摘要:
An improved flatting agent comprising an inorganic hydrogel having a pore volume of at least 1.0 ml/g, an average particle size in the range 1 to 10 microns, and a particle size distribution such that when the flatting agent is dispersed in a coating, the fineness of grind is at least 4.75 on the Hegman scale. The inorganic hydrogel flatting agents of this invention are prepared by milling an inorganic hydrogel under controlled temperature conditions wherein a volatiles content of at least 40 weight percent is maintained, to produce inorganic hydrogel particles characterized by a pore volume of at least 1.0 ml/g, an average particle size in the range of 1 to 10 microns, and a particle size distribution such that when the flatting agent is dispersed in a coating, the fineness of grind is at least 4.75 on the Hegman scale. Also provided in accordance with this invention are improved coating compositions comprising a full gloss coating containing the above described flatting agents dispersed in the full gloss coating in from 3 to 15 weight percent loading on a solids basis.
摘要:
The invention relates to the use of polyacrylic acids which contain organic terminal groups containing sulphur, comprising at least two carbon atoms, having an average molecular weight Mw of 5 000 - 30 000 g/mol and which are at least partially neutralised by a base which is selected from the group of alkali hydroxides and ammonia as auxiliary agents for wet grinding of calcium carbonate. The invention also relates to fine particle aqueous suspensions of calcium carbonate which are produced by wet grinding of calcium carbonate in the presence of said polyacrylic acids.
摘要:
An improved flatting agent comprising an inorganic hydrogel having a pore volume of at least 1.0 ml/g, an average particle size in the range 1 to 10 microns, and a particle size distribution such that when the flatting agent is dispersed in a coating, the fineness of grind is at least 4.75 on the Hegman scale. The inorganic hydrogel flatting agents of this invention are prepared by milling an inorganic hydrogel under controlled temperature conditions wherein a volatiles content of at least 40 weight percent is maintained, to produce inorganic hydrogel particles characterized by a pore volume of at least 1.0 ml/g, an average particle size in the range of 1 to 10 microns, and a particle size distribution such that when the flatting agent is dispersed in a coating, the fineness of grind is at least 4.75 on the Hegman scale. Also provided in accordance with this invention are improved coating compositions comprising a full gloss coating containing the above described flatting agents dispersed in the full gloss coating in from 3 to 15 weight percent loading on a solids basis.
摘要:
Described are high solids aqueous slurries of amorphous precipitated hydrated silica, which slurries are of relatively low viscosity. The slurry typically contains from about 40 to about 60 weight percent of hydrated precipitated high structure silica. The viscosity of the high solids slurry is less than about 1000 centipoises. Processes for producing the aqeuous high solids silica slurry are disclosed. In one embodiment, a wet cake of amorphous precipitated hydrated silica is liquified and the liquified wet cake charged to a high-intensity mill wherein the silica is wet milled until the median agglomerate particle size of the silica is between about 0.3 and about 3 microns. In a further embodiment, finely-divided dry amorphous precipitated silica is slurried in a dispersion mill to the desired solids level and this slurry charged to a high-intensity mill and wet milled therein until the aforesaid agglomerate particle size range is attained. The resulting high solids slurry can be shipped in bulk with only mild agitation to prevent settling. A dispersant may also be added to the slurry prior to milling to retard settling of the silica.
摘要:
A molded catalyst for fitting into a reactor vessel having an inlet and an outlet for a reactant gas, the catalyst having openings therethrough parallel to the direction of a reactant gas which is introduced into the reactor vessel from the inlet, the catalyst comprising: a wear-resistant front surface facing the inlet of the reactor vessel and a continuation of the front surface extending therefrom, the both being the front portion of the catalyst, and the remaining part of the catalyst made so wear-susceptible as to have either:
(a) a wearability of 2-10 % in a shaking abrasion test wherein grinding particles having an average particle size of 1000 µm and a Mohs scale of 9 are placed in the openings of the catalyst in an amount of 50 % by volume based on the total volume of the openings, and the catalyst is shaked for three hours with an amplitude of 77 mm and a frequency of 320 per minute; or (b) a wearability of 7.5-35 % in an air abrasion test wherein an air which contains silica particles having an average particle size of 40 µm in amounts of 70 g/m³ is passed through in a reactor vessel including a rectangular parallelepipedic catalyst of 45 mm wide, 45 mm thick and 100 mm long so fitted thereinto that the catalyst extends longitudinally in the direction of the flow of the air for 30 min. at a superficial velocity of 40 m/sec. at the front face of the catalyst.
摘要:
Konventionelle Vorsinter- und Reaktionssinterverfahren zur Herstellung keramischer Pulver liefern Produkte mit breit verteilter Teilchengröße sowie mitunter unkontrollierten Anhäufungen von Verunreinigungen, welche beim Fertigsintem zur Ausbildung von Duplexstrukturen. führen. Zwecks Fernhaltung oben genannter Materialeigenschaften an keramischen Pulvem, wird erfindungsgemäß ein Verfahren und ein Vorrichtung vorgestellt, welche die Heretellung von chemisch homogenen Pulvern mit eng gestreuter Teilchengrößenverteilung im Teilchengrößenbereich von 0,05 µm bis 10 µm ermöglicht. Zur Durchführung des Verfahres wird ein indirekt beheizter 6, in meherere Temperaturzonen (A, B, C) unterteilter, Fallrohrofen, weicher in Figur 3 dargestellt ist, eingesetzt. Die Rohstoffe, welche über eine hohe spezifische Oberfläche verfügen, werden in Form klassierter Granulate in den Fallrohrofen eingesetzt (1, 2, 3). Die eingesetzten Granulate werden rasch auf Temperatur gebracht und innerhalb von wenigen Sekunden, quasi im freien Fall, unter inerten, oxydierenden oder reduzierenden Bedingungen in keramische Pulver mit gewünschten Materialeigenschaften übergeführt. Nachgeschaltete Kühlsysteme (9, 10, 11) kühlen das Pulver (12) bis auf Raumtemperatur ab. Die Gaszuführung erfolgt über Rohrleitungen (8). Die gebildeten Reaktionsgase werden entweder über den Ofenkopf (4) oder über den Ofenboden (10) abgezogen.
摘要:
L'invention concerne des boues aqueuses de silice hydratée précipitée amorphe à teneur élevée en solides, lesdites boues présentant une viscosité relativement faible. La boue contient typiquement environ 40 à environ 60 % en poids de silice précipitée hydratée de structure élevée. La viscosité de la boue à teneur élevée en solides est inférieure à environ 100 centipoises. L'invention concerne aussi des procédés de production de la boue de silice aqueuse à teneur élevée en solides. Dans un mode de réalisation, on liquéfie un gâteau humide de silice amorphe précipitée hydratée et on charge le gâteau humide liquéfié dans un broyeur d'intensité élevée dans lequel la silice est broyée à l'état humide jusqu'à ce que sa granulométrie d'agglomérat moyenne soit comprise entre environ 0,3 et environ 3 microns. Dans un autre mode de réalisation, on transforme en boue de la silice précipitée amorphe sèche finement divisée dans un broyeur de suspension jusqu'à obtention du niveau de solides désiré, puis on charge cette boue dans un broyeur de haute intensité dans lequel on la broie à l'état humide jusqu'à ce que l'on atteigne la plage granulométrique d'agglomérat précitée. On peut transporter en vrac la boue à teneur élevée en solides ainsi obtenue avec seulement une agitation faible afin d'empêcher le tassement. On peut aussi ajouter un dispersant à la boue avant le broyage afin de retarder le tassement de la silice.