JP7420649B2 - laminate nonwoven fabric - Google Patents

Description

The present invention relates to a laminate nonwoven fabric that can provide stretchable sheets that can be used for medical products, sanitary products, and the like.

In recent years, it has been used as a component for medical and sanitary products such as around the waist of diapers and around the base of the legs, supporters, bandages, medicinal patches, plaster bases, and facial masks due to its excellent conformability. A sex sheet is used. As a specific example of such a stretchable sheet, for example, Japanese Patent Laid-Open No. 2002-1855 (Patent Document 1) discloses a sheet in which short fiber nonwoven webs are laminated and integrated with an intertwined web of thermoplastic elastomer interposed therebetween. A highly stretchable nonwoven fabric composite (laminate nonwoven fabric) is disclosed. It is also disclosed that a stretchable sheet including the laminate nonwoven fabric has high elongation at break and high stretch recovery in both the vertical and horizontal directions.
In addition, Patent Document 1 discloses that short fiber materials are opened and accumulated by means such as carding, random webbing, and air opening, and if necessary, a hydroentangling method, a thermal fusion method, a needle punching method, etc. It is disclosed that a short fiber nonwoven web can be prepared by entangling the fibers by the following means.

JP 2002-1855 A (Claims, 0014, 0028, etc.)

As a result of continued studies by the applicant, we have found that when the stretchable sheet comprising the laminate nonwoven fabric disclosed in Patent Document 1 is used by being attached along a three-dimensional shape, such as by wrapping it around the body, the stretchable sheet It has been found that the problem of unnecessarily stretching the material in the horizontal direction and causing cracks and breaks is likely to occur. It was considered that there is no direct proportional relationship between the ease with which this problem occurs and the physical properties of the stretchable sheet in the horizontal direction. Specifically, even with a stretchable sheet including a laminate nonwoven fabric with increased strength in the transverse direction, the above-mentioned problem still tends to occur.
Further, the applicant of the present application continued to study and found that the above-mentioned problem is likely to occur when the strength in the horizontal direction of the laminate nonwoven fabric is significantly inferior to the strength in the vertical direction.

In other words, the user tends to stretch the stretchable sheet in the horizontal direction, assuming that it will withstand the same stretching while keeping the sensation felt when stretching the stretchable sheet in the vertical direction. However, the laminate nonwoven fabric according to the prior art has significantly lower strength in the horizontal direction than in the vertical direction. Therefore, the stretchable sheet is stretched in the horizontal direction in the same way as in the vertical direction, causing cracks and breaks in the horizontal direction.

For these reasons, if the strength of a laminated nonwoven fabric in the vertical and horizontal directions is significantly different, even if the physical properties of the laminated nonwoven fabric in the vertical and horizontal directions are improved proportionally, it is difficult to use it. Contrary to the user's assumption, the problem remains that the user unnecessarily stretches the elastic sheet in the horizontal direction, causing cracks and breaks.

Therefore, there has been a need to realize a laminate nonwoven fabric that can provide a stretchable sheet that is free from the problem of being prone to cracking or breaking in the horizontal direction, which is caused by something contrary to the user's expectations.

The present invention
"A laminate nonwoven fabric in which a first fiber layer containing crimped fibers and a second fiber layer containing crimped fibers are bonded and integrated with a thermoplastic elastomer," and/or the second fiber layer has at least bidirectional fiber orientation within the main surface direction.
It is.

As a result of continued studies by the applicant, ``a laminate in which a first fiber layer containing crimped fibers and a second fiber layer containing crimped fibers are bonded and integrated with a thermoplastic elastomer. It has been found that in a laminate nonwoven fabric, by adjusting the configuration of the first fiber layer and/or the second fiber layer, the correlation between various physical properties in the longitudinal direction and the lateral direction of the laminate nonwoven fabric can be adjusted.
The first fiber layer and/or the second fiber layer is a fiber layer having at least bidirectional fiber orientation within the main surface direction, such as a cross-lay web or a crisscross-lay web. As a result, a laminate nonwoven fabric is provided in which a large difference in strength in the vertical and horizontal directions is prevented.
Therefore, the laminate nonwoven fabric according to the present invention can provide a stretchable sheet that is free from the problem of being prone to cracking or breaking in the horizontal direction, which is caused by something contrary to the user's expectations.

In the present invention, various configurations can be selected as appropriate, for example, the following configurations. The various measurements described in the present invention were performed under normal pressure and 25° C. unless otherwise specified. Unless otherwise specified or specified, various measurement results described in the present invention were obtained by measurement to a value one digit smaller than the desired value, and the obtained value was calculated by rounding off the value. As a specific example, if the desired value is to the first decimal place, the value to the second decimal place is determined by measurement, and the value to the first decimal place is calculated by rounding the obtained value to the second decimal place. This value was used as the value to be determined. Further, each upper limit value and each lower limit value illustrated in the present invention can be arbitrarily combined.

The laminate nonwoven fabric of the present invention comprises a first fiber layer containing crimped fibers, a second fiber layer containing crimped fibers, and a thermoplastic elastomer bonding and integrating both fiber layers. It is equipped with Note that the fibrous layer in the present invention refers to a layer of a sheet-like fiber aggregate formed by randomly intertwining fibers such as a fiber web or nonwoven fabric.

