CN108699745B

CN108699745B - Long fiber nonwoven fabric having excellent skin touch

Info

Publication number: CN108699745B
Application number: CN201780011534.6A
Authority: CN
Inventors: 中东登志子; 税所一哉; 矢放正广; 加藤一史
Original assignee: Asahi Kasei Corp
Current assignee: Mitsui Chemical Asahi Living Materials Co ltd
Priority date: 2016-02-22
Filing date: 2017-02-20
Publication date: 2020-11-06
Anticipated expiration: 2037-02-20
Also published as: WO2017145993A1; TWI641737B; JP6542974B2; MY184560A; JPWO2017145993A1; CN108699745A; TW201732108A

Abstract

Provided is a bulky long fiber nonwoven fabric which is suitable for a top sheet or a back sheet member of an absorbent article used in a sanitary material, has good skin touch, has bulky flexibility, and is less physically irritated to the skin. The nonwoven fabric of the present invention is a partially thermocompression bonded nonwoven fabric comprising composite long fibers of 2 or more thermoplastic resins, wherein the thermocompression bonded section shape index of the nonwoven fabric is 0.05 or more and less than 1.9, the maximum scratch depth of a pseudo skin model is 10 μm or less, and the cumulative scratch depth is 80 μm or less.

Description

Long fiber nonwoven fabric having excellent skin touch

Technical Field

The present invention relates to a partially thermocompression bonded nonwoven fabric comprising composite long fibers of 2 or more thermoplastic resins, which has good skin feel, little physical irritation to the skin, and bulkiness.

Background

In general, materials used in a portion in contact with the skin, such as a top sheet for a sanitary material such as a disposable diaper and a sanitary napkin, are considered to have a soft texture, and are free from itching, tingling, pain, and the like caused by fuzzing, and have a good skin feel. Among them, it is important that physical irritation to the skin is small. Examples of the physical stimulus include a terminal portion of the fiber, a stimulus caused by fuzz generated by the fiber, and a scratch stimulus caused by the fuzz.

Nonwoven fabrics formed by heat-bonding intersecting portions of fibers to short fibers by a hot air method and forming a sheet (hereinafter, also referred to as "hot air nonwoven fabrics") are generally used for these applications because they are bulky and soft and less fluffed due to heat-bonding intersecting portions of fibers. However, since this nonwoven fabric is composed of short fibers, the fiber ends are present on the surface, and there is a harsh skin feel, and further, the fiber ends cause scratch irritation when rubbing against the skin, and the like, which is not satisfactory in terms of physical irritation.

A nonwoven fabric obtained by partially heat-fusing short fibers by an emboss roller or the like (hereinafter also referred to as "point-bonded nonwoven fabric") is insufficient in terms of physical stimulation because fiber ends are present on the surface, as in the case of a through-air nonwoven fabric, and moreover, since fiber intersections are not completely bonded to each other as compared to the through-air nonwoven fabric, fuzz is likely to occur, and the texture is also poor.

On the other hand, in the long fiber nonwoven fabric obtained by thermally pressing the long fiber nonwoven fabric by an emboss roller or the like, the short fiber ends do not appear on the surface, and physical stimulation due to the fiber ends is not easily generated, but excessive thermal pressing is performed to prevent fluffing of the surface, so that the texture is hard, rough skin touch is brought, and the peripheral portion of the thermally pressed portion becomes a cause of physical stimulation.

The following patent documents 1 and 2 disclose nonwoven fabrics obtained from thermoplastic composite fibers having good fuzz resistance and good texture. However, in order to improve fuzz, thermal compression is performed by flattening thermoplastic fibers by thermal embossing, and thus there are some cases where the flattened thermal fusion bonded part and the nonwoven fabric are deteriorated in bulkiness and poor in texture. Further, the heat-fusion bonded portion is hard, and thus physical stimulation due to friction is large.

Patent document 3 below discloses a polyolefin nonwoven fabric obtained by using a combination of a specific polyether compound and a specific polyether-modified silicon for a long fiber nonwoven fabric partially thermocompressed in a specific thermocompression bonding shape. The disclosed nonwoven fabric has good fuzz resistance and low physical irritation due to friction, but it is insufficient in these respects because polypropylene fibers are bonded only by hot embossing, and therefore, in order to achieve good fuzz resistance, it is necessary to increase the number of thermally fused parts, and the bulk density is high, and fluffy flexibility is not provided.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2001-355176

Patent document 2: japanese patent laid-open No. 2000-290866

Patent document 3: japanese patent laid-open publication No. 2003-52752

Disclosure of Invention

Problems to be solved by the invention

The present invention addresses the problem of providing a bulky long fiber nonwoven fabric which is suitable for a top sheet or a back sheet member of an absorbent article used in a sanitary material, has good skin touch, is bulky and flexible, and has little physical irritation to the skin.

Means for solving the problems

As a result of intensive studies and experiments to solve the above problems, the present inventors have found that a nonwoven fabric composed of composite long fibers containing 2 or more thermoplastic resins can be provided which has low physical irritation to the skin and can be suitably used as a sanitary material by allowing hot air to pass through the nonwoven web while keeping the nonwoven web bulky in the production process of the nonwoven fabric by setting the air permeability of the nonwoven web before joining, the hot air temperature at the time of joining, and the air velocity to fall within certain ranges, and bonding fiber intersections, thereby improving the fuzz resistance and maintaining the bulk density.

Namely, the present invention is as follows.

[1] A nonwoven fabric comprising a partially thermocompression bonded nonwoven fabric of conjugate continuous fibers of 2 or more thermoplastic resins, characterized in that the thermocompression bonded nonwoven fabric has a thermocompression bonding shape index of 0.05 or more and less than 1.9, a maximum abrasion depth of a pseudo skin model of 10 μm or less, and a cumulative abrasion depth of 80 μm or less.

