U.S. patent application number 11/282520 was filed with the patent office on 2006-06-15 for use of cyclodextrins for reducing deposits during paper production.
This patent application is currently assigned to Novozymes North America, Inc.. Invention is credited to Kim Bloomfield, Julie Clemmons, Jing Luo, Hui Xu.
Application Number | 20060124266 11/282520 |
Document ID | / |
Family ID | 36582429 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060124266 |
Kind Code |
A1 |
Xu; Hui ; et al. |
June 15, 2006 |
Use of cyclodextrins for reducing deposits during paper
production
Abstract
The present invention relates to a method for preventing or
reducing deposits in pulp and paper making processes by including a
cyclodextrin during or after pulp formation in an amount effective
for preventing or reducing the deposits. Optionally the
cyclodextrin comprising the deposit is subsequently separated from
the pulp.
Inventors: |
Xu; Hui; (Wake Forest,
NC) ; Luo; Jing; (Raleigh, NC) ; Bloomfield;
Kim; (Raleigh, NC) ; Clemmons; Julie;
(Raleigh, NC) |
Correspondence
Address: |
NOVOZYMES NORTH AMERICA, INC.
500 FIFTH AVENUE
SUITE 1600
NEW YORK
NY
10110
US
|
Assignee: |
Novozymes North America,
Inc.
Franklinton
NC
|
Family ID: |
36582429 |
Appl. No.: |
11/282520 |
Filed: |
November 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60630318 |
Nov 23, 2004 |
|
|
|
Current U.S.
Class: |
162/199 ;
162/175; 162/182; 162/72 |
Current CPC
Class: |
D21C 5/005 20130101;
D21C 9/086 20130101; D21H 21/02 20130101 |
Class at
Publication: |
162/199 ;
162/175; 162/072; 162/182 |
International
Class: |
D21C 3/20 20060101
D21C003/20; D21F 1/32 20060101 D21F001/32 |
Claims
1. A method of preventing or reducing deposits in a pulp and paper
making process by treating a pulp with a cyclodextrin in an amount
effective for preventing or reducing the deposits.
2. The method according to claim 1, wherein the cyclodextrin forms
a solid inclusion complex with the deposit and wherein said complex
is subsequently separated from the pulp.
3. The method according to claim 1, wherein a source of raw fiber
material for pulp formation is provided from printed paper.
4. The method according to claim 3, wherein the printed paper
comprises old newspapers (ONP) and/or waste magazines (WM).
5. The method according to claim 1, wherein the deposits comprise
fatty acid or ester deposits on process equipment.
6. The method according to claim 1, wherein the deposits comprise
stickies.
7. The method according to claim 3, wherein the deposits comprise
ink deposits on pulp fibers.
8. The method according to claim 7, wherein the ink deposits
comprise non-contact laser inks, xerographic toners, letterpress
ink generally used in printing newsprint, magazine print, offset
printing ink, ultraviolet or electron beam cured ink.
9. The method according to claim 1, wherein the cyclodextrin
comprises alpha-, beta- and/or gamma-cyclodextrin.
10. The method according to claim 9, wherein the cyclodextrin is
alpha- or beta-cyclodextrin.
11. The method according to claim 1, wherein the cyclodextrin is
provided partly or completely by enzymatic conversion of starch in
situ.
12. The method according to claim 11, wherein the enzyme comprises
a glycosyltransferase.
13. The method according to claim 12, wherein the
glycosyltransferase comprises a CGTase.
14. The method according to claim 1, wherein cyclodextrin treatment
is combined with enzymatic treatment and wherein the enzyme is
chosen from the group consisting of proteases, amylases,
pullulanases, lipases, hemicellulases, endoglucanases, cutinases,
and pectinases.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119 of
U.S. provisional application No. 60/630,318 filed Nov. 23, 2004,
the contents of which are fully incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for reducing
deposits during paper production.
BACKGROUND OF THE INVENTION
[0003] Wastepaper has long served as a source of raw fiber material
for papermaking. It has been standard practice in the art to
reclaim wastepaper to allow the reclaimed paper fibers to be used
as part or all of the stock of subsequent production of a variety
of paper and paperboard products. Today, greater utilization of
reclaimed fibers has provided incentive for taking steps to upgrade
the reclaimed products.
[0004] These steps include treatment to effectively remove ink from
waste fibers in order to permit their use in the manufacture of
e.g. newsprint and high quality papers. Removal of ink during the
pulp formation process will prevent the ink from re-depositing on
fibers in the pulp. Increasing amounts of e.g. old newspapers (ONP)
and waste magazines (WM) are becoming available with increased
participation of end consumers in recycling. Other steps in order
to reduce deposits during formation of pulp made from waste paper
includes removal of other water insoluble materials which tend to
agglomerate and deposit on various parts of the paper manufacturing
equipment. Such deposits include stickies (waste paper contaminants
of an adhesive character) or hydrophobic fatty acids and
esters.
