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
1998-01-20
2000-04-25
Cain, Edward J.
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...
524800, 524804, C08F 216
Patent
active
060545267
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention concerns the manufacture of composite latexes incorporating especially fine particle sizes, but without conventional surfactants, that is, non-polymeric surfactants, these latexes being intended for any application in which effective impregnation and the imparting of a degree of water-repellency are required.
Dispersion fineness is an imperative in such uses, since it determines the capacity of the dispersion to impregnate the substrate. The advantage of a latex whose particle size ranges between 30 nm and 150 nm is generally recognized.
PRIOR ART
The latexes whose use has become standardized in industry, for example those disclosed in German Patent Application No. DE 25 48393, consist of aqueous dispersions derived from the following successive operations:
1) Synthesis, in a solvent medium (mixable with water) of a prepolymer (hereinafter termed polymer A) based on a combination of hydrophobic and hydrophilic monomers carrying carboxylic acid functions; neutralization of the acid functions; and dilution of the polymer A in water.
2) Emulsion-producing polymerization of a mixture of hydrophobic monomers (B monomers) composed of styrene and of (meth)acrylic esters in the medium produced in step 1, above.
However, interference effects produced in these emulsions may occur: among others, water-sensitivity of the emulsion after film formation caused therein by the presence of surfactants, most notably non-polymeric, non-ionic surfactants such as ethoxylated fatty alcohols, or anionic polymeric surfactants, such as sodium oleate or sodium laurylsulfate, as mentioned, for example, in the process disclosed by U.S. Pat. No. 4,868,259 (Goodyear). Furthermore, the law now tends to remove from the marketplace those products which contain volatile organic solvents. Now, implementation of polymerization techniques according to prior art makes it impossible, first, in the polymer A preparation phase, to avoid the use of solvents, which remain in the preparation, and second, to obtain equally fine particle sizes without using very sizable quantities of non-polymeric surfactants.
STATEMENT OF THE INVENTION
The composite latexes according to the invention fulfill these requirements. These latexes, whose average particle diameter is between 30 and 150 nm, are produced by polymerization of a mixture of ethylenically-unsaturate hydrophobic monomers, for example a mixture of styrene and (meth)acrylic esters, into an emulsion in an aqueous solution of a water-soluble or water-dispersible amphiphilic polymer have a number-average molecular weight (Mn) of between 500 and 5,000 and whose acid number is less than 500, a polymer which is itself composed of a combination of ethylenically-unsaturate hydrophobic monomers and ethylenically-unsaturate hydrophilic monomers incorporating carboxylic acid functions, said aqueous water-soluble amphiphilic polymer solution being free of any other surfactant or protective colloid. This polymer, whose molecular weight is very substantially lower than those of the polymers A according to prior art will hereinafter, and for simplicity of language, be termed "the oligomer." Polymerization is carried out in the presence of a radical-producing initiator.
Latexes of this type were disclosed in EP-A-675177 (Goodrich). The latexes according to the invention have a mass percent of amphiphilic oligomer in relation to the final dry extract of between 10 and 50%, a level constituting a compromise between the conflicting properties of the oligomers and those of the monomers undergoing polymerization, by virtue of which compromise there is now available a finely-particulate dispersion which is stable over time and whose coalescent films are not overly sensitive to water. Analysis of the latexes obtained according to the invention show that their free oligomer percentage is less than the level that would be expected if this oligomer had functioned solely as a monomer dispersant or as a protective colloid. One portion of this oligomer is quite clearly incorporated in
REFERENCES:
patent: 4868259 (1989-09-01), Burroway et al.
Database WPI, Section Ch, Week 8041, Derwent Publications Ltd., London, GB; Class A13, AN 80-72537C, XP002008042 & JP, A,55 112 215 (Sekisui Plastics KK), Aug. 30, 1980.
Betremieux Isabelle
Feret Bruno
Verge Christophe
Cain Edward J.
Elf Atochem S.A.
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