CA2141485A1 - Treatment of waste printed papers with surface active polymeric compositions for improved recyclability - Google Patents

Abstract

This invention relates to a treatment process of wastepaper for making printing grade paper from newsprints and officewastes using surface active polymer composition including a novel surface active terpolymer. In particular, the invention is concerned with a process for removing ink from an aqueous pulp slurry by treating the pulp with a surface active polymer composing of two to three comonomers in which at least one is a hydrophobe and another is a hydrophil, having a glass transition temperature ranging from about 105°C to about 170°C, alkali metal salts of the said surface active polymer and the combination of the said surface active polymer with a fatty oil alkoxy derivative or fatty acid soaps.

Description

21 41~g~
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TREATMENT OF WASTE PRiNTED PAPERS WITH SURFACE ACTIVE
POLYMERIC COMPOSITIONS FOR IMPROVED RECYCLABILITY
k5~r~ n~1 nf Ih~ ;ny.~ntinn S Recycling of ~a,t"~d~ is a key to survival of pulp and paper industries. The driving forces are limited by space for landfills, prevention of forests, and consumer pressure and legislation for recycled content in paper products. To produce good quality recycled paper requires, among other, the removal of ink from ~d~ a~ which is commonly recogni~ed as ~a,t~,~d~J~l deinking. Various lenhno~ iPs are available for 10 doing this, which essentially consists of two steps: detaching in~k from fiber and separating the suspended ink particles from the pulp slurry. For each step a variety of options are open; ink dispersion is usually achieved in the repulping step by the addition of deinking chemicals mostly in an alkaline medium, while ink separation is effected by screening, washing or flotation.
During recent years f~ rarhir printirlg has been developed beyond the printing of paka~ing materials and is an option for newspaper printing. FI~ Y--~rqrhic inks are water -based, providing printing and ~llVilUlllllC;ll~dl benefits, but their presence reduce deinking quality by froth floîation and results in a more difficult effluent ~ cifi~ n from washing devices. A very similar problem is ~u~u~ d for inkjet-printed officewastes. Sales of inkjet printers are increasing rapidly due to more and more use of network computers, electronic mail etc. Pulping of papers printed in Deskjet printer, utilizing a liquid ink system, produces smaller particles than laser printers or rholo~ori~r5. In fact, on pulping, the deskjet-printing inks which are essentially dyes dissolved in water and glycols, totally disperse in aqueous repulping medium to produce a uniformly grey stock.
2s In practice segregation of wastepaper based on the type of printing is impossible. In most cases, ~và,~L~,ud~ containing newsprints printed with offset and lithography are cfm~ with flexo-printed newsprints. Similarly, officewastes containing toner based printed papers are ~ r.l with inkjet-printed officewastes. Although successful deinking technologies by froth flotation are available for offset and lithography printed newsprints, a flexography or inkjet printed paper cull~;~lluilalion into other printed paper is 21~ 485 causing severe deinking problem for the reason mentioned above.
The present invention simplifies the deinking of flexo- and inkjet-printed papers cr~n~ I wastepaper mixtures using repulping and froth flotation processes by treating a repulped slurry in aqueous medium with a surface active polymer composition in S presence or absence of a u~u~ h)llal surfactant to ~ " "~ small ink particles to a size range suitable for flotation and finally removing those A~ d inks by creating air bubbles under constant agitation from the said repulped slurry.

SllmmAI;y of Ihr i vPnlir~n It has been discovered that improved recyclability of ~a~a~eli ~ with flexography- and inkjet-printed papers is simply obtained by treating the w.. .~ pulp, herein designated as repulped slurry, with a limited amount of a surface active polymer compound or a mixture of said compounds. Subjecting printed ~va~ )d~15 ~
with paper printed by flPYrlgrArhir and inkjet processes to shear forces under alkaline 15 condition followed by treatment of this repulped secondary fiber slurry in an aqueous medium with a surface active polymer compound or mixture of compounds having a glass transition ~~ Jcla~Ul~ rAnging from 105 C to 170 C with or without a conventional surfactant, effects separation of the ink particles in minimum time even at a ~ lalul~;
below 35 C. By surface active polymer compound is meant an organic polymer, more 20 specifically, a copolymer or terpolymer having at least one hydrophobic and one hydrophillic monomers, the polymer being adsorbed by the ink particles thereby facilitates repulsion of ink particles from fiber surface and agglomeration of the free irlks. The polymeric i,i~LU~ Ulld:~ are specific ~ ".~ with the l~ydlu~ l);c part being styrene and the hydrophillic part essentially contains an organic acid anhydride of the following 2s structure:
~

0~0~0 More particularly, this invention deals with styrene-acid anhydride copolymer or terpolymer as a surface active polymer compound for treating repulped-secondary fiber.

