US20120041406A1

US20120041406A1 - Absorbent article including a formed fibrous article

Info

Publication number: US20120041406A1
Application number: US13/208,504
Authority: US
Inventors: Marco Antonio Alkmin; José Francisco Cau; Jose Manoel Soares Coutinho; Francisco J.V. Hernandez; Francisco Antonio Rimoli; Francisco Savastano Neto
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-08-12
Filing date: 2011-08-12
Publication date: 2012-02-16
Also published as: BRPI1104024A2; US8394316B2; CA2748774A1; BRPI1104024B1; CN102440870B; RU2011133820A; US20120040171A1; AU2011211440A1; CN102440870A; CO6620003A1; CA2748774C; RU2577490C2; AU2011211440B2; WO2012019264A1

Abstract

The present invention generally relates to a method and apparatus for a making a formed fibrous article and more specifically to method and apparatus for making a formed fibrous article useful as an absorbent core structure in a disposable sanitary article such as a sanitary napkin, panty liner, diaper or the like. The present invention also relates to a disposable sanitary article including a formed fibrous article according to the present invention as a core structure thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patent application Ser. No. 12/855,070, filed Aug. 12, 2010, priority of which is hereby claimed.

FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION

Various methods for making formed fibrous articles from fibrous materials such as cellulose or the like are well know to those of skill in the art. One common method of manufacturing such formed fibrous articles consists of defiberizing a starting material and then creating air-entrained stream of the defiberized material. The air-entrained defiberized material may be formed into a formed fibrous article through the use of a porous mold structure subjected to a vacuum to draw the defiberized material into the mold.
It is also known that formed fibrous articles of the type described above may be subjected to calendering processes to alter the mechanical and fluid handling properties of such articles. A calendering process used in the art is commonly referred to as “pin calendering”. Pin calendering employs the use of a plurality of pins adapted to compress and densify the article.
A problem associated with pin calendering processes of the type described above is that such processes typically require that a “carrier layer” be used during the pin-calendering step. “Carrier layer” as used herein means any material layer used to support the formed fibrous article, such as a conveyer belt or an adjacent material layer such a rolled nonwoven layer or the like. The use of such a carrier layer increases complexity of manufacture. In addition, if the carrier layer is a layer intended to be incorporated into the final product, the inclusion of such layer may increase the cost of the final product and/or undesirably affect the fluid handling characteristics of the product.
In view of the above the inventors of the present invention have discovered, and disclosed herein, a method and apparatus for making a pin-calendered formed fibrous article that does not require the use of a carrier layer. Formed fibrous articles according to the present invention are particularly useful as an absorbent core structure in a disposable sanitary article such as a sanitary napkin, panty liner, diaper or the like.

SUMMARY OF THE INVENTION

In view of the foregoing, the present invention provides

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments of the present invention will now be described with reference to the drawings, in which:

FIG. 1 is a side elevation view of an apparatus according to the present invention;

FIG. 2 is a detailed perspective view of the forming drum that forms part of the apparatus according to the present invention;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a detailed perspective view of a portion of the forming drum shown in FIG. 2;

FIG. 5 is a side elevation view of the forming drum and a calendering station that form part of the apparatus according to the present invention;

FIG. 6 is a detailed perspective view of the calendering station shown in FIG. 5, depicting the vacuum roll and calender roll thereof;

FIG. 7 is a sectional view taken along line 7-7 in FIG. 6;

FIG. 8 is detailed perspective view of that portion of calendering station vacuum roll circled in FIG. 6;

FIG. 9 is a side elevation view of a pin calendering station that forms part of the apparatus according to the present invention;

FIG. 10 is a detailed perspective view of the pin calendering station shown in FIG. 9, depicting the vacuum roll and pin calender roll thereof;

FIG. 11 is a detailed plan view of that portion of the pin calender roll circled in FIG. 10;

FIG. 12 is a sectional view taken along line 12-12 in FIG. 11;

FIG. 13 is sectional view taken along line 13-13 in FIG. 9;

FIG. 14 is a sectional view taken along line 14-14 in FIG. 10;

FIG. 15 is a side elevation view of a transfer wheel that forms part of the apparatus according to the present invention;

FIG. 16 is a detailed perspective view of the transfer wheel shown in FIG. 15;

FIG. 17 is a partially cut away view of an absorbent article including a formed fibrous article according to the present invention as an absorbent core layer thereof; and

