November/December 1992
Laser paper—scrap that's been through a copy machine or laser printer—had been a bother for paper recyclers, but things are looking up.
BY KIMBERLEY R. HARRIS
Kimberley R. Harris is associate market analyst for the Institute of Scrap Recycling Industries (Washington, D.C.).
What do a compact disc player, the Star Wars films, and planetarium shows have in common?
Lasers. These high-tech light beams have infiltrated our society from every angle. We encounter them at the airport, at shopping malls, even in the automobiles that take us there.
Lasers have also revolutionized the office, where they play a starring role in xerographic copy machines and high-speed laser printers. In fact, light-based imaging machines appear in most offices worldwide, representing more than 90 percent of the office machines now operated. This has boosted the supply of so-called laser paper, which has traditionally troubled paper recyclers.
Laser Toner Makes the Difference
There are two basic types of office printing equipment: impact and nonimpact. A typewriter is an example of the first category; it applies ink to paper through the impact of keys against a typewriter ribbon. Nonimpact printers, on the other hand, use light and heat to transfer images to paper. Today, with the exploding population of photocopy machines and laser printers, 50 to 80 percent of mixed office paper collected through office recycling programs can be characterized as laser paper—a grade that has fetched lower prices than its impact-printed counterparts.
What distinguishes nonimpact-printed paper from impact-printed paper is not the paper's fiber, but the type of inks applied to the paper. Unlike impact printers, which generally use oil- or solvent-based inks, nonimpact printers use toners or "dry inks" which are classified by the Technical Association of the Pulp & Paper Industries (TAPPI) (Atlanta ) as "special inks." This classification is based upon several factors, including the ink's chemical type, its special properties, how it sets or dries, and its application.
According to a study by Betz PaperChem (Jacksonville, Fla.) entitled "Deinking of Laser Printed Stock Using Chemical Densification and Forward Cleaning," most toners are made up of the following components, each of which affects the deinking stage of the recycling process:
- a pigment—usually carbon black, although colors are also available.
- a base binder resin. This ingredient, which fuses the toner particles, varies in composition with the type of printing equipment it's used in, but is generally made up of a combination of polyesters, epoxy-type resins, styrene, and butyl acrylate polymers.
- a modifier resin—typically a natural material like abietic acid or rosin—which helps in the transfer of the ink to the paper.
- and a charge-control agent, which gives the toner its ability to accept an electrostatic charge—a necessary part of the laser printing process.
Toner-Based Printing Techniques
Besides using the same type of ink, laser printers and xerographic copy machines share similar printing techniques. The heart of the xerographic process, according to a paper by Ira Seldin of Xerox Corp.'s Paper Technology Center (Webster, N.Y.) presented at the 1985 TAPPI Pulping Conference, is a photoconductive surface that can be electrostatically charged by high voltage and will maintain its charge in the dark. Exposure to light (whether visible or ultraviolet) dissipates this charge and when the exposure is configured as an image, a latent image is created on the photoconductive surface—a rotating drum. When the toner, which sports an opposite electrical charge, contacts the photoconductive surface, Seldin continues, an image is produced, which is then transferred to paper that is brought into contact with the photoconductive drum. Finally, heat and pressure are applied to the paper using heated rollers to bind the toner to the paper. (See diagram on page XXX.)
Laser printers are really only modified xerographic copy machines. According to Seldin, laser printers use their computer brains to generate data in digital form, which is then transmitted to a scanning laser beam, which acts as the light source that creates the latent image on the photoconductor. This image is then applied to the paper by conventional xerographic copying techniques.
Thus, used xerographic copy paper and used laser-printer paper are really the same animal from a recycling perspective, and both are considered "laser-printed paper" by paper mills. In addition, most print shops now use toners to print letterhead stationery, thereby rendering it "laser paper" for scrap purposes regardless of what else is printed on it.
