Búsqueda Imágenes Maps Play YouTube Noticias Gmail Drive Más »
Iniciar sesión
Usuarios de lectores de pantalla: deben hacer clic en este enlace para utilizar el modo de accesibilidad. Este modo tiene las mismas funciones esenciales pero funciona mejor con el lector.

Patentes

  1. Búsqueda avanzada de patentes
Número de publicaciónUS20040224588 A1
Tipo de publicaciónSolicitud
Número de solicitudUS 10/866,210
Fecha de publicación11 Nov 2004
Fecha de presentación10 Jun 2004
Fecha de prioridad24 Dic 1998
También publicado comoCA2356651A1, CA2356651C, CN1281202C, CN1354645A, EP1139961A1, EP1139961A4, EP1139961B1, EP2407135A2, EP2407135A3, US6562743, US6770576, US20030157857, WO2000038607A1, WO2000038607A9
Número de publicación10866210, 866210, US 2004/0224588 A1, US 2004/224588 A1, US 20040224588 A1, US 20040224588A1, US 2004224588 A1, US 2004224588A1, US-A1-20040224588, US-A1-2004224588, US2004/0224588A1, US2004/224588A1, US20040224588 A1, US20040224588A1, US2004224588 A1, US2004224588A1
InventoresJeffery Cook, Robert Bell, Sonja Fields, Byron Jerry Lee Huff, Gerald Morton, Howard Schoggen, David Smith
Cesionario originalBki Holding Corporation
Exportar citaBiBTeX, EndNote, RefMan
Enlaces externos: USPTO, Cesión de USPTO, Espacenet
Absorbent structures of chemically treated cellulose fibers
US 20040224588 A1
Resumen
Disclosed are absorbent structures including fibers bound with a polyvalent cation-containing compound and superabsorbent polymer particles. The fibers exhibit an ion extraction factor of at least 5%. Also disclosed are multi-strata absorbent structures, such as disposable absorbent articles, including the treated fibers and SAP particles. Further disclosed are methods for preparing absorbent structures including the treated fibers; structures including fibers combined with a polyvalent cation-containing compound; and methods for treating or coating SAP particles with polyvalent cation-containing compounds.
Imágenes(8)
Previous page
Next page
Reclamaciones(106)
What is claimed is:
1. An absorbent structure, comprising:
fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; and superabsorbent polymer particles.
2. The structure of claim 1 wherein said fibers exhibit an ion extraction factor of at least 25%
3. The structure of claim 1 wherein said fibers exhibit an ion extraction factor of at least 50%
4. The structure of claim 1 wherein said fibers exhibit an ion extraction factor of at least 90%
5. The structure of claim 1 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
6. The structure of claim 1 wherein the polyvalent cation is present in an amount of between 0.25% and 2.5%, by weight of the fiber.
7. The structure of claim 1 wherein the polyvalent cation is present in an amount of between 0.4% and 1.2%, by weight of the fiber.
8. The structure of claim 1 wherein the polyvalent cation is a transition metal ion.
9. The structure of claim 1 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
10. The structure of claim 1 wherein the polyvalent cation is in the +3 or +4 oxidation state.
11. The structure of claim 1 wherein said compound is a polyvalent metal salt.
12. The structure of claim 9 wherein said compound is selected from the group consisting of hydroxides of aluminum, iron and tin, and mixtures thereof.
13. The structure of claim 9 wherein said compound is selected from the group consisting of water soluble salts of aluminum, iron and tin, and mixtures thereof.
14. The structure of claim 1 wherein said fiber is at least 80% alpha cellulose and has a water retention value of at least 80%.
15. The structure of claim 14 wherein said fiber is at least 95% alpha cellulose, has a curl of at least 25% and has a water retention value of less than 90%.
16. The structure of claim 14 wherein said fiber is crosslinked, has a curl of greater than 50% and has a water retention value of less than 60%.
17. The structure of claim 14 wherein said fiber is a cellulose fiber selected from the group consisting of softwood cellulose, hardwood cellulose, cotton, esparto grass, bagasse, hemp, flax, chemically modified cellulose, physically modified cellulose, regenerated cellulose, bacterially generated cellulose, lyocell, cellulose acetate and mixtures thereof.
18. The structure of claim 1 wherein said fiber is selected from the group consisting of hydrophobic fibers treated with a surfactant, hydrophobic fibers treated with silica, surface-oxidized hydrophobic fibers, and mixtures thereof.
19. The structure of claim 1 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
20. The structure of claim 1 wherein the fiber and polymer are in the form of a mixture.
21. The structure of claim 1 wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.
22. An absorbent structure, comprising:
an acquisition stratum; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5% and superabsorbent polymer particles.
23. The structure of claim 22 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
24. The structure of claim 22 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
25. The structure of claim 22 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
26. The structure of claim 22 wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.
27. An absorbent structure, comprising:
an acquisition stratum; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including hydrophilic fibers combined with a polyvalent cation-containing compound, and superabsorbent polymer particles.
28. The structure of claim 27 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
29. The structure of claim 27 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
30. The structure of claim 27 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
31. The structure of claim 27 wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.
32. A disposable absorbent article, comprising:
a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:
an acquisition stratum in fluid communication with said topsheet; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5% and superabsorbent polymer particles.
33. The article of claim 32 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
34. The article of claim 32 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
35. The article of claim 32 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
36. The article of claim 32 wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber.
37. The article of claim 32 wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.
38. A disposable absorbent article, comprising:
a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:
an acquisition stratum in fluid communication with said topsheet; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers combined with a polyvalent cation-containing compound and superabsorbent polymer particles.
39. The article of claim 38 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
40. The article of claim 38 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
41. The article of claim 38 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
42. The article of claim 38 wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber.
43. The article of claim 38, wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.
44. A disposable absorbent article, comprising:
a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:
an acquisition stratum in fluid communication with said topsheet, said acquisition stratum including fibers combined with a polyvalent cation-containing compound; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers and superabsorbent polymer particles.
45. The article of claim 44 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.
46. The article of claim 44 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
47. The article of claim 44 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
48. The article of claim 44 wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.
49. The article of claim 44 wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.
50. A disposable absorbent article, comprising:
a chassis including a liquid pervious topsheet, and a liquid impervious backsheet;
and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:
an acquisition stratum in fluid communication with said topsheet; a distribution stratum in fluid communication with the acquisition stratum, said distribution stratum including fibers combined with a polyvalent cation-containing compound; and a storage stratum in fluid communication with the distribution stratum, said storage stratum including fibers and superabsorbent polymer particles.
51. The article of claim 50 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.
52. The article of claim 50 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
53. The article of claim 50 wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.
54. The article structure of claim 50 wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.
55. The article of claim 50 wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.
56. A method of preparing an absorbent structure, comprising:
adjusting the pH of a slurry of cellulose fibers to between 3.8 and 4.2; introducing aluminum sulfate to said slurry; agitating the fiber slurry and increasing the pH to between 5.5 and 5.9; forming a web from said fibers; applying an ionizable acid in an amount of between 0.5% and 5% by weight of the fibers to said web; drying and individualizing the fibers; and introducing superabsorbent polymer particles to the fibers to form an absorbent structure.
57. The method of claim 56 wherein said acid is applied by a method selected from the group consisting of spraying, painting and foaming.
58. The method of claim 56 further comprising the step of applying a reducing agent to the web.
59. The method of 58 wherein said reducing agent is applied after said application of said acid.
60. A method of preparing an absorbent structure, comprising:
adjusting the pH of a slurry of cellulose fibers to between 3.8 and 4.2; introducing aluminum sulfate to said slurry;
agitating the fiber slurry and increasing the pH to between 5.5 and 5.9; forming a web from said fibers;
applying aluminum sulfate in an amount of between 6.2% and 6.8% by weight of fibers to said web;
drying and individualizing the fibers; and
introducing superabsorbent polymer particles to the fibers to form an absorbent structure.
61. The method of claim 60 wherein said aluminum sulfate is applied by a method selected from the group consisting of spraying, painting and foaming.
62. The method of claim 60 further comprising the step of applying a reducing agent to the web.
63. The method of 60 wherein said reducing agent is applied after said application of said aluminum sulfate application.
64. A method of preparing an absorbent structure, comprising:
mixing superabsorbent polymer particles with an aqueous solution of a polyvalent cation containing compound; drying said mixture above 100° C. until a dry mixture is formed;
crushing the dry mixture to form particles; and introducing said particles into an absorbent structure containing fibers.
65. A method of preparing an absorbent structure, comprising:
forming a slurry of cellulose fibers;
forming a web from from said fibers;
applying aluminum sulfate in an amount of between 6.2% and 7.0% by weight of fibers to said web;
drying and individualizing the fibers; and
introducing superabsorbent polymer particles to the fibers to form an absorbent structure.
66. The method of claim 65 wherein said aluminum sulfate is applied by a method selected from the group consisting of spraying, painting and foaming.
67. The method of claim 65 further comprising the step of applying a reducing agent to the web.
68. The method of 67 wherein said reducing agent is applied after said application of said aluminum sulfate application.
69. The absorbent structure of claim 1 wherein said fibers form a topsheet.
70. A absorbent structure, comprising:
a non-woven material including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; and
superabsorbent polymer particles.
71. A method of preparing an absorbent structure, comprising:
mixing superabsorbent polymer particles with an non-aqueous solution of a polyvalent cation containing compound;
drying said mixture until a dry mixture is formed; and
introducing said particles into an absorbent structure containing fibers.
72. The method of claim 71, wherein said non-aqueous solution is prepared with a solvent selected from the group consisting of methanol, ethanol, n-propanol, iso-propanol, acetone and mixtures thereof.
