# US 2017/0284028 A1 · Sizing composition, its use and a method for producing paper, board or the like

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- Number: US 2017/0284028 A1
- Document ID: US20170284028A1
- Status: Published application
- Kind: A1
- Application number: 15/508,961
- Filed: 2015-09-04
- Published: 2017-10-05
- Earliest claimed: 2014-09-04
- Assignees: Kemira Oyj
- Applicants: Kemira Oyj
- Inventors: Matti HIETANIEMI; Jan-Luiken HEMMES; Vladimir GRIGORIEV; Asko KARPPI
- Web page: https://patentgrep.com/patent/US20170284028A1

## CPC

- D21H 21/16: Sizing or water-repelling agents
- D21H 11/14: Secondary fibres (working-up waste paper D21C5/02)
- D21H 17/28: Starch
- D21H 17/29: cationic
- D21H 17/37: Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
- D21H 17/375: {Poly(meth)acrylamide}
- D21H 19/54: Starch
- D21H 21/18: Reinforcing agents
- D21H 23/04: Addition to the pulp; After-treatment of added substances in the pulp
- D21H 23/22: Addition to the formed paper
- 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

The invention relates to a composition for sizing of a surface of paper, board or the like and its use for increasing strength properties of paper, board or the like. The composition has a solids content of 3-30%, and it comprises degraded non-ion is starch, and at least 0.5 weight-% of anionic polyacrylamide, which has a molecular weight, MW, >500 000 g/mol and <2 500 000 g/mol and an anionicity in the range of 4-35 mol-%. The invention further relates also to a method for producing paper, board or the like, which comprises addition of a first strength composition, which comprises a cationic agent, to a fibre stock, formation of a fibrous web from the fibre stock, drying of the fibrous web to dryness of at least 60%, and application of a second strength com position, which comprises an anionic hydrophilic polymer and a starch component, on the surface of the fibrous web.

## Claims

### Claim 1

Sizing composition for sizing of a surface of paper, board or the like, the sizing composition having a solids content of 3-30% and comprising
degraded non-ionic starch, and
at least 0.5 weight-% of anionic polyacrylamide, which has an average molecular weight, MW, >500 000 g/mol and <2 500 000 g/mol, and an anionicity in the range of 4-35 mol-%.

### Claim 2 (depends on 1)

Composition according to claim 1, characterised in that the anionic polyacrylamide has the average molecular weight in the range of 530 000-2 000 000 g/mol, preferably 530 000-1 500 000 g/mol, more preferably 650 000-1 400 000 g/mol.

### Claim 3 (depends on 1, 2)

Composition according to claim 1 or 2, characterised in that the anionic polyacrylamide has the anionicity in the range of 4-24 mol-%, preferably 4-17 mol-%, more preferably 5-17 mol-%.

### Claim 4 (depends on 3)

Composition according to claim 3, characterised in that the anionic polyacrylamide has anionicity in the range of 7-15 mol-%, preferably 9-13 mol-%.

### Claim 5 (depends on 1, 2, 3, 4)

Composition according to any of claims 1-4, characterised in that the anionic polyacrylamide is a copolymer of acrylamide and unsaturated carboxylic acid monomers, such as (meth)acrylic acid, maleic acid, crotonic acid, itaconic acid or their mixture.

### Claim 6 (depends on 1, 2, 3, 4, 5)

Composition according to any of preceding claims 1-5, characterised in that the composition comprises 0.5-10 weight-%, preferably 0.75-5 weight-%, preferably 1-2.5 weight-%, of anionic polyacrylamide.

### Claim 7 (depends on 1, 2, 3, 4, 5, 6)

Composition according to any of preceding claims 1-6, characterised in that the starch is enzyme treated or thermally degraded starch.

### Claim 8 (depends on 1, 2, 3, 4, 5, 6, 7)

Composition according to any of preceding claims 1-7, characterised in that the starch, prior to its possible degradation, has an amylose content of 15-30%, preferably 20-30%, more preferably 24-30%.

### Claim 9 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

Composition according to any of preceding claims 1-8, characterised in that the composition is free from inorganic mineral fillers or pigments.

### Claim 10 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9)

Use of sizing composition according to any of claims 1-9 for increasing strength properties of paper, board or the like.

### Claim 11 (depends on 10)

Use according to claim 10, characterised in that the paper, board or the like comprises recycled fibres.

### Claim 12 (depends on 10, 11)

Use according to claim 10 or 11, characterised in that the paper or board is selected from uncoated fine paper, liner, fluting or folding boxboard (FBB).

### Claim 13 (depends on 10, 11, 12)

Use according to any of claim 10, 11 or 12, characterised in that the paper or board has an ash content of at least 6%, preferably at least 12%, more preferably at least 15%.

