KR20230024256A - Spunbond nonwovens and sanitary materials - Google Patents

Abstract

To provide a spunbonded nonwoven fabric that is suitably used for sanitary materials as a spunbonded nonwoven fabric that has sufficient absorbency and quick-drying properties to maintain comfort when worn and has a soft touch. It has a fused portion and an unfused portion, and the ratio (Da/Db) of the average single fiber diameter (Da) of fibers on one surface (A) to the average single fiber diameter (Db) of fibers on the other surface (B) is 1.1 A spunbonded nonwoven fabric having the above, wherein both the surface (A) and the surface (B) have contact angles with water of 30° or less, and the surface (A) has a fiber torsion degree of 1.1 or more.

Description

Spunbond nonwovens and sanitary materials

The present invention relates to a spunbond nonwoven fabric that achieves both excellent absorbency and quick-drying properties and a soft touch, and is particularly suitable for use in sanitary materials, and sanitary materials using the same.

[0002] In recent years, various studies have been conducted to further improve wearing comfort for nonwoven fabrics used for sanitary materials such as disposable diapers, sanitary napkins, and masks. In particular, for surface members that directly come into contact with the skin, both the water absorption property of quickly absorbing moisture and the quick-drying property that transfers the absorbed moisture from the outermost layer to leave the surface in a dry state without excessive moisture, that is, "quick-drying water absorption" It is required. At the same time, a soft feel to the skin is also required.

As a means for imparting water absorption to the nonwoven fabric, using a nonwoven fabric containing hydrophilic fibers or applying a hydrophilic treatment to the nonwoven fabric is effective, but since these techniques do not have the function of transferring absorbed moisture from the outermost layer, The quick-drying wasn't enough.

Against this background, as a spunbond nonwoven fabric having a laminated structure of fibrous layers containing long fibers for the purpose of imparting absorbent and quick-drying properties to nonwoven fabrics, the distance between the hydrophobic layer containing hydrophobic fibers or the flatness of the fibers is within a specific range. A spunbonded nonwoven fabric composed of a hydrophilic layer containing fibers and disposing the hydrophobic layer on the surface of the nonwoven fabric has been proposed (see Patent Document 1).

In addition, as a technology for laminating nonwoven fabrics separately, between the first and third nonwoven fabric component layers containing fibers having an average single fiber diameter in a specific range, and the first and third nonwoven fabric layers, a more average single fiber diameter is obtained. An absorbent article comprising a spunbond nonwoven fabric on which a second nonwoven fabric component layer comprising fine fibers is disposed has been proposed (see Patent Document 2).

International Publication No. 2018/167881 Japanese Patent Publication No. 2013-518698

In the technique of Patent Literature 1, a hydrophilic gradient is formed in the thickness direction of the nonwoven fabric, so that even a surface having a hydrophobic layer disposed on the outermost layer exhibits constant water absorption performance. However, since the outermost surface is a hydrophobic layer, the performance is not sufficient for absorbing a large amount of moisture such as urine, and liquid residue is easily generated, so the quick-drying property is also insufficient. Also, the softness of the surface in contact with the skin was not sufficient.

On the other hand, the technology of Patent Literature 2 relates to a spunbond nonwoven fabric having a structure in which nonwoven fabric layers composed of fibers having different average single fiber diameters are laminated. However, since this nonwoven fabric is used for a barrier cuff, it has a structure that prevents backflow of fluid, that is, does not pass moisture, and liquid residue is easily generated on the surface of the nonwoven fabric. . Also, the softness of the surface in contact with the skin was not sufficient.

Therefore, an object of the present invention has been made in view of the above circumstances, and has sufficient absorbency and quick-drying to maintain comfort when worn, and a spunbond nonwoven fabric having a soft touch, which is suitably used for sanitary materials It is to provide a spunbond nonwoven fabric.

As a result of the present inventors' examination, it is effective to increase the hydrophilicity of the nonwoven fabric itself in order to increase the water absorbency of the nonwoven fabric, but when a nonwoven fabric having only increased hydrophilicity is used, the surface does not dry while containing moisture, and the comfort when worn is improved. It was confirmed that the task of falling occurred. On the other hand, when hydrophobic fibers are used in a part of the nonwoven fabric for the purpose of improving quick-drying or when a hydrophilic hydrophilic gradient is applied in the thickness direction, the water absorbency of the surface of the nonwoven fabric is reduced as a result, and problems such as liquid residue occur. Turned out.

Therefore, in order to achieve the above object, the inventors of the present invention further intensively studied and found that, in a spunbond nonwoven fabric, a fused portion and an unfused portion are provided, and fibers constituting one surface (A) and the other surface (B ), the ratio of the average single fiber diameters of the fibers constituting the surface (A) and the contact angle of water between the surfaces (B) in a specific range, and also by setting the degree of waviness of the fibers constituting the surface (A) in a specific range, It has been found that a nonwoven fabric having sufficient absorbency and quick-drying properties to maintain comfort during wearing and also having a soft touch is obtained.

The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.

The spunbond nonwoven fabric of the present invention has a fused portion and a non-fused portion, and the average single fiber diameter (Da) of fibers on one surface (A) is relative to the average single fiber diameter (Db) of fibers on the other surface (B). The ratio (Da/Db) is 1.1 or more, the contact angles of the surfaces (A) and (B) with water are both 30° or less, and the tortuosity of the fibers of the surface (A) is 1.1 or more.

According to a preferable aspect of the spunbond nonwoven fabric of the present invention, the diameter of the maximum inscribed circle of the non-fused portion is 2.0 mm or more.

