WO2004005365A1

WO2004005365A1 - Polyisocyanurate foams with improved thermal stability

Info

Publication number: WO2004005365A1
Application number: PCT/US2003/020675
Authority: WO
Inventors: Rick L. Tabor; Terry L. Raceina; David J. Norberg; F. Leo Hickey
Original assignee: Stepan Company
Priority date: 2002-07-02
Filing date: 2003-07-01
Publication date: 2004-01-15
Also published as: AU2003258977A1; WO2004005365A8

Abstract

Rigid polyisocyanurate foams having improved thermal stability, foam compositions and dispersions therefor, as well as methods of making the same, are provided with respect to an aromatic polyester polyol or polyol blend thereof having an average hydroxyl functionality of less than about 3.0, a polyisocynate in a sufficient amount to yield an NCO/OH index of at least about 200, a sugar or carbohydrate having a molecular weight of less than about 2000,and a blowing agent. Such foams, foam compositions, and dispersions may also contain flame retardants, stabilizers, and others additives.

Description

POLYISOCYA URATE FOAMS WITH IMPROVED THERMAL STABILITY

RELATED APPLICATIONS This application claims priority to United States Provisional Patent Application, Serial No. 60/393,473 filed on July 2, 2002.

BACKGROUND OF THE INVENTION Field Of The Invention

The present invention relates generally to polyisocyanurate foams, and more specifically, to compositions and methods for preparing rigid polyisocyanurate foams with improved thermal stability.

Description of Related Art

A common process for producing polyurethane and polyisocyanurate foams requires preparing a "resin" or "B component" and subsequently mixing that resin with an isocyanate or "A component" immediately prior to discharge of the final foam-generating mixture. This resin or B component typically contains a polyol or a mixture of polyols, catalysts, silicone or other cell-stabilizing surfactants, and one or more blowing agents which vaporize due to the heat of reaction resulting in expansion of the foam. The resin may also contain water, which functions as an additional blowing agent by chemical generation of carbon dioxide during the reaction with isocyanate in the foam generating mixture.

Rigid foams have been used for a wide variety of applications including, by way of example, insulation for buildings, solid or liquid containing tanks, doors, and picnic coolers. It is often desirable to impart improved thermal stability to rigid polyisocyanurate foams, so as to impart better flammability and heat resistance. Improved thermal stability of polyisocyanurate foams is particularly desirable in, for example, the construction industry - for which various applications are subject to performance testing for thermal stability. By way of example, in the case of laminated insulation board, one performance test for flammability and heat resistance is called the "Factory Mutual Calorimeter Test." In one form of this test, a roof section is produced that comprises insulation board covered with several layers of roofing felt and asphalt. The roof section is then placed on an oven-type structure, by covering an opening in the top, and subjected to high heat for 30 minutes. The total heat contribution of the roof components, over various time intervals, is measured. The major source of heat from the roof section is associated with the asphalt, which gradually melts, and can run into the oven through any openings that develop. For good performance in this test, it is desirable that the foam portion of the insulation board form a strong, unbroken char which prevents, as far as possible, the influx of the molten asphalt into the oven, thus minimizing the heat contribution of this component. The occurrence of splitting or eroding of the char, or other damage that reduces its bulk, increases the opportunities for asphalt to enter the oven, thus adversely affecting performance in the test.

It is therefore desirable to provide a rigid polyisocyanurate foam composition with improved thermal properties, such as reduced cracking and splitting as well as improved char quality.

BRIEF SUMMARY OF THE INVENTION In one aspect, the present invention provides a rigid polyisocyanurate foam having improved thermal stability. In this aspect, the invention comprises the reaction product of an aromatic polyester polyol or polyol blend thereof having an average functionality of less than about 3.0, a polyisocyanate sufficient in amount to yield an index of at least about 200, a sugar or carbohydrate having a molecular weight of less than about 2000, and a blowing agent. In another aspect of the present invention, there is provided a method of making a rigid polyisocyanurate foam having improved thermal stability by combining a polyisocyanate, an aromatic polyester polyol or polyol blend thereof having an average functionality of less than about 3.0, a sugar or carbohydrate having a molecular weight of less than about 2000, and a blowing agent, wherein the reactant composition has an index of at least about 200.

In yet another aspect of the present invention, there is provided a rigid polyisocyanurate foam having improved thermal stability comprising at least 0.1 weight percent of a sugar or carbohydrate, having a molecular weight of less than about 2000, in the foam.

In a further aspect of the present invention, there is provided a dispersion having a water content of less than about 5% which essentially contains a sugar or carbohydrate having a molecular weight of less than about 2000 and an aromatic polyester polyol or polyol blend thereof having an average functionality of less than about 3.0.

In an additional aspect of the present invention, there is provided a dispersion essentially containing a sugar or carbohydrate having a molecular weight of less than about 2000 and a liquid flame retardant.

In another aspect of the present invention, there is provided a dispersion essentially containing a sugar or carbohydrate having a molecular weight of less than about 2000, a liquid flame retardant, and an aromatic polyester polyol or polyol blend thereof having a functionality of less than about 3.0.

In yet another aspect of the present invention, there is provided a foam producing composition having an aromatic polyester polyol or blend thereof having an average functionality of less than about 3.0, a polyiscocyanate in an amount sufficient to yield an index of at least about 200, a sugar or carbohydrate having a molecular weight of less than about 2000, and a blowing agent.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graphic scale representing levels of char.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that the incorporation of one or more sugars or carbohydrates into rigid polyurethane-modified polyisocyanurate foams, made from aromatic polyester polyols or polyol blends, may yield foams having improved thermal stability. This is evidenced by improved performance in tests directed to flammability and high-temperature-resistance.

The "hot plate" test is a small-scale laboratory test, commonly used in the polyurethane industry to estimate the performance of, for example, polyurethane- modified polyisocyanurate foams in the larger-scale, Factory Mutual Calorimeter Test. There are several variations of the hot plate test, but in general, a sample of foam is placed on a hot plate at a high temperature (approximately 300° F to 1200° F or higher) for a given period of time, after which time the sample is inspected for changes in thickness and weight, splitting tendencies, and characteristics of the resulting char. The test can be run on foam alone, or on insulation board with the board facers adhered thereto.

