CN108699745A - Long-fiber nonwoven fabric with excellent skin feel - Google Patents

Abstract

There is provided the top flat of absorbent commodity or egative film component for being suitable for using in hygienic material, skin feel is good, the nonwoven fabric of long fibers with fluffy flexibility, the bulkiness few to the physical stimulation of skin.The non-woven fabrics of the present invention is characterized in that, it is thermally compressed non-woven fabrics for the part of the composite long fiber comprising two or more thermoplastic resin, the hot pressing socket part shape index of the non-woven fabrics is 0.05 or more and less than 1.9, the maximum scratch depth of pseudo- skin model is 10 μm hereinafter, and accumulative scratch depth is 80 μm or less.

Description

Long-fiber nonwoven fabric with excellent skin feel

technical field

The present invention relates to a partially thermocompression-bonded nonwoven fabric comprising composite long fibers of two or more thermoplastic resins, which has good skin feel, less physical irritation to the skin, and bulkiness.

Background technique

In general, for materials used in parts that come into contact with the skin, such as topsheets for sanitary materials such as paper diapers and sanitary napkins, emphasis is placed on having a soft texture that does not cause itching, tingling, pain, etc. due to fluff, and a good skin feel. Among them, less physical stimulation to the skin is important. Examples of the physical stimulation include stimulation at the end of the fiber and/or fluff generated from the fiber, and scratching stimulation due to them.

The non-woven fabric (hereinafter also referred to as "hot-air non-woven fabric") formed by thermally welding the intersecting part of the fiber by the hot air method to form a sheet (hereinafter also referred to as "hot air non-woven fabric") is fluffy and soft, and the intersecting part of the fiber is thermally welded. There is also less occurrence of fluff, so it is often used for these purposes. However, since this nonwoven fabric is composed of short fibers, the fiber ends are present on the surface, causing a tingling skin feeling, and furthermore, when the fiber ends rub against the skin, it causes scratching irritation, etc., which is unsatisfactory in terms of physical stimulation.

A non-woven fabric obtained by partially thermally fusing short fibers with an embossing roll (hereinafter also referred to as "point-bonded non-woven fabric"). Since the fiber ends exist on the surface like air-through non-woven fabrics, it is not affected by physical stimulation. The aspect is insufficient, and compared with the air-through non-woven fabric, the fiber intersections are not all bonded, so it is easy to fluff and the texture is poor.

On the other hand, as for the long-fiber non-woven fabric obtained by thermocompression-bonding the long-fiber non-woven fabric with an embossing roll, etc., the ends of the short fibers do not appear on the surface, and physical stimulation caused by the ends of the fibers is less likely to occur, but in order to prevent The fluff on the surface is excessively thermocompression-bonded, so the texture is hard and gives a rough skin touch, and the peripheral part of the thermocompression-bonded part becomes a cause of physical stimulation.

The following Patent Documents 1 and 2 disclose nonwoven fabrics obtained from thermoplastic conjugate fibers having good fuzz resistance and texture. However, thermoplastic fibers are flattened by thermal embossing and spot thermally pressure-bonded to improve fluffing, resulting in flattened thermally welded parts, and the bulkiness of the nonwoven fabric is impaired and the texture is poor. Furthermore, since the thermally welded portion is hard, physical stimulation due to friction is large.

In addition, the following Patent Document 3 discloses a polyolefin obtained by using a combination of a specific polyether compound and a specific polyether-modified silicon for a long-fiber nonwoven fabric partially thermocompression-bonded in a specific thermocompression bonding shape. It is non-woven fabric. The disclosed nonwoven fabric has good fuzz resistance and low physical irritation caused by friction, but since the polypropylene fibers are joined only by heat embossing, in order to make the fuzz resistance good, it is necessary to increase the number of thermally welded parts, and the bulk density is high. It does not have fluffy softness and is insufficient in these points.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2001-355176

Patent Document 2: Japanese Patent Laid-Open No. 2000-290866

Patent Document 3: Japanese Patent Laid-Open No. 2003-52752

Contents of the invention

The problem to be solved by the invention

The problem to be solved by the present invention is to provide a long-fiber nonwoven fabric suitable for the top sheet or back sheet member of absorbent articles used in hygienic materials, which has good skin touch, has bulky softness, and has bulkiness with less physical irritation to the skin. cloth.

solutions to problems

The inventors of the present invention conducted intensive studies and repeated tests in order to solve the aforementioned problems. As a result, they found that, for a nonwoven fabric composed of composite long fibers containing two or more thermoplastic resins, the nonwoven fabric before joining in the production process of the nonwoven fabric The air permeability of the nonwoven web, the hot air temperature and wind speed during bonding can be set in a certain range so that the hot air can pass through while maintaining the fluffy state of the nonwoven web, and the fiber intersections can be bonded, thereby improving the fuzz resistance and maintain the bulk density, thereby providing a nonwoven fabric that is less physically irritating to the skin and can be suitably used as a hygienic material.

That is, the present invention is as follows.

[1] A nonwoven fabric characterized in that it is a partially thermocompression-bonded nonwoven fabric comprising composite long fibers of two or more thermoplastic resins, and the thermocompression bonded part shape index of the nonwoven fabric is 0.05 or more and If it is less than 1.9, the maximum scratch depth of the pseudo-skin model is 10 μm or less, and the cumulative scratch depth is 80 μm or less.

[2] The nonwoven fabric according to the above [1], wherein the surface fuzz index of the nonwoven fabric is 3 or more.

[3] The nonwoven fabric according to [1] or [2] above, wherein the nonwoven fabric has a vertical and horizontal average of friction coefficient variation (MMD) of 0.015 or less.

