Phenolic foam

Abstract

Phenolic closed-cell foam comprises a hydrocarbon blowing agent and includes an alkali metal silicate in an amount of at least 1% by weight. The foam has an aged thermal conductivity as determined by the procedures of EN13166:2008 of less than 0.025 W/m.Math.K. The foam is formed from a phenolic resole resin mixture having a water content of greater than 15% by weight but less than 24% by weight.

Claims

1. A phenolic foam formed from a phenolic resole resin mixture comprising a phenolic resole resin, a surfactant, a blowing agent and an alkali metal silicate wherein the alkali metal silicate is added into the phenolic resin with a subsequent addition of an acid catalyst, the alkali metal silicate being present in an amount of at least 1% by weight, the phenolic resole resin mixture excluding optional fillers having a water content of from about 12% to about 24% by weight of the composition, the foam having a silica film formed within closed cells of the foam and thereby retain the blowing agent therein, the foam having an aged thermal conductivity as determined by the procedures of EN13166:2008 or EN14314:2009 of less than 0.025 W/m.Math.K.

2. The foam as claimed in claim 1 wherein the alkali metal silicate is present in an amount of from 1% to 10% by weight of the phenolic foam.

3. The foam as claimed in claim 1 wherein the alkali metal silicate is present in an amount of from 2.5% to 5% by weight of the phenolic foam.

4. The foam as claimed in claim 1 wherein the alkali metal silicate is hydrated and has the formula A.sub.2SiO.sub.3.nH.sub.2O in which A is an alkali metal from Group 1 of the Periodic Table and n is an integer from 1 to 9.

5. The foam as claimed in claim 1 wherein the alkali metal silicate is selected from sodium silicate, potassium silicate and lithium silicate or mixtures thereof.

6. The foam as claimed in claim 1 wherein the silicate is sodium silicate pentahydrate.

7. The foam as claimed in claim 1 wherein the silicate is potassium silicate.

8. The foam as claimed in claim 1 wherein the silicate is lithium silicate.

9. The foam as claimed in claim 1 wherein the blowing agent is a hydrocarbon blowing agent.

10. The foam as claimed in claim 9 wherein the hydrocarbon comprises a mixture of cyclopentane and isopentane.

11. The foam as claimed in claim 9 wherein the blowing agent comprises a mixture of isopropyl chloride and isopentane.

12. The foam as claimed in claim 1 wherein the blowing agent comprises perfluoroalkane.

13. The foam as claimed claim 1 wherein the foam is formed from a phenolic resole resin mixture having a water content of greater than 15% by weight but less than 24% by weight and the alkali metal silicate is present in an amount of at least 1% by weight of the foam.

14. The foam as claimed in claim 13 wherein the alkali metal silicate is present in the phenolic resole resin mixture excluding fillers in an amount of from 1% to 10% by weight of the foam.

15. The foam as claimed in claim 13 wherein the alkali metal silicate is present in the resole resin mixture (excluding fillers) in an amount of from 2.5% to 5% by weight of the foam.

16. A method of making a foam product the method comprising forming the foam from a composition comprising: a phenolic resin including surfactant, acid catalyst, blowing agent and alkali metal silicate and optional fillers, wherein the alkali metal silicate is added to the phenolic resin, and emulsified with blowing agent, prior to the addition of the acid catalyst, the composition excluding optional fillers having a water content of from about 12% to about 24% by weight of the composition, to produce a closed cell foam product a silica film within the closed cells of the foam, the foam having an aged thermal conductivity as determined by the procedures of EN13166:2008 or EN14314:2009 of less than 0.025 W/m.Math.K.

17. The foam as claimed in claim 1, wherein the foam is formed from a phenolic resin mixture having a water content of from about 15% by weight to about 24% by weight of the resin mixture.

