JP4566059B2 - Absorbent article surface sheet - Google Patents

Description

  The present invention relates to a surface sheet of an absorbent article such as a disposable diaper, an incontinence pad, a sanitary napkin, and a panty liner (corimono sheet), and an absorbent article using the same.

Conventionally, it is known to use a multilayered nonwoven fabric having two or more layers as a surface sheet of absorbent articles such as disposable diapers and sanitary napkins.
The present applicant has previously proposed to use two or more kinds of fibers having different hydrophilicity due to liquid permeation in such a multilayered nonwoven fabric.
That is, the present applicant uses two kinds of fibers having different hydrophilicity after liquid permeation in both the surface layer forming the skin contact surface and the back layer arranged on the absorber side, respectively, Proposed to achieve both liquid return prevention properties (see Patent Document 1), and the first layer forming the skin contact surface and the second layer arranged on the absorber side are each composed of fibers subjected to hydrophilic treatment. In addition, it has been proposed to use, for the first layer, a fiber whose hydrophilization degree is likely to be lowered by contact with water as compared with the constituent fiber of the second layer (see Patent Document 2).

JP-A-62-261363 JP 2004-166832 A

However, in Patent Document 1, depending on the selection of the fibers used for the back layer, the resistance when the liquid permeates increases, and the liquid drawability may not always be sufficient.
The technique of Patent Document 2 improves to some extent the so-called liquid return prevention effect that the liquid absorbed by the absorbent body returns to the skin contact surface, but the performance required for the absorbent article and its surface sheet is increasing year by year. There is a risk that the demand in recent years cannot be fully met.

  Therefore, the objective of this invention is providing the surface sheet which has the outstanding liquid return prevention property, and the touch is also favorable, and an absorbent article using the same.

  The present invention is a surface sheet of an absorbent article having a first layer that forms a skin contact surface and a second layer that is adjacent to the first layer and is disposed on the absorber side. The second layer is composed of fibers having a fineness greater than that of the first layer, and the hydrophilicity decreases due to liquid permeation. The object is achieved by providing a top sheet for absorbent articles, which contains difficult fibers and fibers whose hydrophilicity tends to decrease due to liquid permeation.

  The present invention achieves the above object by providing an absorbent article comprising a top sheet of the absorbent article, a liquid-impermeable or water-repellent back sheet, and an absorber positioned between both sheets. It is.

The surface sheet of the absorbent article of the present invention has excellent liquid return prevention properties and good touch.
The absorptive article of the present invention has the outstanding liquid return prevention nature, and the touch of the skin contact side is also good.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The absorbent article in which the top sheet of the absorbent article of the present invention is used is generally a liquid-permeable top sheet, a liquid-impermeable or water-repellent back sheet, and a liquid-retaining absorbent located between both sheets. With body.
The surface sheet of the absorbent article of the present invention is made of a nonwoven fabric described in detail below.

  As constituent elements other than the top sheet constituting the absorbent article, for example, the above-described back sheet and absorbent body, the same ones that have been normally used for this type of absorbent article can be used. For example, as the back sheet, a thermoplastic resin film with or without moisture permeability, a water-repellent nonwoven fabric, or a laminate thereof can be used. Absorbents have a structure in which a mixture of pulp fibers and superabsorbent polymer particles is wrapped in paper such as tissue paper, or a structure in which the upper and lower layers of superabsorbent polymer particles are sandwiched between layers of pulp. Things can be used.

  The nonwoven fabric constituting the top sheet has a multilayer structure, and typically has a two-layer structure. The non-woven fabric having a two-layer structure includes a first layer that forms a skin contact surface and a second layer that is adjacent to the first layer and is disposed on the absorber side. That is, the nonwoven fabric is disposed on the absorbent article such that the first layer side faces the wearer's skin and the second layer side faces the absorber side. Note that another sheet may be interposed between the second layer and the absorber. For example, an intermediate sheet called a sublayer made of a single layer or multilayer nonwoven fabric may be interposed between the second layer and the absorber.

The fineness of the constituent fibers of the first layer forming the skin contact surface is 2.2 dtex or less, preferably 0.1 to 2.2 dtex, more preferably 0.8 to 2.0 dtex.
On the other hand, the fineness of the constituent fiber of the second layer arranged on the absorber side is larger than that of the constituent fiber of the first layer. The constituent fibers of the second layer preferably have a fineness of 0.2 to 16.5 dtex, more preferably 1.0 to 7.8 dtex.
In the present invention, fine fibers are used for the first layer facing the wearer's skin, and fibers thicker than the first layer are used for the second layer facing the absorber.
The ratio (d1 / d2) between the fineness d1 of the constituent fibers of the first layer and the fineness d2 of the constituent fibers of the second layer is 0.06 to 0.99, particularly 0.1 to 0.95. preferable.

