WO2001058995A1

WO2001058995A1 - Thermal insulation material

Info

Publication number: WO2001058995A1
Application number: PCT/GB2001/000556
Authority: WO
Inventors: Andrew John Smith; William Henry Player
Original assignee: Winn & Coales International Limited
Priority date: 2000-02-11
Filing date: 2001-02-12
Publication date: 2001-08-16
Also published as: GB0003262D0; AU3206601A; GB2359085A

Abstract

A material for thermal insulation which comprises a phenolic resin, characterised in that one or more fillers and one or more minerals are included as additives during synthesis of the phenolic resin; the one or more fillers being selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and the one or more minerals being selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock. Processes for production of such a material and its use as a fire retardant material are also described.

Description

THERMAL INSULATION MATERIAL

The present invention concerns novel thermal insulation materials, processes for the production of such materials and uses of such materials.

Thermal insulation materials may be usefully employed in a very wide variety of applications which require the maintenance of a temperature differential between two regions. For example, they may be used to manufacture heat resistant coatings, cold storage containers or fire-proof structures.

In the past, asbestos has been used as a thermal insulation material in a wide variety of applications. However, since the discovery of the carcinogenic nature of asbestos, there has been a particular need for the development of thermal insulation materials suitable for its replacement.

Phenolic resins are a class of polymers which are well known to those skilled in the art and they have been used in a variety of products which are subject to severe conditions such as heat-resistant surfaces, electrical insulators and flame-retardant composites. It should be noted that, within the context of the present specification the term "phenolic resin" refers to the final cured form of the resin rather than intermediate partially polymerised resins. The intermediate resins are referred to herein by the term "phenolic resin prepolymer" or just "prepolymer".

Phenolic resins result from the interaction of phenolic compounds and aldehydes. There are various routes by which phenolic resins may be synthesised and the present invention is not intended to be limited to any particular one. However, by way of explanation and illustration the synthetic methodology is broadly outlined below.

Phenolic resins are commonly formed in two stages. In the first stage a phenolic resin precursor composition which essentially comprises one or more phenolic compounds and one or more aldehydes undergoes a prepolymerisation reaction to form a phenolic resin prepolymer (also called an A-stage resin) which may be either liquid or solid. In the second stage the prepolymer is cured to produce a highly cross-linked rigid phenolic resin.

Depending on the reaction conditions, the first stage prepolymerisation reaction can follow one of two routes. In the first route an excess of the one or more phenolic compounds reacts with the one or more aldehydes under acid catalysis to form phenolic resin prepolymers known as "novolaks". Aldehyde to phenol ratios of 0.5 to 0.8 are commonly used with sulphuric, p-toluene-sulphonic, hydrochloric, phosphoric or oxalic acid as catalyst. Novolaks are commonly solid prepolymers. In the second route the one or more phenolic compounds react with an excess of the one or more aldehydes under base catalysis to form phenolic resin prepolymers known as "resoles". Aldehyde to phenol ratios of 1.0 to 3.0 are commonly used with sodium, barium or calcium hydroxide, sodium carbonate or organic amines as catalyst. Resoles are commonly liquid prepolymers.

The procedure for carrying out the second stage curing reaction depends upon the identity of the prepolymer. Novolaks require the addition of a hardener (which may be an aldehyde or a latent source of aldehyde) in order to undergo cross-linking. Hexamethylene- tetramine, paraformaldehyde and trioxane are typical examples of novolak hardeners. The mixture may also be heated to accelerate the cross-linking process. The novolak curing reaction may involve a catalyst such as magnesium or calcium oxide and may also involve the use of certain metal salts, such as zinc, magnesium or calcium acetates. Resoles do not require the addition of a hardener or other additive and may be cured (cross-linked) simply by heating the prepolymer and or by adding a suitable resole hardener, such as an acid catalyst, to accelerate the curing process.

