JP4229815B2 - Manufacturing method of fiber sheet - Google Patents

Description

  The present invention relates to a method for producing a fiber sheet containing a wet heat gelled resin that can be gelled by heating in the presence of moisture. In particular, the present invention relates to a method of manufacturing a fiber sheet that can be wet-heat treated with high productivity and can fix the fibers between constituents substantially uniformly.

  Conventionally, as a method for obtaining a heat-fusible fiber sheet, a method in which a heat-melting resin or heat-melting fiber (hereinafter referred to as “binder”) is mixed and heated to soften and melt the binder is generally used. And when increasing the strength of a fiber sheet, the method of processing in the high temperature atmosphere more than the melting | fusing point vicinity of a binder is performed widely. However, in the above method, shrinkage of the binder occurred as the binder melted. As a result, not only the fiber sheet itself shrinks and the dimensional stability is poor, but also the fixing state between the constituent fibers by the binder becomes non-uniform, or unevenness in the basis weight, thickness, etc. is likely to occur. Yield was decreasing.

  In order to reduce the thickness of the fiber sheet or reduce the pore diameter, a method of applying pressure using a heating body such as a hot roll heated to a high temperature near the melting point of the binder is widely used. However, in the above method, since the fiber on the surface of the fiber sheet that is in direct contact with the heating body is more heated than the fiber in the sheet, the fiber sheet surface is in a dense state with many fusions, while the inside of the sheet is fused. It was easy to become a rough state with little adhesion, and the fixing state between the constituent fibers by the binder was uneven.

  Therefore, a binder that can be bonded at a temperature lower than the melting point of the binder has been studied, and as a resin having a property of gelling and fixing between constituent fibers by heating at a temperature lower than the melting point of the binder in the presence of moisture, ethylene is used. -A fiber sheet using vinyl alcohol copolymer fibers has been studied. For example, in Patent Document 1, an ethylene-vinyl alcohol copolymer fiber is immersed in water and adjusted so as to be 70% of the saturated moisture content of the ethylene-vinyl alcohol copolymer by using a charging time in water and a press roll. Thus, a paper having a small shrinkage during processing and excellent boiling resistance and adhesiveness has been proposed by wet papermaking and dry heat treatment.

Patent Document 2 and Patent Document 3 disclose a method in which moisture is applied to a web containing an ethylene-vinyl alcohol copolymer fiber by spraying, the moisture is attached to the periphery of the fiber, and heated and pressurized by a hot roll or the like. In addition, a nonwoven fabric excellent in adhesiveness is disclosed. In particular, Patent Document 2 attempts to evenly bond the constituent fibers in the web thickness direction.
JP-A-57-66200 JP-A 63-235558 JP-A-2-106871

  However, the manufacturing methods described in Patent Documents 1 to 3 have the following problems. In the production method of Patent Document 1, it is necessary to absorb the ethylene-vinyl alcohol copolymer itself, and since it takes a long time to absorb the water, there is a problem that it is limited to the production method by wet papermaking. It was. There is also a problem that it is difficult to control the water absorption of the ethylene-vinyl alcohol copolymer during continuous production. Furthermore, when the constituent fiber is a hydrophobic fiber, the ethylene-vinyl alcohol copolymer was not gelled uniformly, and fixing between the fibers by the gelled product was not uniform.

  Further, in the production methods of Patent Document 2 and Patent Document 3, since water is merely sprayed by spraying or the like, water cannot be uniformly attached to the ethylene-vinyl alcohol copolymer fiber itself, and a fiber sheet. The gel could not be uniformly formed on the surface and inside. In addition, when the constituent fiber is a hydrophobic fiber, the ethylene-vinyl alcohol copolymer was not gelled uniformly, and fixing between the fibers by the gelled product was not uniform.

  In order to solve the above-mentioned problems, the present invention is excellent in productivity, has a small dimensional change during wet heat treatment, uniformly gels the wet heat gelled resin, and substantially uniformly fixes the constituent fibers by the gelled product. An object of the present invention is to provide a method for producing a fiber sheet.

In order to achieve the above object, the method for producing a fiber sheet of the present invention is a method for producing a fiber sheet containing a wet heat gelled resin that can be gelled by heating in the presence of moisture, wherein the wet heat gelled resin comprises: It is an ethylene-vinyl alcohol copolymer and includes at least the following steps.
A. The process which makes the fiber which comprises a fiber sheet, and the said wet heat gelling resin a hydrophilic process, and makes it a hydrophilic fiber sheet.
B. Providing water to the hydrophilic fiber sheet to form a water-containing sheet.
C. The water-containing sheet is subjected to a wet heat treatment with a heat treatment machine set to a temperature range not lower than the gelling temperature of the wet heat gelled resin and not higher than the melting point of the wet heat gelled resin −20 ° C. The process of fixing between the fibers with the gelled gelled product.

  In the fiber sheet manufacturing method of the present invention, when the hydrophilic treatment in the step A is applied to individual constituent fibers and wet heat gelled resin before forming the fiber sheet, the fibers constituted of the individual fibers and wet heat gelled resin. Any of the case where it applies after forming a sheet | seat and the case where they are combined may be sufficient.

  The hydrophilic fiber sheet refers to an aggregate containing planar continuous fibers such as a fiber web, a nonwoven fabric, a woven fabric, a knitted fabric, and a net, and the form thereof is one in which constituent fibers are not joined to each other, entanglement, adhesion Any of those joined by twisting or the like may be used.

  The wet heat treatment refers to a treatment of heating a water-containing sheet provided with moisture to the hydrophilic fiber sheet containing the wet heat gelled resin, and the method includes a method of exposing to a heated atmosphere, a method of penetrating heated air, And any method such as a method of contacting the heating body.

  The gel processing means processing the wet heat treatment with a heat treatment machine set to a temperature range of not less than the gelation temperature of the wet heat gelled resin and not higher than the melting point of the wet heat gelled resin −20 ° C.

  Moreover, the fiber sheet obtained by the manufacturing method of this invention means the sheet | seat which fixed between the fibers comprised by the gelled product obtained by carrying out the gel process of the said hydrophilic fiber sheet and gelatinizing a wet heat gelled resin.

  The gelled product refers to a resin (solidified product) that is solidified after the wet heat gelled resin is gelled by wet heat.

  The method for producing a fiber sheet of the present invention is a hydrous sheet in which moisture is instantaneously and uniformly imparted to a fiber sheet by subjecting the fibers constituting the fiber sheet before gel processing and the wet heat gelled resin to a hydrophilic treatment. Therefore, it is not necessary to absorb water over the heat-and-humidity gelled resin itself over a long period of time as in the prior art, and the production rate can be improved regardless of the production means. In addition, the method for producing the fiber sheet of the present invention uses a wet heat gelling resin having a property of gelling and swelling, and the water-containing sheet to which moisture is uniformly applied is equal to or higher than the temperature at which the wet heat gelling resin gels. Since the wet heat treatment is performed with a heat treatment machine set to a temperature of -20 ° C. or lower, the fiber sheet has a small dimensional change without shrinkage, the wet heat gelled resin is uniformly gelled, and the gelled product makes it between constituent fibers. Can be fixed substantially uniformly. As a result, a fiber sheet with a more uniform fiber sheet surface and small pore diameter unevenness can be obtained.

