CA1065547A - High resiliency flexible urethane foams - Google Patents

Abstract

A B S T R A C T
This invention pertains to a process for pro-ducing highly resilient flexible polyurethane foams and to polyurethane foams made by the process. The process includes the steps of reacting a polyether polyol and a crosslinking agent with a polyisocyanate in the presence of a catalyst, a cell control agent and a blowing agent and is characterized in that at least a portion of the crosslinking agent is an aminocyclohexylmethanamine having at least seven carbon atoms. The process is suitable for producing molded and slab stock polyurethane foams. The foams are used in cushioning applications such as furniture and automobile seating.

Description

~oG5547 It has now been unexpectedly discovered that flexible polyurethane foam prepared by reacting a crosslinking agent and a polyol with a poly-isocyanate in the presence of a catalyst, a cell control agent and a blowing agent has an improvement in one or more of properties~ such as, for example, elongation, tear strengthJ or load bearing when at least a portion of the crosslinking agent is an aminocyclohexylmethanamine having at least seven carbon atoms.
A crosslinker which has been widely used is 4,4'-methylene-bis~2-chloroaniline), also known as MOCA. Use of this crosslinking agent is declining because of its suspected tumorigenic behavior. At the present time none of the aminocyclohexylmethanamines of the invention are suspected of being tumorigenic.
According to the present invention, there is provided a process for producing flexible polyurethane foams by reacting a polyether polyol having an average hydroxyl equivalent weight of about 900 to about 2500 and a crosslinking agent with a polyisocyanate in the prasence of a catalyst, a silicone oil cell control agent and a blowing agent characterized in that the crosslinking agent is an aminocyclohexylmethanamine and is employed in amounts of from 0.3 to 10 parts by weight per 100 parts by weight of polyol.
In another aspect~ the invention provides flexible poly-urethane foam prepared by raacting a polyether:polyol having an average hydroxyl equivalent weight of about 900 to about 2500 and a crosslinking agent with a polyisocyanate in the presence of a catalyst, a silicone oil cell control agent and a blowing agent, characterized in that at least a portion of the crosslinking agentsis an aminocyclohexylmethanamine having at least seven carbon atoms.
The process according to the inven~ion will now be described in more detail with respect to preparation of polyurethane foams by reacting as essential ingredients (A) crosslinking agent, ~) polyether polyol, ~C) polyisocyanate, ~D) catalyst, ~) cell control agent, and (F) blowing agent. Other agents, optionally used in the production of polyurethane ~1065547 foams, such as, for example, inorganic and organic fillers, fire retar-dant agents may also be included for special desired e:~fects.
. Crosslinking Agent The special crosslinking agents of the present invention are aminocyclohexylmethanamine compounds represented by the formula:

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~ - la -:~ ~' . .

~655~'7 (A)y (Ri)x~
~NH2) Z

S wherein A is the group ,2 -C -NH2, . R3 : each Rl, R2, and R3 is independently hydrogen or a Cl to C4 alkyl group, x has a value from 0 to 4, y has a value of l or 2, z has a value of 0 or l, and the sum of y plus z is 2.
Suitable aminocyclohexylmethanamine compounds which can be employed herein include, for example, men-thanediamine (4-amino-a,a4-trimethylcylcohexylmethanamine), isophoronediamine ~3-amino-3,5,5-trimethylcylcohexylmethan-amine), 4-~aminomethyl)-cyclohexylmethanamine, 3-(amino-methyl)-cyclohexylmethanamine and mixtures thereof. Pre-:
: ferred aminocyclohexylmethanamine compounds include men 20 ~ : thanediamine and isophoronediamine~
:Menthanediamine and isophoronediamine are liguids at room temperature. A~ liquidst they have advantages in handling over solid crosslinking agents such as MOCA, par-ticularly when employed in continuous foaming oparations : 25 where the components of the foaming formulation are metexed to a separate mixing head. Solid crosslinking agents must be dissolved or suspended in a liquid medium before being metered to the mixing head~

Generally the aminocyclohexylmethanamine cross-~30 linking agents are employed in amounts from 0.3 to 10 par~s L7,444B-F ~2-:;
.

