WO2007019051A1 - Polyurethanes made from hydroxyl-containing esters of fatty acids - Google Patents

Abstract

Hydroxy Ester-Substituted Fatty Acid Esters, (HESFAEs) are useful polyols for use in polyurethane formulations, and rigid polyurethane foam formulations in particular. The HESFAE is conveniently prepared from an epoxidized fatty acid ester and a hydroxyl acid.

Description

This application claims benefit of United States Provisional Patent Application No. 60/705,248, filed 3 August 2005.

This invention relates to polyurethane polymers and methods for making such polymers.

Polyurethanes are produced by the reaction of polyisocyanates and polyols.

One type of polyurethane, rigid polyurethane foam, is widely used in thermal insulation and structural applications. The starting materials used to make these rigid polyurethane foams tend to be low equivalent weight, high functionality polyols and high functionality polyisocyanates, as these materials provide a densely crosslinked polymeric structure. The polyols are most typically polyethers and polyesters that are derived from petroleum feedstocks. Rigid polyurethane foams have been made with castor oil or castor oil byproducts.

Polyols for rigid foam applications must meet several demands. They need to prpvide the needed crosslinking to the polymer structure and to form a foam having the necessary mechanical attributes. The polyols must react with the other components in the formulation to form a foam having a fine, uniform and closed-cell structure. This is especially the case when the foam is used in thermal insulating applications. To accomplish this, the polyols must be reasonably compatible with the other components in the formulation, in particular water and the polyisocyanate. It is especially desirable that the polyol can be used with readily available surfactants and catalyst packages. The polyols should be reactive enough that the foam rises and cures quickly without the need for very high levels of catalysts, while still providing for good processing and yielding a high-quality foam.

Because of unpredictable crude oil pricing and a growing desire to find alternative feedstocks for making commodity chemicals, there is an interest in replacing conventional polyols with newer materials that are made using renewable feedstocks such as vegetable oils or animal fats.

One approach to creating vegetable oil-based polyols is described in EP 0 106 491A2. Certain fatty acid mixtures are hydroxymethylated, and esters are formed by reacting the hydroxymethylated material with a polyhydroxyl initiator. More recently, higher functionality versions of these materials have been developed, as described in WO jj,wAJyκ>,ρρzΑ,,,axι ,|.Q4 β.9.6 .83 . ese po yo s are escr e as being usefu n

(P IL I .■•'' Oa! Ui Ib / icB cir ¹W flexible foam and other elastomeric polyurethane applications.

Amides of hydroxymethylated fatty acids with alkanolamines have been described for use in making rigid polyurethane foam. See Khoe et al., "Polyurethane Foams from Hydroxymethylated Fatty Diethanolamides", J. Amer. Oil Chemists' Society 50:331-333 (1973). The foam described therein was made using Freon 11 as a blowing agent. Khoe et al. report that in such a formulation, the amide compound produced foam with inadequate dimensional stability when used as the sole polyol.

Other vegetable oil-based polyols are described in GB 1,248,919. These polyols are prepared in the reaction of a vegetable oil with an alkanolamine (such as triethanolamine) to form a mixture of monoglycerides, diglycerides and reaction products of the alkanolamine and fatty acid groups from the vegetable oil. These materials have free hydroxyl groups on the glycerine and alkanolamine portions of the molecules. The free hydroxyl groups are ethoxylated to increase reactivity and to provide a somewhat more hydrophilic character. That makes the product more compatible with a foam formulation containing water as a blowing agent. These products tend to have hydroxyl numbers in the range of 185-200 (which corresponds to a hydroxyl equivalent weight in the range of about 280-305) and a functionality of about 2.3. The equivalent weights tend to be higher than desired and the functionalities are lower than needed for producing good quality rigid polyurethane foam.

It would desirable to provide a polyol that is based on annually renewable feedstocks such as vegetable oils, and which can be used to make good quality rigid polyurethane foams. It would be desirable to provide a polyurethane foam that is made using a significant proportion of raw materials derived from an annually renewable feedstock.

In one aspect, this invention is a hydroxyl-containing fatty acid ester having at least one hydroxy-functional ester group having up to about 10 carbon atoms pendant from a fatty acid chain. For convenience, such materials are referred to herein as Hydroxy Ester-Substituted Fatty Acid Esters, or HESFAEs. The HESFAEs contain at least two different types of ester groups. One type of ester group corresponds to the reaction product of the carboxylic acid group of a fatty acid with a compound having two or more hydroxyl groups. The second type of ester group is pendant from the fatty acid chain, being bonded to the fatty acid chain through the — O— atom of the ester gr u ,, „ iue.yGn a.nt ester ,_<grqup. l& convenien y orme y epoxi izmg tiαe fatty aci f »" LI Il ^"/" U ¹H O 11» ./ t& i» ibis J ^{' 1}W (at the site of carbon-carbon unsaturation in the fatty acid chain), followed by reaction with a hydroxy acid or hydroxy acid precursor. The pendant ester group includes at least one free hydroxyl group. This invention is also a method for preparing a HESFAE, comprising reacting an ester of an epoxidized fatty acid with a hydroxy acid or hydroxy acid precursor, the hydroxy acid or hydroxyl acid precursor containing up to about 10 carbon atoms, under conditions such that the hydroxy acid or hydroxy acid precursor reacts with at least one epoxide group to form at least one hydroxyl-containing ester group pendant from the fatty acid portion of the ester.

