This invention relates to heat resistant and thermally insulating compositions.

In the complete specification of our co-pending application No. 15650/78 there is described and claimed a heat-resistant, thermally insulating composition comprising organic filler, a silicate binder, raw perlite and inorganic filler other than raw perlite. The materials are chosen so as to give rise to a composition which is light weight and can be manufac- tured in slab form ^' for use as, for instance, cores ■ for doors and panels. The composition can also be moulded into virtually any shape.

The complete specification of- our above mentioned co-pending application also describes and claims a metod for making the above mentioned composition, the method including the steps of forming an aqueous slurry in which the silicate is present at least partially in dissolved form and allowing the slurry to set. T e advantages of the above mentioned composition when used as, for instance, the core of a door are described in some detail in our above mentioned co- pending application. Thus, the presence in the composition of raw perlite, which is an intumescent material, means that v/hen the composition is

to high temperatures as in fire situations it intumesces and accordingly the composition as a whole expands. This expansion results in. the door core firmly gripping the door frame thereby avoiding any possibility of the core falling out of the frame, which is a frequent occurrence in the case of previously known fire doors. In addition the intumescence of the perlite increases the thickness of the core so improving thermal insulation of the core. At the same time the organic component in the . core will burn ^" out on that side of the core adjacent the fire so that the overall result, in the case, for instance, when the organic component is expanded polystyrene or wood chips, is an expanded honey-comb matrix on one side merging into the original composition on the other side of the door, the expanded honey.-comb matrix providing a highly effective heat-resistant structure.

According to a first aspect of the present invention, there is provided a heat-resistant, thermally insulating composition. comprising fibrous vegetable matter, a silicate binder, raw perlite and inorganic filler other than raw perlite, the fibrous vegetable matter being in the form of strands having lengths in the range of from 5 to 100 mm and a water content of from 10 to 20%.

The first aspect of the present invention also provides a method for making a composition in accordance with the first aspect of the present inventio a method including the steps of comminuting fibrous vegetable material to form strands of said material having lengths of from 5 to 100 mm, controlling the water content of said fibrous vegetable material to from 10 to 20% by weight, forming an aqueous slurry of said fibrous vegetable material, a silicate binder, raw perlite and inorganic filler other than raw perlite and in which the silicate is present at least

partially in a dissolved form, and allowing the slurry to set.

A preferred fibrous vegetable material is a sugar cane residue. Accordingly this material may wholly or partially replace the polystyrene, wood chips., or other organic material mentioned specifically in our above mentioned co-pending patent application . It is found that sugar cane waste does not burn out in the same way as expanded polystyrene .beads. Rather it burns out to leave a porous mass of carbon and silicate. However contrary to expectation it does not shrink (indeed it expands) on burning out as might have been expected for such a carbon material in the absence of the silicate and perlite. Accordingly the use of a fibrous vegetable material such as sugar cane ■ waste provides a simple and cheap alternative to an organic filler such as polystyrene beads and yet, due to the combination of this material and the silicate and perlite components of the composition, will result in a composition which has good heat resistance and thermal insulation. In addition compositions having fibrous vegetable material or one of the organic fillers are found to have improved strength when set. Examples of other fibrous vegetable materials which may be used are straw (that is to say stalks from wheat, flax, oats, barley, maize etc.), wood wool from waste sources, peanut shells and the like. Typically such materials have a diameter of from 1 to 5 mm.

Preferably the water content of the fibrous vegetable material is about 15%.

Compositions in accordance with the first aspect of the present invention may be prepared in a manner similar to that described in our above mentioned co-pending patent application, that is to

say, by preparing a slurry and coating the vegetable material with this slurry in a suitable mixture. However since the fibrous vegetable materials are usually waste products and are therefore often stored outside, the moisture content of the material can vary over a wide range. Before mixing the fibrous vegetable material with the components of the slurry, the fibrous vegetable material should be treated, if necessary, to control the fibre length and the water content.

One method of treating the fibrous vegetable material is as follows. The vegetable material is shredded and chopped so that the resultant strands have lengths of from 5 to 100 mm. The material is then dried in a suitable warm air tumble dryer to a moisture content of about 15% by weight (plus or minus 5% by weight) .

The resultant material is then fed through a high speed continuous mixer and coated with a water repellant such as sodium methyl siliconate. An example of a sodium methyl siliconate is Dow Corning 772 (DC 772) manufactured by Dow Corning Ltd. The DC 772 is diluted with water to form a solution containing from 1 to 5% solids. This diluted solution is mixed with the vegetable material in the proportions of 100 parts by volume of vegetable material to 1 part by volume of DC 772 solution.

The resultant treated vegetable material is then re-dried to a moisture content of 15% by weight (plus or minus 5% by weight) and if not required immediately is stored for future use.

When required for use the treated vegetable material is fed into a twin trough continuous mixer. In one trough the vegetable material is coated with sodium silicate solution and in the other trough a mixture in powder form is prepared. This mixture contains raw perlite and other ingredients of the

fire resistant composition. The materials in the twin trough are brought together in the final stages of the mixing and then discharged into moulds to be allowed to set. In another example of a method of preparation of the composition of the first aspect of the present invention the fibrous vegetable material is shredded and chopped as mentioned in the first example above. The material is then dried to a moisture content of 15% by weight (plus or minus 5%) .

The dried material is immersed in a tank containing a dilute solution of sodium silicate. This is then passed through rollers to remove surplus solution and the resultant saturated material is then mixed with a powder mixture in the same way as described in the first example above and discharged from the mixer into suitable moulds.

