EP2334871B1 - Method for manufacturing paper, cardboard and paperboard using endo-beta-1,4 glucanases as dewatering means - Google Patents

Description

The invention relates to a process for the production of paper, paperboard and cardboard in the presence of at least one cationic polymeric retention agent and / or retention agent system using endo-β-1,4-glucanases as dehydrating agents, as well as the papers produced by this process.

The use of drainage and retention aids in the manufacture of paper, paperboard and cardboard has long been known. Suitable retention agents are in particular cationic polymers such as polyacrylamides, polyethyleneimines, polyvinylamines, polydimethyldiallylammonium chloride and any mixtures thereof, but also retention agent systems comprising at least one cationic polymer in combination with an organic and / or inorganic component are known.

Cationic polyacrylamides are for example from EP 0 176 757 A2 known. These may be linear polyacrylamides but also branched polyacrylamides, as in US 2003/0150575 and in the German Offenlegungsschrift DE 10 2004 058 587 A1 described.

Suitable cationic polymeric retention agents are also polyethyleneimines and modified polyethyleneimines, as disclosed in German Offenlegungsschrift DE 24 34 816 are known. In the DE 24 34 816 and the literature cited therein describes the reactions of polyethyleneimine with crosslinkers such as epichlorohydrin, reactions of polyethylenimine or other oligoamines with oligocarboxylic acids to form polyamidoamines, crosslinked products of these polyamidoamines and reactions of the polyamidoamines with ethyleneimine and bifunctional crosslinkers. Other modified polyethylenimines are made WO 00/67884 A1 and WO 97/25367 A1 known.

The use of polyvinylamines in the production of paper, for example, in US 2003/0192664 discloses dosing according to this document to an aqueous fiber slurry, a polymer containing vinylamine units and a particulate, organic, crosslinked polymer.

Another retention aid system which contains cationic polyvinylamine is disclosed in the German Offenlegungsschrift DE 10 2005 043 800 A1 described. There is disclosed a process for making paper in which the retention aid system is comprised of (i) at least one vinylamine units-containing polymer, (ii) at least one linear, anionic polymer having a molecular weight M _w of at least 1 million and / or at least one branched anionic water-soluble polymer and / or a bentonite and / or silica gel and (iii) at least one particulate, anionic, crosslinked polymer having an average particle diameter of at least 1 μm and an intrinsic viscosity of less than 3 dl / g consists.

Retention agent systems are also so-called microparticle systems which, in addition to at least one polymeric component, also contain an organic and / or inorganic component. Generally, in the microparticle systems, polymers such as modified polyethylenimines, polyacrylamides or polyvinylamines are added as flocculants which are further flocculated by subsequent addition of, for example, inorganic microparticles such as bentonite or colloidal silica. The order of addition of the components can also be reversed.

Such a microparticle system is out EP 0 235 893 A1 known. This document describes a process for the production of paper in which an essentially linear synthetic polymer having a molecular weight of more than 500,000 in an amount of more than 0.03% by weight, based on dry paper stock, is initially added to an aqueous fiber suspension , admits the mixture then subjected to the action of a shear field, and added after the last shear stage a bentonite.

Another microparticle system is in DE 102 36 252 A1 described. DE 102 36 252 A1 discloses a process for the production of paper using as cationic polymer of the microparticle system cationic polyacrylamides, vinylamine units containing polymers and / or polydiallyldimethylammonium chloride having an average molecular weight M _w of at least 500,000 daltons and a charge density of at most 4.0 meq./g become. The inorganic component is added as well as the cationic polymer before the last shear stage before the headbox of the fiber suspension. In addition, the retention aid system is free of polymers with a charge density of more than 4 meq./g.

All these combinations have in common that only the retention can be improved.

In addition, the use of enzymes, in particular cellulases, as an aid in the production of paper is known from the literature.

From the EP 0 524 220 B1 For example, a process for the production of pulp is known in which cellulases are used to improve the dewatering of the pulp. The cellulases are dosed into at least 8% by weight stock preparation, preferably the stock preparation has a proportion of 10-20% by weight of fibers. A disadvantage of this method is that only the drainage is improved.

