JP4683959B2 - Nonwoven manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a nonwoven fabric.

  When judging the touch of the nonwoven fabric, the nonwoven fabric can be stretched or wrinkled by applying various forces to the nonwoven fabric, such as trying to grasp the nonwoven fabric, pulling it lightly, touching it, or bending it. It is usual to examine the relationship with deformation such as bending. The touch of the nonwoven fabric is comprehensively judged from these various viewpoints.

  With regard to surface smoothness, which is one of the factors for determining the touch of a nonwoven fabric, a surface sheet of an absorbent article with suppressed surface fluff has been proposed for the purpose of enhancing this property (see Patent Documents 1 and 2). . In Patent Document 1, a short fiber web is formed and obtained from a web in which natural fibers are mixed with a surface layer obtained by suppressing the tip of the short fiber protruding from the surface by a hot roll heated to 120 to 130 ° C. Further, a surface sheet is obtained by laminating two or more layers including the surface layer and the second layer to be laminated. On the other hand, in patent document 2, a nonwoven fabric is pinched | interposed between two rollers, or a roller is rolled on the nonwoven fabric surface, and it presses so that the fiber which fluffs may lie on the nonwoven fabric surface. Suppressing the fluff on the nonwoven fabric surface is an important factor for improving the touch. However, it is not possible to say that the touch is generally good only by suppressing the fluff, and it is insufficient in terms of suppleness and softness, which are other factors that greatly affect the improvement of the touch.

JP 2003-235896 A JP 2003-265528 A

  Accordingly, an object of the present invention is to provide a method for producing a non-woven fabric that can eliminate the various drawbacks of the above-described prior art.

The present invention applies a calendering process to a nonwoven fabric obtained by the air-through method to deform the fibers contained in the nonwoven fabric into a flat shape, and the major axis direction of the cross-section of the flatly deformed fiber is the nonwoven fabric. A method for producing a nonwoven fabric generally oriented in the plane direction of the original fabric,
The calendering is performed in multiple stages, and any calendering is performed using a metal calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees at room temperature under a linear pressure of 20 to 200 N / cm. The above object is achieved by providing a method for producing a nonwoven fabric.

  Further, the present invention provides a non-woven fabric obtained by the air-through method to a metallic calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees at room temperature under a linear pressure of 20 to 200 N / cm. Using the calendering process, the fibers contained in the nonwoven fabric are flatly deformed and the nonwoven fabric is processed so that the major axis direction of the cross section of the flatly deformed fibers is generally oriented in the plane direction of the nonwoven fabric. A method is provided.

  The non-woven fabric produced according to the method of the present invention has a smooth surface with a low surface roughness and a high draping property.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. First, the nonwoven fabric manufactured according to the manufacturing method of this embodiment is demonstrated. In this embodiment, a nonwoven fabric raw material is manufactured by the air through method. The air-through method is a method in which a fiber web such as a card web is placed on a breathable net or drum, and hot air is blown to heat-bond intersections of constituent fibers to form a nonwoven fabric. By adopting the air-through method, it is possible to obtain a non-woven fabric with good productivity and good touch as compared with the case where non-woven fabric is produced by other production methods. The nonwoven fabric raw material manufactured in this embodiment has a multilayer structure having a first layer including one surface and a second layer including the other surface. This multilayer structure is not limited to two layers, and may be a structure of three or more layers in which one or more other layers are interposed between the first layer and the second layer.

  The nonwoven fabric manufactured according to the present embodiment is characterized by good smoothness and suppleness, which are the main judgment factors of the touch. Furthermore, it is also characterized by having a soft feeling which is another main judgment factor. The nonwoven fabric having these three characteristics has a very good touch.

  The smoothness of the nonwoven fabric is a characteristic that is mainly expressed by the first layer in the nonwoven fabric manufactured according to the present embodiment. The nonwoven fabric contained in the first layer has a flat cross section. This flat shape contributes to the smoothness of the nonwoven fabric. From this point of view, it is preferable that the fibers included in the first layer have a flat shape in which the cross-sectional flatness (major axis length / minor axis length) is 1.2 or more, particularly 1.3 or more. The fibers included in the first layer preferably have a flat cross section over the entire length, but are not limited thereto, and the cross section in the portion of 70% or more, particularly 80% or more of the total length is not limited thereto. If it is flat, desired smoothness is provided. In particular, it is preferable that the cross section is flat in the portion between the bonding points of the fibers. In this embodiment, the fiber is deformed flat by calendering the nonwoven fabric under specific conditions.

