Compositions – Humidostatic – water removive – bindive – or emissive
Patent
1994-08-23
1998-07-07
Gibson, Sharon
Compositions
Humidostatic, water removive, bindive, or emissive
210609, 210734, 210735, 525 78, 525293, 525296, 525299, 5253293, 5253294, G02F 1114
Patent
active
057763623
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP93/00904 filed Jun. 30, 1993.
TECHNICAL FIELD
The present invention relates to a sludge dehydrating agent comprising amphoteric polymers, and more particularly to a sludge dehydrating agent comprising amphoteric polymers, which is excellent in storage stability undergoing little deterioration with time.
BACKGROUND ART
Previously dehydrating agents comprising cationic polymers have been known as sludge dehydrating agents. However, conventional dehydrating agents are becoming unsatisfactory in performance because of the recent worsening and diversification in sludge properties and, therefore, an improvement in the performance thereof has been sought. In this connection, sludge dehydrating agents having strong aggregation force and comprising amphoteric polymers have been proposed which are superior in recovery of suspended substances, water content of cake and release of cake from filter cloth. However, conventional sludge dehydrating agents comprising amphoteric polymers had a disadvantage that they undergo deterioration during storage and become water-insoluble while being used. In order to solve this problem, JP-A-3-293100 proposed a sludge dehydrating agent having an improved storage stability by further adding a specific cationic monomer onto an amphoteric polymer comprising a specific cationic monomer, an anionic monomer and a nonionic monomer. With this improved agent, however, the shelf life is not long enough and hence cannot be distributed securely in the market.
The object of the present invention is to provide a sludge dehydrating agent which is excellent in storage stability without becoming water-insoluble during storage by the improvement of conventional sludge dehydrating agents comprising amphoteric polymers.
DISCLOSURE OF INVENTION
In order to attain the object described above, the present invention uses a sludge dehydrating agent comprising a copolymer composed of cationic vinyl monomer units, vinylic carboxylic acid monomer units and nonionic vinyl monomer units and a salt of a group IIA metal of the periodic table.
In the sludge dehydrating agent of the invention it is preferable to use as the cationic vinyl monomer the following compound expressed by the general formula (1), ##STR1## wherein R.sub.1 denotes a hydrogen atom or a methyl group, group, --CH--(OH)--CH.sub.2, or a methyl sulfate group.
Preferable examples of the vinylic carboxylic acid monomer include acrylic acid, methacrylic acid or crotonic acid, while those of the nonionic vinyl monomer include acrylamide or methacrylamide. The metal salts used may be those of mineral acid or organic carboxylic acids, and preferable mineral acid salts include calcium chloride, magnesium chloride or magnesium sulfate.
In the sludge dehydrating agent described above the amount of the cationic vinyl monomer is preferably in the range from 10 to 60 mole %, while the amount of the vinylic carboxylic acid monomer is preferably in the range from 10 to 45 mole %. The molar ratio of the cationic vinyl monomer to the vinylic carboxylic acid monomer is preferably in the range from 0.3 to 3.0, and the content of the salt of a group IIA metal based on the molar ratio to the vinylic carboxylic acid monomer may be preferably in the range from 0.2 to 2.0. Further, an inorganic coagulant can be added to the sludge dehydrating agent of the invention.
THE BEST MODE FOR CARRYING OUT THE INVENTION
The sludge dehydrating agent of the invention is characterized in that a sludge dehydrating agent which comprises a copolymer having cationic vinyl monomer units, vinylic carboxylic acid monomer units and nonionic vinyl monomer units, which will be hereafter designated "Copolymer A", is added with a salt of a group IIA metal of the periodic table.
First, the compounds used in the sludge dehydrating agent of the invention will be explained.
Typical examples of the cationic vinyl monomer are (meth)acryloyloxy(hydroxy)alkyl quaternary or tertiary ammonium salts and (meth)acrylamide(hydroxy)alkyl quaternary or tertiary ammo
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Kawaguchi Shinobu
Ohshimizu Hisao
Sato Shigeru
Fee Valerie
Gibson Sharon
Kurita Water Industries Ltd.
Sanyo Chemical Industries Ltd.
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