CA2216734C - Microcellular foams containing an infrared attenuating agent and a method of using - Google Patents

Abstract

Disclosed is an open-cell microcellular foam comprising an alkenyl aromatic polymer foam, the foam being characterized in that the foam has an average cell size of 70 micrometers or less, the foam being evacuated, the foam containing an infrared attenuating agent in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the infrared attenuating agent. Also disclosed is a closed cell, unevacuated microcellular foam comprising an alkenyl aromatic polymer foam, the foam having an average cell size of 1.0 micrometers or less, the foam being characterized in that it contains an infrared attenuating agent in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the infrared attenuating agent.

Description

MICROCELLULAR FOAMS CONTAINING AN INFRARED
ATTENUATING AGENT AND A METHOD OF USING
This invention relates to evacuated and unevacuated microcellular foams containing an infrared attenuating agent and a method of using.

Microcellular foams have potential commercial value for use in insulating applications. Such foams have a cell size ranging of 70 micrometers or less in average cell size. Foams may be formed from a variety of organic and inorganic substances such as thermoplastic polymers, thermoset polymers, silicate aerogels, ceramics, and glass.
In an insulating foam, it is desirable to minimize thermal conductivity or maximize insulating capability. One means of doing so is to incorporate an infrared attenuating agent (IAA) into the foam. Suitable IAA include particulate flakes of metals such as aluminum, silver, and gold;

carbonaceous substances such as carbon black and graphite;
and certain non-carbonaceous substances such as titanium dioxide. Such incorporation is seen in the art at U.S.
Patent Nos. 4,795,763; 5,210,105; and 5,373,026.

In the present invention, it was surprisingly found that, upon incorporation of IAA into evacuated microcellular foams of cell sizes of 70 micrometers or less, foam thermal conductivity was reduced by a significantly greater proportion than in foams having larger average cell sizes. This greater proportional reduction is particularly observed when comparing the reduction in evacuated microcellular foams to the reduction in unevacuated, closed-cell insulating foams of cell size ranges sold commercially (0.1 to 2.0 millimeters). It was further surprisingly found that incorporation of IAA into unevacuated microcellular foams of cell sizes of 1.0 micrometers or less reduced thermal conductivity by a significantly greater proportion than in unevacuated, closed-cell insulating foams of 0.1 to 2.0 millimeters cell size sold commercial.

According to one aspect of the present inverition, there is provided an open-cell microcellular foam comprising an alkenyl aromatic polymer foam, the'foam being characterized in that the foam has an average cell size of 70 micrometers or less, the foam being evacuated, the foam containing an infrared attenuating agent in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the infrared attenuating agent.

According to another aspect of the present invention, there is provided a closed cell, unevacuated microcellular foam comprising an alkenyl aromatic polymer foam, the foam having an average cell size of 1.0 micrometers or less, the foam being characterized in that it contains an infrared attenuating agent in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the infrared attenuating agent.

The features of the present invention will be better understood upon viewing the drawing together with the remainder of the specification.

Figure 1 illustrates thermal conductivity versus cell size for the foams of Example 6 and Control Example 6.
Further according to the present invention, there is an evacuated microcellular foam comprising an IAA. The IAA is present in a quantity sufficient to reduce the la thermal conductivity of the foam relative to a corresponding foam without the IAA. The microcellular foam has an average cell size of 70 micrometers or less.

Further according to the present invention, there is an evacuated or unevacuated microcellular foam comprising an IAA. The IAA is present in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the IAA. The microcellular foam has an average cell size of 1.0 micrometer or less.