Retention of thickness by the char contributes to good performance in the Factory Mutual Calorimeter Test because a thick char helps to insulate the asphalt from the heat, reducing melting and the resulting influx of molten asphalt. A thick char also forms a physical barrier to passage of the asphalt. An additional result from the hot plate test is an observation as to the character of the char structure. A network of fine voids in the char has been observed to correlate with better performance in the Factory Mutual Calorimeter Test than is observed when larger voids are present. Under high-temperature test conditions, the char produced by the foam of the invention has a considerably finer texture, with shorter and more rounded voids, and a more continuous appearance in the solid portion of the char. A char structure rating scale is used to characterize the fineness of the char obtained under high-temperature conditions.

A test method has been provided to measure the compressive strength of the charred foam resulting from the hot plate test. The strength of the char is believed to be important in helping to maintain the integrity of the insulation board layer in the Factory Mutual Calorimeter Test and to prevent development of gaps through which asphalt would be allowed to pass.

Cracks which develop in the foam under high temperatures can also provide a route of entry for asphalt into the oven.' A test is provided which gives an indication of the tendency of the foam to crack under high-temperature conditions.

Aromatic Polyester Polyol

The composition, method and dispersion of the present invention are preferably directed to use of an aromatic polyester polyol. Preferably, the polyester polyol or polyol blend has an average functionality of less than about 3.0. The term "polyester polyol" as used herein means a polyol having ester linkages. Such a polyester polyol may include minor amounts of unreacted hydroxylated material that remain after preparation of the polyol or polyol blend and/or unesterified low molecular weight poylols added after the preparation of the polyester polyol or polyol blend. Further information regarding suitable polyester polyols to practice the present invention is set forth in U.S. Patent No. 5,922,119, which is hereby incorporated by reference. Suitable aromatic polyester polyols may be prepared by the reaction of an aromatic polycarboxylic acid or a derivative thereof, and a hydroxylated material having a functionality greater than about 1.5. Aromatic polyester polyols may also be formed by the reaction between aromatic polycarboxylic acid adducts and hydroxylated materials having an average functionality greater than about 1.5. Exemplary information regarding these types of polyols may be found in U.S. Patent Nos. 4,444,918; 4,506,090; 4,526,908; 3,647,759; 4,048,104; and 4,714,717. It is contemplated that some (perhaps up to 50 mole % of the polycarboxylic acid) aliphatic polycarboxylic acid or adducts may be used in the preparation of the aromatic polyester polyols.

It should be noted that the esterification reaction used for producing an aromatic polyol may, if desired, be carried out in the presence of a catalyst as those skilled in the art will appreciate. Suitable catalysts include, but are not limited to, organotin compounds, particularly tin compounds of carboxylic acids, such as stannous octoate, stannous aleate, stannous acetate, stannous laurate, dibutyl tin dilaurate, and other such tin salts. Additional suitable catalysts include, for example, metal catalysts, such as sodium and potassium acetate, tetraisopropyl titanates, and other such titanate salts, and the like.

Further, suitable aromatic polyester polyols which may be used in the practice of the present invention include, but are not limited to STEPANPOL^® PS- 2412 which is an aromatic polyester polyol with a nominal hydroxyl value of 240, provided by Stepan Company of Northfield, Illinois. Other suitable aromatic polyester polyols which may be used in the practice of this invention may include, for example, Terate^® 203, Terate^® 2541, STEPANPOL^® PS-2352, STEPANPOL^® PS- 2502A, and STEPANPOL^® PS-2002. Moreover, other types of polyols which may be used in the practice of the present invention include those polyols that can be used in combination with an aromatic polyester polyol, although it is contemplated that the aromatic polyester polyol should amount to at least about 50% of the total polyol of the present invention. Examples of such polyols are thioether polyols, polyester amides and polyacetals containing hydroxyl groups, aliphatic polycarbonates containing hydroxyl groups, amine terminated polyoxyalkylene polyethers, and preferably, polyester polyols, aliphatic polyester polyols, polyester polyether polyols, polyoxyalkylene polyether polyols, and graft dispersion polyols. Mixtures of polyols can be used although it is contemplated that the combination has an average hydroxyl number in the range of about 50 to about 1200.

Polyoxyalkylene polyether polyols, which can be obtained by known methods, can be mixed with the aromatic polyester polyol or polyol blend of the present invention. For example, polyether polyols can be produced by anionic polymerization with alkali hydroxides such as sodium hydroxide or potassium hydroxide or alkali alcoholates, such as sodium methylate, sodium ethylate, or potassium ethylate or potassium isopropylate as catalysts and with the addition of at least one initiator molecule containing 2 to 8, preferably 3 to 8, reactive hydrogens, or by cationic polymerization with Lewis acids such as antimony pentachloride, boron trifluoride etherate, etc., or bleaching earth as catalysts, from one or more alkylene oxides with preferably 2 to 4 carbons in the alkylene radical. Any suitable alkylene oxide may be used such as 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, amylene oxides, styrene oxide, and preferably ethylene oxide and 1,2-propylene oxide and mixtures of these oxides. The polyoxyalkylene polyether polyols may be prepared from other starting materials such as tetrahydrofuran and alkylene oxide- tetrahydrofuran mixtures, epihalohydrins such as epichlorohydrin, as well as aralkylene oxides such as styrene oxide. The polyoxyalkylene polyether polyols may have either primary or secondary hydroxyl groups. Included among the polyether polyols are polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, and polytetramethylene glycol; block copolymers, for example, combinations of polyoxypropylene and polyoxyethylene glycols, poly-l,2-oxybutylene and polyoxyethylene glycols, poly- 1,4-tetramethylene and polyoxyethylene glycols; and copolymer glycols prepared from blends or sequential addition of two or more alkylene oxides. The polyoxyalkylene polyether polyols may be prepared by any known process such as, for example, the process disclosed by Wurtz in 1859 and Encyclopedia of Chemical Technology, Vol. 1, pp. 257-262, published by Interscience Publishers, Inc. (1951) or in U.S. Patent No. 1,922,459.

Suitable polyethers are believed to include the alkylene oxide addition products of polyhydric alcohols such as ethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,2-butanediol, 1,5-pentanediol, 1,6- hexanediol, 1,7-heptanediol, hydroquinone, resorcinol, glycerol, 1,1,1-trimethylol- propane, 1,1,1 trimethylolethane, pentaerythritol, 1,2,6-hexanetriol, alphamethyl glucoside, sucrose, and sorbitol. Also included within the term "polyhydric alcohol" are compounds derived from phenol such as 2,2-bis(4-hydroxyphenyl)-propane, commonly known as Bisphenol A.