18. The foams as claimed in claim 9, wherein the hydrocarbon comprises at least one pentane.

19. A method of making a phenolic foam product, the method comprising forming the foam by mixing an alkali metal silicate with a phenolic resin including a surfactant, prior to a subsequent acid catalyst addition, said phenolic resin having a water content of from 12% by weight to 24% by weight, emulsifying the mixture formed therefrom with blowing agent, and subsequently adding acid to cure the resultant mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying Figures which are scanning electron micrographs of various described herein phenolic foam samples. The scanning electron microscopy (SEM) sample preparation technique is described in Appendix 1.

(2) FIG. 1 is a scanning electron micrograph of the foam of Comparative Example 1 showing that high water phenolic foam cell structure has many pin holes. The formulated phenolic resin, blowing agent and acid catalyst do not contain alkali metal silicate and have a combined water content of 19.05%.

(3) FIG. 2 is a scanning electron micrograph of the foam of Example 1 showing silica gel covered pin holes despite a higher water content, 21.8% for the phenolic resin, blowing agent and acid catalyst but with sodium silicate added which serves to protect the cells.

(4) FIG. 3 is a scanning electron micrograph of the foam of Comparative Example 1 showing high resolution of cellular pin holes.

(5) FIG. 4 is a scanning electron micrograph of foam of Example 3 showing high resolution of silica gel covered cellular pin holes.

DETAILED DESCRIPTION OF THE INVENTION

(6) Experimental Work

(7) It is to be noted that some commercially available resins are formulated with surfactant already present.

(8) Resin A Preparation

(9) On a weight basis, Resin A was prepared by mixing under reflux 57.8 parts of phenol, 3.05 parts of water and 1.07 parts of 50% potassium hydroxide at 20 C. The temperature was raised to 74 to 76 C. and 30.4 parts of 91% paraformaldehyde was added over 2 hours. The temperature was then raised to 80 to 82 C. and held until viscosity reached was 6500 cP. Cooling was commenced whilst adding 3.3 parts of water, 4.1 parts of diethylene glycol and 3.6 parts of ethoxylated castor oil (surfactant). The final resin contained 17% water and 4% by weight of diethylene glycol as a plasticizer. The resin contained 8% free phenol, and less than 2% free formaldehyde. Viscosity was 2500 to 3500 cP at 25 C.

(10) Resin B Preparation. (Distilled Resin A)

(11) On a weight basis, Resin B was prepared by mixing under reflux 57.8 parts of phenol, 3.05 parts of water and 1.07 parts of 50% potassium hydroxide at 20 C. Temperature was raised to 74 to 76 C. and 30.4 parts of 91% paraformaldehyde was added over 2 hours. The temperature was raised to 80 to 82 C. and held until viscosity was 6500 cP. Cooling to 60 C. was commenced whilst adding 4.1 parts of diethylene glycol. 3.3 parts of water were vacuum distilled, cooling was continued to 40 C. and 3.6 parts of ethoxylated castor oil (surfactant) were then added. The final resin contained 11.5% water and 4.2% by weight of diethylene glycol as a plasticizer. The resin contained 7.3% free phenol, and 1.1% free formaldehyde. Viscosity was 7950 to 9000 cP at 25 C.

Examples of Foam Preparation

(12) All Results are shown in Tables 1 and 2.

(13) Examples 1 to 9 (Ex1-Ex9) in Table 1 are all formulations which include alkali metal silicate. Comparative Example 1 is the same as Example 1 except that Comparative Example 1 does not include the silicate. Comparative Example 9 is the same as Example 9 except that Comparative Example 9 does not include the silicate.

(14) When producing laboratory scale foam samples in the following examples and comparative examples, all chemical additions are carried out at room temperature (21 C.) unless stated.

(15) The Examples in Table 1 show that stable low thermal conductivity foams that exhibit desirable aged thermal conductivity values after thermal ageing are produced when the total water content of the formulated phenolic resin mixture including, surfactant, acid and blowing agent but excluding optional fillers; is greater than 15% but less than 24%, provided an alkali silicate is also present at an appropriate concentration of between 1 and 10% by weight in the foam produced from the resin mixture.

