Woven fabric and sliding material

Abstract

To provide a woven fabric which can be bonded to a base material even under high load and high speed sliding conditions, and which is excellent in sliding properties as a sliding material while being difficult to cause a shift between members, and a woven fabric and a sliding material, in which at least one of a warp yarn and a weft yarn contains a twisted yarn of a fluororesin fiber and a para-aramid fiber, and the height of a concave-convex is 1150 μm or less in at least one face of the twisted yarn.

Description

Technical Field

[0001] This invention relates to woven fabrics and sliding materials. Background Technology

[0002] For some time, techniques have been developed that utilize the low coefficient of friction of fluoropolymers to fiberize them into woven or nonwoven fabrics. These fabrics are then sandwiched between sliding components to impart low friction between the components. However, when the thickness of the sliding fabric decreases significantly due to abrasion, the gaps around the sliding components change, causing systemic wobbling. Therefore, in addition to low friction and sliding durability, the sliding fabric must also not experience significant thickness reduction due to abrasion even under harsh sliding conditions.

[0003] Furthermore, fluoropolymers generally lack adhesive properties. Therefore, when applying a sliding material to a substrate to impart sliding properties, in addition to the low friction and sliding durability of the sliding material monomer, it is also important to ensure adhesion.

[0004] As a technology for imparting low friction to sliding fabrics, for example, Patent Document 1 discloses a self-lubricating woven fabric, which is a woven fabric containing a composite yarn formed of fluoropolymer fibers and other fibers, wherein the surface area of ​​the other fibers on one side of the woven fabric is 0 to 30% of the total surface area of ​​the composite yarn.

[0005] As a technique to suppress swaying between components when used as a sliding material, for example, Patent Document 2 discloses a fabric in which fluoropolymer fibers and other fibers are alternately arranged, and the compression of the fabric is less than 25 μm.

[0006] Prior technology documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2017 / 020821

[0009] Patent Document 2: International Publication No. 2018 / 074207 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, in the woven fabric described in Patent Document 1, the high proportion of fluoropolymer fibers in the composite yarn means that when exposed to high-speed sliding under high loads, the discharge of abrasive powder from the fluoropolymer yarn cannot be sufficiently suppressed, leaving room for improvement in suppressing thickness reduction due to abrasion. Furthermore, the high proportion of fluoropolymer fibers means that when low-heat-shrinkage fibers such as para-aramid fibers are selected as other yarns, the difference in heat shrinkage between the fluoropolymer fibers and the fluoropolymer fibers leads to increased unevenness after heat treatment, resulting in reduced adhesion and slip properties.

[0012] The woven fabric described in Patent Document 2 can suppress the shaking between components because of the small amount of compression in the thickness direction under heavy load. However, there is room for improvement in terms of thickness reduction after sliding under high load and high speed.

[0013] Furthermore, all of the aforementioned patent documents have conducted research on sliding properties, but have not disclosed the specific impact on adhesion. When low-heat-shrinkage fibers such as para-aramid fibers are selected as other yarns for the purpose of improving durability, the difference in heat shrinkage between them and fluoropolymer fibers leads to increased unevenness after heat treatment, and sometimes reduced adhesion. There is room for further research in the development of sliding materials that combine sliding and adhesion properties.

[0014] Therefore, the objective of this invention is to provide a woven fabric that combines low friction, sliding durability, and adhesion, and suppresses thickness reduction due to wear even under high load and high speed sliding conditions.

[0015] The objective is to provide a woven fabric with excellent sliding properties, capable of functioning as a sliding material for a long time, suppressing wobbling between components, and bondable to a substrate, by using the woven fabric of the present invention as a sliding material.

[0016] Methods for solving problems

[0017] To solve the aforementioned problem, the present invention has the following configuration.

[0018] A woven fabric comprising a twisted yarn of fluoropolymer fibers and para-aramid fibers in at least one of the warp and weft yarns, wherein the unevenness height of at least one surface exposed above the twisted yarn is less than 1150 μm.

[0019] The aforementioned woven fabrics, wherein the thickness is less than 1.3 mm.

[0020] The aforementioned woven fabric, wherein the aforementioned twisted yarn is included in the warp and weft yarns.

[0021] The aforementioned woven fabric, wherein the aforementioned woven fabric is a multi-faceted woven fabric comprising a first surface as the outermost surface and a second surface as the outermost surface opposite to the aforementioned first surface, wherein at least one of the warp and weft yarns of the aforementioned first surface comprises the aforementioned twisted yarn.

[0022] The aforementioned woven fabric, wherein the ratio (CF1 / CF2) of the coverage factor (CF1) of the first surface to the coverage factor (CF2) of the second surface is less than 1.

[0023] In the aforementioned woven fabric, the mass percentage of fluoropolymer fibers in the overall woven fabric is less than 20% by mass.

[0024] The sliding material comprises the aforementioned woven fabric.

[0025] In the aforementioned sliding material, at least one surface that exposes the aforementioned twisted yarn and has a roughness height of 1150 μm or less is designated as the sliding surface.

[0026] The effects of the invention

[0027] According to the present invention, a woven fabric and a sliding material are provided that combine low friction, sliding durability and adhesiveness, and can suppress thickness reduction due to wear even under high load and high speed sliding conditions. As a result, the sliding material has excellent sliding properties and can perform its function as a sliding material for a long time. At the same time, it is difficult for the components to wobble. The material can be bonded to a substrate. Detailed Implementation

[0028] The woven fabric of the present invention comprises a twisted yarn of fluoropolymer fibers and para-aramid fibers in at least one of the warp and weft yarns.

