WO2019030239A1

WO2019030239A1 - Phenolic foam and method of manufacture thereof

Info

Publication number: WO2019030239A1
Application number: PCT/EP2018/071428
Authority: WO
Inventors: Paul Sykes; Vincent Coppock; Lynne RIPLEY
Original assignee: Kingspan Holdings (Irl) Limited
Priority date: 2017-08-10
Filing date: 2018-08-07
Publication date: 2019-02-14
Also published as: GB201712843D0; GB2565331B; GB2565331A

Abstract

Phenolic foam and method of manufacture thereof is described. The phenolic foam demonstrates decreased formaldehyde emission and excellent thermal insulation performance.

Description

Phenolic foam and method of manufacture thereof

Field of the Invention

[0001] The present invention relates to thermal insulating foams, in particular to thermal insulating phenolic foams having improved properties, including enhanced thermal performance, low environmental impact, and reduced formaldehyde emissions compared to state of the art phenolic foams.

[0002] Phenolic resole resins used in the manufacture of phenolic foams are produced by reacting phenol with an excess of formaldehyde, in the presence of an alkaline catalyst, such as potassium hydroxide. Once the formaldehyde addition has occurred, the resin is reacted until a desired molecular weight or desired end-use application viscosity is achieved. In phenolic foam manufacture, a resin, for example a resole resin, is mixed with an acid curing catalyst, in the presence of a blowing agent, which results in an exotherm which in turn leads to expansion of the blowing agent and foam formation. The resole resin composition, the quantity and nature of the acid curing catalyst and the chemical and physical properties of the blowing agent and any surfactant present in the foam reactants greatly influence the ability to control the exotherm and to form the foam. In order to form thermal insulating foam, a total closed-cell content of greater than 85 percent is generally required, as one of the main determinants in the thermal performance of foam is the ability of the cells of the foam to retain blowing agent that has a low thermal conductivity.

[0003] As a molar excess of formaldehyde is employed in the production of resole resins for phenolic foam formation, once foam formation is complete, the resulting foam contains varying amounts of residual unreacted free formaldehyde. Formaldehyde has some undesirable properties so it is desirable to minimise its presence. Accordingly, reducing the amount of any formaldehyde emission from phenolic foam, and the development of phenolic foams with reduced (and negligible) levels of free formaldehyde content is desirable.

Background to the Invention

[0004] Attempts to address the problem of formaldehyde emission have largely focused on identifying suitable formaldehyde scavengers. In addition, efforts at coating the surface of pre-formed foam bodies with compositions comprising formaldehyde scavengers have had some success in reducing formaldehyde emission.

[0005] For example, Japanese Patent Publication JP2009274409 describes a phenolic resin foam laminate upon which surface facing materials are coated with a composition comprising flame retardant and formaldehyde scavengers. The surface facing material may be woven or non-woven fabric, and may be coated with said composition to provide a coated fabric material, which coated fabric material is subsequently dried prior to attachment of said coated fabric material to a foam laminate. Alternatively, the foam laminate comprising the surface facing material may be coated with said composition after the laminate is constructed.

[0006] While formaldehyde scavengers are known, the incorporation of scavengers into phenolic resinous materials to form closed-cell phenolic foams having low thermal conductivity values remains a challenge. The addition of any additives to a phenolic resin can have a dramatic deleterious effect on the ability to form thermal insulating closed-cell foams. Thus the identification of suitable formaldehyde scavengers and the utility of same to form such closed- cell foams is highly desirable.

[0007] US Patent No. 5705537 describes a phenolic foam comprising a foamed phenol- formaldehyde resole resin which contains a formaldehyde reducing additive which is a peptide, a proteinaceous material, cysteine, glutamic acid, glycine, isoleucine, leucine, lysine, phenylalanine, serine, tryptophan, or mixtures thereof at an amount effective to reduce emission of free formaldehyde from the foamed resin. The formaldehyde scavengers described therein are present at an amount in the range of from about 10 to about 75 parts by weight per hundred parts by weight of the phenol-formaldehyde resole resin. While the presence of such large quantities of formaldehyde scavenger may have a positive impact on reducing the level of formaldehyde emission, the thermal insulation performance of the foam produced therewith is significantly deleteriously impacted. The foams exemplified therein have thermal conductivities in the range of from about 0.035 W/m K to about 0.039 W/m K. This is an example of addition of various components that are present in the resin composition during foaming that ameliorate formaldehyde emission but deleteriously affect other properties of the foam formed. [0008] US Patent No. 4216295 describes a foamable resole resin comprising a resole resin, a blowing agent and a surfactant. Alkaline earth metal hydroxides are employed to catalyse the resole resin formation and the resin is neutralized with oxalic acid or its acid salts, providing inert insoluble oxalate salts dispersed in said resole resin. The particle size of such salts is size controlled and said salts are stabilized in an aqueous resole resin solution having about 60 to 99% resole resin by weight. US Patent No. 4216295 indicates that formaldehyde scavengers comprising low molecular weight nitrogen containing organic compounds which are soluble in the resole resin described therein may be added to the resin at levels of 0.5 to 1 .5 mol equivalents of scavenger per mole of free formaldehyde.

[0009] The successful incorporation of additives into phenolic foam without having a detrimental impact on properties such as cellular integrity, cellular structure, and thermal insulation stability can be extremely challenging. In this regard , high quality phenolic foams are much less versatile than for example, polyurethane or polyisocyanurate foams - which are much more amenable to the incorporation of additives, without deleteriously impacting thermal insulation performance.

Summary of the Invention [0010] In one aspect, the present invention provides a phenolic foam formed by foaming and curing a phenolic resin composition, that comprises: a phenolic resin, a surfactant, a blowing agent, a formaldehyde scavenger selected from the group consisting of: L-arginine, aminoguanidine bicarbonate, carbohydrazide, oxalyldihydrazide, adipic acid dihydrazide and combinations thereof, and an acid catalyst, wherein said foam has a closed-cell content of greater than 85%, and having an aged thermal conductivity 0.025 W/m K or less when measured at a mean temperature of 10°C after heat ageing for 175 ± 5 days at 70 ± 2 °C, in accordance with the procedure specified in European Standard BS EN 13166:2012.

[001 1 ] The phenolic foam may for example emit less than about 60 μg m³ of formaldehyde after 28 days when tested in accordance with ISO 16000-3:201 1 or EN 16516. Suitably, the phenolic foam may emit: less than about 50 μg m³, such as less than about 40 μg m³, such as less than about 30 μg m³, such as less than about 20 μg m³, and most suitably less than about 10 μg m³ of formaldehyde after 28 days when tested in accordance with ISO 16000-3:201 1 or EN 16516.

[0012] The formaldehyde scavenger may be present in an amount of from 1 to 10 parts by weight per 100 parts by weight of the phenolic resin. Suitably, the formaldehyde scavenger is present in an amount of from about 1 to 8 parts by weight, such as 1 to 5 parts by weight per 100 parts by weight of the phenolic resin. Suitably, the formaldehyde scavenger is present in an amount of from 1 .5 to 4.5 parts by weight per 100 parts by weight of the phenolic resin.