  The fibers included in the first layer are preferably all flat fibers, but are not limited thereto. When the longitudinal cross section of the first layer is enlarged with an electron microscope and the cross-sectional shape of the fiber is observed, if the fiber has a flat shape of 70% or more on the basis of the number, the desired smoothness is given.

  In order to impart smoothness to the nonwoven fabric, it is also important that the long-axis direction of the cross-section of the above-mentioned fibers included in the first layer is generally oriented in the plane direction of the nonwoven fabric. . If the angle formed between the major axis direction of the cross section of the fiber and the plane direction of the nonwoven fabric is too large, it is difficult to give a smooth feel. From this viewpoint, it is preferable that the longer axis direction of the cross section is oriented in the plane direction of the nonwoven fabric as the fiber is located on the surface of the first layer and in the vicinity thereof. When the longitudinal section of the first layer is enlarged with an electron microscope and the major axis direction of flat fibers is observed, the major axis direction of 70% or more of the fibers on the basis of the number is non-woven fabric. The angle is within ± 30 degrees with the plane direction.

  In order to orient the major axis direction of the cross section of the fibers contained in the first layer in the plane direction of the nonwoven fabric, in this embodiment, as described above, the nonwoven fabric is calendered. As a result, the fibers are processed to be flat, and at the same time, the major axis direction of the cross section is oriented in the plane direction of the nonwoven fabric.

  From the viewpoint of imparting better smoothness to the nonwoven fabric, it is preferable that the fibers contained in the first layer have fineness. This is because the surface of the first layer becomes dense due to fine fibers. From this viewpoint, it is preferable that the fineness of the fibers contained in the first layer is 0.05 to 2.0 dtex, particularly 0.05 to 1.5 dtex. The fineness is measured by the following method. The longitudinal section of the nonwoven fabric is enlarged with an electron microscope, and the cross section of the fiber is observed. The cross-sectional area of a standard thickness fiber at 10 locations is measured. The fineness is calculated from the value and the density of the resin. The average value is used as the fineness.

  In order to make the surface of the nonwoven fabric smooth, it is also important that there is little fluffing of fibers on the surface. In order to reduce fiber fluff, it is important to ensure that the fibers are bonded together so that the free ends of the fibers are not present on the surface of the fibers. As described above, in the present embodiment, since the nonwoven fabric raw material is manufactured by the air-through method, it is advantageous to use fibers that are easy to fuse in order to reliably bond the fibers together. From this point of view, the fiber contained in the first layer is preferably a heat-fusible fiber made from a thermoplastic resin as a raw material. It is preferably an adhesive fiber. As will be described later, in the process of producing the nonwoven fabric raw material by the air-through method, the first layer side is made to face the breathable material, and hot air is blown from the second layer side, so that the fibers on the surface on the first layer side Fluffing can be further reduced.

  If the method of this embodiment is followed, flexibility will also be provided to the manufactured nonwoven fabric. Even if the surface of the nonwoven fabric is smooth, if the drapeability is not low and flexible, it gives a paper-like hard feel and the texture is not good. In the present embodiment, the raw material of the nonwoven fabric is calendered for the purpose of imparting flexibility to the nonwoven fabric. As a result, an effect of “stagnation” is added to the nonwoven fabric, and the entire structure of the nonwoven fabric is deformed. For example, the bonding points between the fibers are partially deformed or broken.

  According to this embodiment, in addition to the smoothness and flexibility described above, a soft feeling is imparted to the manufactured nonwoven fabric. The soft feeling is perceived by how much the nonwoven fabric can be compressed in the thickness direction, and by how much the thickness recovers when the compression is released. By the way, as mentioned above regarding the smoothness of a nonwoven fabric, it is preferable that the 1st layer contains the fiber of comparatively fineness densely. That is, the density is preferably high. As a result, with the first layer alone, the nonwoven fabric is not easily compressed in the thickness direction, and the thickness is difficult to recover even when the compression is released. Therefore, in the present embodiment, the nonwoven fabric raw material is calendered so that the second layer is not compressed more than the first layer, and the density of the second layer is lower than the first layer, so that the second layer Gives a soft feeling to the nonwoven fabric. Specifically, at the time of calendering, the second layer is made to face a resin roll made of a soft material and difficult to apply a pinching pressure.