  Further, by applying pressure processing as the gel processing, the gelled product can be expanded and permeated between the constituent fibers, so that the fiber sheet surface can be made more uniform and smooth, and the fiber sheet thickness direction A fiber sheet in which fixing between constituent fibers by (internal) gelled product is more uniform can be provided at low cost.

  Furthermore, when a fiber having a small fineness is used as the fiber constituting the fiber sheet, a fiber sheet having a very small pore diameter that can be used as a substitute for the microporous membrane can be obtained.

  As a result of diligent research, the present inventors have found that the wet-heat gelled resin is uniformly gelled when wet-heat-treated in order to fix the fibers formed using the wet-heat gelled resin substantially uniformly. I was inspired by that. To that end, it is necessary to know that it is only necessary to uniformly apply moisture to the fiber sheet before wet heat treatment. To that end, it is sufficient that the fibers and wet heat gelled resin constituting the fiber sheet before wet heat treatment should be hydrophilic. Knew.

  However, wet heat gelling resins such as ethylene-vinyl alcohol copolymers are resins that are highly hydrophilic among olefin-based resins, but do not instantaneously wet or absorb water themselves. Furthermore, if the constituent fiber is a hydrophobic fiber, it will not absorb water. Therefore, the fiber sheet can contain water only non-uniformly.

  Thus, the present inventors have found that moisture can be uniformly applied to the fiber sheet by using a hydrophilic fiber sheet obtained by subjecting the fiber and the wet heat gelled resin to the fiber sheet before wet heat treatment to hydrophilic treatment. And if the water-containing sheet | seat which provided the water | moisture content uniformly to the said hydrophilic fiber sheet is gel-processed with the heat processing machine set to the melting | fusing point-20 degreeC or less of the said wet heat gelled resin, a dimensional change will be small and the said wet heat gel It has been found that a fiber sheet can be obtained in which the fibers constituted by the gelled product in which the fluorinated resin is uniformly gelled are fixed substantially uniformly.

  Hereinafter, the manufacturing method of the fiber sheet of one embodiment of the present invention is explained in detail.

  The wet heat gelling resin used in the present invention refers to a resin that can be wet heat gelled in the presence of moisture and that can fix between fibers constituting the fiber sheet by gelling and swelling at a gelling temperature or higher. The lower limit of the preferred gelation temperature is 50 ° C. A more preferable lower limit of the gelation temperature is 60 ° C. If a resin that can be gelled at a temperature of 50 ° C. or lower is used, adhesion to a roll or the like becomes severe during gel processing, making it difficult to produce a fiber sheet, or difficult to use in summer or high temperature environments. There is a case.

  The wet heat gelled resin may be any resin as long as it has the above-described properties. Among these, an ethylene-vinyl alcohol copolymer having a specific composition is preferable in terms of gel processability and dimensional stability during fiber sheet processing. The ethylene-vinyl alcohol copolymer is a resin obtained by saponifying an ethylene-vinyl acetate copolymer, and the saponification degree is preferably 95% or more. A more preferable lower limit of the degree of saponification is 98%. Moreover, the minimum with preferable ethylene content rate is 20 mol%. A more preferable lower limit of the ethylene content is 25 mol%. On the other hand, the upper limit with preferable ethylene content rate is 50 mol%. A more preferable upper limit of the ethylene content is 45 mol%. If the degree of saponification is less than 95% or the ethylene content is less than 20 mol%, adhesion to a roll or the like may become intense during gel processing, which may make it difficult to produce a fiber sheet. On the other hand, if the ethylene content exceeds 50 mol%, the temperature at which wet heat gelation occurs becomes high, so the set temperature of the heat treatment machine must be raised to the vicinity of the melting point. As a result, there is a possibility of affecting the dimensional stability, such as contraction of the fiber sheet.

  The form of the wet heat gelled resin may be any of powder, emulsion, film, fiber and the like. Especially, it is preferable at the point of productivity of a fiber sheet that wet heat gelled resin is a form of a fiber. In the case of a fiber form, the wet heat gelled resin is preferably a wet heat gelled fiber present on at least a part of the fiber surface. In that case, the single fiber of wet heat gelled resin, the composite fiber which combined wet heat gelled resin and other resin are mentioned. In addition, the cross-sectional shape may be any of a circular shape, a hollow shape, an irregular shape, an elliptical shape, a star shape, a flat shape, and the like. In view of ease of fiber production, the cross-sectional shape is preferably circular. The composite form of the composite fiber may be any one of a concentric core-sheath type, an eccentric core-sheath type, a parallel type, a split type, and a sea-island type. In the case of a composite fiber, examples of other resins to be combined include polyester resins, polyamide resins, polyolefin resins, polyurethane resins, and copolymers thereof.

  The fineness of the wet heat gelled fiber is preferably in the range of 0.005 dtex or more and 10 dtex or less. A more preferable lower limit of the fineness is 0.05 dtex. A more preferable upper limit of the fineness is 5 dtex. The smaller the fineness of the wet heat gelled fiber, the more uniform the pore diameter of the resulting fiber sheet. When the fineness of the wet heat gelled fiber exceeds 10 dtex, it is difficult to maintain the uniformity of the pore diameter, and thus the use may be limited.

  In particular, when obtaining a fiber sheet with a small pore diameter, or when obtaining a fiber sheet with a smaller pore diameter unevenness, the split type composite fiber in which the wet heat gelled resin and the other resin are arranged adjacent to each other is divided. The expressed wet heat gelled fiber is preferable. This is because the split-type composite fiber can easily and inexpensively obtain a wet heat gelled fiber of 0.5 dtex or less. As the composite form of the split-type composite fibers, those in which each other exists independently such as a radial type, a comb shape, and a grid type are preferable. The other resin constituting the split composite fiber is preferably a resin that is incompatible with the wet heat gelling resin. This is because an incompatible resin can be easily split and separated, and by using ultrafine fibers, it is possible to fix the fibers that are more densely configured. Other resins are not particularly limited, but among them, polypropylene, polyethylene, polymethylpentene, and copolymers thereof are preferable, and polypropylene is particularly preferable from the viewpoint of fiber production and cost.

  The ratio of the wet heat gelled resin to the entire fiber sheet can be set to any ratio depending on the intended use. The minimum of the ratio of a preferable wet heat gelling resin is 10 mass%. The minimum of the ratio of a more preferable wet heat gelling resin is 15 mass%. An even more preferable lower limit of the ratio of the wet heat gelling resin is 20 mass%. On the other hand, the upper limit of the ratio of preferable wet heat gelled resin is 50 mass%. The upper limit of the ratio of the more preferable wet heat gelled resin is 45 mass%. An even more preferable upper limit of the ratio of the wet heat gelling resin is 40 mass%. If the ratio of the wet heat gelled resin to the entire fiber sheet is too small, it is difficult to spread the wet heat gelled resin over the entire fiber sheet and fix the fibers when gel processing, particularly pressure processing is applied. There is a case. On the other hand, if the ratio of the wet heat gelled resin to the entire fiber sheet is too large, gel processing, particularly pressure processing, tends to be close to a film, which may not be preferable depending on the application.

