KR102454637B1 - Spunbond Nonwoven - Google Patents

Abstract

The spunbond nonwoven fabric of the present invention comprises a polyolefin-based resin having a single fiber fineness of 0.5 to 2.0 dtex and a flatness of 1.5 or more. It is a spunbonded nonwoven fabric whose roughness SMD is 1.0-3.0 micrometers, and the average bending rigidity B by KES method is 0.001-0.020 gf*cm< ² >/cm.

Description

Spunbond Nonwoven

The present invention relates to a spunbond nonwoven fabric comprising polyolefinic flat cross-section fibers and particularly suitable for use as a sanitary material application.

BACKGROUND ART In general, nonwoven fabrics for sanitary materials such as paper diapers and sanitary napkins are composed of a top sheet having water permeability and being in direct contact with the skin, an absorbent body, and a back sheet having waterproof properties. Among these, since the back sheet is a part in direct contact with the hand in addition to water resistance, it is required to have tactile properties and flexibility, and also to be a nonwoven fabric surface suitable for printing when printing is performed on the nonwoven fabric.

It is known to use a flat cross-section fiber for the printability which is requested|required of these back sheets. For example, the nonwoven fabric for back sheets excellent in printability which made flatness 1.5 or more was proposed (refer patent document 1.).

In addition, a proposal of a nonwoven fabric containing fibers made of flat cross-sectional fibers into fineness has also been separately proposed (refer to Patent Document 2).

Japanese Patent Laid-Open No. 2003-319970 Japanese Patent Laid-Open No. 2001-89963

Certainly, the nonwoven fabric disclosed in Patent Document 1, which is composed of flat cross-section fibers having a flatness of 1.5 or more, tends to have a smooth surface with respect to a round cross-section yarn, and is excellent in printability. However, in this proposal, the single fiber fineness of the fibers used in the examples is 2.8 dtex, and since the nonwoven fabric is manufactured with fibers of a general thickness, the quality of the fabric is inferior, and the surface smoothness is insufficient, and the printability and feel, Furthermore, there was a problem in waterproofness.

Further, in the proposal disclosed in Patent Document 2, since the raw material is polyethylene terephthalate (PET) fiber, the nonwoven fabric to be produced becomes hard, and the surface roughness described in the Examples is large and there is a problem that the feel is poor.

Here, an object of the present invention, in view of the above problems, includes a polyolefin-based flat cross-section fiber with high productivity, with good spinnability and fineness, excellent in feel, flexibility, waterproofness and strength, and printing with a smooth surface To provide a spunbond nonwoven fabric suitable for

The spunbond nonwoven fabric of the present invention comprises a polyolefin-based resin having a single fiber fineness of 0.5 to 2.0 dtex and a flatness of 1.5 or more. A spunbond nonwoven fabric having a roughness SMD of 1.0 to 3.0 μm and an average bending stiffness B of 0.001 to 0.020 gf·cm ² /cm by the KES method.

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the air permeability per unit area of the spunbonded nonwoven fabric is 4 to 18 cc/cm ² ·sec/(g/m ² ).

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the tensile strength per unit area per unit area in the oblique direction of the spunbonded nonwoven fabric is 1.0N/2.5cm/(g/m ² ) or more.

According to a preferred aspect of the spunbonded nonwoven fabric of the present invention, the melt flow rate of the spunbonded nonwoven fabric is 45 to 250 g/10 min.

According to the present invention, it is possible to obtain a spunbond nonwoven fabric suitable for printing because it contains a polyolefin-based flat cross-section fiber having fineness, good spinnability, and high productivity, excellent in touch, flexibility, waterproofness and strength, and has a smooth surface. From these properties, the spunbond nonwoven fabric of the present invention can be suitably used particularly for a sanitary material use, in particular for a back sheet.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view illustrating a fiber having a flat cross-section and a fineness irregular cross-section used in the present invention.
Fig. 2 is a cross-sectional view illustrating a fiber with a flattened cross-section and a fineness irregular cross-section used in the present invention.

The spunbond nonwoven fabric of the present invention comprises a polyolefin-based resin having a single fiber fineness of 0.5 to 2.0 dtex and a flatness of 1.5 or more. It is a spunbonded nonwoven fabric whose roughness SMD is 1.0-3.0 micrometers, and the average bending rigidity B by KES method is 0.001-0.020 gf*cm< ² >/cm.

By doing in this way, it can be set as a spunbond nonwoven fabric which is excellent in touch, flexibility, waterproofness, and strength, and has a smooth surface and is suitable for printing.

