GB1604657A - Phenolic resins and products prepared therefrom - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO PHENOLIC RESINS AND PRODUCTS PREPARED THEREFROM (71) We, LANKRO CHEMICALS LIMITED, a British Company, of Emerson House, Albert Street, Eccles, Manchester, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

This invention concerns improvements in or relating to phenolic resins and products prepared therefrom, and concerns in particular the provision of new resole resin compositions, and products prepared therefrom having more acceptable physical and chemical characteristics.

The term "resole resin" is here used to denote an aqueous solution of a phenolic resin which has been prepared by the reaction, at elevated temperatures, of a phenol with a stoichiometric excess of an aldehyde in the presence of an alkaline catalyst. Most usually the phenol is phenol itself, while the aldehyde is aqueous formaldehyde (formalin) or paraformaldehyde. Resole resins represent an intermediate stage in the process of fully reacting a phenol with an aldehyde. They may be converted into fully reacted fully cured phenolic resinous products (resite resins) by further heating, or by the addition of acidic or alkaline catalysts. The preferred method is the addition of acidic "curing agents" whose strength, concentration and type can be altered to give curing times between one minute and several hours depending on curing conditions.

The phenolic resinous products prepared from resole resins are either foamed or unfoamed. In the latter case they are prepared (as stated above) simply by heating the resole or by curing it with an acid or alkaline curing agent - or both. In the former case they are prepared by effecting an acid curing step in the presence of a foaming agent and preferably, a cell stabilising agent, often together with some heating.

Both foamed and unfoamed phenolic resins are - compared with other types of synthetic resins - relatively non-flammable. Nevertheless they will burn, and even after they have been extinguished they may glow red-hot for several minutes. The present invention seeks to provide both foamed and unfoamed phenolic resins having reduced afterglow characteristics and, possibly, reduced flammability as well.

So far as are concerned foamed phenolic resins, various additional factors influence their suitability. Examples of these factors are: the speed of the foaming reaction (the rate at which the various reactants combine to produce the foam) and the thermal conductivity and water-absorption capability of the produced foam (both of which depend somewhat on the cell structure). The present invention also seeks to provide foamed phenolic resins which have a fast rise (reaction) time, low thermal conductivity (i.e. good insulating capability), and a reduced ability to absorb water.

In one aspect this invention provides a resole resin composition which contains, in addition to the resole resin itself, (as hereinbefore defined, one or more N,N dialkanolaminoalkyl-phosphonate of the general formula:

(wherein R1 and R2, which may be the same or different, each represents an alkyl, hydroxyalkyl, alkyl(oxyalkylene) or hydroxyalkyl(oxyalkylene) group; K" represents a methylene group, or an alkyl-substituted methylene group containing up to 4 carbon atoms; and R4 and R5, which may be the same or different, each represents an alkylene group).

In the compounds of general formula I: Where either R1 and/or R2 represents an alkyl or hydroxyalkyl group the alkyl portion is conveniently a lower alkyl group having from 1 to 6 carbon atoms. Typical such alkyl or hydroxyalkyl groups RIR are the ethyl (especially), hydroxyethyl, isopropyl and hydroxyisopropyl groups.

Where either R and/or R2 represents an alkyl(oxy-alkylene) or hydroxyalkyl(oxyalkylene) group, it is preferably such as is notionally prepared by the reaction of the appropriate alkanol or glycol with a suitable alkylene oxide, the number of moles of a kylene oxide per mole alkanol or glycol varying from 1 to 6. The alkyl moiety is conveniently a lower alkyl group having from 1 to 6 carbon atoms (specifically ethyl or isopropyl), while the oxyalkylene moiety (or moieties - preferably they are all the same) is conveniently an oxyethylene or oxyisopropylene group (as derived from ethylene oxide or propylene oxide respectively). A particularly preferred such group R1/R2 is that notionally denved from di- or tri-propylene glycol.

Most preferably R1 and R2 are the same.

The methylene group R3 is preferably unsubstituted, but the alkyl substituted methylene groups -CH(CH3)-, - H(CH(C2Hs)-, -CH(C3H7)-, -C(CH3)2- and -C(CH3)(C2Hs)-, for example, may be used.

The alkylene groups R4/R5 are conveniently each a lower alkylene group having from 1 to 6 carbon atoms, especially the ethylene or isopropylene group.

Most preferably R4 and R5 are the same.

A particularly preferred dialkanolaminoalkyl-phosphonate of general formula I is O,O'-diethyl N,N-bis(2-hydroxyethyl) aminomethyl-phosphonate, having the structural formula:

Another particularly preferred phosphonate I is an O,O'-di(tripropylene glycol) N,N -bis(2-hydroxyethyl)aminomethyl phosphonate believed to have an "average" formula:

The phosphonates I may be prepared by any conventional process, though a convenient such process is the Mannich-type reaction of the appropriate (OR1)(OR2)-phosphite, the appropriate aldehyde or ketone R3 = 0, and the appropriate secondary amine (HO R4)(Ho-R5)NH. The necessary phosphites may advantageously be prepared either by a transesterification reaction between a dialkyl or diaryl phosphite (from PCl3 and the.

appropriate alcohol) and the appropriate alkanol or glycol, or (for the poloxyalkylene compounds) by the reaction of suitable quantities of the appropriate alkylene oxide (or mixtures thereof) with phosphorous acid. Certain of the phosphonates I are described and claimed, together with processes for their preparation, in the Complete Specification of our Letters Patent No. 1,094,991.

The amount of phosphonate I to be incorporated into the resole resin, or into the curable phenolic resin composition, may vary over a fairly wide range of relatively small quantities.

In general, it has been found that the phosphonates can advantageously be added in amounts ranging from 0.5 to 10 wt.% based on the weight of the resole resin itself.

Amounts at the top end of the range tend to increase curing times (especially in a foaming reaction) without any significant further desirable effect, and for this reason the higher levels are not recommended unless a much higher quantity of curing agent can also be tolerated, or a higher cure temperature can be used, or both. Amounts much below 0.5 wt. % in general exert only a trivial effect. A more preferred range of phosphonate amounts is from 1 to 5 wt.%, with 3 wt.% especially preferred, based on the resole resin. In this area afterglow is significantly improved without any marked increase in resin cure time.

