PRESS FABRICS

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the priority date of U.S. Provisional Application No. 63/721,973, filed Nov. 18, 2024, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to fabrics for paper manufacture.

BACKGROUND

During papermaking processes, after a forming section in which a pulp slurry is formed into a sheet, the sheet is processed in a press section. The sheet is supported by press fabrics (or “felts”) that pass through a series of press nips, typically with increasing load at each nip. The loading of the nips generate a build-up of hydraulic pressure within the sheet, which leads to an expression of water from the sheet into the felt. This mechanical compaction process is known as wet pressing. The press fabric has a “paper side” on which the sheet is supported and a “machine side,” opposite the paper side, in contact with or otherwise adjacent to the machine elements such as rolls.

SUMMARY

Some aspects of this disclosure relate to press fabrics for paper manufacture. For example, described is a press fabric including: a base fabric including polymeric yarns, wherein the polymeric yarns include a hydrophobic additive; one or more first batt layers on a first side of the base fabric; and one or more second batt layers on a second side of the base fabric.

This and other press fabrics described herein can have one or more of at least the following characteristics.

In some implementations, the hydrophobic additive includes siloxane.

In some implementations, the polymeric yarns include polyamide.

In some implementations, the polymeric yarns are present at an interface between the base fabric and the one or more first batt layers and at an interface between the base fabric and the one or more second batt layers.

In some implementations, the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric includes the polymeric yarns including the hydrophobic additive, and wherein the second base fabric is substantially free of the hydrophobic additive.

In some implementations, the one or more first batt layers are on a paper side of the press fabric, and wherein the first base fabric is at an interface between the base fabric and the one or more first batt layers.

In some implementations, the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric is a single-layer fabric, and wherein the second base fabric is a multilayer fabric.

In some implementations, at least 50% of yarns of the base fabric include the hydrophobic additive.

In some implementations, the one or more first batt layers are on a paper side of the press fabric, and wherein at least 50% of yarns of the base fabric present at an interface between the base fabric and the one or more first batt layers are the polymeric yarns that include the hydrophobic additive.

In some implementations, the hydrophobic additive is included in the polymeric yarns with a composition in a range from 0.5% to 6% by weight.

In some implementations, the one or more first batt layers include a plurality of batt layers, wherein the plurality of batt layers includes an inner batt layer including the hydrophobic additive and an outer batt layer substantially free of the hydrophobic additive, and wherein the inner batt layer is closer to the base fabric than is the outer batt layer.

In some implementations, the hydrophobic additive is included in fibers of the inner batt layer.

In some implementations, the inner batt layer is an innermost batt layer of the plurality of batt layers.

In some implementations, the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric includes the polymeric yarns including the hydrophobic additive, and wherein the second base fabric includes the polymeric yarns including the hydrophobic additive.

In some implementations, an outermost batt layer of the one or more first batt layers is substantially free of the hydrophobic additive, and wherein an outermost batt layer of the one or more second batt layers is substantially free of the hydrophobic additive.

In some implementations, the base fabric comprises a woven base fabric.

Some aspects of this disclosure describe a press fabric including: a base fabric; a plurality of first batt layers on a first side of the base fabric, wherein the plurality of first batt layers includes an inner batt layer and an outer batt layer, wherein the inner batt layer is closer to the base fabric than is the outer batt layer, wherein the inner batt layer includes polymeric fibers including a hydrophobic additive, and wherein the outer batt layer is substantially free of the hydrophobic additive; and one or more second batt layers on a second side of the base fabric.

This and other press fabrics described herein can have one or more of at least the following characteristics.

In some implementations, the inner batt layer is an innermost batt layer of the plurality of first batt layers, and wherein the polymeric fibers including the hydrophobic additive are present at an interface between the plurality of first batt layers and the base fabric.

In some implementations, the plurality of first batt layers are on a paper side of the press fabric.

In some implementations, the outer batt layer is an outermost batt layer of the plurality of first batt layers, such that the outer batt layer is at an exterior of the press fabric.

In some implementations, the polymeric fibers include siloxane in a polyamide matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating an example of a press section of a papermaking machine.

FIG. 1B is a diagram illustrating an example of a press fabric.

FIGS. 2 to 6 are diagrams illustrative respective examples of press fabrics.

FIG. 7 is a scanning electron micrograph of an example of a press fabric.

