JP2024041666A - Composite absorbent material and sanitary products using it - Google Patents

Abstract

[Problem] To provide a composite absorbent that can stably exhibit sufficient absorption performance when absorbing blood and can suppress blood leakage. [Solution] The composite absorbent (4) is for use in sanitary products for absorbing blood. The composite absorbent includes a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and at least one of a highly water-absorbent polymer and pulp fibers. In the polymer absorbent, the pore size is in the range of 0.003 to 100 μm, and in the pore distribution showing the relationship between pore size and pore volume, the maximum volumetric pore size at which the pore volume ratio is maximum is in the range of 1 to 95 μm, and the ratio of the pore volume due to pores with a pore size of 7 μm or less is less than 46% of the pore volume of all pores. [Selected Figure] Figure 1

Description

The present invention relates to a composite absorbent material and sanitary products using the same.

BACKGROUND ART Absorbent materials containing pulp fibers and superabsorbent polymers are known as absorbent materials used in sanitary products such as sanitary napkins. By including a super absorbent polymer, the amount of body fluid absorbed by the absorbent body can be increased. However, with superabsorbent polymers, during the absorption process of blood (menstrual blood), red blood cells in the blood adhere to the surface, so it takes time to absorb blood, and the absorption capacity of blood is different from that of urine. Comparatively, there is a possibility of a decline. In this case, the absorbent body may not be able to stably exhibit its absorption performance.

As a means to deal with such a situation, a polymer foam material is disclosed in Patent Document 1. The polymeric foam material is capable of absorbing blood and blood-based fluids and has an open, hydrophilic, flexible, non-ionic polymeric foam structure that communicates with each other and has a defined capillary structure. Characterized by specific surface area, resistance to compressive strain, free absorption capacity, and salt content.

Patent No. 3432828

According to US Pat. No. 5,203,309, the polymer foam material is a porous absorbent body with a three-dimensional network skeletal structure that absorbs blood into its pores. Therefore, during the blood absorption process, red blood cells in the blood can be prevented from adhering to the surface and making it difficult to absorb the blood. Thereby, the absorption rate of blood absorption can be improved. Therefore, for example, it is conceivable to replace part or all of the superabsorbent polymer with a polymer foam material.

However, since the polymer foam material is a structure whose volume does not change before and after absorbing blood, it cannot absorb blood beyond the volume of its pores. Therefore, there is a possibility that sufficient absorption performance may not be obtained, such as difficulty in obtaining a sufficient amount of absorption. Also, if the amount of blood excreted is large, the polymeric foam material may not be able to absorb enough blood. Blood may then leak from the absorbent body containing the polymeric foam material.

The object of the present invention is to provide a composite absorbent that can stably exhibit sufficient absorption performance when absorbing blood and can prevent blood leakage, and a sanitary product using the same.

One aspect of the present invention is a composite absorbent body for sanitary products for absorbing blood, which comprises a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, a super absorbent polymer, and pulp fibers. In the polymer absorbent containing at least one of the above, the pore diameter is in the range of 0.003 to 100 μm, and in the pore distribution indicating the relationship between the pore diameter and the pore volume, the ratio of the pore volume is the largest. A composite absorbent body in which the maximum volume pore diameter is in the range of 1 to 95 μm, and the proportion of the pore volume by pores with a pore diameter of 7 μm or less is less than 46% of the pore volume of all pores. .

Another aspect of the present invention is a sanitary product that includes a topsheet, a backsheet, and the above composite absorbent body located between the topsheet and the backsheet.

The present invention provides a composite absorbent that can stably exhibit sufficient absorption performance when absorbing blood and can also prevent blood leakage, and a sanitary product using the same.

FIG. 1 is a schematic plan view of the sanitary napkin 1 in the unfolded state according to the embodiment, viewed from the skin-facing surface side in the thickness direction. It is a figure explaining the manufacturing process of absorbent A which is an example of the polymer absorbent concerning an embodiment. This is a SEM photograph of absorbent A at a magnification of 50 times. This is a SEM photograph of absorbent A at a magnification of 100 times. This is a SEM photograph of absorbent A at a magnification of 500 times. This is a SEM photograph of absorbent A at a magnification of 1500 times. It is a graph showing the relationship between blood retention magnification and blood sucking time.

This embodiment relates to the following aspects.
[Aspect 1]
A composite absorbent body for sanitary products for absorbing blood, comprising a polymeric absorbent having a hydrophilic continuous skeleton and continuous pores, and at least one of a superabsorbent polymer and pulp fibers, In the polymer absorbent, the pore size is in the range of 0.003 to 100 μm, and in the pore distribution indicating the relationship between pore size and pore volume, the maximum volume pore size at which the pore volume ratio is maximum is A composite absorbent body in which the proportion of pore volume by pores having a pore diameter of 7 μm or less is less than 46% of the total pore volume.

This composite absorbent body contains at least one of a super absorbent polymer and pulp fibers, and a polymer absorbent. That is, at least a portion of the superabsorbent polymer or at least a portion of the pulp fibers in a normal absorbent body are replaced with a polymer absorbent. Here, in the polymer absorbent, there are few pores (less than 46%) with a pore diameter smaller than 7 to 8 μm, which is the size of red blood cells in blood (menstrual blood), so red blood cells do not adhere to the surface of the blood. can enter the pores of the polymer absorbent while suppressing the Furthermore, since the pores are continuous, blood can penetrate into the deep pores of the polymer absorbent. Thereby, the polymer absorbent can absorb blood quickly without being inhibited by red blood cells, and can stably exhibit its blood retention ability to absorb a large amount of blood. That is, it can absorb blood quickly and can be used as a substitute for pulp fibers, and can also absorb a large amount of blood and can be used as a substitute for super absorbent polymers. Therefore, since this composite absorbent contains such a polymer absorbent, it can stably exhibit sufficient absorption performance without being inhibited by red blood cells when absorbing blood, and also prevents blood from leaking. It becomes possible to suppress this. In addition, in the case of a polymer absorbent having a pore distribution in which the maximum volume pore diameter, at which the pore volume ratio is maximum, exceeds 95 μm, there are many pores with too large pore diameters as a whole, and once inside the pores. Blood that has entered the pores is more likely to pass through the pores and be released out of the pores again.

[Aspect 2]
The composite absorbent according to aspect 1, wherein the polymer absorbent has a blood retention ratio of 6.5 g/g or more in 1 minute.
In this composite absorbent, the polymer absorbent has a very high blood retention ratio (more than 6.5 g/g) per minute, so the polymer absorbent quickly and in large quantities collects blood (menstrual blood). Can be absorbed. That is, the polymer absorbent can absorb blood quickly, and can stably exhibit its blood retention ability to absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 3]
The composite according to aspect 1 or 2, wherein in the polymer absorbent, the proportion of pore volume by pores having a pore diameter of 53 μm or more in the pore distribution is less than 29% of the pore volume of all pores. Absorber.
In this composite absorbent, there are few pores (less than 29%) with large pore diameters (53 μm or more) in the polymer absorbent. Therefore, the pore diameter is too large for the red blood cells in the blood (menstrual blood), and it is difficult for red blood cells that once entered the pores to pass through the pores and be released outside the pores again. can do. Therefore, the polymer absorbent can exhibit its blood retention ability more stably and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 4]
In the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 4 μm or less in the pore distribution is less than 40% of the pore volume of all pores, according to any one of aspects 1 to 3. Composite absorbent body described in Section.
In the present composite absorbent, there are few pores (less than 40%) in the polymer absorbent with a pore diameter smaller than 4 μm, which is the size that allows red blood cells in blood (menstrual blood) to deform to enter capillaries. Therefore, blood can enter the interior of the polymer absorbent while further suppressing red blood cells from adhering to the surface. Thereby, the polymeric absorbent can absorb blood quickly, stably exhibit its blood retention ability, and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 5]
The composite according to any one of aspects 1 to 4, wherein in the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 1 μm or more is 90% or more of the pore volume of all pores. Absorber.
In this composite absorbent, there are few (less than 10%) pores in the polymer absorbent with a pore diameter smaller than 1 μm, which is the size that makes it difficult for plasma components (moisture) in blood (menstrual blood) to enter. Therefore, blood can enter the interior of the polymer absorbent while preventing plasma components from adhering to the surface. Thereby, the polymeric absorbent can absorb blood quickly, stably exhibit its blood retention ability, and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 6]
The composite absorber according to any one of aspects 1 to 5, wherein the continuous skeleton of the polymer absorbent has a hydrophilic group.
In this composite absorber, when the polymer absorbent absorbs blood, the hydrophilic groups ionize and repel each other, causing the skeleton and the pores between the skeletons to expand, making the pore volume larger than before absorbing blood. Become. Therefore, the polymer absorbent can absorb blood (menstrual blood) more quickly and in a larger amount. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 7]
7. The composite absorbent material according to any one of aspects 1 to 6, wherein the hydrophilic group has a property of absorbing blood and being negatively charged.
In this composite absorber, when the polymer absorbent absorbs blood, when the negatively charged red blood cells and the polymer absorbent, which absorbs blood and becomes negatively charged, approach each other, the negative charges repel each other. Fit. Therefore, red blood cells can be made difficult to aggregate within the pores, and can be made easier to penetrate into the polymer absorbent. Thereby, the polymer absorbent can absorb blood (menstrual blood) more quickly and in a larger amount. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 8]
The composite absorbent body according to any one of aspects 1 to 7, comprising the pulp fiber.
In this composite absorbent body, blood (menstrual blood) is absorbed extremely quickly by the pulp fibers, and the blood absorbed by the pulp fibers is quickly transferred to the polymer absorbent. Therefore, the pulp fibers are able to absorb blood again, and a decrease in their absorption rate can be suppressed. Furthermore, by mixing pulp fibers, it is possible to increase the absorption capacity of the composite absorbent body while maintaining its softness. Thereby, the absorbent capacity of the sanitary product using the composite absorbent body can be increased without impairing the feeling of wearing the product. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