In the nonwoven fabric manufactured according to this embodiment, when the calendering is performed so that the density of the second layer is 10 to 80%, particularly 20 to 60% smaller than the density of the first layer, a soft feeling is imparted. It is effective. Regarding the density of each layer, the density of the first layer is 0.01 to 0.1 g / cm ³ , particularly 0.02 to 0.05 g / cm ³ , from the viewpoint of imparting smoothness to the nonwoven fabric. preferable. On the other hand, the density of the second layer is preferably 0.005 to 0.04 g / cm ³ , particularly 0.01 to 0.03 g / cm ³ , from the viewpoint of imparting a soft feeling to the nonwoven fabric.

  In order to give a soft feeling to the nonwoven fabric by the second layer, it is preferable that the fibers contained in the second layer have little slack against compression. In order to reduce the sag with respect to compression, it is advantageous to use fibers having a large fineness. From this viewpoint, the fineness of the fibers contained in the second layer is preferably 1.5 to 5.0 dtex, particularly 1.7 to 3.0 dtex. If the fineness is within this range, the fiber roughness of the second layer is less likely to affect the first layer side, and the average deviation of the surface roughness of the surface of the first layer side and the average deviation of the friction coefficient are small. As a result, the smoothness of the nonwoven fabric is improved. It is also preferred that the fineness of the fibers contained in the second layer is greater than the fineness of the fibers contained in the first layer. In this case, if the fineness of the fibers contained in the second layer is 20 to 200%, particularly 40 to 150% greater than the fineness of the fibers contained in the first layer, it is effective for imparting a soft feeling.

  In addition to the low density of the second layer, a large thickness is also advantageous in terms of improving the soft feeling. From this viewpoint, in the nonwoven fabric manufactured according to the present embodiment, the thickness of the second layer is preferably 0.3 to 1.2 mm, particularly preferably 0.4 to 0.8 mm. On the other hand, the thickness of the first layer is preferably smaller than the thickness of the second layer from the viewpoint of improving smoothness, specifically 0.05 to 0.5 mm, particularly 0.1 to 0.3 mm. It is preferable. The total thickness of the nonwoven fabric is preferably 0.5 to 1.5 mm, particularly preferably 0.5 to 1.0 mm.

The basis weights of the first layer and the second layer are not critical from the viewpoint of improving the touch and can be appropriately determined according to the specific use of the nonwoven fabric. The same applies to the basis weight of the nonwoven fabric. When using the nonwoven fabric manufactured according to this embodiment as a constituent material of absorbent articles such as disposable diapers and sanitary napkins, the basis weight of the first layer is 5 to 15 g / m ² , particularly 7 to 12 g / m. ² is preferred. The basis weight of the second layer is preferably 5 to 45 g / m ² , particularly 7 to 25 g / m ² . The basis weight of the entire nonwoven fabric is preferably 10 to 60 g / m ² , particularly preferably 15 to 40 g / m ² . In this case, the tensile strength of the nonwoven fabric is preferably 10 to 100 N / 50 mm, particularly 20 to 70 N / 50 mm in the flow direction (MD), and 4 to 15 N / 50 mm, particularly 5 to 12 N / 50 mm in the width direction (CD). It is preferable that The tensile strength is measured using a tensile tester under conditions of a distance between chucks of 150 mm and a tensile speed of 300 mm / min.

In particular, when the nonwoven fabric produced according to the present embodiment is used as a constituent material of the outermost surface of the absorbent article, the basis weight of the first layer is 5 to 15 g / m ² , particularly 7 to 12 g / m ² . It is preferable. The basis weight of the second layer is preferably 5 to 25 g / m ² , particularly 7 to 20 g / m ² . The basis weight of the whole nonwoven fabric is preferably 10 to 40 g / m ² , particularly preferably 15 to 30 g / m ² .

  There is no restriction | limiting in particular in the constituent fiber of a 1st layer and a 2nd layer, The fiber of a suitable raw material is used according to the specific use of a nonwoven fabric. In the present embodiment, in view of manufacturing the nonwoven fabric raw material by the air-through method, the fibers included in each layer are preferably heat-fusible fibers. In addition to the heat-fusible fiber, a small amount of non-fusible fiber such as rayon, cotton, pulp, etc. is blended in the first layer and / or the second layer in order to give the nonwoven fabric a desired function. May be. In addition, fibers that have inherently heat fusion properties but do not exhibit heat fusion properties at the heat fusion treatment temperature in the production process of the nonwoven fabric of the present invention, such as polyester fibers and polyamide fibers, etc. You may mix | blend with a 1st layer and / or a 2nd layer. Although there is no restriction | limiting in particular also in the fiber length of a fiber, It is preferable to use a short fiber about 38-60 mm from a viewpoint of the formability of the web used as the raw material of an air through method.