Phenol itself is the most common phenolic compound to be used in phenolic resin precursor compositions. However, other aromatic hydroxyl compounds may also be used such as, for example, catechol ( 1, 2-dihydroxy- benzene) , resorcinol (1, 3-dihydroxy-benzene) , quinol (1, 4-dihydroxy-benzene) , cresol (methylphenol, including 3-methylphenol and 4-methylphenol) , xylenol (dimethylphenol) , p-t-butylphenol, p-phenylphenol, diphenols and bisphenol A. The choice of phenolic compound to be included in the precursor composition will depend upon the desired properties of the resultant resin. For example the incorporation of alkyl phenols into the precursor composition provides a resin with reduced reactivity, hardness, cross-link density and colour formation but increased solubility in non-polar solvents, flexibility and compatability with natural oils.

Formaldehyde, principally in its hydrated form, is the most common aldehyde compound to be used in phenolic resin precursor compositions because of its high reactivity. However, other aldehyde compounds may also be used such as, for example, ethanal, benzaldehyde or furfuraldehyde . The aldehyde component may alternatively be provided by a latent source of aldehyde such as, for example, hexamethylenetetramine . The choice of aldehyde or aldehyde precursor to be included in the phenolic resin precursor composition will depend upon the desired properties of the resultant resin.

Other reactants may optionally be included in the phenolic resin precursor composition to provide phenolic resins with specific properties. Examples of other additives include: aniline, rosin, dicyclopentadiene, unsaturated oils such as tung oil and linseed oil, and polyvalent cations for cross- linking.

As mentioned previously, phenolic resins have been used to produce materials which exhibit good thermal and electrical insulation and which may also exhibit favourable fire-retardant properties. In this regard, materials should preferably satisfy three major criteria in order to provide good fire retardant materials. That is to say, the material should be very resistant to heat, non-flammable and should not produce harmful fumes when exposed to heat and/or flame. Prior to the present invention, known fire retardant materials have usually addressed only one or two of these three requirements.

It would be advantageous to provide a material based on a phenolic resin which exhibits improved thermal insulation properties and, in particular, improved fire-retardant properties.

Accordingly, in a first aspect, the present invention provides a material for thermal insulation which comprises a phenolic resin, characterised in that one or more fillers and one or more minerals are included as additives during synthesis of the phenolic resin, the one or more fillers being selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides; and the one or more minerals being selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock.

Preferably, the one or more fillers and the one or more minerals are mixed with a phenolic resin prepolymer prior to curing the prepolymer so as to synthesise the phenolic resin.

Thus, in a second aspect, the present invention provides a material for thermal insulation obtainable by curing a mixture which comprises: (A) a phenolic resin prepolymer,

(B) a filler selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and

(C) a mineral selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock.

It will be appreciated by the person skilled in the art that, depending upon the identity of the phenolic resin prepolymer, curing the mixture may necessitate an increase in temperature and/or the inclusion in the mixture of a suitable hardener. The phenolic resin prepolymer may be either a novolak prepolymer or a resole prepolymer. Thus, where a novolak prepolymer is used, the mixture will additionally comprise a suitable novolak hardener and may optionally be heated during curing. Where a resole prepolymer is used, an increase in temperature and/or addition of a suitable resole hardener will be necessary to cure the mixture.

The present invention is not intended to be limited by the means for producing the phenolic resin. I.e. either a resole prepolymer or a novolak prepolymer may be used. However, it is preferred to use a resole prepolymer such as phenol formaldehyde resole prepolymer. The ratio of aldehyde to phenol in the phenol formaldehyde resole prepolymer may be in the range of from 0.2 to 0.7. This kind of prepolymer may be provided by way of a solution in a suitable solvent, such as acetone. An example of a suitable phenolic resin prepolymer is the phenol formaldehyde resole resin P963 supplied by Borden Chemical UK Ltd.

Improvements in the thermal insulation properties of a phenolic resin can be obtained by the use of widely ranging amounts of filler (s) and mineral (s) as additives during the synthesis of the phenolic resin. Thus, the mixture prior to curing may comprise phenolic resin prepolymer in an amount of from 1 to 90 wt%, one or more fillers in an amount of from 0.8 to 85 wt% and one or more minerals in an amount of from 0.1 to 60 wt%, based on the total weight of the mixture .

The choice of the relative amounts of phenolic resin prepolymer, mineral and filler to be used will depend upon the desired properties of the end product.

