US 3214331 A
Abstract available in
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Description (OCR text may contain errors)
Oct. 26, 1965 D. B. WICKER 3,214,331
DOUBLE FABRIC PAPER PRESS Filed March 14, 1963 2 Sheets-Sheet 1 FROM WEB FORMER TO DRYER i i C J 64 so so so so 32 58 X fXfX fX 30 6 E L 623 F|G.2 1
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United States Patent 3,214,331 DOUBLE FABRIC PAPER PRESS .Dan B. Wicker, Loudonville, N.Y., assignor to Hnyck Corporation, Stamford, Conn., a corporation of New York Filed Mar. 14, 1963, Ser. No. 265,204 8 Claims. (Cl. 162-358) This invention relates to fabric presses of papermaking machines and more particularly to novel combinations and arrangements of felts for use in such presses.
This invention relates more specifically to the step in which water is removed from moist, freshly formed paper sheets by running them between rotating cylindrical in which the roller that runs inside the felt comprises a hollow cylinder with perforations therethrough; a suction box with vacuum is utilized inside the hollow cylinder to apply vacuum to the felt and paper sheet at and adjacent the nip region. The openings in the perforated roll provide void space into which the expressed water moves momentarily while passing beyond the nip region. .Under usual circumstances, most of the Water is thereafter flung out of the roll by centrifugal force and is caught by a guard pan and removed from the system. Some of the water, of course, may be drawn by the vacuum within the suction box and removed through the vacuum pump. Another variation of the suction press heretofore suggested used a wire cloth traveling inside the felt in order 'toprevent marking of the paper sheet by the openings in the suction press roll. However, the relatively incompressible nature of the wire cloth prevented it from achieving the expressed purpose to the desired extent, and it did not carry an adequate amount of water away from the nip.
In an improved apparatus known as a fabric press, plain rollers are used, the sheet being passed therebetween in combination with aconventional felt. I one embodiment there runs inside the felt a mat or fabric with voids therein to provide the space to receive the expressed water while it passes through and beyond the nip region. Such apparatus anticipates the water remaining in the voids of the fabric and being removed in another part of the path of travel by the action of centrifugal force. Another embodiment of the fabric press provides for the expressed water largely to pass through the voids of the fabricand be deposited as a film on the surface of the cooperating roller. A wiper or scraper thereafter removes the film from the roller such that a substantially waterfree surface moves into the ingoing side of the nip.
It is evident that in both modifications of the fabric .press the major consideration is provision of the necessary void space for expressed water to occupy while passing through and beyond the nip region. If such space is not provided, the squeezing action results in a backup and accumulation of excess water at the ingoing side of the nip in such a manner as to dilute the sheet and cause a disturbance or destruction of its formation in an action commonly spoken of as crushing. In the embodiment of the fabric press that anticipates the expressed water largely remaining in the fabric that runs inside the felt, it is desirable to enhance the forces that retain water within this structure. In the embodiment that provides for the water to pass through the fabric and onto the surface of the cooperating roll, it is desirable for the fabric to retain a minimum amount of water and for a maximum amount to be transmitted to the roll surface. In all embodiments of the fabric press the provision of void volume is a major consideration, and, hence, the felt preferably should provide the void space but minimize the possible transmission of water in such space back into the sheet after passing through the emerging side of the nip. In all embodiments, it is desirable that the felt be capable of receiving water from the sheet as pressure is imposed thereon, but also be capable of easily releasing it to the fabric and through the fabric to the roller surface that runs therein. The inside fabrics or mats mentioned all are relatively incompressible in order that the void volume be preserved throughout the high pressure region of the nip. None of the fabrics or mats now in use provide a barrier to impede transfer of water through the structure and onto the surface of the inside roll. Therefore, the embodiments disclosed have the disadvantage of the structure of the foraminate band striking through the felt to emboss and imprint on the paper sheet that is pressed therewith to produce a condition commonly spoken of as marking. Furthermore, in the embodiment of the fabric press that presupposes the retention of the expressed water within the voids of the inside fabric (rather than its transfer to the surface of the inside roll) there is a disadvantage of uninhibited transfer of water entirely through the fabric to a point on the surface of the roll that does not conform to the concept of the disclosure.
It is an object of this invention to provide improved apparatus and a method for removing water from awet paper Web.
It is another object of this invention to provide fabric presses having combinations and arrangements of press felts which will retain increased amounts of water which may be pressed from wet paper webs, and transport the water through the nip region of press rolls to selected de- Watering regions.
A further object of this invention is to provide fabric presses which will minimize the extent of rewetting of a pressed paper web and which will permit press rolls to be operated at higher press loads without crushing the paper web.