The incorporation of the phosphonate I into the resole resin or into the curable phenolic resin composition may be effected by any conventional mixing technique thought suitable.

For example, if the phosphonate is added to the resole immediately after the resole is prepared then it may simply be stirred in. If, however, the phosphonate is added just prior to the resole being mixed with a curing agent, and then, say, foamed and cured, then the phosphonate may be "injected" into all the ingredients as they are brought together for the foaming reaction.

A phosphonate I may be used in accordance with the invention in a resole resin which is then cured to give either a foamed or an unfoamed product. It is in the former case (foamed products), however, that it is felt the main - and rather surprising - advantages of the invention lie, as will now be described.

As stated above, it is well known that phenolic foamed material can be produced by the reaction of resole resins and an acidic curative in the presence of a cell stabilising agent and a foaming agent. These foams may be prepared in open or closed moulds, and the foaming procedure may be undertaken either at ambient temperature or at elevated temperatures by using ovens, heated moulds or radiant heat.

To illustrate the speed with which these foams can be made to rise it is observed that for "fast" foams the rise is complete within 1 to 10 minutes, and the surface is tack-free (i.e. can be touched lightly without being broken) within 1 to 15 minutes. These fast reacting phenolic systems are used in applications such as in-situ panel filling, mould or void filling operations, and also in one or two surface laminating processes. They can also be used in the continuous block making processes. In these instances the exothermic condensation reaction generates enough heat, often without any external heat being necessary, to activate or vaporise the foaming agent, and also to complete the cure reaction.The slower, heat-assisted foaming processes are rarely carried out at temperatures in excess of 75"C, and the cure time can be as long as 3 to 4 hours. Vaporisation of the foaming agent is more controlled and gradual. Generally it is found that phenolic foam prepared by a slow heat-assisted reaction (i.e. using low concentrations of acid with the curing reaction being aided by external heat) will have reduced water absorption and reduced thermal conductivity values compares with those foams produced by the fast rise system.

In common with many other cellular plastic resins, phenolic foams, specifically phenol-formaldehyde foams, are excellent heat insulating materials, and have been used for many types of heat insulation, such as paper laminated ceiling and wall boards, in-situ panel filling, and cut block pipe and tank lagging (the material can be used equally effectively to prevent heat loss as it can be used to keep materials or structures cool). These foams show an excellent degree of heat stability, and, moreover, are generally regarded as having desirably low flammability.Though, as with all organic compounds, phenolic foams will burn under appropriate conditions, these conditions are generally much more severe than are required for most other commonly-used foamed plastics to burn - and a major advantage of these phenolic foams is that on combustion they do not liberate any appreciable quantities of smoke.

When a phenolic foam is subjected to a flame or other type of heat source it will begin to form a carbonaceous char which initially retains the form of the original foam. This char itself provides some degree of thermal insulation which prevents rapid transfer of heat throughout the cellular structure. It is a widely held view that the formation of this char is one of the main reasons why phenolic foamed material possesses such good low flammability characteristics when compared to other foamed materials. It is only when continuous temperatures of 500-700"C are reached that this char, which has a graphite-like appearance and structure, begins to decompose by thermal and/or thermal oxidation pathways. When this begins to happen the char breakdown mechanisms can generate enough heat to induce incandescence, and the charred foam starts to glow. If this glow occurs (as it almost always does) after any visible flames have been extinguished it is called "afterglow", and is often accompanied by a characteristic sound which is termed "punking". The liberated heat may originate in the exothermic adsorption of oxygen onto the carbon surface, followed by an equally exothermic breakdown of peroxide species. At the high temperatures involved the foam structure is destroyed, and, in bad cases, the foam may continue to smoulder until it has all been consumed; it can easily be appreciated that afterglow reduction is an important factor.

There are numerous known methods of reducing the flammability of foamed phenolic resins, and these methods generally result in some reduction of the time of after-glow.

Many well known flame retardant materials have been added to the foam mixture, including boric oxide, boric acid, borax, aluminium trihydrate, alkylaryl phosphates, and the halogenated alkyl phosphates, and although the use of these compounds will result in some degree of after-glow reduction in phenolic foam it is often found that their use has some disadvantages. The inorganic materials, for example, tend to be very difficult to mix uniformly into the resin compositions, while many of the known organic materials suffer from a severe hydrolysis problem (phenolic foams have a water content of around 10 wt. % at ambient temperatures), so that not only does their effect lessen with time but the foams may become somewhat corrosive because of the hydrolysis products formed.Additionally, these known fire retardant materials often cause the foam's physical properties, such as the closed cell nature and water absorption, to be adversely affected. However, by using one or more phosphonate I (as described hereinbefore), which are easily mixed with the resins, and are not easily hydrolysed, the afterglow can be reduced without detrimental effects.

Moreover, the use of a phosphonate I can in some circumstances have a beneficial effect in that it may reduce the foam's ability to absorb water. It is often found that phenol formaldehyde foam designed for thermal insulation purposes will take up water if held under water for any appreciable length of time. It is not uncommon for the water absorption, after one week's immersion, to be in the region of 50-60 volume percent for phenolic foams prepared by a fast rise method. Rather surprisingly, it has been found that the incorporation of a phosphonate I in the foaming mixture provides a foam, cured at ambient temperature, with reduced water absorption characteristics.

As stated above, in one aspect this invention provides a resole resin mixed with one or more phosphonate I. In a further aspect the invention provides a cured phenolic resin, either foamed or unfoamed, containing therein one or more phosphonate I, and, in yet another aspect, the invention provides a process for the preparation of a foamed phenolic resin, in which process a resole resin mixed with one or more phosphonate I is further reacted with an acidic curing agent preferably a cell stabilizing agent is present in the presence of a foaming agent.

Although the preparation of resole resins is well known, as is their curing to give foamed products, it is convenient here briefly to describe the preparation of resoles in general and of conventional phenol/formaldehyde resoles, and of foams made therefrom, in particular.

