METHOD IN A PAPER MACHINE

Abstract: The invention relates to a method in a paper machine in connection with a moving element, such as cylinder, roll, felt, or wire, which is in contact with the paper web to be produced. The conditions are such that the moving element is exposed to substances in the paper web tending to adhere to the moving element and to impair its operation in the process of paper production. A composition is applied to the moving element, such as the central roll (1) in the press section, e.g. by a nozzle structure (4). This composition, such as flushing water, to which a possible releasing chemical has been added, comprises at least one enzyme selected in a way that it acts by a chemical process on at least one substance adhering from the paper web (6) to the moving element, such as the center roll (1). The purpose of the chemical process is to release and/or decompose said at least one adhering substance from the moving element, i.e. the center roll (1), to maintain and/or improve its reliability in the process of paper production.

Description: Method in a paper machine The invention relates to a method in a paper machine in connection with a moving element, such as cylinder, roll, felt, or wire, which is in contact with the paper web to be produced under conditions in which the moving element is exposed to substances in the paper web that can adhere to the moving element and to impair its operation in the process of paper production. Paper machines are currently used at higher and higher running speeds. Thus, in view of controllability of the process of paper manu¬ facture, an important factor is maintaining the reliability of the moving elements in the paper machine, such as cylinders, rolls, felts, and wires. Besides maintaining reliability, another important factor is to im¬ prove the runnability of the moving elements, particularly the center roll of the press section, in order to raise the speed of the paper production process. A paper machine comprises a number of moving elements which come in contact with the paper web at different stages of the process of paper production in a way that substances are released from the paper web in an uncontrolled manner and tend to adhere to the moving element. Such substances include wood components, coatings, such as latices, starch and carboxymethyl cellulose (CMC). When these substances adhere to a moving element, they will, in the long run, cause problems at said stage in the process of paper manufacturing and can, at their worst, cause a break of the paper web. In the following specification, some moving elements of the paper machine are listed as well as problems occurring when above- mentioned substances adhere to them from the paper web. First of all, a substance adhering to the felt will cause problems of runnability, because the dewatering ability of the felt will be reduced. A felt change will always cause a stoppage, and when such change cannot be arranged at the same time with other maintenance work, it will cause an extra stoppage. It is also obvious that if the dewatering ability of the felt is too much reduced, it may result in a break of the paper web, which will always cause considerable costs. Similar problems are also en¬ countered with wires. Their dewatering ability will be impaired, which may result in not only staining of the machine but also in a break of the paper web. For drying cylinders, the problem is staining, which reduces the operability of the process and causes a need for cleaning. Furthermore, substances released from the paper web and adhering to the drying wire reduce the drying capacity when the drying wire is stained. Particularly difficult problems are caused in the press section of the paper machine, where the paper web is released from the center roll of the press section. At this time, the paper web is in the process of paper production for the first time in a situation where the paper web runs, without support, from the center roll of the press section to the draw roll. If the draw ratio must be raised due to the retaining force directed to the paper web by the adhering substances, the paper web is thus exposed to an exponentially increasing load. Particularly when high-speed paper machines are used and when the running speeds of the paper production process are further increased, it is the release of the paper web from the center roll of the press section that is most critical, for the reasons mentioned above. The substances from the pa¬ per web adhering to the surface of the center roll prevent, at this critical stage, the paper web from being released in the optimal way from the surface of the center roll after the press nip. Thus the paper web must be