[0029] Besides methods of producing twisted yarns, other composite forms of fluoropolymer fibers and para-aramid fibers can be considered, such as structures using fluoropolymer fibers in the warp (or weft) and para-aramid fibers in the weft (or warp); structures alternating between fluoropolymer fibers and para-aramid fibers in the warp and weft; or double-woven fabrics where the fluoropolymer fiber layer and the para-aramid fiber layer are completely separated. However, in structures using fluoropolymer fibers in the warp (or weft) and para-aramid fibers in the weft (or warp); and in structures alternating between fluoropolymer fibers and para-aramid fibers, the fluoropolymer fibers are prone to rapid breakage in areas where low-strength fluoropolymer fibers are present (e.g., areas where fluoropolymer fibers are continuously arranged in the warp (or weft), and at the intersections of fluoropolymer fibers used in the warp and weft). These areas can potentially become the starting point for fabric breakage. Therefore, it is difficult to obtain satisfactory performance under conditions requiring extremely excellent sliding durability at high loads and high speeds. In the case of double-woven fabrics where the fluoropolymer fiber layer and the para-aramid fiber layer are completely separated, the fluoropolymer fiber layer wears down while sliding, making it difficult to suppress the reduction in thickness.

[0030] On the other hand, by integrating fluoropolymer fibers and para-aramid fibers into the woven fabric in the form of twisted yarns before weaving, the fluoropolymer fibers and para-aramid fibers are adjacent to each other, and the fluorine abrasion powder generated by sliding is easily transferred to the para-aramid fibers to form a self-lubricating film, thus achieving excellent abrasion durability under high load.

[0031] It should be noted that, as a form of integrating fluoropolymer fibers and para-aramid fibers before weaving, besides twisted yarn obtained by twisting fluoropolymer fibers and para-aramid fibers together, examples include core-spun yarn, in which para-aramid fibers are used as the core yarn and fluoropolymer fibers are wound around it as the sheath yarn; and blended yarns utilizing short fibers of fluoropolymer fibers and short fibers of para-aramid fibers. However, in core-spun yarn, the fluoropolymer fibers are predominantly located on the sheath side, so the soft fluoropolymer fibers are selectively worn during sliding, and the thickness reduction becomes significant. In blended yarns, the low friction of the fluoropolymer fibers makes it difficult for the fluoropolymer fibers and para-aramid fibers to intertwine sufficiently, making it difficult to obtain sufficient durability during sliding.

[0032] On the other hand, the twisted yarn uses para-aramid fibers as the backbone to maintain strength and suppress wear, while the surrounding fluoropolymer fibers act as abrasive powder and are easily transferred to the para-aramid fibers. In addition to excellent low friction and sliding durability, it also suppresses thickness reduction.

[0033] In twisted yarns containing fluoropolymer fibers and para-aramid fibers, the twist number (ply twist number) during twisting is preferably a twist coefficient k of 1000 or more and 25000 or less. More preferably, it is 1000 or more and 10000 or less, and particularly preferably, it is 2000 or more and 7000 or less.

[0034] Here, the twist coefficient k is denoted as T[t / m] for the average number of twists per meter and D[dtex] for the fineness of the twisted yarn, and is calculated by the following formula.

[0035] k = T × D 0.5

[0036] The twisted yarn containing fluoropolymer fibers and para-aramid fibers preferably has the fluoropolymer fibers or para-aramid fibers twisted before twisting. Twisting the yarn suppresses the opening of the para-aramid fibers caused by friction during weaving, thus preventing the fluoropolymer fibers in the twisted yarn from being covered by the opened para-aramid fibers and hindering low friction. In this case, the twist coefficient of the para-aramid fibers before twisting is preferably 500 or more and 5000 or less. Furthermore, if it is 500 or more and 3000 or less, in addition to the above-mentioned effects, the strength of the para-aramid fibers is increased due to the twisting, and when the woven fabric is made, the para-aramid fibers exist more firmly as skeleton fibers, thus improving sliding durability. Particularly preferred is 900 or more and 3000 or less. If the twist coefficient of the para-aramid fibers is greater than 5000, the strength may decrease compared to before twisting. When twisting para-aramid fibers, you can either simply twist the raw yarn of the desired fineness, or you can twist yarns with a fineness smaller than the desired fineness together. For example, to prepare para-aramid fibers with a twist of 33 t / m and a fineness of 850 dtex, you can twist the raw yarn of para-aramid fiber with a fineness of 850 dtex at 33 t / m, or you can twist two raw yarns of para-aramid fiber with a fineness of 425 dtex together at 33 t / m.

[0037] The twisted yarn containing fluoropolymer fibers and para-aramid fibers can be adjusted by varying the yarn length based on the difference in thermal shrinkage between the fluoropolymer fibers and the para-aramid fibers at the highest temperature exposed during processing and use. For example, if the highest temperature exposed during processing and use is 200°C, and the difference in thermal shrinkage between the fluoropolymer fibers and the para-aramid fibers at that temperature is 10%, then during twisting, the yarn length of the fluoropolymer fibers can be set to be 10% longer than that of the para-aramid fibers. In this way, unevenness caused by the difference in thermal shrinkage can be suppressed, and the effects of the present invention can be easily obtained.

[0038] The woven fabric of the present invention comprises, preferably, a twisted yarn of fluoropolymer fibers and para-aramid fibers in at least one of the warp and weft yarns. Alternatively, it may be interwoven with other fibers.

[0039] This invention has discovered that by selecting para-aramid fibers as the interweaving material for fluoropolymer fibers, thickness reduction can be significantly suppressed compared to using other fibers such as PPS fibers, meta-aramid fibers, and liquid crystal polyester fibers. When woven fabrics using fibers other than para-aramid fibers as high-strength fibers are used in sliding materials, for example, by employing weaving techniques to largely incorporate fluoropolymer fibers on the sliding surface and large amounts of high-strength fibers as reinforcement on the non-slip surface, a balance between low friction and sliding durability can be optimized. However, in the initial stages of sliding, the wear rate in areas containing a large amount of fluoropolymer fibers increases rapidly, making it difficult to simultaneously achieve both sliding durability and suppression of thickness changes due to wear.

