EA003200B1 - Dispersion of fine porous oxide inorganic oxide particles and processes for preparing same - Google Patents

Abstract

1. A dispersion comprising porous inorganic oxide particles, wherein the particles have a) a median particle size in the range of 0.05 to about 3 microns; and b) porosity such that when an aqueous dispersion of the particles is dried at least about 0.5 cm<3>/g of pore volume as measured by BJH nitrogen porosimetry is from pores having a pore size of 60 nm (600 angstrom ) or smaller. 2. A dispersion of Claim 1 wherein the inorganic oxide particles comprise silica particles. 3. A dispersion of Claim 2 wherein the silica particles comprise precipitated silica or silica gel. 4. A dispersion of Claim 1 wherein the inorganic particles have a median particle size in the range of 0.05 to about 1 micron. 5. A dispersion of Claim 3 wherein the silica particles have a porosity after drying in which at least about 0.7 cm<3>/g of the pore volume is from pores having a pore size of 60 nm (600 angstrom ) or less. 6. A dispersion of Claim 5 wherein the silica particles comprise silica gel. 7. A dispersion of Claim 1 wherein the porous particles have a viscosity derived pore volume in the range of 0.5 to about 1.5 cm<3>/g. 8. A dispersion of Claim 1 wherein the porous particles have a viscosity derived pore volume of about 1.0 to about 1.5 c/g. 9. A dispersion of Claim 8 wherein the median particle size is about 0.5 micron or smaller, the solids content is about 20 to about 25 weight % and the dispersion comprises at least 90% glycol. 10. A dispersion of Claim 9 wherein the inorganic oxide is silica gel. 11. A dispersion of Claim 7 wherein the porous particles comprise precipitated silica or silica gel. 12. A dispersion of Claim 8 wherein the porous particles comprise precipitated silica or silica gel. 13. A dispersion of Claim 1 comprising 1-30% by weight inorganic oxide particles. 14. A dispersion of Claim 11 wherein the particles comprise silica gel and the particles have a porosity after drying in which at least about 0.7 cm<3>/g of the pore volume is from pores having a pore size less than of 60 nm (600 angstrom ). 15. A dispersion of Claim 11 wherein the porous particles have a viscosity derived pore volume in the range of 0.5 to about 1.5 cm<3>/g. 16. A dispersion of Claim 1 wherein the porous particles have a viscosity derived pore volume of about 1.0 to about 1.5 cm<3>/g. 17. A dispersion of Claim 1 prepared by a process comprising i) forming a slurry of inorganic oxide particles; ii) milling the slurry of particles; iii) creating a supernatant phase and a settled phase from the resulting milled dispersion wherein the supernatant phase comprises porous inorganic oxide particles which have a median particle size in the range of 0.1 to about one micron; and iv) removing the supernatant phase as a dispersion of particles. 18. A dispersion of Claim 17 wherein the inorganic oxide particles in i) comprises silica gel or precipitated silica. 19. A method of preparing a dispersion of particles comprising (a) forming a slurry of inorganic oxide particles; (b) milling the slurry of particles; (c) creating a supernatant phase and a settled phase from the resulting milled slurry; and (d) removing the supernatant phase or redispersing the settled phase as a final product wherein when said product has a porosity after being dried in which at least 0.5 cm<3>/g of pore volume is from pores having a pore size of 60 nm (600 angstrom ) or smaller. 20. A method of Claim 19 wherein the inorganic oxide particles in (a) comprise silica gel or precipitated silica dioxide. 21. A method of Claim 19 wherein the inorganic oxide particles in (a) comprise silica gel and the particles have a porosity in which at least about 0.7 cm<3>/g of the pore volume is from pores having a size of 30 nm (300 angstrom ). or smaller. 22. A method of Claim 19 wherein the final product of (d) has a viscosity derived pore volume in the range of 0.5 to about 1.5 cm<3>/g. 23. A method of Claim 19 wherein the slurry in (a) is an aqueous medium and final product of (d) is distilled with glycol to produce a dispersion comprising at least 90% glycol. 24. A method of Claim 23 wherein the glycol is ethylene glycol.

Description

This invention relates to dispersions of finely divided porous particles of an inorganic oxide having an average particle size of three microns or less. The invention also relates to methods for producing such dispersions.

Fine particles of inorganic oxide are well known. For example, “colloidal silicon dioxide” is well known and typically has an average particle size (diameter) of 0.1 microns (μm) (100 nanometers) or less. See, for example, Canadian Patents Nos. 609,186 and 609,190; and US patent No. 3,012,973. Colloidal silicon dioxide in a dispersed non-aggregated state is not porous, and any surface area available for such particles refers to the outer surface of the primary non-aggregated particles, i.e. such particles do not have a surface area created by the internal porosity of the particles.

Dispersions of relatively small particles of silica gel, known as “silica microgels,” are described in US Pat. No. 4,954,220. Particle dispersions of silica-microgel are obtained by the interaction of alkali metal silicates and acids under conditions that initiate coalescence and gelation of the primary particles. The conditions, however, are also chosen in such a way that the gel-formed particles grow only to a small, i.e., submicron, size. Dispersions in which microgel particles are obtained are not processed until the state where the coalesced particles form a hard macrogel. Macrogels are usually obtained from dispersions of sols having less than 10%, and typically less than 1 wt.% Solids.

European Patent No. 468,070 describes the preparation of a dispersion of gel particles having a particle size in the range of 1 to 50 μm, preferably in the range of 10 to 30 μm, by wet milling larger gel particles. It is reported that particles obtained by wet milling have surface areas of 50 to 700 m ² / g and porosities of 0.3 to 2 cm ³ / g. The wet particles are then spray dried to obtain larger spherical particles in the range of 1 to 200 μm, preferably 30-100 μm. This patent describes the use of spray dried particles as carriers for polyolefin catalysts, and that large spherical particles in the range of 30 to 100 μm are preferred.

US Pat. No. 5,030,286 describes dispersions with a high solids content, for example, from 40 to about 55 wt.% Precipitated silica. Precipitated silica illustrating the dispersions of this patent have average particle sizes of more than one micron. Dispersions are obtained by grinding the precipitated silica. The '286 patent states that grinding the precipitated silica gives less viscous dispersions and allows the use of dispersions at higher solids concentrations. The '286 patent discloses that such high concentration dispersions can be used as paper coatings.

European Patent No. 803,374 describes the use of agglomerated silica particles having an average particle size of 10-300 μm for ink-absorbing paper layers for ink-jet printing. It is described that such particles are obtained by grinding larger particles, for example, having a size of 9 μm. PCT application UO 97/48743 describes wet grinding of inorganic oxide gels to obtain an average particle size of 3 to 6 microns. This patent application discloses that any particles below 1 μm are present in a maximum amount of 40% by weight. The particles described in this application are then spray dried to provide a catalyst support.

US Pat. No. 4,983,369 describes a dispersion of dense spherical particles having an average particle size of from 0.1 to 10 microns. The '369 patent also describes that spherical particles can be either non-porous or porous. The '369 patent also describes that the porosity of porous particles decreases upon contact with water. The porous particles obtained by the method described in the '369 patent have a particle size of more than one micron.

US Pat. No. 5,277,888 describes the use of an organic dispersion medium to obtain stable dispersions of particles having an average particle size in the range of 0.05 to 10 μm. A patent is a dispersion of dense non-porous silica particles.

US Pat. No. 2,731,326 describes populations of dense, low porosity silica spheroids, wherein populations are described as supercolloidal, i.e. more than 100 nanometers (0.1 microns). These aggregated particles have a primary particle size of more than 15 nanometers and the patent describes that they are of such a size that upon receipt in the dispersion they appear as a residue.

US Pat. No. 2,741,600 describes the preparation of silica dispersions having an average particle size below 1 μm, for example, from 0.1 to 0.5 μm. The dispersions described in the '600 patent are prepared by grinding autoclaved silica gels. It is described that the material obtained after the autoclaving step has two phases, i.e. the aquazole phase and the “mud” phase. The mud phase is crushed to obtain a dispersion having, as described, a milky white appearance. Two phases can be used separately or in combination. The porosity of the ground mud phase or the aquazole phase obtained during autoclaving is not reported, is not described in this patent.

In 11eg'8 “Sjetyu o £ 8Shsa”, p. 328-330, (1979) describes porous silicasols that are prepared by various techniques. The porous silicasols described in scientific work 11g vary in size from 0.1 to 0.3 microns. In general, these submicron sized particles are obtained by aggregation of smaller particles. The surface area of the obtained particles is reported to be from 22 m ² / g to over 700 m ² / g, depending on the technique used to obtain the particles. For example, in patent No. 3,607,774, to which reference is made to 11eg, silica sols of 0.5 μm or more are described, for example, up to 1.5 μm. The '774 patent describes the preparation of sols having surface areas of about 103 m ² / g or less. In another patent, referred to in 11E, US patent No. 3,591,518, porous silicasols are described having particle sizes of about 0.2 μm and internal surface areas in the range of 17 to 900 m ² / g. Pore sizes, porosity and stability of the pore volume of the particles of the two above patents are not described.

