PROCESS FOR SEPARATING FILLERS FROM WASTEPAPER

PROCEDE POUR SEPARER LA CHARGE CONTENUE DANS LES PAPIERS USES

English Abstract

Abstract of the Disclosure
Conventional paper filler materials that are present
in aqueous suspensions of filler and paper fiber that do
not contain substantial amounts of ink can be efficiently
separated from the paper fibers by gas froth flotation in
the presence of certain surfactants containing sulfonate
groups. The process is well suited to recycling of printed
wastepaper, after the later has been pulped into an aqueous
suspension and the suspension has been conventionally
deinked.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the separation of filler particles from
an aqueous, substantially ink free, suspension of waste-
paper pulp and filler, said process comprising gas froth
flotation of the suspension while it contains a quantity
corresponding to from 0.1 - 8 grams per kilogram of
equivalent air-dry paper stock fiber in the suspension of
surfactant molecules selected from the group consisting of:
(A) molecules corresponding to general formula I:
<IMG> (I),
in which R represents a linear C6-20 alkyl group; M
represents a hydrogen, alkali metal, ammonium, or
organosubstituted ammonium cation; and M1 represents a
hydrogen, alkali metal, ammonium, or organosubstituted
ammonium cation or a C1-4 alkyl group;
(B) alkali, ammonium, and amine salts of sulfonated
unsaturated fatty acids containing 12 - 22 carbon
atoms per molecule;
(C) alkali, ammonium, and amine salts of mono- and di-
esters, mono- and di-amides, and N-substituted mono-
and di-amides of sulfosuccinic acid; and
(D) alkali, ammonium, and amine salts of secondary C11-17
alkane sulfonates.
2. A process as claimed in claim 1, wherein surfactants
selected from the group of types (A) through (D) are
present during flotation in an amount corresponding to 1 to
4 g/kg of air-dry paper stock in the suspension.

3. A process as claimed in claim 2, wherein the suspen-
sion during flotation contains from 1 to 4 g/kg of air-dry
paper stock in the suspension of surfactants selected from
the group consisting of:
(A') molecules of type (A) in which R is a C10-16 alkyl
radical, M is an alkali metal or ammonium cation, and
M1 is an alkali metal or ammonium cation or a C1-4 alkyl
radical;
(B') molecules of type (B) in which the fatty acid has at
least 16 carbon atoms: and
(C') molecules of type (C) which are
(i) salts of monoesters of sulfosuccinic acid with an
alkyl alcohol having 8 to 18 carbon atoms,
(ii) salts of monoesters of sulfosuccinic acid with an
an alcohol resulting from condensing an alkyl
alcohol having 8 to 18 carbon atoms with 1 to 30
molecules of ethylene oxide,
(iii) salts of monoesters of sulfosuccinic acid with an
an alcohol resulting from condensing any of iso-
octyl, iso-nonyl, and iso-dodecyl phenol with 3
to 30 molecules of ethylene oxide, and
(iv) salts of diesters of sulfosuccinic acid with
alkyl alcohols each having from 4 - 18 carbon
atoms.
11

4. A process as claimed in claim 1, wherein the suspen-
sion during flotation contains from 1 to 4 g/kg of air-dry
paper stock in the suspension of surfactants selected from
the group consisting of:
(A') molecules of type (A) in which R is a C10-16 alkyl
radical, M is an alkali metal or ammonium cation, and
M1 is an alkali metal or ammonium cation or a C1-4 alkyl
radical;
(B') molecules of type (B) in which the fatty acid has at
least. 16 carbon atoms; and
(C') molecules of type (C) which are
(i) salts of monoesters of sulfosuccinic acid with an
alkyl alcohol having 8 to 18 carbon atoms,
(ii) salts of monoesters of sulfosuccinic acid with an
an alcohol resulting from condensing an alkyl
alcohol having 8 to 18 carbon atoms with 1 to 30
molecules of ethylene oxide,
(iii) salts of monoesters of sulfosuccinic acid with an
an alcohol resulting from condensing any of iso-
octyl, iso-nonyl, and iso-dodecyl phenol with 3
to 30 molecules of ethylene oxide, and
(iv) salts of diesters of sulfosuccinic acid with
alkyl alcohols each having from 4 - 18 carbon
atoms.
12