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

[3] The nonwoven fabric according to the item [1] or [2], wherein an average value of an aspect ratio of a deviation value (MMD) of a friction coefficient of the nonwoven fabric is 0.015 or less.

[4]According to the above [1]]～[3]The nonwoven fabric of any one of the above, wherein the nonwoven fabric has an orientation index in the thickness direction by X-ray CT of 0.43 or less and a bulk density of 0.01 to 0.07g/cm³The following.

[5]According to the above [1]]～[4]The nonwoven fabric according to any of the above, wherein the nonwoven fabric has a compression work WC of 0.20 or more and 1.00gf/cm²The following.

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

[7] The nonwoven fabric according to any one of the above [1] to [6], wherein the 2 kinds of thermoplastic resins are polyolefin resins.

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

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

ADVANTAGEOUS EFFECTS OF INVENTION

The nonwoven fabric of the present invention is a nonwoven fabric composed of composite long fibers containing 2 or more thermoplastic resins, and the degree of adhesion of the fibers constituting the nonwoven fabric is adjusted so that the nonwoven fabric exhibits specific friction characteristics and thermocompression bonding shape index, thereby achieving low physical irritation to the skin, good fuzz resistance, soft texture, and suitable use as a sanitary material.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

The long conjugate fibers constituting the nonwoven fabric of the present embodiment include a combination of 2 or more thermoplastic resins. Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, and copolymerized polypropylene, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymerized polyester, polyamide resins such as nylon-6, nylon-66, and copolymerized nylon, and biodegradable resins such as polylactic acid, polybutylene succinate, and polyethylene succinate. Any combination of the above thermoplastic resins may be used as long as the desired action and effect are exhibited, but a combination of thermoplastic resins having a difference in melting point is preferable from the viewpoint of bondability between fibers.

Among them, a polyolefin resin is preferably used in combination from the viewpoint of texture. For example, composite fibers are obtained by combining resins such as polyethylene, polypropylene, and copolymers of these monomers with other α -olefins. The other α -olefin includes α -olefins having 3 to 10 carbon atoms, and specific examples thereof include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

The thermoplastic composite fiber of the present embodiment is preferably used because a crimped yarn is easily obtained when the fiber shape is a side-by-side type (S/S) or an eccentric type (S/C). The eccentric core may be present on the surface of the fiber, and the area ratio of the core to the surface of the fiber is preferably 0 to 50%, and more preferably 0 to 30%. The lower the ratio of the core portion forming the fiber surface, the higher the ratio of the sheath portion resulting from the bonding, and high strength and fuzz suppression can be obtained. In addition, from the viewpoint of the strength of the fiber, the weight ratio of the resin having a high melting point in the combination of thermoplastic resins in the fiber is 20 wt% or more and 80 wt% or less, preferably 30 wt% or more and 80 wt% or less, and more preferably 50 wt% or more and 70 wt% or less.

The fiber shape may be not only a normal circular fiber but also a fiber having a special form such as an irregular fiber.

When the long composite fiber is formed of 2 kinds of thermoplastic resins, the first component is preferably polypropylene and the second component is preferably polyethylene. When the composite fiber is of an eccentric type, it is preferable that the core portion be a first component and the sheath portion be a second component. Polypropylene is preferred because it has high strength, is not easily broken when used, and has excellent dimensional stability when produced into sanitary materials.

The polypropylene as the first component in the case of the 2 kinds of thermoplastic resins may be a polymer synthesized by a conventional Ziegler-Natta catalyst, a polymer synthesized by a single-site active catalyst such as a metallocene, or an ethylene random copolymer polypropylene. These may be 1 kind alone or 2 or more kinds in combination. From the viewpoint of texture, strength, and dimensional stability, homopolypropylene is preferably used as the main component.

The lower limit of MFR of polypropylene may be 20g/10 min or more, preferably more than 30g/10 min, more preferably more than 40g/10 min, most preferably more than 53g/10 min. The upper limit may be 85g/10 min or less, preferably 70g/10 min or less, and most preferably 60g/10 min or less. The MFR was measured in accordance with JIS-K7210 "test method for melt Mass Flow Rate (MFR) and melt volume flow Rate (MVR) of Plastic-thermoplastic" Table 1, test temperature 230 ℃, test load 2.16 kg.

The polyethylene of the second component in the case of 2 kinds of thermoplastic resins is suitably used for sanitary materials because the bonding strength after bonding of the fibers is strong and the texture as a nonwoven fabric is good. The polyethylene may be a polymer synthesized by a conventional ziegler-natta catalyst, or a polymer synthesized by a single-site active catalyst such as a metallocene catalyst. The polyethylene is preferably high-density polyethylene or linear low-density polyethylene, and the density is preferably 0.92-0.97 g/cm³More preferably 0.925 to 0.96g/cm³。

The lower limit of MI of the polyethylene may be 10g/10 minutes or more, preferably more than 15g/10 minutes. The upper limit may be 100g/10 min or less, preferably 60g/10 min or less, and most preferably 40g/10 min or less. MI was measured at 190 ℃ under a test load of 2.16kg in accordance with JIS-K7210 "test method for melt Mass Flow Rate (MFR) and melt volume flow Rate (MVR) of Plastic-thermoplastic" Table 1.

The nonwoven fabric of the present embodiment is preferably produced by forming a long composite fiber nonwoven web by a spunbond method from the viewpoint of strength and productivity. For example, in the case of a long conjugate fiber, different thermoplastic resins are melt-extruded from 2 or more different extruders, and the long conjugate fiber is discharged in the form of a sliver in a state where 2 or more thermoplastic resins are combined from a spinneret having a plurality of spinneret holes. Then, cold air controlled at 5 to 20 ℃ is applied to the ejected sliver, and high-speed drawing is performed by a drawing device while cooling. The sliver exiting from the drawing device is deposited on a conveyor belt and transported in the form of a nonwoven web. The nonwoven webs being conveyed may be stacked to form a multi-layered stacked nonwoven web.

