US5043017A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Acid-stabilized calcium carbonate, process for its production and method for its use in the manufacture of acidic paper
Assignee: Minerals Technologies Inc
•
Filing: 1990-03-09
•
Granted: 1991-08-27
•
Expires: 2010-03-09
Abstract
Abstract A form of calcium carbonate, acid-stabilized by the addition to finely divided calcium carbonate of one of a calcium- chelating agent and a conjugate base, such as sodium hexametaphosphate, followed by the addition of a weak acid, such as phosphoric acid, is disclosed. A process for producing this material, and a method for its use in the making of neutral to acidic paper in order to improve the optical properties of the paper are also disclosed.
Inventors
- 👤 June D. Passaretti
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 02:15
CPC Classifications
C; C01; C01F; C01F11/00; C01F11/18; D; D21; D21H; D21H17/00; D21H17/63; D21H17/67; D21H17/69; C01F11/185; C09; C09C; C09C1/00; C09C1/02; C09C1/021; D21H17/675; C01P; C01P2004/00; C01P2004/10; C01P2004/11; C01P2004/60; C01P2004/61; C01P2004/62; C01P2006/00; C01P2006/12
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
79 words
An acid-stabilized finely divided calcium carbonate comprising a mixture of at least about 0.1 weight percent of a compound selected from the group consisting of a calcium-chelating agent and a conjugate base, together with at least about 0.1 weight percent of weak acid, with the balance to give 100 weight percent being finely divided calcium carbonate, such that the calcium carbonate is coated by and is in equilibrum with the calcium-chelating agent or conjugate base and the weak acid.
Claim 2
Dependent Claim
79 words
An acid-stabilized finely divided calcium carbonate comprising a mixture of at least about 0.1 weight percent of a compound selected from the group consisting of a calcium-chelating agent and a conjugate base, together with at least about 0.1 weight percent of weak acid, with the balance to give 100 weight percent being finely divided calcium carbonate, such that the calcium carbonate is coated by and is in equilibrum with the calcium-chelating agent or conjugate base and the weak acid.
Claim 3
Dependent Claim
38 words
The acid-stabilized finely divided calcium carbonate according to claim 1 wherein the weak acid is selected from the group consisting of phosphoric acid, metaphosphoric acid, hexametaphosphoric acid, citric acid, boric acid, sulfurous acid, acetic acid, and mixtures thereof.
Claim 4
Dependent Claim
23 words
The acid-stabilized finely divided calcium carbonate according to claim 1 wherein the conjugate base is an alkali metal salt of a weak acid.
Claim 5
Dependent Claim
18 words
The acid-stabilized finely divided calcium carbonate according to claim 3 wherein the alkali metal is sodium or calcium.
Claim 6
Dependent Claim
17 words
The acid-stabilized finely divided calcium carbonate according to claim 3 wherein the conjugate base is sodium hexametaphosphate.
Claim 7
Dependent Claim
57 words
The acid-stabilized finely divided calcium carbonate according to claim 1 wherein when the conjugate base is selected, the weak acid part thereof and the weak acid are the same or are different and are selected from the group consisting of phosphoric acid, metaphosphoric acid, hexametaphosphoric acid, citric acid, boric acid, sulfurous acid, acetic acid, and mixtures thereof.
Claim 8
Dependent Claim
24 words
The acid-stabilized finely divided calcium carbonate according to claim 6 wherein the conjugate base is sodium hexametaphosphate and the weak acid is phosphoric acid.
Claim 9
Dependent Claim
28 words
The acid-stabilized finely divided calcium carbonate according to claim 1 wherein the calcium-chelating agent is selected from the group consisting of sodium hexametaphosphate and common multi-dentate chelating ligands.
Claim 10
Dependent Claim
17 words
The acid-stabilized finely divided calcium carbonate according to claim 8 wherein the calcium-chelating agent is sodium hexametaphosphate.
Claim 11
Dependent Claim
39 words
The acid-stabilized finely divided calcium carbonate according to claim 8 wherein the common multi-denate chelating ligands are selected from the group consisting of include ethylene diamine tetra-acetic acid (EDTA), triethylene, tetramine, diethylene triamine, o-phenanthroline, oxalic acid, and mixtures thereof.
Claim 12
Dependent Claim
17 words
The acid-stabilized finely divided calcium carbonate according to claim 2 wherein the weak acid is phosphoric acid.
Claim 13
Dependent Claim
29 words
The acid-stabilized, finely divided calcium carbonate according to claim 1 wherein the calcium carbonate is selected from the group consisting of precipitated calcium carbonate and finely ground natural limestone.
Claim 14
Dependent Claim
30 words
The acid-stabilized, finely divided calcium carbonate according to claim 1 wherein the calcium-chelating agent or conjugate base is from about 1 to about 2 weight percent of the final mixture.
Claim 15
Dependent Claim
27 words
The acid-stabilized finely divided calcium carbonate according to claim 1 wherein the weak acid is from about 1 to about 4 weight percent of the final mixture.
