Fabrics and sliding materials

Abstract

The present invention provides a woven fabric which is capable of suppressing thickness reduction due to friction even under high load and high speed sliding conditions, and which therefore has excellent slidability when used as a sliding material, makes wobble unlikely to occur between members, and can be used adhered to a base material. The present invention provides a woven fabric and a sliding material which each comprise a folded yarn of fluororesin fibers and para-aramid fibers for a warp yarn and / or a weft yarn, wherein the height of a relief pattern on at least one surface on which this folded yarn is exposed is not more than 1,150 μm.

Description

[Technical Field]

[0001] The present invention relates to a fabric and a sliding material. [Background technology]

[0002] Taking advantage of the low coefficient of friction of fluororesin, technologies have been developed to impart low friction between sliding components by turning fluororesin into fibers, forming woven or nonwoven fabrics, and placing these between sliding components. If the thickness of the sliding fabric is significantly reduced due to wear, the clearance around the sliding components changes, causing rattle in the system. Therefore, sliding fabrics are required to not only have low friction and sliding durability, but also not undergo significant thickness reduction due to wear, even under harsh sliding conditions.

[0003] Furthermore, since fluororesins generally have poor adhesive properties, when a sliding material is attached to a substrate to impart sliding properties, it is essential to ensure adhesive properties in addition to the low friction and sliding durability of the sliding material itself.

[0004] As a technique for imparting low friction to a sliding fabric, for example, Patent Document 1 discloses a self-lubricating fabric that is a woven fabric containing a composite yarn formed from a fluororesin fiber and another fiber, in which the surface area of ​​the other fiber on one side of the fabric accounts for 0 to 30% of the surface area of ​​the entire composite yarn.

[0005] As a technology for suppressing rattle between components when used as a sliding material, for example, Patent Document 2 discloses a fabric in which fluororesin fibers and other fibers are arranged alternately and the compression amount of the fabric is 25 μm or less. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 020821 [Patent Document 2] International Publication No. 2018 / 074207 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the woven fabric described in Patent Document 1 has a high proportion of fluororesin fiber in the composite yarn, and when exposed to high-speed sliding under a high load, it is unable to sufficiently suppress the discharge of wear powder from the fluororesin yarn, leaving room for improvement in suppressing thickness reduction due to wear. Furthermore, as a result of the high proportion of fluororesin fiber, when a fiber with a low thermal shrinkage rate such as para-aramid fiber is selected as the other yarn, there is a problem that the difference in thermal shrinkage from the fluororesin fiber results in increased unevenness after heat treatment, reducing adhesion and sliding properties.

[0008] The woven fabric described in Patent Document 2 was able to suppress rattle between components by reducing the amount of compression in the thickness direction when a load was applied. However, there was room for improvement in terms of thickness reduction after sliding under high load and high-speed sliding.

[0009] Furthermore, although all of the above patent documents have examined the sliding properties, they do not disclose any specific influence on the adhesive properties. When a fiber with a low thermal shrinkage rate, such as a para-aramid fiber, is selected as the other yarn for the purpose of improving durability, the difference in thermal shrinkage rate from the fluororesin fiber may cause large irregularities after heat treatment, resulting in a decrease in adhesive properties. Thus, there is room for further investigation into the development of a sliding material that combines sliding properties and adhesive properties.

[0010] Therefore, an object of the present invention is to provide a woven fabric that combines low friction, sliding durability, and adhesiveness, and that suppresses thickness loss due to wear even under high-load and high-speed sliding conditions.

[0011] The object of the present invention is to provide a woven fabric that, when used as a sliding material, has excellent sliding properties, can function as a sliding material for a long period of time, can suppress rattle between members, and can be used by adhering it to a substrate. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention has the following configuration.

[0013] A woven fabric comprising a plied yarn of fluororesin fiber and para-aramid fiber in at least one of the warp and weft yarns, and having an unevenness height of 1150 μm or less on at least one surface where the plied yarn is exposed.

[0014] The woven fabric has a thickness of 1.3 mm or less.

[0015] The woven fabric, which contains the ply-twisted yarn in the warp and weft.

[0016] The woven fabric is a multi-layered fabric including a first surface which is the outermost surface and a second surface which is the outermost surface opposite to the first surface, and the first surface includes the plied yarn in at least one of the warp yarns and weft yarns.

[0017] The woven fabric has a ratio (CF1 / CF2) of the cover factor (CF1) of the first surface to the cover factor (CF2) of the second surface that is smaller than 1.

[0018] The woven fabric, wherein the mass ratio of the fluororesin fiber to the entire woven fabric is 20 mass % or less.

[0019] A sliding material comprising the woven fabric.

[0020] The sliding material has at least one surface as a sliding surface on which the ply-twisted yarn is exposed and on which the height of the irregularities is 1150 μm or less. [Effects of the Invention]

[0021] The present invention provides a woven fabric and a sliding material that combine low friction, sliding durability, and adhesiveness, and that can suppress thickness reduction due to wear even under high-load and high-speed sliding conditions, thereby providing excellent sliding properties when used as a sliding material, being able to function as a sliding material for a long period of time, being less likely to cause rattle between components, and being able to be used by adhering to a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0022] The woven fabric of the present invention contains a plied yarn of fluororesin fiber and para-aramid fiber in at least one of the warp and weft.

