JP5799753B2 - Method for producing fine fiber-containing sheet - Google Patents

Description

  The present invention relates to a method for producing a fine fiber-containing sheet.

  Sheets containing fine fibers having a fiber diameter of 1 μm or less (hereinafter referred to as “fine fiber-containing sheets”) have advantages such as high mechanical strength, and application to various uses is being studied. As a method for producing a fine fiber-containing sheet, for example, a method of continuously making a paper dispersion of an aqueous dispersion containing fine fibers (hereinafter referred to as “fine fiber dispersion”) is known (Patent Document 1).

It is known that if the slurry concentration when making paper products is too high, the viscosity of the slurry becomes too high and the basis weight uniformity (so-called “texture”) becomes poor. A fine fiber dispersion having a fiber diameter of 1 μm or less tends to have a very high viscosity as compared with a paper product papermaking slurry. In view of these points, it is considered that the concentration of the fine fiber dispersion should be lowered. Specifically, in the production method described in Patent Document 1, the fine fiber content is 0.45% by mass or less. The liquid was used.
By the way, the fine fiber-containing sheet is required to have a certain thickness depending on the application. However, in the case of producing a thick fine fiber-containing sheet by continuously making a fine fiber dispersion with a low concentration, the amount of the fine fiber dispersion flowing down from the end in the width direction of the paper making wire is large, so the yield. Was low.

  Patent Document 2 discloses a method of securing a thickness of a sheet by laminating a plurality of thin sheets prepared from a dispersion containing fine fibers. However, the method of laminating sheets has a problem that the process becomes complicated.

JP 2010-202987 A JP 2009-96167 A

The present invention provides a method for producing a fine fiber-containing sheet, which can produce a fine fiber-containing sheet having a certain thickness (specifically, a basis weight of 15 g / m ² or more) at a high yield and easily without damaging the texture. The purpose is to provide.

  The inventors have found that when a fine fiber-containing sheet is produced by continuous papermaking of a dispersion having a high concentration to some extent, a practical level of texture is obtained and the yield is improved.

That is, this invention has the following aspects.
[1] A fine fiber dispersion containing fine fibers having an average fiber diameter of 1 to 1000 nm is dehydrated using a continuous paper machine equipped with a paper making wire and dried to contain fine fibers having a basis weight of 15 g / m ² or more. A method for producing a sheet, wherein the fine fiber dispersion has a viscosity measured according to JIS K7117: 1987 of 100 to 15000 mPa · s and a fine fiber content concentration of 1.5 to 4.0 % by mass. And the fine fiber dispersion is supplied onto the paper making wire using a pre-weighing coater .
[2] The method for producing a fine fiber-containing sheet according to [1], wherein the fine fiber dispersion is supplied to the pre-metering type coater while stirring.
[3] A fine fiber dispersion containing fine fibers having an average fiber diameter of 1-1000 nm is dehydrated using a continuous paper machine equipped with a paper making wire, dried, and contains fine fibers having a basis weight of 15 g / m ² or more. A method for producing a sheet, wherein the fine fiber dispersion has a viscosity measured according to JIS K7117: 1987 of 100 to 1000 mPa · s and a fine fiber content concentration of 0.5 to 2.0 % by mass. And the fine fiber dispersion is supplied onto the papermaking wire using the following inclined surface dispersion flow down means .
(Inclined dispersion liquid flow down means)
A liquid reservoir for storing the fine fiber dispersion; and an inclined surface having a lower end positioned above the papermaking wire, and the fine fiber dispersion overflowing from the liquid reservoir flows down along the inclined surface. Means for feeding to the papermaking wire.
[4] The method for producing a fine fiber-containing sheet according to [3], wherein the fine fiber dispersion is supplied to the liquid reservoir of the inclined surface dispersion flowing down means while stirring .
[5] The method for producing a fine fiber-containing sheet according to any one of [1] to [4], wherein the surface of the fine fiber dispersion supplied to the papermaking wire is scraped and adjusted to adjust the thickness.

  According to the method for producing a fine fiber-containing sheet of the present invention, a fine fiber-containing sheet having a certain degree of thickness can be produced easily with a high yield without damaging the texture.

It is a schematic block diagram of the manufacturing apparatus used with 1st Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention. It is a schematic block diagram of the manufacturing apparatus used with 2nd Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention. It is a schematic block diagram of the manufacturing apparatus used with 3rd Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention.

(Fine fiber-containing sheet)
The fine fiber-containing sheet obtained in the present invention is a sheet containing at least fine fibers.
The fine fibers in the present invention are cellulose fibers or rod-like particles that are much narrower than pulp fibers usually used in papermaking applications. Furthermore, the fine fiber is an aggregate of cellulose molecules in a crystalline state, and its crystal structure is type I (parallel chain).
The width of the fine fiber is 1 nm to 1000 nm, preferably 2 nm to 500 nm, more preferably 4 nm to 100 nm, as observed with an electron microscope. When the width of the fiber is less than 1 nm, since the cellulose molecule is dissolved in water, the physical properties (strength, rigidity, dimensional stability) as the fine fiber are not expressed. If it exceeds 1000 nm, it cannot be said that it is a fine fiber, and is merely a fiber contained in ordinary pulp, and physical properties (strength, rigidity, dimensional stability) as a fine fiber cannot be obtained. In applications where fine fibers are required to have transparency, the width of the fine fibers is preferably 50 nm or less.
Composite materials obtained from fine fibers generally have high strength because they are dense structures, and high elasticity derived from cellulose crystals, as well as transparency due to low visible light scattering. It is done.

Here, the fact that the fine fibers have the I-type crystal structure is that 2θ = 14 to 17 in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418Å) monochromatized with graphite. It can be identified by having typical peaks at two positions near ° and around 2θ = 22-23 °. Moreover, the measurement of the fiber width by electron microscope observation of a fine fiber is performed as follows. An aqueous suspension of fine fibers having a concentration of 0.05 to 0.1% by mass is prepared, and the suspension is cast on a carbon film-coated grid subjected to a hydrophilic treatment to obtain a sample for TEM observation. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight line X and the straight line Y is read for each image. In this way, at least 20 × 2 × 3 = 120 fiber widths are read. The fine fiber width of the present invention is an average value of the fiber widths read in this way.