FIG. 8 is a diagrammatic perspective view of an example of a non-woven base fabric.

DETAILED DESCRIPTION

Aspects of this disclosure describe press fabrics composed of yarns and/or fibers that include a hydrophobic additive such as siloxane. For example, the yarns can be composed of a polymer, such as polyamide, having the siloxane as an additive. In some implementations, the hydrophobic additive can reduce contamination of the press fabric, providing cleaner press fabrics with reduced contaminant absorption and/or adhesion. This can, in turn, promote high drainage and dewatering performance and improve the overall stability of the press fabric over its lifetime. For example, the fabrics described herein can exhibit more steady-state performance over their life, e.g., slower degradation.

FIG. 1A illustrates an example of a portion of a press section of a papermaking machine. In the illustrated press nip 100, a fibrous sheet 104 passes between two rolls 102a, 102b (referred to collectively as rolls 102) supported by a press fabric 106. The rolls 102 exert pressure on the press fabric to squeeze water from the fibrous sheet 104, increasing the solidity and consolidation of the fibrous sheet 104. Characteristics of the pressing process can directly affect characteristics of the manufactured paper, such as smoothness, ink absorption, bulk, and moisture profile.

It will be understood that FIG. 1A is a schematic example, and that other press nip configurations are within the scope of this disclosure. For example, in some implementations, the fibrous sheet 104 is between two press fabrics 106, e.g., one between the fibrous sheet 104 and roll 102a and one between the fibrous sheet 104 and roll 102b. As another example, in some implementations, the fibrous sheet 104 (with one or two press fabrics 106) is compressed between a roll and a shoe, in a “shoe press” configuration.

Compression in the press nip 100 forces, from the fibrous sheet 104 into the press fabric 106, not only water but also filler, furnishes, debris, and/or other contaminants that may be present in the fibrous sheet 104. For example, relatively high levels of furnishes may be present in fibrous sheets 104 formed from recycled paper. Contaminants may build up in the press fabric 106 over time, reducing the performance of the press fabric 106.

FIG. 1B provides a schematic view of the press fabric 106 and the fibrous sheet 104. The press fabric 106 includes a woven base (sometimes referred to as a woven body) 108, which can be composed of one or more fabrics. As discussed below, the base fabric need not be woven, and in some implementations the base is a non-woven base fabric. The press fabric 106 further includes one or more paper-side batt layers 110 on the paper side of the woven base 108, and one or more machine-side batt layers 112 on the machine side of the woven base 108. The fibrous sheet 104 is supported on the one or more paper-side batt layers 110. The machine-side batt layers 112 can be in contact with a roll 102.

According to some implementations of the present disclosure, one or more internal interfaces of the press fabric 106 include a component having a hydrophobic additive, such as siloxane. For purposes of this disclosure, it has been identified that internal interfaces are particularly important for control of fabric cleanliness. For example, contaminants may preferentially accumulate at internal interfaces compared to within layers. Further, internal interfaces are relatively far from high-pressure showering to which the press fabric 106 is exposed, such that standard cleaning processes are less effective at removing contaminants from those interfaces. Providing a hydrophobic additive at the internal interfaces can facilitate contaminant movement through and out of the press fabric 106.

In some cases, including too much hydrophobic additive in the press fabric 106 can degrade dewatering performance of the press fabric 106. For example, making the press fabric 106 overly hydrophobic can inhibit entry of water into the press fabric 106 from the fibrous sheet 104 and/or passage of water through the press fabric 106. Targeting internal interfaces to have the hydrophobic additive can improve fabric cleanliness without making the press fabric 106 too hydrophobic overall. For example, as discussed in further detail below, in some implementations, one or more internal layers include the hydrophobic additive, and one or more other layers, between the one or more internal layers and the exterior of the press fabric 106, have less hydrophobic additive or no hydrophobic additive.

The internal interfaces having the hydrophobic additive can include, for example, an interface between the woven base 108 and the one or more paper-side batt layers 110; an interface between the woven base 108 and the one or more machine-side batt layers 112; an interface between distinct laminated layers of the woven base 108; and/or an interface between distinct batt layers of the one or more paper-side batt layers 110 and/or the one or more machine-side batt layers 112. These configurations are discussed in more detail through the examples below.

