Nonwoven fabric, its manufacturing method and building material

Abstract

The present invention addresses the problem of providing a non-woven fabric that has a smooth surface and has excellent adhesion to adhesive tapes such as waterproof tapes.　The present invention is a non-woven fabric that comprises fibers that include a thermoplastic resin as a principal component. The non-woven fabric has a thickness CV value of 1.0%–10.0%, a surface porosity of 10%–30%, and a surface porosity CV value of 10%–30%.

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric that is excellent in workability. [Background technology]

[0002] In the construction of wooden houses and other buildings, a ventilation layer construction method has become widespread, in which a ventilation layer is provided between the exterior wall material and the insulation material, allowing moisture that has infiltrated the wall to escape to the outside through this ventilation layer. This ventilation layer uses housewrap material, a breathable waterproof sheet that combines waterproofing to prevent rainwater from entering the building from the outside with moisture permeability to allow moisture generated within the wall to escape to the outside. When installing this housewrap, waterproof tape such as butyl tape, which has excellent long-term durability and adhesive properties, is used in areas that require particular waterproofing. This waterproof tape is applied to the building's framework, and then the housewrap material is applied on top of it. Therefore, these housewrap materials are also required to be adhesive to the waterproof tape.

[0003] As such a housewrap material, for example, Patent Document 1 proposes a long-fiber nonwoven fabric made of thermoplastic continuous filaments, in which the fiber orientation of the filaments in the longitudinal direction of the nonwoven fabric is 35 to 70 degrees, and the filaments are pressed together on one surface of the nonwoven fabric, and a large number of partially thermocompressed sections are formed intermittently in both directions throughout the nonwoven fabric, and in these partially thermocompressed sections, at least some of the filaments are fused together and aggregated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-040677 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the nonwoven fabric for house wrap materials disclosed in Patent Document 1 has a problem in that it has insufficient adhesive strength with waterproof tape due to the partial heat-sealed portion, and may peel off from the waterproof tape under its own weight. The present invention has been made in view of the above circumstances, and its object is to provide a nonwoven fabric that has excellent adhesive strength with adhesive tape, such as waterproof tape. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the inventors have conducted extensive research and have discovered that by setting the thickness CV value, which is the coefficient of variation of the thickness of a nonwoven fabric, and the surface porosity, and the surface porosity CV value, which is the coefficient of variation of the surface porosity, within specific ranges, a nonwoven fabric can be obtained that has a smooth surface and excellent adhesive strength with adhesive tape.

[0007] The present invention has been completed based on these findings, and comprises the following features. [1] A nonwoven fabric made of core-sheath composite fibers whose main component is polyester resin, with a basis weight of 20 g / m 2 More than 60g / m 2 or less, and the thickness CV value is 1.0% or more and 10.0% or less, A photograph of the surface side of a nonwoven fabric taken at 500x magnification using a scanning electron microscope is converted into an 8-bit grayscale image, and a threshold is set so that pixel values ​​of 0 to 127 are black and 128 to 255 are white, resulting in binarization. surface Calculated from photos taken from the side The porosity is 10% or more and 30% or less. ,table surface Calculated from photos taken from the side porosity of A nonwoven fabric having a CV value of 10% or more and 30% or less. [2] The nonwoven fabric according to [1], which is for use as a building material. [3] The apparent density of the nonwoven fabric is 0.40 g / cm 3 More than 0.70g / cm 3 The nonwoven fabric according to [1] or [2], which is: [4] A method for producing the nonwoven fabric according to any one of [1] to [3], comprising spinning a thermoplastic resin to form a nonwoven web, lowering the temperature of the nonwoven web to 100°C or higher and 160°C or lower, and then fusion-bonding the nonwoven web so that the ratio A of average single fiber diameters calculated by the following formula (1) is 0.85 or higher and 0.95 or lower. A = (average single fiber diameter (μm) of the nonwoven web before fusion) / (average single fiber diameter (μm) of the nonwoven fabric after fusion) (1) [5] A construction material comprising the nonwoven fabric according to any one of [1] to [3]. [Effects of the Invention]

[0008] According to the present invention, a nonwoven fabric is provided which has a smooth surface and excellent adhesive strength with adhesive tapes such as waterproof tapes. DETAILED DESCRIPTION OF THE INVENTION

[0009] The nonwoven fabric of the present invention is a nonwoven fabric made of fibers whose main component is a thermoplastic resin, and has a thickness CV value of 1.0% to 10.0%, a surface porosity of 10% to 30%, and a surface porosity CV value of 10% to 30%. The components thereof will be described in detail below, but the present invention is not limited to the scope described below as long as it does not deviate from the gist of the invention.

[0010] [Fibers made primarily of thermoplastic resin] First, examples of the thermoplastic resin for the nonwoven fabric of the present invention include polyester, polyamide, polyolefin, and mixtures or copolymers thereof. Among these, polyester is preferably used because of its excellent durability, such as mechanical strength, heat resistance, water resistance, and chemical resistance.

