Mitsubishi Petrochemical Company Limited

Mitsubishi Chemical Corporation

Kenji Yoshinaga

Kiichi Itoh

Toshiko Nakamura

Shuhei Yada

Takeshi Shibano

Hirochika Hosaka

Kiichi Ito

Miho Tanaka

Shozo Kitagawa

There is provided a highly water-absorptive polymer composition comprising:

Highly water-absorptive polymers having enhanced gel strength

A process for producing a highly water absorptive polymer by polymerizing a water-soluble, ethylenically unsaturated monomer in a water-in-oil type of dispersion consisting of the dispersion phase of an aqueous monomer solution comprising the water-soluble, ethylenically unsaturated monomer, water, a water-soluble polymerization initiator and an optional water-soluble crosslinking agent and the continuous phase of an organic solvent containing a dispersant, characterized in that the aqueous monomer solution is added to the organic solvent at such a temperature as to form an oil-in-water type of dispersion, and the oil-in-water type of dispersion is then heated at least to a phase reversal temperature at which it is transformed into the water-in-oil type of dispersion.

Process for the production of highly water absorptive polymers

There is provided a process for producing a substantially water-insoluble, highly water-absorptive polymer which comprises subjecting an aqueous solution of a monomer comprising as a main component acrylic acid and/or its alkali metal salt to polymerization in the presence of a hypophosphorous acid compound.

Process for producing highly water-absortive polymers

A highly water-absorptive powdery polymer composition comprising a mixture of a highly water-absorptive powdery polymer and a porous powder of a high-purity silicon dioxide, said powder having (a) a mean particle size of 0.1 to 30 .mu.m as measured by the Coulter counter method and (b) a specific surface area of 500 m.sup.2 /g or more as measured by the BET (Brunauer-Emmett-Teller) method.

Highly water-absorptive powdery polymer composition

There is provided a process for producing a highly water absorptive polymer, which comprises making up a mixture (A) comprising an aqueous solution of (a) a partially neutralized product of acrylic acid with 20% or more of carboxylic groups being neutralized to an alkali metal salt or ammonium salt, (b) a crosslinking agent having two or more copolymerizable vinyl groups in one molecule, (c) a basic vinyl monomer in a quantity of 20 mol % or less based on said partially neutralized product of acrylic acid, (d) a nonionic surfactant with HLB of 7 or more and (e) an oxidative radical polymerization initiator, said mixture (A) being maintained at a temperature of 50.degree. C. or lower, and a mixture (B) comprising an amine or a reducing agent dissolved in water or in said mixture (A) from which at least the component (e) is removed, and mixing both the mixtures to cause polymerization.

Process for producing highly water absorptive polymer

A process for the preparation of water absorptive resins which comprises supplying a solution containing at least 20% by weight of a water soluble ethylenically unsaturated monomer as a main component to a polymerization vessel accommodating a vapor phase comprising steam or a mixture of steam with at least one gas substantially inert with respect to polymerization, and polymerizing the monomer in the vapor phase under the relative humidity conditions in the vapor phase of 30% or more.

Growing community of inventors

Yokkaichi, Japan

Kenji Yoshinaga