  Fibers used in the fiber sheet of the present invention are cellulose fibers such as cotton, rayon and pulp, organic polymer fibers such as thermoplastic resins and thermosetting resins, fibrous materials such as synthetic pulp, and inorganic materials such as glass fibers. Any may be sufficient if it has in fiber forms, such as a fiber. Also, two or more of these may be included. The form of the above-described fiber may be any of a single fiber and a composite fiber, and the cross-sectional shape may be any of a circular shape, a hollow shape, an irregular shape, an elliptical shape, a star shape, a flat shape, and the like. Absent. In the case of the composite fiber, any of a concentric circular sheath type, an eccentric core sheath type, a parallel type, a sea island type, a split type, and the like may be used. Further, the fineness of the fiber can be appropriately selected depending on the application. In particular, when a dense fiber sheet having a small pore diameter is required, it is preferable that the fineness is fine, and specifically, the fineness is preferably 1 dtex or less.

  In order to substantially uniformly fix the fibers constituting the fiber sheet with the gelled product formed by gelling the wet heat gelled resin, as described above, the wet heat gelled resin is substantially reduced to the inside of the fiber sheet during gel processing. It is important that the gel is uniformly formed, and it is important that moisture is uniformly applied to the fiber sheet before the gel processing. That is, it is important that the water wettability (hereinafter also referred to as hydrophilicity) of the fiber sheet before gel processing is uniform. Therefore, in the production method of the present invention, in order to impart uniform water wettability to the fiber sheet before gel processing, it is necessary to perform hydrophilic treatment to obtain a hydrophilic fiber sheet.

  The hydrophilic treatment refers to a temporary hydrophilic treatment, a permanent hydrophilic treatment, and a treatment using two or more of these in combination. The temporary hydrophilic treatment refers to a treatment in which hydrophilicity is remarkably reduced by washing the fibers and wet heat gelled resin (hereinafter referred to as “treated product”) after the hydrophilic treatment. For example, the process which attaches surfactant etc. to the processed material surface and expresses hydrophilicity is mentioned. In the present invention, this temporary hydrophilic treatment is preferably applied to the fiber sheet before gel processing. On the other hand, the permanent hydrophilic treatment refers to a treatment in which hydrophilicity is hardly reduced even if the treated product after the hydrophilic treatment is washed with water. For example, the process which introduce | transduces a hydrophilic group into each resin surface which comprises a processed material is mentioned. The permanent hydrophilic treatment may be applied to the fiber sheet before gel processing, or may be applied to each of the constituent fibers and wet heat gelled resin before producing the fiber sheet. Examples of the permanent hydrophilic treatment method include corona discharge method, glow discharge method, plasma treatment method, electron beam irradiation method, ultraviolet ray irradiation method, γ-ray irradiation method, photon method, flame method, and a treatment method that exposes to a fluorine gas atmosphere (hereinafter referred to as a “fluorine gas atmosphere”). , Fluorine treatment method), graft treatment method, sulfonation treatment method and the like. Among the above methods, the permanent hydrophilic treatment is less susceptible to the effect of hydrophilicity reduction by water, and thus is preferable when water is applied to the fiber sheet before gel processing as in the present invention.

  The contact angle after 5 seconds of dropping of desalted water on the surface of the hydrophilic fiber sheet obtained by the hydrophilic treatment is preferably 60 degrees or less. The contact angle used here is employed as an index representing the degree of water wettability of the fiber sheet. A more preferable contact angle is 55 degrees or less. An even more preferable contact angle is 50 degrees or less. The most preferable contact angle is 0 degree. By performing a hydrophilic treatment such that the contact angle on the surface of the hydrophilic fiber sheet is 60 degrees or less, it becomes possible to instantaneously and uniformly impart moisture to the hydrophilic fiber sheet before gel processing. In particular, when the contact angle is 0 degree, moisture can be more instantly applied to the hydrophilic fiber sheet, which contributes to an improvement in production rate. In the hydrophilic treatment in which the contact angle exceeds 60 degrees, water wettability tends to be insufficient, and it may be difficult to uniformly apply moisture to the fiber sheet. As a result, the dimensional stability at the time of gel processing is deteriorated, or the wet heat gelled resin is not easily gelled, so that it is difficult to fix the constituent fibers substantially uniformly. As long as the contact angle of the hydrophilic fiber sheet surface is 60 degrees or less, the method for applying moisture can be applied uniformly and uniformly to the entire fiber sheet by any known method such as spraying or impregnation. be able to.

  The hydrophilic fiber sheet obtained by the permanent hydrophilic treatment is a composition ratio of oxygen elements to all elements measured by X-ray photoelectron spectroscopy (ESCA) on the sheet surface after the hydrophilic fiber sheet is sufficiently washed with demineralized water. (Hereinafter referred to as “oxygen ratio”) is preferably in the range of 4 atomic% to 40 atomic%. The oxygen ratio used here is adopted as an index representing the degree of water wettability of the fiber sheet. By adjusting the oxygen ratio within the above range, moisture can be instantly and uniformly applied to the fiber sheet before gel processing. A more preferable lower limit of the oxygen ratio is 7 atomic%. An even more preferable lower limit of the oxygen ratio is 9 atomic%. On the other hand, a more preferable upper limit of the oxygen ratio is 35 atomic%. An even more preferable upper limit of the oxygen ratio is 30 atomic%. If the oxygen ratio is less than 4 atomic%, the hydrophilicity is poor and it may be difficult to uniformly impart moisture to the hydrophilic fiber sheet. On the other hand, when the oxygen ratio exceeds 40 atomic%, the fiber constituting the fiber sheet is greatly deteriorated, and the strength of the obtained fiber sheet may be reduced.

  Among the permanent hydrophilic treatments, treatments having a higher degree of hydrophilicity include fluorine treatment, plasma treatment, graft treatment, and the like. This is because these methods can introduce hydrophilic groups more evenly into the fiber sheet, so that moisture can be instantaneously and evenly applied to the inside of the fiber sheet. In addition, these treatment methods can introduce a hydrophilic group deeper into the treated product, and are particularly effective when a nonpolar and highly hydrophobic resin such as polyolefin resin is the main fiber. It is a simple method. Further, these methods can reduce the decrease in hydrophilicity even after gel processing. Of the above treatment methods, the fluorine treatment is particularly preferred because it can obtain higher hydrophilicity. In the present invention, the fluorine treatment refers to all treatments in which the treated product is exposed to fluorine gas, and the method is to expose to a fluorine gas-containing gas atmosphere even if it is only exposed to a fluorine gas-containing gas atmosphere. At the same time, either a method of performing a discharge treatment or any known method may be used. An example of the fluorine treatment will be described below.