\ Νϋ 97/22670 describes precipitated silicates and suspensions obtained by the degradation of aluminum silicate and silica, grinding in a dry state and the subsequent formation of suspensions by adding water. Suspensions containing degraded materials have a lower viscosity than suspensions of unmilled silica with an equal solids content. These suspensions also have reduced ΌΡΒ values. The average particle size of these particles is much larger than one micron.

In US patent. No. 5,318,833, ethylene glycol suspensions are described containing precipitated silica coagulates having an average particle diameter of 0.5 μm. Precipitated silica has a porosity of 0.09 cm ³ / g and a surface area of 70 m ² / g. A suspension of ethylene glycol is combined with phthalate to form a polyester film. Precipitated silica is used to impart frictional properties to the polyester film so that the film can be easily processed further, for example, to obtain a magnetic recording medium. These films must have frictional properties so that the films do not adhere to equipment that transports the film. However, when using additives such as particulate silicon dioxide, they should be handled in such a way that there is no harmful effect on other properties of the polyester. It is also understood that the particles described in this patent do not provide sufficient surface area for binding to ethylene glycol. As a result, the chances are high that the particles and the ethylene glycol polymer can separate, thereby leading to the appearance of defects in the resulting film.

As indicated above, dispersions of particles can also be used to obtain porous structures, for example, absorbent printing ink coatings for paper. It is desirable that the porosity of such coatings not only provides a means of increasing the absorption speed of the printing ink for certain paper coatings, but also provides a relatively high capacity of the printing ink for storing high-resolution images. Porous gels with a large particle size, for example, more than three microns, have been proposed for this purpose. Submicron colloids have also been used, but the porosity of the colloid particles themselves, for example, the internal porosity of the particles, does not exist. Therefore, any porosity created by colloid particles is the interparticle porosity obtained after drying the colloid dispersion. The interparticle porosity is influenced by many factors that must be carefully controlled if you rely on it as the only source of porosity.

Most paper related applications also require small ones, i.e. submicron, particle sizes. For example, it is known that paper coatings with relatively high glossiness can be obtained from dispersions of submicron particles of colloidal silicon dioxide. In this case, it is desirable that the glossy coating is capable of absorbing printing ink, in addition, it would be advantageous for the dispersion particles to be porous. Therefore, there is an ongoing need to develop dispersions of finely divided porous particles of inorganic oxide.

It would also be desirable to use finely ground, i.e. particles having an average particle size of less than one micron to modify the frictional properties of polyester films. However, to date, such particles have a relatively low porosity. Without claiming to be a specific theory, it is believed that materials with high porosity improve the binding of the organic polymer to inorganic particles, thereby reducing the possibility of formation of defects on the film resulting from the separation of the polymer from inorganic particles.

SUMMARY OF THE INVENTION

The dispersion according to this invention contains particles of a porous inorganic oxide, which have an average particle size in the range from 0.05 to about 3 microns. Particles of these dispersions have a porous structure, such that at least about 0.5 cm ³ / g of pore volume are pores having a pore size of 60 nm (600 A) or less. Pore porosity of less than 60 nm (600 A) is indicated in this description as internal porosity, i.e., the porosity present in the particles themselves. Indeed, the internal porosity is reflected by dispersions having a “porosity derived from viscosity” as defined below and is at least 0.5 cm ³ / g. The internal porosity of the particles in accordance with this invention is relatively stable and reliable. It is believed that the particles of this invention contain a coherent, relatively rigid three-dimensional grid of adjacent particles, sometimes called "elementary" or "primary" particles. The bond between the primary particles according to this invention is quite strong and therefore gives hard aggregated particles. Therefore, the particles are not completely compacted under the influence of capillary pressure created by the evaporation of water from the dispersion during drying, and the porosity inside the particles is preserved.

Embodiments of the present invention, including silica gel particles, also have porosity, which is retained during grinding dispersion. For example, the particle size distribution of embodiments of the invention containing dispersions of silica gel is substantially the same as the distribution of particles in the gel from which the dispersion is obtained. This is because the porosity of the starting material is homogeneous and, in general, below 60 nm (600 A). There are also variants of gel particles in which at least about 0.7 cm ³ / g and 0.9 cm ³ / g of pore volume are pores having sizes less than 60 nm (600 A). In these embodiments, at least 80% of the pore volume is constituted by pores having a pore size of less than 30 nm (300 A). Pores of this size are not affected by grinding, and the homogeneity of such porosity ensures that the porosity is practically the same from particle to particle even after grinding to submicron size.

Dispersions are obtained by forming a suspension of inorganic oxide particles and grinding the suspension under conditions and by a procedure sufficient to obtain a dispersion containing particles having an average particle size of about three microns or less. In embodiments of the invention in which it is desirable to obtain stable ίη Kyi dispersions without the addition of dispersing agents, or if it is desired to obtain dispersions having an average particle size of less than one micron, the process includes:

(a) obtaining a suspension of inorganic oxide particles, (b) grinding the suspension, (c) obtaining a supernatant phase and a precipitated phase from the obtained ground suspension, and (b) removing the supernatant phase or redispersing the precipitated phase as a final product, where the product has porosity after drying, in which at least 0.5 cm ³ / g of pore volume are pores having sizes less than 60 nm (600 A) or less.

Process step (c) is preferably carried out using a centrifuge, which is particularly preferred if it is desired to obtain particles having an average particle size of about one micron or less. In general, particles larger than one micron are precipitated from the dispersion by centrifugation, and the settled phase can be removed in order to leave a dispersion of particles having an average particle size of one micron or less.

The porosity and particle size of the inorganic oxide obtained in this embodiment of the invention makes the particles particularly suitable for use as glossy ink-absorbing coatings on paper or film. For example, a relatively high glossiness is obtained for a coating containing inorganic oxide of submicron size, compared with the glossiness of coatings containing larger particles (average particle size greater than 1 μm).

The submicron particles of the inorganic oxide in accordance with this invention also have an improved reliable ink absorption capacity compared to traditional non-porous colloidal inorganic oxides with the same nominal particle size. As indicated above, porosity is provided by relatively rigid particles and is less susceptible to reduction during drying. Thus, one can be sure of the presence of porosity after drying of the coating containing an example of the present invention.

Brief Description of the Drawings

Τι

In FIG. 1 is a graph of η with respect to the mass fraction of solids for some embodiments of the present invention and colloidal silica of the prior art, where η is the viscosity of the illustrated dispersions and η _ο is the viscosity of water. The mass fraction of solids includes undissolved particles and does not include dissolved salts.

In FIG. 2A is a graph of n with respect to the mass fraction of solid particles, where η is the viscosity of an aqueous silica gel embodiment of the present invention and η _ο is the viscosity of water, (O) represents viscosity and load data before grinding, () represents viscosity and load data after grinding and (Δ) presents data on viscosities and loading of dispersions after grinding and centrifugation at 600 d.

In FIG. 2B is a graph of the same data for precipitated silica, commercially available as Ζοοίΐιίχ ™ 177, where (O) and () represent data of the same type as in FIG. 2A. (Δ) presents data for a dispersion that is ground and centrifuged at 2000d.

In FIG. 2C shows the same data as in FIG. 2A, but obtained for precipitated silica, commercially available as EC310 from Eedi88a. (O), () and (Δ) represent data of the same type as in FIG. 2A.

In FIG. 3 is a graph showing the correlation of measurements of pore volume obtained from viscosity (OPC) and pore volume after drying for particles used in the present invention.

In FIG. 4 is a graph ί with respect to the mass fraction of solids for an embodiment of the present invention containing a non-aqueous medium, for example ethylene glycol.

Detailed Description of Preferred Embodiments (1) Inorganic oxide starting particles.

Inorganic oxides suitable for preparing dispersions include precipitated inorganic oxides and inorganic oxide gels. These inorganic oxides are referred to herein as “starting inorganic oxides”, “starting particles” or “starting dispersions”. Amorphous precipitated silica and silica gels are particularly suitable starting inorganic oxides. Particles can also be obtained from mixed inorganic oxides, including 8ίΟ ₂ · Α1 ₂ Ο ₃ , Μ§Ο · 8ίΟ ₂ · Α1 ₂ Ο ₃ . Mixed inorganic oxides may be prepared by conventional mixing or co-gelation techniques.

