US3853984A — Controlling the leaching of kaolin clay

Claim 1

Independent Claim 219 words

AN IMPROVED METHOD FOR CONTINUOUSLY LEACHING A DISPERSED KAOLIN CLAY AQUEOUS SLURRY FOR REMOVING COLOR IMPURITIES THEREIN TO PROVIDE KAOLIN CLAY PRODUCTS HAVING IMPROVED OPTICAL AND RHEOLOGICAL PROPERTIES WITH AN OPTIMUM AMOUNT OF LEACH COMPOUND, SAID METHOD COMPRISING: A. FORMING AN AQUEOUS SLURRY OF A FINELY DIVIDED KAOLIN CLAY; B. ADDING TO SAID AQUEOUS CLAY SLURRY A LEACHING COMPOUND CAPABLE OF REDUCING INSOLUBLE SALTS PRESENT IN SAID CLAY SLURRY TO A SOLUBLE FORM, SAID LEACHING COMPOUND COMPRISING A COMPOUND CONTAINING AN ACTIVE (S2O4) GROUP OR A COMPOUND CAPABLE OF LIBERATING SUCH GROUPS IN SAID SLURRY; C. ADJUSTING THE PH OF THE SLURRY TO BEETWEEN ABOUT 3.0 TO 4.5 BY THE ADDITION OF A SUFFICIENT AMOUNT OF A FLOCCULATING AGENT; D. MEASURING THE OXIDATION-REDUCTION POTENTIAL IN THE LEACH COMPOUND-CLAY SLURRY MIXTURE AT A SPECIFIED TIME PERIOD SELECTED AT LEAST 20 MINUTES AFTER SAID LEACH COMPOUND ADDITION, SAID OXIDATION-REDUCTION POTENTIAL BEING MEASURED BY INSERTING THE ELECTRODE ASSEMBLY OF AN OXIDATIONREDUCTION POTENTIOMETRIC CELL INTO SAID LEACH-CLAY SLURRY MIXTURE AND READING THE ELECTRIC POTENTIAL BETWEEN SAID ELECTRODES IN SAID MIXTURE; AND E. ADJUSTING THE AMOUNT OF THE LEACH COMPOUND ADDED TO SAID AQUEOUS CLAY SLURRY TO PROVIDE AN OXIDATIONREDUCTION POTENTIAL READING VALUE OF ABOUT -450 TO ABOUT -300 MILLIVOLTS, AS READ WITH A SATURATED CALOMEL CELL ELECTRODE AND A DITHIONITE-CONDITIONED PLATINUM ELECTRODE ASSEMBLY.

Claim 2

Dependent Claim 219 words

AN IMPROVED METHOD FOR CONTINUOUSLY LEACHING A DISPERSED KAOLIN CLAY AQUEOUS SLURRY FOR REMOVING COLOR IMPURITIES THEREIN TO PROVIDE KAOLIN CLAY PRODUCTS HAVING IMPROVED OPTICAL AND RHEOLOGICAL PROPERTIES WITH AN OPTIMUM AMOUNT OF LEACH COMPOUND, SAID METHOD COMPRISING: A. FORMING AN AQUEOUS SLURRY OF A FINELY DIVIDED KAOLIN CLAY; B. ADDING TO SAID AQUEOUS CLAY SLURRY A LEACHING COMPOUND CAPABLE OF REDUCING INSOLUBLE SALTS PRESENT IN SAID CLAY SLURRY TO A SOLUBLE FORM, SAID LEACHING COMPOUND COMPRISING A COMPOUND CONTAINING AN ACTIVE (S2O4) GROUP OR A COMPOUND CAPABLE OF LIBERATING SUCH GROUPS IN SAID SLURRY; C. ADJUSTING THE PH OF THE SLURRY TO BEETWEEN ABOUT 3.0 TO 4.5 BY THE ADDITION OF A SUFFICIENT AMOUNT OF A FLOCCULATING AGENT; D. MEASURING THE OXIDATION-REDUCTION POTENTIAL IN THE LEACH COMPOUND-CLAY SLURRY MIXTURE AT A SPECIFIED TIME PERIOD SELECTED AT LEAST 20 MINUTES AFTER SAID LEACH COMPOUND ADDITION, SAID OXIDATION-REDUCTION POTENTIAL BEING MEASURED BY INSERTING THE ELECTRODE ASSEMBLY OF AN OXIDATIONREDUCTION POTENTIOMETRIC CELL INTO SAID LEACH-CLAY SLURRY MIXTURE AND READING THE ELECTRIC POTENTIAL BETWEEN SAID ELECTRODES IN SAID MIXTURE; AND E. ADJUSTING THE AMOUNT OF THE LEACH COMPOUND ADDED TO SAID AQUEOUS CLAY SLURRY TO PROVIDE AN OXIDATIONREDUCTION POTENTIAL READING VALUE OF ABOUT -450 TO ABOUT -300 MILLIVOLTS, AS READ WITH A SATURATED CALOMEL CELL ELECTRODE AND A DITHIONITE-CONDITIONED PLATINUM ELECTRODE ASSEMBLY.