subjected to a tensile load allowing for an earlier release. This ten¬ sile load is directed to the paper web in an exponentially increasing manner. Because the tension of the paper web is proportional to its susceptibility to break, the release of the paper web from the center roll is a most critical step. Naturally, in the press sections of paper ma¬ chines currently in use, attempts are made to prevent staining of the center roll, e.g., by a doctor blade placed against the surface of the center roll after the point of release of the paper web, as well as by spraying a fluid on the outer surface of the center roll, either pure water or water together with various release chemicals. By this method, the situation can be improved to a great extent such that most of the substances from the paper web adhering to the surface of the center roll can be removed. However, it has been found that present treatment with a doctor blade and a release chemical is not sufficient as a colloid film-like layer is formed on the outer surface of the center roll, which is resistant to the cleaning effect of the release chemicals and the doctor blade. Similar problems are also obvious to a person skilled in the art in other parts of a paper machine, where a moving element comes into contact with the paper web in such a way that a substance released from the paper web adheres to the moving element, impairing the operability of the process of paper manufacturing. In this context, the press section and, particularly, its center roll are regarded as the most critical parts in the paper machine because, as discussed above, the most critical loads in the production process are directed at the paper web when it is released from the center roll of the press section. It is an aim of the present invention to eliminate to a major extent the above-mentioned problems involved in the process of paper production and thus to improve the state of the art. Further aims include enabling the use of higher running speeds in the process of paper production, and simultaneously securing the continuity of the process of paper production. For reaching these goals, the method according to the invention is primarily characterized in that a composition comprising at least one enzyme is applied to the moving element, wherein said at least one enzyme in the composition is adapted to act by a chemical process on at least one substance, which is released from the paper web and adheres to the moving element, for the purpose of releasing and/or decomposing said at least one adhering substance from the moving element to maintain and/or improve the reliability of the moving element in the process of paper production. Consequently, the invention relates to the surprising finding that it is possible to apply an enzyme, effective on a substance which is released from the paper web and adheres to the moving element, in a way that the enzyme is transferred to the moving element and is able to act on the substance present in the moving element by such a chemical process which eliminates the adhering effect, wherein said substance, in a decomposed or modified form, can be removed from connection with the moving element. The method according to the invention provides the advantage that the adhering substances can be influenced separately. A suitable enzyme composition can be selected from widely known enzymes based on their mechanisms of action for each type of adhering substance to at- tain the purpose mentioned above. Thus, it can be noted that according to an advantageous embodiment of the method according to the inven¬ tion, the adhering substance consists of one or several substances from the following group: wood components, such as cellulose, hemicellu¬ lose, pectin, extractives, protein, lignin or lignans, coatings such as la¬ tices, starch and carboxymethyl cellulose (CMC), and that at least one enzyme is selected for the substance to be applied on the basis of the type of the substance adhered or possibly adhering to the moving element. Further, some advantageous embodiments of the invention are pre¬ sented in the other dependent claims. In the following description, the invention will be described more closely with reference to the appended drawing and examples. In the drawings, Figure 1 is a schematic side view of an arrangement according to the invention in the press section of a paper machine, Figure 2 is a schematic enlarged partial view of point I in Fig. 1 , and Figure 3 shows the results of a test run according to Example 5 graphically. With reference to Fig. 1, after the second press nip 2 of the center roll 1 of the paper machine, before the doctor blade 3 in the direction of rotation (arrow PS) of the press roll, a