1. A hollow particle P is composed of a hollow core K and a shell H containing a silicone resin composition Z containing a condensation-crosslinked silicone composition X and a particulate solid F.

2. 2. Hollow particles P according to claim 1, having a median particle size d50 in the range of 0.1 to 100 μm (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 granules, dispersion pressure=2 bar)).

3. 3. Hollow particles P according to claim 1 or 2, having a sphericity SPHT3 of at least 0.8 (measurable according to ISO 9276-6 using a Camsizer X2 from Retsch Technology).

4. 4. Hollow particles P according to claim 1, wherein the shell H has an average diameter of at least 50 nm (measured in each case as the average value of at least 5 individual particles by electron microscopy images, e.g. TEM or SEM micrographs).

5. 5. Hollow particles P according to claim 1, wherein the average ratio of the average diameter of the hollow cores K to the average diameter of the hollow particles P is greater than 0.2 (which can be measured by electron microscope images, e.g. TEM or SEM micrographs, as the average value of at least 5 individual particles).

6. 6. Hollow particles P according to claim 1, wherein the particulate solid F is selected from oxides of aluminum (III), titanium (IV) and silicon (IV).

7. The particulate solid F has a thickness of 30 to 500 m ２ 7. The hollow particles P according to claim 1, which are partially water-wettable fumed or precipitated silicas or mixtures thereof, having a BET specific surface area of ​​1 / g (determinable in accordance with German Industrial Standards DIN 66131 and DIN 66132).

8. Hollow particles P according to any one of claims 1 to 7, wherein the particulate solid F has a methanol value of less than 70 (provided that defined mixtures of water and methanol are prepared for the determination of the methanol value, and in separate experiments these water-methanol mixtures are overlaid with equal volumes of dry particles and shaken under defined conditions to determine water-alcohol mixtures in which the particles have not yet sunk and water-alcohol mixtures with higher alcohol contents in which the particles just sunk, the latter methanol content in the water giving the methanol value).

9. A process for producing hollow particles P according to any one of claims 1 to 8, comprising: In a first step, a dispersion V containing a particulate solid F and water is mixed with a condensation-crosslinkable silicone composition X1 containing an alkoxy group-containing silicone resin A and an alkoxy group-containing silane B, which are liquid at 20°C, to form a continuous water-containing phase and a discontinuous phase containing the condensation-crosslinkable silicone composition X1; In a second step, silicone composition X1 is crosslinked in the discontinuous phase to form silicone composition X, and hollow particles P are formed.

10. Condensation-crosslinkable silicone composition X1 contains, based on the total amount of components (A) and (B), (A) 50 to 90% by weight of at least one silicone resin A composed of units of formulae (Ia), (Ib), (VII) and (Id); [R １７ SiO ３／２ ][SiO ４／２ ][R １７ ３ SiO １／２ ][R １７ ２ SiO ２／２ ] (Ia) (Ib) (VII) (Id) [In the formula, R １７ represent the same or independently different monovalent substituted or unsubstituted organic groups with or without functional groups, or —OH or hydrogen groups; however, at least 20 mol % of formula (Ia) or (Ib) or a combination of the two is present in (A); - not more than 50 mol % of formula (Ib) is present in (A), - The alkoxy group is R １７ to the extent of at least 5% by weight as however, - (A) is a liquid at 20°C. (B) 10 to 50% by weight of at least one silane B of the following general formula: R １ （４－ａ） Si(OR) ａ (II), [In the formula, R is a hydrocarbon group having 1 to 16 carbon atoms, the carbon chain of which may be interrupted by non-adjacent —O— groups; R １ represent the same or independently different monovalent hydrocarbon groups, a represents the value 2, 3 or 4; At least 20 wt. % of silane B, based on the total weight of all silanes B, satisfies characteristic a=3 or 4.

10. The process of claim 9, comprising:

11. The group R is an alkoxy group of the silicone resin A. １７ The process of any of claims 9 to 10, wherein is selected from a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, and a tert-butoxy group.

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

13. A process according to any one of claims 9 to 12, wherein the particulate solid F is selected from oxides of aluminium (III), titanium (IV) and silicon (IV).

14. 14. The process according to any one of claims 9 to 13, wherein the particulate solid F has a median particle size of less than 1000 nm (measured as median hydrodynamic equivalent diameter by photon correlation spectroscopy at 173° (backscattered) using a Malvern Nanosizer ZS).

15. The particulate solid F has a thickness of 30 to 500 m ２ 15. The process according to any one of claims 9 to 14, wherein the silica is a partially water-wettable fumed or precipitated silica or a mixture thereof having a BET specific surface area of ​​1 / 2 g (determinable according to German Industrial Standards DIN 66131 and DIN 66132).

16. 16. The process of any one of claims 9 to 15, wherein the particulate solid F has a methanol number of less than 70 (provided that defined mixtures of water and methanol are prepared for the determination of the methanol number, and in separate experiments these water-methanol mixtures are overlayered with equal volumes of dry particles and shaken under defined conditions to determine water-alcohol mixtures in which the particles have not yet sunk and water-alcohol mixtures with a higher alcohol content in which the particles just sunk, the latter methanol content in the water giving the methanol number).

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