Long-fiber nonwoven fabric, method for producing same, and process protection material

Abstract

A long-fiber nonwoven fabric includes: a fiber including a thermoplastic resin as a main component, in which the long-fiber nonwoven fabric has a surface roughness Rz of 25.0 μm or more and 50.0 μm or less on both surfaces, and an absolute value of a difference between the surface roughness Rz of one surface and the surface roughness Rz of the other surface is 4.0 μm or more and 10.0 μm or less.

Description

TECHNICAL FIELD

[0001] The present invention relates to a long-fiber nonwoven fabric, a method for producing the same, and a construction protective material containing the long-fiber nonwoven fabric.BACKGROUND ART

[0002] In general, when an intermediate product is transported in a horizontal direction in production steps, a belt conveyor or the like is often used. Among these, for precision parts and the like that need to be protected from scratches during transportation, in order to prevent a component to be transported from slipping due to vibration or the like during transportation, a sheet component as a construction protective material is disposed between the conveyor and the component, or the surface of the conveyor itself is used as a sheet component, and the component is transported while being fixed by suction. The sheet component is required to have surface smoothness so as not to scratch the component to be transported, and to have followability to the conveyor or the like so as to transport the sheet component without floating.

[0003] As such a sheet component, synthetic paper may be used. As the synthetic paper, for example, Patent Literature 1 discloses synthetic paper obtained by laminating and integrating a first layer composed of a polyester fiber and a second layer composed of a fiber having a low melting point component in at least a part thereof and a polyester fiber, in which the synthetic paper contains a certain amount of low-oriented polyester fiber having a birefringence of a specific value or less in both the first layer and the second layer.CITATION LISTPatent LiteraturePatent Literature 1: JPS59-228100ASUMMARY OF INVENTIONTechnical Problem

[0005] However, the synthetic paper as disclosed in Patent Literature 1 is composed of a short fiber, and the number of fiber fusing points is large. Therefore, there is a problem that fluffing easily occurs, dust thereof may be mixed in the production steps, and precision parts and the like may be scratched.

[0006] Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a long-fiber nonwoven fabric that has excellent surface smoothness and followability to a conveyor or the like and that can withstand continuous use.Solution to Problem

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that a long-fiber nonwoven fabric in which a surface roughness on both surfaces of the long-fiber nonwoven fabric is in a specific range and an absolute value of a difference between the surface roughness of one surface and the surface roughness of the other surface is in a specific range can not only be smooth and have excellent mechanical strength, but also have improved followability to a conveyor or the like. Further, it has been found that a construction protective material containing the long-fiber nonwoven fabric has excellent wear resistance and can be used again without fluffing.

[0008] The present invention has been completed based on these findings, and the present invention provides the following inventions.

[0009] [1] A long-fiber nonwoven fabric containing: a fiber containing a thermoplastic resin as a main component, in which the long-fiber nonwoven fabric has a surface roughness Rz of 25.0 μm or more and 50.0 μm or less on both surfaces, and an absolute value of a difference between the surface roughness Rz of one surface and the surface roughness Rz of the other surface is 4.0 μm or more and 10.0 μm or less.

[0010] [2] The long-fiber nonwoven fabric according to the above [1], in which the long-fiber nonwoven fabric has an area ratio of a fiber voids' part of 1.0% or more and 15.0% or less.

[0011] [3] The long-fiber nonwoven fabric according to the above [1] or [2], in which the fiber is a multi-component fiber in which a low melting point polymer having a melting point lower than a melting point of a high melting point polymer is disposed around the high melting point polymer.

[0012] [4] The long-fiber nonwoven fabric according to any one of the above [1] to [3], in which the long-fiber nonwoven fabric has an apparent density of 0.40 g / cm3 or more and 0.75 g / cm3 or less.

[0013] [5] The long-fiber nonwoven fabric according to any one of the above [1] to [4], in which the long-fiber nonwoven fabric has a basis weight of 40 g / m2 or more and 75 g / m2 or less.

[0014] [6] A method for producing a long-fiber nonwoven fabric, which is a method for producing the long-fiber nonwoven fabric according to any one of the above [1] to [5], the method sequentially including: a step of spinning a thermoplastic resin from a discharge port of a spinning spinneret and then subjecting the spun thermoplastic resin to suction drawing to obtain a long fiber; a step of collecting the long fiber on a moving net conveyor to form a fiber web; a step of bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web; and a step of performing thermal fusion of the preheated fiber web using a pair of flat rolls, in which a spinning speed in the suction drawing is 3000 m / min or more and 6000 m / min or less, in the preheating, a temperature of the heating surface is a temperature lower than a melting point of the thermoplastic resin by 30° C. or more and 110° C. or less and a linear pressure of the heating surface is 1 N / cm or more and 100 N / cm or less, and in the thermal fusion, a surface temperature of the pair of flat rolls is a temperature lower than the melting point of the thermoplastic resin by 30° C. or more and 70° C. or less and a linear pressure of the pair of flat rolls is 100 N / cm or more and 900 N / cm or less.

[0015] [7] A method for producing a long-fiber nonwoven fabric, which is a method for producing the long-fiber nonwoven fabric according to any one of the above [1] to [5], the method sequentially including: a step of spinning a high melting point polymer and a low melting point polymer having a melting point lower than a melting point of the high melting point polymer by 10° C. or more and 110° C. or less from a discharge port of a composite spinning spinneret, and then subjecting the spun polymers to suction drawing to obtain a long fiber that is a multi-component fiber in which the low melting point polymer is disposed around the high melting point polymer; a step of collecting the long fiber on a moving net conveyor to form a fiber web a step of bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web; and a step of performing thermal fusion of the preheated fiber web using a pair of flat rolls, in which a spinning speed in the suction drawing is 3000 m / min or more and 6000 m / min or less, in the preheating, a temperature of the heating surface is a temperature lower than a melting point of the low melting point polymer by 30° C. or more and 110° C. or less and a linear pressure of the heating surface is 1 N / cm or more and 100 N / cm or less, and in the thermal fusion, a surface temperature of the pair of flat rolls is a temperature lower than the melting point of the low melting point polymer by 30° C. or more and 70° C. or less and a linear pressure of the pair of flat rolls is 100 N / cm or more and 900 N / cm or less.

[0016] [8] A construction protective material containing: the long-fiber nonwoven fabric according to any one of the above [1] to [5].Advantageous Effects of Invention

[0017] According to the present invention, it is possible to provide a long-fiber nonwoven fabric that has excellent surface smoothness and followability to a conveyor or the like and that can withstand continuous use.BRIEF DESCRIPTION OF DRAWINGS

[0018] FIG. 1 is a conceptual cross-sectional view illustrating a configuration of a device for evaluating a long-fiber nonwoven fabric according to one embodiment of the present invention as a construction protective material.

[0019] FIG. 2 is a conceptual cross-sectional view exemplifying and illustrating a configuration of a device for producing a long-fiber nonwoven fabric in a method for producing a long-fiber nonwoven fabric according to one embodiment of the present invention.DESCRIPTION OF EMBODIMENTS

[0020] A long-fiber nonwoven fabric according to one embodiment of the present invention (hereinafter also referred to as “the present embodiment”) is a long-fiber nonwoven fabric including a fiber containing a thermoplastic resin as a main component, in which the long-fiber nonwoven fabric has a surface roughness Rz of 25.0 μm or more and 50.0 μm or less on both surfaces, and an absolute value of a difference between the surface roughness Rz of one surface and the surface roughness Rz of the other surface is 4.0 μm or more and 10.0 μm or less. Hereinafter, the components will be described in detail, but the present invention is not limited to the scope described below without departing from the gist of the present invention, and various modifications can be made without departing from the gist of the present invention.(Fiber Containing Thermoplastic Resin as Main Component)

[0021] The long-fiber nonwoven fabric according to the present embodiment is a long-fiber nonwoven fabric including a fiber containing a thermoplastic resin as a main component. Here, in the present embodiment, “containing a thermoplastic resin as a main component” means that a ratio of a mass of the thermoplastic resin to a mass of the entire fiber is more than 50 mass %.

