CA2005087C - Method for avoiding pitch troubles - Google Patents

Abstract

The method for avoiding pitch troubles comprises the treatment with an acylglycerol lipase.
The method of the present invention overcomes the pitch troubles in a process for the production of mechanical pulp and/or mechanical pulp-containing paper.

Description

-TITLE OF THE INVENTION
Method for avoidlng pltch troubles BACKGROUND OF THE INVENTION

1. Fleld of the Inventlon The present inventlon relates to a method for avoldlng pltch troubles ln a process for the productlon of mechanlcal pulp and/or of mechanlcal pulp-contalnlng paper.

2. Prlor Art Mechanlcal pulp, such as groundwood pulp (herelnafter refered to as GP), reflner groundwood pulp and thermomechanlcal pulp ls produced by a slmple mechanlcal treatment of grlnding logs or chlps by means of a grlnder or reflner. The mechanlcal pulp, has a dlsadvantage that lts strength ls low, but has advantages that lt can be produced at a hlgher yleld at a lower cost and lt has a higher opaclty, compared wlth a chemlcal pulp produced by uslng varlous chemlcals such as alkallne chemlcals. On the contrary, the wood constltuents remaln unchanged ln the mechanlcal pulp.
In general, a wood contalns about 1 - 10% of pltch whlch ls soluble ln and extractable wlth an organlc solvent, besldes three ma~or constltuents, l.e, cellulose, hemicellulose and llgnln. The amount and quallty of pltch vary wlth wood species. However, lt ls well-known that softwood, l.e. a maln raw materlal of mechanical pulp, contalns a large amount of pltch constltuents such as fatty aclds, resln aclds, glycerldes, etc. In the pulplng process, ; 71142-10 -these pltch-constltuents are released from pulp, whereln they exlst as free substances, deposlts on flber surface, and coverlngs thereon. That ls, they transform from a flxed state to a llberated state. Pltches suspended ln reused water (whlte-water) are mlcropartlcles havlng partlcle slzes of about 0.2 - 2~, whlch are known as the so-called "colloldal pltch".
In general, paper ls manufactured as follows: pulp ls prepared ln varlous pulplng processes, ls treated ln a screenlng process, ls mlxed wlth a varlety of auxlllarles to prepare a paper furnlsh. Paper ls made from the paper furnlsh on a paper machlne. In a serles of processes, the llberated pltch or the deposlted pltch ls accumulated ln plpes, tanks, wlre part, or press part, and causes the so-called pltch troubles, such as paper contamlnatlons or paper brokes. In the productlon of paper contalnlng a large amount of mechanlcal pulp, pltch troubles occur frequently. As one of the conventlonal methods for avoldlng pltch troubles, there ls the so-called seasonlng, ln whlch logs after felllng are held outslde and seasoned for a long perlod. In another method, a surface-actlve agent ls added ln a pulplng or paper-maklng process, as descrlbed ln Japanese Patent Publlcatlon No. 50-22606, whereln the surface actlve agent lncludes, for example, a polyoxyethylene alkyl ether wlth varlous addltlon moles, alkyl phenyl derlvatlves and mlxtures, contalnlng them as a maln lngredlent.

-Although the above mentioned seasonlng method causes a change and a decrease of pltch constltuents ln wood malnly by alr-oxldatlon, lt requlres a wlde area and a long perlod, for example, 3 - 6 months, or more. Accordingly, it is practically difficult to avoid the pitch troubles only by the above seasonlng method.
On the other hand, the addltlon of surface actlve agent, whlch ls said to dlsperse the pitch particles and to prevent the pitch deposits, is not recognized as a substantial method for avoiding pitch troubles.

SUMMARY OF THE INVENTION

It is the ob~ect of the present lnvention to avoid pltch troubles ln a process for the production of mechanical pulp or of mechanical pulp-containlng paper. Attemptlng to achieve the above ob~ect according to the present invention, a paper-stock and/or white-water is treated with an acylglycerol lipase in a process for the production of mechanical pulp and/or of mechanical pulp-contalnlng paper. The ob~ect and features of the present lnventlon wlll become more apparent from the followlng descrlptlon.

