Dustproof material, protective clothing, and method for manufacturing dustproof material

Abstract

A dust-proof material according to the present disclosure is provided with: a melt-blown nonwoven fabric layer that has been electreted; and spunbond nonwoven fabric layers laminated and fixed to both main surfaces of the melt-blown nonwoven fabric layer. The melt-blown non-woven fabric layer comprises a melt-blown non-woven fabric. The spunbond non-woven fabric layer comprises a spunbond non-woven fabric. The weight per unit area of the dustproof material is 15 gsm or more and less than 55 gsm. The ratio of the weight per unit area of the melt-blown non-woven fabric layer to the weight per unit area of the dust-proof material is 3% or more and less than 10%.

Description

Technical Field

[0001] The present disclosure relates to a dustproof material, protective clothing, and a method for manufacturing the dustproof material. Background Art

[0002] Conventionally, when working in an environment where dust is flying in the air (for example, asbestos removal work), workers wear protective clothing to protect their bodies from the dust.

[0003] Patent Document 1 discloses a dustproof material for protective clothing. The dustproof material specifically disclosed in Patent Document 1 includes a three-layer structure. The three-layer structure dustproof material is formed by stacking and fixing spunbond nonwoven fabric, meltblown nonwoven fabric and spunbond nonwoven fabric in this order. The meltblown nonwoven fabric is subjected to electret processing (hereinafter also referred to as "electret processing"). The charge density of the meltblown nonwoven fabric is 1.0×10 -9 Coulomb / cm 2 ~8.5×10 -9 Coulomb / cm 2 . Meltblown nonwoven fabrics contain hindered amine additives. Spunbond nonwoven fabrics are not electret-formed. The fixing method is ultrasonic bonding, fixed-point thermal bonding, or adhesive (spray). The ratio of the unit area weight of the meltblown nonwoven fabric contained in the three-layer dustproof material to the unit area weight of the three-layer dustproof material (hereinafter also referred to as "MB content") is 42% to 45%.

[0004] Patent Document 1: International Publication No. 2014 / 208605 Summary of the Invention

[0005] Problems to be solved by the invention

[0006] Electret meltblown nonwoven fabrics are easy to capture dust, and are therefore sometimes referred to as dust-collecting layers in dust-proof materials. Generally, if the quality of the meltblown nonwoven fabric increases, its collection efficiency tends to increase. On the other hand, if the quality of the meltblown nonwoven fabric increases, there is a tendency for the air permeability to decrease. As for the protective clothing disclosed in Patent Document 1 that uses a dust-proof material with a high MB content (i.e., a dust-proof material with a high quality meltblown nonwoven fabric), wearing it for a long time can cause fatigue in the operator, which may reduce the operator's work efficiency. In particular, in high-temperature environments such as summer, due to the accumulation of heat in the protective clothing, the operator may suffer from heat stroke, etc. Therefore, as a dust-proof material with excellent air permeability that allows the heat in the protective clothing to dissipate to the outside of the protective clothing compared to the past, a dust-proof material with a higher collection efficiency than the previous dust-proof material (in other words, a dust-proof material with a low MB content) is required.

[0007] In view of the above problems, one embodiment of the present disclosure aims to provide a dustproof material, protective clothing, and a method for producing a dustproof material that have a high ratio of collection efficiency to the basis weight of an electret meltblown nonwoven fabric layer and excellent air permeability.

[0008] Means for solving problems

[0009] Specific means for solving the above-mentioned problems include the following aspects.

[0010] [1] A dustproof material comprising:

[0011] a meltblown nonwoven fabric layer, which is electretized and comprises a meltblown nonwoven fabric; and

[0012] a spunbond nonwoven fabric layer, which is laminated and fixed to both main surfaces of the meltblown nonwoven fabric layer and comprises a spunbond nonwoven fabric,

[0013] The weight per unit area of ​​the dustproof material is greater than 15 gsm and less than 55 gsm.

[0014] The ratio of the basis weight of the meltblown nonwoven fabric layer to the basis weight of the dustproof material is 3% or more and less than 10%.

[0015] [2] A dustproof material comprising:

[0016] a meltblown nonwoven fabric layer, which is electretized and comprises a meltblown nonwoven fabric; and

[0017] a spunbond nonwoven fabric layer, which is laminated and fixed to both main surfaces of the meltblown nonwoven fabric layer and comprises a spunbond nonwoven fabric,

[0018] The weight per unit area of ​​the dustproof material is greater than 25 gsm and less than 55 gsm.

[0019] The ratio of the basis weight of the meltblown nonwoven fabric layer to the basis weight of the dustproof material is 3% to 10%.

[0020] [3] The dustproof material according to [1] or [2] above, wherein the thickness of the dustproof material is 0.5 mm or less.

[0021] [4] The dustproof material according to any one of [1] to [3] above, wherein the average fiber diameter of the fibers in the meltblown nonwoven fabric layer exceeds 1.0 μm and is less than 3.0 μm.

[0022] [5] The dustproof material according to any one of [1] to [4] above, wherein the meltblown nonwoven fabric layer has a weight per unit area of ​​less than 10 gsm.

[0023] [6] The dustproof material according to any one of [1] to [5] above, comprising a plurality of embossed portions formed by fusing a portion of the meltblown nonwoven fabric layer with a portion of the spunbonded nonwoven fabric layer,

[0024] The embossing rate is 3% to 30%,

[0025] The embossing ratio indicates a ratio of the total area of ​​the plurality of embossed portions formed on one main surface of the dustproof material to the area of ​​the one main surface of the dustproof material.

[0026] [7] The dustproof material according to [6] above, wherein the embossing rate is 3% to 15% and satisfies all of the following (a) to (c).

[0027] (a) The weight per unit area of ​​the dustproof material is not less than 15 gsm and not more than 45 gsm;

[0028] (b) The thickness of the dustproof material is less than 0.42 mm;

[0029] (c) The meltblown nonwoven fabric layer has a weight per unit area of ​​less than 10 gsm.

[0030] [8] The dustproof material according to any one of [1] to [7] above, wherein the fiber linear density of the meltblown nonwoven fabric layer is 2 μm·gsm to 20 μm·gsm,

[0031] The fiber linear density refers to the product of the weight per unit area of ​​the meltblown nonwoven fabric layer and the average fiber diameter of the fibers of the meltblown nonwoven fabric layer.

[0032] [9] The dustproof material according to any one of [1] to [8] above, wherein the spunbond nonwoven fabric layer is an electret-treated spunbond nonwoven fabric layer.

[0033]

[10] The dustproof material according to any one of [1] to [9] above, having an air permeability of 35 ccs or more.

[0034]

[11] The dustproof material according to any one of [1] to

[10] above, wherein the resin composition used in at least one of the meltblown nonwoven fabric layer and the spunbonded nonwoven fabric layer is a polyolefin.

[0035]

[12] A protective garment using the dustproof material described in any one of [1] to

[11] above.

[0036]

[13] A method for manufacturing a dustproof material, which is a method for manufacturing the dustproof material described in any one of [1] to

[12] above, comprising:

[0037] Laminating the meltblown web and the spunbond web in-line to form a first laminate;

[0038] performing embossing on the first laminate to produce a second laminate; and

[0039] The second laminate is subjected to an electret treatment to produce the dustproof material.

[0040]

[14] A dustproof material comprising:

[0041] a meltblown nonwoven fabric layer, which is electretized and comprises a meltblown nonwoven fabric; and

[0042] a spunbond nonwoven fabric layer, which is laminated and fixed to both main surfaces of the meltblown nonwoven fabric layer and comprises a spunbond nonwoven fabric,

[0043] The dustproof material has an air permeability of 120 ccs or more and 200 ccs or less.

[0044]

[15] The dustproof material according to

[14] above, wherein the weight per unit area of ​​the dustproof material is less than 55 gsm.

[0045]

[16] According to the dustproof material described in

[14] or

[15] above, the unit area weight of the above-mentioned meltblown non-woven fabric layer is less than 10 gsm.

[0046]

[17] The dustproof material according to any one of

[14] to

[16] above, wherein the ratio of the unit area weight of the meltblown nonwoven fabric layer to the unit area weight of the dustproof material is 3% to 15%.

[0047]

[18] The dustproof material according to any one of

[14] to

[17] above, comprising a plurality of embossed portions formed by fusing a portion of the meltblown nonwoven fabric layer with a portion of the spunbonded nonwoven fabric layer,

[0048] The embossing rate is 3% to 15%,

[0049] The embossing ratio indicates a ratio of the total area of ​​the plurality of embossed portions formed on one main surface of the dustproof material to the area of ​​the one main surface of the dustproof material.

[0050]

[19] The dustproof material according to any one of

[14] to

[18] above, wherein the thickness of the dustproof material is 0.5 mm or less.

[0051]

[20] The dustproof material according to any one of

[14] to

[19] above, wherein the average fiber diameter of the fibers in the meltblown nonwoven fabric layer exceeds 1.0 μm and is 3.0 μm or less.

[0052]

[21] The dustproof material according to any one of

[14] to

[20] above, wherein the fiber linear density of the meltblown nonwoven fabric layer is 2 μm·gsm to 20 μm·gsm,

[0053] The fiber linear density refers to the product of the weight per unit area of ​​the meltblown nonwoven fabric layer and the average fiber diameter of the fibers of the meltblown nonwoven fabric layer.

[0054]

[22] According to the dustproof material described in any one of

[14] to

[21] above, the spunbond nonwoven fabric layer is an electret-treated spunbond nonwoven fabric layer.

[0055]

[23] The dustproof material according to any one of

[14] to

[21] above, wherein the resin composition used in the meltblown nonwoven fabric layer and / or the spunbonded nonwoven fabric layer is a polyolefin.

[0056]

[24] A protective suit using the dustproof material described in any one of

[13] to

[22] above.

[0057]

[25] A method for manufacturing a dustproof material, which is a method for manufacturing the dustproof material described in any one of

[13] to

[23] above, comprising:

[0058] Laminating the meltblown web and the spunbond web in-line to form a first laminate;

[0059] performing embossing on the first laminate to produce a second laminate; and

[0060] The second laminate is subjected to an electret treatment to produce the dustproof material.

[0061] Effects of the Invention

[0062] According to one embodiment of the present disclosure, there are provided a dustproof material, protective clothing, and a method for producing the dustproof material, which have a high ratio of collection efficiency to the basis weight of an electret meltblown nonwoven fabric layer and excellent air permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] [ Figure 1 ] Figure 1 This is a schematic diagram for explaining the method of measuring charge density. DETAILED DESCRIPTION

[0064] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are provided to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0065] In the numerical ranges described in this disclosure, the upper limit or lower limit of one numerical range may be replaced by the upper limit or lower limit of another numerical range described in this disclosure. In the numerical ranges described in this disclosure, the upper limit or lower limit of the numerical range may be replaced by the value shown in the Examples.

