Melt-blown nonwoven fabric, nonwoven fabric laminate, and melt-blown nonwoven fabric manufacturing method

Abstract

To provide a melt-blown nonwoven fabric constituted by fibers made of polyethylene-based resin, which has excellent mechanical strength as a nonwoven fabric while having excellent workability with suppressed heat shrinkage.SOLUTION: A melt-blown nonwoven fabric is mainly composed of polyethylene-based resin. The MFR of a resin composition constituting the melt-blown nonwoven fabric is 50 g / 10 min or more and 1000 g / 10 min or less. The density of the resin composition is 0.945 g / cm3 or more and 0.960 g / cm3 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to meltblown nonwoven fabrics and nonwoven fabric laminates. [Background technology]

[0002] Polyethylene nonwoven fabrics made from polyethylene fibers are known to have advantages such as softness and a pleasant feel, as well as excellent sterilization resistance and low leachable content in solutions. Meltblown nonwoven fabrics made from polyethylene resins, in particular, have been expected to take advantage of these characteristics and be used in a wide range of applications, including hygiene materials, medical materials, industrial filters, household goods, construction materials, and agricultural materials. However, polyethylene fibers are generally known to have low strength, and improving the sheet strength of meltblown nonwoven fabrics has been a challenge. Furthermore, conventional polyethylene meltblown nonwoven fabrics have a high thermal shrinkage rate, which causes shrinkage during sterilization or when laminated to other materials.

[0003] Patent Document 1 proposes a nonwoven fabric containing meltblown fibers formed from a composition containing polyethylene and a minor portion of at least one polyethylene processing stabilizing component in order to stabilize processability.

[0004] Patent Document 2 proposes a polyethylene nonwoven fabric having a fine fiber diameter and excellent uniformity, which is molded by a melt-blown method using a resin composition containing polyethylene and polyethylene wax.

[0005] Patent Document 3 proposes a method for producing a polyethylene nonwoven fabric, which includes a step of mixing 1.0% by mass to 5.0% by mass of heat-degraded polyethylene wax with polyethylene resin, and a step of melt-spinning the mixture at a temperature of 280°C or higher, in order to produce a nonwoven fabric with excellent productivity and quality. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2000-502411 [Patent Document 2] International Publication No. 2000 / 022219 [Patent Document 3] International Publication No. 2023 / 210758 Summary of the Invention [Problem to be solved by the invention]

[0007] In the nonwoven fabric disclosed in Patent Document 1, components other than polyolefins are contained as polyethylene processing stabilizing components, which not only results in poor spinnability but also weak adhesion between fibers, making it insufficient in terms of mechanical strength.

[0008] The nonwoven fabric disclosed in Patent Document 2 contains a large amount of polyethylene wax, and therefore has low mechanical strength and cannot be put to practical use, and therefore is not sufficient.

[0009] In Patent Document 3, although the amount of polyethylene wax added is low, the fiber diameter is large, and therefore the mechanical strength is not sufficient.

[0010] Furthermore, none of Patent Documents 1, 2, and 3 discusses improving the thermal shrinkage of melt-blown nonwoven fabrics, and there is a need to improve the thermal shrinkage rate.

[0011] Therefore, an object of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyethylene melt-blown nonwoven fabric that has excellent mechanical strength as a nonwoven fabric and a reduced thermal shrinkage rate. [Means for solving the problem]

[0012] As a result of extensive research to achieve the above object, the present inventors have discovered that by using a polyethylene resin having a specific range of MFR and a specific range of density, a melt-blown nonwoven fabric having excellent mechanical strength and suppressed thermal shrinkage can be obtained. The present invention was completed based on these findings.