DETAILED DESCRIPTION OF THE INVENTION

In order to obtaln an effectlve method for avoiding pitch troubles, the inventors have investigated in detail: ll) pitch constituents extracted from Japanese red pine (Pinus denslflora) as a typical pulpwood of mechanlcal pulp and (2) pltch constltuents deposlted ln a process for the productlon of Japanese red plne - GP and/or of paper contalnlng the plne-GP. As a result, it has been found that the main constituents of the deposited pltch are the same as those contalned ln the orlginal wood and consist mainly of triglycerldes, fatty acids, resin acids and metal salts thereof. Further, lt has been demonstrated that the deposited pitch contalns always a large amount of trlglycerides. It has been assumed that the trlglyceride ls responslble for one of the maln constltuents causing pltch troubles. From a point of view that the decomposltion or removal of triglycerides by some method is effective for avoidlng the pltch troubles, the lnventors have lnvestlgated varlous chemlcal or blochemlcal methods.
As a result lt was dlscovered that when an acylglycerol lipase is used, the triglyceride is decomposed and thus the pitch deposits do not occur without giving harmful effects on the pulp or paper qualities and on the run-conditions. That is, it was found that pitch troubles may be avoided by treating the paper-stock and/or reused water with an acylglycerol lipase in a process for the production of mechanical pulp and/or of mechanical pulp-containing paper.
It ls preferred that the acylglycerol llpase is that produced by at least one microorganlsm selected from the group conslsting of AsPerqlllus nlqer, Pseudomonas fluorescens, Pseudomonas fraql, Geotrlchum candldum, and Candlda cyllndracea.

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The acylglycerol lipase used according to the present inventlon is an enzyme for hydrolyzing triglycerides, i.e. one of the main constituents of pitch, wherein any enzyme, as far as it hydrolyzes triglycerides, can be used.
Microorganlsms for produclng the enzyme of the present lnvention include, for example, AsPerqillus niqer, Pseudomonas fluorescens, Pseudomonas fraqi, Geotrichum candidum, Candida cylindricea, Mucor ~avanicus, Rhizopus ~avanicus, Rhizopus delemar, RhizoPus niveus, fungi of genus Rhizopus and the like. Among these fungi, AsPer~ us nlger, Pseudomonas fluorescens, Pseudomonas fraqi, Geotrichum candidum and Candida cYlindracea are more effective.
The purer the acylglycerol lipase produced from the above microorganlsms, the better the effect. Further, the acylglycerol llpases are used alone or in combination. And a good effect can be obtained, too, when the acylglycerol lipase is used in comblnation wlth other decomposition-enzymes, such as cellulase, hemicellulase, pectlnase, protease, etc.
Accordlng to one embodlment of the lnventlon, ln a process for productlon of mechanical pulp and/or of mechanical pulp-containing paper, the acylglycerol lipase is added to a paper-stock slurry, under agltatlon or standlng. In thls case, the enzyme ls added thereto usually ln an amount of 0.1-10,000 ppm (by weight), based on the welght of mechanlcal pulp and the temperature ls preferably 10C - 70C, more preferably 35C - 55C. At a temperature lower than 10C, the enzyme functlonates weakly and slowly. At a temperature hlgher than 70C, the enzyme may become lnactlve. Wlth the lncreased s~

amount of the enzyme, the reactlon ls usually accelerated, whereln 10,000 ppm of the enzyme, based on the welght of mechanlcal pulp, ls satlsfactory. The addltlon of more than 10,000 ppm of the enzyme ls economlcally dlsadvantageous. The sultable pH-value ls 3 - 11, and outslde thls range, the actlvlty of the enzyme ls decreased reasonably.
In a pulplng or paper-maklng process, a large amount of water ls used and a ma~or portlon thereof ls recycled and reused. Slnce the reused water (whlte water) contalns the pltch constituents, the addltlon of the acylglycerol llpase to whlte water prevents pltch troubles.
In thls case, superlor effects are obtalned by the dlrect addltlon of the above acylglycerol llpase lnto the whlte water, or by the addltlon of so-called lmmoblllzed acylglycerol llpase or of the so-called lmmoblllzed mlcroorganlsm capable of produclng acylglycerol llpase extracellularly, whereln the lmmoblllzatlon of the enzyme or mlcroorganlsm ls carrled out by the conventlonal method, such as carrler-blndlng, cross-llnklng, entrapplng, etc.
Slnce the method of present lnventlon causes a hlghly selectlve reactlon known as an enzyme-reactlon agalnst trlglycerlde, and slnce thls reactlon ls mlld, the stock treated wlth the enzyme ls not denatured so that the method of the present lnventlon exerts no harm lnfluence on the usual operatlon.