The joining means for joining nonwoven fabric sheets made of thermoplastic composite fibers is not particularly limited as long as it is heated to a temperature at which the intersection points of the fibers are melted and bonded. As a heating method, various heating methods such as a hot air circulation type, a hot air passing type, an infrared heater type, a method of blowing hot air to both surfaces of the nonwoven fabric, a method of introducing the heated air, and the like can be used. From the viewpoint of obtaining more fiber bonding points at the intersections of the fibers and increasing the breaking strength of the nonwoven fabric, heating with hot air, particularly a hot air through type, is preferable.

The temperature of the hot air is preferably adjusted to a temperature 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, the temperature at which the polyethylene is melted and bonded is 130 to 155 ℃, preferably 135 to 155 ℃, and more preferably 140 to 150 ℃. When the bonding temperature is in this range, bonding between the fibers is exhibited at the intersections of the fibers, and the strength as a nonwoven fabric can be exhibited.

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

When the nonwoven web sheet of the present embodiment is joined by hot air, the air permeability of the nonwoven web sheet significantly affects the joined state. When the air permeability of the nonwoven web is too low, hot air hardly passes through the web, and uniform bonding as a nonwoven fabric is difficult to obtain. On the other hand, too high air permeability is not preferable from the viewpoint of strength retention of the obtained nonwoven fabric. The air permeability of the nonwoven fabric to be finally obtained, which is capable of satisfactorily maintaining the bonding strength, is preferably 300cm³/cm²700 cm/s or more³/cm²Less than s, more preferably 300cm³/cm²650cm at a distance of over s³/cm²The ratio of the water to the water is less than s.

In the present specification, the "thermocompression bonding portion shape index" is defined by a partial thermocompression bonding portion formed on the surface of the nonwoven fabric bonded by the embossing roll, the hot air treatment, or the like, that is, a ratio of a welding area of the heat welding and a welding circumference per a constant area. The fusion area ratio is a ratio of a fusion area of the long fiber nonwoven fabric to the entire area of the nonwoven fabric, and a fusion circumferential length per a predetermined area is a sum of circumferential lengths of fusion portions included in the long fiber nonwoven fabric per 20 square millimeters. Here, although the fusion of the fiber intersection points occurs, when the fusion of the fiber intersection points is exposed on the surface in contact with the skin, the fusion area and the fusion perimeter are calculated as the portion where the fusion portion is formed on the fiber surface including the fiber intersection points and the portion is made thin.

The site where the nonwoven fabric comes into contact with the skin and causes physical irritation is, for example, the ends of short fibers on the contact surface of the nonwoven fabric or the fuzzing on the surface. In addition, in the case of a nonwoven fabric including a long fiber nonwoven fabric thermally bonded by an emboss roller or the like, the short fiber ends do not appear on the surface of the nonwoven fabric, and physical stimulation due to the fiber ends is less likely to occur, but when the thermocompression bonding area is too large to prevent surface fuzzing, or when the thermocompression bonding pressure is too large and the unevenness in the peripheral portion of the welded portion is deep, not only the texture is deteriorated, but also the peripheral portion of the thermocompression bonded portion becomes a cause of physical stimulation. That is, if the area ratio of the film made by fusion bonding is high, the nonwoven fabric becomes hard, and the scratch irritation during friction is large, causing a scratch to the skin. In addition, in the peripheral portion of the heat-fused portion, the heat-fused portion is a concave portion, and the non-heat-fused portion is a convex portion, and the difference in unevenness is large, so that the peripheral portion of the heat-fused portion on the surface of the nonwoven fabric is caught on the skin surface during rubbing, which causes scratching. That is, the ratio of the welding area and the circumferential length of the welded portion are closely related to the scratch during friction. When the thermocompression bonding portion shape index of the nonwoven fabric is large, the nonwoven fabric can prevent the occurrence of fuzz and can prevent the poor touch such as itching and tingling due to the fuzz, but the skin is physically irritated by the thinned hard portion. On the other hand, when the thermocompression bonding portion shape index of the nonwoven fabric is small, physical irritation due to the skin contact of the thin hard portion is reduced, and the nonwoven fabric has a good bulky texture. However, when the thermocompression bonding portion shape index is too small, the nonwoven fabric does not have practically sufficient strength, and further, fuzz is likely to occur by friction, and the touch such as itching or tingling is deteriorated by physical stimulation due to the fuzz. 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. When the shape index of the thermocompression bonded portion is less than 0.05, it is not preferable from the viewpoint of preventing fuzz, and when it exceeds 1.9, the bulky texture is impaired, and it is not preferable from the viewpoint of volume feeling and swelling feeling at the time of compression. The "thermocompression bonding portion shape index" is more preferably 1.8 or less, and still more preferably 1.5 or less. The "thermocompression bonding portion shape index" is more preferably 0.1 or more, and still more preferably 0.3 or more.

When the nonwoven fabric of the present embodiment is used as a top sheet of a sanitary material, the nonwoven fabric of the present embodiment is required to have a maximum scratch depth of a pseudo-skin model of 0 μm or more and 10 μm or less and a cumulative scratch depth of 0 μm or more and 80 μm or less. The maximum abrasion depth and the cumulative abrasion depth of the pseudo skin model are determined by measuring the initial compressive stress of 98mN/cm according to the measurement method described later²The pseudo skin model of (1) is configured such that when the non-woven fabric in contact with the skin is rubbed, a maximum scratch depth of a scratch and a cumulative scratch depth of the scratch are formed on the surface of the pseudo skin model. The scratch here means a physical surface shape change of the pseudo skin model caused by the nonwoven fabric by rubbing the nonwoven fabric and 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 more preferably 9 μm or less. In addition, the cumulative depth of scratching was exceededWhen the particle diameter is larger than 80 μm, the particle diameter is not larger than 60 μm, and more preferably not larger than 50 μm.