Claim 16
Dependent Claim
104 words
A process for producing an acid-stabilized finely divided calcium carbonate comprising the steps of: a) forming a mixture by adding to finely divided calcium carbonate, at least about 0.1 weight percent, based on the dry weight of calcium carbonate, of a compound selected from the group consisting of a calcium-chelating agent and a conjugate base; b) adding at least about 0.1 weight percent of a weak acid, based on the dry weight of calcium carbonate, to the mixture to reduce the pH of the resulting final mixture to from about 5 to about 7; and c) agitating the final mixture to ensure uniform mixing.
Claim 17
Dependent Claim
104 words
A process for producing an acid-stabilized finely divided calcium carbonate comprising the steps of: a) forming a mixture by adding to finely divided calcium carbonate, at least about 0.1 weight percent, based on the dry weight of calcium carbonate, of a compound selected from the group consisting of a calcium-chelating agent and a conjugate base; b) adding at least about 0.1 weight percent of a weak acid, based on the dry weight of calcium carbonate, to the mixture to reduce the pH of the resulting final mixture to from about 5 to about 7; and c) agitating the final mixture to ensure uniform mixing.
Claim 18
Dependent Claim
34 words
The process according to claim 15 wherein the weak acid is selected from the group consisting of phosphoric acid, metaphosphoric acid, hexametaphosphoric acid, citric acid, boric acid, sulfurous acid, acetic acid, and mixtures thereof.
Claim 19
Dependent Claim
25 words
The process according to claim 15 wherein the calcium-chelating agent is selected from the group consisting of sodium hexametaphosphate and of common multi-dentate chelating ligands.
Claim 20
Dependent Claim
13 words
The process according to claim 17 wherein the calcium-chelating agent is sodium hexametaphosphate.
Claim 21
Dependent Claim
39 words
The acid-stabilized finely divided calcium carbonate according to claim 8 wherein the common multi-dentate chelating ligands are selected from the group consisting of include ethylene diamine tetra-acetic acid (EDTA), triethylene tetramine, diethylene triamine, o-phenanthroline, oxalic acid, and mixture thereof.
Claim 22
Dependent Claim
19 words
The process according to claim 15 wherein the conjugate base is an alkali metal salt of a weak acid.
Claim 23
Dependent Claim
14 words
The process according to claim 20 wherein the alkali metal is sodium or calcium.
Claim 24
Dependent Claim
53 words
The process according to claim 15 wherein when the conjugate base is selected, the weak acid part thereof and the weak acid are the same or are different and are selected from the group consisting of phosphoric acid, metaphosphoric acid, hexametaphosphoric acid, citric acid, boric acid, sulfurous acid, acetic acid and mixtures thereof.
Claim 25
Dependent Claim
13 words
The process according to claim 20 wherein the conjugate base is sodium hexametaphosphate.
Claim 26
Dependent Claim
20 words
The process according to claim 22 wherein the conjugate base is sodium hexametaphosphate and the weak acid is phosphoric acid.
Claim 27
Dependent Claim
28 words
The process according to claim 15 wherein the finely divided calcium carbonate is selected from the group consisting of a precipitated calcium carbonate and finely ground natural limestone.
Claim 28
Dependent Claim
29 words
The process according to claim 15 wherein the finely divided calcium carbonate is in a form selected from the group consisting of a dry powder and an aqueous slurry.
Claim 29
Dependent Claim
54 words
The process according to claim 26 wherein when the finely divided calcium carbonate is a dry powder, the calcium-chelating agent or conjugate base is in an aqueous solution and when the finely divided calcium carbonate is an aqueous slurry, the calcium-chelating agent or conjugate base is a solid or is in an aqueous solution.
Claim 30
Dependent Claim
28 words
The process according to claim 15 wherein the weak acid is in a form selected from the group consisting of pure liquid acid and an aqueous solution thereof.
Claim 31
Dependent Claim
26 words
The process according to claim 15 wherein the calcium-chelating agent or conjugate base is from about 1 to about 2 weight percent of the final mixture.
Claim 32
Dependent Claim
23 words
The process according to claim 15 wherein the weak acid is from about 1 to about 4 weight percent of the final mixture.
Claim 33
Dependent Claim
15 words
The acid stabilized finely divided calcium carbonate produced according to the process of claim 15.
Claim 34
Dependent Claim
39 words
The acid-stabilized finely divided calcium carbonate according to claim 8 wherein the common multi-dentate chelating ligands are selected from the group consisting of include ethylene diamine tetra-acetic acid (EDTA), triethylene tetramine, diethylene triamine, o-phenanthroline, oxalic acid, and mixtures thereof.
References Cited (Backward Citations)
US3704158A
Cited
US4115187A
Cited
US3873336A
Cited
US4219590A
Cited
US4175066A
Cited
US4793985A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-26 | 1995-02-25 | 1995-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-26 | 1999-02-25 | 1999-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-26 | 2003-02-25 | 2003-08-27 | $7700.00 | Window Closed / Lapsed |