US3075274A

US3075274A - Method of making and finishing papermaker's felts

Info

Publication number: US3075274A
Authority: US
Inventors: Louis R Mizell
Original assignee: Appleton Mills
Current assignee: Appleton Mills
Priority date: 1959-09-23
Filing date: 1959-09-23
Publication date: 1963-01-29
Anticipated expiration: 1980-01-29

Description

Jan. 29, 1963 R. MIZELL 3,075,274

METHOD OF MAKING AND FINISHING PAPERMAKER'S FELTS Filed Sept. 23. 1959 INVENT OR LOUIS R.M|ZELL" ATTORNEU Uited States Patet 3,075,274 METHOD OF MAKING AND FINISHING PAPERMAKERS FELTS Louis R. Mizell, Montgomery County, Md., assignor to Appleton Mills, a corporation of Wisconsin Filed Sept. 23, 1959, Ser. No. 841,770 3 Claims. (Cl. 28-74) This invention relates to an improved textile fabric consisting predominantly of synthetic fibers and to improved methods of finishing same and more particularly to woven papermakers felts and to methods for making such felts having smooth felt surfaces to prevent the felt from marking paper sheets in the presses of paper machines while water is being pressed from the paper and felt.

Papermakers felts are employed in the manufacture of paper to pick up freshly laid web of wet paper or pulp from the forming wire; to conduct the web through the paper finishing presses; and to remove water from the paper in press sections or the like. Papermakers felts must have a high degree of dimensional stability, properties permitting the felt to pick up and retain the fibers of the paper during the processing thereof and be of sufficient porosity to permit rapid removal of water from the freshly laid pulp. These properties of the felt must be uniform throughout the felt if the paper produced or finished on the felt is to be uniform in quality.

=Felts employed in the papermaking industry have been predominantly all natural wool as experience has shown that natural wool felts have the necessary strength, closeness of weave and dimensional stability to render them suitable for such use. Notwithstanding the current use of paperrnarkers felts woven from natural Wool or blends of wool and synthetic materials containing suflicient wool to render the fabric fullable, such felts have been an expensive item for the industry as the life of a good allwool felt is relatively short.

In United States patent application Serial No. 767,109, L. R. Mizell, filed October 14, 1958, a method of making improved papermakers felts consisting substantially entirely of synthetic thermoplastic fibers is disclosed whereby finished felts having better dimensional stability, improved wear resistance, better Water removal properties, and improved chemical and bacterial resistance over the conventional wool-containing woven felts are produced.

With the discovery of a method of making papermakers felts predominantly of synthetic thermoplastic fibers, the papermaking industry was provided with felts having improved physical properties; however, such felts presented problems in providing the synthetic felts with satisfactory surfaces which would not mark the paper in the presses of paper machines.

Papermakers felts composed of from about 50% to 100% wool fibers can be satisfactorily finished by conventional fulling processes. Pulling involves felting of the wool fibers whereby the fibers in the warp and the filling yarns migrate and intermingle with one another. Felting brings about fabric shrinkage and consolidation, aids in stabilizing the structure of the felt, and most important, it produces a smooth felt surface hiding or obscuring the woven structure.

Papermakers felts made from high percentages of synthetic fibers and especially felts composed of substantially 100% synthetic fibers cannot be fulled or felted to obtain a smooth felt surface.

It is, therefore, a primary object of the invention to produce thermoplastic synthetic fiber felts with smooth, flat, uniform surfaces which may be satisfactorily employed in papermaking machines without marking the paper produced thereon.

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It is a further object to provide such a method and a synthetic textile fabric made thereby having a uniform surface without decreasing any of the desirable functional properties of felts composed predominantly of synthetic fibers.

It is a further object of the present invention to provide a finishing process for synthetic textile fabrics that are dimensionally stable in thickness as well as in length and width and which will maintain their dimensional stability during operation on papermaking machines.