lb According to the present invention, there is a method of insulating a surface or enclosure by applying to the surface or enclosure of any of the above microcell ular foams.
In the present invention, an infrared attenuating agent was incorporated into the microcellular foams to absorb or reflect part or alI of the radiation component of heat transfer which may pass through the foam.
A surprising aspect of the invention is that the incorporation of the IAA into a microcellular foam affords a significantly greater proportional reduction in total foam thermal conductivity relative to a corresponding (substantially equivalent average celi size and density) microcellular foam without the IAA than in a foam of larger average cell size with IAA relative to a corresponding foam of larger cell size without IAA. In other words, the IAA induced a greater proportional reduction in total foam thermal conductivity in microcellular foams than in foams of larger average size. The greatest proportional reduction occurs in evacuated foams of cell size of 70 micrometers or less and in unevacuated (non-evacuated) and evacuated foams of cell size of 1.0 micrometer or less.
Evacuated microcellular foams of the present invention have an average cell size of 70 microns or less, preferably 1 to 30 micrometers, more preferably 1 to 20 micrometers, and most preferably 1 to 10 micrometers.
Unevacuated microcellular foams of the present invention have an average cell size of 1.0 micrometers or less and preferably 0.05 to 1.0 micrometers.
An evacuated foam is a foam having within its open cells a partial vacuum or near total vacuum of subatmospheric absolute pressure. An evacuated foam has preferably has an absolute pressure of 10 torr or less, more preferably 1 torr or less, and most preferably 0.1 torr or less.
An unevacuated (non-evacuated) foam is a foam having within its open or closed cells an atmospheric pressure.
For purposes of the present invention, the term "microcellular foam" is understood to include microporous foams. Microporous foams are those foams which do not have a defined cellular structure, but have an average void diameter of 70 micrometers or less and a level of voidage of 90 percent or more. Microporous foams are seen in U.S. Patent Nos.
4,473,665 and 4,673,695.
In polystyrene insulation foams of conventional cell size, that is, 0.1 to 2.0 millimeters, the incorporation of an IAA has been observed to decrease foam thermal conductivity 10 to 15 percent. Surprisingly, in the microcellular foams of the present invention, the incorporation of an IAA has been observed to decrease foam thermal conductivity up to 70 percent, a much larger decrease, in certain cell size ranges.
The infrared attenuating agent (IAA) may be an infrared reflecting or absorbing substance or both. The IAA is composed of a different substance than the substrate of the foam in which it is incorporated. Useful IAA include particulate flakes of metals such as aluminum, silver, and gold and carbonaceous substances such as carbon black, activated carbon black, and graphite. Useful carbon blacks include thermal black, furnace black, acetylene black, and channel black. Useful graphites are natural graphite and synthetic graphite.
S Preferred IAA are carbon black and graphite. The IAA preferably comprises between 1.0 and 20 weight percent, more preferably 4.0 to 20 weight percent, and most preferably between 4.0 and 10.0 weight percent based upon the weight of the polymer material.
Substantial infrared attenuation activity occurs between 4 percent and 40 percent based upon the weight of the polymer material. In the case of carbon black and graphite, it is desirable to use particles of a size which achieve a high degree of dispersion in the foam.
Graphite has accentuated or enhanced infrared attenuating activity compared to carbon black in the present microcellular foams. In other words, graphite induces a greater proportional reduction in total foam thermal conductivity in the microcellular size range than carbon black. This is unexpected because the two substances both are substantially carbonaceous and typically exhibit similar levels of infrared attenuating activity in foams of larger, that is, conventional, cell size. This enhanced activity may be observed in evacuated foams of cell sizes of 70 micrometers or less and in unevacuated and evacuated foams of cell sizes of 1.0 micrometers or less.
The present microcellular foams can be comprised of any known organic or inorganic substance known to be useful in foaming. Useful substances include thermoplastic polymers, thermoset polymers, aerogels, ceramics, and glass. Useful thermoplastic polymers include ethylene polymers and alkenyl aromatic polymers. Useful ethylene polymers include polyethylenes such as low density polyethylene. Useful thermoset polymers include potyisocyanurates, polyurethanes and phenolics.
The substrate comprising the matrix of the present foam is preferably substantially non-carbonaceous or substantially free of polymeric carbon structures.
Carbonaceous foams and foams with polymeric carbon structures are seen by example in U.S.
Patent No. 5,358,802. In keeping with the present invention however, an elemental carbon substance such as carbon black or graphite may be incorporated or added to substantially non-carbonaceous foam matrix substrates such as those of thermoplastic polymers and thermoset polymers as well as inorganic substances such as glass. Useful substantially non-carbonaceous polymers include those described above such as alkenyl aromatic polymers, ethylene polymers, polyisocyanurates, and polyurethanes.
A preferred microcellular foam comprises an alkenyl aromatic polymer material.
Suitable alkenyl aromatic polymer materials include alkenyl aromatic homopolymers and copolymers of alkenyl aromatic compounds and copolymerizable ethylenically unsaturated comonomers. The alkenyl aromatic polymer material may further include minor proportions of non-alkenyl aromatic polymers. The alkenyl aromatic polymer material may be comprised solely of one or more alkenyl aromatic homopolymers, one or more alkenyl aromatic copolymers, a blend of one or more of each of alkenyl aromatic homopolymers and copolymers, or.blends of any of the foregoing v++iWa non-alkenyl aromaticpolymer..
.-, Regardless of composition, the alkenyT aromatic polymer material comprises greater than .50 and preferably greater than 70 weight percent alkenyl aromatic monomeric units. Most preferably, the ai'kenyl aromatic polymer Enateria.l is comprised entirely of alkenyl aromatic monomeric units:
'Surtable alkenyl aromatic polymers include those derived from aikenyl aromatic compounds such as styrene, alphamethylstyrene, ethylstyrene,~vinyl benzene, vinyi toluene, chiorostyrene, and bromostyrene. A preferred alkenyl aromatic polymer is polystyrene. Minor ' . .
amounts of monoethylenically unsaturated compounds such as t2_6 alkylacids and esters, ionomeric derivatives, and t4.6 dienes may be copolymerized witti.alkenyl aromatic compounds. Examples oi copolymerizabie compounds incFude acrylicac+d, methacrylic acid, ethacrylic acid, male'rc acid, itaconic acid; acryionkfile, maleic anhydride, methyl'acrylate, ethyl acrylate, isobutyl acrylate, n=butyl acrylate; methyl methacrylate, vinyl acetate and butadiene.
Preferred foams comprise substantially (that is; greater thaii 95 percentY and most preferably entirely of polystyrene. Preferably, the alkenyl aromatic polymerfoam -is free of'rubber content such as C4* dienes and thermoset polymer content such as polyisocyanucate or polyurethane.
A useful microceilular foam is an extruded, open-cell alkenyl aromatic polymer foam. The open-cell foam comprises an alkenyl aromatic polymermateriai comprising greater than 50 weight percent ofalkenyl aromatic polymer units. Preferably; the~foam is comprised entirely of polystyrene. The foam has an open cell content ofi70 percent or more, preferably 90 percent or more, and most preferably 95 percent or more open cell according toASTM 2856-A.
The foam has an average cell size of 70 micrometers or less and preferably from 1 to 30 micrometers. The foam is particularly useful in vacuum insulationpanels.
Description of its methods of manufacture are seen below and in U.S. Patent No. 5,780,521.

