JP7830391B2 - Polyphenylene sulfide fabric - Google Patents

Description

This invention relates to a woven fabric using polyphenylene sulfide (hereinafter also referred to as PPS) fibers. The PPS woven fabric of this invention is woven using PPS long fiber filaments under specific conditions in at least a portion of the fabric, and is suitably used as a screen, filter, filter cloth, and electrical insulating material.

PPS fibers possess excellent properties derived from PPS, including superior heat resistance, chemical resistance, and flame retardancy. These characteristics are utilized in a wide range of applications, including various filters, electrical insulation materials, printing screens, and battery separators.

PPS resins are broadly classified into two types: cross-linked PPS and linear PPS. Linear PPS, with its higher toughness, is used for fiber applications. PPS resin can be produced by dissolving sodium sulfide in a polar solvent such as N-methylpyrrolidone and carrying out a polycondensation reaction with paradichlorobenzene. The resulting pellets are melt-spun to obtain staple fibers, spunbond nonwovens, multifilament yarns, and monofilament yarns. Because the reaction products of PPS resin contain various by-reaction products and impurities, the cost of the purification process currently accounts for a significant portion of the manufacturing cost.

The glass transition temperature of PPS fibers is generally 80-90°C, and the melting point is 280-290°C. Other physical properties are similar to those of polyethylene terephthalate (PET), another semi-crystalline material. However, during melt spinning, the PPS resin and oligomer components undergo thermal decomposition, generating toxic and corrosive acidic gases containing sulfur and chlorine. These gases can corrode metal materials such as polymer piping, extruder barrels, screws, and spinning nozzles, and pose a risk to workers' health. After melt spinning, to prevent corrosion of piping by residual PPS resin, it is necessary to completely remove any remaining PPS resin by replacing and cleaning the resin flow path (polymer line) with general-purpose resins such as PET or polypropylene. Thus, there are many points to consider when manufacturing PPS fibers, and it is a synthetic resin material that requires careful maintenance and management.

Various manufacturing methods have been proposed and commercialized for fibers and fiber structures using PPS resin. For example, Patent Document 1 proposes a method for manufacturing PPS long-fiber nonwoven fabric using the spunbond method. Specifically, it discloses a technique in which a resin mainly composed of PPS is extruded from a spinneret, then pulled and stretched at a spinning speed of 3000 m/min or more using an ejector, collected on a net to form a nonwoven web, and then heat-sealed using an embossing roll. This method allows for the production of a nonwoven fabric with small fiber diameter and excellent thermal stability through a simple process. However, long-fiber nonwoven fabrics produced using the spunbond method have drawbacks, including low tear strength and elongation at break, difficulty in following minute bending deformations, and large variations in basis weight and thickness.

Furthermore, Patent Document 2 proposes a method using staple fibers made of PPS resin, which are spun into yarn, then woven into a fabric, and finally subjected to a hydrophilic treatment. While this method is suitable for applications such as separators (where resin impregnation is required) and electrical insulators, when used in filter applications, the staple fibers are ended, raising concerns about contamination due to fiber shedding, breakage, or detachment. Additionally, in applications such as filter press filtration cloths, water drainage and cake release are poor. Therefore, this method is not preferable for screen, filter, or filtration cloth applications.

Furthermore, Patent Document 3 proposes an SM-laminated nonwoven fabric, or an SMS-laminated nonwoven fabric, which is formed by laminating a spunbond nonwoven fabric and a meltblown nonwoven fabric using PPS resin. Here, S refers to spunbond and M refers to meltblown. This method allows for precise filtration of gases and liquids and is favorable in terms of cost and production efficiency. However, because it is a multi-layer laminate, it becomes thick and has the disadvantage of being difficult to follow even minute bending deformations. Alternatively, the use of meltblown nonwoven fabric alone can also be considered. In this case, it is highly flexible and easily follows minute bending deformations, but it is thin, easily becomes electrostatically charged, and has low strength, requiring technical know-how for handling and workability.

WO2011/070999 publication Japanese Patent Publication No. 2018-534441 WO2008/035775 publication

This invention was devised to solve the problems of the prior art described above, and aims to provide a woven fabric, and a composite material using the same, that is suitable as a material for screens, filters, filter cloths, strainers, and electrical insulating materials, and that uses at least a portion of PPS long fiber filaments.

The inventors of this invention conducted intensive research to solve the above problems and, as a result, discovered that by controlling the characteristic values of long-fiber filaments made of PPS resin, which are used as raw materials, within a specific range, it is possible to provide a fabric that satisfies not only high quality but also product safety, production cost, and production stability. Thus, the present invention was completed.

The present invention has the following configurations (1) to (7).
(1) A fabric comprising polyphenylene sulfide long fiber filaments with a single filament fineness of 2 decitex or more and 50 decitex or less, with a constituent single filament count of 1 or more and 4 or less, and a total fineness of 2 decitex or more and 200 decitex or less, arranged as warp and/or weft threads, wherein the polyphenylene sulfide long fiber filaments are made from a linear polyphenylene sulfide resin, the maximum value Tanδmax of the mechanical loss tangent Tanδ at a measurement frequency of 0.5 Hz, which is a viscoelastic structure parameter in the amorphous region of the polyphenylene sulfide long fiber filament, is 0.02 or more and 0.05 or less, the ambient temperature Tmax when Tanδ shows its maximum value is 130°C or more and 160°C or less, and JIS A polyphenylene sulfide fabric characterized in that, in terms of the tensile strength and elongation of polyphenylene sulfide long fiber filaments as specified in L1013.8.5.1 (standard time test), the stress-strain curve has a yield point and the elongation at break is 15% or more and 35% or less.
(2) The polyphenylene sulfide fabric according to (1), characterized in that the fiber cross-section of the polyphenylene sulfide long fiber filament is round, the single fiber diameter of the polyphenylene sulfide long fiber filament is 15 μmφ or more and 70 μmφ or less, and the birefringence Δn of the polyphenylene sulfide long fiber filament is 0.100 or more and 0.300 or less.
(3) The polyphenylene sulfide fabric according to (1), characterized in that the weave structure of the polyphenylene sulfide fabric is composed of plain weave, twill weave, or satin weave, the mesh opening dimension of the polyphenylene sulfide fabric is 1 μm or more and 200 μm or less, and the opening ratio of the polyphenylene sulfide fabric is 10% or more and 60% or less.
(4) A polyphenylene sulfide fabric according to any one of (1) to (3), characterized in that, when the polyphenylene sulfide fabric is placed horizontally, the rate of change in the opening ratio before and after dry heat treatment at a treatment temperature of 160°C for 30 minutes is within ±3%, and the rate of weight change after immersion of the polyphenylene sulfide fabric in cyclohexanone and isofronone solvents for 24 hours in an environment of a temperature of 20±2°C and a relative humidity of 65±5%RH is less than 3.0% in both cases.
(5) A screen characterized by using the polyphenylene sulfide fabric described in (1).
(6) A filter characterized by using the polyphenylene sulfide fabric described in (1).
(7) An electrical insulating material characterized by using the polyphenylene sulfide fabric described in (1).