According to a preferable aspect of the spunbonded nonwoven fabric of the present invention, the thickness Tu of the spunbonded nonwoven fabric in the non-fused portion is 0.5 mm or more.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the ratio (Tu/Tm) of the thickness (Tu) of the spunbond nonwoven fabric in the unfused portion and the thickness (Tm) of the spunbonded nonwoven fabric in the fused portion is 2.0 or higher.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the degree of waviness of the fibers on the surface (B) is 1.1 or less.

The sanitary material of the present invention is composed of at least a part of the spunbond nonwoven fabric.

According to a preferred aspect of the sanitary material of the present invention, the surface (A) is disposed toward the skin side of the wearer.

According to the present invention, it is possible to obtain a spunbond nonwoven fabric that is excellent in absorbent quick-drying and soft touch, and is particularly suitable for use in sanitary materials, and sanitary materials using the same.

1 is a top view conceptual diagram illustrating a method for determining the maximum inscribed circle of an unfused portion in one embodiment of a spunbond nonwoven fabric of the present invention.
Fig. 2 is a top view conceptual diagram illustrating a method for determining the maximum inscribed circle of an unfused portion in another embodiment of the spunbond nonwoven fabric of the present invention.
Fig. 3 is a top view conceptual diagram illustrating a method for determining the maximum inscribed circle of an unfused portion in still another embodiment of the spunbond nonwoven fabric of the present invention.

The spunbond nonwoven fabric of the present invention has a fused portion and a non-fused portion, and the average single fiber diameter (Da) of fibers on one surface (A) is relative to the average single fiber diameter (Db) of fibers on the other surface (B). The ratio (Da/Db) is 1.1 or more, the contact angles of the surfaces (A) and (B) with water are both 30° or less, and the tortuosity of the fibers of the surface (A) is 1.1 or more. Although the components are described in detail below, the present invention is not limited to the range described below at all, unless the gist thereof is exceeded.

[fiber]

The spunbond nonwoven fabric of the present invention preferably contains a thermoplastic resin. One type of thermoplastic resin may be sufficient as it, and what contains a some thermoplastic resin may be sufficient as it.

Examples of the thermoplastic resin used for the fiber according to the present invention include aromatic polyester polymers such as "polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyhexamethylene terephthalate" and copolymers thereof, "polytrimethylene terephthalate" and the like. Aliphatic polyester polymers and copolymers thereof, such as lactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutylate-polyhydroxyvalylate copolymer, and polycaprolactone. , "polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, polyamide 6-12" and the like, aliphatic polyamide polymers and copolymers thereof, "polypropylene, polyethylene, polybutene, poly methylpentene” and other polyolefin polymers and copolymers thereof;

A water-insoluble ethylene-vinyl alcohol copolymer-based polymer containing 25 mol% to 70 mol% of ethylene units;

polystyrene-based, polydiene-based, chlorine-based, polyolefin-based, polyester-based, polyurethane-based, polyamide-based, fluorine-based elastomeric polymers, and the like, and can be selected and used among them. In addition, in the above polymer, even if various additives such as inorganic substances such as titanium oxide, silica and barium oxide, carbon black, colorants such as dyes and pigments, flame retardants, optical whitening agents, antioxidants, or ultraviolet absorbers are included in the polymer. do.

The fiber in the present invention may be a single component fiber as well as a composite fiber obtained by combining two or more types of resins. When the fiber is a composite fiber, it is not particularly limited as long as the effect of the present invention is not impaired, and may be appropriately selected from core sheath type, sea-island type, side-by-side type, eccentric core sheath type, and the like. Furthermore, it may be a split-type conjugate fiber in which a part or all of the fibers are divided into a plurality of fibers from one fiber.

The cross-sectional shape of the fiber in the present invention is not particularly limited as long as the effect of the present invention is not impaired, and may be a triangular, flat, hexagonal, or hollow cross section as well as a circular cross section.

It is preferable that the contact angle with water of all the fibers in this invention is 90 degrees or less. The contact angle with water in the fiber is an index different from the contact angle with water on the surface of the nonwoven fabric described later, and if the contact angle exceeds 90 °, it is hydrophobic, and if it is 90 ° or less, it is hydrophilic. By being composed of fibers having a contact angle with water of 90° or less, the contact angle with water on the surface of the nonwoven fabric can be easily made 30° or less.

In addition, the contact angle of the fiber in the present invention with water is, for example, for a fiber taken out of a nonwoven fabric left for 24 hours or more in a room at a room temperature of 20° C. and a relative humidity of 65%, automatically equipped with an inkjet method water droplet discharge unit. It is obtained by measuring the angle formed between the air interface of the droplet and the fiber when a very small amount (15 pL) of water droplet is applied to the surface of the fiber using a contact angle meter.

In addition, the fiber of the surface (A) and the fiber of the surface (B) may have the same or different types of thermoplastic resins and fiber cross-sections.

[Surface (A)]

The surface (A) of the spunbond nonwoven fabric of the present invention is composed of fibers containing the thermoplastic resin.

The spunbond nonwoven fabric of the present invention preferably contains long fibers, and the constituent fibers of the surface (A) are preferably long fibers. This is because it is easy to achieve both high productivity and excellent mechanical properties by including long fibers.