[0023] In addition to the method of forming a ply-twisted yarn, other possible composite forms of fluororesin fiber and para-aramid fiber include, for example, a structure using fluororesin fiber for the warp (or weft) and para-aramid fiber for the weft (or warp), a structure in which fluororesin fiber and para-aramid fiber are alternately arranged in the warp and weft, or a double woven fabric in which the fluororesin fiber layer and the para-aramid fiber layer are completely separated, etc. However, in a structure using fluororesin fiber for the warp (or weft) and para-aramid fiber for the weft (or warp), or a structure in which fluororesin fiber and para-aramid fiber are alternately arranged, the fluororesin fiber is prone to early breakage in areas where low-strength fluororesin fiber is localized (for example, areas where the fluororesin fiber used as the warp (or weft) is continuously arranged or at the intersection points of the fluororesin fiber used as the warp and the fluororesin fiber used as the weft), and these may become the starting points for fabric breakage. Therefore, when extremely excellent sliding durability is required under high loads and high speeds, it is difficult to achieve satisfactory performance.If a double-layered fabric is used in which the fluororesin fiber layer and the para-aramid fiber layer are completely separated, the fluororesin fiber layer will wear away with sliding, making it difficult to prevent thickness reduction.

[0024] On the other hand, by integrating the fluororesin fiber and the para-aramid fiber into a ply-twisted yarn before weaving and arranging the integrated fiber in the woven fabric, the fluororesin fiber and the para-aramid fiber are adjacent to each other, which makes it easier for fluorine wear powder generated by sliding to transfer to the para-aramid fiber and forms a self-lubricating film, thereby achieving excellent wear resistance under high loads.

[0025] Examples of forms in which fluororesin fibers and para-aramid fibers are integrated before weaving include plied and twisted yarns in which fluororesin fibers and para-aramid fibers are plied and twisted, covered yarns in which para-aramid fibers are used as a core yarn and fluororesin fibers are wrapped around the core yarn as a sheath yarn, and blended yarns of staple fluororesin fibers and staple para-aramid fibers. However, in covered yarns, the fluororesin fibers are unevenly distributed on the sheath side, so the soft fluororesin fibers are selectively worn during sliding, and thickness reduction is likely to be significant. In blended yarns, it is difficult to achieve sufficient entanglement between the fluororesin fibers and the para-aramid fibers due to the low friction of the fluororesin fibers, making it difficult to achieve sufficient durability during sliding.

[0026] On the other hand, in the case of ply-twisted yarn, the para-aramid fiber acts as an aggregate to maintain strength and suppress wear, while the surrounding fluororesin fiber easily transfers to the para-aramid fiber as wear debris, achieving excellent low friction and sliding durability as well as suppressing thickness reduction.

[0027] In a ply-twisted yarn made of a fluororesin fiber and a para-aramid fiber, the number of twists (number of final twists) when plying and twisting is preferably such that the twist coefficient k is 1,000 or more and 25,000 or less, more preferably 1,000 or more and 10,000 or less, and particularly preferably 2,000 or more and 7,000 or less.

[0028] Here, the twist coefficient k is calculated by the following formula, where T [t / m] is the number of twists per meter and D [dtex] is the fineness of the plied yarn. k=T×D 0.5

[0029] In a ply-twisted yarn made of a fluororesin fiber and a para-aramid fiber, the fluororesin fiber or the para-aramid fiber before plying and twisting is preferably twisted. Twisting can suppress the opening of the para-aramid fiber due to friction during weaving, preventing the phenomenon in which the opened para-aramid fiber covers the fluororesin fiber in the ply-twisted yarn, impairing low friction. In this case, the twist coefficient of the para-aramid fiber before plying and twisting is preferably 500 or more and 5,000 or less. Furthermore, if it is 500 or more and 3,000 or less, in addition to the above effects, the strength of the para-aramid fiber is improved by the twisting, and when the fabric is made, the para-aramid fiber exists more firmly as a skeletal fiber, improving sliding durability. A twist coefficient of 900 or more and 3,000 or less is particularly preferable. If the twist coefficient of the para-aramid fiber is greater than 5,000, the strength may be lower than before twisting. When twisting para-aramid fibers, a process of simply twisting raw yarns of a desired fineness may be employed, or a process of twisting together yarns of a fineness smaller than the desired fineness may be employed. For example, when preparing para-aramid fibers with a twist number of 33 [t / m] and a fineness of 850 [dtex], a para-aramid fiber raw yarn of a fineness of 850 [dtex] may be twisted at 33 [t / m], or two para-aramid fiber raw yarns of a fineness of 425 [dtex] may be plied and twisted at 33 [t / m].

[0030] For a plied and twisted yarn made of a fluororesin fiber and a para-aramid fiber, the difference in yarn length should be adjusted to match the difference in thermal shrinkage between the fluororesin fiber and the para-aramid fiber at the maximum temperature to which the yarn will be exposed during processing and use. For example, if the maximum temperature to which the yarn will be exposed during processing and use is 200°C and the difference in thermal shrinkage between the fluororesin fiber and the para-aramid fiber at that temperature is 10%, the yarn length of the fluororesin fiber should be 10% longer than that of the para-aramid fiber during plied and twisted. By adopting such an embodiment, the occurrence of irregularities due to the difference in thermal shrinkage can be suppressed, making it easier to achieve the effects of the present invention.

[0031] The woven fabric of the present invention contains a plied yarn of fluororesin fiber and para-aramid fiber in at least one of the warp and weft, but preferably in both the warp and weft. It is also possible to interweave it with other fibers.

[0032] In the present invention, it was discovered that by selecting para-aramid fiber as the interwoven partner of fluororesin fiber, thickness reduction can be significantly suppressed compared to when other fibers such as PPS fiber, meta-aramid fiber, liquid crystal polyester fiber, etc. When a woven fabric using a fiber other than para-aramid fiber as a high-strength fiber is used in a sliding material, it is possible to optimize the balance between low friction and sliding durability by, for example, arranging a large amount of fluororesin fiber on the sliding surface by ingenuity of the weave, etc., and arranging a large amount of high-strength fiber as aggregate on the non-sliding surface.However, since the wear rate in the area containing a large amount of fluororesin fiber is high in the early stages of sliding, it becomes difficult to achieve both sliding durability and suppression of thickness change due to wear.

