JP6624589B2 - Manufacturing method of laminated nonwoven fabric - Google Patents

Description

  The present invention relates to a method and an apparatus for manufacturing a laminated nonwoven fabric in which a second nonwoven fabric containing a fiber to which an adhesive is attached is laminated on a first nonwoven fabric serving as a base material.

  Fiber non-woven fabrics are used for various purposes in addition to filter media. In recent years, from the viewpoint of increasing the surface area, it has been studied to use nonwoven fabrics using nanofibers having fiber diameters on the order of nm to sub-μm for various uses such as filter media.

  In Patent Document 1, from the viewpoint of improving the shape retention and handling properties of the ultrafine fiber nonwoven fabric, an electric field is applied to the binder solution to form the binder particles, and the ultrafine fibers formed by electrospinning are brought into contact with the ultrafine fibers. It has been proposed that the microfibers be bonded together. Patent Literature 2 proposes laminating a nonwoven fabric on the surface of a deposition member by applying an electric field to cause an adhesive to adhere to the surface of the deposition member, and further depositing nanofibers.

JP 2008-285793 A JP 2009-263819 A

  In Patent Documents 1 and 2, an electric field is applied to an adhesive solution to disperse the adhesive solution, and the nanofibers are bonded by an adhesive. However, some adhesive solutions tend to gel, and it is necessary to continue stirring the adhesive solution during the manufacturing process of the nonwoven fabric, or to re-dissolve the adhesive using ultrasonic vibration or the like before manufacturing.

  An object of the present invention is to provide a method and a manufacturing apparatus capable of manufacturing a laminated nonwoven fabric by a simple method while suppressing gelation of a solution containing an adhesive.

One aspect of the present invention is a step of preparing a first nonwoven fabric containing a first fiber, and a raw material liquid containing a raw material resin and an adhesive, which are raw materials for a second fiber,
By the electrospinning method, the raw material liquid is discharged from a nozzle to generate second fibers to which the adhesive has adhered, and the second fibers to which the adhesive has adhered are deposited on the first nonwoven fabric. laminating a second nonwoven fabric comprising the second fibrous nonwoven fabric, only including,
Particles of the adhesive are attached to the second fiber,
The second nonwoven fabric and the first nonwoven fabric are bonded via particles of the adhesive,
The average fiber diameter D1 of the first fibers and the average fiber diameter D2 of the second fibers satisfy a relationship of D1> D2,
The present invention relates to a method for producing a laminated nonwoven fabric, wherein an average particle diameter Dp of the particles of the adhesive and an average fiber diameter D1 of the first fibers satisfy a relationship of D1> Dp .

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing a laminated nonwoven fabric by electrospinning, the gelation of the solution containing an adhesive can be suppressed. Since the adhesive can be sprinkled and spun by the action of the electric field, the laminated nonwoven fabric can be manufactured by a simple method.

It is a longitudinal section showing typically the lamination nonwoven fabric obtained by the manufacturing method concerning one embodiment of the present invention. It is a figure showing the example of composition of the manufacturing device of the lamination nonwoven fabric concerning one embodiment of the present invention. It is a figure showing the example of composition of the manufacturing device of the lamination nonwoven fabric concerning another embodiment of the present invention. FIG. 4 is a schematic diagram for explaining pressure bonding using a pair of pressure rollers each having an embossed surface on a peripheral surface. FIG. 4 is a schematic diagram for explaining pressure bonding using a pair of pressure rollers each having an embossed surface on a peripheral surface. It is a perspective view showing typically the air cleaner using the lamination nonwoven fabric obtained by the manufacturing method concerning one embodiment of the present invention. 5 is a scanning electron microscope (SEM) photograph taken from the second nonwoven fabric side in a state where the second nonwoven fabric is laminated on the first nonwoven fabric in Example 1. 5 is an SEM photograph of the third nonwoven fabric peeled off from the laminated nonwoven fabric of Example 1 and taken from the second nonwoven fabric side.

(Production method of laminated nonwoven fabric)
The method for producing a laminated nonwoven fabric according to one embodiment of the present invention includes:
A step (first step) of preparing a first nonwoven fabric containing the first fiber, and a raw material liquid containing a raw material resin and an adhesive which are raw materials for the second fiber;
The raw material liquid is discharged from a nozzle by an electrospinning (electrospinning) method to generate a second fiber to which an adhesive is attached, and the second fiber to which the adhesive is attached is deposited on the first nonwoven fabric, and the first nonwoven fabric is deposited on the first nonwoven fabric. Laminating a second nonwoven fabric containing a second fiber (second step).

  When a solution containing only the adhesive is used for spraying the adhesive, the solution tends to gel. However, in the present embodiment, since the raw material liquid contains the adhesive and the raw material resin, the gelation of the adhesive can be unexpectedly suppressed. Although the reason why the gelation is suppressed is not clear, it is considered that when the raw material liquid contains the raw material resin in addition to the adhesive, crystallization and aggregation of the adhesive are suppressed. As described above, according to the present invention, a laminated nonwoven fabric can be produced while suppressing gelation by a simple method of using a raw material liquid containing an adhesive and a raw material resin as a raw material liquid used for electrospinning.

The method for producing a laminated nonwoven fabric further comprises a step of arranging a third nonwoven fabric containing a third fiber on a main surface of the second nonwoven fabric opposite to the first nonwoven fabric to obtain a laminate (third process); A step (fourth step) of pressing the object in the thickness direction and pressing the second nonwoven fabric and the third nonwoven fabric (and the first nonwoven fabric) to obtain a laminated nonwoven fabric may be included. By laminating the third nonwoven fabric, the second nonwoven fabric can be protected. When laminating the third nonwoven fabric, for example, a third nonwoven fabric containing the third fiber may be prepared in the first step.

  In the laminated nonwoven fabric, it is preferable that the particles of the adhesive adhere to the second fibers, and the second nonwoven fabric and the first nonwoven fabric adhere to each other via the particles of the adhesive. At this time, the average fiber diameter D1 of the first fiber and the average fiber diameter D2 of the second fiber satisfy a relationship of D1> D2, and the average particle diameter Dp of the adhesive particles and the average fiber diameter D1 of the first fiber are Preferably satisfies the relationship of D1> Dp. Since the adhesive particles having a small average particle diameter are attached to the second fibers having a small average fiber diameter, a high adhesive strength can be secured between the second nonwoven fabric and the first nonwoven fabric, and the separation between the nonwoven fabrics can be achieved. Can be suppressed. Further, since the respective nonwoven fabrics are bonded through the adhesive particles having a small average particle size, an increase in pressure loss can be suppressed when the laminated nonwoven fabric is used for a filter medium.

  In addition, the average fiber diameter is an average value of the diameter of the fiber. The fiber diameter is the diameter of a cross section perpendicular to the length direction of the fiber. If such a cross section is not circular, the largest diameter may be considered the diameter. Further, the width in a direction perpendicular to the length direction of the fiber when viewed from the normal direction of one main surface of the nonwoven fabric (or the laminated nonwoven fabric) may be regarded as the diameter of the fiber. The average fiber diameter is, for example, an average value of the diameters of arbitrary positions of arbitrary plural (for example, 10) fibers included in the nonwoven fabric. The fiber diameter can be measured, for example, using an electron micrograph of a nonwoven fabric (or a laminated nonwoven fabric) containing fibers. Thus, the average fiber diameter of each of the first fiber, the second fiber, and the third fiber can be obtained.

  The average particle diameter Dp of the adhesive particles is an average value of the diameter of the adhesive particles. If the cross-sectional shape of the adhesive particles is not circular, the maximum diameter may be regarded as the diameter. Further, the diameter of the adhesive particles when viewed from the normal direction of one main surface of the nonwoven fabric (or the laminated nonwoven fabric) may be regarded as the diameter of the adhesive particles. The average particle diameter Dp is obtained, for example, by measuring the diameter of a plurality of arbitrarily selected (for example, 10) particles in an electron micrograph of a nonwoven fabric containing adhesive particles, and calculating the average value of these diameters. If the particles are not spherical, the largest diameter may be considered the diameter.