[0011] Polyesters are polymers containing an acid component and an alcohol component as monomers. In the present invention, examples of the acid component that can be used include aromatic carboxylic acids such as terephthalic acid (ortho-isomer), isophthalic acid, and terephthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid. Examples of the alcohol component that can be used include ethylene glycol and diethylene glycol.

[0012] Specific examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate, polylactic acid, polybutylene succinate, etc. As the polyester used as the high-melting-point polymer described below, polyethylene terephthalate (PET) is most preferably used because it has a higher melting point, excellent heat resistance, and excellent rigidity.

[0013] Additives such as crystal nucleating agents, matting agents, lubricants, pigments, mildew inhibitors, antibacterial agents, flame retardants, metal oxides, aliphatic bisamides and / or alkyl-substituted aliphatic monoamides, and hydrophilic agents can be added to these polyester raw materials, provided that the effects of the present invention are not impaired. Metal oxides such as titanium oxide, among others, improve spinnability by reducing surface friction of the fibers and preventing fusion between the fibers. They also improve the fusion properties of long-fiber nonwoven fabrics by increasing thermal conductivity during fusion molding of the long-fiber nonwoven fabric with a heated roll. Furthermore, aliphatic bisamides such as ethylene bisstearamide and / or alkyl-substituted aliphatic monoamides improve the releasability between the heated roll and the nonwoven fabric web, thereby improving transportability.

[0014] The nonwoven fabric of the present invention is made of fibers whose main component is the thermoplastic resin described above. The "main component" here means a component that accounts for 50% by mass or more of the fiber components.

[0015] The fibers of the present invention are preferably conjugated fibers in which a low-melting-point polymer having a melting point lower than that of a high-melting-point polymer is disposed around the high-melting-point polymer. By using conjugated fibers in this form, the fibers are more likely to be strongly fused within the nonwoven fabric, thereby suppressing fuzzing on the surface of the nonwoven fabric and easily achieving a smooth surface. Furthermore, when used as a housewrap material, for example, the fibers constituting the nonwoven fabric are not only strongly fused to each other, but also have a greater number of fusion points between the fibers in the nonwoven fabric than in a nonwoven fabric in which fibers with different melting points are blended, thereby improving mechanical strength.

[0016] The difference between the melting points of the high-melting-point polymer and the low-melting-point polymer (hereinafter sometimes simply referred to as the melting point difference) is preferably 10°C or more and 140°C or less. In other words, a 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 140°C or less is preferred. By making the difference in melting points 10°C or more, more preferably 20°C or more, and even more preferably 30°C or more, the fusion properties between the fibers can be improved. Furthermore, by making the difference 140°C or less, more preferably 120°C or less, and even more preferably 100°C or less, it is possible to prevent the low-melting-point polymer component from fusing to the heated roll during fusion, which would result in a decrease in productivity.

[0017] The melting point of the high-melting-point polymer in the present invention is preferably in the range of 160°C or higher and 320°C or lower. By setting the melting point to preferably 160°C or higher, more preferably 170°C or higher, and even more preferably 180°C or higher, a nonwoven fabric with excellent shape stability can be obtained, for example, when used as a housewrap material, so that the shape can be maintained even after processing that involves heat application. Furthermore, by setting the melting point to 320°C or lower, more preferably 300°C or lower, and even more preferably 280°C or lower, a large amount of thermal energy required for melting during nonwoven fabric production can be prevented, thereby preventing a decrease in productivity.

[0018] On the other hand, the melting point of the low-melting polymer in the conjugated fiber is preferably in the range of 150°C or higher and 310°C or lower, while ensuring the above-mentioned difference in melting points. By setting the melting point at 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher, a nonwoven fabric with excellent shape stability can be obtained, such that the nonwoven fabric can maintain its shape even when subjected to heat processing when used as a house wrap material. Furthermore, by setting the melting point at 310°C or lower, more preferably 290°C or lower, and even more preferably 270°C or lower, a nonwoven fabric with excellent fusion properties and mechanical strength can be easily obtained when produced.

[0019] In the present invention, the melting point of a thermoplastic resin is measured using a differential scanning calorimeter (for example, a "DSC-2" model manufactured by PerkinElmer) at a heating rate of 20°C / min over a temperature range of 30°C to 350°C, and the temperature at which the obtained melting endothermic curve gives an extreme value is taken as the melting point of the thermoplastic resin. For resins whose melting endothermic curve does not give an extreme value in the differential scanning calorimeter, the resin is heated on a hot plate, and the temperature at which the resin melts under microscope observation is taken as the melting point.

[0020] When the thermoplastic resin is polyester, examples of the combination of a high-melting polyester polymer and a low-melting polyester polymer (hereinafter sometimes referred to in the order of high-melting polyester polymer / low-melting polyester polymer) include PET / PBT, PET / PTT, PET / polylactic acid, and PET / copolymerized PET, among which the combination of PET / copolymerized PET is preferred due to its excellent spinnability. Furthermore, isophthalic acid-copolymerized PET is preferably used as the copolymerization component of copolymerized PET due to its particularly excellent spinnability.