A further object is to provide such a method and a textile fabric made thereby wherein the felt structure is stabilized thereby preventing yarn slippage.

A further object of the present invention is to provide a process for finishing synthetic papermakers felts which may include subjecting the fabric to a resin or latex treatment.

A further object is to provide a method of making synthetic papermakers felts having improved splice holding properties to reduce splice slippage and thereby provide longer life for the felt in operation.

Further objects and advantages are to provide improved papermakers felts and processes of making same having improved Water removal properties; that may be woven from coarser yarns thereby reducing the cost and speeding the production of such felts.

These and other objects and advantages of the invention are provided by the method of making and finishing papermakers felts composed predominantly of thermoplastic synthetic fibers or filaments comprising weaving a fabric from yarn or fibers composed substantially entirely of synthetic thermoplastic synthetic fibers, heatsetting the fabric to stabilize the length and width dimensions thereof and subjecting said fabric to heat and pressure to compress the felt in thickness from about 30% to about 60% based on the thickness of the felt in the heat-set state.

The invention will be more fully described with reference to the illustrated embodiment of the invention diagrammatically showing apparatus suitable for carrying out the finishing of woven synthetic felts in accordance with the teachings of the invention.

In making papermakers felts in accordance with this invention, a wide variety of synthetic thermoplastic fibers, filaments or blends of natural and synthetic fibers or filaments may be employed in the process as long as the synthetic fibers are capable of taking and retaining a set at a temperature above that ordinarily encountered in the use of papermakers felts. Among the fibers hav ing such qualities are fibers known as Dacron, nylon, dynel, Orlon and the like.

Dacron is a synthetic polyester fiber made by the condensation of dimethyl terephthalate and ethylene glycol; dynel is a synthetic fiber made by the copolymerization of, for example, 40% acrylonitrile and 60% vinyl chloride; nylon is a term applied to a series of fibers made of polyamide resins typically formed by the polymerization of a hexamethylenediamine salt of adipic acid; while Orlon is a synthetic fiber made principally from poly acrylonitrile.

The synthetic fibers enumerated are often supplied by the manufacturers in the form of staple fibers to resemble a natural wool fiber. Such fibers may be straight length fibers or crimped, curled or spiraled to more nearly approximate the natural wool fibers they replace and the fibers can be lustrous, dull, or semi-dull in appearance.

Also Dacron, nylon, Orlon and certain other thermoplastic synthetic materials are supplied in multiple fila ment yarn form. These materials may be employed in making papermakers felts in the supplied form or they can be textured or'bulked prior to weaving. v r

While there are a large number of synthetic fibers which may be employed satisfactorily in making papermakers felts in accordance with the teachings of this invention, the preferred fibers are Dacron or nylon as they have been found to be the most durable fibers in papermakers felts. The Dacron or nylon or a combination of these fibers can be used in both the warp and the filling yarns, or one of the fibers can be used in the warp and the other in the filling.

When staple fibers are employed in the process of the invention some of the fibers to form guide lines for the felts may be dyed in bulk form or first carded and spun prior to dyeing. When the material for the papermakers felts is supplied in the yarn form, some of the yarns for felt guide lines may be dyed on spindles or bobbins or the yarn may be removed therefrom and formed into skeins prior to dyeing.

Since both yarns, monofilaments and/ or fibers may be employed in the invention, hereinafter and in the claims appended hereto the term fibers includes monofilaments, bulk staple fibers, yarns spun therefrom, and multiple filament yarns in the bulked or unbulked form.

The selected thermoplastic synthetic fibers are processed through the steps of carding, spinning, weaving, and splicing, where the felt is not woven endless and where desired, burling in substantially the same way that wool and/ or wool synthetic fibers are processed on the woolen or worsted systems.

