AU705988B2 - Cellulated materials and process - Google Patents

Description

Regulation 3.2 -1-

AUSTRALIA

Patents Act 1990 APPLICANT: ALAN JOHNSON NUMBER: PN2895 FILING DATE: Invention Title: CELLULATED MATERIALS PROCESS The following statement is a full description of this invention, including the best method of performing it known to me/us: CELLULATED MATERIALS AND PROCESS This invention relates to products including cellulated materials such as ceramics or glasses, to methods of producing such products and in particular to such products for use as building materials.

It has been proposed to provide cellulated glasses as insulating materials but generally these cellulated products are too weak and lacking in durability for use as building products, either as structural members or as cladding panels or decorative ornaments.

US patents 4119422 to Rostoker and 4990398 to Fukumoto et al are examples of prior art cellulated materials and methods for their production.

The present invention aims to provide an alternative to known cellulated materials and methods for their production.

In one aspect the invention resides broadly in a method of producing a cellulated product, the method including:heating a cellulating glass or ceramics material to cellulate the material, and cooling the cellulated material at a rate sufficient S- to crack the cellulated material.

25 It is preferred that the method includes heating the cellulated material to and/or at a temperature sufficient to heal the cracks but not to substantially further cellulate the glass or ceramics material.

As used herein the expression to crack" means to 30 generate structural imperfections in the material such that at least some of the gas entrained in cells formed during the cellulation process can escape, and the expression "cracks" refers to such structural imperfections.

In a preferred embodiment the material may be washed *ea, in water or other suitable material to remove the (K C %Ap Q< formerly entrained gases released via the cracks.

It is preferred that the firing of the fractured cellulated body is conducted at a temperature of between about 850 0 C and 910 0 C. and in a preferred embodiment the temperature is maintained at between about 890 0 C and 900 0 C for about 10 minutes or for a time sufficient to fuse the material.

A layered product may also be produced by placing a layer of non-cellulating glass or ceramics material on the cellulated body after cooling. Upon re-heating the cellulated body and non-cellulating layer, the cracks from fracturing are healed and the non-cellulating layer is bonded to the cellulated body.

The method may also include locating a glass or ceramic tile on the cellulating mixture. The tile is preferably supported during heating to limit expansion of the mixture during cellulation.

In another aspect this invention resides broadly in a method of producing a cellulated building block for the construction of walls and the like, the method including:producing a cellulated product in sheet form in accordance with the method described above, and cutting the cellulated product to form the building *V 25 block.

It is preferred that the sheet of cellulated product *is of substantially uniform thickness corresponding to the thickness of the building block.

The invention also resides broadly in a cellulated product produced by the method defined above.

It is preferred that the cellulated product has a density of about 1000kg/m 3 or less and a tensile strength of from about 20-30 MPa. although this can increase to about 90 MPa depending on the density of the material.

35 In another aspect the invention resides broadly in a cellulated product having a plurality of cells from which gases have been removed by cooling the cellulated ~material at a rate sufficient to cause cracking of the 4 cells of the cellulated material formed by heating a cellulating glass or ceramics material to cellulate the material.

It is preferred that the cells have been healed by heating the cellulated material to and/or at a temperature sufficient to heal the cracks but not to substantially further cellulate the glass or ceramics material.

The invention shall now be described with reference to non-limiting embodiments, examples and the drawings in which FIGS 1 to 10 relate to products and methods which are not the subject of independent claims of this specification and wherein:- FIG 1 is a schematic view of a mould with components prior to firing; FIG 2 is a schematic view of the mould of FIG 1 after firing; FIG 3 is a schematic view of the mould with further components prior to firing; FIG 4 is a schematic view of the mould of FIG 3 after firing; FIG 5 is a schematic view of the mould with further components prior to firing; r ,FIG 6 is a schematic view of the mould of FIG 25 after firing; FIG 7 shows a schematic cross-section of a failed 0e*@ glass block, and •FIGS 8 to 10 show schematically steps of an improved process.

FIGS 11 to 14 relate to products and methods which are the subject of independent claims of this e specification and wherein:- FIG 11 shows a schematic cross-section of a block which failed through fracturing, and 35 FIGS 12 to 14 schematically illustrate a mould with components according to the present invention.

