Laminate nonwoven fabric

Abstract

To provide a laminated nonwoven fabric forming a constituent member of a medical article or a sanitary article excellent in quality by preventing the occurrence of conspicuous color irregularity.SOLUTION: It has been found that in a laminate nonwoven fabric in which a first fiber layer containing fibers containing a colorant and a second fiber layer having a fiber composition different from that of the first fiber layer are laminated, whether or not the laminate nonwoven fabric has noticeable color unevenness depends on the basis weight of the first fiber layer constituting the laminate nonwoven fabric. It was also found that when the basis weight of the first fiber layer is greater than 16g / m2, the occurrence of color unevenness can be prevented and a layered nonwoven fabric with excellent quality can be provided. Furthermore, it was found that when the first fiber layer has at least bidirectional fiber orientation, or when the first fiber layer does not have a specific fiber orientation, it is possible to effectively prevent the occurrence of color unevenness and to provide a layered nonwoven fabric having more excellent quality.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated nonwoven fabric that can be used for medical supplies, sanitary products, and the like. [Background technology]

[0002] In recent years, nonwoven fabrics have been used as components of medical and sanitary products, such as supports, bandages, patches (poultices and plasters containing functional ingredients), sanitary masks, dust masks, cooling sheets, and sheet packs for moisturizing and whitening. In particular, from the perspective of pursuing high added value in appearance, it is desirable for nonwoven fabrics to have color. For example, by using a nonwoven fabric that appears beige, it is possible to provide medical and sanitary products that are inconspicuous when applied or worn.

[0003] As a nonwoven fabric that meets these demands, Japanese Patent Laid-Open No. 2004-141613 (Patent Document 1) discloses a substrate such as a nonwoven fabric used as a medical hygiene material, which is prepared using fibers kneaded with iron oxide that can be colored to a color close to skin color. Patent Document 1 also discloses that other sheet-like materials can be laminated onto the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-141613 (claims, 0006, 0018, 0031, examples, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] The applicant of the present application prepared a laminated nonwoven fabric according to the prior art as disclosed in Patent Document 1, specifically, a laminated nonwoven fabric comprising a first fiber layer containing dye-containing fibers and a second fiber layer having a fiber composition different from that of the first fiber layer. However, the prepared laminated nonwoven fabric sometimes has noticeable color unevenness on the first fiber layer side, and it has not been possible to provide a laminated nonwoven fabric with excellent quality. [Means for solving the problem]

[0006] The first invention is "A first fiber layer containing a fiber containing a pigment and a second fiber layer having a fiber composition different from that of the first fiber layer are laminated together. Constituting a component of medical or hygiene products A laminated nonwoven fabric, the constituent fibers of the first fiber layer and the second fiber layer are short fibers cut to a specific length, the blending ratio of the colorant-containing fiber contained in the second fiber layer is lower than that of the first fiber layer; The first fiber layer has a basis weight of 16 g / m 2 more than Ku, The weight of the second fiber layer is 75 g / m 2 Below is the Constituting a component of medical or hygiene products Laminated nonwoven fabric." and The second invention is "The first fiber layer has at least bidirectional fiber orientation or no specific fiber orientation. The method according to claim 1 Constituting a component of medical or hygiene products Laminated nonwoven fabric." is. [Effects of the Invention]

[0007] As a result of investigations, the applicant of the present application found that whether or not a laminated nonwoven fabric has noticeable color unevenness depends on the basis weight of the first fiber layer constituting the laminated nonwoven fabric. 2 It has been found that when the amount is greater than this, the occurrence of color unevenness can be prevented and a laminated nonwoven fabric with excellent quality can be provided.

[0008] Furthermore, it has been found that when the first fiber layer has at least a bidirectional fiber orientation, or when the first fiber layer does not have a specific fiber orientation, the occurrence of color unevenness can be effectively prevented, and a laminated nonwoven fabric with higher quality can be provided.

[0009] The reason for this is that if the first fiber layer has fiber orientation in only one specific direction, the dye-containing fibers (hereinafter sometimes referred to as dyed fibers) that make up the first fiber layer will be aligned in that one direction, which is thought to still be a cause of color unevenness. On the other hand, when the first fiber layer has at least a bidirectional fiber orientation, as in the laminate nonwoven fabric of the present invention, or when the first fiber layer does not have a specific fiber orientation, the dyed fibers constituting the first fiber layer are not aligned mainly in one direction, and it is thought that the occurrence of color unevenness can be effectively prevented.

[0010] From the above, the present invention provides a high-quality Constituting a component of medical or hygiene products A laminated nonwoven fabric can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present invention, various configurations can be appropriately selected, such as the following configurations. Note that, unless otherwise specified, the various measurements described in the present invention were performed under normal pressure and a temperature condition of 25°C. Furthermore, unless otherwise specified, the various measurement results described in the present invention were measured to a value one decimal place smaller than the desired value, and the value was calculated by rounding the value. Specifically, when the desired value is measured to one decimal place, the value was measured to two decimal places, and the obtained value was rounded to one decimal place to calculate the value to one decimal place, and this value was used as the desired value. Furthermore, the upper and lower limits exemplified in the present invention can be combined in any combination.