Following the conventional steps of carding, spinning, weaving, and splicing, if not woven endless, of the synthetic thermoplastic fibers into a woven felt or fabric, the fabric is ready for finishing. The endless fabric at this stage maybe treated substantially as disclosed in my copending application Serial No. 767,109 filed October 14, 1958, whereby the felt is mechanically shrunk in width; heat shrunk in width, and then heat-set to stabilize the length and width of the fabric. Following the heat-setting of the fabric, the fabric is compressed in thickness as to be more fully described hereinafter. 1

One form of apparatus suitable for carrying out the process of the present invention is illustrated in the drawing and generally designated 10. The treating apparatus includes a frame 12 having adjacent its ends a pair of rolls 14 and 16. The width of the rolls 14 and 16 should be at least slightly greater than the width of the fabric to be treated. One or both of the rolls 14 and 16 may be driven. However, as illustrated in the drawings, only roll 14 is provided with drive means .18 which drive means is preferably of the adjustable speed type whereby the speed of the web traveling about the pair of rolls is effectively controlled.

The other of the rolls .16 is mounted ,in adjusting means generally designated 20 whereby the distance between the centers of the rolls 14 and 16 may be variously adjusted to accommodate different size webs and to effect mechanical width shrinking of the web as is more fully described in my said copending application. A motor 34 is drivably connected to the speed reducing means 36 which drives a shaft engaging a rack extending along each side of the frames 12 whereby upon actuation of the motor 34 the frames carrying the idler roll 16 are moved toward or away from the driver roll 14 depending upon the direction of rotation of the motor 34. As illustrated in the drawings, the assembly also includes a conventional stand 44 having adjustably mounted thereon a felt roll 46 which maintains the lower flight of the felt A at a predetermined position and prevents sag in the felt.

Between the stand 44 and the idler roll 16 is positioned a tank or trough generally designated 50 which tank has a width greater than the width of the largest felt to be treated on the apparatus. At the inlet end 52 of the tank 50 is rotatably supported a guide roll 54 over which the lower flight of the felt passes. After passing over the guide roll 54, the felt passes under an immersion roll 56 which immersion roll is positioned within the tank below the normal level, generally designated at B, of a treating liquid. .At the other end of the tank 50 are a pair of opposed liquid expressing rolls generally designated 58 which expressing rolls are maintained above the normal level B of the liquid within the tank 50. The lower flight of the felt being treated after passing through the expressing rolls 58 passes over an idler roll 60, thence to the adjustable felt roll 46.

The level of the liquid, where employed in the process of the invention, within the tank 50 is maintained by an inlet conduit 62 and an outlet conduit 64. The outlet conduit is positioned so that its opening into the tank 50 is at the desired level to be maintained within the tank so that immersion roll 56 is below the level of the liquid and expressing rolls 58 are above the level of the liquid.

Positioned above the web, between the rolls f4 and 16, is a heating device generally designated 22 which heating device may comprise an infrared heating unit as disclosed in my said copending application and the heating device extends at least across the width of the felt to be treated.

The driven roll 14 may be provided with heating means which, as illustrated in the drawing, comprises valved conduit means 66 for directing a heating fluid such as superheated steam, oil, etc, into the interior of the roller 14 from a source not shown in the drawing. v

Positioned vertically above the axis of rotation of roll 14 is a support means 68 which adjustably carries a further roll 70. The adjusting means generally designated 72 permits the surface of the roll '70 to be brought into contact with the surface of the felt as it passes over the roller 14 during predetermined periods of treatment of the felt.

The roll 70 is also connected to a source of heating fluid through valve conduit means generally designated 72 whereby the temperature of the roll 70 may also be maintained at a preselected temperature during a portion of the operation of the process.