In embodiments comprising gels, the dispersions are prepared from porous inorganic oxide gels, including, but not limited to, gels comprising 8ίΟ _2, Α1 ₂ Ο ₃ A1RO _4, MgO, ΤίΟ ₂ and ΖτΟ _2. Gels can be hydrogels, aerogels or xerogels. Hydrogel is also known as aqua gel, which is obtained in water, and as a result, its pores are filled with water. Xerogel is a hydrogel with removed water. An airgel is a type of xerogel from which water has been removed in such a way as to minimize gel compaction or alteration due to water removal. Silica gels, commercially available under the name 8u1o1b® gels of various grades, for example, grades 74, 221, 234, 244, \ U300. and silica gels called 6epe818 ™ are suitable starting inorganic oxides.

Gels are well known in the art. See, for example, Pet'z, “Not Sesh181tu οί 8Shea,” p. 462 (1979). Particles of a gel, for example, silica gel, are different from particles of colloidal silicon dioxide or precipitated silica. For example, colloidal silicon dioxide is obtained in the form of a suspension of dense non-porous particles of silicon dioxide. Colloidal silica particles are typically less than 200 nm (0.2 μm). As noted above, these particles do not have internal porosity. Conventional deposited particles, on the other hand, have some internal porosity. In some cases, the internal porosity in these particles, however, is greatly reduced at the capillary pressure created by the outgoing menisci of water during evaporation of the water during drying. The conditions for producing colloidal silicon dioxide and precipitated silica are well known.

Gels, on the other hand, are obtained under conditions that provide coalescence of primary particles (usually having an average particle size of 1 to 10 nm, measured by transmission electron microscopy, i.e. TEM) to obtain a relatively stiff three-dimensional network. Gel coalescence is demonstrated on a macroscale when a dispersion of an inorganic oxide, for example, silicon dioxide, solidifies to a “gel” or a “gel” mass having structural integrity.

Methods for producing inorganic oxide gels are well known in the art. For example, silica gel is prepared by mixing an aqueous solution of an alkali metal silicate (e.g. sodium silicate) with a strong acid such as nitric or sulfuric acid, mixing is carried out under suitable mixing conditions to obtain a transparent silica sol that solidifies into a hydrogel, such as macrogel, over a period of less than about half an hour. The resulting gel is then washed. The concentration of inorganic oxide, e.g., 8ίΟ ₂ obtained in the hydrogel is usually in the range of from about 10 to about 50, preferably from about 20 to about 35, and most preferably from about 30 to about 35 wt.%., Wherein the pH of the the gel is from about 1 to about 9, preferably from about 1 to about 4. A wide range of mixing temperatures can be used, usually this range covers from about 20 to about 50 ° C.

Freshly prepared hydrogels are washed by simple immersion in a continuously moving stream of water, which leaches undesirable salts, leaving about 99.5 wt.% Of a purer inorganic oxide.

The pH, temperature and duration of washing with water depends on the physical properties of silicon dioxide, such as surface area (PP) and pore volume (OD). Silica gel, washed at a temperature of 65-90 ° C at pH 8-9 for 15-36 hours, usually has a PP of 250,400 and forms aerogels with an OD of 1.4-1.7 cm ³ / g. Silica gel, washed at pH 3-5 at a temperature of 50-65 ° C for 15-25 hours, has 1P1 700-850 and forms aerogels with an OD of 0.6-1.3. These measurements were obtained using Ν ₂ porosity analysis.

Methods for producing inorganic oxide gels, such as alumina, and mixed inorganic oxide gels, such as silica / alumina cogels, are also well known in the art. Methods for preparing such gels are described in US Pat. No. 4,226,743, the contents of which are incorporated herein by reference.

In general, alumina gels are prepared by mixing alkali metal aluminates and aluminum sulfate. The gogels are obtained by co-gelation of two metal oxides in such a way that the gels form together. For example, silica / alumina cogels can be prepared by gelation of an alkali metal silicate with an acid or acid salt, followed by addition of an alkali metal aluminate, mixing of the mixture and subsequent addition of aluminum sulfate. Then the gel is washed according to conventional methods.

Another embodiment of the invention is obtained from dispersions of certain precipitated inorganic oxides. For example, grinding certain precipitated silica gives dispersions having a porosity described below. The viscosity of certain precipitation, as a function of mass fraction, is shown in FIG. one.

Reinforced precipitated silica, such as those described in US Pat. No. 4,157,920, can also be used to prepare the dispersions of this invention. The contents of this patent are incorporated herein by reference. For example, enhanced precipitated silica can be obtained by first acidifying an inorganic alkaline silicate to form a starting precipitate. The resulting precipitate is then enhanced or post-treated with additional silicate and acid. The precipitate obtained after the second addition of silicate and acid contains from 10 to 70 wt.% Of the initially obtained precipitate. It is believed that the enhanced structure of this precipitate is more rigid than conventional precipitation due to the second precipitation. It is believed that even after grinding, centrifugation and subsequent drying, the reinforced silicate substantially retains the rigidity and porosity of its mesh.

This differs from the other precipitated silicas described, such as those described in US Pat. No. 5,030,286.

If an inorganic oxide is selected for the initial dispersion, a liquid phase of the selected inorganic oxide is obtained. In general, the initial dispersion should be in such a state that it can be ground in a wet state. The medium for the liquid phase can be aqueous or non-aqueous, for example, organic.

The liquid phase may be residual water in inorganic oxide gels that are dried but not yet dried, to which additional water is added to resuspend the gel. In another embodiment, the dried inorganic oxides, for example, xerogels, are dispersed in a liquid medium. In yet another embodiment, the inorganic oxide can be dispersed in a liquid compound, which is subsequently used as a reagent to obtain a product that requires certain properties of the inorganic oxide particles. A specific example of this embodiment is the dispersion of an inorganic oxide in ethylene glycol, which reacts with phthalate to form a polyester film.

In most embodiments, the initial dispersion has an average particle size of approximately in the range of 10 to 40 microns. However, it is only necessary that the size of the starting particles is sufficient so that the grinding can give a dispersion with the desired average particle size of about or below 3 microns. In embodiments obtained from a dried inorganic oxide gel, the dried gel may first be broken into pieces of the gel and pre-ground to obtain a dispersion of particles in the range of 10 to 40 microns.

(2) Grinding.

Then the initial dispersion is crushed. Grinding is carried out in "wet", i.e. liquid medium. General grinding conditions may vary depending on the starting material, holding time, rotational speeds of the blades and the average size of the grinding medium. Suitable conditions and holding times are described in the examples. These conditions can be changed to obtain the desired size within the range from 0.05 to about 3 microns. Techniques for selecting and modifying these conditions to obtain the desired dispersions are known to those skilled in the art.

The grinding equipment used to grind the inorganic oxide feed particles must be of a type that allows the materials to be finely pulverized and dispersed to particles having sizes of about three microns or less, especially below one micron, for example, by mechanical action. Such mills are commercially available, with a hammer mill and a sand mill being particularly suitable for this purpose. Hammer mills perform the necessary mechanical action using high-speed metal blades, and sand mills operate using a rapidly mixing medium, such as zirconium or sand grains. Impact mills can also be used. Both impact mills and hammer mills reduce particle size by breaking inorganic oxide with metal blades. A dispersion containing particles of three microns or less is then separated as the final product.

The ground dispersion can also be further processed. For example, further processing is desirable if there is a need to obtain relatively stable dispersions without the addition of dispersing agents, or if a significant fraction of the particles has a size of more than three microns after grinding. Further processing may also be necessary in order to make sure that almost the entire particle distribution falls below 2 microns, and especially if dispersions with a particle size of 1 micron or less, for example, for a glossy paper surface, are desired. In this case, the crushed dispersion is treated to separate submicron particles from particles larger than one micron. Separation can be carried out by centrifuging the crushed particles of inorganic oxide into a supernatant phase, which contains particles of the final product, and a precipitated phase, which contains large particles. The supernatant phase is then separated from the settled phase, for example, by decantation. The supernatant phase is a dispersion in accordance with this invention. Conventional centrifuges can be used for this phase separation. Commercially available centrifuges suitable for use in this invention are identified in the Examples below. In some cases, it may be preferable to centrifuge the supernatant phase two, three or more times to further remove large particles remaining after the initial centrifugation. It is also believed that large particles of crushed dispersion can separate themselves after a certain amount of time under the influence of gravity, and the supernatant phase can be separated by decantation.

Depending on the target particle size of the product, the precipitated phase can also be considered particles in accordance with this invention. For example, if the target particle size of the composition is in the range of 0.05 to 3 μm, the precipitated phase can be separated and re-dispersed. In some cases, it is necessary to grind the initial dispersion more than once in order to make sure that the settled phase has a suitable particle size in the range from 0.05 to 3 μm.

The dispersion of particles can also be modified after grinding in order to have confidence in the stability of the dispersion. Such a modification can be achieved by adjusting the pH, for example, by adding alkaline material, or by adding conventional dispersing agents.

