CA1132897A

CA1132897A - Thermal insulation

Info

Publication number: CA1132897A
Application number: CA305,743A
Authority: CA
Inventors: Jan A. Verhave; Hurbert Viault; Peter Colson
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1977-07-15
Filing date: 1978-06-19
Publication date: 1982-10-05
Also published as: JPS5420076A; DK315478A; NL186175B; JPS6340815B2; DE2830914C2; FR2397498A1; ATA508178A; AT359708B; NL7807536A; DE2830914A1; GB1602381A; ES471677A1; SE439795B; DK154569C; NL186175C; BE868747A; SE7807826L; FR2397498B1; DK154569B

Abstract

ABSTRACT
The invention provides a method for providing a flame retardant thermal insulation between a plurality of spaced a-part surfaces having an air-filled cavity between them, which comprises introducing into said cavity a mixture containing cellular particles of expanded polymer, a synthetic polymer latex binder, and an organic bromine-containing compound conferr-ing flame retardant properties on the bound polymer particles, preferably in the form of a flowable suspension concentrate of a solid flame retardant. The invention provides also, for use in the method, a suitable mixing gun and a flowable suspension concentrate of flame retardant.

Description

~13Z8~7 The present invention is concerned with thermal insulation in situ-ations, for example in building structures, in which it is desired to reduce the thermal conductivity between spaced apart surfaces having an air space between them. This may be achieved by filling the air space between such sur-faces with a material of appropriate thermal conductivity characteristics, and in the case of building structures of cavity wall construction it is known to fill the cavity with insulating materials such, for example, as expanded vermiculite, mineral wool, cellular polystyrene or polyurethane foam.
Expanded polystyrene beads have a cellular structure, and are thus in principle well adapted to the insulation of cavities. However, their very low bulk density and free flowing characteristics often make it difficult to ensure that they are retained in the cavities and do not escape through joins or faults in the cavity walls. A solution to this problem developed by the Applicants is to coat the expanded polystyrene beads with a binder of synthet-ic polymer latex. The presence of this latex binder then hinders flow of polystyrene beads through any openings in the cavity walls to such an extent that any flow is stopped before a significant amount of beads has passed through.
One of the most important applications of cavity insulation is in the insulation of buildings, because of the substantial savings in energy con-sumption thereby achieved. In such applications it is important not only to achieve improved thermal insulation but also to ensure satisfactory fire re-tardant properties, and although grades of expanded polystyrene beads are com-mercially available which contain a flame retardant additive, the use of such beads with a synthetic polymeric latex binder does not always provide a suffi-ciently high level of fire retardancy. The Applicants have now devised a method whereby a flame retardant can be introduced with the synthetic poly-meric latex binder into the cavity, thereby providing good fire retardant properties in the cavity fill composition. Accordingly the present invention provides a method of providing a flame

- 2 -il;~Z8g7 retardant thermal insulation between a plurality of spaced apart surfaces having an air-filled cavity between them, which compris-es introducing into said cavity a mixture containing cellular particles of expanded polymer, a synthetic polymer latex binder, and an organic bromine-containing compound conferring flame retardant properties on the bound polymer particles.
Beads of expanded polystyrene are particularly suitable for use as the cellular polymer particles in the method of this invention, but other types of cellular, expanded polymers may also be used. As is well known cellular polystyrene particles are conveniently prepared from expandable particles manufactured in the form of beads or pearls by suspension or emulsion poly-merisation techniques, the expanding agent such as pentane being incorporated therein during or after polymerisation. Upon heat-ing of the expandable pearls or beads, "pre-expansion" occurs, yielding the cellular polystyrene particles suitable for use in the method of this invention. Pre-expansion, a well-known step in the art of cellular polystyrene, comprises steaming the ex-pandable beads or pearls to give an expansion of some 20 to 30 times their original volume, and during cooling, allowing air to penetrate into the individual cells to raise the internal pressure to atmospheric pressure. These expanded cellular polystyrene particles have a spherical shape, an apparent, packed density of, e~g. 6-100 g/l and free-flowing properties. For wall cavity filling the particle size of the beads is suitably in the range of 1-10 mm, and for this application it is desirable to employ self-extinguishing grades of polystyrene beads. A number of additives is known for this purpose, such as brominated or chlorinated organic compounds.
The synthetic polymer latex used as binder in the method

- 3 -~l~Z897 of this invention may be any aqueous colloidal suspension of particles of a polymer obtained by addition polymerisation.
Generally the colloidal suspension is stabilised by the presence of a suitable surface-active agent, and the most suitable poly-mers are those obtained by free-radical emulsion polymerisation.

