Highly efficient cement dispersants

Details Highly efficient cement dispersants Highly efficient cement dispersants

2000-06-12

2001-09-04

Hampton-Hightower, P. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

C528S328000, C528S335000, C525S066000, C525S420000, C525S422000, C106S608000, C106S696000, C106S719000, C106S724000, C106S727000, C106S728000, C106S819000, C106S823000

Reexamination Certificate

active

06284867

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to polymers that function as highly efficient cement dispersants. More particularly, the invention is directed to polycarboxylate polymers comprising a functionalized polyamide main chain polymer onto which are grafted at least some oligomeric or polymeric, hydrophilic side chains, the result being highly efficient cement dispersants.
BACKGROUND
Dispersants are substances that improve the flow characteristics of the cement slurry by breaking up cement agglomerates and freeing the water, thus giving slurries of lower viscosity and allowing desirable flow conditions to be obtained at lower pump pressures. V. S. Ramachandran,
Concrete Admixtures Handbook: Properties, Science, and Technology,
Noyes Publications (Second Edition, 1995). Superplasticizers such as sulfonated melamine formaldehyde condensate (SMF) and sulfonated naphthalene formaldehyde condensate (BNS) are commonly used as dispersants. However, these compounds require more than the desired amount of material to achieve a desired level of concrete workability or water reduction. In addition, these materials do not achieve full range (Type A to Type F) water reducing capability.
It is important that dispersants are used in concrete situations where strength and durability are involved, as dispersants are a necessary component in high strength and high durability concretes. Due to the use of low water amounts in the high performance concretes, sometimes high dispersant amounts are necessary to achieve workable concretes. High BNS levels can lead to undesirable retardation of set and may not provide the required workability retention over time.
It is desirable to provide a material that is several times more efficient as a cement or concrete dispersant than the traditional materials like BNS and SMF. Improving efficiency reduces the amount of material required to achieve a desired level of concrete workability or water reduction. With respect to the presently used dispersants, BNS and SMF, it is also desirable to improve slump retention while maintaining normal setting characteristics. Providing a dispersant with full range (Type A to F) water reducing capability is also a desirable characteristic.
According to German Patent Application No. 4,427,233, aspartic acid is produced by bringing (a) maleic anhydride, maleic acid, fumaric acid, and/or malic acid into contact with (b) ammonia and/or primary or secondary amines in a molar ratio of (a) to (b) of 1:0.1-1:3, possibly in the presence of co-condensable compounds. Components (a) and (b) are brought into contact with each other at temperatures of above 100° C. and thermally condensed, and the polycondensates are then hydrolyzed, if desired. Components (a) and (b) are brought into contact with each other in the presence of condensation products of the reaction products of (a) and (b) and of powders which are inert under the polymerization conditions. Polymers which contain aspartic acid imide units in the backbone are thus formed.
Other methods of producing polyaspartic acid are disclosed in WO Publication No. 97/18249, Great Britain Patent No. 2307689, and Japanese Patent Application No. 5-321720. Japanese Patent Application No. 5-321720 discloses a hydraulic cement admixture for use as a dispersant, a water reduction agent, and a flowing agent. The effective components of this hydraulic cement admixture are polyaspartic acid and monomeric derivatives. A relatively high percentage of these additives is required for performance as dispersants.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a hydraulic cement or concrete dispersant material that is several times more efficient than the traditional dispersants such as BNS and SMF.
It is a further object of the present invention to provide a cement or concrete dispersant material with improved efficiency which reduces the amount of material required to achieve a desired level of concrete workability or water reduction.
It is also an object of the present invention to provide a cement or concrete dispersant material to improve concrete slump retention while maintaining normal setting characteristics.
It is another object of the present invention to provide a cement or concrete dispersant material capable of providing a Type A to Type F water-reducing effect.
The present invention is directed to the use of polycarboxylate polymers, comprising a functionalized polyamide main chain polymer onto which are grafted at least some proportion of oligomeric or polymeric hydrophilic side chains, as highly efficient cement dispersants compared to traditional dispersants such as BNS and SMF. It is previously unknown to attach oligomeric or polymeric hydrophilic side chains to this polymer backbone, and to use this polymer in cementitious compositions.
The invention is directed to a substantially non-crosslinked polymer cementitious composition dispersant comprising a hydrophilic side chain substituted polyimide or polyamide composition, having at least some proportion of grafted oligomeric or polymeric side chains. The grafted side chains may include linking amides, esters, and thioesters. The polymer cementitious composition dispersant is water soluble and substantially non-crosslinked, that is, in one embodiment, crosslinking is minimized such that in a statistical sampling there is greater than zero to less than 0.1 mole % of backbone units involved in crosslinking. The polymer dispersant having a hydrophilic side chain substituted backbone has the general formula:
wherein X is at least one of hydrogen, an alkali earth metal ion, an alkaline earth metal ion, ammonium ion, and amine; R is at least one of C
1
to C
6
alkyl(ene) ether and mixtures thereof and C
1
to C
6
alkyl(ene) imine and mixtures thereof; Q is at least one of oxygen, nitrogen, and sulfur; p is a number from 1 to about 300 resulting in at least one of a linear side chain and branched side chain; R
1
is at least one of hydrogen, C
1
to C
20
hydrocarbon, and functionalized hydrocarbon containing at least one of —OH, —COOH, a derivative of —COOH, sulfonic acid, a derivative of sulfonic acid, amine, and epoxy; Y is at least one of hydrogen, an alkali earth metal ion, an alkaline earth metal ion, ammonium ion, amine, a hydrophobic hydrocarbon or polyalkylene oxide moiety that functions as a defoamer; m, m′, m″, n, n′, and n″ are each independently 0 or an integer between 1 and about 20; Z is a moiety containing at least one of i) at least one amine and one acid group, ii) two functional groups capable of incorporating into the backbone selected from the group consisting of dianhydrides, dialdehydes, and di-acid chlorides, and iii) an imide residue; and wherein a, b, c and d reflect the mole fraction of each unit wherein the sum of a, b, c and d equal one, wherein a, b, c and d are each a decimal of value greater than or equal to zero and less than one, and at least two of a, b, c and d are greater than zero.
DETAILED DESCRIPTION OF THE INVENTION
This invention is directed to a polymer dispersant for cement or concrete comprising a substituted polyimide or polyamide composition, having at least some grafted oligomeric or polymeric side chains. The grafted side chains may include amides, esters, and thioesters. In a preferred embodiment, a majority of the polymer's (grafted) side chains are hydrophilic.
The polymer dispersant is produced by reacting a poly N-succinimide with at least one of an amide-, ester-, and thioester-producing nucleophile followed by further reacting the product thereof with at least one of an alkali or alkaline earth metal, an (alkyl) ammonium hydroxide, and a hydrocarbon ring-opening base. A hydrocarbon ring-opening base is a base capable of opening a hydrocarbon. The hydrocarbon ring-opening base includes a heteroatom.
The grafted polymer dispersant has the general formula:
wherein X is at least one of hydrogen, an alkali earth metal ion, an alkaline earth metal ion, ammonium ion, and amine; R is at least one of C
1
to C
6

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