The fineness of the constituent fibers of each layer (n-th layer) of the surface sheet (and the constituent fibers of each layer of the intermediate sheet described later) is measured as follows.
In the electron microscope observation of the nonwoven fabric, the fiber thickness is measured with respect to the standard thickness fibers at 10 positions of the nth layer, and the fiber thickness average value Dn (μm) is calculated. Next, the fiber resin constituting the n-th layer is specified by DSC (differential scanning calorimetry) or the like, and the theoretical fiber density Pn (g / cm ³ ) is obtained. From the fiber thickness average value Dn (μm) and the theoretical resin density Pn (g / cm ³ ), the number of grams per 10,000 m of fiber length is calculated, and this value is used as the fineness (dtex) of the fibers constituting the nth layer. To do.
In addition, the fineness of the constituent fibers of each layer is measured without particularly distinguishing between fibers that are likely to have a low hydrophilicity due to liquid permeation and fibers that are unlikely to have a low hydrophilicity due to liquid permeation.

  Since the constituent fibers of the first layer have low fineness and low rigidity, the skin facing surface of the top sheet exhibits a soft texture. In addition, since the number of fibers is larger than when using thick fibers with the same basis weight, there is no rough feeling on the skin-facing surface of the top sheet, and a smooth texture is given, giving a softer impression to the wearer. In addition, the concealability with respect to the color of excrement absorbed by the absorber is also increased. The high concealability gives the user a good impression that the absorbent article is clean.

  When thin fibers are simply used on the skin-facing surface of the topsheet, the amount of wetback tends to increase, but fibers thicker than the fibers adjacent to the thin fiber layer, specifically the aforementioned By providing the second layer, it is possible to improve the touch and the like while suppressing an increase in the amount of wetback. The reason why an increase in the wetback amount can be suppressed or the wetback amount can be reduced by the second layer using thick fibers is considered as follows. Since thick fibers have high rigidity, they are difficult to be compressed even if they are subjected to a compressive force during the manufacturing process of the nonwoven fabric, in a state where the absorbent article is packaged, or when the absorbent article is mounted. Therefore, the bulkiness of the second layer is maintained. That is, a large interfiber distance is maintained. As a result, the capillary force of the second layer becomes weak, and the liquid absorbed in the absorber is difficult to move to the second layer. That is, the wetback amount is reduced.

  As the constituent fibers of the second layer, it is preferable to use fibers having high rigidity in addition to using fibers having a fineness greater than that of the constituent fibers of the first layer. From this point of view, it is preferable to use, for example, polyethylene terephthalate fiber, polypropylene fiber, composite fiber composed of polyethylene terephthalate and polyethylene, or composite fiber composed of polypropylene and polyethylene as the constituent fiber of the second layer. These fibers can be used alone or in combination of two or more. Examples of the form of the composite fiber include a core-sheath type (concentric and eccentric) and a side-by-side type. When these fibers are staple fibers, the fiber length is preferably about 38 to 60 mm. When the second layer is mixed with fine fibers, resistance to the liquid that tries to pass through the nonwoven fabric increases. Therefore, it is preferable that the second layer has all the constituent fibers described above.

On the other hand, as the fiber constituting the first layer, it is preferable to use a fiber composed of a resin having a small fineness and a high density. This is because the bulkiness of the topsheet increases and the bulkiness is maintained while maintaining the rigidity of the fibers, and the skin facing surface of the topsheet becomes more flexible. In addition, since the diameter of one fiber is slightly thinner and the space between the fibers is slightly larger than in the case of using fibers composed of a low-density resin having the same basis weight, the skin facing surface in the topsheet This is because the feeling of roughness is eliminated, a smoother texture is exhibited, and the amount of wetback is reduced. As such a fiber, it is preferable to use a composite fiber composed of polyethylene terephthalate and polyethylene or a composite fiber composed of polypropylene and polyethylene. These fibers can be used alone or in combination of two or more. In particular, since polyethylene terephthalate has a higher density than polyethylene and polypropylene, it is preferable to use a composite fiber composed of polyethylene terephthalate and polyethylene, which is a composite fiber containing the polyethylene terephthalate. Further, by using a composite fiber composed of polyethylene terephthalate and polyethylene, there is also an advantage that the skin facing surface of the surface sheet becomes smoother and the texture becomes better. In addition, since polyethylene terephthalate has a higher melting point than polyethylene, when a non-woven fabric is produced by the air-through method or heat roll method described later, melting of polyethylene terephthalate does not occur even when heat treatment is performed at a temperature near the melting point of polyethylene. As a result, the rigidity of polyethylene terephthalate gives stiffness to the non-woven fabric and gives a firm flexibility, not just a softness. The form of the composite fiber and the fiber length can be the same as in the case of the second layer.
The first layer is preferably composed only of fibers having a fineness of 2.2 dtex or less, but may additionally contain other fibers. For example, for the purpose of controlling liquid permeability and touch, about 0.1 to 30% by weight of fibers having a fineness of 0.1 to 5.0 dtex can be blended with respect to the total amount of fibers in the first layer.

