Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-26
2003-11-25
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S312000, C528S313000, C528S315000, C528S299000, C528S322000, C528S328000, C525S054210, C525S054230, C525S054240, C525S054300, C524S742000, C524S755000, C524S777000, C522S024000, C522S025000, C522S027000, C522S029000
Reexamination Certificate
active
06653399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel and useful water absorbent material, a method for producing the same, and a water absorbent article using the water absorbent material. More particularly, it relates to a water absorbent material for absorption of high concentration salt-containing solutions such as blood and body fluids, including water, a method for producing the same, and a water absorbent article using the water absorbent material.
The water absorbent material of the present invention can be employed in various fields such as for disposable sanitary material products (for example, paper diapers and sanitary products), household articles, sealing materials, humectants in agricultural products for soil conditioning, anti-condensation coating, water-storing materials in agriculture/horticulture, chemical absorbents and also in the fields in transportation of fresh food or seafood.
2. Description of Related Art
As the water absorbent material, a crosslinked polyacrylic acid (salt) has hitherto been used. Since the crosslinked polyacrylic acid (salt) cannot be easily decomposed into a lower-molecular weight compound, there have arisen problems in the disposal of paper diapers and sanitary products that use a large amount of the crosslinked polyacrylic acid (salt) with the increase in the sense of global environmental protection.
Therefore, as a polymer material having both high water absorbency and excellent biodegradability, a polyamino acid resin having the same molecular structure as that of the polyacrylic acid (salt) has attracted interest as a material to replace the polyacrylic acid (salt). As such a material, for example, water absorbent resins such as polyaspartic acid, polyglutamic acid, and polylysine are known. Among these, a polyaspartic acid water absorbent resin has attracted special interest because it can be prepared by a chemical polymerization method.
As the polyaspartic acid water absorbent resin, for example, there are disclosed (1) water absorbent resin obtained by hydrolyzing a partially crosslinked compound using polyaspartic acid polyamine (WO99/37624), (2) water absorbent resin wherein a crosslinking agent is a diepoxy compound such as ethylene glycol glycidyl ether (Polym. Mater. Sci. Eng., 79, 232, 1998), (3) crosslinked polysuccinimide derivative obtained by reacting a reaction product of a polysuccinimide derivative and an isocyanate having an ethylenically unsaturated bond with a compound having two or more ethylenically unsaturated bonds in the presence of a polymerization initiator (Japanese Patent Application, First Publication No. 2000-239330, Macromol. Rapid. Commun. 20, 410, 1999), and (4) resin obtained by hydrolyzing a reaction product of a polyamino acid and polysaccharides (Japanese Patent Application, First Publication No. 2000-290370).
Among those obtained conventionally as described above, (1) the water absorbent resin using polyaspartic acid polyamine, (2) the water absorbent resin obtained by crosslinking using a diepoxy compound, and (3) the crosslinked polysuccinimide derivative obtained by reacting a reaction product of a polysuccinimide derivative and an isocyanate having an ethylenically unsaturated bond with a compound having two or more ethylenically unsaturated bonds in the presence of a polymerization initiator have satisfactory biodegradability but are insufficient in water absorption properties. To obtain sufficient water absorption properties suited for practical use, it was indispensable to increase the molecular weight of polyaspartic acid. With respect to (4) the resin obtained by hydrolyzing a reaction product of a polyamino acid and polysaccharides, high concentration of a crosslinking agent is required to impart the water absorption properties. Therefore, the crosslink density becomes too high to obtain sufficient water absorption properties, and moreover, the biodegradability is not sufficient.
As described above, conventionally, a resin composition, which has both high water absorbency and excellent biodegradability, cannot at present be obtained at a low price without passing through complicated steps.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a water absorbent material having high water absorbency regardless of a acidic anhydropolyamino acid having a low molecular weight, a method for producing the same, and a water absorbent article using the water absorbent material.
The present inventors have intensively researched to achieve the object described above, and thus the present invention has been completed.
The present invention provides a water absorbent material comprising, as a main component, a water absorbent resin which has a structure in which a anhydropolyamino acid having an ethylenically unsaturated double bond is grafted with polysaccharides, wherein at least a portion of the anhydropolyamino acid is hydrolyzed and crosslinked.
The present invention also provides a method for producing a water absorbent material comprising a water absorbent resin as a main component, which comprises reacting a anhydropolyamino acid having an ethylenically unsaturated double bond (A) with polysaccharides (B), crosslinking the reaction product with a crosslinking agent (C), and hydrolyzing at least a portion of constituent components of the anhydropolyamino acid.
The present invention also provides a water absorbent article comprising a liquid permeable sheet, a liquid impermeable sheet, and a water absorber containing a water absorbent material and a fiber material, which is formed between the liquid permeable sheet and the liquid impermeable sheet, wherein the water absorbent material used is a water absorbent material comprising, as a main component, a water absorbent resin which has a structure in which a anhydropolyamino acid having an ethylenically unsaturated double bond is grafted with polysaccharides, wherein at least a portion of the anhydropolyamino acid is hydrolyzed and crosslinked.
According to the present invention, it is made possible to provide a anhydropolyamino acid water absorbent material having high water absorbency and high biodegradability in spite of a low molecular weight. The water absorbent material obtained by the present invention can be employed in various fields such as for disposable sanitary material products (for example, paper diapers and sanitary products), household articles, sealing materials, humectants in agricultural products for soil conditioning, anti-condensation coating, water-storing materials in agriculture/horticulture, chemical absorbents and also in the fields in transportation of fresh food or seafood.
DETAILED DESCRIPTION OF THE INVENTION
The water absorbent material, the method for producing the same, and the water absorbent article using the same will now be described in detail.
First, the water absorbent material comprising, as a main component, a water absorbent resin which has a structure in which a anhydropolyamino acid having an ethylenically unsaturated double bond is grafted with polysaccharides, wherein at least a portion of the anhydropolyamino acid is hydrolyzed and crosslinked, will be described.
The water absorbent resin used in the water absorbent material of the present invention is obtained by graft bonding of the ethylenically unsaturated double bond of the anhydropolyamino acid having an ethylenically unsaturated double bond (A) with the polysaccharides (B), substantially crosslinking the resulting graft compounds with a crosslinking agent (C) and hydrolyzing at least a portion of the anhydropolyamino acid.
As the anhydropolyamino acid having an ethylenically unsaturated double bond (A), for example, those prepared by reacting a anhydropolyamino acid (D) with a compound (E) which has an ethylenically unsaturated double bond and a functional group having a reactivity with the anhydropolyamino acid (D) (hereinafter referred to as a double bond-containing compound (E)) and imide polysuccinate having a maleimide terminal group as a terminal group can be u
Hasegawa Yoshiki
Ideguchi Shigeki
Tanaka Hisakazu
Acquah Samuel A.
Armstrong Westerman & Hattori, LLP
Dainippon Ink and Chemicals Inc.
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