[0012] The laminated nonwoven fabric of the present invention comprises a first fiber layer containing dyed fibers and a second fiber layer having a fiber composition different from that of the first fiber layer. The fiber layer in the present invention refers to a layer of a sheet-like fiber assembly such as a fiber web or nonwoven fabric.

[0013] The first fiber layer contains dyed fibers as constituent fibers, for example, dyed fibers of a color that resembles the color of skin (e.g., beige), which makes the laminated nonwoven fabric less noticeable when applied to the human body, thereby adding high added value to the appearance of the laminated nonwoven fabric.

[0014] Furthermore, the second fiber layer is visible when the laminate nonwoven fabric is viewed from the first fiber layer side, and therefore can adjust the color shade and hue of the laminate nonwoven fabric and provide the laminate nonwoven fabric with high added value in terms of appearance, for example, in the case of a laminate nonwoven fabric formed by laminating a first fiber layer containing beige dope-dyed fibers and a white second fiber layer, the laminate nonwoven fabric appears to be light beige. Therefore, in the present invention, the color shade and hue of the laminate nonwoven fabric can be adjusted by the presence of the second fiber layer, without the need to prepare multiple types of dope-dyed fibers with different color shades and hue.

[0015] The polymer forming the fibers of the first fiber layer and the second fiber layer (hereinafter, sometimes collectively referred to as both fiber layers) can be appropriately selected, and examples thereof include polyolefin resins (e.g., polyethylene, polypropylene, polymethylpentene, polyolefin resins having a structure in which a portion of hydrocarbons is substituted with a nitrile group or a halogen such as fluorine or chlorine, etc.), styrene resins, polyvinyl alcohol resins, polyether resins (e.g., polyether ether ketone, polyacetal, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resins (e.g., polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, fully aromatic polyether ketone, etc.), and the like. Known polymers can be used, such as aromatic polyester resins, polyimide resins, polyamideimide resins, polyamide resins (e.g., aromatic polyamide resins, aromatic polyetheramide resins, nylon resins, etc.), resins containing nitrile groups (e.g., polyacrylonitrile), urethane resins, epoxy resins, polysulfone resins (e.g., polysulfone, polyethersulfone, etc.), fluorine-containing resins (e.g., polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resins, polybenzimidazole resins, and acrylic resins (e.g., polyacrylonitrile resins copolymerized with acrylic acid esters or methacrylic acid esters, modacrylic resins copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride). These polymers may be linear or branched polymers, block copolymers or random copolymers, and may have any three-dimensional structure or crystallinity. Furthermore, a mixture of multiple resin components may also be used.

[0016] In particular, when used as a patch substrate, the constituent fibers of both fiber layers preferably do not contain elastomer so that the medicinal ingredients contained in the non-aqueous paste are less likely to be absorbed. From this perspective, the constituent fibers of both fiber layers are preferably fibers composed only of polyolefin resin or polyester resin.

[0017] The constituent fibers may be composed of one type of resin or multiple types of resins. Fibers composed of multiple types of resins may be generally called composite fibers, such as core-sheath type, sea-island type, side-by-side type, orange type, bimetal type, etc.

[0018] The first fiber layer and / or the second fiber layer may contain a functional component. The type of functional component can be appropriately selected depending on the desired function and is not limited to, but examples include antibacterial agents, disinfectants, antiviral agents, antifungal agents, catalysts (e.g., titanium oxide, manganese dioxide, or platinum-supported alumina), humidity conditioners (e.g., silica gel or silica microcapsules), deodorizers such as activated carbon or carbon black, pigments, fragrances, cation exchange resins, anion exchange resins, medicinal ingredients, and cosmetic ingredients.

[0019] The functional component may be present in the form of particles on the surface and / or inside of the constituent fibers of the first fiber layer and / or the second fiber layer, or in the form of a coating that covers part or all of the surface of the first fiber layer and / or the second fiber layer.

[0020] The method for supporting the functional component can be selected appropriately. For example, a method in which a solution or dispersion of the functional component, or a solution or dispersion of the functional component containing a binder, is supported on one or both main surfaces of a fiber web that can constitute each fiber layer, or the first fiber layer and / or the second fiber layer, by spraying or using a known coating method (e.g., kiss coating using a gravure roll, die coating), and then removing the solvent or dispersion medium; or a method in which a fiber web that can constitute each fiber layer, or the first fiber layer and / or the second fiber layer, is immersed in the above-mentioned solution or dispersion and then pulled out, and then the solvent or dispersion medium is removed, can be used.

[0021] The first fiber layer and / or the second fiber layer preferably contain crimped fibers, which can provide a laminated nonwoven fabric with excellent flexibility, conformability, stretchability, and stretch recovery. The crimped fibers referred to here include, for example, fibers with crimp or composite fibers in which the crimp of latent crimped fibers is expressed (e.g., core-sheath, sea-island, side-by-side, orange, and other composite fibers).