  It is preferable that the average particle diameter Dp of the adhesive particles and the average fiber diameter D2 of the second fibers satisfy the relationship of Dp> D2. In this case, even if the amount of the adhesive used is small, a large number of the second fibers can be reinforced at once by the adhesive particles, so that the adhesiveness can be further improved and the separation between the nonwoven fabrics can be easily suppressed.

  Preferably, the second fibers are nanofibers. In this case, the adhesive particles make it easier to bond the nonwoven fabrics to each other, so that the effect of suppressing separation between the nonwoven fabrics is enhanced. Further, an increase in pressure loss can be further suppressed.

The average particle diameter Dp of the adhesive particles may be less than 1 μm, but is preferably 1 μm or more, more preferably 5 μm or more or 10 μm or more. The average particle size Dp is preferably 200 μm or less, more preferably 150 μm or less or 100 μm or less. These lower and upper limits can be arbitrarily combined. The average particle diameter Dp is, for example, 1 to 200 μm, and may be 5 to 150 μm or 10 to 100 μm.
When the average particle diameter Dp of the adhesive particles is in such a range, the separation between the nonwoven fabrics is more easily suppressed.

  A thread-like body of an adhesive may be further attached to the second fiber. The thread may or may not be connected to the adhesive particles. The particulate and filamentous adhesive can be formed by treating the adhesive by an electrospinning method. When the laminated nonwoven fabric includes such a thread-like material in addition to the adhesive particles, it can be said that the adhesive is finely dispersed in the nonwoven fabric. Therefore, at least the amount of the adhesive used is easy to suppress peeling between the nonwoven fabrics. Further, the effect of suppressing an increase in pressure loss can be further enhanced.

  FIG. 1 is a longitudinal sectional view schematically showing a laminated nonwoven fabric obtained by the manufacturing method according to the present embodiment. The laminated nonwoven fabric 10 includes a first nonwoven fabric 1, a second nonwoven fabric 2 laminated on one main surface of the first nonwoven fabric 1, and an adhesive. The laminated nonwoven fabric 10 can include the third nonwoven fabric 3 laminated on the main surface of the second nonwoven fabric opposite to the first nonwoven fabric 1. The first nonwoven fabric 1 includes a first fiber, the second nonwoven fabric 2 includes a second fiber, and the third nonwoven fabric 3 includes a third fiber. An adhesive is attached to the second fiber.

Hereinafter, each step of the manufacturing method will be described more specifically.
(First step)
In the first step, a first nonwoven fabric and the above-mentioned raw material liquid are prepared. If necessary, a third nonwoven fabric may be prepared in the first step.
(1st nonwoven fabric and 3rd nonwoven fabric)
The first nonwoven fabric functions as a base material that holds the shape of the laminated nonwoven fabric. When the laminated nonwoven fabric is pleated, the first nonwoven fabric serves as a base material to maintain the pleat shape. The third nonwoven fabric has a function of collecting relatively large dust and also functions as a protective material for protecting the second nonwoven fabric from various external loads. From the viewpoint of dust collection efficiency, the third nonwoven fabric is preferably subjected to a charging treatment.

  The first nonwoven fabric and the third nonwoven fabric can be prepared by a known method, and the production method is not particularly limited. The first nonwoven fabric and the third nonwoven fabric can be manufactured by, for example, a spun bond method, a dry method (for example, an air laid method), a wet method, a melt blow method, and a needle punch method. The first nonwoven fabric is preferably manufactured by a wet method in that a nonwoven fabric suitable as a substrate is easily formed. The third nonwoven fabric is preferably manufactured by a melt blow method in that a nonwoven fabric having a small fiber diameter suitable as a filter medium is easily formed.

  The first nonwoven fabric includes a first fiber, and the third nonwoven fabric includes a third fiber. The material of the first fiber and the third fiber is not particularly limited, and examples thereof include glass fiber, cellulose, acrylic resin, polyolefin, polyester, and polyamide (PA). Examples of the polyolefin include polypropylene (PP) and polyethylene (PE). Examples of the polyester include polyethylene terephthalate (PET) and polybutylene terephthalate. Each of the first fiber and the third fiber may include one type of these materials, or may include two or more types. As the material of the first fiber, from the viewpoint of shape retention, cellulose, polyester, and / or PA are preferable among these materials. As a material of the third fiber, PP is preferable from the viewpoint of being easily charged.

The average fiber diameter D1 of the first fibers is not particularly limited, and may be, for example, 1 μm or more and 400 μm or less, and may be 5 μm or more and 200 μm or less.
The average fiber diameter D3 of the third fibers is not particularly limited, but is, for example, 0.5 μm or more and 20 μm or less, and 1 μm or more and 20 μm or less.

The pressure loss of the first nonwoven fabric and the third nonwoven fabric is not particularly limited. The initial pressure loss of the first nonwoven fabric is preferably about 1 Pa or more and 10 Pa or less. The pressure loss of the third nonwoven fabric is not particularly limited, but the initial pressure loss of the third nonwoven fabric is preferably about 10 Pa or more and 50 Pa or less. When the initial pressure loss of the first nonwoven fabric and / or the third nonwoven fabric is in these ranges, the pressure loss of the entire laminated nonwoven fabric is also suppressed.
In the present specification, the pressure loss can be measured, for example, using a measuring instrument conforming to the standard of JIS B 9908 type 1.

  The thickness (T1) of the first nonwoven fabric is preferably 50 μm or more and 500 μm or less, and more preferably 150 μm or more and 400 μm or less, from the viewpoint of suppressing an increase in pressure loss as much as possible. The thickness (T3) of the third nonwoven fabric is not particularly limited, and may be 100 μm or more and 500 μm or less, or 150 μm or more and 400 μm or less.

  In addition, in this specification, the thickness of the nonwoven fabric is, for example, an average value of thicknesses measured at arbitrary plural places (for example, 10 places) of the nonwoven fabric in the laminated nonwoven fabric. The thickness of the nonwoven refers to the distance between the two major surfaces of the nonwoven. The thickness of the nonwoven fabric is, specifically, when a line perpendicular to one surface is drawn from an arbitrary point on one main surface of the nonwoven fabric to the other main surface in a cross-sectional photograph of the laminated nonwoven fabric Is determined as the distance between the outer contours of the two fibers at the most distant position among the fibers on this line. The thickness of the nonwoven fabric is similarly measured at other arbitrary points (for example, 9 points), and the numerical value obtained by averaging these values is defined as the thickness of the nonwoven fabric. However, since the thickness of the nonwoven fabric is reduced in the region pressed by the convex portion of the embossed surface, the thickness of the nonwoven fabric is measured in a region other than the region pressed by the convex portion. In calculating the thickness of the nonwoven fabric, a binarized image may be used. Thus, the thickness T1 of the first nonwoven fabric, the thickness T3 of the third nonwoven fabric, and the thickness T2 of the second nonwoven fabric described later can be obtained.

From the viewpoint of reducing the pressure loss as much as possible while ensuring the strength of the laminated nonwoven fabric, the mass per unit area of the first nonwoven fabric is preferably 10 g / m ² or more and 80 g / m ² or less, and 35 g / m 2. It is more preferably ² or more and 60 g / m ² or less. The mass per unit area of the third nonwoven fabric is not particularly limited either, and may be 10 g / m ² or more and 50 g / m ² or less, or 10 g / m ² or more and 30 g / m ² or less.
Note that the mass per unit area may be an average value of the mass per unit area obtained for a region having a predetermined area at a plurality of locations (for example, 10 locations) of the first nonwoven fabric.

(Raw material liquid)
The raw material liquid usually contains a solvent in addition to the raw material resin and the adhesive for the second fiber. The raw material liquid can be prepared by dissolving the adhesive and the raw material resin in a solvent. Since the raw material liquid contains the adhesive and the raw material resin, it is possible to suppress the raw material liquid from gelling due to the adhesive. Also, when the second fibers are deposited and the second nonwoven fabric is laminated, the adhesive is exposed on both the main surface facing the first nonwoven fabric and the main surface opposite to the first nonwoven fabric. In other words, since the adhesive is dispersed on both main surfaces of the second nonwoven fabric, the second nonwoven fabric and the second nonwoven fabric can be used without providing a step of spraying the adhesive before and / or after laminating the second nonwoven fabric. It is easy to increase the adhesive strength with the first nonwoven fabric and / or the third nonwoven fabric. Therefore, the manufacturing process of the laminated nonwoven fabric can be simplified, and the space for the manufacturing apparatus can be saved.