In the laminate nonwoven fabric, the first fibrous layer and the second fibrous layer (hereinafter sometimes referred to as both fibrous layers) containing crimped fibers play the role of forming the main skeleton of the laminate nonwoven fabric. Also, since both fiber layers contain crimped fibers, they play a role in imparting flexibility, conformability, stretchability, and stretch recovery to the laminate nonwoven fabric.

Both fiber layers contain crimped fibers as constituent fibers. The crimped fibers mentioned here include, for example, crimped fibers or composite fibers formed by crimping of latent crimped fibers (e.g., core-sheath type, sea-island type, side-by-side type, orange type, etc.) composite fibers. ), and since both fiber layers contain crimped fibers, they are rich in flexibility, followability, stretchability, and stretch recovery.

In addition to crimped fibers, both fiber layers can also contain single fibers and bonded fibers (fully melted bonded fibers and partially melted bonded fibers such as core-sheath type, sea-island type, side-by-side type, orange type, and bimetal type). It may contain other fibers such as fibers). Fibers other than these crimped fibers can be made of the same resin as the crimped fibers, as will be described later, and can have the same fiber length and fineness as the crimped fibers.

The mass ratio of the crimped fibers to the mass of the fibers constituting both fiber layers is adjusted as appropriate, but in order to provide a laminated nonwoven fabric with more flexibility, followability, elasticity, and stretch recovery, It is preferably at least 40% by mass, preferably at least 50% by mass, preferably at least 60% by mass, preferably at least 70% by mass, and 80% by mass or more. It is preferably at least 90% by mass, more preferably at least 90% by mass, and more preferably the constituent fibers of both fiber layers are only crimped fibers.

The polymer constituting the constituent fibers (including crimped fibers) of both fiber layers can be selected as appropriate. halogen-substituted polyolefin resins, etc.), styrene resins, polyvinyl alcohol resins, polyether resins (e.g. polyetheretherketone, polyacetal, modified polyphenylene ether, aromatic polyetherketone, etc.), polyester resins (e.g., polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin (e.g. , aromatic polyamide resins, aromatic polyetheramide resins, nylon resins, etc.), resins with nitrile groups (e.g. polyacrylonitrile, etc.), urethane resins, epoxy resins, polysulfone resins (e.g. polysulfone, polyether sulfone, etc.), fluorine-based resins (e.g., polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose-based resins, polybenzimidazole resins, acrylic resins (e.g., polyacrylonitrile copolymerized with acrylic esters or methacrylic esters, etc.) Known polymers can be used, such as modacrylic resins, modacrylic resins made by copolymerizing acrylonitrile and vinyl chloride or vinylidene chloride, etc. In addition, these polymers may be made of either a linear polymer or a branched polymer, and the polymer may be a block copolymer or a random copolymer. can be anything. Furthermore, a mixture of multi-component resins may be used.

In particular, it is preferable that the constituent fibers of both fiber layers do not contain an elastomer so that the medicinal ingredients contained in the non-aqueous paste are difficult to absorb when used as a medicinal patch base material. From this point of view, it is preferable that the constituent fibers of both fiber layers are fibers composed only of polyolefin resin or polyester resin, and latent crimped fibers composed only of polyolefin resin or polyester resin. It is more preferable that the fiber be a crimped fiber.

The constituent fibers may be composed of one type of resin or multiple types of resin. The fibers composed of a plurality of types of resins may be in a form generally referred to as a composite fiber, such as a core-sheath type, an island-in-the-sea type, a side-by-side type, an orange type, or a bimetallic type.

In addition to the above-mentioned resins, the constituent fibers also contain additives such as flame retardants, fragrances, pigments, dyes, antibacterial agents, anti-mold materials, photocatalyst particles, emulsifiers, dispersants, surfactants, and thickeners. May contain. By containing the pigment, it is possible to use spun-dyed fibers, such as fibers with a color that resembles skin color (for example, light orange). Additionally, the fibers or fiber layers may be dyed using a dye.

Furthermore, the constituent fibers may include irregular cross-section fibers in addition to substantially circular fibers and elliptical fibers. In addition, the irregular cross-section fibers include hollow shapes, polygonal shapes such as triangular shapes, alphabetic character shapes such as Y-shapes, symbol-type shapes such as irregular shapes, multilobed shapes, and asterisk shapes, or multiple shapes of these shapes. The fibers may have a fiber cross section such as a bonded shape.

The fineness of the constituent fibers of both fiber layers can be selected as appropriate, and can be, for example, 0.01 to 100 dtex, and 0.01 to 100 dtex, so as to provide a laminate nonwoven fabric with excellent flexibility, followability, stretchability, and stretch recovery. It can be from 1 to 50 dtex, it can be from 0.5 to 30 dtex, it can be from 1 to 10 dtex.