[0021] Examples of the composite form of the composite fiber include a concentric sheath-core type, an eccentric sheath-core type, and an islands-in-the-sea type. Of these, the concentric sheath-core type is preferred because it allows the fibers to be fused uniformly and firmly. Furthermore, the cross-sectional shape of the composite fiber may be a circular cross-section, a flat cross-section, a polygonal cross-section, a multi-lobal cross-section, a hollow cross-section, etc. Of these, a circular cross-sectional shape is a preferred embodiment of the composite fiber.

[0022] Furthermore, when the fiber primarily composed of a thermoplastic resin is the aforementioned composite fiber, the mass ratio of the high-melting point polymer to the low-melting point polymer is preferably in the range of 90:10 to 60:40, more preferably 85:15 to 70:30. By adjusting the content of the high-melting point polymer to 60% by mass or more and 90% by mass or less, the durability of the nonwoven fabric can be improved. On the other hand, by adjusting the content of the low-melting point polymer to 10% by mass or more and 40% by mass or less, the fibers constituting the nonwoven fabric are firmly fused together, resulting in a nonwoven fabric with excellent mechanical strength.

[0023] The average single fiber diameter of the fibers according to the present invention is preferably in the range of 10.0 μm or more and 26.0 μm or less. By setting the average single fiber diameter to 10.0 μm or more, preferably 10.5 μm or more, and more preferably 11.0 μm or more, a nonwoven fabric with excellent mechanical strength can be obtained. On the other hand, by setting the average single fiber diameter to 26.0 μm or less, preferably 25.0 μm or less, and more preferably 24.0 μm or less, the uniformity of the nonwoven fabric can be improved, resulting in a nonwoven fabric with a dense surface. For example, when used as a house wrap material, the nonwoven fabric can have little surface unevenness.

[0024] In the present invention, the average single fiber diameter (μm) of the nonwoven fabric is determined by the following method. (i) Ten small samples are randomly taken from the nonwoven fabric. (ii) The surface of the collected small sample is photographed using a scanning electron microscope or the like at a magnification of 500 to 2000 times, allowing the thickness of the fibers to be measured. (iii) From the photographs of each small sample, 10 fibers (100 in total) are randomly selected and their thickness is measured. Assuming that the cross section of the fiber is circular, the thickness is expressed as the single fiber diameter (μm). (iv) The arithmetic mean value is rounded to one decimal place to obtain the average single fiber diameter (μm).

[0025] [Nonwoven fabric] The nonwoven fabric of the present invention is made of fibers containing the above-mentioned thermoplastic resin as a main component. The nonwoven fabric is preferably a long-fiber nonwoven fabric, which generally has excellent productivity and low cost. Among long-fiber nonwoven fabrics, a spunbond nonwoven fabric is more preferred, which has excellent productivity and low cost, and furthermore, can obtain higher mechanical strength by fusing a pre-set web with a pair of thermocompression rollers.

[0026] The nonwoven fabric of the present invention has a thickness CV value of 1.0% or more and 10.0% or less. A thickness CV value of 1.0% or more, preferably 3.0% or more, and more preferably 5.0% or more can further increase the adhesive strength with an adhesive tape. On the other hand, a thickness CV value of 10.0% or less, preferably 8.0% or less, and more preferably 7.0% or less can result in a nonwoven fabric with sufficient mechanical strength.

[0027] In the present invention, the thickness CV value (%) of the nonwoven fabric refers to a value measured and calculated by the following method. (i) Five small sample pieces are taken from the nonwoven fabric so that a cross section perpendicular to the thickness direction can be observed. (ii) A cross section of the collected small sample is photographed at 100x magnification using a scanning electron microscope (SEM, for example, "VHX-D500" manufactured by Keyence Corporation). (iii) Measure the thickness of the small sample every 100 μm across the entire width of the photograph, and calculate the thickness CV value (%) using the following formula from the arithmetic mean value and standard deviation. Thickness CV value (%) = (standard deviation of thickness of 5 small sample pieces (μm)) / (arithmetic mean value of thickness of 5 small sample pieces (μm)) × 100 (iv) The thickness CV value (%) is calculated for each of the five small sample pieces in the same manner, and the arithmetic mean value (%) of the thickness CV values ​​of the five small sample pieces is rounded to two decimal places, and this value is the thickness CV value of the nonwoven fabric.

[0028] The thickness CV value (%) of the nonwoven fabric can be adjusted by using the form of the fibers constituting the nonwoven fabric (such as composite fibers) as described above, or by setting the temperature and pressure conditions of the rolls used when fusing the fiber web, and the tension applied to the fiber web at that time, within the ranges described below.

[0029] In the present invention, the surface porosity of the nonwoven fabric is 10% or more and 30% or less. A surface porosity of 10% or more, preferably 13% or more, and more preferably 15% or more can further increase the adhesive strength with an adhesive tape. On the other hand, a surface porosity of 30% or less, preferably 27% or less, and more preferably 25% or less can result in a nonwoven fabric with sufficient mechanical strength.

[0030] The surface porosity (%) of the nonwoven fabric can be adjusted by using the form of the fibers constituting the nonwoven fabric (such as composite fibers) as described above, or by setting the temperature and pressure conditions of the rolls used when fusing the fiber web, and the tension applied to the fiber web at that time, within the ranges described below.