  The fiber length of the fine fibers in the present invention is preferably 1 μm to 1000 μm, more preferably 5 μm to 800 μm, and particularly preferably 10 μm to 600 μm. When the fiber length is less than 1 μm, it becomes difficult to form a fine fiber-containing sheet, and when it exceeds 1000 μm, the slurry viscosity of the fine fibers becomes very high, and the handleability is lowered. The fiber length can be determined by TEM, SEM or AFM image analysis. The said fiber length is a fiber length which occupies 30 mass% or more of a fine fiber.

  The axial ratio of fine fibers in the present invention is preferably in the range of 100 to 10,000. If the axial ratio is less than 100, it may be difficult to form a fine fiber-containing sheet. If the axial ratio exceeds 10,000, the viscosity of the fine fiber dispersion may be too high.

There are no particular restrictions on the production method of fine fibers, but mechanical actions such as grinders (stone mills), high-pressure homogenizers, ultra-high pressure homogenizers, high-pressure collision type grinders, disk-type refiners, conical refiners, ultrasonic homogenizers, etc. A method of thinning the cellulosic fibers by wet pulverization is preferred.
Further, as will be described later, it may be refined after chemical treatment such as acetylation, chemical treatment such as TEMPO oxidation, ozone treatment, and enzyme treatment.

  Examples of the cellulosic fibers to be refined include plant-derived cellulose, animal-derived cellulose, and bacteria-derived cellulose. Plant-derived cellulose, particularly wood-based cellulose is preferred. Fine fibers obtained from wood-based cellulose can easily control the fiber diameter and fiber length of the fine fibers depending on the degree of chemical treatment and mechanical treatment. This is an aggregate of microfibril fibers (diameter several μm to several tens μm, fiber length 0.1 mm to several mm) made of single nanofibers having a diameter of wood-based cellulose fibers of 2 to 4 nm. The fiber diameter and fiber length can be easily adjusted by the conversion method. Therefore, it is possible to easily control the light diffusivity, scattering property, and transparency. Wood-based cellulose can be obtained by chemically treating wood chips obtained from hardwoods or conifers.

Examples of the chemical treatment before refining the cellulose fiber include degreasing treatment, delignification treatment, dehemicellulose treatment, kraft treatment, sulfite treatment, bleaching treatment, and enzyme treatment.
The cellulosic fibers subjected to these treatments can be suitably used as raw materials of wood chips used in the production of ordinary paper pulp or wood powder obtained by pulverizing wood chips.
Examples of the wood chip include a softwood chip or a hardwood chip having a thickness of 2 mm to 8 mm and a diameter of several centimeters. As wood powder, after drying in the sun or forcibly drying with a drier so that the moisture content of the wood chips is 10% by mass or less, the chips are pulverized in a pulverization process to produce wood powder. Here, the particle diameter of the wood powder is preferably 0.1 mm to 1 mm. If the diameter of the wood flour is reduced, the fiber length of the resulting fine fiber is also shortened.

  In the above degreasing treatment, carbonates such as sodium carbonate, alcohol, benzene which is a 1: 2 mixed solution of alcohol-benzene, lipase, lipase which is an enzyme that decomposes triglycerides of fatty acids, and the like can be appropriately used and stirred at room temperature. Or a method of treating at high temperature and high pressure. Among these, a method using sodium carbonate is preferable because it is inexpensive and not an organic solvent, can be used easily without using a pressure vessel, and has high degreasing efficiency.

  Examples of delignification treatment include peracetic acid, persulfuric acid, percarbonate, perphosphoric acid, hypoperchloric acid, perbenzoic acid, metachloroperbenzoic acid, peroxyacid such as perforic acid, perpropionic acid, Examples include Wise method using chloric acid and acetic acid. Among these, the method using peracetic acid, which is also used for bleaching wood pulp and has good handleability, and the Wise method are preferable.

  In the method using peracetic acid alone or the Wise method, the pH is preferably 4 or less. The blending ratio of the delignifying agent with respect to the defatted raw material is preferably 50 to 500% by mass, and more preferably 90 to 250% by mass. The temperature during delignification treatment is preferably 70 to 99 ° C, more preferably 80 to 98 ° C. If the temperature is less than 70 ° C., the efficiency of the delignification reaction may be reduced and a colored state may be obtained, and if it exceeds 99 ° C., it may be difficult to make fine fibers. The treatment time is preferably 0.5 to 2.0 hours in the case of using peracetic acid, and 4 to 6 hours in the Wise method.

  As the dehemicellulose treatment, a method of immersing in an aqueous solution of an alkali metal hydroxide at room temperature overnight, a method of treating at a high temperature for a short time while stirring in the aqueous solution, and a high temperature and high pressure while stirring in the aqueous solution. The method of processing is mentioned. As the alkali metal hydroxide, potassium hydroxide is preferred because it is inexpensive as a chemical, can be used at normal temperature and pressure, and has high efficiency in dehemicellulose reaction.

Kraft pulp or sulfite pulp can be used as a raw material for fine fibers. Kraft pulp is made from wood chips such as conifers and hardwoods, steamed with an aqueous solution containing sodium hydroxide (NaOH) and sodium sulfide (Na ₂ S) at a high temperature of 100 to 180 ° C. and a high pressure of 0.1 to 0.8 MPa. It can be obtained by removing fat, lignin and hemicellulose in the chip. If necessary, bleaching may be performed with chlorine dioxide, ozone, or the like.
For sulfite pulp, wood chips are steamed at 120 to 180 ° C and 0.4 to 1.0 MPa with an aqueous solution of sulfites such as calcium sulfite and magnesium sulfite to remove fat, lignin and hemicellulose in the wood chips. It is obtained with. If necessary, bleaching may be performed with chlorine dioxide, ozone, or the like.