Examples of the polyolefin-based resin used in the present invention include a polyethylene-based resin and a polypropylene-based resin. Examples of the polyethylene-based resin include a homopolymer of ethylene or a copolymer of ethylene and various α-olefins, and examples of the polypropylene-based resin include a homopolymer of propylene or a copolymer of propylene and various α-olefins. . From the viewpoint of spinnability and strength characteristics, a polypropylene-based resin is particularly preferably used.

As polyolefin resin used by this invention, 2 or more types of mixture may be sufficient and the resin composition containing other olefin resin, a thermoplastic elastomer, etc. can also be used.

To the polyolefin resin used in the present invention, additives such as antioxidants, weathering stabilizers, light stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents and pigments which are commonly used in the range not impairing the effects of the present invention , or other polymers may be added as needed.

It is preferable that melting|fusing point of polyolefin resin used by this invention is 80-200 degreeC, More preferably, it is 100-180 degreeC. The melting point is preferably 80°C or higher, more preferably 100°C or higher, whereby heat resistance that can withstand practical use is easily obtained. Further, by setting the melting point to preferably 200°C or less, more preferably 180°C or less, it becomes easy to cool the yarn discharged from the spinneret, and it becomes easy to suppress the fusion of the fibers and perform stable spinning.

It is important that the fibers constituting the spunbond nonwoven fabric of the present invention have a single fiber fineness of 0.5 to 2.0 dtex. The single fiber fineness is 0.5 dtex or more, preferably 0.6 dtex or more, and more preferably 0.7 dtex or more, thereby preventing a decrease in spinnability and producing a stable and good quality spunbond nonwoven fabric. On the other hand, by making the single fiber fineness 2.0 dtex or less, preferably 1.5 dtex or less, and more preferably 1.0 dtex or less, the flexibility is improved, the surface of the nonwoven fabric is smooth, and a spunbond nonwoven fabric having an excellent feel. can

The cross-sectional shape of the fibers constituting the spunbond nonwoven fabric of the present invention is a flat cross-section, and it is important that the flatness is 1.5 or more. By making the flatness 1.5 or more, preferably 1.7 or more, and more preferably 2.0 or more, the surface is smooth and suitable for printing, and due to the synergistic effect with the fineness, the unevenness of the surface is very small, It can be set as a spunbond nonwoven fabric which has a smooth and tactile surface. Although the upper limit is not specifically set, when flatness becomes 5.0 or more, since a nonwoven fabric may become high density and a touch may become hard, it is unpreferable. In addition, as shown in FIG. 1, the flat cross section referred to in this invention points out the shape in which the long side becomes a substantially straight line as shown in an elliptical shape and FIG. 1 and 2 are cross-sectional views illustrating a fiber with a flat cross-section and a fineness irregular cross-section used in the present invention.

It is important that the spunbond nonwoven fabric of the present invention has a surface roughness SMD of 1.0 to 3.0 µm by the KES method (KAWABATA EVALUATION SYSTEM) of at least one side. The surface roughness SMD by the KES method is 1.0 µm or more, preferably 1.3 µm or more, more preferably 1.6 µm or more, and still more preferably 2.0 µm or more, whereby the spunbond nonwoven fabric is excessively densified. Thus, it is possible to prevent the flexibility from being damaged. On the other hand, the surface roughness SMD by the KES method is 3.0 μm or less, preferably 2.8 μm or less, and more preferably 2.6 μm or less, so that the surface is smooth and has a small rough feeling, excellent tactile feel, and printing. It can be made as a spunbond nonwoven fabric suitable for

It is preferable that the average bending rigidity B by the KES method of the spunbonded nonwoven fabric of this invention is 0.001-0.020gf*cm< ² >/cm. The average bending stiffness B by the KES method is preferably 0.020 gf·cm ² /cm or less, more preferably 0.017 gf·cm ² /cm or less, and still more preferably 0.015 gf·cm ² /cm or less. In particular, when used as a spunbond nonwoven fabric for sanitary materials, sufficient flexibility can be obtained. In addition, when the average bending stiffness B by the KES method is extremely low, handleability may be poor. Therefore, the average bending stiffness B is preferably 0.001 gf·cm ² /cm or more. The average bending rigidity B by the KES method can be adjusted by the weight per unit area, the single fiber fineness, and the thermocompression compression conditions (compression bonding rate, temperature, and linear pressure).