In another aspect, this invention is a polyurethane formed by mixing a polyol composition containing an HESFAE with an organic polyisocyanate and subjecting the resulting mixture to conditions sufficient to cause the HESFAE and the polyisocyanate to react and cure to form a polyurethane polymer. In still another aspect, this invention is a process for preparing a rigid polyurethane foam, comprising

(a) forming a reaction mixture by mixing a polyol or mixture thereof with a polyisocyanate compound in the presence of a blowing agent and a surfactant, wherein the polyol or mixture thereof has an average hydroxyl equivalent weight of from 100 to 350 and an average hydroxyl functionality of at least 2.5, and further wherein the polyol or polyol mixture includes at least one HESFAE; and

(b) subjecting the reaction mixture to conditions such that it cures and expands to form a rigid polyurethane foam.

In another aspect, the invention is a rigid polyurethane foam made by such a process.

In making a polyurethane in accordance with the invention, a polyol or polyol mixture is reacted with an organic polyisocyanate. In embodiments of particular interest, the polyurethane is a rigid foam and the polyol or polyol mixture has an average hydroxyl equivalent weight of from 100 to 350, preferably from 100 to 250 and especially from 110 to 150. "Hydroxyl equivalent weight" is the molecular weight per hydroxyl group contained in the polyol or polyol mixture, as the case may be. In the case of a polyol mixture, the determination of hydroxyl equivalent weight takes into account all isocyanate -re active materials except for water, but does not include catalysts, surfactants, blowing agents or other non-isocyanate-reactive materials. For . . . ngiα ,jpψn apjmcaliQns,, ,me polypi or polyol mixture contains one or more polyols that

1"¹ML. Ii / yf at IUl Ia / \ψ£ H ifcj J ¹Mt in the aggregate have an average hydroxyl functionality of at least 2.5, especially from 2.8 to 6 and most preferably from 3.0 to 4.5.

At least one polyol used in making the rigid foam is an HESFAE. The HESFAE is characterized in being a fatty acid ester that contains one or more fatty acid chains. At least a portion of the fatty acid chains are substituted with at least one pendant hydroxyl-containing ester group having from 2 to 10 carbon atoms. The HESFAE advantageously has a hydroxyl functionality of at least 2.0, preferably from about 2.0 to about 6.0, and more preferably from about 2.5 to about 4.0. The hydroxyl equivalent weight of the HESFAE is advantageously from about 60 to about 250, especially from about 75 to about 150 and most preferably from about 75 to about 125. The HESFAE is conveniently prepared in the reaction of an epoxidized fatty acid ester with a hydroxy acid or a hydroxy acid precursor. As described more below, the hydroxy acid may contain more than one hydroxyl group. The fatty acid ester starting material can be described as the reaction product of at least one epoxidized fatty acid with a compound having multiple hydroxyl groups. The fatty acid ester starting material will in many cases contain multiple fatty acid chains, which are not necessarily all the same, and which are not necessarily all epoxidized. It is preferred that at least 50%, such as from 50 to 100% or from 70 to 95%, of the fatty acid groups in the fatty acid ester starting materials contain at least one epoxide group. It is also possible that any particular fatty acid group on the starting ester molecule contains multiple epoxide groups. The number of epoxy groups/fatty acid group and the proportion of fatty acid chains containing epoxy groups each affect the hydroxyl functionality of the HESFAE. Therefore, these represent parameters which can be manipulated to achieve a desirable hydroxyl functionality and equivalent weight for particular applications.

The epoxidized fatty acid ester starting material may be an animal fat or vegetable oil that has been treated to form epoxide groups at the site(s) of carbon- carbon unsaturation in the fatty acid chain(s). The epoxidized vegetable oils and animal fats are typically mixtures of mono-, di- and triglycerides containing mainly triglyceride materials. Examples of suitable fats and oils which can be so epoxidized include those having constituent fatty acids that have from 1 to 3 preferably non- conjugated carbon-carbon double bonds in the fatty acid chain. Examples of these include, for example, chicken fat, canola oil, citrus seed oil, cocoa butter, corn oil, . , .. _A cotxonseeα oμ, jari. linseed a.il_rpa.t oil, olive oil, palm oil, peanut oil, rapeseed oil, rice

IK C If^" /^' Cl S Ob' / I= o ^β •>•' ^■* bran oil, safflower oil, sesame oil, soybean oil, sunflower oil, or beef tallow. Fats and oils having a high proportion of unsaturated constituent fatty acids are preferred. These materials can be epoxidized by treatment with a peracid, perester or peroxide (such as hydrogen peroxide). General methods for epoxidizing olefins such as fatty acids and vegetable oils are described, for example, by Hudlicky, Oxidations in Organic Chemistry, ACS Monograph 186, American Chemical Society (1990). Epoxidized vegetable oils, in particular epoxidized soybean oil, are readily available as commercial products. The epoxidized soybean oils are a preferred class of starting materials on the basis of availability and cost.

