CA2803650A1

CA2803650A1 - Cellulosic fibre composition

Info

Publication number: CA2803650A1
Application number: CA2803650A
Authority: CA
Inventors: Jeroen Jansen; Anette Monica Heijnesson-Hulten; Marcel Cornelis Paulus Van Eijk; Boen Ho O; Gerard Henk Beijers; Ronald Christopher Lai; Peter Marten Van Der Horst; Jerker Nilsson
Original assignee: Akzo Nobel Chemicals International BV
Current assignee: Nouryon Chemicals International BV
Priority date: 2010-07-12
Filing date: 2011-07-08
Publication date: 2012-01-19
Also published as: CN102971462A; EP2593603A1; AU2011278462A1; WO2012007363A1; BR112013000141A2; TW201213421A; JP2013531749A; KR20130132381A

Abstract

The invention relates to a composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25, and a length weighted mean fibre length up to 1,100 µm and a length weighted mean fibre width over 10 µm, or a length weighted mean fibre length up to 1,100 µm, and wherein at least 50 % by weight of the cellulosic material is insoluble in water, or a length weighted mean fibre length / width ratio up to 30, or a length weighted mean fibre width over 35 µm. The invention also relates to a composition comprising cellulosic fibres having a specific surface area of at least 1.5 m2/g, a length weighted mean fibre length / width ratio up to 30, and a dry solids content of at least 5 % by weight, based on the weight of the composition, or up to 30 % by weight, based on the total weight of the cellulosic fibres, of cellulosic fibres with a length weighted mean fibre length up to 100 µm. Method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres to chemical treatment and mechanical treatment, wherein the chemical treatment comprises treating cellulosic fibres with (i) at least one agent containing a carboxyl group, optionally substituted, (ii) at least one oxidant and at least one transition metal, or (iii) at least one nitroxyl radical, and the mechanical treatment comprises subjecting cellulosic fibres to extrusion with a twin-screw extruder or a planetary roller extruder. The invention also relates to a method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 to extrusion. The invention also relates to a composition comprising cellulosic fibres obtainable by the methods, a process for producing a cellulosic pulp mixture which comprises mixing the composition with cellulosic pulp, a cellulosic pulp mixture obtainable by the process, and the use of the composition and cellulosic pulp mixture as an additive in the production of paper and board, processes for producing paper and board in which the composition or cellulosic pulp mixture is used, paper and board obtainable by the processes, and various uses of the paper and board.

Description

CELLULOSIC FIBRE COMPOSITION

Field of the Invention The present invention relates to a cellulosic fibre composition, a method of making a cellulosic fibre composition, the use of a cellulosic fibre composition in the production of paper and board, a process for making a cellulosic pulp mixture in which a cellulosic fibre composition is used, the use of a pulp mixture for making paper and board, a process for producing paper and board in which a cellulosic fibre composition or pulp mixture is used, paper and board comprising a cellulosic fibre composition or pulp mixture and various uses of paper and board comprising a cellulosic fibre composition or pulp mixture.
Background of the Invention Strength is important to cellulosic products like paper and board, and increasing the strength of such products provides several benefits. For instance, increasing the strength of paper makes it possible to increase filler loadings and reduce virgin fibre usage, thereby reducing raw material costs in paper making processes. Similarly, increasing the strength of board makes it possible to reduce the grammage while maintaining the strength properties of cellulosic products made from the board, which also leads to savings in virgin fibre usage and reduced transportation costs, thus environmental and economic benefits.

A wide variety of additives for improving the strength of paper and board are known in the art, including natural and synthetic polymers, modified fillers, modified cellulosic fibres, etc. One example of modified cellulosic fibres is microfibrillar cellulose, which is obtained from cellulosic fibres that have been delaminated to small fragments with a large proportion of the microfibrils of the fibre walls uncovered. WO 00/47628, WO 2004/055268, WO
2007/001229 and WO 2008/076056 disclose microfibrillar cellulose, methods for preparing same and use of same as an additive in the production of a paper product. WO

discloses microfibrillar cellulose comprising anionic charge which may be used in a papermaking machine to increase the rate of drainage and/or dewatering during paper manufacture and to improve strength of a sheet of paper.

However, there are still some problems associated with modified cellulosic fibres like microfibrillar cellulose and the use thereof in paper and board making processes. While it has been experienced that the use of such products as strength additives in papermaking processes may provide good or even improved initial drainage and/or dewatering in the wet end of the paper machine, it has also been experienced that modified cellulosic fibres like microfibrillar cellulose may absorb and retain a substantial amount of water. These characteristics may lead to higher water content of the cellulosic web entering the press and drying sections of the machine, thereby requiring more energy to remove the remaining water and dry the cellulosic web and/or reducing the paper machine speed and productivity.

Modified cellulosic fibres like microfibrillar cellulose may also contain a substantial amount of fines, i.e. very small cellulosic fibres and fibre fragments. Cellulosic fines are generally difficult to retain in paper and board making processes, which may lead to accumulation of the fines in the white water that is re-circulated in the processes. These problems may be alleviated or solved by reducing the drainage rate, increasing the dosage of retention aids and/or co-using or increasing the dosage of cationic coagulants, e.g. low molecular weight, highly cationic, organic polymers and aluminium compounds.
Modified cellulosic fibres like microfibrillar cellulose may also be difficult to produce, and the methods for producing them may be complicated and provide modified cellulosic fibres in low yields or at low dry solids contents.

Accordingly, there is still a need of cellulosic fibre compositions which impart high strength to paper and board and provide improvements in the manufacture of paper and board, in particular in terms drainage and retention performance, drying of paper and board, and productivity. There is also a need of improved methods for producing cellulosic fibre compositions which impart high strength to paper and board.
Summary of the Invention It is an object of the present invention to provide a cellulosic fibre composition, preferably a high concentration cellulosic fibre composition, which imparts high or increased strength to paper and board. It is another object to provide a cellulosic pulp mixture which provides paper and board with high or increased strength. It is another object to provide a process for producing paper and board which makes use of such a cellulosic fibre composition or cellulosic pulp mixture. By using the composition or mixture in the production of paper and board, e.g. in making multi ply board grades, it is possible to reduce virgin fibre usage and lower the grammage while maintaining the strength properties, which leads to reduced raw material and transportation costs and environmental and economic benefits.

It is another object of the invention to provide a cellulosic fibre composition and a cellulosic pulp mixture, preferably high concentration products, which do not absorb or retain a substantial amount of water. By using the composition or mixture in the production of paper and board it is possible to maintain or increase the speed of drying the cellulosic web obtained when it is fed through the press section of the paper or board making machine. Hereby the present invention leads to improvements in paper and board making processes and increased productivity.

It is a further object of the invention to provide a cellulosic fibre composition and a cellulosic pulp mixture, preferably high concentration products, which have a low or reduced content of fines. By using the composition or mixture in the production of paper and board it is possible to reduce the amount of fines that are re-circulated in the process.
It is also possible to reduce the amount of cationic coagulants and/or drainage and retention aids used in the process, and to run paper and board making machines at higher drainage rates without substantial impairment of the white water quality.
Hereby the present invention leads to improvements in paper and board making processes and increased productivity.

It is yet another object of the invention to provide a method for the production of a cellulosic fibre composition, preferably a process that renders possible production of a cellulosic fibre composition at high productivity and/or as a high-concentration product, whereby concentration steps and/or transportation of dilute low-concentration products can be avoided and the above advantages can be achieved.

Accordingly, in one aspect, the present invention relates to a composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25, a length weighted mean fibre length up to 1,100 pm and a length weighted mean fibre width over 10 pm.

In another aspect, the present invention relates to a composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25, a length weighted mean fibre length up to 1,100 pm, and wherein at least 50 % by weight of the cellulosic material is insoluble in water.

In another aspect, the present invention relates to a composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 and a length weighted mean fibre length / width ratio up to 30.

In another aspect, the present invention relates to a composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 and a length weighted mean fibre width over 35 pm.
In another aspect, the present invention relates to a composition comprising cellulosic fibres having a specific surface area of at least 1.5 m2/g, a length weighted mean fibre length / width ratio up to 30 and a dry solids content of at least 5 % by weight, based on the weight of the composition.
In another aspect, the present invention relates to a composition comprising cellulosic fibres having a specific surface area of at least 1.5 m2/g, a length weighted mean fibre length / width ratio up to 30, and up to 30 % by weight, based on the total weight of the cellulosic fibres, of cellulosic fibres with a length weighted mean fibre length up to 100 pm.
In another aspect, the present invention relates to a method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres to chemical treatment and mechanical treatment, wherein the chemical treatment comprises treating cellulosic fibres with (i) at least one agent containing a carboxyl group, optionally substituted, (ii) at least one oxidant and at least one transition metal, or (iii) at least one nitroxyl radical, and the mechanical treatment comprises subjecting cellulosic fibres to extrusion with a twin-screw extruder or a planetary extruder.

In another aspect, the present invention relates to a method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 to extrusion.

In another aspect, the invention relates to the composition comprising cellulosic fibres obtainable by the methods of the invention. In another aspect, the present invention relates to the use of the composition comprising cellulosic fibres in the production of paper and board, usually as an additive and, in particular, as a strength additive.

