CH624370A5 - Process for the preparation of chemically hydrophobicised lime - Google Patents

Description

624 370

2nd

PATENT CLAIMS

1. A process for producing a chemically hydrophobic lime with an improved physical structure, characterized in that burnt lime is hydrated with water which contains up to 15% by weight of reactive stearates.

2. The method according to claim 1, characterized in that the stearates are formed in situ in the presence of lower alcohols.

Lime is used as a binding agent in many building materials and these building elements are later exposed to various natural influences, which may cause the material to be gradually destroyed by physical, chemical and biological means. Moisture plays the most important role here, so that in many cases protection of the building against the influence of moisture must be provided.

However, the protection of building materials and constructions by painting and coating with water-permeable protective materials, as is characteristic of modern, multilayer, thin-walled facade constructions, for the most part, does not produce the necessary and expected results.

The sensitivity of lime-based building materials to moisture is due to three characteristic properties of this material:

1. due to the capillary-porous structure,

2. by the capillary activity, that is to say water readiness (hydrophilicity) and

3. by the tendency to physical and chemical reactions with the water itself or the substances dissolved in it.

Moisture not only gets into the building material from the outside and not only in the liquid state (e.g. as rain), it can also penetrate in other ways, e.g. through capillary condensation, against which the conventional protective measures are ineffective.

Lime-based building materials can only fulfill their function in the long term if their overall cross-section remains free of moisture in liquid form. This can be achieved by hydrophobizing the raw mass, which results in capillary inactivation of the otherwise hydrophilic structure.

The hydrophobicization of building materials is now generally done in two different ways:

1. Hydrophobizing the surface, that is, impregnating the already built-in material with water-repellent substances and

2. Hydrophobization of the binder, that is, the addition of water-repellent substances in the manufacture of the building materials.

This hydrophobization can be achieved both physically and chemically, depending on whether the water-repellent additive is chemically inactive and thus only bound to the base material by physical forces (adsorption), or whether the hydrophobizing additive is chemically reactive and therefore with the base material reacts chemically.

However, it must be emphasized that in lime-based building materials it is customary today to enter the hydrophobic additive in both cases only after the lime has been extinguished.

It has now been found that the above disadvantages can be avoided by carrying out the chemical hydrophobization by means of reactive stearates during the lime quenching.

The process according to the invention for producing chemically hydrophobized lime with an improved physical structure is characterized in that burnt lime is hydrated with water which contains up to 15% by weight of reactive stearates.

The chemical reaction of lime quenching takes place in several phases:

1. Water absorption: adsorption and absorption of water by calcium oxide

2. Formation of the Intermediate Calcium Oxide Dihydrate:

Ca0 + 2H20 ^ CaO • 2H20

3. Implementation reaction:

CaO • 2H20 ^ Ca (0H) 2 + H20 + 15.5 kcal)

4. Formation of lime flakes and aggregates from the resulting calcium hydroxide particles.

In each of these four reaction phases a favorable influence of the reactive stearate and the resulting hydrophobic calcium stearate can be observed:

1. In the water absorption phase, the reactive stearate, together with the water in which it is dissolved, is initially attached to the high-energy tips and edges of the calcium oxide aggregates, where it partially reacts with the lime to calcium stearate, which, due to its hydrophobic properties, continues the course inhibits hydration and thus enables the water to penetrate deeper into the quicklime aggregates, so that the necessary stoichiometric ratio of lime and water is more fully established. This postponement of the actual deletion process also makes it possible to delete quicklime aggregates with a dense structure that would otherwise be more difficult to delete. In this way, a more complete extinguishing of the quicklime is promoted.

2. The formation of the intermediate CaO • 2H20 is promoted in the same way.

3. In the implementation phase, the stearate reacts chemically with the calcium hydroxide formed, calcium stearate being produced, which makes the lime water-repellent and moreover

4. its dispersing influence prevents the resulting calcium hydroxide particles from precipitating and forming tight structures. This creates a system that consists of many small particles and is very energy-intensive due to this considerable increase in surface area. The lime flakes formed are of a loose structure and therefore high in energy; this leads to a rich «fat» lime, which is reminiscent of lime dough.

In addition, the stearate also influences the physicochemical processes involved in lime quenching: the lime produced in this way is water-repellent on the one hand and has a better physical structure on the other. It generally consists of many small particles with a large surface area in the form of flakes with a loose structure, moreover the hydroxide particles are usually very small, which enables better carbonation and more regular crystallization.

In fact, what is still shown, mortars made of chemically hydrophobicized lime, in addition to their water-repellent properties, also have a higher strength than mortars made of non-hydrophobicized (normal) and / or physically hydrophobicized lime.

tries

The following experiments were carried out at the Faculty of Technology and the Faculty of Mining, Geology and Petroleum Engineering at the University of Zagreb and at the Croatian Institute of Building, Building Construction Department, in Zagreb.