The woven-synthetic felts as hereinbe'fore described are generally woven in the loom to a length approximately equal to the finished length for the particular paper machine. When a fabric containing, for example, Dacron or nylon warp yarns is removed from the loom, the fabric sets back or relaxes in length. It has been found that the relaxation of such a fabric is from about 7% to about 15% based on the length of the loomed fabric. However, the amount of relaxation in the Woven fabric in length depends to a large extent on the tension under which the warp yarns are woven, the type of felt being manufactured, the type of weave employed, and the texture or closeness of the weaving. In view of the relaxation of the woven fabric, after the fabric is placed between the rolls 14 and 16, the tensioning mechanism 20 is employed to stretch the fabric in length to the ordered or specified length of the finished felt or to a length from about 2 to about 3 percent greater than the ordered length.

This mechanical stretching in length brings about a definite proportional amount of mechanical shrinkage in the width direction of the fabric.

For example, a conventionally woven all Dacron felt was stretched 12% in length on apparatus such as shown in the drawing and the fabric shrunk substantially about 17% in width based on the burled dimension.

After the fabric has been stretched in length to a length slightly greater than the desired finished length and mechanically shrunk in width, the fabric is then subjected to thermal shrinkage in width by the application to the fabric of heat from an infrared source. Following the infrared shrinking in width, both the length and the width of the shunken synthetic fabric are set with further applications of infrared rays.

With the fabric stretched between the trolls 14 and 16, the fabric is subjected to heat from infrared radiation producing mechanism 22 while traveling about the rolls 14 and 16. The intensity of the infrared radiation and the speed of travel of the fabric around the rolls 14 and 16 is so adjusted that the entire surface of the fabric will be exposed to the infrared heat for a period of from about 30 seconds to about 90 seconds at a fabric temperature of from about 212 'F. to about 400 F. The preferred heating conditions for thermal shrinkage of the width of the dry fabric are from about 30 to about 60 seconds exposure at a fabric temperature of from about 350 F. to about 370 F. as it has been found that under these conditions maximum thermal shrinkage is provided without scorching or fusing of the synthetic fibers of the fabric.

The amount of thermal shrinkage that occurs in width has been found to range from about 9% to about 30% based on the fabric width at the fully stretched length when Dacron is employed in the filling yarns during weaving. This thermal shrinkage is in addition to the mechanical shrinkage which takes place in the width of the fabric when it is stretched in length as hereinabove described. The amount of thermal shrinkage that occurs depends to a large extent on how close together the yarns are originally woven in the loom and on the type of weave employed as well as on the particular type of synthetic fibers employed in the filling yarns.

After the synthetic felt has made one complete pass under the infrared heating unit and full thermal shrinkage has taken place in the fabric, the felt is ready for heat setting its dimensions. For heat setting, the fabric is again passed under the infrared hood. The temperature, time, and conditions for heat setting the dimensions of the heat-shrunk fabric are not as critical as the temperature and conditions during thermal shrinking thereof. For example, the heat-shrunken fabric can be caused to pass six times under the infrared hood with a 30-second exposure during each pass at a fabric temperature of from about 250 F. to about 400 F. or satisfactory results can be obtained with the fabric making three passes under the infrared hood with a 6-second exposure during each pass at a fabric temperature of about 250 F. to about 400 F. In general, it has been found that with an eX- posure time of about 1 minute at fabric temperatures of from between 350 F. to about 400 F. following the heat shrinking cycle, the felt dimensions are set to within two to three percent of their permanent dimensions.

After heat-setting, the dry endless felt is then run between a set of heated rolls to mechanically and thermally compress the felt in thickness. The heating and compressing means may consist of a pair of heated metal-tometal rolls, a set of three rolls with a pressed cotton or paper or other soft roll between the two heated metal rolls, such as used for calendering apparel fabrics, or a stack of calender rolls such as used in paper mills. The felts are compressed in thickness with these rolls approximately 40% based on the thickness of the felt in the shrunken and heat-set state.