The woven base 108 can be woven from monofilament, plied monofilament, multifilament or plied multifilament yarns, and can be single-layered, multi-layered, and/or laminated. The yarns can be extruded polymer yarns. For example, the yarns can include polyamide (PA) filaments. Other polymers are also within the scope of this disclosure, for example, polyethylene terephthalate (PET). In some implementations, the polymer includes at least one of: polyester, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene naphthalate (PBN), polytrimethylene naphthalate (PTN), poly(cyclohexylene dimethylene terephthalate) acid (PCTA), polybutylene terephthalate (PBT), polyamide (such as PA 6; PA 6,6; PA 6,12; PA 6,10; PA 4,6; PA 10; PA 11; PA 12; MXD6, and aromatic derivatives thereof), polyether ether ketone (PEEK), polyether ketone (PEK) and poly(p-phenylene sulfide) (PPS/RYTON®), polyurethane, PET, or a copolymer thereof.

In some implementations, the woven base 108 includes a single woven fabric layer. In some implementations, the woven base 108 includes multiple fabric layers that are part of the same portion fabric, e.g., in an endless folded configuration. In some implementations, the woven base 108 includes multiple base fabrics laminated to one another. For example, the multiple base fabrics can be needled to one another and/or adhered to one another. Each base fabric can be a single-layer fabric or a multilayer fabric, e.g., can include one layer of CD yarns or multiple layers of CD yarns. Each woven fabric of the woven base 108 can include machine-direction (MD) and cross-machine-direction (CD) yarns interwoven with one another in any suitable weave pattern. For example, the woven base 108 can have a plain weave structure, but is not limited thereto, and any weave structure suitable for press fabrics is within the scope of this disclosure. For example, in some implementations, the woven base 108 includes a triple-layer base fabric with three layers of MD yarns and at least two CD yarn systems. In some implementations, the woven base 108 includes a multilayer base fabric having more MD yarns per unit length at a paper-side layer than at a machine-side layer.

Yarns in one or more base fabrics of the woven base 108 can include a hydrophobic additive. The hydrophobic additive can be included as a component in polymeric yarns of the woven base. For example, the yarns can be extruded from a polymeric resin that includes a primary filament component (such as polyamide and/or another polymer noted above) mixed with siloxane. The siloxane can be any suitable siloxane, such as polysiloxane, a silicone, or a cyclosiloxane. In the yarns, the siloxane can be integrated into the polymer matrix of the primary filament component. In some implementations, the polymeric yarns include one or more additional components, such as a compatibilizer suitable for improving integration/mixing of the primary filament component with the hydrophobic additive. In some implementations, the yarns of the woven base 108 include the hydrophobic additive (e.g., siloxane) in a range from 0.5% to 6% by weight. For example, a yarn that includes the hydrophobic additive can include the hydrophobic additive in a range from 0.5% to 6% by weight.

The hydrophobic additive can be included in MD yarns, CD yarns, or both MD and CD yarns in the woven base 108. In some implementations, the woven base 108 does not include the hydrophobic additive.

The batt layers 110, 112 are composed of fibers bonded together in a disordered arrangement. The batt layers 110, 112 can be attached to the woven base 108, e.g., by needling and/or adhesive layer(s). When the one or more paper-side batt layers 110 includes multiple paper-side batt layers 110, the multiple paper-side batt layers 110 can be needled to one another and/or adhesively attached to one another. When the one or more machine-side batt layers 112 includes multiple machine-side batt layers 112, the multiple machine-side batt layers 112 can be needled to one another and/or adhesively attached to one another.

In some implementations, fibers in one or more batt layers of one or both of the one or more batt layers 110, 112 include a hydrophobic additive. For example, as described for the yarns of the woven base 108, in some implementations, the fibers include polymeric fibers composed of a primary polymer component (such as polyamide and/or any another polymer noted above) and a hydrophobic component, such as siloxane. Fibers in one or both batt layers 110, 112 can have a composition as described above for yarns of the woven base 108. For example, the fibers can be composed of an extruded polymer including siloxane, e.g., in a range from 0.5% to 6% by weight. In some implementations, the one or more paper-side batt layers 110 and/or the one or more machine-side batt layers 112 are substantially free of the hydrophobic additive.

As shown schematically in FIG. 1B, in some implementations, the one or more paper-side batt layers 110 have a total thickness that is greater than a total thickness of the one or more machine-side batt layers 112. In some implementations, the paper-side batt layers 110 includes more batt layers than does the machine-side batt layers 112.