Description

PATENT
Docket D 8 4 4 2
I~IPROV13D PROC~R FOR ~EPARA~ING FXLL13R8 FP~OM WA~T~PAPER
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process or the removal of
fillers from wastepaper, more particularly to the flota-
tional separa~ion of fillers from pulped wastepaper in the
presence of certain surfactants.
_ta ment of the Related Art
Fillers are added to almost all papers to improve
their printability, density, and opacity and to obtain a
1" more uniform degree of light transmission and greater
whiteness. The fillers normally used are mineral in origin
or are synthetically prepared products. Examples are
aluminum silicates, such as kaolins or siliceous alumina;
calcium carbonates, such as chalk or lime; talc; and
calcium and barium sulfates (Cf. Ullmanns Encyklopadie der
technischen Chemie, Vol. 17, 577 et seq. (1979 edition}).
The filler content of the paper stock depends on the
purpose for which the paper is to be used and, in most
cases, is between 7 and 25% by weight.
To be able to produce a paper having standardized
quality features, it is essential that all the materials
used to make the paper be of uniform quality. Printed
wastepaper is used in large quantities in the production oP
printing paper and tissue paper. To obtain high whiteness
in paper made with substantial amounts of printed waste-
paper, the printing inks have to be removed from the
printed wastepaper. This is usually done by deinking
processes essentially comprising the following two steps:
1. Pulping the wastepaper, i.e., fiberizing the
wastepaper in water, in the presence of the chemicals
re~uired for detachment of the printing ink particles;
and

2. Removal of the detached printing ink particles from
the iber suspension.
The second step can be carried out by washing or
flotation ~Cf. Ullmanns Encyklopadie der technischen
Chemie, 4th Edition, Vol. 17, pages 570 - 571 {1979)). In
flotation, which utili~es the difference in wettability
between printing inks and paper fibers, air is forced or
drawn through the fiber suspension. Small air bubbles
attach themselves to the printing ink particles and form a
froth at the surface of the water which is removed by
clarifiers.
The deinking of wastepaper is normally carried out at
alkaline pH values in the presence of alkali hydroxides,
alkali silicates, oxidative bleaches, and surfactants at
temperatures in the range from 30 to 50 C. Soaps and/or
fatty alcohol polyglycol ethers are often used as surfac-
tants to promote the detachment and separation of the
printing inks (Cf. Ullmanns Encyklopadie der technischen
Chemie, 4th Edition, Vol. 17, pages 571 - 572 {1979)). JP
61/207686, as reported in Chem. Abstr., Vol. 106, 121694v,
describes the use of aliphatic ~-sulfocarboxylic acids and
aliphatic ~-sulfocarboxylic acid esters in flotation
deinking processes. According to Russian patents SU 773
174 as reported in Derwent 51102 D/28 and SU 717 95 as
reported in Derwent 72992 C/41, good results are obtained
in the flotation of printing ink when wastepaper is treated
with mixtures containing alkyl sulfonates and soaps. Ac-
cording to Us Patent 1,9~5,372, particularly good deinking
results can be obtained when filler-containing wastepaper
is treated with aqueous solutions containing soaps and/or
sulfonated mineral oils and the paper fibers are sub-
sequently removed by filtration. In the case of filler-
free printed wastepaper, fillers are separately added.
Unfortunately, the known processes for separating the
3~ detached printing ink particles from the fiber suspensions
have serious disadvantages. The high filler content in
wastepaper is only removed very incompletely by flotation,