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3rd

624 370

Production of the hydrophobic limes and lime mortar material

1. The lime used came from IGMO, building materials industry, Ozalj, Yugoslavia.

2. Ground limestone from GIRK «Kalun», Drnis, Yugoslavia, served as a filler.

3. Stearates from Bärlocher GmbH, Munich, Federal Republic of Germany, were used as water-repellent additives, namely:

a) Bärophob-NBL, zinc stearate dry powder, 100%,

b) Barophob-ASP, ammonium stearate dry powder, 100%,

c) Bärophob-FL-1.50% alcoholic solution of triethanol-

amine stearate.

Changing factors

The following factors were varied to investigate their influence on the properties of the treated lime:

1. The water-repellent additives themselves: Bärophob-NBL, Bärophob-ASP and Bärophob-FL-1.

2. The concentration of the water-repellent additives in the cleaning compound in chemical hydrophobization: Barophob-ASP was in the concentrations 0.05; 0.15; 0.25; 0.5 and 0.75% and Barophob-FL-1 in the concentrations 0.025; 0.075; 0.125; 0.25 and 0.375% added, each time based on the total amount of plaster.

3. The manufacturing phase in which the water-repellent additive is added during the chemical hydrophobization of the lime: Bärophob-ASP and Bärophob-FL-1 are added to the water used to extinguish quicklime, in a concentration of 0.8; 2.4; 4.0; 8.0 and 12.0%, which corresponds to the following values of the concentration of the pure stearates in the mortar mass: for Barophob-ASP: 0.05; 0.15; 0.25; 0.5 and 0.75% and for Barophob-FL-1: 0.025; 0.075; 0.125; 0.25 and 0.375%.

The hydrophobized lime was prepared during the lime quenching by using an aqueous solution of reactive stearates (bärophob-ASP and -FL-1) to extinguish the quicklime, in concentrations of 0.8; 2.4; 4.0; 8.0 and Ï2.0%.

In the case of the 0.8% solution, the aqueous solution of the water-repellent additive was applied in an amount of 0.65 kg to 1 kg of quicklime. When the concentration of the reactive stearate was increased, the amount of solution required for quenching also increased, so that in the case of the 12% solution it was 0.72 kg to 1 kg quicklime.

In the case of water without hydrophobic additives, the amount of extinguishing water for 1 kg quicklime was 0.60 kg.

As the concentration of the water-repellent additive increases, the start of the hydration reaction is postponed more and more. For example, when measuring the reactivity of the lime, it was found that the temperature 10 minutes after the addition of an 8% solution of Barophob-FL-1 was only 26 ° C., while it was 10 minutes after the addition of water without addition at 58 ° C. The initial temperature was 15 ° C in both cases.

Production of lime mortar

The lime mortar was made by mixing lime and aggregate in a weight ratio of 1: 7 (about 1: 3 vol.), From:

non-hydrophobic (normal) lime,

physically hydrophobicized lime and chemically hydrophobicized lime.

The amount of water required for mortar preparation depended on the type of lime used. In the case of mortar made from normal (non-hydrophobic) lime, 0.17 kg water per kg dry mortar mixture (lime and aggregates) was used.

For physically hydrophobicized lime with the lowest concentration of water repellant additives (0.8%), 0.15 kg of water was required. As the concentration of the water-repellent additives increased, the water requirement decreased, so that at a concentration of 12% 0.12 kg was sufficient.

With chemically hydrophobicized lime, a regularity similar to the relationship just described was found. In the case of the lowest concentration of the water-repellent additives (0.8%), 0.12 kg of water were required per kg of dry mixture. When the concentration of the water-repellent additives was increased, the amount of water required decreased and at a concentration of 12% it was only 0.09 kg per kg of the dry mixture of lime and aggregates.

Material testing

The test specimens from the lime mortars described were stored under constant conditions and prepared for the test that took place 30 and 90 days after the mortar was produced.

The purpose of testing the limes and lime mortar was to determine, by means of a physical-mechanical test of water absorption, hydrophobicity and strength, which laws govern the influence of hydrophobization on the properties of lime and lime mortar, depending on the type of water repellent Addition, its concentration, the manufacturing phase in which the water-repellent additives are added, and the type of waterproofing (physical or chemical).

Physical-mechanical tests

The physical-mechanical tests (table) were carried out on test specimens made of lime mortar at the age of 30 and 90 days. They include testing the following properties:

1. The water absorption capacity (table) was measured by placing the test specimens in water at a hydrostatic pressure of 5 cm water column for 24 hours. The weight gain was determined at certain intervals.