In one preferred aspect, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 10 to 90 wt%, one or more fillers in an amount of from 5 to 60 wt% and one or more minerals in an amount of from 5 to 60 wt%, based on the total weight of the mixture. More preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 40 to 80 wt%, one or more fillers in an amount of from 10 to 30 wt% and one or more minerals in an amount of from 10 to 30 wt%, based on the total weight of the mixture. Even more preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 60 to 70 wt%, one or more fillers in an amount of from 15 to 20 wt% and one or more minerals in an amount of from 15 to 20 wt%, based on the total weight of the mixture.

In another preferred aspect, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 30 to 70 wt%, one or more fillers in an amount of from 5 to 50 wt% and one or more minerals in an amount of from 1 to 16 wt%, based on the total weight of the mixture. More preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 40 to 60 wt%, one or more fillers in an amount of from 15 to 40 wt% and one or more minerals in an amount of from 3 to 10 wt%, based on the total weight of the mixture. Even more preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 43 to 50 wt%, one or more fillers in an amount of from 20 to 40 wt% and one or more minerals in an amount of from 3 to 7 wt%, based on the total weight of the mixture.

In another preferred aspect, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 1 to 30 wt%, one or more fillers in an amount of from 50 to 85 wt% and one or more minerals in an amount of from 8 to 16 wt%, based on the total weight of the mixture. More preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 1 to 10 wt%, one or more fillers in an amount of from 70 to 85 wt% and one or more minerals in an amount of from 12 to 16 wt%, based on the total weight of the mixture. Even more preferably, the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 1 to 5 wt%, one or more fillers in an amount of from 80 to 85 wt% and one or more minerals in an amount of from 14 to 16 wt%, based on the total weight of the mixture.

As mentioned in the discussion of phenolic resin synthesis above, novolak phenolic resin prepolymers require a suitable hardener in order to cure them to provide the final phenolic resin. Resole phenolic resin prepolymers may also utilise a suitable hardener, such as an acid catalyst. Thus the mixture prior to curing may also comprise a hardener. The amount of hardener required depends upon the identity of the phenolic resin prepolymer and on the identity of the hardener itself. However the hardener is generally present in an amount of from 10 to 20 wt% based upon the weight of the phenolic resin prepolymer. Thus the hardener may be present in an amount of from 0.1 to 20 wt% based on the total weight of the mixture. In one preferred aspect the hardener is preferably present in an amount of from 5 to 20 wt% based on the total weight of the mixture. In another preferred aspect the hardener is preferably present in an amount of from 3 to 14 wt% based on the total weight of the mixture. In another preferred aspect the hardener is preferably present in an amount of from 0.1 to 6 wt% based on the total weight of the mixture. Where a resole prepolymer is used, an example of a suitable hardener is an acid catalyst which is an aqueous mixture of p-toluene sulphonic acid and phosphoric acid such as the product P964 supplied by Borden Chemical UK Ltd.

A very wide variety of materials may also be included as additives during the synthesis of the phenolic resin in order to provide composite materials which exhibit particular chemical and/or physical properties. Thus in further embodiments of the present invention one or more materials selected from the group consisting of ceramic glass (in the form of fine powder, spheres, flakes or fibre) , silicate glass (in the form of fine powder, spheres, flakes or fibre) , carbon fibre, metal particles (such as aluminium trimite, also called aluminium trihydrate) , blowing agents (such as pentane, blends of pentafluorobutane (CF₃CH₂CF₂CH₃) and heptafluoropropane (CF₃CHFCF₃) , or dichlorofluoroethane (C₂H₃C1₂F) ) , fillite, vermiculite, china clay, borax, pumice and diatomaceous earth may also be included as additives during synthesis of the phenolic resin. Silicate glass (especially in powder form) is a particularly preferred additive which is preferably present in an amount of from 0.01 to 1.0 wt% based on the total weight of the mixture.

The present invention also includes within its scope a material for thermal insulation which comprises: (A' ) a phenolic resin in an amount sufficient to bind components (B) and (C) , (B) one or more fillers selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and (C) one or more minerals selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock.