[Aspect 9]
The composite absorbent body has a longitudinal direction and a width direction that are perpendicular to each other, and a pair of linear heights that extend along the longitudinal direction or the width direction and are spaced apart from each other in the width direction or the longitudinal direction. The composite according to any one of aspects 1 to 8, comprising a high-density portion, and the polymer absorbent is located between one and the other of the pair of high-density portions in the width direction or the longitudinal direction. Absorber.
In this composite absorbent body, since the polymer absorbent is located between a pair of high-density areas where blood (menstrual blood) is easily discharged, sufficient absorption capacity can be ensured in that area. Thereby, even when a large amount of blood is excreted, the present composite absorbent body can absorb the large amount of blood and can suppress blood leakage.

[Aspect 10]
The composite absorbent body has a longitudinal direction and a width direction that are perpendicular to each other, and a pair of linear heights that extend along the longitudinal direction or the width direction and are spaced apart from each other in the width direction or the longitudinal direction. 9. The composite absorbent body according to any one of aspects 1 to 8, comprising a dense portion, and wherein the polymer absorbent is located outside each of the pair of high-density portions in the width direction or the longitudinal direction.
In this composite absorbent body, when blood (menstrual blood) is discharged between a pair of high-density parts, the pair of high-density parts diffuse and disperse the blood in the extending direction. The polymer absorbent material on the outside of the body can quickly absorb blood. Thereby, the present composite absorber can suppress blood leakage.

[Aspect 11]
The composite absorbent according to any one of aspects 1 to 10, wherein the polymer absorbent is a monolithic absorbent.
Since the polymer absorbent is a monolithic absorbent, this composite absorbent can more reliably absorb blood discharged into the polymer absorbent, thereby suppressing blood leakage. .

[Aspect 12]
A sanitary product comprising a topsheet, a backsheet, and the composite absorbent body according to any one of aspects 1 to 11 located between the topsheet and the backsheet.
Since the present sanitary product includes the above-described composite absorbent body, it is possible to stably exhibit sufficient absorption performance when absorbing blood, and also to suppress blood leakage.

Hereinafter, a preferred embodiment of the composite absorbent body of the present invention will be described using a sanitary napkin 1, which is an example of a sanitary product to which the composite absorbent body is applied.

In this specification, unless otherwise specified, "an object (e.g., a sanitary napkin, a composite absorbent material, etc.) placed on a horizontal surface in an unfolded state is ``Viewing in the thickness direction of the object from the top sheet side'' is simply referred to as ``planar view.'' Moreover, "longitudinal direction" refers to "the long direction of the length of a vertically elongated object (for example, a sanitary napkin in an unfolded state, a composite absorbent material, etc.) in a planar view." The "width direction" refers to the "shorter length direction of a vertically elongated object in plan view." "Thickness direction" refers to "a direction perpendicular to an object placed on a horizontal surface in an expanded state." The longitudinal direction, width direction, and thickness direction are perpendicular to each other. In addition, in the thickness direction of the sanitary napkin 1, "the side that is relatively proximal to the skin surface of the wearer when wearing the sanitary napkin 1" is referred to as the "skin-facing surface side"; When worn, the "relatively distal side to the wearer's skin surface" is referred to as the "non-skin facing surface side."

[Sanitary napkins]
1 is a schematic plan view of a sanitary napkin 1 in an unfolded state to which a composite absorbent body 4 according to an embodiment is applied. In a plan view, the sanitary napkin 1 has a longitudinal direction L and a width direction W, and has a vertically elongated outer shape with both end edges in the longitudinal direction L protruding outward in an arc shape, and is provided with a pair of flap portions 5 extending outward from both end edges in the width direction W slightly forward of the center of the longitudinal direction L. However, the outer shape of the sanitary napkin 1 is not limited to this mode, and any shape (e.g., oval, rectangular, hourglass, no flap portions, etc.) may be adopted depending on various applications and usage modes as long as it is vertically elongated.

The sanitary napkin 1 includes, in the thickness direction, a liquid-permeable top sheet 2 that forms the surface of the sanitary napkin 1 on the skin-facing side, and a back sheet that forms the surface of the sanitary napkin 1 on the non-skin-facing side. 3 and a composite absorbent body 4 located between these sheets as a basic structure. Further, the sanitary napkin 1 is arranged on the surface of the back sheet 3 (including the pair of flap parts 5) on the non-skin facing side, and the sanitary napkin 1 is adhesively fixed to the inner surface of the wearer's clothes such as underwear. It further includes an adhesive part (not shown).

The sanitary napkin 1 (composite absorbent body 4) extends along the longitudinal direction L, further includes a pair of linear high-density portions 6 arranged at intervals in the width direction W, and extends along the width direction W. , further includes a pair of linear high-density portions 7 arranged at intervals in the longitudinal direction L. However, "along a predetermined direction" includes not only a case parallel to the predetermined direction but also a case offset by ±30 degrees with respect to the predetermined direction. The high-density parts 6 and 7 are formed, for example, by embossing the topsheet 2 and the composite absorbent core 4 in the thickness direction. Note that either one of the high-density portions 6 and 7 may be omitted.

Note that the sanitary napkin 1 is not limited to such a configuration. For example, the sanitary napkin 1 has a leak-proof structure located at both ends of the sanitary napkin 1 in the width direction W at a position closer to the skin-facing surface than the top sheet 2 and extending in the longitudinal direction L. A pair of side sheets for forming walls may be provided. In that case, each of the pair of side sheets may include a plurality of elastic members arranged along the longitudinal direction L.

In the sanitary napkin 1, the composite absorbent 4 is located between the top sheet 2 and the back sheet 3, and is formed from a water-absorbent material capable of absorbing bodily fluids such as menstrual blood (blood) discharged from the wearer and permeating through the top sheet 2. The composite absorbent 4 contains, as the water-absorbent material, a polymeric absorbent having a hydrophilic continuous skeleton and continuous pores.

When absorbing water, polymer absorbents exhibit a unique water absorption behavior in which the water is taken into the continuous skeleton and then into the continuous pores. Therefore, when the polymer absorbent absorbs body fluids such as menstrual blood (blood), the hydrophilic continuous skeleton instantly takes in the body fluids by osmotic pressure and expands, expanding the volume of the continuous pores. Furthermore, body fluid can be taken into the enlarged continuous pores. Therefore, polymer absorbents can instantly absorb large amounts of body fluids. In this embodiment, the absorbed body fluid is further transferred to the super absorbent polymer with high water retention capacity, and can be steadily retained within the super absorbent polymer.

In the sanitary napkin 1, the composite absorbent body 4 includes, as an absorbent member, at least one of a superabsorbent polymer and pulp fibers in addition to a polymer absorbent having a hydrophilic continuous skeleton and continuous pores. There is. In the polymer absorbent, the pore diameter is in the range of 0.003 to 100 μm, and in the pore distribution indicating the relationship between the pore diameter and the pore volume, the maximum volume at which the pore volume ratio is maximum is determined. The pore size is in the range of 1 to 95 μm, and the proportion of the pore volume by pores with a pore size of 7 μm or less is 46% of the pore volume of all pores (with a pore size in the range of 0.003 to 100 μm). less than However, in this specification, the pore diameter refers to the diameter of the pore.

