FI65414C - FOERFARANDE FOER FRAMSTAELLNING AV SYNTETISKT SCAWTIT 6 CAO. SIO2. CACO3. 2 H2O - Google Patents

Description

.... ANNOUNCEMENT

^ §5Γα W <11) utlAggningsskrift 6541 4 C (45) rc.Ur.Ui -: y;: y 10 05 1934 ^ T ^ (51) K ».lk.3 / Int.ci.3 C 01 B 33 / 24 FINLAND — FI N LAND (21) P * t * fittlhik * rnui - P «t * nun * 6ttnln | 772151 (22) Htktmlipllvi —AnsSknlngidag 00.07-77 '' (23) Alkupilvft - Giltl | h «tsda | 08.07.77 (41) Tullut (ulklMktl - Bllvlt offentllj 23.01.78

Patent and Registration Office ......... , . , „..

e ^,. ,,, (44) Date of Nihtiviktlptnon et al. - 31.01.84

Patent and registration authorities AiwOkan utitgd och uti.ikrtftan publicarad (32) (33) (31) Pyydatty etuoikeus - Begird prlorltet 22.07.76

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2632921.5 Proof-Styrkt (71) Rheinische Kalksteinwerke GmbH., Postfach 1340, D-5603 Wiilfrath, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (72) Heinzz, Velbert,

Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (74) Forssen & Salomaa Oy (54) Method for the production of synthetic scawtit 6 CaO · 6 SiO ^ * CaCO 2 · · 2 H 2 O This invention relates to a process for the preparation of synthetic scawtit 6 CaO · 6 SiO 2 · CaCO 2 · 2 H 2 O by a hydrothermal reaction.

Scavtite, which is spelled Scavtite in English, is a naturally occurring mineral. Its occurrence and properties are described, for example, in the following references:

The American Mineralogist: Vol. 22, 222-224;

Butter. 40, 505-509; 510-514;

Butter. 43, 498-502.

Due to the increased technical importance of synthetic calcium hydrosilicates, mainly xonols, tobermors and the like, as fillers, pigments, reinforcing fillers, adjusting agents and the like, the problem arose in a simple manner of preparing a synthetic compound or, accordingly, to improve the properties of hitherto available xonoliths.

It has now surprisingly been found that a synthetic scawtlt is obtained by reacting CaO and / or CaCOH 2 hydrothermally with pilic acid by adding calcium carbonate in the presence of water.

This was very surprising because scawts, as can be seen from numerous studies, are not a mixture of xonoliths and calcium carbonate, but an independent and original mineral with characteristic crystallographic values and, as will be shown, characteristic X-ray diffraction properties.

It has been found that the process according to the invention makes it possible to prepare, in addition to mixtures of xonolites and scawtts, also with pure scawtlt, if the starting materials are added in suitable proportions. Selecting the molar ratios between the lime component, pilic acid and CaCO 2 sn from 6: 6: 0.2 to 6: 6: 1 gives 20% scawtlt and xonolite as pure sxawtlt.

Figure 1 shows four X-ray diffraction patterns for comparison, namely for pure xonolites, xonolites with 25 X and 50% scawtltla, and pure scawtit. These diagrams show that typical xonolite interferences decrease with increasing scawtlt concentration and have disappeared with pure scawtit. Similarly, increasing scawtit interference vo absorbs into the delta.

According to the invention, the ratio of water to solids in the starting mixture is adjusted for the hydrothermal reaction so that the mixture contains 5-70% by weight, preferably 20-40% by weight of solids. When adding CaO, the water required for hydration must also be added.

According to the invention, it is further suitable to carry out the hydrothermal reaction at a temperature of 150 to 240 ° C for a period ranging from 48 hours at the lowest temperature to 5 hours at the highest temperature. The temperature range of 180-220 ° C is preferably used, the reaction times correspondingly varying from 16 to 8 hours.