Other objects will be apparent to those skilled in the art from reading the following description taken in conjunction with the accompanying drawings, in which:
FIGURE 1 is a diagrammatic view of a press section of a papermaking machine;
FIGURE 2 is a schematic cross-sectional view of one embodiment of this invention taken along line A-A of FIGURE 1, being two press felts as used to transport a wet paper web between press rolls;
FIGURE 3 is a schematic cross-sectional view of an alternate embodiment of this invention taken along line A-A of FIG. 1;
FIGURE 4 is a schematic cross-sectional view of still another embodiment of this invention taken along ,line A-A of FIG. 1;
FIGURE 5 is a schematic plan view, on an enlarged basis, of an embodiment of a duplex press felt useful in this invention;
FIGURE 6 is a cross-sectional view of the press felt of FIG. 5 taken along line 6-6;
FIGURE 7 is another cross-sectional view of the press felt of FIG. 5 taken along line 7-7;
FIGURE 8 is an enlarged, schematic, plan view of another duplex press felt useful in this invention;
FIGURE 9 is a cross-sectional view of the press felt of FIG. 8 taken along line 9-9;
FIGURE 10 is another cross-sectional view of the press felt of FIG. 8 taken along line 10-10;
FIGURE 11 is an enlarged, schematic, plan view of another press felt useful in this invention;
FIGURE 12 is a cross-sectional view of the press felt of FIG. 11, taken along line 12-12;
FIGURE 13 is another cross-sectional view of the press felt of FIG. 11 taken along line 13-13; and
FIGURE 14 is an enlarged, schematic cross-sectional view of another duplex press felt useful in this invention.
It has been found that unexpectedly improved results in water removal may be obtained in the press section of papermaking machines by using two press felts running one inside the other to transport a wet paper web between press rolls. Most of the water is retained in the press felts and is removed at a point beyond the press rolls by well known means such as described below.
The objects of this invention may be accomplished by the use of a fabric press in which two press felts are used in combination as a papermakers wet felt means to carry a moist paper web between press rolls where water is forced fom the web into the two felts each of which then transport a portion of the water to regions where the water is removed. Each of the felts is capable of re- 'taining water within its structure against the centrifugal forces normally encountered in the press section of papermaking machines. That .is, the two felts will retain as much water as is received in a fabric press, about 30 to 70% by weight of the felts, and will not release any appreciable part of this water at usual press speeds. The
'felt moisture content at which throwout of water begins,
excluding the effect of wet edges, is termed the threshold moisture. Depending on the tightness of weave, material of construction, etc., the felts operable in the practice of this invention have threshold moistures up to about 70% at centrifugal forces about 85 times the force of gravity.
The capability of the felts to retain water may be due to the tightness of weave and style of weave of the fabric composing the felt. For instance, a fabric may be formed in a tight weave, such that the interstices between the yarns comprising the fabric are of such small size that the capillary attraction of the woven fabric is sufiicient to equal or exceed the centrifugal forces applied. The ability to retain water against centrifugal forces may also be due to the absorptivity of the yarns of which the felt is made. For instance, wool which has a high absorption for water will more easily retain water against the centrifugal forces normally encountered in the press section of papermakingmachines.
The felts useful in the practice of this invention include both simplex and duplex felts. A simplex felt is composed of a single layer of felt, or a single layer of fabric which has been fulled. A duplex felt is composed of two layers of felt or two layers of fabric which have been fulled. A duplex press felt for use in the practice of this invention desirably has one layer of low void volume which is well felted and a second layer of high void volume which is less felted. The low void volume layer may be soft or flexible, and the high void volume layer may be hard or stiff. It is preferred that the low void volume layer be highly compressible, and that the high void volume layer be less compressible, the degree of compressibility of the latter being suflicient to avoid marking the wet paper web. The simplex felts may be selected to have the characteristics of a high or low void volume layer.
The preferred materials for the yarn of a low void volume layer are predominantly natural animal fibers, such as wool. The high void volume layer desirably contains a significant amount of synthetic polymer fibers, such as polyamides, polyesters, and the like. Desirably the synthetic fibers constitute from about 15 to 100% of the high void volume layer, although lesser ratios may be used. The preferred materials for the yarns of the low void volume layer are also predominantly natural animal fibers, such as wool. Simplex felts containing a significant amount of synthetic polymer fibers, such as polyamides, polyesters, and the like are operative in the invention. Desirably the synthetic fibers constitute from about 15 to of the simplex felt, although lesser ratios may be used.