In this way, the present composite absorbent body 4 contains at least one of a superabsorbent polymer and pulp fibers, and a polymer absorbent. That is, at least a portion of the superabsorbent polymer and pulp fibers contained in the absorbent bodies of ordinary sanitary products are replaced with a polymeric absorbent. Here, in the polymer absorbent, there are few pores (less than 46%) with a pore diameter smaller than 7 to 8 μm, which is the size of red blood cells in blood (menstrual blood), so red blood cells do not adhere to the surface of the blood. can enter the pores of the polymer absorbent while suppressing the Furthermore, since the pores are continuous, blood can penetrate into the deep pores of the polymer absorbent. Thereby, the polymer absorbent can absorb blood quickly without being inhibited by red blood cells, and can stably exhibit its blood retention ability to absorb a large amount of blood. That is, it can absorb blood quickly and can be used as a substitute for pulp fibers, and can also absorb a large amount of blood and can be used as a substitute for super absorbent polymers. Therefore, since the present composite absorbent body 4 contains such a polymer absorbent, it can stably exhibit sufficient absorption performance without being inhibited by red blood cells when absorbing blood, and also prevents blood from leaking. It becomes possible to suppress the In addition, in the case of a polymer absorbent having a pore distribution in which the maximum volume pore diameter, at which the pore volume ratio is maximum, exceeds 95 μm, there are many pores with too large pore diameters as a whole, and once inside the pores. Blood that has entered the pores is more likely to pass through the pores and be released out of the pores again.

Therefore, the sanitary napkin 1 equipped with such a composite absorbent body 4 can also stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage. .

The various components of the sanitary product to which the composite absorbent of the present invention is applied will be further explained below using the sanitary napkin 1 described above.

(Top sheet)
As shown in FIG. 1, the top sheet 2 extends from one side edge of the sanitary napkin 1 in the longitudinal direction L to the other side edge in a plan view, and extends from one side edge of the sanitary napkin 1 in the width direction W. It has an external shape extending from near the side edge to near the other side edge. The top sheet 2 is arranged at a position on the skin-facing side of the sanitary napkin 1 in the thickness direction, and forms a contact surface that can come into contact with the wearer's skin, that is, the surface of the sanitary napkin 1 on the skin-facing side. The top sheet 2 is formed of a liquid-permeable sheet-like member.

As shown in FIG. 1, the top sheet 2 is slightly larger in the longitudinal direction L and width direction W than the composite absorbent 4 arranged on the non-skin facing side of the top sheet 2. In this embodiment, it further extends over a pair of flap portions 5 in the width direction W. The top sheet 2 is joined at its periphery to the back sheet 3 located on the non-skin facing side.

In the present invention, the outer shape, various dimensions, basis weight, etc. of the top sheet are not particularly limited as long as they can be used as a top sheet for sanitary products, and are determined according to desired liquid permeability, texture, flexibility, strength, etc. Any external shape, various dimensions, basis weight, etc. can be adopted.

(Back sheet)
The backsheet 3 has an outer shape that, in a plan view, extends from one edge to the other edge in the longitudinal direction L of the sanitary napkin 1, and extends from one edge to the other edge in the width direction W of the sanitary napkin 1. The backsheet 3 is disposed at a position on the non-skin-facing side in the thickness direction of the sanitary napkin 1, and constitutes the non-skin-facing surface of the sanitary napkin 1. The backsheet 3 is formed of a liquid-impermeable sheet-like member, and prevents bodily fluids such as menstrual blood (blood) that have permeated the composite absorbent body 4 from leaking out of the sanitary napkin 1.

In the present invention, the outer shape, various dimensions, basis weight, etc. of the back sheet are not particularly limited as long as they can be used as the back sheet of sanitary products, and are arbitrary depending on the desired leak-proof performance, breathability, strength, etc. The external shape, various dimensions, basis weight, etc. can be adopted.

(Composite absorber)
1, in a plan view, the composite absorbent body 4 has an elongated outer shape that extends over a wide area from the vicinity of one end edge to the vicinity of the other end edge in each of the longitudinal direction L and the width direction W, centered on the central portion in the longitudinal direction L and the width direction W of the sanitary napkin 1. Both end edges of the composite absorbent body 4 in the longitudinal direction L protrude in an arc shape outward in the longitudinal direction L.

The composite absorbent body 4 is disposed between the top sheet 2 and the back sheet 3 in the thickness direction of the sanitary napkin 1, and absorbs and retains body fluids such as menstrual blood (blood) that have passed through the top sheet 2. It is made of a predetermined water-absorbing member. The water-absorbing member includes a water-absorbing material such as a polymer absorbent described below and at least one of pulp fiber and a super-absorbent polymer, and a tissue-like sheet holding the water-absorbing material. There is. That is, the composite absorbent body 4 refers to a water-absorbing member made of a water-absorbing material capable of absorbing and retaining body fluids and a sheet that retains the same. However, the form of pulp fibers and superabsorbent polymers is not particularly limited;

In the sanitary napkin 1, the composite absorbent core 4 is bonded to each of the top sheet 2 and the back sheet 3 using an arbitrary adhesive such as a hot melt adhesive.

As described above, the composite absorbent body 4 includes a polymer absorbent having a hydrophilic continuous skeleton and continuous pores and exhibiting a unique water absorption behavior, and further includes at least one of pulp fibers and a super absorbent polymer. When the polymer absorbent is in the form of particles, the average particle size (when dry) is, for example, several hundred μm (200 to 500 μm). The polymer absorbent may be in the form of a sheet. Details of the polymer absorbent will be described later. The super absorbent polymer is called SAP (Super Absorbent Polymer), and its type is not particularly limited, and materials known in the art can be used. For example, examples of superabsorbent polymers include polyacrylate-based, polysulfonate-based, and maleic anhydride-based water-absorbing polymers. When the superabsorbent polymer is in the form of particles, the average particle size (when dry) is, for example, several hundred μm (200 to 500 μm). The superabsorbent polymer may be in the form of a sheet. The type of pulp fiber is not particularly limited, and materials known in the art can be used. For example, pulp fibers include cellulose fibers. Examples of cellulosic fibers include wood pulp, crosslinked pulp, non-wood pulp, regenerated cellulose, and semi-synthetic cellulose. As for the size of the pulp fibers, the average length of the fibers is, for example, several tens of μm (20 to 40 μm), and the average length of the fibers is, for example, several mm (2 to 5 mm). The composite absorbent body may be enclosed in a core wrap made of a liquid-permeable sheet.

The absorbent material, which is the polymeric absorbent and at least one of pulp fibers and superabsorbent polymer, is generally uniformly arranged throughout the composite absorbent body 4 in plan view, excluding manufacturing errors. However, the invention is not limited to that example and may have other arrangements in which at least one of the absorbent materials is not generally uniform but has a deliberately predetermined distribution. For example, the polymer absorbent may be disposed between one and the other of the pair of high-density parts 6 in the width direction W, with a higher basis weight than other areas, and the polymer absorbent in the pair of high-density parts 6 in the longitudinal direction L may be disposed between one and the other of the high-density portions 7 with a higher basis weight than other regions. Alternatively, the polymer absorbent may be disposed on the outside of each of the pair of high-density areas 6 in the width direction W with a higher basis weight than other areas, and the polymer absorbent may have a higher basis weight than the other areas. It may be arranged outside each of the density portions 7 to have a higher basis weight than other regions. The polymer absorbent material is preferably in contact with the superabsorbent polymer in order to ensure that body fluids absorbed by the pulp fibers are transferred to the superabsorbent polymer.

(Basic weight of pulp fiber)/(Basic weight of polymer absorbent) is more preferably larger than 1 and smaller than 10, and more preferably larger than 1 and smaller than 5. Further, (basis weight of super absorbent polymer)/(basis weight of polymer absorbent) is more preferably greater than 1 and less than 10 from the above viewpoint, and more preferably greater than 1 and less than 5.

The basis weight of the polymer absorbent, the basis weight of the pulp fibers, and the basis weight of the superabsorbent polymer can be appropriately selected depending on the absorption performance required of the composite absorbent body 4. For example, the basis weight of a polymer absorbent is 1 to 100 g/m ³² , the basis weight of pulp fiber is 50 to 500 g/m ³² , and the basis weight of a superabsorbent polymer is: Examples include 50 to 500 g/m ³² .

In the present invention, the external shape, various dimensions, basis weight, etc. of the composite absorbent body are not particularly limited as long as they do not impede the effects of the present invention, and may be any external shape or shape depending on the desired water absorbency, flexibility, strength, etc. Various dimensions, basis weights, etc. can be adopted.

The polymer absorbent used in the composite absorbent of the present invention will be explained in more detail below.