so that ~he proportion of deinked wastepaper usable in
paper manufacture is limited to around 50 ~ by weight,
particularly in the manufacture of newsprint paper.
Although the fillers present in wastepaper can he removed
by washing of the paper fibsrs, there are disadvantages of
a very high fiber loss and very serious water pollution.
It i.s known from l'Wochenblatt fur Paplerfabrikation,
Vol. 17, S46 - 649 ~1985) that the removal of fillers by
flotation can be increased if the wastepaper is treated
with aquenus liquors containing alkyl benzene sulfonates as
surfactants rather than with aqueous liquors containing
soaps or nonionic surfactants. In many ~ases, however, the
improvement in filler removal is not sufficient to meet the
stringent quality requirements which the reusable waste-
paper has to satisfy.
Accordingly, the problem addressed by the present
invention is to develop a process with which a distinct
increase could be obtained in the removal of fillers from
wastepaper.
DESCRIPTION OF THE INVENTION
The invention is based on the surprising observation
that the removal of fillers by flotation from aqueous paper
stock suspensions that are already substantially free from
ink is distinctly increased in thle presence of certain
~5 surfactants containing sulfonate groups.
Accordingly, the present invention relates to a
process for the separation of fillers from wastepaper by
flotation, a~ter separation of the paper fibers from any
printing ink ~ormerly associated with it, in the presence
of a flotation effective amount of one or more surfactants
selected from the group consisting of:
a) compounds corresponding to general formula I:
R - CH - CoO~
(1)
SO3M
in which R represents a linear C620 alkyl group; M
represents a hydrogen, alkali metal, ammonium, or

~ 773~
organosubstituted ammonium cation; and M1 represents a
hydrogen, alkali metal, ammonium, or organosubstituted
ammonium cation or a C~ 4 alkyl group;
b) alkali, ammonium, and amine salts of sulfonated
unsaturated fat~y acids containing 12 - 22 carbon
atoms per molecule;
c) alkali, ammonium, and amine salts of mono- and di-
esters, mono- and di-amides, and N-substituted mono-
and di~amides of sulfosuccinic acid; and
d) alkali, a~monium, and amine salts of secondary C~117
alkane sulfonates.
Preferably the total quantity of surfactants from this
group present in the suspensions of paper fibers in water
at the beginning of flotation is from 0.1 to 8 grams per
kilogram ("g/kg") of air-dry paper stock present in the
suspension. Air-dry paper stock is paper stock in which an
equilibrium state of internal moisture has been estab-
lished. This equilibrium is dependent on the temperature
and relative humidity of the air with which the paper stock
is aquili~rated. In practicing the invention, the amount
of air-dry paper stocX is generally determined by weighing
the wastepaper used before pulping it, after equilibration
in air of 50 % relative humidity at 20 C.
"FillerE" are understood to be the substances typical-
ly used in the paper industry, for example aluminum
silicates, such as kaolins sr siliceous alumina, calcium
carbonates, s~ch as chalk or lime; talc; and calcium and
~arium sulfates.
Preferred compounds of type (A) above for use in the
invention are those with 12 - 18 carbon atoms total, all in
a single chain, for example sodium salts of ~-sulfonated
tallow fatty acid methyl ester, ~-sulfonated coconut oil
fatty acid, and~or ~-sulfonated palm kernel oil fatty acid
methyl ester. The ~-sulfofatty acids and ~-sulfofatty acid
esters may be obtained by sulPonation o~ the corresponding
fatty acids and/or ~atty acid esters. S03-containing gas
mixtures may be used as the sulfonating reagent (Cf.