[0022] Examples of the thermoplastic resin include a polyester, a polyamide, a polyolefin, and a mixture and a copolymer thereof. Among these, a polyester is preferred because of having more excellent mechanical strength and durability such as heat resistance, water resistance, and chemical resistance.

[0023] The polyester is composed of a dicarboxylic acid component and a diol component. As the dicarboxylic acid component, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and phthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid can be used. As the diol component, ethylene glycol, diethylene glycol, and polyethylene glycol can be used.

[0024] Specific examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polylactic acid (PLA), polybutylene succinate (PBS), and a copolymer thereof.

[0025] Additives such as a crystal nucleating agent, a matting agent, a lubricant, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, and a hydrophilic agent can be added to the thermoplastic resin in the present embodiment as long as the effects of the present invention are not impaired.

[0026] In addition, when the thermoplastic resin in the present embodiment contains a metal oxide such as titanium oxide, thermal conductivity of a fiber web is increased during, for example, thermal fusion of a preheated fiber web to be described later in the production stage, and thus a fusion property in the fiber web can be improved, and a long-fiber nonwoven fabric having more excellent mechanical strength can be obtained.

[0027] Further, when the thermoplastic resin in the present embodiment contains an aliphatic bisamide such as ethylenebisstearamide and / or an alkyl-substituted aliphatic monoamide, releasability between a pair of flat rolls and the preheated fiber web used in the thermal fusion of the preheated fiber web to be described later in the production stage is improved, fusion stability in the fiber web can be improved, flexibility is further improved, and a long-fiber nonwoven fabric having excellent followability to a conveyor or the like when used as a construction protective material can be obtained.

[0028] Note that, these additives and the like may adhere to the surface of the fiber containing a thermoplastic resin as a main component to be described later.

[0029] The thermoplastic resin in the present embodiment preferably has a melting point in a range of 100° C. or higher and 320° C. or lower. When the lower limit of the above range is preferably 100° C. or higher, more preferably 120° C. or higher, still more preferably 140° C. or higher, and particularly preferably 160° C. or higher, a desired thermal fusion property can be obtained, and a high density and smooth long-fiber nonwoven fabric is obtained. On the other hand, when the upper limit of the above range is preferably 320° C. or lower, more preferably 300° C. or lower, still more preferably 280° C. or lower, and particularly preferably 250° C. or lower, a multi-component fiber is more flexible, and a long-fiber nonwoven fabric more easily following a conveyor or the like is obtained.

[0030] The fiber according to the present embodiment is preferably a multi-component fiber in which a low melting point polymer having a melting point lower than a melting point of a high melting point polymer is disposed around the high melting point polymer. When the multi-component fiber having such a form is used, the fibers can be more firmly fused to each other, a long-fiber nonwoven fabric having excellent smoothness is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, a component to be transported can be prevented from being scratched.

[0031] A difference between the melting point of the high melting point polymer and the melting point of the low melting point polymer (hereinafter, also simply referred to as a “melting point difference”) is preferably 10° C. or higher and 110° C. or lower. In other words, the low melting point polymer preferably has a melting point lower than the melting point of the high melting point polymer by a range of 10° C. or more and 110° C. or less. When the melting point difference is preferably 10° C. or more, more preferably 20° C. or more, and still more preferably 30° C. or more, a long-fiber nonwoven fabric having a sufficiently excellent fusion property is obtained. In addition, when the melting point difference is preferably 110° C. or less, more preferably 100° C. or less, and still more preferably 90° C. or less, a long-fiber nonwoven fabric having excellent air permeability is obtained without a decrease in productivity due to fusion of the low melting point polymer to a roll used during thermal fusion.

[0032] In the present embodiment, the melting point of the high melting point polymer in the multi-component fiber is preferably in a range of 160° C. or higher and 320° C. or lower. When the melting point of the high melting point polymer in the multi-component fiber is preferably 160° C. or higher, more preferably 170° C. or higher, and still more preferably 180° C. or higher, a long-fiber nonwoven fabric having excellent morphological stability and durability is obtained. In addition, when the melting point of the high melting point polymer in the multi-component fiber is 320° C. or lower, more preferably 300° C. or lower, and still more preferably 280° C. or lower, the multi-component fiber is more flexible, and a long-fiber nonwoven fabric more easily following a conveyor or the like is obtained.

[0033] On the other hand, the melting point of the low melting point polymer in the multi-component fiber is preferably in a range of 100° C. or higher and 250° C. or lower while ensuring the melting point difference. When the melting point of the low melting point polymer in the multi-component fiber is preferably 100° C. or higher, more preferably 120° C. or higher, and still more preferably 140° C. or higher, a desired thermal fusion property can be obtained, and a high density and smooth long-fiber nonwoven fabric can be obtained. In addition, when the melting point of the low melting point polymer in the multi-component fiber is preferably 250° C. or lower, more preferably 240° C. or lower, and still more preferably 230° C. or lower, the multi-component fiber is more flexible, and a long-fiber nonwoven fabric more easily following a conveyor or the like is obtained.

[0034] Note that, in the present embodiment, the melting point of the thermoplastic resin is measured using a differential scanning calorimeter (for example, “DSC-2” manufactured by PerkinElmer) under the conditions of a temperature increase rate of 20° C. / min and a measurement temperature range of 30° C. to 350° C., and the temperature at which an extreme value is obtained in the obtained melting endothermic curve is defined as the melting point of the thermoplastic resin. In addition, a resin whose melting endothermic curve does not exhibit an extreme value in the differential scanning calorimeter is heated on a hot plate, and a temperature at which the resin is melted during microscopic observation is defined as a melting point.

[0035] In the case where the thermoplastic resin is a polyester, examples of a combination of the high melting point polymer and the low melting point polymer (hereinafter, may be referred to as high melting point polymer / low melting point polymer in order) include combinations of PET / PBT, PET / PTT, PET / polylactic acid, and PET / copolymerized PET. Among these, a combination of PET / copolymerized PET is preferably used because of having excellent spinnability. In addition, as a copolymerization component of the copolymerized PET, isophthalic acid copolymerized PET is preferably used because of having particularly excellent spinnability.

[0036] Examples of a composite form of the multi-component fiber include a concentric core-sheath type, an eccentric core-sheath type, and a sea-island type. Among these, a concentric core-sheath type is preferred since the fibers can be uniformly and firmly fused to each other. Further, examples of a cross-sectional shape of the multi-component fiber include a circular cross section, a flat cross section, a polygonal cross section, a multi-leaf cross section, and a hollow cross section. Among these, the cross-sectional shape of the multi-component fiber being a circular cross section is preferred.

[0037] A content ratio of the high melting point polymer to the low melting point polymer in the fiber containing a thermoplastic resin as a main component is preferably in a range of 90:10 to 30:70, and more preferably in a range of 83:17 to 40:60 in mass ratio. When a mass ratio of the high melting point polymer to a total mass of the high melting point polymer and the low melting point polymer contained in the fiber (simply referred to as the content ratio of the high melting point polymer) is preferably 30 mass % or more and 90 mass % or less, and more preferably 40 mass % or more and 83 mass % or less, a long-fiber nonwoven fabric having excellent thermal stability is obtained. On the other hand, when a mass ratio of the low melting point polymer to the total mass of the high melting point polymer and the low melting point polymer contained in the fiber (simply referred to as the content ratio of the low melting point polymer) is 10 mass % or more and 70 mass % or less, and more preferably 17 mass % or more and 60 mass % or less, a long-fiber nonwoven fabric having an excellent thermal fusion property, being smoother, and having a high density is obtained.

[0038] The fiber containing a thermoplastic resin as a main component preferably has an average single fiber diameter of 10 μm or more and 24 μm or less. When the average single fiber diameter is preferably 10 μm or more, more preferably 12 μm or more, and still more preferably 14 μm or more, a long-fiber nonwoven fabric having excellent mechanical strength is obtained.

[0039] On the other hand, when the average single fiber diameter is preferably 24 μm or less, more preferably 22 μm or less, and still more preferably 20 μm or less, a denser long-fiber nonwoven fabric is obtained, so that micro unevenness is small, and when the long-fiber nonwoven fabric is used as a construction protective material, a component to be transported can be prevented from being scratched.