As stated above, resole resins are prepared by reacting at elevated temperatures a phenol with an excess of an aldehyde in the presence of an alkaline catalyst. The excess aldehyde is usually of the order of up to 1 moles per moles phenol, while the alkaline catalyst is commonly an alkali-metal hydroxide like sodium hydroxide. The phenol may be any one (or more) of many phenols well-known for this purpose. It is preferably phenol itself, though substituted phenols, such as the various cresols, xylenols and chlorophenols, can be employed. The aldehyde too may be any one (or more) of the conventionally-used aldehydes, though for commercial reasons formaldehyde, usually as formalin or as paraformaldehyde, is the aldehyde most commonly employed.

Conventional phenol/formaldehyde resole resins can be prepared by condensing 1 mole of phenol with from 1 to 2.3 moles (aqueous) formaldehyde with sodium hydroxide acting as catalyst. Usually the more useful resole resins are prepared using from 1.2 to 1.9 moles of formaldehyde per mole phenol, depending upon the exact application for which the resin is intended, but particular ratios are used for particular purposes. For example, amounts from 1.2 to 1.5 moles formaldehyde per mole phenol may be used for producing foams with increased resilience and reduced friability, while amounts from 1.6 to 1.9 moles formaldehyde per mole phenol may be used for prqducing the more rigid, stronger foams.

The alkaline catalyst can also be potassium, barium or ammonium hydroxide. The condensation reaction is performed at an elevated temperature usually between 50 and 90"C, and, when the requisite degreee of polymerisation has been achieved (judged by viscosity measurements, or otherwise), a reduced pressure is applied to the reaction vessel until the water content of the resin is about 10 to 20wt.%. The resulting resin can be neutralised by any conventional mineral or organic acids if this is deemed necessary for the final application. Typical properties of phenolic resoles designed to produce phenolic foam would be:- viscosity from 10 to 90 poise at 250C, free residual phenol content up to 6 wt.%, and free formaldehyde content up to 2 wt.%.

The resole, once prepared, may be cured into a foam by a reaction with a curing agent in the presence of .a cell stabilising agent and a foaming agent.

Many cell stabilising agents are known for use in phenolic foam systems. They are, in general, surface active compounds, and only a minor amount is needed in the mixture to produce a fine-celled isotropic foam. Siloxane-oxyalkylene copolymers have found wide usage for this purpose, and have been employed in amounts from 1 to 10 parts by weight per hundred parts by weight resin (cf. British Patents No's 1,088,767 and 1,091,238). Suitable commercially available silicone oils of this type include L5420 (Union Carbide) and DC 193 (Dow Corning).

Numerous organic non-ionic cell stabilising agents have also been used in phenolic foam systems, including ethylene oxide adducts with alkylphenols such as nonylphenol. Foam properties may be altered by increasing the number of ethylene oxide molecules reacted with one phenol molecule, but generally this number lies in the range 10 to 30.

Other cell stabilising agents which find use are the ethylene oxide adducts of polyhydroxy alcohols - for example, polyethoxylated sorbitan monoesters (such as polyethoxylated sorbitan monooleate, polyethoxylated sorbitan monopalmitate and polyethoxylated sorbi tan monostearate) and polyethoxylated castor oil - and N-vinyl pyrrolidone/butyl male ate graft copolymers of polyglycols.

In most cases the foaming process is carried out in a heated mould or oven. The foaming agents employed can be solid substances which react with excess acid curatives to give a gaseous product - for example, carbonates, bicarbonates, sulphites or powdered metals.

However, the foam structure obtained by this method is usually very coarse and anisotropic. Also, the disadvantages of handling and mixing a solid in a basically liquid mixture are severe. This procedure becomes even more difficult with the short pot life experienced with most of these chemically-activated foaming agents. Thus, foaming is instead preferably carried out using a "low" boiling inert liquid having a boiling point between -40 C and 90"C in any amount up to about 50 parts by weight of resole resin depending on the desired final foam density.Preferred liquids are alkanes, such as pentane (b.p. 36.1"C) and halogenated alkanes, such as methylene dichloride (b.p. 4Q"), trlchloromonofluoromethane (b.p. 23.8"C) and 1,1 ,2-trichloro-1 2,2-trifluoroethane (b.p.

49"C) (and mixtures of these).

Numerous other additives are known for phenolic foam systems, and these can be mixed thoroughly into the formulation before the addition of acid curative. Thus, additives are known which will improve resilience, friability and colour stability. Moreover, pigments, dyes and wetting agents can also be added.

Phenolic resins, and foam mixtures as described above, can be cured by the addition of very many solid or liquid acidic compounds. These acids may fall under the definition of Lewis- or Bronsted-type acids. The cure reaction may also be instigated by the addition of "latent acids" - compounds which are not themselves acidic but which, on reaction with an aqueous medium, or on heating, will decompose to give an acidic substance or substances.

Examples of such latent acid catalysts are anhydrides, esters and salts of strong acids with weak bases. Since an appreciable amount of water is always present in the resole resins, and more water is formed during the condensation curing reaction, some of the Lewis-type acid catalysts which are known to cure the resole may react effectively by the liberation of mineral acids and thereby themselves may be classed as latent catalysts.

Mineral acids which are known to cure the resin include sulphuric, hydrochloric, phosphoric, nitric and boric acids. Of these only the first three mentioned have found any wide usage, and all suffer from the disadvantage that the acid can be leached out of the foam structure if there is any water contact, possibly causing corrosion of the surroundings.

The overall acidity of foam blocks produced with these acids can be reduced by treatment with gaseous ammonia, but this procedure is generally regarded as undesirable even when necessary.

Principal organic acids which have been used as acid curatives in the phenolic system have been the aromatic sulphonic acids, including benzenesulphonic acid, toluene sulphonic acid, naphthalene sulphonic acid and phenol sulphonic acid. The last named acid has the advantage of being partially or fully built into the resin structure, thereby reducing the acidity of the foam.

