JP2015190081A - Melt-blown nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unprecedented nonwoven fabric which has a high specific surface area, in which mutual fusion of yarns and generation of a polymer sphere are suppressed, and the yarns are extremely fine and uniform.SOLUTION: The nonwoven fabric is composed of fibers of a thermoplastic resin and has a specific surface area which satisfies a formula (1): 2000/(ρ×D)<A<4000/(ρ×D){in the formula, A: a specific surface area (m/g), ρ: a specific gravity of the thermoplastic resin (kg/m), D: an average fiber diameter (μm)}. The laminate nonwoven fabric is formed by laminating the nonwoven fabric and a spun-bonded nonwoven fabric. The filter, the separator and the hygienic material include the laminate nonwoven fabric.

Description

  The present invention relates to a meltblown nonwoven fabric made of ultrafine yarn. More specifically, the present invention relates to a melt-blown nonwoven fabric that suppresses fusion between yarns and generation of polymer spheres, is ultrafine and uniform, and has a high specific surface area that has not been conventionally available.

The general melt-blown method is a method in which a thermoplastic resin having a spinnability is melted and then extruded from a nozzle (from a gap provided so as to sandwich a row of small holes) (hereinafter referred to as an air gap). This is a method of directly obtaining a nonwoven fabric made of ultrafine fibers by pulling and refining a thermoplastic resin with a high-temperature and high-speed spinning gas that is jetted, and collecting the fibers into a net. For example, in Industrial & Engineering Chemistry, Vol. 48, No. 8, pp. 1342-1346 (1956) discloses a basic apparatus and method for the melt blown method. These method apparatuses have a very simple apparatus configuration, and can make ultrafine fibers easily and inexpensively.
A characteristic of general meltblown nonwoven fabrics is that they are composed of ultrafine fibers having a fiber diameter of several μm, and therefore have a larger specific surface area than other nonwoven fabric manufacturing methods.
Melt blown nonwoven fabrics are widely used for various filter applications, separator applications, etc., taking advantage of the above characteristics. Moreover, it is utilized also for leakproof members, such as a disposable diaper which utilized the barrier property by the clearance gap between fibers narrowing.

  In the melt blown nonwoven fabric, in order to further improve the above-described performance, it is required to make the ultrafine fibers formed uniform. By making the fiber diameter uniform, a smaller pore diameter can be obtained and the pore diameter distribution becomes more uniform, so that even if the basis weight is lower than that of a normal meltblown nonwoven fabric, it is possible to obtain the desired filter performance, compactness and This leads to lower costs. In addition, since a small pore diameter can be obtained without pressing, the structure takes advantage of the bulkiness that is one of the features of the meltblown method, and the filter life when used in filter applications is extended. These effects lead to reductions in environmental impact, energy saving, weight reduction, compactness, etc., which have been demanded in recent years. Therefore, there is a high demand for performance improvement from various fields using meltblown nonwoven fabrics, and it contributes to the world. It can be a highly skilled technology.

  As a general technique for making the fiber diameter uniform in the melt blown method, there are a method of reducing the single hole discharge amount and a method of widening the interval between the nozzles. For example, Patent Document 1 below discloses a method for producing a melt-blown nonwoven fabric characterized in that the distance between the nozzles is 0.54 mm or more. Further, Patent Document 2 below discloses a method in which a single-hole discharge amount per minute is 0.01 g or less using a nozzle having a density of at least 100 nozzles per inch. Further, in Patent Document 3 below, a secondary blow air having a temperature of 50 ° C. or higher is blown onto the discharged thermoplastic resin under a melt blown die head to excite additional vibrations on the thermoplastic resin and uniformly. A method of converting is disclosed.

  Although these methods can produce melt-blown nonwoven fabrics with a somewhat uniform fiber diameter distribution, the polymer is caused by the generation of thick fibers that are more than twice the average fiber diameter due to the fusion of fibers that occurs during melt extrusion and stretch breaks. The present situation is that spinning cannot be performed while suppressing the generation of spheres to a small amount, and there is a strong demand for a melt-blown nonwoven fabric that has extremely high uniformity and specific surface area and can achieve high performance.

  In addition to the melt blown method, there is an electrospinning method as a method of obtaining ultrafine and uniform fibers. However, when industrializing in the future, the production scale is small and there are many batch-type production, and scale up In order to achieve this, it is necessary to inject the thermoplastic resin from a plurality of nozzles at the same time, but there are problems such as clogging of the nozzles and fusion of the thermoplastic resin when the nozzle interval is narrowed. Recently, a manufacturing method that does not use a nozzle has been developed. However, when considering environmental burdens, there still remains a problem of solvent-free. In general, it is said that the method of injecting a solution in which a thermoplastic resin is dissolved in a solvent is easier to form ultrafine fibers than the method of injecting a thermoplastic resin directly from a nozzle. When this method is industrialized, it is necessary to completely remove the solvent remaining in the fiber, which requires enormous costs. Furthermore, the sea-island composite spinning method can be cited as a method for obtaining ultrafine and uniform fibers, but because of the limited number of applicable thermoplastic resins and the use of solvents for the removal of the second component, the current ecological thinking is There is a problem that the load is high.

JP 2012-122157 A Special table 2009-534548 gazette JP 2006-83511 A

  In view of the above-mentioned problems of the prior art, the problem to be solved by the present invention is to provide a nonwoven fabric having a high specific surface area that is extremely fine and uniform, suppressing the fusion of yarns and the generation of polymer spheres, and being unprecedented. It is to be.

As a result of diligent investigations and repeated experiments to solve the above problems, the present inventors have produced a melt-blown nonwoven fabric that obtains ultrafine yarn by pulling a thermoplastic resin having spinnability using a high-temperature and high-speed gas. In the above, by performing spinning under the condition that the maximum shear rate (s ^-1 ) of the thermoplastic resin during stretching is in a predetermined range, it is possible to suppress fusion between yarns and generation of polymer spheres, and the fibers are extremely fine and The present inventors have found that a nonwoven fabric having an unprecedented high specific surface area can be obtained, and the present invention has been completed based on such findings.
That is, the present invention is as follows.