[0013] The present invention and its preferred embodiments include the following configurations. [1] A melt-blown nonwoven fabric mainly composed of a polyethylene resin, wherein the MFR of the resin composition forming the melt-blown nonwoven fabric is 50 g / 10 min or more and 1000 g / 10 min or less, and the density of the resin composition is 0.945 g / cm 3 More than 0.960g / cm 3 That is meltblown nonwoven fabric. [2] The melt-blown nonwoven fabric according to [1] above, wherein the average fiber diameter of the melt-blown nonwoven fabric is 0.1 μm or more and 10.0 μm or less. [3] The bulk density of the meltblown nonwoven fabric is 0.05 g / cm 3 More than 0.30g / cm 3 The melt-blown nonwoven fabric according to [1] or [2] above, which is as follows: [4] The nonwoven fabric according to any one of the above [1] to [3], wherein the resin composition has an MFR of 70 g / 10 min or more and 1000 g / 10 min or less. [5] The density of the resin composition is 0.950 g / cm 3 More than 0.960g / cm 3 The melt-blown nonwoven fabric according to any one of the above [1] to [4], which is: [6] A nonwoven fabric laminate having a plurality of nonwoven fabric layers, at least one of which is made of the melt-blown nonwoven fabric described in any one of [1] to [5] above. [7] The nonwoven fabric laminate according to [6] above, wherein the nonwoven fabric layer on one or both surfaces of the nonwoven fabric laminate is a spunbond nonwoven fabric layer. [8] A method for producing the melt-blown nonwoven fabric according to any one of the above [1] to [5], comprising the following steps (a) and (b) in this order: Step (a): A spinneret having a plurality of spinning holes arranged in the width direction is used to spin a spun ... 3 More than 0.960g / cm 3 The following process involves melt-spinning a polyethylene resin to produce fibers. Step (b): The spun fibers are thinned by hot air and collected on a moving net conveyor to form a fiber web. [Effects of the Invention]

[0014] According to the present invention, there are provided a polyethylene melt-blown nonwoven fabric and a laminate thereof which exhibit excellent mechanical strength as a nonwoven fabric while suppressing the occurrence of thermal shrinkage. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a measurement diagram for measuring the dry heat shrinkage of the melt-blown nonwoven fabric of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The components of the present invention will be described in detail below. However, the present invention is not limited to the scope of the following description, and various modifications are possible within the scope of the present invention.

[0017] [Polyethylene resin] The melt-blown nonwoven fabric of the present invention is composed primarily of a polyethylene-based resin. By using a polyethylene-based resin as the primary component, the melt-blown nonwoven fabric can have excellent sterilization resistance when used in medical applications and produces little elution into a solution when used as a liquid filter. In the present invention, "composed primarily of a polyethylene-based resin" means that 50% by mass or more and 100% by mass or less of the constituent components are polyethylene-based resin.

[0018] Examples of the polyethylene resin include ethylene homopolymers and copolymers of ethylene with various α-olefins. The polyethylene resin may also be a mixture of two or more polyethylenes. It may also contain a branched component other than ethylene, such as a polyethylene resin copolymerized with an α-olefin such as butene, hexene, 4-methylpentene, heptene, or octene.

[0019] The polyethylene resin may be a mixture of two or more polyethylene resins, for example, two or more polyethylene resins with different MFRs may be blended in any ratio to adjust the MFR of the resin composition as described below.

[0020] The polyethylene resin preferably contains 60% by mass or more of an ethylene homopolymer, more preferably 70% by mass or more, and even more preferably 80% by mass or more of an ethylene homopolymer, which can maintain good spinnability and improve strength.

[0021] [Resin composition] The resin composition forming the melt-blown nonwoven fabric may contain commonly used additives such as antioxidants, weather stabilizers, light stabilizers, antistatic agents, spinning agents, antiblocking agents, lubricants, nucleating agents, and pigments, or other polymers, within the range that does not impair the effects of the present invention.

[0022] Furthermore, the resin composition preferably does not contain any substances that decompose the polyethylene resin and reduce the MFR, such as free radical agents such as peroxides, particularly dialkyl peroxides. The absence of free radical agents prevents the occurrence of partial viscosity variations due to non-uniform decomposition or gelation, makes it possible to achieve uniform single fiber fineness, and enables stable spinning of thin fibers. It also prevents deterioration of spinnability due to bubbles generated by decomposition gases.