The extruded, open-cell microcellular foam may be prepared,by heating a thermoplastic material to form a plasticized or melt polymer material, incorporating therein a blowing agent to form a foamable gel, and extruding the gel through a-die to4orm the foam product. Prior to mixing w'rth the blowing agent, the polymer material is heated to a temperature at or above its glass transition temperature or melting point. The blowing agent may be incorporated or mixed into the melt polymer material by any means known in the art such as with an extruder, mixer,or blender. The blowing agent is mixed with the melt polymer material at an elevated pressure sufficient to prevent substantial expansion of the melt polymer material and to generally disperse the blowing agent homogeneously therein. The amount of blowing agent incorporated is 0.06 to 0.17 gram-moles.per: kilogram of polymer or less. A nucleating agent such as talc is blended in the poiymer melt or drybiended with the polymer material prior to plasticizing or melting. The foamable gel is typically cooled to a lower foaming temperature to optimize desired physical characteristics of the foam. The gel may be cooled in the extruder or other mixing device or in separate coolers.
The foaming temperature must be high enough to allow formation of the open-cell structure but low enough to prevent foam collapse upon extrusion. Desirable foaming temperatures range from about 118 C to about 160 C and preferably from about 125 C to about 135 C. The gel is then extruded or conveyed through a die of desired shape to a zone of reduced or lower pressure to form the foam. The zone of lower pressure is at a pressure lower than that in which the foamable gel is maintained prior to extrusion through the die. The lower pressure may be superatmospheric or subatmospheric (evacuated or vacuum), but is preferably at an atmospheric level.
Microcellular polyurethane and polyisocyanurate foams can be made by reacting two preformulated components, commonly called the A-component and the B-component.
The blowing agent may be dispersed in either the isocyanate or the polyol or both.
Suitable polyisocyanates include diisocyanates such as m-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, hexamethylene-1,6-diisocyanate, tetramethytene-1,4-diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluene 2,4- and 2,6-diisocyanate, naphthalene-1,5-diisocyanate, diphenyl methane-4,4'-diisocyanate, 4,4'-diphenylenediisocyanate, 3,3'-dimethoxy-4,4'-biphenyldiisocyanate, 3,3'-d i m ethyl -4,4'-bi phenyl d i isocya nate, and 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate; the triisocyanates such as 4,4',4"-triphenylmethane-triisocyanate, polymethylenepolyphenyl isocyanate, toluene-2,4,6-triisocyanate; and the tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate.
Suitable polyols include: ethylene glycol; propylene glycol-(1,2) and -(1,3);
butylene glycol-(1,4) and -(2,3); hexane diol-(1,6); octane diol-(1,8);
neopentyl glycol; 1,4-bishydroxymethyl cyclohexane; 2-methyl-1,3-propane diol; glycerin; tri methylol propane;
trimethylolethane; hexane triol-(1,2,6); butane triol-(1,2,4);
pentaerythritol; quinitol;
mannitol; sorbitol; formitol; a-methyl-glucoside; diethylene glycol;
triethylene glycol;
tetraethylene glycol and higher polyethylene glycols; dipropylene glycol and higher polypropylene glycols as well as dibutylene glycol and higher polybutylene glycols. Suitable polyols further include oxyalkylene glycols, such as diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, trimethylene glycol and tetramethylene glycol.
Polyurethane foams can be prepared by reacting the polyol and the isocyanate on a 0.7:1 to 1.1:1 equivalent basis. The polyisocyanurate foams of the invention are advantageously prepared by reacting the polyisocyanate with a minor amount of polyol to provide 0.10 to 0_70 hydroxyl equivalents of polyol per equivalent of polyisocyanate. Useful WO 96/34039 ' PCT/US96/03481 polyurethanes and polyisocyanurates and processes for making them are seen in U.S. Patent Nos. 3,580,869; 4,795,763; 5,288,766; 5,334,624; and 5,346,928.
Aerogels may be comprised of a variety of materials such as silica, metal oxides, carbon, and formaldehyde derivatives. Teachings to aerogels and methods of making are found in U.S. Patent Nos. 5,081,163; 5,242,647; 5,275,796; 5,358,802;
5,381,149; and 5,395,805.
Microporous thermoplastic foams can be formed by phase separation, by microemulsions, or by use of supercritical fluids such as seen in U. S. Patent Nos. 4,673,695;
4,473,665; 5,037,859; 5,158,986; and 5,334,356.
Microcellular thermoplastic foams may be cross-linked or uncrosslinked. The term "non-crosslinked" means the foam is substantially free of crosslinking. The term is inclusive however, of the slight degree of crosslinking which may occur naturally without the use of crosslinking agents or radiation. Non-crosslinked foams contain no more than 5 percent gel per ASTM D-2765-84 Method A.
The microcellular foams preferably have the density of from 16 to 250 and most preferably from 25 to 100 kilograms per cubic meter according to ASTM D-1622-88.
The microcellular foams may take any physical configuration known in the art such as sheet or plank. The present foam is particularly suited to be formed into a plank, desirably one having a cross-sectional area of 30 square centimeters (cm) or more and a minor dimension in cross-section (thickness) of 3/8 inch (0.95 centimeter) or more.
The average cell size or pore size (diameter) for the microcellular foams is determined according to ASTM D3576-77 except that measurement is taken from an enlarged photograph obtained by scanning electron microscopy instead of measurement taken directly from the foam.
The microcellular foams may be closed cell or open cell. Preferred open cell foams are those having 70 or more percent open cell content according toASTM D2856-A. An open cell foam more preferably has 90 percent or more, and most preferably 95 percent or more open cell content according to ASTM D2856-A. Closed-cell foams are those having closed cell content of about 90 percent or more and preferably about 95 percent or more according to ASTM D-2856-A.
Open cell foams are useful in evacuated or vacuum insulation panels.
Preferably, the open cell foams are maintained at a pressure of 10 torr absolute or less and preferably at 1 torr absolute or less and most preferably 0.1 torr or less.
The microcellular foams may be used to insulate a surface or enclosure by applying to the surface or enclosure an insulating panel fashioned from the present structure.
Such panels are useful in any conventional insulating applications such as roofing, buildings, refrigerators.
The following are examples of the present invention, and are not to be construed as limiting. Unless otherwise indicated, all percentages, parts, or proportions are by weight.