[1] It is composed of thermoplastic resin fibers and has a specific surface area of the following formula (1):
2000 / (ρ × D) <A <4000 / (ρ × D). . . Formula (1)
{In the formula, A: specific surface area (m ² / g), ρ: thermoplastic resin specific gravity (kg / m ³ ), D: average fiber diameter (μm). }
The nonwoven fabric characterized by satisfy | filling.

  [2] The nonwoven fabric according to [1], wherein an average fiber diameter of the fibers is 0.1 μm or more and 3.0 μm or less.

  [3] The fiber diameter distribution of the fibers is Dw / Dn <1.3, where Dw: weight average fiber diameter (μm) and Dn: number average fiber diameter (μm). }, The nonwoven fabric according to [1] or [2].

[4] The nonwoven fabric according to any one of [1] to [3], wherein the polymer spheres observed on the surface of the nonwoven fabric are 0 to 30 / mm ² .

  [5] The nonwoven fabric according to any one of [1] to [4], wherein the thermoplastic resin is a polyolefin resin.

  [6] The nonwoven fabric according to any one of [1] to [4], wherein the thermoplastic resin is a polyester resin.

  [7] The nonwoven fabric according to any one of [1] to [4], wherein the thermoplastic resin is a polyamide-based resin.

  [8] The nonwoven fabric according to any one of [1] to [7], wherein the fibers constituting the nonwoven fabric are continuous long fibers.

[9] After the thermoplastic resin having spinnability is melted, it is fed into the spinning nozzle, discharged from the spinning nozzle in which small holes are arranged in a row, and a gap provided so as to sandwich the small hole row In the method for producing a melt blown nonwoven fabric that can be drawn and thinned by a high-temperature and high-speed spinning gas ejected from the following formula (2):
10 ^8.2 <X <10 ¹⁰ . . . Formula (2)
{Wherein X is the maximum shear rate (s ^-1 ) of the thermoplastic resin during stretching. } The manufacturing method of the melt blown nonwoven fabric characterized by satisfy | filling.

  [10] A laminated nonwoven fabric obtained by laminating the nonwoven fabric according to any one of [1] to [8] and a spunbonded nonwoven fabric.

  [11] The laminate nonwoven fabric according to [10], including the nonwoven fabric according to any one of [1] to [8] between two spunbond nonwoven fabric layers.

  [12] A filter using the laminated nonwoven fabric according to [10] or [11].

  [13] A separator using the laminated nonwoven fabric according to [10] or [11].

  [14] A support using the laminated nonwoven fabric according to [10] or [11].

  [15] A sanitary material using the laminated nonwoven fabric according to [10] or [11].

  The non-woven fabric according to the present invention is a non-woven fabric that can suppress the fusion of yarns and the generation of polymer spheres, and has ultrafine and uniform fibers, and has a high specific surface area that has not existed before. In the melt blown nonwoven fabric spun under the conditions according to the present invention, polymer breakage, fused fibers, and yarn diameter unevenness in the yarn length direction, which are major problems in making the fibers extremely fine and uniform, are remarkably improved. be able to. In the nonwoven fabric according to the present invention, by making the fiber diameter of the continuous long fibers constituting the meltblown nonwoven fabric uniform, a smaller pore diameter can be obtained and the pore diameter distribution becomes sharper. However, the desired filter performance can be obtained, leading to a compact and low cost. In addition, since a small hole diameter can be obtained without pressing, the structure takes advantage of the bulkiness that is one of the features of the meltblown method, and the life when used for a filter is extended. Furthermore, the melt blown method does not require any solvent treatment that is required by many other finer techniques.

It is a whole process figure of a melt blown method. It is detail drawing of the spin head in a melt blown method. It is a figure which shows the relationship between the spinning speed with respect to a shear rate, and spinning gas speed.

Hereinafter, embodiments of the present invention will be described in detail.
The molten resin discharged from the nozzle is thinned by pulling by spinning gas or gravity, and shear is applied in the extending direction inside the molten resin. If the molten resin is crystallized by shear stress, the stretching is completed at that time. If the shear stress acting on the thermoplastic resin during drawing is too weak, the ultrafine yarn that is characteristic of the melt blown nonwoven fabric of the present invention cannot be obtained. On the other hand, if the shear stress acting on the thermoplastic resin being stretched is too strong, polymer spheres are generated due to stretching. Thus, the shear stress acting on the thermoplastic resin during stretching is a very important factor in the melt blown method because it determines the structure of the melt blown nonwoven fabric.

The shear rate X (s ^-1 ) of thermoplastic resin during stretching by the melt blown method varies depending on the spinning conditions, but X (s ^-1 ) is the academic journal AIChE Journal Vol. 36 (1990) No. 2 175-186. It can be estimated from the spinning conditions (nozzle diameter, single hole discharge amount, spinning gas temperature, spinning gas pressure, polymer physical properties) by the calculation method described on the page. As a result of studying using this calculation method, the present inventors performed spinning under the condition that the shear rate X (s ⁻¹ ) of the thermoplastic resin during drawing is 10 ^8.2 <X <10 ^10. It has been found that a melt blown nonwoven fabric in which fusion between each other and generation of polymer spheres can be suppressed and the fibers are extremely fine and uniform can be obtained. When spinning under the condition of X <10 ^8.2 , the yarn diameter unevenness increases in the yarn length direction, and the ultrafine yarn that is a feature of the melt blown nonwoven fabric of the present invention cannot be obtained. Further, when spinning is performed under the condition of X> 10 ¹⁰ , the shear stress acting on the thermoplastic resin being stretched is too strong, causing stretching breakage, and polymer spheres are frequently generated. If it is in the range of 10 ^8.2 <X <10 ¹⁰ , the yarn diameter unevenness in the yarn length direction is remarkably improved, and the fibers become extremely fine and uniform. In addition, it is possible to obtain an ideal ultrafine yarn with very little generation of polymer spheres due to drawing breakage.