fluid composition is sprayed on the outer surface of the center roll 1 by means of a nozzle construc¬ tion 4 or the like. This composition contains at least one enzyme which is selected according to the basic idea of the invention. This at least one enzyme acts on the colloid film-like layer on the outer surface of the center roll 1. The enzyme penetrates said colloid layer and causes in said colloid layer a chemical reaction according to the invention, sub¬ stantially thinning or even totally removing said colloid film-like layer being formed on the outer surface of the center roll 1 , released from the paper web 6 and adhered on the outer surface of the center roll 1. The composition sprayed on the outer surface of the center roll 1 can natu¬ rally contain also chemicals acting on the macroscopic layers which are removed by using the doctor blade. The point of applying can be placed also after the doctor blade 3, because the time of action required by the enzyme corresponds to the duration of several revolutions, and the distance between the point of applying and the doctor blade is not sig- nificant in this respect. Figure 2 shows schematically, by broken lines 5, the effect to be achieved by the method according to the invention, whereby the clean¬ ing of the surface of the center roll 1 leads to the fact that the adher- ence of the paper web 6 on the outer surface of the center roll 1 can be substantially reduced, and the paper web is released from the outer surface of the center roll closer to the ideal tangential situation. This earlier release of the paper web 6 can be utilized either by reducing the draw ratio, i.e. the difference of peripheral speeds between the center roll 1 and the draw roll 7, whereby the tension of the paper web is sub¬ stantially reduced and thus the risk of break of the paper web is re¬ duced, and/or by increasing the running speed of the paper machine while maintaining the same draw ratio as without enzyme treatment. In this way, by applying the method according to the invention, either better reliability of the press section in view of continuous running and/or a higher running speed is achieved in the process of paper production. It is obvious for a person skilled in the art that the corresponding action can also be achieved in less critical moving elements in the process of paper production, such as in wires, felts etc., whereby a composition comprising an enzyme applied on said moving elements is carried with the moving element and generates the desired chemical reaction whereby the moving element is cleaned, maintaining its operability. It is also obvious that the enzyme can be brought in contact with the moving element in any suitable way applicable in paper machines. The enzyme can also be recovered and recycled in the process. Below, enzymes will be listed which contribute to the degradation or modification of substances adhering to a moving element, such as the center rolM , the cylinder, the felt, the wire, etc., and improve the runnability of the process of paper production, e.g. the release of the paper web from the center roll in the press section. Enzymes degrading and modifying cellulose, such as endo¬ glucanases, cellobiohydrolases and β-glucosidases. Enzymes degrading and modifying wood hemicellulose polymers, such as xylan, mannan and arabinogalactan, in¬ cluding xylanases, mannanases, β-xylosidases, β-manno- sidases and enzymes degrading side groups of the above¬ mentioned polymers. Enzymes degrading and modifying wood extractives, par- ticularly lipases hydrolyzing triglycerides. Pectinase enzymes degrading wood pectin polymers. Proteases degrading wood proteins. Oxido-reductase enzymes acting on wood lignin and lignans, including peroxidases and phenol oxidases, particu- larly laccases, used alone or in combination with low-mo¬ lecular organic or inorganic cofactors and mediators. Enzymes degrading starch, such as amylases. In the following examples, the operability of the method according to the invention will be illustrated with a series of examples, wherein laboratory tests, pilot tests and mill test runs are described. The labo¬ ratory tests are the most extensive, and they serve for illustrating the applicability of the invention with a wide range of enzymes. The pilot test series specifies additionally the applicability of the method according to the invention. The mill test run, in turn, shows the applicability of the method in industrial production. The Examples serve to illustrate the invention and are not intended as limiting thereof. Example 1 A laboratory study was conducted to examine the effect of enzyme treatment of the roll surface of a paper machine on the release of the web. The laboratory apparatus