JP2021001418A - Polyphenylene sulfide fiber-containing wet non-woven fabric - Google Patents

Abstract

To provide a PPS fiber-containing wet non-woven fabric which hardly causes paper breakage when be produced by a wet papermaking method, is excellent in a dimension maintenance rate when be heated to 250°C, and improves hydrophilicity.SOLUTION: A polyphenylene sulfide fiber-containing wet non-woven fabric is composed of a polyphenylene sulfide fiber and a fibrillated aramid fiber, contains a polyphenylene sulfide fiber having a modified cross-section as the polyphenylene sulfide fiber, has a multilayer structure, in which at least one layer of the multilayer structure is a layer containing a fibrillated aramid fiber, and has a content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber of 3 mass% or more and 80 mass% or less with respect to the total fiber amount of the layer and a content of the polyphenylene sulfide fiber having the modified cross-section in each of the layers of more than 5 mass% with respect to the total fiber amount in each of the layers.SELECTED DRAWING: None

Description

The present invention relates to a wet nonwoven fabric containing polyphenylene sulfide fibers.

Polyphenylene sulfide (PPS) fiber is a high-performance fiber with excellent heat resistance, chemical resistance, hydrolysis resistance, dimensional stability during moisture absorption, insulation, flame retardancy, and heat retention, so its applications are expanding. doing. For example, filters used for collecting high-temperature gas, cam baths for dryers used in the drying process of industrial products, roll wipes for office copiers, insulating materials for electrical and electronic equipment, molding materials, cushioning materials (cushioning materials). , Thermal insulation cloth, battery separator, etc.

As a heat-resistant non-woven fabric made of PPS fiber, a heat-resistant wet non-woven fabric produced by a wet papermaking method is known. For example, heat-resistant wet non-woven fabrics in which PPS-stretched fibers and PPS-unstretched fibers are used in combination are known (see, for example, Patent Documents 1 to 3). When a wet non-woven fabric is produced by a wet papermaking method, there are a wet press section for squeezing water from a wet paper produced by a papermaking net, a step of transporting the wet paper to a dryer, and the like. The heat-resistant wet non-woven fabric containing the PPS-stretched fiber and the PPS-unstretched fiber has a problem that paper breakage is likely to occur in the wet press portion and the transport process. Further, it is known that by lowering the dry heat shrinkage rate of PPS fibers, a non-woven fabric having high thermal dimensional stability can be obtained even with a low basis weight (see, for example, Patent Document 4). In this case, there is a problem that the specific tensile strength of the wet paper and the non-woven fabric cannot be sufficiently secured. A composite non-woven fabric with aramid fibers is known for the purpose of imparting functions such as thermal dimensional stability to a non-woven fabric produced by a wet papermaking method (see, for example, Patent Document 5). However, Patent Document 5 does not mention the shape of the PPS fiber, and the thermal dimensional stability is also examined only up to 180 ° C., and the thermal dimensional stability at a higher temperature, for example, a temperature exceeding 250 ° C. Has not been considered. Further, it is known that a non-woven fabric composed of PPS fibers has low hydrophilicity, so that, for example, the retention of an alkaline aqueous solution which is an electrolytic solution of an alkaline battery is low, and for the purpose of improving hydrophilicity, for example, It is common to perform plasma treatment or the like (see, for example, Patent Document 6). In this case, there is a problem that the fiber is deteriorated during the plasma treatment and the strength of the PPS non-woven fabric is lowered.

Japanese Unexamined Patent Publication No. 1-272899 Japanese Unexamined Patent Publication No. 2010-24574 Japanese Unexamined Patent Publication No. 2011-106043 Japanese Unexamined Patent Publication No. 2004-285536 JP-A-2009-30187 JP-A-10-64502

An object of the present invention is to provide a PPS fiber-containing wet nonwoven fabric in which paper breakage is unlikely to occur during production by the wet papermaking method, thermal dimensional stability at a temperature exceeding 200 ° C. is excellent, and hydrophilicity is improved. ..