Referring to FIGS 1 and 2 a cellulating mixture is placed in a mould 11. The cellulating mixture z~i is placed in a mould II. The cellulating mixture comprises a mixture of cellulating material and a matrix forming compound.

The matrix forming compound is preferably glass, such as ordinary window glass, low thermal expansion glass or high silica glass, ground to a fine powder. The cellulating or foaming compound may be carbon, calcium carbonate, magnesium sulphate or any suitable oxide or salt which is thermally unstable and which will produce gas or gases upon heating. Production of gas may be by decomposition of the cellulating material or by reaction of the cellulating material with the matrix forming compound.

The matrix compound and cellulating material are both fine powders, preferably ones which pass through a 325 mesh grid. The cellulating material preferably comprises a minimum of 0.2% by weight of the mixture, depending on the degree of cellulation required.

The cellulating mixture is heated to between 8500C and 1000°C for about 20 minutes. This temperature is sufficient to cause the glass powder to bond into a unitary mass while simultaneously the cellulating material reacts to generate gas which foams the glass powder with which it is mixed. The gas is trapped in closed cells of glass and so forms a light weight foamed 25 glass product, as in FIG 2.

6*00 EXAMPLE 1 •The following is an example of an embodiment as described above: 100g of glass cullet consisting of window glass with a small percentage of green and brown glass was mixed 0o with 0.5g of carbon. The glass/carbon mixture was comminuted in a ring mill for about 20 minutes. A portion of the ground mixture was placed in a gypsum 35 mould coated with graphite powder as a release agent and fired in a kiln at about 920°C for about 20 minutes. The kiln was then turned off and allowed to naturally cool to .l qroom temperature, which took about 8 hours.

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\j (o j The resulting cellular glass sample so produced was about 100mm x 8mm x 8mm and had a density of about 1000kg/m 3 When the sample was tested for bending strength it failed at an induced tensile stress of about 28.7MPa.

Referring now to FIGS 3 and 4, the invention provides another embodiment comprised of a first cellulated layer 16 and a solid glass layer The product is produced by first placing a glass only powder layer 13 in a mould 11 covering it with a second glass powder/cellulating material layer 14. Upon firing for a suitable time and temperature the first layer 13 bonds into a solid glass layer 15 while layer 14 cellulates into a foamed, less dense layer 16. Again preferably the layer 16 is comprised of closed cells so as to be impermeable.

EXAMPLE 2 The following is an example of the above described embodiment: A mould of a human face was sprayed with water and a thin layer of glass powder was deposited on the wet oleo o surface. The mould was then filled with a cellulating 25 mixture of glass powder and cellulating material. The

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sample was placed in a kiln at about 920 0 C for about 0@SS minutes, at which time, due to the larger surface area/volume ratio, sufficient cellulation had occurred.

The result was a sample having a dense smooth glass surface backed by a low density cellular glass body.

Referring now to FIGS 5 and 6, there is shown

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another embodiment of the invention.

0o S This embodiment is a body 20 comprising a core layer 35 21 of the cellulated material surrounded by layers 22 and 23 of uncellulated glass material. If the body is of indefinite length layers 22 and 23 may be separate but if of finite length layers 22 and 23 may join together to totally surround the core layer 21.

The body 20 is manufactured by initially placing a first layer 17 of glass powder only in the mould 11 and then placing a second layer 18 of cellulating mixture 18 in the mould 11. A third layer 19 of glass powder only is then placed in the mould 11 to sandwich layer 18 between itself and first layer 17. Firing of the sample causes layers 17 and 19 to bond into solid glass layers 22 and 23 while layer 18 cellulates into foamed layer 21.

EXAMPLE 3 The following is an example of the above described embodiment: A mould was filled to a depth of about 3mm with a first layer of ground glass powder only. A second layer, of a cellulating mixture, was placed over the first layer to a depth of about 8mm. Finally a third layer of ground glass powder only was placed over the second layer to a depth of about 3mm. The sample was fired at about 9200C for about 20 minutes and subsequently annealed. The resulting product had a cellular core enclosed between two layers of solid glass.

The embodiments of the invention described with 25 reference to Examples 2 and 3 provided a glass body

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combining the low density of cellulated glass with the durability and surface finish of solid glass.