designed for the purpose was used to meas¬ ure the releasing tension of the web before and after enzyme treatment of the roll surface. Laboratory sheets were prepared from deinked pulp (DIP) and thermomechanical pulp (TMP) mixture: DIP 50 % unbleached thermo-mechanical pulp 50 % grammage 56 g/m 2 dry substance 42 % after pressing pH 7.0 (non-adjusted) The sheet was pressed against the surface of a Valrok press roll material, generally known in the field of paper production, in two phases under a pressure of 2.2 MPa, with an exchange of the drying sheet in between. The pressing times were 1 min each. The enzyme mixture used was an enzyme available under the trademark PERGALASE A40. Pergalase A40 is an enzyme mixture manufactured by Genencor International, containing cellulase and hemicellulase enzymes of Trichoderma reesei which can hydrolyze colloid carbohydrates on the surface of the center roll. The Pergalase A40 product contains about 2700 cellulase units per millilitre. The de¬ termination of cellulase activity is based on the enzymatic hydrolysis of carboxymethyl cellulose (CMC) in 0.05 M sodium acetate buffer at 50°C and at pH 4.8. One activity unit refers to the quantity of enzyme which releases one micromol of reducing sugars, calculated as glu- cose, from the substrate in one minute. Reducing sugars are deter¬ mined by means of dinitrosalicylic acid (DNS). For enzyme treatment, an accumulation was produced on the surface of the Valrok roll by pressing 10 sheets against the surface in succession, without cleaning the surface in between. The enzyme treatment was conducted by keeping the surface of the Valrok roll for 1.0 h in a solution containing 1.0 % of Pergalase A40 en¬ zyme at a temperature of 50° C. The releasing tension (N/m) was measured according to the method UPM-Kymmene/PHORD. Results: Releasing tension (N/m) DIP/TMP pulp: Before enzyme treatment sheet 1 1.41 sheet 4 1.45 sheet 10 1.45 After enzyme treatment sheet 1 0.99 sheet 2 1.18 sheet 3 1.41 These preliminary tests showed a clear reduction of releasing tension. The release of the web from the roll surface was easier and the releas¬ ing values were clearly reduced. Example 2 This example shows the effects of various enzyme preparations on the releasing properties of paper web. All enzyme preparations are commercial, except Pseudomonas lipase, which was produced and recovered by the methods described in WO 95/30744 and U.S. Patent 5,445,949 and used in a concentration of 100 DLL) U/ml. The DLU lipase activity is determined spectrophotometrically at 550 nm as the amount of resorufin formed in the hydrolysis of 1 ,2 — 0 dilayryl-rac- glycero-3-glutaric acid resorufin ester at pH 6.8 and 37°C (See for example, WO 95/30744). Resinase A2X® is a lipase produced by Novo Nordisk with a standardized activity of 100 KLU/g. Pectinex 3XL® is a pectinase produced by Novo Nordisk with Aspergillus niger and has a standardized activity of 3000 FDU/ml. The enzyme treatments were carried out in a manner corresponding to that in Example 1. The laboratory sheets were prepared from the DIP/TMP mixture as in Example 1 , except that no filler was used and only five sheets were prepared prior to enzyme treatment. For all enzyme liquids, a dosage of 1 % was used. Results of the treatments: Treatment pH Releasing tension (N/m) Before enzyme / After enzyme treatment treatment Reference Sheet 1 2.21 Sheet 1 2.59 Sheet 3 2.25 Sheet 2 2.63 Sheet 5 2.55 Sheet 3 2.63 Reference Sheet 1 2.13 Sheet 1 2.28 Sheet 3 2.25 Sheet 2 2.58 Sheet 5 2.36 Pergalase A40® Sheet 1 2.16 Sheet 1 1.44 (cellulase/hemi- Sheet 3 2.18 Sheet 2 1.71 cellulase) Sheet 5 2.55 Sheet 3 2.17 Pseudomonas Sheet 1 2.16 Sheet 1 1.82 lipase Sheet 3 2.18 Sheet 2 1.92 Sheet 5 2.32 Sheet 3 2.05 Pseudomonas Sheet 1 2.24 Sheet 1 1.94 lipase Sheet 3 2.32 Sheet 2 2.13 Sheet 5 2.32 Sheet 3 2.32 Resinase® Sheet 1 2J7 Sheet 1 2.09 (lipase) Sheet 3 2.28 Sheet 2 2.13 Sheet 5 2.44 Sheet 3 2.28 Resinase® Sheet 1 2.15 Sheet 1 2.02 (lipase) Sheet 3 2.24 Sheet 2 2.34 Sheet 5 2.32 Sheet 3 2.40 Pectinex 3XL® Sheet 1 2.21 Sheet 1 2.40 (pectinase) Sheet 3 2.24 Sheet 2 2.47 Sheet 5 2.51 Sheet 3 2.47 Of the four enzyme preparations Pergalase A40® improved most efficiently the release of paper web, corresponding to about 38 % reduction in the releasing tension. The two lipases showed the greatest reduction of releasing tension at pH 5 and with slightly less efficiency at pH 7. The pectinase showed a moderate releasing effect. Example 3 A laboratory study was carried out to confirm the previous results and to make sure that the formulation chemicals of the most efficient enzymes were not causing the improved release. The experiments were carried out as in example 2, except that new pulp