Tissue: the quest for softness and absorbency.

Long the favorite product attributes of consumers, softness and absorbency have been called "holy grails" for the tissue industry. A variety of effective mechanical and chemical strategies have already been developed to deliver these important product qualities, as well as other desirable properties such as drape and handfeel. Cost effectiveness also remains a key concern for this highly competitive market. Continuing research points the way for promising new technologies in the sector's search for market-expanding products with increasingly refined properties.

To explore the truth behind the "holy grail" mythology, Solutions! magazine has assembled--what else?--a roundtable panel. Our experts included professionals from throughout the global tissue "kingdom," offering insight on the technological developments driving the latest improvements in softness and absorbency, and a glimpse at the opportunities offered by further advancements.

WHY SOFTNESS AND ABSORBENCY?

Joseph Cayetty, who in 1857 was the first to produce toilet tissue on a machine, would find it hard to believe how diverse the range of tissue and toweling products has become, said Dr. Nick Dunlop-Jones, manager, tissue marketing, Clariant-Global Business Paper, Horsforth, Leeds, UK. "Softness, strength and absorbency are key product qualities that manufacturers strive to perfect--despite the fact that improving one of the properties often impairs the other," he said. "Achieving softness is complex, and involves a multi-variable combination of fiber properties (fiber selection and fiber development), mechanically induced properties from the Yankee cylinder, and chemicals."

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Consumers care little for the complexity of the process--but they do know what they like. The tissue industry's highly competitive "at home" sector is comprised of mass-marketed products that rely directly on consumer appeal for success. Softness and absorbency are easily recognized attributes that consumers desire, as attested to by the success of more expensive, "premium" brand products. "Both quality properties are very important--softness is one of the most important properties (together with bulk) for toilet and facial papers, absorbency is the most important property for towel papers and napkins. That is the reason why the search for both properties improvements is so high and persistent," noted Rogerio Berardi, R & D Engineer, and Thomas T. Scherb, R & D manager, Voith Paper Maquinas e Equipamentos Ltda, Sao Paulo, Brazil.

According to Larry Bonday, program manager-tissue and towel grades for Nalco Co., Naperville, Illinois, USA, machine technology and chemical treatments are integrally linked in driving improvements in softness and absorbency. "Dry crepe, through air-drying, shoe press technology, and hybridized machine designs, require the integration of chemical treatments to deliver key product qualities," he said. "Creping programs, softening and lotion, and fiber bonding chemistries are instrumental in delivering softness and absorbency attributes. With these chemistries, unique solutions must be developed for each tissue producer based on machine type, fiber source, and application systems."

Softness and absorbency are indeed key properties of high-quality tissue, according to Jorg Baubock, R & D manager tissue machines, Andritz, Graz/Austria. "However, the importance of a specific property depends on the paper grade," he said. "Furthermore, absorbency is a measurable value, whereas softness is not so well defined and can only be determined subjectively."

The tissue industry's other major segment--the "away from home" segment--should not be ignored, noted John B. Stitt, Market Manager-creped technologies, Buckman Laboratories International, Inc., Memphis, Tennessee USA. "I take issue with the idea that softness and absorbency are 'holy grails' for the tissue industry. They play this role for only for the ultra-premium 'at home' sector of the industry. This segment is, percentage wise, small and highly profitable for affluent countries but of far less significance for the 'away from home' market and for the masses of the world. Lest we forget, there are many successful companies that work with a different business strategy, providing lower margin but much higher volumes of products."

In spite of these important caveats, these two qualities have served to focus the efforts of industry suppliers promising a variety of mechanical and chemical processes to help papermakers achieve product enhancements. As Jeff Peters, market segment manager-tissue & towel, Americas for Hercules Pulp and Paper Division explains, "Driven strongly by consumer preference and willingness to pay a premium, developing softness and absorbency solutions for our tissue customers are ongoing efforts for both our research and applications development efforts."

TAD AND MORE

When discussing softness and absorbency, it's practically mandatory to begin with an acknowledgement of the through-air drying (TAD) process and its impact on the at-home tissue market. "Since the first TAD products entered the market, already quite some time ago, it was immediately clear that an important qualitative improvement of tissue had arrived," said Alfred Watzl, sales & marketing director of Fleissner GmbH. "Today, it is beyond question that TAD products possess physical and mechanical characteristics superior to those made through more traditional techniques, and which results in unmatchable softness. In addition, the continuous development of special fabrics which drive the web along its drying process, together with the use of specially devised chemical agents, improvements and modifications in the paper machine section and real section, further enhance the TAD products' superior characteristics."

Since its introduction more than 40 years ago, papermakers and suppliers have continued to refine and adopt the TAD process; today, most new tissue machine installations rely on it. "Conventional tissue machines actually press the sheet onto the Yankee cylinder surface. In the TAD process, water is removed by pulling high-temperature air through the sheet, leaving up to 75% more bulk than the conventional dry crepe method," according Bjorn Engstrom of Metso Paper. "Because TAD products are structured before drying, absorbency (kg of water removed per kg of fiber) is typically one-and-a-half to two times more than conventionally made products. TAD is the most efficient and effective tissue manufacturing technology for delivering a product that is softer and more absorbent than is possible by conventional tissue making technology."