[0040] Note that, even when a plurality of kinds of fibers are mixed, the single fiber diameter of the fibers measured by the following procedure is preferably within the above range.

[0041] Note that, in the present embodiment, as the average single fiber diameter (μm) of the fiber containing a thermoplastic resin as a main component, a value calculated by the following procedure is adopted.

[0042] (1) Ten small sample pieces (100 mm×100 mm) are randomly collected from the long-fiber nonwoven fabric.

[0043] (2) A surface photograph at a magnification of 500 times or more and 3000 times or less is taken with a microscope (for example, “VHX-D500” manufactured by Keyence Corporation), and 10 single fibers are randomly measured from each sample, that is, a total of 100 single fibers are subjected to measurement.

[0044] (3) An arithmetic average value of the measured values of 100 fibers is rounded off to the first decimal place to calculate the average single fiber diameter (μm).

[0045] The fiber containing a thermoplastic resin as a main component may contain additives such as a lubricant, an antifungal agent, an antibacterial agent, a flame retardant, and a hydrophilic agent in addition to the thermoplastic resin.(Long-Fiber Nonwoven Fabric)

[0046] The long-fiber nonwoven fabric according to the present embodiment includes the fiber described above. The long-fiber nonwoven fabric according to the present embodiment has a surface roughness Rz of 25.0 μm or more and 50.0 μm or less on both surfaces. When the surface roughness Rz on both surfaces is 25.0 μm or more, preferably 30.0 μm or more, and more preferably 35.0 μm or more, a long-fiber nonwoven fabric having appropriate unevenness on the surface is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, a component to be transported can be sufficiently sucked, and the component to be transported can be transported without causing slippage between a conveyor or the like and the component.

[0047] On the other hand, when the surface roughness Rz on both surfaces is 50.0 μm or less, preferably 45.0 μm or less, and more preferably 40.0 μm or less, a long-fiber nonwoven fabric having a denser surface is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, fluffing due to friction with a component to be transported can be prevented.

[0048] In order to adjust the surface roughness Rz on both surfaces of the long-fiber nonwoven fabric to the above range, a temperature and a linear pressure of surfaces of a pair of flat rolls can be adjusted to ranges to be described later in a thermal fusion step in a method for producing a long-fiber nonwoven fabric.

[0049] In addition, in the long-fiber nonwoven fabric according to the present embodiment, the absolute value of the difference between the surface roughness Rz of one surface and the surface roughness Rz of the other surface (hereinafter, may be simply referred to as an “absolute value of difference in surface roughness”) is 4.0 μm or more and 10.0 μm or less. When the absolute value of the difference in surface roughness of the long-fiber nonwoven fabric is 4.0 μm or more, preferably 5.0 μm or more, and still more preferably 6.0 μm or more, a long-fiber nonwoven fabric having a sufficient difference in surface roughness between front and back surfaces is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, a component to be transported can be transported without causing slippage between a conveyor or the like and the component.

[0050] On the other hand, when the absolute value of the difference in surface roughness is 10.0 μm or less, preferably 9.0 μm or less, and more preferably 8.0 μm or less, a long-fiber nonwoven fabric having an appropriate difference in surface roughness between the front and back surfaces is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, fluffing or breakage of the construction protective material can be prevented, and lint can be prevented from being mixed into a component to be transported.

[0051] This absolute value of the difference in surface roughness can be obtained by adjusting, to ranges to be described later, a temperature and a linear pressure of a heating surface to be brought into contact with only one surface of a fiber web in a step of obtaining a preheated fiber web, and the temperature and the linear pressure of the surfaces of the pair of flat rolls in the thermal fusion step in the method for producing a long-fiber nonwoven fabric.

[0052] Note that, the surface roughness (μm) and the difference in surface roughness (μm) of the long-fiber nonwoven fabric are calculated by the following procedure.

[0053] (1) A long-fiber nonwoven fabric of 10 cm×10 cm is randomly collected at 20 locations.

[0054] (2) For the randomly collected nonwoven fabrics, a surface roughness meter (for example, “Surftest SJ-210” manufactured by Mitutoyo Corporation) is used to measure a range of 21 mm in a width direction of a long-fiber nonwoven fabric sheet under the conditions of λc=2.5 mm, λs=8 μm, and a measurement speed of 0.5 mm / s in accordance with the standard in JISB0610: 2001 “Geometrical Product Specification (GPS)-Surface texture: Profile method-Definitions and designation of rolling circle waviness”, and a maximum height Rz (in unit of 0.1 μm) is measured at 20 points of each collected sample on each surface.

[0055] (3) The measured values are arithmetically averaged for each surface to obtain a value, the value is rounded off to the second decimal place, and the difference is determined as the difference in surface roughness.

[0056] (4) In addition, the surface roughness of the surfaces is arithmetically averaged to obtain a value, and the value is rounded off to the second decimal place to determine the surface roughness of the long fiber.

[0057] The long-fiber nonwoven fabric preferably has an area ratio of a fiber voids' part of 1.0% or more and 15.0% or less. When the area ratio of the fiber voids' part in the long-fiber nonwoven fabric is preferably 1.0% or more, more preferably 3.0% or more, and still more preferably 5.0% or more, a long-fiber nonwoven fabric simultaneously having a portion where a large amount of fibers are present and a portion where a small amount of fibers are present is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, the construction protective material can be sufficiently sucked onto a conveyor or the like and a component to be transported can be transported without displacement. On the other hand, when the area ratio of the fiber voids' part in the long-fiber nonwoven fabric is preferably 15.0% or less, more preferably 13.0% or less, and still more preferably 10.0% or less, a long-fiber nonwoven fabric having a uniform density of fibers is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, fluffing or breakage of the construction protective material and damage of a component to be transported can be prevented.

[0058] Note that, the area ratio of fiber voids' part in the long-fiber nonwoven fabric is calculated by the following procedure.

[0059] (1) A long-fiber nonwoven fabric with 30 cm in a longitudinal direction and 21 cm in the width direction is randomly collected at 10 locations.

[0060] (2) The randomly collected nonwoven fabric is scanned at 300 dpi by a scanner (for example, a multifunction device “DocuCentre-VI4471” manufactured by FUJIFILM Business Innovation Corp.).

[0061] (3) The image of the scanned nonwoven fabric is binarized by using image editing software (for example, “GIMP Ver. 2.10.30”) at a threshold value of 175 (when there are 256 levels of black: 0 to gray to white: 255, 175 or less means black, and 176 or more means white).

[0062] (4) By using image analysis software (for example, “ImageJ Ver. 1.53e”) for binarization, the area ratio of black (fiber voids' part) is calculated at each measurement location.

[0063] (5) The numerical values measured at the locations are arithmetically averaged to obtain a value, and the value is rounded off to the second decimal place and calculated as the area ratio of the fiber voids' part in the long-fiber nonwoven fabric.

[0064] The long-fiber nonwoven fabric preferably has an apparent density of 0.40 g / cm3 or more and 0.75 g / cm3 or less. When the apparent density is preferably 0.40 g / cm3 or more, more preferably 0.42 g / cm3 or more, and still more preferably 0.45 g / cm3 or more, a long-fiber nonwoven fabric with less fluffing can be obtained, and the mechanical strength can be further increased. On the other hand, when the apparent density of the long-fiber nonwoven fabric is 0.75 g / cm3 or less, preferably 0.72 / cm3 or less, and more preferably 0.70 g / cm3 or less, when the long-fiber nonwoven fabric is used as a construction protective material, the construction protective material does not float during transportation, and a long-fiber nonwoven fabric having excellent step passability is obtained.

[0065] Note that, the apparent density (g / cm3) of the long-fiber nonwoven fabric is a value calculated by unit conversion by dividing a basis weight (g / m2) of the long-fiber nonwoven fabric to be described later by a thickness (mm) of the long-fiber nonwoven fabric to be described later and rounding off the result (g / cm3) to the third decimal place. Here, the thickness (mm) of the long-fiber nonwoven fabric is calculated by the following procedure.

[0066] (1) Three long-fiber nonwoven fabrics each having a width of 10 cm in the longitudinal direction are collected.