[0033] On the other hand, by plying and twisting para-aramid fibers with fluororesin fibers as in the present invention, the para-aramid fibers exhibit an extremely high aggregate effect, making it possible to produce a woven fabric that provides a sliding material that not only has excellent sliding durability but also suppresses thickness changes due to wear. Furthermore, para-aramid fibers are highly processable, making it possible to produce woven fabrics suitable for thin sliding materials more inexpensively and easily than inorganic fibers such as carbon fibers. Furthermore, it is possible to suppress fuzzing due to abrasion, which is a problem with inorganic fibers. Therefore, even when using this woven fabric alone without being impregnated with a resin to form a composite material, it is possible to prevent impurities such as fuzz from being mixed into the structure, for example, when the sliding material is attached to the structure.

[0034] The woven fabric of the present invention has an irregularity height of 1150 μm or less on at least one surface on which the plied and twisted yarn is exposed. Here, the expression "at least one surface on which the plied and twisted yarn is exposed" satisfies the above range. This means that if the plied and twisted yarn is exposed on only one surface, the irregularity height satisfies the above range on that surface. If the plied and twisted yarn is exposed on both surfaces, the irregularity height satisfies the above range on the surface on which the plied and twisted yarn is more exposed. If the plied and twisted yarn is exposed equally on both surfaces, the irregularity height satisfies the above range on either surface.

[0035] Fluorocarbon resin fibers have a higher thermal shrinkage than para-aramid fibers. After wet heat treatment or dry heat treatment, the difference in shrinkage easily leads to unevenness, with convex areas containing a relatively high proportion of para-aramid fibers and concave areas containing a relatively high proportion of fluorocarbon resin fibers. When unevenness is created in this way, the convex areas containing a high proportion of para-aramid fibers tend to selectively contact the mating material during the initial sliding phase. When the unevenness exceeds a certain level, depending on the surface roughness of the mating material, physical interactions such as snagging between the convex areas and the mating material tend to increase, increasing the coefficient of friction. Furthermore, in this case, stress is concentrated in the convex areas, which can lead to a rapid wear rate. Furthermore, if the unevenness is too large, the adhesive will not penetrate into the concave areas during bonding, reducing the net bonding area and making it difficult to achieve sufficient adhesion. Increasing the adhesive coating weight or clamping pressure to achieve a larger bonding area can result in excessively high adhesive penetration in the convex areas compared to the surrounding areas, or the adhesive may seep onto the sliding surface, causing deterioration of sliding performance. From these perspectives, the height of the unevenness is limited to 1150 μm or less. It is more preferably 1000 μm or less, and even more preferably 800 μm or less. A particularly preferable condition is 500 μm or less. The substantial lower limit of the unevenness height is 0 μm.

[0036] The mass ratio of the fluororesin fiber in the plied and twisted yarn of the present invention is preferably 3 to 97 mass%. If the mass ratio of the fluororesin fiber in the plied and twisted yarn is greater than 97 mass%, the amount of para-aramid fiber capable of capturing the abrasion powder as aggregate relative to the amount of fluororesin abrasion powder generated will be too small, making it difficult to suppress thickness changes. The mass ratio of the fluororesin fiber in the plied and twisted yarn is more preferably 80 mass% or less, and even more preferably 60 mass% or less. If the mass ratio of the fluororesin fiber in the plied and twisted yarn is less than 3 mass%, the amount of fluororesin abrasion powder transferred to the para-aramid fiber will be too small, making it impossible to achieve sufficiently low friction. The mass ratio of the fluororesin fiber in the plied and twisted yarn is preferably 20 mass% or more, and even more preferably 40 mass% or more.

[0037] The thickness of the woven fabric of the present invention is preferably 1.3 mm or less. By using a ply-twisted yarn of fluororesin fiber and para-aramid fiber for at least one of the warp and weft yarns, the rate of thickness reduction of the fabric is significantly reduced even under high load and high-speed sliding, thereby achieving sufficient sliding durability even with a small thickness. Causes of thickness reduction of the fabric include fibers being worn and broken and being expelled from the system, and the single yarns filling the gaps due to pressure or sliding, changing to a close-packed structure. The thickness reduction caused by the latter is greater the greater the absolute amount of voids present in the fabric. In other words, the smaller the thickness of the woven fabric, the more effectively thickness reduction can be suppressed. Among these, a thickness of 1.2 mm or less is preferred, with a thickness of 0.8 mm or less being more preferred, even more preferably 0.5 mm or less, and particularly preferably 0.3 mm or less. Since a thickness that is too small makes it difficult to achieve the desired abrasion resistance, 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.

[0038] The weave 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 allows the thickness to be reduced relatively easily and makes it easier to suppress thickness reduction due to sliding.

[0039] The woven fabric of the present invention can be selected from a single weave, a double weave, or other multi-layer weave, depending on the desired characteristics. A single weave allows for relatively easy thickness reduction, making it easier to suppress thickness loss due to sliding. When a multi-layer fabric is made with a double weave or other multi-layer weave, the outermost surface is designated as the first surface, and the outermost surface opposite 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 contains the plied and twisted yarn. When this multi-layer fabric is used as a sliding material, it is preferable that this first surface be the sliding surface. When only the first surface, which is one side of the multi-layer fabric, is used as a sliding surface, the second surface serves as a non-sliding surface. In a multi-layer fabric, the fibers used in the layer containing the non-sliding surface can be selected appropriately depending on the purpose, but the use of para-aramid fibers facilitates achieving both sliding durability and adhesiveness. From the standpoint of thickness, a double weave is preferable. A double weave can maintain a sufficient thickness for a long period of time even if the thickness is reduced due to sliding, making it easier to improve sliding durability. When the double weave is a double woven fabric including a first side and a second side, it is preferable that at least one of the warp and weft of the first side contains a double-twisted yarn of fluororesin fiber and para-aramid fiber, and it is more preferable that the warp and weft of the first side contain a double-twisted yarn of fluororesin fiber and para-aramid fiber.