(16) The Examples in Table 2 show that even with an appropriate amount of alkali metal silicate present, of between 1 and 50% by weight of the foam, if the water content of the formulated phenolic resin system exceeds about 24% then thermal conductivity after thermal ageing drifts above 0.025 W/m.Math.K. If water content in the resin system is too high, foams may not be strong enough to have sufficient structural integrity to stand freely and can collapse. Such collapsing foams are undesired. Example 1 Ex1 is the same formulation as in Table 1. Comparative Examples 2-4 (Comparative Ex2-Comparative Ex4) show the effect of increasing the overall water content of the resin mixture before it is activated to form the foam product. Comparative 4 resulted in a foam which collapsed and so is not suitable for use as a foam insulation product. Comparative Example 4 foam collapses because of high water content. Comparative Example 5 (Comparative Ex5) reproduces the experimental work of GB135476 and shows that that foam has exceedingly high thermal conductivity and is unsuitable as a modern insulation material.

(17) In ail the Examples and Comparative Examples shown in Tables 1 and 2, acid catalyst C is 65% by weight aqueous phenol sulphonic acid/phosphoric acid blended in a weight ratio of 4:1.

(18) Blowing Agent E is 95% of 85/15 cyclopentane/isopentane and 5% perfluoroalkane blend by weight.

(19) Blowing Agent F is a 60/40 isopropyl chloride/isopentane blend by weight.

(20) Below are two methods of producing laboratory scale phenolic foams as used in Examples 1 to 9 and also for Comparative Examples 1 to 5 and 9.

(21) The total water content and alkali metal silicates of the formulated resin systems and the thermal conductivities of the foam samples are recorded in Table 1 and Table 2.

Example 1 to 9 and Comparative Examples 2 to 4.Foam Manufactured with the Addition of Alkali Metal Silicate to Phenolic Resin a or Resin B with Either Blowing Agent E or F Catalysed by Acid C

(22) Solid or aqueous alkali metal silicate at the appropriate concentration was added to 100 parts by weight of either Resin A or Resin B phenolic resin before the acid addition.

(23) 20 parts by weight of Acid C were mixed with the phenolic resin/silicate blend that had been pre-emulsified with the stated parts by weight of Blowing Agent E or F.

(24) High speed mixing up to 3000 rpm was used. 260 g+/10 g of the resulting mix was added to a picture frame mould of dimensions 300 mm300 mm50 mm at 70 C. for 20 minutes to cure and form 50 mm thickness rigid foam. The foam was dried at 70 C. in an oven. Drying time is 1 hour per 10 mm of cured foam thickness.

(25) A flat foam sample 30030050 mm was produced for thermal conductivity determination.

(26) Foam density was recorded using the procedures given in EN 1602.

(27) Initial and aged values were measured using a Laser Comp heat flow meter at a mean temperature 23 C. The foam was thermally aged for an extended time period (in this case 2 weeks at 110 C.) following the procedures in European Standard EN 13166:2008 (or EN 14314:2009).

Comparative Examples 1 and 9.Foam Manufactured without Addition of Alkali Metal Silicate to Phenolic Resin a with Either Blowing Agent E or F Catalysed by Acid C

(28) 20 parts by weight of Acid C were mixed with 100 parts by weight of Resin A phenolic resin that had been pre-emulsified with the stated parts by weight of Blowing Agent E or F.

(29) High speed mixing up to 3000 rpm was used. 260 g+/10 g of the resulting mix was added to a picture frame mould of dimensions 300 mm300 mm50 mm at 70 C. for 20 minutes to cure and form 50 mm thickness rigid foam. The foam was dried at 70 C. in an oven. Drying time is 1 hour per 10 mm of cured foam thickness.

(30) A flat foam sample 30030050 mm was produced for thermal conductivity determination as above. Foam density was recorded following the procedures given in EN 1602.

(31) When Examples 1 to 9 in Table 1 are compared to Comparative Examples 1 and 9, it is demonstrated that the addition of alkali metal silicate at 1 to 5 parts by weight of phenolic resole, leads to lower thermal conductivity () in a composition in which the overall % water content of the foaming mixture excluding optional fillers is between 15 and 24%.