The average single fiber diameter of the fibers constituting the surface (A) of the spunbond nonwoven fabric of the present invention is preferably 3.0 to 30.0 µm. The average single fiber diameter of the fibers constituting the surface (A) is preferably 3.0 μm or more, more preferably 5.0 μm or more, still more preferably 10.0 μm or more. By setting the average single fiber diameter of the fibers constituting the surface (A) to 3.0 μm or more, when used as a sanitary material, moisture is easily transferred to the adjacent absorber. In addition, the average single fiber diameter of the fibers constituting the surface (A) is preferably 30.0 μm or less, more preferably 28.0 μm or less, still more preferably 25.0 μm or less. By setting the average single fiber diameter of the fibers constituting the surface (A) to 30.0 μm or less, it is easy to obtain a soft texture.

The average single fiber diameter here is determined as follows.

First, an image is taken of a cross section of a fiber constituting one surface at a magnification that allows one fiber to be observed with a scanning electron microscope. Then, using the captured image, using image analysis software (eg, "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.), the area Af (μm ² ) formed by the cross-sectional outline of the single fiber is measured, The diameter of a perfect circle having the same area as this area Af is calculated. This is measured for 20 fibers constituting the same surface randomly extracted, and a simple number average is obtained, the unit is μm, and the value obtained by rounding off to two decimal places is the average single fiber diameter of the surface referred to in the present invention. .

In the spunbond nonwoven fabric of the present invention, the degree of waviness of fibers on the surface (A) is 1.1 or more. The degree of waviness of the fiber on the surface (A) is preferably 1.2 or more, and more preferably 1.3 or more. This is because a high water absorption rate can be obtained when the tortuosity of the fiber on the surface (A) is 1.1 or more. Although the mechanism by which the high absorption rate is obtained is not clear, it is estimated that it is an effect in which various interfiber voids are formed. In addition, when the degree of waviness of the fiber on the surface (A) is 1.1 or more, it becomes easy to obtain a soft feel. The upper limit of the degree of waviness of the fibers on the surface (A) is not particularly limited, but is preferably 10.0 or less from the viewpoint of process stability and productivity.

The degree of flexure of the fiber as used herein is obtained as follows.

First, an image is taken of one surface at a magnification that allows one fiber to be observed over 500 µm or more in a straight line with a scanning electron microscope. Subsequently, using the captured image, using image analysis software (e.g., US National Institute of Health "Image J", etc.), the apparent length of the fiber is measured between two points on the 500 µm fibrous line in a straight line. Then, the apparent length of the fiber is divided by 500 μm to calculate the apparent length/length in a straight line. This is measured for 20 fibers constituting the same surface, which are randomly extracted, and a simple number average is obtained, and the value obtained by rounding off to two decimal places is referred to as the degree of curvature of the fibers on the surface according to the present invention.

[Surface (B)]

Like the surface (A), the surface (B) of the spunbond nonwoven fabric of the present invention is composed of fibers containing the thermoplastic resin.

The spunbond nonwoven fabric of the present invention preferably contains long fibers, and the constituent fibers of the surface (B) are preferably long fibers similarly to the surface (A). This is because it is easy to achieve both high productivity and excellent mechanical properties by including long fibers.

The average single fiber diameter of the fibers constituting the surface (B) of the spunbond nonwoven fabric of the present invention is preferably 1.0 to 25.0 µm. The average single fiber diameter of the fibers constituting the surface (B) is preferably 1.0 μm or more, more preferably 3.0 μm or more, still more preferably 5.0 μm or more. This is because when the fiber is set to 1.0 μm or more, the arrangement of the fibers does not become excessively dense, and when used as a disposable diaper material, moisture easily transfers to the adjacent absorber. The average single fiber diameter of the fibers constituting the surface (B) is preferably 25.0 µm or less, more preferably 20.0 µm or less, still more preferably 16.0 µm or less. It is because it is easy to obtain high capillary force and it becomes excellent water absorption by setting it as 25.0 micrometer or less.

The degree of waviness of the fibers on the surface (B) of the spunbond nonwoven fabric of the present invention is preferably 1.1 or less, more preferably 1.0. This is because when the tortuosity of the fibers on the surface (B) is 1.1 or less, small interfiber voids are easily formed and high capillary force is easily obtained. The lower limit of the degree of waviness of the fiber on the surface (B) is 1.0, which includes the case where the apparent length and the straight line length coincide, which is a preferred embodiment.

[Average short fiber diameter of surface (A) and surface (B)]

In the spunbond nonwoven fabric of the present invention, the ratio of the average single fiber diameter (Da) of one surface (A) to the average single fiber diameter (Db) of fibers on the other surface (B) (Da / Db, hereinafter simply “ Sometimes abbreviated as "average single fiber diameter ratio") is 1.1 or more.

The average single fiber diameter ratio as used herein is the average single fiber diameter (Da) of the fibers constituting the surface (A) and the average single fiber diameter (Db) of the fibers constituting the surface (B) using the method described above. is measured, the ratio (Da/Db) is calculated, and the value is rounded to two decimal places.

In general, in a nonwoven fabric, the size of voids formed by weaving fibers varies depending on the average single fiber diameter of the constituting fibers. For this reason, when layers having different average single fiber diameters are formed, layers having different void sizes between fibers are formed, and when moisture adheres, it is absorbed into the layer containing thick fibers due to the difference in capillary force. Moisture can be transferred to the layer containing thin fibers. Further, as a result of intensive studies, the inventors of the present invention found that by setting this average single fiber diameter ratio within a specific range, not only the water absorption improvement effect due to the difference in capillary effect, but also the surface of the nonwoven fabric layer containing coarse fibers is imparted with quick-drying properties. paid

1.2 or more are preferable, as for average single fiber diameter ratio (Da/Db) in this invention, 1.3 or more are more preferable, and 1.4 or more are still more preferable. By setting the average single fiber diameter ratio (Da/Db) to 1.1 or more, the above-described capillary effect works, and good water absorption and quick-drying properties on the surface (A) can be obtained. The upper limit of the average single fiber diameter ratio in the present invention is not particularly limited, but is preferably 10.0 or less from the viewpoint of process stability and productivity.

