JP2021050459A - Polyphenylene sulfide composite fibers, method of manufacturing the same, and nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyphenylene sulfide composite fiber having a fine fiber diameter, high adhesiveness and mechanical strength, and excellent dimensional stability as well as excellent heat resistance and chemical resistance, a method for producing the same, and a non-woven fabric. do. SOLUTION: Polyphenylene sulfide in which 97 mol% or more of the repeating unit is composed of p-phenylene sulfide unit is a component A, 60 to 97 mol% of the repeating unit is composed of p-phenylene sulfide unit, and 3 to 40 mol% is m. -A core-sheath composite fiber in which copolymerized polyphenylene sulfide composed of phenylene sulfide units is used as component B, component A is arranged in the core portion, and component B is arranged in the sheath portion, and the average fiber length is 1 to 100 mm. Polyphenylene sulfide composite fiber and its manufacturing method, and non-woven fabric. [Selection diagram] None

Description

The present invention relates to a polyphenylene sulfide composite fiber, a method for producing the same, and a non-woven fabric.

Since polyphenylene sulfide has high heat resistance, chemical resistance, electrical insulation, and flame retardancy, various applications that take advantage of these characteristics, such as bag filters, papermaking canvas, electrically insulating paper, battery separators, and various diaphragms, are used. It is used for such purposes.

On the other hand, in recent years, equipment that can be used in extreme environments and for aerospace applications has been attracting attention, and the motors and batteries used for it are also required to have high environmental resistance. Under these circumstances, the demand for electrically insulating papers, battery separators and various diaphragms that can be used in a high temperature environment is increasing, and non-woven fabrics containing polyphenylene sulfide fibers having excellent heat resistance and chemical resistance are attracting attention.

However, in the case of a non-woven fabric composed of only stretched polyphenylene sulfide fibers, there is a problem that a non-woven fabric having mechanical properties that can withstand practical use cannot be obtained because the adhesiveness between the fibers is low. Therefore, in order to solve the above problems, various proposals have been made for polyphenylene sulfide fibers and non-woven fabrics containing them.

For example, a polyphenylene sulfide non-woven fabric composed of stretched polyphenylene sulfide fibers and unstretched polyphenylene sulfide fibers has been proposed (see Patent Document 1). According to this technique, unstretched polyphenylene sulfide acts as a binder during thermal bonding, so that a polyphenylene sulfide non-woven fabric having high mechanical properties can be obtained.

Further, a low heat shrinkable binder fiber in which heat shrinkage in the drying step is suppressed by heat-treating the undrawn polyphenylene sulfide fiber at a temperature lower than the crystallization temperature in advance has also been proposed (see Patent Document 2). According to the technique, in addition to reducing wrinkles and blisters of the non-woven fabric generated in the drying step, the obtained non-woven fabric has excellent thermal dimensional stability.

Further, a binder fiber having a fine fiber diameter having excellent adhesiveness, which is obtained by stretching an unstretched polyphenylene sulfide fiber in an ethylene glycol bath at 110 ° C. to reduce the diameter, has also been proposed (see Patent Document 3). According to this technique, the fiber diameter can be reduced while the molecular chain orientation is low, and a homogeneous polyphenylene sulfide non-woven fabric having a small fiber diameter CV value in the wet non-woven fabric can be obtained even with a low grain size.

Japanese Unexamined Patent Publication No. 7-189169 Japanese Unexamined Patent Publication No. 2010-7544 JP-A-2007-39840

However, in the technique disclosed in Patent Document 1, the unstretched polyphenylene sulfide fiber used as the binder fiber contributes to adhesion, so that the non-woven fabric has high mechanical properties, but the unstretched polyphenylene sulfide fiber is thermally shrunk. Since the rate is extremely high, the fibers shrink during the drying process, causing wrinkles and blisters on the non-woven fabric. Further, the presence of unstretched polyphenylene sulfide fibers having a larger fiber diameter than the skeletal fibers in the stretched polyphenylene sulfide fibers as the skeletal fibers causes uneven texture in the non-woven fabric and impairs the homogeneity of the non-woven fabric. There is also a problem such as

Further, in the technique disclosed in Patent Document 2, although heat shrinkage in the drying step can be suppressed by heat-treating the undrawn polyphenylene sulfide fiber, thermal crystallization proceeds by the heat treatment and the adhesiveness as a binder fiber is improved. There is a problem that the mechanical properties of the non-woven fabric are deteriorated due to the decrease. Further, as in Patent Document 1, there is also a problem that the fiber diameter is large because it is in an unstretched state, which causes uneven basis weight in the non-woven fabric and impairs the homogeneity of the non-woven fabric.

Further, in the technique disclosed in Patent Document 3, undrawn polyphenylene sulfide fibers are stretched in an ethylene glycol bath at 110 ° C. to obtain fibers having a low degree of orientation and a fine fiber diameter. Due to the stretching without crystallization, the heat shrinkage rate of the obtained fiber is extremely high, the fiber shrinks in the drying step, and wrinkles and blisters occur in the non-woven fabric. Further, since the fiber obtained by the above method has low mechanical strength, there is a problem that the mechanical properties of the non-woven fabric are deteriorated when the fiber is used as a binder fiber.

As described above, polyphenylene sulfide fibers, which are suitable fibers for forming non-woven fabrics, have a small fiber diameter, have high adhesiveness and mechanical strength, and are excellent in dimensional stability, and non-woven fabrics containing them have been used so far. Not reported to.

As a result of the study by the present inventors, when a polyphenylene sulfide resin composed of only p-phenylene sulfide units is used, the dimensional stability is improved by crystallizing the obtained fibers by heat treatment, but at the same time, it is amorphous. It was confirmed that it is difficult to achieve both dimensional stability and thermal adhesiveness due to the problem that the thermal adhesiveness is lowered due to the reduction of the portions.

Therefore, as a result of diligent studies, the present inventors have made a core-sheath type composite cross section in which a copolymerized polyphenylene sulfide resin having low crystallinity is arranged in a sheath and a polyphenylene sulfide resin having excellent mechanical properties is arranged in a core. A polyphenylene sulfide composite that not only has excellent heat resistance and chemical resistance, but also has a small fiber diameter, high adhesiveness and mechanical strength, and excellent dimensional stability by stretching and heat setting under specific conditions. It has been found that fibers are obtained and the non-woven fabric containing them has good mechanical properties.

That is, the present invention is intended to solve the above-mentioned problems, and the polyphenylene sulfide composite fiber of the present invention contains polyphenylene sulfide in which 97 mol% or more of the repeating unit is composed of p-phenylene sulfide unit as component A, and the repeating unit. 60 to 97 mol% of the above is composed of p-phenylene sulfide units, and 3 to 40 mol% is composed of m-phenylene sulfide units. Copolymerized polyphenylene sulfide is used as component B, component A is placed in the core, and component B is placed in the sheath. It is a core-sheath type composite fiber, and is a polyphenylene sulfide composite fiber having an average fiber length of 1 to 100 mm.

