CA2026965C - Material for heat and electrical insulation with a capacity of selective absorption of electromagnetic radiation spectrum and vibration, its production process and use - Google Patents

Abstract

New material based on hydrosilicates, containing 11.3 A
tobermorite, crystallized in groups of coral form crystals, with a smaller quantity of fibers of organic or inorganic origin, the production process is "wet", the material is applied in civil engineering and fields of technology with strict conditions requiring temperature resistant materials, with good mechanical strength and good isolation properts.

Description

MATERIAL FOR HEAT AND ELECTRICAL INSULATION WITH A CAPACITY OF
SELECTIVE ABSORPTION OF ELECTROMAGNETIC RADIATION SPECTRUM AND
VIBRATION, ITS PRODUCTION PROCESS AND USE
Technical field of Invention The invention pertains to the field of technology for the production of heat and electrical insulation materials, resistant to high temperatures up to 1100°C, based on calcium hydrosilicates belonging to the following classes of the International Patent Classification: C 048 35/22 and C O1B
32/24.
Technical Problem The technical problem solved by the invention is the production process of a new material resistant to temperatures up to 1100°C, with a heat insulation capacity, having a mechanical strength up to 32 kg/cm2, the capability of selective absorption of electromagnetic waves, radiation and vibration, good electrical resistance, water resistance, resistance to acids and frost, thermal shocks and various industrial combustion gases.
State-of-the-Art Heat insulating material based on calcium hydrosilicates and fibrous raw materials are already known. the commercial titles _under which they are offered to the market are: Marilite 1, Monoiux 500, Monolite, ... Vidasil.
All known materials based on calcium hydrosilicates may be divided into two categories. Materials belonging to the first ~ 5~ ~1 category are those having technical characteristics ranging in the following intervals of values:
volume density 600-850 kg/m3, thermal conductivity 0,2 - 0,35 V~/mo0~
maximum working temperatures 150 - 85U°i;, modulus of rapture 5 - 1? l~iN/m2, neither thermal shocks resistance, nor resistance to water, vibration, ect., has been registeeed.
~1'h6 heat insulating material based on a aalcium hydrosilicate manufactured under the production process described in YU patent application no. P-553/85, falls under the second category. This heat insulating material represents a new quality among products based on calcium hydrosilicates, both fox its homogenous ' mineral composition and for its technical propertied which are, ~~udging by their number and value, a novelty in the area of calcium hydrosilicate based materials. 7:ts properties have extended the application of calcium hydrosilicates to fields in which, prior to its appearance, the use of such a kind of material was not thought possible.
The mechanical properties of the calcium hydrosilicates produced in accordance with 7cU pat, application no. P-553/85, as well as numerous other properties, such a fire resistance, have become challenging. 'fhus;this material has been .fitted into the most diverse places and under the moat diverse conditions, offering a satisfactory solution for numerous technical problems.
applying this heat insulating material, many consumers have noted that an improvement of its mechanical strength would provide greater application possibilities. with ~aore frequent use, stricter requirements had been set before it, in an effort ~to find a material that would, possibly, have the same scope ~ of characteristics, but with increased values. ' 'rhe technical characteristics of the calcium hydrosilioate material containing 11 A tobermorite, well-known in the present state-or-the-art, and produced i.n accordance with the process described.in YU pat, application no. P-553/Fi5 are as follows:

non-combustibility /JUS U1.040 and JUS U.J1.060/, volume density /ASTM C 303/ from 220 to 317.5 kg/m3 -10 compression strength at 5o deformation /ASTM C 165/:
20°C 600° 900°C
1.60 MPa 1.40 MPa 1.22 MPa bending strength /ASTM C 203/ 0.91 MPa thermal conductivity /JUS U.J5. 040/ depending on the temperatures:
mean temperature W/m°K
50 0.079 149 0.107 427 0.157 linear shrinkage at temperatures of 860°C /ASTM C 356/
shrinkage per length 2.Oo shrinkage per width 2.Oo shrinkage per thickness 2.150 weight loss 9.10 strength of bolt support /ASTM D-1037, ASTM C-656/:
transverse force of bolt arrest is 25 kg resistance to rapid temperature changes /DIN 51068/:
resists temperature shocks 20+