- 3a -~l~Z897 Thus, suitable latices include those based on, for example, styrene-butadi-ene copolymers, acrylic copolymers, butadiene-acrylonitrile polymers, vinyl-idene chloride copolymers, butyl rubber, isoprene or, preferably, polymers or copolymers of vinyl alkanoates, such as vinyl acetate or vinyl propionate.
A preferred class of latices are based on vinylacetate copolymers, in partic-ular on copolymers of vinyl acetate with higher vinyl esters such as vinyl caproate, vinyl laurate and vinyl~,~-dimethyloctanoate. It has been found that particularly satisfactory results are obtained if the latex is based on a copolymer of vinyl acetate and a vinyl ester of a carboxylic acid having 6 10 to 16, in particular 8 to 12, carbon atoms per molecule, such copolymers being available commercially under the Trademark "VeoVa". In the latter type of copolymers the weight ratio of vinyl acetate to higher vinyl ester may be from 10:90 to 85:15, preferably from 60:40 to 80:20. The latex may, if de-sired, contain other additives such as silica fillers, thickening agents, cor-rosion inhibitors, pigments and water soluble dyes.
The organic bromine-containing compound used as the flame retardant component in the method of this invention may be any of the compounds of this type conventionally incorporated into polystyrene beads, for example, bromo-phenyl alkenyl ethers such as pentabromophenyl allyl ether, brominated cyclo-alkanes such as hexabromocyclododecane, or organic phosphates such as tris-(2,3-dibromopropyl)phosphate. If the flame retardant is a solid, it may con-veniently and efficiently be introduced into the cavity by means of a flow-able suspension concentrate, which, as such, forms a further feature of this invention and comprises 10-85%w of the solid flame retardant, 0.5-15%w of dis-persing agents, 0.1-10%/w of suspending agents such as protective colloids and thixotropic agents, 0-10%/w of supplementary additives such as flame re-tardant synergists, for example, antimony oxide, defoamers, corrosion inhib-itors, stabilisers, penetrants, bacteriostatic preservatives and stickers, and as carrier, water or an organic liquid in which the flame retardant is substantially insoluble; certain organic solids or inorganic salts may be .

~L3Z897 dissolved in the carrier to assist in preventing sedimentation or as anti-freeze agents for water, for example, ethylene glycols.
The dispersing agent may be nonionic, such as an ethylene oxide/
propylene oxide copolymer, an ethoxylated alkyl phenol or an ethoxylated long chain alcohol, or anionic, such as a metal, suitably sodium or calcium, salt of lignin sulphonic acid, methacrylic acid, or other polyelectrolyte. The suspending agent may be a water-soluble polymer, such as a polysaccharide or hydroxyethyl cellulose, or a finely divided inorganic solid, such as benton-ite, montmorillonite, or other clay powders. The particle size of the flame retardant should desirably be as small as practicable, suitably with a vol-ume median diameter below 10 ~m and preferably between 1 and 5 ~m. The pre-cise nature and proportions of the components incorporated into such a suspen-sion concentrate will naturally be dependant on the physico-chemical proper-ties of the selected flamé retardant component, and it will be understood by those skilled in the art that not every potential dispersing agent will nec-essarily be sufficiently compatible with every suspending agent and every flame retardant. In the case of pentabromo phenyl allyl ether, good results have been obtained using an aqueous suspension concentrate containing a natur-ally occurring polysaccharide and an ethylene oxide/propylene oxide copolymer.
Advantageously, according to a further feature of this invention, the cellular particles of expanded polymer are introduced into the cavity by means of a mixing gun in which streams of particles, latex binder and flame retardant are combined in the desired ratio and the resulting mixture is de-livered into the cavity through the gun nozzle. Such a mixing gun suitably comprises a tube or like device adapted to be connected to a reservoir of par-ticles, such as a feed hopper, and having inserted therein a main jet through which air or other gaseous fluid under pressure can be introduced for the pur-pose of sucking the particles along the tube or the like from the reservoir, and also one or more supplemental jets through which the binder latex and flame retardant component are introduced.