According to a preferred embodiment of the polyphenylene sulfide composite fiber of the present invention, the area ratio of the core portion is 75 to 95% in the cross section of the core-sheath type composite fiber.

According to a preferred embodiment of the polyphenylene sulfide composite fiber of the present invention, the birefringence of the polyphenylene sulfide composite fiber is 0.18 to 0.40.

According to a preferred embodiment of the polyphenylene sulfide composite fiber of the present invention, the average fiber diameter of the polyphenylene sulfide composite fiber is 25 μm or less, the strength is 2.0 cN / dtex or more, and the elongation is 50% or less.

In the polyphenylene sulfide composite fiber of the present invention, the melt mass flow rate MFR (A) of the component A used as a raw material is 50 to 250 g / 10 minutes, and the melt mass flow rate MFR (B) of the component B is MFR (A). ) Is manufactured by a method characterized by being larger than).

The nonwoven fabric of the present invention is a nonwoven fabric containing any of the above-mentioned polyphenylene sulfide composite fibers.

The polyphenylene sulfide composite fiber of the present invention has a polyphenylene sulfide core in which 97 mol% or more of the repeating units are composed of p-phenylene sulfide units, and 60 to 97 mol% of the repeating units is composed of p-phenylene sulfide units in 3 to 40. By forming a core-sheath type composite fiber in which copolymerized polyphenylene sulfide, in which mol% is composed of m-phenylene sulfide units, is arranged in the sheath portion, not only excellent heat resistance and chemical resistance, but also the fiber diameter is small and high adhesiveness is achieved. It is possible to provide a polyphenylene sulfide composite fiber having mechanical strength and excellent dimensional stability and a non-woven fabric having good mechanical properties.

The polyphenylene sulfide composite fiber of the present invention contains polyphenylene sulfide (hereinafter, may be abbreviated as polyphenylene sulfide (A)) in which 97 mol% or more of the repeating unit is composed of p-phenylene sulfide unit as component A, and the repeating unit is 60 to 60 to Component B is a copolymerized polyphenylene sulfide (hereinafter, sometimes abbreviated as copolymerized polyphenylene sulfide (B)) in which 97 mol% is composed of p-phenylene sulfide units and 3 to 40 mol% is composed of m-phenylene sulfide units. It is a core-sheath type composite fiber in which component A is arranged in a core portion and component B is arranged in a sheath portion, and is a polyphenylene sulfide composite fiber having an average fiber length of 1 to 100 mm. Hereinafter, the polyphenylene sulfide composite fiber of the present invention will be described in detail.

[Polyphenylene sulfide (A)]
It is important that 97 mol% or more of the repeating unit of the polyphenylene sulfide (A) used in the present invention is composed of the p-phenylene sulfide unit represented by the structural formula (1). By setting the p-phenylene sulfide unit to 97 mol% or more, preferably 98 mol% or more of the repeating unit, the fiber is excellent not only in chemical resistance and heat resistance but also in spinnability and mechanical properties. Examples of the repeating unit of the rest other than the p-phenylene sulfide unit include aromatic sulfides such as triphenylene sulfide and biphenylene sulfide, and alkyl-substituted and halogen-substituted products thereof.

The polyphenylene sulfide (A) used in the present invention can be blended with other thermoplastic resins as long as the effects of the present invention are not impaired. Examples of the thermoplastic resin include copolymerized polyphenylene sulfide in which m-phenylene sulfide units are copolymerized, polyetherimide, polyethersulfone, polysulfone, polyphenyleneether, polyester, polyarylate, polyamide, polyamideimide, polycarbonate, and polyolefin. And various thermoplastic resins such as polyetheretherketone. The mass ratio of the blendable thermoplastic resin is preferably 5% by mass or less, more preferably 3% by mass, based on the blended composition, in order to fully express the characteristics of the polyphenylene sulfide (A) of the present invention. It is less than or equal to, more preferably 1% by mass or less. The blending referred to here is a melt-mixing / kneading of two or more components of resin, which is different from the compounding technique of arranging two or more components of resin at an arbitrary position on the fiber cross section at the time of spinning. ..

The polyphenylene sulfide (A) used in the present invention contains various metal oxides, inorganic substances such as kaolin and silica, pigments for coloring, matting agents, flame retardants, and antioxidants as long as the effects of the present invention are not impaired. Various additives such as agents, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent whitening agents, terminal group encapsulants, and compatibilizers can be added.

The polyphenylene sulfide (A) used in the present invention preferably has a melting point (hereinafter, may be abbreviated as Tm (A)) of 260 to 300 ° C. By setting Tm (A) to preferably 260 ° C. or higher, more preferably 270 ° C. or higher, a polyphenylene sulfide composite fiber having excellent heat resistance can be obtained. Further, by setting Tm (A) to preferably 300 ° C. or lower, more preferably 290 ° C. or lower, it becomes easy to set the temperature condition at the time of fiber production. In addition, Tm (A) refers to the value measured by the method described in the column B of the Example.

[Copolymerized polyphenylene sulfide (B)]
It is important that 60 to 97 mol% of the repeating unit of the copolymerized polyphenylene sulfide (B) used in the present invention is composed of the p-phenylene sulfide unit represented by the structural formula (1). By setting the p-phenylene sulfide unit to 60 mol% or more, preferably 70 mol% or more, a polyphenylene sulfide composite fiber having excellent heat resistance and chemical resistance can be obtained. Further, when the p-phenylene sulfide unit is 97 mol% or less, preferably 95 mol% or less, the crystallinity of the copolymerized polyphenylene sulfide is lowered, so that the polyphenylene sulfide composite fiber having excellent adhesiveness is obtained.

Further, in the copolymerized polyphenylene sulfide (B) used in the present invention, it is important that 3 to 40 mol% of the repeating unit is composed of the m-phenylene sulfide unit represented by the structural formula (2). By setting the m-phenylene sulfide unit to 3 mol% or more, preferably 5 mol% or more, the crystallinity of the copolymerized polyphenylene sulfide is lowered, so that the polyphenylene sulfide composite fiber having excellent adhesiveness is obtained. Further, by setting the m-phenylene sulfide unit to 40 mol% or less, preferably 30 mol% or less, a polyphenylene sulfide composite fiber having excellent heat resistance and chemical resistance can be obtained.

The mole fractions of the p-phenylene sulfide unit and the m-phenylene sulfide unit of the copolymerized polyphenylene sulfide (B) used in the present invention can be measured by infrared spectroscopic analysis.