[Polymer absorbent]
The polymer absorbent has a hydrophilic continuous skeleton and continuous pores, and when absorbing water, it exhibits a water absorption behavior in which the water is taken into the continuous skeleton and then into the continuous pores, and the pore size is 0.003 to 100 μm. In the pore distribution that shows the relationship between pore diameter and pore volume, which is the range of The proportion of the pore volume by pores is not particularly limited as long as it is less than 46% of the pore volume of all pores (with a pore diameter in the range of 0.003 to 100 μm). Such a polymer absorbent is, for example, a hydrolyzate of a crosslinked polymer of two or more monomers containing at least (meth)acrylic acid ester, and a polymer having at least one hydrophilic group in its functional group. Examples include molecular compounds. More specifically, it is a hydrolyzate of a crosslinked polymer of a (meth)acrylic acid ester and a compound containing two or more vinyl groups in one molecule, and is a polymer having at least a -COONa group, which is a hydrophilic group. Examples include molecular compounds. Such a polymer absorbent is an organic porous material having at least one -COONa group in one molecule, and may further have a -COOH group which is a hydrophilic group. -COONa groups are distributed approximately uniformly in the skeleton of the porous body.

When the polymer absorbent has the above-mentioned structure, the hydrophilic continuous skeleton tends to elongate (i.e., swell) when absorbing body fluids such as menstrual blood (blood), as described later. ), and continuous pores also become easier to expand. Therefore, more body fluids can be taken into the continuous pores more quickly, and the material can exhibit excellent absorption performance as an absorbent material. In addition, because there are few pores (less than 46%) with a pore diameter smaller than 7 to 8 μm, which is the size of red blood cells in blood (menstrual blood), blood is inhibited from adhering to the surface of red blood cells, and absorbs polymers. The drug can stably exhibit its blood retention ability and absorb a large amount of blood. In addition, since the polymer absorbent has a pore distribution in which the maximum volume pore diameter, where the pore volume ratio is maximum, is in the range of 1 to 95 μm, the pore diameter as a whole becomes an appropriate size, and once It becomes easier to appropriately retain blood that has entered the pores.

In this specification, (meth)acrylic ester refers to acrylic ester or methacrylic ester.

The polymer absorbent is formed, for example, from a hydrolyzate of a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene. In such a polymer absorbent, a hydrophilic continuous skeleton is formed by an organic polymer having at least a -COONa group (hydrophilic group), and the liquid to be absorbed (for example, body fluid such as menstrual blood) is formed between the skeletons. Communicating pores (continuous pores) that serve as absorption fields are formed. Note that the hydrolysis treatment converts the -COOR group (i.e., carboxylic acid ester group) of the crosslinked polymer into a -COONa group or -COOH group (see Figure 2), so the polymer absorbent is -COOR. It may have a group.

The presence of -COOH and -COONa groups, which are hydrophilic groups in the organic polymer forming a hydrophilic continuous skeleton, can be confirmed by analysis using infrared spectrophotometry and a quantitative method for weakly acidic ion exchange groups.

Here, FIG. 2 is a diagram illustrating the manufacturing process of absorbent A, which is an example of a polymer absorbent. In this Figure 2, the upper diagram shows the constituent raw materials for polymerization, the middle diagram shows monolith A, which is a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene, and the lower diagram shows monolith A in the middle diagram after hydrolysis and Absorbent A obtained by drying treatment is shown.

The polymer absorbent will be explained below using absorbent A, which is an example of a polymer absorbent and is formed from a hydrolyzate of a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene.

The polymer absorbent is not limited to absorbent A. The polymer absorbent may be, for example, a hydrolysate of a cross-linked polymer of a (meth)acrylic acid ester and a compound having two or more vinyl groups in one molecule. Alternatively, the polymer absorbent may be, for example, a hydrolysate of a cross-linked polymer of two or more monomers including at least a (meth)acrylic acid ester. However, if the polymer absorbent is a monolithic absorbent, it has the advantage that it can quickly absorb body fluids and can more steadily transfer the body fluids temporarily held in the polymer absorbent to the highly water-absorbent polymer.

In addition, in the following explanation, "monolith A" is an organic porous body made of a crosslinked polymer of (meth)acrylic acid ester and divinylbenzene before being subjected to hydrolysis treatment, and "monolith-like organic porous body" It is sometimes referred to as "substance". Moreover, "absorbent A" is a hydrolyzate of a crosslinked polymer (monolith A) of (meth)acrylic acid ester and divinylbenzene that has been subjected to hydrolysis treatment and drying treatment. In addition, in the following description, the absorbent A refers to one in a dry state.

First, the structure of absorbent A will be explained.
Absorbent A has a hydrophilic continuous skeleton and continuous pores as described above. Absorbent A, which is an organic polymer having a hydrophilic continuous skeleton, is obtained by crosslinking polymerization of (meth)acrylic acid ester, which is a polymerization monomer, and divinylbenzene, which is a crosslinking monomer, as shown in Figure 2. It is obtained by further hydrolyzing the crosslinked polymer (monolith A).

The organic polymer forming a hydrophilic continuous skeleton has a polymerized residue of ethylene group (hereinafter referred to as "constituent unit X") and a cross-linked polymerized residue of divinylbenzene (hereinafter referred to as "constituent unit ). Furthermore, the polymerized residue of the ethylene group (constituent unit -COONa group. Note that when the polymerization monomer is a (meth)acrylic acid ester, the polymerization residue of the ethylene group (constituent unit X) has a -COONa group, a -COOH group, and an ester group.

In absorbent A, the proportion of divinylbenzene crosslinked polymer residues (constituent unit Y) in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0.1 to 30 mol% with respect to the total constituent units. , preferably 0.1 to 20 mol%. For example, in absorbent A containing butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, the proportion of divinylbenzene crosslinking polymer residues (constituent unit Y) in the organic polymer forming a hydrophilic continuous skeleton is, for example, about 3%, preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%, based on the total structural units. Note that when the proportion of divinylbenzene crosslinked polymer residues in the organic polymer forming a hydrophilic continuous skeleton is 0.1 mol% or more, the strength of absorbent A is less likely to decrease, and this divinylbenzene When the proportion of cross-linked polymerized residues is 30 mol % or less, the absorption amount of the liquid to be absorbed becomes difficult to decrease.

In addition, in the absorbent A, the organic polymer forming the hydrophilic continuous skeleton may consist of only the structural unit X and the structural unit Y, or in addition to the structural unit X and the structural unit Y, It may have structural units other than structural unit X and structural unit Y, that is, polymerized residues of monomers other than (meth)acrylic acid ester and divinylbenzene.

Examples of structural units other than structural unit X and structural unit Y include styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, isobutene, butadiene, isoprene, chloroprene, vinyl chloride, vinyl bromide, Examples include polymerized residues of monomers such as vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. .

In addition, the proportion of structural units other than the structural unit X and the structural unit Y in the organic polymer forming the hydrophilic continuous skeleton is, for example, 0 to 50 mol%, preferably 0 to 30 It is mole%.

Further, it is preferable that the thickness of the hydrophilic continuous skeleton of the absorbent A is 0.1 to 100 μm. When the thickness of the hydrophilic continuous skeleton of absorbent A is 0.1 μm or more, the spaces (pores) for taking in the liquid to be absorbed (body fluid) in the porous body become difficult to collapse during absorption, and the amount of absorption decreases. It becomes difficult to do. On the other hand, when the thickness of the hydrophilic continuous skeleton is 100 μm or less, an excellent absorption rate can be easily obtained.

The pore structure of the hydrophilic continuous skeleton of absorbent A is an open-cell structure, so the thickness of the continuous skeleton is measured at the cross-section of the skeleton that appears on the test piece for electron microscope measurement. The continuous skeleton is often polygonal in shape, as it is formed by the spaces between water (water droplets) that are removed in the dehydration and drying process after hydrolysis. Therefore, the thickness of the continuous skeleton is the average value of the diameters (μm) of the circles circumscribing the polygonal cross-section. In rare cases, small holes may be present within the polygon, in which case the circumscribing circle of the polygonal cross-section surrounding the small holes is measured.

Further, it is preferable that the average diameter of continuous pores in absorbent A is 1 to 1000 μm. When the average diameter of the continuous pores of absorbent A is 1 μm or more, the spaces (pores) for taking in the liquid to be absorbed (body fluid) in the porous body are difficult to collapse during absorption, and the absorption rate is difficult to decrease. . On the other hand, when the average diameter of the continuous pores is 1000 μm or less, it becomes easier to obtain an excellent absorption rate.

The average diameter (μm) of continuous pores in absorbent A can be measured by mercury porosimetry, and the maximum value of the pore distribution curve obtained by the mercury porosimetry is adopted. Regarding the sample for measuring the average diameter of continuous pores, regardless of the ionic form of the absorbent A, use a sample that has been dried for 18 hours or more in a vacuum dryer set at a temperature of 50°C. Note that the final ultimate pressure is 0 Torr.

