Alkaline and Neutral : Latest Trends and Selection of Specialty Chemicals to Make Fine Quality Cost Effectively

Sztuka John, Murugesan M, Sudheer K. S.

ABSTRACT Alkaline paper making with carbonate has become the global industry standard practice over the past few decades. Now paper makers in India are increasingly adopting this practice to capture the benefits of lower manufacturing costs and improved brightness it brings. Typically newer machines experience little difficulty in converting to alkaline from acid , however, the older machines may require specific chemical and mechanical solutions be successful. Indian mills have creatively adopted neutral sizing or binary sizing as a method to capture at least some of the benefits of alkaline papermaking. Decision criteria on type of size to use are discussed below along with recent trial experiences. Best practices for alkaline papermaking chemistry are included.

INTRODUCTION lower BOD and COD environmental by papermakers world wide: alkyl Paper makers have practiced alkaline loading, increased system closure ketene dimmer (AKD) and alkyl paper making commercially for various etc. succinic anhydride (ASA). Both have paper grades for over 50 years. In the inherent strengths and weaknesses. 1960's fine and Writing Sizing Theory Both need a systems approach within (P&W) grades, egl. and the entire papermaking process to give Archival Bond, were converted to Sizing in paper and board is defined as the optimum results, ie consider other alkaline pH to achieve improved the resistance to penetration of water chemical additives, pulps, fillers, “permanence”, ie better longevity vs and aqueous solutions. Note that water machine setup, and grade requirements. acid , when libraries saw old vapor resistance is not part of the books and documents made with acid definition. A third option commonly practiced in papers deteriorating on the shelf. India has been neutral sizing with talc retained more strength when There are many reasons for sizing paper filler using rosin emulsion sizes, either paper extract pH was raised to alkaline; including: 1. operability on the paper anionic or cationic. paper brightness was also higher. Then machine-this is the most common alkyl ketene dimer (AKD) was the reason and includes better size press An in between option is to combine two principle alkaline size and mainly high holdout, calendar water box holdout, of the above products to meet special brightness clays were used as fillers. and coating holdout. 2. sizing against requirements. This is called binary Retention systems were simple, eg. accidental wetting-eg. for office papers sizing. only wet end and machine and dry product packaging for boxes performance could be less than and bags. 3. paper end use requirements Comparative strengths and optimum in terms of speed, deposits, egl. liquid packaging, offset printing, weakness of AKD vs ASA drying etc. Much has been learned since wet food packaging, glue-ability, water that time. based ink holdout etc. Both AKD and ASA are cellulose reactive type sizing agents. AKD is The European P&W segment first While there are numerous candidate composed of a reactive lactone ring converted to alkaline papermaking to chemistries for internal , only coupled with linear stearic and palmitic capture the economic benefits of filler a few can meet all the practical fatty acids (C16/C18). While ASA is for fiber substitution using local chalk requirements which include: 1. based on olefin feed stocks of C16/C16 (CaCO3); North and South American inherently hydrophobic; 2. uniform and contains an anhydride reactive mills followed in the early 1990's using distribution in the stock system; group. The AKD reaction is more GCC and then PCC; and Asian mills in 3.retention on the fiber; 4. uniform alkalinity sensitive, while ASA is more the mid to late 1990's. Now the Indian distribution on the fiber; 5. anchored to versatile reacting over a pH range of 5 to mills are moving forward in this global the fiber surfaces; 6. proper orientation 8.5. process. on the fiber and filler surfaces; 7. inert to aqueous penetrants; and 8. minimum AKD offers comparative advantages in The benefits of alkaline papermaking adverse impact on the paper making being easy to handle and the most are numerous and include: stronger process effective sizing agent vs a broad range of paper, higher brightness, lower penetrants; however its cellulose manufacturing costs, cleaner machine, Sizing Options reaction rate is moderate to slow and its fewer deposits, improved run-ability, furnish is limited in precision converting Over the past 3-4 decades, two main grades, ie it can contribute to paper slip. Ivax Paper Chemicals Ltd., 6-3-248/B, alkaline sizing chemistries have Road No. 1, Banjara Hills, Hyderabad emerged which are widely used today On the other hand, ASA offers a fast IPPTA J. Vol.19, No. 4, Oct-Dec, 2007 129 cellulose reaction rate and does not emulsion size with or PAC at machines with state of the art forming contribute to paper slip; however it does machine pH of 6-6.5 and talc as filler. sections, press sections and ample require in-mill emulsification as its drying capacity almost never emulsion has a very short shelf life, and Some mills find that AKD, ASA or rosin experience the problems of limited it has poor hold out vs acid penetrants. size alone cannot completely meet their drainage, press picking and lost speed needs, so they choose to employ that can de-rail alkaline conversions