Isocyanate

It is contemplated that any polyisocyanate may be used in accordance with the present invention. Polyisocyanates which may be used in the present invention include, but are not limited to, aliphatic, cycloaliphatic, and aromatic polyisocyanates, and combinations thereof. Representatives of these types of polyisocyanates are diisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4-methoxyphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'- dimethoxy-4,4'-biphenylene diisocyanate, 3,3 '-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate; triisocyanates such as 4,4'4"-triphenylmethane triisocyanate and 2,4,6-toluene triisocyanate; and tetraisocyanates such as 4,4'-dimethyl-2,2'5,5'-diphenylmethane tetraisocyanate; and polymeric isocyanates such as polymethylenepolyphenylene polyisocyanate. It is also contemplated that blends or prepolymers thereof are also suitable for use in accordance with the present invention.

The term "index" means the molar ratio of isocyanate groups to hydroxyl groups ("NCO/OH") multiplied by 100, in the reaction between the polyol and the isocyanate. Water is considered to react with isocyanate in such a way as to require two isocyanate groups per molecule of water, and the calculation for index is adjusted to reflect this requirement, based on the amount of water added to the formulation. In accordance with the present invention, the index is preferably from 170 to about 1000, and most preferably from about 200 to about 400.

Blowing Agents

The blowing agent for use in the practice of the present invention is preferably a hydrocarbon, hydrofluorocarbon, or blends thereof.

In the case of hydrocarbons, an aliphatic or cycloaliphatic C₄-C₇ hydrocarbon is preferred. This material has a boiling point of 70° C or less at 1 atmosphere, preferably 50° C or less. The hydrocarbon is physically active and has a sufficiently low boiling point to be gaseous at the exothermic temperatures caused by the reaction between the isocyanate and polyols, so as to foam the resulting polyurethane matrix. Examples of the C₄-C hydrocarbon blowing agents include linear or branched alkanes, e.g., butane, isobutane, 2,3-dimethylbutane, n- and isopentane and technical-grade pentane mixtures, n- and isohexanes, and n- and isoheptane. Specific examples of alkenes are 1-pentene, 2-methylbutene, 3- methylbutene, and 1-hexene, and of cycloalkanes are cyclobutane, preferably cyclopentane, cyclohexane or mixtures thereof. Preferentially, cyclopentane, n- and isopentane, and mixtures thereof are employed. Suitable hydrofluorocarbons include, but are not limited to, difluoromethane (HFC-32); 1,1,1,2-tetrafluoroethane (HFC- 134a); 1,1,2,2- tetrafluoroethane (HFC- 134); 1,1-difluoroethane (HFC- 152a); 1,2-difluoroethane (HFC- 152); trifluoromethane; 1,1,1-trifluoroethane; 1,1,2-trifluoroethane; 1,1,1,2,2- pentafluoropropane; 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3- tetrafluoropropane; 1 , 1 ,2,3,3-pentafluoropropane; 1,1,1 ,2,3,3,3-heptafluoropropane (HFC-227 ea); and 1,1,1,3,3-pentafluoro-n-butane (HFC-365mfc).

It is also contemplated that other blowing agents can be used in combination with the one or more preferred hydrocarbon and/or hydrofluorocarbon blowing agents of the present invention. These may be divided into the chemically active blowing agents which chemically react with the isocyanate or with other formulation ingredients to release a gas for foaming, and the physically active blowing agents which are gaseous at the exotherm foaming temperatures or less without the necessity for chemically reacting with the foam ingredients to provide a blowing gas. Included within the meaning of physically active blowing agents are those gases which are thermally unstable and decompose at elevated temperatures.

Examples of chemically active blowing agents are preferentially those which react with the isocyanate to liberate a gas, such as CO₂. Suitable chemically active blowing agents include, but are not limited to, water, mono- and polycarboxylic acids having a molecular weight of from 46 to 300, salts of these acids, and tertiary alcohols.

Water may be used as a co-blowing agent. Water may react with the organic isocyanate to liberate CO₂ gas which is the actual blowing agent. However, since water consumes isocyanate groups, an equivalent molar excess of isocyanate must be provided to make up for the consumed isocyanates in the practice of the present invention. The organic carboxylic acids used as the chemically active blowing agents are advantageously aliphatic mono- and polycarboxylic acids, e.g. dicarboxylic acids. However, other organic mono- and polycarboxylic acids are also suitable. The organic carboxylic acids may, if desired, also contain substituents which are inert under the reaction conditions of the polyisocyanate addition or are reactive with isocyanate, and/or may contain olefϊnically unsaturated groups. Specific examples of chemically inert substituents are halogen atoms, such as fluorine and/or chlorine, and alkyl groups, e.g. methyl or ethyl. The substituted organic carboxylic acids may contain at least one further group which is reactive toward isocyanates, e.g. a mercapto group, a primary and/or secondary amino group, or a primary and/or secondary hydroxyl group.

Suitable carboxylic acids are thus substituted or unsubstituted monocarboxylic acids, e.g., formic acid, acetic acid, propio ic acid, 2-chloropropionic acid, 3-chloropropionic acid, 2,2-dichloropropionic acid, hexanoic acid, 2- ethylhexanoic acid, cyclohexanecarboxylic acid, dodecanoic acid, palmitic acid, stearic acid, oleic acid, 3-mercapto-propionic acid, glycolic acid, 3-hydroxypropionic acid, lactic acid, ricinoleic acid, 2-aminopropionic acid, benzoic acid, 4- methylbenzoic acid, salicylic acid and anthranilic acid, and unsubstituted or substituted polycarboxylic acids, preferably dicarboxylic acids, e.g. oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, tartaric acid, phthalic acid, isophthalic acid and citric acid. Preferable acids are formic acid, propionic acid, acetic acid, and 2- ethylhexanoic acid, particularly formic acid.

The salts of carboxylic acids are usually formed using tertiary amines, e.g., triethylamine, dimethylbenzylamine, diethylbenzylamine, trie ylenediamine, or hydrazine. Tertiary amine salts of formic acid may be employed as chemically active blowing agents which will react with the organic isocyanate. The salts may be added as such or formed in situ by reaction between any tertiary amine (catalyst or polyol) and formic acid contained in the polyester polyol resin blend. Combinations of any of the aforementioned chemically active blowing agents may be employed, such as formic acid, salts of formic acid, and/or water.