  Fluorine treatment is a process in which a treated product is brought into contact with a mixed gas of fluorine gas, oxygen gas, sulfurous acid gas, etc., and radicals generated on each resin surface constituting the treated material by fluorine gas are oxygen gas, sulfurous acid gas, etc. It reacts with (hereinafter referred to as a reactive gas) to generate a hydroxyl group, a carboxyl group, a sulfone group, and the like, thereby hydrophilizing each resin surface constituting the treated product. The fluorine gas-containing gas is usually used as a mixed gas diluted with an inert gas such as nitrogen or helium. The dilution concentration of the fluorine gas mixed gas is not particularly limited, but the fluorine gas is preferably in the range of 0.01% by volume to 50% by volume. A more preferable lower limit of the fluorine gas concentration is 0.1% by volume. A more preferable upper limit of the fluorine gas concentration is 30% by volume. The reactive gas is selected from a range of 0.01% by volume or more and 99.9% by volume or less, and is usually diluted with an inert gas and used. A more preferable reactive gas concentration is selected to be higher than the fluorine gas concentration. For example, the reactive gas concentration is preferably in the range of 0.5 volume% or more and 90 volume% or less. When the fluorine gas concentration is less than 0.01% by volume, it is difficult to efficiently form radicals on the surface of the resin to be modified, and hydrophilicity may be insufficient. On the other hand, when the fluorine gas concentration exceeds 50% by volume, the reaction tends to be too intense. Further, when the reactive gas concentration is lower than the fluorine gas concentration, the fluorination reaction is given higher priority, so that it may be difficult to introduce the reactive gas-containing hydrophilic group.

The contact temperature of the fluorine gas mixed gas is selected so that only the direct fluorination reaction does not proceed preferentially. For example, the range is preferably in the range of usually −70 ° C. or higher and 130 ° C. or lower. A more preferable lower limit of the contact temperature is −40 ° C. An even more preferable lower limit of the contact temperature is 0 ° C. On the other hand, the more preferable upper limit of the contact temperature is 90 ° C. An even more preferable upper limit of the contact temperature is 80 ° C. When the contact temperature of the fluorine gas mixed gas is less than −70 ° C., the fluorine reactivity is extremely lowered, and when it exceeds 130 ° C., the fluorination reaction tends to proceed preferentially. This is because a large amount of is introduced and a large number of hydrophobic groups such as —CF ₂ and —CF ₃ are produced, and the water repellency is exhibited. Further, the contact time with the fluorine gas mixed gas is appropriately selected, and it is usually from the viewpoint of processability to carry out usually for 1 second to several hours, preferably 1 second to 1 hour.

  The reaction between the fluorine gas mixed gas and the treated product is carried out by introducing the treated product into a sealed reaction vessel and degassing the vessel, and then introducing the mixed gas or introducing the mixed gas into the reaction vessel in advance. After filling, there is a method of introducing the processed material and bringing it into contact with the fluorine gas mixed gas, or a method of filling the processing chamber with a good gas seal with the fluorine gas mixed gas and running the processed material from outside the processing chamber to the processing chamber. Can be mentioned.

  The method of introducing the fluorine gas mixed gas may be used by mixing the fluorine gas and the reactive gas at a predetermined concentration in advance, or the fluorine gas is introduced after the reactive gas is brought into contact with the processing object. May be. And the method of substituting with inert gas, such as nitrogen, after completion | finish of reaction of a fluorine gas mixed gas and a treatment thing is preferable.

  Further, the composition ratio (hereinafter referred to as “fluorine ratio”) of fluorine elements to all elements measured by ESCA on the sheet surface after the hydrophilic fiber sheet obtained by the fluorine treatment is sufficiently washed with demineralized water is 1 atomic%. It is preferably within the range of 30 atomic% or less. Elemental fluorine is mainly introduced by the fluorine treatment. By adjusting the fluorine ratio to the above range, moisture can be instantly and uniformly applied to the hydrophilic fiber sheet before gel processing. A more preferable lower limit of the fluorine ratio is 2 atomic%. An even more preferable lower limit of the fluorine ratio is 3 atomic%. On the other hand, a more preferable upper limit of the fluorine ratio is 20 atomic%. An even more preferable upper limit of the fluorine ratio is 10 atomic%. If the fluorine ratio is less than 1 atomic%, the hydrophilicity is poor, and it may be difficult to uniformly impart moisture to the fiber sheet. On the other hand, when the fluorine ratio exceeds 30 atomic%, the fiber is greatly deteriorated and the strength of the obtained fiber sheet may be lowered.

  As described above, the fluorine treatment is particularly preferable because hydrophilic groups can be introduced more uniformly and deeply to the fiber and the wet heat gelled resin surface inside the fiber sheet. However, other hydrophilic treatments may be suitable depending on the application (for example, when water repellency is required), processability, the form of the fiber sheet before gel processing, etc., so other methods may be selected. Therefore, examples of other hydrophilization treatment methods are shown below.

  As the temporary hydrophilic treatment, there is a method of attaching a surfactant or the like to the surface of the treatment object, and the surfactant or the like used here is not particularly limited. For example, in nonionic surfactants, polyhydric alcohol type nonionic active agents (ester type) having a polyhydric alcohol such as glycerin, sorbitol, or sugar as a hydrophilic group, or ethylene oxide functioning as a hydrophilic group are hydrophobic. Examples include polyethylene glycol type (ether type) nonionic activator added to the raw material. In addition, an ether ester type nonionic activator obtained by adding ethylene oxide to a polyhydric alcohol type activator may be used. Examples of ionic surfactants include phosphate anion activators such as alkyl phosphate esters, soap anion activators such as aliphatic carboxylic acid soaps, and sulfate anion activators such as alkyl sulfonates. . Two or more of these surfactants may be mixed. The surfactant or the like is preferably attached to the fiber sheet before gel processing. Moreover, any method may be sufficient as the adhesion method. For example, a method of immersing the fiber sheet in a solution containing a surfactant or the like, or a method of spraying and adhering this solution to the fiber sheet may be used.

Next, as a permanent hydrophilic treatment, first, in the case of corona discharge or plasma treatment, as an inert gas, He, Ar, nitrogen or the like, as a reactive gas, air, oxygen, CO, CO ₂ , sulfur oxide (for example, SO ₂ , SO _3, etc.) or nitrogen oxide (eg, NO, NO ₂ , N ₂ O, etc.) may be used. These inert gases and reactive gases generate various chemical species (electrons, ions, radicals, excited molecules, etc.) when an electric field is applied. As a result, it becomes easy to react with the processed material, and brings about an effect that a functional group containing an oxygen atom is effectively introduced to each resin surface. As a discharge condition at this time, if it is a corona discharge, it is good to process on both surfaces of a processed material 1 to 20 times. The discharge amount per time is preferably 0.05 kW · min / m ² or more. The total discharge amount may be processed in the range of 0.05 to 10 kW · min / m ² . When the total discharge amount is less than 0.05 kW · min / m ^2, there is a tendency that hydrophilicity is insufficient, when it exceeds 10 kW · min / m ^2, deterioration of the fibers with the high cost becomes excessive treatment This may cause the fiber sheet strength to decrease.

  In the case of the plasma treatment, since the atmospheric pressure plasma treatment can be carried out at a low voltage, the fiber is less deteriorated and the hydrophilicity can be further increased. As processing conditions, it is preferable to perform processing at an electric field strength of 0.5 to 250 kv / cm and a frequency of about 0.5 to 100 kHz.

  Next, in the case of graft polymerization treatment, a method of immersing the treatment in a solution containing a vinyl monomer and a polymerization initiator and heating, a method of irradiating radiation after applying the vinyl monomer to the treatment, etc. are used. Further, it is preferable that the surface of the treated product is modified by ultraviolet irradiation, corona discharge, plasma discharge, or the like before the vinyl monomer solution and the treated product are brought into contact with each other because efficient graft polymerization can be achieved. Examples of the sulfonation treatment include concentrated sulfuric acid treatment, fuming sulfuric acid treatment, chlorosulfonic acid treatment, and sulfuric anhydride treatment. The method for contacting the acid with the treated product is not particularly limited, but a direct dipping method is often used. For example, when concentrated sulfuric acid is used, it is generally washed after being immersed for 5 to 60 minutes at a temperature of 50 to 120 ° C.