[0023] The melting point of the resin composition is preferably 120° C. or higher and 135° C. or lower. By setting the melting point to preferably 120° C. or higher, more preferably 125° C. or higher, heat resistance sufficient for practical use is easily obtained. Furthermore, by setting the melting point to 135° C. or lower, self-fusion between fibers can be promoted, making it easier to obtain a melt-blown nonwoven fabric with excellent mechanical strength.

[0024] The melting point of the resin composition forming the meltblown nonwoven fabric is obtained by differential scanning calorimetry (DSC), and the value calculated according to the following procedure is adopted. (1) A small piece of melt-blown nonwoven fabric is sampled in an amount of 0.5 mg to 5 mg. (2) Using differential scanning calorimetry (DSC), the temperature is raised from room temperature to 280°C at a rate of 16°C / min to obtain a DSC curve. (3) From the DSC curve, the peak top temperature of the melting endothermic peak is read and used as the melting point (°C) of the polyethylene resin.

[0025] The density of the resin composition is 0.945 g / cm 3 More than 0.960g / cm 3 The density of the polyethylene resin is 0.945 g / cm or less. 3 More preferably, 0.950 g / cm 3 By setting the density of the polyethylene resin to 0.960 g / cm or more, the crystallinity of the fibers can be increased, and therefore, when the polyethylene resin is made into a melt-blown nonwoven fabric, the nonwoven fabric can be one in which thermal shrinkage is suppressed. 3or less, more preferably 0.958 g / cm 3 By setting the temperature to the following, excessive crystallization can be suppressed, and a nonwoven fabric that is flexible and has excellent processability can be obtained.

[0026] The solid density (g / cm) of the resin composition forming the meltblown nonwoven fabric 3 ) shall be calculated using the following procedure. (1) Five small pieces are randomly taken from the melt-blown nonwoven fabric. (2) The small pieces are washed by immersing them in ethanol and then dried in the air. (3) The density of a small piece of melt-blown nonwoven fabric is determined by the sink-float method using a water-ethanol mixed liquid system. (4) Repeat the same measurement on five small pieces and measure the density (g / cm 3 ) and rounded to the fourth decimal place to obtain the solid density of the composite fiber (g / cm 3 )

[0027] The resin composition has an MFR of 50 g / 10 min or more and 1000 g / 10 min or less. By setting the MFR of the polyethylene resin to 50 g / 10 min or more, more preferably 70 g / 10 min or more, the diameter can be reduced without causing thread breakage, and by reducing the diameter, the number of bonding points between fibers increases, resulting in a nonwoven fabric with excellent mechanical strength. On the other hand, by setting the MFR to 1000 g / 10 min or less, more preferably 500 g / 10 min or less, excessive reduction in molecular weight can be prevented, resulting in a nonwoven fabric with sufficient strength for practical use.

[0028] The MFR of the resin composition forming the meltblown nonwoven fabric is measured according to ASTM D1238 (Method A). This standard stipulates that polyethylene should be measured under a load of 2.16 kg and at a temperature of 190°C, and these conditions are also used in the present invention.

[0029] [fiber] The fibers constituting the meltblown nonwoven fabric preferably have an average single fiber diameter of 0.1 μm or more and 10.0 μm or less. By making the average single fiber diameter preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more, the strength of the meltblown nonwoven fabric can be improved. On the other hand, by making the average single fiber diameter 10.0 μm or less, more preferably 8.0 μm or less, and even more preferably 6.0 μm or less, the number of bonding points between fibers can be increased, thereby increasing the mechanical strength of the nonwoven fabric.