[0040] On the other hand, as in this invention, by twisting para-aramid fibers with fluoropolymer fibers, the para-aramid fibers exhibit an extremely high reinforcing effect, enabling the production of woven fabrics that provide not only slip durability but also suppression of thickness changes due to abrasion. Furthermore, para-aramid fibers also have excellent processability, being cheaper and easier to manufacture woven fabrics suitable for thin slip materials compared to inorganic fibers such as carbon fibers. Additionally, fuzzing caused by rubbing, a problem with inorganic fibers, can be suppressed. Therefore, even when used as a single woven fabric unit, for example, when it is used as a slip material attached to a structure, without fabricating a resin-impregnated composite material, it is possible to prevent the introduction of impurities such as lint into the structural system.

[0041] The woven fabric of the present invention has a relief height of 1150 μm or less on at least one side where the aforementioned twisted yarn is exposed. It should be noted that, here, "in at least one side where the twisted yarn is exposed" means that when the twisted yarn is exposed on only one side, and on two sides, or on more sides where the twisted yarn is exposed, the relief height on any one side only needs to satisfy the above range when the exposure is equal.

[0042] Compared to para-aramid fibers, fluoropolymer fibers exhibit greater thermal shrinkage. After wet and dry heat treatments, the difference in shrinkage results in areas with higher concentrations of para-aramid fibers becoming convex and areas with higher concentrations of fluoropolymer fibers becoming concave, easily creating an uneven surface. In this unevenness, the convex portions, which contain a large amount of para-aramid fibers, tend to selectively contact the target material during the initial sliding phase. If the unevenness increases significantly, the physical interactions between the convex portions and the target material, such as entanglement, increase with the surface roughness of the target material, leading to a tendency for an increased coefficient of friction. Furthermore, stress concentration occurs at the convex portions, thus accelerating the wear rate. If the unevenness is excessive, the adhesive may not penetrate the concave portions during bonding, reducing the actual bonding area and hindering sufficient adhesion. Increasing the adhesive application and pressing pressure to increase the bonding area results in excessive adhesive penetration at the convex portions compared to the surrounding areas, causing adhesive leaching onto the sliding surface and deteriorating sliding performance. Based on the above viewpoints, the unevenness height is 1150 μm or less. More preferably, it is 1000 μm or less, and even more preferably, it is 800 μm or less. As a particularly preferred condition, it is 500 μm or less. The practical lower limit of the unevenness height is 0 μm.

[0043] The mass percentage of fluoropolymer fibers in the twisted yarn of the present invention is preferably 3 to 97% by mass. If the mass percentage of fluoropolymer fibers in the twisted yarn is greater than 97% by mass, the amount of para-aramid fibers capable of capturing the abrasion powder as a reinforcing material is too small relative to the amount of fluoropolymer abrasion powder generated, making it difficult to suppress thickness changes. The mass percentage of fluoropolymer fibers in the twisted yarn is more preferably 80% by mass or less, and even more preferably 60% by mass or less. If the mass percentage of fluoropolymer fibers in the twisted yarn is less than 3% by mass, the amount of fluoropolymer abrasion powder transferred to the para-aramid fibers is too small, and sufficient low friction is not obtained. The mass percentage of fluoropolymer fibers in the twisted yarn is preferably 20% by mass or more, and even more preferably 40% by mass or more.

[0044] The thickness of the woven fabric of the present invention is preferably 1.3 mm or less. By using a twisted yarn of fluoropolymer fiber and para-aramid fiber in at least one of the warp and weft yarns, the rate of thickness reduction of the woven fabric is significantly reduced even under high load and high speed sliding, thus achieving sufficient sliding durability even with a small thickness. Reasons for thickness reduction in woven fabric include fiber wear and breakage leading to their rejection by the system, and changes in the density of individual yarns due to pressure and sliding, resulting in a denser filling structure. The greater the absolute amount of voids present in the woven fabric due to the latter, the greater the thickness reduction. In other words, the smaller the thickness of the woven fabric, the better the thickness reduction can be suppressed. A thickness of 1.2 mm or less is preferred, more preferably 0.8 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.3 mm or less. If the thickness is too small, it is difficult to obtain the desired wear durability; therefore, a thickness of 0.05 mm or more is preferred, more preferably 0.1 mm or more, and particularly preferably 0.2 mm or more.

[0045] The weaving structure of the woven fabric of the present invention is not particularly limited, and twill weave, satin weave, plain weave, and variations thereof can be used. Among them, plain weave is preferred because it is easier to reduce thickness and suppress thickness reduction due to slippage.

[0046] The woven fabric of the present invention can be selected from single-layer, double-layer, or other multiple weaves, depending on the desired characteristics. If it is a single-layer weave, the thickness can be reduced more easily, and thickness reduction due to slippage is easily suppressed. When manufacturing a multiple woven fabric with multiple weaves such as double-layer, if the outermost surface is designated as the first surface and the outermost surface opposite to the first surface is designated as the second surface, it is preferable that at least one of the warp and weft yarns of the first surface includes the aforementioned twisted yarn. Furthermore, when this multiple woven fabric is used as a slipping material, it is preferable that the first surface is designated as the slipping surface. If only one side of the multiple woven fabric, i.e., the first surface, is used as the slipping surface as a slipping material, the second surface is a non-slipping surface. In the multiple woven fabric, the fibers used in the layer containing the non-slipping surface can be appropriately selected according to the purpose; by using para-aramid fibers, slippage durability and adhesion can be easily balanced. From the viewpoint of thickness, double-layer woven fabrics are preferred. If it is a double-layer weave, even if thickness reduction occurs due to slippage, sufficient thickness can be maintained for a long time, easily improving slippage durability. When the above-mentioned double structure is used to make a double woven fabric comprising a first side and a second side, it is preferable that at least one of the warp and weft yarns of the first side contains a twisted yarn of fluoropolymer fibers and para-aramid fibers, and more preferably that the warp and weft yarns of the first side contain a twisted yarn of fluoropolymer fibers and para-aramid fibers.

[0047] When a double structure is chosen, it is preferable that the ratio (CF1 / CF2) of the coverage factor of the first face (CF1) to the coverage factor of the second face (CF2) is less than 1. Here, the coverage factor refers to the value obtained by the following formula.

