IE49752B1 - Foamed plastics material,method for preparing same and their use - Google Patents

Description

This invention relates to foamed plastics materials based on phenolic resins.

Foamed plastics materials are widely used in industry, especially for thermal insulation in buildings and as shock absorbent packing materials for packing delicate articles for transport. They have also found use widely in other outlets such as soft furniture.

Polystyrene and polyurethane foams are widely used but are combustible. Even when modified with flame retardants, they give off noxious poisonous fumes or dense smoke when exposed to flame and are a serious hazard in fire. For these reasons, there is a growing prejudice against their use, especially in private dwellings.

Foamed phenolic resins have also been available for many years and can be formulated so as not to support flame and to have a lower tendency than polystyrene or polyurethane foams to generate toxic fumes in the presence of flame. The basic material, i.e. the phenolic resin, is also relatively cheap. Nevertheless, hitherto they have not gained as wide 2ϋ acceptance in industry as polyurethane inter alia because of their generally poor physical strength; they tend to be brittle and friable and easily crushed. Further, while they can be manufactured as simple shapes such as slabs and blocks, they cannot readily be moulded to produce complex shapes. One reason for this is that their poor strength can create difficulties in removing the nrticlc from the mould. Thus, more complex shapes have to be produced from the slabs or blocks by a further operation such as machining.

It has been known for decades that foamed phenolic resin products could be formed directly from a phenolic resole and without the incorporation of gas producing additives if sufficiently forcing conditions were used, e.g. by heat and/or by addition of an acid catalyst and/or by using a resole of high reactivity. For example, it is known from British Patent Specification No. 578838 that if a phenolic resole is heated to 120°C, the whole mix rises up and sets to a very light structure with large cells of about % inch (12.5 ran) diameter. The expansion is effected by steam generated during the exothermic curing reaction from water present in the resole or formed as a by-product of the curing reaction. However, the expanded products obtained by the reaction, sometimes known as boiled resins, were found to have a coarse and non-uniform structure which is largely open-celled and also contain large voids or blow holes (see, for example, CB-A-1088056 and DE-A-1494085) and in practice the production of foamed phenolic resin products in this manner did not prove satisfactory. Apparently it was found difficult if not impossible to achieve by this method a product with a reasonably uniform cell size or to achieve a product of given ί* properties or quality reproducibly. In any event, attempts to produce phenolic foams by this method were largely abandoned many years ago and other methods were developed in which the foaming is effected instead by adding to the mixture of resole and acid hardener a substance which will provide the gas for the foaming action by volatilisation, by decomposition or by reaction with the acid hardener. Such a substance is known as a blowing agent.

The first method, illustrated for example, in Plastics, Vol 29, No. 315 of January 1964 at page 84, Offenlegungsschrift Specification 1694009 published in 1971, and French Patent Specification 1582096, involves using an additive, e.g. a low boiling liquid hydrocarbon such as butane, pentane and hexane or other low boiling liquid organic compound such as petroleum ether, which produces a gas hy volatilisation during hardening. Heat is required for the foaming and curing reaction and reaction times of to 4 hours are mentioned.

The second method employs a compound such as sodium carbonate which decomposes under the influence of the acid hardener or heat or both to yield a gas. Such a method is suggested, for example, iu German Plastics, Vol 51, No. 11, November 1961 at page 104, Plastics, Vol 29, No. 321 at pages 62 to 65, British Patent Specification 652756 and the above-mentioned French patent specification.

The third method employs a component which reacts with the acid hardener to generate hydrogen. This method is described, for example, in International Polymer Science and Technology, Vol 1, Nu. Η, 1974, page:· 7Η-Κ0 where the component employed is aluminium powder. Thi use of such metal powders is also suggested in the above-mentioned French specification, French patent specification 1450476, which is concerned 5 principally with a method of controlling the rate of cure of a phenolic resin by use of a combination of catalyst and inhibitor, proposes varying the density of the product by judicious use of a filler and/or blowing agent. As examples of blowing agents are listed carbonates (which will react with an acid catalyst to yield carbon dioxide), hydrocarbons which will vaporise at the conditions encountered during cure, and certain types of asbestos whicb act as blowing agents because they contain carbonate (see GB-A-1107212 which is the U.K. equivalent of this French patent specification).

Most or all of the foamed phenolic resin products available on the market at present are manufactured by one or other of the above-mentioned methods employing a blowing agent, and generally the first method. However, all of these methods have disadvantages.

Thus, the volatilisable compounds employed in the first method can be expensive and also present handling hazards, and the fire-resistant properties of the product can be adversely affected where the blowing gas, which is to some extent retained in the cells of the product, is inflammable. In the presence of a fire, the trapped gases expand rapidly and sometimes explode and shoot flaming debris from the product thereby presenting a risk of spreading the fire.

The preferred blowing agents for the second method tend to be alkaline, thereby neutralizing the acid hardener and requiring more of it to achieve a proper cure or even preventing a proper cure. Furthermore, the residues of these blowing agents may have an undesirable and sometimes unpredictable effect on the properties of the product.

The third method is disadvantageous because the metal 5 powders are relatively expensive, substantially increase the density of the foam and also interfere with its otherwise valuable electrical insulation and heat insulation properties.

We have now found a method of producing a foamed phenolic resin composition having a cellular structure of substantially uniform cell size and which avoids the need to use an added blowing agent. The method can be employed to provide foamed resin material having very valuable properties, such as a wide range of densities 3 e.g. from 50 to 500 Kg/m , a fine texture of substantially uniform pore (cell) size, excellent fire-resistance, high thermal insulation and good resistance to heat. Moulded products are readily obtainable from the foam-forming composition in simple fashion and without the need for sophisticated or expensive equipment.

In a preferred embediment which employs a modified resole, products may be obtained with a particularly desirable combination of physical properties, notably valuable energy adsorption characteristics, good strength anil relativily low friability.

Thus, by means of the invention, products can be obtained which are valuable in the building industry not only for thermal ’’nsulation hut also as constructional materials such as panels and roofing and even as load-bearing materials such as building blocks.

By suitable adjustment of the variables employed in the process, products can be obtained which combine the above properties with a density similar to and the handling characteristics of wood in that they can be sawn, cut and abraded and will receive and hold screws and nails, in some cases even better than wood in that there is less tendency to split.

The foamed products of the present invention are in general substantially rigid foams, Xn accordance with the present invention, there is provided a method for the production of a foamed phenolic resin material, the method comprising (i) in the absence of blowing agent effecting a curing reaction between (a) a liquid phenolic resole having a reactivity number (as herein defined) of at least 1 and (b) a strong acid hardener for the resole, in the presence Of (c) a finely divided inert (as herein defined) and particulate solid which has a particle size in the range 0.5 to 800 microns (0.5 to 800 pm), is insoluble in the resole is prtsi-nt in an amount of at least 207» by weight of Lhe liquid if·-.iln and is substantially uniformly dispersed through the mixture of resole and hardener; the temperature of the mixture containing resole and hardener due to any applied heat not exceeding 85°C and the said temperature and the concentration of the acid hardener being such that at least one compound present in the resole or generated as a by-product of the curing reaction is volatilised within the mixture before the mixture sets, and (ii) recovering a foamed phenolic resin product having a cellular texture of substantially uniform cell size.