FIG. 18 is a detailed perspective view of that portion of the absorbent article circled in FIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-16, there is illustrated a preferred apparatus 10 for making a formed fibrous article 12 according to the method of the present invention.
As shown in FIG. 1, the apparatus 10 according to the present invention generally includes a forming drum 14, a calendering station 16, a pin calendering station 18, and a transfer wheel 20. Certain details of the apparatus 10, such as electrical lines, have been omitted from the figures to simplify the same. However, these features and other basic elements of the apparatus will be clear to those of skill in the art.
The formed fibrous article 12, which is depicted during various stages of the method according to the present invention in FIGS. 3, 5-7, 10 and 14-16, preferably is formed from cellulosic fibers, and in on preferred embodiment of the invention, includes a mixture of cellulosic fibers and superabsorbent polymer. Cellulosic fibers that can be used in the formed fibrous article 12 are well known in the art and include wood pulp, cotton, flax and peat moss. Wood pulp is preferred. Both softwood and hardwood species are useful. Softwood pulps are preferred.
The fibrous article 12 may also contain any superabsorbent polymer (SAP), which are well known in the art. For the purposes of the present invention, the term “superabsorbent polymer” (or “SAP”) refers to materials, which are capable of absorbing and retaining at least about 10 times their weight in body fluids under a 0.5 psi pressure. The superabsorbent polymer particles of the invention may be inorganic or organic crosslinked hydrophilic polymers, such as polyvinyl alcohols, polyethylene oxides, crosslinked starches, guar gum, xanthan gum, and the like. The particles may be in the form of a powder, grains, granules, or fibers. Preferred superabsorbent polymer particles for use in the present invention are crosslinked polyacrylates, such as the product offered by Sumitomo Seika Chemicals Co., Ltd. Of Osaka, Japan, under the designation of SA70N and products offered by Stockhausen Inc.
The pulp used to form the fibrous article 12 is preferably a bleached softwood pulp, produced by a Kraft process. As shown in FIG. 1, the pulp is provided by the manufacturer as a pulp board 22 in rolled form, the roll identified by the reference numeral 24. The pulp board 22 is conveyed from the roll 24 to a device 26 for grinding the pulp board 22 into fibrous pulp 28. The fibrous pulp 28 is released from the grinding device 26 into a chamber 30 for holding the fibrous pulp 28. The apparatus 10 may further optionally include a device 32 for introducing superabsorbent polymer into the chamber 30 to thereby form a fibrous pulp and superabsorbent mixture. Any conventional device suitable for this purpose, and known to those of skill in the art, may be used for introducing the superabsorbent into the chamber 30.
As best seen in FIG. 3, the chamber 30 has a partially open bottom portion 34 that communicates with the forming drum 14. As seen in FIG. 1, the forming drum 14 includes a hollow cylinder 15 that is structured and arranged to rotate about a fixed axis 17. Any conventional means to rotate the cylinder 15, well known to those of skill in the art, may be used to rotate the cylinder 15. As shown in FIGS. 1-4, the cylinder 15 has a plurality of molds 36 mounted thereto. As the cylinder 15 rotates, each of the molds 36 are sequentially arranged in communication with the open portion 34 of the chamber 30 to thereby receive fibrous pulp 28 from the chamber 30. In FIG. 1, the cylinder 15 rotates in a counterclockwise manner during operation of the apparatus 10.
As shown in FIGS. 1 and 3, the forming drum 14 further includes a vacuum chamber 38 arranged within the interior of the cylinder 15. The vacuum chamber 38 is arranged in a fixed location relative to the rotating cylinder 15 and is operably coupled to a vacuum source (not shown). As best seen in FIG. 4, the mold 36 includes a porous screen 40 structure in the shape of the formed fibrous article 12 to be formed in the mold 36. As the mold 36 passes over the vacuum chamber 38 of the forming drum 14 the vacuum functions to draw the fibrous pulp 28 from the chamber 30 into the mold 36 by drawing air through the porous screen 40 of the mold 36.
As shown in detail in FIG. 4, the mold 36 includes a nonporous mounting plate portion 42 that surrounds the porous screen 40 portion of the mold 36. The mounting plate portion 42 of the mold 36 is mounted to the periphery 44 of the cylinder 15, thereby enabling each of the molds 36 to rotate with the rotating cylinder 15.
After the mold 36 is rotated under the partially open bottom portion 34 of the chamber 30, the mold 36 is further rotated by the rotating cylinder 15, and as described in further detail below, the fibrous article 12 is then transferred to the calendering station 16.
After formation in the mold 36, the formed fibrous article 12 preferably has a basis weight in the range of between about 200 gsm (g/m²) to about 400 gsm, a thickness in the range of about 5 mm to about 20 mm, and a density in the range of about 0.015 g/cc to about 0.03 g/cc.
As shown in FIGS. 1 and 5-7 the calendering station 16 generally includes a vacuum roll 42 and an opposed calender roll 44. As best seen in FIG. 6, the vacuum roll 42 is formed from a rotatable cylinder 46 that is rotatable about a fixed axis 48. Any conventional means to rotate the cylinder 46, well known to those of skill in the art, may be used to rotate the cylinder 46. The cylinder 46 rotates in a clockwise manner during operation of the apparatus 10, as show in FIG. 1. As best seen in FIGS. 6 and 8, the cylinder 46 includes a plurality of holes 50 that extend from the outer surface 52 of the cylinder 46 to the inner surface 54 of the cylinder 46. As shown in FIG. 6, the surface 47 of the calender roll 44 is preferably smooth, however the surface 47 of the calender roll 44 may be provided with surface features if desired.
As shown in FIGS. 5-7, the vacuum roll 42 further includes a vacuum chamber 56 arranged within the interior of the cylinder 46. The vacuum chamber 56 is arranged in a fixed location relative to the rotating cylinder 46 and is operably coupled to a vacuum source 57 (FIG. 1). The vacuum chamber 56 is arranged in flow communication with the plurality of holes 50 that extend through the cylinder 46 and thereby draw air through said holes 50.
As shown in FIG. 5, the vacuum chamber 56 is arranged such that its leading edge 58 is substantially aligned with a trailing edge 60 of the vacuum chamber 38 located within cylinder 15 of the forming drum 14. This arrangement of the vacuum chamber 56 relative to location of the vacuum chamber 38 effectuates a transfer of the formed fibrous article 12 from within the mold 36 on the forming drum 14 to the vacuum roll 42.
Once the formed fibrous article 12 has been transferred to the cylinder 46 of the vacuum roll 43 the cylinder 46 rotates the fibrous 12 article until the article 12 passes through the nip 62 formed between the vacuum roll 42 and the calender roll 44. The nip 62 preferably uniformly compresses the fibrous article 12 along its length. The compression of the fibrous article 12 results in a reduction in thickness of the article 12 and a corresponding increase in density. In a preferred embodiment of the invention the nip 62 has a distance “d” (i.e. the distance between the surfaces of the opposed rolls) of about 0.9 mm. The distance “d” is identified by the reference symbol “d” in FIG. 7.
After passing through the nip 62, the formed fibrous article 12 preferably has a thickness in the range of about 0.5 mm to about 3.5 mm, and a density in the range of about 0.06 g/cc to about 0.5 g/cc.
After the article 12 passes through the nip 62 the article 12 is further rotated in a clockwise direction by the cylinder 46 of the vacuum roll 43, and as will be described in further detail below, transferred to the pin calendering station 18.