All the acids listed above suffer from the disadvantage that, if used in appreciable quantities compared to the resole resin, mixing problems can occur due to the low viscosity of the acid curative and the relatively much higher viscosity of the resole. Polymeric acid hardeners have now been produced, and are in widespread use, which can have viscosities equalling those of the resole, thus making mixing easier. These hardeners are sulphonated Novolak-type phenolic resins; they are produced either by the condensation of formaldehy de with a monophenol sulphonic acid or by the reaction of concentrated sulphuric acid on a Novolak phenolic resin (which has been prepared by the reaction of phenol with formaldehyde under acidic conditions).These polymeric hardeners also have the advantage that they are chemically built into the cured phenol foam, and hence the "free" acidity of the foam is considerably reduced.

To summarise the main advantages of the invention, it may be said that it enables the afterglow of cured phenolic resins to be reduced, it may result in a reduction of the resins' flammability, and it often enables the water absorption value for a foamed resin to be lowered.

The following Examples and Test Data are provided, though by way of illustration only, to show details of various aspects of the inventlon. All parts and percentages are by weight, unless indicated otherwise.

In these Examples are described the results of a number of Tests carried out on the prepared products. These Tests - to determine Critical Oxygen Index, (and Temperature Index), Flame Penetration and Water Uptake - are as follows: Flammability of Plastics using the Oxygen Index Method (ASTM D2863-76) This method describes a procedure for determining the relative flammability of plastics by measuring the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that will just support flaming combustion.

The material to be tested is cut into pieces 12.5 + 0.5 mm wide, 12.5 + 0.5 mm thick and 125 to 150 mm long, and each piece is positioned vertically in the test atmosphere and ignited at the top. The time for flaming combustion is noted. If the flame is extinguished in a time shorter than 3 minutes then the oxygen content of the test atmosphere is increased. If the flame continues to burn for longer than 3 minutes the oxygen content is reduced. In this way an oxygen content can be found above which the sample burns for 3 minutes and below which the flame is extinguished after 3 minutes.This oxygen content, which should be reproducible to within 0.2 of the final oxygen percentage value, is defined as the Critical Oxygen Index (COI). The COI value of a material that is subject to afterglow is difficult to determine, since it is not easy to differentiate between afterglow and flaming combustion.

For the purpose of this work the COI value of the phenolic foam was taken as the oxygen concentration at which afterglow ceases. In general, the higher the COI value of a material, the lower the air flammability as measured in this test.

Bureau of Mines Flame Penetration Test: The material to be tested is cut into 2.5 x 15.2 x 15.2 (cms) pieces and placed vertically in a specially constructed stand such that a propane torch flame can impinge normally on the centre of one of the large foam faces. The propane flame is adjusted such that the temperature of the flame is approximately 1,000 C and the distance between the burner nozzle and test piece is 2.5 cm. The burner is ignited, and the time taken for the flame to burn completely through the sample is recorded. As soon as the flame is observed to have penetrated it is extinguished. The time taken for any afterglow to disappear is also recorded.

This test is not particularly good for measuring burnthrough times; the afterglow times are much more indicative of the time values for this characteristic.

Water Absorption Test: (A) Test specimens of foam are cut into 15.2 x 15.2 x 7.6 (cms) pieces, weighed, and immersed under a 5.1 cm head of water for 4 days at room temperature. The specimen is held under the water surface, and after the immersion period the sample is removed from the water and allowed to drain from one edge. When all the residual surface water has been removed in this way, the surfaces of the sample are lightly blotted, the sample is reweighed, and the water absorption calculated as a volume percentage. The sample is allowed to drain at room temperature for 24 hours, and weighed again. In this way a measure of the water retention of the material can be determined.

(B) A similar test was effected on 5 x 5 x 5 (cms) pieces with seven days immersion.

Temperature Index: In a modified version of the Oxygen Index Method described above an identical procedure is used to determine the CO1 at a range of temperatures. From a plot of the results is found the temperature at which the foam test sample will just burn in air (20.9% oxygen); this temperature is the Temperature Index, and the higher it is the less likely the foam is to burn in a real-life situation.

Preliminary Preparation of three Resole Resins: Three resole resins - resins A, B and C as identified in Table 1 below - were prepared as follows: (I) Phenol was reacted with aqueous formaldehyde, in the molar proportions given in Table 1, in the presence of sodium hydroxide. The reaction was carried out at a temperature between 60 and 70 C, and water was removed under vacuum to leave about 12 to 15 wt.%.

(2) To one resole a small quantity of urea was added (this helps to reduce formaldehyde gas evolution during a later foaming step). There was also added a small amount of a surfactant (a castor oil/ethylene oxide condensate) suitable as a cell stabiliser for the foamed product prepared from this resole.

This resole was designated Resole A.

(3) The second resole was simply neutralised with adipic acid. It was designated Resole B.

(4) The third resole was used without any further refinement. It was designated Resole C.

All three resoles were generally acceptable for use in the production of phenolic resins therefrom. Their viscosities (both on preparation and after several weeks storage) were suitable, as were their reactivities - and other relevant physical and chemical properties.

Table 1 Ingredients Resole A Resole B Resole C Phenol (moles) 1.0 1.0 1.0 Formaldehyde (moles) 1.6 1.9 1.25 Sodium hydroxide (wt.%) 0.5 0.5 0.5 Urea Yes Adipic acid - Yes Cell Stabiliser Yes Viscosity 2,400 820 1,200 (c/s. 25"C) Example 1: Preparation of resole resins containing a phosphonate 1: Resole resins A, B and C were each blended, by simple admixture, with amounts of O,O'-diethyl N,N-bis(2-hydroxyethyl) aminomethyl-phosphonate(referred to hereinafter as Phosphonate A) - 1,3,5 or 10 wt.%. At all levels the formed compositions were acceptable for use in the production of cured phenolic resins (both on preparation and after several weeks storage).

Example 2: Preparation of a foamed product with and without phosphonate I: A Resole B composition was prepared with and without the incorporation of a phosphonate I.