[0005] In the course of conventional paper reclamation, deinking
procedures include steps for converting the wastepaper to pulp and
contacting the pulp with an alkaline aqueous deinking medium
containing a chemical deinking agent. The mechanical action and the
alkalinity of the aqueous medium cause the partial removal of ink
from the pulp fiber. The deinking agent completes this removal and
produces an aqueous suspension and/or dispersion of the ink
particles. The resulting mixture is subsequently treated to
separate the suspended/dispersed ink from the pulp. This separation
may be by flotation and/or washing techniques known in the art.
Conventional deinking chemicals comprise a complex mixture of
chemicals, e.g. sodium hydroxide, sodium silicate, chelating
agents, hydrogen peroxide, surfactants, dispersants, collector
chemicals and agglomeration chemicals. Typical deinking processes
are described in L. D. Fergusen "Deinking Chemistry: part 1" July
1992 TAPPI Journal pp. 75-83; L. D. Fergusen "Deinking Chemistry:
part 2" August 1992 TAPPI Journal pp. 49-58; and J. L. Spielbauer
"Deinking System Overview" Voith Inc. Appleton, pp. 1-9.
[0006] The hydrophobic fatty acids and esters are very problematic
during the paper making process. They can cause severe deposits on
the process equipment. Even after Resinase.TM. (lipase) treatment,
the newly formed long chain fatty acids are still too hydrophobic
to dissolve in the process water. Other types of deposits are
caused by polymers. For example, in the paper industry polymers
comprising vinyl acetate are used as a binder and coating material.
During recycling these polymers tend to agglomerate together with
fibers and other substances to form so-called "stickies", which
reduce the quality of the paper product and results in a
significant downtime of the machine.
[0007] WO 00/34450, WO 01/92502 and U.S. Pat. No. 5,176,796 report
the use of certain lipases and esterase in the manufacture of
paper, viz. for pitch control. According to the above US patent,
pitch is a natural constituent of wood, and triglyceride is a major
component thereof.
[0008] WO 01/98579 discloses the use of lipase and/or esterase for
control of the problem with stickies during recycling of paper.
[0009] A need therefore exists for a method for reducing the
deposit problems associated with papermaking from pulp produced
from waste paper, especially a method by which both of the above
described deposit problems are solved at the same time.
SUMMARY OF THE INVENTION
[0010] A solution to the above problem is provided by the method of
the invention relating to a method of preventing or reducing
deposits in a pulping process by including a cyclodextrin during or
after pulp formation.
[0011] The present invention therefore relates to a method of
preventing or reducing deposits in a pulping process by treating a
pulp with a cyclodextrin in an amount effective for preventing or
reducing the deposits.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The most important feature of cyclodextrin is their ability
to form solid inclusion complexes (host-guest complexes). The
lipophilic cavity of cyclodextrin molecules provides a
micro-environment into which an appropriately sized non-polar
moiety can enter to form an inclusion complex. Inclusion in
cyclodextrins exerts a profound effect on physiochemical properties
of guest molecules as they are temporarily locked or caged within
the host cavity, which give rise to some unique beneficial
modifications of the guest molecules. The properties include
solubility enhancement of highly insoluble guests, stabilization of
labile guests against the degradation, masking off flavors, and
controlled release of drugs and flavors.
[0013] During newspaper deinking, Flexo ink in particular, the
soluble ink tends to re-deposit back to the pulp fiber.
Cyclodextrin can be used to trap those small ink particles and
improve the deinking efficiency, which should result in high
brightness and less dirt count.
[0014] Cyclodextrin may also effectively entrap hydrophobic lipid
materials (fatty acids and esters) and enhance their solubility in
water. Cyclodextrin can also work with Resinase and other enzymes
to improve the efficiency. Along the same line, Cyclodextrin may
also work on the sticky material during recycling.
[0015] As used herein "stickies" designate waste paper contaminants
of an adhesive character causing sticking of paper-machine parts
during reprocessing. As examples of such contaminants, ink, tar,
and latex are mentioned.
[0016] Further examples of stickies are tacky agglomerates of
fibres, adhesives, coatings, binders and other materials, which
form in a recycled papermaking process. Accordingly, stickies are
mainly of concern for paper manufacturing processes in which
recycled paper is used.
[0017] Stickies are water insoluble and tend to agglomerate and
deposit on various parts of the paper manufacturing equipment,
thereby causing paper quality problems, breaks of the paper web,
and costly downtime periods for cleaning the equipment. For
example, stickies may deposit on the paper forming felts thereby
rendering the drainage of water from the forming paper web less
efficient, which again may give rise to problems as described
above.
