JP2021159339A - Non-woven fabric sheet and absorbent article using the same - Google Patents

Abstract

To provide a non-woven fabric sheet that can weakly acidify excretion liquid that has returned from an absorber of an absorbent article while maintaining the water absorption characteristics, has less effect on a skin, facilitates maintenance since the generation of rust on metal portions of manufacturing equipment is suppressed also in a manufacturing process, and can be efficiently manufactured.SOLUTION: In a non-woven fabric sheet in which a plurality of layers is integrated in a laminated manner, a pH adjuster is not added to the surface of the laminated non-woven fabric, but is added to the inside of the laminated non-woven fabric. Further, when a liquid having a pH of 7.0 or higher passes through the non-woven fabric sheet, pH of the liquid after passing through the non-woven fabric sheet becomes lower than pH of the liquid before passing through the non-woven fabric sheet.SELECTED DRAWING: None

Description

The present invention relates to a non-woven fabric sheet preferably used for an absorbent article such as a disposable diaper, and an absorbent article using the non-woven fabric sheet.

Absorbent articles such as disposable diapers include a top sheet that comes into direct contact with the skin and allows excrement such as urine to permeate, an absorber that holds the excrement on the back side, and a liquid-impermeable back sheet. Is widely used.

Most of the top sheets of absorbent articles are made of through-air non-woven fabric. Through-air non-woven fabrics are classified into thermal-bonded non-woven fabrics and are sometimes referred to as air-through non-woven fabrics. As the through-air non-woven fabric used as a top sheet, not only a single non-woven fabric but also a plurality of webs and non-woven fabrics are known to be laminated and integrated. For example, Patent Document 1 describes a top sheet of an absorbent article, which comprises a first top sheet and a second top sheet, and the top sheets are partially joined to each other. Patent Document 1 describes that a top sheet having excellent hardness, touch, etc. can be obtained by shaping and compounding the first top sheet and the second top sheet in a specific manner. ..

By the way, when using an absorbent article such as a disposable diaper, skin troubles such as diaper rash may occur. One of the causes of diaper rash is that waste products in the body contained in urine become irritants to the skin and damage the skin. It is believed that this is because urine that has adhered to the skin for a long time causes the pH of the skin to tilt toward the alkaline side. For this reason, it has been studied to suppress the occurrence of diaper rash by weakly acidifying the top sheet, which is a part of the absorbent article that comes into direct contact with the skin.

For example, Patent Document 2 describes that the surface of the top sheet is weakly acidified by applying a surfactant and a pH adjuster to the top sheet. Patent Document 2 describes that citric acid or sodium citrate is used as a pH adjuster. Although the material and composition of the top sheet are not disclosed, the top sheet is weakly acidified by immersing the top sheet material in an aqueous solution containing a pH adjuster and a surfactant and then air-drying the top sheet. It is stated that it can be obtained.

The invention of Patent Document 3 is an invention relating to a non-woven fabric having a weakly acidic surface and water permeability, and provides a non-woven fabric in which the pH adjuster does not easily run off even with water such as urine or sweat, and the pH of the surface layer does not easily change. The purpose is to do. Patent Document 3 describes that an acidic water permeable agent containing a nonionic surfactant as a main component and a pH adjuster which is an anionic surfactant are used in combination. The non-woven fabric is not particularly limited, and it is described that, for example, a laminated spunbonded non-woven fabric can be used. In the examples of Patent Document 3, it is described that a treatment agent containing an acidic water permeable agent and a pH adjuster is applied to the surface of the spunbonded nonwoven fabric by a gravure method.

Patent Document 4 relates to a fiber treatment agent for water-absorbent articles. An object of the invention of Patent Document 4 is to provide a treating agent which has initial and repeated water permeability while showing weak acidity in the pH of the surface material of a water-absorbent article and which is hard to be washed away by water such as urine and sweat. There is. The invention of Patent Document 4 discloses that by combining a component derived from a specific natural fat or oil as a treatment agent, the water permeability of the top sheet is improved and the surface of the non-woven fabric is maintained to be weakly acidified. It is stated that the method of adhering the treatment agent to the fiber is not particularly limited, and a commonly used method such as an oiling roll method, a dipping method, or a spraying method can be used in any step such as spinning and drawing. There is. In the example, the polypropylene spunbonded non-woven fabric is immersed in a diluent for a treatment agent, squeezed with a mangle, and dried to obtain a treated non-woven fabric.