[0048] Coverage factor = (Total warp fineness [dtex]) 0.5 × Warp density [threads / 2.54cm] + (Total weft fineness [dtex]) 0.5 ×Weft density [threads / 2.54cm]

[0049] It should be noted that the total fineness mentioned above when calculating the coverage factor is converted according to the specific gravity of the fiber type. This technology is a woven fabric containing fluoropolymer fibers and para-aramid fibers. Taking polytetrafluoroethylene (PTFE) fiber as an example, the specific gravity of fluoropolymer fiber is 2.3, which is greater than that of para-aramid fiber (1.4). Therefore, under the same fineness, the actual fiber diameter is larger for para-aramid fiber. Therefore, the coverage factor is calculated by converting the fineness of fluoropolymer fiber to the standard of para-aramid fiber in a way that reflects the actual fiber diameter. That is, the fineness T of the original yarn used for specific gravity D and fineness T0 is converted using the following formula, based on the specific gravity (1.4) of para-aramid fiber.

[0050] T = T0 × 1.4 / D

[0051] For example, the total fineness T of a twisted yarn containing 440 dtex of fluoropolymer fiber with a specific gravity of 2.3 and 800 dtex of para-aramid fiber is calculated by the following formula.

[0052] T = 440 × 1.4 / 2.3 + 800 = 1067

[0053] The ratio (CF1 / CF2) of the coverage factor (CF1) of the first surface to the coverage factor (CF2) of the second surface is less than 1, thereby reducing the unevenness of the first surface (when it is used as a sliding material, the first surface is set as the sliding surface and the second surface is set as the adhesive surface, forming a sliding surface (non-adhesive surface)).

[0054] As mentioned above, the greater the difference in thermal shrinkage between fluoropolymer fibers and para-aramid fibers, the greater the tendency for the woven fabric to have unevenness. The difference in yarn length caused by thermal shrinkage is constrained at the intersection of warp and weft yarns; the longer yarns are convex, and the shorter yarns are concave, creating unevenness. A high cover factor, i.e., high fineness or high density, results in fewer gaps absorbing the difference in yarn length caused by thermal shrinkage, thus increasing unevenness. On the other hand, a low cover factor weakens the constraint between warp and weft yarns, making it difficult to maintain the fabric structure during sliding and reducing sliding durability. Therefore, by making the layer containing the first side a structure with a low cover factor and the layer containing the second side a structure with a high cover factor, the unevenness of the first side is suppressed while the fabric structure is maintained in the second side, resulting in long-term sliding durability. It should be noted that a low cover factor on the first side leads to more gaps, sometimes resulting in unevenness where the fiber portion is convex and the gap portion is concave. In this case, there are sufficient gaps, so the warp and weft yarns are compressed and spread out flat by the interlaced weft and warp yarns. The unevenness caused by the gaps due to the low coverage factor is less than the unevenness caused by the difference in heat shrinkage.

[0055] Based on the above viewpoints, when choosing a double weave, the ratio (CF1 / CF2) of the cover factor (CF1) of the first side to the cover factor (CF2) of the second side is preferably less than 1, and more preferably less than 0.8. If the cover factor (CF2) of the second side is too large, the weaveability deteriorates; if the cover factor (CF1) of the first side is too small, the number of interlacing points is too few relative to the yarn thickness, making it easy for the constituent fibers of only the first side to unravel due to slippage. Therefore, CF1 / CF2 is preferably greater than 0.2, and more preferably greater than 0.4.

[0056] When selecting multi-layered woven fabrics with double or other multiple structures, para-aramid fibers are preferred for the knot yarn. Here, knot yarn refers to the yarn connecting the two layers that constitute a double or other multiple structure. For example, if the warp yarn of the first side is considered the knot yarn, the knot yarn has a normal portion forming the first side and a knotted portion that intertwines with the weft yarn of the second side. At the knotted portion, the yarn is more wrapped than in the normal portion and is under tension. If the knotted portion uses a twisted yarn of fluoropolymer fibers and para-aramid fibers, the tension of the knotted portion is further increased due to heat shrinkage during heating, easily pushing the intertwined weft yarn upwards and forming a protrusion. Based on the above, para-aramid fibers with low heat shrinkage are preferred for the knot yarn.

[0057] The woven fabric of the present invention does not particularly limit the mass ratio of fluoropolymer fibers in the overall woven fabric. However, by setting the mass ratio of fluoropolymer fibers in the overall woven fabric to 20% by mass or less, the unevenness height can be reduced even when heat treatment is included in the process, which is therefore preferable. The mass ratio of fluoropolymer fibers, which have greater heat shrinkage, is reduced compared to para-aramid fibers, thereby suppressing unevenness caused by differential shrinkage after heat treatment. If the composite is other than fluoropolymer fibers and para-aramid fibers, the coefficient of friction increases and durability decreases due to the reduction in fluoropolymer fibers. By selecting para-aramid fibers, an extremely high reinforcing effect is exhibited, and excellent sliding properties are maintained even when the mass ratio of fluoropolymer fibers is low. From the viewpoint of reducing unevenness height, the mass ratio of fluoropolymer fibers in the overall woven fabric is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 10% by mass or less. The mass ratio of fluoropolymer fibers is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more.

[0058] In this invention, the fluororesin, a component of fluororesin fibers, can be any monomer unit containing one or more fluorine atoms in its main chain or side chain. Preferably, it is composed of monomer units with a large number of fluorine atoms.

[0059] The monomeric unit containing one or more fluorine atoms is preferably contained in 70 mol% or more, more preferably in 90 mol% or more, and even more preferably in 95 mol% or more in the repeating structural unit of the polymer.

[0060] Examples of monomers containing one or more fluorine atoms include vinyl monomers containing fluorine atoms such as tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, among which at least tetrafluoroethylene is preferred.

[0061] As fluoropolymers, substances such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-p-fluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), and ethylene-tetrafluoroethylene copolymer (ETFE), either alone or in blends of two or more, can be used.