According to the present invention, it is possible to provide high-quality, safe, and stable textile products made of PPS fibers, suitable for electrical insulating materials such as screens, filters, filter cloths, strainers, and battery separators.

The PPS fabric of this invention is composed of PPS long fiber filaments with a specific range of single-fiber fineness, number of constituent single-fibers, and total fineness, arranged as warp and/or weft threads, wherein the PPS long fiber filaments are made from linear polyphenylene sulfide resin.

The single-fiber fineness of PPS long-fiber filaments is in the range of 2 decitex to 50 decitex, more preferably 3 decitex to 40 decitex, and even more preferably 5 decitex to 35 decitex. Extremely fine filaments with a single-fiber fineness below this range cannot maintain the mechanical strength required for the intended application. Conversely, if the fineness significantly exceeds this range, the fibers become extremely rigid, and the resulting fiber structure tends to be difficult to bend or deform.

The number of individual filaments in a PPS long-fiber filament is between 1 and 4, preferably between 1 and 3. If the number of individual filaments exceeds this range, the specific surface area increases, improving the ability to capture impurities when used in liquid filtration filters or strainers. However, if the fluid contains a large amount of impurities, backwashing becomes difficult to remove them, leading to increased pressure loss over time and premature filtration failure. This ultimately results in increased filter replacement frequency and higher running costs.

The total fineness of the PPS long fiber filaments is in the range of 2 decitex to 200 decitex, preferably 3 decitex to 100 decitex, and more preferably 3 decitex to 50 decitex. If the total fineness is below this range, the strength required for filter, strainer, and screen applications cannot be secured. If it exceeds this range, the mesh opening when woven into filters, strainers, screens, etc., becomes larger, and the effectiveness of capturing impurities tends to decrease.

The PPS fabric of the present invention uses PPS filaments as all, or at least some, of the warp and/or weft threads. More preferably, all of the warp and/or weft threads are used, and even more preferably, all of the warp and weft threads are used. Of course, it is also possible to alternate between PPS filaments and other filaments, one per warp and/or weft thread, and to use filaments with different finenesses. Examples of other filaments that can be suitably combined with PPS filaments include polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), aromatic polyamide (PPA), polyetherimide (PEI), polyamideimide (PAI), polyetheretherketone (PEEK), and polycarbonate (PC).

PPS resin is a crystalline, heat-resistant polymer widely recognized as an engineering plastic exhibiting chemical resistance, flame retardancy, high mechanical properties, and excellent dimensional stability. Commercially available polymer PPS resins include crosslinked and linear (linear, straight-chain) types. The former exhibits high rigidity even at high temperatures, is advantageous against creep deformation, and is used in injection-molded products, while the latter is characterized by its elongation and toughness and is used in fibers, etc. The PPS long fiber filament of this invention uses linear PPS resin as its raw material.

The maximum value of the mechanical loss tangent Tanδ (Tanδmax) at a measurement frequency of 0.5 Hz, which is a viscoelastic structural parameter of the amorphous region of the PPS long-fiber filament used in the PPS fabric of the present invention, is 0.02 or more and 0.05 or less, preferably 0.02 or more and 0.04 or less. The mechanical loss tangent Tanδ is the ratio of the storage modulus E' to the loss modulus E'' (Tanδ = E'/E''), and is a measure of the thermal mobility of the amorphous tie molecules constituting the amorphous region. A lower Tanδ value indicates that crystallization and crystal orientation progress, the structure stabilizes, and contributes to improved mechanical properties and heat resistance. If Tanδmax exceeds the above range, dimensional stability and mechanical strength tend to remain low. Furthermore, if Tanδmax is below the above range, toughness remains low, and problems such as brittle fracture are more likely to occur.

Furthermore, the ambient temperature Tmax when the maximum value of the mechanical loss tangent, Tanδmax, is observed is in the range of 130°C to 160°C, preferably 135°C to 155°C. Crystallization promotion shifts Tmax to the higher temperature side. If Tmax is above the lower limit temperature of the above range, crystallization and oriented crystallization are advanced, and the mechanical strength and thermal stability are in a favorable range for the intended application, and boiling water shrinkage of the fabric can be kept low. Tanδmax and Tmax can be controlled by combinations of stretching conditions such as the stretching ratio, stretching temperature, stretching speed, and heat-fixing temperature during PPS long fiber filament manufacturing, as well as the molecular weight of the PPS resin used. In particular, as the stretching ratio, heat-fixing temperature, and molecular weight of the PPS resin increase, Tanδmax shows a smaller value and Tmax shows a larger value. Furthermore, the mesh opening dimension can be stabilized, and the position of the fabric can be improved. If the temperature exceeds the upper limit temperature of the above range, the toughness remains low. Toughness, in materials terminology, means that both strength and ductility are high. However, in the temperature range exceeding the upper limit, ductility is low, and the material becomes brittle. Conversely, in the temperature range below the lower limit of the above range, ductility is high, but strength is low, making both undesirable.