(3) Dispersion of inorganic oxide.

As noted above, the average particle size, i.e., particle diameter, dispersion may be in the range from 0.05 to about 3 microns. The size is primarily determined by the area of use of the dispersion and can be in the intervals, for example, from 0.06 to 2.9, from 0.07 to 2.8, etc. For example, if the dispersion is intended to be used as an ink-absorbing coating with a high degree of glossiness, the average particle size will generally be less than one micron, and for some common applications, the dispersion will have a particle size below 0.5 microns, and preferably in the range from 0.1 to 0.3 microns. The average particle size is measured using conventional equipment and the method of light scattering. The sizes shown in the examples were determined using a light scattering analyzer of particle size L 900 from Hopa 1n81nite18, 1ps.

The solids content of the dispersion varies and depends on the solids content of the original particle dispersion. The solids content is usually from 1 to 30 wt.% And all values are within this range, although in certain embodiments, the amount may be lower or higher. The solids content in the range from 10 to 20 wt.% Is suitable for many applications.

In certain embodiments of the invention, the dispersion is the final product obtained by grinding or grinding and, for example, centrifugation. In other embodiments, the milled or milled and centrifuged dispersions can be further modified, for example, with pH modifiers or dispersants. Even further, the medium of these dispersions can be replaced by distilling another medium into the dispersion. More specifically, a non-aqueous medium, such as ethylene glycol, can be distilled into a ground aqueous dispersion of inorganic oxide particles so that the final dispersion will have less than 1 wt.% Water. Distillation can be carried out by conventional means. As noted above, suspensions in ethylene glycol can be used by polyester manufacturers to react with phthalate to produce a 13 polyester film. In this embodiment, the aqueous medium is substantially replaced, i.e., at least about 90%, preferably at least about 97%, and most preferably at least 99% is replaced with glycol.

In general, the viscosity of the dispersion must be such that the dispersion is pumpable. The viscosity of the dispersion is largely dependent on the solids content in the dispersion and the porosity of the particles. The viscosity of the liquid phase of the dispersion and the completeness of the dispersion can also affect the entire dispersion. To modify the viscosity of the dispersion, viscosity increasing agents can also be used so that the dispersion matches a specific application. Viscosity can vary from 1 to more than 10,000 mPa-s (centipoise (sp)), measured on a Brookfield viscometer, for example, operating at a shear rate of 73.4 s ^-1 . In most cases, the viscosity is below 100 MPa s (sp).

Embodiments of the invention derived from silica gel typically have viscosities similar to those of the original silica dispersions. For example, if the starting silica gel is crushed at a recommended pH in the range of 9 to 10, for example 9.5, the viscosity of the crushed silica remains relatively unchanged. This differs from the viscosities of ground precipitated silica. The viscosity of the ground precipitated silica is lower than the viscosity of the starting material.

The pH of the dispersion depends on the inorganic oxide and additives used to stabilize the dispersion. The pH can be in the range of 2 to 11 and includes all values within this range. For example, alumina dispersions typically have a pH in the range of 2 to 6. Silicon dioxide dispersions are usually neutral to moderate alkalinity, for example, from 7 to 11. The pH can also be adjusted using conventional pH adjusters.

As for embodiments of the invention containing silica gel, this dispersion is relatively free of impurities compared to dispersions containing, for example, particles of precipitated inorganic oxide. The starting silica gel is usually washed to remove almost all impurities. The content of alkaline salt in the gel is usually not more than 100 ppm, and usually not more than 0.1% relative to the weight of the gel. A low level of impurities in silica gel is particularly advantageous when it is desired to obtain colloid-stable particle dispersions.

The porosity of the particles can be measured in the dry state using nitrogen porosimetry after drying the dispersion. In general, at least 0.5 cm ³ / g of the pore volume of the particles are pores having a pore size of 60 nm (600 A) or less. There are embodiments of the invention containing silica gel in which at least 0.7 cm ³ / g and at least 0.9 cm ³ / g of pore volume are pores having sizes less than 60 nm (600 A) . In such embodiments, up to 100% of the pores have diameters of less than 60 nm (600 A) and at least 80%, and up to 100% of the pores of silica gel have a diameter of 30 nm (300 A) or less. The total porosity of the particles, measured in the dry state, is from about 0.5 to about 2.0 cm ³ / g, for embodiments of the invention containing silica gel, the total porosity is from about 0.5 to about 1.5, and for certain silica gel variants ranging from 0.7 to about 1.2 cm ³ / g. Porosity measurement using ΒΙΗ nitrogen porosimetry is carried out after adjusting the pH of the dispersion, slowly drying the dispersion at 105 ° C for at least 16 hours, activation at 350 ° C in vacuum for 2 hours.

The porosity of the dispersed particles directly affects the viscosity of the dispersed system in accordance with this invention. Compared with less porous particles (with the same mass of loading in the solvent), porous particles occupy a larger volume fraction of the particle-solvent system and, as such, they violate and create greater resistance to shear fluid flow. In FIG. 1 shows that with increasing particle loads, the viscosity (η) increases in such a way that a linear relationship is obtained if it is delayed with respect to a certain particle load interval. η ₍ , is the viscosity of the solvent of the dispersion, for example, water. As shown in Fig. 1, the slope of the curve increases with increasing porosity of the particles. The "porosity obtained from the viscosity" of the particles in accordance with this invention can thus be calculated based on from the slope of these curves These values reflect the pore volume of the dispersed particles.

For example, the effect of the loading of small particles on the dispersion viscosity of these particles in Newtonian fluid is described by Ι.Ι. Kpedeg in Λάν-ΟοΙΙ. 1n1eg £ acce 8sg, 1972, 3, 111.

Cho

The reciprocal of 7 is determined by the following formula (1):

where η represents the viscosity of the dispersion, η ₍ , represents the viscosity of the liquid in which the particles are dispersed,

Φ represents the volume fraction of the suspension occupied by the particles, and represents the "characteristic viscosity" (equal to 2.5 for spherical uncharged particles or for uncharged particles with a very low aspect ratio of uncharged particles),

B represents the volume fraction at which the viscosity becomes infinite.

Formula (2) determines the ratio existing between Φ and the mass of the load (x) of particles in suspension, expressed as the mass fraction of solids, the skeletal density of particles (rb) and their apparent pore volume (OPC), referred to in this description as “porosity, obtained from viscosity. "

where r! represents the density of the liquid phase.

The combination of equations (1) and (2) gives a ratio of 7 to the particle loading mass. For relatively small values of x, this ratio can be illustrated by the following linear expression, which is independent of the parameter b.

This linear ratio is usually used for values of 7 from 0.5 to 1.0. The viscosity data for a system of well dispersed particles can be used to plot in the form of 7 and linear regression, applicable to indicators 7 from 0.5 to 1.0, to determine the slope. From equation (3) it is obvious that such a slope can be associated with the OPC of particles by the following equations.

tilt =

(4) (5)

Knowing the skeletal density of amorphous silicon dioxide (2.1 g / cm ³ ), the density of the liquid phase (water = 1.0 g / cm ³ ) and knowing that the intrinsic viscosity, а, is approximately 2.5, we can calculate the OPC in accordance with this invention. This curve is shown in FIG. 1 for some embodiments of the invention, as well as for comparison with a non-porous colloid.

The values of porosity derived from viscosity for dispersions, especially dispersions of silica particles, are generally determined according to the following procedure.

(1) The dispersion of the selected inorganic- (2) pH of the dispersion is then adjusted to obtain and maintain the dispersion. It is usually obtained by adjusting the pH of the dispersion from the isoelectric point of the particles, but not reaching pH conditions that can cause excessive dissolution of the particles (for example, for silica, the pH is adjusted to 9.7-10.3 by adding ΝαΟΗ). In general, this pH order of the optimal dispersion can be determined by titration of the dispersion with 5 wt.% Solids over the entire range of acceptable low solubility of the particles, and by determining the pH range associated with the minimum viscosity of the dispersion. The ground dispersion from (1) can then be adjusted to a pH in this range.

(3) Measure the viscosity (η) of the dispersion, and determine the viscosity of the dispersion medium (p _o ), for example, water. These viscosities are measured using a Brookfield viscometer at 74 s ^-1 at a temperature of 25.0 ± 0.1 ° C.

2 ”(4) Then the ratio определяют is determined to obtain the values of 7 uniformly distributed within the interval 7 from 0.5 to 1.0. This is achieved by pre-calculating the slope —_ using a reference sample, and then using a pre-calculated slope to determine the concentration of the resulting dispersions to obtain the desired 7o η _ο range of values. If the 7 variance from (2) is greater than 0.5 and less than 0.9, it can be used as a reference sample for calculating the previously calculated slope, PRN, for the 7th graph. If 7 is less than 0.5, the sample of the suspension should be diluted with a solvent (usually DI water),% b then recalculated for 7. If 7 is more than 0.9, a more concentrated sample of the suspension should be obtained.

