FOAM COMPOSITES

Abstract

Polystyrene-phenolic foam composites and processes for their preparation are provided. The composites have very low density yet retain advantageous mechanical properties. The composites have excellent fire resistance properties and find application in the production of insulation panels.

Claims

1. A process for preparing a polystyrene-phenolic foam composite comprising the steps of: a) forming a mixture of thermoplastic microspheres, phenolic resole resin, polystyrene particles and at least one acidic catalyst; and b) curing the mixture formed in a) at a temperature above 40 C.; wherein the polystyrene particles have a density of less than 15 kg/m.sup.3 and; wherein the polystyrene-phenolic foam composite has a density of less than 40 kg/m.sup.3.

2. A process according to claim 1, comprising the steps of: a) forming a mixture of thermoplastic microspheres, phenolic resole resin and at least one acidic catalyst; b) combining the mixture formed in a) with polystyrene particles to form a mixture; and c) curing the mixture formed in b) at a temperature above 40 C.; wherein the polystyrene particles have a density of less than 15 kg/m.sup.3 and; wherein the polystyrene-phenolic foam composite has a density of less than 40 kg/m.sup.3.

3. A process according to claim 1, comprising the steps of: a) forming a mixture of expanded thermoplastic microspheres and phenolic resole resin; b) combining the mixture formed in a) with at least one acidic catalyst; c) combining the mixture formed in b) with polystyrene particles; and d) curing the mixture formed in c) at a temperature above 40 C.; wherein the polystyrene particles have a density of less than 15 kg/m.sup.3 and; wherein the polystyrene-phenolic foam composite has a density of less than 40 kg/m.sup.3.

4. A process according to claim 1, wherein the polystyrene particles are partially or fully expanded.

5. A process according to claim 1, wherein the density of the polystyrene particles is less than 12 kg/m.sup.3.

6. A process according to claim 1, further comprising the step of adding one or more fillers.

7. A process according to claim 6, wherein the filler is added in an amount of 0.5-60% by weight based on the total weight of the composition.

8. A process according to claim 7, wherein the filler is a surface treated filler.

9. A process according to claim 6, wherein the filler is added to the thermoplastic microspheres.

10. A process according to claim 1, further comprising the step of adding an aqueous carbon dispersion.

11. A process according to claim 6, wherein the filler is added to a mixture of thermoplastic microspheres and aqueous carbon dispersion.

12. A process according to claim 1, wherein the phenolic resole resin has one or more of the following properties: (a) a viscosity between 500 and 4,000 cP; (b) a water content between 2 and 7% by weight; (c) a free phenol content less than 25%; or (d) a free formaldehyde content of less than 3%.

13. A process according to claim 1, further comprising the step of adding a surfactant.

14. A process according to claim 13, wherein the surfactant is added to a mixture comprising the phenolic resin.

15. A process according to claim 14, wherein the agitation of the phenolic resin-surfactant mixture increases the volume of said mixture.

16. A process according to claim 1, wherein the thermoplastic microspheres have an average particle size from between 1 and 80 microns.

17. A process according to claim 16, wherein the thermoplastic microspheres have a thermoplastic polymer shell derived from monomers selected from the group consisting of acrylonitrile, methacrylonitrile, -chloroacrylonitrile, -ethoxyacrylonitrile, fumaroacrylonitrile, crotoacrylonitrile, acrylic esters, methacrylic esters, vinyl chloride, vinylidene chloride, vinylidene dichloride, vinyl pyridine, vinyl esters, and derivatives or mixtures thereof.

18. A process according to claim 1, wherein the acidic catalyst is selected from a strong organic acid, an ester of a strong organic acid, a weak inorganic acid, an ester of a weak inorganic acid or mixtures thereof.

19. A process according to claim 1, wherein steam is not added to the curing step.

20. A process according to claim 1, wherein cured polystyrene-phenolic foam composite is added to the mixture prior to curing.

21. A process according to claim 20, wherein the cured polystyrene-phenolic foam composite is in particulate form.

22. A foam composite produced by the process according to claim 1.

23. A foam composite according to claim 22, wherein the specific mass loss rate @ 50 kW/m.sup.2, measured according to ISO 17554, is less than 8 g/m.sup.2.Math.s.

24. A foam composite according to claim 22, wherein the composite exhibits an insulation failure time, according to AS1530.4, for a 100 mm thick panel, of greater than 10 minutes.