[0067] (2) The thickness (in unit of 0.01 mm) is measured at 10 points per 1 m at equal intervals in the width direction of the long-fiber nonwoven fabric under a load of 10 kPa using a pressurizer having a diameter of 10 mm.

[0068] (3) The arithmetic average value of the obtained measured values is calculated for the three collected long-fiber nonwoven fabrics, and the arithmetic average value is rounded off to the fourth decimal place for the three long-fiber nonwoven fabrics.

[0069] The long-fiber nonwoven fabric preferably has a basis weight of 40 g / m2 or more and 75 g / m2. When the basis weight is preferably 40 g / m2 or more, more preferably 45 g / m2 or more, and still more preferably 50 g / m2 or more, a long-fiber nonwoven fabric having excellent mechanical strength is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, breakage of a component to be transported can be prevented.

[0070] On the other hand, when the basis weight is preferably 75 g / m2 or less, more preferably 70 g / m2 or less, and still more preferably 65 g / m2 or less, a long-fiber nonwoven fabric in which a decrease in air permeability is prevented is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, a suction fixing property of a component to be transported can be made excellent.

[0071] Note that, the basis weight (g / m2) of the long-fiber nonwoven fabric is calculated by the following procedure.

[0072] (1) Three long-fiber nonwoven fabrics of 30 cm×50 cm are collected.

[0073] (2) The mass of each sample is measured, the average value of the obtained values is converted into the mass per unit area (g / m2), and the obtained value is rounded off to the first decimal place to calculate the basis weight.

[0074] The long-fiber nonwoven fabric preferably has an air permeation amount of 5 cm3 / (cm2·sec) or more and 30 cm3 / (cm2·sec) or less. When the air permeation amount is preferably 5 cm3 / (cm2·sec) or more, more preferably 10 cm3 / (cm2·sec) or more, and still more preferably 15 cm3 / (cm2·sec) or more, a long-fiber nonwoven fabric having a certain air permeation amount is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, the suction fixing property of a component to be transported can be made excellent.

[0075] On the other hand, when the air permeation amount is preferably 30 cm3 / (cm2·sec) or less, more preferably 27 cm3 / (cm2·sec) or less, and still more preferably 25 cm3 / (cm2·sec) or less, a long-fiber nonwoven fabric having no excessive air permeation amount is obtained, and when the long-fiber nonwoven fabric is used as a construction protective material, breakage of a component to be transported, which is caused by an excessively high suction force to a conveyor, can be prevented.(Construction Protective Material)

[0076] A construction protective material according to the present embodiment include the long-fiber nonwoven fabric according to the present embodiment. Here, the construction protective material is disposed between a conveyor and a component in transporting the component, and protects the component and the conveyor from being into direct contact with each other to be contaminated, damaged, or scratched, or prevents a chemical solution or the like applied to the component from adhering to the conveyor to contaminate subsequent components or the like.

[0077] A width of the construction protective material according to the present embodiment is preferably the same as a width of the conveyor or about several cm narrower than the width of the conveyor, and such a width makes it possible to prevent the construction protective material from being caught in a driving unit of the conveyor.(Method for Producing Long-Fiber Nonwoven Fabric)

[0078] Next, a method for producing a long-fiber nonwoven fabric according to the present embodiment will be described. The long-fiber nonwoven fabric according to the present embodiment is preferably produced by sequentially performing the following steps (a) to (d).

[0079] (a) A step of spinning a thermoplastic resin from a discharge port of a spinning spinneret and then subjecting the spun thermoplastic resin to suction drawing to obtain a long fiber.

[0080] (b) A step of collecting the long fiber on a moving net conveyor to form a fiber web.

[0081] (c) A step of bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web.

[0082] (d) A step of performing thermal fusion of the preheated fiber web using a pair of flat rolls.

[0083] Alternatively, the long-fiber nonwoven fabric according to the present embodiment is also preferably produced by sequentially performing the following steps (a) to (d).

[0084] (a) A step of spinning a high melting point polymer and a low melting point polymer from a discharge port of a composite spinning spinneret, and then subjecting the spun polymers to suction drawing to obtain a long fiber that is a multi-component fiber.

[0085] (b) A step of collecting the long fiber on a moving net conveyor to form a fiber web.

[0086] (c) A step of bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web.

[0087] (d) A step of performing thermal fusion of the preheated fiber web using a pair of flat rolls.

[0088] Hereinafter, each of the above steps will be described in more detail.(a) Step of Obtaining Long Fiber

[0089] First, in this step, the thermoplastic resin is spun from a discharge port of a spinning spinneret.

[0090] In the case where the fiber constituting the long-fiber nonwoven fabric is a multi-component fiber in which a low melting point polymer having a melting point lower than a melting point of a high melting point polymer is disposed around the high melting point polymer, the high melting point polymer and the low melting point polymer having a melting point lower than the melting point of the high melting point polymer by 10° C. or more and 110° C. or less are spun from a discharge port of a composite spinning spinneret. In this case, it is preferable that each of the high melting point polymer and the low melting point polymer be melted at a temperature equal to or higher than the melting point thereof and equal to or lower than (the melting point+70° C.), and melt-extruded from a spinning spinneret having a spinneret temperature equal to or higher than the melting point and equal to or lower than (the melting point+70° C.) so as to form a long fiber that is a multi-component fiber in which the high melting point polymer is surrounded by the low melting point polymer. Note that, the high melting point polymer and the low melting point polymer may be controlled at different temperatures during melting, and may be controlled at the same temperature from the middle.

[0091] Examples of a shape of the discharge port of the spinning spinneret from which the molten thermoplastic resin is extruded include a circular shape, an elliptical shape, a polygonal shape, a multi-leaf shape, or a combination thereof, depending on the cross-sectional shape of the fiber. Among these, the use of a discharge port having a circular cross-sectional shape is a more preferred embodiment from the viewpoint of efficiently obtaining fusing points between fibers and firmly fusing the fibers by thermal fusion.

[0092] Then, the thermoplastic resin thus melt-extruded and spun is pulled and drawn by an ejector to form a fiber. Pulling and drawing are generally performed by air, and a spinning speed at this time is preferably 3000 m / min or more and 6000 m / min or less. When the spinning speed is preferably 3000 m / min or more, more preferably 3500 m / min or more, and still more preferably 4000 m / min or more, the long fiber constituting a fiber web to be obtained can be more highly oriented and crystallized such that the fiber does not shrink to cause wrinkles during preheating or thermal fusion in subsequent steps, or the thermoplastic resin, particularly the low melting point polymer, is not fused to a heated roll or the like to reduce productivity.

[0093] On the other hand, when the spinning speed is preferably 6000 m / min or less, more preferably 5500 m / min or less, and still more preferably 5000 m / min or less, excessively oriented crystallization of the fiber can be prevented, and the thermal fusion property contributing to improvement of the mechanical strength of the spunbond nonwoven fabric can be obtained.(b) Step of Forming Fiber Web

[0094] In this step, the long fiber obtained in the above step is collected on a moving net conveyor to form a fiber web. At this time, the long fiber is preferably collected after arrangement of the fibers is regulated by an opening plate. Specifically, it is more preferable to eject the fiber sucked by the ejector from an opening plate having a slit shape provided in a lower portion of the ejector. The fiber is preferably deposited on the moving net conveyor to form a fiber web.(c) Step of Obtaining Preheated Fiber Web In the method for producing a long-fiber nonwoven fabric according to the present embodiment, a heating surface is brought into contact with only one surface of the fiber web obtained in the above step to preheat the fiber web to obtain a preheated fiber web.

[0095] For the preheating, a method of fusing the collected fiber web using a pair of upper and lower flat rolls, or a method of installing a flat roll or a heating plate above a net conveyor and fusing the fiber web between the net conveyor and the flat roll or the heating plate is preferably used. In this manner, a difference between the front and back surfaces is provided, and when the long-fiber nonwoven fabric is used as a construction protective material, the step passability is improved.