Japanese Unexamined Patent Publication No. 2017-42228 Special Table 2003-516778 Japanese Unexamined Patent Publication No. 2014-91899 Japanese Unexamined Patent Publication No. 2018-35458

As described above, it is known to add a pH adjuster to the non-woven fabric to make it weakly acidic, and to use a pH adjuster and a surfactant in combination to maintain the weak acidity. However, when a water-soluble pH adjuster such as citric acid is applied, there is a problem that it is washed away by water such as urine. According to the inventions of Patent Documents 3 and 4, although the pH adjuster applied to the surface of the non-woven fabric does not easily run off, the surface of the top sheet of the absorbent article is a surface that comes into direct contact with the skin, so that the pH adjuster and surfactant used are used. The type of agent had to be carefully selected in consideration of the effect on the skin.

Further, if citric acid or the like is added to a fiber treatment agent having excellent water absorption characteristics, the water absorption characteristics may be deteriorated. The weakly acidified non-woven fabric may have its water absorption characteristics impaired by the weak acidification, and its water absorption performance is not always high.

Further, in an absorbent article such as a diaper, so-called liquid return may occur in which the excrement liquid such as urine once absorbed by the absorber returns to the surface of the non-woven fabric due to body pressure or the like. Such liquid-returning excrement tends to be alkaline, and even if the surface of the non-woven fabric is maintained weakly acidic, it may cause diaper rash. To solve this problem, it is conceivable to dissolve a pH adjuster in the excrement liquid in order to weakly acidify the excrement liquid such as urine, especially the liquid-returning excrement liquid. For this purpose, a more acidic pH adjuster is required, but in addition to the concern that the non-woven fabric to which the strongly acidic pH adjuster is applied may affect the skin, in the non-woven fabric manufacturing process, a processing line, etc. It is known to be a factor that causes rust on the metal parts of the manufacturing equipment of.

In view of such a situation, the present invention is a non-woven fabric capable of weakly acidifying the excrement liquid returned from the absorbent body of the absorbent article while maintaining the water absorption property, and suppressing the influence on the skin. Further, in the manufacturing process as well, it is an object of the present invention to provide a non-woven fabric sheet which is easy to maintain and can be efficiently manufactured because the generation of rust in the metal portion of the manufacturing equipment is suppressed.

The present inventor has repeated studies to solve the above-mentioned problems, and by adding a pH adjuster to the inside of the laminated non-woven fabric without adding a pH adjuster to the surface of the top sheet itself, the water absorption characteristics of the surface of the non-woven fabric The present invention was completed with the finding that weak acidification of the excrement can be achieved while maintaining the above.

The present invention has the following configurations.
[1] A non-woven fabric sheet in which a plurality of layers are laminated and integrated, and a pH adjuster is not added to the surface of the non-woven fabric sheet, and a pH adjuster is added to the inside of the non-woven fabric sheet. Non-woven sheet.
[2] When a liquid having a pH of 7.0 or higher passes through the non-woven fabric sheet, the pH of the liquid after passing through the non-woven fabric sheet is lower than the pH of the liquid before passing through the non-woven fabric sheet. The non-woven fabric sheet according to [1].
[3] The nonwoven fabric sheet according to the above [1] or [2], which comprises at least one layer to which a pH adjusting agent is added and at least one layer to which a pH adjusting agent is not added.
[4] The item according to any one of [1] to [3], wherein a pH adjuster is not added to at least one of the two layers located on the surface of the laminated structure in which at least two layers are laminated. Non-woven sheet.
[5] The non-woven fabric sheet according to any one of [1] to [4], wherein the pH adjuster contains at least one organic acid.
[6] The non-woven fabric sheet according to any one of [1] to [5], to which a hydrophilic surfactant is attached to the surface.
[7] The non-woven fabric sheet according to any one of [1] to [6], which has been shaped and processed.
[8] An absorbent article comprising the nonwoven fabric sheet according to any one of [1] to [7] as a top sheet.