[0018] Stickies have been distinguished in various ways, e.g. by
size, or by specific gravity:
[0019] Primary stickies are so small as to usually not cause any
problems, whereas secondary stickies or macro stickies are larger
and tend to deposit. Macro stickies are generally of such size as
to be retained on fine screens. Example of fine screens are those
having slots of about 50-200, 60-190, or 70-180, or 80-170, or
80-160, or of about 80-150 micro-meter.
[0020] High density and low density stickies may under certain
conditions be removable by various types of mechanical equipment,
but problems remain in particular with the so-called neutral range
density stickies, i.e. stickies of a specific gravity of about 0.9
to about 1.1, or about 0.95 to about 1.05, or about 0.98 to about
1.02.
[0021] The chemical composition of stickies from various parts of
the world may vary, mainly depending on the characteristics of the
local paper manufacturing processes. Likewise, for the same reason,
the composition of stickies may vary from factory to factory.
[0022] The following components are examples of components, one or
more of which are typically found in stickies: natural wood pitch,
such as fatty acids, resin acids and fatty acids; synthetic coating
binders, printing inks and adhesives, such as Acrylic Resins, Poly
Vinyl Acetate (PVAc), Styren Butadien Resin (SBR), Poly Ethylene
(PE) and Poly Propylene (PP), polyester, hydroxyl polyester,
urethane acrylate, epoxy acrylate, acrylic acid ester, block
copolymers and H/C resins.
[0023] As described above the deposits according to the invention
can in general be in the form of ink deposits, deposits of
hydrophobic lipid materials (fatty acids and esters), or
stickies.
[0024] The ink deposits may contain non-contact laser inks,
xerographic toners, letterpress ink generally used in printing
newsprint, magazine print, offset printing ink, ultraviolet or
electron beam cured ink.
[0025] Depending on the nature of the deposit the cyclodextrin
comprising the deposit should be removed or separated from the
pulp. When applying the cyclodextrin for removing ink particles
from pulp the cyclodextrin should e.g. be separated from the pulp
after treatment.
[0026] Separation of cyclodextrin comprising the deposits from the
pulp can be performed in any suitable way such as washing,
flotation and press.
[0027] The present invention describes a method of treatment of
wood pulps or pulp from printed paper with cyclodextrin alone, or
cyclodextrin and a conventional enzyme (e.g. a lipase), or lipase
and in situ generated cyclodextrin from starch and
glycosyltransferase (CGTase) to reduce pitch or deposit troubles
during pulp and paper making processes. This invention can also be
applied to the deinking process of waste paper to reduce the
residual ink particles in paper by preventing redeposits onto pulp
fibers.
[0028] The deinking agent, the cyclodextrin, would usually be
supplied to the waste paper initially, i.e. when the pulping stage
commences. Alternatively, the deinking agent may be supplied to
wastepaper which is already in the form of a pulp, that is, to
wastepaper which has first been substantially reduced to individual
fibers. In the former case, the pulping step where the deinking
agent is present is also sometimes termed "re-pulping". The
cyclodextrin can in another embodiment be generated enzymatically
in situ by a glycosyl transferase.
[0029] Pulping can be conducted using any of the various
conventional processes and equipment designed for this purpose.
Most conveniently, the wastepaper process feedstock is treated in a
device known as a "hydrapulper", which produces a slurry of the
fibers in water.
[0030] In one aspect of the invention the cyclodextrin is used as a
deinking agent in combination with conventional enzymes used in
deinking processes.
[0031] Accordingly, the method of the invention may be carried out
with a cyclodextrin and a combination of enzymes in order to make
the enzymatic process effective against a broader range of
contaminants, such as proteinaceous impurities, starch-containg
impurities, triglyceride containing impurities as well as
contaminants containing hemi-celluloses and pectins. The enzymes
can be selected from amongst proteases, amylases, pullulanases,
lipases, hemicellulases, endoglucanases, cutinases, and pectinases.
These enzymes may be wild-type enzymes, or mutants or variants
thereof having the relevant enzyme activity, i.e. catalyzing at
least one of the reactions indicated at the following web-site for
the relevant enzyme class: http://www.expasy.ch/enzyme/.
[0032] The lipase enzyme to be used in the present invention is one
that can hydrolyze ester bonds. Such enzymes include, for example,
lipases, such as triacylglycerol lipase (EC 3.1.1.3), lipoprotein
lipase (EC 3.1.1.34), monoglyceride lipase (EC 3.1.1.23),
lysophospholipase, ferulic acid esterase and esterase (EC 3.1.1.1,
EC 3.1.1.2). The numbers in parentheses are the systematic numbers
assigned by the Enzyme Commission of the International Union of
Biochemistry in accordance with the type of the enzymatic
reactivity of the enzyme.