[0040] When a double layer structure is selected, it is preferable that the ratio (CF1 / CF2) of the cover factor of the first surface (CF1) to the cover factor of the second surface (CF2) is smaller than 1. The cover factor here refers to the one calculated by the following formula. Cover factor = (total warp fineness [dtex]) 0.5 × Warp density [threads / 2.54cm] + (total weft density [dtex]) 0.5 × Weft density [counts / 2.54cm]

[0041] When calculating the cover factor, the total fineness is converted based on the specific gravity of the fiber type. This technology is a fabric containing fluororesin fiber and para-aramid fiber. For example, polytetrafluoroethylene fiber is used as the fluororesin fiber. Its specific gravity is 2.3, which is higher than the specific gravity of para-aramid fiber (1.4). Therefore, for the same fineness, the actual fiber diameter of para-aramid fiber is larger. Therefore, to reflect the actual fiber diameter, the fineness of the fluororesin fiber is converted based on the para-aramid fiber to calculate the cover factor. In other words, the fineness T after conversion to the raw yarn used, with specific gravity D and fineness T0, is calculated using the following formula, based on the specific gravity of para-aramid fiber (1.4). T=T0×1.4 / D

[0042] For example, the total fineness T of a ply-twisted yarn consisting of 440 dtex fluororesin fiber and 800 dtex para-aramid fiber with a specific gravity of 2.3 can be calculated using the following formula: T=440×1.4 / 2.3+800=1067

[0043] By making the ratio (CF1 / CF2) of the cover factor of the first surface (CF1) to the cover factor of the second surface (CF2) less than 1, it is possible to reduce the unevenness of the first surface (when used as a sliding material, the first surface serves as the sliding surface, and when the second surface is used as the adhesive surface, it serves as the sliding surface (non-adhesive surface)).

[0044] As mentioned above, the greater the difference in thermal shrinkage between the fluororesin fiber and the para-aramid fiber, the greater the unevenness of the woven fabric. The difference in yarn length caused by thermal shrinkage is constrained at the intersections of the warp and weft yarns, resulting in unevenness with long yarns appearing as convex and short yarns appearing as concave. When the cover factor is high, i.e., when the fineness is high or the density is high, there are fewer voids to absorb the difference in yarn length caused by thermal shrinkage, resulting in greater unevenness. On the other hand, when the cover factor is low, the constraint between the warp and weft yarns is weak, making it difficult to maintain the fabric structure during sliding, resulting in reduced sliding durability. Therefore, by using a low cover factor structure for the layer including the first side and a high cover factor structure for the layer including the second side, the unevenness of the first side can be suppressed while maintaining the fabric structure on the second side, achieving long-term sliding durability. Note that a low cover factor for the first side results in more voids, which can result in unevenness with the fiber areas appearing as convex and the void areas appearing as concave. In this case, there are enough gaps between the warp and weft yarns, so the warp and weft yarns are pushed apart by the intersecting weft and warp yarns, and the fibers spread flat. The unevenness caused by the low cover factor and gaps is smaller than the unevenness caused by the difference in thermal shrinkage.

[0045] From these viewpoints, when selecting a double weave, the ratio (CF1 / CF2) of the cover factor of the first side (CF1) to the cover factor of the second side (CF2) is preferably less than 1, and more preferably less than 0.8. If the cover factor of the second side (CF2) is too large, weaving performance deteriorates, and if the cover factor of the first side (CF1) is too small, the number of crossing points relative to the yarn thickness becomes too small, making it easier for only the constituent fibers of the first side to fray due to sliding. Therefore, CF1 / CF2 is preferably greater than 0.2, and more preferably greater than 0.4.

[0046] When selecting a multi-layer fabric having a multi-layer structure such as a double weave, it is preferable to select para-aramid fiber for the knotting yarn. The term "knotting yarn" here refers to the yarn that connects the two layers of a multi-layer structure such as a double weave. For example, if the warp yarn of the first surface is considered to be the knotting yarn, the knotting yarn has a normal portion that forms the first surface and a knotting portion that intertwines with the weft yarn of the second surface. In the knotting portion, the yarn takes a longer route than in the normal portion, resulting in a state of tension compared to the normal portion. If a ply-twisted yarn of fluororesin fiber and para-aramid fiber or fluororesin fiber is used in the knotting portion, the tension in the knotting portion increases due to thermal shrinkage when heat is applied, which tends to push up the intertwined weft yarn and form a convex portion. For these reasons, it is preferable to select para-aramid fiber, which has a low thermal shrinkage rate, for the knotting yarn.

[0047] The woven fabric of the present invention is not particularly limited in terms of the mass ratio of the fluororesin fiber to the entire fabric. However, a mass ratio of the fluororesin fiber to the entire fabric of 20% by mass or less is preferable because it can reduce the height of irregularities even when heat treatment is included in the fabric manufacturing process. Reducing the mass ratio of the fluororesin fiber, which has a relatively large thermal shrinkage, relative to the para-aramid fiber can suppress the occurrence of irregularities due to the difference in shrinkage after heat treatment. When a composite of fluororesin fiber and a fiber other than para-aramid fiber is used, reducing the fluororesin fiber increases the coefficient of friction and reduces durability. However, selecting para-aramid fiber provides an extremely high aggregate effect, allowing for excellent sliding properties even when the mass ratio of the fluororesin fiber is relatively low. From the perspective of reducing the height of irregularities, the mass ratio of the fluororesin fiber to the entire 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 the fluororesin fiber is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more.