73. The method of claim 71, wherein the drying step is conducted at a temperature of less than 100° C.
74. The method of claim 71, wherein the drying step is conducted at a temperature of less than 40° C.
75. Fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%.
76. The fibers of claim 75 wherein said fibers exhibit an ion extraction factor of at least 25%.
77. The fibers of claim 76 wherein said fibers exhibit an ion extraction factor of at least 50%.
78. The fibers of claim 77 wherein said fibers exhibit an ion extraction factor of at least 90%.
79. The fibers of claim 75 wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.
80. The fibers of claim 79 wherein the polyvalent cation is present in an amount of between 0.25% and 2.5%, by weight of the fiber.
81. The fibers of claim 80 wherein the polyvalent cation is present in an amount of between 0.4% and 1.2%, by weight of the fiber.
82. The fibers of claim 75 wherein the polyvalent cation is a transition metal ion.
83. The fibers of claim 75 wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.
84. The fibers of claim 75 wherein the polyvalent cation is in the +3 or +4 oxidation state.
85. The fibers of claim 75 wherein said compound is a polyvalent metal salt.
86. The fibers of claim 85 wherein said compound is selected from the group consisting of hydroxides of aluminum, iron and tin, and mixtures thereof.
87. The fibers of claim 85 wherein said compound is selected from the group consisting of water soluble salts of aluminum, iron and tin, and mixtures thereof.
88. The fibers of claim 75 wherein said fiber is at least 80% alpha cellulose and has a water retention value of at least 80%.
89. The fibers of claim 75 wherein said fiber is at least 95% alpha cellulose, has a curl of at least 25% and has a water retention value of less than 90%.
90. The fibers of claim 75 wherein said fiber is crosslinked, has a curl of greater than 50% and has a water retention value of less than 60%.
91. The fibers of claim 75 wherein said fiber is a cellulose fiber selected from the group consisting of softwood cellulose, hardwood cellulose, cotton, esparto grass, bagasse, hemp, flax, chemically modified cellulose, physically modified cellulose, regenerated cellulose, bacterially generated cellulose, lyocell, cellulose acetate and mixtures thereof.
92. The fibers of claim 75 wherein said fiber is selected from the group consisting of hydrophobic fibers treated with a surfactant, hydrophobic fibers treated with silica, surface-oxidized hydrophobic fibers, and mixtures thereof.
93. An absorbent structure comprising: fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; superabsorbent polymer particles; and oxalic acid bound to the fiber.
94. An absorbent structure comprising:
(A) fibers, and
(B) superabsorbent polymer particles having surfaces coated with a polyvalent ion salt containing a polyvalent cation and one or more anions.
95. The structure of claim 94, wherein the polyvalent cation is present in an amount from about 0.25 percent to about 5 percent.
96. The structure of claim 95, wherein the polyvalent cation is present in an amount from about 0.25 percent to about 2.5 percent.
97. The structure of claim 96, wherein the polyvalent cation is present in an amount from about 0.4 percent to about 1.2 percent.
98. The structure of claim 94, wherein the polyvalent cation is a transition metal ion.
99. The structure of claim 94, wherein the polyvalent cation is in the +3 or +4 oxidation state.
100. The structure of claim 94, wherein the polyvalent cation is aluminum, iron, tin, or a mixture thereof.
101. The structure of claim 99, wherein the anion is water soluble.
102. The structure of claim 99, wherein the salt is hydroxide.
103. The structure of claim 99, wherein the anion is sulfate.
104. The structure of claim 103, wherein the salt is aluminum sulfate.
105. The structure of claim 94, wherein the superabsorbent polymer is a starch-acrylate graft co-polymer, a polyacrylate, a carboxymethylcellulose derivative or a mixture thereof.
106. The structure of claim 105, wherein the superabsorbent polymer is a polyacrylate.
Descripción
    CROSS-REFERENCE TO RELATED APPLICATIONS
  • [0001]
    This application is a continuation application of U.S. patent application Ser. No. 10/360,147, filed Feb. 7, 2003, which is a divisional application of U.S. patent application Ser. No. 09/469,930, filed Dec. 21, 1999, which has issued into U.S. Pat. No. 6,562,743, which claims priority under 35 U.S.C. § 119, based on U.S. Provisional Application Ser. No. 60/117,565, filed Jan. 27, 1999, and Provisional Application Ser. No. 60/113,849, filed Dec. 24, 1998, the entire disclosures of which are hereby incorporated by reference.
  • FIELD OF THE INVENTION
  • [0002]
    The present invention relates to a fiber treated to enhance permeability of an absorbent structure prepared from such fibers. More particularly, the invention relates to fibers treated with polyvalent metal ion-containing compounds for use in absorbent structures made with such fibers, and absorbent articles containing such absorbent structures.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Absorbent structures are important in a wide range of disposable absorbent articles including infant diapers, adult incontinence products, sanitary napkins and other feminine hygiene products and the like. These and other absorbent articles are generally provided with an absorbent core to receive and retain body liquids. The absorbent core is usually sandwiched between a liquid pervious topsheet, whose function is to allow the passage of fluid to the core and a liquid impervious backsheet whose function is to contain the fluid and to prevent it from passing through the absorbent article to the garment of the wearer of the absorbent article.
  • [0004]
    An absorbent core for diapers, adult incontinence pads and feminine hygiene articles frequently includes fibrous batts or webs constructed of defiberized, loose, fluffed, hydrophilic, cellulosic fibers. Such fibrous batts form a matrix capable of absorbing and retaining some liquid. However, their ability to do so is limited. Thus, superabsorbent polymer (“SAP”) particles, granules, flakes or fibers (collectively “particles”), capable of absorbing many times their weight of liquid, are often included in the absorbent core to increase the absorbent capacity of the core, without having to substantially increase the bulkiness of the core. In an absorbent core containing matrix fibers and SAP particles, the fibers physically separate the SAP particles, provide structural integrity for the absorbent core, and provide avenues for the passage of fluid through the core.
  • [0005]
    Absorbent cores containing SAP particles have been successful, and in recent years, market demand has increased for thinner, more absorbent and more comfortable absorbent articles. Such an article may be obtained by increasing the proportion of SAP particles to the cellulose or other matrix fibers in the absorbent core.
  • [0006]
    However, there are practical limits to increasing the proportion of SAP particles in the absorbent core. If the concentration of SAP particles in an absorbent core is too high, gel blocking can result. When SAP particles distributed through an absorbent core of matrix fibers are exposed to liquid they swell as they absorb the liquid, forming a gel. As adjacent SAP particles swell, they form a barrier to free liquid not immediately absorbed by the SAP particles. As a result, access by the liquid to unexposed SAP particles may be blocked by the swollen (gelled) SAP particles. When gel blocking occurs, liquid pooling, as opposed to absorption, takes place in the core. As a result, large portions of the core remain unused, and failure (leaking) of the absorbent core can occur. Gel blocking caused by high concentrations of SAP particles results in reduced core permeability, or fluid flow, under pressures encountered during use of the absorbent product.
  • [0007]
    One way to minimize gel block (and maintain core permeability) is to limit the proportion of SAP particles to matrix fibers in the absorbent core. In this way, there is sufficient separation between particles, such that even after the particles have been swollen by exposure to liquid they do not contact adjacent particles and free liquid can migrate to unexposed SAP particles. Unfortunately, limiting the concentration of SAP particles in the absorbent core also limits the extent to which the core can be made thinner and more comfortable. To avoid gel block, commercial absorbent cores are presently limited to SAP particle concentrations of 20% to 50% by weight of the core.
  • [0008]
    It would be highly desirable to provide an absorbent core capable of bearing a SAP particle concentration exceeding 50% by weight, preferably 50% to 80% by weight, while maintaining core permeability and avoiding the problem of gel block. It would also be desirable to provide an absorbent core, which exhibits improved permeability for a given SAP concentration. At the same time, it is important to be able to blend the matrix fiber and SAP particles into an absorbent core using conventional material shipping and handling processes to provide attractive economics for the manufacture of infant diapers, feminine hygiene pads, adult incontinence pads, and the like.
  • [0009]
    Other methods for increasing SAP particle concentrations while minimizing gel block, have been directed to modifying the superabsorbent polymer itself. Modification of the superabsorbent polymer usually involves reducing the gel volume of the superabsorbent polymer particles by increasing the crosslinking of the polymer. A crosslinked SAP particle is restricted in its ability to swell, and therefore has a reduced capacity, or gel volume. Although modified SAP particles are less susceptible to gel block, they also absorb less liquid by weight due to their reduced gel volume. Modified SAP particles also tend to be brittle and fracture and crack during or after processing into the final absorbent product. A variety of crosslinkers are known in the art. It is also known to use polyvalent metal ions, including aluminum, during the manufacture of SAPs, to serve as an ionic crosslinking agent. See for example, U.S. Pat. No. 5,736,595.
  • [0010]
    Crosslinking of SAP particles affects the permeability of the particle, i.e., the ability of liquid to permeate the particle to the center, thereby fully utilizing the capacity of the SAP particle. As used in this specification, SAP particle permeability is distinguished from the permeability of the “core” or absorbent structure. Core permeability refers to the ability of liquid to permeate through an absorbent structure containing SAP particles. As used herein, such permeability is measured by methods including “vertical” permeability and “inclined” permeability. A core “permeability factor” may be determined from both vertical and inclined permeability measurements.
  • [0011]
    A method for improved utilization of the superabsorber is disclosed in U.S. Pat. No. 5,147,343, where particle size distribution of the granules is controlled. By controlling the particle size of the superabsorber and hence the surface area, the rate of fluid uptake can be optimized to the core design. However, the utilization of the absorbent core is reduced at higher concentrations of SAP particles due to gel blocking.
  • SUMMARY OF THE INVENTION
  • [0012]
    The present invention is directed to absorbent structures including fibers bound with a polyvalent cation-containing compound and superabsorbent polymer particles. The fibers exhibit an ion extraction factor of at least 5%. The present invention is also directed to multi-strata absorbent structures, such as disposable absorbent articles, including the treated fibers and SAP particles.