Description of solution ~t'he proposed invention represents a new process oI obtaining calcium hydrosilicate material, resistant to high temperatures, having universal insulation ctualities and a good mechanical strength, as well as resistance to thermal and other shocks.
'rhe proposed process differs from that disclosed in YU pat, application, no, 553/85, because the product manufactured through it represents a new member in the family of materials of this kind, with significant differences in the values of technical characteristics.
'rhe new process allows the production of a new material, the therwo-physical properties of which are twice as great as those pertaining to the calcium hydroailitsate produced in the process designed by the same author, and filed under YU patent application no, t'-553/g5, ~1'he values of other technical characteristics rise also increased, wome of them that are hardly present in the calcium hydrosilicate 11 a tobermorite produced in accordance witli YU yet, application no,. 553/85,are increased in proportion to other properties, giving the material new values in usd, ftre difference lies in the ratio of the constituents of the process UaU:~i4~, as well as in the altored concentration of additives, and in the relationship between the liquid and solid phase, in the change of temperature, e,i, of pressure at which the reaction between c:a0 and X102 takes places and in the duration of this reaction, as well as in the change of the fiber length and quantity of water used, liy increasing the temperature and Finding an optimal quantity of liquid in relatioxi to the solid phase, better conditions have been obtained for a synthesis s~eaction of calcium hydrosilicate 11.3 ~i tobermorite, it is interdsting to note that the form of tobermorite mineral crystals is similar to that of sea corals. ~fhis crystalline form in the newly created tobermorite phase, as well as the total degree of crystallisation of this phase, considerably effect the technical characteristics. .trues distribution and other properties of the fibrous component, should also be added to this, Npart from these significant positive et~ects on the quality, the proposed process is more economical in the sense that i,t provides a greater degree of nominal equipment capacity exploitation, as well as of energy saving, because the pulp contains a smaller , quantity of liquid phaeE which, besides bc:inE a part of the product,also sreves as a medium for the development of the chemical synthesis of tobermorite. It is certain that these findings are not ultimate, and that each knowledge requires a verification and affirmation of its role in respect to the quality of the material.
~t'hrough the new process, a material is obtained, the technical properties of which are strictly reproductional, and are within a tolerance range equal to the scope of incoming parameters, The invention which is the proposed proeess,is conducted in the following manner:
natrium carboxymethyl cellulose solution is prepared, and is successively dosed by Ca/UH/2 and quartz powder. 'then, a suspension of water and fibers is added to this suspension, and mixed. 'rhe obtained pulp is poured into dies which are then subject to treatment with~eaturated water vapor of 11.5 - 12,5 bars, for a period of 16 to 28 hours. ':che material is removed from the cooled dies and is air-dried at tetnperatures up to 250oU. . .
~fhe process of pulp hardening unCil~:. reaching the strength of the new material, ie the result of the following chemical reaction:
a Ca/OH/2 6 HiU2 5,5 H2U q/J/