[4] The nonwoven fabric according to any one of [1] to [3] above, wherein the nonwoven fabric has an orientation index in the thickness direction based on X-ray CT of 0.43 or less and a bulk density of 0.01 or more And 0.07g/cm ³ or less.

[5] The nonwoven fabric according to any one of [1] to [4], wherein the nonwoven fabric has a compression work WC of 0.20 to 1.00 gf/cm/cm ² .

[6] The nonwoven fabric according to any one of [1] to [5] above, wherein the composite long fibers are of a side-by-side type or an eccentric type.

[7] The nonwoven fabric according to any one of [1] to [6] above, wherein the two types of thermoplastic resins are both polyolefin-based resins.

[8] The nonwoven fabric according to any one of [1] to [7], wherein the nonwoven fabric contains a hydrophilic agent.

[9] A hygienic material comprising the nonwoven fabric according to any one of [1] to [8].

The effect of the invention

The non-woven fabric of the present invention is a non-woven fabric composed of composite long fibers containing two or more thermoplastic resins, and the non-woven fabric is configured by adjusting the non-woven fabric so that it exhibits specific friction characteristics and a shape index of a thermocompression bonded part. The bonding degree of the fibers of the spun fabric is small, so that the physical irritation to the skin is small, the fuzz resistance is good, the texture is soft, and it can be suitable for use as a hygienic material.

Detailed ways

Embodiments of the present invention will be described in detail below.

The composite long fibers constituting the nonwoven fabric of this embodiment contain a combination of two or more thermoplastic resins. Examples of thermoplastic resins include polyolefin-based resins such as polyethylene, polypropylene, and copolymerized polypropylene, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Polyester-based resins such as esters and co-polyesters, polyamide-based resins such as nylon-6, nylon-66, and co-polyesters, polylactic acid, polybutylene succinate, polyethylene succinate, etc. Degradable resins, etc. Any combination of the aforementioned thermoplastic resins may be used as long as desired effects are exhibited, but a combination of thermoplastic resins having a difference in melting point is preferable from the viewpoint of bondability between fibers.

Among these, polyolefin-based resins are preferably used in combination from the viewpoint of texture. For example, a conjugate fiber obtained by combining polyethylene, polypropylene, or a copolymer of these monomers and other α-olefins may be used. Examples of other α-olefins include α-olefins having 3 to 10 carbon atoms, specifically, propylene, 1-butene, 1-pentene, 1-hexane, and 4-methyl-1-pentene , 1-octene, etc.

When the fiber shape of the thermoplastic conjugate fiber of this embodiment is a side-by-side type (S/S) or an eccentric type (slant S/C), crimped yarn is easily obtained, which is preferable. An eccentric core may appear on the fiber surface, and the area ratio of the core to the fiber surface is preferably 0 to 50%, more preferably 0 to 30%. The lower the ratio of the core part forming the fiber surface, the higher the ratio of the sheath part caused by bonding, and high strength and fuzz suppression can be obtained. In addition, from the viewpoint of the strength of the fiber, in the combination of thermoplastic resins, the weight ratio of the resin with a relatively high melting point in the fiber is 20 wt % or more and 80 wt % or less, preferably 30 wt % or more and 80 wt % or less, more preferably 50 wt% or more and 70 wt% or less.

The fiber shape may be not only ordinary round fibers but also fibers of special shapes such as irregularly shaped fibers.

When the composite long fibers are formed from two kinds of thermoplastic resins, it is preferable that the first component is polypropylene and the second component is polyethylene. When the conjugate fiber is an eccentric type, it is preferable to make the core part the first component and the sheath part the second component. Polypropylene is preferred because it has high strength, is not easily broken during use, and has excellent dimensional stability during production of sanitary materials.

When the above-mentioned first component polypropylene is formed of two types of thermoplastic resins, it may be a polymer synthesized using a conventional Ziegler-Natta catalyst, or a polymer synthesized using a single-site active catalyst represented by a metallocene , In addition, ethylene random copolymerized polypropylene may also be used. These may be used alone or in combination of two or more. From the viewpoint of texture, strength, and dimensional stability, it is preferable to use homopolypropylene as the main component.

In addition, the lower limit of the MFR of polypropylene may be 20 g/10 minutes or more, preferably more than 30 g/10 minutes, more preferably more than 40 g/10 minutes, most preferably more than 53 g/10 minutes. The upper limit may be 85 g/10 minutes or less, preferably 70 g/10 minutes or less, most preferably 60 g/10 minutes or less. The measurement method of MFR is based on Table 1 of JIS-K7210 "Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) Test Methods of Plastics-Thermoplastics", the test temperature is 230° C., and the test load is 2.16 kg.

When the polyethylene as the second component is formed of two types of thermoplastic resins, it can be suitably used for hygienic materials because of its high bonding strength after joining fibers and good texture as a nonwoven fabric. In addition, polyethylene may be a polymer synthesized using a conventional Ziegler-Natta catalyst, or a polymer synthesized using a single-site active catalyst represented by a metallocene. The polyethylene is preferably high-density polyethylene or linear low-density polyethylene, and the density is preferably 0.92 to 0.97 g/cm ³ , more preferably 0.925 to 0.96 g/cm ³ .

In addition, the lower limit of MI of polyethylene may be 10 g/10 minutes or more, preferably more than 15 g/10 minutes. The upper limit may be 100 g/10 minutes or less, preferably 60 g/10 minutes or less, most preferably 40 g/10 minutes or less. The measurement method of MI is based on Table 1 of JIS-K7210 "Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) Test Methods of Plastics - Thermoplastics", the test temperature is 190° C., and the test load is 2.16 kg.