[0013] The formaldehyde scavenger may for example be present in an amount of from 1 .4 to 4.2 parts by weight per 100 parts by weight of the phenolic resin, such as from 2 to 4 parts by weight per 100 parts of the phenolic resin. The formaldehyde scavenger preferably may be present in an amount of from 1 .7 to 3.5 parts by weight per 100 parts by weight of the phenolic resin, such as in about 2.5 parts by weight per 100 parts by weight of the phenolic resin. [0014] The phenolic resin is preferably a resole resin.

[0015] The phenolic resin may have a molar ratio of phenol groups to aldehyde groups in the range of from about 1 : 1 to about 1 :3; suitably the molar ratio of phenol groups to aldehyde groups is from 1.5 to 2.3. [0016] The phenolic resin may have a weight average molecular weight of from 700 to

2,000. Suitably, the phenolic resin has a weight average molecular weight of from 700 to 1600. The phenolic resin may have a number average molecular weight of from 330 to 1 ,000, preferably from 350 to 800, and more preferably 350 to 700. [0017] The blowing agent may comprise a C1-C7 hydrocarbon. For example, the C1-C7 hydrocarbon may comprise at least one of butane, pentane, hexane, heptane and isomers thereof.

[0018] The blowing agent may additionally or alternatively comprise a chlorinated aliphatic hydrocarbon. For example, the chlorinated aliphatic hydrocarbon may be a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms. Suitably, the chlorinated aliphatic hydrocarbon having from 2 to 5 carbon atoms will have from 1 to 4 chlorine atoms. Suitably, the chlorinated aliphatic hydrocarbon containing 2 to 5 carbon atoms is selected from the group consisting of dichloroethane, n-propyl chloride, isopropyl chloride, butyl chloride, isobutyl chloride, pentyl chloride, and isopentyl chloride. [0019] Additionally, or alternatively, the blowing agent may comprise a halogenated hydroolefin, such as a hydrofluoroolefins and hydrochlorofluoroolefins. For example, the halogenated hydroolefin may be selected from the group consisting of 1-chloro-3,3,3- trifluoropropene, 1 ,3,3,3-tetrafluoro-1-propene, 2,3,3,3-tetrafluoro-1-propene, 1 , 1 , 1 ,4,4,4- hexafluoro-2-butene and combinations thereof. The blowing agent may comprise 1-chloro- 3,3,3-trifluoropropene, suitably trans-1-chloro-3,3,3-trifluoropropene or cis-1-chloro-3,3,3- trifluoropropene or combinations thereof, preferably, trans-1-chloro-3,3,3-trifluoropropene.

[0020] The blowing agent may comprise a blend of any of the aforementioned blowing agents. For example, the blowing agent may comprise a blend of a halogenated hydroolefin and a C1-C7 hydrocarbon. Alternatively, the blowing agent may comprise a blend of a halogenated hydroolefin and a chlorinated aliphatic hydrocarbon. Alternatively, the blowing agent may comprise a blend of a halogenated hydroolefin, a C1-C7 hydrocarbon and a chlorinated aliphatic hydrocarbon. Alternatively, the blowing agent may comprise a blend of a C1-C7 hydrocarbon and a chlorinated aliphatic hydrocarbon.

[0021 ] The blowing agent may comprise 1 to 20 parts by weight per 100 parts by weight of phenolic resin.

[0022] The phenolic foam may further comprise at least one of a plasticiser, an inorganic filler, a flame retardant, a pigment, a toughening agent and combinations thereof.

[0023] The phenolic foam comprises a surfactant which may be present in an amount of

1 to 6 parts by weight per 100 parts by weight of phenolic resin, suitably the surfactant is a castor oil-ethylene oxide adduct wherein more than 5 moles but less than 60 moles of ethylene oxide are added per 1 mole of castor oil. For example the surfactant may be a castor oli- ethylene oxide adduct wherein more than 20 moles but less than 40 moles of ethylene oxide are added per 1 mole of castor oil. Alternative surfactants include but are not limited to alkylene oxide / alkyl phenol condensates (nonyl phenol and dodecyl phenol), silicone compounds such as dimethyl siloxane and commercial surfactants such as DC 193.

[0024] The plasticiser may be present in an amount of 0.1 to 10 parts by weight per 100 parts by weight of phenolic resin, suitably the plasticiser is present in an amount of about 5 parts by weight per 100 parts by weight of phenolic resin. [0025] The plasticiser may be a polyester polyol that is a reaction product of a polybasic carboxylic acid selected from a dibasic to a tetrabasic carboxylic acid with a polyhydric alcohol selected from a dihydric, trihydric, tetrahydric or a pentahydric alcohol. The plasticiser could also be a glycol such as ethylene glycol or a polyether polyol.

[0026] The polybasic carboxylic acid used to synthesise the polyester polyol comprises at least one of phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,3-dicarboxylic acid, naphthalene-1 ,4-dicarboxylic acid, napththalene-2,6-dicarboxylic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, cyclohexane-1 ,2-dicarboxylic acid, cyclohexane- 1 ,3-dicarboxylic acid, and cyclohexane-1 ,4-dicarboxylic acid , preferably the polybasic carboxylic acid used to synthesise the polyester polyol comprises one or more of phthalic acid , isophthalic acid , or terephthalic acid.

[0027] The polyhydric alcohol used to synthesise the polyester polyol comprises at least one of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1 ,4-butane diol, 1 ,5-pentane diol, 1 ,6-hexane diol, neopentyl glycol, 1 ,2-cyclohexane dimethanol, 1 ,3- cyclohexane dimethanol, and 1 ,4-cyclohexane dimethanol, preferably the polyhydric alcohol used to synthesise the polyester polyol comprises one or more of diethylene glycol, propylene glycol, dipropylene glycol, 1 ,4-butane diol.

[0028] Optionally, the phenolic foam may comprise one or more inorganic fillers.

Suitably, the inorganic filler comprises at least one of a metal oxide such as aluminium oxide or zinc oxide, a metal powder such as zinc powder, or a metal hydroxide such as aluminium hydroxide, magnesium hydroxide, or a metal carbonate such as calcium carbonate, magnesium carbonate, barium carbonate, or zinc carbonate.

[0029] The inorganic filler may be present in an amount of 0.1 to 20 parts by weight per

100 parts by weight of phenolic resin, suitably the inorganic filler is present in an amount of 1 to 10 parts by weight per 100 parts by weight of phenolic resin. [0030] Suitably, the inorganic filler comprises a metal hydroxide or metal carbonate having an ionic equilibrium solubility (Ksp) less than 10^~8 when measured at 25°C.

[0031] The metal carbonate may be calcium carbonate or magnesium carbonate.

Suitably, the metal carbonate has an average particle size of 100 - 300 μιτι, preferably 150 - 200 μιτι. Suitably the inorganic filler comprises calcium carbonate having an average particle size of from about 120 μιτι to about 200 μιτι and an ionic equilibrium solubility (Ksp) of less than 10^~8 when measured at 25°C.

[0032] The phenolic foam may have a pH of from about 2 to about 8, suitably, of from about 2 to about 6. The phenolic foam may have a pH of 4 or more. [0033] The phenolic foam may have a density of from 10 to 100 kg/m³. Suitably, the phenolic foam has a density of from 10 to 60 kg/m³, such as from 20 to 60 kg/m³.

[0034] The phenolic foam suitably, has a compressive strength of from 50 to 500 kPa, suitably, the compressive strength is of from 80 kPa to 220 kPa.