In the illustrated form of the invention, heat is directed to roll 14 through valve conduit means 66 and heat is directed to roll 70 by valve conduit 72. Roll 70 is then moved toward roll 14 by the height-adjusting means 72 to place the felt under a roll pressure of from about 50 to about 150 p.s.i. The heating of the rolls is such as to maintain a surface temperature of from about 300 F. to about 400 F. for nylon and/or Dacron felts. Under these temperature and pressure conditions a dwell time in the nip of the rolls from about 1 second to about 5 seconds provides very satisfactory results. A dynel fabric may be heat compressed at a temperature as low as about 250 F. and at a pressure of about 75 p.s.i. at a dwell time of from about 1 to 3 seconds.

It will be understood that these factors are all interrelated and as one condition, such as temperature, is increased, the others can be decreased and vice versa. For example, if the roll temperature is 400 F., then a pressure of about 50 p.s.i. pressure can be used. The dwell time in the nip of the pressure rolls is governed also by the size, that is, the diameter of the rolls and the speed of travel of the felts through the rolls and is also dependent on the temperature of the rolls and the pressure between the rolls.

Tests have shown that the specific preferred conditions for most synthetic felts are the temperature of about 350 F., pressure of about p.s.i. with a 3-second dwell time in the nip of the rolls.

It will be understood by those skilled in the art that when the felts are woven from synthetic fibers having lower fusion and lower melting temperatures than, for example, regular nylon or Dacron, lower temperatures and/or lower pressures and/or dwell times would be used to compress the felts 40% to 60% in thickness from the heat-set state. It is further pointed out that the process of the present invention includes compression temperatures substantially to the fusion temperature of the thermoplastic fibers in the felt although it is particularly pointed out that the fusion or melting temperature of the thermoplastic fibers should not be reached or exceeded for if the thermoplastic fibers melt, the felt structure may be substantially weakened forming water impermeable places or thin'spots in the finished product.

While heated pressure rolls such as those illustrated in the drawing are preferred as a means for carrying out the present process, other methods or equipment can be employed to compress the felts while being subjected to elevated temperatures. Such other equipment may include hydraulic or pneumatic flat-bed presses provided with means for heating the platens thereof. It will be appreciated that where platen presses are employed, the advantages of continuous felt treatment would be lost.

EXAMPLE I A paper pickup type felt composed of a mixture of 75% wool with 25% nylon in the warp yarns and allshrinkable Dacron in the filling yarns was woven as a double-faced felt with all-Dacrons filling yarns on both sides. After weaving the felt was mechanically shrunk, heat-shrunk and heat-set as hereinabove described on apparatus of the type disclosed in the drawing. Following the heat-setting of the felt, the felt was found to have a thickness of .125 inch. This felt was compressed by rolls in thickness at a temperature of 350 F. at a pressure of 55.5 p.s.i. at a dwell time of 15 sec.- onds. After compression, the felt had a thickness of .059 inch and was compressed 53%. The surface of the compressed felt was smooth and provided a very satisfactory pickup felt for papermaking machines.

EXAMPLE II A felt composed of Dacron was woven (plain weave, 2 cut Warp and filling staple yarns), mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have a thickness of .086 inch. The heat set felt was then compressed at 'a temperature of 350 F. under a pressure of 50 p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 41.5% and had a smooth felt surface.

EXAMPLE III 'A'felt composed of Dacron was woven, as set forth in Example II, mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have a thickness of .086 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of 100 p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 43.5%, and had a smooth felt surface.

EXAMPLE IV A felt composed of Dacron was woven, as set forth in Example II, mechanically shrunk in width, heat-shrunk in Width, and heat set. After heat-setting the felt was found to have a thickness of .086 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 46.0% and had a smooth felt surface.

EXAMPLE V A felt composed of Dacron was woven, as set forth in Example II, mechanically shrunk in Width, heat-shrunk in Width, and heat set. After heat-setting the felt was found to have a thickness of .0860 inch. The heat set felt was then compressed at a temperature of 375 F. under a pressure of 75 p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 42.1% and had a smooth felt surface.