[0062] From the viewpoint of sliding properties, the content of tetrafluoroethylene units in fluororesins containing tetrafluoroethylene units is preferably high, preferably 90 mol% or more, more preferably 95 mol% or more, of tetrafluoroethylene copolymers, and most preferably polytetrafluoroethylene fibers as homopolymers of tetrafluoroethylene are used.

[0063] The form of the fluoropolymer fiber used in this invention can be either a monofilament consisting of one filament or a multifilament consisting of multiple filaments. From the viewpoint of weavability and surface unevenness when the fabric is made, a multifilament is preferred.

[0064] Furthermore, the total fineness of the fluoropolymer fibers used in this invention is preferably in the range of 50 to 6000 dtex. More preferably, it is in the range of 500 to 5500 dtex, and even more preferably, it is in the range of 400 to 1500 dtex. If the total fineness of the fibers constituting the fabric is 50 dtex or more, the strength of the fibers can be guaranteed to a certain extent, and yarn breakage during weaving can be reduced, thus improving processability. If it is 6000 dtex or less, good processability during weaving is obtained.

[0065] The lower the dry heat shrinkage rate of the fluoropolymer fiber used in this invention, the smaller the difference in heat shrinkage between it and the para-aramid fiber, which helps to suppress unevenness after heating, and is therefore preferred. From this viewpoint, the dry heat shrinkage rate is preferably 15% or less, more preferably 10% or less, and particularly preferably 5% or less. The substantial lower limit of the dry heat shrinkage rate is 0%. The dry heat shrinkage rate of the fluoropolymer fiber can be appropriately controlled by methods commonly used in the art, such as oxidation treatment or heat treatment after stretching. The above-mentioned dry heat shrinkage rate is a value determined by the method described later.

[0066] The form of the para-aramid fibers constituting the woven fabric of the present invention is not particularly limited; both filaments (long fibers) and short fibers (yarns) can be used. From the viewpoint of tensile strength and tensile stiffness, filaments are preferred. Furthermore, either monofilaments composed of a single filament or multifilaments composed of multiple filaments can also be used. If it is a multifilament, the surface area is large, so the fluorinated abrasion powder generated by the wear of fluoropolymer fiber A is easily transferred to fiber B, which is therefore particularly preferred.

[0067] The total fineness of the para-aramid fibers is preferably in the range of 50 to 4000 dtex. More preferably, it is in the range of 200 to 4000 dtex, and even more preferably, it is in the range of 800 to 3300 dtex. If the total fineness of the fibers constituting the fabric is 200 dtex or more, the fibers have high strength, which can suppress fiber breakage during abrasion. In addition, it can reduce yarn breakage during weaving, thus improving processability. If it is 3300 dtex or less, the surface roughness of the fabric is small, which can suppress the effect on low friction.

[0068] As mentioned above, the unevenness of woven fabrics is easily affected by the shrinkage behavior of fluoropolymer fibers and para-aramids. Therefore, in post-weaving processing, temperature and humidity are controlled to ensure the unevenness falls within the range specified in this invention. There are no restrictions on the post-processing method as long as the resulting woven fabric falls within the range specified in this invention. To ensure the unevenness falls within the range specified in this invention through heat treatment during post-processing, it is preferable to choose a method that does not perform heat treatment or to suppress heat treatment conditions. Specifically, by lowering the temperature or shortening the time of wet heat treatment or dry heat treatment, or by performing wet heat treatment only or dry heat treatment only, the heat treatment conditions can be mitigated, thereby controlling the unevenness performance. In the design of the woven fabric to obtain the desired woven fabric, the post-processing conditions can be determined by considering the above-mentioned factors to achieve the unevenness range specified in this invention.

[0069] The wet heat treatment mentioned here refers to the refining, relaxation, and dyeing steps performed for the purpose of washing and removing residual stress from woven fabrics. This treatment helps to suppress unevenness caused by the difference in thermal shrinkage between fluoropolymer fibers and para-aramid fibers. It should be noted that careful attention must be paid to the conditions of washing and refining the woven fabric; therefore, it is preferable not to sizing during weaving.

[0070] The dry heat treatment mentioned here refers to the drying steps following the refining, relaxation, and dyeing steps, the heat setting step, and the drying step after coating, as described later. By paying attention as described above, the unevenness caused by the difference in thermal shrinkage between the fluoropolymer fiber and the para-aramid fiber can be suppressed.

[0071] To further improve the abrasion durability of the aforementioned woven fabric, a resin can be coated onto the fabric. The resin used can be a thermosetting resin or a thermoplastic resin. There are no particular limitations; preferred thermosetting resins include phenolic resin, melamine resin, urea resin, unsaturated polyester resin, epoxy resin, polyurethane resin, diallyl phthalate resin, silicone resin, polyimide resin, vinyl ester resin, and their modified resins. For thermoplastic resins, preferred resins include vinyl chloride resin, polystyrene resin, ABS resin, polyethylene resin, polypropylene resin, fluoropolymer resin, polyamide resin, polyacetal resin, polycarbonate resin, polyester resin, acrylic resin, and further thermoplastic polyurethane, butadiene rubber, nitrile rubber, chloroprene rubber, polyester elastomer, and other synthetic rubbers or elastomers. Among these, resins with phenolic resin and polyvinyl butyral resin as main components, unsaturated polyester resin, vinyl ester resin, polyethylene, polypropylene, and other polyolefin resins and polyester resins are preferred due to their impact resistance, dimensional stability, strength, and price. The thermosetting and thermoplastic resins may contain various commonly used additives for industrial purposes, applications, manufacturing processes, or to improve productivity or properties during processing. For example, they may contain modifiers, plasticizers, fillers, release agents, colorants, diluents, etc. It should be noted that the term "main component" here refers to the component with the largest mass ratio among all components except the solvent. In the case of resins with phenolic resin and polyvinyl butyral resin as main components, it means that the mass ratio of these two resins is the first and second largest (in different orders).

