Application of enzymes and flocculants for enhancing the freeness of paper making pulp

Abstract: A process for improving freeness of paper pulp which comprises these steps: a) Adding to the pulp at least ⊘.⊘5% based on the dry weight of the pulp, of a cellulolytic enzyme; b) Allowing the pulp to contact the cellulolytic enzyme for at least 2⊘ minutes at a temperature of at least 2⊘°C; c) Adding at least ⊘.⊘⊘⊘7% based on the dry weight of the pulp of a water soluble cationic polymer, and then d) Forming the thus treated pulp into paper.

Description: Field of the invention The present invention relates to a process for improving the freeness of paper pulp by adding cellulase as a cellulolytic enzyme in a specific amount and then adding a specific amount of a water-soluble cationic polymer to paper pulp before forming the thus treated paper pulp into paper. Background of the invention More and more the papermaking industry uses recycled papers. For example, for the manufacture of corrugated cardboard, more often raw materials are used which are based on recycled fibers and, at the same time, the number of recyclings is increased. With each recycling, the quality of the raw materials is lessened. To obtain a satisfactory level of mechanical characteristics, refining of the pulps in aqueous suspension is generally carried out, which leads to difficulties in runnability because of high concentrations of fines. The pulps in aqueous suspension which are ready to be worked on a paper machine can be characterized by various parameters, one of which is particularly significant for predicting the draining capability of the pulp. A measure of the drainability of the pulp is frequently expressed in the term "freeness". Specifically, freeness is measured and is specifically designated Canadian Standard Freeness, CSF. CSF measures the drainage of 3 grams (oven dried weight) of pulp suspended in 1 liter of water. Since pulp slurry is not homogeneous, it is difficult to take an exact required weight of pulp equivalent to 3 grams. Therefore, at the time of freeness testing, with respect to the data hereafter presented, the consistency of pulp stock was determined by stirring well and then drained in a Buchner funnel. The pulp pad was dried at 105°C to determine the exact weight of the pad. The CSF data hereafter reported was corrected to a 0.3 % consistency using the table of freeness corrections prepared by the Pulp and Paper Research Institute of Canada and has been described in TAPPI manual (T227). The CSF values were measured at 20°C. A process for improving the freeness (drainability) of biological sludge by adding a combination of cellulolytic enzymes and cationic flocculants has already been known from EP-A-0 291 665. Since the sludge being treated in the prior art process includes anionic trash such as polysaccharides and protein, this process requires the use of a combination of various hydrolytic enzymes, especially a mixture consisting of amylases, cellulases and proteases in order to be able to effectively dewater the biological sludge. On the other hand, the use of cellulolytic enzymes, e.g. cellulases and/or hemicellulases,for treating recycled paper pulps to improve freeness or drainage characteristics has already been disclosed in US-A-4 923 565 and in "TAPPI Journal", 1989, pages 187-191. However, the degree of drainability which can be obtained according to the latter processes of the prior art by using cellulolytic enzymes is not sufficient and leaves room for further improvement. Therefore, the object of the present invention is to provide a process for further improving the freeness (drainability) of paper pulp. According to the present invention it has been found that this object can be achieved by treating paper pulp in a specific manner with a combination of a specific amount of cellulase as a cellulolytic enzyme and a specific amount of a water-soluble cationic polymer which are added one after the other allowing the pulp to contact the cellulase for a certain time at a specific temperature