7~3~
Ullmanns Encyklo~ ie der technlsc~en_Chemle, 4th Eclition,
Vol. 22, page 482 (Verlag Chemie, Weinheim, 19823).
Alkali, ammonium and/or amine salts of sulfonated
unsaturated fatty acids containing 12 to 22 carbon atoms
S are also o~tainahle by known methods. They may b~ produced
from mono- and/or poly-unsaturated C1222 or preferably Cl622
fatty acids, for example palmitoleic acid, oleic acid,
elaidic acid, linoleic acid, linolenic acid, erucic acid,
and mixtures of such unsaturated fatty acids. The sulfona-
tion of unsa~urated fatty acids can be carried out withsulfuric acid, chlorosulfonic acid, or S03-containing gas
mixtures. However, sulfonation is preferably carried out
in accordance with GB 1,278,421 at temperatures of 20 to
C using gas mixtures of S03 and air or inert gases, for
example ni~rogen, in which the S03 content is between 1 and
15 % by volume. The sulf;nation reactions may carried out
continuously or discontinuously in standard reactors of any
type tha~ is suitable and typically used for the sulfona-
tion of fatty acid esters or olefins, preferably of the
falling ~ilm type fCf. Kirk-OthmeF: Encyclo~edia of Chemi-
cal Technoloqy, Vol. 22, page 28 et seq. ~1983 edition)).
On completion of the sulfonation reaction, the reaction
mixture is usually hydrolyzed with alkalis, for example
NaOH, KOH, ammonia, and/or ethanolamines, in aqueous
solution.
Alkali, ammonium, and/or amine sa:Lt~ of sulfosuccinic
acid mono- and/or di-esters and/or sulfosuccinic acid mono-
and/or di~amides may be obtained by reaction of maleic acid
monoester and/or diester and/or the corresponding amides
with alkali hydrogen sulfites, sulfi~es, pyrosulfites, or
disulfites (Cf. Ullmanns EncyXlopadie _der
Chemie, Vol. 22, pages 482 to 483 ~Verlag Chemie, Weinheim,
1982~). Sulfosucoinic acid diesters and diamides are
preferably prepared by reaction of maleic anhydride with
approximately 2 moles, per mole of maleic anhydride, of a
linear, branch~d, or cyclic alkyl alcohol or the corre-
sponding alkyl amine containing 4 to 18 carbon atoms,

~$~ 3~
followed by sulfonation in agueous or mixed aqueous/organic
media, for example with alkali disulfites, such as sodium
disulfite, or with alkali pyrosulfites in accordance with
EP 87 711. It is preferred, when sulfosuccinic acid
diesters are used, that they be estexs of iso-hexanol, iso-
octanol, iso-nonanol, iso-decanol and/or iso-trid~canol
either on their own or in combination with sulfosuccinic
acid diestexs of the corresponding linear alkyl alcohols.
Sulfosuccinic acid monoesters and sulfosuccinic acid
monoamides are preferably prepared by reaction of each mole
of maleic anhydrlde with approximately 1 mole of a linear,
branched, or cyclic, opti~nally alkoxylated, alkyl alcohol;
or an optionally alkoxylated mono-, di-, or tri-alkyl
phenol containing 1 to 12 carbon atoms in each alkyl chain;
or a linear, branched or cyclic, optionally alkoxylated
alkyl amine to produce a monoester or monoamide of maleic
acid. This product may then be sulfonated, for example,
with sodium or ammonium sulfite. It is more preferred,
when sulfosuccinic acid monoesters are use, to use esters
of C818 alkyl alcohols, optionally condensed with up to 30
moles of ethylene oxide per mole of alcvhol, and/or of iso-
octyl, isc-nonyl and/or iso-dodecyl phenols condensed with
from 3 to 30 moles of ethylene oxide per mole of phenol.
In addition, alkali, ammonium, and/ox amine salts of
secondary C~ alkyl sulfonates, which can be produced on
an industrial scale by reaction of linear paraffins with,
for example, SO2 and oxygen in the presence of radical-
forming substances, such as oz~ne and organic peroxides, or
of W light ICf. Winnacker/Kuchler in Chemische Technolo-
~, 4th Edition, Vol. 7, pages 114 - 116 ~Carl ~anser
Verlag, Munchen, 1986)), are also suitable for a process
according to the invention.
In the practice of t~e in~ention, surfactants
containing sulfonate groups are preferably added to the
aqueous paper stock suspensions at 20 to 60C after
separation of the printing ink from the suspension, most
pxeferahly in a quantity of 1 to 4 grams ("g") of surfac-