In the practice of this invention in a double felt press, one felt runs outside the other felt in contact with the wet web. The other felt runs inside the one, in contact with the side of the outside felt that does not contact the wet web and in contact with the inner press roll.
Either of the inside and outside felts may be a simplex or duplex felt as described above. That is, the inner felt may be a simplex felt and the outer felt may be a simplex felt or a duplex felt. Conversely the inner felt may be a duplex felt and the outer felt may be a simplex felt. The combination of an inside duplex felt with an outside duplex felt is contained in the co-pending application of D. B. Wicker, Serial No. 253,549, filed January 24, 1963.
As shown in FIGURE 1, moist paper web 2 from the web forming section (not shown) of a papermaking machine is carried by endless press felts 4, 6 between press roll 8 and inside press roll 10. The pressed paper web then continues on to the dryer section (not shown). Part of the expressed water passes through the press felts 4, 6 and is transferred to the surface of inner press roll 10 from which it may be removed by Wiper or doctor blade 11. Part of the water is retained in the felt and may be removed as press felts 4, 6 pass compressed air supply conduits 12, 14, respectively. The water desirably is blown into receiving trays 16, 18 from which it drains. Water may also be removed as felts 4, 6 pass over suction boxes 20, 22, respectively, and enter the suction boxes from which it drains.
FIGURE 2 shows one embodiment of this invention. FIGURE 2 is a schematic cross-sectional view of the wet paper web and supporting felts as they pass between press rolls 8, 10. In this embodiment simplex felts 30, 32 are used as both inside and outside felts. Felt 30 runs inside felt 32 and contacts inner press roll 10. Felt 32 runs outside of felt 30 and contacts wet paper web 2.
FIGURE 3 shows another embodiment of this invention, being a cross section of the press felts and wet paper web as they pass between the press rolls. In this embodiment simplex felt 34 runs inside duplex felt 36 and is in contact with press roll 10. Duplex felt 36 is made up of high void volume layer 38 and low void volume layer 40. High void volume layer 38 runs in contact with inner felt 34; low void volume layer 40 runs in contact with wet paper web 2. Because of the small void volume of layer 40, water which is pressed from wet paper web 2 into layer 40 is forced into high void volume layer 38, and some of the water passes into inner felt 34. It is the nature of this embodiment that there is little tendency for water to return from felt 34 or high void volume layer 38 through low void volume layer 40 and back into the Wet web after the pressure of the press rolls is removed.
FIGURE 4 shows still another embodiment of the combination of press felts useful in the fabric press of this invention. In this embodiment the inner felt 42 is a duplex felt made up of low void volume layer 44 and high void volume layer 46. High void volume layer 46 runs in contact with outer simplex felt 48 which is in contact with wet paper web 2. Low void volume layer 44 runs in contact with inner press roll 10. It is char acteristic of this embodiment of the invention that water pressed from wet web 2 into and through simplex outer felt 48 and into the high void volume 46 of inner felt 42 has little tendency to pass through the low void volume: layer 44 of felt 42. Thus, less water is transferred to the inner press roll when this embodiment is used.
A preferred embodiment of a duplex felt useful in this invention is shown in FIGURES 5, 6 and 7. Duplex felt 50 is made up of fine textured, low void volume felted and provide good cushion.
layer 52 and coarse textured, high void volume layer 54 which are woven together into a unitary fabric by yarns 56. Fine layer 52 is made up of yarns 58 and 60, which comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. The yarns 58 and 60 are of soft, low twisted construction, are easily In this embodiment layer 52 is preferentially disposed on the paper web-contacting side of duplex felt 6 and on the press-roll-contacting side of duplex felt 4.
Layer 54 is made up of yarns 62 and 64 which comprise 'a plain weave in a relatively coarse, high void volume structure. Yarns 62, 64 are of relatively incompressible construction, and if made of wool are hard twisted and are less easily felted than yarns 58, 60.
Yarns 56 stitch the two layers 52, 54 together. If yarns 56 were absent, layers 52 and 54 would come out of the loom as two entirely separate pieces. With the yarns 56 joining them, layers 52 and 54 have the character of one fabric with a fine, Well felted structure with low void volume for layer 52, and a coarse, less felted high void volumestructure for layer 54.
An alternate embodiment of a duplex felt useful in this invention is the 4-harness satin shown in FIGS. 8, 9 and 10. In this embodiment the duplex felt 70 is formed of yarns 72, 74. Yarns 72 have a soft twist, a high .tendency to felt and are compressible to provide cushion.
Yarns 74 have a hard twist, have less tendency to felt and are less compressible. Yarns 72 are disposed predominantly adjacent to face side 71 of press felt '71 andso contact wet paper web 2. Due to the predominant layering of yarns 72, 74, felt 70 has a fine, felted, low void volume layer on face side 71, and a coarse layer with a high void volume on rear side 73.