A method for improving the dewatering of paper pulp using a cellulase is also out EP 0 536 580 A1 known. Accordingly, first a cellulase in an amount of at least 0.05 wt .-%, based on the dry pulp, metered into the pulp. The contact time of the cellulase with the pulp is at least 20 minutes at a temperature of at least 20 ° C before subsequently adding a water-soluble cationic polymer in an amount of at least 0.007 wt .-%, based on the dry pulp. A disadvantage of this method is that the cellulase must be used in high amounts in order to achieve a good drainage effect.

WO97 / 38164 describes a method of forming paper from recycled paper pulp by adding a dewatering-enhancing amount of a starch-hydrolyzing enzyme, preferably amylase, to the pulp suspension. This document also refers to the use of an amylase in combination with a cellulase such as endoglucanase.

Thus, there is a continuing need in the paper industry for improved and new paper auxiliaries and papermaking systems that improve retention and dewatering alike.

It is an object of the present invention to provide a process for producing paper, paperboard and paperboard using a papermaking system which provides improved retention and drainage.

The object has been achieved by a method for producing paper, paperboard and cardboard by draining a stock on a wire in the presence of at least one cationic polymeric retention agent and / or retention system to sheet and dry the sheets, prior to the addition of the at least one cationic polymeric retention agent and / or retention aid system an endo-β-1,4-glucanase in an amount of 0.00001 to 0.01 wt .-%, based on the dry pulp, is metered into the pulp,
wherein the cationic polymeric retention aid is a polyacrylamide and the intrinsic viscosity of the polyacrylamide ranges from 7 to 15 dL / g.

According to the process of the invention, endo-β-1,4-glucanases are used as dehydrating agents in an amount of from 0.00001 to 0.01% by weight, based on the dry pulp. Preferably, the endo-β-1,4-glucanases in an amount of 0.00001 to 0.005 wt .-%, more preferably in the range of 0.00001 to 0.001 wt .-%, each based on the dry paper stock used.

Endo-β-1,4-glucanases are enzymes belonging to the group of cellulases. These are involved in the hydrolysis of cellulose. For the hydrolysis of native cellulose three main types of cellulases are known: endoglucanases, exoglucanases and β-glucosidases. According to the invention, endo-β-1,4-glucanases which belong to the group of endoglucanases act.

Endoglucanases act randomly on soluble and insoluble cellulose chains. They are most reactive with non-crystalline or amorphous cellulose, whereas they show a very low reactivity towards crystalline cellulose. Examples of endo-β-1,4-gluconases (EC No. 3.2.1.4) are the commercial products Novozym® 476 from the company

Novozymes and Polymin® PR 8336 from BASF SE. The Novozym® 476 commercial product from Novozymes has an activity of 4500 ECU / g in accordance with the standard unit definition of Novozymes.

Endoglucanases are described in detail in WO 98/12307 A1 and the literature cited therein, which is incorporated herein by reference. In addition, modified endoglucanases are in EP 0 937 138 B1 which is also referred to here.

In general, cellulases are produced by a large number of microorganisms such as fungi, actinobacteria and myxobacteria, but also by plants. Especially endoglucanases from a wide variety of species have been identified so far. For commercial use, they are mostly isolated from cultures of microscopic fungi of the genus Trichoderma (e.g., T. reesei) that occur in the soil and are considered to be the deuteromycetes (Fungi imperfecti).

The endo-β-1,4-glucanase can be dosed into both the thick and the thin pulp of the stock. The thick material usually has a consistency of more than 2 wt .-%, for example 2.5 to 6 wt .-%, preferably 3.0 to 4.5 wt .-%, each based on the dry pulp, on. Subsequently, the thick material is transferred by supplying water into the so-called thin material, which has a substance concentration below 1.5% by weight, based on the dry paper stock. In most cases, the substance concentration of the thin material is below 1.2% by weight, for example from 0.5 to 1.1% by weight, preferably from 0.6 to 0.9% by weight, in each case based on the dry paper stock.

In a preferred embodiment of the process according to the invention, the endo-β-1,4-glucanase is metered into the thick stock of the paper stock.

It is essential to the invention that the dosage of the endo-β-1,4-glucanase takes place before the addition of the at least one cationic polymeric retention agent and / or retention agent system.

Retention agent systems in the context of this invention consist of cationic polyacrylamides in combination with an organic and / or inorganic component.

In the process according to the invention, it is possible to use linear, branched or crosslinked polyacrylamides as cationic polymeric retention aids.

