Catalyst blend containing 1,2-dimethylimidazole

Abstract

Disclosed is a synergistic catalytic combination of 1,2-dimethylimidazole with tris(3-dimethylaminopropyl)amine and a salt of 1,8-diazabicyclo(5,4,0)undecene-7. The combination catalyst is useful in polyurethane systems such as elastomers, microcellular, rigid, semirigid, and flexible foams, such as integral skin semiflexible foams used in the manufacture of steering wheels.

Description

BACKGROUND OF THE INVENTION

In preparing polyurethane foams advantages have been achieved by the use of the combination of a triethylenediamine-type of amine catalyst and an organic tin salt. With the multiplicity of raw materials used, namely, polyols, isocyanates, blowing agents, surfactants and additives, catalysis of polyurethane reactions has required continual modification mostly because of economic and ecological factors. Shortened demolding times for example, in rigid, flexible and microcellular molding operations are desirable to effect savings in labor and fixed costs. Moreover, the versatility of urethane has lead to the development of numerous production techniques; freerise molding, injection, casting, spray and others. Each require a specific reactivity profile, attainable in most cases only through catalysis. These developments and requirements have created a need for improved catalysts. Moreover, a commonly used catalyst for making urethane foams is triethylenediamine such as DABCO available from Air Products Co., which is a solid material. While effective as a catalyst for this purpose, solid catalysts are somewhat difficult to work with and liquid or semi-liquid catalytic materials would be desirable.

SUMMARY OF THE INVENTION

The improved catalyst of the present invention comprises a blend of 1,2-dimethylimidazole and tris(3-dimethylaminopropyl)amine together with 1,8-diazabicyclo-5,4,0-undecene 7 (DBU) blocked with 2-ethylhexanoic acid. The latter materials are available from Abbott Laboratories as POLYCAT 9 and POLYCAT SA-102, respectively. Other salts of DBU can be used such as for example those formed with phenol, formic acid, acetic acid, oleic acid or paratoluene sulfonic acid. A mixture of from about 20-80% 1,2-dimethylimidazole; 8-60% tris(3-dimethylaminopropyl)amine (PC-9); and 2-50% 1,8-diazabicyclo-5,4,0-undecene 7 blocked with 2-ethylhexanoic acid (SA-102) will provide a satisfactory combination. A preferred mixture is from 25-50% 1,2-dimethylimidazole; 40-60% PC-9; and 2-30% DBU salt. If desired, the 1,2-dimethylimidazole and PC-9 can be combined in a blend to be subsequently mixed with the SA-102. A blend of 40% 1,2-dimethylimidazole and 60% PC-9 for example, can be used satisfactorily. The combination catalyst can be used in polyurethane systems such as elastomers, microcellular, rigid semirigid and flexible foams. Specific examples such as shoe soles and integral skin semiflexible foams such as are used in the manufacture of automotive steering wheels.

DETAILED DESCRIPTION OF THE INVENTION

In order to illustrate the manner in which catalytic combinations of the present invention can be prepared and used, reference is made to the following examples, which, however, are not meant to limit or restrict the scope of the invention in any respect.

EXAMPLE 1

Polyester Base Microcellular Foam (Shoe-Soles)

The following cup pours were made:

Polyester polyol with 3% trichlorotrifluoromethane (polyol blend): 100 grams Polyisocyanate: Mondur E501 90 grams Component temperature=40.degree. C. Room temperature=71.degree.-73.degree. F. Relative humidity=42-46% Cup size=pint Mixing speed=3000 RPM ______________________________________ Catalyst Triethylene- PC9 = 0.42 PC9 = 0.42 diamine, 0.65% SA102 = 0.18 SA102 = 0.28______________________________________Mix Time, Sec. 6 6 6Cream Time, Sec. 8-9 15 14-16Tack Free, Sec. 30-35 50 35-37Pull, Sec. 65-85 80-90 50-52Remarks Slow hard cure Very Soft Very soft______________________________________

EXAMPLE 2

Microcellular Polyester Base Resins

Based on the cup pour results of Example 1, a ratio of 2/1: PC9/SA102 was utilized to determine molding characteristics of the two component blend of Example 1.

______________________________________Formula______________________________________Polycat 9: 100 parts = 0.50 PHR (parts per hun-Polycat SA102: 50 parts = 0.25 phR dred of resin 150 parts polyol blend)______________________________________

Reactivity

Mix time=6 seconds Cream time=13 seconds Tack free=39-40 seconds Pull=50-51 seconds.

Molding characteristics

______________________________________Mix time = 6 secondsAmount of Polyol Blend = 237 gramsfoam mixed Polyisocyanate = 213 grams Catalyst = 1.78 grams - 451.78 grams______________________________________ Mold Dimension: 5.times.10.times.1 inch Mold temperature=140.degree. F. Mold release=chem trend P5 Cl Demold time=3 minutes Results--Bottom of part green, cheesey, very soft, upper part satisfactory.