[0048] In the present invention, the fluororesin that is a component of the fluororesin fiber may be any fluororesin composed of monomer units containing one or more fluorine atoms in the main chain or side chain, and among these, those composed of monomer units with a large number of fluorine atoms are preferred.

[0049] The monomer units containing one or more fluorine atoms preferably account for 70 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more of the repeating structural units of the polymer.

[0050] Examples of the monomer containing one or more fluorine atoms include fluorine atom-containing vinyl monomers such as tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and among these, it is preferable to use at least tetrafluoroethylene.

[0051] As the fluororesin, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-p-fluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer (ETFE), etc. can be used alone or in a blend of two or more types.

[0052] In fluororesins containing tetrafluoroethylene units, a higher content of tetrafluoroethylene units is preferable in terms of sliding properties, and copolymers in which 90 mol % or more, preferably 95 mol % or more of the total is tetrafluoroethylene are preferred, and it is most preferred to use polytetrafluoroethylene fibers as a tetrafluoroethylene homopolymer.

[0053] The fluororesin fiber used in the present invention may be in the form of either a monofilament consisting of one filament or a multifilament consisting of multiple filaments, but is preferably a multifilament from the viewpoint of weaving properties and surface irregularities when made into a fabric.

[0054] The total fineness of the fluororesin fibers used in the present invention is preferably in the range of 50 to 6000 dtex, more preferably in the range of 500 to 5500 dtex, and even more preferably 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 ensured to a certain extent, and thread breakage during weaving can be reduced, improving processability. If it is 6000 dtex or less, good processability during weaving can be obtained.

[0055] The fluororesin fiber used in the present invention preferably has a smaller dry heat shrinkage because the difference in heat shrinkage from the para-aramid fiber is smaller, and the occurrence of unevenness after heating is suppressed. From this perspective, the dry heat shrinkage 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 is 0%. The dry heat shrinkage of the fluororesin fiber can be appropriately controlled by a method commonly used in the industry, such as an oxidation treatment or a heat treatment after stretching. The dry heat shrinkage is a value measured by the method described below.

[0056] The form of the para-aramid fiber constituting the woven fabric of the present invention is not particularly limited, and either filament (long fiber) or staple fiber (spun yarn) can be used, but filament is preferred from the viewpoint of tensile strength and tensile rigidity. Furthermore, either monofilament consisting of one filament or multifilament consisting of multiple filaments can be used, but multifilament is particularly preferred because it has a large surface area and fluorine abrasion powder generated by abrasion of fluororesin fiber A can easily be transferred to fiber B.

[0057] The total fineness of the para-aramid fibers is preferably in the range of 50 to 4000 dtex, more preferably in the range of 200 to 4000 dtex, and even more preferably in the range of 800 to 3300 dtex. When the total fineness of the fibers constituting the fabric is 200 dtex or more, the fibers are strong, preventing fiber breakage during abrasion and reducing thread breakage during weaving, improving processability. When the total fineness is 3300 dtex or less, the unevenness of the fabric surface is small, minimizing the impact on low friction properties.

[0058] As described above, the unevenness height of a woven fabric is easily affected by the shrinkage behavior of the fluororesin fiber and para-aramid. Therefore, in post-processing after weaving, the temperature and humidity are controlled so that the unevenness height falls within the range specified in the present invention. There are no limitations on the post-processing method as long as the resulting woven fabric falls within the range specified in the present invention. To achieve the unevenness height within the range specified in the present invention through the thermal history in the post-processing, it is preferable to select a method that does not involve heat treatment or to suppress the heat treatment conditions. Specifically, the occurrence of unevenness height can be controlled by relaxing the heat treatment conditions, such as by lowering the temperature or shortening the time of the wet heat treatment or dry heat treatment, or by using only wet heat treatment or only dry heat treatment. When designing a woven fabric to obtain a desired woven fabric, the post-processing conditions can be determined in consideration of the above so that the unevenness height falls within the range specified in the present invention.

[0059] The term "moist heat treatment" as used herein refers to processes such as scouring, relaxation, and dyeing, which are carried out for the purpose of washing the woven fabric and removing residual stress. By carrying out such treatment, it is possible to suppress the occurrence of unevenness due to the difference in thermal shrinkage between the fluororesin fiber and the para-aramid fiber. Note that, because care must be taken with the conditions for washing, scouring, etc., of the woven fabric, it is preferable not to apply sizing during weaving.

[0060] The dry heat treatment referred to here refers to the drying steps following the scouring step, the relaxing step, and the dyeing step, the heat setting step, and the drying step after coating, which will be described later. By taking the above into consideration, it is possible to suppress the occurrence of unevenness due to the difference in thermal shrinkage between the fluororesin fiber and the para-aramid fiber.

[0061] To further enhance the abrasion resistance of the woven fabric, a resin can be applied to the woven fabric. The resin used here can be a thermosetting resin or a thermoplastic resin. While not particularly limited, thermosetting resins include, for example, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, epoxy resin, polyurethane resin, diallyl phthalate resin, silicone resin, polyimide resin, vinyl ester resin, and modified resins thereof. Thermoplastic resins include, for example, vinyl chloride resin, polystyrene resin, ABS resin, polyethylene resin, polypropylene resin, fluororesin, polyamide resin, polyacetal resin, polycarbonate resin, polyester resin, and acrylic resin. Furthermore, synthetic rubbers or elastomers such as thermoplastic polyurethane, butadiene rubber, nitrile rubber, neoprene, and polyester elastomers are preferred. Among these, resins primarily composed of phenolic resin and polyvinyl butyral resin, polyolefin resins such as unsaturated polyester resin, vinyl ester resin, polyethylene, and polypropylene, and polyester resins are preferred due to their impact resistance, dimensional stability, strength, and cost. These thermosetting and thermoplastic resins may contain various additives that are commonly used industrially for their purpose, application, productivity in the manufacturing and processing steps, or to improve properties. For example, modifiers, plasticizers, fillers, release agents, colorants, diluents, etc. may be added. Note that the term "major component" as used herein refers to the component with the largest mass ratio among the components excluding the solvent. In the case of a resin whose main components are a phenolic resin and a polyvinyl butyral resin, this means that the mass ratios of these two resins are first and second (in no particular order).

