Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1987-03-23
1989-01-17
Page, Thurman K.
Coating processes
With post-treatment of coating or coating material
Heating or drying
427391, 427392, B05D 302
Patent
active
047987448
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the fixation of polymers retaining liquids inside a support with an open porous structure, as well as to the complex obtained by this process.
Polymers retaining liquids are insoluble hydrophilic macromolecules capable of forming a gel in the presence of a liquid. They are called improved retention additives (abbreviated as IRA), hydrogels, hydroretainers and superabsorbents. The best known products are alginates, for example those sold under the trade name CECALGUM, cross-linked carboxymethylcellulose (trade name AKUCELL of ENKA-AKZO), grafted starches (trade name SANWET of SANYO CHEMICAL), synthetic derivatives of the acrylamide type (trade name AQUASORB of FLOERGER) or acrylate type (trade names AQUAUKEEP of SEITETSU, AQUALIC of NIPPON SHOKUBAI or ARASORB of ARAKAWA).
Numerous processes exist for fixing powder on or in a support. The powder can be bonded to the support by passing steam, as described in patent FR No. 2,066,324. A deposit of polymer can also be fixed by spraying latex (patent FR No. 2,402,474), or else held in a tangle of fibres (patent FR No. 2,446,357).
The polymer can be deposited on fibres by oiling (patent FR No. 2,283,255), on non-woven material (patent EP No. 72569) or in a foam.
The polymer can be formed directly on the support (patent EP No. 123,500. Polymerization is effected by electron-bombardment of the monomers deposited on the support. It is obtained in a very short time, limiting the formation of long macromolecular chains. According to the patent cited above, the polymer obtained after electron-bombardment of monomers has a salt-water absporption capacity of about 10 ml/g. For this reason, the complex obtained, to be very absorbent, must contain a large quantity of this polymer, between 3 and 12 times its own weight.
In the same field, patent application JP No. 5,884,804 describes a method for the polymerization of a mixture of monomers impregnated in a porous support. However, the polymerization time is long, limiting production capacity. In addition, the polymerization reaction is carried out at a high temperature, making it necessary to select supports stable at these temperatures.
According to another method described in patent GB No. 2,084,487, particles of a superabsorbent polymer are immobilized on a porous support by suspending the particles of the polymer, initially in a dry state, in an organic solvent, and then applying the suspension in the form of a liquid film to the support and, finally, removing the solvent by drying. In U.S. Pat. No. 4,235,237, the polymer particles are swollen and suspended in water and then applied to the support.
The object of the invention is to provide a new, simple to use method for the deposition of superabsorbent polymers onto a support, yielding a complex with improved properties.
The polymers covered by the invention are polymers obtained by a water-in-oil process. It relates to a reverse emulsion or suspension process in reversible phase. In processes of this type, the aqueous phase contains the monomers and is dispersed in a continuous oil phase, that is, a solvent not miscible with water, by means of one or several surfactants generally of more lipophilic than hydrophilic character. Surfactants of non-ionic character, like sorbitan esters, are used preferentially.
According to the reverse emulsion process, the polymerization initiator is generally a peroxide soluble in the solvent, as described in patent DE No. 1,089,173.
According to the suspension processes in reversible phase, the polymerization initiator, which is generally a persulfate, is contained in the aqueous phase. This is described, for example, in patent EP No. 36,463 for the manufacture of superabsorbent products known under the trade name AQUAKEEP or in patent DE No. 3,331,644 for the manufacture of a superabsorbent product sold under the trade name of KAO SOAP.
After the reaction, the polymer obtained is found to be dispersed in the solvent in the continuous phase. The solvent is generally a cyclic or cyclic saturated hy
REFERENCES:
patent: 4059552 (1977-11-01), Zweigle et al.
patent: 4235237 (1980-11-01), Mesek et al.
Goldstein Guy
Pierre Michel
Beghin-Say S.A.
Breiner A. W.
Page Thurman K.
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