[0030] In the present invention, the average single fiber diameter (μm) is determined by the following method. (i) Measurement samples of 3 mm x 3 mm are taken from three points across the width of the melt-blown nonwoven fabric (two points on the side edges and one point in the center), plus five points every 5 cm along the length, for a total of 15 points. (ii) Using a scanning electron microscope (SEM, for example, Keyence Corporation's VHX-D500) with a magnification of 3000x, one photograph of each fiber surface was taken from each of the collected measurement samples, for a total of 15 photographs. (iii) Measure the single fiber diameter of fibers whose fiber diameter (single fiber diameter) can be clearly identified in the photograph. (iv) For all measurement samples, perform (iii) and round off the arithmetic mean value (μm) of the single fiber diameters of all fibers to the nearest tenth.

[0031] [Melt-blown nonwoven fabric] The meltblown nonwoven fabric of the present invention has a basis weight of 3 g / m 2 More than 100g / m 2 The weight of the melt-blown nonwoven fabric is preferably 3 g / m or less. 2 More than 5g / m 2 More preferably, 10 g / m 2 By increasing the density above 100g / m, the number of fibers increases and the number of bonding points increases, which makes it possible to suppress the thermal shrinkage of the melt-blown nonwoven fabric. 2 or less, more preferably 80 g / m 2 or less, more preferably 60 g / m 2By setting the thickness as follows, the thickness of the melt-blown nonwoven fabric can be reduced and the processability can be improved.

[0032] The melt-blown nonwoven fabric of the present invention has a bulk density of 0.05 g / cm 3 More than 0.30g / cm 3 The bulk density of the meltblown nonwoven fabric is preferably 0.05 g / cm or less. 3 More preferably, 0.07 g / cm 3 By satisfying the above conditions, the adhesion between the fibers becomes stronger, and the melt-blown nonwoven fabric is suppressed in thermal shrinkage. 3 or less, more preferably 0.28 g / cm 3 When the thickness is below 100 mm, the melt-blown nonwoven fabric has appropriate breathability.

[0033] The bulk density of the meltblown nonwoven fabric can be calculated from the basis weight of the meltblown nonwoven fabric and the thickness described below using the following formula, and the result is rounded to two decimal places to obtain the bulk density (g / cm 3 ) will be calculated. Bulk density (g / cm 3 ) = basis weight (g / m 2 ) / (thickness (mm) x 1000) ...(formula).

[0034] The thickness of the meltblown nonwoven fabric is measured at 10 equally spaced points in the width direction, and the average value is rounded to two decimal places to calculate the thickness (mm) of the nonwoven fabric. For example, a TECLOCK (registered trademark) SM-114 manufactured by TECLOCK Corporation can be used as a thickness meter.

[0035] The meltblown nonwoven fabric of the present invention has a tensile strength per unit area of ​​0.10 (N / 5cm) / (g / m 2 It is preferable that the tensile strength is 0.10 (N / 5cm) / (g / m 2 ) or more, more preferably 0.12 (N / 5cm) / (g / m 2 ) or more, more preferably 0.15 (N / 5cm) / (g / m 2) or more, the mechanical strength required for processing can be obtained, and the increased mechanical strength can also suppress thermal shrinkage.

[0036] In the present invention, the tensile strength per unit area of ​​the meltblown nonwoven fabric ((N / 5cm) / (g / m 2 )) shall be the value determined by the following method in accordance with 6.3 "Tensile strength and elongation" of JIS L1913:2010 "Test methods for general long-fiber nonwoven fabrics." (i) Three samples measuring 30 cm x 5.0 cm are taken from the nonwoven fabric at equal intervals in the MD direction. (ii) Apply a load until the sample breaks, with a grip distance of 20 cm and a tensile speed of 100±10 mm / min. (iii) The strength of the sample at the maximum load is taken as the tensile strength (N / 5cm), the average value of three points in the MD direction is calculated, and the sum of these average values ​​is taken as the tensile strength of the melt-blown nonwoven fabric. (iv) The tensile strength per unit area of ​​the meltblown nonwoven fabric ((N / 5cm) / (g / m 2 )) and round off to the third decimal place. Tensile strength per unit area of ​​meltblown nonwoven fabric ((N / 5cm) / (g / m 2 )) = [Tensile strength of melt-blown nonwoven fabric (N / 5cm)] / Basis weight (g / m 2 ).

