CA1139049A - Use of low molecular weight polyhydroxy compounds in methylene chloride blown polyurethane foams - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The use of methylene chloride as a blowing agent for resinous foams, particularly urethane foams is improved by incorporating a low molecular weight poly-hydroxy aliphatic compound having more than two hydroxyl groups. Simultaneously with the addition, the amount of gelling catalyst (e.g., stannous octoate) required to obtain very soft foams, is reduced over that required using the methylene chloride without the polyhydroxy com-pound. When the polyhydroxy compound is used, smaller amounts of the gelling catalyst are employed for equal foam properties when the fluorinated halocarbons are employed either alone or in combination with the methyl-ene chloride.

Description

USE OF LOW MOLECULAR WEIG~
POLYHYDROXY COMPOUNDS IN M:ETHYLENE
C~ILORIDE BLOWN POLYURETHAN$ FOAMS

In recent months the conventional blowing agents, the fluorocarbons, e.g., fluorotrichloromethane, have come under attack from environmentalists. The ure-thane foam industry, which has had very good results using these agents, has had to use other blowing agents to replace all or part of the conventional fluorocarbons.
The logical choice was methylene chlorlde, a blowing agent which has been used by industry on a selective basis a-t lower concentrations in the past. The urethane foam industry found that methylene chloride was not a suitable blowing agent at higher concentrations because it required excessive amounks of gelation catalysts to ix the urethane in its risen or foam state prior to final cure, and these increased amounts of gelation catalyst reduced processing flexibility. The practice today is to use a co-blowing agent with the methylene chloride, or to use large amounts of the gelling cata-lyst. As a result, the industry has used the methylene chloride sparingly.

28,037-F -1-The present lnvention is a method for prepar-ing a polyurethane oam by reacting a polyether polyol having a molecular weight of from 800 to 5000, an isocya-nate, water, a metal salt ca-talyst, an amine catalyst, a silicone surfactant and a halogenated hydrocarbon blowing agent, which blowing agent is at least 10 percent methyl-ene chloride, characterized by incorporating with the reactants from 0.1 to 1.5 parts of a polyhydroxy aliphatic compound having more than two hydroxyl groups and a molec-ular weight of not more than 195, while employing from1.4 to 1.6 times the metal salt catalyst of that used where a fluorocarbon is the sole blowing agent.

Surprisingly it has been found that by the incorporation of the polyhydroxy aliphatic compound of the type above-described the foam is pre-set with only slightly more metal salt catalyst than is commonly employed when using a fluorocarbon blowing agent alone.
The proportions of the metal catalysts can vary over almost as wide a range when employing the meth~lene chlo-ride and the polyhydroxy compounds o~ the present inven-tion, and yet obtain a high quality, very soft foam, as when one employs only the fluorocarbons, the standard of the industxy. In addition, the amount of metal cakalyst is reduced by as much as 30 percent over that required to obtain an equivalent foam from a ~ormulation employing methylene chloride, as a replacement for a part or all of the conventional fluorocarbon blowing agents, wi-thout the polyhydroxy compound of the present invention.

The process according to the invention is preferably carried out utlliæing the same components commercially ernployed in the manufacture of polyurethane 28,037-F 2-foams except Eor the s~bstitution oE methylene chlo~i~e for all or apart o~ the conventional 1uorocar~on blo~~
ing agent by the addition of small amounts o~ a poly-hydroxy compound as hereinafter defined. The combination permits the use of less gelation catalyst than previously necessary to obtain a foam, although denser or less soft.
It is to be understood that the optional components o commercial formulations such as fillers, activators, sta-biliziers and pigments may likewise be employed.