Microcellular polystyrene foams containing carbon black and graphite of the present invention were prepared as described below. The foams were tested for insulating capability in an evacuated (vacuum) environment at 0.2 torr,-1 torr, and 5 torr and at atmospheric pressure (760torr). Insulating tapability was measured as "R value per inch", which corresponds to the reciprocal of thermal conductivity in units of Btu.in/hr=ft4=F .
Example 1 Foams were prepared with two different extrusion systems, each comprising an extruder, a mixer, a cooler, and an extrysion die in series. The two systems operated at different extrusion rates, 10 pounds per hour (Ib/hr) (4.5 kilogramsJhour (kgfhr) and 220 ib/hr (100 kg/hr), They are referred to as the first and the second extrusion systems, respectivety.
The foams of the first extrusion system were made with the following formulation: a bfowingagent of 7.5 parts per hundred (pph) of HCFC-142b, 2.0 pph EtCI, and TM
1.4 pph C02); optionally carbon black (Raven 430 of Cabot Corp.); 0.5 pph talc; a minor amount of calcium stearate; and a polystyrene resin of 200,000 weight average molecular weight according to size exdusion chromatography (SEC).
The foams of the second extrusion system were made with the following formulation: a blowing agent of 6.8 pph HFC-134a,1.9 pph HFC- 1 52a, and 0.6 pph CO2;
carbon black (Thermat.Btack FT 239 of Huber Cor:p.); 0.4 pph talc; minor amount of calcium stearate; and polystyrene resin of 200,000 weight average molecular weight according to size exclusion chromatography (SEC).
Foams were made in both extrusion systems with various carbon black loadings and at various foaming temperatures. The R value for foamswas measured at atmospheric pressure (760 torr) and in a vacuum (1 torr). R vafue was measured according to ASTM C-S18-91 in an environmental pressure control system capable of maintaining its set point condition within 0.01 torr wherein the control system is employed in conjunction with a heat flow meter apparatus.
Microcellular foams of small average cell size and high open cell content were produced. Cell size, open-cell content, density, and R value are set forth in Table 1. For microcellular foams made in both extrusion systems, increasing the level of carbon black increased R value.
Example 2 -Foams of the present invention were prepared with the second extrusion system except as indicated below and in Table 2.
The foams were prepared with various blowing agents and mixtures thereof as specified in Table 2. The blowing agent loadings were pph based upon polymer weight. The foams were made with various carbon black loadings and at various foaming temperatures.
The R value for foams was measured at various pressures.