Physically active blowing agents suitable for use in combination with the preferred hydrocarbon and/or hydrofluorocarbon blowing agents of the present invention include, but are not limited to those which boil at the foaming exotherm temperature or less, preferably at 50° C or less at 1 atmosphere. The most preferred physically active blowing agents are those which have an ozone depletion potential of

0.05 or less. Examples of other physically active blowing agents include dialkyl ethers, cycloalkylene ethers and ketones; hydrochlorofluorocarbons (HCFCs); perfluorinated hydrocarbons; fluorinated ethers; and decomposition products.

Any hydrochlorofluorocarbon blowing agent may be used in the present invention. Preferred hydrochlorofluorocarbon blowing agents include, but are not limited to l-chloro-l,2-difluoroethane, l-chloro-2,2-difluoroethane (142a), 1-chloro- 1,1-difluoroethane (142b), 1,1-dichloro-l-fluoroethane (141b), 1 -chloro- 1,1,2- trifluoroethane, 1 -chloro- 1,2,2-trifluoroethane, l,l-dichloro-l,2-difluoroethane, 1- chloro- 1,1,2,2-tetrafluoroethane (124a), 1 -chloro- 1,2,2,2-tetrafluoroethane (124), 1,1- dichloro- 1,2,2-trifluoroethane, l,l-dichloro-2,2,2-trifluoroethane (123), 1,2-dichloro- 1,1,2-trifluoroethane (123a), monochlorodifluoromethane (HCFC-22), l-chloro-2,2,2- trifluoroethane (HCFC-133a), gem-chlorofluoroethylene (R-1131a), chloroheptafluoropropane (HCFC-217), chlorodifluoroethylene (HCFC-1122), and transchlorofluoroethylene (HCFC-1131). The most preferred hydrochlorofluorocarbon blowing agent is 1,1-dichloro-l-fluoroethane (HCFC-141b).

Suitable perfluorinated hydrocarbons and fluorinated ethers include, but are not limited to, hexafluorocyclopropane (C-216); octafluorocyclobutane (C-318); perfluorotetrahydrofuran; perfluoroalkyl tetrahydrofurans; perfluorofuran; perfluoro- propane, -butane, -cyclobutane, -pentane, -cyclopentane, -hexane, -cyclohexane, - heptane, and -octane; perfluorodiethyl ether; perfluorodipropyl ether; and perfluoroethyl propyl ether.

Decomposition type physically active blowing agents which release a gas through thermal decomposition may also be utilized in the practice of the present invention and include, but are not limited to pecan flour, amine/carbon dioxide complexes, and alkyl alkanoate compounds, especially methyl and ethyl formates.

The total and relative amounts of blowing agents used in the present invention will depend upon the desired foam density, the type of hydrocarbon or hydrofluorocarbon, and the amount and type of additional blowing agents employed. Polyurethane foam densities typical for rigid polyurethane insulation applications range from free rise densities of 1.0 to 5.0 pounds per ft.³ (pcf), preferably from 1.3 to 3.5 pcf, and overall molded densities preferably from about 1.5 to 4.0 pcf. The amount by weight of all blowing agents in the resin blend is generally 5 to 60 pphp (pphp means parts per hundred parts of all polyols), and preferably 10 to 50 pphp. Based on the weight of all the foaming ingredients (i.e., the resin blend and the isocyanate), the total amount of blowing agent is generally from 2 wt % to 20 wt %. The amount of hydrocarbon/hydrofluorocarbon blowing agent, based on the weight of all the foaming ingredients, may also be from 2 to 20 wt. %, preferably from 3 to 15 wt %.

Generally, the amount of the hydrocarbon blowing agent based on the resin or B component may be from about 1-35% by weight.

Water is typically found in minor quantities in the polyols as a byproduct and may be sufficient to provide the desired blowing from a chemically active substance. Optionally, however, water may be additionally introduced into the polyol resin blend in amounts from 0.05 to 5 pphp, preferably from 0.25 to 2.0 pphp. The physically active blowing agents, if employed, make up the remainder of the blowing agent for a total of from 2 to 35 wt. % based on the total resin blend, or 1 to 15 wt. % based on the weight of all the foaming ingredients.

Catalysts

Suitable trimerization catalysts are known in the art and include quaternary ammonium salts and alkali metal salts of carboxylic acids such as, for example, potassium octoate and potassium acetate. Further exemplary information regarding suitable trimerization catalysts may be found in U.S. Patent No. 5,308,883.

In addition to the trimerization catalyst, polyisocyanurate foam formulations may include a polyurethane catalyst. Suitable polyurethane catalysts include tertiary amines such as, for example, N,N,'N"-tris(3-dimethylaminopropyl)-s- hexahydrotriazine, pentamethyldiethylene triamine, triethylenediamine, N- methylmorpholine, N-ethylmorpholine, diemylethanolamine, N-cocomorpholine, 1- memyl-4-dimethylaminoethylpiperazine, 3 -methyoxypropyldirnethylamine, N,N,N ' - trimethylisopropyl propylenediamine, 3-diethylaminopropyl-diethylamine, dimethylbenzylamine, dimethylcyclohexylamine, and the like.

Cell-Stabilizing Surfactant

In general, the present invention contemplates the potential use of a cell- stabilizing surfactant in the preparation of the final foam product to prevent cellular instability during the foaming reaction. Suitable surfactants include, but are not limited to, silicone surfactants and polyoxyalkylene block copolymer surfactants.

Flame Retardants

The present invention also contemplates the addition of liquid or solid flame retardants in the resin mixture and/or the isocyanate to prepare the final foam product. Suitable liquid flame retardants include, but are not limited to, halogenated phosphate esters, other halogenated compounds, alkyl and aryl phosphates and phosphonates. Halogenated phosphate esters include, but are not limited to, tris-(2- chloroethyl)phosphate, tris-(2-chloropropyl)phosphate, and tris-(dichloropropyl) phosphate. Other halogenated compounds include, but are not limited to, tetrabromophthalate esters, alkyl esters of brominated benzoic acid, and dibromopropane. Alkyl phosphates include, for example, triethyl phosphate. Aryl phosphates include, for example, triphenyl phosphate and tricresyl phosphate. Phosphonates include, for example, dimethyl methyl phosphonate and diethyl ethyl phosphonate. Solid flame retardants which may be used include, but are not limited to, tetrabromobisphenol A, decabromodiphenyl oxide, melamine, and expanded graphite. A preferred flame retardant which may be utilized in the practice of the present invention is a liquid halogenated phosphate ester flame retardant.

