Semiannual Patents Review January—June 1998

Marguerite Sykes and Julie Blankenburg

KEYWORDS or adding an inorganic electrolyte [1]. Another method controls the contact angle between the Chemicals, Deinking, Patent, Recycling, Review, aqueous solution and the ink particles [2]. This Stickies, Waste paper. patent claims that flotation is most efficient when the contact angle is at least 70°, which is accomplished by adjusting slurry pH or adding INTRODUCTION silicon- or fluorine-containing organic compounds and fatty acids. In a third patent, flotation is This review summarizes patents in the area of pa- enhanced through adding cationic, amine, and per recycling that appeared during the first half of ampholytic compounds to process white water [3]. 1998 in either of two on-line data bases: Derwent Flotation efficiency can also be improved by adding World Patent Index or Claims/U.S.Patents Ab- fine particles with a hydrophobic phase boundary stracts. The information in these data bases is in- [4] or by changing the pH several times during the tended to keep readers informed about the latest flotation process [5]. equipment, chemicals, and technology in this field. The abstracts provide only a brief summary of the The Sunds Defibrator facilitates flotation through inventions. Readers will need to access the full texts equipment design [6]. The flotation tank inlets are of specific patents for complete information. positioned so that the incoming jet of pulp slurry and gas bubbles does not break the suspension sur- The patents summarized in this review cover a face, ensuring good separation even at increased broad spectrum of recycling processes, equipment, slurry concentrations and a short. retention time and products made with recycled fiber. Some pat- in the flotation cell. ents deal with additives to adhesives and papermaking materials that make adhesives easier to In a patent issued to the Thermo Black Clawson remove during recycling. Others address the envi- Company, flotation is used following the pulping ronmental impact of deinking effluents and solid and beading of mixed recovered papers [7]. After waste resulting from recycling. high consistency kneading, the paper stock is diluted and separated by flotation and washing to remove different types of inks. No additional dis- DEINKING PROCESSES persion step is required prior to bleaching or papermaking. The KAO Corporation has been issued five new patents that focus on various mechanisms to Agglomeration chemistry is used to separate ink improve flotation efficiency. One method controls particles from fiber in a continuous batch recovery the interracial charge potential between ink system in a patent assigned to the Pellerin Milnor particles and pulp by adjusting the pH of the slurry Corporation [8]. A combined deinking/agglomerat- ing/densifying agent is added during the fiberization stage, which is followed by washing and The authors are Forest Products Technologist and ink separation. Librarian, respectively, with USDA Forest Service, Forest Products Laboratory, One Gifford Pinchot Dr, Madison, WI 53705-2398, USA

Page 54 Progress in Paper Recycling / November 1998 Union Camp Corporation targets stickies for ag- Another process with environmental implications glomeration with one or more long-chain alcohols involves deinking solutions containing hydrogen and then removes them by mechanical filtering [9]. peroxide. A patent assigned to Sued-Chemie mini- The corporation has found that long-chain alcohols mizes the quantity of sodium silicate required for used at pH 7 or above effectively agglomerate stick- stabilization and reduces puiping alkahnity to less ies. PPG Industries Inc. simultaneously controls flo- than pH 9, thereby decreasing the amount of per- tation froth and reduces stickies by using a non- oxide needed to prevent brightness loss [16]. Ink is ionic surfactant alone or in combination with other separated by flotation using a cationic surfactant. deinking chemicals or other froth-moderating agents [10]. EQUIPMENT Allied Colloids Ltd. has patented a process to separate cellulosic solids from aqueous suspensions by Two pieces of equipment invented by Lindahl, a dispersed air flotation [11]. After coarse fibers are dewatering press and a device to measure drain. removed by screening, the suspension is subjected age, can be used in recycling. The dewatering press to dispersed air flotation in which various additives extracts liquid from partially dewatered material are used to separate hydrophobic material (fillers) (such as sludge or pulp) with absorbent felt rollers from cellulosic fines. and several press nips [17]. The drainage device, which is designed to simulate paper machine con- High Point Chemical Corporation has developed a ditions, has a cylinder for measuring drainage and process that can both enhance brightness and re- a hydraulic cylinder for measuring the resilience move ink efficiently [12]. The method uses an al- of partially dewatered material [18]. Drainage prop- kaline earth metal tallate prior to flotation. The erties can be measured quickly, without having to tallate, a dispersion prepared by double displace- make handsheets. This device could be used to study ment, increases pulp brightness by more thoroughly the effects of different chemicals on drainage, com- removing ink and other contaminants contained pressibility, shrinkage, or wet bulk. in newsprint, colored printed papers, cardboard, and magazines. Thermo Fibertek Inc. has patented an apparatus for washing, thickening, and solids recovery that In a process patented by the Valmet Corporation, uses rotating wash sprays to facilitate removal of two pulpers operating at different consistency lev- contaminants and fillers through screens [19]. This els (high and low) are linked in sequence [13]. Af- apparatus is less bulky than the equipment usu- ter the pulp goes through the secondary low-con- ally required to handle high-solids furnishes at a sistency pulper, it is screened and screen rejects high removal rate. are recycled to the primary high-consistency pulper for additional processing before passing through A recovered paper baler equipped with a shredder the deinking system. and high friction rollers designed to compact material into compressed bales without the need for Voith Sulzer Stoffaufbereitung has patented a pro- strapping is described in a patent assigned to Star cess for recovering paper fiber and plastic material Farm Machinery Manufacturing Company Ltd. from fast food waste [14]. Plastic plate material is [20]. disintegrated with hot alkali and later precipitated and reclaimed; food particles and other contami- Cellwood Machinery has patented a temperature- nants are removed by flotation. The separated pa- controlled reactor screw and related process for per fiber is bleached to remove residual color and bleaching recycled pulp [21]. After dewatered fiber residual printing inks. is steam heated and dispersed in a disperser unit, it is compacted in a screw press or plug screw to A process for decolonizing brown fibers in recycled which oxidative or reductive bleach agents are pulp based on fine screening for fiber separation is added. Appropriate bleaching temperatures can be covered by a patent assigned to International Pa- maintained in the unit for each bleaching stage per Company [15]. Screened brown fibers are se- used. No auxiliary devices are required. quentially bleached with oxidative and reductive chemicals at high temperature in a pressurized dispersion unit and recombined with the deinked pulp accepts.