[Spunbond non-woven fabric]

As described above, the spunbond nonwoven fabric of the present invention has a fused portion and a non-fused portion. The fused portion is a location where the fibers on the surface (A) and the fibers on the surface (B) are fused, and the non-fused portion refers to a region surrounded by the fused portion among other locations on the spunbond nonwoven fabric. In the fused portion, since it is a location where the fibers on the surface (A) and the fibers on the surface (B) are fused, the periphery tends to be dense. Since there is a high-density fused portion and a relatively low-density non-fused portion within the surface of the spunbond nonwoven fabric, the movement of water within the surface becomes easy, making it easier to express more efficient water absorption and quick-drying performance than simple movement of water in the thickness direction. can

Further, in the present invention, in any part of the spunbond nonwoven fabric, whether or not the location is a fused portion, that is, a location where the fibers of the surface (A) and the fibers of the surface (B) are fused, is determined by the spunbond nonwoven fabric. The cross section of the portion of the bonded nonwoven fabric is observed with a scanning electron microscope at a magnification in which the thickness direction of the spunbond nonwoven fabric is in the field of view, and the randomly selected portion where the surface (A) is fused is placed in the plane direction. If the surface (B) is fused at the same position on the surface, it is determined that the location is a fused portion.

Further, in the spunbond nonwoven fabric of the present invention, it is preferable that the diameter of the maximum inscribed circle of the non-fused portion is 2.0 mm or more. The diameter of the largest inscribed circle is more preferably 3.0 mm or more, and more preferably 4.0 mm or more. This is because, when the diameter of the maximum inscribed circle is 2.0 mm or more, it is easy to form a low-density portion that is sufficiently far from the fused location, so that a high absorption rate is easy to obtain. Moreover, it is preferable also from the point which is easy to obtain a soft touch. The diameter of the largest inscribed circle is preferably 10.0 mm or less, more preferably 9.0 mm or less, still more preferably 8.0 mm or less. It is because it is easy to suppress fluffing by friction etc. as the diameter of the largest inscribed circle is 10.0 mm or less.

As illustrated in FIGS. 1 to 3 , the diameter of the maximum inscribed circle in the present invention, when the surface of the spunbond nonwoven fabric 1 is observed from above, is unfused surrounded by the fused portion 11 with a microscope. A field of view with a size of 10 mm × 10 mm or more is taken where the part can be observed. Next, the diameter of the maximum inscribed circle 13 that can be arranged on the unfused portion 12 using the captured image and using image analysis software (for example, "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.) to measure This is measured for 20 places constituting the same surface randomly extracted, and a simple number average is obtained, the unit is mm, and the value obtained by rounding off the second decimal place is the diameter of the maximum inscribed circle of the surface referred to in the present invention.

The spunbond nonwoven fabric of the present invention has one surface (A) having an average single fiber diameter of fibers Da and the other surface (B) having an average single fiber diameter of fibers Db, and, as described above, an average single fiber weave The cost (Da/Db) is greater than or equal to 1.1. In this way, the surface (A), which has a large average single fiber diameter and tends to enlarge the voids between fibers in the nonwoven fabric layer, becomes the outermost layer, and when moisture is absorbed from the surface (A) side, moisture is rapidly transferred to the surface (B) side. Since it is transferred, quick-drying can be obtained on the outermost surface on the surface (A) side.

In addition, in the spunbond nonwoven fabric of the present invention, both the surface (A) and the surface (B) of the spunbond nonwoven fabric have contact angles with water of 30° or less. When both the front and back surfaces of the spunbond nonwoven fabric have contact angles of 30° or less, preferably 20° or less, and more preferably 10° or less, water contacting the surface of the spunbond nonwoven fabric is easily absorbed into the nonwoven fabric, which is preferable. . In addition, the lower limit of the contact angle with water in the present invention is 0°, but the contact angle with water of 0° refers to a state in which all water is absorbed into the nonwoven fabric in the measuring method described later.

In addition, the contact angle of the surface of the spunbond nonwoven fabric with water can be controlled by the hydrophilicity of the thermoplastic resin used in the fibers constituting the spunbonded nonwoven fabric or by applying a hydrophilic emulsion in a subsequent step. For example, the higher the hydrophilicity of the thermoplastic resin and the greater the amount of the hydrophilic oil applied, the smaller the contact angle with water tends to be.

The contact angle of the surface of the spunbond nonwoven fabric of the present invention with water refers to a value measured and calculated by the following method.

(1) The spunbond nonwoven fabric is left to stand for 24 hours or more in a room with a room temperature of 20°C and a relative humidity of 65%.

(2) The spunbonded nonwoven fabric subjected to the above treatment is set on a stage of a contact angle meter installed in the same room so that the surface (A) becomes the measurement surface.

(3) A droplet of 2 μL containing ion-exchanged water is made at the tip of a needle and applied to a nonwoven fabric.

(4) The contact angle with the droplet is determined from the image 2 seconds after the droplet lands on the nonwoven fabric. In addition, when all the water is absorbed into the nonwoven fabric within 2 seconds, it is determined that the interface between the liquid droplet and the air is on the same plane as the surface of the nonwoven fabric layer, and the contact angle with water is defined as 0°.

(5) For one level, the measurement position is changed and the measurement is performed 5 times, and the arithmetic average value is taken as the contact angle between the surface (A) and water.