In addition, the fiber length of the constituent fibers of both fiber layers can be selected as appropriate, including short fibers cut to a specific length, long fibers, and continuous fibers (such as fibers prepared using a direct spinning method that are not cut to a specific length). However, it is preferable that the fibers be cut to a specific length so as to provide a laminate nonwoven fabric with excellent flexibility, followability, stretchability, and stretch recovery. The fiber length can be 20 to 150 mm, can be 25 to 100 mm, can be 30 to 90 mm, and can be 40 to 80 mm, especially when the web is created using a dry method. be able to. Further, especially when the web is created using a wet method, the thickness can be 1 to 30 mm, 3 to 20 mm, and 5 to 15 mm. In addition, "fiber length" refers to the fiber length measured according to JIS L1015 (2010), 8.4.1c direct method (C method).

The constituent fibers of both fiber layers include one or more resin components selected from, for example, melt spinning, dry spinning, wet spinning, direct spinning (melt blowing, spunbond, electrostatic spinning, etc.), composite fibers, etc. It can be obtained by known methods such as a method of extracting fibers with a fine fiber diameter by removing them, and a method of obtaining split fibers by beating the fibers.

The fiber composition and/or various structures such as basis weight and thickness of the first fiber layer and the second fiber layer may be the same or different. However, the physical properties of the fibrous layer (e.g., the first fibrous layer) existing on one main surface side of the laminate nonwoven fabric and the fibrous layer (e.g., the second fibrous layer) existing on the other main surface side The closer these are, the more likely it is that a stretchable sheet can be provided that is less likely to curl when stretched and can easily follow three-dimensional shapes, such as when wrapped around the body. Therefore, it is preferable that the first fiber layer and the second fiber layer have the same fiber composition and/or structure such as basis weight and thickness. It is preferable that the nonwoven fabric is a laminate having a fiber layer of .

In the laminate nonwoven fabric according to the present invention, the first fiber layer and/or the second fiber layer have at least bidirectional fiber orientation within the main surface direction. Here, the direction of the main surface of the first fiber layer refers to the direction perpendicular to the thickness direction of the first fiber layer, and the direction of the main surface of the second fiber layer refers to the direction of the thickness of the first fiber layer. Refers to the direction perpendicular to the thickness direction. Note that the thickness direction refers to a direction perpendicular to the main surface. In addition, whether the first fiber layer and/or the second fiber layer included in the laminate nonwoven fabric has at least bidirectional fiber orientation within the main surface direction can be determined by the following method. You can judge by using it.

(Method of confirming whether or not the fibers have at least bidirectional fiber orientation in the main surface direction)
(1) A fiber layer constituting the measurement object is collected from the measurement object (for example, a laminate nonwoven fabric, etc.). Note that the fiber layer is sampled such that the main surface of the object to be measured and the main surface of the fiber layer to be sampled are parallel to each other. Then, it is confirmed that the collected fiber layer contains crimped fibers. Note that, in addition to visual observation, a microscope can be used for confirmation.
Note that if it is difficult to collect the fiber layer from the object to be measured, observe the fiber layer portion of the object to be measured and confirm that the fiber layer portion contains crimped fibers. Note that, in addition to visual observation, a microscope can be used for confirmation.
(2) A test piece (square, length: 100 mm, width: 100 mm) is taken from the collected fiber layer or the observed fiber layer portion. The test piece is taken so that the main surface of the sampled fiber layer or the observed fiber layer portion is parallel to the main surface of the test piece. At this time, if the direction of production of the object to be measured is known, the test piece is taken such that the direction of production of the object to be measured is parallel to the vertical direction of the test piece. In addition, if the production direction of the object to be measured is not known, test pieces taken from various directions of the sampled fiber layer or the observed fiber layer portion should be measured for the tensile strength (unit: N/50mm) described below. As a result of subjecting each test piece to the measurement method, the direction parallel to the direction showing the highest breaking strength is defined as the production direction of the object to be measured.
(3) The test piece is subjected to a constant speed extension type tensile tester (manufactured by Orientech Co., Ltd., Tensilon, distance between chucks (gripping interval): 50 mm, tensile speed: 100 mm/min), and the distance between the chucks is 75 mm. Pull the test piece in the vertical direction until the distance between the chucks reaches 50 mm, and then return the distance between the chucks to 50 mm at the same speed. Next, the test piece was subjected to a constant speed extension type tensile tester (manufactured by Orientec, Tensilon, distance between chucks (gripping interval): 50 mm, tensile speed: 100 mm/min) until the distance between the chucks became 75 mm. Pull the test piece in the horizontal direction, and then return the distance between the chucks to 50 mm at the same speed.
(4) As in item 3, stretch and contract the test piece alternately 10 times in the vertical and horizontal directions.
(5) The test piece that has been stretched through item 4 is stretched in the vertical and horizontal directions to a size of 150 mm x 150 mm, and fixed on a mount.
(6) Among the fibers constituting one main surface of the test piece fixed to the mount, when viewed from the one main surface side, the longitudinal direction of the fibers with respect to the vertical direction of the test piece Fifty fibers are randomly selected that exist in a state where the angle is greater than 0° and less than 90° clockwise. Note that the length direction of the fiber refers to the direction of the long side of the smallest rectangle that surrounds the fiber in a micrograph or electron microscope photograph of the target fiber.
(7) Calculate the standard deviation from the angle that the length direction of the selected 50 fibers forms with respect to the vertical direction of the test piece and the average value thereof. At this time, if the value of the standard deviation is within 20, the fiber layer constituting the measurement object has fiber orientation A having an angle greater than 0° and less than 90° clockwise with respect to the vertical direction of the test piece. Then judge.
(8) Among the fibers constituting one main surface of the test piece fixed to the mount, when viewed from the one main surface side, the longitudinal direction of the fibers with respect to the vertical direction of the test piece Fifty fibers are randomly selected that exist in a state where the angle is greater than 0° and less than 90° counterclockwise.
(9) Calculate the standard deviation from the angle that the length direction of the selected 50 fibers forms with respect to the horizontal direction of the test piece and the average value thereof. At this time, if the standard deviation value is within 20, the fiber layer constituting the measurement object has fiber orientation B having an angle greater than 0° and less than 90° counterclockwise with respect to the vertical direction of the test piece. Then judge.
From the above measurement results, if the fiber layer constituting the measurement object has both fiber orientation A and fiber orientation B, it is determined that the fiber layer has at least bidirectional fiber orientation within the main surface direction. do.