  • [0013]
    The present invention is also directed to methods for preparing absorbent structures including the treated fibers; structures including fibers combined with a polyvalent cation-containing compound; and methods for treating or coating SAP particles with polyvalent cation-containing compounds.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0014]
    [0014]FIG. 1 is a perspective view of an inclined permeability test apparatus employed in the Examples of the present specification.
  • [0015]
    [0015]FIG. 2 is a graph illustrating the inclined permeability of absorbent structures of the present invention compared with conventional structures.
  • [0016]
    [0016]FIG. 3 is a perspective view of a vertical permeability test apparatus employed in the Examples of the present specification.
  • [0017]
    [0017]FIG. 4 is a graph illustrating vertical permeability of SAP-containing absorbent structures after application of 0.9% saline solution having various compounds dissolved in the saline at different concentrations.
  • [0018]
    [0018]FIG. 5 is a graph illustrating vertical permeability of SAP-containing absorbent structures made with fibers treated with various compounds, or absorbent structures having various compounds applied to thereto.
  • [0019]
    [0019]FIG. 6 is a graph illustrating the relationship between permeability factor and ion removal, for absorbent structures prepared according to the present invention.
  • [0020]
    [0020]FIG. 7 is a graph illustrating the relationship between permeability factor and disposable diaper performance as measured by fluid wicked to diaper extremity, for absorbent structures prepared according to the present invention.
  • [0021]
    [0021]FIG. 8 is a graph illustrating the relationship between permeability factor and absorbent structure performance, as measured by fluid wicked to structure extremity, for absorbent structures prepared according to the present invention.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • [0022]
    All patents, patent applications, and publications cited in this specification are hereby incorporated by reference in their entirety. In case of conflict in terminology, the present disclosure controls.
  • [0023]
    It has now been surprisingly and unexpectedly discovered that by treating fibers with a polyvalent ion-containing compound, an absorbent structure (or core) made from such fibers and SAP particles exhibits reduced gel blocking and increased core permeability. As a result, the concentration of SAP particles in an absorbent core may be increased without experiencing gel block or loss in permeability of the core. This allows for better utilization of the absorbent core, because a high fluid flow can be maintained under usage pressure in the absorbent core, thus enabling manufacturers to produce thinner, more absorbent and more comfortable absorbent structures.
  • [0024]
    [0024]FIG. 8 exemplifies the improvement in absorbent cores as the permeability is increased. In the figure, the fluid wicked to the core extremity refers to the last three inches of the core material as measured by the horizontal wicking test as described in the procedures section. For two types of SAP, an improvement in core utilization is noted. Further, FIG. 7 shows that for machine-made diapers, the permeability improvement also provides an improvement in core utilization as measured by the horizontal wicking test.
  • [0025]
    When an absorbent core made with SAP particles and fibers treated with a polyvalent metal-ion containing compound according to the present invention is exposed to liquid, the polyvalent metal ion is released from the fibers, carried by the liquid and contacts the surface of the SAP particle. The polyvalent metal ion inhibits the rate of swelling of the SAP particle sufficiently to enable liquid to permeate beyond the swelling SAP particles to contact unexposed SAP particles. Although the rate of swelling is reduced, the extent of swelling of the SAP particles is not significantly affected by contact with liquid containing the polyvalent metal ion.
  • [0026]
    To prepare fibers suitable for use in an absorbent core, any compatible polyvalent metal ion-containing compound may be employed, provided that the compound releases the polyvalent metal ion upon exposure of the treated fiber to the liquid encountered in the core. The degree to which the polyvalent ion is released from the fiber upon exposure to liquid is referred to herein as “ion extraction”. The degree of “ion extraction” is related to the permeability of cores as illustrated in FIG. 6. In this figure increasing ion extraction provides increased permeability.
  • [0027]
    It is not necessary that the compound chemically bond with the fibers, although it is preferred that the compound remain associated in close proximity with the fibers, by coating, adhering, precipitation, or any other mechanism such that it is not dislodged from the fibers during normal handling of the fibers, absorbent core or absorbent article before contact with liquid. For convenience, the association between the fiber and the compound discussed above may be referred to as the “bond,” and the compound may be said to be bound to the fiber.
  • [0028]
    This concept is exemplified as follows: sheeted cellulosic fibers treated with a water insoluble aluminum compound had the same aluminum concentration before and after hammer mill disintegration (Kamas mill). Sheeted cellulosic fibers treated with a water soluble aluminum compound the same aluminum concentration before disintegration (Kamas mill) and after disintegration. Sheeted cellulosic fibers treated with a water insoluble and a water soluble aluminum compound had the same aluminum concentration before disintegration (Kamas mill) and after disintegration.
  • [0029]
    Any polyvalent metal salt including transition metal salts may be used, provided that the compound is capable of releasing the polyvalent metal ion upon contact with liquid encountered in the absorbent core. The polyvalent metal containing compound selected for this application should be compatible with safe contact with human skin and mucous membranes. Examples of suitable polyvalent metals include beryllium, magnesium, calcium, strontium, barium, titanium, zirconium, vanadium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc, aluminum and tin. Preferred ions include aluminum, iron and tin. The preferred metal ions have oxidation states of +3 or +4. The most preferred ion is aluminum. Any salt containing the polyvalent metal ion may be employed, provided that the compound is capable of releasing the polyvalent metal ion upon contact with liquid encountered in the absorbent core. Examples of suitable inorganic salts of the above metals include chlorides, nitrates, sulfates, borates, bromides, iodides, fluorides, nitrides, perchlorates, phosphates, hydroxides, sulfides, carbonates, bicarbonates, oxides, alkoxides phenoxides, phosphites, and hypophosphites. Examples of suitable organic salts of the above metals include formates, acetates, butyrates, hexanoates, adipates, citrates, lactates, oxalates, propionates, salicylates, glycinates, tartrates, glycolates, sulfonates, phosphonates, glutamates, octanoates, benzoates, gluconates, maleates, succinates, and 4,5-dihydroxy-benzene-1,3-disulfonates. In addition to the polyvalent metal salts, other compounds such as complexes of the above salts include amines, ethylenediaminetetra-acetic acid (EDTA), diethylenetriaminepenta-acetic acid (DTPA), nitrilotri-acetic acid (NTA), 2,4-pentanedione, and ammonia.
  • [0030]
    It has been surprisingly discovered that trivalent aluminum ions are the preferred polyvalent metal ions for minimizing gel block. FIG. 4 shows the effect of a variety of polyvalent metal containing compounds on vertical permeability of test cores containing SAP and cellulose fiber. This data indicates that several polyvalent metal cations produce a higher vertical permeability in the test core than the aluminum salts, when the polyvalent metal containing compounds are dissolved in the mobile phase (0.9% saline) of the vertical permeability test. FIG. 5 shows the effect of a variety of polyvalent metal containing compounds on the vertical permeability test cores containing SAP and cellulose fiber pretreated with the polyvalent metal salt, or test cores that are a mixture of SAP and cellulose fiber and the polyvalent metal salt. This data indicates that the test cores containing the aluminum salts have superior vertical permeability to those containing other polyvalent metal containing compounds. Accordingly, preferred compounds are those which contain aluminum and are capable of releasing aluminum ions upon contact with liquid encountered in the absorbent core. Examples of such compounds include aluminum salts such as aluminum chloride, aluminum sulfate and aluminum hydroxide.
  • [0031]
    Depending on the polyvalent metal ion containing compound used to treat the fiber, it may be necessary to provide other components, to cause or enhance ionization when liquid contacts the treated fiber. For example, if aluminum hydroxide is employed as the metal ion containing compound, and is precipitated onto the hydrophilic fibers, it is necessary to also treat the fiber with an ionizable acid, for example citric acid. When the treated fiber is exposed to liquid, such as urine for example, the liquid will solubilize the acid, reducing the pH of the liquid and thereby ionizing the aluminum hydroxide to provide aluminum ions in the form of aluminum citrate. A variety of suitable acids may be employed, although the acid preferably should have a low volatility, be highly soluble in water, and bond to the fiber. Examples include inorganic acids such as sodium bisulfate and organic acids such as formic, acetic, aspartic, propionic, butyric, hexanoic, benzoic, gluconic, oxalic, malonic, succinic, glutaric, tartaric, maleic, malic, phthallic, sulfonic, phosphonic, salicylic, glycolic, citric, butanetetracarboxylic acid (BTCA), octanoic, polyacrylic, polysulfonic, polymaleic, and lignosulfonic acids, as well as hydrolyzed-polyacrylamide and CMC (carboxymethylcellulose). Among the carboxylic acids, acids with two carboxyl groups are preferred, and acids with three carboxyl groups are more preferred. Of these acids, citric acid is most preferred.
  • [0032]
    In general, the amount of acid employed is dictated by the acidity and the molecular weight of that acid. Generally it is found that an acceptable range of acid application is 0.5%-10% by weight of the fibers. As used herein, the “percent by weight,” refers to the weight percent of dry fiber treated with the polyvalent metal containing compound. For citric acid the preferred range of application is 0.5%-3% by weight of the fibers.
  • [0033]
    As discussed above, the treatment of fibers with a polyvalent ion-containing compound increases core permeability. Such treatment results in stiffening of the fibers. The stiffened fibers do not swell in water to the extent that untreated fibers do. Consequently existing interfiber channels or other avenues for liquid to flow through an absorbent structure formed from the fibers are kept open to a greater extent by the stiffened fibers than by the untreated fibers. The reduction in wet swell that is produced by polyvalent ion treatment of the fibers, represents an important contribution to the overall improved permeability of an absorbent core containing SAP particles and the treated fibers of the present invention.
  • [0034]
    Water retention value (WRV) is an indication of a fiber's ability to retain water under a given amount of pressure. Cellulose fibers that are soaked in water swell moderately, and physically retain water in the swollen fiber walls. When an aqueous fiber slurry is centrifuged, the majority of the water is removed from the fibers. However, a quantity of water is retained by the fiber even after centrifugation, and this quantity of water is expressed as a percentage based on the dry weight of the fiber. All of the fibers treated according to the present invention, have lower WRV values than corresponding untreated fibers. Consequently, all the treated fibers are stiffer than conventional fluff fibers, thus contribute to improved core permeability.