[0022] The mass percentage of crimped fibers in the mass of the constituent fibers of the first fiber layer and / or the second fiber layer can be adjusted as appropriate, but in order to provide a laminated nonwoven fabric with better softness, conformability, stretchability, and stretch recovery, it is preferably 30 mass% or more, more preferably 40 mass% or more, more preferably 50 mass% or more, more preferably 60 mass% or more, more preferably 70 mass% or more, more preferably 80 mass% or more, and more preferably 90 mass% or more, and it is more preferable that the constituent fibers of the first fiber layer and / or the second fiber layer are all crimped fibers.

[0023] The constituent fibers may include irregular cross-section fibers in addition to substantially circular and elliptical fibers. The irregular cross-section fibers may have a cross section of a hollow shape, a polygonal shape such as a triangle, an alphabetic shape such as a Y-shape, an irregular shape, a multi-lobed shape, a symbolic shape such as an asterisk, or a shape combining multiple of these shapes.

[0024] The fineness of the constituent fibers of both fiber layers can also be appropriately selected, and can be, for example, 0.01 to 100 dtex, 0.1 to 50 dtex, 0.3 to 30 dtex, or 0.5 to 10 dtex so as to provide a laminated nonwoven fabric excellent in softness, conformability, stretchability, and stretch recovery.

[0025] The fiber length of the constituent fibers of both fiber layers can be selected appropriately and can be short fibers, long fibers, or continuous fibers (e.g., fibers not cut to a specific length but prepared using a direct spinning method) cut to a specific length. However, fibers cut to a specific length are preferred to provide a laminated nonwoven fabric with excellent flexibility, conformability, stretchability, and stretch recovery. When preparing a fiber web using a dry method, the fiber length can be 20 to 150 mm, 25 to 100 mm, 30 to 90 mm, or 40 to 80 mm. When preparing a fiber web using a wet method, the fiber length can be 1 to 30 mm, 3 to 20 mm, or 5 to 15 mm. The term "fiber length" refers to the fiber length measured according to JIS L1015 (2010), 8.4.1c, direct method (method C).

[0026] The first fiber layer according to the present invention contains fibers containing a pigment (dyed fibers). Examples of such fibers include fibers prepared using a resin kneaded with a pigment and dyed fibers. The type of pigment can be appropriately selected and can be beige, red, black, blue, green, yellow, or the like.

[0027] The percentage of the mass of the dyed fibers in the mass of the constituent fibers of the first fiber layer can be appropriately selected depending on the application of the laminated nonwoven fabric and the form of the second fiber layer to be laminated, but the higher this percentage, the easier it is to impart the intended high added value in appearance to the laminated nonwoven fabric. Therefore, this percentage is preferably 10% by mass or more, more preferably 30% by mass or more, more preferably 50% by mass or more, more preferably 50% by mass or more, more preferably 70% by mass or more, and most preferably 90% by mass or more, and it is most preferable that the constituent fibers of the first fiber layer are dyed fibers only.

[0028] When the laminated nonwoven fabric is used as a patch substrate, it is preferable to select fibers that comply with the Pharmaceutical and Medical Products Division Notification No. 341, "Handling of Approval Applications for Changes to the Support or Liner of Over-the-Counter Drug Patches." In particular, a low ash content (mass%), i.e., impurities contained in 5 g of the nonwoven fabric constituting the laminated nonwoven fabric, of 1.5 mass% or less, can provide a laminated nonwoven fabric more suitable for use as a patch substrate. For example, even if the first fiber layer uses spun-dyed fibers with a high ash content, the second fiber layer can be made of fibers with a low ash content, thereby providing a laminated nonwoven fabric more suitable for use as a patch substrate.

[0029] The second fiber layer according to the present invention has a fiber composition different from that of the first fiber layer. Here, "different fiber composition" means that the fiber compositions of the first fiber layer and the second fiber layer are not the same.

[0030] As a concrete example, The second fiber layer does not contain the dyed fibers contained in the first fiber layer; The first fiber layer and the second fiber layer both contain the same dyed fibers, but the percentage of the dyed fibers in the total fiber mass of each fiber layer is different. The type and composition of the fibers other than the base-dyed fibers constituting the first fiber layer are different from the type and composition of the fibers other than the base-dyed fibers constituting the second fiber layer; Examples include:

[0031] In particular, in the case of a laminated nonwoven fabric in which a first fiber layer (e.g., a beige first fiber layer) whose constituent fibers are only dyed fibers is laminated with a second fiber layer (e.g., a white second fiber layer) that does not contain the dyed fibers, when the laminated nonwoven fabric is viewed from the first fiber layer side, the second fiber layer can be seen through, making it possible to adjust the color shade (in the example described above, the laminated nonwoven fabric appears to have a light beige color when viewed from the first fiber layer side) and color tone of the laminated nonwoven fabric, and therefore it is easy to give the laminated nonwoven fabric the intended high added value in appearance.

[0032] In order to adjust the color intensity of the laminated nonwoven fabric, the laminated nonwoven fabric may have a first fiber layer made of a blend of dyed fibers and non-dyed fibers. However, since it is not easy to mix dyed fibers and non-dyed fibers uniformly, there is a risk of noticeable color unevenness in the first fiber layer, which tends to make it difficult to provide a high-quality laminated nonwoven fabric.