~`

For wall cavity filling the amount of latex is suitably such as to provide 5-10%, preferably 6-8%w of latex solids, based on the weight of the polymer particles. The solids content of the latex itself may be 10-20%/w while the total weight ratio of polymer particles to latex is usually in the range of 10:1 to 10:10 for these types of applications. The proportion of flame retardant will normally be between 0.1-10%/w based on the weight of the polymer particles.
- Although the latex binder and the flame retardant component may, if desired, be fed separately into the mixing gun ~or even separately into the cavity), it has been found that the practical operation of the cavity filling method is significantly simplified if the flame retardant agent, suitably in the form of a suspension concentrate, is pre-blended with the latex binder, and the cellular polymer particles are coated with the resultant mixture, conveniently in the mixing gun. This procedure not only simplifies the design of the mixing gun by reducing thé number of separate feeds and supplemental jets, but also makes it possible for the latex/flame retardant mixture to be formulated at a central location and transported to the individual sites where the cavity filling is to take place. This procedure thus reduces the number of separate formulation components required at the site of operation, and thereby both reduces the demands of logistical organisation and storage space, and also eliminates the need to provide for independant measurement by the operator of the quantity of flame retardant. However, it will be appreci-ated that such a centralised formulation of the latex/flame retardant mixture is possible only if the resultant mixture has adequate storage stability, the achievement of which is largely contingent upon the use of a suitable formula-tion of the flame retardant component. The Applicants have found that the use of a suspension concentrate of the flame retardant component generally enables satisfactory storage stability to be obtained when it is admixed with the latex binder.
After the cavity has been filled by the method of this invention , Z89~

the resulting filling is allowed to dry and set. Upon sufficient evaporation of water the latex polymer will coalesce upon the cellular polystyrene par-ticles and function as a permanent binding agent. After moistening the poly-styrene particles by the latex, before setting, the free-flowability of the particles is somewhat reduced which will prevent the beads from undue spill-ing.
The setting time of the composition - usually 1/2 to 3 hours -depends upon a number of factors, such as environmental temperature and rel-ative humidity, free passage of air, and composition and amount of the latex employed. Generally the temperatures for setting are in the range of 15-40C.
The minimum film formation temperature may, if desired, be reduced to as low as 5C by the addition of small amounts of high molecular weight alcohols, e.g. 1-5%/w on latex. Suitable alcohols for this purpose are polyethylene glycols, polypropylene glycols and ester-alcohols.
It will be understood that, although the method of this invention is particularly convenient for the insulation of the cavities in existing buildings incorporating a cavity wall construction, it is by no means limited to this application. Thus, blocks or panels used in building construction are often formed with cavities to reduce their weight, and the method of this invention may be employed to fill those cavities and increase the thermal insulation properties of the product. Other applications, including many outside the field of building, will be apparent to those skilled in the art.
The invention is illustrated in the following Examples.
Example I
Pentabromophenyl allyl ether ~PEPAE) was formulated as a suspension concentrate (SC) containing, by weight, 65 parts PBPAE, 1.25 parts of the ethylene oxide/propylene oxide copolymer available under the Trademark "Pluronic" P.105 and 0.3 parts of the naturally occurring xanthan gum avail-able under the Trademark "Kelzan" XC. This suspension concentrate was mixed in varying amounts (shown in Table 1 below) with a latex of a vinylacetate ..~

ll~Z897 copolymer with "VeoVa" 10, a registered Trademark for a vinyl ester of ~
dimethyloctanoic acid in a monomer weight ratio of 70:30, containing 3%wt, of an anionic emulsifier and having a solids content of 17%wt, and a pH of