[0037] The melt-blown nonwoven fabric of the present invention preferably has a dry heat shrinkage of 15% or less, more preferably 10% or less, which reduces shrinkage due to heat during lamination with other substrates or sterilization treatment, and prevents a decrease in barrier properties and a decrease in breathability.

[0038] The dry heat shrinkage rate of the melt-blown nonwoven fabric in the present invention is determined by the following method with reference to 6.10.3 of JIS L1913:2010 "Testing methods for general long-fiber nonwoven fabrics." (i) Three samples measuring 10 cm x 10 cm are taken from randomly selected locations on the nonwoven fabric, and on each sample, a marking line is marked to measure 5 cm intervals in both the vertical and horizontal directions, and a line segment between the marking lines is marked so that the two line segments are perpendicular to each other. (ii) Leave the sample in a thermostatic oven at 110°C ± 5°C for 3 minutes, then remove it and cool it to room temperature. (iii) Measure the length between the marked lines in both the vertical and horizontal directions to the nearest 0.01 cm, round off the average value to the third decimal place for each vertical and horizontal direction, apply this to the following formula, and round off to the first decimal place to calculate the dry heat shrinkage. Dry heat shrinkage rate (%)=100-(((L3×L4) / (L1×L2))×100) where: L1: Average length between the vertical gauge lines before heating (cm) L2: Average length between the gauge lines in the horizontal direction before heating (cm) L3: Average length between the vertical marks after heating (cm) L4: Average length between the gauge lines in the horizontal direction after heating (cm).

[0039] [Nonwoven fabric laminate] The meltblown nonwoven fabric of the present invention can also be laminated with other nonwoven fabrics to form a laminated nonwoven fabric. That is, the nonwoven fabric laminate of the present invention is a nonwoven fabric laminate having multiple nonwoven fabric layers, at least one of which is made of the meltblown nonwoven fabric of the present invention. For example, the meltblown nonwoven fabric of the present invention can be laminated with a sheet having higher rigidity than the meltblown nonwoven fabric of the present invention to increase its mechanical strength, or can be used in combination with a nonwoven fabric having high chemical resistance or heat resistance. Any method for laminating the meltblown nonwoven fabric of the present invention with another nonwoven fabric can be used as long as it does not impair the effects of the present invention. Examples of such methods include bonding the nonwoven fabrics together using an adhesive, spraying a moisture-curing urethane resin, spraying a thermoplastic resin or heat-sealing fiber, placing the nonwoven fabrics on a moving conveyor, and passing them through a heating furnace to bond them together, or laminating the nonwoven fabric by the meltblown method on top of a nonwoven fabric manufactured by a method other than the meltblown method.

[0040] As a method of laminating a nonwoven fabric produced by a method other than the meltblowing method, there can be employed a method in which fibers formed by the meltblowing method are deposited directly on a nonwoven fabric layer obtained by the spunbonding method to form a meltblown nonwoven fabric layer, and then the spunbonded nonwoven fabric layer and the meltblown nonwoven fabric layer are fused together; a method in which the spunbonded nonwoven fabric layer and the meltblown nonwoven fabric layer are superimposed on each other and fused together by heating and pressurizing; or a method in which the spunbonded nonwoven fabric layer and the meltblown nonwoven fabric layer are bonded together with an adhesive such as a hot melt adhesive or a solvent-based adhesive.

[0041] From the viewpoint of productivity, a method in which a meltblown nonwoven fabric layer is formed directly on a spunbonded nonwoven fabric layer is a preferred embodiment.

[0042] [Melt-blown nonwoven fabric manufacturing method] The melt-blown nonwoven fabric of the present invention can be preferably produced by the method for producing a melt-blown nonwoven fabric of the present invention, which is a method for producing a melt-blown nonwoven fabric of the present invention and includes the following steps (a) and (b) in this order:

[0043] [Step (a): Step of spinning fibers] In step (a), a spinneret having a plurality of spinning holes in the width direction is used to spin a spun ... 3 More than 0.960g / cm 3 The polyethylene resin described below is melt-spun to form fibers.