  Next, the hydrophilic fiber sheet obtained by the hydrophilic treatment is provided with moisture to form a water-containing sheet. And it is preferable that the ratio (henceforth a moisture content) of the water | moisture content provided to the said water-containing sheet exists in the range of 20 mass% or more and 300 mass% or less. A more preferable lower limit of the moisture content is 30 mass%. An even more preferable lower limit of the moisture content is 40 mass%. A more preferable upper limit of the moisture content is 200 mass%. An even more preferable upper limit of the moisture content is 150 mass%. If the moisture content is less than 20 mass%, gelation may not occur sufficiently. On the other hand, when the moisture content exceeds 300 mass%, it is difficult to apply heat uniformly to the surface and inside of the fiber sheet during gel processing, and the degree of gelation in the thickness direction of the obtained fiber sheet becomes non-uniform, and the fiber sheet thickness direction There is a tendency that the fixing between the constituent fibers is non-uniform. As a method for applying moisture, any known method such as spraying or dipping into a water tank may be used.

  Next, the water-containing sheet needs to be subjected to gel processing by wet heat treatment with a heat treatment machine set to a temperature range of not lower than the gelling temperature of the wet heat gelled resin and not higher than the melting point -20 ° C. The minimum of the preferable gel processing temperature is 50 degreeC. A more preferable lower limit of the gel processing temperature is 60 ° C. On the other hand, the upper limit of the preferable gel processing temperature is the melting point of the wet heat gelled resin −25 ° C. A more preferred upper limit of the gel processing temperature is the melting point of the wet heat gelled resin −30 ° C. When the gel processing temperature is lower than the gelation temperature of the wet heat gelled resin, the wet heat gelled resin does not gel, and therefore, the fibers constituting the fiber sheet cannot be fixed by the gelled product. On the other hand, if the gel processing temperature exceeds the melting point of the wet heat gelled resin −20 ° C., the fiber sheet becomes close to the melting point of the wet heat gelled resin, so that the fiber sheet shrinks and the variation in basis weight and thickness increases, When processed by a heating body such as a roll, the wet heat gelled resin is likely to adhere to the roll or the like, which may reduce the yield. The gel processing temperature was set to the preset temperature when the non-woven sheet containing moisture was gel processed, and when the set temperature of the heat treatment machine was set to 100 ° C. or higher, the moisture in the nonwoven sheet first evaporates. . At that time, since the gelation of the wet heat gelled resin proceeds, the actual temperature of the gel processing tends to be lower than the set temperature. Therefore, it may be difficult to specify the gel processing temperature strictly. Therefore, even when the melting point of the other fiber is lower than the set temperature of the heat treatment machine, it may not melt or shrink substantially, and the gel processing temperature is a temperature at which the other fiber does not substantially shrink. It is preferable to process.

  The said gel processing can be implemented by methods, such as exposing the said water-containing sheet | seat to a heating atmosphere, making heated air penetrate, and making it contact a heating body. In particular, by applying pressure, the gelled product can be expanded, or the gelled product can be more penetrated between the constituent fibers. Furthermore, it is preferable to apply pressure processing using a heating body because the wet heat gelled resin can be gelled more instantly without unevenness of the degree of gelation. Therefore, when the surface of the fiber sheet to be obtained is made smoother, when the fixing between the constituent fibers is made more uniform, when the hole diameter unevenness of the fiber sheet is reduced, and when the hole diameter of the fiber sheet is reduced preferable.

  The gel processing is particularly pressure processing using a hot roll, and the linear pressure of the hot roll is preferably in the range of 350 N / cm or more and 10,000 N / cm or less. According to such a method, gelation can be instantaneously performed, and the gelled gelled product can be spread and penetrated more into the interior between the fibers that are formed, so that the gel processing can be performed with high production efficiency. Furthermore, since it is pressure processing, the wet heat gelled resin of the entire fiber sheet can be gelled more instantly without more unevenness of the degree of gelation. A more uniform fiber sheet can be obtained. This tendency becomes more conspicuous as the pressure of pressure processing becomes higher. In particular, when a pore diameter that can be used as a substitute for the microporous membrane is required, it is preferable to select a fiber having a small fineness and pressurize it with the above linear pressure. A more preferable lower limit of the linear pressure of the hot roll is 400 N / cm. On the other hand, a more preferable upper limit of the linear pressure is 9000 N / cm. If the linear pressure of the hot roll is less than 350 N / cm, it may be difficult to exert the above-described functions and effects, and for example, it will be difficult to apply to applications such as substitution of a microporous film. On the other hand, when the linear pressure exceeds 10,000 N / cm, the pressure is too large, so that the fiber is likely to be cut, and thus the through hole tends to be easily formed. As a result, the hole diameter and the hole diameter unevenness may increase, or the mechanical strength of the fiber sheet may decrease.

  Moreover, in the manufacturing method of the fiber sheet of the present invention, by performing the gel processing under pressure, the wet heat gelled resin is expanded while gelling to become a film-like gelled product, and the fiber sheet surface is partially It comes to coat. At this time, the ratio of the film-form gelled product to the entire surface of the fiber sheet (hereinafter referred to as “film degree”) is preferably in the range of 40% to 90%. A more preferable lower limit of the film degree is 45%. An even more preferable lower limit of the film degree is 50%. On the other hand, the upper limit of the more preferable filminess is 80%. An even more preferable upper limit of the film degree is 70%. This filminess is an index representing the degree of spread of the gelled product, that is, the degree of penetration between the constituent fibers, and the larger the value, the more uniformly the gelled product spreads on the fiber sheet surface. When the filminess is less than 40%, the gelled product is insufficiently penetrated between the constituent fibers, and therefore the pore diameter and the pore diameter unevenness tend to increase. On the other hand, if the filminess exceeds 90%, the fiber sheet tends to become a film and the area where no holes are present tends to increase.

  In addition, the hole diameter as used in the field of this invention is an average hole diameter measured based on ASTMF31686. This hole diameter may be any value depending on the intended application. In this invention, the more preferable average hole diameter of the fiber sheet obtained by pressurization is 20 micrometers or less. For example, when used in a precision filter as an alternative to a microporous membrane, the preferred average pore size is 10 μm or less, and the more preferred average pore size is 5 μm or less.

  Further, the pore diameter unevenness referred to in the present invention is a substitute characteristic based on a ratio of the average pore diameter and the maximum pore diameter (maximum pore diameter / average pore diameter) measured in accordance with ASTM F31686, and the smaller the value, the wider the pore diameter width. It is small, that is, the hole diameter unevenness is small. This ratio is preferably 15 or less by the production method of the present invention. A more preferable ratio of the average pore diameter to the maximum pore diameter is 10 or less, and a more preferable ratio of the average pore diameter to the maximum pore diameter is 7 or less.

Furthermore, by carrying out the gel processing under pressure, the gelled product is expanded into the fiber sheet. As a result, the average pore diameter of the fiber sheet (hydrophilic fiber sheet) before gel processing is X, when the average pore size of the fiber sheet was X _B, when the value obtained by the following equation was defined as the average pore size reduction rate (%) average pore size reduction rate is preferably 60% or more.