  The constituent fibers of the first layer show hydrophilicity at the initial stage (that is, before use of the absorbent article). When the constituent fibers of the first layer are hydrophilic, the surface of the fibers is easily wetted, and the liquid can be quickly absorbed as a surface sheet. Further, from the viewpoint of wet back, the main constituent fiber of the first layer is preferably one in which the liquid is less likely to be absorbed into the fiber, and therefore, it is preferable that the hydrophobic fiber is subjected to a hydrophilic treatment. On the other hand, the constituent fibers of the second layer are hydrophilic in the initial stage. As a result, the liquid that has passed through the first layer smoothly passes through the second layer and is guided to the absorber. The constituent fibers of the second layer are preferably those obtained by subjecting hydrophobic fibers to a hydrophilic treatment or hydrophilic fibers. The first layer and the second layer may contain fibers exhibiting hydrophobicity as long as the absorption and permeation of the liquid are not inhibited.

The basis weight of the first layer is preferably 5 to 30 g / m ² , particularly preferably 8 to ²⁰ g / m ² . The basis weight of the second layer is preferably 5 to 45 g / m ² , particularly 8 to 40 g / m ² . The basis weight of the whole nonwoven fabric including the first layer and the second layer is preferably 10 to 75 g / m ² , and particularly preferably 18 to 45 g / m ² . The basis weight of the second layer is preferably the same or higher than the basis weight of the first layer.

The constituent fibers of the first layer are fibers whose hydrophilicity is likely to be lowered by liquid permeation. In other words, the constituent fibers of the first layer tend to have a low degree of hydrophilicity upon contact with water, and after the liquid has permeated through the top sheet and absorbed into the absorbent body, the first portion of the part that has permeated the liquid. One layer of the constituent fibers is substantially hydrophobic.
On the other hand, the second layer includes both fibers that are less likely to be hydrophilic due to liquid permeation and fibers that are likely to be less hydrophilic due to liquid permeation. Fibers that are less likely to decrease hydrophilicity due to liquid permeation contained in the second layer are those that are less likely to decrease in hydrophilicity upon contact with water, and the liquid that has permeated the first layer further permeates the second layer. Even after being absorbed by the absorber, the hydrophilicity is substantially maintained.
In addition, even if the liquid comes into contact with the top sheet again, the liquid is transmitted from the first layer to the second layer by the second layer that maintains hydrophilicity and the momentum of the liquid. The transition of the liquid to the layer and the transition from the second layer to the absorber are performed smoothly.

The fibers that constitute the first layer and whose hydrophilicity is likely to be reduced by liquid permeation (hereinafter also referred to as non-durable fibers in the first layer) are liquids supplied to the skin contact surface side (excreted urine, etc.) ) Decreases the degree of hydrophilicity when passing through the non-woven fabric, and dries in the time until the next liquid passes to make the surface substantially hydrophobic. As a result, the liquid absorbed by the absorber is prevented from returning to the skin contact surface, and the amount of wetback is reduced.
On the other hand, since the fibers constituting the second layer include fibers whose hydrophilicity is not easily lowered by liquid permeation (hereinafter also referred to as durable fibers in the second layer), the liquid supplied to the skin contact surface side ( When the liquid passes again after the excreted urine or the like passes through the nonwoven fabric, the liquid permeability of the nonwoven fabric as a whole is maintained and the fibers constituting the second layer are hydrophilic by liquid permeation. From the absorbent body to the skin contact surface in combination with the high fineness of the fibers constituting the second layer, since the fibers contain fibers that tend to decrease (hereinafter also referred to as non-durable fibers in the second layer). The reversion of the liquid is more effectively prevented.

  From the viewpoint of further improving the liquid permeability and liquid return prevention performance of the entire nonwoven fabric after liquid permeation, the mass ratio of the durable fiber in the second layer to the non-durable fiber in the second layer (durable fiber: The non-durable fiber) is preferably 30:70 to 70:30, and more preferably 40:60 to 60:40.

The non-durable fiber in the first layer and the fiber used as the non-durable fiber in the second layer can be obtained, for example, by controlling the hydrophilizing agent, conditions and the like when hydrophilizing the hydrophobic fiber. For example, it is preferable to use a nonionic surfactant mainly as a hydrophilizing agent, specifically, contact with water such as polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester. It is preferable to use a substance that is relatively easily removed from the fiber surface and apply the hydrophilizing agent to the surface of the hydrophobic fiber.
Similarly, the fibers used as the durable fibers in the second layer can also be obtained by controlling the hydrophilizing agent and conditions when hydrophilizing the hydrophobic fibers. For example, polyglycerin fatty acid ester, polyether-polyester block copolymer, polyether-modified silicone, and fatty acid ester of ethylene oxide-added polyhydric alcohol as a hydrophilizing agent can be easily contacted with water from the fiber surface. It is obtained by using a substance that does not leave and applying the hydrophilizing agent to the surface of the hydrophobic fiber, or kneading the hydrophilizing agent into the fiber in advance.
The durable fibers of the second layer are preferably those obtained by subjecting hydrophobic fibers to a hydrophilic treatment, but the hydrophilic fibers such as cotton and rayon are 0.1 to 40% by weight based on the total amount of the second layer. You may mix | blend a grade. In addition, natural fibers such as cotton have a fineness distribution and include a portion of 2.2 dtex or less. Therefore, from the viewpoint of easy control of the fiber diameter and the like, the durable fibers of the second layer are hydrophilized. It is preferable to use a synthetic fiber to which is applied and / or a semi-synthetic fiber (regenerated fiber) such as rayon.