Examples of the copolymerization mode of the copolymerized polyphenylene sulfide (B) used in the present invention include random copolymerization and block copolymerization, but random copolymerization is preferably used because the melting point can be easily controlled. ..

The copolymerized polyphenylene sulfide (B) used in the present invention may contain other copolymerized components as long as the effects of the present invention are not impaired. Examples of other copolymerization components include aromatic sulfides such as triphenylene sulfide and biphenylene sulfide, and alkyl-substituted and halogen-substituted products thereof. The mass ratio of the other copolymerization component is preferably 5% by mass or less, more preferably 3% by mass or less, and further, in order to fully express the characteristics of the copolymerized polyphenylene sulfide (B) of the present invention. It is preferably 1% by mass or less.

The copolymerized polyphenylene sulfide (B) used in the present invention can be blended with a thermoplastic resin as long as the effects of the present invention are not impaired. Thermoplastic resins include, for example, polyphenylene sulfide, polyetherimide, polyethersulfone, polysulfone, polyphenylene ether, polyester, polyarylate, polyamide, polyamideimide, polycarbonate, polyolefin and Examples thereof include various thermoplastic resins such as polyetheretherketone. The mass ratio of the blendable thermoplastic resin is preferably 5% by mass or less based on the blended composition, more preferably 3 in order to fully express the characteristics of the copolymerized polyphenylene sulfide (B) of the present invention. It is 1% by mass or less, more preferably 1% by mass or less. The blending referred to here is a melt-mixing / kneading of two or more components of resin, which is different from the compounding technique of arranging two or more components of resin at an arbitrary position on the fiber cross section at the time of spinning. ..

The copolymerized polyphenylene sulfide (B) used in the present invention includes various metal oxides, inorganic substances such as kaolin and silica, pigments for coloring, matting agents, flame retardants, as long as the effects of the present invention are not impaired. Various additives such as antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent whitening agents, terminal group encapsulants, and compatibilizers can be added.

The copolymer polyphenylene sulfide (B) used in the present invention preferably has a melting point (hereinafter, may be abbreviated as Tm (B)) of 200 to 270 ° C. By setting Tm (B) to preferably 200 ° C. or higher, more preferably 210 ° C. or higher, a polyphenylene sulfide composite fiber having excellent heat resistance can be obtained. Further, by setting Tm (B) to preferably 270 ° C. or lower, more preferably 260 ° C. or lower, and further preferably 255 ° C. or lower, a polyphenylene sulfide composite fiber having high adhesiveness can be obtained. In addition, Tm (B) refers to the value measured by the method described in the column B of the Example.

[Polyphenylene sulfide composite fiber]
It is important that the polyphenylene sulfide composite fiber of the present invention is a core-sheath type composite fiber in which polyphenylene sulfide (A) is arranged in a core portion and copolymerized polyphenylene sulfide (B) is arranged in a sheath portion. By using the core-sheath type composite fiber, the polyphenylene sulfide (A) in the core becomes the skeleton, so that excellent mechanical strength is exhibited, and the copolymer polyphenylene sulfide (B) in the sheath becomes the heat-bonded part. Therefore, it becomes a polyphenylene sulfide composite fiber having high adhesiveness.

The cross-sectional shape of the polyphenylene sulfide composite fiber of the present invention is not limited in any way, and may be any shape such as a round cross section, a triangular cross section or the like, a flat cross section or an S-shaped cross section, a ten o'clock cross section, or a hollow cross section. However, when it is necessary to disperse short fibers in a medium for papermaking applications, resin reinforcing applications, etc., a round cross section is preferable from the viewpoint of fiber dispersibility.

The polyphenylsulfide composite fiber of the present invention is a short fiber, and it is important that the average fiber length is 1 to 100 mm. By setting the average fiber length to 1 mm or more, preferably 3 mm or more, and more preferably 4 mm or more, the fibers are appropriately entangled with each other during the non-woven fabric processing, and the obtained non-woven fabric has excellent mechanical strength. Further, by setting the average fiber length to 100 mm or less, preferably 60 mm or less, more preferably 30 mm or less, uneven texture due to excessive entanglement during non-woven fabric processing can be prevented, and a homogeneous non-woven fabric with few wrinkles can be obtained. Obtainable. The average fiber length in the present invention refers to a value measured by the method described in column C of Examples.

In the polyphenylene sulfide composite fiber of the present invention, the area ratio of the core portion to the total cross-sectional area is preferably 75 to 95% in the cross section of the core-sheath type composite fiber. By setting the area ratio of the core portion to preferably 75% or more, more preferably 85% or more, the ratio of the core portion serving as the skeleton portion increases, so that the polyphenylene sulfide composite fiber having excellent dimensional stability can be obtained. Further, by setting the area ratio of the core portion to preferably 95% or less, more preferably 92% or less, exposure of the core component to the fiber surface can be prevented, and the polyphenylene sulfide composite fiber having high adhesiveness can be obtained. The area ratio of the core portion in the present invention refers to a value measured by the method described in column E of Examples.

The polyphenylene sulfide composite fiber of the present invention preferably has a birefringence of 0.18 to 0.40. By setting the birefringence to preferably 0.18 or more, more preferably 0.22 or more, the fiber has a highly oriented molecular chain, and a polyphenylene sulfide composite fiber having excellent mechanical properties can be obtained. Further, by setting the birefringence to preferably 0.40 or less, more preferably 0.30 or less, excessive orientation crystallization of the copolymer polyphenylene sulfide (B) in the sheath portion can be prevented, and high adhesion can be prevented. It becomes a polyphenylene sulfide composite fiber having a property. The birefringence of the fiber in the present invention refers to a value measured by the method described in column F of Examples.

The polyphenylene sulfide composite fiber of the present invention preferably has an average fiber diameter of 25 μm or less. By setting the average fiber diameter to preferably 25 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less, cooling unevenness during melt spinning is less likely to occur, resulting in excellent spinnability and good fiber diameter uniformity. It becomes a polyphenylene sulfide composite fiber having. The average fiber diameter in the present invention refers to a value measured by the method described in column D of Examples.

The polyphenylene sulfide fiber of the present invention preferably has a strength of 2.0 cN / dtex or more. By setting the strength to preferably 2.0 cN / dtex or more, more preferably 3.0 cN / dtex or more, the handleability at the time of processing the non-woven fabric is improved, and the mechanical strength of the obtained non-woven fabric is improved. The upper limit of the strength is not particularly limited, but the upper limit that can be reached industrially is about 7.0 cN / dtex.