[0072] As a method for coating resin onto the aforementioned woven fabric, in the case of liquid resin, solvent-based resin, or water-based resin, coating can be performed by methods such as spraying, roller coating, knife coating, comma coating, gravure coating, flexographic printing, brush coating, and melt extrusion lamination. Furthermore, in the case of powdered resin particles, methods such as electrostatic coating can be used. After coating, the solvent may evaporate, or the resin may be heat-cured or melt-formed into a film. At this time, heat treatment is performed as needed. From the viewpoint of reducing heat treatment temperature and suppressing unevenness, processing with low moisture adhesion is preferred; specifically, methods such as spraying, flexographic printing, and brush coating are suitable.

[0073] In the woven fabrics of the present invention, lubricants may also be added as needed. The type of lubricant is not particularly limited, but silicone-based lubricants and fluorine-based lubricants are preferred.

[0074] The woven fabric obtained in this way is a woven fabric using twisted yarns of fluoropolymer fibers and para-aramid fibers, and with suppressed unevenness, thus possessing both low friction, sliding durability, and adhesion. Therefore, the woven fabric of the present invention can exhibit higher sliding durability than before in applications where it has been difficult to use for a long time due to high-speed sliding under high loads. In addition, it can suppress shaking and is easier to attach to a substrate, thus achieving extremely high industrial applicability as a sliding material. Furthermore, when using the woven fabric of the present invention as a sliding material, it is preferable to use at least one surface that exposes the aforementioned twisted yarn and has an unevenness height of 1150 μm or less as the sliding surface.

[0075] Example

[0076] Hereinafter, embodiments and comparative examples of the present invention will be described together.

[0077] It should be noted that the methods for measuring the various characteristics used in this embodiment are as follows.

[0078] (1) Fineness

[0079] The fineness was determined according to method 8.3.B (simplified method) of JIS L1013:2010 "Test Methods for Filaments of Chemical Fibers". It should be noted that when determining the total fineness of fibers contained in a woven fabric, the decomposed yarn is removed from the woven fabric for measurement. However, if the amount of decomposed yarn required for the above-mentioned measurement method cannot be guaranteed, the result of the maximum guaranteed length and the number of trials should be used instead.

[0080] (2) Weaving density

[0081] According to section 8.6.1 of JIS L1096:2010 "Test Methods for Base Fabrics of Woven and Knitted Fabrics", place the sample on a flat platform, eliminate unnatural wrinkles and tension, count the number of warp and weft yarns contained in a 50mm interval at different locations, and calculate the average value per unit length.

[0082] (3) Thickness

[0083] The thickness was measured at 23.5 kPa after standing for 10 seconds, according to method 8.4.A of JIS L1096:2010 "Test methods for base fabrics of woven and knitted fabrics".

[0084] (4) Concave-convex height

[0085] Place the sample on a flat stage, eliminating unnatural wrinkles and tension. Observe the sample using a 3D-linked digital microscope (KEYENCE VHX-7000), photographing a 25mm × 25mm area. The height difference between the two points of maximum and minimum height within this area is defined as the convexity / concavity height. It should be noted that if only one side of the sample exposes the twisted yarn, observe the sample with that side facing upwards. If the twisted yarn is exposed on both sides, observe the sample with the side exposing more exposed facing upwards. If both sides are exposed equally, observe the sample with either side facing upwards. Perform the above measurements on five locations for each sample, and calculate the average of the three points after removing the maximum and minimum values.

[0086] (5) Coefficient of kinetic friction

[0087] According to Method A of JIS K7218:1986 "Test Method for Sliding Abrasion of Plastics", the woven fabric sample was 30 mm long and 30 mm wide, and placed and fixed on the sample stage on an SUS plate of the same size and about 3 mm thick, with the surface whose unevenness height was measured in (4) above sliding with the ring described later. The object material used was a hollow cylindrical ring made of S45C with an outer diameter of 25.6 mm, an inner diameter of 20 mm, and a length of 15 mm. The surface of the ring was ground with sandpaper and adjusted to achieve a surface roughness of Ra = 0.8 μm ± 0.1. The roughness was measured using a roughness measuring instrument (Mitsutoyo "SJ-210"). The ring abrasion tester used was A&D "MODEL: EFM-III-EN", and the test was conducted at a friction load of 10 MPa and a friction speed of 400 mm / s. The sliding torque was measured and the average friction coefficient until fracture was calculated.

[0088] (6) Sliding durability distance

[0089] In the above ring abrasion test, the sliding continued until the woven fabric broke, and the cumulative sliding distance until the breakage was defined as the sliding durability distance.

[0090] (7) Thickness reduction rate

[0091] In the above ring abrasion test, the test was stopped 1 minute after the sliding began (sliding distance 24m). After the sample was removed, the cross-section of the sliding part was cut out and observed using an electron microscope (KEYENCE "VHX-7000") to determine the thickness D1 after sliding. A new sample was prepared, and a load of 10MPa was applied using the ring abrasion testing machine. After standing for 1 minute, the sample was similarly removed, and the cross-section of the pressurized part was cut out and observed using an electron microscope (KEYENCE "VHX-7000") to determine the thickness D0. The thickness reduction rate D [μm / min] was calculated using the following formula.

[0092] D = D0 - D1

[0093] It should be noted that the new samples used are the same type of samples as those used in the ring wear test, and are taken from the closest possible locations.

[0094] (8) Adhesion

[0095] The test was conducted according to JIS K6850:1999 "Adhesives - Tensile shear strength test method for rigid bonded materials". For the woven fabric sample, a length of 100 mm and a width of 25 mm was used as the test material. SS400 boards with a thickness of 15 mm, a length of 100 mm, and a width of 25 mm were prepared. Epoxy adhesive (Sleebond Co., Ltd. "2088E") was used. The coating weight was set to 150 g / m². 2 The overlap length was set to 12.5 mm. Adhesive was evenly applied to an SS400 plate. The woven fabric was then overlapped with the object material on the opposite side of the surface where the unevenness of the woven fabric was measured in (4) above. A pressure of 16 kPa was applied, and the plate was left to stand for 48 hours. The resulting sample was then stretched using a tensile testing machine (Instron "5965") at a tensile speed of 5 mm / min. The tensile shear bond strength was calculated by dividing the maximum force at failure by the bonded area.

