GB2079803A - Drainage elements - Google Patents

Abstract

Drainage elements used in the manufacture of paper, cardboard and paperboard have, in contact with the wire 1, a surface made from a layer 3 of a soft hydrophylic polymeric gel; for example, a partly hydrolysed polyacrylonitrile. The layer 3 is attached at 4 to a supporting element 2 at its leading edge 6. The drainage element may act as a dewatering foil or may be incorporated in the cover of a suction box. <IMAGE>

Description

SPECIFICATION Drainage elements The invention concerns drainage elements used in the manufacture of fibrous fleeces from a suspension of fibres by means of felting on a sieve screen, especially in the manufacture of paper, cardboard and paperboard. In this manufacture are the felted fibres carried by means of a sieve or another textile fabric with a contemporaneous removing of water through the openings of the sieve or the pores of the textile fabric. The drainage elements that cooperate with the sieve or with the textile fabric serve to a more efficient removing of water. A part of the surface of drainage element comes always in touch with the surface of the sieve or of another textile fabric in the time of this interaction.

The drainage elements serve usually also to the support of the sieve or for limiting its track. A mutual abrasion takes place during the operation as a consequence of the contact of the drainage medium (a sieve or another textile fabric) with the drainage element that unfavourably influences partly the service life of the drainage elements, partly also the service life of the drainage medium. This problem gains significance with the increasing width and velocity of the movement of the drainage medium as it will be especially in the modern high speed machines and double sieve machines for the manufacture of paper and cardboard. The drainage elements cause the removing of water according to its construction either by a wiper or suction effect or by a combination of the same.In that the suction effect is created either by the construction of the drainage element itself or by the underpressure that is created by the suction pump. There serves as an example of the above mentioned drainage elements for instance cylinders, draining bars, vacufoils, suction boxes, baffles (deflectors), rota belt and so on. The mentioned constructions of the drainage elements influence in a great extent and of the drainage media (the sieve or another textile fabric). It is nevertheless not possible always, with regard to the technical and technologic reasons, to use the drainage elements that with regard to the view point of the abrasion are optimum. The use of register cylinders in the high speed paper machines with polyester sieves form an example of unfitness.It is not succeeded until now in a satisfactory manner to solve the problem of a mutual abrasion of the drainage medium and the drainage element by means of the constructions of the drainage elements. The choice of the materials for the drainage elements and the drainage media had a substantially greater influence for the solution of the problem of the abrasion. One passed over so in the drainage elements from the classic materials that form the functional surface of these elements, as for instance is wood, rubber, copper, steel, to synthetic materials having a great resistance to the abrasion as is for instance polyurethan, polypropylen, low-pressure high-molecular polyethylen and so on in that are added for instance molybdenum disulphide, glass balls and other hard materials.

There was used gradually materials with a greater and greater hardness, as for instance are stainless steel, glass, cast basalt. There took place in the contemporaneous time in the drainage elements the use of materials having the hardness of corundum. It is recommended for instance according to the GFR patent no.

1,239,557 for the lining of the suction boxes to use impermeable, against abrasion resistant crystalic hard matters as are silicon carbide, tungsten carbide, aluminum oxide and so on.

One passes over, as concerns the material of drainage media, in the contemporaneous time steadily more to the use of synthetic materials that are subjected to a lower abrasion on the drainage elements that are lined with hard materials. The phosphore bronze sieves for instance are substituted by polyester drainage textile fabrics and the wool felts are substituted by all-synthetic stab-felts.