~65547 by weight per 100 parts by weight of polyol. Preferably the aminocyclohexylmethanamine crosslinking agents are employed in amounts from 0.5 to 5 parts by weight per 100 parts by weight of polyol. Most prefe:rably the crosslink-iny agents are employed in amounts from 1 to 2 parts by weight per 100 parts of polyol.
Optionally, one or moxe auxiliary crosslinking agents known in the art is added to the foaming formula-tion in addition to the aminocyclohexylmethanamine cross-linking agent. Suitable auxiliary crosslinking agents ; includel for example, tris(polyoxyalkylene alkanol)amines;
mono-, di-~ and triethanolamines; mono-, di-, and tri-isopropanolamines; oxyhydrocarbon or oxyhydrocarboxy derivatives of isocyanuric acid or aryl substituted iso-cyanuric acid; oxydianiline; an aliphatic diol or a poly-ether aiOl having an hydroxyl equivalent weight less than 300 and preferably less than 200; aliphatic and aromatic ; polyamines having from one to 30 carbon atoms; or mixtures thereof. Auxiliary crosslinking agents, i~ used, are g~nerally employed in the range from 0.1 ~o 5 parts by weight per 100 parts hy weight of polyolO
B. Pol~ether P~yol Suitable polyether polyols are primary-hydroxyl containing triols obtained by reacting an initiator such as~ for example, glycerol, . tri~e~hylolpropan~ hexanetriol, or mixtures ~hereof, with a 1,2-alkylene oxide having from two to four carbon atoms or a mixture of such alky-lene oxides and subsequently end-capping the resultant polyol with at least one mole of ethylene oxide per hy-droxyl groupO The resultant end-capped triol have averaye - 17,4 ~ B-F -3-~)65S~47 hydroxyl equivalent weights from 900 to 2500, prefer-ably from 1200 to ~000. The primary hydroxyl contain-ing polyether polyol usually contains from 4 to 20 per-cent by weight ethylene oxiae reacted on the end of the molecule.
Suitable polyether triols may optionally con-tain diols, other triols, polymer containing diols, poly-mer containing triols or mlxtures thereof. Such diols and other triols include those prepared by the reaction of a compound having ~wo or three active hydrogen groups such as, for example, ethylene glysol, propylen~ glycol, 1,4-butanediol, 1,6-hexanediol, glycerine, trimethyol-~he~e~
B propane, or mixtures _ vic-epoxy contain-ing compounds such as, for example, ethylene oxide, 1,2--propylene oxide, 1,2-butylene oxidey 2,3-butylene oxide, styrene oxide, or mixtures thereof and which have an average hydroxyl equivalen~ weigh~ of from 900 to 2500, preferably from 1000 to 2000. Other diols are polyester ~: dio}s having an average hydroxyl equivalent weight from 900 to 2500~ preferably from 1000 to 2000.
Polymer containing diols and triols include those diols and triols having an average hydroxyl eguiva-lent weight from 900 to 2500, preferably from 1000 to : 2000r and which contain from 2 to 50, preferably from 5 to 20 parts by weight of polymer having an average molecular weight o~ at least 5000, preerably at least 20,000. Such polymers may be physically blended with the diol or triol ox they may be prepared in situ in the diol or triol wherein the diol, triol or mixture L7,444B-F -4-~L065~47 thereof is employed as the solv~nt or reaction medium for the polymeri~ation. In some instances, the polymers are grafted onto the diol or triolO
The polymers may also be prepareA by aqueous emulsion techniques common to the "late~x" art or as a dispersion in a non-isocyanate reactive medium. The polymers may be employed in the dry from, i.e. added to the triol or diol after removal of the water or non-iso-cyanate reaction medium therefrom or preferably the "la-~ tex" or dispersion itself may be added to the triol or diol and the water or non-isocyanate reaction medium sub-sequently removed therefrom by known procedure~ for re-moving water or other components from polyols such as, for example, evaporation under vasuum.
The polymers employed herein may contain groups which are reactive with the isocyanate groups contained in the polyisocyanate, but it is not a requirement here in that the polymers contain such groupsO Particularly suitable polymers are those prepared by polymerizing one or more monomars containing ethylenic unsaturation such as, for example, styrene, acrylic acid, methacrylic acid~
acrylonitrile, butadiene, crotonic acid, itaconic acid, dimethylaminomethylmethacrylate, acrylamide, maleic acid, ethyl acrylate, methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate,

