Note: Descriptions are shown in the official language in which they were submitted.
CA 02832775 2013-11-13
Description
TITLE OF INVENTION
A novel FWA formulation used for the papermaking process
CROSS-REFERENCE TO RELATED APPLICATIONS
In the following references of related patents, optical brighteners, optical
brightening agents (OBA 's)
and fluorescent whitening agents (FWA 's) refer to the same type of specialty
chemical. The
brightening chemicals present in these patents do not solve the problem
brightness gain limit of
OBA/FWA as well as the yellowing caused by overdosage. In addition, none of
the patents below
discuss the use of OBA 351 or/and OBA 71 formulation on the application of wet-
end and coating
papermaking process.
US7812156 proposes a modified OBA which maintains the high solubility and
strong fluorescent
whitening effects of previous OBA' s while decreases the anionic load that
stresses the papermaking
system.
US7566349 explores the use of a new FWA of amphoteric bis-
triazinylaminostilbene derivative on
the process of whitening synthetic or natural organic materials such as paper.
This new type of FWA
is not usually suppressed in performance when put in the cationic papermaking
environment or when
combined with residual anionic FWA's.
US3790443 presents a technique of utilizing a water-soluble
hydroxymethylaminonitrile salt in the
form of dry powder on papermaking materials to quench the fluorescence of
optical brightening
agents present in the papermaking materials. By adding an acid along with the
quencher, some
undesirable whitening effects of the OBA's could be neutralized.
US20120211188 discloses the preparation techniques for a specific concentrated
aqueous disulfo-
stilbene based FWA for optically whitening paper.
US8475630 introduces an aromatic ring based additive that can increase the
retention rate of OBA's
on paper materials. By using the aromatic ring on the additive to associate
with the OBA molecules
chemically, capacity for retention is improved.
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US7789917 reveals the composition of an amphoteric stilbene OBA, which
consists of a substrate
and the associated stilbene (one of 4,4'-diamino-2,2'-stilbene disulfonic
acid, biarylsulfonate-4,4'-
diamino-2,2'-stilbene disulfonic acid, biaryldisulfonate-4,4'-diamino-2,2'-
stilbene disulfonic acid,
derivatives thereof, salts thereof, and mixtures thereof).
US7497971 describes the use of a mixture of FWA's based on dicyano-1,4-bis-
styrylbenzenes and
bisbenzoxazoles. Such mixtures of two or more components may exhibit a higher
degree of
whiteness than that of the sum of the individual components alone.
US8262858 and US7914646 identify the use of oxidative agents for the paper
process which
enhances the performance of OBA' s and chelants. By analyzing various stages
of the papermaking
process that involve oxidative compositions and processes that preserve and
enhance the brightness
and improve color of pulp or paper, it was found that the use of an oxidative
agent could also reduce
the photoyellowing of aged, bleached pulp materials.
US7638016 proposes a method of brightening pulp fibres with at least one
stilbene-based OBA after
the last bleaching/extraction stage with a chlorine based bleaching agent.
US20120199302 presents a new composition using at least two specific disulfo-
stilbene based FWA
for optically whitening paper or board.
US5064570 introduces a new preparation method for fluorescent brightener that
involves the use of
specific water-insoluble aromatic or carbon-substituted fatty alcohol
auxiliaries.
EP1253191 presents the composition of detergents, which includes stilbene-
triazine-based optical
brightener (FB #71).
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM
Not applicable.
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BACKGROUND OF THE INVENTION
[0001] Optical brightening agents (OBA's) or fluorescent whitening agent
(FWA's) have chemical
properties that absorb light in the ultraviolet region (340-370 nm) and then
re-emitting it back into
the visible spectrum, usually in the color blue or indigo (420-470 nm). The
absorption and re-
emission happen at a rapid pace unlike the slow phosphorescence behaviour. The
newly added blue
light compensates the yellowness of paper products and produces a net
whitening effect that is
observable to the naked eye.
SUMMARY OF THE INVENTION
[0002] One of the biggest hurdles to using conventional FWA is the limit on
brightness gain. This is
especially prominent in lower brightness paper that has significant mechanical
pulp present. As an
increasing amount of excess conventional FWA has been input into the system in
an attempt to
increase the brightness further, the paper materials coming off the machine
would have more of a
yellow tinge due to the natural appearance of the conventional FWA.
[0002] The new generation FB #351 does not encounter this problem as it has a
totally different
molecular structure which exhibits an almost pure white appearance. There is a
plateauing effect for
brightness gain associated with injection (at which point the cost
effectiveness decreases), but the
paper products will no longer have a yellowish tinge. In short, the machine
tender can inject as much
FWA as needed to increase the brightness to a certain point, without the
risking yellowing caused by
overdosing. FB #351 re-emits light in the range of 435-440 nm (violet light).
[0003] Due to the fact that FW #351 is in a different chemical family, its
large number of ethylene
bonds allows better interactions with the fibres and hence higher retention
rates. This is a totally
different case than the conventional FWA, which relies heavily on Van de Waals
forces for charge
binding. Instead of having a significant amount of conventional FWA left over
in the white water
system for a prolonged period of time after injection has ceased, a sharp
decrease in concentration
for the FB #351 in white water can be observed.
[0004] FB #71 has been historically used in the detergent industry as a
brightener. However its
application in papermaking process has not been successful due to the
extremely low solubility in
water caused by its morpholino functional group. Even though theoretically
speaking, it is possible
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to be used to brighten paper, it was never commercially practical. Therefore
FB #71 was not sought
after by papermakers.