(A) Comparison foam, without phosphonate 1: Two kg of the Resole B were intimately mixed with 30g (1.5 phr - parts per hundred resin) cell stabilising agent (silicone oil DC 193), 200 g (10 phr) foaming agents (consisting of a blend of. trichlorofluoromethane and 1,1 ,2-trichloro-1,2,2-trifluorethane in the proportion of 7:3), and 400g (20 phr) acid curing agent (phenol sulphonic acid as a 70% aqueous solution). The resole, silicone oil and foaming agent were given an initial mix for one minute at 600 rpm in an open container using a laboratory stirrer. The phenol sulphonic acid was then added, and dispersed into the formulation by using a high speed mixer (1,400 rpm for 30 seconds). The mixture was then transferred to a 15" square mould, and allowed to rise at ambient temperature.

This mixture creamed (i.e. began to rise) in 20 seconds, finished rising after 4 minutes, and had a tack-free surface after about 8 minutes from the initial mix. The formed foam had a a good fine-celled structure, and did not crack on conditioning for one week at room temperature. The resulting foam density was 33.2 kg/m3.

(B) Inventive foam, with phosphonate I: To a foamable Resole B formulation as described in (A) above were added 60 g (3 phr) of Phosphonate A. This additive was stirred into the resole resin, with which it is miscible, immediately before addition of the foaming agent.

The mixture began to rise in 1 minute 30 seconds, the rise was complete in 8 minutes, and the foam was tack-free after between 14 and 15 minutes. The resulting foam density after the one week conditioning period was 36.2 kg/m3.

Test Results: Both foams were subjected to COI, Flame Penetration and Water Uptake Tests. The results are shown in Table 2 hereafter.

Comments: As will be apparent from the figures given, the COI is considerably increased by the addition of the phosphonate, and although there is a slightly shorter burnthrough time, the afterglow time is halved. The water absorption of the foam is reduced from 26% to 13%.

Example 3: Preparation of a foamed product with and without phosphonate I: Six foams were prepared in a manner similar to that of Example 2 but using a different acid curing agent.

The polymeric acid curing agent used in this Example was prepared by reacting 1 mole of phenol with 0.5 moles of aqueous (37%) formalin in the presence of a catalytic amount of oxalic acid at elevated temperatures, then reacting the formed Novolak resin with 1 mole of concentrated sulphuric acid with continuous stirring. After cooling, the level of water in the reaction solution was adjusted to 25% by weight. The viscosity of the resulting aqueous polymeric acid - the sulphonated Novolak resin - was in the region of 1500 - 1600 centipoise at 25"C.

(A) Comparison foam, without hosphonate I: The phenolic foam was prepared in the same way as in Example 2, but here the sulphonated Novolak-type polymeric acid hardener described above was used as the acid curative (the Novolak was employed in a 20% by weight proportion, based on the weight of the resin). Moreover, onl 8 phr foaming agent were employed.

The mixture creamed in 20 seconds, finished rising in 5 minutes, and was tack-free in 6 to 7 minutes. The foam density was 34.5 kg/m3 after conditioning for one week at room temperature.

(B) (i) Inventive foam, with phosphonate I: 3 phr Phosphonate A were added to the foamable Resole B formulation described in (A) above (despite the diluting effect, the Novolak polymeric acid hardener was held the same (20 phr)). There resulted a foam which creamed in 30 seconds, had finished rising in 7 minutes 45 seconds, and was tack-free in 10 minutes. The resulting foam density was 37.2 kg/m3.

(B) (ii), (iii), (iv) and (v) Inventive foams, with phosphonate I: Four other foams similar to that of (B) (i) above - 20 phr Novolak curing agent - were prepared from Resole B compositions containing 0.5, 1, 5 and 10 phr Phosphonate A respectively.

Test Results: All the prepared foams were subjected to the three Tests. The results are shown in Table 2 hereinafter.

Comments: As can be seen from the Table, as the proportion of phosphonate is increased from 0.5 to 10 phr the COI increases steadily from 33.2 to 53.7%. The afterglow is considerably reduced. The water absorption value is reduced by over 50% by the addition of 3 phr phosphonate.

Example 4: Preparation of a foamed product, with or without phosphonate I, and incorporating a plasticiser: The addition of phthalate type plasticisers is known in phenolic foam systems (of British Patent Specification No. 1,415,742). The presence of some of these types of plasticiser will increase the rate of cure of the foamed phenolic resin, and, in particular, will reduce the tack-free time of the foam.

(A) Comparative foam, without phosphonate I: 3 phr of a dialkyl phthalate (a mixture of compounds having alkyl groups composed of C7 to C:g alcohols) were added to the foam formulation described in Example 3 (A) to give a mixture which creamed in 40 seconds, had finished rising in 3 minutes 15 seconds, and was tack-free in 4 minutes. The density of the resulting foam was 56.2 kg/m3.

(B) Inventive foam, with phosphonate I: Similarly, 3 phr of the dialkyl phthalate were added to the foam formulation described in Example 3 (B) (i) (3 phr Phosphonate A, 20 phr Novolak acid curative). Here the cream time was 40 seconds, the foam rise time was 5 minutes, and the foam was tack-free in 61/2 to 7 minutes. The density of the resulting foam was 42.6 kg/m3.

Test Results: Both foams were subjected to the three Tests, and the results are shown in Table 2 hereinafter.

Comments: As will readily be apparent from the figures, the addition of 3 phr plasticiser reduced the tack-free and rise times. Hence the foam reaction times can in this way be modified without changing the proportion of acid hardener in the formulation and thus without thereby increasing the acidity of the resulting foam.

Example 5: Preparation of a foamed product with and without phosphonate I: Two foams were prepared using p-toluene sulphonic acid as the curing agent.

(A) Comparison foam, without phosphonate I: A foaming formulation was prepared as described in Example 2A, but using 700g (35 phr) of acid curing agent (p-toluene sulphuric acid as a 70% aqueous solution).

The mixture creamed in 3 minutes, finished rising after 13 minutes 30 seconds, and was tack-free in 17 to 19 minutes. The resulting foam density was 46.6 kg/m3.

