Water absorbent crosslinked polymer and a method of producing the same containing cellulosis fibers
AssigneeHayashikane Shipbuilding & Engineering Co., Ltd.
InventorKazuo Saotome
Life of this patent
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Abstract
A water absorbent crosslinked polymer having at least 70% by weight of acrylic acid monomeric units, 60 to 90% of the carboxyl groups of which are in the form of an alkali metal salt, produced by a method in which a mixture comprised of acrylic acid, 60 to 90% of the carboxyl groups of which are in the form of an alkali metal salt, and a fibrous cellulosic material is heated in the presence of a radical initiator. The polymerization temperature can be effectively controlled by smooth evaporation of water. The cross-linked polymer can absorb such a large amount of water as several hundred times the weight of the polymer in an excellent absorption rate, and finds applications as, for example, a disposable diaper and a sanitary napkin.
Claims12
A water absorbent crosslinked polymer having at least 70% by weight, based on the total weight of said polymer, of acrylic acid monomeric units, 60 to 80% of the carboxyl groups of said acrylic acid monomeric units being in the form of an alkali metal salt, produced by a method comprising the steps of:
- (1) providing an aqueous solution comprising water, at least 30% by weight, based on the total weight of said aqueous solution, of acrylic acid as a monomeric component, 60 to 80% of the carboxyl groups of said acrylic acid being in the form of an alkali metal salt, and a radical initiator;
- (2) mixing the aqueous solution with a fibrous cellulosic material to obtain an aqueous mixture, thereby enabling the water of said mixture to smoothly evaporate at heating so that when said mixture is heated in the following step (3), the maximum temperature of said mixture is controlled as a result of a balance between the heat generation due to the polymerization reaction and the heat radiation by smooth water evaporation due to the fibrous cellulosic material;
- (3) heating the obtained mixture to effect polymerization of said monomeric component, thereby obtaining a reaction product containing a crosslinked polymer together with the fibrous cellulosic material;
- and
- (4) subjecting said reaction product to heat drying, followed by pulverizaton.
A method of producing a water absorbent crosslinked polymer having at least 70% by weight, based on the total weight of said polymer, of acrylic acid monomeric units, 60 to 90% of the carboxyl groups of said acrylic acid monomeric units being in the form of an alkali metal salt, which comprises the steps of:
- (1) providing an aqueous solution comprising water, at least 30% by weight, based on the total weight of said aqueous solution, of acrylic acid as a monomeric component, 60 to 90% of the carboxyl groups of said acrylic acid being in the form of an alkali metal salt, and a radical initiator;
- (2) mixing the aqueous solution with a fibrous cellulosic material to obtain an aqueous mixture, thereby enabling the water of said mixture to smoothly evaporate at heating so that when said mixture is heated in the following step (3), the maximum temperature of said mixture is controlled as a result of a balance between the heat generation due to the polymerization reaction and the heat radiation by smooth water evaporation due to the fibrous cellulosic material;
- (3) heating the obtained mixture to effect polymerization of said monomeric component, thereby obtaining a reaction product containing a crosslinked polymer together with the fibrous cellulosic material;
- and
- (4) subjecting said reaction product to heat drying, followed by pulverization.
Dependencies are inferred from the claim text.