[0096] (9) Mass ratio of fluoropolymer fiber in twisted yarn

[0097] The woven fabric was cut into 200mm warp x 200mm weft sections, and the warp and weft yarns were then separated to obtain decomposed yarns. Five yarns were randomly selected from each of the decomposed warp and weft yarns and twisted together to separate them into fluoropolymer fibers and para-aramid fibers. The mass of each fiber was measured. The total mass of the five twisted yarns is denoted as W, and the total mass of the fluoropolymer fibers in the five twisted yarns is denoted as WF. The mass ratio α of the fluoropolymer fibers in the twisted yarns is calculated using the following formula.

[0098] α = WF / W × 100 [mass%]

[0099] However, if the amount of yarn required by the above-mentioned measurement method cannot be guaranteed by the decomposed yarn, the maximum length that can be guaranteed and the results of the test based on the number of attempts shall be used instead.

[0100] (10) Mass percentage of fluoropolymer fibers in the overall woven fabric

[0101] After cutting the woven fabric into 200mm warp × 200mm weft sections, the warp and weft yarns were separated, and the total mass W of the separated yarns was measured. Next, only the twisted yarns were selected from the separated yarns, and the total mass W1 of the twisted yarns in the woven fabric was measured. Then, fluoropolymer fibers that were not twisted yarns but existed independently in the woven fabric were selected, and their total mass W2 was measured. The mass ratio Y of the fluoropolymer fibers A in the woven fabric was calculated using the following formula. α uses the value α measured in the aforementioned (9).

[0102] Y = (W1 × α / 100 + W2) / W × 100 [mass %]

[0103] However, if the amount of yarn required by the above-mentioned measurement method cannot be guaranteed by the decomposed yarn, the maximum length that can be guaranteed and the results of the test based on the number of attempts shall be used instead.

[0104] (11) Dry heat shrinkage rate

[0105] The following method was used to determine the properties of fluoropolymer fibers.

[0106] Fold the sample in half and tie it to form a ring-shaped specimen. Apply an initial load (6% of the fineness (g)) to the specimen and measure the lengths of both ends of the ring-shaped specimen. Remove the initial load, heat-treat it in a dryer at 230°C for 30 minutes, and then remove it and cool it to room temperature. Subsequently, apply the initial load again and measure the lengths of both ends of the ring-shaped specimen.

[0107] The dry heat shrinkage rate is calculated according to the following formula, and the average of the three calculations is rounded to one decimal place.

[0108] ΔL=(L1-L2) / L1×100

[0109] Here, ΔL: dry heat shrinkage rate (%), L1: length before heat treatment (mm), and L2: length after heat treatment (mm).

[0110] Example 1

[0111] A twisted yarn was obtained by twisting PTFE fiber ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc.), with a total fineness of 1330 dtex and a single yarn count of 180 filaments, and a dry heat shrinkage rate of 9% when heated at 230°C for 30 minutes, with para-aramid fiber ("Kevlar" (registered trademark), manufactured by Toray Industries, Inc.), with a total fineness of 880 dtex and a single yarn count of 534 filaments, at a twist rate of 81 t / m. This twisted yarn was then used as both warp and weft yarns to produce a single-layer plain weave on a loom. No sizing or other treatments to improve weave properties were applied to the warp yarns.

[0112] Comparative Example 1

[0113] The woven fabric of Example 1 was refined in a refining tank at 80°C for 20 minutes, dried at 130°C for 2 minutes, and then heat-set at 180°C for 1 minute.

[0114] Example 2

[0115] PTFE fiber (Toyoflon, a registered trademark, manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% after heating at 230°C for 30 minutes) with a total fineness of 440 dtex and a single yarn count of 60 filaments was twisted with para-aramid fiber (Kevlar, a registered trademark, manufactured by Toray Industries, Inc.) with a total fineness of 440 dtex and a single yarn count of 267 filaments at a twist rate of 167 t / m to obtain a twisted yarn. The aforementioned twisted yarn was used in the warp and weft yarns of the first side, while para-aramid fiber (Kevlar, a registered trademark, manufactured by Toray Industries, Inc.) with a total fineness of 3300 dtex and a single yarn count of 1333 filaments was used in the warp and weft yarns of the second side. A double plain weave was produced using a loom. Sizing or other methods to improve weaveability were not applied to the warp yarns. It was then refined in a refining tank at 80°C for 20 minutes and dried at 130°C for 2 minutes.

[0116] Example 3

[0117] As the weft yarn of the first side, para-aramid fiber ("Kevlar" (registered trademark) manufactured by Toray Dupont Co., Ltd.) with a total fineness of 3300 dtex and a single yarn count of 1330 filaments was used. Otherwise, a double plain weave was made by the same method as in Example 2, and then refined in a refining bath at 80°C for 20 minutes and dried at 130°C for 2 minutes.

[0118] Comparative Example 2

[0119] PTFE fiber (Toyoflon, a registered trademark, manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% after heating at 230°C for 30 minutes) with a total fineness of 880 dtex and a single yarn count of 120 filaments was twisted with liquid crystal polyester fiber (Shiberas, a registered trademark, manufactured by Toray Industries, Inc.) with a twist rate of 167 t / m to obtain a twisted yarn. The aforementioned twisted yarn was used in the warp yarn, and liquid crystal polyester fiber (Shiberas, a registered trademark, manufactured by Toray Industries, Inc.) with a total fineness of 1700 dtex and a single yarn count of 288 filaments was used in the weft yarn. A 3 / 1 twill fabric was then produced on a loom. No sizing or other treatments to improve weave properties were applied to the warp yarn. Subsequently, the fabric was refined in a refining bath at 80°C for 20 minutes, dried at 130°C for 2 minutes, and then heat-set at 180°C for 1 minute.