The fibrous layer according to the present invention having at least bidirectional fiber orientation in the main surface direction can be a fibrous layer derived from, for example, a crosslay web or a crisscrosslay web. Note that a crosslay web is a fiber web formed by folding a unidirectional fiber web such that the fiber orientation of the unidirectional fiber web is not parallel to the production direction, and the crosslay web is a fiber web formed by folding a unidirectional fiber web such that the fiber orientation of the unidirectional fiber web is not parallel to the production direction. This is a fiber web in which the directions in which the constituent fibers in each folded unidirectional fiber web portion are oriented are different from each other without being parallel to the production direction. Therefore, the fiber layer derived from the crosslay web has bidirectional fiber orientation within the main surface direction.

Moreover, a criss-cross lay web is a fibrous web formed by laminating a unidirectional fiber web whose fiber orientation is parallel to the production direction and a cross-lay web. Therefore, the fiber layer derived from the crisscross lay web not only has bidirectional fiber orientation within the main surface direction, but also has fiber orientation in the production direction.

A laminate in which the first fiber layer and/or the second fiber layer can be constructed using a cross-lay web or a criss-cross lay web, but the strength in the vertical direction and the horizontal direction are prevented from greatly differing. Since it is easy to realize a nonwoven fabric, the first fiber layer and/or the second fiber layer are preferably fiber layers derived from a crosslay web, and the first fiber layer and the second fiber layer are preferably derived from a crosslay web. Preferably, it is a fibrous layer of origin.

In addition, a fiber layer consisting only of a random web in which the constituent fibers are non-uniformly oriented, or a parallel web consisting only of fibers parallel to the production direction without stacking or folding unidirectional fiber webs, It does not have at least bidirectional fiber orientation within the main surface direction.

Note that the first fiber layer and/or the second fiber layer may contain a functional component. The types of functional ingredients can be selected as appropriate depending on the desired function and are not limited, but examples include antibacterial agents, bactericidal agents, antiviral agents, antifungal agents, catalysts (such as titanium oxide, manganese dioxide, or platinum (supported alumina, etc.), moisture conditioning agents (e.g., silica gel, silica microcapsules, etc.), deodorizing agents such as activated carbon and carbon black, pigments, fragrances, cation exchange resins, anion exchange resins, medicinal and beauty ingredients, etc. can be mentioned.

The functional component is contained in particulate form on the surface and/or inside of the constituent fibers of the first fiber layer and/or the second fiber layer, or on the surface of the first fiber layer and/or the second fiber layer. It can exist in the form of a film covering part or all of it. The method of supporting the functional component on the first fiber layer and/or the second fiber layer can be selected as appropriate, but for example, a solution or dispersion of the functional component, or a solution or dispersion of the functional component containing a binder can be selected as appropriate. The liquid is applied by spraying or by a known coating method (for example, using a gravure roll) onto one or both main surfaces of a fibrous web capable of forming a fibrous layer, a first fibrous layer, and/or a second fibrous layer. A method of removing a solvent or a dispersion medium after supporting using a kiss coating method, a die coating method, etc., or a method of removing a fibrous web, a first fibrous layer, and/or a second fibrous layer that can form a fibrous layer, A method can be adopted in which the solvent or dispersion medium is removed after being immersed in a solution or dispersion liquid and then pulled up.

Although the various structures and physical properties such as the basis weight and thickness of the first fiber layer and/or the second fiber layer can be adjusted as appropriate, the basis weight can be from 5 to 1000 g/m2, and from 10 to 1000 g/ ^m2. It can be 500 g/m ² , it can be 20-200 g/m ² , it can be 30-100 g/m ² . And the thickness can be 0.05-5 mm, 0.1-3 mm, 0.5-2 mm. In addition, the "fabric weight" as used in the present invention refers to the mass per 1 m ² of area on the main surface, and the main surface refers to the surface with the largest area. In addition, "thickness" as used in the present invention is a value measured by a high-precision digital length measuring machine (Lightmatic (registered trademark) manufactured by Mitutoyo Co., Ltd.), and specifically, it is a value measured with respect to the main surface of the object to be measured. It refers to the thickness value in the area when a load of 100 gf is applied to a load area of 5 cm ² .