[0033] The lipase may be a microbial lipase, e.g. from bacteria or
fungi such as Humicola or Pseudomonas, particularly lipase from H.
lanuginosa (this lipase being referred to as Resinase A
2x.RTM.).
[0034] Preferred microbial lipases to be used in the methods of the
present invention may be of bacterial, yeast or fungal origin, and
suitable examples include a lipase derived or obtainable from a
strain of Humicola spp., Rhizomucor spp., Candida spp., Aspergillus
spp., Rhizopus spp. or Pseudomonas spp., especially from a strain
of H. lanuginosa, Rh. miehei, C. antarctica, Aspergillus niger or
Pseudomonas cepacia. Specific examples of such lipases are lipase A
and lipase B of C. antarctica, described in WO 88/02775, the Rh.
meihei lipase described in EP 238 023, the H. lanuginosa lipase
described in EP 305 216, and the P. cepacia lipase described in EP
214 761 and WO 89/01032.
[0035] The lipase may be a native enzyme found in nature, or it may
be a variant thereof obtained by altering the amino acid sequence.
Examples of such variants are those described in WO 92/05249, WO
94/25577, WO 95/22615, WO 97/04079 and WO 97/07202, WO 98/08939, WO
99/42566, EP 943 678, and WO 00/60063.
[0036] Specific examples of suitable, commercially available,
lipases are, e.g., Resinase A 2.times., Novozyme 735, and Novozyme
525 (all available from Novozymes A/S, Denmark).
[0037] It is known from WO 95/14807 that, in the case of starch
coated paper, the deinking effect can be improved by including a
treatment with a starch-degrading enzyme and, consequently, in a
further embodiment of the invention, the pulping is carried out in
the presence of a starch degrading enzyme.
[0038] The starch-degrading enzyme is preferably an amylase, e.g.
an .alpha.-amylase, a glucoamylase or a debranching enzyme. A
single enzyme or a combination may be used, e.g. .alpha.-amylase
together with glucoamylase and/or a debranching enzyme. Examples of
preferred .alpha.-amylases are those derived from strains of
Bacillus, e.g. B. amyloliquefaciens (B. subtilis), B. licheniformis
or B. stearothermophilus and from strains of Aspergillus, e.g. A.
oryzae. Examples of commercial products are BAN.TM., Termamyl.TM.,
Aquazyme Ultra.TM. and Fungamyl.TM. (products of Novozymes
A/S).
[0039] Preferred glucoamylases are the glucoamylases derived from a
strain of Aspergillus niger, e.g. the commercial product AMG
(product of Novozymes A/S).
[0040] The debranching enzyme is preferably a pullulanase,
particularly one derived from a strain of Bacillus
acidopullulyticus, e.g. the commercial product Promozyme.TM.
(product of Novozymes A/S).
[0041] In addition, it is well known that cellulases may aid the
deinking process. Furthermore, it is well known that cellulases may
improve the drainability of the paper pulp. Consequently, in a
still further embodiment of the invention the pulping is carried
out in the presence of a cellulase.
[0042] Such cellulases are typically be derived from bacteria and
fungi, such as Aspergillus niger, Trichoderma virde, Thielatia
terrestris, Humicola sp. and Bacillus sp. The cellulase may be a
mono component or multi component cellulase, although mono
component cellulases are preferred. A class of cellulases that are
especially useful are cellulases lacking a cellulose binding-domain
(CBD). Cellulose-binding domains have been described by P. Tomme et
al. in J. N. Saddler & M. H. Penner (eds.), "Enzymatic
Degradation of Insoluble Carbohydrates" (ACS Symposium Series, No.
618), 1996. A number of cellulases are known to contain a catalytic
domain without a CBD; such a cellulase may be used as such in the
invention. It is also known that other cellulases contain a
catalytic domain and a CBD; such a cellulase may be truncated to
obtain a catalytic core domain without the CBD, and this core may
be used in the invention.
[0043] Cellulases may be classified into families on the basis of
amino-acid sequence similarities according to the classification
system described in Henrissat, B. et al.: Biochem. J., (1991), 280,
p. 309-16, and Henrissat, B. et al.: Biochem. J, (1993), 293, p.
781-788. Some preferred cellulases are those belonging to Family 5,
7, 12 and 45.
[0044] A preferred Family 5 cellulase without CBD is an alkaline
cellulase derived from a strain of Bacillus. One such Family 5
cellulase is the endo-glucanase from Bacillus strain KSM-64 (FERM
BP-2886). The cellulase and its amino acid sequence are described
in JP-A 4-190793 (Kao) and Sumitomo et al., Biosci. Biotech.
Biochem., 56 (6), 872-877 (1992).