FIG. 3 is an SEM photograph of absorbent A at a magnification of 50 times, FIG. 4 is an SEM photograph of absorbent A at a magnification of 100 times, and FIG. 5 is an SEM photograph of absorbent A at a magnification of 500 times. FIG. 6 is a SEM photograph of absorbent A at a magnification of 1500 times. The absorbent A shown in FIGS. 3 to 6 is an example of an absorbent using butyl methacrylate as a polymerization monomer and divinylbenzene as a crosslinking monomer, and each has a cubic structure of 2 mm square.

The absorbent A shown in FIGS. 3 to 6 has a large number of bubble-like macropores, and further has a portion where these bubble-like macropores overlap. Absorbent A has an open cell structure in which the overlapping portions of the macropores form a common opening (mesopore), that is, an open cell structure (continuous macropore structure).

The area where these macropores overlap is a common opening (mesopore) with an average diameter in a dry state of 1 to 1000 μm, preferably 10 to 200 μm, particularly preferably 20 to 100 μm, and most of the macropores have an open pore structure. It becomes. When the average diameter of the mesopores in a dry state is 1 μm or more, the absorption rate of the liquid to be absorbed becomes better. On the other hand, when the average diameter of the mesopores in a dry state is 1000 μm or less, the absorbent A becomes less likely to become brittle.
Note that the number of overlaps between such macropores is about 1 to 12 per macropore, and about 3 to 10 in most cases.

In addition, since the absorbent A has such an open cell structure, macropore groups and mesopore groups can be formed uniformly, and particle agglomeration type as described in JP-A No. 8-252579 etc. It has the advantage that the pore volume and specific surface area can be significantly increased compared to porous materials.

The total pore volume of the pores (holes) of absorbent A is preferably 0.5 to 50 mL/g, more preferably 2 to 30 mL/g. When the total pore volume of the absorbent A is 0.5 mL/g or more, a sufficient pore volume can be ensured in the absorbent A, and therefore, a sufficient amount of water absorption can be ensured. Moreover, the spaces (holes) for taking in the liquid to be absorbed (body fluid) in the porous body can be made difficult to collapse during absorption, and the water absorption amount and water absorption rate can be made difficult to decrease. On the other hand, when the total pore volume of the absorbent A is 50 mL/g or less, the strength of the absorbent A can be made difficult to decrease.

The total pore volume can be measured by mercury intrusion porosimetry. The sample for measuring the total pore volume is dried for 18 hours or more in a vacuum dryer set at a temperature of 50°C, regardless of the ion form of absorbent A. The final pressure reached is 0 Torr. The mercury intrusion porosimetry can obtain the cumulative (integrated) pore volume distribution (relationship between pore diameter (or pore radius) and cumulative pore volume) and the log differential pore volume distribution (relationship between pore diameter (or pore radius) and log differential pore volume). Based on this, the pore distribution in which the pore diameter (or pore radius) is in a predetermined range, the proportion of the pore volume of pores in the pore distribution whose pore diameter (or pore radius) is less than/more than a predetermined value (proportion to the pore volume of all pores) (%), etc. can be calculated. In addition, the total pore volume (mL/g), average pore radius (μm), maximum pore radius (μm), pore volume (mL/g) and percentage (%) of pores larger than (or smaller than) a certain pore diameter (or pore radius) can be calculated.

Below, we will explain what happens when absorbent A comes into contact with a liquid such as a body fluid (hereinafter simply referred to as "body fluid"). The same is true. Furthermore, since the mass of the absorbed body fluid is approximately proportional to the amount of body fluid, in the following description, the mass of the body fluid may be simply referred to as "the amount of body fluid."

First, the continuous pores provided in the absorbent A shown in FIGS. 3 to 6 are pores in which a plurality of pores (holes) are in communication with each other, and it can be seen from the appearance that a large number of pores are provided. can be seen with the naked eye. When body fluids such as menstrual blood (blood) come into contact with absorbent A, which has such a large number of pores, first, the hydrophilic continuous skeleton instantly takes in some of the body fluids by osmotic pressure and expands (i.e., expand). This continuous skeletal elongation occurs in almost all directions. The absorbent A, which has become larger by absorbing a certain amount of body fluid in this way, can further absorb a predetermined amount of body fluid into the enlarged continuous pores due to capillary action. As described above, when absorbing water (body fluid), absorbent A exhibits a unique water absorption behavior in which the water is taken into the hydrophilic continuous skeleton and then taken into the continuous pores for absorption.

Here, the body fluid absorbed into the hydrophilic continuous skeleton of absorbent A is difficult to be released from the continuous skeleton (that is, it is difficult to separate water). On the other hand, body fluids absorbed into the continuous pores are easily separated. Therefore, within the composite absorbent body, body fluids absorbed into these continuous pores are separated, transferred to the super absorbent polymer with high water retention ability, and are steadily retained within the super absorbent polymer. . In addition, the amount of body fluid absorbed into the continuous skeleton of absorbent A and the amount of body fluid absorbed into the continuous pores are the total amount of body fluid absorbed by absorbent A during centrifugation (150G/90 seconds). The amount of body fluid separated from absorbent A (the amount of syneresis) becomes the amount of body fluid absorbed into the continuous pores, and the amount of other body fluids (the amount of body fluid that was not separated from absorbent A during centrifugation) is absorbed into the continuous skeleton. This is the amount of body fluid absorbed.

Furthermore, more body fluids absorbed into the absorbent A remain within the pores than are absorbed into the hydrophilic continuous skeleton. Most of the absorption of body fluids by absorbent A is carried out by retaining body fluids within the pores by capillarity, so the porosity (absorbent A The larger the volume of the pores (to the volume of the pores), the more body fluids can be absorbed. Note that this porosity is preferably 85% or more.

For example, when determining the porosity of the absorbent A shown in FIGS. 3 to 6 above, it is as follows. First, the specific surface area of absorbent A obtained by mercury porosimetry is 400 m ² /g, and the pore volume is 15.5 mL/g. This pore volume of 15.5 mL/g means that the volume of pores in 1 g of absorbent A is 15.5 mL. Assuming that the specific gravity of absorbent A is 1 g/mL, the volume occupied by pores in 1 g of absorbent A, that is, the pore volume, is 15.5 mL, and the volume of 1 g of absorbent A is 1 mL. Then, the total volume (volume) of 1 g of absorbent A is 15.5+1 (mL), and the porosity is the ratio of the pore volume, so the porosity of absorbent A is 15.5/( 15.5+1)×100≒94%.

The absorbent A having such a hydrophilic continuous skeleton and continuous pores, that is, the polymer absorbent, is in the form of particles or sheets, for example, in the form of composite absorbent 4 of sanitary napkin 1 described above. It is applied to composite absorbers for absorbing body fluids such as menstrual blood (blood). As mentioned above, when absorbing water (directly or through pulp fibers), this polymer absorbent has a unique water absorption property in which water is taken into the hydrophilic continuous skeleton and then into the continuous pores. Show behavior. Therefore, this polymer absorbent can instantly absorb a large amount of surrounding body fluid (in the pulp fibers), and has the ability to retain water (mainly body fluid absorbed into continuous pores). It can be delivered to a highly water-absorbent polymer with a high water-absorbency and be steadily retained within the super-absorbent polymer. Therefore, a composite absorbent body to which such a polymer absorbent is applied can exhibit high absorption performance as an absorbent body. In addition, in absorbent material A, that is, a polymer absorbent, there are few pores (less than 46%) with a pore diameter smaller than 7 to 8 μm, which is the size of red blood cells in blood (menstrual blood). Adhesion to the surface is suppressed, and a large amount of blood can be absorbed by stably exhibiting the blood retention ability of the polymer absorbent.

In this embodiment, the blood retention ratio of the polymer absorbent is preferably 6.5 g/g or more in 1 minute (60 seconds). In this way, in the composite absorber 4, the 1-minute value of the blood retention ratio of the polymer absorbent is extremely high (6.5 g/g or more). can absorb menstrual blood). That is, the polymer absorbent can absorb blood quickly, and can stably exhibit its blood retention ability to absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

The blood retention ratio of the polymer absorbent containing absorbent A is more preferably 7.0 g/g or more in 1 minute (60 seconds), and even more preferably 8.0 g/g or more. Thereby, the polymer absorbent can absorb blood (menstrual blood) more quickly and in large quantities.

However, the blood retention ratio is measured by the following method.