samples were used and the level of releasing force needed was Iower than in example 2. All enzyme and reference treatments were carried out at pH 5. Treatment Releasing tension (N/m) Before enzyme / After enzyme treatment treatment Reference Sheet 1 1.28 Sheet 1 1.60 Sheet3 1.35 Sheet2 1.66 Sheet5 1.66 Sheet3 1.77 Inactivated Pergalase A40® Sheet 1 1.28 Sheet 1 1.47 (boiling for 20 min) Sheet 3 1.49 Sheet2 1.66 Sheet 5 1.50 Sheet3 1.77 The formulation chemicals of Sheet 1 1.28 Sheet 1 1.71 Pergalase A40® Sheet3 1.43 Sheet2 1.81 Sheet5 1.58 Sheet3 1.92 The formulation chemicals of Sheet 1 1.20 Sheet 1 1.43 Pseudomonas lipase Sheet 3 1.39 Sheet2 1.47 Sheet5 1.58 Sheet3 1.60 Pseudomonas lipase Sheet 1 1.28 Sheet 1 1.12 Sheet 3 1.43 Sheet2 1.28 Sheet 5 1.54 Sheet3 1.39 Pergalase A40® Sheet 1 1.24 Sheet 1 0.78 Sheet3 1.43 Sheet2 1.05 Sheet5 1.54 Sheet3 1.20 The results clearly show that the active enzyme proteins are causing the reduction in the releasing tension. Thus, the paper sheet can be removed easier from the Valrok surface than in the reference treatments. Example 4 This example shows the effects of cellulase/hemicellulase and lipase enzymes on the release of paper web from press roll surface material, when the paper sheets were prepared from the furnish from a paper machine producing SC paper of 56 g/m2 basis weight. 1 % enzyme solutions were used in the treatments at pH 5. The paper sheets were prepared and the measurements were carried out in a manner corresponding to that in example 3. Pulp mixture bleached / unbleached TMP 50/50 chemical pulp / TMP 20/80 grammage 56 g/m2 ash content 24 % pH 4.7 retention agent (Fennopol K 3400 R) 470 g/t (0.27 %) Dry substance after pressing 40 %. The main purpose was to see how the enzymes affect the release when applied alone or in combination. The following results were obtained. Treatment Releasing tension (N/m) Before enzyme / After enzyme treatment treatment Reference Sheet 1 1.50 Sheet 1 1.75 Sheet 3 1.67 Sheet 2 2.05 Sheet 5 1.81 Sheet 3 2.21 Pergalase A40® Sheet 1 1.45 Sheet 1 1.07 Sheet 3 1.47 Sheet 2 1.12 Sheet 5 1.79 Sheet 3 1.41 Pseudomonas lipase Sheet 1 1.43 Sheet 1 1.26 Sheet 3 1.53 Sheet 2 1.35 Sheet 5 1.60 Sheet 3 1.52 Pergalase A40® Sheet 1 1.45 Sheet 1 0.72 and Pseudomonas lipase Sheet 3 1.52 Sheet 2 0.78 Sheet 5 1.64 Sheet 3 0.97 The enzymes reduced the releasing tension to about the extent as with the pulp mixtures containing DIP. Surprisingly, the two enzymes when applied together gave the highest degree of reduction of the force needed to release the paper web from the Valrok surface. The releasing tension was as much as 56 % Iower after the enzyme treatment. Futhermore, the treatment also appeared to decrease the speed of new deposit formation on the surface. Example 5 This example shows the test runs carried out in pilot scale in a test apparatus corresponding substantially to the press section shown in Fig. 1. The aim was to find out the effect of Pergalase A40® enzyme on the center roll of the press section in a paper machine and how said Pergalase A40® enzyme acts on the release of the paper web from the center roll. The main dimensions of the test apparatus and the process conditions were the following: roll diameter 1230 mm, nip load 120 kN/m, roll material Valrok, roll speed 22 m/s. The temperature of the system was 47°C and the pH value 4.3. The furnish in the test run was SC paper furnish, i.e. the process in¬ volved was the production of magazine printing paper. A reference run R was conducted at the first stage of the test run, and it took 3 hours. The application of the Pergalase A40® enzyme, i.e. the actual test run K took about 2.5 hours after the reference run. The feed dosage of the enzyme mixture during the test run was 2 l/ton of paper. The appended Table 1 and Figure 3 show the effect of both the refer- ence run R and the actual test run K, i.e. the application of the enzyme, at the point of release of the paper web from the center roll. It must be noted that the draw difference was kept constant, i.e. in a numerical value of 0.49 m/s, during both the reference run R and the actual test run K, i.e. the application of the enzyme. The enzyme mixture was added to and mixed in raw water and sprayed on the surface of the center roll via nozzles placed after the doctor blade, after which there was a second doctor blade. Table 1 The table shows that the point A in Fig. 2, i.e. the point of release of the paper web in the initial situation, during the reference run R, shifted for about 2 cm (transition S, A→B, Fig. 2) in a direction opposite to the di¬ rection of rotation of the center roll. The ash percent and the grammage were substantially constant during the test run. The test run shows