The air permeability per unit area of the spunbond nonwoven fabric of the present invention is preferably 4 to 18 cc/cm ² ·sec/(g/m ² ). The air permeability per unit area weight is preferably 18 cc/cm ² sec/(g/m ² ) or less, more preferably 17 cc/cm ² sec/(g/m ² ) or less, still more preferably By setting it to 16 cc/cm ² ·sec/(g/m ² ) or less, it is possible to sufficiently satisfy the waterproofness required for the back sheet. On the other hand, the air permeability per unit area weight is preferably 4 cc/cm ² sec/(g/m ² ) or more, more preferably 5 cc/cm ² sec/(g/m ² ) or more, More preferably, by setting it to 6 cc/cm ² ·sec/(g/m ² ) or more, it is possible to prevent the spunbond nonwoven fabric from being excessively densified and the flexibility being impaired. Aeration amount can be adjusted by the weight per unit area, single fiber fineness, and thermocompression-compression conditions (compression-compression rate, temperature, and linear pressure).

It is preferable that the tensile strength per weight per unit area in the oblique direction of the spunbonded nonwoven fabric of this invention is 1.0N/2.5cm/(g/m< ² >) or more. The tensile strength per unit area weight is preferably 1.0 N/2.5 cm/(g/m ² ) or more, more preferably 1.2 N/2.5 cm/(g/m ² ) or more, still more preferably By setting it as 1.5N/2.5cm/(g/m< ² >) or more, it becomes what can withstand the process passability at the time of manufacturing a paper diaper etc., and use as a product. Moreover, about an upper limit, when too high, since there exists a possibility of impairing a softness|flexibility, it is preferable that it is 3.0 N/2.5cm/(g/m< ² >) or less. The tensile strength can be adjusted by the fineness of the single fibers, the spinning speed, the compression ratio of the embossed roll, the temperature, the linear pressure, and the like. Regarding the relationship between single fiber fineness and tensile strength, the tensile strength can be improved by increasing the adhesion point between fibers by finerization.

It is preferable that the melt flow rate of the spunbonded nonwoven fabric of this invention (it may describe as MFR hereafter) is 45-250 g/10min. The MFR is preferably 45 to 250 g/10 min, more preferably 55 to 230 g/10 min, and still more preferably 65 to 220 g/10 min, so that it is drawn at a high spinning speed in order to increase productivity. Even if it does, it can easily follow with respect to a deformation|transformation, and stable spinning|fiber-formation becomes possible. In addition, since it is possible to draw at a stable and high spinning speed, the orientation and crystallization of the fibers can be advanced, and the fibers having high mechanical strength can be obtained, and thus the strength of the nonwoven fabric can be increased.

The melt flow rate (MFR) of the spunbond nonwoven fabric is measured under the conditions of a load of 2160 g and a temperature of 230° C. according to ASTM D-1238.

The MFR of the polyolefin-based resin, which is a raw material for the spunbond nonwoven fabric of the present invention, is preferably 45 to 250 g/10 min, more preferably 55 to 230 g/10 min, and still more preferably 65 to 220 g/10 min. The MFR of this polyolefin resin is also measured by ASTM D-1238 on condition that the load is 2160 g and the temperature is 230°C.

In the spunbond nonwoven fabric of the present invention, in order to improve slipperiness and flexibility, it is a preferred embodiment that a fatty acid amide compound having 23 or more carbon atoms and not more than 50 carbon atoms is contained in the polyolefin-based fiber containing the polyolefin-based resin in the part serving as the constituent fiber. .

It is known that the speed of movement of the fatty acid amide compound to the fiber surface varies depending on the number of carbon atoms of the fatty acid amide compound mixed into the polyolefin-based fiber. By setting the carbon number of the fatty acid amide compound to preferably 23 or more, more preferably 30 or more, excessive exposure of the fatty acid amide compound to the fiber surface is suppressed, the spinning and processing stability are excellent, and high productivity is achieved. can keep On the other hand, when the number of carbon atoms of the fatty acid amide compound is preferably 50 or less, and more preferably 42 or less, the fatty acid amide compound is more likely to migrate to the fiber surface, so that the spunbond nonwoven fabric can be provided with slipperiness and flexibility.

Examples of the fatty acid amide compound having 23 or more and 50 or less carbon atoms used in the present invention include a saturated fatty acid monoamide compound, a saturated fatty acid diamide compound, an unsaturated fatty acid monoamide compound and an unsaturated fatty acid diamide compound.

