Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H13/00—Other non-woven fabrics
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4326—Condensation or reaction polymers
  • D04H1/4334—Polyamides
  • D04H1/4342—Aromatic polyamides
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/44—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling
  • D04H1/46—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres
  • D04H1/498—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres entanglement of layered webs
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/08—Felts
  • D21F7/083—Multi-layer felts

Definitions

• This invention relates to paper making machine fabrics, commonly referred to as paper machine clothing.
• the textile structures normally used as clothing in the pressing section of a paper making machine consist generally of a woven base structure covered by a layer of batt fibers needled thereto.
• the process of paper making comprises the deposit of a slurry of the paper making constituents on a forming fabric and then deliquifying the slurry to produce a self-coherent sheet. This sheet is then transported on a fabric to various stations at which deliguification is progressed to produce the final paper sheet.
• Deliguification is usually effected by a combination of pressing and drying at elevated temperatures together with various other treatments that may be desirable depending, of course, upon the final grade and type of paper to be produced. The combination of pressing and drying, together with the quality and nature of the fiber constituents, will determine the quality of the end product.
• the primary functions of the paper machine clothing and, in particular, of the press fabrics are to absorb paper expressed from the paper sheet in the press nip, to support the sheet in the press nip, to prevent crushing, to provide uniform pressure distribution over the paper in the nip between the press rolls, and to impart the desired surface finish to the sheet during its passage through the pressing and drying sections.
• the paper machine clothing or press fabric in contact with the sheet serves to equalize pressure distribution during pressing, and to eliminate or to reduce shadow marking which may be caused by grooves or suction pressure rolls.
• the item of paper making machine clothing also serves to transfer the sheet from one position to another, and to act as a power transmission belt for driving all the undriven rolls in the machine.
• a paper machine fabric particularly a press fabric, should be capable of extended operations without substantial degradation of its performance.
• the high loading of the fabric in the press nip produces over a period of time mechanical damage to components of the fabric, and this, in practice, limits the longevity of the fabric and the consistency of the desirable properties thereof.
• fine fibers are limited since the breaking load of the fibers themselves is self- evidently reduced in proportion to their cross- sectional area.
• extremely fine fiber of conventional materials such, for example, as nylon, do not have sufficient tensile strength and inherent integrity to withstand the rigors of extended use in the press and dryer sections of a paper making machine.
• the present Applicants have found, however, that they can provide an improved dewatering technique within a paper making machine by operating the press rolls at a higher temperature and using a modified press fabric.
• a method of forming a paper sheet which method comprises depositing a slurry of paper forming ingredients on a forming fabric, dewatering said slurry to form a self-cohesive sheet and thereafter further dewatering said sheet by passing said sheet through the nip of a pair of press rolls characterized in that at least one roll is heated to a temperature in excess of 250"F, and in that the paper sheet is supported on a press fabric, the surface of which is glazed sufficiently to provide increased dewatering under the conditions prevailing at the roll temperature employed.
• the invention also includes an article of paper machine clothing for use in the pressing and/or drying section of a paper making machine which item comprises a sheet-contacting layer in which the sheet-contacting surface is glazed.
• the sheet-contacting layer of the press fabric may be either partially glazed or more substantially glazed and the glazed surface is preferably smooth.
• an item of paper making machine clothing may comprise a woven support layer and a layer of batt fibers needled thereto; the batt layers serving as the paper support layer.
• the glazing of the exposed surface of the batt layer may be effected by the application of heat and/or pressure. In a particular embodiment of the present invention, the glazing may be effected by heating to a temperature in excess of 250°F.
• the batt layer may be composed of cross-linked nylon fibers.
• the cross-linking may be effected with an aqueous formaldehyde treatment of the individual nylon fibers or of the batt after formation of the batt and prior to formation of the press fabric, or of the press fabric after manufacture, or may be effected after installation of the item of paper making machine clothing on the machine.
• the press roll temperature employed may be at a temperature in excess of 250°F, the pressure in the nip of the press may be greater than 300 lbs/linear inch.
• the glazing or formation of an extremely smooth and also almost completely sealed press fabric surface has been considered detrimental to dewatering in paper making machines. It is well known, to those skilled in the art, and as described in the introduction to the specification, that the formation of an extremely uniform surface by fine denier fibers or by other methods is beneficial to other conventional dewatering as a result of improved uniformity of pressure application. However, when the surface becomes so smooth as to substantially seal over, dewatering generally decreases substantially.
• the present invention provides for an effective impulse drying process which operates by a mechanism different from that of conventional pressing.
• the use of a very high temperature press roll, i.e. greater than 250°F and normally greater than 300°F is considered to form a steam pressure gradient which then drives a wall of water through the sheet. This produces extremely high levels of sheet dryness as it leaves the nip of the press rolls.
• a glazed press fabric surface is capable of providing exceptionally high sheet dryness values.
• the fabric types required to achieve the appropriate level of glazing either during a breaking-in period on a machine or by pre-treat ent may be selected from a number of individual fiber types or blends with adequate heat resistance, but with the property to flatten and deform into a glazed configuration when exposed to the nip pressure and temperature conditions.
• a blend of Nomex and Kevlar fibers was found to be particularly effective. Also effective were blends of Teflon with other fibers with adequate heat resistance.
• Nomex and Kevlar fibers are aromatic polyamide fibers.
• Nomex fibers are fibers of poly(meta- phenylene isophthalamide) ; Kevlar fibers are fibers of poly(para-phenylene terephthalamide) .
• Teflon is a fluoropolymer , and, specifically, is polytetrafluoroethylene (PTFE) .
• PTFE polytetrafluoroethylene
• Other fluoropolymers and copolymers of fluoropolymers may be used in place of Teflon.
• the other fibers having adequate heat resistance may be fibers of polyaryletherketones or polyphenylene sulfide or cross-linked polyamides.
• the contacting surface of the press fabric may be composed of nylon fibers which are cross-linked by an aqueous formaldehyde treatment to form a glazed press fabric surface in accordance with the present invention.
• the advantage of this latter embodiment is that the imparted cross-linking also raises temperature resistance, but the fibers still retain a sufficient degree of deformability under moist hot conditions to provide a satisfactory glazed surface.
• a press fabric comprising a batt layer formed of a 50% blend of Nomex and Kevlar fibers needled to a woven backing support fabric.
• the press fabric was operated on the press section of a machine with a heated roll temperature of 400°F under a pressure of 375 lbs/linear inch and at a speed sufficient to provide a 40 millisecond nip residence time at a felt moisture ratio of 0.2.
• Example 1 was repeated in that a non-glazed press fabric construction was employed in which the press fabric contacting layer was a batt structure of cross- linked nylon. Hand sheets of newsprint furnish were prepared as described in Example 1 and were then subjected to a pass through the heated press section of the machine with the non-glazed fabric construction. Again, a sheet dryness of 60-65% was obtained. The press fabric was then glazed as described in Example 1 to produce a glazed surface. A repeat of the experiment showed sheet dryness factors of 70-75% or more and good sheet release.
• EXAMPLE 3 A press fabric was produced comprising a surface batt layer of 85% Teflon with 15% polyphenylene sulfide. Several batt layers of a high temperature resistant polyamide fiber were located beneath the Teflon surface layer. The fabric was produced using a standard needling procedure with a standard woven polyamide base fabric.
• the press fabric was tested on a pilot press section of a paper machine operated at the following high temperature pressing conditions: heated roll temperature - 400°F, nip pressure - 500 psi, and a machine speed to yield a nip residence time of 35 milliseconds.
• Two types of handsheets were used to evaluate the press fabric: LWC (light weight coated) and newsprint.
• the LWC handsheets were comprised of 60% groundwood with 40% Kraft.
• the newsprint handsheets were comprised of 80% TMP (thermal mechanical pulp) with 20% Kraft. Both types of handsheets were prepared to a solids content of approximately 37%.
• TMP thermo mechanical pulp
• the press fabric was allowed to cycle through the heated nip. After approximately 3000 cycles, the press fabric's surface appeared glazed and sealed. At this time, fabric air permeability was measured to be 150 in. of H 2 0 vac. - indicating a sealed surface. Once the fabric became glazed and sealed, pressing trials were repeated. Results of the pressing trials showed that the glazed fabric produced handsheets with higher final dryness than the unglazed fabric. With the glazed fabric, final sheet dryness values of 69% to 74% were achieved with the LWC and 67% to 71% with the newsprint.
• the glazed fabric continued to produce these high sheet dryness values throughout the duration of the trial - 28,000 cycles.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Treatment Of Fiber Materials (AREA)
• Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=10722558