By a phenolic resole is meant a solution in a suitable solvent of the acid-curable prepolymer composition obtained by condensing, usually in the presence of an alkaline catalyst such as sodium hydroxide, at least one phenolic compound with at least one aldehyde, in well-known manner. Examples of phenols that may be employed are 40752 phenol itself and substituted, usually alkyl-substituted, derivatives thereof provided that the three positions on the phenolic benzene ring o- and p- to the phenolic hydroxyl group are unsubstituted. Mixtures of such phenols may also be used. Mixtures of one or more than one of such phenols with substituted phenols in which one of the ortho or para positions has been substituted may also be employed where an---— ---9 improvement in the flow characteristics of the resole is required but the cured products will be less highly cross-linked. However, in general, the phenol will be comprised mainly or entirely of phenol itself, for economic reasons.

The aldehyde will generally be formaldehyde although the use of higher molecular weight aldehydes is not excluded.

The phenol/aldehyde condensation product component of the resole is suitably formed by reaction of the phenol with at least 1 mole of formaldehyde per mole of the phenol, the formaldehyde being generally provided as a solution in water, e.g. as formalin. It is preferred to use a molar ratio of formaldehyde to phenol of at least 1.25 to 1 but ratios above 2,5 to 1 are preferably avoided. The most preferred range is 1.4-2.0 to 1.

In accordance with the preferred embodiment referred to above, the mixture also contains a compound having two active H atoms (dihydric compound) which will react with the phenol/ aldehyde reaction product of the resole during the curing step to reduce the density of cross-linking. Preferred dihydric compounds are diols, especially alkylene diols or diols in which the chain of atoms between the Oil groups contains not only methylene and/or alkyl-substituted methylene groups but also one or more hetero atoms, especially oxygen atoms, e.g. ethylene glycol, propylene glycol, propane-1,3-diol, butane-1,4-diol and neopentyl glycol. Particularly preferred diols are poly-, especially di-, (alkylene ether) diols e.g. diethylene glycol and, especially, dipropyiene glycol. Preferably the dihydric compound is present in an amount of from 0 to 357. by weight, more preferably 0 to 257. by weight, based on the weight of phenol/aldehyde condensation product. Most preferably, the dihydric compound, when used, is present in an amount of from 5 to 15% by weigbt based on the weight of phenol/ aldehyde condensation product. When such resoles containing dihydric compounds are employed in the present process, products having a particularly good combination of physical properties, especially strength, can be obtained.

Suitably, the dihydric compound is added to the formed resole and preferably has 2-6 atoms between OH groups.

The resole may comprise a solution of the phenol/ aldehyde reaction product in water or In any other suitable solvent or in a solvent mixture which may or may not include water.

Where water is used as the sole solvent, it is preferred to be present in an amount of from 15 to 35% by weight of the resola, preferably 20 to 30%. Of course the water content may be substantially less if it is used in conjunction with a cosolvent, e.g. an alcohol or one of the above-mentioned dihydric compounds where one is used.

As indicated above, the liquid resole (i.e. the solution of phenol/aldehyde product optionally containing dihydric compound) must have a reactivity number of at least 1. The reactivity number 10 is x where x is the time in minutes required to harden the resole using 107. by weight of the resole of a’66-677. aqueous solution of p-toluene sulfonic acid at 60°C. The test involves mixing about 5ml of the resole with the stated amount of the p-toluene sulfonic acid solution in a test tube, immersing the test tube fn a water bath heated to 60°C and measuring the time required for the mixture to become hard to the touch.

The resole must have a reactivity number of at least 1 for useful foamed products to be produced by the method of the invention, and preferably the resole has a reactivity number of at least 5, most preferably at least 10.

The pH of the resole, which is generally alkaline, is preferably adjusted to about 7, if necessary, for use in the process of the invention, suitably by the addition of a weak organic acid such as lactic acid.

Examples of strong acid hardeners are inorganic acids such as hydrochloric acid, sulphuric acid and phosphoric acid, and strong organic acids such as aromatic sulphonic acids, e.g. toluene sulphonic acids, and trichloroacetic acid. Weak acids such as acetic acid and propionic acid are generally not suitable. The preferred hardeners for the process of the invention are the aromatic sulfonic acids, especially toluene sulfonic acids.

The acid may be used as a solution in a suitable solvent such as water.

For certain applications and in particular, for example, in applications which require the mixture of resole, hardener and solid (c) to be poured e.g. into a mould and in slush moulding applications, the amount of inert solid that can 49758 be added to the resole and hardener is determined by the viscosity of the mixture of resole and hardener in the absence of the solid. For these applications, it is preferred that the hardener is provided in a form, e.g, solution, such that when mixed with the resole in the required amount yields a liquid having an apparent viscosity not exceeding about 50 poises(5 Pa.s) at the temperature at which the mixture is to be used, and the preferred range is 5-20 (0.5-2 Pa.s) poises. Below 5 poises (0.5 Pa.s), the amount of solvent present tends to present difficulties during the curing reaction.

The curing reaction is exothermic and will therefore of itself cause the temperature of the mixture containing resole and acid hardener to be raised. The temperature of the mixture may also be raised by applied heat but the temperature to which said mixture may then be raised (that is, excluding the effect of any exotherm) must not exceed 85°C.

If the temperature of the mixture exceeds 85°C before addition of the hardener, it is difficult or impossible thereafter to properly disperse the hardener through the mixture because of incipient curing. On the other hand, it is difficult, if not impossible, to uniformly heat the mixture above 85°C after addition of the hardener.

Increasing the temperature towards 85°C tends to lead to coarseness and non-uniformity of the texture of the foam but this can be offset at least to some extent at moderate temperatures ~ 49752 by reducing the concentration of hardener. However, we have found that at temperatures much above 75°C, even the minimum amount of hardener required to cause the composition to set is Often too much to avoid these disadvantages. Thus, temperatures above 75°C are preferably avoided and preferred temperatures for most applications are from ambient temperature to about 75°C, The preferred temperature range appears to depend to some extent on the nature of the solid (c). For most solids it is from 25 to 65°C but for some solids, in particular wood flour and grain flour, the preferred range is 25 to 75°C. The most preferred temperature range is 30 to 50°C. Temperatures slightly below ambient, e.g. down to 10°C can be used, if desired, but no advantage is gained thereby. In general, at temperatures up to 75°C, increase in temperature leads to decrease in the density of the foam and vice versa.

The amount of hardener present also affects the nature of the product as well as the rate of hardening. Thus, increasing the amount of hardener not only has the effect of reducing the time required to harden the composition but above a certain level dependent on the temperature and nature of the resole it also tends to produce a less uniform cell structure.

It also tends to increase the density of the foam because of the increase in the rate of hardening. In fact, if too high a concentration of hardener is used, the rate of hardening may be so rapid that no foaming occurs at all and under some 9752 conditions the reaction can become explosive because of the build up of gas Inside a hardened shell of resin.