The use of synthetic sieves and textile fabrics in combination with a hard surface of the drainage elements namely led to a substantial increase of their service, especially in some sorts of the manufactured papers, nevertheless the problem of the abrasion of drainage sieves and other textile fabrics (further mentioned only as drainage media) was not solved. Especially in papers with a great content of filling agents takes place a fast mechanic wear of these drainage media. The wear of the same influences unfavourably the costs for the manufacture of the paper with regard to the high price of the synthetic drainage elements. The hard materials used for the creation of the surface of the drainage elements are also very expensive and the working of the same is very laborious. These materials are for this ground sometimes used only in the form of inserts in the more soft material.Combinations of materials of this sort on the surface of drainage elements are described for insance in the FGR patent specification no. 2,136,442 and in the USA patent specification no. 3,404,066. The fragility of these hard materials beside this causes the material, in the case of an impact, to delaminate or crack and this damage causes further damage of the drainage medium. There are, as concerns the construction of drainage elements, concerned substantially the drainage elements in the form of cylinders and in the form of draining bars that are alternatively used in the cases where it is necessary to remove a relatively great amount of water from the felting fibrous suspension and further concerns the suction boxes with covers that are provided with openings or cut-outs that are used for removing the water from relatively more dry fibrous fleece or from textile fabrics.It concerns always solid constructions with a hard surface that do not assimilate the movement and the form of the drainage media. An assimilation to the changes of the conditions of the drainage may be in these drainage elements performed only in mechanical and little precise methods as for instance by the decrease of the underpressure, the change of the angle of the drainage off by the removing of some drainage elements. A consequence of the impossibility of assimilation of these elements to the character of the fibrous material and to the conditions of the drainage consists for instance in elution of fine parts of the felted textile fabric, an unevenness of the drainage, relative high costs of the drainage and so on.

The mentioned disadvantages are removed by this invention. The object of the invention consists in drainage elements for removing water from the felted fibrous suspension and from the fibrous fleece in conctact with the drainage medium that are provided at least on a part of the functional surface of the supporting profile with a layer of a hydrophylic gel on the basis of polymers or copolymers of hydrophylic monomers, with advantage on the basis of partially hydrolysed polyacrylonitrile.

The object of the invention consists further in drainage elements for removing water from the felted fibrous suspension and of fibrous fleece in the contact with a drainage medium, as described above, in that the layer of hydrophylic gel has the form of a profile that is partly built in the functional surface of the supporting profile of the drainage element.

The mentioned layer in a further embodiment of the invention consists of some longitudinal profiles that are built in the functional surface of the drainage element whose profiles form with the entering (leading) edge of the drainage element an angle from 0 to 90".

The mentioned layer is according to a further embodiment of the invention formed at least by one belt of hydrophylic gel that is fixed on a supporting profile and that in the direction of the drainage medium overlaps the width of the supporting profile on which it is fixed.

The mentioned layer according to a further embodiment of the invention consists of some belts of hydrophylic gel that are of different length, are fixed on one supporting profile and are situated one on another so that in the direction to the surface of the drainage medium the length of the belts is gradually diminished.

The object of the invention consists further in the described drainage elements for removing water from the felted fibrous suspension and from the fibrous fleece in contact with the drainage medium in that the belts of the hydrophylic gel fasten on the supporting profiles are situated one behind other so that they partly mutually overlap.

The object of the invention consists further in the above described drainage elements for removing water from the felted fibrous suspension and from the fibrous fleece in contact with the drainage medium in that the belt of hydrophylic material is fixed on the supporting profile at least by one end in a sliding man ner.

The supporting profile according to a further embodiment of the invention consists of some plates situated one behind other that arse arranged so that they may perform a mutually oscilatory motion.

The supporting profile according to a further embodiment of the invention is adjustable in the direction to the surface of the drainage medium.

A further object of the invention consists further in drainage elements for removing water from a felting fibrous suspension and from a fibrous fleece in that the layer of hydrophylic material is reinforced with advantage for instance by glass fibres, by soot (black) or by molybdenum disulphide and so on.

It was now with astonishment ascertained in contradistinction to the hitherto applied routes of development that it is possible practically fully eliminate the mechanical wear (abrasion) and the damaging of the drainage media by the use of extreme soft hydrophylic materials (hydrophylic gels). The applicable hydrophylic gels are essentially presented by hydrogels of the type of poly (-2-hydroxyethylmetacrylate), further of the type of substituted polyacrylamide and so on and of the type of a partly hydrolysed polyacrylonitrile.