In another aspect, the present invention relates to a process for producing a cellulosic pulp mixture which comprises mixing the composition comprising cellulosic fibres with cellulosic pulp. In another aspect, the present invention relates to the cellulosic pulp mixture obtainable by the process, and to the use of the cellulosic pulp mixture in the production of paper and board. In another aspect, the present invention relates to a process for producing paper and board which comprises forming an aqueous suspension comprising the cellulosic pulp mixture and dewatering the obtained suspension.

In another aspect, the present invention relates to a process for producing paper and 5 board which comprises adding the composition comprising cellulosic fibres to an aqueous cellulosic pulp suspension and dewatering the obtained suspension. In another aspect, the present invention relates to a process for producing paper and board which comprises mixing a composition comprising cellulosic fibres subjected to extrusion with cellulosic pulp.
In another aspect, the present invention relates to paper and board containing the composition comprising cellulosic fibres or cellulosic pulp mixture, and to paper and board obtainable by the processes of the invention.

In another aspect, the present invention relates to various board grades, and to the production thereof. In another aspect, the present invention relates to various uses of the paper and board, e.g. for packaging of beverages and liquid food.

These and other objects and aspects of the invention will be described in further detail hereinafter.

Brief Description of the Drawing Fig. 1 is a side view of the configuration of an extruder screw.
Detailed Description of the Invention The composition comprising cellulosic fibres of the invention, herein also referred to as "the cellulosic fibre composition" or "the composition", contains cellulosic fibres which can be derived from a wide variety of sources including wood fibres, non-wood fibres and mixtures thereof.

Wood fibres may be derived from hardwood and softwood, e.g. from chemical pulps, mechanical pulps, thermo-mechanical pulps, chemical thermo-mechanical pulps, recycled fibres and newsprint. Examples of suitable wood fibres include birch, beech, aspen, e.g.
European aspen, alder, eucalyptus, maple, acacia, mixed tropical hardwood, pine, e.g.

loblolly pine, fir, hemlock, larch, spruce, e.g. Black spruce or Norway spruce, and mixtures thereof.

Non-wood fibres may be derived from seed fibres, e.g. cotton linters, seed hull fibres, e.g.
soybean hulls, pea hulls and corn hulls, bast fibres, e.g. flax, hemp, jute, ramie and kenaf, leaf fibres, e.g. manila hemp and sisal hemp, stalk and straw fibres, e.g.
bagasse, corn and wheat, grass fibres, e.g. bamboo and reed canary grass, cellulosic fibres from algae, e.g. velonia, bacteria and fungi, and parenchymal cells, e.g. vegetables such as sugar beets, and fruits, e.g. citrus fruits such as lemons, limes, oranges and grapefruits.
The cellulosic fibres of the composition may or may not contain ionic groups.
According to one preferred embodiment, the cellulosic fibres of the composition are free or essentially free from anionic groups, e.g. the cellulosic fibres of the composition have an average degree of substitution of anionic groups of below 0.001. According to another preferred embodiment, the cellulosic fibres of the composition have an average degree of substitution of anionic groups of from 0.001, usually from about 0.01, or from about 0.02, up to 0.25, or up to about 0.20, usually up to about 0.15, or up to 0.10, or up to about 0.05. At these low degrees of substation, the cellulosic fibres are preferably dispersible in water, but not water-soluble. The term "average degree of substitution", or "DS" as used herein, means the average number of anionic groups, or substituent groups, per anhydroglucose unit of cellulose. The degree of substitution of anionic groups can be determined by the methods of ASTM D1439-03 and conductometric titration as described by S. Katz, R.P. Beatson and A.M. Scallan in Svensk Papperstidning No. 6/1984, pp. 48-53.
Examples of suitable anionic groups include carboxyl groups and substituted carboxyl groups, e.g. carboxyalkyl groups such as carboxymethyl groups. The counter-ion of the anionic group is usually an alkali metal or alkaline earth metal, e.g. sodium or potassium, suitably sodium. The carboxyl group can be illustrated by the formula -COO-Na+, and the carboxymethyl group by the formula -CH2OO0- Na+. Examples of suitable cellulosic fibres of the composition of the invention include carboxylated cellulosic fibres and carboxyalkylated cellulosic fibres, e.g. carboxymethylated cellulosic fibres, having a degree of substitution as defined above.

The cellulosic fibre composition of the invention may contain both water-soluble cellulosic material and water-insoluble cellulosic material. In one embodiment, at least 50, or at least 70, preferably at least 80 or at least 85 % by weight of the cellulosic material present in the composition is insoluble in water, measured on an aqueous cellulosic composition containing 1 % by weight of cellulosic material at 20 C. The water-insoluble material is usually swellable and dispersible in water.

The cellulosic fibres of the composition of the invention may have a specific surface area of at least 1.5, or at least about 2, usually at least about 3 m2/g, and the specific surface area may be up to about 150, usually up to about 50, up to about 15, or up to about 10 m2/g. The specific surface area is determined by adsorption of N2 at 177 K according to the BET method using a Micromeritics TriStar 3000 instrument, which operates according to ISO
9277:1995.
The cellulosic fibres of the composition of the invention may have a length weighted mean fibre length of from about 150, or from about 200, usually from about 300 pm, and the length weighted mean fibre length may be up to about 2,000, usually up to about 1,500, or up to about 1,100, usually up to about 1,000, or up to about 800 pm; and they may have a length weighted mean fibre width of from about 10, usually from about 15 pm, and the length weighted mean fibre width may be up to about 60, usually up to about 50, or up to about 45, usually up to about 30 pm. In one embodiment, the cellulosic fibres of the composition of the invention have length weighted mean fibre width over 35 pm, or from about 40, up to about 60, or up to about 50. The cellulosic fibres of the composition of the invention may have a length weighted mean fibre length / width ratio up to about 40, or up to about 35, usually up to about 30, or up to about 25, and the length weighted mean fibre length / width ratio may be at least about 5, or at least about 10, usually at least about 12. The length weighted mean fibre length and length weighted mean fibre width, as referred to herein, are measured by means a Fiber Tester of Lorenzen & Wettre, Sweden, which operates according to ISO 16065-2:2007, and the length weighted mean length / width ratio is calculated from such data.

The cellulosic fibre composition of the invention may contain fines in an amount of from about 1, or from about 2, usually from about 5 % by weight, based on the total weight of the cellulosic fibres, and the composition may contain fines in an amount of up to about 40, or up to about 35, usually up to about 30 % by weight, based on the total weight of the cellulosic fibres. The term "fines", as used herein, means cellulosic fibres having a length weighted mean fibre length up to 100 pm.

The cellulosic fibre composition of the invention may have a dry solids content of at least about 0.1, or at least about 0.5, usually at least about 5, or at least about 10, or at least about 15 % by weight, and the dry solids content may be up to about 90, or up to about 70, usually up to about 50, or up to about 45 % by weight, based on the total weight of the composition. As the dry solids of the composition usually consist or essentially consist of cellulosic fibres, the composition may have a cellulosic fibre content which is the same as the dry solids content stated above. The remainder of the cellulosic fibre composition may be water.

According to a preferred embodiment, the method of producing the cellulosic fibre composition of the invention comprises subjecting cellulosic fibres to chemical treatment and mechanical treatment. The chemical treatment may be carried out prior to or simultaneously with the mechanical treatment, usually prior to the mechanical treatment.
Cellulosic fibres for use in the method can be derived from a wide variety of sources including wood fibres, non-wood-fibres and mixtures thereof, as further defined above in respect of the cellulosic fibre composition of the invention.

According to another preferred embodiment, the method of producing the cellulosic fibre composition of the invention comprises subjecting cellulosic fibres having anionic groups to mechanical treatment, wherein the cellulosic fibres may have anionic groups and an average degree of substitution of anionic groups as defined above in respect of the cellulosic fibre composition of the invention. The cellulosic fibres for use in the process can be derived from a wide variety of sources including wood fibres, non-wood-fibres and mixtures thereof, as further defined above in respect of the cellulosic fibre composition of the invention, and cellulosic fibres suitable for use in the process can be provided by any method for introducing anionic groups in cellulose that is known in the art.

In one embodiment, the chemical treatment of the invention comprises treating cellulosic fibres with at least one agent containing a carboxyl group, optionally substituted, which chemical treatment is suitably carried out with an amount of the agent containing a carboxyl group, optionally substituted, and any compounds that are co-used as defined below so as to achieve the desired degree of substitution, which can be determined by the method defined above in respect of the cellulosic fibre composition of the invention. In another embodiment, the chemical treatment of the invention comprises treating the cellulosic fibres with at least one oxidant and at least one transition metal.
In yet another embodiment, the chemical treatment of the invention comprises treating the cellulosic fibres with at least one nitroxyl radical.
Examples of suitable agent containing a carboxyl group, optionally substituted, include carboxylating agents and carboxyalkylating agents. Examples of suitable carboxyalkylating agents include chloroacetic acid, e.g. monochloroacetic acid, and salts thereof, suitably the sodium salt. The treatment may be conducted under alkaline conditions by contacting the cellulosic fibres with strong alkali, e.g. sodium hydroxide, and the agent containing a carboxyl group. These reagents may be applied to the cellulosic fibres separately or together. The reaction is conveniently performed in an aqueous system which comprises a water-miscible organic solvent, e.g. ethanol or isopropanol, to suppress swelling and dissolution of carboxyalkylated cellulose. Reference may be made to WO 94/16746, WO 00/47628 and US 6,548,730 for a general discussion of the reaction between cellulosic fibres and agents containing a carboxyl group, optionally substituted, e.g. carboxyalkylating agents like monochloroacetic acid, and further methods for carboxyalkylation include those disclosed in US 4,634,438, US 4,634,439 and WO
95/19795, which are all hereby incorporated herein by reference.

