Bulky long-fiber nonwoven fabric

Abstract

To provide a bulky long-fiber nonwoven fabric suitable for sanitary material applications, offering excellent slip resistance and handling while maintaining optimal flexibility; a sanitary material containing bulky, long-fiber nonwoven fabrics; and high-quality absorbent products by combining various materials while keeping manufacturing costs for sanitary materials low.SOLUTION: There is provided a bulky long-fiber nonwoven fabric composed of two or more thermoplastic resins, wherein the quotient of its KES friction coefficient and a fluctuation value of the KES friction coefficient is 0.5 or more per basis weight of 1 g / m2. There are also provided sanitary materials containing the bulky long-fiber nonwoven fabric, and absorbent articles whose surface sheet and / or outer sheet comprises the bulky long-fiber nonwoven fabric.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a bulky nonwoven fabric made of two or more types of thermoplastic long fibers and suitable for use as a sanitary material. [Background technology]

[0002] Traditionally, the qualities required for diapers have been an undergarment-like appearance and a soft, comfortable, and cushiony flexibility. From the standpoints of productivity and cost, spunbond and other long-fiber nonwoven fabrics have been widely used in diapers for hygiene materials such as the top sheet, second sheet, core wrap, and back sheet. However, thin long-fiber nonwoven fabrics often lack the cushioning required for hygiene materials.

[0003] Patent Document 1 below discloses a nonwoven fabric with improved cushioning properties. However, while the disclosed nonwoven fabric provides a bulky and smooth surface feel, the long fibers make the surface smooth and slippery. For example, when this spunbonded nonwoven fabric is used as a top sheet for absorbent articles such as diapers, the nonwoven fabric slides against the skin, making it difficult to achieve a sense of close contact between the nonwoven fabric and the skin. Furthermore, when this spunbonded nonwoven fabric is used as a back sheet, adjacent diapers slide against each other during packaging, making handling difficult. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6714982 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above-mentioned state of the art, the problem to be solved by the present invention is to provide a bulky long-fiber nonwoven fabric suitable for use as a sanitary material, which is non-slip and easy to handle while maintaining suitable flexibility, and a sanitary material containing the bulky long-fiber nonwoven fabric; and to provide a high-quality absorbent article by combining various materials while reducing the production cost of the sanitary material. [Means for solving the problem]

[0006] As a result of extensive research and experiments to solve the above-mentioned problems, the inventors of the present application discovered that by setting the coefficient of friction, the variation in the coefficient of friction, the bending rigidity, etc. of a bulky long-fiber nonwoven fabric within specific ranges, it is possible to produce a sanitary material that is excellent in flexibility and in handleability after commercialization, and have thus completed the present invention.

[0007] That is, the present invention is as follows. [1] A bulky long fiber nonwoven fabric made of two or more thermoplastic resins, the quotient of the KES friction coefficient and the variation value of the KES friction coefficient is 1 g / m 2 Bulky long fiber nonwoven fabric with a fiber density of 0.5 or more. [2] The bulky long-fiber nonwoven fabric according to [1], wherein the KES friction coefficient is 0.3 or less. [3] A sanitary material comprising the bulky long-fiber nonwoven fabric according to [1] or [2] above. [4] An absorbent article, the top sheet and / or outer sheet of which comprises the bulky long-fiber nonwoven fabric according to [1] or [2]. [Effects of the Invention]

[0008] The bulky long-fiber nonwoven fabric of the present invention has cushioning softness and a coefficient of friction suitable for use in sanitary materials such as diapers, and is therefore suitable for use as a material for topsheets and exterior sheets. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is a bulky long-fiber nonwoven fabric made of two or more thermoplastic resins, in which the quotient of the KES friction coefficient and the variation of the KES friction coefficient is 1 g / m 2 It is a bulky long fiber nonwoven fabric with a density of 0.5 or more per unit area.

[0010] In this specification, the term "surface sheet for hygienic materials" refers to a sheet placed close to the body across from the absorbent body, such as a top sheet or second sheet. The term "exterior sheet" refers to a sheet placed on the clothing side across from the absorbent body, such as a back sheet.

[0011] In this specification, the term "MD direction" refers to the direction (machine direction) in which the bulky long-fiber nonwoven fabric of the present invention is transported as a web in the production thereof, and the direction perpendicular to the MD direction is called the CD direction (cross direction).

