JP2020066818A - Wet type nonwoven fabric including polyphenylene sulfide fiber - Google Patents

Abstract

To provide a wet type nonwoven fabric including a polyphenylene sulfide fiber which hardly causes broken paper when produced by wet type papermaking method and has excellent chemical resistance.SOLUTION: The wet type nonwoven fabric including a PPS fiber is characterized by consisting of only a polyphenylene sulfide fiber, including a polyphenylene sulfide fiber having a variant cross section and a polyphenylene sulfide fiber having a circular cross section with a diameter of the fiber of 5 μm or under, and having a basis weight of 8 g/mor more and 200 g/mor under, wherein the content of the polyphenylene sulfide fiber having a circular cross section with a diameter of the fiber being 5 μm or under is 5 mass% or more and 70 mass% or under with respect to the total fiber mass.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 that has excellent heat resistance, chemical resistance, hydrolysis resistance, dimensional stability when absorbing moisture, insulation, flame retardancy, and heat retention, so its applications are expanding. is doing. For example, filters used for collecting high-temperature gas dust, canvases for dryers used in the drying process of industrial products, roll wipes for office copiers, insulating materials for electrical equipment, molding materials, cushioning materials, heat insulating cloth. Examples include applications such as battery separators.

  As a heat-resistant nonwoven fabric made of PPS fibers, a heat-resistant wet nonwoven fabric manufactured by a wet papermaking method is known. For example, heat-resistant wet non-woven fabrics using a combination of drawn PPS fibers and undrawn PPS fibers are known (see, for example, Patent Documents 1 to 3). When a wet non-woven fabric is produced by the wet paper making method, there are a wet press section for squeezing water from a wet paper produced by a paper making net, a step of conveying the wet paper to a dryer, and the like. The heat-resistant wet non-woven fabric containing the stretched PPS fiber and the unstretched PPS fiber has a problem that paper breakage is likely to occur in the wet press section and the conveying step. It is also known that by reducing the dry heat shrinkage rate of PPS fibers, a nonwoven fabric having high heat-resistant dimensional stability can be obtained even with a low basis weight. (For example, refer to Patent Document 4). In this case, there is a problem that the specific tensile strength of the wet paper and the nonwoven fabric cannot be sufficiently secured. It is known to use polyvinyl alcohol fiber or polyester fiber as the binder fiber in order to sufficiently secure the tensile strength of the wet paper and the nonwoven fabric (for example, Patent Documents 5 and 6). In this case, there is a problem that the chemical resistance is lowered.

JP-A-1-272899 JP, 2010-24574, A JP, 2011-106043, A JP, 2004-285536, A JP, 2017-218693, A JP, 2017-226928, A

  An object of the present invention is to provide a polyphenylene sulfide fiber-containing wet non-woven fabric which is less likely to cause paper breakage during production by a wet papermaking method and has excellent chemical resistance.

  The above problems can be solved by the following inventions.

(1) Polyphenylene sulfide fiber consisting only of polyphenylene sulfide fiber, containing polyphenylene sulfide fiber having an irregular cross section and polyphenylene sulfide fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less, and having a basis weight of 8 g / m ² or more and 200 g / m ² or less A wet non-woven fabric containing polyphenylene sulfide fibers.

(2) The content of the polyphenylene sulfide fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less is 5% by mass or more and 70% by mass or less based on the total fibers, and the polyphenylene sulfide fiber is contained. Wet non-woven fabric.

  According to the present invention, a polyphenylene sulfide fiber consisting of only polyphenylene sulfide fiber and having a modified cross section and a polyphenylene sulfide fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less are produced by a wet papermaking method. A polyphenylene sulfide fiber-containing wet non-woven fabric which is less likely to cause paper breakage and has excellent chemical resistance can be provided.

  The polyphenylene sulfide fiber-containing wet non-woven fabric of the present invention is characterized in that it is composed only of polyphenylene sulfide fibers, and contains PPS fibers having an atypical cross section and PPS fibers having a circular cross-section having a diameter of 5 μm or less. The PPS fiber-containing wet non-woven fabric of the present invention preferably contains PPS stretched fibers as main fibers and PPS unstretched fibers as binder fibers. Most of the undrawn PPS fibers have an amorphous structure and can be melted by applying heat to act as a binder. The stretched PPS fiber has a strong single fiber strength and is excellent in dimensional stability by being stretched in the fiber manufacturing process. In the present invention, when the stretched PPS fiber and the unstretched PPS fiber are used in combination, it becomes easy to provide a nonwoven fabric having excellent chemical resistance and heat resistance.