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Pltch troubles occur ln a compllcated system comprlslng pulp flbers, pltches, metal lons, flllers, etc.
Although the reason for causlng pltch troubles ls not perfectly known, lt ls sald that the pltch troubles depend upon varlous factors, such as pltch conslstency, pulp conslstency, pH-value, temperature, metal-lon conslstency, metal-lon klnds and the llke. In general, X0050~37 an adsorption onto a solid surface is due to the exertion of Van der Waals-force which fixes the substance adhered onto a solid surface.
As the mutual interaction between the substance and the solid, there are various types of actions, among which a hydrophobic bond, a reciprocal action of dipole moments, etc. are important. And a hydrophobic or non-polar molecule or a hydrophobic molecule-portion is easily attracted to a hydrophobic or non-polar surface, whereas a hydrophilic or polar molecule is easily attracted to a polar surface.
Considering the mechanism for the pitch deposition in a pulp- or paper-making process, accordingly, tryglycerides play the following roll. Through Van der Waals force, triglycerides, i,e. the non-polar constituent in colloidal pitch, adheres to the hydrophobic or non-polar surface, such as the metal surface of tank, pipe, etc.; the surface of the center roll of paper-making press section; and the like. The adhered portion exerts as a nucleus, to which the hydrophobic or non-polar molecules or the hydrophobic molecule-portions in pitch-constituents adhere successive~y to form the pitch deposits.

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The mechanism for avoiding the pitch depositions according to the present invention is as follows. The acylglycerol lipase exerts on the non-polar tryglyceride which exits in pulp surface-pitch or in colloidal pitch (such as pitch in white water) and which has high tackiness to the hydrophobic and non-polar surface, whereby triglyceride is hydrolyzed to water-soluble glycerol and polar fatty acid.
Accordingly, the pitch depositions to hydrophobic surface of metal-pipes, chests, rolls, etc. are avoided.
Since the pitch depositions are avoided in the early stage, the growth of the pitch deposits do not occur, which avoids pitch troubles.

The method of present invention has an advantage of avoiding pitch troubles, such as pitch spots and holes in a paper-web, etc., caused by pitch deposited in a process for the production of mechanical pulp and of mechanical pulp containing paper. Further, the method of the present invention has no harm effect on the paper qualities and the practical run, it is simplified and applied to a conventional pulp- and paper making process without installing additional equipments.

_ ~_ ~0050~37 , . , The present invention will be understood more readily with reference to the following examples.
However, these examples are intended to illustrate the present invention and are not to be contrued to limit the scope of the present invention. Throughout the Examples, samples without enzyme-treatment are shown as "control".

[Example 1]
Fresh Japanese red pine chip was extracted with methanol, using a soxhlet extractor. lOg of the obtained extracts were dissolved in a mixed solution of lOOme isopropanol, 60me acetone and 5me water to obtain a pitch solution. -lOme of the pitch solution were charged in a beaker containing le of water and were dispersed under vigorous stirring to prepare a pitch dispersion. In such a manner, the resultant pitch was obtained in an yield of 4.7%, based on the weight of oven-dry chip, and it contained 3i.8% triglycerides Then, the pH-value of the pitch dispersion was adjusted to 7 by adding hydrochloric acid and/or sodium hydroxide. The acylglycerol lipase was added thereto in _~ _ di~erent consistel)cies at various temperatures, as sllown in Table l, and was treated under gentle stirring ~or 4 hours to prepare a treated solution. In ~ccordance with Tappi ~outine Control Method ~C-324, a cylinder built from polyetllylelle plate of 22cm width and 7cm lengtll was set 2.5cm above the water level. Tlle adjusted solution was stirred for 30 minutes by using a Vibromixer (~initator, manuactured by U.S. Heidon Co.) Polyettlylene-cylindrical plate was taken out and dried. The weight of the deposited pitch and the percentage to untreated pulp were indicated in Table 1.

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Ta~le 1 Enzyme Temperature Concentra- 2UC 4~C 60C
Kindtio~l(4) 115mg 102mg 117mg co~trol ------- (100~) (10U%) (100~) 50ppm g3mg (80.9%) Li. oF(l) 500ppm 58mg 3Smg 90mg 28mg 1~00ppm (24.3%J

Li. ~(2) SU0ppm (57-4%) (47-0%3 (P3-5~) I,i p(3J 500ppm 67mg 60mg 83mg (58.3%) (52.2%) (72-7~) ~Note 1) Li,OF; trade name = Llpase OF (manuactured by Meitosangyo Co.), produced from Candida cylindracea.
(Note 2) Li,A; trade name = Lipase A (manufactured by ~mano~Seiyaku Co.), produced from As~ergillus niger.