-Z1~148~
Henceforth the term surface active polymer compound and surface active polymer composition will be used illtv~ a~ ;ably to designate a single compound or a mixture of u.~ By terpolymer is meant an organic polymer containing three different monomer units in polymer chain and by treatment of repulped slurry is meant a process 5 which is adopted to incorporate the surface active polymeric ~:u-n~o~iLiull in an alkaline medium to facilitate separation of inks from secondary fiber. The said polymericcr~mrr~ition is beleived to produce the ink separation effect by ;~gy,ll~ 1 i. .g ink particles, perferably small ink particles of average particle size 10 microns and smaller by two different ll~ l)c by charge neutralization of ink binder in an alkaline medium in 10 presence of an aqueous solution of metal halide or by ~Ir,~ ;LdLill~ them in a ~midly alkaline medium as small solid particles followed by their ~ ",~ iorl with other ink particles of similar size and preventing them from deposition on the pulp surface and, finally floating them out with controlled air flow and agitation. Regardless of the correct exrl~n~ )n, it is observed that the treatment of the pulp in alkaline medium with said surface active 15 polymeric Co~ u~iliull enhances the ~lomrrati~ n of small ink particles to the size range of about 5 to 200 microns and then removes them from aqueous pulp slurry by froth flotation, thereby completely or partially eliminates a pulp washing stage usually required to remove small inks from repulped newsprints. It is in the aforesaid sense of being enhanced ~lonn.or~ion and reducing the residual small ink particles below S microns in removing 20 inks that deinking the secondary fiber is to be understood herein.
Perferred c~ mr- oiti~n~ of surface active polymer are those in which styrene and an organic acid anhydride are essential chemical components in a copolymer, more particularly, the acid anhydrides being 2,5 filr~n~ nr, 2- dodecenyl succinic anhydride arld 2-methylene succinic anhydride.
Preparationofthesaidsurfaceactivepolymerwhereinthel.""l,~,~;l;.. ,.isastyrene-2,5 furandione copolymer is described in the Eur. Pat. No. 27, 274, the disclosure of which is ill~vluulatrd herein by reference. Novel compounds of surface active polymer in which the polymer being a mixture of a styrene-2,5 furandione copolymer and, a terpolymer of styrene, 2,5 furandione and a third comorom~r are prepared by bulk 2~ 8~
copOly~ aLiull of the particular l~y~lu~llùb~ employed with 10 to 40 mole percents 2,5 furandione and l to 20 mo~e percents of a third l,ULUUIIUIII~,I chosen from 2-dodecenyl succinic anhydride, citraconic anhydride and 2-methylene succinic anhydride. This preparation may typically be a~,u~u~ as follows.
S Two to four molar equivalents of styrene is heated with one to three molar r~u~uiv_h,llL~ of 2,5 furandione at a t~ ,.aLul~; ranging from about 60 C to 90 C with a catalytic amount of a free radical initiator such as laouryl peroxide, benzoyl peroxide in an inert liquid medium such as toluene, benzene, xylene. These catalysts and diluent systems and their amounts are well known and will not be described in detail. A typical c.-nn~ nfr~til n of catalyst and a preferred diluent system of this invention are particularly suitable for ink removal described in US Pat. No.3, 725, 360, the teachings of which are il~UU~U~ ~,d herein by reference. The heating of styrene and 2,5 furandione is conùnued for 10 to 60 minutes in oxygen free a~lllo6~JII.,.~ in order to initiate the reaction between styrene and 2,5 succinic anhydride, as evidenced by a marginal increase in the viscosity of 15 solution, and then about 0.1 to 1.5 mole e~luiv~h,~i, of a third m~monr~mrr such as 2-dodecenyl succinic anhydride is added. The reaction may be ddval~ vu~ly carried out at slight pressure, for example, at about 5 pounds per square inch pressure in a glass apparatus. The preferred ~IllfJ~ Ul~ during the third .~..". ,- - .l).. . addition is above 75 C.
Temperature below 75 C may be used, but the reaction is quite slow. After addition of a third comonomer the reaction is continued for another l to 3 hours. When the required extent of reaction is achieved, as determined by the viscosity of solution, the batch is then stripped to remove liquid diluent, the product is recovered first by dissolving in sufficient amount of acetone followed by ~l~Li~;td~ g it in water. The unique property of these surface active polymers is that they are soluble in aLcali.
It should be noted that the said surface active polymer compositions with good ink sl~el~m~r~fi~r~ and sufficient frothing character herein disclosed are obtainable only when 2-dodecenyl succinic anhydride is added as a third comonomer during the reaction. No addition of 2-dodecenyl succinic anhydride leads to products which are efficient in ink agglomeration but do not possess sufficient frothing ability to remove most of the 21414~5 .
