Mitsubishi Rayon Company, Limited

Nitto Chemical Industry Co., Ltd.

Diafloc Co., Ltd.

Nitto Kagaku Kogyo Kabushiki Kaisha

Nitto Kagaku Kabushiki Kaisha

Jun Hosoda

Ryoji Handa

Norimasa Yoshida

Akihisa Furuno

Nobuo Kurashige

Yasuo Ogawa

Kenzo Ariyama

Takeshi Narita

Shoichi Kanda

Iwao Ohshima

Susumu Seki

Zengiro Kawamura

Osamu Okushima

Apparatus for stirring hydrogel particles of a water-soluble polymer made as a tank defined by a drum within which is housed an inner drum. Water-soluble polymers are introduced through a top opening in the tank into an annular space defined by the inner wall surfaces of the tank and the outer wall surfaces of the inner drum. The water-soluble polymer contents in the annular space are stirred by vanes mounted on a corresponding vertically disposed driven arms. The vanes have leading surfaces advanced in different circular paths within the annular space. One of the vane stirring arms and vane thereon is disposed to travel along a circular path in the vicinity of the inner surfaces of the tank and the other stirring arm vane and corresponding vane are advanced along a circular path in the vicinity of the outer wall surfaces of the inner drum. The leading surfaces of the vanes are disposed at an angle relative to a corresponding radial plane passing the annular space within which the water-soluble polymer contents are stirred. The vanes urge the contents inwardly of the space away from the inner wall surfaces of the tank and outer wall surfaces of the inner drum respectively. The leading surfaces can be disposed to effectively urge the contents being stirred upwardly away from the bottom by an upward component of the force applied upon advancement of the vanes.

Apparatus for stirring hydrogel particles of water-soluble polymer

A method of stabilizing an aqueous solution of xanthan gum is described, comprising incorporating at least one stabilizing agent selected from the group consisting of 2-mercaptobenzimidazole and derivatives thereof in an aqueous solution of xanthan gum.

Stabilization of xanthan gum in aqueous solution

Polyacrylamide in the form of aquagel is partially hydrolyzed in such a manner that small pieces of the aquagel are mixed with an alkali agent in a specified quantity and maintained at a temperature of 50.degree. to 95.degree. C. until the hydrolysis reaches substantial completion. The quantity of the alkali agent is that corresponding to 1/1.1 to 1/3 of the hydrolysis percentage desired of the final partially hydrolyzed polyacrylamide. The partially hydrolyzed polyacrylamide thus produced is characterized by uniform hydrolysis evidenced by its improved solubility in water and a pH around 7 of its aqueous solution. The term 'aquagel' is herein used interchangeably with a term 'hydrogel'.

Process for producing partially hydrolyzed acrylamide polymer

Acrylamide polymers having remarkably high molecular weights can be obtained by polymerizing acrylamide or a monomer mixture comprising a preponderant quantity of acrylamide in an aqueous medium with the use of a specific redox initiator and a specific azo compound initiator. The polymerization initiator used in this porcess comprises a combination of a persulfate, formaldehyde sodium sufoxylate and 2,2'-azobis-2-amidinopropane.

Process for preparing acrylamide polymers

When an alkaline substance is added to and mixed with aggregates of the mutually adhering blobs of a hydrogel of an acrylamide polymer, (1) a mixing tank in which the portion to be contacted with the hydrogel of an acrylamide polymer is made of a chromium-plated material is used, and (2) to said hydrogel aggregates is added at least one compound represented by the general formulae: ##STR1## wherein R.sub.1 is a residue obtained by removing two OH groups from a saturated dihydric alcohol having 2 to 4 carbon atoms, and R.sub.2 is a residue obtained by removing three OH groups from a saturated trihydric alcohol having 3 to 6 carbon atoms, and having an average molecular weight of 500 to 5,000, whereby the hydrolysis of the acrylamide polymer can be achieved at a high efficiency while preventing the mutual adhesion of the hydrogel aggregates and also reducing the adhesion of the aggregates to the interior surface of the mixing tank to such an extent that there is substantially no problem of adhesion.

Modification of acrylamide polymers

In the production of a dried acrylamide polymer by polymerizing, in an aqueous medium, acrylamide alone or a monomer mixture comprising 50 mole % or more of acrylamide and at least one monomer copolymerizable therewith with a radical initiator, and then drying the resulting hydrous acrylamide polymer, the allowing of at least one of the following compounds [I], [II] and [III] to be present in the drying step or a step prior thereto enables the dried acrylamide polymer having a high molecular weight and a good dissolvability in water to be obtained:

Method for preparing acrylamide polymers

In the production of a dried acrylamide polymer by polymerizing, in an aqueous medium, acrylamide alone or a monomer mixture comprising 50 mole % or more of acrylamide and at least one monomer copolymerizable therewith with a radical initiator, and then drying the resulting hydrous acrylamide polymer, the allowing of 2-mercaptobenzimidazole to be present in the drying step or a step prior thereto enables the dried acrylamide polymer having a high molecular weight and a good dissolvability in water to be obtained.

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Yokohama, Japan

Jun Hosoda