Additives for mineral building materials containing cement

Details Additives for mineral building materials containing cement Additives for mineral building materials containing cement

2001-03-16

2003-04-08

Cain, Edward J. (Department: 1714)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S004000, C524S005000, C524S599000

Reexamination Certificate

active

06545067

ABSTRACT:

The invention relates to mixtures of at least one air detrainer and at least one polycarboxylate-based plasticizer for mineral building materials which comprise cement, and to the use of aqueous solutions of such mixtures as additives for mineral building materials comprising cement.
WO-A-83/02938 discloses hydraulic cement mixtures which comprise ethoxylated or propoxylated polyamines or polyethylenimines for strength enhancement. DE-A-44 20 444 discloses additives for cement-comprising compositions. They include at least one cement plasticizer and at least one antifoam. Examples of appropriate plasticizers are aqueous solutions of copolymers containing, in copolymerized form, monoethylenically unsaturated carboxylic acids and polyalkylene glycol esters of acrylic or methacrylic acid. The plasticizers are used in combination with an antifoam which is either dissolved in the polymer solution or dispersed therein in particles having a diameter of not more than 20 &mgr;m. Examples of the antifoams are adducts of ethylene oxide and/or propylene oxide with alcohols or phenols. Insofar as such mixtures are not clear aqueous solutions, additives of this kind lack sufficient stability on storage and separate into two phases.
DE-A-19653524 discloses copolymers of ethylenically unsaturated carboxylic acids and polyalkylene glycol esters of acrylic or methacrylic acid that are obtainable by polymerizing the monomers in the presence of compounds comprising phosphorus in bonded form. Such copolymers are highly effective plasticizers for cement mixtures such as concrete or mortar. They are used in amounts of, for example, from 0.01 to 10% by weight, preferably from 0.05 to 3% by weight, based on the weight of the cement. Advantageously, the plasticizers are used in conjunction with antifoams in order to reduce the level of air pores. Examples of air detrainers suitable for achieving reduction in air pores are products based on polyalkylene oxides, such as adducts of ethylene oxide or propylene oxide with alcohols or phenols; phosphates such as tributyl phosphate or triisobutyl phosphate, phthalates such as dibutyl phthalate, siloxanes such as polydimethylsiloxane, or phosphates of ethoxylated fatty alcohols, such as ethylene oxide stearyl phosphate. Air detrainers of this kind are customarily employed in amounts from 0.05 to 10% by weight, preferably from 0.5 to 5% by weight, based on the polymers that are used as plasticizers.
Further plasticizers used for mineral building materials are homopolymers and copolymers of ethylenically unsaturated carboxylic acids and dicarboxylic acids with styrene (EP-A-0 306 449) or isobutene or diisobutene (EP-A-0 338 293, U.S. Pat. No. 4,586,960 and U.S. Pat. No. 4,906,298). When polycarboxylate-based plasticizers are incorporated into mineral building materials considerable amounts of air are introduced. As a result of the air pores, voids are formed in the concrete, leading to a significant deterioration in the mechanical properties and stability of the concrete. To reduce the level of air pores in the concrete when using plasticizers, it is usual to employ the plasticizers together with air detrainers. Mixtures of polycarboxylate-based plasticizers with air detrainers of the type described above, however, are not sufficiently stable on storage.
It is an object of the present invention to provide storage-stable mixtures of at least one air detrainer and a polycarboxylate-based plasticizer for mineral building materials comprising cement.
We have found that this object is achieved, in accordance with the invention, by mixtures of at least one air detrainer and at least one polycarboxylate-based plasticizer for mineral building materials comprising cement if said mixtures comprise butoxylated polyalkylenepolyamines or their salts as air detrainers. Particular preference is given to mixtures comprising water-soluble butoxylated polyethylenimines as air detrainers.
By mineral building materials are meant preparations comprising as essential constituents mineral binders such as lime and/or, in particular, cement and also—as aggregates—sands, gravels, crushed rocks or other fillers, such as natural or synthetic fibers. The mineral building materials are generally converted, by commixing the mineral binders such as cement and the aggregates together with water, into a ready-to-use formulation which hardens both in air and under water to a stonelike material. So that the cement-comprising mineral building materials have favorable service properties—i.e., are pumpable—while keeping the ratio of water to cement as low as possible, use is made, for example, of polycarboxylates, which are described in the above references. Examples of suitable polycarboxylates are homopolymers and copolymers of acrylic or methacrylic acid, copolymers of styrene and maleic anhydride, copolymers of isobutene and maleic anhydride, and copolymers of diisobutene and maleic anhydride. Particularly preferred plasticizers for cement-comprising mineral building materials are, for example, polyalkylene glycol-acrylic and/or methacrylic acid copolymers esterified with one mole of acrylic or methacrylic acid. Such copolymers are disclosed, for instance, in the cited prior art documents DE-A 4420444 and DE-A 19653524.
Since the use of polycarboxylates alone as plasticizers for cement-comprising mineral building materials is accompanied by a relatively sharp increase in the air pore content of said materials, the invention involves using the customary plasticizers in conjunction with butoxylated polyalkylenepolyamines or their salts in order to reduce the air pore content of mineral building materials. Examples of the polyalkylenepolyamines to be butoxylated are diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, 3-(2-aminoethyl)aminopropylamine, 2-(diethylamino)ethylamine, 3-(dimethylamino)propylamine, dimethyldipropylenetriamine, 4-aminoethyl-1,8-octanediamine, 3-(diethylamino)propylamine, N,N-diethyl-1,4-pentanediamine, dipropylenetriamine, bis(hexamethylene)triamine, N,N-bis(aminopropyl)methylamine, N,N-bis(aminopropyl)ethylamine, N,N-bis(aminopropyl)hexylamine, N,N-bis(aminopropyl)octylamine, N,N-dimethyldipropylenetriamine, N,N-bis(3-dimethylaminopropyl)amine, N-(aminoethyl)butylenediamine, N-(aminopropyl)butylenediamine, bis(aminopropyl)butylenediamine, and polyethylenimines. The polyethylenimines have molecular masses, for example, of from 200 to 5000, preferably from 400 to 3000. With particular preference, polyethylenimines having molecular masses from 600 to 2000 are used for the butoxylation.
The butoxylated polyalkylenepolyamines contain, for example, from 0.1 to 10 mol of butylene oxide added on per nitrogen group. Preference is given to the use of air detrainers obtainable by butoxylating polyethylenimines having molecular masses from 200 to 5000 with from 0.1 to 10 mol of butylene oxide per mole of ethylenimine units in the polyethylenimine. Air detrainers used with particular preference are the reaction products obtainable by butoxylating polyethylenimines having molecular masses from 400 to 3000 with from 0.3 to 5 mol of butylene oxide per mole of ethenimine units in the polyethylenimine. The best results in terms of air detrainment are obtained with reaction products obtainable by butoxylating polyethylenimines having molecular masses from 600 to 2000 with from 0.8 to 2 mol of butylene oxide per mole of ethylenimine units in the polyethylenimine.
The reaction products of butylene oxide with polyalkylenepolyamines can be used directly in the form as obtained from the butoxylation or else in the form of a salt with, for example, mineral or organic acids such as carboxylic acids or sulfonic acids. The polyalkylenepolyamines can be butoxylated in either one or two stages. In the one-stage procedure, for example, the polyalkylenepolyamines are charged to a reactor together with an alkaline catalyst and the required amount of butylene oxide is injected. The reaction temperature can be, for example, from 25 to 150° C. In the case of multistage ad

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