As noted above, one or more components of the press fabric 106 can include a hydrophobic additive. Examples of the press fabric 106 including the hydrophobic additive will be described with respect to FIGS. 2-6.

As shown in FIG. 2, a press fabric 206 includes a woven base 208, one or more paper-side batt layers 110, and one or more machine-side batt layers 112. The woven base 208, paper-side batt layers 110, and machine-side batt layers 112 can have characteristics as described above for the woven base 108, paper-side batt layers 110, and machine-side batt layers 112.

The woven base 208 includes yarns having a hydrophobic additive. For example, the woven base 208 can include a single base fabric having yarns that include the hydrophobic additive. The woven base 208 can include multiple base fabrics, each of which has yarns that include the hydrophobic additive. The woven base 208 can include multiple base fabrics, fewer than all of which have yarns that include the hydrophobic additive. The yarn composition, for yarns that include the hydrophobic additive, can be a composition as described above with respect to the woven base 108.

In some implementations, based on the presence of the hydrophobic additive (e.g., siloxane) in the woven base 208, yarns having the hydrophobic additive are present at at least one interface of the woven base 208 with batt. For example, yarns having the hydrophobic additive can be present at an interface 209 between the woven base 208 and the one or more paper-side batt layers 110. In that case, when the woven base 208 includes multiple base fabrics, yarns of a base fabric closest to the one or more paper-side batt layers 110 can include the hydrophobic additive. Instead, or additionally, yarns having the hydrophobic additive can be present at an interface 215 between the woven base 208 and the one or more machine-side batt layers 112. In that case, when the woven base 208 includes multiple base fabrics, yarns of a base fabric closest to the one or more machine-side batt layers 112 can include the hydrophobic additive.

In some implementations, to retain high dewatering performance of the press fabric 206, at least portions of the batt layers 110, 112 include less hydrophobic additive than a portion of the woven base 208 (e.g., a base fabric of the woven base 208) that includes the hydrophobic additive. For example, in some implementations, the batt layers 110, 112 are substantially free of the hydrophobic additive. For example, fibers of the batt layers 110, 112 can be substantially free of the hydrophobic additive. In some implementations, at least one paper-side batt layer 110 of the one or more paper-side batt layers 110, and/or at least one machine-side batt layer 112 of the one or more machine-side batt layers 112, is substantially free of the hydrophobic additive. In that case, in some implementations, at least one paper-side batt layer 110 of the one or more paper-side batt layers 110, and/or at least one machine-side batt layer 112 of the one or more machine-side batt layers 112, can include the hydrophobic additive. Accordingly, the hydrophobic additive can be located specifically at interface(s) where contaminants may accumulate, without compromising dewatering performance of the press fabric 206.

As used herein, “substantially free of the hydrophobic additive” or “includes substantially no hydrophobic additive” refer to layers composed of materials, yarns, fibers, etc., that do not intentionally include the hydrophobic additive in their composition. Incidental or trace amounts of the hydrophobic additive may be present, e.g., from mixing with layers that include the hydrophobic additive.

FIG. 3 illustrates an example of a press fabric 306. The press fabric 306 is an example of the press fabric 206 (shown in FIG. 2) and includes the one or more paper-side batt layers 110, the one or more machine-side batt layers 112, and a woven base 308, which is an example of the woven base 208. The woven base 308 includes two base fabrics: a paper-side base fabric 314 and a machine-side base fabric 316. The paper-side base fabric 314 and the machine-side base fabric 316 are laminated to form a laminated woven base 308. For example, the paper-side base fabric 314 and the machine-side base fabric 316 can be needled to one another and/or adhesively attached to one another. The paper-side base fabric 314 includes CD yarns 318 interwoven with MD yarns 320. The machine-side base fabric 316 includes CD yarns 322 interwoven with MD yarns 324.

In the example of the press fabric 306, the paper-side base fabric 314 includes a hydrophobic additive (such as siloxane), and the machine-side base fabric 316 includes less of the hydrophobic additive than the paper-side base fabric 314. As used herein, in some implementations, a first layer or fabric having “less of the hydrophobic additive” than a second layer can refer to yarns or fibers of the first layer or fabric that include the hydrophobic additive having a lower weight % of the hydrophobic additive than do yarns or fibers of the second layer or fabric that include the hydrophobic additive. It can refer to a total weight % of the hydrophobic additive in the first layer or fabric being less than a total weight % of the hydrophobic additive in the second layer or fabric. It can refer to a proportion of CD yarns and/or MD yarns in the first layer or fabric that include the hydrophobic additive being less than a proportion of CD yarns and/or MD yarns in the second layer or fabric that include the hydrophobic additive. It encompasses the second layer or fabric being substantially free of the hydrophobic additive.