Microcellular foams of small average cell size, high open cell content, and high R
value were produced.
Example 3 Foams of the present invention were prepared with the second extrusion system except as indicated below and in Table 3.
The foams were prepared with various blowing agents and mixtures thereof as specified in Table 3. The blowing agent loadings were pph based upon polymer weight. The foams were made with various carbon black loadings and at various foaming temperatures.
The R value for foams was measured at various pressures.
Microcellular foams of small average cell size, high open cell content, and high R
value were produced.
Example 4 Foams of the present invention were prepared with the second extrusion system except as indicated below and in Table 4.
Microcellular foams of small average cell size and high open cell content were produced.
Due to the addition of carbon black, the cross-section of Run 42 could be made larger than that of Run 41. The carbon black increased gel viscosity, and allowed the die opening to be enlarged without losing die pressure and causing pre-foaming.
The increase in die opening resulted in a foam of larger cross-section being produced. The larger cross-section affords improved skin quality and greater process versatility.
Example 5 Foams of the present invention were prepared with the second extrusion system except as indicated below and in Table 5.
The foams were prepared with various blowing agents and mixtures thereof as specified in Table 5. The blowing agent loadings were pph based upon polymer weight. The foams were made with various carbon black loadings and at various foaming temperatures.
The R value for foams was measured at various pressures.
Microcellular foams of small average cell size, high open cell content, and high R
value were produced.
Example and Control Example 6 Extruded, open-cell, microcellular polystyrene foams with and without carbon black were tested for thermal conductivity to determine the approximate level of enhancement due to the inclusion of carbon black. The foams were tested at an absolute air pressure of 1 torr at 75 F. The carbon black was thermal black FT239 (Huber Corp.).
Thermal conductivity as a function of average cell size with and without carbon black was plotted in Figure 1.

