Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B25/00—Phosphorus; Compounds thereof
  • C01B25/16—Oxyacids of phosphorus; Salts thereof
  • C01B25/26—Phosphates
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23K—FODDER
  • A23K20/00—Accessory food factors for animal feeding-stuffs
  • A23K20/20—Inorganic substances, e.g. oligoelements
  • A23K20/28—Silicates, e.g. perlites, zeolites or bentonites
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23P—SHAPING OR WORKING OF FOODSTUFFS, NOT FULLY COVERED BY A SINGLE OTHER SUBCLASS
  • A23P10/00—Shaping or working of foodstuffs characterised by the products
  • A23P10/40—Shaping or working of foodstuffs characterised by the products free-flowing powder or instant powder, i.e. powder which is reconstituted rapidly when liquid is added
  • A23P10/43—Shaping or working of foodstuffs characterised by the products free-flowing powder or instant powder, i.e. powder which is reconstituted rapidly when liquid is added using anti-caking agents or agents improving flowability, added during or after formation of the powder
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
  • A61K47/02—Inorganic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/30—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic using agents to prevent the granules sticking together; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/02—Preparation of sulfur; Purification
  • C01B17/10—Finely divided sulfur, e.g. sublimed sulfur, flowers of sulfur
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F5/00—Compounds of magnesium
  • C01F5/02—Magnesia