on Global Trends in Printing & “binary sizing”, ie use a combination of older machines. Writing Papers products to obtain the benefits of one which can offset the detrimental effects Alkaline trials on the older machines The major trend in P&W grades is the of the other. have been much more challenging as move toward increased ash content to many experienced moderate to severe achieve filler for fiber cost savings. For example, a P&W producer may press picking and reduced speeds due to This is driving the prevalence of size want the fast on machine cure of ASA poor drying after the size press which press surface treatments to meet for size press hold out, coupled with the terminated alkaline conversion activity increasing demands of the printer as hard sizing provided by AKD. in many cases. Certainly there are well as to minimize internal size examples of successful alkaline addition and machine deposits while Some MG machines combine AKD conversions on older machines; at least meeting sizing requirements in hard to with rosin emulsion in a “neutral one has been running AKD in P&W size highly filled grades. sizing” pH environment; here cationic grades including copy paper for over 10 rosin emulsion size provides MG years. This mill runs good retention and Combining these trends with the performance together with AKD for biocide programs as well. This machine comparative strengths of AKD and hard sizing in the finished paper. also has good drainage and drying ASA, papermakers are making a clear which combine with proper chemistry choice: ASA is the dominant size in At least one conventional P&W to keep AKD furnishes low. commodity or precision converting machine combines ASA and cationic P&W grades, eg copy paper, envelop, rosin emulsion to optimize size press Recent Copy Paper Experience and forms bond where paper slip cannot run-ability and meet Cobb targets. be tolerated; while AKD is still Major Indian copy paper producers dominant in specialty grades eg highly There are mills in India which now with integrated mills have run filled offsets, financial papers, catalog, practice each of these options. various alkaline trials with AKD and bible papers, photo base etc where hard ASA using talc filler and GCC. Some sizing is required. AKD- the initial sizing choice experienced machine run-ability issues during early trials including press Indian Mill Experience Numerous alkaline sizing trials have picking and lost speed. been run in recent years in P&W grades, Filler for Fiber as Economic Driver mostly with AKD due to its simple Recent trials at one of these has focused handling requirements. Another reason on copy papers with ASA as earlier Much alkaline conversion activity in for the early adoption of AKD in India AKD trials demonstrated paper slip India is centered on P&W grades, is the relatively low Cobb, ie hard sizing issues on converting equipment and lost including copy paper which is a fast specifications in the industry. Many speed, ie poor size press hold out on one growing grade. The major benefits P&W mills run copy papers to a machine. The company intends to realized range from increased paper 22gm/M2 Cobb test vs 30gm convert all its P&W machines to ASA to brightness vs acid papermaking for the specification in mills outside India. The standardize its grade formulations. integrated mills, to the reuse of reason given is that these papers are Challenges arose during the trials as all secondary fibers which contain CaCO3 multi use for both copy paper and the machines did not respond the same for the de-inking mills, or recycled school paper which needs way to alkaline papermaking as they CaCO3 coated broke. Most mills hard sizing to meet pen and ink feather were varying ages with varying continue to use only talc as filler, requirements. This increases sizing limitations in drainage, press design however, a few mills are now using c o s t s a n d d e s e r v e s f u r t h e r and drying. GCC or PCC for at least a portion of investigation. their filler requirements. GCC and PCC In general, this group found simple use will continue to grow as supply Alkaline Conversions of alkaline sizing systems gave better increases and cost becomes more Modern vs Older Machines performance on their machines, ie a competitive with talc. India's imports of chemical system comprised of a foreign P&W papers containing In India the more modern machines coagulant added to the thick stock CaCO3 will also drive consumer h a v e c o n v e r t e d t o a l k a l i n e followed by alum to the fan pump inlet demand for these higher brightness papermaking with few problems as the and ASA to the pressure screen accepts. papers. machines experienced no problems This system provides approximately converting from acid to alkaline. All equivalent First Pass Retention(FPR) Neutral or Binary Sizing for use retention and biocide programs to and First Pass Ash Retention(FPAR) P&W and MG papers optimize their systems. Several use levels as they had with acid/neutral internal starch for strength and sizing and good run-ability. Higher Neutral sizing has been commonly retention. Some are equipped with film FPR levels with retention systems had adopted in India as a step to capture at transfer type size presses and add earlier resulted in press picking. least a portion of the benefits of alkaline surface size to augment internal sizing. sizing. This practice employs rosin It is important to realize that modern A recent trial on a sister machine

