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
2000-08-03
2002-04-09
Seidleck, James J. (Department: 1711)
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...
C524S524000, C524S563000, C523S334000
Reexamination Certificate
active
06369153
ABSTRACT:
The present invention relates to water-redispersible powders of film-forming polymers prepared from ethylenically unsaturated monomers, to a process for preparing them and to their use.
Redispersible powders obtained by spraying and drying dispersions of acrylic film-forming polymers, and especially dispersions of polymers of vinyl esters, are already known.
Film-forming polymers prepared from ethylenically unsaturated monomers are frequently used as adjuvants in inorganic hydraulic binding compositions to improve their use and their properties after hardening, such as adhesion to various substrates, leaktightness, flexibility and mechanical properties.
Redispersible powders have the advantage, compared to aqueous dispersions, that they can be premixed with cement in the form of ready-to-use pulverulent compositions which are usable, for example, for the manufacture of mortars and concretes intended for affixing to building materials, or for the manufacture of adhesive mortars or for the production of protective and decorative coatings for the inside or outside of buildings.
To achieve success in obtaining powders that do not agglomerate during storage through the effect of pressure and temperature and which are satisfactorily redispersible in water, it is customary to add relatively large amounts of inert substances and of protective colloids to them.
Thus, it has already been proposed to add to the dispersions, before spraying, melanine/formaldehyde/sulphonate (U.S. Pat. No. 3,784,648) or naphthalene/formaldehyde/sulphonate (DE-A-3143070) condensation products and/or vinylpyrrolidone/vinyl acetate copolymers (EP-078449).
French Patent FR-A-2,245,723 relates to a stable and water-dispersible preparation dried by freezing, containing a powder of a polymer latex and a water-soluble dispersing agent which is a saccharide.
The object of the present invention is to provide a new pulverulent composition which is completely or almost completely redispersible in water, based on a film-forming polymer prepared from ethylenically unsaturated monomers.
Another object of the present invention is to provide a redispersible powder of the above type which is stable on storage without agglomeration.
Another object of the present invention is to provide a process for preparing the powders of the above type from latices of film-forming polymer.
Another object of the present invention is to provide a redispersible powder of the above type which, in powder form or after redispersion, where appropriate, in water in the form-of a pseudolatex, is usable in all the fields of application of latices to produce coatings (in particular paints, paper coating composition) or adhesive compositions (in particular pressure-sensitive adhesives, tile adhesives).
Another object of the present invention is to provide a redispersible powder of the above type (or the pseudolatex derived therefrom) for the purpose, more especially, of use as additives to hydraulic binders of the mortar or concrete type.
These and other objects are achieved by the present invention which relates, in effect, to a water-redispersible pulverulent composition obtained by mixing and then drying an emulsion of at least one water-insoluble film-forming polymer, at least one main surfactant and at least one water-soluble compound, comprising:
an emulsion of at least one water-insoluble film-forming polymer prepared from ethylenically unsaturated monomers,
at least one main surfactant whose water/surfactant binary phase diagram contains an isotropic phase which is fluid at 25° C. up to a concentration of at least 50% by weight of surfactant, followed by a hexagonal or cubic type rigid liquid crystal phase at higher concentrations which is stable at least up to the drying temperature,
at least one water-soluble compound.
The subject of the invention in, in addition, a process for preparing such a pulverulent composition, consisting in:
removing the water from an aqueous emulsion consisting of a water-insoluble film-forming polymer prepared by aqueous emilsion polymerization and containing at least one main surfactant, at least one water-soluble compound and, where appropriate, at least one additional surfactant or one anti-caking agent,
and spraying the dry residue to a powder of desired particle size.
The composition according to the invention has the advantage of redispersing spontaneously in water, to give an emilsion again having a particle size close to that of the initial emulsion.
Other advantages and features of the invention will become more clearly apparent on reading the description and the examples which follow.
The invention relates, in the first place, to a water-redispersible pulverulent composition obtained by mixing and then drying an emulsion of at least one water-insoluble film-forming polymer, at least one main surfactant and at least one water-soluble compound, comprising:
an emulsion of at least one water-insoluble film-forming polymer prepared from ethylenically unsaturated monomers,
at least one main surfactant whose water/surfactant binary phase diagram contains an isotropic phase which is fluid at 25° C. up to a concentration of at least 50% by weight of surfactant, followed by a hexagonal or cubic type rigid liquid crystal phase at higher concentrations which is stable at least up to the drying temperature,
at least one water-soluble compound.
The water-insoluble film-forming polymers are prepared from ethylenically unsaturated monomers, in particular of the vinyl and/or acrylate type.
The water-insoluble film-forming polymers are preferably vinyl or acrylate homopolymers or vinyl acetate, styrene/butadiene, styrene/acrylate, acrylate and styrene/butadiene/acrylate copolymers.
The film-forming polymers preferably have a glass transition temperature of between approximately −20° C. and +50° C., preferably between 0° C. and 40° C. These polymers may be prepared in a manner known per se, by emulsion polymerization of ethylenically unsaturated monomers using polymerization initiators and in the presence of standard emulsifying and/or dispersing agents. The content of polymer in the emulsion generally lies between 30 and 70% by weight, and more specifically between 35 and 65% by weight.
As monomers, there may be mentioned vinyl esters, and more especially vinyl acetate; alkyl acrylates and methacrylates in which the alkyl group contains from 1 to 10 carbon atoms, for example methyl, ethyl, n-butyl and 2-ethylhexyl acrylates and methacrylates; and vinylaromatic monomers, especially styrene. These monomers may be copolyserized with one another or with other ethylenically unsaturated monomers.
As non-limiting examples of monomers which can be copolymerized with vinyl acetate and/or acrylic esters and/or styrene, there may be mentioned ethylene and olefins such as isobutene; the vinyl esters of saturated, branched or unbranched monocarboxylic acids having from 1 to 12 carbon atoms, such as vinyl propionate, “Versatate” (registered trade mark for the esters of branched C
9
-C
11
acids), pivaloate and laurate; the esters of unsaturated mono- or dicarboxylic acids possessing 3 to 6 carbon atoms with alkanols possessing 1 to 10 carbon atoms, such as methyl, ethyl, butyl and ethylhexyl maleates and fumarates; vinylaromatic monomers such as methylstyrenes and vinyltoluenes; vinyl halides such as vinyl chloride and vinylidene chloride, and diolefins, especially butadiene.
The emulsion polymerization of the monomers is carried out in the presence of an emulsifier and a polymerization initiator.
The monomers employed may be introduced as a mixture or separately and simultaneously into the reaction medium, either all at once before the beginning of the polymerization, or during the polymerization in successive fractions or in continuous fashion.
As emulsifying agent, the traditional anionic agents are generally employed, represented, in particular, by fatty acid salts, alkyl sulphates, alkylsulphonates, alkylaryl sulphates, alkylarylsulphonates, aryl sulphates, arylsulphonates, sulphosuccinates, alkyl phosphates of alkali
Guerin Gilles
Morvan Mikel
Asinovsky Olga
Rhodia Chimie
Seidleck James J.
Shedden John A.
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