Definitions

• Hydrophilic powders tend to agglomerate under the influence of atmospheric moisture and the pressures of packaging and storage. They, thereby, lose the valuable properties of their original finely divided state. For instance, they no longer can be dusted without difiiculties as clusters of agglomerated particles are formed. The agglomeration in practice leads to particle sizes which are much coarser than the sizes obtained in their original state.
• Such agglomeration also occurs during the process of preparation of the finely divided substances such as, for example, during grinding. Grinding of products of all types often leads to disturbances with regard to the stability of the original fineness of the particles reached in the grinding and their dispersibility. Also, insufficient grinding properties, especially with substances not having sufficient grinding hardness, often leads to difficulties.
• a blatant example is in the grinding of spices during which the comminution, which originally occurs, is immediately followed by agglutination of the ground particles which leads to clogging of the mill. Sulfur behaves similarly on grinding and causes clogging of the mill. Attempts to hinder the agglomeration occurring during such grinding process by the addition of finely divided pyrogenic silica have not been lacking. However, the amounts required are comparatively high and in particular are undesirably high in pharmaceutical and food products and in some instances they undesirably affect the activity of the materials.
• hydrophobic silicas employed according to the invention can be finely divided wet precipitated silicas, pyrogenic silicas produced by pyrogenic decomposition of volatile silicon halides or electric arc silicas which have been hydrophobized in a known manner with organohalosilanes, such as, dimethyl dichlorosilane.
• Wet precipitated hydrophobized silicas can, for instance, have a BET surface area of about 20 to 200 m./g., preferably, about -150 m./g., such as, for example, in a hydrophobized precipitated silica containing 89-99.0 percent of silica and about 0.9 to 2.8 percent of carbon derived from chemically bound methyl groups which cause the hydrophobicity, and having a primary particle size of 20-300 my, a secondary particle size of 0.7-9 a BET surface area of I00 mF/g. and a pH of 3.4-4.9 (4 percent in water:acetone, for instance, DEGUSSA hydrophobized silicas D 17 and D 500).
• Pyrogenic silicas for instance, have a surface area between about 100 to 200 m./g. and an average primary particle size of about 10 to 50 mp, and a carbon content of about 112 to 116 percent, corresponding to about 0.6-0.8 m.
• hydrophilic silicas which can be used in combination with the hydrophobic silicas according to one embodiment of the invention can either be wet precipitated or pyrogenic silicas which have not been hydrophobized.
• the hydrophilic silica or mixture of hydrophobic and hydrophilic silica employed must be incorporated and intimately mixed with the substance to be protected against agglomeration or reagglomeration by a grinding operation either in that the hydrophilic silica is added to the substance before it is finely ground and such substance is finely ground in contact with such added hydrophobic silica or in that a mixture of hydrophobic and hydrophilic silicas is added to the substance after it already is in the finely ground state and intimately mixed therewith in a mill having a grinding action. In both instances the addition of the silicas can be before or during the grinding operation.
• the finely divided products which have been treated according to the invention in practice have the advantages of improved dustibility, improved stability of their finely divided nature or dispersibility against agglomeration and caking, improved dosibility in automatic weighings and improved behavior when conveyed pneumatically.
• the accumulation of electrostatic charges which also is a cause of undesired agglomeration is avoided in powders normally having a tendency to accumulate such charges.
• EXAMPLE I A raw chromium phosphate was finely ground in a mill after addition of 3 wt. percent of hydrophobic precipitated finely divided silica (D 17) having a BET surface area of about m./g. containing 89.20 wt. percent of silica and about 2.80 wt. percent of carbon derived from methyl groups. A finely divided powder was obtained in which the original particle fineness was stabilized against reagglomeration'for a long period aftel' the grinding.
• D 17 hydrophobic precipitated finely divided silica
• hydrophobic silicas is considerably more effective at considerably lower quantities than the sole addition of hydrophilic silica as a so-called grinding assistant.
• the windsifting operations which may follow the grinding operation proceed more rapidly and more effectively with regard to particle size separation the less the particles are agglomerated with each other.
• EXAMPLE 2 A magnesium oxide in very finely ground state was intimately mixed in a mill having grinding action with a mixture of finely divided hydrophobized precipitated silica (D 17) and a finely divided hydrophilic precipitated silica (Ultrasil VN 3) having a surface area of about 240 mfl/g. and containing about 87 percent of silica and having an percent loss on calcination and a particle size of about 16 m once in a wt. ratio of l:9 (b) and once in a wt. ratio of 5:5.
• the quantity of the mixture of the silicas was such that it was l wt. percent of the total mixture with the magnesium oxide.
• a product was obtained whose original fine-particled nature after the grinding was stabile against the influences of atmospheric moisture and the agglomerating influences of storage and packaging. The same effects were obtainable whether the addition of the silica mixture and mixture thereof under grinding conditions was effected immediately after the magnesium oxide had been finely ground and before it has reagglomerated or whether it was effected after reagglomeration had taken place.
• the effects of the incorporation of the silica mixture in the finely ground magnesium oxide can easily be seen from electron microphotographs at an enlargement of 30,000 taken of the untreated finely ground magnesium oxide (which had reagglomerated) and that of the mixture of the silica mixtures with the magnesium oxide prepared as described above using the finely ground magnesium in its reagglomerated state as starting material.
• the silica magnesium oxide mixtures exhibit a considerably lower agglomeration and a more uniform average secondary structure.
• the average secondary structure of the mixture is about 10 times smaller than that of the original magnesium oxide, this effect being raised with increase in the proportion of the hydrophobic silica.
• the mixture of magnesium oxide with hydrophobic plus hydrophilic silicas prepared as described above are especially advantageous when used to decrease the low temperature corrosion in large boiler installations as the disadvantages of untreated technical magnesium oxide powders, such as insufficient spray behavior, premature settling in the combustion chamber, deficient stability of the magnesium oxide during storage and distant transportation are avoided.
• the presence of, for example 8 to 10 percent of the mixture of 59 parts of hydrophilic silica and l5 parts of hydrophobic silica (the silica mixture as a whole being hydrophobized by the presence of the hydrophobic silica) produces a substantial improvement in the spray behavior and the stability of the magnesium oxide.
• a further substantial advantage is that in view of the lowering of the tendency to reagglomerate caused by the presence of the silicas, the treated magnesium oxide can be metered without difficulty and can be blown with greater effectiveness over greater distances. Even portions of the boiler having unfavorable flow conditions can be well dusted with the finely divided stabilized MgO-SiO mixture according to the invention. It is possible thereby to reduce the quantity of MgO previously necessary by about 40 percent.
• the quantities of finely divided hydrophobic silica or mixtures of hydrophobic silica with hydrophilic silica which can be incorporatedaccording to the invention in finely divided products having a tendency to agglomerate or reagglomerate can, depending upon the substance to be protected, be about 0.1 to 20 wt. percent, preferably, about 0.1 to 10 percent in the case of inorganic powders and about 0.1 to 0.5 percent in the case of organic powders, such as spices, based upon the total mixture.
• a method of protecting finely divided powdered sub stances against agglomeration or reagglomeration during grinding and subsequent thereto which comprises adding a finely divided synthetically produced hydrophobized active silica together with a finely divided synthetically produced hydrophilic silica to the substance to be protected and grinding the mixture whereby a finely divided powder which is free of agglomeration and substantially protected against subsequent agglomeration is obtained.
• hydrophobized silica is a silica which has been hydrophobized by treatment with an organic halogen silane and has a carbon content of 0.9 to 2.8 percent, a BET surface area of about -450 mF/g.
• the finely divided powdered substance to be protected is magnesium oxide and such magnesium oxide is admixed in finely divided powdered state with about 8-- 10 wt. percent of a mixture of 59 wt. parts of the hydrophobized silica and 51 wt. parts of the hydrophilic silica and such admixture is intimately mixed in a mill having a grinding action.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Polymers & Plastics (AREA)
• Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Animal Behavior & Ethology (AREA)
• Zoology (AREA)
• Animal Husbandry (AREA)
• Medicinal Chemistry (AREA)
• Pharmacology & Pharmacy (AREA)
• Epidemiology (AREA)
• Geology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Silicon Compounds (AREA)
• Soil Conditioners And Soil-Stabilizing Materials (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

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Cited By (13)

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Citations (7)

• 1967
  • 1967-03-23 DE DE19671642998 patent/DE1642998B2/de active Pending
• 1968
  • 1968-03-05 CH CH323468A patent/CH500001A/de not_active IP Right Cessation
  • 1968-03-06 FR FR1555348D patent/FR1555348A/fr not_active Expired
  • 1968-03-07 NL NL6803231.A patent/NL163969C/xx not_active IP Right Cessation
  • 1968-03-09 ES ES351408A patent/ES351408A1/es not_active Expired
  • 1968-03-21 SE SE03804/68A patent/SE339458B/xx unknown
  • 1968-03-22 GB GB03931/68A patent/GB1213494A/en not_active Expired
  • 1968-03-23 JP JP1886268A patent/JPS5411277B1/ja active Pending
  • 1968-03-25 US US715581A patent/US3580519A/en not_active Expired - Lifetime

Patent Citations (7)

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