Before the refined cellulose fiber is refined, chemical modification may be performed to facilitate defibration. Here, the chemical modification is a chemical modification in which a hydroxyl group in cellulose reacts with a chemical modifier.
As functional groups introduced by chemical modification, carboxy group, acetyl group, sulfuric acid group, sulfonic acid group, acryloyl group, methacryloyl group, propionyl group, propioroyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, Acyl such as heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, cinnamoyl group Group, isocyanate group such as 2-methacryloyloxyethylisocyanoyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group, hexyl group, hept Group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, an alkyl group such as a stearyl group, an oxirane group, an oxetane group, a thiirane group, or the like thietane group.

The chemical modification of cellulose can take a normal method. That is, it can be chemically modified by reacting cellulose with a chemical modifier. If necessary, a solvent and a catalyst may be used, or heating, decompression, etc. may be performed.
Examples of the chemical modifier include cyclic ethers such as acid, acid anhydride, alcohol, halogenating reagent, alcohol, isocyanate, alkoxysilane, and oxirane (epoxy). These may be used individually by 1 type and may use 2 or more types together.
Examples of the acid include acetic acid, acrylic acid, methacrylic acid, propanoic acid, butanoic acid, 2-butanoic acid, and pentanoic acid.

  After chemical modification, it is preferable to thoroughly wash with water in order to terminate the reaction. If the unreacted chemical modifier remains, it may cause coloring later or may become a problem when compounded with a resin. After sufficiently washing with water, it is preferable to further replace with an organic solvent such as alcohol. In this case, it is replaced by immersing cellulose in an organic solvent such as alcohol.

Resin or rubber | gum may be contained in a fine fiber containing sheet as needed. When resin or rubber is contained, the resulting fine fiber-containing sheet becomes a composite material.
The composite material can be prepared by mixing a polymer emulsion in a fine fiber dispersion and paper making.
Here, the polymer emulsion is an emulsion of a natural polymer or a synthetic polymer, and is a fine polymer particle having a particle diameter of about 0.001 to 10 μm, preferably about 0.01 to 1.0 μm. It is a milky white liquid dispersed in.
The polymer emulsion is sometimes referred to as a polymer latex that is usually produced by emulsion polymerization.
The polymer that can be used as the polymer emulsion is not particularly limited, but polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, poly (meth) acrylic acid alkyl ester polymer, ( (Meth) acrylic acid alkyl ester copolymer, resin emulsion such as poly (meth) acrylonitrile, polyester, polyurethane, natural rubber, styrene-butadiene copolymer, (meth) acrylonitrile-butadiene copolymer, polyisoprene, polychloroprene, Examples thereof include styrene-butadiene-methyl methacrylate copolymer and styrene- (meth) acrylic acid alkyl ester copolymer.
Further, polyethylene, polypropylene, polyurethane, ethylene-vinyl acetate copolymer or the like may be emulsified by a post-emulsification method.

The mixing ratio of the fine fibers and the emulsion is not particularly limited, and the amount of the emulsion is preferably less than 500 parts by mass, more preferably 10 to 200 parts by mass, and more preferably 25 to 100 with respect to 100 parts by mass of the fine fibers. More preferably, it is part by mass.
If the amount of emulsion is not less than the lower limit value, it sufficiently functions as a composite material, and if it is not more than the upper limit value, it is possible to prevent a decrease in peelability from the wire.
As a method for mixing the fine fibers and the emulsion, there is a method in which the polymer emulsion is added to the fine fiber dispersion while stirring with a stirrer.
As the stirring device, an agitator, a homomixer, a pipeline mixer, or the like can be used.

  In addition, the fine fiber-containing sheet may contain a sizing agent, a paper strength enhancer, a filler, and the like, as necessary, as in general paper.

The basis weight of the fine fiber-containing sheet produced in the present invention is 15 g / m ² or more, and preferably 25 g / m ² or more. When the basis weight is less than the lower limit, the thickness is insufficient for the use of a thick sheet. In addition, the basis weight of the fine fiber-containing sheet is preferably 150 g / m ² or less, more preferably 100 g / m ² or less, from the viewpoint of productivity.

<First Embodiment>
1st Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention is described.
(Production equipment for fine fiber-containing sheets)
The manufacturing apparatus used with the manufacturing method of the fine fiber containing sheet | seat of this embodiment is demonstrated.
In FIG. 1, the manufacturing apparatus used with the manufacturing method of the fine fiber containing sheet | seat of this embodiment is shown. The manufacturing apparatus 1 of this embodiment is a continuous paper machine, and includes a dewatering section 10, a drying section 20 provided on the downstream side of the dewatering section 10, and a winding section 30 provided on the downstream side of the drying section 20. It comprises.

[Dehydration section]
The dewatering section 10 is a section that obtains the water-containing web B by dewatering the fine fiber dispersion A.
In the present embodiment, the dehydrating section 10 includes a papermaking wire 11 as a filter medium, an inclined surface dispersion flowing-down means 12 (dispersion supplying means) for supplying the fine fiber dispersion A to the papermaking wire 11, and an inclined surface dispersion. The supply tank 13 for supplying the fine fiber dispersion A to the flow-down means 12, the suction means 14 provided on the lower side of the papermaking wire 11, and the surface of the dispersion supplied on the papermaking wire 11 are scraped. A leveling blade 15, a delivery reel 16 that sends out the papermaking wire 11, and a guide roll 17 that turns the traveling direction of the papermaking wire 11 sent out from the delivery reel 16 are provided.

The papermaking wire 11 is disposed horizontally, and the fine fiber dispersion A is dehydrated by the papermaking wire 11.
As the papermaking wire 11, a porous film (for example, a membrane filter), a plastic wire, a metal wire, a woven or non-woven fabric such as a fine fiber, or paper (for example, fine paper, coated paper, etc.) may be used. Of these, paper is preferred.

The inclined surface dispersion flowing-down means 12 in this embodiment has a liquid reservoir 12a for storing the fine fiber dispersion A and an inclined surface 12b for flowing down the fine fiber dispersion A overflowing from the liquid reservoir 12a. The lower end of the inclined surface 12b is disposed on the papermaking wire 11.
The supply tank 13 has a stirrer 13a that stirs the fine fiber suspension A accommodated therein. In addition, the supply tank 13 is provided with a pipe 13b for supplying the fine fiber suspension A to the liquid reservoir 12a of the inclined surface dispersion liquid flowing-down means 12.
The suction means 14 has a number of suction holes formed on the upper surface thereof, and a vacuum pump (not shown) is connected to the suction holes.