The polyol components used are known and are preferably polyethers having molecular weight of from 800 to 5000 and preferably from 2500 to 4500. They can be used in admixture with low molecular weight polyols and with the addition of activators and blowing agents.
Mineral fillers, foam stabilizers, anti-agers and simi-lar additives of the kind normally used in polyurethane chemistry may also be added to the polyols. The poly-ethers suitable for use include those obtained by polym-erizing tetrahydrofuran or epoxides suchas ethylene oxide, propylene oxide, butylene oxide, styrene oxide or epichlorohydrin in the presence of a catalyst such as BF3, or by adding these epoxides in admi~ture or in suc-cession to starter components containing reactive hydro-gen atoms such as water, alcohols or amines. Suitable starter components inclwde ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, trimethylol propane, 4,41_ -dihydroxy dipehnyl propane, aniline, ammonia, ethanol-amine, ethylenediamine and water. Sucrose polyethers of the type described in U.S. Patent 2,927,918 may also be used in accordance with the invention.
In manycases, it is preferred to use polyethers of the type generally known which contain sub-stantial amounts of primary OH groups (up to 90 percent 28,037-F - 3 -,~ , by weight, based on all the OH groups present in the polyether). Polyethers modified with vinyl polymers of the type formed by polymerizing styrene and acrylonitrile in the presence of polyethers are also suitable as are polybutadie~es containing O~ groups.

Instead of using polyethers, it is al~o pos-sible, as is recognized in the polyurethane art, to uti-lize polyesters, polythioethers, polyacetals, polycarbon-ates, polyester amides, or mixtures thereof, having molecular weights in the range from 400 to 10,000 and preferably from 1000 to 6000.

The polyesters containing hydroxyl groups suitable for use include the reaction products of poly-hydric (preferably dihydric and optionally trihydric) alcohols with polyvalent (preferably divalent) carbox-ylic acids. Instead of using the free polycarboxylic acids, it is also possible to use the corresponding poly-carboxylic acid anhydrides or corresponding polycarbox-ylic acid esters of lower alcohols or mixtures thereof for producing the polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or hetero-cyclic and may be substituted (e,g., with halogen atoms) and/or unsaturated. Examples of carboxylic acids and anhydrides of this kind include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexahydro phthalic acid anhydride, tetrachlorophthalic acid anhy-dride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhy-drida, fumaric acid, dimeric and trimeric fatty acids, 28,037-F -4-such as oleic acid, which may be in admixture with mono-meric fatty acids, terephthalic acid dimethyl ester and terephthalic acid bisglycol estar. Examples of suitable polyhydric alcohols include ethylene glycol, 1,2-propyl-ene glycol, 1,3-propylene glycol, 1,4- and 2,3-butylene glycol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, cyclohexane dimethanol (1,4-bis-hydroxy methyl cyclohex-ane), 2-methyl 1,3-propane diol, glycerol, trimethylol pro-pane, 1,2,6-hexane triol, 1,2,4~butane triol, trimethylol ethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycols, dibutylene glycol, and polybutylene glycols. The polyesters may contain some terminal carboxyl groups. It is also possible to use polyesters of lactones such as ~-caprolactone, or hydroxy carboxylic acids such as l~hydroxy caproic acid.

The polythioethers that can be used include the condensation products of thiodiglycol alone or thio-diglycol with other glycols, dicarboxylic acids, formal-dehyde, amino carboxylic acids or amino alcohols. The products can be characterized as polythio mixed ethers, polythioether esters or polythioether es-ter amides, depending upon the components used.

Examples of suitable polyacetals include the compounds obtained from glycols, such as diethylene gly-col, triethylene glycol, 4,4'-dioxethoxydiphenyl dimethyl methane, and hexanediol, and formaldehyde. Polyacetals suitable for use in accordance with the invention can also be obtained by polymerizing cyclic acetals~

28,037-F -5-~6-Suikable polycarbonates containing hydroxyl groups are those of the type which are generally known and which may be obtained by reacting diols, such as 1,3-propanediol, 1,4-butanediol and/or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol, with diaryl carbonates (for example, diphenyl carbonate) or phosgene.

The polyester amidPs and polyamides suitable for use herein include the predominantly linear conden-sates obtained from polyvalent saturated and unsaturatedcarboxylic acids or their anhydrides, and polyvalent saturated and unsaturated amino alcohols, diamines, poly-amines and mixtures thereof.