Examples of suitable oxidants include radical generating oxidants, e.g.
inorganic or organic peroxy compounds, ozone, ozonides, e.g. dimethyloxiran, halogen (e.g.
chlorine or bromine) containing oxidants, and oxygen, preferably inorganic peroxy compounds such as those selected from hydrogen peroxide and hydrogen peroxide generating compounds like alkali metal salts of percarbonate, perborate, peroxysulfate, peroxyphosphate or peroxysilicate, or corresponding weak acids, preferably hydrogen peroxide. Examples of suitable organic peroxy compounds include peroxy carboxylic acids, e.g. peracetic acid and perbenzoic acid, and hydroperoxides, e.g.
isopropyl cumyl hydroperoxide, 1,1,3,3-tetramethyl butyl hydroperoxide, cumyl hydroperoxide, t-butyl hydroperoxide and t-amyl hydroperoxide. Examples of suitable halogen containing oxidants include alkali metal chlorite, alkali metal hypochlorite, chlorine dioxide and chloro sodium salt of cyanuric acid. It is also possible to use ultrasonic sound or photo or electro Fenton reactions, i.e. in situ generation of hydroxyl radicals by radiation or electric currents. The oxidant may be used in the treatment an amount of from about 0.05 to about 5, usually from about 0.1 to about 3 % by weight, based on the weight of the cellulosic fibres.
Examples of suitable transition metals include iron, copper, manganese, tungsten, molybdenum, tin, chromium and combinations thereof, preferably iron. The transition metal is suitably used in ionic form, e.g. Fee+, and it may be used in the form of a salt, e.g.
FeS04, or complex with common complexing agents, e.g. EDTA, DTPA, phosphates or complexing agents based on phosphoric acid, oxalic acid, ascorbic acid, nitrite acetate, garlic acid, fulvic acid or polyoxomethalates. The amount of transition metal used depends on the amount of oxidant used and in most cases it is from about 0.000001 to about 20, or from about 0.00001 to about 10, usually from about 0.0001 to about 1 % by weight, based on the weight of the oxidant. The transition metal, suitable in ionic form, can be added to the cellulosic fibres before, after or simultaneously with adding the oxidant, for example in the form of an aqueous solution.

Examples of suitable nitroxyl radicals include the 2,2,6,6-tetramethyl piperidine-1-oxyl (TEMPO) radical and derivatives thereof, e.g. 4-hydroxy-TEMPO. In the treatment with the nitroxyl radical, one or more compounds are preferably co-used. Examples of such one or more compounds include sodium hypochlorite (NaCIO), e.g. as disclosed by Saito, 10 Kimura, Nishiyama and Isogai; Biomacromolecules 2007, 8, 2485-2491, the disclosure of which is hereby incorporated herein by reference, and sodium bromide. The nitroxyl radical may be used in the treatment in an amount of from about 0.05 to about 5, usually from about 0.1 to about 3 % by weight, based on the weight of the cellulosic fibres. Each of the compounds that are preferably co-used with the nitroxyl radical in the treatment can be used in an amount of from about 1 to about 20 % by weight, based on the weight of the cellulosic fibres, suitably sodium hypochlorite is used in an amount of from about 3 to about 20 % by weight and sodium bromide is used in an amount of from about 2 to about 10 % by weight.

In the chemical treatment, the cellulosic fibres may be dispersed in water, alcohol or any other suitable liquid, usually in an aqueous suspension. The dry solids content of the aqueous suspension of cellulosic fibres in the chemical treatment may be from about 1, or from about 5, usually from about 10, up to about 60, or up to about 50, usually up to about 40 % by weight, based on the total weight of the suspension.
Further additives that may be used in the chemical treatment include mineral acids, e.g.
hydrochloric acid and sulphuric acid, or sodium hydroxide, and the chemical treatment may be carried out at a pH from about 1 to about 10. In one embodiment, e.g.
when using at least one oxidant and at least one transition metal, the chemical treatment may be carried out at acidic or neutral pH from about 1 to about 8, or from about 2 to about 6, usually from about 3 to about 5. In another embodiment, e.g. when using a nitroxyl radical or an agent containing a carboxyl group, optionally substituted, e.g. a carboxyalkylating agent, the chemical treatment may be carried out at alkaline pH from about 8 to about 10.
The chemical treatment may be carried out for about 10 to about 120, or from about 20 to about 80, usually from about 40 to about 60 minutes, and the temperature may be from about 5, usually from about 20, or from about 60, up to about 100, usually to about 80, or up to about 30 C. In one embodiment, e.g. when using at least one oxidant and at least one transition metal, the temperature may be from about 20 to about 100, usually from about 60 to about 80 C. In another embodiment, e.g. when using the nitroxyl radical, the temperature may be from about 5, usually around about 20, up to about 30 C.

In one embodiment, the cellulosic fibres are subjected to a chemical treatment at a dry solids content of from about 1 to about 50 % by weight with from about 0.1 to about 3 %
by weight of H202 as the oxidant, based on the weight of dry cellulosic fibres, and an aqueous solution of about 0.00001 to about 10 % by weight of FeSO4 as the transition metal, based on the weight of the oxidant, during from about 20 to about 80 minutes at from about 70 to about 95 C at a pH from about 3 to about 5.

In another embodiment, the cellulosic fibres are subjected to a chemical treatment at a dry solids content of from about 1 to about 50 % by weight with from about 0.1 to about 3 %
by weight of TEMPO, from about 3 to about 20 % by weight of NaCIO, and from about 2 to 10 % by weight of sodium bromide, during from about 20 to about 80 minutes at from about 5 to about 30 C at a pH from about 9 to about 10, where the amounts of chemicals are based on the weight of dry cellulosic fibres.

When the chemical treatment is carried out prior to the mechanical treatment, the cellulosic fibre composition obtained by the chemical treatment may be washed one or more times with water and/or solvents to remove any chemicals, diluted with water and/or dried or concentrated to a dry solids content suitable for the subsequent mechanical treatment.

The mechanical treatment of the invention comprises subjecting cellulosic fibres to extrusion by using one or more extruders, and the extrusion may be continuous or batch-wise. In the mechanical treatment, when subjected to extrusion, the cellulosic fibres may have a dry solids content of from about 5, or from about 8, usually from about 10, or from about 15, up to about 70, usually up to about 55, or up to about 50, often up to about 45, or up to about 40 % by weight. The remainder of the cellulosic fibre composition may be water.

Examples of suitable extruders for use in the process include twin-screw extruders, or double shaft extruders. The screws may be co-rotating or counter rotating, preferably co-rotating. The screws may have one or more screw elements, including conveying, mixing and kneading elements, along the length of the extruder. Other examples of suitable extruders include planetary roller extruders, also referred to as planetary mixers. The planetary roller extruder usually has a central main spindle and from 4 to 20 rolling planetary spindles. The length of the screw of twin-screw extruders, or the main spindle /
barrel of planetary roller extruders, may be at least about 3, or at least about 5, usually at least about 10, or at least about 15 times the diameter of the screw or main spindle /
barrel, and the length may be up to about 70, or up to about 60, usually up to about 50 times the diameter of the screw or main spindle / barrel. The diameter of the screw or main spindle is usually at least about 15 mm and may be up to about 150 mm or even higher. Preferably, the extruder comprises one or more kneading elements. The extruder may have a flexible screw configuration with intermeshing screw elements that can be assembled into several conveying, mixing and kneading sections. Hereby the cellulosic fibres may be fed into the extruder, passed through alternating sets of transport, mixing and kneading sections until the kneaded cellulosic fibres are ejected. The cellulosic fibres may be passed through the extruder one or more times. In the process, the cellulosic fibres are preferably subjected to shearing and kneading forces. The extrusion may be carried out at a temperature of from about 20 to about 100, usually from about 40 to about 80 C. The extruder or parts thereof, e.g. one or more barrels, may be subjected to cooling during the extrusion process. Twin-screw extruders and planetary roller extruders are commercially available from several manufacturers such as Buhler, Berstorff, e.g.
Berstorff ZE 25 and Berstorff ZE 40, Bottenfeld Extrusionstechnik, and Entex, e.g. Extex PLWE100.

The cellulosic fibres and the composition thereof obtained by these chemical and/or mechanical treatment steps of the invention may have a specific surface area, length weighted mean fibre length, length weighted mean fibre width, length weighted mean fibre length / width ratio, fines content, dry solids content, degree of substitution of anionic groups and cellulosic fibre content as defined above in respect of the cellulosic fibre composition of the invention.