[0035] Optionally, the phenolic foam may comprise a flame retardant. Suitably, the flame retardant may be present in an amount of from about 1 to about 10 parts by weight per hundred parts by weight of the phenolic resin. Optionally, the flame retardant is selected from a group selected from liquid organophosphorus compounds, such as but not limited to triethyl phosphate, diphenyl phosphite, diethyl ethyl phosphonate and solid phosphorus based materials such as ammonium polyphosphate, and red phosphorus. Flame retardants such as aluminium trihydrate, zinc borate and halogenated flame retardants can be used.

[0036] The phenolic foam may comprise a toughening agent. A toughening agent is an organic modifier for co-reacting with the phenolic resin, which toughens i.e. reduces brittleness of the phenolic foam. The toughening agent may be selected from the group consisting of urea, dicyandiamide and melamine. [0037] The toughening agent may be present in an amount of from 1 to 10 parts by weight per 100 parts by weight of the phenolic resin.

[0038] The toughening agent may be urea and be present in about 5 parts by weight per

100 parts by weight of the phenolic resin.

[0039] The acid catalyst may be present in an amount of 5 to 25 parts by weight per 100 parts by weight of phenolic resin. Suitably, the acid catalyst comprises at least one of benzenesulfonic acid, para-toluene sulfonic acid, xylene sulfonic acid, naphthalene sulfonic acid , ethylbenzene sulfonic acid and phenol sulfonic acid. Inorganic acids are less preferred but phosphoric acid can be used with organic sulfonic acids to regulate reactivity and enhance fire performance.

[0040] The acid catalyst may comprise para-toluene sulfonic acid and xylene sulfonic acid. [0041 ] The phenolic foam may have a facing on at least one surface thereof, preferably the facing comprises at least one of a glass-fibre non-woven fabric, a spun-bonded non-woven fabric, a bonded non-woven fabric, a metal sheet, a metal foil (e.g. aluminium foil), ply wood, a calcium silicate board, a plaster board, a Kraft or other paper product, and a wooden board including fibre board such as MDF (medium density fibreboard) and OSB (oriented strand board).

[0042] At least one of the facings may be perforated. A facer made of non-porous material can be perforated. Facings may include for example, glass tissue, or metallic foils, such as aluminium. Suitably, the facing is a laminate comprising a metallic foil laminated onto a glass tissue, or a metallic foil laminated onto a Kraft paper. [0043] Suitably, at least one of the facings is porous. Optionally, each of the facings is porous.

[0044] The facing may be coated with, or impregnated with, a formaldehyde scavenger and/or flame retardant.

[0045] For example, the facing may be coated with a composition comprising a binder and one or more formaldehyde scavengers and/or flame retardants.

[0046] Suitably, the facing may be impregnated with a formaldehyde scavenger, such as a urea or sodium sulfite solution.

[0047] Optionally, the facing comprises greater than about 20 g/m², such as greater than about 30 g/m², such as greater than about 40 g/m² of the formaldehyde scavenger. [0048] Suitably, the facing may be impregnated with urea in about 25 to 50 g/m².

[0049] Optionally, the phenolic foam comprising a facing on at least one surface thereof, said facing optionally being impregnated or coated with a formaldehyde scavenger, preferably emits: less than 30 μg/m³, such as less than about 20 μg/m³, and most suitably less than about 10 μg/m³ of formaldehyde after 28 days when tested in accordance with ISO 16000-3:201 1 or EN 16516. [0050] The facing may optionally be impregnated with a neutralising agent, such as a carbonate, an oxide or a hydroxide of: an alkali metal, an alkaline earth metal, or aluminium. Suitably, the neutralising agent is calcium carbonate. For example the facing may optionally be impregnated with one or more of urea, sodium sulfite, carbohydrazide, aminoguanidine bicarbonate, arginine, oxalylhydrazide, or adipic acid dihydrazide.

[0051] A coated or impregnated facer may optionally comprise a binder to facilitate binding of a formaldehyde scavenger or flame retardant in or to the facer.

[0052] Also provided is a method for manufacturing a closed-cell phenolic foam as described above, comprising foaming and curing a foamable phenol resin composition containing a phenol resin, a surfactant, a formaldehyde scavenger, a blowing agent and a curing catalyst, wherein the formaldehyde scavenger is selected from the group consisting of: L- arginine, aminoguanidine bicarbonate, carbohydrazide, oxalyldihydrazide, adipic acid dihydrazide and combinations thereof.

Detailed Description of the Invention

[0053] Suitable testing methods for measuring the physical properties of phenolic foam are described below.

0) Foam Density:

This was measured according to BS EN 1602:2013 - Thermal insulating products for building applications - Determination of the apparent density.

(ii) Thermal Conductivity:

A foam test piece of length 300 mm and width 300 mm was placed between a high temperature plate at 20°C and a low temperature plate at 0°C in a thermal conductivity test instrument (LaserComp Type FOX314/ASF, Inventech Benelux BV). This provides a mean plate temperature of 10°C. The thermal conductivity (TC) of the test pieces was measured according to EN 12667: "Thermal performance of building materials and products - Determination of thermal resistance by means of guarded hot plate and heat flow meter methods, Products of high and medium thermal resistance".

(iii) Thermal Conductivity after Accelerated Ageing: This was measured using European Standard BS EN 13166:2012 - "Thermal insulation products for buildings - Factory made products of phenolic foam (PF)" - Specification Annex C section.4.2.3. The thermal conductivity is measured after exposing foam samples for 25 weeks at 70°C and stabilisation to constant weight at 23°C and 50% relative humidity. This thermal ageing serves to provide an estimated thermal conductivity for a time period of 25 years at ambient temperature. Alternatively, thermal conductivity may be determined at a mean plate temperature of 10°C in accordance with EN12667 and EN12429 after ageing at 1 10°C for 2 weeks.

(iv) 2T±

The pH was determined according to the standard BS EN 13468.

(v) Closed-cell Ratio:

The closed-cell ratio was determined according to ASTM D6226 test method. (vi) Friability:

Friability is measured according test method ASTM C421 - 08(2014).

(vii) Formaldehyde emission:

Formaldehyde emission was assessed as described below using a HtV-m Formaldemeter, manufactured by PPM Technology UK. Foams which demonstrated a significant reduction in formaldehyde emission were subsequently assessed for formaldehyde emission according to test method ISO 16000-3:201 1 or European Standard EN 16516.

(viii) Average cell diameter

A piece of foam was roughly cut measuring approximately 20 mm x 10 mm. from one coated surface to the other. From this piece the surfaces were trimmed with a razor blade to approximately 8 mm square. The foam was then snapped sharply to reveal a clean surface and the majority of the sample was removed to leave a thin (~1 mm) slice.

The slice was fixed onto an aluminium sample stub using a double sided conducting sticky tab.

The samples were then given a thin (-2.5 Angstroms) conducting coat of gold/palladium using a Bio-Rad SC500 sputter coater. The reason for coating the sample is (a) to add a conducting surface to carry the electron charge away and (b) to increase the density to give a more intense image. At the magnifications involved in this study the effect of the coating is negligible.

The samples were imaged using an FEI XL30 ESEM FEG Scanning Electron Microscope under the following conditions: 10kV accelerating voltage, working distance ~10mm, spot size 4, and Secondary Electron Detector. Images were saved at the following magnifications x350, x1200 and x5000 and saved as .tiff files to disc. The images at x350 show the general size distribution of the cells and higher magnifications at x1200 and x5000 show the nature of the cell surfaces.