Whether the constituent fiber of the first layer and the second layer is a fiber (durable fiber) whose hydrophilicity is hardly lowered by liquid permeation or a fiber (non-durable fiber) whose hydrophilicity is easily lowered by liquid permeation For example, the determination can be made based on the sedimentation time measured by the following method.
<Method of measuring sedimentation time>
The fibers in the raw material stage before producing the top sheet are uniformly loosened for each fiber type and used for measurement. 5.0 ± 0.1 g of fiber is packed so as not to protrude into the cylindrical wire container described in ASTM D1117-80 5.2.1.1, and this container is filled with 1000 cc of ion-exchanged water at a temperature of 23 ° C. The time T1 (s) until the entire cylindrical wire-container completely sinks below the surface of the water after measuring in the cylindrical cup container having a diameter of 115 mm is measured.
Next, the fiber is taken out from the cylindrical wire container and air-dried at room temperature. After confirming that the moisture has been completely removed by air drying, perform the same operation as above using the air-dried fiber, and place the cylindrical wire container filled with the air-dried fiber under the water surface in the container filled with ion-exchanged water. Force to sink completely.
Next, the fiber is taken out from the cylindrical wire container and air-dried at room temperature. After confirming that the moisture has been completely removed by air drying, perform the same operation as above using the air-dried fiber until the cylindrical wire container filled with the air-dried fiber is completely submerged in a container filled with ion-exchanged water. The time T2 (s) is measured. The same measurement was performed with n = 3 on the same fiber, and the average value was calculated as the sedimentation time (s).

Times T1 (s) and T2 (s) are measured by the above method, and if T1 (s) is a fiber of 200 seconds or less, it is determined that the fiber is a hydrophilic fiber. That is, it is judged as a durable fiber or a non-durable fiber. And if T2 (s) which becomes the 3rd liquid contact after being settled in water twice is 200 seconds or less, it will judge that it is a durable fiber, and if it exceeds 200 seconds, it will be a non-durable fiber It is judged that.
The T1 (s) of the durable fiber and the non-durable fiber is preferably within 100 seconds, more preferably within 50 seconds, and even more preferably within 10 seconds. Further, T2 (s) of the durable fiber is more preferably 150 seconds or shorter, and even more preferably 100 seconds or shorter, from the viewpoint of liquid permeability.
It is preferable that the non-durable fiber in the first layer and the non-durable fiber in the second layer have a lower degree of decrease in hydrophilicity due to liquid permeation in the latter than the non-durable fiber in the first layer.
In the examples described later, whether or not the fibers are durable fibers and non-durable fibers was determined by a method of measuring the settling times T1 (s) and T2 (s).

A contact angle with ion-exchanged water may be used as a reference for determining non-durable fibers and durable fibers.
The contact angle is an angle between a water droplet on the fiber and the fiber surface, and it can be determined that the smaller the contact angle, the higher the hydrophilicity. Measure the contact angle before and after liquid permeation.
The measurement may be in a fiber state or a non-woven state. In the state of the nonwoven fabric, a total of 50 g of ion-exchanged water is allowed to pass through a circle having a diameter of 10 mm, dried at 30 ° C. for about 2 hours, and measured for the contact angle of the ion-exchanged water. To do.
The non-durable fiber preferably has a contact angle of 30 ° to 80 ° before liquid permeation, and preferably has a contact angle of 50 ° to 100 ° after liquid permeation. The contact angle before the liquid permeation of the durable fiber is preferably 30 ° to 80 °, and the contact angle after the liquid permeation is preferably 35 ° to 80 °. When the contact angle after liquid permeation is 20 ° or more larger than the contact angle before liquid permeation, it is determined that there is no durability.
The measurement method of the contact angle before liquid permeation in the nonwoven fabric is as follows.

[Measurement method of contact angle]
Measurement was performed using a Keyence microscope VH-8000 with a medium-magnification zoom lens (with illumination ring) tilted to 90 ° and setting the condition to 500 times. The measurement sample used was cut into a size of MD 150 mm × CD 70 mm with the upper and lower layers integrated. The measurement environment was 20 ° C./50% RH, and the measurement sample was set on the measurement stage so that the measurement surface can be observed from the CD direction of the web (nonwoven fabric).

The reason for observing the web from the CD direction is that the fibers of the web are generally oriented in the MD direction, and the possibility that the fibers are arranged in the width direction of the measurement screen increases. By setting in this way, the lens is observed from a direction perpendicular to the fiber length direction.
When the contact angle of the constituent fibers of the first layer is obtained, the fibers on the surface of the first layer are used as measurement targets, and when the contact angle of the adult fibers of the second layer is obtained, the surface of the second layer (when used as a surface sheet) Is the measurement target of the fiber on the surface facing the absorption structure. Usually, in a fiber sheet having a multilayer structure, it is possible to divide the sheet at the interface, but depending on the condition of the interface, fibers in another layer may be mixed. For this reason, when it is necessary to measure the first layer and the second layer separately for some reason, the contact angle is measured on a non-overlapping surface.