2-ethylhexyl acrylate, vinyl chloride, and monomethyl maleate.
C. Polyisocyanate In preparing the polyurethane foam of the pres ent invention, any of a wide variety of polyisocyanates 17,444B-F ~5-~65~

are employed either alone, as isomer mixtures or as mix-tures of different polyisocyanates. Aromatic, aliphatic, alicyc~ic diisocyana~es or combinations o those types are useful. Representative polyisocyanates include 2,4--toluenediisocyanate, 2,6-toluenediisocyanate, methyl-ene-bis(p-phenylisocyanate), polymethy~ene polyphenyl-iso~yanate, crude or undistilled isocyanates, dimers or trimers of toluenediisocyantes, and prepol~mers made by the reaction of a stoichiometric excess of such isocya~
l`O nates with amine initiated polyols or any of the above mentioned polyols. Arylene diisocyanates, i.e. those in which each of the two isocyanate groups is attached directly to an aromatic ring, are preferred.
D. Catalyst Catalyst systems employed includ~, for example, tertiary amine catalysts such as triethylenediamine,-N--ethylmorpholine, N~dimethylaminoethyl)piperazine~ N,N'--bis~dimethylaminoathyl)piperazine, tetramethylbutanedi-amine, dimethylethanolamine, bis(2-diemthylaminomethyl)-ether, or mixtures thereof. Organometal catalysts such as, for example, stannous octoate and dibu~yltindilaurate may be employed either alone or together with the ter-tiary amine catalyst if desired. Sufficient catalyst is used to produce desired foaming parameters such as, for example, cream time and rise time. The optimum concentration of the catalyst system for a given foaming formulation is determined by incrementally adjusting the concentration until the desired conditions are met.
E Cell Control Agent Commonly silicone surfactants such asr for example silicone-glycol copolymers are employed to 17,444B-F -6-1~655~t' improve the mi~cibility o~ the components and aid in con-trolling the size of the cells in the oam. Suitable si-licone oils include polymers of dimethylsiloxane having a viscosity at 25C o 5 centistokes.
F. Blowing A~nt The density o~ the foam is varied by using dif-ferent proportions of a blowing agent. Partly by reasons of commercial considerations, water is the most convenient blowing agent to employ. Water o~ers an additional ad-vantage as a blowing ag~nt in that it not only undergoes an in situ reaction with the isocyanate group to produce carbon dioxide but also results in urea linkage, which serve as crosslinking sites. Other b}owing agents which may be employed include aliphatic hydrocarbons boiling below 110 such as, for example, dichlorodifluoromethane, trichlorofluoromethane, hexane, hexene, or pentane.
In organic and organic fillers such as, for ex-ample, calcium carbonate, barytes, sand, or expandable polystyren~ beadsr may be included in the foams of the present invention. Fire retardant agents such as, for example, tris(2,3-dibromopropyllphosphate, tris(2-chloro-ethyl)phosphate, tris(dichloropropyl)phosphate, triethyl-phosphate, or mixtures thereof may also be employed in the foams of the present invention.
In order that the invention be well u~derstood, the following examples are given by way of illustration only. Foam properties were measured according to AS~M
D-1564-71.
In each of the following Examples and Comparative Runs, the crosslinking agen~, optional auxiliary crosslinking 17,444B-F -7-~:16~ 7 agent, polyol, catalyst, and water were blended together until the components were equally dispersed. Then the polyisocyanate component was quickly added and the com-plete foamin~ formulation stirred for several seconds.
After stirring, the foaming ormulation was poured into a 15 inch x 15 inch x 4 1/2 inch (38.1 cm x 38.1 cm x 11.4 cm) vented closed mold heated to 120F (48~9C)o The foam-ing ormulation for each Example and Compaxative Run con-tained 2.5 parts by weight of water.