  • [0035]
    Reducing Agents
  • [0036]
    If desired, reducing agents may be applied to the treated fibers to maintain desired levels of fiber brightness, by reducing brightness reversion. Addition of acidic substances may cause browning of fibers when heated during processing of webs containing the fibers. Reducing agents counter the browning of the fibers. The reducing agent should also bond to the fibers. Preferred agents are sodium hypophosphite and sodium bisulfite, and mixtures thereof.
  • [0037]
    Fibers
  • [0038]
    A wide variety of fiber types may be treated with the polyvalent metal ion containing compound. However, the use of hydrophilic fibers is preferred. Suitable hydrophilic fibers for use in the present invention include cellulosic fibers, modified crosslinked cellulose fibers, rayon, polyester fibers, hydrophilic nylon, silk wool and the like. Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers. Fibers may be hydrophilized by treatment with surfactants, silica, or surface oxidation, e.g. by ozone in a corona discharge. Such fibers may be derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylics, polyamides, polystyrenes, polyurethanes and the like.
  • [0039]
    For absorbent product applications, the preferred fiber is cellulose. Examples of suitable sources of cellulose fibers include softwood cellulose, hardwood cellulose, cotton, esparto grass, bagasse, hemp, flax, chemically modified cellulose and cellulose acetate. The preferred wood cellulose is bleached cellulose. The final purity of the preferred cellulose fiber of the present invention may range from at least 80% alpha to 98% alpha cellulose, although purity of greater than 95% alpha is preferred, and purity of 96.5% alpha cellulose, is most preferred. As used herein, the term “purity” is measured by the percentage of alpha cellulose present. This is a conventional measurement in the dissolving pulp industry. Methods for the production of cellulose fiber of various purities typically used in the pulp and paper industry are known in the art.
  • [0040]
    Curl is defined as a fractional shortening of the fiber due to kinks, twists and/or bends in the fiber. The percent curl of the cellulose fibers of the present invention is preferably from 25% to 80%, and is more preferably 75%. For the purpose of this disclosure, fiber curl may be measured in terms of a two dimensional field. The fiber curl is determined by viewing the fiber in a two dimensional plane, measuring the projected length of the fiber as the longest dimension of a rectangle encompassing the fiber, L (rectangle), and the actual length of the fiber L (actual), and then calculating the fiber curl factor from the following equation:
  • Curl Factor=L (actual)/L(rectangle)−1
  • [0041]
    A fiber curl index image analysis method is used to make this measurement and is described in U.S. Pat. No. 5,190,563. Fiber curl may be imparted by mercerization. Methods for the mercerization of cellulose typically used in the pulp and paper industry are known in the art.
  • [0042]
    The preferred water retention value (WRV) of the cellulose fibers of the present invention is less than 85 %, and more preferably between 30% and 80%, and most preferably 40%. The WRV refers to the amount of water calculated on a dry fiber basis, that remains absorbed by a sample of fibers that has been soaked and then centrifuged to remove interfiber water. The amount of water a fiber can absorb is dependent upon its ability to swell on saturation. A lower number indicates internal cross-linking has taken place. U.S. Pat. No. 5,190,563 describes a method for measuring WRV.
  • [0043]
    Another source of hydrophilic fibers for use in the present invention, especially for absorbent members providing both fluid acquisition and distribution properties, is chemically stiffened cellulose fibers. As used herein, the term “chemically stiffened cellulose fibers” means cellulose fibers that have been treated to increase the stiffness of the fibers under both dry and wet aqueous conditions. In the most preferred stiffened fibers, chemical processing includes intrafiber crosslinking with crosslinking agents while such fibers are in a relatively dehydrated, defibrated (i.e., individualized), twisted, curled condition. These fibers are reported to have curl values greater than 70% and WRV values less than 60%. Fibers stiffened by crosslink bonds in individualized form are disclosed, for example U.S. Pat. No. 5,217,445 issued Jun. 8, 1993, and U.S. Pat. No. 3,224,926 issued Dec. 21, 1965.
  • [0044]
    Saps
  • [0045]
    The term “superabsorbent polymer particle” or “SAP” particle is intended to include any particulate form of superabsorbent polymer, including irregular granules, spherical particles (beads), powder, flakes, staple fibers and other elongated particles. “SAP” refers to a normally water-soluble polymer which has been cross-linked to render it substantially water insoluble, but capable of absorbing at least ten, and preferably at least fifteen, times its weight of a physiological saline solution. Numerous examples of superabsorbers and their methods of preparation may be found for example in U.S. Pat. Nos. 4,102,340; 4,467,012; 4,950,264; 5,147,343; 5,328,935; 5,338,766; 5,372,766; 5,849,816; 5,859,077; and U.S. Pat. Re. 32, 649.
  • [0046]
    SAPs generally fall into three classes, namely starch graft copolymers, cross-linked carboxymethylcellulose derivatives and modified hydrophilic polyacrylates. Non-limiting examples of such absorbent polymers are hydrolyzed starch-acrylate graft co-polymer, saponified acrylic acid ester-vinyl co-polymer, neutralized cross-linked polyacrylic acid, cross-linked polyacrylate salt, and carboxylated cellulose. The preferred SAPs, upon absorbing fluids, form hydrogels.
  • [0047]
    Suitable SAPs yield high gel volumes or high gel strength as measured by the shear modulus of the hydrogel. Such preferred SAPs contain relatively low levels of polymeric materials that can be extracted by contact with synthetic urine (so-called “extractables”). SAPs are well known and are commercially available from several sources. One example is a starch graft polyacrylate hydrogel marketed under the name IM1000™ (Hoechst-Celanese, Portsmouth, Va.). Other commercially available superabsorbers are marketed under the trademark SANWET™ (Sanyo Kasei Kogyo Kabushiki, Japan), SUMIKA GEL™ (Sumitomo Kagaku Kabushiki Haishi, Japan), FAVOR™ (Stockhausen, Garyville, La.) and the ASAP™ series (Chemdal, Aberdeen, Miss).
  • [0048]
    Suitable SAP particles for use in the present invention include those discussed above, and others, provided that the SAP particle provides improved permeability of an absorbent core made with the SAP and a hydrophilic fiber treated according to the present invention. Most preferred for use with the present invention are polyacrylate-based SAPs.
  • [0049]
    As used in the present invention, SAP particles of any size or shape suitable for use in an absorbent core may be employed.
  • [0050]
    Absorbent Core Structures
  • [0051]
    The treated fibers of the present invention may be used in combination with SAP particles, to form a stratum of an absorbent core, useful in forming an absorbent structure for use in manufacturing an absorbent article. The treated fibers begin to show improved core permeability in a mixture of 20% SAP and 80% fiber in an absorbent core, even better permeability is displayed in a mixture of 40% SAP and 60% fiber in an absorbent core, and further improvement in permeability is observed in a mixture of 60% to 80% SAP and 40% to 20% fiber in an absorbent core. Preferably, the treated fibers will be used to form one stratum of a multi-strata absorbent structure. Absorbent structures particularly useful in infant diapers and adult incontinence products often include at least two defined strata—an upper acquisition stratum and a lower storage stratum. Sometimes, a distribution stratum is provided between the acquisition and storage strata. Optionally, a wicking stratum is provided below the storage stratum.
  • [0052]
    Typically SAP particles are provided in the storage stratum, although such SAP particles may also, or alternatively be provided in a distribution stratum. The treated fibers or other treated substrates of the present invention may be located in any stratum, provided that upon exposure of the absorbent structure to a liquid insult, the liquid contacts the treated fiber, and then carries the polyvalent metal ion to the SAP particles. Preferably, in a multi-strata absorbent structure, the treated fiber of the present invention will be provided in the storage layer.
  • [0053]
    Absorbent Articles
  • [0054]
    The treated fibers of the present invention may be employed in any disposable absorbent article intended to absorb and contain body exudates, and which are generally placed or retained in proximity with the body of the wearer. Disposable absorbent articles include infant diapers, adult incontinence products, training pants, sanitary napkins and other feminine hygiene products.
  • [0055]
    A conventional disposable infant diaper generally includes a front waistband area, a rear waistband area and a crotch region there between. The structure of the diaper generally includes a liquid pervious topsheet, a liquid impervious backsheet, an absorbent structure, elastic members, and securing tabs. Representative disposable diaper designs may be found, for example in U.S. Pat. No. 4,935,022 and U.S. Pat. No. 5,149,335. U.S. Pat. No. 5,961,505 includes representative designs for feminine hygiene pads.
  • [0056]
    The absorbent structure incorporating the treated fibers of the present invention may be formed in place by blending individualized fibers and SAP particles and applying them to a form under applied vacuum to create an absorbent structure of desired shape. Alternatively, the absorbent structure may be formed separately as a continuous roll good, preferably using airlaid (or “dryformed”) technology.
  • [0057]
    Fiber Treatment
  • [0058]
    The fibers suitable for use in absorbent structures may be treated in a variety of ways to provide the polyvalent metal ion-containing compound in close association with the fibers. A preferred method is to introduce the compound in solution with the fibers in slurry form and cause the compound to precipitate onto the surface of the fibers. Alternatively, the fibers may be sprayed with the compound in aqueous or non-aqueous solution or suspension. The fibers may be treated while in an individualized state, or in the form of a web. For example, the compound may be applied directly onto the fibers in powder or other physical form. Whatever method is used, however, it is preferred that the compound remain bound to the fibers, such that the compound is not dislodged during normal physical handling of the fiber in forming the absorbent structure and absorbent articles or use of the article, before contact of the fiber with liquid. Upon contact of the treated fibers with liquid, the applied compound should be released from the fiber to provide ions within the liquid.