For PPS long fiber filaments, a round cross-section is preferable as it maximizes strength utilization. While triangular, flattened, multi-lobed, and other hollow cross-sections can be produced by changing the die-cutting mechanism, the resulting yarns tend to exhibit lower physical properties such as tensile strength and elongation compared to high-polymerization PET long fiber filaments of the same fineness.

Furthermore, the single fiber diameter of the PPS long fiber filament is in the range of 15 μmφ to 70 μmφ, more preferably 20 μmφ to 60 μmφ, and even more preferably 30 μmφ to 60 μmφ. If the single fiber diameter is below the above range, it is prone to fiber breakage due to abrasion damage, which is undesirable considering the intended applications of the present invention. Conversely, if the single fiber diameter exceeds the above range, it becomes extremely rigid, which may be applicable to some industrial material applications, but is not suitable for the intended applications of the present invention.

The birefringence Δn of the PPS long fiber filament is preferably in the range of 0.100 to 0.300, more preferably 0.150 to 0.300, and even more preferably 0.200 to 0.250. The birefringence Δn is a surrogate characteristic of the degree of crystal orientation in the fiber axial direction, and its value increases as the stretch ratio increases. If the birefringence Δn is below the above range, the degree of crystal orientation is low, and the yarn strength tends to be poor. Conversely, if it exceeds the above range, the yarn strength increases, but the ductility and toughness tend to be poor. By controlling the birefringence Δn within the above range, the physical properties (toughness) and thermal properties of the fiber are also improved, making it suitable for use in the intended applications of the present invention.

The weight-average molecular weight of the PPS resin used in this invention is preferably 20,000 or higher, more preferably 25,000 or higher, and even more preferably 30,000 or higher. A weight-average molecular weight of 30,000 or higher improves mechanical properties such as yarn strength and toughness, as well as heat resistance and chemical resistance. The upper limit of the weight-average molecular weight is preferably 150,000 or less, more preferably 120,000 or less, and even more preferably 100,000 or less, in order to obtain good melt-spinning properties. In particular, a weight-average molecular weight of 40,000 to 80,000 makes it easier to control Tanδmax and Tmax within the aforementioned appropriate ranges. The weight-average molecular weight can be calculated in polystyrene equivalent, for example, by the method described in the examples.

Furthermore, the PPS long fiber filament, in the tensile strength and elongation (standard time test) specified in JIS L1013.8.5.1, has a stress-strain curve that has a yield point, and a fracture elongation of 15% to 35%, preferably 20% to 30%. Having a yield point in the stress-strain curve means having either an "upper yield point only" or "an upper yield point, a lower yield point, and a yield shelf." The upper yield point and lower yield point are defined in JIS G 0202, "Mechanical Tests," specifically in sections 1162 and 1162 of the "Tensile Test." If there is no yield point, the material will have poor toughness. Toughness is "resilience," and materials with poor toughness do not follow tensile deformation and are prone to brittle fracture. It is desirable that the PPS long fiber filament used in the PPS fabric of the present invention has a yield point and is highly tough. The upper yield point of PPS filaments preferably appears at an elongation of 2% to 20%, and more preferably at 3% to 10%. When the upper yield point appears within this elongation range, the toughness of the yarn improves, resulting in a flexible yarn with high tensile strength, elongation, and superior strength, leading to improved woven fabric quality. The yield point and elongation at break can be controlled by combining stretching conditions such as the stretching ratio, stretching temperature, stretching speed, and heat-fixing temperature during PPS filament manufacturing, as well as the molecular weight of the PPS resin used. In particular, excessively high stretching ratios are undesirable, as they result in a yarn without a yield point and with low elongation at break. It is essential to determine an appropriate combination of stretching conditions, taking into account the fineness after stretching.

PPS long fiber filaments can be manufactured using conventional melt spinning or air gap spinning methods. Air gap spinning is particularly effective in preventing operational and quality problems such as cooling efficiency issues and fiber adhesion, especially when the single fiber fineness is high. Furthermore, spinning and drawing can be carried out using known techniques, such as the so-called spindraw method where spinning and drawing are directly linked, or a two-step method where spinning and drawing are separated into two processes.

Furthermore, in addition to conventional dry drawing, the drawing process can also suitably utilize bath drawing (drawbath drawing) and zone drawing methods, which involve drawing the filament in a heat transfer medium such as hot water controlled to a temperature above the glass transition temperature of the long fiber filament. The drawing process can be performed in multiple stages, not just one. Since the thermal shrinkage stress is high after the drawing process, it is even more preferable to reduce the thermal shrinkage stress by performing a relaxation heat treatment under hot roller heating or steam heating. Moreover, considering the efficiency of the spinning process, it is also possible to obtain a predetermined long fiber filament by performing spinning and drawing in the state of a multifilament and then dividing it into single filaments (one filament) or several filaments at a time using a fiber splitter. There are no limitations on the winding shape of the filament; in addition to cheese winding onto a paper tube, known winding shapes such as warp winding, filling winding, and compound winding can be used on metal or resin bobbins. In particular, with thicker denier, the contact area between fibers becomes smaller, making winding slippage more likely, so it is preferable to use single-flange or double-flange bobbins.

As mentioned above, the stretching process can be performed in one or multiple stages, but in the case of multiple stages, the total stretching ratio, which is the sum of the stretching ratios of each stage, is preferably 1.5 to 6.0. More preferably, it is 2.5 to 5.5, and even more preferably 2.8 to 5.2. By setting the total stretching ratio within this range, a yield point can be established and the elongation at break can be kept within an appropriate range. If the stretching ratio is less than 1.5, the elongation at break will become too high and the birefringence will become low, which may make it difficult to obtain practical yarn strength. If the total stretching ratio exceeds 6.0, the yield point may disappear, and the elongation at break may decrease, resulting in poor toughness.

The boiling water shrinkage rate of the PPS fabric (raw material) of the present invention is preferably -3% to 3%. More preferably -2.5% to 2.5%, and even more preferably -2.0% to 2.5%. By setting the boiling water shrinkage rate of the raw material within the above range, fluctuations in the opening ratio during high-temperature use as a filter product can be suppressed, enabling stable and precise filter performance.

