Views: 0 Author: Site Editor Publish Time: 2021-12-05 Origin: Site
Most of us can't imagine living without toilet paper. The average American uses over 100 single rolls—about 21,000 sheets—each year. It's used not only for bathroom hygiene, but for nose care, wiping up spills, removing makeup, and small bathroom cleaning chores. Manufacturers estimate that an average single roll lasts five days.
Toilet paper, paper towels, napkins, and facial tissues are sanitary papers, personal products that need to be clean and hygenic. They're made from various proportions of bleached kraft pulps with relatively little refining of the stock, rendering them soft, bulky, and absorbent. Sanitary papers are further distinguished from other papers in that they are creped, a process in which the paper is dried on a cylinder then scraped off with a metal blade, slightly crimping it. This softens the paper but makes it fairly weak, allowing it to disintegrate in water.
Toilet paper can be one-or two-ply, meaning that it's either a single sheet or two sheets placed back-to-back to make it builder and more absorbent. Color, scents, and embossing may also be added, but fragrances sometimes cause problems for consumers who are allergic to perfumes. The biggest difference between toilet papers is the distinction between virgin paper products, which are formed directly from chipped wood, and those made from recycled paper. Most toilet paper, however, whether virgin or recycled, is wrapped around recycled cardboard cylinders.
Toilet paper is generally made from new or "virgin" paper, using a combination of softwood and hardwood trees. Softwood trees such as Southern pines and Douglas firs have long fibers that wrap around each other; this gives paper strength. Hardwood trees like gum, maple and oak have shorter fibers that make a softer paper. Toilet paper is generally a combination of approximately 70% hardwood and 30% softwood.
Other materials used in manufacture include water, chemicals for breaking down the trees into usable fiber, and bleaches. Companies that make paper from recycled products use oxygen, ozone, sodium hydroxide, or peroxide to whiten the paper. Virgin-paper manufacturers, however, often use chlorine-based bleaches (chlorine dioxide), which have been identified as a threat to the environment.
The Manufacturing Process
Treesarive at the mill and are debarked, a process that removes the tree'souter layer while leaving as much wood on the tree as possible.
Thedebarked logs are chipped into a uniform size approximately 1 in x 1/4 in.These small pieces make it easier to pulp the wood.
The batchof wood chips—about 50 tons—is then mixed with 10,000 gallons of cookingchemicals; the resultant slurry is sent to a 60-ft (18.3-m)-tall pressurecooker called a digester.
Duringthe cooking, which can last up to three hours, much of the moisture in thewood is evaporated (wood chips contain about 50% moisture). The mixture is reducedto about 25 tons of cellulose fibers, lignin (which binds the wood fibers together) and othersubstances. Out of this, about 15 tons of usable fiber, called pulp,result from each cooked batch.
The pulpgoes through a multistage washer system that removes most of the ligninand the cooking chemicals. This fluid, called black liquor, is separatedfrom the pulp, which goes on to the next stage of production.
Thewashed pulp is sent to the bleach plantwhere a multistage chemical process removes color from the fiber. Residuallignin, the adhesive that binds fibers together, will yellow paper over time and mustbe bleached to make paper white.
The pulpis mixed with water again to produce paper stock, a mixture that is 99.5%water and 0.5% fiber. The paper stock is sprayed between moving meshscreens, which allow much of the water to drain. This produces an 18-ft(5.5-m) wide sheet of matted fiber at a rate of up to 6,500 ft (1981 m)per minute.
The matis then transferred to a huge heated cylinder called a Yankee Dryer thatpresses and dries the paper to a final moisture content of about 5%.
Next, the paper is creped, a process that makes it very soft and gives it a slightly wrinkled look. During creping, the paper is scraped off the Yankee Dryerwith a metal blade. This makes the sheets somewhat flexible but lowerstheir strength and thickness so that they virtually disintegrate when wet.The paper, which is produced at speeds over a mile a minute, is then woundon jumbo reels that can weigh as much as five tons.
The paperis then loaded onto converting machines that unwind, slit, and rewind it onto long thin cardboard tubing, making a paper log. The paper logs are then cut into rolls and wrapped packages.
Recycled toilet paper
Toilet tissue made from recycled paper is made from both colored and white stock, with staples and pins removed. The paper goes into a huge vat called a pulper that combines it with hot water and detergents to turn it into a liquid slurry. The recycled pulp then goes through a series of screens and rinses to remove paper coatings and inks. The pulp is whitened somewhat and sanitized with oxygen-based products like peroxide. It then goes through steps 7 through 10 like virgin paper products, producing a cheaper, less-white paper.
Paper companies often maintain their own tree stands in order to ensure the quality of the paper they manufacture. The chemicals used in the pulping process are also carefully tested and monitored. Temperatures at which a slurry is cooked is ensured, too, by checking gauges, machinery, and processes. Completed paper may be tested for a variety of qualities, including stretch, opacity, moisture content, smoothness, and color.
The first waste product produced in the papermaking process, the bark removed from tree trunks, burns easily and is used to help power the paper mills. In addition, black liquor, the fluid removed from the pulp after cooking, is further evaporated to a thick combustible liquid that is also used to power the mill. This reduction process, in turn, yields a byproduct called tall oil that is widely used many household products. About 95% of the cooking chemicals are recovered and reused.
But other problems associated with the industry are less easily solved. The production of virgin toilet paper has spawned two current controversies: the destruction of trees, and the use of chlorine dioxide to bleach the paper. While virgin paper processing does necessitate the destruction of trees, they are a readily renewable resource and paper companies maintain large forests to feed their supply. Despite this, some activists have proposed that toilet paper be manufactured only from recycled products and suggest that consumers boycott toilet paper made of new materials.
These activists object to new paper processing because it often uses chlorine bleaching, which produces dioxins, a family of chemicals considered environmental hazards, as a byproduct. Paper and pulp mills are the primary producers of dioxins, and manufacturers must carefully assess their effluvia to counteract the emission of dioxins. Increasingly, virgin paper makers use alternative bleaching methods that substitute oxygen, peroxide, and sodium hydroxide for chlorine. Some simply reduce the amount of chlorine used in the process. Others experiment with cooking the wood chips longer, removing more lignin earlier in the process, which requires less bleach. Better pulp washing also removes more lignin, and reduces the amount of bleach needed for whitening.