cleariy that the application of Pergalase A40® en¬ zyme in water to be sprayed on the surface of the center roll caused a transition S of the point of release of the paper web (Fig. 2), which is significant. Figure 2 further illustrates the transition, point A indicating the initial situation, that is, that during the reference run, and point B in- dicating the effect of the enzyme, that is, the transition. With reference to Fig. 3, the actual test run K also shows that the enzyme started to act in about one hour from the start of the application. Example 6 The purpose of the test run carried out in industrial scale was not only to find out the effect of Pergalase A40® studied in Example 2 on the re- lease of the paper web from the center roll in the press section and on maintaining the center roll clean, but also the possible effect on the properties of the broke pulp and the paper, because Pergalase A40® gets from the center roll to the broke system. Conditions in the test run: paper grade: 50 g/m 2 SC paper (ash 30 %), and 60 g/m 2 SC paper (ash 32 %) production: 55 t h running speed: 1550 m/min Test arrangements: Different mixtures of substances with the following compositions were applied by spraying on the center roll in the press section, before the doctor blade: Test part 1. water + conventional releasing chemical (Celfix®), i.e. reference A Test part 2. test run K, i.e. Pergalase A40®, dose 0.2 l/ton of paper, water quantity as in references A and B Test part 3. pure water, i.e. reference B Test part 4. reference A When a dosage according to test part 1 was on, the pulper of the first press was emptied at intervals of 1 — 2 hours to convey Pergalase A40® more evenly to the broke system. Follow-up and measurements: draw difference; staining of the center roll in 4 min, lubrication of the center roll being stopped; quality of the dosage broke; paper quality; dewatering and retention Course of the test run and results: The reference for the test part 2 at the beginning of the test run was the test part 1 and at the end of the test run test parts 3 (2 hours) and 4. The results of the test run with reference to the draw difference and staining of the center roll are shown in Table 1. It can be seen that Per¬ galase A40® reduced the need for a draw difference from 3.42 % to 3.31 %, the reference being either pure water (test part 3) or water + a releasing chemical (test parts 1 and 4). Further, it should be noted that when the test part 2, i.e. Pergalase A40®, was started, a time span of ca. 1.0 to 1.5 h was required before an improvement was observed in the release of the paper web from the center roll, and after 2.5 h from starting the test part 2, the effect could be confirmed and the draw dif¬ ference was then reduced. In a corresponding manner, in 0.5 to 1.0 h after stopping the application of Pergalase A40®, i.e. starting test part 3, the release from the center roll was clearly impaired and the draw difference had to be increased. Table 1. Effect on different treatments on the tensile difference Test part Draw differ¬ ence, % 1 3.42 2 3.31 3 3.43 4 3.42 The effect of Pergalase A40® can be clearly seen when studying the staining of the center roll. The difference between pure water (test part 3) and water + a releasing chemical (test parts 1 and 4) is small, but during treatment with Pergalase A40® (test part 2), the quantity of material adhered to the center roll was considerably reduced in com¬ parison with test parts 1 , 3 and 4. During the test run, also the quality of the broke, paper quality, dewatering and retention were observed, but no deviations from the normal variation were found. The test run conducted in industrial scale showed clearly that by lubri¬ cating the center roll of the press section by a fluid containing enzymes (mixture Pergalase A40® / water), a considerably better result was achieved with regard to both the release of the paper web and main¬ taining the center roll clean than by conventional methods, i.e. either by pure water or by a mixture of water and a releasing chemical. From the center roll, the fluid containing enzymes (Pergalase A40®) is conveyed to the broke system, but no significant effect was observed in the quality properties of the broke or paper nor in dewatering or retention. Example 7 Experiments were carried out in laboratory to remove impurities with enzymes from a wire material obtained from a paper machine which produces newsprint and uses thermomechanical pulp and DIP as pulp raw materials. Pergalase A40® cellulase/hemicellulase mixture and Pseudomonas lipase were studied in wire treatments at pH 5 and 50° C. Pieces of wire were kept in enzyme solutions (Pergalase A40® 2700 U/ml, Pseudomonas lipase 500 