The weave structure of the PPS fabric of the present invention is preferably composed of plain weave, twill weave, or satin weave. Plain weave includes plain weaves woven with multiple warp and/or weft threads, such as star weave and diagonal weave. Twill weaves preferably include 2/1 twill, 3/1 twill, 2/2 twill, 3/2 twill, 3/3 twill, 3/1 broken diagonal, and herringbone weave, which changes the direction of the diagonal pattern at a certain period. Satin weaves include five-ply satin with warp and weft, such as 4/1 and 3/2 satin, seven-ply satin, eight-ply satin, and double-sided satin weaves of these. In the case of satin weaves, even with the same 4/1 five-ply satin with warp and weft, there are multiple types such as 2-ply and 3-ply, but all are included. The optimal weave structure should be selected according to the purpose and application. For example, when used for liquid/solid separation, particularly filtration with a high solid content, satin weave is preferred due to its good cake-releasing properties. When used for gas/solid separation with a low solid content, plain weave or twill weave is preferred due to its low pressure loss.

The finished density of the raw PPS fabric of the present invention, after scouring and heat setting, is preferably 120 threads/2.54 cm or more and 320 threads/2.54 cm or less for both warp and weft. If the finished density is below this range, the mesh opening size becomes too large, making it difficult to achieve sufficient filtration performance. If it exceeds this range, the mesh opening size becomes too small, making clogging more likely. The balance of warp and weft density (warp density/weft density) is preferably 1.3 to 0.9 for plain weave or twill weave. A value greater than 1.3 or less than 0.9 may reduce precise filtration performance. For satin weave, the warp density relative to the weft (warp density/weft density), or the weft density relative to the warp (weft density/warp density), is preferably 1.8 to 3.0. Outside this range, stable filtration performance becomes difficult to obtain.

The weave structures of the present invention are not limited to those described above. They may be combined as appropriate depending on the application, and multiple layers of the same or different weave structures can be used depending on the application. When using multiple layers, the filtration efficiency can be further improved by varying the intersection angles of each layer, for example, to 45°. Twill weave is effective when the diameter of the fibers used is larger compared to plain weave, and is adopted as appropriate depending on the fibers used and the desired performance.

Furthermore, the PPS fabric of the present invention preferably has a mesh opening dimension of 1 μm to 200 μm, and an opening ratio of 10% to 60%. If the mesh opening dimension is less than the above range, filtration efficiency increases, but clogging occurs quickly, and the filtration time tends to increase. Conversely, if it exceeds the above range, the mesh opening becomes too large and coarse, potentially preventing sufficient filtration and separation. If the opening ratio is less than the above range, filtration efficiency decreases, and clogging and blockage may occur quickly. Conversely, if it exceeds the above range, it becomes too coarse, potentially preventing sufficient filtration and separation.

Weaving can be carried out using known looms such as air jet looms, water jet looms, rapier looms, projectile looms, needle looms, and shuttle looms. Regarding the warping process, which is a preparatory step for weaving, in addition to partial warping using a partial warping machine and rough warping using a warper and beamer, a method can also be used in which warp threads are directly supplied to the loom from yarns arranged on a weaving yarn creel without going through the warping process.

The resulting raw fabric is processed using conventional methods, including scouring, washing, drying, and heat setting, to produce the textile products of the present invention. While known equipment can be used for each of the above processes, due to the large mesh size and susceptibility to twisting and wrinkling, consistent beam-to-beam processing in an expanded state is preferable. During this process, avoiding excessive tension and correcting the weave are crucial for ensuring product quality and yield.

The resulting product is wound into a roll, slit-cut to a specified width, and supplied to the customer. By using known cutting methods such as ultrasonic welders or high-frequency welders, fraying of the cut edges can be prevented.

The PPS fabric of the present invention, by being configured as described above, can achieve a variation in the aperture ratio before and after dry heat treatment at 160°C for 30 minutes in a horizontal, stationary state of ±3%, preferably within ±2.5%, and more preferably within ±2.2%. The aperture ratio is an important characteristic in applications such as printing screens and filter cloths, and it is preferable that its variation rate, i.e., the change in aperture ratio due to temperature, is small. If the variation rate of the aperture ratio exceeds the above range, a decrease in filtration accuracy is likely to occur due to a large change in the captured particle size, i.e., the filtration diameter.

The solvent used in solvent-based screen inks must be a good solvent for the binder resin. Examples include glycol ether solvents, ester solvents, ketone solvents, aliphatic solvents, aromatic solvents, alcohol solvents, and ether solvents. It is also possible to mix two or more of these as needed. However, if the boiling point of the solvent used in solvent-based screen inks is too low, it will dry out on the screen plate, making it unsuitable for printing. For screen printing inks, solvents with a melting point around 200°C are desirable in terms of workability and print quality, such as cyclohexanone (boiling point around 155°C) or isophorone (boiling point around 215°C).

The PPS fabric of the present invention is characterized by a weight change rate of less than 3.0% after immersion in cyclohexanone and isoflon, both solvents classified as cyclic ketones among the above-mentioned solvents, at a temperature of 20±2°C and a relative humidity of 65±5%RH for 24 hours. In other words, the weight change rate due to swelling or dissolution is less than 3.0%, and the change in mesh opening is minimal. Furthermore, PPS resin is generally a crystalline polymer with a crystallinity of 40-60%. In areas where stress concentrates, such as the texture points of the fabric, solvent can penetrate crazes, causing solvent cracks. These cracks can grow and potentially lead to fracture. Therefore, it is necessary to reduce the tension applied during weaving, appropriately combine the density and structure of the fabric, and set conditions to prevent craze formation and brittle fracture.

The components of solvent-based screen inks, other than the solvent, consist of multiple components, including organic and inorganic pigments and dyes, metal powders such as aluminum and brass (in the case of glitter prints), solid microparticles such as silica, binder resins such as urethane resins and acrylic ester resins, and crosslinking agents such as blocked isocyanates. The viscosity, penetration into the substrate, and drying properties of the ink vary depending on the mixing ratio of each agent, temperature, type of solvent, and formulation amount. It is desirable to adjust these appropriately according to the application and purpose to avoid problems such as gum-up and roll-over. For printing on the substrate, known methods such as flat screen printing and rotary screen printing can be used. In the case of screen printing, it is preferable to attach the screen fabric diagonally to the mold, for example at 45° or 60°, to prevent moiré patterns.