In the dewatering section 10, the paper making wire 11 is sent out from the sending reel 16, the running direction of the paper making wire 11 is turned by the guide roll 17, and it is made to run on the suction means 14 toward the drying section 20. It has become.
Further, the fine fiber dispersion A in the supply tank 13 is supplied to the liquid reservoir 12a of the inclined surface dispersion flowing-down means 12 through the pipe 13b while being stirred by the stirrer 13a.
In addition, the fine fiber dispersion A overflowing from the liquid reservoir 12 a of the inclined surface dispersion flowing-down means 12 can flow down along the inclined surface 12 b and supplied to the upper surface of the papermaking wire 11.
The fine fiber dispersion A supplied to the paper making wire 11 can be dehydrated by sucking the fine fiber dispersion A from the back side of the paper making wire using the suction means 14.
Also, the thickness of the coating film of the fine fiber dispersion A can be adjusted by scraping and leveling the surface of the fine fiber dispersion A supplied to the papermaking wire 11 by the blade 15.

[Drying section]
The drying section 20 is a section for drying the water-containing web B to obtain the fine fiber-containing sheet C.
The drying section 20 in the present embodiment includes a first dryer 21, a second dryer 22 provided on the downstream side of the first dryer 21, and a water-containing web guide roll that guides the traveling direction of the water-containing web B being dried. 23, an endless felt cloth 24 arranged along a part of the outer peripheral surface of the first dryer 21, a felt cloth guide roll 25 for guiding the traveling direction of the felt cloth 24, the first dryer 21 and the first dryer 21. 2 and a hood 26 for accommodating the dryer 22.
The 1st dryer 21 and the 2nd dryer 22 are comprised from the cylinder dryer, and can be heated.
The felt cloth 24 is made endless and is circulated around a felt cloth guide roll 25.

In the drying section 20, the surface of the water-containing web B that has not been in contact with the paper making wire 11 in the dewatering section 10 is wound around and brought into contact with the outer peripheral surface of the heated first dryer 21. . Further, the surface in contact with the papermaking wire 11 in the dewatering section 10 is pressed and supported by a circulating felt cloth 24. Thereby, the water-containing web B is dried by the first dryer 21.
Further, the water-containing web B dried by the first dryer 21 is transferred to the second dryer 22 via a water-containing web guide roll 23.
Further, the surface of the water-containing web B is wound around and brought into contact with about 3/4 of the outer peripheral surface of the heated second dryer 22 so that the water-containing web B is further dried.

[Winding section]
The winding section 30 is a section for separating the fine fiber-containing sheet C from the papermaking wire 11 and winding it.
The winding section 30 in this embodiment includes a pair of separation rollers 31a and 31b for separating the fine fiber-containing sheet C from the paper making wire 11, a take-up reel 32 for winding the fine fiber-containing sheet C, and used paper making. And a collection reel 33 that winds and collects the wire 11 for use. The separation roller 31b is disposed on the papermaking wire 11 side, and the separation roller 31a is disposed on the fine fiber-containing sheet C side.

In the winding section 30, after the papermaking wire 11 and the fine fiber-containing sheet C are sandwiched between the pair of separation rollers 31a and 31b, the fine fiber-containing sheet C is separated from the papermaking wire 11 and the surface of one separation roller 31a It is supposed to be transferred to.
In addition, the fine fiber-containing sheet C separated from the surface of the separation roller 31 a is taken up by the take-up reel 32, and the used paper making wire 11 is taken up by the collection reel 33.

(Method for producing fine fiber-containing sheet)
The manufacturing method of the fine fiber containing sheet | seat of this embodiment using the said manufacturing apparatus 1 is demonstrated. The method for producing a fine fiber-containing sheet of the present embodiment includes a dehydration step of dehydrating the fine fiber dispersion A to obtain a water-containing web B, a drying step of drying the water-containing web B to obtain a fine fiber-containing sheet C, A winding step of winding the fiber-containing sheet C.

[Dehydration process]
In the dehydration step, first, the paper making wire 11 is sent out from the sending reel 16, the running direction of the paper making wire 11 is turned around by the guide roll 17, and it is made to run on the suction means 14 toward the drying section 20.
In addition, the fine fiber dispersion A in the supply tank 13 is supplied to the liquid reservoir 12a of the inclined surface dispersion flowing-down means 12 through the pipe 13b while being stirred by the stirrer 13a. Subsequently, the fine fiber dispersion A overflowing from the liquid reservoir 12 a of the inclined surface dispersion flowing-down means 12 flows down along the inclined surface 12 b and is supplied to the upper surface of the papermaking wire 11.
Next, the surface of the fine fiber dispersion A supplied to the papermaking wire 11 is leveled by the blade 15 to adjust the thickness of the coating film of the fine fiber dispersion A. Further, the water in the fine fiber dispersion A is sucked using the suction means 14 to dehydrate the fine fiber dispersion A on the papermaking wire 11 to obtain the water-containing web B.

Before supplying the fine fiber dispersion A to the papermaking wire 11, the papermaking wire 11 may be impregnated with water in advance to be in a wet state. When the fine fiber dispersion A is discharged onto the papermaking wire 11, the wire may be stretched due to water absorption and wrinkles may be generated. However, if it is previously wetted, the generation of the wrinkles can be prevented.
Examples of means for bringing the papermaking wire 11 into a wet state include a water tank in which the papermaking wire 11 is immersed in water and a water coating apparatus. As the water coating apparatus, a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, a die coater, or the like can be used.

  When the fine fiber-containing sheet C contains a resin, the fine fiber dispersion A may contain a resin emulsion in which particles of a natural resin or synthetic resin having a particle diameter of 0.001 to 10 μm are emulsified in water. . When the fine fiber-containing sheet C contains rubber, the fine fiber dispersion A may contain a rubber emulsion in which particles of natural rubber or synthetic rubber having a particle diameter of 0.001 to 10 μm are emulsified in water. .