[0045] Another Family 5 cellulase from Bacillus is the
endo-glucanase from strain KSM-635 (FERM BP-1485). The cellulase
and its amino acid sequence are described in JP-A 1-281090 (Kao),
U.S. Pat. No. 4,945,053 and Y. Ozaki et al., Journal of General
Microbiology, 1990, vol. 136, page 1973-1979. A third Family 5
cellulase from Bacillus is the endo-glucanase from strain 1139. The
cellulase and its amino acid sequence are described in Fukumori F.
et al., J. Gen. Microbiol., 132:2329-2335 (1986) and JP-A 62-232386
(Riken). Yet another preferred Family 5 cellulase without CBD is an
endo-beta-1,4-glucanase derived from a strain of Aspergillus,
preferably A. aculeatus, most preferably the strain CBS 101.43,
described in WO 93/20193 (Novo Nordisk).
[0046] The Family 7 cellulase may be derived from a strain of
Humicola, preferably H. insolens. An example is endo-glucanase EG I
derived from H. insolens strain DSM 1800, described in WO 91/17244
(Novo Nordisk). The mature cellulase has a sequence of the 415
amino acids shown at positions 21-435 in FIG. 14 of said document
and has a specific activity of 200 ECU/mg (based on pure enzyme
protein). This cellulase may further be truncated at the C-terminal
by up to 18 amino acids to contain at least 397 amino acids. As
examples, the cellulase may be truncated to 402, 406, 408 or 412
amino acids. Another example is a variant thereof denoted
endo-glucanase EG I* described in WO 95/24471 (Novo Nordisk) and
having a sequence of 402 amino acids shown in FIG. 3 therein.
Alternatively, the Family 7 cellulase may be derived from a strain
of Myceliophthora, preferably M. thermophila, most preferably the
strain CBS 117.65. An example is an endo-glucanase described in WO
95/24471 (Novo Nordisk) comprising the amino acids 21-420 and
optionally also the amino acids 1-20 and/or 421-456 of the sequence
shown in FIG. 6 therein. As another alternative, the Family 7
cellulase may be derived from a strain of Fusarium, preferably F.
oxysporum. An example is an endo-glucanase derived from F.
oxysporum described in WO 91/17244 (Novo Nordisk) and Sheppard, P.
O. et al., Gene. 150:163-167, 1994. The correct amino acid sequence
is given in the latter reference. This cellulase has a specific
activity of 350 ECU/mg.
[0047] A preferred Family 12 cellulase without CBD is CMC 1 derived
from Humicola insolens DSM 1800, described in WO 93/11249 (Novo
Nordisk). Another preferred Family 12 cellulase without CBD is EG
III cellulase from Trichoderma, particularly Trichoderma viride or
Trichoderma reesei, described in WO 92/06184 (Genencor).
Alternatively, the Family 12 cellulase may be derived from a strain
of Myceliophthora, preferably M. thermophila, most preferably the
strain CBS 117.65. Such a cellulase (termed C173) can be produced
by cloning DNA from CBS 117.65, and subsequently transforming
Aspergillus oryzae, a non-cellulolytic host organism, and
expressing the cellulase by cultivation of the transformed host,
and separating the only cellulolytic active ingredient from the
culture broth. C173 has optimum activity at pH 4-6.5, a specific
activity of 226 ECU per mg protein and a molecular weight of 26 kDa
(for the mature protein).
[0048] A preferred Family 45 cellulase without CBD is the EG V-core
derived from Humicola insolens, described in Boisset, C., Borsali,
R., Schulein, M., and Henrissat, B., FEBS Letters. 376:49-52, 1995.
It has the amino acid sequence shown in positions 1-213 of SEQ ID
NO: 1 of WO 91/17243 (Novo Nordisk). Another preferred Family 45
cellulase without CBD is FI-CMCase from Aspergillus aculeatus
described by Ooi et al., Nucleic Acids Research, Vol. 18, No. 19,
p. 5884 (1990).
[0049] Examples of commercially available cellulases include
Novozym 613, Novozym 476, and Novozym 342 (all available from
Novozymes A/S, Denmark).
[0050] In a particular embodiment the cyclodextrin can be generated
in situ by the enzymatic action of a glycosyl transferase
converting starch to cyclodextrin. Particularly the glycosyl
transferase is CGTase. Additional cyclodextrin may or may not be
added. In case a glycosyltransferase is added incubation time
should be long enough to allow formation of sufficient amounts of
the cyclodextrin. In one embodiment the treatment should be in the
range from 15 to 120 minutes.