[0062] The resin can be applied to the woven fabric by methods such as spraying, roll coating, knife coating, comma coating, gravure coating, flexographic printing, brush coating, and melt extrusion lamination when using liquid, solvent-based, or water-based resins. For example, powdered resin particles can be applied by applying static electricity. After application, the solvent can be removed, the resin can be thermally cured, or a melt film can be formed. Heat treatment can be performed as needed. From the viewpoint of reducing the heat treatment temperature and suppressing unevenness, a process that minimizes moisture adhesion is preferred, and specifically, methods such as spraying, flexographic printing, and brush coating are preferred.

[0063] A lubricant or the like can be added to the woven fabric of the present invention as needed. The type of lubricant is not particularly limited, but a silicon-based lubricant or a fluorine-based lubricant is preferred.

[0064] The woven fabric of the present invention thus obtained uses a ply-twisted yarn of fluororesin fiber and para-aramid fiber and has reduced unevenness, and therefore combines low friction, sliding durability, and adhesiveness. Therefore, in applications where long-term use has traditionally been difficult due to high-speed sliding under high loads, the woven fabric of the present invention can exhibit higher sliding durability than conventional fabrics, as well as reduced rattle. Furthermore, it can be easily attached to a substrate for use, making it industrially highly practical as a sliding material. When the woven fabric of the present invention is used as a sliding material, it is preferable that at least one side on which the ply-twisted yarn is exposed and on which the unevenness height is 1150 μm or less serves as the sliding surface. [Example]

[0065] Examples of the present invention will be described below together with comparative examples.

[0066] The methods for measuring various properties used in the present examples are as follows.

[0067] (1) Fineness The total fiber fineness was measured in accordance with JIS L1013:2010 "Testing Methods for Chemical Fiber Filament Yarns" 8.3.B (simplified method). When measuring the total fiber fineness contained in a woven fabric, the disassembled yarn is removed from the woven fabric and measured. However, if the amount of disassembled yarn required for the above measurement method cannot be secured, the results of testing using the maximum length and number of trials that can be secured shall be used instead.

[0068] (2) Weave density In accordance with 8.6.1 of JIS L1096:2010 "Testing methods for woven and knitted fabrics," the sample was placed on a flat table, and unnatural wrinkles and tension were removed. The number of warp and weft threads within 50 mm intervals at different points was counted, and the average value for each was calculated for each unit length.

[0069] (3) Thickness The thickness was measured after leaving the sample standing for 10 seconds under 23.5 kPa in accordance with 8.4.A method of JIS L1096:2010 "Testing methods for woven and knitted fabrics."

[0070] (4) Height of unevenness The sample was placed on a flat table, and after removing any unnatural wrinkles or tension, a 25mm x 25mm area was photographed using a digital microscope (Keyence VHX-7000) for 3D interlocking observation. The height difference between the maximum and minimum heights in this area was defined as the unevenness height. If the plied / twisted yarn was exposed on only one side of the sample, the sample was placed and observed with that side facing up. If the plied / twisted yarn was exposed on both sides, the sample was placed and observed with the more exposed side facing up. If the yarn was exposed equally, the sample was placed and observed with one of the sides facing up. The above measurements were performed at five locations on each sample, and the average of the three points, excluding the maximum and minimum values, was calculated.

[0071] (5) Coefficient of kinetic friction According to Method A of JIS K7218:1986, "Sliding Abrasion Test Method for Plastics," a 30 mm x 30 mm sample of the fabric was placed on a 3 mm thick stainless steel plate of the same size, so that the surface where the asperity height was measured in (4) above would slide against the ring described below. The sample was then fixed in a sample holder. The mating material was a hollow cylindrical ring made of S45C steel, 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 polished with a sandpaper to achieve a surface roughness of Ra = 0.8 μm ± 0.1. A Mitutoyo SJ-210 roughness tester was used to measure the roughness. An A&D Model EFM-III-EN ring abrasion tester was used, and the test was performed 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 up to fracture was calculated.

[0072] (6) Sliding durability distance In the ring abrasion test, sliding was continued until the fabric broke, and the cumulative sliding distance until the fabric broke was defined as the sliding durability distance.

[0073] (7) Thickness reduction rate In the ring wear test, the test was stopped one minute after the start of sliding (sliding distance 24 m), the sample was removed, a cross section of the sliding area was cut out, and the cross section was observed using a digital microscope (Keyence VHX-7000) to measure the thickness after sliding D1. Separately, a new sample was prepared and a load of 10 MPa was applied using the ring wear tester, and after leaving it for one minute, the sample was similarly removed and a cross section of the pressurized area was cut out. The cross section was observed using a digital microscope (Keyence VHX-7000) to measure the thickness D0. The thickness reduction rate D [μm / min] was calculated using the following equation. D=D0-D1

[0074] The new samples used were of the same type as the samples used in the ring wear test, and were sampled from positions as close as possible to each other.