As stated earlier, even very small quantities of filler (s) and mineral (s) can provide improvements in the thermal insulation properties of phenolic resins. Thus the material may comprise phenolic resin in an amount of from 1 to 99 wt%, one or more fillers in an amount of from 0.8 to 85 wt% and one or more minerals in an amount of from 0.1 to 60 wt%, based on the total weight of the composite material.

In one preferred aspect, the material may comprise phenolic resin in an amount of from 10 to 90 wt%, one or more fillers in an amount of from 5 to 60 wt% and one or more minerals in an amount of from 5 to 60 wt%, based on the total weight of the composite material. More preferably, the material comprises a cured phenolic resin in an amount of from 40 to 80 wt%, one or more fillers in an amount of from 10 to 30 wt% and one or more minerals in an amount of from 10 to 30 wt%, based on the total weight of the composite material. Even more preferably, the material comprises a cured phenolic resin in an amount of from 60 to 70 wt%, one or more fillers in an amount of from 15 to 20 wt% and one or more minerals in an amount of from 15 to 20 wt%, based on the total weight of the composite material .

In another preferred aspect, the material may comprise phenolic resin in an amount of from 30 to 77 wt%, one or more fillers in an amount of from 5 to 50 wt% and one or more minerals in an amount of from 1 to 16 wt%, based on the total weight of the composite material. More preferably, the material comprises a cured phenolic resin in an amount of from 40 to 66 wt%, one or more fillers in an amount of from 15 to 40 wt% and one or more minerals in an amount of from 3 to 10 wt%, based on the total weight of the composite material. Even more preferably, the material comprises a cured phenolic resin in an amount of from 43 to 55 wt%, one or more fillers in an amount of from 20 to 40 wt% and one or more minerals in an amount of from 3 to 7 wt%, based on the total weight of the composite material.

In one preferred aspect, the material may comprise phenolic resin in an amount of from 1 to 33 wt%, one or more fillers in an amount of from 50 to 85 wt% and one or more minerals in an amount of from 8 to 16 wt%, based on the total weight of the composite material. More preferably, the material comprises a cured phenolic resin in an amount of from 1 to 11 wt%, one or more fillers in an amount of from 70 to 85 wt% and one or more minerals in an amount of from 12 to 16 wt%, based on the total weight of the composite material. Even more preferably, the material comprises a cured phenolic resin in an amount of from 1 to 6 wt%, one or more fillers in an amount of from 80 to 85 wt% and one or more minerals in an amount of from 14 to 16 wt%, based on the total weight of the composite material.

The material may also comprise one or more further additives depending on the desired properties of the final product. These additives may be selected from the group consisting of ceramic glass (in the form of fine powder, spheres, flakes or fibre), silicate glass (in the form of fine powder, spheres, flakes or fibre), carbon fibre, metal particles (such as aluminium trimite, also called aluminium trihydrate) , blowing agents (such as pentane or dichlorofluoroethane (C₂H₃C1₂F) ) , fillite, vermiculite, china clay, borax, pumice and diatomaceous earth.

Preferably, the filler is selected from one or more of hydrated calcium sulphate (CaS0₄.2H₂0, commonly called gypsum), calcium sulphate hemihydrate (CaS0₄.0.5H₂0, commonly called plaster of Paris) , anhydrous calcium sulphate (CaS0₄) and calcium oxide (CaO, commonly called lime or limestone) .

When mica is present as the mineral component it may be in the form of natural or synthetic mica.

When igneous rock or a mineral derivable from igneous rock is present as the mineral component it is preferably a mineral which comprises silica, alumina, magnesia and ferric oxide. Even more preferably it includes these components in the following amounts: silica in an amount of from 20 to 80 wt%, alumina in an amount of from 5 to 30 wt%, magnesia in an amount of from 0.05 to 30 wt% and ferric oxide in an amount of from 0.05 to 10 wt%, based on the total weight of the mineral.