[0012] Nonwoven fabrics are the main material used in absorbent articles such as diapers, and are used in a wide variety of applications, including topsheets, secondsheets, SAP sheets, leg cuffs, and backsheets. The performance requirements for nonwoven fabrics vary depending on the part in which they are used: surface sheets require water permeability, cushioning, bulk, flexibility, and fluff resistance, while exterior sheets require cushioning, bulk, flexibility, breathability, and aesthetic appeal. Depending on the desired performance, nonwoven fabrics for each part are selected and used in combination with materials of the same or different configurations.

[0013] The bulky long-fiber nonwoven fabric of this embodiment has a quotient of the KES friction coefficient (hereinafter also referred to as MIU) and the variation of the KES friction coefficient (hereinafter also referred to as MMD) (hereinafter also referred to as the quotient of MIU and MMD) of 1 g / m2 or less in terms of achieving both the texture of the nonwoven fabric and ease of handling and adhesion to the skin when made into a diaper. 2 The average value is 0.5 or more.

[0014] MIU and MMD were measured using a surface testing machine by Kato Tech's KES, which will be described later, and were calculated using the following formula (1): Quotient of MIU and MMD = {MIU / MMD} / weight (g / m 2 )...Equation (1) This results in a basis weight of 1g / m 2 The basis weight in the above formula (1) was calculated by measuring the mass of the sample used in the test and converting it into a value per unit area.

[0015] The bulky long-fiber nonwoven fabric of this embodiment preferably has an MIU of 0.3 or less. If the MIU is 0.3 or less, the diaper slippage is suppressed and handling is improved while maintaining the surface texture.

[0016] From the viewpoint of surface smoothness, the MMD of the bulky long-fiber nonwoven fabric is preferably 0.010 or less.

[0017] The surface texture of the bulky long-fiber nonwoven fabric of this embodiment can be indexed by measuring the KES surface roughness mean deviation (hereinafter also referred to as SMD). The SMD of the bulky long-fiber nonwoven fabric of this embodiment can be 3.5 μm or less. The SMD is an index that indicates the unevenness of the surface, and a smaller value indicates less unevenness of the surface.

[0018] In this specification, MIU, MMD, and SMD were each measured using a surface tester (KES-FB4) manufactured by Kato Tech Co., Ltd. First, three 20cm x 20cm samples were taken from the bulky long-fiber nonwoven fabric so that they were evenly spaced in the CD direction. Next, the samples were attached to the measurement table of a Kato Tech surface testing machine (KES-FB4) so ​​that the MD direction was the same as the measurement direction (the direction in which the friction probe slides). A standard friction probe (a 10mm square metal wire friction probe and a 0.5mm piano wire contact probe) was moved 30mm over the sample with a measurement load of 50gf, a tension of 400gf / 20cm, and a movement speed of 1mm / min, and data was collected. On the measurement software screen attached to the device, when the measurement start position was set to 0 mm, MIU, MMD, and SMD were measured in the region of 5 mm to 25 mm.

[0019] The surface roughness of each material can also be evaluated using the surface roughness wavelength (SRW) of the FTT test. Information on the FTT test method can be found in the article "A Simultaneous Measurement Method to Characterize Touch Properties of Textile Materials" by Xiao Liao et al. in Fibers and Polymers 2014, Vol. 15, No. 7.

[0020] The KES bending rigidity of the bulky long fiber nonwoven fabric of this embodiment is 1 g / m 2 By keeping the density to 0.005 or less, the surface of the nonwoven fabric becomes less stiff when made into a diaper, and a sanitary material with a good texture can be obtained. The KES bending rigidity was measured using KES-FB2 manufactured by Kato Tech Co., Ltd. First, three 10cm x 10cm samples were taken from the bulky long fiber nonwoven fabric so that they were evenly spaced in the CD direction. The samples were held in a chuck spaced 1cm apart and measured at a curvature of -2.5 to +2.5cm. -1 In the range of 0.50 (cm -1 The measurement was performed in a pure bending test at a deformation rate of 1 / 2000. The MD and CD directions of the sample were evaluated, and the bending stiffness values ​​in the MD and CD directions were averaged. Then, the bending stiffness was calculated using the following formula (2): KES bending stiffness = {(average MD bending stiffness + average CD bending stiffness) / 2} / basis weight (g / m 2 )...Equation (2) The value of the KES bending rigidity was calculated by the following equation: The mass of the sample used in the test was measured and converted into a value per unit area, and used as the basis weight in the above formula (2).