[0096] The “flat roll” used in these methods is a metal roll or an elastic roll having no unevenness on the surface of the roll, and the pair of upper and lower flat rolls is a pair of a metal roll and a metal roll, a pair of a metal roll and an elastic roll, or the like. Here, the elastic roll is a roll composed of a material having elasticity as compared with a metal roll. Examples of the elastic roll include so-called paper rolls composed of paper, cotton, aramid paper, or the like, and resin rolls composed of a urethane-based resin, an epoxy resin, a silicon-based resin, a polyester-based resin, a hard rubber, or a mixture thereof.

[0097] Note that, in the preheating, in the case of perform fusion using a pair of upper and lower flat rolls, only one of the flat rolls is used as the heating surface. In one embodiment, only one flat roll is a roll (heat roll) having a heating mechanism such as a heater to heat the fiber web to a temperature to be described later, and the other flat roll is a roll having no such a heating mechanism or a roll having a heating mechanism but in a state where the heater is switched off. In this embodiment, the “heating surface” refers to the surface of the heat roll.

[0098] In the preheating, in the case where a flat roll is installed above a net conveyor for preheating between the net conveyor and the flat roll, the flat roll is preferably composed of a metal, and only the flat roll is provided with a heating mechanism such as a heater to heat the fiber web to the temperature to be described later. The flat roll is a heat roll, and the surface of the heat roll is the “heating surface”.

[0099] In addition, in the preheating, in the case where a heating plate is installed above a net conveyor for preheating between the net conveyor and the heating plate, the heating plate is preferably composed of a metal, and only the heating plate is provided with a heating mechanism such as a heater to heat the fiber web to the temperature to be described later. The surface of the heating plate on the side in contact with the fiber web is the “heating surface”.

[0100] In the preheating in this step, the temperature of the heating surface is a temperature lower than the melting point of the thermoplastic resin (the melting point of the low melting point polymer in the case where the fiber is a multi-component fiber in which the low melting point polymer having a melting point lower than the melting point of the high melting point polymer is disposed around the high melting point polymer) by 30° C. or more and 110° C. or less, and the linear pressure of the heating surface is 1 N / cm or more and 100 N / cm or less. When the preheating is performed under such conditions, heat is applied only to the fiber web on the heating surface, crystallization of the fiber is promoted only on the contact surface of the fiber, and a nonwoven fabric having a sufficient difference in surface roughness Rz between the front and back surfaces can be obtained after the thermal fusion to be described later.

[0101] In particular, when the temperature range is lower than the melting point of the thermoplastic resin (the melting point of the low melting point polymer in the case where the fiber is a multi-component fiber in which the low melting point polymer having a melting point lower than the melting point of the high melting point polymer is disposed around the high melting point polymer) by 30° C. or more ([melting point −30]° C. or lower), and preferably by 40° C. or more ([melting point −40]° C. or lower), the surface temperature of the fiber web on the heating surface is not too high, and the fiber web can be transported to a subsequent step without being taken up by the pair of flat rolls during the thermal fusion; and when the temperature range is lower than the melting point by 110° C. or less ([melting point −110]° C. or higher), and preferably by 100° C. or less ([melting point −100]° C. or higher), the fiber web on the heating surface can be sufficiently preheated.

[0102] On the other hand, when the lower limit of the linear pressure range is 1 N / cm or more, and preferably 5 N / cm or more, the fiber web on the heating surface can be sufficiently preheated. On the other hand, when the upper limit of the above range is 100 N / cm or less, and preferably 50 N / cm or less, heat is transferred into the fiber web on the heating surface, thermal crystallization is prevented, and crimping can be sufficiently performed during the thermal fusion.(d) Step of Performing Thermal Fusion

[0103] In the method for producing a long-fiber nonwoven fabric according to the present embodiment, the preheated fiber web obtained in the above step is thermally fused using a pair of flat rolls. In the thermal fusion, the surface temperature of the pair of flat rolls is a temperature lower than the melting point of the thermoplastic resin (the melting point of the low melting point polymer in the case where the fiber is a multi-component fiber in which the low melting point polymer having a melting point lower than the melting point of the high melting point polymer is disposed around the high melting point polymer) by 30° C. or more and 70° C. or less, and the linear pressure of the pair of flat rolls is 100 N / cm or more and 900 N / cm or less. When the thermal fusion is performed under such conditions, the preheated fiber web can be sufficiently thermally fused, and a nonwoven fabric having a desired small surface roughness and a sufficient difference in surface roughness Rz between the front and back surfaces can be obtained.

[0104] In particular, when the temperature range is lower than the melting point of the thermoplastic resin (the melting point of the low melting point polymer in the case where the fiber is a multi-component fiber in which the low melting point polymer having a melting point lower than the melting point of the high melting point polymer is disposed around the high melting point polymer) by 30° C. or more ([melting point −30]° C. or lower), and preferably by 40° C. or more ([melting point −40]° C. or lower), the surface temperature of the pair of flat rolls is not too high, and the preheated fiber web can be transported to a subsequent step without being wound around the flat rolls. When the temperature range is lower than the melting point by 70° C. or less ([melting point −70]° C. or higher), and preferably by 60° C. or less ([melting point −60]° C. or higher), the preheated fiber web is sufficiently thermally fused, and a long-fiber nonwoven fabric having sufficient mechanical strength is obtained.

[0105] On the other hand, when the lower limit of the linear pressure range is 100 N / cm or more, and preferably 500 N / cm or more, the preheated fiber web is sufficiently thermally fused, and a long-fiber nonwoven fabric having a desired surface roughness is obtained. On the other hand, when the upper limit of the above range is 900 N / cm or less, and preferably 800 N / cm or less, partial film formation of the long-fiber nonwoven fabric can be prevented without strong thermal fusion.(e) Device for Producing Long-Fiber Nonwoven Fabric

[0106] Finally, FIG. 2 shows an example of a production device for performing the method for producing a long-fiber nonwoven fabric described in the above (a) to (d).

[0107] A thermoplastic resin 10 (as described above, the spun thermoplastic resin 10 may be a high melting point polymer and a low melting point polymer) spun from a discharge port of a spinning spinneret 5 (as described above, the spinning spinneret 5 may be a composite spinning spinneret) is subjected to suction drawing using an ejector 6 to obtain a long fiber. The long fiber is collected on a moving net conveyor 7 to form a fiber web 11. Thereafter, the fiber web 11 is transported in a direction of an arrow 13 indicating a transportation direction of the fiber web, and is preheated by bringing a heating surface 8 into contact with only one surface of the fiber web 11, thereby forming a preheated fiber web. The preheated fiber web is thermally fused using a pair of flat rolls 9, and a long-fiber nonwoven fabric 12 is finally obtained.

[0108] Of course, the above device is merely a preferred embodiment, and the present invention is not limited to the above range. It goes without saying that various modifications can be made without departing from the gist of the present invention.EXAMPLES

[0109] Next, the nonwoven fabric roll according to the present embodiment and the method for producing the same will be specifically described based on Examples. However, the present invention is not limited these Examples. In the measurement of each physical property, the measurement was performed based on the above method unless otherwise specified.[Measurement Method](1) Intrinsic Viscosity IV:

[0110] An intrinsic viscosity IV of a polyethylene terephthalate resin was measured by the following method. 8 g of a sample was dissolved in 100 mL of orthochlorophenol, and a relative viscosity ηr was determined according to the following equation using an Ostwald viscometer at a temperature of 25° C.ηr=η / η0=(t×d) / (t0×d0)(η represents the viscosity of the polymer solution, no represents the viscosity of orthochlorophenol, t represents the dropping time (sec) of the solution, d represents the density (g / cm3) of the solution, t0: represents the dropping time (sec) of orthochlorophenol, and d0 represents the density (g / cm3) of orthochlorophenol.)