As soon as the reference ob7 is received. "

sample 7 from 0.5 to 0.9, using conventional techniques determine the load mass x, and calculate the PRN from the following equation.

- ref .- / pr Lli .---- X ref.

(5) Then, in order to determine the RPC, calculate the concentration (x value) for a number of samples using the following formulas.

This oxide is crushed at a rate of one liter per minute and centrifuged for thirty minutes at 600 d or at 2000 d.

.9-1 ^X CRN .8-1 ^x PRN .7-1 ^x ~ PRN .6-1 x = --- PRN .5-1 ^X ~ PRN tL

Target = -. nine . 8 . Ί. 6 .5 (6) Then dispersions are obtained with these loading masses whose pH is in a suitable range defined in (2).

(7) The viscosity of each of these samples is determined using a Brookfield viscometer at a shear rate of 73.4 s ^-1 after equilibration at a temperature of 25.0 ± 1 ° C. Then this data is used to plot.

(8) Regression analysis is used to calculate the slope of the curve of the obtained data, and the slope, ρδ and pG are substituted into the slope formula —2.5 | - + OPK for calculation (OPK).

\ rv)

The dispersions of silica particles used in this invention produce curves having an absolute slope of about 2.40 or more, and typically in the range of 2.4 to 10.0. These data are mainly given for dispersions having a porosity obtained from a viscosity (OPK) of at least 0.5 cm ³ / g. In general, the embodiments of this invention have a slope in the range of 3.50-5.0, and have an OPK from about 1.0 to about 1.5 cm ³ / g.

The stability of the porosity of the dispersed particles according to this invention is proved by calculating the loss of pore volume after drying the dispersion. As stated above, the porosity of particles dispersed in water having a less rigid network of primary particles can be significantly reduced by evaporation of water from dispersions. A comparison of the OPC of the particles and the porosity measured after drying the dispersion showed that at least 40% of the OPC is stored for the dispersions in accordance with this invention. Certain embodiments of the invention show that at least 60% OPC is retained. See FIG. 3 and example VII. Moreover, variants in which only 40% of the OPK was retained have porosity in the dried state of about 0.5 cm ³ / g or more.

The dispersions in accordance with this invention are also stable. By “stable dispersion” is meant a dispersion of finely divided particles that remains in suspended form for a long period of time. Particle dispersion stability depends on many factors, including particle size, charge, porosity, particle density and pH of the dispersion. These factors may vary and depend on how dispersion is obtained. Conventional dispersing agents can be used for this purpose. As described above, “ίη 8 Yi" stable particle dispersions can also be obtained by centrifuging the crushed particles and separating particles having an average particle size below one micron, preferably in the range from 0.01 to about 0.5 microns. Variants containing particles obtained by this technique typically have an average particle size of less than one micron.

The dispersions in accordance with this invention are suitable for many applications and are particularly suitable for those applications in which it is preferable to use porous particles having small particle sizes. It has been found, for example, that the invention is well suited for ink-absorbing coatings. A high degree of porosity of the paper coating contributes to a reduction in the drying time of the printing ink, a minimum increase in the size of the raster dot (fading), good image resolution, high degrees of loading of the printing ink (such as for photo printing) and an exceptional range of inks.

Ink-absorbent coating compositions typically contain an inorganic pigment, such as an inorganic oxide (e.g., silica gel), a binder, and additives, such as ink curing agents, etc. Particles in accordance with this invention can be used as an inorganic pigment. As described above, the inorganic oxide particles in accordance with this invention are structurally different from other forms of amorphous silicon dioxide, such as ordinary silica glass and colloidal silica, as well as some precipitated silicon dioxide, due to the fact that the dispersions in accordance with this invention contain particles with stable porosity. Thus, ink-absorbing coatings obtained using particles of this dispersion have high porosity. Moreover, such porosity is significantly consistent and is not influenced by factors that affect the porosity of coatings obtained using conventional pigments.

The dispersions in accordance with this invention can be directly used as a coating composition as such. For most applications, it is preferred, however, that the dispersions be combined with a bonding agent and any other coating additives that paper manufacturers require. As noted above, the solids content, pH, and viscosity of the dispersions can be adapted to the characteristics of the paper to be coated.

The fine particle size and porosity in accordance with this invention are suitable for glycol suspensions described above to produce polyester films. The fine particle size in accordance with this invention not only provides the frictional properties necessary in the processing of such films, but it is also believed that the porosity of the particles provides improved binding of organic particles to inorganic ones. Without claiming any theory, it is believed that glycol penetrates the porous structure of an inorganic oxide. Accordingly, when glycol, for example, reacts with phthalate during the production of PET, it forms a polymer structure. The polymer structure created inside the porous structure has a physical integrity and, thus, is firmly fixed inside, or fixed in the pores, like puzzle elements of the type rikhkh1e. Such binding subsequently improves the additional chemical binding that occurs between the glycol and the hydroxyl groups of the surface of the inorganic oxide.

Other applications of this invention include binders (for example, for catalysts), fillers, stiffening agents for cardboard, rheological agents, abrasive additives in toothpaste compositions, corrosion inhibitors, skin treating agents, insulation coatings, cosmetic additives, protective fiber optic coatings and the like.

The following examples of this invention are illustrative and do not in any way limit the invention defined by the claims.

Examples

Example I. Submicron silica gel obtained from the original hydrogel.

A well-drained hydrogel (hydrogel obtained at about 1.5 pH to give 19 wt.% Silica and washed with diluted ΝΗ ₄ ΟΗ) is pre-sized in a Prater mill to obtain an average particle size of approximately 30 μm. The powder is then suspended in deionized water (DI) to obtain a suspension of about 20 wt.% Solids and a pH of about 8. This suspension is loaded into a five (5) liter Drai mill with grinding media (model ΡΜ5Β6Η, 1.5 mm, glass medium) at a rate of 1 l / min to obtain a viscous suspension.

The suspension is then processed to obtain a stable dispersion having an average particle size of less than one micron. The separation of large and finely divided (submicrons) fractions of the crushed silica gel product is carried out by two-stage centrifugation (90 min at 1400 d, decantation, then 40 min at 2000 d). The final suspension of submicron particles is obtained by simple decantation. The solids content of the supernatant dispersion is 13 wt.%, And a certain yield is 41% (based on dry 8X2).

Particle size distribution (HbPa 900) (Particle size distribution requires the separation of large and finely divided fractions by centrifugation, measuring the particle size of each fraction on a HbPa 900 particle size analyzer, and then constructing the composition distribution by summing the masses. This distribution, like all the presented distributions, was measured on particles in deionized water at a refractive index of 1.12-1.25. The samples were also sonicated two minutes before measuring the particle size.)

10% <, 13 μm

50% <, 22 μm

90% <, 38 μm

99.9% <, 77 μm

Example II Submicron silica gel obtained from a starting aqueous gel.

Another submicron silica gel product was prepared according to the procedure of Example I, except that the starting gel was pre-sized in a pneumatic classification mill to obtain silica gel particles with an average size of approximately 15 μm. The gel is partially dried during this process, so that the moisture content in it (measured as the total mass of volatile components) drops from about 67% to about 55 wt.%, Forming an aqueous gel material.

After grinding in a medium and centrifugation according to the procedure of Example I (except for 27% solids instead of 20% in Example I), a supernatant phase containing a dispersion of 12 wt.% Solids with a yield of 10% is obtained. The supernatant phase has the following particle size distribution:

Particle Size Distribution (Hopa 900)

10% <, 13 μm

50% <, 18 μm

90% <, 30 μm

99.9% <, 55 μm

Example III Submicron silica gel obtained from the original airgel.

The wet ground Oeyeksch ™ gel is suspended in approximately 20 wt.% Solids in deionized water, and the pH is adjusted to about 8. Then, the suspension is ground in a wet state using a No. 1 × 5s11 6ΜΖ-11 mill (from 0.6-0.8 mm medium 8ΕΡΚ) at a rate of 3.8 l / min. The ground suspension is then diluted to 14.9% solids with DI water using a Myers mixer.

The separation of large and finely divided fractions of the crushed gel is carried out by two-stage centrifugation, for example, for 90 min at 1050 d, they are decanted, then centrifuged again under the same conditions.

The total solids content is 8.8% and the particle size distribution is as follows:

Particle size distribution (HbLa 900) 10% <, 086 μm

50% <, 121 μm

90% <, 181 μm 99.9% <, 322 μm

Example IV The dispersion obtained from the original xerogel.

8γ1οίά®74χ6500 silicaxergel suspended in DI water to obtain a dispersion with 24 wt.%. solids, and ΝΗ ₄ ΟΗ is added to adjust the pH to about 8.