DLU/ml) for 24 hours. Prior to treatments deposits were studied and marked in stereo microscope and the same deposits were examined after the treatments. A further washing was performed with a pressure washer for 5 seconds after enzyme treatment. The deposits were examined after enzyme treatment and after pressure washing. Treatment The number of deposits The number of deposits before / after enzyme in enzyme treated wire treatment before / after pressure washing Reference 6/6 10/10 Pergalase A40® 7/7 8/8 Pseudomonas lipase 8/8 9/2 Pergalase A40® 8/8 8/2 + Pseudomonas lipase The observations made in the stereo microscope clearly demonstrate that after enzyme treatment the deposits are still attached to the wire, but are far more easily removable with mechanical force such as with pressure washing. High pressure water showers are frequently used at paper mills to wash the wires and felts when the paper machine is running. Example 8 This example describes a mill trial carried out at a paper machine which is producing newsprint from thermomechanical and deinked pulp. The release of the paper web was studied at the 4th press nip after the center press roll. The purpose of the trial was to improve the release with the use of enzyme. The enzyme was applied in a manner similar to that described in Fig. 1. For the trial, a mixture of cellulase and lipase enzymes was produced. The enzyme contained the following activities: Cellulase: 2463 CMC U/ml Lipase: 82 DLU /ml Conditions in the test run: Paper grade: 45 g/m2 Production: 34.8 t/h Speed of paper machine: 1447 m/min Test arragements: Reference period: conventional chemical Enzyme period: Cellulase-lipase mixture, dosage 0J8 l/t Follow-up and measurements: draw difference between 4th press nip and drying section paper quality wet-end measurements The draw difference between the 4th press nip and drying section was 13.1 m/min during the reference period. 15 minutes after the addition of enzyme had started, the release point of the paper web started to change and during the next two hours it was clearly visible that the release angle was smaller than before enzyme addition. Four hours after the start of the enzyme addition, the draw difference was reduced to 12.2 m/min, which corresponds to about 7 % reduction. The enzyme caused no negative effects on paper quality or wet-end chemistry. Example 9 This example describes a mill trial in order to study the release of the chemical pulp web from the two press rolls in the pulp drying machine. The release has been especially difficult with pulps containing high amounts of extractives and hemicelluloses. As a release chemical, a surface active agent diluted with water is used at both press rolls. The chemical and the enzyme was added to the top of the press, forming a Iiquid layer in front of the doctor blade. Conditions in the test run: pulp: unbleached birch chemical pulp production: 12 tons/h Test arrangements: A mixture of cellulase and lipase was added instead of the sur ace active agent at the press rolls to improve the release of pulp web. The enzyme Iiquid contained the following activities: cellulase: 2488 CMC U/ml lipase: 407 DLU U/ml The enzyme was applied to the two press rolls in the following dosages: Press 1 Press 2 Day 1 : 0.24 l/t 0.24 l/t Day 2: 0.125 l/t 0.125 l/t Day 3: 0.08 l/t 0.08 l/t 0.24 l/t 0.08 l/t The release of the pulp web using the enzymes was equal to that using the surface active agent at day 1 and day 2. At day 3, the reduction of the dosage to 0.08 l/t at both press rolls caused a significantly increased adhesion of the pulp web to the second press. 15 minutes after changing the enzyme dosage back to the level of 0.24 l/t level at the second press the release improved back to the same level as at day 1 and day 2. During the trial no breaks occured at the press section whereas during a reference run with the current chemical the number of breaks at the press section was normally about 1 — 2 per a three day run. It can be concluded that enzymes can also be used to improve the release of pulp web. From the above description, it is obvious for a person skilled in the art that the mixture of water + enzyme addition + conventional releasing chemical is also fully possible, because the mechanisms of action of /11225 PC17FI96/00493 21 different components differ to such an extent that a harmful interaction is not possible, whereby the cleaning mechanisms of action of the components water, the enzyme addition and the releasing chemical support each other. It is obvious that the invention will also be effective in connection with other moving elements in a paper machine. For example in the felt, an at least equally effective action of the enzyme is to be expected.

