CA2007736A1

CA2007736A1 - Process for separating fillers from wastepaper

Info

Publication number: CA2007736A1
Application number: CA 2007736
Authority: CA
Inventors: Ansgar Behler; Rainer Hoefer; Klaus Hornfeck; Wolfgang Von Rybinski
Original assignee: Individual
Current assignee: Henkel AG and Co KGaA
Priority date: 1989-01-14
Filing date: 1990-01-15
Publication date: 1990-07-14
Also published as: JPH04502789A; CS276516B6; ES2041172T3; FI95606B; PT92860A; CS9000170A2; YU3490A; NO912125L; DE59001624D1; TR24119A; EP0453449B1; EP0453449A1; AU630403B2; FI95606C; AU4808590A; NO912125D0; DE3900940A1; FI913327A0; WO1990008219A1; ATE90122T1

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.

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) 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 -_ _

Claims

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:

(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.

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.