The above problem can be solved by the following invention.

(1) It is composed of polyphenylene sulfide fiber and fibrillated aramid fiber, contains polyphenylene sulfide fiber having an irregular cross section as polyphenylene sulfide fiber, has a multilayer structure, and at least one layer of the multilayer structure is a layer containing fibrillated aramid fiber. , The content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and the polyphenylene sulfide fiber having an irregular cross section of each layer A polyphenylene sulfide fiber-containing wet non-woven fabric having a content of more than 5% by mass based on the total fiber content of each layer.
(2) The difference (AB) between the content A in the layer having the maximum content of the fibrillated aramid fiber and the content B in the layer having the minimum content of the fibrillated aramid fiber is 70% by mass or less. A wet non-woven fabric containing a polyphenylene sulfide fiber according to the above (1).
(3) The polyphenylene sulfide fiber-containing wet non-woven fabric according to (1) or (2) above, which has a basis weight of 16 g / m ² or more and 200 g / m ² or less.

According to the present invention, it is possible to provide a PPS fiber-containing wet nonwoven fabric in which paper breakage is unlikely to occur during production by the wet papermaking method, thermal dimensional stability at a temperature exceeding 200 ° C. is excellent, and hydrophilicity is improved. ..

The PPS fiber-containing wet non-woven fabric of the present invention comprises polyphenylene sulfide fibers and fibrillated aramid fibers, contains polyphenylene sulfide fibers having an irregular cross section as polyphenylene sulfide fibers, has a multilayer structure, and at least one layer of the multilayer structure is fibrillated aramid It is a fiber-containing layer, and the content of fibrillated aramid fibers in the layer containing fibrillated aramid fibers is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and is a variant of each layer. The content of the polyphenylene sulfide fiber having a cross section is more than 5% by mass with respect to the total fiber amount of each layer. The PPS fiber-containing wet nonwoven fabric of the present invention preferably contains PPS drawn fibers as the main fiber and PPS undrawn fibers as the binder fiber. Most of the PPS undrawn fibers have a non-crystalline structure and can be melted by applying heat to act as a binder. The PPS drawn fiber is stretched in the fiber manufacturing process, so that the short fiber strength of the fiber is strong and the dimensional stability is excellent. In the present invention, when the PPS stretched fiber and the PPS unstretched fiber are used in combination, it becomes easy to provide a non-woven fabric having excellent heat resistance.

The polyphenylene sulfide (Polyphenylenesulfide) fibers, as a polymer structural unit _- a synthetic fiber made of a polymer whose main structural unit (PPS _{polymer) - (C 6 H 4 -S} ). Representative examples of PPS polymers include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, and the like. Moreover, these random copolymers, block copolymers and the like can also be mentioned. Further, a mixture of the above-mentioned polymers can be mentioned. Particularly preferred PPS polymers, as the main structural units of the _{polymer, - (C 6 H 4 -S} ) - a represented by p- phenylene units, and the like, preferably a PPS polymer containing more than 90 wt%.

In the PPS fiber having a deformed cross section, the deformed cross section means that the cross section shape when cut perpendicularly to the length direction of the fiber is other than the circular cross section shape and the elliptical cross section shape, and has a triangular shape, a Y shape, and a flat shape. , Dogbone shape, trefoil shape, etc. For example, these can be obtained by a method of directly spinning using a deformed mold, a method of melting or dividing a composite fiber, etc., but PPS fibers having a deformed cross section obtained by directly spinning using a deformed mold can be used. It is preferably used in the present invention. The cross-sectional shape is not particularly limited, but from the viewpoint of improving strength, PPS fibers having a Y-shaped or trefoil-shaped cross-sectional shape are more preferable. The Y-shaped or trefoil shape has a larger specific surface area than the circular cross-sectional shape, increases the bonding points between fibers, and not only improves the wet paper strength and the base paper strength after the papermaking process, but also the non-woven fabric during thermal calendar processing. Since it is deformed and adhered so as to enter the internal space, it can contribute to improving the strength of the non-woven fabric.