  • [0059]
    Preferred Method of Treating Fibers
  • [0060]
    In a preferred embodiment, the treated fibers of the present invention are made from cellulose fiber, obtained from Buckeye Technologies Inc. (Memphis, Tennessee). The pulp is slurried, the pH is adjusted to about 4.0, and aluminum sulfate (Al2(SO4)3) in aqueous solution is added to the slurry. The slurry is stirred and the consistency reduced. Under agitation, the pH of the slurry is increased to approximately 5.7. The fibers are then formed into a web or sheet, dried, and sprayed with a solution of citric acid at a loading of 2.5 weight % of the fibers. The web is then packaged and shipped to end users for further processing, including fiberization to form individualized fibers useful in the manufacture of absorbent products. If a reducing agent is to be applied, preferably it is applied before a drying step and following any other application steps. The reducing agent may be applied by spraying, painting or foaming.
  • [0061]
    Without intending to be bound by theory, it is believed that by this process, the soluble Al2(SO4)3 introduced to the pulp slurry is converted to insoluble Al(OH)3 as the pH is increased. The insoluble aluminum hydroxide precipitates onto the fiber. Thus, the resultant fibers are coated with Al(OH)3 or contain the insoluble metal within the fiber interior. The citric acid sprayed on the web containing the fibers dries on the fibers. When the Al(OH)3 treated fibers are formed into an absorbent product, the citric acid creates a locally acidic environment when the citric acid-treated fibers of the absorbent product are exposed to a liquid insult (e.g., urine). The decreased pH created by the acid environment converts the Al(OH)3 to the soluble form of aluminum including a citric acid complex of this metal. In this way, aluminum ions may become available in solution to locally and temporarily inhibit the swelling of superabsorbent polymers (also present in the absorbent material) thereby minimizing or preventing gel-blocking.
  • [0062]
    In another preferred embodiment, the above procedure is followed to treat the fibers with precipitated Al(OH)3, and in a subsequent step, aluminum sulfate is applied, preferably by spraying, onto the Al(OH)3-treated fibers. Preferably the aluminum sulfate is applied to the web, before the web is introduced to web dryers. Application to the wet web provides better distribution of the aluminum sulfate through the web. The acidic environment provided by the aluminum sulfate is also conducive to release of soluble aluminum ions from the Al(OH)3 precipitate.
  • [0063]
    A hierarchy of preferred embodiments is exemplified as follows: a two component mixture of (1) cellulosic fibers pretreated with a water soluble aluminum compound and (2) SAP particles in an absorbent core (Example 4), provides a higher level of core permeability than a comparable three component mixture of (1) cellulosic fibers and (2) a water soluble aluminum compound and (3) SAP particles in an absorbent core (Example 12), and a higher level of core permeability than a two component mixture of (1) SAP particles pretreated with a water soluble aluminum compound in an aqueous solution and (2) cellulosic fibers in an absorbent core (Example 15). These results are exemplified in the procedures set forth below.
  • [0064]
    Treatment of SAP Particles
  • [0065]
    Improved core permeability may be obtained by coating the surface of SAP particles with a polyvalent ion salt, and combining the coated SAP particle with a fiber in an absorbent structure. The particles are coated in contrast to reacting or complexing the SAP particles with a polyvalent cation salt. Coating of the SAP particle with the salt is accomplished by mixing the SAP particles with a non-aqueous solution of the polyvalent ion salt, and subsequently removing the non-aqueous solvent, leaving a coating of the salt on the surface of the SAP particle. For example, an anhydrous methanol solution of aluminum sulfate may be mixed with SAP particles at room temperature, for example Favor™ SXM 9100, the mixture dried, and the granular coated SAP particles mixed with fluff fiber in an absorbent core. The core permeability for such a structure is much higher than that obtained when an equivalent amount of polyvalent ion salt in aqueous solution is used to treat SAP particles, indicating superior core permeability with aluminum sulfate-coated particles compared to aluminum cation-complexed SAP particles. Although methanol is the preferred non-aqueous solvent, any solvent which dissolves the salt but does not swell the SAP particle, may be used. Examples include alcohols, such as ethanol, n-propanol, iso-propanol and acetone.
  • [0066]
    The following procedures are employed in the Examples set forth at the end of the specification.
  • [0067]
    Formation of Air Laid Structures
  • [0068]
    A Kamas mill (Kamas Industri AB, Sweden) is used to disintegrate pulp sheets into fluff pulp. A pad former (Buckeye Technologies, Memphis, Tenn.) is used to combine the fluff and SAP particles.
  • [0069]
    Laboratory air-laid absorbent structures are made by combining fiber and SAP particles in the laboratory to simulate the process of an absorbent core construction on a full-scale commercial line. Fiber and SAP particles are loaded into the pad former. Fiber and SAP particles are combined through air vortices and become one single structure via the applied vacuum. The air-laid structure is then die-cut to dimensions specific for performance testing. For testing purposes, the airlaid structure should have dimensions of 14″×14″ at a target basis weight (0.30 g/in2 or 0.22 g/in2).
  • [0070]
    Measurement of Ion Content
  • [0071]
    Metal ion content, including aluminum or iron content, in pulp samples is determined by wet ashing (oxidizing) the sample with nitric and perchloric acids in a digestion apparatus. A blank is oxidized and carried through the same steps as the sample. The sample is then analyzed using an inductively coupled plasma spectrophotometer (“ICP”) (e.g., a Perkin-Elmer ICP 6500). From the analysis, the ion content in the sample can be determined in parts per million. The polyvalent cation content should be between 0.25% and 5.0% by weight of fibers, preferably between 0.25% and 2.5% by weight of fibers, and more preferably between 0.4% and 1.2% by weight of fibers.
  • [0072]
    Measurement of Ion Extraction
  • [0073]
    The percentage of ions extracted from fibers in a saline solution is measured by submerging the test fibers in a saline solution that is shaken for 24 hours. During this period, ions are extracted from the fibers and into the solution. The ion concentration in the solution is measured using an ICP and compared with the ion content in the original fiber sample to determine the percentage of ion removed due to prolonged exposure to saline under agitation. The ion extraction should exceed 5%, preferably exceed 25%, more preferably exceed 50%, and most preferably exceed 90%.
  • [0074]
    Measurement of Vertical Permeability
  • [0075]
    Vertical Permeability is determined using the following procedure. This procedure was adapted from the method disclosed in U.S. Pat. No. 5,562,642.
  • [0076]
    A Kamas Cell Mill (Kamas Industri AB, Sweden) apparatus is used to form disintegrated pulp sheets that in turn are used to produce fluff. A pad former (Buckeye Technologies Inc., Memphis, Tenn.) is used to combine SAP particles and fiber to prepare 14″×14″ test pads. Test pads are constructed at a basis weight of 0.3 g/in2 and pressed to a density of 0.15 g/cc. Samples are die-cut to 2¼″ diameter circles and conditioned before testing. The circles are dried in a forced air oven, then placed in a dessicator until the permeability test is run. The sample is then positioned into a vertical cylinder that contains a base (sample platform) constructed from wire mesh. See FIG. 3 for an illustration of the vertical permeability test apparatus. The vertical cylinder has an inside diameter of 2¼″. A weight placed onto the sample supplies about 0.3 lb/in2 of pressure perpendicular to the sample. The sample is saturated in fluid (0.9% saline) for one hour. After one hour, the vertical cylinder containing the sample is secured over (but not in contact with) a weighing balance. The sample is initially insulted with 50 ml of 0.9% saline via a ⅜″ hole centered in the weight. A 25-ml insult is added for every 25 grams of fluid that transferred to the balance until the balance reads 100 grams. Fluid transferred by the sample is measured per unit of time to quantify the permeability for a given sample. Absorption capacity for the samples is also recorded.
  • [0077]
    Measurement of Inclined Permeability
  • [0078]
    The following procedure is used to measure inclined permeability. This procedure was adapted from the procedure disclosed in U.S. Pat. No. 5,147,343. A Kamas Cell Mill (Kamas Industri AB, Sweden) apparatus is used to form disintegrated pulp sheets that in turn are used to produce fluff. A pad former was used to combine SAP particles and fibers to prepare 14″×14″ test pads. Test pads are constructed at a basis weight of 0.22 g/in2 and pressed to a density of 0.15 g/cc. Permeability samples are die-cut to eleven square inches and conditioned before testing. Refer to FIG. 1 for an illustration of the inclined permeability test apparatus used in the procedure. Permeability samples are placed on a Teflon coated block inclined at a 45-degree angle. Attached to this block is a fluid head box connected by ¼″ tubing to a vertically adjustable fluid reservoir. The front edge of the sample pad is centered onto and secured to the head box. The head box is designed with three {fraction (3/16)}″ diameter holes that are spaced {fraction (9/16)}″ apart. A top block coated with Teflon, with a congruent 45-degree angle, is placed on top of the sample pad. Lubricated pegs are inserted into the bottom block (sample platform) at a 60-degree angle to prevent the top block from slipping while allowing for uniform sample expansion after saturation. A 724.4 g weight, along with the weight of the top block supplies about 0.3 lbs/in2 of pressure perpendicular to the sample. The fluid (0.9% saline) level is adjusted to produce and maintain an inverted meniscus. Once saturation occurs, the sample pad acts as a siphon by transferring fluid to a tared receiving container atop a balance located below the end of the sample. Liquid transferred by the sample is measured per unit time to establish a flow rate. Permeability for a given sample is quantified after the flow rate reaches equilibrium. For example, FIG. 2 shows the incline permeability at various time intervals for 50% SAP and 50% cellulose fiber mixtures, and 70% SAP and 30% cellulose fiber mixtures. The figure also shows the increased permeability produced by the invention fiber in a mixture with SAP (Example 3).
  • [0079]
    Calculation of Permeability Factor
  • [0080]
    The permeability factor is determined by summing the permeability in gm/min from the vertical permeability and the inclined permeability. The sum is taken as follows:
  • Perm Factor=(vertical2+inclined2)1/2
  • [0081]
    where “vertical” permeability and “inclined” permeability are express as gm/min. The factor is reported as a dimensionless number although the actual dimensions are gm/min.