[0031] Furthermore, in the present invention, the surface porosity CV value of the nonwoven fabric is 10% or more and 30% or less. A surface porosity CV value of 10% or more, preferably 13% or more, and more preferably 15% or more results in a nonwoven fabric with an appropriate amount of voids, which can further increase the adhesive strength with an adhesive tape. On the other hand, a surface porosity CV value of 30% or less, preferably 25% or less, and more preferably 20% or less results in a more uniform nonwoven fabric with higher mechanical strength.

[0032] In the present invention, the surface porosity (%) and surface porosity CV value (%) of the nonwoven fabric refer to values ​​measured and calculated by the following methods. (i) Take 10 small sample pieces from the nonwoven fabric so that the surface can be observed. (ii) The surface of the collected small sample is photographed at 500x magnification using a scanning electron microscope (SEM, for example, "VHX-D500" manufactured by Keyence Corporation). (iii) The photographs of each small sample are converted into grayscale images (8-bit images), and a threshold is set so that pixel values ​​of 0 to 127 are black and 128 to 255 are white, and the images are binarized. (iv) Using image analysis software (such as "ImageJ"), the ratio of the black area to the entire photograph (white area, black area) is taken as the surface porosity. (v) The surface porosity (%) of each of the 10 small sample pieces is calculated in the same manner, and the arithmetic mean value (%) and standard deviation (%) of the surface porosity of each of the 10 small sample pieces are calculated. (vi) The arithmetic mean value (%) of the surface porosity of the 10 small sample pieces obtained in (v) is rounded to one decimal place, and this value is the surface porosity (%) of the nonwoven fabric. (vii) Calculate the surface porosity CV value (%) using the following formula from the arithmetic mean value (%) and standard deviation (%) of the surface porosity of the 10 small sample pieces obtained in (v). Surface porosity CV value (%) = (standard deviation (%) of surface porosity of 10 small sample pieces) / (arithmetic mean value (%) of 10 small sample pieces) × 100 (viii) The surface porosity CV value (%) obtained in (vii) is rounded to one decimal place, and this value is defined as the surface porosity CV value (%) of the nonwoven fabric.

[0033] This surface porosity CV value (%) can be adjusted by using the form of the fibers constituting the nonwoven fabric (such as composite fibers) as described above, or by setting the temperature and pressure conditions of the rolls used when fusing the fiber web, and the tension applied to the fiber web at that time, within the ranges described below.

[0034] The basis weight of the nonwoven fabric of the present invention is 20 g / m 2 More than 60g / m 2 The weight of the nonwoven fabric is preferably 20 g / m or less.2 or more, preferably 25 g / m 2 More preferably, 25 g / m 2 By setting the weight of the nonwoven fabric to 60 g / m or more, it is possible to obtain a nonwoven fabric with excellent mechanical strength. 2 Less than 55 g / m 2 Less than 50 g / m 2 By satisfying the above condition, a lightweight nonwoven fabric with excellent workability can be obtained.

[0035] In the present invention, the basis weight of the nonwoven fabric is determined by the following procedure in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "Testing methods for general nonwoven fabrics." (i) Take three 25cm x 25cm test pieces per meter of sample width. (ii) Weigh the mass (g) of each at standard conditions. (iii) The average value is 1 m 2 Mass per unit (g / m 2 ) and rounded to the first decimal place.

[0036] The apparent density of the nonwoven fabric of the present invention is 0.40 g / cm 3 More than 0.70g / cm 3 The apparent density of the nonwoven fabric is preferably 0.40 g / cm or less. 3 More preferably, 0.43 g / cm 3 When the apparent density of the nonwoven fabric is 0.70 g / cm or more, the surface of the nonwoven fabric becomes smoother and the mechanical strength can be further increased. 3 or less, more preferably 0.67 g / cm 3 By satisfying the condition below, an anchor effect between the adhesive tape and the nonwoven fabric can be easily exhibited, and a nonwoven fabric having excellent adhesive strength to the adhesive tape can be obtained.

[0037] In the present invention, the apparent density of the nonwoven fabric is calculated in the following manner using the thickness value measured in accordance with "5.1" of JIS L1906:2000 "Testing methods for woven and knitted fabrics" as follows: (i) Using a pressure probe with a diameter of 10 mm, measure the thickness of the nonwoven fabric at 10 points per meter at equal intervals across the width with a load of 10 kPa to an accuracy of 0.01 mm. (ii) The average value of the above 10 points is rounded to two decimal places to obtain the thickness of the nonwoven fabric (mm), and calculated using the following formula: Apparent density (g / cm 3 ) = basis weight (g / m 2 ) / Thickness (mm) / 1000 In addition, the "weight per unit area (g / m 2 )" shall use the basis weight value obtained by the above method.

[0038] The nonwoven fabric of the present invention is particularly suitable for use as a building material. That is, the building material of the present invention comprises the nonwoven fabric of the present invention.