[0112] Next, the intrinsic viscosity IV was calculated based on the relative viscosity ηr according to the following equation.Intrinsic⁢ viscosity⁢ IV⁢=0⁢0⁢2⁢4⁢2⁢ηr+0⁢.2634.(2) Melting Point (° C.):

[0113] The melting point of the thermoplastic resin used was measured under the above conditions using a differential scanning calorimeter (“Q100” manufactured by TA Instruments), and the average value of endothermic peak top temperatures was calculated and used as the melting point of the measurement target.(3) Average Single Fiber Diameter (μm) of Fiber

[0114] The average single fiber diameter (μm) of the fiber was measured and calculated by the above method using a microscope “VHX-D500” manufactured by Keyence Corporation.(4) Basis Weight (g / m2), Thickness (Mm), and Apparent Density (g / Cm3):

[0115] The basis weight, the thickness, and the apparent density of the long-fiber nonwoven fabric were measured and calculated by the methods described above.(5) Air Permeation Amount (Cm3 / (Cm2·Sec))

[0116] As the air permeation amount of the long-fiber nonwoven fabric, 10 fiber sheets cut into a 15 cm square were subjected to measurement at a test pressure of 125 Pa using an air permeability tester “FX3300” manufactured by TEXTEST INSTRUMENTS according to “6.8.1 Frazier method” in “Test methods for nonwovens” in JIS L1913: 2010. Then, the average value of the obtained values was rounded off to the second decimal place.(6) Absolute Value of Difference Between Surface Roughness Rz (μm) and Surface Roughness Rz

[0117] The absolute value of the difference between the surface roughness Rz (μm) and the surface roughness Rz of the long-fiber nonwoven fabric was calculated by the method described above.(7) Area Ratio (%) of Fiber Voids' Part

[0118] The area ratio (%) of the fiber voids' part in the long-fiber nonwoven fabric was calculated by the above method using a multifunction device “DocuCentre-VI4471” manufactured by FUJIFILM Business Innovation Corp. as a scanner, “GIMP Ver. 2.10.30” as image editing software, and “ImageJ Ver. 1.53e” as image analysis software.(8) Evaluation as Construction Protective Material

[0119] The long-fiber nonwoven fabric (a short-fiber nonwoven fabric in Comparative Example 4) was divided (slit) in the width direction, and a test piece having a width of 25 cm and a length of 55 m was collected from a total of four locations including both end portions and two central portions, and was evaluated from the following three viewpoints (8-2) to (8-4) when the test piece was used as a construction protective material in a transportation operation in (8-1).(8-1) Transportation Operation

[0120] The transportation was evaluated using the device shown in the conceptual cross-sectional view in FIG. 1. Specifically, a belt conveyor 3 composed of a polyester plain fabric having a conveyor length of 30 cm, a width of 30 cm, and a curvature radius of 0.5 cm was used, a test piece 1 was placed on the belt conveyor 3, and a transportation component 2 composed of plastic having a bottom surface being a square 150 mm square and a mass of 260 g was transported from a feeding mechanism 4 on the right side toward the left side in FIG. 1 while being sucked to an inner side of the belt conveyor 3 by a suction unit (not shown) under a condition of a wind speed of 5.0 m / min such that the transportation component 2 was sucked to the belt conveyor 3. Note that, a dynamic friction coefficient between the transportation component 2 and the test piece 1 was 0.35, and an operation of transporting 50 pieces at a transporting speed of 1 second / piece was repeated five times.(8-2) Presence or Absence of Sheet Loose

[0121] After the transportation operation, the presence or absence of sheet loose at both end portions of the construction protective material was checked.(8-3) Suction Fixation Degree of Transportation Component

[0122] After the transportation operation, it was checked whether the transportation component was shifted in the width direction, and it was checked whether the transportation component was shifted by 1 cm or more.(8-4) Fluffing Property

[0123] The surface of the long-fiber nonwoven fabric was visually observed at three locations before and after the transportation per roll, and further observed using a scanning electron microscope (SEM, “VHX-950H” manufactured by Keyence Corporation). A case where no change was observed in the surface state before and after the transportation operation was denoted by “5”, a case where the fluffing was unclear by visual observation but slightly observed by SEM observation was denoted by “4”, a case where the fluffing was unclear by visual observation but clearly observed by SEM observation was denoted by “3”, a case where the fluffing could be observed by visual observation was denoted by “2”, and a case where the sheet form could not be held was denoted by “1”.[Resin Used]

[0124] Next, details of the resins used in Examples and Comparative Examples will be described.

[0125] High melting point polymer: polyethylene terephthalate dried to a moisture content of 50 ppm by mass or less and having an intrinsic viscosity (IV) of 0.65 and a melting point of 260° C. (in Tables 1 and 2, this is referred to as PET).

[0126] Low melting point polymer: copolymerized polyethylene terephthalate dried to a moisture content of 50 ppm by mass or less, having an intrinsic viscosity (IV) of 0.64, a copolymerization rate of isophthalic acid of 11 mol %, and a melting point of 230° C. (in Tables 1 and 2, this is referred to as Co-PET).Example 1(Step of Obtaining Long Fiber)

[0127] The high melting point polymer and the low melting point polymer were melted at temperatures of 295° C. and 280° C., respectively. Thereafter, using the high melting point polymer as a core component and the low melting point polymer as a sheath component, spinning was performed from a discharge port of a circular spinning spinneret at a spinneret temperature of 295° C. and a mass ratio of core:sheath=80:20.

[0128] Thereafter, the spun thermoplastic resin was pulled and drawn by an ejector at a spinning speed of 4900 m / min to form a long fiber having a circular cross-sectional shape.(Step of Forming Fiber Web)

[0129] The arrangement of the long fibers was regulated by an opening plate, then the long fibers were collected on a moving net conveyor to form a fiber web having a basis weight of 50 g / m2 and composed of a multi-component fiber having an average single fiber diameter of 12.3 μm.(Step of Obtaining Preheated Fiber Web)

[0130] The formed fiber web was transported by a net conveyor, and a heating plate (made of a metal, temperature of heating surface: 155° C.) installed above the net conveyor was brought into contact with the surface of the fiber web not in contact with the net conveyor at a linear pressure of 10 N / cm, to preheat only one surface of the fiber web, so as to obtain a preheated fiber web.(Step of Performing Thermal Fusion)

[0131] The preheated fiber web was passed through a calender roll composed of a pair of metal flat rolls having a linear pressure of 700 N / cm at a surface temperature of both flat rolls of 185° C. to be thermally fused to obtain a long-fiber nonwoven fabric. The results are shown in Table 1.

[0132] The long-fiber nonwoven fabric had an apparent density of 0.58 g / cm3, an air permeation amount of 25 cm3 / (cm2·sec), a surface roughness Rz of 35.8 μm and 43.4 μm on respective surfaces, and an area ratio of fiber voids' part of 5.0%.

[0133] As a result of using the long-fiber nonwoven fabric as a construction protective material, there was no sheet loose, the suction fixation degree of the transportation component was not problematic, and the fluffing property was rated 5.Example 2

[0134] The method same as that in Example 1 was performed except that, in (Step of Obtaining Preheated Fiber Web), a metal flat roll was used instead of the metal heating plate, and the linear pressure was changed to 50 N / cm instead of a linear pressure of 10 N / cm during the preheating. The results are shown in Table 1.

[0135] The obtained long-fiber nonwoven fabric had a basis weight of 50 g / m2, an apparent density of 0.61 g / cm3, an air permeation amount of 18 cm3 / (cm2·sec), a surface roughness Rz of 36.2 μm and 43.6 μm on respective surfaces, and an area ratio of fiber voids' part of 10.0%.

[0136] As a result of using the long-fiber nonwoven fabric as a construction protective material, there was no sheet loose, the suction fixation degree of the transportation component was not problematic, and the fluffing property was rated 5.Example 3

[0137] The method same as that in Example 2 was performed except that, in (Step of Forming Fiber Web), a speed of the moving net conveyor was adjusted to obtain a long-fiber nonwoven fabric having a basis weight of 70 g / m2, instead of being adjusted to obtain a long-fiber nonwoven fabric having a basis weight of 50 g / m2. The results are shown in Table 1.

[0138] The obtained long-fiber nonwoven fabric had an apparent density of 0.59 g / cm3, an air permeation amount of 7 cm3 / (cm2·sec), a surface roughness Rz of 32.1 μm and 39.8 μm on respective surfaces, and an area ratio of fiber voids' part of 0.2%.