~ ~7 b~3~
tant per kg of air-dry paper stock. The pH value of the
suspensions preferably is between 7 and 11 and more prefer-
ably between 8 and 10. The paper stock content in the sus-
pensions is preferably from 0.5 to 2 % by weight of the
total suspension. Flotation is then carried out in a
conventional manner, preferably at teMperatures of 20 to
95C and more preferably at temperatures of 45 to 604C,
for example in a ~enver flotation cell.
The fibrous material (recycled paper pulp) obtained by
a process according to the invention is distinguished from
fibrous ma~erial flotated in the presence of typical
surfactants by a distinctly lower filler content. It is
now possible by use of the process according to the inven-
tion tG increase the proportion of deinked wastepaper in
paper manufacture to more than 50 % by weight.
The followinq examples are intended to illustrate the
invention without limiting it.
Examples
Flotation was carried out in an approximately 9 liter
size Denver laboratory flotation cell using aqueous filler
suspensions and aqueous paper stock suspensions.
Example and Comparison Example Type 1~: Filler suspensions
An amount of 23 g of each filler as specified in Table
1 below was dispersed in 9 liters ("ln) of water, and the
2~ resulting dispersion was adjusted with sodium hydroxide to
a p~ value of 8 . 5 to 90 O. After the addition of an amount
of surfactant or its solution containing 0.2 g of pure
surfactant of the type as specified below, flotation was
carried out for 7 minutes in the Denver laboratory
flotation cell. The solids component in the overflow from
the flotation cell was filtered off and dried at 1054 C to
constant weight. The results are shown in Table 1 as the
percentage of the total filler content of the suspension
removed by flotation under these specified conditions.

7t73~
. . . ~
Table 1
~ . , . _ . . . _
Surfact~nts Fillers Filler in the
S used used overflow in ~ by
weight
Accordinq to the inventiQn
Sulfosuccinic acid ) Kaolin 94
10mono C121~-alkyl ) CaC03 ~4
ester, sodium salt) Kaolin/CaC03) 77
Oleic ~cid sulfonate,3 Xaolin 80
sodium salt ) ~aCo3 82
Kaolin/CaC03~ 61
For comparison
n-Dodecyl benzene ) Kaolin 3
sulfonate, sodium) CaC03 4
salt ) Kaolin/CaC03~) 4
~-c~4.16-olefin ) Kaolin 42
sulfonate, sodium) CaC03 43
salt ) Kaolin/CaC03 60
Dodecyl diphenyl ether~ Kaolin 30
disulfonate, sodium ) CaC03 72
salt ) Xaolin/CaC03) 34
.
) Mixture of 70% by weight kaolin and 30~ by weight CaC03
. ~
Exam~le Tye~ Paper stock suspensions
Air-dry paper stock from newspapers and magazines (in
a ratio by weight of 1:1) was subjected to removal of
printing in~ by flotation in khe presence of ~he chemicals
normally used. After flotation of the printing ink, the
pap~r stock suspension had a stock density of 1 % by
weight, a temperature of 40D C, a pH value of 9.0, and an
ash content of 16 ~ by weight of the solids content. An
amount of surfactant or its solution containing 0.2 g of
pure surfactant was added to 9 1 of the deinked paper stock

suspension havi~g a stock density of 1% by weight, followed
by flotation for 10 minutes in the same type of Denver
laboratory flotation cell as for Example ~ype 1. After
flotation, the paper stock was freed from water in pap~r
filters and dried at 105~ C to constant weight, and its ash
content was determin~d in accordance with DIN 54 371. The
results are shown in Table 2~
. . _ .
Table 2
.. . .
Surfactants used Filler content in
the paper in ~ by weight
after flotation
Oleic acid sulfona~e, 6 0
sodium salt
Sulfosuccinic acid
mono-c~ 8-alkyl 5-3
ester~ sodium salt
-_ _