Next, water droplets are attached to the fiber surface with a spray bottle filled with ion exchange water (using a tool that makes the fog state as fine as possible) to the set measurement sample, and within 5 seconds (2 to the best possible). 3 seconds). The reason why it is necessary to capture an image in a short time after attachment is to prevent the attached water droplet from evaporating due to the light emitted from the measurement part of the microscope and to prevent contact angle change due to the oil agent. The contact angles of 10 observation results with clear focal points at both ends or one end of the water droplet were measured, and the average value thereof was defined as “contact angle”. The contact angle is measured by drawing a tangent line to the fiber of a water droplet on an image or a printed photograph and performing image analysis or a protractor as shown in FIG. The contact angle can be measured by taking out each constituent fiber from the upper and lower layers instead of the surface sheet.

In addition, it is necessary to pay attention to the following items when measuring the contact angle.
(A) The contact angle on the upper surface of the fiber is measured. The measurement is not performed on water droplets that fall on the bottom of the fiber, or on two or more fibers.
(B) When the fiber has a fine crimp such as a spiral, it is measured at a place where the crimp is small or the fiber is stretched to eliminate the crimped state.
(C) The measurement result of the contact angle is an arithmetic average of 10 measurement values at different locations. However, if the hydrophilicity is high, water droplets hardly stay on the fibers during measurement and may flow. In that case, the “contact angle” is determined according to the flow rate.
-The total number of measurements (total number of measurement points where contact between the fiber and water was observed, the sum of cases where water droplets flowed and did not flow after contact, and so on) until the measurement value reached 10 When less than 40% has flowed, the average result of 10 measured values is defined as “contact angle”.
・ If 40% or more of the total number of measurements has flowed to 10 measurement values, or if 40% or more has flowed at the time of measurement at 10 locations, the “contact angle” Is 20 ° or less.

  As the nonwoven fabric constituting the surface sheet according to the present invention, those obtained by various nonwoven fabric manufacturing methods can be used. In particular, it is preferable to be obtained by an air-through method or a heat roll method from the viewpoints of good texture, bulkiness, and the like. The air-through method is a method in which a fiber web such as a card web is placed on a breathable net or drum, and hot air is blown to heat-bond intersections of constituent fibers to form a nonwoven fabric. In the heat roll method, a fiber web such as a card web is passed between an engraving roll heated to a predetermined temperature and a smooth roll, or sandwiched between a pair of smooth rolls, and the intersection of the constituent fibers is thermally fused. This is a method of making a nonwoven fabric. Of these two methods, it is preferable to use the air-through method because a nonwoven fabric having a better texture and a bulkier bulk can be obtained.

  As is clear from the manufacturing method described above, the nonwoven fabric obtained by the air-through method (hereinafter also referred to as air-through nonwoven fabric) is a net or drum facing surface (hereinafter also referred to as net facing surface) and a hot air blowing surface (hereinafter referred to as “air-through nonwoven fabric”). 2 surfaces). Of these two surfaces of the air-through nonwoven fabric, the nonwoven fabric is preferably disposed on the diaper so that the net facing surface faces the wearer's skin. That is, in the air through nonwoven fabric manufacturing method, the nonwoven fabric is manufactured so that the first layer side is the net facing surface side. In other words, the non-woven fabric is manufactured so that the second layer side becomes the spray surface, and the non-woven fabric is arranged on the diaper so that the second layer side is the side facing the absorber. The reason why the air-through nonwoven fabric is arranged in this way is that the net facing surface has less fuzz and the net facing surface is smooth and has a low feeling of catching.

  Next, the preferable manufacturing method of the nonwoven fabric which comprises the surface sheet which concerns on this invention is demonstrated taking manufacture of the air through nonwoven fabric of a 2 layer structure as an example. First, a first fiber web and a second fiber web are manufactured. The first fiber web is composed of fine fibers having a fineness of 2.2 dtex or less. On the other hand, the second fiber web is composed of thick fibers having a fineness exceeding 2.2 dtex. As a manufacturing method of each fiber web, for example, when a staple fiber is used as a fiber, a card method can be used. When the fibers constituting each web are hydrophobic, a hydrophilic treatment is performed using a hydrophilizing agent. At this time, it is preferable to control the degree of hydrophilicity of the fibers constituting each web as described above.

The first fiber web is overlaid on the second fiber web, and the web is made into a non-woven fabric by the air-through method. First, the web in an overlapped state is placed on a net or drum made of a breathable material. At this time, the web is placed so that the first fiber web faces the net or the drum. As the breathable material, a resin net or a metal net is generally used.
And while the web is placed on the net or drum, hot air is blown from the second fiber web side, that is, the web side made of thick fibers, and the intersections of the fibers in the web are heat-sealed.

  The obtained air-through nonwoven fabric may be additionally subjected to ultrasonic embossing or hot roll embossing. Thereby, the texture of the nonwoven fabric is further improved and the contact area with the skin is further reduced. The air-through nonwoven fabric obtained in this way is used in-line or as a constituent member of the topsheet in a separate process after being wound up and used in the manufacturing process of the absorbent article.