Images acquired at x350 magnification for both samples typically show a size range of -100 to 200 microns. In the preparation of the foam samples for evaluation by electron microscopy, the manual snapping of the foam sample - to create a surface to examine - can induce some damage at the cell walls.

The images collected at x1200 and x5000 magnification are substantially free of defects and holes.

(ix) Compressive strength (kPa) was measured in accordance with European Standard EN 826. [0054] The phenolic foam is formed by foaming and curing a phenolic resin composition that comprises a phenolic resin, a blowing agent, an acid catalyst, a formaldehyde scavenger selected from the group consisting of: L-arginine, aminoguanidine bicarbonate, carbohydrazide and oxalyldihydrazide, adipic acid dihydrazide and combinations thereof. The phenolic resin is mixed with a formaldehyde scavenger. Blowing agent is added to the resulting mixture under emulsifying conditions. To the resulting emulsion, acid catalyst is added and foaming commences. The resulting foam is then cured under heat and pressure, for example by heating in clamped heated mould in an oven.

[0055] The foam of the invention has a closed-cell content of greater than 85%, and an aged thermal conductivity 0.025 W/m K or less when measured at a mean temperature of 10°C after heat ageing for 175 ± 5 days at 70 ± 2°C, in accordance with the procedure specified in European Standard BS EN 13166:2012. The invention provides phenolic foam with excellent thermal insulating performance, and with reduced formaldehyde emission compared to that of commercially available phenolic foams.

[0056] Suitably, the formaldehyde scavenger is present in an amount of from about 1 to 10 parts by weight based on the total weight of the phenolic resin. For example, the formaldehyde scavenger may be present in an amount of from about 1.4 to about 4.2 parts by weight based on the total weight of the phenolic resin. Preferably, the formaldehyde scavenger is present in an amount of from about 1.7 to about 4.2 parts by weight based on the total weight of the phenolic resin. When the formaldehyde scavenger is present in less than about 1.7 parts by weight of the phenolic resin, a lower level of formaldehyde emission reduction is achievable. When the formaldehyde scavenger is present in more than about 4.2 parts by weight of the phenolic resin, the thermal conductivity of the phenolic foams produced therefrom is deleteriously impacted. More preferably, the formaldehyde scavenger is present in an amount of from about 2 to about 4 parts by weight, such as about 2.2 parts to 3.8 parts based on the total weight of the phenolic resin. Most preferably about 2.5 parts by weight of formaldehyde scavenger is used, based on the total weight of phenolic resin. The foams demonstrate excellent thermal performance, reduced formaldehyde emission and the incorporation of a formaldehyde scavenger according to the invention did not deleteriously impact the friability of the foam. [0057] A preferred type of phenolic resin to use in the present invention is a resole resin. Such resole resin can be obtained from the chemical reaction of phenol or a phenol based compound such as cresol, xylenol, para-alkylphenol, para-phenylphenol, resorcinol, and the like with an aldehyde such as formaldehyde, furfural, acetaldehyde and the like using a catalytic amount of alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, or an aliphatic amine such as trimethylamine, or triethylamine. These types of chemical constituent are commonly used in standard resole resin production, but the invention is not limited to just those chemicals listed here.

[0058] The molar ratio of phenol groups to aldehyde groups is in the range from 1 : 1 to

1 :3, suitably from 1 : 1 .5 to 1 :2.5, and more suitably from 1 : 1 .6 to 1 :2.3. As the molar ratio of phenol to aldehyde groups decreases foams have increased residual formaldehyde.

[0059] A preferred weight average molecular weight suitable for the phenolic resin is from 700 to 2,000, such as from 700 to 1600.

[0060] The number average molecular weight is suitably from 330 to 1 ,000, and preferably from 350 to 800, such as from 350 to 700. [0061] Suitably, the weight average molecular weight may be from 700 to 1600, and the number average molecular weight is at least 350.

[0062] The water content of the resin may be from about 6 wt% to about 16 wt%, such as from about 1 1 wt% to about 15 wt% based on the total weight of the resin, and as determined by Karl Fisher analysis. [0063] The phenolic resin composition preferably has a free formaldehyde content of less than 3 wt% based on the total weight of the phenolic resin composition, prior to the addition of the formaldehyde scavenger, such as a free formaldehyde content of less than 2 wt% based on the total weight of the phenolic resin composition. The phenolic resin composition may comprise a free formaldehyde content of from about 0.5 wt% to about 2 wt% based on the total weight of the phenolic resin composition, prior to the addition of the formaldehyde scavenger.

[0064] The blowing agent preferably has low global warming impact and low ozone depletion characteristics and imparts good fire performance properties (i.e. fire retardancy or fire resistance properties) to foams made therewith. [0065] Suitably, the blowing agent comprises a halogenated hydroolefin.

[0066] The halogenated hydroolefin may have the formula:

Wherein each R is independently CI, F, Br, I or H R' is (CR₂)_nY, Y is CRF₂, and n is 0, 1 , 2, or 3, preferably 0 or 1.

[0067] Preferably, Y is CF3, n is 0 or 1 and at least one of the remaining R is F.

Preferably no Br is present. [0068] The halogenated hydrofluoroolefin may for example be selected from the group: hexafluoropropene; 2-fluoropropene, 1-fluoropropene; 1,1-difluoropropene; 3,3-difluoropropene; 3,3,3-trifluoropropene; 2,3,3-trifluoropropene; 1,3,3,3-tetrafluoropropene; 1,1,3,3- tetrafluoropropene; 1 ,2,3,3,3-pentafluoropropene; 4,4,4-trifluoro-1-butene; 3,4,4,4-tetrafluoro-1- butene; 1,1,3,3,3-pentafluoro-2-methyl-1-propene; octafluoro-1-butene; octafluoro-2-butene; 2,3,3,4,4,4-hexafluoro-1 -butene; 1,1,1 ,4,4,4-hexafluoro-2-butene; 1,1,1 ,2,4,4,4-heptafluoro-2- butene; 3-fluoropropene, 2,3-difluoropropene; 1,1,3-trifluoropropene; 1,3,3-trifluoropropene; 1,1,2-trifluoropropene; 1-fluorobutene; 2-fluorobutene; 2-fluoro-2-butene; 1,1-difluoro-1 -butene; 3, 3-difluoro-1 -butene; 3,4,4-trifluoro-1-butene; 2,3,3-trifluoro-1-butene; 1 ,1 ,3,3-tetrafluoro-1- butene; 1,4, 4, 4-tetrafluoro-1 -butene; 3,3,4,4-tetrafluoro-1-butene; 4, 4-difluoro-1 -butene; 1,1,1- trifluoro-2-butene; 2,4,4,4-tetrafluoro-1-butene; 1,1,1,2-tetrafluoro-2-butene; 1,1,4,4,4- pentafluoro-1 -butene; 2,3,3,4,4-pentafluoro-1-butene; 1 ,2,3,3,4,4,4-heptafluoro-1-butene; 1,1,2,3,4,4,4-heptafluoro-1-butene; and 1,3,3,3-tetrafluoro-2-(trifluoromethyl)-propene.

