Use of synthetic surface-active substances and method for milling Portland clinker for the production of gypsumless Portland cements

Abstract: The invention relates to admixtures and a method for milling Portland clinker for the production of gypsumless Portland cements with specific surfaces of from 350 to 750 m²/kg. According to the invention, the milling is carried out in the presence of 0.01 to 0.15 mass-% of a synthetic organic surface-active substance with wetting properties which is stable in alkaline media of pH values 9 to 12.

Description: The invention relates to a method for milling Portland clinker for the production of gypsumless Portland cements of a specific surface area of 350 to 750 m²/kg with use of admixtures comprising synthetic organic surface-active substances. The use of specific admixtures added during the milling of cements has been known already from the thirties. Milling admixtures, also called milling intensifiers, are substances preventing the aggregation of particles during the milling process or helping the scattering of the grist during the milling process. The milling admixtures must fulfill the basic condition not to impair the quality of the cements. The milling admixtures further inhibit adhering of the grist to the milling bodies, thus increasing the output of the mill. The use of milling admixtures reduces the cost of milling and allows the production of high-quality cements. The milling admixtures ameliorate as well the starting resistance, facilitate the emptying of silos and/or improve the storage life of cements. Actually, quite a number of substances are used industrially as milling admixtures for the production of cements, especially for the production of Portland cements, such as (cf. W. H. Duda: Cement - Data Book, 1985) calcium lignosulfonate containing no monosaccharides, mixtures of triethanolamine with calcium lignosulfonate, various types of fatty acids, various types of diols, especially glycols, and many other commercial mixtures. In the Federal Republic of Germany liquid milling admixtures comprising substances of aminoacetate, ethyleneglycol or propyleneglycol type are used for the production of PC 550 (O. Labahn, B. Kohlhaas, Ratgeber für Zement-Ingenieure, 1982). The research work in this field is absolutely concentrated on gaining new milling admixtures having the following properties: Positive influence on the milling process, reduction of power consumption in milling, greater specific surface area of the product, and no negative influence on the quality of the cements. From those points of view many substances before all influencing positively the milling process of cements are mentioned in the technical and patent literature. Lists and surveys of these substances are to be found e.g. in Cement-Research-Progress 1974 - 1987. The problem of milling admixtures is also relevant for a new type of inorganic hydraulic binding agents, namely the gypsumless cements. These cements are based on Portland clinker or white cement and are usually ground in the absence of gypsum. The regulation influence of gypsum is achieved by synergistically acting mixtures of alkaline metal compounds, e.g. carbonates, hydrogen carbonates, silicates or hydroxides, and sulfonated polyelectrolytes, e.g. derivatives of lignin, sulfonated polyphenolates or other liquefying agents applied as plastifiers. Gypsumless Portland cements (referred to as GL cements) are outstanding because of their better qualities as compared with common Portland cements, especially for the preparation of pastes, mortars and concretes with a substantially lower cement-water ratio. The properties of these GL cements have already been described, e.g. in CS-A-257 315. These properties of GL cements can also be obtained by increasing the milling fineness beyond that of common Portland cements. The mentioned prior art solutions are directed, however, only to the possibility of getting a higher specific surface area of the cements. The solution described in US-A-3 689 294 relates to another view of the problems of GL cements. In this document, as well as in the publication of M. Yudenfreund "Hardened portland cement pastes of low porosity, Cement and Concrete Research 2, 313 - 330, 1972", compositions of freely flowing liquid pastes or mortars and concretes in the expanding state, based on ground cement clinkers of specific surface areas of 600 to 900 m²/kg containing at least 0.002 parts of milling admixtures and at least 0.0025 parts of alkaline lignosulfonates of alkaline earths or sulfonated lignin and at least 0.0025 parts of alkali carbonates with a cement-water ratio of 0.20 to 0.28, are described. These publications specify the following milling admixtures: Kraft lignin (alkali lignin), oleic acid, diethyl-carbonate, ethoxylated nonylphenols with different numbers of ethoxy groups, sodium dodecylbenzene sulfonate, mixtures of alkylsulfonates and sulfocarboxylates, sulfosuccinates, alkylated sulfosuccinates, and/or sulfosuccinates with amines and alkylsulfates or with alkylphenol polyglycolethers, triethanolamine, ethylene glycol, and alkylphenol sulfonates. The simultaneous presence of polar and non-polar groups in the molecule is regarded as the main feature of milling admixtures. It has come out that it was not possible to prepare additives for GL cements of a low cement-water ratio with given workability with application of Brunauer's criterion (US-A-3 689 294), but by selecting additives which are unstable in the alkaline medium. The stability of the matter adsorbed onto the surface of the cement in the alkaline medium is necessary with regard to the fact that admixtures replacing gypsum, e.g. soda + lignosulfonate, form solutions having a pH value of up to 11.5. Furthermore, a very strongly alkaline and limy medium is formed by the contact of the clinker with water. Other materials, though stable in the alkaline medium, have no wetting property for powder materials, e.g. triethanolamine, silanes, siloxanes, stearates, etc., so that they cannot be used for the preparation of additives for GL cements with a low cement-water ratio. From all matters known up to now and applied as admixtures for the milling of Portland clinkers for GL cements only one single compound gives the required effects, namely the triethanolamide of dodecylbenzene sulfonic acid. Its application, however, used to be accidental, and its effectivity had obviously not been realized. It is the object of the invention to provide the use of particular admixtures and a method for milling Portland clinkers for the production of gypsumless Portland cements with a specific surface area of 350 to 750 m²/kg, wherein the above-described disadvantages may be overcome. The above object is achieved according to the independant claims. The dependent claims relate to preferred embodiments. The present invention provides the use of one or more synthetic organic surface-active substances having wetting properties which are stable in media of a pH value ≦ 12 and particularly within the pH range of 9 to 12, with exception of dodecylbenzene sulfonic acid triethanolamide, as admixtures or components of admixtures for milling Portland clinker for the production of gypsumless cements with a specific surface area of 350 to 750 m²/kg. In accordance with preferred embodiments, the synthetic organic surface-active substances are selected from alkylpolyglycolether sulfates and alkylated alkanolamine-polyglycolethers comprising C₁₀₋₁₅-alkyl groups, alkanolamides of C₁₂₋₁₅-acids with aliphatic C₁₀₋₁₅-alcohols and/or sulfated ethoxylated aliphatic C₁₀₋₁₅-alcohols comprising 3 to 10 ethoxy groups, esteramides and esters of sulfated or sulfonated linear fatty acids and sulfonated alkylaryl acids, where the linear chain comprises 5 to 20 carbon atoms, condensation products of naphtholsulfonic acid or cresol with formaldehyde, and alkylbetaines and sulfoalkylbetaines comprising C₈₋₁₆-alkyl groups. In accordance with further preferred embodiments, the synthetic organic surface-active substances are selected from alkanolamine derivatives of ethoxylated nonylphenol, sodium alkylpolyglycolether sulfates, ethoxylated sulfated alkylphenols, mixtures of sulfated ethoxylated alcohols with coconut acid monoethanolamide, triethanolamine salts of alkyllbenzenesulfonic acids (alkyl mixtures C₈₋₁₄), the ammonium salt of dodecylbenzene sulfonic acid, alkylbenzenesulfonic acid salts based on α-olefins (alkyl mixture C₁₀₋₁₂), sodium salts of condensation products of β-naphtholsulfonic acid and cresol with formaldehyde, and alkanolamine salts of sulfated ethoxylated alcohols (3 to 10 ethoxy groups, alkyl mixtures C₁₂₋₁₅). Depending on the specific application, it may be advantageous to use the admixtures in the form of an aqueous solution or dispersion, and particularly a concentrate to be diluted before use. Packaging may be in the form of appropriate dosage units. If necessary, the admixtures may also comprise further, known additives. The method of this invention for milling Portland clinker for the production of gypsumless cements with a specific surface area of 350 to 750 m²/kg in the presence of a milling admixture is characterized in that synthetic organic surface-achive substances are used, preferably in an amount of 0.01 to 0.15 mass-%, based on the total mass of the Portland clinker, as defined above. The method according to the invention enables the application of a large range of substances as milling admixtures