As shown in FIGS. 1 and 9-10 the pin calendering station 18 generally includes a vacuum roll 64 and an opposed pin calender roll 65. As best seen in FIG. 10, the vacuum roll 64 is formed from a rotatable cylinder 66 that is rotatable about a fixed axis 68. Any conventional means to rotate the cylinder 66, well known to those of skill in the art, may be used to rotate the cylinder 66. The cylinder 66 rotates in a counterclockwise direction during operation of the apparatus 10. As shown in FIG. 10, the cylinder 66 includes a plurality of holes 70 that extend from the outer surface 72 of the cylinder 66 to the inner surface 74 of the cylinder 66. In a preferred embodiment of the invention each of the plurality of holes 70 has a diameter of about 1.5 mm and is spaced from an adjacent hole by a distance of about 4 mm (center to center).
As shown in FIG. 10 the pin calender roll 65 is structured and arranged to rotate about a fixed axis 67. As shown in FIGS. 10-14 the pin calender roll 65 includes a plurality of individual pins 78 that extend outwardly from a surface 80 of the roll 65. The individual pins 78 are arranged in one of a plurality of arrays 82 that are arranged over the surface 80 of the roll 65, as shown in FIG. 10. Each array 82 includes a plurality of the pins 78 and each array 82 is adapted to emboss an individual formed fibrous article 12. As shown in FIG. 10, each array 82 is arranged in spaced relationship to an adjacent array 82. In one preferred embodiment of the invention each array 82 is adapted to uniformly pin emboss the formed fibrous article 12 over its entire surface. Alternatively, each array 82 may be structured to pin emboss only a portion of the fibrous article, e.g. a central pin embossed zone extending along the center of the product in a longitudinal direction thereof. In preferred embodiments of the invention each of the pins 78 are spaced from an adjacent pin by a distance of about 4 mm (center to center), have height of about 1.5 mm and have an effective contact area of from about 0.8 mm²to about 1.2 mm².
As shown in FIGS. 13 and 14, each of the pins 78 are arranged such that they do not overlap with any of the plurality of holes 70 in the cylinder 66 of the vacuum roll 64. This arrangement of the pins 78 relative to the holes 70 insures that no pulp is forced into any of the plurality of holes 70, thereby improving the efficiency of pulp use and the efficiency of the process as a whole.
As shown in FIGS. 9-10 and 13-14, the vacuum roll 64 further includes a vacuum chamber 86 arranged within the interior of the cylinder 66. The vacuum chamber 86 is arranged in a fixed location relative to the rotating cylinder 66 and is operably coupled to the vacuum source 57 (FIG. 1). The vacuum chamber 86 is arranged in flow communication with the plurality of holes 70 that extend through the cylinder 66 and thereby draws air through said holes 70.
As shown in FIG. 9, the vacuum chamber 86 is arranged such that its leading edge 88 is substantially aligned with a trailing edge 90 of the vacuum chamber 56 located within the cylinder 46 of the vacuum roll 42. This arrangement of the vacuum chamber 86 relative to the location of the vacuum chamber 56 effectuates a transfer of the formed fibrous article 12 from the vacuum roll 42 to the vacuum roll 64.
Once the formed fibrous article 12 has been transferred to the cylinder 66 of the vacuum roll 64, the cylinder 66 rotates the formed fibrous article 12 until the article 12 passes through the nip 92 formed by the vacuum roll 64 and the pin calender roll 65. The plurality of pins 78 in an individual array 82 function to compress the fibrous article 12 at areas corresponding in location to the pins 78. The compression of fibrous article 12 in this manner results in a reduction in thickness of the article 12 and a corresponding increase in density in those areas of the article 12 corresponding in location to the pins 78.
In a preferred embodiment of the invention the nip 92 has a distance (i.e. the distance between the surfaces of the opposed rolls) of about 0.8 mm. Also in a preferred embodiment of the invention the pin calender roll 65 is heated to a temperature of between about 176° F. to about 212° F. by means of any suitable conventional heating means. It has been found that heating the pin calender roll 65 in this manner helps prevent the formed fibrous article 12 from adhering to the surface of the pin calender roll 65.
After passing through the nip 92, the fibrous article 12 preferably has a thickness in the range of about 0.2 mm to about 1.0 mm, and a density in the range of about 0.1 g/cc to about 0.9 g/cc, in those areas compressed by the pins 78. After passing through the nip 92, the fibrous article 12 preferably has a thickness in the range of about 0.8 mm to about 3.5 mm, and a density in the range of about 0.06 to about 0.5 g/cc, in those areas outside the individual pins 78.
After the article 12 passes through the nip 92 the article 12 is further rotated in a counter clockwise direction by the cylinder 66 of the vacuum roll 64 as shown and, as will be described in further detail below, transferred to the transfer wheel 20.
As shown in FIG. 15 the transfer wheel 20 comprises a vacuum roll 94 that is formed from a rotatable cylinder 96 that is rotatable about a fixed axis 98. Any conventional means to rotate the cylinder 96, well known to those of skill in the art, may be used to rotate the cylinder 96. The cylinder 96 rotates in a counterclockwise manner during operation of the apparatus 10, as show in FIG. 1. As shown in FIG. 16, the cylinder 96 includes a plurality of holes 100 that extend from the outer surface 102 of the cylinder 96 to the inner surface 104 of the cylinder 96.
As shown in FIGS. 15 and 16, the vacuum roll 94 further includes a vacuum chamber 106 arranged within the interior of the cylinder 96. The vacuum chamber 106 is arranged in a fixed location relative to the rotating cylinder 96 and is operably coupled to the vacuum source 57 (FIG. 1). The vacuum chamber 106 is arranged in flow communication with the plurality of holes 100 that extend through the cylinder 96 and thereby draw air through said holes 100.
The transfer wheel 20 further includes a porous conveyor belt 97 that extends around the cylinder 96 and travels with the cylinder 96, i.e. in a counterclockwise direction shown in FIG. 16.
As shown in FIG. 15, the vacuum chamber 106 is arranged such that its leading edge 108 is substantially aligned with a trailing edge 110 of the vacuum chamber 86 located within the cylinder 66 of the vacuum roll 64. This arrangement of the vacuum chamber 106 relative to the location of the vacuum chamber 86 effectuates a transfer of the formed fibrous article 12 from the vacuum roll 64 to the vacuum roll 94. Specifically, formed fibrous article 12 is transferred to the conveyor belt 97 and held in place by the vacuum chamber 106 that functions to draw air through the porous conveyer belt 97 via the holes 100 in the cylinder 96.
Once the fibrous article 12 is rotated past vacuum chamber 106, the porous conveyer belt 97 functions to further convey the formed fibrous article 12 in a machine direction. The formed fibrous article 12 may be conveyed in a machine direction for incorporation into a final product structure such as a sanitary napkin, panty liner, incontinence article, diaper or the like.
It is noted that the formed fibrous article 12 is formed and pin-calendered without the use of any “carrier layer”. In addition, is noted that the fibrous article is transferred from the forming drum 14 to the calendering station 16 then to the pin calendering station 18 without the use of any “carrier layer”. “Carrier layer” as used herein means any material layer used to support the fibrous article, such as a conveyer belt or an adjacent material layer such a rolled nonwoven layer or the like.
In connection with the various vacuum chambers disclosed herein any suitable vacuum source may be employed. In a preferred embodiment of the invention the vacuum source is an air blower having an air flow of about 2,200 cubic meters per hour.
Reference is made to FIG. 17 which depicts a disposable absorbent article 200 in accordance with the present invention. Although disposable absorbent articles according to the present invention will be described herein with reference to a sanitary napkin 200, other disposable absorbent articles such as panty liners, adult incontinence articles, and diapers are considered within the scope of the present invention. The sanitary napkin 200 includes a cover layer 210, an optional transfer layer 212, an absorbent core 214 and a barrier layer 216. The absorbent core 214 layer is formed from a formed fibrous article 12 of the type described above.