The nonwoven fabric of the present embodiment is preferably manufactured by forming a composite filament nonwoven web sheet by a spunbond method from the viewpoint of strength and productivity. For example, for composite long fibers, different thermoplastic resins are melt-extruded from two or more different extruders, and a sliver is formed in a state where two or more thermoplastic resins are composited from a spinneret having a plurality of spinneret holes. form ejected. Next, cool air controlled at 5°C to 20°C is applied to the ejected sliver, and it is pulled at a high speed by a pulling device while cooling. The sliver leaving the drawing device is accumulated on a conveyor belt and transported in the form of a nonwoven web. The nonwoven web in transit can be laminated to form a multilayer laminated nonwoven web.

The method of joining nonwoven web sheets made of thermoplastic conjugate fibers to form a nonwoven fabric is not particularly limited as long as it is heated to a temperature above which the intersection points of fibers can be melted and bonded. As the heating method, various heating methods such as hot air circulation type, hot air passing type, infrared heater type, method of blowing hot air on both sides of the nonwoven fabric, method of introducing heated air, etc. can be used. From the viewpoint of obtaining more fiber bonding points at intersections between fibers and increasing the breaking strength of the nonwoven fabric, heating by hot air is preferred, and a hot air passing type is particularly preferred.

The temperature of the hot air is preferably adjusted to be suitable for a thermoplastic resin having a low melting point and contributing to bonding among the thermoplastic resins to be combined. For example, when the thermoplastic resin is polyethylene, it is 130°C to 155°C, preferably 135°C to 155°C, more preferably 140°C to 150°C, at which the polyethylene is melted and bonded. If the bonding temperature is within this range, the bonding of fibers will be expressed at the intersection points of fibers, and the strength as a nonwoven fabric can be expressed.

Next, the wind speed of the hot air is 0.5 to 3.0 m/s, preferably 0.7 to 2.5 m/s, more preferably 2.0 m/s or less.

When the nonwoven web of this embodiment is joined by hot air, the air permeability of the nonwoven web significantly affects the joining state. When the air permeability of the nonwoven web sheet is too low, it is difficult for hot air to pass through, and it is difficult to obtain uniform bonding as a nonwoven fabric. On the other hand, it is not preferable that the air permeability is too high from the viewpoint of maintaining the strength of the obtained nonwoven fabric. The air permeability of the finally obtained nonwoven fabric, which satisfactorily maintains the joint strength, is preferably 300 cm ³ /cm ² /s or more and 700 cm ³ /cm ² /s or less, more preferably 300 cm ³ /cm ² /s s or more and 650 cm ³ /cm ² /s or less.

In this specification, "thermocompression bonded part shape index" refers to the ratio of the part of the thermocompression bonded part formed on the surface of the nonwoven fabric bonded by embossing rolls, hot air treatment, etc. The perimeter specification of a weld in a certain area. The welded area ratio refers to the proportion of the area of the welded part of the long-fiber non-woven fabric to the overall area of the non-woven fabric, and the welded perimeter in each certain area refers to the proportion of the welded area of the long-fiber non-woven fabric per 20 square millimeters The sum of the perimeters of the included welds. Here, although the fusion of the fiber intersection occurs, when the fusion of the fiber intersection is exposed on the surface in contact with the skin, the fiber surface including the fiber intersection forms a welded portion and is thinned, and is included in the fusion area and the fusion circumference.

Examples of the site where the nonwoven fabric contacts the skin and causes physical irritation include short fiber ends on the contact surface of the nonwoven fabric and fluffing on the surface. In addition, for non-woven fabrics including long-fiber non-woven fabrics thermally bonded by embossing rolls, etc., short fiber ends do not appear on the surface of the non-woven fabric, and physical stimulation caused by fiber ends is less likely to occur, but in order to prevent If the surface is fluffed and the thermocompression bonding area is too large, or if the thermocompression bonding pressure is too large and the unevenness of the peripheral part of the welded part is deep, not only the texture will deteriorate, but also the peripheral part of the thermocompression bonding part will become a source of physical stimulation. reason. That is, when the area ratio of thinning by welding is high, the nonwoven fabric becomes hard, and the scratching stimulation is large when rubbed, causing scratches to the skin. In addition, regarding the peripheral portion of the thermally welded portion, the thermally bonded portion becomes a concave portion, and the non-thermally bonded portion becomes a convex portion. The difference between the unevenness is large, and the peripheral portion of the welded portion on the surface of the nonwoven fabric is caught on the skin surface during friction, which becomes Cause of scratches. That is, the ratio of the welded area and the circumference of the welded portion are closely related to scratches during friction. When the shape index of the thermocompression bonded part of the nonwoven fabric is large, the occurrence of fluff of the nonwoven fabric is suppressed, and it is possible to prevent poor touch such as itching and tingling caused by fluff, but the hard part due to thinning Causes physical irritation to skin. On the other hand, when the shape index of the thermocompression-bonded part of the nonwoven fabric is small, the physical stimulation caused by contacting the skin with the thinned hard part becomes small, and the fluffy texture of the nonwoven fabric is good. However, when the shape index of the thermocompression bonded part is too small, the nonwoven fabric cannot obtain practically sufficient strength, and fluffing tends to occur due to friction, and physical stimulation due to fluffing causes poor tactile sensations such as itching and tingling. In view of the above, in the present embodiment, the "thermocompression bonding portion shape index" must be 0.05 or more and less than 1.9. If the shape index of the thermocompression bonding part is less than 0.05, it is not preferable from the viewpoint of preventing fluff, and if it exceeds 1.9, the fluffy texture will be impaired, and it is not preferable from the viewpoint of volume feeling and swelling feeling during compression. The "shape index of thermocompression bonded portion" is more preferably 1.8 or less, and more preferably 1.5 or less. The "shape index of thermocompression bonded portion" is more preferably 0.1 or more, and more preferably 0.3 or more.