[0039] [Nonwoven fabric manufacturing method] In the method for producing the nonwoven fabric of the present invention, a thermoplastic resin is spun to form a nonwoven web, and then the temperature of the nonwoven web is set to 100°C or higher and 160°C or lower, and the nonwoven web is fused so that the ratio A of average single fiber diameters calculated by the following formula (1) is 0.85 or higher and 0.95 or lower. A = (average single fiber diameter (μm) of the nonwoven web before fusion) / (average single fiber diameter (μm) of the nonwoven fabric after fusion) (1) This will be explained in more detail below.

[0040] The nonwoven fabric of the present invention is preferably produced by sequentially carrying out the following steps (a) to (c): (a) A process for spinning a thermoplastic resin. (b) forming a nonwoven web; (c) fusing the resulting nonwoven web; Each of the above steps will be described in more detail below.

[0041] (a) A step of spinning a thermoplastic resin First, a thermoplastic resin is melt-extruded through a spinneret. In particular, when a composite fiber in which a low-melting-point polymer having a melting point lower than that of a high-melting-point polymer is disposed around the high-melting-point polymer is used as a fiber mainly composed of a thermoplastic resin, it is preferable to melt the polyester high-melting-point polymer and the polyester low-melting-point polymer at temperatures above their melting points and below (melting point + 70°C), respectively, and then to form a composite fiber in which a low-melting-point polymer having a melting point 10°C to 140°C lower than that of the high-melting-point polymer is disposed around the high-melting-point polymer, and then to spin the composite fiber through a spinneret having a spinneret temperature above the melting point and below (melting point + 70°C).

[0042] The thermoplastic resin that is melt-extruded and spun from the spinneret is preferably spun into fibers having a circular cross section.

[0043] (b) forming a fibrous web Subsequently, a fiber web is formed from the fibers spun in step (a). Preferably, the spun fibers are sucked into an ejector, ejected from a slit-shaped fiber-spreading plate at the bottom of the ejector, and further deposited on a moving net conveyor to form a fiber web.

[0044] In the method for producing a nonwoven fabric of the present invention, it is preferable to preheat the fiber web collected on the net conveyor and then carry out step (c) immediately after step (b).Preferably, the preheating method involves preheating the collected fiber web with hot air from above the net conveyor, or placing a flat roll on the net conveyor and preheating the web between the net conveyor and the flat roll.

[0045] This preheating is preferably carried out to a temperature of 100° C. or higher and 160° C. or lower. By maintaining the temperature of the nonwoven web at 100° C. or higher, preferably 110° C. or higher, and more preferably 120° C. or higher, the transportability of the nonwoven web can be improved. On the other hand, by maintaining the temperature of the nonwoven web at 160° C. or lower, preferably 150° C. or lower, and more preferably 140° C. or lower, the appropriate crystallization of the nonwoven web can be promoted.

[0046] (c) fusing the resulting nonwoven web Furthermore, the nonwoven web obtained in step (b) is fused. In particular, it is preferable to fused the nonwoven web so that the ratio A of the average single fiber diameters calculated by the following formula (1) is 0.85 or more and 0.95 or less. A = (average single fiber diameter (μm) of nonwoven web before fusion) / (average single fiber diameter (μm) of nonwoven fabric after fusion) (1).

[0047] It is preferable to set the temperature of the nonwoven web obtained in step (b) within the above range and to fuse the nonwoven web so that the ratio A is 0.85 or more and 0.95 or less. By fusing the nonwoven web so that the ratio A is preferably 0.85 or more, preferably 0.88 or more, a nonwoven fabric with excellent adhesive strength to adhesive tape can be obtained. On the other hand, by fusing the nonwoven web so that the ratio A is preferably 0.95 or less, preferably 0.92 or less, a nonwoven fabric with excellent mechanical strength can be obtained.

[0048] In the method for producing a nonwoven fabric of the present invention, the average single fiber diameter (μm) of the nonwoven web before fusion in the above formula (1) is a value determined by the following method, and the average single fiber diameter (μm) of the nonwoven fabric after fusion is a value determined by the same method as the method for measuring and calculating the average single fiber diameter of the nonwoven fabric described above. (i) Ten small samples are randomly taken from the fibrous web obtained in step (b). (ii) The surface of the collected small sample is photographed using a scanning electron microscope or the like at a magnification of 500 to 2000 times, allowing the thickness of the fibers to be measured. (iii) From the photographs of each small sample, 10 fibers (100 in total) are randomly selected and their thickness is measured. Assuming that the cross section of the fiber is circular, the thickness is expressed as the single fiber diameter (μm). (iv) The arithmetic mean value is rounded to one decimal place to obtain the average single fiber diameter (μm) of the nonwoven web before fusion bonding.

[0049] The ratio A can be adjusted by changing the amount of thermoplastic resin discharged in step (a) or the pressure in step (b).

[0050] Among these, fusion using a heated roll or a combination of an ultrasonic oscillator and a roll is preferred. Fusion using a heated roll is particularly preferred from the viewpoint of improving the strength of the nonwoven fabric. The temperature for fusion using a heated roll is preferably 5°C to 60°C lower than the melting point of the thermoplastic resin with the lowest melting point present on the surface of the fibers constituting the fiber web. Excessive fusion can be prevented by setting the temperature 5°C or more, more preferably 10°C or more lower than the melting point of the thermoplastic resin with the lowest melting point present on the fiber surface of the nonwoven fabric produced by a heated roll. On the other hand, a uniformly fused nonwoven fabric can be obtained by setting the temperature 60°C or less, more preferably 50°C or less lower than the melting point.