EXAMPLE VI A felt composed of Dacron was woven as set forth in Example II, mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have a thickness of .0860 inch. The heat set felt was then compressed at a temperature of 400 F. under a pressure of 75 psi. at a dwell time of 3.5 seconds. The felt was compressed in thickness 44.9% and had a smooth felt surface.

EXAMPLE VII A textured nylon and Dacron plate type felt with 3/ 1 weave, composed of textured nylon filament filling yarns cut after texturing, and 34 picks per inch finished), and textured Dacron filament warp yarns (11.2 out after texturizing' with 35-36 ends per inch finished), was mechanioally shrunk in Width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have an average thickness of .0585 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of 75 psi. at a dwell time of 3.5 seconds. The felt was compressed in thickness 41.0% and had a smooth felt surface.

EXAMPLE VIII A felt woven as set forth in Example VII was mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have an average thickness of .0585 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of 100 p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 46.5% and had a smooth felt surface.

EXAMPLE IX A felt composed of 14 cut regular staple fiber Dacron yarns with 41-42 ends per inch finished and 6 cut shrinkable Dacron staple filling yarns with 48 picks per inch was mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have a thickness of .0706 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of 50 psi. at a dwell time of 3.5 seconds. The felt was compressed in thickness 38.0% and had a smooth felt surface.

EXAMPLEX A felt as set forth in Example IX was mechanically shrunk in width, heat-shrunk in width, and heat set. After heat-setting the felt was found to have a thickness of .0706 inch. The heat set felt was then compressed at a temperature of 350 F. under a pressure of 100 p.s.i. at a dwell time of 3.5 seconds. The felt was compressed in thickness 49.5% and had a smooth felt surface.

While it is unnecessary to apply any form of coating or impregnating solution to synthetic felts prior to hot compression to accomplish the objects of the present invention, treatment of the felts with a synthetic rubber latex or resin has been found to be very beneficial, particularly for splice holding. It has been found that a resin or latex treatment combined with the hot compress-ion method of the present invention are also beneficial in im proving water removal properties of the felts, the resistance to, soiling and other physical properties of the felts are improved. When a section of the woven fabric hav-. ing a splice therein is subjected to the hot compression method of the invention, the interwoven splice ends of the yarns are bedded into either the Warp or filling yarns and their crimped intercourse with the Woven structure of the fabric substantially reduces splice slippage. When the fabric is also resin or latex treated, a further reduction in splice slippage is experienced.

Satisfactory results have been obtained by applying to the felts from about 5% to 10% solids by weight of felt of either an aacrylonitrile-butadiene rubber (such as Hycar 1571), a polyvinyl chloride resin (such as Geon 576), or a nylon resin with catalyst. The rubber or latex or resin can be applied to the felts either before or after the heatshrinking or heat-setting steps. However, if the treatment is applied after heat-setting, the felts should be dried before the felt is compressed by heat and pressure.

Satisfactory treatment of the felts with a liquid resin or latex is provided by subjecting the felts to the liquid impregnating composition maintained in the tank 50 illustrated in the drawing and expressing such treating substance from the felt to leave therein from 5% to 10% of the chemical solids. Satisfactory treatment may also be provided by dipping the felt in a solution of the impregnating agent and centrifugally expressing said agent to leave therein the predetermined percentage.

A suitable latex treating solution may comprise an acrylonitpile-b utadiene type synthetic rubber latex water solution containing 20% rubber solids and .2% of sodium aluininate based on the latex solids in the solution. The sodium aluminate is employed as a curing catalyst. The solution should be neutral or slightly alkaline and if it is found to be acidic, aqua ammonia may be added to bring the pH to about 9. After the felt has been passed through this solution, the solution should be extracted from the felt to only 50% to 55% pickup of the liquor. The treated felt is dried at about 200 to about 300 F. to aid in the curing of the latex.

The latex or resin treated felt may then be compressed in thickness in accordance with the procedures of the examples herein.

