Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-30
2002-05-21
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S005000, C524S002000, C524S171000, C524S366000, C524S342000
Reexamination Certificate
active
06391952
ABSTRACT:
The present invention relates to water-redispersible powders of film-forming polymers prepared from monomers with ethylenic unsaturation.
Film-forming polymers prepared from monomers with ethylenic unsaturation are frequently used as adjuvants in hydraulic inorganic binder compositions in order to improve the processing thereof and the properties after hardening, such as adhesion to various substrates, leaktightness, flexibility or mechanical properties. They are generally provided in the form of aqueous dispersions (latices).
They can also be provided in the form of powders, it being possible for the said powders to be redispersed in water. Redispersible polymer powders exhibit the advantage, with respect to aqueous dispersions, of being able to be premixed with cement in the form of ready-for-use pulverulent compositions which can be used, for example, for the manufacture of mortars and concretes intended to be applied to construction materials, for the manufacture of bonding mortars or for the production of protective or decorative coatings inside or outside buildings.
These redispersible powders are obtained by spraying and drying dispersions of film-forming polymers, generally acrylic polymers. In order to obtain readily redispersible polymer powders, provision has been made to add to the dispersions, before spraying, melamine-formaldehyde-sulphonate (U.S. Pat. No. 4,784,648) or naphthalene-formaldehyde-sulphonate (DE-A-3,143,070) condensation products and/or vinylpyrrolidone-vinyl acetate copolymers (EP-78,449).
These additives have the disadvantage of being complicated to synthesize, due to the synthesis of a first product and then to its condensation with another.
The aim of the present invention is to provide a novel pulverulent composition which is completely or virtually completely redispersible in water and which is based on a film-forming polymer prepared from monomers with ethylenic unsaturation.
Another aim of the present invention is to provide a process for the preparation of the powders of above type from film-forming polymer latices.
Another aim of the present invention is to provide a redispersible powder of the above type which, in the powder form or after optional redispersion in water in the form of a reconstituted latex, can be used in all the fields of application of latices for producing coatings (in particular paints or composition for the coating of paper) or adhesive compositions (in particular pressure-sensitive adhesives or tiling adhesives).
Another aim of the present invention is to provide a redispersible powder of the above type (or the reconstituted latex resulting therefrom) with a view more particularly to its use as additives in formulations with a hydraulic binder (cement or plaster) of the grout, mortar or concrete type, in order to improve the properties thereof: adhesion to various supports, impact and abrasion strengths, flexural and compressive strengths, or flexibility.
These aims and others are achieved by the present invention, which relates to a water-redispersible pulverulent composition comprising:
at least one water-insoluble film-forming polymer, the said polymer (a) being prepared from at least one monomer with ethylenic unsaturation, and
at least one naphthalenesulphonate (b) of general formula (I):
in which:
X and X′, which are identical or different, represent OH or NH
2
,
Y represents SO
3
−
M
+
, with M alkali metal,
x≧0, x′≧0 and x+x′≧1,
y≧0, y′≧0 and y+y′≧1.
The invention also relates to a process for the preparation of such a redispersible pulverulent composition, in which process the water is removed from an aqueous dispersion of the water-insoluble film-forming polymer (a) prepared by emulsion polymerization and comprising appropriate amounts of naphthalenesulphonate (b) of formula (I) and optionally of polyphenol (c), of ethoxylated surface-active agent (d) and of inorganic filler (e).
The invention therefore first of all relates to a water-redispersible pulverulent composition comprising:
at least one water-insoluble film-forming polymer, the said polymer (a) being prepared from at least one monomer with ethylenic unsaturation, and
at least one naphthalenesulphonate (b) of general formula (I):
in which:
X and X′, which are identical or different, represent OH or NH
2
,
Y represents SO
3
−
M
+
, with M alkali metal,
x≧0, x′≧0 and x+x′≧1,
y≧0, y′≧0 and y+y′≧1.
In the composition according to the invention, the water-insoluble film-forming polymer (a) is prepared from monomers with ethylenic unsaturation.
The glass transition temperature (Tg) of the film-forming polymer (a) can be between approximately −20° C. and +50° C., preferably between −10° C. and +40° C. This polymer can be prepared in a way known per se by emulsion polymerization of monomers with ethylenic unsaturation using polymerization initiators in the presence of conventional emulsifying and/or dispersing agents. The content of polymer in the emulsion is generally between 30 and 70% by weight, more specifically between 35 and 65% by weight.
Mention may be made, as monomers of use in the synthesis of the film-forming polymer (a), of:
vinyl esters and more particularly vinyl acetate;
acrylic esters, such as alkyl acrylates and methacrylates, the alkyl group of which comprises from 1 to 10 carbon atoms, for example methyl, ethyl, n-butyl or 2-ethylhexyl acrylates and methacrylates;
vinylaromatic monomers, in particular styrene.
These monomers can be copolymerized with one another or with other monomers with ethylenic unsaturation.
Mention may be made, as non-limiting examples of monomers copolymerizable with vinyl acetate and/or acrylic esters and/or styrene, of ethylene and olefins such as isobutene; vinyl esters of branched or unbranched saturated monocarboxylic acids having from 1 to 12 carbon atoms, such as vinyl propionate, vinyl “Versatate” (registered trade name for branched C
9
-C
11
acid esters), vinyl pivalate or vinyl laurate; esters of unsaturated mono- or dicarboxylic acids having 3 to 6 carbon atoms with alkanols having 1 to 10 carbon atoms, such as methyl, ethyl, butyl or ethylhexyl maleates or fumarates; vinylaromatic monomers, such as methylstyrene or vinyltoluene; vinyl halides, such as vinyl chloride or vinylidene chloride; or diolefins, particularly butadiene.
It is also possible to add, to the monomers defined above, at least one other monomer chosen from the following list: acrylamide, sodium 2-acrylamido-2-methylpropanesulphonate (AMPS) or sodium methallylsulphonate. These monomers are added in an amount of at most 2% by weight with respect to the total weight of the monomers. These monomers are added during the polymerization; they ensure the colloidal stability of the latex.
The water-insoluble film-forming polymer is preferably chosen from:
vinyl or acrylate homopolymers,
vinyl acetate, styrene/butadiene, styrene/acrylate or styrene/butadiene/acrylate copolymers.
The polymerization of the monomers is generally carried out in an emulsion in the presence of an emulsifier and of a polymerization initiator.
The monomers employed can be introduced as a mixture or separately and simultaneously into the reaction mixture, either before the beginning of the polymerization, in a single step, or during the polymerization, in successive fractions or continuously.
Use is generally made, as emulsifying agent, of conventional anionic agents represented in particular by salts of fatty acids, alkali metal alkyl sulphates, alkylsulphonates, alkylaryl sulphates, alkylarylsulphonates, aryl sulphates, arylsulphonates, sulfosuccinates or alkyl phosphates, or hydrogenated or non-hydrogenated salts of abietic acid. They are generally employed in a proportion of 0.01 to 5% by weight with respect to the total weight of the monomers.
The emulsion polymerization initiator is represented more particularly by hyroperoxides, such as hydrogen peroxide, cumene hydroperoxide. diisopropylbenzene hydrop
Bett William
Colombet Jean-Francois
Egwim Kelechi
Rhodia Chimie
Wu David W.
LandOfFree
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