A preferred mineral which comprises silica, alumina, magnesia and ferric oxide is perlite. Perlite is a volcanic glassy rock which has a concentric or onionlike structure and a pearly lustre. It usually comprises silica in an amount of from 65 to 75 wt%, alumina in an amount of from 9 to 20 wt%, magnesia in an amount of from 0.05 to 1 wt% and ferric oxide in an amount of from 0.05 to 3 wt%, based on the total weight of the mineral. It may also comprise small amounts (i.e. less than 5 wt%) of a number of other oxides such as, ferrous oxide, lime, soda, potash, titanium dioxide phosphorous pentoxide and manganous oxide. Perlite may also contain up to approximately 6 wt% water which causes it to expand to a considerable extent upon heating. In the present invention the perlite may be used in its unexpanded form although it is preferable to use it in its expanded form.

Another preferred mineral which comprises silica, alumina, magnesia and ferric oxide is vermiculite. Vermiculite has a platy, laminated structure and it usually comprises silica in an amount of approximately 40 wt%, alumina in an amount of approximately 15 wt%, magnesia in an amount of approximately 25 wt% and ferric oxide in an amount of approximately 5 wt%, based on the total weight of the mineral. It may also contain from 4 to 14 wt% water which also causes it to expand to a considerable extent upon heating. In the present invention the vermiculite may be used in its unexpanded form although it is preferable to use it in its expanded form.

The material of the present invention exhibits excellent properties as a fire retardant material. In this regard the material is found to satisfy the three major criteria for fire retardant materials. That is to say, the material is very resistant to heat, it is non-flammable and it does not produce harmful fumes when exposed to heat and/or flame. Prior to the present invention, known fire retardant materials have usually addressed only one or two of these three requirements .

Furthermore, the material of the present invention also exhibits other properties which make it very suitable for a wide variety of industrial uses. In particular, the material shows excellent thermal insulation efficiency which is not only benificial in its use as a fire retardant but also makes it suitable for protection against severe cold temperatures or for maintaining any desired temperature, such as the accurate control of sustained liquid temperatures within pipelines. The material is very light and strong and may be readily handled and cut. It is fully mouldable into any desired shape and it does not shrink, expand or distort when exposed to very low and/or very high temperatures. The material is also extremely resistant to common industrial chemicals such as detergents, oils, petrochemicals, acids and alkalis. It is not affected by UVA radiation and it is non-soluble in common solvents and impervious to water. Finally, it will seal a wide range of known construction and manufacturing materials and is therefore suitable for use as a thermally insulating and/or fire retardant sealing or cladding material.

Thus, further aspects of the present invention provide for the use of the material described herein as a thermal insulation and/or a fire retardant material.

In common with known phenolic resins the material may be shaped and processed by methods known in the art such as compression moulding, roller application, pultrusion, brush application, filament winding, infusion, injection moulding, sheet forming, vacuum forming, extrusion, fibre spinning, wet lay-up, spray application and trowel application.

The present invention also includes within its scope a process for forming a thermal insulation material comprising mixing a phenolic resin prepolymer with one or more fillers selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and with one or more minerals selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock, and curing the mixture so as to convert the phenolic resin prepolymer into a phenolic resin.

Curing may be achieved by simply heating the mixture. Curing may also be achieved by adding a suitable catalyst or hardener and optionally heating the resultant mixture in, for example, an oven. Temperatures in the range of from 50 to 120°C, preferably 60 to 80°C are commonly used.

In a preferred process, when the prepolymer is a resole prepolymer and curing is effected using heat and an acid catalyst as hardener, the prepolymer, filler and mineral are mixed together and then preheated to the curing temperature. The mould is also pre-heated to the curing temperature. The catalyst is then added to the mixture which is immediately poured into the pre-heated mould. The mould is then maintained at the curing temperature until curing is complete. This pre-heating process results in foaming of the mixture during curing which in turn results in an open cell or honeycomb structure in the cured product. This is advantageous for applications where a lightweight product is desirable. In a further embodiment of this preferred process the pre-heated mould is sprayed with a thin layer of the mixture prior to injection of the rest of the mixture. The thin layer cures prior to foaming of the bulk mixture and creates a thin skin which surrounds the open cell or honeycomb structure. This process is particularly preferred where a lightweight material which still exhibits excellent thermal insulation and fire retardant properties is desired.

The present invention is further described by way of the following examples.

