A CLOSED CELL PHENOLIC FOAM

Abstract: A closed cell phenolic foam is formed from a phenolic resin, a blowing agent such as HCFC141b, a catalyst and less than 2.5 % by weight relative to the resin of at least one hydrofluoroether or an azeotrope formulation thereof. 1-methoxy-nonafluorobutane and especially an azeotrope formulation thereof with trans-1,2-dichloroethylene are preferred hydrofluoroethers. The phenolic foam has a stable closed cell content of greater than 90 % and a stable thermal conductivity.

Description: "A closed cell phenolic foam" Introduction This invention relates to a closed cell phenolic foam and to a process for preparing such foams from resins. Phenolic foams are widely used in building applications in view of their thermal insulation and fire resistant properties. Such phenolic foams are generally prepared by mixing a phenol formaldehyde resin with a blowing agent, a cell stabiliser and a hardener. EP - A - 0170357 describes one such process for preparing a phenolic foam using Freon as a blowing agent, aqueous sulphuric acid as a hardener, and a cell stabiliser derived by oxylating castor oil with ethylene oxide or mixtures thereof with proplylene oxide. Freon is a particular chlorofiuorocarbon (CFC). EP-A-0439283 describes the use of a complex blend of materials as an alternative blowing agent to a CFC. The blend comprises: at least one perfluoroalkane (PFA) (especially perfluoropentane, perfluorohexane or perfluoroheptane); and at least one component selected from a hydrogenated chlorofiuorocarbon (HFC) and a specific alkane or cycloalkane. EP-A-0579321 describes a phenolic foam including perfluro-N-methyl morpholine. WO-A-9811715 describes the manufacture of resol foams using perfiuorinated ethers as part of the blowing agent blend. There is a need for an improved phenolic foam which is easily processed, environmentally friendly and has good thermal conductivity properties. Statements of Invention According to the invention there is provided a closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and at least one hydrofluroether or an azeotrope formulation thereof in an amount of less than 2.5% by weight relative to the resin to form a phenolic foam having a closed cell content of greater than 90% and a stable thermal conductivity. Most preferably the hydrofluroether is present in an amount of from 0.5% to 1.5% by weight relative to the resin. In a preferred embodiment of the invention the hydrofluoroether is of the general formula C a F b OCH 3 or C a F b OC 2 H 5 wherein: b = 2a + 1 Preferably the hydrofluoroether is C4F9OCH3 (l-methoxy-nonafiuorobutane). Ideally the hydrofluoroether is in an azeotrope formulation, especially with trans- 1 ,2-dichloroethylene. In a particularly preferred embodiment the azeotrope formulation is a 50/50 formulation of 1-methoxy-nonafluorobutane with trans 1,2, dichloroethylene. The azeotrope formulation may be formed by a reaction of two or more components, at least one component being present in the phenolic resin. The blowing agent may include a hydrogenated chlorofiuorocarbon (HCFC). Ideally, the HCFC is HCFC 141b (CC1 2 F-CH 3 ). Alternatively the blowing agent may include a hydrogenated fluorocarbon (HFC). The foam may include an alkane or cycloalkane. In a particularly preferred aspect the invention provides a closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and less than 2.5% by weight relative to the resin of l-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene. In a preferred aspect the invention provides a closed cell phenolic foam from a phenolic resin, HCFC 141 b (CC1 2 F-CH 3 ) a catalyst and less than 2.5% by weight relative to the resin of l-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene. In an especially preferred aspect the invention provides a closed cell phenolic foam formed from a phenolic resin, HCFC 1416 (CC1 2 F-CH 3 ), a catalyst and less than 2.5% by weight relative to the resin of an azeotrope of 1-mehoxy nonaflurobutane with trans-1, 2-dichloroethylene. Preferably the catalyst is a strong mineral acid such as sulphuric acid containing at least 20% water, preferably at least 40% water. The invention further provides a blend for forming a closed cell phenolic foam of the invention, the blend comprising a blowing agent, a catalyst and less than 2.5% by weight relative to a phenolic resin of at least one hydrofluroether or an azeotrope formulation thereof. Detailed Description The invention will be more clearly understood from the following description thereof given by way of example. The invention