[0044] The fibers are preferably melted at a temperature above their melting point and below 150°C above their melting point, and are melt-extruded from a spinneret at a temperature above their melting point and below 150°C above their melting point.

[0045] The shape of the nozzle of the spinneret through which the fiber is extruded can be circular, elliptical, polygonal, multi-lobed, or a combination of these shapes, depending on the cross-sectional shape of the fiber. Among these, a circular shape is more preferred from the viewpoint of efficiently obtaining bonding points between the fibers and firmly bonding the fibers together by thermocompression bonding.

[0046] [Step (b): A step of thinning the spun fibers with hot air and collecting them to form a fiber web] In step (b), the spun fibers are thinned by blowing hot air onto them, and are then collected on a moving net conveyor to form a fiber web.

[0047] In step (b), the temperature of the hot air blown onto the spun fibers is preferably equal to or higher than the spinning temperature and equal to or lower than (spinning temperature + 60°C). By blowing the hot air at a temperature equal to or higher than the spinning temperature, more preferably equal to or higher than (spinning temperature + 10°C), and even more preferably equal to or higher than (spinning temperature + 20°C), the fibers spun out from the spinneret can be efficiently thinned. On the other hand, by blowing the hot air at a temperature equal to or lower than (spinning temperature + 60°C), more preferably equal to or lower than (spinning temperature + 50°C), and even more preferably equal to or lower than (spinning temperature + 40°C), a stable spinning state can be maintained.

[0048] [Other post-processing processes] In the method for producing the melt-blown nonwoven fabric of the present invention, it is preferable to further carry out various post-processing steps, as in the case of general melt-blown nonwoven fabrics. Of course, in the present invention, the melt-blown nonwoven fabric obtained by carrying out these post-processing steps is also considered to be the melt-blown nonwoven fabric of the present invention.

[0049] For example, functional agents such as the above-mentioned antibacterial agents, antifungal agents, antiallergen agents, antiviral agents, vitamin supplements, flame retardants, etc. may be attached to the fiber surface by post-processing. In particular, when the melt-blown nonwoven fabric of the present invention is used as a filter, the effect of imparting these functions can be significantly improved compared to conventional filters.

[0050] Preferred methods for attaching a functional agent to a fiber surface include coating methods using a gravure roll or a kiss roll, impregnation methods, and spraying methods. Furthermore, because of their excellent safety and low environmental impact, the solvent used to dilute the functional agent is preferably aqueous. Here, aqueous solvents include water alone, or aqueous solutions containing water-soluble organic solvents such as lower alcohols (e.g., methanol, ethanol, etc.), lower ketones (e.g., acetone, methyl ethyl ketone, etc.), lower carboxylic acids (e.g., acetic acid, etc.), and glycols (e.g., ethylene glycol, propylene glycol, diethylene glycol, etc.), and can be selected depending on the purpose.

[0051] Furthermore, by subjecting the melt-blown nonwoven fabric of the present invention to electret treatment, the dust removal performance is improved by utilizing electrostatic action in addition to physical action, and the fabric can be used alone as a coarse dust filter.

[0052] The electret treatment method is not particularly limited, but suitable examples include corona charging, charging a nonwoven fabric sheet by adding water and then drying it (e.g., methods described in JP-A-9-501604 and JP-A-2002-249978), and thermal electret. In the case of corona charging, the electric field strength is preferably 15 kV / cm or more, and more preferably 20 kV / cm. This strengthens the charge and improves the electrostatic collection performance. The charging process may be performed continuously during the production of the nonwoven fabric, or the nonwoven fabric may be wound up once produced and processed in a separate process.