  The type of the adhesive is not particularly limited, and examples thereof include a hot melt adhesive mainly containing a thermoplastic resin. The hot melt adhesive may be either a reactive hot melt adhesive or a non-reactive hot melt adhesive. Specific examples of the hot melt adhesive include an ethylene-vinyl acetate copolymer adhesive, a polyolefin adhesive, a polyester adhesive, a polyamide adhesive, an acrylic adhesive, a polyurethane adhesive, and an elastomer adhesive. And the like. The thermoplastic resin contained in each adhesive may be either a homopolymer or a copolymer. For example, examples of the polyolefin-based adhesive include PE, PP, and an olefin copolymer containing an ethylene unit or a propylene unit. Examples of the polyester-based adhesive include polyalkylene terephthalate such as PET, and modified polyester such as urethane-modified copolymer polyester. One kind of the adhesive may be used alone, or two or more kinds may be used in combination.

  The raw material resin used as the raw material of the second fiber is not particularly limited. For example, PA, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polyacetal (POM), polycarbonate (PC), Ether ether ketone (PEEK), polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyarylate (PAR), polyacrylonitrile (PAN), polyvinylidene fluoride ( (PVDF), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), PP, PET, and polymers such as polyurethane (PU). The polymer may be either a homopolymer or a copolymer. Further, precursors of these polymers may be used as a raw material resin. For example, when the second fiber is made of PI, a PI precursor such as polyamic acid may be used as a raw material resin. These raw material resins may be used alone or in a combination of two or more. When the second fiber is formed by the electrospinning method, PES is preferably used as a raw material resin. PVDF is preferably used as a raw material resin in that the average fiber diameter D2 is easily reduced.

It is desirable that the molecular weight of the raw material resin of the second fiber is larger than the molecular weight of the resin constituting the adhesive. In particular, when the raw material resin of the second fiber and the resin forming the adhesive are of the same type, the molecular weight of the raw material resin is usually larger than the molecular weight of the resin forming the adhesive. In Mw ₂ -Mw _a is preferably 10,000 or more, 20,000 or more, or 50,000: the difference between the weight average molecular weight Mw _a resin constituting the adhesive weight average molecular weight Mw ₂ of the raw material resin of the second fiber There may be.

  The solvent may be appropriately selected depending on the type of the raw material resin and the production conditions. As a solvent, water or an organic solvent is used. Examples of the organic solvent include alcohols, ethers, ketones, esters, carboxylic acids (such as formic acid and acetic acid), nitriles (such as acetonitrile), amides, nitrogen-containing heterocyclic compounds (such as pyridine), sulfoxides (such as dimethyl sulfoxide), and phenol. , Hydrocarbons and the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, hexafluoroisopropanol, tetraethylene glycol, triethylene glycol, dibenzyl alcohol and the like. As the ether, cyclic ethers such as 1,3-dioxolan, 1,4-dioxane, and tetrahydrofuran are preferable. Examples of the ketone include acetone, hexafluoroacetone, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-hexyl ketone, methyl-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, and cyclohexanone. Examples of the ester include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl benzoate, ethyl benzoate, propyl benzoate, dimethyl phthalate, diethyl phthalate, and dipropyl phthalate. . Examples of the amide include N, N-dimethylformamide and N, N-dimethylacetamide (DMAc). Examples of the hydrocarbon include hexane, cyclohexane, cyclopentane, benzene, toluene, xylene o-xylene, p-xylene, and m-xylene. The raw material liquid may contain one kind of these solvents or two or more kinds. An amide such as DMAc is preferred from the viewpoint of easily dissolving the raw material resin such as an adhesive or PES. Amides are also suitable solvents for electrospinning.

  In the first step, the raw material liquid is prepared by mixing a first solution containing an adhesive and a first solvent that dissolves the adhesive, and a second solution containing a raw material resin and a second solvent that dissolves the raw material resin. May be. In this case, the time of the dissolution (preparation) step can be reduced, and a uniform solution can be prepared. The first solution and the second solution can be prepared before the preparation of the raw material liquid. The first solvent and the second solvent may be appropriately selected from the solvents exemplified above according to the types of the adhesive and the raw material resin, respectively. The first solvent and the second solvent may be different. From the viewpoint of obtaining a uniform raw material liquid, the first solvent and the second solvent are preferably compatible with each other, and may contain the same solvent. When the first solvent and the second solvent contain the same solvent, solution preparation and cleaning of the nozzle are also facilitated. In consideration of the ease of electrospinning, it is preferable that each of the first solvent and the second solvent is an amide such as DMAc or a case where the first solvent and the second solvent include an amide such as DMAc.

  The ratio of the solvent in the raw material liquid varies depending on the type of the selected solvent, the type of the adhesive and the type of the raw material resin. The ratio of the solvent in the raw material liquid is, for example, 50% by mass to 95% by mass.

If necessary, a known additive, an anti-gelling agent, and the like may be added to the raw material liquid. An inorganic solid material may be added to the raw material liquid. As the inorganic solid material, for example, an inorganic compound (for example, oxide, carbide, nitride, boride, silicide, fluoride, sulfide) containing a metal and / or a typical nonmetal (B, Si, P, As, etc.) is used. And the like). From the viewpoint of workability and the like, it is preferable to use an oxide. Specific examples of the oxide include Al ₂ O ₃ , SiO ₂ , TiO ₂ , MgO, and CaO. One kind of the inorganic solid material may be used alone, or a plurality of kinds may be used in combination.

  In the present invention, gelation of the raw material liquid can be suppressed, but the degree of gelation of the raw material liquid can be measured by a change in viscosity of the raw material liquid. For example, the rate of increase in the viscosity of the raw material liquid to be subjected to electrospinning (for example, after 5 hours or more from the preparation of the raw material liquid) with respect to the viscosity immediately after the preparation of the raw material liquid (initial viscosity) can be suppressed to 10% or less. it can.

(2nd process)
In the second step, the second fiber to which the adhesive is adhered is deposited by electrospinning the raw material liquid on one main surface of the first nonwoven fabric, and the second nonwoven fabric is laminated. In the electrospinning, a high voltage is applied to the raw material liquid, and the raw material liquid having a charge is discharged from a nozzle to generate the second fiber. At this time, the adhesive is also discharged from the nozzle and adheres to the second fibers. When the second nonwoven fabric is formed by the electrospinning method, the second fibers are concentrated and deposited on the first fibers. Therefore, in addition to the fact that the nonwoven fabrics are easily bonded to each other, the pressure loss is further easily suppressed.

  The second nonwoven fabric includes second fibers having an average fiber diameter D2 smaller than the average fiber diameter D1 of the first fibers, and has a function of capturing dust. The second nonwoven fabric is laminated on one main surface of the first nonwoven fabric.

  The average fiber diameter D2 is preferably 1/10 or less (D2 ≦ D1 / 10) of the average fiber diameter D1, and more preferably D2 ≦ D1 / 100. The average fiber diameter D2 is preferably at least 1/1000 of the average fiber diameter D1 (D1 / 1000 ≦ D2). When the average fiber diameter D2 is in this range, it is easy to further suppress the pressure loss and to increase the dust collection efficiency. Specifically, it is preferable that the average fiber diameter D2 is 30 nm to 3 μm or 30 nm to 1 μm. The second fiber is preferably a nanofiber from the viewpoint of further improving the dust collection efficiency while suppressing the pressure loss. The average fiber diameter D2 of such second fibers is, for example, 30 to 800 nm, and preferably 50 to 800 nm.