Assuming that it is used as a top sheet of sanitary materials, the nonwoven fabric of this embodiment must have a maximum scratch depth of the pseudo-skin model of 0 μm to 10 μm, and a cumulative scratch depth of 0 μm to 80 μm. The maximum scratch depth and cumulative scratch depth of the pseudo-skin model refer to the following measurement method, when a non-woven fabric in contact with the skin is rubbed with a pseudo-skin model with an initial compressive stress of 98mN/cm ² . The maximum scratch depth of scratches formed on the surface and the cumulative scratch depth of scratches. The "scratch" as used herein refers to a change in the physical surface shape of the pseudo-skin model caused by the non-woven fabric caused by rubbing the non-woven fabric against the pseudo-skin model. When the maximum scratch depth exceeds 10 μm, it is not preferable from the viewpoint of physical stimulation to the skin, and it is more preferably 9 μm or less. In addition, it is not preferable that the cumulative scratch depth exceeds 80 μm, and it is more preferably 60 μm or less, and still more preferably 50 μm or less.

That is, the frictional irritation of the nonwoven fabric is expressed on the pseudo-skin phantom as the number of scratches, the depth of scratches, and the width of scratches according to the degree of physical stimulation caused by friction with the pseudo-skin phantom. The surface of the pseudo-skin model was adjusted and used so that the surface was flat, but fine unevenness on the surface before the friction stimulus was applied was not regarded as a scratch. For the pseudo-skin model with the same composition, the maximum scratch depth and the cumulative scratch depth of the scratches are used for comparative evaluation, so that the degree of friction stimulation of non-woven fabrics can be compared.

A number of research team members studied the maximum scratch depth and cumulative scratch depth of scratches caused by friction between non-woven fabric and pseudo-skin model, and physical irritation caused by friction between non-woven fabric and actual skin It can be confirmed that the non-woven fabric with the larger maximum scratch depth and cumulative scratch depth tends to feel stronger stimulation when actually rubbing the skin with the non-woven fabric. After observing the condition of the skin surface after rubbing When , it can be confirmed that the disappearance of the skin texture also tends to be large. Based on the results, the maximum scratch depth and cumulative scratch depth of scratches generated by rubbing the pseudo-skin phantom with the nonwoven fabric were measured, thereby evaluating the rubbing irritation of the nonwoven fabric in contact with the skin to the skin. According to studies by the present inventors, it has been found that when the maximum scratch depth exceeds 10 μm and the cumulative scratch depth exceeds 80 μm, the frictional stimulation of the nonwoven fabric in contact with the skin is large and the skin is easily scratched.

In the present embodiment, the "surface fluff index" of the nonwoven fabric is preferably 3 or more. When the surface fluff index is less than 3, fluffing occurs on the surface of the nonwoven fabric due to friction with the skin, etc., giving a stinging skin feeling, and furthermore, physical stimulation is formed on the skin surface due to friction.

In the present embodiment, the vertical and horizontal average values of the variation values (MMD) of the coefficient of friction of the nonwoven fabric are preferably 0.015 or less. When it exceeds 0.015, it is not preferable in terms of smoothness to the touch of the skin and little physical irritation, and it is more preferably 0.017 or less, and still more preferably 0.015 or less.

The friction with the skin has both longitudinal and transverse directions, and it is preferable that the coefficient of friction in either direction is low, smooth and has little resistance. However, when there is a difference in the magnitude of the frictional resistance between the longitudinal and lateral directions, the stress of the frictional resistance is concentrated in the direction where the friction coefficient values in the longitudinal and lateral directions are small, and as a result, the frictional resistance stresses in the longitudinal and lateral directions are averaged. Therefore, the vertical and horizontal average values of the variation values of the coefficient of friction are important as a value representing the load of physical stimulation to the skin.

This is because the averaging of the frictional resistance stress occurs in relation to the difference in the size of the frictional resistance, and in the longitudinal and lateral values of the deviation value of the friction coefficient, the deviation value of the friction coefficient in the smaller direction is different from that in the larger direction. When the ratio of the variation of the coefficient of friction exceeds 20 times, the influence of the value in the larger direction becomes greater, and even if the vertical and horizontal average of the variation of the friction coefficient is 0.015 or less, the skin feel becomes rough.

The orientation index by X-ray CT of the nonwoven fabric of this embodiment is preferably 0.43 or less, more preferably 0.425 or less. When the orientation index based on X-ray CT is in this range, the number of fibers occupying the thickness direction of the nonwoven fabric increases, and the bulkiness is not destroyed even under a load, and a nonwoven fabric with bulkiness can be obtained, and excellent cushioning properties can be obtained. of non-woven fabrics. The lower limit is better, and is preferably 0.30 or more, more preferably 0.33 or more.