The fibrillated aramid fiber is a refiner, beater, mill, grinder, a rotary homogenizer that applies shearing force by a high-speed rotary blade, a cylindrical inner blade that rotates at high speed, and a fixed outer blade. A double-cylindrical high-speed homogenizer that generates shear force between the fibers, an ultrasonic crusher that is refined by the impact of ultrasonic waves, and a high-speed fiber suspension that is passed through a small-diameter orifice with a pressure difference of at least 20 MPa. It is obtained by treating the fiber with a high-pressure homogenizer or the like, which applies a shearing force and a cutting force to the fiber by colliding the fiber and rapidly decelerating the fiber.

The fibrillated fiber refers to a fiber that is not in the form of a film but mainly has a portion that is very finely divided in a direction parallel to the fiber axis, and at least a part thereof has a fiber diameter of 1 μm or less. Fibrilized As for the degree of fibrillation in the aramid fiber, the modified drainage degree is preferably 500 ml or less, and more preferably 100 ml or more and 450 ml or less. When the modified drainage degree exceeds 500 ml, the fiber diameter distribution becomes wide, and the PPS fiber-containing wet non-woven fabric may have formation spots or thickness spots. Further, the length-weighted average fiber length of the fibrillated aramid fiber is preferably 0.2 mm or more and 2.0 mm or less. If the length-weighted average fiber length is less than 0.2 mm, it may fall off from the PPS fiber-containing wet non-woven fabric or the PPS fiber-containing wet non-woven fabric may fluff. If the length-weighted average fiber length is longer than 2.0 mm, lumps may occur. May become.

The modified water drainage degree in the present invention is defined as JIS P 811-2: 2012 except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and a mesh size of 0.18 mm is used as a sieving plate and the sample concentration is 0.1%. It is a value measured in accordance with it. The length-weighted average fiber length is a length-weighted average fiber length measured in a projected fiber length (Proj) mode using KajaniFiberLab V3.5 (manufactured by Metso Automation).

Wet non-woven fabric made of only PPS fibers has extremely low water retention in the wet paper state when it is made into a sheet by the wet paper making method, so paper breakage in the process of transporting it to the wet press part of the paper machine or the dryer There was a problem that it was easy to occur. The multi-layered PPS fiber-containing wet nonwoven fabric of the present invention contains PPS fibers having a modified cross section and fibrillated aramid fibers, so that an effect that paper breakage is unlikely to occur when manufactured by the wet papermaking method can be obtained. More specifically, the inclusion of PPS fibers and fibrillated aramid fibers with atypical cross sections improves the specific surface area of the fibers and increases the number of adhesion points between the fibers to increase the strength of wet paper, which makes it possible to use a paper machine. Fiber peeling and paper breakage in the wet press portion are less likely to occur, and the water retention of the wet paper is increased, so that the paper can be smoothly transported to the dryer and paper breakage can be suppressed. Further, the strength of the base paper after drying by the dryer is improved, and the post-processability is also excellent.

In the present invention, at least one layer of the multilayer structure is a layer containing fibrillated aramid fibers.

In the present invention, in the layer containing the fibrillated aramid fiber, the content of the PPS fiber having a modified cross section is more than 5% by mass and more preferably 10% by mass or more with respect to the total fiber of the layer. , 30% by mass or more is more preferable. Further, it is preferably 97% by mass or less, more preferably 95% by mass or less, and further preferably 70% by mass or less. When the content of PPS fibers having a modified cross section is 5% by mass or less, the strength of the base paper after drying and the strength of the non-woven fabric after heat calendering are not sufficiently improved. Further, when the content of the PPS fiber having a modified cross section is more than 97% by mass, the strength of the wet paper is not sufficiently improved, and there is a possibility that paper breakage is likely to occur.