In the laminate nonwoven fabric according to the present invention, the first fiber layer and the second fiber layer are bonded and integrated with a thermoplastic elastomer. The thermoplastic elastomer referred to in the present invention is an elastomer having thermoplasticity, and can be a polymer such as polyolefin, polystyrene, polyurethane, or polyester, or a copolymer having each repeating unit. It may be. In addition to the resins mentioned above, thermoplastic elastomers also contain additives such as flame retardants, fragrances, pigments, antibacterial agents, antifungal materials, photocatalyst particles, emulsifiers, dispersants, surfactants, and thickeners. You may do so.

The term "bonded and integrated" as used in the present invention refers to one main surface of the first fiber layer and one main surface of the second fiber layer being bonded together by a thermoplastic elastomer. The structure and physical properties of the thermoplastic elastomer included in the laminate nonwoven fabric can be adjusted as appropriate, such as the basis weight and thickness, but the basis weight can be 1 to 300 g/ ^m2 , and 3 to 200g/ ^m2 . It can be from 5 to 100 g/m ² , and from 10 to 60 g/m ² .

In addition, when the ratio of the mass of the thermoplastic elastomer to the total mass of the laminate nonwoven fabric is higher than 6.0% by mass and less than 27.7% by mass, a laminate nonwoven fabric with excellent handleability due to increased stiffness is provided. This is preferable because it is easy to do. The stiffness of the laminated nonwoven fabric can be evaluated by the average value of the bending resistance in the vertical and horizontal directions of the laminated nonwoven fabric, and the higher the average value of the laminated nonwoven fabric, the better the handling properties tend to be. be. In order to provide a laminated nonwoven fabric with excellent handling properties, the bending resistance of the laminated nonwoven fabric is preferably 25 mm or more, preferably 30 mm or more, preferably 35 mm or more, and preferably 40 mm or more. .

The mode of existence of the thermoplastic elastomer in the laminate nonwoven fabric can be selected as appropriate; It may exist in the form of a film, a web, or a non-continuous form such as an amorphous shape or a dot shape. However, by reducing the amount of thermoplastic elastomer used to bond and integrate the first fiber layer and the second fiber layer, and by having a porous structure, it has excellent flexibility, followability, stretchability, and stretch recovery. Preferably, the thermoplastic elastomer is present in the form of a web so that a laminate nonwoven fabric can be provided. Whether or not it is in the form of a web can be determined by peeling off the first fibrous layer portion or the second fibrous layer portion from the laminate nonwoven fabric and checking the state of the exposed thermoplastic elastomer. In addition, by preparing a laminate nonwoven fabric by interposing a hot melt web made of a thermoplastic elastomer between the fiber web constituting the first fiber layer and the fiber web constituting the second fiber layer, A laminate nonwoven fabric can be prepared in which a first fiber layer and a second fiber layer are bonded and integrated by a web-like thermoplastic elastomer.

The various configurations and physical properties such as the basis weight and thickness of the laminate nonwoven fabric can be adjusted as appropriate, but the basis weight can be 10 to 1000 g/m ² , 20 to 500 g/m ² , It can be from 30 to 300 g/ ^m2 , and it can be from 40 to 200 g/ ^m2 . And the thickness can be 0.1-5 mm, 0.3-3 mm, 0.5-2 mm.

The tensile strength of the laminate nonwoven fabric is preferably 20 N/50 mm or more, preferably 40 N/50 mm or more, and preferably 60 N/50 mm or more so that it is difficult to break when stretched in one direction. preferable. Note that the higher the "tensile strength", the less likely it is to break during stretching.

In order to obtain a laminate nonwoven fabric with excellent extensibility, the elongation of the laminate nonwoven fabric is preferably 20% or more, preferably 60% or more, and preferably 100% or more. On the other hand, if the elongation is too high, the usability of the laminate nonwoven fabric may be poor, so it is realistic to set it to 500% or less. Note that the higher the "elongation", the better the extensibility.

The strength at 50% elongation of the laminate nonwoven fabric is preferably 50 N/50 mm or less, more preferably 30 N/50 mm or less, so as to provide excellent application feeling when used as a medicinal patch base material. On the other hand, if the elongation strength is too low, the above-mentioned characteristics of the laminate nonwoven fabric may deteriorate, so it is realistic to set it to 0.1 N/50 mm or more. Furthermore, the strength at 100% elongation of the laminate nonwoven fabric is preferably 100 N/50 mm or less, more preferably 50 N/50 mm or less. On the other hand, if the elongation strength is too low, the above-mentioned characteristics of the laminate nonwoven fabric may deteriorate, so it is realistic to set it to 0.1 N/50 mm or more.

In order for the laminate nonwoven fabric to have excellent shrinkability after stretching, the recovery rate at 50% elongation of the laminate nonwoven fabric is preferably 20% or more, preferably 30% or more, and preferably 40% or more. is preferred.