Claims: Claims: 1. Method in a paper machine in connection with a moving element, such as cylinder, roll, felt, or wire, which is in contact with the paper web to be produced under conditions in which the moving element is exposed to substances in the paper web tending to adhere to the mov¬ ing element and to impair its operation in the process of paper produc¬ tion, characterized in that a composition is applied to the moving ele¬ ment which comprises at least one enzyme, wherein said at least one enzyme in the composition is adapted to act by a chemical process on at least one substance released from the paper web and adhering to the moving element, for the purpose of releasing and/or decomposing said at least one adhering substance from the moving element to maintain and/or improve the reliability of the moving element in the process of paper production. 2. Method according to claim 1 , wherein the adhering substance is one or several of the following group: wood components, such as cellu¬ lose, hemicellulose, pectin, extractives, protein, lignin or lignans, coatings such as latices, starch, carboxymethyl cellulose (CMC), char¬ acterized in that at least one enzyme is selected for the composition to be applied on the basis of the type of the substance adhered or possi¬ bly adhering to the moving element. 3. Method according to claim 1 or 2, characterized in that the enzyme is a cellulase, such as endoglucanase, cellobiohydrolase, or β-glu- cosidase. 4. Method according to claim 1 or 2, characterized in that the enzyme is a hemicellulase, such as endoxylanase, endomannase, an enzyme degrading arabinogalactane, β-xylosidase, β-mannosidase, an esterase degrading acetyl groups of hemicelluloses, α-arabinosidase, α-glu- curonidase, or α-galactosidase. 5. Method according to claim 1 or 2, characterized in that the enzyme is a lipase. 6. Method according to claim 1 or 2, characterized in that the enzyme is a protease. 7. Method according to claim 1 or 2, characterized in that the enzyme is a pectinase. 8. Method according to claim 1 or 2 , characterized in that the en¬ zyme is an oxido-reductase enzyme, such as peroxidase or laccase. 9. Method according to claim 1 or 2, characterized in that the enzyme is amylase. 10. Method according to any of the preceding claims 3 to 8, character¬ ized in that the composition to be applied comprises two or more enzymes of different groups, selected from the following groups: - cellulase, - hemicellulase, - lipase, - protease, - pectinase, - oxido-reductase enzyme, - amylase. 11. Method according to any of the preceding claims 1 to 10, charac- terized in that the composition to be applied comprises at least one enzyme together with at least one non-enzymatic releasing chemical. 12. Method according to claim 1 in a paper machine, particulariy in the press section of the same, wherein the moving element is the center roll in the press section, characterized in that a composition compris¬ ing at least one enzyme is applied on the outer surface of the center roll (1) in the press section, wherein said at least one enzyme in the composition is adapted to act by a chemical process on at least one substance adhering from the paper web (6) to the center roll (1), for the purpose of releasing and/or decomposing said at least one adhering substance from the center roll (1), particularly for the purpose of im¬ proving the controllability of the release of the paper web from the cen¬ ter roll.

Inventors: AHO PEKKA, JOKINEN OLLI, KANTELINEN ANNE, KUKKAMAEKI ESKO, PAERNAENEN PERTTI, AHO, PEKKA, JOKINEN, OLLI, KANTELINEN, ANNE, KUKKAMAEKI, ESKO, PAERNAENEN, PERTTI
Applicants: AHO PEKKA, CIBA GEIGY AG, JOKINEN OLLI, KANTELINEN ANNE, KUKKAMAEKI ESKO, PAERNAENEN PERTTI, UPM KYMMENE CORP, AHO, PEKKA, CIBA-GEIGY AG, JOKINEN, OLLI, KANTELINEN, ANNE, KUKKAMAEKI, ESKO, PAERNAENEN, PERTTI, UPM-KYMMENE CORPORATION
Application year: 1996
Main classification: D21F7
IPC codes: D21F1, D21F11, D21G3