Example 1

1 kg of phenol-formaldehyde phenolic resin prepolymer (Borden Resin P963, a phenol-formaldehyde resole solution in acetone) was mixed with 0.5 kg of a mixture of 49.75 wt% gypsum powder, 49.75 wt% perlite granules and 0.5 wt% glass powder. To this mixture was added 0.1 kg of hot cure catalyst (Borden Hardener P964, an aqueous solution containing 50 to 70 wt% p- toluenesulfonic acid and 15 to 20 wt% phosphoric acid) . The mixture was placed in a mould and the mould was placed in an oven for 1 hr at 60°C. After cooling the cured product was removed from the mould.

Examples 2 to 26

Phenol-formaldehyde phenolic resin prepolymer (Borden Resin P963) was mixed with gypsum powder, perlite granules, glass powder and, optionally, C₂H₃C1₂F (Solkane 141B, obtained from A-Gas UK Ltd) , fillite, vermiculite, china clay, glass spheres, borax, pumice and/or aluminium trihydrate. To this mixture was added a hot cure catalyst (Borden Hardener P964) . The mixture was placed in a mould and the mould was placed in an oven for 1 hr at 60°C. After cooling the cured product was removed from the mould. The relative quantities of the starting materials in % by weight for each example are given in Tables 1, 2 and 3 below:

Table 1

Table 2

Table 3

Examples 27 to 34

Phenol-formaldehyde phenolic resin prepolymer (Borden Resin P963) was mixed with gypsum powder, perlite granules, glass powder and, optionally, C₂H₃C1₂F (Sokane 141B, obtained from A-Gas UK Ltd), fillite, vermiculite, china clay, glass spheres, borax, pumice and/or aluminium trihydrate. To this mixture was added a cold cure catalyst (Pyrocat 70, a mixture of phosphoric acid ester and inorganic acid, obtained from Alderley Materials) . The mixture was placed in a mould and allowed to cure at room temperature. Afterwards, the cured product was removed from the mould. The relative quantities of the starting materials in % by weight for each example are given in Table 4 below:

Table 4

Example 35

30 g of a novolak phenol-formaldehyde phenolic resin prepolymer (Cellobond Powder Resin (grade JlOllH) from Borden Chemicals) was mixed with 970 g of a mixture of 84 wt% gypsum powder, 15 wt% perlite granules and 1 wt% glass powder. The mixture was placed in a mould and the mould was heated in an oven until the resin was cured. After cooling the cured product was removed from the mould.

Flame Tests

Samples of material were manufactured according to some of the examples described above. The samples were manufactured in the form of tiles having a honeycomb structure with an average pore diameter of about 0.5mm. The faces of the tiles were all aproximately 300mm x 300mm in size. Other details of the composition of each sample are given in the table below.

Each of these samples were subjected to the following test procedure:

The panels were mounted vertically in a test rig and securely held at the upper and lower edges. K-type thermocouples were used to measure temperatures and were of welded tip construction with glass fibre insulation. They were attached to the test panels with an acrylic adhesive with high thermal conductivity to ensure good thermal contact with the sample.

A thermocouple was attached to the rear of each test panel, at a position 25mm directly below the centre point of the test panel to record the rise in temperature as the flame broke through the sample. A second thermocouple was located at a point away from the test piece to record the ambient air temperature within the testing room. The thermocouples were linked to a datalogger which was set to record readings at 1 second intervals.

An oxy-acetylene burner was fixed in a position normal to the face of the test-pieces at a position 25mm below the centre of the samples so that it was in line with the thermocouple located at the rear of the test- piece. The distance between the nozzle and the sample was 125mm for each test. The burner used was of conventional design fitted with a standard 1/8 inch metal burning nozzle. Acetylene gas was delivered to the nozzle at a pressure of approximately 6psi and oxygen at 120psi. This arrangement provides a temperature of approximately 2500°C at the surface of the test-piece. The burner was lit and the time taken for the flame to burn through the samples was measured. The results are summarised in the table below.

Combustability Test

Five samples of material of the composition of Example 26 were manufactured according to the process described above. The samples were all 50mm thick and each had a specific gravity of 0.6.