Specifically, as a fatty acid amide compound having 23 or more and 50 or less carbon atoms, tetradocosic acid amide, hexadocosic acid amide, octadocosic acid amide, nervonic acid amide, tetracosapentaenoic acid amide, nisinic acid amide, ethylenebislauric acid Amide, methylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenehydroxystearic acid amide , distearyl adipic acid amide, distearyl sebacic acid amide, ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, and the like, and a plurality of these may be used in combination.

In the present invention, ethylenebisstearic acid amide, which is a saturated fatty acid diamide compound, is particularly preferably used among these fatty acid amide compounds. Ethylene bis stearic acid amide can be melt-spun because of its excellent thermal stability, and the polyolefin-based fiber blended with ethylene bis stearic acid amide is used to produce a spunbond nonwoven fabric with excellent sliding properties and flexibility while maintaining high productivity. can be obtained

In this invention, it is a preferable aspect that the addition amount of the fatty acid amide compound with respect to polyolefin fiber is 0.01-5.0 mass %. The addition amount of the fatty acid amide compound is preferably 0.01 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, and still more preferably 0.1 to 1.0% by mass, so that proper slidability and flexibility can be achieved while maintaining spinnability. can be given

The addition amount as used herein refers to the mass percentage of the fatty acid amide compound added to the total resin constituting the polyolefin-based fibers constituting the spunbond nonwoven fabric of the present invention, specifically, the polyolefin-based fibers. For example, even when the fatty acid amide compound is added only to the sheath component constituting the core-sheath type composite fiber, the addition ratio with respect to the total amount of the core-sheath component is calculated.

The weight per unit area of the spunbond nonwoven fabric of the present invention is preferably 10 to 100 g/m ² . A spunbond having a mechanical strength that can be practically provided by a weight per unit area of preferably 10 g/m ² or more, more preferably 13 g/m ² or more, and still more preferably 15 g/m ² or more. Non-woven fabric can be obtained. On the other hand, the weight per unit area is preferably 100 g/m ² or less, more preferably 50 g/m ² or less, and still more preferably 30 g/m ² or less, so that it is suitable for use as a nonwoven fabric for sanitary materials. It can be set as the spunbond nonwoven fabric which has flexibility.

Next, the preferable aspect of the method of manufacturing the spunbonded nonwoven fabric of this invention is demonstrated concretely.

The spunbond nonwoven fabric of the present invention is a long fiber nonwoven fabric produced by the spunbond (S) method. As a manufacturing method of a nonwoven fabric, although a spunbonding method, a flash spinning method, a wet method, a card method, an air-laid method, etc. are mentioned, The spunbonding method is excellent not only in productivity and mechanical strength, but also fluffing which easily occurs in a single fiber nonwoven fabric. I can suppress the loss of fibers. In addition, by laminating a spunbond (S) nonwoven fabric layer in multiple layers such as SS (2 layers), SSS (3 layers) and SSSS (4 layers), productivity and uniformity of fabric quality can be improved.

In the spunbonding method, first, a molten thermoplastic resin (polyolefin resin) is discharged as a long fiber from a spinneret, and this is sucked and drawn with compressed air by an ejector, and then the fibers are collected on a moving net to form a nonwoven fiber web. Further, the obtained nonwoven fibrous web may be subjected to a heat bonding treatment to obtain a spunbond nonwoven fabric.

As a shape of a spinneret and an ejector, the thing of various shapes, such as a circle and a rectangle, is employable. Among them, a combination of a rectangular nozzle and a rectangular ejector is preferably used from the viewpoint that the amount of compressed air used is relatively small and the energy cost is excellent, the fusion or abrasion between the yarns does not easily occur, and the yarn opening is also easy. In addition, the shape of the discharge hole of the spinneret is preferably a rectangular shape in order to obtain a flat cross-sectional yarn.

In the present invention, the polyolefin-based resin is melted in an extruder, metered, fed to a spinneret, and discharged as long fibers. The spinning temperature at the time of melting and spinning the polyolefin resin is preferably 200 to 270°C, more preferably 210 to 260°C, still more preferably 220 to 250°C. By making the spinning temperature within the above range, it is possible to obtain a stable molten state and excellent spinning stability.

The yarns of the discharged long fibers are then cooled. As a method of cooling the discharged thread, for example, a method of forcibly blowing a cold wind to the thread, a method of naturally cooling at the ambient temperature around the thread, and a method of adjusting the distance between the spinneret and the ejector, etc., or , or a method combining these methods may be employed. In addition, cooling conditions can be suitably adjusted and employ|adopted in consideration of the discharge amount per single hole of a spinneret, radiation temperature, atmospheric temperature, etc.

