# US 9,752,283 B2 · Anionic preflocculation of fillers used in papermaking

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- Number: US 9,752,283 B2
- Document ID: US9752283B2
- Status: Granted
- Kind: B2
- Application number: 14/330,839
- Filed: 2014-07-14
- Published: 2015-06-18
- Granted: 2017-09-05
- Earliest claimed: 2007-09-12
- Assignees: Ecolab USA Inc.
- Applicants: Nalco Company
- Inventors: Weiguo Cheng; Katherine M Broadus; Dorota Smoron; Shawnee M Wilson
- Web page: https://patentgrep.com/patent/US9752283B2

## CPC

- D21H 17/74: {of organic and inorganic material}
- D21H 17/375: {Poly(meth)acrylamide}
- D21H 17/67: Water-insoluble compounds, e.g. fillers, pigments
- D21H 17/675: {Oxides, hydroxides or carbonates}
- D21H 17/68: siliceous, e.g. clays
- D21H 17/69: modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
- D21H 21/18: Reinforcing agents
- D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR

## Abstract

A method of preparing a stable dispersion of flocculated filler particles for use in papermaking processes comprises use of an anionic first flocculating agent to an aqueous dispersion of filler particles, followed by addition of a second anionic flocculating agent to the dispersion and further optional shearing of the resultant filler flocs to the desired particle size resulting in shear resistant filler flocs with a defined and controllable size distribution.

## Claims

### Claim 1

A method of preparing a stable dispersion of flocculated filler particles having a specific particle size distribution for use in papermaking processes comprising:
a) adding a first flocculating agent to an aqueous dispersion of filler particles, the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles the first flocculating agent being anionic and having an RSV of at least 3 dL/g;
b) adding a second flocculating agent to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent wherein the second flocculating agent is anionic;
c) shearing the flocculated dispersion to provide a dispersion of filler flocs having the desired particle size; and
d) causing or allowing flocculation of the filler particles prior to adding them to a paper stock and wherein no paper stock is present during the flocculation.

### Claim 2 (depends on 1)

The method of claim 1, wherein the filler flocs have a median particle size of 10-100 μm.

### Claim 3 (depends on 1)

The method of claim 1, wherein the filler is selected from the group consisting of calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate and magnesium hydroxide.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first flocculating agent is a copolymer of acrylamide and sodium acrylate having an anionic charge of 5-75 mole percent and an RSV of at least 15 dL/g.

### Claim 6 (depends on 1)

The method of claim 1, wherein the filler particles are selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate and kaolin clay, and mixtures thereof.

### Claim 7 (depends on 1)

The method of claim 1, wherein the filler flocs have a median particle size of 10-70 μm.

### Claim 8 (depends on 1)

The method of claim 1, further comprising adding one or more microparticles to the flocculated dispersion after addition of the second flocculating agent.

### Claim 9 (depends on 1)

A method of making paper products from pulp comprising:
forming an aqueous cellulosic papermaking furnish,
adding an aqueous dispersion of filler flocs prepared according to the method of claim 1 to the furnish,
draining the furnish to form a sheet, and
drying the sheet.

### Claim 10 (depends on 1)

The method of claim 1, wherein the first flocculating agent comprises an anionic charge of greater than 50 mole % up to about 75 mole %.

### Claim 11 (depends on 1)

The method of claim 1, wherein the first flocculating agent comprises an anionic charge of about 75 mole %.

### Claim 12 (depends on 1)

The method of claim 1, wherein the filler flocs have a median particle size between 10 μm and less than 50 μm.

### Claim 13 (depends on 1)

The method of claim 1, wherein the filler flocs have a median particle size of about 10 μm.