The nonwoven fabric which concerns on this invention is comprised from the fiber of a thermoplastic resin, and a specific surface area is following formula (1):
2000 / (ρ × D) <A <4000 / (ρ × D). . . Formula (1)
{In the formula, A: specific surface area (m ² / g), ρ: thermoplastic resin specific gravity (kg / m ³ ), D: average fiber diameter (μm). }
It is characterized by satisfying.
The specific surface area (A) is 2000 / (ρ × D) <A <4000 / (ρ × D), preferably 2500 / (ρ × D) <A <4000 / (ρ × D), 3000 / (ρ × D) <A <4000 / (ρ × D) is more preferable, and 3500 / (ρ × D) <A <4000 / (ρ × D) is more preferable. Here, A = 4000 / (ρ × D) is a specific surface area in an ideal state in which the fiber diameter of the fibers constituting the nonwoven fabric is theoretically completely uniform and there are no entanglement points between the fibers. is there. In addition, when A ≦ 2000 / (ρ × D), the fiber diameter distribution is non-uniform due to the occurrence of yarn diameter unevenness and fiber fusion in the yarn length direction, and the surface area is minimized due to the generation of polymer spheres. The specific surface area becomes a small value, which is not suitable for various filters and separators.

In the nonwoven fabric according to the present invention, the average fiber diameter is preferably 0.1 μm or more and 3.0 μm or less. The average fiber diameter is more preferably 0.1 μm or more and 2.0 μm or less, and further preferably 0.1 μm or more and 1.0 μm or less. Also, considering the recent high performance and compactness (thinness) of various filter applications, the upper limit of the average fiber diameter is preferably 0.8 μm or less, more preferably 0.5 μm or less, which gives the characteristic advantages of nanofibers. More preferably, it is 0.3 μm or less. When the fiber is thinned to 0.3 μm or less, the following new physical properties that cannot be obtained with conventional fibers appear.
(1) The resistance of air becomes very small.
The air and liquid flow gets slower as it gets closer to the object, which becomes the air resistance of the filter. However, the phenomenon of “slip flow effect” occurs in the nano-sized material, and the flow velocity hardly slows down. For this reason, making a filter with nanofibers has the advantage that the air is smooth even if a fine filter is made.
(2) The specific surface area increases.
Since nanofibers have a very large specific surface area and can adsorb many foreign substances on the fiber surface, the performance of the purification device can be improved. In addition, the efficiency of chemical reactions and electrical reactions occurring on the fiber surface is increased, leading to increased efficiency of fuel cells and the like.

In the nonwoven fabric according to the present invention, the fiber diameter distribution is preferably Dw / Dn <1.3. Here, Dn is the number average fiber diameter, and Dw is the weight average fiber diameter.
The fiber diameter distribution determined from the fiber diameters of 100 formed fibers is preferably Dw / Dn <1.3, more preferably Dw / Dn <1.2, and further preferably Dw / Dn <1.1. As Dw / Dn is closer to 1, the fiber diameter distribution is more uniform, so that it has a high specific surface area and is preferable for use as a filter.

In the nonwoven fabric according to the present invention, the number of polymer spheres observed on the surface of the nonwoven fabric is preferably 0 to 30 per 100 fibers.
When 100 or more of the formed fibers are randomly photographed with an SEM and the fiber diameter is measured, the drawing force from the spinning gas is too strong, resulting in polymer breakage. Measure the number of spherical parts. The number of polymer spheres per 100 fibers formed is 30 or less, preferably 10 or less, and more preferably 3 or less. When there are few polymer spheres, a melt-blown nonwoven fabric having a more uniform and high specific surface area can be obtained.

  The thermoplastic resin constituting the fiber may be a polyolefin resin, a polyester resin, or a polyamide resin. Specifically, ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene. , High-pressure method low density polyethylene, linear low density polyethylene (LLDPE), high density polyethylene, polypropylene (propylene homopolymer), polypropylene random copolymer, which is a homopolymer or copolymer of α-olefin such as 1-octene, Poly-1-butene, poly-4-methyl-1-pentene, ethylene / propylene random copolymer, ethylene-1-butene random copolymer, polyolefin such as propylene-1-butene random copolymer, polyester (polyethylene terephthalate, Polybutylene terephthalate, polyethylene naphthalate ), Polyamide (nylon-6, nylon-66, polymetaxylene adipamide, etc.), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymer, polyacrylonitrile, polycarbonate, polystyrene, ionomer or a mixture thereof can do.

The melt flow rate is 100 to 2500 g / 10 minutes, preferably 1000 to 2000 g / 10 minutes, and more preferably 1300 to 1800 g / 10 minutes.
In the present invention, the melt flow rate was measured in accordance with ASTM D1238 using a melt indexer manufactured by Nippon Dynisco Corporation.

となる。
ここで、π：円周率(-)、r：糸半径(m)、v：紡速(m s^-1)、z：紡糸方向(m)、η：溶融樹脂粘度(Pa s)、C_f：空気抵抗係数(-)、ρ_a：ガス密度(kg m^-3)、ρ_f：溶融樹脂密度(kg m^-3)、Q：溶融樹脂体積吐出量(m³ s^-1)、g：重力加速度(m s^-2)であり、v < v_a の時j = -1、v > v_aの時j = +1であり、

となる。
ここで、v_a：ガス速度(m s^-1)、μ_a：ガス粘度(Pa s)、β (-)とn (-)は経験的なパラメータ(>0)である。 The method for producing the nonwoven fabric of the present invention is the melt blown method, wherein the following formula (2):
10 ^8.2 <X <10 ¹⁰ . . . Formula (2)
{Wherein X is the maximum shear rate (s ^-1 ) of the thermoplastic resin during stretching. }
It is characterized by satisfying.
X (s ^-1 ) is a calculation method written in the academic journal AIChE Journal Vol. 36 (1990) No. 2 pp. 175-186. Spinning conditions (nozzle diameter, single-hole discharge rate, spinning gas temperature, It can be estimated from the spinning gas pressure. With this method, X (s ⁻¹ ) was calculated as follows.
Viscous force, pulling force by spinning gas, inertial force, and gravity act on the molten resin.
Therefore, the momentum balance equation is the following equation (3):

It becomes.
Here, π: Circumference ratio (−), r: Yarn radius (m), v: Spinning speed (ms ⁻¹ ), z: Spinning direction (m), η: Molten resin viscosity (Pa s), C _f : Air resistance coefficient (-), ρ _a : Gas density (kg m ^-3 ), ρ _f : Molten resin density (kg m ^-3 ), Q: Molten resin volume discharge (m ³ s ^-1 ), g: Gravitational acceleration (ms ^-2 ), j = -1 when v <v _a , j = +1 when v> v _a ,

It becomes.
Here, v _a : gas velocity (ms ⁻¹ ), μ _a : gas viscosity (Pa s), β (−) and n (−) are empirical parameters (> 0).