[0066] In the present disclosure, each component may include multiple corresponding substances. When the amount of each component in the composition is mentioned in the present disclosure, if multiple substances corresponding to each component are present in the composition, unless otherwise specified, it refers to the total amount of the multiple substances present in the composition.

[0067] In the present disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process can be achieved. In the present disclosure, the numerical range expressed by "to" indicates a range that includes the numerical values ​​recorded before and after the "to" as the minimum and maximum values, respectively. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the content of each component in the composition refers to the total amount of the plurality of substances present in the composition.

[0068] In the present disclosure, “electret” refers to a substance that maintains electric polarization for a long time even in the absence of an external electric field and forms an electric field on the surroundings.

[0069] (1) First embodiment

[0070] (1.1) Dust-proof materials

[0071] The dustproof material of the first embodiment of the present disclosure includes: an electret-treated meltblown nonwoven fabric layer (hereinafter also referred to as an "MB layer"); and a spunbond nonwoven fabric layer (hereinafter also referred to as an "SB layer") laminated and fixed to both main surfaces of the meltblown nonwoven fabric layer. The meltblown nonwoven fabric layer includes a meltblown nonwoven fabric (hereinafter also referred to as an "MB"). The spunbond nonwoven fabric layer includes a spunbond nonwoven fabric (hereinafter also referred to as an "SB"). The basis weight of the dustproof material is 15 gsm or more and less than 55 gsm. Preferably, the basis weight of the dustproof material is 25 gsm or more and less than 55 gsm. The ratio of the basis weight of the meltblown nonwoven fabric layer to the basis weight of the dustproof material (hereinafter also referred to as the "MB content") is 3% or more and less than 10% (in this specification, "3% or more and less than 10%" is synonymous with "3% to 10% (the dustproof material of the first embodiment does not include the dustproof material having the above ratio of 10%).")

[0072] The present inventors have found that by setting the MB content of a dustproof material including an MB layer and an SB layer within the above range, a dustproof material having both collection efficiency and air permeability can be provided even if the basis weight of the meltblown nonwoven fabric layer is low.

[0073] In the present disclosure, "nonwoven fabric" refers to a planar fiber assembly having a predetermined level of structural strength obtained by a physical method and / or a chemical method other than weaving, knitting, and papermaking.

[0074] "Meltblown nonwoven fabric" refers to a nonwoven fabric produced on a meltblown web using one or more combined processes. "Meltblown web" refers to a web produced by meltblowing lamination. "Meltblown lamination" refers to a method of producing a web by extruding a molten polymer into a high-speed, high-temperature airflow to form fibers, which are then laminated onto a moving wire mesh. The average fiber diameter of a meltblown nonwoven fabric is typically less than 10 μm.

[0075] The “electret meltblown nonwoven fabric layer” indicates a charge density of 1×10 -10 Coulomb / cm 2 The above meltblown nonwoven fabric layer.

[0076] "Spunbond nonwoven fabric" refers to a nonwoven fabric produced by one or more bonding methods on a spunbond web. "Spunbond web" refers to a web produced by spunbond lamination. "Spunbond lamination" refers to a method of producing a web by extruding a molten or dissolved polymer through a nozzle and laminating the filaments onto a moving web. The average fiber diameter of spunbond nonwoven fabrics is typically 10 μm or greater.

[0077] Since the dust-proof material of the first embodiment has the above-mentioned structure, its collection efficiency is high relative to the weight per unit area of ​​the electret meltblown nonwoven fabric layer, and it has excellent air permeability. Therefore, when the dust-proof material of the first embodiment is used in protective clothing, the dust-proof material of the first embodiment can make the weight of the protective clothing lighter than before. As a result, the protective clothing using the dust-proof material of the first embodiment is not likely to cause fatigue to the operator even when worn for a long time, and the operator's work efficiency can be less likely to decrease. In addition, the protective clothing using the dust-proof material of the first embodiment is not likely to accumulate heat in the protective clothing. As a result, the protective clothing using the dust-proof material of the first embodiment can also suppress the occurrence of heat stroke in high temperature environments such as summer.

[0078] The dustproof material is a sheet-like material. The structure of the dustproof material can be appropriately selected depending on the intended use, and may include, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a structure with five or more layers. A three-layer dustproof material comprises an MB layer and an SB layer laminated and fixed to both main surfaces of the MB layer. A four-layer dustproof material is formed by laminating and fixing an SB layer, an MB layer, an SB layer, and other layers in that order. Other layers will be described later.

[0079] The dustproof material preferably has a three-layer structure. The fibers contained in the MB layer have relatively low mechanical strength. The fibers contained in the SB layer have relatively high mechanical strength. The three-layer structure of the dustproof material allows the pair of SB layers to function as protective layers for the MB layer. Therefore, even if the three-layer dustproof material is subjected to mechanical impact, the MB layer is less susceptible to damage. As a result, the dustproof material maintains excellent collection efficiency. Therefore, three-layer dustproof materials are suitable for use in protective clothing.

[0080] The MB content of the dustproof material should be at least 3% and less than 10%. If the MB content of the dustproof material is 10% or more, air inside the protective suit becomes difficult to vent. Heat accumulates inside the protective suit, potentially degrading the wearer's comfort during prolonged work. If the MB content of the dustproof material is less than 3%, the dustproof material may not achieve the collection efficiency required for its intended use.

[0081] From the viewpoint of air permeability and collection efficiency, the MB content of the dustproof material is preferably 5% or more and less than 10%.

[0082] The method for measuring the MB content of the dustproof material is the same as the method described in the examples.

[0083] The thickness of the dustproof material is not particularly limited and can be appropriately selected depending on the intended use of the dustproof material, but is preferably 0.5 mm or less. As a result, the thermal conductivity of the dustproof material is superior to that of a material having a thickness exceeding 0.5 mm. Therefore, when the dustproof material is used in protective clothing, heat is less likely to accumulate within the clothing. Furthermore, the dustproof material is softer than when the thickness exceeds 0.5 mm. Therefore, when the dustproof material is used in protective clothing, the clothing allows the operator to move more easily. As a result, the protective clothing provides an excellent wearing feel and improves the operator's work efficiency.

[0084] If the dustproof material is too thin, it may not achieve the strength required for the intended use. If it is too thick, it may not exhibit the required air permeability. Therefore, from the perspective of achieving both strength and air permeability, the thickness of the dustproof material is more preferably 0.2 mm to 0.5 mm.

[0085] The method for measuring the thickness of the dustproof material is the same as the method described in the examples.

[0086] From the perspective of reducing carbon dioxide emissions corresponding to the amount of resin used (hereinafter also referred to as "environmental load reduction"), the weight per unit area of ​​the dustproof material is 15 gsm or more and less than 55 gsm.

[0087] In recent years, there has been a demand for dustproof materials that have good performance even if the carbon dioxide emissions are small. However, if only the amount of resin used is reduced (especially the meltblown unit area weight for the dust collection layer is reduced), there is a tendency for the dustproof performance to decrease. Therefore, dustproof materials with a unit area weight of 55 gsm or more have been used (for example, the unit area weight of the MB layer for the dust collection layer is 25 gsm or more). The dustproof material of the first embodiment can provide a dustproof material with good performance even if the unit area weight is less than 55 gsm by using a specific laminated structure, and can greatly improve the collection efficiency of the MB layer per unit area weight. Furthermore, since the dustproof material of the first embodiment becomes a protective suit with less mass, the dustproof material of the first embodiment can reduce the load on the operator when wearing the protective suit. In particular, the dustproof material of the first embodiment can improve the operator's operability and wearing feel during long-term wear.

[0088] From the viewpoint of the strength of the dustproof material, the basis weight of the dustproof material is more preferably 25 gsm to 55 gsm, further preferably 25 gsm to 50 gsm, and further preferably 25 gsm to 45 gsm.

[0089] Even if the basis weight of the dustproof material is less than 55 gsm, by setting the MB content to 3% or more and less than 10%, a higher effect can be achieved in terms of the collection efficiency per MB basis weight.

[0090] The method for measuring the basis weight of the dustproof material is the same as that described in the examples.

[0091] The air permeability of the dustproof material is not particularly limited and can be appropriately selected according to the use of the dustproof material, but is preferably 35 ccs or more. This improves the workability of the worker when wearing the dustproof material for a long time.

[0092] From the perspective of improving the workability of workers wearing the dustproof material for extended periods of time, the air permeability of the dustproof material is more preferably 40ccs to 200ccs, further preferably 60ccs to 200ccs, particularly preferably greater than 105ccs and less than 200ccs, and even more preferably 120ccs to 200ccs. Conventional dustproof materials have an air permeability of less than 100ccs, demonstrating the difficulty of achieving both dustproof performance and air permeability. However, in the first embodiment, the MB weight per unit area can be reduced through a specific laminated structure, making it possible to design a dustproof material with superior air permeability.

[0093] The method for measuring the air permeability of the dustproof material is the same as the method described in the examples.

[0094] Methods for bonding the SB layer to the MB layer include ultrasonic bonding, thermal bonding using a hot embossing roller or a hot calendering roller, and lamination using an adhesive to prevent the SB and MB layers from melting or fusing beyond their desired state due to excessive heat. When laminating the SB and MB layers, it is preferred that the SB and MB layers overlap, and the bonded portions are heat treated. In the dustproof material of the first embodiment, the SB and MB layers may be in direct contact. In other words, in the dustproof material of the first embodiment, there may not be an adhesive layer between the SB and MB layers. The adhesive layer is formed using a known adhesive.

[0095] The dustproof material preferably has a plurality of embossed portions formed by fusing a portion of the MB layer with a portion of the SB layer, with an embossing ratio of 3% to 30%. The embossing ratio represents the ratio of the total area of ​​the plurality of embossed portions formed on one main surface of the dustproof material to the area of ​​the one main surface of the dustproof material.

[0096] The "embossed portion" refers to a non-fibrous portion formed by thermally bonding a portion of a plurality of fibers. Examples of the shape of the embossed portion include a circle, an ellipse, an oval, a square, a rhombus, a rectangle, a quadrilateral, and continuous shapes based on these shapes.