[0021] The thickness of the bulky long-fiber nonwoven fabric of this embodiment is selected appropriately depending on the application, since the preferred range varies depending on the part where it is used. The bulky long-fiber nonwoven fabric of this embodiment has a thickness of 0.5 gf / cm as measured by the KES compression characteristic. 2The thickness T0 is preferably 0.1 mm or more. If the thickness T0 is 0.1 mm or more, it is easy to feel a softness with cushioning properties. The method for evaluating the KES compression characteristics will be described later. In addition, the compression energy (WC), compression stiffness (LC), and recovery rate (RC) of KES can also be used as indicators for evaluating cushioning. 2 If the above conditions are met, the nonwoven fabric can be suitably used as a sanitary material.

[0022] In this specification, the KES compression properties were measured using a compression testing device (KES-G5) manufactured by Kato Tech Co., Ltd. First, five 5 cm square test pieces were taken from the bulky long fiber nonwoven fabric so that they were evenly spaced in the CD direction. The test pieces were placed on a metal sample stage and pressed over a 2 cm area. 2 The compression speed was 0.002 cm / s and the maximum compression load was 50 gf / cm. 2 The recovery process was also measured at the same speed, and from the obtained data, the initial load thickness (T0), compression stiffness (LC), compression energy (WC), and recovery (RC) were calculated using measurement software, and the average values ​​for each were calculated. Note that the compression energy and compression stiffness of each material can also be evaluated as compression work (CW) and compression average stiffness (CAR) in the FTT test.

[0023] The softness of the bulky long-fiber nonwoven fabric of this embodiment can be evaluated by the TS7 and TS750 values ​​using the EMTEC Tissue Softness Analyzer (algorithm FACIAL III). According to EMTEC, TS7 indicates the inherent softness of the sample, and TS750 can evaluate the surface smoothness. The bulky long-fiber nonwoven fabric of this embodiment may have a TS7 value of 10 or less and a TS750 value of 5.0 or less.

[0024] The bulky long-fiber nonwoven fabric of this embodiment may have a glossiness of less than about 5.3. Without being bound by any particular theory, a reduction in glossiness may affect the diaper user's perception of texture. Generally, a lower glossiness tends to result in a softer feel. Glossiness can be measured using a glossmeter such as a microglossmeter with 45-degree lighting (manufactured by BYK-Gardener) or its equivalent. In this specification, light is irradiated onto a test surface, and the amount of reflection is measured. The gloss test was carried out in a room maintained at 23±2°C and 50±5% relative humidity. First, five 5cm square test pieces were taken from the bulky long-fiber nonwoven fabric, evenly spaced in the CD direction. The test pieces were placed flat on the measuring table with the measurement surface facing upward, taking care not to wrinkle. The gloss meter was placed vertically on the nonwoven fabric sample, and the results were read, recorded, and calculated as gloss.

[0025] The bulky long-fiber nonwoven fabric of this embodiment is made of fibers of two or more thermoplastic resins. As the fibers constituting the web, long fibers produced by a spunbonding method are preferred in terms of productivity, the possibility of mass-producing products with a low basis weight, surface feel, tear strength, and tape releasability. Examples of thermoplastic resins constituting the fibers include, but are not limited to, polyolefin resins such as polyethylene, polypropylene, and copolymer polypropylene; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and copolymer polyester; polyamide resins such as nylon-6, nylon-66, and copolymer nylon; and biodegradable resins such as polylactic acid and polybutylene succinate. Furthermore, the bulky long-fiber nonwoven fabric of this embodiment may be made from petroleum-derived, biomass-derived, or recycled (chemically recycled or material recycled) raw materials, and is not particularly limited. While any combination of the above thermoplastic resins is possible as long as the desired effects are achieved, a combination of thermoplastic resins with different melting points is preferred from the standpoint of bonding the fibers together and preventing fuzzing due to friction. From the viewpoint of texture, it is preferable to use a polyolefin resin in combination as the thermoplastic resin constituting the fiber. For example, conjugated fibers made of resins such as polyethylene, polypropylene, or copolymers of these monomers with other α-olefins can be used. The other α-olefins have 3 to 10 carbon atoms, and specific examples include propylene, 1-butene, 1-pentene, 1-hexane, 4-methyl-1-pentene, and 1-octene.

[0026] Known functional agents, such as inorganic particles such as titanium oxide and surfactants, can be kneaded into the fibers constituting the bulky long-fiber nonwoven fabric of this embodiment to adjust gloss or to impart functions such as hydrophilicity and flexibility. Fatty acid amides are preferred examples of additives for improving flexibility. Specific examples of fatty acid amides include, but are not limited to, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, and erucic acid amide.