Family Applications (1)

Country Status (12)

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Citations (6)

Family Cites Families (4)

• 1992
  • 1992-09-25 GB GB929220351A patent/GB9220351D0/en active Pending
• 1993
  • 1993-09-24 KR KR1019940701740A patent/KR0123010B1/ko active
  • 1993-09-24 EP EP93922728A patent/EP0620874A4/de not_active Withdrawn
  • 1993-09-24 NZ NZ256765A patent/NZ256765A/en unknown
  • 1993-09-24 JP JP6509174A patent/JPH07501861A/ja active Pending
  • 1993-09-24 AU AU51637/93A patent/AU5163793A/en not_active Abandoned
  • 1993-09-24 BR BR9305646A patent/BR9305646A/pt not_active Application Discontinuation
  • 1993-09-24 CA CA002123790A patent/CA2123790A1/en not_active Abandoned
  • 1993-09-24 WO PCT/US1993/009051 patent/WO1994008082A1/en not_active Application Discontinuation
  • 1993-09-27 MX MX9305938A patent/MX9305938A/es unknown
  • 1993-09-27 ZA ZA937149A patent/ZA937149B/xx unknown
• 1994
  • 1994-05-24 FI FI942409A patent/FI942409A/fi unknown

Patent Citations (6)

Non-Patent Citations (1)

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