The polyphenylene sulfide composite fiber of the present invention preferably has an elongation of 50% or less. By setting the elongation to preferably 50% or less, more preferably 40% or less, the fiber has a sufficiently high molecular orientation, so that it is difficult to be plastically deformed (stretched) and the handleability during non-woven fabric processing is improved. .. The lower limit of elongation is not particularly limited, but the lower limit that can be reached industrially is about 8%. The strength and elongation in the present invention refer to the values measured by the method described in the column G of Examples.

The polyphenylene sulfide composite fiber of the present invention is not only excellent in heat resistance and chemical resistance, but also has a small fiber diameter, high adhesiveness and mechanical strength, and excellent dimensional stability. Taking advantage of its features, it can be used for bug filters, chemical filters, food filters, chemical filters, oil filters, engine oil filters, air cleaning filters, paper applications such as electrically insulating paper, and heat-resistant work clothing applications such as firefighting clothing. Safety clothing, experimental work clothing, heat insulating clothing, flame-retardant clothing, high-visibility textile, papermaking felt, sewing thread, heat-resistant felt, shape-removing material, papermaking dryer cambus, battery separator, electrode separator, various diaphragms, heart patch Suitable for various applications such as artificial blood vessels, artificial skin, printed substrate base material, copy rolling cleaner, ion exchange base material, oil holding material, heat insulating material, cushioning material, brush, net conveyor, motor binding thread, motor binder tape, etc. Although it can be used, it is particularly preferably used in the form of a non-woven fabric, and is preferably used for paper applications such as electrically insulating paper, battery separator applications, and various diaphragm applications.

[Non-woven fabric]
The non-woven fabric of the present invention is a non-woven fabric containing the polyphenylene sulfide composite fiber of the present invention. By containing the polyphenylene sulfide composite fiber of the present invention, a non-woven fabric having good heat resistance and chemical resistance can be obtained. In addition, since it has a structure in which a binder portion having excellent adhesiveness is uniformly arranged around a skeleton portion having excellent mechanical strength, a uniform non-woven fabric with less uneven basis weight can be obtained. Further, by reducing the uneven adhesion between the fibers, the non-woven fabric has good mechanical properties.

The nonwoven fabric of the present invention preferably has a basis weight of 3 to 100 g / m ^2. By setting the basis weight to preferably 3 g / m ² or more, more preferably 5 g / m ² or more, and further preferably 10 g / m ² or more, paper breakage during the papermaking process is less likely to occur, and process passability is improved. .. Further, by setting the basis weight to preferably 100 g / m ² or less, more preferably 80 g / m ² or less, and further preferably 60 g / m ² or less, a lightweight and highly flexible non-woven fabric can be obtained. The basis weight of the non-woven fabric in the present invention refers to a value measured by the method described in column H of Examples.

The non-woven fabric of the present invention preferably has a tensile strength of 5 to 300 N / 15 mm. By setting the tensile strength to preferably 5 N / 15 mm or more, more preferably 10 N / 15 mm or more, and further preferably 15 N / 15 mm or more, paper breakage during the papermaking process is less likely to occur. In addition, the non-woven fabric is not easily torn even when tensile stress is applied during the post-process or during use. Further, by setting the tensile strength to preferably 300 N / 15 mm or less, more preferably 250 N / 15 mm or less, still more preferably 200 N / 15 mm or less, the flexibility of the non-woven fabric can be maintained, and when used for a diaphragm or the like. It becomes a non-woven fabric with excellent assembling property. The tensile strength of the non-woven fabric in the present invention refers to a value measured by the method described in column J of Examples.

The non-woven fabric of the present invention preferably has a tear strength of 20 to 1000 gf. By setting the tear strength to preferably 20 gf or more, more preferably 50 gf or more, and further preferably 100 gf or more, even if cracks occur in the non-woven fabric during the process, the cracks are less likely to propagate to the entire non-woven fabric and are less likely to be torn. It becomes a non-woven fabric. Further, by setting the tear strength to preferably 1000 gf or less, more preferably 900 gf or less, still more preferably 800 gf or less, problems are less likely to occur when cutting the non-woven fabric. The tear strength of the non-woven fabric in the present invention refers to a value measured by the method described in item K of column K of Examples.

The non-woven fabric of the present invention preferably has a breathability of 0.01 cc / cm ² / s to 300 ^{cc / cm 2} / s. Preferably the air permeability is 0.01cc / ^cm 2 / s or more, more preferably 0.10cc / ^cm 2 / s or more, more preferably by a 1.0cc / ^cm 2 / s or more, is used for the diaphragm, etc. The permeability of ions and the like at the time is improved. Further, the non-woven fabric has sufficient mechanical strength by setting the air permeability to preferably 300 cc / cm ² / s or less, more preferably 250 cc / cm ² / s or less, and further preferably 200 cc / cm ^{2 / s or less.} Therefore, paper breakage during the papermaking process is less likely to occur, and process passability is improved. Further, when it is used for a diaphragm or the like, tearing or cracking during assembly is less likely to occur. The air permeability of the non-woven fabric in the present invention refers to a value measured by the method described in the column L of Examples.

The non-woven fabric of the present invention preferably has a thickness of 5 μm to 300 μm. By setting the thickness to preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more, paper breakage during the papermaking process is less likely to occur, and process passability is improved. Further, by setting the thickness to preferably 300 μm or less, more preferably 250 μm or less, still more preferably 200 μm or less, the permeability of ions or the like when used for a diaphragm or the like is improved. Further, when the device is mounted as a diaphragm or the like, the volume occupied by the non-woven fabric is reduced, so that the device can be made smaller and lighter. The thickness of the non-woven fabric in the present invention refers to a value measured by the method described in the column M of Examples.

[Manufacturing method of polyphenylene sulfide composite fiber]
In the method for producing a polyphenylene sulfide composite fiber of the present invention, the polyphenylene sulfide (A) and the copolymerized polyphenylene sulfide (B) used as raw materials are referred to as the melt mass flow rate of the polyphenylene sulfide (A) (hereinafter referred to as MFR (A)). (May be abbreviated) is 50 to 250 g / 10 minutes, and the melt mass flow rate (hereinafter, may be abbreviated as MFR (B)) of the copolymerized polyphenylene sulfide (B) is larger than that of MFR (A). It is characterized by. Hereinafter, the method for producing the polyphenylene sulfide composite fiber of the present invention will be described in detail.

As a method for producing the polyphenylene sulfide composite fiber of the present invention, it is preferable to use polyphenylene sulfide (A) having an MFR (A) of 50 to 250 g / 10 minutes. By setting the MFR (A) to 50 g / 10 minutes or more, preferably 80 g / 10 minutes or more, more preferably 100 g / 10 minutes or more, the fluidity at the time of melting is increased, so that the spinnability is improved and the fiber diameter is uniform. It becomes a polyphenylene sulfide composite fiber having excellent properties. Further, by setting the MFR (A) to 250 g / 10 minutes or less, preferably 230 g / 10 minutes or less, more preferably 200 g / 10 minutes or less, a polyphenylene sulfide composite fiber having good mechanical strength can be obtained. The melt mass flow rate in the present invention refers to a value measured by the method described in column A of Examples.