  The nonwoven fabric used in the present invention exhibits softness even when disposed on almost any absorber. Examples of the absorber include an absorber of a type having a layer made only of pulp on the side facing the wearer and having an absorption holding layer mainly composed of a superabsorbent polymer on the lower side. It is preferable to dispose the non-woven fabric on an absorbent body of a type in which a polymer and pulp are mixed because the effect of suppressing wet back is enhanced.

  When the nonwoven fabric is used as a surface sheet in the case of trying to improve wearability (fitness) and portability as an absorbent article by thinning the absorbent body, the texture of the absorbent article can be obtained without hindering those characteristics. Since it increases, it is preferable. The nonwoven fabric is particularly useful when the thickness of the absorber is 5 mm or less, especially 3 mm or less. In addition, the absorbent body may be hardened due to thinning of the absorbent body. Even in such a case, if the nonwoven fabric is used, the hardness of the absorbent body is directly given to the wearer. There is also an advantage of not letting you feel it.

  The absorbent article of the present invention is an absorbent article comprising a liquid-permeable surface sheet, a liquid-impermeable or water-repellent back sheet, and an absorbent body positioned between the two sheets, the liquid-permeable surface As the sheet, the above-described top sheet of the present invention is used so that the first layer forms a skin contact surface.

  The absorbent article of the present invention is preferably one in which the top sheet according to the present invention is used in a state where an intermediate sheet is disposed between the top sheet and the absorber. The intermediate sheet is a so-called sublayer. The cushion feeling can be improved by interposing the intermediate sheet.

The intermediate sheet is made of a non-woven fabric (typically a non-woven fabric having a two-layer structure) having a third layer located on the top sheet side and a fourth layer located adjacent to the third layer and located on the absorber side. The fineness of the constituent fibers of the layer is preferably larger than the fineness of the constituent fibers of the fourth layer.
Since the fineness of the constituent fibers of the fourth layer is small, the number of fibers in contact with the absorbent body and the length of contact with the absorbent body increase, so that the liquid can be transferred to the absorbent body. When the fineness is large, liquid return from the absorber to the top sheet can be effectively prevented.

The fineness of the constituent fibers of the third layer is preferably 1.0 to 20 dtex, more preferably 2.0 to 10 dtex.
The fineness of the constituent fibers of the fourth layer is preferably 0.5 to 15 dtex, more preferably 1.0 to 6.0 dtex.
The ratio (d3 / d4) between the fineness d3 of the constituent fibers of the third layer and the fineness d4 of the constituent fibers of the fourth layer is preferably 1.1 to 40, particularly 1.3 to 10.

The fineness of the constituent fibers of the third layer is preferably equal to or greater than the fineness of the constituent fibers of the second layer of the top sheet. When the liquid supplied to the skin contact surface passes through the top sheet, the flow speed thereof decreases. By using thick fibers in the third layer, the liquid in which the fibers in the first layer and the second layer become resistant and weak in force can be efficiently transferred to the fourth layer to further improve the liquid return prevention performance. it can.
The ratio (d3 / d2) between the fineness d3 of the constituent fibers of the third layer and the fineness d2 of the constituent fibers of the second layer is 1.0 to 11.0, particularly 1.3 to 5.0. preferable.

The fineness of the constituent fibers of the fourth layer is preferably smaller than the fineness of the constituent fibers of the second layer. As a result, the force of the liquid is weakened by the dense first layer and cannot move to the absorbent body, so that the capillary force generated by the fiber thickness gradient between the second layer and the fourth layer with respect to the liquid remaining in the nonwoven fabric As a result, the remaining liquid moves to the absorber side, and even after the same wearer wears the same diaper for a long time after urination, the liquid does not remain on the skin contact surface and the feeling is improved. It will be.
The ratio (d4 / d2) between the fineness d4 of the constituent fibers of the fourth layer and the fineness d2 of the constituent fibers of the second layer is 0.006 to 0.999, particularly 0.5 to 0.95. preferable.

  Moreover, it is preferable that all the fibers constituting the third layer and the fourth layer of the intermediate sheet are fibers whose hydrophilicity hardly decreases after liquid permeation. By configuring the third layer with durable fibers similar to the durable fibers in the second layer, the drawability of the liquid can be further improved, and the wetback amount can be further reduced. When the third layer and the fourth layer are compared, it is preferable that the hydrophilicity of the fourth layer is less likely to decrease.

  As the fibers constituting the third and fourth layers, the same fibers as the durable fibers in the second layer described above can be used. The durable fiber is preferably a hydrophobic fiber that has been subjected to a hydrophilic treatment. However, the hydrophilic fiber such as cotton or rayon is blended in an amount of about 0.1 to 40% by weight based on the total amount of the third and fourth layers. May be. In addition, natural fibers such as cotton have a fineness distribution and include a portion of 2.2 dtex or less. Therefore, from the viewpoint of easy control of the fiber diameter, the durable fibers of the third and fourth layers are hydrophilic. It is preferable to use synthetic fibers that have been subjected to a chemical treatment and / or semi-synthetic fibers (regenerated fibers) such as rayon.