でなければならない。
他方、延伸過程における熱収支式は、下記式（７）：

である。
ここで、C_p：溶融樹脂熱容量(J Kg^-1 K^-1)、T：溶融樹脂温度(K)、h：熱伝達係数(J m^-2 s^-1 K^-1)、T_a：紡糸ガス温度(K)であり、下記式（８）：

である。
ここで、Nu：ヌッセルト数(-)、δ：境膜厚み(m)、k_a：ガス熱伝導度(J m^-1 s^-1 K^-1)、γ (-)とm (-)は経験的なパラメータ(>0)である。 In order of the left side and the first, second, and third terms on the left side of equation (3), the viscous force acting on the molten resin, the traction force due to the spinning gas, the inertial force, and the gravity are obtained.
In addition, since the molten resin is drawn as a continuous long fiber as observed with a high-speed camera, the following formula (6):

Must.
On the other hand, the heat balance equation in the stretching process is the following equation (7):

It is.
Here, C _p : molten resin heat capacity (J Kg ⁻¹ K ⁻¹ ), T: molten resin temperature (K), h: heat transfer coefficient (J m ⁻² s ⁻¹ K ⁻¹ ), T _a : spinning Gas temperature (K), the following formula (8):

It is.
Where Nu: Nusselt number (-), δ: film thickness (m), k _a : gas thermal conductivity (J m ^-1 s ^-1 K ^-1 ), γ (-) and m (-) are Empirical parameter (> 0).

となり、式（１０）の左辺、右辺第1、2、3項の順に各項は粘性力、紡糸ガスによる牽引力、慣性力、重力に対応する。 When Expression (4), Expression (5), and Expression (6) are substituted into Expression (3) and transformed, the following Expression (10):

Thus, each term corresponds to the viscous force, the traction force by the spinning gas, the inertial force, and the gravity in order of the left side, the first side, the right side, and the third term of the formula (10).

となる。
以上により、式（３）、式（６）、及び式（７）の運動量、物質、熱収支式は、式（１０）と式（１１）に変形される。 Further, when Expression (6), Expression (8), and Expression (9) are substituted into Expression (7), the following Expression (11):

It becomes.
As described above, the momentum, substance, and heat balance equations of Equation (3), Equation (6), and Equation (7) are transformed into Equation (10) and Equation (11).

The spinning parameters in the melt blown method described by the equations (10) and (11) are three: v _a : spinning gas speed, T _a : spinning gas temperature, and Q: molten resin discharge amount. v _a, effects on T _a, the fiber diameter of Q is, v when _a the larger traction force by the spinning gas (equation (10) the second term on the right side) of the molten resin while the fiber diameter of which narrows so easy to increase the cooled It is easy (formula (11)) and has a high possibility of solidifying before being made fine. Since T _a greatly the molten resin is hardly cooled (Equation (11)), but is less likely to solidify before being fine繊化likely stretching breakage occurs too fine繊化. When Q is increased, the pulling efficiency by the spinning gas is poor, and the fiber diameter becomes large while the molten resin is difficult to cool (Formula (11)) (Formula (10), right-side second term). The possibility of solidifying is reduced. Furthermore, v _a , T _a , and Q may affect the melt resin viscosity and the spinning gas density.
As described above, the influence of the spinning parameters v _a , T _a and Q on the fiber diameter is very complicated. It is very difficult to find appropriate values of v _a , T _a , and Q that give a strong shearing force.

に変形し、4次Runge-Kutta法で解いた。4次Runge-Kutta法とは、下記微分方程式：

について、ある点tにおけるA, Bの値から、隣の点t + hにおけるA, Bの値を、下記公式：

を用いて求め、更に隣の点を順々と求めていく方法である。 Here, the maximum shear rate X (s ⁻¹ ) = dv / dz (s ⁻¹ ) of the thermoplastic resin during stretching can be obtained by numerically solving equation (10). The fiber diameter at the nozzle outlet and the drawing stop position was given as the boundary condition of the equation (10).
Hereinafter, the numerical solution method of Formula (10) is shown concretely. Equation (10) is converted into the following binary simultaneous first-order differential equation:

And solved by the fourth-order Runge-Kutta method. The fourth-order Runge-Kutta method is the following differential equation:

From the values of A and B at a certain point t, the values of A and B at the adjacent point t + h are expressed as follows:

This is a method of finding the next point in order.

The parameters used for the calculation were as follows.
Molten resin density ρ _f : 1.00 × 10 ³ kg m ^-3
Molten resin viscosity η: 1.00 Pa s
Gravity acceleration g: 9.81 ms ^-2
Spinning gas viscosity μ _a : 1.80 × 10 ⁻⁵ Pa s
Parameter β: 3.70 × 10 ^-1
Parameter n: 6.10 × 10 ^-1
Nozzle outlet position: 0.00 m
Fiber diameter at the nozzle outlet position: 3.00 × 10 ^-4 m
Stretch stop position: 1.00 × 10 ^-3 m (X is fixed at 1 mm because it hardly affects the stretch stop position)
Fiber diameter at drawing stop position: Experimental result Spin gas density ρ _a : Experimental condition Spin gas velocity v _a : Experimental condition

The state of “spinning speed <spinning gas speed” is Y = 0, and the state of “spinning speed> spinning gas speed” is Y = 1. Will result shown in FIG. 3 is plotted Y against X obtained in the above manner, X> 10 spinning speed at ^8.2 condition exceeds the spinning gas velocity was found to microfine fibers. On the other hand, under the condition of X <10 ¹⁰ , the shear rate was too strong and the polymer stretch was broken.