Polyphenylene sulfide (Polyphenylene sulfide) fiber is a synthetic fiber composed of a polymer (PPS polymer) having — (C ₆ H ₄ —S) — as a main structural unit as a polymer constitutional unit. Typical examples of the PPS polymer include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, and the like. Moreover, these random copolymers, block copolymers, etc. are also mentioned. Further, a mixture of the above polymers may 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 a PPS fiber having a modified cross section, the modified cross section has a cross section other than a circular cross section when cut perpendicular to the length direction of the fiber, such as a triangular shape, a Y shape, a flat shape, and a dockbone shape. , Having a cross section such as a trilobal shape. For example, these are obtained by a method such as direct spinning using a modified mold, a method of dissolving or splitting composite fibers, and a PPS fiber having a modified cross section obtained by directly spinning using a modified mold is obtained. It is preferably used in the present invention. The cross-sectional shape is not particularly limited, but PPS fibers having a Y-shaped or trefoil-shaped cross-sectional shape are more preferable from the viewpoint of improving strength. The Y-shaped or trefoil shape has a larger specific surface area than the circular cross-sectional shape, increases the bonding points between fibers, improves the strength of the wet paper web and the strength of the base paper after the papermaking process, as well as the inside of the nonwoven fabric during thermal calendering. Since it deforms and adheres so as to enter the space, it can contribute to improving the strength of the nonwoven fabric.

  A wet non-woven fabric made only of PPS fibers has a very low water retention in a wet paper state when formed into a sheet by a wet paper making method, so that the paper breaks in the step of conveying to a wet press section of a paper machine or a dryer. There was a problem that was likely to occur. The PPS fiber-containing wet non-woven fabric of the present invention contains the PPS fiber having an irregular cross section and the PPS fiber having a circular cross section having a diameter of 5 μm or less, so that a paper break occurs during the production by the wet papermaking method. The effect of difficulty is obtained. More specifically, by including the PPS fiber having an atypical cross section and the PPS fiber having a circular cross section having a diameter of 5 μm or less, the specific surface area of the fiber is improved and the number of bonding points between the fibers is increased. The strength of the wet paper becomes stronger, the peeling of fibers and paper breakage at the wet press section of the paper machine are less likely to occur, and the increased water retention of the wet paper allows it to be smoothly transported to the dryer. The paper break can be suppressed. Further, the strength of the base paper after drying with a dryer is improved, and the post-processability is also excellent.

  In the PPS fiber-containing wet non-woven fabric of the present invention, the content of the PPS fiber having an irregular cross section is preferably 10% by mass or more and 95% by mass or less, and more preferably 30% by mass or more and 90% by mass or less. preferable. When the content of the PPS fiber having a modified cross section is less than 10% by mass, the strength of the base paper after drying and the strength of the nonwoven fabric after thermal calendering may not be sufficiently improved. Further, when the content of the PPS fiber having the atypical cross section is more than 95% by mass, the strength of the wet paper web may not be sufficiently improved and the paper may be easily broken.

  In the PPS fiber-containing wet non-woven fabric of the present invention, the content of the PPS fiber having a circular cross-sectional shape having a diameter of 5 μm or less is preferably 5% by mass or more and 70% by mass or less, and 10% by mass or more and 40% by mass. % Or less is more preferable. When the content of the PPS fiber having a circular cross-sectional shape with a fiber diameter of 5 μm or less is less than 5% by mass, the wet paper web strength may not be sufficiently improved and paper breakage may easily occur. When the content of the PPS fiber having a circular cross-sectional shape with a fiber diameter of 5 μm or less is more than 70% by mass, the strength of the base paper after being dried by a dryer is not sufficiently improved, and the post-processability is deteriorated. There is. The diameter of the fiber having a circular cross-sectional shape was obtained by cutting the PPS fiber-containing wet non-woven fabric with a sharp blade and observing the cross-section with a scanning electron microscope (SEM) of 2000 times, each of 100 fibers randomly extracted. It is the average of the diameter measurements.