The appropriate amount of hardener will depend primarily on the temperature of the mixture of resole and hardener prior to the commencement of the exothermic curing reaction and the reactivity number of the resole and will vary inversely with the chosen temperature and the reactivity number. The preferred range of hardener concentration is the equivalent of 2 to 20 parts by weight of p-toluene sulfonic acid per 100 parts by weight of phenol/aldehyde reaction product in the resole assuming that the resole has a substantially neutral reaction, i.e. a pH of about 7. By equivalent to p-toluene sulfonic acid, we mean the amount of chosen hardener required to give substantially the same setting time as the stated amount of p-toluene sulfonic acid. The most suitable amount for any given temperature and combination of resole and finely divided solid is readily determinable by simple experiment. For use with the preferred temperature range of 25-75°C and a resole having a reactivity number of at least 10, the best results are generally obtained with tbe use of hardener in amounts equivalent to 3 to 10 parts of p-toluene sulfonic acid per 100 parts by weight of the phenol/aldehyde reaction product. For use with temperatures below 25°C or resoles having a reactivity number below 10, it may be necessary to use more hardener. 9 7 5 2 It may be necessary to make some adjustment of the r hardener composition in accordance with the nature, especially shape and size, of the mould and this can be established by experiment.

An important aspect of the invention is that by suitable control of the temperature and of the hardener concentration, the time lapse between adding the hardener to the resole and the composition becoming hard (referred to herein as the setting time) can be varied at will from a few seconds to up to an hour or even more, without substantially affecting the density and cell structure of the product.

Another factor which controls the amount of hardener required can be the nature of the inert solid. Very few are exactly neutral and if the solid has an alkaline reaction, even if only very slight, more hardener may be required because of the tendency of the filler to neutralize it. It is therefore to be understood that the preferred values for hardener concenttration given above do not take into account any such effect of the solid. Any adjustment required because of the nature of the solid will depend on the amount of solid used and can be determined by simple experiment.

The exothermic curing reaction of the resole and acid hardener leads to the formation of by-products, particularly aldehyde and water which, in the method of the present invention, are at least partially volatilised.

An essential feature of the invention Is that the curing reaction is effected in the presence of a finely divided inert and insoluble particulate solid which is substantially uniformly dispersed throughout the mixture of resole and hardener. By an inert solid we mean that in the quantity it i3 used it does not prevent the curing reaction.

Although we do not wish to be bound by this theory, it is believed that the finely divided particulate solid provides nuclei for the gas bubbles fonned by the volatilisation of the small molecules, primarily CH^O and/or HgO, present in the resole and/or generated by the curing action, and provides sites at which bubble formation is promoted, thereby assisting uniformity of pore size. The presence of the finely divided solid may also promote stabilization of the individual bubbles and reduce the tendency of bubbles to agglomerate and eventually cause likelihood of bubble collapse prior to cure. The phenomenon may be similar to that of froth flotation employed in the ceoncentration of low grade ores in metallurgy. In any event, as illustrated in Example 1 below, the presence of the solid (c) is essential to the formation of the product.

To achieve the desired effect, the solid should be present in an amount of not less than 20% by weight based on the weight of the resole. 9 7 5 2 σ Any finely divided particulate solid which is insoluble in the reaction mixture appears to be suitable, provided it is inert and does not act as a blowing agent. The fillers may be organic or inorganic (including metallic), and crystalline or amorphous. Even fibrous solids have been found to be effective, although not preferred.

Examples are clays, clay minerals, talc, vermiculite metal oxides, refractories, solid or hollow glass microspheres, fly ash, coal dust, wood flour, grain flour, nut shell flour, silica, mineral fibres such as finely chopped glass fibre and finely divided asbestos, chopped fibres, finely chopped natural or synthetic fibres, ground plastics and resins whether in the form of powder or fibres, e.g. reclaimed waste plastics and resins, pigments such as powdered paint and carbon black, and starches. e Solids having more than a slightly alkaline reaction, e.g. silicates of alkali metals, are preferably avoided because of their tendency to react with the acid hardener. Solids such as talc, however, which have a very mild alkaline reaction, are acceptable.

Some materials, especially fibrous materials such as wood flour, can be absorbent and it may therefore be necessary to use generally larger amounts of these materials than non-fibrous materials, to achieve valuable foamed products.

The solids have a particle size in the range 0.5 to 800 microns (0.5 to 800 um). If the particle size is too great, the cell structure of the foam tends to become undesirably coarse. On the 49753 other hand, at very small particle sizes, the foams obtained tend to be rather dense. The preferred range is 1 to 100 microns (j to K)0pm)P most preferably 2 to 40 microns (2 to 40 pm). Uniformity of cell structure appears to be encouraged by uniformity of particle size.

Mixtures of solids may be used If desired.

Preferably, the finely divided solid (c) has a density which is not greatly different from that of the resole, so as to reduce the possibility of the finely divided solid tending to accumulate towards the bottom of the mixture after mixing.

One preferred class of solids is the hydraulic cements, e.g. gypsum and plaster, but not Portland cement because of its alkalinity. These solids will tend to react with water present in the reaction mixture to produce a hardened skeletal structure within the cured resin product. Morover, the reaction with the water is also exothermic and assists in the foaming and curing reaction. Foamed products obtained using these materials have particularly valuable physical properties. Moreover, when exposed to flame even for long periods of time they tend to char to a brick-like consistency which is still strong and capable of supporting loads. The products also have excellent thermal insulation and energy absorption properties and are particularly suitable for use as wood substituents. The preferred amount of such materials is from 20 to 200 parts by weight per 100 parts by weight of resole.

Another class of solids which is preferred because its use yields products having properties similar to those obtained using hydraulic cements comprises talc and fly ash. The preferred amounts of these solids are also 20 to 200 parts by weight per 100 parts by weight of resole. o For the above classes of solid, tbe most preferred range 5 is 50 to 150 parts per 100 parts of resole.

Thixotropic foam-forming mixtures can be obtained If a very finely divided solid such as Aerosil (finely divided silica) is included.

If a finely divided metal powder is included, electrically 10 conducting properties can be obtained and the foamed product can even be electroplated. The metal powder, which will not be such as to generate gas by reaction with the acid hardener, is preferably used in amounts of from 50 to 250 parts per 100 parts by weight of resole. c 48752 In general, the maximum amount of solid that can be employed is controlled only by the physical problem of incorporating it into the mixture and handling the mixture. In general it is desired that the mixture is pourable but even at quite high solids concentrations, when the mixture is like a dough or paste and cannot be poured, foamed products with valuable properties can be obtained.

In general, it is preferred to use the fibrous solids only in conjunction with a non-fibrous solid since otherwise the jO foam texture tends to be poorer.

Other additives may be included in the foam-forming mixture; e.g. surfactants, such as anionic materials e.g. sodium salts of long chain alkyl benzene sulfonic acids, non-ionic materials such as those based on poly(ethylene oxide) or copolymers thereof,and cationic materials such as long chain quaternary ammonium compounds or those based on polyacrylamides; viscosity modifiers such as alkyl cellulose especially methyl cellulose, and colorants such as dyes or pigments. Plasticisers for phenolic resins may also be included provided the curing and foaming reactions are not suppressed thereby, and polyfunctional compounds other than the dihydric compounds referred to above may be included which take part in the cross-linking reaction which occurs on curing; e.g. di- or poly-amines, di- or poly-isocyanates, di- or f5 poly-carboxylic acids and aminoalcohols.