  Since the adhesive has a lower spinnability than the raw material resin of the second fiber, the adhesive tends to be in the form of particles rather than in the form of a fine fiber like the second fiber. Therefore, the adhesive may adhere to the second fiber in the form of particles. However, depending on the type of the adhesive, the electrospinning may form, together with the adhesive particles, a thread-like material of the adhesive connected to the adhesive particles such that a thread is pulled from the adhesive particles. Since the adhesive has a lower spinnability than the raw material resin of the second fiber, even if a thread is formed, the fiber diameter thereof is extremely thin as compared with the second fiber. As described above, when the raw material liquid is subjected to the electrospinning treatment, the adhesive is dispersed throughout the second nonwoven fabric, so that the effect of suppressing the separation between the second nonwoven fabric and the first nonwoven fabric (and the third nonwoven fabric) is enhanced. . It is not clear why the spinnability of the adhesive is lower than that of the raw material resin of the second fiber, but the difference in molecular weight between the adhesive (the resin forming the adhesive) and the raw material resin of the second fiber, It is considered that the difference is caused by a difference in solubility of the compound and / or a difference in interaction force between molecules.

  It is desirable that the filament is extremely fine and finer than the second fiber. The average fiber diameter of the filament is, for example, 10 to 200 nm, and may be 10 to 100 nm. The average fiber diameter of the filament can be determined according to the case of the average fiber diameter of the first fibers.

  The raw material liquid is preferably discharged from the nozzle in a direction perpendicular to the surface direction of the first nonwoven fabric. In this case, the spun fibers are prevented from flying up, and are suitable for producing a relatively thin and uniform nonwoven fabric. In addition, the direction perpendicular to the plane direction of the first nonwoven fabric is not only a direction completely perpendicular to the surface but also a direction close to perpendicular (for example, a range of 70 ° to 100 ° with respect to the surface direction of the first nonwoven fabric) ).

  In the second step, if necessary, a solution containing an adhesive is electrospinned on one main surface of the first nonwoven fabric to adhere the adhesive, and then the second nonwoven fabric is laminated as described above. Is also good. Also, after laminating the second nonwoven fabric on the first nonwoven fabric, a solution containing an adhesive is subjected to an electrospinning treatment to cause the adhesive to adhere to the main surface of the second nonwoven fabric on the side opposite to the first nonwoven fabric. Then, a third nonwoven fabric may be further laminated in the next step. In these cases, peeling of the second nonwoven fabric from the first nonwoven fabric or the third nonwoven fabric can be further suppressed. Further, in the electrospinning treatment, the solvent is removed in the process of attaching the adhesive to the nonwoven fabric, so that there is no need to provide a separate solvent removal step.

  In addition, when the adhesive is subjected to electrospinning treatment, adhesive particles having a small particle diameter are easily obtained, so that the adhesive can be finely and evenly dispersed. Further, when the adhesive is subjected to the electrospinning treatment, the adhesive particles are easily concentrated on the fiber. Therefore, the effect of suppressing the pressure loss can be further enhanced while securing the adhesive strength between the nonwoven fabrics.

  The thickness T2 of the second nonwoven fabric is preferably 0.5 μm or more and 50 μm or less (or 10 μm or less), more preferably 1 μm or more and 5 μm or less, from the viewpoint of minimizing pressure loss. The initial pressure loss of the second nonwoven fabric is preferably about 5 Pa or more and about 40 Pa or less.

Mass per unit area of the second nonwoven fabric, while ensuring a low pressure loss, a further enhanced easily viewpoint of dust collection efficiency, it is preferable that 0.05 g / m ² or more and 8 g / m ² or less, 0 More preferably, it is not less than 0.5 g / m ^{2 and not} more than 7 g / m ² .
As described above, even when a relatively thick (or large mass per unit area) second nonwoven fabric is used, the adhesive (particularly, the adhesive particles having a small average particle size) adheres to the second fibers. This makes it easier to suppress separation between the nonwoven fabrics.

  In the laminated nonwoven fabric, the nonwoven fabrics constituting each layer are bonded to each other with an adhesive. However, when the adhesive strength is increased, the pressure loss generally increases in filter media applications such as air cleaners. Further, when the mass per unit area of the nonwoven fabric increases, it becomes more difficult to increase the adhesive strength between the respective layers. Even in such a case, if a large amount of adhesive is used to increase the adhesive strength, the mass of the laminated nonwoven fabric increases, and the adhesive spills out in the process of manufacturing the laminated nonwoven fabric. Further, when the nonwoven fabric is peeled off, the dust collection efficiency is significantly reduced when the laminated nonwoven fabric is used as a filter medium. In the laminated nonwoven fabric, when the adhesive particles are adhered to the second fibers, the second nonwoven fabric and the first nonwoven fabric and / or the third nonwoven fabric can be bonded via the adhesive particles. In this case, since the nonwoven fabrics can be bonded to each other by using the point bonding of the adhesive particles, the pressure loss of the laminated nonwoven fabric can be suppressed while the separation between the nonwoven fabrics is suppressed.

The average mass of the adhesive that adheres to the laminated nonwoven fabric is not particularly limited, either, but from 0.5 g / m ² or more and 15 g / m ² or less from the viewpoint of easily obtaining high adhesiveness while reducing pressure loss. Is preferably 1 g / m ² or more, and more preferably 10 g / m ² or less, and particularly preferably 3 g / m ² or more and 9 g / m ² or less.

(3rd step)
In the third step, a third nonwoven fabric is further arranged on the second nonwoven fabric laminated on the first nonwoven fabric to obtain a laminate. The third nonwoven fabric is laminated on the other main surface of the second nonwoven fabric (the main surface opposite to the first nonwoven fabric).

  In the third step, if necessary, the adhesive may be melted by heating before placing the third nonwoven fabric on the second nonwoven fabric. By temporarily melting the adhesive in the third step, the third nonwoven fabric is easily arranged, and the adhesive is prevented from dropping. In particular, when a pressure-bonded member having an embossed surface is used in the fourth step described below, the adhesive that has not been pressed by the convex portion of the embossed surface is likely to fall off, but the adhesive is temporarily melted in the third step. Also, the falling off of the adhesive is suppressed in the subsequent steps.

  The heating of the adhesive can be performed using, for example, a heater. The heating is preferably performed under the condition that the fibers (first fiber and second fiber) constituting the nonwoven fabric are not melted while the adhesive is melted. Therefore, the heating temperature and the heating time may be appropriately selected according to the type of the adhesive, the material of the first fiber and the second fiber, and the like.

  When heating the adhesive in the third step, it is sufficient to heat at least the second nonwoven fabric side, but if the heating is performed so as to melt the entire adhesive contained in the laminate of the first nonwoven fabric and the second nonwoven fabric, It is effective in increasing the adhesiveness between the nonwoven fabrics. Heating may be performed so that the temperature of the main surface of the second nonwoven fabric opposite to the first nonwoven fabric is, for example, 100 to 200C, preferably 120 to 170C.

(4th process)
In the fourth step (press bonding step), the laminate obtained in the second step and the laminate obtained in the third step are pressed in the thickness direction to press the nonwoven fabrics together. By performing pressure bonding, a laminated nonwoven fabric can be obtained. When the laminate is pressed in the fourth step with the adhesive melted in the third step, the second nonwoven fabric, the first nonwoven fabric and / or the third nonwoven fabric are bonded via the melted adhesive. . In the fourth step, pressure bonding may be performed under heating as needed. When the third nonwoven fabric is disposed without melting the adhesive in the third step, it is preferable to perform heating in the fourth step. In the case where heating is performed in the fourth step without melting the adhesive in the third step, a heater and a melting step for melting the adhesive can be omitted in the third step, so that the steps can be simplified and the apparatus can be simplified. Space can be saved.

The pressure bonding can be performed using a known pressure bonding member such as a roller. In the fourth step, for example, the second nonwoven fabric and the first nonwoven fabric (and the third nonwoven fabric) are bonded via an adhesive by sandwiching the laminate between a pair of pressure rollers and applying pressure with the rollers. .
When performing pressure bonding under heating, the heating temperature is, for example, 40 to 200 ° C. In the case of pressing with a roller, the pressing can be performed under heating by using a heatable roller. Examples of the heatable roller include a roller having a built-in heater and a roller heatable from a connected heater.

  The main surface (peripheral surface in the case of a roller) of the crimping member that comes into contact with the laminate may be a smooth surface. Further, the pressure bonding member may include an embossed surface having a convex portion. In the roller, the peripheral surface of the roller constitutes an embossed surface. The peripheral surface of one of the pair of rollers may be an embossed surface, or the peripheral surface of each of the rollers may be an embossed surface.