As a method for producing the polyphenylene sulfide composite fiber of the present invention, it is preferable to use a copolymerized polyphenylene sulfide (B) having an MFR (B) larger than that of the MFR (A). As a result of further studies, the present inventors have found that a polyphenylene sulfide composite fiber having excellent mechanical strength can be obtained by using a copolymerized polyphenylene sulfide (B) having an MFR (B) larger than that of the MFR (A). It was confirmed. This is because the MFR (B) is larger than the MFR (A), so that it is possible to suppress the occurrence of the difference in the orientation of the inner and outer layers due to the high orientation of the molecular chains on the fiber surface that occurs in the cooling process during spinning, and it is uniform in the subsequent drawing step. This is because it can be stretched. Furthermore, as a result of diligent studies, the present inventors have found that by using a copolymerized polyphenylene sulfide (B) having an MFR (B) larger than that of the MFR (A), the fiber has excellent adhesiveness. This is because, in the fiber manufacturing process such as spinning and drawing, excessive orientation crystallization can be suppressed by reducing the spinning stress burden on the copolymer polyphenylene sulfide (B) which is the sheath portion. As a result, the proportion of amorphous portions that contribute to thermal adhesion can be increased, resulting in a fiber having excellent adhesiveness. The MFR (B) is preferably larger than the MFR (A) by 5 g / 10 minutes or more, and more preferably 10 g / 10 minutes or more.

In the method for producing a polyphenylene sulfide composite fiber of the present invention, it is preferable to use a copolymer polyphenylene sulfide (B) having an MFR (B) of 60 to 350 g / 10 minutes. By setting the MFR (B) to preferably 60 g / 10 minutes or more, more preferably 80 g / 10 minutes or more, and further preferably 100 g / 10 minutes or more, the fluidity at the time of melting is increased and the spinnability is improved. It is a polyphenylene sulfide composite fiber having excellent fiber diameter uniformity. Further, by setting the MFR (B) to preferably 350 g / 10 minutes or less, more preferably 300 g / 10 minutes or less, and further preferably 280 g / 10 minutes or less, the polyphenylene sulfide composite fiber having good mechanical strength can be obtained. Become.

As a method for producing polyphenylene sulfide (A) used in the present invention, for example, an alkali metal sulfide such as sodium sulfide is reacted with p-dichlorobenzene in an organic amide solvent such as N-methyl-2-pyrrolidone. A method for obtaining polyphenylene sulfide can be mentioned.

As a method for producing the copolymerized polyphenylene sulfide (B) used in the present invention, for example, in an organic amide solvent such as N-methyl-2-pyrrolidone, an alkali metal sulfide such as sodium sulfide and p-dichlorobenzene and m are used. -A method of reacting dichlorobenzene to obtain polyphenylene sulfide can be mentioned.

The polyphenylene sulfide (A) and the copolymerized polyphenylene sulfide (B) used in the present invention are preferably dried before being subjected to melt spinning for the purpose of preventing water contamination and removing oligomers in order to improve the silk-reeling property. As the drying conditions, vacuum drying at 100 to 200 ° C. for 1 to 24 hours is usually used.

In melt spinning, a melt spinning method using an extruder such as a pressure melter type, a single shaft or a twin shaft extruder type can be applied. The extruded polyphenylene sulfide is weighed by a measuring device such as a gear pump via a pipe, passed through a foreign matter removing filter, and then guided to each spinneret. Each polymer led to the spinneret is shaped and merged so that polyphenylene sulfide (A) is arranged in the core and copolymerized polyphenylene sulfide (B) is arranged in the sheath in the spinneret, and the core sheath type is formed. It is discharged from the base hole as a composite fiber. At this time, the temperature from the polymer pipe to the spinneret (spinning temperature) is preferably 280 ° C. or higher in order to increase the fluidity, and preferably 380 ° C. or lower in order to suppress thermal decomposition of the polymer.

The spinneret used for discharge preferably has a hole diameter D of the mouthpiece hole of 0.1 to 0.6 mm, and a land length L of the mouthpiece hole (the length of a straight pipe portion having the same hole diameter as the mouthpiece hole). ) Is divided by the pore size, and the L / D defined by the quotient is preferably 1 to 10.

The polyphenylene sulfide composite fiber discharged from the mouthpiece hole is cooled and solidified by blowing cooling air (air). The temperature of the cooling air can be determined in balance with the cooling air speed from the viewpoint of cooling efficiency, but it is preferably 30 ° C. or lower. By setting the temperature of the cooling air to preferably 30 ° C. or lower, the solidification behavior due to cooling is stabilized, and a polyphenylene sulfide composite fiber having high fiber diameter uniformity is obtained.

Further, it is preferable that the cooling air flows in a substantially vertical direction to the undrawn fibers discharged from the mouthpiece. At that time, the speed of the cooling air is preferably 10 m / min or more from the viewpoint of cooling efficiency and the uniformity of the fiber diameter, and preferably 100 m / min or less from the viewpoint of yarn-making stability.

The undrawn fibers that have been cooled and solidified are taken up by a roller (godet roller) that rotates at a constant speed. The take-up speed is preferably 300 m / min or more in order to improve fiber diameter uniformity and productivity, and 2000 m / min or less in order not to cause yarn breakage.

The undrawn fibers thus obtained are subjected to a drawing step after being wound once or continuously after being taken up. Stretching is performed by running on a heated first roller or a heating device provided between the first roller and the second roller, for example, in a heating bath or on a hot plate. The drawing conditions are determined by the mechanical properties of the obtained undrawn fibers, but the drawing temperature is determined by the temperature of the heated first roller or the heating device provided between the first roller and the second roller, and the drawing is performed. The magnification is determined by the ratio of the peripheral speeds of the first roller and the second roller.

The stretching ratio in the stretching step is preferably 2.0 times or more. By setting the draw ratio to preferably 2.0 times or more, more preferably 2.5 times or more, the fiber has a highly oriented molecular chain, and a polyphenylene sulfide composite fiber having excellent mechanical properties can be obtained. The upper limit of the draw ratio is not particularly limited, but the upper limit that can be reached industrially is about 8.0 times.

The temperature of the heated first roller or heating device in the stretching step is preferably 80 to 130 ° C. By setting the temperature of the first roller or the heating device to 80 ° C. or higher, the stretching point is fixed and stable stretching is possible. Further, by setting the temperature of the first roller or the heating device to 130 ° C. or lower, yarn breakage in the process can be suppressed and the process passability is improved. Further, the temperature of the second roller is preferably set to + 20 ° C. or less, which is the temperature of the heated first roller or the heating device, from the viewpoint of fixing the drawing point.