Cationic polyacrylamides are, for example, copolymers prepared by copolymerizing acrylamide and at least one di-C _{1 to} C ₂ -alkylamino-C _{2 to} C ₄ -alkyl (meth) acrylate or a basic acrylamide in the form of the free bases, the salts with organic or inorganic acids or the alkyl halides quaternized compounds are available. Examples of such compounds are dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyloacrylyl, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, diethylaminopropyl methacrylate, diethylaminopropyl acrylate and / or dimethylaminoethylacrylamide. Further examples of cationic polyacrylamides may be the references cited in the prior art such as EP 0 910 701 A1 and US 6,103,065 be removed. One can use both linear and branched or crosslinked polyacrylamides. Such polymers are commercial products.

Branched polymers, the z. Example, by copolymerization of acrylamide or methacrylamide with at least one cationic monomer in the presence of small amounts of crosslinking agents can be produced, for example, in the references cited in the prior art US 5,393,381 . WO 99/66130 A1 and WO 99/63159 A1 described. Further branched cationic polyacrylamides are as component (b) in DE 10 2004 058 587 A1 discloses, to which reference is expressly made at this point.

Preferably, in practice, the branched or crosslinked (co) polyacrylamide is a cationic copolymer of acrylamide and a non-saturated cationic ethylene monomer selected from dimethylaminoethyl acrylate (ADAME), dimethylaminoethylacrylamide, dimethylaminoethyl methacrylate (MADAME) quaternized or salted by various acids and quaternizing agents such as benzyl chloride, methyl chloride, alkyl or aryl chloride, dimethyl sulfate, furthermore dimethyldiallylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC) and methacrylamidopropyltrimethylammonium chloride (MAPTAC). Preferred cationic comonomers are dimethylaminoethyl acrylate methochloride and dimethylaminoethylacrylamide methochloride, which are obtained by alkylation of dimethylaminoethyl acrylate or dimethylaminoethylacrylamide with methyl chloride.

This copolymer is branched, as known to those skilled in the art, through a branching agent consisting of a compound having at least two reactive moieties selected from the group comprising double, aldehyde or epoxy bonds. These compounds are known and are for example in the document EP 0 374 458 A1 described.

Of course, it is also possible to use branched cationic polyacrylamides which consist of a mixture of branched and linear polyacrylamides, as described in the prior art, by the process according to the invention. Such a mixture usually consists of a branched cationic polyacrylamide as described above and a linear polyacrylamide in a ratio of 99: 1 to 1: 2, preferably in a ratio of 90: 1 to 2: 1, and particularly preferably in a ratio of 90: 1 to 3: 1.

The cationic polyacrylamide may also be crosslinked, wherein the polymerization of the monomers is carried out in the presence of a conventional crosslinker. Crosslinkers are known compounds containing at least two ethylenically unsaturated double bonds in the molecule, such as methylenebisacrylamide, pentaerythritol triacrylate or glycol diacrylates.

Of course, mixtures of linear, branched and crosslinked polyacrylamides may also be used in the process according to the invention, but preference is given to using only one polyacrylamide.

The intrinsic viscosity is determined according to ISO 1628/1, October 1988, "Guidelines for the standardization of methods for the determination of viscosity number and polymer in dilute solution".

Of course, the said cationic polymeric retention agents can be used alone or in any desired mixture with one another in the process according to the invention. Preferably, only a cationic polymeric retention agent is used.

Usually, the at least one cationic polymeric retention agent is added in an amount of 0.001 to 0.1, preferably 0.03 to 0.5 wt .-%, each based on the dry paper stock.

Furthermore, retention aid systems, as known from the prior art, can be used in the process according to the invention. These retention aid systems consist of the cited cationic polymers and a further organic and / or inorganic component.

A retention agent system with a further organic component which is suitable in the process according to the invention also contains, in addition to one of the abovementioned cationic polymers, a water-insoluble, anionic, organic component which crosslinks a diameter of less than 750 nm and uncrosslinked a diameter of less than 60 nm. This anionic component is preferably an anionic, crosslinked polyacrylamide. Such a system is in EP 0 462 365 A1 describe. Optionally, such a system may still contain an inorganic component as described below.

Furthermore, a retention aid system in which the organic component is an anionic polymer such as preferably polyacrylamide is suitable. This polyacrylamide may be linear, branched or crosslinked. Such a system of cationic polymer, anionic, branched polymer and inorganic component is, for example, in EP 1 328 683 A1 described. Similar retention systems are in WO 02/33171 A1 described here, wherein an anionic, crosslinked polyacrylamide is used as organic components. In addition, this is suitable in WO 01/34910 A1 discloses retention system containing an anionic, linear polyacrylamide as an organic component.