The viscosity of the fine fiber dispersion A is 30 to 20000 mPa · s. Here, the viscosity is a value measured according to JIS K7117: 1987. If the viscosity in the fine fiber dispersion A is less than the lower limit, the yield is low, and if it exceeds the upper limit, the texture is impaired. In this embodiment using the inclined surface dispersion flowing-down means 12, the viscosity of the fine fiber dispersion A is preferably 100 to 1000 mPa · s, and more preferably 150 to 850 mPa · s.
The viscosity can be adjusted by the fine fiber content concentration. The viscosity tends to increase as the average fiber diameter of the fine fibers decreases.

The fine fiber content concentration in the fine fiber dispersion A is more than 0.45 mass% and 5.5 mass% or less. When the fine fiber content concentration in the fine fiber dispersion A is not more than the lower limit value, the yield is lowered, and when the upper limit value is exceeded, the texture is impaired.
In the present embodiment using the inclined surface dispersion flowing-down means 12, the fine fiber content concentration in the fine fiber dispersion A is preferably 0.5 to 2.0% by mass, and 0.7 to 1.8% by mass. It is more preferable that

[Drying process]
In the drying step, first, the water-containing web B on the papermaking wire 11 is brought into contact with the outer peripheral surface of the first dryer 21 to evaporate water remaining on the water-containing web B. The evaporated water passes through the pores of the papermaking wire 11 and further passes through the felt cloth 24 to evaporate.
Next, the water-containing web B is brought into contact with the outer peripheral surface of the second dryer 22 to further evaporate water remaining on the water-containing web B. Thereby, the fine fiber containing sheet C is obtained.

[Winding process]
In the winding process, the papermaking wire 11 and the fine fiber-containing sheet C are sandwiched between a pair of separation rollers 31a and 31b, and the fine fiber-containing sheet C is separated from the papermaking wire 11 and transferred to the surface of one separation roller 31a. . Then, the fine fiber-containing sheet C is pulled away from the surface of the separation roller 31 a and taken up by the take-up reel 32. At the same time, the used paper making wire 11 is taken up by the collection reel 33.

(Function and effect)
The method for producing a fine fiber-containing sheet of the above embodiment is a method of continuously making a fine fiber dispersion having both a high viscosity and a fine fiber-containing concentration, and is simple because it is not necessary to laminate thin films. Moreover, by continuously making a high concentration fine fiber dispersion A, the amount of fine fiber dispersion flowing down from the end in the width direction of the paper making wire 11 can be reduced, and the yield can be improved. Furthermore, the texture of the resulting fine fiber-containing sheet C is improved.
Moreover, in the manufacturing method of the said embodiment, since the surface of the fine fiber dispersion liquid A supplied to the papermaking wire 11 is scraped and leveled with the blade 15, the thickness is more easily secured. The texture of the obtained fine fiber-containing sheet C becomes better.

Many of the fine fibers have a specific gravity greater than 1. In the fine fiber dispersion A, the fine fibers settle and the concentration tends to be non-uniform, but the non-uniform concentration contributes to the loss of texture. However, in the above embodiment, since the fine fiber dispersion A is stirred by the stirrer 13a in the supply tank 13 to make the concentration uniform and then supplied to the paper making wire 11 to make paper, The texture is better.
Moreover, even if the fine fiber dispersion liquid has a high concentration and a high viscosity, the fine fiber dispersion liquid A is made to flow down toward the paper making wire 11 using the inclined surface dispersion flow down means 12 as the dispersion supply means. The texture of the resulting fine fiber-containing sheet C becomes better.

Second Embodiment
2nd Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention is described.
(Production equipment for fine fiber-containing sheets)
In FIG. 2, the manufacturing apparatus used with the manufacturing method of the fine fiber containing sheet | seat of this embodiment is shown. The manufacturing apparatus 2 of this embodiment is the same as the manufacturing apparatus 1 used in the first embodiment except that the dispersion supply means is a die coater 18.
Here, the die coater 18 has a head 18b formed with an opening 18a that can discharge the fine fiber dispersion A and expands in the width direction. The fine fiber dispersion liquid A is supplied from the supply tank 13 to the head 18b via the pipe 13b. The width of the opening 18a is substantially equal to the width of the papermaking wire 11. The gap (length in the direction perpendicular to the width direction) of the opening 18a is preferably 0.1 to 3.0 mm, and more preferably 0.2 to 2.0 mm. If the gap of the opening 18a is not less than the lower limit value, the fine fiber dispersion A having a high concentration and high viscosity can be easily discharged, and if the gap is not more than the upper limit value, the thickness can be made appropriate.
For discharging the fine fiber dispersion A, a method of ejecting the fine fiber dispersion A by applying pressure inside the head 18b is applied.

(Method for producing fine fiber-containing sheet)
The manufacturing method of the fine fiber containing sheet | seat of this embodiment using the said manufacturing apparatus 2 is demonstrated. Similarly to the first embodiment, the method for producing the fine fiber-containing sheet of the present embodiment also includes a dehydration step of dehydrating the fine fiber dispersion A to obtain the hydrous web B, and drying the hydrous web B to obtain the fine fiber-containing sheet. A drying step for obtaining C, and a winding step for winding the fine fiber-containing sheet C.
However, the manufacturing method of this embodiment differs from the first embodiment in the method of supplying the fine fiber dispersion A to the papermaking wire 11 in the dehydration step.
That is, in this embodiment, the fine fiber dispersion A in the supply tank 13 is supplied to the head 18b of the die coater 18 through the pipe 13b while being stirred by the stirrer 13a. Next, the fine fiber dispersion A is supplied to the upper surface of the traveling papermaking wire 11 from the opening 18a of the die coater 18, and the water in the fine fiber dispersion A is sucked by the suction means 14 to obtain the water-containing web B. .
And the fine fiber containing sheet | seat C is obtained from the water-containing web B similarly to 1st Embodiment.