Claim 3

Dependent Claim 179 words

A continuous process for improving the leachIng of dispersed kaolin clay aqueous slurries with an optimum amount of leaching compound to provide kaolin clay products having improved optical and rheological properties, said method comprising: a. forming a flowing stream of an aqueous kaolin clay slurry; b. adding to said aqueous clay slurry a dithionite leaching compound to form a leach reaction mixture; c. adjusting the pH of the mixture to between about 3.0 and 4.5; d. measuring the oxidation-reduction potential in the mixture at a specified time period selected at least 20 minutes after addition of said leaching compound, said oxidation-reduction potential being measured by inserting the electrode assembly of an oxidation-reduction potentio-metric cell into said flowing stream and reading the electric potential between said electrodes; and e. adjusting the amount of the leaching compound added to said aqueous clay slurry to provide an oxidation-reduction potential reading value of about -450 to about -300 millivolts, as read with a saturated calomel cell electrode and a dithionite-conditioned platinum electrode assembly; whereby improved optical properties and dispersed clay viscosities are maintained.

Claim 4

Dependent Claim 179 words

A continuous process for improving the leachIng of dispersed kaolin clay aqueous slurries with an optimum amount of leaching compound to provide kaolin clay products having improved optical and rheological properties, said method comprising: a. forming a flowing stream of an aqueous kaolin clay slurry; b. adding to said aqueous clay slurry a dithionite leaching compound to form a leach reaction mixture; c. adjusting the pH of the mixture to between about 3.0 and 4.5; d. measuring the oxidation-reduction potential in the mixture at a specified time period selected at least 20 minutes after addition of said leaching compound, said oxidation-reduction potential being measured by inserting the electrode assembly of an oxidation-reduction potentio-metric cell into said flowing stream and reading the electric potential between said electrodes; and e. adjusting the amount of the leaching compound added to said aqueous clay slurry to provide an oxidation-reduction potential reading value of about -450 to about -300 millivolts, as read with a saturated calomel cell electrode and a dithionite-conditioned platinum electrode assembly; whereby improved optical properties and dispersed clay viscosities are maintained.