In the present invention having the above-mentioned structure, the pH adjusting agent is not added to the surface of the non-woven fabric sheet, and by adding the pH adjusting agent to the inside of the laminated structure of the non-woven fabric sheet, the pH adjusting agent does not easily flow down and , The water absorption property of the surface of the non-woven fabric sheet can be maintained. In addition, the pH adjuster added to the non-woven fabric sheet can weakly acidify the excrement liquid that has returned from the absorbent body of the absorbent article, thereby preventing skin troubles such as diaper rash. Further, since the pH adjuster is added to the inside of the non-woven fabric sheet, the pH adjuster applied to the non-woven fabric sheet is less likely to come into contact with the skin, and there is less concern about the influence of the pH adjuster on the skin. In addition, since the pH adjuster does not come into contact with metal parts such as processing lines in the manufacturing process of the non-woven fabric sheet, the occurrence of rust and the like is suppressed. Therefore, it is possible to increase the concentration of the pH adjuster.

Hereinafter, the present invention will be described in detail.
(Structure of non-woven fabric sheet)
The non-woven fabric sheet of the present invention has a laminated structure in which a plurality of layers, that is, at least two types of layers are laminated and integrated. The number of layers is not particularly limited, but may be, for example, 2 to 6 layers, preferably 2 to 4 layers, and more preferably 2 or 3 layers. In the present specification, when the number of layers is two, each of the layers is referred to as an upper layer and a lower layer, and when the number of layers is three, each of the layers is referred to as an upper layer, an intermediate layer and a lower layer. In the case of the non-woven fabric sheet of the present invention, a pH adjuster is added to the upper surface of the lower layer in the case of a two-layer structure, the upper and lower surfaces of the intermediate layer in the case of a three-layer structure, or the upper surface of the lower layer. The non-woven fabric sheet of the present invention has a feature that a pH adjuster is not added to the surface thereof and a pH adjuster is added to the inside. For convenience of explanation, the non-woven fabric sheet of the present invention is referred to as an upper layer or a lower layer, but the vertical direction is not defined in actual use, and either the upper layer or the lower layer is designated as the upper layer (table) depending on the purpose or application. You may use it.

In the present specification, the "surface" of the non-woven fabric sheet means a portion exposed on the surface of the laminated non-woven fabric sheet, and the "inside" refers to a portion of the non-woven fabric sheet having a laminated structure other than the exposed portion. say. Further, "no pH adjuster added to the surface of the non-woven fabric sheet" does not mean that the pH adjuster on the surface of the non-woven fabric sheet is zero, but it does not mean that the pH adjuster is zero in the surface of the non-woven fabric sheet. It also includes the case where some pH regulator is present on the surface due to agent transfer. For example, when the amount of the pH adjuster present on the inside is 3 times or more the amount of the pH adjuster present on the surface, "the pH adjuster is not added to the surface and the pH is adjusted inside. It corresponds to the constitution of the present invention that "the agent is added".

In the non-woven fabric sheet which is a laminated non-woven fabric, the pH adjuster is not added to the surface and the pH adjuster is added to the inside. , XPS measurement is performed, and it can be confirmed by a known method such as detecting a functional group derived from a pH adjuster.

The nonwoven fabric sheet of the present invention is characterized in that a plurality of layers are laminated and integrated, a pH adjusting agent is not added to the surface of the nonwoven fabric sheet, and a pH adjusting agent is added to the inside of the nonwoven fabric sheet. And. Specifically, this configuration can be realized by laminating and integrating at least one layer to which the pH adjuster is added and at least one layer to which the pH adjuster is not added. For example, when the non-woven fabric sheet has two layers, the web to which the pH adjuster is added and the web to which the pH adjuster is not added are overlapped so that the side to which the pH adjuster is added is on the inside. The non-woven fabric sheet of the present invention can be obtained by integrating by heat treatment. When the non-woven fabric sheet has three layers, two webs to which the pH adjuster is added are stacked so that the side to which the pH adjuster is added is on the inside, and the pH adjuster is further added on the webs. The non-woven fabric sheet of the present invention can be obtained by superimposing the non-woven fabrics and integrating them by heat treatment. Similarly, when the number of layers is larger, the nonwoven fabric sheet of the present invention can be obtained by laminating in such a manner that the layers (surfaces) to which the pH adjuster is added are not exposed on the surface.

