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
2002-01-29
2003-12-09
Wu, David W. (Department: 1713)
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...
C524S556000, C524S558000, C524S560000, C524S589000, C524S005000, C106S638000, C106S727000, C106S719000, C106S703000, C106S706000
Reexamination Certificate
active
06660799
ABSTRACT:
The present invention relates to the technical field of mortars, concretes, and other compositions based on cement and/or plaster, i.e. generally hydraulic binders and compounds, and in particular to agents capable of modifying their rheological characteristics, in particular workability.
Workability can be defined as being the property of a mortar or cement slip or slag, or more generally of a hydraulic binder of remaining workable during as long a time as possible, i.e. of being capable of being displaced from one container to another, of being stored, of being pumped with ease or with relative ease, and of being transported to a site on which it is to be used, and of having analogous characteristics, and therefore of being usable for a prolonged period. That property can be evaluated by means of the fluidity time of the hydraulic binder. The essential influence of such agents lies in the fact that the viscosity of the slag or slip remains stable for a prolonged period. The viscosity is stable for a long period, but is not necessarily lower than with other substances.
Such agents should be distinguished from retarding agents whose function is to retard the setting of the hydraulic binder.
For a long time now, the person skilled in the art has being studying additives designed to be used as cement thinners without having any significant effect on the setting delay.
Thus, Patent EP 0 303 747 describes copolymers of (meth)acrylic acid (20% molar to 40% molar) and of hydroxyalkylated (meth)acrylic esters (80% molar to 60% molar) of high molecular weight (minimum of 70,000 g.mole).
Patent EP 0 556 061 describes copolymers of maleic anhydride and of surfactant monomers that are allylated, oxyalkylated, and functionalized by groups of short alkyls (1 to 4 carbons).
It is indicated that a mixture of such copolymers is capable of replacing advantageously the formulations described in Patent EP 0 490 681.
That patent describes an additive designed to improve the workability of cements and mortars and to improve workability time. That additive is constituted by a mixture of three components:
a lignosulfonate salt;
a copolymer of maleic anhydride and of an alkyl oxyalkylene allyl (for respective molar ratios varying in the range 1 to 3, and claimed molecular weights lying in the range 1,000 to 200,000); and
an anionic surfactant.
The person skilled in the art is acquainted with Patent WO 94/05606 which relates to a specific dispersing agent making it possible to reduce the quantity of bubbles in cements. That dispersion agent is a dispersant, water-soluble polymer which can be a polyacrylate grafted with a methoxy-polyethyleneglycol (methoxy-PEG), a copolymer of maleic anhydride functionalized with a methoxy-PEG, or a copolymer of maleic anhydride and of methoxy-PEG allyl.
That document also describes a viscosity-reducing agent function which can be an alkaline agent, an alkaline-earth agent, an amine of low molecular weight, or a urea or thiocyanate salt.
The person skilled in the art is also acquainted with Patent WO 95/09821 which describes a hydraulic cement additive designed to improve rheology, and defined as being derived from acrylic polymers. Such polymers are exclusively imidized acrylates obtained by thermal condensation of primary amines with polyacrylic acids (180° C.—2 hours of reaction) or by catalyzed reaction with dicyclohexylcarbodiimide (70° C.—4 hours of reaction). The substitution ratios claimed vary over the range 10% to 50%.
Similarly, Patent WO 95/16643 describes a thinning additive designed for hydraulic cements. That additive is chosen from terpolymers of alkyl-PEG (meth)acrylate, of (meth)acrylic acid, and of a sulfonated (meth)allyl monomer. Those polymers are obtained by radical polymerization and in aqueous medium.
Patent EP 0 725 043 is extremely general, claiming a large number of molecules obtained by implementing widely differing chemical methods, and no practical teaching can be discerned from that patent.
It would seem that document describes a dispersing agent for cement and mortar that limits shrinkage on drying, thus preventing cracks from appearing. The macromolecule is defined as being a polycarboxylic acid (and its salts) grafted or modified with oligoalkylene glycols and polyalkylene glycols.
The extremely general definition of the polyacids includes the following copolymers: styrene-maleic, allylether-maleic, diisobutylene-maleic, acrylic, and methacrylic.
The oligomers are ethers of low molecular weight that are widely used in paints as coalescence solvents.
The styrene-maleic anhydride and allyl-maleic copolymers are synthesized in the solvent and then the resulting polyanhydride is grafted by means of alcohols.
In the case of acrylics, oxyalkylated monomers are formed with acryloyl chloride, and they are then copolymerized in isopropanol in the presence of (meth)acrylic acid.
Patent EP 0 753 488 is also a patent that claims chemical structures very broadly. Those structures are described as being dispersing agents that are extremely effective in reducing workability problems, even for cements having very low water contents.
The polymers described are all obtained by direct radical polymerization. They are terpolymers of methacrylic or acrylic acid (6% to 60%), of a methacrylate or acrylate of alkoxy (C
1
to C
5
) PEG (polyethylene glycol) (40% to 94%), and of a third monomer (0% to 10%).
The synthesis of each of the molecules is given in detail, and they are compared with molecules that are identical but of different polydispersity.
The person skilled in the art can also make reference to Patent EP 0 271 435 which concerns the synthesis of an additive for a hydraulic binder or compound. The product is defined as being a grafted polymer and is obtained by radically polymerizing an acrylic monomer in a medium constituted only by surfactants (polyethylene glycol: PEG, polypropylene glycol: PPG). The mixture is then diluted with water and then neutralized. No information is given about the grafting yields, but the effectiveness of the products was workability tested.
The products currently on the market correspond to the chemistry of the agents described in Patents EP 0 612 702, EP 0 792 850, EP 0 816 298, U.S. Pat. No. 5,362,829, U.S. Pat. No. 5,633,298 or in U.S. Pat. No.5,668,195. In the same chemistry of polyacrylic or grafted polyacrylate acids including oligoalkyleneglycol and/or polyalcohol chains and polyalkylene glycols, U.S. Pat. No. 5,660,626 describes dispersing agents for reducing the shrinkage of compositions of cements, mortars and concretes, which agents are active at low concentrations.
Unfortunately, all of those agents give workability characteristics that are not entirely satisfactory to the person skilled in the art.
Mention should also be made of French Patent Application No. 9808484 that is unpublished on the priority date of the present application, and that describes the use, with cements, of polycondensates obtained by causing polyethylene glycols and their derivatives to react with isocyanates and alcohols of low molecular weight so as to synthesize polymers that are soluble in water or partially soluble in water, which makes it possible to improve significantly the workability of mortars, concretes, and other compositions based on cement and/or on plaster, and defined as hydraulic binders or compounds. Such workability leads to an increase in the fluidity time of the resulting hydraulic compound, making it possible to use the compound for prolonged periods. The products described consist of polycondensates obtained by causing polyethylene glycols (PEGs) and their derivatives such as, for example, ethylene oxide and propylene oxide copolymers, to react with mono-, di-, or tri-isocyanates and optionally alcohols of low molecular weight.
The general state of the art shows that, outside the above-mentioned unpublished application, all of the new thinners designed to impart workability to cement are water-soluble acrylic or maleic and/or allyl polymers (unlike the prior art in which, as indicated above, lignosulfonates,
Kensicher Yves
Suau Jean-Marc
Coatex S.A.
Sastri Satya B
Wu David W.
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