Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-21
2002-09-17
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S560000, C524S561000, C524S320000, C524S366000, C526S320000, C526S328000
Reexamination Certificate
active
06451880
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to additives for masonry mortar and compositions comprising such admixtures, and more particularly to improving workability, board life, and water retention in masonry mortar using a low molecular weight, water soluble humectant comprising a polymer having oxyalkylene groups, alcohol groups, oxyalkylene adducts of monoalcohols and/or polyols, or mixtures thereof in combination with an alkali-soluble, emulsion polymer.
BACKGROUND OF THE INVENTION
Masonry mortar is a combination of hydratable cement or cementitious binder, fine aggregate (e.g., sand), and water which is used for binding together masonry units, such as bricks and masonry blocks, into a building structure.
Among the characteristics of masonry mortar which are of central concern to masons are “workability” and “board life.” Workability refers to the consistency and feel of the mortar when it is being trowelled and applied by the mason. Masons prefer that their mortars have a particular ease of movement, a certain plasticity or “fattiness,” that makes for easy application, while also having a certain degree of “body” or cohesiveness that means that the mortar holds together. Board life, on the other hand, refers to the working time or duration in which the mortar retains workability.
The present inventor also believes that water retention is a further desirable feature and benefit that should be provided by the masonry mortar additive, because this contributes to enhancing workability and board life.
It is one of the purposes of the present invention to provide an improved additive for enhancing workability, board life, and water retention in masonry mortar.
SUMMARY OF THE INVENTION
An exemplary masonry additive of the invention comprises: (a) an alkali-soluble, emulsion polymer; and (b) a low molecular weight, water-soluble humectant comprising a polymer having oxyalkylene groups, polyhydric monoalcohol and/or polyolgroups, or a mixture thereof. An exemplary humectant comprises a polymer comprising at least one oxyalkylene group, and preferably an alkylene or oxyalkylene glycol; an oxyalkylene ether adduct of mono alcohols or polyols; or a mixture thereof.
One preferred humectant contemplated for use as a suitable water-soluble humectant comprises polyethylene glycol (PEG) having the formula H—(OCH
2
CH
2
)
n
—OH wherein “n” represents an integer of 3 to 90, and more preferably 3-70, and most preferably 3-55. The humectant is preferably added with the alkali soluble emulsion polymer together into a masonry cement, or it may be added into a masonry cement as a separate liquid component added simultaneously with the alkali soluble emulsion polymer (component (a)) or introduced at a different time. The component (a) alkali-soluble emulsion polymer is preferably hydrophobically-modified. The use of a low molecular weight, water-soluble humectant provides a substantial improvement over masonry mortar containing the emulsion polymer alone.
The present invention also provides a masonry mortar composition (e.g., comprising a hydratable cementitious binder and fine aggregate (e.g., sand) and the above described component (a) alkali-soluble emulsion polymer and component (b) low molecular weight, water-soluble humectant. The invention also provides a method for enhancing workability, boardlife, and water retention in a masonry mortar, comprising introducing to a cement binder, fine aggregate, the polymer of component (a), and the low molecular weight, water-soluble humectant of component (b).
Preferred masonry mortars of the invention have an entrained air content of 6-25% by volume, and more preferably 8-22% by volume (ASTM C 91)(1998).
Further features and advantages of the invention are described in further detail hereinafter.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
The term “masonry mortar” as used herein refers to a composition containing a hydratable cementitious binder (e.g., Portland cement, gypsum, ground limestone, slag, lime, and various other pozzolans) and fine aggregate (e.g., sand) in a general range (binder: fine aggregate) of 1:2 to 1:8 by dry weight. The “masonry mortar” composition of the invention encompass the mix in dry and wet forms.
As previously discussed in the background, the present invention is directed at improving workability, board life, and water retention in masonry mortar. Mortar workability enhancers, such as hydroxyethyl cellulose, or high molecular weight PEG, are known for adding viscosity and water binding (humectant) quality which produces a desirable consistency or “fattiness” of the mortar paste. However, hydroxyethyl cellulose is in the form of a powder, and this is not desirable because this creates problems when dispensing the additive into the mortar. It is more desirable to use additives that can be added in the form of a liquid because this is more accurately dosed and more easily dispensed, for example, during intergrinding of the cementitious binder. Liquids can also be formulated in a single component system with grinding aids, set modifiers (e.g., accelerators, retarders), and/or air entraining agents (AEAs). Thus, another benefit of the present invention is achieving workability through a viscosifying and wetting ability in an additive that is introduced in a high solids/low viscosity liquid form and thus can be more accurately dosed and dispense. This approach is therefore considered by the inventor to be far superior to powdered additives.
Another objective met by the present invention was to produce the desired “water binding quality” or creaminess desired by masons without having the workability-enhancing additive function as a water-reducer or “superplasticizer. To the contrary, the present inventor sought a liquid additive that had a “water holding” power that would both increase workability and extend board life, without functioning as a water-reducer.
It is believed that the use of low molecular weight, water-soluble humectants, (such as PEG) of molecular weight 100-2500 may also have benefits in improving grindability of cement clinker and limestone.
Thus, the present inventors discovered a desirable synergy of characteristics by employing (a) an alkali-soluble emulsion polymer (preferably one which is hydrophobically modified by incorporation of one or more fatty acid groups or moieties); and (b) a low molecular weight, water-soluble humectant selected from (i) an alkylene or oxyalkylene glycol or (ii) oxyalkylene ether adducts of alcohols, or polyols.
The molecular weight of these humectants may be up to 4000 and more preferable up to 2500. The glycol can be represented by the formula HO(AO)
n
H where A represents a C
2
-C
10
alkylene group, such as ethylene, propylene, butylene and the like, with mixtures of ethylene and propylene being preferred, and ethylene by itself being most preferred; O represents an oxygen atom and “n” represents an integer from 3 to 90 and more preferably 3-55. The AO groups in a particular glycol molecule may all be the same or may be different. Exemplary glycols (e.g., polyalkylglycols) therefore may include poly(oxyalkyelne)glycol, having molecular weights of 100 to about 2500. The AO groups forming the chain of such glycols may contain a single type of alkylene ether group or a mixture of alkylene ether groups which may be in block or random arrangement.
The oxyalkylene compounds used in forming the present admixture can also be oxyalkylene ether adducts of mono alcohols or polyols. The oxyalkylene adduct of monoalcohols is represented by the formula RO(AO)
m
H wherein R is hydrocarbon group, such as a C
1
-C
7
alkyl group. Examples of such R groups are believed suitable for use in the invention include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl and the like. The preferred R groups are C
3
-C
5
alkyl such as n-propyl, isopropyl, n-butyl, t-butyl, and the like. A is a C
2
-C
4
(preferably C
2
-C
3
) alkylene group, such as ethylene, propylene, and the like, and mixtures thereof in the same chain, and “m” represents an integer of f
Asinovsky Olga
Baker William L.
Leon Craig K.
Seidleck James J.
W. R. Grace & Co.,-Conn.
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