[0097] The "embossing rate" refers to the proportion of the embossed portion in the dust-proof material that has been subjected to embossing treatment and ultrasonic treatment. Specifically, when the MB layer and the SB layer are thermally bonded using a pair of embossing rollers with convex and concave shapes, the "embossing rate" refers to the proportion of the portion where the convex portion of one embossing roller overlaps the convex portion of the other embossing roller and abuts the dust-proof material (i.e., the embossed portion) in the dust-proof material. When the MB layer and the SB layer are thermally bonded using an embossing roller with convex and concave shapes and a mirror roller, the "embossing rate" refers to the proportion of the portion where the convex portion of the embossing roller with convex and concave shapes abuts the dust-proof material (i.e., the embossing portion) in the dust-proof material. When sufficient heat is applied to the embossing portion during thermal bonding and the fibers in the embossing portion are partially fused to each other, the proportion of the embossed portion in the dust-proof material during the embossing treatment can be regarded as the same value as the engraved area ratio (also called "embossing area ratio") of the embossing roller that has been embossed on the first laminate (the laminate of the MB layer and the SB layer). In addition, when ultrasonic bonding is performed, the "embossing ratio" refers to the ratio of the portion heat-fused by ultrasonic processing (ie, the embossed portion) to the entire dustproof material.

[0098] The embossing rate helps improve collection efficiency. It can be seen that by setting the embossing rate of the dustproof material of the first embodiment to 3% or higher, better collection efficiency can be achieved. An embossing rate of 3% to 30% creates a dustproof material with a soft touch, thus improving the wearer's comfort.

[0099] From the viewpoint of collection efficiency, the embossing rate is more preferably 3% to 20%.

[0100] From the viewpoint of collection efficiency and wearing feeling of the worker (softness of the dustproof material), the embossing rate is more preferably 3% to 15%, and further preferably 10% to 15%.

[0101] When lamination is performed using an adhesive, the adhesive used in the above process is not particularly limited, and examples thereof include hot melt adhesives, powder adhesives, and solution adhesives. Among them, hot melt adhesives are preferred from the perspectives of cost and the ability to be evenly applied to the object. Examples of hot melt adhesives include synthetic rubber adhesives, olefin adhesives, and EVA (ethylene vinyl acetate) adhesives. Synthetic rubber adhesives and olefin adhesives are preferred from the perspectives of excellent adhesion and excellent affinity between the SB layer and the MB layer. When using a hot melt adhesive as the adhesive, from the perspective of being able to extrude the hot melt adhesive more evenly from a T-die, the melt viscosity of the hot melt adhesive at 140°C is preferably 2000 mPa·s or less, and more preferably 1500 mPa·s or less. On the other hand, the melt viscosity of the hot melt adhesive at 140°C is preferably 300 mPa·s or more, and more preferably 500 mPa·s or more.

[0102] Methods for laminating the SB and MB layers using hot melt adhesive include applying the adhesive to the substrate from a patterned roller; applying a powdered adhesive to the substrate and then heating and bonding; and applying a molten adhesive in a spray form. Among these, spray application of the hot melt adhesive from a T-die extruder is preferred. This method allows the SB and MB layers to be laminated without significantly compromising the feel and air permeability of the dustproof material. It also improves the adhesion between the SB and MB layers with a low application amount, allowing for more uniform application of the hot melt adhesive. When the hot melt adhesive has a melt viscosity of 2000 mPa·s or less at 140°C, the temperature of the hot melt adhesive during extrusion from the T-die is preferably 100°C or higher, and more preferably 130°C or higher, to ensure more uniform extrusion of the hot melt adhesive from the T-die. On the other hand, from the viewpoint of suppressing damage to the dustproof material caused by the high-temperature hot melt adhesive, the temperature of the hot melt adhesive during extrusion from the T-die is preferably 180° C. or lower, more preferably 160° C. or lower.

[0103] The absolute value of the difference between the water contact angle of the surface of one SB layer (i.e., one main surface of the dustproof material) and the water contact angle of the surface of the other SB layer (i.e., the other main surface of the dustproof material) of the dustproof material can be less than 20°.

[0104] The water contact angle of the SB layer surface is the average of the values ​​measured using a contact angle meter using the drop method under the following measurement conditions. If the water permeates the SB layer within 5000 mS after the test solution is dropped onto the SB layer, preventing measurement, the water contact angle is set to "0°."

[0105] [Measurement conditions]

[0106] Test solution: distilled water, 2 μL

[0107] ·Measurement period: 5000mS after adding the test solution

[0108] ·Analytical method: θ / 2 method

[0109] ·N number: 10

[0110] (1.1.1) Meltblown nonwoven fabric layer

[0111] The MB layer functions as a filter for dust flying in the air. Specifically, the MB layer captures dust flying in the air and prevents the dust from passing through the dustproof material.

[0112] The MB layer contains MB. The MB content is not particularly limited; however, from the perspective of improving the dust collection efficiency of the dustproof material, it is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, further preferably 90% to 100% by mass, and particularly preferably 100% by mass, relative to the total amount of the MB layer.

[0113] The basis weight of the MB layer can be appropriately selected depending on the intended use of the dustproof material, but is preferably less than 10 gsm. The dustproof material of the first embodiment, even with an MB layer basis weight of less than 10 gsm, can still achieve the desired collection efficiency due to its specific laminated structure. A high MB layer basis weight tends to reduce air permeability. Since the MB layer basis weight of the dustproof material of the first embodiment is less than 10 gsm, the dustproof material exhibits excellent air permeability, improving the wearer's comfort.

[0114] From the viewpoint of achieving both collection efficiency and breathability (wearing feel), the basis weight of the MB layer is more preferably 1 gsm or more and less than 10 gsm, further preferably 1 gsm to 8 gsm, and particularly preferably 1 gsm to 5 gsm.

[0115] The method for measuring the basis weight of the MB layer is the same as that described in Examples.

[0116] When the MB layer has a basis weight of 8 gsm or less, by setting the MB content to 3% or more and less than 10%, a higher effect is achieved in terms of the collection efficiency per MB basis weight.

[0117] From the viewpoint of improving the collection efficiency of the dust-proof material, the charge density of the MB layer is preferably 1×10 -10 Coulomb / cm 2 More than 1×10 -9 Coulomb / cm 2 More than 1×10 -8 Coulomb / cm 2 above.

[0118] The charge density of the MB layer is calculated using Figure 1 Specifically, Figure 1 As shown, a grounded metal box 1 and a metal flat electrode 2 (area 100cm 2 , material: brass) between which a sample 3 is sandwiched, and the charge generated by electrostatic induction is measured by an electrometer 5 via a capacitor 4. From the measured potential, the surface charge density is calculated by the following formula (1).

[0119] Formula (1): Q = C × V / S

[0120] In formula (1), Q represents the surface charge density (coulomb / cm 2 ), C represents the capacitor capacity, V represents the potential, and S represents the area of ​​the plate electrode.

[0121] (1.1.1.1) Fiber

[0122] The average fiber diameter of the fibers constituting the MB layer (hereinafter referred to as "MB fibers") is preferably greater than 1.0 μm and less than 3.0 μm. This allows for a balanced balance between air permeability and collection efficiency. Generally, a smaller average fiber diameter of the MB fibers improves collection efficiency, but this also reduces air permeability. To ensure even better air permeability, the average fiber diameter of the MB fibers in the dustproof material of the first embodiment is more preferably greater than 1.0 μm and less than 3.0 μm, and even more preferably greater than 1.5 μm and less than 3.0 μm.

[0123] From the viewpoint of achieving both air permeability and collection efficiency, the average fiber diameter of the MB fibers is more preferably 2.0 μm or more and less than 3.0 μm.

[0124] The method for measuring the average fiber diameter of MB fibers is the same as the method described in Examples.

[0125] The fiber linear density of the MB layer is not particularly limited, but is preferably 2 μm·gsm to 20 μm·gsm. Fiber linear density refers to the product of the weight per unit area of ​​the MB layer and the average fiber diameter of the fibers in the MB layer. By setting the fiber linear density of the MB layer to 2 μm·gsm to 20 μm·gsm, good collection efficiency can be achieved even with a low MB weight per unit area, while also improving the wearing feel.

[0126] From the viewpoint of improving the collection efficiency per unit area weight of the meltblown nonwoven fabric layer, the fiber linear density of the MB layer is more preferably 3 μm·gsm to 10 μm·gsm.

[0127] "gsm" means Grams per Square Meter (g / m 2 ).

[0128] MB fibers may be long fibers or short fibers. The cross-sectional shape of MB fibers is not particularly limited, and examples thereof include circular, elliptical, and irregular cross-sectional shapes.

[0129] MB fiber can be a composite fiber or a single component fiber. The composite fiber preferably has two or more thermoplastic resins as constituent components. Examples of the composite fiber include core-sheath type, side-by-side type, island-in-the-sea type, and side-by-side type.

[0130] (1.1.1.2) Resin composition for meltblown nonwoven fabrics

[0131] MB fibers are composed of a resin composition for MB (hereinafter also referred to as "MB composition").

[0132] (1.1.1.2.1) Polyolefins

[0133] The MB composition may contain a polyolefin (hereinafter also referred to as a "polyolefin-based polymer." The same applies to other raw materials). The polyolefin used in the meltblown nonwoven fabric of the first embodiment refers to a homopolymer of an α-olefin, a copolymer composed of two or more α-olefins, or a mixture of two or more selected from these. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, isopentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0134] Examples of the polyolefin polymer include polyethylene, polypropylene, polybutene-1, poly-4-methyl-1-pentene, ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 4-methyl-1-pentene copolymers, propylene / 1-butene copolymers, and 4-methyl-1-pentene / 1-decene copolymers. Among these, polyolefin polymers preferably include polypropylene, polybutene-1, or poly-4-methyl-1-pentene from the perspectives of high strength, ease of adjustment to a suitable melt viscosity, and ease of molding by meltblowing. Polypropylene is more preferably included from the perspectives of ease of molding and easy electret formation.

[0135] This polyolefin polymer exhibits moderate flow properties, making it easy to form by meltblown lamination and providing a nonwoven fabric with excellent strength. [η] is preferably 0.5 to 3 dl / g, more preferably 0.7 to 1.5 dl / g, and even more preferably 0.8 to 1.3 dl / g. [η] is a value measured in decalin at 135°C.

[0136] The melt flow rate (MFR) of the polyolefin polymer is not particularly limited as long as the MB composition can be melt-spun, but is preferably 50 to 5000 g / 10 min, more preferably 200 to 4000 g / 10 min, and even more preferably 500 to 2500 g / 10 min.

[0137] The MFR of the polyolefin polymer is measured in accordance with ASTM D-1238 under the following conditions: 230° C. and a load of 2.16 kg.