Other Additives

The present invention also contemplates the addition of other additives in the resin mixture to prepare the final foam product. Such additives may include, but are not limited to, viscosity-reducing agents, compatibility agents, fillers, pigments, and antioxidants.

Incorporation of Sugar or Carbohydrate

It has been found that the incorporation of sugars or carbohydrates into the foam may reduce cracking or splitting of the char during the hot plate test and increase the strength of the char that forms under test conditions. At least some sugars or carbohydrates have been observed to reduce the size of the small voids that normally form in the char, which are believed to be capable of initiating cracking and splitting that results in an additional loss of integrity. A network of fine voids in the char has been observed to correlate with better performance in the Factory Mutual Calorimeter Test than is seen when larger voids are present. The various forms of sugar and carbohydrates that may be used in the practice of the present invention are discussed further below.

The usual practice in the production of polyurethane or polyisocyanurate foams is to blend a "resin" or "B component", which is comprised of one or more of each of the following: polyol, catalyst, cell-stabilizing surfactant (e.g., silicone surfactant), and blowing agent. Other additives, such as flame retardants, may be included. The resin is then mixed with a polyisocyanate to form a foam.

In accordance with the present invention, one or more sugars or carbohydrates may be incorporated into the resin in dry solid form, as a dispersion in a liquid in which the sugar or carbohydrate is insoluble, or as a solution in a liquid in which the sugar or carbohydrate is soluble. If a sugar or carbohydrate is to be added in dry solid form, it may be dispersed in part or all of the polyol in advance, by typical medium-shear or high-shear mixing. This mixture is then utilized in forming the resin or B component, using the typical mixing equipment used in the art. The sugar or carbohydrate may also be incorporated into other liquid ingredients, or into an inert liquid carrier, to form a dispersion that can be used in the resin. The sugar or carbohydrate may be ground to a finer particle size after it is mixed into one or more of the liquid ingredients or an inert carrier, as by ball milling or agitated-media milling. Preferably, the dispersion of the present invention has a water content of less than about 5% by weight. The sugar or carbohydrate may also be added directly to the resin at the time that mixture is produced, again using standard mixing equipment. Although it is less desirable, the sugar or carbohydrate may also be added to the polyisocyanate that will be used in the generation of the final foam.

If the sugar or carbohydrate is to be in solid form, in one of the preceding techniques, it is preferable that it be a finely divided powder, both to retard separation in the liquid πvixture and to increase the effectiveness in modifying high-temperature behavior in the final foam. The resin-sugar (and/or resin-carbohydrate) mixture is combined with polyisocyanate, using standard foam machinery, to generate the final foam product.

If the sugar or carbohydrate is to be used as a liquid solution, it may likewise be added to the polyol in advance of blending the resin, or it may be added in to the resin in blending. If the sugar is to be added as a liquid solution or pre-formed dispersion, it will be most convenient to add it to the resin in blending, while other liquids are being transferred into the mixing vessel. Aqueous solutions are one preferable form, as they can be made at high sugar concentrations, are commercially available, are physically stable, and will not add unnecessary ingredients to the resin.

The small amount of water that is added with the sugar will function as an auxiliary blowing agent by reaction with the polyisocyanate to form carbon dioxide. One particularly desirable aqueous solution is molasses, which has a high concentration of solids and is readily available commercially at an economically attractive cost.

The preferred levels of sugar or carbohydrate in the resin are those that result in levels of 0.1% to 10% by weight in the final foam. If higher levels of sugar or carbohydrate are required to achieve the desired effects in flammability and high- temperature-resistance tests, it may be desirable to maintain low levels of added water to minimize the generation of carbon dioxide in the foam-forming reaction in order to maintain maximum insulation value of the foam. In such case, dispersions of finely divided solid sugar will be preferred over aqueous solutions.

Suitable sugars and carbohydrates that may be used in accordance with the present invention include, but are not limited to, fructose, glucose, sucrose, maltose, lactose, maltodextrins, and other mono- and polysaccharides having a molecular weight of less than about 2000. Presently preferred sugars are disaccharides, including but not limited to, sucrose. A preferred form of sucrose is a finely divided powder which is dispersed in a liquid flame retardant, in a polyol, or in a blend of a flame retardant and a polyol, for ease of handling. Another preferred source of sugars is molasses. Cane molasses, for example, contains 30-40% sucrose, 15-20% reducing sugars, and total solids of 75-81%. Further information regarding types of molasses which may be used in the present invention may be found in the Encyclopedia of Chemical Technology, Fourth Edition, Vol. 23, pp. 602-604. A preferred carbohydrate is maltodextrin.

If a solid sugar or carbohydrate is to be used in the form of a dispersion in liquid flame retardant, polyol, or a blend of flame retardant and polyol, it may be advantageous to add a stabilizer to the mixture to retard separation of the solid on standing. Stabilizers are normally added in relatively small amounts, typically 10% or less of the total dispersion. One preferred stabilizer for sucrose dispersions is potassium octoate. Other surface-active additives which increase viscosity of the dispersion at low shear rates may also be used. Additives which act as stabilizers by tliickening or gelling organic liquids, such as gelling agents and rheology-control agents, may also be used. An example of an inorganic clay-based gelling and rheology-control agent is Garamite 1958, produced by Southern Clay Products, Incorporated, a division of Rockwood Specialties Incorporated of Princeton, New Jersey. An example of an organic gelling agent is Ircogel 900, an organic sulfonate produced by Lubrizol Corporation of Wicliffe, Ohio.

One skilled in the art will recognize that modifications may be made in the present invention without deviating from the spirit or scope of the invention. The invention is illustrated by the following examples which are not to be construed as limiting the invention in spirit or scope to the specific procedures or compositions described therein.

EXAMPLES The following Examples are provided to illustrate the improved thermal stability of the present invention through inclusion of a sugar or carbohydrate. Test Methods

Preliminary Char/Intumescence Test: 25 g of the polyol, sugar, or other additive is placed in an 8-oz. glass jar and placed in a muffle furnace at 300° C for 2 hours. After removal and cooling, the material in the jar is inspected for char development and an increase in volume (as by foaming followed by solidification in the foamed state, for instance).