in an intermediate step. Summary of the invention Therefore, subject-matter of the present invention is a process for improving the freeness of paper pulp, which comprises the sequential steps of: a) adding to the pulp from 0.01 to 10 %, based on the dry weight of the pulp, of cellulase as a cellulolytic enzyme; b) allowing the pulp to contact the cellulase for at least 20 minutes at a temperature of at least 20°C; c) adding at least 0.0007 %, based on the dry weight of the pulp, of a water soluble cationic polmyer, and then, d) forming the thus treated pulp into paper. According to the present invention the drainage or the freeness of a wide variety of paper pulps including both Kraft and other types of pulp can be substantially improved. The invention is particularly useful in treating pulps that contain recycled fibers. The effectiveness of the invention in improving drainage is most notable when the pulps contain at least 10 % by weight of recycled fiber, with great improvements being evidenced when the recycled fiber content of the pulp being treated is at least 50 % or more. While the invention produces particularly good results when used to treat pulps which contain substantial quantities of recycled fibers, it is also applicable in treating pulps which contain little or no recycled fibers. According to a preferred embodiment of the present invention the cellulolytic enzyme cellulase is added in amount of from 0.1 to 10 weight percent. The paper pulp treated according to the process of the present invention preferably contains at least 10 % by weight, preferable at least 50 % by weight of recycled fibers. The water soluble cationic polymer used in the process of the present invention preferably is a copolymer which contains from 30 to 80 % by weight of acrylamide. According to a further preferred embodiment of the present invention the used cationic acrylamide copolymer is an acrylamide-diallyldimethyl ammonium chloride (DADMAC) copolymer. In the following the process of the present invention is described in more detail by reference to the enclosed drawings which illustrate the effect of cellulolytic enzyme and polymer dosage at various pHs and times of paper pulp contact with the cellulolytic enzymes on Canadian Standard Freeness (CSF) (drainability). Specifically: Fig. 1 shows the effect on CSF at pH 4.6 with an enzyme contact time of 10 minutes and at a temperature of 40°C. Fig. 2 shows the effect on CSF at pH 4.6 with an enzyme contact time of 60 minutes and at a temperature of 40°C. Fig. 3 shows the effect on CSF at pH 6 with an enzyme contact time of 10 minutes and at a temperature of 40°C. Fig. 4 shows the effect on CSF at pH 6 with an enzyme contact time of 60 minutes and at a temperature of 40°C. Fig. 5 shows the effect on CSF at pH 7.07 with an enzyme contact time of 10 minutes and at a temperature of 40°C. Fig. 6 shows the effect on CSF at pH 7.07 with an enzyme contact time of 60 minutes and at a temperature of 40°C. Fig. 7 shows the effect on CSF at pH 4.765 with an enzyme contact time of 30 minutes and at a temperature of 30°C. Fig. 8 shows the effect on CSF at pH 4.768 with an enzyme contact time of 45 minutes and at a temperature of 45°C. Fig. 9 shows the effect on CSF at pH 4.768 with an enzyme contact time of 60 minutes and at a temperature of 60°C. Figs. 10 - 15 show the effects on CSF of various polymer enzyme combinations. The cellulolytic enzymes As the cellulolytic enzymes the cellulases and/or the hemicellulases disclosed in US-A-4 923 565 may be used in the practice of the present invention. Specific commercial cellulolytic enzymes are available and may be used in the practice of the present invention. THE CATIONIC WATER SOLUBLE POLYMERS A variety of water soluble cationic flocculants may be used in the practice of the invention. Both condensation and vinyl addition polymers may be employed. For a relatively extensive list of water soluble cationic polymers, reference may be had to disclosure of CA-A-731,212. A preferred group of cationic polymers are the cationic