[0138] (1.1.1.2.1.1) Propylene-based polymers derived from biomass

[0139] The polyolefin polymer may be a propylene polymer derived from biomass. The main component of the modified polyolefin (A) or polyolefin mixture (B) described below may also be a propylene polymer derived from biomass. From the perspective of reducing carbon dioxide emissions when used as protective clothing compared to when using fossil fuels such as coal and petroleum, it is preferred to use a propylene polymer derived from biomass as the polyolefin polymer.

[0140] "Biomass-derived propylene polymer" refers to a propylene polymer produced from raw material monomers containing biomass-derived propylene. Biomass-derived propylene polymers are carbon-neutral materials and can therefore reduce the environmental load in the production of nonwoven fabric laminates.

[0141] The biomass-derived propylene-containing monomer serving as the raw material for the biomass-derived propylene polymer can be synthesized from biomass-derived ethylene by cracking biomass naphtha. The biomass-derived propylene polymer is obtained by polymerizing the thus synthesized biomass-derived propylene-containing monomer using the same method as conventionally known methods using petroleum-derived propylene.

[0142] A propylene polymer synthesized using a monomer containing bio-derived propylene as a raw material is called a biomass-derived propylene polymer. The content of the bio-derived propylene polymer in the raw material monomers may exceed 0% by mass, may be 100% by mass, or may be less than 0% by mass relative to the total amount of the raw material monomers.

[0143] Monomers serving as raw materials for biomass-derived propylene-based polymers may include, in addition to bio-derived propylene, propylene derived from fossil fuels such as petroleum and / or α-olefins other than ethylene and propylene (such as 1-butene and 1-hexene).

[0144] Biomass-derived propylene polymers can be obtained by using a specific gas to synthesize olefins from methanol (MTO: Methanol-to-Olefins) to obtain propylene, and then polymerizing the resulting propylene. "Specific gas" refers to the gas produced by thermally decomposing empty fruit bunches (EFB: Empty Fruit Bunches) (for example, coconut shells). Biomass-derived propylene polymers can also be obtained by using a specific gas to synthesize propylene from methanol (MTP: Methanol-to-Propylene) to obtain propylene, and then polymerizing the resulting propylene.

[0145] Furthermore, a propylene-based polymer derived from biomass can also be obtained by producing isopropyl alcohol by fermentation from a biomass raw material mainly composed of inedible plants (for example, chestnut, etc.), and polymerizing propylene obtained by dehydrating the isopropyl alcohol.

[0146] When the content of radioactive carbon (C14) in monomers such as propylene as a raw material is referred to as PC14, the content rate Pbio (%) of biomass-derived carbon in the raw material can be calculated by the following formula (2).

[0147] Formula (2): Pbio (%) = PC14 / 105.5×100

[0148] That is, if the raw materials for the propylene-based polymer are all derived from biomass, the theoretical content of biomass-derived carbon is 100%. Therefore, the biomass degree of the propylene-based polymer derived from biomass is 100%. Since raw materials derived from fossil fuels contain almost no C14, the biomass-derived carbon content in the propylene-based polymer produced solely from raw materials derived from fossil fuels is 0%, and the biomass degree of the propylene-based polymer derived from fossil fuels is 0%.

[0149] "Biomass content" indicates the carbon content derived from biomass and can be calculated by measuring radioactive carbon (C14). C14 is contained in a certain proportion (approximately 105.5 pMC) of carbon dioxide in the atmosphere. Therefore, it is known that the C14 content in plants that absorb carbon dioxide in the atmosphere (such as corn) is also around 105.5 pMC. It is also known that fossil fuels contain almost no C14. Therefore, by measuring the proportion of C14 contained in all carbon atoms in the propylene-based polymer, the carbon content derived from biomass in the raw material can be calculated.

[0150] The biomass degree of the propylene-based polymer used as a raw material for the MB layer is preferably 10% or more.

[0151] The content of the biomass-derived propylene polymer used in the MB layer may be 5 to 99 mass%, 10 to 75 mass%, or 20 to 50 mass% relative to 100 mass% of the total of the fossil fuel-derived polypropylene resin and the biomass-derived polypropylene resin.

[0152] The propylene-based polymer used as a raw material of the MB layer may include a propylene-based polymer obtained by recycling, so-called recycled polymer.

[0153] "Recycled polymers" include polymers obtained by recycling waste polymer products. Recycled polymers can be produced, for example, by the method described in DE102019127827 (A1). Recycled polymers may also include a mark that identifies them as recycled.

[0154] (1.1.1.2.2) Charging agent

[0155] The MB composition may contain a charging agent. This facilitates electret formation of the MB layer, which results in improved dust collection efficiency of the dustproof material.

[0156] Examples of charging agents include graft-modified copolymers, hindered amine compounds, and triazine compounds. The charging agent preferably comprises at least one of a graft-modified copolymer, a hindered amine compound, and a triazine compound. It may be a graft-modified copolymer or at least one of a hindered amine compound and a triazine compound. The charging agent may not contain a hindered amine compound. Details of the graft-modified copolymer, hindered amine compound, and triazine compound are described below.

[0157] When the MB composition contains a charging agent, the content of the charging agent is preferably 0.01% by mass to 7.0% by mass, and more preferably 0.05% by mass to 6.0% by mass, relative to the total amount of the MB composition.

[0158] (1.1.1.2.2.1) Graft-modified copolymers

[0159] The MB composition may include a first graft-modified copolymer or a second graft-modified copolymer. The first graft-modified copolymer is formed by graft-copolymerizing a monomer having a polar group onto a non-polar polymer. The second graft-modified copolymer is formed by graft-copolymerizing a monomer having a polar group onto a specific polymer. The specific polymer is formed by introducing polar groups into the side chains or main chain of the non-polar polymer through oxidation or halogenation. When the charging agent is a graft-modified copolymer, corona charging is used as the charging method.

[0160] Examples of polar groups include halogen atoms such as chlorine, fluorine, bromine, or iodine; atomic groups such as carbonyl or nitro groups; and groups represented by -COOCH3, -COOC2H5, -OCOCH3, -OC2H5, -OCH2C6H5, -COOH, -OH, -NH2, -CONH2, or -COONH4. The MB composition may contain one or more of these polar groups.

[0161] The graft-modified copolymer formed by graft copolymerizing a monomer having a polar group may comprise a modified polyolefin (A) or a polyolefin mixture (B). The modified polyolefin (A) refers to a modified polyolefin modified with at least one modifying monomer selected from unsaturated carboxylic acids and their derivatives. The polyolefin mixture (B) comprises the modified polyolefin (A) and an unmodified polyolefin. In the polyolefin mixture (B), the modified polyolefin (A) and the unmodified polyolefin may be formed from the same polyolefin or different polyolefins.

[0162] The amount of polar groups in the MB composition is preferably 1 mol% or less, more preferably 0.5 mol% or less.

[0163] The polyolefin serving as the main component of the modified polyolefin (A) or the polyolefin mixture (B) is a homopolymer of an α-olefin, a copolymer comprising two or more α-olefins, or a mixture of two or more thereof. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, isopentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0164] The unmodified polyolefin as the main component of the modified polyolefin (A) or the polyolefin mixture (B) is preferably a resin mixture from the viewpoint of obtaining an MB having an excellent balance between strength and hot workability. The resin mixture comprises (a) 98% to 40% by mass of polypropylene and (b) a polyolefin having a density of less than 0.900 g / cm 3 The ethylene / α-olefin copolymer having a crystallinity of 5% to 40% is composed of 2% to 60% by mass (the total of (a) + (b) is 100% by mass).

[0165] The modified polyolefin (A) or the modified polyolefin (A) as a component of the polyolefin mixture (B) is obtained by graft-modifying a polyolefin with at least one modifying monomer selected from unsaturated carboxylic acids and their derivatives.

[0166] Examples of the polyolefin as the main component of the modified polyolefin (A) include homopolymers of α-olefins and copolymers of two or more α-olefins. Examples of the homopolymers of α-olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, isopentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-hexadecene, 1-octadecene, and 1-eicosene.

[0167] Examples of the polyolefin include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 4-methyl-1-pentene copolymers, propylene / 1-butene copolymers, and 4-methyl-1-pentene / 1-decene copolymers. Among these, unmodified polyolefins or polyolefins with excellent compatibility are preferably used. For example, when polypropylene is used as the unmodified polyolefin, polypropylene is preferably used as the raw material polyolefin for the graft-modified polyolefin.

[0168] Examples of the unsaturated carboxylic acid or its derivative used as the modifying monomer include unsaturated carboxylic acid, anhydride, ester, amide, imide or chloride thereof.

[0169] Examples of the unsaturated carboxylic acid or its derivative include acrylic acid, methacrylic acid, vinylacetic acid, ethylacrylic acid, 2,4-pentadienoic acid, carboxystyrene, maleic acid, fumaric acid, itaconic acid, citraconic acid, allylsuccinic acid, mesaconic acid, glutaconic acid, nadic acid, methylnadic acid, tetrahydrophthalic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, monomethyl citrate, dimethyl citrate, monoethyl citrate, diethyl citrate, monomethyl nadic acid, dimethyl nadic acid, monoethyl nadic acid, diethyl nadic acid, acrylic acid. Glycidyl acrylate, glycidyl methacrylate, maleic anhydride, itaconic anhydride, citraconic anhydride, methylhexahydrophthalic acid, 3,6-terminal methylenephthalic anhydride, methyltetrahydrophthalic anhydride, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N,N-diethylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N,N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, or potassium methacrylate. These may be used alone or in combination of two or more. Among them, maleic anhydride is preferably used.

[0170] Various known methods can be used to prepare the modified polyolefin (A) by grafting the modified monomer onto a polyolefin. For example, the modified polyolefin and the modified monomer can be reacted by heating the polyolefin and the modified monomer to a high temperature with or without the addition of a free radical initiator in the presence or absence of a solvent. Other vinyl monomers such as styrene may also be present during the reaction.

[0171] The content of the modifying monomer in the modified polyolefin (A) (i.e., the grafting ratio of the modified polyolefin (A)) is preferably 3 mol% or less, more preferably 1.5 mol% or less. In particular, when the electret nonwoven fabric is formed from the modified polyolefin (A) alone, the grafting ratio is preferably 1 mol% or less.

[0172] The intrinsic viscosity (135°C, decalin) of the modified polyolefin (A) is preferably 0.1 dl / g to 3.0 dl / g, more preferably 0.3 dl / g to 2.0 dl / g, and even more preferably 0.5 dl / g to 1.5 dl / g, from the viewpoint of facilitating uniform mixing with the unmodified polyolefin, having appropriate flow properties, and facilitating production of a nonwoven fabric by a melt-blowing method.