  FIG. 1 shows a schematic diagram of a suitable apparatus used in the production method of the present invention. The apparatus 10 shown in FIG. 1 includes a web forming unit 20, a heat fusion unit 30, and a calendar unit 40.

  As shown in FIG. 1, the web forming unit 20 is provided with first and second card machines 21 and 22. The 1st card machine 21 is for manufacturing the 1st web for formation of the 1st layer. The second card machine 22 is for producing a second web for forming the second layer. The raw fiber is supplied from the raw fiber supply unit (not shown) to each of the card machines 21 and 22, and the fiber is carded. As a result, the first web 11 and the second web 12 are formed. The second web 12 is overlaid on the first web 11. Thereby, an overlapping web 13 of both webs is formed.

  The web 13 is conveyed by an endless belt 31 made of a breathable material such as a net such as a wire mesh, and is introduced into the heat fusion part 30. In the heat fusion part 30, the blower 32 of a hot air is installed in the position facing the web 13 conveyed on the endless belt 31. As shown in FIG. A suction box 33 is installed at a position facing the blower 32 with the endless belt 31 in between. When the web 13 passes under the blower 32, hot air heated to a predetermined temperature passes through the web 13, and the heat-fusible fiber contained in the web is softened or melted by the heat applied at that time. And the intersection of the fibers joins. As a result, an air-through nonwoven fabric 14 is obtained. Hot air passing through the web 13 is collected by a suction box 33.

The blowing temperature of the hot air is appropriately determined according to the melting point of the constituent resin of the heat-fusible fiber contained in the web 13, the conveyance speed of the web 13, the basis weight, and the like. When the resin of the heat fusion component is polyethylene, it is preferable that the temperature of the hot air is 120 to 150 ° C., particularly 130 to 145 ° C. from the viewpoint that the intersections of the fibers can be reliably bonded. For the same reason, the hot air blowing time is preferably 5 to 30 seconds, particularly 5 to 20 seconds.

  When hot air is blown to the web 13, the first web 11 side of the web 13 faces the belt 31, and hot air is blown from the second web 12 side. As a result, the side of the first web 11 is pressed against the belt 31, and fuzz is suppressed and a flat surface is obtained.

  The nonwoven fabric raw material 14 obtained in this way is introduced into the calendar unit 40 which is a subsequent process. In the calendar part 40, the nonwoven fabric raw fabric 14 is subjected to multistage calendering. In this production method, any calendering in multistage calendering is performed at room temperature under a linear pressure of 20 to 200 N / cm, a metal calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees. It is characterized in that it is performed using The calendar unit 40 includes a metal calendar roll 41 and first and second resin rolls 42 and 43. The resin rolls 42 and 43 are arranged to face each other so as to contact the calendar roll 41. Each roll 41,42,43 is arrange | positioned at the vertical type. The first resin roll 41 is disposed on the upstream side and the second resin roll 43 is disposed on the downstream side in the transport direction of the nonwoven fabric original fabric 14.

  The non-woven fabric 14 is first introduced between the first resin roll 42 and the calender roll 41 arranged on the upstream side, and subjected to the first stage calendering. At this time, the nonwoven fabric raw fabric 14 is introduced so that the first layer side faces the calendar roll. The first layer side facing the calendar roll 41 is clamped by calendar processing, and the fibers contained in the first layer are deformed and flattened. The first layer is densified by the clamping pressure. Further, the “slack” action is applied to the nonwoven fabric 14 by the clamping pressure, and a part of the bonding point between the fibers is deformed or destroyed, and the nonwoven fabric fabric 14 becomes flexible. The fibers contained in the second layer facing the first resin roll 42 are difficult to be subjected to pinching pressure and difficult to deform because the resin roll 42 is made of a soft material. Moreover, it is difficult to increase the density. The fibers contained in the first layer deformed flat are oriented in the plane direction of the nonwoven fabric original fabric 14 in the long axis direction in the cross section.