Average pore diameter reduction rate (%) = {(X−X _B ) / X} × 100
A more preferable average pore diameter reduction rate is 65% or more. The reduction of the average pore diameter by this gel processing is particularly important when obtaining a fiber sheet having a small pore diameter, and is achieved by processing under a high pressure using a hot roll or the like as described above. When the average pore size reduction rate is less than 60%, it tends to be difficult to obtain a fiber sheet having a particularly small pore size that can be used as a substitute for the microporous membrane.

  Further, in the present invention, in addition to the fibers constituting the fiber sheet and the wet heat gelled resin, a resin binder, inorganic powder, functional particles and the like may be mixed. For example, the resin binder may be mixed in advance with the aqueous dispersion to be provided when the hydrophilic fiber sheet is hydrated. In addition, in the case of inorganic powder or functional particles, when water is contained in the hydrophilic fiber sheet, it is preferable to preliminarily mix with the water dispersion to be provided. Examples of the inorganic powder or the functional particles include abrasives, harmful gas adsorption / decomposition agents, antiviral adsorption / decomposition agents, antibacterial agents, deodorants, conductive agents, antistatic agents, humidity control agents, One or more desiccants, insect repellents, fungicides and the like can be used. According to the method for producing a fiber sheet of the present invention, by mixing the inorganic powder or the functional particles or the like, the inorganic powder or the functional particles themselves are not embedded in the gelled product, but on the surface of the gelled product. Since it can fix in the state where at least one part was exposed, the function of those powder or particle | grains can fully be exhibited.

  Moreover, in the case of gel processing, the fiber sheets containing wet heat gelled resin may be laminated | stacked, respectively. Moreover, you may laminate | stack with the fiber sheet from which the mixing ratio of wet heat gelled resin differs. Furthermore, you may laminate | stack with the other fiber sheet which does not contain wet heat gelled resin, or another sheet | seat. The other sheet may be any sheet that can be laminated, such as a film or a net. In addition, the other sheet may include a wet heat gelled resin or may not include the wet heat gelled resin. And when laminating | stacking, a lamination | stacking form may be two layers, a multilayer may be sufficient, and the fiber sheet containing wet heat gelled resin may be an outer layer or an inner layer. Further, the sheet before and after the gel processing may be subjected to any processing such as needle punch processing, hydroentanglement processing, thermal bond processing, and chemical bond processing. Moreover, the hydrophilic process should just be given to the fiber sheet containing a wet heat gelled resin at least.

  The resulting fiber sheet is suitable as a wiper, for example, because of its uniform surface, and is excellent in touch when used for applications that touch the skin. In addition, when the gel processing is pressure processing, for example, because the pore diameter unevenness of the obtained fiber sheet is small, it is excellent in filter performance, etc., or in the uniform retention of the electrolyte, and excellent in short circuit prevention It can be used for battery separators, capacitors, and other sanitary materials that are excellent in preventing leakage of urine and the like and excellent in liquid diffusibility. Furthermore, when the gel processing is pressure processing, for example, since the hole diameter of the obtained fiber sheet is small, it can be suitably used for a high-accuracy filter, a battery separator, a capacitor, or the like. Even in applications other than those described above, the fiber sheet surface is more uniform, or is fixed substantially uniformly by a gelled product between constituent fibers, and therefore can be used for various applications. In addition, by supporting the inorganic powder or the functional particles on a fiber sheet, by selecting the function of the powder or particles according to the application, it can be used as a functional fiber sheet.

Hereinafter, the contents of the present invention will be described with reference to examples. It should be added that the following embodiments are merely examples for specifically explaining the present invention. First, melting point, single fiber fineness, single fiber strength, thickness, average pore diameter, maximum pore diameter, pore diameter irregularity, fiber sheet surface film degree, contact angle, oxygen ratio, fluorine ratio, fiber sheet surface shrinkage during processing, and wet heat The wet heat gelation temperature of the gelled resin was measured by the following method.
(1) Melting point: Measured according to JIS K 7121 (DSC method).
(2) Single fiber fineness: Measured according to JIS L 1013.
(3) Single fiber strength: According to JIS L 1015, using a tensile tester, the gripping interval of the sample was 20 mm, and the load value when the fiber was cut was measured to obtain the single fiber strength.
(4) Thickness: 175 kPa load (measured with a micrometer according to JIS-B-7502), the thickness was measured at 10 different points of each of the three samples, and the average value of a total of 30 locations was determined.
(5) Average pore diameter / maximum pore diameter: measured using a palm porometer (made by porous Materials Inc.) according to ASTM F31686.
(6) Pore diameter unevenness: calculated by dividing the maximum hole diameter by the average hole diameter.
(7) Filminess on the surface of the fiber sheet: The surface of any 10 positions of the fiber sheet is photographed with an electron microscope at a magnification of 200 times. For example, as shown to Fig.3 (a)-(d), the percentage with respect to the fiber sheet total area of the area where the fiber which each fiber adjoins is continuously fixed in this fiber sheet surface was calculated.
(8) Contact angle: Contact angle of fiber sheet surface: Kyowa Interface Chemical Co., Ltd., contact angle meter (cleaning degree evaluation system), model: CA-X150, as shown in FIG. Then, a sample 2 having a length of 1 cm and a width of 5 cm is placed and fixed with tape. Next, 2 microliters of pure water 3 is accurately dropped onto the sample 2 with a microsyringe. After standing for 5 seconds, the diameter a and height h of the water droplet shown in FIG. 1 are measured. From the diameter a and the height h, the contact angle θ is obtained using the following formula.
tan (θ / 2) = h / (a / 2)
(9) Oxygen ratio and fluorine ratio: ESCA-3000 (manufactured by Shimadzu Corporation) was used to perform elemental composition analysis on the fiber sheet surface. Measurement conditions are Mg / Al, output 8 kW, 30 mA, measurement area 50 mm ² , fiber constituting fiber sheet and / or wet heat gelled resin surface at a depth of 10 nm from fiber and / or wet heat gelled resin surface The ratio of the elements and functional groups present in the sample was measured, and as the oxygen ratio, the percentage of the value obtained by dividing the amount of oxygen element by the total element amount and the fluorine ratio by dividing the amount of fluorine element by the total element amount was adopted.
(10) Fiber sheet area shrinkage ratio (%) during processing: Calculated according to the following formula.
[1- (fiber sheet area after gel processing / fiber sheet area before gel processing)] × 100
(11) Wet heat gelation temperature of the wet heat gelled resin: A wet nonwoven fabric composed of 20% by mass or more of the wet heat gelled resin and pulp is prepared, and the obtained wet nonwoven fabric is cut into a width of about 30 mm and a length of about 100 mm. Next, two cut samples are stacked. About 50 mass% of moisture is applied to the sample, and the heat seal temperature is raised by 10 ° C. under a pressure of 0.1 MPa using a heat seal stamper having a seal width of about 5 mm. And the temperature when it begins to adhere is defined as the wet heat gelation temperature.
(12) Breaking length of fiber sheet According to JIS-L-1096, a test piece cut to a width (non-woven fabric lateral direction) of 50 mm and a length (non-woven fabric longitudinal direction) of 150 mm is held at a grip interval of 100 mm, and is a constant-speed extension type. The value obtained by dividing the load value (tensile strength) at the time of cutting the test piece when stretched using a tensile tester by the basis weight of the sample piece was taken as the breaking length.