In the present invention, in the layer containing no fibrillated aramid fiber, the content of the PPS fiber having a modified cross section is more than 5% by mass and 10% by mass or more with respect to the total fiber of the layer. It is preferably 30% by mass or more, and more preferably 30% by mass or more. When the content of PPS fibers having a modified cross section is 5% by mass or less, the strength of the base paper is not sufficiently improved. The upper limit of the content of the PPS fiber having a modified cross section in the layer containing no fibrillated aramid fiber is preferably 100% by mass.

In the multi-layered PPS fiber-containing wet non-woven fabric of the present invention, the content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber of the layer. It is preferably 5% by mass or more and 70% by mass or less, and further preferably 10% by mass or more and 40% by mass or less. When the content of the fibrillated aramid fiber is less than 3% by mass, the wet paper strength is not sufficiently improved and paper breakage is likely to occur. In addition, when the content of the fibrillated aramid fiber is less than 3% by mass, the hydrophilicity becomes low. Further, when the content of the fibrillated aramid fiber is more than 80% by mass, the hydrophilicity is high, but the strength of the base paper after drying by a dryer is not sufficiently improved, and the post-processability is deteriorated.

In the PPS fiber-containing wet non-woven fabric having a multilayer structure of the present invention, the content of PPS undrawn fibers in each layer is preferably 20% by mass or more and 90% by mass or less, more preferably, with respect to the total amount of fibers in each layer. Is 40% by mass or more and 80% by mass or less. If the content of the PPS undrawn fibers is less than 20% by mass, the binder effect for adhering the fibers to each other is insufficient, and sufficient tensile strength may not be obtained as a non-woven fabric. Further, if the content of the undrawn PPS fiber is more than 90% by mass, the shrinkage in the width direction becomes large during the thermal calendering process, which may deteriorate the profile.

Considering the production efficiency in the wet papermaking method, the diameter of the PPS fiber is preferably 0.1 to 30 μm, more preferably 1.0 to 25 μm, and further preferably 2 to 20 μm. If the diameter of the PPS fiber is less than 0.1 μm, it may fall off from the paper making net of the wet paper machine. On the other hand, when the diameter of the PPS fibers exceeds 30 μm, the degree of entanglement between the fibers in the slurry becomes insufficient, the effect of suppressing paper breakage in the wet papermaking process is not sufficient, and the contact points between the fibers are reduced. It may be difficult to maintain the strength. Further, when the fibrillated aramid fiber is not contained, the strength of the wet paper is not sufficiently improved, and the paper breakage is likely to occur. The diameter of the PPS fiber is determined by cutting a wet non-woven fabric containing PPS fiber with a sharp cutting tool, observing the cross section with a scanning electron microscope (SEM) of 2000 times, and randomly extracting 100 fibers in each area. It is an average value calculated from the diameter of a perfect circle.

The fiber length of the PPS fiber used in the PPS fiber-containing wet nonwoven fabric having a multilayer structure of the present invention is preferably 1 to 20 mm, more preferably 2 to 15 mm, and further preferably 3 to 10 mm. If it is less than 1 mm, it may come off from the papermaking net during wet papermaking, and sufficient strength may not be obtained. On the other hand, if it exceeds 20 mm, entanglement or the like may occur when it is dispersed in water, and a uniform texture may not be obtained.

In the present invention, a multi-layered PPS fiber-containing wet nonwoven fabric is produced by a wet papermaking method. First, the fibers are uniformly dispersed in water, and then a slurry is prepared through steps such as a screen (removal of foreign substances, lumps, etc.). The final fiber concentration of the slurry is preferably 0.01 to 0.50% by mass. The slurry is made with a paper machine to obtain wet paper. In the process, chemicals such as dispersants, defoamers, hydrophilic agents, antistatic agents, polymer viscous agents, mold release agents, antibacterial agents, and bactericidal agents may be added.