Reactivity Test (For Foams^'): The resin and the polymeric isocyanate are combined in a 32-oz. paper cup at 20° C, mixed for 8 seconds with a motor-driven mixing blade rotating at 3600 rpm, poured into a 165-oz. paper cup, and allowed to rise in the cup. Cream time (initiation of rise) and gel time (time at which strings of polymer can be drawn from the reacting mass) are observed. The density is calculated from the weight of the foam remaining in the body of the cup after the foam protruding above the top edge of the cup is cut off.

Test Sample Production (Of Foams): To produce foam samples for the 30- second hot plate test, the required amounts of the resin and the isocyanate are combined and mixed, and immediately poured into an open-top box having a base 10 V x 10 ^lA inches and a height of 8 inches. The box is lined with polyethylene film. The resulting foam is allowed to cure for at least 24 hours at room temperature.

Samples are cut from the interior of the foam block to be used as test pieces.

To produce foam samples for testing in the 15 -minute hot plate test, the resin and the isocyanate are combined and mixed in the same way as for the reactivity test, and immediately poured into a 2 x 13 x 25-inch rectangular mold, the surfaces of which are maintained at 125° F. The mold is underfilled so that a panel of about 2 x 13 x 22 inches is produced. After 15 minutes, the foam panels are removed from the mold and placed in an oven at 200° F for 24 hours to complete curing. Blocks are cut from the interior of the panels for use as test pieces. Hot Plate Test-30 second: A 30-second hot plate test is carried out on foam samples produced for this purpose which are cut from the box pours described above, in order to evaluate splitting tendencies under high-temperature conditions. A sample of dimensions 1 x 1 x 4 inches is cut from the box pour, with the foam rise direction aligned with one of the 1-inch dimensions. The hot plate used for the 15- minute test described below is also used in this test, but the temperature is maintained constant at 1200° F. The sample is placed on the hot plate with the direction of foam rise vertical, left in place for 30 seconds, and removed. The total length of all of the cracks on the bottom surface is added together. Three samples of each foam are run and averaged.

Hot Plate Test- 15 minute: A hot plate test is carried out on samples cut from the molded panels, in order to evaluate resistance to high-temperature conditions. The hot plate used is an infrared radiant panel heater with a 12 x 12 inch surface, with a well in the quartz top plate which allows a thermocouple probe to be inserted to the center of the plate. Temperature is controlled by means of a microprocessor-based programmable temperature controller. The controller is programmed so that, over the 15-minute duration of the test, the temperature begins at 1200° F and declines linearly to 1000° F at the end.

A foam sample for the 15-minute hot plate test is cut from the interior of the panel to dimensions of 4 x 4 x 1.25 inches. A piece of cement fireboard, 4 x 4 x % inches, and weighing approximately 120 g, is placed on top of the foam sample. The sample, with fireboard on top, is placed in the center of the hot plate, and a circular metal air shield is placed on the hot plate so that it surrounds the sample. The 15- minute temperature-control program is started.

At the end of the 15-minute program, the sample is removed from the hot plate and allowed to cool. The sample is cut in half with a band saw, and the final thickness at the center 2 inches of the cross-section is measured to the nearest 0.01 inch. The test causes charring of at least that part of the foam that was nearest the hot plate, and the interior of this char is exposed at the saw cut. The appearance of the charred foam in this cross-section is observed, and any unusual characteristics are noted.

Char Structure Rating: Because of the observation that a finer char structure correlates with better performance in high-temperature tests, a char structure rating scale was used to characterize the fineness of the char obtained under high- temperature conditions. To assign a rating, the center cross-section of a sample from the 15-minute hot plate test is compared with the rating scale, and the number of the char structure on the scale that most closely resembles the char structure of the sample is the char rating of that sample. An example of such a char structure rating scale can be found in Fig. 1. On this scale, a lower number corresponds to a finer char structure.

Char Compressive Strength Test: The samples described above, which have been subjected to the hot plate test and which have been cut in half, are trimmed to eliminate irregular side areas, resulting in test pieces of approximately 3 inches long and 1.5 inches wide, with a height determined by the final thickness obtained in the hot plate procedure. The trimmed samples are subjected to a compressive strength test by means of a testing machine. Compressive strengths are placed on a percent deflection basis, in pounds per square inch (psi). The compressive strength at 3% deflection in psi is used as an indicator of the strength of the char in the initial stage of compression.

Materials for Testing

STEPANPOL^® PS-2412 is an aromatic polyester polyol with a nominal hydroxyl value of 240, provided by Stepan Company of Northfield, Illinois. Polyol 1669-82 is an aromatic polyester polyol with a hydroxyl value of 273. It is a reaction product of phthalic anhydride and diethylene glycol, and is used internally by Stepan Company.

Fyrol^® CEF is tris (beta-chloroethyl) phosphate, a flame retardant provided by Akzo Nobel Chemicals, Incorporated of Chicago, Illinois.

Powdered sucrose used as 12X fondant sugar was supplied by Chicago Sweetners, Incorporated of Des Plaines, Illinois.

Molasses used in the Examples was a cane sugar-type purchased from a retail source.

Maltrin® Ml 50 is a maltodextrin having a theoretical average molecular weight of 1200, provided by Grain Processing Corporation of Muscatine, Iowa.

Pel-Cat^® 9540A is potassium 2-ethylhexanoate, a catalyst provided by

Pelron Corporation of McCook, Illinois.

Dabco® TMR is a proprietary catalyst provided by Air Products and Chemicals, Incorporated of Allentown, Pennsylvania.

Polycat^® 41 is N,N%N"-tris(3-dimethylaminopropyl)-s-hexahydrotriazine, a catalyst provided by Air Products and Chemicals, Incorporated.

Niax^® L-6900 is a silicone surfactant provided by Crompton OSi Specialties of South Charleston, West Virginia.

Mondur^® 489 is a polymeric isocyanate provided by Bayer Corporation of Pittsburgh, Pennsylvania.

Test Results

The materials in Table 1 were subjected to the Preliminary Char/Intumescence Test, and the following results were obtained.