Examples 1 through 6 illustrate the e~fect upon foam properties by varying: the concentration of the cross-linking agent, the nature of the polyisocyanate, the con-centration of catalysts, and the type and concentration of the cell control agents. No auxiliary crosslinking agents were employed.
Examples 1 through 6 employed menthanediamine hereinafter known as Crosslinking Agent A, and a polyol, hereinafter known as Polyol F, which was the reaction product o~ glycerine with propylene oxide and end-capped with ethylene oxide. Polyol F had an hydroxyl equiva-lent weight of 1650 and contained from 13 to 15 percent by weight of ethylene oxide end-capping. The polyiso-cyanate used in Examples 1, 2 and 4, hereinafter known as Polyisocyanate H was a crude toluenediisocyanate comprising 66.6~ of the 2,4-isomer, 26% of the 2,6--isomer, and the remainder high~r polyisocyanates.
Polyisocyanate H has an isocyanate equivalent weight of 91~2. In Example 3, the polyisocyanate, hereinafter 17,144B-F -8~

3~6S~7 known as Polyisocyanate I, was an 80/20 mlxkure of 2,4-/2,6-toluenedi-isocyanate having an isocyanate equivalent weight of 87. In Example 5, the polyisocyanate, hereinafter known as Polyisocyanate J, was a pre-polymer adduct of Polyisocyanate I with a diol having an hydroxyl equiva-lent weight o 255. The diol was prepared by reacting bisphenol A with ethylene oxide. Polyisocyanate J has an isocyanate conten~ of 39.4% and an average isocyanate equivalent weight of 107. In Example 6, the poly-isocyanate, hereinafter known as Polyisocyanate K, was a prepolymer adduct of Polyisocyanate I with a glycerine initiated polyoxypropylene glycol having an average hydroxyl equivalent weight of 500. Polyisocyanate K
has an isocyanate content of 42% and an average isocyanate equivalent weight of 100.
All six Examples used three catalyst. Catalyst M was a 33%
solution of triethylenediamine in dipropylene glycol. Catalyst N was bis~2-dimethylaminoethyl)ether. Catalyst 0 was a tin catalyst known as Markure UL-l* commercially from the Argus Chemical Corporation.
Examples 1, 2, 3, S and 6 employed a cell control agent, here-inafter known as Cell Control Agent S, which was a silicone oil commercially available from The Dow Corning Corporation as DCF-1-1630. Example 4 employed as a cell control agent, hereinafter known as Cell Control Agent R, which was a block copolymer silicone oil commercially available from The Union Carbide Corporation as L-5303. The formulations and foam properties are shown in Table I.

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*Trade Mark ~5547 TABLE I
Formulation, Parts by ~eig~t ` 1 _ 3 4 5 6 Crosslinking Agent A 2 0.5 2 2 2 2 Polyol F 100 100 100 100 100 100 Polyisocyanate ~ 36.5 33.1 --- 37.1 --- ---Polyisocyanate I --- --- 3~.7 --_ __ ___ Polyisocyanate J --- --- --- --- 41.1 ---Polyisocyanate K --- --~ --- --- --- 38 Catalyst M 0.6 0.6 0.3 0.3 0.3 0.3 Catalyst N 0.1 0.1 0(.1 0.1 0.1 0.1 Catalyst O 0.01 0.01 0.01 0.01 0.01 0.03 Cell ~ontrol Agent R --- --- --- 0.25 --- ---Cell Control Agent S 0.03 0.03 0.03 --- 0.03 0.03 Foam Properties Density, kg/m 43 43 43 46 43 43 Tensile, kg/cm2 1.35 1.38 1.65 1.73 1.66 1.65 Elongation, % 186 225 285 210 226 285 Tear Resistance, kg/cm 0.40 0.38 0.52 0.45 0.49 0.52 Resiliency, % 57 59 55 59 51 55 Compression set at 75%
Deflection, % 9.5 9.8 9.9 8.7 10.4 9.9 ILD*, 25%, 30 32 25 42 33 25 ILD, 65%, 89 86 71 119 89 71 ILD Modulus 3.0 2.7 2.8 2.8 2.7 2.8 * In this Table, and in Tables II and III below the ILD tests results are pounds/force, per 50 square inches. The test samples were 15 inches square and 4.5 inches thick.
All six Examples ~ad superior tear resistance, i.e., above 0.36 kilograms per centime~er. Tear resistance in the range of 0.30 to 0.36 is considered satisfactory for such applications as, for example, automotive seating.
EXAMPLES 7 THROUGH 9 AND COMRAR~TIVE RUNS A AND B
Examples 7 and 8 ill~strate the use of auxiliar~ cross-linking agents. Oxydianiline, hereinafter known as ~1655~!