The constructional embodiment of the invention consists in the creation of a continuous or discontinuous layer at least on a part of the functional surface of the supporting profile of the drainage element. The discontinuous layer has usually the form of profile that steps forth---casually when it is swelled up-from the functional surface of the drainage element. The continuous layer has a form of a belt that is fixed at least by its end on the leading edge to the supporting profile usually in the form of a plate directed in a perpendicular or oblique manner to the surface of the drainage medium or that is to the same parallel and is in this direction adjustable. The supporting profile may also consist of some plates arranged one behind the other that by its setting enable a cascade arrangement of the belt of a hydrophylic material. At the same time the belt of hydrophylic material may be fixed to the first plate and by its length in the direction of the movement of the drainage medium overlap the sum of the lengths of all plates. A cascade arrangement may be according to the invention also achieved by a location of some belts of hydrophylic material of various length one above the other so that their length is gradually in the direction to the surface of the drainage medium diminished.

The individual plates or the supporting profiles situated one behind the other may be arranged so that they shall perform a mutually oscillatory motion.

There is of use in the preparation of layers from the hydrophylic gel according to the invention with advantage the polyacrylonitrile or metacrylonitrile inclusive of binary or ternary polymers that contain at least 80 per cent of acrylonitrile in a molecule of the polymer. The copolymer may contain 90-98 per cent acrylonitrile and 2-20 per cent of another monomere that contains a C = C group and that is polymerizable with the acrylonitrile (for instance acrylamid, vinyl acetate, acrylates, vinyl-lactams and so on). The polymers and copolymers of the acrylonitrile suitable for the creation of an elastic polymer layer may have a degree of hydrolyse from 1 8 to 95 mol per cent conversion with advantage with a temperature below 25"C.

The above mentioned layer of the elastic gel on the basis of polymers and copolymers of acrylonitrile may be in a swelled up state treated by agents that increase the hydrophylity of the surface and with advantage by agents that causes a further hydrolysis or evokes a meshing or another reaction. It is suitable for instance the treatment with a hot mixture of a concentrated sulphuric acid and a glycerol or ethylenglycol, or diethylenglycol or triethyelnglycol.

The layer according to the invention has a primary function of the contacting layer where it has at the same time also a nevertheless important drainage function and with advantage there will be used also on a part of the functional surface of the drainage element that gets not a contact with the drainage medium.

The layer according to the invention works as a solid water film on that the drainage medium floats on a water film of the water that shall be removed. The mechanical wear will be, in the use of drainage element according to the invention, of the drainage media from the metal as also the synthetic materials eliminated and this also in the manufacture of felted fibrous fleeces with the use of highabrasive filling agents.

There is at the same time substantially diminished the consumption of energy for the drive of the drainage medium and this at least by 10 per cent. The invention enables at the same time also a substantial increase of the speed of the paper machine without an exigency of the increase of the consumption of energy. An important contribution of the invention in this circustance consists in that it removes the unfavourable effect that originates in the drainage on the sieve as a consequence of a high specific pressure in the contacting places between the bendings of the wires or of the nap of fabric and the functional surface of the drainage element that amounts some MPa. The contacting layer on the surface of the drainage element is during the operation assimilated to the surface of the sieve and it creates so the drainage effect directly in the weave of the sieve.The hydrophylic character of this contacting layer secures the creation and the holding of a continuous fluid water film which water is dissipated from the fibrous suspension. The above mentioned properties of the drainage elements according to the invention contribute to an intensive, nevertheless economical drainage on the sieve and to a high retention of fine parts of the filling agents.

The drainage element according to the invention enables in all embodiments an easy adaptation to the concrete conditions of the drainage. The supporting profile forms an important constructional part of the drainage element according to the invention that enables to adjust the length of the functional surface and also the shape of the surface of the drainage element and supplies to the element the necessary support on the contacting place.