[0051] Cyclomaltodextrin glucanotransferase (E.C. 2.4.1.19), also
designated cyclodextrin glucanotransferase or cyclodextrin
glycosyltransferase, in the following termed CGTase, catalyses the
conversion of starch and similar substrates into cyclomaltodextrins
via an intramolecular transglycosylation reaction, thereby forming
cyclomaltodextrins, in the following termed cyclodextrins (or CD),
of various sizes. Commercially most important are cyclodextrins of
6, 7 and 8 glucose units, which are termed alpha-, beta-, and
gamma-cyclodextrins, respectively. Commercially less important are
cyclodextrins of 9, 10, and 11 glucose units, which are termed
delta-, epsilon-, and zeta-cyclodextrins, respectively. Most
CGTases have both starch-degrading activity and transglycosylation
activity. Although some CGTases produce mainly alpha-cyclodextrins
and some CGTases produce mainly beta-cyclodextrins, CGTases usually
form a mixture of alpha-, beta- and gamma-cyclodextrins. Selective
precipitation steps with organic solvents may be used for the
isolation of separate alpha-, beta- and gamma-cyclodextrins. To
avoid expensive and environmentally harmful procedures, the
availability of CGTases capable of producing an increased ratio of
one particular type of cyclodextrin, in particular with respect to
alpha-, beta- or gamma-cyclodextrin, is desirable.
[0052] Useful CGTases for the purpose of the present invention are
described in the following. CGTases which primarily form
alpha-cyclodextrin, also called alpha-CGTase, such as, for example,
the CGTase from Bacillus macerans (U.K. Patent No. 2,169,902), from
Klebsiella pneumoniae (EPA 220,714) and from Bacillus
stearothermophilus (U.K. Pat. No. 2,169,902). CGTases which
primarily form beta-cyclodextrin, or beta-CGTase, such as, for
example, the CGTase from Bacillus circulans (U.S. Pat. No.
4,477,568), from Bacillus megaterium (U.S. Pat. No. 3,812,011),
from Bacillus ohbensis (Japan Patent No. 74,124,285), from
Micrococcus sp. (EPA No. 017,242) and from alkalophilic Bacillus
sp. (J. Gen. Microbiol. 1988, 134, 97-105; Appi. Microbiol.
Biotechnol. 1987, 26, 149-153). Two articles (Agric. Biol. Chem.,
1986, 50, (8), 2161-2162 and Denpun Kagaku 1986, 33, 137) describe
a gamma-CGTase from Bacillus subtilis No. 313. This CGTase is
distinguished by the formation of gamma-cyclodextrin and linear
oligosaccharide. Since CGTases generate only cyclic products from
starch, this "CGTase" is a transitional form between an
alpha-amylase (generates linear oligosaccharide from starch) and a
CGTase. This "gamma-CGTase" is unsuitable for preparing
gamma-cyclodextrin because only low yields can be achieved (see EPA
327,099, page 2, lines 40-43).
[0053] A preferred CGTase is derived from a strain of Bacillus,
e.g. the commercial product Toruzyme.TM. (product of Novozymes
A/S).
[0054] Since enzyme activity usually is affected by temperature it
is important to maintain an appropriate pulp slurry temperature
while the deinking agent is contacted with the pulp slurry in the
case when an enzyme is also applied. The temperature has to be
consistent with the activity temperature profile of the enzyme, and
preferably the process is run at a temperature where the employed
enzyme, e.g. a lipase or a CGTase, has maximum activity. Since a
number of commercially available lipases have a substantial
activity in the temperature range of from 25 to 75.degree. C. it is
contemplated that the process can be run using temperatures, which
do not deviate substantially from the temperatures normally used in
such processes. Typically, pulping with the deinking agent is
carried out at a temperature from 25 to 75.degree. C., preferably
from 30 to 70.degree. C., such as from 35 to 65.degree. C., e.g.
from 40 to 60.degree. C., more preferably from 45 to 60.degree. C.,
such as from 45 to 55.degree. C., e.g. about 50.degree. C.
[0055] For in situ generation of CDs with CGTases, the treatment
temperature of the pulp should be in between 25-100.degree. C.,
preferably from 30 to 90.degree. C., such as from 35 to 85.degree.
C., more preferably from 45 to 75.degree. C., e.g. about 70.degree.
C.
[0056] The efficiency of the deinking agent can be significantly
influenced by the pH of the pulp slurry while contacting the
deinking agent with the pulp slurry, since fluctuations in the pH
can result in deactivation of the optionally added enzyme. The pH
of the pulp slurry should be in the range of from 4 to 9. In a
preferred embodiment of the invention, the pulping with the
deinking agent is carried out at a pH between 4.5 and 8.5, in
particular between 5 and 8.5, such as between 5.5 and 8.5, more
preferably between 6 and 8.5, such as from 6.5 to 8.5, e.g.,
between 7.5 and 8.5. The pulp slurry pH has to be consistent with
the activity pH range of the enzyme or combination of enzymes, and
in a preferred embodiment the process is run at a pH where the
employed enzymes has optimal activity. The pH of the pulp may be
adjusted by means of buffering agents, such as sodium citrate,
sodium carbonate, sodium phosphate and the like. It is particularly
preferred, however, that hydroxides, in particular alkali metal
hydroxides, such as sodium hydroxide, is not added at any stage,
i.e. prior to, during or after pulping.