[0005] On the other hand, the low solubility of the FB #71 would yield a
significantly higher
retention rate on fibers than any other FWA's ever used. By carefully
optimizing the dosage in water
of various temperatures, dissolution was achieved. FB #71 re-emits light in
the range of 440-450 nm
(indigo light).
[0006] When FB #351 and FB #71 are combined together as a formulation, these
two FWA's on low
dosage can absorb UV-light on a broader spectrum and re-emit a net brightness
higher than that of
either FWA's alone at a higher dosage.
[0007] When FB #351 and FB #71 are combined together as a formulation, these
two FWA's has
higher retention than either FWA's alone.
[0008] The present invention relates to a novel, low-cost method of producing
high final brightness
values in paper production not previously achieved, and reducing brightness
reversion of paper
material.
[0009] According to the present invention there is provided an FWA formulation
for making high
brightness paper. The usage of the FWA formulation comprises of approximately
0.01 %-1.0% by
weight on dried pulp.
[MO] The invention provides several advantages over conventional FWA's:
1. Lower cost benefits due to the decreased addition of FWA while still
achieving the same, or
greater, ISO brightness values.
2. Increased brightness values and retention rates for paper materials over
conventional FWA's. This
increases the number and variety of applications for the product,
significantly expanding its
marketability.
[0011] The invention and its advantages will be illustrated in more details by
the examples below
which however, are only intended to illustrate the invention without limiting
the same. The
percentage and parts stated in the description, claims and examples refer to
percent by weight and
parts by weight, respectively, unless otherwise stated.
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DETAILED DESCRIPTION OF THE INVENTION
[0012] The invention will be further described with reference to the following
non-limiting
examples:
[0013] Pulp brightness (ISO brightness) is measured with a brightness meter,
which determines the
brightness of a split sheet at a wavelength of 457 nm (ISO D65 Standard
Method).
[0014] The FWA's described in this invention are the following:
1. FB #351 has a chemical name of 4,4"-Bis(2-sulfostyryl)biphenyl disodium
salt (100% purity), and
a CAS number of 27344-41-8.
2. FB #71 has a chemical name of 4,4'-bis[4-anilino-6-morpholino-1,3,5-triazin-
2-yl] amino-2,2'-
stilbene disodium salt (100% purity), and a CAS number of 16090-02-1.
3. Disulfo-stilbene based FWA has a chemical name of Disodium 4,4Lbis[(4-
anilino-6-
hydroxyethylamino-1,3,5-triazin-2-yDamino]stilbene-2,2'-disulphonatel (100%
purity), and a CAS
number of 12224-06-5.
4. Tetrasulfo-stilbene based FWA has a chemical name of Tetrasodium 4,4'-bisR4-
[bis(2-
hydroxyethyl)amino]-6-(4-sulphonatoanilino)-1,3,5-triazin-2-yllaminolstilbene-
2,2'-disulphonate]
(100% purity), and a CAS number of 16470-24-9.
[0015] EXAMPLE 1
Laboratory Studies
The incoming samples of 30% Kraft and 70% mechanical pulp mixture (from a pulp
mill in British
Columbia, Canada) with a brightness of 78 ISO and a concentration of 0.7%, was
treated with
different FWA's at 40 C and 5 minutes of retention time.
From the results shown in TABLE 1, it is evident that under the same dosage,
the new FWA
formulation (50% FB #351 and 50% FB #71) can obtain a significantly higher
brightness value
compared to the conventional FWA's when used on production that requires more
mechanical pulp
than Kraft pulp.
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Table 1
Unbleached ISO Formulation
Disulfo-OBA (%) Tetrasulfo-OBA (%) ISO Brightness
Brightness (%)
78 0.01 0 0 79
78 0.1 0 0 87
78 1.0 0 0 83
78 0 0.01 0 78.5
78 0 0.1 0 84
78 0 1.0 0 83
78 0 0 0.01 82
78 0 0 0.1 98
78 0 0 1.0 100
[0016] EXAMPLE 2
Laboratory Studies
The incoming paper samples (from a paper mill in British Columbia, Canada)
with a brightness of
84 ISO were coated with coating color and different FWA's.
From the results shown in TABLE 2, it is evident that under the same dosage,
the new FWA
formulation (0.1% FB #351 and 99.9% FB #71) can obtain a significantly higher
brightness
compared to the conventional FWA's when used on production that requires
coating materials.
Table 2
Uncoated Basesheet Formulation
Tetrasulfo-OBA (%) Coated Paper ISO
Brightness
Paper ISO Brightness (%)
84 0.01 0 85
84 0.1 0 90
84 1.0 0 87
84 0 0.01 91
84 0 0.1 107
84 0 1.0 110
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[0017] EXAMPLE 3
Laboratory Studies
The incoming samples of 100% Kraft pulp (from a pulp mill in British Columbia,
Canada) with a
brightness of 88 ISO and a concentration of 1.0%, was treated with different
FWA's at 40 C and 5
minutes of retention time.
From the results shown in TABLE 3, it is evident that the new FWA formulation
(99.9% FB #351
and 0.1% FB #71) can achieve significantly higher brightness when compared to
the two
conventional FWA's that cause plateauing (and even yellowing) once overdosing
occurs.
Table 3
Unbleached ISO Fomulation
Disulfo-OBA (%) Tetrasulfo-OBA (%) ISO Brightness
Brightness (%)
88 0.1 0 0 105
88 0.2 0 0 112
88 0.3 0 0 115
88 0 0.1 0 100
88 0 0.2 0 108
88 0 0.3 0 110
88 0 0 0.1 121
88 0 0 0.2 132
88 0 0 0.3 137
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