1 CMC used in Paper Industry
1.1 Surface Sizing
Carried by surface sizing paper finishing can increase stiffness, smoothness, improve surface strength, air permeability, control curl and get a good printability. CMC is generally used as a surface sizing viscosity at 30 ~ 700mPa • s, the degree of substitution of 0.7 to 0.85. As the surface sizing, CMC has excellent film forming and the whole film transfer performance, can form a layer on the paper surface continuous complete and flexible film. This film has good humidity function, helping to eliminate the drying section of the paper causing internal strain, to prevent warping deformation of paper or cardboard, and when the size of the error elimination overprint; at the same time, the surface of the paper or paperboard good closure resistance and oil resistance. Plant test data indicate that the expansion carried out using a single aqueous solution of CMC surface sizing layer of flexible film can be formed on the surface sizing, produce very good sizing effect, its oil repellency one indicator, concentration of 1% CMC may be produced by the effect of an aqueous solution of 12% starch solution with a concentration comparable.
1.2 wet end additives
CMC viscosity is usually used for wet-end additives is 0.3 ~ 0.6Pa • s in viscosity products, to control the degree of substitution of 0.4 to 0.8, so that not only can minimize the negative charge of CMC, and can form a clear three-dimensional gel structure The viscous solution. However, CMC should generally be used simultaneously with the cationic starch, a small amount of CMC in place of part of cationic starch, a good synergistic effect can be obtained.
Since the introduction of carboxymethylcellulose CMC, its sodium salt is soluble in water and form a clear viscous solution. The viscosity of this solution was added to the pulp, CMC molecules penetrate into the sub-fibrillated fibers or "coated" around the fiber, due to a hydroxyl group and carboxymethyl itself contained in the sheet forming the dehydration process, not only between the molecule and the molecules through hydrogen bonding to form a certain bonding strength, but also between the fibers forming more hydrogen bonds bridging role through its own, thereby increasing the binding force between fibers, and to improve the strength of the paper.
CMC can be added at the wet end to improve the internal bonding force of fibers, the fibers are uniformly dispersed in order to achieve better molding, thereby enhancing the physical strength of the paper material; CMC can also be used as a dispersant, the pigment particles will be compatible with its use or other colloidal fully dispersed particles, so that the whole system of rubber or paint composition to form a stable homogeneous system, to obtain good results.