DK174100B1 - Heat-insulating mat or sheet and the use of connected fibres as heat insulation - Google Patents

Description

in DK 174100 B1

This invention relates to heat insulating mats or sheets made of fibers made from silica, calcium oxide, magnesium oxide and optionally alumina. Furthermore, the invention relates to the use of these fibers.

For many years, inorganic fibers, commonly referred to in the industry as "mineral wool fibers," have been made from slag, rock, fly ash, and other by-product raw materials. These fibers have almost invariably had a certain content of alumina, and have typically been produced by melting the slag, rocks, etc. containing alumina and other oxides such as silica, after which the molten material is blown by gas or steam. or bristled to impinge on fast-running rotors, then collecting the obtained blown or spun fibers on an interface. These fibers are then used in bulk or in the form of mats, sheets and the like as high temperature insulators. However, while such mineral wool insulation products have some commercial acceptance, they have certain disadvantages.

First, the slag, rocks and other materials from which mineral wool fibers are usually made may contain relatively large amounts of undesirable oxides and other materials which do not impart a degree of refractory to the fibers produced and, in many cases, actually degrade it. This also adversely affects the general fire resistance properties of the fibers. Since the slag, rocks and other by-product raw materials vary so much in composition, it is further very time-consuming, laborious and in many cases, in fact, impossible to try to adequately control the metal oxide content of the fibers produced within set limits. This unfortunately means that 35 mineral wool fibers used in loose form or in the form of mats, sheets or the like cannot really guarantee a continuous use temperature. The problems mentioned in the manufacture and use of traditional mineral wool fibers show that improvements are needed.

The industry needs a relatively inexpensive and efficient replacement for traditional mineral wool fibers.

In particular, it is desirable to have a replacement fiber which is easy to manufacture and control composition 10 within set limits and which provides a continuously high operating temperature. Fibers with good fire resistance properties are also highly desirable and sought after by the people of the industry.

In the present invention, a heat insulating mat made of inorganic fibers has been developed which is an economical and effective substitute for traditional mineral wool fibers. These mats and sheets have an operating temperature exceeding 650 ° C and are characterized by being made from 20 inorganic refractory fibers of the composition (wt%):

0.1 - 30% MgO

0 to 9.3% Al 2 O 3, the remainder up to 100% being CaO, SiO 2 and not more than 2% random impurities such as any other oxides. It has been found that the mats and sheets in question not only have a high application temperature, but that the fibers also surprisingly also have a high solubility in certain liquids.

In a preferred embodiment, said fibers have a composition consisting essentially of SiO 2, CaO, 0.1-30 wt% MgO and 0-8 wt% Al 2 O 3. These fibers have been found to have particularly good refractory properties.

In another preferred embodiment, said fibers have a composition consisting essentially of: 29-44 wt% CaO, 55-64 wt% SiO2, 0.1-8 wt% MgO and 0-4 weight% Al 2 C> 3. These fibers have very good fire resistance properties and good refractory properties.

By preparing said fiber composition directly from a melt of metal oxides rather than by-product materials of very varying composition which may contain relatively large amounts of materials other than the desired metal oxides, the above problems associated with the manufacture and use of traditional mineral wool fibers.

Since said fibers are made directly from the oxide form of the metals used, no time-consuming and cumbersome methods are required to formulate the desired composition within a fixed range. Said fibers will now further have a continuous use temperature which guarantees their usefulness in situations where such continuous use temperature is needed.

The fibers mentioned have, as will become apparent hereinafter, a continuous operating temperature of up to 815 ° C. Since most of the undesirable components of slag, rock, etc. previously found in traditional mineral wool fibers are not present in said fibers, the latter are very refractory and thus can be used in the lower operating temperature range of normal refractory fibers with a high alumina content, which tends to make them relatively expensive.

This, other aspects and several advantages of the invention will become apparent from the description and appended claims.

The invention further relates to use as a thermal insulation with an operating temperature above 650 ° C.

DK 174100 B1 4 of pulp, blanket or plate forms of joined inorganic refractory fibers of the following composition (wt%): 0.1 - 30% MgO; 0 to 9.3% A 2 O 2, the remainder up to 100% being CaO, SiO 2 and at most 2% 5 random impurities such as any other oxides. Said fiber compositions can be prepared from a melt consisting essentially of SiO 2, CaO, 0.1-30 wt% MgO and 0-9.3 wt% A 2 O 2. In a preferred embodiment, said fibers are made from a melt consisting essentially of SiC> 2, CaO, 0.1-30% by weight

MgO and 0-8 wt% Al 2 O 2. In another preferred embodiment, the aforementioned fibers are made from a melt consisting essentially of: 29-44 wt% CaO, 55-64 wt% SiO 2, 0.1-8 wt% MgO and 0-4 wt% Al 3. The aforementioned fibers have a continuous operating temperature up to the range of from approx. 743 ° C to approx. 815 ° C.