Other epoxidized fatty acid ester starting materials are conveniently prepared from animal fats or vegetable oils. In one approach, an epoxidized fat or oil as just described is reacted with an additional polyol compound under transesterification conditions. Suitable conditions include the use of an elevated temperature (such as from 70 to 180⁰C) and the use of a transesterification catalyst such as a Lewis acid, and in particular tin and/or titanium compounds. The resulting product is a mixture of glycerides (mainly mono- or diglycerides possibly containing a small amount of triglycerides) and esters of the fatty acid groups with the additional polyol compound. It is possible that glycerine can be used as the additional polyol compound, in which case the effect of the reaction is to produce a product mixture containing mainly mono- and diglycerides. In another approach, the animal fat or vegetable oil is reacted with the additional polyol compound prior to epoxidation, and the resulting mixture of ester compounds is then epoxidized. In either of these approaches, the fatty acid portions of the resulting ester products will reflect the fatty acid composition of the starting animal fat or vegetable oil.

Both of the just-mentioned approaches permit a tailoring of product equivalent weight and the possibility of increasing or tailoring the hydroxyl functionality by introducing hydroxyl groups through selection of the additional polyol compound. The reaction of the ester starting material with additional polyol usually will increase the hydroxyl functionality of the HESFAE and reduce hydroxyl equivalent weight because free (unreacted) hydroxyl groups are introduced with the additional polyol compound. The amount and type of additional polyol compound therefore can be selected to optimize the hydroxyl functionality and/or equivalent weight for specific applications. . - _{• o} __{. o}

,,.„. ,,,,P, ;iμae,, additional .polyQLxQmnpund may contain from 2 to 8 or more hydroxyl

IH IL- l( / U & U 1» ,/ BB O .,»' "all groups/molecule. It preferably contains from 2 to 4 and especially from 3 to 4 hydroxyl groups/molecule. Mixtures of additional polyol compounds can be used, in which case the average functionality of the mixture is advantageously within the aforementioned ranges. The hydroxyl equivalent weight of the additional polyol compound is preferably less than 150 and especially less than 75. Examples of suitable polyol compounds include glycerine, trimethylolpropane, ethylene glycol, propylene glycol, 1,4-butane diol, polymers of propylene glycol and/or ethylene glycol, pentaerythritol, sorbitol, sucrose, triethanolamine, trϋsopropanolamine, cyclohexane dimethanol, and the like. Alkoxylates of any of the foregoing, such as an ethoxylate and/or propoxylate, can be used.

All of the hydroxyl groups of the additional polyol compound, or some portion thereof, may be esterified with a fatty acid group, provided that at least one hydroxyl group/molecule is esterified, on average. Typically, less than all of the hydroxyl groups of the additional polyol compound will become esterified.

It is also within the scope of the invention to use a single fatty acid (or defined mixture of fatty acids) as a starting material. The single fatty acid or defined mixture is epoxidized and reacted with the additional polyol compound (in either order) to form the epoxidized ester starting material, in a manner analogous to that already described.

The epoxidized fatty acid ester starting material is reacted with a hydroxy acid compound or precursor thereto to introduce pendant hydroxyl-containing ester groups.

A "hydroxy acid" is a compound having a carboxylic acid group and one or more hydroxyl groups. The hydroxyl group(s) may be on a carbon atom adjacent to the carbonyl carbon of the carboxylic acid group, or may be separated from the carbonyl carbon by two or more carbon atoms, such as from 2 to 8, especially from 2 to 4 carbon atoms. Examples of suitable hydroxy acids include lactic acid, glycolic acid and 2,2- dimethylolpropionic acid, and linear dimers or higher oligomers thereof.

Hydroxy acid precursors are materials that can react or decompose to generate a hydroxy acid. Precursors of particular interest are cyclic oligomers, particularly cyclic ester-containing dimers, of one or more hydroxy acids. These cyclic oligomers can react with water to generate the hydroxy acid. Examples of such oligomers include lactide, glycolide and the like. _r,,,_/l'ne,Λyclrpxy_fracid, reacts with epoxide groups on the epoxidized fatty acid ester to form a pendant ester group that contains one or more hydroxyl groups (corresponding to the number of hydroxyl groups on the hydroxy acid or precursor). The pendant ester group contains up to about 10 carbon atoms. It preferably contains from 2 to 6 carbon atoms and most preferably contains from 3 to 4 carbon atoms. The polyol of the invention advantageously contains an average of at least one such pendant ester group/molecule, such as from 1 to 4 or from 1.2 to 2.5 such groups/molecule.