The annexed drawings show schematically some examples of the embodiment of the invention. The individual drawings illustrate: Figure 1: a front view of the draining element that is provided with a single belt of hydrophylic material, Figure 2: a front view of the draining element that is provided with two belts of hydrophylic material, Figure 3: a front view of the draining element with zoning with means of a supporting profile.

Figure 4: a front view of the draining element that consists of multisupporting profiles provided with hydrophylic belts, Figure 5: a front view of the draining element with a supporting profile of a cylindrical shape, Figure 6: an alternative embodiment with a supporting profile of a cylindrical shape, Figure 7: a front view of the draining element with a variable efficient length of the hydrophylic belt.

Figure 8: an alternative embodiment with some supporting profiles, Figure 9: an alternative embodiment with a cylindrical supporting profile, Figure 10: a front view of the draining element with a combined supporting profile, Figure 11: an axonometric view of the draining element that is provided with hydrophylic material in the form of a cylindrical profile, Figure 12: a front view of the draining element in the form of a suction box, Figure 13: an axonometric view of the draining element that is provided with hydrophylic material in the form of rectangular plates, and Figure 14: an axonometric view of the draining element shown in the front view of Fig. 4.

The drainage element in the wet part of the paper machine (Fig. 1) with the drainage medium 1 (for instance a sieve) that consists of a supporting profile 2 in the form of a broken plate whose upper part includes with the surface of the drainage medium 1 an angle of 45 and further consists of a layer 3 of hydrophylic material in the form of a belt that is fastened to the supporting profile 2 by means of an attaching element 4. The belt is made of partly hydrolysed polyacrylonitrile and is fixed on the entering (leading) side 6 of the drainage element by one end Sa, whereas the second end 5b is superposed over the supporting profile 2 whose length overlaps in the direction of the movement of the drainage medium (sieve) 1. The width of the layer 3 is with advantage 8mm.

According to Fig. 2 the arrangement is similar as shown in Fig. 1, nevertheless the layer 3 of hydrophylic material has the form of a foil having the width of 1 mm (approximately) whose attachment to the supporting profile 2 is performed by means of an attaching element that consists of a groove 8 in the supporting profile 2 and of a fixing rod 1 0.

The loop of the foil is in the groove 8 with the fixing rod 10 and both the ends Saand Sbof the layer 3 of the hydrophylic material in the form of a foil are superposed over the sup -porting profile 2 that unevenly overlaps the same.

A drainage element in the wet part of the paper machine (Fig. 3) that consists of the supporting profile 2 that is represented by a series of plates 2a, 2b, 2c, 2d, 2e and that are normally situated to the surface of the drainage medium 1 and that are adjustable in this direction. The upper part of the first plate 2a is on the entering (leading) part 6 of the drainage element widened against the direction of the movement of the drainage medium 1. In the plate 2a is under the widened part by means of the attaching element 4 that consists of a fixing bar 11 and of fixing belts 1 2 attached the layer 3 of hydrophylic material, in the form of a belt, by the end 5a. The belt overlaps by its length in the direction of the movement of the drainage medium 1 the length of the supporting profile 2.The width of the layer 3 of the hydrophylic material is with advantage about 11 mm. The belt is made of meshed poly/2-hyd roxyethylmetacry- late/.

The drainage element according to Fig. 4 in the wet part of the paper machine consists at least of two layers 3', 3" and so on of hydrophylic material that are fastened to the supporting profiles 2', 2" and so on in the form of plates arranged one behind the other and that are directed to the surface of the drainage medium 1 with an angle of 35 and are in this direction adjustable. The belts 3', 3" and so on are fastened always on the entering (leading) side 6 of the relevant supporting profile 2. At the same time the length of the individual belts 3', 3" and so on is such that the free ends 5b that are superposed over the supporting profiles 2 partly mutuaily ormers lap and form so the cascade-form of the surface.The thickness of the individual belts is about 2 mm and their number in the drainage element complies with the location of the element in the individual parts of the wet portion of the paper machine. The material of the belt 3' consists partly of hydrophylic polyacrylonitrile, the material of the other belts consists of a substituted polyacrylamide.