[0051] The linear pressure of the heated roll for fusing is preferably 290 N / cm or more and 890 N / cm or less. By setting the linear pressure of the heated roll for fusing to 290 N / cm or more, more preferably 390 N / cm or more, a nonwoven fabric with sufficient mechanical strength can be obtained. By setting the linear pressure for fusing to 890 N / cm or less, more preferably 790 N / cm or less, excessive fusing can be prevented. [Example]

[0052] Next, the nonwoven fabric of the present invention will be specifically described based on examples. However, the present invention is not limited to these examples. In addition, in measuring each physical property, unless otherwise specified, the measurement was performed based on the above-mentioned method.

[0053] [Measurement method] (1) Melting point of thermoplastic resin (℃) Measurement was carried out using a differential scanning calorimeter "DSC-2" manufactured by PerkinElmer Co., Ltd., at a temperature rise rate of 20°C / min, and the temperature at which the extreme value was obtained in the obtained melting endothermic curve was taken as the melting point.

[0054] (2) Intrinsic viscosity (IV) of thermoplastic resin The intrinsic viscosity (IV) of the thermoplastic resin was measured by the following method. Dissolve 8 g of sample in 100 mL of orthochlorophenol, and measure the relative viscosity η using an Ostwald viscometer at 25°C. r was calculated using the following formula: η r =η / η0=(t×d) / (t0×d0) (where η is the viscosity of the polymer solution, η0 is the viscosity of orthochlorophenol, t is the solution drop time (seconds), and d is the solution density (g / cm 3 ), t0 is the fall time of orthochlorophenol (seconds), and d0 is the density of orthochlorophenol (g / cm 3 ) respectively. Next, the relative viscosity η r The intrinsic viscosity (IV) was calculated using the following formula: Intrinsic viscosity (IV)=0.0242η r +0.2634.

[0055] (3) Average single fiber diameter (μm) of the nonwoven web before fusion The average single fiber diameter of the nonwoven web before fusion was calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0056] (4) Average single fiber diameter (μm) of the nonwoven fabric after fusion The average single fiber diameter of the nonwoven fabric according to the present invention after fusion of the fibers was calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0057] (5) Weight of nonwoven fabric (g / m 2 ) The basis weight of the nonwoven fabric was calculated by the method described above.

[0058] (6) Thickness of nonwoven fabric (mm) The thickness of the nonwoven fabric was evaluated by the above-mentioned method using a thickness meter "Teclock" (registered trademark) SM-114 manufactured by Teclock Corporation.

[0059] (7) Apparent density of nonwoven fabric (g / cm 3 ) The apparent density of the nonwoven fabric was calculated by the method described above.

[0060] (8) Thickness of nonwoven fabric CV value (%) The thickness CV value of the nonwoven fabric was calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0061] (9) Surface porosity (%) and surface porosity CV value (%) of nonwoven fabric The surface porosity and surface porosity CV value of the nonwoven fabric were calculated by the above-mentioned method using a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation.

[0062] (10) Adhesion strength between nonwoven fabric and adhesive tape (N / 25mm) Peel adhesive strength was measured and evaluated under the following conditions in accordance with "10.3.2 Test Procedures" of JIS Z0237:2022 "Test Methods for Adhesive Tapes and Adhesive Sheets," "a) Procedure for testing adhesive strength to test plate," and "g) Procedure for testing in a low-temperature environment," as well as "10.4 Measurement of Peel Adhesion Strength," "10.4.5 Method 5: 180° Peel Adhesion Strength to Test Plate in a Low-Temperature Environment." Note that in Tables 1 and 2, this is simply referred to as "adhesion strength with adhesive tape." Test temperature: -10℃ Adhesive tape used: Waterproof and airtight tape "Zenten (registered trademark) Tape No. 692" manufactured by Nitto Denko Corporation Testing machine: Shimadzu Corporation's "AGS-X" was used as the tensile testing machine (testing device A). Peeling speed: 30±1cm / min.

[0063] [Resin used] Next, the resins used in the examples and comparative examples will be described in detail. Polyester resin A: Polyethylene terephthalate (referred to as PET in Tables 1 and 2) dried to a moisture content of 50 mass ppm or less, with an intrinsic viscosity (IV) of 0.65 and a melting point of 260°C. Polyester resin B: Copolymerized polyethylene terephthalate (referred to as CO-PET in Tables 1 and 2) dried to a moisture content of 50 mass ppm or less, with an intrinsic viscosity (IV) of 0.64, an isophthalic acid copolymerization rate of 11 mol%, and a melting point of 230°C.

[0064] [Example 1] (Thermoplastic resin spinning process) The polyester resin A and the polyester resin B were melted at temperatures of 295°C and 280°C, respectively. Thereafter, the polyester resin A was used as the core component and the polyester resin B was used as the sheath component, and the mixture was spun through a fine hole at a spinneret temperature of 295°C in a core:sheath mass ratio of 80:20, followed by spinning into filaments having a circular cross section.