The above immersion test in organic solvents should be conducted in a fume hood with local ventilation. After immersion in the organic solvent for 24 hours, a weight decrease indicates dissolution, a weight increase indicates swelling, and no weight change indicates neither swelling nor dissolution. By constructing the PPS fabric of the present invention as described above, the weight change rate after 24 hours of immersion in cyclohexanone and isoflon, respectively, in an environment of 20±2°C and 65±5% RH, is less than 3.0%. This results in a fabric suitable for screen printing with solvent inks and for precision filtration of organic solvents, as it avoids strength reduction due to swelling during solvent ink use and prevents changes in wire diameter and mesh opening due to swelling or dissolution.

The finished PPS fabric of the present invention, after inspection, is used in products such as filters, filter cloths, strainers, screens, and electrical insulating materials. However, if defects such as surface defects or holes are found during inspection, those parts will have reduced filtration performance and cannot be used as products. Therefore, it is important to minimize the number of holes, reduce variations in mesh opening, and ensure uniform surface irregularities in the fabric to improve product yield. Preferably, there should be 10 or fewer partial defects such as holes within a 50m length, and overall poor appearance due to variations in mesh opening or surface irregularities is undesirable.

The PPS fabric of the present invention has applications in filters, filter cloths, strainers, screens, and electrical insulating materials. Applications in electrical insulating materials include insulating separators for fuel cells and hydrogen generators. Filters, filter cloths, and strainers are primarily for separation applications such as gas/solid separation, liquid/solid separation, and solid/solid separation. Screens are mainly used for printing applications, where dispersions of fine particles uniformly dispersed in a dispersion medium such as emulsions, suspensions, or slurries are uniformly weighed and applied. In all cases, if the fibers dissolve or swell due to the solvent or dispersion medium, the required functions cannot be achieved. Furthermore, applications in electrical insulating materials leverage the characteristics of PPS, such as heat resistance, chemical resistance, hydrolysis resistance, and flame retardancy. If necessary, the fabric can be treated with special processes such as water-repellent or flame-retardant finishes after scouring, and can also be resin-treated with epoxy resins, methylol-melamine resins, or phenolic resins. Depending on the application, it can also be used as a multilayer laminate, such as a two-layer, three-layer, or four-layer laminate. When creating a multi-layered structure, for example, in the case of a three-layered structure, shifting the warp and weft threads so that the biases are 0°, +45°, and -45° improves the separation efficiency when used as a filter or filter cloth.

The effects of the present invention are demonstrated by the following examples, but the present invention is not limited to these examples. The evaluation method for each characteristic value of the present invention is as follows.

(Fineness)
The true fineness was determined based on Method A described in section 8.3.1a) of JIS L-1013 2010 edition.

(Single fiber diameter)
PPS long fiber filaments were embedded in epoxy resin, frozen using a Reichert FC-4E cryosectioning system, and then cut using a Reichert-Nissei ultracut N (ultramicrotome) equipped with a diamond knife. The cut surface was then photographed using a Hitachi H-7100FA transmission electron microscope (TEM) at a magnification sufficient to observe the entire long fiber filament. The fiber diameter (μmφ) of all individual fibers was measured from these images using image processing software. The measurement values were taken for each of the 10 photographs taken at any 10 locations on the PPS long fiber filament, and the average value of the 10 locations was used.

(Confirmation of tensile strength, elongation, and yield point)
Tensile strength and elongation were calculated according to the standard time test method described in Section 8.5.1 of JIS L-1013, 2010 edition. The test was performed using a low-speed elongation test machine with a grip spacing of 20 cm and a tensile speed of 20 cm/min. A stress-strain curve chart was created, and the tensile strength, elongation (elongation at fracture), and yield point were read from the chart. The arithmetic mean of 10 trials was used as the measured value.

(Viscoelasticity measurement)
A TA Instruments DMA Q800 dynamic viscoelasticity analyzer was used, with a measurement frequency of 0.5 Hz and a heating rate of 2°C/min, and evaluation was performed in the measurement temperature range of 20°C to 250°C. The test samples were prepared by aligning the fibers to a length of approximately 10 mm, a width of approximately 7 mm, and a thickness of 0.15 mm. Tanδmax, the maximum value of the mechanical loss tangent Tanδ, which is a viscoelastic structure parameter, was the peak value in the obtained Tanδ profile, and the ambient temperature at that time was defined as Tmax (°C).

(Birefringence)
Using a Nikon POH polarizing microscope, a Leitz Berec compensator, and a Toshiba SLS-3-B spectral light source activation device (sodium light source), samples of fibers 5-6 mm in length, cut at a 45° angle to the fiber axis, were prepared. The samples were positioned on the polarizing microscope's stage with the cut surface facing upwards, and after inserting the analyzer to create a dark field, the compensator was set to 30 and the number of fringes was counted. (n samples) The compensator was rotated in the right-hand direction to measure the scale 'a' at which the sample first became darkest, and the compensator was rotated in the left-hand direction to measure the scale 'b' at which the sample first became darkest (both readings were taken to 1/10th of a division). Furthermore, the compensator was returned to 30, the analyzer was removed, the diameter 'd' of the sample was measured, and the birefringence (Δn) was calculated based on the following formula (average value of 20 measurements).
Δn=T/d(T=nλ ₀ +ε)
λ ₀ =589.3 mμ
[However, ε is determined from C/1000 and i in the Leitz compensator manual, and i is (a - b) (the difference in the compensator readings).]

(Weight average molecular weight)
The weight-average molecular weight of PPS polymers and PPS fibers was calculated in polystyrene equivalent using gel permeation chromatography (GPC), a type of size exclusion chromatography. The measurement conditions are as follows.
Device: SSC-7110 manufactured by Senshu Science Co., Ltd.
Column name: Showa Denko Shodex UT-806M, 2 columns in series; Eluent: 1-Chloronaphthalene; Detector: Differential refractive index detector; Column temperature: 210°C
Pre-temperature bath temperature: 250°C
Pump constant temperature bath temperature: 50°C
Detector temperature: 210°C
Flow rate: 1.0mL/min
Sample injection volume: 300 μL (slurry: approximately 0.2% by weight)

(Finished density)
The density of the warp and weft of the finished fabric was measured according to the density method specified in JIS L1096:2010 8.6.