is based on the surprising finding that closed cell phenolic foams can be produced by using relatively small quantities of at least one hydrofluoroether (HFE). It is believed that the HFE acts as a surfactant. Ethers are usually strong solvents which can have an adverse cell opening effect on foam and would therefore not normally be considered as suitable components for closed cell foams. We have however, surprisingly found that hydrofiuoretheres can be effectively used as surfactants in foam formulations. In addition to this unexpected use of such ethers, there is the f rther major advantage that these solvents have much less environmental impact than conventional solvents used in foam manufacture. Such solvents have a very low global warming potential when compared with conventional solvents used in such foam formulations. Most importantly and unexpectedly we have found that not only is a highly closed cell foam produced using a hydrofluroether with a low global warning potential but also the foam produced has an extremely favourable stable thermal conductivity profile. The closed cell value may be measured by the method described in B.S. 4370/ASTM D2856. The foam of the invention has a closed cell content of greater than 90% when measured by this method. The K value is measured as described in method 7A of B.S. 4370 part 2 with reference to BS3927. ASTM C177 is equivalent. The preferred foam of the invention has a K value at 30 days or longer of less than about 0.018 W/M°C. Even more surprisingly the thermal conductivity remains stable when tested at high temperatures of about 70°C over prolonged periods. Example 1 A phenolic resin was used which was prepared from the ingredients and using the process described in Examples 1 to 3 of EP-A-0170357. This specification is incorporated herein by reference. Foams were manufactured in the laboratory using the formulations below. The chemicals were mixed using a high speed laboratory stirrer and dispensed into a mould having a volume as approximately 0.03m 3 . The mould was subsequently placed in an oven at 70°C for a minimum of 3 hours. After demoulding, the foam was allowed to cool down to ambient temperature prior to commencement of thermal conductivity testing. *The catalyst is 50% sulphuric acid/50% water. Thermal conductivity testing was performed at ambient and at 70°C and the results are shown in the Table below. It is very clear that without the HFE surfactant, the drift in thermal conductivity is very rapid both at ambient and 70°C whilst with HFE 7100 as surfactant, the thermal conductivity drifts to a value in the region of 0.018 W/M°K - 0.019 W/M°K. HFE 7100 is 1-methoxy-nonafiuorobutane having the formula C 4 H 9 OCH 3 . It has a boiling point of 60°C. Example 2 Discontinuous block foam, was manufactured on a commercial scale plant to produce blocks of dimensions of approximately 2440 x 1000 x 1000mm. The foam mix was dispensed through a low pressure mixer into a heated mould. The product was put through a three hour curing cycle prior to demould. The foam was manufactured according to the following formulation. amount Phenolic resin (example 1): lOOpbw Blowing agent: HCFC 141b 10.8pbw HFE 71 DE 1.2pbw Catalyst*: 11.68pbw colour: KDS black 0.3bw * The catalyst is a blend of sulphuric and phosphoric acid containing 42.5% sulphuric, 13.6% phosphoric (as a fire retardant) and the balance water. The density of the foam thus formed was 35kg/m 3 HFE 71 DE is a 50/50 blend of HFE 7100 with trans 1, 2 dichloroethylene of the formula CHCl.CHCl. The material is available from 3M. The particular advantage of this material is that it is an azeotrope and boils at 40°C which gives good processing characteristics, especially in producing a laminated product. We have found that these foams have excellent thermal conductivity stability as follows: Example 3 Using the method described in Example 2 a foam was manufactured according to the following formulation. Amount Phenolic Resin (Example 1) lOOpbw Blowing Agent: HCFC 141b 10.8ρbw HFE 71 DE 1.2 pbw Catalyst * (Example 2) 11.7pbw Colour: KDS Black 0.3ρbw The density of the foam thus formed was 35kg/m 3 The foam of this example has excellent thermal conductivity stability as follows. Example 4 Using the method described in Example 2 a foam was manufactured according to the following formulation. Amount Phenolic Resin (Example 1) lOOpbw Blowing Agent: HCFC 141b 10.8pbw HFE 17 DE 0.57pbw Catalyst (Example 2) 11.7pbw Colour: KDS black 0.3ρbw The density of the foam thus formed was 35 kg/M 3 The foam of this example has excellent