  In the fourth step, when pressure bonding is performed by pressing the laminate in the thickness direction on the embossed surface of the pressure-bonding member, a part of a part of the adhesive particles included in the laminate is formed by the convex portion of the embossed surface. The fibers are pressed to form streak-like depressions, thereby forming first particles. Then, the second nonwoven fabric and the first nonwoven fabric and / or the third nonwoven fabric are bonded via the first particles. The remaining adhesive particles are present as second particles as they are without forming streak-like depressions at positions facing the regions other than the convex portions of the embossed surface. That is, in the laminated nonwoven fabric, the adhesive particles can include first particles having streak-like depressions and other second particles. In each of the first particles, at least a part of the region of the particles may be crushed, or the whole particles may be crushed.

Thus, the streak-like depression of the first particle is a fiber mark formed by pressing the fiber (first fiber, second fiber, and / or third fiber) against the adhesive particles. It is preferable that the fiber is embedded in the streak-like recess. By pressing the fiber, the first particles may be in a state of being crushed and spread.
When the adhesive particles include the first particles and the second particles, the average particle diameter Dp of the adhesive particles is calculated for the second particles.

  Even when it is difficult to bond the nonwoven fabrics by pressure bonding because the particle size of the adhesive particles is small, the fibers are embedded in a part of the adhesive particles by pressing with a pressure bonding member having an embossed surface, so that the first particles are formed. Formed, whereby the adhesion between the nonwoven fabrics can be ensured. On the other hand, if pressure bonding is performed with a strong pressure using a smooth pressure bonding member, the nonwoven fabrics can be bonded to each other even if the particle size of the adhesive particles is small. However, when many adhesive particles are crushed and spread, the pressure loss of the laminated nonwoven fabric tends to increase. When pressure bonding is performed with a pressure bonding member having an embossed surface, a part of the adhesive particles remains as the second particles, so that the pressure loss can be more easily suppressed.

  On the embossed surface, the shape and distribution of the projections are not particularly limited. For example, the projections may be in a state in which a plurality of point-shaped projections are dispersed, or in a state in which a plurality of linear or band-shaped projections are arranged. The arrangement of the linear or band-shaped convex portions is not particularly limited, and may be, for example, a stripe shape or a zigzag shape. For example, a belt-shaped sheet may be wound around the peripheral surface of the roller to form the convex portion, or the convex portion may be formed by cutting the peripheral surface of the roller. The point-shaped protrusions may be, for example, prismatic, cylindrical, or elliptical. In addition, the convex portions may be formed in a lattice shape or a net shape.

  The material of the pressure-bonding member such as a roller is not particularly limited as long as it has a hardness required for pressure-bonding, and for example, a known material used for a pressure-bonding member such as a resin, a metal, and a ceramic is used. A portion of the pressure-bonding member that comes into contact with the laminated nonwoven fabric (for a roller, at least a peripheral surface or a convex portion on an embossed surface) may be formed of these materials.

Since the second nonwoven fabric and the first nonwoven fabric (and the third nonwoven fabric) are respectively bonded via the first particles having the streak-like dents (or crushed and spread), high bonding strength can be secured. On the other hand, the pressure loss can be further suppressed because the second particles remain. For use as a filter medium, the number n ₂ of the second particles is preferably larger than the number n ₁ of the first particles. In order to satisfy n ₂ > n ₁ , for example, the area of the other area may be larger than the area of the convex area on the embossed surface. The ratio to the number n ₁ of the first particle number n ₂ of the second particles: n ₂ / n ₁ is preferably 1.1 to 10, more preferably from 1.2 to 5. When the ratio: n ₂ / n ₁ is in such a range, it is easy to balance the adhesive strength and the pressure loss.

As the n ₁ and n _2, in the electron micrograph of the laminated nonwoven fabric, a predetermined area (e.g., vertical 1 mm × horizontal 1 mm, vertical 10 mm × horizontal 10 mm, the size of the vertical 50 mm × horizontal 50 mm) was measured for any region of what is available, it may also be used in terms of the values of n ₁ and n ₂ in the entire laminated nonwoven fabric. Further, an average value of values measured for a plurality of arbitrary regions may be used.

From the viewpoint of easily adjusting the ratio n ₂ / n ₁ , the ratio of the total area S ₂ of the other areas to the total area S ₁ of the convex areas on the embossed surface: S ₂ / S ₁ is, for example, 1.1 to 10, preferably 1.2 to 5.
In addition, from the viewpoint of easily increasing the adhesiveness, the height of the convex portion on the embossed surface is preferably from 100 to 5000 μm, more preferably from 200 to 1000 μm.

In the laminated nonwoven fabric, to the total area s ₁ of the pressed region projections of the embossed surface, the ratio of the total area s ₂ in the other regions: s ₂ / s _1, for example, be from 1.1 to 10 , 1.2 to 5. In the laminated nonwoven fabric, the average thickness of the region pressed by the convex portion of the embossed surface of the third nonwoven fabric is, for example, 50 to 95% of the thickness T3 of the third nonwoven fabric measured in a region other than this region. Yes, it is preferably 60 to 80%. When the ratio s ₂ / s ₁ and / or the average thickness of the region pressed by the convex portion of the third nonwoven fabric is in such a range, it is easy to increase the adhesive strength between the nonwoven fabrics while suppressing the pressure loss.

  The laminated nonwoven fabric thus obtained has a high adhesive strength between the second nonwoven fabric and the first nonwoven fabric (and the third nonwoven fabric), and the peeling is suppressed. In the laminated nonwoven fabric, the peel strength between the second nonwoven fabric and each of the first nonwoven fabric and the third nonwoven fabric is, for example, 50 to 300 mN / 25 mm when measured by a method based on JISZ0237.

(Laminated nonwoven fabric manufacturing equipment)
The laminated nonwoven fabric can be manufactured by, for example, a manufacturing apparatus that conveys the first nonwoven fabric from upstream to downstream of the production line and stacks the second nonwoven fabric on the main surface of the conveyed first nonwoven fabric. Such a manufacturing apparatus accommodates, for example, (1) a first nonwoven fabric supply unit that supplies a first nonwoven fabric to a manufacturing line, and (2) a raw material liquid containing a raw material resin that is a raw material of a second fiber and an adhesive. (2) A second fiber is generated by electrospinning the raw material liquid supplied from the tank, and the second fiber to which the adhesive is attached is deposited on the first nonwoven fabric, and the second nonwoven fabric is applied to the first nonwoven fabric. An electrospinning mechanism for stacking. When laminating the third nonwoven fabric on the second nonwoven fabric, the manufacturing apparatus further includes (4) a third nonwoven fabric supply unit for supplying the third nonwoven fabric to the second nonwoven fabric. Further, the manufacturing apparatus may include (5) a pressure bonding section for pressing the second nonwoven fabric and the first nonwoven fabric (and / or the third nonwoven fabric).

  Hereinafter, an apparatus for producing a laminated nonwoven fabric will be described with reference to FIG. 2, but the following apparatus does not limit the present invention. FIG. 2 is a diagram schematically illustrating a configuration of an example of a manufacturing apparatus of the laminated nonwoven fabric 10. The manufacturing device 200 includes a manufacturing line for manufacturing the laminated nonwoven fabric 10.

  First, the first nonwoven fabric 1 is prepared. In the manufacturing device 200, the first nonwoven fabric 1 is transported from upstream to downstream of the manufacturing line. At the uppermost stream of the manufacturing apparatus 200, there is provided a first nonwoven fabric supply unit 201 in which the first nonwoven fabric 1 wound in a roller shape is accommodated. The first nonwoven fabric supply unit 201 rotates the supply reel 12 by the motor 13 and supplies the first nonwoven fabric 1 wound on the supply reel 12 to the transport roller 11 of the production line.