Crosslinking Agent D, was employed in Example 7 in combi-nation with CrosslinkIn~ ~gent A.. Ethylene glycol, herein-after known as Crosslinking Agent E, was employed in Example 8 in combination with Crosslinking Agent A.
Example 9 and Comparative Runs A and B are com-parisons of foams produced using menthanediamine, known as Crosslinking Agent A, and MOCA, hereinafter known as Cross-linking Agen~ C. Polyol F, Polyisocyarlate I, Catalysts M
and N, Cell Control Agent S and water were employed in each foaming formulation. The formulations and foam properties are shown in Table II.
TABLE II
Formulation, Parts~ t 7 8 9 A B
Crosslinking Agent A 0.3 0.3 2.0 Crosslinking Agent B
Crosslinking Agent C ~ 2.0 4.0 Crosslinking Agent D 2.5 _w_ ___ ___ ___ Crosslinking Agent E --- 2 ---PolyoI F 100 100 100 100 lO0 Polyisocyanate I 34.2 37.7 35.3 32.2 33~8 Catalyst M 0.3 0~3 0.3 0.3 0 3 Catalyst N 0.1 0.1 0.1 0~1 0.1 Catalyst O 0.01 0.01 - ~
Cell Control Agenk S 0.03 0.03 0.025 0.025 0.025 F m Pro~ ies Density, kg/m3 42 41 44 43 " ~
Tensile, kg~cm 1.47 1.62 1.40 ~ 1.46 ~
Elongation, % 208 216 183 183 : Tear resistance, kg/cm 0.40 0~38 0.33 ~ 0.33 Resiliency, % 60 53 47 ,~ 49 Compression set at 75%
Deflection, ~ 7.9 9.6 7.8 ~ 7.9 IhD, 25% J pounds 35 23 32 ~ 31 ILD, 65%, pounds 91 68 85 ~ 83 o ILD Modulus 2.6 3.0 2~7 ~ 2~7 17,444B F ~

3L~65S47 The foams of Examples 7 and 8 had superior tear resistanceJ
comparing favourably wlth Example 3 o Table I, although E~amples 7 and 8 were run at much lower level of Crosslinking Agent A.
Example 9 and Comparative Run B show that four parts of Crosslinking Agent C were required to produce a Eoam having satisfactory tear resistance as compared with two parts of Crosslinking Agent A.
Comparative Run A shows that when only tuo parts of Crosslinking C were used, the resulting foam collapsed. Comparing the molecular weight of Crosslinking Agent C (267) with the molecular weigh~ of Crosslinking Agent A ~170), it would be expected tha~ it would require more than two parts ~2.5 parts) of Crosslinking Agent A to produce a foam comparable to one containing four parts of Crosslinking Agent C.
In addition to the advantages of being a liquid and not being known as turmoigenic, Crosslinking Agent A offers an economic advantage ; in that less of the component is needed to produce a satisfactory foam compared with Crosslinking Agent C. At the present time Crosslinking Agents A and C sell at comparable prices on a weight unit bases.
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Examples 10 through 13 employed isophoronediamine, hereinafter known as Crosslinking Agent B. For Example lO, Polyol F, Polyisocyanate I, Catalysts M and N, and Cell Control Agent S have all been previously described. Two additional catalysts were employed. Catalyst P was an ~ amine catalyst commercially available from The Jefferson :;:
:~