Identifying laser-printed paper isn't nearly as technical as its printing method. In fact, the tried-and-true method relies on one simple tool: a black marker. When the market is used to cross out a word printed in toner, the word is still readable at some angles because the toner shines through. Impact-printed ink, on the other hand, would be obscured by the marker. On a more scientific level, a chemical test kit that identifies ink type when a solution is applied to it is now available. Of course—particularly because of the potential difficulty and expense in sorting out laser paper from other grades—the best and most efficient way to identify laser paper is through education of and communication with scrap suppliers.
The Laser-Printed Paper Problem
For paper mills and deinking facilities, the trouble with laser paper begins and ends with one issue—the toner, which literally melts into the paper's surface so it is absorbed throughout the fiber. For laser paper to be recycled into tissue paper or high-quality printing or writing grades, the toner must be effectively removed.
The problem is, the base binder resins of laser toners are thermoplastics, which are very difficult to remove using traditional deinking methods. Thus, wrenching them free from the fibers during deinking is the main challenge to recycling laser paper.
Deinking scrap paper is generally a two-step mechanical or chemical process whereby ink is removed from paper fibers and then the ink must be separated from the pulp. With most types of ink, this is relatively simple. But toner particles are large—according to Tom Woodward of Betz PaperChem in a paper called "Deinking: What's Right for You?" they are usually greater than 25 microns (a micron is a 1,000,000th of a meter)—and the shape of these particles is flat and flakelike, which causes them to remain with the fibers when using a traditional washing procedure. The result, say experts, is a lower quality pulp.
Many paper industry officials believe that the answer to this laser paper recycling problem lies in the combined use of chemical and mechanical deinking processes, which, they say, yields a much cleaner fiber. Indeed, various mills are now developing chemical/mechanical systems for deinking toner-printed paper.
One of those mills is Prime Fiber Corp. (Appleton, Wis.), which for the last year has been successfully using a combination mechanical/chemical deinking process that it began designing in 1988, reports the firm's vice president, John Peil. The mill uses primarily postconsumer white and colored office scrap paper—a mix of laser and nonlaser paper—as the line's infeed material.
Prime Fibers's pulper chemically modifies the troublesome base binder resin in the laser toner into spherical balls, which increases the density of the material. Peil says that this "makes the particles hate water more than they usually do," easing separation from the fibers. Finally, multiple cycles of cleaning, screening, and washing purge the loose contaminates from the batch.
Betz PaperChem has also developed a similar process for deinking laser printed paper, according to Tom Woodward. The system chemically alters the toner ink so that it can be effectively removed. Like the Primer Fibers method, it changes the shape of the toner particles, which causes them to group together so they can be removed by conventional centrifugal cleaning.
A Growing Market
Thus far, the advent of such combination deinking systems seems to have strengthened the market potential for recycling laser-printed paper, and this trend is expected to continue as more mills retrofit.
The value of laser-printed paper, too, has increased over the past few years. In one region of the country, for example, the increase has been 21 percent compounded annually since 1990, moving up from $130 a ton to approximately $190 a ton.
The future of laser paper supply also appears bright, simply because the number of copy machines and laser printers continues to grow in the business world. Laser-printed paper is available from practically every office, so businesses participating in office paper recycling programs are the ultimate postconsumer sources for laser-printed material.
But scrap paper processors should remember that laser printers and xerographic equipment are not restricted to traditional offices. Printing shops, libraries, government facilities, book stores, churches, and other organizations are also potential sources of this scrap material.
Illustrating the magnitude of the potential laser paper supply available, Seldin notes that one high-speed copy machine operating at an output of 7,200 copies per hour, running five days per week, 24 hours a day, for 50 weeks per year would consume 216 tons of paper—all of which could end up in the laser paper recycling bin. Another study indicates that an average office employee generates more than 50 pounds of used laser paper per month.
With prospects for improved deinking, growing demand from mills, and no shortage of supply, it's a safe bet laser paper provides a growth opportunity for scrap paper processors.•
Laser paper—scrap that's been through a copy machine or laser printer—had been a bother for paper recyclers, but things are looking up.