Also in this embodiment in which the dispersion supply means is the die coater 18, the viscosity of the fine fiber dispersion A is in the range of 30 to 20000 mPa · s, and in that range is 100 to 15000 mPa · s. It is preferably 500 to 10000 mPa · s, more preferably 1000 to 8000 mPa · s.
Also in this embodiment, the dispersion content concentration of the fine fiber dispersion A is in the range of more than 0.45% by mass and less than 5.5% by mass, and the fine fiber content concentration is within that range. It is preferably 1.0 to 4.5% by mass, and more preferably 1.5 to 4.0% by mass.
If either one of the viscosity and the fine fiber-containing concentration is less than the lower limit, the yield may be lowered, and if either the viscosity or the fine fiber-containing concentration exceeds the upper limit, the texture may be impaired. There is.

(Function and effect)
Also in the method for producing a fine fiber-containing sheet of the above embodiment, since a fine fiber dispersion having both a high viscosity and a fine fiber-containing concentration is continuously formed, a thick fine fiber-containing sheet C can be easily produced and fine. The texture of the fiber-containing sheet C can be improved.
In this embodiment, since the fine fiber dispersion A is applied to the papermaking wire 11 using the die coater 18 as the dispersion supply means, the texture is excellent even if the viscosity and concentration of the fine fiber dispersion A are high. High effect.

<Third Embodiment>
3rd Embodiment of the manufacturing method of the fine fiber containing sheet | seat of this invention is described.
(Production equipment for fine fiber-containing sheets)
In FIG. 3, the manufacturing apparatus used with the manufacturing method of the fine fiber containing sheet | seat of this embodiment is shown. In the manufacturing apparatus 3 of the present embodiment, the drying section 20 and the winding section 30 are the same as the manufacturing apparatus 1 used in the first embodiment, but the dehydrating section 10 is different from the manufacturing apparatus 1 used in the first embodiment. .

In the dewatering section 40 in the present embodiment, the upstream side of the papermaking wire 41 is an inclined portion 41a that is inclined so as to become higher toward the downstream side, and the downstream side is a horizontal portion 41b. The inclination angle of the inclined portion 41a is preferably 0.1 ° or more and 10 ° or less with respect to the horizontal direction, and more preferably 0.2 ° or more and 5 ° or less. The horizontal portion 41b may not be completely horizontal, and may be inclined so that, for example, the downstream side becomes higher.
As the papermaking wire 41 in the present embodiment, the same papermaking wire 11 used in the first embodiment can be used.

In the dewatering section 40, a dam plate 42 is erected so that the fine fiber dispersion A is accumulated above the inclined portion 41a. More specifically, the barrier plate 42 is provided along the longitudinal direction of the papermaking wire 41 at both ends in the width direction of the inclined portion 41a, and the papermaking wire 41 is disposed upstream of the inclined portion 41a. It is provided along the width direction.
In the dewatering section 40, the surface of the fine fiber dispersion A supplied to the papermaking wire 41 on the suction means 44 provided below the papermaking wire 41 and the horizontal portion 41 b of the papermaking wire 41. Are provided with a blade 45 for scraping and a feeding reel 46 for feeding the papermaking wire 41. The suction means 44, the blade 45, and the delivery reel 46 are the same as the suction means 14, the blade 15, and the delivery reel 16 in the first embodiment.

(Method for producing fine fiber-containing sheet)
The manufacturing method of the fine fiber containing sheet | seat of this embodiment using the said manufacturing apparatus 3 is demonstrated. Similarly to the first embodiment, the method for producing the fine fiber-containing sheet of the present embodiment also includes a dehydration step of dehydrating the fine fiber dispersion A to obtain the hydrous web B, and drying the hydrous web B to obtain the fine fiber-containing sheet. A drying step for obtaining C, and a winding step for winding the fine fiber-containing sheet C. However, the manufacturing method of the present embodiment is different from the first embodiment in the dehydration process.
That is, in the dehydration process in the present embodiment, first, the fine fiber dispersion liquid A is supplied and stored in a portion surrounded by the inclined portion 41a and the weir plate 42. Next, the paper making wire 41 is caused to travel from the delivery reel 46 toward the drying section 20, and the fine fiber dispersion A on the inclined portion 41 a is sucked by the suction means 44. Thereby, the fine fiber dispersion A is adhered to the upper surface of the papermaking wire 41. Next, in the horizontal portion 41b, water in the fine fiber dispersion A on the papermaking wire 41 is sucked by the suction means 44, and the surface of the fine fiber dispersion A is smoothed by smoothing with the blade 45. Get web B.
Next, the fine fiber-containing sheet C is obtained from the water-containing web B as in the first embodiment.

(Function and effect)
Even in the method for producing a fine fiber-containing sheet of the above embodiment, since a fine fiber dispersion having both a high viscosity and a fine fiber-containing concentration is continuously produced, a thick fine fiber-containing sheet can be easily produced and has a good texture. Can be.

<Other embodiments>
In addition, this invention is not limited to the said embodiment. For example, the blades 15 and 45 are not provided, and the surface of the fine fiber dispersion A supplied to the papermaking wires 11 and 41 may not be leveled.
In the first embodiment and the second embodiment, the papermaking wire 11 is horizontal, but may be inclined. A support for conveying the papermaking wire 11 to the winding section 30 may be disposed below the papermaking wire 11. Further, the papermaking wire 11 may have an endless belt shape.
In the second embodiment, a pre-weighing type coater such as a curtain coater or a slide bead coater may be used instead of the die coater.
Moreover, the dryer in the drying section in the first to third embodiments may be one, or three or more. Moreover, there is no restriction | limiting in the arrangement | positioning of a dryer.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples, “%” means “mass%”.

(Example 1)
Add water to conifer bleached kraft pulp (manufactured by Oji Paper Co., Ltd., moisture 50%, Canadian standard freeness (CSF) measured in accordance with JIS P8121) to a concentration of 5.0%. After disaggregation, a pulp dispersion was obtained. This pulp dispersion liquid was refined by performing a defibrating process three times using a mass colander manufactured by Masuko Sangyo Co., Ltd. having a grinder portion having a major axis of 250 mm. Next, water was added to dilute the solution to a concentration of about 1%, and the mixture was stirred with a homomixer to obtain a fine fiber dispersion. When the viscosity of this dispersion was measured according to JIS K7117: 1987, it was 263 mPa · s. Moreover, it was 1.03% when the fine fiber content density | concentration was measured according to JISP8225.