### Claim 14 (depends on 10, 11, 12, 13)

Use according to any of preceding claims 10-13, characterised in that the application temperature of the sizing composition is 50-90° C., preferably 65-85° C.

### Claim 15 (depends on 10, 11, 12, 13, 14)

Use according to any of preceding claims 10-14, characterised in that the sizing composition is applied 5-80 kg/ton paper as dry, preferably 10-50 kg/ton paper as dry.

### Claim 16

Method for producing paper, board or the like, which method comprises
adding a first strength composition, which comprises a cationic agent, to a fibre stock,
forming a fibrous web from the fibre stock,
drying the fibrous web to dryness of at least 60%,
applying on the surface of the fibrous web a second strength composition, which comprises an anionic hydrophilic polymer and a starch component.

### Claim 17 (depends on 16)

Method according to claim 16, characterised in that the cationic agent in the first strength composition comprises cationic starch or at least one cationic synthetic polymer or a mixture of cationic starch and cationic synthetic polymer(s).

### Claim 18 (depends on 17)

Method according to claim 17, characterised in that the cationic synthetic polymer is selected from a group comprising copolymers of (meth)acrylamide and cationic monomers; glyoxylated polyacrylamide; polyvinylamine; N-vinyl formamide; copolymer of acrylamide and diallyldimethylammonium chloride (DADMAC); polyamidoamine epihalohydrin and any of their mixtures.

### Claim 19 (depends on 17, 18)

Method according to claim 17 or 18, characterised in that the cationic synthetic copolymer is a copolymer originating from >20 mol-% of non-ionic monomers and 3-30 mol-%, preferably 5-20 mol-%, more preferably 6-10 mol-%, of cationic monomers.

### Claim 20 (depends on 17, 18, 19)

Method according to claims 17-19, characterised in that the cationic synthetic polymer has an average molecular weight of 200 000-6 000 000 g/mol, preferably 300 000-3 000 000 g/mol, more preferably 500 000-2 000 000 g/mol, even more preferably 600 000-950 000 g/mol.

### Claim 21 (depends on 16, 17, 18, 19, 20)

Method according to any of preceding claims 16-20, characterised in that the cationic agent has charge density of 0.05-5 meq/g, preferably 0.1-3 meq/g, more preferably 0.3-2 meq/g, even more preferably 0.5-1.4 meq/g, at pH 7.

### Claim 22 (depends on 16, 17, 18, 19, 20, 21)

Method according to any of claims 16-21, characterised in adding the first strength composition to the fibre stock in amount of 0.2-15 kg/ton, preferably 0.4-9 kg/ton produced paper, more preferably 1-5 kg/ton produced paper, calculated as dry product.

### Claim 23 (depends on 16, 17, 18, 19, 20, 21, 22)

Method according to any of claims 16-22, characterised in that the second strength composition comprises 0.1-20 weight-%, preferably 0.5-10 weight-%, more preferably 0.7-4 weight-% of anionic hydrophilic polymer, and 80-99.9 weight-%, preferably 90-99 weight-%, more preferably 96-99 weight-% of starch.

### Claim 24 (depends on 16)

Method according to claim 16, characterised in that the anionic hydrophilic polymer is a copolymer of (meth)acrylamide and an anionic monomer.

### Claim 25 (depends on 24)

Method according to claim 24, characterised in that the anionic monomer is selected from unsaturated mono- or dicarboxylic acids.

### Claim 26 (depends on 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)

Method according to any of preceding claims 16-25, characterised in that the anionic hydrophilic polymer of the second strength agent has an average molecular weight of 50 000-8 000 000 g/mol, preferably 150 000-3 000 000 g/mol, more preferably 250 000-1 500 000 g/mol, even more preferably 350 000-950 000 g/mol.

### Claim 27 (depends on 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)

Method according to any of preceding claims 16-26, characterised in that the anionic hydrophilic polymer of the second strength agent originates from >20 mol-% of non-ionic monomers and 1-50 mol-%, preferably 2-25 mol-%, more preferably 4-17 mol-%, of anionic monomers.

### Claim 28 (depends on 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)

Method according to any of preceding claims 16-27, characterised in that the fibre stock comprises at least 10-30%, more preferably 11-19% of inorganic mineral filler, measured by ash content at 525° C.

### Claim 29 (depends on 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)

Method according to any of preceding claims 16-28, characterised in that the fibre stock comprises at least 20 weight-%, preferably at least 50 weight-%, of fibres originating from recycled paper or board.

### Claim 30 (depends on 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)

Method according to any of claims 16-29, characterised in applying the second strength composition on the fibre web in such amount that the anionic hydrophilic polymer is applied on the web in amount of 0.1-5 kg/t, preferably 0.2-3 kg/t, more preferably 0.5-2 kg/t.