<Method for measuring blood retention ratio>
(1) Place a plastic cylinder with an inner diameter of 26 mm and a height of 40 m in an aluminum foil cup with a diameter of 45 mm, and put 0.1 g of the sample into it.
(2) Pour 2 ml of defibrinated horse blood into a plastic cylinder using a pipetman, and let the sample absorb the blood for a predetermined period of time.
(3) A 500 μm nylon mesh manufactured by NBC Industries was placed on the sample, and a 10×10 cm No. 1 mesh manufactured by ADVANTEC was placed on top of the sample. 2. 20 g of filter paper is placed on the nylon mesh, and a load of 930 g is placed on the filter paper.
(4) After 3 minutes, remove the load and measure the mass M (g) of the filter paper. Then, the blood retention ratio, which is the amount of blood absorbed (g) per unit mass (g) of the sample, in a predetermined period of time (example: 1 minute) is calculated using the following formula.
Blood retention ratio = 2-(M-20)/0.1(g/g)
Note that this measurement method is performed under conditions of a temperature of 25° C. and a humidity of 60%.

In the present embodiment, in the polymer absorbent, the proportion of pore volume by pores having a pore diameter of 53 μm or more in the pore distribution is preferably less than 29% of the pore volume of all pores. As described above, in the present composite absorbent body 4, there are few (less than 29%) pores with large pore diameters (53 μm or more) in the polymer absorbent. Therefore, the pore diameter is too large for the red blood cells in the blood (menstrual blood), and it is difficult for red blood cells that once entered the pores to pass through the pores and be released outside the pores again. can do. Therefore, the polymer absorbent can exhibit its blood retention ability more stably and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

In the present embodiment, in the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 4 μm or less in the pore distribution is preferably less than 40% of the pore volume of all pores. In this way, in the composite absorber 4, there are fewer pores (40% less than). Therefore, blood can enter the interior of the polymer absorbent while further suppressing red blood cells from adhering to the surface. Thereby, the polymeric absorbent can absorb blood quickly, stably exhibit its blood retention ability, and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

In this embodiment, in the polymer absorbent, the proportion of the pore volume of pores with a pore diameter of 1 μm or more is preferably 90% or more of the pore volume of all pores, and preferably 95% or more. is more preferable. In this way, in the composite absorber 4, there are few (less than 10%) pores with a pore diameter smaller than 1 μm, which is the size that makes it difficult for plasma components (moisture) in blood (menstrual blood) to enter in the polymer absorbent. . Therefore, blood can enter the interior of the polymer absorbent while further suppressing the adhesion of plasma components to the surface. Thereby, the polymeric absorbent can absorb blood quickly, stably exhibit its blood retention ability, and absorb a large amount of blood. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

In this embodiment, it is preferable that the continuous skeleton of the polymer absorbent has a hydrophilic group. Examples of hydrophilic groups include -COONa groups or -COOH groups. Thus, in this composite absorbent 4, when the polymer absorbent absorbs blood, the hydrophilic groups ionize and repel each other, causing the skeleton and the pores between the skeletons to expand, and the pore volume becomes larger than before the blood was absorbed. Therefore, the polymer absorbent can absorb blood (menstrual blood) more quickly and can absorb a larger amount of blood. Therefore, this composite absorbent can stably exhibit sufficient absorption performance when absorbing blood, and can suppress blood leakage.

In this embodiment, the hydrophilic group preferably has the property of absorbing blood and becoming negatively charged. In this way, in the composite absorber 4, when the polymer absorbent absorbs blood, when the negatively charged red blood cells and the polymer absorbent, which absorbs blood and becomes negatively charged, approach each other, the negatively charged repel each other. Therefore, red blood cells can be made difficult to aggregate within the pores, and can be made easier to penetrate into the polymer absorbent. Thereby, the polymer absorbent can absorb blood (menstrual blood) more quickly and in a larger amount. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

In this embodiment, it is preferable that pulp fibers are included. In this way, in the present composite absorbent body 4, blood (menstrual blood) is absorbed extremely quickly into the pulp fibers, and the blood absorbed into the pulp fibers is quickly transferred to the polymer absorbent. Therefore, the pulp fibers are able to absorb blood again, and a decrease in their absorption rate can be suppressed. Furthermore, by mixing pulp fibers, it is possible to increase the absorption capacity of the composite absorbent body while maintaining its softness. Thereby, the absorbent capacity of the sanitary product using the composite absorbent body can be increased without impairing the feeling of wearing the product. Therefore, the present composite absorbent body can stably exhibit sufficient absorption performance when absorbing blood, and can also suppress blood leakage.

In this embodiment, the composite absorbent body 4 includes a pair of linear high-density portions 6 extending along the longitudinal direction L and spaced apart in the width direction W, and the polymer absorbent is It is preferable to be located between one and the other of the pair of high-density parts 6 in . And/or the composite absorbent body 4 includes a pair of linear high-density portions 7 that extend along the width direction W and are spaced apart in the longitudinal direction L, and the polymer absorbent is It is preferable to be located between one and the other of the pair of high-density parts 7. In this way, in the present composite absorbent body 4, since the polymer absorbent is located between the pair of high-density areas 6 and/or 7 from which blood (menstrual blood) is easily discharged, sufficient absorption can be achieved in that area. Capacity can be secured. Thereby, even when a large amount of blood is excreted, the composite absorbent body 4 can absorb the large amount of blood, and can suppress blood leakage.

In this embodiment, the composite absorbent body 4 includes a pair of linear high-density portions 6 extending along the longitudinal direction L and spaced apart in the width direction W, and the polymer absorbent is It is preferable to be located on the outside of each of the pair of high-density parts 6 in . And/or the composite absorbent body 4 includes a pair of linear high-density portions 7 that extend along the width direction W and are spaced apart in the longitudinal direction L, and the polymer absorbent is It is preferable that it is located outside each of the pair of high-density parts 7. In this way, in the present composite absorbent body 4, when blood (menstrual blood) is discharged between the pair of high-density parts 6 and/or 7, the pair of high-density parts 6 and/or 7 extend. Since the blood is diffused and dispersed in the direction, the blood can be quickly absorbed by the polymer absorbent on the outside of the pair of high-density parts 6 and/or 7. Thereby, the present composite absorber can suppress blood leakage.

In this embodiment, the polymer absorbent is preferably a monolithic absorbent. In this way, since the polymer absorbent is a monolithic absorbent, the present composite absorber 4 can more reliably absorb the blood discharged into the polymer absorber, thereby making it possible to absorb blood more reliably. Leakage can be suppressed.

In this embodiment, as described above, the sanitary napkin 1 (hygienic product) includes a top sheet 2, a back sheet 3, and the above-mentioned composite absorbent body 4 located between the top sheet 2 and the back sheet 3. It is equipped with. As described above, since the sanitary napkin 1 (hygienic product) is equipped with the above-described composite absorbent body 4, it can stably exhibit sufficient absorption performance when absorbing blood, and prevent blood from leaking. It becomes possible to suppress the

Hereinafter, a method for producing such a polymer absorbent will be explained in detail using the above-mentioned absorbent A as an example.

[Production method of polymer absorbent]
The above-mentioned absorbent A can be obtained through a crosslinking polymerization process and a hydrolysis process, as shown in FIG. Each of these steps will be explained below.

(Crosslinking polymerization process)
First, an oil-soluble monomer for crosslinking polymerization, a crosslinkable monomer, a surfactant, water, and, if necessary, a polymerization initiator are mixed to obtain a water-in-oil emulsion. This water-in-oil emulsion is an emulsion in which the oil phase is a continuous phase and water droplets are dispersed therein.

In the above-mentioned absorbent A, as shown in the upper diagram of FIG. Monolith A is obtained by crosslinking polymerization using sorbitan monooleate as an activator and isobutyronitrile as a polymerization initiator.

Specifically, in absorbent A, as shown in the upper diagram of FIG. 2, first, 9.2 g of t-butyl methacrylate as an oil-soluble monomer, 0.28 g of divinylbenzene as a crosslinking monomer, 1.0 g of sorbitan monooleate (hereinafter abbreviated as "SMO") as a surfactant and 0.4 g of 2,2'-azobis(isobutyronitrile) as a polymerization initiator were mixed and uniformly mixed. Dissolve in.

Next, a mixture of t-butyl methacrylate/divinylbenzene/SMO/2,2'-azobis(isobutyronitrile) was added to 180 g of pure water, and the mixture was added to 180 g of pure water. (manufactured by E Co., Ltd.) under reduced pressure to obtain a water-in-oil emulsion.

