Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2000-03-02
2002-12-24
Elve, M. Alexander (Department: 1725)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S312600, C428S314400, C428S315500, C428S317900
Reexamination Certificate
active
06497945
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a foamlike mineral building and structural material produced from an alkali-silicate and/or ammonium-silicate matrix, a method of producing the mineral foam as well as an apparatus for carrying out the method according to the present invention.
BACKGROUND OF INVENTION
Various mineral foams are already known. A glass foam granulate is, for example, known, which is produced from glass powder having added thereto an expanding agent which releases a propellant at high temperatures. Glass foam granulates are used for many purposes, e.g. as light-weight aggregate for mortars and plasters. They are, however, many times heavier than plastic foams and because of the higher thermal conduction they are suitable to be used as an insulating material only to a limited extent.
Furthermore, it has already been suggested to use, in addition to glass powder also other substances, such as crushed rocks, silt and clay as raw materials for mineral foams. The resultant products are dimensionally stable up to 1000° C. and pressure resistant, but they are not suitable to be used as insulating materials either.
Water glass is known as a raw material in the field of civil engineering, e.g. also as an accompanying raw material for the production of mineral foams. In the case of the known mineral foams, it is common practice to add water glass, e.g. for improving the opening up of the raw materials. Water glass is here, however, added and used as an auxiliary agent which does not contribute much to the characteristic and the quality of the mineral foam. Water glass loses its reactivity at the high expanding temperatures of 700° C.-1200° C. which have been necessary up to now.
Furthermore, water glass is used as a binding agent. Water glass does, however, not act as a foaming agent in these cases.
It is already known to use water glass as a foaming agent for fire-retarding plates, fire-retarding fillers and fire-retarding paints. The water-glass property of expanding in case of fire spontaneously and in an uncontrolled manner under the influence of high temperatures is here utilized for these industrial fire-precaution products.
The water content of known fire-precaution products is between 20% by weight and 40% by weight in relation to the total recipe, including fillers.
The use of commercially available alkali silicates having a water content of more than 40% by weight results, due to the high water content, in explosive, uncontrolled foaming in response to the energy input from outside which will normally take place. As a result, large-pored and non-homogeneous products are formed in which the smaller water vapour bubbles combine and form larger bubbles. The foams formed from the molecular water in the case of fire by the above-mentioned fire-precaution products have, as is generally known, no compressive strength and are already destroyed when subjected to minimal external influences. They are only suitable for short-time fire protection.
Altough alkali silicates, such as sodium, potassium or ammonium silicates, are used in a broad range of industrial applications as binding agents, adhesive agents, detergents, etc., it has up to now been impossible to produce from a water-glass raw material industrial foams of uniformly good quality, e.g. for the purpose of thermal insulation, light-weight construction and other applications.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide an improved building and structural material for high-quality industrial products for the first time.
This object is achieved by a foamlike mineral building and structural material based on a substantially uniformly foamed alkali-silicate and/or ammonium-silicate matrix encompassing an open and/or closed porous structure.
Preferred embodiments of the foam according to the present invention are described in subclaims 2 to 13.
The present invention additionally provides a method of producing foamlike mineral building and structural materials, said method comprising the following steps,
adjusting the water content of an alkali-silicate and/or ammonium-silicate starting material to a specific value, and
foaming the pretreated alkali-silicate and/or ammonium-silicate material.
The method according to the present invention permits the production of high-quality and uniformly fine-pored foams with an alkali-silicate matrix, which have a very low thermal conductivity and a good compressive strength. The present invention permits in particular the use of commercially available raw materials, e.g. water glass, i.e. materials which, up to now, have not been suitable to be used as starting materials for mineral building and structural materials. Since commercially available products can be used as raw materials, the method according to the present invention is also advantageous with regard to the costs entailed.
The adjustment of the water content according to the present invention is preferably achieved by drying the alkali-silicate and/or ammonium-silicate matrix material. It proved to be particularly advantageous when the alkali-silicate and/or ammonium-silicate matrix material has, after the drying step, a water content of less than 20% by weight, but more than 5% by weight, in relation to the alkali-silicate and/or ammonium-silicate matrix material. Particularly good results are achieved with a residual water content of 15% by weight to 10% by weight.
Drying can be carried out in two different ways according to the present invention. One way is drying and foaming in one process in two temperature stages, the main raw material component being a slightly or non-predehydrated alkali-silicate and/or ammonium-silicate matrix and the removal of water taking place in the first stage of the process by energy input at temperatures of up to 110° C., preferably, however, at temperatures between 80° C. and 90° C. The slightly or non-predehydrated alkali-silicate and/or ammonium-silicate matrix is here, prior to the drying step, a highly viscous, aqueous solution whose consistency may vary between still flowable and already solidified and which can also serve as an enveloping material for the dissolved water and, if desired, for additive substances.
The other way is the production by applying temperature and pressure to an alkali-silicate and/or ammonium-silicate matrix bed which is used as raw material in the form of a dried or a calcined powder or a granular material. An addition of water and/or an aqueous solution and/or an aqueous suspension and/or an alkali-silicate and/or ammonium-silicate liquid may here be expedient under certain circumstances so as to be able to produce a matrix having precisely the consistency desired. The semifinished product produced in both ways is a highly viscous, from pasty to solidified, compact solution having the desired water content in the range between 20% by weight and 5% by weight.
Furthermore, it turned out that the drying step can be carried out in an advantageous manner making use of microwaves at temperatures of up to 100° C., preferably at temperatures between 80° C. and 90° C.
The use of microwave heating permits the intensity and the duration of the energy input to be dosed in a very simple manner and to guarantee simultaneously a careful treatment of the starting material.
Microwave heating can subsequently also be used for foaming the pretreated starting material according to the present invention.
According to the present invention, a mineral foam can be produced from the alkali-silicate and/or ammonium-silicate matrix starting material, the volume of said mineral foam being, according to requirements, 10 to 30 times as large as the initial volume. Depending on the intensity and the duration of energy input, a product will be obtained, which is either closed-pored to a large extent when energy is supplied carefully or open-pored and highly disperse when the energy input is of a more intensive nature.
It follows that the method according to the present invention permits the production of both close-pored and open-po
Choyna Kathrin
Franke Matthias
Niedner Peter
Elve M. Alexander
Marshall Gerstein & Borun
Niedner Peter
Stoner Kiley
LandOfFree
Foamlike mineral building and structural material as well as... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Foamlike mineral building and structural material as well as..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Foamlike mineral building and structural material as well as... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2932462