[0065] (Process for forming a fiber web) The obtained fibers were sucked by an ejector, and the basis weight of the obtained nonwoven fabric was 25 g / m 2 The fiber web was collected by depositing it on a net conveyor whose moving speed was adjusted to 160°C, with the fiber arrangement regulated by a fiber spreader. The average single fiber diameter of this fiber web before fusion was 11.3 μm. The collected fiber web was then preheated at 160°C.

[0066] (Step of fusing the obtained nonwoven web) Following the above process, the preheated nonwoven web was fused using a pair of flat rolls in a calender under the conditions of a surface temperature of 185°C for each of the upper and lower flat rolls and a linear pressure of 686 N / cm. The fused nonwoven fabric had an average single fiber diameter of 12.1 μm and an average single fiber diameter ratio A of 0.93. The resulting nonwoven fabric had a thickness CV value of 6.5%, a surface porosity CV value of 25%, and a basis weight of 25 g / m. 2 , apparent density is 0.42 g / cm 3The adhesive strength with the adhesive tape was 15.1 N / 25 mm. The results are shown in Table 1.

[0067] [Example 2] (Step of forming a fiber web) 2 The speed of the net conveyor was adjusted to achieve a weight of 40g / m 2 A nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the net conveyor traveled at a rate of 1 / 2000 rpm, and the fiber web was preheated at 150°C instead of 160°C. In Example 2, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 12.4 μm, and the ratio A of the average single fiber diameters was 0.91. The obtained nonwoven fabric had a thickness CV value of 6.8%, a surface porosity of 21%, a surface porosity CV value of 21%, and a basis weight of 40 g / m 2 , apparent density is 0.57 g / cm 3 The adhesive strength with the adhesive tape was 16.4 N / 25 mm. The results are shown in Table 1.

[0068] [Example 3] (Step of forming a fiber web) 2 The speed of the net conveyor was adjusted to achieve 60g / m 2 A nonwoven fabric was obtained under the same conditions as in Example 1, except that the moving speed of the net conveyor was adjusted so that the net conveyor traveled at a rate of 1 / 2000 rpm, and the fiber web was preheated at 130°C instead of 160°C. In Example 3, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 12.5 μm, and the ratio A of the average single fiber diameters was 0.90. The obtained nonwoven fabric had a thickness CV value of 7.3%, a surface porosity of 15%, a surface porosity CV value of 15%, and a basis weight of 60 g / m 2 , apparent density is 0.60 g / cm 3 The adhesive strength with the adhesive tape was 18.9 N / 25 mm. The results are shown in Table 1.

[0069] [Example 4] A nonwoven fabric was obtained under the same conditions as in Example 3, except that in the step of forming a fiber web, the fiber web was preheated at 100°C instead of 130°C. In Example 4, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 13.1 μm, and the ratio A of the average single fiber diameters was 0.86. The obtained nonwoven fabric had a thickness CV value of 6.5%, a surface porosity CV value of 10%, a surface porosity CV value of 29%, and a basis weight of 60 g / m 2 , apparent density is 0.67 g / cm 3 The adhesive strength with the adhesive tape was 15.7 N / 25 mm. The results are shown in Table 1.

[0070] [Table 1]

[0071] [Comparative Example 1] A nonwoven fabric was obtained under the same conditions as in Example 1, except that in the step of forming a fiber web, the collected fiber web was preheated at 90°C instead of 160°C. In this Comparative Example 1, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 13.3 μm, and the ratio of the average single fiber diameters was 0.85. The obtained nonwoven fabric had a thickness CV value of 4.7%, a surface porosity of 12%, a surface porosity CV value of 34%, and a basis weight of 25 g / m 2 , apparent density is 0.63 g / cm 3 The adhesive strength with the adhesive tape was 10.1 N / 25 mm. The results are shown in Table 2.

[0072] Comparative Example 2 A nonwoven fabric was obtained under the same conditions as in Example 1, except that in the step of forming a fiber web, the collected fiber web was preheated at 170°C instead of 160°C. In this Comparative Example 2, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 11.8 μm, and the ratio of the average single fiber diameters was 0.96. The obtained nonwoven fabric had a thickness CV value of 10.3%, a surface porosity CV value of 33%, a surface porosity CV value of 27%, and a basis weight of 25 g / m 2 , apparent density is 0.36 g / cm 3 The adhesive strength with the adhesive tape was 12.4 N / 25 mm. The results are shown in Table 2.

[0073] Comparative Example 3 A nonwoven fabric was obtained under the same conditions as in Example 2, except that in the step of forming a fiber web, the collected fiber web was preheated at 90°C instead of 150°C. In this Comparative Example 3, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 13.4 μm, and the ratio of the average single fiber diameters was 0.84. The obtained nonwoven fabric had a thickness CV value of 5.1%, a surface porosity of 11%, a surface porosity CV value of 35%, and a basis weight of 40 g / m 2 , apparent density is 0.80 g / cm 3 The adhesive strength with the adhesive tape was 8.9 N / 25 mm. The results are shown in Table 2.