Main Body—Cover Layer

The cover layer 210 may be a relatively low density, bulky, high-loft non-woven web material. The cover layer 210 may be composed of only one type of fiber, such as polyester or polypropylene or it may include a mixture of more than one fiber. The cover may be composed of bi-component or conjugate fibers having a low melting point component and a high melting point component. The fibers may be selected from a variety of natural and synthetic materials such as nylon, polyester, rayon (in combination with other fibers), cotton, acrylic fiber and the like and combinations thereof. Preferably, the cover layer 210 has a basis weight in the range of about 10 gsm to about 75 gsm.
Bi-component fibers may be made up of a polyester layer and a polyethylene sheath. The use of appropriate bi-component materials results in a fusible non-woven fabric. Examples of such fusible fabrics are described in U.S. Pat. No. 4,555,430 issued Nov. 26, 1985 to Chicopee. Using a fusible fabric increases the ease with which the cover layer may be mounted to the absorbent layer(s) of the article and/or to the barrier layer 216.
The cover layer 210 preferably has a relatively high degree of wettability, although the individual fibers comprising the cover may not be particularly hydrophilic. The cover material should also contain a great number of relatively large pores. This is because the cover layer 210 is intended to take-up body fluid rapidly and transports it away from the body and the point of deposition. Therefore, the cover layer contributes little to the time taken for the napkin 200 to absorb a given quantity of liquid (penetration time).
Advantageously, the fibers that make up the cover layer 210 should not lose there physical properties when they are wetted, in other words they should not collapse or lose their resiliency when subjected to water or body fluid. The cover layer 210 may be treated to allow fluid to pass through it readily. The cover layer 210 also functions to transfer the fluid quickly to the underlying layers of the absorbent article. Thus, the cover layer 210 is advantageously wettable, hydrophilic and porous. When composed of synthetic hydrophobic fibers such as polyester or bi-component fibers, the cover layer 210 may be treated with a surfactant to impart the desired degree of wettability.
In one preferred embodiment of the present invention the cover is made from a 25 gsm thermally bonded nonwoven material constructed from 100% hydrophilic polypropylene fibers, such nonwoven material being commercially available from Polystar Company, Salvador, Brazil under the product name Multidenier Telao 25 cover.
Alternatively, the cover layer 210 can also be made of a polymer film having large pores. Because of such high porosity, the film accomplishes the function of quickly transferring body fluid to the underlying layers of the absorbent article. A suitable cover material of this type is commercially found on the Stayfree Dry Max Ultrathin product distributed by McNeil-PPC, Inc.
The cover layer 210 may be embossed to the underlying absorbent layers in order to aid in promoting hydrophilicity by fusing the cover to the adjacent underlying layer. Such fusion may be effected locally, at a plurality of sites or over the entire contact surface of cover layer 210. Alternatively, the cover layer 210 may be attached to the other layers of the article by other means such as by adhesion.

