CA2062892A1

CA2062892A1 - Mineral wool product

Info

Publication number: CA2062892A1
Application number: CA002062892A
Authority: CA
Inventors: Gerd-Ruediger Klose; Karl Rudolph
Original assignee: Individual
Current assignee: Deutsche Rockwool Mineralwoll GmbH and Co OHG
Priority date: 1991-03-13
Filing date: 1992-03-12
Publication date: 1992-09-14
Also published as: NO920974D0; NO920974L; EP0503555A1; CZ278250B6; SK278928B6; FI920761A0; CS74992A3; FI920761A

Abstract

ABSTRACT OF THE DISCLOSURE

Mineral wool products essentially consist of mineral fibers, in particular rockwool, and a binder hardening under heat treatment. To create a mineral wool product withstanding high thermal stresses and releasing no noxious gases and further retaining the conventional strengths, the invention proposes that the binder be water-dissolved/water-dispersed aluminum meta-phosphate Al(PO3)3 or alternatively water-dissolved monoaluminum phosphate Al(H2PO4)3.

Description

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TITLE OF THE INVENTION
A MINERAL WOOL PRODUCT
BACKGROUND OF THE INVENTION
The invention relates to a heat-hardened mineral wool product consisting essentially of mineral wool fibers, in particular rockwool, and a binder(s) which will harden when heat-treated.
The expression "mineral wool product" includes most products made from mineral wool, such as mineral wool rolled insulating felts, insulating panels, insulating mats, laminar mats and other shaped bodies, such as insulating tubes for covering pipes, and virtually any type body which is subject to pêrmanent or changing thermal stresses (heat). Illustra-tively, a "mineral wool product" includes a product formed of mineral wool fibrous material used for heat insulating appli-cations, such as insulation for ovens, homes, pipes or con-duits, or the like.
The manufacture of mineral wool products, particularly mineral wool insulation, is carried out by transforming silicate melts into fibers. The diameters of the vitreously solidified mineral fibers range from about l~m to about lO~m with averages of 4~m to 5~m.
Aqueous solutions of phenol-urea formaldehyde resins have been found to be practical binders for the manufacture of mineral wool products/insulation. Such resins, when present at an early stage of polycondensation, are substantially soluble in water and, therefore, are highly dispersible when introduced into the flow of fibers with the result that the fine mineral fibers are very thinly coated with the resin and link or bond together substantially at point-contact sites.
The binder content in the insulation is generally less than 8%

2 ~

by weight with the remaining 92% by weight being the mineral wool fibers. Moreover, lubricants are added to enhance hydrophobic properties and to increase the "touch" or "feel."
Such lubricants can consist of, for example, oil-in-water emulsions, mineral oils, silicone oils, silicone resins and modified silicon resins.
Because an aqueous medium is used to disperse the phenol-formaldehyde resin, the emission of possibly ecologically injurious organic solvents is avoided, and industrially more significant, the cooling rate of the fibers is raised to such an extent that they solidify in a vitreous manner at tempera-tures so low that pre-hardening of the fiber films or droplets on the fibers in associated conventional collecting chambers is prevented. The process requires the individual mineral fibers to be collected in the collecting chamber after which they are stratified to a desired thickness and are fed between a pair of compression belts in a constant flow of fibers to a conventional hardening oven. It is in the hardening oven that the manufacture of the insulaticn material is completed with the thickness and density being determined by the predeter-mined space between the compression belts and the initial density/thickness of the fibers sandwiched and/or compressed therebetween. The heat of the hardening oven irreversibly hardens the phenol-formaldehyde resin into a pressure-setting plastic at temperatures of between 250C - 300C.
A substantial deficiency of utilizing organic phenol-urea formaldehyde resin is that it will decompose at relatively high temperatures and in the process of decomposing odorous and possibly health-damaging gasses are generated. The thermal resistance of the hinder is roughly 250C to 325C
and, therefore, is well below the melting point of the fibers 2 a ~