[0075] (8) Adhesiveness The test was carried out in accordance with JIS K6850:1999 "Adhesives - Test method for tensile shear adhesive strength of rigid adherends." The fabric was sampled to a length of 100 mm and a width of 25 mm, and an SS400 plate with a thickness of 15 mm, a length of 100 mm, and a width of 25 mm was prepared as the mating material. An epoxy adhesive ("2088E" manufactured by ThreeBond Co., Ltd.) was used as the adhesive. The coating amount was 150 g / m. 2 The adhesive was evenly applied to the SS400 plate with an overlap length of 12.5 mm, and the woven fabric was placed on top of it, with the mating material overlapping the surface opposite to the surface on which the unevenness height was measured in (4) above. The fabric was then left to stand for 48 hours under a pressure of 16 kPa. The resulting sample was pulled at a pulling rate of 5 mm / min using a tensile tester (Instron "5965"), and the tensile shear adhesive strength was calculated by dividing the maximum force at break by the adhesive area.

[0076] (9) Mass ratio of fluororesin fiber in ply-twisted yarn The fabric was cut into 200mm warp x 200mm weft pieces, and then the warp and weft yarns were separated to obtain separated yarns. Five plied yarns were randomly selected from the resulting separated yarns for each of the warp separated yarns and weft separated yarns, and they were separated into fluororesin fiber and para-aramid fiber, and the masses of each were measured. The total mass of the five plied yarns was defined as W, and the total mass of the fluororesin fiber in the five plied yarns was defined as WF. The mass ratio α of the fluororesin fiber in the plied yarn was calculated using the following formula: α=WF / W×100 [mass%] However, if the amount of yarn required for the above measurement method cannot be secured for the disassembled yarn, the results of the test using the maximum length and number of trials that can be secured shall be used instead.

[0077] (10) Mass ratio of fluororesin fibers to the entire fabric After cutting the fabric into 200mm warp x 200mm weft pieces, the warp and weft were separated and the total mass W of the separated yarns was measured. Next, only the plied yarns were selected from the separated yarns and the total mass W1 of the plied yarns in the fabric was measured. Next, fluororesin fibers that were present alone in the fabric, rather than the plied yarns, were selected and their total mass W2 was measured. The mass ratio Y of fluororesin fiber A in the fabric was calculated using the following formula. The value α measured in (9) above was used for α. Y=(W1×α / 100+W2) / W×100[mass%]

[0078] However, if the amount of yarn required for the above measurement method cannot be secured for the disassembled yarn, the results of the test using the maximum length and number of trials that can be secured shall be used instead.

[0079] (11)Dry heat shrinkage rate Measurement was carried out using fluororesin fibers by the following method.

[0080] The sample was folded in half and knotted to form a loop. An initial load (6% of the fineness (g)) was applied to the sample, and the lengths of both ends of the loop sample were measured. The initial load was then removed, and the sample was heat-treated in a dryer at 230°C for 30 minutes, then removed and cooled to room temperature. Thereafter, the initial load was applied again, and the lengths of both ends of the loop sample were measured.

[0081] The dry heat shrinkage was calculated using the following formula, and the average value of three measurements was rounded to one decimal place. ΔL=(L1-L2) / L1×100

[0082] where ΔL: dry heat shrinkage (%), L1: length before heat treatment (mm), L2: length after heat treatment (mm)

[0083] Example 1 A ply-twisted yarn was obtained by plying together PTFE fiber ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc.; dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with para-aramid fiber ("Kevlar" (registered trademark), manufactured by DuPont-Toray Co., Ltd.) having a total fineness of 1330 dtex and 180 filaments in single yarn at a twist rate of 81 t / m. This ply-twisted yarn was then used as the warp and weft to produce a single plain woven fabric on a loom. No sizing or other treatment to improve weaving properties was applied to the warp yarn.

[0084] Comparative Example 1 The woven fabric of Example 1 was scoured in a scouring tank at 80°C for 20 minutes, dried at 130°C for 2 minutes, and then heat-set at 180°C for 1 minute.

[0085] Example 2 A plied and twisted yarn was obtained by plying and twisting PTFE fiber ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc.; dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with para-aramid fiber ("Kevlar" (registered trademark), manufactured by DuPont-Toray Co., Ltd.) with a total fineness of 440 dtex and a single filament count of 267 filaments at a twist rate of 167 t / m. A double plain woven fabric was produced on a loom using the plied and twisted yarn for the warp and weft of the first surface and para-aramid fiber ("Kevlar" (registered trademark), manufactured by DuPont-Toray Co., Ltd.) with a total fineness of 3300 dtex and a single filament count of 1333 filaments for the warp and weft of the second surface. The warp yarns were not sizing or otherwise treated to improve weaving properties. The fabric was then scoured in a scouring tank at 80°C for 20 minutes and dried at 130°C for 2 minutes.

[0086] Example 3 A double plain weave fabric was produced in the same manner as in Example 2, except that the weft yarn for the first surface was a para-aramid fiber ("Kevlar" (registered trademark) manufactured by DuPont-Toray Co., Ltd.) with a total fineness of 3,300 dtex and a single filament count of 1,330, and then the fabric was scoured in a scouring tank at 80°C for 20 minutes and dried at 130°C for 2 minutes.

[0087] Comparative Example 2 A PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc.) with a total fineness of 880 dtex and a single filament count of 120 (9% dry heat shrinkage when heated at 230°C for 30 minutes) and a liquid crystal polyester fiber ("Scivellus" (registered trademark) manufactured by Toray Industries, Inc.) with a total fineness of 850 dtex and a single filament count of 144 (167 t / m) were plied and twisted to obtain a plied yarn. A 3 / 1 twill fabric was then produced on a loom using the plied yarn as the warp and a liquid crystal polyester fiber ("Scivellus" (registered trademark) manufactured by Toray Industries, Inc.) with a total fineness of 1700 dtex and a single filament count of 288 (1700 dtex) as the weft. The warp yarns were not sizing or otherwise treated to improve weaving properties. The fabric was then scoured in a scouring tank at 80°C for 20 minutes, dried at 130°C for 2 minutes, and heat-set at 180°C for 1 minute.

