Pulp: Where paper begins
Before paper can be formed, wood has to be broken down into its most useful component: cellulose fiber. Pulping separates these fibers from the natural materials that bind them together, creating the raw material from which paper is made. How those fibers are separated, treated and blended has a direct impact on nearly every characteristic of the finished sheet—from strength and bulk to smoothness, opacity and printability.
Pulp is the foundation of paper. Separating cellulose fibers from wood creates the raw material whose properties determine the strength, appearance and performance of the finished sheet.
Pulp: Where paper begins
Prefer to watch rather than read the Pulp chapter? Check out the video above.
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The pulping process
Watch the short video to see the pulping process, demonstrating the complexity of the entire process and circular nature of the subprocesses where chemicals are recycled and reused. Learn more about Billerud’s premium pulp.
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Debarking and chipping
Before fibers can be separated, logs must first be prepared. The bark is removed because it contains impurities that can interfere with the papermaking process. The bark, along with pins and fines generated during chip preparation, is collected and sent to the boiler to be burned as fuel, helping provide energy for the mill. The remaining wood is then cut into uniform chips that can be processed efficiently.
Consistent chip size is critical. Chips that are too large may not cook evenly during pulping, while chips that are too small can reduce yield. Proper preparation helps ensure efficient fiber extraction and consistent pulp quality, while the recovery of bark, pins and fines as boiler fuel helps make use of these residual materials.
While there are several methods of debarking, our Escanaba mill utilizes state-of-the-art rotary debarkers to efficiently remove bark. Watch the short video to see the debarking process prepares logs for the next stage of production.
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Cellulose fundamentals
Cellulose is the primary building block of paper. Found within the cell walls of plants, cellulose fibers provide the strength and structure that make paper possible. These microscopic fibers are remarkably strong for their size and can bond together naturally when suspended in water and formed into a sheet.
The ability of cellulose fibers to intertwine and bond is what gives paper its unique combination of strength, flexibility and versatility.
Fiber length and strength characteristics
Fiber length is one of the most important factors affecting paper performance. Longer fibers create stronger bonds and contribute to greater tear resistance and durability. Shorter fibers help improve formation, smoothness and printability.
The balance between long and short fibers is carefully controlled during papermaking. Different products require different combinations depending on their intended use and performance requirements.
Videos
Forestry for the future.
Todd Proctor, Fiber Supply Manager at our Quinnesec Mill in Michigan, talks with pride and passion about modern forestry at Billerud.