which is preferably higher than 1000C with respect to fibers such as those fused from raw materials, namely, greenstone, basalt or the like.
Many attempts have been made to replace organic fibers by inorganic fibers, illustratively water glasses have been tried as substitutes to bind the fibers. The same is also true for making solid fibers with clay minerals keing suitable in this respect. Such fibers can be bound by using the sol-gel process, for instance with sodium-boron-silicon compounds.
This creates a very brittle binder and very large amounts of binder are required. As a result, the conventional process/
technology of the mineral wool industry are generally inappli-cable. Furthermore, insulation made in the latter convention-al manner lacks desired/mandatory flexibility as, for example, an initial density range < 200 kg/m3 required in numerous applications. In other applications elasticity is a mandatory property but is found wanting n such conventionally manufac-tured fiber insulation.
It is also known that aluminum metaphosphate in the binary system Al203-P205 is a re]ati.vely yood vitrifying agent.
Compositions with higher contents of aluminum oxides, for instance AlPO4, are found unsuitable before they solidify in crystalline form, they differ substantially in their expansion coefficients with respect to the expansion coefficients of the associated binder and mineral wool/glass wool/fiberglass fibers, and they detach from the latter and fail to achieve the desired bond.
There are also chain-structured polyphosphates, for instance sodium polyphosphate, which, however, can only form water-soluble glasses but even in such cases, there is no 2 ~
assurance that a long-lasting bond between the fibers can be achieved.
_UMMARY OF THE INVENTION
An object of the present invention is to avoid the disadvantages heretofore noted in the manufacture of a mineral wool product and, of course, the mineral wool product per se by producing a mineral wool product possessing requisite strength properties even when subject to high thermal stress (high heat) and can be manufactured by a process which will not generate odorous or health damaging gases.
The object of the present invention is achieved by utilizing as a binder aluminum metaphosphate Al(PO3)3 dispersed/dissolved in water. In practice, the aluminum metaphosphate can be prepared as a micro-fine powder which is dispersed in water and is sprayed in uniform very finely dis-persed form onto hot mineral wool fibers. Due to the latter, a substantial aclvantage is achieved in that the mineral wool product or insulation can be processed or stressed thermally up to the softening point of the mineral fibers without the formation of noxious gases.
A further advantage of the invention is an excellent and long-lasting bond is achieved between the binder and the mineral fibers. One reason for this advantage is that the meta-phosphoric acid forms annular molecules of different sizes. The conventional strength properties are thereby retained, and the final mineral wool product of the invention can be processed into rolled insulating felts, insulating panels, insulating mats, laminar mats, or into any arbitrary shaped bodies desired for a particular application, such as cylinders for insulating heating/air conditloning ducts, liquid conveying pipes or the like.
'L

~3~2 Advantageously the proportion of aluminum meta-phosphate is about 3% to 20% by weight, and is preferably 7% to 12% by weight relative to the total weight.
The mineral wool product of the invention is preferably made from mineral fibers, foremost alkali-poor fibers, such as rock wool.
In ~urther accordance with this invention, a lubricant such as mineral oil or oil-in-water emulsions is added in a finely dispersed form during the manufacture of the mineral wool product.
Preferably, the impregnation of the binder and/or the lubricant and/or the thickener with the mineral fibers is achieved by impregnation through conventional impregnating means or through the utilization of an aerosol or a steam phase which creates total saturation/impregnation of the mineral wool product or insulating material.
P.n example of a speciflc ~process for producing a mineral wool product or insulating material of the present invention is as follows:
Aluminum meta-phosphate Al(P03)3 is dispersed in water and modified by the various plastics as earlier defined, and is sprayed alone or together with lubricants, such as mineral oils, oil-in-water emulsions in finest form (atomized), etc.
onto the hot mineral fibers. The plastic additives used jointly with the natural hydration content of the aluminum meta-phosphate first cause adequate bonding of the binder films or droplets to the fibers. At the same time the binder reactivity is retained. This is the basic presumption for the fibers so impregnated be:ing collected and beiny fed in a known manner to a hardening oven. The fibers so impregnated are fed at a predetermined thickness/density as a constant flow of 2 ~ ~ 2 ~ ~ 3 fibers between compression belts, as described earlier, into a hardening oven. The end product is, of course, dependent upon the space between the compression belts, the dwell time and the density of the fiber flow, the thickness, the initial density of the fibers, the fiber orientation, etc. but the end product can be so regulated to produce a desirably flexible mineral wool product, particularly adapted for heat insulation applications. During the latter heating, the moisture and the proportion of plastic are removed by means of a flow of hot air between 250C and 500C, preferably between 250C ad 350C. The desired phosphate glass bond is formed both with the preferably alkali-poor mineral fibers and with each other.
Thus, because of the very similar expansion coefficients of the phosphate glass and the fiber glass, permanent bonds are achieved.
Alternatively, the aforementioned prior art problems are by utilizing as a monoalumlnum phosphate Al(H2PO4)3.
The expression "monoaluminum phosphate" shall be con-strued herein as being generic. The literature also uses the general designation of "aluminum hydrogen phosphate" or "aluminum dihydrogen phosphate." Within the scope of the invention, the binder used also may be in a special form, namely, it may be water-dissolved monoaluminum phosphate trihydrate Al(P03)3.3H20 or an aluminum dihydrogen phosphate of chemical formula Al(H2PO4)3.3H20.
By thermally treating the fibers impregnated with the de-scribed binders at a temperature higher than 250C, an acid triphosphate AlH2P301o is formed and upon further raising the temperature above 500C, especially to 600~C, the binder is transformed into a long-chain aluminum polyphosphate and a t'~ ~