EXAMPLE 3

Evaluation of Methylimidazoles as a Co-catalyst for Improving Demold Characteristics of Polyester Base Resins Systems

______________________________________Foam RatioPolyol Blend: 100 parts (237 grams)Polyisocyanate: 90 parts (213 grams) Catalyst PC9 = 0.50 PC9 = 0.50 SA102 = 0.20 SA102 = 0.22 1,Methyl- 1,Methyl- Imidazole = 0.20 Imidazole = 0.22______________________________________Room temperature 70 70.degree.F.Component tempera- 40 C. 40 C.ture .degree.C.Relative humidity 60% 60%Foam ratio: 100/90 100/90Polyester/ISOMix time, Sec. 8Cream time, Sec. 14String time, Sec. 30Rise time, Sec. 50Tack free, Sec. 40Density, LBS/FT.sup.3Pull, Sec. 52Molded Part, Mixed 450 grams 450 gramsMold temperature 128.degree. F. 135.degree. F.Results NG, cheesy, Slight improve- soft ment; still cheesy______________________________________ Same conditions as Example 2 plus 0.2 or 0.22 1-methyl-imidazole. No improvement noted.

EXAMPLE 4

Evaluation of 1,2-Dimethylimidazole as a Co-catalyst to Improve Demold Time of Polyester Based Microcellular Foam Formulations

______________________________________Formulation______________________________________Polyol Blend: 100 partsPolycat 9: 0.50 partsPolycat SA102: 0.20 partsPolyisocyanate: 90.0 parts1,2-Dimethyl-imidazole: 0.2 to 0.4 parts______________________________________Molded 10" .times. 5" .times. 1" partsAluminum mold PC9 = 0.50 PC9 = 0.50 SA102 = 0.20 SA102 = 0.20 1,2 Dimethyl- 1,2 Dimethyl- Imidazole = 0.20 Imidazole = 0.40 per 100 parts Resin per 100 parts Resin______________________________________Resin 237 grams 237 gramsE501 213 grams 213 gramsMix time 10 103000 RPMMold release agent P5 Cl P5 ClMold temperature 130.degree.-135.degree. F. 130.degree.-135.degree. F.Demold after Fair-Slight Fair3 minutes Loss of skin Slight loss of skin______________________________________

EXAMPLE 5

______________________________________ Blend A Blend BFormulation % Weight % Weight______________________________________1,2 Dimethyl Imidazole 40.00 33.00Tris (3-Demethylaminopropyl) 60.00 67.00amine (Polycat 9) 100.00 100.00______________________________________ Triethyl- Blend A = Blend B = Belnd A = enediamine 0.90 0.80 0.80 0.65 SA102 = SA102 = SA102 = Control 0.20 0.20 0.20______________________________________Cream time, 9 10 12 11sec.Top of Cup, 25 24 27 26sec.String time, 28 27 30 28sec.Tack free, 32 31 36 34sec.Pull time, 45 47 59 55sec.Density 14.5 15.0 14.9 15.3LBS/FT.sup.3______________________________________

EXAMPLE 6

Polyester Base Microcellular Shoe-Soles

Comparison between Blend A, Blend B (see example 5) and triethylenediamine.

______________________________________Formulation Control 1 2 3______________________________________Triethylenediamine 0.65 -- --Blend A -- 0.90 -- 0.80Blend B -- -- 0.80 --SA102 -- 0.20 0.20 0.20Polyisocyanate 90.0 90.0 90.0 90.0Polyol Blend -- 100.0 100.0 100.0Component 40.degree. C. 40.degree. C. 40.degree. C. 40.degree. C.temperatureMold temperature 125.degree.- 125.degree.- 125.degree.- 125.degree.- 130.degree. F. 130.degree. F. 130.degree. F. 130.degree. F.Mold release agent DPM286 DPM286 DPM286 DPM286Mix time, sec. 6 6 6 6 80/72 80/72 80/72 80/72Demold time 3 min. 31/2 min. 41/2 min. 4 min.Shore A Hardness 60 62 60 63Weight of Part 105 108 109 106Mold Dimension: 5 .times. 10 .times. 0.25 inchTotal Weight of Components: 152 grams______________________________________

EXAMPLE 7

The formulation used in the preparation of the microcellular shoe sole system is shown below:

______________________________________Polyester resin Witco F108 83.01,4 Butane Diol 17.0Water 0.2Trichloromonofluoromethane 4.0Polyisocyanate Mondur E-501 100 Index______________________________________ The results are summarized in the following table. ______________________________________MICROCELLULAR SHOE SOLEPOURS BASED ON POLYESTER RESIN Control 1A 2A 3A______________________________________1/3 Triethylenediamine 0.60 0 02/3 DipropyleneglycolPolycat 77 (N,N,N', 0.40 0 0N",N"--Pentamethyl-dipropylenetriamine)2:1 Blend, Polycat 9:1, 0 0.80 0.80 0.802-DimethylimidazoleSA102 0 0.05 0.10 0Components temper- 40 40 40 40ature .degree.C.Foam ratio: polyol 105/108 105/108 105/108 108/108blend isocyanateMix time, sec. 8 8 8 8Cream time, sec. 10 11 10 11String time, sec. 28 33 28 36Rise time, sec. 40 42 38 48Pull time, sec. 61 72 49 81Density, LBS/FT.sup.3 14.40 16.14 15.14 16.45Remarks No ShrinkageMolded pad density, 31.0 32.3 32.6 30.8LBS/FT.sup.3Mold temperature, .degree.F. 128.degree. 130.degree. 130.degree. 128.degree.Mold release agent M 286 M 286 M 286 M 286Demold time minutes 3 31/2 21/2 5______________________________________

The following table records the results of a reactivity study as between various imidazole compounds. As is apparent, 1,2-dimethylimidazole produced improved results with respect to a faster initiation time, rise time, foaming time, a faster rate of rise, time to maximum rate of rise, gel time and time to peak pressure. The formulation used comprised 100 parts polyol, 1.5 parts silicone surfactant, 36.5 parts trichlorofluoromethane, 122.8 parts methylene diisocyanate and 1.6 parts of the imidazole catalyst.

TABLE 1______________________________________Rigid 1,Methyl- 2,Methyl- 1,2-Dimethyl- PC 8 imidazole imidazole imidazole______________________________________Foam 15.51 12.94 15.69 15.01Height, inchesInitiation 66 64 81 44Time, secondsRise time, 108 93 142 69SecondsFoaming time, 42 29 61 25SecondsRate of Rise, 29.04 34.49 17.47 49Inches/minutesTime to dx/dt, 69 67 86 47SecondsPressure, 3.06 3.88 2.41 3.83PSIGGel time, 94 66 97 51SecondsTime to Peak 207 144 231 123Pressure,Seconds______________________________________

Referring to the examples, it can be seen in Example 1 that the two component system approaches but does not produce the reactivity of the commonly utilized solid catalyst, triethylenediamine. In this example, the noted catalyst or combination catalyst was added to the polyol blend and polyisocyanate. In Example 3, no improvement was noted in comparison to the results obtained in Example 2 when 1-methyl imidazole was added to the two component systems. In Example 4, improved results are apparent with the addition of 1,2-dimethylimidazole in comparison to the addition of the 1-methylimidazole added in Example 3 or the two component systems of Example 2.

In Example 5 it can be seen that the combination catalyst of the invention produces results comparable to the commonly used catalyst triethylenediamine with increased amounts of 1,2-dimethylimidazole producing generally more advantageous results. Examples 6 and 7 illustrate the comparable or improved demold time resulting from the use of the combination catalyst of the present invention. Being semiliquid in form, the combination catalyst provides the further advantage of ease of handling as well as faster processing time.

Claims

1. A catalytic combination comprising from about 20 to 80% 1,2-dimethylimidazole, from about 8 to 60% tris(3-dimethylaminopropyl)amine, and from about 2 to 50% of a salt of 1,8-diazabicyclo-5,5,0-undecene 7.

2. The catalytic combination of claim 1 wherein the salt of 1,8-diazabicyclo-5,4,0-undecene 7 is selected from those formed with phenol, formic acid, acetic acid, oleic acid, paratoluene sulfonic acid or 2-ethylhexanoic acid.

3. A catalytic combination of claim 1 which comprises from about 25 to 50%, 1,2-dimethylimidazole, from about 40 to 60% tris(3-dimethylaminopropyl)amine, and from about 2 to 30%, 1,8-diazabicyclo-5,4,0-undecene 7 blocked with 2-ethylhexanoic acid.

4. In the method of producing a polyurethane product by reacting a polyester or polyether polyol with a polyiso-cyanate, the improvement which consists in conducting said reaction in the presence of a catalytic combination comprising from about 20 to 80% 1,2-dimethylimidazole, from about 8 to 60% tris(3-dimethylaminopropyl)amine, and from about 2 to 50% of a salt of 1,8-diazabicyclo-5,5,0-undecene 7.

5. The method of claim 4 wherein the salt of 1,8-diazebicyclo-5,4,0-undecene 7 is selected from those formed with phenol, formic acid, acetic acid, oleic acid, paratoluene sulfonic acid or 2-ethylhexanoic acid.

6. The method of claim 4 wherein the 1,8-diazabicyclo-5,4,0-undecene 7 is blocked with 2-ethylhexanoic acid.