2. The compressive strengths (table) were tested according to standard methods on 4 x 4 x 16 cm prisms.

3. The hydrophobicity was measured as:

a) wettability of the surface,

b) Beading off and sucking up water drops and c) Water absorption at a hydrostatic pressure of 25 cm water pressure.

The results of the tests on the wettability of the surface are shown in the table.

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Table 1

Results of the physical-mechanical test of water-repellent lime mortar

Type of water repellent Type of water repellent

Physical hydrophobization Bärophob-NBL zinc stearate, 100% powder

% pure stearate in the mortar mass 0.1 0.3 0.5 1.0

Name of the test specimen

Chemical waterproofing

Bärophob-ASP not Bärophob-FL-1 Bärophob-ASP not

Ammonium stearate, 100% powder hydro- triethanolamine.stea., 50% alk. Solution ammonium stearate, 100% powder hydro-

phobic phobic

1.5 0.1 0.3 0.5 1.0 1.5 - 0.025 0.075 0.125 0.25 0.375 0.05 0.15 0.25 0.5 0.75 -

1*

Oil

-t w

CS

SC ©

CS

Ci

O

M

O"

■ <* CS

72

CS

■ x-o

1; CS

* t rc

CS

O

03

Ö

«

s

6

Ù

6

6

6

O

m

«

CQ

ffl

6

6

6

6

6

O

-

»■ H

CO

-

-

T

* 7 *

* 7 *

"O

CS

CS

CS

CS

CS

CS

CS

CS

CS

CS

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

fO

0.4

0.2

0.2

0.2

1.4

1.2

0.4

0.3

0.2

1.2

0.6

0.8

0.3

0.2

0.2

0.9

0.6

0.5

0.4

0.3

2.4

0.4

0.2

0.2

0.1

1.5

1.5

0.3

0.3

0.1

1.1

0.9

0.9

0.6

0.3

0.3

2.1

1.0

0.8

0.5

0.2

2.6

0.9

0.3

0.3

0.3

2.0

2.2

0.5

0.6

0.4

2.1

1.0

1.5

0.4

0.2

0.3

1.4

0.6

0.5

0.4

0.3

5.4

0.5

0.2

0.2

0.1

2.9

2.5

0.5

0.5

0.1

2.0

1.4

1.1

0.8

0.3

0.3

3.4

1.6

1.1

0.6

0.3

5.7

0.9

0.4

0.4

0.3

2.7

3.1

0.6

0.7

0.4

2.9

1.4

1.8

0.5

0.4

0.3

1.7

0.7

0.7

0.5

0.4

8.6

0.6

0.3

0.3

0.1

4.3

3.4

0.5

0.6

0.2

2.7

1.8

1.2

0.8

0.3

0.3

4.9

1.9

1.2

0.7

0.3

7.9

1.1

0.5

0.5

0.4

4.0

4.2

0.7

0.7

0.6

4.5

1.9

2.9

0.8

0.4

0.4

2.4

0.8

0.8

0.6

0.5

11.1

0.8

0.3

0.4

0.3

6.7

4.7

0.6

0.7

0.3

4.6

2.3

1.3

0.8

0.4

0.4

6.9

2.2

1.4

0.9

0.4

11.0

1.0

0.4

0.5

0.3

5.3

5.1

0.8

0.8

0.7

■ 5.7

2.4

2.9

0.8

0.5

0.5

3.0

0.8

0.8

0.6

0.5

11.2

1.0

0.4

0.5

0.3

9.0

6.1

0.6

0.8

0.3

6.0

2.8

1.3

0.9

0.4

0.4

8.4

2.5

1.6

1.0

0.5

11.1

1.1

0.5

0.5

0.4

7.8

6.1

0.7

0.9

0.7

8.0

2.8

3.0

0.8

0.5

0.5

4.2

0.9

0.9

0.7

0.6

11.2

1.2

0.4

0.5

0.3

10.0

7.4

0.7

0.9

0.4

7.9

3.3

1.3

0.9

0.4

0.4

10.2

2.8

1.6

1.0

0.5

11.1

1.4

0.5

0.5

0.4

9.1

6.6

0.8

0.9

0.8

10.0

3.3

3.1

0.8

0.5

0.5

5.8

1.0

0.9

0.7

0.6

11.2

1.4

0.4

0.5

0.3

10.1

8.3

0.7

0.9

0.4

9.5

3.8

1.4

0.9

0.5

0.4

10.6

3.1

1.7

1.1

0.5

11.2

1.8

0.8

0.8

0.5

10.8

8.0

1.1

0.8

0.7

11.6

5.8

3.4

0.8

0.5

0.7

9.8

1.4

1.1

0.9

0.7

11.2

2.0

0.5

0.7

0.4

10.3

9.2

0.9

1.1

0.5

11.3

5.8

1.5

1.0

0.5

0.5

10.9

3.6

1.8

1.1

0.5

11.2

2.5

1.2

1.2

0.9

11.4

9.3

1.7

1.4

1.2

11.9

8.4

3.8

1.2

0.9

0.8

10.5

2.0

1.6

1.2

1.1

11.2

2.6

0.8

0.8

0.6

10.5

9.5

2.1

1.3

0.7

11.5

7.2

1.7

1.1

0.7

0.6

11.1

4.2

2.1

1.5

0.7

11.2

22.0

17.1

12.0

9.1

27.2

23.4

20.0

18.6

14.3

26.4

35.3

32.0

28.9

23.4

15.5

36.8

33.5

32.7

20.4

14.1

32.4

42.5

36.0

27.3

20.1

48.2

43.4

37.3

29.5

23.8

47.1

56.3

51.6

49.2

40.7

35.0

58.2

53.1

50.8

43.0

33.4

50.6

90

70

30th

50

100

90

80

60

20th

100

90

70

60

30th

10th

100

80

50

30th

10th

100

70

60

20th

0

90

80

40

10th

0

100

90

60

30th

10th

0

90

60

30th

10th

0

100

Exam type

5 sec. 30 sec. 1 min.

5 min. 10 min. 30 min.

1 H.

6 hours 24 hours

2. Compressive strength (kp / cm2)

3. Hydrophobicity, wettability of the surface (%)

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I.