(6) The spunbond nonwoven fabric subjected to the same treatment as in (1) is set so that the surface (A) is the back side, and the above operations (2) to (5) are repeatedly performed, and the arithmetic average value is calculated as the surface (B). ) and the contact angle of water.

The spunbond nonwoven fabric of the present invention has the highest breaking strength σ with respect to the lowest breaking strength σ _min among the breaking strengths measured by rotating any one direction at 0 ° and rotating it up to 180 ° every 22.5 ° within the plane of the spunbond nonwoven fabric. It is preferable that the ratio of _max (σ _max /σ _min , hereinafter sometimes simply abbreviated as breaking strength ratio) is 1.2 to 4.0. By setting the breaking strength ratio to preferably 1.2 or more, and more preferably 1.3 or more, the fibers are easily oriented within the nonwoven fabric surface and high capillary force is easily expressed, resulting in fiber migration within the surface, resulting in higher water absorption and quick-drying. it becomes possible to obtain In addition, by setting the breaking strength ratio to preferably 4.0 or less, more preferably 3.5 or less, since there is no angle with extremely low breaking strength, tearing of the nonwoven fabric during process passage or product processing can be suppressed.

The breaking strength ratio of the spunbond nonwoven fabric of the present invention is based on "6.3 Tensile Strength and Elongation (ISO Method)" of JIS L1913: 2010 "General Nonwoven Fabric Test Method", measured and calculated by the following method. Refers to a value.

(1) Any one direction of the spunbond nonwoven fabric is set to 0°, and a test piece of 300 mm in length x 25 mm in width is cut out so that the longitudinal direction coincides with the above direction, the location is changed, and three test pieces are taken.

(2) The test piece is set in a tensile tester at a fixed interval of 200 mm.

(3) A tensile test is performed at a tensile speed of 100 m/min, and the strength at break [N] is obtained for the three specimens taken, and the arithmetic average value thereof is taken as the strength at break σ.

(4) A test piece measuring 300 mm in length x 25 mm in width is cut so that the direction rotated clockwise by 22.5° in the surface of the spunbond nonwoven fabric in any one direction at 0° as an axis, and the longitudinal direction coincides with the axial direction. out, change the location, and take three test pieces. Then, operation of said (2) - (3) is performed, and breaking strength sigma is calculated.

(5) The operation of (4) is repeated until the in-plane rotation angle of the spunbonded nonwoven fabric becomes 180°, and the breaking strength σ at each angle is calculated.

(6) Among the breaking strengths σ calculated by the above method, the ratio of the highest breaking strength σ _max to the lowest breaking strength σ _min (σ _max / σ _min ) is calculated, and used as the breaking strength ratio of the spunbond nonwoven fabric.

In the spunbond nonwoven fabric of the present invention, the layer (S) of the spunbond nonwoven fabric and the layer (M) of the meltblown nonwoven fabric can be disposed depending on the purpose within a range that does not impair the effects of the present invention. Examples of these arrangements include aspects such as SMS, SMMS, SSMMS and SMSMS. In these cases, one surface of the laminated nonwoven fabric is regarded as the surface (A) of the spunbond nonwoven fabric, and the other surface is regarded as the surface (B).

The spunbond nonwoven fabric of the present invention preferably has a water absorption rate of 20 seconds or less measured on the surface (A). By setting the water absorption rate to preferably 20 seconds or less, more preferably 15 seconds or less, and even more preferably 10 seconds or less, a nonwoven fabric having good ability to remove moisture adhering to the surface, that is, excellent water absorption is obtained.

The water absorption rate as used herein is measured based on the "7.1.1 dripping method" of JIS L1907: 2010 "Testing methods for water absorption of textile products". Drop one drop of water on the spunbond nonwoven fabric, measure the time until it is absorbed and the specular reflection of the surface disappears, calculate the simple average of the measured values at 10 different places, set the unit as seconds, and calculate the first decimal place Let the value obtained by rounding off the place be the absorption rate as used in the present invention.

The weight per unit area of the spunbonded nonwoven fabric of the present invention is preferably 10 to 100 g/m ² . By setting the weight per unit area to preferably 10 g/m ² or more, more preferably 13 g/m ² or more, and even more preferably 15 g/m ² or more, a spunbonded nonwoven fabric having mechanical strength that can be used for practical use can be obtained. there is. Further, by setting the weight per unit area to preferably 100 g/m ² or less, more preferably 50 g/m ² or less, a spunbond nonwoven fabric having appropriate flexibility suitable for use as a nonwoven fabric for sanitary materials can be obtained.

In addition, the unit area weight (g/m ² ) of the spunbond nonwoven fabric of the present invention is based on "6.2 mass per unit area" of JIS L1913: 2010 "General nonwoven fabric test method", a test piece of 20 cm × 25 cm was taken as a sample It shall refer to the mass per 1 m 2 calculated from the average value obtained by collecting three sheets per 1 m of width, measuring the mass ( ^g ) of each in a standard state.

In addition, the spunbond nonwoven fabric of the present invention may be provided with a hydrophilic agent for the purpose of further enhancing water absorption. Examples of the hydrophilic agent include surfactants, among which nonionic surfactants are preferred.

In the spunbond nonwoven fabric of the present invention, it is preferable that the thickness (Tu) of the unfused portion is 0.5 mm or more. When Tu is 0.5 mm or more, more preferably 0.7 mm or more, and still more preferably 0.9 mm or more, the spunbond nonwoven fabric has appropriate cushioning properties. On the other hand, when the thickness is 1.50 mm or less, more preferably 1.40 mm or less, and even more preferably 1.30 mm or less, the spunbond nonwoven fabric is bent and has excellent flexibility.