Main Body—Transfer Layer

Adjacent to the cover layer 210 on its inner side and bonded to the cover layer 210 is the optional transfer layer 212. The transfer layer 212 provides means for receiving body fluid from the cover layer 210 and holding it until the underlying absorbent core 214 has an opportunity to absorb the fluid, and therefore acts as a fluid transfer or acquisition layer. The transfer layer 212 is, preferably, more dense than and has a larger proportion of smaller pores than the cover layer 210. These attributes allow the transfer layer 212 to contain body fluid and hold it away from the outer side of the cover layer 210, thereby preventing the fluid from rewetting the cover layer 210 and its surface. However, the transfer layer is, preferably, not so dense as to prevent the passage of the fluid through the layer 212 into the underlying absorbent core 214.
The transfer layer 212 may be composed of fibrous materials, such as wood pulp, polyester, rayon, flexible foam, or the like, or combinations thereof. The transfer layer 212 may also comprise thermoplastic fibers for the purpose of stabilizing the layer and maintaining its structural integrity. The transfer layer 212 may be treated with surfactant on one or both sides in order to increase its wettability, although generally the transfer layer 212 is relatively hydrophilic and may not require treatment. The transfer layer 212 is preferably bonded or adhered on both sides to the adjacent layers, i.e. the cover layer 210 and the underlying absorbent core 214.
Examples of suitable materials for the transfer layer 212 are through air bonded pulp sold by Buckeye Technologies of Memphis, Tenn., under the designation VIZORB 3008, which has a basis weight of 110 gsm, VIZORB 3042, which has a basis weight of 100 gsm, and VIZORB 3010, which has a basis weight of 90 gsm.

Main Body—Absorbent Core

Reference is made to FIG. 18 which depicts an absorbent core 214 according to the present invention. The absorbent core 214 consists of a formed fibrous article 12 of the type described herein above.
In one preferred embodiment of the invention, the absorbent core 214 is a blend or mixture of cellulosic fibers and superabsorbent disposed therein. Cellulosic fibers that can be used in the absorbent core 214 are well known in the art and include wood pulp, cotton, flax and peat moss. Wood pulp is preferred.
The absorbent core 214 can contain any superabsorbent polymer (SAP), which are well known in the art. For the purposes of the present invention, the term “superabsorbent polymer” (or “SAP”) refers to materials, which are capable of absorbing and retaining at least about 10 times their weight in body fluids under a 0.5 psi pressure. The superabsorbent polymer particles of the invention may be inorganic or organic crosslinked hydrophilic polymers, such as polyvinyl alcohols, polyethylene oxides, crosslinked starches, guar gum, xanthan gum, and the like. The particles may be in the form of a powder, grains, granules, or fibers. Preferred superabsorbent polymer particles for use in the present invention are crosslinked polyacrylates, such as the product offered by Sumitomo Seika Chemicals Co., Ltd. Of Osaka, Japan, under the designation of SA70N and products offered by Stockhausen Inc.
The absorbent core 214 preferably has a total basis weight in the range of about 200 gsm to about 400 gsm. In preferred embodiments of the present invention the absorbent core 214 includes about 50%-100% pulp by weight and about 0% to about 50% superabsorbent by weight.
As shown in FIG. 18, the absorbent core 214 in accordance with the invention generally includes a first region 218 and a plurality of second regions 220. The plurality of second regions 220 represent those portions of the core 214 that have been compressed by the pins 78 as described above and the first region 218 represents that portion of the core 214 located outside the areas compressed by the pins 78.
The first region 218 preferably has a thickness in the range of about 0.5 mm to about 3.5 mm, and a density in the range of about 0.06 g/cc to about 0.5 g/cc, and each of the plurality of second regions 220 preferably has a thickness in the range of about 0.15 mm to about 0.7 mm, and a density in the range of about 0.1 to about 0.9 g/cc. The absorbent core preferably includes between about 8 to about 10 second regions 220 per square cm. Each one of the second regions 220 preferably has an individual size ranging from about 0.8 mm²to about 1.2 mm². The plurality of second regions 220 preferably extend over a surface area of between about 88 mm²and 93.6 mm²(i.e. the summation of the area over which the second regions 220 extend). The first region 218 preferably extends over a surface area of between about 6.4 mm²and 12 mm².
In one specific example of the invention, the absorbent core 214 consists of a 305 gsm fluff pulp and superabsorbent mixture, the mixture including about 89% fluff pulp by weight, commercially available as Golden Isles Fluff Pulp 420#HD 7% Moisture, from GP Cellulose, Brunswick, Ga., USA, and 11% superabsorbent polymer by weight, commercially available as Aqua Keep SA70N from Sumitomo Seika Chemicals Co., Ltd., Osaka, Japan.

