Compositions: ceramic – Ceramic compositions – Pore-forming
Reexamination Certificate
2001-11-21
2003-11-04
Marcantoni, Paul (Department: 1755)
Compositions: ceramic
Ceramic compositions
Pore-forming
C501S084000, C252S062000
Reexamination Certificate
active
06642164
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lightweight heat-insulating building material having frost resistance.
BACKGROUND OF THE INVENTION
Foamed glass is used as interior materials, exterior materials, and walls of housings and buildings due to its heat insulation and sound absorbing properties.
The following Japanese patent publications describe foamed glass.
(i) JP S61-2618B discloses foamed glass which has bulk density of 0.20-0.34 g/cm
3
and which is produced by adding 1.5-9.5% by weight dolomite (MgCO
3
.CaCO
3
) powder as a foaming agent into glass powder of soda-lime glass or the like so as to form a mixture, and heating the mixture at 700-780° C. at least for one hour.
(ii) JP H06-99160B discloses laminated foamed glass consisting of a foamed glass layer having bulk density of 0.3-0.6, a medium-foamed glass layer (bulk density 1.0-1.7), and a non-foamed glass layer. Raw materials for the respective layers are successively molded to be laminated integrally and fired under pressure, thereby producing the laminated foamed glass.
(iii) JP H11-79866A discloses foamed glass which is produced by coating foamed glass beads with coating material comprising clay and glass, dry-pressing the coated beads, and firing the dry-pressed body at 800-1100° C.
The foamed glass of the above (i) and the laminated foamed glass of the above (ii) have poor frost resistance because they have high water absorption. The foamed glass of (i), (ii) has thin cell walls and boundary faces between glass phases and crystal phases, and the thin cell walls and the boundary faces can be dissolved by water so as to form pores through which the water can easily enter into the glass. The foamed glass of (i), (ii) has small pores which are already formed in glass at cell walls during firing. In the early stage of water absorption, the glass seems to have low water absorption in appearance due to insufficient replacement between gas or air in the cells and water. However, the glass absorbs a large amount of water finally to have high water absorption. Although the foamed glass has relatively low water absorption of 5-15% by weight in the normal condition, the foamed glass has significantly high water absorption of 50-100% by weight when boiled or soaked for a long period of time. Therefore, the foamed glass is easy to be damaged or broken due to repetitions of freezing and thawing of absorbed water.
The foamed glass of the above (iii) is produced with a large amount of the coating material which is 30-80 wt. % relative to the foamed glass beads. The foamed glass of (iii) is produced through many steps including of producing the foamed glass beads, molding them, and firing them at a high temperature of 800-1100° C., so that the foamed glass has a high manufacturing cost.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a lightweight heat-insulating building material having frost resistance which has excellent frost resistance and can be manufactured at low cost.
The building material of the present invention is produced by molding a mixture of raw materials containing glass powder, a foaming agent, a crystallization inhibitor, and a frost inhibitor so as to form a molded body, and firing the molded body so as to foam the molded body.
The building material of the present invention has excellent frost resistance, lightweight, and heat insulation property.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lightweight heat-insulating building material having frost resistance according to the present invention is produced by mixing raw materials including glass powder, a foaming agent, a crystallization inhibitor, and a frost inhibitor, molding the mixture, and firing the molded body to foam the molded body.
Raw material for the glass powder may be soda-lime glass used for glass plates and glass bottles. Examples of the raw material include glass cullet obtained by grinding waste glass such as scraps of glass plates or glass bottles from plants for manufacturing glass plates and plants for processing glass, and construction and demolition waste glass.
The foaming agent can be at least one selected from the group consisting of carbonate and aluminium metal. The carbonate includes dolomite and calcium carbonate. The calcium carbonate may be limestone.
When the foaming agent is composed of carbonate only, the mixture of raw materials contains carbonate preferably in an amount of 0.3 to 10% by weight, more preferably 0.5 to 6% by weight.
When the foaming agent is composed of aluminium metal only, the mixture of raw materials contains aluminium metal preferably in an amount of 0.1 to 5% by weight, more preferably 0.3 to 1.5% by weight.
When the foaming agent is composed of carbonate and aluminium metal, the mixture of raw materials contains carbonate preferably in an amount of 0.5 to 5% by weight and aluminium metal preferably in an amount of 0.3 to 1.0% by weight. Carbonate and aluminium metal are present in the mixture preferably in an amount of 1.0 to 5% by weight in total, more preferably 2 to 4% by weight in total.
If the proportion of carbonate exceeds the aforementioned range, calcium oxide (CaO) and/or magnesium oxide (MgO) as decomposition products of the carbonate may crystallize the glass so as to increase the softening point of the glass. The increase in the softening point suppresses the glass to foam whereby decreasing the bulk density of obtained foamed glass. If the proportion of carbonate is lower than the aforementioned range, the amount of carbonic acid gas generated from the carbonate should be insufficient to foam the glass whereby decreasing the bulk density of obtained foamed glass. If the proportion of aluminium metal exceeds the aforementioned range, the foamed glass has continuous cells due to excessive foaming so as to unduly increase the water absorption, leading to poor frost resistance. On the other hand, if the proportion of aluminium metal is lower than the aforementioned range, the glass foams insufficiently so as to reduce the bubble ratio and the bulk density of the foamed glass.
When the foaming agent is composed of aluminium metal only, the foamed glass appears to be black colored that may sometimes spoil the appearance of the foamed glass. When the foaming agent is composed of aluminium metal and carbonate, the foamed glass appears to be light color that may be good in appearance.
The crystallization inhibitor can be at least one selected from the group consisting of water glass, sodium silicate, boric acid, borax, and Glauber's salt (Na
2
SO
4
.10H
2
O). The mixture of raw materials contains the crystallization inhibitor preferably in an amount of 1 to 10% by weight, more preferably 3 to 7% by weight expressed as sodium silicate. The crystallization inhibitor lower than this range of proportion allows glass to be easily crystallized, thus suppressing the glass to foam. The crystallization inhibitor exceeding this range of proportion unduly lowers the softening point of glass so as to allow the glass to foam excessively, whereby the foamed glass has poor strength and poor frost resistance.
The frost inhibitor is preferably material of calcium silicate series and may be at least one selected from the group consisting of lightweight aerated concrete, mortar, concrete, cement, calcium silicate plate, asbestos cement plate, wollastonite, and asbestos. The frost inhibitor may be construction and demolition waste of calcium silicate series.
The mixture of raw materials contains the frost inhibitor preferably in an amount of 0.5 to 30% by weight, more preferably 3 to 12% by weight.
The frost inhibitor lower than this range of proportion insufficiently prevents the frost damage. The frost inhibitor exceeding this range of proportion allows the glass to be crystallized so as to increase the softening point of the glass, thus suppressing the glass to foam. Foamed glass containing excess amount of frost inhibitor suffers easily frost damage because water is absorbed via the frost inhibitor.
The mixture of raw materials may cont
Kanesaka & Takeuchi
Marcantoni Paul
Nippon Sheet Glass Co. Ltd.
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