[0053] Furthermore, the meltblown nonwoven fabric of the present invention can be given a shape by subjecting the sheet to a pleating process, which involves repeating mountain and valley folds. [Example]

[0054] Next, the meltblown nonwoven fabric of the present invention will be specifically described based on examples, although the present invention is not limited to these examples.

[0055] [Measurement method] The evaluation methods and measurement conditions used in the examples are explained below. Unless otherwise specified, the measurements of each physical property were carried out according to the above-mentioned methods.

[0056] (1) MFR (g / 10 min) of polyethylene resin The MFR of the polyethylene resin was measured according to ASTM D1238 (Method A) under conditions of a load of 2.16 kg and a temperature of 190°C.

[0057] (2) Solid density of polyethylene resin (g / cm 3 ) The solid density of the polyethylene resin was calculated by the method described above.

[0058] (3) Melting point of polyethylene resin (℃) The melting point of the polyethylene resin was calculated by the above-mentioned method using a differential scanning calorimeter, "DSC-2 Model" manufactured by PerkinElmer Co., Ltd.

[0059] (4) Average single fiber diameter (μm) The average single fiber diameter of the fibers was calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0060] (5) Bulk density of melt-blown nonwoven fabric (g / cm 3 ) The bulk density of the melt-blown nonwoven fabric was calculated by the above-mentioned method using a thickness gauge "TECLOCK (registered trademark) SM-114" manufactured by TECLOCK Corporation.

[0061] (6) Tensile strength per unit area of ​​meltblown nonwoven fabric ((N / 5cm) / (g / m 2 )) The tensile strength per unit area of ​​the spunbond nonwoven fabric was measured by the above-mentioned method using a constant-speed extension tensile tester "RTG-1250" manufactured by Baldwin.

[0062] (7) Dry heat shrinkage rate of meltblown nonwoven fabric The dry heat shrinkage of the spunbond nonwoven fabric was measured by the method described above.

[0063] [Resin used] The resins used in the examples and comparative examples are described in detail below. Polyethylene resin A (PE_A): MFR 90g / 10min, solid density 0.955g / cm 3 Polyethylene with a melting point of 130°C. Polyethylene resin B (PE_B): MFR 200g / 10min, solid density 0.954g / cm 3 Polyethylene with a melting point of 130°C. Polyethylene resin C (PE_C): MFR 1000g / 10min, solid density 0.956g / cm 3 , polyethylene with a melting point of 131°C. Polyethylene resin D (PE_D): MFR 50g / 10min, solid density 0.955g / cm 3 Polyethylene with a melting point of 130°C. Polyethylene resin E (PE_E): MFR 90g / 10min, solid density 0.945g / cm 3 , polyethylene with a melting point of 129°C. Polyethylene resin F (PE_F): MFR 90g / 10min, solid density 0.960g / cm 3 , polyethylene with a melting point of 132°C. Polyethylene resin G (PE_G): MFR 20g / 10min, solid density 0.935g / cm 3 , polyethylene with a melting point of 126°C. Polyethylene resin H (PE_H): MFR 90g / 10min, solid density 0.940g / cm 3 , polyethylene with a melting point of 128°C. Polyethylene resin I (PE_I): MFR 40g / 10min, solid density 0.955g / cm 3 Polyethylene with a melting point of 130°C. Polyethylene resin J (PE_J): MFR 100g / 10min, solid density 0.935g / cm 3 , polyethylene with a melting point of 121°C.

[0064] [Example 1] (Fiber spinning process) The polyethylene resin A was melted at a temperature of 260° C. Then, the polyethylene resin was spun out from a circular nozzle at a nozzle temperature of 260° C.

[0065] (Process for forming a fiber web) The fibers spun by the above process were blown with hot air at a temperature of 280°C at the upper limit of the flow rate at which no thread breakage occurred, and the weight of the resulting nonwoven fabric was 30 g / m 2 The melt-blown nonwoven fabric was formed by stacking the mixture on a net conveyor whose moving speed was adjusted so that the melt-blown nonwoven fabric was formed.