(32) Table 2 reproduces the Example of GB 1351 476, in Comparative Example 5 where the alkali metal silicate content is 4.69% based on the weight of phenolic resole, acid, and blowing agent but excludes vermiculite filler. The % water content is 37.28% which is very detrimental to foam having low thermal conductivity. Therefore the foam system of GB 1351 476 whilst, having a similar amount of sodium silicate does not produce stable low thermal conductivity foams. The uncured composition is slurry-like and even upon being foamed and cured does not form a phenolic foam of a type that is suitable for forming a foam product which has a desirable closed cell structure and is sufficiently rigid, for example for a foam board, panel or c-section. So immediately its physical properties rule it out as a viable material. Even if it did have desirable physical properties then it fails to have a desirable thermal conductivity.

(33) Comparative Examples 2, 3, and 4 contain similar alkali metal silicate content as used in GB 1351476 but have the benefit of lower % water content, than GB 1351476. However Comparative Examples 2, 3, and 4 still fail to achieve stable low thermal conductivity when aged. (It is an objective of the invention to achieve and aged thermal conductivity of <0.025 W/m.Math.K.).

(34) TABLE-US-00001 TABLE 1 Comparative Ex 1 Ex1 Ex 2 Ex3 Ex 4 Ex58 Resin A (17% water content) 100 100 100 100 100 0 Resin B (distilled to 11% water) 0 0 0 0 0 100 Added Water 0 0 0 0 0 0 Solid Anhydrous Sodium 0 0 2.5 0 0 0 Silicate Solid Sodium Silicate 0 0 0 4.4 0 0 pentahydrate 43% aqueous sodium silicate 0 10 0 0 0 0 (solid alkali silicate) (4.3) 35% aqueous potassium silicate 0 0 0 0 12.6 12.6 (solid alkali silicate) (4.4) (4.4) 52% aqueous potassium silicate 0 0 0 0 0 0 (solid alkali silicate) 23% aqueous lithium silicate 0 0 0 0 0 0 (solid alkali silicate) Blowing Agent E (85/15 cyclo- 6 6 6 6 6 6 isopentane with 5 parts PF5052) Blowing Agent F (60/40 ipC/iP) 0 0 0 0 0 0 Catalyst C (PSA/PA (4:1) acid) 20 20 20 20 20 20 % Total Water Content 19.05 21.8 18.7 18.4 23.2 18.9 % Solid Alkali Silicate Content 0 3.16 1.94 3.37 3.17 3.17 Dry Density (kg/m3) 49.5 40.8 46.6 40.7 39.6 40.5 Initial lambda (W/mK) at 23 C. 0.0263 0.0227 0.0201 0.0214 0.0223 0.0217 mean temp 2 weeks at 110 C. Aged lambda 0.0400 0.0243 0.0232 0.0242 0.0249 0.0239 (W/mK) Comparative Ex 6 Ex7 Ex 8 Ex9 Ex 9 Resin A (17% water content) 0 100 0 100 100 Resin B (distilled to 11% water) 100 0 100 0 0 Added Water 0 0 0 0 0 Solid Anhydrous Sodium 0 0 0 0 0 Silicate Solid Sodium Silicate 0 0 0 0 0 pentahydrate 43% aqueous sodium silicate 0 0 0 10 0 (solid alkali silicate) (4.3) 35% aqueous potassium silicate 0 0 0 0 0 (solid alkali silicate) 52% aqueous potassium silicate 8.5 8.5 0 0 0 (solid alkali silicate) (4.4) (4.4) 23% aqueous lithium silicate 0 0 13.9 0 0 (solid alkali silicate) (3.2) Blowing Agent E (85/15 cyclo- 6 6 6 0 0 isopentane with 5 parts PF5052) Blowing Agent F (60/40 IpC/IP) 0 0 0 6.8 6.8 Catalyst C (PSA/PA (4:1) acid) 20 20 20 20 20 % Total Water Content 16.4 20.8 20.5 21.7 18.9 % Solid Alkali Silicate Content 3.27 3.27 2.29 3.14 0 Dry Density (kg/m3) 42.1 42.5 41.1 42.3 39 Initial lambda (W/mK) at 23 C. 0.0209 0.0232 0.0219 0.0217 0.0261 mean temp 2 weeks at 110 C. Aged lambda 0.0236 0.0243 0.0247 0.0249 0.0327 (W/mK)