  • [0082]
    Measurement of Horizontal Wicking (Core Utilization)
  • [0083]
    Horizontal wicking samples of about 4″×14″ are placed onto a level platform with bordering grooves to capture “runoff” fluid (0.9% saline). Both laboratory test cores or manufactured diaper cores may be used. For laboratory cores, an acquisition-distribution layer (ADL) from a commercial diaper cut to 3″×7″ is placed on top of the sample where fluid is introduced. Then a second board is placed on top of the sample and ADL. The top board contained an insult reservoir with a {fraction (11/2)}″ inside diameter. The insult region, relative to the sample, was 5″ centered from the front end or end closest to the insult reservoir. Two 10 lb. weights placed on the top board along with the weight of the top board supplied about 0.40 lbs/in2 of pressure perpendicular to the sample. Three 100 ml insults were introduced to the sample in twenty-minute intervals. After one hour, the sample was sectioned and weighed to determine the distance that liquid was transported away form the insult region. Horizontal wicking was quantified by the sum of the last three inches, on a gram of fluid per gram of core sample basis.
  • [0084]
    The following examples are intended to illustrate the invention without limiting its scope.
  • COMPARATIVE EXAMPLE 1
  • [0085]
    A slurry of bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies consisting of 4.5 parts fiber/100 parts slurry was diluted with sufficient water to provide 0.9 parts fiber/100 parts slurry and adjusted to a pH of 5.5. The resultant slurry was continuously dewatered on a sheeting machine where a sheet was formed at rush/drag ratio of 1.0, couched, then pressed and densified through three stages of pressing to 48 parts fiber/100 parts slurry. The sheet was dried using conventional drum dryers to 93.5 percent solids. The sheet was reeled on a continuous roll.
  • [0086]
    Sheets from the roll were defiberized in a Kamas mill. An ion extraction test was performed on the fibers as described above. The ionic extraction of the fiber was measured at 0%. Vertical and inclined permeability tests were performed as described above using test cores that were a mixture of 70% by weight of SAP particles and 30% by weight of fibers. The permeability factor was then calculated. When FAVOR™ SXM 70 SAP (obtained from Stockhausen, Inc.) was used, a permeability factor of 16 was obtained.
  • COMPARATIVE EXAMPLE 2
  • [0087]
    Comparative Example 1 was repeated, except that SAP FAVOR™ SXM 9100 was used instead of FAVOR™ SXM 70. The permeability factor obtained was 141.
  • EXAMPLE 1
  • [0088]
    Cellulose fibers were treated as follows. A total of 9.36 parts hydrated aluminum sulfate (Al2(SO4)3*14 H2O) from General Chemical Corporation, per 100 parts bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies were added to a slurry consisting 4.5 parts fiber/100 parts slurry. The slurry had a pH of 3.2. After 25 minutes of mixing 3.0 parts sodium hydroxide/100 parts fiber were added along with sufficient water to provide 0.9 parts fiber/100 parts slurry at a pH of 5.7. The temperature was adjusted to 60° C. The resultant slurry was continuously dewatered on a sheeting machine where the sheet was formed at 1.0 rush/drag ratio, couched, then pressed and densified using three stages of pressing to 48 parts fiber/100 parts total. The sheet was dried using conventional drum dryers to 93.5 percent solids. While continuously reeling, a spray of 50% citric acid solution was applied to one surface of the sheet at a loading of 2.5 parts per 100 parts of fiber. The reeled sheet was then sized into individual rolls.
  • [0089]
    The sheet was defiberized in a Kamas mill, and the ionic extraction test described above was performed. The fiber was found to have an ionic extraction of 34% and an aluminum content of approximately 7,500 ppm. Vertical and inclined permeability tests were performed on test cores using a mixture of 70% by weight of SAP particles and 30% by weight of fibers. The permeability factor using FAVOR™ SXM 70 SAP was 31.
  • EXAMPLE 2
  • [0090]
    Example 1 was repeated except that the SAP used was FAVOR™ SXM 9100. The permeability factor obtained was 177.
  • EXAMPLE 3
  • [0091]
    A slurry of bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies consisting of 4.5 parts fiber/100 parts slurry was diluted with sufficient water to provide 0.9 parts fiber/100 parts slurry and adjusted to a pH of 5.5. The resultant slurry was continuously dewatered on a sheeting machine and a sheet was formed at a rush/drag ratio of 1.0, couched, then pressed and densified through three stages of pressing to 48 parts fiber/100 parts slurry. The sheet was dried using conventional drum dryers to 93.5 percent solids. The sheet was then reeled. During reeling, 6.1 parts of hydrated aluminum sulfate (Al2(SO4)3*14 H2O, 50% aqueous solution) is applied by spraying per 100 parts fiber. The fiber was reeled on a continuous roll. The resultant reel was sized into individual rolls. The sheets were defiberized in a Kamas mill and the ionic extraction measured, and determined to be 86%. The aluminum content of the fibers was 5,500 ppm. Permeability tests were conducted as described above using test cores that were a mixture of 70% by weight SAP and 30% by weight fibers. The permeability factor using FAVOR™ SXM 70 SAP was 44.
  • EXAMPLE 4
  • [0092]
    Example 3 was repeated except that the aluminum content of the fibers was 5445 ppm, and the SAP used was FAVOR™ SXM 9100. The permeability factor obtained was 212. The ion extraction was 86%.
  • EXAMPLE 5
  • [0093]
    12.1 g of ferric nitrate (Fe(NO3)3) (Fisher Chemical Co.) per 152 g bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies were added to a slurry of 4.5 parts fiber/100 parts slurry. The slurry had a pH of 2.76. After mixing and dilution to 0.9 parts fiber/100 parts slurry, 27.1 ml of 10% sodium hydroxide were added to provide a pH of 5.7. The resultant slurry was dewatered on a dynamic handsheet former (Formette Dynamique Brevet, Centre Technique de L'Industrie, Ateliers de Construction Allimand, Appareil No. 48) and was pressed to 48 parts fiber/100 parts total. The sheet was dried to 93.5 percent solids. After drying, 2.5 parts of 50% citric acid solution per 100 parts of fiber were applied to the sheet.
  • [0094]
    The sample sheet was defiberized in a Kamas mill as described above. Permeability was determined on test cores formed as described above, that were a mixture of FAVOR™ SXM 9100, at 70% by weight and fiber 30% by weight. The permeability factor was calculated to be 178.
  • EXAMPLE 6
  • [0095]
    9.36 parts hydrated aluminum sulfate (Al2(SO4)3*14 H2O) per 100 parts bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies were added to a slurry consisting of 4.5 parts fiber/100 parts slurry. After addition of the aluminum sulfate, the slurry had a pH of 3.2. After 25 minutes of mixing, 3.0 parts sodium hydroxide/100 parts fiber were added along with sufficient water to provide 0.9 parts fiber/100 parts slurry at a pH of 5.7 and temperature of 60° C. The resultant slurry was continuously dewatered on a sheeting machine and a sheet formed at a 1.0 rush/drag ratio, couched, then pressed and densified using three stages of pressing to 48 parts fiber/100 parts total. The sheet was dried to 93.5 percent solids. To this sheet sample was applied three parts 1,2,3,4-butanetetracarboxylic acid (BTCA) from Aldrich Chemical Company per 100 parts of fiber by spraying a solution.
  • [0096]
    The sheet was defiberized in a Kamas mill and the fiber was determined to have an ionic extraction of 12.4%. All permeability factor testing was performed using pads made with 70% by weight of FAVOR™ SXM 70 SAP and 30% weight of fiber. The permeability factor was determined to be 38.
  • EXAMPLE 7
  • [0097]
    9.36 parts hydrated aluminum sulfate (Al2(SO4)3*14 H2O) per 100 parts bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies were added to a slurry consisting of 4.5 parts fiber/100 parts slurry. After addition of the aluminum sulfate, the slurry had a pH of 3.2. After 25 minutes of mixing, 3.0 parts sodium hydroxide/100 parts fiber were added along with sufficient water to provide 0.9 parts fiber/100 parts slurry at a pH of 5.7 and temperature of 60° C. The resultant slurry was continuously dewatered on a sheeting machine and a sheet formed at a 1.0 rush/drag ratio, couched, then pressed and densified using three stages of pressing to 48 parts fiber/100 parts total. The sheet was dried to 93.5 percent solids. To this sheet sample was applied one part para-toluenesulfonic acid (PTSA) from Aldrich Chemical Company by spraying per 100 parts of fiber.
  • [0098]
    The sheet was defiberized in a Kamas mill and the fiber was determined to have an ionic extraction of 13.4%. All permeability factor testing was performed using test cores made with 70% by weight of FAVOR™ SXM 70 SAP and 30% by weight of fiber. The permeability factor was determined to be 32.
  • EXAMPLE 8
  • [0099]
    High porosity commercial fiber (HPZ) was obtained from Buckeye Technologies Inc. in sheet form. The fibers had a WRV of 78.7, a curl of 51% and a 96.5% alpha cellulose content. A total of 7.7 parts of hydrated aluminum sulfate octadecahydrate (Aldrich Chemical Company) per 100 parts fiber were applied to the sheeted material by spraying.
  • [0100]
    Ion extraction was measured for the fiber as 100%. Permeability was measured after preparing a test pad that was 30% by weight of fibers and 70% by weight of FAVOR™ SXM 9100 SAP. The permeability factor was 241.
  • EXAMPLE 9
  • [0101]
    High purity commercial cotton fiber (GR702) was obtained from Buckeye Technologies Inc. in sheet form. A total of 7.7 parts of aluminum sulfate octadecahydrate per 100 parts fiber were applied to the sheeted material by spraying. Ion extraction was measured for the fiber as 99.0%. Permeability was measured after preparing a pad that was 30% by weight of fibers and 70% by weight of FAVOR™ SXM 9100 SAP. The permeability factor was 219.
