The present invention relates to the use of selected triaminophosphonates in cement, a process for grinding clinker in the presence of such selected aminophosphonates and to methods of using cement-based products, such as concretes, containing the triamino-phosphonates.

Aminopolyphosphonates are well-known and have found application in numerous applications, inclusive of building materials. The prior art phosphonates have been suggested for use in cement technology to thereby produce benefits, for example retarder properties. German patent application 20.37.586 discloses the use of especially aminodiphosphonic acids as a retarder in plastering compositions ; German Offenlegungsschrift 28.51.841 describes alkyldiphosphonic acids for use in burnt gypsum ; DE-A-34.10.820 divulges additives for cement and cement mortar comprising, inter alia, a phosphonic acid retardant. DE-OS-37.27.907 describes a process for the recovery of non-used concrete mixtures containing specific DEQUEST alkylaminopolymethylene phosphonic acids. DE-OS-40.38.147 pertains to an arrangement for the spraying of concrete containing a calcium binding stabilizer inclusive of specific DEQUEST species. Triaminononane-hexamethylenephosphonates having metal ion sequestering properties are known from Japanese patent Kokai N° 53-137886 to Asahi Chemical Industry Co, Ltd. Tris(2- aminomethyl)amine hexa ethylene phosphonate scale inhibitor is known from US-A-3 974 090 to Monsanto Company.

The known cement-phosphonate technology provides either narrowly defined benefits and/or is, from a commercial standpoint, marginally effective, and not likely to lead to commercially viable executions capable of providing a broad spectrum of benefits.

It has now been found that narrowly defined triaminophosphonates can serve as beneficially effective cement additives with a much better cost-performance ratio as compared to state-of-the art additives and will generate meaningful benefits with broad spectrum benefits.

The essential aminophosphonate (also called triaminophosphonate) component is a triaminoalkane polymethylenephosphonate or a tris(aminoalkyl)amine polymethylene phosphonate represented by the general formula :

(CR ⁴ ₂ ),

X x

wherein A is C-R ¹ or N; X is H or CH ₂ P0 ₃ M ₂ ; M is hydrogen or a salt-forming cation; whereby at least one X on each individual N is CH ₂ P0 ₃ M ₂ ; a, b, and c are integers from 0 to 6 whereby, in any given formula, not more than one of said numbers a, b, and c can be equal to 0; each R ¹ , R ² , R ³ and R ⁴ is selected independently from H and Cj-C ₆ alkyl; and the phosphonate is present in an amount of from 0,002% to 5% by weight of the dry cement. When A is N, a, b, and c are preferably from 2 to 6, more preferably from 2 to 4.

The polyphosphonates of the present invention may be used as the corresponding acids or salts, more particularly the Na, K, Ca, ammonium or triethanolammonium salts.

Preferably, in the above general formula R ¹ is hydrogen or C,-C ₂ alkyl; R ² , R ³ and R ⁴ are hydrogen and at least four of the X moieties are CH ₂ P0 ₃ M ₂ . This triaminophosphonate is

advantageously present in an amount of from 0,01% to 2% by weight of dry cement.

More preferably, R ¹ , R ² , R ³ and R ⁴ are hydrogen, a, b and c are, selected independently, such that their sum is an integer in the range from 6 through 10 and X is CH ₂ P0 ₃ M ₂ . The triaminophosphonate is preferably present in an amount of from 0,01% to 1% by weight of the dry cement.

A very preferred triaminophosphonate compound herein is represented by 4-aminomethyl-l, 8-diamino-octane N,N,N' ,N' ,N' ' ,N' ' hexakismethylene phosphonic acid or a salt thereof (TANHMP) . Other preferred triaminophosphonates are: tris(2-aminoethyl)amine N,N,N' ,N' ,N", N" hexakis(methylene phosphonic acid) (TAEAHMP) and tris(3-a inopropyl)amine N,N,N' ,N' ,N",N" hexakis(methylenephosphonic acid) (TAPAHMP) .

While the inventive triaminophosphonates can be used economically with cements broadly, such phosphonates are especially beneficial for use with cement having a C3A content of above 1%, preferably above 5%, most preferably from 8% to 12%.

The essential triaminophosphonates can be prepared by conventional phosphomethylation techniques starting from the corresponding amines with formaldehyde and phosphorous acid as, for example, described by Moedritzer and Irani, J. Org. Chem. 1966, vol 31, p. 1603.