As surmised from the plots, the reduction in foam thermal conductivity in the cell size range of about 30 to 50 micrometers was approximately 35-40 percent. This reduction is far in excess of the typical 10-15 percent reduction observed in conventional extruded, closed cell polystyrene foams of 0.1-1.0 millimeter cell size.
Example 7 and Control Example 7 Open-celi, microporous polystyrene foams with and without carbon black were tested for thermal conductivity to deterrinine the approximate level' of enhancement due to the inclusion of carbon black. The foams were tested at atmospheric pressure and at an absolute TM
pressure of 0.1 torr, both at 75 F. The carbon black was furnace black Monarch 1400 (Cabot Corp.). The pore sizes in each of the foams ranged in a distribution from about 0.1 to about 0.5 micrometers.
As seen in Table 6, the incorporation oftarbon black resulted in a reduction in thermal conductivity of approximately 25-45 percent for foams at atmospheric pressure of comparable density. For evacuated foams of comparable density at 0.1 torr, incorporation of carbon black resulted in a reduction in thermal conductivity of approximately 60-70 percent.
This reduction is far in excess of the typical 10-15 percent reduction observed in conventional extruded, closed cell polystyrene foams of 0:1-1.0 millimeter cell size.

w, w ~' v vi o v- o ~0 Table 1 Foams Prepared in Example 1 Run Ext. Rate Carbon Foaming Foam Density Cell Size Open Cell R/inch R/ inch lb/hr Black Temp. pcf (kg/m3) (mm) (percent) 1 torr 760 torr Number (kg/hr) (pph) ( C) 1 10(4.5) 10.0 155 1.82 (29.12) 0.04 99 7.41 ---2 10(4.5) 15.0 145 1.94 (31.04) 0.02 99 13.7 --- >
3* 220 (100) 0.0 133 2.75 (44) 0.02 94.6 9.09 3.92 4 220 (100) 7.0 132 3.31 (52.96) 0.011 92.7 15.38 4.37 220 (100) 10.0 132 4.15(66.4) 0.006 95.7 16.13 4.52 ~ 6 220 (100) 15.0 132 4.08 (65.28) 0.01 94.3 17.86 4.55 *not an example of the present invention o0 -+

w p VNi O Vt O

~
Table 2 Foams Prepared in Example 2 Run Carbon Foaming Foam Density Cell Size Open Cell R/ inch R/ inch Number Blowing Agent Black Temp. pcf (kg/m3) (mm) (percent) 1 torr 760 torr (pph) ( C) 7* 9.0 HFC-134a / 3.0 EtCl 0.0 131 2.49 (39.84) 0.043 99.7 --- ---8* 8.0 HFC 134a / 1.0 EtCI / 0.0 131 3.07 (49.12) 0.024 99.5 --- --- y 0.6 COZ
9 4.0 COZ / 0.5 EtOH 10.0 131 2.53 (40.48) 0.068 88.4 --- --- ;
4.0 HFC-152a / 1.0 EtCl / 10.0 131 2.51 (40.16) 0.049 84.1 -- ---1.5C0z o 11 8.0 HFC-152a / 0.6 COz 10.0 133 2.31 (36.96) 0.049 97.1 --- --- ' 12 5.0 HFC-152a / 3.5 HFC-134a 10.0 133 2.32 (37.12) 0.038 95.5 --- ---13 6.8 HFC-134a / 1.9 HFC-152a / 10.0 131 4.39 (70.24) 0.005 94.3 16.39 ---.27 Argon 14 6.8HFC-134a/2.4HFC-152a/ 10.0 131 2.87(45.92) 0.005 95.4 12.21 ---.19 N2 *not an example of the present invention W vi t!t O V1 O vi O