[0139] As a result of using the long-fiber nonwoven fabric as a construction protective material, there was no sheet loose, the suction fixation degree of the transportation component was not problematic, and the fluffing property was rated 5.TABLE 1Example 1Example 2Example 3ThermoplasticHigh melting pointPolymer kindPETPETPETresinpolymerMelting point [° C.]260260260Low melting pointPolymer kindCo-PETCo-PETCo-PETpolymerMelting point [° C.]230230230FiberSpinning speed [m / min]490049004900Average single fiber diameter [μm]12.312.312.3PreheatingTemperature [° C.] of heating surface155155155Linear pressure [N / cm]105050ThermalSurface temperature [° C.] of flat roll185185185fusionLinear pressure [N / cm] between flat rolls700700700Long-fiberBasis weight [g / m2]505070nonwovenApparent density [g / cm3]0.580.610.59fabricAir permeation amount [cm3 / (cm2 · sec)]25187SurfaceOne surface (A) [μm]35.836.232.1roughness RzThe other surface (B) [μm]43.443.639.8Absolute value [μm] of7.57.57.8difference between (A) and (B)Area ratio [%] of fiber voids' part5.010.00.2ConstructionSheet looseNoNoNoprotectiveSuction fixation degree of transportation componentNoNoNomaterialFluffing property555Comparative Example 1

[0140] The method same as that in Example 1 was performed except that, in (Step of Obtaining Preheated Fiber Web), the heating plate was taken out and preheating was not performed (that is, the fiber web was transported as it was by the moving net conveyor), and in (Step of Performing Thermal Fusion), the fiber web was thermally fused by passing through a calender roll composed of a pair of metal flat rolls having a linear pressure of 700 N / cm at a surface temperature of both flat rolls of 195° C. The results are shown in Table 2.

[0141] The obtained long-fiber nonwoven fabric had a basis weight of 50 g / m2, an apparent density of 0.81 g / cm3, an air permeation amount of 7 cm3 / (cm2·sec), a surface roughness Rz of 32.3 μm and 32.9 μm on respective surfaces, and an area ratio of fiber voids' part of 0.1%.

[0142] As a result of using the long-fiber nonwoven fabric as a construction protective material, the suction fixation degree of the transportation component was not problematic, the fluffing property was rated 5, but sheet loose occurs.Comparative Example 2

[0143] The method same as that in Example 1 was performed except that, in (Step of Obtaining Preheated Fiber Web), the heating plate was taken out and preheating was not performed (that is, the fiber web was transported as it was by the moving net conveyor), and in (Step of Performing Thermal Fusion), the fiber web was thermally fused in two stages by passing through a calender roll composed of a pair of metal flat rolls having a linear pressure of 700 N / cm at a surface temperature of both flat rolls of 150° C. and then passing through a calender roll composed of a pair of metal flat rolls having a linear pressure of 700 N / cm at a surface temperature of both flat rolls of 195° C. The results are shown in Table 2.

[0144] The obtained long-fiber nonwoven fabric had a basis weight of 50 g / m2, an apparent density of 0.57 g / cm3, an air permeation amount of 22 cm3 / (cm2·sec), a surface roughness Rz of 36.2 μm and 37.1 μm on respective surfaces, and an area ratio of fiber voids' part of 2.1%.

[0145] As a result of using the long-fiber nonwoven fabric as a construction protective material, the suction fixation degree of the transportation component was not problematic, the fluffing property was rated 5, but sheet loose occurs.Comparative Example 3(Step of Obtaining Long Fiber)

[0146] The high melting point polymer and the low melting point polymer were melted at temperatures of 295° C. and 280° C., respectively. Thereafter, using the high melting point polymer as a core component and the low melting point polymer as a sheath component, spinning was performed from a discharge port of a circular spinning spinneret at a spinneret temperature of 295° C. and a mass ratio of core:sheath=80:20.

[0147] Thereafter, the spun thermoplastic resin was pulled and drawn by an ejector at a spinning speed of 4900 m / min to form a long fiber having a circular cross-sectional shape.(Step of Forming Fiber Web)

[0148] The arrangement of the long fibers was regulated by an opening plate, then the long fibers were collected on a moving net conveyor to form a fiber web having a basis weight of 35 g / m2 and composed of a multi-component fiber having an average single fiber diameter of 11.4 μm.(Step of Obtaining Preheated Fiber Web)

[0149] The formed fiber web was transported by a net conveyor, and a heating plate (made of a metal, temperature of heating surface: 135° C.) installed above the net conveyor was brought into contact with the surface of the fiber web not in contact with the net conveyor at a linear pressure of 10 N / cm, to preheat only one surface of the fiber web, so as to obtain a preheated fiber web.(Step of Performing Thermal Fusion)

[0150] The preheated fiber web was passed through a calender roll composed of a pair of metal flat rolls having a linear pressure of 490 N / cm at a surface temperature of both flat rolls of 135° C. to be thermally fused to obtain a nonwoven fabric sheet. Further, two layers of the obtained nonwoven fabric sheet were laminated, and the obtained laminate was passed through three (i.e., upper, middle, and lower) stages of flat rolls, in the order of passing between the middle-stage and lower-stage rolls and between the middle-stage and upper-stage rolls to be further thermally fused, and finally, the laminate was brought into contact with a metal cooling roll having a surface temperature of 45° C. for 1 second to obtain a long-fiber nonwoven fabric. Here, the details of the three (i.e., upper, middle, and lower) stages of flat rolls are as follows.

[0151] Upper-stage flat roll: resin elastic roll (surface temperature: 130° C.) having a hardness (Shore D) of 91 and a surface average roughness Ra of 4 μm

[0152] Middle-stage flat roll: metal roll (surface temperature: 195° C.)

[0153] Lower-stage flat roll: resin elastic roll (surface temperature: 130° C.) having a hardness (Shore D) of 91 and a surface average roughness Ra of 4 μm

[0154] Linear pressure between upper-stage flat roll and middle-stage flat roll: 1850 N / cm

[0155] Linear pressure between middle-stage flat roll and lower-stage flat roll: 1850 N / cm

[0156] The results are shown in Table 2.

[0157] As a result of using the long-fiber nonwoven fabric as a construction protective material, there was no sheet loose, the fluffing property was rated 5, but the suction fixation degree of the transportation component was weak, causing the transportation component to shift.

[0158] The obtained long-fiber nonwoven fabric had a basis weight of 70 g / m2, an apparent density of 0.83 g / cm3, an air permeation amount of 1 cm3 / (cm2·sec), a surface roughness Rz of 24.8 μm and 30.0 μm on respective surfaces, and an area ratio of fiber voids' part of 0.1%.Comparative Example 4

[0159] A drawn yarn (30 parts by mass) composed of the high melting point polymer having an average single fiber diameter of 17.0 μm and a fiber length of 64 mm, 20 parts by mass of a drawn yarn composed of the high melting point polymer having an average single fiber diameter of 10.0 μm and a fiber length of 38 mm, and 50 parts by mass of an undrawn yarn composed of the high melting point polymer having an average single fiber diameter of 22.0 μm and a fiber length of 38 mm were mixed, and a mixed fiber web was prepared by a carding machine. The prepared mixed fiber web was passed through a calender roll composed of a pair of metal flat rolls having a linear pressure of 600 N / cm at a surface temperature of both flat rolls of 180° C. to thermally fusing the entire surface of the mixed fiber web, to obtain a short-fiber nonwoven fabric having a basis weight of 63 g / m2. The results are shown in Table 2.

[0160] The obtained short-fiber nonwoven fabric had an apparent density of 0.60 g / cm3, an air permeation amount of 8 cm3 / (cm2·sec), a surface roughness Rz of 40.8 μm and 44.6 μm on respective surfaces, and an area ratio of fiber voids' part of 0.4%.

[0161] As a result of using the short-fiber nonwoven fabric as a construction protective material, there was no sheet loose, the suction fixation degree of the transportation component was not problematic, but the fluffing property was rated 2.Comparative Example 5

[0162] The method same as that in Example 1 was performed except that, in (Step of Obtaining Preheated Fiber Web), a metal flat roll was used instead of the metal heating plate, the temperature of the heating surface was changed to 205° C., and the linear pressure was changed to 50 N / cm instead of a linear pressure of 10 N / cm during the preheating. The results are shown in Table 2.

