Browse Prior Art Database

REDUCING CONTENT OF HEXENURONIC ACIDS IN CELLULOSIC PULP

IP.com Disclosure Number: IPCOM000239344D
Publication Date: 2014-Oct-31

Publishing Venue

The IP.com Prior Art Database

Related People

Henrik Lund, Klaus Skaalum Lassen, Bjoern Lennart Pierre Alexander Cassland, Pedro Emanuel Garcia Loureiro: INVENTOR

Abstract

The present invention provides an enzymatic method for reducing the content of hexenuronic acids in a chemical cellulosic pulp and/or improvement of the brightness of cellulosic pulp using haloperoxidase.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 6% of the total text.

Page 01 of 34

12524-WO-PCT

REDUCING CONTENT OF HEXENURONIC ACIDS IN CELLULOSIC PULP

Reference to a Sequence Listing

    This application contains a Sequence Listing in computer re adable form. The computer readable form is incorporated herein by reference.

5

FIELD OF THE INVENTION

    This invention generally relates to enzymatic reduction of hexenuronic acids from a chemical cellulosic pulp and/or improvement of the brightness of cellulosic pulp. A second aspect relates to an enzymatic method for the improvement of the brightness of cellulosic pulp

10

without reducing the content of hexenuronic acids in the cellulosic pulp.

BACKGROUND

    Wood comprises several different components: cellulose; hemicelluloses, such as xylan; lignin and extractives. During chemical pulping for instance in a kraft, i.e. sulphate, pulp mill the

15

xylan chain forms side groups ca lled hexenuronic acids (HexAs) which are unsaturated sugars. The amount of HexAs varies from pulp to pulp, because different wood species contain different amounts of xylan, which can be transformed into HexAs during the cooking process. Also, cooking parameters contribute to different amounts of HexAs.

The process of kraft pulping comprises alkaline cooking and bleaching, and it begins wit h 20

wood handling where wood is debarked and made into chips. The chips are screened so fine material and oversized chips are eliminated. The chips are then fed to a digester where they first are treated with steam and then with cooking liquid, while the temperature is raised to the desired cooking temperature. When desired rate of delignification is achieved, cooking is interrupted and the content in the digester is moved to a blow ta nk and onwards to a screener.

25

After the pulp is screened it is washed several times and pumped to the following delign ification stage, i.e. initial bleaching. The cooking chemicals are recov ered in the chemical recovery plant.

    The main target for chemical pulping process is delignifica tion in order to liberate the fibres without harming them. Alkaline delignification occurring during cooking is alkaline hydrolyses of phenol ether bonds that make lignin soluble. Phenols are weak acids that

30

dissociate in alkali environment (pH >10). The lignin will be partly demethylated by nucleophilic attack of sulfide ions on methoxyl groups in lignin. Bleaching of the obtained pulp comprises typically a number of discrete steps or stages. In the oxygen delignification, which may occur either as pre-bleaching or bleaching step, more lignin is diss olved and washed away. This is also the case in the different following bleaching stages; peroxide bleaching, ozone bleaching

35

and chlorine dioxide bleaching. Finally the pulp is moved to the papermaking process in

1


Page 02 of 34

12524-WO-PCT

integrated pulp and paper mills or it is traded as market pulp after the drying machine where it is dried, cut and packed for further transportation to paper mills.

    Oxygen delignification occurring in...