The metal oxides for said composition are available in a relatively pure form from many commercial sources. Physical variables such as particle size may be selected on the basis of cost, handling and similar considerations. The purity of the oxides used must be maintained at a relatively high level, so that no more than approx. 1% to 2% impurities in the form of other oxides, organic materials and the like in the finished fibers, since the presence of such impurities will have adverse effects on the design temperature of the fibers.

As used in this specification, the "application temperature" of fibers is determined by two parameters. The first is the obvious condition that the fibers must not melt or sinter at the specified temperature. It is this criterion which precludes the use of many glass and mineral pulses at temperatures above approx.

650 ° C. The second parameter is that a felt or sheet made of the fibers must not exhibit excessive shrinkage 35 at the application temperature. "Heavy shrinkage" is usually defined to be a maximum of 5% linear shrinkage after prolonged exposure (usually 24 hours) to the application temperature. Shrinkage of mats or sheets used as furnace liners and the like is, of course, a critical feature, because as the mats or sheets shrink there may be gaps between them through which the heat can flow, thereby failing the purpose of the insulation. Thus, a fiber designated as an "815 ° C fiber" will be defined as one which does not melt or sinter and which has an acceptable shrinkage at this temperature but which begins to be insufficient with respect to one or both of the standard parameters at temperatures above ca. 815 ° C.

The fibers are formed in ordinary equipment for inorganic fibers and standard methods are used for the production of inorganic fibers. The preparation will usually take place by electric furnace melting. The various raw materials are granulated to a size usually used for fiber melt materials, or they can be purchased already 20 thus granulated. The granulated raw materials are mixed together and passed to the electric furnace where they are melted by electric resistance melting. The melt formation may be continuous or batch-wise melting, although the former is definitely preferred. The molten mixture of oxides is then fed to fiber forming devices such as spinning machines or blowers. Various types of fiber forming devices are well known and need not be described herein. The fibers thus formed will have a length of from 0.5 to 20 cm and 30 θη diameter in the order of 0.5 to 10 µm with an average fiber diameter of from approx. 1.5 to 3.5 µm.

After forming the fibers, they may be collected in loose form or inserted into separate devices for the purpose of forming the fibers into mats, sheets or similar structures. The hitherto commonly used techniques for forming similar articles of refractory high temperature alumina silicate fibers are quite suitable for use with the fibers used in the mats and boards of the invention.

5

Example 1

A series of fibers used in the mats and plates of the invention were prepared in accordance with the above generalized method. Their respective compositions together with their operating temperature are given in Table I.

DK 174100 B1 7 O æ co in (Ti ^ iN i— r * 2: co in o Γ "i> ln co r- © σ> cr.

CO t- ^ r- in i £> o lo in co vo p- ^ m cm tn oo co LH cn <- ^ r ^ ^ o on in vo oo n ro co r- μ o σ \ ιο lo o in CN r- r- EE o tv n 00 cn H in ro 00 Γ 'r — f <u jQ OO Ν' ID O ^

<0 LO CN CN LD

EH r-

Cm o <3 · m <r- r- in ro i— r- r- W o <- o σ \ om ro r- 10 r- QO i— O (Ti 00 m rj <00 r- U o σι 00 ro o

r) * (N CN ID

Γ- ΡΟ o -¾1 cd id r- rr N <r— Γ- Γ ΟΟ <o · ** 10 o 00 (71 -tf N · 1— I—

C I

• Η W

C <D U

-p ω p tø -H 4-1 M O) cd c Td u M (D dP Π Cd) <D E -P O CN O) D (Λ E! J1 0) 0 o o> e

r (I «s ri -H {OCTiCOU

fcw> <co υ S! << -p 0 DK 174100 B1 8

The above data clearly shows that said fibers will be very useful in high temperature ranges, e.g. from 743 ° C to 8150 ° C, while it was either virtually impossible or very difficult to produce 5 traditional mineral wool fibers which could be used in this area. It should be noted that fiber H was extremely fast melting and that fiber L had very good fiber forming properties.

Example 2

A series of fibers with compositions were prepared as set forth in Table II.