[0163] The obtained long-fiber nonwoven fabric had a basis weight of 50 g / m2, an apparent density of 0.45 g / cm3, an air permeation amount of 32 cm3 / (cm2·sec), a surface roughness Rz of 24.1 μm and 40.2 μm on respective surfaces, and an area ratio of fiber voids' part of 16.3%.

[0164] As a result of using the long-fiber nonwoven fabric as a construction protective material, the fluffing property was rated 5, but sheet loose occurred, and regarding the suction fixation of the transportation component, the suction degree was too strong and the transportation component was deformed.TABLE 2ComparativeComparativeComparativeComparativeComparativeExample 1Example 2Example 3Example 4Example 5ThermoplasticHigh meltingPolymer kindPETPETPETPETPETresinpoint polymerMelting point [° C.]260260260260260Low meltingPolymer kindCo-PETCo-PETCo-PET—Co-PETpoint polymerMelting point [° C.]230230230—230FiberSpinning speed [m / min]490049004900—4900Average single fiber diameter [μm]12.312.311.4—12.3PreheatingTemperature [° C.] of heating surface——135—205Linear pressure [N / cm]——10—50ThermalSurface temperature [° C.] of flat roll195150135180205fusionat first timeLinear pressure [N / cm] between flat700700490600700rolls at first timeSurface temperature [° C.] of flat roll—195130——at second timeLinear pressure [N / cm] between flat—700———rolls at second timeLinear pressure [N / cm] between——1850——upper-stage flat roll and middle-stageflat roll at second timeLinear pressure [N / cm] between——1850——middle-stage flat roll and lower-stageflat roll at second timeLong-fiberBasis weight [g / m2]5050706350nonwovenApparent density [g / cm3]0.810.570.830.600.45fabricAir permeation amount7221832[cm3 / (cm2 · sec)]SurfaceOne surface (A) [μm]32.336.224.840.824.1roughness RzThe other surface (B)32.937.130.044.640.2[μm]Absolute value [μm] of0.60.83.83.816.1difference between (A)and (B)Area ratio [%] of fiber voids' part0.12.10.10.416.3ConstructionSheet looseYesYesNoNoYesprotectiveSuction fixation degree ofNoNoYesNoYesmaterialtransportation componentFluffing property55525Summary

[0165] As described above, as a result of using the long-fiber nonwoven fabrics obtained in Examples and Comparative Examples as a construction protective material, it was found that the long-fiber nonwoven fabrics in Example 1 to 3 had no sheet loose of the long-fiber nonwoven fabric, had no problem in suction fixation of the transportation component, had a good fluffing property, and had excellent scratch resistance. On the other hand, in the long-fiber nonwoven fabrics in Comparative Examples 1 and 2, there was no difference between the front and back surfaces of the long-fiber nonwoven fabric, the sheet end portion was easily curled, and loose occurred in a part of the sheet. In addition, in the long-fiber nonwoven fabric in Comparative Example 3, since the surface was smooth at a high density, the transportation component could not be sufficiently sucked and fixed during transportation, and a transportation failure occurred. In addition, in the short-fiber nonwoven fabric in Comparative Example 4, there was no problem in transportability, but as a result of surface observation with SEM in the same processing twice, fluffing was observed, and as a result of performing the same processing five times in total, fluffing was observed even visually, and continuous productivity was poor. Further, in the long-fiber nonwoven fabric in Comparative Example 5, the temperature was high in the preheating step, the difference in surface roughness of the long-fiber nonwoven fabric was large, the sheet was curled, and sheet loose occurred during transportation. In addition, since the temperature on the preheating surface side was high and crystallization proceeds, the fusion property during the thermal fusion decreased, and the air permeation amount was increased, and thus the suction degree was increased as described above, and the transportation component was deformed.

[0166] From the above results, the long-fiber nonwoven fabric according to the present invention was a long-fiber nonwoven fabric that had excellent followability to a conveyor, that could be transported, that had excellent scratch resistance, and that could withstand continuous use.

[0167] Although the present invention has been described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Note that, the present application is based on Japanese Patent Application No. 2023-025789 filed on Feb. 22, 2023, and the content thereof is incorporated herein by reference. All references cited herein are incorporated as a whole.REFERENCE SIGNS LIST1: test piece

[0169] 2: transportation component

[0170] 3: belt conveyor

[0171] 4: feeding mechanism

[0172] 5: spinning spinneret

[0173] 6: ejector

[0174] 7: net conveyor

[0175] 8: heating surface

[0176] 9: flat roll

[0177] 10: spun thermoplastic resin

[0178] 11: fiber web

[0179] 12: long-fiber nonwoven fabric

[0180] 13: arrow indicating transportation direction of fiber web

Claims

1. A long-fiber nonwoven fabric comprising:a fiber comprising a thermoplastic resin as a main component, whereinthe long-fiber nonwoven fabric has a surface roughness Rz of 25.0 μm or more and 50.0 μm or less on both surfaces, andan absolute value of a difference between the surface roughness Rz of one surface and the surface roughness Rz of the other surface is 4.0 μm or more and 10.0 μm or less.

2. The long-fiber nonwoven fabric according to claim 1, wherein the long-fiber nonwoven fabric has an area ratio of a fiber voids' part of 1.0% or more and 15.0% or less.

3. The long-fiber nonwoven fabric according to claim 1, wherein the fiber is a multi-component fiber in which a low melting point polymer having a melting point lower than a melting point of a high melting point polymer is disposed around the high melting point polymer.

4. The long-fiber nonwoven fabric according to claim 1, wherein the long-fiber nonwoven fabric has an apparent density of 0.40 g / cm3 or more and 0.75 g / cm3 or less.

5. The long-fiber nonwoven fabric according to claim 1, wherein the long-fiber nonwoven fabric has a basis weight of 40 g / m2 or more and 75 g / m2 or less.

6. A method for producing the long-fiber nonwoven fabric according to claim 1, the method sequentially comprising:spinning a thermoplastic resin from a discharge port of a spinning spinneret and then subjecting the spun thermoplastic resin to suction drawing to obtain a long fiber;collecting the long fiber on a moving net conveyor to form a fiber web;bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web; andperforming thermal fusion of the preheated fiber web using a pair of flat rolls, whereina spinning speed in the suction drawing is 3000 m / min or more and 6000 m / min or less,in the preheating, a temperature of the heating surface is a temperature lower than a melting point of the thermoplastic resin by 30° C. or more and 110° C. or less and a linear pressure of the heating surface is 1 N / cm or more and 100 N / cm or less, andin the thermal fusion, a surface temperature of the pair of flat rolls is a temperature lower than the melting point of the thermoplastic resin by 30° C. or more and 70° C. or less and a linear pressure of the pair of flat rolls is 100 N / cm or more and 900 N / cm or less.

7. A method for producing the long-fiber nonwoven fabric according to claim 3, the method sequentially comprising:spinning a high melting point polymer and a low melting point polymer having a melting point lower than a melting point of the high melting point polymer by 10° C. or more and 110° C. or less from a discharge port of a composite spinning spinneret, and then subjecting the spun polymers to suction drawing to obtain a long fiber that is a multi-component fiber in which the low melting point polymer is disposed around the high melting point polymer;collecting the long fiber on a moving net conveyor to form a fiber web;bringing a heating surface into contact with only one surface of the fiber web to preheat the fiber web to obtain a preheated fiber web; andperforming thermal fusion of the preheated fiber web using a pair of flat rolls, whereina spinning speed in the suction drawing is 3000 m / min or more and 6000 m / min or less,in the preheating, a temperature of the heating surface is a temperature lower than a melting point of the low melting point polymer by 30° C. or more and 110° C. or less and a linear pressure of the heating surface is 1 N / cm or more and 100 N / cm or less, andin the thermal fusion, a surface temperature of the pair of flat rolls is a temperature lower than the melting point of the low melting point polymer by 30° C. or more and 70° C. or less and a linear pressure of the pair of flat rolls is 100 N / cm or more and 900 N / cm or less.

8. A construction protective material comprising:the long-fiber nonwoven fabric according to claim 1.

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