Further, this emulsion is quickly transferred to a reaction vessel, sealed, and allowed to stand still for polymerization at 60° C. for 24 hours. After the polymerization is completed, the contents are taken out, extracted with methanol, and then dried under reduced pressure to obtain monolith A having a continuous macropore structure. In addition, as a result of observing the internal structure of monolith A by SEM, monolith A had an open cell structure, and the thickness of the continuous skeleton was 5.4 μm. Further, the average diameter of continuous pores measured by mercury porosimetry was 36.2 μm, and the total pore volume was 15.5 mL/g.

The content of divinylbenzene based on all monomers is preferably 0.3 to 10 mol%, more preferably 0.3 to 5 mol%. Further, the ratio of divinylbenzene to the total of butyl methacrylate and divinylbenzene is preferably 0.1 to 10 mol%, more preferably 0.3 to 8 mol%. In addition, in the above-mentioned absorbent A, the ratio of butyl methacrylate to the total of butyl methacrylate and divinylbenzene is 97.0 mol%, and the ratio of divinylbenzene is 3.0 mol%.

The amount of surfactant added can be set depending on the type of oil-soluble monomer and the desired size of emulsion particles (macropores), and is approximately 2 to 70% based on the total amount of oil-soluble monomer and surfactant. It is preferable to set it as the range of %.

In addition, in order to control the bubble shape and size of monolith A, alcohols such as methanol and stearyl alcohol; carboxylic acids such as stearic acid; hydrocarbons such as octane, dodecane, and toluene; and cyclic ethers such as tetrahydrofuran and dioxane. It may be allowed to coexist within the polymerization system.

Furthermore, the mixing method for forming a water-in-oil emulsion is not particularly limited. Any mixing method can be employed, such as a method in which the components and a water-soluble component such as water or a water-soluble polymerization initiator are separately and uniformly dissolved, and then the respective components are mixed.

Further, the mixing device for forming the emulsion is not particularly limited, and any device such as a normal mixer, homogenizer, high-pressure homogenizer, etc. can be adopted depending on the desired emulsion particle size. A so-called planetary stirring device or the like may also be used, which stirs and mixes the objects to be processed by placing the objects in a mixing container and rotating the mixing container while rotating around the revolution axis in an inclined state.

Furthermore, the mixing conditions are not particularly limited, and the stirring rotation speed, stirring time, etc. can be arbitrarily set depending on the desired emulsion particle size. In addition, with the above-mentioned planetary stirring device, water droplets in the W/O emulsion can be uniformly generated, and the average diameter thereof can be arbitrarily set within a wide range.

Various conditions can be adopted as the polymerization conditions for the water-in-oil emulsion depending on the type of monomer and initiator. For example, when using azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, etc. as a polymerization initiator, heat polymerization at a temperature of 30 to 100°C for 1 to 48 hours in a sealed container under an inert atmosphere. If hydrogen peroxide-ferrous chloride, sodium persulfate-acidic sodium sulfite, etc. are used as a polymerization initiator, in a sealed container under an inert atmosphere at a temperature of 0 to 30°C for 1 to 48 hours. All it has to do is polymerize.

After completion of the polymerization, the contents are taken out and unreacted monomers and residual surfactant are removed by Soxhlet extraction with a solvent such as isopropanol to obtain monolith A shown in the middle diagram of Figure 2. .

(Hydrolysis process)
Next, the process (hydrolysis process) of hydrolyzing monolith A (crosslinked polymer) to obtain absorbent A will be explained.

First, monolith A was immersed in dichloroethane containing zinc bromide, stirred at 40°C for 24 hours, and then brought into contact with methanol, 4% hydrochloric acid, 4% aqueous sodium hydroxide solution, and water in this order to perform hydrolysis. , to obtain block-shaped absorbent A. Further, this block-shaped absorbent A is pulverized to a predetermined size to obtain particulate absorbent A. Note that the form of this absorbent A is not limited to particulate, and for example, it may be formed into a sheet during or after drying.

In addition, the method of hydrolysis of monolith A is not particularly limited, and various methods can be adopted. For example, aromatic solvents such as toluene and xylene, halogen solvents such as chloroform and dichloroethane, ether solvents such as tetrahydrofuran and isopropyl ether, amide solvents such as dimethylformamide and dimethylacetamide, alcohol solvents such as methanol and ethanol, carboxylic acid solvents such as acetic acid and propionic acid, or water as a solvent are contacted with a strong base such as sodium hydroxide, or with a hydrohalic acid such as hydrochloric acid, a Brønsted acid such as sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, and p-toluenesulfonic acid, or a Lewis acid such as zinc bromide, aluminum chloride, aluminum bromide, titanium (IV) chloride, cerium chloride/sodium iodide, and magnesium iodide.

In addition, among the polymerization raw materials of the organic polymer forming the hydrophilic continuous skeleton of the absorbent A, (meth)acrylic acid ester is not particularly limited, but C1 to C10 of (meth)acrylic acid (i.e., carbon number (1 to 10) alkyl esters are preferred, and C4 (ie, 4 carbon atoms) alkyl esters of (meth)acrylic acid are particularly preferred.
Note that examples of the C4 alkyl ester of (meth)acrylic acid include t-butyl (meth)acrylate, n-butyl (meth)acrylate, and iso-butyl (meth)acrylate.

In addition, the monomers used for crosslinking polymerization may be only (meth)acrylic ester and divinylbenzene, or in addition to (meth)acrylic ester and divinylbenzene, other monomers other than (meth)acrylic ester and divinylbenzene may be used. may contain.
In the latter case, other monomers include, but are not particularly limited to, styrene, α-methylstyrene, vinyltoluene, vinylbenzyl chloride, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobutene, butadiene, isobrene. , chloroprene, vinyl chloride, vinyl bromide, vinylidene chloride, tetrafluoroethylene, (meth)acrylonitrile, vinyl acetate, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and the like.
The proportion of monomers other than (meth)acrylic acid ester and divinylbenzene in all monomers used for crosslinking polymerization is preferably 0 to 80 mol%, more preferably 0 to 50 mol%.

Further, the surfactant is not limited to the above-mentioned sorbitan monooleate, and any surfactant may be used as long as it can form a water-in-oil (W/O) emulsion when the monomer for crosslinking polymerization and water are mixed. . Examples of such surfactants include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, and polyoxyethylene sorbitan. Nonionic surfactants such as monooleate, anionic surfactants such as potassium oleate, sodium dodecylbenzenesulfonate, dioctyl sodium sulfosuccinate, cationic surfactants such as distearyldimethylammonium chloride, lauryl dimethyl betaine, etc. Examples include amphoteric surfactants. These surfactants may be used alone or in combination of two or more.

Further, as the polymerization initiator, a compound that generates radicals when exposed to heat and light is preferably used. Furthermore, the polymerization initiator may be water-soluble or oil-soluble, and includes, for example, azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, Azobiscyclohexanecarbonitrile, azobis(2-methylpropionamidine) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide-ferrous chloride, sodium persulfate-acidic sodium sulfite, tetramethylthiuram disulfide, etc. can be mentioned. However, in some cases, there are systems in which polymerization proceeds only by heating or light irradiation without adding a polymerization initiator, so in such systems, addition of a polymerization initiator is unnecessary.

When trying to obtain (change) desired absorption performance and pore distribution in polymer absorbents, the main focus is on the amount of surfactant added in the crosslinking polymerization process (example: surfactant/monomer ratio). It is possible to adjust the pore diameter, pore distribution, and absorption performance by changing the mixing conditions (eg, stirring rotation speed, stirring time).

[Method for manufacturing composite absorbent material containing polymer absorbent]
The composite absorbent body is not particularly limited and may be manufactured using a known method, for example, using a fiber stacking device equipped with a material feeder and a rotating drum. The rotating drum has suction means on its inner surface, and includes a fiber stacking support that is arranged on the outer peripheral surface of the rotating drum and is rotatably arranged together with the rotating drum. The fiber stacking support has a deposition recess in which pulp fibers, a polymer absorbent material, and a superabsorbent polymer are deposited. The material supply device supplies pulp fibers whose basis weight (mixing ratio) has been adjusted, a polymer absorbent, and a superabsorbent polymer in a mixed state to the fiber stacking support. In the manufacturing method, pulp fibers, a polymer absorbent material, and a superabsorbent polymer supplied in a mixed state by a material feeder are deposited in a stacking recessed portion of a fiber stacking support by a suction means to form a fiber stack. Then, the fiber stack is transferred from the fiber stack support to a sheet member whose surface is coated with an adhesive, and the composite absorbent body is manufactured by wrapping the fiber stack with the sheet member. Alternatively, a fiber stack of pulp fibers and a superabsorbent polymer may be created by the above method, and a polymer absorbent may be separately sprinkled onto the fiber stack before wrapping it in a sheet member, and then the fiber stack may be wrapped.