Preference is given to so-called microparticle systems in which an inorganic component is metered into the paper stock together with the cited cationic polymers. This inorganic component is preferably bentonite and / or silica gel. Bentonites are finely divided, water-swellable minerals, such as bentonite itself, hectorite, attapulgite, montmorillonite, nontronite, saponite, sauconite, hormitol and sepiolite. For example, modified and unmodified silicic acids are suitable as silica gel. Bentonite and / or silica gel are usually used in the form of an aqueous slurry. If a microparticle system with an inorganic component is used in the process according to the invention, in the case of bentonite the amount is 0.05 to 0.5, preferably 0.1 to 0.3,% by weight, in each case based on the dry paper stock, and in the case of silica gel usually 0.005 to 0.5, preferably 0.01 to 0.3 wt .-%, calculated on the basis of the SiO ₂ content in the silica gel and in each case based on the dry pulp.

If a microparticle system is used in the process according to the invention, the inorganic component can be metered into the stock both before and after the last shear stage before the headbox. Preferably, the dosage takes place before the last shear stage before the headbox.

Surprisingly, according to the process of the invention, considerably improved dewatering is achieved with equally good retention compared with the use of cationic polymeric retention aids and / or retention aid systems. The use of endo-β-1,4-glucanases in a lower dosage compared to the prior art in combination with the use of retention aids and retention aid systems leads to a significant improvement in the drainage properties.

All the paper materials can be processed by the process according to the invention. For example, it is possible to start from cellulose fibers of all kinds, both from natural as well as recovered fibers, in particular recycled paper fibers. Suitable pulps for the production of the pulps are all qualities customary for this purpose, for example wood pulp, bleached and unbleached pulp and pulps from all annual plants. Wood pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemo-thermo-mechanical pulp (CTMP), pressure groundwood, semi-pulp, high yield pulp, and refiner mechanical pulp (RMP). As pulp, for example, sulphate, sulphite and soda pulps come into consideration. Preferably, unbleached pulp, also referred to as unbleached kraft pulp, is used. Suitable annual plants for the production of pulps are, for example, rice, wheat, sugar cane and kenaf. For the production of pulps can also be used with advantage waste paper or old cardboard, which is used either alone or in admixture with other fibers, or it is based on fiber blends of a primary material and recycled scrap Committee, eg bleached pine sulfate in admixture with recycled scrap Committee.

In accordance with the method of the invention, the endo-β-1,4-glucanases are added to the stock as a dehydrating agent prior to the addition of the cationic polymeric retention aid and / or retention aid system. Of course, in the process according to the invention, the usual process chemicals can additionally be used for the production of paper and paper products. Typical process chemicals include, for example, additives such as starch, pigments, optical brighteners, dyes, biocides, paper strength agents, sizing agents, fixatives, defoamers and deaerators. The additives mentioned are used in the otherwise customary amounts known to those skilled in the art. For example, all starches such as native starches or modified starches, in particular cationically modified starches, can be used as starches. Examples of suitable fixing agents are optionally modified polyethyleneimines, polydimethyldiallylammonium chloride, dicyandiamide resins, epichlorohydrin-crosslinked condensation products of a dicarboxylic acid and a polyamine, polyaluminum chloride, aluminum sulfate and polyaluminum chlorosulphate. Sizing agents are e.g. Rosin size, alkyl diketenes, alkenyl succinic anhydrides or polymeric sizing agents and mixtures thereof.

In particular, the use of solidifiers for paper is advantageous in the process according to the invention. Suitable solidifiers are, for example, the polymers containing polyvinylamines or vinylamine units mentioned above, which are usually present in an amount of from 0.01 to 0.5, preferably from 0.1 to 0.3,% by weight, based in each case on the dry paper stock , are used. In addition, so-called carrier systems which are fillers treated with amphoteric polymers, such as calcium carbonate, are also suitable as solidifiers. Such carrier system are for example in the German Offenlegungsschrift DE 10 334 133 A1 disclosed.

The invention will be further illustrated by the following non-limiting examples.