Main Body—Barrier Layer

Underlying the absorbent core 214 is a barrier layer 216 comprising liquid-impervious film material so as to prevent liquid that is entrapped in the absorbent core 214 from egressing the sanitary napkin 200 and staining the wearer's undergarment. The barrier layer 216 is preferably made of polymeric film, although it may be made of liquid impervious, air-permeable material such as repellent-treated non-woven or micropore films or foams.
The barrier layer may be breathable, i.e., permits vapor to transpire. Known materials for this purpose include nonwoven materials and microporous films in which microporosity is created by, inter alia, stretching an oriented film. Single or multiple layers of permeable films, fabrics, melt-blown materials, and combinations thereof that provide a tortuous path, and/or whose surface characteristics provide a liquid surface repellent to the penetration of liquids may also be used to provide a breathable backsheet. The cover layer 210 and the barrier layer 216 are joined along their marginal portions so as to form an enclosure or flange seal that maintains the absorbent core 214 captive. The joint may be made by means of adhesives, heat-bonding, ultrasonic bonding, radio frequency sealing, mechanical crimping, and the like and combinations thereof.
In one specific example of the invention, the barrier layer consists of a liquid impermeable 24 gsm polyethylene film commercially available from Clopay do Brasil, Sau Paulo, SP, Brazil.
Positioning adhesive may be applied to a garment facing side of the barrier layer 216 for securing the napkin 200 to the garment during use. The positioning adhesive may be covered with removable release paper so that the positioning adhesive is covered by the removable release paper prior to use.
Absorbent articles of this invention may or may not include wings, flaps or tabs for securing the absorbent article to an undergarment. Wings, also called, among other things, flaps or tabs, and their use in sanitary protection articles is described in U.S. Pat. No. 4,687,478 to Van Tilburg; U.S. Pat. No. 4,589,876 also to Van Tilburg, U.S. Pat. No. 4,900,320 to McCoy, and U.S. Pat. No. 4,608,047 to Mattingly.
The sanitary napkin 200 of the present invention may be applied to the crotch by placing the garment-facing surface against the inside surface of the crotch of the garment. Various methods of attaching absorbent articles may be used. For example, chemical means, e.g., adhesive, and mechanical attachment means, e.g., clips, laces, ties, and interlocking devices, e.g., snaps, buttons, VELCRO (Velcro USA, Inc., Manchester, N.H.), zipper, and the like are examples of the various options available to the artisan.
Adhesive may include pressure sensitive adhesive that is applied as strips, swirls, or waves, and the like. As used herein, the term pressure-sensitive adhesive refers to any releasable adhesive or releasable tenacious means. Suitable adhesive compositions, include, for example, water-based pressure-sensitive adhesives such as acrylate adhesives. Alternatively, the adhesive composition may include adhesives based on the following: emulsion or solvent-borne adhesives of natural or synthetic polyisoprene, styrene-butadiene, or polyacrylate, vinyl acetate copolymer or combinations thereof; hot melt adhesives based on suitable block copoylmers—suitable block copolymers for use in the invention include linear or radial co-polymer structures having the formula (A-B)x wherein block A is a polyvinylarene block, block B is a poly(monoalkenyl) block, x denotes the number of polymeric arms, and wherein x is an integer greater than or equal to one. Suitable block A polyvinylarenes include, but are not limited to Polystyrene, Polyalpha-methylstyrene, Polyvinyltoluene, and combinations thereof. Suitable Block B poly(monoalkenyl) blocks include, but are not limited to conjugated diene elastomers such as for example polybutadiene or polyisoprene or hydrogenated elastomers such as ethylene butylene or ethylene propylene or polyisobutylene, or combinations thereof. Commercial examples of these types of block copolymers include Kraton™ elastomers from Shell Chemical Company, Vector™ elastomers from Dexco, Solprene™ from Enichem Elastomers and Stereon™ from Firestone Tire & Rubber Co.; hot melt adhesive based on olefin polymers and copolymers where in the olefin polymer is a terpolymer of ethylene and a co-monomers, such as vinyl acetate, acrylic acid, methacrylic acid, ethyl acrylate, methyl acrylate, n-butyl acrylate vinyl silane or maleic anhydride. Commercial examples of these types of polymers include Ateva (polymers from AT plastics), Nucrel (polymers from DuPont), Escor (from Exxon Chemical).
Any or all of the cover layer 210, transfer layer 212, absorbent core 214, barrier layer 216, and adhesive layers may be colored. Such coloring includes, but is not limited to, white, black, red, yellow, blue, orange, green, violet, and mixtures thereof. Color may be imparted according to the present invention through dying, pigmentation, and printing. Colorants used according the present invention include dyes and inorganic and organic pigments. The dyes include, but are not limited to, anthraquinone dyes (Solvent Red 111, Disperse Violet 1, Solvent Blue 56, and Solvent Green 3), Xanthene dyes (Solvent Green 4, Acid Red 52, Basic Red 1, and Solvent Orange 63), azine dyes (Jet black), and the like. Inorganic pigments include, but are not limited to, titanium dioxide (white), carbon black (black), iron oxides (red, yellow, and brown), chromium oxide (green), ferric ammonium ferrocyanide (blue), and the like.
Organic pigments include, but are not limited to diarylide yellow AAOA (Pigment Yellow 12), diarylide yellow AAOT (Pigment Yellow 14), phthalocyanine blue (Pigment Blue 15), lithol red (Pigment Red 49:1), Red Lake C (Pigment Red), and the like.
The sanitary napkin 200 may include other known materials, layers, and additives, such as, foam, net-like materials, perfumes, medicaments or pharmaceutical agents, moisturizers, odor control agents, and the like. The sanitary napkin 200 can optionally be embossed with decorative designs.
The sanitary napkin 200 may be packaged as unwrapped absorbent articles within a carton, box or bag. The consumer withdraws the ready-to-use article as needed. The sanitary napkin 200 may also be individually packaged (each absorbent article encased within an overwrap).
Also contemplated by the present invention are asymmetrical and symmetrical absorbent articles having parallel longitudinal edges, dog bone- or peanut-shaped, as well as articles having a tapered construction for use with thong-style undergarments.
From the foregoing description, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications. Embodiments set forth by way of illustration are not intended as limitations on the variations possible in practicing the present invention.