[0033] The constituent fibers of both fiber layers can be obtained by known methods, such as melt spinning, dry spinning, wet spinning, direct spinning (melt-blowing, spunbonding, electrostatic spinning, etc.), a method of extracting fibers with a small fiber diameter by removing one or more resin components from composite fibers, or a method of beating fibers to obtain split fibers.

[0034] The fiber web and nonwoven fabric constituting both fiber layers can be prepared by, for example, a dry method in which the above-mentioned fibers are fed into a carding device or an air-laying device to entangle the fibers; a wet method in which the fibers are dispersed in a solvent and then laid into a sheet to entangle the fibers; or a method in which fibers are spun and collected using a direct spinning method (such as a melt-blowing method, a spunbonding method, an electrospinning method, or a method in which a spinning solution and a gas stream are discharged in parallel to each other to perform spinning (e.g., the method disclosed in JP-A-2009-287138), etc.).

[0035] The constituent fibers of the prepared fiber web can be entangled and / or integrated to prepare a nonwoven fabric. Examples of methods for entangling and / or integrating the constituent fibers include entanglement using needles or a water jet, and heat treatment of the fiber web to bond or fuse the constituent fibers together using a binder or adhesive fiber.

[0036] The heat treatment method can be appropriately selected, and examples thereof include a method of heating or heating and pressurizing with a roll, a method of heating by subjecting to a heater such as an oven dryer, a far-infrared heater, a dry heat dryer, or a hot air dryer, and a method of irradiating infrared rays without pressure to heat the resin contained therein.

[0037] The first fiber layer according to the present invention has a basis weight of 16 g / m 2 By increasing the amount of the first fiber layer, it is possible to prevent the occurrence of color unevenness and provide a laminated nonwoven fabric with excellent quality. In order to further prevent the occurrence of color unevenness and provide a laminated nonwoven fabric with excellent quality, the basis weight of the first fiber layer is set to 20 g / m 2 It is preferable that the thickness is 25 g / m or more. 2 It is preferable that the density is 25 g / m or more, and more preferably 25 g / m to realize a laminated nonwoven fabric with excellent quality. 2 It is more preferable that the basis weight of the first fiber layer is 100 g / m. On the other hand, if the basis weight of the first fiber layer is too high, the conditions for entangling the fibers, such as hydroentanglement or needle punching, must be made stronger in order to entangle the constituent fibers of the first fiber layer. As a result, the constituent fibers of the first fiber layer may be unevenly dispersed, which may cause unintended color unevenness in the first fiber layer, making it impossible to provide a high-quality laminated nonwoven fabric. Therefore, the basis weight of the first fiber layer is set to 100 g / m. 2 Preferably less than 95 g / m 2 Preferably, it is 75 g / m or less. 2 Preferably, it is:

[0038] The basis weight of the second fiber layer can be adjusted as needed, but it is generally 10 to 100 g / m 2 and 20 to 75 g / m 2and can be 30 to 50 g / m 2 It can be.

[0039] In this invention, "basis weight" refers to the area of ​​the main surface per square meter. 2 The term "main surface" refers to the mass per unit area, and the term "main surface" refers to the surface with the largest area.

[0040] In the case of a laminated nonwoven fabric in which each fiber layer constituting the laminated nonwoven fabric can be easily separated from the laminated nonwoven fabric, or in the case of a laminated nonwoven fabric in which each fiber layer is simply superimposed, the fiber layer containing the highest cotton blend ratio (the ratio of the number of component fibers to be measured to the total number of observed component fibers) among the separated fiber layers is designated as the first fiber layer, and the fiber layer laminated with the first fiber layer but having a different fiber composition from the first fiber layer is designated as the second fiber layer. The basis weight of each fiber layer can then be determined to determine the basis weight of the first fiber layer and the second fiber layer constituting the laminated nonwoven fabric. The type and cotton blend ratio of the component fibers can be confirmed using well-known analytical techniques, such as an electric microscope, an optical microscope, an analytical method using a fiber dye such as Kayastain Q, visual inspection, FT-IR, elemental analysis, and NMR.