In the non-woven fabric sheet of the present invention, when a liquid having a pH of 7.0 or higher passes through the non-woven fabric sheet, the pH of the liquid after passing through the non-woven fabric sheet is lower than the pH of the liquid before passing through the non-woven fabric sheet. Is preferable. As for the measurement of the pH of the liquid after passing through the non-woven fabric sheet, the method described in Example <Method for measuring the pH of the solution after passing the liquid> can be used. The liquid having a pH of 7.0 or more is a liquid such as urine or menstrual blood when the non-woven fabric sheet of the present invention is used for an absorbent article. The degree of decrease in pH is not particularly limited, but for example, it is preferable that the liquid having a pH of 7 to 9 reaches the pH of 5 to 7 after passing through the non-woven fabric sheet of the present invention. Further, it is preferable that the pH of the liquid drops by 0.3 to 3.0 before and after passing through the non-woven fabric sheet, and the pH of the liquid after passing through the non-woven fabric sheet is weakly acidic (generally in the range of pH 3.0 to 6.5). ) Is preferable. Since the liquid after passing through the non-woven fabric sheet shows weak acidity, the risk of skin troubles such as diaper rash can be reduced even when the liquid returns to the absorbent article.

The non-woven fabric sheet of the present invention can be suitably used as a top sheet for absorbent articles. As the non-woven fabric constituting the top sheet, the non-woven fabric of the present invention is preferably a non-woven fabric of through-air because the non-woven fabric of the present invention has the best tactile sensation. Further, each layer constituting the non-woven fabric sheet is preferably a hydrophilic short fiber layer. Specifically, as a raw material for the non-woven fabric sheet of the present invention, a composite fiber having heat adhesiveness can be mentioned. The heat-adhesive component of the composite fiber may be a thermoplastic resin component that heat-melts by passing hot air through the web made of the fiber to form an adhesive point. The thermal adhesion points between the fibers are formed by melting the thermoplastic resin component having a low melting point by hot air treatment. Specifically, as the resin component constituting the composite fiber, a polyolefin-based (for example, polypropylene, propylene copolymer [a polymer containing propylene as a main component and this and another α-olefin; for example, ethylene-propylene) Binary copolymer, propylene-butene-1 binary copolymer, propylene-hexene-1 binary copolymer, etc.], polyethylene, etc.), polyester-based (for example, polyethylene terephthalate), polyamide-based (for example, nylon 6) Etc.) can be exemplified. Specific combinations of the low melting point component and the high melting point component in the composite fiber include polyethylene (low melting point component) and polypropylene (high melting point component), polyethylene (low melting point component) and polyethylene terephthalate (high melting point component), and the like. In particular, from the viewpoint of bulkiness and strength of the non-woven fabric, it is preferable to use a composite fiber made of polyethylene and polyethylene terephthalate.

Further, in the web for producing the through-air non-woven fabric, which is the non-woven fabric sheet of the present invention, in addition to the above-mentioned composite fibers having heat adhesiveness, natural fibers (wooden fibers, etc.), recycled fibers (rayon, etc.), and semi-synthetic fibers are used. Fibers (hereinafter referred to as "non-thermally adhesive fibers") that are not so-called heat-adhesive fibers such as fibers (acetate and the like), chemical fibers, and synthetic fibers (polyester, acrylic, nylon, vinyl chloride, etc.) may be included. The "non-thermally adhesive fiber" refers to a fiber that does not undergo a thermal change (melting or softening) that is involved in thermal bonding in the thermal bonding performed when manufacturing a non-woven fabric. When non-heat-adhesive fibers are included, the proportion of non-heat-adhesive fibers to the total weight of the web is not limited as long as it does not interfere with the effects of the invention, but can be, for example, 1-30% by weight, preferably 1-30% by weight. It is 3 to 15% by weight.

The fineness of the composite fiber is not particularly limited, but is preferably in the range of 0.5 to 8.0 dtex, and more preferably in the range of 1.0 to 6.0 dtex. Within this range, the obtained through-air non-woven fabric has a good feel to the touch.

The shape of the composite fiber can be exemplified by a concentric sheath core type, an eccentric sheath core type, a parallel type, a radial type, etc. Is preferable. In the case of a concentric sheath-core type composite fiber or an eccentric sheath-core type composite fiber, it is particularly preferable that the low melting point component constitutes the sheath component and the high melting point component constitutes the core component.

Through-air nonwoven fabric having a basis weight of a nonwoven sheet of the present invention is not particularly limited as long as can exhibit the effects of the present invention, for example, the case of stacking, the basis weight of each layer of the single layer can be a 10 to 20 g / m ² , 5 to 15 g / m ² is preferable. The total basis weight upon laminating each layer, be in the range of 15 to 40 g / m ^2, void of nonwoven fabric is sufficiently secured, liquid permeability is improved, also, if a basis weight of 40 g / m ² or less , The voids of the non-woven fabric can be sufficiently secured, and the liquid return can be suppressed.