[0088] Comparative Example 3 A PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc.) with a total fineness of 440 dtex and 60 filaments (dry heat shrinkage of 9% when heated at 230°C for 30 minutes) was combined with a liquid crystal polyester fiber ("Scivelas" (registered trademark) manufactured by Toray Industries, Inc.) with a total fineness of 425 dtex and 72 filaments (dry heat shrinkage of 9% when heated at 230°C for 30 minutes) to obtain a plied yarn at a twist rate of 167 t / m. This plied yarn was then used as the warp and weft to produce a single plain woven fabric on a loom. No sizing or other treatments were applied to the warp yarn to improve weaving properties. The fabric was then scoured in a scouring tank at 80°C for 20 minutes, dried at 130°C for 2 minutes, and heat-set at 180°C for 1 minute.

[0089] Comparative Example 4 The warp yarns were composed of PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc., dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with a fineness of 440 dtex and 60 filaments, and liquid crystal polyester fiber ("Scivelas" (registered trademark) manufactured by Toray Industries, Inc.) with a fineness of 1700 dtex and 288 filaments, arranged in a 2:2 ratio. The weft yarns were composed of PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc., dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with a fineness of 2660 dtex and 360 filaments, and liquid crystal polyester fiber ("Scivelas" (registered trademark) manufactured by Toray Industries, Inc.) with a fineness of 425 dtex and 72 filaments, arranged in a 2:2 ratio. A single plain woven fabric was produced on a loom. No sizing or other treatments were applied to the warp yarns to improve weaving properties. The fabric was then refined in a refining tank at 80°C, dried at 130°C for 2 minutes, and then set at 200°C for 1 minute.

[0090] Comparative Example 5 A single plain weave fabric was produced on a loom using a warp yarn consisting of PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc.; dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with a fineness of 440 dtex and 60 filaments alternately arranged in a 2:2 ratio with a 1670 dtex and 1000 filament para-aramid fiber ("Kevlar" (registered trademark) manufactured by DuPont-Toray Co., Ltd.). The weft yarn consisted of PTFE fiber ("Toyoflon" (registered trademark) manufactured by Toray Industries, Inc.; dry heat shrinkage of 9% when heated at 230°C for 30 minutes) with a fineness of 2660 dtex and 360 filaments alternately arranged in a 2:2 ratio with a 440 dtex and 267 filament para-aramid fiber ("Kevlar" (registered trademark) manufactured by DuPont-Toray Co., Ltd.). The warp yarns were not sized to improve weaving properties. They were then scoured in a scouring tank at 80°C, dried at 130°C for 2 minutes, and set at 200°C for 1 minute.

[0091] Example 4 The fabric described in Example 1 was heat set at 120°C for 1 minute.

[0092] Example 5 The fabric described in Example 1 was heat set at 140°C for 1 minute.

[0093] Example 6 The fabric described in Example 1 was heat set at 160°C for 1 minute.

[0094] Example 7 The fabric described in Example 1 was heat set at 180°C for 1 minute.

[0095] Example 8 The woven fabric described in Example 1 was scoured in a scouring tank at 80°C for 1 minute.

[0096] Example 9 The woven fabric described in Example 1 was scoured in a scouring tank at 80°C for 20 minutes.

[0097] Example 10 The woven fabric described in Example 1 was scoured in a scouring tank at 60°C for 20 minutes.

[0098] Example 11 A single plain weave fabric was produced in the same manner as in Example 1, except that a PTFE fiber with a total fineness of 1,330 dtex and 180 filaments ("Toyoflon" (registered trademark), manufactured by Toray Industries, Inc., dry heat shrinkage rate of 4% when heated at 230°C for 30 minutes) was used as the fluororesin fiber. The fabric was then scoured in a scourer at 80°C for 20 minutes, dried at 130°C for 2 minutes, and heat-set at 180°C for 1 minute.

[0099] The evaluation results of the ply-twisted yarn configuration, fabric configuration, unevenness height, thickness reduction rate, dynamic friction coefficient, adhesiveness, and sliding durability distance for the woven fabrics described in Examples 1 to 3, Example 11, and Comparative Example 1 are summarized in Table 1.

[0100] Table 2 shows the evaluation results of the woven fabrics described in Comparative Examples 2 to 5 regarding the ply-twisted yarn configuration, fabric configuration, thickness reduction rate, dynamic friction coefficient, adhesiveness, and sliding durability distance. Table 3 shows the evaluation results of the ply-twisted yarn configuration, fabric configuration, treatment details, and unevenness height for the woven fabrics described in Example 1, Comparative Example 1, and Examples 4 to 10.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

Claims

1. A woven fabric comprising a plied yarn of fluororesin fiber and para-aramid fiber in at least one of the warp and weft yarns, and having an unevenness height of 1150 μm or less on at least one surface where the plied yarn is exposed.

2. 2. The woven fabric of claim 1, having a thickness of 1.3 mm or less.

3. The woven fabric according to claim 1 or 2, wherein the warp and weft yarns contain the plied yarn.

4. The woven fabric according to any one of claims 1 to 3, wherein the woven fabric is a multi-layered fabric including a first surface which is the outermost surface and a second surface which is the outermost surface opposite to the first surface, and at least one of the warp yarns and weft yarns of the first surface includes the plied yarn.

5. The woven fabric according to claim 4 , wherein the ratio (CF1 / CF2) of the cover factor (CF1) of the first surface to the cover factor (CF2) of the second surface is less than 1.

6. The woven fabric according to any one of claims 1 to 5, wherein the mass ratio of the fluororesin fiber to the entire woven fabric is 20 mass% or less.

7. A sliding material comprising the woven fabric according to any one of claims 1 to 6.

8. 8. The sliding material according to claim 7, wherein at least one surface on which the plied and twisted yarn is exposed and on which the height of the irregularities is 1150 μm or less serves as a sliding surface.

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