[0041] On the other hand, in the case of a laminated nonwoven fabric in which the individual fiber layers cannot be easily separated as described above, the individual fiber layers constituting the laminated nonwoven fabric and their basis weights can be determined by the following method. 1. In the laminated nonwoven fabric, on main surface A on the side containing dyed fibers at the highest cotton blend ratio among the constituent fibers, confirm the type of constituent fibers and the cotton blend ratio of those constituent fibers, and determine the cotton blend ratio (ratio of the number of constituent fibers A to the number of constituent fibers) of the constituent fiber with the highest cotton blend ratio (constituent fiber A). 2. A section having both main surfaces parallel to the main surface A is taken from the main surface A side of the laminated nonwoven fabric. 3. After the slice is taken, the cotton blend ratio of the constituent fiber A on the main surface on the main surface A side of the laminated nonwoven fabric is confirmed. 4. Repeat steps 2 and 3, and continue to collect slices until the blended cotton ratio of constituent fiber A on the main surface on the main surface A side of the laminated nonwoven fabric after the slices have been collected is half of the blended cotton ratio of constituent fiber A confirmed in step 1. 5. The sections taken in steps 1 to 4 are combined to form a first fiber layer, and the weights of the sections taken in steps 1 to 4 are added together to form the weight of the first fiber layer. 6. After taking the slices, check the type of constituent fibers and the blend ratio of those constituent fibers on the main surface A and the opposite main surface B of the laminated nonwoven fabric, and determine the blend ratio of the constituent fiber with the highest blend ratio (constituent fiber B) (the ratio of the number of constituent fiber B to the number of constituent fibers). 7. A section having both main surfaces parallel to the main surface B is taken from the main surface B side of the laminated nonwoven fabric. 8. After the section has been taken, the cotton blend ratio of constituent fiber B on the main surface on the main surface B side of the laminated nonwoven fabric is confirmed. 9. Repeat steps 7 and 8, and continue to collect sections until the blend ratio of constituent fiber B on the main surface on the main surface B side of the laminated nonwoven fabric after the sections have been collected is half of the blend ratio of constituent fiber B confirmed in step 6. 10. The sections taken in steps 6 to 9 are combined to form a separate fiber layer, and the weights of the sections taken in steps 6 to 9 are added together to form the weight of the separate fiber layer. 11. Repeat steps 6 to 10 until the laminated nonwoven fabric is used up, and another fiber layer that was laminated with the first fiber layer and has a fiber composition different from that of the first fiber layer is used as a second fiber layer, and the basis weight of the second fiber layer is used as the basis weight of the second fiber layer.

[0042] In addition, if the basis weight of the fiber web or nonwoven fabric used to form the first fiber layer or second fiber layer of the laminated nonwoven fabric (for example, the basis weight of a fiber web containing dyed fibers used to form the first fiber layer) is known, that basis weight can be considered to be the basis weight of each fiber layer.

[0043] The thickness of the first fiber layer and the second fiber layer can be selected as appropriate. The thickness can be 0.1 to 3 mm, 0.2 to 2 mm, or 0.3 to 1.5 mm. The thickness can be determined from a cross-sectional photograph of the laminated nonwoven fabric in the thickness direction, as described below, or by measuring with a high-precision digital length measuring instrument (Litematic (registered trademark) manufactured by Mitutoyo Corporation) (specifically, a distance of 5 cm from the main surface of the object to be measured). 2 The thickness can be determined by applying a load of 100 gf to a load area of ​​the sample and measuring the thickness in that area.

[0044] The first fiber layer according to the present invention preferably has at least a bidirectional fiber orientation, or has no specific fiber orientation. By satisfying this constitution, the dyed fibers constituting the first fiber layer are not aligned mainly in one direction within the first fiber layer, and the occurrence of color unevenness can be effectively prevented.

[0045] Whether the first fiber layer has at least a bidirectional fiber orientation or has no specific fiber orientation can be determined by the following confirmation method. (How to check fiber orientation) (1) A test piece (square, length: 100 mm, width: 100 mm) is taken from the main surface of a measurement object (e.g., a laminated nonwoven fabric). The test piece is taken so that the main surface of the measurement object and both main surfaces of the taken test piece are parallel to each other. As a specific example, the fiber orientation of the first fiber layer constituting the main surface of the laminated nonwoven fabric can be confirmed from a test piece taken from the first fiber layer. (2) The collected test piece is stretched in both the vertical and horizontal directions until it measures 150 mm x 150 mm and is fixed to a mount. (3) From the fibers constituting one main surface of the test piece fixed to the mount, 50 fibers are randomly selected such that, when viewed from the side of the main surface, the length direction of the fibers forms an angle greater than 0° and less than 90° clockwise with respect to the longitudinal direction of the test piece. The length direction of the fibers refers to the direction of the long side of the smallest rectangle that encloses the fiber in a photomicrograph or electron photomicrograph of the target fiber. (4) Calculate the standard deviation from the angles formed by the length direction of the selected 50 fibers with respect to the longitudinal direction of the test piece and the average value of these angles. If the standard deviation is within 20, the fiber layer constituting the object to be measured is determined to have fiber orientation A, which is an angle greater than 0° and less than 90° clockwise with respect to the longitudinal direction of the test piece. (5) From the fibers constituting one of the main surfaces of the test piece fixed to the mount, 50 fibers are randomly selected such that, when viewed from the side of the main surface, the length direction of the fibers forms an angle of more than 0° and less than 90° counterclockwise with respect to the vertical direction of the test piece. (6) Calculate the standard deviation from the angles formed by the length direction of the selected 50 fibers with respect to the longitudinal direction of the test piece and the average value of these angles. If the standard deviation is within 20, the fiber layer constituting the object to be measured is determined to have fiber orientation B, which has an angle greater than 0° and less than 90° counterclockwise with respect to the longitudinal direction of the test piece.