FIG. 1 is an overall process diagram of the melt blown method, and FIG. 2 is a detailed view of a spin head.
In the condition range of the formula (2), the molten thermoplastic resin is fed into the melt blown nozzle and discharged from the nozzle (see reference numeral 12 in FIG. 2) in which a large number of small holes are arranged in a row. The fiber is thinned by being pulled by a high-speed and high-speed spinning gas ejected from an air gap provided so as to sandwich the row. Furthermore, an extremely fine and uniform melt-blown nonwoven fabric can be produced by accumulating fibers on a collector net having a suction fan (see reference numeral 4 in FIG. 1).

  The polymer melting temperature in the extruder is in the range of 10 ° C to 60 ° C or higher, preferably 20 ° C to 50 ° C or higher, more preferably 30 ° C to 40 ° C or higher, than the melting point of each thermoplastic tree. If the polymer melting temperature in the extruder (see reference numeral 2 in FIG. 1) is too low, the fluidity of the molten resin discharged from the nozzle will be insufficient, and the fibers will not be sufficiently fined in the spinning process, resulting in a melt blown nonwoven fabric with a hard texture End up. Conversely, when the polymer melting temperature in the extruder is too high, decomposition of the molten resin proceeds and it becomes difficult to perform stable spinning, which is not preferable.

  The hole of the nozzle (see reference numeral 12 in FIG. 2) preferably has a diameter of 0.05 mm to 0.50 mm, more preferably 0.08 mm to 0.40 mm, and still more preferably 0.10 mm to 0.30 mm. If the nozzle hole is too small, the pressure generated by the molten resin is applied to the nozzle hole, so that the nozzle hole may break. On the other hand, if the nozzle hole is too large, it is difficult to apply pressure from the molten resin to the nozzle hole, and a phenomenon called surging occurs in which the molten resin cannot be stably discharged.

  The L / D of the nozzle hole is preferably in the range of 5 to 30, more preferably 7 to 25, and still more preferably 10 to 20. If L / D is too small, it is difficult for pressure to be applied to the nozzle hole by the molten resin, and a phenomenon called surging occurs in which the molten resin cannot be stably discharged. On the other hand, if L / D is too large, the pressure applied by the molten resin to the nozzle holes increases, and the nozzle holes may break.

  The air gap (see reference numeral 11 in FIG. 2) is preferably in the range of 0.10 mm to 3.00 mm, more preferably 0.15 mm to 2.00 mm, and still more preferably 0.25 mm to 1.00 mm. If the air gap is too narrow, it is difficult for the spinning gas to pass through and the spinning gas pressure rises, so that the desired spinning gas flow rate cannot be obtained. On the other hand, if the air gap is too wide, a speed difference occurs in the spinning gas flow velocity, so that the melt blown nonwoven fabric has a nonuniform fiber diameter distribution.

  The spinning gas temperature is preferably 50 ° C to 300 ° C higher than the melting point of each thermoplastic resin, more preferably 100 ° C to 250 ° C higher, and even more preferably 150 ° C to 200 ° C higher. If the spinning gas temperature is too low, the melted resin cannot be made fine, and a meltblown nonwoven fabric in which thick yarns are mixed is obtained. On the other hand, if the spinning gas temperature is too high, the die temperature rises due to heat transfer from the spinning gas, so that the molten resin is decomposed and does not become yarn.

  The distance from the spinning nozzle to the collection support (hereinafter referred to as distance) is preferably in the range of 50 mm to 700 mm, more preferably 80 mm to 500 mm, and still more preferably 100 mm to 300 mm. If the distance is too small, the spinning nozzle is cooled by the suction portion located at the lower part of the collection support, and the molten resin viscosity becomes high. Moreover, since the temperature drop of the injection gas is insufficient because the high-temperature gas is injected, the melt-blown nonwoven fabric is caused by re-melting the pulverized fibers on the collection support and causing self-adhesion or large shrinkage. The texture becomes extremely hard. On the other hand, if the distance is too large, not only the spinning gas jetted by the suction fan but also the surrounding air is sucked as an accompanying flow, and the molten resin discharged from the nozzle cannot be completely sucked, and the fibers are Is not entangled on the collection support, and a phenomenon of fly in which the fibers scatter occurs.

  The single-hole discharge rate of the molten resin is preferably 0.01 g / min to 0.50 g / min, more preferably 0.05 g / min to 0.30 g / min, and even more preferably 0.10 g / min to 0.20 g / min. If the single-hole discharge amount is too small, the productivity of the meltblown nonwoven fabric is deteriorated. Furthermore, since no pressure is applied to the nozzle tip, the molten resin cannot be discharged stably. On the other hand, if the single-hole discharge amount is too large, the molten resin is discharged with a high viscosity. In addition, since the pulling force per unit weight of the molten resin by the spinning gas becomes small, it is difficult to make it thin.

  In the nonwoven fabric according to the present invention, it is preferable that the fibers to be formed are continuous long fibers. In order to confirm that the fibers constituting the nonwoven fabric according to the present invention are continuous long fibers, a single-hole spinning nozzle having only one hole for the nozzle is manufactured, and the single-hole spinning nozzle is used in the region of the present invention. I photographed the behavior of the yarn during spinning with a high-speed camera. In the melt blown method, until now it has been unclear whether the finening phenomenon is due to splitting or due to stretching. became. Although it is very difficult to control the fiber diameter and the fiber diameter distribution in the fiber separation method, since the yarn is fined with one yarn within the scope of the present invention, the fiber has a high uniformity and a desired average fiber diameter. It becomes possible to obtain the nonwoven fabric comprised from a fiber.