Next, the cooled and solidified thread is drawn and stretched by compressed air sprayed from the ejector.

The spinning speed is preferably 3,500 to 6,500 m/min, more preferably 4,000 to 6,500 m/min, and still more preferably 4,500 to 6,500 m/min. By setting the spinning speed to 3,500 to 6,500 m/min, high productivity is attained, and the orientation and crystallization of the fibers proceeds to obtain high-strength long fibers. Normally, if the spinning speed is increased, spinning deteriorates and yarn shape cannot be stably produced. .

Subsequently, the obtained long fibers are collected on a moving net to form a nonwoven fiber web. In the present invention, in order to draw at a high spinning speed, the thread coming out of the ejector is injected at a high speed. Thus, by opening the yarns sprayed at high speed in a controlled state and collecting them in a net, a spunbond nonwoven fabric with little fiber entanglement and high uniformity can be obtained.

As a method of opening the thread sprayed from the ejector in a controlled state, a method for guiding the thread by installing a flat plate with an angle between the ejector and the net, and providing a plurality of grooves with different angles on the flat plate, falling along the flat plate A method of separating and opening yarns in the direction of sheet flow by separating them into yarns and yarns falling along the grooves, and arranging a plurality of flat plates with different angles at the ejector outlet in a comb-tooth shape, and dropping the yarns along each flat plate to flow the sheet The method of disperse|distributing to the direction and opening the fiber etc. are mentioned.

Among them, in terms of efficiently dispersing threads of fine fiber diameter in the sheet flow direction and opening in a controlled state without decelerating as much as possible, a plurality of flat plates with different angles at the ejector outlet are arranged in a comb-tooth shape, It is a preferable aspect to use the method of opening by falling along each flat plate.

Further, in the present invention, it is also a preferable aspect to temporarily bond the nonwoven fibrous web by abutting a hot flat roll from one side thereof on a net. By doing in this way, it is possible to prevent the quality of the fabric from being deteriorated due to the surface layer of the nonwoven fibrous web being rolled up or blown up during transport on the net, and the transportability from collecting the threads to thermocompression can be improved.

Then, the intended spunbond nonwoven fabric can be obtained by integrating the obtained nonwoven fibrous web by thermal bonding.

As a method of unifying the nonwoven fibrous web by thermal bonding, a heat embossed roll in which the surfaces of a pair of upper and lower rolls are engraved (concave-convex portions) respectively, one roll with a flat (smooth) surface and the other roll A method of thermal bonding with various rolls, such as a thermal embossing roll including a combination of rolls with engraving (concave-convex portions) on the surface, and a thermal calendering roll including a combination of a pair of upper and lower flat (smooth) rolls; , methods such as ultrasonic bonding in which thermal welding is performed by ultrasonic vibration of the horn.

Among them, in terms of excellent productivity, imparting strength in the partial thermal bonding portion, and maintaining the texture and tactile feel of the nonwoven fabric alone in the non-adhesive portion, engraving (concave-convex portions) is performed on the surface of a pair of upper and lower rolls, respectively. It is a preferred embodiment to use a hot embossed roll, or a hot embossed roll comprising a combination of a roll having a flat (smooth) surface on one of the rolls and a roll having engraving (concave-convex portions) on the surface of the other roll. .

As a surface material of the heat embossing roll, a pair of metal rolls and metal rolls is used in order to obtain a sufficient thermocompression effect and to prevent fragments (concave-convex portions) of one embossing roll from being transferred to the other roll surface. It is a preferable aspect to set it as

It is preferable that the embossing adhesion area ratio by such a heat embossing roll is 5 to 30 %. By setting the bonding area ratio to preferably 5% or more, more preferably 8% or more, and still more preferably 10% or more, strength that can be practically provided as a spunbond nonwoven fabric can be obtained. On the other hand, the bonding area is preferably 30% or less, more preferably 25% or less, and still more preferably 20% or less, so that it is suitable for use in a spunbond nonwoven fabric for sanitary materials, especially in paper diaper applications. A suitable suitable flexibility can be obtained. Even when ultrasonic bonding is used, the bonding area ratio is preferably in the same range as described above.