  In the PPS fiber-containing wet nonwoven fabric of the present invention, the content of PPS unstretched fibers is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 80% by mass with respect to the total fiber amount. % Or less. If the content of the unstretched PPS fibers is less than 30% by mass, the binder effect for adhering the fibers to each other may be insufficient, and sufficient tensile strength as a nonwoven fabric may not be obtained. Further, when the content of the unstretched PPS fiber is more than 90% by mass, shrinkage in the width direction becomes large during thermal calendering, 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. When the diameter of the 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, if the fiber diameter exceeds 30 μm, the degree of entanglement of the fibers in the slurry becomes insufficient, the effect of suppressing paper breakage in the wet papermaking process is not sufficient, and the number of contacts between fibers becomes too small. Therefore, it may be difficult to maintain the strength. Further, when the PPS fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less is not contained, the strength of the wet paper is not sufficiently improved, and the paper break easily occurs. The diameter of the PPS fiber having an atypical cross section was obtained by cutting the PPS fiber-containing wet non-woven fabric with a sharp blade and observing the cross section with a SEM of 2000 times, and measuring the area from 100 randomly extracted fibers. It is the average value calculated as the diameter of the circle.

  The fiber length of the fibers used in the PPS fiber-containing wet non-woven fabric 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 fall off from the paper making net during wet paper making, and sufficient strength may not be obtained. On the other hand, when it exceeds 20 mm, entanglement may occur when dispersed in water, and uniform formation may not be obtained.

  In the present invention, a PPS fiber-containing wet non-woven fabric is produced by a wet papermaking method. First, the fibers are uniformly dispersed in water, and then a slurry is prepared through a process such as a screen (removes foreign matters and lumps). 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 a wet paper. In the process, chemicals such as a dispersant, a defoaming agent, a hydrophilic agent, an antistatic agent, a polymeric viscous agent, a release agent, an antibacterial agent and a bactericide may be added.

  As the paper machine, for example, a paper machine using a paper net such as a Fourdrinier, a cylinder, a slanted wire, or a combination paper machine in which two or more paper nets of the same type or different types are installed online is used. be able to. When the non-woven fabric has a multi-layered structure of two or more layers, a papermaking method in which wet papers made by each paper machine are laminated, or after one layer is formed, fibers are dispersed on the layer The nonwoven fabric can be manufactured by a casting method or the like in which the prepared slurry is cast to form a laminate. When casting the slurry in which the fibers are dispersed, the layer previously formed may be in a wet paper state or in a dry state. Alternatively, two or more dry layers may be heat-sealed to form a multilayer nonwoven fabric.

  In the wet papermaking method, the wet paper produced by the paper making net and squeezed by the wet press section is dried by a dryer such as a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, etc. A wet non-woven base paper is obtained. When the wet paper web is dried, it is brought into close contact with a hot roll such as a Yankee dryer and dried under heat and pressure, whereby the smoothness of the adhered surface is improved. Hot-pressure drying refers to pressing a wet paper web against a hot roll with a touch roll or the like to dry it. 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 PPS fiber-containing wet non-woven fabric of the present invention is preferably subjected to thermal calendering. As the calender unit used for the thermal calendering of the PPS fiber-containing wet nonwoven fabric, a calender unit having a combination of rolls such as metal roll-metal roll, metal roll-elastic roll, metal roll-cotton roll, and metal roll-silicon roll is used. Can be mentioned. These calendar units can be used alone or in combination of two or more kinds.

  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 unstretched PPS fiber may not be melted, and the fiber-fiber bond may not proceed. When the temperature of the metal roll is higher than 260 ° C., the fibers constituting the PPS fiber-containing wet type nonwoven fabric may stick to the metal roll and impair the uniformity of the nonwoven fabric surface.

  The nip pressure of the nip during the heat calender treatment 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.

  In the present invention, when the PPS fiber-containing wet non-woven fabric has a multi-layered structure, it may have a multi-layered structure in which the fiber composition of each layer is the same or may have a multi-layered structure in which the fiber composition of each layer is different. In the case of a multi-layer structure, the fiber density of the slurry can be lowered by lowering the basis weight of each layer, so that the formation of the PPS fiber-containing wet non-woven fabric is improved and, as a result, the formation of the PPS fiber-containing wet non-woven fabric is uniform. The property is improved. Further, even when the formation of each layer is not uniform, it can be compensated by stacking. In addition, the papermaking speed can be increased, and the operability can be improved.

