A method for treating starch in pulp, paper and board making processes

• US 20190024306A1
• Filed: 08/26/2016
• Published: 01/24/2019
• Est. Priority Date: 08/27/2015
• Status: Active Grant

• Current Assignee: Kemira Oyj
• Original Assignee: Kemira Oyj
• Inventors: Hietaniemi, Matti, Ekman, Jaakko, Karppi, Asko, Kolari, Marko
• Granted Patent: US 10,640,923 B2
• Time in Patent Office: Days
• CPC Class Codes: D21C 5/005 Treatment of cellulose-containing material with microorganisms or enzymes
• CPC Class Codes: D21C 5/02 Working-up waste paper mechanical part D21B1/08, D21B1/32
• CPC Class Codes: D21H 11/14 Secondary fibres working-up waste paper D21C5/02
• CPC Class Codes: D21H 17/375 Poly(meth)acrylamide
• CPC Class Codes: D21H 17/43 Carboxyl groups or derivatives thereof
• CPC Class Codes: D21H 17/455 comprising tertiary amine or being at least partially quaternised
• CPC Class Codes: D21H 21/18 Reinforcing agents
• CPC Class Codes: D21H 21/36 Biocidal agents, e.g. fungicidal, bactericidal, insecticidal agents
• CPC Class Codes: Y02W 30/64 Paper recycling

Abstract

The invention relates to a method for treating starch in pulp, paper and board making processes, in which processes recycled fibre material is used as raw material wherein the recycled fibre material is pulped in a pulper and obtaining a pulp flow comprising an aqueous phase and at least recycled fibres and starch dispersed in the aqueous phase. The method comprising the following steps: —adding amylase enzyme inhibitor and/or at least one biocide to pulp flow or to an aqueous process flow comprising starch for preventing starch degradation, and—adding an amphoteric polymer obtained by copolymerisation of (meth)acrylamide with cationic and anionic monomers to pulp flow or to an aqueous process flow comprising starch for binding starch to the fibres.

Claims

1. A method for treating starch in pulp, paper and board making processes, in which processes recycled fibre material is used as raw material wherein the recycled fibre material, such as paper, board and/or broke, is pulped in a pulper and obtaining a pulp flow comprising an aqueous phase and at least recycled fibres and starch dispersed in the aqueous phase,

wherein the method comprising the following steps:

adding amylase enzyme inhibitor and/or at least one biocide to pulp flow or to an aqueous process flow comprising starch for preventing starch degradation, and

adding an amphoteric polymer obtained by copolymerisation of (meth)acrylamide with cationic and anionic monomers, which amphoteric polyacrylamide has the mass average molecular weight over 1 500 000 g/mol, to pulp flow or to an aqueous process flow comprising starch for binding starch to the fibres.

2. The method according to claim 1, wherein the starch is a low molecular weight starch comprising an acid or enzyme modified surface size starch.

3. The method according to claim 1, wherein the mass average molecular weight of the amphoteric polyacrylamide is in the range of 1 500 000-6 000 000 g/mol, preferably 2 500 000-4 500 000 g/mol, and more preferably 2 700 000-4 300 000 g/mol.

4. The method according to claim 1, wherein the net charge of the amphoteric polyacrylamide is cationic.

5. The method according to claim 1, wherein 10-90%, preferably 30-90%, more preferably 50-85%, even more preferably 60-80%, of the charged groups in the amphoteric polyacrylamide are cationic.

6. The method according to claim 1, wherein the total ionicity of the amphoteric polyacrylamide is in the range of 2-70 mol-%, preferably 2-50 mol-%, more preferably 4-30 mol-% and even more preferably 6-10 mol-%.

7. The method according to claim 1, wherein the cationic groups in the amphoteric polyacrylamide originate from monomers selected from 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl] trimethylammonium chloride (ADAM-Cl), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADAM-Cl), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryloylamino)propyl] trimethylammonium chloride (APTAC), [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC) and diallyldimethyl¬

ammonium chloride (DADMAC).

8. The method according to claim 1, wherein the anionic groups in the amphoteric polyacrylamide originate from monomers selected from unsaturated mono- or dicarboxylic acids, such as acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid, isocrotonic acid, angelic acid or tiglic acid.

9. The method according to claim 1, wherein amylase enzyme inhibitor comprises zinc ions.

10. The method according to claim 1, wherein

at least one cationic coagulant is added to pulp flow or to an aqueous process flow comprising starch for improving starch retention.

11. The method according to claim 10, wherein the cationic coagulant is selected from the group comprising:

bentonite, colloidal silica and conventional papermaking fixatives, such as polydiallyldimethylammonium chloride (poly-DADMAC) or polyamines, polyvinyl amine (PVAm), cationic polyacrylamide (C-PAM), polyethyleneimine (PEI), polyamidoamine-epichlorohydrin (PAAE), polyaluminum chloride, alum, methacrylamidopropyltrimethylammonium chloride (MAPTAC) or their mixtures.

12. The method according to claim 1, wherein biocide and/or amylase enzyme inhibitor are added simultaneously with the amphoteric polymer to pulp flow or process flow.

13. The method according to claim 1, wherein biocide and/or amylase enzyme inhibitor are added prior to the addition of said amphoteric polymer to pulp flow or process flow.

14. The method according to claim 1, wherein amphoteric polymer is added to the broke system, pulp, pulp storage tanks, to the water entering the pulper or into the pulper, water storage tanks or to pipe line before the broke or pulp storage tanks.

15. The method according to claim 1, wherein at least one coagulant is added simultaneously with the amphoteric polymer or after the addition of said amphoteric polymer to pulp flow or process flow.