[0173] In the polyolefin mixture, the content ratio of the modified polyolefin (A) to the unmodified polyolefin (modified polyolefin (A) / unmodified polyolefin) is preferably 0.1 / 99.9 to 20 / 80, more preferably 1 / 99 to 5 / 95 by mass.

[0174] (1.1.1.2.2.2) Hindered amine compounds

[0175] The charging agent may contain a hindered amine compound or may be a hindered amine compound. The charging agent may not contain a hindered amine compound. When the charging agent is a hindered amine compound, a hydrocharge method is used as the charging method.

[0176] Examples of hindered amine compounds include poly[(6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino)], dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidinyl succinate polycondensate, and bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-n-butylmalonate.

[0177] (1.1.1.2.2.3) Triazine compounds

[0178] The charging agent may contain a triazine compound or may be a triazine compound. When the charging agent is a triazine compound, a water electret method is used as a charging method.

[0179] Examples of the triazine compound include poly[(6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidinyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidinyl)imino)] and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-((hexyl)oxy)-phenol.

[0180] (1.1.1.2.3) Additives

[0181] The MB composition may be blended with various additives within a range that does not impair the purpose of the present disclosure. Examples of additives include antioxidants, ultraviolet absorbers, pigments, dyes, nucleating agents, fillers, slip agents, anti-blocking agents, lubricants, flame retardants, and plasticizers.

[0182] (1.1.1.2.4) Preparation method

[0183] The MB composition can be prepared using various commonly used methods. For example, the modified polyolefin (A) and the unmodified polyolefin, along with various additives as needed, can be mixed and then melt-kneaded. Examples of mixers include ribbon blenders, V-type blenders, drum mixers, and Henschel mixers. Melt-kneading can be performed using, for example, a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a twin-roll mill.

[0184] (1.1.2) Spunbond nonwoven fabric layer

[0185] The SB layer functions as a protective layer for the MB layer. Specifically, the SB layer relieves stress applied to the MB layer when a mechanical impact is applied to the dustproof material.

[0186] The SB layer contains SB. The content of SB is not particularly limited; however, from the perspective of improving the collection efficiency of the dust-proof material, the SB content is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, further preferably 90% to 100% by mass, and particularly preferably 100% by mass, relative to the total amount of the SB layer.

[0187] The SB layer may be an SB layer that has been subjected to an electret treatment, or may be an SB layer that has not been subjected to an electret treatment.

[0188] The SB layer is preferably an electret-treated SB layer. By stacking an electret-treated SB layer and an electret-treated MB layer, the dust-proof material's collection efficiency, particularly the collection efficiency per unit area weight of the MB layer, can be improved. In this case, the SB layer may or may not contain a charging agent. More preferably, at least one of the SB layers contains a charging agent. The phrase "at least one of the SB layers contains a charging agent" includes the case where, by stacking the SB layer and the electret-treated MB layer, a portion of the charging agent added to the MB layer migrates (bleeds) into the SB layer, thereby containing the charging agent in at least one of the SB layers.

[0189] The weight per unit area of ​​the SB layer can be appropriately selected depending on the purpose of the dustproof material, etc. From the perspective of the flexibility of the dustproof material and reducing the environmental load, it is preferably 50 gsm or less, and from the perspective of the strength of the dustproof material, it is preferably 10 gsm or more. From these two perspectives, it is more preferably 15 gsm to 50 gsm.

[0190] The method for measuring the basis weight of the SB layer is the same as that described in Examples.

[0191] (1.1.2.1) Fiber

[0192] The average fiber diameter of the fibers constituting the SB layer (hereinafter also referred to as "SB fibers") is not particularly limited, but is generally 10 μm to 50 μm.

[0193] The method for measuring the average fiber diameter of the SB fibers is the same as the method described in Examples.

[0194] SB fibers can be either long or short fibers. The cross-sectional shape of the SB fibers is not particularly limited, and examples thereof include circular, elliptical, or irregularly shaped cross-sections (e.g., hollow fibers, V-shaped, cross-shaped, or T-shaped). In order to achieve low weight per unit area and reduce CO₂ emissions, the cross-sectional shape of the SB fibers is preferably hollow.

[0195] SB fibers may contain commonly used additives as needed. Examples of additives include charging agents, antistatic agents, absorbent particles, nanoparticles, ion exchange resins, deodorants, fragrances, adhesives, surface modifiers, biocides, antibacterial agents, antiviral agents, flame retardants, stabilizers, antioxidants, weathering stabilizers, heat stabilizers, light stabilizers, antifogging agents, lubricants, conductive materials, dyes, pigments, natural oils, synthetic oils, and waxes. These additives may be known additives.

[0196] The SB fiber can be a composite fiber, a monocomponent fiber, a crimped fiber, or a single fiber. The composite fiber preferably comprises two or more thermoplastic resins as constituent components. Examples of the composite fiber include core-sheath type, side-by-side type, island-in-the-sea type, and side-by-side type. When the SB fiber is a single fiber, the SB fiber may also comprise a variety of resins.

[0197] (1.1.2.2) Resin composition for spunbond nonwoven fabrics

[0198] The SB fibers are composed of a resin composition for spunbonded nonwoven fabrics (hereinafter also referred to as "SB composition").

[0199] (1.1.2.2.1) Polyolefins

[0200] The SB composition preferably contains a polyolefin-based polymer. Examples of the polyolefin-based polymer include the same ones exemplified as the olefin in the MB fiber.

[0201] The melt flow rate (MFR) of the polyolefin polymer is not particularly limited as long as the SB composition can be melt-spun, but is preferably 1 g / 10 min to 1000 g / 10 min, more preferably 5 g / 10 min to 500 g / 10 min, and even more preferably 10 g / 10 min to 100 g / 10 min.

[0202] The MFR of the polyolefin polymer is measured in accordance with ASTM D-1238 under the following conditions: 230° C. and a load of 2.16 kg.

[0203] The content of the polyolefin polymer is preferably 55.0 to 95.0% by mass, more preferably 65.0 to 95.0% by mass, further preferably 75.0 to 95.0% by mass, and particularly preferably 85.0 to 95.0% by mass, based on the total amount of the SB composition.

[0204] The polyolefin-based polymer may be a commercially available product.

[0205] (1.1.2.2.2) Other polymers

[0206] The SB composition may contain polymers other than polyolefin polymers (hereinafter also referred to as "other polymers") or may not contain other polymers. Examples of other polymers include thermoplastic elastomers and thermoplastic resins other than polyolefin polymers.

[0207] Examples of the thermoplastic elastomer include styrene-based elastomers, polyester-based elastomers, polyamide-based elastomers, thermoplastic polyurethane-based elastomers, vinyl chloride-based elastomers, and fluorine-based elastomers.

[0208] Examples of thermoplastic resins other than polyolefin polymers include polyesters, polyamides (e.g., nylon-6, nylon-66, or poly(m-xylylene adipamide), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymers, ethylene / vinyl acetate / vinyl alcohol copolymers, ethylene / (meth)acrylic acid copolymers, ethylene / acrylate / carbon monoxide copolymers, polyacrylonitrile, polycarbonate, and polystyrene.

[0209] Examples of the polyester include aliphatic polyesters and polyester copolymers. Examples of the polyester copolymer include those obtained by polymerizing an aliphatic dicarboxylic acid alone or a mixture of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid with one or more diols.

[0210] The content of the polyolefin polymer in the SB layer is preferably more than 90% by mass and less than 100% by mass, more preferably 95% to 100% by mass, relative to the total of the polyolefin polymer and other polymers (i.e., thermoplastic elastomer and thermoplastic resin other than the polyolefin polymer).

[0211] (1.1.2.2.3) Charging agent

[0212] The SB composition may contain a charging agent. This facilitates the electretization of the SB layer, thereby improving the dust collection efficiency of the dustproof material.

[0213] Examples of the charging agent include the same ones exemplified as the charging agent in the MB fiber. When the SB composition contains the charging agent, the content of the charging agent may be 0.01% by mass to 7.0% by mass relative to the total amount of the SB composition.

[0214] (1.1.2.2.4) Additives

[0215] The SB composition may be formulated with various additives within a range that does not impair the purpose of the present disclosure. Examples of additives include antioxidants, ultraviolet absorbers, pigments, dyes, nucleating agents, fillers, slip agents, antiblocking agents, lubricants, flame retardants, and plasticizers.

[0216] (1.1.3) Other layers

[0217] The dustproof material may or may not include other layers depending on the intended use. The other layers are laminated on at least one of the main surfaces of the dustproof material.

[0218] Examples of the other layers include knitted fabrics, woven fabrics, nonwoven fabrics, and films. The method for laminating (bonding) the other layers to the dustproof material is not particularly limited, and examples thereof include heat embossing, heat fusion (e.g., ultrasonic fusion), mechanical interlacing (e.g., needle punching, water jetting), methods using adhesives (e.g., hot melt adhesives, urethane adhesives, etc.), and extrusion lamination.

[0219] Examples of the nonwoven fabric include spunbond nonwoven fabric, meltblown nonwoven fabric, wet-laid nonwoven fabric, dry-laid nonwoven fabric, dry-laid pulp nonwoven fabric, flash-spun nonwoven fabric, and open-fiber nonwoven fabric. These nonwoven fabrics may be stretchable or non-stretchable.

[0220] The term "non-stretchable nonwoven fabric" refers to a nonwoven fabric that does not generate recovery stress after being stretched in the MD (machine direction) or CD (cross direction) of the nonwoven fabric.

[0221] As a film, preferably an air permeable (moisture permeable) film. As an air permeable film, a film formed by a thermoplastic elastomer with moisture permeability (for example, a polyurethane elastomer, a polyester elastomer, or a polyamide elastomer, etc.), a porous film, etc. can be cited. The porous film is formed by stretching a film formed by a thermoplastic resin containing inorganic particles or organic particles to make it porous. As the thermoplastic resin for the porous film, a polyolefin is preferably used. As a polyolefin, for example, high-pressure low-density polyethylene, linear low-density polyethylene (so-called LLDPE), high-density polyethylene, polypropylene or polypropylene random copolymer can be cited. These polyolefins can be used alone or in combination of two or more. However, in the case where it is not necessary to maintain the air permeability and hydrophilicity of the non-woven fabric laminate, a film of a thermoplastic resin such as polyethylene, polypropylene or a combination thereof can also be used.