a~ u~ a~d inks from aqueous pulp slurry. Such copolymers with a third Culllullulllr,l other than 2-dodecenyl succinic anhydride or without any third cl~ml~nom~r are also suitable for use as ink agglomerating agents in a-,~ol~dll~r to this invention are styrene-acid anhydride copolymers or terpolymers.
The styrene-acid anhydride copûlymer is one having a styrene content at least about 50 mole percents, preferably from about 60 to 80 mole percents and a glass transition b, u~ Lul~ in the range from about lûS C to about 170 C, preferably from about 110 C to about 160 C. Preferred styrene-acid anhydride Cu,u~lyl~ and terpolymers are styrene-citraconic anhydride copolymer, styrene-2,5 filrr~~i( 2 methylene succinic anhydride terpolymer, styrene-2,5 furandione-citraconic anhydride terpolymer, styrene-2,5 furandione copolymer, the later being ,u~-liuul~ly preferred. The styrene-acid anhydride copolymers and terpolymers other than those containing 2-dodecenyl succinic anhydride can be prepared using techniques well known to the art. The preferred systems are alternating and random copolymers as described by Moore in I.E.C. Prod. R.D. on page 315, V-25, 1986 and described as random copolymers on pages 359, 364 and 390, Trivedi and Culbertson, Maleic anhydride, Plenum Press, New York, 1982. See also Czech CS.
Pat. No. 247, 037 for preparation of block copolymers.
More particularly this invention comprises the process to incorporate the said surface active polymer ~ in a wastepaper repulped-slurry in an aqueous alkaline 20 medium in order to agglv-~ L~ free small inks, preferably small inks generated from repulping of flexogarphic newsprints and inkjet-printed officewastes containing waste printed paper mixtures and then separating the A~l~ml'rAl~d inks in the size range of about 5 to 200 microns from the pulp slurry by froth flotation.
The treatment of waste printed paper is preceeded by an alkaline repulping step.Repulping of secondary fiber may be effected using any conventional process and apparatus. Typically waste paper is subjected to m~ hAnirAI shearing in a so called high uu--~i~L~ ,y laboratory pulper. The function of a pulper in waste paper recycling operations is to defiber the paper and detach ink particles from fibers. The pulper produces a high uu~ ,y pulp slurry herein designated as "repulped slurry", when waste printed paper is 21~148~
agitated with a high speed rotor in an aqueous alkaline medium. The consistency of repulped slurry typically varies from about 5 to 20 percent and usually from about 7 to 13 percents by weight of paper fiber basis dry weight of waste printed paper relative to the total weight of the slurry. The pH of the aqueous alkaline medium ranges from about 7.5 5 to about 11.5, more frequently the pH is maintained in the vicinity of about 8.0 to 10.5.
Repulping chemicals may be added to the pulper. The reason for adding chemica~s to the pulper is to assist in the easy release of the u~ld~ ~lc materials such as ink and sticikes, from waste paper and to make these uad~ abl~ materials accessible for separation by conventional deinking processes such as screening, flotation and washing. The principal 10 repulping chemicals used in this invention are: sodium hydroxide, sodium silicate, chelating agent and hydrogen peroxide. A typical repulping chemical ~bll,~bsi~iu~. contains 1.0 to 4.0 percent sodium silicate, 0.5 to 2.0 percent hydrogen peroxide, 0.1 to 0.25 percent chelant such as dic~ , .; "~-pentaacetic acid (DTPA), sodium hydroxide as required to adjust the pH from 7.5 to 11.5. In some cases dilute hydrochloric acid is also 15 used for pH adjustment depending on the resulting pH of the pulp slurry after addition of all pulping chemicals except sodium hydroxide. The L~ a~ul~ of the pulper is held in the range of about 25 C to 60 C. A t. ., .1,., ..1 1 1, ~ above 60 C may be used with an ullde~ildble loss in mechanical shear during the repulping process. The time of repulping may be from about 10 to 30 minutes. Usually, a repulping time of about 15 to 25 minutes is 20 advantageous In most cases, the repulped slurry contains free ink particles ranging from about 0.1 micron to about 200 microns or more. It has been discovered that the treatment of a diluted repulped slurry with a surface active polymer composition surprisingly improved the ml rr11ion of small ink particles ranging frûm about 0.1 micron to about 10 microns. A
25 subsequent flotation of the aforesaid treated slurry in a conventional flotation cell has readily removed the inks from aqueous slurry. Since the invention process is particularly applicable to waste printed paper c-.ni: ' with papers printed with fl~Yrl~r~rhir and inkjet processes, such ink removal process may also be applied for flotation deinking of flexo- or inkjet-printed wastepapers alone.