Basis weight of the PPS fiber-containing wet-laid nonwoven fabric of the present invention, JIS P 8124: measured in accordance with 2011 are 8~200g / ^{m 2,} more preferably from 12~150g / ^{m 2.} If the basis weight is less than 8 g / m ² , the uniformity and tensile strength of the PPS fiber-containing wet nonwoven fabric will be insufficient. If the basis weight exceeds 200 g / m ² , it becomes difficult to uniformly apply heat to the PPS fiber-containing wet non-woven fabric during the heat calender treatment.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples. All parts and percentages in the examples are by mass unless otherwise specified.

<PPS fiber 1>
The PPS drawn fiber having a modified cross-section with a three-leaf 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>
PPS fiber 2 having a circular cross section, a fineness of 1.1 decitex, a diameter of 10 μm, and a fiber length of 5 mm was designated as PPS fiber 2.

<PPS fiber 3>
PPS unstretched fiber having a modified cross section with a three-leaf 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 3.

<PPS fiber 4>
PPS unstretched fiber having a circular cross-section, a fineness of 1.7 decitex, a diameter of 13 μm, and a fiber length of 5 mm was designated as PPS fiber 4.

<Thin diameter PPS fiber>
A PPS drawn fiber having a circular cross section, a fineness of 0.2 decitex, a diameter of 4 μm and a fiber length of 3 mm was used as a small diameter PPS fiber.

<PVA fiber>
Polyvinyl alcohol fiber having a fineness of 1.1 decitex and a fiber length of 3 mm was used as PVA fiber.

<PET fiber>
The core is polyethylene terephthalate (melting point: 260 ° C), and the sheath is an amorphous copolyester (polyethylene terephthalate containing isophthalic acid as a copolymerization component) (glass transition point: 72 ° C) with a fineness of 1.1 decitex. A polyester core-sheath fiber having a fiber length of 5 mm was used as PET fiber.

<Examples 1 to 11, Comparative Examples 1 to 6>
With the fiber composition shown in Table 1, the fiber was dispersed in water at a dispersion concentration of 0.2% by mass for 10 minutes, a wet paper web was formed using a cylinder paper machine, and then a Yankee dryer with a surface temperature of 150 ° C was used. And dried under heat and pressure to obtain a wet type nonwoven fabric base paper.

(Thermal calendar processing)
The wet non-woven base paper was subjected to thermal calendering twice by a calender unit of a metal roll and an elastic roll at a metal roll temperature of 230 ° C. and a processing speed of 10 m / min so that both sides of the metal roll were in contact and nipped, and the PPS fiber A wet nonwoven fabric containing was obtained.

  In Examples and Comparative Examples, the unit weight and thickness were measured, and the productivity and the alkali resistance were evaluated, and the results are shown in Table 1.

(Basis weight)
Based on JIS P 8124: 2011, a PPS fiber-containing wet non-woven fabric was cut into 100 mm × 100 mm test pieces, and the average value of 20 values measured using an electronic analytical balance (Shimadzu Corporation) was found. And

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

(Productivity)
The productivity at the time of manufacturing a wet type nonwoven fabric base paper was evaluated by the following indexes.

"5": Wet paper and wet nonwoven base paper in each part of the paper machine were stable in running property, and no paper break occurred. Acceleration is also possible.
“4”: The wet paper web and wet nonwoven base paper runability in each part of the paper machine is stable. No paper breaks occur, but fiber peeling is slightly observed.
"3": The wet paper web and wet nonwoven fabric base paper runability in each part of the paper machine is stable. No paper breakage, but more fiber peeling than "4".
“2”: The strength of the wet paper web in the press part is weak, but the wet paper web can be manufactured at a lower speed than “3”. Occasionally, a paper break may occur at the dryer outlet.
“1”: The strength of the wet paper in the press part is weak, and the paper breaks frequently.