The reaction of the epoxidized starting material and the hydroxy acid (or ester) is conveniently performed using an acidic catalyst which favors the reaction at the site of the epoxide group (rather than strongly promoting a transesterification reaction at existing ester groups on the starting material). The esterification reaction is generally conducted at an elevated temperature, such as from 70 to 180⁰C, for a period on the order of minutes to tens of hours. Elevated pressures can be used if desired to maintain the hydroxy acid as a liquid and/or to help drive the reaction. The HESFAE can be represented by the structure

[HO] (_P._X)-R-[O-C(O)-R¹]x

wherein R represents the residue, after removal of hydroxyl groups, of a compound having p hydroxyl groups, R¹ represents the hydrocarbon portion of a fatty acid, and x is a number from 1 to p. p is 2 or more, as discussed before. Each -R-O-C(O)- linkage represents an ester group of the first type discussed above. At least a portion of the R¹ chains are substituted with at least one hydroxyl-containing ester group, which can be represented as

-O-C(O)-R²-OH_y

wherein R² is a hydrocarbyl group that may be inertly substituted, and y is 1 or more, preferably 1 or 2. The bond shown at the left of the structure attaches to a carbon atom of the fatty acid chain. Inert substituents in this context are those which do not interfere with the formation of the HESFAE or its use in making a polyurethane.

Among the inert substituents suitable in this context are ester linkages, such as are formed when a cyclic dianhydride of a hydroxy acid is used as a hydroxy acid precursor. _{^ n r},;.φe .M SJb₄ . is,,use ,AS^axomponent o a po yuret ane- ormmg composition.

IH L. It ,/ UHbi Lit o y irfITbli B ./ ":»

Of particular interest are rigid polyurethane foam applications, polyurethane cast elastomer applications, flexible polyurethane foam applications, and other elastomeric polyurethane applications. The HESFAE may be the sole polyol in a polyurethane- forming composition, or may be used as part of a mixture of such polyols. In general, the polyurethane-forming composition will include the HESFAE, optionally at least one other polyol, and at least one polyisocyanate compound. The composition may contain in addition one or more catalysts, surfactants, crosslinkers, chain extenders, blowing agents, flame retardants, colorants, antioxidants, fillers, reinforcing agents or other useful ingredients. The use of such materials is in general well-known in the polyurethanes field.

It has been found that the HESFAE can be readily used as the sole or primary polyol in a rigid polyurethane foam formulation. Although the HESFAE can provide benefits when it constitutes as little as 10% of the weight of the polyols used in these formulations, increased benefits (in particular the replacement of polyols that are based on non-renewable resources such as petroleum) are seen when the HESFAE constitutes from 50 to 100%, especially from 70 to 100% or from 80 to 100%, of the weight of the polyols in the rigid polyurethane foam formulation.

Rigid polyurethane foam is prepared by forming a polyol component containing the HESFAE, and contacting the polyol component with at least one polyisocyanate compound in the presence of a blowing agent and a surfactant. The resulting reaction mixture is subjected to conditions at which the polyol(s) react with the polyisocyanate and a gas is generated to expand the reacting mixture and form a foam.

Suitable polyols that can be used in conjunction with the HESFAE are compounds having at least two isocyanate-reactive hydroxyl groups per molecule. The functionality of the individual polyols preferably ranges from about 2 to about 12, more preferably from about 2 to about 8. The hydroxyl equivalent weight of the individual polyols may range from about 31 to about 2000 or more. However, the equivalent weight of the polyols is selected in conjunction with that of the HESFAE so the polyol component as a whole has an equivalent weight as described above. Preferably, the hydroxyl equivalent weight of the individual polyols is from about 31 to about 500, more preferably from about 31 to about 250, even more preferably from about 31 to about 200. use n com nat on w t t e HESFAE inclu e

compounds such as alkylene glycols (e.g., ethylene glycol, propylene glycol, 1,4-butane diol, 1,6-hexanediol and the like), glycol ethers (such as diethylene glycol, Methylene glycol, dipropylene glycol, tripropylene glycol and the like), glycerine, trimethylolpropane, tertiary amine-containing polyols such as triethanolamine, triisopropanolamine, and ethylene oxide and/or propylene oxide adducts of ethylene diamine, toluene diamine and the like, polyether polyols, polyester polyols, and the like. Among the suitable polyether polyols are polymers of alkylene oxides such as ethylene oxide, propylene oxide and 1,2-butylene oxide or mixtures of such alkylene oxides. Preferred polyethers are polypropylene oxides or polymers of a mixture of propylene oxide and a small amount (up to about 12 weight percent) ethylene oxide. These preferred polyethers can be capped with up to about 30% by weight ethylene oxide.