2~41~g~
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Flotation of the repulped flber may be effected using any conventional process and apparatus. Typically repulped slurry from pulper is treated in a flotation cell under controlled agitation and air flow. The choise of an agitator, an agitator speed and an air flow rate are well known art and will not be discussed here in detail. The pulp consistency 5 in the flotation cell may be varied from about 0.2 percerlt to about 1.2 percent of dry pulp in relation to the total weight of slurry. More preferred pulp ~:UII~;:/t~,ll.,y is from about 0.3 percent to about 0.8 percent by weight. Treating the low ~;u~i~L~O y pulp with an aqueous medium containing a surface active polymer ~o~ ,osiLiu.. may be cu., .~ ly effected in a flotation cell by simply adding the surface active polymer composition to the repulped 10 slurry. The pH of the fiber slurry may range from about 7.5 to about 10.5. More preferred pH range is from about 8.0 to about 9.5. The pH can be adjusted by addition of an acid or a base as required.
All alkali soluble cu~ol~.~.c.s and terpolymers herein described as surface active polymer compunds may be hl.,ul~JoldL~(l in the flotation cell as their alkali metal salts more 15 preferably as their sodium salts. In their anionic form, an aqueous solution of metal chloride is also added to the pulp slurry together with the surface active polymer romro~i~ion. Generally, calcium chloride, potassium chloride and ~ chloride are used as met~l chlorides but calcium chloride dihydrate is preferred.
The amount of the said surface active polymer composition used typically ranges zo from about 0.3 percent to about 2.5 percent and usually about 0.5 percent to about 2.0 percent on dry basis weight of waste printed paper in repulped slurry. The amount of metal chloride is usually about the same as the said surface active polymer cu~ùsiLiull~
Another suitable method to introduce the said surface active polymer compositions which are insoluble in aqueous alkaline solution having a pH less than 10.5, in an aqueous 25 pUlp slurry in a flotation cell is in the form of a water-based dispersion. A water-based dispersion of a surface active polymer composition may be prepared by first dissolving the solid polymer in a water insoluble organic solvent in a ~.UllC.,ll~ Liull range of about 3 percent to about 8 percent by weight of the solvent and then dispersing this polymeric solution in water. The organic solvents which are suitable for this application are esters and 21~14~5 .
ethers, more particularly phthalate and adipate type esters such as dioctyl phthalate, dibutyl adipate. The water is the domimant phase in the aqueous dispersion of the said polymeric solution. Preferred ratio is 40 parts of polymerlc solution to 60 parts of water by weight.
Water based dispersion may be suitably made by stirring the mixture at high speed with a 5 propeller in presence of a small amount of a dispersant. A sodium salt of benzene napthyl sulfonate in the c--n~PntrAti-)n range of about 0.05 to 0.1 percent of dispersion may be used as a dispersant. It should be noted that the use of this water based dispersion is limited to an aqueous pulp slurry having pH less than about 10.5.
Because removing the ink particles as much as possible is most desirable in the 15 deinking of repulped secondary fibers, an important feature of secondary pulp recycling is agglomeration of small ink particles having particle size below S microns. In general, water-based dispersion of surface active polymer composition may be employed forAFel~m~-rAtine small inks in practicing the present invention. The water-based dispersion is believed to produce the aforesaid effect by ~Jlr~ dLill~ the dispersed surface active 15 polymer as solid particles of small sizes on their introduction to an aqueous pulp slurry having pH about 10 or less and once precipitates promoting AeelomrrAf ion of free small ink particles.
The introduction of a surface active polymer composition in the form of a water-based dispersion in flotation cell improves deinking for repulped secondary fiber, more 20 preferably for repulped fiber containing xerography, laser printed papers and old newsprints (ONP). The function of a water insoluble solvent is beleived to be the swelling of ink-fiber interface of fused large ink particles and breaking them to small particles suitable for ~ &1~ ion and flotation. The amount of water-based dispersion typically ranges from about 0.1 percent to about 2.0 percent by weight of surface active polymer 25 c~mr~it;--n based on dry basis weight of pulp in aqueous slurry.
Of course, the aqueous slurry in flotation cell may contain other additives commonly used in flotation deinking operation. Examples of such are chelating agents, frothers, conventional deinking agents, defomers etc. Nonionic or anionic deinking agents may be employed together with water-based dispersion in the practice of this invention.