(Note 3) Li,P trade name = Lipase P (manufactured by ~mano Selyaku Co.), proau~ed Erom P~eudomona~
fluorèscens.
(Note 4J Concentation = Concentration oE enzyme addition, based 011 pitch.

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- C~1 l~x~m~le 21 Tlle plI-value of the pitcIl dispersion wa~
adjusted to 7 Wittl hydrochloric acid and/or sodium ~Iydroxide. The acylglycerol lipa3e was added thereto in an amount of 500ppm, based on ttle weight of pitch, and was stirred a~ 40C. ~fter a certain time, the amount of deposited pitch was obtained in tlle same manner as in Example 1 and was indicated in Table 2.

Table 2 Enz~me ~emperature Concentra- 2hour~ 4hours 6hours Klnd tion coIltrol - - - 105mg 101mg 107mg (100%)- (100%) (10~%) Li. ~F 500ppm 67mg 31mg 31mg (63.~) (30-7%) (24.4~) Li. GC-(5) 500ppm 85mg. 70mg 59mg (81.0~) (69.3%) (55.1%) (Note 5) Li. GC-5 ~rade name : Llpa~e GC-5 (manuactured by ~mano Seiyaku Co.), produced Erom Geo~richum candidum.

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Example 3]
le of a slurry containing lOg GP of 63me CSF(Canadian Standard Freeness) was prepared from -Japanese red pine.
The acylglycerol lipases were added thereto in various consistencies and was treated under different pH-values in the same manner as in Example 1.
The amount of pitch deposited to polyethylene-cylindrical plate was measured as shown in Example 1, and was indicated in Tab.le 3.

~`p Table Enz~,rme p~

~ind Concentration(~ 3 5 7 9 Cont_ol - 118mg 1~2ma 102m5 '2'ns (100%) 1100%) (100~) (100%) 10pp - - 90mg (88.2%) Li. OF 50ppm 80mg 58ms 2amg 62mg ~67.8%) (51.8%~ (27.5%) (5i.2%) 250ppm 21mg (20.6~) ,_ 10ppm - - 96mg (79-3%) Li. 3(6~ 50ppm 95mg 65mg 42mg 27mg (80.5~ (S8.3%~ (41.2%-~ (22.3%) 250ppm - - - 24mg (19.8%) ~i. A 50ppm 84mg 66mg 49m5 88ms (71.2%) (58.9%) (48.0%) (72.7%) (40C, Treating period = 4 hours) (Note 6) Li, B; trade name = ~ipase B (manu'actured by SAPPORO
B~EWE~IES L ~IT~D), produced from Pseudomonas fraqi 22-39 B.
(Note 7) Concent-ation-- Concentration of e~zyme addition, based N on the weight of pulp.
o [Example 4]
The same sample as in Example 3 was used. The enzyme of the present invention was added to the sample in an amount of 50ppm, based on~the weight of pitch, and was treated in the same manner as in Example 1, at different temperatures and times. The amount of deposited pitch was measured and indicated in Table 4.

/b Table 4 Enzyme Temperature Treating Kind pH period 20C 40C 60C

Control --- ll5mg 102mg 117mg (100%) (100%) (100%) ? 2hours ------- 44mg - ----(53.9%) Li. OF 4hours 64mg 29mg 100mg (55.7%) (28.4%) (85.5%) 8hours - -- 27mg -~
(26.5%) .
`3 Control - . 128mg 121mg 134mg cOn - ( 100% ) ( lO 0% )( 100 9 2hours ~ 43mg (32.3%) Li. B 4hours 97mg 27mg 26mg (75.8%) (22.3%) (19.4%) 8hours ~-~ - 25mg (18.7%) [Example 5]
1% pulp slurry consisting of 20% of waste newspaper pulp (105 me CSF), 25% of GP (63me CSF), 25%
of thermomechanical pulp (107me CSF) and 30% of kraft pulp was prepared. le of this pulp slurry was used as a sample. The enzyme of the present invention was added thereto in an amount of 50ppm, based on the weight of pulp, treated at 40C for 4 hours, stirred for 120 minutes by a Vibromixer equipped with polyethylene cylindrical plate. The amount of deposited pitch was measured and indicated in Table 5.

Table 5 Amount of deposited pitch Control 65mg (100%) Lip,ase OF 18mg (27.7%) l~
_~g _ tExample 6]
3e of white water obtained by filtering Japanese red pine GP in a screening-stage were used as a sample. The enzyme of the present invention was added to the sample in an amount of 0.5ppm, based on the weight of the white water, treated at 40C for 2 hours, and stirred with a Vibromixer for 120 minutes. The amount of pitch deposited to polyethylene cylindrical plate was measured and indicated in Table 6.