For example, yarns of the machine-side base fabric 316 that include the hydrophobic additive can have a lower weight % of the hydrophobic additive than do yarns of the paper-side base fabric 314 that include the hydrophobic additive. Instead, or additionally, a total weight % of the hydrophobic additive in the machine-side base fabric 316 can be less than a total weight % of the hydrophobic additive in the paper-side base fabric 314. Instead, or additionally, a proportion of CD yarns and/or MD yarns in the machine-side base fabric 316 that include the hydrophobic additive can be less than a proportion of CD yarns and/or MD yarns in the machine-side base fabric 316 that include the hydrophobic additive. In some implementations, the machine-side base fabric 316 is substantially free of the hydrophobic additive.

In some implementations, as noted for the press fabric 206, at least some layer(s) of the batt layers 110, 112 are substantially free of the hydrophobic additive.

In the paper-side base fabric 314, the hydrophobic additive can be present in the CD yarns 318 and/or the MD yarns 320. In FIG. 3, the woven base 308 is illustrated as including two laminated-together single-layer base fabrics 314, 316. However, this is only an example, and the configuration of the woven base 308 is not limited thereto. For example, in some implementations, one or both base fabrics 314, 316 is a multilayer fabric. For example, the paper-side base fabric 314 that includes a hydrophobic additive can be a single-layer fabric, and the machine-side base fabric 316 that includes less or substantially no hydrophobic additive can be a multilayer (e.g., double-layer) base fabric. Further, it will be understood that laminate woven bases having three or more base fabrics, any one or more of which includes a hydrophobic additive, are also within the scope of this disclosure. For example, an upper and low base fabric can include the hydrophobic additive, and a middle base fabric can include less or substantially no hydrophobic additive. Further, variations on the woven base 308 are also within the scope of this disclosure. For example, in some implementations, the machine-side base fabric 316 includes a hydrophobic additive, and the paper-side base fabric 314 includes less or substantially no hydrophobic additive. In some implementations, both the paper-side base fabric 314 and the machine-side base fabric 316 include a substantial content of the hydrophobic additive, e.g., include yarns having a proportion of the hydrophobic additive in a range from 0.5% to 6% by weight.

In the press fabric 306, hydrophobic additive is present at an interface 309 between the paper-side base fabric 314 and at an interface 311 between the paper-side base fabric 314 and the machine-side base fabric 316. Accordingly, contaminants that might otherwise accumulate at these interfaces 309, 311 can more efficiently pass through the press fabric 306 for removal. Further, other portions of the press fabric 306 (e.g., closer to a paper-side or machine-side exterior of the press fabric 306) can include less hydrophobic additive or no hydrophobic additive, such that the press fabric 306 provides overall high dewatering performance.

FIG. 4 illustrates another example of a press fabric 406. The press fabric 406 includes multiple paper-side batt layers 410. In this example, the press fabric 406 includes four paper-side batt layers 410a, 410b, 410c, 410d, but other numbers of paper-side batt layers 410 are also within the scope of this disclosure. The press fabric 406 further includes one or more machine-side batt layers 112.

The press fabric 406 includes a woven base 408. The woven base 408 is illustrated as including two laminated base fabrics 414, 416, and the woven base 408 can have characteristics as described for the woven base 308 of FIG. 3, including the variations noted above. For example, in some implementations, the paper-side base fabric 414 includes a hydrophobic additive, and the machine-side base fabric 416 includes less or substantially no hydrophobic additive. However, other configurations of the woven base 408 are also within the scope of this disclosure. For example, the woven base 408 can be substantially free of the hydrophobic additive. As another example, both the paper-side base fabric 414 and the machine-side base fabric 416 can include the hydrophobic additive. Moreover, the laminate configuration of the woven base 408 is an example; the woven base 408 can have any suitable woven configuration as described for woven bases 108, 208.