[0057] With regard to the in situ generation of CDs with CGtases,
the treatment pH of the pulp should be in between 4-9, preferably
from pH 5 to 8, more preferably from 5.5-7, e.g. about pH 6.
[0058] The waste paper to be deinked according to the invention may
be any reclaimed fiber, such as old newspapers (ONP), waste
magazines (WM), mixed and sorted office waste, computer print outs,
white ledger waste paper, etc.
[0059] In a preferred embodiment of the invention the wastepaper
comprises ONP, WM or a combination thereof.
[0060] In one embodiment of the invention the amount of ONP
constitutes at least 10% by weight of the total amount of
wastepaper, preferably at least 20% by weight, e.g. at least 30% by
weight, e.g. at least 40% by weight, more preferably at least 50%
by weight, such as at least 60% by weight, e.g. at least 70% by
weight, most preferably at least 80% by weight, such as at least
90% by weight, e.g. at least 95% by weight of the total amount of
wastepaper. In a further embodiment of the invention the wastepaper
consists essentially of ONP.
[0061] In another embodiment of the invention the amount of WM
constitutes at least 10% by weight of the total amount of
wastepaper, preferably at least 20% by weight, e.g. at least 30% by
weight, e.g. at least 40% by weight, more preferably at least 50%
by weight, such as at least 60% by weight, e.g. at least 70% by
weight, most preferably at least 80% by weight, such as at least
90% by weight, e.g. at least 95% by weight of the total amount of
wastepaper. In a further embodiment of the invention the wastepaper
consists essentially of WM.
[0062] In a still further embodiment of the invention the
wastepaper comprises 1-60% by weight of WM and 40-99% by weight of
ONP, preferably 10-50% by weight of WM and 50-90% by weight of ONP,
such as 20-50% by weight of WM and 50-80% by weight of ONP, e.g.
30-50% by weight of WM and 50-70% by weight of ONP.
[0063] In addition to water, pulp and deinking agent, the pulp may
further contain substances conventionally employed in deinking
process, e.g. brightening agents, solvents, antifoam agents and
water softeners, in particular brightening agents.
[0064] Although not particularly preferred the pulp may also
contain additional surfactants, such as non-ionic and cationic
surfactants. Examples of non-ionic surfactants are, e.g.,
alkoxylated fatty acids, such as DI 600.RTM. from High Point
Chemical Corp.; alkyl phenyl ethers of polyethylene glycol, such as
the Tergitol.RTM. series from Union Carbide; alkylphenolethylene
oxide condensation products, such as the Igepal.RTM. series from
Rhone Poulenc; and aryl alkyl polyether alcohols, such as Rohm and
Haas' Triton.RTM. X 400 series, e.g. Trition.RTM. X 100. Exarhples
of cationic surfactants include imidazole compounds, such as
Amasoft.RTM. 16-7 and Sapamine.RTM. P from Ciba-Geigy and
quaternary ammonium compounds, such as Quaker.RTM. 2001 from Quaker
Chemicals and Cyanatex.RTM. from American Cynamid.
[0065] The overall deinking process generally comprises pulping or
maceration of the wastepaper and ink removal by a flotation system,
a water washing system or a combined flotation/washing system. A
screening or coarse cleaning stage can be utilized to remove
contaminants such as glass, stone, metal and staples. A centrifugal
cleaning stage (or stages) can be utilized to remove light weight
materials such as plastic. Typical deinking processes are described
in L. D. Fergusen "Deinking Chemistry: part 1" July 1992 TAPPI
Journal pp. 75-83; L. D. Fergusen "Deinking Chemistry: part 2"
August 1992 TAPPI Journal pp. 49-58; and J. L. Spielbauer "Deinking
System Overview" Voith Inc. Appleton, pp. 1-9.
[0066] Separation of ink particles or hydrophobic lipid materials
entrapped in cyclodextrin complexes may be performed by well known
techniques in the art such as by washing and/or flotation.
[0067] The invention will be further illustrated in the
accompanying examples below.
EXAMPLES
Example 1
Removal of Fatty Acids from Solution by .alpha.-Cyclodextrin
[0068] Removal of fatty acids from solutions by addition of
.alpha.-cyclodextrin was tested by preparing a 0.1% linoleic acid
suspension and a 1.0% .alpha.-cyclodextrin solution as follows:
1. 250 .mu.l linoleic acid was transferred to a 250 ml volumetric
flask.
2. Deionized water was slowly added while agitating on a whirly
mixer.
3. Linoleic acid solution stays suspended as long as agitation is
continued.