TAD does have its limitations, including significant capital investment requirements and high energy use. In the fight for improved softness and absorbency, there are other weapons in the tissue makers mechanical arsenal, which can be used instead of or in conjunction with TAD.

"For softness and absorbency together, the most significant technology improvement came with advanced process control, statistical and electromechanical," said John Stitt of Buckman. "Maintaining high softness and absorbency are dependent on optimum parameters maintained with very low variability. Absorbency is a property that has varied both better and worse; the expanded use of secondary fiber has resulted in lower absorbency and more challenges for the producer, while better understanding of absorbency mechanics and formation improvements have resulted in better premium products."

For softness improvements, Voith Paper's Berardi recommends running the headbox with two or three layers instead of a single layer. "By running the headbox with two layers, it is possible to run the short fibers, which are softer, against the Yankee cylinder for even more softness, and the long fibers (responsible for tensile strength) against the hood protected from the action of the doctor blade, for more tensile. After doing that, it is recommended to convert the toilet or facial paper with two plies, keeping the short fibers of both plies outside for softness and hiding the long fibers for tensile inside," he said. "By running the headbox with three layers it is possible to run the short fibers for softness improvement on the outside layers and the long fibers or the recycled fibers on the inside layer only for tensile."

Finally, it's important to recognize that wide differences in regional markets and consumer preferences have created a huge product range within the sector. Different grades require a balance of different properties, said Andritz's Jorg Baubock. "For facial grades, surface softness (handfeel) is the most important factor; for bathroom paper, bulk (structural softness) and handfeel are essential; and for kitchen towel, the main issues are absorbency capacity and absorbency rate. The special demands of each different grade can be fulfilled by machine concepts that are tailor-made for specific properties. Best quality for each grade can be achieved on single-purpose machines, whereas production lines for the whole range of grades (from light-weight facial paper to heavy-weight towel grades) have to make compromises with regard to the product quality."

CHEMICALLY ENHANCED

To enhance the effectiveness of its selected mechanical processes, tissue makers must choose carefully a chemical program focused on achieving the desired product qualities, including softness and absorbency. "Chemicals work in a number of ways--they affect Yankee adhesion/release; or they interfere with inter-fiber bonding, giving an increase in bulk, and modify the fiber surface, altering the 'feel' and 'handle' of the tissue," said Dunlop-Jones of Clariant.

"On the chemistry side, the innovations that are key to both higher softness and better absorbency are modern Yankee dryer coatings, chemical softeners/debonders and absorbency aids," added Stitt. "I would also say that charge understanding and control have contributed significantly."

Even with the same desired qualities in mind, effective chemical programs will vary depending on the grade being produced. "There are several pathways to achieving improved softness in both tissue and towel grades," said Raj Bazaj, NAFTA marketing director for LANXESS Corp. "Grades rely on refining to different degrees as a means to develop needed tensile strength and other properties. However, refining will also have adverse impacts on fiber length, fines generation, bulk development, absorbency and softness. Depending upon the amount of refining, sheet properties such as suppleness ('drape') and handfeel can fall below desired levels."

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Many chemical companies serving tissue makers continue to develop suites of related products and services to meet the sector's specific needs. "This is a response to the tissue maker's need to be even more inventive in his process and finished product development as he strives to meet the ever increasing demands from the consumer," noted Geoff Sheridan, business manager, BIM Kemi, Sweden.

NEW TECHNOLOGIES

Continued growth in tissue markets, especially in developing countries, guarantee the need for new technologies. We asked our experts for an inside look at their companies' emerging technologies for tissue product enhancement--specifically in regards to qualities of absorbency and softness.

Jorg Baubock, Andritz: "For facial and bathroom tissue, the use of a shoe press is an excellent tool. Gentle dewatering and drying retains bulk as much as possible, thus improving the structural softness and handfeel of the sheet and allowing an extremely fine crepe. An example from Voith and Andritz is the TissueFlex[TM] concept."

Geoff Sheridan, BIM: "BIM has developed TISTEK, which includes a web uniformity improvement technology that benefits overall machine and converting productivity. This technology controls fragmentation of the fibers during creping, which minimizes dust on the machine and in converting. This aspect can improve health and safety, as well as productivity and quality.

"The portfolio also includes technologies that can impart softness, absorbency, bulk increase as well as a wide range of lotions, balms and converting adhesives. The ability to manage substrate properties in order to maximize the capability to achieve the required value-added with the minimum of disruption to productivity is a critical step."

John B. Stitt, Buckman Laboratories: "The most promising emerging technology, in my opinion, will be with enzyme fiber modification. It takes a total systems approach and understanding of the chemistry and mechanics for each type of enzyme. Already, mills are realizing great improvements in softness, strength and dust control through the designed use of enzymes to modify the nature of the fiber."