The third layer is preferably a three-dimensional crimped fiber in which all or part of the constituent fibers are three-dimensionally crimped. The three-dimensional crimped fiber is a fiber expressing a three-dimensional spiral crimp, for example, an eccentric core-sheath type composite fiber or a side-by-side component composed of two types of thermoplastic polymer materials having different shrinkage rates. Made of type composite fiber. As the three-dimensional crimped fiber, various known ones can be used.
The three-dimensional crimped fiber is excellent in the ability to form a space between fibers for the thickness of the fiber. Therefore, by using a three-dimensional crimped fiber, a liquid having a relatively high speed can be satisfactorily transferred to the fourth layer through a relatively wide space between the fibers, and a liquid having a relatively low speed can also be used. To move to the fourth layer. Thereby, the absorbent article which was further excellent in the drawability of a liquid and the liquid return prevention property can be obtained.
The content of the three-dimensional crimped fiber in the third layer is preferably 1 to 100% by mass, particularly preferably 30 to 100% by mass.

  The present invention is not limited to the embodiment. For example, in the nonwoven fabric constituting the top sheet, one or more additional layers may be further arranged below the second layer.

  The present invention can be applied to various absorbent articles including, for example, disposable diapers, sanitary napkins, incontinence pads, panty liners (cage sheets), and the like.

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

[Example 1]
Polyethylene terephthalate (PET, core) / core-sheath type composite fiber (fineness of 2.0 dtex made of polyethylene (PE, sheath)) (hydrophilicized with octyl alcohol (EO) 1 phosphate salt, non-layered in the first layer) The first fiber web was manufactured by the card method using a durable fiber). The basis weight was 10 g / m ² .
Apart from this, core-sheath type composite fiber (5.6 dtex) made of polypropylene (PP, core) / polyethylene (PE, sheath), hydrophilized with polyglycerin fatty acid ester, durability in the second layer Core-sheath type composite fiber with a fineness (5.6 dtex) consisting of polyethylene terephthalate (PET, core) / polyethylene (PE, sheath) (hydrophilized with sorbitan fatty acid ester, in the second layer) (Corresponding to the non-durable fiber) was mixed with a card machine, and a second fiber web was produced by the card method using this as a raw material. The basis weight was 15 g / m ² .

The first fiber web was superimposed on the second fiber web, and both were placed on a metal endless net made of wire mesh. At this time, the web was placed so that the first fiber web was opposed to the net. While running the net at a speed of 20 m / min, hot air at a temperature of 140 ° C. was blown from the second fiber web side at a speed of 60 m / min for 18 seconds. Thereby, the intersections of the constituent fibers of the web were heat-sealed to obtain an air-through nonwoven fabric having a basis weight of 25 g / m ² . The obtained non-woven fabric had a two-layer structure of a first layer composed of fibers having a fineness of 2.0 dtex and a second layer composed of two types of fibers each having a fineness of 5,6 dtex.

  The obtained air-through nonwoven fabric was used as a top sheet for disposable diapers. Further, a moisture-permeable film made of polyethylene was used as the back sheet, and a laminated fiber body (pulp / polymer weight ratio = 50/50) of fluff pulp and superabsorbent polymer particles was used as the absorber. . A surface sheet was placed directly on the absorbent body, and a disposable diaper was produced according to a conventional method. At this time, the air-through nonwoven fabric used as the top sheet was placed on the diaper so that the first layer side would be the skin facing surface of the diaper. That is, the spraying surface in the air-through nonwoven fabric was made to be the absorber-facing surface in the diaper.

[Examples 2 and 3 and Comparative Examples 1 to 4]
Using the fibers shown in Table 1 as constituent fibers of the first layer and the second layer, an air-through nonwoven fabric and a disposable diaper were obtained in the same manner as in Example 1.

Example 4
Using the fibers shown in Table 1 as the constituent fibers of the first layer and the second layer, an air-through nonwoven fabric for a surface sheet is produced in the same manner as in Example 1, and a nonwoven fabric for an intermediate sheet is produced as follows. A disposable diaper was obtained in the same manner as in Example except that the air-through nonwoven fabric was used as a top sheet and an intermediate sheet was interposed between the top sheet and the absorbent body below the top sheet.

Production method of intermediate sheet: Core-sheath type composite fiber of a fineness (7.8 dtex) composed of polypropylene (PP, core) / polyethylene (PE, sheath) (hydrophilized with polyglycerin fatty acid ester, in the third layer A third fiber web was produced by the card method using a durable fiber). The basis weight was 13 g / m ² . Separately, a core-sheath type composite fiber (3.3 dtex) made of polyethylene terephthalate (PET, core) / polyethylene (PE, sheath), hydrophilized with polyoxyethylene alkyl ether, in the fourth layer Was used as a raw material, and a fourth fiber web was produced by the card method. The basis weight was 13 g / m ² .
A third fiber web was placed on the fourth fiber web, and both were placed on a metal endless net made of wire mesh. At this time, the web was placed so that the third fiber web was opposed to the net. While running the net at a speed of 20 m / min, hot air having a temperature of 140 ° C. was blown from the side of the fourth fiber web at a speed of 60 m / min for 18 seconds. As a result, the intersections of the constituent fibers of the web were thermally fused to obtain an air-through nonwoven fabric having a basis weight of 26 g / m ² . The obtained nonwoven fabric had a two-layer structure of a third layer composed of fibers having a fineness of 7.8 dtex and a fourth layer composed of two types of fibers having a density of 3.3 dtex.