(B) Inventive foam, with phosphonate I: To a foaming formulation as described in (A) above were added 3 phr of Phosphonate A (it was stirred into the resole resin immediately before addition of the foaming agent).

The mixture creamed in 3 minutes, finished rising after 19 minutes, and was tack-free in about 28 minutes. The resulting foam density was 39.6 kg/m3.

Test Results: Both foams were subjected to the various Tests, and the results are shown in Table 2 hereinafter.

Comments: It will be apparent that the addition of phosphonate to the foaming formulation increases the rise and tack-free times but reduces the final foam density slightly. The afterglow result is quite dramatically reduced from over 6 minutes to about 10 seconds.

Example 6: Preparation of a foamed product, with and without phosphonate I: Three foams were prepared using sulphuric acid (50% w/) as the curing agent, by a slow rise procedure. (A) Comparison foam, without phosphonate I: 400 g of Resole A were mixed with 16 g (4 phr) of entrant (the blowing agent). To this mixture were added 28 g (7 phr) of sulphuric acid (50% w/w), and the foam was cured in an oven at 600C for 1 hour 15 minutes. The resulting foam density was 36.6 kg/m3.

(B) (i) and (II) Inventive foams, with phosphonate I: Two other foams similar to that of (A) above were prepared from Resole A compositions containing 0.5 and 1 phr Phosphonate A. The first of these foams had a density of 35.5 kg/m3, whereas the second had a density of 49.1 kg/m3.

Test Results: All three foams were subjected to the COI and Water Absorption Tests, and the results are shown in Table 2 hereinafter.

Comments: It can be seen that the addition of phosphonate reduces the flammability of the foams.

Example 7: Preparation of a foamed product with and without phosphonate I: Three foams were prepared, two using an 0,0' - di(tripropylene glycol)- N,N bis(2-hydroxyethyl)aminomethyl-phosphonate (Phosphonate B), following a slow rise procedure.

(A) Comparison foam, without phosphonate I: 400g of Resole A were mixed with 48g (12 phr) of the foaming agent blend as used in Example 2 (A). To this mixture were added 36 g (9 phr) of sulphuric acid (50 % w/w), and the foam was cured in an oven at 600C for 1 hour 30 minutes. The resulting foam density was 35.2 kg/m3.

(B) (i) and (ii) Inventive foams, with phosphonate 1: Two other foams were prepared with a similar formulation to that given in (A) above but from a Resole A composition containing 0.5 and 5 phr of the Phosphonate B.

The foam prepared containing 0.5 phr phosphonate had a density of 31.9 kg/m3, and that containing 5 phr phosphonate had a density of 40.8 kg/m3.

Test Results: The three foams were subjected to the COI and Water Absorption Tests, and the results are shown in Table 2 hereinafter.

Comments: It will be apparent that the use of phosphonate considerably increases the COI value.

Example 8: Preparation of a resin-impregnated paper laminate, with and without phosphonate I: Phenolic resoles designed for use as laminating resins can also be modified by the addition of phosphonate I to render the laminate more flame retardant.

(A) Comparison laminate, without phosphonate I: Resole B was diluted with 40% industrial methylated spirit. Kraft paper was immersed in this solution, and then allowed to drain in a current of warm air until dry to the touch. Solid laminates were produced by pressing together 12 such pieces of impregnated paper for 1 hour at 1400C at a pressure of about 80 kg/cm2.

The COI of this laminate was 32.6%.

(B) Inventive laminates, with phosphonate I: Three other laminates were prepared in a similar fashion but from Resole B compositions containing 1, 5 or 10 phr Phosphonate A. The COI's of the formed laminates were, respectively, 32.8 44.6 and 47.2%.

Comments: It will be apparent that the use of phosphonate in a resin-impregnated laminate considerably increases the COI value.

Table 2 Example Acid Curing Phosphonate A Foam COI Flame Penetration Water Absorption Agentlphr (phr) Density (%) (Vol.%) (kg/m3) Burn- After 4 days 4 days through glow Immersion Immersion (seconds) (seconds) 24 hours draining 2A PSA 20 - 33.2 31.8 78 185 25.9 20.5 2B PSA 20 3 36.2 45.8 60 90 13.2 8.3 3A Novolak 20 - 34.5 31.1 85 128 41.3 35.5 3B(ii) Novolak 20 0.5 34.9 33.2 70 90 25.0 19.9 3B(iii) Novolak 20 1 36.9 34.9 75 60 24.3 18.8 3B(i) Novolak 20 3 37.2 42.5 105 10 17.5 13.1 3B(iv) Novolak 20 5 37.8 47.4 60 10 18.0 13.6 3B(v) Novolak 20 10 42.3 53.7 100 10 12.7 7.8 4A Novolak 20 -) plus 56.2 38.1 135 207 *54.7 *45.2 )plasticiser 4B Novolak 20 3) 42.6 45.6 95 18 *26.6 *18.3 5A PTSA 35 - 46.6 37.5 83 368 28.1 5B PTSA 35 3 39.6 43.5 87 10 28.9 6A H2SO4 7 - 36.6 36.6 - - *6.9 *1.0 6B(i) H2SO4 7 0.5 35.5 40.2 - - *5.5 *0.7 6B(ii) H2SO4 7 1 49.1 47.1 - - *6.8 *1.2 7A H2SO4 9 -) tripropylene 35.2 41.3 - - *5.1 *1.0 7B(i) H2SO4 9 0.5) glycol 31.9 50.8 - - *5.6 *1.4 7B(ii) H2SO4 9 5 ) derivative 40.8 49.5 - - *6.9 *1.3 The Immersion figures marked with an asterisk were carried out using the B Water Absorption Test described hereinbefore.

Example 9 Preparation of a foamed product with and without phosphonate 1: A Resole C composition was prepared with and without the incorporation of a phosphonate I.