The thickness of the through-air nonwoven fabric is also not particularly limited, but for example, the thickness when each layer is laminated and integrated can be 0.2 to 2.0 mm, and is 0.5 to 1.7 mm. It is more preferable if there is. If the thickness is 0.2 mm or more, the cushioning property is excellent and a soft touch is obtained.

(Surfactant)
It is preferable that a treatment agent such as a surfactant is applied to the composite fibers constituting the through-air nonwoven fabric which is the nonwoven fabric sheet of the present invention. In the present invention, a surfactant is used to modify a thermoplastic resin, which is generally hydrophobic, to develop hydrophilicity. Surfactants are roughly classified into nonionic surfactants and ionic surfactants. Examples of the ionic surfactant include anionic surfactant and cationic surfactant.

The surfactant used in the present invention is not particularly limited, but a surfactant having excellent static electricity that does not generate static electricity during card processing or passing through an equipment line is preferable.

The surfactant used in the present invention is a surfactant having excellent water absorption characteristics at the first time (referred to as an initial hydrophilic surfactant), and even if water is repeatedly absorbed, the decrease in water absorption is small and water absorption is small. It can be appropriately selected according to the purpose of use of the water-absorbent article such as a hydrophilic surfactant having excellent properties (referred to as a highly durable hydrophilic surfactant).

The liquidity (pH) of the surfactant used in the present invention is, for example, 4.0 or more and 9.0 or less, preferably 5.0 or more and 8.0 or less. When the pH is 4.0 or more, there is no risk of rusting on the metal part touched in the card process when manufacturing the non-woven fabric, the line for producing the product using the non-woven fabric, or the like. When the pH is 9.0 or less, the non-woven fabric treated with the surfactant does not have a too high pH of the non-woven fabric itself, and there is no risk of rash due to contact with the skin such as the buttocks.

As the surfactant used in the present invention, one having a pH higher than that of acid is suitable so as not to give a burden to the skin. The non-woven fabric sheet of the present invention has the effect of lowering the pH of the excreted liquid, but since the surfactant itself dissolves when the excreted liquid passes through the top sheet of the non-woven fabric, it plays an auxiliary role in lowering the pH. To bear. Therefore, if the pH of the surfactant is higher than acidic, the amount of the pH adjuster to be added can be reduced, and if the pH of the surfactant is high, the amount of the pH adjuster to be added also increases.

The amount of the surfactant applied is not particularly limited as long as it has the effect of the present invention. For example, when a highly durable surfactant is used as the surfactant, it is 0.2 to 0.2 to the weight of fibers constituting the non-woven fabric. It can be 1.0% by weight, more preferably 0.3 to 0.8% by weight. Further, when the nonwoven fabric sheet of the present invention is a through-air nonwoven fabric, the surfactant may be added at the stage of producing a web from short fibers as a material, or may be added at another step, particularly. Not limited.

(PH regulator)
An organic acid is preferably used as the pH adjuster used in the present invention. The pH regulator preferably contains at least one organic acid. Examples of organic acids include organic hydroxy acids, organic sulfonic acids, organic phosphoric acids and the like. Specific examples of the organic hydroxy acid include glycolic acid, lactic acid, malic acid (DL-aronic acid), tartaric acid, citric acid and the like, and examples of the organic sulfonic acid include paratoluenesulfonic acid and dodecylbenzenesulfonic acid. Examples of the organic phosphoric acid include octyl phosphate and dodecyl phosphate. Of these, malic acid or citric acid is preferably used in consideration of safety, versatility, and cost. Further, fatty acids, plant-derived fats and oils such as oleic acid, etc. are also mentioned as pH adjusters.

The pH adjuster used in the present invention can be applied as an aqueous solution. As the solvent used for the aqueous liquid, an aqueous liquid having a pH of 3 or more and less than 7 is preferably used. Examples of the water to be used in the aqueous liquid include ion-exchanged water, distilled water, hard water, soft water and the like, and among them, ion-exchanged water, distilled water and the like are preferable. The aqueous liquid refers to an aqueous liquid containing a liquid containing an aqueous component as a main solvent, such as an aqueous solution, an aqueous suspension, and an aqueous emulsion. The pH adjuster is added to the material of the non-woven fabric sheet as, for example, an aqueous solution of 1.0 to 10.0% (wt / vol), preferably 2.0 to 8.0% (wt / vol), and then heated to a solvent. Can be applied to the non-woven fabric sheet by removing.