The fine fiber containing sheet | seat was manufactured using the manufacturing apparatus 1 shown in FIG.
That is, the fine fiber dispersion A was stored in the supply tank 13 and supplied to the liquid reservoir 12a of the inclined surface dispersion flowing-down means 12 while being stirred by the stirrer 13a. A portion of the fine fiber dispersion A overflowing from the liquid reservoir 12a is caused to flow down along the inclined surface 12b having an inclination angle of 30 °, and on the papermaking wire 11 made of a fabric sheet running at a speed of 0.25 m / min. Supplied to. Next, the fine fiber dispersion A on the papermaking wire 11 was dehydrated by suction from the inner surface side of the papermaking wire 11 using the suction means 14 to obtain a water-containing web B.
The portion for dewatering the dispersion of the papermaking wire 11 was 6.2 m long, and was provided so that the downstream side was higher at an inclination angle of 1.5 °. Further, at the time of the dehydration, the surface of the fine fiber dispersion A was smoothed and smoothed by a blade 15 installed 2 m downstream from the inclined surface dispersion flowing-down means 12.
Subsequently, the hydrous web B was sent to the drying section 20 and dried by the first dryer 21 (set temperature: 150 ° C.) and the second dryer 22 (set temperature: 150 ° C.) to obtain a fine fiber-containing sheet C.
Next, the papermaking wire 11 and the fine fiber-containing sheet C were separated by the separation rollers 31 a and 31 b, the fine fiber-containing sheet C was taken up by the take-up reel 32, and the papermaking wire 11 was taken up by the collection reel 33.

(Examples 2 to 8)
In Examples 2-8, while changing the dilution amount at the time of fine fiber dispersion A preparation, and changing the fine fiber content density | concentration and the viscosity of the fine fiber dispersion liquid A as shown in Table 1, run of the papermaking wire 11 A fine fiber-containing sheet C was produced by the same method as in Example 1 except that the speed was changed as shown in Table 1.

(Comparative Example 1)
In Comparative Example 1, the fine fiber content concentration and the viscosity of the fine fiber dispersion A were changed as shown in Table 1 by changing the dilution amount at the time of preparing the fine fiber dispersion, and fine by the same method as in Example 1. An attempt was made to produce a fiber-containing sheet, but a film of fine fiber dispersion A could not be formed on the papermaking wire 11.

Example 9
In Example 9, the dispersion supplying means of the manufacturing apparatus 1 shown in FIG. 1 is changed to a curtain coater, and the dilution amount at the time of preparing the fine fiber dispersion A is changed to change the fine fiber content concentration and the viscosity of the fine fiber dispersion A. Was changed as shown in Table 1, and a fine fiber-containing sheet C was produced in the same manner as in Example 1 except that the traveling speed of the papermaking wire 11 was changed as shown in Table 1.
That is, the fine fiber-containing sheet C is stored in the same manner as in Example 1 except that the fine fiber dispersion A is stored in the head of the curtain coater from the supply tank 13 and supplied onto the papermaking wire 11 traveling from the opening 18a. Was made. The curtain coater is installed at the same position as the dispersion liquid supply means 12 in FIG. 1, and the dispersion liquid discharged from the curtain coater is applied to the papermaking wire 11 vertically.

(Example 10)
In Example 10, the dilution amount at the time of preparing the fine fiber dispersion A was changed, and the fine fiber content concentration and the viscosity of the fine fiber dispersion A were changed as shown in Table 1 by the same method as in Example 9. A fine fiber-containing sheet C was produced.

(Example 11 and Reference Example 12)
In Example 11 and Reference Example 12, the dilution amount at the time of preparing the fine fiber dispersion A was changed to change the fine fiber content concentration and the viscosity of the fine fiber dispersion A as shown in Table 1, Instead, a fine fiber-containing sheet C was produced in the same manner as in Example 9 except that a die coater was used and the surface was smoothed by the opening of the die without using the blade 15.

( Reference Example 13)
50 parts by mass of the anionic polypropylene resin emulsion (trade name “HITEC P-5800”, manufactured by Toho Chemical Co., Ltd., average particle size 0.15 μm) diluted to a concentration of 1% was added to 50 parts by mass of the fine fiber dispersion A in Example 1. Mixed. Furthermore, 1 part by weight of a cationic coagulant having a concentration of 0.2% (trade name “Fixage 621”, manufactured by Kurita Kogyo Co., Ltd.) was added, and the mixture was stirred with a homomixer for 1 minute. Table 1 shows the concentration and viscosity of the obtained dispersion.
A fine fiber-containing sheet C was obtained in the same manner as in Examples 11 and 12 except that the obtained dispersion was used.

( Reference Example 14)
A fine fiber-containing sheet C was obtained in the same manner as in Examples 11 and 12 except that the fine fiber dispersion obtained without being diluted after the defibrating treatment in Example 1 was used.

(Example 15)
Hardwood kraft pulp (LBKP) was dried at 105 ° C. for 3 hours to obtain a dry pulp having a water content of 3% by mass or less. Next, 4 g of dried pulp and 2 g of maleic anhydride (50 parts by mass with respect to 100 parts by mass of dried pulp) were filled in an autoclave and treated at 150 ° C. for 2 hours. Next, the pulp treated with maleic anhydride was washed with 500 mL of water three times, and then ion-exchanged water was added to prepare 490 mL of slurry.
Then, while stirring the slurry, 10 mL of 4N aqueous sodium hydroxide solution was added little by little to adjust the pH of the slurry to 12 to 13, and the pulp was alkali treated. Thereafter, the pulp after alkali treatment was washed with water until the pH became 8 or less.
Next, ion-exchanged water was added to the pulp after the alkali treatment to prepare a pulp dispersion liquid having a solid content concentration of 2.0% by mass. This pulp dispersion liquid was defibrated for 2 hours under a condition of 7000 rpm using a defibrating apparatus (Cleamix-11S, manufactured by M Technique Co., Ltd.) to obtain a defibrated liquid.
Water was added to dilute the fibrillation solution to a concentration of about 1.5%, and the mixture was stirred with a homomixer to obtain a fine fiber dispersion.
A fine fiber-containing sheet C was obtained in the same manner as in Example 11 except that this fine fiber dispersion was used.