That is, the frictional irritation of the nonwoven fabric is expressed as the number of scratches, the depth of the scratches, and the width of the scratches on the dummy skin model according to the degree of physical irritation caused by friction with the dummy skin model. The surface of the dummy skin model was adjusted to be flat, but the fine irregularities on the surface before the application of the frictional stimulus were not regarded as scratches. The degree of frictional irritation of the nonwoven fabric can be compared by performing comparative evaluation using the maximum abrasion depth and the cumulative abrasion depth of the scratch in the pseudo skin model having the same composition.

When the relationship between the maximum scratch depth and the cumulative scratch depth of a scratch caused by the friction between a nonwoven fabric and a dummy skin model and the physical irritation caused by the friction between the nonwoven fabric and the actual skin was investigated by a plurality of panelists, it was confirmed that the nonwoven fabric having the larger maximum scratch depth and the larger cumulative scratch depth tended to feel stronger irritation when the skin was actually rubbed with the nonwoven fabric, and that the disappearance of the skin texture tended to be large when the condition of the skin surface after the friction was observed. From the results, the maximum scratch depth and the cumulative scratch depth of the scratch generated by rubbing the pseudo skin model with the nonwoven fabric were measured, and the friction irritation of the nonwoven fabric in contact with the skin to the skin could be evaluated. According to the studies by the present inventors, it was found that when the maximum abrasion depth exceeds 10 μm and the cumulative abrasion depth exceeds 80 μm, the nonwoven fabric in contact with the skin has a large frictional irritation to the skin, and the skin is easily scratched.

In the present embodiment, the "surface fuzz index" of the nonwoven fabric is preferably 3 or more. When the surface fuzz index is less than 3, fuzz occurs on the surface of the nonwoven fabric due to friction with the skin or the like, and a harsh skin touch is formed, and further physical stimulation is formed on the skin surface due to friction.

In the present embodiment, the average value of the variation in the coefficient of friction (MMD) of the nonwoven fabric in terms of the aspect ratio is preferably 0.015 or less. When the amount exceeds 0.015, the amount is not preferably 0.017 or less, more preferably 0.015 or less, because the smoothness to the skin touch and the reduction in physical irritation are not preferable.

The friction with the skin is preferably low in friction coefficient, smooth, and low in resistance in both the longitudinal and transverse directions. However, when the magnitude of the frictional resistance in the longitudinal direction differs from that in the lateral direction, the stress of the frictional resistance concentrates in the direction in which the coefficient of friction values in the longitudinal direction and the lateral direction are small, and as a result, the frictional resistance stress in the longitudinal direction and the lateral direction is averaged. Therefore, the vertical and horizontal average values of the deviation values of the friction coefficient are important as values representing the load of physical stimulation on the skin.

This is because, as for the occurrence of the difference in the magnitude of the frictional resistance, the frictional resistance stress is averaged, and when the ratio of the deviation value of the frictional coefficient in the smaller direction to the deviation value of the frictional coefficient in the larger direction exceeds 20 times among the values in the vertical and horizontal directions of the deviation value of the frictional coefficient, the influence of the value in the larger direction becomes high, and even if the vertical and horizontal average value of the deviation value of the frictional coefficient is 0.015 or less, the skin feel becomes rough.

The orientation index of the nonwoven fabric of the present embodiment by X-ray CT is preferably 0.43 or less, and more preferably 0.425 or less. When the orientation index by 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 bulky nonwoven fabric can be obtained, and a nonwoven fabric having excellent cushioning properties can be obtained. The lower limit 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 temperature and the air velocity of hot air in the joining step of the nonwoven fabric and the air permeability of the nonwoven web. When the temperature of the hot air is high, the solubility of the fiber surface becomes very high, and the texture becomes hard. When the wind speed of the hot wind is high, the hot wind passes through, but the fibers are collapsed at the same time, and the nonwoven fabric with low bulk is formed. Further, when the air permeability of the nonwoven web is too low, hot air cannot pass through the nonwoven web, and when the air permeability is too high, the hot air cannot apply sufficient heat to the fiber intersections to melt the fibers, and therefore, it is difficult to form fiber bonding points that achieve both bulk and strength. The bulk density of the nonwoven fabric of the present embodiment is preferably 0.01g/cm³Above and 0.07g/cm³The following range is more preferably 0.03g/cm from the viewpoint of strength³From the viewpoint of texture, the amount of the additive is more preferably 0.07g/cm³The following.

The nonwoven fabric of the present embodiment preferably has a compression work WC of 0.20gf cm/cm²Above and 1.00gf cm/cm²Less than, more preferably 0.25gf cm/cm²Above and 0.80gf cm²The following. When the compression work WC is kept in this range, it is preferable from the viewpoint of cushioning properties of the nonwoven fabric used as a sanitary material.

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

The composite long fibers preferably have a helical crimp in view of maintaining the texture and bulkiness of the nonwoven fabric. The crimp number of the fiber is preferably 5 pieces/inch or more and 45 pieces/inch or less, more preferably 10 pieces/inch or more and 40 pieces/inch or less. If the number of crimps is less than 5 pieces/inch, the bulk of the obtained nonwoven fabric is insufficient, and if it exceeds 45 pieces/inch, the appearance is impaired due to uneven fiber dispersion of the obtained nonwoven fabric.