[0222] (1.1.4) Preferred method

[0223] In the dustproof material of the first embodiment, it is preferable that the resin composition used in at least one of the meltblown nonwoven fabric layer and the spunbonded nonwoven fabric layer is a polyolefin.

[0224] In the dustproof material of the first embodiment, the embossing rate is preferably 3% to 15%. This increases the collection efficiency per MB unit area weight, and the dustproof material has moderate softness, which makes it difficult for hot air to accumulate (good breathability), thereby improving wearing comfort and workability.

[0225] From the viewpoint of achieving a better effect and reducing environmental load, the dustproof material of the first embodiment preferably has an embossing rate of 3% to 15% and satisfies any one of the following (a1) to (d1).

[0226] (a1) The weight per unit area of ​​the dustproof material is not less than 15 gsm and not more than 50 gsm;

[0227] (b1) The average fiber diameter of the MB layer exceeds 1.5 μm and is 2.6 μm or less;

[0228] (c1) The weight per unit area of ​​the MB layer is less than 4 gsm and exceeds 1.5 gsm;

[0229] (d1) The fiber linear density is 2 μm·gsm to 10 μm·gsm.

[0230] From the viewpoint of better collection efficiency and softness, and better skin feel and wearing comfort, the dustproof material of the first embodiment preferably has an embossing rate of 3% to 15% and satisfies any one of the following (a2) to (c2).

[0231] (a2) The weight per unit area of ​​the dustproof material is not less than 15 gsm and not more than 40 gsm;

[0232] (b2) The thickness of the dustproof material is less than 0.41 mm;

[0233] (c2) The basis weight of the SB layer is 40 gsm or less.

[0234] From the viewpoint of better collection efficiency and breathability and better softness, touch and wearing feel, the dustproof material of the first embodiment preferably has an embossing rate of 3% to 15% and satisfies any one of the following (a3) ​​to (c3).

[0235] (a3) The weight per unit area of ​​the dustproof material is not less than 15 gsm and not more than 45 gsm;

[0236] (b3) The thickness of the dustproof material is less than 0.42 mm;

[0237] (c3) The MB layer has a weight per unit area of ​​less than 10 gsm.

[0238] From the viewpoint of achieving an excellent balance between collection efficiency and air permeability, the dustproof material of the first embodiment preferably satisfies the following (a4) and (b4).

[0239] (a4) embossing rate is 8% to 15%;

[0240] (b4) The weight per unit area of ​​the dustproof material is 15 gsm or more and 35 gsm or less.

[0241] (1.2) Protective clothing

[0242] The protective clothing of the first embodiment uses the dustproof material of the first embodiment.

[0243] Due to the above-described structure, the protective clothing of the first embodiment is lighter than conventional protective clothing. Consequently, even when worn for extended periods, the protective clothing of the first embodiment is less likely to fatigue the worker, minimizing the reduction in worker efficiency. Furthermore, compared to conventional protective clothing, the protective clothing of the first embodiment is less likely to accumulate heat within the garment. Consequently, the protective clothing of the first embodiment can suppress the occurrence of heatstroke even in high-temperature environments such as summer.

[0244] The form of the protective clothing is not particularly limited, and examples thereof include a body suit, a cape, or a gown that covers the entire body.

[0245] The protective clothing of the first embodiment can be obtained, for example, by cutting the dustproof material of the first embodiment into a predetermined shape to obtain protective clothing components, and then joining the obtained protective clothing components. The joining method may be any known method, including sewing, crimping, and bonding. By using a single material of a propylene-based polymer for the SB layer and the MB layer, it is possible to produce dustproof materials, protective clothing components, and protective clothing that reduce environmental impact through raw material recycling.

[0246] (1.3) Manufacturing method of dustproof material

[0247] The method for manufacturing the dustproof material of the first embodiment is a method for manufacturing the dustproof material of the first embodiment. The method for manufacturing the dustproof material of the first embodiment includes: laminating a meltblown web (hereinafter also referred to as an "MB web") and a spunbond web (hereinafter also referred to as an "SB web") online to produce a first laminate (hereinafter also referred to as an "online lamination process"); embossing the first laminate to produce a second laminate (hereinafter also referred to as an "embossing process"); and electret-treating the second laminate to produce the dustproof material (hereinafter also referred to as an "electret-treating process"). The online lamination process, the embossing process, and the electret-treating process are performed in this order.

[0248] "In-line lamination of meltblown and spunbond webs" means that meltblown lamination and spunbond lamination are performed on the same moving web to produce a first laminate in a single step. Specifically, in the case of a three-layer dustproof material, spunbond lamination, meltblown lamination, and spunbond lamination are performed in this order on the same moving web to produce a first laminate with a three-layer structure in a single step.

[0249] "Embossing" refers to a process in which the first laminate is sandwiched between an embossing roll and a mirror-finished roll, thermally pressing a portion of the plurality of fibers contained in the first laminate to form a plurality of embossed portions. During embossing, the MB web becomes the MB layer, the SB web becomes the SB layer, and the MB and SB layers are laminated and fixed.

[0250] The “electret treatment” refers to a treatment in which a nonwoven fabric in the absence of an external electric field is transformed into a nonwoven fabric that retains electric polarization for a long time and forms an electric field in the surrounding area.

[0251] The method for producing the dustproof material of the first embodiment has the above-described configuration, and therefore can produce a dustproof material having a high ratio of collection efficiency to the basis weight of the electret meltblown nonwoven fabric layer and excellent air permeability.

[0252] (1.3.1) Online Lamination Process

[0253] In the in-line lamination step, the MB web and the SB web are laminated in-line to produce a first laminate.

[0254] The first laminate is a precursor of a dustproof material. The first laminate comprises an MB web and an SB web laminated on at least one main surface of the MB web. The MB web and the SB web are not fixed.

[0255] The method of laminating the MB web and the SB web in-line can be performed using a known manufacturing apparatus. The raw material of the MB web is the above-mentioned MB composition. The raw material of the SB web is the above-mentioned SB composition.

[0256] (1.3.2) Embossing process

[0257] In the embossing step, the first laminate is embossed to produce a second laminate.

[0258] The second laminate is a precursor of the dustproof material. The second laminate comprises an MB layer and an SB layer laminated and fixed to at least one main surface of the MB layer. The second laminate has the same structure as the first laminate except that it is embossed.

[0259] In the embossing process, the first stack is sandwiched between an embossing roller and a mirror roller to form a plurality of embossed portions. The embossing roller has a plurality of convex portions arranged in a regular pattern on its surface. The embossing roller transfers the shape of the top surface of the plurality of convex portions to a portion of the plurality of fibers contained in the first stack. Thus, the embossing roller forms a plurality of embossed portions arranged in a regular pattern on the dustproof material. The shape of the top surface of the plurality of convex portions arranged in a regular pattern of the embossing roller is the same as the shape exemplified above as the embossed portion. The preferred range of the area ratio of the plurality of convex portions of the embossing roller (hereinafter also referred to as the "embossing area ratio") is the same as the above-mentioned embossing ratio.

[0260] The surface temperature of the embossing roller is preferably (resin melting point - 20°C) to (resin melting point + 20°C), more preferably (resin melting point - 15°C) to (resin melting point + 10°C), and even more preferably (resin melting point - 15°C) to the resin melting point.

[0261] (1.3.3) Electret treatment process

[0262] In the electret treatment step, the second laminate is subjected to an electret treatment to produce a dustproof material.

[0263] The method of electret treatment is not particularly limited as long as the nonwoven fabric contained in the second laminate can be electretized, and examples thereof include: a corona charging method; a method of electretizing the second laminate by applying water or a water-soluble organic solvent aqueous solution and then drying it (for example, the method described in Japanese Unexamined Patent Publication No. 9-501604 or Japanese Patent Application Laid-Open No. 2002-115177, also known as a water electret method), etc.

[0264] When the electret treatment is performed using corona charging, the electric field strength is preferably 10 kV / cm or higher, more preferably 15 kV / cm or higher, and even more preferably 25 kV / cm or higher. To prevent damage to the dustproof material, the electric field strength is preferably less than 50 kV / cm. In the case of a three-layer dustproof material, the MB layer is electretized by performing an electret treatment using corona charging on one main surface of the dustproof material. In the case of a three-layer dustproof material, to improve the dust collection efficiency of the dustproof material, it is preferable to perform an electret treatment on both main surfaces of the dustproof material using corona charging.

[0265] According to one method of the first embodiment, a dust-proof material, protective clothing, and dust-proof material are provided, which have a high ratio of capture efficiency to the unit area weight of the electret meltblown nonwoven fabric layer and excellent air permeability. Therefore, the dust-proof material of the first embodiment effectively utilizes the above-mentioned characteristics and can also be widely used as surgical work clothes, clean room work clothes, work clothes in various fields (such as biology, medicine, food, or electronics-related fields), and work clothes in special environments (such as laboratory coats, radiation protection clothing, and work clothes for operations (such as dust / powder operations, dismantling operations, or asbestos removal operations). The dust-proof material of the first embodiment can also be used as protective clothing for operations involved in the above-mentioned uses (such as aprons, vests, outer pants, sleeves, hats, masks, gloves, or shoe covers, etc.).

[0266] (2) Second embodiment

[0267] The dustproof material of the second embodiment of the present disclosure comprises: an electret-treated meltblown nonwoven fabric layer; and a spunbond nonwoven fabric layer laminated and secured to both main surfaces of the meltblown nonwoven fabric layer. The meltblown nonwoven fabric layer comprises a meltblown nonwoven fabric. The spunbond nonwoven fabric layer comprises a spunbond nonwoven fabric. The dustproof material has a weight per unit area of ​​25 gsm or more and less than 55 gsm. The ratio of the weight per unit area of ​​the meltblown nonwoven fabric layer to the weight per unit area of ​​the dustproof material is 3% to 10%. However, the dustproof material of the second embodiment does not include a dustproof material having the aforementioned ratio of 10%.

[0268] Due to the above-mentioned structure, the dust-proof material of the second embodiment has a high collection efficiency relative to the unit area weight of the electret meltblown non-woven fabric layer, and has excellent air permeability. Therefore, when the dust-proof material of the second embodiment is used in protective clothing, the dust-proof material of the second embodiment can make the weight of the protective clothing lighter than before. As a result, the protective clothing using the dust-proof material of the second embodiment is not likely to cause fatigue to the operator even if worn for a long time, and the operator's work efficiency can be less likely to decrease. In addition, the protective clothing using the dust-proof material of the second embodiment is not likely to accumulate heat in the protective clothing. As a result, the protective clothing using the dust-proof material of the second embodiment can also suppress the occurrence of heat stroke in high temperature environments such as summer.