As the paper machine, for example, a paper machine that uses a paper machine such as a long net, a circular net, or an inclined wire alone, or a combination paper machine in which two or more paper machines of the same model or different types are installed online is used. be able to. In addition, when the non-woven fabric has a multi-layer structure of two or more layers, a laminating method in which wet papers made by each paper machine are laminated, or after forming one layer, fibers are dispersed on the layer. A non-woven fabric can be produced by a casting method or the like in which a slurry is cast and laminated. When the slurry in which the fibers are dispersed is cast, the previously formed layer may be in a wet paper state or a dry state. Further, two or more dried layers can be heat-sealed to form a multilayer structure non-woven fabric.

In the wet papermaking method, wet paper produced by a papermaking net and squeezed by a wet press section is dried by a dryer such as a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, or an infrared dryer. , Wet non-woven fabric base paper can be obtained. When the wet paper is dried, it is brought into close contact with a heat roll such as a Yankee dryer and heat-pressure dried, so that the smoothness of the adhered surface is improved. Hot-pressure drying refers to drying by pressing wet paper against the hot roll with a touch roll or the like. The surface temperature of the heat roll is preferably 100 to 180 ° C, more preferably 120 to 160 ° C. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

The multi-layered PPS fiber-containing wet nonwoven fabric of the present invention is preferably subjected to thermal calendering as a post-processing after papermaking. As a calendar unit used for thermal calendar processing of a wet non-woven fabric containing PPS fiber, a calendar unit having a combination of rolls such as metal roll-metal roll, metal roll-elastic roll, metal roll-cotton roll, metal roll-silicon roll, etc. Can be mentioned. These calendar units can be used alone or in combination of two or more.

During the thermal calendar treatment, the surface temperature of the metal roll is preferably 100 to 260 ° C, more preferably 150 to 250 ° C. If the temperature of the metal roll is lower than 100 ° C., the melting of the undrawn PPS fibers does not proceed, and the binding between the fibers may not proceed. Further, if the temperature of the metal roll is higher than 260 ° C., the fibers constituting the wet non-woven fabric containing PPS fibers may stick to the metal roll and impair the uniformity of the surface of the non-woven fabric.

The nip pressure of the nip during the thermal calendar processing is preferably 190 to 1800 N / cm, more preferably 390 to 1500 N / cm. The processing speed is preferably 5 to 150 m / min, more preferably 10 to 80 m / min.

The PPS fiber-containing wet nonwoven fabric having a multi-layer structure of the present invention may have a multi-layer structure in which the fiber composition of each layer is the same, or may have a multi-layer structure in which the fiber composition of each layer is different. In the case of a multi-layer structure as compared with a single-layer structure, the basis weight of each layer is lowered, so that the fiber concentration of the slurry can be lowered, so that the texture of the base paper is improved, and as a result, the texture of the base paper is uniform. Is improved. Further, even if the formation of each layer is uneven, it can be compensated by laminating. Further, the papermaking speed can be increased, and the effect of improving the operability can be obtained.

The PPS fiber-containing wet nonwoven fabric of the present invention may have a multi-layer structure in which the content of the fibrillated aramid fibers in each layer is the same, and the multi-layer structure in which the content of the fibrillated aramid fibers in each layer is different. Is also good. In each layer of the PPS fiber-containing wet nonwoven fabric having a multi-layer structure, the content A in the layer having the maximum content of the fibrillated aramid fiber (maximum content layer) and the layer having the minimum content of the fibrillated aramid fiber (minimum content). The difference (AB) from the content B in the (quantity layer) is preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. When the difference (AB) is 70% by mass or less, the productivity in producing the wet non-woven fabric base paper is improved, and the base paper strength after drying by the dryer is sufficiently improved, and the post-workability is improved. It tends to improve.