polymers of acrylamide which in a more preferred embodiment of the invention, contain from 4⊘-6⊘% by weight of acrylamide. Larger or smaller amounts of acrylamide in the polymers may be used, e.g., between 3⊘-8⊘%. Typical of the cationic monomers, polymerized with acrylamide are the monomers diallyldimethyl ammonium chloride, (DADMAC), dimethylaminoethyl/acrylate methyl chloride quaternary ammonium salt, (DMAEA.MCQ). When these cationic acrylamide polymers are used they should have a RSV (reduced specific viscosity) of at least 3 and preferably the RSV should be within the range of 5-2⊘ or more. RSV was determined using a one molar sodium nitrate solution at 3⊘°C. The concentration of the acrylamide polymer in this solution is ⊘.⊘45%. THE PAPER PULPS BEING TREATED As indicated, the invention has utility in improving the drainage or the freeness of a wide variety of paper pulps, including both Kraft and other types of pulp. The inventibn, is particularly useful in treating pulps that contain recycled fibers. The effectiveness of the invention in improving drainage is most notable when the pulps contain at least 1⊘% by weight of recycled fiber, with great improvements being evidenced when the recycled fiber content or the pulp being treated is at least 5⊘% or more. TREATMENT OF THE PULPS WITH THE ENZYMES AND CATIONIC POLYMERS As indicated, the invention requires that the pulp first be treated with the enzyme and then with the cationic polymer. It is also important to the successful practice of the invention, that the conditions under which the treatment with the enzyme occurs is such to provide optimum reaction time of the enzyme with the pulp. The treatment of the pulp with the enzyme is preferably conducted for a period of time not greater than 6⊘ minutes. The minimum treating time is about 2⊘ minutes. A typical treating time would be about 4⊘ minutes. The pH of the pulp to achieve optimum results should be between the ranges of 4 and 8. The temperature of the treatment should not be below 2⊘°C, and usually should not exceed 6⊘°C. A typical average reaction temperature is favorably conducted is 4⊘°C. The preferred dosage of the polymer, as actives, is from ⊘.⊘⊘26% to ⊘.⊘196% polymer based on the dry weight of the pulp. A general dosage which may be used to treat the pulp with the polymer is from ⊘.⊘⊘⊘7% to ⊘.⊘653% by weight. The enzyme dosage based on the dry weight of the pulp in a preferred embodiment ranges from ⊘.1 to 1⊘% by weight. A general treatment range of the enzyme that may be used is from ⊘.⊘1 to 1⊘% by weight. It is obvious that in order for the enzyme to have sufficient reaction time and mixing described above, it is necessary that they be added to the pulp at the point in the paper making system to allow sufficient time for the above conditions to occur. Thus, a typical addition point in paper making system would be the machine chest. Other places where suitable contact time would occur may also be used as additional points. The polymers, in our examples contain the following components: Polymer 1 : An acrylamide polymer containing 1⊘ mole percent of DMAEA.MCQ. This polymer has an RSV of 17. It is in the form of an emulsion which contained approximately 26% by weight of polymeric ingredient. Polymer 2 : This polymer is a 34.8 percent by weight of active polymer ingredients in the form of a water-in-oil emulsion. It contains 5⊘ weight per cent of DADMAC; copolymerized with acrylamide. The polymer has an RSV of 5. Polymer 3 : Polymer 3 is an acrylamide polymer containing 3⊘ mole percent by weight, DMAEA-MCQ. It has an RSV of 19, the polymer is in the form of a water-in-oil emulsion being 29.6 percent by weight. EXAMPLE 1 A. Response Surface Factorial Design I A 3⊘ run response surface factorial design Table 1 was setup, in which the effects of enzyme. polymer dosages, pH, time and temperature were simultaneously investigated on the freeness of pulp prepared using a mixture of old corrugated containers and newsprints (OCC and NP 75:25, polymer 1). The pulp slurry (3 g. dry weight) under these specified conditions was first treated under continuous agitation (250 rpm) with an enzyme solution of Celluclast 1:5 L (NOVO ⊘ to 2⊘% based on dry weight of pulp), and then treated at 2⊘°C with Polymer 1 at a dosage of ⊘.