Because of the low foaming nature of these solid surface active polymeric particles in pulp slurry, usually a frothing agent is used to float out the ;le~l.,ll,r,,.lr,l ink particles from aqueous medium. Examples of satisfactory frothing agents include those materialsdescribed as 'polyalkylene oxide block ~V~JOIy~ ' on pages 300-371, Schick, Nonionic 5 Sllrf~ Marcel Dekker, rnc., New York, 1966. See also JP. Pat. No. 05, 51 887.
Conventional fatty acid soaps and other nonionic surfactants may also be used as frothing agents.
Using surfactant to provide sufficient foaming ability is a well known art and surfactant compositions of secondary fiber recyclates provide a wide selection from which 10 to choose a frothing agent for practicing the present invention. Usually the amount of frothing agents is small and typically ranges from about 0.01 percent to about 0.1 percent by weight based on dry pulp for nonionic type frothing agents and ranges from about 0.1 percent to about 0.5 percent by weight on dry pulp for fatty acid soap type frothers. A
chelating agent may be introduced in the pulp slurry imm, ,' 'y after flotation process.
15 The amount of chelating agent may range from about 0.1 percent to about 2.0 percent of the dry basis weight of pulp.
The alkaline salts and the water-based ~licrt rcinnc of surface active polymericcomposition disclosed in this invention may be used for deinking of waste papers printed by li~llv~laL)II~, offset, flexography processes and office wastes processed by xerography, 20 laserjet and deskjet printers. More preferentially, alkaline metal salts of said surface active polymer compositions may be used to deink waste printed papers ~, ~ with significant amount of flexo and inkjet printed papers and the water- based dispersions can be more suitably used for mixture of officewastes and old newsprints (ONP) including flexo printed newsprints. The vrrl~ w a ~t~ in this invention include xerography, laser and 25 inkjet printed papers.
Description of ~h, prefered r ~ ,n. 1; ., ..., 1 ~
As illustrative of deinked waste printed-paper ~omrnciti~n comprising of both newsprints and vrrl- -,wa ,l~, wa~t~Ja~ with two separate, v.ll~,o~iLiolls were repulped in f~ 4 3 ~
a laboratory high ~UIIDi~Ltll~,y pulper. About 920 grams of waste printed papers were torn into about 3- inch squares and charged in a laboratory pulper containing appropriate amount of warm water to adjust the required ~:UII~i~t~ y. The repulping was carried out in alkaline medium of pH 10.5 by adding 2.0 percent sodium silicate, 3.0 percent hydrogen peroxide, S 0.1 percent chelant-.li~Lllyl~ .;,lrL)- .,~ ;r acid and sodium hydroxide in required quantity to adjust the pH. In these cllll~ù:iilllclll~ and u ,llbu~:lilll~,.l~a hereafter, all weights and concentrations are based on weight percent of dry basis weight of paper unless otherwise specified. The repulping was carried out by mixing the ,UIIILIUCi~iUll in the pulrer for about 20 minutes with a rotor speed of about 1500 revolutions per minute. The lû l~ lulc of the pulp slurry was about 45 C. These two repulped ~r/mrnci~ nC before treatment with surface active polymer ~UIIILIUsiLiUII of styrene-acid anhydride copolymer or terpolymer in a flotation cell are designated as 'H-l and H-2 Repulped Stocks' as in given below .
H-1 and H-2 REPULPED STOCKS
Repulped stock H-1 H-2 OLD NEWSPRINT (wt.%) (wt.%) Flexographic 30 30 Offset 70 40 OFFICEWASTE
HP-laserjet NIL 10 HP-deskjet NIL 10 Photocopy NIL 10 The 'w~l~L~ used in these examples of repulped stocks are old newsprints 25 printed by offset and water-based flf-Yr,~r~rhir processes. The Orrl~ cs used in these examples were 21.6 cm x 27.9 cm sheets printed on one side with uniform alfabetic text generated by HP-laserjet and HP-deskjet printers. The laserjet printed text was photocopied on one side of a white paper of same size using SAVIN 7500 copier employing a toner. The pulp ~u~ if c in the repulped stocks were 8 percent and 13 ~14~
.
percent for H-l and H-2 repulped stocks l~ ,ly.
F.~AMPr,~ I
The H-l and H-2 repulped stocks are made into handsheets by passing through a Handsheet mæhine according to TAPPI test method T-272-om-92 and through a Buchner funnel according to TAPPI method T-218-om-92. These two methods were used to justify the effect of small ink particles on deinking. It is already understood that TAPPI method T-218-om-92 is more suitable for brightness ~ lL of stocks containing large ~mountof small ink particles wherein a filter paper of 2.5 microns pore size was used in the present invention to make hqn;ChPPts On the other hand, the handsheets making in accordance with TAPPI method T-272-om-92 was performed using a 140 mesh screen. The handsheets made according to Tappi methods T-2 1 8-om-92 and T-272-om-92 from control repulped stock H-l had average hriehrnPccps of 39-40% ISO and 42-43% ISO
15 ~ u~,Li~ly determined in accordance with the Technical ~ssociation of Pulp and Paper Industry (TAPPI) method T-217. The H-2 repulped control handsheets made according to Tappi test method T-272-om-92 had an average brightness of 54% ISO ~PtPrrninPd in accordance with TAPPI method T-217 and an average ink particles surface area of 0.0174 meter square per meter square of paper as ffPtPrrninP~ by an image analy~er 'Ultimage 20 version 2.1' coupled with an optical I.i.lvs~uL/e, Carl Zeiss, Germany and determined on handsheets with 60 grams per meter square basis weight.
F,XAMPJ,h~ IT
This example illustrates the preparation of styrene-2,5 furandione- 2, dodecenylanhydride terpolymer ~Ulll~U~iLiUII followed by deinking of repu,'ped stocks H- 1 and H-2 as described in Example I with this prepared sur~ace active polymer ~ mrr~cifi~-n in accordance with one r:l . ,1.~.1; " ,. . f of the treatment of this invention.
One hundred and four parts Of ~rr~ ir ^~^'y I molar equivalent of a commercial Il grade freshly distilled styrene, was charged in a flask equipped with a stirring system.