Polyhydroxyl compounds already containing urethane or urea groups and modified natural polyols, such as castor oil, carbohydrates or starch, may also be used. Addition products of alkylene oxides with phenol-formaldehyde resins or even with urea-formalde-hyde resins may also be used in accordance with the invention.

Examples o the many and varied t~pes of com-pounds suitable for use in accordance with the invention are described in "High Polymers", Vol. XVI; "Polyure-thanPsr Chemistry and Technology", by Saunders-Frisch, Interscience Publishers, New York, London, Vol~ I, 1962, pages 32 to 42 and pages 44 to 54, and Vol. II, 1964, pages 5 to 6 and 198 to 199, and also in Kunststoff--~andbuch, Vol. VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Munlch, 1966, pages 45 to 71.

28,037-F -6-Essentially any o~ganic polyisoc~anate m~
be used herein. Thus, it is possible i.n ~ccor~ance with the inventlon ~o utilize aralipha~ic, aromatic and heter~
cyclic pOlyisocyânates. Specific examples of useful iso-cyanates include, 1,3- and 1,4-phenylene diisocyanate, 1,4- and 3,6-tolylene diisocyanate and mixutes of these isomers; diphenyl methane-2,4'- and/or 4,4'-diisocyanate;
naphthylene-1,5-diisocyanate; triphenylmethane-4,4',4"--triisocyanate; polyphenyl polymethylene polyisocyanates which may be obtained by condensing anilin~ with formalde-hyde, followed by phosgenation and which a.re of the type ~escribed, for example, in British Patents 874,430 and 848,671, perchlorinated aryl polyisocyanates of the type described in German Patent 1,092,007; the diisocyanates described in U.S. Patent 2,492,330; polyisocyanates con-taining allophanate groups of the type described, for exam-ply, in British Patent 994,890 and Belgian Patent 761,626;
polyisocyanates containing isocyanate groups of the type described, for example, in German Patents 1,022,789; 1,222,067 and 1,027,394 and in German Offenlegungsschrifts 1,929,034 and 2,004,048, both published December 10, 1970; polyisocyanate.s containing urethane groups as described in U.S. Patent 3,394,164;
the polyisocy~nates containing acylated urea groups described in German Patent 1,230,778; polyisocyanates containiny biuretgro~p-s of the type described, for example, in German Patent 1,101,394i in British Pabent 880,050 and in French Patent 70-17514i polyisocyanates obtained by telomerization reactions as described in Belgian Patent 723,640; polyiso-cyanates containing ester groups of the type described, for example, in British Patents 956,474 and 1,072,956; in U.S.
Patent 3,567,763 and in German Patent 1,232,688; and reaction products of the above-mentioned isocyanates with acetals as described in German Patent 1,072,385.

28,037-F - 7 -~8-It is also possible to use the distillation residues containing isocyanate groups which accumulate ln the indu~trlal-scale production of isocyanates, option-ally in solution in one or more of the above~mentioned polyisocyanates. It is also possible to use mix~ures of the above-mentioned polyisocyanates.

In general, it is particularly preferred to use readily availa~le polyisocyanates, such as 2,4- and

2,6-tolylene diisocyanate and mixtures of these isomers (TDI), polyphenylpolym~thylene polyisocyanates of the type obtained by condensing aniline with formaldehyde, followed by phosgenation (crude MDI); and polyisocyanates contain-ing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups (modified polyisocyanates).

Blowing agents suitable for use in combination with the methylene chloride in accordance with the instant invention include water and/or readily volatile organic substances. Examples of organic blowing agents include acetone; ethyl acetate; halogen-substituted alkanes such as chloroform, ethylene chloride, vinylidene chloride, monofluorotrichloromethane, chlorodi~luoromethane and dichlorodifluoromethane, butane, hexane, heptane and diethylethers.