5 UaU 6 8102 10.5 ti20/tobermorita/

'fhe technical properties of the mirterial depend on the degree of the transition of (:a0 and 8102 into the new mineral form, but apart from the quantity of the newly formed tobermorite phase, the properties of the material are also influenced by ' the form arid size of the crystals in the new phase, its distribution in the product, as well as the overall microstructure of the obtained material. In order, to achieve continuity of the chemical reaction for the production of calcium hydroailicate out of the solution, it is necessary, to have a liquid phase provided with sufficient quantities of Ga and 8102 ions, at all times, as well as with such queatities of energy necessary for creating the new mineral phase.
As the mechanism of the reaction for the formation of calcium hydrosilicate, tobermorite lacks clarity from a theoretical point of view, one thing is certain, that it is possible to prove by this process that the formation of tobermorite runs directly, and that the state of the formed phase may range from amorphous to exceptionally fine crystalline. It has also been shown that the micro shape of the crystal may be in the form of sheets or fibers arranged in a radial or uneven crossed pattern, The mobility of the liquid phase in the synthesis period seems to be very important, as well as the fact that it always contains Ca and alU2 ions, capable of bonding and remaining bonded, ~fhe role and quantity of the liquid phase becomes crucial, and the texture of the material is in function of the microstructure of the new phase, of pore size and distribution, ~1'hese are only the basic parameters effecting the establishment of technical properties of ttie material, and it is probable that in this process, not all the inter-relations .between, the process parameters and the quality of the synthesis of the new material have been detected, 'fhe organic tibers that may be used in the process are of cellulose composition, approximately 5 mm long, Nmong the inorganic fibers, chrisotile asbestos with 6 mm long fibers, may be used. Furthermore, medium class vermiculite may be used and all other mineral fibers showing resistance in an alkaline medium at a temperature of 200°C.
~1'he material has a wide application range, which proves that it incorporates a number of necessary properties, which make it fit to be built into various places in whioh oalcium hydrosilieate material had never before been used:
hs the surface layer of industrial plant hearths in which light fuel oil, propane-butane gas and natural gas are burnt, es a protective coating of steel constructuona, However, with thd appearance of the calcium hydrosilicate, produced in accordance with YU pat, application no. P-553/85, the requirements set by consumers regarding their desire to have a calcium hydrosilicate material with improved mechanical properties were defined more clearly then ever, 'fhe new type of calcium hydrosilicate with 11,3 A tobermorite, according to the ~.nvention /tiidasil 4UU/, fulfills all the strictest requirements for fire resistant materials built into housing constructions, public buildings and public transportation means, The technical properties of this new type of calcium hydrosilicate, Yidasil 4UU, will help solve problems related to protection against natural electromagnetic radiation. 'rhe electrical resistance of this material goes up to 200,UU0 ~i~1 for 10 rum thick plates, Tta properties of not conducting heat and not burning, of enduring direct. contact with molten metal and hot gaaea, provide excellent possibilities and widespread application, '1'hia also ~ustifiea the belief that through different production processes, raw materials CaU and X102, may serve for the manufacturing of materials with a very wide spectrum of technical possibilities.
ixample 1, 1,6 kg of hydraterd lima containing ?2 wt w of Ca0 and~1,632 ~kg of quartz powd~rr with g6 wt io of aiU2, and having a particle size of below 63 microna,were successively added to g~litere of water containing. 12 g of natrium carboxylcelluloae, 'Po this suspension, a mixture of ~~. liters of water and 161 g of 4 mm long cellulose fibers waa added, 'i'hd mixed components were 'poured into a die dimensioned 0,6 x 0,2 x U,2 m, 'fhe die containing the pulp was subject to saturated water vapor preadure of 11,0 - 12,5 bars, over a period of 18 hours, after the die had cooled, a block with a moisture content of approximately 67,masa ~o was removed from the die, and air-dried at a temperature of approkimately 100°C, Lxample 2, 55?.6 kg of calcium hydroxide containing ?2 wt io of .CaU and 5o5.f3 kg of quartz powder containing g8 wt io of u102, were aucceaeively added to 2600 liters of water, in whack 5,3 kg of natrium carboxylcelluloae had been dissolved, Into the obtained suspension, 1560 liters of water containing 56,13 kg of 5 mm long cellulose fibers was added, .after thorough mixing, the pulp waa poured into dies, which were then exposed to a pressure of 11.5-12.5 bars, over a period o:f 14 hours. After cooling, blocks having a moisture content of approximately 67 wt o were removed from the dies and air-dried at temperatures of 200°C.
Technical properties of the material for heat and electrical insulation according to the invention /Vidasil-400/ are as follows:
SHAPE: Flat plates and pipe profiles DENSITY: At room temperature 400 kg/m3 BOARDER TEMPERATURE OF APPLICATION IN CONDITIONS OF LONG
EXPLOITATION IS 1000°C
RAY DIFFRACTION ANALYSES: 1 Tobermorite 2 Quartz THERMAL CONDUCTIVITY FOLLOWING THERMAL TREATMENT AT 900°C
- Temperature °C Thermal Conductivity Hot Face Cold Face Mean W/mK
201 27 114 0.118 400 41 220 0.127 800 91 448 0.166 SPECIFIC HEAT
Mean temperature °C 65,209,320,427,483 Specific heat J/kgK 721,771,866,894,928,947 PRESSURE RESISTANCE
At 5o To Maximum T°C deformation destruction MPa MPa room 3.28 4.30 over 900°C 2.42 4.57 BENDING RESISTANCE
Temperature°C MPa Psi room 1.48 215 over 900 0.61 88 RESISTANCE TO BOLT DRAWING
Temperature°C Max Load/kg/ Max Load(~N) room 32.7 0.32 over 900 30.4 0.30 THERMAL SHOCK RESISTANCE
The material when annealed at a temperature of 1100°C "survived"
a quench test in cold water. this test was carried out in order to obtain good quality results.
DETERMINATION OF THERMAL SHOCK RESISTANCE
PARAMETER Rst The Rst parameter value of 44.80 m1~2 was obtained for material treated at 900°C