The adhesion area ratio here means the ratio which an adhesion part occupies in the whole spunbond nonwoven fabric. Specifically, in the case of thermal bonding by means of a pair of uneven rolls, the convex portion of the upper roll and the convex portion of the lower roll overlap and the portion (adhesive portion) in contact with the nonwoven fiber web means the proportion of the spunbond nonwoven fabric as a whole. do. In addition, in the case of thermal bonding by means of a roll having irregularities and a flat roll, it means the ratio of the portion (adhesive part) in which the convex portions of the roll having irregularities abut against the nonwoven fiber web occupies the entire spunbond nonwoven fabric. In addition, in the case of ultrasonic bonding, it means the thing of the ratio which occupies for the whole spunbonded nonwoven fabric of the part (adhesive part) to be heat-welded by ultrasonic processing.

As a shape of the bonding part by a heat embossing roll or ultrasonic bonding, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc. can be used. Moreover, it is preferable that the adhesive part exists uniformly at fixed intervals, respectively in the longitudinal direction (conveyance direction) and the width direction of a spunbonded nonwoven fabric. By doing in this way, the fluctuation|variation in the intensity|strength of a spunbonded nonwoven fabric can be reduced.

As for the surface temperature of the thermal embossing roll at the time of thermal bonding, it is a preferable aspect to set it as -50--15 degreeC with respect to melting|fusing point of the polyolefin resin used. By setting the surface temperature of the hot roll to preferably -50°C or higher with respect to the melting point of the polyolefin-based resin, and more preferably -45°C or higher, the spunbond nonwoven fabric having a strength that can be applied to practical use by appropriate thermal bonding. can get In addition, by setting the surface temperature of the thermal embossing roll to preferably -15°C or less with respect to the melting point of the polyolefin-based resin, and more preferably -20°C or less, excessive thermal adhesion is suppressed, and spunbond for sanitary materials As the nonwoven fabric, suitable flexibility can be obtained, particularly suitable for use in paper diaper applications.

It is preferable that the linear pressure of the thermal embossing roll at the time of thermal bonding shall be 50-500 N/cm. The linear pressure of the roll is preferably 50 N/cm or more, more preferably 100 N/cm or more, and still more preferably 150 N/cm or more. A bond nonwoven fabric can be obtained. On the other hand, by setting the linear pressure of the heat emboss roll to preferably 500 N/cm or less, more preferably 400 N/cm or less, and still more preferably 300 N/cm or less, as a spunbond nonwoven fabric for sanitary materials, particularly Adequate flexibility suitable for use in paper diaper applications can be obtained.

In addition, in the present invention, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, before and/or after thermal bonding by the thermal embossing roll, thermal compression is performed by a thermal calender roll comprising a pair of upper and lower flat rolls. can be carried out. The pair of upper and lower flat rolls are metal rolls or elastic rolls having no unevenness on the surface of the rolls, and can be used as a pair of a metal roll and a metal roll, or a pair of a metal roll and an elastic roll.

In addition, the elastic roll here is a roll containing the material which has elasticity compared with the metal roll. Examples of the elastic roll include so-called paper rolls such as paper, cotton and aramid paper, and resin rolls containing urethane-based resins, epoxy-based resins, silicone-based resins, polyester-based resins and hard rubbers, and mixtures thereof. have.

The spunbond nonwoven fabric of the present invention contains a polyolefin-based flat cross-section fiber having high fineness, good spinnability, and high productivity, has excellent feel, flexibility, waterproofness and strength, and has a smooth surface and is suitable for printing. It can be used suitably for a hygiene material use, especially for the object for the back sheet of a paper diaper.

Example

Next, based on Examples, the spunbond nonwoven fabric of the present invention will be described in detail.

(1) Melt flow rate (MFR) of polyolefin resin:

The melt flow rate of the polyolefin-based resin is measured in accordance with ASTM D-1238 under conditions of a load of 2160 g and a temperature of 230°C.

(2) single fiber fineness (dtex):

The obtained fiber is embedded in an epoxy resin, and then it is cut horizontally with respect to the fiber length direction with a microtome to obtain a sample piece. Then, a photograph of 1000 times was taken with a scanning electron microscope, and the area of the cross section of 50 arbitrary single fibers was measured. From the measured cross-sectional area and the solid density of the resin to be used, the weight per 10,000 m in length was used as the single fiber fineness, and it was calculated by rounding to two decimal places.

(3) spinning speed (m/min):

The spinning speed was calculated based on the following formula from the single fiber fineness and the discharge amount of the resin discharged from the spinneret single hole set under each condition (hereinafter, abbreviated as single hole discharge amount) (g/min).

-Spun speed (m/min)=(10000×[single hole discharge amount (g/min)])/[average single fiber fineness (dtex)].

(4) Flatness:

From the photograph taken at the single fiber fineness, the minor axis length a and the major axis length b of the single fiber cross section were measured, and the value obtained by dividing the major axis length b by the minor axis length a was defined as flatness.