EXAMPLES

Specific inventive examples of the present invention, and comparative examples, are described below.

Inventive Example #1

An example of an sanitary napkin according to the invention was constructed as follows. The body facing cover layer was constructed from a 25 gsm thermal bonded nonwoven material constructed from 100% hydrophilic polypropylene fibers, commercially available from Polystar Company, Salvador, Brazil under the product name Multidenier Telao 25 cover.
A 100 gsm transfer layer was arranged below the cover layer, the transfer layer consisting of an through air bonded pulp commercially available from Buckeye Technologies, Memphis, Tenn., under the designation VIZORB 3042.
A 305 gsm formed fibrous absorbent core was arranged below the transfer layer and was formed by the process described herein above with reference to FIGS. 1-16. The absorbent core included a first region and a plurality of second regions. The first region had a thickness of 1.0 mm and a density of 0.30 g/cc. Each of the plurality of second regions had a thickness of 0.2 mm and a density of 0.54 g/cc. The absorbent core included 9 second regions per square cm. Each one of the second regions had an individual size of 1.0 mm². The first region extended over a surface area of 9.2 mm²and the plurality of second regions extended over a surface area of 90.8 mm²(i.e. the summation of the area over which the second regions extend).
The absorbent core had a composition of 89% by weight of pulp and 11% by weight of superabsorbent polymer. The pulp was Golden Isles Fluff Pulp 420#HD 7% Moisture, commercially available from GP Cellulose, Brunswick, Ga., USA. The superabsorbent polymer was Aqua Keep SA70N commercially available from Sumitomo Seika Chemicals Co., Ltd., Osaka, Japan.
A barrier layer was arranged below the core and was formed from a 24 gsm polyethylene film commercially available from Clopay do Brasil, Sao Paulo, SP, Brazil.
Each of the layers of the sanitary article were adhered to one another using a conventional hot melt adhesive.

Inventive Example #2

A sanitary napkin was constructed that had an identical structure to Inventive Example #1 but for the fact that the cover thereof was replaced with an apertured film cover layer of the type found on the Stayfree Dry Max Ultrathin product distributed by the Personal Products Company Division of McNeil-PPC, Inc., Skillman, N.J.

Comparative Example #1

Comparative Example #1, representative of a prior art sanitary napkin, consisted of the Intimus Gel Sensitive, commercially available from Kimberly-Clark Kenko Industria e Comercio Ltda, Sao Paulo, Brazil.

Comparative Example #2

Comparative Example #2, representative of a prior art ultrathin product, was constructed as follows.
The body facing cover layer was constructed from a 25 gsm thermal bonded nonwoven material constructed from 100% hydrophilic polypropylene fibers, commercially available from Polystar Company, Salvador, Brazil under the product name Multidenier Telao 25 cover.
A 100 gsm transfer layer was arranged below the cover layer, the transfer layer consisting of an through air bonded pulp commercially available from Buckeye Technologies, Memphis, Tenn., under the designation VIZORB 3042.
An absorbent core was arranged below the transfer layer and was formed from a 208 gsm highly compressed pulp/superabsorbent mixture including 25% superabsorbent by weight, commercially available from EAM Corporation, Jessup, Ga., under the designation NVT 208 gsm, 25% SAP.
A barrier layer was arranged below the core and was formed from a 24 gsm polyethylene film commercially available from Clopay do Brasil, Sao Paulo, SP, Brazil.
Each of the layers of the sanitary article were adhered to one another using a conventional hot melt adhesive.

Test Procedures

Absorbent articles according to the present invention provide superior fluid handling characteristics. A number of test procedures are described below that highlight the fluid handling properties of absorbent articles according to the present invention. Prior to conducting any of the described test procedures described below the test product samples should be conditioned for two hours at 21+/−1° C. and 50+/−2% humidity.

Procedure for Measuring Fluid Penetration Time

Fluid Penetration Time is measured by placing a product sample to be tested under a Fluid Penetration Test orifice plate. The orifice plate consists of a 7.6 cm×25.4 cm plate of 1.3 cm thick polycarbonate with an elliptical orifice in its center. The elliptical orifice measures 3.8 cm along its major axis and 1.9 cm along its minor axis. The orifice plate is arranged such that the center of the orifice is aligned with the intersection of the longitudinal and transverse axis of the article, i.e. at the center of the article.
Test fluid was made of the following mixture to simulate bodily fluids:
49.5% of 0.9% sodium chloride solution (VWR catalog #VW 3257-7), 49.05% Glycerin (Emery 917), 1% Phenoxyethanol (Clariant Corporation Phenoxetol™) and 0.45% Sodium Chloride (Baker sodium chloride crystal #9624-05).
A graduated 10 cc syringe containing 7 ml of test fluid is held over the orifice plate such that the exit of the syringe is approximately 3 inches above the orifice. The syringe is held horizontally, parallel to the surface of the test plate. The fluid is then expelled from the syringe at a rate that allows the fluid to flow in a stream vertical to the test plate into the orifice and a stop watch is started when the fluid first touches the sample to be tested. The stop watch is stopped when a portion of the surface of the sample first becomes visible above the remaining fluid within the orifice. The elapsed time on the stop watch is the Fluid Penetration Time. The average Fluid Penetration Time (FPT) is calculated from taking the average of readings from three product samples.

