Bleaching and dyeing; fluid treatment and chemical modification – Chemical modification of textiles or fibers or products thereof – Treating textiles or fibers from synthetic resin or natural...
Reexamination Certificate
2001-11-13
2004-05-18
Einsmann, Margaret (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Chemical modification of textiles or fibers or products thereof
Treating textiles or fibers from synthetic resin or natural...
C008S115540, C008S115560, C008S115640, C008S115650
Reexamination Certificate
active
06736858
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fiber-treating agent suitable for fiber to be processed into nonwoven topsheet of diapers and sanitary napkins and the fiber and fiber product applied with the agent. More precisely, the present invention provides a fiber-treating agent, which minimizes “wet-back”, i.e., the wetting of a wearer's skin caused from the backflow of excreted liquid (urine, etc.) through topsheet after the liquid is absorbed in a diaper or sanitary napkin, and improves the liquid permeability and the durable hydrophilicity of the topsheet of diapers and sanitary napkins; and fiber and fiber products treated with the agent.
Absorbent products, such as diapers or sanitary napkins, consist of nonwoven topsheet, which is made of polyester fibers as major material and of triacetate fiber or hydrophobic polyolefin fiber being included partially and imparted with hydrophilicity; water-repellent back sheet; and absorbent of fibriform pulp or absorbent polymer placed between the topsheet and back sheet. When excreted liquid (urea etc.) is absorbed into absorbent through topsheet, topsheet is expected to pass the liquid with excellent liquid permeability that shorten the absorption time of the liquid into absorbent without leaving wet touch on topsheet surface, and is also expected to prevent the absorbed liquid from backflow out of the topsheet surface. In addition, the fiber treating agent is required to impart durable hydrophilicity to topsheet without flowing off from topsheet surface after a few times of excretion passing and reducing the water permeability of topsheet for the purpose of minimizing the frequency of diaper exchange and keeping the surface property of topsheet against time-dependent deterioration.
For smooth nonwoven processing, the fiber applied with the treating agent must have satisfactory antistaticity that prevents fiber from wrapping on cylinders in carding and contributes to uniform web forming.
Comfortable diapers must have topsheet that has superior liquid permeability with minimum wet-back and durable hydrophilicity that keeps the liquid permeability of the topsheet after repeated liquid passing through the topsheet. Several techniques and treating agents have already been suggested for improving those properties. A method for treating fiber with C
12-22
linear potassium alkyl phosphate is disclosed in Japanese Patent Publication 63-14081, a fiber-treating agent formulated by blending C
10-30
alkyl phosphate salt with C
10-30
betaines, sulfates or sulfonates is disclosed in Japanese Patent Laid-Open 60-215870, a technique utilizing a blend of alkyl phosphate salt and polyether-modified silicone is disclosed in Japanese Patent Laid-Open 4-82961, and a technique utilizing a blend of alkyl phosphate salt and two betaines is disclosed in Japanese Patent Laid-Open 2000-170076. Further a fiber-treating agent of alkoxylated ricinolein or hydrogenated product thereof, an agent being different from the above-mentioned agents, is disclosed in Japanese Patent Laid-Open 3-82871.
All of the treating agents mentioned above cannot sufficiently prevent the wet-back of absorbed liquid though they impart desirable surface properties to nonwoven topsheet to some extent. Hydrophilic agents are preferable for improving liquid permeability of topsheet while hydrophobic agents are preferable for minimizing wet-back. However, improved liquid permeability and minimized wet-back not only depend on the hydrophilic and hydrophobic components of fiber treating agents but also depend on other factors such as chemical structure of the components of agents, ratio between hydrophilic and hydrophobic components and the interaction between those components. In the conventional processes, wet-back has been minimized by modifying the structure of diapers or sanitary napkins, e.g., forming double layer topsheet of two nonwoven variants having different hydrophilic properties or controlling the layout and quantity of fibriform pulp or absorbent polymer, because it has been difficult to attain both of improved liquid permeability and minimized wet-back only with fiber-treating agents.