  The first nonwoven fabric 1 is transported by the transport rollers 11 to an electrospinning apparatus 202 including an electrospinning unit (not shown). The electrospinning mechanism included in the electrospinning unit is provided with an emitter 23 for discharging a raw material liquid containing a raw resin and an adhesive of the second fiber, which is installed at an upper part in the apparatus; And a conveyor 21 that conveys the first nonwoven fabric 1 from the upstream side to the downstream side, which is disposed so as to face the emitter 23. The transport conveyor 21 functions as a collector for collecting the second fibers 2F together with the first nonwoven fabric 1. The number of electrospinning units is not particularly limited, and may be one or two or more.

  In the case where there are a plurality of electrospinning units and / or emission bodies 23, if necessary, the average fiber diameter of the second fibers 2F formed may be changed for each electrospinning unit or for each emission body 23. good. The average fiber diameter of the second fibers 2F is changed by adjusting the discharge pressure of the raw material liquid, the applied voltage, the concentration of the raw material liquid, the distance between the emitter 23 and the first nonwoven fabric 1, the temperature, the humidity, and the like, which will be described later. be able to. The deposition amount of the second fiber 2F is controlled by adjusting the discharge pressure of the raw material liquid, the applied voltage, the concentration of the raw material liquid, the transport speed of the first nonwoven fabric 1, and the like.

  A plurality of discharge ports (not shown) for the raw material liquid are provided on the side of the discharge body 23 facing the main surface of the first nonwoven fabric 1. The distance between the discharge opening of the discharge body 23 and the first nonwoven fabric 1 depends on the scale of the manufacturing apparatus and the desired fiber diameter, but may be, for example, 100 to 600 mm. The emission body 23 has its own longitudinal direction set by the second support 25 extending downward from the first support 24 parallel to the transport direction of the first nonwoven fabric 1 and installed above the electrospinning unit. Is supported so as to be parallel to the main surface. The first support 24 may be movable so that the emission body 23 swings in a direction perpendicular to the direction in which the first nonwoven fabric 1 is transported.

  The charging means includes a voltage application device 26 for applying a voltage to the emitter 23 and a counter electrode 27 installed in parallel with the conveyor 21. The counter electrode 27 is grounded. Thereby, a potential difference (for example, 20 kV to 200 kV) corresponding to the voltage applied by the voltage applying device 26 can be provided between the emitter 23 and the counter electrode 27. The configuration of the charging unit is not particularly limited. For example, the counter electrode 27 may be negatively charged. Instead of providing the counter electrode 27, the belt portion of the conveyor 21 may be formed of a conductor.

  The discharge body 23 is formed of a conductor, has an elongated shape, and has a hollow interior. The hollow portion serves as a storage portion for storing the raw material liquid 22. The raw material liquid 22 is supplied from the raw material liquid tank 29 to the hollow of the discharge body 23 by the pressure of the pump 28 communicating with the hollow part of the discharge body 23. Then, the raw material liquid 22 is discharged from the discharge port toward the main surface of the first nonwoven fabric 1 by the pressure of the pump 28. Since the raw material liquid 22 stored in the raw material liquid tank 29 contains the adhesive 4 and the raw material resin that is the raw material of the second fiber 2, gelation of the raw material liquid is suppressed. Therefore, the electrospinning can be stably performed.

  The raw material liquid 22 discharged from the discharge port causes an electrostatic explosion while moving in a space (generation space) between the discharge body 23 and the first nonwoven fabric 1 in a charged state, and generates a fibrous material (second fiber). 2F). At this time, the adhesive is also discharged from the outlet and adheres to the surface of the second fiber 2F. The adhesive that adheres to the second fibers 2F is preferably in the form of adhesive particles (and a thread of the adhesive). Then, the generated second fibers 2F and the adhesive attached to the second fibers 2F are deposited on the first nonwoven fabric 1 to form the second nonwoven fabric 2.

  The electrospinning mechanism for forming the second fibers 2F to which the adhesive is attached is not limited to the above configuration. In the predetermined fiber generation space, the second fibers 2F and the adhesive particles (and the filaments) are generated from the raw material liquid 22 by electrostatic force, and the generated second fibers 2F and the adhesive particles (and the filaments) are removed. Any mechanism that can be deposited on the main surface of one nonwoven fabric 1 can be used without particular limitation. The nozzle is not particularly limited, and may be, for example, a V-shaped nozzle or a needle-type nozzle in which the shape of the cross section perpendicular to the longitudinal direction of the emitter gradually decreases from the top to the bottom.

  When laminating the third nonwoven fabric 3 on the second nonwoven fabric 2, the adhesive may be melted by the heating device 204 having the heater 42 before lamination. In the heating device 204, the solvent contained in the second nonwoven fabric 2 is also removed. The manufacturing apparatus 200 does not necessarily need to include the heating device 204. However, when the manufacturing device 200 includes the heating device 204, the adhesive strength between the nonwoven fabrics is easily increased, and the adhesive is prevented from dropping in a subsequent process. it can.

  Next, the second nonwoven fabric 2 laminated on the first nonwoven fabric 1 is transported to the third nonwoven fabric laminating device 205. In the third nonwoven fabric laminating apparatus 205, the third nonwoven fabric 3 is supplied to the main surface of the second nonwoven fabric 2 from above. When the third nonwoven fabric 3 is long, the third nonwoven fabric 3 may be wound around a reel 52, similarly to the first nonwoven fabric 1. In this case, the third nonwoven fabric 3 is disposed on the main surface of the second nonwoven fabric 2 while being unwound from the reel 52.

  After arranging the third nonwoven fabric 3 on the main surface of the second nonwoven fabric 2, the obtained laminate is sandwiched and pressed by a crimping portion having a pair of pressure rollers 53 (53 a and 53 b) arranged vertically. As a result, the second nonwoven fabric 2 and the first nonwoven fabric 1 and the third nonwoven fabric 3 are bonded to each other via the adhesive particles (and the filaments), and the laminated nonwoven fabric 10 is formed.

  Lastly, the laminated nonwoven fabric 10 is carried out from the third nonwoven fabric laminating device 205, and is conveyed via the rollers 61 to the collection device 206 arranged further downstream. The collecting device 206 includes, for example, a collecting reel 62 that winds up the conveyed laminated nonwoven fabric 10. The collection reel 62 is driven to rotate by a motor 63. In the case where the third nonwoven fabric 3 is not laminated, the second nonwoven fabric 2 laminated on the first nonwoven fabric 1 may be pressed by the crimping section.

  Before forming the second nonwoven fabric 2, the first nonwoven fabric 1 may be transported to an adhesive spraying device as necessary. In the adhesive spraying device, the adhesive is sprayed from above the first nonwoven fabric 1. The adhesive may be sprayed, for example, by a spray method, free fall, or the like, but is applied to the main surface of the first nonwoven fabric 1 by an electrospinning method using a device similar to or similar to the electrospinning device 202. Is also good. Similarly, after forming the second nonwoven fabric 2, the second nonwoven fabric 2 laminated on the first nonwoven fabric 1 may be conveyed to an adhesive spraying device as needed. When a plurality of electrospinning devices 202 are provided, an adhesive spraying device may be provided between the plurality of electrospinning devices 202.

  FIG. 3 is a schematic view showing another configuration example of the manufacturing apparatus of the laminated nonwoven fabric. The manufacturing apparatus in FIG. 3 includes an adhesive spraying device 203 before and after the electrospinning device 202 in addition to the configuration in FIG. The adhesive dispersing device 203 may be provided either before or after the electrospinning device 202. In the adhesive spraying device 203, the adhesive 4 is sprayed using the adhesive solution 32 by an electrospinning method according to the same principle as the electrospinning device 202. Note that a known additive, an anti-gelling agent, and the like may be added to the adhesive solution.

  The first nonwoven fabric 1 is transported by the transport roller 11 to the adhesive spraying device 203. The electrospinning mechanism provided in the adhesive dispersing device 203 includes a discharging member 33 for discharging an adhesive solution 32 containing an adhesive and a solvent, which is installed above the device, and the discharged adhesive solution 32 being positive. The charging device includes a charging unit for charging, and a transport conveyor 31 that is arranged to face the emitter 33 and transports the first nonwoven fabric 1 from the upstream side to the downstream side. The number of the emitters 33 is not particularly limited, and may be one or two or more. A plurality of discharge ports (not shown) for the adhesive solution are provided on the side of the discharge body 33 facing the main surface of the first nonwoven fabric 1. The emission body 33 has a longitudinal direction of itself and a main surface of the first nonwoven fabric 1 by a second support body 35 that extends downward from a first support body 34 that is installed above and that is parallel to the transport direction of the first nonwoven fabric 1. It is supported to be parallel. The first support 34 may be movable so as to swing the discharge body 33 in a direction perpendicular to the direction in which the first nonwoven fabric 1 is transported.