The paper-side batt layers 410 include at least one batt layer having less hydrophobic additive than another batt layer (e.g., having no hydrophobic additive). For example, as shown in FIG. 4, an innermost paper-side batt layer 410a can include the hydrophobic additive, and at least one of the other, more-exterior paper-side batt layers 410b, 410c, 410d can include less hydrophobic additive, e.g., can be substantially free of the hydrophobic additive. For example, fibers of the innermost paper-side batt layer 410a can be composed of a polymer and include the hydrophobic additive as an additive in the polymer matrix. As a result, the hydrophobic additive is present at least at an interface 409 between the innermost paper-side batt layer 410a and the woven base 408, and at an interface 413 between the innermost paper-side batt layer 410a and the adjacent paper-side batt layer 410b. The hydrophobic additive is therefore arranged to target more-interior interfaces of the press fabric 406. At least one more-exterior interface of the press fabric 406 (e.g., an interface between paper-side batt layers 410c, 410d) can be substantially free of the hydrophobic additive, permitting effective dewatering while reducing press fabric contamination.

Variations on the configuration shown in FIG. 4 are also within the scope of this disclosure. For example, paper-side batt layers 410a, 410b can include the hydrophobic additive, and paper-side batt layers 410c, 410d can include less or substantially no hydrophobic additive. As another example, paper-side batt layer 410b can include the hydrophobic additive, and paper-side batt layers 410a, 410c, 410d can include less or substantially no hydrophobic additive. Any of the batt layers 110, 410, 112 described herein, and variations thereof, can include a first batt layer and a second batt layer, where the first batt layer is more interior and includes a hydrophobic additive, and where the second batt layer is more exterior and includes less or substantially no hydrophobic additive. In the example of FIG. 4, the first batt layer is the innermost paper-side batt layer 410a, and the second batt layers are paper-side batt layers 410b, 410c, 410d.

In any of the implementations described herein, when multiple batt layers include the hydrophobic additive, the multiple batt layers can include a same type of fiber (e.g., same diameter and composition). However, the batt layers are not limited thereto, and in some implementations different batt layers have different fiber diameters and/or compositions.

In some implementations, the woven base includes multiple base fabrics, multiple of which (e.g., all of which) include a hydrophobic additive. For example, FIG. 5 illustrates another example of a press fabric 506. In this example, the press fabric 506 includes a woven base 508 having a paper-side base fabric 514 and a machine-side base fabric 516, e.g., with a laminated configuration as described for the woven base 308. For example, the base fabrics 514, 516 can be needled to one another. Both the paper-side base fabric 514 and the machine side base fabric 516 include a hydrophobic additive. Accordingly, the hydrophobic additive is present at least at an interface 511 between the base fabrics 514, 516; at an interface 509 between the paper-side base fabric 514 and the one or more paper-side batt layers 110; and at an interface 515 between the machine-side base fabric 516 and the one or more machine-side batt layers 112. Based on this configuration, the hydrophobic additive can promote internal cleanliness of the press fabric 506. In some implementations, less or substantially no hydrophobic additive can be present in other portions of the press fabric 506, e.g., in at least one of the one or more paper-side batt layers 110 and/or in at least one of the machine-side batt layers 112. Accordingly, the press fabric 506 can retain dewatering effectiveness while achieving improved cleanliness through hydrophobic additive at its internal interfaces.

In any of the implementations described herein, when multiple base fabrics include a hydrophobic additive, such as the base fabrics 514, 516, the multiple base fabrics may include a same type of yarn (e.g., same diameter and composition).

In some implementations, at least a portion of the one or more machine-side batt layers 112 includes a hydrophobic additive. For example, FIG. 6 illustrates another example of a press fabric 606. The press fabric 606 includes multiple machine-side batt layers 612, of which at least one includes the hydrophobic additive. In this example, the press fabric 606 includes two machine-side batt layers 612a, 612b, though their number is not limited thereto. An innermost machine-side batt layer 612a includes the hydrophobic additive, and a more-exterior machine-side batt layer 612, such as the outermost machine-side batt layer 612b, includes less or substantially no hydrophobic additive. In this case, the hydrophobic additive is present at least at an interface 615 between the innermost batt layer 612a and the woven base 108, and at an interface 617 between the innermost machine-side batt layer 612a and the adjacent machine-side batt layer 612b. This configuration can provide the advantages associated with inner additive placement discussed throughout this disclosure.