The air permeability of the laminate nonwoven fabric is preferably 10 cm ³ /cm ² /sec or more, and 30 cm ³ /sec so as not to cause discomfort due to stuffiness even if it is attached to the skin or wrapped around it for a long time. It is preferably at least cm ² /sec, more preferably at least 50 cm ³ /cm ² /sec, and even more preferably at least 70 cm ³ /cm ² /sec. Note that this "air permeability" refers to a value measured by JIS L1913:2010 "General Nonwoven Fabric Testing Method" 6.8.1 (Fragile method).

In addition, the various physical properties of the laminate nonwoven fabric listed above are the same as those of the test piece taken from the object to be measured in (Method for confirming whether or not it has at least bidirectional fiber orientation in the main surface direction). It can be determined by subjecting another test piece taken to the following measurement method. In addition, various physical properties in the vertical direction are determined by measuring the test piece with the vertical direction as the length direction and the horizontal direction as the width direction, with the length direction and elongation direction being parallel. be able to. In addition, various physical properties in the horizontal direction are determined by measuring the test piece with the horizontal direction as the length direction and the vertical direction as the width direction, with the length direction and elongation direction being parallel. be able to.

(Method for measuring tensile strength (unit: N/50mm))
A test piece with a length of 250 mm and a width of 50 mm was subjected to a constant-speed extension type tensile tester (manufactured by Orientec, Tensilon, distance between chucks (gripping interval): 200 mm, tensile speed: 500 mm/min). , pull the test piece and measure the maximum load until the test piece breaks. This maximum load is measured for three test pieces, and the arithmetic average of these maximum loads is determined as "tensile strength". The higher the measured value, the better the strength.

(Method of measuring elongation (Sr, unit: %))
When measuring the tensile strength described above, the elongation of the test piece at maximum load (Smax, unit: mm) [= (length at maximum load, unit: mm) - (grabbing interval = 200 mm)] It is a percentage of the gripping interval (200mm). In other words, it is a value obtained from the following formula. This measurement is performed three times, and the arithmetic mean value of the percentages is defined as the "elongation".
Sr=(Smax/200)×100

(Measurement method of stretching strength (unit: N/50mm))
A test piece with a length of 250 mm and a width of 50 mm was subjected to a constant-speed extension type tensile tester (manufactured by Orientec, Tensilon, distance between chucks (gripping interval): 200 mm, tensile speed: 500 mm/min). , the maximum load measured before elongating the test piece by 100 mm (=50%), and the maximum load measured until elongating the test piece by 200 mm (=100%), respectively. This maximum load is measured for three test pieces, and the arithmetic average of these maximum loads is defined as "strength at 50% elongation" and "strength at 100% elongation."

(Method of measuring recovery rate (unit: %) at 50% elongation)
A test piece with a length of 250 mm and a width of 50 mm was subjected to a constant-speed extension type tensile tester (manufactured by Orientec, Tensilon, distance between chucks (gripping interval): 200 mm, tensile speed: 500 mm/min). , with this grasping interval of 200 mm as the starting point, and after pulling at a speed of 500 mm/min to a position 100 mm from the starting point, that is, 50% extension position (L50 = 100 mm), return to the starting point at the same speed. The length (Lf) obtained by subtracting the length of the initial grip interval (200 mm) from the length of the grip interval when the tensile stress of the test piece becomes 0.3N during this tension, and the tensile stress of the test piece when returning. Measure the length (Lb) obtained by subtracting the length of the initial gripping interval (200 mm) from the length of the gripping interval when the gripping interval becomes 0.3N.
By performing this measurement on three test pieces and taking the arithmetic average of the respective lengths, the average value (Lf1) of the length of the gripping interval (Lf) and the average value (Lb1) of the length of the gripping interval (Lb) are calculated. ), and the value calculated from the following formula is taken as the recovery rate at 50% elongation.
Recovery rate at 50% elongation (%) = [[(L50-Lf1)-(Lb1-Lf1)]/(L50-Lf1)] x 100

(Measurement method of bending resistance)
The bending resistance (unit: mm) is determined by subjecting a test piece of length: 150 mm and width: 20 mm to the cantilever method specified in JIS L1096.

The laminate nonwoven fabric according to the present invention may be composed only of the first fiber layer, the second fiber layer, and a thermoplastic elastomer, but may also be composed of a fabric, a film (nonporous film or porous film), a foam (nonporous film, or porous film), or a foam (nonporous film or porous film). It may also have a structure in which other members such as a porous foam or a porous foam are further laminated. The method of laminating other members can be selected as appropriate, but even if it is simply laminated, or it is laminated and integrated by bonding with a binder such as a powder binder, spray binder, or hot melt web, It may also be an embodiment in which constituent components such as adhesive fibers are bonded and laminated by melting to form an integral structure. Incidentally, the materials of the other members, and various configurations such as basis weight and thickness can be adjusted or selected as appropriate depending on the aspect required of the laminate nonwoven fabric.