(35) TABLE-US-00002 TABLE 2 Comparative Ex 5 Ex1 Comparative Ex2 Comparative Ex3 Comparative Ex4 (GB 1351476 Phenolic Resin GB 1351476 0 0 0 0 100 (28.5% water content) Resin A (17% water content) 100 100 100 100 0 Added Water 0 5.5 11.3 0 0 GB 1351476 47.5% aqueous sodium 0 0 0 0 20 (9.5) silicate (solid sodium waterglass) 43% aqueous sodium silicate 10 (4.3) 10 (4.3) 10 (4.3) 32.6 (14.0) 0 (solid alkali silicate) Blowing Agent E (85/15 cyclo- 6 6 6 6 0 isopentane with 5 parts PF5052) GB 1351476 Blowing Agent pentane 0 0 0 0 7.5 Catalyst C (PSA/PA (4:1) acid) 20 20 20 20 0 GB 1351476 Catalyst (50% TSA) 0 0 0 0 75 % Total Water Content 21.8 24.9 27.8 26.8 37.28 % Solid Alkali Silicate Content 3.16 3.04 2.91 8.8 4.69 Initial lambda (W/mK) at 23 C. mean temp 0.0227 0.0235 0.0242 * 0.0543 2 weeks at 110 C. Aged lambda (W/mK) 0.0243 0.0253 0.0270 * Unsuitable for insulation * In Comparative Ex 4, the foam collapsed as it is too unreactive. In the foam of Comparative Ex 5 for GB 1351476, the filler was included in the Comparative Ex 5 example formulation to make a direct comparison with GB 1351476. However, the presence of the filler was excluded from the calculated values for % Total Water Content and % Solid Alkali Silicate Content. In this case the foam had very high thermal conductivity.

(36) The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

APPENDIX 1

(37) Scanning Electron Microscopy Sample Preparation.

(38) A 20 mm10 mm piece of phenolic foam was cut from the sample. From this piece, the surfaces were trimmed with a razor blade to approximately 8 mm square. The foam was then snapped by hand to expose a clean surface in the rising foam direction. The majority of this sample was removed to leave a thin 1 mm slice of the foam in the rise direction.

(39) It is possible that manual snapping of the foam sample to create a surface to examine can induce some minor damage of the foam cells.

(40) This slice of foam was fixed on to an aluminium sample stub using a double-sided conducting sticky tab.

(41) The sample, (or samples), were then given a thin (approximately 2.5 Angstroms) conducting coat of gold/palladium using a Biorad SC500 sputter coater. The reason for coating the samples is (a) to add a conducting surface to carry 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.

(42) The samples were imaged using an FEI XL30 ESEM FEG Scanning Electron Microscope under the following conditions, 10 kV accelerating voltage, working distance approximately 10 mm. Images were examined at 1200 to 20000 magnification. The differing magnifications allow cell size distribution and defects present on the foam cells.

(43) Scanning Electron Microscope (SEM) photographs are shown in FIGS. 1 to 4 for Example 1, Example 3 and Comparative Example 1.

(44) SEM 1 (FIG. 1) and SEM 3 (FIG. 3)These photographs shows phenolic foam made in Comparative Example 1. A substantial number of pinholes in the cell walls can be seen.

(45) SEM 2 (FIG. 2)This photograph shows phenolic foam from Example 1. The pinholes in the cell walls appear to be fewer and largely covered with a film as a result of the sodium silicate-addition which may be due to silica gel formation.

(46) SEM 4 (FIG. 4) shows Example 3 with 4.4 parts sodium silicate pentahydrate. The pinholes in the cell walls are largely covered with a film which may be due to silica gel formation.