It is also possible to further dry or concentrate the cellulosic fibre composition by suitable drying techniques, e.g. freeze drying, etc., to higher dry solids contents, e.g. up to about 90 % by weight. Hereby transportation of the obtained cellulosic fibre composition may be simplified. It is also possible to add water to or dilute the cellulosic fibre composition to a dry solids content lower than about 10 % by weight, e.g. from about 0.1 to about 10, usually from about 0.5 to about 5 % by weight. Hereby the use of the obtained cellulosic fibre composition may be simplified, e.g. for mixing with an aqueous cellulosic pulp suspension for use in paper and board making.

The invention also relates to the use of the cellulosic fibre composition of the invention or obtained by the method of the invention in the production of paper and board.
The invention also relates to the use of a composition comprising cellulosic fibres subjected to extrusion, as described above, as an additive in the production of paper and board, wherein the composition subjected to extrusion may have or may not have been subjected to chemical treatment, as described above. Paper and board can be produced from an aqueous suspension comprising the cellulosic fibre composition. Preferably, the cellulosic fibre composition is used as an additive to an aqueous cellulosic pulp suspension to impart strength to paper and board produced from the resulting aqueous cellulosic pulp suspension. The cellulosic fibre composition may be mixed with or added to the cellulosic pulp suspension in an amount of from about 0.1 to about 25, suitably from about 0.5 to about 15, or from about 1 to 10, usually from about 2 to about 8 % by weight, calculated as dry cellulosic fibres of the composition on dry cellulosic pulp.

The invention further relates to a process for producing a cellulosic pulp mixture which comprises mixing the cellulosic fibre composition of the invention or obtained by the method of the invention with cellulosic pulp.

The cellulosic pulp can be derived from a wide variety of sources including wood fibres, non-wood fibres and mixtures thereof. Examples of suitable wood and non-wood fibres include those defined above in respect of the cellulosic fibre composition of the invention.
Preferably, the cellulosic pulp is derived from wood fibres such as hardwood, softwood and mixtures thereof, and preferably comprising softwood fibres.

The cellulosic pulp may be derived from chemical pulp, e.g. sulfate and sulfite pulp, organosolv pulp, recycled fibers, and/or mechanical pulp including e.g.
refiner mechanical pulp (RMP), pressurized refiner mechanical pulp (PRMP), pretreatment refiner chemical alkaline peroxide mechanical pulp (P-RC APMP), thermo-mechanical pulp (TMP), thermo-mechanical chemical pulp (TMCP), high-temperature TMP (HT-TMP) RTS-TMP, alkaline peroxide pulp (APP), alkaline peroxide mechanical pulp (APMP), alkaline peroxide thermomechanical pulp (APTMP), thermopulp, groundwood pulp (GW), stone groundwood pulp (SGW), pressure groundwood pulp (PGW), super pressure groundwood pulp (PGW-S), thermo groundwood pulp (TGW), thermo stone groundwood pulp (TSGW), chemi-mechanical pulp (CMP), chemirefinermechanical pulp (CRMP), chemithermo-mechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), sulfite-modified thermo-mechanical pulp (SMTMP), reject CTMP (CTMPR), groundwood CTMP (G-CTMP), semichemical pulp (SC), neutral sulfite semi chemical pulp (NSSC), high-yield sulfite pulp (HYS), biomechanical pulp (BRMP), pulps produced according to the OPCO process, explosion pulping process, Bi-Vis process, dilution water sulfonation process (DWS), sulfonated long fibers process (SLF), chemically treated long fibers process (CTLF), long fiber CMP
process (LFCMP), and modifications and combinations thereof. The pulp may be a bleached or non-bleached pulp.

The cellulosic fibre composition may be mixed with or added to the cellulosic pulp in an amount of from about 0.1 to about 25, suitably from about 0.5 to about 15, or from about 1 to 10, usually from about 2 to about 8 % by weight, calculated as dry cellulosic fibres of the composition on dry cellulosic pulp.

In one embodiment, the mixing is made in a substantially dry state. The mixing of the cellulosic fibre composition with the cellulosic pulp may be made to form a cellulosic pulp mixture, which may have a dry solids content of at least about 10, usually at least about 15, usually from about 20, up to about 90, or up to about 50 % by weight, based on the total weight of the cellulosic pulp mixture. The remainder of the cellulosic pulp mixture may be water. The cellulosic pulp mixture may be added to or mixed with water to form an aqueous suspension comprising the cellulosic pulp mixture and then dewatering the obtained suspension. The aqueous suspension may have a dry solids content of up to about 10 % by weight, e.g. from about 0.1, or from about 0.2, usually from about 0.3, up to about 10, or up to about 8, up to about 6, usually up to about 5 % by weight, based on the total weight of the cellulosic pulp mixture.

In another embodiment, the mixing is made in a substantially wet state. The mixing of the cellulosic fibre composition with the cellulosic pulp may be made to form a cellulosic pulp mixture in the form of an aqueous suspension and then dewatering the obtained suspension. The process may comprise adding the cellulosic fibre composition to an aqueous cellulosic pulp suspension and dewatering the obtained suspension. The aqueous suspension may have a dry solids content of up to about 10 % by weight, e.g.
from about 0.1, or from about 0.2, usually from about 0.3, up to about 10, or up to about 8, up to about 6, usually up to about 5 % by weight, based on the total weight of the cellulosic pulp mixture.

Preferably, the cellulosic pulp mixture is used in the production of paper and board wherein the cellulosic pulp mixture may constitute at least part of the cellulosic pulp used in the process, usually the total amount of cellulosic pulp used in the process. Preferably, when producing paper and board, an aqueous suspension comprising the cellulosic pulp mixture is formed and then dewatered. Various additives may be introduced in the aqueous suspension comprising the cellulosic pulp mixture prior to dewatering, including the additives and their addition levels as defined below in respect of the process for producing paper and board of the invention, in particular one or more drainage and 5 retention aids.

The invention further relates to a process for producing paper and board which comprises providing an aqueous suspension comprising the cellulosic fibre composition according to the invention or produced according to the process of the invention and dewatering the 10 obtained suspension. The invention further relates to a process for producing paper and board which comprises adding the cellulosic fibre composition according to the invention or produced according to the process of the invention to an aqueous suspension comprising cellulosic pulp and dewatering the obtained suspension. The invention further relates to a process for producing paper and board which comprises mixing a composition 15 comprising cellulosic fibres subjected to extrusion, as described above, with cellulosic pulp, wherein the composition subjected to extrusion may have or may not have been subjected to chemical treatment, as described above. Preferably, in the process, use is made of an aqueous suspension of the cellulosic fibre composition. The cellulosic pulp used in the process may be derived from the cellulosic pulp defined above.
Examples of suitable wood and non-wood fibres include those defined above in respect of the cellulosic fibre composition of the invention. Preferably, the cellulosic pulp is derived from wood fibres such as hardwood, softwood and mixtures thereof, and preferably comprising softwood fibres.

In the process, the cellulosic fibre composition can be added to the cellulosic pulp suspension in an amount of from about 0.1 to about 25, suitably from about 0.5 to about 15, or from about 1 to 10, usually from about 2 to about 8 % by weight, calculated as dry cellulosic fibres of the composition on dry cellulosic pulp.

Further additives may also be used in the process of the invention, and they may be added to the cellulosic fibre composition, to the aqueous suspension comprising the cellulosic fibre composition, to the aqueous suspension comprising cellulosic pulp and/or to the aqueous suspension comprising the cellulosic pulp mixture, usually to the aqueous suspension comprising cellulosic fibre composition and/or cellulosic pulp and/or cellulosic pulp mixture. Examples of suitable further additives include one or more drainage and retention aids, cationic coagulants, dry strength agents, wet strength agents, e.g.
polyamine-epichlorohydrin and polyamidoamine-epichlorohydrin based resins, optical brightening agents, dyes, sizing agents, e.g. rosin-based sizing agents, styrene acrylates and cellulose-reactive sizing agents, e.g. alkyl and alkenyl ketene dimers and multimers, and alkenyl succinic anhydrides, etc.

The further additives preferably comprise one or more drainage and retention aids. The expression "drainage and retention aid", as used herein, refers to one or more additives which, when added to an aqueous cellulosic suspension, give better drainage and/or retention than is obtained when not using said one or more additives. The one or more drainage and retention aids may comprise anionic polymers, cationic polymers, siliceous materials and combinations thereof, preferably at least one cationic polymer.
Examples of suitable anionic polymers include anionic polyacrylamide and anionic naphthalene-formaldehyde condensation polymers, e.g. anionic naphthalene sulfonates.
Examples of suitable cationic polymers include cationic polysaccharides, e.g. cationic starches, and cationic synthetic polymers, e.g. cationic polyacrylamides, cationic poly(diallyldimethyl-ammonium chlorides), cationic polyethylene imines, cationic polyamines and cationic polyamidoamines. The weight average molecular weight of the anionic and cationic polymers may be above about 5,000, or above about 10,000, usually above about 1,000,000 g/mole.
The upper limit is not critical; it can be about 50,000,000 g/mole, usually 30,000,000 g/mole.