Polyester polyols are also suitably used together with the HESFAE in a polyurethane formulation. These polyester polyols include reaction products of polyols, preferably diols, with polycarboxylic acids or their anhydrides, preferably dicarboxylic acids or dicarboxylic acid anhydrides. The polycarboxylic acids or anhydrides may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may be substituted, such as with halogen atoms. The polycarboxylic acids may be unsaturated. Examples of these polycarboxylic acids include succinic acid, adipic acid, terephthalic acid, isophthalic acid, trimellitic anhydride, phthalic anhydride, maleic acid, maleic acid anhydride and fumaric acid. The polyols used in making the polyester polyols preferably have an equivalent weight of about 150 or less, especially 75 or less, and include ethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 2,3- butane diol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol, cyclohexane dimethanol, 2-methyl-l,3-propane diol, glycerine, trimethylol propane, 1,2,6-hexane triol, 1,2,4- butane triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol and the Kke. Polycaprolactone polyols such as those sold by The Dow Chemical Company under the trade name "Tone" are also useful.

Preferred polyols for use in conjunction with the HESFAE in rigid polyurethane foam formulations are alkylene glycols, glycol ethers of up to about 75 equivalent weight, glycerine, trimethylolpropane, triethanolamine, triisopropanolamine, and poly(propylene oxide) polyols of up to about 200 equivalent weight. - ___ _. _. ^„ _ . _{can 36 uge(} oge ₊t ,er w_it t e JtIJUBJt¹AlU inclu e

D' 37 tertiary amine-containing polyols and/or amine-functional compounds. Such tertiary amine-containing polyols include, for example, triisopropanol amine, triethanolamine and ethylene and/or propylene oxide adducts of ethylene diamine, toluene diamine or aminoethylpiperazine having a molecular weight of up to about 800, preferably up to about 400.

Suitable amine-functional compounds have at least two isocyanate-reactive groups, of which at least one is a primary or secondary amine group. Among these are monoethanolamine, diethanolamine, monoisopropanol amine, diisopropanol amine and the like, and aliphatic polyamines such as aminoethylpiperazine. Also included among these compounds are the so-called aminated polyethers in which all or a portion of the hydroxyl groups of a polyether polyol are converted to primary or secondary amine groups. Suitable such aminated polyethers are sold by Huntsman Chemicals u'nder the trade name JEFF AMINE®. Typical conversions of hydroxyl to amine groups for these commercial materials range from 70 to 95%, and thus these commercial products contain some residual hydroxyl groups in addition to the amine groups. Preferred among the aminated polyethers are those having a weight per isocyanate-reactive group of from 100 to 1700, especially from 100 to 250, and having from 2 to 4 isocyanate-reactive groups per molecule. In order to impart toughness to the rigid foam, a minor amount of a high (i.e.

800 or higher, preferably from 1500 to 3000) equivalent weight polyol may be present in the polyol mixture. This high equivalent weight polyol is preferably a polyether polyol having two to three hydroxyl groups per molecule. It more preferably is a poly(propylene oxide) that may be end-capped with up to 30% (by weight of the polyol) of poly(ethylene oxide). The high equivalent weight polyol may contain dispersed polymer particles. These materials are commercially known and are commonly referred to as "polymer polyols" (or, sometimes "copolymer polyols"). The dispersed polymer particles may be, for example, polymers of a vinyl monomer (such as styrene, acrylonitrile or styrene-acrylonitrile particles), polyurea particles or polyurethane particles. Polymer or copolymer polyols containing from about 2 to about 50% or more by weight dispersed polymer particles are suitable. When used, this polymer or copolymer polyol may constitute up to about 45%, preferably from about 5 to about 40%, of the weight of all isocyanate-reactive materials in the polyol component. _Ii /„ (j^am^aDie., , ,,polyis,ocya.nates-₍, .^include aromatic, cycloaliphatic and aliphatic

isocyanates. Exemplary polyisocyanates include m-phenylene diisocyanate, toluene-2- 4-diisocyanate, toluene-2-6-diisocyanate, isophorone diisocyanate, 1,3- and/or 1,4- bis(isocyanatomethyl)cyclohexane (including cis- or trans-isomers of either), hexamethylene-l,6-diisocyanate, tetramethylene-l,4-diisocyanate, cyclohexane-1,4- diisocyanate, hexahydrotoluene diisocyanate, methylene bis(cyclohexaneisocyanate) (H12MDI), naphthylene-l,5-diisocyanate, methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'- biphenyl diisocyanate, 3,3'-dimethyl-4-4'-biphenyl diisocyanate, 3,3'-dimethyldiphenyl methane-4,4'-diisocyanate, 4,4',4"-triphenyl methane trϋsocyanate, a polymethylene polyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and 4,4'- dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate. Preferably the polyisocyanate is diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-dϋsocyanate, PMDI, toluene-2-4-dϋsocyanate, toluene-2-6-diisocyanate or mixtures thereof. Diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate and mixtures thereof are generically referred to as MDI, and all can be used. Toluene-2-4- diisocyanate, toluene-2-6-diisocyanate and mixtures thereof are generically referred to as TDI, and all can be used.