A panel, for instance, a door or a partition, having a frame and, within the frame, a core made of heat resisting, thermally insulating material, may be made by forming a pourable composition which on setting is a suitable heat-resistant, thermally insulating material and pouring the composition into a mould the sides of which are provided by the frame so that on setting the core is located in position in the frame.

The heat-resistant thermally insulating material may for instance bs a composition which is the subject of our first mentioned co-pending application No. 15650/78 This method of forming a core "in situ" within a frame simplifies the production of panels having heat- resistant cores. Where the frame is made of, for instance timber or a composite material, any water exuded from the composition during setting tends to be absorbed into the material of the frame and therefore

does not adversely affect the adhesion between the core and the frame. However even where the frame is made of such a "porous" material it is necessary to allow the compositions to dry, for instance by applying heat or warm air to them within the frame.

If the frame is made of a material or materials which are of an impervious nature, for instance metal or plastics, there is a problem of adhesion between the core and the frame as a result of water exuded from the composition.

According to a second aspect of the present invention there is provided a heat-resistant, thermally insulating composition comprising organic filler, a silicate binder, raw perlite, inorganic filler other than raw perlite, and an agent, for instance, a powder or filler which is capable of combining with the water released by the composition during setting thereof.

In the case where a filler is used to "mop up" the water, it may be the same filler as one or both of the organic filler and the inorganic filler or it may be an additional filler added to the composition.

By incorporating such a component, it is ensured that water exuded from the composition during setting does not prevent adhesion of the composition with the sidesand bottom and top panels of the frame into which the composition is cast. Furthermore it is not necessary to dry the composition as mentioned above although a curing period is normally still required to allow the composition to reach full strength.

A preferred agent for taking up water in the manne described is the hardener dicalcium silicate.

Preferably the dicalcium silicate is present in an amount of from 20 to 65% by weight of the amount by weight of sodium silicate in the composition. More preferably the dicalcium silicate is present in an amount of from 25 to 50% by weight of the amount by

weight of sodium silicate.

Whether a heat-resistant, thermally insulating composition of the type with which this invention is concerned is formed in an ordinary mould or in situ within a panel frame, it is normally formed by loading the pourable composition into the mould and compressing the composition in the mould. It is desired however to obtain panel cores as light as possible for certain applications for instance the use as cores for metal faced doors.

According to a third aspect of the present invention there is provided, a method of forming a core for a panel, the core being made of heat- resistant, thermally insulating material, the method comprising forming a pourable composition which on setting is a suitable heat-resistant, thermally insul¬ ating material, the composition including an expanding agent, locating the composition in a suitable mould and allowing it to expand to fill the mould. The composition may be a composition as described in our co-pending application No. 15650/78 or as described above in accordance with the first aspect of the present invention. The mould may be a normal mould or may be formedfrom thepanel frame and the method of this third aspect of the present, invention is particularly advantageous when the article being manufactured has contoured faces.

The amount of expansion brought about by the expanding agent may be a relatively small amount, for instance, from 10 to 50% by volume. A preferred expanding agent is ferrosilicon which acts as an expanding agent in the presence of sodium silicate. It gives off hydrogen during its expansion. Preferably the ferrosilicon is present in an amount of from 5 to 50% by weight of the amount of sodium silicate used in

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the composition. A preferred range is from 10 to 30% by weight.

When the composition containing the expanding agent is located within a mould, heating of the assembly to"a .temperature of from say 50 to 100 C will activate the expanding agent so that the composition then swells to fill the entire space v/ithin the mould.

By combining the three aspects of ^" the present invention it is possible to make fire-resistant, thermally insulating panel cores having a filler derived from a fibrous vegetable material, such as sugar cane waste. The cores,may be formed in situ within a metal or plastics frame, together with metal or plastics facings, because the presence in the composition of a filler. or hardener which takes up water. Furthermore due to the presence of an expanding agent in the composition a very low weight core can be formed and if" desired one having contoured faces.

For instance a composition incorporating all aspects of the present invention 'may include raw perlite, pulverised fly ash, kaolin, calcium carbonate, dolomite, a powder hardener such as sodium fluosilicate or dicalcium silicate.

Compositions in accordance wiϋhthe present invention will now be described by way of examples.

The amounts of components given in the samples are amounts in kilograms which are such as to produce one cubic metre of composition in accordance with the invention.

Example 1.

Sodium silicate Q79 220.0

Sodium fluosilicate 11.0

E G D A 5.5 Raw perlite ore 30.0

P F A Dry 60.0

Pentrone 1.0

Sodium methyl siliconate D C 772 2.0

Dry sugar cane residue (untreated) 150.0

*%- W

Sodium silicate Q79 is a neutral sodium silicate manufactured by I.C.I.

This example illustrates the first aspect of the present invention. Example 2

Sodium silicate M 75 200 Sugar cane residue treated + dried 150

Dicalcium silicate 42

E G D A 6 Diacetin 2

P F A dry 35

Pentrone 1

Kaolin . 15

Raw perlite ore 30 This example illustrates the first and second aspects of the present invention. The composition is formed in accordance with the method described above in which the sugar cane is treated with a water repellant such as Dow Corning 772. Sodium silicate M 75 is manufactured by I.C.I.

Example 3

Sodium silicate M ^' 75 150

Sugar cane residue dry untreated 150

Water 50 Dicalcium silicate 75

E G D A 6

Diacetin 2

P F A dry 20

Pentrone 1 Raw perlite 35

This example illustrates the first and second aspects of the present invention. The composition is formed as described above in which the sugar cane waste is immersed in a diluted solution of sodium silicate. Example 4

Sodium silicate 100

Sodium fluosilicate 5

Dry P F A 15

Raw perlite ore 25 Calcium carbonate 15

Ferrosilicon 20

Wood waste granules 100

This example illustrates the third aspect of the present invention.