[0069] Additionally or alternatively, the halogenated hydrofluorolefin may be selected from the group consisting of 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene. [0070] Suitably, the halogenated hydroolefin is 1-chloro-3,3,3-trifluoropropene, 1,3,3,3- tetrafluoropropene, 2,3,3,3-tetrafluoropropene, 1,1,1, 4,4, 4-hexafluoro-2-butene or combinations thereof. [0071 ] Advantageously, foams produced using halogenated hydroolefins as blowing agents demonstrate excellent thermal performance and have low global warming impact and low ozone depletion.

[0072] The blowing agent may comprise an aliphatic hydrocarbon containing from 3 to 7 carbon atoms.

[0073] For example, the aliphatic hydrocarbon containing from 3 to 7 carbon atoms may be propane, butane, isobutane, pentane, isopentane, cyclopentane, hexane, cyclohexane, isohexane, neohexane, heptane, isoheptane, cycloheptane.

[0074] The blowing agent may comprise a blend of a halogenated hydroolefin and an aliphatic hydrocarbon containing from 3 to 7 carbon atoms.

[0075] Optionally, said blowing agent may comprise the halogenated hydroolefin in at least 60 wt% based on the total weight of the blowing agent, preferably at least 70 wt% based on the total weight of the blowing agent, more preferably at least 80 wt% based on the total weight of the blowing agent, even more preferably at least 85 wt% based on the total weight of the blowing agent.

[0076] Suitably, the aliphatic hydrocarbon containing from 3 to 7 carbon atoms in the aforesaid blend will be present in an amount of from 1 to 40 wt% based on the total weight of the blowing agent. Preferably, in an amount of at least 5 wt% based on the total weight of the blowing agent. More preferably in an amount of at least 10 wt% based on the total weight of the blowing agent, even more preferably in an amount of at least 15 wt% based on the total weight of the blowing agent, such as in an amount of at least 20 wt% based on the total weight of the blowing agent.

[0077] The weight ratio of the halogenated hydroolefin to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms may be from 99:1 to 60:40. Suitably, the weight ratio the halogenated hydroolefin to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms is 95:5, or 90: 10, or 85: 15, or 80:20, or 75:25, or 70:30. Preferably, the weight ratio of the halogenated hydroolefin to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms is 85: 15.

[0078] Suitably, the blowing agent may comprise a blend of 1-chloro-3,3,3- trifluoropropene and one or more of propane, butane, pentane, hexane, heptane and isomers thereof.

[0079] For example the blowing agent may comprise a blend of 1-chloro-3,3,3- trifluoropropene and at least one pentane, such as isopentane. The 1-chloro-3,3,3- trifluoropropene may be present in at least 60 wt% based on the total weight of the blowing agent, such as in an amount of at least: 70 wt%, or 75 wt%, or 80 wt%, or 85 wt% or 90 wt% or 95 wt%. The pentane (such as isopentane) may be present in up to 40 wt% based on the total weight of the blowing agent, such as in an amount of: 35 wt%, or 30 wt% or 25 wt% or 20 wt% or 15 wt% or 10 wt%, or 5 wt% based on the total weight of the blowing agent. The blowing agent blend may have a weight ratio of 1-chloro-3,3,3-trifluoropropene to a pentane (such as isopentane) of 60:40, or 65:35, or 70:30, or 75:25, or 80:20, or 85: 15, or 90: 10, or 95:5.

[0080] Suitably the blowing agent comprises a blend of 1-chloro-3,3,3-trifluoropropene and at least one pentane, such as isopentane, in a weight ratio of 75:25 to 95:5, preferably in a weight ratio of 80:20 or 85: 15. [0081 ] Optionally, the blowing agent comprises about 85 wt% 1-chloro-3,3,3- trifluoropropene and about 15 wt% isopentane.

[0082] Advantageously, foams produced using 1-chloro-3,3,3-trifluoropropene and isopentane as provided above demonstrate excellent thermal insulation performance, excellent flame retardancy and have low global warming potential. [0083] Alternatively, the blowing agent may comprise a blend of a halogenated hydroolefin and a chlorinated aliphatic hydrocarbon containing 2 to 5 carbon atoms.

[0084] It has been found that a blend of chlorinated aliphatic hydrocarbon containing 2 to

5 carbon atoms, such as isopropyl chloride, and low boiling hydrocarbon can be used as a blowing agent for phenolic foam. The foams produced are essentially free of cellular defects, and give stable low thermal conductivity values. Such foams are used as insulation products for buildings and transport.

[0085] The blowing agent may comprise a chlorinated aliphatic hydrocarbon having from

2 to 5 carbon atoms. Suitably, the said chlorinated aliphatic hydrocarbon having from 2 to 5 carbon atoms is selected from the group consisting of dichloroethane, propyl chloride, isopropyl chloride, butyl chloride, isobutyl chloride, pentyl chloride, and isopentyl chloride.

[0086] Isopropyl chloride (2-chloropropane) can be selected for its favourable environmental characteristics. Isopropyl chloride (2-chloropropane) has been reported as having no global warming potential or ozone depletion characteristics (according to United States Environmental Protection Agency, 40 CFR Part 82. FLR-6718-2 Protection of Stratospheric Ozone. Section II Listing of Acceptable Substitutes, B Foam Blowing lb, 2-chloropropane).

[0087] When the blowing agent comprises a blend of halogenated hydroolefin and a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms, suitably such a blend may comprise at least 60 wt% halogenated hydroolefin, more suitably at least 75 wt%, even more suitably, at least 85 wt% halogenated hydroolefin based on the total weight of the blowing agent. Suitably, the halogenated hydroolefin is selected from 1-chloro-3,3,3-trifluoropropene, 1 ,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene, 1 , 1 , 1 ,4,4,4-hexafluoro-2-butene or combinations thereof. Preferably, the halogenated hydroolefin may be 1-chloro-3,3,3- trifluoropropene. [0088] A blend of halogenated hydroolefin and a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms, suitably comprises from 5 to 40 wt% chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms, more suitably from 10 to 30 wt%, even more suitably, from 10 to 20 wt% chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms based on the total weight of the blowing agent. Suitably, the chlorinated aliphatic hydrocarbon containing 2 to 5 carbon atoms is selected from dichloroethane, propyl chloride, isopropyl chloride, butyl chloride, isobutyl chloride, pentyl chloride, and isopentyl chloride. More suitably, the chlorinated aliphatic hydrocarbon containing 2 to 5 carbon atoms is isopropyl chloride.

[0089] A blend of halogenated hydroolefin and a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms, may for example comprise 1-chloro-3,3,3-trifluoropropene and isopropyl chloride. The 1-chloro-3,3,3-trifluoropropene may be present in at least 60 wt% based on the total weight of the blowing agent, such as in an amount of at least: 70 wt%, or 75 wt%, or 80 wt%, or 85 wt% or 90 wt% or 95 wt%. The isopropyl chloride may be present in up to 40 wt% based on the total weight of the blowing agent, such as in an amount of: 35 wt%, or 30 wt% or 25 wt% or 20 wt% or 15 wt% or 10 wt%, or 5 wt% based on the total weight of the blowing agent. The blowing agent blend may have a weight ratio of 1-chloro-3,3,3- trifluoropropene to isopropyl chloride of 60:40, or 65:35, or 70:30, or 75:25, or 80:20, or 85: 15, or 90: 10, or 95:5.