[0269] The dustproof material of the second embodiment can be similar to the first embodiment except that the basis weight of the dustproof material is 25 gsm or more and less than 55 gsm.

[0270] (3) Third embodiment

[0271] (3.1) Dust-proof materials

[0272] The dustproof material of the third embodiment comprises: a meltblown nonwoven fabric layer (hereinafter also referred to as the "MB layer") that has been electret-treated and comprises a meltblown nonwoven fabric (hereinafter also referred to as the "MB"); and a spunbond nonwoven fabric layer (hereinafter also referred to as the "SB layer") that is laminated and fixed to both main surfaces of the meltblown nonwoven fabric layer. The air permeability of the dustproof material is 120 ccs or more and 200 ccs or less.

[0273] Due to the above-mentioned structure, the dust-proof material of the third embodiment has a high collection efficiency relative to the unit area weight of the electret meltblown nonwoven fabric layer, and has excellent air permeability. Therefore, when the dust-proof material of the third embodiment is used in protective clothing, the dust-proof material of the third embodiment can make the weight of the protective clothing lighter than before. As a result, the protective clothing using the dust-proof material of the third embodiment is not likely to cause fatigue to the operator even when worn for a long time, and the operator's work efficiency can be less likely to decrease. In addition, the protective clothing using the dust-proof material of the third embodiment is not likely to accumulate heat in the protective clothing. As a result, the protective clothing using the dust-proof material of the third embodiment can also suppress the occurrence of heat stroke in high temperature environments such as summer.

[0274] The dust-proof material of the third embodiment has an SB layer fixed to the two main surfaces of the MB layer, and the air permeability of the dust-proof material is greater than 120ccs and less than 200ccs. It may not have a structure in which the ratio of the unit area weight of the above-mentioned meltblown non-woven fabric layer to the unit area weight of the dust-proof material (hereinafter also referred to as "MB content") is greater than 3% and less than 10%. Except for this, the first embodiment can be used.

[0275] The structure, MB content, thickness, basis weight, air permeability, embossed portion, MB layer, SB layer, and other layers of the dustproof material of the second embodiment are the same as those of the first embodiment.

[0276] In the third embodiment, the air permeability of the dustproof material is 120 ccs or more and 200 ccs or less. This air permeability can be achieved when the pressure loss of the dustproof material is 10.0 Pa or less, thereby improving the collection efficiency per unit area weight. The pressure loss of the dustproof material is preferably 3.0 Pa to 10.0 Pa, more preferably 4.8 Pa to 10.0 Pa. The collection efficiency per unit area weight of the MB layer of the dustproof material is preferably 15% / gsm or more. The value obtained by dividing the collection efficiency per unit area weight of the MB layer of the dustproof material by the average fiber diameter of the MB layer is preferably 6.0% / (gsm·μm) or more.

[0277] Examples of methods for adjusting the air permeability of the dustproof material to a range of 120 ccs to 200 ccs include adjusting the basis weight and fiber diameter of the meltblown nonwoven fabric layer and the spunbond nonwoven fabric layer, the embossing rate, the porosity by thickness control, the MB content, or the electret rate.

[0278] In the third embodiment, the dustproof material is preferably 0.5 mm or less in thickness. This improves thermal conductivity compared to a dustproof material with a thickness exceeding 0.5 mm. As a result, the protective clothing provides a superior wearing feel and improves the operator's work efficiency.

[0279] In the third embodiment, from the perspective of reducing the amount of carbon dioxide emissions corresponding to the amount of resin used (hereinafter also referred to as "the perspective of reducing the environmental load"), the unit area weight of the dust-proof material is preferably less than 55 gsm, more preferably 15 gsm to 50 gsm, further preferably 25 gsm to 50 gsm, and further preferably 25 gsm to 50 gsm.

[0280] In the third embodiment, the dustproof material preferably has a plurality of embossed portions formed by fusing a portion of the MB layer with a portion of the SB layer, and the embossing ratio is preferably 3% to 15%. The embossing ratio represents the ratio of the total area of ​​the plurality of embossed portions formed on one main surface of the dustproof material to the area of ​​the one main surface of the dustproof material.

[0281] The embossing rate helps improve collection efficiency. It can be seen that setting the embossing rate of the dustproof material of the third embodiment to 3% or higher improves collection efficiency. An embossing rate of 3% to 30% creates a dustproof material with a soft, skin-friendly feel, thus improving the wearer's comfort.

[0282] (3.1.1) Meltblown nonwoven fabric layer

[0283] In the third embodiment, the MB layer preferably has a basis weight of less than 10 gsm. The dustproof material of the third embodiment can achieve the desired collection efficiency due to its specific laminated structure, even with an MB layer weight of less than 10 gsm. A high MB layer weight tends to reduce air permeability. However, the dustproof material of the third embodiment, with an MB layer weight of less than 10 gsm, exhibits excellent air permeability, improving wearer comfort.

[0284] In the third embodiment, the average fiber diameter of the fibers in the MB layer is preferably greater than 1.0 μm and less than 3.0 μm, more preferably greater than 1.0 μm and less than 3.0 μm, and even more preferably greater than 1.5 μm and less than 3.0 μm. This allows for both air permeability and collection efficiency to be achieved.

[0285] In the third embodiment, the fiber linear density of the MB layer is preferably 2 μm·gsm to 20 μm·gsm. Fiber linear density represents the product of the weight per unit area of ​​the MB layer and the average fiber diameter of the fibers in the MB layer. By setting the fiber linear density of the MB layer to 2 μm·gsm to 20 μm·gsm, good collection efficiency can be achieved even with a low MB weight per unit area, and the wearing feel can also be improved.

[0286] In the third embodiment, the ratio of the basis weight of the meltblown nonwoven fabric layer to the basis weight of the dustproof material is preferably 3% to 15%.

[0287] (3.1.2) Spunbond nonwoven fabric layer

[0288] In the third embodiment, the SB layer is preferably an electret-treated SB layer. By laminating the electret-treated SB layer and the electret-treated MB layer, the dust collection efficiency of the dustproof material can be improved, especially the collection efficiency per MB unit area weight.

[0289] (3.1.3) Optimal method

[0290] In the dustproof material of the third embodiment, it is preferable that the resin composition used in the meltblown nonwoven fabric layer and / or the spunbonded nonwoven fabric layer is a polyolefin-based polymer.

[0291] (3.2) Protective clothing

[0292] The protective clothing of the third embodiment uses the dustproof material of the third embodiment.

[0293] The protective clothing of the third embodiment has the above-mentioned structure, so even if worn for a long time, it is not easy to make the operator tired, and the operator's work efficiency is not easily reduced. In addition, the protective clothing of the third embodiment can also suppress the occurrence of heat stroke in high temperature environments such as summer.

[0294] The protective clothing of the third embodiment is the same as the protective clothing of the first embodiment, except that the dustproof material of the third embodiment is used instead of the dustproof material of the first embodiment.

[0295] (3.3) Manufacturing method of dustproof material

[0296] A method for manufacturing a dustproof material according to a third embodiment includes laminating a meltblown web and a spunbond web in-line to form a first laminate; embossing the first laminate to form a second laminate; and electretizing the second laminate to form the dustproof material.

[0297] The method for producing a dustproof material according to the third embodiment has the above-described configuration, and therefore can produce a dustproof material having a high ratio of collection efficiency to the basis weight of the electret meltblown nonwoven fabric layer and excellent air permeability.

[0298] The method for manufacturing the dustproof material of the third embodiment is the same as the method for manufacturing the dustproof material of the first embodiment.

[0299] Example

[0300] Hereinafter, the present disclosure will be further described in detail based on the examples, but the present disclosure is not limited to the following examples. The materials, usage amounts, ratios, processing steps, etc. shown in the following examples can be appropriately changed as long as they do not depart from the main purpose of the present disclosure. It should be noted that, unless otherwise specified, "parts" means "parts by mass".

[0301] [1] Examples and Comparative Examples

[0302] [1.1] Example 1

[0303] [1.1.1] Online lamination process

[0304] As described below, spunbond lamination, meltblown lamination, and spunbond lamination were sequentially performed on the same moving screen to produce a three-layer laminate in one step.

[0305] A propylene homopolymer with an MFR of 60 g / 10 minutes was used, and a spunbond nonwoven fabric forming machine with a spinneret having a diameter of 0.6 mm was used to carry out melt spinning at 230°C using a conventional spunbond stacking method. The fibers obtained by spinning were deposited on the collecting surface of the wire mesh to obtain a first spunbond fiber web with an average fiber diameter of 17 μm and a weight per unit area of ​​14 gsm.

[0306] Next, a resin composition obtained by adding 0.9 parts by mass of maleic anhydride-modified polypropylene (maleic anhydride grafting amount: 2.7% by mass, intrinsic viscosity: 0.3 dl / g) to 100 parts by mass of a propylene homopolymer having an MFR of 1000 g / 10 minutes was melted at 280°C using an extruder. The resulting melt was discharged from a spinneret and heated air at 280°C was ejected to perform meltblowing lamination using a conventional method. This deposited fibers having an average fiber diameter of 2.2 μm on the first spunbond web, forming a meltblown web having a basis weight of 2 gsm. The diameter of the spinning nozzle of the die was 0.38 mm.

[0307] Next, fibers were deposited on the meltblown web in the same manner as in the spunbond web to form a second spunbond web having an average fiber diameter of 17 μm and a basis weight of 14 gsm.

[0308] Thus, a first laminate having a three-layer structure was obtained. The first laminate had a meltblown web and a spunbond web laminated on both main surfaces of the meltblown web.

[0309] The MFR of the propylene homopolymer is measured in accordance with ASTM D-1238 under the following conditions: 230° C. and a load of 2.16 kg.

[0310] [1.1.2] Embossing process

[0311] The resulting first laminate was then integrated using a hot embossing roll set at 155°C for an embossing roll and 160°C for a mirror-finished roll with an embossing area ratio of 12%, yielding a three-layer second laminate. The second laminate comprised a meltblown nonwoven fabric layer and spunbond nonwoven fabric layers laminated on both principal surfaces of the meltblown nonwoven fabric layer. The second laminate had a basis weight of 30 gsm.

[0312] [1.1.3] Electret treatment process

[0313] One principal surface of the resulting second laminate was charged using a corona charging method at an electric field strength of 20 kV / cm. Subsequently, the other principal surface of the second laminate was charged using a corona charging method at an electric field strength of 20 kV / cm. This resulted in a three-layer dustproof material. The dustproof material comprises a meltblown nonwoven fabric layer and a spunbond nonwoven fabric layer laminated and secured to both principal surfaces of the meltblown nonwoven fabric layer.