PoLymerisable unsaturated compounds may also be included possibly together with free-radical polymerisation initiators that are activated during the curing action e.g. acrylic monomers, so-called urethane acrylates, styrene, maleic acid and derivatives thereof, and mixtures thereof.

Other resins may be included e.g. as prepolymers which are cured during the foaming and curing reaction or as powders, emulsions or dispersions. Examples are polyacetals such as polyvinyl acetals, vinyl polymers, olefin polymers, polyesters, acrylic polymers and styrene polymers, polyurethanes and prepolymers q thereof and polyester prepolymers, as well as melamine resins, phenolic novolaks, etc.

In a modification of the invention, conventional blowing agents may also be included to enhance the foaming reaction, e.g. low boiling organic compounds or compounds which decompose or react to produce gases.

The foam-forming compositions may also contain dehydrators, if desired. 49753 A preferred method of forming the foam-forming composition comprises first mixing the resole and inert filler to obtain a substantially uniform dispersion of the filler in the resole, and thereafter adding the hardener. Uniform distribution of both the filler and the hardener throughout the composition is essential for the production of uniformly textured foam products and therefore thorough mixing is required.

If it is desired that the composition is at elevated temperature prior to commencement of the exothermic reaction, this can be achieved by heating the resole or first mixing the resole and the solid (c) and then heating the mixture. Preferably the solid (c) is added to the resole just before the addition of the hardener. Alternatively, the mixture of resole, solid and hardener may be prepared and the whole mixture then heated, e.g. by short wave irradiation, preferably after it has been charged to a mould. A conventional radiant heat oven may also be used, if desired, but it is difficult to achieve uniform heating of the mixture by this means.

An important feature of the invention is that mouldings of complex shape can readily be obtained. Open or closed moulds may be used but it is important that the mould is not such as to act as a heat sink to the extent that the rate of heat loss from the mixture is so great that volatilisation of small molecules in the resole and/or produced by the curing reaction is suppressed.

Thus, mould designs which result in a large surface area of the moulding composition (relative to the volume of the composition) being exposed to air at ambient temperature or to a mould surface which is a good conductor of heat and which is at a temperature which is low compared to that reached by the moulding composition during the curing reaction, should preferably be avoided.

Nevertheless, it is a particular feature of the invention that relatively thin-section mouldings of large surface area can readily be obtained. The preferred method is to arrange the mould with the plane containing the two largest dimensions horizontal, or preferably at a small angle to the horizontal to assist the escape of any excess gas produced during the foaming and curing. If only one of the large faces of the moulding is to be contoured, this is preferably formed against the bottom face of the mould. If the opposite face is also to be contoured, then the mould should be closed by a top plate *9752 which is also appropriately contoured and the foaming should be against a back pressure which may be provided e.g. by employing more of the foam-forming composition than is required to fill the mould after foaming or by permitting the top plate to float.

One method of permitting escape of excess gas generated during • moulding is to locate the top plate slightly above the top edges of the mould to leave a gap. However, the edges of the moulding may thereafter require a trimming operation. Another method is to provide vents at suitable locations on the mould surface.

Mouldings of e.g. up to 10ft by 4ft (305 x 122 cm) or more and less than 1 inch (25.4 mm) thick can be obtained by this method.

If the mould design is such that heat loss from the mixture is substantially non-uniform through the body of the mixture, the cell structure of the foam may vary through the body of the product.

So far as concerns the material from which the mould is formed, preferred mould materials are wood and plastic, e.g. glass fibre reinforced resin. Plaster, rubber or elastomeric moulds may also be used. Metals should generally be avoided unless heated moulds are used.

An advantage of the invention, however, is that in general provided mould surfaces having low thermal conductivity are used it is not necessary to heat the moulds, even for the production of thin slabs.

A further advantage of the invention is that with mixtures which are sufficiently fluid, hollow articles of complex shape may be produced by slush moulding. For example, statues, figurines and human heads, arms, legs and other parts of the human body may be reproduced in remarkable detail, e.g. for use in the • production of mannequins.

It is a particular feature of the foamed products of the present invention that they can be demoulded without damage even in the absence of a mould release agent whereas one difficulty with conventional phenolic foams is that their strength is such that demoulding them is a problem except from moulds of the simplest shape.

A further advantage of the invention is that by choice of suitable conditions, the mixtures can be caused to produce foamed products which are self-skinned. This may be achieved, for example, by heating the mould surface to such a temperature that the mixture in the immediate vicinity thereof sets hard before any volatilisation can occur or preferably, by maintaining the mould surface at a sufficiently low temperature that volatilisation is suppressed in the mixture in the immediate t? vicinity thereof. In many cases, using a mould at ambient temperature is sufficient, especially where rotational or slushing moulding is employed.

If desired, at least a part of the mould surface may be coated e.g. with a gel coat which is preferably phenolic resolebased and which may be reinforced, e.g. with glass fibres or 48752 other fibrous materials which may be in the form of tissues, mats, woven fabrics or rovings. Also materials or objects may be bonded on to or into the foamed product hy locating them appropriately in the mould and causing the mixture to foam and set in contact with them. By this means,for example, laminated products may be obtained with a layer of the foamed resin bonded to a layer of other material or sandwiched between layers of other materials which may be the same or different and may he e.g. plastics, wood e.g. plywood or veneer, metal e.g. aluminium foil, or steel sheet, cement products e.g. concrete, etc.

In general, no adhesive is required.

For example, a laminate of a layer of the foamed material bonded on at least one face to a waterproof membrane such as a conventional waterproof roofing membrane, may he obtained in this manner. Excellent bonding may be achieved between the foamed material and such waterproof membranes.

Also, fixing means such as clips or bolts can he moulded into the foam in this manner.

Foamed products can he obtained by the present invention having a wide range of densities and other properties, and suitable for use in a wide variety of applications from packaging to thermal insulation and to structural building applications such as building blocks, panels, roofing members such as tiles or slabs, and architectural mouldings.

By means of the invention, foamed products may be 48752 obtained, particularly where minerals such as talc or fly ash, or hydraulic cement fillers such as plaster are used, which are characterised by good resistance to heat and the spread of flame and it is possible to produce products which are zero-rated for fire resistance and the spread of flame whereby they may be used, for example, for or in structural components such as walling or partitioning in domestic buildings or for or in doors, partitions or cladding or for decorative purposes such as in wall or ceiling tiles.

The foamed products obtained by the invention are generally characterised by good thermal insulation properties and are suitable for use, for example, in pipe lagging and heat shields and in the production of roofing for both flat and pitched roofs, e.g. in roofing tiles and sheet roofing.