Table 1

Polyurethane resins are blended and then mixed with polymeric isocyanate to generate foams. Compositions in parts per hundred parts of polyol (pphp) and reactivity test results are listed in Table 2. For purposes of calculating index, it is assumed that the sugar or carbohydrate is present in particulate form, so that only the hydroxyl groups on the surface are available for reaction. It is further assumed that such hydroxyl groups will consume only a very small proportion of the available isocyanate groups, and can therefore be neglected in index calculations. Water added to the formulations is accounted for in the index calculations, as explained above.

Table 2 Formulations and Reactivities

Example 5 Example 6 Example 7 Example 8 Example 9 Example 10

Composition (pphp): (comparative) (invention) (invention) (invention) (invention) (invention)

STEPANPOL^® PS-2412 100.00 100.00 100.00 100.00 100.00 100.00

Fyrol^® CEF 7.50 7.90 7.60 7.70 9.47 9.92

Powdered sugar (sucrose) 15.00 3.60 91.78 94.29

Molasses 2.50

Dispersion of Example 16

Maltrin^® M150

Pelcat^® 9540A 4.70 5.65 5.00 6.80 4.65 6.46

Dabco^®TMR

Polycat^® 41 0.20 0.20 0.20 0.20 0.14 0.15

Max^® L-6900 3.00 3.00 3.00 3.00 2.93 2.93

Water 0.50 0.50 0.50 0.50 0.50 0.50 n-pentane 25.70 25.30 26.00 29.00 25.65 36.27

Total resin 141.60 157.55 145.90 149.20 235.12 250.53

Mondur^® 489 213.53 216.60 214.50 220.31 211.74 217.96

Isocyanate index 300 300 300 300 300 300

% Sugars and other 4.0 1.0 0.4* 20.5 20.1 carbohydrates in foam mix % Fyrol CEF in foam mix 2.11 2.11 2.08 2.08 2.12 2.12 Reactivity and density (20° C):

Cream time (sec) 16 17 15 19 16 13

Gel time (sec) 43 45 46 48 68 54

Density (pcf) 1.74 1.79 1.61 1.65 2.42 1.75

*Estimated from typical composition of cane molasses.

Table 2, continued.

Example Example Example

11 Example 12 13 Example 14 15

Composition (pphp): (invention) (comparative) (invention) (comparative) (invention)

STEPANPOL^® PS-2412 100.00 100.00 100.00 100.00 100.00

Fyrol^® CEF 8.40 9.00 9.25 9.00

Powdered sugar (sucrose) 6.00

Molasses

Dispersion of Example 16 15.20

Maltrin^® M150 1.50**

Pelcat^® 9540A 8.10 4.80 5.50 2.00 2.00

Dabco^®TMR 2.17 2.40

Polycat^® 41 0.20 0.20 0.20 0.39 0.41

Niax^® L-6900 3.00 3.00 3.00 3.00 3.00

Water 1.00** 0.50 0.50 0.50 0.50 n-pentane 25.90 24.65 24.90 24.85 22.80

Total resin 148.10 142.15 149.35 141.91 146.31

Mondur^® 489 247.41 213.85 216.11 212.18 212.96

Isocyanate index 300 300 300 300 300

% Sugars and other carbohydrates 0.4 1.6 1.7 in foam mix

% Fyrol CEF in foam mix 2.12 2.53 2.53 2.54 2.54

Reactivity and density (20° C):

Cream time (sec) 14 17 16 18 18

Gel time (sec) 40 46 44 45 45

Density (pcf) 1.63 1.72 1.70 1.69 1.77

**Maltrin Ml 50 and water pi re-mixed and added as solution.

Sample foams were made with each formulation in Table 2, following the procedures outlined above. Samples were cut from the panels and tested in the 15-minute Hot Plate Test. Test results, including final thickness and char rating, are presented in Table 3. Foams containing sugars typically showed a slight loss in the final thickness, but improved char rating. For example, the final thickness for Example 5 was measured at 1.36 in., and for Example 6, at 1.28 in. The char produced by the foam from Example 5 was typical of that obtained with formulations currently used in commercial production, with numerous small internal splits of a somewhat flattened shape, roughly parallel to the 4 x 4 inch faces of the sample. The char produced by the foam from Example 6 had a considerably finer texture, with shorter and more rounded voids, and a more continuous appearance in the solid portion of the char. Small flattened internal splits, although present, were seen in a smaller proportion of the cross-sectional area of the sample, and, on the average, were shorter in length than in the case of Example 5.

Table 3

15-Minute Hot Plate Test Results

% Sugars

Foam and Other Final

Formul Carbohydrates in Thickn Char ation Foam Mix ess (in.) Rating

Exampl 0 1.36 5 e 5

Exampl 4 1.28 3 e 6

Exampl 1 1.32 4 e 7

Exampl 0.4 (est.) 1.22 4 e 8

Exampl 20.5 1.60 3 e 9

Exampl 20.1 0.86 3 e lO

Exampl 0.4 1.22 3 e l l

Exampl 0 1.40 6 e 12

Exampl 1.6 1.35 4 e l3

Exampl 0 1.47 5 e l4

Exampl 1.7 1.36 3 e l5

Samples from Examples 5, 6 and 8, which had been subjected to the

15-minute Hot Plate Test, were then subjected to the char compressive strength test. Increased char strength of the sugar-containing foams, compared with a foam without sugar added, is indicated by the results of Table 4 below.

Table 4

Char Compressive Strength Test Results

Char Compressive

% Sugars Strength (psi, average, 3%

Foam in Foam Mix deflection)

Formulation

Example 5 0 0.52

Example 6 4% sucrose 0.83

Example 8 0.4% total 0.82 sugars (estimated; 0.68%) molasses)

Additionally, the 30-Second Hot Plate Test was carried out to compare resistance to cracking under high-temperature conditions on Examples 12 and 13. The results of that test (Table 5) indicate that sugar in the foam reduces cracking.

Table 5

30-Second Hot Plate Test Results Foam % Sugars Average

Formulation in Foam Mix Total Crack Length

Example 0 4.5 12

Example 1.6% 1.7 13 sucrose

Further contemplated formulations and test results of the present invention are illustrated in Examples 16-21 below.

Example 16

599 g of Fyrol CEF and 400 g of powdered sucrose were combined and mixed for 1 minute with a stirrer equipped with a double 2-inch disk-type blade rotating at 3600 rpm. 1 g of Pelcat 9540 A was added, and the mixture was stirred 1 minute additional. A smooth viscous white dispersion was obtained. Viscosity at 25° C was 9,070 cP (Brookfield Viscometer, Small Sample Adapter, spindle no. 31, 3 rpm).