The percentages in the examples are by weight unless otherwise indicated in the context. The dosage of the individual components enzyme, polymer, fixing agent and bentonite is given in% by weight and refers to the dry amount of the respective component per ton of paper. The following components were used in the examples: Enzyme A: Endo-β-1,4-glucanase (Polymin® PR 8336 from BASF SE) Polymer A: high molecular weight cationic polyacrylamide emulsion having a molecular weight of about 5,000,000, a charge density of 1.8 meq./g and an intrinsic viscosity of 10.5 dL / g (Polymin® KE 440 from BASF SE) Fixative A: low molecular weight polyethyleneimine having a molecular weight of about 800,000 and a charge density of about 11 meq./g (Catiofast® SF from BASF SE) bentonite: Microfloc® XFB from BASF SE

The retention effect (total retention FPR) was determined according to Britt Jarr.

The dewatering time was determined according to ISO Standard 5267 with a Schopper-Riegler tester by dewatering each 1 L of the fiber slurry to be tested with a consistency of 2 g / L therein and determining the time in seconds to pass through 600 mL Filtrate was necessary. In the examples the improvement of the dewatering time in% was given, which results from the formula [1 - (dewatering time (experiment) / dewatering time (comparison)] x 100.

To determine the zeta potential (surface charge of fibers), a SZP-06 Zeta Potential system from Mütek was used.

The water retention value (WRV) was determined by empirical measurement of the water absorption capacity of a fiber mat. For this purpose, 2.50 ml of a 4% strength by weight fiber slurry were introduced into an anion exchange extraction column which had a glass frit installed at about half the height (Merck, SAX, 1.02025.0001 or Fa. Strata, C8, 8B-S005-HBJ). Subsequently, the suspension was centrifuged at 3000 g for 15 minutes. The wet fiber mat was removed from the sieve and weighed (weight G1). Then, the fiber mat was dried at 105 ° C to constant weight and weighed again (weight G2). The WRV was given in% in the examples and results from the formula (G1-G2) / G2 × 100.

example 1

In a 2 L beaker, a 1% by weight stock suspension of 100% recycled paper (old courrugated container) was charged. In a second 2 L beaker, a 3 wt .-% solids suspension of 100% waste paper (old corrugated container) was filled. The pH of the stock suspensions was adjusted to pH 7.5 with an aqueous sodium hydroxide solution or with hydrochloric acid, if necessary. Subsequently, the amounts of the enzyme A indicated in Table 1 were added to the various stock suspensions and stirred with the aid of a Heiltof stirrer at 800 revolutions per minute (rpm) for one hour at a temperature of 55 ° C. After this treatment, the stock suspensions were diluted with water to a consistency of 2 g / L and the drainage time was determined.

For comparison, the dehydration time of a 1- or 3% by weight stock suspension was determined as a comparison value which was subjected to the same treatment but did not contain enzyme A. The results are summarized in Table 1. Table 1: Improvement of the dehydration time at different enzyme concentrations depending on the initial substance concentration Test no. Enzyme A [wt%] Improvement of the dewatering time [%], 1% by weight stock suspension Improvement of the dewatering time [%], 3% by weight stock suspension 1 0.001 2.41 11.11 2 0.005 7.23 19.75 3 0.01 13.25 25.93 4 0.05 21.69 32,10 5 0.1 22.89 35,80 6 0.3 26,51 38.27 7 0.5 32.53 43.21

From Table 1 it can be seen that at an initial substance concentration of 3 wt .-%, the efficiency of the enzyme is much better.

Example 2

Example 1 was repeated, but only 1 wt .-% fabric suspensions were used. These were stirred after enzyme addition with the aid of a Heiltof stirrer at different stirring speeds (250 rpm and 800 rpm). The further treatment was carried out as in Example 1. Subsequently, the drainage time was determined.

For comparison, the dewatering time of a 1% by weight stock suspension was determined as a comparison value which was subjected to the same treatment but did not contain enzyme A. The results are summarized in Table 2. Table 2: Improvement of the dewatering time at different enzyme concentrations as a function of the stirring speed (initial substance concentration 1% by weight) Test no. Enzyme A [wt%] Improvement of drainage time [%], 250 rpm Improvement of drainage time [%], 800 rpm 8th 0.005 23.91 7.23 9 0.01 28.26 13.25 10 0.05 31.52 21.69 11 0.1 34.78 22.89 12 0.3 39.13 26,51 13 0.5 43.48 32.53

From Table 2 it can be seen that a reduction of the stirring speed leads to an increased efficiency of the enzyme.