The PPS fiber-containing wet nonwoven fabric of the present invention may have a multilayer structure in which the basis weights of the layers are the same, or may have a multilayer structure in which the basis weights of the layers are different. When the basis weight is different on the front and back sides of the base paper, paper breakage in the wet papermaking process is less likely to occur.

Basis weight of the PPS fiber-containing wet-laid nonwoven fabric of the present invention, JIS P 8124: conforms to 2011 measured is preferably 16~200g / ^{m 2,} more preferably from 20 to 150 g / ^{m 2.} When the basis weight is 16 to 200 g / m ² , the productivity in producing the wet nonwoven fabric base paper tends to be improved, and the uniformity of the wet nonwoven fabric containing PPS fibers tends to be improved. Further, during the heat calender treatment, which is a post-processing, it becomes easy to uniformly apply heat to the wet non-woven fabric containing PPS fibers.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the present examples. Unless otherwise specified, all parts and percentages in the examples are based on mass.

<PPS fiber 1>
A PPS stretched fiber having a trefoil-shaped cross section, a fineness of 1.3 decitex, a diameter of 11 μm, and a fiber length of 5 mm was designated as “PPS fiber 1”.

<PPS fiber 2>
A PPS-drawn fiber having an elliptical cross-sectional shape, a fineness of 0.2 decitex, a diameter of 4 μm, and a fiber length of 5 mm was designated as “PPS fiber 2”.

<PPS fiber 3>
A PPS drawn fiber having a circular cross-sectional shape, a fineness of 1.1 decitex, a diameter of 10 μm, and a fiber length of 5 mm was designated as “PPS fiber 3”.

<PPS fiber 4>
The PPS undrawn fiber having a trefoil-shaped cross section, a fineness of 2.6 decitex, a diameter of 16 μm, and a fiber length of 5 mm was designated as “PPS fiber 4”.

<PPS fiber 5>
An undrawn PPS fiber having a circular cross-sectional shape, a fineness of 1.7 decitex, a diameter of 13 μm, and a fiber length of 5 mm was designated as “PPS fiber 5”.

<Aramid fiber>
The aramid fiber was beaten with a refiner, and the fibrillated aramid fiber having a modified drainage degree of 350 ml was designated as "aramid fiber".

<Examples 1 to 21, Comparative Examples 1 to 4>
With the fiber formulation shown in Table 1, the fibers were dispersed in water at a dispersion concentration of 0.2% for 10 minutes, and a second layer of wet paper was formed with a tilted wire using a tilted / circular net composite paper machine. After forming the first layer of wet paper on the circular net, it was hot-pressure dried with a Yankee dryer having a surface temperature of 150 ° C. to obtain a wet non-woven fabric base paper having the target texture shown in Table 1.

(Thermal calendar processing)
The wet non-woven fabric base paper is subjected to thermal calendar treatment twice by a metal roll-elastic roll calendar unit so that the metal rolls come into contact with each other and are niped at a metal roll temperature of 230 ° C. and a processing speed of 10 m / min. A wet non-woven fabric containing the mixture was obtained.

In Examples and Comparative Examples, the basis weight and thickness were measured, and the productivity, heating dimension retention rate and water contact angle were evaluated, and the results are shown in Table 2.

(Metsuke)
In accordance with JIS P 8124: 2011, a wet non-woven fabric containing PPS fiber was cut into 100 mm × 100 mm to make a test piece, and the average value of each value measured by 20 sheets using an electronic analysis balance (manufactured by Shimadzu Corporation) was calculated. And said.

(thickness)
In accordance with JIS P 8118: 2014, the average value of each value measured on 20 sheets was taken as the thickness using a micrometer (manufactured by Mitutoyo Co., Ltd.) one by one from the test pieces collected at the time of basis weight measurement.

(Productivity)
The productivity in producing the wet non-woven fabric base paper was evaluated by the following indexes.