⊘131 to ⊘.⊘392% on dry weight of pulp. Polymer (0,454 kg/908 kg) Enzyme pH Time Temperature Run Order CSF Values 1 0 4.60 10 55°C 27 393.0 3 0 4.60 10 25°C 7 528.57 1 .2 4.60 10 25°C 1 448.78 3 .2 4.60 10 55°C 26 645.95 1 0 7.07 10 25°C 9 344.63 3 0 7.07 10 55°C 29 457.0 1 .2 7.07 10 55°C 28 397.15 3 .2 7.07 10 25°C 6 508.82 1 0 4.6 60 25°C 5 345.0 3 0 4.6 60 55°C 23 526.46 1 .2 4.6 60 55°C 22 483.69 3 .2 4.6 60 25°C 4 622.53 1 0 7.07 60 55°C 25 331.46 3 0 7.07 60 25°C 8 490.31 1 .2 7.07 60 25°C 3 439.75 3 .2 7.07 60 55°C 24 522.10 0 .1 6 35 40°C 10 456.88 4 .1 6 35 40°C 12 690.81 2 0 6 35 40°C 16 421.88 2 .3 6 35 40°C 14 708.44 3 .1 4.07 35 40°C 13 674.50 2 .1 8.1 35 40°C 11 398.22 2 .1 6 10 40°C 21 506.63 2 .1 6 85 40°C 15 622.60 2 .1 6 35 25°C 2 541.0 2 .1 6 35 70°C 30 558.84 2 .1 6 35 40°C 20 601.0 2 .1 6 35 40°C 18 578.85 2 .1 6 35 40°C 19 578.64 2 .1 6 35 40°C 17 590.88 A predictive equation was developed using all the experimental data. Statistical analysis of the data Table 2 and 3, resulted in a model with a R-Square value of ⊘.9662 and R-Square Adj. value of ⊘.951⊘. These values demonstrated the accuracy of the model used in this investigation. Data given in Tables 4, 5 and 6 are the initial setting of the experiments, and the theoretical optimal values obtained. The CSF values increased using separately Celluclast 1.5L (1⊘% w/w) or polymer ⊘.⊘392% on dry weight of pulp). Using both cellulase and polymer increased the CSF from 24⊘ to 717 ml. In contrast enzyme and polymer alone increased CSF from 24⊘ to 462 and 55⊘ ml respectively. Figures 1 to 6 showed steep curvatures with the increase of enzyme and polymer dosages, and the higher increase in freeness values was achieved at pH 4.6 compared to pH 6 and pH 7. B. Response Surface Factorial Design 2 A 36 run response surface factorial design, Table 7 was setup where the effects of Celluclast 1.5L (⊘ to ⊘.4% based on dry weight of pulp) were determined. Polymer No. 1, (⊘ to ⊘.⊘392% on dry weight of pulp), and the enzyme reaction time (3⊘, 45 and 6⊘ min.) were simultaneously investigated on the freeness of the same pulp as mentioned in A. In this series of experiments, no buffer of any specific pH was used, as was used in all earlier series of experiments. The pH of the pulp suspension was found to be about 7, and was adjusted nearly to pH 4.8 by adding to pulp about ⊘.3 mℓ 6 N sulfuric acid. Statistical analysis of the data, Table 8, 9 and 1⊘ resulted in a model with R-Square value of ⊘.9928, without Least Squares Coefficients, Response C, Model JAW_REG2_COPY 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 568.618689 6.728681 84.51 0.0001 2 ∼P 65.004913 4.772179 13.62 0.0001 3 ∼E -46.609390 10.126620 -4.60 0.0002 4 ∼M 9.873872 5.081876 1.94 0.0662 5 ∼P*PH -14.785273 7.036308 -2.10 0.0485 6 ∼E*PH -12.466267 7.053722 -1.77 0.0924 7 ∼PH*T -13.709016 6.995056 -1.96 0.0641 8 ∼E**2 -113.082895 8.900433 -12.71 0.0001 9 ∼E**3 85.671459 6.769722 12.66 0.0001 10 ∼PH**3 -56.112785 5.538101 -10.13 0.0001 0 Term 5 Transformed Term 1 1 2 ∼P (P-2) 3 ∼E ((E-1e-01)/1e-01) 4 ∼M ((M-3.5e+01)/2.5e+01) 5 ∼P*PH (P-2)*((PH-6)/1.5) 6 ∼E*PH ((E-1e-01)/1e-01)*((PH-6 7 ∼PH*T ((PH-6)/1.5)*((T-4e+01)/ 8 ∼E**2 ((E-1e-01)/1e-01)**2 9 ∼E**3 ((E-1e-01)/1e-01)**3 10 ∼PH**3 ((PH-6)/1.5)**3 No. cases = 30 R-sq. = 0.9662 RMS Error = 23.24 Resid. df = 20 R-sq-adj. = 0.9510 Cond. No. = 5.72 ~ indicates factors are transformed. Least Squares Summary ANOVA, Response C Model JAW_REG2 0 Source 1 df 2 Sum Sq. 3 Mean Sq. 4 F-Ratio 5 Signif. 1 Total(Corr.) 29 319441.1 2 Regression 9 308637.5 34293.1 63.48 0.0000 3 Linear 3 113923.0 37974.3 70.30 0.0000 4 Non-linear 6 139205.5 23200.9 42.95 0.0000 5 Residual 20 10803.6 540.2 6 Lack of fit 17 10456.7 615.1 5.32 0.0969 7 Pure error 3 346.9 115.6 R-sq. = 0.9662 R-sq-adj. = 0.9510 F(17,3) as large as 5.319 is a moderately rare event => some evidence of lack of fit. 