Where the resoles contain a dihydric compound as described above and the solid (c) is selected from minerals such as talc or fly ash and hydraulic cements such as gypsum or plaster, moulded products may be obtained which can reproduce even complex mould surfaces in fine detail and yet which have densities and working characteristics resembling wood in that they may be sawn, cut and abraded and receive and hold even large nails and screws. They are therefore particularly suitable for use as architectural mouldings such as cornices, ceiling decorations, architraves, door and window surrounds and mouldings etc., where they will be cheaper than wood mouldings and less 48752 fragile and more easily handled than mouldings in fibrous plaster. They are also suitable as a replacement for wood in other fields such as furniture and fittings.

Foamed products obtained from resoles containing a dihydric compound are also less friable than conventional phenolic foams of corresponding density.

By suitable choice of finely divided materials, e.g. finely divided lead, products which are particularly suitable for sound insulation e.g. as in partitioning, or in casings for machinery and engines, may be produced. By use of finely divided lead, relatively light-weight materials having radioactive shielding properties can also be produced. The finely divided lead may advantageously be used together with another suitable solid e.g. talc or plaster.

Light weight concrete structures can be obtained by including in a fluid concrete mix foamed phenolic resin spheres made by the process of this invention.

The invention is now illustrated by the following Examples in which all parts are by weight unless otherwise indicated.

EXAMPLE 1 In a first experiment 100 parts by weight of a poly (alkylene ether) diol-containing aqueous resole (Resole A) having a solids content of 807. and a reactivity number of approximately 12 and sold commercially by Abrasive Products Limited of Wolverhampton, England, as PL 12/1663 were mixed with 15 parts of a 677- by weight solution of p-toluene sulfonic acid (Hardener solution X) and allowed to cure at room temperature. The product was a toffee-coloured substantially transparent resin which contained no evidence of foaming.

In a second experiment, 100 parts by weight of the same resole wete mixed with 25 parts by weight of dry finely divided talc purchased as Talc 300 from English China Clay Ltd. No foaming or curing occurred.

In a further experiment, a portion of the same talc was mixed with 15 parts by weight of the p-toluene sulfonic acid solution and, again, no foaming or curing occurred.

In a last experiment, the sec The above series of experiments was repeated but replacing the resole with a poly(alkylene ether) diol-containing aqueous resole having a solids content of 807. and a reactivity number of approximately 10 and sold commercially by C D F Chcmie of France as Norsophen 1200 (Resole B) with the same results.

The series was repeated again using the following solids instead of talc and with the same results: plaster, fly ash, glass microspheres (ArmOSphereS from Bondaglass Voss Ltd of England).

EXAMPLE 2 A series of experiments were carried out employing the following ingredients and method:resole: 100 parts of Resole A hardener: 10 parts of Hardener solution X solid (c):' dry talc, used in Example 1, in various amounts as set out in the table below.

The resole was heated to 50°C and then mixed with the • designated amount of talc. The hardener was then mixed in and about 130 ml of the resultant mixture was poured into a substantially cylindrical plastics mould having a diameter of about 6.5 cm and a height of about 20 cm. The setting time (defined as the time between adding the hardener and the mixture setting hard) and the nature of the foam obtained were observed and recorded in the table below.

Experiment Amount of Setting time talc (parts by weight) Comments A 1 (Comparative) 1.25 minutes little or no foaming has occurred 2.0 minutes very fine celled foam of uniform structure greater than 10 minutes excellent foam of very fine and uniform celled structure; lower density than B D 40 (Comparative) no cure too much solid (c) for the catalyst since the talc is slightly alkaline 100 (1) minutes very fine low density foam and substantially lower density than C 150 (2) not measured the material was doughlike prior to curing. Excellent fine celled foam of uniform structure obtained. (1) (2) parts by weight of hardener used. parts by weight of hardener used.

In all of experiments B, C, E and F, hard foams were obtained.

EXAMPLE 3 Experiment 2B was repeated but with varying amounts of hardener.

The results are set out in the table below.

Experiment Parts by weight of hardener Setting time J (Comparative) 5 no cure K 10 1,0 minute L 15 0.75 minute M 20 0,67 minute N 30 0.5 minute P (Comparative) 40 explosion Comments insui I ici t'lit caLalyst due to slight alkalinity of talc hard uniformed foam of moderate density coarser foam than in K and the structure showing some signs of non-uniformity texture of foam similar to I, but the density of foam is greater fairly dense foam with a less uniform structure than K, L or M setting occurred so fast that there was an explosion shortly after setting due to build up of gas pressure within hardened shell of resin 9752 EXAMPLE 4 Experiment 3K was repeated but varying the temperature to which the resole is heated. The results are set out in the table below. & Experiment Temperature Setting time Comments R (Comparative) 90°C 0,6 minute S 80°C 1.0 minute T 70°C 1.1 minutes V 60°C 1.3 minutes W jO°C 1.5 minutes X 40°C 3.75 minutes Y 30°C 7 minutes very large and non-uniform celled hard foam of coarse structure and low density.

Not fully cured throughout. slightly less coarse foam than R and uniformity improved Density about the same as R. fairly fine uniformed textured hard foam of low density. good fine-celled and uniform foam slightly denser than that of Experiment T. hardly distinguishable from Experiment V. much denser foam thanW but still of good texture. good fine uniform-celled foam structure but denser than X.

EXAMPLE 5 Two foams were prepared using the method and compositions of Examples 3L and 3N except that the resole was at ambient temperature (22°C). 48752 In the first experiment (composition 3L) a dense but very fine uniform-celled hard foam was obtained. With composition 3N, the density of the foam was greater. In the third experiment, employing 50 parts by weight of hardener, the foam 5 was even denser and the conditions were close to the explosive limit.

In the experiment with composition 3L, the setting time was 23 minutes and this was reduced to 7.75 minutes using composition 3N.

EXAMPLE 6 (Comparative) Example 3K was repeated but preheating the resole to 110°C. Hardening was so rapid that no foaming occurred and it was impossible to properly disperse the hardener so that curing was incomplete in parts of the mass.

EXAMPLE 7 100 parts of Resole A were heated at 45°C and 80 parts of plaster (CUD Plaster obtained from British Gypsum Limited) were then thoroughly mixed in to the heated resole. 15 parts of Hardener X were then thoroughly mixed in and sufficient of the resultant mixture was added to a mould to fill it full. The mould had a rectilinear cavity measuring 30 cm by 30 cm by 5 cm and was made from 2 grp sheets providing the 30 cm by 30 cm sides, the sheets being spaced apart by wooden spacers. The mould was positioned with the grp sheets vertical and the mixture was poured into the mould from the top which was then closed.

A hard foamed block measuring 30 cm by 30 cm by 5 cm was obtained. The foam had a substantially uniform fine celled structure and low friability. Little or no dust was obtained by scratching the surface of the foam with a thumb nail.

The flame from a propane gas burner was applied to one face of the block and after 6 minutes, although the face was charred, the block still retained its integrity and the opposite face of the block was still sufficiently cool that a hand could be applied to it without discomfort.

The density of the foam was approximately .5 g/cc.

EXAMPLE 8 100 parts of Resole A were heated to 20 60°C and 40 parts each of the plaster used in Example 7 and the talc used in Example 2 were thoroughly mixed in to the heated resole. 10 parts of Hardener solution X were then thoroughly mixed in and sufficient of the resultant mixture was poured in to a mould for the production of a roofing tile having the dimensions and shape *8783 of a Roman Pantile manufactured by Redland Limited of England.