Additionally, catalysts are often used in the process of the instant invention. Suitable catalysts include tertiary amines such as triethylamine, tributyl-amine, N-methyl morpholine, N-ethyl morpholine, N-cocomor-pholine, N,N,N',N'-tetramethyl ethylenediamine, 1,4 diaza-bicyclo-(2,2,2)-octane, N-methyl-N'~dimethyl aminoethyl 28,037-F w8-piperazine, N,N~dimethyl benzylamine, bis-~N,N-diethyl aminoethyl)-adipate, N,N-diethyl benzylamine, pentamethyl diethylenetriamine, N,N-dime-thyl cyclohexylamine, N,N,N',N'--tetramethyl-1,3-~utanediamine, N,N-dimethyl.-~-phenylethyl-amine, 1,2-dimethyl imidazole and 2-methyl imidazole.

Suitable metal catalysts include metal che-lates, bicyclic amidines and monocyclic amidines, either alone or especially in combination with monocarboxylic or dicarboxylic acids, with metal octoates being preferred.

Suitable bicyclic amidines include compounds corresponding to the general formula ~(CH2)n\

~N C ~ N
~ (C~2)m ~

in which m = 2 or 3 and n - 3, 4 or 5.

EY.amples o~ monocyclic amidines i.nclude com-pound5 corresponding to the general ormula C
R-N / ~ N

28,037-F -9 in which R is an optionally branched and/or heteroatom--containing aliphatic, cycloaliphatic, araliphatic or aro-matic radical havin~ 1 to 15 carbon atoms. R may thus be, for example, methyl, cyclohexyl, 2-ethylhexyl, benzyl, cyclohexylmethyl, ethoxyl or a radical corresponding to the fonmula CH3-CH3-N / ~ N

In addition, other catalysts may also be used in the process according to the invention. Examples of these catalysts and information about the manner in which they perform may be found in Kunststoff-Handbuch, Vol. III, Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, pages 96 to 102.

It is advantageous, although not essential, to use surface-active additi.ves such as emulsifiers and o~lm stabilizers of the type commonly used in the producti.on of foamed polyurethanes, in the process according to the inven~ion. Silicone-containing skabilizers are particu-larly desirable where the reactive mixture is prefoamed by "whipping in" air and "whip-foaming" before or during the chemical reaction.

Polyols containing fillers may also be used for the process according to the invention. Examples of suitable fillers include naturally occurring minerals 28,037-F -10-~3~

such as chalk, kaolin or baryta in finely divided fo~n, aluminum oxide hydrates, mixtures thereof and mixtures with other fillers and/or flameproofing additives.

The reaction components may be generally reacted in known manner by the one-stage process, by the prepolymer process or even by ~he semi~prepolymer process, advantageously using machinery of the kind described, for example in Kunststoff-Handbuch, Vol. VII, Vieweg-Hochtlen, Carl-~anser-Verlag, Munich 1966, on pages 121 to 205.

The following examples illustrate that very soft polyurethane foams can be prepared using smaller amounts of the metal catalyst when methylene chloride is employed as the principle auxiliary blowing agènt, together with the low molecular weight polyhydroxy com-pounds in accordance with the present invention, than previously employed when the low molecular weight poly-hydroxy compound of the present invention was omitted.
Further, the amount of catalyst employed when a polyure-thane foam is prepared in accordance with the presentinvention is nearly that which one would expect to employ when using the fluorocarbons of the present day art.

In order to obtain a fair comparison of prop-erties the comparative examples have been run on similar laboratory foam apparatus to produce slabs 3 feet by 30 feet (0.91 m by 9.1 m). While the properties are not the same as those obtained on commercial scale con-tinuous apparatus, the laboratory scale apparatus pro duces foams which are consistently comparable, although having slightly poorer characteristics than the commer-cial scale equipment-produced foams.