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value 1 Factors 2 POLYMER 0 0 3 ENZYME 0 to .20 0.1 0.082558 4 PH 4.5 to 7.5 6 6.6764 5 MINUTES 10 to 60 35 59.962 6 TEMPERATURE 40 40 7 8 Responses 9 CSF MAX 461.87 Converged to a tolerance of 0.0377 after 32 steps. 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value 1 Factors 2 POLYMER 1 to 3 2 2.9998 3 ENZYME 0 0 4 PH 4.5 to 7.5 6 4.5011 5 MINUTES 10 to 60 35 59.998 6 TEMPERATURE 40 40 7 8 Responses 9 CSF MAX 549.64 Converged to a tolerance of 0.0377 after 138 steps. 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value 1 Factors 2 POLYMER 1 to 3 2 2.999 3 ENZYME 0 to .20 0.1 0.08707 4 PH 4.5 to 7.5 6 4.5013 5 MINUTES 10 to 60 35 59.989 6 TEMPERATURE 40 40 7 8 Responses 9 CSF MAX 716.5 Converged to a tolerance of 0.0377 after 110 steps. 0 1 POLYMER 2 ENZYME 3 TIME 4 pH 5 CSF 1 0.0 0.000 30 4.76 242.00 2 0.0 0.002 30 4.80 263.80 3 0.0 0.004 30 4.64 306.00 4 1.5 0.000 30 4.91 407.00 5 1.5 0.004 30 4.86 478.16 6 3.0 0.000 30 4.67 524.75 7 3.0 0.002 30 4.68 550.60 8 3.0 0.004 30 4.73 545.00 9 1.5 0.002 30 4.76 438.58 10 1.5 0.002 30 4.86 434.60 11 1.5 0.002 30 4.60 428.61 12 1.5 0.002 30 4.95 442.87 13 0.0 0.000 45 4.76 252.00 14 0.0 0.002 45 4.76 266.70 15 0.0 0.004 45 4.72 315.70 16 1.5 0.000 45 4.75 410.00 17 1.5 0.004 45 4.67 482.52 18 3.0 0.000 45 4.72 516.75 19 3.0 0.002 45 4.81 555.28 20 3.0 0.004 45 4.70 565.41 21 1.5 0.002 45 4.59 450.31 22 1.5 0.002 45 4.74 449.00 23 1.5 0.002 45 4.63 450.12 24 1.5 0.002 45 4.81 450.50 25 0.0 0.000 60 4.91 245.00 26 0.0 0.002 60 4.78 290.50 27 0.0 0.004 60 4.60 324.80 28 1.5 0.000 60 4.58 413.70 29 1.5 0.004 60 4.74 493.60 30 3.0 0.000 60 4.67 526.80 31 3.0 0.002 60 4.81 563.90 32 3.0 0.004 60 4.76 571.10 33 1.5 0.002 60 4.84 450.20 34 1.5 0.002 60 4.81 449.70 35 1.5 0.002 60 4.90 448.60 36 1.5 0.002 60 4.90 452.40 Least Squares Coefficients, Response C, Model JAW_REG1 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 447.393686 3.427031 130.55 0.0001 2 ∼P 133.857931 2.395596 55.88 0.0001 3 ∼E 30.714437 2.679827 11.46 0.0001 4 ∼T 6.878700 1.759408 3.91 0.0008 5 ∼PH 2.173969 3.570057 0.61 0.5491 6 ∼P*E -7.869880 2.797020 -2.81 0.0104 7 ∼P*T -1.231124 2.719064 -0.45 0.6554 8 ∼P*PH 2.349784 7.511788 0.31 0.7575 9 ∼E*T 4.340487 2.786138 1.56 0.1342 10 ∼E*PH 3.716614 5.719449 0.65 0.5229 11 ∼T*PH 0.439370 3.617493 0.12 0.9045 12 ∼P**2 -32.617088 3.531662 -9.24 0.0001 13 ∼E**2 -0.037503 3.396388 -0.01 0.9913 14 ∼T**2 -2.162876 3.474620 -0.62 0.5403 15 ∼PH**2 0.261631 6.253606 0.04 0.9670 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-2e-03)/2e-03) 4 ∼T ((T-4.5e+01)/1.5e+01) 5 ∼PH ((PH-4.765)/1.85e-01) 6 ∼P*E ((P-1.5)/1.5)*((E-2e-03) 7 ∼P*T ((P-1.5)/1.5)*((T-4.5e+0 8 ∼P*PH ((P-1.5)/1.5)*((PH-4.765 9 ∼E*T ((E-2e-03)/2e-03)*((T-4. 10 ∼E*PH ((E-2e-03)/2e-03)*((PH-4 11 ∼T*PH ((T-4.5e+01)/1.5e+01)*(( 12 ∼P**2 ((P-1.5)/1.5)**2 13 ∼E**2 ((E-2e-03)/2e-03)**2 14 ∼T**2 ((T-4.5e+01)/1.5e+01)**2 15 ∼PH**2 ((PH-4.765)/1.85e-01)**2 No. cases = 36 R-sq. = 0.9957 RMS Error = 8.522 Resid. df = 21 R-sq-adj. = 0.9928 Cond. No. = 5.784 ~ indicates factors are transformed. Least Squares Coefficients, Response $log_C, Model JAW_REG1_COPY 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 6.099356 0.003720 1639.80 0.0001 2 ∼P 0.343841 0.004153 82.79 0.0001 3 ∼E 0.075537 0.004354 17.35 0.0001 4 ∼T 0.016980 0.003227 5.26 0.0001 5 ∼P*E -0.040127 0.004945 -8.12 0.0001 6 ∼P*T -0.010994 0.004770 -2.30 0.0288 7 ∼P*PH 0.028204 0.012556 2.25 0.0328 8 ∼P**2 -0.134348 0.005304 -25.33 0.0001 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-2e-03)/2e-03) 4 ∼T ((T-4.5e+01)/1.5e+01) 5 ∼P*E ((P-1.5)/1.5)*((E-2e-03) 6 ∼P*T ((P-1.5)/1.5)*((T-4.5e+0 7 ∼P*PH ((P-1.5)/1.5)*((PH-4.765 8 ∼P**2 ((P-1.5)/1.5)**2 No. cases = 36 R-sq. = 0.9971 RMS Error = 0.01578 Resid. df = 28 R-sq-adj. = 0.9964 Cond. No. = 2.544 ~ indicates factors are transformed. Least Squares Summary ANOVA, Response Source 1 df 2 Sum Sq. 3 Mean Sq. 4 F-Ratio 5 Signif. Total(Corr.) 35 2.400112 Regression 7 2.393139 