In order to improve the fiber orientation in the thickness direction of the nonwoven fabric, it is important to control the hot air temperature and wind speed in the joining process of the nonwoven fabric, and the air permeability of the nonwoven web. When the hot air temperature is high, the solubility of the fiber surface becomes very high, and the texture becomes hard. When the hot air speed is fast, the hot air passes through, but the fibers also collapse at the same time, becoming a non-woven fabric with low bulkiness. Furthermore, when the air permeability of the nonwoven web is too low, hot air cannot pass through it, and when it is too high, the hot air cannot apply enough heat to the fiber intersections to melt them, so it is difficult to form fiber bonding points with both bulkiness and strength. The bulk density of the nonwoven fabric of this embodiment is preferably in the range of 0.01 g/cm ³ to 0.07 g/cm ³ , more preferably 0.03 g/cm ³ or more from the viewpoint of strength, and more preferably from the viewpoint of texture. Make it 0.07g/cm ³ or less.

The compression work WC of the nonwoven fabric of this embodiment is preferably 0.20 gf cm/cm ² or more and 1.00 gf cm/cm ² or less, more preferably 0.25 gf cm/cm ² or more and 0.80 gf cm cm 2 ² or less. It is preferable to maintain the compression work WC in this range from the viewpoint of the cushioning properties of the nonwoven fabric used for sanitary materials.

The average monofilament fineness of the conjugated filaments constituting the nonwoven fabric of the present embodiment is preferably from 0.5 dtex to 10.0 dtex, more preferably from 0.7 dtex to 8.0 dtex, still more preferably from 0.9 dtex to 5.0 dtex. It is preferably 0.5 dtex or more from the viewpoint of spinning stability, and preferably 10.0 dtex or less from the viewpoint of the texture of a nonwoven fabric used for sanitary materials.

The aforementioned composite long fibers preferably have spiral crimps from the viewpoint of maintaining the texture and bulkiness of the nonwoven fabric. The number of crimps of the fibers is preferably 5 crimps/inch to 45 crimps/inch, more preferably 10 crimps/inch to 40 crimps/inch. When the number of crimps is less than 5 crimps/inch, the bulkiness of the nonwoven fabric obtained is insufficient, and when it exceeds 45 crimps/inch, the appearance of the nonwoven fabric obtained is impaired due to non-uniform fiber dispersion.

The weight per unit area of the nonwoven fabric of this embodiment is preferably 8 g/m ² to 80 g/m ² , more preferably 10 g/m ² to 40 g/m ² , still more preferably 10 g/m ² to 30 g / ^m2 or less. If it is more than 8g/m ² , it will satisfy the strength of the nonwoven fabric used for sanitary materials ^; It will give the impression of being thick in appearance.

The nonwoven fabric of this embodiment may contain a hydrophilic agent. As the hydrophilic agent used, in consideration of the safety to the human body and the safety in the process, etc., it is preferable to use a non-ionic system such as a higher alcohol, a higher fatty acid, an alkylphenol, etc., to which ethylene oxide has been added, alone or in a mixture. Active agents, anionic active agents such as alkyl phosphate ester salts and alkyl sulfates, etc.

As a method of containing a hydrophilic agent, it is preferable to use a diluted hydrophilic agent in general, using existing methods such as a dipping method, a spray method, and a coating (kiss coater, gravure coater, die coater) method, according to It is necessary to dilute and apply the pre-mixed hydrophilic agent with a solvent such as water.

When the hydrophilic agent is diluted with a solvent such as water and applied, a drying step may be required. As the drying method at this time, conventional methods using convective heat transfer, conductive heat transfer, radiation heat transfer, etc. can be used, and drying methods using hot air, infrared rays, or thermal contact, etc. can be used.

The amount of the hydrophilic agent attached varies depending on the required performance, but usually it is preferably in the range of 0.05% by weight to 1.00% by weight relative to the fiber, more preferably 0.15% by weight to 0.8% by weight, and still more preferably 0.2% by weight Above and below 0.6% by weight. When the adhesion amount is within this range, the hydrophilic performance of the top sheet as a sanitary material is satisfied, and the processing suitability is also improved.

When the non-woven fabric is treated with a hydrophilic agent to improve its hydrophilicity and used as a top sheet of sanitary materials, urine and blood will pass through the surface of the non-woven fabric, so it will not remain on the skin and reduce chemical irritation such as ammonia. The physical stimulation to the skin is small, and it is not easy to scratch the skin, so it is not easy to cause inflammation such as dermatitis under chemical stimulation.

The nonwoven fabric of the present embodiment uses a composite long-fiber nonwoven fabric containing two or more thermoplastic resins, and is realized by adjusting the welded part of the surface that contacts the skin. Since the composite long-fiber nonwoven fabric is used, a part of the fiber intersection is not completely thinned, but the low-melting point component of the composite fiber is thermally bonded, so when it comes into contact with the skin, the degree of freedom of the fiber is not impaired, and Stress concentration does not occur in the thinned part, so physical stimulation is reduced. In addition, the strength in use and the prevention of fluff are realized by thermal fusion bonding of fiber intersections.

The degree of freedom of the constituent fibers of the long-fiber nonwoven fabric depends on the degree of thermal fusion bonding of the thinned part and the low-melting point component of the conjugate fiber by thermocompression bonding, etc., and is represented by the toughness index of the long-fiber nonwoven fabric. The toughness index is a value obtained by dividing the product of the breaking elongation and the breaking elongation of the nonwoven fabric by the basis weight of the nonwoven fabric, and is preferably 40 to 250, more preferably 50 to 150.

Example

Although the present invention is specifically described using examples, the present invention is not limited to these examples.

Various properties of the nonwoven fabrics in Examples were measured by the following methods.

The evaluation method of each characteristic is as follows, and the obtained physical properties are shown in Table 1 below. Hereinafter, the flow direction of fibers, which is the line direction, is referred to as MD direction, and the direction perpendicular to the flow direction of fibers, that is, the width direction is referred to as CD direction.

