Production of calcium hydroxide nanoparticles and their use as accelerators in mineral binder compositions

Patent metadata

Field	Value
Publication number	US-11780738-B2
Application number	US-201916976704-A
Country	US
Kind code	B2
Filing date	Mar 22, 2019
Priority date	Mar 22, 2018
Publication date	Oct 10, 2023
Grant date	Oct 10, 2023

Abstract

An aqueous suspension including 5 to 65 wt. % of calcium hydroxide, wherein at least 50 wt. % of the calcium hydroxide is present in the form of nanoparticles, and at least one compound for stabilizing the suspension. The aqueous suspension accelerates the setting of mineral binder compositions without adversely affecting the processing properties of the composition.

First claim

The invention claimed is:

1. A method for producing an aqueous suspension, comprising: (a) providing an aqueous solution A comprising at least 5 weight % of a water-soluble calcium salt, (b) providing an aqueous solution B comprising at least 5 weight % of an alkali metal hydroxide, (c) metering solution A and solution B simultaneously into a continuous reactor and contacting solution A and solution B such that solution A and solution B are mixed rapidly and intensely to form a suspension, wherein the rapid and intense mixing of the solution A and the solution B takes place continuously and a mixing time is below 1 minute, wherein the solution A and solution B are metered under pressure of at least 5 bar into the continuous reactor by means of pumps, wherein the pressure and a resulting velocity of the solution A and the solution B on introduction into the continuous reactor produces the rapid and intense mixing, and (d) discharging the suspension from the continuous reactor, where a compound for stabilizing the suspension is added to the solution A, to the solution B or to both solutions, or to the suspension produced, wherein the suspension includes calcium hydroxide in the form of nanoparticles having a particle size D90 of below 800 nm, measured by dynamic light scattering with photon cross-correlation spectroscopy, and wherein the suspension is free from calcium silicate hydrate.

2. The method as claimed in claim 1 , wherein the compound for stabilizing the suspension is a comb polymer and comprises structural units of formula I and structural units of formula II,

where:
R 1 , in each case independently of one another, is —COOM, —SO 2 —OM, —O—PO(OM) 2 , —PO(OM) 2 , —(CO)—NH—C(CH 3 ) 2 —CH 2 —SO 3 M, —CH 2 —SO 3 M, =

R 2 , in each case independently of one another, is H, —CH 2 COOM or an alkyl group having 1 to 5 carbon atoms,
R 3 , R 5 and R 6 , in each case independently of one another, are H or an alkyl group having 1 to 5 carbon atoms,
R 4 and R 7 , in each case independently of one another, are H, —COOM or an alkyl group having 1 to 5 carbon atoms,
M, independently of one another, represents H + , an alkali metal ion or an alkaline earth metal ion;
m is 0, 1 or 2,
p is 0 or 1,
X, in each case independently of one another, is —O—, NH— or —NR 8 —, and
R 8 is a group of the formula -[AO] n —R a , where A is a C 2 to C 4 alkylene, R a is H or a C 1 to C 20 alkyl, cyclohexyl or alkylaryl group, and n is 1 to 250.

3. The method as claimed in claim 1 , wherein the suspension comprises 0.01 to 2.5 mol of an alkali metal salt based on 1 mol of calcium hydroxide.

4. The method as claimed in claim 1 , wherein the water-soluble calcium salt is selected from the group consisting of calcium nitrate, calcium chloride, calcium acetate, calcium formate, calcium thiocyanate, or a mixture thereof.

5. The method as claimed in claim 1 , wherein the water-soluble calcium salt is calcium nitrate.

6. The method as claimed in claim 1 , wherein the aqueous solution A contains the calcium salt in an amount within a range of 10 to 87 weight %.

7. The method as claimed in claim 1 , wherein the aqueous solution A contains the calcium salt in an amount within a range of 20 to 80 weight %.

8. The method as claimed in claim 1 , wherein the aqueous solution B comprises the alkali metal hydroxide in an amount in a range of 20 to 40 weight %.

9. The method as claimed in claim 1 , wherein the alkali metal hydroxide is sodium hydroxide.

10. The method as claimed in claim 1 , wherein the aqueous solution A and the aqueous solution B are metered into the continuous reactor such that a molar ratio of calcium salt to alkali metal hydroxide is in a range of 1:2.0 to 2.4:1.

11. The method as claimed in claim 1 , wherein the mixing time is below 30 seconds.

12. The method as claimed in claim 1 , wherein the mixing time is below 1 second.

13. The method as claimed in claim 1 , further comprising concentrating the suspension to increase a solids content by removal of water.

14. The method as claimed in claim 1 , further comprising cleaning the suspension to remove auxiliaries or byproducts by means of ion exchange, filtration, or ultrafiltration.

15. The method as claimed in claim 1 , wherein a mixing energy with which the solution A and the solution B are rapidly and intensely mixed is not more than 200 kJ per kilogram of calcium hydroxide suspension produced.

Assignees

• Sika Tech Ag

Inventors

• Juilland Patrick
• Gallucci Emmanuel
• Schönenberger Denise
• Pegado Luis
• Frunz Lukas
• Eberhardt Arnd

Classifications

• C01F11/02 Primary

  Oxides or hydroxides (production of lime C04B2/00) · CPC title

• C04B22/064

  of the alkaline-earth metals · CPC title

• C04B24/2647

  containing polyether side chains · CPC title

• C04B40/0039 Primary

  Premixtures of ingredients · CPC title

• B82Y40/00

  Manufacture or treatment of nanostructures · CPC title