The examples of FIGS. 1B and 2-6 have been discussed separately. However, it will be understood that the paper-side batt layers, woven bases, and machine-side batt layers described for any of these examples can be combined with one another. For example, the woven bases 108, 208, 308, 408, and 508, and the discussed variations thereof, can be included in a press fabric with the paper-side batt layers 110, 410 and/or the machine-side batt layers 112, 612, and the discussed variations thereof.

Some implementations of the press fabrics described herein are notable for not including hydrophobic additive at their outer batt layers. For example, an outermost paper-side batt layer 110 and/or an outermost machine-side batt layer 112 can be substantially free of the hydrophobic additive. This represents a counterintuitive approach, as additives such as siloxane may be known for their anti-abrasion properties that are most advantageous when the additives are present at the fabric's exterior faces/in the fabric's exterior layers. However, for purposes of this disclosure, it has been recognized that selective provision of the hydrophobic additive at the press fabric interior can provide target cleanliness characteristics, while the press fabric's outer layers can be substantially free of the hydrophobic additive to retain high water in-flow/out-flow capacity. In some implementations, these advantages can be realized through the use of multiple paper-side and/or machine-side batt layers, where inner batt layer(s) include a hydrophobic additive and exterior batt layer(s) are substantially free of the hydrophobic additive. In some implementations, these advantages can be realized through the inclusion of the hydrophobic additive in the woven base of a press fabric, which is separated from the exterior by batt layers (e.g., as opposed to forming fabrics in which the woven base may be exposed to the exterior). In some implementations, these advantages are realized through substantially excluding the hydrophobic additive from exterior batt layers.

FIG. 7 is a scanning electron micrograph of an example of a press fabric as described herein. The press fabric includes a woven base 708 including CD yarns 718 and MD yarns 720. The woven base 708 is sandwiched between a paper-side batt layer 710 and a machine-side batt layer 712. In this example, the MD yarns 720 include a siloxane additive. Energy-dispersive x-ray spectroscopy (EDX) was used to detect siloxane in the yarns. Examples of locations where siloxane was detected are indicated with a circle. As shown in FIG. 7, the siloxane is present at surfaces of the MD yarns 720. Further, the siloxane is present at interfaces between the woven base 708 and the batt layers 710, 712.

For the press fabrics described above (e.g., with respect to FIGS. 1B and 2 to 6), in some implementations, in a fabric or layer described as including a hydrophobic additive, at least 50% of the yarns (in the case of a woven layer) or fibers (in the case of a batt layer) of the layer include the hydrophobic additive. For the press fabrics described above (e.g., with respect to FIGS. 1B and 2 to 6), in some implementations, for an interface between a first layer and a second layer at which the hydrophobic additive is described as being present, at least 50% of yarns (for a woven layer) or fibers (in the case of a batt layer) present at the interface, in at least one of the first layer or the second layer, include the hydrophobic additive.

Examples of press fabrics within the scope of this disclosure include at least the following:

Example 1: A press fabric including: a base fabric including polymeric yarns, wherein the polymeric yarns include a hydrophobic additive; one or more first batt layers on a first side of the base fabric; and one or more second batt layers on a second side of the base fabric.

Example 2: The press fabric of example 1, wherein the hydrophobic additive includes siloxane.

Example 3: The press fabric of example 1 or 2, wherein the polymeric yarns include polyamide.

Example 4: The press fabric of any one of examples 1 to 3, wherein the polymeric yarns are present at an interface between the base fabric and the one or more first batt layers and at an interface between the base fabric and the one or more second batt layers.

Example 5: The press fabric of any one of examples 1 to 4, wherein the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric includes the polymeric yarns including the hydrophobic additive, and wherein the second base fabric is substantially free of the hydrophobic additive.

Example 6: The press fabric of any one of examples 1 to 5, wherein the one or more first batt layers are on a paper side of the press fabric, and wherein the first base fabric is at an interface between the base fabric and the one or more first batt layers.

Example 7: The press fabric of any one of examples 1 to 6, wherein the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric is a single-layer fabric, and wherein the second base fabric is a multilayer fabric.

Example 8: The press fabric of any one of examples 1 to 7, wherein at least 50% of yarns of the base fabric include the hydrophobic additive.

Example 9: The press fabric of any one of examples 1 to 8, wherein the one or more first batt layers are on a paper side of the press fabric, and wherein at least 50% of yarns of the base fabric present at an interface between the base fabric and the one or more first batt layers are the polymeric yarns that include the hydrophobic additive.