This suspension is then crushed in a wet state using a mill Νοίζδοίι ΕΜΖ-05 (with 0.4 - 0.6 medium 8EPK) with a recirculation rate of 0.75 l / min. The entire load is passed through the crusher six times, the pH after grinding is 8.20.

The final particle size of the crushed suspension is:

Particle size distribution (HbLa 900) 10% <, 72 μm

50% <1.30 μm

99.9% <4.59 μm

Example V. Porosity obtained from viscosity (OPK) and porosity of a dried dispersion of various dispersions.

Sample 1. Aqueous gel.

An aqueous gel having 55 wt.% Volatiles is suspended in 10 wt.% Solids, the pH is adjusted to 9.6 using ΝαΟΗ. The dispersion is ground in a four liter Drai mill (1.5 mm glass layers) at a rate of 1 l / min using six passes.

The resulting suspension is then centrifuged for thirty minutes at 600d, 2000d or 27000d. The porosity obtained from viscosity (OPC), the pore volume after drying (SN nitrogen porosimetry), as well as the distribution of particle size and BET surface area, measured using nitrogen porosimetry, are measured for the initial dispersion, the ground dispersion, and each of the centrifuged dispersions. The results are presented in table. 1 below.

Sample 2. Dispersion of precipitated silica.

A dispersion of 11.4% solids is obtained using precipitated silica EK310 from Eedi ^ a. The pH of the dispersion is adjusted to 9.3, then the dispersion is crushed, centrifuged, measured and tested according to the method of sample 1. The results are presented in table. one.

Sample 3. Dispersion of silica gel.

A dispersion of 21.4% solids is obtained using 8u1o1b® 63 silica gel from Sgase Όανίδοη οί \ ν.Κ. Sgase & Co.-Sopp. The pH of the dispersion is adjusted to 9.8.

Then the dispersion is crushed (with the exception of 8 passes instead of 6), centrifuged, measured and tested according to the method of sample 1. The results are presented in table. one.

Sample 4. Dispersion of precipitated silica.

A dispersion of 8.4% solids was obtained using precipitated silica Ceox ™ 177 from Ni. Then the dispersion is crushed (using a crusher No. ΐζ§Λ), centrifuged (only at 2000d for 30 minutes), measured and tested according to the method of Sample 1. The results are presented in table. one.

Sample 5. Dispersion of the Sepeyk ™ gel.

A dispersion of 18.2% solids is obtained using a SepecC ™ gel from Sgase OauCop. The pH of the dispersion is adjusted to 9.8. The dispersion is crushed in a Reitz mill (0.016 filter) in three passes and then crushed eight more times in a Drai mill. Both mills are charged with inorganic oxide at a rate of 1 l / min. The crushed dispersion is then centrifuged, measured and tested according to the procedure of sample 1. The results are presented in table. one.

Sample 6. Colloidal silicon dioxide.

Colloidal silica sample No. 11co 1140 from No. 11co is measured and tested according to the procedure of sample 1. The average particle size of 0.015 μm is taken from the literature available in the art. The results are presented in table. one.

Table 1

wt. % tv things pH Particle Size (Hopa 900), microns Viscosity @ (1) 10% tv things at 25 ° C Visible (2), pore volume N2 porosimetry on neutralized / dried 10% fifty% 90% 99.9% cn cm ³ / g PP OD at, 967 R / R _about OD at, 995 R / Ro Sample 1 Water gel Initial suspension 18.5 9.6 4.4 8.8 15.8 32.1 1.82 1.31 265 1,163 1,179 Shredding Dray nineteen 9.6 , 36 , 60 1,6 4.2 1.82 1.33 215 0.932 0.936 Chopped. and centrif. 30 min at 600d 11.2 9,4 , 29 44 , 84 2.7 1.83 1.33 230 0.962 0.962 2000d 15.8 9.2 , 23 , 38 , 71 2,3 1.95 1.47 236 1,051 1,054 27000d 10.1 9.3 08 ,eleven ,fifteen , 24 1.93 1.45 252 0.859 0.868 Sample 2 Precipitated Silicon Dioxide GK310 Initial suspension 11,4 9.3 3.4 6.6 11.3 21.6 2.41 1.86 330 1,141 1,423 Shredding Dray 11.9 9.5 , 37 , 68 1.9 5,4 1.81 1.31 233 0.878 1,113 Chopped. and centrif. 30 min 600d 7.5 9.8 ,twenty , 33 , 55 1,6 1.88 1.40 288 1,122 1,254 2000d 4.8 9.5 ,12 ,twenty , 36 78 1.80 1.30 268 1,070 1,072 27000d 0.4 9.5 - - - - Sample 3 Silica gel 8у1оИ®63 Initial suspension 21,4 9.8 2,5 7.5 16.3 35.7 1.31 , 48 326 , 366 , 368 Shredding Dray 21.5 9.8 , 26 , 66 1.7 4,5 1.41 , 68 212 , 298 , 388 Center. 600d 13.6 9.9 , 24 , 37 , 55 1,2 1.43 , 72 212 , 423 , 572 2000d 6 9.9 ,eleven ,sixteen , 24 , 45 185 , 666 , 716 27000d 0.5 - - - - Sample 4 Precipitated Silicon Dioxide 7GoY ™ ™ 177 Initial suspension 8.4 9.9 1,5 3,7 7.1 15.6 10.5 3.14 109 , 408 , 598 Shredding (ΝΊΗζ8 ^ ι) 15.7 9.7 , 29 , 59 4.2 1.83 1.33 130 696 , 855 Center. (2000d) 14.6 9.6 0.14 , 26 ,fifty 1.8 1.83 1.33 145 , 827 956 Sample 5 Gel Oepe§18 The initial suspension (grinding Κόϊϊζ) 18.2 9.8 6.7 29.4 70.3 143.3 2.25 1.75 267 1,140 1,155 Shredding Dray 18.5 9.8 0.35 0.65 2,4 32.8 2.25 1.75 246 0.938 0.972 Chopped. and centrif. 30 min at 600d 17.5 9.8 0.28 0.48 1.7 6.1 2.25 1.75 256 1,062 1,073 2000d 16.6 9.8 0.20 0.42 1.3 4.0 2.25 1.75 263 0,998 1.003 27000d 13,2 9.8 0.09 0.14 0.26 0.76 265 0.979 0,085 Sample 6 Colloidal silicon dioxide Ν; ι1ο 1140 40.8 9.9 015 1.28 , 40 155 , 403 , 405

In FIG. 1 presents data on viscosity and mass fraction of solids used to plot for determining the OPC of the dispersions described in examples 1, 2, 3, 4, and 6. The graph shown in FIG. 1, confirms the calculations of OPK obtained by the method described above. The viscosity and charge data for the dispersion of sample 1 centrifuged at 600 d are indicated in FIG. 1 as (). The same data for samples 2 and 3 centrifuged at 600 d are designated as () and (O), respectively. Data for the dispersion of sample 4 centrifuged at 2000e are indicated in FIG. 1 as (Δ). The data for sample 6, as such, are indicated in FIG. 1 as (- -).

The slopes of the curves in FIG. 1 are calculated using regression analysis and substituted into formula (4) presented above, together with additional data presented below, to determine the indicators of the defense industry.

η, p _about determined using a viscometer

Brookfield LUTO using a coated low viscosity element, controlled at temperatures from 25.0 to (±) 0.1 ° C, at a shear rate of 73.4 s ^-1 .

a - 2.5, adopted for spherical particles;

p £ - 1.0 g / cm ³ for water;

rz is the skeletal density of an inorganic oxide, for example, 2.1 g / cm ³ for silicon dioxide.

Example VI Porosity obtained from the viscosity of silica particles sample 1.

The viscosity (centipoise), measured using a Brookfield viscometer at 73.4 s ^-1 , is used to measure the initial dispersion, the dispersion crushed in a Dray mill, and the centrifuged (600 d) dispersion of sample 1 (water gel) from Example 5, and based on the data obtained, build a graph of the dependence (η) in on the mass fraction of solids, where η ,, is the viscosity of water. The data for the initial (O), ground () and centrifuged (Δ) dispersions are shown in FIG. 2A. The average particle size and OPC for each are 8.8 μm and 1.34, 0.60 μm and 1.33, and 0.44 μm and 1.33, respectively.

Sample 2.

The viscosity (centipoise) is measured (using a Brookfield viscometer at 73.4 s ^-1 ), the initial dispersion, the dispersion, the ground dispersion and the centrifuged (2000e) dispersion of sample 4 (ίΐοοίΐιίζ ™) from Example 5;

value (η) in 7 of the mass fraction of solids, where n _about is the viscosity of water. The data for the initial (O), ground () and centrifuged (Δ) dispersions are shown in FIG. 2B. The average particle size and OPC for each are 3.7 μm and 3.14, 0.59 μm and 1.33, and 0.26 μm and 1.33, respectively.