for the milling of Portland clinkers for the production of gypsumless cements which have not been applied yet up to now and which at the same time meet the requirements such as good wetting properties for powdery materials, high intensification of the milling process, non-toxicity, and positive influence onto both the starting and long-life resistance of GL cements. In the following, the invention will be further explained with reference to examples. Example 1 The clinker used for the research milling admixtures has been taken from the current production of a cement factory (Lochkov Works, CS). This clinker has been used for determining the dependance of the milling process of the reached specific surface area up to the value of 750 m²/kg with use of a Seger milling machine. For further experiments a ball mill with a volume of 50 l has been used. Into the mill was poured a very fine clinker (fraction below 2.5 mm), the milling admixture having been dosed in advance in a concentration of 0.03 to 0.15 mass-% of the clinker mass (based on 100 % of active matter, or dry matter). The time duration of the different milling processes has been varied. The final product has been evaluated according to the reached specific surface area. The efficiency of the different milling admixtures has been evaluated with the help of a Seger apparatus and of the results of the ball mill experiments. The used milling admixtures are listed in Table 1. The letters A, B, C, D, E, F, G, H, I, J correspond to known milling admixtures, whereas the letters K, L, M, N, O, P, R, S, T, U, V designate milling admixtures according to the invention. Table 2 shows results of the evaluation of the efficiency of these milling admixtures. The efficiency of the milling admixtures has been evaluated with regard to a control test, i.e. milling of the same clinker without admixture addition. Example 2 The same clinker as in Example 1 was used for the experiments. It was ground in a ball mill of 20 l together with the milling admixture up to a specific surface area of 480 to 520 m²/kg. The thus produced cement has been worked up in the form of a paste with a low cement-water ratio w (w = 0.25 and 0.21), with admixture of 0.4 mass-% of Kortan FM (dried sulfonated sodium - ferric polyphenolate) and 1 mass-% of soda (based on the mass of the cement). The workability of the pastes has been evaluated according to the following empirical scale: 0 unworkable paste 1 paste flowing during vibrations only 2 paste flowing out from the agitation tank on hammering 3 paste flowing out from the agitation tank by gravitation 4 paste freely flowing out from the agitation tank 5 paste of low viscosity freely flowing out from the agitation tank. Table 3 shows the results of the evaluation of milling admixtures affecting the rheologic properties of pastes and their workability, at a low cement-water ratio. The indicated percentages are by mass. Concentration and kind of Milling Admixture Visual Workability at Cement-Water ratio w = 0.25 w = 0.21 0.05 % A 3 1 0.05 % B 2 0 0.05 % C 2 0 0.05 % D 2 0 0.05 % E 4 1 0.1 % F 4 0 0.06 % G 2 - 3 0 0.05 % H 5 3 0.05 % I 3 1 0.03 % J 5 3 0.05 % K 4 2 0.05 % L 3 2 0.05 % M 4 2 0.05 % N 5 2 - 3 0.05 % I O 4 2 0.05 % P 5 2 - 3 0.05 % R 4 2 0.05 % S 4 2 0.05 % T 4 2 - 3 0.05 % U 5 2 - 3 0.05 % V 4 2 According to producer's data the substances designated with A, B, C, and D are not stable in an alkaline medium of pH 8 to 12. It is evident from the evaluation of these experiments that pastes with a low cement-water ratio prepared from cements ground together with milling admixtures having surface-active characteristics but no wetting property (admixture C - silicone oil, partly admixture F - ethylene glycol, admixture E - triethanolamine) have a very bad workability. Pastes prepared of cements ground in the presence of surface-active substances with wetting properties, but with a low stability in a strongly alkaline medium (admixtures A to D), have as well a bad workability. The method according to the invention thus eliminates the problem of an arbitrary choice of milling admixtures from a great number of available surface-active substances. The evaluation results show too, that it is unsuitable to use classical milling admixtures as applied in the production of Portland cements (especially triethanolamine). Example 3 The same clinker as in Example 1 was used for the experiments. It was ground with liquid milling admixtures. From the obtained cements pastes (w = 0.25) have been prepared with admixture of 1 % of soda, and 0.4 % of Kortan FM (dried sulfonated sodium - ferric polyphenolate). The workability of the pastes has been evaluated according to the empiric scale indicated in Example 2. Further, the strength