  • EXAMPLE 10
  • [0102]
    Fibers were prepared as disclosed in U.S. Pat. No. 5,190,563 by applying 4.7% citric acid and 1.6% sodium hypophosphite to a Southern Softwood Kraft pulp sheet. After individualizing and curing at 340° F. for 7.5 minutes, the pulp had a WRV of 44 and a curl of about 75%. The individualized fibers were treated by spraying 3.42 parts of hydrated aluminum sulfate (Al2(SO4)3*14 H2O) per 100 parts fiber were added to the fibers and the fibers allowed to dry. The ionic extraction for the fibers was measured at 49.8%. The aluminum content of the fibers was measured at 10,869 ppm. Test pads were made with 30% by weight of the treated fibers and 70% by weight FAVOR™ SXM 9100 SAP and the permeability factor measured. The factor was found to be 231.
  • EXAMPLE 11
  • [0103]
    A sheet of synthetic hydrophilic non-woven material from BBA corporation, product number H018B7W, was selected and treated with 1.03 grams of aluminum sulfate octadecahydrate per square foot of material by spraying and allowed to dry. Test pads were made from 30% by weight bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies and 70% by weight FAVOR™ SXM 9100 SAP, with the treated non-woven material as a topsheet, and the permeability factor measured. The permeability factor was 191.
  • EXAMPLE 12
  • [0104]
    An absorbent core of improved permeability was prepared by adding 2.4 parts of aluminum sulfate octadecahydrate (51.3% aluminum sulfate) in powder form to 100 parts of a 30% by weight fiber and 70% by weight SAP core as described in the method for producing cores. The permeability factor with FAVOR™ SXM 9100 at 70% SAP was 207.
  • EXAMPLE 13
  • [0105]
    A slurry of bleached southern softwood Kraft (BSSK) fibers Buckeye Technologies consisting of 4.5 parts fiber/100 parts slurry was diluted with sufficient water to provide 0.9 parts fiber/100 parts slurry and adjusted to a pH of 5.5. The resultant slurry was continuously dewatered on a sheeting machine where the sheet was formed at a rush/drag ratio of 1.0, couched, then treated by spraying with 12.35 parts of hydrated aluminum sulfate and 3.17 parts of sodium hypophosphite per one hundred parts of fiber, then pressed and densified through three stages of pressing to 48 parts fiber/100 parts slurry. The sheet was dried using conventional drum dryers to 93.5 percent solids. The fiber was reeled on a continuous roll. The resultant reel was sized into individual rolls.
  • [0106]
    The sheets were defiberized in a Kamas mill and the ionic extraction of the fiber was measured at 95%. The permeability factor was determined to be 216, using at test core that was 30% by weight fiber and 70% by weight FAVOR™ SXM 9100.
  • EXAMPLE 14
  • [0107]
    A total of 9.36 parts of hydrated aluminum sulfate (Al2(SO4)3*14 H2O) per 100 parts of bleached southern softwood Kraft (BSSK) fibers from Buckeye Technologies were added to a slurry consisting of 4.5 parts fiber/100 parts slurry. The slurry had a pH of 3.2. After 25 minutes of mixing, 3.0 parts of sodium hydroxide per 100 parts of fiber were added with sufficient water to provide 0.9 parts fiber per 100 parts slurry at a pH of 5.7 and at a temperature of 60° C. The resultant slurry was continuously dewatered on a sheeting machine where the sheet was formed at a rush/drag ratio of 1.0, couched, then treated by spraying with 12.35 parts of hydrated aluminum sulfate and 3.17 parts of sodium hypophosphite per one hundred parts of fiber, then pressed and densified through three stages of pressing to 48 parts fiber/100 parts slurry. The sheet was dried using conventional drum dryers to 93.5 percent solids. The fiber was reeled on a continuous roll. The resultant reel was sized into individual rolls.
  • [0108]
    The sheets were defiberized in a Kamas mill and the ionic extraction of the fiber was measured at 38.2% and the aluminum content was 9475 ppm. The permeability factor was determined to be 213, using a test core that was 30% by weight fiber and 70% by weight FAVOR™ SXM 9100.
  • EXAMPLE 15
  • [0109]
    An absorbent core was prepared by combining three parts of defiberized fluff fiber by weight with seven parts by weight of pretreated FAVOR™ SXM 9100 SAP. The FAVOR™ SXM 9100 SAP had been pretreated with aqueous aluminum sulfate octadecahydrate at ratio of 3.7 parts of dry aluminum sulfate octadecahydrate to 100 parts of SAP, dried at 125° C. for 3 hours, crushed and sieved to the same particle size as the untreated SAP. The permeability factor for this core was determined to be 187.
  • EXAMPLE 16
  • [0110]
    An absorbent core was prepared by combining three parts of defiberized fluff fiber by weight with seven parts by weight of pretreated FAVOR™ SXM 9100 SAP. The FAVOR™ SXM 9100 SAP had been pretreated with a methanol solution of aluminum sulfate octadecahydrate at a ratio of 3.7 parts of dry aluminum sulfate octadecahydrate to 100 parts of SAP, air dried in an exhaust hood to remove visible liquid, and oven dried at 40° C. for two hours. The permeability factor for this core was determined to be 268.
Citas de patentes
Patente citada Fecha de presentación Fecha de publicación Solicitante Título
US213100 *11 Mar 1879 Improvement in preparing paper and other fabrics and materials for protecting metals
US1571048 *28 Ago 192426 Ene 1926 Ments
US1990292 *16 Ene 19335 Feb 1935Leatherman MartinProcess for fireproofing cellulosic materials
US2032645 *18 Ago 19333 Mar 1936Northern Paper MillsAbsorbent paper product and process of producing the same
US2097589 *24 Ago 19352 Nov 1937Henry DreyfusTreatment of textile materials
US2289282 *25 Oct 19397 Jul 1942Gen Aniline & Film CorpMethod of delustering
US2525049 *22 Ago 194610 Oct 1950Du PontCellulose titanate film production
US2739871 *15 Sep 195027 Mar 1956Daubert Chemical CoComposition and sheet material for inhibition of corrosion of metals
US2983722 *6 Nov 19579 May 1961Yardney International CorpFungicidal compounds
US3053607 *2 Jun 195811 Sep 1962Du PontProcess of making wool-like cellulosic textile materials
US3224926 *22 Jun 196221 Dic 1965Kimberly Clark CoMethod of forming cross-linked cellulosic fibers and product thereof
US3873354 *24 Mar 197225 Mar 1975Preco CorpElectrostatic printing
US3935363 *16 Sep 197427 Ene 1976The Dow Chemical CompanyAbsorbent product containing flocculated clay mineral aggregates
US3998690 *2 Oct 197221 Dic 1976The Procter & Gamble CompanyFibrous assemblies from cationically and anionically charged fibers
US4043952 *9 May 197523 Ago 1977National Starch And Chemical CorporationSurface treatment process for improving dispersibility of an absorbent composition, and product thereof
US4090013 *7 Mar 197516 May 1978National Starch And Chemical Corp.Absorbent composition of matter
US4102340 *9 May 197725 Jul 1978Johnson & JohnsonDisposable article with particulate hydrophilic polymer in an absorbent bed
US4295987 *26 Dic 197920 Oct 1981The Procter & Gamble CompanyCross-linked sodium polyacrylate absorbent
US4302369 *8 Abr 198024 Nov 1981Henkel CorporationAluminum modified water absorbent composition
US4306911 *7 Feb 198022 Dic 1981Amiantus, (A.G.)Method for the production of a fiber-reinforced hydraulically setting material
US4406703 *4 Dic 198027 Sep 1983Permawood International CorporationComposite materials made from plant fibers bonded with portland cement and method of producing same
US4447570 *1 Mar 19828 May 1984Air Products And Chemicals, Inc.Binder compositions for making nonwoven fabrics having good hydrophobic rewet properties
US4467012 *13 Jun 198321 Ago 1984Grain Processing CorporationComposition for absorbent film and method of preparation
US4469746 *1 Jun 19824 Sep 1984The Procter & Gamble CompanySilica coated absorbent fibers
US4558091 *7 Ago 198410 Dic 1985Grain Processing CorporationMethod for preparing aluminum and polyhydric alcohol modified liquid absorbing composition
US4699823 *21 Ago 198513 Oct 1987Kimberly-Clark CorporationNon-layered absorbent insert having Z-directional superabsorbent concentration gradient
US4715931 *24 Mar 198729 Dic 1987Betz Laboratories, Inc.Process for inhibiting aluminum hydroxide deposition in papermaking felts
US4838885 *18 Mar 198713 Jun 1989Kimberly-Clark CorporationForm-fitting self-adjusting disposable garment with a multilayered absorbent
US4888238 *16 Sep 198719 Dic 1989James River CorporationSuperabsorbent coated fibers and method for their preparation
US4898642 *1 Feb 19896 Feb 1990The Procter & Gamble Cellulose CompanyTwisted, chemically stiffened cellulosic fibers and absorbent structures made therefrom
US4919681 *16 Feb 198824 Abr 1990Basf CorporationMethod of preparing cellulosic fibers having increased absorbency
US4935022 *11 Feb 198819 Jun 1990The Procter & Gamble CompanyThin absorbent articles containing gelling agent
US4950264 *4 Ene 198921 Ago 1990The Procter & Gamble CompanyThin, flexible sanitary napkin