Table 6 - Amount of deposited pitch Control 37mg .(100%) Li.oF 7mg (18.9%) ~Example 7]
A newsprint paper of circa 46g/m2 bases weight was made by means of a Bel-Baie former multi-dryer paper machine with 5080mm width and 830m/min speed, wherein the paper stock consists of 30% GP, 45% waste newspaper pulp (deinked), 10~ softwood KP and 15% thermo-mechanical pulp.

1~
_~ _ In this case, GP was prepared from red pine, and was adjusted to a freeness of 60-70 me CSF by the post refining, storaged as a stock-pulp for a while, opitionally mixed with other pulps and anxiliaries, again storaged and then Eed to a paper-making process.
It takes 90 minutes from the post refiner through chests, tanks to the paper-making machine. The enzyme of the present invention was added to the GP slurry of 3.8% consistency before the post refiner so that Lipase OF has a concentration of 3ppm. The enzyme was continuously added to GP for two weeks.
There were determined the amounts of pitch deposited at the wire and press parts, and the interval between the removals of pitch deposited onto the center roll. The practical output of the paper machine was about 270 tons per day. The removal of pitch deposited on the center roll aims at preventing the excess pitch deposition for the good run, and the interval between the removals of pitch deposited onto the center roll is shorten with the increased amount of pitch deposits.
The obtained results were compared with those of "control", and were indicated in Table 7.

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Table 7 Control Li OF
Amount of Max 895 89 pitch Min 73 0 deposited Aver 207 43 (g/day) age Interval Max 120 240 between the Min 30 120 removals of Aver 80 170 pitch a~e deposited (minutes) [Example 8]
A light-weight printing paper of 34g/m2 basis weight was produced in accordance with Example 7, wherein the paper-stock consists of 20% GP, 50% waste newspaper pulp (deinked), 15% softwood KP and 15%
thermomechanical pulp. Lipase OF was added to GP slurry in an amount of 3ppm. The practical output of the paper machine was about 200 tons per day. For the comparison with the results of "Control", there were determined the amount of pitch deposited in the wire and press parts, and the pitch holes of the paper due to pitch deposition at the breaker stack. The results were indicated in Table 8.

2l Table 8 Control Li OF
Amount of Max 590 98 pitch Min 132 15 deposited Aver 221 47 (g/day) age Number of Max 65 14 pitch holes* Min 13 0 (per day) Aver 38 6 age * Expressed by number of small paper slips peeled off in the breaker stack.

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Claims (10)

1. A method for avoiding pitch troubles in a process for the production of mechanical pulp or of mechanical pulp-containing paper, which comprises treating a paper-stock or reused water with acylglycerol lipase.

2. The method according to Claim 1, wherein the acylglycerol lipase is that produced by at least one microorganism selected from the group consisting of Aspergillus niger, Pseudomonas fluorescens, Pseudomonas fragi, Geotrichum candidum and Candida cylindracea.

3. The method according to Claim 1, wherein the acylglycerol lipase is added to a paper-stock slurry in an amount of 0.1-10,000 ppm, based on the weight of mechanical pulp.

4. The method according to Claim 1, wherein the paper-stock or reused water is at a temperature of from 10°C to 70°C.

5. The method according to Claim 4, wherein the temperature of the paper-stock or reused water ranges from 35°C to 55°C.

6. The method according to Claim 1, wherein the paper-stock or reused water has a pH value of from 3 to 11.

7. The method according to claim 1, where the acylglycerol lipase is added to a paper-stock slurry under agitation or standings or to reused water, in an amount of from 0.1 to 10,000 ppm (by weight) based on the weight of mechanical pulp, the paper-stock slurry and the reused paper having a pH value of from 3 to 11 and a temperature of from 10°C to 70°C.

8. The method according to claim 7, wherein the acylglycerol lipase is used as such, or in the immobilized acylglycerol lipase form or in the immobilized microorganism form capable of producing acylglycerol lipase extracellularly.

9. The method according to claim 8, wherein the acylglycerol lipase is that produced by at least one microorganism selected from the group consisting of Aspergillus niger, Pseudomonas fluorescens, Pseudomonas fragi, Geotrichum candidum and Candida cylindracea.

10. The method according to claim 7, 8, or 9 wherein the pH value is 3 to 9 and the temperature is 20°C to 60°C.