The five samples were submitted to the test criteria specified in Section 2 of the Annex to International Maritime Organisation Resolution MSC61 (67); Annex 1, Part 1. This is identical to the BS476 part 4 test which requires that (a) the product must not have a sustained duration of flaming of more than 10 seconds, (b) the maximum permissible temperature rise in the furnace is 10°C and (c) the maximum permissible weight loss of the sample is 18%.

Thus, in accordance with the test criteria specified in Section 2 of the Annex to IMO Resolution MSC61 (67); Annex 1, Part 1, the product would be classified as "non-combustible". Smoke Emission Tests

An 8mm thick tile of material was manufactured according to Example 7. The sample weighed 36.2 grams The sample was tested according to the standard test methods FAR 25.853 (d) /JAR 25.853(c)

The following results were obtained:

The sample passed the requirements of FAR 25.853(d), APP.F Pt.V(b) and JAR 25.853(c), APP.F Pt.V(b).

Claims

CLAIMS :

1. A material for thermal insulation which comprises a phenolic resin, characterised in that one or more fillers and one or more minerals are included as additives during synthesis of the phenolic resin; the one or more fillers being selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and the one or more minerals being selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock.

2. A material for thermal insulation obtainable by curing a mixture which comprises:

(A) a phenolic resin prepolymer,

3. A material as claimed in claim 2 wherein the phenolic resin prepolymer is a novolak resin.

4. A material as claimed in claim 2 wherein the phenolic resin prepolymer is a resole resin.

5. A material as claimed in any one of claims 2 to 4 wherein the mixture prior to curing comprises phenolic resin prepolymer in an amount of from 1 to 90 wt%, one or more fillers in an amount of from 0.8 to 85 wt% and one or more minerals in an amount of from 0.1 to 60 wt% based on the total weight of the mixture.

6. A material as claimed in any one of claims 2 to 5 wherein the mixture prior to curing also comprises a hardener in an amount of from 0.1 to 20 wt% based on the total weight of the mixture.

7. A material as claimed in claim 6 wherein the hardener is an aqueous mixture of p-toluene sulphonic acid and phosphoric acid.

8. A material as claimed in any one of claims 1 to 7 wherein one or more materials selected from the group consisting of ceramic glass, silicate glass, carbon fibre, metal particles, blowing agents, fillite, vermiculite, china clay, borax, pumice and diatomaceous earth are also included as additives during synthesis of the phenolic resin .

9. A material for thermal insulation which comprises:

(A' ) a phenolic resin in an amount sufficient to bind components (B) and (C) ,

(B) one or more fillers selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides, and

(C) one or more minerals selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock.

10. A material as claimed in claim 9 which comprises a phenolic resin in an amount of from 1 to 99 wt%, one or more fillers in an amount of from 0.8 to 85 wt% and one or more minerals in an amount of from 0.1 to 60 wt%, based on the total weight of the composite material.

11. A material as claimed claim 9 or 10 which further comprises one or more materials selected from the group consisting of ceramic glass, silicate glass, carbon fibre, metal particles, blowing agents, fillite, vermiculite, china clay, borax, pumice and diatomaceous earth.

12. A material as claimed in any one of claims 1 to

11 wherein the one or more fillers are selected from the group consisting of hydrated calcium sulphate, calcium sulphate hemihydrate, anhydrous calcium sulphate and calcium oxide.

13. A material as claimed in any one of claims 1 to

12 wherein the mineral is igneous rock or a mineral derivable from igneous rock which comprises silica in an amount of from 20 to 80 wt%, alumina in an amount of from 5 to 30 wt%, magnesia in an amount of from 0.05 to 30 wt% and ferric oxide in an amount of from 0.05 to 10 wt%, based on the total weight of the mineral.

14. A material as claimed in any one of claims 1 to

13 wherein the mineral is expanded perlite.

15. Use of a material as claimed in any one of claims 1 to 14 as a thermal insulation or fire retardant material .

16. A process for forming a thermal insulation material comprising mixing a phenolic resin prepolymer with one or more fillers selected from the group consisting of alkaline earth metal sulphates and alkaline earth metal oxides and with one or more minerals selected from the group consisting of mica, igneous rock and minerals derivable from igneous rock and curing the mixture so as to convert the phenolic resin prepolymer into a phenolic resin.