Besides other advantages, that are above mentioned, this arrangement enables to use minor working stress of the drainage medium 1.

Two layers 3 of hydrophylic material having various length are according to Fig. 5 fastened on the supporting profile 2 so that in the direction to the surface of the drainage medium 1 the length of the belts 3', 3" is gradually diminished. The supporting profile 2 has the form of a small cylinder that is adapted for a swivelling in both directions.

The belts 3', 3" are fastened on the supporting profile 2 in an analogous manner as is shown in Fig. 2. The thickness of the belt 3' is with advantage about 2 mm and the thickness of the belt 3" is with advantage about 15mum.

According to the Fig. 6, is to the supporting profile 2 in the form of a swivelling small cylinder, as shown in Fig. 5, fastened a layer 3 of hydrophylic material having a thickness of about 20 mm.

The drainage element with an adjustable length according to Fig. 7 consists of a supporting profile 2 in the form of a plate that is located parallely with the surface of the drainage medium 1. The layer 3 of hydrophylic material is fastened by the end 5a under the plate on the entering (leading) side 6 of the drainage element, whereas the second end Sb is shiftingly located below the plate on the following part 7 of the drainage element. The surface element that is functional is by the shifting of the second end 5b lengthened or shortened that enables to control the drainage ability of the element in a large scale (range).

The arrangement according to Fig. 8 is analogous to the arrangement shown in the Fig. 4, nevertheless the supporting elements 2', 2" and so on are one from another so retracted that between the same originate free gaps 13', 13" and so on intervene the ends 5b of the belts 3', 3" and so on. There takes place by sealing of these gaps 1 3 a creation of a sucking effect by means of the columns of water in the gaps 13', 13" and so on.

The drainage element according to Fig. 9 in the form of a cylinder has a metal core 1 5 having a diameter of about 1 50 mm on a shaft 1 7 whose ends are situated on the bearings 18. The functional surface 21 of the supporting profile 2 is formed by a contacting layer 3 of hydrophylic gel on the basis of a partly hydrolyzed polyacrylonitrile having a thickness of about 3mm. A so created drainage element that is used in a paper machine with a phosphor-bronze longitudinal sieve for the manufacture of graphic papers/squared papers/ instead of the commonly used register cylinders removes the abrasion of the sieve on the register cylinders. It eliminates at the same time also the back splattering of the water into the sieve.

The drainage element (Fig. 10) in the form of a draining bar consists of a supporting profile 2 that is fixed to T-beam 22 having a functional surface 21 that is divided into a supporting part 23 and a drainage part 26 that is deflected from the sieve with an angle from 0 5 to 5" according to the location of the bar. The functional surface 21 is provided with a layer 3 of hydrophylic gel of the type of a copolymer of ethylenglycolmetacrylate so that the layer 3 covers the supporting part 23 and one third part of the drainage part 26 of the functional surface 21.The so created drainage element is suitable to be caused in the register part of the high-speed paper machine with a polyester sieve for the manufacture of newsprint paper instead of draining bars made of hard material of ceramics where at the same time the supporting profile 2 is made from a cheap material, with advantage from wood. The use of these drainage elements causes a substantial decrease of the mechanical wear in the register part of the machine and the decrease of the consumption of energy for the drive of the sieve.

The drainage element shown in Fig. 11 in the form of a draining bar that consists of a supporting profile 2 made of low-molecular polyethylen that is situated on a T-beam 22 has in the supporting part 23 of the functional surface 21 an inserted contacting layer 3 made of hydrophylic material in the form of a profile 3a with a circular section. The profile 3a has a diameter of about 1 5 mm and it is conducted along all the length of the supporting profile 2 parallelly with its entering (leading) edge 6. The profile 3a is inserted into a cut out 8 that is made in the supporting profile 2. The advantage of this embodiment of the invention consists in the removing of the abrasion of the drainage medium on the draining bar and a relative decrease of the consumption of energy for the drive of the sieve.The profile 3a is in this case made of hydrogel on the basis of a substituted polyacrylamide.