[0069] A 1.0% .alpha.-cyclodextrin solution was prepared by
dissolving 2 g of .alpha.-cyclodextrin in 200 ml deionized
water.
[0070] The 0.1% linoleic acid suspensio was mixed with the 1.0%
cyclodextrin solution at different ratios of fatty acid to
cyclodextrin and the increase in turbidity was determined. The
results are given in the Table 1 below. TABLE-US-00001 TABLE 1
Turbidity (NTU, Nephelometric Turbidity Units) measurements of
mixtures of fatty acid (FA) and cyclodextrin (CD). Fatty acid
Volume Cyclodextrin, Volume Water Ratio Turbidity Test tube 0.1%
(ml) 1.0% (ml) (ml) FA:CD (NTU) 1 Linoleic 0 -- 0 30 -- 0 acid 2
Linoleic 20 .alpha. 1 9 2:1 64 acid 3 Linoleic 20 .alpha. 10 0 1:5
168 acid 3b Linoleic 20 -- 0 10 -- 72 acid 4 Linoleic 10 .alpha. 10
10 1:10 252 acid 5 Linoleic 10 .alpha. 20 0 1:20 378 acid 5b
Linoleic 10 -- 0 20 -- 40 acid 6 Linoleic 6 .alpha. 24 0 1:40 414
acid 6b Linoleic 6 -- 0 24 -- 24 acid 7 Linoleic 4 .alpha. 20 6
1:50 342 acid 7b Linoleic 4 -- 0 26 -- 20 acid
[0071] The results show that it is possible to remove fatty acids,
exemplified by linoleic acid, from solution by entrapment in
cyclodextrin. It is observed that an optimal ratio of fatty acid to
cyclodextrin of 1:40 exists. Optimal ratios of cyclodextrin to
fatty acid may depend on the 5 particular fatty acid to be removed
and can be easily determined by simple experimentation.
Example 2
Use of Cyclodextrin for Wash Deinking of ONP
[0072] Deinking of old newspaper (ONP) by adding cyclodextrin
during pulp formation and subsequent washing was tested using the
following protocol:
[0073] Add 50 g of shredded old newspaper, 1500 ml of water and 4
kg/ton of Tomah wash deinking surfactant to a pulper. Set the
temperature at 45.degree. C. Add cyclodextrin (2 kg/t) and mix for
10 minutes. Transfer slurry into a bucket with 1.5 l of water at
the same temperature as the slurry and stir the slurry for 30 min.
Make No Wash (NW), Wash (W), and Hyper Wash (HW) pads after 5
minutes and 30 minutes of stirring.
[0074] For a No Wash pad (NW), weigh out 180 g of slurry, fill up
to 300 ml with water, stir, and pour into filter with a Whatman 40
ashless filter paper. For Wash pad (W), weigh out 180 g of slurry,
and wash with 1 L of DI water in a Britt jar. Hyper Wash (HW) pads
were made in the same manner as the wash pad (W) except using 5 L
of DI water during washing.
[0075] The pads are evaluated for brightness on a MacBeth Color Eye
analyser using Tappi test methods T452. The results of the
brightness readings are given in table 2 below. TABLE-US-00002
TABLE 2 Brightness Control Alpha CD Beta CD 5 min NW 41.5 41.3 41.4
5 min W 43.9 45.2 44.8 5 min HW 44.9 45.8 45.7 30 min NW 39.6 41.7
41.3 30 min NW 43.5 44.7 44.2 30 min HW 44.7 45.6 45.3
[0076] It is clear that both alpha-cyclodextrin and
beta-cyclodextrin significantly improved the pulp brightness during
wash deinking.
Example 3
Use of Cyclodextrin for Deinking of ONP by Flotation
[0077] Deinking of old newspaper (ONP) by adding cyclodextrin
during pulp formation and subsequent removal by flotation was
tested using the following protocol:
[0078] Set pulper temperature to 50.degree. C. Add 2 L water, 250 g
ONP, 2 kg/ton of Huntsman flotation deinking surfactant and 2.5
kg/ton of cyclodextrin to the pulper. Mix for 10 min and transfer
the slurry into a bucket with 3 L of water and stir it for 30 min
at 50.degree. C.
[0079] Add pulp slurry and 10 L water to a flotation cell (Delta 25
from Voith). Float for 5 min. By the end of the flotation make No
Wash pads (NW) and determine brightness as mentioned above. The
test results of the brightness evaluation are given in table 3
below. TABLE-US-00003 TABLE 3 Brightness Control Alpha CD Beta CD
NW Pads 46.07 47.03 48.23 Std Dev. 0.06 0.25 0.12
[0080] It is evident that the addition of cyclodextrin to the
flotation deinking process improved the pulp brightness. It appears
that .beta.-cyclodextrin is more effective than
.alpha.-cyclodextrin for brightness improvement.
* * * * *
References