[0046] When the fiber layer constituting the object to be measured has both fiber orientation A and fiber orientation B, the fiber layer from which the test specimen was taken is determined to have at least a bidirectional fiber orientation. Furthermore, if each of the measured standard deviations is greater than 20, it is determined that the fiber layer from which the test specimen was taken does not have a specific fiber orientation. On the other hand, if the fiber layer constituting the object to be measured has only fiber orientation A or fiber orientation B, the fiber layer from which the test specimen was taken is determined to have fiber orientation in only one direction.

[0047] The fiber layer having at least bidirectional fiber orientation can be, for example, a fiber layer derived from a cross-lay web or a criss-cross-lay web, or a fiber layer derived from a nonwoven fabric prepared using such a fiber web. Note that a cross-lay web is a fiber web formed by folding a unidirectional fiber web so that the fiber orientation of the unidirectional fiber web is not parallel to the production direction, and the folded portions of the unidirectional fiber web have bidirectional fiber orientation.

[0048] A crisscross lay web is a fiber web formed by laminating a unidirectional fiber web, in which the fiber orientation is parallel to the production direction, and a crosslay web. Therefore, the fiber layer derived from the crisscross lay web has fiber orientation in the production direction in addition to bidirectional fiber orientation.

[0049] The first fiber layer can be constructed using a crosslay web or a crisscrosslay web, but it is preferable that the first fiber layer be a fiber layer derived from a crosslay web, as this makes it easier to realize a laminated nonwoven fabric in which the strength in the warp and weft directions is prevented from differing greatly. Also, the fiber layer having no particular fiber orientation can be, for example, a fiber layer derived from a random web.

[0050] For example, if a unidirectional fiber web is used as a fiber layer without being laminated or folded, the fiber layer will have fibers oriented in only one direction and will not satisfy the requirements of the present invention. Therefore, in a laminated nonwoven fabric including a first fiber layer formed by using a unidirectional fiber web as a fiber layer, it is difficult to effectively prevent color unevenness, making it difficult to provide a laminated nonwoven fabric with higher quality.

[0051] The second fiber layer may be a fiber layer having at least bidirectional fiber orientation, a fiber layer having no particular fiber orientation, or a fiber layer obtained by using a unidirectional fiber web in its original state without laminating or folding it. However, if the constituent fibers of the second fiber layer are uniformly dispersed, the appearance of the second fiber layer seen through the laminated nonwoven fabric when viewed from the first fiber layer side will be uniform, which makes it easy to impart the intended high added value in appearance to the laminated nonwoven fabric. Therefore, it is preferable that the second fiber layer also has at least bidirectional fiber orientation or no particular fiber orientation.

[0052] The lamination method for the first fiber layer and the second fiber layer can be appropriately selected, for example, a method of laminating the first fiber layer and the second fiber layer and then subjecting them to an entanglement treatment such as hydroentanglement or needle punching to entangle them, a method of bonding them together using a binder or a hot melt web, a method of bonding the layers together using adhesive fibers when the constituent fibers contain adhesive fibers, or a method of partially melting and integrating them using heat sealing or ultrasonic sealing.

[0053] The composition and properties of the laminated nonwoven fabric, such as its basis weight and thickness, can be adjusted as needed. 2 More than 200g / m 2 can be less than 36 g / m 2 More than 175g / m 2 can be less than 46 g / m 2 More than 150g / m 2 The thickness can be 0.2 to 6 mm, 0.4 to 4 mm, or 0.6 to 3 mm.

[0054] The laminated nonwoven fabric can be used in various industries as it is, but it may also be subjected to various secondary processes, such as a process of processing by punching a shape according to the application or mode of use, or a process of adjusting various physical properties such as thickness and surface smoothness by reliant press treatment, before being subjected to the thermoforming process.

[0055] The method for producing the laminated nonwoven fabric of the present invention can be appropriately selected, but for example, it can be prepared through the following steps. (1) A step of preparing a crosslay web A composed only of potentially crimped fibers, which are dope-dyed fibers; (2) A step of preparing a crosslay web B composed only of latent crimped fibers that are not doped fibers; (3) A step of laminating the crosslay web A and the crosslay web B and subjecting them to an entanglement treatment to prepare a laminated web in which the two fiber webs are laminated and integrated; (4) A step of subjecting the laminated web to a heat treatment to develop the crimp of each latent crimp fiber; can be adopted.

[0056] In the above-described steps (1) and (2), a crosslay web is used as an example of a fiber web capable of forming a fiber layer having at least bidirectional fiber orientation. A crosslay web can be prepared, for example, as follows: A group of fibers containing latent crimped fibers is fed to a carding machine or an air-laying machine to prepare a unidirectional fiber web. The prepared unidirectional fiber web is then fed to a crosswrapper or the like to fold the unidirectional fiber web and form a laminated portion of the unidirectional fiber web.

[0057] In the above-mentioned step (3), the method for entangling the constituent fibers can be appropriately selected, and the fiber entanglement step can be a needle punching process, a hydroentanglement process, etc. In particular, it is preferable to entangle the constituent fibers of both fiber webs by hydroentanglement, since this facilitates the production of a laminated nonwoven fabric that is excellent in strength and has little fuzz on the surface.

