Low alpha dose barium sulfate particle, and use and process for producing the same

A process for producing a low alpha dose barium sulfate particle comprising:

• a step (1) for subjecting
• (1) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 0.65% by weight or more and 1.6% by weight or less, or
• (2) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 1.6% by weight or more and 2.5% by weight or less, or
• (3) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 2.5% by weight or more,
• wherein the crushed ore is obtained by crushing barite ore, to
• (a) an elutriation treatment, or
• (b) a sieving treatment, or
• (c) an elutriation treatment and a sieving treatment,
• thereby obtaining as a first product:
• a crushed ore having a silica content of 0.65% by weight or less in the case of the crushed ore (1), or
• a crushed ore having a silica content of 1.55% by weight or less in the case of the crushed ore (2), or
• a crushed ore having a silica content of 2.5% by weight or less in the case of the crushed ore (3);
• a step (2) in which the first product is reduced with a reducing agent to generate barium sulfide as a second product, and the barium sulfide is leached into water to obtain an aqueous solution of barium sulfide;
• and
• a step (3) in which, to the aqueous solution of barium sulfide,
• (a) an aqueous solution of an alkali metal sulfate is added, or
• (b) sulfuric acid is added, or
• (c) hydrochloric acid is added to obtain an aqueous solution of barium chloride;
• the barium chloride is precipitated;
• the barium chloride obtained is dissolved in water to obtain an aqueous solution of barium chloride;
• to the aqueous solution of barium chloride an aqueous solution of an alkali metal sulfate is added to effect the reaction of the aqueous solution of barium chloride with the alkali metal sulfate, or
• (d) hydrochloric acid is added to obtain an aqueous solution of barium chloride, the barium chloride is precipitated, the barium chloride obtained is dissolved in water to obtain an aqueous solution of barium chloride, the aqueous solution of barium chloride is caustified to obtain an aqueous solution of barium hydroxide, and the aqueous solution of barium hydroxide is reacted with sulfuric acid,
• thereby to generate barium sulfate as a third product, the barium sulfate is precipitated and recovered to obtain a low alpha dose barium sulfate particle having a silica content of 0.6% by weight or less and an alpha dose of 0.07 cph/cm2 or less.

A process for producing a surface-treated low alpha dose barium sulfate particle having an alpha dose of 0.07 cph/cm2 or less, comprising:

• a step (1) for subjecting
• (1) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 0.65% by weight or more and 1.6% by weight or less, or
• (2) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 1.6% by weight or more and 2.5% by weight or less, or
• (3) a crushed ore having an average particle diameter of 5-50 μm, an alpha dose of 1 cph/cm2 or less, and a silica content of 2.5% by weight or more,
• wherein the crushed ore is obtained by crushing barite ore, to
• (a) an elutriation treatment, or
• (b) a sieving treatment, or
• (c) an elutriation treatment and a sieving treatment,
• thereby obtaining as a first product:
• a crushed ore having a silica content of 0.65% by weight or less in the case of the crushed ore (1),
• a crushed ore having a silica content of 1.55% by weight or less in the case of the crushed ore (2), and
• a crushed ore having a silica content of 2.5% by weight or less in the case of the crushed ore (3);
• a step (2) in which the first product is reduced with a reducing agent to generate barium sulfide as a second product, and the barium sulfide is leached into water to obtain an aqueous solution of barium sulfide;
• and
• a step (3) in which, to the aqueous solution of barium sulfide,
• (a) an aqueous solution of an alkali metal sulfate is added, or
• (b) sulfuric acid is added, or
• (c) hydrochloric acid is added to obtain an aqueous solution of barium chloride, the barium chloride is precipitated, the barium chloride obtained is dissolved in water to obtain an aqueous solution of barium chloride, an aqueous solution of an alkali metal sulfate to effect the reaction of the aqueous solution of barium chloride with the alkali metal sulfate, or
• (d) hydrochloric acid is added to obtain an aqueous solution of barium chloride, the barium chloride is precipitated, the barium chloride obtained is dissolved in water to obtain an aqueous solution of barium chloride, the aqueous solution of barium chloride is caustified to obtain an aqueous solution of barium hydroxide, and the aqueous solution of barium hydroxide is reacted with sulfuric acid,
• thereby to generate barium sulfate as a third product, the barium sulfate is precipitated and recovered to obtain a low alpha dose barium sulfate particle having a silica content of 0.6% by weight or less and an alpha dose of 0.07 cph/cm2 or less;
• and
• a step (4) in which the low alpha dose barium sulfate particle is surface-treated with at least one of silica, silica hydrate and aluminum hydroxide.