A method of adding an aqueous solution of the pH adjuster according to the present invention to a non-woven fabric sheet will be described. As the addition method, a known method can be applied, and examples thereof include a roller touch method, a spray method, a shower method, and a dipping method. The step of adding the aqueous liquid containing the pH adjuster may be added to the web during the step of preparing the non-woven fabric sheet before laminating and integration, or may be added to the non-woven fabric sheet in the step after preparing the non-woven fabric sheet. May be good. Among these, a method of adding a pH adjuster on the web by a spray method is preferable. By adding the pH adjuster by the spray method, the pH adjuster can be applied to only one side of the web, and the configuration of the present invention in which the pH adjuster is not exposed on the surface of the non-woven fabric sheet can be realized. Further, another web is laminated on the web and heat-treated to obtain the non-woven fabric sheet of the present invention. According to this method, the step of drying the aqueous liquid can be omitted by the heat treatment when producing the nonwoven fabric, and the nonwoven fabric sheet of the present invention is completed without the pH adjuster coming into contact with the metal part of the processing line or the like. ..

In the nonwoven fabric sheet of the present invention, the amount of the pH adjusting agent applied is not particularly limited as long as the effect of the present invention can be obtained. For example, when citric acid is used as the pH adjusting agent, it is 1.0 with respect to the weight of the nonwoven fabric sheet. It can be ~ 10.0% by weight, more preferably 2.0 to 8.0% by weight. The non-woven fabric sheet of the present invention can contain a larger amount of the pH adjuster than the conventional one by adding a pH adjuster to the inside of the laminated non-woven fabric sheet.

(Production method)
The non-woven fabric sheet of the present invention is a through-air nonwoven fabric, and can be produced by appropriately selecting a known method and conditions for producing the through-air nonwoven fabric.
For example, in order to produce a laminated non-woven fabric, a composite fiber as a raw material is used for carding to obtain a first layer of a card web of the composite fiber. Next, the same process is performed to obtain a second layer card web. A pH adjuster is added to the upper surface of the second layer by a spray method or the like, and the first layer to which the pH adjuster is not added is laminated on the upper surface thereof. Subsequently, the stacked card webs are placed on a transport support (belt conveyor) and fed into the heat treatment apparatus. In the heat treatment apparatus, heating is performed to a temperature at which only the low melting point resin of the composite fiber is melted. When the melted low melting point resins are bonded (heat bonded) to each other, the intersections of the fibers are fused to produce a laminated and integrated non-woven fabric having a three-dimensional structure. Since this heating temperature is treated at a temperature higher than the low melting point component of the composite fiber, the water content of the applied pH adjuster evaporates, which is also a drying step.

The non-woven fabric sheet thus obtained may be cut into an appropriate size and used as it is, or may be shaped or perforated by an embossing roll or a needle roll. By performing appropriate shaping processing, when the non-woven fabric sheet is used as the top sheet of the absorbent article, an absorbent article having more excellent absorbency and liquid return prevention property can be obtained.

(Absorbent article)
The non-woven fabric sheet of the present invention can be used as a top sheet for absorbent articles such as diapers such as disposable diapers, urine pads, and menstrual blood absorption pads.

Absorbent articles include a top sheet, an absorber, and a waterproof back sheet. As the top sheet, one of the above-mentioned through-air non-woven fabrics can be used as the top sheet. On the lower surface side of the top sheet, an absorber mainly for absorbing and retaining water such as excrement is arranged. The absorber is typically composed of an absorbent material. As the absorbent material, a known absorbent material that can be used for absorbent articles such as disposable diapers can be used. Specific examples thereof include fluff pulp, super absorbent polymer (SAP), hydrophilic sheet and the like, and one or more of these can be used.

Hereinafter, the present invention will be described in more detail by way of examples, but the following examples are for purposes of illustration only. The scope of the present invention is not limited to this embodiment.

