Fibrillated pulp

Laboratory Hollander refining - a Hollander beater design consists of a circular or ovoid water raceway with a beater wheel at a single point along the raceway. The beater wheel is made with multiple blades mounted on an axle-Uke shaft, similar to the construction of a water wheel. Under power, the blades rotate to beat the fibre into usable pulp slurry or highly fibrillated pulp suspension composed of ceUulosic fibrils and fibres. In our study, we used a valley beater, and, hence, in this study the words Hollander and valley beater are used interchangeably. Co-refining of pulp fibre and lime was carried out to a maximum of 30 min in the Hollander beater. 

Comparing the light scattering produced by composite fillers and reference blends, the composite material is found to give significantly better optical properties than a simple blend of PCC and fibrillated pulp. 

Nakagaito and Yano (2004, 2005) developed MFC, which consists of mechanically fibrillated pulp into nano to submicron wide fibers forming a web-like network (Fig. 21.4), shows much promise as reinforcement of composites. The pulp has a smooth surface with 30-50 pm in diameter, refiner-treated pulp has a fibrillated surface with a diameter similar to pulp and MFC is completely disintegrated into nano to submicron wide fibers forming a network. 

Fibrillated Fibers. Acrylic fibers are sold in the form of fibrillated pulps for use as highly efficient binders. These fibrillated fibers have a tree-like structure with limbs (fibrils) attached to the main trunk (fiber). The trunk is 20-50-fx diameter and the limbs range from a few microns to snbmicron. The product is generated from a special precursor fiber by intense mechanical action. Commercial examples are CCF from Sterling Fibers, Acri-Pulp from Solntia, and Dolanit lOD from Acordis. 

Wet pulps are used in specialty paper applications such as speaker cones, filtration, and specialty papers. These pulps have been successfully processed on cylinder, rotoformer, and Fonrdrinier paper machines. As little as 15% of a highly fibrillated pulp can interlock other fibers or powders without the need for resin binders. 

Fibrillated Fibers. Instead of extmding cellulose acetate into a continuous fiber, discrete, pulp-like agglomerates of fine, individual fibrils, called fibrets or fibrids, can be produced by rapid precipitation with an attenuating coagulation fluid. The individual fibers have diameters of 0.5 to 5.0 ]lni and lengths of 20 to 200 )Jm (Fig. 10). The surface area of the fibrillated fibers are about 20 m /g, about 60—80 times that of standard textile fibers. These materials are very hydrophilic an 85% moisture content has the appearance of a dry soHd (72). One appHcation is in a paper stmcture where their fine fiber size and branched stmcture allows mechanical entrapment of small particles. The fibers can also be loaded with particles to enhance some desired performance such as enhanced opacity for papers. When filled with metal particles it was suggested they be used as a radar screen in aerial warfare (73). 

Since the glass mat supplies sufficient stiffness, high backweb thickness was no longer needed These fleeces are made of organic fibers (polyester and polypropylene, as well as so-called synthetic pulp , i.e., fibrillated polypropylene) on paper machines. 

Fig. 2. Flow diagram of kraft pulp mill (1) debarking, (2) chipping, (3) screening, (4) steaming, (5) impregnating, (6) digesting, (7) fibrilizing, (8) screening, (9) fibeiizing. OOi washing, (11) chemical recovery...

We have shown by our ISO brightness and Ak measurements that the lignin was attacked by the reactive species created by the y irradiation. The results indicate that the reactive species created attack indiscriminately the phenolic hydroxyl or coniferalde-hyde groups and the quinone groups. The decrease in physical properties is associated with die attack on the micro fibrils cellulose. However, at 3000 krad/h, the increase in the ISO brightness is smaller than the one observed around 300 krad/h for the TMP, while the physical properties of the pulp are affected more profoundly at 3000 krad/h than at 300 krad/h. The physical properties of the P-TMP behave similarly, while the increase in brightness is negligible at 3000 krad/h for P-TMP. 

At first, a water suspension of pulp has to go through a mechanical treatment that consists of a spring-loaded valve assembly (refiner), where the slurry is pumped at high pressure. The formed MFC is moderately degraded and extremely expanded in surface area. In recent years, cellulose with a nanoscale web-like structure (Fig. 4c) has been made. The fiber diameters are in the range 10-100 nm [19,20]. The degree of fibrillation depends on the number of passes through the refiner (Fig. 4b, c). 

Fibril and CMC Mixture A blend of CMC and fibrils was made by mixing CMC prepared in the manner described above in the ratio of 1 50 with cotton pulp that had been beaten in a blender for 3 h. 

Two types of wood pulp provided the fibrils used for patching. The first was a moderately beaten wood pulp obtained from the Department of Pulp and Paper Science, North Carolina State University. The second was Cellunier P, a cellulose provided by the ITT Rayonier Company. Portions of the pulp and Cellunier P were dyed with 0.5% Cuprophenyl Navy Blue RL (from the Ciba-Geigy Corporation) and 0.5% tetrasodium phosphate for 30 min at 82°C to provide greater visual contrast between the fibers and the substrates. The wood pulp was diluted with distilled water to form 0.5 and 0.1% slurries. The Cellunier P was diluted to a 0.05% slurry. Both were treated in a blender to separate lumps formed during dyeing. 

One application of the 0.5% slurry made of undyed wood pulp produced samples that were heavily and unevenly coated with fibrils. The holes in the samples were partially or completely filled, but the paper-like coating peeled easily from the substrate. 

Repeated applications (up to nine) of the 0.1% slurry of undyed wood pulp to the substrate with holes deposited a layer of fibrils in the holes. The thickness of the layer appeared to be directly proportional to the number of treatments. One to four applications partially filled the holes, and five to nine filled them completely. Typical fabrics after zero, two, four, five, and six passes of the 0.1% slurry are shown in Figures 1-5. Samples that had been treated seven to nine times, however, were... 

---