Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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.
71142-10
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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
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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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71142-10
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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
71142-10
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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,
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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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2005087
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.
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~0050~37
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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.
71142-10
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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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71142-10
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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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71142-10
'~OOS0~37
?~'~
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
2005087
[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%)
2005087
[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 _
Z005087
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.
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_~ _
XOOS087
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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200508~
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
2005087
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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