BE516445A

BE516445A -

Info

Publication number: BE516445A
Authority: BE
Priority date: 1951-12-24
Also published as: FR1068505A

Description

       

  PROCEDE DE TRAITEMENT D'ELEMENTS FILTRANTS EN MATIERES FIBREUSES OU GRANULEUSES.

  
Les éléments filtrants constitués par des fibres organiques ou inorganiques de faible longueur, comme par exemple les fibres de cellulose et les fibres d'amiante, ou par des mélanges de ces fibres avec des matières en poudre à fines particules, telles que du charbon actif, de la terre d'infusoires des échangeurs d'ions etc., formant des couches, bougies, gâteaux, etc., présentent l'inconvénient que pendant la filtration, des fines particules de fibres ou de matières de remplissage absorbantes sont entraînées de la texture du filtre et passent dans le filtrat. Il

  
se manifeste aussi très souvent un manque de résistance mécanique de la couche filtrante. Pour éviter ces inconvénients, on a essayé de consolider la. texture du filtre en le revêtant d'une couche formant pellicule,

  
par exemple des esters du type nitro-cellulose, et ce par immersion dans

  
un bain ou par application au pistolet. Il existe encore d'autres procédés qui consistent à imprégner les constituants de filtres par l'addition de produits de prépolymérisation encore solubles, par exemple de la mélamine ou des éthylène-imines, ceci s'effectuant dans des moulins à cylindres dans toute la masse avant le moulage de l'élément filtrant proprement dit, afin de procurer à ce dernier une résistance mécanique plus grande

  
à l'état humide. L'évacuation et la récupération des vapeurs de solvants, généralement inflammables et toxiques, développées lors de l'application d'une couche de matières dissoutes formant pellicule, entraîne des difficultés techniques. Il peut aussi se former par ce procédé une pellicule plus ou moins étanche sur la surface du filtre ainsi traité, ce qui influence défavorablement sa perméabilité. Lors du traitement au moyen

  
de résines de mélamine, d'imines de polyéthylène et l'équivalent,utilisées sous forme de produits de précondensation ou de polymérisation à grosses molécules, solubles dans l'eau, et s'effectuant de préférence dans la masse avant le moulage de l'élément de 'filtration, il se produit très souvent un blocage préjudiciable des centres actifs des fibres et des matières d'addition ce qui dans de nombreux cas diminue l'efficacité du filtre.



  PROCESS FOR TREATMENT OF FILTER ELEMENTS IN FIBROUS OR GRANULAR MATERIALS.

  
Filter elements consisting of organic or inorganic fibers of short length, such as for example cellulose fibers and asbestos fibers, or of mixtures of these fibers with powdered materials with fine particles, such as activated carbon, diatomaceous earth from ion exchangers etc., forming layers, candles, cakes etc. have the disadvantage that during filtration fine particles of absorbent fibers or fillers are carried away from the texture of the filter and pass into the filtrate. he

  
There is also very often a lack of mechanical strength of the filter layer. To avoid these drawbacks, we tried to consolidate the. texture of the filter by coating it with a film forming layer,

  
for example esters of the nitro-cellulose type, by immersion in

  
a bath or by spray application. There are still other processes which consist in impregnating the components of filters by the addition of still soluble prepolymerization products, for example melamine or ethylene-imines, this being carried out in roller mills throughout the mass. before the molding of the filter element itself, in order to provide the latter with greater mechanical resistance

  
in the wet state. The evacuation and recovery of solvent vapors, generally flammable and toxic, developed during the application of a layer of dissolved materials forming a film, leads to technical difficulties. A more or less waterproof film can also be formed by this process on the surface of the filter thus treated, which adversely affects its permeability. When processing with

  
melamine resins, polyethylene imines and the like, used in the form of precondensation or large molecule polymerization products, soluble in water, and preferably carried out in the mass before the molding of the As a filter element, very often detrimental blocking of the active centers of fibers and adducts occurs which in many cases reduces the efficiency of the filter.

Claims

The preferential absorption of acid dyes from liquids to be filtered, by

basic groups of these impregnating agents, also exerts an action

detrimental in many use cases.

The present invention avoids the drawbacks mentioned

and consists in introducing into the filter element or in applying on its surface, particles of synthetic materials from dispersions of which

the dispersion medium is then removed by evaporation. Use

dispersions of water-soluble synthetic materials, offers the advantage of allowing this process to be technically applied without the need to take special safety measures with regard to

the danger of fire and ventilation of the premises.

The application or introduction of finely divided particles of material

Synthetics make film formation impossible if the concentration of the dispersion is appropriate.

The particles become lodged in the texture of the filter so that the

fibers, absorbent materials and the like are only bonded to the points

reciprocal contact. During the subsequent drying these small particles agglomerate the materials constituting the filter, so that we obtain

solid internal textures, or hardened surfaces. In this case, it does

does not block the pores of the filter, so that these elements

filters have the same efficiency as untreated ones.

This process can be applied to all filter media

known for advanced filtration, and which may for example consist of

by celluloses of different types, fibranne, rayon and wool, fibers of asbestos and silicates (glass), as well as absorption materials,

such as diatomaceous earth, activated carbon, bleaching earth, ion exchangers and the like, used either alone or

in the form of mixtures Treatment with synthetic dispersions can be carried out throughout the thickness of the filter layer

or only in the surface layer, but then preferably on

the exit face.

The dispersions can be introduced into the filter element, or

applied thereon, by vacuum impregnation or not, by application

superficial with a brush, spray gun, or by calendering.

These dispersions can also be added to the mass of the filter, before

the formation of the filter element, the filter layer or the equivalent,

or be used for impregnation after molding, in the wet state,

partially or completely dry.

The most advantageous dispersions of synthetic materials are those in which the dispersion medium consists of water and

of which the material in dispersion, consists of thermoplastic products partially or fully hardened and finally divided such as

polyacrylic acid, polymethacrylic acid, polyvinyl compounds, polystyrenes, products of mixed polymerizations and the like. The use of synthetic materials in dispersions whose point

softening is high, hardens the filter elements which,

when used at high temperature, show no

tendency to stick.

With such layers it is also possible to filter liquids under high pressure, without the texture of the filter tearing.

or breaks between the supports.

CLAIMS.

1.- Process for the treatment of filter elements made up of <EMI ID = 1.1>

tières, characterized in that one introduces into these filter elements or that one applies on their surface particles of synthetic materials

from dispersions from which the dispersion medium is then removed by evaporation.

2.- A method according to claim 1, characterized in

that we use dispersions of synthetic materials whose particles are smaller than the pore diameter of the materials constituting the filter.

that dispersions of synthetic materials are used which are insoluble in the liquids to be filtered and do not react with the latter.

4. A process according to claims 1 to 3, characterized in that thermoplastic plastics with a high softening point are used.

5. A method according to claim 1, characterized in that the dispersions are applied to the surface of the filter element by spraying, calendering or brushing, in a concentration such that the formation of a film is avoided.

6.- A method according to claim 1, characterized in

that the dispersions are applied by complete or partial impregnation of the entire filter element or its surface layers.

7.- A method according to claim 1, characterized in

that the plastics applied to the filter element or introduced into the filter element are hardened by application of hardening chemicals, ultraviolet rays etc., before or after impregnation, for example by heating, by compounds hardening chemicals, ultraviolet rays, etc. applied before or after treatment.