28,037-F

The following table sets forkh the results obtained employing laboratory equipment. The data illus-trate that the addition of glycerine to a foam formula-tion in which methylene chloride i5 to be used as a blow-ing agent to produce very soft foams reduces the amountof metal catalyst, such as stannous octoate, required to produce substantially equivalent foams. Comparative Runs 1 to 4 illustrate the characteristics obtained in the laboratory equipment producing foams 3 feet by 30 feet (0.91 m by 9.1 m) when using methylene chloride and no glycerine as is co~mon practice in the industry today.
The amounts of metal catalyst are 150 to 175 percent greater than that metal catalyst commonly used by the industry when fluorotrichloromethane is used as the blowing agent rather than methylene chloride (see Com-parative Runs 5 and 6). Runs 1 to 6 illustrate the inven-tion and show the marked reduction in metal catalyst required to obtain oams of equivalent properties when 0.5 part of glycerine is used per 100 parts of polyol.
In Compara-tive Runs 2 to 4 the TDI Index and isomer ratio and amoun-ts of polyol, water, fluoro-trichloromethane, methylene chloride, silicone surfactant and amlne cata-lyst were the same as in Comparative Run 1. I~ Run 2 of the present invention the data for the first e.ight com-ponents listed in the table are the same as for Run 1,and in Runs 5 and 6 the data for the same eight compo-nents are the same as for Run 4.

28,037-F

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28,037-F - 15-Example II illustrates runs in ~hich a fluoro-carbon was employed as the blowing agent with and without the polyhydroxy compound, showing that smaller amounts of gelation catalyst can be used with a fluorocarbon and glycerine (Run 7) and no glycerine (Comparative Run 7).
Su~stantially equivalent foams were obtained.

Exam~le II

Compara-tlve 10 Formula~ion Run 7 Run 7 Polyol 3010 100.0 100.0 TDI Index 108.0 108.0 TDI 46.4 48.0 H2O 3.5 3.5 Fluorotrichloromethane 23.0 23.0 Silicone surfactant 1.5 1.5 Two amine catalysts 0 22 0 22 Stannous Octoate 0.37 0.2 20 Glycerine - 0.5 Example III
In this example another polyol - an adduct o~
propylene oxide (PO) and glycerine - which ls soluble in methylene chloride was used in place of the ~lycerine of the previous examples. The adduct contained 1.6 moles of PO per mole of glycerine. Again, foams of comparable 28,037-F -16--17~

properties were produced while employing less metal cata-lyst when the glycerine-PO adduc-t was employed according to the invention. Comparative Run 8 contains no adduct and Runs 8 to 10 were performed in accordance with the invention (all components in Runs 8 to 10 are the same as in Comparative Run 8 except where noted).

Com-para-tive Formulation Run 8 Run 8 Run 9Run 10 Polyol 3010 100.0 TDI Index 108.0 TDI 46.4 47.2 47.046.9 H2O 3.5 MeCl2 22.0 Silicone Surfactant 1.50 Amine 0.17 Catalysts 0.08 Stannous Octoate 0.575 0.50 0.45 0.50 Adduct none 0.50 0.400.30 28,037-F -17-

Claims (4)

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

1. A method for preparing a polyurethane foam by reacting a polyether polyol having a molecular weight of from 800 to 5000, an isocyanate, water, a metal salt catalyst, an amine catalyst, a silicone surfactant and a halogenated hydrocarbon blowing agent, which blow-ing agent is at least 10 percent methylene chloride, characterized by incorporating with the reactants from 0.1 to 1.5 parts of a polyhydroxy aliphatic compound hav-ing more than two hydroxyl groups and a molecular weight of not more than 195, while employing from 1.4 to 1.6 times the metal salt catalyst of that used where a fluoro-carbon is the sole blowing agent.

2. The method of Claim l wherein the poly-hydroxy compound is glycerine.

3. The method o Claim 1 wherein the poly-hydroxy compound is an adduct of glycerine and propylene oxide.

4. The method of Claim 3 wherein the adduct contains 1.6 moles of propylene oxide per mole of glycerine.

2B,037-F -18-Patent Agents