thermal conductivity stabiHty as follows: Typical global warming potentials for perfluoroalkanes are as follows: CF 4 6500 C 2 F 0 9200 C 3 F 8 7000 C 5 F 12 7500 This is in complete contrast to HFE 7100 which has a global warming potential of 500 and especially HFE 71DE which has a global warming potential of 250. Thus, the use of HFE's in phenohc foam formulations has considerable environmental advantages compared with perfluoroalkanes. It is envisaged that the HCFC's used in the phenohc foam blowing agent blend of the invention may be selected, for example, from one or more of: HCFC 141b CC1 2 F-CH 3 HCFC 142b CH 3 CC1F 2 HCFC 123 CF 3 -CHC1 2 HCFC 124 CHC1F 2 HCFC 225ca CHC1 2 -CF 2 -CF 3 HCFC 225cb CC1F 2 -CF 2 -CHC1F It is also envisaged that the blowing agent blend may include a suitable hydrogenated fluorocarbon selected, for example, from one or more of: HFC 134 a CF 3 CH 2 F HFC 152 a CH 3 -CHF 2 HFC 245fa CF 3 -CH 2 -CHF 2 HFC 365mfc CF 3 -CH 2 -CF 2 -CH 3 The HFC's may be represented by the formula C R H P F Q whenever: R is an integer from 1 to 4 P is an integer from 1 to 5 and Q = (2R+2)-P for an open chain HFC and (2R-P) for a cyclic HFC. It is further envisaged that the phenohc foam blowing agent blend may include an alkane, especially n-pentane, or a cycloalkane, especially cyclopentane. The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims: Claims 1. A closed cell phenolic foam formed from a phenolic resin, a blowing agent, a catalyst and at least one hydrofluroether or an azeotrope formulation thereof in an amount of less than 2.5% by weight relative to the resin to form a phenolic foam having a closed cell content of greater than 90% and a stable thermal conductivity. 2. A foam as claimed in claim 1 wherein the hydrofluroether is present in an amount of from 0.5% to 1.5% by weight relative to the resin. 3. A foam as claimed in any preceding claim wherein the hydrofluoroether is of the general formula C a F b OCH 3 or C a F b OC 2 H 5 wherein: b = 2a + 1 4. A foam as claimed in any preceding claim wherein the hydrofluoroether is C4F9OCH3 (1-methoxy-nonafluorobutane). 5. A foam as claimed in any preceding claim wherein the hydrofluoroether is in an azeotrope formulation. 6. A foam as claimed in claim 6 wherein the hydrofluoroether is in an azeotrope formulation with trans-1, 2-dichloroethylene. 7. A foam as claimed in claim 6 wherein the azeotrope formulation is a 50/50 formulation of 1-methoxy-nonafluorobutane with trans 1,2, dichloroethylene. 8. A foam as claimed in any of claims 5 to 7 wherein the azeotrope formulation is formed by a reaction of two or more components, at least one component being present in the phenolic resin. 9. A foam as claimed in any preceding claim wherein the blowing agent includes a hydrogenated chlorofiuorocarbon (HCFC). 10. A foam as claimed in claim 9 wherein the HCFC is HCFC 141b (CC1 2 F- CH 3 ). 11. A foam as claimed in any preceding claim wherein the blowing agent includes a hydrogenated fluorocarbon (HFC). 12. A foam as claimed in any preceding claim wherein the blowing agent includes an alkane or cycloalkane. 13. A closed cell phenohc foam formed from a phenolic resin, a blowing agent, a catalyst and less than 2.5% by weight relative to the resin of l-methoxy- nonaflurobutane or an azeotrope formulation thereof with trans-1, 2- dichloroethylene. 14. A closed cell phenohc foam formed from a phenohc resin, HCFC 141 b (CC1 2 F-CH 3 ), a catalyst and less than 2.5% by weight relative to the resin of l-methoxy-nonaflurobutane or an azeotrope formulation thereof with trans-1, 2-dichloroethylene. 15. A closed cell phenohc foam formed from a phenohc resin, HCFC 141b (CC1 2 F-CH 3 ), a catalyst and less than 2.5% by weight relative to the resin of an azeotrope of 1-mehoxy nonafiurobutane with trans-1, 2- dichloroethylene. 16. A closed phenolic foam as claimed in any preceding claim wherein the catalyst is a mineral acid containing at least 20% water. 17. A blend for producing a closed cell phenolic foam as claimed in any preceding claim, the blend comprising a blowing agent, a catalyst and less than 2.5% by weight relative to a phenohc resin of at least one hydrofluroether or an azeotrope formulation thereof.

Inventors: EDGERLEY GRAHAM MORGAN, HARRIS MARK STANLEY, EDGERLEY, GRAHAM, MORGAN, HARRIS, MARK, STANLEY
Applicants: EDGERLEY GRAHAM MORGAN, HARRIS MARK STANLEY, KINGSPAN IND INSULATION LIMITE, EDGERLEY, GRAHAM, MORGAN, HARRIS, MARK, STANLEY, KINGSPAN INDUSTRIAL INSULATION LIMITED
Application year: 1999
Main classification: C08J9
IPC codes: C08J9, C08L61