The nonwoven fabric according to the present invention can be used as a part of various configurations depending on its application. Examples thereof include a laminated nonwoven fabric having the formed meltblown nonwoven fabric between two spunbond nonwoven fabric layers and a laminated nonwoven fabric in which the formed meltblown nonwoven fabric is laminated on the spunbond nonwoven fabric.
The nonwoven fabric which concerns on this invention may laminate | stack another layer according to various uses. Specifically, a knitted fabric, a woven fabric, a nonwoven fabric, a film, etc. can be mentioned, for example. When laminating the nonwoven fabric according to the present invention and other layers, thermal embossing, thermal fusion methods such as ultrasonic fusion, mechanical entanglement methods such as needle punch and water jet, hot melt adhesive, urethane adhesive Various known methods such as a method using an adhesive such as an agent, extrusion lamination, and the like can be employed.

Examples of the nonwoven fabric laminated with the nonwoven fabric according to the present invention include spunbond nonwoven fabric, wet nonwoven fabric, dry nonwoven fabric, dry pulp nonwoven fabric, flash spun nonwoven fabric, and spread nonwoven fabric.
The nonwoven fabric obtained by the method of the present invention can be a nonwoven fabric laminate in which a spunbond nonwoven fabric is laminated on at least one side, preferably on both sides.

｛式中、Xi＝繊維径Di の存在比率＝Ni/ΣNiである。｝と、

｛式中、Wi＝繊維径Di の重量分率＝Ni・Di/ΣNi・Diである。｝で計算した。 The present invention will be specifically described by the following examples and comparative examples. In Examples and the like, the following measuring methods and apparatuses were used.
<Average fiber diameter>
Device type: JSM-6510 manufactured by JEOL Ltd. was used.
The obtained nonwoven fabric was cut into 10 cm × 10 cm and pressed on an iron plate at 60 ° C. at a pressure of 0.30 MPa for 1 minute and a half, and then the nonwoven fabric was vapor-deposited with platinum. Then, using the above SEM, images were taken under the conditions of an acceleration voltage of 15 kV and a working distance of 21 mm. The photographing magnification was 10,000 times for yarns of less than 0.5 μm, 6000 times for yarns of 0.5 μm or more and less than 1.5 μm, and 4000 times for yarns of 1.5 μm or more. The field of view at each magnification was 12.7 μm × 9.3 μm at 10000 ×, 21.1 μm × 15.9 μm at 6000 ×, and 31.7 μm × 23.9 μm at 4000 ×. 100 or more fibers were randomly photographed, and the average fiber diameter was determined by measuring all fiber diameters. At this time, fibers fused in the yarn length direction were omitted from the measurement. Here, how to obtain Dn: number average fiber diameter and Dw: weight average fiber diameter is described.
When Ni fibers having a fiber diameter Di exist, Dn and Dw are respectively expressed by the following formulas (15) and (16):

{Wherein, Xi = abundance ratio of fiber diameter Di = Ni / ΣNi. }When,

{In the formula, Wi = weight fraction of fiber diameter Di = Ni · Di / ΣNi · Di. }.

｛式中、P₀：飽和蒸気圧(Pa)、Vm：単分子層吸着量(mg/g)、C：吸着熱等に関するパラメータ(−)>0、であり、本関係式は特にP/P₀＝0.05〜0.35の範囲でよく成り立つ。｝を適用し、比表面積値を求めた。すなわち、BET式とは、一定温度で吸着平衡状態である時、吸着平衡圧Pと、その圧力での吸着量Vの関係を表した式である。 <Specific surface area>
Device model: Gemini 2360 Shimadzu Corporation was used.
The nonwoven fabric was rolled into a cylindrical shape and packed in a cell for measuring the specific surface area. In this case, the weight of the sample to be charged is preferably about 0.20 to 0.60 g. The cell charged with the sample was dried at 60 ° C. for 30 minutes and then cooled for 10 minutes. Thereafter, the cell is set in the above specific surface area measuring apparatus, and nitrogen gas adsorption to the sample surface is performed to obtain the following BET formula (17):

{In the formula, P ₀ : saturated vapor pressure (Pa), Vm: monolayer adsorption amount (mg / g), C: parameter (−)> 0 related to heat of adsorption, etc. This holds well in the range of P ₀ = 0.05 to 0.35. } Was applied to determine the specific surface area value. That is, the BET formula is a formula that represents the relationship between the adsorption equilibrium pressure P and the adsorption amount V at that pressure when the adsorption equilibrium state is maintained at a constant temperature.

<High-speed camera photography>
Equipment: HPV-2A manufactured by Shimadzu Corporation was used.
Using the above high-speed camera, under the conditions of shooting speed of 250,000-1 million frames / sec, the melt blown method is refined by shooting the polymer as it is ejected from the nozzle with a field of view of 1cm-10cm. The behavior was clearly captured.

<Polymer sphere>
The produced nonwoven fabric was photographed with SEM. The field of view at each SEM imaging magnification was 12.7 μm × 9.3 μm at 10000 ×, 21.1 μm × 15.9 μm at 6000 ×, and 31.7 μm × 23.9 μm at 4000 ×. When measuring the fiber diameter of 100 or more fibers photographed in the above field of view, the thermoplastic resin is stretched by the pulling force of the spinning gas and changed into a spherical polymer by the surface tension of the thermoplastic resin. The number of polymer spheres adhering to the fiber was measured.

[Example 1]
As a result of measurement according to ASTM D1238 using a melt indexer manufactured by Nippon Dainisco Co., Ltd., a polypropylene resin having a melt flow rate of 1800 g / 10 min was used. This resin was melted by an extruder and extruded from a spinning nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.03 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, the spinning gas was set to a spinning gas temperature of 450 ° C. and a spinning gas pressure of 0.50 MPa, and a melt blown nonwoven fabric composed of continuous long fibers was produced by pulling the thermoplastic resin.
The produced melt blown nonwoven fabric has a specific surface area of 25.2 m ² / g, a fiber diameter of 0.10 μm, a maximum shear rate of 10 ^9.91 acting on the thermoplastic resin during stretching, Dw / Dn: 1.02, and polymer spheres: 6 pieces / mm ² Thus, an ultrafine and uniform meltblown nonwoven fabric that could not be obtained by the conventional meltblown method was obtained.