Derivatives of any of the foregoing polyisocyanate groups that contain biuret, urea, carbodiimide, allophonate and/or isocyanurate groups can also be used. These derivatives often have increased isocyanate functionalities and are desirably used when a more highly crosslinked product is desired.

Suitable blowing agents include physical blowing agents such as various low- boiling chlorofluorocarbons, fluorocarbons, hydrocarbons and the like. Fluorocarbons and hydrocarbons having low or zero global warming and ozone-depletion potentials are preferred among the physical blowing agents. Chemical blowing agents that decompose or react under the conditions of the polyurethane-forming reaction are also useful. By far the most preferred chemical blowing agent is water, which reacts with isocyanate groups to liberate carbon dioxide and form urea linkages. Sufficient blowing agent is used to provide the desired foam density. Foam densities in the range from 0.75 to 10 pounds/cubic foot (pcf) (12 to 160 kg/m³), especially about 1 to 2.5 pcf (16 to 40 kg/m³), are generally suitable. If used as the sole blowing agent, water is typically used in amount of from 1 to 7, especially from 1.5 to 5, parts by weight per 100 parts by weight of isocyanate-reactive materials. Water . . _A . may,, «s&ψ ,De_[i ise _|i«in .,.cqm mat^Qil wi a physica owing agent, particularly a

1?" IL* It ->' ¹U' ._m,l! IUI IUI ,/ IC, β iCir J .β fluorocarbon or hydrocarbon blowing agent. In addition, a gas such as carbon dioxide, air, nitrogen or argon may be used as the blowing agent in a frothing process. It is preferred to use at least 1 part of water per 100 parts by weight isocyanate -re active materials (exclusive of water), particularly when the HESFAE constitutes 70% or more of the weight of the isocyanate-reactive materials used in the rigid foam formulation.

A wide variety of silicone surfactants as are commonly used in making polyurethane foams can be used in making the foams in accordance with this invention. Examples of such silicone surfactants are commercially available under the tradenames Tegostab™ (Th. Goldschmidt and Co.), Niax™ (GE OSi Silicones) and Dabco™ (Air Products and Chemicals).

The reaction mixture may contain a wide variety of other additives as are conventionally used in making polyurethanes of various types. These include, for example, catalysts, blowing agents, surfactants, cell openers; fillers such as calcium carbonate; pigments and/or colorants such as titanium dioxide, iron oxide, chromium oxide, azo/diazo dyes, phthalocyanines, dioxazines and carbon black; reinforcing agents such as fiber glass, carbon fibers, flaked glass, mica, talc and the like; biocides; preservatives; antioxidants; flame retardants; and the like. Catalysts are particularly preferred additives, as are blowing agents and surfactants in cases where a cellular polyurethane is desired.

The selection of a particular catalyst package will vary somewhat with the particular application, the particular polyol or polyols that are used, and the other ingredients in the formulation. The catalyst may catalyze the "gelling" reaction between the polyol(s) and the polyisocyanate and/or, in many polyurethane foam formulation(s), the water/polyisocyanate (blowing) reaction which generates urea linkages and free carbon dioxide to expand the foam.

A wide variety of materials are known to catalyze polyurethane forming reactions, including tertiary amines, tertiary phosphines, various metal chelates, acid metal salts, strong bases, various metal alcoholates and phenolates and metal salts of organic acids. Catalysts of most importance are tertiary amine catalysts and organotin catalysts. Examples of tertiary amine catalysts include trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, N, N-dimethylethanolamine, N, N, N', N' -tetramethyl- 1 , 4-butane diamine, N, N- is(<ϋmethylaminoethyl)et er,

triethylenediamine and dimethylalkylamines where the alkyl group contains from 4 to 18 carbon atoms. Mixtures of these tertiary amine catalysts are often used. Examples of suitably commercially available surfactants include Niax™ Al (bis(dimethylaminoethyl)ether in propylene glycol available from GE OSi Silicones), Niax™ B9 (N,N-dimethylpiperazine and N-N-dimethylhexadecylamine in a polyalkylene oxide polyol, available from GE OSi Silicones), Dabco™ 8264 (a mixture of bis(dimethylaminoethyl)ether, triethylenediamine and dimethylhydroxyethyl amine in dipropylene glycol, available from Air Products and Chemicals), and Dabco™ 33LV (triethylene diamine in dipropylene glycol, available from Air Products and Chemicals), Niax™ A-400 (a proprietary tertiary amine/carboxylic salt and bis (2- dimethylaminoethy)ether in water and a proprietary hydroxy! compound, available from GE OSi Silicones); Niax™ A-300 (a proprietary tertiary amine/carboxylic salt and triethylenediamine in water, available from GE OSi Specialties Co.); Polycat™ 58 (a proprietary amine catalyst available from Air Products and Chemicals), Polycat™ 5 (pentamethyl diethylene triamine, available from Air Products and Chemicals) and Polycat™ 8 (N,N-dimethyl cyclohexylamine, available from Air Products and Chemicals).

