PROCESS FOR PRODUCING CALCIUM SILICATE HYDRATE

Abstract

The present invention relates to a process for producing calcium silicate hydrate under hydrothermal conditions, wherein an organic compound is added in at least one of the process steps and wherein the organic compound has a molecular weight of 100 to 600 g/mol and from 0.02 to 0.035 functional groups per gram of the organic compound, wherein the functional groups being selected from —OH, —COOH, 'COOM.sub.a, —SO.sub.3H or —SO.sub.3M.sub.a, or —C(═O)H, wherein M is hydrogen, a mono-, di- or trivalent metal cation, ammonium ion or an organic amine radical and a is ⅓, ½ or 1. Further the invention is directed to the calcium silicate hydrate produceable according to the process of the present invention and its use as curing accelerator for hydraulic binders.

Claims

1.-13. (canceled)

14. A process for producing a composition comprising calcium silicate hydrate, the process comprising the steps of a) reacting a calcium hydroxide source with a silicon dioxide source in the presence of water under hydrothermal conditions at a temperature in the range of from 100° C. to 400° C. for a period of from 1 hours to 30 hours, b) bringing in contact i) the process product from step a) and ii) a water-soluble polymeric dispersant in an aqueous medium while introducing kinetic energy, wherein an organic compound is added in at least one of the steps a), b) or to the process product after completion of step b), wherein the organic compound has a molecular weight of 100 to 600 g/mol and from 0.015 to 0.035 functional groups per gram of the organic compound, wherein the functional groups being selected from —OH, —COOH, —COOM.sub.a, —SO.sub.3H, —SO.sub.3M.sub.a, or —C(═O)H, wherein M is hydrogen, a mono-, di- or trivalent metal cation, ammonium ion or an organic amine radical and a is ⅓, ½ or 1, wherein when the organic compound is added in step a), the temperature in step a) is chosen below the melting point of the organic compound used and wherein when the organic compound is added to the process product after completion of step b), and if the process comprises a step c) in which the process product of step b) is added to a building material mixture comprising a hydraulic binder or latent hydraulic binder, the organic compound is added between steps b) and c).

15. A process according to claim 14, wherein the organic compound is selected from the group consisting of dextrose, galactose, tartaric acid, sodium tartrate, gluconic acid, sodium gluconate, citric acid and sodium citrate.

16. A process according to claim 14, wherein the organic compound is added in an amount of 0.5 to 6% by weight based on the amount of the calcium silicate hydrate, calculated as dry component, of the produced composition.

17. A process according to claim 14, wherein the organic compound is added to the process product after completion of step b).

18. A process according to claim 14, wherein the molar ratio of calcium to silicon in step a) is in a range of from 0.5 to 2.5.

19. A process according to claim 14, wherein the kinetic energy in step b) is effected by introduction of mixing or shearing energy.

20. A process according to claim 19, wherein the kinetic energy in step b) is effected by milling.

21. A process according to claim 14, wherein step b) is carried out until the process product from step a) has a d(50) particle size of ≤800 nm, determined by static light scattering according to ISO 13320:2020.

22. A process according to claim 14, wherein the reaction in step a) is made in the presence of a foaming agent.

23. A process according to claim 14, wherein the water-soluble polymeric dispersant is a comb polymer having polyether side chains.

24. A process according to claim 14, wherein the water-soluble polymeric dispersant is a polycondensation product having polyalkylene oxide side chains.

25. A calcium silicate hydrate composition comprising 60-85% by weight of calcium silicate hydrate 10-20% by weight of water-soluble polymeric dispersant 0.4-3.6% by weight of the organic compound based on the dry weight of the composition, wherein the organic compound has a molecular weight of 100 to 600 g/mol and from 0,015 to 0,035 functional groups per gram of the organic compound, wherein the functional groups being selected from —OH, —COOH, —COOM.sub.a, —SO.sub.3H, —SO.sub.3M.sub.a or —C(=O)H, wherein M is hydrogen, a mono-, di- or trivalent metal cation, ammonium ion or an organic amine radical and a is ⅓, ½ or 1.