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

(A) Sample The polymer absorbents produced by the above-mentioned production method were referred to as Examples 1 to 3, the Infinity particles were referred to as Comparative Example 1, and the superabsorbent polymer was referred to as Comparative Example 2. However, the samples of Examples 1 to 3 were obtained by changing the surfactant/monomer ratio (wt%) and stirring time (minutes) when forming a water-in-oil emulsion in the manufacturing method. The Infinity particles of Comparative Example 1 are particles described in Patent Document 1, and are an absorbent manufactured by P&G, and have a structure similar to a polymer absorbent (foamed structure), but unlike a polymer absorbent, , does not have the ability to absorb water and swell. The superabsorbent polymer of Comparative Example 2 is UG840 manufactured by Sumitomo Seika Co., Ltd. The samples of Examples 1 to 3 and Comparative Example 1 all had pore diameters in the range of 0.003 to 100 μm, and the pore distribution showing the relationship between pore diameter and pore volume. The maximum volumetric pore diameter at which the ratio of .

(B) Evaluation All or part of the above samples were evaluated on the following items. The item is the percentage of pore volume by pores whose pore diameter (or pore radius) is less than or greater than a predetermined value (of all pores) in a pore distribution where the pore diameter (or pore radius) is within a predetermined range. (ratio to pore volume) (%), and blood retention ratio (g/g).

(C) Results (1) Percentage of pore volume by pores with a pore diameter of 7 μm or less In a pore distribution with a pore diameter in the range of 0.003 to 100 μm, the pore diameter is The proportion of the pore volume due to pores of 7 μm or less was calculated based on the pore volume distribution measured by mercury intrusion method. The results were 11%, 36%, and 45% in Examples 1, 2, and 3, respectively. In Comparative Example 1, it was 47%. Therefore, in a polymer absorbent, the proportion of pore volume by pores with a pore diameter of 7 μm or less in a pore distribution with a pore diameter in the range of 0.003 to 100 μm is 46% of the pore volume of all pores. It was confirmed that the

(2) Percentage of pore volume by pores with a pore diameter of 53 μm or more In a pore distribution with a pore diameter in the range of 0.003 to 100 μm, pores with a pore diameter of 53 μm or more to the pore volume of all pores. The proportion of pore volume due to pores was calculated based on pore volume distribution measured by mercury intrusion method. The results were 14%, 6%, and 3% in Examples 1, 2, and 3, respectively. In Comparative Example 1, it was 3%. Therefore, in a polymer absorbent, the proportion of pore volume by pores with a pore diameter of 53 μm or more in a pore distribution with a pore diameter in the range of 0.003 to 100 μm is 29% of the pore volume of all pores. It was confirmed that the

(3) Percentage of pore volume by pores with a pore diameter of 4 μm or less In a pore distribution with a pore diameter in the range of 0.003 to 100 μm, pores with a pore diameter of 4 μm or less to the pore volume of all pores. The proportion of pore volume due to pores was calculated based on pore volume distribution measured by mercury intrusion method. The results were 4%, 10%, and 31% in Examples 1, 2, and 3, respectively. In Comparative Example 1, it was 40%. Therefore, in a polymer absorbent, the proportion of pore volume by pores with a pore diameter of 4 μm or less in a pore distribution with a pore diameter in the range of 0.003 to 100 μm is 40% of the pore volume of all pores. It was confirmed that the

(4) Percentage of pore volume by pores with a pore diameter of 1 μm or more In a pore distribution with a pore diameter in the range of 0.003 to 100 μm, pores with a pore diameter of 1 μm or more to the pore volume of all pores. The proportion of pore volume due to pores was calculated based on pore volume distribution measured by mercury intrusion method. The results were 99.7%, 99.9%, and 99.6% in Examples 1, 2, and 3, respectively. In Comparative Example 1, it was 65%. Therefore, in a polymer absorbent, the proportion of pore volume by pores with a pore diameter of 1 μm or more in a pore distribution with a pore diameter in the range of 0.003 to 100 μm is 90% of the pore volume of all pores. The above was confirmed.

(5) Blood retention ratio Blood retention ratio (1 minute) (g/g) was measured by the method for measuring blood retention ratio described above. The results are shown in Table 1, and a representative graph is shown in FIG. However, FIG. 7 is a graph showing the relationship between blood retention ratio (g/g) and blood sucking time (minutes). The vertical axis shows the blood retention ratio (g/g) of each absorbent body, and the horizontal axis shows the blood sucking time (minutes) in each absorbent body. The thick solid line and circles represent Example 1, the thin solid lines and triangles represent Comparative Example 1, and the broken lines and diamonds represent Comparative Example 2. The polymer absorbent (Example 1) rapidly and rapidly absorbed a large amount of blood in the initial stage compared to Infinity particles (Comparative example 1) and super absorbent polymer (Comparative example 2). was confirmed. Although not shown in the figure, pulp fibers had almost the same tendency as Comparative Example 2. The blood retention ratio (1 minute) was 7.4 g/g, 8.1 g/g, and 10.4 g/g in Examples 1, 2, and 3, respectively. In Comparative Examples 1 and 2, the amount was 5.5 g/g. Therefore, it was confirmed that the blood retention ratio of the polymer absorbent was 6.5 g/g or more per minute. The above results are shown in Table 1.

In addition to the pants-type disposable diaper of the above-described embodiment, the composite absorbent body of the present invention can be used, for example, in tape-type disposable diapers, sanitary napkins, absorbent liners, absorbent pads (e.g., incontinence pads, bedsore pads, etc.). Postpartum pads, etc.), absorbent sheets, breast milk pads, disposable diapers for pets, absorbent pads for pets, excrement disposal sheets for pets, wet sheets, wet tissues, cosmetic wipes, masks, and various other sanitary products. Can be applied. Therefore, the body fluids to be absorbed by the composite absorbent material are fluids discharged from the wearer of the sanitary product, such as urine, sweat, feces, menstrual blood, vaginal discharge, breast milk, blood, and exudate. It will be done.

The present invention is not limited to the above-described embodiments, etc., and can be appropriately combined, substituted, changed, etc. without departing from the purpose and gist of the present invention.

1 Sanitary napkin 2 Top sheet 3 Back sheet 4 Composite absorbent material

Claims (12)

A composite absorbent body for sanitary products for absorbing blood, comprising:
comprising a polymer absorbent having a hydrophilic continuous skeleton and continuous pores, and at least one of a super absorbent polymer and pulp fiber,
In the polymer absorbent, the pore size is in the range of 0.003 to 100 μm, and in the pore distribution indicating the relationship between pore size and pore volume, the maximum volume pore size at which the pore volume ratio is maximum is The proportion of pore volume by pores in the range of 1 to 95 μm and with a pore diameter of 7 μm or less is less than 46% of the pore volume of all pores,
Composite absorber. The blood retention ratio of the polymer absorbent is 6.5 g/g or more in 1 minute value.
The composite absorbent body according to claim 1. In the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 53 μm or more in the pore distribution is less than 29% of the pore volume of all pores.
The composite absorbent body according to claim 1 or 2. In the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 4 μm or less in the pore distribution is less than 40% of the pore volume of all pores.
The composite absorbent body according to any one of claims 1 to 3. In the polymer absorbent, the proportion of pore volume by pores with a pore diameter of 1 μm or more is 90% or more of the pore volume of all pores.
The composite absorbent body according to any one of claims 1 to 4. the continuous skeleton of the polymer absorbent has a hydrophilic group;
The composite absorbent body according to any one of claims 1 to 5. The hydrophilic group has the property of absorbing blood and becoming negatively charged,
The composite absorbent body according to any one of claims 1 to 6. comprising the pulp fibers,
The composite absorbent body according to any one of claims 1 to 7. The composite absorbent body has a longitudinal direction and a width direction that are orthogonal to each other,
A pair of linear high-density portions extending along the longitudinal direction or the width direction and arranged at intervals in the width direction or the longitudinal direction,
The polymer absorbent is located between one and the other of the pair of high-density parts in the width direction or the longitudinal direction,
The composite absorbent body according to any one of claims 1 to 8. The composite absorbent body has a longitudinal direction and a width direction that are orthogonal to each other,
A pair of linear high-density portions extending along the longitudinal direction or the width direction and arranged at intervals in the width direction or the longitudinal direction,
The polymer absorbent is located outside each of the pair of high-density portions in the width direction or the longitudinal direction.
The composite absorbent body according to any one of claims 1 to 8. The polymer absorbent is a monolithic absorbent,
The composite absorbent body according to any one of claims 1 to 10. A sanitary product comprising a topsheet, a backsheet, and the composite absorbent body according to any one of claims 1 to 11 located between the topsheet and the backsheet.

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