The method for producing a laminate nonwoven fabric of the present invention will be explained by giving an example. Although the method for preparing the laminate nonwoven fabric of the present invention can be selected as appropriate, for example, it can be prepared through the following steps.
(1) Step of preparing two crosslay webs containing latent crimped fibers.
(2) a step of subjecting each crosslay web to a fiber entanglement process;
(3) a step in which each crosslay web subjected to the fiber entanglement step is subjected to heat treatment to cause crimping of the latent crimped fibers;
(4) preparing a laminate by interposing a web-like thermoplastic elastomer between them and laminating the crosslay webs after being subjected to heat treatment;
(5) a step of bonding and integrating the crosslay webs by subjecting the laminate to heat treatment to soften the web-shaped thermoplastic elastomer;
can be adopted.

In the above step (1), a crosslay web is used as an example of a fiber web that can constitute a fiber layer having at least bidirectional fiber orientation within the main surface direction. For example, it can be prepared as follows. A unidirectional fiber web is prepared by subjecting a fiber group containing latent crimped fibers to a carding machine, an airlay machine, or the like. The prepared unidirectional fibrous web is then folded over by applying it to a cross wrapper or the like, thereby preparing a fibrous web having a portion where the unidirectional fibrous webs are laminated. At this time, the directions in which the constituent fibers in each laminated unidirectional fiber web portion are oriented are different from each other without being parallel to the production direction, and have at least bidirectional fiber orientation within the main surface direction. Adjust as follows.

In the above-mentioned step (2), the method of entangling the constituent fibers of the crosslay web can be selected as appropriate, and a method of subjecting the fibers to needle punch treatment, a method of subjecting them to hydroentanglement treatment, etc. can be adopted as the fiber entanglement step. In particular, since it is easy to provide a laminate nonwoven fabric with excellent strength and less fuzz on the surface, it is preferable to entangle the constituent fibers of the crosslay web by subjecting it to hydroentanglement treatment.

In the above-mentioned step (3), the method of heat treatment can be selected as appropriate, but for example, heating with a roll or heating and pressurizing, applying to a heating machine such as an oven dryer, far infrared heater, dry heat dryer, hot air dryer, etc. A method of heating, a method of heating the contained organic resin by irradiating infrared rays under no pressure, etc. can be used.
In addition, the heating temperature is the temperature at which crimping of the latent crimped fibers that make up the crosslay web occurs, but no unintended denaturation occurs in the constituent components of the crosslay web (constituent fibers, binders, functional components, etc.). It is preferable to adjust the temperature. In this step, the constituent fibers of the crosslay web may be bonded and integrated by melting the binder and/or by allowing the adhesive fibers to exhibit a fiber bonding function.
Note that the crosslay web that has been subjected to the heat treatment can be left to cool or be directly used in the next process without being cooled; You can.

In step (4) described above, a laminate nonwoven fabric can be prepared by interposing a web-like thermoplastic elastomer between the cross-lay webs after being subjected to heat treatment. A molten thermoplastic elastomer may be applied to the main surface in the form of a web. Furthermore, when preparing a laminate by laminating crosslay webs, the laminate may be prepared by applying pressure in the thickness direction by, for example, using a roll device.

In step (5) described above, the method of heat treatment can be appropriately selected as described above. In addition, the heating temperature is a temperature at which the thermoplastic elastomer is softened and the crosslay webs can be bonded and integrated, but the constituent components of the crosslay web (constituent fibers, binders, functional components, etc.) are not unintentionally modified. It is preferable to adjust the temperature. In this step, the constituent fibers of the crosslay web may be bonded and integrated by melting the binder and/or by allowing the adhesive fibers to exhibit a fiber bonding function. When bonding and integrating the crosslay webs, pressure may be applied in the thickness direction by, for example, applying the crosslay webs to a roll device.
Then, after being subjected to heat treatment, a laminate nonwoven fabric can be prepared by allowing it to cool or cooling it.

The laminate nonwoven fabric of the present invention may further include other members such as porous bodies, films, and foams. Furthermore, the laminate nonwoven fabric of the present invention may be subjected to a pressure treatment process such as Reliant press treatment to smooth the surface. In addition, we also carry out various secondary processing processes, such as heat-forming after punching a shape according to the purpose and usage, a process to support functional ingredients, and a hydrophilic treatment process to improve affinity with drugs. You can also serve it.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these are not intended to limit the scope of the present invention.

(Preparation of fiber web)
Latently crimped fiber A of polyester resin configured in a side-by-side type (fiber cross-sectional shape: circular, fineness: 2.2 dtex, fiber length: 51 mm, does not melt under heating conditions of 160°C, and can be rolled at 120°C or higher. A random web in which latent crimped fibers were non-uniformly oriented was prepared by subjecting only the material (at which shrinkage had begun) to a random card machine. The random web thus prepared was submitted to a hydroentanglement device to entangle the constituent fibers, and then submitted to an oven (heating temperature: 160°C) to develop crimping of the latent crimped fibers. . In this way, a hydroentangled random web A (fabric weight: 50 g/m ² ) was prepared. In addition, in the hydroentangled random web A, the constituent fibers were non-uniformly oriented and did not have bidirectional fiber orientation within the main surface direction.
Only the latent crimped fibers A were subjected to a carding machine to prepare a unidirectional fiber web. The unidirectional fiber web thus prepared was subjected to a crosslapper device to prepare a crosslay web in which the latent crimped fibers had bidirectional fiber orientation within the main surface direction. The crosslay web thus prepared is subjected to a hydroentanglement device to entangle the constituent fibers, and then submitted to an oven (heating temperature: 160°C) to develop crimps in the latent crimped fibers. Ta. In this way, a hydroentangled crosslay web B1 (fabric weight: 50 g/m ² ) was prepared. Note that the hydroentangled crosslay web B1 had bidirectional fiber orientation within the main surface direction.
In addition, a hydroentangled crosslay web B2 (fabric weight: 85 g/m ² ) was prepared in the same manner as the hydroentangled crosslay web B1, except that the amount of latent crimped fibers A to be fed to the carding machine was increased. did. Note that the hydroentangled crosslay web B2 had bidirectional fiber orientation within the main surface direction.