The measurement method and definition of the physical property values used in the examples are shown below.
<Standard raw cotton>
Concentric sheath-core type heat-adhesive composite fiber of polyethylene (melting point 130 ° C., melt mass flow rate 16 g / 10 min) as a low melting point component and polypropylene (melting point 160 ° C., melt mass flow rate 20 g / 10 min) as a high melting point component, weight component ratio 50 / 50%, fineness 2.2dtex, cut length 51mm, highly durable hydrophilic surfactant adhesion (adhesion amount pure 0.50%, pH 7.0 / manufactured by Matsumoto Yushi Seiyaku Co., Ltd., "Marpoteron E-800")
<Absorbent>
Kim towel, wiper white 4 layers (manufactured by Nippon Paper Crecia Co., Ltd.) 9 cm x 9 cm, weight 5 g
<Making artificial urine>
1. 1. Artificial urine (pH 7.0) composition:
(1) Urea 2.00% by weight
(2) Sodium chloride 0.80% by weight
(3) Magnesium sulfide heptahydrate 0.08% by weight
(4) Calcium chloride dihydrate 0.03% by weight
(5) Ion-exchanged water 97.09% by weight

<Rust test>
An iron plate (length 10 cm × width 10 cm × thickness 0.2 cm / weight 150 g) whose surface was wiped with toluene after polishing the surface was prepared. After passing 10 cc of ion-exchanged water through the non-woven fabric sheet as a sample, an iron plate was placed on the non-woven fabric sheet for 5 seconds. The iron plate removed from the non-woven fabric sheet was stored for 7 days in a constant temperature and humidity chamber having a temperature of 50 ° C. and a humidity of 65%. After storage, the state of rust on the iron plate surface was visually confirmed.
<Method of measuring pH of solution after passing liquid>
-Measuring device (pH meter) / "S220" manufactured by METTLER TOLEDO
A Kim towel / non-woven fabric / LISTER was placed on an acrylic plate (length 10 cm × width 10 cm × thickness 5 mm), and 20 ml of artificial urine (pH 7.0) was passed through the plate. After passing the liquid, the LISTER was removed, another acrylic plate was installed, a weight of 4 kg was placed on the acrylic plate, and the mixture was left for 1 minute. After 1 minute, the weight and the acrylic plate were removed, and the pH value of the liquid adhering to the removed acrylic plate was measured.

<Repeated liquid flow time measurement>
-Measuring device (liquid flow rate measuring device) / "LISTER" manufactured by LENZING TECHNIK
Kim towel / non-woven fabric / LISTER were placed on an acrylic plate (length 10 cm × width 10 cm × thickness 5 mm) in this order, and the flow time of 15 ml of artificial urine was measured. After the measurement, the mixture was left in that state for 1 minute, the Kim towel was replaced, and the second and third liquid passing times were measured in the same manner.

<pH adjuster>
-Citric acid (crystal) pure content 99.5%, manufactured by Fuso Chemical Industry Co., Ltd.-DL-malic acid (crystal) pure content 99.0%, manufactured by Fuso Chemical Industry Co., Ltd.
・ Presence or absence of carboxy group (-COOH) derived from organic acid by XPS measurement ・ Equipment: X-ray photoelectron spectroscopy analyzer PHI Quantera SXM [ULVAC-PHI]
・ X-ray source: Monochromatic AIkα
・ X-ray output: 25W / 15kV
-Measurement method: The surface of the non-woven fabric was transferred onto an indium foil for measurement. (The surface of the non-woven fabric was brought into close contact with the indium foil and rubbed from the back side of the non-woven fabric about 10 times to transfer the surface components to the indium foil, which was measured by XPS.)

[Example 1]
^Two webs with a basis weight of 20 g / m 2 were collected by a carding method using reference raw cotton. An aqueous solution having a pure citric acid content of 4% was sprayed on the surface of one of the two webs as a pH adjuster (this was used as the lower layer). ^{The amount of adhesion to the web was 4.0 g / m 2} when calculated based on the change in the weight of the web after drying. Another web (upper layer) is laminated on the surface layer of the web sprayed with the pH adjuster, and a hot air circulation type suction band dryer (temperature 135 ° C., line speed 8 m / min, wind speed 1.3 m / sec, heat treatment distance 2 m). By passing hot air through the web, the interfiber entanglement points constituting the web were adhered and dried, to prepare a through-air non-woven fabric having a grain ^{size of 40 g / m 2 and a thickness of 1.5 mm.}
When the rust test was carried out from the upper layer side of the through-air non-woven fabric, no rust was confirmed. When the pH of the solution was measured after passing the solution, the pH value was 6.0, and the pH of artificial urine was slightly acidified from 7.0. Moreover, when the liquid passing time was repeatedly measured, the performance of the highly durable hydrophilic surfactant was not impaired.