Claim 5

Dependent Claim 202 words

In a continuous method for producing kaolin clay products having improved optical properties which comprises forming a continuous flow stream of a dispersed kaolin clay aqueous slurry, leaching said slurry with dithionite leaching agent, adjusting the pH of the slurry to about 3.0 to 4.5, and dewatering the resultant slurry mixture to remove soluble salts, the improvement comprising: controlling the amount of leaching compound added to said aqueous clay slurry to thereby obtain a finished clay product having improved optical properties and viscosities upon dispersion with an optimum amount of leaching compound, the amount of said leaching compound added to said slurry being controlled by measuring the oxidation-reduction potential in the slurry mixture at a point in the continuous flow stream after a selected time period selected at least 20 minutes after addition of said leaching compound has elapsed, said oxidation-reduction potential being measured by inserting the electrode assembly of an oxidation-reduction potentiometric cell into said slurry mixture and reading the electric potential between said electrodes; and adjusting the amount of leaching compound added responsive to such measurement to maintain the potential between about -450 and -300 millivolts as measured with a saturated calomel cell electrode and a dithionite-conditioned platinum electrode assembly.

Claim 6

Dependent Claim 202 words

In a continuous method for producing kaolin clay products having improved optical properties which comprises forming a continuous flow stream of a dispersed kaolin clay aqueous slurry, leaching said slurry with dithionite leaching agent, adjusting the pH of the slurry to about 3.0 to 4.5, and dewatering the resultant slurry mixture to remove soluble salts, the improvement comprising: controlling the amount of leaching compound added to said aqueous clay slurry to thereby obtain a finished clay product having improved optical properties and viscosities upon dispersion with an optimum amount of leaching compound, the amount of said leaching compound added to said slurry being controlled by measuring the oxidation-reduction potential in the slurry mixture at a point in the continuous flow stream after a selected time period selected at least 20 minutes after addition of said leaching compound has elapsed, said oxidation-reduction potential being measured by inserting the electrode assembly of an oxidation-reduction potentiometric cell into said slurry mixture and reading the electric potential between said electrodes; and adjusting the amount of leaching compound added responsive to such measurement to maintain the potential between about -450 and -300 millivolts as measured with a saturated calomel cell electrode and a dithionite-conditioned platinum electrode assembly.

Claim 7

Dependent Claim 30 words

The improved method of claim 1, wherein: the oxidation-reduction potential in the leach compound-clay slurry mixture is measured at a time period of 20-50 minutes after said leach compound addition.

Claim 8

Dependent Claim 26 words

A process in accordance with claim 1, wherein: an aqueous clay slurry is formed containing from about 10 to about 35 percent by weight clay solids.

Claim 9

Dependent Claim 37 words

A process in accordance with claim 1 wherein said leaching compound is added to said aqueous clay slurry at a rate within the range of about 3 to about 10 pounds leach compound per ton of clay.

Claim 10

Dependent Claim 17 words

A process in accordance with claim 6 wherein said leaching compound is zinc dithionite or sodium dithionite.

Claim 11

Dependent Claim 30 words

The improved method of claim 2 wherein: the oxidation-reduction potential in the leach compound-clay slurry mixture is measured at a time period of 20-50 minutes after said leach compound addition.

Claim 12

Dependent Claim 26 words

A process in accordance with claim 2, wherein: an aqueous clay slurry is formed containing from about 10 to about 35 percent by weight clay solids.

Claim 13

Dependent Claim 37 words

A process in accordance with claim 2 wherein said leaching compound is added to said aqueous clay slurry at a rate within the range of about 3 to about 10 pounds leach compound per ton of clay.

Claim 14

Dependent Claim 30 words

The improved method of claim 3, wherein: the oxidation-reduction potential in the leach compound-clay slurry mixture is measured at a time period of 20-50 minutes after said leach compound addition.

Claim 15

Dependent Claim 26 words

A process in accordance with claim 3 wherein: an aqueous clay slurry is formed containing from about 10 to about 35 percent by weight clay solids.

Claim 16

Dependent Claim 37 words

A process in accordance with claim 3 wherein said leaching compound is added to said aqueous clay slurry at a rate within the range of about 3 to about 10 pounds leach compound per ton of clay.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1977-12-09	1978-06-10	1978-12-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1981-12-09	1982-06-10	1982-12-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1985-12-09	1986-06-10	1986-12-10	$7700.00	Window Closed / Lapsed

Controlling the leaching of kaolin clay

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