0.341877 1373.00 0.0000 Linear 3 2.067889 0.689296 2768.00 0.0000 Non-linear 4 0.191848 0.047962 192.60 0.0000 Residual 28 0.006973 0.000249 Lack of fit 27 0.006937 0.000257 7.22 0.2873 Pure error 1 0.000036 0.000036 R-sq. = 0.9971 R-sq-adj. = 0.9964 (27,1) as large as 7.222 is not a rare event => no evidence of lack of fit. having revealed any direct positive interaction between enzyme and polymer. Table 11 contains the data of initial setting of experiment and the theoretical values obtained. The pretreatment of the pulp suspension with Celluclast 1.5L (⊘.4% based on dry weight of pulp), followed by the treatment with polymer (⊘.⊘392% on dry weight of pulp), resulted in the increase of freeness from 242 mℓ to 57⊘ mℓ, while when the pulp suspension was pretreated with reduced dosages of Celluclast 1.5L and polymer (⊘.2% and ⊘.⊘196% on dry weight of pulp, respectively, the freeness increased from 242 to 45⊘ mℓ. In contract, the freeness increased to 4⊘7 and 55⊘ mℓ by only treatment with polymer dosages of ⊘.⊘196% and ⊘.⊘392% respective, (Figs. 7, 8 and 9). 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value 1 Factors 2 POLYMER 0 to 3 1.5 2.9992 3 ENZYME 0 to 0.004 0.002 0.003997 4 T 30 to 60 45 42.495 5 PH 4.765 4.765 6 7 Responses 8 CSF MAX 568.6 Converged to a tolerance of 0.0329 after 48 steps. EXAMPLE 2 ENZYME POLYMER APPLICATIONS IN PULP AND PAPER INDUSTRY A. Source of Recycled Fiber The pulp slurry consisting mainly of old corrugated containers (OCC) was obtained from a midwestern recycle mill. The pulp stock was diluted with tap water and the freeness (Canadian Standard Freeness) measured. The freeness of this pulp was 35⊘ mℓ. In order to examine the effect of enzymes and polymers on the freeness of pulp, the freeness of pulp was decreased from 35⊘ mL to 25⊘ mℓ by beating it using a Valley Beater. B. Treatment of Pulp with Celluclast (NOVO) and Polymer No. 2 A response surface design, Table 12, was setup in which the effects of enzyme and polymer dosages was investigated on the freeness of pulp. The pulp slurry (about 3 g. dry weight) which had a pH of 5.⊘5 was first treated for 6⊘ min. at 45°C under continuous agitation (25⊘ rpm) with an enzyme solution of Celluclast 1.5 L (⊘ to ⊘.5% based on dry weight of pulp) and then treated at 2⊘°C with polymer No. 2, ⊘.261% and ⊘.⊘522%. The R-Square adjusted value of the fit was ⊘.97⊘6: Table 13. This value demonstrated the accuracy of the model used in this investigation. The freeness values, using separately either Celluclast (⊘.46% wt/wt basis) or Polymer 1 (⊘.⊘522%)were increased from 241 to 365 and 35⊘, respectively. But when the enzyme pretreated pulp was further treated with polymer, the freeness increased from 241 to 497 mℓ, Table 14. POLYMER=91PD030 ENZYME=CELLUCLAST TIME=60 0 1 Poly_Dose 2 Enz_Dose 3 CSF 1 0.0 0.000 241.4 2 0.0 0.234 342.4 3 0.0 0.528 361.7 4 1.5 0.000 302.0 5 1.5 0.454 420.5 6 3.0 0.000 344.6 7 3.0 0.225 424.3 8 3.0 0.447 474.2 9 1.5 0.218 364.0 10 1.5 0.231 367.0 11 1.5 0.201 365.0 12 1.5 0.245 360.0 Least Squares Coefficients, Response C, 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 378.519410 4.625556 81.83 0.0001 2 ∼P 42.201910 7.112547 5.93 0.0019 3 ∼E 65.965186 5.082299 12.98 0.0001 4 ∼P*E 7.570605 5.951252 1.27 0.2593 5 ∼P**2 6.602749 6.374128 1.04 0.3477 6 ∼E**2 -20.846166 7.985141 -2.61 0.0476 7 ∼P*E**2 17.220552 10.397590 1.66 0.1586 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-2.64e-01)/2.64e-01) 4 ∼P*E ((P-1.5)/1.5)*((E-2.64e- 5 ∼P**2 ((P-1.5)/1.5)**2 6 ∼E**2 ((E-2.64e-01)/2.64e-01)* 7 ∼P*E**2 ((P-1.5)/1.5)*((E-2.64e- No. cases = 12 R-sq. = 0.9866 RMS Error = 10.17 Resid. df = 5 R-sq-adj. = 0.9706 Cond. No. = 3.935 ~ indicates factors are transformed. 