The tile size was approximately 40 cm by 31 cm with a maximum thickness of 2.5 cm. The mould was arranged so that the faces of the tile were vertical and the composition was poured into the mould from the top. A grip (glass reinforced polyester) mould was used and the mould was warmed to about 50°C prior to the addition of the mixture.

The top of the mould was left open and the mixture was allowed to expand and overflow from the mould. The excess was then sawn off. The tile so obtained weighed approximately 1.3 kg and had the following properties: K value: 0.025 to 0.03 W/m/°C Flexural Strength: approximately 7MN/m Resistance to acid: attacked only by strong acids of above N/I concentration Resistance to alkali .: attacked only by strong caustic alkalis of above N/I concentration Action of ultra violet light: unattacked Action of water: none Weathering: a sand surfaced sample of the tile showed no effect as a result of weathering and no mould or dirt build up after 18 months exposure Fire propogation test (British Standard 476 Part 6): satisfactory Surface spread of flame (British Standard 476 Part 7): satisfactory (Class 1, no ignition) 49753 EXAMPLE 9 Sufficient of the mixture described in Example 8 was added to a mould of the kind described in Example7', but wherein, the small dimension was reduced from 5 cm to 2.3 cm ,to fill the mould ¾ full. Prior to adding the mixture, the two 30 cm by 30 cm faces of the mould were coated with a curable phenolic resole gel coat and glass fibre. The resole was preheated to 60°C but the mould was not heated. A sandwich panel was obtained comprising a foamed plastics core between two faces of glass fibre reinforced phenolic resin. This panel was subjected to the following tests with the results indicated:Fire Propagation Test (British Standard 476 Part 6): satisfactory Surface spread of flame(British Standard 476 Part 7): satisfactory (Class 1, no ignition) Modulus of rupture: 5.7 MN/m Tensile strength: 11,000 Kg/m Compressive strength: good EXAMPLE ID 100 parts of Resole B was heated to 50°C and 100 parts of a mixture comprising parts of the plaster used in Example 7, 40 parts of the talc used In Example 2 and 20 parts of glass beads Armospheres obtainable from Bondaglass Voss Limited of England were thoroughly mixed in to the preheated resole followed by 10 parts of the hardener employed in Example 1. Sufficient of the mixture was added to a mould of the kind described in Example 7 but having the internal dimensions 32 cm by 32 cm by 2.5 cm, to fill the mould approximately % full and the mould was then closed and the mixture allowed to foam and set to produce a very strong and rigid panel measuring 32 cm by 32 cm by 2.5 cm and having a substantially unfoamed skin. Removal of the skin showed that the core had a fine and uniform cell structure.

The panel was suitable for use in building for load-bearing applications. It had a density of 0.55 g/cc. Substantially no dust could be obtained from the exposed foamed surface of the panel when scratched with a thumb nail, indicating a remarkably low degree of friability for a phenolic resin-based foam. Physical properties, thermal insulation and fire resistance are comparable with those of the products described in Examples?, 8 and 9. .

The panel could be sawn and machined and 6-inch (about 150 mm) nails could be hammered into it without any signs of splitting. The nails were very strongly retained by the panel. Screws could also be screwed into the panel by conventional means.

The panel thus had properties making it very suitable for use in the building and construction industry, particularly as a wood substitute.

EXAMPLE η A casting of a statuette of the Venus de Milo standing approximately 1.5 metres high was prepared from a foam-forming composition according to the invention using a vinyl-rubber mould supported in a grp casing, the mould being held head downwards and the composition being poured into the mould through an opening at the top. The composition was prepared by thoroughly mixing 100 parts of the plaster used in Example 7 into the same weight of Resole A and then adding 20 parts of Hardener solution X. The resin was not preheated and the mould was also at ambient temperature. Sufficient of the foamforming composition was poured into the mould to fill it approximately full and the composition was allowed to expand and set at ambient temperature. There was a slight overflow from the top of the mould )5 and this was removed. On demoulding, a statuette was obtained which followed very closely the contours of the mould and which had a non-porous, substantially continuous skin. Sectioning the statuette showed that it consisted essentially of a very fine-celled and substantially uniform foam with an un-foamed skin. Thus, from general examination of the statuette, it was not possible to tell that the core was a foamed plastic. The statuette could be painted with ordinary or metal paints to give an attractive final effect. 40752 EXAMPLE 12 λ model of a human head was produced from the foamforming composition of Exanple 8 (but preheating the resole to 40°C), using a vinyl rubber mould supported in grp, such as is conventionally used in the production of mannequins and mannequin parts.

The head, which was approximately 20 cm high, was prepared by charging approximately 1.1 kg of the composition to the mould, closing it and then rotating the mould rapidly about two mutually perpendicular axes, as in a slush moulding technique.

The resultant head had a substantially unfoamed skin with a core of dense very fine and uniform celled foam. The contours of the mould were closely reproduced in the moulding, even in the complicated areas such as the ears.

EXAMPLE 13 A cylindrical block approximately 20 cm in diameter and 20 cm high was made from a foam-forming composition prepared by preheating 100 parts of Resole A to 50°C, thoroughly mixing into the preheated resole 60 parts of the talc used in Example 1 and 20 parts of the Armospheres used in Example 10, and then adding 10 parts ol Hardener solution X. Approximately 1.5 litres of the composition were placed in a cylindrical mould having the dimensions of the required block and allowed to foam and set. The mould was left open at the top and there was a slight overflow of the foamed composition which was removed.

The resultant block exhibited particularly good energy absorption characteristics and was able to receive and hold tenaciously 6-inch (about 150 mm) nails hammered into it without any sign of cracking or splitting. The block also showed very good strength, thermal insulation properties·and resistance to fire and the spread of flame. The block could, nevertheless, be sawn. Little or no dust was generated by scratching an exposed foamed surface of the block with a thumb nail.

EXAMPLE 14 lg 100 parLs of Resole B were heated to 50°C and 120 parts of powdered lead obtained from Bondaglass Voss Limited of England were added to the preheated resole. 12 parts of the hardener used in Example 1 were then added and approximately 130 ml of the resultant mixture was allowed to foam and set in a substantially cylindrical plastics mould having a diameter of 6,5 cm and a height of 20 cm.

The product was a heavy black foam with a substantially continuous un-foamed skin. The product could be electroplated using conventional techniques.

EXAMPLE J5 A foam was prepared from approximately 130ml of the mixture of Example 4W but using 50 parts of talc and 10 parts of hardener, in the mould described in the preceding Example. The resultant foam had a fine and substantially uniform texture.

In a second experiment, the procedure used in the first experiment was repeated with the same ingredients except that the resole was replaced by the same weight of an aqueous phenolformaldehyde resole having a solids content of approximately 777. and a reactivity number of 20. A product was obtained which was similar to that of the first experiment but it was more friable.

EXAMPLE 1/).