  The charging unit includes a voltage application device 36 that applies a voltage to the emitter 33 and a counter electrode 37 that is installed in parallel with the conveyor 31. The counter electrode 37 is grounded. Instead of providing the counter electrode 37, the belt portion of the conveyor 31 may be formed of a conductor. The discharge body 33 is formed of a conductor, has a long shape, and has a hollow inside. The hollow part becomes a storage part that stores the adhesive solution 32. The adhesive solution 32 is supplied from the adhesive solution tank 39 to the center of the discharge body 33 by the pressure of a pump 38 communicating with the hollow portion of the discharge body 33. The adhesive solution 32 is discharged from the discharge port toward the main surface of the first nonwoven fabric 1 by the pressure of the pump 38. The released adhesive solution 32 becomes particles of the adhesive 4 while moving in a space (generation space) between the emitter 33 and the first nonwoven fabric 1 in a charged state. At this time, a thread-like body of the adhesive 4 may be formed. The generated particles of the adhesive 4 (and the filaments of the adhesive 4) adhere to the main surface of the first nonwoven fabric.

The adhesive dispersing device 203 disposed after the electrospinning device 202 is configured such that the adhesive 4 is sprayed on the main surface of the second nonwoven fabric 2 laminated on the first nonwoven fabric 1 supplied from the electrospinning device 202. , The same as the case where it is arranged before the electrospinning device 202.
In the adhesive solution tank 39 and the raw material liquid tank 29, the adhesive 4 may be suppressed from gelling by continuously or completely stirring the adhesive solution 32 and the raw material liquid 22.

  When the size of the adhesive particles is small and the peripheral surface of the pressure roller (pressure bonding member) of the pressure bonding portion is a smooth surface, it may be difficult to increase the adhesive strength. In addition, when pressure is applied under high pressure to increase the adhesive strength, the pressure loss tends to increase. In such a case, by using a pressure-bonded member having an embossed surface, it is possible to further increase the adhesive strength between the nonwoven fabrics while suppressing pressure loss. In the case of a pressure roller, an embossed surface may be provided on the peripheral surface. An embossed surface may be provided on one of the pair of pressure rollers, or an embossed surface may be provided on both rollers.

  4 and 5 are schematic diagrams for explaining pressure bonding using a pressure roller having an embossed surface on a peripheral surface. FIG. 4 shows that, of the pair of pressure rollers, one roller 153a has an embossed surface having a plurality of protrusions 154 formed on the peripheral surface, and the peripheral surface of the other roller 153b is a smooth surface. I have. FIG. 4 shows an example in which the upper roller 153a has an embossed surface. However, the present invention is not limited to this case, and the embossed surface may be provided only on the lower roller. FIG. 5 shows an example in which an embossed surface is arranged on both peripheral surfaces of a pair of rollers 253a and 253b. Each embossed surface of the rollers 253a and 253b has a plurality of convex portions 254.

  Crimping can be performed under heating. In the case of heating, it is efficient to perform pressure bonding with a heated roller. A heatable roller may be used as one of the pair of rollers, or a heatable roller may be used for both. When a roller having an embossed surface and a roller having a smooth peripheral surface are used, any of the rollers may be heatable. From the viewpoint of efficiently embedding the fibers into the adhesive particles, it is advantageous to use a heatable roller as the roller having the embossed surface. From the viewpoint of easily increasing the bonding strength, when the heating device 204 is not used, it is advantageous to perform the pressure bonding under heating.

(Air cleaner)
The laminated nonwoven fabric obtained by the production method of the present invention is particularly suitable for use as a filter medium for an air purifier. FIG. 6 illustrates an air cleaner provided with a laminated nonwoven fabric. As illustrated in FIG. 6, the air purifier 100 includes a gas suction unit 101, a gas discharge unit 102, a laminated nonwoven fabric 10 disposed between the gas suction unit 101 and the gas discharge unit 102, Is provided. The laminated nonwoven fabric 10 may be pleated and arranged in a bellows shape. The laminated nonwoven fabric 10 is a filter medium that captures dust in the atmosphere. The air purifier provided with the laminated nonwoven fabric 10 has a small pressure loss and is excellent in dust collection efficiency. In terms of dust collection efficiency, the laminated nonwoven fabric 10 is preferably disposed between the suction unit 101 and the discharge unit 102 such that the second nonwoven fabric 3 is located on the suction unit 101 side.

  The air cleaner 100 takes in the outside air from the suction unit 101 into the air cleaner 100. The dust contained in the captured air is captured while passing through the laminated nonwoven fabric 10 and the like, and the purified air is released from the discharge unit 102 to the outside. The air purifier 100 may further include a pre-filter 103 and the like between the suction unit 101 and the laminated nonwoven fabric 10 for capturing large dust and the like. Further, a deodorizing filter 104, a humidifying filter (not shown), and the like may be provided between the laminated nonwoven fabric 10 and the discharge section 102.

  Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

(Example 1)
A laminated nonwoven fabric was produced by the following procedure.
First, a DMAc solution (first solution) containing 20% by mass of an adhesive (polyester-based hot melt resin, melting point: about 100 ° C.) and a DMAc solution (second solution) containing PES at a concentration of 20% by mass Were mixed at a mass ratio of 1: 1 to prepare a raw material liquid for electrospinning treatment. The viscosity at 25 ° C. of the raw material liquid immediately after preparation was measured with a B-type viscometer and found to be 21 Pa · s. Similarly, the viscosity at 25 ° C. of the raw material liquid 8 hours after the preparation was measured, and was 22 Pa · s. The viscosity was almost unchanged from immediately after the preparation and gelation was suppressed.

Next, a first nonwoven fabric (thickness: 300 μm, D1: 15 μm, mass per unit area: 42 g / m ² ) formed of cellulose fiber, polyester fiber, and acrylic fiber was prepared.

The raw material liquid is subjected to electrospinning treatment using a manufacturing apparatus as shown in FIG. 2 to generate second fibers to which the adhesive particles and the adhesive thread are attached, and to deposit them on the first nonwoven fabric to be conveyed. Was. Thus, the second nonwoven fabric was laminated on the first nonwoven fabric. The average fiber diameter D2 of the obtained second fibers was 273 nm, and the average mass per unit area was 0.93 g / m ² .

  FIG. 7 shows an SEM photograph taken from the second nonwoven fabric side. As shown in FIG. 7, adhesive particles are attached to the second fibers, and a thread-like body of the adhesive formed to draw a thread can be observed.

Next, after the surface of the second nonwoven fabric is heated to 158 ° C. from the second nonwoven fabric side, a melt-blown nonwoven fabric mainly composed of polypropylene fibers (thickness: 165 μm, D3: 5 μm, unit) as the third nonwoven fabric from the second nonwoven fabric side (Mass per area: 18 g / m ² ). The obtained laminate was supplied between a pair of pressure rollers and pressed in the thickness direction to be pressed to obtain a laminated nonwoven fabric. As one of the pair of pressure rollers, a roller having an embossed surface having a plurality of convex portions (a cylindrical shape having a diameter of 5 mm × a height of 1 mm, a distance between adjacent convex portions of 10 mm) on a peripheral surface was used. The pressure for pressure bonding was 10 kPa.

  A 30 cm square sample was cut out from the obtained laminated nonwoven fabric and folded into a pleated shape (pleated width: 2.5 cm). Next, the laminated nonwoven fabric was spread, and the surface on the third nonwoven fabric side was checked with an electron microscope. As a result, no lifting (peeling) of the third nonwoven fabric was found. The thickness T2 of the second nonwoven fabric in the laminated nonwoven fabric (the average thickness of the second nonwoven fabric in a region other than the region pressed by the convex portion) was 2.3 μm.