About 1600 milliliters of benzene and thirty seven parts of commercial grade 2,5-furandione was added in the flask and the total charge was heated at 60 C for 10 minutes to dissolve all 2,5-furandione. Then about 0.85 part by weight of freshly crystallized benzoyl 5 peroxide was added to the flask in an oxygen free atmosphere and a positive pressure of about S pounds per square inch was m:~irt~inrd in the flask. The t~ Lulti of themixture was raised to about 75 C and held for about I hour until the reaction between styrene and 2,5-furandione started as evident by an increase in the turbidity of the solution.
Twenty parts of appoximately 0.1 molar equivalent of a commercial grade 2-dodecenyl LO succinic anhydride was added to the mixture. Reaction was carried out for another 90 minutes ~ the mixture L~ Lul~; in the range of 75 to 80 C. The batch was then cooled to 60 C, benzene was stripped off and polymer was ~..,.,;~iL~L~d from acetone solution by adding water. The aforesaid ~yllLll~,SiL~,.I product, a mixture of terpolymer of styrene-~,5 furandione-2 dodecenyl succinic anhydride having a glass transition 15 t~ Lul~ of about 137 C and a copolymer of styrene-2,5 furandione having glasstransition temperature of about 160 C, herein designated as 'terpolymer composition' was used to deink repulped stocks H-l and H-2 . The sodium salt of this terpolymer Cu~ u~;Liull was made by dissolving the product in aqueous sodium hydroxide solution.
A number of flotation ~I...i,,,..,l~ were made using varying consistency of 20 repulped slurries H-l and H-2 (1). The treatment of varing weight percent of prepared sodium salt of terpolymer ~ull~l~osiLiul~ (2) with repulped slurries was made in a laboratory open-Top Leeds cell type flotation cell. With minor differences, the treatment procedure used in each experiment was as follows.
Varying repulped slurry .~ . .,. ;..5 from about 0.3 to 1.0 percent by weight of2s dry pulp was made by diluting the stock H-l and H-2 as described in Example I by adding required amount of warm water with constant stirring and then adjusting the pH of the diluted pulp slurry to a given pH (3). The pH of pulp slurry was varied from about 8.0 to about 10Ø Varying amounts of the said terpolymer composition were added in the form of a sodium salt to provide from 0.1 to 2.0 percent by weight of terpolymer composition ~14~5 .
based on dry pulp together with an aqueous solution of calcium chloride of about equal amount to terpolymer connr~iti~-n by weight of calcium chloride. The temperature of the slurry was adjusted from about 30 C to about 60 C (5). This pulp slurry containing the said terpolymer ~Ulll,uo~iLiull was then treated by mixing at high speed of about 1200 5 revolutions per minute for about I to S minutes (4). This treatment period is designated herein as 'conditioning period'.
Air was introduced in the flotation cell to remove agglomerated inks after c~n~iiti- nin~ of repulped slurry. The air flow rate was about 3000 milliliters per minute.
Flotation was carried out for about 10 rrlinutes and then air flow was stopped. About 0.3 lû percent of chelant-di~ yl~ ilia ~ ,-pentaacetic acid by weight of dry pulp was added to the flotation cell and slurry was agitated for another one minute. The pH of the resulting deinked pulp slurry was then adjusted tû 8.5 and slurry is made into handsheets by passing through a Handsheet machine according to TAPPI test method T-272-om-92 and through a Buchner furmel according to TAPPI method T-218-om-92 as described in Example 1. The 15 brightness of the handsheets were determined in accordance with the TAPPI method and residual ink surface area was determined by image analysis mentioned in Example I. The Table I ~-".. - ;, s the results of seven t 'I" ' ;1ll' 'Il` It is evident that a brightness gain of about 8 points is achieved.
EXAMPI,E III
This example, illustrates treatment of repulped stocks H- I and H-2 of Example I in ~C~,OIdall~,~ with another ~ l,U-lilllc llL of this invention, using a surface active polymer c.~mr.~ .n having a glass transition ~~ a~ulc; of about 162 C comprises of sodium 25 salt of styrene-2,5 furandione copolymer prepared by so' lhili7in~ 50 parts of the said copolymer in 1200 milliliters of 0.5 molal sodium hydroxide. The g~ hili7~ion was carried out under constant stirring for 3 hours at about 45 C. Treatment of repulped stocks and then flotation of ~lf)nnrr~t---1 inks were carried out in a similar fâshion as described in Example II, except that a sodium salt of styrene-2,5 furandione copolymer was used for 2 ~
pulp treatment instead of a terpolymer composition. ~arying amounts of sodium salt of styrene-2,5 furandione copolymer together with an aqueous solution of calcium chloride of about equal amount of the copolymer ~ l by weight of calcium chloride was added in the pulp slurry in flotation cell. The % ISO brightness and ink surface area of deinked 5 pulp are given in Table 11. A marked illl~)lU ~ ;IIL in % ISO brightness and a decrease in the ink surface area is evident aher treatment.
EXAME'LE IV
As illust}ative of another ~ .I.bo.lilll.,.lL, a surface active polymer composition containing an anionic frothing agent was prepared by heating 50 parts by weight of styrene-2,5 furandione copolymer having glass transition ttlll~ Lu~ of about 128 C with 10 parts of by weight of sodium oleate in 1200 milliliters of 0.5 molar sodium hydroxide solution under constant stirring. The mixing was carried out for about 3 hours at a ~ ldLul :i of 15 about 45C. Six series of ~ ,.lL~ were made using this alkaline solution of surface active polymer Culll~o~iLiOI~ for treating the repulped stocks H- I and H-2 of Example I with varying pulp UUll~; ,t~ and then flotating out the agglomerated inks from the slurry by repeating the procedure of Example 11. The amount of the aforesaid alkaline solution of surface active polymer ~ulll~u~iliol~ added to the repulped stocks contained 1.6 weight 20 percent by weight of styrene-2,5 furandione copolymer on dry basis weight of pulp in the slurry. An aqueous solution of calcium chloride containing 2.0 percent by weight of calcium chloride on dry basis weight of pulp in the slurry was also added to the pulp slurry before c~n~ in~ period. The pH of the slurry was adjusted to about 8.5 in each experiment and the pulp slurry L~ Lul~ was about 45 C for all exr~ rim~ n~ A flotation 2s time of about 10 minutes was used for all r~ Handsheets made from deinked pulps aher flotation of treated repulped stocks H-l and H-2 had brightness values and ink surface areas as shown in Table Ill.