Example 3

Example 1 was repeated, but only 3 wt .-% solids suspensions were used. These were stirred after enzyme addition with the aid of a Heiltof stirrer at different stirring speeds (250 rpm and 800 rpm). The further treatment was carried out as in Example 1. Subsequently, the drainage time was determined.

For comparison, in each case the dewatering time of a 3% by weight stock suspension was determined as a comparison value which was subjected to the same treatment but did not contain enzyme A. The results are summarized in Table 3. Table 3: Improvement of the dewatering time at different enzyme concentrations as a function of the stirring speed (initial substance concentration 3% by weight) Test no. Enzyme A [wt%] Improvement of drainage time [%], 250 rpm Improvement of drainage time [%], 800 rpm 14 0.001 34.12 11.11 15 0.005 42,35 19.75 16 0.01 44.71 25.93 17 0.05 45.88 32,10 18 0.1 45.88 35,80 19 0.3 47.06 38.27 20 0.5 48.24 43.21

It has been shown that the reduction of the stirring speed in combination with an increased initial substance concentration contributes to a significant increase in the efficiency of the enzyme.

Example 4

In a 2 L beaker, a 6% by weight stock suspension of 100% old paper (old corrugated container) was charged. The pH of the stock suspension was adjusted to pH 7.5 with an aqueous sodium hydroxide solution or hydrochloric acid, if necessary. Subsequently, the amounts of the enzyme A indicated in Table 4 were added and stirred with the aid of a Heiltof stirrer at 250 rpm for 1 hour at 55 ° C. After this treatment, 500 ml of this stock suspension were taken and diluted with water to a substance concentration of 0.5 wt .-%.

From this diluted stock suspension, the zeta potential was determined. In addition, the retention effect (total retention FPR) according to Britt Jarr of this diluted stock suspension, and the chemical oxygen demand (COD) of the white water (filtrate) was determined, the following time sequence was observed: t = 0 s Start of the stirrer t = 10 s optional addition of 0.03% by weight of polymer A) t = 30 s Acceptance of 100 mL of the suspension for measuring the retention effect (FPR) or the chemical oxygen demand (COD) of the white water (filtrate)

For comparison, the zeta potential, the retention effect (FPR) and the chemical oxygen demand (COD) of a stock suspension were determined, the same treatment However, the 0.46 wt .-% of the enzyme Celluclast® 1.5L (Novozymes, according to EP 536 580 A ) were added. The results are summarized in Table 4 Table 4: Zeta Potential, Retention Effect (FPR) and Chemical Oxygen Demand (COD) Enzyme [% by weight] Zeta potential [mV] COD without addition of polymer A [μeq / L] COD with addition of polymer A [μeq / L] FPR without addition of polymer A [%] FPR with addition of polymer A [%] Enzyme A, 0 -23.6 142 31.1 73.9 82.2 Enzyme A, 0.0001 -24.4 186 154 77.9 81.5 Enzyme A, 0.0003 -25.0 221 186 77.9 78.8 Enzyme A, 0.01 -24.9 293 257 75.7 79.0 Enzyme A, 0.03 -24.8 413 312 75.4 78.9 Enzyme A, 0.46 -19.4 2020 2037 73.6 78.8 Celluclast® 1.5L, 0.46 -10.4 2023 2020 70.5 78.4

From the results, it is clear that a large excess of the enzyme significantly affects the effectiveness of the retention agent Polymer A with a simultaneous increase in COD in white water (filtrate). The addition of the enzyme in a concentration of 0.46% by weight produces large amounts of impurities.

Without addition of the retention agent polymer A, the total retention action (FPR) is markedly improved in the range of the low dosage of the enzyme according to the invention. The addition of the retention agent polymer A in conjunction with the low dosage of the enzyme according to the invention results in an overall effect in the overall retention (FPR).

