Sumitomo Seika Chemicals Co., Ltd.

Hideki Yokoyama

Hiroki Yabuguchi

Tetsuhiro Hinayama

Atsushi Heguri

Nobuhiro Maeda

Masahiro Murakami

Sachi Kikuno

Yasuhiro Nawata

Maoki Hama

Misaki Taniguchi

Hiromi Miyashita

Disclosed are water-absorbent resin particles comprising a crosslinked polymer comprising a monomer unit derived from a water-soluble ethylenically unsaturated monomer, wherein an artificial menstrual blood volume increase rate as measured in an artificial menstrual blood swelling test conducted in the order of i), ii), and iii) is 70% or more. i) putting 1.0 g of water-absorbent resin particles into a measuring cylinder with an inner diameter of 27 mm. ii) injecting 10 ml of artificial menstrual blood into the cylinder at once to swell the water-absorbent resin particles. iii) measuring a volume (A) of the swollen water-absorbent resin particles after 60 seconds from the injection and calculating an artificial menstrual blood volume increase rate according to Equation (I) below. Artificial menstrual blood volume increase rate (%)=(A&#x2212;B)/B&#xd7;100 . . . (I), A . . . Volume (ml) of swollen water-absorbent resin particles, B . . . Volume (ml) of injected artificial menstrual blood.

Water-absorbent resin particle

Disclosed are water-absorbent resin particles comprising a crosslinked polymer comprising a monomer unit derived from a water-soluble ethylenically unsaturated monomer, wherein an initial swelling force as measured according to a swelling force test conducted by a predetermined method is 8 N or more, and further, a ratio of the particles having a particle diameter of more than 250 &#x3bc;m and 850 &#x3bc;m or less is 70% by mass or more and a ratio of the particles having a particle diameter of 250 &#x3bc;m or less is 20% by mass or less, with respect to the total amount of the water-absorbent resin particles.

Water-absorbent resin particles

Provided is a method of producing a water-absorbent resin comprising a step of polymerizing a water-soluble ethylenically unsaturated monomer in the presence of an internal-crosslinking agent, and a step of performing post-crosslinking, wherein:

Water-absorbent resin and method of producing water-absorbent resin

Provided is: a water-absorbent resin which has a better water absorption performance and with which it is possible to improve absorption performance under a load when used in an absorbent material. This water-absorbent resin, obtained by polymerising a water soluble ethylenically unsaturated monomer in the presence of an internal-crosslinking agent and by post-crosslinking using a post-crosslinking agent, has a water-absorption capacity of physiological saline under a load of 4.14 kPa of 16 mL/g or more, has a mass proportion of particles from 150 to 850 &#x3bc;m relative to the whole proportion of 85 mass % or more, moreover has a mass proportion of particles from 300 to 400 &#x3bc;m relative to the whole proportion of 20 mass % or more, and has an absorption capacity elasticity index represented by formula (I) of 68,000 or more. Absorption capacity elasticity index=storage elastic modulus [Pa]&#xd7;centrifugal retention rate [g/g] . . . (I).

Water-absorbent resin and absorbent article

Provided are: a water-absorbent resin which, when used as an absorbent material, retains a high water-absorption performance, increases the diffusivity of a to-be-absorbed liquid and makes it possible to effectively decrease the amount of re-wet; and an absorbent article formed using an absorbent material including the water-absorbent resin. The water-absorbent resin according to the present invention is a water-absorbent resin obtained by polymerizing a water-soluble ethylenically monomer in the presence of an internal-crosslinking agent and thereafter post-crosslinking the polymer with a post-crosslinking agent, characterized in that when subjected to a liquid flow test, the water-absorbent resin has an effective absorbent material index (K) indicated by equation (I) of 250 or greater.Effective absorbent material index ()=[(the amount of liquid flow) (g)]&#xd7;[(artificial-urine absorption ratio) (g/g)]&#x2003;&#x2003;(I)

The following are provided: a water-absorbent resin in which, in the formation of an absorbent material forming an absorbent article, dispersion is satisfactory even in a moisture absorption state, which prevents the occurrence of troubles at the time of manufacturing of the absorbent article and which allows efficient manufacturing; and an absorbent article using an absorbent material containing the water-absorbent resin. The water-absorbent resin according to the present invention is obtained by polymerizing a water-soluble ethylenically unsaturated monomer and performing post-crosslinking thereon with a post-crosslinking agent, and the water-absorbent resin satisfies the requirements below:

Provided are a water-absorbent resin having better water-absorption performance and being prevented from discoloring before and after storage for a long time under high temperature and high humidity, and an absorbent article including the absorbent resin. The water-absorbent resin according to the present invention is prepared by polymerizing a water-soluble ethylenically unsaturated monomer in the presence of an internal-crosslinking agent and performing post-crosslinking with a post-crosslinking agent, wherein the water-absorbent resin satisfies the following properties: (A) a water-absorption capacity of physiological saline of 55 g/g or more, a water-absorption capacity of physiological saline under a load of 4.14 kPa of 15 mL/g or more, and a residual monomer content of 300 ppm or less; and (B) a yellow index of 5.0 or less and a yellow index change ratio (&#x394;YI) after leaving for 10 days under 70&#xb0; C. and 90% RH of 10 or less.

