Calcium silicate powders

Abstract

Calcium silicate powders are provided. The calcium silicate powders comprise porous calcium silicate particles and an additive, the additive being at least partially penetrated into the pores of the particles. The additive is present in an amount of between 1.5 and 50%w, wherein %w is the weight ratio, expressed as percentage, of the dry weight of the additive over the dry weight of the combination of the calcium silicate particles and additive.

Claims

1. A calcium silicate powder comprising discrete porous calcium silicate particles having a specific surface area with a BET value of 30 to 60 m.sup.2/g and a pore size of at least 0.01 microns and no greater than 5 microns, and separate particles of an additive, said additive being at least partially penetrating into the pores of said calcium silicate particles, the additive is present in an amount of between 1.5 and 50%w, wherein %w is the weight ratio, expressed as percentage, of the dry weight of the additive over the dry weight of the combination of said calcium silicate particles and additive, and the additive is an alkali silicate or a combination of alkali silicates.

2. A calcium silicate powder according to claim 1, wherein at least 25%w of the additive is penetrated into the pores of the particles.

3. A calcium silicate powder according to claim 2, wherein more than or equal to 50%w of the additive is penetrated into the pores of the particles.

4. A calcium silicate powder according to claim 2, wherein more than or equal to 75%w is penetrated into the pores of the particles.

5. A calcium silicate powder according to claim 1, said calcium silicate particles comprise synthetic porous calcium silicate particles.

6. A calcium silicate powder according to claim 1, said calcium silicate particles comprise synthetic porous calcium silicate, wherein said porous calcium silicate particles are porous calcium silicate hydrate particles.

7. A calcium silicate powder according to claim 6, wherein said porous calcium silicate particles comprise xonotlite and/or tobermorite crystals.

8. A calcium silicate powder according to claim 7, wherein the weight ratio xonotlite/tobermorite is in the range of 95/5 to 5/95, inclusive.

9. A calcium silicate powder according to claim 5, wherein the porous calcium silicate particles comprise crystalline material in an amount in the range of 60 to 95%w, this %w being based upon the total weight of the particles.

10. A calcium silicate powder according to claim 1, wherein the porous calcium silicate particles have pores providing at least 75% of the particle volume.

11. A calcium silicate powder according to claim 1, wherein said additive is sodium silicate.

12. A calcium silicate powder according to claim 11, wherein the additive is sodium silicate with a SiO2:Na2O ratio of no more than 3.5.

13. A calcium silicate powder according to claim 11, wherein the additive is sodium silicate with a SiO2:Na2O ratio of at least 1.60.

14. A calcium silicate powder according to claim 11, wherein the SiO2:Na2O ratio is at least 3.00.

15. A friction brake comprising the calcium silicate powder according to claim 1.

16. A calcium silicate powder according to claim 1, consisting of said porous calcium silicate particles and said alkali silicate or combination of alkali silicates at least partially penetrating into the pores of the calcium silicate particles.

17. A calcium silicate powder according to claim 1, wherein the discrete porous calcium silicate particles have a specific surface area with a BET value of 30 to 50 m.sup.2/g.

18. A calcium silicate powder according to claim 1, wherein the additive is present in an amount of between 13 and 45%w.

19. A calcium silicate powder according to claim 18, wherein the additive is present in an amount of between 20 and 40%w.

20. A calcium silicate powder according to claim 1, wherein the calcium silicate particles have a pore size of at least 0.1 microns and no greater than 5 microns.

21. A calcium silicate powder according to claim 12, wherein the SiO2:Na2O ratio is no more than 3.25.

22. A calcium silicate powder according to claim 13, wherein the SiO2:Na2O ratio is at least 3.00.

23. A calcium silicate powder according to claim 12, wherein the SiO2:Na2O ratio is at least 1.60.

24. A calcium silicate powder according to claim 14, wherein the SiO2:Na2O ratio is no more than 3.25.

25. A calcium silicate powder according to claim 1, wherein the additive is in the form of waterglass when combined with the discrete calcium silicate particles.

Description

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(1) The present invention will be described with respect to particular embodiments.

(2) It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, steps or components as referred to, but does not preclude the presence or addition of one or more other features, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

(3) Throughout this specification, reference to “one embodiment” or “an embodiment” are made. Such references indicate that a particular feature, described in relation to the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, though they could.

(4) Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art.

(5) According to an embodiment of the invention, Promaxon D of Promat International (BE) is provided and added in a cyclomixer of Hosokawa.

(6) Promaxon D is a crystalline calcium silicate powder, in particular are synthetic porous calcium silicate hydrate particles, comprising 95%w of crystalline calcium silicate hydrate, in particular 80%w of xonotlite and 15%w of tobermorite. These %w are based upon the dry weight of the synthetic porous calcium silicate hydrate particles. The powder has an average particle size in the range of 35 to 85 μm, an oil absorption of about 300 g/100 g and a BET specific surface area of more than 40 m.sup.2/g.

(7) To this powder, while gently agitating the powder, an amount waterglass type sodium silicate waterglass with solid content of about 36%w is provided. The waterglass solution used was Crystal 0075. This amount of waterglass, being the sodium silicate and the solvent being water, was absorbed into the particulates. The SiO.sub.2:Na.sub.2O ratio in the waterglass was 3.22.

(8) This mixture is mixed at high shear during about 5 minutes at 750 rpm using a closed mixing unit. The mixed slurry is sieved using a sieve retaining particles of 400 μm and more, and dried to the air. As an alternative, the mixed and sieved slurry is dried using a fluidized bed drying unit.

(9) 7 mixtures were prepared, wherein for each 100 gram of Promaxon D (dry weight), an amount of waterglass (about 36%w of sodium silicate (dry state) with SiO.sub.2:Na.sub.2O ratio of 3.22) and 64%w of water) was added, the amounts being (in gram) 25, 50, 75, 100, 125, 150 and 200.

(10) As such, calcium silicate powder comprising porous calcium silicate particles and sodium silicate present in an amount of 8.25%w, 15.25%w, 21.25%w, 26.47%w, 31.03%w, 35.06%w and 41.86%w are provided, wherein %w means the ratio, expressed as percentage, of the dry weight of the sodium silicate over the dry weight of the calcium silicate particles and the sodium silicate.

(11) It was noticed that substantially all waterglass was penetrated or infiltrated in the pores of the calcium silicate powder partials. As such calcium silicate hydrate powders comprising porous calcium silicate particles, the sodium silicate and water, which water is either present as such in the calcium silicate powder, or chemically bound to the sodium silicate.

(12) As an alternative, a Nauta mixer type Vrieco-Nauta® conical screw mixer can be used.

(13) As an alternative, the used additive may be a silicone, provided as an aqueous slurry to the mixer. An example of a suitable silicone is Z6289 silicone emulsion of Dow Corning added in ratio between 0.1-10%w, preferably between 2.5 and 3.5%w, such as 3%w, %w being the weight over the dry weight of the Promaxon D.

(14) As a further alternative, the used additive may be a siloxane comprising component, provided as an aqueous slurry to the mixer. An example of a such suitable component is organo modified siloxane Tegomer VSI 4042 of Evonik, added in ratio between 0.1-10%w, preferably between 2.5 and 3.5%w, such as 3%w, %w being the weight over the dry weight of the Promaxon D.

(15) It is to be understood that although preferred embodiments and/or materials have been discussed for providing embodiments according to the present invention, various modifications or changes may be made without departing from the scope and spirit of this invention.