[0090] Suitably the blowing agent comprises a blend of 1-chloro-3,3,3-trifluoropropene and isopropyl chloride, in a weight ratio of 75:25 to 95:5, preferably in a weight ratio of 80:20 or 85: 15.

[0091 ] Optionally, the blowing agent comprises about 85 wt% 1-chloro-3,3,3- trifluoropropene and about 15 wt% isopropyl chloride.

[0092] Advantageously foams produced using 1-chloro-3,3,3-trifluoropropene and isopropyl chloride as provided above demonstrate excellent long term thermal performance and excellent flame retardancy. The aged thermal conductivity of such foams is less than 0.0175 W/m K when measured at a mean temperature of 10°C after heat ageing for 175 ± 5 days at 70 ± 2°C, in accordance with BS EN 13166:2012. [0093] Alternatively, the blowing agent may comprise a blend (i.e. a mixture) of an aliphatic hydrocarbon containing 3 to 7 carbon atoms and a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms.

[0094] Optionally, said blowing agent may comprise a chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms in at least 60 wt% based on the total weight of the blowing agent, preferably at least 70 wt% based on the total weight of the blowing agent, more preferably at least 75 wt% based on the total weight of the blowing agent, even more preferably at least 80 wt% based on the total weight of the blowing agent.

[0095] Suitably, the aliphatic containing from 3 to 7 carbon atoms in the aforesaid blend will be present in an amount of from 1 to 40 wt% based on the total weight of the blowing agent. Preferably, in an amount of at least 5 wt% based on the total weight of the blowing agent. More preferably in an amount of at least 10 wt%, such as at least 15 wt% based on the total weight of the blowing agent, even more preferably in an amount of at least 20 wt% based on the total weight of the blowing agent. [0096] The weight ratio of the chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms may be from 99:1 to 60:40. Suitably, the weight ratio of the chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms is 95:5, or 90: 10, or 85: 15, or 80:20, or 75:25, or 70:20. Preferably, the weight ratio of the chlorinated aliphatic hydrocarbon containing from 2 to 5 carbon atoms to the aliphatic hydrocarbon containing from 3 to 7 carbon atoms is 80:20.

[0097] Suitably, the blowing agent may comprise a blend of isopropyl chloride and one or more of propane, butane, pentane, hexane, heptane and isomers thereof. For example the blowing agent may comprise a blend of isopropyl chloride and at least one pentane, such as isopentane. The isopropyl chloride may be present in at least 60 wt% based on the total weight of the blowing agent, such as in an amount of at least: 70 wt%, or 75 wt%, or 80 wt%, or 85 wt% or 90 wt% or 95 wt%. The pentane (such as isopentane) may be present in up to 40 wt% based on the total weight of the blowing agent, such as in an amount of: 35 wt%, or 30 wt% or 25 wt% or 20 wt% or 15 wt% or 10 wt%, or 5 wt% based on the total weight of the blowing agent. [0098] Suitably the blowing agent comprises a blend of isopropyl chloride and at least one pentane, such as isopentane, in a weight ratio of 75:25 to 95:5, preferably in a weight ratio of 80:20 or 85: 15.

[0099] Optionally, the blowing agent comprises about 85 wt% isopropyl chloride and about 15 wt% isopentane, or about 80 wt% isopropyl chloride and 20 wt% isopentane. [00100] A blowing agent additive, for example a gas such as air, nitrogen, helium, argon, carbon dioxide, or a fluorocarbon may be added to the foamable phenolic resin composition in such an amount that does not impair characteristics or physical properties of the phenolic foam of the present invention. A preferred amount of the substance to be added is 0.1 to 10 % by weight, and more preferred is 0.5 to 1.5 % by weight of blowing agent used.

[00101 ] Hydrocarbons such as isopentane and isobutane have low potential for global warming and do not deplete the ozone layer of the Earth.

[00102] The amount of the blowing agent used in the present invention is from 1 to 20 parts by weight relative to 100 parts by weight of phenolic resin, more preferably from 6 to 14 parts by weight per 100 parts by weight of phenolic resin.

[00103] Suitably, the phenolic foams of the present invention have a closed-cell content of greater than 85%, preferably greater than 90%, such as greater than 95%, even more preferably greater than 98%.

[00104] The phenolic foams of the present invention suitably, have an aged thermal conductivity of 0.025 W/m K or less, such as 0.022 W/m K or less, preferably less than 0.020 W/m K or less, such as 0.018 W/m K or less, most preferably 0.016 W/m K or less, when measured at a mean temperature of 10°C after ageing for 175 ± 5 days at 70 ± 2°C, in accordance with the procedure specified in European Standard BS EN 13166:2012.

[00105] The present invention is explained in detail by the Examples and Comparative Examples.

Phenolic Resin Preparation

[00106] The phenolic resin used in the examples is a phenolic resole resin commercially available liquid phenol-formaldehyde resin supplied by Hexion UK and Sumitomo Bakelite under the trade name R330U. This resin has a viscosity of 7000 to 14000 cP at 25°C, a weight average molecular weight of 700 to 2000, and a pH of 6.5 to 7.5. R330U resin contains from 2 wt% to 4 wt% free phenol and less than 1 wt% free formaldehyde based on the total weight of the resin. R330U resin has a water content of 1 1 to 14 wt% (measured by Karl Fisher analysis) based on the total weight of the resin. R330U resin contains 3 to 5 wt% plasticiser and 2 to 5 wt% surfactant as previously described herein, based on the total weight of the resin. R330U has a number average molecular weight of from 330 to 700. .

Phenolic Foam Preparation

[00107] Phenolic foam samples were prepared as follows: The above identified phenolic resole resin was mixed with a scavenger at 20°C. Each sample contained 2.5 pbw of scavenger per 100 pbw phenolic resole. The resulting mixture was allowed to stand for between 18 and 48 hours. To 190 g of said mixture was added at 10°C 17.5 g of a pre-blended blowing agent mixture at -18°C. Once a uniform emulsion had formed, said emulsion was cooled to between 0 and 4°C. To said emulsion was added while mixing 37 g of a blend of para-toluene sulfonic acid and xylene sulfonic acid (in a weight ratio of 65:35 (ptsa:xsa) at 92% minimum concentration and at a temperature of 5°C. Foaming commences immediately. Mixing of the acid into the resin takes less than 10 seconds and 200 g of the foaming mixture was quickly poured into a 30 x 30 x 5 cm picture frame mould which was preheated to 70 - 75°C. A pressure of 40 to 50 kPa is applied to the lid of the mould to pressurise the rising foam. The foam is cured at 70 - 75°C for 10 minutes. The foam sample is then post-cured in an oven for 2 to 12 hours at 70°C. The density of the foam board produced was subsequently measured.

Formaldehyde emission (Formaldemeter Method)

[00108] Formaldehyde emission of foam cubes having a side length of 50 mm, which were cut from a 30 x 30 x 5 cm lab foam, was qualitatively assessed using a HtV-m Formaldemeter, manufactured by PPM Technology. To standardise the test method, the formaldehyde emission from a cube of the same size of standard phenolic foam, which does not contain formaldehyde scavengers, and which was prepared by the same methodology as the foam samples comprising formaldehyde scavengers, was simultaneously assessed.