4-4.5. This composition was then mixed in a mixing gun with cellular poly-styrene beads having a diameter of 3-5 mm, a true density of 20 g/l, and in-corporating 0.6% wt of PBPAE as flame retardant, the mixing ratio being about 60 parts by wt of PBPAE/latex mixture to 500 parts by wt of polystyrene par-ticles, and the mixture injected at 2SC into a cavity.
After 1 hour the mixture had set in the cavity to an apparent bulk density of 10 g/l (based on polystyrene), and the flame retardancy of this filling was then evaluated using both the time of flame to extinguish ~as defined in the flammability test of BS 3837), and the "oxygen index" deter-mination as described in Modern Plastics, March 1970, pages 124-130 (also ASTM D 2863). The precise compositions of the different mixtures evaluated, and the results of the fire retardancy tests, are set out in Table 1 below.

Composition ~parts by weight) Flame Retardancy EPS Beads Latex PEPAE SC Flammability-BS 3837 Oxygen Index-(incorporated ~time in secs. for ASTM D2863 in latex)flame to extinguish) t% oxygen) 100 12 0.5 11 100 12 1.0 14 22 100 12 1.5 4 100 12 2.0 2 24.5 Example II
The vinyl acetate/"VeoVa" latex described in Example I was mixed with varying amounts (as shown in Table 2 below) of the liquid flame retard-ant tris-(2,3-dibromopropyl)phosphate (T23P) and 1%wt (based on T23P) of ~1~2897 glyceryl monostearate, and the resulting mixture diluted with two volumes of water. This diluted latex mixture was injected, together with cellular poly-styrene beads, into a cavity, following the procedure described in Example I;
the procedure being carried out both with PBPAE - containing beads ("F"
grade) and similar beads in which no flame retardant had been incorporated ~"R" grade). Flammability tests were then carried out on the composition filling the cavity, and the results are shown in Table 2 below:-Flammability, in secs. to extinguish % T23P (BS 3837) (based on beads) "F" beads "R" beads 1.5 over 20 over 20 2.0 over 20 over 20 2.5 2-3 2-3

5.0 o o

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for providing a flame retardant thermal insul-ation between a plurality of spaced apart surfaces having an air-filled cavity between them, which comprises introducing into said cavity a mixture containing cellular particles of expanded polymer, a synthetic polymer latex binder, and an organic bromine-containing compound conferring flame retardant proper-ties on the bound polymer particles.

2. A method as claimed in claim 1 wherein the expanded polymer is expanded polystyrene.

3. A method as claimed in claim 2 wherein the synthetic polymer latex binder is a copolymer of vinyl acetate and a vinyl ester of a carboxylic acid having 6 to 16 carbon atoms per molecule.

4. A method as claimed in claim 1 wherein the organic bromine-containing compound is a solid which is introduced into the mixture as a flowable suspension concentrate comprising 10-85% wt of the solid flame retardant, 0.5-15% wt of dispersing agents, 0.1-10% wt of suspending agents, and, as carrier, water or an organic liquid in which the flame retardant is subtantially insoluble.

5. A method as claimed in claim 4 wherein the dispersing agent is an ethylene oxide/propylene oxide copolymer, the sus-pending agent is a polysaccharide and the flame retardant has a particle size of volume median diameter below 10 µm.

6. A method as claimed in claim 1 wherein the organic bromine-containing compound is pentabromophenyl allyl ether.

7. A method as claimed in claim 1 wherein the amount of latex and flame. retardant introduced are such as to provide, based on the weight of the polymer particles, respectively 5-10%
wt of latex solids and 0.1-10% wt of flame retardant.

8. A method as claimed in claim 1 wherein the cellular particles of expanded polymer are introduced into the cavity by means of a mixing gun in which streams of cellular particles, latex binder and flame retardant are combined in the desired ratio and the resulting mixture is delivered into the cavity through the gun nozzle.

9. Spaced apart surfaces having a flame retardant thermal insulation between them when produced by a method as claimed in claim 1, 2 or 3.

10. Spaced apart surfaces having a flame retardant thermal insulation between them when produced by a method as claimed in claim 4, 5 or 6.

11. Spaced apart surfaces having a flame retardant thermal insulation between them when produced by a method as claimed in claim 7 or 8.