The thickness (Tu) of the non-fused portion of the spunbond nonwoven fabric of the present invention is not particularly limited, but refers to the thickness at no load, measured with, for example, a shape measuring instrument (eg, "VR3050" manufactured by Keyence Corporation).

In the spunbond nonwoven fabric of the present invention, the ratio (Tu / Tm) of the thickness of the unfused portion (Tu) to the thickness (Tm) of the fused portion is preferably 2.0 or more, more preferably 5.0 or more, and more preferably 10.0 or more. When Tu/Tm is 2.0 or more, the difference in density between the periphery of the fused location and the location away from the fusion location increases, resulting in high water absorption in the high-density area around the fusion location and low density at the location away from the fusion location. This is because it is easy to achieve both excellent softness in the part. The upper limit is not particularly limited, but is usually 50 or less.

The thickness (Tm) of the fused portion of the spunbond nonwoven fabric of the present invention is not particularly limited. Then, using the photographed image, the thickness is measured using image analysis software (for example, "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.). This is measured for 10 randomly selected places, a simple number average is obtained, the unit is mm, and the value obtained by rounding off the third decimal place is the thickness (Tm) of the fused portion of the spunbond nonwoven fabric according to the present invention.

In addition, the ratio (Tu/Tm) of the thickness (Tu) of the unfused portion and the thickness (Tm) of the fused portion is obtained by dividing the measured and calculated Tu (mm) by Tm (mm), and taking the second decimal place. It is calculated by rounding up.

[sanitary material]

At least a part of the sanitary material of the present invention is composed of the spunbond nonwoven fabric. By doing so, a sanitary material excellent in water absorbency and quick-drying property is obtained. The sanitary material of the present invention is mainly a disposable product used for health-related purposes such as medical care and nursing care, and includes paper diapers, sanitary napkins, gauze, bandages, masks, gloves, bandages, and the like. Members such as a topsheet, backsheet, side gathers and the like of a diaper are also included.

Among them, a sanitary material in which the surface (A) of the spunbond nonwoven fabric is disposed toward the wearer's skin side can immediately absorb moisture adhering to the skin surface side into the inside of the spunbond nonwoven fabric, causing discomfort to the wearer. Since it can be reduced, it is more preferable.

For example, in the case where the sanitary material is a disposable diaper and the spunbond nonwoven fabric is disposed inside the disposable diaper, when the surface (A) is disposed toward the wearer's skin side, sweat and excretion generated during wearing are disposed. The urine is quickly absorbed, and the liquid is quickly transferred to the surface (B), so that the surface can be maintained in a dry state without excessive moisture.

In addition, in the case where the sanitary material is a mask and the spunbond nonwoven fabric is used inside the mask, when the surface (A) is disposed toward the wearer's skin side, sweat or exhaled air condenses and moisture is formed on the skin side. Even if it is attached, it is immediately absorbed into the inside of the spunbond nonwoven fabric, and then the liquid is quickly transferred to the surface (B), so that the skin surface can also be kept dry without excessive moisture.

[Method for producing spunbond nonwoven fabric]

Next, a preferred mode for producing the spunbond nonwoven fabric of the present invention will be described in detail.

The spunbond nonwoven fabric of the present invention melts a thermoplastic resin as a raw material, spins it from a spinneret, and then cools and solidifies the yarn obtained by drawing it with an ejector and drawing it, collecting it on a moving net to form a nonwoven fiber web, It is manufactured by the spunbond method, which requires a step of heat-sealing.

As the shape of the spinneret and ejector to be used, various shapes such as circular and rectangular shapes can be employed. Among them, it is preferable to use a combination of a rectangular spinneret and a rectangular ejector from the viewpoint that the amount of compressed air used is relatively small and that fusion or abrasion between yarns is difficult to occur.

The spinning temperature in the present invention is preferably set to (the melting temperature of the thermoplastic resin as the raw material + 10°C) or more (the melting temperature of the thermoplastic resin as the raw material + 100°C) or less. By setting the spinning temperature within the above range, a stable molten state can be obtained and excellent spinning stability can be obtained.

The spun yarn is then cooled, but as a method of cooling the spun yarn, for example, a method of forcibly blowing cold air to the yarn, a method of naturally cooling at the ambient temperature around the yarn, and a distance between the spinneret and the ejector. A method of adjusting , or the like, or a method of combining these methods can be employed. In addition, the cooling conditions can be appropriately adjusted and employed in consideration of the discharge amount per single hole of the spinneret, the spinning temperature, and the ambient temperature.

Then, the cooled and solidified yarn is pulled by compressed air ejected from the ejector and stretched.

In the spunbond nonwoven fabric of the present invention, control of the average single fiber diameter of the fibers constituting the surface (A) and the surface (B) becomes important.

The average single fiber diameter of fibers is determined by the amount of discharge per discharge hole of the spinneret and the pulling speed, that is, the spinning speed. For this reason, it is preferable to determine the discharge amount and spinning speed according to the desired average single fiber diameter.

In spinning speed, it is preferable that it is 2000 m/min or more, More preferably, it is 3000 m/min or more. By setting the spinning speed to 2000 m/min or more, high productivity is obtained, and orientation crystallization of fibers proceeds to obtain long fibers with high strength.

The long fiber yarns thus stretched by traction are collected in a moving net to form a sheet, and then subjected to a process of thermal fusion.