Subsequent testing with a 310 grade stainless steel mould measuring 90 x 90 x 400 mm indicated a preference that a lid cover the mould. Referring to FIG 7 it was found that use of a lid inhibited any tendency for the *o foamed glass 70 to delaminate in a zone 71 from the S* S sintered glass 72 during firing.

During testing with larger samples it was found that 35 a glass block having a foamed glass core and two unfoamed faces tended to crack on the upper layer if made from powdered glass alone. This is believed to be due to the middle layer not rising evenly when foaming but rather rising in a dome shape which can split the top layer of dense fluid glass. To avoid this problem a tile of sintered glass may be made by placing powdered glass in a suitable mould and partially firing the glass.

Referring to FIGS 8 to 10, the mould 50 for the block is filled with a bottom layer of glass powder 51 and a layer of cellulating powder 52. The sintered glass tile 53 is then placed on top of the mould and the lid 54 placed on the tile. The tile is preferably supported by the mould walls, rather than within the mould.

The mould is then placed in the oven and fired.

Initially the powders melt to about half their previous volume as in FIG 9 and then the cellulating mixture commences cellulating and expands. The foaming glass expands to abut and adhere to the tile and thus has a planar interface as in FIG The thickness of the tiles 3 is such as to prevent breakage. A heavy lid will maintain the tile on the mould against the upward force of the foaming glass and assist in preventing breakage whereas a light-weight lid may not resist the foaming glass, so that the tile and lid are lifted from the mould, thereby allowing the edges of the tile to slump and cause tile failure.

The rate of heating of the mould and its 25 constituents is controlled so that the cellulating mixture tends to cellulate at the same time.

The release agent used at the base of the mould has an effect on the finished product and preferably matches the action of the bottom layer of glass. Sand has been found unsuitable, probably because it resists the movement of the glass and causes cracking. FIG 11 shows "the typical cracking 73 caused when sand is use. While the glass initially cellulates evenly, it is believed that as cellulation continues the outermost layers are 35 compressed and move laterally. However it is believed the outer layer tends to adhere to the sand which prevents lateral movement. Accordingly cracks occur in the outer layers which typically require about 25% of the i. Dog 4< mass of the block to be removed.

As can be seen in FIGS 12 to 14, a cellulating mixture 61 is placed in mould 60 and subsequently fired to form a cellulated layer. The cellulated layer is cooled at a rate sufficient to cause cracking of the cellulated material to form a cracked layer 62 and noxious gasses trapped within the cellulated layer 62 escape. Non-cellulating glass or ceramics powder 64 is then placed on top of the cracked cellulated layer 62 and the product is refired to heal the cracks and to bond layer 64 to layer 63.

EXAMPLE 4 The following is an example of the above described embodiment: A cellulated body measuring 70mm by 130mm by was made as per a method described above. The body was cooled from its cellulating temperature of 930 0 C at the rate of 4000C per hour by kiln temperature control to crack the body.

The body was then reheated at a rate of about 2300C per hour to a temperature of between 890 0 C and 900 0 C and was maintained at this temperature for approximately .minutes to fuse the body.

In another example, a cellulated body (which can be either moulded or cut to size) and which has been quench cracked as above, has placed on and/or beneath it a tile made from sintered material and cut to size. The material is then reheated at the above rate of about 230°C per hour to a temperature of about 8700C and maintained at this temperature for between 10 and 20, and preferably 15 minutes. Alternatively the material is reheated to a temperature of about 9000C and maintained at this temperature for about 5 minutes to fuse the body.

35 Alternatively in a manner not shown, the noncellulating glass or ceramics powder can be placed on top of the cracked cellulated layer prior to initial firing "in the manner described previously and the material '^JiT l Ar fired, cooled to cracking and re-fired to heal the cracks.

It has been found that upon refiring, the compressive strength of the material shows surprising increases from between about 4 to 8 MPa when cracked to in excess of 20 MPa.

Use of a simple glass powder for the sintered layers results in a less dense and less impervious layer.

Accordingly it is proposed to use a glass powder having a small amount of very fine glass particles which will sit at the interstices of the larger particles. Use of a flux increases the flow characteristics of the glass and reduces voids in the glass.