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It is further suitable to introduce lead acid and calcium carbonate in finely ground form, preferably in a grain size such that 90% by weight is less than 100. In order to achieve a shorter reaction time and a purer product, these substances are best used in a grain size of less than 40 μm.

Lead acid is added in the form of quartz powder. As calcium carbonate, suitable limestone powders can be used in a similar manner, e.g. filter materials from grinding plants and ground calcite or chalk. The surface area of these 2 substances is more than 1 m / g measured by the BET method.

In the hydrothermal reaction, a solid cake with a hardness of about 0.10 to 150 kg / cm is formed from the starting mixture, depending on the chosen ratio of water to solids. It contains considerable amounts of moisture and, after crushing and grinding, can be made into xonollt scawtit suspensions or, as the case may be, into pure scawtit suspensions or, by suitable drying operations, into a finely ground powder.

The curves in Figure 2 show how the increase in the light reference value occurs with increasing scawtit concentration. At the same time, the BET surface area decreases. The light reference value A is specified according to DIN.

When practically tested scawtlt according to the invention as a filler with pigment thiol properties for colors, it turned out that excellent fieldability is achieved with a high degree of whiteness. At the same time, the so-called oil number is lower than with all other calcium hydrosilicates, i.e. the need for a binder is reduced. Compared to the known white pigment, titanium oxide, a considerable reduction in pigment costs is obtained for the colors. Replacing 80% of titanium oxide with scavtit achieves the same fieldability as using titanium oxide alone. This means that pigmenting costs are about 50% lower with the same color opacity.

Example; Commercially available calcium hydroxide, quartz powder and calcite powder are used as raw material for the preparation of scawtlt, with scawtlt pltols of 25, 50 and 100 Z and a residue of xolollt. More than 90% of the powder has a grain size of less than 40 μm.

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The raw material analysis is shown in the following table:

Raw material analysis

Calcium Quartz Calcite hydroxide powder powder

SiO 2 0.18 99.15 0.59

Fe 2 O 3 0.06 0.05 0.12 Al 2 O 3 0.06 0.30 0.18

Mn 2 O 3 0.005 0.005 0.005

CaO 74.00 0.10 53.88

MgO 0.40 1.38 SO 3 0.04 0.00

Na 2 O + K 2 O 0.2

Annealing loss 24.93_0.2_43.81_ These raw materials are added in the amounts indicated by weight in the following table by adding 60 parts by weight of water, calculated per 40 parts by weight of the mixture of solids.

Appendix table

Scawtit 100 50 25

Xonolite 0 50 75

CaCO 3 (40 μm) 12.49 6.24 3.12

Calcium hydroxide 48.49 51.95 53.68

Quartz powder (40 ym) _39.02_41.81_43.20_

After good mixing, the pulp is filled into this mixture and reacted hydrothermally for 10 hours at 15 ° C at a vapor pressure corresponding to 200 ° C.

In the hydrothermal reaction, a solid cake is formed with a spray strength 2 of about 50 kg / cm and containing 52 Z of water. This cake can be dried and then ground or further processed directly into suspensions. The following analytical values are obtained for the dried reaction products:

Scawtit 100 50 25

Xonolite 0 50 75

SiO 2 42.95 45.98 47.49

Fe 2 O 3 0.06 0.06 0.06 Al 2 O 3 0.18 0.18 0.18

Mn 2 O 3 0.005 0.005 0.005

CaO 46.44 45.91 45.65

MgO 0.39 0.32 0.29 SO 3 0.02 0.02 0.02

Na 2 O + K 2 O 0.09 0.09 0.09

Loss on ignition 9.85 7.42 6.21 of which CO2 5.47 2.73 1.37 H 2 O 4.38 4.69 4.84

If the data in the example above are followed, but calcium carbonate and quartz powder are added, which have a grain size smaller than 100 μπ up to 90% by weight, the hydrothermal reaction must begin to be extended to 60 hours. Scawtit is formed compared to the data in the example to 80%.