The nonwoven fabric of the present embodiment preferably has a weight per unit area of 8g/m²Above and 80g/m²Less than, more preferably 10g/m²Above and 40g/m²The lower, more preferably 10g/m²Above and 30g/m²The following. If it is 8g/m²The above results satisfy the strength of the nonwoven fabric for sanitary materials, and 80g/m²The nonwoven fabric for sanitary materials, which is the object of the present invention, satisfies the flexibility and does not give an impression of a thick appearance.

The nonwoven fabric of the present embodiment may contain a hydrophilic agent. As the hydrophilic agent to be used, in view of safety to the human body, safety in the process, and the like, it is preferable to use a nonionic active agent such as a higher alcohol, a higher fatty acid, an alkylphenol, etc. to which ethylene oxide is added, an anionic active agent such as an alkyl phosphate, an alkyl sulfate, etc. singly or in the form of a mixture.

As a method of containing the hydrophilic agent, it is preferable to use a diluted hydrophilic agent in general, and to dilute and coat the hydrophilic agent mixed in advance with a solvent such as water as necessary by a conventional method such as a dipping method, a spraying method, and a coating (kiss coater, gravure coater, die coater).

When the hydrophilic agent is diluted with a solvent such as water and applied, a drying step may be required. As the drying method in this case, conventional methods using convection heat transfer, conduction heat transfer, radiation heat transfer, or the like can be used, and drying methods using hot air, infrared rays, thermal contact, or the like can be used.

The amount of the hydrophilic agent to be attached varies depending on the required performance, and is usually preferably in the range of 0.05 to 1.00 wt% with respect to the fiber, more preferably 0.15 to 0.8 wt%, and still more preferably 0.2 to 0.6 wt%. When the amount of adhesion falls within this range, the hydrophilic performance of the top sheet as a sanitary material is satisfied, and the processability is also improved.

When the nonwoven fabric is treated with a hydrophilizing agent to improve hydrophilicity and used as a top sheet for sanitary materials, urine and blood permeate the surface of the nonwoven fabric, and therefore, the nonwoven fabric is not left on the skin, chemical irritation such as ammonia is reduced, physical irritation to the skin is small, and the skin is less likely to be scratched, and therefore inflammation such as dermatitis is less likely to occur due to chemical irritation.

The nonwoven fabric of the present embodiment is realized by using a conjugate long fiber nonwoven fabric containing 2 or more thermoplastic resins and adjusting the welded portion of the skin-contacting surface. Since the conjugate long-fiber nonwoven fabric is used, the fiber intersections are not completely thinned, but the low-melting-point component of the conjugate fiber is thermally fused, so that the degree of freedom of the fiber is not impaired when the conjugate fiber is in contact with the skin, and stress concentration is not generated in the thinned portion, thereby reducing physical irritation. Further, the strength in use and the prevention of fuzz are achieved by the thermal fusion bonding of the fiber intersections.

The degree of freedom of the constituent fibers of the long fiber nonwoven fabric is determined by the degree of thermal fusion bonding of the thin film portion to the low melting point component of the composite fiber by thermocompression bonding or the like, and is expressed by the tenacity index of the long fiber nonwoven fabric. The toughness index is a value obtained by dividing the product of the breaking strength and the breaking elongation of the nonwoven fabric by the basis weight of the nonwoven fabric, and is preferably 40 or more and 250 or less, more preferably 50 or more and 150 or less.

Examples

The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

The properties of the nonwoven fabrics in the examples were measured by the following methods.

The evaluation methods of the properties are as follows, and the obtained physical properties are shown in table 1 below. Hereinafter, the production line direction, i.e., the fiber flow direction, is referred to as the MD direction, and the width direction perpendicular to the fiber flow direction is referred to as the CD direction.

(1) Average single filament fineness (dtex)

A1 cm square specimen was sampled, and the fiber diameter at 20 points was measured one by one using a microscope VHX-700F manufactured by Keyence, to calculate the fineness from the average value.

(2) Weight per unit area (g/m)²)

The mass was measured by collecting 5 test pieces of 20cm in the MD direction and 5cm in the CD direction as desired in accordance with JIS-L1906, and the average value was calculated by converting the weight per unit area.

(3) Air permeability (cm)³/cm²/s)

Measured by the Frazier method described in JIS L-1096. 10 points were collected and measured, and the average value of the measured values was calculated.

(4) Number of crimps

A5-point 5-cm square test piece was sampled in the CD direction, and the number of crimps per 1 inch (2.54cm) was measured using a Keyence microscope VH-Z450 in a state where no load was applied to the fibers in the test piece, and the number of crimps was calculated from the average value thereof.

(5) Maximum and cumulative depth of gouge

(I) A3-point 5 cm. times.5 cm sample was prepared from an arbitrary position of the nonwoven fabric.

(II) the sample was attached to a friction terminal of a friction feel tester (KES-SE) manufactured by Kato Tech Co.

(III) Using the frictional feeling tester, the sample was brought into contact with an initial compressive stress of 98mN/cm described later²At a contact pressure of 4.9 x 10³Pa, contact area 1cm²And rubbing for 1 time under the condition of a rubbing distance of 2 cm.

(IV) the center part of the friction trace having a width of 1cm and a width of 2cm in the friction direction on the surface of the dummy skin model by friction, and the maximum abrasion depth having a width of 1cm in the direction orthogonal to the friction direction, and the cumulative abrasion depth were measured by using a noncontact laser measuring machine.

(V) the maximum abrasion depth and cumulative abrasion depth of the surface of the dummy skin model when 10 positions were rubbed at 1cm intervals in the longitudinal and transverse directions of the sample were measured, and the average value of the longitudinal and transverse directions was used as the maximum abrasion depth and cumulative abrasion depth of the sample piece. The maximum scratch depth and the cumulative scratch depth of the sample were the average of the above 3 points.