Sample 3.

The viscosity (centipoise) is measured (using a Brookfield viscometer at 73.4 s ^-1 ), the initial dispersion, the dispersion, the ground dispersion and the centrifuged (600 d) dispersion, based on the data obtained, 2 g are built. plot of (η) in 7 on the mass fraction of solids, where o is the viscosity of water. The data for the initial (O), ground () and centrifuged (Δ) dispersions are shown in FIG. 2C. The average particle size and OPC for each are 6.6 μm and 1.86, 0.68 μm and 1.31, and 0.33 μm and 1.40, respectively.

The graph shown in FIG. 2A shows that the initial, ground and centrifuged dispersions of silica gel have almost the same viscosity and, accordingly, the same OPK. This indicates that the pore volume is not measurably reduced by grinding the dispersion of the starting silica gel.

The graphs in FIG. 2B and 2C show that the precipitated silica in accordance with this invention has a reduced viscosity after grinding compared to their initial dispersion at comparable loads. It is believed that this is a consequence of the destruction of porosity.

Example VII Preservation of porosity during drying.

The porosity measured for the dispersions obtained in Example VI is compared, and the data are used to plot the dependences of the measured RPC of these dispersions. The comparison results are presented in FIG. 3. The pH of the dispersions is adjusted, they are dried at a temperature of 105 ° C for about 16 hours, activated at a temperature of 350 ° C for two hours, and then measured using high-temperature nitrogen porosimetry.

The dashed (-) line represents the comparison line at which the porosity of the HW is equal to OPK. This line indicates the absence of loss of porosity during drying. Other data presented in FIG. 3 are identified using the following notation:

• GO (sample 1);

About Iedizza (sample 2);

Δ NiBet GeoX 177 (sample 4);

8U1OI 63 (sample 3);

No. 11so 1140 (sample 6);

B = Unmilled stock suspension;

M = Ground non-centrifuged suspension;

= Colloidal supernatant phase after centrifugation at 600 d;

= After centrifugation at 2000d.

The upper data point represents the porosity calculated at 0.985 P / P _about , and the lower data point represents the porosity calculated at 0.985 P / P _about .

The data for silica gel 8u1oI 63 () show that the dispersions of the present invention retain at least 40% OPC after drying. Other silica dispersions, for example, GO (·) gel, retain at least 60% OPC. These data and data demonstrating that at least 0.5 cm ³ / g of pore volume are pores having sizes below 60 nm (600 A) show that porosity is an internal porosity that is less susceptible to factors that affect the dispersion of the prior art.

Example VIII Glossy coatings for paper - obtaining coatings with improved glossiness compared to silica gels of the prior art.

Source materials:

(a) a Dispersion of submicron particles of silicon dioxide obtained by the method of example

1. The total solids content in sus27 suspension is 16.0% of the mass. Particle size in suspension:

Particle size distribution HbLa <10% 0.193 <50% 0.339 <90% 0.584 <99.9% 1.670 (b) For comparison, use a dispersion of silica gel 5> UBO1BK \ Y300 (Cgass Ωανίδοη). the total solids content of which is 45 wt.%. The product has an average particle size (ϋ ₅₀ ) of about 8 microns.

(c) Latex is used as a binding agent (Ushas XX210 non-ionic polyvinyl acetate latex, available from Ap Rgobis18).

(b) The substrate is an ordinary film.

Procedure: Coating compositions are prepared at a constant solids content and a silica / binder ratio so that the effect of particle size on film gloss can be determined. Silicon dioxide is mixed into latex and this composition is applied to a white film using K Sop1go1 CoaCsg and rod No. 6. Wet coatings are dried using an air jet dryer and then heated in an oven at 80 ° C for 5 minutes. Glossiness measurements are carried out with the help of Wook-Sagpeg 61occ MScg on coated sheets at a temperature of 20, 60 and 85 ° C from normal. High values correspond to a high degree of glossiness. The results are presented in the table below.

You can see that the use of submicron silicon dioxide allows to obtain coatings with a glossiness higher than the glossiness of coatings obtained using silicon dioxide No. 300.

Sample No. Silica Tv content things-in coverage Silicon dioxide / binding agent (wt.) Glossiness 20 ° C 60 ° C 85 ° C one Submicron Silicon Dioxide 37 0.28 1.3 8.1 32,7 2 Submicron Silicon Dioxide 32 0.46 1.4 10.3 62.0 3 Number 300 37 0.28 1,2 4.1 6.0 4 Number 300 32 0.47 1,2 3.0 4.2

Example IX Improved drying time for ink compared to non-porous colloidal silicon dioxide.

Source materials:

(a) The dispersion of submicron particles of silicon dioxide is obtained by the method of grinding in a wet state of silicon dioxide No. 500 with a total solids content of 18.6%, using a mill with a medium No. ΐζκΛ ΕΜΖ-11, which is loaded with 0.6-0.8 mm Wednesday. The pH of this suspension is 8.6 and the particle size of the sample is as follows:

Particle size НпЬа ϋ ₁₀ , μm 0.318

Ό ₅₀ , μm 0.512 Ό _{99> 9} , μm 3.18 (b) the ground suspension is then centrifuged at 1060 d for 30 minutes. The separated supernatant phase has a solids content of 17.4% and a particle size of:

Particle Size

Ό ₁₀ , μm 0.254

Ό ₅₀ , μm 0.403

Ό _{99> 9} , μm 2.344 (s) As nonporous silica, sample No. 11co 1140 from Example V (sample 6) was used.

Methodology

Coating compositions are prepared with a constant solids content and a constant silica / binder ratio so that the effect of silica porosity on the drying time of the printing ink can be measured. The composition used for comparison has 100 parts of silicon dioxide, 30 parts of polyvinyl alcohol) [A1g Rgobis! To Apuo1 823] and 15 parts of a poly (diallyldimethylammonium chloride) paint fastener [Ca1dop SR261BU]. Silicon dioxide is obtained having 17.4% solids, then they are loaded into the mixer and the pH is lowered by adding 1.0 M HCl to 2.8-3.3. Then Apuo1 823 was added and the silica / RUOH mixture was stirred for 1-2 minutes. Finally, the paint fixer CP261BU is added dropwise, after dilution with water, with vigorous stirring. The final pH is adjusted to a value of from 2.8 to 3.5.

The composition is applied in the form of a coating on a film substrate (1C1 MeHxx # 454), using CoCoGo1 Coa! E and rod No. 8. Wet coatings are dried using a jet air dryer and then heated in an oven at 80 ° C for 5 min . A visual examination of the films showed that they did not have significant defects.

To measure the drying time of the printing ink, the Netei-Raskagb 550C printer is used to apply a black strip of printing ink along the length of the coated film. At intervals of ~ 1 min, a strip of paper is applied to the printed surface and pressed with a fixed-weight roller. The amount of printing ink transferred from the film to the paper is examined visually. The time after which transfer of printing ink is practically not observed is given below for each of the samples (a) - (s).

Sample (a) - ground \ U500 - 2 min <1 <4 min;

sample (b) - ground centrifuged ν500 - 2 min <1 <4 min;

sample (c) - Ναΐοο (non-porous) silicon dioxide - 4 min <1 <6 min.

Thus, the film dries in a period of time from 2 to 4 minutes when using porous silicon dioxide, but requires a longer drying time when applying a coating based on non-porous silicon dioxide.

Example X. Improved drying time of the ink compared to non-porous colloidal silicon dioxide.

Source materials:

In this example, the same materials are used as in example IX.

Methodology

Coating compositions are prepared with a constant solids content and a constant silica / binder ratio so that the effect of silica porosity on the drying time of the printing ink can be measured. The composition used for comparison has 69 parts of silicon dioxide, 21 parts of poly (vinyl alcohol) [Λιγ Ргобис18 Άπνοί 325] and 10 parts of poly (ethyleneimine) new paint curing agent [VL8P Lira8o1 635]. Silica having 17.4% solids is obtained for each sample, then they are loaded into the mixer and the pH is lowered by adding 1.0 M HCl to 2.8-3.3. Then, Άπνο добавляют 325 was added and the silica / RUON mixture was stirred for 1-2 minutes. Finally, a paint fixing agent Lira8o1 635 is added dropwise, after dilution with water, with vigorous stirring. The final pH is adjusted to a value of from 2.8 to 3.5.

The composition is applied in the form of a coating on a film substrate (1C1 Μ βίίηίχ # 454), using K Sop1go1 Coal and rod No. 8.

Wet coatings are dried using a jet air dryer and then heated in an oven at 80 ° C for 5 minutes. A visual examination of the films showed that they did not have significant defects.

