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...
Patent
1995-04-12
1996-07-30
Yoon, Tae
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...
524556, 524815, 524817, 524828, 524829, 524831, 523132, 523335, 523340, C08L 3300, C08J 303
Patent
active
055412521
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an at least three step process for increasing the content of the active substance during the production of low viscosity, water soluble polymer dispersions PD with a high content of the active substance, containing at least one polymeric dispersing agent D) and one polymerizate A) comprising a1) at least one water soluble monomer, a2) at least one hydrophobic monomer and optionally a3) at least one amphiphilic monomer.
STATE OF THE ART
Aqueous dispersions of water soluble polymerizates are used as flocculating agents during waste water treatment, as de-watering agents following the separation of the aqueous phase, as retention agents during the production of paper, as soil conditioners or as dispersing agents.
The EP 170 394 describes a fluid, which can be mixed with water and comprises particles, constructed from a high molecular polymer gel, which exhibits particle sizes exceeding 20 .mu.m, in aqueous solution as the continuous phase, which contains an equilibrating agent, which holds the water content of the gel particles in equilibrium with the water content in the continuous phase and thus prevents the gel particles from agglomerating. The sodium salt of polyacrylic acid or polydiallyldimethylammonium chloride (poly-DADMAC) is used as the preferred equilibrating agent.
In the EP 183 466 a process for the preparation of a water soluble polymer dispersion is described. Said process is characterized by the polymerization of a water soluble monomer while stirring in an aqueous solution of at least one salt in the presence of a dispersing agent. In so doing, polyols, polyalkylene ethers, alkali salts of the polyacrylic acid and alkali salts of poly-2-acrylamido-2-methylpropane sulfonic acid are used as the dispersing agents.
The DE-PS 29 44 663 relates to a process for the preparation of an aqueous dispersion from a water soluble polymerizate with good stability and flowability, wherein the water soluble polymerizate contains at least one water soluble ethylenicly unsaturated monomer and wherein as the dispersing agent polyalkylene ether, polyethylene imine and other polymerizates can be present. The aqueous dispersion prepared in such a manner can be used, optionally following dilution with water, as a flocculating agent, thickening agent, soil conditioning agent and for other applications.
In the JP Kokkai 59 108 074 thickening agents are described that comprise polymerizates in aqueous solution, which contain as the monomeric component (meth)acrylic acid and/or their salts, (meth)acrylamides and methylacrylate or ethylacrylate, with polyethylene glycol as the dispersing agent.
The German patent application P 42 16 167.3 describes aqueous dispersions of water soluble polymerizates, formed through polymerization of a mixture comprising water soluble, hydrophobic and optionally amphiphilic monomers in the presence of a polymeric dispersing agent. A two step process for preparing low viscosity dispersions of water soluble polymerizates according to the German patent application P 42 16 167.3 with increased content of the active substance is included from the German patent application P 43 16 200.2.
PROBLEM AND SOLUTION
The aqueous solutions, which are described in the EP 170 394 and contain gel particles, have the drawback that after prolonged residence time, they exhibit extremely raised viscosities, which can be reduced only by using shear gradients, such as intensive stirring. The rheological properties depend on a complex equilibrium between polymerizate, equilibrating agent, water content and particle size of the gel particles.
In the EP 183 466 water soluble polymerizates as dispersions in aqueous salt solutions with the aid of a dispersing agent are claimed. The drawback with these dispersions is the high salt content of the aqueous phase (up to 30% by weight) as compared to a relatively low polymerizate (=active substance) content (up to 20% by weight), which leads to waste water problems in specific applications of such dispersions.
The high co
REFERENCES:
patent: 4021399 (1977-05-01), Hunter et al.
patent: 4052353 (1977-10-01), Scanley
patent: 4435528 (1984-03-01), Domina
patent: 5403883 (1995-04-01), Messner et al.
Braum Manfred
Carl Joachim
Quis Peter
Schliessmann Petra
Schmitt Gunter
Rohm GmbH
Yoon Tae
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