[0074] Comparative Example 4 A nonwoven fabric was obtained under the same conditions as in Example 2, except that in the step of forming a fiber web, the collected fiber web was preheated at 180°C instead of 150°C. In this Comparative Example 4, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 11.7 μm, and the ratio of the average single fiber diameters was 0.96. The obtained nonwoven fabric had a thickness CV value of 14.3%, a surface porosity CV value of 31%, a surface porosity CV value of 28%, and a basis weight of 40 g / m 2 , apparent density is 0.50 g / cm 3 The adhesive strength with the adhesive tape was 10.4 N / 25 mm. The results are shown in Table 2.

[0075] Comparative Example 5 A nonwoven fabric was obtained under the same conditions as in Example 3, except that in the step of forming a fiber web, the collected fiber web was preheated at 90°C instead of 130°C. In this Comparative Example 5, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 13.4 μm, and the ratio of the average single fiber diameters was 0.84. The obtained nonwoven fabric had a thickness CV value of 5.3%, a surface porosity of 7%, a surface porosity CV value of 36%, and a basis weight of 60 g / m 2 , apparent density is 0.75g / cm 3 The adhesive strength with the adhesive tape was 5.9 N / 25 mm. The results are shown in Table 2.

[0076] Comparative Example 6 A nonwoven fabric was obtained under the same conditions as in Example 3, except that in the step of forming a fiber web, the collected fiber web was preheated at 180°C instead of 130°C. In this Comparative Example 6, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 11.5 μm, and the ratio of the average single fiber diameters was 0.98. The obtained nonwoven fabric had a thickness CV value of 18.5%, a surface porosity CV value of 27%, a surface porosity CV value of 31%, and a basis weight of 60 g / m 2 , apparent density is 0.46 g / cm 3 The adhesive strength with the adhesive tape was 8.2 N / 25 mm. The results are shown in Table 2.

[0077] Comparative Example 7 In the step of forming a fiber web, the thickness of the resulting nonwoven fabric was set to 0.06 mm, but a nonwoven fabric was obtained under the same conditions as in Example 1, except that the thickness was adjusted to 0.08 mm during fusion bonding. In this Comparative Example 7, the average single fiber diameter of the fiber web before fusion was 11.3 μm, the average single fiber diameter of the nonwoven fabric after fusion was 11.6 μm, and the ratio of the average single fiber diameters was 0.97. The resulting nonwoven fabric had a thickness CV value of 12.1%, a surface porosity of 34%, a surface porosity CV value of 37%, and a basis weight of 25 g / m 2, apparent density is 0.31 g / cm 3 The adhesive strength with the adhesive tape was 10.8 N / 25 mm. The results are shown in Table 2.

[0078] [Table 2]

[0079] The properties of the obtained nonwoven fabrics are as shown in Tables 1 and 2. The spunbonded nonwoven fabrics of Examples 1 to 4 had excellent adhesive strength with adhesive tape and exhibited favorable properties as nonwoven fabrics. On the other hand, the spunbonded nonwoven fabrics of Comparative Examples 1 to 6 either had excessive fusion, resulting in poor adhesive strength with adhesive tape in the film-like portions, or preheating promoted fiber crystallization, resulting in weak fusion of the nonwoven fabric, a poor adhesive area with adhesive tape, and poor adhesive strength with adhesive tape. The spunbonded nonwoven fabric of Comparative Example 7 also had weak fusion of the nonwoven fabric, a poor adhesive area with adhesive tape, and poor adhesive strength with adhesive tape.

Claims

1. A nonwoven fabric made of core-sheath composite fibers whose main component is polyester resin, with a basis weight of 20 g / m ２ 60g / m or more ２ a thickness CV value of 1.0% or more and 10.0% or less; a porosity calculated from the photograph taken from the surface side, which is obtained by converting a photograph of the surface side of the nonwoven fabric taken at 500x magnification using a scanning electron microscope into an 8-bit grayscale image and binarizing it by setting a threshold value so that pixel values ​​of 0 to 127 are black and pixel values ​​of 128 to 255 are white, of 10% or more and 30% or less; and a CV value of the porosity calculated from the photograph taken from the surface side of 10% or more and 30% or less.

2. The nonwoven fabric of claim 1 , wherein the nonwoven fabric is for use as a building material.

3. The apparent density of the nonwoven fabric is 0.40 g / cm ３ 0.70g / cm or more ３ 3. The nonwoven fabric according to claim 1 or 2, wherein:

4. 3. A method for producing the nonwoven fabric according to claim 1 or 2, comprising spinning a thermoplastic resin to form a nonwoven web, adjusting the temperature of the nonwoven web to 100°C or higher and 160°C or lower, and then fusion-bonding the nonwoven web so that the ratio A of average single fiber diameters calculated by the following formula (1) is 0.85 or higher and 0.95 or lower. A = (average single fiber diameter (μm) of nonwoven web before fusion bonding) / (average single fiber diameter (μm) of nonwoven fabric after fusion bonding) (1)

5. A building material comprising the nonwoven fabric according to claim 1 or 2.

Images