Example 10: The press fabric of any one of examples 1 to 9, wherein the hydrophobic additive is included in the polymeric yarns with a composition in a range from 0.5% to 6% by weight.

Example 11: The press fabric of any one of examples 1 to 10, wherein the one or more first batt layers include a plurality of batt layers, wherein the plurality of batt layers includes an inner batt layer including the hydrophobic additive and an outer batt layer substantially free of the hydrophobic additive, and wherein the inner batt layer is closer to the base fabric than is the outer batt layer.

Example 12: The press fabric of example 11, wherein the hydrophobic additive is included in fibers of the inner batt layer.

Example 13: The press fabric of example 11 or 12, wherein the inner batt layer is an innermost batt layer of the plurality of batt layers.

Example 14: The press fabric of any one of examples 1 to 13, wherein the base fabric includes a first base fabric and a second base fabric needled to one another, wherein the first base fabric includes the polymeric yarns including the hydrophobic additive, and wherein the second base fabric includes the polymeric yarns including the hydrophobic additive.

Example 15: The press fabric of any one of examples 1 to 13, wherein an outermost batt layer of the one or more first batt layers is substantially free of the hydrophobic additive, and wherein an outermost batt layer of the one or more second batt layers is substantially free of the hydrophobic additive.

Example 16: A press fabric including: a base fabric; a plurality of first batt layers on a first side of the base fabric, wherein the plurality of first batt layers includes an inner batt layer and an outer batt layer, wherein the inner batt layer is closer to the base fabric than is the outer batt layer, wherein the inner batt layer includes polymeric fibers including a hydrophobic additive, and wherein the outer batt layer is substantially free of the hydrophobic additive; and one or more second batt layers on a second side of the base fabric.

Example 17: The press fabric of example 16, wherein the inner batt layer is an innermost batt layer of the plurality of first batt layers, and wherein the polymeric fibers including the hydrophobic additive are present at an interface between the plurality of first batt layers and the base fabric.

Example 18: The press fabric of example 16 or 17, wherein the plurality of first batt layers are on a paper side of the press fabric.

Example 19: The press fabric of any one of examples 16 to 18, wherein the outer batt layer is an outermost batt layer of the plurality of first batt layers, such that the outer batt layer is at an exterior of the press fabric.

Example 20: The press fabric of any one of examples 16 to 19, wherein the polymeric fibers include siloxane in a polyamide matrix.

Example 21: The press fabric of any one of examples 1 to 20, wherein the base fabric includes a woven fabric.

Example 22: The press fabric of any one of examples 1 to 21, wherein the base fabric includes a laminated woven base fabric.

While the foregoing description refers to “woven bases,” in some implementations, a press fabric base is, or includes, a non-woven component. For example, FIG. 8 illustrates an example of a base fabric 808 that is non-woven. The non-woven base fabric 808 includes multiple stacked filament arrays. For example, the base fabric 808 includes a first array of filaments 840 extending in a first direction and a second array of filaments 842, on the first array, extending in a second direction different from the first direction (e.g., perpendicular to the first direction). Filaments in a non-woven base fabric can be joined to one another by, for example, chemical, mechanical, adhesion, heat, or solvent treatment. Another non-woven layer may also be provided, for example, spunbond or spunlace. Other configurations of non-woven base fabric are also within the scope of this disclosure, e.g., a composition including staple fibers and long fibers.

The filaments in a non-woven base fabric can be any suitable type, e.g., monofilament, plied monofilament, multifilament or plied multifilament. In some implementations, the filaments (or yarns) in a non-woven base fabric have a composition including a hydrophobic additive as described above, e.g., include a siloxane additive. For example, a non-woven base fabric can include one or more layers of polymeric yarns (e.g., polyamide yarns) including a siloxane additive. In some implementations, a non-woven base fabric is free of the hydrophobic additive. In some implementations, a non-woven base fabric includes multiple non-woven fabrics (e.g., needled or otherwise adhered to one another), any one or more (or none) of which can include yarns including a hydrophobic additive. For example, a non-woven base fabric can have a multi-fabric configuration as described with respect to FIGS. 3, 4, and/or 5.

The woven base in the press fabrics of any of FIGS. 1B and 2-6 can be replaced with a non-woven base fabric (e.g., a non-woven base fabric including polymeric yarns including a hydrophobic additive), to achieve a press fabric within the scope of this disclosure.

While this disclosure contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular implementations of particular inventions. Certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.