The dispersion of Example 16 was used in the foam formulation of Example 15, and produced the same effects on char structure as direct addition of powdered sugar to the resin formulation.

Example 17

550 g of Fyrol CEF and 450 g of powdered sucrose were combined and mixed as in Example 16. After 3 days the dispersion exhibited a trace of clear liquid at the top. At 13 days the clear layer at the top occupied 8% of the total sample volume, and when the dispersion was poured out of the container, caked semi-solid material was observed at the bottom. Observations on Example 17 indicate that such a dispersion can be premixed and held in storage on a short-term basis, but if stored for longer periods may begin to cake at the bottom and present handling difficulties when transferred to the resin formulation.

Example 18

550 g of Fyrol CEF and 450 g of powdered sucrose were combined and mixed for 1 minute as in Example 16. 2.5 g of Pelcat 9540A was added, and the mixture was stirred 1 minute additional. After 13 days, the dispersion was examined for separation. It exhibited a trace of clear liquid at the top, and no caked material at the bottom.

Observations on Example 18 demonstrate that the physical stability of a sugar/flame retardant dispersion can be improved by the addition of a stabilizing agent, improving handling properties.

Example 19

240 g of Fyrol CEF, 360 g of Polyol 1669-82, and 400 g of powdered sucrose were combined and mixed for 2 minutes as in Example 16. A smooth viscous white dispersion was obtained. After 14 days a sample of the dispersion exhibited 1% clear liquid at the top, and no caked material at the bottom. After 21 days a second sample had 11% clear liquid at the top, and caked material at the bottom indicative of settling of the sucrose.

Example 19 indicates that a dispersion of a sugar in a combination of flame retardant and polyol can also be premixed and held in storage on a short-term basis without undergoing excessive separation. Example 20

240 g of Fyrol CEF, 360 g of Polyol 1669-82, and 400 g of powdered sucrose were combined and mixed for 1 minute as in Example 16. 0.5 g of Pelcat 9540A was added, and the mixture was stirred 1 minute additional. After 14 days a sample of the dispersion exhibited a trace of clear liquid at the top, and no caked material at the bottom. After 21 days a second sample had 1% clear liquid at the top, and no caked material at the bottom.

Observations on Example 20 demonstrate that, in this type of dispersion also, the physical stability can be improved by the addition of a stabilizing agent, improving handling properties.

Example 21

600 g of Polyol 1669-82 and 400 g of powdered sucrose were combined and mixed for 1 minute as in Example 16. A smooth viscous white dispersion was obtained. After 7 days, the dispersion showed no separation.

Example 21 indicates that a dispersion of a sugar in a polyol can be premixed and held in storage on a short-term basis without undergoing excessive separation.

All documents (e.g., patents and journal articles) cited above are hereby incorporated by reference in their entirety.

Claims

1. A rigid polyisocyanurate foam comprising the reaction product of : an aromatic polyester polyol or blend thereof having an average functionality of less than about 3.0; a polyisocyanate sufficient in amount to yield an NCO/OH index of at least about 200; a sugar or carbohydrate having a molecular weight of less than about 2000; and a blowing agent.

2. The rigid polyisocyanurate foam of claim 1, wherein the blowing agent is a hydrocarbon or hydrofluorocarbon blowing agent.

3. A method of making a rigid polyisocyanurate foam comprising the step of combining a polyisocyanate, an aromatic polyester polyol or blend thereof having an average functionality of less than about 3.0, a sugar or carbohydrate having a molecular weight of less than about 2000, and a blowing agent, wherein the reactant composition has an NCO/OH index of at least about 200.

4. The method of claim 3, wherein the blowing agent is a hydrocarbon or hydrofluorocarbon blowing agent.

5. A rigid polyisocyanurate foam having improved thermal stability comprising at least 0.1 weight percent of a sugar or carbohydrate, having a molecular weight of less than about 2000, in said foam.

6. A dispersion consisting essentially of: a sugar or carbohydrate having a molecular weight of less than about 2000; and an aromatic polyester polyol or blend thereof having an average functionality of less than 3.0; wherein the water content of said dispersion is less than about 5% by weight.

7. The dispersion of claim 6, wherein said dispersion further includes a stabilizer.

8. The dispersion of claim 7, wherein the stabilizer comprises a potassium salt of a carboxylic acid.

9. The dispersion of claim 7, wherein the stabilizer comprises an organic or inorganic gelling or rheology-control agent.

10. A dispersion consisting essentially of: a sugar or carbohydrate having a molecular weight of less than about 2000; and a liquid flame retardant ; wherein the water content of said dispersion is less than about 5% by weight.

11. The dispersion of claim 10, wherein said flame retardant is a liquid halogenated flame retardant.

12. The dispersion of claim 10, wherein said dispersion further includes a stabilizer.

13. The dispersion of claim 12, wherein said stabilizer comprises a potassium salt of a carboxylic acid.

14. The dispersion of claim 12, wherein said stabilizer comprises an organic or inorganic gelling or rheology-control agent.

15. A dispersion consisting essentially of: a sugar or carbohydrate having a molecular weight of less than about 2000; a flame retardant; and an aromatic polyester polyol or blend thereof having a functionality of less than about 3.0; wherein the water content of said dispersion is less than about 5% by weight.

16. The dispersion of claim 15, wherein said flame retardant is a liquid flame retardant.

17. The dispersion of claim 16, wherein said liquid flame retardant is a halogenated liquid flame retardant.

18. The dispersion of claim 15, wherein said dispersion further includes a stabilizer.

19. The dispersion of claim 18, wherein said stabilizer comprises a potassium salt of a carboxylic acid.

20. The dispersion of claim 18, wherein said stabilizer comprises an organic or inorganic gelling or rheology-control agent.

21. A foam producing composition comprising: an aromatic polyester polyol or blend thereof having an average functionality of less than about 3.0; a polyisocyanate sufficient in amount to yield an NCO/OH index of at least about 200; a sugar or carbohydrate having a molecular weight of less than about 2000; and a blowing agent.

22. The foam producing composition of claim 21, wherein the blowing agent is a hydrocarbon or hydrofluorocarbon blowing agent.

23. The foam producing composition of claim 21, wherein the mixture further comprises a liquid flame retardant.

24. The foam producing composition of claim 23, wherein the liquid flame retardant is a halogenated liquid flame retardant.