[ method for producing pseudo skin model ]

AGAR (AGAR POWDER, Wako pure chemical industries, Ltd., reagent) 1 part and gelatin (GIFCO, reagent) 8 parts were dissolved in water 91 parts, and the resulting solution was solidified in a refrigerator. Adjusted in such a way that the surface becomes flat.

The initial compressive stress was measured by compressing the sample with a compression area of 200mm using a portable compression tester KES-G5(Kato Tech Co., Ltd.,. Ltd.)²When the pseudo skin model was measured at a compression rate of 0.1 mm/sec, the compressive stress at a displacement of 0.1mm was measured. The amount of water added was fine tuned as needed to match the initial compressive stress.

(6) Hot press bonding part shape index

(I) Samples of 5cm × 5cm were collected from arbitrary positions of the nonwoven fabric.

(II) from the above samples, 25 samples of 1 cm. times.1 cm were prepared, and the surface was photographed with a microscope to obtain 25 photographs at 25 magnifications.

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

(IV) from the obtained photograph, a value showing the total of the peripheral lengths of the welded and thinned portions contained in 20 square millimeters per fixed area was obtained.

(V) the thermocompression bonding portion shape index is obtained by the following numerical expression (1). The thermocompression bonding shape index was the average value of the above 25 points.

Hot press bonding part shape index (heat fusion area ratio) x fusion perimeter formula (1) per fixed area

{ in formula, weld area ratio: the ratio of the area of the welding part of the long fiber non-woven fabric to the whole area of the long fiber non-woven fabric; fusion perimeter per certain area: the sum of the circumferential lengths of the welded portions contained in each 20 mm square long-fiber nonwoven fabric. }

(7) Deviation value of coefficient of friction

(I) A3-point 6 cm. times.8 cm sample was prepared from an arbitrary position of the nonwoven fabric.

(II) the test specimen was mounted on a measuring table of a friction feel tester (KES-SE) manufactured by Kato Tech Co.

(III) Using the standard friction terminal (10mm square wire terminal) of the test piece and the frictional feeling tester, the load was measured at 25g/cm²The variation (MMD) of the friction coefficient was measured, and the average value of the longitudinal and transverse dimensions of the sample was measured.

(8) Index of surface fuzzing

The method was carried out according to JIS P8136 in the following manner.

(I) 3-point samples having a length of 25cm and a width of 3cm were prepared from arbitrary positions of the nonwoven fabric.

(II) the sample was attached to the sample table of a abrasion resistance tester, and a No. 3 scrim (4 cm. times.5 cm) was attached to a friction piece.

(III) A rubbing test was performed by placing a rubbing implement (500g) on the nonwoven fabric and repeating the rubbing test 100 times.

(IV) sensory evaluation of the fluffing state of the nonwoven fabric surface after rubbing. The average value of 3 points is represented by the following criterion.

[ evaluation criteria: index of surface fuzzing

And 5, dividing: no fuzz was observed due to rubbing, and no damage was confirmed due to surface rubbing.

And 4, dividing: surface shape change due to friction was slightly observed, but fuzz was not observed.

And 3, dividing: fuzz due to rubbing was slightly observed, but 10 or less fiber ends were peeled off.

And 2, dividing: fluffing due to rubbing was observed, and 11 or more and 49 or less peeled fiber ends were observed.

1 minute: fluffing occurred in a large amount due to rubbing, and 50 or more peeled fiber ends were observed.

(9) Orientation index (X-ray CT)

A test piece 5mm in MD direction × 5mm in CD direction was arbitrarily cut out, and the measurement was performed with a visual field of about 3mm × 3mm at the time of image analysis. The measuring apparatus used a high-resolution 3 DX-ray microscope nano3DX (manufactured by Rigaku corporation) to perform CT measurement based on low-energy high-brightness X-rays, which can obtain contrast even with light elements. The detailed conditions are shown below.

An X-ray target: cu

X-ray tube voltage: 40kV

X-ray tube current: 30mA

Lens: 1.08 μm/pix

Dividing the bins: 2

Rotation angle: 180 degree

Projection number: 1000 sheets

Exposure time: 10 seconds per sheet

The number of camera pixels: 3300 × 2500

Reconstruction: feldkamp method

The three-dimensional tomogram obtained by CT measurement is subjected to image analysis to obtain orientation indexes Ix, Iy, Iz of orthogonal 3 axes (X, y, z). The thickness direction of the sample to be evaluated is mainly aligned with the z direction. Here, the orientation indexes Ix, Iy, Iz are defined as follows, taking the sum of the areas of the fiber surface observed from each direction of x, y, z (the sum of the total projected areas of the layers of the fiber surface in each direction) as Ax, Ay, Az, respectively.

Ix＝Ax/(Ax+Ay+Az)

Iy＝Ay/(Ax+Ay+Az)

Iz＝Az/(Ax+Ay+Az)

Ax, Ay, and Az are obtained from tomograms. In this index, the orientation is in the direction of small value. In addition, 1/3 is the most common isotropic structure.

(10) Bulk Density (g/cm)³)

Both ends of a nonwoven fabric sample were 10cm removed, and a peacock type thickness meter (5g/4 cm) was used so as to be uniform in the width direction²) 20 points were measured to calculate the average thickness. From the average value, the bulk density was calculated using the following equation.

Bulk Density (g/cm)³) Weight per unit area (g/m)²) Thickness (mm)/1000

(11) Amount of compression Work (WC)

5-point 5-cm square test pieces were collected in the CD direction and measured using a compression test apparatus (KES-G5) manufactured by Kato Tech Co., Ltd. The test piece was set on a metal sample table and had a pressurizing area of 2cm²The steel plates of the circular plane are compressed. The compression speed was set to 0.067mm/s and the maximum compression load was set to 3.4kPa (35 gf/cm)²). The recovery process was also measured at the same speed, and the average value of the compression work amount was calculated.

