CS199191B1 - Filter cloth substrate - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base filter sheet for liquids used to protect against damage to top filter fabrics on a variety of filter devices, particularly filter presses and vacuum filters.

At present, only woven base cloths are used on filter presses to filter dyes, chemicals, sugars, building materials in liquid form. The most common are fabrics in which the warp and weft are made of jute yarns, or the warp is made of jute and wipes made of polypropylene tapes.

For previously used cotton top filter fabrics, these types of base cloths have proven to be effective both in terms of filter effect and in terms of frame tightness in filter presses.

Cotton top filter fabrics showed a relatively short lifespan and were often damaged by careless handling. Therefore, they started to be made only from synthetic yarns. Although this has prolonged the life of the top filter fabrics, the problem of frame tightness has remained, and to a greater extent, the frequency of damage caused by careless handling has decreased only insignificantly.

Vacuum filters use woven base cloths to avoid damaging the top filter fabrics attached to the filter drums with wires, but the woven base cloths reduce the flow rate of the filtered liquid by approximately 50%,

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It is an object of the present invention to eliminate the underlying filter sheet for liquids used to protect against damage to the top filter fabrics of various filtering devices, in particular filter presses and vacuum filters, and is based on the needled fabric of synthetic material, comprising a carrier fabric provided on at least one side with a fibrous web formed of alternating fibers having a fineness of 6 to 33 dtex, wherein 25 to 50 wt. % of the nonwoven fibers occupy a position across the thicknesses of the needled fabric. The fibrous web consists either of fibers of the same fineness or of a mixture of different finenesses ranging from 6 to 33 dtex. It is possible to use fibers having 4 to 8 arches at a distance of 1 cm, thereby increasing the elasticity of the cloth. The preferred weight of the underlay is 250 to 500 g / m and at least one of the underlay can be smooth and at least partially melted and glued together fibers. A suitable material for making the sheet is polypropylene, polyamide and polyester, or a mixture of at least two of these materials.

The main advantage of the invention is that by converting 25 to 50 wt. % of fibers from a predominantly horizontal position to a predominantly vertical position, i.e., support points are formed across the thickness of the underlying filter ηΐβ; which act on the surface of the cloth as a spring allowing to flexibly compress the cloth and thereby dampen various shocks that occur during handling and frames during the opening and closing of the filter press, the clamping of the filter press itself and the fixing of the sheets by tightening wires. The elasticity of the mold can be increased by using curved fibers.

Said displaced fibers increase the thickness of the filter cloths according to the invention by 200 to 400% compared to the known woven cloth cloths, with the same weight per unit area for both cloth cloths. Another important advantage of the invention is the uniform filling of the plaque in its area and its thickness. This protects the killer filter fabric, which, in combination with the needled base filter cloth according to the invention, exhibits up to six times the lifetime of the previously known fabrics.

With synthetic top filter fabrics that are relatively stiff, the sheet of the present invention fills leaks better between filter plates and frames, so that the flow of filtered liquid outside the filter press is greatly reduced.

In vacuum filters, a higher flow rate is achieved with the same filter effect and due to the good compressibility of the sheet, the top filter fabrics are not damaged by the attachment wires.

The functional suitability of the base filter sheet according to the invention is clearly shown in the table below from the differences in the original thickness and thickness after the state load found in the woven base filter sheet and in the sheet made according to Example 1 of the invention.

When comparing the effect of the load time on the thickness of the sheets, it is clear from the table that the fabric is less supple than the needled fabric, so that it absorbs less shock.

Further advantages of the underlying filter sheet according to the invention will be better understood from the examples of its embodiment.

Type of underlying filter Thickness Thickness difference in % po sails In ^mm short-term load long term 700 kPa / oin ² 700 kPa / cm ² after 2 min. after 60 min. jute fabric bp; 16 5 jute fabric jute outline 0.8 27 Mar: 5 Escape POP Strap needle-punched fabric KAF 15 / o (waste fibers) 2,0 36 15 Dec needle-punched fabric KAF ' 15 / s (from standard 3.1 46 <16

fibers)

He did

A fiber web of weight 2 is placed on a 100 g / m polypropylene fabric

200 g / m, prepared from 100% polypropylene fibers with a fineness of 17 dtex and with 4 curves per cm. It is also possible to use waste of the same fine fibers.

The layered body is stitched from the fleece side until it displaces about 30 masses. % fibers from a predominantly horizontal position to a predominantly vertical position, ie across the thickness of the fabric. "

Then, both surfaces of the needled body are slightly heat treated. The thickness of the fabric filter sheet thus produced is about 3.1 mm for standard fibers and about 2.0 mm for waste fibers. The thickness difference of this sheet after short-term loading is 36 to 46%. Plschetka is intended for frame filter presses for filtration of sugar juices.

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Example.2,

Two needlepunched fiber webs are prepared, each having a weight of 2 about 150 g / m 2 and made of 100% polyamide fibers with a fineness of 13 dtex and 5 turns per m.

A 80 g / m 2 polyamide fabric is placed between the webs, and then the superimposed body is stitched first from one side and then from the other side with the super-special needles so that 45 wt. it is predominantly vertical, ie across the thickness of the formation.

The needle-punched form has a thickness of 2.5 mm, which is reduced by 40 to 52% under short-term loading.

of- .

It is advantageous to heat treat the first needling side of those sheets which are intended to be used for filtering sugar juices on a vacuum filter.

Example 3

Two needlepunched webs are prepared, each having a weight of about p

200 g / m and is made of 100% polyester fiber with a fineness of 20 dtex with 4 curves per

Between these webs is placed a fabric weighing 100 g / m, made of polypropylene)

tapes. The layered body is stitched from both sides with conventional felting needles until about 25 wt. % of the fibers occupy a substantially vertical position, i.e. across the thickness of the formation.

Then, the needled body is calendered. So the fabric is 4.0 mm thick

J at short-term load, it has a thickness difference of 44 to 55%.

The product is intended for the base cloth used on filter presses - for filtering pigment inks and various other chemicals with a p e to 6.

. Example 4

A fibrous tensile resistance of p

180 g / m, prepared from a blend of polypropylene fibers and consisting of 40 wt.% Fibers of 6 dtex, 50 wt. % of fibers of 17 dtex and 10 wt. % fibers of a fineness of 33 dtex, all of the fibers having 4 to 8 arcs of not 1 oa.

The layered body is then punctured from the side by a standard NKU needle with up to 50 wt. % of the fibers occupy a predominantly vertical position, i.e. across the canvas.

The needled body is thermally treated on the fiber web side. The tarpaulin covered in this way is 3 mm thick. E, at short-term load, there is a difference in the sound pressure gauge e 47 to 55.

Claims (3)

Substrate filter cloth for liquids, used to protect against deterioration of the top filter fabrics on various filtering devices, in particular filter presses and vacuum filters, characterized in that it consists of a punctured fabric of synthetic material comprising a non-woven fabric provided with at least one layer a fibrous web formed of staple fibers having a fineness of 6 to 33 textex and having 4 to 8 arcs at a distance of 1 µm, wherein 25 to 50 wt. % of the nonwoven fibers occupy a position across the thickness of the needled fabric, the difference of which in the case of a load of 700 kPa / em ² is 36 to 55 # # ·· / · ^: · · ·. ₍ 2. The filter mat according to claim 1, wherein the needled fabric has a weight of 250 to 500 g / m &lt; ^{2 &gt;} and has at least one smooth surface containing at least partially melted and stuck together fibers. 3. The pad according to claim 1, wherein the synthetic material is polypropylene, polyamide, polyester or a mixture of at least two of these materials.