(1) Average monofilament fineness (dtex)

A 1 cm square test piece was sampled, and the fiber diameters at 20 points were measured one by one with a microscope VHX-700F manufactured by Keyence Corporation, and the fineness was calculated from the average value.

(2) Weight per unit area (g/m ² )

According to JIS-L1906, 5 test pieces of 20 cm in MD direction x 5 cm in CD direction were collected arbitrarily, the mass was measured, and the average value thereof was converted into weight per unit area to obtain it.

(3) Air permeability (cm ³ /cm ² /s)

Measured according to the Fraser method described in JIS L-1096. Ten points were collected and measured, and the average value of the measured values was calculated.

(4) Number of crimps

Sampling a 5 cm square test piece at 5 points along the CD direction, using a microscope VH-Z450 manufactured by Keyence, measured the number of crimps per 1 inch (2.54 cm) under the condition that no load was applied to the fibers in the test piece, and obtained the average The value calculates the number of crimps.

(5) Maximum scratch depth and cumulative scratch depth

(1) From an arbitrary position of the nonwoven fabric, prepare 3 samples of 5 cm x 5 cm.

(II) A sample is attached to the friction terminal of the Kato Tech Co., Ltd. friction tester (KES-SE).

(III) Using the above-mentioned friction testing machine, rub the sample against the pseudo-skin model with an initial compressive stress of 98mN/cm ² described later under the conditions of a contact pressure of 4.9×10 ³ Pa, a contact area of 1 cm ² , and a friction distance of 2 cm for 1 Second-rate.

(IV) Use a non-contact laser measuring machine to measure the central part of the friction trace with a width of 1 cm and a friction direction of 2 cm on the surface of the pseudo-skin model, the maximum scratch depth of a width of 1 cm in the direction perpendicular to the friction direction, and the cumulative friction. depth of injury.

(V) Measure the maximum scratch depth and cumulative scratch depth on the surface of the pseudo-skin model when 10 positions are rubbed at 1 cm intervals in the vertical and horizontal directions of the sample, and take the vertical and horizontal average as the maximum scratch of the sample piece Depth, cumulative scratch depth. The maximum scratch depth and cumulative scratch depth of the sample are the average values of the above three points.

[Manufacturing method of pseudo-skin model]

1 part of agar (AGAR POWDER, manufactured by Wako Pure Chemical Industries, Ltd., reagent) and 8 parts of gelatin (manufactured by GIFCO, reagent) were dissolved in 91 parts of water, and used after solidification in a refrigerator. Adjust in such a way that the surface becomes flat.

The initial compressive stress refers to the compression when the pseudo skin model is measured with a compression area of 200 mm ² and a compression speed of 0.1 mm/sec using a portable compression tester KES-G5 (manufactured by Kato Tech Co., Ltd.) when a displacement of 0.1 mm is performed stress. Fine-tune the amount of water added to match the initial compressive stress as needed.

(6) Shape index of thermocompression joint

(1) Collect a sample of 5 cm × 5 cm from any position of the non-woven fabric.

(II) 25 samples of 1 cm x 1 cm were produced from the above-mentioned samples, and the surface was photographed with a microscope to obtain 25 magnified photos of 25 times.

(III) The ratio of the area of the welded portion of the nonwoven fabric to the surface area of the nonwoven fabric was determined from the obtained photograph.

(IV) From the obtained photographs, a value representing the sum of the perimeter lengths of the welded and thinned portions included in a constant area of 20 mm2 was obtained.

(V) The shape index of the thermocompression bonded portion was obtained by using the following formula (1). The average value of the above-mentioned 25 points was used as the shape index of the thermocompression bonded portion.

Shape index of thermocompression joint = ratio of thermally welded area × length of weld perimeter in a certain area (1)

{In the formula, the ratio of welded area: the ratio of the area of the welded part of the long-fiber non-woven fabric to the overall area of the long-fiber non-woven fabric; The sum of the perimeters of the welds. }

(7) Deviation value of friction coefficient

(1) Prepare three samples of 6 cm x 8 cm from any position of the nonwoven fabric.

(II) A sample is mounted on the measuring table of the Kato Tech Co., Ltd. friction tester (KES-SE).

(III) Use the sample and the standard friction terminal (10mm square metal wire terminal) of the friction tester to measure the deviation value (MMD) of the friction coefficient with a test load of 25g/ ^cm2 , and measure the vertical and horizontal average values of the sample.

(8) Surface fluffing index

According to JIS P 8136, it implemented by the following method.

(1) Three samples with a length of 25 cm and a width of 3 cm are produced from any position of the nonwoven fabric.

(II) Paste the sample on the sample table of the abrasion resistance testing machine, and install the No. 3 plain cotton cloth (4cm×5cm) on the friction member.

(III) A rubbing element (500 g) was placed on the nonwoven fabric, and a rubbing test was performed by counting 100 times of reciprocation.

(IV) Sensory evaluation of the fuzzy state of the surface of the nonwoven fabric after rubbing. According to the following judgment criteria, it represented by the average value of 3 points.

[Evaluation criteria: surface fluffing index]

5 points|pieces: The fluff by friction was not observed, and the damage by surface friction was not confirmed.

4 points: A change in surface shape due to friction was slightly confirmed, but fluffing was not confirmed.

3 points|pieces: Fluff by rubbing was observed slightly, but the number of the fiber ends which peeled off was 10 or less.

2 points: Fluffing due to friction is observed, and 11 or more and 49 or less fibers are confirmed to be peeled off.

1 point: A large amount of fuzzing occurred due to friction, and 50 or more peeled fiber ends were confirmed.