A drainage element shown in Fig. 1 2 in the form of a suction box in that it is provided with a cover 1 9 having openings 20 that are represented by cutouts arranged in the form of a "fishbone". The cover 1 9 of the suction box 1 6 is provided with a layer 3 of hydrophylic gel on the surface that is formed forward turning to the surface of the drainage medium 1. The used hydrogel for the layer 3 of the hydrophylic gel is made on the basis of a partly hydrolysed polyacrylonitrile. The layer 3 of the hydrophylic gel consists in this case of a lower close meshed part and of an upper surface part having a structure with a considerable prevalence of a hydrophylic amorphous component. The layer 3 provides the same system of openings 20 as the cover 1 9 of the suction box 16. This drainage element enables a considerable decrease of the consumption of energy and eliminates the abrasion of the drainage medium in comparison with the usual type of the suction box.

The arrangement shown in Fig. 1 3 is analogous as in Fig. 11, the contacting layer 3 has nevertheless the form of some profiles 3a, 3b and so on having a rectangular section that are located manually parallelly and perpendicularly to the entering (leading) edge 6 of the drainage element. The layer 3 is here made of hydrogel on the basis of a partly hydrolysed polyacrylonitrile.

Claims (11)

1. Drainage elements for removing water from a felting fibrous suspension and from a fibrous fleece in contact with a drainage medium, wherein they are formed at least on a part of the functional surface of a supporting profile by a layer of hydrophylic gel on the basis of polymers or copolymers of hydrophylic monomers, with advantage on the basis of a partly hydrolyzed polyacrylonitrile.

2. Drainage elements as claimed in claim 1, wherein the layer of a hydrophylic gel has the form of at least one profile that is partly built in the functional surface of the supporting profile of the drainage element.

3. Drainage elements as claimed in claim 1 or 2, wherein the layer of the hydrophylic gel consists of some longitudinal profiles that are partly built in the functional surface of the drainage element which profiles form with the entering (leading) edge of the drainage element an angle from 0" to 90 ,

4. Drainage elements as claimed in claim 1, wherein the layer of the hydrophylic gel is represented at least by one belt of hydrophylic gel that is fixed on one supporting profile and that in the direction of the movement of the drainage medium overlaps the width of the supporting profile on that it is fixed.

5. Drainage elements as claimed in claim 4, wherein the layer of the hydrophylic gel consists of belts of hydrophylic gel that are of different lengths and that are fixed on a supporting profile and that are situated one on another so that in the direction to the surface of the drainage medium the length of the belts is diminished gradually.

6. Drainage elements as claimed in claim 4, wherein the layer of the hydrophylic gel consists of belts of hydrophylic gel that are fastened on the supporting profiles that are situated one behind another so that the belts parly mutually overlap.

7. Drainage elements as claimed in claim 4, wherein the layer of the hydrophylic material is made by a belt that is fixed on the supporting profile at least by one end in a sliding manner.

8. Drainage elements as claimed in claim 5 or 6, wherein the supporting profile consists of some one behind another situated plates arranged so that they may perform a mutually oscillatory motion.

9. Drainage elements as claimed in any one of claims 1 to 4, wherein the supporting profile is adjustable with regard to the surface of the drainage medium.

10. Drainage elements as claimed in any one of claims 1 to 8, wherein the layer of the hydrophylic material is reinforced with advantage for instance by glass fibres, by soot (black) or by molybdenum disulphide.

11. Drainage elements for removing water from a felting fibrous suspension and from a fibrous fleece in contact with a drainage medium substantially as described herein with reference to the accompanying drawings.