  The linear pressure in the first calendar process is preferably 50 to 700 N / cm, more preferably 100 to 300 N / cm. By calendering under these conditions, the fibers contained in the first layer can be easily deformed flatly while maintaining a highly productive line speed. The calendar roll 41 and / or the resin rolls 42 and 43 are used in a non-heated state, and the calendar process is performed under room temperature conditions. The calendar roll 41 may be a mirror-finished smooth one or may be provided with fine irregularities such as a satin finish. As the resin roll 42, for example, a resin roll made of a resin such as hard rubber, silicon rubber, urethane rubber, NBR, EPDM or the like can be used. These resins have a D hardness (JIS K6253) of 40 to 100 degrees, preferably 70 to 95 degrees. When a resin roll having a D hardness of less than 40 degrees is used, the flatness of the cross section of the fiber on the first layer side becomes small, and sufficient smoothness cannot be imparted. Further, the entire structure of the nonwoven fabric is not easily deformed, and sufficient flexibility is not imparted. If a resin roll exceeding 100 degrees (including a metal roll or the like) is used, the fibers are formed with a high density, a sufficient soft feeling is not imparted, a paper-like hard feeling is exhibited, and the texture is not good.

  Next, the nonwoven fabric is introduced between the second resin roll 43 and the calender roll 41 arranged on the downstream side, and subjected to the second stage calendering. Also at this time, the nonwoven fabric 14 is introduced so that the first layer side faces the calendar roll 41. By the second-stage calendering, the first layer facing the calender roll 41 is further pinched, and the fibers contained in the first layer are further deformed to increase the degree of flatness. The first layer is further densified by the clamping pressure. Further, the fibers contained in the first layer deformed into a flat shape have the major axis direction in the cross section thereof further oriented in the plane direction of the nonwoven fabric 14. In addition, the “non-woven fabric” 14 is added with the effect of “stagnation”, and the flexibility is further improved.

  The linear pressure in the second stage calendering is selected from the range of 20 to 200 N / cm described above. In particular, the linear pressure in the second-stage calendering is less than the linear pressure in the first-stage calendering within the range described above, and the second layer side is less likely to be densified by the pinching pressure, Thereby, the linearity value of the compression characteristic described later is lowered, which is preferable from the viewpoint that a sufficient soft feeling can be imparted. Specifically, it is preferably 20 to 150 N / cm. As the 2nd resin roll 43, the thing of the material which has D hardness of the range similar to the range mentioned above regarding D hardness of the 1st resin roll 42 is used.

  Thus, the manufacturing method of this embodiment has one of the features in that calendar processing is performed in multiple stages. As a result of the study by the present inventors, when calendering is performed in one step, the fiber cannot be sufficiently flattened even if the calendering conditions are severe. Even if it can be deformed flat, the long axis direction of the flat fiber cannot be reliably oriented in the plane direction of the nonwoven fabric.

  In the calendering, the average deviation (hereinafter referred to as SMD) of the surface roughness on the first layer side in the nonwoven fabric obtained after the processing is preferably as low as 2.5 μm, more preferably 2.3 μm or less. Preferably it is applied. Moreover, the average deviation (hereinafter referred to as MMD) of the coefficient of friction on the surface on the first layer side in the nonwoven fabric obtained after calendering is preferably less than 0.008, more preferably 0.006 or less, It is preferable that calendar processing is performed.

  The lower limit of SMD is not particularly limited and is preferably closer to 0. However, if calendering is performed so that the lower limit is as low as 1.0 μm, particularly about 0.5 μm, the nonwoven fabric has sufficient smoothness. Is granted. Similarly, the lower limit of MMD is not particularly limited and is preferably closer to 0. However, if calendering is performed so that the lower limit is as low as 0.004, especially about 0.003, the nonwoven fabric is sufficient. Smoothness is given.