Examples of organotin catalysts are stannic chloride, stannous chloride, stannous octoate, stannous oleate, dimethyltin dilaurate, dibutyltin dilaurate, other organotin compounds of the formula SnR_n(OR)4-n, wherein R is alkyl or aryl and n is from 0 to 2, and the like. Commercially available organotin catalysts of interest include Dabco™ T-9 and T-95 catalysts (both stannous octoate compositions available from Air Products and Chemicals). Catalysts are typically used in small amounts, for example, each catalyst being employed from about 0.0015 to about 5% by weight of the high equivalent weight polyol.

A polyurethane is formed by bringing the components of the reaction mixture together under conditions that they react and form a polyurethane polymer. These reactions usually occur spontaneously upon mixing the polyisocyanate with the polyol component at room temperature or an elevated temperature. Accordingly, no special conditions are needed in most cases to form a polyurethane foam having good properties. The amount of polyisocyanate used is sufficient to provide an isocyanate index, i.e., 100 times the ratio of NCO groups to isocyanate-reactive groups in the

y water use as a ow ng agent , o from 85 to 300, especially from 95 to 150 and particularly from 110 tolδO. The use of an isocyanate index above about 150 favors the formation of isocyanurate groups in the polymer. The urethane-forming reactions (as well as the water-isocyanate reaction) often proceed well even at room temperature, and are usually exothermic enough to drive the polyurethane-forming reactions nearly to completion.

The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

Example 1: Preparation of 2,2-dimethylolpropane ester of epoxidized soybean oil

401.1 parts of an epoxidized soybean oil (4.38 mmol epoxy/gram, 228.6 g/mol epoxy) and 228.2 parts 2,2-dimethylol propionic acid are stirred together to form a slurry. A solution of tetrabutylphosphonium acetate in methanol is added. The mixture is heated at 80⁰C with stirring under a nitrogen purge. The temperature is then increased to 15O⁰C for 17 hours. A viscous, yellow liquid is obtained. 612.2 parts (96% yield) of the 2-2-dimethylolpropane ester of the epoxidized soybean oil are obtained.

Example 2A: Preparation of lactic acid ester of epoxidized soybean oil

A lactic acid ester of an epoxidized soybean oil is prepared in a manner analogous that described in Example 1, using lactide (the cyclic dianhydride dimer of lactic acid) as the source of lactic acid. In the presence of water, lactide undergoes a ring-opening reaction to form a hydroxyl-containing, linear, ester-containing dimer of lactic acid. That linear dimer contains a free carboxyl group and a free hydroxyl group. The carboxyl group of the linear dimer forms an ester with the epoxide oxygen(s) on the epoxidized soybean.

Example 2B: Preparation of Rigid Polvurethane Foam

A rigid polyurethane foam is prepared from the following foam formulation: a e

^xMixture of pentamethylenediamine, dimethylcyclohexylamine and potassium salt in diethylene glycol, all available from Air Products and Chemicals. ²Niax™ L-6900 silicone surfactant, from GE Silicones. ³Polymeric MDI having an isocyanate functionality of 2.7 and an isocyanate equivalent weight of 134.

All of the foregoing ingredients are stirred together, except for the polyisocyanate. The isocyanate is then mixed in, and the mixture is poured into an open container, where it is allowed to rise and cure at room temperature (i.e., without applied heat). Gel time is determined as the time after mixing in the isocyanate until such time as the mixture forms strings when a metal spatula is touched to it and pulled away. Tack free time is determined as the time after mixing in the isocyanate until such time as the mixture no longer leaves a residue when touched. Free rise density is determined by cutting a 4" X 4" X 4" section from the core of the cured foam, and weighing the section.

The gel time is 104 seconds. The tack free time is 149 seconds. The free rise density of the foam is 1.48 lb/ft³ (~24kg/m³).

For comparison, a foam is made using the same formulation, except a 360-OH number poly(propylene oxide) polyol (Voranol® 360 from Dow Chemical) is used in place of the polyol from Example 2A. The gel time is 36 seconds and the tack time is 56 seconds, indicating a somewhat higher reactivity in this formulation than that of the invention. Density is 1.52 lb/ft³ (~24kg/m³), which is not materially different from that of the foam of the invention.

Claims

' * s s s > a

1. A hydroxyl-containing ester of a fatty acid or mixture of fatty acids, wherein at least a portion of the fatty acids is substituted with at least one pendant hydroxy-functional ester group having up to about 10 carbon atoms.

2. The hydroxyl-containing ester of claim 1, which contains from about 1 to about 4 pendant hydroxyl-functional ester groups/molecule.

3. The hydroxyl-containing ester of claim 2, which contains from about 1.2 to about 2.5 pendant hydroxyl-functional ester groups/molecule.

