houtpulps

Houtpulps are fibrous cellulose materials derived from wood, produced for papermaking and a range of related products. They are typically categorized into chemical pulps, mechanical pulps, and chemi-mechanical pulps, with differences in fiber structure, brightness, and strength.

Chemical pulps use chemical reactions to remove lignin and other components from wood chips. Kraft (sulfate) and sulfite processes are the most common chemical pulping methods. Kraft pulp yields are high and fibers tend to be long, producing strong papers, while sulfite pulps generally yield shorter fibers and are often used for lighter or specialty papers.

Mechanical pulps are produced by physically reducing wood to liberate fibers, usually by grinding or refining. They retain most of the lignin and therefore have higher yield but lower strength and brightness compared with chemical pulps. Thermomechanical pulping (TMP) and refiner mechanical pulping (RMP) are common mechanical methods, with CTMP (chemi-thermomechanical pulping) combining chemical pretreatment and mechanical refining.

Chemi-mechanical pulps sit between chemical and mechanical pulps, using a limited chemical treatment before mechanical defibration to improve brightness and strength relative to purely mechanical pulps.

Fibers from softwoods and hardwoods influence pulp properties. Softwood fibers are typically longer and provide high tensile strength, while hardwood fibers are shorter and improve printability and opacity. Blending fibers from both sources can tailor strength, bulk, and brightness.

Bleaching further enhances brightness by removing remaining lignin. Common approaches include elemental chlorine-free (ECF) and totally chlorine-free (TCF) processes to reduce environmental impact. Houtpulps are used in writing and printing papers, newsprint, tissue, and various packaging grades, depending on the chosen pulping method and subsequent processing.