(9) Orientation index (X-ray CT)

Randomly cut out a test piece of 5 mm in MD direction x 5 mm in CD direction, and measure it with a field of view of about 3 mm x 3 mm during image analysis. The measurement device uses a high-resolution 3D X-ray microscope nano3DX (manufactured by Rigaku Co., Ltd.), and performs CT measurement by low-energy high-intensity X-rays that can obtain contrast even for light elements. Detailed conditions are shown below.

X-ray target: Cu

X-ray tube voltage: 40kV

X-ray tube current: 30mA

Lens: 1.08μm/pix

Sub-warehouse: 2

Rotation angle: 180°

Number of projections: 1000

Exposure time: 10 seconds/picture

Camera pixel count: 3300×2500

Reconstruction: Feldkamp method

Image analysis was performed on the three-dimensional tomograms obtained by CT measurement, and orientation indices Ix, Iy, and Iz of three orthogonal axes (x, y, z) were obtained. The thickness direction of the sample mainly to be evaluated is aligned with the z direction. Here, the orientation index Ix, Iy, and Iz refer to the sum of the area of the fiber surface observed from each direction of x, y, and z (the sum of the total projected area of each layer of the fiber surface in each direction) Ax, Ay, and Az are defined as follows.

Ix=Ax/(Ax+Ay+Az)

Iy=Ay/(Ax+Ay+Az)

Iz=Az/(Ax+Ay+Az)

Ax, Ay, and Az were obtained from X-ray tomograms. In this index, the orientation is in the direction with a smaller value. In addition, both are 1/3 in the isotropic structure.

(10) Bulk density (g/cm ³ )

10 cm of both ends of the fabric sample of the nonwoven fabric were removed, and 20 points were measured with a peacock-shaped thickness gauge (5 g/4 cm ² ) so as to be uniform in the width direction, and the average thickness was calculated. From this average value, the bulk density was calculated using the following formula.

Bulk density (g/cm ³ ) = weight per unit area (g/m ² )/thickness (mm)/1000

(11) Compression power (WC)

A 5-cm-square test piece at 5 points was collected along the CD direction, and measured using a compression tester (KES-G5) manufactured by Kato Tech Co., Ltd. The test piece was set on a metal sample stand, and compressed between steel plates having a circular plane with a pressurized area of 2 cm ² . The compression speed was set to 0.067 mm/s, and the maximum compression load was set to 3.4 kPa (35 gf/cm ² ). The recovery process is also measured at the same speed, and the average value of the compression work is calculated.

(12) Texture

The softness of the sample was judged by the sensory evaluation by 5 monitors. The texture of the samples was classified as "hard" or "soft" and judged by an average of 5 people.

(13) Toughness Index

According to JIS L-1906, collect 5 samples of 20 cm in the MD direction and 5 cm in the CD direction, and use a tensile testing machine to carry out a longitudinal tensile test with a grip interval of 100 mm and a tensile speed of 300 mm/min. According to the measured breaking strength and The elongation at break and the toughness index were calculated from the following formula.

Toughness index = breaking strength (N/50mm) x breaking elongation (%)/weight per unit area (g/m ² )

[Examples 1 to 3, Comparative Examples 1 and 2]

A polypropylene (PP) resin with an MFR of 55g/10min (measured at a temperature of 230°C and a load of 2.16kg according to JIS-K7210) is used as the first component, and an MI of 26g/10min (measured at a temperature of 190°C according to JIS-K7210 , Load 2.16kg measurement) high-density polyethylene (HDPE) resin as the second component, the discharge amount of the first component is 0.4g/min per hole, the discharge rate of the second component is 0.4g/min per hole and The total single-hole ejection amount is 0.8g/min per hole, the fiber shape is set as an eccentric sheath core structure, and the ratio of the first component to the second component is 50/50 by spunbonding at a spinning temperature of 220°C The fibers were extruded to the moving collection surface at a spinning speed of 3000 m/min using an air-jet-based high-speed airflow traction device to prepare a long-fiber nonwoven web sheet with an average single-filament fineness of 2.8 dtex.

Next, hot air with a hot air temperature of 142° C. and a hot air velocity of 0.7 m/s was passed through the obtained nonwoven web, and then pressure bonding was performed with a thermal pressure bonding roll formed by combining an engraved roll and a smooth roll. Adjust the conveying speed when the hot air is passed, the temperature and pressure of the thermocompression bonding roller, the speed of the conveyor belt and the take-up device, and obtain the specified thermocompression bonding part shape index of Examples 1 to 3, Comparative Examples 1 and 2, A composite long-fiber nonwoven fabric with an average monofilament fineness of 2.8 decitex, a crimp number of 30/inch, and a weight per unit area of 20 g/m ² .

[Example 4]

The composite long-fiber nonwoven fabric obtained in the same manner as in Example 2 was passed through a corona discharge treater under the condition of a discharge capacity of 40 W·min/m ² (discharge degree 4.0 W/cm ² ) in an atmosphere at room temperature of 22°C to obtain Non-woven fabric with a wetting tension of 39mN/m. A polyether-based hydrophilic agent was applied to the obtained nonwoven fabric by a spray method, followed by hot air drying at 110° C. for 30 seconds to obtain a long-fiber nonwoven fabric having a chemical concentration adhesion of 0.3% by weight. The obtained nonwoven fabric had satisfactory properties as a top sheet of a diaper.