( Reference Example 16 and Comparative Example 2)
In Reference Example 16 and Comparative Example 2, the production apparatus 3 shown in FIG. 3 was used, and the dilution amount at the time of preparing the fine fiber dispersion was changed, and the fine fiber content concentration and the viscosity of the fine fiber dispersion A are shown in Table 1. A fine fiber-containing sheet C was produced by the same method as in Example 1 except for the change as shown.
That is, the fine fiber dispersion A is accumulated on the inclined portion 41a, the paper making wire 41 is caused to travel from the delivery reel 46 toward the drying section 20, and the moisture of the fine fiber dispersion A on the inclined portion 41a is obtained by the suction means 44. The fine fiber dispersion liquid A was adhered to the papermaking wire 41. Next, in the horizontal portion 41b, moisture in the fine fiber dispersion A on the papermaking wire 41 is sucked by the suction means 44, and the surface of the fine fiber dispersion A is smoothed by smoothing with the blade 45. Web B was obtained. Except this, it carried out similarly to Example 1, and produced the fine fiber containing sheet C.

Table 1 shows the measurement results of the basis weight, the yield of fine fibers, and the texture of the obtained fine fiber-containing sheet.
Here, the basis weight of the fine fiber-containing sheet is a value measured according to JIS P8124.
The yield of fine fibers was determined by the formula: (the fine fiber mass in the fine fiber-containing sheet / the fine fiber mass in the fine fiber dispersion supplied to the papermaking wire) × 100 [%].
The texture was evaluated according to the following criteria by visually observing the surface of the obtained fine fiber-containing sheet.
○: The thickness is uniform and the texture is good.
Δ: Although there is a slightly non-uniform thickness, it is in a practical level.
X: Thickness is not uniform and the texture is insufficient.

In Examples 1 to 11 and 15 and Reference Examples 12 to 14 and 16, in which the fine fiber dispersions having the viscosity and the fine fiber content concentration are within the range defined in the invention according to claim 1 of the present application, A fiber-containing sheet could be easily obtained with a high yield. Moreover, despite the thickness, a good texture was obtained.
In Comparative Example 1 in which the viscosity and concentration of the fine fiber dispersion were lower than the range defined in the invention according to claim 1 of the present application, the fine fiber dispersion film could not be formed on the papermaking wire. A sheet was not obtained.
In Comparative Example 2 in which the viscosity and concentration of the fine fiber dispersion were lower than the range defined in the invention according to claim 1 of the present application, a sufficient basis weight could not be obtained, and the yield was low.

  The fine fiber-containing sheet produced according to the present invention is thick and has a separator for a battery, a separator for a capacitor, a filter for a filter membrane, a substrate for an electronic component, a substrate for an optical component, a housing for home appliances, and an electronic device. It can be suitably used for housings, building materials, automobile interior materials and exterior materials.

1, 2, 3 Manufacturing apparatus 10 Dewatering section 11 Paper making wire 12 Inclined surface dispersion liquid flowing means 12a Liquid reservoir 12b Inclined surface 13 Supply tank 13a Agitator 14 Suction means 15 Blade 16 Delivery reel 17 Guide roll 18 Die coater 18a Opening 18b Head 20 Drying section 21 First dryer 22 Second dryer 23 Hydrous web guide roll 24 Felt cloth 25 Felt cloth guide roll 26 Hood 30 Winding section 31a, 31b Separating roller 32 Winding reel 33 Recovery reel 40 Dewatering section 41 Papermaking wire 41a Inclined portion 41b Horizontal portion 42 Weir plate 44 Suction means 45 Blade 46 Delivery reel A Fine fiber dispersion B Hydrous web C Fine fiber containing sheet

Claims (5)

A fine fiber dispersion containing fine fibers having an average fiber diameter of 1 to 1000 nm is dehydrated using a continuous paper machine equipped with a paper making wire and dried to produce a fine fiber-containing sheet having a basis weight of 15 g / m ² or more. A way to
As the fine fiber dispersion, one having a viscosity measured according to JIS K7117: 1987 of 100 to 15000 mPa · s and a fine fiber content concentration of 1.5 to 4.0 % by mass ,
The method for producing a fine fiber-containing sheet, wherein the fine fiber dispersion is supplied onto the papermaking wire using a pre-weighing type coater . The method for producing a fine fiber-containing sheet according to claim 1, wherein the fine fiber dispersion is supplied to the pre-metering type coater while stirring. A fine fiber dispersion containing fine fibers having an average fiber diameter of 1 to 1000 nm is dehydrated using a continuous paper machine equipped with a paper making wire and dried to produce a fine fiber-containing sheet having a basis weight of 15 g / m ² or more. A way to
As the fine fiber dispersion, one having a viscosity measured according to JIS K7117: 1987 of 100 to 1000 mPa · s and a fine fiber content concentration of 0.5 to 2.0 % by mass is used .
The method for producing a fine fiber-containing sheet, characterized in that the fine fiber dispersion is supplied onto the papermaking wire using the following inclined surface dispersion flowing-down means .
(Inclined dispersion liquid flow down means)
A liquid reservoir for storing the fine fiber dispersion; and an inclined surface having a lower end positioned above the papermaking wire, and the fine fiber dispersion overflowing from the liquid reservoir flows down along the inclined surface. Means for feeding to the papermaking wire. The manufacturing method of the fine fiber containing sheet | seat of Claim 3 supplied to the said liquid storage part of the said inclined surface dispersion | distribution liquid flow-down means, stirring fine fiber dispersion .   The method for producing a fine fiber-containing sheet according to any one of claims 1 to 4, wherein the thickness of the fine fiber dispersion supplied to the papermaking wire is scraped and adjusted to adjust the thickness.

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