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value Factors ENZYME ONLY POLY_DOSE 0 0 ENZ_DOSE 0 to 0.528 0.264 0.462 Responses CSF MAX 365.3 Factors POLYMER ONLY POLY_DOSE 0 TO 3 1.5 3 ENZ_DOSE 0 0 Responses CSF MAX 350.16 Factors POLYMER AND ENZYME POLY_DOSE 0 to 3 1.5 2.9982 ENZ_DOSE 0 to 0.528 0.264 0.52788 Responses CSF MAX 497.11 Converged to a tolerance of 0.0233 after 5 steps. C. Treatment of Pulp with Celluclast and Polymer No. 3 A 24 response surface design. Table 15 was setup in which the effects of enzyme, polymer dosages, enzyme reaction time were investigated on the freeness of pulp. The pulp slurry was first treated with enzyme and then with polymer as described above. The R-Square adjusted value was ⊘.9978 (Table 16). The pretreatment of pulp suspension with Celluclast (⊘.485% based on dry weight of pulp, reaction time - 1⊘⊘ min.) followed by the treatment of polymer No. 3, ⊘.⊘444% on dry weight of pulp, resulted in the increase of freeness from 25⊘ mℓ to 675 mℓ. When the pulp suspension was pretreated with reduced dosages of Celluclast and polymer (⊘.28% and ⊘.⊘222%, respectively) the freeness increased from 25⊘ to 528 mℓ. No difference in freeness values were found when pulp was pretreated with enzyme for 6⊘ or 1⊘⊘ minutes. D. Treatment of Pulp with Celluclast and Polymer NO. 1 (Example 1) shows the effect of Celluclast 1.5L and polymer No. 1 on various laboratory prepared recycled fibers. When these investigations were extended to a mill recycled fiber similar results were obtained. A 12-run response surface design (Table 17) was set up in which the effects of enzyme and polymer dosages were investigated exactly as described above. Statistical analysis of the data, Table 18 and 19 resulted in a model with an R-Square adjusted value of ⊘.9994. The pretreatment of the pulp suspension with Celluclast (⊘.3% based on dry weight of pulp, 6⊘ min., reaction time) followed by treatment of the polymer NO. 1 ⊘.⊘392% resulted in the increase of freeness from 235 mL to 574mℓ, while POLYMER= 3 ENZYME=CELLUCLAST 0 1 Poly_Dose 2 Enz_Dose 3 Minute 4 CSF 1 0.0 0.0000 60 250.00 2 0.0 0.2326 60 337.20 3 0.0 0.4858 60 422.50 4 1.5 0.0000 60 464.00 5 1.5 0.4332 60 558.00 6 3.0 0.0000 60 608.00 7 3.0 0.2198 60 654.00 8 3.0 0.4528 60 664.00 9 1.5 0.2182 60 528.00 10 1.5 0.2264 60 526.25 11 1.5 0.2469 60 525.00 12 1.5 0.2182 60 522.50 13 0.0 0.0000 100 251.00 14 0.0 0.2449 100 339.00 15 0.0 0.4563 100 418.00 16 1.5 0.0000 100 458.00 17 1.5 0.4688 100 575.00 18 3.0 0.0000 100 604.00 19 3.0 0.2290 100 653.00 20 3.0 0.4494 100 676.00 21 1.5 0.2247 100 528.00 22 1.5 0.2182 100 529.00 23 1.5 0.2344 100 531.00 24 1.5 0.2120 100 536.00 Least Squares Coefficients, Response C 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 516.739319 9.237230 55.94 0.0001 2 ∼P 153.135457 1.626186 94.17 0.0001 3 ∼E 35.134252 13.626143 2.58 0.0202 4 ∼P*E -27.201967 2.094032 -12.99 0.0001 5 ∼P**2 -31.786505 2.445110 -13.00 0.0001 6 ∼E**2 -12.540811 2.731146 -4.59 0.0003 7 ∼M 1.645517 1.020927 1.61 0.1266 8 ∼E*M 2.589306 1.522845 1.70 0.1084 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-2.428999e-01)/2.4289 4 ∼P*E ((P-1.5)/1.5)*((E-2.4289 5 ∼P**2 ((P-1.5)/1.5)**2 6 ∼E**2 ((E-2.428999e-01)/2.4289 7 ∼M SQRT(M) 8 ∼E*M ((E-2.428999e-01)/2.4289 No. cases = 24 R-sq. = 0.9985 RMS Error = 5.613 Resid. df = 16 R-sq-adj. = 0.9978 Cond. No. = 21.42 ~ indicates factors are transformed. POLYMER= 2 ENZYME=CELLUCLAST TIME=60 0 1 Poly_Dose 2 Enz_Dose 3 CSF 1 0.0 0.0000 235.0 2 0.0 0.1412 279.2 3 0.0 0.3008 321.0 4 1.5 0.0000 385.0 5 1.5 0.2597 448.2 6 3.0 0.0000 509.0 7 3.0 0.1412 546.0 8 3.0 0.2778 570.0 9 1.5 0.1395 419.0 10 1.5 0.1493 428.0 11 1.5 0.1432 422.0 12 1.5 0.1429 420.0 Least Squares Coefficients, Response 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 424.186960 1.131305 374.95 0.0001 2 ∼P 132.144409 1.042865 126.71 0.0001 3 ∼E 37.101858 1.144858 32.41 0.0001 4 ∼P*E -5.338573 1.331804 -4.01 0.0071 5 ∼P**2 -10.086667 1.610348 -6.26 0.0008 6 ∼E**2 -4.028245 1.822527 -2.21 0.0691 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-1.504e-01)/1.504e-01 4 ∼P*E ((P-1.5)/1.5)*((E-1.504e 5 ∼P**2 ((P-1.5)/1.5)**2 6 ∼E**2 ((E-1.504e-01)/1.504e-01 No. cases = 12 R-sq. = 0.9997 RMS Error = 2.537 Resid. df = 6 R-sq-adj. = 0.9994 Cond. No. = 2.937 ~ indicates factors are transformed. Least Squares Summary ANOVA, Response 0 Source 1 df 2 Sum Sq. 3 Mean Sq. 4 F-Ratio 5 Signif. 