25. A composite block, panel or sheet for use in construction comprising the foam composite according to claim 22.

26. A polystyrene-phenolic foam composite comprising: a) expanded polystyrene having a density of less than 15 kg/m.sup.3; b) cured phenolic resole resin; and c) expanded thermoplastic microspheres; wherein the composite has a density of less than 40 kg/m.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0121] The FIGURE illustrates a flow diagram of a process according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0122] It will now be convenient to describe the disclosure with reference to particular embodiments and examples. These embodiments and examples are illustrative only and should not be construed as limiting upon the scope of the disclosure. It will be understood that variations upon the described disclosure as would be apparent to the skilled addressee are within the scope of the disclosure. Similarly, the present disclosure is capable of finding application in areas that are not explicitly recited in this document and the fact that some applications are not specifically described should not be considered as a limitation on the overall applicability of the disclosure.

Thermoplastic Microspheres

[0123] When thermoplastic microspheres are heated, the polymeric shell gradually softens, and the liquid within the shell begins to gasify and expand. When the heat is removed, the shell stiffens and the microsphere remains in its expanded form. When fully expanded, the volume of the microspheres may increase more than 40 times. Significant density reductions can be achieved with even a small concentration of, for example, 3% thermoplastic microspheres by weight. A benefit of the hollow microsphere is the potential to reduce part weight, which is a function of density. Compared to traditional mineral-based additives, such as calcium carbonate, gypsum, mica, silica and talc, hollow microspheres have much lower densities. Loadings may be 1-5% by weight, which can equate to 25% or more by volume.

[0124] Thermoplastic microspheres suitable for preparing the foam composites as disclosed herein may be utilised in various forms. They may be in the form of a slurry dispersed in water or they may be utilised in dry form. Aqueous dispersions are preferred. Suitable microspheres are supplied by AkzoNobel under the trade mark Expancel.

Phenolic Resole Resin

[0125] A suitable phenolic resole resin may be produced by the base-catalysed condensation reaction of a molar excess of an aldehyde, with a substituted or unsubstituted phenol. Preferred substituted phenols are those in which the substituent does not impede the condensation of the phenol(s) with the aldehyde(s). Suitable substituents include halogens or a hydroxy, alkyl or an aryl group. Unsubstituted phenol is most preferred. Suitable aldehydes are formaldehyde (including oligomers/polymers such as trioxane), furfural, sugars and cellulose hydrolysates. A preferred aldehyde is formaldehyde. In one embodiment the molar ratio of aldehyde to phenol is from 1.4 to 1.8:1, for example, about 1.6:1. The temperature at which the phenolic resole resin is prepared may be less than 65 C., for example no more than 60 C.2 C., or no more than about 60 C. This temperature of less than 65 C. is preferably maintained while the basic catalyst is active, that is, until the basic catalyst is neutralised. This temperature may allow the maximum substitution of the phenol aromatic ring by reactive methylol (CH.sub.2OH) groups and results in only low molecular weight development in the polymer. Water may then be optionally distilled off to the preferred specification. Due to the resulting low molecular weight (preferably less than 1000 Daltons), the phenolic resole resin is highly soluble in water without phase separation and remains sufficiently reactive to cross-link under dilute aqueous conditions.

[0126] Suitable alkaline condensation catalysts are ammonia, ammonium hydroxide, sodium hydroxide, potassium hydroxide and barium hydroxide. Sodium hydroxide is a preferred catalyst.

[0127] The phenolic resole resin may be produced from phenol with a molar excess of formaldehyde in the presence of sodium hydroxide as a condensation catalyst.

[0128] Conventional phenolic resins may be produced by carefully increasing the temperature to around 602 C. and holding there for a period of about 1 hour, after which the temperature is increased to around 80 C. for a further period of 2-4 hours. The two stages essentially are:

[0129] 1. Ring Substitution at 60 C. by formaldehyde into the phenol aromatic ring; and

[0130] 2. Condensation Polymerisation at 80 C. to increase molecular weight.

[0131] In contrast, the phenolic resole resin as used herein may be obtained, for example, by only heating to no more than 65 C., for example, no more than 602 C. or no more than about 60 C. for a period of about 5 hours or until an intermediate viscosity of 13.5-14.5 centiStokes at 25 C. is reached for the reaction mixture. This leads to maximum substitution by methylol (CH.sub.2OH) groups in ortho-, meta- and para-positions of the aromatic ring and only low molecular weight build. The mixture may then be neutralised with an acid such as para-toluene sulphonic acid to a pH of less than 7, or between 5.5-6.6, or about 6 and most of the process and reaction water may then be distilled off under vacuum down to a level of around 2-7%, resulting in a highly reactive material.

Fillers

[0132] The composites may comprise one or more fillers. Suitable, non limiting fillers include inorganic compounds, particularly particulate inorganic compounds.