after 24 hours was measured. Table 4 contains the results. Milling Admixture Specific Surface Area (m²/kg) Workability Strength after 24 h (MPa) 0.1 % F 428 3 59 0.05 % H 421 5 55.5 0.05 % D 390 2 56 0.05 % I 390 3 45 0.03 % J 462 5 62 0.05 % N 390 5 60 0.05 % K 390 4 69 0.05 % S 400 4 57 0.05 % T 390 4 46 0.03 % U 390 4 59 0.05 % O 450 4 53 0.05 % R 340 4 62 0.05 % V 470 4 69 Example 4 The same clinker as in Example 1 was used for the experiments. It was ground with liquid milling admixtures. The following additional admixtures have been used: W: 0.4 mass-% of Kortan FM (dried sulfonated sodium - ferric polyphenolate) + 1 mass-% of soda X: 0.85 mass-% of sodium lignosulfonate + 1.2 mass-% of potassium carbonate. Table 5 shows the results for the obtained GL cements. Milling admixture 0.1 % N 0.1 % N 0.03 % U Specific surface area of the cement (m²/kg) 550 550 550 Additional admixture W X W w 0.22 0.22 0.23 Setting time (min) 65 15 110 Strength (MPa) after setting - 2 h 7.5 3.5 4.0 - 24 h 65 60 72 - 7 d 80 81 89 - 28 d 96 101 115 - 180 d 137.5 142 165 Example 5 The clinker used for the experiments has been taken from the current production of a cement factory (Prachovice works). It was ground with liquid milling admixtures. From the obtained GL cements have been prepared concretes with a low cement-water ratio. The following additional admixtures have been used: Soda + Ralentol (liquid sulfonated sodium - ferric polyphenolate). As lean materials have been used aggregates of 8 to 16 mm, and sand of 0 to 8 mm. Table 6 shows the obtained results. The strength of concretes prepared with milling admixtures U and J was 50 MPa after 24 hours. Milling admixture 0.05 % U 0.05 % J 0.05 % E Specific surface of the cement (m²/kg) 520 450 510 w 0.25 0.25 0.25 0.23 Composition of the concrete (cement: sand:aggregates) 1:1.4:1.5 1:1.3:1.4 1:1.41:1.52 1:1.41:1.52 Dose of cement (kg/m³) 560 560 560 590 Workability 8 with VeBe 12-15 with VeBe 5 with VeBe dry uncompactable mixture

Claims: Use of synthetic organic surface-active substances having wetting properties which are stable in media of a pH value ≦ 12 and particularly within the pH-range of 9 to 12, with exception of dodecylbenzene sulfonic acid triethanolamide, as admixtures or components of admixtures for milling Portland clinker for the production of gypsumless cements with a specific surface area of 350 to 750 m²/kg. Use according to claim 1, characterized in that the synthetic organic surface-active substances are selected from alkylpolyglycolether sulfates and alkylated alkanolamine-polyglycolethers comprising C₁₀₋₁₅-alkyl groups, alkynolamides of C₁₂₋₁₅-acids with aliphatic C₁₀₋₁₅-alcohols and/or sulfated ethoxylated aliphatic alcohols comprising 3 to 10 ethoxy groups, esteramides and esters of sulfated or sufonated linear fatty acids and sulfonated alkylaryl acids, wherein the linear chain comprises 5 to 20 carbon atoms, condensation products of naphtholsulfonic acid or cresol with formaldehyde, and alkylbetaines and sulfoalkylbetaines. Use according to claim 1 or 2, characterized in that the synthetic organic surface-active substances are selected from alkynolamine derivates of ethoxylated nonylphenol, sodium alkylpolyglycolether sulfates, ethoxylated sulfated alkylphenols, mixtures of sulfated ethoxylated alcohols with coconut acid monoethanolamide, triethanolamine salts of alkylbenzenesulfonic acids (alkylmixtures C₈₋₁₄), the ammonium salt of dodecylbenzenesulfonic acid, alkylbenzenesulfonic acid salts based on α-olefins (alkyl mixtures C₁₀₋₁₂), sodium salts of condensation products of β-naptholsulfonic acid and cresol with formaldehyde, and alkanolamine salts of sulfated ethoxylated alcohols (3 to 10 ethoxy groups, alkyl mixtures C₁₂₋₁₅). Use according to one of claims 1 to 3, characterized in that the surface-active substances are present in the form of an aqueous solution or dispersion, particularly a concentrate to be diluted before use. A method for milling Portland clinker for the production of gypsumless cements with a specific surface area of 350 to 750 m²/kg in the presence of a milling admixture, characterized by the use of synthetic organic surface-active substances according to one of claims 1 to 4. The method according to claim 5, characterized in that the synthetic organic surface-active substances are used in an amount of 0.01 to 0.15 mass-%, based on the total mass of the Portland clinker.

Inventors: HRAZDIRA JAROSLAV DIPL-ING, SKVARA FRANTISEK RNDR DRCS, VSETECKA TONAS DIPL-ING, HRAZDIRA, JAROSLAV, DIPL.-ING., SKVARA, FRANTISEK RNDR DRCS, VSETECKA, TONAS, DIPL.-ING., Vsetecka, Tonás, Dipl.-Ing.
Applicants: CESKOSLOVENSKA AKADEMIE VED
Application year: 1990
Main classification: C04B7
IPC codes: B02C23, C04B24