For the first time, the filter paper has been appliedeven in ancient China, of course, for this purpose used the usual material, but the principle was laid. Currently, it is produced only at several specialized enterprises. This is due to the fact that the filter paper, despite its apparent simplicity, is a product for the production of which involved a whole range of technologies. Except for the cellulose bases, it contains special fibers and chemicals, dyes, polymers.
Such a wide range of applicationsIt is provided with unique properties of each of its kind, developed specially for a specific purpose. The indicators depend on the initial components and conditions for further use. Therefore, the task of the technologists responsible for the production of this material is to ensure that the filter paper conforms to the physico-mechanical and chemical characteristics of the often aggressive media in which it will be used.
The process of its manufacture has the goal of giving ita certain porous structure that will ensure a deep containment of foreign impurities from the filtered gases and liquids. In this case, the filter paper must have certain strength properties, which basically give it a uniform distribution of fibers in the material and deep impregnation of the substrate with polymeric binders. The technology of its production consists of three main stages: synthesis of the fibrous composition, preparation of the substrate, impregnation of the paper base with a binder polymer.
For the third operation, a largea number of components. True, most often in modern industry, styrene-acrylic copolymers (acrylic impregnation), phenol-formaldehyde resins (phenolic) are used. The first has a number of advantages. In particular, when manufacturing paper with acrylic impregnation there is no need for an additional technological operation - heat treatment, such filters are also considered environmentally friendly, which is especially important when processing air. Phenolic impregnation is a traditional way of producing material for the automotive industry. Two types of resins (novolac or resole) or their mixtures can be used. The main advantage of novolak in comparison with the resole is a lower content of free phenol.
Filters can be installed afterembossing, and also in several layers, which can be of different varieties. This increases the working surface, strength, spectrum of types of captured particles.