US4950265 *17 Oct 198821 Ago 1990Hart Enterprises, Inc.Arming device for a medical instrument
US4952550 *8 Mar 199028 Ago 1990Micro Vesicular Systems, Inc.Particulate absorbent material
US5147343 *10 Abr 198915 Sep 1992Kimberly-Clark CorporationAbsorbent products containing hydrogels with ability to swell against pressure
US5149335 *23 Feb 199022 Sep 1992Kimberly-Clark CorporationAbsorbent structure
US5190563 *17 Oct 19902 Mar 1993The Proctor & Gamble Co.Process for preparing individualized, polycarboxylic acid crosslinked fibers
US5217445 *17 Dic 19908 Jun 1993The Procter & Gamble CompanyAbsorbent structures containing superabsorbent material and web of wetlaid stiffened fibers
US5294299 *3 Feb 199315 Mar 1994Manfred ZeunerPaper, cardboard or paperboard-like material and a process for its production
US5300192 *17 Ago 19925 Abr 1994Weyerhaeuser CompanyWet laid fiber sheet manufacturing with reactivatable binders for binding particles to fibers
US5328935 *26 Mar 199312 Jul 1994The Procter & Gamble CompanyMethod of makig a superabsorbent polymer foam
US5338766 *26 Mar 199316 Ago 1994The Procter & Gamble CompanySuperabsorbent polymer foam
US5350799 *7 May 199127 Sep 1994Hoechst Celanese CorporationProcess for the conversion of fine superabsorbent polymer particles into larger particles
US5360420 *17 Dic 19901 Nov 1994The Procter & Gamble CompanyAbsorbent structures containing stiffened fibers and superabsorbent material
US5372766 *31 Mar 199413 Dic 1994The Procter & Gamble CompanyFlexible, porous, absorbent, polymeric macrostructures and methods of making the same
US5399591 *18 Ene 199421 Mar 1995Nalco Chemical CompanySuperabsorbent polymer having improved absorption rate and absorption under pressure
US5413676 *30 Sep 19939 May 1995ChicopeeCellulosic fiber of improved wettability
US5417977 *7 Jun 199323 May 1995Isolyser Co., Inc.Method of producing an absorbent composition
US5427844 *15 Dic 199327 Jun 1995New Japan Chemical Co., Ltd.Articles of natural cellulose fibers with improved deodorant properties and process for producing same
US5432000 *22 Mar 199111 Jul 1995Weyerhaeuser CompanyBinder coated discontinuous fibers with adhered particulate materials
US5451613 *17 Mar 199519 Sep 1995Nalco Chemical CompanySuperabsorbent polymer having improved absorption rate and absorption under pressure
US5462972 *18 May 199531 Oct 1995Nalco Chemical CompanySuperabsorbent polymer having improved absorption rate and absorption under pressure
US5484896 *24 Mar 199416 Ene 1996The Procter & Gamble CompanyEsterified high lignin content cellulosic fibers
US5489469 *28 May 19936 Feb 1996Kao CorporationAbsorbent composite
US5492759 *27 Sep 199020 Feb 1996Molnlycke AbFibres of increased specific surface area, a method for their manufacture, fluff pulp consisting of such fibres and the use of the fibres as absorption material
US5506684 *7 Jun 19959 Abr 1996Nikon CorporationProjection scanning exposure apparatus with synchronous mask/wafer alignment system
US5548847 *9 Dic 199427 Ago 1996Spicijaric; JohnCap with a picture retaining pocket
US5562642 *4 May 19958 Oct 1996Creative Products Resource, Inc.Separately packaged applicator pads for topical delivery of incompatible drugs
US5562646 *6 Abr 19958 Oct 1996The Proctor & Gamble CompanyAbsorbent members for body fluids having good wet integrity and relatively high concentrations of hydrogel-forming absorbent polymer having high porosity
US5589256 *17 Ago 199231 Dic 1996Weyerhaeuser CompanyParticle binders that enhance fiber densification
US5601921 *28 Jun 199411 Feb 1997Molnlycke AbAluminium-salt impregnated fibres, a method for their manufacture, fluff consisting of such fibres, and the use of the fibres as absorption material
US5611890 *7 Abr 199518 Mar 1997The Proctor & Gamble CompanyTissue paper containing a fine particulate filler
US5721295 *3 May 199324 Feb 1998Chemische Fabrik Stockhausen GmbhPolymer composition, absorbent composition, their production and use
US5736595 *3 May 19937 Abr 1998Chemische Fabrik Stockhausen GmbhPolymer composition, absorbent material composition, their production and their use
US5773542 *22 Mar 199630 Jun 1998Kao CorporationProcess for producing polymer particles
US5789326 *19 Nov 19964 Ago 1998Weyerhaeuser CompanyParticle binders
US5795439 *31 Ene 199718 Ago 1998Celanese Acetate LlcProcess for making a non-woven, wet-laid, superabsorbent polymer-impregnated structure
US5795515 *8 Jul 199618 Ago 1998Nueva AgMethod of producing formed articles of a fiber reinforced, hydraulically setting material
US5847031 *3 May 19938 Dic 1998Chemische Fabrik Stockhausen GmbhPolymer composition, absorbent composition, their production and use
US5849816 *31 Ene 199615 Dic 1998Leonard PearlsteinMethod of making high performance superabsorbent material
US5858021 *26 Sep 199712 Ene 1999Kimberly-Clark Worldwide, Inc.Treatment process for cellulosic fibers
US5859077 *19 Dic 199512 Ene 1999Nova-Sorb Ltd. Novel AbsorbentsApparatus and method for producing porous superabsorbent materials
US5961505 *23 Feb 19945 Oct 1999Kimberly-Clark-Worldwide, Inc.Absorbent article exhibiting improved fluid management
US5998695 *29 Jun 19987 Dic 1999The Procter & Gamble CompanyAbsorbent article including ionic complexing agent for feces
US6040251 *7 Jun 199521 Mar 2000Nextec Applications Inc.Garments of barrier webs
US6074530 *21 Ene 199813 Jun 2000Vinings Industries, Inc.Method for enhancing the anti-skid or friction properties of a cellulosic fiber
US6080277 *15 Feb 199627 Jun 2000Tfm Handels-AktiengesellschaftCellulose particles, method for producing them and their use
US6099950 *30 Jul 19988 Ago 2000The Procter & Gamble CompanyAbsorbent materials having improved absorbent property and methods for making the same
US6127593 *25 Nov 19973 Oct 2000The Procter & Gamble CompanyFlushable fibrous structures
US6159335 *20 Feb 199812 Dic 2000Buckeye Technologies Inc.Method for treating pulp to reduce disintegration energy
US6222091 *28 Oct 199824 Abr 2001Basf AktiengesellschaftMulticomponent superabsorbent gel particles
US6228217 *13 Ene 19958 May 2001Hercules IncorporatedStrength of paper made from pulp containing surface active, carboxyl compounds
US6235965 *22 Jul 199822 May 2001Basf AktiengesellschaftMulticomponent superabsorbent gel particles
US6296737 *12 Jun 20002 Oct 2001Weyerhaeuser CompanyMethod of making readily debonded pulp products
US6340408 *10 Abr 199722 Ene 2002Stora Kopparbergs Bergslags Aktiebolag (Publ)Method of preparation of a fluffed pulp to be used in absorbent products
US6433058 *7 Dic 199913 Ago 2002Dow Global Technologies Inc.Superabsorbent polymers having a slow rate of absorption
USRE32649 *10 Jun 198719 Abr 1988The Procter & Gamble CompanyHydrogel-forming polymer compositions for use in absorbent structures
Citada por
Patente citante Fecha de presentación Fecha de publicación Solicitante Título
US894610019 Jun 20063 Feb 2015Buckeye Technologies Inc.Fibers of variable wettability and materials containing the fibers
US20170183817 *29 Dic 201529 Jun 2017Weyerhaeuser Nr CompanyModified fiber from shredded pulp sheets, methods, and systems
WO2008135011A2 *19 Abr 200813 Nov 20083Mach GmbhCovering and sleeve
WO2008135011A3 *19 Abr 20085 Mar 20093Mach GmbhCovering and sleeve
Clasificaciones
Clasificación de EE.UU.442/153, 442/59
Clasificación internacionalD21C9/00, A61F13/49, D06M101/06, A61F13/53, D06M11/00, A61L15/60, D04H1/40, D06M11/45, D06M13/207, B32B5/02, D06M11/57, D06M15/11, A61L15/28, D06M13/192, D06M15/09, D06M15/263, D06M11/17, D06M23/08, A61F13/15
Clasificación cooperativaD06M23/08, D21C9/002, A61F2013/530481, Y10T442/699, D06M13/192, A61L15/28, Y10T442/696, A61F13/53, Y10T442/60, Y10T442/20, Y10T442/2492, A61F2013/15544, A61F13/537, Y10T442/69, Y10T442/277, D06M11/45, D06M15/263, D06M15/09, Y10T442/2484, D06M11/17, A61L15/60, D06M11/57, Y10T442/2508, D06M13/207, D06M15/11, B32B5/02
Clasificación europeaA61F13/53, A61L15/28, D21C9/00B2, D06M13/207, A61L15/60, D06M23/08, D06M15/09, D06M11/57, D06M11/17, D06M15/263, D06M13/192, D06M15/11, B32B5/02, D06M11/45
Eventos legales
FechaCódigoEventoDescripción
10 Nov 2004ASAssignment
Owner name: FLEET NATIONAL BANK, MASSACHUSETTS
Free format text: SECURITY INTEREST;ASSIGNOR:BKI HOLDING CORPORATION;REEL/FRAME:015365/0368
Effective date: 20041030
13 Jul 2007ASAssignment
Owner name: BUCKEYE TECHNOLOGIES INC., TENNESSEE
Free format text: MERGER;ASSIGNOR:BKI HOLDING CORPORATION;REEL/FRAME:019550/0501
Effective date: 20070630
Owner name: BUCKEYE TECHNOLOGIES INC.,TENNESSEE
Free format text: MERGER;ASSIGNOR:BKI HOLDING CORPORATION;REEL/FRAME:019550/0501
Effective date: 20070630
31 Jul 2007ASAssignment
Owner name: BKI HOLDING CORPORATION, DELAWARE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:COOK, JEFFERY T.;BELL, ROBERT IRVIN;FIELDS, SONJA MCNEIL;AND OTHERS;REEL/FRAME:019617/0379
Effective date: 20000204