(Mesh opening dimensions)
The mesh opening dimension A (μm) was calculated using the following formula. The wire diameter d (μm) used in this calculation was also calculated based on the following formula. However, the formula for calculating the wire diameter d (μm) is applicable only to round cross-section yarns. For specific gravity SG, a value of 1.35 g/ ^cm³ was used for PPS, and a value of 1.12 g/ ^cm³ was used for polyamide 6.
A (μm) = {25.4 / [Warp or weft density (threads/inch)]} × 1000 - d
d (μm) = 11.91 × √[(Fineness (decitex) ÷ 1.11) / SG]
In this invention, when there are multiple strands in the yarn structure, the wire diameter d is calculated as if there were one strand (approximating a monofilament).

(Opening ratio)
The aperture ratio ε (%) was calculated using the following formula.
ε(%)=[A/(A+d)] ² ×100

(Boiling water shrinkage rate of the fabric)
A woven fabric sample was cut into approximately 50 cm squares, marked at 200 mm intervals along the warp and weft threads, and then subjected to a boiling treatment in 98 ± 2°C hot water for 30 minutes. After the boiling treatment, the sample was removed from the hot water, spread out on paper filter paper, and air-dried on a flat surface. After air-drying, the length L mm of the marks made in the warp and weft directions was measured, and the boiling shrinkage rate (SHW (%)) in the warp and weft directions was evaluated using the following formula. The arithmetic mean of five measurement trials was taken as the measured value.
SHW (%) = [(200-L)/200] x 100

(Variation in aperture ratio during dry heat treatment at 160°C)
The opening ratio OP1 (%) of the PPS fibers to be used as a sample before dry heat treatment was confirmed. Then, using a Yamato Scientific DKN303 constant temperature incubator and a mesh fabric using Teijin's para-aramid fibers (trademark name Technora) in both warp and weft directions, the para-aramid mesh fabric was horizontally mounted inside the incubator. The sample (PPS fabric) was placed horizontally on the para-aramid mesh fabric so that it did not come into contact with the metal inner walls or shelves of the incubator, and the sample was treated with dry heat at 160°C for 30 minutes. After that, the PPS fabric sample was removed with the mesh fabric still on it, cooled at room temperature, and the opening ratio OP2 (%) of the PPS fibers after dry heat treatment was confirmed. The change in opening ratio was calculated according to the following formula. However, the opening ratio (%) before and after treatment was the average value of 10 measurement points.
Change in aperture ratio (%) = |OP1 - OP2| / OP1 × 100

(Percentage change in weight after immersion in organic solvent)
Two stainless steel trays, 30 cm long, 15 cm wide, and 5 cm deep, were prepared in a fume hood controlled by negative pressure suction in a room with temperature and humidity controlled to 20 ± 2°C and relative humidity of 65 ± 5% RH. 300 ml each of cyclohexanone and isophoron were poured into the trays, and pre-weighed PPS fabric was immersed in them. After 24 hours, the fabric was removed, air-dried on blotting paper for 5 minutes, and then weighed to check the weight change before and after immersion. The weight change rate (%) was calculated from the weight A (g) before immersion and the weight B (g) after immersion according to the following formula.
Weight change rate (%) = |A - B| / A × 100

(fabric quality)
The results of a visual inspection of a finished example fabric measuring 100 cm in width and 50 m in length were evaluated using a fabric inspection machine. Fabrics with more than 10 holes or defects within a 50 m length, large variations in stitch opening, or overall surface irregularities resembling wrinkles were deemed unacceptable.

(comprehensive evaluation)
After evaluating the changes in mesh opening and opening ratio before and after boiling water shrinkage treatment of the fabric, the presence or absence of differences in mesh opening and opening ratio, and the presence of uneven wrinkles in the fabric after boiling water shrinkage were visually confirmed, and the overall quality was evaluated comprehensively in the following three categories.
○…Good quality △…Slightly questionable quality, but still acceptable ×…Poor quality, unacceptable In addition, items with more than 10 defects such as holes were marked as ××, and items with no defects were marked as ○, and the frequency of partial defects was evaluated. The worse of the overall quality and partial defect evaluations was used as the overall evaluation.

(Example 1)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, using a known melt spinning method, they were melt-spun at a spinning temperature of 300°C to obtain undrawn PPS long fiber filaments. These undrawn filaments were introduced into a drawer offline, subjected to two-stage heat stretching in a bath, followed by a constant-rate relaxation heat treatment, and then separated into individual monofilaments using a fiber splitter to obtain PPS long fiber monofilaments. Incidentally, the surface temperature of the stretching preheating roller was set to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 3.0 times, to obtain 33 decitex PPS long fiber monofilaments.

A plain weave fabric was woven using the PPS long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed minimal changes in fabric dimensions, mesh opening, and opening ratio after boiling water treatment. A solvent-based screen ink was prepared and used as a screen for a flat screen printing machine equipped with an explosion-proof structure and local exhaust system to print on the fabric. No swelling, dissolution, clogging, or distortion or holes caused by the solvent occurred, resulting in a desirable fabric for screen printing.

(Example 2)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, PPS long fiber monofilaments were obtained by air gap spinning at a spinning temperature of 300°C. For reference, the cooling water bath temperature was set to 50±2°C, the air gap to 30 mm, the surface temperature of the stretch preheating roller to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 5.0 times, resulting in 33 decitex 2 filaments of PPS long fiber.

Using the PPS long-fiber filaments in both the warp and weft, a 2/2 twill weave fabric was woven. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed minimal changes in fabric dimensions, mesh opening, and opening ratio after boiling water treatment. The obtained fabric was used as the screen unit material for the cylindrical screen of a classification sieve (turbo screener) and used for the classification of aluminum hydroxide powder. Dry classification was performed without any operational problems.