Further, after passing through the second roller, the drawn fibers may be heated by a heated third roller or a heating device provided between the second roller and the third roller to perform heat setting. The heat setting temperature for heat setting is preferably 210 ° C. or lower. By setting the heat setting temperature to 210 ° C. or lower, more preferably 190 ° C. or lower, and further preferably 150 ° C. or lower, excessive thermal crystallization is suppressed and a polyphenylene sulfide composite fiber having high adhesiveness is obtained.

It is preferable to add a papermaking dispersant or the like to the polyphenylene sulfide composite fiber of the present invention, if necessary. The dispersant is usually applied in a toe state using a kiss roller or guide lubrication. The above-mentioned papermaking dispersant adhesion rate is preferably 1 to 6% by mass with respect to the fiber mass. By setting the dispersant adhesion rate to preferably 1% by mass or more, more preferably 2% by mass or more, the dispersibility of the fibers in the dispersion liquid which is the precursor of the non-woven fabric is improved, so that a homogeneous non-woven fabric is obtained. Further, by setting the dispersant adhesion rate to preferably 6% by mass or less, more preferably 5% by mass or less, the process passability during non-woven fabric processing is improved.

Next, the polyphenylene sulfide composite fiber of the present invention may be crimped by a crimper and heat-fixed by a setter. By imparting crimping, the fibers are entangled with each other to increase the adhesive area between the fibers, resulting in a non-woven fabric having excellent mechanical strength.

The number of crimps in the above crimps is preferably 2 to 15 peaks / 25 mm. By preferably setting the number of crimps to 2 ridges / 25 mm or more, the fibers are easily entangled with each other, and a non-woven fabric having excellent mechanical strength is obtained. Further, by setting the number of crimps to preferably 15 threads / 25 mm or less, the dispersibility of the fibers in the dispersion liquid is improved, and a homogeneous non-woven fabric is obtained.

Further, the heat fixing temperature by the setter is preferably 80 ° C. or higher and 100 ° C. or lower. By setting the heat fixing temperature preferably 80 ° C. or higher, the crimped form can be fixed, and by setting the heat fixing temperature preferably 100 ° C. or lower, the adhesiveness is impaired by excessive thermal crystallization. prevent.

Then, the obtained polyphenylene sulfide composite fiber is cut to a predetermined length with a cutter to obtain a cut fiber.

[Manufacturing method of non-woven fabric]
Hereinafter, the method for producing the nonwoven fabric of the present invention will be described in detail.

The papermaking liquid for producing the non-woven fabric of the present invention is obtained by mixing the cut fibers obtained as described above alone or in an arbitrary ratio with the cut fibers of other fibers and dispersing them in water. Be done. Here, as the cut fiber of other fibers, it is preferable to use a cut fiber of a heat resistant fiber such as polyphenylene sulfide fiber, metaaramid fiber, or fluorine fiber from the viewpoint of obtaining a paper having excellent heat resistance. A non-woven fabric can be obtained by supplying this paper making liquid to a paper machine.

The fiber concentration of the papermaking solution is preferably 0.05 to 5% by mass. If the fiber concentration is less than 0.05% by mass, the production efficiency is lowered and the load of the dehydration step is increased. On the contrary, if it exceeds 5% by mass, the dispersed state of the fibers deteriorates, and it becomes difficult to obtain a uniform non-woven fabric.

The papermaking liquid contains a dispersant or oil agent composed of cationic, anionic, nonionic, etc. surfactants in order to improve water dispersibility, and a viscosity that increases the viscosity of the dispersion to prevent the papermaking liquid from agglomerating. An agent and an antifoaming agent that suppresses the generation of bubbles may be added.

The paper making liquid prepared as described above is made by using a paper machine such as a round net type, a long net type, or an inclined net type or a handmade paper machine, and this is dried with a Yankee dryer, a rotary dryer, or the like to obtain moisture. Remove and tentatively bond the fibers to obtain a dry web.

The drying temperature is preferably 80 to 150 ° C. Preferably, when the temperature is 80 ° C. or higher, temporary adhesion between the fibers proceeds sufficiently, and a dry web having sufficient mechanical properties is obtained. Further, by setting the drying temperature to 150 ° C. or lower, crystallization proceeds excessively, and the adhesiveness in the subsequent thermocompression bonding step is lost, and as a result, the mechanical properties of the obtained non-woven fabric are deteriorated. Here, the drying temperature refers to the maximum temperature at the processing temperature (atmospheric temperature) at the time of drying in the papermaking process.

By thermocompression bonding the dry web obtained as described above, the polyphenylene sulfide composite fibers of the present invention are adhered to each other, resulting in a non-woven fabric having excellent mechanical strength. Any means may be used for thermocompression bonding, and for example, a heat press on a flat plate or the like, a calendar, or the like can be adopted. Of these, a calendar that can be processed continuously is preferable. As the calender roll, a metal-metal roll, a metal-paper roll, a metal-rubber roll, or the like can be used.

The thermocompression bonding temperature is preferably 170 to 250 ° C. When the thermocompression bonding temperature is preferably 170 ° C. or higher, the fibers are bonded by the adhesion of the copolymer polyphenylene sulfide (B) in the sheath portion, and a wet non-woven fabric having excellent mechanical strength is obtained. Further, by setting the thermocompression bonding temperature to preferably 250 ° C. or lower, the thermal shrinkage of the non-woven fabric during thermocompression bonding can be suppressed.

When calender processing is adopted as the thermocompression bonding means, the linear pressure is preferably 98 to 7000 N / cm. By setting the linear pressure to 98 N / cm or more, the fibers are firmly pressure-bonded via the copolymerized polyphenylene sulfide (B) in the sheath portion, and a wet non-woven fabric having excellent mechanical strength is obtained. Further, by setting the linear pressure to preferably 7,000 N / cm or less, it is possible to suppress a decrease in tear strength and air permeability due to excessive crushing of the constituent fibers to form a film. The process speed is preferably 1 to 30 m / min. By preferably setting the process speed to 1 m / min or more, it is possible to suppress a decrease in the mechanical strength of the non-woven fabric due to excessive thermal crystallization, and it is possible to obtain good work efficiency. Further, by preferably setting the process speed to 30 m / min or less, heat can be conducted to the fibers inside the non-woven fabric, and the effect of heat fusion of the fibers can be obtained.

Hereinafter, the polyphenylene sulfide composite fiber of the present invention and the non-woven fabric containing the same will be described more specifically by way of examples. Each characteristic value in the examples was obtained by the following method.