[Example 2, Comparative Examples 1 and 2]
The through-air non-woven fabric prepared in the same manner as in Example 1 except that an aqueous solution of DL-malic acid pure content of 4% was sprayed as a pH adjuster (Example 2), and the same as in Example 1 except that the pH adjuster was not sprayed. The through-air non-woven fabric (Comparative Example 1) prepared in 1) was laminated with the upper web on the lower web (without spraying), and an aqueous solution of DL-malic acid pure 4% was sprayed on the upper surface as a pH adjuster. Table 1 shows the results of the through-air non-woven fabric (Comparative Example 2) prepared in the same manner as in Example 1 except for the above.

[Example 3]
Three webs with a basis weight of 10 g / m ^{2 were collected by a carding method using reference raw cotton.} Three webs were used as the upper layer, middle layer and lower layer, respectively. An aqueous solution having a pure citric acid content of 2% was sprayed on the lower surface as a pH adjuster. Subsequently, a web was laminated as an intermediate layer on the surface on the lower layer side on which the pH adjuster was sprayed, and an aqueous solution having a pure citric acid content of 2% was also sprayed on the surface of the intermediate layer. Table 1 shows the results of the through-air non-woven fabric (Example 3) obtained by laminating (upper layer) the web on the surface of the sprayed intermediate layer and performing the heat treatment in the same manner as in Example 1.

As shown in Table 1, none of Examples 1 to 3 rusted in the rust test. Moreover, the performance of the highly durable hydrophilic surfactant was not impaired. Furthermore, in the pH measurement of the solution after passing the liquid, when the pH value of the rehydrated artificial urine was measured, it was changed to the acidic side. As for the presence or absence of a pH adjuster on the surface of the non-woven fabric, XPS measurement was performed, and a peak of a carboxy group (-COOH) derived from citric acid and DL-malic acid was confirmed on the surface to which the organic acid was added. ..

On the other hand, in Comparative Example 1 in which the pH adjuster was not sprayed, the pH value of the rehydrated artificial urine was measured in the pH measurement of the solution after passing the solution, and the pH value remained 7.0 and did not change. rice field. In Comparative Example 2 in which the pH adjuster was sprayed on the most surface layer side of the non-woven fabric, rust was generated in the rust test, and the performance of the highly durable hydrophilic surfactant was also deteriorated.

The non-woven fabric sheet of the present invention weakly acidifies the excreted liquid against the return of the liquid from the absorber without impairing the absorbability of the excreted liquid such as urine, so that it is possible to prevent skin irritation and the like. In addition, since the pH adjuster is applied to the inner layer of the non-woven fabric, it is also considered to reduce the burden on the equipment, such as suppressing the generation of rust on the metal parts such as the processing line. The non-woven fabric sheet of the present invention can be used as a diaper such as a disposable diaper, a urine pad, a menstrual blood absorption pad, and the like.

Claims (8)

A non-woven fabric sheet in which multiple layers are laminated and integrated,
No pH adjuster was added to the surface of the non-woven fabric sheet.
A non-woven fabric sheet in which a pH adjuster is added to the inside of the non-woven fabric sheet. When a liquid having a pH of 7.0 or more passes through the non-woven fabric sheet, the pH of the liquid after passing through the non-woven fabric sheet is lower than the pH of the liquid before passing through the non-woven fabric sheet. Item 2. The non-woven fabric sheet according to Item 1. The non-woven fabric sheet according to claim 1 or 2, which includes at least one layer to which a pH adjuster is added and at least one layer to which a pH adjuster is not added. No pH adjuster has been added to at least one of the two layers located on the surface of the laminated structure in which at least two layers are laminated.
The non-woven fabric sheet according to any one of claims 1 to 3. The non-woven fabric sheet according to any one of claims 1 to 4, wherein the pH adjusting agent contains at least one organic acid. The nonwoven fabric sheet according to any one of claims 1 to 5, wherein a hydrophilic surfactant is attached to the surface thereof. The non-woven fabric sheet according to any one of claims 1 to 6, which has been shaped and processed. An absorbent article comprising the nonwoven fabric sheet according to any one of claims 1 to 7 as a top sheet.