Each fiber was then tested for its fire resistance in accordance with the following simulated fire resistance test procedure:

For testing purposes, a small oven was prepared with an electrically heated flat plate element on the back of the heat source. A 15 cm x 15 cm x 5 cm (thick) sample with a density of 0.028 to 0.048 g / cm 2 of each of the formulated fibers is placed parallel to the element and 2.5 cm from it. Thermocouples are then placed in the center of the fiber sample surfaces. A computer was used to adjust the current via a simple on / off relay system to the heating element. The position of the relay was based on the reading of the thermocouple disposed on the surface of the sample closest to the heating element and the programmed fire-test heating scheme.

The oven was heated so that a standard ASTM E-119 time / temperature curve was followed for a period of 30 hours and 2 hours respectively. In the test used herein, fiber failure is considered to occur when the furnace is unable to maintain the standard temperature per day. ASTM E-119 because the fiber insulation is sintered so much that heat can flow through the furnace wall.

The test results for each of the fibers are given in Table II.

DK 174100 B1 9

W I> - Π (N

M - - - - I

O CN ID O CM

a ro

σι W O (N (N

and - - - - i

O 00 O O CM

in vi m o oo r- cn U - 'v k | o σ we m cm m ro ro τ— nj Vi »-

CM - - - - I

t— in ro o Cm in ro r ~ f \ J io o og · -

W - - - - I

H in a o σι Pm H in ro

I h

Φ

jQ

<d

E-ι o o o o ία - - - - I

in id i— oo Cm in ro «- oo r- o» - o ---- 1

o «- σ σ Cm .µ -P

\ / in ro tn tn <U QJ • P -P w tn Ό Ό Φ <u r- o oj æ «- js x: CQ - - - - I cn oo O vi ko O Cm -rH · µ V m ro i— Ό t CC <β (ΰ P -P tn tn <u tu «- r- oo in η X) xi d, - - - - i ό Ό

O ID we co Cm C C

V m co (0 (0

• P P P

P Cn XI XJ

Cn 0) * h mj

c -P -P> tn P

• h m tu w tu <u

C -P · ιβ Pi E E

-P I — I -P (U Ή · Η

B) P tn Λ -P + J

tn t n tu ή C Φ pq Cm r- cg µ <U dp co µ

<U E -P O (N -P II II II II

Xigcn omOOO tn

HtCirH-pmcnd) di Cm ^ m CMcn> <wu2E-i DK 174100 B1 10

The data in Table II shows the clearly superior fire resistance of fibers G to I compared to fibers A to F. It is of particular importance that these compositions achieve their fire resistance (four ratings) 5 at room densities of fiber diameters that are significantly smaller than with ordinary mineral wool fibers. . The fibers G to I obtained the desired fire resistance at room densities of 0.028 to 0.048 g / cm 2 and fiber diameters from 1½ to 3½ µm. In comparison, ordinary 10 mineral wool fibers achieve their fire resistance at room densities typically from 0.26 to 0.29 g / cm 2 and fiber diameters from 4 to 6 µm.

Thus, the data clearly show that the preferred fibers mentioned have surprisingly superior heat resistance properties.

Example 3

A series of fibers of various formulations listed in Table III were tested for solubility in a saline solution according to the following procedure: A buffered saline solution was prepared by adding to the following concentrations to 6 liters of distilled water: Component Concentration, g / 1 25 MgCl2.6H2 O 0.160

NaCl 6.171 KCl 0.311

Na2HPO4 0.149

Na 2 SC> 4 0.079 CaCl 2

NaHCOg 1.942

NaC2H302 1.066 1 g of each sample of the fibers listed in Table III was then placed in separate closed plastic bottles together with 300 cm 2 of the brine produced and transferred to an ultrasonic bath for 5 hours. The ultrasonic vibration source was set to give a temperature of 40 ° C at the end of the 5 hour period. At the end of the test period, each saline solution containing the fibers was chemically analyzed for SiC> 2 content. The concentration of 5 SiC> 2 in the saline solution was used as a measure of the amount of fibers dissolved during the 5 hour test period. In addition, the continuous use temperature for each of the fibers was measured. The results are given in Table III.

Table III

Fiber Fiber Composition Weight% SiO2 Concentrate Contains AI2O3 SiC> 2 CaO MgO Other in saline application after sap temp __5 hours wt% rature 15 A 46 54 - - - 0.6 1315 B 40 50 6 4 0, 5 871 C 23 60 3 14 - 0.7 754 D 22 48 17 13 - 0.5 749 E 10.7 52 22 16 - 0.7 743 20 F 10.2 52 21 15 - 0.5 743 G 8, 9 52 22 16 - 1.2 743 H 8.7 52 22 16 - 1.7 743 I 8.0 56 30 7 - 5.1 754 J 9.1 40 37 11 2.6 7.7 649 25 K 9 , 3 39 38 14 - 13.0 749 LO 49 28 23 - 67.0 749 temperature for 3% maximum linear shrinkage for 24 hours.