(12) Texture of

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

(13) Toughness index

According to JIS L-1906, samples of 20cm in the MD direction and 5cm in the CD direction were sampled at 5 points, and a longitudinal tensile test was carried out with a tensile tester at a holding interval of 100mm and a tensile speed of 300 mm/min, and the toughness index was calculated from the following formula based on the measured breaking strength and breaking elongation.

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

Examples 1 to 3 and comparative examples 1 and 2

The fiber shape was an eccentric sheath-core structure, wherein a polypropylene (PP) resin having an MFR of 55g/10 min (measured at 230 ℃ C. and a load of 2.16kg in accordance with JIS-K7210) was used as a first component, a high-density polyethylene (HDPE) resin having an MI of 26g/10 min (measured at 190 ℃ C. and a load of 2.16kg in accordance with JIS-K7210) was used as a second component, the first component was discharged at a rate of 0.4 g/min/hole, the second component was discharged at a rate of 0.4 g/min/hole, and the total single-hole discharge rate was 0.8 g/min/hole, a long-fiber nonwoven web having an average single-filament fineness of 2.8dtex was prepared by extruding a fiber having a ratio of the first component to the second component of 50/50 by a spunbond process at a spinning temperature of 220 ℃ and extruding the filament group at a spinning speed of 3000 m/min onto a moving collection surface using a high-velocity air jet based drawing device.

Subsequently, hot air at a hot air temperature of 142 ℃ and a hot air wind speed of 0.7m/s was passed through the obtained nonwoven web, and further, pressure bonding treatment was performed by a thermocompression bonding roller formed by combining an engraved roller and a smooth roller. The average fineness of the filaments was 2.8dtex, the number of crimps was 30/inch, and the basis weight was 20g/m, for examples 1 to 3 and comparative examples 1 and 2, each having a predetermined index of the shape of the thermocompression bonded part, by adjusting the conveying speed when passing hot air, the temperature and pressure of the thermocompression bonding roll, and the speeds of the conveyor and the take-up device²The composite long fiber nonwoven fabric of (1).

[ example 4]

The composite long fiber nonwoven fabric obtained in the same manner as in example 2 was discharged at 40 W.min/m at room temperature in an atmosphere of 22 ℃²(degree of discharge 4.0W/cm²) The nonwoven fabric was passed through a corona discharge processor under conditions of (1) to obtain a nonwoven fabric having a wet tension of 39 mN/m. The obtained nonwoven fabric was provided with a polyether-based hydrophilic agent by a spraying method, and then dried with hot air at 110 ℃ for 30 seconds to obtain a long-fiber nonwoven fabric having a chemical concentration adhesion amount of 0.3 wt%. The resulting nonwoven fabric has satisfactory properties as a topsheet for diapers.

[ example 5]

A polypropylene (PP) resin having an MFR of 40g/10 min (measured at 230 ℃ C. and a load of 2.16kg in accordance with JIS-K7210) was used as a first component, a high-density polyethylene (HDPE) resin having an MI of 26g/10 min (measured at 190 ℃ C. and a load of 2.16kg in accordance with JIS-K7210) was used as a second component, the first component was discharged at a rate of 0.4 g/min/hole, the second component was discharged at a rate of 0.4 g/min/hole, and the total single-hole discharge rate was 0.8 g/min/hole, and the fiber shape was set to an eccentric sheath-core structure, a long-fiber nonwoven web having an average single-filament fineness of 2.8dtex was prepared by extruding a fiber having a ratio of the first component to the second component of 50/50 at a spinning temperature of 235 ℃ by a spunbond process, and extruding the filament group toward a moving collection surface at a spinning speed of 2500 m/min using a cold-air-blowing type air-flow drawing device.

Subsequently, hot air having a hot air temperature of 145 ℃ and a hot air speed of 1.0m/s was passed through the obtained nonwoven web, and the nonwoven fabric was thermally bonded. The conveying speed and the speed of the winding device during the passage of hot air were adjusted to obtain a weight per unit area of 20g/m having a predetermined shape index of the thermocompression bonded portion²The composite long fiber nonwoven fabric of (1).

[ example 6]

The composite long fiber nonwoven fabric obtained in the same manner as in example 5 was discharged at a rate of 40 W.min/m at room temperature in an atmosphere of 25 ℃²(degree of discharge 4.0W/cm²) The nonwoven fabric was passed through a corona discharge processor under conditions of (1) to obtain a nonwoven fabric having a wet tension of 39 mN/m. The obtained nonwoven fabric was provided with a polyether-based hydrophilic agent by a spraying method, and then dried with hot air at 120 ℃ to obtain a long fiber nonwoven fabric having a chemical concentration deposition amount of 0.35 wt%. The resulting nonwoven fabric has satisfactory properties as a topsheet for diapers.

Comparative example 3

A polypropylene (PP) resin having an MFR of 55g/10 min (measured at 230 ℃ C. and a load of 2.16kg in accordance with JIS-K7210) was extruded as a single component by a spunbond method at a spinning temperature of 220 ℃ C. and the group of filaments was extruded at a spinning speed of 3000 m/min onto a moving collecting surface by using a high-velocity air-jet drawing device by air jet to prepare a long-fiber nonwoven web having an average single-fiber fineness of 2.8 dtex.

Then, the obtained nonwoven web was passed between a flat roll and an embossing roll (pattern specification: circular shape with a diameter of 0.425mm, zigzag arrangement, transverse pitch of 2.1mm, longitudinal pitch of 1.1mm, and press-contact area ratio of 6.3%) at 141 ℃ to bond the fibers to each other, thereby obtaining a weight per unit area20g/m²And has an air permeability of 456cm³/cm²And/s, a thermocompression bonding part shape index of 1.9. The obtained nonwoven fabric has high bulk density, no cushioning property, and hard texture.