Table 2 (Continued) w Foams Prepared in Example 2 ~
Carbon Foaming Run Foam Density Cell Size Open Cell R/ inch R/ inch Number Blowing Agent Black Temp. cf (k /rn3 (pph) ( C) p g ) (mm) (percent) 1 torr 760 torr 15 6.8 HFC-134a / 2.4 HFC-152a 10.0 131 5.13 (82.08) 0.005 93.3 14.29 ---16 6.8 HFC-134a / 2.4 HFC-152a / 10.0 131 3.51 (56.16) 0.007 95.4 15.38 --- >
.34 Celogen AZ 130 17 6.8 HFC-134a / 1.9 HFC-152a / 7.0 132 3.31 (52.96) 0.011 92.7 15.38 ---0.6 CO2 18 10.6 HFC-134a 6.9 127 3.48 (55.68) 0.025 98.0 --- ---N p 19 8.5 HFC-134a / 0.9 HCFC-142b 6.9 125 4.35(69.6) 0.008 98.0 --- ---20 7.0 HFC-143a / 0.9 HCFC-142b 6.9 126 4.08 (65.28) 0.007 --- --- ---21 5.5 HFC-143a / 2.4 HCFC-22 6.9 123 4.28 (68.48) 0.012 96.0 13.51 4.31 22 8.0 HCFC-22 6.9 130 3.15(50.4) 0.065 97.0 --- ---23 8.4 HFC-134a / 0.8 HCFC-22 10.0 126 3.89 (62.24) 0.009 97.0 13.51 4.46 Celogen AZ130 is a chemical blowing agent of Uniroyal Corp. -d ~
~
oo w OD

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~
Table 3 W
Foams Prepared in Example 3 Run Carbon Foaming Cell Size Open Cell Vacuum Blowing Agent Black Temp. R/inch Pressure Number (pph) (oC) (mm) (percent) (torr) 24* 8.0 HFC-134a / 2.0 EtCl 0.0 131 0.041 95.5 12.5 0.2 25* 8.0 HFC-134a / 2.0 EtCI 0.0 131 0.041 95.5 8.62 1.0 26* 8.0 HFC-134a / 2.0 EtCl 0.0 131 0.041 95.5 6.58 5.0 27* 8.0 HFC-134a / 2.0 EtCI 0.0 131 0.041 95.5 5.71 10.0 28 8.0 HFC-134a / 2.0 EtCI 10 129 0.048 96 18.18 0.2 29 8.0 HFC-134a / 2.0 EtCI 10 129 0.048 96 11.49 1.0 30 8.0 HFC-134a / 2.0 EtCI 10 129 0.048 96 7.25 5.0 31 8.0 HFC-134a / 2.0 EtCI 10 129 0.048 96 6.02 10.0 32 8.6 HFC-134a / 2.4 HFC-152a 10 123 0.005 98 18.0 0.2 33 8.6 HFC-134a / 2.4 HFC-152a 10 123 0.005 98 12.4 1.0 34 8.6 HFC-134a / 2.4 HFC-152a 10 123 0.005 98 9.5 5.0 *not an example of the present invention tid ~

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1/1 O ~j1 N ~ '~ V1 O t.n p ~
Table 3 (Continued) Foams Prepared in Example 3 Run Carbon Foaming Cell Size Open Cell Vacuum Blowing Agent Black Temp. R/inch Pressure Number (pph) (,C) (mm) (percent) (torr) 35 8.6 HFC-134a / 2.4 HFC-152a 10 123 0.005 98 7.0 10.0 36 7.5 HFC-134a / 2.0 HFC-152a 6.9 127 0.006 97 20.8 0.2 37 7.5 HFC-134a / 2.0 HFC-152a 6.9 127 0.006 97 18.87 1.0 38 7.5 HFC-134a / 2.0 HFC-152a 6.9 127 0.006 97 9.26 5.0 39 7.5 HFC-134a / 2.0 HFC-152a 6.9 127 0.006 97 5.09 10.0 0 w w-.

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~ O

Table 4 Foams Prepared in Example 4 Carbon Foaming Open Board Dimen.
Run Blowing Density Cell Size inch x inch Number ng Agent Black Temp. pcf (kg/m3) (mm) Cell (cm x cm) (pph) ( C) (percent) Ver. x Hor.
40* 8.0 HFC-134a / 1.0 EtCI / 0.6 C02 0.0 131 3.07 (49.12) 0.030 99.5 3/8 x (.95 x 6.35) 41 8.0 HFC-134a / 1.0 EtCI / 0.6 COZ 10.0 131 2.60(41.6) 0.040 98.6 5/8 x 31/2 (1.59x8.89) *not an example of the present invention Ver. x Hor. - vertical direction and horizontal direction in cross-section o~