[Example 2]
A polypropylene resin having a melt flow rate of 1800 g / 10 min was melted by an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.06 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 370 ° C. and a spinning gas pressure of 0.35 MPa.
Meltblown nonwoven fabric produced has a specific surface area: 5.32m ² / g, a fiber diameter: 0.45 [mu] m, the extending direction of the shear rate acting on solidification just before the thermoplastic resin: 10 ^9.62, Dw / Dn: 1.08, polymer spheres: 4 / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 3]
A polypropylene resin having a melt flow rate of 1600/10 min was melted by an extruder and extruded from a nozzle nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.12 g / min. As the dimensions of the nozzle, the setback was adjusted to -1.00mm and the air gap was adjusted to 1.00mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 310 ° C. and a spinning gas pressure of 0.45 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.46 m ² / g, a fiber diameter of 1.81 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^8.65 , Dw / Dn: 1.17, and 0 polymer spheres / A melt-blown nonwoven fabric having a thickness of mm ² that was extremely fine and uniform and could not be obtained by the conventional melt-blown method was obtained.

[Example 4]
A polypropylene resin having a melt flow rate of 1800 g / 10 min was melted by an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.30 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was prepared by pulling the polymer extruded under conditions of a spinning gas temperature of 380 ° C. and a spinning gas pressure of 0.35 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.58 m ² / g, a fiber diameter of 1.66 μm, a shear rate of 10 ^{8.76 in the} drawing direction immediately before the thermoplastic resin is solidified, Dw / Dn: 1.13, and 0 polymer spheres / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 5]
Polyethylene terephthalate resin having a melt flow rate of 1300 g / 10 min was melted by an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.36 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 380 ° C. and a spinning gas pressure of 0.25 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.06 m ² / g, a fiber diameter of 2.99 μm, a shear rate in the stretching direction that works immediately before solidification of the thermoplastic resin: 10 ^8.32 , Dw / Dn: 1.23, and polymer spheres: 0 / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 6]
A polypropylene resin having a melt flow rate of 1700 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.06 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 400 ° C. and a spinning gas pressure of 0.35 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 5.57 m ² / g, a fiber diameter of 0.43 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^9.61 , Dw / Dn: 1.02, and polymer spheres: 5 / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 7]
A polypropylene resin having a melt flow rate of 1700 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.12 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 330 ° C. and a spinning gas pressure of 0.25 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.41 m ² / g, a fiber diameter of 1.91 μm, a shear rate in the stretching direction that works immediately before solidification of the thermoplastic resin: 10 ^8.21 , Dw / Dn: 1.28, and 0 polymer spheres / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 8]
A polypropylene resin having a melt flow rate of 1700 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.20 mm at a single hole discharge rate of 0.09 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 255 ° C. and a spinning gas pressure of 0.30 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.59 m ² / g, a fiber diameter of 1.58 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^8.29 , Dw / Dn: 1.19, and 0 polymer spheres / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 9]
A polypropylene resin having a melt flow rate of 1700 g / 10 min was melted by an extruder and extruded from a nozzle nozzle having a nozzle diameter of 0.25 mm at a single hole discharge rate of 0.03 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was prepared by pulling a polymer extruded under conditions of a spinning gas temperature of 400 ° C. and a spinning gas pressure of 0.25 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 7.03 m ² / g, a fiber diameter of 0.37 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^9.85 , Dw / Dn: 1.07, and 4 polymer balls: An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Example 10]
A polypropylene resin having a melt flow rate of 1700 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.12 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 370 ° C. and a spinning gas pressure of 0.45 MPa.
The melt blown nonwoven fabric produced has a specific surface area of 2.50 m ² / g, fiber diameter: 0.91 μm, shear rate in the stretching direction acting just before the thermoplastic resin solidifies: 10 ^9.50 , Dw / Dn: 1.11, polymer spheres: 5 / An ultrafine and uniform meltblown nonwoven fabric that was ² mm and could not be obtained by the conventional meltblown method was obtained.

[Comparative Example 1]
Polypropylene resin having a melt flow rate of 1600 g / 10 min was melted by an extruder and extruded from a spinning nozzle having a nozzle diameter of 0.25 mm at a single hole discharge rate of 0.03 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was prepared by pulling a polymer extruded under conditions of a spinning gas temperature of 400 ° C. and a spinning gas pressure of 0.25 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 4.53 m ² / g, a fiber diameter of 0.37 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^10.21 , Dw / Dn: 1.18, and polymer spheres: 57 / It was mm ² and was a melt blown nonwoven fabric outside the range of the formulas (1) and (2).

[Comparative Example 2]
Polyethylene terephthalate resin having a melt flow rate of 1300 g / 10 min was melted by an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.25 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 320 ° C. and a spinning gas pressure of 0.25 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 0.63 m ² / g, a fiber diameter of 2.78 μm, a shear rate in the stretching direction acting immediately before solidification of the thermoplastic resin: 10 ^7.90 , Dw / Dn: 1.40, and 0 polymer spheres / It was mm ² and was a melt blown nonwoven fabric outside the range of the formulas (1) and (2).

[Comparative Example 3]
A polypropylene resin having a melt flow rate of 1800 g / 10 min was melted by an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.24 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.20mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric composed of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 255 ° C. and a spinning gas pressure of 0.50 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 0.95 m ² / g, a fiber diameter of 2.05 μm, a shear rate in the stretching direction that works immediately before the thermoplastic resin is solidified: 10 ^8.08 , Dw / Dn: 1.37, and 3 polymer balls / It was mm ² and was a melt blown nonwoven fabric outside the range of the formulas (1) and (2).

[Comparative Example 4]
A polypropylene resin having a melt flow rate of 1600 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.30 mm at a single hole discharge rate of 0.06 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.50mm and the air gap was adjusted to 0.50mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 280 ° C. and a spinning gas pressure of 0.30 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 1.01 m ² / g, a fiber diameter of 1.90 μm, a shear rate in the stretching direction that acts immediately before solidification of the thermoplastic resin: 10 ^7.60 , Dw / Dn: 1.35, and 0 polymer spheres / It was mm ² and was a melt blown nonwoven fabric outside the range of the formulas (1) and (2).