Progress in Paper Recycling / November 1998 Page 55 ENVIRONMENTAL nano-filtration, suspended solids are diluted at acid pH and elevated temperature. This process is es- Effluents pecially useful for treating organic substances in effluents from the production of colored paper, tis- Several patents aim to improve bleaching of re- sue, and cartons. cycled pulps through chelation. Kemira Chem Oy has developed new biodegradable, low nitrogen- Sludge Treatment content bis or tris dicarboxyethoxyethyl amine de- rivative chelators [22]. Unlike the commonly used A patent issued to Minerals Technologies Inc. de- chelators that do not degrade readily in water- scribes a process for recycling mineral fillers from courses, these new compounds should be more en- deinking sludge [28]. Filler residues are oxidized vironmentally acceptable. Sunds Defibrator has at high temperature, releasing carbon dioxide, heat, taken a different approach by using conventional and water. These products can be captured and re- chelators to bind metal ions [23]. In this process, used in the process. Ashed particles are subse- the chelation liquid is separated and oxidized be- quently reacted with an aqueous slurry of calcium fore being returned to the pulp slurry. Since the hydroxide into which carbon dioxide is bubbled to bound metal ions are removed from the process precipitate calcium carbonate (PCC). The recycled water, it can be reused. The environmental advan- PCC, using mineral ash as the crystal “core”, has tage is theminimization of water discharged from properties similar to those of virgin PCC. this process, a plus for the trend toward closing the white water system. BIOLOGICAL APPLICATIONS Recycling often adds color, contaminants, ash, and turbidity to process waters. Four patents focus on Biotechnology continues to make inroads into the effluent clarification. General Chemical Corpora- pulp and paper industry. Four new patents for en- tion has patented a process for using alum-contain- hancing freeness, increasing brightness, and im- ing process residues, a papermaking by-product, proving deinking appeared in the data bases to remove color from effluent [24]. The addition of searched. up to 5 ppm of a polyelectrolyte polymer improves the removal of color and turbidity as well as en- The International Paper Company holds a patent hances the settling rate of solids. for treating recovered fiber with an enzyme mixture to enhance pulp freeness while maintaining Nalco Chemical Company has developed a hydro- brightness and strength [29]. Deinked pulp is philic dispersion flocculent for clarifying ink-laden treated at low consistency with celulase, xylanase, water from deinking [25]. The flocculent is a co- and pectinase for several hours. These enzymes polymer of dimethylaminoethyl methacrylate methyl eliminate the need for polymer drainage aids and chloride quat (DMAEA A LMCQ) cationic monomer addition of softwood pulp in papermaking. and acrylamide (AcAm). This dispersion flocculates ink and other suspended impurities, which can then Novo-Nordisk describes a new endo-gluconase from be removed from process water by dissolved air flo- Cellvibrio species and related DNA that can be used tation. for deinking and improving the drainage of recovered paper [30]. The presence of other enzymes such ECC International Ltd. describes a process for re- as xylanase and lipase could also provide other moving solids, ink particles, and calcium compounds benefits for recycled pulp. The unique advantage of from deinking effluents in their recently, granted the endo-gluconase preparation is its broad cellulolytic patent [26]. The process dilutes and solubilizes cal- activity over acid, neutral and alkaline pH. cium solids and separates out undissolved residues. Removal of these solids from process water con- A different biological approach is taken by BK tributes to brighter, higher grade recycled fiber, Ladenburg in their patent for maintaining pulp which could reduce bleach and additional process brightness during flotation deinking [31]. A bacte- requirements. A clarified effluent also reduces en- rial (Bacillaceae or Pseudomonadaceae) suspension vironmental impact. is added to recovered paper after repulping with alkaline peroxide. After incubation, the bacteria- A closed-circuit paper mill effluent treatment pro- containing pulp slurry is floated with fatty acid cess developed by Maierminimizes the discharge agents. of organic residues [27]. To oxidize solids prior to