The figure graphically shows the ratio of the alumina content of each fiber to its silica extraction (i.e., solubility) in the brine produced.

The figure clearly shows that said fibers GL containing 10% by weight or less alumina clearly have a surprisingly higher solubility in the prepared saline solution than the AF fibers which are not in accordance with the invention and have greater alumina. miniumoxidindhold. What is surprising according to the invention is evident, in that there is a marked difference in solubility between the fiber F as compared to the fiber G used for the mats or plates according to the invention, although their difference in alumina content is relatively small (ie 10.2 wt. % vs. 8.9% by weight).

Likewise, the fiber J, which has a content of 2.6% impurities, shows that a content of more than 2% impurities reduces the operating temperature of the fiber to below 10 650 ° C.

Particularly noteworthy is the high solubility of the fiber L ".

Reasonable variations and modifications of the above are possible without departing from the spirit of the present invention.

Claims (10)

1. Heat-insulating mat or sheet with an operating temperature exceeding 650 ° C, characterized in that it is made of inorganic refractory fibers of the composition (by weight%): 0.1 - 30% MgO 0 - 9, 3% Al2 O3, the remainder up to 100% being CaO, SiO2 and not more than 2% random impurities such as any other oxides. Heat insulating mat or plate according to claim 1, characterized in that the fiber is soluble in a saline solution prepared by adding the following distilled water ingredients to obtain the stated concentrations: Ingredient Concentration, g / l MgCl2, 6H20 0.160 NaCl 6171 KCl 0.311 Na2HPO4 0.149 Na2SO4 0.079 CaCl2, 2H20 0.060 NaHCO3 1.942 NaC2H302 1.066 Heat insulating mat or sheet according to claim 1 or 2, characterized in that the fiber has a composition comprising at least 22% by weight CaO. Heat insulating mat or sheet according to claim 30, characterized in that the fiber has a composition comprising: a) 0.1 - 8% by weight MgO; b) 0-4 wt% Al 2 O 3; c) 55-64 wt% SiO 2; and d) 29 - 44 wt% CaO. DK 174100 B1 Heat insulating mat or plate according to any one of claims 1 to 4, characterized in that it has an operating temperature of 743 ° C or more. Heat insulating mat or plate according to any one of claims 1 to 5, characterized in that the fiber has a solubility in a saline solution prepared by adding the following distilled water ingredients to obtain the stated concentrations: Ingredient Concentration, g / 1 MgCl 2, 6H 2 O 0.160 NaCl 6.171 KCl 0.311 0.149 Na2 SO4 0.079 CaCl2, 2H20 0.060 NaHCO3 1.942 NaC2H302 1.066 20 on 1.2 ppm SiO2 or greater after 5 hours. 7. Use as thermal insulation with an operating temperature exceeding 650 ° C of pulp, blanket or plate forms of joined inorganic refractory fibers of the following composition (wt%): 25 0.1 - 30% MgO 0 - 9.3% A1203, the remainder up to 100% being CaO, SiC> 2 and at most 2% random impurities such as any other oxides. 30 35 DK 174100 B1 Use according to claim 7, characterized in that the fiber is selected based on the property to be soluble in a saline solution prepared by adding the following ingredients to distilled water 5 to obtain the stated concentrations: Ingredient Concentration, g / 1 MgCl 2, 6H 2 O 0.160 NaCl 6.171 KCl 0.311 0.079 CaCl2, 2H2 O0 .60 NaHCO3 1.942 NaC2H302 1.066 Use according to claim 7 or 8, characterized in that the fiber has a composition comprising at least 22% by weight CaO. Use according to claim 9, characterized in that the fiber has a composition comprising: a) 0.1-8% by weight MgO; b) 0-4 wt% Al 2 O 3; c) 55-64 wt% SiO 2; and d) 29 - 44 wt% CaO. Use according to any one of claims 7 to 10, characterized in that the insulation in mass, mat or plate form has an operating temperature of 743 ° C or more. 30 35 DK 174100 B1 Use according to any one of claims 7 to 11, characterized in that the fiber has a solubility in a saline solution prepared by adding the following ingredients to distilled water to obtain the stated concentrations: Ingredient Concentration, g / l MgCl 2, 6H 2 O 0.160 NaCl 6.171 KCl 0.311 0.149 Na2 SO4 0.079 CaCl2, 2H20 0.060 NaHCO3 1.942 NaC2H302 1.066 15 1.2 ppm SiC> 2 or more after 5 hours.