As a method for obtaining fibers having a degree of waviness of 1.1 or more on the surface (A) of the spunbond nonwoven fabric of the present invention, conjugate spun fibers using thermoplastic resins having different characteristics are used, or depending on the degree of cooling, the fiber cross-section bears By forming regions with different stresses, the degree of curvature can be controlled. In the case of conjugate spun fibers, the degree of waviness can be set to 1.1 or more by using a thermoplastic resin having a large melting point difference or a thermoplastic resin having a large viscosity difference. Further, by increasing the cooling condition difference between one side surface of the fiber and the opposite side surface, the bending degree can be set to 1.1 or more.

As a method for obtaining fibers having a bending degree of 1.1 or less, which is a preferred form of the surface (B) of the spunbond nonwoven fabric of the present invention, conjugate spun fibers using thermoplastic resins having different properties, or single component spun fibers by single or blend It is important to equalize the stress imposed on the fiber cross section by the degree of cooling. Therefore, in the case of conjugate spun fibers, the bending degree can be set to 1.1 or less by using a thermoplastic resin having a small difference in melting point or a thermoplastic resin having a small difference in viscosity. In addition, it is also important to uniformly cool the fibers in order to make the bending degree 1.1 or less.

The spunbond nonwoven fabric of the present invention has a surface (A) and a surface (B) having different fiber diameters. Moreover, the degree of waviness of the fibers constituting the surface (A) is 1.1 or more. As a method for obtaining such a spunbond nonwoven fabric, for example, from a spinneret for surface (A), a fiber web obtained by collecting on a collecting net as described above is disposed on the downstream side of the collecting net, for surface (B) A method of depositing a fibrous web from a spinneret, heat-sealing and fixing these at once can be employed.

As a method of heat-sealing the spunbond nonwoven fabric of the present invention, in a pair of upper and lower rolls, a hot embossed roll in which flakes (convex portions) are applied to the surface of one roll, and a flat (smooth) surface without flakes on the surface of the other roll ) Thermal embossing rolls comprising a combination of rolls and thermal calender rolls comprising a combination of upper and lower flat (smooth) rolls, etc. A method by thermal fusion such as ultrasonic fusion can be employed.

When the spunbond nonwoven fabric of the present invention is produced by heat-sealing with an embossing roll, it is easy to fuse both the fibers of the surface (A) and the surface (B) at a position corresponding to the convex portion of the embossing roll, so it is preferable. It is also a preferable aspect in terms of being able to control the maximum inscribed circle of unfused locations by designing the positions of the convex portions of the embossing roll.

A hydrophilizing agent may be applied to the spunbond nonwoven fabric obtained in this way before winding. As a method for applying the hydrophilic agent to the spunbond nonwoven fabric, application by a kiss roll or spray, dip coating, etc. are exemplified, but application by a kiss roll is preferable in terms of uniformity and ease of control of the amount of adhesion.

Example

Next, the present invention will be described in detail based on examples. However, the present invention is not limited only to these examples. In addition, in the measurement of each physical property, what is not specifically described is the measurement based on the method mentioned above.

(1) Thickness

Measurements were made as described above.

(2) Weight per unit area

Measurements were made as described above.

(3) The ratio of the average single fiber diameter (Db) of the surface (B) to the average single fiber diameter (Da) of the surface (A) (Da/Db)

For each fiber, a fiber sample was randomly taken from the nonwoven fiber web collected on the net, and the cross section of the fiber was observed with a scanning electron microscope "S-5500" manufactured by Hitachi High-Technologies Co., Ltd. The image was taken at the magnification possible. Then, it measured as mentioned above using "WinROOF2015" by Mitani Shoji Co., Ltd. as image analysis software.

Measure the average single fiber diameter (Da) of the fibers constituting the surface (A) and the average single fiber diameter (Db) of the fibers constituting the surface (B), calculate the ratio (Da/Db), and calculate the decimal point This is the value rounded to the second digit.

(4) Curvature

Measurements were made as described above.

(5) Contact angle of spunbond nonwoven fabric with water

The measurement was performed as described above using a contact angle meter "DMo-501" manufactured by Kyowa Science and Technology Co., Ltd.

(6) Presence or absence of welded part

Observation and measurement were performed as described above.

(7) Absorption quick drying

In the spunbond nonwoven fabric, 1 drop of water droplet was dropped on the surface (A), and after 1 minute, healthy general adults (30 people, 15 men and women) touched with their hands, and the next 3 steps was evaluated. The average score of the evaluation results was calculated for each nonwoven fabric, and the feel of the spunbonded nonwoven fabric was determined.

5: The surface is smooth and does not feel moisture.

3: There is no moisture on the surface, but it is moist

1: The surface is moist and moist

(8) Soft touch

The spunbond nonwoven fabric was touched by healthy general adults (30 people, 15 male and female), and the touch of the surface was evaluated in the following three steps. The average score of the evaluation results was calculated for each nonwoven fabric, and the soft touch of the nonwoven fabric was obtained.

5: Very soft (the touch when touching the surface is soft, and the touch feels moderate elasticity in the thickness direction)

3: Not so soft

1: Cannot feel softness (catch feeling when touching the surface, strong rebound feeling when pressed, or disappearing)

[Example 1]

(fibrous web forming the surface (A))

Polypropylene (PP) and ethylene-copolymerized polypropylene (copolymerized PP) are melted in separate extruders to form side-by-side composite fibers (mass ratio: 1:1), and a round hole diameter φ of 0.4 mm is formed. From the rectangular spinneret with holes, the single hole discharge amount was discharged at 0.9 g/min. After the discharged yarns were cooled and solidified, they were pulled and stretched with compressed air at a pressure of 0.08 MPa in the ejector in a rectangular ejector, and collected on a moving net to obtain a nonwoven fibrous web. The average single fiber diameter of the fibers constituting the obtained surface (A) was 18.4 µm.