Another embodiment of the duplex felt useful in this invention is shown in FIGURES 11, 12 and 13. The felt 80 is comprised of yarns in two distinct woven patterns. Yarns 82, 84 comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. Yarns 82 are of soft, low twisted construction, are easily felted and provide cushion. Yarns 82 are preferntially disposed to face side 86 of felt 80. Yarns 84 are highly twisted, less susceptible to felting and less compressible. Yarns 84 are preferentially disposed on rear side 83 of fabric 80.
Yarns 90, 92 comprise a plain weave in a coarse, high void volume structure. Yarns 90 are similar to yarns 82 and are disposed predominantly on face side 36. Yarns 92 are similar to yarns 84 and are disposed predominantly on rear side 88. Yarns 94 comprise looking stitches inserted at regular intervals in order more firmly to interlock the two woven elements of felt 80. Without yarns 94 the two woven elements would be loosely interlocked; with the locking stitches therein, the final felt 80 has the character of one fabric with a fine, well-felted, low void volume structure disposed preferentially to face side 86 and a coarse, less felted, high void volume structure preferentially disposed to rear side 88.
Other weaves are operable in the practice of this invention, such as a S-harness or 6-harness satin, or the like, for the low void volume layer, and a basket weave, twill, broken twill, or the like for the high void volume layer. In general, any two layered felt or fabric is operable in the practice of the invention which has one layer of a fine, felted, compressible, low void volume structure and a second layer of a coarse, high void volume, less felted and less compressible structure.
Another embodiment of this invention is shown in FIGURE 14. Duplex felt 100 desirably comprises a scrim or base fabric 102 woven in the manner described above or woven with other weaves such as a plain weave, a twill weave, a 4-harness satin, or the like. A nonwoven batt 104 formed by carding machines or garnetts may be applied to scrim 102 by the use of barbed needles which so entangle the batt with the woven structure that there is a high degree of adhesion between the two layers. In this combination, the batt side, or face side 106 of the felt may be provided with a denser structure and lower void volume than the scrim, or rear side 108. Moreover batt side 106 may be made denser than textile structures that are made by weaving alone. The water removal effect of the needled batt structure will be at least as great and, in most instances, may be greater than woven structures.
Although the duplex felts useful in this invention are operable in their natural state, their effectiveness may be enhanced by treating them to make them water attractive or water repellent. For instance, by treating the web contacting felt to render it water repellent the tendency of water to return from the roll contacting felt into the web contacting felt is reduced. Thus, the re-wetting of the paper web as it emerges from the press rolls is reduced. The repellent nature of the paper contacting felt will not prevent water from being forced from the wet paper web through it by the mechanical pressure applied by the press rolls. Where it is desired that as much water as possible be retained in the felts, their treatment to render them water receptive will increase their water retention capability.
There are various methods of rendering textile structures, including fibers, yarns and fabrics, Water repellent. One method comprises the application of fluorocarbon, such as Minnesota Mining & Manufacturing Corporations compound FC-208. This compound has the chemical formula C F and is a modified acrylate. It is available as a non-ionic emulsion of the fluorocarbon resin containing 28% solvent. An impregnating solution may be prepared by dissolving 0.1 part of sodium chloride or sodium acetate in parts by weight of a bath. The fluorocarbon resin emulsion equal to 3.5 parts'by weight of the bath is added with sufiicient agitation to distribute the resin. A solution is prepared containing one part of fluorocarbon solids which is sufficient to fairly wet a fabric. Isobutanol may be added to the solution in'the amount of 4% of the bath volume as a fugitive wetting agent if the fabrics do not wet out readily. The remainder of the bath is water. After the material has been thoroughly wetted, the bath solution is drained, and the material is brought to a wet pick-up of about 100% of its dry weight. The treated material is then dried and cured at 250-300 F.,for five to ten minutes to provide a dry weight pick-up of about 1%. Thereafter, the resultant fabric is water repellent, has a noticeably decreased tendency to absorb water and has an increased tendency to release or shed water.
Another method of treating textile materials to make them water repellent is to apply an organo-polysiloxane containing a zirconium or tin salt. Such a material is available under the name Cravenette SWS with catalyst 54. The latter material is an emulsion consisting of 30% by weight of silicone solids and employing a metallic organic salt as a catalyst. The materials to be treated are immersed in a bath and extraneous material removed from it. The repellent in the amount of 5% by Weight of dry material is diluted with its own volume of water and distributed throughout the bath by agitation. The catalyst in the amount of 2% by weight of the dry material is similarly diluted and added to the bath. The pH of the bath varies between about 2.5 and 7. The material is retained in the bath for 30 minutes or until the milky appearance caused by the repellent disappears and is then removed and dried. No thermal cure is required because the resin cures at room temperature. A dry weight pick-up of about 1% is obtained and will produce the water repellent properties desired.