cyclical aluminum tetrametaphosphate. The temperature-dependent different degree of transformation of the particular binder is deliberately made use of to achieve, on one hand, flexible binders low in dust to insulate periodically operated highly thermally stressed equipment, such as furnaces and the like. When used in such equipment, the binder in the thermal-ly highly stressed zones of the equipment will be transformed irreversibly into water-insoluble polyphosphates or tetrameta-phosphates. In the outer, thermally less stressed zone of the equipment, the binder remains reversible. Thereafter, the mineral wool product with the compound contained in it remains markedly flexible and elastic on account of the binder.
Another advantage of this reversible state is that the binder permits, for instance during equipment rests, atmospheric moisture being absorbed by the mineral wool product, whereby the dust bonding of the mineral wool product is advantageously influenced.
Advantageously with respect to other practical applica-tions, the binder shall already be in the desired transforma-tion stage in the course of manufacturing the mineral wool product in that the length of insulating mineral wool is made to pass through an oven set to the corresponding temperature.
The above discussion regarding the aluminum metaphosphate also applies to the previously cliscussed group of monoaluminum phosphates. In this case, as well, the advantage is achieved that the mineral wool products or insulators can be used thermally up to the softening point c,f the mineral fibers without forming, for instance by thermal dissociation of organic substances, noxious or unpleasantly odorous gases.
Several advantageous implementations of the invention are discussed below. ~dvantageously a thickener such as polysaccharides, carbo-oxyl-methyl cellulose, polyvinyl alcohol or a mixture of phenol-formaldehyde-urea-resin may be added.
The aluminum meta-phosphate dispersed in water and modified by the various plastics, or the monoaluminum phos-phate dissolved in water, is sprayed, alone or together with lubricants such a mineral oils, oil-in-water emulsions in finest form, onto the fibers. The plastic additives used jointly with the natural hydration content of the aluminum meta-phosphate or the monoaluminum phosphate first cause adequate bonding of the binder films or droplets to the fibers. At the same time the binder reactivity is retained.
This is the basic presumption for the fibers so impregnated being collected and being fed in a known manner to a hardening oven. Because of the spacing between the compression belts or rollers and on account of the corresp~nding setting of the dwell time and the density of fiber flow, the thickness, initial density, orientation and also the structure of the mineral-wool product or insulator can be determined.
Both the moisture still present and the proportion of plastic are removed by means of a flow of hot air between 250C and 500C, preferably between 275C and 350C. The desired phosphate glass bond is formed both with the prefera-bly alkali-poor mineral fibers and with each other. Because of the very similar expansion coefficients of the phosphate glass and the fiber glass, permanent bonds are achieved.
Although preferred emhodiments of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the apparatus without departing from the spirit and scope of the invention, as defined the appended claims.

Claims

1. A mineral wool product essentially consisting of mineral fibers, in particular rockwool, and a binder which is thermally hardening, characterized in that the binder is water-dissolved/water dispersed aluminum meta phosphate Al(PO3)3.

2. The mineral wool product as defined in claim 1, characterized in that the proportion of aluminum meta-phosphate relative to the total weight is approximately 3% to 20% by weight, preferably 7% to 12%-weight.

. ,

3. A mineral wool product essentially consisting of mineral fibers, in particular rockwool, and of a binder which can harden under heat treatment, characterized in that water-dissolved monoaluminum phosphate Al(H2PO4)3. is provides as the binder.

4. The mineral wool product as defined in claim 1, characterized in that a thickener, such as polysaccharides, carbo-oxymethyl cellulose or polyvinyl alcohol or a mixture of phenol, formaldehyde and urea-resin is added.

5. The mineral wool product as defined in claim 1, characterized in that fibers low in alkali, such as rockwool, are used.

6. The mineral wool as defined in claim 1, characterized in that additionally a lubricant such as mineral oil or oil-in-water emulsion is provided in most finely dispersed form.

7. The mineral wool product as defined in claim 1, characterized in that additionally impregnating means are introduced by means of an aerosol or steam phase.

8. The mineral wool product as defined in claim 3, characterized in that the proportion of monoaluminum phosphate is approximately 3% to 20% by weight referred to the total weight.