IPPTA J. Vol.19, No. 4, Oct-Dec, 2007 130 demonstrated that severe press picking addition, pulp size-ablity varies widely flocculent and a micro particulate, resulted from high FPR and lost with type, eg Indian mills use many or small amount of alum as a drainage as evidenced by a two point types of fiber furnishes ranging from coagulant. The starch and alum increase in sheet moisture leaving the wood to agro based to recycled waste should be co-mixed with the size. couch making a weaker sheet in the which vary widely in charge demand, Retention levels should be press section. It was theorized that conductivity and size-ability. Water maximized (FPR>80% and increased water release on the table quality also plays an important role in FPAR>50%). with the alkaline system resulted in wet end chemistry and varies greatly ! A good biocide program is also “sheet sealing” ie wire side fines from location to location in terms of important to maintain system accumulation which inhibited further hardness, alkalinity, and conductivity. cleanliness and minimize deposits drainage on the wire, so steps were and sheet defects. taken to slow drainage by removing As a result, suppliers need to offer tailor ! table foils and moving addition points made products which are designed for Avoid close addition of size to for ASA and talc back from the dilute to specific applications to optimize filler, , and oxidizers. thick stock. After these changes the machine performance and economic ! Utilize surface size to minimize sheet moisture in the press section requirements. internal size furnishes. returned to normal and the machine ran acceptably. Customer References For ASA we add the following:

Advantage of starch in ASA Ivax alkaline sizing P&W papers ! Make a good quality emulsion emulsions customers include: Shreyans Paper using proper equipment. Mills Ltd who was the initial straw o Maintain proper particle size Another observation during our ASA based mill to convert to alkaline using and distribution for good trials has been about the benefit of using AKD and talc to capture the benefits of retention. cationic starch vs cationic polymer to higher brightness, higher productivity o Use proper starch for prepare the ASA emulsion. Starch is and lower costs. Other alkaline mills emulsion stability and most widely used in other countries for using AKD and talc include: retention. Minimize machine this purpose as it stabilizes the ASA Sheshashayee Paper Board, and West deposits. emulsion and provides retention Coast . benefits. In India an additional benefit CONCLUSION of reduced deposit tendencies on Two mills on binary sizing include machines with integrated pulp mills has Century Paper using AKD with ASA; Alkaline papermaking has evolved been observed when using liquid starch and APPM using AKD with cationic over the past 50 years to become the vs polymer to emulsify ASA. rosin on MG machines. Other machines standard practice of the global industry. at these mills use AKD with talc; APPM Out side of India, CaCO3 in various These mill trial experiences produces specialty grades using GCC forms is the alkaline filler of choice, demonstrate that even older machines and AKD. Both units of JK Paper are however, in India CaCO3 filler is just with various mechanical limitations primarily using ASA with talc and now beginning to replace talc. The Indian can successfully convert to alkaline trialing PCC. paper industry is becoming aware of the papermaking given time and benefits of alkaline papermaking and is experiment to optimize mechanical Best Practices with Alkaline now adopting this technology. settings and chemical systems. The Sizing most needed support is commitment While the newer machines are from upper management to make the With the combined experiences from successfully converting to alkaline conversion a success. around the globe, we can offer some papermaking following global guidelines to the best alkaline sizing practices, the older machines often Indian Raw Material Requirements practices which apply equally well to require unique, tailor made solutions to AKD as ASA. These include: successfully overcome various design Size demand for any type of sizing limitations. These specific solutions chemistry primarily depends on the raw ! Alkaline size, AKD or ASA, is require a systems approach to include materials in the papermaking system: usually added to the thin stock chemical systems, pulps, fillers, and water, filler and pulp types. between the fan pump and mechanical changes to meet specific pressure screen accepts. grade specifications and machine run- The choice of fillers is a primary factor ability targets. This can only be ! A good multi component retention determining size demand as sizing achieved via a team approach between system is important especially on efficiency is dependant on particle size, the mill and its suppliers, together with newer faster machines. This eg PCC with its fine particle size mill management's commitment to should include starch, for strength requires more size than GCC or talc. In make the alkaline conversion a success. and retention purposes, a

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