The invention is also directed to a process for the grinding of clinker in the presence of additive to subadditive levels of a triaminophosphonate grinding additive of the above general formula. The phosphonate grinding additive represents preferably from 0,002 % to 2% by weight of the dry clinker (100 %) . The grinding process according to the invention may include the specific use of 4-aminomethyl-l,8-dia ino-octane N,N,N' ,N' ,N' ' ,N' '

-4 - hexakismethylene phosphonic acid or a salt thereof in an amount of 0,01% to 2% by weight of dry clinker. The grinding process may also include the specific use of TAEAHMP or TAPAHMP in the specified (0.002% to 2%) amounts.

According to another preferred embodiment of the invention, there is provided a cement composition containing a triaminophosphonate, as described above, in combination with from 0,01 % to 5% by weight of other phosphonated or non-phosphonated cement additives, with a view to achieve benefits and augment performance based on their art- established functionality. Examples of such additives embrace plasticizers, additional retarders and/or commercial non- phosphonated additives. In such systems, the triamino phosphonate represents from 0.001% to 2%, preferably from 0.02% to 1% expressed by weight of the dry cement or clinker. The triaminophosphonate additive and the sum of additives, other than the triamino phosphonate, are frequently utilized in a weight ratio of 5:95 to 80:20, preferably from 30:70 to 60:40.

The non-phosphonated additives, inclusive of grinding additives, can be selected routinely among non-phosphonated cement-additives and grinding-additives which additives are well known in the relevant domain. Typical examples of the like performance additives are : sodium chloride; lignosulfonate salts; naphthalenesulfonate salt; α- or β- poly-naphthalenesulfonates or the salts thereof; polycarboxylic acids and the salts thereof; anti-agglomerants such carbon black (soot) ; finely divided carbon black having a particle diameter between l and 80 micrometers; salts of di-, and tri-ethanolamines; carboxylic acids or the salts thereof; acetone; polyglycols and polysaccharides. Suitable and preferred phosphonate additives other than the essential triaminophosphonates can be represented by the species recited in EP-A-95870120.3 passage page 4, line 18 through page 6, line 5. The addition of, for example, additif system

of this invention to cement and/or clinker can be effected with the aid of dosing techniques routinely available.

Cement and clinker compositions in accordance with this invention can contain, in addition to the additives recited above, other additifs in levels not exceeding normally 7% by weight of the dry cement or clinker. Well-known examples of the like further additives are : gypsum (calcium sulfate) , calcium hemihydrates, calcium anhydride and phosphogypsum.

Examples

The benefits of the invention herein are illustrated by means of the comparative showings below.

Set retardation was measured by preparing mortar samples to which a sodium phosphonate salt was added at a level equivalent to 0.05% of phosphonic acid on the dry cement weight. The water/cement weight ratio was 0.48 and the sand/cement weight ratio was 0.75.

Two types of Portland cement were used. Cement 1 is a cement having a C3A content of about 9%; cement 2 is low C3A (1%) cement. Set retardation was determined in a conventional manner by measuring the temperature of the mortar as a function of time. The testing results quantify the time needed to reach maximum temperature. These measurements correlate well with and are directly relatable to the setting time.

The comparative testing results were as follows :

Example

I II

Time to maximum

Phosphonate temperature (hr)

Cement 1 Cement 2 none 10.5 11.8

ATMP 16.3 18.7

HEDP 22.8 16.2

DTPMP 17.3 15.7

PBTC 13.8 14.2

TANHMP 33.0 18.0

The phosphonate abbreviations have the following meaning; the partially neutralized sodium salts are used.

ATMP amino N,N,N tris(methylene phosphonic acid); HEDP 2-hydroxy ethane-1,1-diphosphonic acid; DTPMP diethylene triamine N,N,N' ,N",N ^H pentakis ( ethylenephosphonic acid) ;

PBTC 2-phosphono butane 1,2,4 tricarboxylic acid; TANHMP 4-aminomethyl-l , 8-octanediamine- N,N,N',N',N",N" hexakis(methylene phosphonic acid) .

The results are confirmatory of unusually beneficial improvements conferred by the use of the narrowly defined triaminopolyphosphonates of this invention as compared to structurally closely related polyphosphonate species.

Example III

Set retardation was measured as described in examples I and II above.

The cement used contained 10% C3A and about 11% C2S, and 69% C3S :

The experimental results were as follows :

Phosphonate Time to max temperature (hr)

NONE 10.7

ATMP 21.7

HEDP 26.8

DTPMP 25.7

PBTC 15.8

TANHMP 32.2

The testing results show that the use of the essential triaminophosphonates in cement having C3A level in the range of from 8% to 12% can constitute a preferred domain of application.

Exa ple IV

Set retardation testing data were generated under conditions identical to those recited in Example I.

The comparative testing results were as follows:

Phosphonate Example IV Time to max temperature (hr)

None 10.5

TAEAHMP 22.8

The use of TAPAHMP in lieu of TAEAHMP, in Example IV, also shows significant set retardation benefits.