Page 56 Progress in Paper Recycling / November 1998 A new Chysosporium lucknowense strain, and the PSA, used for labels or tape, has a silicone-free neutral or alkaline cellulases produced by it, com- release coat made of polyacrylonitrile- prise another claim [32]. Enzymes isolated from this polybutadiene copolymer [37]. Finally, Saiden wild-type or mutant Chrysospotium can be used Kagaku has patented a water-dispersible PSA for deinking and bleaching recovered paper at neu- consisting of a mixture of an acrylic acid alkyl ester, tral or alkaline pH. vinyl acetate, acrylic acid, and caprolactone adduct of acrylic acid [38]. Since this PSA can be repulped A patent issued to BASF AG describes the use of a readily with pulp, the usual stickie problems can different type of chelating agent based on disuccinic be avoided. or diglutaric acids [33]. These amino-acid chelators have been used in washing agents, but they can be A thermoplastic, biodegradable, starch-based ad- applied to the deinking and bleaching of recycled hesive has been designed for use on paper, glass, or fiber. Their use eliminates the need for silicate in polyethylene recyclable or biodegradable packag- these processes. ing and labeling [39]. The precursor for making this adhesive can be sold as a solid material (granules, strands, or sheets) and is converted to a low viscos- CHEMICALS ity, degradable adhesive only during use.

Several new chemicals for deinking and papermak- Another common venue for new products included ing with recycled fiber also appear in the patents in this patent review is recyclable containers. reviewed. These patents address the continuing Dainippon Printing Company, Ltd. has patented a problems caused by stickies and inks, especially in recyclable paper carton for storing fluids [40]. The regard to pulp brightness. container includes an alkali-soluble resin between the paper and gas barrier layers. This construction A deinking agent consisting of maleic anhydride allows the paper layer to be peeled away for sepa- and a copolymer has been developed by Nippon Oils rate processing. and Fats Company Ltd. [34]. When this agent is used to deink newsprint and office paper, frothing Bloch and Finestone patented a high-strength seal- is minimized during flotation and the resulting pulp ing tape for cartons that is designed to be stripped is bright. entirely from the carton for reuse or recycling [41]. The surfaces of the plastic film base layer are Zuckerforschung Tulln GMBH has developed a treated with dual corona discharge, which enables modified starch that is effective when used in one side of the paper to be bonded with water-based combination with cationized amylopectin starch adhesive and the other side with water- and either ASA or AKD for paper sizing [35]. The remoistenable adhesive [41]. polyelectrolyte properties reduce the formation of stickies and eliminate the need to add alum to A novel use for recycled paper is as an oil-absorb- systems with high calcium content. This modifed ing material [42]. Fiber is mixed with an aqueous starch is effective on furnishes with a relatively solution of a lipophilic resin made by polymerizing high fraction of recovered paper. fatty acid with an emulsifier, surfactant, and water. The resulting mixture is dewatered and hot pressed at a cross-linking temperature to produce PRODUCTS a felt-like sheet.

New recyclable products predominate in this Finally, sludge from papermaking seines as a re- category. Three repulpable pressure-sensitive placement for fiber in multilayer paperboard [43]. adhesives (PSAs) and one thermoplastic adhesive Paper sludge is mixed with an adhesive and fiber head the list of new products. Avery Dennison has suspension in acidic or neutral medium. A floccu- patented a multi-layered PSA made with two types lent is added to promote retention of filler on a of laminates: a tacky polymer layer that is not paperboard machine. The board has multiple lay- dispersible in water and a tacky water-dispersible ers and weighs between 450 and 5,000 g/m2. The polymer layer [36]. The dispersible layer is advantage of this patented product is that it uses positioned closer to the facestock than the waste materials. nondispersible layer, thereby improving both adhesive performance and recyclability. Another

Progress in paper Recycling / November 1998 Page 57 PATENTS CITED

Page 58 Progress in Paper Recycling / November 1998 Progress in Paper Recycling / November 1998 Page 59 Key to Abbreviations

DE = German patent EP = European patent GB = British patent HU = Hungarian patent JP = Japanese patent SE = Swedish patent US = United States patent WO = World patent

Page 60 Progress in Paper Recycling / November 1998