The data shows that the treated repulped-secondary fiber has improved brightnesseven with a smaller concentration of styrene-2,5 furandione copolymer in a short 21~8~
.
..... ~1;1;.",;"t~ time.
MPT,F V
S In still another e~l~b()~ a surface active polymer composition containing anonionic frothing agent was prepared by heating 100 parts of styrene-2,5 furandione copolymer having a glass transition L~ Lul~ of about 128 C with 2.5 parts of DI 600 (product of Kao Corp.) in 1200 milliliters of I molal sodium hydroxide solution under constant stirring. The mixing was carried out for about 3 hours at a ~ Lul~ of about 10 55C. Four runs were made using this alkaline solution of surface active polymer composition for treating the repulped stocks H-l and H-2 of Example I and then flotating the agglomerated inks by repeating the procedure of Example II. The amount of the aforesaid alkaline solution of surface active polymer composition added to the repulped stocks contained 1.6 weight percent by weight of styrene-2,5 furandione copolymer on dry 15 basis weight of pulp in the slurry. An aqueous solution of calcium chloride containing 2.0 percent by weight of calcium chloride on dry basis weight of waste printed paper in pulp slurry was also added to the flotation cell before 1 . .,,.l;l;. .,,;,,~ period. The pH of the slurry was adjusted to about 8.5 in each experiment and the pulp slurry t~ UIC; was about 45C for all ~l1rl;1". .,1~ A flotation time of about 10 minutes was used in each set of 20 ~ run. ~ chPPtC made from deinked pulps after flotation of treated repulped stocks H-l and H-2 had brightness values and ink surface areas as shown in Table IV. A
recycled fiber with ISO brightness of about 54% had been obtained for newsprints~. - ' with about 30% by weight of flexo-printed newspaper.
2s EX~MPT,~, VI
The following illustrate ~,IIlb~ Li.ll~ of the invention in which a surface active polymer, styrene-2,5 furandione copolymer having a glass transition temperature 147 C
had been treated with the repulped stocks H-2 as in Example I in a flotation cell in the form of a water-based dispersion.
The water-based dispersion of the aforesaid copolymer was prepared by dissolving80 parts of the copolymer in 1000 rnilliliters of dioctyl phthalate. The dissolution had been carried out at about 60 C under constant stirring for about 6 hours. Fourty parts of this S polymer solution was then dispersed in 60 parts of water by high speed mixing of the composition with a propeller. About 0.01 part of sodium salt of dOdeCyll~f-7f .If ~ r(lilii, acid by 100 parts of the copolymer was added as a dispersant.
Treatment of the repulped H-2 stock as described in Example I had been carried out in a flotation cell by adding a Yarying amount of the said water-based dispersion at about 10 60 C to the repulped slurry with a varying pulp ~Ullsi~Lt.l~y and then mixing the slurry for about 15 minutes. About 1.0 percent by weight of sodium oleate by weight of dry pulp and about same amount of calcium chloride in the form of an aqueous solution had been added to the pulp slurry. The pH of the repulped slurry was adjusted to about 8.5 and the slurry was c~ for about 2 minutes and then flotation of the agglomerated ink particles 15 were carried out in the same fashion as described in Example 11. Results of the brightness values of the handsheets made from deinked pnlp and the ink surface areas on thehAnrl~hfets are summarized in Table V. The present treatment process, which by :UllI,UaldliV~ evaluation with other standard treatment process known to the prior art, serve to prove the superiority of our novel pulp treatment process. Thus, in a separate treatment 2û process a ~u..~.lLiullal ink collector system known to the prior art, comprises of about l percent by weight of sodium oleate and I percent by weight of calcium chloride in the form of an aqueous solution, had been used to treat repuled stock H-2 in a similar fashion as described above without any addition of a water-based dispersion of styrene-2,5 furandione copolymer. The resulting brightness value and ink particle surface area of this standard 2s treatment process is also given in Table V for c ~ " ~ only and is outside the teachings of the present invention.
In Table V, data illustrates clearly the relative superiority of our novel treatment process of repulped slurry with water-based dispersion of ester solution of styrene-2,5 furandione copolymer with regard to its improved brightness and decreased surface area of - 21~1485 ~.
the ink particles. All treatment processes involving water-based dispersion. namely.
i"~ nos. ~1 and ~2, are in accordance with present invention are herein defined and claimed.
All of these treatment processes, it will be noted, are acceptable when measured S against the standards described in Example I and experiment no. E3 of l~xample V.
Although the invention has been illustrated by typical examples, it is not limited thereto. Changes and m-~rlifi~ :~til-nc of the examples, of the invention herein chosen for the purposes of disc~osure can be made which do not constitute departure from the spirit and scope of the invention.