Examples of suitable siliceous materials include anionic silica-based particles and anionic clays of the smectite type, e.g. bentonite. Preferably, the siliceous material has particles in the colloidal range of particle size. Anionic silica-based particles, i.e.
particles based on Si02 or silicic acid, are preferably used and such particles are usually supplied in the form of aqueous colloidal dispersions, so-called sols. Examples of suitable silica-based particles include colloid-al silica and different types of polysilicic acid, either homopolymerised or co-polymerised, for example polymeric silicic acid, polysilicic acid microgel, polysilicate and polysilicate microgel.
The silica-based sols can be modified and contain other elements, e.g.
aluminum, boron, magnesium, nitrogen, zirconium, gallium, titanium and the like, which can be present in the aqueous phase and/or in the silica-based particles.
Examples of preferred drainage and retention aids for use in the process include cationic starches, cationic polyacrylamides, anionic polyacrylamides, anionic siliceous materials and combinations thereof. Examples of suitable combinations of drainage and retention aids comprise (i) cationic starch and anionic siliceous material, preferably silica-based particles, (ii) cationic polyacrylamide and anionic siliceous material, preferably silica-based particles, (iii) cationic starch, cationic polyacrylamide and anionic siliceous material, preferably silica-based particles, (iv) cationic polyacrylamide, anionic polyacrylamide and anionic siliceous material, preferably silica-based particles, and (v) cationic starch, anionic polyacrylamide and anionic siliceous material, preferably silica-based particles.

The one or more drainage and retention aids can be added to the suspension in amounts which can vary within wide limits depending on, inter alia, type and number of additives, type of suspension, point of addition, etc. When used, the anionic polymers are usually added in an amount of at least 0.001, often at least 0.005 % by weight, based on dry weight of the suspension, and the upper limit is usually 3 and suitably 1.5 % by weight.
When used, the cationic polymers are usually added in an amount of at least about 0.001, often at least about 0.005 % by weight, based on dry weight of the suspension, and the upper limit is usually about 3 and suitably about 1.5 % by weight. When used, the siliceous materials are usually added in an amount of at least about 0.001, often at least about 0.005 % by weight, based on dry weight of the suspension, and the upper limit is usually about 1.0 and suitably about 0.6 % by weight.
The drainage and retention aids can be added in conventional manner and in any order.
When using a siliceous material, it is common to add a cationic polymer before adding the siliceous material, even if the opposite order of addition may also be used.
It is further common to add a cationic polymer before a shear stage, which can be selected from pumping, mixing, cleaning, etc., and to add the siliceous material after that shear stage.
Examples of suitable coagulants include organic and inorganic coagulants.
Examples of suitable organic coagulants include low molecular weight cationic polymers, e.g. homo and copolymers of diallyl dimethyl ammonium chloride (DADMAC), polyamines, polyamideamines, polyethylene imines, and dicyandiamide condensation polymers having a molecular weight in the range of from 1,000 to 700,000, suitably from 10,000 to 500,000. Examples of suitable inorganic coagulants include aluminium compounds, e.g.
alum and polyaluminium compounds, e.g. polyaluminium chlorides, polyaluminium sulpha-tes, polyaluminium silicate sulphates and mixtures thereof.
When used, the coagulant is preferably added prior to adding the one or more drainage and retention aids. The cationic coagulant can be added in an amount of at least about 0.001, or from about 0.05, usually from about 0.1, up to about 3.0, usually up to about 2.0 % by weight, calculated as dry coagulant on dry suspension, When used, each of the dry strength agent, wet strength agent and sizing agent as defined above can be added to the suspension in an amount of from about 0.01 to about 1, usually from about 0.1 to about 0.5 % by weight, calculated as dry agent on dry suspension.

The process of the invention may comprise the use of mineral fillers of conventional types, e.g. kaolin, china clay, titanium dioxide, gypsum, talc and natural and synthetic calcium carbonates, e.g. chalk, ground marble and precipitated calcium carbonate.

The process may produce single ply paper or board in which the cellulosic fibre composition, as defined herein, is distributed throughout the paper or board, preferably substantially uniformly distributed throughout the paper and board. Single ply paper and board contain just one ply or layer containing cellulosic fibres.

The process may also produce multi ply paper and board comprising two or more plies or layers containing cellulosic fibres wherein at least one of said two or more plies or layers comprises the cellulosic fibre composition, as defined herein. Preferably, the cellulosic fibre composition is distributed throughout at least one of said two or more plies, more preferably substantially uniformly distributed throughout at least one of said two or more plies. Multi ply board according to the invention can be produced by forming at least one ply comprising the cellulosic fibres composition, as defined herein, and attaching said at least one ply to one or more plies containing cellulosic fibres to form the multi ply board.
For example, multi ply board can be produced by forming the individual plies or layers separately in one or several web-forming units and then couching them together in the wet state. Examples of suitable grades of multi ply board of the invention include those comprising from two to seven plies or layers comprising cellulosic fibres and wherein at least one of said plies or layers comprises the cellulosic fibre composition, as defined herein, preferably one or more of the middle (internal) plies or layers.

In the process of the invention, the board, e.g. single or multi ply board, can be subjected to further process steps. Examples of suitable process steps include coating, e.g. starch coating and pigment coating, creasing, printing and cutting. Accordingly, examples of suitable boards of the invention include coated board, e.g. starch and/or pigment coated, and printed board.

The term "board, as used herein, refers to board comprising cellulosic fibres including solid board, e.g. solid bleached sulphate board (SBS) and solid unbleached sulphate board (SUS), paper board, carton board, e.g. folding boxboard (FBB), folding carton board, liquid packaging board (LPB), including all types of aseptic, non-aseptic autoclavable packaging boards, white lined chipboard (WLC), unbleached kraftboard, grey chipboard and recycled board, liner board and container board, including white sulphate kraftliner, fully bleached kraftliner, testliner, white sulphate testliner, unbleached kraftliner, unbleached testliner and recycled liner, fluting and corrugated fluting. The board may have a grammage of at least about 130, usually at least about 140 or at least about 150 g/m2, and it may be up to about 1,400, or up to about 1,300 g/m2. The board may have a bulk density of at least about 120, usually at least about 150, or at least about 200 kg/m3, and it may be up to about 1,400, usually up to about 800, or up to about 600 kg/m3.

The invention further relates to a method for producing a packaging material which comprises providing board comprising one or more plies comprising the cellulosic fibres composition, as defined herein, and subjecting the board to one or more converting operations selected from printing, varnishing, coating, e.g. plastics coating, extrusion coating and barrier coating, laminating, e.g. plastic film laminating and metal foil laminating, e.g aluminium foil laminating, metallizing, die cutting, i.e.
stamping out blanks, creasing, scoring, stripping, i.e. removal or debris, blanking, i.e.
separation of blanks, foil blocking, embossing and folding. The term "creasing", as used herein, is also referred to as scoring and grooving. Usually, the method includes one or more converting operations comprising scoring or creasing, more preferably two or more operations comprising scoring or creasing, for example cutting and scoring or creasing.

The invention also relates to a packaging material comprising board which comprises one or more plies comprising the cellulosic fibre composition, as defined herein, wherein it further comprises one or more creases. The creases, also referred to as scores, grooves or folding lines, make it easier to fold and erect the packaging material prior to filling. The packaging materials of the invention can have one or more layers of plastic film, metal foil, e.g. aluminium, and/or barrier coating.

The invention further relates to a procedure of making a package which comprises providing a blank of packaging material comprising board comprising one or more plies comprising the cellulosic fibre composition, as defined herein, filling the blank with a solid or liquid content to obtain an unsealed package, and then sealing the obtained package.
Preferably the packaging material comprises one or more grooves, creases or scores. The term "blank", as used herein, means an unfilled package or packaging material.
Preferably the blank is folded and erected prior to filling. Examples of suitable methods for sealing include gluing and heat sealing. The invention further relates to a procedure of making a package which comprises providing a reel of packaging material comprising board comprising one or more plies comprising the cellulosic fibre composition, as defined herein, whereupon the reel of packaging material is introduced into a filling machine, filled with a solid or liquid content, sealed and cut into separate packages which may be folded to the desired shape.

Examples of suitable solid and liquid contents include solid and liquid foodstuffs, e.g.
tomato products, soup, cream, chocolate and cereals, beverages, e.g. milk, fruit juice, wine and water, pharmaceuticals, cosmetics, cigarettes, tobacco and detergents. In one embodiment, the invention further comprises sterilizing the package and/or the solid or 10 liquid content. The term "sterilizing", as used herein, means reducing the number of microorganisms. Examples of suitable methods and means for sterilization include heat, e.g. rapid heating and cooling, chemicals, e.g. ozone and hydrogen peroxide, irradiation, e.g. IR and UV irradiation. The filling can be made under high hygiene or sterile conditions.
The invention also relates to a packaging comprising board comprising one or more plies containing the cellulosic fibre composition, as defined herein, wherein it further comprises a solid or liquid content. The invention further relates to uses of the packaging material comprising board, which comprises one or more plies containing the cellulosic fibre composition, as defined herein, for packaging of solid or liquid foodstuffs, beverages, pharmaceuticals, cosmetics, cigarettes, tobacco or detergents.