A. Melt mass flow rate:
The melt mass flow rate MFR (A) of polyphenylene sulfide (A) and the melt mass flow rate MFR (B) of copolymerized polyphenylene sulfide (B) are JIS K7210 using a melt indexer (F-F01 manufactured by Toyo Seiki Seisakusho Co., Ltd.). -1: According to "Chapter 8 Method A: Mass Measurement Method" of 2014, measure 3 times per level at a temperature of 315 ° C. with a load of 5.0 kg, and obtain the arithmetic mean value, and obtain MFR (A) (g / g /). 10 minutes) and MFR (B) (g / 10 minutes).

B. Melting point The melting point Tm (A) of polyphenylene sulfide (A) and the melting point Tm (B) of copolymerized polyphenylene sulfide (B) are in the range of 25 ° C to 320 ° C using a differential scanning calorimeter (DSC Q2000 manufactured by TA Instruments). The temperature was raised at 10 ° C./min and measured three times per level to obtain the arithmetic mean value of the peak top temperature of the largest heat absorption peak of the obtained DSC curve, and Tm (A) (° C.) and Tm. (B) (° C.).

C. Average fiber length:
100 polyphenylene sulfide composite fibers were randomly extracted and stretched using an optical microscope (BX53M manufactured by Olympus Co., Ltd.) under the conditions of an objective lens of 10 times and an eyepiece lens of 10 times to the extent that plastic deformation does not occur. The distance between both ends of the lens was measured, and the arithmetic average value was calculated and used as the average fiber length (mm).

D. Average fiber diameter:
100 polyphenylene sulfide composite fibers were randomly extracted, and the fiber diameter (μm) was measured from the side surface of the fibers using an optical microscope (BX53M manufactured by Olympus Corporation) under the conditions of an objective lens of 40 times and an eyepiece of 10 times. , The arithmetic average value was calculated and used as the average fiber diameter (μm).

E. Core area ratio:
100 polyphenylene sulfide composite fibers were randomly extracted, and a cross-sectional area photograph of the fibers was taken at 1000 times using a scanning electron microscope (VE-7800 type manufactured by KEYENCE), and the total cross-sectional area and core of each fiber were taken. The area ratio of the core was calculated by measuring the area of the part, obtaining the arithmetic mean value of each, and dividing the area of the core by the total cross-sectional area.

F. Birefringence of fibers:
Ten polyphenylene sulfide composite fibers were randomly extracted, and the retardation and optical path length of the single fibers were measured using an optical microscope (BX53M manufactured by Olympus Corporation) to obtain birefringence, and the arithmetic mean value was obtained to obtain birefringence. And said.

G. Strength, elongation:
For the strength and elongation of the polyphenylene sulfide composite fiber, Tensilon (UTM-III-100 manufactured by Orientec Co., Ltd.) was used, and the sample length was 200 mm according to "Chapter 8.5 Tensile Strength and Elongation Rate" of JIS L1013: 2010. The measurement was performed 5 times per level under the condition of a tensile speed of 200 mm / min, and the arithmetic mean value was obtained and used as the strength (cN / dtex) and the elongation (%).

H. Non-woven fabric weight:
From the non-woven fabric obtained in the examples, three 5 cm × 5 cm sample pieces were collected, the mass (g) of each was measured in the standard state, and the average value was measured by ^{the mass per 1 m 2} (g / m ² ). expressed.

I. Number of wrinkles on non-woven fabric:
Using an optical microscope (BX53M manufactured by Olympus Corporation), the number of wrinkles (/ 100 cm ² ) of the dry web obtained in the examples was confirmed under the conditions of an objective lens of 40 times and an eyepiece lens of 10 times. The wrinkles of the dry web here refer to linear wrinkles that occur in places where the rate of change in thermal dimensions in the dry web is locally different due to poor dispersibility of fibers, etc., and wrinkles with a total length of 0.1 cm or more. The number of wrinkles was confirmed by measuring 3 sheets per level, and the arithmetic mean value was calculated and used as the number of wrinkles (pieces) of the dry web.

J. Tensile strength of non-woven fabric:
From the non-woven fabric obtained in the examples, measurements were carried out in each of the vertical (progress direction of the non-woven fabric manufacturing process) and horizontal (width direction of the non-woven fabric manufacturing process) of the non-woven fabric. Using Tencilon (UTM-III-100 manufactured by Orientec Co., Ltd.), the maximum point load was measured under the conditions of a sample width of 15 mm, an initial length of 20 mm, and a tensile speed of 20 mm / min. Each level was measured 5 times in each of the vertical and horizontal directions, and the arithmetic mean value was calculated and used as the tensile strength (N / 15 mm) of the non-woven fabric.

K. Non-woven fabric tear strength:
From the non-woven fabric obtained in the examples, a 63 mm × 100 mm test piece was measured in each of the vertical (progress direction of the non-woven fabric manufacturing process) and horizontal (width direction of the non-woven fabric manufacturing process) of the non-woven fabric. Using an Elmendorf type tear tester (manufactured by Yasuda Seiki Seisakusho), a 20 mm cut was made at a right angle at the center of both grips of the test piece, and the strength shown when the remaining 43 mm was torn in the vertical and horizontal directions was measured. Each level was measured 5 times in each of the vertical and horizontal directions, and the arithmetic mean value was calculated and used as the tear strength (gf) of the non-woven fabric.

L. Non-woven fabric breathability:
According to the JIS L1913 (2010) Frazier method, 10 sample pieces of 5 cm x 5 cm were collected from the non-woven fabric obtained in the examples, and a breathability tester (FX3300 manufactured by Textest Co., Ltd.) was used. The air volume of 10 test pieces was measured at a test pressure of 125 Pa, and the arithmetic mean value was taken as the air permeability (cc / cm ² / s).

M. Nonwoven thickness:
According to JIS P8118 (2014), 10 sample pieces of 5 cm × 5 cm were collected from the non-woven fabric obtained in the example, and 10 test pieces were taken one by one using a micrometer (manufactured by Mitutoyo Co., Ltd.). The thickness was measured, and the arithmetic mean value was taken as the thickness (μm) of the non-woven fabric.

[Example 1]
The repeating unit is polyphenylene sulfide (A) having 100 mol% of p-phenylene sulfide unit, MFR (A) of 160 g / 10 minutes, and Tm (A) of 284 ° C., and the repeating unit is 75 mol of p-phenylene sulfide unit. %, M-phenylene sulfide unit is 25 mol%, MFR (B) is 200 g / 10 minutes, and Tm (B) is 243 ° C. After vacuum drying of copolymerized polyphenylene sulfide (B) at 150 ° C. for 12 hours. , Molten spinning was performed at a spinning temperature of 320 ° C. In melt spinning, polyphenylene sulfide (A) and copolymerized polyphenylene sulfide (B) were melt-extruded by a twin-screw extruder, respectively, and supplied to a spinning pack while being weighed by a gear pump. After that, polyphenylene sulfide (A) is arranged in the core portion and copolymerized polyphenylene sulfide (B) is arranged in the sheath portion in the spinneret, and the shape is regulated so that the area ratio of the core portion in the cross section of the composite fiber is 75%. And spun through a spinneret having 36 round discharge holes.