[0133] Exemplary fillers include elemental metal selected from the group consisting of metals of Groups I, II, III and IV, transition metals or the like of the periodic table, oxides or complex oxides of these metals, salts of these metals, such as fluorides, carbonates, sulfates, silicates, hydroxides, chlorides, sulfites, and phosphates of these metals, and composites of these salts of metals. Preferably used are metal oxides such as amorphous silica, quartz, alumina, titania, zirconia, barium oxide, yttrium oxide, lanthanum oxide, and ytterbium oxide, silica-based complex oxides such as silica-zirconia, silica-titania, silica-titania-barium oxide, and silica-titania-zirconia, glass such as borosilicate glass, glass fibres, aluminosilicate glass, or fluoroaluminosilicate glass, metal fluorides such as barium fluoride, strontium fluoride, yttrium fluoride, lanthanum fluoride, and ytterbium fluoride; inorganic carbonates such as calcium carbonate, magnesium carbonate, strontium carbonate, and barium carbonate; and metal sulfates such as magnesium sulfate and barium sulfate. Other suitable fillers include particulate silica, talc, kaolin, clay, nanocomposites and nanoparticles. Other inorganic compounds such as boric acid may be utilised as a filler.

[0134] The filler may be present in amounts of 0.5-60% by weight, or 1-20% by weight or 2-15% by weight, based on the total weight of the composite.

[0135] The filler may have a particle size between 0.1 mm and 5 mm, or between 0.5 mm and 2 mm. One preferred particulate filler is granular boric acid. Granular boric acids of particle size of about 1 mm may be suitable.

[0136] The filler may contribute to fire inhibition. For example, at 170 C. boric acid dehydrates to metaboric acid releasing a water molecule and thus quenching combustion by exclusion of oxygen. Above 300 C. a further dehydration occurs releasing another water molecule and forming the non-combustible compound boron trioxide.

Modified Fillers

[0137] Often it is advantageous to treat fillers with a modifiying agent so as to modify the surface properties of the filler. For example fillers may be modified with agents so as to change the fillers solubility properties. Suitable modifiying agents are well known in the art. One class of modifying agents are silanes. One class of silanes are haloalkylsilanes examples of which are 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltripropoxysilane, chloropropylmethyldimethoxysilane, chloropropylmethyldiethoxysilane, chloropropyldimethylethoxysilane, chloropropyldimethylmethoxysilane, chloroethyltrimethoxysilane, chloroethyltriethoxy-silane, chloroethylmethyldimethoxysilane, chloroethylmethyldiethoxysilane, chloroethyldimethylmethoxysilane, chloroethyldimethylethoxysilane, chloromethyltriethoxy-silane, chloromethyltrimethoxysilane, chloromethylmethyl-dimethoxysilane, chloromethylmethyldiethoxysilane, chloro-methyldimethylmethoxysilane or chloromethyldimethylethoxysilane.

[0138] Granular boric acid may be treated with one or more of the above silanes so as to reduce the solubility of the boric acid in water.

[0139] In one embodiment expanded thermoplastic microspheres, filler (for example surface treated boric acid) and aqueous carbon dispersion are combined. In a separate vessel phenolic resin is treated with surfactant and the mixture aerated to increase the volume. The volume of the mixture may double. The mixture is then added to the mixture containing the thermoplastic microspheres. Acidic catalyst is then added and the resulting mixture added to expanded polystyrene. The resulting coated polystyrene is then moulded, compressed and cured.

Materials and Process

[0140] Expanded polystyrene of density less than 15 kg/m.sup.3 was prepared by steam expansion of commercially available expandable polystyrene. Expanded polymeric microspheres were Expancel 461WE 40 available from Akzo Nobel. Granular boric acid was technical grade and was treated with chloropropyltrimethoxysilane before use. Aqueous carbon black dispersion was Gold Cup Black-CB RF from Racing Colours Ltd. Surfactant was a polyether modified hydroxyl-functional polysiloxane. Hydrophobe was aqueous silicone emulsion from Dow Corning.

[0141] Referring to the FIGURE there is illustrated a flow diagram of the process according to an embodiment of the present disclosure.

[0142] A volume of expanded polystyrene and equivalent to approximately 1.6 times (160%) of the final desired block volume was transferred to a blender.

[0143] Phenolic resole resin (as hereinbefore described) a mixture of expanded thermoplastic microspheres, granular boric acid and carbon black dispersion and a surfactant were blended in an aerating slurry mixer to an even consistency.