Example 5

In a 2 L beaker, a 6% by weight stock suspension of 100% old paper (old corrugated container) was charged. The pH of the stock suspension was adjusted to pH 7.5 with an aqueous sodium hydroxide solution or hydrochloric acid, if necessary. Subsequently, the amounts of the enzyme A indicated in Table 5 were added and stirred with the aid of a Heiltof stirrer at 250 rpm for 1 hour at 55 ° C. After this treatment, the stock suspension was diluted with water to a consistency of 2 g / L. To this diluted stock suspension became optional With stirring, 0.03 wt .-% polymer A was added. Subsequently, the dehydration time was determined and the results are summarized in Table 5. Table 5: Improvement of the dewatering time at different enzyme concentrations depending on the addition of a polymeric retention agent Test no. Enzyme A [wt%] Improvement of the dewatering time [%], without addition of polymer A Improvement of the drainage time [%], with addition of polymer A 21 0 - 41.7 22 0.0001 27.4 51.2 23 0.0003 39.3 58.3

These results show the synergistic effect with a low dosage of an enzyme according to the invention in combination with a cationic polymeric retention agent. At an enzyme dosage of 0.003 wt .-%, the addition of the cationic polymeric retention agent causes an increase in the dewatering performance by about 20%.

Example 6

Example 5 was repeated except that enzyme A was added only in an amount of 0.001% by weight. Further, an optional fixing agent A, polymer A and a bentonite were added. Subsequently, the dehydration time was determined, the results are summarized in Table 6. Table 6: Improvement of drainage time as a function of the addition of a fixing agent, a polymeric retention agent and a bentonite Test no. Enzyme A [wt%] Fixer A [wt%] Polymer A [% by weight] Bentonite [% by weight] Improvement of drainage time [%] 24 0 0 0 0 - 25 0.001 0 0 0 35.0 26 0 0.01 0 0 3.3 27 0.001 0.01 0 0 32.5 28 0 0 0.03 0 41.7 29 0 0.01 0.03 0 39.2 30 0.001 0.01 0.03 0 51.7 31 0 0.01 0.03 0.2 46.7 32 0.001 0.01 0.03 0.2 54.2

From the results it is clear that the combination of low dose enzyme with a cationic polymeric retention agent as well as with a cationic polymer and inorganic microparticle component retention aid system results in a significant improvement in drainage.

Example 7

In a 2 L beaker, a 4% by weight stock suspension of 100% old paper (old corrugated container) was charged. The pH of the stock suspension was adjusted to pH 7.5 with an aqueous sodium hydroxide solution or hydrochloric acid, if necessary. Subsequently, the amounts of the enzyme A indicated in Table 7 were added and stirred with the aid of a Heiltof stirrer at 800 rpm for 1 hour at 55 ° C. After this treatment, the stock suspension was diluted with water to a consistency of 2 g / L. To this diluted stock suspension, 0.03% by weight of polymer A was optionally added with stirring. Subsequently, the water retention value (WRV) was determined, the results are summarized in Table 7. Table 7: Water retention value at different enzyme concentrations depending on the addition of a polymeric retention agent Test no. Enzyme A [wt%] WRV without addition of polymer A [%] WRV with addition of polymer A [%] 33 0 116 112 34 0.001 103 98 35 0.005 99 101 36 0.01 101 99 37 0.05 102 102 38 0.1 104 98 39 0.3 103 101 40 0.5 102 101

The results show that the addition of the enzyme in a low dosage leads to an improvement of the fiber modification.

Claims (8)

1. A process for the production of paper, board and cardboard by draining a paper stock on a wire in the presence of at least one cationic polymeric retention aid and/or retention aid system with sheet formation and drying of the sheets, wherein an endo-β-1,4-glucanase is metered in an amount of from 0.00001 to 0.01% by weight, based on the dry paper stock, into the paper stock before the addition of the at least one cationic polymeric retention aid and/or retention aid system,
   where the cationic polymeric retention aid is a polyacrylamide and the intrinsic viscosity of the polyacrylamide is in the range from 7 to 15 dl/g.
2. The process according to claim 1, wherein the endo-β-1,4-glucanase is metered in an amount of from 0.00001 to 0.005% by weight, based on the dry paper stock, into the paper stock.
3. The process according to claim 1 or 2, wherein the endo-β-1,4-glucanase is metered in an amount of from 0.00001 to 0.001% by weight, based on the dry paper stock, into the paper stock.
4. The process according to any of the preceding claims, wherein the endo-β-1,4-glucanase is metered into the high-consistency paper stock.
5. The process according to any of the preceding claims, wherein a linear, branched or crosslinked polyacrylamide is used.
6. The process according to any of the preceding claims, wherein the cationic polymeric retention aid is metered in an amount of from 0.001 to 0.1% by weight, based on the dry paper stock.
7. The process according to any of claims 1 to 4, wherein the retention aid system is a microparticle system comprising an inorganic component.
8. The process according to claim 7, wherein the inorganic component is selected from bentonite and silica gel.