(5) Weight per unit area of spunbond nonwoven fabric:

The weight per unit area of the spunbond nonwoven fabric is based on JIS L1913 (2010) 6.2 "Mass per unit area", 20 cm x 25 cm test pieces are sampled 3 pieces per 1 m width of the sample, and each mass in a standard state (g) was measured, and the average value was expressed as mass per 1 m ² (g/m ² ).

(6) Surface roughness SMD by KES method of spunbond nonwoven fabric:

In a standard test by the KES method, the surface roughness SMD of the spunbond nonwoven fabric was measured. First, three test pieces with a width of 200 mm × 200 mm are taken at equal intervals in the width direction of the spunbond nonwoven fabric, and using a KES-FB4-AUTO-A automated surface tester manufactured by Kato Tech, the test piece is set on the sample stand, and 10 gf of The surface of the test piece was scanned with a load-applied contactor for surface roughness measurement (material: phi 0.5 mm piano wire, contact length: 5 mm), and the average deviation of the surface concavo-convex shape was measured. This measurement was performed in the longitudinal direction (longitudinal direction of the nonwoven fabric) and the transverse direction (the width direction of the nonwoven fabric) of all test pieces, the average deviation of these six points was averaged and rounded to two decimal places, and the surface roughness SMD (μm) ) was made. The surface roughness SMD was measured on both sides of the spunbond nonwoven fabric, and the value of the smaller one of these was described in Table 1.

(7) Bending stiffness B by KES method of spunbond nonwoven fabric:

In a standard test by the KES method, the bending stiffness B value of the spunbond nonwoven fabric was measured. First, three specimens each having a width of 200 mm × 200 mm were taken in the warp direction (longitudinal direction of the nonwoven fabric) and the weft direction (the width direction of the nonwoven fabric). holding the sample with a chuck, holding the sample with a chuck at intervals of 1 cm, performing a forward bending test at a deformation rate of 0.50 cm ^-1 in a range of curvature -2.5 to +2.5 cm ^-1 , and averaging the measured values, The bending stiffness B value was obtained by rounding off the fourth decimal place.

(8) Aeration amount per unit area weight of spunbond nonwoven fabric:

According to 6.8.1 Frazier method of JIS L 1913 (2010), at a pressure of 125 Pa of a barometer, measurements were made for 20 arbitrary points in a nonwoven fabric of 80 cm × 100 cm, and the average value was calculated by rounding up to two decimal places. did. Then, the calculated airflow amount (cc/cm ² ·sec) is obtained from the weight per unit area (g/m ² ) obtained in (5) above, and the airflow amount per unit area weight per unit area is obtained by rounding up to two decimal places from the following formula. calculated.

·Aeration amount per weight per unit area = Aeration amount (cc/cm ² ·sec)/weight per unit area (g/m ² ).

(9) Tensile strength per unit area weight of spunbond nonwoven fabric:

According to 6.3.1 of JIS L1913 (2010), a tensile test was performed at three points in the MD and CD directions under the conditions of a sample size of 2.5 cm × 30 cm, a fixed spacing of 20 cm, and a tensile rate of 10 cm/min. The strength at the time was referred to as tensile strength (N/2.5 cm), and it was calculated by rounding off the average value to two decimal places. Then, from the calculated tensile strength (N/2.5 cm), from the weight per unit area (g/m ² ) calculated in (5) above, the following formula is rounded to two decimal places to calculate the tensile strength per weight per unit area did.

· Tensile strength per weight per unit area = tensile strength (N/2.5 cm)/weight per unit area (g/m ² ).

(Example 1)

A polypropylene resin containing a homopolymer having a melt flow rate (MFR) of 70 g/10 min is melted in an extruder, and the spinning temperature is 235 ° C. From a spinneret of flat cross section, a single hole discharge rate of 0.43 g / min. After cooling and solidification, the rectangular ejector was pulled and stretched by compressed air with an ejector pressure of 0.30 MPa, and collected on a moving net to obtain a nonwoven fibrous web containing polypropylene filaments. The obtained polypropylene long fibers had a single fiber fineness of 0.9 dtex, a flatness of 2.1, and a spinning speed converted from the single fiber fineness of 5,024 m/min. With respect to spinning, yarn breakage was not observed in spinning for 1 hour and was good.