The polymer discharged from the mouthpiece was passed through a heat retention region of 50 mm, and then air-cooled over 1.0 m under the conditions of a temperature of 25 ° C. and a wind speed of 18 m / min using a uniflow type cooling device. Then, an oil agent was applied, and all 36 filaments were wound with a winder via a first godet roller and a second godet roller at 1000 m / min to obtain undrawn fibers.

The above undrawn fibers are taken up by a feed roller attached to the nip roller, tension is applied to the undrawn fibers with the first roller, and then the first roller and the second roller are heated to 90 ° C. and 100 ° C., respectively. The roller was rotated 6 times to carry out heat stretching. Further, the third roller heated to 120 ° C. was rotated 6 times to set the heat. The draw ratio was 3.85 times, and after taking up with a non-heating roller having a peripheral speed of 400 m / min after the third roller, a dispersant of 2% by mass was added to the fiber weight using guide lubrication. .. Subsequently, after crimping 8 ridges / 25 mm with a crimper, heat fixation was performed at 70 ° C. for 1 minute with a setter. Then, the obtained fiber was cut with a cutter to obtain a polyphenylene sulfide composite fiber having an average fiber length of 6 mm.

By dispersing the obtained polyphenylene sulfide composite fiber in water, an aqueous dispersion with a fiber concentration of 1% by mass was prepared, and then a handmade paper machine (with automatic cooling of a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd.) was used. A wet paper (10 cm square) having a grain size of 50 g / m ^{2 was obtained.} The web obtained by dehydrating with a roller is put into a dryer (KRK rotary dryer standard type manufactured by Kumagai Riki Kogyo Co., Ltd.) and processed at a temperature of 140 ° C. and a processing time of about 2.5 minutes / time. , Got a dry web. Subsequently, the other surface was thermocompression bonded at an iron roll surface temperature of 220 ° C., a linear pressure of 490 N / cm, and a roll rotation speed of 3 m / min to obtain a non-woven fabric.

[Examples 2 to 4, Comparative Example 1]
Polyphenylene sulfide composite fibers and non-woven fabric were obtained in the same manner as in Example 1 except that the copolymerization ratio of the copolymerized polyphenylene sulfide (B) arranged in the sheath was changed and the stretching ratio in the stretching step was 3.61 times. .. Table 1 shows the evaluation results of the obtained polyphenylene sulfide composite fiber and non-woven fabric.

[Example 5, Example 6, Comparative Example 2]
Polyphenylene sulfide composite fibers and non-woven fabrics were obtained in the same manner as in Example 1 except that the average fiber length of the polyphenylene sulfide composite fibers was changed. Table 1 shows the evaluation results of the obtained polyphenylene sulfide composite fiber and non-woven fabric.

[Example 7]
Polyphenylene sulfide composite fibers and a non-woven fabric were obtained in the same manner as in Example 1 except that the area ratio of polyphenylene sulfide (A) arranged in the core was changed. Table 1 shows the evaluation results of the obtained polyphenylene sulfide composite fiber and non-woven fabric.

[Example 8]
The polyphenylene sulfide composite fiber and the non-woven fabric were obtained by the same method as in Example 1 except that the stretching ratio in the stretching step was 3.31 times and the fibers were taken up by a non-heating roller without heat setting. Table 1 shows the evaluation results of the obtained polyphenylene sulfide composite fiber and non-woven fabric.

The polyphenylene sulfide composite fibers obtained in Examples 1 to 7 have a small number of wrinkles in the non-woven fabric and show good values in tensile strength and tear strength of the non-woven fabric, and thus constitute a non-woven fabric having excellent mechanical properties. It was a polyphenylene sulfide fiber suitable as a fiber.

On the other hand, the polyphenylene sulfide composite fiber obtained in Comparative Example 1 had a low copolymerization ratio of the sheath portion and was inferior in adhesiveness, so that the fibers were loosened and the tensile strength and tear strength of the non-woven fabric were lowered. Further, since the polyphenylene sulfide composite fiber obtained in Comparative Example 2 has a large average fiber length, a large amount of uneven basis weight occurs due to excessive entanglement of the fibers during the non-woven fabric processing, and the number of wrinkles of the obtained dry web is large. became. As described above, both of them are not suitable as fibers constituting the non-woven fabric.

The polyphenylene sulfide composite fiber of the present invention is a polyphenylene sulfide composite fiber that not only has excellent heat resistance and chemical resistance, but also has a small fiber diameter, high adhesiveness and mechanical strength, and excellent dimensional stability. By using the polyphenylene sulfide composite fiber of the present invention in the form of a non-woven fabric, it becomes a non-woven fabric having less dry wrinkles and good mechanical properties, and is suitably used for paper applications such as electrically insulating paper, battery separator applications and various diaphragm applications. Be done.

Claims (6)

Polyphenylene sulfide consisting of 97 mol% or more of repeating units consisting of p-phenylene sulfide units is used as component A, and 60 to 97 mol% of repeating units are composed of p-phenylene sulfide units, and 3 to 40 mol% is m-phenylene sulfide units. A core-sheath composite fiber having a copolymer polyphenylene sulfide composed of a component B as a component B, a component A as a core portion, and a component B as a sheath portion, and a polyphenylene sulfide composite having an average fiber length of 1 to 100 mm. fiber. The polyphenylene sulfide composite fiber according to claim 1, wherein the area ratio of the core portion is 75 to 95% in the cross section of the polyphenylene sulfide composite fiber. The polyphenylene sulfide composite fiber according to any one of claims 1 to 2, wherein the birefringence is 0.18 to 0.40. The polyphenylene sulfide composite fiber according to any one of claims 1 to 3, wherein the average fiber diameter is 25 μm or less, the strength is 2.0 cN / dtex or more, and the elongation is 50% or less. The method for producing a polyphenylene sulfide composite fiber according to any one of claims 1 to 4, wherein the melt mass flow rate MFR (A) of the component A used as a raw material is 50 to 250 g / 10 minutes, and the component B is used. A method for producing a polyphenylene sulfide composite fiber, which comprises a melt mass flow rate MFR (B) larger than that of MFR (A). A non-woven fabric containing the polyphenylene sulfide composite fiber according to any one of claims 1 to 4.