Plate width 0.5 mm 20 Plate width 10 mm 200,000 MODULES OF ELASTICITY
Temperature°C GPa Psi room 1.57 227650 over 900 0.74 107300 SHRINKAGE o AFTER 24 HOUR HEATING
SHRINKAGE
Temperature°C
Length Width Thickness 600 1.4 1.97 0.94 800 3.43 2.89 2.55 TOTAL OPEN POROSITY 80%
/figure 1/ and on the ultraviolet radiation spectrum absorption /figure 2/ are presented

Claims (9)

1. Material for electrical and heat insulation with the capacity of selective absorption of the electromagnetic spectrum of radiation and vibration, water resistant, resistant to acids, molten metals and temperatures up to -180°C, with a great mechanical strength, based on calcium hydrosilicates, wherein calcium hydrosilicate 11.3 A tobermorite, contained in the material in 90 wt %, with a coral-like microstructure form, is mixed with a quantity of approximately 5 wt % of fibers of organic or inorganic origin, with a micropore area of over 60 m2/gr, and a total porosity of approximately 80 %.

2. Material according to claim 1, having the following properties /ASTM/:
volume density of approximately 400 kg/m3, thermal conductivity of approximately 0.11 - 0.16 W/mK, pressure resistance of approximately 3.2 MPa, linear shrinkage after 24 hour heating at 1273.15 K max. 3.5 %, thermal shock resistance 26, bending resistance approximately 1.48 MPa, module of elasticity approximately 32 kg, electrical resistance of sample plates, 10 mm thick, approximately 200,000 M.OMEGA., absorbs electromagnetic radiation spectrum of 0.8 - 3 microns, micropore area of over 60 m2/gr.

3. Material according to claim 1, wherein the organic fibers are based on cellulose/paper, flax, hemp/, length of fiber approximately 5 mm.

4. Material according to claim 1, wherein the inorganic fibers are chrisotile asbestos, length of fiber 6 mm, or vermiculite, size of sheets approximately 5 mm.

5. Process for the production of a material for electrical and heat insulation with the capacity of selective absorption of the electromagnetic spectrum of radiation and vibration, water resistant, resistant to acids, molten metals and temperatures up to -180°C, with a great mechanical strength, based on the calcium hydrosilicate 11.3 A tobermite, wherein, hydrated lime and quartz powder containing a minimum of 97.0 wt % of SiO2 and with a pore size below 53 microns, the CaO:SiO2 weight ratio being 0.6 -0.73, is successively added to water, in which, in relation to the solid phase, 0.3 - 0.45 wt of atrium carboxylmethil cellulose is dissolved, then to this suspension, a mixture of water and 3.5 -5.5 wt % of fibers in relation to the solid phase, is added, so that the ratio liquid/solid phase is 2.9 - 4, thenceforth, NaOH
is added to the pulp in a quantity of 0.02 wt % in relation to SiO2, the obtained pulp is poured into dies which are exposed to saturated water vapour pressure of 11.00 - 12.5 bars for a duration of 16 - 20 hours, then the hard molded material is removed from the dies and air-dried at temperature to 250 °C.

6. Process in accordance to claim 5, wherein the organic fibers are based on cellulose/paper, flax, hemp/, length of fiber approximately 5 mm.

7. Process according to claim 5, wherein the inorganic fibers are chrisotile asbestos, length of fiber 6 mm, or vermiculite, size of sheets approximately 5 mm.

8. Products containing the material according to claims 1 to 4.

9. Products containing the material produced in accordance with the process contained in claims 5 to 7.