(Alkali resistance)
According to JIS P 8113: 2006, using a constant-speed tension type tensile testing machine “Tensilon tabletop material testing machine, model number: STA-1150” (manufactured by Orientec Co., Ltd.) with a long side in the MD direction of 15 mm × 150 mm A strip was cut into a test piece. This was set to a distance between chucks of 100 mm, the chuck was moved at a speed of 100 mm / min, tension was performed at a constant speed, and the strength when the test piece broke was measured and defined as the tensile strength (tensile strength 1). After immersing the PPS fiber-containing wet non-woven fabric in a 10% NaOH aqueous solution at room temperature for 50 hours, thoroughly washing with water and air-drying, and similarly using the value measured for tensile strength (tensile strength 2), the strength was maintained from the following formula. The rate was calculated.

Strength retention rate = tensile strength 2 / tensile strength 1 x 100

  The alkali resistance of the PPS fiber-containing wet nonwoven fabric was evaluated by the following indexes.

"5": 100%
"4": 97% or more, less than 100% "3": 93% or more, less than 97% "2": 90% or more, less than 93% "1": less than 90%

By comparing Examples 1 to 12 and Comparative Examples 1 to 6, PPS fibers composed of only PPS fibers and having a modified cross section and PPS fibers having a circular cross-sectional shape with a diameter of 5 μm or less are contained, and the basis weight is The PPS fiber-containing wet non-woven fabrics of Examples 1 to 12 having an amount of 8 g / m ² or more and 200 g / m ² or less are more productive than the PPS fiber-containing wet non-woven fabric of Comparative Example 1 that does not contain PPS fibers having an irregular cross section. It turns out to be excellent. Further, it is understood that the PPS fiber-containing wet non-woven fabrics of Comparative Examples 2 and 3 in which the PVA fiber or the PET fiber is contained in a part of the binder fiber have excellent alkali resistance. Further, it can be seen that the PPS fiber-containing wet non-woven fabric of Comparative Example 4 containing no PPS fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less is excellent in productivity. Further, the PPS fiber of Comparative Example 5 is composed of only PPS fibers and has a modified cross section and a PPS fiber having a circular cross section with a fiber diameter of 5 μm or less, but having a basis weight of less than 8 g / m ^2. It can be seen that the contained wet non-woven fabric and the PPS fiber-containing wet non-woven fabric of Comparative Example 6 having a basis weight of more than 200 g / m ² are excellent in productivity.

From the comparison of Examples 1 to 5, it can be seen that the productivity is more excellent when the basis weight is 12 g / m ² or more and 150 g / m ² or less.

  From the comparison of Examples 6 to 9, when the content of the PPS fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less is 5% by mass or more and 70% by mass or less based on the total fibers, the productivity is more excellent. You can see that

  From the comparison of Examples 8, 9 and 10, the PPS fiber-containing wet non-woven fabric of Example 8 in which the content of PPS undrawn fiber is 30% by mass or more has the content of PPS undrawn fiber of less than 30% by mass. It can be seen that the PPS fiber-containing wet non-woven fabrics of Examples 9 and 10 are more excellent in productivity.

  From the comparison of Examples 1, 11 and 12, when the content of the circular cross-section PPS fibers having the fiber diameter of 5 μm or less is the same, the fiber diameter is larger than the circular cross-section PPS fiber content of 5 μm or more. Also, it can be seen that the higher the content of the PPS fiber having the atypical cross section, the better the productivity.

  The PPS fiber-containing wet non-woven fabric of the present invention is a filter used for high temperature gas dust collection, a canvas for a dryer used in the drying process of industrial products, a roll wiper for office copying machines, an insulating material for electric equipment, a molding material, and a cushioning material. It can be used as a material (cushion material), a heat insulating cloth, and the like.

Claims (2)

Containing polyphenylene sulfide fibers having atypical cross-section and polyphenylene sulfide fibers having a circular cross-section having a diameter of 5 μm or less, and having a basis weight of 8 g / m ² or more and 200 g / m ² or less A wet non-woven fabric containing polyphenylene sulfide fibers, characterized by:   The polyphenylene sulfide fiber-containing wet non-woven fabric according to claim 1, wherein the content of the polyphenylene sulfide fiber having a circular cross-sectional shape having a fiber diameter of 5 μm or less is 5% by mass or more and 70% by mass or less with respect to all the fibers.