In a scries of experiments, foamed products were obtained from compositions comprising ResoleA, the hardener employed in Example 1 and a variety of finely divided solids. With each finely · divided solid, a number of experiments were performed in which the resole was preheated to different temperatures within the range 30 to 80°C and the amount of hardener was varied from 2¾ to 15 parts per 100 parts of resole. For all the finely divided solids employed, it was found that the preferred range of hardener was from 5 to 10 parts per 100 parts of resole and the preferred temperature range for preheating the resole was generally from 25 to 65°C. For the wheat flour, wood flour and powdered glass, however, the preferred temperature range for preheating the resole was 25 to 75°C. The finely divided solids employed in the experiments were as follows: (a) plaster (CBD Plaster from British Gypsum Limited of England) (b) talc (Talc 300 from English China Clay Company Limited of England) (c) carbon black (d) wheat flour (normal baking grade from McDougalls of United Kingdoifi) (e) wood flour (120 mesh (0.125 mm particle size) wood flour from Wood Treatment Limited of Macclesfield, England) (f) powdered glass (g) glass microspheres (Armospheres from Bondaglass Voss Limited of England) (h) lead powder obtained from Bondaglass Voss Limited (j) copper powder obtained from Bondaglass Voss Limited (k) brass powder obtained from Bondaglass Voss Limited (1) wood ash (powdered and dried) (m) builders sand (n) Cementone a colourant employed for products based on Portland cement 48752 (p) Alabastine from Alabastine Limited of Welwyn Garden City, England M table salt (s) a powdered domestic detergent (Vim from Proctor & Gamble of United Kingdom) (t) paint dust (the dried dust obtained from TKS paint) (u) china clay obtained from English China Clay Company Limited All the above materials except the metal powders were dried prior to use.

Particularly good fine-textured and substantially uniform foams were obtained from wheat flour, wood flour, builders sand and the dried paint dust. The foamed product obtained from the builders sand was particularly notable for its hardness and its ability to resist exposure to flame, such as from a propane gas torch, 15 EXAMPLE 17 A composition comprising 100 parts of Resole B, 25 parts of the talc used in Example 1 and the hardener used in Example 1 was placed In an oven which had been preheated to 180°C. After about four minutes, when the temperature of the composition had reached about 50°C, foaming and setting occurred. The product was a substantially uniformly textured foamed product having a density louer than that obtained by allowing the composition to foam and set at ambient temperature, EXAMPLE 18 The process of Example 17 Has repeated but using 156 parts of the plaster used in Example ? in place of the talc and an oven temperature of 80°C. After about 1 minute, when the temperature of the composition had reached about 30°C, foaming and setting occurred. A strong hard foam of uniform texture was obtained. Nails and screws driven into the foam were held fast in it.

EXAMPLE 19 Using the procedure described in Example 17, 100 parts of Resole B were mixed with 25 parts of the talc used in Example 1 and 5 parts of Aniphen a boron-based dehydrator sold commercially by CDF Chemie of France. parts of the hardener used in Example 1 were then mixed in and the mould containing the resultant composition was placed in an oven at 200°C. After 2 minutes, when the temperature of the composition had reached about 50°C, foaming and setting occurred. The product was a large pored low density rigid foam suitable for use in packaging or thermal insulation.

EXAMPLE 20 The process of Example 19 was repeated but replacing the talc with other finely divided materials and using various oven temperatures. The results are tabulated below. 48752 Finely Divided Material Oven Temperature Product Powdered brass 224 parts 180°C foamed product with metallic sheen Powdered copper 150 parts 180°C tl tt »1 Lead Powder ) 100 parts Talc ) 25 parts 130 C heavy foam.

In all cases, foaming and setting occurred before the temperature of the composition had reached 60°C. All the metal powders were obtained from Bondaglass Voss Limited and the talc was that used in Example 1.

EXAMPLE 21 A mixture of 100 parts of Resole A, parts of the talc used in Example 1 and 50 parts of a diol, 111. 52, sold by Abrasive Products Ltd were heated in an oven at 17(I°C for 10 minutes. The mixture was then removed from the oven and cooled to about ambient temperature. 15 parts of the hardener used in Example 1 were mixed in, and the resultant composition was placed in an oven at 120°C. Before the mixture reached 85°C, foaming and seLting occurred and a rubbery foam was produced. The degree of rubberiness may be reduced by reducing the amount of HL 52, a suitable range generally being about 5-50 parts by weight.

Examples 17 to 20 above illustrate the production of foams according to the invention by heating the foam-forming composition and including the hardener in a mould in an oven. While foamed products were produced in all cases, this method Was not as satisfactory as pre-heating the resole prior to addition of the hardener because of the difficulty of achieving uniform heating of Lhe composition and accordingly a uniform texture through the foamed product. 48753 EXAMPLE 22 Using the mould described in Example 10, a ceiling tile was obtained by first coating one of the opposed faces of the mould with a gel coat of phenolic resin/hardener mixture to a depth of 3 mm average and then applying a layer of chopped glass fibres and allowing the resin to cure and then, with the opposed faces vertical, pouring in a composition comprising Resole B (100 parts) which had been preheated to 40-50°C, china clay (25 parts) and hardener used in Example 1 (15 parts) antf allowing the whole to cure at room temperature. The result was a light-weight tile comprising a glass fibre backed gel coat face rigidified by a foamed resin backing.

EXAMPLE 23 A ceiling tile was obtained using the same mould as 15 in Example 22 but the gel coat layer was obtained by painting on two layers of the resin/hardener mixture and chopped glass fibres were omitted. When the gel coat was tacky, the foamable mixture was poured in and allowed to foam and set without the application of heat, giving a light weight tile having an unfoamed face and a foamed backing. The exotherm from the foaming and setting of the foam-forming composition assisted in completing the cure of the gel coat.

EXAMPLE 24 Several foam forming compositions were prepared comprising Resole A preheated to 30-40°C (100 parts), plaster, talc or mixtures thereof (100 parts) and Hardener solution X (3.5 to 5 parts).

In a first series of experiments, these compositions were employed to form foamed boards having dimensions of up to 6 ft (183 cm) long by up to 2 ft (61 cm) wide and from f to 3 inches (15.9 to to 76.2 mm) deep employing moulds formed of chipboard. The moulds were laid almost flat, i.e. plane of large dimensions substantially horizontal and a floating top plate was employed. The products were strong and hard and could be used for panelling, partitioning, ceilings and flooring.

In a second series of experiments, ceiling roses 15 and lengths of moulded cornice were produced using rubber inserts providing the moulding details in grp mould cases, again with the moulds laid flat and again using a floating top plate. Excellent reproducibility of the mould design was obtained and the products could be cut, sawn and abraded like wood, painted and fixed to walls and ceilings using adhesives, nails or screws, i.e. generally employed as if they were made of wood.

In a third series of experiments laminated products approximately 9x6xl (229x152x25.4 mm) thick were obtained by providing skins against one or both of the opposed large faces of a rectangular mould located witn its large faces vertical. By this means laminates of the following constructions were obtained. corrugated metal/foam/aluminium foil bronze powder filled polyester*/foam lead powder filled polyester*/foara bronze powder filled phenolic resin*/foam/glass fibre reinforced phenolic resin* asbestos-reinforced bitumen sheet/foam.