Examples of suitable packaging of the invention include foodstuff packaging, beverage packaging, sterile packaging and aseptic packaging.
Examples The invention is further illustrated in the following examples which, however, are not intended to limit the same. Parts and % relate to parts by weight and % by weight, respectively, and all suspensions are aqueous, unless otherwise stated.

Chemical and mechanical treatments were conducted as described below. When both treatments were conducted, the chemical treatment was conducted before the mechanical treatment:
Chemical Treatment 1 Chemical treatment 1 (referred to as "CT1") was carried out using cellulosic fibres at a dry solids content of 10 % by weight with 40 ppm Fe +2 (added as FeSO4) and 1 %
H202, based on the weight of dry cellulosic fibres, at pH 4 (adjusted with H2SO4) and a temperature of 70 C for 30 min.
Chemical Treatment 2 Chemical treatment 2 (referred to as "CT2") was carried out as in Chemical Treatment 1 except that the amount of H202 used was 0.1 % by weight, based on the weight of dry cellulosic fibres, and the temperature was 90 C

Chemical Treatment 3 Chemical treatment 3 (referred to as "CT3") was carried out using cellulosic fibers at a dry solid content of 2 % by weight with 1 ,6 % by weight TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical), based on the weight of dry cellulosic fibers, and 10 %
by weight of NaBr and 3.7 % by weight of NaCIO, based on the weight of dry cellulosic fibers, at pH 10 (adjusted with NaOH) and temperature of 20 C for 60 min.

Chemical Treatment 4 Chemical treatment 4 (referred to as "CT4") was carried out by treating cellulosic fibers with monochloroacetic acid under alkaline conditions according to the general procedure for preparation of carboxymethyl cellulose disclosed by WO 00/47628. By using varying amounts of reactants, cellulosic compositions having different degrees of substitution of anionic / carboxymethyl groups were obtained.

Mechanical Treatment 1 Mechanical treatment 1 (referred to as "MT1" in the tables below) was carried out using untreated or chemically treated cellulosic fibres. The cellulosic fibres were washed with water and concentrated to a desired dry solids content and then passed through a co-rotating twin-screw extruder (Berstorff ZE 25A-UTS-UG) which had a screw diameter of 25 mm, core diameter of 17 mm, centre distance of 21.5 mm and extrusion unit length of 48D
(1200 mm) having 10 barrels with individual heating/cooling possibilities which were cooled with tap water. The extruder screws were built up with conveying and kneading elements and had the screw configuration as shown in Figure 1, where left and right screws were equal. The drive power at maximum admissible screw speed (1200 rpm) was 22.6 kW (Siemens DC motor, type 1 GG5134-OGH46-6WV1).

The pulp was fed gravimetrically with a feeding device (K-Tron-Soder T20). The extruder was run at a screw speed of 1000 rpm. The cellulosic fibres were fed at a feed rate of 0.8 kg dry solids/h, unless otherwise stated.

Mechanical Treatment 2 Mechanical treatment 2 (referred to as "MT2" in the tables below) was carried out using untreated or chemically treated cellulosic fibres. The cellulosic fibres were washed with water and concentrated to a desired dry solids content and then passed through a planetary roller extruder (Entex PLWE100 with a 5.25 I/d barrel). The cooled central spindle had a diameter of 100 mm and the planetary roller extruder had 6 rolling planetary spindles.

Mechanical Treatment 3 Mechanical treatment 3 (referred to as "MT3" in the tables below) was used for comparison and carried out according to the procedure of Example 1 b of WO 2007/001229 in which a cellulosic fibre suspension at a desired dry solids content was passed through a pearl mill (Drais PMC 25TEX) once or twice, unless otherwise stated, using zirconium oxide pearls (2.0 mm in diameter, 65% filling grade), rotor speed of 1200 rpm and a flow rate of 100 I/h.

Mechanical Treatment 4 Mechanical treatment 4 (referred to as "MT4" in the tables below) was used for comparison and carried out according to the general procedure for microfibrillation of carboxymethyl cellulose disclosed by WO 00/47628 in which a cellulosic fibre suspension at a fibre content of about 1 % by weight was subjected to homogenization.

Analysis of Cellulosic Fibres Length weighted mean fibre length (referred to as "Fibre Lengh" in the tables below) and length weighted mean fibre width (referred to as "Fibre Width" in the tables below) of the cellulosic fibres were measured by means a Fiber Tester of Lorenzen & Wettre, Sweden, which operates according to ISO 16065-2:2007. The length weighted mean fibre length / width ratio (referred to as "Length / Width Ratio" in the tables below) was calculated from such data.
The content of cellulosic fibres having a length weighted mean fibre length up to 100 pm (referred to as "Fines Content" in the tables below) was determined using the same Lorenzen & Wettre Fiber Tester.

Specific surface areas were determined by adsorption of N2 at 177 K according to the BET
method using a Micromeritics TriStar 3000 instrument, which operates according to ISO
9277:1995. The cellulosic fibres to be analysed were frozen in a freezing equipment at the consistency received after any chemical and/or mechanical treatments, freeze dried in a Heto FD3 freeze drier, degassed at 90 C for 3 hours and thereafter analysed for specific surface area.

Water retention values (referred to as "WRV" in the tables below) were determined according to SCAN-C 62:00. The samples to be analysed were aqueous pulp suspensions at a consistency of 0.5 % in which the dry pulp consisted of 95 %
by weight of CTMP and 5 % by weight of cellulosic fibre composition according to the invention or cellulosic composition used for comparison, unless otherwise stated. The water retention value is a measure of the capacity of the pulp to hold or retain water, and an indication of the energy needed to remove the water and dry the cellulosic sheet; a lower water retention value indicates less energy to remove water and dry the cellulosic sheet.
Average degree of substitution of anionic / carboxymethyl groups (referred to as "DS" in the tables below) was determined by the method of conductometric titration as described by S. Katz, R.P. Beatson and A.M. Scallan in Svensk Papperstidning No. 6/1984, pp. 48-53.

Production and Analysis of Paper and Board Cellulosic compositions were used as additives in a paper and board making process in which paper or board sheets with a grammage of approximately 150 g/m2 were made according to ISO 5269-1:1998 using a dynamic sheet former (Formette Dynamic, supplied by Fibertech AB, Sweden). The pulp used consisted of 90 % high bulk CTMP (CSF

ml) and 10 % softwood (SR 28). Pulp suspensions at a consistency of 0.5 % and conductivity 1.0 mS/cm at pH 7 were formed in a mixing chest and the following additions were made:

(i) chemically treated and/or mechanically treated cellulosic composition, if any, was added to the suspension in an amount of 5 % by weight, calculated as dry cellulosic composition on dry suspension, whereupon the obtained suspension was mixed for 15 seconds, (ii) cationic potato starch (Pearlbond 970) was added to the suspension in an amount of 10 kg/t, based on dry suspension, whereupon the suspension was mixed for 30 seconds, and (iii) a siliceous material in the form of silica-bases particles (Eka NP 442, Eka Chemicals) was added to the suspension in an amount of 0.3 kg/t, calculated as Si02 and based on dry suspension, whereupon the suspension was mixed for 15 seconds, and then the obtained suspension was pumped from the mixing chest through a traversing nozzle on a wire positioned on a rotating drum of the dynamic sheet former where it was dewatered for 90 seconds for sheet formation.
The obtained paper or board sheets were pressed in a plane press at 5 bar for 5 minutes and thereafter dried restrained in a plane drier at 115 C for 12 minutes. The paper or board sheets were conditioned in a climate room according to ISO 187:1990 and thereafter analysed in terms of tensile strength index (Nm/g) according to ISO

3:2005 using an Alwetron TH1 of Lorenzen & Wettre, Sweden.

The obtained results were compared to the tensile strength index of a reference where no or a differently treated cellulosic fibre composition was used as an additive according to (i) in the production process described above, and expressed as change in tensile strength index, if any, in percent, over the reference (referred to as "Strength Contribution" in the tables below), where + and - indicate an increase and decrease, respectively, in tensile strength index.

Example 1 Cellulosic fibres of bleached kraft birch pulp were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were analysed. The results are shown in Table 1, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test Nos. 1 and 2 refer to cellulosic fibre compositions subjected to extrusion (MT1).

Table 1 Test Chem. Mech. Fibre Fibre Length/ Specific No. Treat- Treat- Length Width Width Surface ment ment [ m] [ m] Ratio Area [m2/g]
1 - MT1 (40) 790 22 36 4.0 2 CT1 MT1 (40) 710 25 28 5.0 Example 2 Cellulosic fibres of bleached kraft birch pulp were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were analysed. The results are shown in Table 2, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the cellulosic fibres derived from the bleached birch kraft pulp used as a reference. Test Nos. 2 and 3 refer to cellulosic fibre compositions which had been passed through the pearl mill (MT3) used for comparison once and twice, respectively.

Table 2 Test Chem. Mech. Fibre Fines No. Treat- Treat- Length Content ment ment [ m] [%]

2 CT1 MT3 (2.0) 500 31 3 CT1 MT3 (2.0) 400 42 Example 3 Cellulosic fibres of bleached kraft birch pulp were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board and analysed. The results are shown in Table 3, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the cellulosic fibres derived from bleached birch kraft pulp used as a reference. Test Nos. 2 and 3 refer to cellulosic fibre compositions subjected to extrusion (MT1) at a feed rate of 0.8 and 1.2 kg dry solids/h, respectively.