[Comparative Example 5]
A polypropylene resin having a melt flow rate of 1800 g / 10 min was melted with an extruder and extruded from a nozzle having a nozzle diameter of 0.20 mm at a single hole discharge rate of 0.03 g / min. As the dimensions of the nozzle, the setback was adjusted to -0.25mm and the air gap was adjusted to 0.25mm. When extruding the thermoplastic resin, a melt blown nonwoven fabric made of continuous long fibers was produced by pulling the polymer extruded under conditions of a spinning gas temperature of 400 ° C. and a spinning gas pressure of 0.35 MPa.
The produced melt blown nonwoven fabric has a specific surface area of 4.29 m ² / g, a fiber diameter of 0.33 μm, a shear rate in the stretching direction that acts immediately before the thermoplastic resin is solidified: 10 ^10.05 , Dw / Dn: 1.15, and polymer spheres: 63 / It was mm ² and was a melt blown nonwoven fabric outside the range of the formulas (1) and (2).

  From the results shown in Table 1, the melt blown nonwoven fabric spun under the condition within the range of the formula (2) has a high specific surface area, can significantly suppress the generation of fused fibers and polymer spheres, and the fiber diameter distribution is extremely uniform. It was an ideal melt-blown non-woven fabric with no yarn diameter unevenness.

In the comparative example 1, the melt blown nonwoven fabric spun under the condition exceeding the range of the formula (2) has too much shear stress acting on the thermoplastic resin being stretched, so that the polymer breakage occurs, and the continuous characteristic peculiar to the melt blown nonwoven fabric. As a result, the melted fibers and polymer spheres were frequently generated (fused fiber locations: 13 locations / 100, polymer spheres: 57 / mm ² ).

  In the comparative example 2, the melt blown nonwoven fabric spun under the condition of the range of the formula (2) is too weak in the shear stress acting on the thermoplastic resin being stretched, so that the yarn diameter unevenness in the yarn length direction becomes remarkable. It was a meltblown nonwoven fabric with non-uniform fiber diameter distribution (Dw / Dn: 1.43).

  From the results of Table 2, the specific surface area of the meltblown nonwoven fabric spun under the condition within the range of the formula (2) falls within the range of the formula (1), but the ratio of the meltblown nonwoven fabric spun outside the range of the formula (2). It was found that the surface area was out of the range of formula (1).

  Melt blown nonwoven fabric spun under the condition of the formula (2) significantly improves polymer breakage, fused fibers, and yarn diameter unevenness in the yarn length direction, which are major problems in making fibers fine and uniform. can do. By making the fiber diameter of the continuous long fibers that make up the meltblown nonwoven fabric uniform, a smaller pore diameter can be obtained and the pore diameter distribution becomes sharper, so even if the basis weight is lower than that of a normal meltblown nonwoven fabric, the desired filter performance Can be obtained, leading to compactness and low cost. In addition, since a small hole diameter can be obtained without pressing, the structure takes advantage of the bulkiness that is one of the features of the meltblown method, and the life when used for a filter is extended. Furthermore, the melt blown method does not require any solvent treatment that is required by many other finer techniques. Therefore, the present invention leads to reduction of environmental load, energy saving, weight reduction, and compactness that have been demanded in recent years, and is therefore a highly contributing technology.

1 Hopper 2 Extruder 3 Spin Head 4 Suction Fan 5 Press Machine 6 Winding Machine 7 Gear Pump 8 Distribution Pack 9 Spinning Gas 10 Lip 11 Air Gap 12 Spinning Nozzle

Claims (15)

It is composed of thermoplastic resin fibers and has a specific surface area of the following formula (1):
2000 / (ρ × D) <A <4000 / (ρ × D). . . Formula (1)
{In the formula, A: specific surface area (m ² / g), ρ: thermoplastic resin specific gravity (kg / m ³ ), D: average fiber diameter (μm). }
The nonwoven fabric characterized by satisfy | filling.   The nonwoven fabric according to claim 1, wherein an average fiber diameter of the fibers is 0.1 µm or more and 3.0 µm or less.   The fiber diameter distribution of the fibers is Dw / Dn <1.3, where Dw: weight average fiber diameter (μm) and Dn: number average fiber diameter (μm). } The nonwoven fabric of Claim 1 or Claim 2 which is. Polymer spheres observed in the surface of the nonwoven fabric is 0-30 pieces / mm ^2, the nonwoven fabric according to any one of claims 1 to 3.   The nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyolefin resin.   The nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyester resin.   The nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyamide-based resin.   The nonwoven fabric of any one of Claims 1-7 whose fiber which comprises the said nonwoven fabric is a continuous long fiber. After the thermoplastic resin having spinnability is melted, it is fed into a spinning nozzle, discharged from a spinning nozzle in which small holes are arranged in a row, and ejected from a gap provided so as to sandwich the row of small holes. In the method for producing a melt blown nonwoven fabric that can be drawn and thinned by a high-temperature and high-speed spinning gas, the following formula (2):
10 ^8.2 <X <10 ¹⁰ . . . Formula (2)
{Wherein X is the maximum shear rate (s ^-1 ) of the thermoplastic resin during stretching. } The manufacturing method of the melt blown nonwoven fabric characterized by satisfy | filling.   A laminated nonwoven fabric obtained by laminating the nonwoven fabric according to any one of claims 1 to 8 and a spunbond nonwoven fabric.   The laminated nonwoven fabric of Claim 10 which has a nonwoven fabric of any one of Claims 1-8 between two spunbond nonwoven fabric layers.   A filter using the laminated nonwoven fabric according to claim 10 or 11.   The separator using the laminated body nonwoven fabric of Claim 10 or 11.   The support body using the laminated nonwoven fabric of Claim 10 or 11.   A sanitary material using the laminate nonwoven fabric according to claim 10 or 11.

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