(Example 3)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51,500) pellets were vacuum dried for 12 hours. Then, 33 decitex 3 filaments of PPS long fibers were obtained by spin-drawing. The spinning temperature was 310°C, the preheating roller temperature for drawing was 100°C, and the total drawing ratio was 1.6 times.

A 2/2 twill weave fabric was woven using the PPS long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed minimal changes in fabric dimensions, mesh opening, and opening ratio after boiling water treatment. The resulting fabric was impregnated with epoxy resin and used as a substrate for printed circuit boards for electronic equipment. A thin, space-saving material with excellent electrical insulation properties, suitable for circuit boards, was obtained.

(Example 4)
Using a vacuum dryer set to an ambient temperature of 160°C, the PPS raw material resin (linear type, weight-average molecular weight 51500) Repetto was dried for 12 hours. Then, it was melt-spun at a spinning temperature of 300°C using a known melt-spinning method to obtain undrawn PPS long fiber filaments. The undrawn yarn was introduced into a drawer offline, and subjected to two-stage heat-stretching in air, followed by a constant-rate relaxation heat treatment to obtain 33 decitex 4 PPS long fiber filaments. For reference, the surface temperature of the stretching preheating roller was set to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 3.0 times.

A 1/2 twill weave fabric was woven using the PPS long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed minimal changes in fabric dimensions, mesh opening, and opening ratio after boiling water treatment. The resulting fabric was used as a heat-resistant air filter. It exhibited excellent heat and chemical resistance, making it suitable as a primary collection filter for air containing chemical mist, dust, and other particles.

(Example 5)
Using a vacuum dryer set to an ambient temperature of 160°C, the PPS raw material resin (linear type, weight-average molecular weight 51500) Repetto was dried for 12 hours. Then, it was melt-spun at a spinning temperature of 300°C using a known melt-spinning method to obtain undrawn PPS long fiber filaments. The undrawn yarn was introduced into a drawer offline, subjected to two-stage heat-stretching in air, and then subjected to a constant-rate relaxation heat treatment to obtain 33 decitex 3 PPS long fiber filaments. For reference, the surface temperature of the stretching preheating roller was set to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 3.0 times.

A plain weave fabric was woven using the PPS long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed minimal changes in fabric dimensions, mesh opening, and opening ratio after boiling water treatment. A solvent-based screen ink was prepared and used as a screen for a flat screen printing machine equipped with an explosion-proof structure and local exhaust system to print on the fabric. No swelling, dissolution, clogging, or distortion or holes caused by the solvent occurred, resulting in a desirable fabric for screen printing.

(Example 6)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, PPS long fiber monofilaments were obtained by air gap spinning at a spinning temperature of 300°C. For reference, the cooling water bath temperature was set to 50±2°C, the air gap to 30 mm, the surface temperature of the stretch preheating roller to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 5.0 times, resulting in a 33 decitex PPS long fiber monofilament.

The PPS long-fiber filaments were used for both the warp and weft, and an eight-ply satin weft (1/7 (5-fly)) was woven. The resulting raw fabric was beaten, then scouring and relaxing in a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. Afterward, it was introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and then finished setting in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric was used as a filter cloth for a filter press. The solid-liquid separation of the slurry was smooth, and the cake release was good, making it suitable as a filter cloth for a filter press.

(Example 7)
Using a vacuum dryer set to an ambient temperature of 160°C, the PPS raw material resin (linear type, weight-average molecular weight 51500) Repetto was dried for 12 hours. Then, it was melt-spun at a spinning temperature of 300°C using a known melt-spinning method to obtain undrawn PPS long fiber filaments. The undrawn yarn was introduced into a drawer offline, subjected to two-stage heat-stretching in air, and then subjected to a constant-rate relaxation heat treatment to obtain 33 decitex 3 PPS long fiber filaments. For reference, the surface temperature of the stretching preheating roller was set to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 3.0 times.

The PPS long-fiber filaments were used for both warp and weft, and a five-ply satin weave (4/1 (3-fly)) was produced. The resulting raw fabric was beaten, then scouring and relaxing in a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. Afterward, it was introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and then finished setting in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric was used as a filter cloth for a filter press. The solid-liquid separation of the slurry was smooth, and the cake release was good, making it suitable as a filter cloth for a filter press.

(Comparative Example 1)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, using a known melt spinning method, they were melt-spun at a spinning temperature of 300°C to obtain undrawn PPS long fiber filaments. These undrawn filaments were introduced into a drawer offline, subjected to two-stage heat stretching in a bath, followed by a constant-rate relaxation heat treatment, and then separated into individual monofilaments using a fiber splitter to obtain PPS long fiber monofilaments. Incidentally, the surface temperature of the stretching preheating roller was set to 85°C, the stretching temperature to 90±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 1.8 times, resulting in a PPS long fiber 55 decitex monofilament.

A plain weave fabric was woven using the PPS long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The fabric exhibited significant changes in opening ratio after boiling water treatment and after dry heat treatment at 160°C, resulting in surface irregularities and uneven opening, making it unsuitable for screens, filters, and electrical insulation materials.

(Comparative Example 2)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, PPS long fiber monofilaments were obtained by air gap spinning at a spinning temperature of 300°C. For reference, the cooling water bath temperature was set to 50±2°C, the air gap to 50 mm, the surface temperature of the stretch preheating roller to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 150°C, and the total stretch ratio to 4.0 times, resulting in a PPS long fiber monofilament of 75 decitex.

Using the PPS long-fiber filaments in both the warp and weft, a 2/2 twill weave fabric was woven. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. Both the change in opening ratio after boiling water treatment and the change in opening ratio after dry heat treatment at 160°C were somewhat large, indicating variation in opening. Although the weave structure was a 2/2 twill weave and surface irregularities were not significant, it was not suitable for the intended applications of the present invention, such as screens, filters, and electrical insulation materials.

(Comparative Example 3)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51,500) pellets were vacuum dried for 12 hours. Then, 33 decitex and 18 filaments of PPS long fibers were obtained by spin-drawing. For reference, the spinning temperature was 310°C, the preheating roller temperature for drawing was 100°C, and the total drawing ratio was 1.6 times.