The layers marked * were obtained by coating the mould face or faces with the curable liquid resin gel coat containing the ]0 filler mentioned and then adding the foam-forming composition to the mould. The heat generated by the foaming and curing reaction also cures the gel coat.

In another experiment, a rectangular open mould was placed with its large face substantially in the horizontal plane and brick slips were placed on the upward facing face of the mould in a pattern to simulate a brick wall, the slips, being located by spaces moulded into the mould face. On adding the foam forming composition and allowing it to foam and set a slab was obtained in which the slips were firmly bonded to the foam backing and having a face resembling that of a brick wall. The slab could be fixed to the outer wall of an existing building to improve the thermal insulation without detracting from its exterior appearance.

One or more of the trade names AEROSIL, NORSOPHEN, ARMOSPHERES, CEMENTONE, ALABASTINE, VIM and ANIPHEN may be Registered pc Trade Marks in one or more States.

Claims (30)

1. A method for the production of a foamed phenolic resin material, the method being characterised in that it comprises (i) in the absence of blowing agent effecting a curing 5 reaction between (a) a liquid phenolic resole, by which is meant a solution of an acid-curable composition obtained by condensing at least one phenolic compound with at least one aldehyde, which resole has a reactivity number, IP dt-fined as —where x is the time In minutes required to harden the resole using 107. by weight of the resole of a 66-677. aqueous solution of p-toluene sulfonic acid at 60°C, of at least 1 and (b) a strong acid hardener for the resole, in the 15 presence of (c) a finely divided particulate solid which ii insoluble in the resole, is present in an amount of at least 207. by weight of the liquid resole, is inert in that in the amount in which it is used it does not 20 prevent the curing reaction, has a particle size in the range 0,5-800 microns (0,5-800 /Jm) and is substantially uniformly dispersed through the mixture of resole and hardener; the temperature of the mixture containing resole and hardener due to 25 any applied heat not exceeding 85°C and the said temperature and the concentration of the acid hardener being such that at least one compound present in the resole or generated as a by-product of the 48752 curing reaction is volatilised within the mixture before the mixture sets, and (ii) recovering a foamed phenolic resin product having a cellular texture of substantially uniform cell size.

2. A method as claimed in claim 1 wherein the mixture contains a compound having two active hydrogen atoms and capable of reacting with the phenol/aldehyde condensation product in the resole.

3. A method as claimed in claim 2 wherein the compound having two active hydrogen atoms is an ether diol.

4. A method as claimed in claim 3 wherein the diol is a di(hydroxy alkyl) ether.

5. A method as claimed in claim 2 wherein the compound having two active hydrogen atoms is an alkylene glycol. b. A method as claimed in any one of claims 2 to 5 in which the compound having two active hydrogen atoms is present in an amount of up to 35 percent by weight of the phenol/aldehyde condensation product in the resole.

6. 7. A method as claimed in claim 6 wherein the amount of compound having two active hydrogen atoms is up to 25 percent by weight.

7. 8. A method as claimed in claim 6 wherein the amount of compound having two active hydrogen atoms is from 5 to 15 percent by weight.

8. 9. A method as claimed in any one of claims 1 to 8 wherein the phenol/aldehyde condensation product component of the resole is formed by the reaction of formaldehyde with phenol in a molar ratio of 1.25-2.5:1.

9. 10. A method as claimed in claim 9 wherein the formaldehyde : phenol molar ratio is 1.4-2.0:1. Π. A method as claimed in any one of claims 1 to 10 wherein the resole has a reactivity number of at least 5. 497 52

10. 12. A method as claimed in claim 11 wherein the resole has a reactivity number of at least 10.

11. 13. A method as claimed in any one of claims 1 to 12 wherein the acid hardener is employed in an amount which gives substantially the same setting time as an amount of p-toluene sulfonic acid which is in the range of from 2 to 20 parts thereof by weight per 100 parts by weight of the phenol/aldehyde condensation product in the resole.

12. 14. A method as claimed in any one of claims 1 to 13 in which the mixture is heated by applied heat to 25 to 75°C.

13. 15. A method as claimed in claim 14 in which the mixture is heated to 30 to 50 C.

14. 16. A method as claimed in claim 14 or claim 15 in which the resole is heated and then mixed with the solid (c) and finally the hardener (b) is added.

15. 17. A method as claimed in any one of claims 14 to 16 in which the hardener is employed in an amount which gives substantially the same setting time a·, an amount of p-toluenc sulfonic acid which is in the range 3 to 10 parts by weight thereof per 100 parts by weight of phenol/aldehyde condensation product in the resole, and the resole has a reactivity number of at least 10.

16. 18. A method as claimed in any one of tbe preceding claims in which the finely divided particulate solid has a particle size in the range 1 micron to 100 microns (1 to 100 ym).

17. 19. A method as claimed in any one of the preceding claims in which the finely divided particulate solid includes talc and/or fly ash.

18. 20. A method as claimed in any one of claims 1 to IP in which the finely divided particulate solid includes a hydraulic cement other than Portland cement,

19. 21. A method as claimed in claim 20 in which the hydraulic cement 5 is plaster and/or gypsum.

20. 22. A method as claimed in any one of claims 19 to 21 in which the solid is present in an amount of up to 200 parts per 100 parts by weight of the resole.

21. 23. A method as claimed in claim 22 in which the solid is present 10 in an amount of from 50 to 150 parts per 100 parts of the resole.

22. 24. A method as claimed in any one of claims 1 to 23 in which the finely divided particulate solid includes metal particles.

23. 25. A method as claimed in claim 24 in which the metal particles are present in an amount of from 50 to 250 parts per 100 parts by 15 weight of resole. 24. A method as claimed in any one of claims 1 to 25 in which the finely divided solid is mixed into the resole and the hardener is then added and the mixture so obtained is placed in a mould in which it is allowed to foam and set. 20 27. A method as claimed in any one of the preceding claims carried out in a mould and in which at least a part of the mould wall is coated with a curable resin composition which is cured by the curing reaction between the resole, hardener and solid (c).

24. 28. A method as claimed in claim 27 in which the curable resin pc composition comprises a phenolic resole composition. ?'). Λ mod IΠ rn 11 uti of lhe method rlnimed In any one of the preceding claims in which the mixture of resole, acid hardener and inert solid also includes a blowing agent to enhance the foaming reaction.

25. 30. A foamed product obtained by the process claimed in any one 5 of the preceding claims.

26. 31. A laminate including a layer of the foamed product- claimed·'-in claim 30,

27. 32. A laminate as claimed in claim 31 including a waterproof membrane bonded to said layer of foamed product. Id 3!. A laminate as claimed in claim 31 including a sheet of a wood product and/or metal bonded to said layer of foamed product.

28. 34. A foamed product as claimed in claim 30 in the form of an architectural moulding. 15. A moulding as claimed in claim 34 wherein solid (c) is 15 selected from talc, fly ash, hydraulic cements (other than Portland cement) and n.ixcures thereof.

29. 36. A method for the production of a foamed phenolic resin material substantially as described herein with reference to the Examples.

30. 37. A foamed phenolic resin material whenever prepared by a process as claimed in claim 36.