Where a resin or latex impregnation is provided for the synthetic woven papermakers felts, the felts may be provided with colored guide lines so that the paper machine operators can more easily run the felt straight on the machine. The several strands of filling yarns to be colored a contrasting color from the other yarns in the felt and used as guide lines across the Width of the felt, may be colored by treating them, before they are woven into the felt, in a rubber latex (or resin) bath containing dispersed colored pigment. The American Cyanamid Companys Calcotone water-dispersable pigment pastes have been found to be suitable coloring agents. Very satisfactory results have been obtained by using Calcotone Blue GP paste, 23% pigment solids as supplied, and Calcotone Black paste, about 25% solids as. supplied. A suitable dyeing bath containing from 2% to 10% of the latex solids and from 1% to 5% of the pigment solids may be padded onto the portion of the yarns forming the guide lines. The yarns are extracted to 50% to pick-up of liquor and air dried, and they are then ready for weaving into the felt. The uncolored resin or latex may then be added to the entire felt following heat shrinking and heat setting or prior to heat shrinking and heat setting to insure that the dyed portion of the felts have the same functional performance as to wear, water removal, surface smoothness, and the like as the undyed portion of the elt.

From the foregoing description of the invention, it will be seen that the aims and objects thereof are fully accomplished by the improved process for finishing textile fabrics whereby papermakers felts composed predominantly of thermoplastic synthetic fibers are provided with exceptionally fine surfaces. While details of methods for carrying out the improved processes have been disclosed, it will be understood by those skilled in the art that variations may be made in the process Without departing from the inventive concepts thereof.

1 claim:

1. A method of making a papermakers felt characten. ized by increased structural stability, uniform thickness, improved splice-holding properties, and a surface which has a smooth, flat, paperlike finish wherein the enmeshed yarn structure of the surface is substantially obscured comprising weaving a fabric from yarns composed predominantly of heat-shrinkable synthetic resinous materials, heat-shrinking the WOVBD. fabric to stabilize the dimensions thereof, compressing the thickness of the heatshrunk fabric by subjecting it in a dry state to heat from about 300 F. to about 400 F. and simultaneously to pressure from about 50 to about 150 pounds per square inch for a dwell time of from about 1 to about 5 seconds to thereby reduce the thickness thereof from about 30% to about 60% based on the thickness of the fabric in the heat-shrunk state.

2. The method of claim 1 which also comprises the following steps prior to said compression step: impregnating said Woven fabric with a latex solution selected from the group consisting of synthetic resins and synthetic rubbers, curing said latex within the fabric, and thereafter drying said cured, impregnated fabric.

3. The method of claim 2 which also comprises the introduction at intervals during the weaving of said fabric of contrasting colored firll yarns, said colored fill yarns produced by impregnating fill yarns with a latex solution containing a dispersed coloring agent, and thereafter drying said impregnated fill yarns.

References Cited in the file of this patent UNITED STATES PATENTS 2,121,005 Bener June 21, 1938 2,669,002 Dalton et a1 Feb. 16, 1954 2,712,170 Phillips July 5, 1955 2,821,771 Skeer Feb. 4, 1958 3,009,234 Blackburn et a1. Nov. 21, 1961

Claims

1. A METHOD OF MAKING A PAPERMAKERS'' FELT CHARACTERIZED BY INCREASED STTRUCTURAL STABILITY UNIFORM THICKNESS IMPROVED SPLICE-HOLDINGG PROPERTIES, AND A SURFACE WHICH HAS A SMOOTH, FFLAT, PAPERLIKE FINISH WHEREIN THE ENMESHED YARN STRUCTURE OF THE SURFACE IS SUBSTANTIALLY OBSCURED COMPRISING WEAVING A FABRIC FROM YARNS COMPOSED PREDOMINANTLY OF HEAT-SHRINKABLE SYNTHETIC RESINOUS MATERIALS, HEAT-SHRINKING THE WOVEN FABRIC TO STABILIZE THE