[0027] Regarding the fiber form, the fibers may be crimped to impart bulkiness and a cushioning texture. The number of crimps is preferably 45 crimps per inch (2.5 cm) or less in terms of the coefficient of friction and the appearance of the diaper. Methods for crimping the fibers include forming the fiber cross section into a modified cross section and unevenly cooling the fiber during spinning and cooling, or using two or more thermoplastic resins to form a side-by-side or eccentric sheath-core crimp. In the case of an eccentric sheath-core crimp, the core may be covered or exposed on the fiber surface. The fibers constituting the bulky long-fiber nonwoven fabric of this embodiment are not limited to circular fibers, and may be fibers of special shapes such as modified fibers or hollow fibers, or may be a mixture of fibers of different diameters and shapes.

[0028] The average fiber diameter of the fibers constituting the bulky long-fiber nonwoven fabric of this embodiment is preferably 38 μm or less. If it is greater than 38 μm, the desired texture of the nonwoven fabric cannot be obtained, and defects such as inability to cool during the spinning process and fusion of the yarns may occur. To measure the fiber diameter, the nonwoven fabric was divided into five equal sections in the width direction, and 1 cm square test pieces were sampled from each section. Then, the fiber diameter was measured at 20 points for each section using a Keyence VHX-700F microscope, and the average value was calculated.

[0029] The fibers are deposited on a transport conveyor and transported as a web. The web being transported may be a single layer or a multilayer web consisting of two or more layers, and is not particularly limited. In the case of a multilayer web, the structures of the layers may be the same, but in order to achieve the water permeability and flexibility suitable for a nonwoven fabric for sanitary materials, different basis weights, fiber diameters, fiber structures, number of crimps, types of additives, and additive contents for each layer can be adjusted, and layers with different characteristics can be combined. For example, a nonwoven fabric laminate may be constructed so that the first layer of the nonwoven fabric for the permeable top sheet is more hydrophobic than the second layer, thereby creating a gradient in water permeability between the layers. Another example is laminating webs with different fiber diameters or crimp numbers to achieve both smoothness and breathability when used as an exterior sheet, and to diffuse body fluids so that the absorbent can be used efficiently as a top sheet, as well as to improve rewetability and water retention.

[0030] In order to obtain the desired bulkiness and cushioning properties for sanitary material applications, the method for bonding the bulky long-fiber nonwoven fabric of this embodiment is preferably a method in which the fiber surfaces are melted by heating to bond the fibers together, rather than bonding by thermal embossing using a pair of rolls. Various heating methods can be used, including hot air circulation, hot air penetration, infrared heater, blowing hot air onto both sides of the nonwoven fabric, and introducing the nonwoven fabric into heated gas, and are not particularly limited.

[0031] To achieve the desired performance, the bulky long-fiber nonwoven fabric of this embodiment may be coated with a water-permeable agent or softening agent by post-processing. From the viewpoints of safety for the human body and process stability, known agents such as higher alcohols, higher fatty acids, nonionic surfactants with ethylene oxide added thereto, alkyl phosphate salts, and alkyl sulfate salts may be used alone or in combination, and are not particularly limited. Examples of water-permeable agents and softening agents include polyether compounds, polyethylene ether-modified silicones, polyether-modified silicones, polyester compounds, polyamide compounds, and polyglycerin compounds.

[0032] The agent can be applied by conventional methods such as coating with a kiss coater or gravure coater, or spraying. Furthermore, pretreatment such as corona discharge treatment or atmospheric pressure plasma discharge treatment may be applied to the nonwoven fabric before coating, as needed. When using a spraying method, one or both sides can be selected as the surface to which the agent is sprayed, depending on the required performance. When spraying the agent on only one side, a difference in performance can be achieved between the front and back sides. For example, when a water-permeable agent is sprayed on one side, a difference in water permeability can be achieved between the front and back sides of the nonwoven fabric, resulting in a nonwoven fabric that combines hydrophilicity and rewetability. On the other hand, when spraying on both sides, a nonwoven fabric with no difference in performance between the front and back sides can be obtained.

[0033] The bulky long-fiber nonwoven fabric of this embodiment may be subjected to post-processing such as aperture treatment and shaping. Examples of aperture treatment methods include, but are not limited to, rotary knife perforation, hot pin perforation, hydroentanglement, and needle punching. Examples of shaping methods include, but are not limited to, processing with a pair of rolls and hot air blowing.