With respect to water-absorbent resins, there are provided a method of manufacturing a water-absorbent resin having an appropriate BET specific surface and a water-absorption rate and a water-absorbing agent and an absorbent article that are formed by using the water-absorbent resin. In a first aspect of the present invention, when reverse phase suspension polymerization of two steps or more is performed on a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium in the presence of at least an azo compound, a peroxide and an internal-crosslinking agent, the used amount of the internal-crosslinking agent at the time of the polymerization of a first step is adjusted to fall within a range of 0.015 to 0.150 mmol per mole of the water-soluble ethylenically unsaturated monomer used at the time of the polymerization of the first step and he polymerization is performed such that, the BET specific surface area of secondary particles formed by agglomeration of primary particles obtained is controlled.

Method of manufacturing water-absorbent resin, water-absorbent resin, water-absorbing agent and absorbent article

A method for producing a water-absorbent resin comprising at least two stages of reversed-phase suspension polymerization, wherein the first stage of the at least two stages of reversed-phase suspension polymerization comprises the following steps of: (A) performing a primary dispersion by stirring to mix in the absence of surfactants an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a hydrophilic polymeric dispersion agent with a petroleum hydrocarbon dispersion medium in which a hydrophobic polymeric dispersion agent dissolves or disperses; (B) further performing a secondary dispersion by adding a surfactant to the resultant dispersion liquid; and (C) performing a polymerization by using a water-soluble radical polymerization initiator to obtain a water-absorbent resin as particles in a hydrous gel state which disperse in the petroleum hydrocarbon dispersion medium, and a water-absorbent resin obtained by the method.

Method for producing a water-absorbent resin

A method is disclosed for producing a water-absorbent resin by a reversed-phase suspension polymerization method, wherein an odor originating from a raw material component, in particular, a petroleum hydrocarbon dispersion medium, is further reduced as compared with a water-absorbent resin obtained by a conventional method, and a water-absorbent resin obtained by the method. More specifically, a method is disclosed for producing a water-absorbent resin by performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium, comprising adding and dispersing an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a hydrophilic polymeric dispersion agent to a petroleum hydrocarbon dispersion medium in the presence of a surfactant under stirring, and performing a reversed-phase suspension polymerization using a radical polymerization initiator, and a water-absorbent resin obtained by the method.

A purpose of the present invention is to reduce odor of a water-absorbent resin during absorption of water. Such the invention is attained by a process for production of a water-absorbent resin by subjecting a water-soluble ethylenically unsaturated monomer to reversed-phase suspension polymerization. The process comprises the following steps (A) to (C): (A) adding an aqueous solution of water-soluble ethylenically unsaturated monomer to a petroleum hydrocarbon dispersion medium to disperse the aqueous solution in the dispersion medium; (B) adding a surfactant to the emulsion to further disperse the emulsion; and (C) performing the reversed-phase suspension polymerization using a water-soluble radical polymerization initiator, optionally in the presence of an internal-crosslinking agent.

Process for production of water-absorbent resin

A method for producing a water-absorbent resin by performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium, comprising the following steps of: (A) performing a primary dispersion in the absence of surfactants by adding an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a hydrophilic polymeric dispersion agent to a petroleum hydrocarbon dispersion medium in which a hydrophobic polymeric dispersion agent was heat-dispersed or heat-dissolved, under stirring; (B) further performing a secondary dispersion by adding a surfactant to a dispersion liquid obtained after the primary dispersion; and (C) performing the reversed-phase suspension polymerization by using a radical polymerization initiator; and the water-absorbent resin obtained by the method.

A method for producing a water-absorbent resin having a further reduced odor as compared with a water-absorbent resin obtained by a conventional method as well as a water-absorbent resin produced by the same method, by maintaining the addition rate V from the pouring nozzle for the aqueous solution of the water-soluble ethylenically unsaturated monomer in a polymerization reaction tank not more than 0.30 [min], in the first stage polymerization step which is within the step of the conventional method upon performing multi-stages such as two or more stages of reversed-phase suspension polymerizations in a method for producing a water-absorbent resin, and thereby by being able to reduce the amount of the petroleum hydrocarbon dispersion medium remaining in the above water-absorbent resin.

The present invention provides a method for producing a water-absorbent resin by a reversed-phase suspension polymerization method, wherein an odor originating from a raw material component, in particular, a petroleum hydrocarbon dispersion medium, was reduced, and a water-absorbent resin obtained by the method. More specifically, the present invention provides a method for producing a water-absorbent resin comprising performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium by using a surfactant, wherein an aqueous solution of the water-soluble ethylenically unsaturated monomer is dispersed in the dispersion medium at a specific pouring rate to reduce an odor, and a water-absorbent resin obtained by the method, are provided.

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Himeji, Japan

Hideki Yokoyama