Table 3 Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength No. Treat- Treat- Length Width Width Content Surface Contri-ment ment [ m] [ m] Ratio [%] Area bution [m2/g] [%]
1 - - 840 21 40 5 1.0 0 2 CT3 MT1 (30) 680 25 27 11 >1.5 +12 3 CT3 MT1 (30) 760 25 30 7 >1.5 +5 Example 4 Cellulosic fibres of birch were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board and analysed. The results are shown in Table 4, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the reference pulp suspension when no cellulosic fibre composition was used as an additive. Test No. 2 refers to the composition of cellulosic fibres derived from birch used for comparison, and Test Nos. 3 to 8 refer to different cellulosic fibre compositions used as additives.
Table 4 Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength No. Treat- Treat- Length Width Width Content Surface Contri-ment ment [ m] [ m] Ratio [%] Area bution [m2/g] [%]

2 - - 840 21 40 5 1.0 -2 3 CT2 - 840 21 40 5 1.3 -5 Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength No. Treat- Treat- Length Width Width Content Surface Contri-ment ment [ m] [ m] Ratio [%] Area bution [m2/g] [%]
4 CT2 MT1 (20) 675 25 27 11 3.7 +11 CT2 MT1 (30) 560 26 22 15 2.6 +9 6 CT2 MT1 (35) 500 26 19 20 4.3 +7 7 CT2 MT1 (40) 415 27 15 26 5.4 +4 8 CT2 MT1 (45) 360 27 13 30 5.6 +6 Table 4 shows that the use of the compositions comprising cellulosic fibres according to the invention in Test Nos. 4-8 resulted in paper / board with improved tensile strength index over the compositions comprising cellulosic fibres used for comparison.

Example 5 Cellulosic fibres of birch were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were analysed. The results are shown in Table 5, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the composition of cellulosic fibres derived from birch.
Test Nos. 2 to 4 refer to cellulosic fibre compositions derived from birch which had been passed through the pearl mill (MT3) used for comparison.

Table 5 Test Chem. Mech. Fibre Fines No. Treat- Treat- Length Content ment ment [ m] [%]

2 - MT3 (0.5) 315 34 3 CT2 MT3 (0.5) 270 42 4 CT2 MT3 (1.0) 300 42 Example 6 Cellulosic fibres of pine were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board an analysed. The results are shown in Table 6, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test No. 2 refers to the cellulosic fibres derived from pine used for comparison. Test Nos. 3 to 8 refer to different cellulosic fibre compositions used as additives.

Table 6 Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength No. Treat- Treat- Length Width Width Content Surface Contri-ment ment [ m] [ m] Ratio [%] Area bution [m2/g] [%]

2 - - 2010 29 69 5 1.2 0 3 CT2 - 1995 29 69 5 0.9 -1 4 CT2 MT1 (10) 845 32 26 16 5.3 +22 5 CT2 MT1 (15) 765 31 25 17 5.8 +13 6 CT2 MT1 (20) 715 31 23 20 5.5 +7 7 CT2 MT1 (30) 545 30 18 27 6.2 +18 8 CT2 MT1 (35) 485 30 16 30 6.7 +17 Table 6 shows that the use of the compositions comprising cellulosic fibres according to the invention in Test Nos. 4-8 resulted in paper / board with significantly improved tensile strength index over the compositions comprising cellulosic fibres used for comparison.

Example 7 Cellulosic fibres of pine were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board and analysed. The results are shown in Table 7, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the composition of cellulosic fibres derived from pine used for comparison. Test Nos. 2 to 5 refer to cellulosic fibre compositions which had been subjected to extrusion (MT1) according to the invention.
Table 7 Test Chem. Mech. Strength No. Treat- Treat- Contri-ment ment bution [%]

2 - MT1 (30) +11 3 - MT1 (35) +12 4 CT2 MT1 (30) +18 5 CT2 MT1 (35) +17 Example 8 Cellulosic fibres of pine were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were analysed. The results are shown in Table 8, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the composition of cellulosic fibres derived from pine.
Test Nos. 2 to 4 refer to cellulosic fibre compositions which had been passed through the pearl mill (MT3) once and twice, respectively, used for comparison.

Table 8 Test Chem. Mech. Fibre Fines No. Treat- Treat- Length Content ment ment [ m] [%]

2 - MT3 (0.5) 265 53 3 CT2 MT3 (0.5) 600 31 4 CT2 MT3 (1.0) 240 52 Example 9 Cellulosic fibres of bamboo were subjected to chemical treatment and/or mechanical 5 treatment and used as additives in the production of paper / board and analysed. The results are shown in Table 9, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as 10 an additive. Test No. 2 refers to the cellulosic fibres derived from pine used for comparison. Test Nos. 3 to 5 refer to different cellulosic fibre compositions used as additives.

Table 9 Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength No. Treat- Treat- Length Width Width Content Surface Contri-ment ment [ m] [ m] Ratio [%] Area bution [m2/g] [%]

2 - - 1270 20 64 - 0.3 -1 3 CT2 - 1270 20 64 5 0.6 +3 4 CT2 MT1 (10) 600 23 26 27 3.8 +19 5 CT2 MT1 (15) 585 22 26 27 4.5 +10 Table 9 shows that the use of the compositions comprising cellulosic fibres according to the invention in Test Nos. 4-5 resulted in paper / board with significantly improved tensile strength index over the compositions comprising cellulosic fibres used for comparison.
Example 10 Cellulosic fibres of pine were subjected to chemical treatment and/or mechanical treatment and used as additives in the production of paper / board and analysed. The results are shown in Table 10, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test Nos. 2 to 3 refer to different cellulosic fibre compositions used as additives according to the invention.

Table 10 Test Chem. DS Mech. Fibre Fibre Length/ Strength No. Treat- Treat- Length Width Width Contri-ment ment [ m] [ m] Ratio bution [%]

2 CT4 0.05 MT1 (40) 750 36 21 +19 3 CT4 0.05 MT1 (45) 490 33 15 +17 Example 11 Cellulosic fibres were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper /
board and analysed. The results are shown in Table 11, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test Nos. 2 to 6 refer to different cellulosic compositions used as additives.
Table 11 Test Chem. DS Mech. Fibre Fibre Length/ Strength WRV
No. Treat- Treat- Length Width Width Contri- [g/g]
ment ment [ m] [ m] Ratio bution [%]
1 - - - - - - 0 1.25 2 CT4 0.10 MT4 (1) - - - +46 2.36 3 CT4 0.07 MT1 (50) 780 38 21 +25 1.32 4 CT4 0.08 MT1 (50) 760 38 20 +29 1.34 5 CT4 0.11 MT1 (55) 845 41 21 +18 -6 CT4 0.23 MT1 (35) 500 51 10 +35 1.88 Table 11 shows that the use of the compositions comprising cellulosic fibres of pine in Test Nos. 3-5 and cotton linter in Test No. 6 according to the invention resulted in paper /
board with a good balance between improved tensile strength index and low water retention values which indicate less energy to remove water and dry the cellulosic sheet over the composition according to Test No. 2 used for comparison.
Example 12 Cellulosic fibres were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper /
board and analysed. The results are shown in Table 12, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.

Water retention values were determined as described above except that the samples were made from aqueous pulp suspensions in which the dry pulp consisted of 99, 97 and 95 % by weight of CTMP and 1, 3 and 5 % by weight, respectively, of composition comprising cellulosic fibres of pine according to the invention or cellulosic composition used for comparison, which is indicated as "Content at WRV Tests" in the table below.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test Nos. 2 to 4 refer to the cellulosic composition used for comparison and Test Nos. 5-7 refer to the cellulosic fibre composition according to the invention.

Table 12 Test Chem. DS Mech. Fibre Fibre Strength Content WRV
No. Treat- Treat- Length Width Contri- at WRV [g/g]
ment ment [ m] [gm] bution Tests [%] [%]
1 - - - - - - - 1.25 2 CT4 0.10 MT4 (1) - - +14 1 1.42 3 CT4 0.10 MT4 (1) - - +30 3 1.84 4 CT4 0.10 MT4 (1) - - +46 5 2.36 5 CT4 0.08 MT1 (50) 760 38 +9 1 1.20 6 CT4 0.08 MT1 (50) 760 38 +23 3 1.24 7 CT4 0.08 MT1 (50) 760 38 +29 5 1.34 Table 12 shows that, at a tensile strength index improvement of paper / board of about 30 %, the composition of the invention according to Test No.7 resulted in a lower water retention value which indicate less energy to remove water and dry the cellulosic sheet over the composition used for comparison according to Test No. 3. Table 12 also shows that, at about the same water retention value, the composition of the invention resulted in increased tensile strength index over the composition used for comparison.