(Comparative example 1)
After applying a styrene resin, which is a thermoplastic elastomer, in the form of a web onto one main surface of the hydroentangled random web A (basis weight: 10 g/m ² ) using a hot melt spray, the styrene resin is applied between the two. Another prepared hydroentangled random web A was laminated through the web.
Thereafter, the styrene resin was crimped using nip rolls while still retaining its thermoplastic properties, and was left to cool to prepare a laminate nonwoven fabric.

(Example 1)
A laminate nonwoven fabric was prepared in the same manner as in Comparative Example 1, except that the hydroentangled crosslay web B1 was used instead of the hydroentangled random web A.

(Comparative example 2)
A laminate nonwoven fabric was prepared in the same manner as in Comparative Example 1, except that the coating amount of the thermoplastic elastomer was changed to 20 g/m ² .

(Example 2)
A laminate nonwoven fabric was prepared in the same manner as in Comparative Example 2, except that the hydroentangled crosslay web B1 was used instead of the hydroentangled random web A.

(Comparative example 3)
A laminate nonwoven fabric was prepared in the same manner as in Comparative Example 1, except that the coating amount of the thermoplastic elastomer was changed to 40 g/m ² .

(Example 3)
A laminate nonwoven fabric was prepared in the same manner as in Comparative Example 3, except that the hydroentangled crosslay web B1 was used instead of the hydroentangled random web A.

The various physical properties of each of the prepared laminate nonwoven fabrics were evaluated and summarized in Tables 1 and 2. The thickness of each of the prepared laminate nonwoven fabrics was 0.9 mm.

In all of the laminate nonwoven fabrics prepared in the comparative examples, the tensile strength in the vertical direction was 3.4 times or more stronger than the tensile strength in the horizontal direction. Therefore, the laminate nonwoven fabrics prepared in the comparative examples all had significantly different physical properties (especially tensile strength) in the vertical direction and the horizontal direction.
In contrast, all of the laminate nonwoven fabrics prepared in Examples had a tensile strength in the longitudinal direction that was less than twice (1.5 times or less) the tensile strength in the transverse direction.
Therefore, in all of the laminate nonwoven fabrics prepared in Examples, the physical properties (especially tensile strength) in the vertical direction and the horizontal direction were prevented from being significantly different.

(Examples 4 to 7)
A laminate nonwoven fabric was prepared in the same manner as in Example 1, except that the hydroentangled crosslay web B2 was used instead of the hydroentangled crosslay web B1.
In addition, in Example 4, the coating amount of the thermoplastic elastomer was adjusted to 10 g/ ^m2 , in Example 5, the coating amount of the thermoplastic elastomer was adjusted to 20 g/ ^m2 , and in Example 6, the coating amount of the thermoplastic elastomer was adjusted to 20 g/m2. was adjusted to 40 g/m ² , and in Example 7, the coating amount of the thermoplastic elastomer was adjusted to 60 g/m ² .

The various physical properties of each of the prepared laminate nonwoven fabrics were evaluated and summarized in Tables 3 and 4. The thickness of the prepared laminate nonwoven fabric of Example 4 was 1.5 mm, the thickness of the laminate nonwoven fabric of Example 5 was 1.7 mm, and the thickness of the prepared laminate nonwoven fabric of Example 6 was 1.5 mm. The thickness of the laminate nonwoven fabric of Example 7 prepared was 1.4 mm.

The laminate nonwoven fabrics prepared in Examples 4 to 7 also had a tensile strength in the vertical direction that was less than twice the tensile strength in the horizontal direction, and had high physical properties (especially tensile strength) in the vertical and horizontal directions. The difference was prevented.

From the above, the laminate nonwoven fabric according to the present invention can provide a stretchable sheet that is free from the problem of being prone to cracking or breaking in the horizontal direction, which is caused by something contrary to the user's expectations. there were.

By using the laminate nonwoven fabric of the present invention, stretchable sheets can be used, for example, around the waist of diapers, around the base of the legs, as supports, bandages, medicinal patch base materials, plaster base materials, facial masks, and other medical and sanitary products. can be provided.

Claims (1)

A laminate nonwoven fabric in which a first fiber layer containing crimped fibers and a second fiber layer containing crimped fibers are bonded and integrated with a thermoplastic elastomer,
The first fiber layer and/or the second fiber layer have at least bidirectional fiber orientation within the main surface direction.
Laminated non-woven fabric.