SMD and MMD are measured using KESFB4-AUTO-A (trade name) manufactured by Kato Tech Co., Ltd. according to the method described in the following books. Specifically, it is measured by the following method.
Kakio Kawabata, “Standardization and analysis of texture evaluation”, 2nd edition, Japan Textile Opportunity Society, Texture Measurement and Standardization Research Committee, published on July 10, 1980

[Measurement method of average deviation SMD of surface roughness]
A test piece of 20 cm × 20 cm is prepared and attached to a smooth metal flat test bench. The contact is pressed against the test piece with 9.8 cN (within ± 0.49 cN error). The specimen is moved 2 cm horizontally at a constant speed of 0.1 cm / sec. The specimen is given a uniaxial tension of 19.6 cN / cm. The contact consists of a 0.5 mm diameter piano wire bent in a U shape with a width of 5 mm, and a test piece is crimped at 9.8 cN. The contact is crimped with a spring. The spring constant is 24.5 cN / mm (within an error of ± 0.98 cN / mm), and the resonance frequency is 30 Hz or more in a state away from the surface contact. The measured value of the average deviation of the surface roughness is represented by the SMD value. This measurement is performed for both MD and CD, and an average value is obtained from the following formula (1), which is defined as an average deviation SMD of the surface roughness.
Average deviation of surface roughness SMD = {(SMD _MD ² + SMD _CD ² ) / 2} ^1/2 (1)

[Measuring method of mean deviation MMD of friction coefficient]
A test piece of 20 cm × 20 cm is prepared and attached to a smooth metal flat test bench. The contact surface is pressure-bonded to the test piece with a force of 49 cN, and the test piece is moved horizontally by 2 cm at a constant speed of 0.1 cm / sec. The specimen is given a uniaxial tension of 19.6 cN / cm. The contact was made by arranging 20 piano wires with the same diameter of 0.5 mm as the contact used for measuring the surface roughness and bending it into a U shape with a width of 10 mm. Crimped to a piece. The measured value of the average deviation of the friction coefficient is expressed as an MMD value. This measurement is performed for both MD and CD, and an average value is obtained from the following formula (2), which is defined as an average deviation MMD of the friction coefficient.
Mean deviation of friction coefficient MMD = {(MMD _MD ² + MMD _CD ² ) / 2} ^1/2 (2)

In the calendering, the bending rigidity (hereinafter also referred to as B) of the nonwoven fabric obtained after the processing is preferably 0.03 cN · cm ² / cm or less, more preferably 0.025 cN · cm ² / cm or less. It is also preferable to be applied. The lower limit of the bending rigidity B is not particularly limited and is preferably closer to 0. However, if the lower limit is as low as 0.015, particularly about 0.01, the nonwoven fabric is sufficiently flexible. The bending stiffness B is a physical property value widely used in the technical field as a scale representing the degree of flexibility of a nonwoven fabric. In the present invention, the bending stiffness B is a value measured using a pure bending tester (KESFB2-AUTO-A manufactured by Kato Tech Co., Ltd.) according to the method described in the above-mentioned “Standardization and analysis of texture evaluation”. Say. Specifically, it is measured by the following method.

[Measurement method of bending stiffness B]
A test piece of 20 cm × 20 cm is prepared, mounted on a test stand, and the test piece is gripped by a chuck having a 1 cm interval. The specimen is subjected to pure bending with a constant velocity curvature in the range of curvature K = −2.5 to +2.5 cm ⁻¹ . The deformation rate is 0.50 cm ⁻¹ / sec, and one cycle deformation is performed. The bending stiffness value B is calculated from the inclination of the bending moment between the curvatures of 0.5 to 1.5 and −0.5 to −1.5 in the description of “Standardization and analysis of texture evaluation” described above. In the measurement of non-woven fabrics, there are cases where bending occurs between these curvatures, and accurate numerical values are difficult to represent. Therefore, the bending stiffness B in the present invention is calculated from the inclination at 0 to the maximum bending moment value and 0 to the minimum bending moment value. This measurement is performed for both MD and CD, and an average value is obtained from the following formula (3), and this is set as the bending rigidity B. Bending rigidity B = {(B _MD ² + B _CD ² ) / 2} ^1/2 (3)

  Further, the calendering may be performed so that the linearity (hereinafter also referred to as LC) of the compression characteristics of the nonwoven fabric obtained after the processing is preferably a low value of 0.3 or less, more preferably 0.25 or less. preferable. The lower limit of LC is not particularly limited and is preferably closer to 0. However, when the lower limit is as low as 0.2, particularly about 0.15, the nonwoven fabric is sufficiently soft. In the present invention, LC refers to a value measured using KESFB3-AUTO-A manufactured by Kato Tech Co., Ltd. LC is measured according to the method described in “Standardization and analysis of texture evaluation” described above. Specifically, it is measured by the following method.