"5": The runnability of the wet paper and the wet non-woven fabric base paper in each part of the paper machine was stable, and no paper break occurred.
"4": The runnability of the wet paper and the wet non-woven fabric base paper in each part of the paper machine is stable. No paper breaks occur, but slight fiber peeling is seen.
"3": The runnability of the wet paper and the wet non-woven fabric base paper in each part of the paper machine is stable. Paper breaks do not occur, but fiber peeling is more than "4".
"2": The strength of the wet paper in the press part is weak, but it can be manufactured if it is slower than "3". Occasionally, paper breaks may occur at the dryer outlet.
"1": The strength of the wet paper in the press part is weak, and the paper breaks frequently.

(Heating dimension maintenance rate)
According to JIS K 7212: 1999, a wet non-woven fabric containing PPS fiber was cut into a size of 100 mm × 100 mm from the center and both ends of the roll to obtain a test piece. After measuring the vertical (L1) and horizontal (T1) dimensions of the test piece under the conditions of 23 ° C. and 50% relative humidity, one end of the test piece is sandwiched between metal clips in an oven set at 250 ° C. , Suspended on the test piece mounting frame and heated for 2 hours. After the heating is completed, the test piece is cooled to the temperature and humidity conditions before heating, the dimensions in the vertical direction (L2) and the horizontal direction (T2) are measured, and the vertical direction (ΔL) and the horizontal direction (ΔT) are measured from the following equations. The dimension maintenance rate was calculated, and the average value was taken as the heating dimension maintenance rate. The higher the heating dimension retention rate, the better the thermal dimension stability.

Vertical dimension retention rate ΔL = (L2 / L1) × 100

Lateral dimension retention rate ΔT = (T2 / T1) × 100

(Water contact angle)
4 μL of ion-exchanged water having a conductivity of 1 μS / cm or less was dropped as a test solution on the front and back surfaces of the PPS fiber-containing wet non-woven fabric in an environment of a temperature of 23 ° C. and a humidity of 50% RH, and dynamically 3 seconds after the dropping. The contact angle (degrees) was measured. The contact angle was measured by using a contact angle meter PG-X + manufactured by FIBRO System AB, and measuring 5 points in the width direction of the wet non-woven fabric containing PPS fiber, and calculating the average value thereof.

By comparing Examples 1 to 21 with Comparative Example 1, it is composed of PPS fibers and fibrillated aramid fibers, contains PPS fibers having an irregular cross section as PPS fibers, has a multi-layer structure, and at least one layer of the multi-layer structure is fibrils. The layer containing the fibrillated aramid fiber, and the content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and each layer. The PPS fiber-containing wet non-woven fabrics of Examples 1 to 21 in which the content of PPS fibers having the irregular cross section of the above is more than 5% by mass with respect to the total fiber amount of each layer are composed of PPS fibers and fibrillated aramid fibers, and are multilayered. Although it has a structure, it can be seen that the productivity and the heat dimension retention rate are excellent as compared with the PPS fiber-containing wet non-woven fabric of Comparative Example 1 which does not contain PPS fiber having an irregular cross section as PPS fiber.

By comparing Examples 1 to 21 with Comparative Example 2, it is composed of PPS fibers and fibrillated aramid fibers, contains PPS fibers having an irregular cross section as PPS fibers, has a multi-layer structure, and at least one layer of the multi-layer structure is fibrils. The layer containing the fibrillated aramid fiber, and the content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and each layer. The PPS fiber-containing wet non-woven fabrics of Examples 1 to 21 in which the content of the PPS fiber having the irregular cross section of the above is more than 5% by mass with respect to the total fiber amount of each layer are made of PPS fiber and have a multi-layer structure. It can be seen that the productivity, heating dimension retention rate and hydrophilicity are superior to those of the PPS fiber-containing wet non-woven fabric of Comparative Example 2 which does not contain fibrillated aramid fibers and contains PPS fibers having an irregular cross section as PPS fibers.