Example 13 Cellulosic fibres of various sources were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board and analysed. The results are shown in Table 13, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test Nos. 2 to 6 refer to different cellulosic compositions used as additives.
Table 13 Test Fibre Chem. DS Mech. Fibre Fibre Length/ Strength WRV
No. Type Treat- Treat- Length Width Width Contri- [g/g]
ment ment [ m] [ m] Ratio bution [%]
1 - - - - - - - 0 1.31 2 Bamboo CT4 0.04 MT1 (45) 900 21 42 +10 1.40 3 Birch CT4 0.04 MT1 (55) 520 26 20 +12 1.42 4 Pine CT4 0.04 MT1 (45) 1035 34 30 +21 1.47 5 Pine CT4 0.07 MT1 (55) 765 37 21 +27 1.57 6 Pine CT4 0.11 MT1 (55) 845 41 21 +18 1.85 Table 13 shows that the use of the compositions comprising cellulosic fibres according to the invention in Test Nos. 2-6 resulted in paper / board with significantly improved tensile strength index and low retention values.
Example 14 Cellulosic fibres of various sources were subjected to chemical treatment and/or mechanical treatment and the obtained compositions were used as additives in the production of paper / board and analysed. The results are shown in Table 14, in which the dry solids content (% by weight) of the cellulosic fibres in the mechanical treatment is given in parenthesis. Cotton means cotton linter.

Test No. 1 refers to the pulp suspension when no cellulosic fibre composition was used as an additive. Test Nos. 2 to 7 refer to different cellulosic fibre compositions used as additives. The mechanical treatment MT2* was carried out by feeding the cellulosic fibre composition through the planetary roller extruder twice.

Table 14 Test Fibre Chem. DS Mech. Fibre Fibre Length/ Fines Strength No. Type Treat- Treat- Length Width Width Content Contri-ment ment [ m] [ m] Ratio [%] bution [%]

2 Birch - - MT2 (25) 470 26 18 32 +6 3 Birch - - MT2 (55) 530 28 19 30 +3 4 Birch CT4 0.23 MT2 (40) 905 24 38 8 +14 5 Birch CT4 0.23 MT2 (55) 845 23 37 11 +22 6 Birch CT4 0.23 MT2*(55) 770 22 35 12 +21 7 Cotton CT4 0.23 MT2 (25) 905 43 21 13 +21 8 Cotton CT4 0.23 MT2 (40) 810 44 18 20 +31 9 Cotton CT4 0.23 MT2 (55) 555 44 13 30 +39 10 Cotton CT4 0.23 MT2*(55) 495 43 12 38 +50 11 Pine CT4 0.07 MT2 (55) 805 38 21 24 +22 12 Pine CT4 0.07 MT2*(55) 735 38 19 33 +32 Table 14 shows that the use of the compositions comprising cellulosic fibres according to the invention resulted in paper / board with significantly improved tensile strength index.

Claims

1. Composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25, a length weighted mean fibre length up to 1,100 µm and a length weighted mean fibre width over 10 µm.

2. Composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25, a length weighted mean fibre length up to 1,100 µm, and wherein at least 50 % by weight of the cellulosic material is insoluble in water.

3. Composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 and a length weighted mean fibre length /
width ratio up to 30.

4. Composition comprising cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 and a length weighted mean fibre width over 35 µm.

5. Composition comprising cellulosic fibres having a specific surface area of at least 1.5 m2/g, a length weighted mean fibre length / width ratio up to 30, and a dry solids content of at least 5 % by weight, based on the weight of the composition.

6. Composition comprising cellulosic fibres having a specific surface area of at least 1.5 m2/g, a length weighted mean fibre length / width ratio up to 30, and up to 30 % by weight, based on the total weight of the cellulosic fibres, of cellulosic fibres with a length weighted mean fibre length up to 100 µm.

7. The composition according to any one of claims 1 to 6, wherein the cellulosic fibres have up to 35 % by weight, based on the total weight of the cellulosic fibres, of cellulosic fibres with a length weighted mean fibre length up to 100 µm.

8. The composition according to any one of the claims 1 to 3 and 5 to 6, wherein the cellulosic fibres have a length weighted mean fibre length / width ratio of at least 12.

9. The composition according to any one of the preceding claims, wherein the cellulosic fibres have an average degree of substitution of anionic groups of from 0.001 to 0.25 which ionic groups are carboxyl and/or carboxymethyl groups.

10. The composition according to any one of the preceding claims, wherein the cellulosic fibres have an average degree of substitution of anionic groups of at least 0.02.

11. The composition according to any one of the preceding claims, wherein the cellulosic fibres have a length weighted mean fibre length of from 200 to 1,000 µm.

12. The composition according to any one of the preceding claims, wherein it has a dry solids content of from 10 to 90 % by weight, based on the weight of the composition.

13. The composition according to any one of the preceding claims, wherein the cellulosic fibres have a specific surface area in the range from 2 to 50 m2/g.

14. The composition according to any one of the preceding claims, wherein at least 70 % by weight of the cellulosic material is insoluble in water.

15. The composition according to any one of the preceding claims, wherein the cellulosic fibres are derived from wood fibres.

16. The composition according to any one of claims 1 to 14, wherein the cellulosic fibres are derived from non-wood fibres.

17. Method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres to chemical treatment and mechanical treatment, wherein the chemical treatment comprises treating cellulosic fibres with (i) at least one agent containing a carboxyl group, optionally substituted, (ii) at least one oxidant and at least one transition metal, or (iii) at least one nitroxyl radical, and the mechanical treatment comprises subjecting cellulosic fibres to extrusion with a twin-screw extruder or a planetary roller extruder.

18. Method of producing a composition comprising cellulosic fibres which comprises subjecting cellulosic fibres having an average degree of substitution of anionic groups of from 0.001 to 0.25 to extrusion.

19. The method according to claim 17 or 18, wherein the chemical treatment comprises treating cellulosic fibres with at least one oxidant comprising hydrogen peroxide, and at least one transition metal comprising iron.

20. The method according to any one of claim 17 to 19, wherein the chemical treatment comprises treating cellulosic fibres with monochloroacetic acid or a salt thereof under alkaline conditions.

21. The method according to any one of claim 17 to 20, wherein the cellulosic fibres have a dry solids content of from 10 to 50 % by weight in the mechanical treatment.

22. The method according to any one of claim 17 to 21, wherein it comprises extrusion with a co-rotating twin-screw extruder.

23. The method according to any one of claim 17 to 21, wherein it comprises extrusion with a planetary roller extruder.

24. Composition comprising cellulosic fibres obtainable by the method of any one of claims 17 to 23.

25. Use of the composition according to any one of claims 1 to 16 and 24 in the production of paper and board.

26. Use of a composition comprising cellulosic fibres subjected to extrusion as a strength additive in the production of paper and board.

27. Process for producing a cellulosic pulp mixture which comprises mixing the composition comprising cellulosic fibres according to any one of claims 1 to 16 and 24 with cellulosic pulp.

28. Cellulosic pulp mixture obtainable by the process according to claim 27.

29. Use of the cellulosic pulp mixture according to claim 28 in the production of paper and board.

30. Process for producing paper and board which comprises forming an aqueous suspension comprising the cellulosic pulp mixture according to claim 28 and dewatering the obtained suspension

31. Process for producing paper and board which comprises adding the composition comprising cellulosic fibres according to any one of claims 1 to 16 and 24 to an aqueous cellulosic pulp suspension and dewatering the obtained suspension.

32. Process for producing paper and board which comprises mixing a composition comprising cellulosic fibres subjected to extrusion with cellulosic pulp.

33. The process according to any one of claims 30 to 32, wherein it comprises mixing the composition comprising cellulosic fibres with cellulosic pulp to form a cellulosic pulp mixture, forming an aqueous suspension comprising the cellulosic pulp mixture and dewatering the obtained suspension.

34. The process of according to any one of claims 30 to 33, wherein it comprises mixing the composition comprising cellulosic fibres with cellulosic pulp to form a cellulosic pulp mixture in the form of an aqueous suspension and dewatering the obtained suspension.

35. The process according to any one of claims 30 to 34, wherein the composition comprising cellulosic fibres is mixed with the cellulosic pulp in an amount of from 1 to % by weight, calculated as dry cellulosic fibres of the composition on dry cellulosic pulp.

36. The process according to claim 31 or 35, wherein the composition comprising cellulosic fibres is used in the form of an aqueous suspension.

37. The process according to any one of claims 30 to 36, further comprising adding one or more drainage and retention aids to the suspension prior to dewatering.

38. The process according to claim 37, wherein the one or more drainage and retention aids comprise a cationic polymer which is cationic starch and/or cationic polyacrylamide.

39. The process according to any one of claims 37 to 38, wherein the one or more drainage and retention aids comprise a siliceous material which is bentonite or silica-based particles.

40. Paper and board obtainable by the process according to any one of claims 30 to 39.

41. Paper and board according to claim 40 which is a multiply board which comprises from two to seven plies or layers comprising cellulosic fibres.

42. Paper and board according to any one of claims 40 to 41 which is a liquid packaging board.

43. Paper and board according to any one of claims 40 to 41 which is a folding box board.

44. Use of the board according to claim 43 for packaging of beverages and liquid food.

45. Packaging comprising board according to any one of claims 40 to 43 comprising a solid or liquid foodstuff, beverage, pharmaceutical, cosmetic, cigarettes, tobacco or detergent.