[Measurement method of linearity LC of compression characteristics]
A test piece of 20 cm × 20 cm is prepared and attached to a test bench. The specimen is compressed between steel plates having a circular plane with an area of 2 cm ² . The compression speed is 20 μm / sec, and the maximum compression load is 4.9 kPa. The recovery process is also measured at the same rate. The linearity of the compression characteristic is represented by an LC value. The LC value is defined by the following formula (4).

  After the calendering is finished, various post-processing may be applied to the nonwoven fabric as necessary. For example, when using a nonwoven fabric as a surface material of an absorbent article, as will be described later, a hydrophilic treatment using various hydrophilizing agents can be performed.

  In this way, the intended nonwoven fabric is obtained. The obtained non-woven fabric is suitably used as a constituent material of absorbent articles such as disposable diapers and sanitary napkins, sheet-shaped pack cosmetics, substrates for wiping sheets, substrates for impregnated sheets, and the like. In particular, since the nonwoven fabric produced according to this embodiment has a smooth and smooth first layer side, when the nonwoven fabric is used as a constituent material of an absorbent article, the first layer side of the nonwoven fabric is on the user's skin. It is preferable to arrange so as to contact. Specific usage forms in which the non-woven fabric is placed in contact with the user's skin include forms using the non-woven fabric as a liquid-permeable surface material, forms using the outermost constituent material of the absorbent article, and the like. However, it is not limited to these forms. When the nonwoven fabric is used as a constituent material of the outermost surface of the absorbent article, the nonwoven fabric is often used by folding it back to the surface material side at the edge and / or side edge of the absorbent article. By arranging the nonwoven fabric so that the layer side faces the outside of the absorbent article, the side of the first layer in the folded portion comes into contact with the user's skin.

  As mentioned above, although the nonwoven fabric of this invention was demonstrated about the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the above-described embodiment, the calendar processing is two steps, but instead of this, three or more steps of calendar processing may be performed.

  In the embodiment, the second stage calendering is performed using a metal calender roll and a resin roll having a D hardness of 40 to 100 degrees at room temperature under a linear pressure range of 20 to 200 N / cm. However, it is only necessary that any one stage of calendaring be performed under these conditions.

  Moreover, although the nonwoven fabric raw material of the said embodiment was a thing of 2 layer structure, it may replace with this and may use the nonwoven fabric raw material of a single layer structure.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

[Examples 1-8]
The nonwoven fabric was manufactured using the apparatus shown in FIG. The short fibers having the composition shown in Table 1 were carded so as to have the basis weight shown in the same table to form the first and second webs. The second web was overlaid on the first web and air-through processed under the conditions shown in Table 1 to obtain a nonwoven fabric. At this time, the first web was opposed to the belt, and hot air was blown from the second web side. The obtained nonwoven fabric was subjected to a two-step calendar process at room temperature. Processing conditions were as shown in Table 1. The calendar roll was a metal roll provided with a pattern having a fine surface pattern of 350. The first and second resin rolls were hard rubber rolls having a D hardness of 90 degrees.

[Comparative Example 1]
Nonwoven fabrics were obtained under the conditions shown in Table 1. In this comparative example, calendar processing is not performed.

[Comparative Example 2]
A nonwoven fabric was obtained in the same manner as in Example 1 except that the calendering was one step.

[Comparative Example 3]
The linear pressure in calendering is as shown in Table 1, and the same procedure as in Example 1 except that a silicon rubber roll having a D hardness of 27 degrees (A hardness is 75 degrees) is used as the second-stage calendering resin roll. A nonwoven fabric was obtained.

[Evaluation]
Table 2 shows the basis weight and thickness of the nonwoven fabric obtained in Examples and Comparative Examples, and the basis weight and density of the first layer and the second layer. Moreover, the longitudinal cross-section of the nonwoven fabric was expanded with an electron microscope, and the cross-sectional shape of the fiber contained in the first layer was observed to obtain the flatness. The results are shown in Table 2. Further, SMD and MMD on the first layer side of the nonwoven fabric, and compression stiffness LC, bending stiffness B and tensile strength of the nonwoven fabric were measured. The results are shown in Table 2. Furthermore, the electron microscope image of the surface by the side of the 1st layer of the nonwoven fabric obtained in Example 1 and the longitudinal cross-section of a nonwoven fabric is shown in FIG.2 and FIG.3, respectively. Moreover, the electron microscope image of the surface by the side of the 1st layer of the nonwoven fabric obtained by the comparative example 1 is shown in FIG.

