Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-08-31
2001-05-22
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S555000, C526S303100, C526S303100, C526S201000
Reexamination Certificate
active
06235828
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel method of producing an acrylic amide-based polymer dispersion. More particularly, it relates to a novel method of producing an aqueous dispersion of a water-soluble acrylic amide-based polymer, which is in wide use as flocculants or dehydrating agents for waste water treatment, additives or agents for use in paper manufacturing, dispersion stabilizers for suspensions, soil conditioners and so on.
PRIOR ART
An acrylic amide-based polymer dispersion has so far been manufactured by dispersing a water-soluble polyacrylamide in aqueous inorganic salt solution (e.g. JP-A 2-99574) or by polymerization, mostly in aqueous solution, of an acrylic amide monomer. In the process comprising polymerization in aqueous solution, increase in monomer concentration will result in formation of a gel-like matter due to water absorption by the polymer, making it very difficult to handle the polymer in the step of dissolution, for instance. Therefore, the polymer is diluted and supplied In the form of low-concentration solution, which is fluid, or it is used in the pulverized form obtained by drying. However, handling them at low concentrations uneconomically involves increased transporting expenses, while to obtain the pulverized form by drying requires an enormous quantity of heat energy for drying and, in addition, may produce such a problem as thermal three-dimensional crosslinking upon heating, which leads to insolubilization of the polymer.
A method is also known for producing an acrylic amide-based polymer which comprises water-in-oil type emulsion polymerization, or suspension polymerization in a hydrophobic solvent (e.g. JP-A 5-194613). However, the resulting organic solvent-containing product needs a device and measure in relation to the use of an inflammable solvent. Furthermore, from the production viewpoint as well, the inflammability and strong odors, among others, of organic solvents involve a huge cost in an equipment such as the polymerization apparatus so as to cope with possible working environment problems.
The organic solvent-free production process which comprises precipitation polymerization in an aqueous salt solution is worthy of attention and involves a low cost of equipment. However, such mode of polymerization has a drawback in that the resulting polymer particles tend to aggregate into large lumps, which are very difficult to handle.
Another method of precipitation polymerization is further known which comprises carrying out the polymerization in an aqueous salt solution, which contains a small amount of a polyhydric alcohol such as glycerol or a polyelectrolyte, such as sodium polyacrylate, added as a protective colloid (e.g. JP-B 4-39481 and JP-B 6-72170). This method can indeed prevent mutual adhesion of precipitated polymer particles to a certain extent but the concentration of the raw material water-soluble monomer or monomers has to be reduced. It is further necessary to hold down the degree of anionization or cationization in terms of the solubility in the aqueous salt solution.
SUMMARY OF THE INVENTION
In view of the current situation mentioned above, the object of the present invention is to provide a method of producing a highly concentrated aqueous dispersion of acrylic amide-based polymer which is inexpensive, good in fluidity and easy to handle.
As a result of their intensive investigations in an attempt to solve the above problems, the present inventors has accomplished the invention by finding that a highly concentrated aqueous dispersion of acrylic amide-based polymer which is inexpensive, good in fluidity and easy to handle can be produced when a water-soluble monomer composition containing an acrylic amide monomer is subjected to polymerization in an aqueous solution of an inorganic salt in the presence of a polymer comprising a vinylpyrrolidone as an essential component. Thus, the present invention relates to a method of producing an acrylic amide-based polymer dispersion which comprises polymerizing a water-soluble monomer composition containing an acrylic amide monomer in an aqueous solution of an inorganic salt in the presence of a homopolymer of vinylpyrrolidone and/or a copolymer of vinylpyrrolidone and other monomer(s), while allowing precipitation of fine polymer particles.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention is described in detail.
As the water-soluble monomer composition containing an acrylic amide monomer, which is used in the present invention, there may be mentioned, among others, acrylamide, methacrylamide (hereinafter, these two compounds are collectively referred to as (meth)acrylamide for short), a mixture of (meth)acrylamide and an anionic monomer copolymerizable therewith, and a mixture of (meth)acrylamide and an cationic monomer copolymerizable therewith.
Said anionic monomer includes, among others, alkali metal salts, alkaline earth metal salts and ammonium salts of (meth)acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, fumaric acid, crotonic acid, maleic acid and styrenesulfonic acid, and mixtures thereof. Among these, alkali metal salts of (meth)acrylic acid and alkaline earth metal salts of (meth)acrylic acid are preferred.
As said alkali metal salts of (meth)acrylic acid and alkaline earth metal salts of (meth)acrylic acid, there may be mentioned, for example, lithium (meth)acrylate, sodium (meth)acrylate, potassium (meth)acrylate, magnesium (meth)acrylate, calcium (meth)acrylate, etc. Among these, sodium acrylate is readily available and economical, hence most preferred.
The cationic monomer mentioned above includes, among others, (meth)acrylamidoethyltrimethylammonium chloride, (meth)acrylamidopropyltrimethylammonium chloride and the like.
In cases where a mixture of (meth)acrylamide and an anionic monomer or a cationic monomer is used as the water-soluble monomer composition containing an acrylic amide monomer, the content of the anionic monomer or cationic monomer is preferably not more than 40 mole percent based on the whole amount of said water-soluble monomer composition containing an acrylic amide monomer. A content exceeding 40 mole percent is unfavorable since the polymer formed is dissolved in the aqueous inorganic salt solution.
Said water-soluble monomer composition containing an acrylic amide monomer, preferably accounts for 1 to 70% by weight based on the sum total of the inorganic salt, the homopolymer of vinyl pyrrolidone and/or the copolymer of vinylpyrrolidone and other monomer(s), and the water-soluble monomer composition containing an acrylic amide monomer, which are to be used in the production method of the present invention. A proportion below 1% by weight will be economically disadvantageous and, at a proportion exceeding 70% by weight, the viscosity will increase within the system, making operation difficult.
The inorganic salt to be used in the present invention includes ammonium salts of inorganic acid such as ammonium sulfate, ammonium nitrate, ammonium hydrogen sulfate, diammonium hydrogen phosphate, etc.; alkali metal salts and alkaline earth metal salts of inorganic acid such as potassium sulfate, sodium sulfate, magnesium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride, calcium chloride, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, and aluminum sulfate, aluminum chloride and the like.
These can be used alone or in the form of an adequate mixture. Ammonium salts of inorganic acid and sodium salts of inorganic acid are preferred among others, and ammonium sulfate and sodium sulfate are more preferred. Other salts than these, if aqueous solutions thereof do not dissolve the product polymer, also fall within the scope of the present invention.
The concentration of said aqueous inorganic salt solution is not particularly restricted but it is preferred that a state of saturation be always kept even during the polymerization reaction so that the resulting polymer can precipitate with ease.
The homopolymer of vinylpyrrolidone and/or copolymer of vinylp
Fujikake Masato
Fujimoto Nobutaka
Hamamoto Shigeki
Kondo Kimihiko
Nakamura Morio
Connolly Bove & Lodge & Hutz LLP
Egwim Kelechi C.
Sumitomo Seika Chemicals Co. Ltd.
Wu David W.
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