(fibrous web forming the surface (B))

Polypropylene was melted in an extruder and discharged at a single hole discharge rate of 0.3 g/min from a rectangular mold having round holes with a hole diameter of 0.4 mmφ. After the discharged yarn is cooled and solidified by cold air, it is pulled and drawn by compressed air with the ejector at a pressure of 0.08 MPa in a rectangular ejector, and on a moving net, on a fiber web forming the surface (A). captured. The average single fiber diameter of the fibers constituting the obtained surface (B) was 10.6 µm.

(spunbond non-woven fabric)

The laminated fiber web obtained in this way is constituted by using a metal embossing roll arranged in a so-called quilting pattern in which a pattern of straight lines formed by circular convex portions orthogonally intersect on the upper roll, and a metal flat roll on the lower roll. Using an embossing roll having a pair of upper and lower heating mechanisms, the linear pressure was 300 N/cm and the thermal fusion temperature was 125° C. to obtain a spunbonded nonwoven fabric having a weight per unit area of 40 g/m ² . . Thereafter, as a hydrophilic treatment, a nonionic surfactant was applied to the nonwoven fabric using a kiss roll so that the active ingredient was 0.5 wt% based on the weight of the spunbond nonwoven fabric.

Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Example 2]

A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that a metal embossing roll in which circular convex portions were staggered at the same pitch in both MD and CD directions was used on the upper roll.

Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Example 3]

A spunbonded nonwoven fabric was obtained in the same manner as in Example 2, except that the single hole discharge amount of the fibrous web forming the surface (A) was 0.53 g/min.

Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Example 4]

A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that an embossing roll was used and heat-sealed at a linear pressure of 10 N/cm.

Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Example 5]

Polypropylene and ethylene-copolymerized polypropylene were melted in separate extruders for the fibrous web forming the surface (B), respectively, to form side-by-side composite fibers (mass ratio: 1: 1) and discharged, except that A spunbond nonwoven fabric was obtained in the same manner as in Example 1.

Table 1 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 1]

Both the fiber web constituting the surface (A) and the fiber and fiber web constituting the surface (B), each with a single hole discharge amount of 0.6 g/min, ethylene copolymerized polypropylene and the same ethylene copolymerized polypropylene were melted in separate extruders. A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the spunbond nonwoven fabric was released.

Table 2 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 2]

A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that instead of thermal fusion using an embossing roll, the obtained fiber web was heated and thermally fused with hot air at 150°C. In the fusion by hot air, adjacent fibers are fused to each other, but a "fusion zone" in which the fibers on the surface (A) and the fibers on the surface (B) are fused is not formed.

Table 2 shows the evaluation results of the obtained spunbond nonwoven fabric.

[Comparative Example 3]

The fibrous web forming the surface (A) is melted with ethylene-copolymerized polypropylene and the same ethylene-copolymerized polypropylene in separate extruders to form side-by-side composite fibers (mass ratio: 1:1), and discharge A spunbond nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 2 shows the evaluation results of the obtained spunbond nonwoven fabric.

In Examples 1 to 5, the average single fiber diameter ratio (Da/Db) is large, the surface (A) has a large degree of waviness, and the fibers of the surface (A) and the fibers of the surface (B) are both fused together. From the fact that it has, it can be seen that it has excellent water-absorbent quick-drying property and excellent soft touch.

On the other hand, in Comparative Example 1, since the average single fiber diameter ratio was small, moisture did not migrate to the surface (B) side within the nonwoven fabric, and the water absorption quick-drying property was poor. Further, since Comparative Example 2 does not have a place where both the fibers on the surface (A) and the fibers on the surface (B) are fused, it is difficult to cause water to move into the surface, and the water absorption and quick-drying performance is poor. In Comparative Example 3, since the surface (A) had a small degree of waviness, it was difficult to obtain a water absorption rate, the water absorption quick-drying performance was not sufficient, and the soft touch was poor.

1: spunbond nonwoven fabric
11: fusion part
12: unfused part
13: maximum inscribed circle of unfused part

Claims (7)

It has a fused portion and an unfused portion, and the ratio (Da/Db) of the average single fiber diameter (Da) of fibers on one surface (A) to the average single fiber diameter (Db) of fibers on the other surface (B) is 1.1 A spunbonded nonwoven fabric having the above, wherein both the surface (A) and the surface (B) have contact angles with water of 30° or less, and the surface (A) has a fiber torsion degree of 1.1 or more. The spunbond nonwoven fabric according to claim 1, wherein the diameter of the maximum inscribed circle of the unfused portion is 2.0 mm or more. The spunbond nonwoven fabric according to claim 1 or 2, wherein the thickness (Tu) of the spunbond nonwoven fabric in the unfused portion is 0.5 mm or more. The method according to any one of claims 1 to 3, wherein the ratio of the thickness (Tu) of the spunbonded nonwoven fabric in the unfused portion to the thickness (Tm) of the spunbonded nonwoven fabric in the fused portion (Tu/Tm) ) is 2.0 or more, a spunbond nonwoven fabric. The spunbond nonwoven fabric according to any one of claims 1 to 4, wherein the fiber of the surface (B) has a degree of waviness of 1.1 or less. A sanitary material comprising at least a part of the spunbond nonwoven fabric according to any one of claims 1 to 5. The sanitary material according to claim 6, wherein the surface (A) is disposed toward the wearer's skin side.

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