SUMMARY OF THE INVENTION
The present invention aims to provide a fiber treating agent for minimizing wet-back, which has been attained by modifying the structure of diapers and sanitary napkins, improving the durable hydrophilicity of topsheet and minimizing the time-dependent reduction of the hydrophilicity and to provide fiber and fiber products having excellent properties on their surface.
DETAILED DISCRIPTION OF THE INVENTION
The aim of the present invention can be attained by a fiber treating agent for imparting liquid permeability, which comprises (a) 20 to 60 weight percent of alkyl phosphate salts, (b) 10 to 30 weight percent of a trialkylglycine derivative, (c) 5 to 20 weight percent of a polyoxyalkylene-modified silicone and (d) 10 to 35 weight percent of an ester consisting of dicarboxylic acid and alkoxylated ricinolein and/or hydrogenated product thereof, in which at least one of hydroxyl groups is esterified with saturated and/or unsaturated monocarboxylic acid.
The preferable alkyl phosphate salts for the present invention are those having C
6-18
alkyl groups, more preferably those having C
8-14
alkyl groups. Phosphates of which alkyl groups have more than 18 carbon atoms reduce hydrophilicity of fiber applied with resultant fiber-treating agent and those of which alkyl groups have less than 6 carbon atoms decrease lubricity of fiber applied with resultant fiber-treating agent. Applicable bases for forming the said phosphates are alkali metals and amines, and alkali metals are preferable. The preferable ratio of the said alkyl phosphate salts in the fiber-treating agent of the present invention is 20 to 60 weight percent, more preferably 25 to 55 weight percent. The ratio greater than 60 weight percent will reduce the durable hydrophilicity of the resultant nonwoven fabric while the ratio less than 20 weight percent will give adverse effect to the processability of the resultant fiber in carding.
A polyoxyalkylene alkyl phosphate salt, which is a polyoxyalkylene adduct of the said alkyl phosphate salts, can be blended to the said alkyl phosphate salts for supplementing the hydrophilicity of the resultant fiber. The preferable ratio of such polyoxyalkylene alkyl phosphate salt is 10 to 30 weight percent of the said alkyl phosphate salts.
The said trialkylglycine derivative contains so-called betaine structure, i.e., the internal salt consisting of a carboxyl group and a quaternary ammonium of a nitrogen atom in a glycine molecule to which three alkyl groups are bonded. The alkyl groups can be selected among those having 1 to 22 carbon atoms. The examples of the said trialkylglycine derivatives are dimethyldodecylglycine hydroxide, dimethyltetradecylglycine hydroxide, dimethyloctadecylglycine hydroxide, heptadecylimidazoliumhydroxyethylglycine hydroxide and &bgr;-hydroxyoctadecyldimethylglycine hydroxide. Among those mentioned above, the glycine derivatives of which three alkyl groups consist of two lower alkyl groups such as methyl and ethyl groups and one long-chain alkyl group having 12 or more carbon atoms are preferable. And most preferable are dimethyloctadecylglycine hydroxide and heptadecylimidazoliumhydroxyethylglycine hydroxide. The preferable ratio of the said trialkylglycine derivatives is 10 to 30 weight percent. The ratio lower than 10 weight percent cannot attain satisfactory durable hydrophilicity of resultant nonwoven topsheet and the ratio higher than 30 weight percent will result in increased wet-back and reduced dry touch of topsheet though higher ratio contributes to more durable hydrophilicity of topsheet.
The preferable polyoxylalkylene-modified silicones are those described in the general formula shown below:
wherein Me is a methyl group, R is a methylene, propylene, N-(aminoethyl) methylimino or N-(aminopropyl) propylimino, X is a polyoxyalkylene group, and n and m are the figures selected among those with which the ratio of s
Kita Setuo
Komeda Haruhiko
Nakamura Yoshishige
Einsmann Margaret
Matsumoto Yushi-Seiyaku Co. Ltd.
Sherman & Shalloway
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