Furthermore, the touch of the nonwoven fabric was subjected to sensory evaluation from the viewpoints of softness and smoothness. The evaluation was performed on the following five stages for 10 panelists. The results are shown in Table 3 with an average score of 10 people.
・ Softness “Soft and soft to the touch.”
5: I think so 4: Somewhat like 3: I can't say it either 2: I don't think so much 1: I don't think so · About smoothness “Smooth and soft to the touch”
5: I think so 4: Somewhat like 3: I can't say either 2: I don't think so much 1: I don't think so

  As is clear from the results shown in Tables 1 and 2, the nonwoven fabric obtained in each example has a low SMD and MMD value on the surface on the first layer side, and is found to be smooth. It can also be seen that the flexural rigidity value is low and supple. Further, it can be seen that the compression stiffness is low and the soft feeling is high. Furthermore, it turns out that it has sufficient intensity | strength. Further, as is apparent from the results shown in Table 3, it can be seen that the nonwoven fabric obtained in each example is softer and smoother than the nonwoven fabric of the comparative example.

  Further, as apparent from FIGS. 2 and 3, the nonwoven fabric obtained in Example 1 has a flat fiber in the first layer, and the fiber has a long-axis direction in the transverse cross section of the nonwoven fabric. It can be seen that they are generally oriented in the plane direction. In contrast, in the nonwoven fabric of Comparative Example 1, it can be seen that the fibers contained in the first layer are circular. Although not shown in the drawings, the fibers contained in the first layer of the nonwoven fabric obtained in the examples other than Example 1 are flat, and the fibers have a long axis direction in the transverse cross section of the nonwoven fabric. It was confirmed that the film was generally oriented in the plane direction.

It is a schematic diagram which shows the suitable apparatus used for the manufacturing method of this invention. 2 is an electron microscopic image of the surface on the first layer side of the nonwoven fabric obtained in Example 1. FIG. 2 is an electron microscope image of a longitudinal section of a nonwoven fabric obtained in Example 1. FIG. 4 is an electron microscopic image of the surface of the nonwoven fabric obtained in Comparative Example 1 on the first layer side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 11 1st web 12 2nd web 13 Web 14 Non-woven fabric raw material 20 Web formation part 30 Thermal fusion part 40 Calendar part 41 Calendar roll 42 1st resin roll 43 2nd resin roll

Claims (6)

The nonwoven fabric obtained by the air-through method is calendered to deform the fibers contained in the nonwoven fabric into a flat shape, and the major axis direction of the cross section of the flatly deformed fiber is the plane of the nonwoven fabric A method of manufacturing a nonwoven fabric that is generally oriented in a direction,
The nonwoven fabric is a multilayer structure having a first layer including one surface and a second layer including the other surface;
The fineness of the fibers contained in the second layer is greater than the fineness of the fibers contained in the first layer;
Apply the calendar process so that the first layer side faces the calendar roll,
The calendering is performed in multiple stages, and any calendering is performed using a metal calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees at room temperature under a linear pressure of 20 to 200 N / cm. The manufacturing method of the nonwoven fabric performed.   The calendering is performed in two steps, and the second calendering is performed at room temperature under a linear pressure of 20 to 200 N / cm and a metal calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees. The manufacturing method of Claim 1 performed using. The production method according to claim 1 or 2, wherein the linear pressure in the second stage calendering is lower than the linear pressure in the first stage calendering .   The manufacturing method of Claim 3 which makes a 1st layer side oppose an air permeable material in the process of manufacturing a nonwoven fabric original fabric by an air through method, and sprays a hot air from the 2nd layer side.   The calendering is performed so that the average deviation SMD of the surface roughness on the first layer side after the calendering is 2.5 μm or less and the average deviation MMD of the friction coefficient is less than 0.008. The manufacturing method as described in. The nonwoven fabric obtained by the air-through method is calendered using a metal calender roll and a resin roll having a D hardness (JIS K6253) of 40 to 100 degrees at room temperature under a linear pressure of 20 to 200 N / cm. A nonwoven fabric processing method for making the fibers contained in the nonwoven fabric flat and deforming it flat, and orienting the major axis direction of the transversely deformed fibers in the plane direction of the nonwoven fabric ,
The nonwoven fabric is a multilayer structure having a first layer including one surface and a second layer including the other surface;
The fineness of the fibers contained in the second layer is greater than the fineness of the fibers contained in the first layer;
A method for processing a non-woven fabric, which is calendered so that the first layer side faces the calender roll .