Procedure for Measuring Rewet Potential

The three product samples used for the Fluid Penetration Time (FPT) procedure described above are used for the Rewet Potential test described below.
The rewet potential is a measure of the ability of a napkin or other article to hold liquid within its structure when the napkin contains a relatively large quantity of liquid and is subjected to external mechanical pressure. The rewet potential is determined and defined by the following procedure.
The apparatus for the Rewet Potential test is the same as that set forth above with regard to the FPT test and further includes a quantity of 3 inch×4 (7.62 cm×10.16 cm) inch rectangles of Whatman #1 filter paper from (Whatman Inc., Clifton, N.J.) and a weighing machine or balance capable of weighing to an accuracy of +/−.0.001 g, a quantity of said Whatman paper, a standard weight of 2.22 kg (4.8 pounds) having dimensions 5.1 cm (2 inches) by 10.2 cm (4.0 inches) by approximately 5.4 cm (2.13 inches) which applies a pressure of 4.14 kPa (0.6 psi) over the 5.1 by 10.2 cm (2 inches by 4 inches) surface.
For purposes of the test procedure set forth herein, the same three product samples used for the fluid penetration test should be used for the rewet potential test. After the test fluid is applied within the orifice plate in the FPT test described above, and as soon as the cover layer of the napkin first appears through the top surface of the fluid, the stop watch is started and an interval of 5 minutes is measured.
After 5 minutes have elapsed, the orifice plate is removed and the napkin is positioned on a hard level surface with the cover layer facing upwards.
A fifteen (15) layer stack of the pre-weighed filter paper is placed on and centered over the wetted area and the standard 2.22 kg weight is placed on top of the filter paper. The filter paper and the weight are arranged over the absorbent article such that they are centered over the area to which the fluid was applied. The filter paper and the weight are arranged such that their longer dimensions are aligned with the longitudinal direction of the product. Immediately after placing the paper and weight on the product, the stopwatch is started and after a 3 minute interval has elapsed the standard weight and filter paper are quickly removed. The wet weight of the filter paper is measured and recorded to the nearest 0.001 grams. The rewet value is then calculated as the difference in grams between the weight of the wet 15 layers of filter paper and the dry 15 layers of filter paper. The average Rewet Potential is calculated from taking the average of readings from three product samples.

Procedure for Measuring the Thickness of a Sanitary Article

The thickness measurement of the product should be conducted at the intersection of the longitudinal and transverse axis of the article, i.e. at the center of the article. Disposable sanitary articles according to the present invention preferably have a thickness of less than 5.0 mm.
The apparatus required to measure the thickness of the sanitary napkin is a footed dial (thickness) gauge with stand, available from Ames, with a 2″ (5.08 cm) diameter foot at a pressure of 0.07 psig (4.826 hPa) and a readout accurate to 0.001″ (0.0254 mm). A digital type apparatus is preferred. If the sanitary napkin sample is individually folded and wrapped, the sample is unwrapped and carefully flattened by hand. The release paper is removed from the product sample and it is repositioned back gently across the positioning adhesive lines so as not to compress the sample, ensuring that the release paper lies flat across the sample. Flaps (if any) are not considered when taking the thickness reading.
The foot of the gauge is raised and the product sample is placed on the anvil such that the foot of the gauge is approximately centered on the location of interest on the product sample. When lowering the foot, care must be taken to prevent the foot dropping onto the product sample or undue force being applied. A load of 0.07 psig (4.826 hPa) is applied to the sample and the read out is allowed to stabilize for approximately 5 seconds. The thickness reading is then taken. This procedure is repeated for three product samples and the average thickness is then calculated.
The measured Fluid Penetration Time, Rewet Potential and Product Thickness of the Inventive Examples and Comparative Examples described above are summarized in the table set forth below.


Thickness (mm)	FPT (s)	Rewet (g)

Inventive	2.9	4.5	0.03
Example #1
Inventive	3.2	4.0	0.03
Example #2
Comparative	3.8	5.5	0.6
Example #1
Comparative	2.2	7.5	0.6
Example #2

As shown above, disposable absorbent articles according to the present provide superior fluid handling characteristics.

Claims

We claim:

1. An absorbent article comprising:

a liquid permeable cover layer;

a liquid impermeable barrier layer;

an absorbent core arranged between the cover layer and barrier layer;

wherein the absorbent core comprises a pin-calendered fibrous formed by way of a pin-calendering process that does not use a carrier layer during the pin-calendering step.

2. The absorbent article according to claim 1, further comprising a transfer layer arranged between the cover layer and the absorbent core.

3. The absorbent article according to clam 1, wherein the pin calendering process comprises conveying the fibrous article through a nip defined between a first roll and a second roll without the use of a carrier layer.

4. The absorbent article according to claim 3, wherein the first roll comprises a vacuum roll and the second roll comprises a pin calender roll.

5. The absorbent article according to claim 4, wherein a surface of the vacuum roll includes a plurality of holes and the pin calender roll includes a plurality of pins extending outwardly from a surface of the roll.

6. The absorbent article according to claim 5, wherein each one of the plurality of pins is arranged such that it does not overlap with any of the plurality of holes.

7. The absorbent article according to claim 1, wherein the absorbent core includes a first region and a plurality of second regions.

8. The absorbent article according to claim 7, wherein the first region has a thickness in the range of from about 0.5 mm to about 3.5 mm and a density in the range of about 0.06 g/cc and 0.5 g/cc and each of the plurality of second regions has a thickness in the range of about 0.15 mm to about 0.7 mm and a density in the range of about 0.1 g/cc and 0.9 g/cc.

9. The absorbent article according to claim 8, wherein the absorbent core includes between about 8 and 10 of the second regions per square centimeter.

10. The absorbent article according to claim 9, wherein each of the second regions preferably has an individual size ranging from about 0.8 mm²to about 1.2 mm².