[0058] In the above-mentioned step (4), the heat treatment method can be appropriately selected. For example, a method of heating or heating and pressurizing with a roll, a method of heating by subjecting to a heater such as an oven dryer, a far-infrared heater, a dry heat dryer, or a hot air dryer, or a method of irradiating infrared rays without pressure to heat the organic resin contained therein can be used.

[0059] The heating temperature is preferably adjusted to a temperature at which the crimp of each latent crimp fiber is expressed, but not to a temperature at which unintended denaturation of the constituent components of both fiber webs (constituent fibers, binder, functional components, etc.) occurs. In this step, the constituent fibers of both fiber webs may be bonded together by melting the binder and / or by using the adhesive fibers to exert their fiber bonding function. Furthermore, if a hydroentanglement treatment is performed in step (3), the heat treatment may also be used to remove moisture remaining in the laminated web.

[0060] After the heat treatment, the laminate web is allowed to cool or is cooled to prepare a laminate nonwoven fabric.

[0061] The laminated nonwoven fabric of the present invention may further comprise other components such as a porous body, a film, or a foam. The laminated nonwoven fabric of the present invention may then be subjected to a pressure treatment, such as a reliant press treatment, to smooth the surface. It may also be subjected to various secondary processing steps, such as a heat molding step after punching out a shape according to the intended use or mode of use, a step of loading a functional component, or a hydrophilization step to improve affinity with a drug. [Example]

[0062] The present invention will be specifically described below with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0063] (Preparation of fiber web constituting first fiber layer) A unidirectional fiber web was prepared by feeding only side-by-side polyester resin latent crimp fiber A (beige dope-dyed fiber containing a beige pigment, fiber cross-sectional shape: circular, fineness: 2.2 dtex, fiber length: 51 mm). The unidirectional fiber webs prepared in this manner were stacked with different fiber orientations to prepare a crosslay web in which the latent crimped fibers had a bidirectional fiber orientation. Five types of crosslay webs A1 to A5, differing only in basis weight, were prepared by varying the amount of latent crimped fiber A fed to the carding machine. Furthermore, only the latent crimped fiber A was fed into a carding machine to prepare a unidirectional fiber web A.

[0064] (Preparation of fiber web constituting second fiber layer) A unidirectional fiber web was prepared by feeding only side-by-side polyester resin latent crimped fiber B (white fiber, not doped fiber, fiber cross section: circular, fineness: 2.2 dtex, fiber length: 51 mm) into a carding machine. The unidirectional fiber webs prepared in this manner were overlapped with different fiber orientations to prepare a crosslay web in which the latent crimped fibers had a bidirectional fiber orientation. Two types of crosslay webs, B1 and B2, differing only in basis weight, were prepared by varying the amount of latent crimped fiber B fed into the carding machine. Furthermore, only the latent crimped fiber B was fed into a carding machine to prepare a unidirectional fiber web B.

[0065] (Comparative Example 1) Crosslay web A1 and crosslay web B1 were stacked to form a laminated web, and the laminated web was subjected to a hydroentanglement treatment to entangle the two crosslay webs. The remaining water was then removed without expressing the crimp of the constituent fibers, which are potentially crimpable fibers, to prepare a laminated nonwoven fabric in which a first fiber layer derived from crosslay web A1 and a second fiber layer derived from crosslay web B1 were laminated. In the laminated nonwoven fabric prepared in this manner, both the first fiber layer containing the dyed fibers and the second fiber layer had bidirectional fiber orientation.

[0066] (Examples 1 to 3) A laminated nonwoven fabric was prepared in the same manner as in Comparative Example 1, except that the crosslay webs A2 to A4 having larger basis weight were used instead of the crosslay web A1. In each of the laminated nonwoven fabrics prepared in this manner, the first fiber layer and the second fiber layer containing the dyed fibers both had bidirectional fiber orientation.

[0067] When each of the laminated nonwoven fabrics prepared as described above was observed with the naked eye from the first fiber layer side, the color was a light beige.

[0068] The physical properties of each of the prepared laminated nonwoven fabrics were evaluated and are summarized in Table 1. The "quality" in the table was evaluated as follows. (Quality evaluation method) The laminated nonwoven fabric was observed with the naked eye from the side of the fiber layer derived from the fiber web containing the spun-dyed fibers. As a result of the observation, laminated nonwoven fabrics that were found to have noticeable color unevenness and were felt to be of poor quality were rated as "X". On the other hand, laminated nonwoven fabrics that were found to have slight color unevenness but were not noticeable and were felt to be of excellent quality were rated as "O". Furthermore, laminated nonwoven fabrics that were found to have less color unevenness than laminated nonwoven fabrics rated as "O" and were felt to have better quality were rated as "◎".