w 0 1Nn 0 j ~ tn Table 5 NO
Foams Prepared in Example 5 Run Carbon Black Foaming Foam Density Cell Size Open R/inch R/inch Blowing Agent (pph) Temp. Cell Number ( C) pcf (kg/m3) (mm) (percent) 1 torr 760 torr 42 7.1 HFC-134a 10 pph syn graphi 130 3.82 (61.12) 0.009 100 20.6 ---43 7.1 HFC-134a 5 pph syn graph 130 3.68 (58.88) 0.008 99 20.0 ---pph ther black2 44 7.1 HFC-134a 10 pph nat graph3 131 3.6658.56) 0.007 95 18.3 --- ~
45 12.2 HFC-134a 10 pph furn black4 130 2.96 (47.36) 0.008 98 17.2 ---rn 1 syn graph - synthetic graphite LS2849 of Graphite Products.
2 ther black - thermal black FT 239 of Huber Corp.
3 nat graph - natural graphite GP601 of Graphite Products.
4 furn black - furnace black Monarch 1400 of Cabot Corp.

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w V+
Ln o v+ o 4-n o rn Table 6 Foams Tested in Example 7 and Control Example 7 Run Carbon Black Foam Density K-factorl R/inch K-factor R/inch Number (percent) pcf (kg/m3) (atm. press.2) (atm. press.2) (0.1 torr3) (0.1 torr3) 46 * 0 2.28 (36.48) 0.266 3.76 0.163 6.13 47 * 0 2.46 (39.36) 0.302 3.31 0.210 4.76 48 * 0 2.70(43.2) 0.252 3.97 0.153 6.54 N
49 * 0 2.99 (47.84) 0.283 3.53 0.189 S.29 50 * 0 3.12 (49.92) 0.245 4.08 0.147 6.80 51 10 2.58 (41.28) 0.187 5.35 0.070 14.3 52 10 2.92 (46.72) 0.174 5.75 0.065 15.4 53 10 3.18 (50.88) 0.168 5.95 0.059 16.9 54 10 3.02 (48.32) 0.157 6.37 --- ---55 10 3.04 (48.64) 0.159 6.29 --- ---I BTU-in/ft2=hr=F (thermal conductivity) 2 atm. press. - foam at atmospheric pressure * Examples 46 to 50 are comparative examples since .10.1 torr - foam at 0.1 torr absolute pressure they contain no infrared attenuating agent While embodiments of the foam of the present invention have been shown with regard to specific details, it will be appreciated that depending upon the manufacturing process and the manufacturer's desires, the present invention may be modified by various changes while still being fairly within the scope of the novel teachings and principles herein set forth.

Claims (16)

CLAIMS:

1. An open-cell microcellular foam comprising an alkenyl aromatic polymer foam, the foam being characterized in that the foam has an average cell size of 70 micrometers or less, the foam being evacuated, the foam containing an infrared attenuating agent in a quantity sufficient to reduce the thermal conductivity of the foam relative to a corresponding foam without the infrared attenuating agent.

2. The foam of claim 1, wherein the foam has an average cell size of 1 to 30 micrometers.

3. The foam of claim 1 or 2, wherein the foam has in its open cells an absolute pressure of 10 torr or less.

4. The foam of claim 1 or 2, wherein the foam has in its open cells an absolute pressure of 1 torr or less.

5. The foam of claim 1 or 2, wherein the foam has in its open cells an absolute pressure of 0.1 torr or less.

6. The foam of any one of claims 1 to 5, wherein the foam has an open cell content of 70 percent or more.

7. The foam of any one of claims 1 to 5, wherein the foam has an open cell content of 90 percent or more.

8. The foam of any one of claims 1 to 5, wherein the foam has an open cell content of 95 percent or more.

9. The foam of any one of claims 1 to 8, wherein the infrared attenuating agent is carbon black.

10. The foam of any one of claims 1 to 8, wherein the infrared attenuating agent is graphite.

11. The foam of any one of claims 1 to 10, wherein the foam has a density of 16 to 250 kilograms per cubic meter.

12. The foam of any one of claims 1 to 10, wherein the foam has a density of 25 to 100 kilograms per cubic meter.

13. The foam of any one of claims 1 to 12, wherein the infrared attenuating agent is present at from 1 to 20 weight percent based upon polymer weight.

14. The foam of any one of claims 1 to 12, wherein the infrared attenuating agent is present at from 4 to 10 weight percent based upon polymer weight.

15. The foam of any one of claims 1 to 14, wherein the foam is a polystyrene foam.

16. The foam of any one of claims 1 to 14, wherein the foam is an extruded polystyrene foam.