  Separately, a sample having a width of 25 mm and a length of 200 mm was cut out from the laminated nonwoven fabric. The peel strength between the first nonwoven fabric and the third nonwoven fabric of the sample was measured by a method based on JISZ0237. The peel strength was 88 mN / 25 mm.

FIG. 8 is an SEM photograph taken from the second nonwoven fabric side by peeling the third nonwoven fabric from the laminated nonwoven fabric. In the region on the left side of the photograph, the small adhesive particles maintain a spherical shape (second particles), while in the region on the right side, the adhesive particles are crushed and spread, and the fibers are embedded. A streak-like recess is formed, and the adhesive particles and the fibers are in a bonded state (first particles). The portion where the fibers are embedded in the adhesive particles corresponds to the convex portion of the embossed surface of the pressure roller, and the portion where the spherical shape of the adhesive particle is maintained corresponds to the region other than the convex portion. ing. The number n ₁ of the first particles and the number n ₂ of the second particles were measured for an arbitrarily selected region of 10 mm × 10 mm in the SEM photograph, and the n ₂ / n ₁ ratio was determined. It was 4.

(Comparative Example 1)
A DMAc solution containing an adhesive (polyester hot melt resin, melting point: about 100 ° C.) at a concentration of 20% by mass was prepared. The viscosity was measured in the same manner as in Example 1 immediately after the preparation of this solution and after a lapse of 8 hours from immediately after the preparation. The viscosity of the solution immediately after preparation was 20 Pa · s. After 8 hours from the preparation, the solution was gelled, and its viscosity was 31 Pa · s, 1.6 times that immediately after the preparation.

  Using the above solution immediately after preparation, an adhesive was discharged onto one main surface of the same first nonwoven fabric as in Example 1 by electrospinning. Next, by using a DMAc solution containing PES at a concentration of 20% by mass as a raw material liquid and depositing the second fiber on the main surface of the first nonwoven fabric to which the adhesive was adhered in the same manner as in Example 1, Two nonwoven fabrics were laminated.

  Next, after heating the surface of the second nonwoven fabric to 158 ° C. from the second nonwoven fabric side, the same third nonwoven fabric as in Example 1 was laminated from the second nonwoven fabric side. The obtained laminate was supplied between a pair of pressure rollers having a smooth peripheral surface, and pressed in the thickness direction to obtain a laminated nonwoven fabric. The pressure for pressure bonding was 10 kPa.

  A 30 cm square sample was cut out from the obtained laminated nonwoven fabric. In the same manner as in Example 1, the obtained sample was folded in a pleated shape, spread, and the surface on the third nonwoven fabric side was checked with an electron microscope. As a result, lifting (peeling) of the third nonwoven fabric was confirmed. Separately, when the peel strength was measured by the same method as in Example 1, it was 43 mN / 25 mm.

(Comparative Example 2)
By depositing the second fibers on one main surface of the same first nonwoven fabric as in Example 1 by using a DMAc solution containing PES at a concentration of 20% by mass as a raw material liquid in the same manner as in Example 1, Two nonwoven fabrics were laminated. Next, a DMAc solution containing an adhesive was prepared in the same manner as in Comparative Example 1, and the adhesive was discharged onto the main surface of the second nonwoven fabric by electrospinning using the solution immediately after the preparation.

  After the surface of the second nonwoven fabric to which the adhesive was applied was heated to 158 ° C. from the second nonwoven fabric side, the same third nonwoven fabric as in Example 1 was laminated from the second nonwoven fabric side. The obtained laminate was supplied between a pair of pressure rollers having a smooth peripheral surface, and pressed in the thickness direction to obtain a laminated nonwoven fabric. The pressure for pressure bonding was 10 kPa.

  A 30 cm square sample was cut out from the obtained laminated nonwoven fabric. In the same manner as in Example 1, the obtained sample was folded in a pleated shape, spread, and the surface on the third nonwoven fabric side was checked with an electron microscope. As a result, lifting (peeling) of the third nonwoven fabric was confirmed. Separately, when the peel strength was measured by the same method as in Example 1, it was 35 mN / 25 mm.

  According to the method for producing a laminated nonwoven fabric of the present invention, gelation of a solution containing an adhesive can be suppressed, and a laminated nonwoven fabric can be obtained by a simple method. In addition, since exfoliation between nonwoven fabrics is suppressed, filter materials for air purifiers or air conditioners, separation sheets for batteries, membranes for fuel cells, extracorporeal examination sheets such as pregnancy test sheets, and medical use such as cell culture It is suitable as a dust-proof cloth such as a sheet or a dust-proof mask, dust-proof clothing, a cosmetic sheet, a wiping sheet for wiping dust, and the like.

1: first nonwoven fabric, 2F: second fiber, 2: second nonwoven fabric, 3: third nonwoven fabric, 10: laminated nonwoven fabric, 11: transport roller, 12: supply reel, 13: motor, 21, 31: transport conveyor, 22: raw material liquid, 32: adhesive solution, 23, 33: emission body, 24, 34: first support, 25, 35: second support, 26, 36: voltage applying device, 27, 37: counter electrode , 28, 38: pump, 29: raw material liquid tank, 39: adhesive solution tank, 41: transport roller, 42: heater, 51: transport roller, 52: reel, 53, 53a, 53b, 153a, 153b, 253a, 253b: pressure roller, 154, 254: convex portion of embossed surface, 61: roller, 62: collection reel, 63: motor, 100: air cleaner, 101: suction unit, 102: discharge unit, 103: prefi , 104: deodorizing filter, 200: manufacturing device (manufacturing system), 201: first nonwoven fabric supply unit, 202: electrospinning device, 203: adhesive dispersing device, 204: heating device, 205: third nonwoven fabric laminating device , 206: Collection device

Claims (9)

A step of preparing a first nonwoven fabric containing a first fiber, and a raw material liquid containing a raw material resin and an adhesive which are raw materials for a second fiber;
By the electrospinning method, the raw material liquid is discharged from a nozzle to generate second fibers to which the adhesive has adhered, and the second fibers to which the adhesive has adhered are deposited on the first nonwoven fabric. laminating a second nonwoven fabric comprising the second fibrous nonwoven fabric, only including,
Particles of the adhesive are attached to the second fiber,
The second nonwoven fabric and the first nonwoven fabric are bonded via particles of the adhesive,
The average fiber diameter D1 of the first fibers and the average fiber diameter D2 of the second fibers satisfy a relationship of D1> D2,
A method for producing a laminated nonwoven fabric, wherein an average particle diameter Dp of the adhesive particles and an average fiber diameter D1 of the first fibers satisfy a relationship of D1> Dp . The method for producing a laminated nonwoven fabric according to claim 1 , wherein the average particle diameter Dp of the particles of the adhesive and the average fiber diameter D2 of the second fibers satisfy a relationship of Dp> D2. The second fiber is a nanofiber production method of a multilayer nonwoven fabric according to claim 1 or 2. In the step of preparing the raw material liquid, a first solution containing the adhesive and a first solvent for dissolving the adhesive is mixed with a second solution containing the raw material resin and a second solvent for dissolving the raw material resin. The method for producing a laminated nonwoven fabric according to any one of claims 1 to 3 , wherein the raw material liquid is prepared. The method for producing a laminated nonwoven fabric according to claim 4 , wherein the second solvent and the first solvent include the same solvent. The method for producing a laminated nonwoven fabric according to any one of claims 1 to 5 , wherein the raw material liquid is discharged from the nozzle in a direction perpendicular to a surface direction of the first nonwoven fabric. further,
A step of arranging a third nonwoven fabric containing a third fiber on a main surface of the second nonwoven fabric opposite to the first nonwoven fabric to obtain a laminate, and pressing the laminate in a thickness direction to form the second nonwoven fabric. The method for producing a laminated nonwoven fabric according to any one of claims 1 to 6 , further comprising a step of pressure-bonding the second nonwoven fabric and the third nonwoven fabric. The method for producing a laminated nonwoven fabric according to any one of claims 1 to 7, wherein an average particle diameter Dp of the particles of the adhesive is 1 to 200 µm. The thread of the adhesive is further attached to the second fiber,
The method for producing a laminated nonwoven fabric according to claim 8 , wherein the filament is connected to the particles of the adhesive.