US 5,906,804 A · Magnesium hydroxide slurries

Abstract

Magnesium hydroxide slurries having the following characteristics: (i) having a solids content of between 40-80 wt. % based on the weight of the slurry with the balance being water; (ii) containing between 0.01-5.0 wt.% of at least one viscosity modifying agent or dispersant based on the weight of the slurry selected from the following groups: (1) inorganic acids having a molecular weight less than 130 amu and their inorganic salts excluding H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, silicic acid and salts having an alkali metal as sole cation; (2) low molecular weight (i.e. less than 200 amu) carboxylic acids optionally containing one or more hydroxyl groups and their inorganic salts excluding salts having alkali metal as sole cation; (3) polyhydric alcohols or carbohydrates containing two or more hydroxyl groups and having a molecular weight less than 500 amu; and (4) alkaline earth oxides and/or hydroxides; (v) being sedimentation stable for at least seven days without substantial agitation; and (vi) maintaining a viscosity of less than 1000 cP at a shear rate of 139 sec.sup.-1 over a period of at least seven days.

Claims39

Dependent claims

A magnesium hydroxide slurry, comprising:

(i) between about 40-80% of a solids content based on the weight of the slurry with the balance being water;
and
(ii) between about 0.01-5.0 wt % of at least one viscosity modifying agent or dispersant based on the weight of the slurry selected from the group consisting of:
(1) inorganic acids having a molecular weight less than 130 amu, and inorganic salts thereof excluding H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, silicic acid and salts thereof having an alkali metal as a sole cation;
(2) carboxylic acids having a molecular weight of less than 200 amu optionally containing one or more hydroxyl groups, and salts thereof excluding salts having alkali metal as a sole cation;
(3) polyhydric alcohols, and carbohydrates containing two or more hydroxyl groups and having a molecular weight of less than 500 amu;
and
(4) alkaline earth oxides, hydroxides, and a combination thereof;
said slurry being sedimentation stable for at least 7 days without substantial agitation;
and maintaining a viscosity of less than 1000 cP at a shear rate of 139 sec.sup.-1 over a period of at least 7 days;
said slurry excluding polymeric viscosity modifying agents.

8 more elements

A process for producing a magnesium hydroxide slurry, comprising:

(i) subjecting calcined magnesia of a particle size of about 25 mm or less to a first particle reduction zone wherein said calcined magnesia is mixed with water and ground;
(ii) passing said finely divided material through a screening means to ensure passage therethrough of finely divided magnesia having a particle size of about 2 mm or less and returning oversize magnesia particles to said first reduction zone;
(iii) hydrating said finely divided magnesia in a hydration zone wherein said finely divided magnesia is mixed with water under agitation and heat so as to produce a magnesium hydroxide slurry having at least 80% hydration;
(iv) passing said slurry through a second particle reduction zone so as to produce slurry particles wherein 90% of said slurry particles have a size less than 50 microns;
(v) adding a viscosity modifying agent prior to or during steps (i), (ii), (iii), or (iv) so as to ensure a maximum viscosity of 1000 cP;
and
(vi) obtaining after step (v) as a final product stable, pumpable, magnesium hydroxide slurries having a solids content of at least 40%, and excluding polymeric viscosity modifying agents;
said viscosity modifying agent being selected from the group consisting of:
(1) inorganic acids having a molecular weight less than 130 amu, and inorganic salts thereof excluding H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, silicic acid and salts thereof having an alkali metal as a sole cation;
(2) carboxylic acids having a molecular weight of less than 200 amu optionally containing one or more hydroxyl groups and salts thereof excluding salts having alkali metal as a sole cation;
(3) polyhydric alcohols, and carbohydrates containing two or more hydroxyl groups and having a molecular weight of less than 500 amu;
and
(4) alkaline earth oxides, hydroxides and a combination thereof.

10 more elements

A process for producing a magnesium hydroxide slurry, comprising:

(i ) continuously feeding magnesia to a hydration zone wherein the slurry is subjected to a continual agitation;
(ii) hydrating said magnesia in the hydration zone under agitation and heat so as to produce a magnesium hydroxide slurry having at least 80% hydration;
(iii) adding a viscosity modifying agent prior to or during steps (i) or (ii) so as to ensure a maximum viscosity of 1000 cP;
and
(iv) obtaining as a final product stable, pumpable magnesium hydroxide slurries having a solids content of at least 40%, and excluding polymer viscosity modifying agents;
said viscosity modifying agent being selected from the group consisting of:
(1) inorganic acids having a molecular weight less than 130 amu, and inorganic salts thereof excluding H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, silicic acid and salts thereof having an alkali metal as a sole cation;
(2) carboxylic acids having a molecular weight of less than 200 amu optionally containing one or more hydroxyl groups and salts thereof excluding salts having alkali metal as a sole cation;
(3) polyhydric alcohols, and carbohydrates containing two or more hydroxyl groups and having a molecular weight of less than 500 amu;
and
(4) alkaline earth oxides, hydroxides and a combination thereof.

8 more elements

Dependencies are inferred from the claim text.

Magnesium hydroxide slurries

Life of this patent

Magnesium hydroxide slurries

Life of this patent

Abstract

Claims39