[0066] The melt-blown nonwoven fabric obtained was evaluated, and the results are shown in Table 1.

[0067] [Example 2] In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin B. Otherwise, a melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0068] [Example 3] In the fiber spinning process, polyethylene resin A was changed to polyethylene resin C. A melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0069] [Example 4] In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin D. Otherwise, a melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0070] [Example 5] In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin E. Otherwise, a melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0071] [Example 6] In the fiber spinning process, polyethylene resin A was changed to polyethylene resin F. A melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0072] [Comparative Example 1] In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin G. Otherwise, a melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0073] Comparative Example 2 In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin H. A melt-blown nonwoven fabric was otherwise obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0074] Comparative Example 3 In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin I. A melt-blown nonwoven fabric was otherwise obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0075] Comparative Example 4 In the fiber spinning process, polyethylene resin A was replaced with polyethylene resin J. Otherwise, a melt-blown nonwoven fabric was obtained using the same procedures and conditions as in Example 1. The evaluation results of the obtained melt-blown nonwoven fabric are shown in Table 1.

[0076] [Table 1]

[0077] The meltblown nonwoven fabrics of Examples 1 to 6 have a tensile strength per unit area of ​​0.11 ((N / 5cm) / (g / m 2 ))~0.23((N / 5cm) / (g / m 2 )) and had excellent mechanical strength, and the dry heat shrinkage was also suppressed at 4.4% to 10.3%, resulting in a nonwoven fabric with excellent processability.

[0078] On the other hand, the nonwoven fabrics of Comparative Examples 1, 2, and 4 had dry heat shrinkage rates of 18.3% to 30.0%, which were 10% or more, and were poor in processability. The melt-blown nonwoven fabric of Comparative Example 3 had a tensile strength per unit area weight of 0.07 ((N / 5cm) / (g / m 2 )) and had poor mechanical strength. [Explanation of symbols]

[0079] 1: Vertical line segment 2: Horizontal line segment L1 (L3): Length of the vertical line before (after) heating (cm) L2 (L4): The horizontal straight line length (cm) before (after) heating.

Claims

1. A melt-blown nonwoven fabric mainly composed of a polyethylene resin, wherein the resin composition forming the melt-blown nonwoven fabric has an MFR of 50 g / 10 min or more and 1000 g / 10 min or less, and a density of the resin composition is 0.945 g / cm ３ 0.960g / cm or more ３ The following is a meltblown nonwoven fabric.

2. The meltblown nonwoven fabric according to claim 1, wherein the average fiber diameter of the meltblown nonwoven fabric is 0.1 μm or more and 10.0 μm or less.

3. The bulk density of the meltblown nonwoven fabric is 0.05 g / cm ３ 0.30g / cm or more ３ The meltblown nonwoven fabric according to claim 1 or 2, wherein:

4. The melt-blown nonwoven fabric according to claim 1 or 2, wherein the resin composition has an MFR of 70 g / 10 min or more and 1000 g / 10 min or less.

5. The density of the resin composition is 0.950 g / cm ３ 0.960g / cm or more ３ The meltblown nonwoven fabric according to claim 1 or 2, wherein:

6. A nonwoven fabric laminate having a plurality of nonwoven fabric layers, at least one of the plurality of nonwoven fabric layers comprising the meltblown nonwoven fabric according to claim 1 or 2.

7. The nonwoven fabric laminate according to claim 6, wherein the nonwoven fabric layer on one or both surfaces of the nonwoven fabric laminate is a spunbond nonwoven fabric layer.

8. A method for producing the melt-blown nonwoven fabric according to claim 1 or 2, comprising the following steps (a) and (b) in this order: Step (a): A spinneret having a plurality of spinning holes arranged in the width direction is used to spin a spun ... ３ 0.960g / cm or more ３ The following process involves melt-spinning a polyethylene resin to produce fibers. Step (b): The spun fibers are thinned by hot air and collected on a moving net conveyor to form a fiber web.

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