[0314] [1.2] Examples 2 to 6, Comparative Examples 1 to 4

[0315] The dustproof material was obtained in the same manner as in Example 1 except that the lamination conditions of the spunbond lamination, the lamination conditions of the meltblown lamination, the imprinting area ratio of the embossing roller, etc. were adjusted so that the unit area weight of the dustproof material became the unit area weight described in Tables 1 and 2.

[0316] [2] Measurement method

[0317] The basis weight and the like of the dustproof material are measured by the following method.

[0318] [2.1]Weight per unit area (gsm)

[0319] Three samples measuring 50 cm in length and 50 cm in width were collected from the dustproof material. The mass of each sample was measured. The average of the mass values ​​was converted to a weight per unit area and rounded off to the nearest decimal place to obtain the weight per unit area (gsm).

[0320] [2.2] Average fiber diameter of the fibers in the MB layer (μm)

[0321] Using an electron microscope (S-3500N, manufactured by Hitachi, Ltd.), photograph the meltblown nonwoven fabric layer at 1000x magnification. Randomly select 100 fibers from the plurality of fibers constituting the meltblown nonwoven fabric layer and measure the width (diameter) of these selected fibers. The average of these measured values ​​is used as the average fiber diameter of the fibers in the MB layer.

[0322] [2.3]Thickness (mm)

[0323] Use a thickness gauge (manufactured by PEACOCK, model "R1-250") to measure the terminal ), with a load of 7g / cm 2 The thickness of the sample for which the basis weight was measured was measured at five points, namely the center and four corners. The thickness of 10 samples for which the basis weight was measured was measured using this method, and the average value was defined as the thickness (mm).

[0324] [2.4] Embossing rate and embossing area ratio (%)

[0325] The embossing rate was measured at three points by the following procedure, and the average value was defined as the embossing rate.

[0326] (i) Select the part of the dustproof material with the highest embossing rate and cut the dustproof material to be measured into 10 cm × 10 cm pieces to prepare a measurement sample. If the dustproof material to be measured cannot be cut into a 10 cm × 10 cm size, cut it into the largest possible size.

[0327] (ii) With the measurement sample placed horizontally, an observation image is captured and the area ratio of the film-forming portion in a 50 mm x 50 mm square of the observation image is measured as the embossing ratio.

[0328] [2.5] Collection efficiency (%)

[0329] The collection efficiency of the dustproof material was measured using the following method. Three 15 cm x 15 cm samples were collected from any part of the dustproof material. The collection efficiency of each sample was measured using a collection performance measuring device (Model 8130, manufactured by Tokyo DYLEC Co., Ltd.). When measuring the collection efficiency, a nebulizer was used to generate NaCl dust particles with a number median diameter of 0.07 μm. The sample was then placed on a rack and the air volume was adjusted using a flow control valve to achieve a filter flow rate of 5.3 cm / sec, maintaining a dust concentration of 15 mg / m 3 ~20 mg / m 3 The median diameter represents the diameter corresponding to a cumulative probability of 50% for the number distribution. A laser particle detector is used to detect the number of dust particles D2 upstream and D1 downstream of the sample. The value obtained by the following formula (3) is rounded to the second decimal place to calculate the collection efficiency (%). It should be noted that the collection efficiency (%) listed in Tables 1 and 2 is the arithmetic mean value measured using three samples.

[0330] Formula (3): Collection efficiency (%) = [1-(D1 / D2)] × 100

[0331] In formula (3), D1 represents the number of dust particles downstream, and D2 represents the number of dust particles upstream.

[0332] [2.6] Ratio of collection efficiency to unit area weight of meltblown nonwoven fabric layer

[0333] The ratio of the collection efficiency to the basis weight of the meltblown nonwoven fabric layer was calculated using the measured value of the basis weight of the MB layer and the measured value of the collection efficiency of the dustproof material.

[0334] The permissible range of the collection efficiency relative to the basis weight of the meltblown nonwoven fabric layer is 15.0% / gsm or more.

[0335] [2.7] Breathability (ccs)

[0336] Five samples of the obtained laminate, measuring 150 mm in length and 150 mm in width, were collected and their air permeabilities were measured using a Frazier air permeometer according to JIS L1096:2010 at a flow rate with a pressure difference of 125 Pa. The average value was defined as the air permeability (ccs).

[0337] The permissible range of air permeability (ccs) is 35ccs to 200ccs.

[0338] [2.8] Strength (MD) and strength (CD)

[0339] The resulting dustproof material was measured for strength (MD) and strength (CD) in accordance with JIS L1913. Specifically, a 50 mm wide x 300 mm long test piece was collected from the dustproof material and measured using a tensile testing machine with a chuck distance of 200 mm. The tensile speed was set at 200 mm / min. The tensile strength at MD was measured at five points, and the average value was used as the strength (MD). Similarly, the tensile strength at CD was measured at five points on the same test piece, and the average value was used as the strength (CD).

[0340] [2.9] Pressure loss (Pa)

[0341] The pressure loss was determined by reading the static pressure difference between the upstream and downstream sides of the sample during the collection efficiency (%) measurement using a pressure gauge. The pressure loss values ​​listed in Tables 1 and 2 are the arithmetic mean values ​​determined using three samples.

[0342] [2.10] Confirmation of electretization

[0343] By using the above method, Figure 1 The charge density of the MB layer of the dustproof material was measured using the device shown in FIG. The charge density of the MB layer of the dustproof material of Examples 1 to 6 and Comparative Examples 1 to 4 was 1×10 -10 Coulomb / cm 2 That is, it was confirmed that the MB layers of the dust-proof materials of Examples 1 to 6 and Comparative Examples 1 to 4 were electretized.

[0344] [Table 1]

[0345]

[0346] [Table 2]

[0347]

[0348] In Tables 1 and 2, "PP-SMS" indicates a three-layer structure consisting of a spunbond nonwoven fabric layer, a meltblown nonwoven fabric layer, and a spunbond nonwoven fabric layer stacked and fixed in that order. "Collection efficiency / unit weight of MB layer" indicates the ratio of the collection efficiency to the unit weight of the meltblown nonwoven fabric layer. "Collection efficiency / unit weight of MB layer / average fiber diameter of MB layer" indicates the collection efficiency / unit weight of MB layer per 1 μm of average fiber diameter of the fibers constituting the meltblown nonwoven fabric.

[0349] In Comparative Examples 1 to 4, the MB content was not within the range of 3% or more and less than 10%. Therefore, the ratio of the collection efficiency to the basis weight of the meltblown nonwoven fabric layer was less than 15.0% / gsm. Furthermore, the air permeability (ccs) of Comparative Examples 1 to 3 was less than 35 ccs. These results indicate that the dustproof materials of Comparative Examples 1 to 4 do not exhibit high collection efficiency relative to the basis weight of the electret-treated meltblown nonwoven fabric layer and excellent air permeability.

[0350] In Examples 1 to 6, the MB content was within a range of 3% to less than 10%. The total weight per unit area of ​​the dust-proof material was within a range of 15 gsm to less than 55 gsm. Therefore, the ratio of the capture efficiency to the weight per unit area of ​​the meltblown nonwoven fabric layer was 15.0% / gsm or greater. Furthermore, the air permeability (ccs) was within a range of 35 ccs to 200 ccs. These results indicate that the dust-proof materials of Examples 1 to 6 exhibited a high capture efficiency relative to the weight per unit area of ​​the electret-treated meltblown nonwoven fabric layer and excellent air permeability.

[0351] The entire disclosure of Japanese Patent Application No. 2023-013428 filed on January 31, 2023 is incorporated into this specification by reference.

[0352] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A dustproof material comprising: a meltblown nonwoven fabric layer, which is electretized and comprises a meltblown nonwoven fabric; and a spunbond nonwoven fabric layer, which is laminated and fixed to the two main surfaces of the meltblown nonwoven fabric layer and comprises a spunbond nonwoven fabric, The weight per unit area of ​​the dustproof material is greater than 15 gsm and less than 55 gsm. The ratio of the basis weight of the meltblown nonwoven fabric layer to the basis weight of the dustproof material is 3% or more and less than 10%. 2 . The dustproof material according to claim 1 , wherein the thickness of the dustproof material is 0.5 mm or less. 3 . The dustproof material according to claim 1 , wherein the average fiber diameter of the fibers of the meltblown nonwoven fabric layer exceeds 1.0 μm and is less than 3.0 μm. The dust-proof material according to claim 1 , wherein the meltblown non-woven fabric layer has a weight per unit area of ​​less than 10 gsm.

5. The dustproof material according to claim 1, comprising a plurality of embossed portions formed by fusing a portion of the meltblown nonwoven fabric layer with a portion of the spunbond nonwoven fabric layer. The embossing rate is 3% to 30%, The embossing ratio indicates a ratio of the total area of ​​the plurality of embossed portions formed on one main surface of the dustproof material to the area of ​​the one main surface of the dustproof material.

6. The dustproof material according to claim 5, wherein the embossing rate is 3% to 15% and all of the following (a) to (c) are satisfied: (a) the weight per unit area of ​​the dustproof material is not less than 15 gsm and not more than 45 gsm; (b) the thickness of the dustproof material is less than 0.42 mm; (c) The meltblown nonwoven fabric layer has a weight per unit area of ​​less than 10 gsm.

7. The dustproof material according to claim 1, wherein the fiber linear density of the meltblown nonwoven fabric layer is 2 μm·gsm to 20 μm·gsm. The fiber linear density refers to the product of the weight per unit area of ​​the meltblown nonwoven fabric layer and the average fiber diameter of the fibers of the meltblown nonwoven fabric layer. The dustproof material according to claim 1 , wherein the spunbond nonwoven fabric layer is an electret-treated spunbond nonwoven fabric layer.

9. The dustproof material according to claim 1, wherein the air permeability is 35 ccs or more. 10 . The dustproof material according to claim 1 , wherein the resin composition used in at least one of the meltblown nonwoven fabric layer and the spunbonded nonwoven fabric layer is a polyolefin.

11. Protective clothing using the dustproof material according to any one of claims 1 to 10.

12. A method for manufacturing a dustproof material, which is a method for manufacturing the dustproof material according to any one of claims 1 to 10, comprising: Laminating the meltblown web and the spunbond web in-line to form a first laminate; performing embossing on the first laminate to produce a second laminate; as well as The second laminate is subjected to an electret treatment to produce the dustproof material.

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