[0144] A hydrophobic agent and acidic catalyst were then added and the resulting mixture added to the expanded polystyrene.

[0145] After mixing, the blend was fed into a pre-heated mould at, for example, 45-55 C. The blend was then compressed to the required level using a hydraulic press.

[0146] The filled mould was then heated to cure the mixture.

[0147] Once cured, the mould was demoulded. The block was then placed in a post-cure oven, for example at 70-80 C., for 48+ hrs to allow remaining moisture to evaporate, residual formaldehyde to be captured and, if required, to complete the cure.

[0148] Finally, the block was cut into sheets of the specified thickness using an abrasive wire cutter or horizontal band saw.

[0149] The following examples describe composites made according to the above process.

Example 1

[0150] A composite was prepared utilising the following raw materials (based on the dry weight of the materials). The composite had a density of 34.5 kg/m.sup.3.

TABLE-US-00001 Raw material Composition (wt. %) EPS (10.5 kg/m.sup.3) 38.4 Phenolic resin 44.4 Surfactant 0.89 Microspheres 4.44 Boric acid 6.67 Carbon emulsion 2.22 Hydrophobe 0.44 Acid catalyst 2.44

Example 2

[0151] A composite was prepared utilising the following raw materials (based on the dry weight of the materials). The composite had a density of 25.5 kg/m.sup.3.

TABLE-US-00002 Raw material Composition (wt. %) EPS (5 kg/m.sup.3) 27.8 Phenolic resin 52.1 Surfactant 1.04 Microspheres 5.21 Boric acid 7.82 Carbon emulsion 2.61 Hydrophobe 0.52 Acid catalyst 2.87

Example 3

[0152] A composite was prepared utilising the following raw materials (based on the dry weight of the materials). The composite had a density of 34.1 kg/m.sup.3.

TABLE-US-00003 Raw material Composition (wt. %) EPS (11 kg/m.sup.3) 37.9 Phenolic resin 44.8 Surfactant 0.90 Microspheres 4.48 Boric acid 6.72 Carbon emulsion 2.24 Hydrophobe 0.45 Acid catalyst 2.46

[0153] It was found that all of the composites had excellent physical properties (low interstitial volume and low water absorption) demonstrating advantage over a wide range of relative component amounts. The mechanical properties of the composites were equivalent to expanded polystyrene.

Fire Resistance Testing

[0154] Test specimens consisted of insulated wall panels comprising foam composites as prepared by the processes disclosed herein. The panels were 3.0 m high, 1.2 m or 0.6 m broad and had a thickness of 50 mm, 100 mm and 250 mm. A comparative test was performed with a 125 mm thick expanded polystyrene panel. Tests were conducted in accordance with AS 1530.4 Methods for fire tests on building materials, components and structures, Part 4: Fire resistance tests of elements of construction, Section 3 WallsVertical Separating Elements. The results are collected in the below Table.

TABLE-US-00004 Insulation failure time Material and thickness (minutes) Inventive composite 50 mm 15 Inventive composite 100 mm 31 Inventive composite 250 mm 115 Comparative Polystyrene 125 mm 6

[0155] It is clear from the results that the composites prepared by the processes disclosed herein significantly outperform expanded polystyrene in fire resistance.

[0156] Tests were conducted following ISO 17554. This is a small-scale method for assessing the mass loss rate of essentially flat specimens exposed in the horizontal orientation to controlled levels of radiant heating with an external igniter under well-ventilated conditions. The mass loss rate is determined by measurement of the specimen mass and is derived numerically. Mass loss rate can be used as an indirect measure of heat release rate.

[0157] Under the conditions of the test expanded polystyrene had an average specific mass loss rate @ 50 kW/m.sup.2, over three tests, of 9.88 g/m.sup.2.Math.s, whereas composites prepared by the processes disclosed herein had an average specific mass loss rate @ 50 kW/m.sup.2, over three tests, of 1.26 g/m.sup.2.Math.s. Accordingly, significantly slower combustion was observed with the inventive composites.

[0158] A composite was also prepared absent both boric acid and carbon emulsion as in the following Table. Small amounts of surfactant and hydrophobe were also added, although these are optional.

TABLE-US-00005 Raw material Composition (wt. %) EPS 42.3 Phenolic resin 49.9 Microspheres 5.0 Acid catalyst 2.9

[0159] This composite had an average specific mass loss rate @ 50 kW/m.sup.2 of 1.63 g/m.sup.2.Math.s. Therefore, the presence of boric acid and carbon fillers, while slightly improving the mass loss rate, are both not necessary components in providing a composite with significantly enhanced fire resisting properties, compared to EPS.