1 Total(Corr.) 11 111960.4 2 Regression 5 111921.8 22384.4 3478.00 0.0000 3 Linear 2 107622.3 53811.1 8360.00 0.0000 4 Non-linear 3 514.8 171.6 26.66 0.0007 5 Residual 6 38.6 6.4 R-sq. = 0.9997 R-sq-adj. = 0.9994 when the pulp suspension was pretreated with reduced dosages of Celluclast and polymer (⊘.14% and ⊘.⊘196 respectively), the freeness increased from 235 mL to 428 mL. (Fig. 11). E. Treatment of Pulp with Multifect CL (GENENCOR) and Polymer No. 1 1⊘ mole % DMAEA-MCQ/AcAMm RSV = 17 Although cellulolytic enzymes of Novo and Genecor have comparable International Endoglucanase Units (IEU), their origin and the other components present in them are quite different. A 12 response surface design (Table 2⊘) was set-up similar to Celluclast as mentioned above. Slightly higher freeness values were obtained with Multifect CL compared to Celluclast 1.5L. This is simply due to higher Hultifect dosages (⊘.2185% to ⊘.46512%), compared to Celluclast (⊘.1412% to ⊘.2778%). Statistical analysis of the data (Table 21) resulted in a model with an R-Square adjusted value of ⊘.9956. The freeness values increased using separately either Multifect (⊘.46% wt/wt basis) or polymer (⊘.⊘392%) were from 245 to 371 and 5⊘8 mℓ, respectively. But when enzyme pretreated pulp was further treated with polymer, the freeness increased from 245 mℓ to 634 mℓ. (Table 22) POLYMER= 2 ZYME=MULTIFECT TIME=60 0 1 Poly_Dose 2 Enz_Dose 3 CSF 1 0.0 0.0000 245.4 2 0.0 0.22901 319.8 3 0.0 0.46512 366.2 4 1.5 0.0000 436.0 5 1.5 0.43636 521.0 6 3.0 0.0000 503.0 7 3.0 0.21818 598.0 8 3.0 0.46512 635.0 9 1.5 0.22642 484.4 10 1.5 0.22305 484.0 11 1.5 0.25000 501.0 12 1.5 0.22989 487.0 Least Squares Coefficients, Response 0 Term 1 Coeff. 2 Std. Error 3 T-value 4 Signif. 1 1 491.637655 3.280291 149.88 0.0001 2 ∼P 140.611206 5.153843 27.28 0.0001 3 ∼E 43.321860 5.515963 7.85 0.0005 4 ∼P**2 -34.642576 4.562820 -7.59 0.0006 5 ∼E**2 -17.400366 4.750113 -3.66 0.0145 6 ∼P*E**2 -9.007258 6.311847 -1.43 0.2129 7 ∼P**2**E 19.793444 6.613689 2.99 0.0303 0 Term 5 Transformed Term 1 1 2 ∼P ((P-1.5)/1.5) 3 ∼E ((E-2.3256e-01)/2.3256e- 4 ∼P**2 ((P-1.5)/1.5)**2 5 ∼E**2 ((E-2.3256e-01)/2.3256e- 6 ∼P*E**2 ((P-1.5)/1.5)*((E-2.3256 7 ∼P**2**E ((P-1.5)/1.5)**2*((E-2.3 No. cases = 12 R-sq. = 0.9980 RMS Error = 7.273 Resid. df = 5 R-sq-adj. = 0.9956 Cond. No. = 3.871 ~ indicates factors are transformed. CSF Optimization for Polymer and Enzyme 0 Factor, Response or Formula 1 Range 2 Initial Setting 3 Optimal Value Factors ENZYME ONLY POLY_DOSE 0 0 ENZ_DOSE 0 to 0.46512 0.2326 0.46512 Responses CSF MAX 371.11 Factors POLYMER ONLY POLY_DOSE 0 TO 3 1.5 3 ENZ_DOSE 0 0 Responses CSF MAX 508.08 Factors POLYMER AND ENZYME POLY_DOSE 0 to 3 1.5 3 ENZ_DOSE 0 to 0.46512 0.2326 0.4641 Responses CSF MAX 634.27 Converged to a tolerance of 0.039 after 11 steps.

Claims: A process for improving the freeness of paper pulp, which comprises the sequential steps of: a) adding to the pulp from 0.01 to 10 %, based on the dry weight of the pulp, of cellulase; b) allowing the pulp to contact the cellulase for at least 20 minutes at a temperature of at least 20°C; c) adding at least 0.0007 %, based on the dry weight of the pulp, of a water soluble cationic polmyer, and then, d) forming the thus treated pulp into paper. The process according to claim 1, wherein the cellulase is added in an amount of from 0.1 to 10 % by weight. The process of claim 1, wherein the paper pulp contains at least 10 % by weight, preferably at least 50 % by weight of recycled fibers. The process of any of claim 1 to 3 wherein the water soluble cationic polymer is a copolymer which contains from 30 to 80 % by weight of acrylamide. The process of claim 4 wherein the cationic acrylamide copolymer is an acrylamide-diallyldimethyl ammonium chloride (DADMAC) copolymer.

Inventors: COSPER DAVID R, SARKAR JAWED M, COSPER, DAVID R., SARKAR, JAWED M.
Applicants: NALCO CHEMICAL CO, NALCO CHEMICAL COMPANY
Application year: 1992
Main classification: D21C5
IPC codes: D21C5, D21D1, D21H11, C12S3, D21C9, D21H17, D21H21