[Example 5]

A polypropylene (PP) resin with an MFR of 40g/10min (measured at a temperature of 230°C and a load of 2.16kg according to JIS-K7210) is used as the first component, and an MI of 26g/10min (measured at a temperature of 190°C according to JIS-K7210 , Load 2.16kg measurement) high-density polyethylene (HDPE) resin as the second component, the discharge amount of the first component is 0.4g/min per hole, the discharge rate of the second component is 0.4g/min per hole and The total single-hole ejection amount is 0.8g/min per hole, the fiber shape is set as an eccentric sheath core structure, and the ratio of the first component to the second component is 50/50 by spunbonding at a spinning temperature of 235°C The fibers are extruded to the moving collection surface at a spinning speed of 2500m/min by using a cold air-driven air draft device to prepare a long-fiber nonwoven web sheet with an average single filament fineness of 2.8dtex.

Next, hot air with a hot air temperature of 145° C. and a hot air velocity of 1.0 m/s was passed through the obtained nonwoven web to thermally bond the nonwoven fabric. The conveying speed and the speed of the take-up device were adjusted to obtain a composite long-fiber nonwoven fabric with a predetermined thermocompression bonded portion shape index and a weight per unit area of 20 g/m ² when the hot air was passed.

[Example 6]

The composite long-fiber nonwoven fabric obtained in the same manner as in Example 5 was passed through a corona discharge treater under the condition of a discharge capacity of 40 W·min/m ² (discharge degree 4.0 W/cm ² ) in an atmosphere at room temperature of 25° C. to obtain Non-woven fabric with a wetting tension of 39mN/m. A polyether-based hydrophilic agent was applied to the obtained nonwoven fabric by a spray method, followed by hot air drying at 120° C. to obtain a long-fiber nonwoven fabric having a chemical concentration adhesion amount of 0.35% by weight. The obtained nonwoven fabric had satisfactory properties as a top sheet of a diaper.

[Comparative example 3]

A polypropylene (PP) resin with an MFR of 55g/10min (measured at a temperature of 230°C and a load of 2.16kg according to JIS-K7210) was extruded as a single component by a spunbond method at a spinning temperature of 220°C, using an air-jet based The high-speed airflow traction device extrudes the filament group to the moving collection surface at a spinning speed of 3000m/min to prepare a long-fiber nonwoven web sheet with an average single filament fineness of 2.8dtex.

Next, the obtained nonwoven mesh was passed between a flat roller at 141°C and an embossed roller (pattern specifications: circular diameter 0.425mm, zigzag arrangement, horizontal spacing 2.1mm, vertical spacing 1.1mm, crimping area ratio 6.3%) In between, the fibers were bonded to each other to obtain a long-fiber nonwoven fabric with a weight per unit area of 20 g/m ² , an air permeability of 456 cm ³ /cm ² /s, and a thermocompression bonded portion shape index of 1.9 without fibers being crimped. The obtained nonwoven fabric had a high bulk density, had no cushioning properties, and had a hard texture.

[Comparative example 4]

The core component as the first component is polypropylene with a melting point of 162°C, the sheath as the second component is high-density polyethylene with a melting point of 130°C, and staple fibers with a fineness of 2.5 dtex and a cut length of 38 mm are used as constituent fibers, A nonwoven web is obtained by carding.

Next, for the obtained nonwoven web, the fibers are bonded to each other by hot air bonding at a hot air temperature of 140°C and a hot air speed of 1.0m/s to obtain a weight per unit area of 18g/m ² and an air permeability of 717cm ³ /cm ² /s , Composite staple fiber non-woven fabric with crimp number 5/inch. The obtained non-woven fabric has low elongation, low toughness index and hard texture.

[Table 1]

Industrial availability

The composite long-fiber nonwoven fabric of the present invention has cushioning properties, softness and bulkiness, and has high strength and elongation, so it can be suitably used in the production of hygiene materials. As a hygienic material, it can be applied to disposable diapers, sanitary napkins, or incontinence pads, and can be used as a top sheet on the surface and a back sheet on the outside. In addition, the use is not limited, for example, it can also be used for facial masks, heaters, tape base fabrics, waterproof sheet base fabrics, patch base fabrics, bandage base fabrics, packaging materials, wiping products, medical gowns, straps, clothing, skin care Use sheet etc.

Claims (9)

1. A nonwoven fabric, characterized in that it is a partially thermocompression-bonded nonwoven fabric comprising composite long fibers of two or more thermoplastic resins, and the shape index of the thermocompression-bonded part of the nonwoven fabric is 0.05 or more and less than 0.05. 1.9, the maximum abrasion depth of the pseudo-skin model is less than 10 μm, and the cumulative abrasion depth is less than 80 μm. 2. The nonwoven fabric according to claim 1, wherein the surface fluff index of the nonwoven fabric is 3 or more. 3. The nonwoven fabric according to claim 1 or 2, wherein the vertical and horizontal average values of the variation values MMD of the coefficient of friction of the nonwoven fabric are 0.015 or less. 4. The nonwoven fabric according to any one of claims 1 to 3, wherein the nonwoven fabric has an orientation index in the thickness direction based on X-ray CT of 0.43 or less, and a bulk density of 0.01 to 0.07 g /cm ³ or less. 5 . The nonwoven fabric according to claim 1 , wherein the nonwoven fabric has a compression work WC of 0.20 to 1.00 gf/cm/cm ² . 6. The nonwoven fabric according to any one of claims 1 to 5, wherein the composite long fibers are of a side-by-side type or an eccentric type. 7. The nonwoven fabric according to any one of claims 1 to 6, wherein the two kinds of thermoplastic resins are both polyolefin-based resins. 8. The nonwoven fabric according to any one of claims 1 to 7, wherein the nonwoven fabric contains a hydrophilic agent. A hygienic material comprising the nonwoven fabric according to any one of claims 1 to 8.