  The fiber raw material used for an Example and a comparative example was prepared as follows.

[Fiber 1]
The first component (wet heat gelling resin) is an ethylene-vinyl alcohol copolymer (EVOH, wet heat gelation temperature 70 ° C., melting point 170 ° C.) having an ethylene content of 38 mol% and a saponification degree of 99%, and the second component is Polypropylene (PP, melting point: 163 ° C.) split composite fiber having a fiber length of 6 mm having a fineness of 1.4 dtex (fiber 1A), a fineness of 1.2 dtex (fiber 1B), and a radial 16-divided cross-sectional shape (product) The name DF-2, manufactured by Daiwabo Co., Ltd.) was used.

[Fiber 2]
High density polyethylene (HDPE, melting point 132 ° C.) as sheath component and polypropylene (melting point 163 ° C.) as core component, concentric circular sheath core type composite fiber (trade name NBF (H , Daiwabo Co., Ltd.).

[Fiber 3]
A round cross-section polypropylene single fiber (trade name PZ, manufactured by Daiwabo Co., Ltd.) having a fineness of 0.5 dtex and a fiber length of 10 mm made of polypropylene (melting point: 163 ° C.) was used.

[Example 1]
Mix the fiber 1A to 50 mass%, the fiber 2 to 30 mass%, and the fiber 3 to 20 mass% to prepare a water dispersion slurry so that the total fiber has a concentration of 0.5 mass%. Slurry was made from a wet web paper machine and a short web wet paper machine by making wet paper webs each having a basis weight of 15 g / m ² and then heat treated at 135 ° C. using a cylinder dryer and dried. At the same time, it was temporarily bonded with the wet heat gelled resin of the fiber 1A and the sheath component of the fiber 2 to prepare a wet nonwoven fabric with a basis weight of 30 g / m ² . In the obtained wet nonwoven fabric, the fiber 1A is almost 100% divided, and the wet heat gelled fiber having a fineness of about 0.09 dtex and the polypropylene fiber having a fineness of about 0.09 dtex are expressed in a substantially uniform manner in the nonwoven fabric. It was dispersed. The dividing rate is calculated by calculating the ratio of divided fibers by bundling so that the longitudinal direction of the nonwoven fabric is a cross section, passing through a metal plate with a 1 mm diameter hole, and expanding by 400 times using an electron microscope. Asked.

  Next, the wet nonwoven fabric is introduced into a mixed gas processing device, and after the atmosphere of the processing device is vacuum-substituted, a mixed gas composed of 25 ° C., gas composition of 1% by volume of fluorine, 73% by volume of oxygen, and 26% by volume of nitrogen is processed. Introduced into the vessel, the pressure was 1 atm, and the treatment time was 1 minute. Then, after evacuation, the pressure was restored with nitrogen. Then, it wash | cleaned with 60 degreeC hot water, and it dried at 70 degreeC with the hot air dryer, and was set as the hydrophilic fiber sheet. The contact angle of the obtained hydrophilic fiber sheet with demineralized water was 0 degree. FIG. 2 shows an SEM micrograph of 200 times the surface of the obtained hydrophilic fiber sheet.

  Next, using a sprayer, moisture was uniformly applied to the hydrophilic fiber sheet by spraying so as to be 100 mass% with respect to the hydrophilic fiber sheet to obtain a water-containing sheet.

  Next, the hydrous sheet was subjected to gel processing with a pair of metal flat rolls heated to 130 ° C. under conditions of a linear pressure of 500 N / cm and a processing speed of 3.3 m / min, to obtain a fiber sheet of the present invention. . The SEM micrograph of 200 times of the obtained fiber sheet surface is shown to Fig.3 (a)-(d). In Fig.3 (a), the part which looks like a film | membrane from the center right to the lower part is a film-form gelled material. Similarly, in FIG. 3 (b), the gelled product is a film-like gelation in the vertical direction of the central portion, in FIG. 3 (c) the left side portion, and in FIG. 3 (d), the left side portion and the upper right diagonal portion. It is. In FIG. 4, the SEM micrograph of the cross section of the obtained fiber sheet 500 times is shown.

[Example 2]
Except having provided 25 mass% of water | moisture content, the process similar to Example 1 was implemented and the fiber sheet of this invention was obtained.

[Example 3]
Except having provided 180 mass% of water | moisture content, the process similar to Example 1 was implemented and the fiber sheet of this invention was obtained.

[Example 4]
Except that the hot roll temperature was 100 ° C., the same treatment as in Example 1 was performed to obtain the fiber sheet of the present invention.

[Example 5]
Except that the hot roll temperature was 140 ° C., the same treatment as in Example 1 was performed to obtain the fiber sheet of the present invention.

[Example 6]
Except that the hot roll linear pressure was 400 N / cm, the same treatment as in Example 1 was performed to obtain the fiber sheet of the present invention.

[Example 7]
Except that the hot roll linear pressure was 700 N / cm, the same treatment as in Example 1 was performed to obtain the fiber sheet of the present invention.

[Example 8]
50 mass% of fiber 1B, 30 mass% of fiber 2, and 20 mass% of fiber 3 were mixed, and an aqueous dispersion slurry was prepared so as to have a concentration of 0.5 mass%. The obtained water-dispersed slurries were each made by making wet paper webs having a basis weight of 12.5 g / m ² from a circular mesh wet paper machine and a short mesh wet paper machine. Subsequently, it heat-processed at 130 degreeC using the cylinder dryer machine, and it was made to dry temporarily, and was temporarily bonded with the wet heat gelled resin of the fiber 1B, and the sheath component of the fiber 2, and produced the wet nonwoven fabric of 25 g / m < ² > of fabric weight. In the obtained wet nonwoven fabric, the fiber 1B is divided almost 100%, and the wet heat gelled fiber having a fineness of about 0.075 dtex and the polypropylene fiber having a fineness of about 0.075 dtex are divided and expressed substantially uniformly in the nonwoven fabric. It was dispersed.

  Next, the wet nonwoven fabric is introduced into a mixed gas processing device, and after the atmosphere of the processing device is vacuum-substituted, a mixed gas composed of 25 ° C., gas composition of 1% by volume of fluorine, 73% by volume of oxygen, and 26% by volume of nitrogen is processed. Introduced into the vessel, the pressure was 1 atm, and the treatment time was 1 minute. Then, after evacuation, the pressure was restored with nitrogen. Then, it wash | cleaned with 60 degreeC hot water, and it dried at 70 degreeC with the hot air dryer, and was set as the hydrophilic fiber sheet. The contact angle of the obtained hydrophilic fiber sheet with demineralized water was 0 degree.

  Next, using a sprayer, moisture was uniformly applied to the hydrophilic fiber sheet by spraying so as to be 100 mass% with respect to the hydrophilic fiber sheet to obtain a water-containing sheet.