[00109] The Formaldemeter test method is as follows: A pair of foam cubes having a side length of 50 mm (which are not coated with any facing material) were cut using a band saw from a 30 x 30 x 5 cm lab foam. The foam cubes were placed into a 5.8 dm³ glass desiccator along with the Formaldemeter HtV-m. The lid was placed on the desiccator in order to hermetically seal it and the concentration of the formaldehyde in the desiccator was then measured by the Formaldemeter over a period of 30 minutes. The final concentration was recorded after 30 minutes. As formaldehyde emissions are subject to variation depending on atmospheric conditions, the laboratory temperature of 23°C was controlled to within ±2°C, and 50% relative humidity (±10%), and the measurement was also performed simultaneously with a standard (or reference) foam using the same equipment.

[001 10] The Formaldemeter test was conducted on foam samples within 3 days of foam manufacture.

Formaldehyde Emission by ISO 16000-3 or EN 16516:2016

[001 11 ] Foams which performed well under the Formaldemeter formaldehyde emission assessment were subsequently assessed for formaldehyde emission according to ISO 16000- 3:201 1 or European Standard EN16516:2016. The EN16516 test was conducted on samples from 4 to 8 weeks after foam production. A foam board having a given thickness was cut to the following size: 725 mm x 725 mm x foam thickness. Said foam is housed in a ventilated chamber having a volume of 1 m³, with constant airflow therethrough. An air exchange rate of 0.5 m³ per hour was maintained through the chamber with the temperature being maintained at 23°C, and a relative humidity of 50% being maintained in the chamber. After 28 days under said conditions, the air in the chamber is analysed for formaldehyde content.

Examples and Comparative Examples

[00112] The pre-blended blowing agent mixture employed in the following examples was a blend of isopropyl chloride and isopentane in a ratio of 80:20.

Table 1

Examples & Scavenger Scavenging Open/closed- Thermal Formaldehyde Key comparative Candidate effect cell conductivity Emission

Examples (mW/m-K) (ppm) using

@10°C Formaldemeter test

C1 Standard phenolic N/A Closed 20.6 0.35 STD foam (no

scavenger)

1 Oxalyldihydrazide Very Closed 20.5 0.245 A positive

2 Adipic acid Very Closed 20.9 0.245 A dihydrazide positive

3 Carbohydrazide Very Closed 21.3 0.245 A positive

4 Aminoguanidine Very Closed 20.2 0.245 A bicarbonate positive

5 L-Arginine Very Closed 20.5 0.245 A positive

C2 Phenol Positive Closed 20.3 0.315 B

C3 Benzoguanamine Positive Closed 20.8 0.315 B

C4 Ammonium None Closed 20.6 0.35 C phosphate

(dibasic)

C5 Ethylacetoacetate None Closed 21.5 0.35 C

C6 Ammonium None Closed 22.4 0.35 C acetate

C7 Acetoacetamide None Closed 22 0.35 C

C8 Guanidine None Closed 21.5 0.35 C phosphate

C9 Guanidine None Closed 22.2 0.35 C carbonate

C10 Melamine None Closed 20.5 0.35 C

C1 1 Dicyandiamide None Closed 20.9 0.35 C

C12 Casein None Closed 20.4 0.35 C

C13 D-Glucose Positive Closed 20.8 0.315 C

C14 Sorbitol None Closed 21.2 0.35 C

C15 Sodium bisulfite N/A Open 32.6 N/A D

C16 Sodium N/A Open 32.4 N/A D metabisulfite

C17 Ammonium N/A Open 29.4 N/A D chloride C18 Polyethyleneimine E E E E E

C19 Ethylenediamine E E E E E

C20 Ethanolamine E E E E E

C21 Sodium sulphite Negative Part-closed 23.7 2.7 F

C22 Ammonium Negative Closed 19.4 0.5 F phosphate

(monobasic)

Legend

A = Thermal conductivity <0.022 W/m-K, >20% formaldehyde emission reduction;

B = Thermal conductivity <0.022 W/m-K, 10-20% formaldehyde emission reduction;

C = Thermal conductivity <0.022 W/m-K, no formaldehyde emission reduction;

D = Thermal conductivity≥0.028 W/m- K, open celled foam;

E = foam curing retarded/incomplete cure;

F = increased formaldehyde emission;

STD = standard.

Closed implies≥90% closed-cell; Open implies <80% closed-cell; Part-closed implies 80- 89% closed-cell

[00113] The performance of foams which performed well in the formaldemeter test method was assessed in accordance with EN16516. A representative example is outlined below. [00114] The properties of a foam in accordance with Example 4 were measured as outlined in Table 2. The formaldehyde emission was measured after 28 days in the ventilated chamber as described above.

[00115] The words "comprises/comprising" and the words "having/including" when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[00116] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

Claims

1. A phenolic foam formed by foaming and curing a phenolic resin composition, that comprises a phenolic resin, a surfactant, a blowing agent, an acid catalyst, a formaldehyde scavenger selected from the group consisting of: L-arginine, aminoguanidine bicarbonate, carbohydrazide, oxalyldihydrazide, adipic acid dihydrazide and combinations thereof, wherein said foam has a closed-cell content of greater than 85%, and having an aged thermal conductivity 0.025 W/m K or less when measured at a mean temperature of 10°C after heat ageing for 175 ± 5 days at 70 ± 2°C, in accordance with the procedure specified in European Standard BS EN 13166:2012.

2. The phenolic foam as claimed in claim 1 , wherein said foam emits less than 60 μg/m³ after 28 days when tested in accordance with EN 16516.

3. The phenolic foam as claimed in any preceding claim, wherein the formaldehyde scavenger is present in an amount of from 1 to 5 parts by weight per 100 parts by weight of the phenolic resin.

4. The phenolic foam as claimed in claim 3, wherein the formaldehyde scavenger is present in an amount of from 2 to 4 parts by weight per 100 parts by weight of the phenolic resin.

5. The phenolic foam as claimed in any preceding claim, wherein the phenolic resin has a molar ratio of phenol groups to aldehyde groups in the range 1 : 1 to 1 :3.

6. The phenolic foam as claimed in claim 5, wherein the molar ratio of phenol groups to aldehyde groups is from 1 .5 to 2.3.

7. The phenolic foam as claimed in any preceding claim, wherein the phenolic resin has a weight average molecular weight of from 700 to 2,000.

8. The phenolic foam as claimed in any preceding claim, wherein the phenolic resin has a number average molecular weight of from 330 to 800, such as from 350 to 700.

9. The phenolic foam as claimed in any preceding claim, wherein the blowing agent comprises a C1-C7 hydrocarbon.

10. The phenolic foam as claimed in claim 9, wherein the C1-C7 hydrocarbon comprises at least one of butane, pentane, hexane, heptane and isomers thereof.

1 1 . The phenolic foam as claimed in any preceding claim , wherein the blowing agent comprises a halogenated hydroolefin selected from the group consisting of hydrofluoroolefins and hydrochlorofluoroolefins.

12. The phenolic foam as claimed in claim 1 1 , wherein the halogenated hydroolefin is selected from the group consisting of 1 -chloro-3,3,3-trifluoropropene, 1 ,3,3,3-tetrafluoro-1 - propene, 2,3,3,3-tetrafluoro-1 -propene, 1 , 1 , 1 ,4,4,4-hexafluoro-2-butene and combinations thereof.