Drying time is measured by the method of example IX. It is:

sample (a) - ground \ U500 - 4 min <1 <5 min;

sample (b) - ground centrifuged ν500 - 5 min <1 <6 min;

sample (c) - No. 11so (non-porous) silicon dioxide - 6 min <1 <7 min.

Thus, the film dries in a period of time from 4 to 6 minutes when using porous silicon dioxide, but requires a longer drying time when applying a coating based on non-porous silicon dioxide.

Example XI Improved capacity.

Get compositions containing crushed \ U500 and crushed and centrifuged \ U500. described in example IX, containing 80 parts of pigment and 20 parts of a binder, and the resulting composition is applied to a vinyl substrate and allowed to dry under the conditions described in example IX. The coating is removed from the substrate and its porosity is measured using high density nitrogen porosimetry. Porosity measurements showed that such coatings have an ink absorption capacity of 10.2 cm ³ per 10 g of coating. Other coatings can be obtained with an ink absorption capacity in the range of 3 to 50 cm ³ per 10 g of coating and all other values within this range.

The composition and coating according to the same procedure are obtained from colloidal material No. 11co described in Example IX. The coating is dried, separated from the substrate and the porosity of the coating is measured. Such coatings have an ink absorption capacity of 2.2 cm ³ per 10 g, and typically, such coatings have an ink absorption capacity of less than 3 cm ³ per 10 g.

Example XII. Fine silica in ethylene glycol to produce polyester films.

Two dispersions in ethylene glycol are obtained using the two silica products indicated below. In process I, the pulverized and centrifuged suspension is further treated by distillation of ethylene glycol into water by conventional methods. Specifically, a sample of an aqueous suspension of ground hydrogel weighing 1800 g (17% wt. Solids) is transferred to a 4-liter flask of a rotary vacuum evaporator and heated to a temperature of 100 ° C. About 1100 g of ethylene glycol is added to the vessel in which the vacuum is maintained. After one hour, the distillate in the vessel is almost pure ethylene glycol, which means almost complete removal of water from the suspension. 1390 g of product (22% 8X2) are then separated.

Process II involves grinding silica gel in an ethylene glycol medium as described above.

Process I Process II Water milling / distillation Grinding directly in ethylene glycol Process Silicon dioxide base GO Hydrogel (55% of the total content. Years. Substances) 8у1ох 2 (about 10% of the total content. years old. substances) Medium grinding Liquid phase Deionized water Ethylene glycol Grinding plants Time required (min) about 6-12 minutes 22

Centrifugation Yes Not Product Tv substances,% 22.8 30,4 H2O content,% <1 <2 Particle size 50%, microns , 27 , 29 90%, microns , 43 , 49 > 1.0, μm,% , 00 , 33 OPK, cm ³ / g 1.3 0.95

Both dispersions have a particle size, solids content and H ₂ O content suitable for use as an anti-block dispersion for use in polyester films. 8y1oh 2 gives OPK (porosity obtained from viscosity) slightly lower than the product of GO gel (95 against 1.3 cm ³ / g). It is believed that a longer processing time in the mill and the properties inherent in the GO gel itself lead to the destruction of porosity, compared to process I.

Example XIII

An experiment is conducted to confirm the binding of ethylene glycol to an inorganic oxide. The bonding is especially illustrated by options that use the distillation process to obtain a suspension of porous submicron particles in glycol for use as an anti-block in polyester films.

Since it is necessary to capture silica particles for analysis, this experiment is carried out using silica having an average particle size of 6 microns, in contrast to the usual 0.25-0.3 microns polyester anti-block material.

One sample of silica \ U-500 from Ogase BauCop is suspended in water, then distilled into ethylene glycol according to the method of process I from example XII. Then the material is filtered, washed with acetone to remove excess (unreacted) ethylene glycol and then dried in vacuum at a temperature of 50 ° C. For comparison, samples are prepared in which 500 (1) are suspended in ethylene glycol (instead of distillation), then washed with acetone and dried, (2) only washed with acetone and dried in vacuum, and (3) only dried in vacuum. Samples are estimated by the total amount of volatile substances (OKLV) and carbon, the results are presented below.

The results show that the product obtained by glycol distillation has a higher volatile content and carbon content. This means improved glycol retention within the silica structure of distilled suspensions compared to products dispersed in other ways. It is believed that improved retention may be due to the binding effect described above.

Demonstration of the interaction of ethylene glycol with a surface of silicon dioxide during E / G distillation

Glycol distillation, washing with acetone, drying in vacuum Suspension in glycol, washing with acetone, drying in vacuum Acetone washing, vacuum drying Drying in kouume Acetone washing, vacuum drying OSLV at 945, 4 ° С (1750 ° Р) 11.9 5.3 5,0 4.4 5,0 Carbon% 4,5 1,1 1,1 0.04 0.04

CLAIM

Claims (24)

CLAIM 1. The dispersion containing porous particles of inorganic oxide, where the particles have a) an average particle size in the range from 0.05 to 3 microns; and b) a porosity such that, after drying the aqueous particle dispersion of at least 0.5 cm ³ / g of the pore volume determined by BS nitrogen porosimetry, pores having a pore size of 60 nm (600 A) or less. 2. The dispersion according to claim 1, in which the particles of inorganic oxide contain particles of silicon dioxide. 3. The dispersion according to claim 2, in which the particles of silicon dioxide contain precipitated silicon dioxide or silica gel. 4. The dispersion according to claim 1, in which the inorganic particles have an average size in the range from 0.05 to about 1 micron. 5. The dispersion according to claim 3, in which the particles of silicon dioxide have porosity after drying, in which at least 0.7 cm ³ / g of pore volume are pores having a pore size of 60 nm (600 A) or less. 6. The dispersion according to claim 5, in which the particles of silicon dioxide contain silica gel. 7. The dispersion according to claim 1, in which the porous particles have a porosity obtained from a viscosity in the range from 0.5 to 1.5 cm ³ / g 8. The dispersion according to claim 1, in which the porous particles have a porosity obtained from a viscosity in the range from 1.0 to 1.5 cm ³ / g 9. The dispersion of claim 8, in which the average particle size is about 0.5 microns or less, the solids content is from about 20 to about 25 wt.% And the dispersion contains at least 90% glycol. 10. The dispersion according to claim 9, in which the inorganic oxide is silica gel. 11. The dispersion according to claim 7, in which the porous particles contain precipitated silica or silica gel. 12. The dispersion of claim 8, in which the porous particles contain precipitated silica or silica gel. 13. The dispersion according to claim 1, containing 1-30 wt.% Particles of inorganic oxide. 14. The dispersion according to claim 11, in which the particles contain silica gel and have porosity after drying, in which at least 0.7 cm ³ / g of pore volume are pores having a pore size of 60 nm (600 A). 15. The dispersion according to claim 11, in which the porous particles have a porosity obtained from a viscosity in the range from 0.5 to 1.5 cm ³ / g 16. The dispersion according to claim 1, in which the porous particles have a porosity obtained from a viscosity in the range from 1.0 to 1.5 cm ³ / g 17. The dispersion according to claim 1, obtained by a method including: ί) the formation of a suspension of particles of inorganic oxide; ίί) grinding a suspension of particles; ϊϊΐ) obtaining a supernatant phase and a precipitated phase from the obtained crushed dispersion, where the supernatant phase contains porous inorganic oxide particles that have an average particle size in the range from about 0.1 to about 1 micron; and ίν) separating the supernatant phase as a dispersion of particles. 18. The dispersion of claim 17, wherein the inorganic oxide particles in step ί) contain silica gel or precipitated silica. 19. A method of obtaining a dispersion of particles, including: (a) the formation of a suspension of particles of inorganic oxide; (b) grinding a suspension of particles; (c) obtaining a supernatant phase and a precipitated phase from the obtained ground dispersion; and (b) separating the supernatant phase or redispersing the precipitated phase as a final product, wherein said product has porosity after drying, in which pores having a pore size of 60 nm are at least 0.5 cm ³ / g pore volume ( 600 A) or less. 20. The method according to claim 19, in which the inorganic oxide particles in step (a) contain silica gel or precipitated silica. 21. The method according to claim 19, in which the particles of the inorganic oxide in stage (a) contain silica gel, and the particles have a porosity at which pores having a pore size of 30 nm are at least 0.7 cm ³ / g of pore volume (300 A) or less. 22. The method according to claim 19, in which the final product of stage (b) has a porosity obtained from a viscosity in the range from 0.5 to 1.5 cm ³ / g. 23. The method according to claim 19, in which the suspension in stage (a) is in an aqueous medium and the final product in stage (b) is distilled with glycol to obtain a dispersion containing at least 90% glycol. 24. The method according to item 23, in which the glycol is ethylene glycol.