Comparative example 4

A nonwoven web was obtained by carding using as the constituent fibers a polypropylene having a melting point of 162 ℃ as the core component, a high-density polyethylene having a melting point of 130 ℃ as the sheath component, and a short fiber having a fineness of 2.5dtex and a cut length of 38mm as the sheath component.

Then, the obtained nonwoven web was bonded to each other by hot air bonding at a hot air temperature of 140 ℃ and a hot air speed of 1.0m/s, to obtain a weight per unit area of 18g/m²And has an air permeability of 717cm³/cm²A composite short fiber nonwoven fabric having a crimp number of 5/inch. The obtained nonwoven fabric has low elongation, low toughness index and hard texture.

[ Table 1]

Industrial applicability

The conjugate long fiber nonwoven fabric of the present invention has bulkiness with softness having cushioning properties and high strength and elongation, and therefore, can be suitably used for production of sanitary materials. The sanitary material is suitable for use in disposable diapers, sanitary napkins, and incontinence pads, and can be used as a top sheet on the surface and a back sheet on the outside. The use is not limited, and the present invention can be applied to, for example, a mask, a heater, a tape base, a waterproof sheet base, a patch base, a bandage base, a packaging material, a wiping article, a medical gown, a band, clothing, a skin care sheet, and the like.

Claims

1. A nonwoven fabric comprising a partially thermocompression bonded nonwoven fabric of conjugate long fibers of 2 or more thermoplastic resins, characterized in that the thermocompression bonded nonwoven fabric has a thermocompression bonding shape index of 0.05 or more and less than 1.9, a maximum abrasion depth of a pseudo skin model of 10 μm or less, and a cumulative abrasion depth of 80 μm or less,

wherein the thermo-crimping portion shape index is defined by the following formula (1):

a heat-crimping part shape index is a heat-crimping area ratio x a welding circumference formula (1) per a fixed area,

in the formula, the ratio of weld area: the ratio of the area of the welding part of the long fiber non-woven fabric to the whole area of the long fiber non-woven fabric; fusion perimeter per certain area: the sum of the circumferential lengths of the welded portions contained in each 20 mm square long-fiber nonwoven fabric,

wherein the maximum abrasion depth and the cumulative abrasion depth of the pseudo skin model are determined as follows:

(I) preparing 3-point 5cm × 5cm samples from any position of the non-woven fabric;

(II) mounting a sample on a friction terminal of a Kato Tech Co., Ltd. friction feel tester KES-SE;

(III) Using the frictional feeling tester, the sample was brought into contact with an initial compressive stress of 98mN/cm described later²At a contact pressure of 4.9 x 10³Pa, contact area 1cm²Rubbing for 1 time under the condition of a rubbing distance of 2 cm;

(IV) measuring the maximum depth of abrasion and the cumulative depth of abrasion at the central part of the frictional trace having a width of 1cm and a width of 2cm in the frictional direction on the surface of the dummy skin model by using a non-contact laser measuring machine, and at a width of 1cm in the direction orthogonal to the frictional direction;

(V) measuring the maximum abrasion depth and the cumulative abrasion depth of the surface of the dummy skin model when 10 positions are rubbed at intervals of 1cm in the longitudinal direction and the transverse direction of the sample, and using the average value of the longitudinal direction and the transverse direction as the maximum abrasion depth and the cumulative abrasion depth of the sample piece;

the maximum scratch depth and the cumulative scratch depth of the sample were the average of the above 3 points.

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

wherein the surface fuzz index is determined as follows:

(I) preparing 3-point samples with the longitudinal length of 25cm and the transverse length of 3cm from any position of the non-woven fabric;

(II) adhering the sample to a sample table of a wear resistance tester, and mounting a 4cm multiplied by 5cm muslin No. 3 on a friction piece;

(III) placing 500g of a friction piece on the non-woven fabric, and performing a friction test of counting 100 times in a reciprocating manner;

(IV) sensory evaluation of the fluffing state of the nonwoven fabric surface after rubbing;

the surface fuzz index is represented by an average of 3 points.

3. The nonwoven fabric according to claim 1 or 2, wherein an aspect average value of a deviation value MMD of a friction coefficient of the nonwoven fabric is 0.015 or less.

4. The nonwoven fabric according to claim 1 or 2, 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 0.01g/cm³Above and 0.07g/cm³In the following, the following description is given,

wherein the orientation index is determined as follows:

performing image analysis on a three-dimensional X-ray tomogram obtained by CT measurement to obtain orientation indexes Ix, Iy and Iz of orthogonal 3-axis X, y and z; the thickness direction of a sample mainly to be evaluated is made to coincide with the z direction; here, the orientation indexes Ix, Iy, and Iz are defined as Ax, Ay, and Az, respectively, by taking the sum of the areas of the fiber surface observed from each direction of x, y, and z, that is, the sum of the total projected areas of the layers of the fiber surface in each direction,

Ix＝Ax/(Ax+Ay+Az)

Iy＝Ay/(Ax+Ay+Az)

Iz＝Az/(Ax+Ay+Az)

ax, Ay, and Az are obtained from tomograms.

5. The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric has a compression work WC of 0.20gf/cm²Above and 1.00gf/cm²The following.

6. The nonwoven fabric according to claim 1 or 2, wherein the long conjugate fibers are of a side-by-side type or an eccentric type.

7. The nonwoven fabric according to claim 1 or 2, wherein the 2 thermoplastic resins are each a polyolefin-based resin.

8. The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric contains a hydrophilic agent.

9. A sanitary material comprising the nonwoven fabric according to any one of claims 1 to 8.