[0069] [Table 1]

[0070] The laminated nonwoven fabrics of Examples 1 to 3 were all superior in quality, with less color unevenness than the laminated nonwoven fabric of Comparative Example 1. The reason for this is that the basis weight of the first fiber layer containing the dyed fibers was 16 g / m 2 This was thought to be because there were more of them. Furthermore, the laminated nonwoven fabrics of Examples 2 and 3 were superior in quality to the laminated nonwoven fabric of Example 1, with less color unevenness being generated. This is because the basis weight of the first fiber layer was 25 g / m 2 This was thought to be because there were more of them.

[0071] Example 4 Crosslay web A5 and crosslay web B2 were stacked to form a laminated web, and the laminated web was subjected to a hydroentanglement process to entangle the two crosslay webs. The remaining water was then removed without developing crimps in the constituent fibers, and the web was then placed in an oven to develop crimps in the constituent fibers, producing a laminated nonwoven fabric consisting of a first fiber layer derived from crosslay web A5 and a second fiber layer derived from crosslay web B2. In the laminated nonwoven fabric prepared in this manner, both the first fiber layer containing the dyed fibers and the second fiber layer had bidirectional fiber orientation.

[0072] Example 5 A laminated nonwoven fabric was prepared in the same manner as in Example 4, except that the unidirectional fiber web B was used instead of the crosslay web B2. In the laminated nonwoven fabric prepared in this manner, the first fiber layer containing the dyed fibers had a bidirectional fiber orientation, and the second fiber layer had only a unidirectional fiber orientation.

[0073] Example 6 A laminated nonwoven fabric was prepared in the same manner as in Example 4, except that the unidirectional fiber web A was used instead of the crosslay web A5. In the laminated nonwoven fabric prepared in this manner, the first fiber layer containing the dyed fibers had only a unidirectional fiber orientation, and the second fiber layer had a bidirectional fiber orientation.

[0074] Example 7 A laminated nonwoven fabric was prepared in the same manner as in Example 4, except that unidirectional fiber web A was used instead of crosslay web A5 and unidirectional fiber web B was used instead of crosslay web B2. In the laminated nonwoven fabric prepared in this manner, both the first fiber layer containing the dyed fibers and the second fiber layer had fiber orientation in only one direction.

[0075] When each of the laminated nonwoven fabrics prepared as described above was observed with the naked eye from the first fiber layer side, the color was a light beige.

[0076] [Table 2]

[0077] The laminate nonwoven fabrics of Examples 4 and 5 had even less color unevenness and were of higher quality than the laminate nonwoven fabrics of Examples 6 and 7. This was thought to be due to the bidirectional fiber orientation of the first fiber layer.

[0078] The laminate nonwoven fabric of Example 4 had slightly less color unevenness and was of higher quality than the laminate nonwoven fabric of Example 5. This was thought to be because the second fiber layer also had a bidirectional fiber orientation.

[0079] From the above, it has been found that the present invention can provide a laminated nonwoven fabric with excellent quality.

[0080] Each of the prepared laminated nonwoven fabrics was cut in the thickness direction, and the cut surfaces were photographed using a stereomicroscope. In each of the cross-sectional photographs, the constituent fibers of the first fiber layer and the constituent fibers of the second fiber layer were entangled, but the boundary between the first fiber layer and the second fiber layer could be visually determined.

[0081] Then, the following measurements were made on each of the obtained cross-sectional photographs. (1) A boundary line was drawn on the boundary between the first and second fiber layers in the cross-sectional photograph. (2) A line segment was drawn on the cross-sectional photograph connecting both main surfaces of the laminated nonwoven fabric over the shortest distance, and the length of the line segment was recorded as the thickness (unit: mm) of the laminated nonwoven fabric measured using the cross-sectional photograph of the laminated nonwoven fabric. (3) The length between the end of the line segment on the first fiber layer side and the boundary line was taken as the thickness (unit: mm) of the first fiber layer measured using a cross-sectional photograph of the laminated nonwoven fabric, and the length between the end of the line segment on the second fiber layer side and the boundary line was taken as the thickness (unit: mm) of the second fiber layer measured using a cross-sectional photograph of the laminated nonwoven fabric.

[0082] The measurement results are summarized in Table 3.

[0083] [Table 3] [Industrial Applicability]

[0084] The laminated nonwoven fabric of the present invention can provide a laminated nonwoven fabric that can be used as a component of medical and sanitary products, such as supports, bandages, patches (poultices and plasters containing functional ingredients), sanitary masks, dust masks, cooling sheets, and sheet-like packs for moisturizing or whitening.

Claims

1. A laminated nonwoven fabric constituting a medical or sanitary product, comprising a first fiber layer containing dye-containing fibers and a second fiber layer having a fiber composition different from that of the first fiber layer, the constituent fibers of the first fiber layer and the second fiber layer are fibers cut to a specific length, the blending ratio of the colorant-containing fiber contained in the second fiber layer is lower than that of the first fiber layer; The basis weight of the first fiber layer is 16 g / m ２ More than The second fiber layer has a basis weight of 75 g / m 2 or less. A laminated nonwoven fabric that is a component of medical or sanitary products.

2. The first fiber layer has at least bidirectional fiber orientation or no specific fiber orientation.

2. A laminated nonwoven fabric constituting a component of a medical or sanitary product according to claim 1.

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