The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m.sup.2/g, and satisfies the following: a) the pore volume of 1.9 nm to 100 nm pore radius measured by the mercury press-in method (V.sub.HP-Hg) ranges from 1.40 to 2.00 cm.sup.3/g; b) total pore volume in the range of 1.6 nm to 100 nm pore radius by the nitrogen adsorption/desorption method (V.sub.N2) ranges from 1.60 to 2.20 cm.sup.3/g; and c) the pore volume ratio of (a) and (b) V.sub.HP-Hg/V.sub.N2 ranges from 0.70 to 0.95. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.

The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m.sup.2/g, and satisfies the following: a) the pore volume of 1.9 nm to 100 nm pore radius measured by the mercury press-in method (V.sub.HP-Hg) ranges from 1.40 to 2.00 cm.sup.3/g; b) total pore volume in the range of 1.6 nm to 100 nm pore radius by the nitrogen adsorption/desorption method (V.sub.N2) ranges from 1.60 to 2.20 cm.sup.3/g; and c) the pore volume ratio of (a) and (b) V.sub.HP-Hg/V.sub.N2 ranges from 0.70 to 0.95. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.

Precipitated silica having large median particle size for use as reinforcing filler in elastomeric compositions as well as its method of manufacture. In particular, a precipitated silica characterised by a CTAB surface area S.sub.CTAB in the range from 70 to 350 m.sup.2/g; an amount W.sub.M of at least one metal M selected from elements of groups 3, 4 and 5 of at least 0.1 mol %; and a median particle size d50, measured by centrifugal sedimentation, such that: |d50|≥183×|R.sub.ION|×|W.sub.M|−0.67×|S.sub.CTAB|+233 (I) wherein |d50| represents the numerical value of median particle size d50 measured by centrifugal sedimentation and expressed in nm; |R.sub.ION|, the numerical value of the ionic radius of metal M expressed in nm; |S.sub.CTAB|, the numerical value of the CTAB surface area S.sub.CTAB expressed in m.sup.2/g; and |W.sub.M|, the numerical value of the percentage molar amount of the metal W.sub.M.

Precipitated silica having large median particle size for use as reinforcing filler in elastomeric compositions as well as its method of manufacture. In particular, a precipitated silica characterised by a CTAB surface area S.sub.CTAB in the range from 70 to 350 m.sup.2/g; an amount W.sub.M of at least one metal M selected from elements of groups 3, 4 and 5 of at least 0.1 mol %; and a median particle size d50, measured by centrifugal sedimentation, such that: |d50|≥183×|R.sub.ION|×|W.sub.M|−0.67×|S.sub.CTAB|+233 (I) wherein |d50| represents the numerical value of median particle size d50 measured by centrifugal sedimentation and expressed in nm; |R.sub.ION|, the numerical value of the ionic radius of metal M expressed in nm; |S.sub.CTAB|, the numerical value of the CTAB surface area S.sub.CTAB expressed in m.sup.2/g; and |W.sub.M|, the numerical value of the percentage molar amount of the metal W.sub.M.

A silica that is superior in terms of fluidity, oil absorption ability, and compression moldability to conventional silica used as a pharmaceutical additive, and is suitable as an additive for formulations such as pharmaceuticals. A porous silica particle composition having the following properties: (1) a BET specific surface area from 250 to 1,000 m.sup.2/g; (2) an average particle diameter from 1 to 150 μm; (3) a pore volume from 0.1 to 8.0 cm.sup.3/g; and (4) an oil absorption capacity from 2.2 to 5.0 mL/g.

A silica that is superior in terms of fluidity, oil absorption ability, and compression moldability to conventional silica used as a pharmaceutical additive, and is suitable as an additive for formulations such as pharmaceuticals. A porous silica particle composition having the following properties: (1) a BET specific surface area from 250 to 1,000 m.sup.2/g; (2) an average particle diameter from 1 to 150 μm; (3) a pore volume from 0.1 to 8.0 cm.sup.3/g; and (4) an oil absorption capacity from 2.2 to 5.0 mL/g.

A precipitated silica having large particle size for use in tire applications. In particular, a precipitated silica characterised by a CTAB surface area S.sub.CTAB equal to or greater than 160 m.sup.2/g; a median particle size d50, measured by centrifugal sedimentation, such that

|d50|>25000/|S.sub.CTAB|  (I)

wherein |d50| represents the numerical value of the median particle size d50 measured by centrifugal sedimentation and expressed in nm and |S.sub.CTAB| represents the numerical value of the CTAB surface area S.sub.CTAB expressed in m.sup.2/g; and
an aluminium content not exceeding 4500 ppm.

A precipitated silica having large particle size for use in tire applications. In particular, a precipitated silica characterised by a CTAB surface area S.sub.CTAB equal to or greater than 160 m.sup.2/g; a median particle size d50, measured by centrifugal sedimentation, such that

|d50|>25000/|S.sub.CTAB|  (I)

wherein |d50| represents the numerical value of the median particle size d50 measured by centrifugal sedimentation and expressed in nm and |S.sub.CTAB| represents the numerical value of the CTAB surface area S.sub.CTAB expressed in m.sup.2/g; and
an aluminium content not exceeding 4500 ppm.

Provided is a system and a method for preparing ultrafine silica by leaching silicate ore using hydrogen chloride gas, comprising an ore raw material feeding device, an ejector, a stirring tank and a liquid-solid separation device. A circulated material outlet of a stirred tank is connected with a liquid inlet of an ejector through a circulation pipe; a liquid outlet of the ejector is connected with a circulated material inlet of the stirred tank; a material outlet of a raw ore feeding apparatus is connected with the circulation pipe; and the circulated material outlet of the stirred tank is connected with a solid-liquid separation apparatus. Based on the system and method in the present disclosure, an industrially feasible solution for preparing silica by continuously leaching a silicate ore is provided. The dissolution efficiency of ores and the utilization of hydrochloric acid are greatly increased.

Provided is a system and a method for preparing ultrafine silica by leaching silicate ore using hydrogen chloride gas, comprising an ore raw material feeding device, an ejector, a stirring tank and a liquid-solid separation device. A circulated material outlet of a stirred tank is connected with a liquid inlet of an ejector through a circulation pipe; a liquid outlet of the ejector is connected with a circulated material inlet of the stirred tank; a material outlet of a raw ore feeding apparatus is connected with the circulation pipe; and the circulated material outlet of the stirred tank is connected with a solid-liquid separation apparatus. Based on the system and method in the present disclosure, an industrially feasible solution for preparing silica by continuously leaching a silicate ore is provided. The dissolution efficiency of ores and the utilization of hydrochloric acid are greatly increased.