26. A method comprising utilizing the calcium silicate hydrate according to claim 25 as curing accelerator for hydraulic or latent hydraulic binder.

Description

EXAMPLES

[0250] Dextrose (CAS-number: 50-99-7) (Sigma Aldrich). Dextrose with the chemical formula C.sub.6H.sub.12O.sub.6, has a molecular weight of 180,16 g/mol and 0.033 functional groups per gram of the organic compound according to the invention.

[0251] Na-gluconate (CAS-number: 527-07-1) (Sigma Aldrich). Na-gluconate with the chemical formula C.sub.6H.sub.11NaO.sub.7, has a molecular weight of 218,137 g/mol and 0.0275 functional groups per gram of the organic compound according to the invention.

[0252] Na-tartrate (CAS-number: 51307-92-7, racemic mixture) (Sigma Aldrich). Na-tartrate with the chemical formula C.sub.4H.sub.4Na.sub.2O.sub.6, has a molecular weight of 194,08 g/mol and 0.0206 functional groups per gram of the organic compound according to the invention.

[0253] Na-citrate (CAS-number: 18996-35-5) (Sigma Aldrich). Na-citrate with the chemical formula C.sub.6H.sub.5Na.sub.3O.sub.7, has a molecular weight of 258,07 g/mol and 0.0155 functional groups per gram of the organic compound according to the invention.

[0254] Hydrothermal C—S—H (ht—C—S—H) has been prepared according to WO 2018/154012, page 33, line 6-14 and exhibited a moisture content of 42 wt.-% and a particle size d.sub.90<1 mm after crushing (determined via Laser granulometrie according to ISO 13320:2020).

[0255] A precharge of 1000 kg was prepared containing 566 kg of h—C—S—H (58 wt.-% solids content), 158 kg of the dispersing agent P3 described in WO 2018/154012, page 32, line 4-8 (45 wt.-% solids content), 1.4 kg of defoamer (Semifinish 2, BASF, 57% solids content) and 275 kg of water yielding a slurry with a solids content of 40 wt.-%.

[0256] The slurry in the precharge was continuously stirred at a moderate rate with a dissolver and then fed into a milling aggregate (MacroMedia, fabricated by Buhler group) in a circular fashion to carry out a first pregrinding step. The milling chamber exhibited a volume of 6 L and was equipped with a rotor-stator element with attached steel bars of a size of 300 mm and Y-stabilized ZrO.sub.2 balls of a size of 3 mm. The pregrinding was performed for 75 minutes with a throughput rate of 18.7 m.sup.3/h and agitator velocity of 10.2 m/s yielding an energy input of 21 kWh/t suspension. The pregrinding was terminated when a d.sub.50 of 8.8 μm and a d.sub.90 of 14.6 μm was reached—determined via Laser diffraction (Horiba LA 950 V2 instrument fabricated by RESCH).

[0257] The so obtained preground suspension was then diluted to a solids content of 28 wt.-% and 2 kg of the material was finegrinded with a laboratory scaled agitated ball mill. The utilized agitated ball mill (Labstar, fabricated by Netzsch) was characterized by a volume of 0.7 L. The grinding chamber consisted of a rotor shaft and discs made of polyurethane and a slit size of 0.4 mm. Grinding beads of Y-stabilized ZrO.sub.2 with a size of 0.5 mm were used up to a degree of filling of ˜80 vol.-%.

[0258] The suspension was ground batch-wise with two passes in total. The mill was operated at a power of 1.0 kW with the agitator having a rotational speed of 9 m/s.

[0259] The final suspension showed a fine particle size distribution with a d.sub.50 of 190 nm. Furthermore, the suspension displayed a viscosity of ˜100 mPas (23° C., Brookfield spindle 64, 12 rpm) directly after grinding and was thus perfectly suited for pratical use (pumping, spraying). Additionally, the acceleration potential was determined with heat-flow calorimetry. The experimental protocol is described in WO 2018/154012, page 36, line 37 to page 37, line 7. All samples were dosed at 6 wt.-% of suspension based on cement weight. the acceleration potential was then quantified by calculating the total heat released during 0.5 and 6 hours of the cement reaction as a measure for the progression of the silicate reaction.