Subsequently, the obtained nonwoven fibrous web was subjected to a pair of upper and lower heat embossing rolls composed of a metal flat roll as the lower roll and an embossing roll having an adhesive area ratio of 16% in which the metal polka dots were formed on the upper roll. was used, the linear pressure was 300 N/cm, and the thermal bonding temperature was 130° C. to obtain a spunbond nonwoven fabric having a weight per unit area of 18 g/m ² . The obtained spunbond nonwoven fabric was evaluated by measuring the surface roughness SMD, bending stiffness B, air permeability per weight per unit area, and tensile strength per weight per unit area. A result is shown in Table 1.

(Example 2)

A spunbond nonwoven fabric containing polypropylene filaments was obtained in the same manner as in Example 1, except that the MFR of the polypropylene resin containing the homopolymer was 200 g/10 min and the ejector pressure was 0.45 MPa. . The obtained polypropylene long fibers had a single fiber fineness of 0.8 dtex, a flatness of 1.6, and a spinning speed converted from the single fiber fineness of 5,492 m/min. With respect to spinning, yarn breakage was not observed in spinning for 1 hour and was good. The obtained spunbond nonwoven fabric was evaluated by measuring the surface roughness SMD, bending stiffness B, air permeability per weight per unit area, and tensile strength per weight per unit area. A result is shown in Table 1.

(Example 3)

A spunbond nonwoven fabric containing long polypropylene fibers was obtained in the same manner as in Example 1, except that 0.5% by mass of ethylenebisstearic acid amide was added as a fatty acid amide compound to the polypropylene resin containing the homopolymer. . The obtained polypropylene long fibers had a single fiber fineness of 0.9 dtex, a flatness of 2.1, and a spinning speed converted from the single fiber fineness of 5,037 m/min. With respect to spinning, yarn breakage was not observed in spinning for 1 hour and was good. The obtained spunbond nonwoven fabric was evaluated by measuring the surface roughness SMD, bending stiffness B, air permeability per weight per unit area, and tensile strength per weight per unit area. A result is shown in Table 1.

(Comparative Example 1)

Polypropylene in the same manner as in Example 1, except that the MFR of the polypropylene resin containing the homopolymer was 35 g/10 min, the single hole discharge rate was 0.83 g/min, and the ejector pressure was 0.20 MPa. A spunbond nonwoven fabric containing long fibers was obtained. The obtained polypropylene long fibers had a single fiber fineness of 2.7 dtex, a flatness of 2.9, and a spinning speed converted from the single fiber fineness of 3,074 m/min. With respect to spinning, yarn breakage was not observed in spinning for 1 hour and was good.

The obtained spunbond nonwoven fabric was evaluated by measuring the surface roughness SMD, bending stiffness B, air permeability per weight per unit area, and tensile strength per weight per unit area. A result is shown in Table 1.

Since the spunbond nonwoven fabrics of Examples 1 to 3 were composed of fine-fine flat cross-section yarns, they had a smooth surface and excellent feel, and had high flexibility and waterproofness. In addition, the fibers exhibited excellent mechanical strength by stretching at a high spinning speed while being fine. In addition, the spunbond nonwoven fabric of Example 3 to which ethylenebisstearic acid amide was added had more flexibility and was particularly suitable for use as a sanitary material.

On the other hand, in Comparative Example 1, since the single-fiber fineness was as thick as 2.7 dtex, the roughness of the surface was large even if it was composed of, for example, a flat cross-section yarn, and the touch and tactile feeling were inferior.

Although this invention was detailed and demonstrated with reference to the specific embodiment, it is clear for those skilled in the art that various changes and correction can be added without deviating from the mind and range of this invention. This application is based on the JP Patent application (Japanese Patent Application No. 2017-200994) of an application on October 17, 2017, The content is taken in here as a reference.

Claims (4)

A spunbond nonwoven fabric comprising a polypropylene-based resin, having a single fiber fineness of 0.5 to 1.0 dtex, and having a flat cross-section having a flatness of 1.5 or more, a spunbond nonwoven fabric composed of fibers with a flattened cross-section of at least one side, the surface roughness SMD by the KES method of at least one side is 1.0 to 3.0 μm, the average bending stiffness B according to the KES method is 0.001 to 0.020 gf·cm ² /cm, and the melt flow rate is 55 to 250 g/10 min. The spunbond nonwoven fabric according to claim 1, wherein the air permeability per unit area is 4 to 18 cc/cm ² ·sec/(g/m ² ). The spunbond nonwoven fabric according to claim 1 or 2, wherein the tensile strength per unit area in the warp direction is 1.0 N/2.5 cm/(g/m ² ) or more. delete

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