Claims (17)

1. A treated wastepaper composition useful for making printing grade paper obtained by exposing printed waste paper repulped-slurry comprising of of offset, photocopy, laser and inkjet printed papers contaminated with waster-based flexographic ink printed papers in direct contact with a surface active polymer, the said surface active polymer being an alkaline salt or an oil soluble organic material having a glass transition temperature in the range 105°C to 170°C, characterized by being adsorbable to small ink particle surfaces, and enhancing the receptivness of the said ink particles to other small inks, agglomerating and then floating them out from an aqueous medium to enhance the brightness of the repuled wastepaper.

2. The treatment of waste printed paper of claim 1 in which the wastepaper is a mixture of newsprints and officewastes and, the surface active polymer is a copolymer or a terpolymer having a glass transition temperature in the range 105°C to 170°C degrees centigrade.

3. The treatment of claim 1 in which the copolymer or the terpolymer contains at least one comonomer with an acid anhydride functionality.

4. The treatment of claim 2 in which mixtures of newsprints and officewaste comprise offset and flexo-printed old newsprints (ONP) as well as xerographic, laserjet and inkjet printed of officewastes.

5. The treatment of claim 3 in which a copolymer or a terpolymer containing acid anhydride functionality is a styrene-2,5 furandione copolymer or a terpolymer of styrene, 2,5 furandione and a third comonomer.

6. The treatment of claim 5 in which the third comonomer is an acid anhydride other than 2,5 furandione.

7. The treatment of claim 6 in which the terpolymer is a styrene-2,5 furandione-2 dodecenyl succinic anhydride.

8. The process for preparing the terpolymer of claim 7 in which the 2-dodecenyl succinic anhydride content is less than 20 mole percent by weight of the terpolymer.

9. The treatment in claim 1 in which the copolymer or the terpolymer is soluble in an alkali.

10. The treatment of claim 1 in which the alkali salt of the copolymer or the terpolymer is a sodium salt.

11. The treatment of claim 1 in which an aqueous solution of a metal chloride is introduced together with the sodium salt of the coploymer or terpolymer.

12. The treatment of claim 11 in which the aqueous solution of the metal chloride is calcium chloride.

13. The treatment of claim 1 in which the copolymer or terpolymer is soluble in water insoluble oil.

14. The treatment of claim 13 in which the water insoluble oil is an ester.

15. The treatment of claim 14 in which the ester is dioctyl phthalate.

16. The treatment of claim 13 in which the oil solubilized copolymer or terpolymer is incorporated into the said aqueous pulp slurry in the form of a water dispersion.

17. The treatment of claim 16 in which a conventional frothing agent is added to stabilize the froth during flotation.