13. The phenolic foam as claimed in any preceding claim , wherein the blowing agent comprises isopropyl chloride.

14. The phenolic foam as claimed in claim 12, wherein the blowing agent comprises 1 - chloro-3,3,3-trifluoropropene, suitably trans-1 -chloro-3,3,3-trifluoropropene or cis-1 -chloro-3,3,3- trifluoropropene or combinations thereof, preferably, trans-1 -chloro-3,3,3-trifluoropropene.

15. The phenolic foam as claimed in claim 14, wherein the blowing agent further comprises a C1-C7 hydrocarbon selected from at least one of isopropyl chloride, butane, pentane, hexane, heptane and isomers thereof.

16. The phenolic foam as claimed in claim 14 or 15, wherein the blowing agent comprises at least 60 wt% 1 -chloro-3,3,3-trifluoropropene based on the total weight of the blowing agent.

17. The phenolic foam as claimed in claim 16, wherein the blowing agent comprises 85 wt% 1 -chloro-3,3,3-trifluoropropene and 15 wt% iso-pentane based on the total weight of the blowing agent.

18. The phenolic foam as claimed in any preceding claim , wherein the blowing agent comprises 1 to 20 parts by weight per 100 parts by weight of phenolic resin.

19. The phenolic foam as claimed in any preceding claim, further comprising at least one of a plasticiser, an inorganic filler, a flame retardant, a toughening agent and combinations thereof.

20. The phenolic foam as claimed in any preceding claim, wherein the surfactant is present in an amount of 1 to 6 parts by weight per 100 parts by weight of phenolic resin, preferably the surfactant is a castor oil-ethylene oxide adduct wherein more than 20 moles but less than 40 moles of ethylene oxide are added per 1 mole of castor oil.

21 . The phenolic foam as claimed in claim 19 or 20, wherein the plasticiser is present in an amount of 0.1 to 10 parts by weight per 100 parts by weight of phenolic resin, preferably the plasticiser is present in an amount of 5 parts by weight per 100 parts by weight of phenolic resin.

22. The phenolic foam as claimed in claim 21 , wherein the plasticiser is a polyester polyol that is a reaction product of a polybasic carboxylic acid selected from a dibasic to a tetrabasic carboxylic acid with a polyhydric alcohol selected from a dihydric, a trihydric, a tetrahydric and a pentahydric alcohol.

23. The phenolic foam as claimed in claim 22, wherein the polybasic carboxylic acid used to synthesise the polyester polyol comprises at least one of phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,3-dicarboxylic acid, naphthalene-1 ,4-dicarboxylic acid, napththalene-2,6-dicarboxylic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, cyclohexane-1 ,2-dicarboxylic acid, cyclohexane-1 ,3-dicarboxylic acid, and cyclohexane- 1 ,4-dicarboxylic acid, preferably the polybasic carboxylic acid used to synthesise the polyester polyol comprises one or more of phthalic acid , isophthalic acid , or terephthalic acid.

24. The phenolic foam as claimed in claim 22 or 23, wherein the polyhydric alcohol used to synthesise the polyester polyol comprises at least one of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, neopentyl glycol, 1 ,2-cyclohexane dimethanol, 1 ,3-cyclohexane dimethanol, and 1 ,4-cyclohexane dimethanol, preferably the polyhydric alcohol used to synthesise the polyester polyol comprises one or more of diethylene glycol, propylene glycol, dipropylene glycol, 1 ,4-butanediol.

25. The phenolic foam as claimed in any one of claims 19 to 24, wherein the inorganic filler comprises a metal hydroxide or metal carbonate with an ionic equilibrium solubility (Ksp) less than 10^"8 when measured at 25 °C.

26. The phenolic foam as claimed in claim 25, wherein the metal carbonate is calcium carbonate.

27. The phenolic foam as claimed in claim 26, wherein the calcium carbonate has an average particle size of 100 - 300 μιτι, preferably 150 - 200 μιτι.

28. The phenolic foam as claimed in any preceding claim, having a pH of 4 or more.

29. The phenolic foam as claimed in any preceding claim, wherein the phenolic foam has a density of from 10 to 100 kg/m³.

30. The phenolic foam as claimed in any preceding claim, wherein the phenolic foam has a density of from 10 to 60 kg/m³.

31 . The phenolic foam as claimed in any preceding claim, wherein the phenolic foam has a compressive strength of from 80 kPa to 220 kPa.

32. The phenolic foam as claimed in one of claims 19 to 31 , wherein the flame retardant is selected from the group selected from : organophosphorus compounds, and inorganic phosphorus compounds, such as triethyl phosphate, diphenyl phosphite, diethyl ethyl phosphonate, ammonium polyphosphate, and red phosphorus, or aluminium trihydrate, zinc borate or halogenated flame retardants.

33. The phenolic foam as claimed in any one of claims 19 to 32, wherein the toughening agent is selected from the group consisting of urea, dicyandiamide and melamine.

34. The phenolic foam as claimed in any one of claims 19 to 33, wherein the toughening agent is present in an amount of from 1 to 10 parts by weight per 100 parts by weight of the phenolic resin.

35. The phenolic foam as claimed in claim 34, wherein the toughening agent is urea and is present in about 5 parts by weight per 100 parts by weight of the phenolic resin.

36. The phenolic foam as claimed in any preceding claim, wherein the acid catalyst is present in an amount of 5 to 25 parts by weight per 100 parts by weight of phenolic resin, preferably the acid catalyst comprises at least one of benzenesulfonic acid, para-toluene sulfonic acid, xylene sulfonic acid, naphthalene sulfonic acid, ethylbenzene sulfonic acid and phenol sulfonic acid.

37. The phenolic foam as claimed in claim 35 wherein the acid catalyst comprises para- toluene sulfonic acid and xylene sulfonic acid.

38. The phenolic foam as claimed in any preceding claim, wherein the phenolic foam has an aged thermal conductivity 0.022 W/m K or less, such as 0.020 W/m K or less, or 0.018 W/m K or less, or 0.016 W/m K or less, when measured at a mean temperature of 10°C after heat ageing for 175 ± 5 days at 70 ± 2°C, in accordance with the procedure specified in European Standard BS EN 13166:2012.

39. The phenolic foam as claimed in any preceding claim, wherein the phenolic has a facing on at least one surface thereof, preferably the facing comprises at least one of glass fibre-non woven fabric, spun bonded-non woven fabric, aluminium foil, bonded-non woven fabric, metal sheet, metal foil, ply wood, calcium silicate-board , plaster board , Kraft or other paper product, and wooden board.

40. The phenolic foam as claimed in claim 39, wherein at least one of the facings is perforated.

41 . The phenolic foam as claimed in claim 39 or 40, wherein the facing is coated with or impregnated with a formaldehyde scavenger and/or flame retardant.

42. The phenolic foam as claimed in claim 41 wherein the facing is impregnated with urea, sodium sulfite, carbohydrazide, aminoguanidine bicarbonate, arginine, oxalyldihydrazide, or adipic acid dihydrazide.

43. A method for manufacturing a closed-cell phenolic foam according to any preceding claim, comprising foaming and curing a foamable phenol resin composition containing a phenol resin, a surfactant, a formaldehyde scavenger, a blowing agent and a curing catalyst, wherein the formaldehyde scavenger is selected from the group consisting of: L-arginine, aminoguanidine bicarbonate, carbohydrazide, oxalyldihydrazide, adipic acid dihydrazide and combinations thereof.