  About the obtained diaper, the texture of the surface sheet was evaluated by the following method, and the wetback amount and the drawability of the liquid were measured. The results are shown in Table 2 below.

[Texture of surface sheet]
A sensory test was conducted with 20 women as monitors, and the texture of the surface sheet in the diaper was scored according to the following evaluation criteria, and the average score was calculated. The items of the sensory test were softness, smoothness, and touch, and the surface sheet in the diaper of Comparative Example 1 was used as a reference.
Evaluation criteria +5 points ... good +4 points ... slightly +3 points ... Neither (Comparative Example 1)
+2 points ... slightly bad + 1 points ... bad

[Wetback amount]
200 g of physiological saline was absorbed from the top surface sheet of the disposable diaper and left for 10 minutes. Next, Advantech's No. 1 was placed on the absorption site of the physiological saline. 20 sheets of 4A filter paper were stacked, and further, a load was applied for 2 minutes to absorb the physiological saline on the filter paper. The load was such that 34.3 N was applied to an area of 10 cm × 10 cm. After 2 minutes, the load was removed, and the weight of the filter paper that absorbed physiological saline was measured. The weight of the filter paper before absorption was subtracted from this weight, and the value was taken as the wetback amount.

[Liquid drawability]
The disposable diaper was fixed on a plate inclined at 45 degrees so that the surface material faced upward. 50 g of physiological saline was flowed to a position 200 mm inside from the upper end of the diaper, and the distance of the physiological saline flowing down on the surface material was measured. The same measurement was repeated 3 times, and the distance of each time was measured. It means that the shorter the distance is, the better the drawability of the liquid. Evaluation was performed according to the following criteria.

◎ ・ ・ The initial liquid flow distance is 60 mm or less, and the liquid flow distance does not become long even if it is repeatedly measured.
○ The liquid flow distance for the first time is more than 60 mm to 100 mm, and the liquid flow distance does not become long even if it is repeatedly measured.
Δ ·· The initial liquid flow distance is 100 mm or less, but the liquid flow distance is gradually increased by repeated measurement. However, the liquid flow distance does not exceed 200 mm, and the liquid does not leak from the end of the diaper.
× ·· In the first or repeated measurement, the liquid flow distance exceeds 200 mm, and the liquid leaks from the end of the diaper.

  As is clear from the results shown in Table 2, the disposable diapers of Examples 1 to 4 (the absorbent article using the top sheet according to the present invention or the absorbent article of the present invention) have a good texture on the top sheet. In addition, it can be seen that the amount of wetback is small and the liquid drawability is excellent. On the other hand, it can be seen that the surface sheets of Comparative Examples 1 to 3 are inferior in the drawability of the liquid, and the surface sheet of Comparative Example 4 has a large amount of wetback.

FIG. 1 is a diagram for explaining a method of measuring a contact angle, and (a) and (b) are diagrams in which the contact angle is preferably measured. In addition, (a ') and (b') are figures which show the fiber after the droplet on a fiber evaporates, and are used in order to measure the tangent of the fiber surface in a boundary part with a water droplet.

Claims (1)

Absorption comprising a liquid-permeable top sheet, a liquid-impermeable or water-repellent back sheet, and an absorber positioned between both sheets , and an intermediate sheet disposed between the top sheet and the absorber In the sex goods,
The liquid-permeable surface sheet has a first layer that forms a skin contact surface, and a second layer that is adjacent to the first layer and disposed on the absorber side,
The first layer is made of a fiber having a fineness of 2.2 dtex or less and hydrophilicity is liable to decrease due to liquid permeation,
The second layer is composed of fibers having a fineness greater than that of the constituent fibers of the first layer, and includes fibers that are less likely to be reduced in hydrophilicity due to liquid permeation and fibers that are likely to be lower in hydrophilicity due to liquid permeation.
The mass ratio of the fibers constituting the second layer, the fibers whose hydrophilicity is hardly lowered by liquid permeation and the fibers whose hydrophilicity is easily lowered by liquid permeation, is 30:70 to 70:30,
The intermediate sheet has a third layer located on the top sheet side, and a fourth layer located on the absorber side adjacent to the third layer, and the fineness of the constituent fibers of the third layer is Larger than the fineness of the constituent fibers of the fourth layer,
The fineness of the constituent fibers of the third layer is equal to or greater than the fineness of the constituent fibers of the second layer,
The fineness of the constituent fibers of the fourth layer is smaller than the fineness of the constituent fibers of the second layer,
The constituent fibers of the third layer and the fourth layer are fibers whose hydrophilicity is hardly lowered by liquid permeation,
An absorbent article , wherein all or part of the constituent fibers of the third layer are three-dimensional crimped fibers .

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