(A) Comparison foam, without phosphonate I: Two kg of the Resole C were intimately mixed with 30 g (1.5 phr - parts per hundred resin) cell stabilising agent (a 40 mole/mole ethoxylated castor oil), 240 (12 phr) foaming agent (consisting of the fluorocarbon blend of Example 2 hereinbefore), and 400g (20 phr) acid curing agent (the polymeric sulphonated Novolak material prepared and used in Example 3). The resole, cell stabiliser and foaming agent were given an initial mix for one minute at 600 rpm in an open container using a laboratory stirrer. The acid curing agent was then added, and dispersed into the formulation by using a high speed mixer (1,400 rpm for 30 seconds). The mixture was then transferred to a 15" square mould, and allowed to rise at ambient temperature.

This mixture creamed (i.e. began to rise) in 45 seconds, and finished rising after 11 minutes (when it had a tack-free surface). The formed foam had a good fine-celled structure, and did not crack on conditioning for one week at room temperature. The resulting foam density was 36.6 kg/m3.

(B) Inventive foam, with phosphonate I: To a foamable Resole C formulation described in (A) above were added 60 g (3 phr) of Phosphonate A. This additive was stirred into the resole resin, with which it is miscible, immediately before addition of the foaming agent.

The mixture began to rise in 30 seconds, and this rise was complete in 14 minutes (when the foam was tack-free). The resulting foam density after the one week conditioning period was 36.7 kg/m3.

Test Results: Both foams were subjected to COI, Temperature Index and Flame Penetration Tests.

The results are shown in Table 3 hereinafter.

Comments: As will be apparent from the figures given, the COI is considerably increased bytthe addition of the phosphonate, as is the burnthrough time, the afterglow time is very markedly reduced, and the Temperature Index is considerably increased.

Foaming systems as described in this Example are used where foam of high resilience and resistance to cracking is desirable. For example, it has been found that such foam formulations are ideal for use in the continuous production of sheets of phenolic foam with a surface protection of soda-kraft paper or other cellulose-based fibre material.

Example 10: Preparation of a foamed product, with and without phosphonate I: Four foams were prepared using sulphuric acid (50% w/w) as the curing agent, by a slow rise procedure.

(A) (i) Comparison foam, without phosphonate I: Two kilograms of Resole A were mixed with 100 g (5 phr) of pentane (the blowing agent). To this mixture were added 180 g (9 phr) of sulphuric acid (50% w/w), and the foam was cured in an oven at 60"C for 1 hour 40 minutes. The resulting foam density was 35.5 kg/m3.

(B) (i) Inventive foam, with phosphonate 1: A second foam similar to that of (A) above was prepared from a Resole A composition containing 3 phr Phosphonate A. The foam had a density of 30.4 kg/m3.

(A) (ii) and (B) (ii) Comparison and Inventive foams, with and without phosphonate I: The preparation of the (A) (i) and (B) (i) foams was repeated, but using 12 phr of the fluorocarbon mixture blowing agent described in Example 2. The first foam had a density of 38.8 kg/m3, while the second (with phosphonate) had a density of 36.0 kg/m3.

Test Results: All the foams were subjected to the COI, Temperature Index and Flame Penetration Tests. The results are shown in Table 3 hereinafter.

Comments: It can be seen that the addition of phosphonate reduces the flammability of the foams.

Although phenolic foam produced by continuous processes such as sheet lamination, continuous slabstock or spray techniques are satisfactory for many low-flammability insulation applications, there are some disadvantages associated with this type of production. Fast cure foams (i.e. cure times up to 20 minutes) are generally associated with irregular cell structure, high thermal conductivity and high water absorption. Foams produced under slower, more controlled cure conditions are found to possess very fine homogeneous cell structures linked with low water uptake, low moisture vapour permeability and low thermal conductivity. The formulations of this Example are suited for use in a heat cured discrete slabstock process.

Example 11: Preparation of a foamed product with phosphonate I: Two foams were prepared using Phosphonate B (the O,O'-di(tripropylene glycol) derived analogue of Phosphonate A) following a slow rise procedure and using the formulation of Example 10 (A) (ii). One foam contained 0.5 phr of the phosphonate, while the other contained 5 phr.

The foam prepared containing 0.5 phr phosphonate had a density of 37.7 kg/m3, and that containing 5 phr phosphonate had a density of 36.4 kg/m3.

Test Results: Both foams were subjected to the COI, Temperature Index and Flame Penetration Tests.

The results are shown in Table 3 hereinafter.

Comments: It will be apparent that the use of phosphonate considerably increases the COI and Temperature Index values.

Example 12: Preparation of a foamed product, with and without phosphonate 1: It is sometimes advantageous to produce a fast-rise foam using a high molecular weight resin such that on post-curing the foam shows reduced tendency to crack. However, high molecular weight resin are usually highly viscous, show low reactivity, and cannot be handled on conventional continuous foam-producing machines. To handle these materials it is necessary to dilute the resin with liquid phenol, and to use the resin at higher than ambient temperatures.

(A) Comparison foam, without phosphonate I: Two kilograms of Resole A were mixed with 60 g (3 phr) of phenol and 140 g (7 phr) of 1,1,2-trichloro-1,2,2-trifluoroethane (as blowing agent). This mixture was heated to 300C, and 400 g (20 phr) of acid curing agent were added (phenolsulphonic acid, as a 65% aqueous solution).

The mixture began to rise in 45 seconds, and finished rising in 4l/2 minutes (when it was tack-free).

(B) Inventive foam, with phosphonate I: To the Resole A formulation as described above in (A) were added 60 g (3 phr) of Phosphonate A.

The foam began to rise in 50 seconds, and finished rising in 6l/2 minutes (when it was tack-free).

Test Results: Both foams were subjected to the COI, Temperature Index and Flame Penetration Tests, and the results are shown in Table 3 hereinafter.

Comments: It will be apparent that the use of phosphonate considerably increases the COI and Temperature Index values.