[0260] The suspension was then devided into several samples containing either no further additives (Comparative examples 1 and 2) or with 3.0 and 5.4 wt.-% addition of low molecular weight additives with a high degree of functionalization (based on weight of solid ht—C—S—H) (Inventive examples 3 to 16).

[0261] The suspensions were then stored unagitatedly in a sealed glass vial on the laboratory bench at room temperature or at 40° C. and the rheological and acceleration properties were monitored over time.

[0262] It was observed that the reference suspension without further additive stored at room temperature was prone to a progressive viscosity build-up over time which eventually led to a gel formation after a couple of months (Comp.1 and Comp. 2 in Table 1), denoted by a viscosity>50,000 mPas in the given measurement setup. The same behavior was accelerated by a higher storage temperature.

[0263] Surprisingly, it was found that samples containing the low molecular weight additives with a high degree of functionality were able to strongly retard the viscosity build-up while still maintaining a high acceleration power of the C—S—H suspension. The acceleration factor displayed Table 1 is calculated as the heat of hydration in the presence of the additive containing suspension normalized to the mix with the reference suspension at the given storage temperature. The value thus serves as a quantitative measure for the retarding influence of the viscosity controlling additives.

[0264] Especially the dosage of sodium tartrate and glucose only had a very minor effect on the acceleration potential of the suspension while clearly preventing the gel formation over more than 35 weeks at room temperature.

TABLE-US-00001 TABLE 1 Summery of the viscosity and acceleration performance of the comparative and inventive suspensions (Comp. = Comparative Example; Inv. = Example according to the invention) Storage Viscosity of susp. @ Experiment temperature 23° C. [mPas] HoH Rel. number Sample description [° C.] 4 weeks 10 weeks 35 weeks [J/g] AF Comp. 1 Ground ht-CSH (28%) 23 100 20000 >50000 107.5 1.00 Comp. 2 Ground ht-CSH (28%) 40 1700 >50000 >50000 112.9 1.00 Inv. 1 6.1% Ground ht-CSH (28%) + 3 wt-% Dextrose 23 100 100 100 104.8 0.98 Inv. 2 6.1% Ground ht-CSH (28%) + 3 wt-% Na-gluconate 23 100 100 100 99.9 0.93 Inv. 3 6.1% Ground ht-CSH (28%) + 3 wt-% Na-tartrate 23 100 100 100 103.0 0.96 Inv. 4 6.1% Ground ht-CSH (28%) + 3 wt-% Na-citrate 23 100 100 320 103.3 0.96 Inv. 5 6.1% Ground ht-CSH (28%) + 3 wt-% Dextrose 40 100 1000 >50000 110.2 0.98 Inv. 6 6.1% Ground ht-CSH (28%) + 3 wt-% Na-gluconate 40 100 7200 >50000 100.8 0.89 Inv. 7 6.1% Ground ht-CSH (28%) + 3 wt-% Na-tartrate 40 100 400 >50000 105.1 0.93 Inv. 8 6.1% Ground ht-CSH (28%) + 3 wt-% Na-citrate 40 100 2500 >50000 105.7 0.94 Inv. 9 6.2% Ground ht-CSH (28%) + 5.4 wt-% Dextrose 23 100 100 100 103.5 0.96 Inv. 10 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-gluconate 23 100 100 100 89.5 0.83 Inv. 11 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-tartrate 23 100 100 100 100.6 0.94 Inv. 12 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-citrate 23 100 100 210 97.7 0.91 Inv. 13 6.2% Ground ht-CSH (28%) + 5.4 wt-% Dextrose 40 200 1800 >50000 118.3 1.05 Inv. 14 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-gluconate 40 2300 7400 >50000 93.1 0.82 Inv. 15 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-tartrate 40 100 2300 >50000 105.6 0.94 Inv. 16 6.2% Ground ht-CSH (28%) + 5.4 wt-% Na-citrate 40 100 1100 >50000 103.0 0.91