: ~g ~S547 Chemical Company as Thancat DM-70. Catalyst Q was dibutyltin-dilaurate.
Example 11 employed Polyol F alone, while Examples 12 and 13 employed Polyol F in combination with a grafted polymer polyol, herein-after known as Polyol G. Polyol G was a glycerine initiated polyoxy-propylene polyol end-capped with 15% ethylene oxide, having a molecular welght of 4700, and contained additlonally 20% of a 50-50 ratio styrene-acrylonitrile polymer grated to the polyether polyol. Examples 11, 12 and 13 employed a combination of Polyisocyanate I and polymethylene polyphenylisocyanate, hereinafter known as Polyisocyanate L. Polyiso-cyanate ~ is commercially available from the Upjohn Company as PAPI.
All three examples also employed a cell control agent, hereinafter known as Cell Control Agent T which was a blend of 10 parts of Cell Control Agent R, 1 part of Cell Control Agent S, and 9 par~s of dioctyl phthalate. The formulations and foam properties are shown in Table III.

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~65547 TABLE III
Formulatlon, Parts b~ weight 10 11 12 13 Crosslinking Agent B 1.0 0.6 0.6 1.0 Polyol F 100 100 90 90 Polyol G ~ 10 10 s Polyisocyanate I 32.4 29~5 29.3 30.15 Polyisocyanate L --- 3.3 3.3 3.35 Catalyst M 0.4 0.3 0.3 0.3 Catalyst N 0.1 0.1 0.1 0.1 Catalyst P 0.25 0.25 0.25 0.25 Catalyst Q 0.01 0~01 0.01 0.01 Cell Control Agent S 0.03 ~
Cell Control Agent T -- 0.6 0.6 0.5 Foam Properties Density, kg/m3 44 42 44 45 Tensile, kg/cm 1.53 1~54 1.65 1077 Elongation, % 228 217 225 232 Tear Resistance, kg/cm 0.40 0~38 0.39 0.42 Resiliency, % 59 57 63 61 Compression set at 75%
; Deflection, % 6.4 7.4 8.0 8.0 ILD, 25%, pounds 35 30 33 32 ILD, 65%, pounds 88 83 90 89 ILD Modulus ~.S 2.8 2.7 2.8 Examples 10 through 13 illustrate the use o lower levels of Crosslinking Agent B to produce foams having superior tear resistanceO A foaming formulation ; similar to Example 10 but containing 1.0 part of Cross-: 25 linking Agent C rather than Crosslinking Agent B pro-duced a foa~ that collapsed during molding. Foams having satisfactory-to-superior tear resistance can be produced using Crosslinking Agents A or B at lower levels than for Crosslinking Agent C.

: 17,444B-F -14-

Claims (6)

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

1. A process for producing flexible polyurethane foams by reacting a polyether polyol having an average hydroxyl equivalent weight of about 900 to about 2500 and a crosslinking agent with a polyisocyanate in the presence of a catalyst, a silicone oil cell control agent and a blowing agent characterized in that the crosslinking agent is an aminocyclohexyl-methanamine and is employed in amounts of from 0.3 to 10 parts by weight per 100 parts by weight of polyol.

2. The process of claim 1 characterized in that the aminocyclo-hexylmethanamine is represented by the formula:

wherein A is the group each R1, R2 and R3 is independently hydrogen or a C1 to C4 alkyl group, x has a value from 0 to 4, y has a value of 1 or 2, z has a value of 0 or 1, and the sum of y plus z is 2.

3. The process of claim 1 characterized in that the aminocyclo-hexylmethanamine is employed in amounts from 0.5 to 5 parts by weight per 100 parts by weight of polyol.

4. The process of claim 2 characterized in that the aminocyclo-hexylmethanamine is menthanediamine or isophoronediamine or mixtures thereof.

5. A flexible polyurethane foam prepared by reacting a polyether having an average hydroxyl equivalent weight of about 900 to about 2500 and a crosslinking agent with a polyisocyanate in the presence of a catalyst, a silicone oil cell control agent and a blowing agent, characterized in that at least a portion of the crosslinking agent is an aminocyclohexylmethanamine having at least seven carbon atoms.

6. The polyurethane foam of claim 5 characterized in that the aminocyclohexylmethanamine is menthanediamine or isophoronediamine or mixtures thereof, and is used in an amount of from 0.3 to 10 parts by weight per 100 parts by weight of polyol.