Table 3 Example Acid Curing Phosphonate A Foam COI Flame Penetration Temperature Agent (phr) Density (%) Burnthrouth Afterglow Index (phr) (kg/m3 (secs) (secs) ( C.) 9A Novolak 20 - 36.6 31.3 166 97 260 9B Novolak 20 3 36.7 43.1 302 10 380 10A (i) Sulphuric acid - 35.5 38.1 250 23 364 10B (i) " " 3 30.4 46.7 275 5 404 10A (ii) " " - 38.8 40.1 135 42 348 10B (ii) " " 3 36.0 46.3 130 7 468 11 (i) Sulphuric acid 0.5)tripropylene 37.7 38.9 130 25 346 )glycol 11 (ii) " " 5.0)derivative 36.4 43.1 180 8 474 12A PSA 20 - 50 26.2 105 Completely 144 destroyed 12B PSA 20 3 50 39.5 160 23 264

Claims (31)

WHAT WE CLAIM IS:

1. A resole resin composition which contains, in addition to the resole resin (as hereinbefore defined) itself, one or more N,N-dialkanolaminoalkyl-phosphonate of the general formula:

(wherein: Rl and R2, which may be the same or different, each represents an alkyl, hydroxyalkyl, alkyl(oxyalkylene) or hydroxyalkyl(oxyalkylene) group; R3 represents a methylene group, or an alkyl-substituted methylene group containing up to 4 carbon atoms; and R4 and R5, which may be the same or different, each represents an alkylene group).

2. A resole composition as claimed in claim 1, wherein the phosphonate is such that where either R1 and/or R2 represents an alkyl or hydroxy alkyl group the alkyl portion is a lower alkyl group having from 1 to 6 carbon atoms.

3. A resole composition as claimed in claim 2, wherein the phosphonate is such that an alkyl or hydroxyalkyl group Rl/R2 is the ethyl, hydroxyethyl, isopropyl or hydroxyisopropyl group.

4. A resole composition as claimed in claim 1, wherein the phosphonate is such that where either R1 and/or R2 represents an alkyl(oxyalkylene) or hydroxyalkyl(oxyalkylene) group it is such as is notionally prepared by the reaction of an alkanol or glycol with an alkylene oxide, the number of moles of alkylene oxide per mole alkanol or glycol varying from 1 to 6.

5. A resole composition as claimed in claim 4, wherein the alkyl moiety of the alkyl- or hydroxyalkyl-(oxyalkylene)group R'/R2 is a lower alkyl group having from 1 to 6 carbon atoms, while the oxyalkylene moiety (or moieties) is an oxyethylene or oxyisopropylene group. A

6. A resole composition as claimed in claim 5, wherein the phosphonate is such that the group R'/R2 is that notionally derived from di- or tri-propylene glycol.

7. A resole compositin as claimed in any of the preceding claims, wherein the phosphonate is such that Rl and R2 are the same.

8. A resole composition as claimed in any of the preceding claims, wherein the phosphonate is such that the methylene group R3 is unsubstituted.

9. A resole composition as claimed in any of the preceding claims, wherein the phosphonate is such that the alkylene groups R4/R5 are each a lower alkylene group having from 1 to 6 carbon atoms.

10. A resole composition as claimed in any of the preceding claims, wherein the phosphonate is such that each alkylene group R4/R5 is an ethylene or isopropylene group.

11. A resole composition as claimed in any of the preceding claims, wherein the phosphonate is such that R4 and R5 are the same.

12. A resole composition as claimed in any of the preceding claims, wherein the phosphonate is O,O'-diethyl N,N-bis(2-hydroxyethyl) aminomethyl-phosphonate or an 0,0 -di(tripropylene glycol) N,N -bis(2-hydroxyethyl)aminomethyl phosphonate.

13. A resole composition as claimed in any of the preceding claims, wherein the amount of phosphonate I incorporated into the resole resin is from 0.5 to 10 wt. Wo based on the weight of the resole resin itself.

14. A resole composition as claimed in claim 13, wherein the amount of phosphonate is from 1 to 5 wt Wo based on the resole resin.

15. A resole composition as claimed in claim 14, wherein the amount of phosphonate is 3 wt % based on the resole resin.

16. A resole composition as claimed in any of the preceding claims, wherein the resole resin is the product of reacting, at an elevated temperature, phenol with an excess of formaldehyde in the presence of an alkaline catalyst.

17. A resole composition as claimed in claim 16, wherein mole ratio of formaldehyde to phenol is up to 2.5:1, the excess formaldehyde thus being up to 1.5 moles per mole phenol.

18. A resole composition as claimed in either of claims 16 and 17, wherein the alkaline catalyst is sodium hydroxide.

19. A resole resin composition as claimed in any of the preceding claims, and substantially as described hereinbefore.

20. A cured phenolic resin containing therein one or more N,N-dialkanolaminoalkylphosphonate I as defined in any of claims 1 to 12.

21. A cured phenolic resin as claimed in claim 20 which is in the form of a foam.

22. A process for the preparation of a cured phenolic resin as claimed in either of claim 21, in which a resole resin (as hereinbefore defined) is reacted with an acidic curing agent in the presence of a foaming agent and an N,N-dialkanolaminoalkyl-phosphonate I as defined in any of claims 1 to 15, to produce the desired cured phenolic resin foam.

23. A process as claimed in claim 22, in which there is employed a resole resin composition as claimed in any of claims 1 to 19.

24. A process as claimed in either of claims 22 and 23, in which the acid curing agent is å mineral acid, aromatic sulphonic acid, or sulphonated Novolac resin.

25. A process as claimed in Claim 24, in which the acid curing agent is sulphuric acid, toluene sulphonic acid or phenol sulphonic acid.

26. A process as claimed in any of claims 22 to 25, in which the foaming agent is a low boiling inert liquid having a boiling point between -40 C and 90CC.

27. A process as claimed in claim 26, in which the foaming agent is an alkane or halogenated alkane.

28. A process as claimed in any of claims 22 to 27, in which there is additionally employed a cell stabilising agent.

29. A process as claimed in claim 28, in which the cell stabilising agent is a siloxane-oxyalkylene copolymer or a polyethoxylated castor oil.

30. A process as claimed in any of claims 22 to 29 and substantially as described hereinbefore.

31. A cured phenolic resin whenever prepared by a process as claimed in any of claims 22 to 30.