Another type of water repellent treatment for textile materials comprises the application of stearamidomethylpyridinium chloride. A representative bath is prepared by dispersing at -l40 F. an amount of the compounds equivalent to 6% of the weight of the bath, using an amount of solvent equivalent to 30% of the final bath volume. The bath is continuously stirred and diluted to the desired volume with water. Sodium acetate in the amount of of the weight of the compound added is dissolved separately in water and added to the bath. The final bath temperature should be about 100 F. A sufficient amount of liquid is added to cause a wet weight pick-up-of 60% of the dry weight of the material. After the material is dried it is cured at 300 F. for two minutes to provide a final dry weight pick-up of about 4%. The resultant fabric will thereafter show water repellent properties.
Other methods of treating textile materials to render them water repellent involve the application of such material as Atcodri Z which is a mixture of a zirconium salt and a paraffin wax. The zirconium salt may be zirconium stearate.
Still another method of making textile materials water repellent is to apply thermo-setting resins, such as Phobotex FTC along with a catalyst.
A method for treating textile materials to render them more water receptive comprises the application of an anionic exchange resin containing polyoxyethyl chains and ionic groups. Such a material is available under the name Aston 108 from Onyx Oil & Chemical Company. It is applied to the material in the form of soluble polymers containing reactive groups together with soluble multi-functional cross-linking agents. The reaction is carried out at elevated temperatures up to about 212 .F. A solution containing 25% of Aston 108, a crosslinking agent in the ratio of 7:3 to the Aston 108, and about 0.5% of an aromatic polyglycol ether, such as Neutronyx 600 is applied to the material. Thereafter the material is dried and cured with infra-red radiation at as high a temperature as it will withstand without damage thereto, but in any event at 212 F. or higher.
The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. For instance, while the invention has been described for use with wet paper webs in papermaking processes, it is applicable as well to other absorbent materials in related processes.
What is claimed is:
1. Paperrnakers wet felt means for use in the press roll section of a papermaking machine which comprises the combination of first and second felts, said first felt running inside said second felt and being a duplex felt formed of a felted first layer which has a relatively low void volume and is compressible and a second layer having a relatively high void volume and being less felted and less compressible than said first layer, said second layer of said first felt running in contact wtih said second felt,
said void volumes of first and second layers being high or low relative to each other.
2. A double felt press for removing increased amounts of water from a wet web of paper and similar absorbent structures in the papermaking and related industries comprising a pair of cooperating press rolls, and meansto transport the wet web between said press rolls comprising first and second felts, said first felt running inside said second felt and being a duplex felt comprising a felted, compressible, relatively low void volume first layer and a less felted, less compressible, relatively high void volume second layer, said void volumes being high and low relative to each other, said second layer of said first felt being in contact with said second felt, whereby water pressed from said wet web through said second felt passes into said second layer of said first felt and is retained therein.
3. A double felt press as described in claim 2 wherein the wet webcontacting felt is water repellent.
4. A double felt press as defined in claim 2 wherein the wet web contacting felt is water repellent and the other felt is water receptive.
5. A double felt press as described in claim 2 wherein said first and second felts are water receptive.
6. A double felt press as described in claim 2 wherein both of said first and second felts are subjected to dewatering treatment at points remote from said web.
7. An improved fabric press for removing increased amounts of water from a wet web of paper and similar absorbent structures in the papermaking and related industries comprising a pair of cooperating press rolls, and means to transport the wet web between said press rolls comprising first and second felts, said first felt being a simplex felt and running inside said second felt, said second felt being a duplex felt comprising a felted, compressible, relatively low void volume first layer and a less felted, less compressible, relatively high void volume second layer, said first layer of said second felt running in contact with said wet web, said void volumes being high and low relative to each other, whereby water pressed from said wet web through said first layer of said second felt passes into said second layer of said second felt and is retained therein and hindered from returning to said wet we 8. A double felt press as described in claim 2 wherein said second felt is a simplex felt.
References Cited by the Examiner UNITED STATES PATENTS 3,093,535 6/63 Brauns et al. l62358 FOREIGN PATENTS 624,831 8/61 Canada. 1,198,432 6/59 France.
DONALL H. SYLVESTER, Primary Examiner. MORRIS O. WOLK, Examiner.