From the comparison between Example 21 and Comparative Example 3, it is composed of PPS fibers and fibrillated aramid fibers, contains PPS fibers having an irregular cross section as PPS fibers, has a multi-layer structure, and at least one layer of the multi-layer structure contains fibrillated aramid fibers. The content of the fibrillated aramid fiber in the layer containing the fibrillated aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and the atypical cross section of each layer is obtained. The PPS fiber-containing wet non-woven fabric of Example 21 having a PPS fiber content of more than 5% by mass with respect to the total fiber content of each layer has a PPS fiber-containing wet fabric of Comparative Example 3 which does not contain PPS fibers having an irregular cross section. It can be seen that the productivity, the heat dimension retention rate, and the hydrophilicity are superior to those of the non-woven fabric.

From the comparison between Examples 1 to 21 and Comparative Example 4, it is composed of PPS fibers and fibrillated aramid fibers, contains PPS fibers having an irregular cross section as PPS fibers, has a multilayer structure, and at least one layer of the multilayer structure is fibrillated aramid. It is a fiber-containing layer, and the content of fibrillated aramid fibers in the layer containing fibrillated aramid fibers is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and is a variant of each layer. The PPS fiber-containing wet non-woven fabrics of Examples 1 to 21 in which the content of PPS fibers having a cross section is more than 5% by mass with respect to the total fiber content of each layer have a content of PPS fibers having a modified cross section of each layer. It can be seen that the productivity, the heat dimension retention rate, and the hydrophilicity are superior to those of the PPS fiber-containing wet non-woven fabric of Comparative Example 4, which is 5% by mass or less based on the total fiber amount of each layer.

From the comparison between Example 15 and Example 16, the PPS fiber-containing wet non-woven fabric of Example 15 having a difference (AB) of 70% by mass has a difference (AB) of 75% by mass. It can be seen that the productivity is superior to that of the wet non-woven fabric containing PPS fiber.

Comparison of Comparative and Example 5 and Example 19 with Example 2 and Example 18, PPS fiber-containing wet of Example 5 having a basis weight is Example 2 and the basis weight is 16g / ^{m 2} is 200 g / ^{m 2} nonwoven fabric, basis weight than in example 18 and example 19 basis weight is 250 g / ^{m 2} is 12 g / ^{m 2,} the productivity is seen to be excellent.

The multi-layered PPS fiber-containing wet non-woven fabric of the present invention includes a filter used for collecting high-temperature gas, a cambus for a dryer used in a drying process of an industrial product, a roll wiper for an office copy machine, and an insulation for electrical equipment and electronic equipment. It can be used as a material, a molding material, a cushioning material (cushion material), a heat insulating cloth, a separator for a battery, and the like.

Claims (3)

It is composed of polyphenylene sulfide fibers and fibrillated aramid fibers, contains polyphenylene sulfide fibers having an irregular cross section as polyphenylene sulfide fibers, has a multi-layer structure, and at least one layer of the multi-layer structure is a layer containing fibrillated aramid fibers and is fibrillated. The content of the fibrillated aramid fiber in the layer containing the aramid fiber is 3% by mass or more and 80% by mass or less with respect to the total fiber amount of the layer, and the content of the polyphenylene sulfide fiber having an irregular cross section of each layer is , A wet non-woven fabric containing polyphenylene sulfide fibers, which is more than 5% by mass based on the total amount of fibers in each layer. Claim that the difference (AB) between the content A in the layer having the maximum content of the fibrillated aramid fiber and the content B in the layer having the minimum content of the fibrillated aramid fiber is 70% by mass or less. The polyphenylene sulfide fiber-containing wet non-woven fabric according to 1. The polyphenylene sulfide fiber-containing wet non-woven fabric according to claim 1 or 2, which has a basis weight of 16 g / m ² or more and 200 g / m ² or less.