4. The hydroxyl-containing ester of a fatty acid of claim 3, wherein the pendant hydroxyl-functional ester group is the reaction product of lactic acid, glycolic or 2,2-dimethylolpropionic acid with an epoxide group on a fatty acid group.

5. A method for preparing a hydroxyl-containing ester of claim 1, comprising contacting an epoxidized fatty acid ester with a hydroxy acid or hydroxy acid precursor, the hydroxy acid or hydroxy acid precursor containing up to about 10 carbon atoms, under conditions such that the hydroxy acid or hydroxyl acid precursor reacts with at least one epoxide group on the epoxidized fatty acid ester to form a hydroxyl-substituted ester group pendant from the fatty acid ester.

6. The method of claim 5 wherein the hydroxy acid is lactic acid, glycolic acid or 2,2-dimethylolproprionic acid.

7. The method of claim 6 wherein the epoxidized fatty acid ester is an epoxidized vegetable oil or animal fat.

8. The method of claim 7 wherein the epoxidized fatty acid ester is an epoxidized soybean oil.

P w erein e epoxi ize ra y aci es er is e

transesterification product of an epoxidized vegetable oil or animal fat with at least one additional polyol compound.

10. The method of claim 5 wherein the epoxidized fatty acid ester is formed by epoxidizing a transesterification product of a vegetable oil or animal fat and at least one additional polyol compound.

11. A polyurethane formed by mixing a polyol composition containing an hydroxyl-containing ester of claim 1 with an organic polyisocyanate and subjecting the resulting mixture to conditions sufficient to cause the hydroxyl-containing ester and the polyisocyanate to react and cure to form a polyurethane polymer.

12. A polyurethane formed by mixing a polyol composition containing an hydroxyl-containing ester of claim 2 with an organic polyisocyanate and subjecting the resulting mixture to conditions sufficient to cause the hydroxyl-containing ester and the polyisocyanate to react and cure to form a polyurethane polymer.

13. A polyurethane formed by mixing a polyol composition containing an hydroxyl-containing ester of claim 3 with an organic polyisocyanate and subjecting the resulting mixture to conditions sufficient to cause the hydroxyl-containing ester and the polyisocyanate to react and cure to form a polyurethane polymer.

14. A polyurethane formed by mixing a polyol composition containing an hydroxyl-containing ester of claim 4 with an organic polyisocyanate and subjecting the resulting mixture to conditions sufficient to cause the hydroxyl-containing ester and the polyisocyanate to react and cure to form a polyurethane polymer.

15. A process for preparing a rigid polyurethane foam, comprising (a) forming a reaction mixture by mixing a polyol or mixture thereof with a polyisocyanate compound in the presence of a blowing agent and a surfactant, wherein the polyol or mixture thereof has an average hydroxyl equivalent weight of from 100 to 350 and an average hydroxyl functionality of at least 2.5, and further wherein the polyol or polyol mixture includes at least one hydroxyl-containing ester of claim 1; and )_rsμDjectongι;_!;tJae|i:rea qαMπiϊS! sαfe o con i ions suc a i cures an expan s o form a rigid polyurethane foam.

16. A process for preparing a rigid polyurethane foam, comprising (a) forming a reaction mixture by mixing a polyol or mixture thereof with a polyisocyanate compound in the presence of a blowing agent and a surfactant, wherein the polyol or mixture thereof has an average hydroxyl equivalent weight of from 100 to 350 and an average hydroxyl functionality of at least 2.5, and further wherein the polyol or polyol mixture includes at least one hydroxyl-containing ester of claim 2; and (b) subjecting the reaction mixture to conditions such that it cures and expands to form a rigid polyurethane foam.

17. A process for preparing a rigid polyurethane foam, comprising

(a) forming a reaction mixture by mixing a polyol or mixture thereof with a polyisocyanate compound in the presence of a blowing agent and a surfactant, wherein the polyol or mixture thereof has an average hydroxyl equivalent weight of from 100 to 350 and an average hydroxyl functionality of at least 2.5, and further wherein the polyol or polyol mixture includes at least one hydroxyl-containing ester of claim 3; and

(b) subjecting the reaction mixture to conditions such that it cures and expands to form a rigid polyurethane foam.

18. A process for preparing a rigid polyurethane foam, comprising

(a) forming a reaction mixture by mixing a polyol or mixture thereof with a polyisocyanate compound in the presence of a blowing agent and a surfactant, wherein the polyol or mixture thereof has an average hydroxyl equivalent weight of from 100 to 350 and an average hydroxyl functionality of at least 2.5, and further wherein the polyol or polyol mixture includes at least one hydroxyl-containing ester of claim 4; and

(b) subjecting the reaction mixture to conditions such that it cures and expands to form a rigid polyurethane foam.

19. A polyurethane made by the process of claim 15.

20. A rigid polyurethane foam made by the process of claim 15.