[0034] The preferred range of the basis weight of the bulky long-fiber nonwoven fabric of this embodiment varies depending on the part where it is used, so it is selected appropriately depending on the application. The material constituting the top sheet is preferably thicker from the viewpoint of water permeability, and a thickness of 50 g / m is preferred. 2 The following materials can be used. The outer sheet material is thin, 8g / m², from the viewpoint of productivity and thinning of the diaper. 2The weight per unit area was determined by randomly selecting five 20cm x 20cm test pieces, measuring their mass, and converting the average value into the weight per unit area.

[0035] The breaking strength of the bulky long-fiber nonwoven fabric of this embodiment is set to 1 g / m from the viewpoint of process suitability for producing sanitary materials. 2 The breaking strength is preferably 0.5 N / 5 cm or more. The breaking strength was measured in accordance with JIS L-1906, by cutting five samples of 5 cm in the CD direction and 20 cm in the MD direction so that they were uniform in the CD direction, and measuring them with a tensile tester at a grip distance of 10 cm and a pulling speed of 30 cm / min. The five samples in each MD direction were measured, and the breaking strength was calculated by averaging the measured values.

[0036] Furthermore, the CD tear strength of the bulky long-fiber nonwoven fabric of this embodiment is preferably 1.0 N or more from the viewpoint of process suitability during diaper manufacturing. The tear strength was measured using an Elmendorf tester. Alternatively, other evaluation methods such as the single tongue method may be used to measure the CD tear strength.

[0037] Since the bulky long-fiber nonwoven fabric of this embodiment is used as a sanitary material and comes into direct contact with the skin or clothing, the fluffing grade may be lower than grade 3 (no fluffing occurs). The fuzziness was evaluated using a Groz-Beckert Martindale abrasion and pilling tester. A 155 mm diameter polyurethane foam (model number HEA786-255, purchased from Groz-Beckert Japan) was first placed on the measurement table, and then the sample to be measured was placed on top and set. A nonwoven fabric identical to the sample was set between polyurethane foam (38 mm diameter: same model number as above) and the friction element. The side of the nonwoven fabric attached to the friction element was set to be the same as the side of the nonwoven fabric to be measured. The sample was subjected to abrasion treatment under a load of 9 kPa for 160 cycles of friction. The fluffing condition of the sample after abrasion treatment was observed from a 45-degree angle to the sample and graded visually according to the following criteria: Measurements were made on both sides of the sample with N=5 for each, the average was calculated, and the grade of the side with the lowest fluffing grade (the side with the least amount of fluffing) was adopted. Grade 1: No change Grade 2: Rough surface Grade 3: Less than 5 pillings Grade 4: There are 5 or more pilling spots on the entire surface. Grade 5: There are holes or tears. The abrasion can also be measured using a Japan Society for the Promotion of Science durability testing machine.

[0038] Other embodiments of the present invention are sanitary materials containing the above-mentioned bulky long-fiber nonwoven fabric, and absorbent articles in which the top sheet and / or outer sheet comprise the above-mentioned bulky long-fiber nonwoven fabric. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications can be made within the scope of the gist of the invention. [Industrial Applicability]

[0039] The bulky long-fiber nonwoven fabric of the present invention has a bulkiness that provides cushioning softness while being easy to handle, and therefore can be suitably used in the production of sanitary materials. The bulky long-fiber nonwoven fabric of the present invention can be suitably used as sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads, and can be used as a surface top sheet, second sheet, SAP sheet, or other sanitary material component that requires hydrophilicity, as well as an outer back sheet.

[0040] Furthermore, the uses of the bulky long-fiber nonwoven fabric of the present invention are not particularly limited, and it can also be used, for example, for masks, body warmers, tape bases, waterproof sheet bases, patch bases, first aid bandage bases, packaging materials, wipe products, medical gowns, bandages, clothing, skin care sheets, etc.

Claims

1. A bulky long fiber nonwoven fabric made of two or more thermoplastic resins, in which the quotient of the KES friction coefficient and the variation of the KES friction coefficient is 1 g / m ２ A bulky long fiber nonwoven fabric having a bulk density of 0.5 or more per unit area.

2. 2. The bulky long-fiber nonwoven fabric according to claim 1, wherein the KES friction coefficient is 0.3 or less.

3. A sanitary material comprising the bulky long-fiber nonwoven fabric according to claim 1 or 2.

4. An absorbent article, the top sheet and / or outer sheet of which comprises the bulky long-fiber nonwoven fabric according to claim 1 or 2.