  Next, the fiber sheet of the present invention is obtained by subjecting the water-containing sheet to gel processing under the conditions of a linear pressure of 8000 N / cm and a processing speed of 7 m / min with a hot roll composed of a pair of plain rolls heated to 90 ° C. It was. The 300 times SEM micrographs of the obtained hydrophilic fiber sheet surface are shown in FIGS. 5A to B, and the 300 times cross-sectional photographs are shown in FIGS. Moreover, the 300-times SEM micrograph of the obtained fiber sheet surface of this invention is shown to FIG.

[Comparative Example 1]
Except that no moisture was applied, the same treatment as in Example 1 was performed, but the shrinkage of the nonwoven fabric was large during the hot roll processing, and the sample could not be collected.

[Comparative Example 2]
The same treatment as in Example 1 was performed except that the hot roll temperature was 60 ° C. Since the wet heat gelled resin did not gel, the average pore size reduction rate was as small as 48%. Moreover, the film form degree of the nonwoven fabric surface was as small as 33%.

[Comparative Example 3]
Except that the heat roll temperature was set to 160 ° C., the same treatment as in Example 1 was performed. However, the wet heat gelled resin was adhered to the roll, and the nonwoven fabric was greatly contracted and could not be collected.

[Comparative Example 4]
The same treatment as in Example 1 was performed except that the hydrophilic treatment was not performed. Since the contact angle before gel pressurization processing became large, it was not possible to uniformly impart moisture to the nonwoven fabric. As a result, a non-woven fabric having large variations in pore diameter and filminess was obtained.

  As is apparent from Table 1, in any of Examples 1 to 8, since the fiber sheet before gel processing was subjected to hydrophilic treatment, the contact angle due to demineralized water on the surface of the hydrophilic fiber sheet was reduced, and moisture was instantly and uniformly obtained. It was able to be imparted and had good gel processability. Moreover, since the wet heat gelled resin was uniformly gelled, the fibers constituted by the gelled product were fixed substantially uniformly. In addition, since fibers having a small fineness were used in this example, the pore diameter is very small, the pore diameter unevenness is small, the pore diameter reduction rate is large, and the membrane shape on the nonwoven fabric surface can be an alternative to a suitable microporous membrane. A nonwoven fabric could be obtained.

  On the other hand, in Comparative Example 1 shown in Table 2, since the moisture was not impregnated, the fiber sheet contracted greatly during the hot roll processing, and could not be collected. In Comparative Example 2, since the heat roll temperature was lower than the gelation temperature of the wet heat gelled resin, the wet heat gelled resin did not gel. As a result, the degree of film thickness reduction on the nonwoven fabric surface and the average pore diameter of the obtained nonwoven fabric were small, and as a result, the fixing between the constituent fibers by the gelled product was insufficient. In Comparative Example 3, since the hot roll temperature was higher than the melting point of the used wet heat gelled resin −20 ° C., the wet heat gelled resin adhered to the roll and the nonwoven fabric contracted greatly, so that the sample could not be collected. In Comparative Example 4, since the hydrophilic treatment was not performed, the contact angle before gel processing was large, and moisture could not be uniformly applied to the fiber sheet. As a result, the shrinkage of the non-woven fabric was large, and the non-woven fabric had a large variation in pore diameter and filminess, resulting in uneven fixing between constituent fibers due to the gelled product.

[Example 9]
As a functional particle solution, a solution was prepared by suspending “alumina” (average particle size 0.7 μm) manufactured by Nippon Light Metal Co., Ltd. in water at a ratio of 3 mass%. And the hydrophilic fiber sheet of the said Example 1 was immersed in the said functional particle solution, and it squeezed with the mangle roll, and it adjusted so that a pick-up rate might be about 200%, and became a water-containing sheet. The pickup rate is a value obtained by multiplying the sum of the amount of moisture and the amount of functional particles with respect to the mass of the nonwoven fabric by 100. Next, a canvas net was stretched between upper and lower hot plates heated to 120 ° C., the water-containing sheet was sandwiched between them, and gel processing was performed at a pressure of 0.064 MPa for 2 seconds to obtain a fiber sheet of the present invention. In the obtained fiber sheet, the fibers composed of the gelled product were fixed substantially uniformly. Furthermore, the functional particles were partially exposed and fixed on the surface of the gelled product.

  The fiber sheet of the present invention can be suitably used for battery separators, capacitors, filters, wipers, patches, absorbent bodies, sanitary materials, and the like.

It is sectional drawing which shows the method of measuring the contact angle of the hydrophilic fiber sheet surface used for this invention. It is a 200-times SEM micrograph of the hydrophilic fiber sheet surface obtained in Example 1 of this invention. (A)-(d) is a 200-times SEM micrograph of the fiber sheet surface obtained in Example 1 of this invention. It is a 500-times SEM micrograph of the fiber sheet cross section obtained in Example 1 of the present invention. 300-times SEM micrographs of the hydrophilic fiber sheet surface obtained in Example 8 of the present invention, and FIGS. 300-times SEM micrographs of the fiber sheet surface obtained in Example 8 of the present invention, and FIGS.

Explanation of symbols

1 Glass plate 2 Sample 3 Pure water a Water drop diameter h Water drop height

Claims (9)

A method for producing a fiber sheet containing a wet heat gelled resin that can be gelled by heating in the presence of moisture,
The wet heat gelled resin is an ethylene-vinyl alcohol copolymer,
The manufacturing method of the fiber sheet including the following process at least.
A. The process which makes the fiber which comprises a fiber sheet, and the said wet heat gelling resin a hydrophilic process, and makes it a hydrophilic fiber sheet.
B. Providing water to the hydrophilic fiber sheet to form a water-containing sheet.
C. The water-containing sheet is subjected to a wet heat treatment with a heat treatment machine set to a temperature range not lower than the gelling temperature of the wet heat gelled resin and not higher than the melting point of the wet heat gelled resin −20 ° C. The process of fixing between the fibers with the gelled gelled product.   The manufacturing method of the fiber sheet of Claim 1 which exists in the range whose moisture content provided to the said hydrophilic fiber sheet is 20 mass% or more and 300 mass% or less.   The manufacturing method of the fiber sheet according to claim 1 or 2, wherein a contact angle after 5 seconds of dropping of desalted water on the surface of the hydrophilic fiber sheet is 60 degrees or less.   The composition ratio (oxygen ratio) with respect to all the elements of the oxygen element measured by the X ray photoelectron spectroscopy (ESCA) in the said hydrophilic fiber sheet exists in the range of 4 atomic% or more and 40 atomic% or less. The manufacturing method of the fiber sheet of description.   The method for producing a fiber sheet according to any one of claims 1 to 4, wherein the hydrophilic treatment is a treatment exposed to a fluorine gas atmosphere.   6. The fiber sheet according to claim 5, wherein a composition ratio (fluorine ratio) of fluorine element to all elements measured by X-ray photoelectron spectroscopy (ESCA) in the hydrophilic fiber sheet is in a range of 1 atomic% to 30 atomic%. Production method. The method for producing a fiber sheet according to any one of claims 1 to 6 , wherein the wet heat gelled resin is wet heat gelled fiber in which the resin is present on at least a part of the fiber surface. The method for producing a fiber sheet according to any one of claims 1 to 7 , wherein the gel processing is pressure processing. The method for producing a fiber sheet according to any one of claims 1 to 8 , wherein the gel processing is pressure processing using a hot roll, and the linear pressure of the hot roll is in a range of 350 N / cm to 10000 N / cm. .

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