EP0377283A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Paper coating pigments
Assignee: Imerys Minerals Ltd
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Filing: 1989-11-29
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Granted: —
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Expires: 2009-11-29
Abstract
Abstract There is disclosed a process for preparing an aqueous suspension containing at least 50% by weight of a mixed pigment comprising a first pigment which releases into aqueous solution cations of valency greater than 1 and a second pigment, which process comprises: (a) forming first and second aqueous suspensions of each of the first and second pigments respectively, each of the first and second aqueous suspensions containing not greater than 50% by weight of the first and second pigments respectively; (b) combining the first and second suspensions to form a flocculated suspension; (c) mechanically dewatering the flocculated suspension formed in step (b) to form a cake; and (d) mixing the cake formed in step (c) with water containing a dispersing agent to form a suspension containing at least 50% on a dry weight basis, of the mixed pigments. Also disclosed is a process for preparing an aqueous paper coating composition.
Inventors
- 👤 Kenneth Michael Beazley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 04:24
CPC Classifications
D; D21; D21H; D21H21/00; D21H21/50; D21H21/52; C; C09; C09D; C09D17/00; C09D17/004; D21H19/00; D21H19/36; D21H19/38; D21H19/385; D21H19/40
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
135 words
A process for preparing an aqueous suspension containing at least 50% by weight of a mixed pigment comprising a first pigment which releases into aqueous solution cations of valency greater than 1 and a second pigment, which process comprises: (a) forming first and second aqueous suspensions of each of the first and second pigments respectively, each of the first and second aqueous suspensions containing not greater than 50% by weight of the first and second pigments respectively; (b) combining the first and second suspensions to form a flocculated suspension; (c) mechanically dewatering the flocculated suspension formed in step (b) to form a cake; and (d) mixing the cake formed in step (c) with water containing a dispersing agent to form a suspension containing at least 50% on a dry weight basis, of the mixed pigments.
Claim 2
Dependent Claim
135 words
A process for preparing an aqueous suspension containing at least 50% by weight of a mixed pigment comprising a first pigment which releases into aqueous solution cations of valency greater than 1 and a second pigment, which process comprises: (a) forming first and second aqueous suspensions of each of the first and second pigments respectively, each of the first and second aqueous suspensions containing not greater than 50% by weight of the first and second pigments respectively; (b) combining the first and second suspensions to form a flocculated suspension; (c) mechanically dewatering the flocculated suspension formed in step (b) to form a cake; and (d) mixing the cake formed in step (c) with water containing a dispersing agent to form a suspension containing at least 50% on a dry weight basis, of the mixed pigments.
Claim 3
Dependent Claim
21 words
A process according to claim 1, wherein the first pigment is one which releases into aqueous solution calcium or magnesium cations.
Claim 4
Dependent Claim
13 words
A process according to claim 2, wherein the first pigment is calcium sulphate.
Claim 5
Dependent Claim
26 words
A process according to any one of claims 1 to 3, wherein the second pigment is chosen from kaolin, natural or precipitated calcium carbonate or talc.
Claim 6
Dependent Claim
24 words
A process according to any one of claims 1 to 4, wherein the second aqueous suspension formed in step (a) is a deflocculated suspension.
Claim 7
Dependent Claim
39 words
A process according to any one of claims 1 to 5, wherein the first pigment has a particle size distribution such that from 60 to 75% by weight consists of articles having an equivalent spherical diameter smaller than 2microns.
Claim 8
Dependent Claim
34 words
A process according to any one of the preceding claims, wherein there is added to the mixed suspension formed in step (b) sufficient of an alkali to raise the pH to at least 9.
Claim 9
Dependent Claim
22 words
A process according to any one of the preceding claims, wherein there is added to the mixed pigments an anionic wetting agent.
Claim 10
Dependent Claim
32 words
A process according to claim 8, wherein the anionic wetting agent is added in an amount of from 0.1 to 1.5% by weight, based on the weight of the dry mixed pigments.
Claim 11
Dependent Claim
18 words
A process according to claim 8 or 9, wherein the anionic wetting agent is calcium dodecyl benzene sulphate.
Claim 12
Dependent Claim
48 words
A process according to any one of claims 8 to 10, wherein there is further added, to the aqueous suspension of mixed pigments formed in step (b), a defoamer in an amount of from 0.05 to 0.2% by weight, based on the weight of the dry mixed pigments.
Claim 13
Dependent Claim
66 words
A process according to any one of the preceding claims, wherein the first and second pigments are employed in amounts such as to provide, in the mixed suspension of pigments formed in step (b), from 1% by weight of the first pigment and 99% by weight of the second pigment to 75% by weight of the first pigment and 25% by weight of the second pigment.
Claim 14
Dependent Claim
26 words
A process according to any one of the preceding claims, wherein the aqueous suspension of first pigment employed in step (a) is in a flocculated state.
Claim 15
Dependent Claim
168 words
A process for preparing an aqueous paper coating composition containing at least 50% by weight of a mixed pigment comprising a first pigment which releases into aqueous solution cations of valency greater than 1 and a second pigment, which process comprises: (a) forming first and second aqueous suspensions of each of the first and second pigments respectively, each of the first and second aqueous suspensions containing not greater than 50% by weight of the first and second pigments respectively; (b) combining the first and second suspensions to form a flocculated suspension; (c) mechanically dewatering the flocculated suspension formed in step (b) to form a cake; (d) mixing the cake formed in step (c) with water containing a dispersing agent to form a suspension containing at least 50% on a dry weight basis, of the mixed pigments; and (e) combining with the suspension formed in step (d) an adhesive to form an aqueous paper coating composition containing at least 50%, on a dry weight basis, of the mixed pigments.
Claim 16
Dependent Claim
168 words
A process for preparing an aqueous paper coating composition containing at least 50% by weight of a mixed pigment comprising a first pigment which releases into aqueous solution cations of valency greater than 1 and a second pigment, which process comprises: (a) forming first and second aqueous suspensions of each of the first and second pigments respectively, each of the first and second aqueous suspensions containing not greater than 50% by weight of the first and second pigments respectively; (b) combining the first and second suspensions to form a flocculated suspension; (c) mechanically dewatering the flocculated suspension formed in step (b) to form a cake; (d) mixing the cake formed in step (c) with water containing a dispersing agent to form a suspension containing at least 50% on a dry weight basis, of the mixed pigments; and (e) combining with the suspension formed in step (d) an adhesive to form an aqueous paper coating composition containing at least 50%, on a dry weight basis, of the mixed pigments.
References Cited (Backward Citations)
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