Dr. Nick Dunlop-Jones, Clariant: "Clariant has recently introduced Cartaflex TNS, a patented chemistry for optimizing the softness of tissue papers. Based on a renewable resource, its backbone consists of fatty-acid esters that are both ethoxylated and quaternized (cationic). The performance of Cartaflex TNS comes from its ability to give bulk and affect the feel and handle of the fibers. However, a key feature of the product is that it has been engineered to be readily biodegradable and so meet the strict requirements of the Nordic Swan ecolabel.

"Cartaflex TNS is a cationic surfactant that can adsorb onto cellulose fibers at the wet end of a paper machine. After treatment, the surface energy of the paper is significantly increased, allowing rapid penetration of water and aqueous fluids."

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Alfred Watzl, Fleissner GmbH: "The recent agreement between A. Celli Paper and Fleissner is based on the intention of optimizing both initial investment and all operational costs, thus offering tissue producers a system that will enable them to enter the market with superior products at reasonable prices. The TAD tissue line is sized in order to find the optimum between the investment costs and the production capacity. Particular attention is also dedicated to the quality-price ratio of each component in order to optimize the advantages capital investment.

"The profitable TAD plant can be adopted both by the market leaders developing new markets and by local private label producers wishing to implement their production range with premium TAD products, to differentiate their product range."

Jeff Peters, Hercules Pulp and Paper: "Taking a holistic or 'Complete Solutions' approach and assuming the fiber furnish is fixed, we first survey the machine to make sure everything mechanically is set up properly. If the mechanical solution falls short of product requirements, we then consider chemical solutions.

"Hercules' tissue and towel product line includes Crepetrol[R], ProSoft[R] and Rezosol[R] technologies. A Yankee coating package has a major impact on softness and absorbency. A very tacky, manageable coating adhesive married with the proper non-oil based coating modifier/release will improve softness and absorbency. If an additional tweak to absorbency is needed, Hercules will use an internal absorbency aid. Additional softness improvements can be obtained with the addition of an internal debonder and/or surface softener."

Raj Bazaj, LANXESS Corp.: "LANXESS Corp. specializes in an approach using a tailored strength resin to replace or reduce refining. Selecting the right strength resin is the critical first step. This requires a machine survey to understand the wet-end chemistry and furnish characteristics, as well as sheet properties. Then, depending upon whether the grade is tissue or towel, a resin providing dry strength, or both wet and dry strength, can be recommended. The trial involves introducing the strength resin into the system and allowing sheet strength properties to increase. We refer to this as 'putting strength in the bank.' We then 'withdraw' strength back to target levels by reducing refining. What follows is a positive response in those properties adversely affected by refining.

"Not all systems respond with dramatic improvements in all properties, and softness gains will vary; however, we have certainly seen positive impacts most notably in softness and absorbency. The key is to fully understand a given machine's flexibility to make changes in refining."

Bjorn Engstrom, Metso Paper: "The heart of Metso Paper's TAD process is the open face HONEYCOMB ROLL[R] drying cylinder. With an open area in the roll shell of more than 94%, large volumes of drying air is allowed to pass through the sheet. This yields a higher evaporation rate over a much longer period than conventional Yankee cylinder drying. Enhancements continue to be developed on our full scale TAD pilot tissue machine at our Tissue Technology Center in Karlstad, Sweden."

Larry Bonday, Nalco Co.: "Nalco's 'Smart Soft' approach balances the tradeoffs between softness and strength. It allows a more comprehensive path to addressing the specific goals of bulk and/or surface softness. For example, bulk softness could be addressed by both mechanical and chemical means-through debonder chemistry and creping technology. Finding the right mix of chemical and mechanical solutions will allow development of the desired softness attribute while managing program economics."

Rogerio Berardi, Voith: "Voith Fabrics is developing a new concept at the Voith Paper tissue pilot machine to produce a premium tissue paper with less capital investment and energy consumption than TAD machines.

WHAT YOU WILL LEARN:

* How tissue makers achieve softness and absorbency.

* Which new developments promise even more gains in these important properties.

ADDITIONAL RESOURCES:

* "A beginner's guide to towel and tissue, Parts 1 and 2" Solutions!, September 2004 and November 2004, TAPPI Product Codes 04SEPSO32 and 04NOVSO30. (To access, enter code into search window at www.tappi.org).

* "Characterization of facial tissue softness," TAPPI JOURNAL, April 2004, Product Code 04APR03.

* "Commercial tissue: Big market kept under wraps," Solutions!, September 2002, Product Code 02SEPSO54.

EDITED BY JANICE BOTTIGLIERI, SENIOR EDITOR

ABOUT THE AUTHOR:

Jan Bottiglieri is senior editor of Solutions! and editor of TAPPI Journal. Contact her at [e-mail].

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