It is possible to include colouring agents in the material of the solid glass layers to provide coloured surfaces of the finished bodies. Since only the surface layers require colouring the amount of colouring agent required is reduced substantially compared to a solid glass body.

When referring to the outer layers of glass as being solid or sintered, it will be apparent that the exactness of this description depends on the degree of melting of the glass layers and accordingly it is not essential that *666 the outer layers be solid or sintered.

S 25 It will be appreciated that this invention provides a building unit that has many advantages over known 'materials. A vitrified cellular brick produced in accordance with the invention constitutes a building unit which can be made in a brick, block or panel form and can be utilised as replacement material for masonry bricks, concrete and timber for walling, flooring and roofing.

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.o The vitrified cellular building unit of the present invention is durable, has high structural strength and being impervious to water is suitable for complex roofing 35 installations and in wall constructions where rising damp is a problem. Moreover the material is lightweight, substantially fireproof and a good thermal insulator.

It will also be appreciated that the methods of the 11 present invention enable suitable finishes to be selectively applied.

The invention can provide substantial run-on cost savings in building because labour requirements are reduced due to simplified construction and reduced structural requirements because of the light weight of the material and the high strength-to-weight ratio.

Furthermore the method of the invention can utilise a wide range of sandy materials and does not require high quality sand as in the manufacture of glass. It can tolerate many salts and impurities and can be made commercially of calcined volcanic ash. It can use substantial quantities of readily available recycled glass.

The methods and products of the invention as claimed herein are particularly advantageous in that the cellulated products do not contain noxious gases in the cells thereof, which in prior art insulating products can be released when the products are worked or cut during building and which can also leach from the product. Such gases can be poisonous and carcinogenic.

Moreover, in the longer term, buildings utilising the material can be demolished and the building envelope S.material substantially reconstituted.

It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is hereinafter claimed.

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Claims (14)

1. A method of producing a cellulated product, the method including:- heating a cellulating glass or ceramics material to cellulate the material, and cooling the cellulated material at a rate sufficient to crack the cellulated material.

2. A method as claimed in claim 1, and including:- heating the cellulated material to and/or at a temperature sufficient to heal the cracks but not to substantially further cellulate the glass or ceramics material.

3. A method as claimed in claim 1, wherein the material is washed in water or other suitable material to remove the formerly entrained gases released via the cracks.

4. A method as claimed in claim 2 or claim 3, wherein the firing of the fractured cellulated body /is conducted at a temperature of between about 850 0 C and 910 0 C.

5. A method as claimed in claim 4, wherein the 25 temperature is maintained at between about 890 0 C and 900°C for about 10 minutes or for a time sufficient to fuse the material.

6. A method as claimed in any one of claims 1 to 5, and including:- placing a layer of non-cellulating glass or ceramics material on the cellulated body after cooling, and re-heating the cellulated body and non-cellulating layer.

7. A method as claimed in any one of claims 1 to 6, and including:- S"locating a glass or ceramic tile on the cellulating .r mixture.

8. A method as claimed in claim 7, wherein the tile is supported during heating to limit expansion of the mixture during cellulation.

9. A method of producing a cellulated building block for the construction of walls and the like, the method including:- producing a cellulated product in sheet form in accordance with the method claimed in any one of claims 1 to 8, and cutting the cellulated product to form the building block. A method as claimed in claim 9, wherein the sheet of cellulated product is of substantially uniform thickness corresponding to the thickness of the building block.

11. A cellulated product produced by a method claimed in any one of claims 1 to

12. A cellulated product as claimed in claim 12, the cellulated product has a density of about 1000kg/m 3 or less and a tensile strength of from about 20-30 MPa.

13. A cellulated product having a plurality of cells from which gases have been removed by cooling the cellulated material at a rate sufficient to cause cracking of the cells of the cellulated material formed by heating a cellulating glass or ceramics material to cellulate the material.

14. A cellulated product as claimed in claim 13, wherein 35 the cells have been healed by heating the cellulated material to and/or at a temperature sufficient to heal the cracks but not to substantially further cellulate the glass or ceramics material.s defined above. f( 14 A method of producing a cellulated product substantially as described with reference to FIGS 12 to 14.

16. A cellulated product substantially as described with reference to FIGS 12 to 14. we S S we C e C. S SC. *SC* C S em S S C CC C. C C. SC Se C. we C S S V