Using the PPS long-fiber filaments in both the warp and weft, a 2/2 twill weave fabric was woven. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. The resulting fabric showed little change in fabric dimensions, mesh opening, or opening ratio after boiling water treatment, but the weight change after immersion in cyclohexanone and isophoron was somewhat large, making it unsuitable for the intended applications of the present invention, such as screens, filters, and electrical insulation materials.

(Comparative Example 4)
Using a vacuum dryer set to an ambient temperature of 160°C, PPS raw material resin (linear type, weight-average molecular weight 51500) pellets were vacuum dried for 12 hours. Then, using a known melt spinning method, they were melt-spun at a spinning temperature of 300°C to obtain undrawn PPS long fiber filaments. These undrawn filaments were introduced into a drawer offline, subjected to two-stage heat stretching in a bath, followed by a constant-rate relaxation heat treatment, and then separated into individual monofilaments using a fiber splitter to obtain PPS long fiber monofilaments. Incidentally, the surface temperature of the stretching preheating roller was set to 90°C, the stretching temperature to 95±3°C, the chamber temperature in the relaxation heat treatment area after stretching to 180°C, and the total stretch ratio to 10.0 times, resulting in 33 decitex and 6 filaments of PPS long fiber.

Using the PPS long-fiber filaments in both the warp and weft directions, a 2/2 twill weave fabric was woven. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 90°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 120°C, and finally set in a heat setter adjusted to an ambient temperature of 180°C. The characteristic values are shown in Table 1. While thermally stable and exhibiting good stability against ketone-based chemicals, the high fiber stretch ratio resulted in low toughness, leading to perforation with even slight deformation. Therefore, it was not suitable for the intended applications of the present invention, such as screens, filters, and electrical insulation materials.

(Comparative Example 5)
Using a vacuum dryer set to an ambient temperature of 110°C, polyamide 6 raw material resin pellets were vacuum dried for 12 hours. Then, polyamide 6 long fibers (33 decitex 1 filament) were obtained by spin-drawing. The spinning temperature was 250°C, and the total draw ratio was 1.6 times.

A plain weave fabric was woven using the polyamide 6 long-fiber filaments in both the warp and weft. The resulting fabric was subjected to beating, scouring, and relaxation treatments using a continuous water washing machine with an ultrasonic cleaning mechanism at a treatment bath temperature of 80°C. It was then introduced into a fabric straightening device, pre-dried in a heat cylinder at a surface temperature of 100°C, and finally set in a heat setter adjusted to an ambient temperature of 150°C. The characteristic values are shown in Table 1. While the boiling water shrinkage of the fabric remained somewhat high, the opening ratio fluctuated significantly after dry heat treatment at 160°C, resulting in large variations in mesh opening. Furthermore, cyclohexanone and isophoron immersion caused the fibers to swell, resulting in large variations in mesh opening and opening ratio. The resulting fabric was not structurally sound and therefore unsuitable for the intended applications of this invention, such as screens, filters, and electrical insulation materials.

(Comparative Example 6)
We attempted spinning using the same method as in Example 1, except that we changed the PPS resin from a linear type to a cross-linked type. However, due to the gradual increase in pressure loss over time, we were unable to obtain stable spinning operation conditions, and as a result, we were unable to obtain fibers.

The PPS fabric of this invention possesses the heat resistance, chemical resistance, and flame retardancy properties of PPS resin, and further improves mechanical strength and dimensional stability by controlling the physical properties of the yarn. Taking advantage of these characteristics, the PPS fabric of this invention can be used safely and stably in a wide range of applications, including screens, filters, battery separators, and electrical insulating materials including partitions in hydrogen generators, making it extremely useful in this industry.

Claims (7)

A woven fabric comprising polyphenylene sulfide long fiber filaments with a single filament fineness of 2 decitex or more and 50 decitex or less, with a constituent single filament count of 1 to 4, and a total fineness of 2 decitex or more and 200 decitex or less, arranged as warp and/or weft threads, wherein the polyphenylene sulfide long fiber filaments are made from a linear polyphenylene sulfide resin, the maximum value Tanδmax of the mechanical loss tangent Tanδ at a measurement frequency of 0.5 Hz, which is a viscoelastic structure parameter in the amorphous region of the polyphenylene sulfide long fiber filament, is 0.02 or more and 0.05 or less, the ambient temperature Tmax when Tanδ shows its maximum value is 130°C or more and 160°C or less, and JIS A polyphenylene sulfide fabric characterized in that, in terms of the tensile strength and elongation of polyphenylene sulfide long fiber filaments as specified in L1013.8.5.1 (standard time test), the stress-strain curve has a yield point and the elongation at break is 15% or more and 35% or less, and the weight change rate after immersion of the polyphenylene sulfide fabric in cyclohexanone and isophoron solvents for 24 hours in an environment of 20±2°C and 65±5% RH is less than 3.0% in both cases . The polyphenylene sulfide fabric according to claim 1, characterized in that the fiber cross-section of the polyphenylene sulfide long fiber filament is round, the single fiber diameter of the polyphenylene sulfide long fiber filament is 15 μmφ or more and 70 μmφ or less, and the birefringence Δn of the polyphenylene sulfide long fiber filament is 0.100 or more and 0.300 or less. The polyphenylene sulfide fabric according to claim 1, characterized in that the weave structure of the polyphenylene sulfide fabric is composed of plain weave, twill weave, or satin weave, the mesh opening dimension of the polyphenylene sulfide fabric is 1 μm or more and 200 μm or less, and the opening ratio of the polyphenylene sulfide fabric is 10% or more and 60% or less. A polyphenylene sulfide fabric according to any one of claims 1 to 3, characterized in that, when the polyphenylene sulfide fabric is placed horizontally and still, the rate of change in the opening ratio before and after dry heat treatment at a treatment temperature of 160°C for 30 minutes is within ±3%. A screen characterized by using the polyphenylene sulfide fabric described in claim 1. A filter characterized by using the polyphenylene sulfide fabric described in claim 1. An electrical insulating material characterized by using the polyphenylene sulfide fabric described in claim 1.