[0120] Comparative Example 3

[0121] PTFE fiber (Toyoflon, a registered trademark, manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% after heating at 230°C for 30 minutes) with a total fineness of 440 dtex and a single yarn count of 60 filaments was twisted with liquid crystal polyester fiber (Silas, a registered trademark, manufactured by Toray Industries, Inc.) with a total fineness of 425 dtex and a single yarn count of 72 filaments at a twist rate of 167 t / m to obtain a twisted yarn. This twisted yarn was then used for both warp and weft yarns, and a single-layer plain weave was produced on a loom. No sizing or other treatments to improve weave properties were applied to the warp yarns. Subsequently, the yarn was refined in a refining bath at 80°C for 20 minutes, dried at 130°C for 2 minutes, and then heat-set at 180°C for 1 minute.

[0122] Comparative Example 4

[0123] The warp yarns are alternately arranged in a 2:2 ratio of PTFE fiber ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% when heated at 230°C for 30 minutes) with liquid crystal polyester fiber ("Shiberas" (registered trademark), manufactured by Toray Industries, Inc.), with a fineness of 1700 dtex and a single yarn count of 288 filaments. The weft yarns are alternately arranged in a 2:2 ratio of PTFE fiber ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc., with a fineness of 2660 dtex and a single yarn count of 360 filaments) with a dry heat shrinkage rate of 9% when heated at 230°C for 30 minutes, with a fineness of 425 dtex and a single yarn count of 72 filaments. This is used to produce a single plain weave fabric on a loom. No sizing or other treatments to improve weaveability were applied to the warp yarns. Subsequently, the yarns were refined in a refining tank at 80°C, dried at 130°C for 2 minutes, and then set at 200°C for 1 minute.

[0124] Comparative Example 5

[0125] The warp yarns alternate between PTFE fibers ("Toyoflon" (registered trademark), 60 filaments per yarn, manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% after heating at 230°C for 30 minutes) and para-aramid fibers ("Kevlar" (registered trademark), 1670 dtex, 1000 filaments per yarn) in a 2:2 ratio. The weft yarns also alternate between PTFE fibers ("Kevlar" (registered trademark), PTFE fibers ("Kevlar"), PTFE fibers ("Toray Dupont" (registered trademark), and PTFE fibers ("Kevlar" (registered trademark)). A single-layer plain weave was produced using alternating 2 (2) PTFE fibers ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 9% after heating at 230°C for 30 minutes) and para-aramid fibers ("Kevlar" (registered trademark), manufactured by Toray Dupont Co., Ltd., with a fineness of 440 dtex and a yarn count of 267 filaments) on a loom. No sizing or other treatments to improve weave properties were applied to the warp yarns. The fabric was then refined in a scouring bath at 80°C, dried at 130°C for 2 minutes, and set at 200°C for 1 minute.

[0126] Example 4

[0127] The woven fabric described in Example 1 was heat-set at 120°C for 1 minute.

[0128] Example 5

[0129] The woven fabric described in Example 1 was heat-set at 140°C for 1 minute.

[0130] Example 6

[0131] The woven fabric described in Example 1 was heat-set at 160°C for 1 minute.

[0132] Example 7

[0133] The woven fabric described in Example 1 was heat-set at 180°C for 1 minute.

[0134] Example 8

[0135] The woven fabric described in Example 1 was refined in a refining tank at 80°C for 1 minute.

[0136] Example 9

[0137] The woven fabric described in Example 1 was refined in a refining tank at 80°C for 20 minutes.

[0138] Example 10

[0139] The woven fabric described in Example 1 was refined in a refining tank at 60°C for 20 minutes.

[0140] Example 11

[0141] As the fluoropolymer fiber, a PTFE fiber with a total fineness of 1330 dtex and a single yarn count of 180 filaments ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc., with a dry heat shrinkage rate of 4% when heated at 230°C for 30 minutes) was used. In addition, a plain weave was made by the same method as in Example 1, and then refined in a refining bath at 80°C for 20 minutes, dried at 130°C for 2 minutes, and heat-set at 180°C for 1 minute.

[0142] The evaluation results of the twisted yarn composition, fabric composition, unevenness height, thickness reduction rate, dynamic friction coefficient, adhesion, and sliding durability distance of the woven fabrics described in Examples 1 to 3, Example 11, and Comparative Example 1 are summarized in Table 1.

[0143] The evaluation results for the woven fabrics described in Comparative Examples 2 to 5, including the composition of the twisted yarn, fabric composition, thickness reduction rate, coefficient of kinetic friction, adhesion, and sliding durability distance, are summarized in Table 2.

[0144] The evaluation results of the composition of the twisted yarn, fabric composition, processing content, and unevenness of the woven fabrics described in Examples 1, 1 Comparative Examples, and 4 to 10 are summarized in Table 3.

[0145] [Table 1]

[0146]

[0147] [Table 2]

[0148]

[0149] [Table 3]

[0150]

Claims

1. A sliding material comprising a woven fabric bonded to a substrate, wherein, The woven fabric contains at least one of the warp and weft yarns that is a twisted yarn of fluoropolymer fibers and para-aramid fibers, and the unevenness height of at least one side of the aforementioned twisted yarn is less than 1150 μm. The sliding material uses at least one side of the aforementioned twisted yarn with an unevenness height of less than 1150 μm as the sliding surface.

2. The sliding material according to claim 1, wherein, The thickness of the woven fabric is less than 1.3 mm.

3. The sliding material according to claim 1 or 2, wherein, The woven fabric contains the aforementioned twisted yarn in both the warp and weft yarns.

4. The sliding material according to claim 1 or 2, wherein, The aforementioned woven fabric is a multi-faceted woven fabric comprising a first surface as the outermost surface and a second surface as the outermost surface opposite to the aforementioned first surface, wherein at least one of the warp and weft yarns of the aforementioned first surface comprises the aforementioned twisted yarn.

5. The sliding material according to claim 4, wherein, The ratio of the coverage coefficient CF1 of the first surface to the coverage coefficient CF2 of the second surface is less than 1.

6. The sliding material according to claim 1 or 2, wherein, The mass percentage of fluoropolymer fibers in the aforementioned woven fabric is less than 20% by mass.

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