1)

ß

• see

1

C / Î CO cd ^

To

30 days 0.8

90 days 0.7

30 days 1.4

90 days 1,2

30 days 1.8

90 days 1.7

30 days 2.4

90 days 2.4

30 days 2.9

90 days 3.4

30 days 3.7

90 days 4.6

30 days 4,5

90 days 5.7

30 days 7.0

90 days 7.8

30 days 7.8

90 days 8.3

30 days 26.0

90 days 44.8

30 days 100

90 days 90

Remarks:

1. Each result given is the average of three measurements.

2. The names of the test specimens are taken from the literature.

The last number in each case is the concentration of the hydrophobic substance based on the lime (physical hydrophobization) or the extinguishing water (chemical hydrophobization)

3. Mixing ratio (lime: aggregates) = 1: 7

4. Dimensions of the test specimens:

7x5 x3 cm (to determine the water absorption capacity)

Test specimen surface: 142 cm2 = 0.0142 m2 Test specimen volume: 105 cm3

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624 370

When comparing the results of the physical and chemical hydrophobization, it is noticeable that the results achieved by chemical hydrophobization are considerably more favorable, which is particularly true for the alcoholic solution of triethanolamine stearate (Barophob-FL-1). Obviously the presence of alcohol is beneficial. Since the chemical hydrophobization was carried out with much lower stearate concentrations (especially in the case of ammonium stearate and triethanolamine stearate), but the results (table) are comparable or even significantly better, the chemical hydrophobization is considerably cheaper than the physical one. This is also due to the distribution of the hydrophobic particles in the lime mass, which is much more homogeneous in chemical hydrophobization than in physical and approaches the ideal state. The properties of the mortar improve over time (storage).

The water absorption capacity decreases with physical as well as chemical hydrophobization with increasing concentration of the water repellent additive. In order to reduce the water absorption capacity to the same extent, however, a lower increase in the concentration of the water-repellent additive is required for chemical hydrophobization. The water absorption capacity in chemical hydrophobization with 0.2 to 0.5% reactive stearate is reduced to less than 1% - compared to approximately 11% for mortar without hydrophobic additives. In the case of physical hydrophobization, 0.5 to 1.5% and more stearate is required for the same reduction in the water absorption capacity.

The compressive strength decreases with increasing stearate concentration. In the case of physical hydrophobization, 5 the strength is reduced even at the lowest concentrations of the additive; only a slight increase can be ascertained only with ammonium stearate, which was physically admixed. In chemical hydrophobization, an initial significant increase in the compressive strength at the lowest concentrations of the water-repellant additives is noticeable. When the concentration is increased, the strength decreases, namely in a much narrower concentration range than with physical hydrophobization. Apparently there is a kind of "saturation".

i5 In the case of chemical hydrophobization, the optimum concentrations of the reactive stearates for influencing the water absorption capacity and the strength are 0.1-0.5% based on the mortar mass. In this area, the strength of the mortar is approximately the same or slightly 20 times greater than that of mortars made from non-hydrophobic lime.

It was found that favorable results were also obtained when using the following water repellent mixture: NH4OH (24% strength) 11.0 parts by weight of stearic acid and 13.4 parts by weight

25 CH3OH 10.0 parts by weight

C2HsOH 10.0 parts by weight mixed with water in a ratio of 1: 1 to 1: 9 (by weight).

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